I3RARY 
 
 NIVERSITY or 
 CALIFORNIA 
 
\J' 
 
 
J\ Q 
 
 THE 
 
 STEAM ENGINE: 
 
 ITS INVENTION AND PROGRESSIVE IMPROVEMENT, 
 
 INVESTIGATION OF ITS PRINCIPLES, 
 
 LONDON 
 
 AND ITS APPLICATION TO 
 
 NAVIGATION, MANUFACTURES, AND RAILWAYS. 
 
 BY THOMAS TREDGOLD, CIVIL ENGINEER, 
 
 MEMBER OP THE INSTITUTION OF CIVIL ENGINEERS; AUTHOR OF ELEMENTARY PRINCIPLES OF CARPENTRY; 
 A PRACTICAL TREATISE ON THE STRENGTH OF IRON, &c. 
 
 A NEW EDITION, 
 
 ENLARGED BY THE CONTRIBUTIONS OP EMINENT SCIENTIFIC MEN, AND EXTENDED 
 
 TO THE SCIENCE OP 
 
 REVISED AND EDITED 
 
 BY W. S. B. W O O L H O U S E, F. R. A. S., &c., 
 
 ACTUARY TO THE NATIONAL LOAN FUND LIFE ASSURANCE SOCIETY. 
 
 IN TWO VOLUMES, 
 
 WITH ONE HUNDRED AND TWENTY-FIVE ENGRAVINGS AND NUMEROUS WOOD-CUTS. 
 
 VOL. I. 
 
 LONDON: JOHN WEALE. 
 
 MDCCCXXXVIII. 
 
LONDON : 
 
 PRINTED BY W. HUGHES, (SUCCESSOR TO MR. VALPY,) 
 KING'S HEAD COURT, COUGH SQUARE. 
 
TO HER MOST GRACIOUS MAJESTY 
 
 VICTORIA, 
 
 QUEEN OF GREAT BRITAIN AND IRELAND, 
 
 &c. &c. &c. 
 
 THESE VOLUMES 
 ON THE PRINCIPLES AND CONSTRUCTION OF THE 
 
 STEAM ENGINE, 
 
 INVENTED AND PERFECTED BY THE TALENT AND ENTERPRISE OF BRITISH SUBJECTS, 
 AND ESSENTIAL TO THE PROGRESS OP CIVILISATION IN EVERT NATION, 
 
 ARE (BY HER MAJESTY'S GRACIOUS PERMISSION) INSCRIBED, 
 BY HER MAJESTY'S DEVOTED SUBJECTS,' 
 
 W. S. B. WOOLHOUSE, EDITOR. 
 JOHN WEALE, PUBLISHER. 
 
 345 
 
ADVERTISEMENT. 
 
 THE work of Tredgold on the Steam Engine, from its first appearance 
 in the year 182/ up to the present time, has maintained the highest 
 reputation, both in this country and on the continent. Since the pub- 
 lication of the first edition, the boundless resources of steam power 
 have been directed, on the most enlarged scale, to almost every im- 
 portant purpose of mankind, and the steam engine has achieved the 
 greatest triumphs of human ingenuity. The present edition contains 
 several valuable contributions from professional gentlemen of acknow- 
 ledged ability and experience; and, with these and the many revisions 
 and additions which the work has undergone, it is hoped that it will be 
 found suited to the present advanced state of the science, and that it 
 may continue to occupy the same favorable position which it has hitherto 
 enjoyed. A considerable number of errors have been corrected which 
 appeared in the first edition; and, amongst many other improvements, 
 the principles of parallel motion, so important to the manufacturer, 
 have been put in a complete form. 
 
 The Appendix consists of the following original papers : 
 
 I. On the practical nature and general management of marine boilers, 
 by Mr. DINNEN. 
 
VI ADVERTISEMENT. 
 
 II. A form of steam journal for keeping a proper record of the 
 operations of the engines in all steam vessels, by Lieut. BALDOCK, R.N. 
 
 III. On the motion of steam vessels and the principles of paddle 
 wheels, by Mr. P. W. BARLOW. 
 
 IV. Time and traverse table for ascertaining the effects obtained 
 with a steam vessel upon an oblique course assisted with canvas, com- 
 pared with the same vessel upon a direct course without canvas, and 
 with a diminished velocity, by Captain OLIVER, R.N. 
 
 V. Memoir of Her Majesty's steam ship the ' Medea,' by Lieutenant 
 BALDOCK, R.N. 
 
 VI. On the present state of steam navigation in the United States, 
 by Professor RENWICK, of Columbia College, New York. 
 
 VII. Theory of the motion and action of paddle wheels, with a 
 comparison of the principal inventions that have appeared for the pro- 
 pelling of steam vessels, by Mr. MORNAY. 
 
 VIII. On the indicator, with practical illustrations of its nature and 
 use, by Mr. GLYNN. 
 
 IX. Account of Mr. HOWARD'S new principle of vaporization. 
 
 X. On the general theory of the steam engine, in which the theory of 
 the crank, the transmission of effect through the boiler and cylinder, 
 the general principles of action, the theory of paddle wheels, and the 
 nature of the resistance of fluids, are succinctly treated. 
 
ADVERTISEMENT. Vll 
 
 The scientific and practical paper by Mr. Barlow, the ingenious 
 theoretical investigations of Mr. Mornay, together with the article con- 
 tained in this last paper, constitute a very extended, and, perhaps, 
 complete discussion of the interesting subject of paddle wheels. 
 
 XL Practical rules for calculating the steam engine, illustrated by 
 numerous examples. To a person engaged in actual practice, even 
 though he be a first-rate mathematician, a rule and example put down 
 exactly in the order of work is much superior, in every respect, to 
 any mathematical formulae that can be set before him ; and this becomes 
 a matter of indispensable necessity and importance to such as are, 
 exclusively, practical men. It is hoped that these rules and examples, 
 and the copious index, prepared by Mr. Hann, a gentleman intimately 
 acquainted, both theoretically and practically, with the principles of 
 the steam engine, will add greatly to the utility of the edition now 
 offered to the public. 
 
 In the explanation of the plates will be found a very lucid and 
 elaborate description, still further illustrated by the aid of numerous 
 wood-cuts in the text, of Stephensons' newest patented locomotive 
 engine ; and for this very able, complete, and popular account, we are 
 indebted to the liberality of Mr. Stephenson, engineer of the London 
 and Birmingham and other Railways : also, an account of Mr. Samuel 
 Hall's condenser, now much used in sea-bound vessels. 
 
 To render the work of still greater utility, the Publisher has, after 
 much painful opposition, succeeded in producing examples of the 
 best sea and river vessels, practically illustrating the application of 
 steam-machinery to the purposes of navigation, in reference to the 
 principles of naval architecture ; and the Editor is indebted to Mr. 
 
Vlll ADVERTISEMENT. 
 
 Oliver Lang, of Her Majesty's Dock-yard, Woolwich ; Mr. Fincham, of 
 Her Majesty's Dock-yard, Sheerness ; and Mr. Ditchburn, of Limehouse ; 
 for the able scientific descriptions which accompany these subjects. 
 
 It is due to the eminent individuals who have mainly assisted the 
 undertaking, to state that the Publisher and Editor are most grateful 
 to those whose names appear in the work as contributors, as well as 
 to others for many valuable communications and services. 
 
 Mr. Weale, the Publisher and Proprietor of the work, has, for 
 nearly two years, held in communication some of the most scientific 
 men in this and other countries, for the purpose of obtaining the most 
 extensive and valuable information; and it will at once be observed, 
 that no expense has been spared, and that neither taste nor skill has 
 been wanting in the getting up of the volumes, to make the present 
 a splendid national work. The Editor, however, cannot presume to 
 suppose that he has similarly succeeded in the execution of his task; 
 and he will, at all times, through the Publisher, be most thankful to 
 receive and acknowledge any suggestion or amendment. 
 
PREFACE. 
 
 OF the various books published on that important and national subject the 
 Steam Engine, there is not one in our own or any foreign language, which I 
 consider as a fully satisfactory illustration of its principles ; it is therefore only 
 requisite for me to state this fact to render any apology unnecessary for the work 
 I now offer to the notice of the Public. I have frequently and successfully 
 claimed attention as an author ; and in this case I hope to meet with equal 
 success, and to show by the labour and attention I have bestowed on this im- 
 portant subject, how highly I value the ostensible character I have acquired, 
 and the extensive encouragement I have received. 
 
 It has been too common of late for mathematicians to complain of want of 
 patronage, and to censure official authorities for not encouraging science, for- 
 getting that research will always be estimated by its intermediate utility ; and 
 while they continue to confine their attention to abstract knowledge, while they 
 do not devote a greater part of their time to its application to the wants and 
 the welfare of society, they must be contented with a small share of those ad- 
 vantages, which result from combining with practical skill the power afforded 
 by abstract reasoning. They should recollect that a Watt could have earned no 
 fame, in an age or in a country where the value of mechanical power was unknown. 
 In following the application of science to art, I have not, however, I hope, been 
 unsuccessful in adding also to the stores of pure science ; and, so far from being 
 insensible to the value of abstract research, I wish it to be pursued with redoubled 
 vigour by those who have spirit to break through the prejudices of existing 
 systems, and study from nature : but it should be cultivated with a desire to 
 promote the great end of human research, that is, the improvement of the con- 
 dition of man ; otherwise the fantasies of the Greek philosophers might with 
 equal force claim the student's regard. 
 
 b 
 
x PREFACE. 
 
 I hope these remarks will tend to encourage those who pursue knowledge, 
 whether with the energy of youth or the more steady enthusiasm of riper years ; 
 and as all nature, so all art, must ever be the result of those immutable pro- 
 portions and laws of action which it has pleased our Creator to impress on matter, 
 its objects are truly boundless. Our imperfection consists generally in not being 
 able to foresee all the circumstances which have an influence on the effects of 
 causes ; but in proportion as we proceed in knowledge, we also acquire greater 
 powers of perception : that which was at first difficult becomes easy, and the 
 mind is often roused by the bright gleam of truth, breaking as it were accidentally 
 upon a mass of obscure ideas, and rendering the true solution of the difficulty at 
 once obvious ; and as my gifted countryman Emerson has remarked, " the labour 
 and fatigue of seeking after it instantly vanishes." 
 
 I proceed now to give some idea of this work. It appears to be large for its 
 object ; but, though confined to a single source of power, that power is gigantic, 
 and involves so many new and important doctrines in mechanical science and 
 practice, that it was impossible in justice to comprise it in less space. The work 
 is in Ten Sections. 
 
 In the First, the history of the progressive improvement of the steam engine 
 is traced, from the period of its first suggestion by the Marquis of Worcester, to 
 its present state of high perfection. 
 
 The Second Section presents an analysis of the nature of steam and of other 
 species of vapour ; the laws of their combination with heat, and of their elastic 
 force, density, and comparative power ; with the principles of calculating their 
 velocity when in motion, loss of force by cooling, &c. In this section it is shown 
 that water is of all other known fluids that best adapted for producing steam. 
 
 The Third Section treats of the laws of combustion, and of the effect of different 
 species of fuel in producing steam ; the proportions of fire places and chimneys 
 of boilers, and the precautions necessary for their security and effect : the nature 
 and application of safety apparatus is fully discussed. The section closes with a 
 developement of the principles of condensing steam. 
 
 In the Fourth Section, the power afforded by a given quantity of steam, and 
 all the methods of developing it, are illustrated both in a popular and scientific 
 manner; and the theoretical defect of the rotary action of steam is investigated. 
 
PREFACE. xi 
 
 The various modes of applying the power of steam are shown, with a classification 
 of engines ; and the velocity and proportions which give a maximum of effect in 
 engines, as well as the nature and office, and the power lost in working the air 
 pumps of engines, are investigated. 
 
 The Fifth Section treats of the construction of the essentially different varieties 
 of noncondensing steam engines : these engines are all of the high pressure kind ; 
 and the causes of loss of power, and means of employing steam to the best ad- 
 vantage, and the mode of calculating the power and proportion of the parts, are 
 given in detail for each species. 
 
 The Sixth Section treats, in like manner, of the construction, proportions, 
 power, and economy of condensing engines : in these sections, for the first time, 
 those minute causes which affect the action of steam are not only stated, but are 
 reduced to measure ; and I trust in such a manner as to be most useful, both to 
 those who wish to apply, and to those who wish to improve, the steam engine. 
 
 In the Seventh Section the proportions and construction of the parts of steam 
 engines are considered, as of cocks, valves, slides, pistons, stuffing boxes, &c. ; 
 also the modes of opening and closing valves, and the like ; followed by a de- 
 scription of the different kinds of piston-rod guides, and an investigation of crank 
 motions, and of the combinations for producing parallel motion : also practical 
 rules for the strength of the various parts of steam engines are added, and 
 especially for boilers of different kinds. 
 
 The Eighth Section treats, first, of the modes of equalizing the action of the 
 steam engine, as by fly wheels, or counter weights ; secondly, of regulating the 
 power of engines, as by valves, governors, regulators, &c. ; thirdly, the method of 
 ascertaining the state and intensity of the forces in engines, and the means of 
 measuring their effective power ; and, fourthly, of the mode of working a steam 
 engine. 
 
 The Ninth Section illustrates the application of steam power to raising water, 
 to the drainage and business of mining, to impelling machinery for manufacturing 
 and for agricultural purposes, and its application to land carriage by means of 
 railways. 
 
 The Tenth Section is on steam navigation ; and the stability of vessels, their 
 resistance to motion in fluids, the means of propelling them, and the modes of 
 
xii PREFACE. 
 
 proportioning the power to the effect, are investigations altogether new ; and of 
 necessity so, for the theory of the resistance of fluids hitherto taught in schools 
 is erroneous and cannot be applied. I have therefore endeavoured to explain the 
 methods of my own researches in popular rather than strictly scientific discussions, 
 reserving for a separate work the full developement of my views on this im- 
 portant branch of science. 
 
 The tables will be useful in practice ; and the plates are accompanied by 
 descriptions, so as to render them of easy reference, and also to enable me to 
 refer to the parts of the work which they tend to illustrate. 
 
 I am indebted to the friendly assistance of some of my professional brethren 
 for access to information, which otherwise I could not have obtained : in a few 
 instances their favours arrived too late, except for my own satisfaction in finding 
 that they conformed to the principles laid down in this treatise. Of Mr. Bevan's 
 interesting experiments on the resistance of boats I have given only part, because 
 the others were evidently affected by the limited section of the canal. One of 
 the plates (xm.) was furnished by Mr. White, engineer ; and a few of the others 
 are selected from the very accurate plates drawn by Clement, and published in 
 Partington's ' History of the Steam Engine : ' the rest are engraved from my own 
 drawings, and are aided by a great number of wood engravings on the pages. 
 
 My great object has been to lead the reader to study the principles of the 
 steam engine, and to furnish him not only with materials for study, but also with 
 methods of reasoning, and in sufficient variety to enable him to examine any new 
 case likely to occur ; and in proportion to the care and pains he bestows on the 
 inquiry, he will feel the advantage of the few steps I have taken in this interesting 
 and important subject. 
 
 I shall conclude in the language of Sir Isaac Newton on a greater occasion : 
 " I heartily beg that what I have here done may be read with candour, and that 
 the defects I have been guilty of upon this difficult subject may not be so much 
 reprehended as kindly supplied and investigated by new endeavours of my readers." 
 
 THOMAS TREDGOLD. 
 
 16, GROVE PLACE, 
 
 LISSON GROVE, LONDON. 
 August 13, 1827. 
 
CONTENTS. 
 
 SECTION I. 
 
 AN ACCOUNT OF THE INVENTION AND PROGRESSIVE IMPROVEMENT OF THE 
 
 STEAM ENGINE ........ 1 
 
 SECTION II. 
 
 OF THE NATURE AND PROPERTIES OF STEAM, ITS ELASTIC FORCE, EXPANSIVE 
 
 FORCE, AND POWER OF MOTION . . . . . .47 
 
 SECTION III. 
 
 OF THE GENERATION AND CONDENSATION OF STEAM, AND THE APPARATUS 
 
 FOR THOSE PURPOSES ....... 105 
 
 SECTION IV. 
 
 OF THE MECHANICAL POWER OF STEAM, AND THE NATURE, GENERAL PROPOR- 
 TIONS, AND CLASSIFICATION OF STEAM ENGINES .... 150 
 
 SECTION V. 
 
 OF THE CONSTRUCTION OF NONCONDENSING ENGINES .... 173 
 
 SECTION VI. 
 
 OF THE CONSTRUCTION OF CONDENSING ENGINES . . 184 
 
xiv CONTENTS. 
 
 PAGE 
 
 SECTION VII. 
 
 OF THE PROPORTIONS, AND THE CONSTRUCTION, OF THE PARTS OF STEAM 
 
 ENGINES ......... 203 
 
 SECTION VIII. 
 
 OF EQUALIZING THE ACTION, REGULATING THE POWER, MEASURING THE 
 
 USEFUL EFFECT, AND MANAGING THE STEAM ENGINE . . . 256 
 
 SECTION IX. 
 
 OF THE APPLICATION OF STEAM ENGINES TO DIFFERENT PURPOSES . 
 
 SECTION X. 
 
 OF STEAM NAVIGATION ..... 288 
 
 TABLES. 
 
 r 
 
 TABLE I. OF THE PROPERTIES OF THE STEAM OF WATER OF DIF- 
 FERENT DEGREES OF ELASTIC FORCE .... 322 
 
 TABLE II. OF THE PROPORTIONS OF SINGLE ACTING STEAM ENGINES 323 
 
 TABLE III. OF THE PROPORTIONS OF DOUBLE ACTING STEAM ENGINES 324 325 
 
 EXPLANATION OF THE PLATES ....... 32? 
 
CONTENTS. xv 
 
 APPENDIX. 
 
 iCTION PAGE 
 
 I. On Marine Boilers. By J. DINNEN, Esq., Assistant Engineer, Her Majesty's 
 
 Dock-yard, Woolwich ........ 1 
 
 II. A Form of Steam Journal, with remarks on the necessity of keeping a proper 
 
 record of the operations of the engines in all steam vessels, and directions for 
 marking the Steam Journal, &c. By T. BALDOCK, Lieut. R.N., K.T.S. . 31 
 
 III. On the Motion of Steam Vessels. By P. W. BARLOW, Esq., Civil Engineer 40 
 
 IV. Time and Traverse Table. By Captain ROBERT OLIVER, R.N. . . 78 
 
 V. Memoir of Her Majesty's steam ship MEDEA, during a service of nearly four 
 
 years. By T. BALDOCK, Lieut. R.N., K.T.S. .... 80 
 
 VI. On the Steam Boats of the United States of America. By JAMES RENWICK, 
 L.L.D., Professor of Natural Experimental Philosophy and Chemistry in 
 Columbia College, New York ....... 101 
 
 VII. On Paddle Wheels. By ARISTIDES A. MORNAY, Esq. . . . 117 
 
 VIII. On the Indicator. By JOSEPH GLYNN, Esq., C.E., F.R.S. . . 167 
 
 IX. HOWARD'S Method of Vaporisation ...... 1?1 
 
 X. On the General Theory of the Steam Engine. By the EDITOR . . 173 
 
 XI. Practical Rules for calculating the Steam Engine. Do. . . . 205 
 
 XII. INDEX. By JAMES HANN, Esq., of King's College . . . 233 
 
LIST OF PLATES. 
 
 PLATE EXPLANATION. 
 
 PAGE 
 
 i. Isometrical projection of a rectangular steam boiler .... 328 
 
 ii. Two sections of a cylindrical steam boiler ..... 329 
 
 in. Brunton's apparatus for feeding furnaces by machinery . . . 330 
 
 iv. High pressure engine with four-passaged cock ..... 331 
 
 v. Section of a double acting condensing engine for working expansively . . 332 
 
 vi. Section of a common atmospheric engine ..... 333 
 
 vn. Represents the construction of pistons ..... 334 
 
 viii. Parts of Fenton and Murray's double engine ..... 335 
 
 ix. Apparatus for opening and closing steam passages .... 337 
 x. (A), x. (B). Parallel motions or combinations used to produce rectilinear motion 
 
 from motion in a circular arc ....... 338 
 
 xi. Plan and elevation of an atmospheric pumping engine for raising water from a 
 
 mine .......... 339 
 
 xn. Boulton and Watt's single acting engine ..... 340 
 
 xin. Double acting engine for raising water ..... 341 
 
 xiv. for impelling machinery, by Fenton, Murray & Co. . 342 
 
 xv. Maudslay's portable engine ....... 343 
 
 xvi. Indicator for measuring the force of steam in the cylinder . . . 345 
 
 Diagrams to illustrate the comparative stability of opposite classes of vessels ibid 
 
 xvn. Section of a steam vessel with its boiler in two parts . . . 346 
 
LIST OF PLATES. xvii 
 
 PLATE EXPLANATION. 
 
 PAGE 
 
 xvni. Isometrical projection of a steam boat engine as first arranged by Boulton 
 
 and Watt ......... 347 
 
 xix. Section and plan of steam boat engine ..... 349 
 
 xx. Side elevation and cross section of a steam carriage .... 350 
 
 xxi. Kingston's valves ........ 353 
 
 blow off valves ........ ibid 
 
 injection valves ........ ibid 
 
 hand pump valves ........ 354 
 
 xxn. Boilers of H. M. steam vessel African ..... 355 
 
 xxin. Boilers of H. M. steam frigate Medea ..... ibid 
 
 xxiv. Paddle wheels of Morgan and Seaward . . . . .357 
 
 xxv. Positions of a float of a radiating wheel, and also of a vertical acting wheel, in 
 
 a vessel in motion ........ ibid 
 
 xxvi. Cycloidal paddle wheel fitted to the Great Western . . . ibid 
 
 xxvu., xxvin. Illustrate Capt. Oliver's paper ..... 358 
 
 xxix. Exhibits the various situations of a trial at sailing of the Medea, with the 
 
 Caledonia, Vanguard, and Asia ..... Appendix 100 
 
 xxx. Side view of the engines of the Red Rover, and City of Canterbury, steam 
 
 vessels ......... 358 
 
 xxxi. Longitudinal section of ditto ...... 359 
 
 xxxii. Cross section of engines of ditto . . . . . . 360 
 
 xxxin. Side elevation of the engine of the Nile steam ship . . . 361 
 
 xxxiv. Plan of the engine of the Nile ...... ibid 
 
 xxxv., xxxvi. Cross sections of engines of the Nile .... 362 
 
 xxxvii., xxxvin., xxxix. Engines of H. M. steam frigate Phoenix . . 363 
 
 XL. Engines of the Ruby Gravesend packet ..... 364 
 
 XLI. Section of one of the engines of the Don Juan Peninsula Company's packet . 368 
 
 XLII. Boilers of H. M. ships Hermes, Spitfire, and Firefly . . . ibid 
 
xviii LIST OF PLATES. 
 
 PLATE EXPLANATION. 
 
 PAGE 
 
 XLIII., XLIV., XLV., XLVI. Elevation, plan, and two sections of the engines of the 
 
 armed Russian steam ships Jason and Colchis .... 369 
 
 XLVII., XLVIII. Hall's improvements on steam engines .... 370 
 
 XLIX., L. Engines of H. M. steam ship Megaera ..... 378 
 
 LI., LII., LIII., LIV. Engines of the Hull and London packet William Wilberforce 382 
 
 LV. (A). Longitudinal section of Humphrys's patent marine engine . . 390 
 LV. (B). Longitudinal elevation of Humphrys's marine engine . . .391 
 LVI. (A). Midship section of the steam packet Dartford, showing a front elevation 
 
 of a pair of Humphrys's engines ...... ibid 
 
 LVI. (B). Plan of the engines of the Dartford ..... 392 
 
 LVII., LVIII., LIX. Forty-five-horse power engine, constructed by W. Fairbairn 
 
 and Co. ......... ibid 
 
 LX., LXI., LXII., LXIII. Ten-horse power engine, constructed by W. Fairbairn and Co. 393 
 LXIV. Elevation of a locomotive engine, Stanhope and Tyne Railway ; constructed by 
 
 Messrs. R. Stephenson and Co., of Newcastle-upon-Tyne . . . 394 
 
 LXV. Section of ditto ........ 396 
 
 LXVI. Safety valves of ditto ....... ibid 
 
 LXVII. (A). Cylinder cover and connecting rods of ditto .... 397 
 
 LXVII. (B). Cylinder and piston at large of ditto ..... 398 
 
 LXVIII. Plan and section of boiler seating for a twenty-horse engine, at the manu- 
 factory of Messrs. Whitworth and Co., Manchester .' 399 
 LXIX. Messrs. Hague's double acting cylinder, with slides, &c. . . . ibid 
 
 LXX. (A). LXX. (B). Sections of the engines of the Berenice steam vessel . . 400 
 
 LXXI., LXXII. Beale's patent rotatory engine ..... 401 
 
 LXXIII. Mr. Ayre's contrivance for preventing a locomotive engine from running off 
 
 a railway ......... 403 
 
 LXXIV. to LXXXIII. Relate to Mr. Mornay's paper on paddle wheels . Appendix 117 
 LXXXIV. to LXXXVIII. Sixty-five inch cylinder engine, erected by Messrs. Maudslay, 
 
 Sons and Field, at Chelsea water-works ..... 404 
 
LIST OF PLATES. xix 
 
 PLATE EXPLANATION. 
 
 PAGE 
 
 LXXXIX. to xcn. Patent locomotive engine, made by Messrs. R. Stephenson and 
 
 Co. for the London and Birmingham Railway .... 407 
 
 xciu. Drawings of the Comet, the first steam boat in Europe . . . 470 
 
 xciv. The Pacha's steam vessel of war, the Nile . 471 
 
 xcv., xcvi. The Hon. East India Company's steam vessel Berenice . . ibid 
 
 xcvn. Draught of the Forbes steamer, Chinese rigged .... 473 
 
 xcviu. Herne Bay steam packet Red Rover ..... 474 
 
 xcix. Diamond Company's steam packet Ruby ..... 475 
 
 c. to cm. Her Majesty's steam vessel of war Medea . . . . 477 
 
 civ. to cvn. Construction of the Nile steam ship, built for the Pacha of Egypt . 483 
 
 cvm., cix., ex. His Imperial Majesty's armed steam vessel Colchis . . 492 
 
 cxi., cxi. (A). Engines of the steam ship Tiger ..... 497 
 
 cxn. The Admiralty yacht Firebrand ... . 498 
 
 CXHI. Portrait of the late Mr. Watt ...... 500 
 
 cxiv. Portrait of the late Mr. Tredgold . . . . . ibid 
 
 cxv., cxvu., cxvm. Illustrate the state of steam navigation in America . . ibid 
 
MEASURES, WEIGHTS, &c. USED IN THIS WORK. 
 
 Temperature is measured by degrees of Fahrenheit's scale, of which the freezing point is 
 32, and the boiling point 212. 
 
 Heat is commonly measured by the number of degrees it would increase the temperature of 
 a given quantity of water at 60, with the barometer at 30 inches. 1 
 
 Mechanical power is measured by the elementary horse power, as settled by Watt. A 
 horse power is = 33,000 ffis. raised one foot high per minute, or = 550 Ibs. raised one 
 foot high per second ; and a day's work of a horse is this power acting 8 hours. 
 
 This horse power is, in French measures, 4661 kilogrammes raised one metre high per 
 minute. 
 
 The pound is the avoirdupois pound, = 7000 troy grains, = '4535 French kilogrammes. 
 The foot is = -3048 French metre. 
 
 ( 30 inches 1 , 
 An atmosphere is = | .^ 62 metre j of mercury. 
 
 = 14*70 Tbs. per square inch. 
 = 11 '55 circular 
 
 1 It is more properly measured by the volume of water at 60, which it would raise exactly one degree ; this measurement 
 being strictly proportional to the absolute quantity of heat. ED. 
 
THE STEAM ENGINE. 
 
 SECTION I. 
 
 AN ACCOUNT OF THE INVENTION AND PROGRESSIVE IMPROVEMENT OF 
 
 THE STEAM ENGINE. 
 
 ART. 1. WHEN an efficient mechanical power is produced by the generation, or 
 generation and condensation, of the steam or vapour of any liquid, the combination 
 of vessels and machinery for that purpose is called a Steam Engine. This engine 
 was for a considerable time after its invention called a Fire Engine, and not 
 improperly, for the active agent is heat or fire. The liquid almost universally 
 employed for obtaining steam is water, but it may be obtained from alcohol, ether, 
 and other fluids ; fortunately, however, water, the most easily procured, is equal 
 if not superior to any other. 
 
 2. That the application of heat would generate steam from water, and that 
 the steam so generated would issue with much force from a small aperture in the 
 vessel employed to generate it in, must have been known at a very early period. 
 The eolipile, and some other similar instruments for illustrating natural pheno- 
 mena, were well known among the Egyptians, Greeks, and Romans. Vitruvius, 
 who wrote during the reign of Augustus Caesar, refers to the eolipile as an illus- 
 tration of the effect of heat in producing winds; 1 but he clearly had no idea of 
 steam being rendered useful as a mechanical power. Philibert de 1'Orme pro- 
 posed placing an eolipile over a fire as a means of impelling smoke up a chimney, 2 
 and several applications of this instrument are described in the works of Solomon de 
 Caus, Brancas, Van Drebbel, and various other writers, the greater part of whom 
 are mentioned by M. Montgery, 3 an author who has been at considerable trouble 
 to show that the invention of the steam engine is not of English origin. 
 
 3. But unless it be shown that an engine had been actually invented, and was 
 undoubtedly applicable to some of the purposes for which the steam engine is now 
 
 1 Vitruvius, lib. i. cap. vi. 2 Traite d' Architecture, folio, Paris, 1567. 
 
 3 Notice Historique sur 1'Invention des Machines a Vapeur. 
 
 A 
 
2 THE HISTORY OF [SECT. i. 
 
 employed, and for which alone it has become valuable, it appears to be mere 
 trifling to search for authorities, and absolutely unworthy of occupying the time 
 or attention of a man of real science. The blast of an eolipile is certainly not a 
 mode of employing steam capable of producing the species of useful effect which is 
 obtained by a steam engine, and, as a proof of its inefficiency, the same principle 
 of action (that is, by impulse) has never been rendered applicable to produce 
 mechanical power for useful purposes in a steam engine. 
 
 It is not my object, therefore, to inquire when it was first ascertained that steam 
 has force ; but, to endeavour to trace the history of its suggestion in a practical 
 form, and of its employment in the arts and manufactures ; to develop the various 
 changes and improvements the steam engine has received ; and to exhibit, among 
 the host of projectors, those who have really advanced our knowledge, either 
 regarding the principles, the construction, or the arrangement of this powerful 
 prime mover. 
 
 It is easy to perceive that I have assigned myself a difficult task, but it is equally 
 evident that if it be accomplished in a judicious and candid manner, it will form 
 a valuable addition to an interesting and useful branch of mechanical science ; 
 hence, I am encouraged to proceed, and trust to leave my reader with an impres- 
 sion, that I have been just in deciding between the claimants of the invention of 
 each of the parts of the steam engine. 
 
 1663. MARQUIS of WORCESTER, died 1667. 
 
 4. The idea of employing the impulsive force of the eolipile seems to be the 
 only one which had been formed for using steam as a source of motion before the 
 time of the Marquis of Worcester ; and he, in a little work entitled ' A Century of 
 the Names and Scantlings of Inventions,' undoubtedly describes a method of 
 employing the pressure of steam for raising water to great heights. l His work was 
 first published in 1663, and under the sixty-eighth invention we have the following 
 name and scantling : 
 
 " LXVIII. A Fire Water Work. An admirable and most forcible way to drive 
 up water by fire, not by drawing or sucking it upwards ; for that must be, as the 
 philosopher calleth it, infra sph&ram activitatis, which is but at such a distance. 
 But this way hath no bounder if the vessels be strong enough ; for I have taken a 
 piece of a whole cannon, whereof the end was burst, and filled it three-quarters 
 full of water, stopping and screwing up the broken end, as also the touchhole, and, 
 
 1 Another engine, which the marquis terms a " Water-commanding Engine," seems to have been 
 the one for which he obtained an act of parliament, allowing him the monopoly of the profits 
 arising from its use. 
 
SECT. I.] 
 
 THE STEAM ENGINE. 
 
 making a constant fire under it ; within twenty-four hours it burst and made a 
 great crack ; so that having a way to make my vessels so that they are strengthened 
 by the force within them, and the one to fill after the other, I have seen the water 
 run like a constant fountain stream forty feet high. One vessel of water rarefied 
 by fire driveth up forty of cold water. And a man that tends the work is but to 
 turn two cocks, that, one vessel of water being consumed, another begins to force 
 and refill with cold water, and so successively, the fire being tended and kept 
 constant ; which the selfsame person may likewise abundantly perform in the 
 interim between the necessity of turning the said cocks." 
 
 This description puts it beyond a doubt that the Marquis of Worcester knew that 
 steam, heated in a close vessel, acquires an immense degree of force, and that this 
 force could be effectively applied to raise water. The effect of condensation he does 
 not appear to have been at all acquainted with, and therefore his mode of operation 
 must have been exceedingly simple, and probably, of the nature exhibited in the 
 annexed figure : where B is the boiler ; C, one of the vessels with a pipe to deliver 
 the water to an elevated cistern D. 
 
 FIG. 1. 
 
 Now suppose the vessel C to be supplied from a cistern of cold water A by a pipe, so 
 that it would be filled on opening the cock E, and afterwards closing it ; if, when 
 the steam in the boiler is of sufficient strength, the cock F be opened, the pressure 
 of the steam on the water in C would cause it to ascend from C, through the pipe a 
 into the cistern D. The vessel C being emptied, and the cock F being shut, it would 
 refill with water on again opening the cock E. Another vessel C, and its cocks and 
 
THE HISTORY OF 
 
 [SECT. i. 
 
 pipes, are necessary to complete the species of water engine indicated by the 
 description, and these may be on the other side of the boiler. 
 
 Such a mode of raising water would be most expensive from the quantity of 
 condensation when the steam came in contact with cold water, but it was fully 
 capable of producing the quantity of effect mentioned, for it is only equivalent to 
 raising 20 cubic feet of water or 1250 Ibs. one foot high by one pound of coal, 
 or about the 200th part of the effect of a good steam engine. Hence, it appears, 
 that to the Marquis of Worcester must be ascribed the first invention and trial of 
 a practical mode of applying steam as a prime mover, and of applying it to one of 
 those great purposes for which it has been so useful to society. 
 
 1683. SIR SAMUEL MORLAND, died 1695. 
 
 5. From a part of a manuscript in the Harleian collection in the British 
 Museum, it appears that a mode of raising water by steam, similar to that of the 
 Marquis of Worcester's, was proposed, among other methods, to Louis XIV. of 
 France, by Sir Samuel Morlaud. It contains no description of the method he 
 intended to employ, but there is sufficient to indicate that its author was not with- 
 out knowledge of his subject. 
 
 The title of the part which treats of the power of steam is, ' The Principles of 
 the New Force of Fire, invented by Chev. Morland in 1682, and presented to his 
 most Christian Majesty in 1683 ;' and these principles are explained as follows : 
 " Water being converted into vapour by the force of fire, these vapours shortly 
 require a greater space (about 2000 times) than the water before occupied, and, 
 sooner than be constantly confined, would split a piece of cannon. But being 
 duly regulated according to the rules of statics, and by science reduced to measure, 
 weight, and balance, then they bear their load peaceably (like good horses) and 
 thus become of great use to mankind, particularly for raising water, according to 
 the following table, which shews the number of pounds that may be raised 1800 
 times per hour, to a height of six inches, by cylinders half filled with water, as 
 well as the different diameters and depths of the said cylinders." 
 
 Cylinders. 
 
 Weight of the Load to be raised, 
 
 Diam. in feet. 
 
 Depth in feet. 
 
 in pounds. 
 
 1 
 
 2 
 
 15 
 
 2 
 
 4 
 
 120 
 
 3 
 
 6 
 
 405 
 
 4 
 
 8 
 
 960 
 
 5 
 
 10 
 
 1875 
 
 6 
 
 12 
 
 3240 
 
SECT, i.] THE STEAM ENGINE. 5 
 
 These numbers are' obviously proportional to the capacity of the cylinders. 
 
 The table is continued in the original to show the effect of a number of cylinders 
 of the largest of the above sizes, each one being capable of raising 3240 Ibs. 
 
 Morland has given the increase of volume, which water occupies in the state of 
 vapour at common pressures, so nearly, that we may suppose it to be the result of 
 experiment ; while his allusion to the force of steam being sufficient to burst a 
 cannon, and his proposal of the method to a foreign prince, render it probable that 
 he was not a stranger to the volume the Marquis of Worcester had published 
 twenty years before. 
 
 Morland's researches seem to have had little influence on the progress of the 
 practical application of steam. 
 
 6. In 1695, Dr. Papin suggested the idea of employing the expansion and 
 contraction of steam to form a partial vacuum under a piston for raising water, and 
 making the pressure of the atmosphere on the upper side of the piston the moving 
 power. 1 The real authors of the atmospheric engine were very likely indebted to 
 this suggestion ; but neither Papin himself, nor his rival Savery, discovered how to 
 turn this suggestion to advantage. Indeed, it was proposed in a form which was 
 not practicable : the fire was to be alternately applied to, and removed from, the 
 cylinder, and the expansion of the water in it, by heat, was to raise the piston, and 
 its contraction, by cooling, when the fire was removed, was to cause a partial 
 vacuum, and, consequently, the descent of the piston was to be produced by the 
 pressure of the atmosphere. If such a scheme was ever tried, the result must have 
 been sufficiently discouraging for Papin to abandon it, and adopt a new one, which 
 it will be found he actually did, after seeing an engraving of Savery's engine. 
 
 1698. THOMAS SAVERY. 
 
 7. These projects were speedily followed by a direct practical application of the 
 steam engine to raising water, for which " letters patent " were granted to Captain 
 Thomas Savery, in July, 1698, (these being the first on record granted for a steam 
 engine) ; and, Dr. Robison says, it was " after having actually erected several 
 machines," of which Savery gave a description in a pamphlet he published in 
 1699, 2 called ' The Miner's Friend,' which was republished with additions in 1702. 
 
 In June, 1699, Captain Savery exhibited a model of his engine before the Royal 
 Society ; and the experiments he made with it succeeded to their satisfaction. 3 It 
 
 i Phil. Trans. Abridg. iv. 155. 1697. 
 
 * Robison makes it 1696, but this does not appear to be correct. Switzen's date, 1699, is taken 
 as likely to be the right one, from his System of Hydrostatics, ii. 326. 
 3 Phil. Trans. Abridg. iv. 198. 1699. 
 
THE HISTORY OF 
 
 [SECT. i. 
 
 consisted of a furnace and boiler B ; from the latter two pipes, provided with cocks 
 C, proceeded to two steam vessels S, which had branch pipes from a descending 
 
 FIG. 2. 
 
 main D, and also to a rising main pipe A ; each pair of branch pipes had valves 
 a, b, to prevent the descent of the water raised by the condensation or by the force 
 of steam. Only one vessel, S, is shown, the other being immediately behind it. 
 One of the steam vessels being filled with steam, condensation was produced by 
 projecting cold water, from a small cistern E, against the vessel ; and into the 
 partial vacuum made by that means, the water, by the pressure of the atmosphere, 
 was forced up the descending main D, from a depth of about twenty feet ; and, on 
 the steam being let into the vessels again, the valve b closed, and prevented the 
 descent of the water, while the steam having acquired force in the boiler, its 
 pressure caused the water to raise the valve a, and ascend to a height proportional 
 to the excess of the elastic force of the steam above the pressure of the air. 
 
 Captain Savery afterwards simplified this engine considerably, by using only one 
 
SECT. ,.] THE STEAM ENGINE. 7 
 
 steam vessel. To prevent the risk of bursting the boiler, he applied the steelyard 
 safety valve V ; invented by Papin for his digester. The cocks were managed by 
 hand ; and, to supply the boiler with water, he had a small boiler adjoining to 
 heat water for the use of the large one, and thus prevent the loss of time which 
 must have occurred on refilling it with cold water. 
 
 Several engines for raising water appear to have been erected according to 
 Savery's plan, and to have succeeded tolerably where the water had not to be 
 raised more than forty feet ; but this was not sufficient for mines, where a new and 
 powerful machine was most wanted. 
 
 The new principles, introduced into the steam engine by Savery, consist of the 
 use of condensation in the steam vessel by cold applied externally. He also used a 
 method of supplying the boiler with hot water, contrived a mode of ascertaining 
 the quantity of water in the boiler, by inserting the cock g, called a gauge cock, 
 and applied the safety valve of Papin's digester as a means of preventing accidents. 
 
 The defects of his engine are obvious. A cold vessel and cold fluid must at each 
 operation condense, and therefore waste a great quantity of steam ; and the height 
 to which water could be raised, unless by the use of such powerful steam as to 
 render it dangerous, was too limited to be applicable to mining purposes. Its 
 effect would however be vastly superior to that of the Marquis of Worcester's. 
 Whether Captain Savery did or did not know of the previous schemes, his claims 
 to original invention are certainly considerable ; and to his enthusiasm and talent 
 we undoubtedly owe the first effective steam engine. 
 
 1698. DR. DENNIS PAPIN. 
 
 8. Dr. Papin, professor of mathematics at Marbourg, whose former project I 
 have noticed (art. 6), is said to have made many experiments on raising water by 
 the force of fire, in 1698, by the order of Charles, Landgrave of Hesse ; and in 
 1707 he published a small treatise on the subject, in which he ascribes to the land- 
 grave the whole merit of the first idea of a steam engine. Papin's trials in 1698, 
 whatever they were, did not end in producing any thing in a useful shape ; and, 
 while he candidly acknowledges that Savery's scheme was not borrowed from any 
 thing done in Germany, it appears that he did not follow up his experiments till 
 after he had seen an engraving of Savery's engine, in June, 1705 ; a pretty con- 
 clusive argument, that no satisfactory results had been arrived at in these experi- 
 ments ; and there is a wide distinction between unsuccessful experiments and 
 invention. 
 
 To do justice to the claims of Papin, it will be sufficient to describe his engine 
 in its most improved state, and as he gives it after knowing what Savery had 
 
THE HISTORY OF 
 
 [SECT. i. 
 
 effected. It consisted of a boiler B, provided with a safety valve V ; and a cylinder 
 G H, connected to the boiler by a steam pipe S. The cylinder was closed at the 
 
 FIG. 3. 
 
 top, and contained a floating piston P ; and the base of the cylinder terminated in 
 a curved tube T, which ascended into a cylinder M ; the bent tube had a pipe Y, 
 from a reservoir of water communicating with it, and it was provided with a valve 
 at r. Now suppose the cylinder G H, to be filled with cold water by the pipe Y, 
 from the reservoir, and the boiler to contain strong steam ; by opening the cock E, 
 the steam would be admitted, and, pressing on the floating piston P, cause the 
 water to ascend into the cylinder M : its return is prevented by the valve K, and 
 the steam cock E being shut, and the cock R opened, to let the condensed steam 
 escape at the pipe R, the water from the reservoir refills the steam cylinder through 
 the pipe Y, and it is ready for repeating the operation. The water raised to be 
 directed to any useful object by the pipe D. 1 
 
 A reference to the Marquis of Worcester's plan will show, that Papin did no 
 more than repeat his experiments. The scheme of adding to the effect by the 
 introduction of red hot irons into the cylinder G H, is too absurd to insert; but it is 
 in some measure redeemed by the suggestion, that the water raised by the engine 
 might be applied to drive a water wheel ; thus giving the idea of a steam engine 
 being applicable to impel machinery. 
 
 9. In 1699, Mr. Amontons published a description of a machine, designed to 
 be moved by the spring of air when expanded by heat, and afterwards condensed 
 by contact with cold water. 2 The continual access of heated air to water would 
 
 1 Belidor's Archi. Hydrau. ii. p. 328. 
 
 2 Prony's Nouvelle Archi. Hydrau. ii. p. 89 (note), where it is described. 
 
SECT, i.] THE STEAM ENGINE. 9 
 
 ultimately render the air saturated with vapour ; but even then it would not be 
 more than an air engine, and a very indifferent one, being exceedingly complex. 
 
 1705. THOMAS NEWCOMEN. 
 
 10. The trials of Savery's engines made known their defects, yet evidently 
 strengthened the idea that steam could be effectively applied to raise water ; and 
 the immense expense of raising water from deep mines so embarrassed their pro- 
 prietors, that there were most powerful incentives at that period to engage in 
 further researches on the subject. To this stimulus we are indebted for another 
 construction of the steam engine, by Thomas Newcomen, a smith, of Dartmouth, 
 who, in conjunction with John Cawley, a plumber of the same place, and Captain 
 Savery, obtained letters patent for the invention in 1705. 1 The novelty of this 
 construction consists entirely in condensing the steam below an air-tight piston, in 
 a cylindrical vessel having an open top ; and the idea was very probably taken 
 from the project of Papin in 1695 (see art. 6) ; for it appears that Newcomen was 
 in correspondence with Dr. Hook on the subject, to whom the speculations of Papin 
 were well known ; but the mode of effecting the object was entirely different from 
 Papin's. It consists in admitting steam below a piston ; and, at first, the steam 
 was condensed by applying cold water to the outside of the cylinder ; but injection 
 of cold water by a jet into the interior was soon found to be a more effective 
 method, and is said to have been discovered by accident. 2 The following is a 
 description of the engine, as far as it was improved by Newcomen. B represents 
 the boiler with its furnace for producing steam ; and at a small height above the 
 boiler is a steam cylinder, C, of metal, bored to a regular diameter, and closed at 
 the bottom, the top remaining open. A communication is formed between the 
 boiler and the bottom of the cylinder, by means of a short steam pipe, S. The 
 lower aperture of this pipe is shut by the plate p, which is ground flat, so as to 
 apply very accurately to the whole circumference of the orifice. This plate is called 
 the regulator, or steam cock, and it turns horizontally on an axis a, which passes 
 through the top of the boiler, and is fitted steam-tight ; and has a handle to 
 open and shut it. 
 
 1 Switzer says, on report, that Newcomen was as early in his invention as Savery. Sys. of 
 Hydros ii. 342. 
 
 2 Desaguliers' Experimental Philosophy, ii. p. 533. The piston was kept tight by a quantity 
 of water on the top of it ; and as they were working by condensing from the outside, they were 
 surprised to see the engine make several strokes very quickly, and found that it was owing to a 
 hole in the piston letting down water to condense the steam. This suggested the idea of injection. 
 
 B 
 
10 
 
 THE HISTORY OF 
 
 [SECT. i. 
 
 Fig. 4. 
 
 A piston P is fitted to the cylinder, and rendered air-tight by a packing, round 
 its edge, of soft rope well filled with tallow to reduce the friction, and its upper 
 surface is kept covered with water to render it steam-tight. The piston is con- 
 nected to a rod P A, which is suspended by a chain from the upper extremity D of 
 the arched head of the lever, or working beam, which turns on the gudgeon G. 
 This beam has a similar arched head E F, at its other end, for the pump rod H, 
 which receives the water from the mine. The end of the beam to which the pump 
 rod is attached, is made to exceed the weight and friction of the piston in the steam 
 cylinder ; and when the water is drawn from such a depth, that the steam piston 
 is too heavy for this purpose, counterpoise weights must be added at I, till the piston 
 will rise in the steam cylinder at the proper speed. At some height above the top 
 of the cylinder is a cistern L, called the injection cistern, supplied with water from 
 
SECT, i.] THE STEAM ENGINE. 11 
 
 the forcing pump R. From this descends the injection pipe M, which enters the 
 cylinder through its bottom, and terminates in one or more small holes at N. This 
 pipe has at O a cock, called the injection cock, fitted with a handle. At the 
 opposite side of the cylinder, a little above its bottom, there is a lateral pipe, 
 turning upwards at the extremity, and provided with a valve at V, called the 
 snifting valve, which has a little dish round it to hold water for keeping it 
 air-tight. 
 
 There proceeds also from the bottom of the cylinder a pipe Q, of which the lower 
 end is turned upwards, and is covered with a valve v : this part is immersed in a 
 cistern of water called the hot well, and the pipe itself is called the eduction pipe. 
 To regulate the strength of the steam in the boiler, it is furnished with a safety 
 valve, constructed and used in the same manner as that of Savery's engine, but not 
 loaded with more than one or two pounds on the square inch. 
 
 The mode of operation remains to be described. Let the piston be pulled down 
 to the bottom of the steam cylinder, and shut the regulator or steam valve p. 
 Then the piston will be kept at the bottom by the pressure of the atmosphere. 
 Apply the fire to the boiler till the steam escapes from the safety valve, and then, 
 on opening the steam regulator, the piston will rise by the joint effect of the 
 strength of the steam, and action of the excess of weight on the other end of the 
 beam. When it arrives at the top of the cylinder, close the regulator p, and, by 
 turning the injection cock O, admit a jet of cold water, which condenses the steam 
 in the cylinder, forming a partial vacuum, and the piston descends by the pressure 
 of the atmosphere, raising water by the pump rod H from the mine. The air 
 which the steam and the injection water contain, is impelled out of the snifting 
 valve V, by the force of descent, and the injection water flows out at the eduction 
 pipe Q ; and by repetition of the operations of alternately admitting steam and 
 injecting water, the work of raising water is effected. 
 
 These operations were done by hand, till a boy, named Humphrey Potter, con- 
 trived to attach strings and catches to the working beam, for opening and shutting 
 them while he was at play ; 1 after which, more permanent appendages were added 
 to answer the purpose, and the engine became a step nearer to a self-regulating 
 machine. 
 
 The engine in this simple and efficient state was termed the Atmospheric 
 Engine. It was brought to this degree of perfection about 1712; and such 
 engines were erected in various places. 
 
 The novelty of this engine is chiefly in its mechanism ; but as this mechanism 
 produces all the difference between an efficient and an inefficient engine, I am 
 
 1 Desaguliers' Experimental Philosophy, ii. 533. 
 
12 THE HISTORY OF [SECT. i. 
 
 inclined to set a higher value upon it than on the fortuitous discovery of a new 
 principle. To point out what is actually due to Newcomen would be difficult, and 
 for want of evidence we must be content with examining the state of the engine. 
 The admission of steam below an air-tight piston, attached to the impelled point of 
 a lever properly counterpoised ; its rapid condensation by injection of water, which 
 is essential to gain effect ; and the mode of clearing the cylinder of air and water 
 after the stroke, are all additional to the principles and mechanism before in use ; 
 and these are wholly due to Newcomen, or those connected with him. 
 
 1718. HENRV BRIGHTON, F.R.S. ; died 1743. 
 
 11. The arrangement of the parts of the atmospheric engine, the mode of 
 fixing, and the mechanism for opening and shutting the valves, were greatly 
 improved by Mr. Henry Beighton, an engineer, of Newcastle-upon-Tyne. He also 
 seems to have been the first to reduce the calculation of the powers of engines to a 
 regular system, and published a ' Table of the Dimensions and Power of the 
 Steam Engine,' in 1717, which has been found to accord with practice ; 2 and he 
 directed the construction of several large engines. He also remarked the fact of 
 steam heating a very large proportion of water in condensing, and communicated 
 to Dr. Desaguliers some experiments on the bulk of steam formed by a given 
 quantity of water, the result of which was erroneously stated, in consequence of a 
 singular mistake in the calculation ; and it is also obvious, that the mere quantity 
 of water, and bulk of the cylinder, could not possibly give the result he expected, 
 even on the supposition that the cylinder was maintained at 212 during the 
 experiment. 3 I cannot leave the memory of Beighton without the remark, that 
 
 1 Dr. Hutton remarks, it is probable that Mr. Beighton died in 1743 or 1744, as it appears that 
 he conducted the Ladies' Diary for the Stationers' Company, from 1714 to 1744 inclusively ; 
 discharging that trust with such satisfaction to the Company, that they permitted his widow to 
 enjoy it for many years afterward, by employing a deputy to compile that very useful annual little 
 book. In that almanack, for the year 1721, Mr. Beighton inserted a curious table of calculations 
 on the steam engine. Phil. Trans. Abrid. vii. p. 442. 
 
 2 Desaguliers' Course of Experimental Philosophy, ii. 534. 
 
 3 In Mr. Beighton's experiment (Desaguliers' Ex. Phil. ii. 533.) made on the steam engine, to 
 know what quantity of steam a given quantity of water produces, he found by several trials with a 
 divided steelyard on the safety valve on the top of the boilers at Griff and Wasington, that when 
 the elasticity of the steam was just one pound on a square inch, it was sufficient to work the 
 engine ; and that about 5 pints in a minute would feed the boiler, as fast as it was consumed in 
 producing steam for the cylinder at 16 strokes per minute. Griffs cylinder held 113 gallons 
 of steam every stroke; hence 113x16=1808 gallons=14464 pints; therefore 5 pints of water 
 produced 14464 pints of steam ; consequently, 1 pint would produce 2893 pints of steam of that 
 
SECT. I.] 
 
 THE STEAM ENGINE. 
 
 13 
 
 though he was not distinguished by the novelty of his views, yet the sound 
 knowledge he had of science seems to have been of more real advantage to those 
 who sought benefit from the steam engine, than the undirected efforts of his 
 predecessors. 
 
 1720. LEUPOLD. 
 
 12. About this period various writers gave notices of the different engines 
 that had appeared ; but those who added nothing, either in theory, experiment, or 
 construction, it would be as tedious as useless to notice. But in this class, Leupold, 
 the industrious German collector of mechanical inventions, ought not to be placed, 
 he having given the first sketch for a high-pressure engine with a piston ; it is 
 further remarkable as having a four-passage cock for the admission and emission of 
 steam. 
 
 The scheme of Leupold is simple : over a boiler B, he placed two cylinders C C, 
 fitted with steam-tight pistons, pp. A four-way steam-cock, S, is placed between 
 
 FIG. 5. 
 
 the boiler and cylinders, so as to alternately admit steam into one cylinder, and let 
 it out from the other. The piston, by the admission of strong steam from the 
 
 density and temperature which it had in the cylinder at the termination of the stroke ; but this tem- 
 perature and density not being ascertained, the experiment does not show the bulk corresponding 
 to the atmospheric pressure ; for the elastic force in the boiler differs considerably from that m 
 the cylinder. 
 
14 THE HISTORY OF [SECT. i. 
 
 * 
 
 boiler below it, is raised, and depresses the other end of a lever connected to the 
 rod of a plunger of a pump, which causes the water to rise through the pipe, and 
 by the alternate action of the steam in the two cylinders a continual stream of 
 water is raised. Thus the first rude notice of the principle of employing high- 
 pressure steam under a piston was given. 
 
 13. It does not appear that any thing was added to the existing knowledge 
 of the steam engine by Dr. Desaguliers, though, from his fondness for experimental 
 philosophy, we are led to expect he would have taken an important place in 
 reducing to fixed principles the phenomena he was daily called upon to witness 
 and make known to the world. This was not the case ; and, for historical inform- 
 ation, he was evidently too prejudiced in favour of particular individuals to allow 
 him to detail facts with candour and fairness ; therefore, the matter he collected, 
 in his ' Experimental Philosophy,' is no further valuable, than by making the state 
 of the engine at that period, and part of the researches of Beighton, known. 
 
 1736. JONATHAN HULLS. 
 
 14. The atmospherical steam engine, as improved by Beighton, began to be 
 very generally adopted in the coal works and copper mines ; and it does not seem 
 to have required any great stretch of invention to direct such an efficient power 
 to other purposes, besides that of raising water. 
 
 The first attempt, however, on record, was one to apply steam to navigation, 
 and was made by Jonathan Hulls, who, on the 21st of December, 1736, obtained 
 a patent, for what may strictly be considered a steam boat. 
 
 The letters patent, and a description of this boat, illustrated by a plate, was 
 published in a tract, by Hulls, in 1737, under the following title: 'A Descrip- 
 tion and Draught of a new-invented Machine for carrying Vessels or Ships out of 
 or into any Harbour, Port, or River, against Wind or Tide, or in a Calm.' 
 As the origin of the invention of steam boats has been strongly contested, this 
 pamphlet, which it is now very difficult to obtain on account of its rarity, has been 
 brought forward to prove that Jonathan Hulls was the first person who suggested 
 the power of steam as a means of propelling paddle wheels. His mode of con- 
 verting the reciprocating motion of the engine into a rotatory one, is less simple 
 than the crank, but it appears to have been the first attempt, and was done in the 
 following manner : Let a, b, c, be three wheels on one axis, and d, e, two wheels 
 loose on another axis A, with ratchets, so as to move the axis only when they move 
 forward ; /, g, h, are three ropes, and P is the piston of the engine. When the 
 
SECT. 1.] 
 
 THE STEAM ENGINE. 
 
 15 
 
 FIG. 6. 
 
 piston descends, the wheels a, b, c, move forward, and the ropes g, h, cause the 
 wheels e, d, to move, the wheel e forward, and the wheel d backward, and the 
 latter raises the weight G, which moves the wheel d forward during the ascent of 
 the piston ; consequently, the axis A B, with the paddle wheels, would be constantly 
 moved round in the same direction and by an equable force. This is certainly 
 a beautiful contrivance for rendering so irregular a first mover equable ; and, con- 
 sidering the object it was intended for, it is not a complex arrangement ; for 
 besides equalizing the power, it gives a means of increasing or diminishing the 
 velocity in the ratios of the diameters of the wheels. The pamphlet of Hulls bears 
 evidence of being the work of an ingenious and well-informed mind ; and we must 
 regret the causes which prevented his views meeting the encouragement they 
 merited. ' 
 
 1739. BERNARD BELIDOR; born 1698, died 1761. 
 
 15. Belidor, so eminently distinguished as a writer on the theory and practice 
 both of civil and military engineering, treated of the steam engine in 1739, and 
 undoubtedly presented the most accurate information then existing in France on 
 the subject. " He gives a slight sketch of its history ; and infers, from his in- 
 quiries, that the three nations of Europe most advanced in the pursuit of know- 
 
 1 Hulls's pamphlet may be seen at the British Museum or the London Institution ; and many 
 civil engineers have succeeded in adding it to their own collections. 
 
 2 Architecture Hydraulique, torn. ii. p. 300 331. 
 
16 THE HISTORY OF [SECT. i. 
 
 ledge, each furnished a man of science to participate in the glory of the important 
 discovery : that Papin in Germany, Savery in England, and Amontons in France, 
 were each occupied in studying the means of making use of the action of jire for 
 moving machines ; but the first suggestion of the idea, in an intelligible form, he 
 acknowledges to be due to the Marquis of Worcester. Belidor closes his historical 
 notice, by remarking, that all the fire engines that had been constructed out of 
 Great Britain, had been executed by English workmen ; and then proceeds to 
 describe the atmospheric engine at Fresnes, near Conde, in that minute, clear, and 
 practical manner, which renders his writings so valuable. To the theory of the 
 action of steam Belidor added nothing ; and the formulae he has given for calcu- 
 lating the load to be lifted by an engine are neither very simple nor accurate : like 
 those of Beighton, they apply only to the statical equilibrium of the machine. 
 
 1741. JOHN PAYNE. 
 
 16. The first direct experiment to determine the density of steam was made 
 by John Payne. * His process was well devised, but wanted the addition of a 
 thermometer. He took a copper globe twelve inches in diameter, having two 
 cocks fitted to it, and a small valve. The vessel thus prepared was hung over a 
 large vessel, in which water was rarefied into steam, and by a pipe the steam was 
 admitted at one of the cocks into the globe, and the other being also open, the 
 steam being allowed to blow through, forced out the air that was in the globe, and 
 supplied its place ; when both cocks were suddenly shut, and the globe taken down 
 and hung over a vessel of cold water with the lower cock immersed in water. The 
 cock was opened under water, on which the water rushed violently into the globe 
 till it had supplied the vacuum, when the cock was again shut, and the globe, 
 with the water, was put in the scales, and found to weigh 713 oz., which taken 
 from 727 oz. the whole weight before, there remains only 14 oz. for the dif- 
 ference ; from which he inferred that all the air was nearly excluded out of the 
 globe by the steam. He again excluded the air out of the globe with steam as 
 before, and both the cocks being closed, with the globe full of steam, he put the 
 globe in the scales, and it weighed 202-5 oz. He then opened one of the cocks 
 and let in the air, and by adding weight in the other scale it was found to weigh 
 203 oz., which showed that the weight of the air the globe contained was '5 oz. 
 or 218'75 grains. The globe being filled with steam as before, and condensed 
 with cold water on the outside of the globe, and the metal again made very dry, 
 and the air let into the globe, the water from the condensed steam was found to 
 weigh 96 grains. It is worthy of remark here, that this gives the density 
 
 1 PhiL Trans, vol. xli. p. 821. or Ab. vol. viii. p. 518. 
 
SECT. i. ] THE STEAM ENGINE. 17 
 
 of steam at 212 to that of air at 60, as 96 : 21875, or as O44 : 1. The true 
 density of steam at 212 is nearly as O48 : 1. 
 
 The globe was filled with steam as before ; only, not knowing the effect of 
 temperature, he continued the globe longer with the steam passing through it, by 
 which it acquired a greater degree of heat ; for he found by these experiments, 
 that the least degree of cold less than the steam would condense a part of it again 
 into water, and hence the quantity could not be ascertained which would exclude 
 the air out of a given space, which was the chief end of the experiment. In this 
 experiment he succeeded in excluding the air with less steam ; for, on weighing 
 the globe, when the steam was condensed, the air let in, and all cold, it was found 
 that the weight of the water condensed from the steam was only about forty-eight 
 grains, which filled, when converted into steam, 925 cubic inches of space, so as 
 to exclude nearly all the air. From which he concluded that one cubic inch of 
 water will form 4000 inches of steam. To admit of comparison, the temperature 
 should have been observed, as I have little doubt that the steam was so rarefied by 
 heat as to cause this result. 
 
 17. Mr. Payne also attempted to introduce a new mode of generating steam ; 
 his apparatus consisted of a cast iron vessel of the figure of a frustrum of a cone, 
 its diameter at the bottom being four feet, with a semi-globular end of copper of 
 about five feet and a half diameter. In the inside a small vessel was inserted, 
 which Payne calls a disperser, which vessel had pipes round the sides fixed to it ; 
 the bottom rested on a central pin, on which it revolved, so as to spread the water 
 it received from above, through an iron pipe. The end of this pipe passed up 
 through the head, and was enclosed very tightly, but so as to be easily moved 
 with a circular motion, so that the water might be dispersed or showered round 
 on the sides of the red hot cone, or ignited vessel, in a very exact manner. From 
 experiment he states that a pot or vessel, of the size and shape here mentioned, 
 will, being kept to a dark red heat and the water regularly dispersed, convert 6'5 
 cubic feet of water into steam in an hour. And that, by experiments made at 
 Wednesbury and Newcastle-upon-Tyne, 112 Ibs. of pit coal will by this method 
 convert twelve cubic feet of water into steam. This is near the truth of what may 
 be done ; but the method has no advantages, and the apparatus soon fails. It is 
 a duty, however, to an ingenious man to record his attempts to establish useful 
 truths, even when he fails in his object : it shows the state of knowledge at the 
 time on these subjects ; and it saves others from repeating useless experiments. The 
 mode of generating steam, just described, has been more than once revived lately. l 
 
 18. The engine of Savery had hitherto required the attendance of a person 
 
 1 [This is the recorded opinion of Tredgold. Since his time, however, Mr. Howard has adopted 
 a similar principle with success, an account of which is given in the Appendix. ED.] 
 
 C 
 
18 THE HISTORY OF [SECT. i. 
 
 to open and shut the cocks. This defect appears to have been first removed by 
 Gensanne, a Frenchman, who contrived a self-acting apparatus for the purpose in 
 1744 ; and afterwards De Moura, a Portuguese, sent a model of another method 
 to the Royal Society, which is ably described by Smeaton, in the Transactions for 
 1751. 1 His general description is sufficient for the purpose of showing how the 
 action is obtained. The engine consists of a receiver with a steam and an injec- 
 tion cock. It has a suction and a forcing pipe, each furnished with a valve, and 
 a boiler, which may be of the common globular shape. Having nothing particular 
 in its construction, a description of it will not be necessary : also the rest of the 
 parts already mentioned being essential to every machine of this kind, a further 
 account of them may be dispensed with. What is peculiar to this engine is a float 
 within the receiver, composed of a light ball of copper, which is not loose in it, but 
 fastened to the end of an arm made to rise and fall by the float, while the other 
 end of the arm is fastened to an axis ; and, consequently, as the float moves up 
 and down, the axis is turned round one way or the other. The axis is made 
 conical, and passes through a conical socket, which last is fixed to the side of the 
 receiver. On one of the ends of the axis, which projects beyond the socket, is 
 fitted a second arm, which is also moved backwards and forwards by the axis as 
 the float rises or falls. By these means, the rising or falling of the surface of the 
 water within the receiver communicates a corresponding motion to the outside, 
 in order to give the proper motions to the rest of the apparatus which regulates 
 the opening and shutting of the steam and injection cocks, and serves the same 
 purpose as the plug frames, &c. in Newcomen's engine. 
 
 1751. FRANCIS BLAKE, F.R.S. 
 
 19. A paper on the best proportions for steam engine cylinders, by Mr. Francis 
 Blake, was published in 1751 ; 2 which merits attention both as one of the first 
 steps in theoretical inquiry respecting the proportions of engines, and on account 
 of the result he obtained. It is evident, he remarks, from the principles of 
 mechanics, that the contents of the cylinder remaining the same, the quantity of 
 water discharged at each lift will in all cases be equal ; and this equality is obtained 
 by only adjusting the distance of the centre of the piston from the fulcrum of the 
 beam. It will be granted also, that the excess of the column of atmosphere above 
 that of water, is equivalent to a weight on the piston, driving it to a depth of 
 about five feet within the cylinder with an accelerated motion, till friction and 
 resistance from the uncondensed steam which remains in the cylinder even after 
 the injection, and which is increased in elasticity while its bounds are dimi- 
 
 1 Phil. Trans, vol. xlvii. p. 436. or Abridg. vol. x. p. 252. 
 
 2 Phil. Trans, vol. xlvii. p. 197. or Abridg. vol. x. p. 187. 
 
SECT. 1.] 
 
 THE STEAM ENGINE. 
 
 19 
 
 nished, shall equal the accelerative force ; and that then again the piston may be 
 retarded the rest of the way. But, independent of friction, we can, notwithstand- 
 ing this diminution of force by the remainder of steam within the cavity of the 
 cylinder, demonstrate the ratio of the velocities, and the times of descent of the 
 pistons in cylinders of unequal altitudes, to be exactly the same as if the resistance 
 were nothing ; whence we shall without difficulty arrive at some conclusion in this 
 matter. Let M N be the working part of a steam engine cylinder of the usual 
 height, equal in diameter to a shorter one m n and the rarefaction in both of them 
 being supposed the same, A Q=a q may represent the excess of the atmosphere's 
 weight above the column of water; RQ=r r , the resistances to the pistons from 
 the remainder of the steam, and A R=a r the effective forces. Make a k : A K : : 
 
 A RQ 
 
 a n : A N, and at all similar positions, the resistance b c of mn, and force k c on 
 its piston, will be equal to the resistance B C of M N, and force K C on its piston ; 
 and (by Newton's Princip. prop. 39.) in the descent of bodies, we have jakcr: 
 
 . K C R : : celerity in k : celerity in K. But these areas being evidently as 
 the corresponding parallelograms k q and K Q, and these again as their heights, 
 the celerities generated are in the subduplicate ratio of a A: to A K, as if the resist- 
 ance had been invariable. 
 
 To apply this to steam engines, if T W be a cylinder of equal content with the 
 cylinder M N, the quantity of water delivered by both will, as observed above, 
 be the same at each lift ; but the cylinder T W is no higher than m n, and their 
 rarefactions are supposed equal ; therefore, by what has been proved with regard 
 to the times, the time of the piston's descent in T W will be to that of the piston's 
 descent in m n : : \/E W : VAN; whence, in any given time, the short cylinder 
 T W will perform more than the longer one M N of equal content, and that in 
 the ratio of their diameters ; for as T E x E W=M A 2 x A N ; and E W : AN:: 
 MA 2 : T E 2 J therefore, v/EW : N/A~N : : MA: T E. And he further remarks, 
 the friction is diminished with the slowness of the motion, because the periphery 
 of the piston increases in a less ratio than its area. 
 
 The result of his whole reasoning is in favour of a short cylinder, and it must 
 be allowed to be ingenious ; but the proper question is, What form of the cylinder 
 
20 THE HISTORY OF [SECT. i. 
 
 will enable us to do the most work with the least steam, and not the most work 
 in the least time with a cylinder of a given capacity ? (Sect, iv.) 
 
 Mr. Blake also investigated the relation between the power and resistance which 
 gives a maximum effect in a given time when the motion accelerates from rest, 
 both when the force is uniform, and when variable, increasing as the distance. 1 
 (See Sect, iv.) 
 
 1757. KEANE FITZGERALD, F.R.S. 
 
 20. It was natural to expect that the atmospheric engine being now in con- 
 siderable use, the means of saving fuel would be considered, in places where it was 
 expensive. Mr. Keane Fitzgerald, in 1757, 2 proposed, with this object, to agitate 
 the water in the boiler by a stream of air, on Dr. Hales' plan for evaporating ; not 
 perceiving the difference between forming steam and accelerating evaporation. 
 But in consequence, Dr. Hales applied to him respecting working ventilators for 
 mines by steam engines ; and a rotary motion being necessary to that end, Fitz- 
 gerald contrived one to render the steam engine applicable to the purpose. The 
 method he adopted nearly resembled, in principle, that before contrived by Hulls for 
 his steam boat, (art. 14.) ; but instead of regulating it by a weight, Fitzgerald pro- 
 posed to use a fly wheel ; and remarks, that the steam engine by such means may 
 be applied to corn mills, raising coals, &c. Fitzgerald also showed the impropriety 
 of the then usual mode of constructing the working beam with its axis below its 
 centre of gravity, and altered the place of the axis of the engine beam of the York 
 water-works engine, with much advantage to its effect. 
 
 1758. WILLIAM EMERSON ; born 1701, died 1782. 
 
 21. A brief but clear description of the atmospheric engine was published by 
 Emerson in his ' Mechanics,' with the mode of computing its power, as far as 
 statical equilibrium between the power and resistance is concerned. He also, in 
 his ' Miscellanies,' gives a solution of a problem, which has for its object to deter- 
 mine the relation between the power and resistance when the effect is greatest. It 
 may be stated as follows : In a steam engine there is given the effective pressure 
 of the atmosphere upon the piston, and the length of the stroke, to find the water 
 to be drawn at a stroke, so that the greatest quantity shall be drawn in a given 
 time, supposing the force uniform, and the arms of the beam of equal length. 
 Emerson's solution differs from Blake's (art 19.), in taking the whole time of the 
 
 - 
 
 1 Phil. Trans, vol. li. p. i. or Abridg. vol. xi. p. 317. 
 
 2 Phil. Trans, vol. 1. p. 53 and 157. 
 
SECT, i.] THE STEAM ENGINE. 21 
 
 ascending and descending strokes into the account; and in not considering the 
 moving power as a gravitating mass of matter. It is, therefore, more strictly 
 applicable to the question, though still not perfectly so, as the space, not the time, 
 should be given. (See Sect, iv.) 
 
 22. The celebrated practical engineer", James Brindley, attempted to improve 
 the construction of the steam engine boiler by forming it of wood and stone, and 
 inserting a fire place and chimney of cast iron in the internal part of the boiler, so 
 as to surround both as far as possible, on all sides, by the water of the boiler. 
 This plan he expected would render more of the heat of the fuel effective ; and 
 therefore obtained a patent, in 1759, for the arrangement. That it was founded on 
 mistaken views of the nature of combustion, and of the quantity of the loss of heat, 
 would not be difficult to prove, (see art. 190.) ; and, accordingly, it never was 
 adopted in general practice. 
 
 1762. Dr. JOSEPH BLACK ; born 1723, died 1799. 
 
 23. The relation between the quantity of fuel and the effect of steam in an 
 engine became now an important subject ; but the different quantities of heat com- 
 bined with the same body according as it was in a solid, a liquid, or gaseous state, 
 or with different bodies at the same temperatures, had not yet been determined, or 
 rather the fact was not distinctly known ; and therefore crude opinion must have 
 directed the wisest, as it now directs the ignorant man, in his attempts to improve 
 the steam engine. To Dr. Black we owe the first investigation of the combination 
 of heat with bodies in the solid, liquid, and gaseous state, which he began to teach 
 publicly in 1762 : the heat so combining with them, he showed was insensible to 
 the thermometer, and hence he called it latent heat. 
 
 The quantity of heat required to convert boiling hot water into steam, he found 
 exceeded five times the quantity which made water boil. Dr. Black also showed 
 that different bodies required different quantities of heat to produce the same 
 change of temperature, and denoted the property by the phrase, capacity for heat ; 
 the term now usually employed is specific heat. (See Sect. n. art. 70.) 
 
 The principles of managing confined fires, and the nature and effect of fuel, 
 were also taught by Dr. Black. 
 
 In the inquiries respecting heat he was followed by Dr. Irvine and Dr. Craw- 
 ford, who made experiments to determine the specific heat and latent heat of 
 various substances. 
 
 1765. JOHN SMEATON, F.R.S. ; born 1724, died 1792. 
 
 24. Smeaton was not of a cast of mind likely to seize the views of Dr. Black, 
 
22 THE HISTORY OF [SECT. i. 
 
 and turn them to account in managing the action of steam ; his talent was chiefly 
 confined to improving the construction and proportions of existing machines, by 
 selecting the best methods known, and making experiments : accordingly, we find 
 he designed a portable atmospheric engine to make trials upon, in 1765 ; and these 
 experiments he was preparing for in 1769. 1 Smeaton afterwards directed the 
 erection of several large atmospheric engines, and brought them to a degree of 
 perfection which has not been exceeded in later times. I propose briefly to follow 
 through the most interesting of his inquiries ; commencing with his portable 
 engine. This seems to have been the first attempt to make an engine capable of 
 being removed from place to place. The fire place was formed entirely within the 
 boiler ; and in the place of an ordinary beam, a wheel 6'2 feet in diameter, with a 
 chain, communicated the motion from the piston to the pump rod. 
 
 The diameter of the cylinder was eighteen inches, its area, in circular inches, 324 
 inches ; and allowing seven pounds to the inch, which such a cylinder, he remarks, 
 would very well carry, we have 2268 Ibs. The number of strokes per minute 
 is stated to be ten of six feet each ; hence the effect is 2268 x 10x6=136080 Ibs. 
 raised one foot, or four horses' power : he reckoned it equivalent to six horses ; and 
 therefore his value of the horse power is 22680 Ibs. raised one foot high per 
 minute, instead of the usual standard of 33000 Ibs. 
 
 Respecting fuel, he remarks, it has been found by experience that a two feet 
 cylinder requires 174 Ibs. of Newcastle coal per hour ; which, reduced in the ratio 
 of the capacity, gives ninety-seven pounds and a half per hour for the eighteen 
 inch cylinder, or a four horse engine, according to the common application of fire ; 
 but he had reason to think an engine constructed like his would not require above 
 sixty-five pounds per hour for a four horse engine. 
 
 The fire place was of a spherical figure, of cast iron, and entirely within the 
 boiler ; the coals were introduced by a large pipe from the outside of the boiler to 
 the fire place, and the smoke passed off by a curved pipe with an iron funnel to 
 promote a sufficient draught. The ashes fell through a pipe covered by a grate 
 eighteen inches diameter, the whole being joined to the boiler by proper flanches, 
 and always covered with water. In so short a flue the force of the fire cannot be 
 wholly exhausted within the compass of the boiler, therefore the curved pipe was 
 surrounded by a copper vessel adapted to its shape, into which was brought the 
 feeding water, that it might be raised to a greater degree of heat than if brought 
 immediately from the hot well into the boiler. It is also obvious, that by this 
 arrangement the coolest part of the water comes in contact with the flue, to take 
 the heat from the smoke before it ascends the chimney. The bars of the grate 
 
 Reports, vol. i. p. 223. and ii. 338. 
 
SECT, i.] THE STEAM ENGINE. 23 
 
 were cast into a loose ring capable of being taken out, and replaced when occasion 
 required. On the large scale also, Smeaton's boilers were admirably adapted for 
 generating steam, little inferior to any that have since been contrived. 
 
 In a report to the London bridge water works, in 1771, Smeaton proposed to 
 regulate the power of the engine by the injection, whereby the engine-keeper 
 would be enabled, while the engine was working, to vary the quantity in propor- 
 tion to the column to be lifted, and avoid the ill effects arising from a variation of 
 the column, and save fuel. 
 
 Smeaton's first effective introduction of the improvements resulting from his expe- 
 riments on the engine seems to have been in the early part of 1774 ; l and by these 
 improvements he appears to have reduced the expenditure of fuel about one-third. 
 In 1775, he designed the Chase Water Engine, the cylinder of which was seventy- 
 two inches in diameter, and the stroke nine feet. Its power was equivalent to the 
 exertion of 108 horses, and its consumption of fuel was estimated at 1136 Ibs. of 
 Newcastle coal per hour. At its full power it was proposed to make nine strokes 
 per minute, but to be regulated by the cataract to four strokes and a half per 
 minute. The construction of the beam, and other parts of the engine, are 
 sufficiently curious to entitle it to the strict attention of the student. 2 
 
 There seemed to be few practical circumstances that escaped Smeaton's inquiry 
 respecting the atmospheric engine ; and he drew up for his own use a table of the 
 proportions of the parts for different sized engines, which still exists in the col- 
 lection of his papers, purchased by Sir Joseph Banks. But the most important of 
 his researches relate to the load upon the piston, on which he remarks he had 
 found engines calculated to carry a load, varying from under five pounds to 
 upwards of ten pounds to the square inch, those lightly loaded being expected to 
 go with the greatest velocity, so that an engine carrying five pounds to the inch 
 must go with double the velocity of one loaded to ten pounds, the cylinders being 
 of equal area, in order that the effects of the power might be equal. He further adds, 
 that in engines, however, as in other machines, there is a maximum, which, with- 
 out new principles of power, cannot be exceeded : bad proportions of the parts, and 
 bad workmanship, may make an engine fall short, in any degree, of what it should 
 do, but its maximum cannot be exceeded by the most accomplished artists. 
 
 Experience had, however, suggested the idea of a mean burden. The 
 original patentees (Newcomen and Co.), from some of their first performances, laid 
 it down as a rule to load the piston, so as but little to exceed eight pounds to the 
 inch ; but, on more experience, they diminished that load, and amongst the best 
 engines previous to Smeaton's time the load was made about seven pounds to 
 the square inch. 
 
 1 Reports, vol. ii. p. 337. 2 Smeaton's Reports, vol. ii. p. 350. 
 
24 THE HISTORY OF [SECT. i. 
 
 He further states, that any load will do if the parts be properly proportioned ; 
 but, from a long course of very laborious experiments, he had fixed his scale 
 near upon, but somewhat under, eight pounds to the inch, including raising 
 the injection water. 
 
 The labours of Smeaton show the imperfect state of mechanical science, as 
 applied to practice, in a remarkable degree. He actually designed an engine, to be 
 erected at Long Benton, to raise water for turning a water wheel to draw coals 
 from a pit; 1 and in 1781 proposed one of Boulton and Watt's engines to be 
 erected for raising water for driving a corn mill ; 2 using such arguments as these 
 in support of his opinion. " It is to be apprehended that no motion communicated 
 from the reciprocating beam of an engine can ever act with perfect equality and 
 steadiness in producing a circular motion like the regular efflux of water in turning 
 a water wheel ; and much of the good effect of a water mill is well known to 
 depend upon the motion communicated to the millstones being perfectly equable 
 and smooth : the least tremor or agitation takes off from the complete performance. 
 Secondly, all the engines he had seen were liable to stoppages, and so suddenly, 
 that in making a single stroke the machine is capable of passing from nearly its 
 full power and motion to rest ; for whenever the steam gets lowered in its heat 
 below a certain degree, for want of renewing of the fire in due time or otherwise, 
 the engine is then incapable of performing its functions. Jn the raising of water, 
 (a business for which the fire engine seems peculiarly adapted,) the stoppage of the 
 engine is of no other ill consequence than the loss of so much time ; but in the 
 motion of millstones grinding corn, such stoppages would have had a particularly 
 bad effect." 
 
 It was certainly not a gratifying circumstance to Smeaton to find that his tedious 
 inquiries had been rendered nearly useless by a new mode of operation ; to find 
 that his cautious system of analysis was not in all cases the best mode of rendering 
 the powers of nature useful to man. Yet if it were his labours on the steam engine 
 alone on which his fame rested, there would be sufficient to command our esteem 
 and respect : its further improvements, its close cylinder, its double action, un- 
 doubtedly owed much of their perfection to the use of the modes of construction 
 applied by Smeaton to the air pump. 
 
 g 1766. JOHN BLAKEY. 
 
 25. Though there are so many circumstances in the mode of action which 
 reduce the effect of an engine of Savery's construction, these defects seem only to 
 
 1 Smeaton's Reports, vol. ii. p. 435. * Reports, vol. ii. p. 378. 
 
SECT . 
 
 THE STEAM ENGINE. 25 
 
 hotd out an inducement to speculative men to attempt to remove them, and among 
 these Blakey was one of the most sanguine. He obtained, in 1766, a patent for a 
 new mode of constructing Savery's engine, by using two receivers, one placed over 
 the other, with a pipe of communication between them. The contact of the steam 
 and water was to be prevented by a stratum of oil, forming a species of fluid 
 floating piston. He further proposed to admit air to occupy the place between the 
 steam and water, so as to prevent condensation during the process of forcing : both 
 methods inferior to the floating piston of Papin. Blakey had, however, sufficient 
 art to persuade the public that he had made a valuable discovery, and to get 
 Ferguson, the lecturer, to show off its advantages by a steam fountain. 1 In practice 
 his method was found to be worthless. 
 
 In generating steam, Blakey seems to have first proposed cylindrical tubes for 
 boilers, the description of which he published in 1774. He was also the author of 
 a pamphlet entitled, ' A Short Historical Account of the Invention, Theory, and 
 Practice of Fire Machinery,' printed in London in 1793, which was chiefly filled 
 with short notices of his own labours on the subject, now of no interest. 
 
 
 
 1769. JAMES WATT, LL.D. F.R.S. ; born 1735, died 1819. 
 
 26. The commencement of the researches of Mr. Watt appears to have been 
 in 1764, two years after Dr. Black began to teach his doctrines regarding heat. 
 Mr. Watt began by making experiments on the elastic force and bulk of steam, 
 and gradually developed those principles which form the basis of his valuable 
 improvements on the steam engine ; but he did not so far mature his plans as to 
 apply for a patent till 1768, which was enrolled in 1769. The specification is brief, 
 and not illustrated by figures ; hence I will give it entire, and then distinguish the 
 principles and methods of construction which had not been anticipated. 
 
 Mr. Watt's patent of 1769 was for his ' Methods of Lessening the Consumption 
 of Steam, and consequently of Fuel in Fire Engines;' and his specification is as 
 follows : " First ; that vessel in which the powers of steam are to be employed to 
 work the engine, which is called the cylinder in common fire engines, and which I 
 call the steam vessel, must, during the whole time the engine is at work, be kept 
 as hot as the steam that enters it ; first, by enclosing it in a case of wood, or any 
 other materials that transmit heat slowly ; secondly, by surrounding it with steam, 
 or other heated bodies ; and, thirdly, by suffering neither water, nor any other 
 substance colder than the steam, to enter or touch it during that time. Secondly ; 
 in engines that are to be worked wholly or partially by condensation of steam, the 
 
 1 Ferguson's Lectures, vol. i. p. 312. 
 
 
26 THE HISTORY OF [SECT. i. 
 
 steam is to be condensed in vessels distinct from the steam vessels or cylinders, 
 although occasionally communicating with them : these vessels I call condensers ; 
 and, whilst the engines are working, these condensers ought at least to be kept as 
 cold as the air in the neighbourhood of the engines, by application of water or 
 other cold bodies. Thirdly ; whatever air or other elastic vapour is not condensed 
 by the cold of the condenser, and may impede the working of the engine, is to be 
 drawn out of the steam vessels or condensers by means of pumps wrought by the 
 engines themselves or otherwise. Fourthly ; I intend in many cases to employ the 
 expansive force (pressure) of steam to press on the pistons, or whatever may be 
 used instead of them, in the same manner as the pressure of the atmosphere is now 
 employed in common fire engines. In cases where cold water cannot be had in 
 plenty, the engines may be wrought by this force of steam only, by discharging the 
 steam into the open air after it has done its office. Fifthly ; where motions round 
 an axis are required, I make the steam vessels in form of hollow rings or circular 
 channels, with proper inlets and outlets for the steam, mounted on horizontal axles 
 like the wheels of a water mill ; within them are placed a number of valves that 
 suffer any body to go round the channel in one direction only : in these steam 
 vessels are placed weights so fitted to them, as entirely to fill up a part or portion 
 of their channels, yet rendered capable of moving freely in them by the means 
 hereinafter mentioned or specified. When the steam is admitted in these engines 
 between these weights and the valves, it acts equally on both, so as to raise the 
 weight to one side of the wheel, and by the re-action on the valves successively, 
 to give a circular motion to the wheel, the valves opening in the direction in which 
 the weights are pressed, but not in the contrary ; as the steam vessel moves round, 
 it is supplied with steam from the boiler ; and that which has performed its office 
 may either be discharged by means of condensers, or into the open air. Sixthly, 
 I intend in some cases to apply a degree of cold not capable of reducing the steam 
 to water, but of contracting it considerably, so that the engines shall be worked by 
 the alternate expansion and contraction of the steam. Lastly ; instead of using 
 water to render the piston or other parts of the engines air and steam-tight, I 
 employ oils, wax, resinous bodies, fat of animals, quicksilver, and other metals, in 
 their fluid state. 
 
 " Be it remembered, that the said James Watt doth not intend that any thing in 
 the fourth article shall be understood to extend to any engine where the water to 
 be raised enters the steam vessel itself, or any vessel having an open communica- 
 tion with it." 1 
 
 The great and valuable improvement described in this specification is that of 
 
 1 Robisou's Mech. Phil. vol. ii. p. 119. Repertory of Arts, i. 217. 1794. 
 
SECT, i.] THE STEAM ENGINE. 27 
 
 condensing in a separate vessel ; and it necessarily involved a method of clearing 
 the condenser of air and water. The application of the principle could be ren- 
 dered perfect only by keeping the cylinder as hot as the steam, and the condenser 
 as cold as it could be done with economy ; and the methods proposed by Mr. Watt 
 for accomplishing these objects are at once novel and efficient. 
 
 The idea of using steam pressure was not new, not even when applied to a piston, 
 (see art. 12.) but the application of it in a close cylinder by means of a stuffing 
 box, such as Smeaton had applied to the air pump, was a new mode of construc- 
 tion, which, it may be inferred, was intended in the engine specified, though it is 
 not described. The scheme of a rotary steam vessel, or steam wheel, was also first 
 made public in this specification, though in a very imperfect manner. 
 
 27. Mr. Watt's steam wheel not answering on trial, his next object seems to 
 have been to convert the reciprocating motion of the piston rod into a rotary one. 
 Methods for this purpose had been contrived by Hulls and Fitzgerald ; and patents 
 had been obtained for similar ones by Stewart in 1769, and by Washborough in 
 1778, also by Steed in 1781, for the simple crank motion. 
 
 Notwithstanding the existence of these methods, Mr. Watt obtained a patent for 
 five others in 1781, one of which was the sun and planet wheel motion, which he 
 used for some time on account of the crank being Steed's patent. 
 
 In 1782 Mr. Watt obtained another patent, embracing various methods of 
 applying steam. First, for an expansive steam engine, with six different con- 
 trivances for equalizing the power ; secondly, the double power steam engine, in 
 which the steam is alternately applied to press on each side of the piston, while 
 a vacuum is formed on the other ; thirdly, a new compound engine, or method of 
 connecting together the cylinders and condensers of two or more distinct engines, 
 so as to make the steam which has been employed to press on the piston of the 
 first, act expansively upon the piston of the second, &c. ; and thus derive an 
 additional power to act either alternately or conjointly with that of the first cylinder; 
 fourthly, the application of toothed racks and sectors to the end of the piston or 
 pump rods, and to the arches of the working beams, instead of chains ; fifthly, 
 a new reciprocating semirotative engine, and a new rotative engine or steam 
 wheel. 
 
 By the double engine the same cylinder was rendered capable of doing double 
 the quantity of work in the same time, the steam pressure acting, and condensation 
 taking place, both during the ascent and descent of the piston. Simple as this 
 change appears, after being made, it is attended with many striking advantages ; 
 it renders the power nearly uniform, diminishes the proportion of cooling surface, 
 a less boiler is necessary, and it reduces the bulk and weight of the engine. 
 
 Of the modes of regulating the power of steam engines, the most effective were, 
 
28 THE HISTORY OF [SECT. i. 
 
 first, by limiting the opening of the regulating valves which admit the steam to 
 act on the piston, and letting it continue so open during the whole length of the 
 stroke ; secondly, by letting them open fully at first, and shutting them completely 
 when the piston has proceeded only part of its stroke ; or, thirdly, by the use of 
 a throttle valve placed in the steam pipe, which, acting in the same manner as the 
 floodgate of a mill, admits no more steam than gives the desired power. 
 
 The second of these methods of regulating the power of the engine is the best, 
 and forms the basis of Watt's Expansive Engine ; which renders available more of 
 the power of the steam than when the piston is acted upon by the whole force of 
 the steam through the entire length of the cylinder. This principle was adopted 
 in an engine erected at Soho manufactory, and some others, in 1776, and at 
 Shad well water works in 1778 ; the same principle was publicly made known in 
 1781 by Hornblower, though applied in a different manner. 
 
 28. There yet remained another step to complete the mechanism of the double 
 engine, viz. a guide for the piston rod ; and this appears to have been first accom- 
 plished, in 1784, by the invention of the parallel motion. This is an ingenious 
 combination of levers, one point of which describes a line nearly straight, and to 
 this point the piston rod is connected, so that its rectilineal movement causes the 
 beam to vibrate. This Mr. Watt secured by patent in 1784, together with a new 
 rotative engine, in which the steam vessel was to turn upon a pivot, and be placed 
 in a dense fluid, the resistance of which to the action of the steam was to cause 
 the rotative motion ; an improved method of applying the steam engine to work 
 pumps or other alternating machinery, by making the rods balance each other; 
 a new method of applying the power of steam engines to move mills which have 
 many wheels required to move round in concert ; a simplified method of applying 
 the power of steam engines to the working of heavy hammers or stampers ; a new 
 construction and mode of opening the valves, with an improved working gear; 
 and a portable steam engine and machinery for moving wheel carriages. 
 
 Mr. Watt obtained a patent, in 1785, for a method of constructing furnaces, in 
 which the best principles the philosophy of the period could furnish, are applied 
 to elicit the heat and consume the smoke of the fuel. He also applied to the 
 steam engine the conical pendulum as a governor, the steam gauge, condenser 
 gauge, and a useful little instrument for ascertaining the state of the steam in the 
 cylinder, called an indicator. 
 
 29. The principal part of the theory of the action of steam, which Mr. Watt 
 has investigated on scientific principles, is the power it affords by expansion ; and 
 this is done with great clearness. He devoted a considerable portion of the latter 
 part of his life to chemical philosophy, and particularly its application to the arts. 
 As an author, he has also contributed some historical notices of his own inventions, 
 
SECT, i.] THE STEAM ENGINE. . 29 
 
 a few corrections of Dr. Robison's article in his 'Mechanical Philosophy,' and several 
 notes to it, containing his experiments on the latent heat and elastic force of steam. 
 
 30. The share which Boulton had in the improvement and introduction of 
 the steam engine must not be forgotten ; for as it has been remarked by Baron 
 Dupin, " Watt's engine was, when invented by him, but an ingenious speculation, 
 when Boulton, with as much courage as foresight, dedicated his whole fortune to 
 its success." He did not hesitate even when Smeaton declared his conviction that 
 it could never be generally applied as a useful agent. Besides, Boulton rendered 
 no small service to Watt and to Great Britain, when, by his extraordinary talents 
 in manufactures and commerce, he exempted his partner from all the cares of life, 
 from all commercial speculations, and from all those difficulties which are the 
 inevitable consequences of great enterprise in trade. Boulton did still more ; he 
 triumphed over all those interests and prejudices which necessarily arose in the 
 beginning to retard the success of the new steam engines and their application. 
 " Men," continues Dupin, " who devote themselves entirely to the improvement 
 of industry, will feel in all their force the services that Boulton has rendered to the 
 arts and mechanical sciences, by freeing the genius of Watt from a crowd of extra- 
 neous difficulties, which would have consumed those days that were far better 
 dedicated to the improvement of the useful arts." 
 
 31. A curious apparatus for trying the elastic force of different vapours was 
 invented by T. H. Zeigler, which he describes in a memoir published at Basle in 
 1769, with tables of the results of his experiments; but it appears he had not taken 
 care to free his apparatus from air before the trials ; they are therefore useless. 
 
 1781. JONATHAN HORNBLOWER. 
 
 32. In 1781, a patent was obtained by Mr. Hornblower, for a mode of apply- 
 ing the expanding power of steam. For when steam is confined on one side of 
 a piston, and a partial vacuum is formed on the other, the steam will move the 
 piston till its force be in equilibrium with the friction and uncondensed steam ; 
 and as much power as is communicated during this motion is in addition to the 
 ordinary effect of steam pressure. To gain power in this manner, Mr. Hornblower 
 used two vessels in which the steam was to act, and which, in other steam engines, 
 are called cylinders, employing the steam after it had acted in the first vessel to 
 operate a second time in the other, by permitting it to expand itself, which he did 
 by connecting the vessels together, and forming proper passages and apertures, 
 whereby the steam might at proper times go into and out of the said vessels. l 
 
 1 Repertory of Arts, vol. iv. p. 361. 1796. 
 
30 THE HISTORY OF [SECT. i. 
 
 The effect would be nearly the same as that derived from cutting off the steam 
 before the piston arrives at the end of its stroke, as was afterwards done by 
 Mr. Watt, (art. 28.) but has the decided advantage of being a more equable 
 method of employing steam power ; and in large engines the construction of Horn- 
 blower's is also superior, because strong steam can be used in a small cylinder with 
 less risk : he however does not appear to have intended to use powerful steam ; 
 and he could not use his invention, because the improved mode of condensation 
 remained the right of Boulton and Watt. 
 
 Like Watt, many other engineers imagined that a rotary motion might be com- 
 municated with advantage by the direct action of steam ; and two combinations 
 for that purpose were made by Hornblower. His first was an ingenious but com- 
 plicated machine, for which he had a patent in 1798. 1 The second was more 
 simple; it was secured by a patent in 1805. It consists of four vanes revolving 
 in a cylinder round its axis. The vanes are like those of a smoke jack, but of 
 thickness sufficient to form a groove in their edges, to hold stuffing for the purpose 
 of making them steam-tight in their action. They are mounted on an arbor, which 
 has a hollow nave in the middle. Into this nave the tails of the vanes are inserted, 
 and each opposite vane affected alike by having a firm connexion with one 
 another ; so that if the angle of one of the vanes with the arbor be altered, the 
 opposite one will be altered also, and the opposite ones are set at right angles to 
 each other ; so that when a vane is flatly opposed to the steam, the opposite vane 
 will present its edge to it, and thus they are constantly doing in their rotation on 
 their common arbor ; so that the steam acts against the vane on its face for about 
 a quarter of a circle, or ninety degrees, in the cylinder where it is destined to act ; 
 and as soon as it has gone through the quarter of the circle, it instantly turns its 
 edge to the steam, while at the same instant another vane has entered the working 
 part of the revolution, and the rotation proceeds without interruption. This engine 
 was to be furnished with the condenser and discharging pump of Watt, but Horn- 
 blower added what he considered an improved method of discharging the air from 
 the condenser. 
 
 It is easy to show that the friction, and other sources of loss of power, are much 
 greater in the rotary than in the rectilineal action of steam, while the loss by 
 rendering a reciprocating motion rotary is very small (Sect. iv. and vn.) ; but I 
 notice this as one of the most simple combinations proposed for a rotary engine. 
 
 33. A series of experiments on the elastic force of steam from 32 to 212 was 
 published by Mr. Achard in 1782. He also examined the elastic force of the 
 vapour of alcohol ; and observed, that when steam and alcohol vapour were of 
 
 1 Repertory of Arts, vol. ix. p. 289. Old Series. 
 
SECT, i.] THE STEAM ENGINE. 31 
 
 equal elastic force, the temperature of the latter was about thirty-five degrees 
 lower, but that the difference of temperature was not constant ; it seemed to be 
 greater or less as the elastic force was greater or less. 
 
 1782. MARQUIS DE JOUFFROY. 
 
 34. The idea of employing the steam engine to propel vessels, which had 
 been suggested by Hulls, (art. 14.) was first tried in practice by the Marquis De 
 Jouffroy, who, in 1782, constructed a steam boat to ply on the Saone, at Lyons; 
 it was 140 feet long and 15 feet wide, and drew 3*2 feet of water. He made 
 several experiments with it, and it was in use fifteen months on the Saone. * 
 
 35. In 1785 M. Perronet gave a very full description, in the French Ency- 
 clopaedia, of an atmospheric engine erected near Saint Guilain, in Hainault : this 
 description is remarkable for its clearness and practical details, and not less so 
 from its being introduced by stating Papin to be the inventor of the steam engine 
 in a most unqualified manner ; though admitting the first to have been constructed 
 in England. 
 
 1788. PATRICK MILLER. 
 
 36. About this time various competitors for the application of steam to navi- 
 gation appeared, (1785-88.); in America, two rivals, James Rumsey of Virginia, 
 and John Fitch of Philadelphia. In Italy the application of steam power to vessels 
 was proposed by D. S. Serratti, and in Scotland by Mr. Miller of Dalswinton, who 
 afterwards, on the sight of a model of a steam carriage invented by Mr. William 
 Symington of Falkirk, was so much pleased with the model, that he desired Mr. 
 Symington to make him a small steam engine, to work a twin or double boat on 
 Dalswinton Loch. The engine having been accordingly executed, and put on 
 board the boat, the experiment was made at Dalswinton in the autumn of 1788, 
 and it succeeded so well, that Mr. Miller commissioned Mr. Symington to pur- 
 chase a gabert, or large boat, at Carron, and to fit up a steam engine on board of 
 it, to make a trial on a larger scale. Every thing being completed, the trial was 
 made on the Forth and Clyde canal, in the summer of 1789, Messrs. Miller, 
 Stainton, Taylor, &c. being on board ; and the result answered their most sanguine 
 expectations ; but most unaccountably, after having thus established, at a consider- 
 able expense, the practicability of employing the power of steam in navigation, 
 Mr. Miller seems to have neglected it entirely. 2 
 
 1 Dictionnaire de Physique, art. Chaloupe a Vapeur. 
 
 - ' Short Narrative of Facts relative to Steam Navigation,' Edinb. Phil. Journal. 
 
32 THE HISTORY OF [SECT. i. 
 
 37. The theory of the steam engine still made small progress, though it 
 excited some degree of attention. 
 
 Bossut had described an atmospheric engine in the first edition of his ' Hydro- 
 dynamique,' in 1771, with some formula for its statical equilibrium; in the 
 edition of 1786, he investigated the proportion of counterweight, but for a particular 
 case, and not including the actual circumstances of the moving forces. 
 
 38. A rotary engine was proposed in 1789 by Cooke, * and a patent was 
 obtained for one in 1790 by Bramah and Dickinson, 2 and for another in 1791 by 
 Sadler. 3 The peculiar construction of all these engines I need not describe, as the 
 principle of a rotary engine will be shown to be attended by a loss of effect, which 
 mechanical combinations cannot remove. (See Sect, iv.) 
 
 39. Bramah and Dickinson's patent included three varieties ; the most simple 
 of which is designed with pistons sliding in an eccentric wheel, the steam to enter 
 at s ; and the opening to the condenser being at c, the pressure causes the smaller 
 wheel to revolve, and the pistons to slide in it. All the varieties are specimens of 
 
 Fio. 8. 
 
 that beautiful style of executing machinery, which Bramah contributed so much 
 to introduce in this country, and which has been carried to such high perfection 
 by his pupil, the celebrated Maudslay. 
 
 1790. BETTANCOURT. 
 
 40. Chev. Bettancourt, who was employed by the Spanish government to 
 collect models of hydraulic machines, made a series of experiments on the force of 
 yapour of water and of alcohol, at different temperatures. They are more accurate 
 than those which were at that time before the public, but still had not that pre- 
 cision which is necessary to develop the laws of the force of vapour. He made a 
 
 1 Repertory of Arts, vol. iii. p. 401. 1795. * Idem, vol. ii. p. 73. 
 
 3 Idem, vol. vii. p. 170. 
 
SECT, i.] THE STEAM ENGINE. 33 
 
 model of the double acting engine, with a new mode of forming the valves ; and, 
 Prony says, from merely seeing the exterior of a double acting engine when at 
 work. 1 
 
 1790. R. PRONY. 
 
 41. M. Prony is the author of one of the most extensive of the French works 
 on the steam engine : it forms a part of his ' Architecture Hydraulique,' which 
 commences in the first volume, and occupies nearly the whole of the second. 
 
 M. Prony begins with the properties of caloric, and the tables of Bettancourt on 
 the force of vapour ; and from the latter constructs an empirical formula for cal- 
 culating the force of vapour at different temperatures. These are not a little 
 complex, considering their want of conformity with experiment. He then proceeds 
 to the description of engines as then constructed, and their parts ; which are illus- 
 trated by plates having figures on a large scale. When he arrives at the parallel 
 motion, the nature of the curve described by the extremity of the piston rod is very 
 fully investigated, with tables to show its variation from a straight line for a given 
 range in the curve. It is followed by the proposal of a method for determining the 
 diameter of the steam cylinder, which is little better than telling the artist to guess 
 at it, and correct his guess by an intricate formula. The part on the steam engine 
 terminates with a calculation of the effect produced by a given quantity of fuel, 
 where the time of combustion is certainly erroneously introduced. 
 
 The rest of the volume is occupied by an analytical investigation of empirical 
 formulae for the expansive forces of elastic fluids and vapours at different tem- 
 peratures ; which has been rendered wholly useless by later researches having 
 shown the experiments to be inaccurate. 
 
 It is remarkable that Prony had not acquired a knowledge of the advantage of 
 steam acting expansively ; though, when his second volume appeared, it had been 
 fifteen years a contested discovery in England. Of his labours it may be said, that 
 they afford the strongest evidence that mere mathematical talent is not sufficient 
 for the promotion of mechanical science, otherwise the principles of the steam 
 engine would not have remained to be investigated. 
 
 1795. JOHN BANKS. 
 
 42. Mr. Banks, in a work on mills published in 1795, has treated of the 
 maximum of useful effect in atmospheric steam engines. He considers the space, 
 or length of the stroke, the given quantity ; in which his investigation differs from 
 
 1 Archit. Hydraulique, vol. i. p. 574. 
 E 
 
34 THE HISTORY OF [SECT. i. 
 
 those of Blake and Emerson. He has, however, by considering the atmospheric 
 pressure as a gravitating weight, failed in giving a correct solution. 
 
 One of his problems includes the weight of the moving parts of the engine ; and 
 he adds some useful practical formula for the statical equilibrium of engines for 
 raising water, with examples. 
 
 In 1803, Mr. Banks gave some rules for the strength of engine beams, both for 
 wood and cast iron ; and also a description of a gauge for determining the state of 
 rarefaction in the cylinders and condensers of steam engines, in principle the same 
 as the common barometer, and differing from the ordinary condenser gauge by 
 having a cistern instead of a syphon for the mercury. His rules for the strength 
 of beams are, to find the relation between the pressure and breaking weight, and to 
 let the breaking weight exceed the pressure by six, eight, or ten times. 1 
 
 1797. Dr. EDMUND CARTWRIGHT ; born 1742, died 1823. 
 
 43. The simple and neat combination of Cartwright next claims attention, 
 and on more grounds than one. He attempted to condense the steam by means of 
 cold applied externally to the condenser ; it consisting of two metal cylinders lying 
 one within the other, and having cold water flowing through the inner one and 
 enclosing the outer one. By this construction, a very thin body of steam is 
 exposed to a very great quantity of cooling surface ; and, by placing the valve to 
 change the steam in the piston, a constant communication is at all times open 
 between the condenser and the cylinder, so that, whether the piston ascends or 
 descends, the condensation is always taking place. 
 
 One of the chief objects of this arrangement was the opportunity it afforded of 
 substituting ardent spirit or alcohol, either wholly or in part, in the place of water, 
 for working the engine ; for as the fluid with which it is worked is intended to 
 circulate through the engine without mixture and very little loss, the using alcohol, 
 after the first supply, it was expected, would be attended with little or no expense. 
 The power obtained from alcohol, it was then imagined, would require only half 
 the fuel which was necessary to obtain the same power from water (see Sect, iv.) ; 
 and Cartwright proposed, in some cases, to apply this engine to a still, to obtain 
 mechanical power by the distillation of ardent spirit, so as to save the whole of the 
 fuel. 2 How he was to keep the engine in a workable state, and yet obtain a pure 
 spirit, neither he nor his friends seem to have considered. 
 
 In order to reduce the friction of the piston, which, when fresh packed in the 
 common way, lays a very heavy load upon the engine, Cartwright made his solely 
 
 1 Power of Machines, p. 103. Phil. Mag. vol. i. p. 3. 
 
SECT. I.] 
 
 THE STEAM ENGINE. 
 
 35 
 
 of metal, and expansive : by this method he further expected some advantage from 
 saving of time and expense in the packing, and from the piston fitting more accu- 
 rately, if possible, the more it was worked. (See Sect, vn.) Cartwright was very 
 desirous of simplifying all the other parts of his engine, having only two valves, 
 and those are as nearly self-acting as may be. Cartwright's engine is represented 
 in the annexed figure. It is a single acting engine, and A is the cylinder ; B, the 
 piston ; I, the pipe which conducts the steam to C, the condenser, which is a 
 double cylinder ; the steam passes between the inner and outer one into the pump 
 D, which returns the condensed fluid back into the boiler, through E, the air box, 
 with e its valve. 
 
 As the pipe from the pump, through which the condensed fluid is returned into 
 the boiler, passes through the air box, what air or elastic vapour may be mixed 
 with the fluid rises in the box, till the ball which keeps the valve e shut, falls and 
 suffers it to escape. 
 
 FIG. 9. 
 
 F is the steam valve ; a the piston valve ; H, H, two cranks, upon whose axles 
 are two equal wheels working in each other, for the purpose of giving a rectilinear 
 direction to the piston rod ; and M is the cistern that contains the condensing 
 water. The metallic pistons he formed of metal rings, as shown by the section of 
 
36 THE HISTORY OF [SECT. i. 
 
 the piston, which by springs are forced outwardly against the surface of the cylinder, 
 so that the piston may adapt itself to any inequality in its form. The piston rod is 
 also made steam-tight by a metallic box, constructed in the same manner as shown 
 at N. O is the fly wheel for regulating the motion of the engine. 
 
 The metallic piston is the only part of the engine which was really new in 
 principle, and for its invention we are undoubtedly indebted to Cartwright ; and 
 though we cannot say any other part is new except in arrangement, we admire the 
 appearance of simplicity and originality which distinguish his design, even knowing 
 that both theory and practice forbid us attempting to use the methods he proposed. 
 
 Cartwright included in his patent a rotary engine, which is simple in appear- 
 ance, but in reality involves many difficulties in construction, besides the loss of 
 effect which must necessarily follow from steam acting on a rotary piston. 
 
 1797. JOHN CURR. 
 
 I 
 
 44. A work containing the proportions of the parts of atmospheric engines, as 
 they were executed in 1797, with brief technical directions for constructing them, 
 illustrated by plates showing the parts on a large scale, was published at Sheffield, 
 by John Curr. 1 It contains no general description of the engine, and he assigns no 
 reasons for any of the proportions he has given, except when speaking of the 
 pressure on the piston, he says, that when the pressure was increased from seven to 
 eight pounds and a half per square inch, the engine did less, and also when reduced 
 to 6'1 Ibs. it did somewhat less ; and he does not recommend a greater load than 
 six and a quarter or six and a half pounds. 4 The engine had a sixty-one inch 
 cylinder, and made twelve strokes, of eight feet and a half each, per minute. The 
 consumption of coals was ten hundred weight of small coal, or sleek, per hour. 
 The power of the engine would be nearly equal to fifty-four horses' power ; and as 
 the ratio of coal to sleek is about as three is to four, it is equivalent to about 
 840 Ibs. of coal per hour : and at this ratio, one pound of sleek raises 97,600 Ibs. 
 of water one foot high, and one pound of coals 130,000 Ibs. one foot high. 
 
 45. In 1797 an engine on Savery's principle was described by William 
 Nicholson in his ' Philosophical Journal,' which Mr. Kier had erected in 1793. 
 It acted wholly by condensation ; the steam vessel being raised somewhat above 
 the height to which the water was to be raised. It had a provision for letting in 
 a small portion of air between the steam and the water, and the construction was 
 extremely simple and judicious. The boiler was seven feet long, five feet deep, 
 and five feet wide ; and it consumed six bushels (522 Ibs.) of good coal in twelve 
 
 1 The Coal Viewer and Engine Builder's Practical Companion. * Idem, p. 40. 
 
SECT. ,.] THE STEAM ENGINE. 37 
 
 hours in its best state, and seven in its worst state. Under these circumstances 
 it made ten strokes per minute, and raised seventy cubic feet of water twenty feet 
 high in a minute. 
 
 According to this statement, in the best state of the engine, 87 Ibs. of coal were 
 consumed in 2 hours or 120 minutes, and 1400 cubic feet of water raised one foot 
 high per minute; or 1400x120=168,000 cubic feet by 87 Ibs. of coal, which 
 multiplied by 62|- Ibs., the weight of a cubic foot of water, and divided by 87, 
 gives 120,000 Ibs. for the load raised one foot by one pound of coal ; which is 
 about one half the effect produced by an engine with a piston and Watt's con- 
 denser, and less than the effect of the common atmospheric engine as used for the 
 coal mines. 
 
 An attempt was also made by John Nancarrow, to improve Savery's engine, by 
 condensing in a separate vessel ; but the nature of the engine does not permit of 
 this being applied with much effect. 
 
 1799. MATTHEW MURRAY ; died 1826. 
 
 46. In the construction and improvement of some of the parts of engines, 
 much was done by Mr. Murray, of the firm of Fenton, Murray, and Wood, of 
 Leeds. These improvements were made the subjects of patents ; and though it 
 appeared that some of them had been before used by Boulton and Watt, they did 
 not become publicly recorded till Mr. Murray obtained patents for them. 
 
 In his patent of 1799, in order to save fuel, Murray proposed to place a small 
 cylinder with a piston on the top of the boiler, connected to a rack, by means of 
 which the force of the steam within the boiler opens or closes the damper fixed 
 on an axis in the chimney, thus increasing or decreasing the draught of the fires, 
 so as to keep up a regular degree of elastic force in the steam. Mr. Murray also 
 thought some advantage would be gained by placing the steam cylinder in a 
 horizontal instead of a vertical position, with a view of rendering the engine more 
 compact than the usual construction ; he also adopted a new method of converting 
 the reciprocating motion of the piston rod to a rotary one of equal power, by means 
 of a property of the rolling circle, and showed how to fix the wheels for producing 
 motion alternately in perpendicular and horizontal directions. J 
 
 47. Mr. Murray's patent of 1801 was for six different objects: First, for a 
 method of constructing the air pump. Second, for a method of packing stuffing 
 boxes, &c. by bringing the moveable parts of each in immediate contact, which 
 prevents the piston rod receiving any oblique pressure, by the lid being screwed 
 down more upon one side than the other. The third and fourth methods relate to 
 
 1 Repertory of Arts, vol. xi. p. 311. Old Series. 
 
38 THE HISTORY OF [SECT. i. 
 
 the construction and motion of the valves. The fifth was a method of connecting 
 the piston rod to the parallel motion. And the last, for the construction of fire 
 places, by which the smoke arising from the fire was to be consumed. In most of 
 these, however, he had been anticipated in practice. 
 
 48. Another patent was obtained by Mr. Murray, in 1802, for a portable 
 engine ; but as it included some of the methods for which Messrs. Boulton and 
 Watt had patents, it was at their instance repealed in the following year. Boulton, 
 Watt and Co.'s portable engine was first constructed in 1806. 
 
 1799. WILLIAM MURDOCH. 
 
 49. Mr. Murdoch, a partner in the firm of Boulton, Watt and Co., obtained 
 in 1799 a patent for some new methods of construction, which consist of a mode of 
 boring the metallic cylinders and pumps more equably by means of an endless 
 screw, worked by a toothed wheel ; and a method of simplifying the construction 
 of the steam vessel and steam case, in engines formed on Mr. Watt's plan, by 
 casting the steam case of one entire piece, to which the cover and bottom of the 
 working cylinder are to be attached. He also proposed to cast the cylinder and 
 steam case in one piece of considerable thickness, and bore a cylindric interstice 
 between the steam case and steam vessel, leaving the two cylinders attached at one 
 end, and to close the other by a ring of metal. Another improvement included in 
 the patent was, a plan for simplifying the construction of the steam valves or 
 regulators of the double engine, by connecting together the upper and lower valves, 
 so as to work with one rod or spindle. The tube which connects them being 
 hollow serves as an eduction pipe to the upper end of the cylinder, and a saving 
 of two valves is effected ; and lastly, he adds a scheme for a rotary engine con- 
 sisting of two toothed wheels working in an air-tight vessel, which he imagined 
 would work with considerable power. Mr. Murdoch's modes of moving the valves 
 have added much to the simplicity and neatness of the double engine, and to his 
 skilful superintendence the steam engine owes many of its perfections ; and its 
 success in Cornwall was greatly aided by his activity, integrity, and resources for 
 overcoming the difficulties which the drainage of the mines presented. 
 
 1801. DR. JOHN ROBISON; born 1739, died 1805. 
 
 50. Dr. Robison, to whom the mixed mechanical sciences are so much 
 indebted for a more judicious combination of theory with practice than is to be 
 found in any preceding author, and for treating them in a more popular style, 
 seems to have bestowed much attention on the principles and construction of the 
 
SECT, i.] THE STEAM ENGINE. 39 
 
 steam engine. His analytical knowledge was ample for the purpose, and the 
 access of the friend of Watt to practical data must have been easy in proportion as 
 Watt was the liberal friend of science ; therefore, much is expected when we take 
 up the volume which contains the articles of Dr. Robison on the steam engine. 
 
 The first article contains a rather diffuse statement of the physical properties of 
 steam. The phenomena of boiling, and the effect of pressure in altering the 
 temperature necessary for ebullition, and the popular doctrines of latent heat, are 
 fully stated. It also contains a series of experiments on the elastic force of the 
 steam of water, and of alcohol (see art. 95 and 104) ; and we have only here 
 to remark on them, that they were not made with sufficient accuracy, even to 
 establish the justness of some of his own views on the subject ; also, the rule for 
 the elastic force of steam derived from these experiments, and stated to be " suffi- 
 ciently exact for practical purposes," is very far from being so, and has had a little 
 effect in misleading some of the engineers who have ventured to speculate on the 
 improvement of steam engines. But, on the whole, Dr. Robison's is the best 
 article on steam I have seen. 
 
 The article on the steam engine consists of the history, mixed with detailed 
 descriptions, of the engines of Savery, Newcomen, Watt, &c. ; and such theoretical 
 discussion as he has given is also blended in the same mass. In the historical 
 portion the memory of Papin is not quite so respectfully treated as we could have 
 wished ; and the circumstance of Watt being the private friend and countryman 
 of the author has not been without its effect on the historian. In other respects 
 Dr. Robison has been impartial. In description there is a want of system, but 
 he is full and particular ; and he has been of unknown value in giving informa- 
 tion to the competitors of Boulton and Watt, and in furnishing matter for minor 
 writers. In theory he has reprinted the speculations of Bossut respecting the 
 best velocity for atmospheric engines, with some additions, and Watt's mode of 
 computing the pressure on the piston of the expansive engine ; but neither 
 of these inquiries are conducted in such a manner as to be of use to engine 
 makers. 
 
 The reputation of Dr. Robison has given much additional value to his articles 
 on the steam engine : hence their effect has been unparalleled ; and if we find 
 little of novelty in his labours, it was no small favour to have the scattered know- 
 ledge on the subject collected with so much skill, and treated with so much clear- 
 ness and good taste. 
 
 51. A modification of Watt's manner of constructing boiler fire places was 
 contrived in 1800 by Messrs. Roberton, of Glasgow, which is more convenient in 
 practice, though the same in principle. (See Sect, m.) They also attempted to 
 make the steam which escapes by the sides of pistons useful in adding to the 
 
40 THE HISTORY OF [SECT. i. 
 
 effective power of engines. But the complexity and expense of apparatus to 
 obtain so small an increase of power, renders this and some other expedients of 
 that time of little if any value. 
 
 1801. JOSEPH BRAMAH ; born 1749, died 1814. 
 
 52. The rotary engine, the joint product of Messrs. Bramah and Dickinson, 
 has already been noticed. (Art. 39.) In 1801 Mr. Bramah obtained a patent for 
 a new mode of applying the four-passaged cock to steam engines, with some other 
 variations in their construction. 
 
 The four-passaged cock he made to turn continually in the same direction, and 
 yet produce the same effect as by turning it backwards and forwards ; but by turn- 
 ing constantly the same way, the wear is rendered more equable, and consequently 
 the combination is more durable. 
 
 He also adjusted the movements so as to give, at the proper time, as instantaneous 
 and free a passage to the cylinder and condenser as possible ; and formed the 
 apertures so that the cone might be pressed equally into its seat by the force of 
 the steam. 
 
 53. A series of tables for the proportions of the cylinders of atmospheric 
 engines, to produce a given effect, were published in 1801 by Mr. Thomas Fen- 
 wick, whose employment in the management of coal works near Newcastle gave 
 him a good opportunity of knowing what would answer best in practice. 
 
 He infers from some experiments, that the whole friction of the atmospheric 
 engine is about four pounds per square inch, on the area of the piston ; and on 
 account of the frequent bad effects attending designing an engine with too small 
 an allowance for excess above its ordinary work, he makes his computations at 
 five pounds and a half effective power for each square inch of piston. 
 
 In a later edition of his work he gives tables for an improved atmospheric engine 
 with a separate condenser, in which the ratio of the effect is as 17 : 10, when the 
 same sized cylinder is used. The saving of fuel he does not mention, as at coal 
 works it is not considered of much importance ; for if the first expense of an engine 
 be small, and its operation simple and efficient, it is of more value to a coal owner 
 than a finer piece of machinery. 
 
 1801. JOHN DALTON. 
 
 54. At this period a knowledge of the nature and properties of vapours began 
 to become important in chemical science, in meteorology, and in other branches of 
 natural philosophy ; and therefore a wholly different class of writers engaged in the 
 
SECT. i. ] THE STEAM ENGINE. 41 
 
 investigation, which had made so little progress in the hands of mechanical people. 
 The first chemist who distinguished himself by attempting a full investigation of 
 the theory of vapour, was Mr. John Dalton. He made an accurate series of 
 experiments on the expansive force of steam at temperatures lower than 212, 
 made experiments and ascertained various phenomena relative to the expansion 
 of gases, the mixture of air and vapour, the nature of evaporation and of com- 
 bustion. And though he failed in his attempt to reduce any of these to general 
 laws, yet he gave such an impulse to the inquiry, as rendered it one of universal 
 research among chemical philosophers. The importance of Dalton's inquiries, 
 and even their connexion with the theory of the steam engine, did not appear, 
 at first, to be much noticed. The idea that Watt had done every thing possible 
 to be done respecting the power of steam had stopped inquiry among men of 
 science, and left the manufacturers and capitalists of the country, who were wishful 
 to encourage improvement, to be guided by vain and ignorant projectors, or ruined 
 by pretending knavery. 
 
 1802. WILLIAM SYMINGTON. 
 
 55. In 1801, Mr. Symington was encouraged to proceed with a steam boat, 
 by Thomas, Lord Dundas, of Kerse, who wished that one might be applied to drag 
 vessels on the Forth and Clyde Canal in place of horses ; and accordingly a series 
 of experiments on a large scale, which cost nearly 3000, were set on foot in the 
 year 1801, and completed in 1802. The boat Mr. Symington made was for towing, 
 and it had a steam cylinder twenty-two inches in diameter, and four feet stroke. 
 A complete model of it, with a set of ice-breakers attached, may be seen at the 
 rooms of the Royal Institution in London. This tow-boat proved to be very much 
 adapted for the intended purpose, but no direct practical application of steam power 
 to this object resulted from it. 
 
 1802. TREVITHICK and VIVIAN. 
 
 56. The idea of a high pressure engine had occurred to Leupold, (art. 12.) 
 and to Watt, 1 (art. 26.) but neither of them had reduced their notions to practice ; 
 and it was not till 1802 that this simple mode of applying steam was brought into 
 use by Messrs. Trevithick and Vivian. 2 Their object seems to have been to form 
 
 1 It was generally understood, that, although Mr. Watt patented the high pressure engine, it 
 was not his intention that it should he employed, except in situations where condensing water could 
 not he had. He considered the risk too great, and life too valuable, to be endangered for a saving 
 in the mere original cost of the engine, there being none in respect of the consumption of fuel. 
 
 Repertory of Arts, vol. iv. p. 241. New Series. 
 
 F 
 
42 THE HISTORY OF [SECT. i. 
 
 a simple and portable engine for cases where water was scarce, or where gaining 
 the whole effect of the fuel was of less consequence than moving a cumbrous 
 load. 
 
 Indeed their high pressure engines were intended chiefly for propelling 
 carriages upon rail-roads ; and when used for this purpose the boiler was composed 
 of cast iron, of a cylindrical form, mounted horizontally upon a frame with four 
 wheels, the cylinder of the engine being placed vertically within the boiler near 
 to one end. The piston rod moved a cross head, between two guides ; and by 
 a connecting rod descending from each end of the cross head to two cranks, the 
 motion was communicated to the wheels of a carriage : a fly wheel in this case is 
 not required, because the momentum of the carriage supplies its place. 1 
 
 The first trial of this species of moving power for carriages took place on a 
 railway at Merthyr Tidvil in 1805. Its use was not at that period followed up, 
 but it is now with some slight modifications extensively employed on rail-roads. 
 
 Several projects for trifling variations in the construction of engines, and for 
 methods of applying fuel, appeared about this time, but none of either sufficient 
 novelty or importance to claim particular attention. 
 
 The nature and application of heat had been so well illustrated by Rumford, 
 and many of its more recondite properties so ably developed by Leslie, that there 
 seemed to be little reason to expect any material improvement beyond the best 
 mode then in practice. The cylindrical boilers which Blakey projected, and Rum- 
 ford had tried, were again remodelled by Woolf ; but in his practice we find he 
 has reverted to methods nearly like those of Rumford, instead of continuing to 
 follow his own. The steam engine itself had also apparently obtained its most 
 simple and efficient form, except in the eyes of those who expected to use its direct 
 rotary action. The fact however was otherwise, for by a most simple change of 
 a previous combination it had to be materially improved. 
 
 1804. AUTHUR WOOLF. 
 
 57. The mode of condensation invented by Watt being now public property, and 
 the term of Hornblower's patent having expired, Mr. Woolf adopted the arrange- 
 ment of the latter, with the alteration of using high pressure steam in the small 
 cylinder, and employing the condensing apparatus of Watt. But a change of the 
 working force of the steam would have been too slight a ground to have claimed 
 a patent upon, and therefore he commences his specification with a claim of the 
 
 1 It is but justice to observe, that Mr. Murdock made his working model of a locomotive engine 
 in 1782, and that, as Mr. Trevithick was a pupil of Murdock's, then in Cornwall, it is natural to 
 suppose that he received many of his ideas of locomotion from that gentleman. 
 
SECT. 
 
 THE STEAM ENGINE. 43 
 
 discovery of a new law of the expansibility of steam. This law of expansibility he 
 stated, with much confidence, as the result of experiment ; but no doubt he had 
 deceived himself. His assumed law of expansion is, that steam generated at any 
 number of pounds above the pressure of the atmosphere will expand to an equal 
 number of times its volume, and still be equal in elastic force to the pressure of the 
 atmosphere, the temperature being unaltered : hence steam generated at forty 
 pounds on the square inch was expected to expand to forty times its bulk, and yet 
 be equal to the elastic force of the atmosphere. But it is a well-known law of the 
 expansion of fluids, that the temperature being constant, the bulk is inversely as 
 the pressure ; and calling the pressure of the atmosphere fourteen pounds, we have 
 14 : 14+40 : : 1 : 4, nearly. Therefore steam generated at fifty-four pounds on 
 the square inch, or forty pounds above the pressure of the atmosphere, would 
 expand only to four instead of forty times its volume. (See art. 120.) And though 
 Woolf s assertions were so directly opposed to the laws of the constitution of elastic 
 fluids, they have found their way as undoubted experimental truths into works 
 which ought to have high claims to respectability. 
 
 The employment of high pressure steam to act expansively by means of a double 
 cylinder, gives the utmost degree of power in the most equable manner and with 
 the most safety : hence either for machinery engines, or mine engines, it seems 
 the most economical mode of obtaining power. I object to strong steam on account 
 of its danger,- but my readers may not have like apprehensions. Woolf's other 
 patents are for projects of little if any value. 
 
 58. It would be an omission to pass without notice the exertions made by 
 Oliver Evans about this period to get into use the high pressure steam engine. 
 His scheme for employing it had not at first many supporters, and he had some 
 rivals. His engine differs little from that of Trevithick and Vivian in construction, 
 but from a work called ' The Abortion of the Young Steam Engineer's Guide,' 
 it appears, that the expansive force of the steam was to be employed. The ' Abor- 
 tion' is a curious work ; it betrays that strange mixture of absurd speculation and 
 indistinct perception of truth, which distinguishes the generality of enthusiastic 
 projectors, and is valuable only to those who can select by means of previous 
 knowledge or experience. A volcanic steam engine, and the idea of employing 
 the force of solar heat by means of a burning glass to work an engine, are among 
 his projects. 
 
 59. The claims of our American brethren to improvement, and to judicious 
 construction and application, are however much stronger than those of our conti- 
 nental neighbours ; and of American claims we have reason to speak with pride 
 rather than with other feeling. British genius and industry have not been extin- 
 guished by transplanting to another climate. It is true that many of the 
 
44 THE HISTORY OF [SECT. i. 
 
 projects they have yet formed are rather extravagant than novel, being seldom 
 founded on the sober reasoning of science. Time will, however, check this evil, 
 and we may expect them to hold that rank in the New World which Britain has 
 held with such honour for some centuries in the older portion. The chief object 
 of their engineers has been to render steam useful in navigation ; and considering 
 the importance to America of navigating her immense rivers, it is not surprising 
 that the application of the power of steam to propelling vessels should by perse- 
 vering efforts have been first carried into successful practice in that continent. 
 This was achieved through the activity and zeal of Mr. Fulton, who appears 
 evidently, however, to have derived much of his knowledge of the subject from what 
 was done in Scotland. The first American steam boat that completely succeeded 
 was launched at New York on the 3rd of October, 1807, fitted with a steam 
 engine made by Boulton and Watt for Mr. Fulton in 1804 ; * and soon afterwards 
 this vessel plyed between that city and Albany, a distance of 160 miles. 
 
 60. The successful introduction of steam navigation in Britain we owe to 
 Mr. Henry Bell, who in 1811 built a steam vessel according to his own plans, 
 with a forty feet keel, and ten feet six inch beam, fitted it up with an engine and 
 paddles, and called it the Comet, because it was built and finished the same year 
 that a large comet appeared. 
 
 Since that time the progress of steam navigation has been exceedingly rapid, 
 and has had a most beneficial influence on the trade of the country. 
 
 61. An almost innumerable quantity of schemes for improvements on the 
 steam engine have been crowded on the public eye within the last ten years ; but 
 except a few for improvements in construction, of small importance, there has 
 been nothing done that is worthy of detaining the reader to notice, towards either 
 the improvement of the engine, or of the mode of generating steam, so as to 
 increase the power of a given quantity of fuel. 
 
 62. Some valuable experiments on the elastic force, bulk, and latent heat of 
 steam, made by Mr. John Southern in 1803, were published by Mr. Watt ; and 
 the experiments of Dr. Ure and Mr. P. Taylor on the elastic force of steam have 
 led to a considerable advance in theoretical investigation. The improvements in 
 the manufacture of steam engines have also been important, but we have no 
 reason to expect any material increase of its power ; it seems to have reached its 
 limit, and we might equally hope to add strength to a man or a horse. New 
 modes of applying the power of steam may be devised, and new objects may be 
 found to which it may be applied with advantage ; and its theoretical principles 
 will become more generally and more perfectly known. 
 
 1 Fifth Report on Holyhead Roads' Steam Boats. Mr. Watt's letter, p. 210. 
 
SECT, i.] THE STEAM ENGINE. 45 
 
 It may also be found that the vapour of some other substance may be used with 
 advantage, in certain cases, instead of that of water ; of this, however, there is not 
 much hope ; and my reasons for this opinion will be shown in treating of the 
 properties of vapour, (art. 115.) Probably some other source of power will be 
 discovered which will divert the attention of projectors, and the only one in nature 
 which appears unemployed by man seems to be that of the electric fluid ; how far 
 it may be rendered useful is a matter of curious inquiry, and dangerous in propor- 
 tion to its power and our ignorance of its nature. 
 
 63. Some idea of the rapid progress of the application of steam power may be 
 formed from the circumstance, that, in the year 1789, the first steam engine was 
 erected in the town of Manchester : before that time the manufactories were 
 dispersed throughout the remotest districts, as they depended chiefly upon falls of 
 water for power, the more expensive one of animal force being the only remaining 
 expedient. The engines of Watt produced the most complete revolution in this 
 respect. The factories were transported from the most wild and inaccessible places 
 to towns and cities, and furnished with the means of uniting, under the same roof, 
 the various branches of manufacture ; so that the raw material is now, with 
 astonishing rapidity, converted into the most perfect cloth. 
 
 In Glasgow, the first steam engine erected for spinning cotton was put up in 
 January, 1792, by Mr. Robert Muir, at Scott, Stevenson and Co.'s cotton mill, 
 near Springfield. This was seven years after Boulton and Watt put up their first 
 steam engine for spinning cotton in Messrs. Robinsons' mills, at Papplewick, in 
 Nottinghamshire. 
 
 In the year 1812 (January 18) Mr. Henry Bell, of Helensburgh, completed his 
 vessel, the Comet, of thirty tons' burthen, with a steam engine of three horse power, 
 and launched her on the Clyde, at Glasgow. This was the first vessel successfully 
 propelled by steam in Europe. 
 
 The number of steam engines in Glasgow and its neighbourhood in 1825, as 
 collected by Dr. Cleland, is 
 
 Number of Engines. Horse power. 
 
 In manufactories 176 2970 
 
 In collieries 58 1411 
 
 In stone quarries 7 39 
 
 In steam boats - 68 1926 
 
 In Clyde iron works - 1 60 
 
 Total 310 6406 
 
 The average horses' power of the engines is 20f . 
 
46 HISTORY OF THE STEAM ENGINE. [SECT. i. 
 
 The steam engines in Great Britain and Ireland, employed in the year 1817 in 
 the manufacture of cotton yarn, amounted to more than 20,000 horses' power ; and 
 such has been the advantages resulting from the application of machinery, that one 
 person can produce more yarn in a given time, than 200 could have produced 
 about sixty years ago. 
 
 In the iron, woollen, and flax manufactures, the beneficial effects from employing 
 the steam engine have been equally important. 
 
 The total extent to which steam power is applied in Great Britain was estimated 
 by Baron Dupin, in 1825, to be equivalent to the power of 320,000 horses in con- 
 stant action ; and up to the present time it has prodigiously increased, indepen- 
 dently of our rapidly extending railways. To this immense command of power our 
 country owes much of its commercial prosperity, besides a vast addition to the 
 comforts and conveniences of life. 
 
 The increased employment of steam has however in no instance been so great 
 as in its application to navigation in Britain. A solitary steam boat navigated the 
 Clyde in 1812 ; in 1825, fifty-one steam boats plyed on that river : and from the 
 first successful trial in 1812, up to 1822, the number of steam vessels in Britain 
 increased to about 140, with a power equivalent to the exertion of 4700 horses, 
 and a tonnage of 16,000 tons. 1 
 
 64. In concluding this historical sketch, it is of some importance to remark, 
 that the whole tends to prove that the steam engine, in the highest state of perfec- 
 tion it has yet attained, is entirely of British origin. The remark extends to the 
 discovery of physical principles, as well as of mechanical combinations. No new 
 principle, no new combination of principles, has yet been derived from a foreign 
 source ; the most perfect of foreign steam engines being professedly copied from 
 British ones, and not unfrequently manufactured by British workmen. 
 
 1 From the establishment of Boulton and Watt alone, since 1814, a power has been sent forth 
 for propelling steam vessels amounting to 9143 horses, and employing a tonnage of 27,406 tons. 
 This, and the streams of power emanating from other factories, for the same exclusive purpose, 
 is immense. It cannot be doubted that steam navigation will be highly productive of benefit to 
 all civilized countries, and will contribute even to the cultivation and advancement of civiliza- 
 tion itself: there is no portion of the habitable globe, however remote, which may not in the 
 course of time derive advantage from the creations of Watt's genius. 
 
SECTION II. 
 
 OF THE NATURE AND PROPERTIES OF STEAM, ITS ELASTIC FORCE, 
 EXPANSIVE FORCE, AND POWER OF MOTION. 
 
 ART. 65. NATURAL bodies exist in three states ; the solid, the liquid, and the 
 gaseous. The state of many of them may be changed : thus, water may be in the 
 solid state as ice, in the liquid as water, in the gaseous as steam, and these 
 changes take place only under particular degrees of heat and pressure ; but there 
 are some gaseous bodies which cannot be reduced to the liquid form by the means 
 we at this time are acquainted with ; though there has been so much accomplished 
 as to render it tolerably certain, that all the gases known would be reduced to 
 liquids, were they exposed to sufficient pressure and reduction of temperature. 
 
 66. Those gases which are not changed into liquids by the ordinary changes 
 of temperature and pressure, are called PERMANENT GASES. 
 
 The gases which condense into liquids by the common changes of temperature 
 and pressure, are called VAPOURS, or STEAMS : we shall use the term ' steam' in 
 preference to 'vapour.' 
 
 67. Heat, free and uncombined, is diffused through all bodies in nature, 
 whether they be in the state of solids, liquids,' or gases ; and it constantly tends to 
 an equilibrium ; so that, when by any means it is accumulated in particular sub- 
 stances, a portion is quickly given off to the surrounding bodies, so as to bring the 
 whole to one common temperature. On the other hand, where bodies have been 
 deprived of a portion of it, heat is given off to them by, or heat passes to them 
 from, the surrounding bodies, to restore the equilibrium. 
 
 68. When there is an equilibrium of heat, or the adjoining bodies are of the 
 same temperature, if it be destroyed by the introduction of a fresh quantity of heat, 
 different bodies will be found to absorb different quantities of the new portion of 
 heat in restoring the equilibrium. The peculiar quantity which each body absorbs 
 under the same circumstances, is denominated the SPECIFIC HEAT of that body. In 
 
48 THE NATUKE AND [SECT. n. 
 
 comparing the specific heats of bodies, that of water at 60 is considered to be 
 unity, and therefore becomes a measure of all the rest. 1 
 
 69. The property of bodies to hold different quantities of heat at the same 
 temperature, is sometimes called CAPACITY FOR HEAT ; but this term should be applied 
 only to the whole quantity of heat in a body, otherwise it becomes the same as 
 specific heat. Hence, when I speak of the capacity of a body for heat, it must be 
 understood as applied to the whole quantity of heat the body contains. 
 
 70. The dimensions of bodies are enlarged when heat is poured into them, 
 and they contract when it is taken from them : and the natural consequence of 
 bodies absorbing different quantities of heat to cause an equal change of tempera- 
 ture, is, that they do not all expand nor contract alike by the change. 
 
 The incontrovertible fact, that different substances have different capacities for 
 heat, being established, another necessarily presents itself, which, though it could 
 not possibly escape observation, has seldom been properly applied : it is, that in 
 everj 7 chemical change we effect, we are altering the capacities of bodies for heat, 
 and, consequently, deranging the equilibrium of heat ; for the products differ in 
 their capacity from the ingredients. 
 
 71. By the mere addition of heat many solids assume the form of liquids, and 
 liquids the gaseous state. On the other hand, gases, by an abstraction of heat, 
 become liquids, and liquids solids. But even this change of state is accompanied 
 by a change of capacity. The capacity of steam for heat is greater than that of 
 water ; for steam requires an additional quantity of heat ; and that heat which is 
 required to expand the particles of a liquid to the distance they are apart in the 
 state of steam, does not affect the thermometer ; that is, when a given quantity of 
 water, after being heated to 212, is converted into steam of the same temperature, 
 the heat necessary to produce the entire change, from water to steam, would raise 
 the temperature of nearly six times as much water from the mean temperature 
 to 212. 
 
 72. The heat absorbed by steam or vapour during its formation, is called 
 LATENT HEAT : it is, however, a term which conveys a false notion of the state of heat 
 in bodies ; for the heat is not latent, it is simply a difference of quantity, and not 
 of quality ; and some term that would convey a more accurate idea of the pheno- 
 mena would be better. 
 
 1 The specific heat of a body is the quantity of heat requisite to change its temperature any 
 stated number of degrees, compared with that which would produce the same effect on water at 
 60 ; and it is therefore expressed by the fraction 
 
 quantity of heat to change the temperature by any given amount, say 1 
 quantity of heat to change an equal weight of water at 60 by the same amount. 
 An equal volume of water may be taken instead of an equal weight. In any case, therefore, it is 
 necessary to understand whether the term ' specific heat ' is applied to volumes or weights. 
 
SECT, ii.] PROPERTIES OF STEAM. 49 
 
 73. The heat combined or disengaged by a change of the state of a 
 body, called latent heat, is measured in the same manner as specific heat ; that is, 
 by means of the quantity of heat necessary to raise the temperature of water 
 one degree at 60. 
 
 It was the eminent Dr. Black who first discovered (in 1762) that a change of 
 state in natural bodies requires a certain addition or diminution of heat ; and that 
 the quantity is different for different bodies, and also different according to the 
 nature of the change. The importance of this discovery to general science is great, 
 and its finest practical application is to the principles of the steam engine. 
 
 74. The additional heat in the vapour or steam of any liquid is not very 
 easily determined ; but since the discovery of Dr. Black, experiments have been 
 made by several philosophers, distinguished for their accuracy and skill in such 
 delicate researches. The method adopted by Dr. Black is simple and easily tried, 
 but not accurate. When a vessel containing water is placed on a fire, the water 
 gradually becomes hotter till its temperature reaches 212, but after that its tempe- 
 rature does not increase. The water is flying off" in steam, and the heat not raising 
 the temperature higher, as we know it would do if the vessel were closed, we 
 must conclude, that the heat which would be communicated to the water in a 
 close vessel combines with the steam in an open one, and yet does not increase the 
 temperature of that steam to more than that of boiling water. To ascertain the 
 quantity of heat which is combined with steam, Dr. Black put some water in a tin 
 plate vessel upon a red hot iron. The water was of the temperature 50; in four 
 minutes it began to boil, and in twenty minutes it was all boiled off". During the 
 first four minutes it had received 162 or 40|- per minute. If we suppose that it 
 received as much per minute during the whole process of boiling, the heat which 
 entered into the water and converted it into steam would amount to 40j x 20 = 
 810. This 810 degrees of heat is not indicated by the thermometer, for the tem- 
 perature of steam is only 212; therefore Dr. Black called it latent heat. * But the 
 result is obviously inaccurate, because steam is formed during the heating of the 
 water to the boiling point, and the vessel is losing heat from its surfaces in un- 
 equal quantities ; and the effect of the fire is also unequal, being less as the heat of 
 the water increases. 
 
 75. The heat required to form steam may be more accurately determined by 
 condensing the steam by a cold fluid, and the heat communicated to the fluid by 
 a given weight of steam gives the additional quantity of heat contained in the 
 steam. Mr. Watt made various trials in this manner in 1781, and those on which 
 he placed the most reliance gave 950 for the additional heat in the steam of 
 
 1 Dr. Thomson's System of Chemistry, vol. i. p. 101. 
 
 G 
 
50 THE NATURE AND [SECT. n. 
 
 water. J Count Rumford, Mr. Southern, and Dr. Ure also made experiments on 
 this principle. 2 
 
 Also water may be heated in Papin's digester to 400 without boiling ; because 
 the steam is forcibly compressed, and prevented from making its escape. If when 
 heated to 400 the mouth of the vessel be suddenly opened, part of the water 
 rushes out in the form of steam, but the greater part still remains in the form of 
 water, and its temperature instantly sinks to 212; consequently, 188 of heat 
 have suddenly disappeared. This heat must have been carried off by the steam. 
 Now as about one-fifth of the water is converted into steam, that steam must con- 
 
 1 Watt's Notes on Robison's Mech. Phil. vol. ii. p. 7. 
 
 2 This mode of conducting the experiment has sometimes led to erroneous results, through a 
 want of attention to the mode of calculation. The quantity of heat being measured by the specific 
 heat of water, let 
 
 W be the weight of water used to condense the steam ; 
 t, its temperature after the steam has been condensed in it ; 
 t', the quantity its temperature is raised ; 
 w, the weight of steam ; 
 s, its specific heat when condensed ; 
 
 and x the whole heat required for its formation into steam. 
 
 Then the heat communicated to the water by the steam, is as its weight multiplied by the rise 
 of temperature, or W /. 
 
 The condensed steam has the temperature t after the operation ; and as its whole heat was x w 
 before condensation, it must be t s w after. Therefore 
 W t' = x to t s w, 
 
 W if 
 
 or + t s = x = the measure of the heat that will form the weight 
 
 10 
 
 of steam w. 
 
 If T be the temperature of the steam before condensation, and s' its specific heat ; then 
 
 W t' 
 
 1- t s T s' = the heat of conversion into steam ; 
 
 w 
 
 and it appears from experiment to be nearly a constant quantity for the same liquid. 
 
 But it is usual to suppose the specific heat of equal weights of the steam and the liquid which 
 forms it to be the same, and then 
 
 W t' 
 
 s (T t) = the heat of conversion. 
 
 w 
 
 And for water where s=l, it becomes 
 
 W t' 
 
 + t T = the heat of conversion. 
 
 w 
 
 Hence we have this RULE : Multiply the weight of the water used to condense the steam by the 
 increase of its temperature, and divide the product by the weight of the condensed steam. The 
 quotient will express the quantity of heat evolved from the steam, and by adding to it the tempe- 
 rature after condensation, the sum will express the total amount of heat ; from which, deducting the 
 temperature of the steam before condensation, there will remain the quantity of heat due to the 
 conversion into steam. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 51 
 
 tain not only its own 188, but also the 188 lost by each of the other four parts ; 
 that is to say, it must contain 188 x 5, or about 940 of heat. 
 
 76. The experiments of Dr. Black are not greatly different from the result 
 obtained by Schmidt, for the latter found the heat of steam to be 5'33 times the 
 heat which is required to boil water of the temperature 32, the barometer being 
 at 29*84 inches. l This is the best mode of expressing the heat, for there is reason 
 to believe that the specific heat of water is not the same for every rise of tempe- 
 rature. But to reduce it to the usual measure in degrees, there are 180 between 
 the boiling and freezing point, hence 180x5-33=959 0> 4 for the additional heat of 
 steam. 
 
 77. Mr. Southern, and Mr. W. Creighton in 1803, made some experiments 
 by condensing steam with a considerable degree of care ; the steam being gene- 
 rated at different temperatures and pressures. The pressure, temperature, heat of 
 formation, and bulk of the steam, from a cubic inch of water, are shown in the 
 following table : 
 
 Pressure in inches 
 of mercury. 
 
 Temperature. 
 
 Heat required to 
 form the steam. 
 
 Bulk of steam 
 from one cubic 
 inch of water 
 at 60. 
 
 Bulk calculated 
 from the first ex- 
 periment. 
 
 40 
 
 229 
 
 1157 
 
 208 
 
 1208 
 
 80 
 
 270 
 
 1244 
 
 588 
 
 635 
 
 120 
 
 295 
 
 1256 
 
 404 
 
 427 
 
 If from the whole heat we deduct the difference of temperature, we have 1 157, 
 1203, and 1190; whence it appears that the heat to form steam is nearly a 
 constant quantity when the temperature is the same, being independent of the 
 density. 
 
 Therefore the most convenient mode of expressing the quantity of heat is that 
 adopted by Mr. Southern, which consists in ascertaining the constant quantity of 
 heat required to be added to the actual temperature of the steam to give the whole 
 heat necessary to form it. This quantity is 
 
 1157-229=928; 1244-270=974; and 1256-295=961; and the mean 
 is 954. 
 
 In another set of experiments, made under the same pressures and tempera- 
 tures, the quantities of heat required in addition to the temperature were 942, 942 
 and 950, 2 the mean being nearly 945, and the mean of both sets 949. In this 
 set of experiments an allowance was made for the heat communicated to the 
 vessel ; in the former set none was made. 
 
 1 Nicholson's Philosophical Journal, vol. v. p. 208. octavo series. 
 
 2 Robison's Mechan. Phil. vol. ii. p. 160166. 
 
52 THE NATURE AND [SECT. n. 
 
 These experiments are valuable, because they afford a proof that the additional 
 heat required for steam is either accurately or nearly a constant quantity. 1 
 
 78. And they also show that the bulk or volume of steam is inversely as the 
 pressure, when the temperature is not altered. For as 80 : 40 : : 1208 : 604, which 
 added to the expansion would be 635, nearly; and 120 : 40 : : 1208 : 402, and 
 adding the expansion it is 427, nearly ; and conversely the density is directly 
 as the pressure ; the experiments being quite as near as could be expected in so 
 extremely delicate an operation. 
 
 79. Count Rumford obtained a higher result ; and from his known skill in 
 such inquiries, much confidence may be placed in his experiments. The heat 
 was measured by means of the temperature communicated to a copper vessel 
 filled with water, which he called his calorimeter. Within this calorimeter a thin 
 serpentine pipe of copper contained the steam to be condensed ; hence the fluids 
 did not mix together, and loss by the escape of vapour was prevented. 
 
 The water which the calorimeter contained was of a lower temperature than that 
 of the room by 5 or 6 ; and when the thermometer of the calorimeter announced 
 an augmentation of temperature of 10 or 12, an end was put to the experiment. 
 
 The water produced by the condensation of the vapour in the serpentine was 
 carefully weighed, and from its quantity, as well as from the heat communicated 
 to the calorimeter, the heat developed by the vapour in its condensation was deter- 
 mined. 
 
 As a small part of the heat communicated to the calorimeter was produced 
 from the cooling of the water, condensed in the serpentine pipe after the vapour 
 had been changed into water, an account was kept of this heat. It was supposed 
 that the water at the moment of condensation was at the temperature of 212, 
 being that of boiling water ; and it was determined by calculation, what part of 
 the heat communicated to the calorimeter must have been owing to the boiling- 
 water. 
 
 In making this calculation, Count Rumford remarks, no " account was taken of 
 the difference in the capacity of water for heat, which depends on its temperature : 
 this is but imperfectly known ; and besides, the correction which would have been 
 the result could not but have been very small." 
 
 The following are the details and results of two experiments made on the 21st 
 of January, 1812. The duration of each of the two experiments was from ten to 
 eleven minutes. The water had been boiled for some time to drive out the air 
 which it contained, before the steam was directed into the serpentine pipe of the 
 calorimeter. 
 
 1 M. Despretz, Ann. de Chim. et de Phys. xxiv. 329. makes it 955 c -8. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 53 
 
 Temperature of 
 the room. 
 
 State of the calorimeter, equal in specific heat to 
 42909 grains of water. 
 
 Quantity of va- 
 pour condensed 
 into water. 
 
 Heat of conver- 
 sion of the water 
 into vapour 
 in degrees. 
 
 Temperature at 
 the beginning. 
 
 Temperature at 
 the end. 
 
 Elevation of its 
 temperature. 
 
 61 
 62i 
 
 551 
 57 
 
 67i 
 67| 
 
 121 
 
 10* 
 
 Grains. 
 
 457 
 377 
 
 1029-3 
 1052-3 
 
 Mean - - 1040-8 > 
 
 The result of the second experiment being compared by our formula, (note to 
 
 art. 75,) we have 
 
 42909 x 
 
 o77 
 
 from whence, deducting 212 on the supposition that the specific heat of steam is 
 equal to that of water, we have 1050 0> 5 for the constant quantity of heat for con- 
 version into steam. The very small difference between this and Count Rumford's 
 result, arises from the fractions neglected in reducing the French to English weights. 
 80. Count Rumford also made experiments on the quantity of heat developed 
 in the condensation of the vapour of alcohol : the results of these experiments were 
 less regular than those of the experiments made with water, as might have been 
 expected, but they were nevertheless sufficiently uniform to give the quantity of 
 heat with considerable certainty. 
 
 The vapour which is extricated from spirit of wine, when boiled, varies a little 
 with the intensity of the fire used in boiling it ; he took care therefore to note the 
 time which was taken in every experiment, in order to be able to judge, by com- 
 paring the quantity of vapour condensed with the time employed to form it, of 
 the intensity of the heat employed to boil the liquid. In the following table will 
 be found the details and results of five experiments made on the same day, 
 (January 21, 1812,) with alcohol of different degrees of strength. The specific heat 
 of the calorimeter and the water it contained, was always equal to that of 42909 
 grains of water ; and the thermometer employed was that of Fahrenheit. 
 
 
 
 
 State of the calorimeter. 
 
 
 
 Specific gra- 
 vity of the 
 alcohol em- 
 ployed. 
 
 Time em- 
 ployed in the 
 experiment. 
 
 Temperature 
 of the apart- 
 ment. 
 
 Temperature 
 at the begin- 
 ning. 
 
 Temperature 
 at the end. 
 
 Elevation of 
 its tempera- 
 ture. 
 
 Quantity of 
 alcohol con- 
 densed in the 
 calorimeter. 
 
 Heat of con- 
 version of the 
 liquid into 
 vapour. 
 
 
 
 
 
 
 
 Grains 
 
 
 81763 
 
 4i min. 
 
 61 
 
 56 
 
 661 
 
 10JP 
 
 875 
 
 479 Q -92 
 
 84714 
 
 8 
 
 eo* 
 
 55i 
 
 65i 
 
 10 
 
 755 
 
 500-03 
 
 85342 
 
 7 
 
 61 
 
 54i 
 
 681 
 
 i 
 
 1079 
 
 499-54 
 
 85342 
 
 5 
 
 61 
 
 56 
 
 661 
 
 iof 
 
 805 
 
 476-83 
 
 85342 
 
 6*- 
 
 64 
 
 57 
 
 711 
 
 141 
 
 1102 
 
 499-65 
 
 
 
 
 
 
 
 Mean - 49113 
 
 1 Philosophical Mag. vol. xliii. p. 65. 
 
54 THE NATURE AND [SECT. 11. 
 
 On determining, by calculation, the quantity of water which may be heated 
 one degree, by the heat developed in the condensation of the vapour, he took care 
 to keep an account of the difference of the capacity of water for heat from that of 
 alcohol. l 
 
 The result of Count Rumford's calculation is nearly the same as by the formula, 
 (art. 75, note,) when we assume the specific heat of the alcohol vapour and liquid 
 to be the same, and equal to 58. Thus from the second experiment 
 
 42909_x 10 + (>5g x Q.^ = ^.^ 
 
 from whence, deducting 173 x -58 for the heat due to the temperature of the 
 vapour, we have 506 nearly, for the heat of conversion from liquid to vapour. 
 The Count's number is 500-03. 
 
 Count Rumford also ascertained that the vapour of sulphuric ether afforded 
 only about half the heat in condensation that alcohol afforded, or one-fourth of 
 the heat furnished by condensing the steam of water. 
 
 81. Important as a knowledge of the heat of conversion into vapour is, it was 
 not further investigated till 1817, when Dr. Ure made a few experiments on diffe- 
 rent bodies. 2 His mode of experiment was exceedingly simple. The apparatus 
 consisted of a glass retort of very small dimensions, with a short neck, inserted 
 into a globular receiver, of very thin glass, about three inches in diameter. The 
 glass was fixed steadily in the centre of 32340 grains of water, at a known tempe- 
 rature, contained in a glass basin. Of the liquid, whose vapour was to be 
 examined, 200 grains were introduced into the retort, and rapidly distilled into the 
 globe by the heat of an Argand lamp. The temperature of the air was 45, that 
 of the water in the basin from 42 to 43 ; and the rise of temperature occasioned 
 by the condensation of the vapour never exceeded that of the air by four degrees. 
 As the communication of heat is very slow between bodies which differ little in 
 temperature, the air could exercise no perceptible influence on the water in the 
 basin during the experiment, which was always completed in five or six minutes. 
 A thermometer of great delicacy was continually moved through the water, and its 
 indications were read off, by the aid of a lens, to small fractions of a degree. 
 
 The distillation was rapidly performed ; and we are assured by Dr. Ure, that in 
 the numerous repetitions of the same experiment, the accordances were excellent. 
 The following table gives the mean result, the last column being calculated by the 
 formula, (of note to art. 75.) 
 
 i Philosophical Mag. vol. xliii. p. 67. Philosophical Transactions for 1818. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 55 
 
 
 
 Temperature of the water in the basin, 
 
 
 
 
 
 
 
 
 
 Heat of con- 
 
 Liquid. 
 
 Specific 
 
 At the 
 
 At the end. 
 
 Difference. 
 
 Boiling point. 
 
 version into 
 
 
 gravity. 
 
 beginning. 
 
 
 
 
 vapour. 
 
 Water 
 
 1-000 
 
 42 -5 
 
 49- 
 
 6-5 
 
 212 
 
 942- 
 
 Alcohol 
 
 0-825 
 
 42- 
 
 45- 
 
 3- 
 
 175 
 
 425-5 
 
 Sulphuric ether 
 
 0-7 
 
 42- 
 
 44. 
 
 2- 
 
 112 
 
 302-6 
 
 Oil of turpentine 
 
 0-888 
 
 42- 
 
 43-5 
 
 1-5 
 
 316 
 
 146-0 
 
 Petroleum 
 
 0-75 
 
 42-5 
 
 44- 
 
 1-5 
 
 306 
 
 150-0 
 
 Nitric acid 
 
 1-494 
 
 42- 
 
 45-5 
 
 3-5 
 
 165 
 
 517-0 
 
 Ammonia 
 
 0-978 
 
 42- 
 
 47-5 
 
 5-5 
 
 140 
 
 840-0 
 
 Vinegar 
 
 1-007 
 
 42-5 
 
 48-5 
 
 6- 
 
 
 870-0 
 
 The quantity of water of which the specific heat would be equivalent to the 
 heat absorbed by the vessels, Dr. Ure has not given ; but in assuming it to be 
 about 1660 grains, we shall be not far distant from the truth. Hence we have 
 32340 + 1660=34000 for the water equivalent to the specific heat of the cooling 
 apparatus ; and by the formula, (art. 75, note) 
 34000 x 6-5 
 
 And 
 
 200 
 
 34000x3 
 200 
 
 +49212 = 942, for water. 
 
 + -65 (175-45) = 425-5, for alcohol. 
 
 The others being calculated in the same manner, afford the results in the last 
 column, taking the specific heat from the usual tables. Through an oversight in 
 calculation, Dr. Ure's numbers in the ' Philosophical Transactions ' are erroneous. 
 
 82. A further correction might be applied for the quantity of steam remaining 
 in the retort, and the loss of heat in the operation. Dr. Ure has, in a recent cor- 
 rection for loss of heat, made the heat of conversion of water into steam 1000 ; and 
 under the impression that Count Rumford's are the most accurate experiments on 
 the subject, I am inclined to think this number about right. If for these sources 
 of loss we make a further allowance in Dr. Ure's experiments of the specific heat of 
 2000 grains of water, we shall have 
 
 36000x6-5 
 
 200 
 
 + 49-212 = 1007; 
 
 and correcting the rest of the numbers in this manner, the following are obtained. 1 
 
 Liquid. 
 
 Equal 
 weights. 
 
 Equal 
 volumes. 
 
 Liquid. 
 
 Equal 
 
 weights. 
 
 Equal 
 volumes. 
 
 Water into steam 
 
 1007 
 
 1007 
 
 Petroleum into vapour 
 
 165 
 
 124 
 
 Alcohol into vapour 
 
 455-5 
 
 375 
 
 Nitric acid into vapour 
 
 552 
 
 830 
 
 Sulphuric ether into vapour 
 
 322-6 
 
 227 
 
 Ammonia into vapour 
 
 895 
 
 875 
 
 Oil of turpentine into vapour 
 
 161-0 
 
 143 
 
 Vinegar into vapour 
 
 930 
 
 930 
 
 Ure's Dictionary of Chemistry, art. Caloric. 
 
56 THE NATURE AND [SECT. n. 
 
 Having followed through the best information hitherto laid before the public, on 
 the heat required to produce steam, our next object must be to convert it into a 
 form more directly useful for our purpose ; for the quantity of heat which converts 
 a liquid into vapour, requires the additional facts of the volume of the vapour, 
 and its elastic force, to render it valuable. 
 
 OF THE ELASTIC FORCE OF STEAM. 
 
 83. To obtain a rule for determining the force of steam at any temperature, or 
 the temperature corresponding to any given force, we must have recourse to a rule 
 found by trial from the best experiments : it is not a satisfactory method, but we 
 have no other means of arriving at a rule in a case where the real causes of vari- 
 ation are not understood. We still, however, may gain some assistance, from pre- 
 vious reasoning, in forming our conclusions. In the first place, the index of the 
 power representing the law of variation must be of such a simple kind as to render 
 it probable that it is the true one. Hence the index 5'13 employed by Mr. 
 Southern l is not likely to represent the law of nature : Mr. Creighton's index 6, 2 
 or Dr. Young's, which is 7, s are either of them more likely to be accurate. The 
 true equation may be very complex, but this is not probable, and while we are 
 ignorant of its nature, and can represent the results sufficiently near for practical 
 use, by one index, it is best to adopt the simplest form, and particularly when it is 
 equally as likely to be the true one as one of a more complex kind. In any 
 attempt to find the index by the usual method of differences, the errors of expe- 
 riment will have too great an influence. 
 
 84. Secondly. It appears probable that there is a degree of cold at which 
 steam cannot exist ; * and this must be the case when it is condensed by cold, till 
 the cohesive attraction of the particles exceeds the repellent force of the caloric 
 interposed between them ; and the change from an elastic fluid to a solid may then 
 take place without the intermediate stage of liquidity. This physical circumstance 
 enables us to fix another element in the calculation ; for there must be a tem- 
 perature when the force is nothing. 
 
 85. Thirdly. The greatest possible force of steam must next be considered ; 
 for we are certain that our formula must be in error if it exceeds that limit. 
 Suppose a given quantity of water, a cubic inch for example, to be confined in a 
 
 1 Robison's Mechanical Phil. vol. ii. p. 172. - Phil. Mag. vol. liii. p. 266. 
 
 3 Natural Phil. vol. ii. p. 400. 
 
 * An interesting paper on this subject by Mr. Faraday renders it equally so, and shows that 
 the limit is different for different vapours : my formula had led me to the same conclusion ; 
 hence it has another property, justified by experience. See Phil. Mag. vol. kviii. p. 344. 
 
SECT, ii.] PROPERTIES OF STEAM. 57 
 
 close vessel which it exactly fills ; and that in this state it is exposed to a high tem- 
 perature. Then, as the bulk when expanded is to the quantity the bulk is increased 
 by expansion, without change of state, so is the modulus of elasticity of water of 
 that temperature to the force of steam of the same density as water. If our rule 
 therefore gives steam a greater force than this at the same density and temperature, 
 it must be erroneous. With these limitations we must in a considerable degree be 
 guarded against error, and the method followed is next to be explained. 
 
 86. Let / be the elastic force of steam, in inches of mercury, and t the cor- 
 responding temperature ; and let a be the temperature at which the expansive force 
 is 0. Consider f the abscissa, and t a the ordinate of a curve, of which the 
 equation is A/= (ta) n , whence the coefficient 
 
 Let the abscissa increase to /', and the ordiuate to t'a ; then 
 
 (t-a) n = (t'-a) . Qr log. /' - log. / = n 
 
 f f log. (t'-a) - log. (t-a) 
 
 Now, if these points be near one extremity of the range of experiment, and two 
 other points be taken near the other extremity, then 
 
 log. /'" - log. /" 
 
 , - g-^ - , J - = n. and consequently 
 log. (f"-a) - log. (t'-a) 
 
 log, f" - log. /" = log, (f"-a) - log, (t'-a) 
 log. /' - log. / log. (t'-a) - log. (t-a) 
 
 From four results of Mr. Southern's experiments on steam from water, we find 
 that a =100 very nearly satisfies the conditions; and this value of a being 
 inserted, we find n=6 and A=177, or its logarithm =2'24797. 
 
 Therefore, for water, 
 
 In logarithms, 
 
 log. /=6 log. (t + 100) - 2-24797 . 
 
 87. If the expansion of confined water, when its temperature is raised to 1150 
 degrees of heat, be 0-9693 of its bulk, the force necessary to confine it to its bulk at 
 60, when exposed to a heat of 1150, the modulus of water being 22100 atmo- 
 spheres at 60, would be about 6925 atmospheres. 1 Our rule gives for the force of 
 
 1 The expanding power of heat, and the decrease of the modulus of elasticity, must be in the 
 same ratio ; and most probably both vary as the square of the central distances of the atoms, and 
 
 H 
 
58 
 
 THE NATURE AND 
 
 [SECT. u. 
 
 steam at that temperature and density 4137 atmospheres; and in the uncertainty 
 both as to what the actual expansion of water would be in such high temperatures, 
 and the decrease of its modulus, it is more prudent to be within than beyond the 
 limit. But at or near the temperature 1150, the rule will cease to be of any use, 
 because then it is simply the expansive power of compressed water ; and it varies 
 as the quantity of water expands by a given change of temperature. 
 
 Having thus far explained the methods by which the rules have been obtained, it 
 only remains to give them the most simple form for use, with illustrative examples. 
 88. RULE i. To find the force of steam from water in inches of mercury, the 
 temperature being given. 1 
 
 consequently as the - power of the volume. Hence, if e be the expansion, the original bulk being 
 unity, and m the modulus, it must be 
 
 , = the modulus at any expansion e ; 
 
 m e 
 
 and consequently (by art. 85.) 
 
 the force of compression capable of retaining the fluid in its original state of density. 
 
 The expansion varies as the expanding power of heat, and as the temperature ; hence it will be 
 as the f power of the temperature ; and it must be at 40 : consequently, A (/ 40)=e, and as 
 from 40 to 212 it is found to be -04333, we have f log. (t 40) 5-08909=e ; which suggests 
 the following Rule : Subtract 40 from the temperature ; under the logarithm of the difference, 
 write its one-third part twice over, and add all three up ; from the sum subtract 5-08909, and the 
 remainder will be the logarithm of the expansion. 
 
 The agreement of this formula and rule with experiment is shown in the following table : 
 
 Temperature. 
 
 Expansion by 
 formula. 
 
 Expansion by 
 experiment. 
 
 Temperature. 
 
 Expansion by 
 formula. 
 
 Expansion by 
 experiment. 
 
 40 
 
 0-00 
 
 0-00 
 
 400 
 
 0-1484 
 
 
 64 
 
 0-00159 
 
 0-00133 
 
 800 
 
 0-5155 
 
 
 102 
 
 0-00791 
 
 0-0076 
 
 1150 
 
 0-9693 
 
 
 212 
 
 0-0433 
 
 0-04333 
 
 1171 
 
 1-0000 
 
 
 In the equation for the force at 1150 degrees of temperature, we have 
 
 me _ 22100 x -9693 
 
 (1-9693)* 
 
 = 6925 atmospheres. 
 
 : Mr. Southern's Rule, which applies with considerable accuracy up to very high temperatures 
 and pressures, is in substance as follows : 
 
 Add 51-3 to the temperature, and multiply the logarithm of the sum by 5-13 ; from the pro- 
 duct deduct 10-94123 ; then, finding the natural number answering to the remainder, and 
 increasing it by one tenth, the result will express the required pressure in inches of mercury. 
 
SECT, ii.] PROPERTIES OF STEAM. 59 
 
 Add 100 to the temperature, and divide the sum by 177 ; the sixth power of the 
 quotient is the force in inches required. 
 
 Example. To find the force of steam for the temperature 312. 
 
 312+100 _ 0.0077 
 -- 
 
 Raise this to the sixth power, and it gives 159 inches for the force of the steam in 
 inches of mercury. 
 
 Or by logarithms. Add 100 to the temperature, and from the logarithm of this 
 sum subtract 2*24797 ; and six times the difference is the logarithm of the force 
 in inches of mercury. 
 
 Example. To find the force of steam for the temperature 250. 
 
 Log. (250 + 100=350) is - 2-54407 
 Subtract constant log. - 2*24797 
 
 Difference - 0-29610 
 
 6 
 
 Log. of force in inches of mercury = log. 59*79 = 1-77660 
 
 89. RULE n. The force of the steam of water being given to determine its 
 temperature. 
 
 Multiply the sixth root of the force in inches by 177, and subtract 100 from the 
 product, which gives the temperature required. 
 
 Example. Let the force of steam be eight atmospheres, or 240 inches of mer- 
 cury, to find its temperature. 
 
 The sixth root of 240 may be easily found by a table of squares and cubes, by 
 first finding its square root, and then the cube root of the square root. Thus the 
 square root of 240 is 15*492, and the cube root of 15*492 is 2*493 ; hence, 
 (2*493 x 177) - 100=341-20. Mr. Southern's experiment gives 343'6. 
 
 Or by logarithms. To one-sixth of the logarithm of the force in inches add 
 2-24797 : the sum is the logarithm of a number, from which 100 being subtracted 
 the remainder will be the temperature required. 
 
 Example. Let the force of steam be equal to sixty inches of mercury, which is 
 nearly fifteen pounds on the square inch above the pressure of the atmosphere, to 
 find its temperature. 
 
60 
 
 THE NATURE AND 
 Log. 60 is - - 1-77815 
 
 and one sixth is 
 constant log. 
 
 Log. 350-2 - 
 
 [SECT. ii. 
 
 0-29636 
 2-24797 
 
 2-54433 
 
 from which subtract 100, and it gives 250 0> 2 for the temperature. Mr. Southern's 
 experiment gives 250 g 3. 
 
 90. When sea water is employed, as it boils at a different temperature, the 
 force of the steam is different. The correction in the rules is easily made by find- 
 ing the constant number which corresponds to a force of thirty inches of mercury, 
 at the boiling point, with different degrees of saturation with salt. Many of the 
 people employed about boat engines are not yet aware that there is a difference 
 between the temperature of steam from common water, and that from salt water, 
 when the force is the same. I will show in another place (Sect, iv.) the effect this 
 has on the power of the steam engine, but at present our object is to determine the 
 force of the steam. Mr. James Watt was the only person who had made experi- 
 ments on the steam of salt water ; they were made in 1774. 1 He does not give 
 them as being very accurate ones, but they are sufficient to establish the fact that 
 there is a difference ; and Mr. Faraday has lately had occasion to satisfy himself 
 on the same point, by various experiments. 2 
 
 91. The following table gives the boiling points of solutions of different salts 
 in water. 
 
 Name of salt. 
 
 Dry salt in 100 
 parts by weight 
 of the solution. 
 
 Boiling point. 
 
 Authority. 
 
 Acetate of soda 
 Nitrate of soda 
 Common salt 
 Muriate of soda 
 Ditto 
 Sulphate of magnesia 
 Sulphate of lime 
 Alum 
 Sulphate of iron 
 Sulphate of soda 
 Ditto 
 
 60 
 60 
 37 
 30 
 
 57-5 
 45 
 52 
 64 
 31-5 
 
 256 
 246 
 226 
 224 
 222-35 
 222 
 220 
 220 
 216 
 213 
 217-6 
 
 Griffiths. 3 
 
 My trials. 
 Griffiths. 
 Achard. 4 
 Griffiths. 
 
 
 
 
 Achard. 
 
 1 Robison's Mechanical Phil. vol. ii. p. 34. " Quarterly Journal of Science, vol. xiv. p. 440. 
 3 Quarterly Journal of Science, vol. xviii. p. 90. 4 Thomson's Chemistry, vol. ii. p. 14. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 61 
 
 92. According to the analysis of Dr. John Murray, 10,000 parts of sea water, 
 of the specific gravity 1-029, 1 contain 
 
 Muriate of soda 220-01 
 
 Sulphate of soda - 33-16 
 
 Muriate of magnesia - 42'08 
 
 Muriate of lime - - 7 -84 = ITTS- 
 
 = 4V 
 
 = TJTJ 
 
 303-09 = A 
 Or 1 part of sea water contains '030309 parts of salts = TJ of its weight. 
 
 93. Now as the salts do not rise with the steam, the water in a boiler supplied 
 with sea water becomes gradually more saturated, and after a certain time begins 
 to deposit salt, if the means that have been invented for that purpose be not 
 employed to prevent it. 2 (See Sect, m.) And even then a certain degree of 
 saturation must be allowed to take place. The following table, with the constant 
 numbers for different degrees of saturation, will serve to illustrate this matter. The 
 boiling point of water appears to be increased one degree by each addition of 2'6 
 parts to the proportion of common salt in 100 parts of water ; at least, so nearly, 
 that this regular law does not materially differ from the mean results of my experi- 
 ments, which were made with a considerable degree of care ; but it is difficult to 
 make them, on account of the degree of saturation constantly varying during the 
 experiment. 
 
 Proportion of salt in 100 parts by weight. 
 
 Boiling point. 
 
 Constant number. 
 
 Constant log. 
 
 Saturated J 3fi . 37 = ^ 
 solution J 
 
 226 
 
 185-0 
 
 2-26703 
 
 33-34 = U 
 
 224-9 
 
 184-3 
 
 2-26556 
 
 30-30 = 
 
 223-7 
 
 183-6 
 
 2-26396 
 
 27-28 = & 
 
 222-5 
 
 183-0 
 
 2-26234 
 
 24-25 = A 
 
 221-4 
 
 182-3 
 
 2-26086 
 
 21-22 = & 
 
 220-2 
 
 181-6 
 
 2-25923 
 
 18-18 = A 
 
 219-0 
 
 181-0 
 
 2-25760 
 
 15-15 = & 
 
 217-9 
 
 180-4 
 
 2-25610 
 
 12-12 = & 
 
 216-7 
 
 179-7 
 
 2-25446 
 
 9-09 = ^ 
 
 215-5 
 
 179-0 
 
 2-25281 
 
 6-06 = ^ 
 
 214-4 
 
 178-3 
 
 2-25130 
 
 Sea water 3-03 = ^ 
 
 213-2 
 
 177-6 
 
 2-24950 
 
 Common water o 
 
 212- 
 
 177-0 
 
 2-24797 
 
 1 Philosophical Magazine. 
 
 2 On the first trip of the City of Edinburgh steam ship to Leith, in 1821, this was found to take 
 place to the detriment of the boiler ; and the deposit was so considerable as to require its being 
 cleared out during the passage, while the vessel proceeded under her canvas. This circumstance 
 led Boulton and Watt, who manufactured the engines, to adopt a method of extracting the satu- 
 
THE NATURE AND 
 
 [SECT. 11. 
 
 94. The next point is to compare the formula with experiment ; and we shall 
 commence with Mr. Watt's experiments on salt water. The water was nearly 
 saturated with salt : it was more free from air than common water, but it parted 
 with difficulty from that which it contained. The results compared with the 
 formula for saturated salt are shown in the following table. 
 
 WATT'S EXPERIMENTS ON THE STEAM FROM SALT WATER. 
 
 
 Force in inches of mercury. 
 
 
 Force in inches of mercury. 
 
 Temperature. 
 
 Watt's observa- 
 
 Formula for satu- 
 
 Temperature. 
 
 Watt's observa- 
 
 Formula for satu- 
 
 
 tions. 
 
 rated solution. 1 
 
 
 tions. 
 
 rated solution. 1 
 
 46^ 
 
 0-01 
 
 0-24 
 
 195-5 
 
 15-34 
 
 16-64 
 
 85 
 
 0-58 
 
 1-00 
 
 201-5 
 
 17-16 
 
 18-77 
 
 113 
 
 1-72 
 
 2-33 
 
 207 
 
 19-34 
 
 20-92 
 
 139 
 
 354 
 
 4-66 
 
 210 
 
 21-8 
 
 22-18 
 
 160 
 
 6-27 
 
 7-72 
 
 212 
 
 22-74 
 
 23-05 
 
 169 
 
 8-12 
 
 9-47 
 
 216 
 
 24-6 
 
 24-87 
 
 180 
 
 10-85 
 
 12-04 
 
 218 
 
 25-52 
 
 25-84 
 
 187 
 
 12-67 
 
 13-01 
 
 220 
 
 26-5 
 
 26-84 
 
 In these, as in all the early experiments on the force of steam, the force is less 
 than it ought to be at low temperatures. 
 
 Mr. Watt's experiments on pure water afford a like discrepancy, as will be found 
 by comparing the following table of results taken at random out of his series. 2 
 
 WATT'S EXPERIMENTS ON PURE WATER. 
 
 
 Force in inches of mercury. 
 
 Temperature. 
 
 Watt's observa- 
 
 By our Rule, 
 
 
 tions. 
 
 page 59. 
 
 55 
 
 0-15 
 
 0-45 
 
 118 
 
 2-68 
 
 3-59 
 
 180 
 
 14-73 
 
 15-67 
 
 225 
 
 37 
 
 38-32 
 
 240 
 
 49 
 
 50-24 
 
 261 
 
 68 
 
 72-00 
 
 272-5 
 
 82 
 
 86-89 
 
 rated water from the bottom, or lower part of the boiler, by means of a pump, and subsequently by 
 means of their blow-off pipes and cocks, now generally followed : the operation of blowing off is 
 usually attended to every three or four hours. 
 
 1 The results in this column are calculated by the Rule I, by logarithms, given at page 59, with 
 this difference, that instead of subtracting 2-24797 as for common water, the number 2-26703, as 
 given in the preceding table, is used for saturated solution. 
 
 2 Robison's Mechan. Phil. vol. ii. p. 3234. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 FIG. 10. 
 
 The explanation offered by Mr. Watt himself is not sufficient to account for the 
 difference, except in the lower temperatures. He supposes the stationary baro- 
 meter must have had its scale placed '2 of an inch too low ; and if so, the same 
 addition would be required to the forces in the preceding table on salt water. 
 These tables, however, are not selected for minute accuracy, but to show the 
 important fact, that the force of the steam of water depends on the temperature of 
 the liquid which produces it, or which is in contact with it. For this they are 
 sufficiently correct ; and it is a circumstance which affects its elastic force both in 
 the boiler and in the condenser, and is peculiarly interesting to those concerned in 
 steam vessel engines. The temperatures not being the same, the comparison is not 
 so easy ; but at 180 the force of salt water is 1O85 ; that of pure water 14'73 
 inches : at 212 salt water has a force of 22*74 ; pure water 29'56. 
 
 95. The experiments made by Professor Robison were tried in a similar 
 manner ; and as a method the same in effect was used by Bettancourt, whose 
 results agree extremely well with Robison's, the description of it may be useful. 
 
 Professor Robison's apparatus for determining 
 the force of steam. This apparatus, in the first 
 trials, consisted of a small digester of copper, A B 
 C D, in the figure : the top had a thermometer 
 inserted through the centre, and a loaded valve at 
 V ; and a third hole for inserting a barometer tube 
 S G F, to ascertain the force at lower temperatures 
 than 212. The force at the higher temperatures 
 than 212 was measured by the steelyard on the 
 valve, a plug being inserted in the place of the tube 
 S G F ; but the results with the valve were irre- 
 gular and unsatisfactory. Hence, the glass tube 
 M N K, having a cistern L for mercury, was adapted 
 to the hole in the digester ; and instead of mea- 
 suring the force by the valve, it was measured by 
 the ascent of the mercury in the tube M N. The 
 digester was heated by a lamp. 
 
 To determine the pressure at temperatures below 212, the tube SGF was 
 inserted as in the figure, and a basin of mercury provided at F. The lamp being 
 applied, the water in the digester produced steam till it issued at both the valve 
 and the pipe F, so as to expel the air : the lamp being removed, and both the 
 valve and tube being closed, the latter by immersing it in the mercury, the mer- 
 cury rose in the tube F G as the apparatus cooled, and the heights corresponding 
 to different temperatures were noted : like observations were made as it re-heated. 
 
 M 
 
THE NATURE AND 
 
 [SECT. ii. 
 
 To determine the pressure at higher temperatures with the apparatus, the end K 
 of the tube M N K was inserted at E ; and as the temperature increased, the 
 pressure of the steam in the cistern L caused the mercury to ascend, and con- 
 sequently afforded a means of measuring the amount of expansive force. 
 
 The objection to this mode of trial is, that the temperature of the mercury must 
 be continually changing during the trial, and steam must be either condensing or 
 generating on its .surface during the time of observation. At each observation the 
 temperature of the whole of the apparatus ought to be the same, and then the 
 column exhibiting the pressure ought to be reduced to its equivalent at the mean 
 temperature. The only observation where these circumstances would have place 
 was that which appears to have been made when the thermometer was at 42 ; 
 then the column in the syphon was 29'7, and the barometer stood at 29'84 : the 
 difference is the force of steam at 42, and is 0-14 inches. By cooling down to 32 
 the force was not perceptibly different, and we know from later trials that this is 
 nearly correct. Professor Robison, however, seems to have thought it was neces- 
 sary to have the force at 32 . 1 
 
 ROBISON'S EXPERIMENTS ON THE FORCE OF STEAM. 
 
 Temperature of 
 the steam. 
 
 Force of steam in inches of mercury. 
 
 Temperature of 
 the steam. 
 
 Force of steam in inches of mercury. 
 
 By Dr. Robisou's 
 experiments. 
 
 By our Rule, | 
 page 59. 
 
 By Dr. Robison's 
 experiments. 
 
 By our Rule, 
 page 59. 
 
 32 
 
 0-0 
 
 0-172 
 
 160 
 
 8-65 
 
 10-05 
 
 40 
 
 0-1 
 
 0-245 
 
 170 
 
 11-05 
 
 12-6 
 
 50 
 
 0-2 
 
 0-37 
 
 180 
 
 14-05 
 
 15-67 
 
 60 
 
 0-35 
 
 0-55 
 
 190 
 
 17-85 
 
 19-35 
 
 70 
 
 0-55 
 
 0-78 
 
 200 
 
 22-62 
 
 23-71 
 
 80 
 
 0-82 
 
 1-106 
 
 210 
 
 28-68 
 
 28-86 
 
 90 
 
 1-18 
 
 1-53 
 
 220 
 
 35-8 
 
 34-92 
 
 100 
 
 1-6 
 
 2-08 
 
 230 
 
 44-5 
 
 42-0 
 
 110 
 
 2-25 
 
 2-79 
 
 240 
 
 54-9 
 
 50-24 
 
 120 
 
 3-0 
 
 3-68 
 
 250 
 
 66-8 
 
 59-79 
 
 130 
 
 3-95 
 
 4-81 
 
 260 
 
 80-3 
 
 70-8 
 
 140 
 
 5-15 
 
 6-21 
 
 270 
 
 94-1 
 
 83-45 
 
 150 
 
 6-72 
 
 7-94 
 
 280 
 
 105-9 
 
 97-92 
 
 If the elastic force '14, from which Robison began to register, had been added to 
 all the experiments below 212, as it ought to have been, they would have agreed 
 extremely near with the results of later experiments. The experiments made by 
 Achard seldom vary more than a degree or two from those in the above table. 
 
 96. Mr. Dalton's inquiries were conducted by a different method. He took a 
 
 1 Mechan. Phil. vol. ii. p. 36. 
 
SECT, ii.] PROPERTIES OF STEAM. 65 
 
 barometer tube, made perfectly dry, and filled it with mercury just boiled, marking 
 the place where it was stationary ; then graduated the tube into inches and tenths 
 by means of a file : into this tube he poured a little water, (or any other liquid the 
 subject of experiment,) so as to moisten the whole inside ; after this, he again 
 poured in mercury, carefully inverting the tube to exclude all air. The baro- 
 meter, by standing, sometimes exhibited a portion of water, &c. of one eighth or 
 one tenth of an inch, upon the top of the mercurial column, because being lighter 
 it ascends by the side of the tube ; which may now be inclined, and the mercury 
 will rise to the top, manifesting a perfect vacuum from air. He then took a 
 cylindrical glass tube, open at both ends, of 2 inches diameter, and 14 inches in 
 length ; to each end of which a cork was adapted, perforated in the middle so as to 
 admit the barometer tube, to be pushed through and to be held fast by them : the 
 upper cork was fixed two or three inches below the top of the tube, and half cut 
 away so as to admit water, &c. to pass by ; its service being merely to keep the 
 tube steady. Things being thus circumstanced, water of any temperature may be 
 poured into the wide tube, and made to surround the upper part of the vacuum of 
 the barometer ; and the effect of temperature in the production of vapour within can 
 be observed from the depression of the mercurial column. In this way, he says, he 
 had water as high as 155 surrounding the vacuum ; but as the high temperature 
 might endanger a glass apparatus, instead of it he used the following one for higher 
 temperatures. 
 
 Having procured a tin tube of four inches in diameter, and two feet long, with a 
 circular plate of the same soldered to one end, having a round tube in the centre, 
 like the tube of a reflecting telescope ; he got another smaller tube of the same 
 length soldered into the larger, so as to be in the axis or centre of it : the small 
 tube was open at both ends ; and on this construction, water could be poured into 
 the larger vessel to fill it, whilst the central tube was exposed to its temperature. 
 Into this central tube he could insert the upper half of a syphon barometer, and fix 
 it by a cork, the top of the narrow tube also being corked : thus the effect of any 
 temperature under 212 could be ascertained, the depression of the mercurial 
 column being known by the ascent in the exterior leg of the syphon. Mr. Dalton 
 also remarks, that the force of vapour from water between 80 and 212 may be 
 determined by means of an air pump ; and the results exactly agree with those 
 determined as above. Take a florence flask half filled with hot water, into which 
 insert the bulb of a thermometer ; then cover the whole with a receiver on one of 
 the pump plates, and place a barometer gauge on the other : the air being slowly 
 exhausted, mark both the thermometer and barometer at the moment ebullition 
 commences, and the height of the barometer gauge will denote the force of vapour 
 from water of the observed temperature. This method may also be used for other 
 
(JO 
 
 THE NATURE AND 
 
 [SECT. ii. 
 
 liquids. It may be proper to observe, that the various thermometers used in these 
 experiments were duly adjusted to a good standard one. 
 
 After repeated experiments by all these methods, and a careful comparison of 
 the results, he was enabled to digest a table of the force of steam from water of all 
 the temperatures from 32 to 212V The only experimental results were the fol- 
 lowing, which are compared with our formula. 
 
 DALTON'S EXPERIMENTS ON THE FORCE OF STEAM. 
 
 
 Force in inches of mercury. 
 
 
 Force in inches of mercury. 
 
 Temperature of 
 
 Dalton's obser- 
 
 By Rule 
 
 Temperature of 
 
 Dalton's obser- 
 
 By Rule 
 
 steam. 
 
 vations. 
 
 page 59. 
 
 steam. 
 
 vations. 
 
 page 59. 
 
 32 
 
 0-2 
 
 0-172 
 
 133! 
 
 4-76 
 
 5-24 
 
 43| 
 
 0-297 
 
 0-281 
 
 1441 
 
 6-45 
 
 695 
 
 54 
 
 0-435 
 
 0-442 
 
 155f 
 
 8-55 
 
 9-10 
 
 65f 
 
 0-63 
 
 0-675 
 
 167 
 
 11-25 
 
 11-7 
 
 77 
 
 0-91 
 
 1-00 
 
 178J- 
 
 14-6 
 
 15-1 
 
 881 
 
 1-29 
 
 1-447 
 
 189| 
 
 18-8 
 
 19-15 
 
 991 
 
 1-82 
 
 2-05 
 
 200f 
 
 240 
 
 24-07 
 
 HOf 
 
 254 
 
 2-85 
 
 212 
 
 30-0 
 
 300 
 
 122 
 
 35 
 
 3-89 
 
 
 
 
 From these results he determined the ratio belonging to each interval, and filled in 
 the intermediate degrees by interpolation, considering the forces to increase in a 
 geometrical progression. Above 212 he made no trials at that period, though the 
 table was extended to 325, and has since been found to be erroneous for the 
 temperatures above 212. 
 
 97. Mr. Dalton afterwards re-examined the subject, and considers from va- 
 rious trials, that the force of steam at 32 cannot be less than - 2 of an inch ; and 
 is most probably 0*25 : but with the advantage of having seen the results of 
 Dr. Ure's and Mr. Southern's experiments, and having made new experiments 
 himself for the temperatures between 212 and 300, he gives the following table, 
 formed from what he considers the most correct experiments on the subject. 2 
 
 
 Force of steam in inches of mercury. 
 
 
 Force of steam in inches of mercury. 
 
 Temperature of 
 steam. 
 
 Dalton's numbers. 
 
 By Rule 
 page 59. 
 
 Temperature of 
 steam. 
 
 Dalton's numbers. 
 
 By Rule 
 
 page 59. 
 
 36 
 
 0-29 
 
 0-201 
 
 173 
 
 13-18 
 
 13-46 
 
 64 
 
 0-75 
 
 0-633 
 
 220 
 
 34-20 
 
 34-92 
 
 96 
 
 1-95 
 
 1-84 
 
 272 
 
 88-9 
 
 86-2 
 
 132 
 
 5-07 
 
 5-07 
 
 340 
 
 231-0 
 
 236- 
 
 i Nich. Phil. Journal, vol. vi. p. 263. 8vo. 
 
 - Annals of Philosophy, vol. xv. p. 130. for 1820. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 67 
 
 It will appear from this, that there is a greater difference between the results of 
 different trials, than between the numbers found by our rule and those results ; and 
 hence it may be presumed to be sufficiently exact. 
 
 98. For the further satisfaction of the reader, the principal results of Dr. lire's 
 experiments shall be given, and his simple and elegant mode of making the experi- 
 ments described ; as, in the event of any other species of fluid being found better 
 adapted than water for furnishing vapour, the same mode might be usefully 
 adopted to try its force. 1 
 
 FIG. 11. 
 
 FIG. 12. 
 
 FIG. 13. 
 
 o 
 
 The preceding figure (fig. 11.) represents the construction employed for tempe- 
 ratures under and a little above the boiling point. Figures 12 and 13 were used 
 for higher temperatures ; the latter is the more convenient of the two. It was 
 suspended from a lofty window ceiling, and placed with the tube L D in a true 
 vertical position by means of a plumbline. One simple principle pervades the 
 whole train of experiments, which is, that the progressive increase of elastic force 
 developed by heat from the liquid, incumbent on the mercury at /, is measured 
 by the length of column which must be added over L, in order to restore 
 the quicksilver to its primitive level at /. These two stations, or points of 
 departure, are nicely defined by a ring of fine platina wire twisted firmly round 
 the tube. 
 
 Philosophical Transactions for 1818. 
 
68 THE NATURE AND [SECT. n. 
 
 At the commencement of the experiment, after the liquid, well freed from air, 
 has been let up, the quicksilver is made to coincide with the edge of the ring /, 
 by cautiously pouring mercury in a slender stream into the open leg of the syphon 
 D. The level ring at L is then carefully adjusted. 
 
 From the mode of conducting the experiments, there remained always a quantity 
 of liquid in contact with the vapour, a circumstance essential to accuracy in this 
 research. Suppose the temperature of the water, or the oil in A (fig. 11.) to be 
 32, as denoted by a delicate thermometer, or by the liquefaction of ice ; and let 
 L D be a column equal to the atmospheric pressure ; communicate heat to the 
 cylinder A, by means of two Argand flames, playing gently against its shoulder 
 at each side. When the thermometer indicates 42, modify the flames, or remove 
 them, so as to maintain an uniform temperature for a few minutes. Then the 
 elasticity will be faithfully represented and measured, by the mercurial column 
 which must be added over D, in order to return the quicksilver to the line /, its 
 zero or initial level. 
 
 At E a piece of cork is fixed, between the parallel legs of the syphon, to sustain 
 it, and to serve as a point by which the whole is steadily suspended. 
 
 For temperatures above the boiling point, the part of the syphon under E is evi- 
 dently superfluous, merely containing in its two legs a useless weight of equipoised 
 mercury. Accordingly for high heats, either the apparatus fig. 12 or 13 is 
 employed, and the same method of procedure is adopted. The aperture at 
 (fig. 13) admits the bulb of the thermometer, which rests against the tube. The 
 recurved part of the tube is filled with mercury, and then a little liquid is passed 
 through it to the sealed end. Heat is applied by an Argand flame to the bottom 
 of c, which is filled with oil or water, and the temperature is kept steadily at 212 
 for some minutes. Then a few drops of quicksilver may require to be added at 
 D, till L and / be in the same horizontal plane. The further conduct of the 
 experiment differs in no respect from what has already been described. The liquid 
 in c is progressively heated, and at each stage mercury is progressively added 
 over L to restore the initial level, or volume at /, by equipoising the progressive 
 elasticity. The column above L being the accession of elastic force. When this 
 column is desired to be extended very high, the vertical tube requires to be placed 
 for support in the groove of a long wooden prism. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 URE'S EXPERIMENTS ON THE FORCE OF STEAM. 
 
 Temperature of 
 steam. 
 
 Force in inches of mercury. 
 
 Temperature of 
 steam. 
 
 Force in inches of mercury. 
 
 Ure's observa- 
 tions. 
 
 By Rule 
 page 59. 
 
 Ure's observa- 
 tions. 
 
 By Rule 
 page 59. 
 
 24 
 
 0-170 
 
 0-118 
 
 190 
 
 19-000 
 
 19-35 
 
 32 
 
 0-200 
 
 0-172 
 
 200 
 
 23-600 
 
 23-71 
 
 40 
 
 0-250 
 
 0-245 
 
 210 
 
 28-880 
 
 28-86 
 
 50 
 
 0-360 
 
 0-37 
 
 212 
 
 30-000 
 
 30-00 
 
 55 
 
 0-416 
 
 0-45 
 
 220 
 
 35-540 
 
 34-92 
 
 60 
 
 0-516 
 
 0-55 
 
 225 
 
 39-110 
 
 38-32 
 
 70 
 
 0-726 
 
 0-78 
 
 230 
 
 43-100 
 
 42-00 
 
 80 
 
 1-010 
 
 1-106 
 
 240 
 
 51-700 
 
 50-24 
 
 90 
 
 1-360 
 
 1-53 
 
 250 
 
 61-900 
 
 59-79 
 
 100 
 
 1-860 
 
 2-08 
 
 260 
 
 72-300 
 
 70-8 
 
 110 
 
 2-456 
 
 2-79 
 
 270 
 
 86-300 
 
 82-45 
 
 120 
 
 3300 
 
 3-68 
 
 280 
 
 101-900 
 
 97-92 
 
 130 
 
 4-366 
 
 4-81 
 
 290 
 
 120-150 
 
 114-4 
 
 140 
 
 5-770 
 
 6-21 
 
 295 
 
 129-000 
 
 123-5 
 
 150 
 
 7-53 
 
 7-94 
 
 300 
 
 139-700 
 
 133-2 
 
 160 
 
 9-600 
 
 10-05 
 
 310 
 
 161-300 
 
 154-5 
 
 170 
 
 12-050 
 
 12-6 
 
 312 
 
 167-000 
 
 159- 
 
 180 
 
 15-160 
 
 15-67 
 
 312 
 
 165-5 
 
 
 If a nice agreement with a particular set of observations had been attempted, 
 the formula could have easily been arranged to represent these better ; but by so 
 doing it appears to me that the elastic forces would have increased in a higher 
 ratio than we are warranted in expecting from other experiments, and the later 
 inquiries of Mr. Dalton justify the numbers being higher at or about 150 than 
 Dr. Ure's. 
 
 99. Mr. Southern's experiments on high pressure steam were made with a 
 digester, with a thermometer fitted to a metallic tube, so that the stem of the ther- 
 mometer might be immersed as far as it contained mercury. Also, instead of 
 measuring the force of the steam by a loaded valve, a nicely bored cylinder was 
 used, with a piston fitting it so as to have very little friction, to the rod of which a 
 lever was applied, constructed to work on edges like those of a scale beam ; and 
 that no error might arise from this construction, a column of mercury was substi- 
 tuted, and the correspondence was within TOT of an inch. 
 
 The observations at each of the points of temperature and pressure were con- 
 tinued some minutes, the temperature being alternately raised and lowered, so 
 as to make the pressure in excess and defect ; and a mean temperature was taken 
 for the result. This method seems to me entitled to great confidence, and hence 
 I have made the results the principal data for my formula. (See art. 86.) 
 
 The experiments below 212 were conducted nearly as Dr. Robison's, and those 
 below 62 were made by Mr. W. Creighton. These low pressure experiments do 
 not seem to be of equal value with the four high pressure ones. 
 
70 
 
 THE NATURE AND 
 SOUTHERN'S EXPERIMENTS ON THE FORCE OF STEAM. 1 
 
 [SECT. ii. 
 
 
 Force in inches of mercury. 
 
 
 Force in inches of mercury. 
 
 Temperature of 
 the steam. 
 
 Observed force. 
 
 By Rule 
 page 59. 
 
 Temperature of 
 the steam. 
 
 Observed force. 
 
 By Rule 
 
 page 59. 
 
 32 
 
 0-16 
 
 0-172 
 
 132 
 
 4-71 
 
 5-07 
 
 42 
 
 0-23 
 
 0-266 
 
 142 
 
 6-10 
 
 6-53 
 
 52 
 
 0-35 
 
 0-401 
 
 152 
 
 7-90 
 
 8-33 
 
 62 
 
 0-52 
 
 0-587 
 
 162 
 
 10-05 
 
 10-52 
 
 72 
 
 0-73 
 
 0-842 
 
 172 
 
 12-72 
 
 13-17 
 
 82 
 
 1-02 
 
 1-182 
 
 182 
 
 16-01 
 
 16-35 
 
 92 
 
 1-42 
 
 1-629 
 
 212 
 
 30-00 
 
 30-00 
 
 102 
 
 1-96 
 
 2-21 
 
 250-3 
 
 60-00 
 
 60-00 
 
 112 
 
 2-66 
 
 2-95 
 
 293-4 
 
 120-00 
 
 120-50 
 
 122 
 
 3-58 
 
 3-89 
 
 343-6 
 
 240-00 
 
 247-80 
 
 100. A scale of the elastic force of steam at high temperatures was published 
 in 1822 by Mr. Philip Taylor, 2 which was formed by means of an apparatus 
 not described ; but it appears to correspond with the best experiments, and is likely 
 to be near the effect in practice where we may expect some loss of elastic force, 
 compared with the temperature. 
 
 TAYLOR'S SCALE OF THE FORCE OF STEAM. 
 
 
 Force in inches of mercury. 
 
 Temperature of 
 
 Taylor's obser- 
 
 By our Rule 
 
 the steam. 
 
 vations. 
 
 page 59. 
 
 212 
 
 30-00 
 
 30-00 
 
 220 
 
 34-95 
 
 34-92 
 
 230 
 
 41-51 
 
 42-00 
 
 240 
 
 50-00 
 
 50-24 
 
 250 
 
 59-12 
 
 59-79 
 
 260 
 
 70-10 
 
 70-8 
 
 270 
 
 82-50 
 
 83-45 
 
 280 
 
 97-75 
 
 97-92 
 
 290 
 
 11450 
 
 114-4 
 
 300 
 
 133-75 
 
 133-2 
 
 320 
 
 179-40 
 
 178-5 
 
 101. The experiments of Schmidt present a surprising accordance with the 
 rule, at the temperatures from 60 to 230; at these points they slowly sepa- 
 rate, the rule being in defect in the highest temperature 290 by 11 inches, 
 and in excess at 43^ by 0-163. 3 
 
 Robison's Mechanical Philos. vol. ii. p. 173. 
 Dr. Young's Nat. Phil. vol. ii. 
 
 2 Philosophical Mag. vol. ix. p. 452. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 71 
 
 102. The force of steam at high temperatures is still wanting to complete 
 the experimental part of the inquiry. A few experiments have been made, which 
 appear to me to be entitled to some confidence, by Professor Arsberger, of Vienna. 1 
 
 ARSBERGER'S EXPERIMENTS ON HIGH PRESSURE STEAM. 
 
 
 Force in inches of mercury. 
 
 Temperature of 
 the steam. 
 
 By experiment. 
 
 By our Rule 
 page 59. 
 
 232 
 
 44-4 
 
 43-56 
 
 249 
 
 59-1 
 
 58-7 
 
 274 
 
 88-8 
 
 89-0 
 
 322 
 
 176-0 
 
 183-6 
 
 372 
 
 325-0 
 
 362- 
 
 432 
 
 620-0 
 
 737- 
 
 Here the rule is in excess at 432 by more than one sixth ; but in an ex- 
 periment reported by M. Clement, to M. Poisson, * the force of steam at 419 
 is said to be 35 atmospheres, or 1050 inches of mercury, while our rule gives only 
 635 inches. I doubt the accuracy of the statement. 
 
 103. M. Cagniard de la Tour 3 made some essays to ascertain the space and 
 temperature in which a given quantity of water became wholly steam ; but from 
 the frequent rupture of the glass tubes, and their loss of transparency, it was 
 difficult to obtain a result. He states, however, that at a temperature but little 
 removed from the melting point of zinc, water could be converted into vapour in 
 a space nearly four times its volume. If this could have been really ascertained 
 with accuracy, it would have given an important datum ; but on the above rude 
 approximation no reliance can be placed. * 
 
 1 Bulletin des Sciences Tech. vol. i. p. 294. - Philosophical Magazine, vol. Ixi. p. 60. 
 
 3 Philosophical Magazine, vol. Ixi. p. 58. 
 
 4 In a paper on the elastic force of steam which has just been published by Mr. Ivory, in the 
 ' Philosophical Magazine,' a completely different process is followed for calculating the force of 
 steam from that I have given ; it does not however afford results much nearer to the experiments 
 it is founded on, than those by my formula, while it is somewhat more difficult to apply, and 
 becomes erroneous in high temperatures. 
 
 Counting t the temperature from 212 and/ the elastic force, his formula is 
 
 log.^- = -0087466 t - -000015178 t*+ 000000024825 1*. 
 
 tJ\J 
 
 It is derived from a comparison of Dr. Ure's experiments ; and the following table shows the 
 results by those experiments, by Mr. Ivory's formula, by other experiments, and by my formula. 
 
72 
 
 THE NATURE AND 
 
 [SECT. ii. 
 
 In the absence therefore of proper experiments to ascertain the force of steam, 
 it is difficult to determine a rule that can be depended upon for high temperatures, 
 and we must now try to discover if the force of other vapours will afford any 
 further insight into the subject. 
 
 OF THE ELASTIC FORCE OF THE VAPOUR OF ALCOHOL. 
 
 104. The elastic force of the vapour of alcohol, or spirit of wine, has been 
 tried by several philosophers. The greater part of the experiments were made in 
 
 Temperature of 
 the steam. 
 
 Elastic force of steam in inches of mercury. 
 
 Dr. Ure's 
 experiments. 
 
 Mr. Ivory's 
 formula. 
 
 Various experiments. 
 
 By our Rule 
 page 59. 
 
 32 
 
 0-2 
 
 0-185 
 
 0-16 Creighton 
 
 0-172 
 
 50 
 
 0-36 
 
 0-36 
 
 
 0-37 
 
 70 
 
 0-726 
 
 0-721 
 
 
 0-78 
 
 90 
 
 1-360 
 
 1-378 
 
 
 1-53 
 
 110 
 
 2-456 
 
 2-634 
 
 
 2-79 
 
 130 
 
 4-336 
 
 4-408 
 
 
 4-81 
 
 150 
 
 7-530 
 
 7-424 
 
 
 7-94 
 
 170 
 
 12-05 
 
 12-05 
 
 
 12-60 
 
 190 
 
 19-00 
 
 18-93 
 
 
 1935 
 
 210 
 
 28-88 
 
 28-81 
 
 
 28-86 
 
 230 
 
 43-10 
 
 42-63 
 
 41-51 Taylor 
 
 42-00 
 
 250 
 
 61-90 
 
 61-50 
 
 60-0 Southern 
 
 59-79 
 
 270 
 
 86-30 
 
 86-70 
 
 82-5 Taylor 
 
 83-45 
 
 290 
 
 120-15 
 
 119-9 
 
 114-5 Taylor 
 
 114-40 
 
 310 
 
 161-30 
 
 162-8 
 
 
 154-5 
 
 337 
 
 
 240 
 
 234 Christian 1 
 
 226-5 
 
 343-6 
 
 
 264 
 
 240 Southern 
 
 247-8 
 
 419 
 
 
 714 
 
 1050 Clement 
 
 635-0 
 
 432 
 
 
 1852 
 
 620 Arsberger 
 
 737-0 
 
 At a temperature of about 770 Mr. Ivory's formula gives an elastic force equal to the 
 modulus of elasticity of water ; the steam would, if this were correct, be more dense than water ; 
 while La Tour found it required a space four times its volume to become steam at about the same 
 heat. Arsberger's experiments had not been seen by Mr. Ivory, or he would have had reason 
 for doubting the accuracy of M. Clement's observation ; but as it is quite unsupported either by 
 a description of the process, or any observations at other temperatures, its deviation in 
 excess both from formulae founded on a considerable range of experiments, and also from other 
 results, is to be regarded as a motive for doubt rather than for altering our formula. Mr. Ivory 
 most justly remarks, that this furnishes l< another instance of the great difficulty of detecting 
 general properties or laws by means of a comparison of particular results ;" and it is a difficulty 
 which ought to induce mathematicians possessed of such great powers as Mr. Ivory certainly is, 
 to endeavour to develope the first principles, rather than investigate a formula from experiments 
 alone. 
 
 i M6canique Industrielle, vol. ii. p. 232. 
 
SECT, ii.] PROPERTIES OF STEAM. 73 
 
 the lower ranges of temperature, and in the same manner as those on the force of 
 the steam of water ; but in describing them it will be some advantage to begin 
 with the experiments of Cagniard de la Tour, on the space alcohol occupies when 
 converted wholly into vapour. To ascertain this point, alcohol of the specific 
 gravity '837 was introduced into small tubes of glass, and hermetically sealed, 
 with a handle of glass attached to each tube. A tube was two-fifths filled with 
 alcohol, and then slowly and carefully heated : as the fluid dilated, its mobility 
 increased ; and when its volume was nearly doubled, it completely disappeared, 
 and became a vapour so transparent, that the tube appeared quite empty. On 
 leaving it to cool for a moment, a very thick cloud formed in its interior, and the 
 liquor returned to its first state. A second tube, nearly half occupied by the 
 same fluid, gave a similar result ; but a third, containing rather more than half, 
 burst. 
 
 A process was next adopted to ascertain the pressure. It consisted in bending 
 a tube into a syphon, one leg to hold the liquid to be tried, and the other leg 
 containing air kept at a constant temperature of 73 by a cooling apparatus, and 
 separated from the fluid by mercury : both legs being sealed, the end containing 
 the liquid was heated, and when the liquid became vapour the diminution in the 
 bulk of the air was marked. 
 
 Alcohol of the specific gravity '837 was reduced into vapour at a temperature of 
 497 in a space a little less than 3 times its original bulk; and 476 parts of 
 air were reduced to 4 ; indicating a pressure, according to M. Cagniard de la 
 Tour, of 119 atmospheres, or 3570 inches of mercury. 1 
 
 105. The experiments on alcohol vapour at lower temperatures are collected 
 in the following table. 
 
 1 By the same process as was adopted in finding the constants for calculating the force of the 
 steam of water (art. 86.) the formula for the vapour of alcohol of sufficient purity to boil at 
 173 is 
 
 f- (* + 100 \ 6 
 " V 154-9 ) ' 
 
 or, in logarithms, 
 
 log./ = 6 (log. (t + 100) - 2-1900o) 5 
 
 where t is the temperature of the vapour, and/ its force in inches of mercury. By this rule the 
 force for a temperature of 497 is 3280 inches : the experiment of M. Cagniard de la Tour 
 gives 3570 inches. 
 
74 
 
 THE NATURE AND 
 
 [SECT. n. 
 
 EXPERIMENTS ON THE FORCE OF THE VAPOUR OF ALCOHOL. 
 
 Temperature 
 of vapour. 
 
 Force in inches of mercury. 
 
 Ure's 
 
 experiments. 
 
 Watt's 
 experiments. 
 
 Robison's 
 experiments. 
 
 Dalton's 
 experiments. 
 
 Bettancourt's 
 experiments. 
 
 By Formula 
 page 73. 
 
 32 
 
 0-40 
 
 
 0-0 
 
 
 o-o 
 
 0-383 
 
 40 
 
 0-56 
 
 0-929 
 
 0-1 
 
 
 
 0-546 
 
 50 
 
 0-86 
 
 
 
 
 
 0-826 
 
 54-5 
 
 
 
 
 
 48 
 
 0-986 
 
 60 
 
 1-23 
 
 
 0-8 
 
 1-4 
 
 
 1-215 
 
 64 
 
 
 
 
 1-51 
 
 
 1-41 
 
 70 
 
 1-76 
 
 
 
 
 
 1-75 
 
 77 
 
 
 
 
 
 1-62 
 
 2-228 
 
 80 
 
 2-45 
 
 
 1-8 
 
 
 
 2-465 
 
 90 
 
 3-40 
 
 
 
 
 
 3-41 
 
 96 
 
 
 
 
 4-07 
 
 
 4-11 
 
 99-5 
 
 
 
 
 
 3-63 
 
 4-57 
 
 100 
 
 4-50 
 
 
 3-9 
 
 
 
 4-64 
 
 110 
 
 6-00 
 
 5-63 
 
 
 
 
 6-22 
 
 120 
 
 8-10 
 
 7-12 
 
 6-9 
 
 
 
 8-22 
 
 122 
 
 
 
 
 
 7-36 
 
 8-67 
 
 130 
 
 10-60 
 
 
 
 
 
 10-73 
 
 132 
 
 
 10-34 
 
 
 11-0 
 
 
 11-3 
 
 140 
 
 13-90 
 
 
 12-2 
 
 
 
 13-85 
 
 144-5 
 
 
 
 
 
 13-7 
 
 15-48 
 
 150 
 
 18-00 
 
 
 
 
 
 17-7 
 
 160 
 
 22-60 
 
 20-71 
 
 21-3 
 
 
 
 22-4 
 
 167 
 
 
 24-47 
 
 
 
 25-4 
 
 26-25 
 
 170 
 
 28-30 
 
 
 
 
 
 28-1 
 
 173 
 
 30-00 
 
 
 
 29-70 
 
 
 30-00 
 
 180 
 
 34-73 
 
 
 34- 
 
 
 
 34-92 
 
 189-5 
 
 
 
 
 
 42-0 
 
 42-66 
 
 190 
 
 43-20 
 
 
 
 
 
 43-11 
 
 200 
 
 53-00 
 
 
 52-4 
 
 
 
 52-83 
 
 210 
 
 65-00 
 
 
 
 
 
 64-3 
 
 212 
 
 
 
 
 
 68- 
 
 66-84 
 
 220 
 
 78-50 
 
 
 78-5 
 
 80-20 
 
 
 77-81 
 
 230 
 
 94-10 
 
 
 
 
 
 93-6 
 
 234-5 
 
 
 
 
 
 105- 
 
 101-5 
 
 240 
 
 111-24 
 
 
 115- 
 
 
 
 112-0 
 
 250 
 
 132-30 
 
 
 
 
 
 133-2 
 
 260 
 
 155-20 
 
 
 
 
 
 157-7 
 
 264 
 
 166-10 
 
 
 
 
 
 168-6 
 
 The specific gravity of the alcohol used by Dr. Ure was -813, and its boiling 
 point 173. l The properties of the alcohol employed by Mr. Watt are not given ; 2 
 his experiments are very irregular. Dr. Robison's boiled at 173 ; 3 and above 100 
 agree well with later observations. Mr. Dalton's appears to have boiled at 175;* 
 
 i Phil. Trans. 1818. 
 
 3 Robison's Mech. Phil. vol. ii. p. 35. 
 
 s Robison's Mech. Phil. vol. ii. p. 33. 
 4 Annals of Philo. 1820. vol. xv. p. 130. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 7-3 
 
 Bettancourt's boiling point is not stated, but appears to have been at 173, l and 
 his results like Dr. Robison's are too small at low temperatures. 
 
 Dr. Ure's experiments are confirmed by those of Mr. Dalton, and may be relied 
 on as approaching very near the truth. The formula, it will be observed, repre- 
 sents them with considerable accuracy. 
 
 OF THE ELASTIC FORCE OF THE VAPOUR OF SULPHURIC ETHER. 
 
 106. M. Cagniard de la Tour made several experiments on ether in the 
 same manner as those on alcohol, art. 104. The ether was converted into vapour 
 in a space less than twice its original volume by a temperature of 392. This 
 experiment was thrice repeated, with the same result, and 528 parts of air were 
 compressed to 14, giving an elastic force of 37'7 atmospheres. 2 
 
 107. Other trials were made, the results of which are shown in the following 
 table. 
 
 M. CAGNIARD DE LA TOUR'S EXPERIMENTS ON ETHER. 
 
 
 Volume in the liquid state 7 parts. 
 Volume in the state of vapour 
 20 parts. 
 
 Force as ex- 
 
 Volume in the liquid state 3J parts. 
 Volume in the state of vapour 
 20 parts. 
 
 Force of va- 
 
 
 
 
 
 Temperature 
 by Fahrenheit. 
 
 Force of vapour 
 in atmospheres. 
 
 Differences. 
 
 panding gas in 
 atmospheres, by 
 formula below. 
 
 Force of vapour 
 in atmospheres. 
 
 Differences. 
 
 pour in atmo- 
 spheres, by for- 
 mula below. 
 
 212 
 
 5-6 
 
 
 
 
 
 5'78 
 
 234-5 
 
 7-9 
 
 2-3 
 
 
 
 
 7-9 
 
 257 
 
 10-6 
 
 2-7 
 
 
 14-0 
 
 
 1063 
 
 279-5 
 
 12-9 
 
 2-3 
 
 
 17-5 
 
 3-5 
 
 14-1 
 
 302 
 
 18-0 
 
 5-1 
 
 
 22-5 
 
 5-0 
 
 18-4 
 
 324-5 
 
 22-2 
 
 4-2 
 
 
 28-5 
 
 6-0 
 
 23-8 
 
 347 
 
 369-5 
 392 
 
 55* r State of 
 " ' " I vapour. 
 
 48-5 
 
 6-1 
 9-2 
 
 11-0 
 
 
 gr State of 
 ** u 1 vapour. 
 50-5 
 
 6-5 
 7-0 
 8-5 
 
 30-6 
 
 38-7 
 48-0 
 
 414-5 
 
 59-7 
 
 11-2 
 
 
 58-0 
 
 7-5 
 
 60-7 
 
 447 
 
 68-8 
 
 9-1 
 
 68-8 
 
 63-5 
 
 5-5 
 
 823 
 
 469-5 
 
 78-0 
 
 9-2 
 
 70-5 
 
 66-0 
 
 2-5 
 
 100-7 
 
 492 
 
 86-3 
 
 8-3 
 
 72-2 
 
 70-5 
 
 4-5 
 
 
 514-5 
 
 92-3 
 
 6-0 
 
 73-9 
 
 74-0 
 
 3-5 
 
 
 537 
 
 104-1 
 
 11-8 
 
 75-6 
 
 78-0 
 
 4-0 
 
 
 559-5 
 
 112-7 
 
 8-6 
 
 77-4 
 
 81-0 
 
 3-0 
 
 
 572 
 
 119-4 
 
 6-7 
 
 78-3 
 
 85-0 
 
 4-0 
 
 
 594-5 
 
 123-7 
 
 4-3 
 
 80-0 
 
 89-0 
 
 4-0 
 
 
 617 
 
 130-9 
 
 7-2 
 
 81-8 
 
 94-0 
 
 5-0 
 
 
 1 Prony's Architecture Hydraulique, vol. ii. p. 180. 
 
 3 The experiments on sulphuric ether may be very nearly represented by the formula, 
 
 or 
 
 - 2-25212) 
 
 when the ether boils at 104 or 105 ; but for ether boiling at 98, the constant logarithm should 
 be 2-23953. 
 
 In the above experiment the formula for ether boiling at 105 gives 48 atmospheres for its elastic 
 force at 392 ; but the correspondence with the tabular experiments is nearer. 
 
76 
 
 THE NATURE AND 
 
 [SECT. ii. 
 
 On comparing the two series it will be observed, that the pressure up to the 
 point where the liquids change wholly into vapour is greater in the tube con- 
 taining the least proportion of liquid ; but this I expect is entirely owing to the 
 mode of trial not being susceptible of much accuracy. Up to the point where the 
 change to vapour takes place, the formula derived from Dr. Ure's experiments 
 applies with admirable precision ; a new formula is necessary after the change. 
 The formation of vapour from the mercury in the apparatus most probably affects 
 the results in high temperatures. 
 
 108. URE'S AND DALTON'S EXPERIMENTS ON ETHER. 
 
 Temperature 
 of vapour. 
 
 Force in inches of mercury. 
 
 Temperature 
 of vapour. 
 
 Force in inches of mercury. 
 
 Ure's 
 experiments. 
 
 Dalton's 
 experiments. 
 
 Formula, 
 page 75. 
 
 Ure's 
 experiments. 
 
 Dalton's 
 experiments. 
 
 Formula, 
 page 75. 
 
 34 
 
 6-20 
 
 
 6-48 
 
 140 
 
 56-90 
 
 
 56-4 
 
 36 
 
 
 7-5 
 
 6-8 
 
 
 
 
 
 44 
 
 8-10 
 
 
 8-25 
 
 
 
 
 
 54 
 
 10-30 
 
 
 10-4 
 
 150 
 
 67-60 
 
 
 66-9 
 
 64 
 
 13-00 
 
 15-0 
 
 13-0 
 
 
 
 
 
 74 
 
 16-10 
 
 
 161 
 
 160 
 
 80-30 
 
 
 78-8 
 
 84 
 
 20-00 
 
 
 19-83 
 
 
 
 
 
 94 
 
 24-70 
 
 
 24-2 
 
 170 
 
 92-80 
 
 
 92-5 
 
 96 
 
 
 30-00 
 
 25-2 
 
 173 
 
 
 120-0 
 
 96-9 
 
 104 
 
 30-00 
 
 
 30-00 
 
 
 
 
 
 
 Second kind 
 
 
 
 
 
 
 
 
 of ether. 
 
 
 
 
 
 
 
 105 
 
 30-00 
 
 
 30-00 
 
 
 
 
 
 110 
 
 32-54 
 
 
 33-00 
 
 180 
 
 108-30 
 
 
 108-1 
 
 115 
 
 35-90 
 
 
 362 
 
 
 
 
 
 120 
 
 39-47 
 
 
 397 
 
 190 
 
 124-80 
 
 
 125-8 
 
 125 
 
 43-24 
 
 
 43-4 
 
 
 
 
 
 130 
 
 47-14 
 
 
 47-4 
 
 200 
 
 142-80 
 
 
 146- 
 
 132 
 
 
 60-0 
 
 49-1 
 
 
 
 
 
 135 
 
 51-90 
 
 
 51-8 
 
 210 
 
 166-00 
 
 
 168-5 
 
 
 
 
 
 220 
 
 
 240 
 
 194- 
 
 The ether employed by Mr. Dalton boiled in a tube at 96 , 1 and will be very 
 nearly represented by increasing the calculated quantity one fifth for the tem- 
 perature. Thus, for 132, we have 
 
 and for 220, we have 
 
 49-1 + = 58-92, 
 5 
 
 194 + = 232-8, 
 5 
 
 Dr. Ure's ether boiled at 104 or 105, and his experiments are very regular. 5 
 1 Thomson's Annals of Philosophy, vol. xv. p. 130. Diet, of Chemistry. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 77 
 
 OF THE ELASTIC FORCE OF THE VAPOUR OF SULPHURET OF CARBON. 
 
 109. There is a remarkable compound of sulphur with carbon, which is 
 usually distinguished by the name sulphuret of carbon, but is sometimes called 
 carburet of sulphur. It is liquid, and as transparent and colourless as water. It 
 has an acrid and pungent taste, somewhat aromatic : its smell is nauseous and 
 peculiar: its specific gravity is 1-272, and it boils briskly and distils at from 110 
 to 116, depending on its purity. When heated to about 680 or 700 in the air, it 
 takes fire and burns with a blue flame. It is scarcely soluble in water. It appears 
 to be a compound of 
 
 Sulphur - 84-21 
 
 Carbon - 15-79 
 
 100-00 
 
 It may be prepared by mixing about 10 parts of well-calcined charcoal in 
 powder with 50 parts of pulverized native pyrites, and distilling the mixture from 
 a retort into a tubulated receiver surrounded by ice : somewhat more than one part 
 of sulphuret of carbon may be obtained from the above quantities. 
 
 110. It appears to me that it might be used in a steam engine with some 
 advantage, provided it does not act too much on the metallic parts, nor undergo a 
 change by the continued transition from heat to cold ; for^it has a high elastic 
 force at a low temperature, being equal to about 4 atmospheres at 212, and 
 therefore the advantage of a high pressure engine might be obtained without the 
 inconvenience of a high temperature. 
 
 EXPERIMENTS ON THE ELASTIC FORCE OF VAPOUR FROM SULPHURET OF CARBON. 
 
 Temperature. 
 
 Force in inches of mercury. 
 
 Observed. 
 
 Calculated by for- 
 mula, page 78. 
 
 53-5 
 72-5 
 110 
 
 7-4 
 12-55 
 30-00 
 
 11-73 
 16-35 
 30-00 
 
 These experiments I have attempted to represent by calculation : as the rule by 
 which the numbers were calculated was formed from the experiments in the fol- 
 
78 
 
 THE NATURE AND 
 
 [SECT. n. 
 
 lowing table, they serve here to indicate that the observed numbers are probably 
 too low for the true ones. 1 
 
 111. EXPERIMENTS ON THE FORCE OF THE VAPOUR OF SULPHURET OF CARBON, 
 
 BY M. CAGNIARD DE LA TOUR. 
 
 Degrees of heat by 
 Fahrenheit. 
 
 Volume in liquid state 8 parts. 
 Volume in the state of vapour 20 parts. 
 
 Force of vapour by 
 formula below. 
 
 Force. 
 
 Difference. 
 
 
 Atmospheres. 
 
 Atmospheres. 
 
 Atmospheres. 
 
 212 
 
 4-2 
 
 
 4-03 
 
 2345 
 
 5-5 
 
 1-3 
 
 5-3 
 
 257 
 
 7-9 
 
 2-4 
 
 6-8 
 
 279-5 
 
 10-0 
 
 2-1 
 
 8-7 
 
 302 
 
 130 
 
 30 
 
 11-0 
 
 324-5 
 
 16-5 
 
 3-5 
 
 13-8 
 
 347 
 
 202 
 
 3-7 
 
 17-3 
 
 369-5 
 
 24-2 
 
 4-0 
 
 21-3 
 
 392 
 
 28-8 
 
 4-6 
 
 26-2 
 
 414-5 
 
 33-6 
 
 4-8 
 
 31-9 
 
 447 
 
 40-2 
 
 6-6 
 
 42-0 
 
 469-5 
 
 47-5 
 
 7-3 
 
 50-3 
 
 492 
 
 57-2 
 
 9-7 
 
 60-2 
 
 514-5 
 537 
 
 177.0 /State of 
 
 9-3 
 11-3 
 
 71-4 
 84-5 
 
 559-5 
 
 89-2 
 
 11-4 
 
 99-5 
 
 572 
 
 98-9 
 
 9-7 
 
 
 594-5 
 
 1143 
 
 15-4 
 
 
 617 
 
 1296 
 
 15-3 
 
 
 62825 
 
 133-5 
 
 3-9 
 
 
 The irregularities in all M. Cagniard de la Tour's experiments would be in part 
 occasioned by the expansion of the tubes under such high pressures and tem- 
 peratures ; hence, to attempt a minute comparison would only show a want of 
 attention to physical effects too common in such inquiries. The usual practice of 
 attempting to supply want of observation by minute calculations, is one of the 
 great defects of the present mode of scientific inquiry, as applied to improve the 
 scientific arts. 
 
 112. The forces of various other substances have been tried, but not with 
 much attention to the selection of such as are adapted for the acting vapours in an 
 engine ; as, for that purpose, one should be chosen which affords the highest power 
 
 1 The rule in logarithms for sulphuret of carbon, by which the calculated numbers in these 
 tables were found, is 
 
 log. /=6 (log. (t +280) - 2-34488) 
 to the point where the liquid becomes wholly vapour. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 79 
 
 with the least range of temperature above the one convenient for condensation : to 
 a vapour of this kind, heat may be applied without requiring so extensive a surface 
 for the fire to act on as when water is used. 
 
 On the other part, a fluid which has a low elastic force at a high temperature 
 may sometimes be conveniently and safely applied to afford a regular heat to the 
 acting vapour ; hence, it becomes difficult to say to what objects it is improper to 
 extend our inquiries. 
 
 Mr. Dalton made some experiments on the vapour of ammonia. The ammonia 
 he used boiled at 140 ; and its specific gravity was '9474. It had a force of 4'3 
 inches at 60 ; but on increasing the temperature, the volatile parts separated first, 
 and left the rest with a greater proportion of water, requiring a still higher tem- 
 perature to convert them into steam : this fluid is therefore inapplicable. 
 
 113. The force of the vapours of petroleum, and of oil of turpentine, has been 
 ascertained by Dr. Ure : the following tables contain his results : 
 
 EXPERIMENTS ON THE FORCE OF VAPOUR OF PETROLEUM, * OR NAPHTHA. 
 
 
 Force in inches of mercury. 
 
 . 
 
 Force in inches of mercury. 
 
 Temperature. 
 
 Ure's experi- 
 ments. 
 
 Formula. 
 
 Temperature. 
 
 Ure's experi- 
 ments. 
 
 Formula. 
 
 316 
 
 30-00 
 
 3000 
 
 350 
 
 46-86 
 
 48-1 
 
 320 
 
 31-70 
 
 31-8 
 
 355 
 
 50-20 
 
 
 325 
 
 34-00 
 
 34-1 
 
 360 
 
 5330 
 
 54-8 
 
 330 
 
 36-40 
 
 36-6 
 
 365 
 
 56-90 
 
 
 335 
 
 38-90 
 
 
 370 
 
 60-70 
 
 62-4 
 
 340 
 
 41-60 
 
 42- 
 
 372 
 
 61-90 
 
 
 345 
 
 44-10 
 
 
 375 64-00 
 
 66-5 
 
 EXPERIMENTS ON THE FORCE OF THE VAPOUR OF OIL OF TURPENTINE. 
 
 
 Force in inches of mercury. 
 
 
 Force in inches of mercury. 
 
 Temperature. 
 
 Ure's experi- 
 ments. 
 
 Formula. 
 
 Temperature. 
 
 Ure's experi- 
 ments. 
 
 Formula. 
 
 304 
 
 30-00 
 
 30-00 
 
 340 
 
 47-30 
 
 50-10 
 
 307-6 
 
 32-60 
 
 31-6 
 
 343 
 
 49-40 
 
 52-5 
 
 310 
 
 33-50 
 
 32-7 
 
 347 
 
 51-70 
 
 
 315 
 
 35-20 
 
 35-3 
 
 350 
 
 53-80 
 
 57-3 
 
 320 
 
 37-06 
 
 38-0 
 
 354 
 
 5660 
 
 
 322 
 
 37-80 
 
 39-0 
 
 357 
 
 58-70 
 
 
 326 
 
 40-20 
 
 41-1 
 
 360 
 
 60-80 
 
 65-4 
 
 330 
 
 42-10 
 
 43-6 
 
 362 
 
 62-40 
 
 
 336 
 
 45-00 
 
 
 
 
 
 For the steam of petroleum, the boiling point being 316, the rule in logarithms is 
 
 log./ = 6 (log. (t + 100) - 2-37291). 
 For the steam of oil of turpentine, which boils in a tube at 304, the rule in logarithms is 
 
 log./ = 6 (log. t + 100) - 2-36019 ). 
 
80 THE NATURE AND [SECT. n. 
 
 114. There yet remains a substance which seems to possess the properties 
 desirable in the acting vapour of an engine. It is called oil gas vapour, and is 
 separated from oil gas by the compression used to render that gas portable. It 
 has been examined by Mr. Faraday, * who found that it is insoluble in water 
 except in very minute quantities. It boils at about 170, but remains liquid at 
 common temperatures : it consists of a combination of fluids of different degrees 
 of volatility, and by repeated distillations at different temperatures the volatile 
 fluids may be separated; the most abundant separates between 170 and 200. 
 
 At common temperatures the fluid which separates between 170 and 200 
 appears as a colourless transparent liquid, of the specific gravity 0'85 at 60, having 
 the general odour of oil gas. Below 42 it is a solid body, which contracts much 
 during its congelation. At zero it appears as a white or transparent substance, 
 brittle, pulverulent, and of the hardness nearly of loaf sugar. It evaporates entirely 
 in the air, and when its temperature is raised to 186, it boils, furnishing a vapour, 
 which is 2 - 7 times the weight of the same bulk of common air. It appears, how- 
 ever, that at a higher temperature the vapour is decomposed, depositing carbon. 
 
 It is composed of six volumes of carbon, and three volumes of hydrogen, con- 
 densed into one. 
 
 115. In a paper in the 'Philosophical Transactions' on the application of 
 liquids formed by the condensation of gases as mechanical agents, Sir H. Davy 
 anticipates the probability of the application of the elastic force of compressed gases 
 to the movement of machines. * He founds this anticipation upon the immense 
 difference between the increase of elastic force in gases uiider high and low tem- 
 peratures by similar increments of temperature. The force of carbonic acid was 
 found to be equal to that of air compressed to ^V at 12, and of air compressed 
 to -$& at 32, making an increase of pressure equal to the weight of 13 
 atmospheres. 
 
 116. I think, however, it will be found, that two other circumstances should 
 be considered in estimating the fitness of compressed gases as mechanical agents. 
 First, The distance through which the force will act ; for if this distance of its 
 action be less in the same proportion, as the force is increased by compression, no 
 advantage will be gained ; the power of a mechanical agent being jointly as the 
 force, and the distance through which that force acts. Secondly, The quantity of 
 heat required to produce the change of temperature is also to be considered. For 
 if the mechanical power requires as great an expenditure of heat as common 
 steam, no advantage worthy of notice w r ould be gained. In fact the only prospect 
 they afford of being useful, is through lessening the extent of surface to be heated. 
 
 1 Philosophical Transactions, 1826. = Idem, for 1823. 
 
SECT, ii.] PROPERTIES OF STEAM. 81 
 
 The idea of employing very powerful pressures, acting through a short space, 
 seems more valuable at first sight than it proves on examination. It is considered 
 that an engine of high power can be got into a small place, and will be of less 
 weight. But the real inconveniences are, the large mass of fuel required to 
 supply the engine a given time, and the immense surface that must be exposed 
 to an intense heat to obtain a given quantity of heat in a given time. Besides, 
 when we attempt to use high degrees of pressure, an accuracy of workmanship, 
 and attention to the elasticity of materials, becomes necessary, which renders the 
 work expensive and of short duration. 
 
 The success of Mr. Faraday in reducing various gases into the liquid state is 
 not however the less important. His method consisted in generating the sub- 
 stances in a bent tube of glass hermetically sealed at both ends. Then, by cooling 
 one end of the bent tube and heating the other, when heat was necessary, the gas 
 was condensed in a liquid state at the cold end of the tube. 
 
 117. Carbonic acid required the greatest precautions to effect the conden- 
 sation with safety. The liquid obtained is a limpid, colourless body, extremely 
 fluid, and floated upon the contents of the tube without mixing. It distils readily 
 at the difference of temperature between 32 and : its refractive power is much 
 less than that of water, and its vapour exerts a pressure of 36 atmospheres 
 at a temperature of 32. In endeavouring to open the tubes which contained 
 it, at one end, Mr. Faraday states, that they uniformly burst with powerful 
 explosions. * 
 
 The gases reduced to a liquid state by Mr. Faraday, with their densities as far 
 as they are known, are collected in the following table, with a column to show 
 the mechanical power compared with steam. * 
 
 1 The ingenious Mr. Brunei is attempting to work an engine where the acting vapour is to be 
 from liquid carbonic acid. It is to be regretted that his great talent for mechanical combination 
 should be employed where there is so little chance of success. 
 
 2 The power is as the force and the space through which the gas passes in its reduction to the 
 state of liquid. (See Sect, iv.) The space is found by comparing the density of the body in the 
 liquid state with its density in the gaseous under the same pressure ; and as the weight of air is 
 to water as 1 : 828, to find the mechanical power of equal volumes of the liquid, we have simply 
 to multiply 828 by the specific gravity of the liquid, and divide the product by the specific gravity 
 of the body in the state of gas. The force does not enter into the calculation, because the density 
 of the gas must obviously be greater in the same proportion. The quantity of heat is most pro- 
 bably in the ratio of the power : if this be the case, all substances will afford equal powers with 
 equal quantities of heat. 
 
82 
 
 THE NATURE AND 
 
 [SBCT. II. 
 
 Body. 
 
 Specific gravity 
 of the gas, air 
 being unity. 
 
 Specific gravity of 
 liquid, water 
 being unity. 
 
 Temperature. 
 
 Force in 
 atmospheres. 
 
 Mechanical power 
 of equal weights 
 of the gases. 
 
 Carbonic acid gas 
 
 1-527 
 
 
 32 
 
 36 
 
 
 Sulphuric acid gas 
 
 2-777 
 
 1-42 
 
 45 
 
 2 
 
 426 
 
 Sulphuretted hydrogen gas 
 
 1-192 
 
 0-9 
 
 50 
 
 17 
 
 630 
 
 Euchlorine gas 
 
 2-3&5 
 
 
 
 
 
 Nitrous oxide 
 
 1-527 
 
 
 45 
 
 50 
 
 
 Cyanogen 
 
 1-818 
 
 0-9 
 
 45 
 
 3-6 
 
 395 
 
 Ammonia 
 
 0-5962 
 
 0-76 
 
 50 
 
 6-5 
 
 1057 
 
 Muriatic acid gas 
 
 1-285 
 
 
 50 
 
 40- 
 
 
 Chlorine 
 
 2.496 
 
 1-33 
 
 50 
 
 4- 
 
 440 
 
 Steam of water 
 
 0-48 
 
 1-000 
 
 212 
 
 1- 
 
 1711 
 
 These are the principal researches that have been made on the force of vapours 
 at different temperatures, when in contact with liquids ; but, in order to render 
 the subject more complete, we must consider the force when not in contact with 
 the liquids which generate them, and also their density and volume. 
 
 OF THE ELASTIC FORCE OF VAPOUR SEPARATED FROM THE LIQUIDS FROM 
 WHICH THEY WERE GENERATED. 
 
 118. It has been remarked, that the elastic force of steam or vapour produced 
 by increase of temperature ceases to follow the same law where it is not in 
 contact with the liquid from which it was formed. (Art. 87.) The density of the 
 steam no longer increases, the force being solely that which prevents it expanding, 
 and is measured from the quantity it would expand if unconfined. The expansion 
 by the same increase of temperature having been found to be the same in all 
 gases and vapours, and the density as the compressing force, as far at least as 
 60 atmospheres, it becomes an easy task to compute this species of force within 
 that range of compression. 
 
 This will also be further useful in determining the volume occupied by steam 
 of a given density and temperature as far as about 60 atmospheres : higher we 
 need not attempt to go for useful purposes ; and if we did, our rules would fail, for 
 there is not even a probable chance of the law, of the density being as the force, 
 extending to very high degrees of compression. 
 
 119. The quantity a gas or vapour expands under a constant pressure, is 
 found by the following rule. 
 
 RULE. To each of the temperatures before and after expansion, add 459. Then 
 divide the greater sum by the less, and the quotient multiplied by the volume at 
 the lower temperature will give the volume at the higher temperature. 
 
 Or let t be the temperature with the volume v, and t' any other temperature, 
 then 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 459 + t' 
 
 v = the volume at the temperature /'. 
 
 RULE. As the volume the vapour occupies is to the volume it would become 
 by expansion, so is the elastic force at the lower temperature to that at the 
 higher one. 
 
 Or, 
 
 459 +S 459 
 
 Taking as an example M. Cagniard de la Tour's experiments on ether, it is 
 stated that it was completely in a state of vapour at a lower degree ; but the 
 differences do not indicate this to have taken place till it was 447, and its force 
 was 68 - 8 atmospheres; required its force at 617. In this case 
 
 459 + 617 
 
 ~\- 44 / 
 
 ca , _ 
 x 68-8 = 81-7 atmospheres. 
 
 In the experiment he states it as 94 atmospheres, and undoubtedly in conse- 
 quence of the vapour of mercury forming in the apparatus, (art. 107.) ; and a like 
 remark applies to all his experiments ; for our rule for the expansion rather 
 exceeds the truth than otherwise. 
 
 120. By reversing the process, we may find the volume steam will occupy 
 under any compressive force not exceeding 60 atmospheres, when its volume is 
 known for a given temperature and pressure. For example, at 60 its force being 
 30 inches of mercury, its volume is 1324 times its volume in water. 1 Now by 
 increasing its temperature to the degree t' its volume would be, 
 
 1 The volume of any vapour or gas at 60 and 30 in. is easily found from chemical tables con- 
 taining their specific gravity, compared with air at that temperature and pressure ; for air is 828 
 times the volume of an equal weight of water ; consequently, the number 828 being multiplied 
 by the specific gravity of the liquid, and divided by the specific gravity of the vapour in question, 
 gives its proportion of volume to an unit of volume of the liquid. 
 Thus steam is of the specific gravity '625 ; and 
 
 828 
 
 625 
 
 = 1324. 
 
 The following table may be found useful in similar calculations with various liquids. 
 
 Substance. 
 
 Specific gra- 
 vity in liquid 
 state, water 
 being unity. 
 
 Specific gra- 
 vity in vapour, 
 air being unity. 
 
 Volume of va- 
 pour for one of 
 liquid at 60 
 and 30 in. 
 
 Constant 
 number for 
 formula. 
 
 Volume at the 
 boiling point 
 of the liquid. 
 
 Boiling point. 
 
 Water 
 
 1-000 
 
 0-625 
 
 1324 
 
 76-5 
 
 1711 
 
 212 
 
 Alcohol 
 
 825 
 
 1-6133 
 
 423 
 
 24-5 4 
 
 476 
 
 173 
 
 Sulphuric ether 
 
 632 
 
 2-586 
 
 203 
 
 11-7 
 
 220 
 
 104 
 
 Sulphuret of carbon 
 
 1-272 
 
 2-6447 
 
 398 
 
 23-0 
 
 440 
 
 116 
 
 Naphtha 
 
 758 
 
 2-833 
 
 224 
 
 13-0 
 
 280 
 
 186 
 
 Oil of turpentine 
 
 792 
 
 5-013 
 
 130 
 
 7-5 
 
 193 
 
 314 
 
 Oil gas liquid 
 
 85 
 
 2-7 
 
 260 
 
 15-0 
 
 337 
 
 186 
 
 From this table it appears that one volume of water produces more vapour than an equal volume 
 of any other substance in the list. 
 
84 THE NATURE AND [ SECT . n. 
 
 And /: 30 : : 2-55 ( 459 + t' } : 30 x 2>55 ^ 45i) + O = 76-5 (459 + f) 
 \ I f f 
 
 the volume at the force /and temperature t'. 
 
 121. Hence, we have this convenient rule for finding the volume or space 
 the steam of a cubic foot of water occupies, when the steam is of any given elastic 
 force and temperature. 
 
 RULE. To 459 add the temperature in degrees, and multiply the sum by 76'5. 
 Divide the product so obtained by the force of the steam in inches of mercury, 
 and the result will be the space in cubic feet the steam of a cubic foot of water 
 will occupy. 
 
 Example. If the force of the steam be 4 atmospheres, or 120 inches of 
 mercury, the temperature to that force being, according to Mr. Southern's experi- 
 ments 295 (art. 77.) ; then 459 + 295 = 754 and 
 
 754 x 76-5 _ 57681 ^ _ 
 
 120 ~120~ 
 
 Its volume found by experiment was 404 ; and considering the difficulty of 
 ascertaining the volume, on account of the allowances to be made for escape of 
 steam of such a high temperature, it agrees very well with the calculated result. 
 According to Dr. Ure's experiments, the force of steam at 295 is 129 inches, 
 which gives 446 for the number of times the volume is increased by converting 
 into steam of that force and pressure. 
 
 OF THE MIXTURE OF Am AND STEAM. 
 
 122. It is a well-known fact that common water contains a considerable por- 
 tion of air or other uncondensible gaseous matter ; and when water is converted 
 into steam, this air mixes with it, and when the steam is condensed, remains in the 
 gaseous state. If means were not taken to remove this gaseous matter from the 
 condenser of an engine, it would collect so as to obstruct the motion of the piston : 
 but even when means for removing it are employed, a certain quantity constantly 
 remains in the condenser of an engine ; and, in order to determine its state, we 
 must consider the effects produced by mixing air with steam, or vapour, at different 
 temperatures and pressures. 
 
 Let us suppose that we have air and vapour of the same temperature t, and 
 elastic force p ; and that the volumes are v and v'. If they were now put one on 
 the other in a closed vessel of the capacity v+v', it is plain they could preserve an 
 equilibrium, because the temperature is the same, and the mutual pressures are 
 equal ; but this equilibrium would not be stable. 
 
SECT, ii.] PROPERTIES OF STEAM. 85 
 
 Experience proves that these gases would gradually mix together till they 
 became completely intermixed. It further shows that during this operation heat 
 is neither evolved nor absorbed ; so that after a certain time the mixture is per- 
 fectly homogeneous, the two gases holding the same proportion in every part, and 
 the temperature and pressure being t and p. From these facts, established by 
 observation, we may deduce another equally well verified by experience. 
 
 123. If two gases, or a gas and vapour, mixed together at the temperature t, 
 fill a volume v ; and if p and f denote the pressures they would separately exert 
 when separately occupying the same volume v, at the same temperature t, the 
 pressure of the mixture will be p +f. 
 
 In effect, let us suppose that the two gases at first are distinct, and let f be 
 greater than p ; then dilating the gas under the pressure /, until f changes to p, 
 its volume will become 
 
 I/ 
 P 
 
 provided the same temperature t has been preserved. Placing the two gases now 
 one on the other, their united volume is 
 
 v + L/ or I (p+f). 
 P P 
 
 124. These gases, according to what we have said above, will equally intermix 
 without changing their temperature or common pressure p. Now according to the 
 law of the volume being inversely as the pressure, which is true of mixed as well 
 as of simple gases, if we compress the mixture without changing its temperature 
 
 until its volume - (p+f) becomes v, the pressure p will become p+f, the same 
 
 as we had to prove. 
 
 Equally good would the principle hold with three or more gases, or with a mix- 
 ture of gases and vapour : in all cases the united pressure will be equal to the sum 
 of all the pressures which the gases or vapours would each exert, when separately 
 occupying the same volume v at the same temperature t. 
 
 When a change of temperature takes place, either after or during the mixture, 
 the first temperature being t ; then 
 
 = the volume at the new temperature t', and pressure p. 
 
 125. This is compared with General Roy's experiments in the following table, 
 formed from the mean results which he obtained. 1 Commencing at zero, 1000 
 parts of air, in contact with water, and under a pressure of 32'18 inches, is 
 
 Philosophical Transactions, vol. Ixvii. p. 653. 
 
THE NATURE AND 
 
 [SECT. H. 
 
 increased in volume by the formation of vapour, and increase of temperature, as 
 shown in the second column of the table ; while the third is the force of vapour at 
 these temperatures by our rule, page 59 : the fourth is computed by the rule in the 
 preceding article. 1 
 
 Temperature. 
 
 Volume of air 
 and vapour by 
 experiment. 
 
 Force of vapour, 
 by Rule 
 
 page 59. 
 
 Volume of air and 
 vapour by formula, 
 art. 124. 
 
 
 
 1000-00 
 
 0-032 
 
 1000 
 
 32 
 
 1071-29 
 
 0-172 
 
 1076 
 
 52 
 
 112305 
 
 0-401 
 
 1132 
 
 72 
 
 1182-50 
 
 0-842 
 
 1190 
 
 92 
 
 1255-14 
 
 1-629 
 
 1260 
 
 112 
 
 1353-75 
 
 295 
 
 1360 
 
 132 
 
 1491-06 
 
 5-07 
 
 1500 
 
 152 
 
 1688-96 
 
 8-33 
 
 1680 
 
 172 
 
 1929-78 
 
 13-17 
 
 1930 
 
 192 
 
 2287-44 
 
 20-16 
 
 2300 
 
 212 
 
 2671-94 
 
 30-00 
 
 2850 
 
 The agreement with experiment is in this case very near, and it affords a further 
 confirmation of the accuracy of our rule for the force of steam, below the boiling 
 point. 
 
 126. In the condenser of a steam engine the vapour will be of the elastic force 
 corresponding to its temperature, and that temperature is determined by that of the 
 fluids which condense it. 
 
 It will also always become, after a few strokes of the engine, mixed with as much 
 air as it will saturate at the given temperature and pressure ; and by the preceding 
 inquiry it appears, that this saturation will take place when there is an equal mix- 
 ture of air and vapour in the condenser ; consequently, only half the quantity 
 drawn out by the air pump at one stroke will be air, the rest will be uncondensed 
 vapour ; and the quantity of air drawn out at each stroke must be at least equal to 
 all the air which enters both from the boiler, from the injection water, and from 
 leakage at the joints in the time between stroke and stroke : a slight variation on 
 either side, however, will not, it may easily be proved, have much effect in 
 retarding the engine. 
 
 As the volume the air and vapour occupy determines the air pump to be of a 
 large size, and consequently expensive both in construction and power, in order to 
 
 1 An erroneous formula for this purpose has been copied into several works : it is 
 
 V -~. = the volume ; and does not at all agree with the experiments. 
 Pf 
 
 I gave an analysis of the correct rule in my work on Warming and Ventilating, p. 291. It has 
 also been investigated by M. Poisson, whose mode of illustration is followed in the above. 
 
SECT . .] PROPERTIES OF STEAM. 87 
 
 lessen its bulk, a second injection might be made within the air pump ; but the 
 utmost that could be gained by this method would be very little more than the 
 difference of volume due to temperature, not perhaps one-tenth of the volume of 
 the pump in any case. 
 
 It is important to remark, that in steam from salt water, the same quantity of air 
 will occupy more space, on account of the steam being of less elastic force at the 
 same temperature ; but perhaps this is more than compensated for, by salt water 
 containing less air. 
 
 OF THE MOTION OF ELASTIC FLUIDS AND VAPOURS. 
 
 127. A knowledge of the principles and circumstances which affect the motion 
 of elastic fluids, is of considerable importance, in assigning the relative proportion of 
 the parts of a steam engine. It is a subject that has been very little studied in 
 discussing the theory of this invaluable machine, and therefore it is one which will 
 engage a considerable share of our attention in this work. Steam is in motion 
 during its action ; it must move through passages to perform its office, and be 
 forced through others as it retires ; and the effect of disproportion it is difficult to 
 determine from practice alone, because the result depends on so many contingent 
 circumstances. 
 
 The best method, therefore, must be to separate the effects, and study each 
 independently : there is then reason to hope that they may be united into a perfect 
 system ; and at least it shall be our endeavour to forward this desirable end to the 
 extent of our power. 
 
 128. The condition of free elastic fluids has been shown to be regulated by 
 the pressure and temperature of the atmosphere ; and, when an elastic fluid is con- 
 fined in a close vessel, its condition as to temperature and pressure must be similar 
 to that it would be in, if in an atmosphere of the same fluid capable of producing 
 the same pressure upon it. 
 
 129. The most convenient method of investigating the motion of an elastic 
 fluid, is, to find the height of a homogeneous column of the same fluid, capable of 
 producing the same pressure as that to which the fluid is subjected ; for then the 
 fluid would rush into a perfect vacuum with the velocity a heavy body would 
 acquire by falling through the height of the homogeneous column, when a proper 
 reduction is made for the contraction of the aperture. 
 
 130. If a pipe of communication be opened between two vessels containing 
 elastic fluids of different elastic forces, the velocity of the efflux through the pipe at 
 the first instant will be that which a heavy body would acquire by falling through 
 the difference between the heights of homogeneous columns, of the fluid of greatest 
 
88 THE NATURE AND [SECT. n. 
 
 elastic force, equivalent to the pressures : and it would be as the velocity acquired 
 by falling through the difference between the heights of the columns equivalent to 
 the pressure at any other instant ; the height to be ascertained for the instant at 
 which the velocity is required. After a certain time, the pressures or elastic forces 
 would become equal, and the velocity of course would be nothing. 
 
 131. The consideration of chimneys is another case of the motion of elastic 
 fluids, where, by increase of temperature, a part of an atmospheric column is ren- 
 dered of a different density. Some mistakes have been committed in treating this 
 case ; but we must proceed to treat of the motions which take place in engines, and 
 first of the allowances to be made for contractions. 
 
 132. In the motion of elastic fluids, it appears from experiments, that oblique 
 action produces nearly the same effect as in the motion of water, in the passage of 
 apertures ; and that eddies take place under the same circumstances, tending to 
 retard the motions in a considerable degree. 
 
 133. The velocity of motion that would result from the direct unretarded 
 
 action of the column of the fluid which produces it being unity - I'OOO or 8 
 
 The velocity through an aperture in a thin plate by the same pressure is - -625 l or 5 
 
 Through a tube from two to three diameters in length projecting outward - -813 or 6'5 
 
 Through a tube of the same length projecting inwards - - -681 or 5-45 
 
 Through a conical tube, or mouth piece, of the form of the contracted vein - -983 or 7-9 
 
 134. Every enlargement of a pipe which is succeeded by a contraction 
 reduces the velocity of the motion, and in proportion to the nature of the con- 
 traction, and every bend and angle in a pipe, is attended with a diminution of 
 velocity. Hence, as far as convenience will admit, these causes of loss should be 
 avoided ; and where they must be introduced, such forms should be given as will 
 lessen the defect as much as possible. 
 
 OF THE MOTION OF STEAM IN AN ENGINE. 
 
 135. We have stated (art. 129.) that the most convenient mode of determining 
 the motion of steam, is, by finding the height of a column of the same fluid which 
 would produce an equal pressure upon a base of equal area : the manner of deter- 
 mining this column is therefore the first point to be considered. The force of 
 steam is sometimes expressed by the pounds on a square inch ; sometimes by the 
 inches in height of a column of mercury, and not unfrequently by the number of 
 atmospheres : it will therefore be an advantage to find the height of a column of 
 water equivalent to each of these measures ; and then, that being multiplied by the 
 
 1 According to experiments on air made by Mr. Banks, 0-634. See Power of Machines, p. 13. 
 
SECT. ii. J PROPERTIES OF STEAM. 89 
 
 relative bulk and pressure of the steam, the height of the column of steam will be 
 
 found. 
 
 C~ 1 Ib. per square inch is 2'31 feet. 
 
 The height of a column of water at 60 equivalent to I 1 Ib. per circular inch is 2-94 feet. 
 the pressure of j 1 inch of mercury is 1'133 feet. 
 
 [_ the atmosphere is 34-0 feet. 
 
 The water is supposed to be of the temperature 60, and the atmosphere equal to 
 a pressure of 30 inches of mercury : the bulk of the steam will depend on the 
 pressure and temperature, and will be given for the range of practice in a table at 
 the end of the volume, or may be found by art. 121. For example, the volume 
 of steam at 212 being 1711 times the bulk of the equivalent quantity of water at 
 60, and the pressure being 30 inches of mercury, or 34 inches of water, we have 
 1711x34=58174 feet, the height of an atmosphere of steam at 212. 
 
 136. If an aperture were formed so that there would be no oblique action in 
 passing it, a gaseous fluid or vapour would rush through it into a perfect vacuum, 
 with the velocity a heavy body would acquire in falling through the height of the 
 column of the same fluid equivalent to the pressure. 
 
 And this velocity in feet per second is equal to eight times the square root of the 
 height of the column ; l but through pipes and other apertures the velocity will be 
 only 5, or 6^, or other number of times the square root of the height of the column, 
 as shown in the table, art. 133. for each kind of aperture. 
 
 137. RULE. If the height of a column of steam equivalent to the pressure of 
 steam in a boiler be determined, and also the height of a column of the same steam 
 equivalent to the pressure on the piston of a steam cylinder, then the velocity will 
 be equal to 6 '5 times the square root of the difference between the heights of the 
 two columns. This result is the velocity in feet per second through a straight pipe. 
 
 1 In algebraic notation ; let / be the inches of mercury equal to the force of the steam or the 
 pressure on the fluid, b the bulk of the fluid when the same weight of water is 1, and h = the 
 height of an atmosphere of the fluid of uniform density. Then, 1-13 fb^=h ; and 
 
 8 >/* = w = 8 V 1-13/4, 
 
 when the fluid flows into a perfect vacuum without contraction at the aperture. In the best 
 formed pipes it is 
 
 in common formed ones 
 
 6-5 Jh = v. But * = 76-5(459 + (art m) . 
 
 hence 
 
 v = 6-5 v/86-5 (459 + ^), the velocity into a vacuum, 
 when t' is the temperature of the steam. 
 
 X 
 
90 THE NATURE AND [SECT. n. 
 
 138. The quantity of steam generated may be considered to be equal to the 
 quantity consumed in the same time, or that the boiler is of sufficient capacity to 
 admit of its being taken at intervals without a sensible loss of elastic force ; and as 
 these conditions are essential to a good engine, we shall consider them to be 
 fulfilled. (See sect. in. art. 210. for the proportion of space in boilers.) 
 
 139. The volume of steam required in a second is equal to the area of the 
 piston multiplied by its velocity in feet per second : and its density or elastic force 
 must be as much less than that of the steam in the boiler, as to allow the same 
 weight of steam to pass in a second through the steam passages ; for if it passed 
 through the steam passages with no greater velocity than that of the piston, those 
 passages must be of the same area as the cylinder ; but as they are less than the 
 cylinder, the excess of velocity must be produced by a corresponding excess of force 
 in the boiler. 
 
 140. The steam, till it has passed the narrowest part of the passages, will have 
 the same density as in the boiler, but in the cylinder it must expand till its density 
 be so reduced as to cause the difference of pressure producing the velocity through 
 the contracted passages ; and as the density is as the elastic force, the force of the 
 steam in the boiler multiplied by the velocity, and the area of the passage, must be 
 equal to the elastic force on the piston multiplied by its area and velocity. 
 
 That is, fa v = p A V, when / is the force of the steam in the boiler in inches of 
 mercury ; a the area of the steam passages ; v the velocity ; p the force on the 
 piston in inches, A its area, and V its velocity. 
 
 From this we have 
 
 P A V 
 
 V = . 
 
 But by the rule (art. 137.) 
 
 t, = 6-5 v'TTSK/^)"; 
 
 therefore = 6-5 V MS b (f- P ). 
 
 If the area of the steam passage be required, we have 
 
 'AL_ - 
 
 f\ T _ 
 
 ~ 6-5 / */l-13b(f-p) ' ~ 6-5 / V 86 5 (459+7) ' 
 
 when nf=fp = the loss of force, which should not be exceeded. 
 
 141. In practice for low pressure engines it is usual to make the diameter of 
 the passage about one-fifth of the diameter of the cylinder, and then its area is zV 
 of the area of the cylinder : and as this proportion is grounded upon the experience 
 of the difficulties involved by making the passages larger, it ought not to be 
 departed from without a sufficiently obvious advantage. 
 
 142. This formula applies only to the case of a pipe without obstructions, and 
 
SECT, ii.] PROPERTIES OF STEAM. 91 
 
 we have no experiments by which the effect of these causes of diminution can be 
 estimated with accuracy, but we may endeavour to allow for them on the principles 
 which operate in similar circumstances. For this purpose let the part of the pipe 
 from whence the change of figure takes place, be considered a vessel with an aper- 
 ture of the kind nearest resembling the figure of the branching pipe, and the loss 
 of motion at the place equal to that which such an aperture would cause. 
 
 Thus when the angle is a right angle, the loss of velocity may be considered half 
 that which takes place when a pipe is inserted in the side of a vessel, as the dimi- 
 nutions in the exterior half of the aperture will not be so great in this case ; there- 
 fore the loss will be 
 
 1-000 -813 
 
 _ = -094 nearly ; 
 
 and may be allowed for by diminishing the velocity one-tenth, for each right-angled 
 bend. 
 
 The same allowance for loss should be made when one pipe branches at right 
 angles from another. 
 
 143. In a pipe formed to a regular curve, or bent only to an obtuse angle, the 
 reduction will not exceed that which happens with a conical mouth-piece, which is 
 about THT of the velocity. 
 
 If a pipe be terminated in a valve box, the allowance of two-tenths should be 
 made for the loss of velocity in passing the valve. 1 
 
 144. Few engines have less than three obstructions equivalent to passing so 
 many different apertures, which together may be expected to reduce the velocity so 
 as to require the number 6'5 to be reduced to 4'5 ; consequently, the formula may 
 
 be stated 
 
 ^A V A V (1 - ) 
 
 a = 
 
 4-5 / >/ 86-5 (459 + t') 42 V (459 + t') 
 
 1 When a series of obstructions of the same kind occur in a pipe, the reduction for the first 
 
 being , the velocity will be reduced from V to 
 1 
 
 (1 \ n 
 1 - -j 
 
 y 
 
 in passing n obstructions. For the loss of velocity at the first obstruction must be ; hence it 
 
 will be reduced to 
 
 a 
 
 a 
 
 and this quantity will be similarly reduced in the same proportion at each contraction. 
 To calculate the amount of such a succession of diminutions, we have 
 
 log. V + log. ( 1 ) = the logarithm of the reduced velocity. 
 
92 THE NATURE AND [SECT. n. 
 
 which will enable us to compare with practice after considering the other causes 
 of loss. 
 
 145. Loss of force by cooling. But much of the force of the steam will also 
 be lost in the passage through the steam pipe by cooling. The quantity of steam 
 exposed during a second is as the area and velocity of the steam ; or 
 
 = , cubic feet : 
 144 
 
 a being in inches, the rest in feet. 
 
 The surface is as the length and circumference, or 
 
 *-rf 4/a 
 = I x -r-r = , square ieet. 
 
 I "- I - a 
 
 Hence the loss of heat being directly as the surface, and inversely as the quantity 
 exposed, we have for cooling in metals 
 
 8-1 (T-Q 4/a 144 
 
 60 12rf av~ 
 
 the loss of heat in a second ; or rather the loss of heat which the quantity passing 
 in one second experiences. 1 By reducing the expression to its lowest fraction it 
 becomes 
 
 f , _l-7 I (T - f) 
 dv 
 
 In this equation 
 
 T is the temperature of the surface of the steam pipe, which will be about 
 
 one-twentieth less than that of the steam ; 
 t' 1 is the temperature of the air, 
 / the length of the pipe in feet, 
 d its diameter in inches, 
 and t; the velocity in feet per second. 
 
 146. In applying this formula to find the loss of heat, there are no other 
 circumstances to be considered ; but in its application to determine the loss of 
 elastic force, there is a most important point, to which I would particularly direct 
 the attention of manufacturers of engines. It is the degree to which the 
 temperature of the steam is reduced by passing through the pipe. It is said to be 
 frequently as much as would reduce its temperature below 212; when this is the 
 case, we know that part of the steam must become water, and the rest of it become 
 of the force equivalent to a temperature of 212, and therefore all the excess of 
 force which was generated in the boiler, would be destroyed by the cooling in the 
 passage to the engine. 
 
 1 Tredgold on Warming and Ventilating, art. 44. 
 
8ECT . .] PROPERTIES OF STEAM. 93 
 
 147. A knowledge of this cause of the reduction of the force of steam to 
 atmospheric elastic force, and of the importance of not losing force where either 
 economy of heat or of space is desirable, creates a strong desire to know its amount, 
 knowing that the most esteemed manufacturers of steam-boat engines cause the 
 steam to pass round between the jacket and the cylinder; as if to expose it 
 as much as possible to the cooling 'effect of the atmosphere, to reduce its elastic 
 force before it enters the cylinder to exert its power. 
 
 148. The reduction of the temperature of steam reduces its elastic force to 
 that of a lower temperature, and during this reduction a portion of the steam 
 becomes water. If/ denote the elastic force in the boiler, and /' that after the heat 
 has been lost, 
 
 will be the quantity reduced to water, and this multiplied by its heat of conversion 
 into steam must be equal to the heat the whole has lost by cooling ; therefore 
 
 And here it will be remarked, that when t'" is equal to the whole heat of con- 
 version, f will be nothing ; or the whole will be cooled into water as it is in an 
 apparatus for warming buildings. We are now in a condition to give an answer 
 to the question of what is the loss of force in any particular case. Let the tempe- 
 rature of the steam be 220, and its force 35 inches of mercury, the length of the 
 steam pipe 12 feet, its diameter 6 inches, the velocity of the steam in the pipe 
 80 feet per second, and the temperature of the air 60. Then by art. 145. 
 we have 
 
 = 220-- =209 
 20 
 
 -O = 1-7 x 12 x (209-60) = 
 
 dv 6 x 80 
 
 and therefore by the equation above we have 
 
 '('-) -(>-) -"" 
 
 consequently there is in this case a loss of force equivalent to 0*23 inches of 
 mercury, or TTTT of the force ; but this is one of the most favourable of the cases 
 that usually occur in practice. In steam-boat engines where the steam has to 
 pass round the cylinder, the force in the cylinder is stated, from observation, 
 
 1 The number 967 is here taken as the heat of conversion into steam, but in general I use 
 1000 as more accurate. (See art. 82.) 
 
94 THE NATURE AND ' [ SEC T. n. 
 
 not to exceed about twenty-eight inches, when the force in the boiler is about 
 thirty-six inches. 
 
 149. It is obvious that the higher the force and temperature, the greater will 
 be the reduction by cooling, and therefore the loss in engines of Woolf s method 
 of construction, where the steam has to make its way round the cylinders, must 
 be greater, and take away much from that increase of effect arising from the use 
 of high pressure steam, to gain which so much risk at the boiler is encountered. 
 
 OF THE AREA OF THE STEAM PASSAGES. 
 
 150. The formula for calculating the motion of steam in an engine has no 
 maximum value to assist us in the choice of a proportion for applying it in 
 practice ; but it shows that the larger we make the aperture, the less we shall lose 
 of the elastic force of the steam. On the other hand, we have shown that the 
 loss of force by loss of heat is greater, the less the velocity and diameter of the 
 pipe. The proportions, however, which about render the loss by the two causes 
 equal have been found most convenient in practice, and therefore claim the pre- 
 ference. There are two rules in use, and neither of these is exactly the same as 
 the theoretical one. 
 
 151. The one is to make the diameter of the steam ways one-fifth of the 
 diameter of the cylinder. This appears to be Boulton and Watt's proportion. 
 
 152. The other is to make the area of the passage one superficial inch for 
 each horse power. 
 
 153. The obvious intention of these rules is, that the steam should move 
 with the same velocity, or require the same impelling force, in any sized engine. 
 Either of them gives nearly the result, but neither of them gives it exactly. For 
 the horse power in a small engine requires more steam than in a large one, and 
 therefore the aperture should be greater in small engines, or less in large ones, than 
 one inch area for each horse power. 
 
 Again, engines having a short stroke move slower than those with a long one, 
 and therefore should have the steam passage of a different proportion of the 
 diameter according to the velocity. 
 
 154. To render the velocity very nearly the same in all cases, we have this 
 rule. 1 
 
 1 From the equation (art. 144.) we have, when n = -00694, supposing -^ part of the force to 
 be lost in producing the velocity, 
 
 _ AV _ 
 ~ 3-357 V 459 + i 
 
SECT. .] ' PROPERTIES OF STEAM. 95 
 
 Multiply the length of the stroke by the number of strokes per minute, and 
 divide the product by 2400 ; the square root of the quotient multiplied by the 
 diameter of the cylinder is the diameter of the pipe. 
 
 Example. To find the diameter for the steam pipe of an engine of which the 
 diameter of the cylinder is 2 feet, the length of the stroke 2'5 feet, and the 
 number of strokes per minute 38 ; 
 
 38 x 2-5 _ _95_ J_ 
 2400 = 2400 ~~ 25' 
 
 and the square root of TS is one-fifth ; hence the diameter of the steam pipe in this 
 case is one-fifth of that of the cylinder. 
 
 The same rule applies to both high pressure and low pressure steam engines, 
 and both to the steam passages and the passages to the condenser ; and the excess 
 of force necessary to produce the velocity is very nearly one- 144th part of the 
 force of the steam. 
 
 OF THE Loss OF FORCE BY THE COOLING OF THE CYLINDER. 
 
 155. The steam after it gets within the cylinder is liable to a loss of force 
 by cooling. It is, in large engines, usually inclosed by a case called a jacket, and 
 steam is introduced between this case and the cylinder to keep the latter hot ; but 
 the loss in fuel by this mode is the same as with a naked cylinder, and there is 
 clearly no advantage in preserving the force of the steam by adding this case, 
 unless it be supplied with steam by a separate pipe. (See art. 147.) 
 
 156. The investigation for the loss of force in the steam pipe applies in the 
 case of a naked cylinder with a very slight alteration. The steam in this case is 
 progressively exposed to the sides of the cylinder ; hence the loss will be some 
 
 and when we use the length of the stroke I, and the number per minute m ; 2 / m = 60 V, and we 
 may take 
 
 Aim 
 
 a =- 
 
 90 V 459 + t 
 
 When t' = 220, it becomes 
 
 Aim 
 2400 
 
 which is the same as the rule. If t' = 320, then 
 
 _ Aim 
 ~ 2520 
 
 showing that a rather smaller aperture will do for high pressure steam. A is the area of the 
 cylinder, and a the area of the pipe, in superficial inches. 
 
96 THE NATURE AND [SECT. n. 
 
 little, but not materially less, than that which would take place were it kept con- 
 stantly exposed to the sides. But to the convex surface the ends of the cylinder 
 have to be added. 
 
 With the addition of the ends to the surface, the quantity of cooling in degrees 
 per second, (from art. 145.) becomes 
 
 t'" = -07(24/+d) (T-Q 
 dv 
 
 where / is the length of the cylinder in feet, d its diameter in inches, v the velocity 
 of the piston in feet per second, T the temperature of the steam less -jV part, and 
 t" the temperature of the air. The force is reduced to 
 
 (t'" \ 
 1 Q=), the force on the piston, as in art. 148. 
 
 157. When low pressure steam is employed, the temperature T will be 212 C > 
 and putting t" = 60, and supposing 
 
 / = , and v = 3-5, 
 12 
 
 we shall have 
 
 07 (9A r a- d) (T t'') 
 
 = 15-2 degrees ; 
 
 967 10U 
 
 Therefore in low pressure engines there is a constant loss for all sized engines of 
 about TffTT of the power. When a casing is used and kept constantly filled with 
 steam, the loss of heat and constantly of power from the same fuel will be greater ; 
 because the surface will be constantly kept at the temperature of the steam. I hope 
 this will be sufficient to establish the truth, that the steam case is a useless addi- 
 tion to the expense of an engine. 
 
 158. In a high pressure engine working at 300, the loss by a naked cylinder 
 is only about sV part of the force. 
 
 159. The best mode of preventing loss is to put a case with an air-tight cavity 
 between it and the cylinder, instead of filling this case with steam ; and besides the 
 advantage of saving fuel the engine-rooms will not be heated so much. 
 
 160. The single engine will lose more heat but not quite double the quantity 
 of the double engine ; hence we shall be about its amount in stating the cylinder 
 at losing A of the power. It will also lose double the quantity by the passage 
 of the steam from the boiler to the cylinder. 
 
 161. In atmospheric engines the loss of force by cooling in the cylinder, when 
 a separate vessel is used for a condenser, is an interesting inquiry. Assuming that 
 the piston is kept steam-tight without the use of water, the loss must be greater 
 
SECT, ii.] PROPERTIES OF STEAM. 97 
 
 than in the single steam engines by the amount lost in cooling the inside of the 
 cylinder half the time ; hence the value of / the length of the cylinder must be 
 increased one-half, besides doubling the area exposed in a given time. This will 
 render the equation for the loss of temperature, (art. 156.) 
 
 ?' = '14 (36 I + <*) (T - t") 
 
 ' dv 
 
 With the proportions and temperatures of the example, (art. 157.) the loss by 
 cooling is about A of the power; therefore it is not this species of loss which 
 should prevent this simple kind of engine being employed for mines. 
 
 If water be applied to keep the cylinder tight, the additional loss from convert- 
 ing this water into vapour will be considerable. If the mean temperature of this 
 water be 180, the effect of each foot of area will be to abstract, or to destroy a 
 cubic foot of steam per minute, this being the quantity of evaporation from a foot 
 of surface of water sustained at that temperature. Therefore in an engine working 
 at the rate of 170 feet per minute, that is, expending 85 cubic feet of steam of 
 atmospheric density per minute, for each foot in area of the cylinder the loss will 
 be -$ = A of its power ; hence, adding this to the cooling effect, we have iV + iV 
 = about TV of the power. 
 
 162. In the common atmospheric engine where the injection is made within 
 the cylinder, the only person who had attempted to calculate the loss of force was 
 Smeaton ; of which some account has been given by Mr. Farey, in Rees's ' Cyclo- 
 paedia.' The mode of calculation is not very clearly given, and it was formed at 
 a time when the properties of heat were less known. 
 
 163. Cylinders are usually made of the same thickness, or so nearly so as to 
 render the variation not worthy of notice ; hence we will assume them to be of the 
 same thickness. The quantity of matter in them is cooled by the injection from 
 212 to about 150, rarely lower, and in good engines not lower than 170 or 
 180; the mean 160 may be taken for the effect. The specific heat of iron is 
 about 200 times that of steam, and calculating the mass of iron which must have 
 its temperature raised from 160 to between 160 and 212 by each cylinder 
 full of steam, we have the quantity which that of the steam must be lowered. 
 
 The surface of a cylinder is equal to its length, increased by half its diameter, 
 multiplied by its circumference = (/ + | d) d w ; and the thickness, with an allowance 
 equivalent to the escape of heat from the external surface, is one inch and a half 
 = one-eighth of a foot ; and the mass of metal equivalent to the absorption of 
 heat is 
 
 N 
 
98 THE NATURE AND [SECT. n. 
 
 its specific heat, allowing for the exposed side of the cylinder decreasing, is equal 
 to that of 
 
 200 ( / + d) d v 
 
 16 
 
 cubic feet of steam heated one degree ; but the temperature will rise to the mean 
 between the condensing and boiling points, or to 
 
 160 + 212 _ 18fi o 
 2~ 
 
 or the addition of heat will be 26 degrees. The whole quantity of heat consumed 
 will therefore be 
 
 200 x 26 (/ + d)dv 
 
 This divided by the capacity of the cylinder, or - , gives 
 
 16 
 
 - 
 
 50 x 26 (/ + d) 
 Id ~~> 
 
 the loss it would sustain in temperature, or 
 
 1300 (/ + rf) 
 
 ^ -- > * an d d being here both expressed m feet. 
 
 When the length of the cylinder is twice its diameter, or 2 d = I, the loss becomes 
 
 1950 
 
 d 
 
 Now one-fifth of the whole power is lost by imperfect condensation, more 
 than in engines with a separate condenser ; which is equal to 
 
 -i 197 
 
 iigi- = 225 degrees of heat ; 
 
 and by the condensation and cooling in the cylinder, we have found 
 
 1950 
 
 d ' 
 
 Hence the total heat, over and above what is required in other engines, is equi- 
 valent to converting into steam 
 
 1500 
 
 times the water necessary for the steam engine, with a condenser and steam 
 pressure. 
 
 With a cylinder 1*5 feet diameter, double the fuel is required, but for a 6-feet 
 cylinder only one-third more than in the single engine of Watt's construction. 
 
 164. This enables us to illustrate the fact observed by Mr. Watt, when he 
 
SECT . .] PROPERTIES OF STEAM. 99 
 
 repaired a working model of a steam engine for the university of Glasgow, in 
 1763. The cylinder of the model was O5 feet stroke, and 2 inches, or one- 
 sixth of a foot diameter. He " was surprised to find that its boiler would not 
 supply it with steam, though apparently quite large enough." By blowing the 
 fire it was made to make a few strokes, but required an enormous quantity of 
 injection water, though it was very lightly loaded by the column of water in the 
 pump. It soon occurred, that this was caused by the little cylinder exposing 
 a greater surface to condense the steam, than the cylinders of larger engines did 
 in proportion to their respective contents. 1 
 
 There is no doubt this difficulty was the cause of Mr. Watt turning his thoughts 
 to improve the steam engine. Our rule being applied to this case, / = i, d = i, 
 and, 
 
 1300 (I + d) 1300 a + i) in/im , 10400 + 967 
 
 ;, T ; = - =10400; and - ~<x*, or 12 times the volume 
 
 id -% x g- yo/ 
 
 of steam which would fill the cylinder would be consumed to condense at 160. 
 By lessening the load lifted, and consequently not condensing the steam to so low 
 a temperature, Mr. Watt made the engine work. 
 
 165. Now in our formula it will be observed, that 26 is half the degrees the 
 temperature of the steam falls by condensation, and that if we lessen this, the 
 quantity of heat lost will lessen in the same proportion, but the loss by uncon- 
 densed steam will be greater. The effect of the engine will be greatest when 
 the sum of these losses is a minimum, and its load should be arranged 
 accordingly. 
 
 The loss by cooling the cylinder is 
 
 25 (212-Q (* + *). 
 
 nr 
 
 when t is the temperature of condensation. 
 The loss by imperfect condensation is 
 
 1127 /' 
 30 
 
 but by our formula (art. 86.) 
 
 ., 
 
 - 
 
 Hence, with respect to t, 
 
 1127 (t + 100)6 25 (212 - t) (I + t) 
 
 30x177- -~nr = a 
 
 1 Robison's Mechan. Phil. vol. ii. p. 114. Note by Mr. Watt. 
 
100 THE NATURE AND [SECT. n. 
 
 Its differential must therefore be = 0, or 
 1127 x 6(t 
 
 30x1776 Id 
 
 whence 
 
 /30 x 1776 x 25 (l+d)\ i lftn 
 
 -ESFxtnr 
 
 Which reduces to 
 
 t = 321 (-^0 * - 100. 
 
 166. When / = 2 d, or the length of stroke is double the diameter, 
 
 , = **?_ 100; 
 
 rfi 
 
 or in logarithms, log. (t + 100) = 2-54180 - i (log. d in feet). 
 
 167. Hence it appears, that when the length of the cylinder is double its 
 diameter, the temperature of condensation, which gives the minimum loss of heat, 
 varies inversely as the fifth root of the diameter of the cylinder. When the dia- 
 meter d = 6 feet, the temperature of condensation t = 143-3 ; when d = 3 feet, the 
 temperature of condensation should be 179'5 ; and by using a table of logarithms, 
 the best temperature for condensation for any other diameter may be easily found 
 by the rule. 1 
 
 OF THE ASCENT OF SMOKE IN CHIMNEYS. 
 
 168. If a bent tube, of uniform diameter, A C B, were continued to the sur- 
 face of the atmosphere, the lowest point of the curve being at C, the centre of the 
 aperture of a chimney, and the tube of the same size as a chimney, then the tem- 
 peratures being equal at the same height in the two branches, the whole would be 
 in equilibrio ; but if a part, C D, be of a more elevated temperature than the 
 corresponding part of the other branch of the tube, that air being of less density 
 than cold air, the balance will be destroyed, and motion will take place, the moving 
 force being the difference between the weights of the columns of air. Now a 
 chimney may be considered part of such a tube ; for though, in a chimney, the 
 column of air is confined only as far as the short canal or tube of the chimnev 
 extends, the actual pressures which occur in the atmosphere are equivalent to the 
 pressures in the bent tube, and must be measured in the same manner. 
 
 1 The Rule suggested by the formula is as follows : Take out from a table of logarithms the 
 logarithm of the diameter, expressed in feet, and divide it by 5 : subtract the quotient from 
 2'54180, and the remainder will be the logarithm of a number, which diminished by 100, the result 
 will express the required temperature of condensation, in degrees. 
 
SECT. II.] 
 
 PROPERTIES OF STEAM. 
 
 101 
 
 FIG. 14. 
 
 169. When C A is the height of a uniform 
 atmosphere, C D the height of the chimney, and 
 D E the quantity the air expands by the heat it 
 receives in passing through the fire, the height E D, 
 or F G its equal, represents the height of the co- 
 lumn of air which produces the motion, and the 
 velocity will be that a heavy body would acquire 
 by falling through the height F G. If the whole 
 of C A were empty, then B H, the height of the 
 atmosphere, would be the height through which the 
 body must fall to acquire the velocity with which 
 the air would move into the tube, provided it suf- 
 fered no contraction at the entrance ; but such a 
 contraction is well known to take place in air as 
 well as in water. 
 
 170. When this is applied to a chimney, the smoke being sometimes of a 
 density different from common air at the same pressure and temperature, the same 
 excess of temperature will produce a greater or less effect in proportion as it is of 
 less or greater density than common air. This will be found by subtracting from 
 the expansion the specific gravity of the smoke or vapour, that of air of the same 
 temperature and pressure being unity. Or it may be done by an allowance of a 
 portion of the temperature for the difference of density : either method gives the 
 same result when properly calculated. In this case I intend to adopt the former 
 method. The latter is followed in my book ' On Warming and Ventilating 
 Buildings.' 1 
 
 171. Let h be the height in feet from the place where the flue enters to the 
 top of the chimney ; e = the bulk to which one foot of air increases by the change 
 
 1 The principles of calculation followed, both in this and in the work referred to, are perfectly 
 identical with those employed by Mr. Gilbert, in an excellent paper on the subject in the 
 ' Quarterly Journal of Science,' vol. xiii. p. 113 : but the notation and methods of managing the 
 processes are different ; and Mr. Gilbert's mode of calculating the expansion does not afford quite 
 satisfactory results : besides, he makes no allowances for the contractions and loss of force in 
 curvilinear motion. I mention the circumstance, because some people compare and criticise, and 
 imagine those things to be different which are in reality identical, as may easily be shown by 
 putting both in the same notation, and reducing by the rules of algebra. The great object of a 
 practical analyst is to render the final equation as easy of application as possible. As to those who 
 question principles, it is rather unfortunate for them to question those established principles of 
 pneumatics which are confirmed by experiment. It is only when theory and experiment do not 
 agree, that the principles can be called in question. 
 
102 THE NATURE AND [ SEC T. n. 
 
 of temperature ; v the velocity ; s the specific gravity of the smoke, air being 1 ; 
 and a = the area of the chimney in inches. 
 
 Then h = C D, and the expansion being as the height in feet, k (e - 1) 
 = D E = F G. But the velocity is that which a heavy body would acquire by 
 falling through the height F G ; hence, v = 8 V F G = 8 V h (e s). 1 When F G 
 is equal to B H, the line A B representing the upper line of a uniform atmosphere, 
 it becomes v = 8 V B H ; and in all other cases it is as the difference, D C - C E 
 = E D, when E C is reduced to the same density as G H. 
 
 If B be the volume of air before it be heated, then in its heated state it is B e ; 
 therefore, 
 
 va 80 , 8a 
 
 144 ~~ 144 ^ h ( e ~ s ) =Be; or-j^ */h(es) = B; 
 
 also, 
 
 a B e , 
 
 IT V 
 
 144 8 h(e-s) 
 
 The expansion e may be found from the table, ' Treatise on Warming,' &c. (art. 220.) 
 But the bulk of a gaseous body at the temperature t' is 
 
 ^ 459 + t' 
 45^+7' 
 
 when the bulk at the temperature t is unity ; hence, 
 
 459 + 1' 
 
 e s = - s. 
 
 459 + t 
 
 Substituting these expressions in the preceding equation, we have 
 
 a Be B (459 + Q (459 + Q 
 
 144 " = 8 V h (e - ) = ; 8 (459 + t) V h (t' -ts- 459 (s - 1) ) ' 
 
 172. The divisor, 8, should be changed according to the species of aperture, 
 (see art. 133.) but that which generally applies is 5 ; and t will be the mean 
 temperature of 52 ; in this case B being the quantity per hour, 
 
 B (459 + f ) 1 
 
 5 x 22-6 x 25 x V * (f - 52s- 459 (s - 1) ) ' 
 
 1 [This, in strictness, should be 8 v h e - 1 ; since h = the column of vapour equivalent to 
 
 S S 
 
 the column h of atmosphere, and A h = h e -is the excess through which a heavy body 
 
 must fall to acquire the requisite velocity : but the omission in the text cannot affect the final 
 results, as * is so nearly equal to unity, and the coefficient 8 of the expression itself offers only a 
 rude approximation, though sufficient for common practical purposes. See art. 172. ED.] 
 
SECT, ii.] PROPERTIES OF STEAM. 103 
 
 For coal smoke s = 1'05, and the formula 
 
 B (459 + 
 
 a = 
 
 2825 V h (f 78) ' 
 For low pressure steam 
 
 - = , the area in square inches. 
 56 / h 
 
 The application of the formula, with some simple rules suggested by it for 
 engines of different powers, will be given with the proportions of fire-places : the 
 investigation is given here to separate in some measure scientific inquiry from 
 practical details. 
 
 OF THE ESCAPE OF STEAM AT SAFETY VALVES. 
 
 173. This is a subject which has been little studied. If we suppose the steam 
 to be of the same density as atmospheric air, its elastic force is nearly twice as 
 great, and it would rush into the atmosphere with the same velocity that atmo- 
 spheric air rushes into a vacuum. Also, in any case, whether the elastic force of 
 the steam be greater or less than this, if n be the number of times its specific 
 gravity exceeds that of atmospheric steam, when that of air at the same pressure 
 is 1, we shall have v = S */ (n 1) A, h being the height of a uniform atmosphere 
 of air. A uniform atmosphere equivalent to thirty inches of mercury is 28,000 
 feet; hence, 1340 */ n 1 =v in feet per second. 
 
 174. In certain cases this will be aided by the buoyancy of the escaping 
 steam, and in very dense steam it may be slightly retarded by the same cause ; but 
 these effects are not so great as to need to be introduced in the calculation. They 
 may, however, be sensibly observed by turning the aperture up or down ; a light 
 fluid escaping with the greatest velocity when the aperture is turned up, a heavy 
 one when it is downwards. 
 
 175. Let a be the area of the aperture in square inches ; then, reducing the 
 velocity for the contraction in passing the aperture, we have 300 a *J n 1 = the 
 quantity of steam escaping in cubic feet per minute ; n being the number of times 
 the density is greater than that of atmospheric steam : or making c = the number 
 of cubic feet of steam generated in a second, then 
 
 = a, the area in inches. 
 
 5n V 1 
 
 This quantity should obviously be the greatest which the fire could, under any 
 possible circumstances, produce. 
 
 When n is less than 1, or the density less than the density of atmospheric steam, 
 
104 THE NATURE AND PROPERTIES OF STEAM. [SECT. n. 
 
 that is, steam at 212 and thirty inches pressure, the equation becomes negative, 
 and steam rises only by the difference between this negative quantity and the 
 buoyancy ; leading us to the beautiful theory of evaporation. 
 
 An equivalent rule is given in my book ' On Warming and Ventilating ;' but 
 though it is from the same principles, it is not there so directly nor so generally 
 derived. 1 
 
 1 Treatise on Warming, &c. p. 148. 
 
SECTION III. 
 
 OF THE GENERATION AND CONDENSATION OF STEAM, 
 AND THE APPARATUS FOR THOSE PURPOSES. 
 
 ART. 176. STEAM is generated by the application of heat, and it is condensed by 
 cold (art. 71.) ; and we have now to consider the best sources for obtaining the 
 heat for its generation with economy, and the means of applying it so as to obtain 
 the most effect. Our section therefore naturally divides itself into an inquiry con- 
 cerning combustion and fuel ; the effect of and application of fuel ; the structure 
 of boilers and fire-places ; the principles of condensation, and the apparatus. 
 
 OF COMBUSTION AND COMBUSTIBLES. 
 
 177. There are various substances, which, when heated to a certain tempera- 
 ture depending on their nature, begin to give out heat, and continue to do so till 
 the whole of the substance be completely changed into new products, most of them 
 gaseous, which in ordinary cases are dissipated in the atmosphere. A substance 
 which undergoes this change is termed a combustible, or burning body ; and if it be 
 commonly used for producing heat, it is called fuel. 
 
 178. The quantity of heat given out during combustion is the difference 
 between that which the matter operated upon contained before, and that which it 
 contains after combustion. This is an invariable quantity when the same quantity 
 of matter is operated upon, and proportional simply to the quantity of fuel used ; 
 unless indeed the process be imperfectly managed, or that we could render the 
 products of such a nature, that they would contain a less quantity of heat than 
 those usually produced. The latter would perhaps be a fruitless research ; but 
 chemistry is making rapid advances in the means of fully establishing this point. 
 It is however of the utmost importance, since the application of steam to naviga- 
 tion, to determine the effect of the mixture of combustible bodies, both with a view 
 to fix on those which contain most heat to a given quantity of matter, and to 
 
 o 
 
106 OF THE GENERATION AND [SECT. in. 
 
 render the products of less capacity for heat, so as to gain the greatest effect ; using 
 capacity to signify the whole heat these products contain, as denned art. 69. 
 
 179. There is no question that a solid contains less heat than the same sub- 
 stance when liquid, and the substance in the liquid less than in the gaseous state ; 
 provided it remain the same chemical compound : but if to a solid, which is a mix- 
 ture of different simple substances, heat of a certain degree of intensity be applied, 
 the parts of the mixture act on each other, and gaseous products are obtained 
 which contain less heat than the mixture. This is the case with gunpowder, which 
 is a mixture of charcoal, nitre, and sulphur ; and it seems necessary in this species 
 of combustion that one of the substances composing the mixture should be easily 
 fusible. It is a completely mistaken notion to suppose that the presence of any 
 particular substance is essential to combustion ; for it must take place in any mix- 
 ture of bodies which act chemically on one another at a certain temperature, so as 
 to form new products containing less heat than the substances mixed. 
 
 180. That which takes place in a mixture of bodies will also take place if 
 either a simple body or a chemical compound be exposed to the action of another 
 body, with which it always forms a new chemical combination if they be brought 
 in contact at a high temperature. Thus charcoal, heated to about 700, in con- 
 tact with oxygen burns ; and the new product formed is carbonic acid gas ; 
 consisting of the charcoal united to oxygen. At about 800, charcoal abstracts the 
 oxygen freely from the atmospheric air, and therefore burns. Now as the oxygen 
 gas changes neither its volume nor its elastic force, it may be inferred that the 
 whole of the heat contained in the charcoal is liberated, besides some portion of 
 that previously in the oxygen. 
 
 181. It is important in this inquiry to know in what state the elements of 
 bodies exist, because this must greatly affect the quantity of heat. If hydrogen in 
 solid compounds be itself in its solid state, then it ought to give out less heat than 
 gaseous hydrogen : but I am of opinion that hydrogen, carbon, and other per- 
 manent gases exist in combination in the state of highly compressed gases, and not 
 in their solid state. The experiments I have to compare on combustion will be 
 found to support this opinion ; rendering it tolerably certain, that, in the range of 
 temperature we can command, these elementary bodies are never, even in the liquid 
 state, in combination ; and we are thus freed from what I had regarded as the 
 greatest difficulty in rendering the theory of combustion applicable to useful 
 objects. 1 That this theory has been so neglected, since Count Rumford paid 
 
 1 It has been assumed by the few who have considered this subject, that the combination of oxy- 
 gen and hydrogen developed the same quantity of heat, whether the hydrogen was in a gaseous, a 
 liquid, or a solid compound ; but this could not happen if in a solid compound the hydrogen were 
 
SECT . m .] CONDENSATION OF STEAM. 107 
 
 attention to it, is wonderful, considering that it becomes every day more important. 
 It is universally admitted that steam navigation loudly calls for some inquiry. 
 The immense weight of a supply of ordinary fuel renders long voyages almost 
 impracticable ; and while the possibility of making fuel more effective, or of 
 selecting one fuel more effective than another, remains probable, it is worthy of 
 inquiry. 
 
 182. The first and most difficult point is, to determine the heat afforded when 
 two simple or elementary bodies unite and form a compound body ; but when the 
 heat is determined for each of the binary combinations, that afforded by any other 
 combinations of them may be calculated. 
 
 183. The measure of the effect of a combustible is, the number of degrees the 
 heat developed in its combustion will raise the temperature of the same weight of 
 water ; or the weight of water that would be heated one degree, the weight of the 
 substance being unity. 
 
 184. The heat afforded by carbon when it combines with oxygen is variously 
 stated, and the results are in some measure dependent on the method employed for 
 taking the quantity of heat, and in others the difference is owing to the quality of 
 the charcoal. 1 It combines with two-thirds of its weight of oxygen. 
 
 According to Dr. Crawford, 1 Ib. of carbon raises - 10369 Ibs. of water 1 degree. 
 
 Lavoisier ... 13370 >> 
 
 Count Rumford - - 9720 
 
 Clement and Desormes - - 13300 
 
 Hassenfratz - - 12880 
 
 Dalton 5600 
 
 6)65239 
 Mean - 10873 
 
 The greatest discrepancy is in Dalton's experiments, which it appears was owing 
 to the method he employed ; and in taking 10800 Ibs. of water raised one degree 
 as the measure of the effect of carbon, we shall be nearly correct. 
 
 185. The heat afforded by hydrogen when it combines with oxygen is also 
 
 united particle to particle ; and hence I conclude it exists only as a highly compressed gas in solids 
 containing it, for it appears that it does afford the same quantity of heat in all states. 
 1 Phil. Mag. vol. xli. p. 295 ; Thomson's System of Chemistry, vol. i. p. 148. 
 
108 OF THE GENERATION AND [ SECT . ,. 
 
 differently stated : it combines with eight times its weight of oxygen ; and 
 according to the experiments of 
 
 Dr. Crawford . 67200 
 
 Lavoisier . 41440 
 
 Dalton - - . 44800 
 
 3)153440 
 
 Mean 51146 Ibs. of water is 
 raised 1 by one pound of hydrogen. 
 
 The number 50,000 therefore represents the mean effect of hydrogen very 
 nearly, and, as far as we have compared it with other experience, seems to be 
 about the true effect. 
 
 186. By the experiments of 
 
 Lavoisier, 1 Ib. of phosphorus combining with oxygen 
 
 raises 15400 Ibs. of water 1. 
 
 Dalton - 8400 
 
 2)23800 
 Mean 1 1900 
 
 Sulphur combining with oxygen, according to Dalton, heats 2800 times its weight 
 of water one degree. 
 
 187. From these we may proceed to compare the several compound bodies 
 on which experiments have been made, and also to show the proportions of 
 oxygen they consume. The first column of the following table contains the name 
 of the substance, and the author of the analysis ; the second column, its compo- 
 sition in decimal parts of its weight ; the third shows the quantity of oxygen each 
 of its components requires, and their sum, or that required for the substance ; the 
 fourth column shows the heat each component affords, and their sum is the whole 
 the substance yields ; the fifth and last column contains the whole heat afforded 
 by the substance according to experiment. 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 109 
 
 Name. 
 
 Composition of combus- 
 tible portion. 
 
 Weight of oxy- 
 gen to support 
 combustion, the 
 weight of the 
 combustible 
 being unity. 
 
 Weight of water, in Ibs., heated 
 1 by 1 Ib. of the combustible. 
 
 GASES. 
 
 Carbureted hydrogen 
 
 Olefiant gas 
 Carbonic oxide 
 
 f Hvdrogen -25 
 \ Carbon -75 
 
 f Hydrogen 1 
 \ Carbon % 
 
 Carbon -43 
 
 2- 
 2- 
 
 By 
 
 calculation. 
 
 12500 
 
 8100 
 
 By 
 
 experiment. 
 
 11900 Da. 
 
 12300 Da. 
 3500 Da. 
 
 4- 
 
 20600 
 
 1-14 
 2-3 
 
 7143 
 9257 
 
 3-44 
 
 16400 
 
 57 
 
 4744 
 
 LIQUIDS. 
 
 Alcohol, specific gravity -812 
 Ure's analysis 
 
 Sulphuric ether, spec. grav. '7 
 Ure's analysis 
 
 Oil of turpentine 
 Ure's analysis 
 
 Naphtha 
 Ure's analysis 
 
 Olive oil 
 Rape oil, or oil of colza 
 
 ( Hydrogen -1224 
 I Carbon -4785 
 
 f Hydrogen -133 
 I Carbon -596 
 
 ( Hydrogen -0962 
 \ Carbon -825 
 
 f Hydrogen -123 
 \ Carbon -83 
 
 f Hydrogen -1336 
 \ Carbon -772 
 
 98 
 1-27 
 
 6120 
 5167 
 
 f 8120 Da. 
 \11150Ru. 
 
 f 8680 Da. 
 1 14454 Ru. 
 
 8400 Da. 
 
 13200 Ru. 
 
 f 20720 La. 
 J 12460 Cr. 
 ] 16300 Ru. 
 1 14560 Da. 
 
 16750 Ru. 
 
 2-25 
 
 11287 
 
 1-06 
 1-59 
 
 6650 
 6437 
 
 2-65 
 
 13087 
 
 77 
 2-2 
 
 4810 
 8910 
 
 2-97 
 
 13720 
 
 98 
 2-22 
 
 6150 
 8964 
 
 3-20 
 
 15114 
 
 1-07 
 2-06 
 
 6680 
 8337 
 
 3-13 
 
 15017 
 
 
 
110 
 
 OF THE GENERATION AND 
 
 [SECT. in. 
 
 Name. 
 
 Composition of combus- 
 tible portion. 
 
 Weight of oxy- 
 gen to support 
 combustion, the 
 weight of the 
 combustible 
 being unity. 
 
 Weight of water, in Ibs., heated 
 1 by 1 Ib. of the combustible. 
 
 SOLIDS. 
 Bees' wax, yellow 
 
 Bees' wax, white 
 Tallow 
 
 Oak wood, dry and pure fibre 
 Gay Lussac and Thenard's 
 experiments 
 
 Oak wood 
 
 Caking coal from Newcastle 
 Thomson's analysis 
 
 Cherry coal from Glasgow 
 Thomson's analysis 
 
 Splint coal from Glasgow 
 Thomson's analysis 
 
 Splint coal, earthy matters"! 
 not stated > 
 tire's analysis J 
 
 Ditto 
 
 Cannel coal from near Coventry 
 Thomson's analysis 
 
 f Hydrogen -1137 
 \ Carbon -8069 
 
 f Hydrogen -0569 
 | Carbon -5253 
 
 f Allowing 20 per"! 
 < cent for water, > 
 l_ mucilage, &c. 
 
 f Hydrogen -0416 
 \ Carbon -7516 
 
 f Hydrogen -100 
 \Carbon -666 
 
 f Hydrogen '044 
 \ Carbon -568 
 
 Hydrogen -043 
 Carbon -709 
 
 f Allowing 10 per "1 
 !_ cent for ashes J 
 
 f Hydrogen '2 
 \ Carbon -626 
 
 91 
 2-15 
 
 By 
 
 calculation. 
 
 5685 
 8710 
 
 By 
 
 experiment. 
 
 f 18620 La. 
 1 13580 Cr. 
 
 f 17673 Ru. 
 1 14560 Da. 
 
 ( 15064 Ru. 
 1 14560 Da. 
 
 5662 Ru. 
 
 f 9230 Black 
 1 8675 Watt 
 
 3-06 
 
 14395 
 
 455 
 1-4 
 
 2845 
 5673 
 
 1-855 
 
 8518 
 
 1-484 
 
 334 
 
 2-000 
 
 6825 
 
 2080 
 8100 
 
 2-334 
 
 10180 
 
 8 
 1-78 
 
 2-58 
 
 5000 
 7192 
 
 12192 
 
 35 
 
 1-52 
 
 2200 
 6134 
 
 1-87 
 
 8334 
 
 345 
 
 1-89 
 
 2150 
 7657 
 
 2-235 
 
 9807 
 
 1-6 
 
 1-67 
 
 8826 
 
 10000 
 6760 
 
 3-27 
 
 16760 
 
 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 Ill 
 
 Name. 
 
 Composition of combus- 
 tible portion. 
 
 Weight of oxy- 
 gen to support 
 combustion, the 
 weight of the 
 combustible 
 being unity. 
 
 Weight of water, in Ibs. , heated 
 1 by 1 Ib. of the combustible. 
 
 Cannel coal from Woodhall "j 
 near Glasgow > 
 Ure's analysis 
 
 Ditto 
 
 Hydrogen -0393 
 Carbon -722 
 
 f Allowing 10 per "1 
 \ cent for ashes J 
 
 315 
 1-93 
 
 By 
 
 calculation. 
 
 1965 
 7799 
 
 By 
 experiment. 1 
 
 2-245 
 
 9764 
 
 
 8788 
 
 Charred peat 1 
 Klaproth's analysis J 
 
 Carbon -525 
 
 1-4 
 
 5670 
 
 
 Coke prepared in a close vessel ~| 
 Mean of Dr. Thomson's > 
 
 Carbon -84 
 
 2-27 
 
 9070 
 
 91282 
 
 experiment 
 
 
 
 
 
 188. These are the results as far as the latest researches in chemistry enable 
 us to carry the comparison : it is sufficient to show that the correspondence is very 
 close, and that the numbers we have selected for the binary compounds are very 
 nearly the true ones. It will be particularly remarked, that in wax, oil, and those 
 substances which are likely to afford the most accurate results, theory and 
 experiment agree. 
 
 There is, however, still another mode of prosecuting our inquiries, and perhaps 
 with equally satisfactory results. 
 
 189. In gas works, from the quantity of gas and coke afforded by a given 
 quantity of coal or other matter, we have an approximate means of measuring 
 its effect as fuel ; but from the want of a correct knowledge of the density of 
 the gas, in each case, we are obliged to assume it to be the same as carbureted 
 hydrogen. 
 
 1 The experiments marked Da. were made by Dalton, Ru. Rumford, and Cr. Crawford. The 
 analyses of the substances are referred to their authors ; Dr. Ure's will be found in his ' Chemical 
 Dictionary,' and Dr. Thomson's in his 'Annals of Philosophy.' 
 
 z This is the result collected from a comparison of Lavoisier's experiments. Treatise on Warm- 
 ing Buildings, art. 31. 
 
112 
 
 OF THE GENERATION AND 
 
 [SECT. in. 
 
 Kind of fuel. 
 
 Composition. 
 
 Oxygen. 
 
 Heat. 
 
 Wigan cannel coal 1 
 
 ( -134 gas 
 \ '635 coke 
 
 0-54 
 1-45 
 
 2750 
 5759 
 
 
 
 1-99 
 
 8509 
 
 Staffordshire coal, inferior 2 
 
 ( -123 gas 
 I -61 coke 
 
 49 
 1-39 
 
 2460 
 5534 
 
 
 
 1-88 
 
 7994 
 
 Peat. Klaproth's analysis 3 
 
 f -100 gas 
 I -200 carbon 
 
 4 
 535 
 
 2060 
 2160 
 
 
 
 935 
 
 4220 
 
 
 
 
 
 190. When any of these species of fuel is used for generating steam, there 
 must be a loss of effect equivalent to the quantity of vapour formed from the 
 hydrogen, and from the water in the fuel : one pound of hydrogen will form nine 
 pounds of steam, and in practice the loss of effect will be one-fifth of the power of 
 the hydrogen. This proportion being deducted from the whole effect, and also 
 1170 for each pound of water the fuel contained, we have the following table for 
 the power of the most important species of fuel. 4 
 
 Species of fuel. 
 
 Effect in Ibs. 
 of water heated 
 one degree by 
 1 Ib. of fuel. 
 
 Effect in Ibs. 
 of water con- 
 verted into 
 steam of 220. 
 
 Quantity to 
 convert a cubic 
 Foot of water 
 into low pres- 
 sure steam. 
 
 Quantity to con- 1 
 vert acubic foot of 
 water into steam, 
 allowing 10 per 
 cent for loss. 
 
 Olive oil 
 
 13700 Ibs. 
 
 11-7 Ibs. 
 
 5-3 Ibs. 
 
 5-89 Ibs. 
 
 Caking coal 
 
 9800 
 
 8-4 
 
 7-45 
 
 8-22 
 
 Coke prepared in close vessels 
 
 9000 
 
 7-7 
 
 8-1 
 
 9-00 
 
 Splint coal 
 
 7900 
 
 6-75 
 
 9-25 
 
 10-28 
 
 Staffordshire coal 
 
 7500 
 
 6-4 
 
 9-75 
 
 10-83 
 
 Oak wood, dry 
 
 6000 
 
 5-13 
 
 12-2 
 
 13-6 
 
 Charred peat, charred in close vessels 
 
 5670 
 
 4-85 
 
 12-9 
 
 14-3 
 
 Peat compact and dry 
 
 3900 
 
 3-35 
 
 18-7 
 
 20-8 
 
 Ordinary oak 
 
 3600 
 
 3-07 
 
 20-31 
 
 22-6 
 
 Peat compact in the ordinary state of dryness 
 
 3250 
 
 2-8 
 
 22-5 
 
 25-0 
 
 1 Murdoch, Phil. Trans. 1808. 2 Art. Gas Lights, Napier's Suppl. to Eucycl. Brit. 
 
 3 Philosophical Magazine, vol. xvii. p. 312. 
 
 * The latent heat of steam is 1000, (art. 82.) the temperature of low pressure steam is 220, and 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 113 
 
 These quantities, derived entirely from theoretical considerations, are so near to 
 the actual effects obtained in practice, that they show us we have little to expect in 
 the form of improvement ; and with the addition of one-tenth for various causes 
 tending to decrease the effect, they may be adopted as the measure of effect in 
 those computations we have to make ; and the table affords an easy means of 
 comparing the expense of different kinds of fuel. 
 
 191. The trials of the quantity of steam a given quantity of fuel will produce, 
 are by no means so numerous as might be expected by those who know not the 
 difficulty of ascertaining the results with precision. People shrink from the task of 
 making accurate trials, either in consequence of the great degree of attention and 
 labour they require, or the expense. The adoption of methods arising out of a 
 competent knowledge of the subject reduces both these in a considerable 
 proportion. 
 
 The following brief collection may be useful. 
 
 Kind of fuel. 
 
 Effect in Ibs. of 
 water heated 
 1 by 1 Ib. 
 of fuel. 
 
 Low pressure steam of 220 from 52. 
 
 Weight of water con- 
 verted into steam by 
 1 Ib. of fuel. 
 
 Weight of fuel to 
 form a cubic foot of 
 water into steam. 
 
 Newcastle or Swansea coal, according to 1 -n 
 Mr. Watt } From 
 To 
 Mean 
 Newcastle coal, according to Dr. Black 
 Newcastle coal, Wall's End, by my trials 
 Wednesbury coal, according to Mr. Watt, From 
 To 
 Mean 
 Pine wood (dry), Count Rumford's experiments 
 
 6950 Ibs. 
 
 10400 
 8675 
 9230 
 10050 
 5200 
 7800 
 6500 
 3618 
 
 5fifJ-> 
 
 5-93 Ibs. 
 
 8-9 
 7-4 
 7-9 
 8-6 
 4-45 
 6-68 
 5-56 
 3-1 
 
 4..QK 
 
 10-5 Ibs. 
 
 7-0 
 8-75 
 7-9 
 7-25 
 14-0 
 9-34 
 11-67 
 20-02 
 19-Q 
 
 Peat, compact, from Dartmoor, in the ordinary 1 
 state of dryness, by my trials J 
 
 2400 - 
 
 QQQO 
 
 2-05 
 0.05 
 
 30-5 
 22-0 
 
 ]7. K. 
 
 Culm fWrkM 
 
 41 75 
 
 3.K& 
 
 
 
 
 
 Sleek, or refuse small coal, produces about three-fourths of the effect of good 
 coal of the same species. 
 
 We have hitherto considered effect only when fuel gives the whole, or nearly the 
 whole, of its heat ; but a certain rate of combustion and perfect management are 
 requisite to obtain this end. 
 
 the mean temperature of the air being about 52, we have 1000 + 220 52 = 1170 nearly ; hence 
 dividing the effect in pounds of water heated 1 by 1170 we have the pounds of water that would 
 be converted into steam, and by proportion, the quantity which converts 62-5 Ibs. or a cubic 
 foot of water into steam. * 
 
114 OF THE GENERATION AND [SECT. in. 
 
 PROCESS OF COMBUSTION. 
 
 192. The elementary bodies -require very different degrees of heat to cause 
 them to form new combinations. Sir H. Davy has rendered it probable that 
 charcoal and oxygen combine at about 700, when common air is not present ; and 
 hydrogen and oxygen at about 800. But when the oxygen is afforded by the 
 common air, about 800 for carbon, and 950 1 for hydrogen, seems to be nearer the 
 temperatures at which they inflame readily ; and when the fuel affords in- 
 combustible gases, the intensity will still require to be increased. Hence we need 
 not be surprised to find, in the common mode of applying heat, that except in as 
 far as it increases the draught through the fire, it is of little or no advantage for a 
 fuel to contain a large proportion of hydrogen. On the other hand, if the intensity 
 of the heat be too great, the earthy parts of the fuel combine with some portion of 
 the carbon and fuse, forming the glassy scoriae called clinkers, by which some 
 combustible matter is lost. We may expect this effect to take place in a con- 
 siderable degree whenever the heat approaches to about 1500, and therefore infer 
 that an average heat not exceeding about 1200 is the best for the production of 
 effect. 
 
 The circumstances which must be attended to, that the fuel and its products 
 may remain in this temperature till they be consumed, are next to be considered. 
 
 193. First. A quantity of air sufficient to supply the oxygen required for 
 combustion must have as free access as possible to all the parts of the burning 
 mass, and with as little exposure of the surface of the mass to the cooling effect of 
 other air as the draught of the chimney will allow. 
 
 194. Secondly. The quantity or mass of fuel in combustion must be of such a 
 proportion to the quantity and temperature of the surface to which it communicates 
 heat, that it can only lose as much heat as it generates when it arrives at the best 
 temperature for combustion ; allowing for the cooling effect of the surface acted on 
 by the air required in the process. 
 
 195. Thirdly. The flame and smoke must be kept in contact with the vessel 
 as long as it is capable of affording heat. 
 
 196. Fourthly. The fluid to be evaporated should enter so as first to receive 
 the heat where the smoke last acts on the fluid, so that there may be the greatest 
 possible difference of temperature between the smoke and the fluid ; and, con- 
 sequently, that the fluid may deprive the smoke of heat, as it becomes gradually 
 heated to the temperature of the vapour before it arrives over the fire. 
 
 1 Dr. Thomson says about 1000 from his own experiments. System of Chemistry, vol. i. p. 224. 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 115 
 
 SUPPLY OF Am AND AREA OF FIRE GRATING. 
 
 197. The most effective method of supplying fuel regularly with air, that has 
 yet been tried, is that of burning it on a grate placed over a pit to receive the 
 ashes. 
 
 And in examining this subject, we have first to inquire what quantity of air must 
 pass through the fire for the combustion of each species of fuel. It has been shown 
 that the different species of fuel require different quantities of oxygen. For the 
 different kinds of coal it varies from 1-87 to 31bs. for each pound of coal, and 
 twelve cubic feet of oxygen weigh one pound ; also to obtain one pound of 
 oxygen five pounds of air must pass through the fire ; consequently, sixty cubic 
 feet of air will be necessary to afford one pound of oxygen. But it is not possible 
 to render the whole of the air effective ; part of it will escape unchanged by com- 
 bustion, and the allowance I have usually made is that only two-thirds is effective ; 
 therefore we require ninety cubic feet of air for each pound of oxygen, and the 
 product when carbon alone is consumed is carbonic acid, and the specific -gravity of 
 the air after thus changed by combustion will be 1'05. But a fuel sometimes 
 contains hydrogen, and in that case the oxygen and hydrogen form steam of 
 double the volume of the oxygen ; and the bulk of the mixture of air and vapour 
 will be 102 feet for each pound of oxygen combining with hydrogen, and its 
 specific gravity will be 0'9. The last column of the following is computed from 
 the numbers given in the last column of the preceding table, (art. 190.) 
 
 Kind of fuel. 
 
 Air and smoke 
 for each pound. 
 
 Specific gravity 
 of smoke. 
 
 Air and smoke for one cu- 
 bic foot of water converted 
 into low pressure steam. 
 
 Caking coal 
 Cherry coal 
 Splint coal 
 Cannel coal 
 Coke 
 Ordinary wood 
 
 214 
 242 
 172 
 315 
 216 
 173 
 
 1-03 
 1-00 
 1-02 
 1-01 
 1-05 
 0-90 
 
 1780 cubic feet. 
 
 17ftO 
 
 1050 
 
 3900 
 
 
 It appears therefore that we may state the quantity of air and smoke in round 
 numbers, for coal and coke, at 2000 cubic feet, for each cubic foot of water 
 converted into steam, and for wood at 4000 cubic feet. 
 
 198. The grate must be sufficient to admit the air required for combustion in 
 the state of expansion due to the temperature of the burning fuel ; and it is moved 
 through the fire by the joint effect of the draught of the chimney and the ash-pit ; 
 hence, as deep an ash-pit below as possible should be procured, the ash-pit 
 narrowing to a uniform breadth, the same width as the grate before it arrives at 
 
116 OF THE GENERATION AND [SECT. in. 
 
 the fire, the object being to increase the action of the fire without hastening the 
 smoke too rapidly along the flues. By means of the formula in art. 172. we 
 easily compute the area of the spaces between the grating under these circum- 
 stances. For coals, the quantity for generating the steam of a cubic foot of water 
 is 2000 cubic feet, the temperature not less than 800, and the height producing 
 the motion being A feet, we have 
 
 70 
 
 -= = the area of the spaces ; 
 
 V " 
 
 and, the bars being usually equal in thickness to about three times the space 
 between them, 
 
 '280 
 
 = = the area of the grating for coals in inches ; 
 
 2 
 
 or = = the area in feet for one horse power. 
 \/ h 
 
 When the height from the ash-pit, to where the smoke enters the chimney, is 
 four feet, then the area is one foot ; and one foot of area of grate for each horse 
 power is the common rule of practical engineers. 
 
 The proportion of aperture to the solid part of the bar is not always the same, 
 but it ought to be about in the proportion above stated, as air expands to nearly 2^ 
 times in bulk while in the fire. 
 
 199. For burning wood and peat the area of the grate must be 
 
 for each cubic foot of water converted into steam ; where h is the depth of the ash- 
 pit in feet ; the increased area being gained by increasing the size of the bars. 
 
 OF THE SURFACE OF BOILER TO RECEIVE THE EFFECT OF THE FIRE. 
 
 200. The surface of boiler to produce a given effect must be sufficient to 
 receive the heat which will produce the supply of steam ; and as fire or bottom 
 surface is the most effectual, that kind of surface should be of sufficient area to 
 receive the whole effect of the fire ; while the flue surface, or sides, may receive the 
 effect of the smoke. Hence we have an easy mode of determining the proportions. 
 The mean heat of a close fire-place may be considered T ; and if t be the tem- 
 perature of the steam, and s the bottom surface, then the heat of conversion of 
 water to steam being 1000, added to its temperature less 52, we have, from an 
 
SECT. m .] CONDENSATION OF STEAM. 117 
 
 experiment, made by Professor Leslie, 1 '828 s (T t) = 948 + t, when one cubic 
 foot of water is to be converted into steam in an hour ; or 
 
 948 + t 
 
 828 (T - 
 
 201. When a mass of fuel is in combustion in a close fire-place, we have 
 shown that it is not desirable for its temperature to exceed 1200, (art. 192.) 
 Now the surface of the boiler must be at some distance from the fuel, to allow it to 
 develope flame, and therefore the heat having a larger surface to act upon its 
 intensity is less, but at a mean ought not to be less than about 800, for coal ; 
 consequently we may insert 800 for T. For low pressure steam t = 225, hence, 
 
 For steam of 300, the force of which is about 40 Ibs. per circular inch above 
 the pressure of the atmosphere, we have 
 
 948 + 300 
 
 = = ' 
 
 These examples will be sufficient to show the increased quantity of surface 
 required for high pressure steam, and we may now proceed to estimate the quantity 
 of side flue. 
 
 202. At an average for coal, 2000 cubic feet of gaseous matter, heated to 
 800, is generated, and required for combustion to produce the above effect ; and 
 the specific heat of air being '00032, its effect will be equivalent to heating a cubic 
 foot of water -00032 x 2000 x (800 - f) = -64 (800 - t). Now it will be suf- 
 ficiently accurate for our purpose to consider the effective excess of temperature to 
 be a little less than the mean between 800 and t ; consequently, 
 
 <) = -64 (800 - ; or S ' = 1-94 feet. 
 
 203. Comparing -64 (800 - f) with 948 + t, we find that the whole energy of 
 the side of flues will amount only to about one-fourth of the effect of the bottom 
 ones ; we may therefore reduce the fire surface found by the rule one-fourth for 
 each cubic foot of water evaporated per hour. The rule will then become 
 
 3 (948 + t ) 948 + t 
 
 4 x -828 (800 - o 1-1 (800 - *)' 
 
 204. But in a steam engine boiler this would barely keep the boiler supplied, 
 whereas it is shown that there should be a capability of supplying steam with 
 double the rapidity actually required, otherwise the pressure on the piston will be 
 
 1 Inquiry into the Nature of Heat. Experiment 51 and 52. 
 
118 
 
 OF THE GENERATION AND 
 
 [SECT. in. 
 
 less, and the effect less in the same ratio (see art. 331 339) ; according therefore 
 to this condition the proportion of bottom should be 
 
 2J948JM) 
 
 800 -t 
 
 The side flue constantly = 2 x 1'94 = 3'88 which may be called 4 feet. 
 
 Common or low pressu 
 steam, temperature 22 
 2 Atmospheres, 
 temperature 250 
 3 Atmospheres, 
 temperature 275 
 4 Atmospheres, 
 temperature 293 
 5 Atmospheres, 
 temperature 308 
 8 Atmospheres, 
 temperature 343 
 
 re r Bottom of boiler . . 4-1 feet"" 
 3 I Side of boiler flue . . 4- 
 r Bottom .... 4-36 
 I Side 4 
 
 r Bottom 
 I Side 
 
 . . . . 4-6 
 . 4 
 
 r Bottom 
 1 Side . 
 ( Bottom 
 I Side 
 
 . . . . 4-9 
 . . . . 4 
 . . . . 5-1 
 . 4 
 
 r Bottom 
 I Side . 
 
 . . . . 5-65 
 . . . . 4 
 
 For converting 1 cubic foot of 
 water per hour into steam. 
 
 For sea-water, and low pressure or atmospheric steam, 
 
 Temperature 230, 
 it requires 
 
 f Bottom of boiler 
 I Side of do. 
 
 4-14 
 4-0 
 
 For converting 1 cubic foot of 
 water per hour into steam. 
 
 205. In comparing these with the usual rules, the sum of the bottom and 
 sides must be taken ; and it may be remarked that one cubic foot of steam per 
 hour is so nearly equivalent to the horse power used in steam engine calculations, 
 for the larger kinds of engines, that they may be considered the same in these 
 comparisons. Also a bushel of Newcastle coals may be considered equivalent to 10 
 cubic feet of water converted into steam. 
 
 Smeaton, with his wonted care, prepared a table showing the surface of boiler 
 required to be exposed to the effect of the fire and smoke for atmospheric engines, 
 and the quantity of coals to be consumed per hour. His quantity of surface for 
 1 bushel per hour is 88 feet, and for 13 bushels per hour, not quite 82 feet of 
 surface per bushel. l This is equivalent to 8'2 feet of surface for converting 1 
 cubic foot of water into steam per hour. Our deduction, from calculation, is 
 8'1 feet for low pressure steam. 
 
 Mr. Watt says, he finds that, "with the most judiciously constructed furnace, 
 it requires 8 feet of surface of the boiler to be exposed to the action of the fire and 
 
 Rees's Cyclopaedia, art. Steam Engine. 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 119 
 
 flame to boil off a cubic foot of water in an hour ;" 1 which is only the rule of 
 Smeaton in general terms. 
 
 206. The proportion of the bottom surface, or that within the immediate 
 effect of the fire and flame, seems to have been subjected to no fixed rule : the 
 proportions used in practice vary from 3 to 5 feet of bottom surface for each cubic 
 foot of water boiled off per hour. Mr. Millington seems to have first indicated 
 the use of measuring the power of a boiler by its bottom surface ; and gives as 
 examples, that a boiler for 20 horse power is usually 15 feet long and 6 wide, 
 having 90 feet of surface, or 4|- feet to 1 horse power ; a boiler for a 14 horse 
 power, 60 feet of surface = 4*3 feet to 1 horse power. 2 I have observed boilers 
 to be incapable of supplying the proposed quantity of steam when they had less 
 than 4 feet ; and that those were effective which have the proportion assigned 
 by the rule above, provided they also had a proper quantity of flue surface. 
 
 207. In regard to high pressure steam, some interesting trials were made by 
 Mr. Wood 3 with steam carriage engines, which show the disadvantage of attempt- 
 ing to form steam by intensity of heat instead of quantity of surface. 
 
 The first was with a steam carriage boiler 8 feet in length, and 3 feet 9 inches 
 in diameter, with a tube 20 inches diameter, passing through its length, which 
 contains the grate for the fuel from whence the smoke passes along to an upright 
 tube at the end, serving as a chimney : the pressure of the steam in the boiler 
 was limited to 50 Ibs. per square inch above the atmosphere. 
 
 The whole surface of the tube forming the fire-place and flue would be only 
 40 feet ; and it was the same in all the trials, but of this not more than two-thirds 
 or 27 feet could be effective as fire surface. 
 208. 
 
 Time of 
 experiment. 
 
 Coals consumed 
 per hour. 
 
 Water boiled off 
 per hour. 
 
 Weight of fuel to 
 boil off a cubic 
 foot of water. 
 
 Surface of boiler 
 to each cubic 
 foot. 
 
 9 hrs. 35 min. 
 
 264 Ibs. 
 
 15-5 feet 
 
 17-0 Ibs. 
 
 1-74 feet 
 
 9 27 
 
 268 
 
 15-1 
 
 17-6 
 
 1-79 
 
 4 48 
 
 323 
 
 15-8 
 
 20-5 
 
 1-71 
 
 The mean intensity of the fire must have been equal to 1200, to produce this 
 effect ; and the fuel consumed is somewhat more than double the quantity which 
 ought to have generated the same quantity of steam. 
 
 209. In another trial the length of the boiler was 9 feet 2 inches, its diameter 
 ^ feet, the diameter of the tube 22 inches, and the force of the steam limited 
 
 1 Robison's Mechan. Phil. vol. ii. p. 147. 
 3 Treatise on Rail Roads, p. 249. 
 
 Epitome of Natural Philosophy, p. 266. 
 
120 
 
 OF THE GENERATION AND 
 
 [SECT. in. 
 
 to the excess of 50 Ibs. per square inch. In this case the whole surface of the 
 tube in contact with the water of the boiler could not exceed 52 feet ; and two- 
 thirds of this being taken as effective, we have 35 feet for the surface. 
 
 Time of 
 experiment. 
 
 Coals consumed 
 per hour. 
 
 Water boiled off 
 per hour. 
 
 Weight of coal to 
 boil off a cubic 
 foot of water. 
 
 Surface to a cubic 
 foot of water 
 per hour. 
 
 6 hrs. 32 min. 
 1_ 261 
 
 230 Ibs. 
 410 
 
 12-2 feet 
 23-0 
 
 18-8 Ibs. 
 17-8 
 
 2-87 feet 
 1-52 
 
 The difference of the results in these trials is chiefly owing to a difference in 
 the density of the steam in the boiler, its state not having been ascertained ; and 
 though it might be done in an indirect manner from the number of strokes per 
 minute and the resistance, it would not be accurate enough to furnish us with 
 any useful conclusions. 
 
 OF THE SPACE FOR STEAM AND WATER IN BOILERS. 
 
 210. A boiler must obviously contain as much steam as will supply the 
 engine at each stroke without any material decrease in its elastic force ; and the 
 space will therefore depend on the manner the steam is to be supplied. If it be 
 admitted to the engine only during part of the time of the piston's descent, there 
 must be so much steam that the use of the quantity required may not lessen the 
 elastic force. If the steam be generated equably, and the space for it be only 
 equal to the quantity consumed at each stroke, and all the quantity be wanted 
 during the descent of the piston, the elastic force in the boiler will vary one-half, 
 and the loss of effect be very considerable: this subject is therefore worthy of 
 further inquiry, in order that we may see how far the maxims of practice are 
 confirmed by just principles. Without specifying the kind of engine, it is stated 
 that a boiler should have space for five or six times the volume of steam required 
 for a stroke ; l others mention eight times : Dr. Young quotes a remark that it 
 should contain ten times the volume, 2 and Prony has stated that it is one of the 
 advantages of a double acting engine, that it requires a smaller boiler than a single 
 acting one. * 
 
 211. Let it be supposed that the action of the fire is uniformly the same, and 
 that during a unit of time it generates a unit of volume of steam, and that this 
 volume is sufficient to supply the engine ; but jhat the whole of it is required in 
 
 1 Millington's Epitome of Natural Phil. p. 251. 
 3 Architecture Hydraulique, vol. ii. p. 106. 
 
 - Natural Phil. vol. ii. p. 259. 
 
SECT. ,.] CONDENSATION OF STEAM. 121 
 
 some less time i ; and that c is the capacity of the space for steam in the boiler, and 
 p the elastic force at the commencement of letting on the steam. Then c + t 1 
 is the quantity of steam in the space c at the end of letting on the steam ; and the 
 elastic force being inversely as the space, it will be 
 
 p(c + t-\) 
 c 
 
 at the time it is shut off ; and the variation will be 
 
 Now in a single acting engine the time t when it acts at full pressure is one- 
 half, hence -j is the loss of elastic force ; but if we make c = eight times the 
 quantity required, the loss is only TV p, or the elastic force varies only T V, or about 
 one pound on the square inch. 
 
 212. If the steam be cut off before the stroke be completed, the variation will 
 obviously be greater ; for example, in a single engine cut the steam off at half the 
 
 o 
 
 descent, and the variation of elastic force in the boiler will be p -j-, or TT nearly, 
 
 when the capacity for steam in the boiler is eight times the quantity required 
 for the stroke. 
 
 213. In the double acting engine, the steam acting at full pressure, the time 
 t is nearly the same as the time denoted by 1, and about three times the quantity 
 required for the stroke may be sufficient ; but if the steam be cut off at any 
 fractional portion of the stroke, put t equal to that fraction, and it will be found 
 to what the capacity must be increased, to render the variation of force incon- 
 siderable. Thus if it be cut off at half the stroke, then 
 
 , (1 - f) = P 
 
 p \~~rJ 27' 
 
 the same as in single engines, and we should not make c less than 8. But it must 
 be remarked, that it is in all these cases c times the volume of steam as it is in 
 the boiler, and not c times the capacity of the cylinder, because during the time 
 the steam acts by expansion, there is none entering the cylinder. 
 
 214. For each cubic foot of water converted into steam in an hour by a low 
 pressure boiler, we may assume that one cubic foot of steam is used at a stroke 
 without material error ; and if, as agrees with other parts of the arrangement of 
 an engine, the variation be limited to ^V of the force of the steam, we shall have 
 
 '-^r- -55 r 30 (1 - = c. 
 That is, calling the interval 1 from the time the steam valves are opened to the 
 
122 OF THE GENERATION AND [SECT. m. 
 
 cylinder to a succeeding time of opening them ; let the fraction of that interval 
 during which the steam valves are open be subtracted, and 30 times the 
 difference will be the space for steam in cubic feet in a low pressure engine. 
 
 Thus, let it be a double acting engine where the steam is cut off at two-thirds 
 of the stroke ; then the whole stroke is the distance of the times of opening the 
 steam valves, and two-thirds is the fraction ; therefore 1 f is i, and 30 x $ is 
 10 cubic feet. 
 
 215. In a high pressure boiler the same rule applies; only instead of being 
 the space in feet, 30 times the difference must be divided by the density of the 
 steam compared with the atmospheric steam as unity. 
 
 This may be done with sufficient nearness in practice, by dividing by the number 
 of atmospheres equal to the force of the steam in the boiler. 
 
 If in a double acting high pressure engine, which admits the steam only during 
 half the stroke, the force of the steam in the boiler be 4 atmospheres, then for each 
 cubic foot of water the boiler is to boil off per hour there should be 
 
 ( ~ $> = 3-8 cubic feet of space for steam. 
 
 216. Even in a double engine, which is intended to act at full pressure 
 throughout the stroke, there is the time of opening and closing the valves to be 
 deducted ; and in some of the usual modes one-fourth of the stroke at least is 
 expended, so that we can scarcely in any case say that less than 8, divided by the 
 atmospheres representing the force of the steam in the boiler, should be allowed as 
 the space in feet for steam for each cubic foot of water boiled off" per hour. 
 
 217. Space for Water in a Boiler. That there should be water to cover the 
 sides of the boiler a little higher than the flues, is clear ; but there is another con- 
 dition which is less obvious but of considerable importance in effect, and it is 
 particularly interesting in steam boats, where we wish to have neither more of 
 space nor weight than is absolutely necessary. 
 
 The quantity of water an engine consumes is not admitted with perfect re- 
 gularity; it is most equably done when forced in by a pump worked by the 
 engine, and the portion admitted regulated by a float ball. See Plate i. Fig. 2. 
 
 The quantity necessary to produce the steam must however be admitted, and its 
 temperature we will suppose to be 100; now the water in the boiler we will 
 suppose to be 225, and the proportion of the quantity in the boiler to that admitted 
 ought to be such that the temperature should not be lowered, so as to reduce the 
 force of the steam one-thirtieth part ; otherwise a manifest disadvantage must take 
 place in the action of the steam. But the depression of the temperature of the 
 water 2 will diminish its elastic force one-thirtieth ; hence, supposing the quantity 
 
SECT, in.] CONDENSATION OF STEAM. 123 
 
 introduced at each time to be 1, and the quantity in the boiler to be #, we must 
 have 
 
 (1 x 100) + (x x 225) = 225 - 2 = 223- 
 
 l+x 
 
 whence we find x = 62 nearly ; that is, there must be 62 times as much water in 
 the boiler as is introduced at one feed, otherwise the force of the steam will be 
 lowered more than one-thirtieth. The rule applies to both high and low pressure 
 steam ; for the variation by a change of 2 of temperature is nearly proportional. 
 The more frequently the feeding apparatus acts, the less water we require, and we 
 also see a stronger motive for using hot water for the boiler than that of barely 
 saving fuel ; as the colder it is, the more the steam will be reduced. If a boiler be 
 fed at every stroke, it should have 5 cubic feet of water for each cubic foot of 
 steam it is capable of boiling off per hour, whether the boiler be high or low 
 pressure. 
 
 218. The self-acting feeding apparatus must be delicately adjusted to reduce its 
 intervals to even twice that time, and therefore such boilers require at least 10 cubic 
 feet of water for each cubic foot of water boiled off per hour. But a mode of 
 rendering the self-acting feed regular is shown in Plates i. and n. 
 
 219. It is shown therefore, that to limit a low pressure steam boiler of a double 
 acting engine, with a self-acting feed, to a change of elastic force not exceeding 
 one-thirtieth, we must have 10 feet space for steam and 10 for water for each 
 cubic foot of water the boiler commonly generates in an hour, or for each horse 
 power ; and that if the steam be cut off before the stroke is completed, a greater 
 space must be allowed for steam. 
 
 220. It is usually stated that there should be 25 cubic feet of boiler for each 
 horse power, others say 20 is sufficient, and even so low as 8 has been proposed ; 
 while another party states that there is no relation between the cubic contents of the 
 boiler and the power. We have now however shown, on unquestionable principles, 
 what ought to determine the least contents of the boiler ; and it appears that to 
 omit the estimation either of the surface to receive heat or the capacity, would 
 be erroneous. Both should be considered and determined from the circumstances 
 of the case. 
 
 s 
 
 OF THE POWER OF Low PRESSURE BOILERS. 
 
 221. The power of boilers to produce steam is considerably affected by the 
 loss of heat, and a small boiler more so than a large one. 
 
 It is one of those cases which seems to be incapable of being investigated 
 otherwise than by experience. In a boiler proportioned to the effect to be pro- 
 
124 
 
 OF THE GENERATION AND 
 
 [SECT. in. 
 
 duced, the loss of energy seems to be in the fuel, and it appears to agree very well 
 with practice to consider the loss proportional to the ratio between the surface and 
 capacity of the quantity of fuel, supposing it to be bounded by similar figures. In 
 this manner the following table is derived. 
 
 Cubic feet of steam per 
 hour equivalent to 
 power of boiler. 
 
 Bottom surface for 
 each horse power. 
 
 Side surface for each 
 horse power. 
 
 Horse power for low 
 pressure steam. 
 
 Quantity of water in boiler 
 with common feed for 
 each horse power. 
 
 2-16 cubic feet 
 1-73 
 
 8-8 feet 
 7-1 
 
 8-6 feet 
 6-9 
 
 1 horse power 
 2 
 
 22 cubic feet 
 17 
 
 l-p6 
 
 6-4 
 
 6-2 
 
 3 
 
 ift 
 
 1-16 
 
 6-0 
 
 5-8 
 
 4 
 
 15 
 
 1-39 
 
 5.7 
 
 5-5 
 
 5 
 
 
 1-35 
 
 5-6 
 
 5-4 
 
 Q 
 
 1Q. 
 
 1-3 
 
 5-4 
 
 5-3 
 
 7 
 
 1R.O 
 
 i.oq 
 
 5-3 
 
 5-2 
 
 g 
 
 1S-0 
 
 l-2fi 
 
 5-2 
 
 5-1 
 
 9 
 
 1Q-K 
 
 1-25 
 
 5-1 
 
 5-0 
 
 
 13-K 
 
 I.QO 
 
 5-0 
 
 4-9 
 
 1 
 
 10-0 
 
 J.O 
 
 4-9 
 
 4-8 
 
 Id 
 
 10 
 
 1-18 
 
 4-8 
 
 4-7 
 
 16 
 
 18 
 
 1-17 
 
 4-8 
 
 4-7 
 
 18 
 
 10 
 
 1*18 
 
 4-75 
 
 4-6 
 
 "0 
 
 10 
 
 1-13 
 
 4-6 
 
 4-5 
 
 05 
 
 
 1-18 
 
 4-6 
 
 4-5 
 
 30 
 
 
 1-10 
 
 4-5 
 
 4-4 
 
 40 
 
 11 
 
 
 
 
 
 
 When a boiler is made of a larger size than would supply an engine of 30 or 40 
 horse power with steam, it is much better to make two boilers, and to set them 
 side by side, and besides these there should be a reserve boiler to put in use during 
 repairs. That is, for a 40 horse engine I would recommend three 20 horse power 
 boilers ; for a 60 horse engine three 30 horse power boilers, and so on ; and for 
 smaller engines two boilers, each equivalent to the power of the engine. 
 
 OF THE FORM OF BOILERS AS IT DEPENDS ON EFFECTS. 
 
 222. The quantity of fire and of flue surface having been ascertained, and the 
 capacity, the next object is to consider the form of boiler best adapted for ob- 
 taining these proportions in a convenient manner. If we were to consider the 
 strength of the metal alone, they would be nearly spherical, but we well know 
 that a sphere has the least quantity of surface of any solid having the same 
 capacity. 
 
 223. The first boilers used for engines were nearly of a spherical shape. The 
 bottom was next altered to a concave surface, the flue sides were made nearly 
 perpendicular, and the upper part still retained a hemispherical shape. This form 
 
SECT, in.] CONDENSATION OF STEAM. 125 
 
 was essentially a short cylinder placed on its base, and terminating in a hemi- 
 spherical head. 
 
 224. Watt's Boilers. A rectangular form was adopted by Mr. Watt for the 
 lower portion of the boiler ; the upper part he made half a cylinder : the bottom 
 was made concave, but the sides flat. For low pressure steam a boiler may be 
 made abundantly strong of this form, and it affords a little more surface without 
 materially increasing the space the boiler occupies. Making the bottom concave 
 towards the fire also may cause the sediment to settle in the angles instead of 
 immediately over the fire. In large boilers a flue was formed through the middle 
 of the boiler, so as to be covered by the water within. 
 
 It was justly remarked by Mr. Watt, that the sole object of the arrangement of 
 his boilers "was to economise the fuel as much as possible. It is not the 
 shallowness or depth of the boiler that produces this effect ; but the making of the 
 boilers of such a shape that the air which passes through the fire shall be robbed of 
 almost all its heat before it can make its escape." 1 Mr. Watt assured Dr. Thomson 
 that this object is very well attained by the construction he had adopted, and it 
 undoubtedly is so. 
 
 225. When a boiler of a rectangular plan (see Plate i.) is used, the relations 
 of the length, width, and depth to obtain the necessary quantity of surface and of 
 capacity are easily found, when it has no internal flues ; and it is doubtful whether 
 any advantage is gained by such flues or not. The following is an approximate 
 rule for the purpose. 
 
 RULE. Take the capacity of the boiler for water, and divide it by the quantity of 
 bottom surface, (art. 221.) the result will be the depth of water. 
 
 Multiply together the bottom and side surface for fire and flue, (art. 221.) and 
 divide the product by twice the capacity for water, less the area of the bottom 
 surface, and the result will be one of the dimensions of the bottom. 
 
 Divide the bottom surface by the dimensions found, and it gives the other. 
 
 Example. To find the proportions of a boiler for an engine of 12 horse power, 
 the capacity for water being 12' 2 cubic feet for each horse power. 
 
 In this case 12 x 12'2 = 146 - 4 = the capacity of the boiler for water ; and the 
 bottom surface 5 x 12 = 60 feet, hence 
 
 60 
 the depth of water. 
 
 146 ' 4 = 2-44 feet, 
 
 Dr. Thomson's Annals of Philosophy, vol. vii. p. 173. 
 
126 OF THE GENERATION AND [SECT. in. 
 
 Also the bottom surface multiplied by the side surface = 60 x 59 = 3540 ; 
 which divided by (2 x 146*4) 60 = 232-8 is 
 
 !U 15 feet nearly, 
 
 for one dimension. 
 Consequently, 
 
 -4 feet, 
 
 15 
 
 for the other dimension ; or the boiler should be 15 feet long and 4 feet wide. 
 
 226. If the capacity of the top for steam be the same as that for water, 
 and the form a semi-cylinder, the whole depth of the boiler may be found with 
 sufficient accuracy for practice, by making it twice the depth of the water added to 
 one-tenth of that depth; in the example it will be (2 x 2*44) + -244 = 5-124 feet. 
 
 The proportions given by the rule are different from those commonly used, not 
 much in capacity, but considerably in extent of surface for receiving heat, and in 
 having greater length and less width. Boilers of such proportions are undoubtedly 
 stronger as well as more effective. 
 
 227. Cylindrical Boilers. Cylindrical boilers, with the ends rather flat 
 segments of spheres, should always be used for the production of strong or high 
 pressure steam ; and even for low pressure steam this form seems best. See 
 Plate n. Many schemes have been suggested for using combinations of cylinders 
 or tubes ; but it is extremely questionable whether any plans have been suggested 
 superior to a simple cylinder with convex ends, and applying as many of these as 
 are necessary for the object. 
 
 228. Sometimes the cylinder forming the boiler has the fire wholly within it ; 
 and in consequence of this arrangement it is impossible to get surface for the fire to 
 act on, unless the boiler be of such diameter as to render it extremely dangerous. 
 The immense waste of fuel is shown by the experiments of Mr. Wood, (art. 208.) 
 and yet these boilers have a diameter of 4 feet, with a pressure of 4 atmospheres, 
 tending to separate the parts of the boiler with a force exceeding 140 tons, and 
 only a rude safety valve to limit the steam to this force. 
 
 229. RULE for Cylindrical Boilers. When a fire is applied externally to a 
 cylinder which is to contain both water and steam, let the capacity for water and 
 for steam be added together, and also the quantities of fire surface ; then divide 
 twice the capacity by the quantity of fire surface, and the result will be the 
 diameter. Also 1 '27 times the capacity divided by the square of the diameter will 
 be the length. 
 
 Example I. Let the proportions of a high pressure boiler be determined, so that 
 
SECT, in.] CONDENSATION OF STEAM. 127 
 
 it shall be capable of converting 7 cubic feet of water into steam per hour, at a 
 pressure of 4 atmospheres. 
 
 A boiler for this purpose should contain about 9 cubic feet of space for each 
 cubic foot of water boiled off per hour ; consequently, its whole content will be 63 
 cubic feet. The surface for the fire should be 7 x (4-9 + 4) = 62'3 feet, (see art. 
 204.) Therefore 
 
 ?J1|? = 2-02 feet, the diameter. 
 
 ' 
 
 And 
 
 1-27 x 63 ,. 
 
 2-02 x 2-02 = 20 feet ' the 
 
 Example II. Let the boiler be required to boil off 24 cubic feet of steam per 
 hour, at 3 atmospheres, with 11 feet of space in the boiler for each cubic foot 
 boiled off. 
 
 The content = 11 x 24 = 264 feet. The surface 24 x (4-6 + 4) = 206-4 feet ; 
 therefore 
 
 n v 2R4 
 
 * = 2-6 feet nearly, the diameter. 
 206-4 J 
 
 And 
 
 1^?64 =50 feet nearly; 
 
 but two boilers each 25 feet long would be better. 
 
 Example III. If a low pressure steam boiler be made cylindrical for a 12 horse 
 power, under the same conditions as a rectangular one, (art. 225.) 
 
 Then the content = 12 x 2 x 12-2 = 292-8 feet. And the surface =12(5 + 4-9) 
 = 118-8 feet; therefore, 
 
 2 x 292-8 
 
 = 5 feet nearly, the diameter ; 
 
 118-8 
 
 , 1-27 x" 292-8 
 5x5 
 
 The boiler should therefore be 14-8 feet long, and 5 feet in diameter, and this 
 I think a better form for boilers than the usual rectangular ones. See Plate n. 
 
 230. The steam pipe S should lead from immediately over the fire, and the 
 water should be admitted at the opposite end at N ; and in order that the 
 sediment may be with more certainty deposited where the fire has least force, I 
 would insert a partition O across the boiler, to rise within about four or five 
 inches of the surface of the water. This would prevent cold water checking the 
 steam, and also cause the deposit of sediment to take place where the water entered 
 
128 OF THE GENERATION AND [SECT. HI. 
 
 the boiler, and would confine the cooler parts of its content to where the smoke 
 was of the lowest temperature. 
 
 231. Smaller cylinders, or rather tubular boilers, have frequently been pro- 
 posed for generating steam ; Blakey's has already been mentioned, (art. 25.) and 
 Count Rumford had one put up at the Royal Institution, in 1796, for generating 
 steam for warming the rooms. His ideas on the application of his construction to 
 steam engine boilers are worthy of attention. 
 
 232. Count Rumford's Boiler. The object of this boiler was to get a larger 
 quantity of surface, and the Count had a model of it made and presented to the 
 French Institute. (October, 1806.) This model, as far as it differs from an 
 ordinary steam boiler, being described, the reader will easily understand how to 
 apply it on the large scale. 
 
 The body of the boiler is in the shape of a drum : it is a vertical cylinder of 
 copper, 12 inches in diameter and 12 inches high, closed at the top and bottom by 
 by circular plates. 
 
 In the centre of the upper plate there is a cylindrical neck 6 inches in diameter, 
 and 3 inches high, shut at the top by a plate of copper, 3 inches in diameter and 
 3 lines in thickness, fastened down by screws. 
 
 The flat circular bottom of the body of the boiler, which as before stated is 12 
 inches in diameter, being pierced by seven holes, each 3 inches in diameter, seven 
 cylindrical tubes of thin sheet copper, 3 inches in diameter and 9 inches long, 
 closed at the lower ends by circular plates, are fixed in these holes, and firmly 
 riveted, and then soldered to the flat bottom of the boiler. 
 
 On opening the communication between the boiler and the supply cistern, the 
 water first fills the seven tubes, and then rises to the cylindrical body of the boiler ; 
 but it can never rise above six inches in the body of the boiler, for when it has got 
 to that height, the floater is lifted to the height necessary for shutting the cock 
 that admits the water. As the seven tubes that descend from the flat bottom of the 
 body of the boiler into the fire-place are surrounded on all sides by the flame, the 
 liquid contained in the boiler is heated, and made to boil in a short time, and with 
 the consumption of a relatively small quantity of fuel ; and when the vertical sides 
 of the body of the boiler, and its upper part, are suitably enveloped, in order to 
 prevent the loss of heat by these surfaces, this apparatus may be employed with 
 much advantage in all cases where it is required to boil water for procuring 
 steam. 
 
 And in the case where the boiler is constructed on a great scale, the seven tubes 
 that descend from the bottom of the boiler into the fire may be made of cast iron, 
 whilst the body of the boiler is composed of sheet iron or sheet copper. 
 
 But in all cases where it is required to produce a great quantity of steam, it will 
 
SECT. m.J CONDENSATION OF STEAM. 129 
 
 always be preferable to employ several of these boilers of a middling size, placed 
 beside each other, and heated each by a separate fire, instead of using one large 
 boiler heated by one fire. For Count Rumford has shown by experiment, in his 
 Sixth Essay ' On the Management of Fire and Economy of Fuel,' that beyond a 
 certain limit, there is no advantage derived from augmenting the capacity of a 
 boiler. 
 
 The additional surface obtained by using tubes is unquestionable ; and the 
 construction proposed by the Count might be applied with much benefit where 
 much surface is to be gained in a small space. The tubes should, however, have 
 that proportion of capacity necessary for an engine boiler, and not be too small to 
 contain an ascending and descending current. 
 
 233. Woolf s Boilers. The idea of cylindrical tubes and a magazine for water 
 and steam was further expanded by Mr. Woolf into a variety of forms, which were 
 successively adopted and abandoned. His first project was to have a horizontal 
 cylinder for containing steam and water, with a series of horizontal tubes below it, 
 crossing it at right angles, and connected to the cylinder by short necks ; the 
 lower tubes and half the cylinder to be filled with water, and the flame and smoke 
 to pass alternately over and under the tubes in a waving course. And where very 
 strong steam was required, he had two other smaller cylinders, one on each side, 
 in lines parallel to the large one and above the cross tubes, which are connected 
 alternately to these by short necks ; the larger cylinder communicating only with 
 the side cylinders. 1 The immediate object of this arrangement is to introduce the 
 cold water so as not to interrupt the rising of the steam, which is the fault of both 
 the first arrangement and also of Count Rumford's. 
 
 Another mode of application adopted by Mr. Woolf consists in placing the tubes 
 longitudinally, as the larger cylinder, parallel to each other, but in a gently sloping 
 direction : the upper ends of the tubes all open into the large cylinder near to its 
 end. The tubes are about ten inches in diameter, and extend the whole length of 
 the fire-place, which is formed below them ; and the fire acts directly on the lower 
 surfaces of the tubes, and the flame and smoke on the lower side of the principal 
 cylinder. This plan seems to be the latest he has contrived, and a wonderful stock 
 of ingenuity has been exhausted to very little purpose. 
 
 234. But there is another form given by Woolf to the boiler, which is too 
 ingenious to be passed without notice : it consists in forming an upper and a lower 
 boiler, and connecting them by short tubes. For a low pressure boiler the arrange- 
 ment gives much surface, but would be more troublesome to execute than the 
 
 * Philosophical Magazine, vol. xvii. p. 40. 
 
 R 
 
130 OF THE GENERATION AND [SECT. HI. 
 
 common boiler, with scarcely any sensible advantage, or at most not more than is 
 gained by making a flue through the boiler. 
 
 235. The reasons for avoiding the complicated forms of the tubular boilers of 
 Rumford and Woolf require very little illustration. We are certain that if a boiler 
 has the proper quantity of surface and capacity, it will be effective ; and that all that 
 can be done in this respect by a tubular boiler is to obtain these proportions 
 perhaps in a less space : but if a more simple form be afforded, it certainly 
 claims our preference. As to safety there can be no difference, unless the capacity 
 of the cylinder be reduced to less than would contain the proper store of steam : 
 for it is to be recollected that the stress on the larger cylinder is unalterable by 
 either the disposition or the size of the small tubes ; and half the capacity of this 
 cylinder must be capable of holding the store of steam. 
 
 Another objection to these boilers is the necessity of using cast iron ; but of the 
 defect of this material for boilers it will be necessary to treat further in giving 
 the rules for the strength of them. 
 
 236. We have now to consider boilers which have the fire within them. 
 They have been long a favourite species with speculative mechanics, and par- 
 ticularly since the high pressure steam engine was brought into use by Trevithick. 
 It seems a most compact and convenient mode of applying heat, and if we could 
 for a moment forget the current of heat blown up the chimney, one might with 
 some people imagine that the whole of the fire-place being within the boiler it 
 must give out its heat to it alone : such an opinion is however absurd. 
 
 It is also urged that it is safe, because the part exposed to the heat of the fire 
 being within the boiler, when it is destroyed the steam will burst inwardly ; and 
 this is freely admitted to be true, only it imposes the necessity of having a larger 
 boiler, which of course is more dangerous. 
 
 237. The proportions of these boilers will be found to depend on the following 
 circumstances. That part of the area of the tube appropriated to supply air to the 
 ash-pit must be of sufficient size for the purpose ; which determines the diameter 
 of the tube. The area of the grating must be considered, (see art. 198.) and then 
 the length of the tube must be at least sufficient to make its superficial contents 
 equal to the surface required for the fire. (See art. 204.) The capacity of the 
 boiler must next be adjusted, so that deducting the space occupied by the tube 
 containing the fire, the quantity remaining will contain the necessary store of water 
 and steam. (See art. 215.) 
 
 238. If the nature of the application admit of a supply boiler being added, to 
 receive and heat the water required to replace that boiled off, then the internal flue 
 should have only the quantity of fire surface, and the smoke should be returned 
 
SECT, in.] CONDENSATION OF STEAM. 131 
 
 under the supply boiler, as Oliver Evans proposed. When a supply boiler cannot 
 be used, somewhat more than one-fourth of the effect of the fuel will be lost by 
 the smoke escaping at such an elevated temperature. 
 
 239. The construction of boilers for steam boats must be such as will render 
 them secure against danger from the fire, and also with as little of either bulk or 
 weight of materials as possible. When they are low pressure boilers, and I 
 would strongly recommend that no other should be used at sea, the force of the 
 steam does not prevent the use of plane surfaces, to bound the flues and fire. The 
 object then is to arrange the fire-place and flues within the boiler, so as to afford 
 the proper quantities of fire, and flue surface, and of capacity, and admit of being 
 cleaned with facility. 
 
 Various methods are adopted, but I have observed that the common tendency of 
 a few years' practice is to simplify both the construction and the means of ob- 
 taining effect. 
 
 240. The boiler is sometimes made so as to admit a clear passage of about 
 eighteen inches between the timbers and the boiler ; but this excellent practice is 
 by no means so general as it ought to be ; for it not only gives a great degree of 
 security against accident by fire, but also renders the examination and repair of 
 the boiler easy and satisfactory. 
 
 241. The grate should not be less than about 2 feet from the floor, and the 
 sum of the areas of the flues of the fires should be somewhat larger than the area of 
 the chimney, or simply larger than the chimney when there is no more than one 
 fire. It will be an advantage to have as many separate fire-places as is convenient, 
 for several reasons. First, The fire is easier to manage, and a less interruption to 
 the generation of steam is caused by feeding it. Secondly, The flue and fire 
 surface are obtained in less space, because two flues have more surface than one 
 capable of conveying the same quantity of smoke. It is, however, scarcely pos- 
 sible to point out the limits which should determine the choice in different cases, as 
 first expense is too often avoided, under the impression that it is more than 
 equivalent to an unknown loss, which will become as regular as it is certain. 
 
 242. A flue in about the proportion of 12 inches wide, and 18 or 24 
 inches high, with one of its ends easily accessible, is a good proportion ; height 
 rendering the flue more effective than width, in consequence of the hottest part 
 of the smoke pressing against the upper part of the flue, while the bottom gets 
 speedily covered with a coat of sooty matter, which being a bad conductor of heat, 
 the bottom surface has very little effect. Hence, in estimating the quantity of 
 surface, the bottom of the flue should not be calculated. 
 
 243. The fire-place is necessarily surrounded by water, but there is no ad- 
 vantage in this ; for water is so rapid a conductor of heat, that it absorbs it too fast 
 
132 OF THE GENERATION AND [SECT. in. 
 
 from the fuel which is in combustion, whereas nothing can be more injurious to the 
 perfectness of that process than a rapid abstraction of heat. The sides of the fire 
 ought to be lined with fire bricks as far as the burning fuel extends ; and the saving 
 arising from the more perfect combustion of the fuel, and in the duration of the 
 boiler, would more than balance the inconvenience of the construction. 
 
 A boiler for a steam boat constructed in this manner is shown in Plate xvn. 
 Fig. 1, 2, and 3. It differs in some respects from the usual forms, but not in any 
 essential points : the great object is to obtain a sufficient quantity of fire surface, 
 and facility of clearing the flues is of considerable importance. 
 
 244. Portable high pressure Boilers. Boilers for steam carriages, and other 
 purposes where a permanent seat of brickwork cannot be applied, should be 
 arranged in the same manner as those for steam boats, with the exception of the 
 forms being adapted to resist the effect of the steam. 
 
 Both the boiler and the flues within it should be cylindrical. The difficulty of 
 the case consists in obtaining even the due proportion of fire surface, without 
 rendering the boiler too large in diameter. Hence, the only thing that seems 
 capable of being done to improve the present construction, is to make the boilers 
 much longer with less diameter ; to have the boiler filled with water, and the fire 
 tube larger, with the spaces for steam formed by short vertical cylinders round the 
 steam cylinders. 
 
 OF FIRE-PLACES. 
 
 245. Various methods have been tried for improving the construction and the 
 mode of supplying the fuel to the fire-places of steam boilers. Smeaton improved 
 them so far that there has been little more useful effect obtained since, than 
 was done by some of his boilers. The later researches on combustion induced 
 Mr. Watt to add a few further improvements, but experience taught him that what 
 might be done by scrupulous attention and just principles was not to be expected 
 in ordinary practice. 
 
 246. Watt's Fire-place. In improving the furnace, Mr. Watt proceeded nearly 
 on the principles of Argand's lamp. The grate and dead plates were laid in a 
 sloping direction downwards from the fire door, at an angle of about 25 to the 
 horizon ; the fire being lighted in the usual manner, and a small quantity of air 
 admitted through one or two openings in the fire door, so as to blow directly on 
 the blazing part of the fire. The fire at first was kept near the dead plate, and the 
 fresh coals with which it was supplied were laid upon that plate close to the 
 burning fuel, but not upon it. When it needed mending, the burning coals and 
 those upon the dead plate were pushed further down without being mixed, and 
 more coals were laid upon the dead plate, but never thrown on the top of those 
 
SECT, in.] CONDENSATION OF STEAM. 133 
 
 already on fire, as that would instantly send out a volume of smoke. In this 
 situation they were gradually dried, and the smoke which issued from them con- 
 sumed by the current of air from the fire door, in passing over the bright burning 
 fuel. The opening or openings, to admit the air, are regulated so as just to admit 
 the quantity which consumes the smoke ; more would be prejudicial. He at first 
 constructed these furnaces in a rather different manner; but found the above 
 method the most convenient, and, when properly attended to, answers the purpose 
 perfectly with free burning coals, but is more difficult to manage with coal 
 which cakes. 
 
 247. Robertoii's Furnace. Various methods of construction have been contrived 
 to accomplish the objects proposed by Mr. Watt : that of Messrs. Roberton is 
 perhaps on the whole the best. The opening through which the fuel is intro- 
 duced into the furnace is shaped somewhat like a hopper, and is made of cast 
 iron, built into the brickwork, inclining from the mouth downward to the place 
 where the fire rests on the grate. The coals in this mouth-piece or hopper answer 
 the purpose of a door, and those that are lowest are by this means brought into 
 a state of ignition before they are forced into the furnace. Below the lower plate 
 of the hopper the furnace is provided with upright front bars, which serve to admit 
 air among the fuel, and to admit an implement to force the fuel back, from time 
 to time, to make room for fresh quantities to fall into the furnace from the hopper. 
 By this arrangement the fuel is brought into a state of ignition before it reaches 
 the further end of the bottom grate, where it is stopped by the rising breast of the 
 brickwork, so that any smoke liberated from the raw coals at the front must pass 
 over these red hot coals before it can reach the flue. 
 
 Below the upper side of the mouth-piece or hopper, and about the distance of 
 three-fourths of an inch from it, is introduced a cast iron plate. This plate is 
 above the fuel, and the space between it and the top of the hopper is open to admit 
 a very thin stream of air, which, rushing down the opening, comes first in contact 
 with that part of the fire which is giving off the greatest quantity of smoke, mixes 
 with it before it passes over the hot fuel in the interior, and therefore in passing 
 it inflames and escapes undecomposed. This is the worst part of the apparatus ; 
 for air so admitted cools the bottom of the boiler. 
 
 The quantity of air admitted to pass over the upper surface of the fire is 
 regulated by inserting a wedge-formed piece of iron. The front bars are closed 
 by doors, which, when shut, prevent the heat from coming out, and incommoding 
 the workmen. 
 
 248. A considerable improvement was added by Mr. Woolf, to enable them 
 to get rid of clinkers and scoriae. The contrivance is extremely simple. The com- 
 bustion of the fuel commences, and is chiefly carried on, on the part of the bottom 
 
134 OF THE GENERATION AND [SECT. in. 
 
 grate next the hopper, and the fuel is pushed back from time to time along the 
 grate, and at the end vitrified portions fall into a cavity, the bottom of which 
 is furnished with horizontal slides. These, when drawn out by an iron hook 
 applied to the handle of the slide, discharge the clinkers into the ash-pit. (See 
 Plate ii.) 
 
 249. The defect of Roberton's method as well as Mr. Watt's consists in 
 admitting a regular current of cold air when it is not regularly wanted, and where 
 it has an injurious effect in cooling the smoke as it rises against the bottom of the 
 boiler. This is greatly remedied by admitting air by means of small side flues, 
 or at the back of the fire, whence having to pass from the ash-pit, through small 
 channels in the hot brickwork, it becomes heated before it issues into the fire-place. 
 But abundance of air will pass the grate if it be properly constructed, and the 
 modification I would recommend is described in Plate 11. 
 
 Air flues, when used, should have valves to open or close them ; and, on the whole, 
 very little good is derived from them unless they be attended to with more care 
 than is usually bestowed on the fire of an engine. 
 
 250. Bruntons Fire-place. In consequence of the difficulty of supplying a 
 fire equably by hand, so as to sustain the regular demand for steam in a steam 
 engine, it has been attempted to use machinery for that purpose. Several schemes 
 have been tried, but the only one which has succeeded in practice is that invented 
 by Mr. William Brunton. 
 
 The method consists in an apparatus for dropping the coals on the grate by 
 small quantities at short intervals of time, (not more than three or four seconds,) 
 and in such a manner that the smoke rising from the fresh fuel must pass over 
 that which is in a further stage of combustion, and consequently be consumed; 
 the uniform supply of air for that purpose being admitted. 
 
 The machine is also so contrived that a quantity of coal is put on proportioned 
 to the quantity of work, and the air admitted is regulated in a similar manner. 
 
 The advantages of such a method are obvious, and the increase of expense of 
 erection not so considerable as might be expected. 
 
 A circular horizontal grate which receives the coals is 5 feet in diameter, and 
 revolves on a vertical axis at the rate of about one revolution per minute. During 
 its revolution the coals fall, from a hopper placed over the boiler, through a 
 vertical narrow rectangular opening, formed through the top of the boiler, of the 
 length and in the direction of the radius of the grate. The quantity discharged 
 at once by the hopper is regulated by the force of the steam in the boiler, and the 
 discharge is made at every fourth or fifth second of time ; by this means an 
 uniform fire, regulated by the work it is to perform, is obtained, and with a 
 certainty as absolute as the nature of things will admit. To prevent air being 
 
SECT, in.] CONDENSATION OF STEAM. 135 
 
 admitted without passing through the channels which are properly regulated, a 
 thin rim on the under edge of the grate runs in a circular trough filled with sand. 
 These parts, however, will be more clearly understood by a reference to the 
 description of Plate n., where its application to two boilers, which had been 
 previously erected by Boulton and Watt, is shown. The saving of fuel by using 
 this apparatus is stated to be about 25 per cent ; and a grate 5 feet in diameter 
 burns 260 pounds (three bushels) of Newcastle coals per hour, and 336 pounds, 
 or three cwt. of Staffordshire coals ; that is, 13 pounds for each foot of surface of 
 grate for the former; and 17 pounds each foot for the latter kind. I suppose it. 
 requires these quantities also to produce equal effects. The quantity of grate is 
 about two-thirds of that required in the ordinary method. 
 
 APPARATUS FOR BOILERS. 
 
 251. Feeding Apparatus. The use of the feeding apparatus is to supply the 
 boiler with water, in the place of that which is converted into steam. The feed 
 pipe is a vertical pipe passing through the top of the boiler. The lower part of 
 this pipe is turned at the end to prevent steam rising through it ; and where it 
 passes through the top of the boiler, it is made steam-tight, and fixed very correctly 
 in a vertical position. The top of the pipe terminates in a small cistern head, 
 which is kept supplied with water by a small pump from the hot water cistern ; 
 and at the bottom of the small cistern head there is a conical valve, opening 
 upwards, connected by a chain to a lever, which turns on a centre, with a wire 
 attached to the opposite end. This wire passes through an air-tight stuffing box 
 to a flat stone or piece of metal in the boiler, which is so balanced by a weight, 
 on the opposite end of the lever, as to float on the surface of the water. The stone 
 should be so large, in proportion to the surface of water, as to act sensibly on a 
 very slight depression of the water. 
 
 Its action is performed in this manner : when part of the water is evaporated 
 from the boiler, the float descends with the water's surface, and consequently raises 
 the conical valve ; now, the small cistern head, being kept constantly full of 
 water by the pipe from the hot water pump, as soon as the valve is raised, water 
 enters the boiler, and when it is filled to the proper level, it raises the float and 
 shuts the valve, till a repetition of the operation becomes necessary. The surplus 
 water raised by the pump runs off by a water pipe from the cistern head. 
 
 252. The principal circumstance to be attended to in the construction of this 
 apparatus is to make the height of the water in the cistern sufficient to balance 
 the strength of the steam ; for if this height be too small, the water in the boiler 
 
13G OF THE GENERATION AND [SECT. in. 
 
 will be forced up the feed pipe by the pressure of the steam, and be driven out 
 at the valve. 
 
 For water at 60, 2'94 feet in height is equivalent to 1 Ib. on the circular 
 inch, but the water in the feed pipe will generally be nearly 212, and then 
 3 feet is required. Hence, three feet in height for each pound per circular inch is 
 the proper height. 
 
 The stone float should obviously be in that part of the boiler where it will be 
 least disturbed by the formation of steam ; and the feed pipe should deliver its 
 supplies as far from the point where the steam is principally generated as possible. 
 253. On account of the force of steam required in high pressure engines, an 
 ordinary feed pipe cannot be applied to supply the boiler, without making it of 
 a very inconvenient height : water is therefore supplied to the boiler by a small 
 forcing pump, worked by a lever connected with one of the reciprocating parts 
 of the engine; and this water, instead of passing immediately into the boiler, should 
 pass through a pipe or receptacle which traverses back and forward in the steam 
 which escapes from the engine, so as to become considerably heated before it 
 enters the boiler, that it may not check the production of steam. A much better 
 method, however, is to make the smoke pass round and heat a small supply 
 boiler, which should have a communication with the proper boiler. The pump 
 in the former case supplies the small boiler. 
 
 In supplying a boiler by a pump worked by the engine, the same supply is 
 given at all times, whatever may be the quantity converted into steam and used. 
 Now as the consumption of steam is variable, the quantity injected by the pump 
 must often be in excess. This may be remedied by the use of a float, in land 
 engines. Let A, B, (Fig. 2. Plate i.) be two connected valves, in the box which 
 receives the water from the pump, the one A opening to the boiler, the other B 
 opening to the waste pipe. If the stem of these valves be connected to the lever 
 of a balanced float, as indicated in the figure, the increase of water in the boiler 
 above its proper level will cause the valves to descend, and close the communica- 
 tion to the boiler, while the waste valve opens and admits the superfluous water 
 to run off by the pipe. In this construction the boiler will receive the supply 
 from the pump regularly at all times, except where it is in excess for the quantity 
 used, and then the float F rises, and shuts the passage of entrance to the boiler, 
 and opens the one to the waste, till the quantity no longer exceeds the consump- 
 tion. This simple arrangement renders the feed regular, which is of much 
 importance. l 
 
 1 In the early boilers of Mr. Watt, a whistle was attached : the pipe connected with the whistle 
 descended through an orifice in the top of the boiler to a few inches below the proper level at 
 
SECT, in.] CONDENSATION OF STEAM. 137 
 
 254. The same construction applied to the feeding pipe of a low pressure 
 steam engine would be much superior to the common stone float; and I think 
 it would apply, as shown in Plate n. Fig. 2. even to the steam boat ; for the 
 oscillation would not prevent either its rise or fall, when an over-supply took 
 place or otherwise ; and employing the rise instead of the fall of the water to act 
 on the valve, would be a means of safety as well as of preventing irregular influxes 
 of water to check the steam. (See art. 217.) 
 
 255. In a method of admitting water to high pressure boilers invented by 
 Mr. Franklins, the waste water has to raise a loaded valve to escape, and the 
 passage to the boiler is regulated by a balance float placed wholly within the 
 boiler : it is ingenious, but has not the advantage of rendering the supply con- 
 tinuous ; it must, as with the ordinary feed pipe, stop till the water has descended 
 so as to raise the valve. 
 
 OF REGULATING THE FlRE OF A STEAM BoiLER. 
 
 256. The force of the steam may be made a means of regulating the fire, 
 either by diminishing the supply of air, or by contracting the chimney by a plate 
 called the damper. As a means of regulation the former ought to be preferred ; 
 it being obvious, that a direct diminution of the quantity of oxygen at its entrance 
 to the fire must have both a more immediate and a more beneficial effect than 
 contracting the chimney ; the effect of the latter being to increase the tempera- 
 ture and force of the smoke in proportion as the aperture is contracted ; and, 
 consequently, the smoke escapes at a higher temperature, carrying off a consider- 
 able quantity of heat. The regulation by the damper is the kind generally used ; 
 the other method is the same in principle, and only differs in being applied to the 
 ash-pit instead of the flue. 
 
 257. Self-regulating Dampers. Dampers are frequently under the control 
 of those who have the management of the fire ; but in the self-regulating damper 
 the fire is made a means of controlling itself, so as to burn with more or less 
 rapidity as it may be more or less wanted, in the following manner. An iron 
 plate or damper, of sufficient size entirely to close the chimney or flue, slides up 
 
 which the water was required to be kept : notice of its evaporation below that point was given by 
 the steam forcing its way through the pipe, and producing a whistling noise, sufficiently loud to 
 call the attention of the engine tender, even if at some distance from his post. Subsequently, the 
 feeding and damper apparatus above described was applied to the Soho Mint engine, about the 
 year 1798 ; also to Retford cotton mills, near Nottingham, in 1803 ; and the same arrangement 
 continues to be much in use up to the present time. 
 
 S 
 
138 OF THE GENERATION AND [SECT. in. 
 
 and down, vertically, in iron grooves, (see Plate in.) with as little friction as 
 possible. To its upper part is attached a chain, which passes over the two pulleys 
 n and n, through a tube in the bottom of the cistern head of the feed pipe, and 
 down the centre of the feed pipe C, to a hollow or bucket-shaped cast iron weight ; 
 the feed pipe being made of larger diameter in this part, when a self-regulating 
 damper is applied to a boiler, to admit the weight without blocking up the pipe 
 so as to prevent the descent of the feeding water. The weight is so adjusted by 
 filling it partly with lead, that it may just overcome the weight and friction of the 
 damper plate, chains, and pulleys, when there is no fire under the boiler ; con- 
 sequently, the damper plate will then be drawn up, and the chimney completely 
 open, at which time the weight will rest on the shoulders or projections at the 
 bottom of the feed pipe ; the chain being properly adjusted in length for that 
 purpose. Now as soon as a fire is applied so as to generate steam in the boiler, 
 the steam presses upon the surface of the water, and drives it up to a certain 
 height in the feed pipe ; and the weight, by becoming immersed in water, has part 
 of its gravitating force balanced, and therefore becomes no longer able to retain 
 the damper plate at its former height ; it will consequently descend till equilibrium 
 takes place, and partly closes the chimney, by which the draught of the fire will be 
 checked. Should it move so as to check it too much, less steam will be formed, 
 and the water will rise to a less height in the feed pipe, and part of the force of 
 the weight will be restored so as to raise the damper again : should the fire ever 
 become so fierce as to drive the water up into the cistern head, the weight 
 should be so far raised as nearly to shut the chimney ; when a damper shuts 
 perfectly close, there is a risk of inflammable air collecting and exploding in the 
 flues. 
 
 A hand damper is, however, an appendage which a boiler should always have, 
 for when an engine is not in action, it will be useful partially to close it ; and no 
 boiler can be considered perfect which has not both a damper and the means of 
 entirely closing the aperture by which the air enters to supply the fire. 
 
 258. Self-acting Air Regulator. The most direct method of governing the 
 action of a fire is to provide the passages which admit air with the means of 
 opening or closing them at pleasure ; and it is a still further advantage when this 
 is done by means of the force of the steam, so that as the steam increases beyond 
 its proper strength, it closes the aperture which admits air to the fire. A method 
 of constructing a self-acting regulator of this kind is shown in Plate i. It is 
 essential in applying it to make all other entrances to the burning fuel to shut as 
 perfectly close as possible. 
 
SECT, in.] CONDENSATION OF STEAM. 139 
 
 SAFETY VALVES. 
 
 259. The precautions for safety are of much importance : the boilers of steam 
 engines should never be constructed without them, and they should be done with 
 every care to render them effective in preventing accidents. l 
 
 Safety valves are called external or internal, according to the nature of the 
 evil to be prevented. An internal safety valve is to prevent the pressure of the 
 atmosphere crushing in the sides of the boilers or pipes to which it is applied. 
 It is usually an inverted conical valve, retained in its seat by a rod connected to 
 a lever, having a weight at its opposite end, such that the force of the atmospheric 
 pressure will overcome it, when its pressure is three or four pounds on the circular 
 inch greater than the elastic force of the steam in the boiler. 
 
 In Plate i. Fig. 1. this valve is shown as inserted in the man-hole plate ; a being 
 the valve kept in its seat by the weight on the lever at b. 
 
 260. The external safety valve is to prevent the risk of explosion, should the 
 steam become stronger than that which the boiler is intended to confine ; therefore 
 it is of the greatest importance that it be properly constructed and not liable to 
 derangement. 
 
 The application of a loaded valve to limit the force of steam appears to have 
 been first made by Papin to his digesters ; and it was applied by Savery to the 
 boilers of his steam engines. It consisted of a conical valve retained in its seat 
 by a weight on a lever ; and, from its resemblance to a steelyard, was called the 
 steelyard safety valve. It is still much used, but it has the obvious defect that 
 the weight may be increased at the will of the workman, or even may be done 
 through the ignorance of a stranger; hence valves of this form should not be 
 employed unless the lever and valve be wholly inclosed in a box kept locked by 
 the proprietor. Such a box should have a pipe leading into the chimney, to carry 
 off the steam, and a slight wire or chain to lift the valve by, lest it should stick 
 fast by corrosion. 
 
 261. For low pressure steam, the form is rendered more convenient. The 
 conical valve has its load directly upon it, and it ought to be sufficiently large. 
 Its clear area in the narrowest part not being less than is calculated by the 
 annexed rule, and the power of the steam having been determined, a fixed and 
 unalterable weight agreeing with that power should be formed and attached to the 
 rod on the top of the valve ; and the whole should be inclosed in a metal box, 
 having a passage larger than the area of the valve, to convey the steam away to 
 the chimney or other place. 
 
 1 See description of safety valve applied to Boulton and Watt's Marine Engine, Plate xxi. 
 
140 OF THE GENERATION AND [SECT. in. 
 
 The greatest power of steam should be a little more than is required to work 
 the engine ; suppose it be 5 Ibs. on the circular inch, and the diameter of the 
 lowest part of the seat of the safety valve should be 3 ; then 3 times 3 = 9, the 
 area of the valve in circular inches, and 9 times 5 = 45 Ibs., which is the required 
 weight for the load to be placed upon the valve. This valve will not open 
 till the steam presses it with greater force than 5 Ibs. on the circular inch. 
 The metal box for the valve being locked up, of course no one but the pos- 
 sessor of the key could alter the load on the valve ; but a handle passing through 
 the cover is necessary to move it, to prevent it rusting fast. 
 
 For further security it has been proposed that another safety valve should be 
 placed upon the same boiler, but with rather less load upon it, in order that it 
 may open first, and give notice to the engine man when the steam is likely to 
 become too strong. This should have a stronger handle for moving it, either for 
 letting off the steam when not required, or other purpose ; but the handle to raise 
 the locked valve should be either connected by a chain or slight wire, so that it 
 could not be fixed so as to increase the load on the valve. It would be better 
 to rely on the common valve, than one locked up till it had become stuck fast 
 with rust. 
 
 262. A conical seated valve does not appear to me to be the best ; for the 
 locked valve I would prefer a flat seat, and that the metallic surfaces in contact 
 should be narrow, and of metal not liable to corrosion, nor to fix by unequal 
 expansion. 
 
 263. To prevent the danger of adhering in steam boat boilers, Mr. Nimmo 1 
 proposed that the valve should be a hemisphere with its convex surface down- 
 wards, to rest in a seat formed to fit it, and the weight he proposed to hang to 
 the lowest part of the valve. See U, Plate xvii. Fig. 1. By this means the 
 motion of the boat would be constantly changing the position of the valve, while 
 its form would render it steam-tight in all positions, without danger of adherence. 
 A chain might be also attached to the upper side of the valve, to lift it without 
 opening the case inclosing it. This method deserves attention : its defect would 
 most likely be want of stability in its seat. 
 
 264. The most certain and safe method for low pressure boilers, is to balance 
 the pressure of the steam by a column of water, of a diameter adequate to allow 
 of the escape of the steam as rapidly as it would be possible for the fire to generate 
 it. A feed pipe is to a certain degree a safety tube of this kind, but neither of 
 the size nor construction which safety requires. The tube or pipe T W should 
 be made recurved at the lower end T, Plate n. Fig. 2. its mouth being not lower 
 
 1 Report on Steam Boats ; or, Partington's Historical Account of the Steam Engine, p. 92. 
 
SECT, in.] CONDENSATION OF STEAM. 141 
 
 than level with the upper edge of the fire flues. At the upper end it should be 
 provided with a pipe U, to convey down the hot water without the danger of 
 scalding any one, and the upper part should terminate in a higher pipe V, to 
 convey away the steam. The action of this safety tube is, first to lower the water 
 in the boiler to bring the feeding pipe into action, if it be not so before, and then 
 to allow the escape of the steam. I have had two boilers done in this manner ; 
 and the effect of endeavouring to render the steam stronger than it ought to be 
 is completely counteracted, and the boiler restored again to its regular pressure 
 in a few minutes after the tube has discharged its column of water. The dis- 
 charge of a portion of hot water by the tube, and the admission of colder by the 
 feed pipe, tends to lower the steam ; but by the feed pipe alone this does not 
 happen, as the hot water then rises in the feed pipe and prevents the entrance of 
 cold. Another advantage of this construction is, that should the water fall below 
 the mouth of the tube, the steam would escape, and if the noise of its escape did 
 not warn the engineer of the state of the boiler, the want of steam would soon be 
 a motive to look after it. 
 
 The height of the tube for different pressures is easily calculated, for the height 
 of a column of water equivalent to 1 Ib. on the circular inch is, for ordinary 
 temperatures, 3'1 feet; hence for a pressure of 4 Ibs. on the circular inch, 
 
 4 x 3-1 = 12-4 feet, the height for the tube, that is, equal to a little more than 
 
 5 Ibs. per square inch. It is obvious that it is adapted only for low pressure 
 steam. 
 
 265. Other modes have been proposed for constructing valves, some of which 
 are deficient in principle, others are complex in construction and operation. The 
 solid piston valve proposed by Chevalier Edelcrautz would either stick fast with 
 high pressure steam or allow a constant escape ; and to this difficulty is added the 
 nicety of fitting a solid piston so as to be and remain steam-tight. If an elastic 
 metallic piston be used instead of a solid one, the expense of construction becomes 
 considerable ; and a common packed piston is not to be depended on for the pur- 
 pose, its friction is so irregular. 
 
 266. For high pressure boilers, more careful attention to the means of security 
 are necessary than for low pressure ones, as it is easy to show that the risk is much 
 greater; indeed some most dreadful accidents have had the effect of rendering 
 people more cautious respecting them. Several methods have been used to guard 
 against these accidents by Trevithick, who first brought the high pressure engine 
 into use. He proposed that the safety valve should be inclosed in an iron case 
 and locked, so that no person could get access to it to increase the load beyond 
 what was intended to be employed : he also had a hole drilled in the boiler, 
 which he plugged up with lead, at such a height from the bottom that the boiler 
 
142 OF THE GENERATION AND [SECT. in. 
 
 could never boil dry without exposing the lead to be melted, and consequently 
 making an opening for the steam to escape. This contrivance he expected to pre- 
 vent the boiler being burst, by suddenly forcing water into it when it had been 
 allowed through inattention to boil dry and become red hot. 
 
 267. A plug of fusible metal riveted into a hole in the bottom of a boiler, so 
 that it may melt and allow the water and steam to escape into the fire, whenever 
 the contents of the boiler attain that degree of heat which produces steam of 
 a dangerous elasticity, is a method of a like nature. 
 
 268. The mercurial steam gauge is generally applied to boilers to show the 
 state of the steam ; it is a curved tube, or inverted siphon, in which the mercury 
 rises by the force of the steam, and indicates the pressure. See Section vm. 
 When this steam gauge is applied to a high pressure boiler, it requires a tube of 
 considerable length, and is an additional security against the bursting of the 
 boiler, because when the steam is too strong, the mercury will be displaced into 
 a proper receiver, and the steam escape through the tube, when the pressure 
 exceeds that which the boiler is designed to sustain. This steam gauge is a most 
 desirable appendage to a high pressure boiler, because it shows at once the state of 
 the steam ; but as a means of safety we had better inquire how far either it or 
 metallic plugs are likely to be effective, lest, under an impression of being secure, 
 the reliance may involve us in more of these fatal accidents. 
 
 269. In the first place, it is obvious that the aperture or apertures by which 
 the steam is to escape, should be so large that it may escape as fast as the fire can 
 generate it ; if it does not, it must accumulate, and eventually explode. Now it is 
 possible to convert a cubic foot of water into steam from somewhat less than 1'5 
 feet of fire surface, (see art. 200.) and it is making only a small allowance for 
 security to admit that each foot of surface may convert a cubic foot of water into 
 steam. 
 
 Hence we derive the following RULE : Let the density of the steam cor- 
 responding to the pressure be found : then multiply 7'5 times this density, by 
 the square root of the quantity the density is greater than 1, and divide the feet of 
 fire surface by the product ; this quotient is the square of the diameter of the 
 narrowest part of the valve in inches. Or, divide the area of the fire surface by 
 the number corresponding to the pressure or temperature, under the head divisor 
 in the following table ; and the quotient will be the square of the diameter of the 
 valve, in the narrowest part, in inches. 
 
SECT. III.] 
 
 CONDENSATION OF STEAM. 
 
 143 
 
 Pressure in inches 
 of mercury. 
 
 Temperature. 
 
 Density of steam. 
 
 Divisor. 
 
 30 
 
 212 
 
 1-00 
 
 
 
 35 
 
 225 
 
 1-28 
 
 5 
 
 60 
 
 250 
 
 2-00 
 
 15 
 
 90 
 
 275 
 
 2-85 
 
 29 
 
 120 
 
 293 
 
 3-70 
 
 45 
 
 150 
 
 308 
 
 4-70 
 
 60 
 
 The rule, it is to be remarked, is for the smallest aperture that ought to be used, 
 but there is much reason either to use two valves, or to double the area determined 
 by the rule. 
 
 Example I. Required the area of a safety valve for a low pressure boiler, fifteen 
 feet long by 4 feet wide, the fire surface being considered equal to the area of 
 the bottom of the boiler. In this case 15 x 4 = 60, and the divisor is 5 for low 
 pressure steam ; hence, 
 
 60 
 
 = 12, the square of the diameter of the aperture ; 
 
 and the square root is 3| inches nearly, for the diameter. And either two valves 
 of this diameter, or one of about 5 inches diameter, ought to be used. 
 
 Example II. A high pressure boiler with 60 feet of fire surface is used for gene- 
 rating steam of four times the atmospheric pressure, what should be the least 
 diameter of the safety valve aperture ? 
 
 In this case the divisor is 45, and 
 
 60 
 45 
 
 = 1-34 = the square of the diameter, 
 
 and the square root is 1'16. 
 
 270. Hence we find that the diameter of a mercurial gauge capable of giving 
 passage to the steam, is not so large as to prevent it being applied in practice and 
 with success, as a means of rendering boilers safe. A safety valve in addition 
 should of course be used, as the bends in the pipe would in some degree retard the 
 escape of the steam. 
 
 271. The use of fusible metal plugs I do not think so likely to afford security, 
 for were the plug fusible at the pressure for which the boiler was adapted, it would 
 be so softened by the continued temperature of the working state, as to be incapable 
 of retaining the steam when made of sufficient power to be useful. Lead 
 would be wholly unfit, its melting point being at 612, a temperature at which the 
 force of the steam would be about 150 atmospheres. Tin melts at 442, and at this 
 temperature the force is upwards of 25 atmospheres. Alloys may be formed to 
 melt from 212 to 600, but we have no evidence that the melting points remain 
 
144 OF THE GENERATION AND [SECT. in. 
 
 permanent in alloys which are regularly exposed to a heat so nearly approaching 
 to that at which they fuse when newly formed. 
 
 Alloys and Metals. Melting point. 
 
 An alloy of lead 1 part, tin 3 parts, bismuth 5 parts, melts at 212 
 
 Lead 1 tin 4 - - bismuth 5 - 246 
 
 Tin 1 - - bismuth 1 - 286 
 
 Tin 2 - - bismuth 1 - 336 
 
 Lead 2 - - tin 3 - 334 
 
 Tin 8 - - bismuth 1 - 392 
 
 Tin 442 
 
 Bismuth 472 
 
 Lead 612 
 
 Zinc 648 
 
 But if a range of about two atmospheres above the working pressure be ne- 
 cessary to fuse the plug, and with a less range than that it is scarcely probable it 
 would withstand the working pressure, this mode of obtaining safety ought not to 
 be relied upon in practice. As an additional precaution the fusible plug may be 
 adopted, but not as a principal one, certainly not as one in which great dependence 
 may be placed. 
 
 272. It has also been proposed to add a pipe to some part of the boiler, of 
 such thin metal that it may burst rather than the boiler ; but this plan, like that of 
 the metallic plugs, can only be useful in cases where the ordinary safety valves do 
 not act, for if it be made at first so that it would break on a small increase above 
 the working pressure, it would be constantly failing at that pressure, it being well 
 known that a metal strained to near its ultimate force will gradually break. 
 Besides, it is exceedingly difficult to determine the strain such a pipe will bear 
 without fracture, within the limits that would render it safe to depend on where 
 life is at hazard. 
 
 273. The risk on high pressure boilers, even at their working pressure, be- 
 comes considerable in proportion as that pressure is high, and therefore too much 
 caution cannot be employed about them. At least one good safety valve, and a 
 mercurial gauge of sufficient diameter to allow the escape of the steam, should 
 be applied to each ; but it is the practice of careful engineers to apply two safety 
 valves. 
 
 On the common safety valve an improvement might be made by constructing it 
 so as to be relieved of part of the load on the valve as it rises. 
 
SECT, in.] CONDENSATION OF STEAM. 145 
 
 THE AREA OF CHIMNEYS FOR STEAM ENGINE BOILERS. 
 
 274. Previous to giving particular rules for the area of chimneys, it may be 
 useful to remark, that a chimney may afterwards be convenient, if considerably 
 larger than is necessary for the use of the engine it is erected for, while the expense 
 bears a small ratio to the increase of size. Hence I would recommend that one 
 double the size of that given by the rule should be built, for the rules apply only to 
 one for the actual power of the engine. 
 
 The height should not be less than about 50 feet, and should be higher if it be 
 desirable to avoid the nuisance of smoke in the immediate neighbourhood of the 
 chimney ; for though by increasing the height of the chimney there is no dimi- 
 nution of smoke, yet it is spread so as to fall over a large surface. 1 
 
 275. RULE. The area of a chimney for a low pressure steam engine, when 
 above 10 horse power, should be 112 times the horse power of the engine, divided 
 by the square root of the height of the chimney. 
 
 For less than 10 horse power, it should be 90 multiplied by the number opposite 
 the horse power in the first column of the table, (art. 221.) instead of 112. 
 
 Example. Required the area of a chimney for an engine of 40 horse power, 
 the height of it being 70 feet. 
 
 In this case 
 
 40 x 112 4480 
 
 - -g^- = 533-2 square inches. 
 
 The square root of this is 23 inches, which will be the side of a square chimney. 
 Or multiply 533 by 1*27 and extract the square root for the diameter of a 
 circular one. 
 
 But in either case I would advise to build a chimney of double the area, or 
 1066'4 area, that is, to make the side of the square 33 inches. 
 
 In this rule it is supposed that the engine is done in the best manner, and 
 worked with the best coals, that is, one requiring only from 9 Ibs. to 11 Ibs. 
 
 1 It is a curious circumstance, that when high pressure steam and smoke ascend in the same 
 chimney, the smoke becomes nearly invisible. It seems to have been first observed in Trevithick's 
 engine, when applied to a steam carriage in 1805 ; and was communicated to Nicholson's Journal 
 (vol. xii. p. 1.) by Mr. Gilbert, who offers no explanation, but states that the admission of the 
 steam into the chimney improved tha draught. Nicholson made an experiment which accounts 
 for the vapour becoming invisible, through the heat of the smoke preventing that degree of con- 
 densation which is essential to its being seen. (Journal, vol. xii. p. 47.) The disappearance of the 
 smoke is not accounted for ; but I think it seems to be deposited in consequence of the density 
 being diminished, by intermixture with steam, till it becomes incapable of suspending the particles 
 of sooty matter. 
 
 T 
 
146 OF THE GENERATION AND [SECT. in. 
 
 of coal per hour, for each horse power, of an engine above 10 horse power. But 
 where 14 or 16 Ibs. of coal per hour is necessary, the flue should be increased 
 in direct proportion to the quantities to be consumed. See the mode of finding 
 the rule in art. 168. 
 
 276. When wood is used for fuel, it affords a much larger quantity of smoke, 
 but it is also much lighter, and about one and a half times the area necessary for 
 coals will be sufficient. 
 
 277. The same rules may be applied to high pressure engines ; taking the 
 cubic feet of water per hour, or the one-eleventh part of the pounds of coal per 
 hour, instead of the number of horse power. 
 
 278. The engine chimneys for steam boats and steam carriages are circular, 
 and should not be larger than is absolutely required to give effect to the fuel. 
 This will be about obtained when the square of the diameter is equal to 90 
 multiplied by the horse power, and divided by the square root of the height 
 in feet. 
 
 But here it must be remarked, that where a chimney is less than about 40 or 50 
 feet in height, the smoke must be allowed to rise at a much higher temperature. 
 It must not therefore be allowed to cool too much by giving its heat to the boiler, 
 otherwise there will be a want of draught. Hence in low chimneys the fuel will 
 not produce its full effect. 
 
 Different modes of finishing chimney tops are shown in Plate i. The least 
 expensive is one of the form of an Egyptian obelisk, and it offers least obstruction 
 to the wind. 
 
 OF THE CONDENSATION OF STEAM. 
 
 279. When any substance or body colder than steam itself is put in contact 
 with it, the steam condenses till the temperature of the cold body becomes the 
 same as that of the steam, or till the whole mass of steam be condensed to a 
 degree of elasticity corresponding to the temperature to which the cold body is 
 raised by the heat of the steam. The greater the quantity of the cold body, the less 
 its temperature will be raised ; and also the colder it is, the more the elastic force 
 will be reduced. Hence, to reduce the elastic force of steam as low as possible, the 
 coldness and the quantity of the cooling body should be as great as possible. 
 
 280. Any cold body condenses steam ; but that it may be effectively done, the 
 body should be capable of presenting a large quantity of surface, and be a good 
 conductor of heat ; as when power is to be obtained by condensation, the more 
 rapid the condensation is, the more power is obtained. It may be easily proved 
 that if steam were so condensed as to lose only equal degrees of elastic force in 
 equal times during the action, half the power would be lost. (See art. 294.) 
 
SECT, in.] CONDENSATION OF STEAM. 147 
 
 This is the cause of the failure of every method of slow condensation. It cannot be 
 too prompt, unless a sacrifice of power is made in some other way to gain that 
 promptness, and to which the effect gained by condensation is not equivalent. 
 
 281. Water has been found the most effective cold body for condensation ; 
 it has great specific heat, perhaps greater than any other body; it is a rapid 
 conductor of heat, and in a jet applies an immense proportion of cooling surface 
 to the steam. 
 
 Now since water is frequently difficult to be procured of a low temperature, and 
 sometimes not in sufficient quantity, it becomes important to inquire what effect is 
 produced by given proportions at given temperatures. 
 
 282. The weight of the water, W, required for condensation, multiplied by 
 the quantity x t its temperature is raised, gives the heat it absorbs ; and in the 
 steam engine, where the operation is repeated in the same vessels and at the 
 same temperatures, the excess of the temperature T x of the steam above that to 
 which the condensing water is raised, added to 1000, and the sum multiplied by 
 the weight w of the steam, must be equal to the heat absorbed by the condensing 
 water. That is 
 
 W (* - = (1000 + T - x) i 
 or W w ( 10 + T x) , _ w (1000 + T) + W t 
 
 X t W + W 
 
 283. When the temperature of the condensed water is equal to the tem- 
 perature of the steam, the quantity of water would be equal to that which simply 
 reduces the steam to water without change of temperature ; or 
 
 w _1000tt> 
 T-t 
 
 But in this case no effect would be obtained. Any greater quantity of cold water 
 reduces the elastic force, but it must be so far reduced as to render the accession of 
 power more than equivalent to that required to work an air pump, and cover the 
 expense of a supply of water, and the extra cost of the engine. 
 
 284. In low pressure steam T = 220, and t may be taken at 52 the mean 
 temperature, and if the temperature of the condenser be 100, then 
 
 w _ w (1000 + T x) _ w (1000 + 220 100) _ , 
 ,-* 100-52 
 
 That is, 23 i- times the quantity of the water required for steam, will be the 
 
 1 To make this equation general, let s be the specific heat of the condensing body, and C the heat 
 of conversion, and s' the specific heat of the body in vapour, then W s (x t) = w s (C + T x). 
 
148 OF THE GENERATION AND [SECT. HI. 
 
 \ 
 
 quantity of water necessary for condensation. And since a cubic inch of water 
 produces about a cubic foot of steam of the rarity it is in the cylinder of an engine 
 working at this temperature, and one-tenth being added for each foot of the 
 capacity of the stroke, 23i x Tl = 25f cubic inches for each foot of the contents 
 of the stroke of the cylinder. 1 
 
 If x = 130, it requires of cold water only 14 times the weight of the steam to 
 condense it, and for 120 it requires 16'2 times the weight. 2 
 
 The force of steam at 100 is 2-08 inches of mercury, its force at 130 is 4-81 
 inches ; consequently the gain of power is 2*73 inches, or about one in thirteen, by 
 condensing at the lower temperature. 
 
 If the temperature of the cold water be 70, and of the condenser 130, then we 
 find cold water 18 times the weight of the steam will condense it ; and that it 
 requires 37 times the weight to condense at 100, when the cold water is at 70. 
 
 285. From these equations the comparative effects of different temperatures 
 may be calculated, and the economy of using or sparing water will be known and 
 acted upon, instead of the usual method of endeavouring to get the greatest power 
 of the steam in places where water is expensive. 
 
 When steam is of considerable density, it does not condense freely ; the reason is 
 obvious, the same surface of injection water acting on steam of greater density, and 
 consequently containing a greater proportion of heat, it abstracts the heat more 
 slowly. To avoid this, the condenser should be so large that the steam may 
 expand to the bulk corresponding to a pressure not greater than about one atmo- 
 sphere and a half. But it is better to make the steam act expansively in the 
 cylinder by Watt's method, (art. 27.) or expand in a second cylinder by Horn- 
 blower's method, (art. 32.) 
 
 When a lower temperature than 180 cannot be obtained by condensation, it is 
 not worth the extra expense, and at 180 we have for low pressure steam 
 
 w _ (1000 + 220 - 180) _ ,, . nearl . 
 180 ^ o^ 
 
 or eight times the quantity of water required for steam will be necessary to 
 condense it. 
 
 286. These computations apply to where condensation is made in a separate 
 vessel, the first idea of which we owe to Mr. Watt. When the condensation is 
 made within the cylinder, the metal of the cylinder has to be cooled down to the 
 temperature of condensation as well as the steam, and a large proportion of the 
 
 1 Mr. Watt says a wine pint, or 28| inches, is " amply sufficient." Robison's Mech. Phil, 
 vol. ii. p. 147. 
 
 2 The usual temperature is about 120, or just what the hand can bear. 
 
SECT, in.] CONDENSATION OF STEAM. 149 
 
 steam is lost in heating it again at each stroke. The means of obtaining a 
 maximum of useful effect from condensing in that manner has been shown, 
 (art. 165.) 
 
 287. To find the quantity of water for injection into an engine condensing in 
 the cylinder, the formula is the same as when a separate condenser is used, the 
 difference being in the quantity of steam required ; and the water for condensation 
 is greater than when Watt's condenser is employed by 
 
 14 (T - 
 
 x t 
 
 for each stroke, 
 
 i being the weight of the mass of iron contained in the cylinder. 
 
 288. The following tabular view of the modes of condensation may perhaps 
 present the subject to the reader in a clearer view than any other kind of con- 
 cluding summary. 
 
 Steam may be f 1- * the vessel where its power is exerted { J^ m 1698 ' 
 
 < I JVewcomen m 170o. 
 
 IS. in a separate vessel Watt in 1769. 
 
 f 1. by projecting a cold fluid against the vessel containing it Savery. 
 
 I 2. by injecting a cold fluid among it Newcomen. 
 
 Steam may be J 3. by exposing it to large surfaces of cold fluids or solids ( att< 
 
 condensed I Cartwright. 
 
 4. by the pressure of cold fluids against the vessels containing it Perkins. 
 l_5. by the union of two or more of these methods. 
 
SECTION IV. 
 
 OF THE MECHANICAL POWER OF STEAM, AND THE NATURE, GENERAL 
 PROPORTIONS, AND CLASSIFICATION OF STEAM ENGINES. 
 
 289. The force of steam when confined, according to its density and tem- 
 perature, and the circumstances which affect its motion, having been considered, 
 our next object is to investigate the power of steam to produce useful effect, and 
 in this purpose I am desirous of proceeding with the simplicity and fulness 
 this important subject requires. 
 
 FIG. 15. 
 
 OF THE POWER OF STEAM, AND THE MODES OF 
 OBTAINING IT. 
 
 290. The generation or production of steam, it has been 
 shown, takes place on the application of heat. Conceive a 
 cylindric vessel, A B, to be placed in a vertical position, with 
 a given depth of water in it ; and an air-tight piston on the 
 water balanced by a weight equal to its own weight and 
 friction. In this state let heat be applied to the base, A C, 
 then as the water becomes converted into steam, of slightly 
 greater force than the atmospheric pressure, the piston will rise 
 till the whole of the water be in the state of steam. It will be 
 remarked, that the generation of this steam of atmospheric 
 elastic force affords no power, the motion being barely pro- 
 duced ; it has simply balanced the column of atmospheric air, 
 and excluded it from a given 'height of the cylinder. 
 
 291. By Condensation. But in this state of things if the steam be suddenly 
 condensed into water again, it is obvious that the piston will be impelled by a force 
 
SECT, iv.] POWER OF STEAM, &c. 151 
 
 equal to the pressure of the atmosphere on the piston, and through a height equal 
 to that the piston had been raised by the generation of the steam. 
 
 292. It thus appears that the power of steam of the elastic force of the 
 atmosphere is, when speadily condensed, directly as the space it occupies. That 
 is, multiply the area of the cylinder in inches by the pressure of the atmosphere 
 in pounds on an inch of area, and by the height in feet ; and the result, deducting 
 the friction, will be the quantity in pounds the steam would raise one foot in 
 height. 
 
 293. The space occupied by steam of atmospheric elastic force may be in- 
 creased by raising its temperature above 212, the increase being equal to the 
 expansion of steam by the given change of temperature ; but a quantity of heat 
 nearly equivalent to the increase of volume will be absorbed, and hence the effect 
 of a given quantity of fuel would not be increased by the expedient. 
 
 294. If the steam be slowly condensed, as it would be by applying external 
 cold, the effect would be much reduced, because the moving force at any period 
 of the stroke would be only the difference between the elastic force of the steam 
 and the atmospheric pressure ; and the most rapid condensation leaves a vapour 
 of some elastic force : but as it acts through the same space as the power of the 
 steam, it does not cause a sensible deviation from the ratio of the power, being 
 as the space the steam occupies, when the power is gained by rapid conden- 
 sation. 
 
 295. By Generation. Conceive the same cylinder and apparatus to have 
 heat applied to its base, with only the difference of the piston being loaded with 
 a given pressure per inch of its area. The generation of the steam will raise the 
 loaded piston, but the height through which it will be raised will be less. The 
 steam being acting in opposition both to the pressure of the atmosphere and the 
 load on the piston, the space it will occupy will be in the inverse ratio of the 
 pressures which oppose it in the two cases, supposing the steam of atmospheric 
 elastic force to have been of the same temperature. Thus, if the load on the 
 piston be twice the atmospheric pressure, the piston will be raised only one-third 
 of the height ; but on rapid condensation it descends with three times the pressure, 
 and, therefore, whether the steam be generated of atmospheric elastic force, or of 
 a greater force, the power it affords by generation and condensation is the same 
 at the same temperature, and this power is directly as the elastic force of the 
 steam, multiplied by the space it occupies, when the motion of the piston is 
 rectilinear. 
 
 296. But if, as in the last case, a loaded piston be raised, and then a valve 
 be opened which allows the steam to escape, the whole power gained will be equal 
 only to the weight raised descending from the height to which it was raised ; and 
 
152 OF THE POWER OF STEAM, [SECT. n. 
 
 the power which would have resulted from condensation will be lost, and the loss 
 is equal to the pressure of the atmosphere acting through the height to which the 
 piston was raised by the steam. This is the nature of the common high 'pressure 
 steam engine. It is obvious, that the greater the elastic force of the steam, the 
 less is the loss by neglecting to condense it under these circumstances ; but it may 
 be remarked, that unless the valve aperture be equal to the diameter of the 
 cylinder, the steam cannot escape at the necessary rate without part of the load 
 acting to expel it ; and so much more of the effective force will of course be lost. 
 The effective power is as the space the steam occupies, multiplied by the excess 
 of elastic force above the atmospheric pressure. 
 
 297. By Expansion. Retaining the same loaded piston, let it be raised by 
 the conversion of a given quantity of water into steam, to the height which cor- 
 responds to the load and temperature ; then if the load on the piston be wholly 
 removed at that height, the steam will raise the piston by expanding till it becomes 
 nearly of the same elastic force as the atmosphere, and its condensation will pro- 
 duce the same effect as if the steam had been generated of atmospheric elastic 
 force at first ; consequently, the effect in raising the load on the piston is wholly 
 additional, and the joint effect of a high pressure and condensing engine is pro- 
 duced by the same steam. The effective power of steam applied in this manner 
 is equal to the space it occupied, as high pressure steam, multiplied by the excess 
 of its elastic force above the atmospheric pressure, added to the amount arising 
 from multiplying the space it occupies when of atmospheric elastic force by the 
 atmospheric pressure. Hence, by this combination of effect the power of steam 
 of high elastic force will be nearly doubled. 
 
 298. This is not, however, the mode by which steam can be applied with the 
 greatest advantage ; for, instead of removing the load on the piston wholly at the 
 height to which it was raised by the generation of the high pressure steam, a part 
 of it may be removed, and then the steam would expand to a height depending 
 on the portion of the load removed ; at that height remove a second portion, and 
 so on, successively, till the steam becomes of atmospheric elastic force. In this 
 case, as far as the load was raised in parts by the expansion of the steam, the effect 
 is greater than in the preceding combination : the mode of calculating it will be 
 afterwards shown, but the principle is that of the expansion steam engines. 
 
 299. The preceding is not the only mode of deriving advantage from expan- 
 sion ; indeed it is only a late discovery 7 , and most probably belongs to Woolf as 
 far as he was capable of appreciating it. The methods of Hornblower and Watt 
 only apply to the case now to be considered. Let the piston be raised unloaded, 
 as in the first case, by the conversion of a certain quantity of water into steam of 
 atmospheric elastic force. When the piston is at that height, add a weight equal 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 153 
 
 to half the atmospheric pressure to the line passing over the pulley ; then the 
 elastic force of the steam being unbalanced, the piston would rise till that elastic 
 force would be half the atmospheric pressure, or till the piston would be at double 
 its former height. Now conceive the steam to be condensed, and the weight 
 removed from the pulley at the same instant, and the power of the descent, less 
 the power added to produce the ascent, will be one half more than by simply con- 
 densing steam of atmospheric elastic force ; and even this ratio may be increased 
 by adding the weight in portions to the line over the pulley, and diminishing the 
 elastic forces of the steam. This is the principle of the expansion engines of 
 Watt and Hornblower. 
 
 300. It has been assumed that steam at least of atmospheric elastic force was 
 generated ; but this is not a necessary condition, for it frequently occurs that 
 engines work with steam of less elastic force. The same mode of illustration will 
 show whence this happens. Let half the pressure of the atmosphere on the piston 
 be balanced by a weight over a pulley. Then, on the application of heat, steam of 
 half the atmospheric elastic force would be generated, and raise the piston to 
 double ,the height that it would be raised by steam capable of supporting the 
 atmospheric pressure ; consequently, on its being condensed, the descending force 
 will be half the atmospheric pressure acting through double the height ; and the 
 steam produces the same effect as before. 
 
 We shall have occasion to show the value of this principle in regulating the 
 power of atmospheric engines. 
 
 301. In all these illustrations of the modes of obtaining power from steam, 
 I have taken the atmospheric pressure as one of the active forces ; in some cases 
 steam pressure is employed in practice, but the difference in employing this or 
 that kind of pressure is dependent on other circumstances than its force, such as 
 the rate of cooling and the like, and does not affect the relations of the forces of 
 steam acting with only small alterations of temperature. 
 
 OF COMPUTING THE PoWER OF STEAM TO PRODUCE RECTILINEAR MOTION. 
 
 302. If we suppose the force of steam in a cylinder to be equal to the mean 
 pressure of the atmosphere, we may easily compute the power of the steam of a 
 given quantity of water, as far as it possibly can be obtained by condensation, and 
 not acting expansively. Thus the space occupied by steam of 212 is 1711 times 
 the bulk of the water which produces it, (art. 120.) when it is capable of resisting 
 the mean pressure of the atmosphere, and that mean pressure is 2120 Ibs. on 
 a square foot; hence 1711 x 2120 = 3,627,320 Ibs. raised 1 foot by the 
 steam of a cubic foot of water. Or multiplying by the area of a circle whose 
 
 u 
 
154 OF THE POWER OF STEAM, [SECT. iv. 
 
 diameter is unity, we have 2,860,000 Ibs. raised 1 foot for the utmost power 
 of a cylindric foot of water converted into steam. To deduct from this there is 
 the waste steam, the friction of the piston, and the resistance of the uncon- 
 densed vapour. I shall not attempt at present to compute the extent of these 
 deductions, for it would be premature, but shall give an analytical form to the 
 calculation, for the purpose of applying it to the expansive and other species of 
 engines. 
 
 303. Iff be the force of the steam in inches of mercury, and t its temperature, 
 the weight of a cubic foot in grains is 
 
 5700 / 
 459 + t ' 
 
 Now a cubic foot of water, at the lowest temperature it is likely to be when con- 
 densed, will be 436500 grains ; hence, 
 
 436500 (459 + t) .. 76-58 (459 + t) 
 5700 / / 
 
 is the bulk of the steam when that of the water is unity. 
 
 Now neglecting the taking of unity for the bulk of the water, we have 7075 / 
 = the force of steam on a square foot ; and we have 
 
 70-75/ x 76-58(459 + = 5418(459 + t) 
 
 for the Ibs. 1 cubic foot of water converted into steam, of the temperature t, 
 would raise 1 foot high, without reduction for loss by friction, uncondensed 
 vapour, or waste. 
 
 This conclusion, that the power of steam is independent of its elastic force, 
 is the same as resulted from the more popular mode of investigation, (art. 
 294.) 
 
 304. But if/* be the force corresponding to the temperature of the condensed 
 water, or of the condenser, then 
 
 5418 (459 + t)f _ t h e resistance. 
 
 For the condensed steam is limited to the space which the whole occupied in 
 its elastic state, and therefore offers a resistance proportional to its force acting 
 
 through that space. Thus we found the space - - ; and the force is 
 
 70'75/'; consequently, the resistance of the uncondensed steam is 
 
 5418 (459 + *)/' 
 
SECT. iv.] AND PROPORTIONS OF ENGINES. 155 
 
 305. For the present let the proportion of waste be 1 w, and let the friction 
 of the piston be denoted by F, then the power of the steam of a cubic foot of water, 
 of the temperature t, = 
 
 5418 (459 + - M18(Q + OCr + g)- = 5418 (459 + (l - S+I) .. 
 
 / 
 
 306. We may next ascertain the effect of EXPANSION ; which is easily com- 
 puted, for when the temperature does not sensibly alter during the action, the 
 force of the steam is inversely as the space it occupies ; therefore if b be its bulk, 
 its force, x any increase of bulk, and 8 x its variation ; then b + x : b : : p : -- . 
 
 U "T* X 
 
 and |-ilf = the power developed in expanding through the space 8 x ; and the 
 integral of this quantity is p b hyp. log. (b + x) + C ; but when x = o, p b hyp. 
 lo-. (b + .r) + C = o ; hence the power is 
 
 P b hyp. log. - 
 
 But, to return to our previous notation, suppose the volume of expansion to be n 
 times the volume of steam, and make x = n 1 b ; then since 
 
 b = 76-58 (459+Q and p = 7 Q. 75/; 
 
 we have s = p b hyp. log. b -~ = 5418 (459 + hyp. log. , 
 
 for the additional power gained by the steam expanding. 
 
 307. When the expansive principle is employed, that is, if the steam be to 
 expand during its action on the piston, an increased length of cylinder becomes 
 necessary ; and the reduction of effect which must follow from this cause has been 
 totally overlooked. If n be the bulk of the steam in its expanded state, when its 
 bulk corresponding to the force /and temperature t is unity, then 
 
 5418 (459 +0 (l - " ( f + F >) w + s 
 
 is the mechanical power of a cubic foot of water, when is the additional power 
 gained by employing the expansion of the steam. 
 
 On the value of s being inserted in the expression it becomes 
 
 5418 (459 + (l + hyp. log. - " (f ' + F) ) w =, 
 
 for the mechanical power of a cubic foot of water, when the expansive force of the 
 steam is employed. 
 
156 OF THE POWER OF STEAM, [SECT. iv. 
 
 308. This equation has a maximum, which will be when 
 
 hyp. log. n ( S + F ) = a maximum. 
 
 That is, when 
 
 Consequently, we shall have the greatest possible quantity of mechanical power 
 
 when f - in inserted for n ; or 
 
 / + F 
 
 5418 (459 + t) w hyp. log. ,, = the greatest mechanical power. 
 
 And where a table of hyperbolic logarithms cannot be conveniently referred 
 to, the result may be obtained by multiplying the logarithm of , F , found 
 
 from the common tables of logarithms, by 2'302585, which will give the cor- 
 responding hyperbolic logarithm. 
 
 309. In the best constructed engines, the waste of steam is not less than 
 one-tenth ; and, to get the extreme power of the steam of a given quantity of 
 water at this rate of waste, we have 1 T V = w '9; and the expression becomes 
 
 4876 (459 + hyp. 
 
 for the greatest possible power the steam of a cubic foot of water can afford, 
 when acting expansively. 
 
 310. In like manner taking the same loss by waste, we have from art. 304. 
 
 4876 
 
 (459 + (l - ^' + F ) 
 
 for the greatest possible power of the steam of a cubic foot of water, when the 
 expansive power of the steam is not used. Consequently, 
 
 4876 
 
 (459 + ,) { hyp . log. ^ - (l - 
 
 
 is the gain by employing the expansive power. 
 
 311. Though these equations show us the limits of steam power, and are 
 fittest for illustrating the advantages or disadvantages of difference of temperature 
 and elastic force, clearly exhibiting the economy of using steam of considerable 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 157 
 
 elastic force, yet they still require to be applied to engines of different species. 1 
 This will be done in Sect. v. and vi. ; but before I quit the illustration of general 
 principles, it will be desirable to investigate the rotary action of steam. 
 
 OF COMPUTING THE POWER OF STEAM TO PRODUCE RoTARY MOTION. 
 
 312. In a great variety of the cases where steam is employed, a continuous 
 circular motion is to be produced ; and it is very generally imagined that a great 
 advantage would be gained if the rotary motion were produced by the direct action 
 of steam, instead of being obtained by the intervention of moving parts, for con- 
 verting the rectilineal motion produced by steam into a rotary one. 
 
 But the fact that every person who has attempted to produce an engine acting by 
 the rotary power of steam, has in a greater or less degree failed in rendering it 
 as effective as a reciprocating engine, makes the theoretical principle of rotary 
 action, an interesting subject of investigation. 
 
 313. Conceive a piston, D E, to be fitted to a regularly curved vessel A B, so 
 that it may move round C, the centre of curvature of the vessel, and consequently 
 the centre of motion. Now whether the piston be moved by the force of high 
 pressure steam, or otherwise, the pressure on an inch of area of the piston will 
 
 FIG. 16. 
 
 C C. 
 a* 
 
 be equal on all its parts ; that is, the pressure on an inch, at the most distant part 
 D from the centre of motion, is the same as the pressure on an inch at the 
 part E, nearest to that centre. But since the piston is constrained to move in 
 a circle, the effects of these equal pressures are as their distances from the 
 centre of motion, and limited by the effect of the pressure at the most distant 
 part D. Hence, if the effective pressure of the steam be 10 Ibs. on the inch, 
 we have, 
 
 1 A series of tables calculated by these formulae were published in my ' Treatise on Rail Roads,' 
 p. 161166. 
 
158 OF THE POWER OF STEAM, [SECT. iv. 
 
 10 x EC 
 
 D C : E C : : 10 : 
 
 DC 
 
 the effect at E, that at D being 10. If the centre of curvature C were nearer to 
 the side of the vessel, the effect at E would be less ; therefore the effect of the 
 pressure to produce motion is less than in a straight vessel, having the same base ; 
 and if the bases be the same, the space the pressure acts through will be as the 
 quantity of steam. Consequently, the quantities of steam being equal, the power 
 of rotary action will be less than that of rectilineal action. 
 
 314. If a rectangular piston, D C, revolve round a centre C, then nearly 
 half the power of the steam will be lost. 
 
 This rough inquiry will be sufficient to show that much is lost by attempting to 
 employ the rotary action of steam, besides the various other objections arising out 
 of the excess of friction, and the difficulties of executing the parts so as to act 
 properly, usually called practical difficulties. 
 
 315. To conduct the inquiry so as to reduce the effect to more accurate cal- 
 culation, put 
 
 a = D E, the diameter of the piston ; 
 
 r = E C, the radius of the interior circle ; 
 
 x = any variable portion of the diameter of the piston counted 
 
 from E; 
 
 y = the breadth of the piston, 
 and /= the force of the steam on an inch of area. 
 Then r + a = D C ; and, 
 
 f 
 
 r + a ' 
 
 the force at the distance x from E ; and 
 
 /y(r + x)d* 
 r + a 
 
 is the differential of the pressure at that point ; and the space described being 
 2 r (r + x) we have 
 
 2ff/y(r + x)~ dx 
 r + a 
 
 for the differential of the power. 
 
 When y is uniform and therefore constant, the integral is 
 
 + xY p. 
 
 and making this expression nothing, when x o, that is, when the power is 
 nothing, it becomes 
 
SECT. 1V .] AND PROPORTIONS OF ENGINES. 159 
 
 _ 
 
 3 (r + a) 
 
 and when x = a, we have 
 
 for the power of the steam acting in a rotary direction, the piston being the rect- 
 angle ay. 
 
 316. If the piston D C revolve on an axis in the centre C, then r = o, and 
 
 2 *-/y g2 the rotary power. 
 3 
 
 But the space occupied by the steam is ir a (2 r + a) y, and its rectilineal power 
 is TT/ (2r + 0) y. Hence the rectilineal is to the rotary effect of the steam, as 
 
 or as 
 
 2r 2 + 3ra + a 2 :2 (r* + ra + % a*). 
 
 When r = o, or the piston revolves on a centre, then the ratio becomes 3 : 2, 
 or one-third of the power is lost; the same conclusion resulting however the 
 steam acts. 
 
 317. We have supposed the piston to be of parallel width, but in some 
 
 schemes it has been made circular ; and in such a case the value of \ y is */ a x .1*. 
 Consequently, 
 
 r a 
 
 is the differential of the rotary power. Its integral, from x = o to .r = a, is 
 
 * f *(* + **+ -ft**} 
 
 2 J r + a 
 
 the entire power. 
 
 This is a little less than the effect of a rectangular piston. When the piston 
 revolves round an axis in its edge, the rectilineal power of a given quantity of 
 steam is to its rotary power as 3 - 2 : 2. In the rectangular one it was as 3 : 2. 
 Hence, we see there is no possibility of applying steam with the same advantage 
 in a rotary as in a rectilineal engine ; and, even to approximate to it, the radius 
 of the circle described must be great in comparison wtth the diameter of the 
 piston, and consequently difficult to execute. To employ any other than a circular 
 
160 OF THE POWER OF STEAM, [SECT. iv. 
 
 form for the piston, would cause more friction, and expose a larger portion of 
 surface to the cooling effect of the atmosphere. These are radical objections to 
 the rotary action of steam that cannot be removed by art. 
 
 318. It is so obvious, that it is not necessary to show, that the impulse of 
 steam cannot be employed without great loss of fuel ; we may, however, take a 
 general view of the modes in which the action of steam may be applied. 
 
 MODES OF APPLYING THE POWER OF STEAM. 
 
 319. The arrangement being presented in a tabular form, will be more clear 
 than in continued description. The modes of obtaining the different species of 
 power, and the measures of their effects, have already been explained ; for conden- 
 sation, in art. 291. ; for generation, in art. 295. ; and for expansion, in art. 297. 
 
 f 1. the generation of steam. (Worcester.) 
 320. The action of steam as a moving force is I 
 
 < 2. the expansion of steam. (Hornblower. 
 derived from - 
 
 I 3. the condensation of steam. (Savery.) 
 
 Of the species of action there may be used 
 
 The action may be J * 
 
 L by impulse. 
 
 f generation, 
 separately ( 
 
 . condensation. 
 
 1 and 2. 
 
 1 and 3. (Savery.) 
 t 2 and 3. (Hornblower.) 
 [_ 1, 2, and 3. (Woolf.) 
 
 a solid, (Newcomen,) ) f continuous. 
 
 successive. 
 
 _,, . f a solid, (JNewcomen,) i ( 
 
 The action may be exerted on ( aflu . d> (Worcester>) } and may be { 
 
 The motion of the surface acted upon may be in a ( strai ht 1 j; ne 
 
 I curved / 
 
 321. The pressure of steam is the kind of action which is employed in prac- 
 tice ; and the reasons for giving the preference to rectilineal motion have been 
 shown, art. 317. In order that it may be economically employed, it is found 
 that a solid is best adapted to receive its action, fluids being liable to decompose 
 by contact with hot steam, or to condense and waste the steam. And, in con- 
 sequence of a cylinder being the figure adapted to the object, and possessing the 
 greatest capacity with the least surface, and therefore having the least loss both 
 by cooling and by friction, it is almost universally employed. The action is 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 161 
 
 necessarily successive to render it rectilineal ; but all the species of action are used 
 either jointly or separately. From these species of action, therefore, the engines may 
 be classed. 
 
 322. It will be remarked that steam must be either condensed, or generated 
 under pressure, to afford power by expansion ; hence engines may be divided 
 into two classes, depending on condensation being used, or not ; this arrangement 
 being most convenient. 
 
 CLASSIFICATION OF STEAM ENGINES. 
 
 323.-I. Non-condensing engines acting by the / l ' g enerative P ower of steam. 
 
 12. generation and expansive power of steam. 
 
 C\. condensation of steam. 
 
 324. II. Condensing engines acting I 2. condensation and expansion of steam, 
 
 by the - j 3. generation and condensation of steam. 
 
 [_4. generation, expansion, and condensation of steam. 
 
 325. All the engines of the first class, and the third and fourth kinds of the 
 second class, require high pressure steam. Engines of the first class are remarkable 
 for simplicity of construction, but they never give the whole power of the steam. 
 Engines of the second class require a considerable quantity of cold water for con- 
 densation, and therefore in some cases cannot be applied. The greatest effect is 
 obtained by the second and fourth kinds of the second class ; or rather it is only 
 in these two species that the whole power of the steam is obtained. 
 
 326. In both classes there are certain proportions between the length of the 
 stroke, and the diameter of the cylinder, and between the length of the stroke 
 and the velocity, which give a maximum of useful effect to a given quantity of 
 steam. These being considered, and also the proportions of the additional parts 
 required in condensing engines, the general rules for the power of engines may 
 be established. 
 
 i 
 
 OF THE RATIO BETWEEN THE LENGTH OF THE STROKE, AND THE DIAMETER 
 
 OF THE CYLINDER. 
 
 327. The relation between the diameter of a steam cylinder and the length 
 of the stroke, and consequently the proportions of the cylinder, have now to be 
 considered. If all the apertures, and all other parts be duly proportioned, and 
 the velocity regulated so as to be esteemed uniform, then there is no circumstance 
 relating to the motion, which has any influence on the proportions of the steam 
 
 x 
 
162 OF THE POWER OF STEAM, [SECT. iv. 
 
 cylinder, excepting the small difference arising from the friction not increasing 
 exactly in the same proportion as the square of the diameter ; and this difference 
 is so small in ordinary proportions, that we may safely neglect it. 
 
 328. The only other circumstance which renders it necessary to attend to the 
 proportions of a cylinder is the quantity of cooling surface to which the steam is 
 exposed during its action. This surface ought to be the least possible ; for its 
 effect in condensing, and therefore of destroying the power of the steam, is con- 
 siderable. (See art. 156.) 
 
 The quantity of surface consists of one end of the cylinder, one side of the 
 piston, and the concave surface of the cylinder ; but the latter is only gradually 
 brought into contact with the steam during the stroke, and its effect, therefore, 
 only equivalent to about half the effect of an equal surface bounding the steam 
 during the whole of the stroke. Now the power of an engine is greatest when the 
 effect of a given quantity of steam is the most possible ; hence the question is 
 to find the least surface capable of confining a given quantity of steam, during 
 its action. 
 
 329. When the length of the stroke is twice the diameter of the cylinder, a 
 given quantity of steam is bounded by the least possible quantity of surface during 
 its action in the cylinder ; 1 hence I conclude it is the best proportion for the 
 cylinder of a steam engine, except when the space for the engine limits the length 
 of the stroke : and the same conclusion applies to both atmospheric and steam 
 pressure engines. 
 
 1 Let the diameter of the cylinder be x, its length /, its capacity C, and ir = 3-1416. Then, 
 
 C = * x the sum of the areas of the bases = ^L. ; and the area of half the concave surface 
 4 2 
 
 =- - = - ; hence the whole surface of the steam exposed to cooling surfaces during its 
 
 action is 
 
 * 9 C 
 
 ~2~ ~ 5 
 
 and this surface is to be a minimum, which is determined by taking its differential and making it 
 equal to zero. That is, 
 
 , 2C<r 
 x dx - = o ; 
 
 whence, 
 
 and substituting for C its preceding value, we have 2 x = /; or a cylinder is of the best proportion 
 when its length is twice its diameter. 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 163 
 
 330. If we refer to the practice of engine makers, we find no indication of a 
 settled rule for the proportions of the cylinder, when the length of the stroke is not 
 limited by convenience. The proportions followed at different times by Boulton 
 and Watt, in cases where the stroke was not limited, vary from If to nearly 3 to 1, 
 the most common about 2'7 to 1, the changes having no regularity. In Smeaton's 
 table of the proportions of atmospheric engines, 1 the length of the stroke is made 
 to vary nearly as the square root of the diameter, and commences at the lower 
 part of the scale with the proportion of 4 to 1 ; why the square root of the 
 diameter was fixed upon does not appear. Equally irregular are Maudslay's 
 proportions, but approaching to 2 to 1 ; Fenton, Murray, and Wood's about as 2^ 
 is to 1. The object seems to have been to render the velocity nearly the same in 
 all engines : the circumstances which regulate the velocity may therefore next be 
 considered. 
 
 OF THE MAXIMUM OF USEFUL EFFECT IN STEAM ENGINES. 
 
 331. In steam engines there is a certain velocity for the piston, which gives a 
 maximum quantity of useful effect. 
 
 In an engine already constructed, the velocity which gives the most useful effect 
 that the engine is capable of producing, is limited by the proportions which have 
 been given to the parts of the engine. 
 
 But in an engine to be designed, all the parts should be arranged to agree with 
 the velocity which gives the maximum effect of a given quantity of steam : the 
 difference between these cases is considerable ; but in illustrating each by example, 
 I shall have an opportunity of showing that a general rule could not be derived 
 from experiments on a particular engine. 
 
 OF THE MAXIMUM FOR ENGINES EQUALISED BY A FLY. 
 
 332. Our most simple case for consideration is that where the pressure on the 
 piston is the same throughout its stroke ; and we must suppose the fly, conjointly 
 with the mass of matter in the engine, to be so proportioned as to render its 
 velocity as nearly as possible uniform. 
 
 Then the greatest uniform velocity the engine could possibly acquire, would be 
 equal to half that which a falling body would acquire in descending the length 
 of the stroke ; and with this velocity the work done would be nothing ; as the 
 whole force of the steam would be expended in keeping the engine moving at that 
 velocity. 
 
 1 Rees's Cyclopaedia, art. Steam Engine. 
 
164 OF THE POWER OF STEAM, [SECT. iv. 
 
 It must be evident that a regulated or uniform velocity cannot be greater than 
 half the velocity a falling body would acquire in descending the length of the 
 stroke ; because with any other velocity the mass moved would not be capable of 
 receiving and imparting equal quantities of motion in equal times, a circumstance 
 essential to the uniform motion of an engine moved by an uniform force. 
 
 333. As at the greatest possible velocity an engine has no useful power, and, 
 on the other hand, if the resistance be equal to the pressure of the steam, it will 
 have no velocity, there must be an intermediate velocity, which is the best possible 
 for the engine to work with ; and this velocity is one-half the greatest uniform 
 velocity. 1 Now the velocity a falling body would acquire in descending through 
 the length of the stroke is equal to eight times the square root of the length of 
 the stroke, in feet per second ; therefore the velocity which corresponds to the 
 maximum of useful effect, being one-fourth of this velocity, is twice the square 
 root of the length of the stroke in feet per second, and 120 times the square root 
 of that length in feet per minute. 
 
 334. Hence, for engines regulated by a fly, if the pressure on the piston were 
 the same throughout the stroke, the best velocity for the piston in feet per minute 
 would be 120 times the square root of the length of the stroke in feet. 
 
 That is, if the length of the stroke be 4 feet, the square root of 4 being 2, the 
 velocity for a 4 feet stroke is 2 x 120 = 240 feet per minute ; but the action of the 
 valves not allowing this perfection, almost all engines belong to the next case. 
 
 335. If the steam act expansively, the velocity must be less, because the 
 pressure on the piston varies, and the uniform motion the steam would generate in 
 the length of the stroke would be less. 
 
 336. In a steam engine where the steam acts expansively, the supply of steam 
 
 being cut off at the part of the stroke, the best velocity for the steam piston will 
 be found by multiplying the -- part of the length by ? added to 2'3 times the 
 
 1 Let V be the greatest uniform velocity ; m the force producing it ; and w = the mass of 
 matter by which it is rendered uniform ; v being any other velocity. In this case m v w v = 
 the effective action ; and since m v = V w, we have 
 
 m V v mv* 
 
 for the effective part, which is to be the greatest possible. 
 
 The differential gives V dv 2 v dv = o when the expression is a maximum ; whence, 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 165 
 
 logarithm of n; then 120 times the square root of the product is the velocity in 
 feet per minute. 1 
 
 Example. Let the steam be cut off at one-fourth of the stroke, then n = 4 ; 
 and let the length of the stroke be 8 feet. The logarithm of n is O60206 ; 
 therefore, 0-60206 x 2-3 + -7 is 2-0847, which multiplied by one-fourth of the 
 length, or 2, is 4'169. The square root of 4-169 is 2'04 ; consequently, 2-04 x 120 
 = 245 feet per minute, the velocity for an 8 feet stroke when the steam is cut off' 
 at one-fourth of the stroke. 
 
 337. In the usual construction of engines not intended to act expansively, put 
 n = | ; and then take 103 times the square root of the length of the stroke. 
 
 For steam engines working expansively at the ordinary pressure of about 8 
 Ibs. on a circular inch of the safety valve of the boiler, the best proportion 
 for cutting off the steam is about one-half the stroke, and then the rule becomes 
 100 times the square root of the length of the stroke in feet, for the best velocity in 
 feet per minute. 
 
 Other rules may be easily derived from the investigation in the note. 
 
 338. In single acting engines, regulated by a fly, the same relation would 
 obtain between the length of the stroke and the velocity of the piston ; but such 
 engines cannot be used with advantage for producing a continuous motion. 
 
 OF THE MAXIMUM OF USEFUL EFFECT IN ENGINES FOR RAISING WATER. 
 
 339. In single engines for raising water we have two strokes to consider, of 
 different species ; the piston being caused to ascend by a counter weight, which 
 should be capable of raising the piston in a short time without adding materially 
 
 1 It has been shown (art. 306) that the expanding power of steam is p b hyp. log. ^ + J , 
 
 b 
 
 which added to the uniform portion, and the resistance r from friction and uncondensed vapour 
 being subtracted, it is 
 
 p b ( 1 + hyp. log. - - r j = the power ; 
 
 but b + x = I, the length of the stroke, and b = ; hence, 
 
 n 
 
 S- (1 + hyp. log. n r) = the power. 
 n 
 
 In ordinary circumstances r = -3, consequently, 
 
 120 V (-7 + hyp. log. n) = the velocity in feet per minute. 
 
166 OF THE POWER OF STEAM, [ SECT . , v . 
 
 to its load in the descent : and the descending stroke should not be slower than 
 gives the maximum of useful effect, because in both cases a considerable loss of the 
 power of the steam is taking place during its action. 
 
 340. In the ascent of the piston it must be evident that it should never 
 acquire a greater velocity than one which the steam can follow, so as to press it 
 with a force nearly equal to the pressure of the atmosphere ; and when the 
 apertures for the steam are arranged for the descending stroke, the ascending one 
 will be regulated by the passage of the steam through the same apertures ; and if 
 this be the case, and in the present construction of these engines it always is so, 
 our inquiry may be confined to the descending stroke. 
 
 341. The descent of the piston, if the effect of the steam alone were con- 
 sidered, it . is obvious, should be determined by the condition which gives the 
 greatest effect by a given quantity of steam ; but it is dependent on the resistance 
 of the water increasing as the square of the velocity, and the decreasing effect of 
 the steam in the simple ratio of the increase of the velocity. 
 
 342. Now we may be allowed to consider the motion an uniform one, as it is 
 nearly so during the greater part of the stroke ; and then when the steam acts at 
 full pressure during the whole of the descent, the velocity in feet per minute should 
 be 98 times the square root of the length of the stroke. 1 
 
 1 Suppose the arms of the beam to be of equal length ; the steam apertures being the same, the 
 ascending and descending strokes should be made in equal times. The greatest possible velocity 
 V will be generated when the resistance to the water in the pumps is equal to the counter weight ; 
 and as the forces in both directions are to be equal, if m be the force producing the motion ; 
 m = the resistance at the velocity V ; and the resistance to motion in pipes being as the square 
 
 of the velocity, ^^- 2 = the resistance at v, to which the counter weight must be equal ; con- 
 sequently, 
 
 m v 
 
 "* 
 
 
 - 
 
 = the effective power which is to be the greatest possible. 
 
 The maximum takes place when V 2 dv 3 v e dv = o, that is, when 3t> s = V 2 ,ort; = -577 V. 
 To determine V, it may be remarked, that the motion commences with an excess of power, whicli 
 diminishes by the increase of resistance, till the motion becomes uniform ; that the areas of the 
 passages of the valves are only half the area of the pump, and that the mass of matter moved is 
 twice the excess of moving force ; hence, V 2 = 8 s, and since 3 v* = V 2 , it is 
 
 v = v L = 1-633 V s, the velocity in feet per second. 
 3 
 
 When the velocity is in feet per minute, it is 
 
 60 x 1-633 -J~g = 98 >/l. 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 167 
 
 343. When the steam acts expansively, the velocity may be found from that 
 of an expansive engine regulated by a fly, (art. 336 to 338.) as O8 times that 
 velocity will be the proper velocity for an engine for raising water. 
 
 Thus we found the velocity for an 8 feet stroke, in an expansive engine where 
 the steam was cut off at one-fourth of the stroke, to be 245 per minute, (art. 336.) 
 and 0-8 of 245 is 196 feet per minute. 1 
 
 In these investigations I have not attempted to enter into those minute par- 
 ticulars which embarrass the calculation, without producing any material effect on 
 the result. 
 
 OF THE PROPORTIONS OF AIR PUMPS AND CONDENSERS FOR STEAM ENGINES. 
 
 344. The water used for producing steam, and for condensing it, contains a 
 considerable quantity of air, and sometimes carbonic acid and other gases. These 
 gases separate when water is boiled, and rise with the steam ; hence, were there not 
 some method provided to take the air away when the steam is condensed, the 
 cylinder of a steam engine would become filled with hot air, so as to impede, and 
 in the end resist, the pressure of the steam. 
 
 345. To estimate, therefore, the proper size for an air pump, the quantity of 
 air or other gas contained in water should be known. 
 
 Experiments on this subject have been made by Mr. Dalton, 2 Dr. Henry, M. 
 Saussure, and Dr. Ure. M. Saussure 3 ascertained that boiling alone was not 
 capable of freeing liquids completely from air, but that it may be done by the 
 joint action of heat and the air pump. In a steam engine both these causes 
 operate in extracting air from the water introduced into the engine. According 
 to his experiments 100 volumes of water absorb about 5 volumes of atmo- 
 spheric air. 
 
 In an experiment made by Dr. Henry 4 on spring water, he found that it 
 afforded by boiling 4'74 per cent of gaseous matter ; of which 3'38 per cent was 
 atmospheric air, and T38 per cent carbonic acid : but as it is probable that this 
 water was fully saturated, it follows from Saussure's remarks, that a greater 
 proportion would have been obtained if it had been subjected to the combined 
 action of boiling and the air pump ; and the whole proportion of gaseous matter in 
 spring water could not be estimated at less than seven per cent. 
 
 1 [It may be proper here to observe, that in practice it is considered that from 96 to 100 feet per 
 minute should be the maximum, since at higher velocities the buckets, &c. wear rapidly, besides 
 other disadvantages. ED.] 
 
 2 Philos. Mag. vol. xxiv. s Annals of Philosophy for 1815, vol. vi. p. 329. 
 4 Thomson's Chemistry, vol. iii. p. 204. 
 
168 OF THE POWER OF STEAM, [SECT. iv. 
 
 Dr. Ure's 1 experiments were also made by boiling different kinds of water, and 
 measuring the result by a pneumatic apparatus, and at the temperature of about 
 55: the proportions of gaseous matter in 100 volumes of water were found to be 
 as stated below. 
 
 Canal water (in winter) ..... 2'67 per cent. 
 Filtered river water supplied to Glasgow by the 
 
 pipes of the Cranstonhill Water Company . 2 '52 
 
 Filtered river water from the pipes of the Glasgow 
 
 Water Company ..... 2'50 
 
 Water from the river Clyde, when swollen by 
 
 winter rains ...... 2'80 - 
 
 It cannot be supposed that in these experiments the whole of the gaseous 
 contents of the water were obtained, but assuming that two-thirds of the total 
 gaseous contents are obtained by boiling, the quantity will vary from 3'75 to 4'2 
 per cent; and therefore, for river and canal water, we may assume that water 
 contains 5 per cent of air, or w of its volume. 
 
 The action of pumping it appears, from Dr. Ure's researches, expels a portion of 
 air from water. 
 
 346. The preceding articles afford us data sufficiently accurate for the general 
 purposes of inquiry, and in such inquiry we may suppose that, at the mean tem- 
 perature and pressure, 
 
 River or canal water contains ?V~I 
 
 c . n , f ot its volume of gaseous matter. 
 
 Spring or well water T V J 
 
 347. The quantity of water which enters into a steam engine will all of it give 
 out nearly the whole quantity of air it contains ; therefore, calculating the volume 
 of water used for steam at each stroke of the engine, and adding to it that used 
 for injection in the same time, we have 2*0 part for the volume of air at 60 ; 
 but in the condenser it will be of the temperature of the hot well, or about 120; 
 and the quantity the air expands by this increase of temperature being calculated, 
 (see art, 119.) the bulk is found to be 5'6 per cent of that of the water, or iV of the 
 bulk of the water nearly. 
 
 348. Let the injection water added to the water of the condensed steam be 
 of the volume of the cylinder for each stroke, then A of yV, or -gw of the cylinder's 
 volume of air, would accumulate at each stroke if there were no air pump. Now a 
 cubic foot of air mixes with a cubic foot of steam, when both are of the same force 
 
 1 Quarterly Journal of Science, vol. xxi. p. 71. 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 169 
 
 and temperature (art. 122.) ; consequently this air must accumulate and fill half 
 the capacity of the condenser after a few strokes, and the capacity of the air pump 
 must be such as will remove 7$? of air, and 7^5 of vapour, or both together T^TJ, 
 in order to get rid of the air which enters at each stroke, when it is of such a 
 degree of density that its force is equal to the force of steam corresponding to the 
 temperature of the hot well. 
 
 349. If it be assumed that the elastic force of the uncondensed vapour is equal 
 to 2 inches of mercury, and the air pump be equal to the condenser, then the 
 bulk of the air and vapour being shown above to be TJT, at the pressure of 30 
 inches, and the bulk being inversely as the pressure, we shall have 2 : 30 : : TT<J : ?g. 
 
 Thus the air pump has to clear the engine of -jV of the volume of the cylinder of 
 air and vapour, and of ?V of its volume of water ; the sum of these is, in the 
 nearest fraction, -fa of the capacity of the cylinder, for each stroke. 1 
 
 350. In a double engine the air pump makes only one stroke for each 
 cylinder of steam, but since the condenser receives a new quantity to replace 
 that taken by the pump, there is no expansion : hence TF part of the capacity 
 of the cylinder of a double engine is the least proportion for the air pump, so that 
 the engine may work effectively in the same manner as for a single engine. In 
 both cases the condenser and air pump are supposed to be of equal size to render 
 this proportion applicable, and it is also understood that river water is used. 
 
 1 Let be the volume of air contained in the injection water and the steam, t' the tem- 
 perature of the condenser, and /' the force of steam corresponding to it,/ being the force in the 
 
 cylinder. Then -^ . ( ^^ ) = the volume of air, and a = that of water for each stroke. 
 / \ oil / 
 
 The condenser must contain both these quantities, and also what the pump leaves ; and with 
 an allowance of half for leakage and imperfect action of the valves, its least capacity must 
 obviously be 
 
 When the pump ascends, the air will saturate with vapour, and become of twice its former 
 volume; hence if the air pump and condenser jointly contain it in this state, they will be of equal 
 size, and the quantity required will be removed at each stroke of the pump. Putting t' = 100, 
 /' = 2, and/= 30 inches, we have 
 
 3 a ( - + '67 ] = capacity of air pump = condenser. 
 \ n J 
 
 / 
 
 If n = 20, as for river water, then 4-48 a = capacity of pump. 
 If n = 14, as for well water, then 5-55 a = capacity of pump. 
 
 Y 
 
170 OF THE POWER OF STEAM, [SECT. iv. 
 
 351. For well water the same mode of calculation gives about ^ for 
 the relation between the capacity of the air pump and the cylinder. The usual 
 proportion in Boulton and Watt's practice is i ; and as I have made no 
 allowance for leakage nor imperfect action of valves, this proportion appears to be 
 nearly correct for the case considered. l 
 
 352. There is one thing very evident in this operation : it is that an air 
 pump half the size would be as effective as the present construction, if we could 
 condense in the pump itself; and I see no difficulty in doing so, and propose to 
 show its application to a simple atmospheric engine. (See art. 400.) The ad- 
 vantage, however, will be better understood if we show the power an air pump 
 requires to work it. 
 
 POWER REQUIRED FOR WORKING AN AlR PuMP OF A STEAM ENGINE. 
 
 353. Let v = the velocity in feet per second ; p' = the force of the steam or 
 vapour in Ibs. per circular inch ; r = the friction of the piston and piston rod, 
 and resistance of the valves ; a = the diameter of the pump in inches ; and 
 
 a = the area of the valves. 
 
 n 
 
 The head capable of producing the velocity n v through the valves, (see art. 
 136.) is n v = 6-5 Jh ; and, 
 
 42 
 
 In a mixture of air and steam, at the mean force in such a pump, 2100 feet 
 in height is equivalent to a pressure of 1 Ib. per circular inch ; hence, 
 
 n 1 v* n a 
 
 2100 x 42 88200 
 
 the pressure in Ibs. 
 
 Put / = the length of the stroke ; and the resistance to the descent of the piston 
 will be, 
 
 *'/ /tt^ X 
 
 88200 \ * 88200/ 
 
 The resistance to the ascent of the piston will be found by considering that the 
 air and vapour is compressed till its elastic force becomes of such an excess above 
 the atmospheric pressure, that it escapes through the valve at the velocity cor- 
 responding to the motion of the piston. The friction of the piston and weight of 
 the water is to be added ; and the force of the vapour in its expanded state may 
 
 1 In some instances air pumps for double engines have been made about two-thirds of the 
 diameter of the steam cylinder, and half the stroke : such pumps are undoubtedly too large. 
 
SECT, iv.] AND PROPORTIONS OF ENGINES. 171 
 
 be considered equal to the sum of the forces necessary to cause it to pass the 
 valves. 
 
 By art. 306, the resistance of the air and vapour is, 
 
 pbx 
 
 and making b + x = I, we have b = ; therefore, 
 
 IP' fl + hyp. log. JL_) = the power ; 
 
 and when the pressure of the atmosphere p = 11 '55 Ibs. and the force of the 
 vapour p' = '77 Ibs. or 2 inches of mercury, it becomes 
 
 lp' fl + hyp. log. P - \ = 2-85 /, nearly. 
 
 The quantity of water will be one-sixth of the capacity, or -055 / a 2 Ibs. raised 
 1 foot. Hence, the whole power required for the ascending stroke will be 
 
 a* / (2-85 + -055 / + r). 
 354. The whole power to work the pump is therefore, 
 
 ^.(2-85 + -055 / + |yil + 2r ) Ibs. raised 1 foot per second. 
 
 Example. Let the velocity be 1'8 feet per second; the diameter of the pump 
 24 inches ; the length of its stroke 4 feet ; the friction 2 Ibs. per circular inch ; 
 and the area of the valves half the area of the pump. These numbers being 
 inserted, we have, 
 
 24 * * >< ** 2-85 + -055 x 4 + 2 * 2 * ** + 4 = 
 
 518-4 (2-85 + -22 + -00015 + 4^ = 3665 Ibs. raised 1 foot per second. 
 
 As 550 Ibs. raised 1 foot per second is the steam engine horse power, the 
 power is, 
 
 3670 , , 
 
 -TQ- = of horse power nearly. 
 
 The pump would answer for a double engine of about 134 horse power: there- 
 fore in this case about one-twentieth part of the power of the engine is required 
 for the air pump ; or one-tenth in the case of a single engine of the same sized 
 
172 OF THE POWER OF STEAM, &c. [SECT. iv. 
 
 cylinder ; or a loss equivalent to 13 horse power in an air pump of the size in 
 the example. To reduce this loss one-half by the mode proposed in art. 352 
 is certainly worthy of attention. 
 
 355. It is important to remark the circumstances which contribute to this 
 loss of power. The loss is proportional to the capacity of the pump ; therefore the 
 smaller it is the better, provided it be sufficient to take the air. The friction is 
 four-sevenths of the power, the actual resistance of the vapour nearly three- 
 sevenths, and that of the water about one thirty-second. The resistance is greater 
 the smaller the passages and valves are, but such increase does not affect the 
 whole power in a material degree. The increase of the size of the air pump, 
 beyond the proportions I have given, can give advantage only in an ill-constructed 
 and leaky engine ; but its decrease, after a very short range, reduces the power 
 considerably. 
 
SECTION V. 
 
 OF THE CONSTRUCTION OF NONCONDENSING ENGINES. 
 
 356. NONCONDENSING ENGINES, usually called high pressure engines, are moved 
 by steam generated under a considerable degree of pressure ; and it is the excess of 
 this pressure above the pressure of the atmosphere, which constitutes their power to 
 produce motion. From 30 to 40 Ibs. on a circular inch is the excess above 
 atmospheric pressure, commonly employed in this country. 
 
 357. The working parts of the engine consist of a cylinder, having passages 
 provided with cocks or valves for steam to enter into it, either at the top or at the 
 bottom ; and also the means of letting out the steam to the atmosphere, either at 
 the top or bottom. The cylinder has an air-tight piston, to be moved from one 
 end to the other by the pressure of the steam, with a rod fixed to it, called the 
 piston rod, which slides through an air-tight box at the top of the cylinder, to 
 give motion to a crank or some other piece of machinery. 
 
 358. Now, with steam in the boiler having a force of 30 Ibs. to the cir- 
 cular inch, if the piston be at the bottom of the cylinder, and the passage from 
 the boiler to the bottom, and that to the atmosphere at the top, be both open, and 
 the rest shut, the steam will exert a pressure of nearly 30 Ibs. on each inch of 
 the area of the piston, and cause it to ascend. A little before it arrives at the 
 top, the cocks must be shut, and the moment it has got to the top, the other two 
 cocks should be opened ; the steam from the boiler will then press the piston 
 downwards, and the steam before let in will flow out into the open air. Again, the 
 passages must be closed a little before the completion of the stroke, and in this 
 manner the operation may be continued. 
 
 359. The close of the cocks before the termination of the stroke prevents either 
 concussion against the end of the cylinder, or strain on the crank shaft; and, when 
 
174 OF THE CONSTRUCTION OF [SECT. v. 
 
 properly managed, the elasticity of the steam destroys the momentum of the piston, 
 and recoils it back without loss of force. 
 
 This will afford the reader a general notion of the action of steam in non- 
 condensing engines, and prepare him for entering more closely into their minutiae. 
 I have divided them into two kinds ; and of the varieties depending on different 
 forms of construction there is an immense number. 
 
 360. Noncondensing engines, 
 
 fLeupoId, (art. 12.) 1720. 
 
 t . f e . j Watt, (art. 26.) 1769. 
 
 (1. the eenerative force of steam, < _ 
 
 ] Trevithick, (art. 56.) 1802. 
 
 Acting by -I (^Evans, (art. 58.) 
 
 r Oliver Evans, (art. 58.) 
 I 2. the generative and expansive force of steam, < 
 
 I Taylor and Martineau. 
 
 361. First Species. When the power is derived solely from generating the 
 steam under pressure, (art. 295.) the construction of the parts constituting the 
 engine is very simple. The common method is represented in Fig. 1. Plate iv. 
 With the object of losing as little heat as possible by the cooling of the cylinder, it 
 is generally placed partly within the boiler, and the steam is admitted and let out 
 by a four-passage cock A, placed just without the boiler, with a throttle valve V to 
 regulate the entrance of the steam. The steam escapes to the atmosphere by a 
 pipe E, which is generally surrounded by water W, for the supply of the boiler, 
 which has the effect of partially condensing the escaping steam, and facilitating its 
 escape from the cylinder, as well as of increasing the temperature of the water 
 before it be admitted to the boiler. 
 
 362. This construction is defective, in as far as there must be an absolute loss 
 of all the steam in those parts of the admission pipes which are between the cock 
 and the cylinder ; and the great density of high pressure steam renders the loss of 
 power considerable. To avoid it, there should be two double-way cocks, one at the 
 bottom and one at the top of the cylinder ; or the passages may be opened and 
 closed by a slide, as shown in Fig. 2. where it will be obvious that the spaces 
 between the stops and the cylinder are as small as possible. 
 
 363. If we now trace the action of the steam, and the opening of the passages, 
 we shall find to what points to attend in perfecting the operation of the engine. 
 In Plate iv. Fig. 1. represents an engine, of which C is the cylinder, and P the 
 piston at the top ready for descending. The motion of the cock A might end with 
 the end of the stroke, but the steam would be cut off", and indeed all the passages 
 stopped when it is half turned. The closing, when quickly done, commences 
 sufficiently before the end of the stroke, to effect the recoil of the piston (art. 359.) ; 
 
SECT, v.] NONCONDENSING ENGINES. 175 
 
 and at the instant of its change of motion, the steam is fully on it. The com- 
 pression which the steam left in the cylinder receives when the cock is closed, is 
 not only a means of changing the motion without loss of force, but also occupies 
 the space at the end of the stroke, so as to require only a small quantity to refill it 
 with steam. We might arrange the motion so that the cocks would be half 
 turned, and all the passages closed just at the end of the stroke : this, however, 
 would not be so good a method, as when the cock turns with proper quickness 
 there would be DO sensible accumulation of steam to recoil the piston, and the 
 force of that in the boiler would not be fully on, till a part of the stroke was 
 made ; and the waste at the terminations of the strokes would be greater. Hence, 
 to complete the motion of the cock with the termination of the stroke, is the better 
 method. 
 
 364. In the construction, Fig. 1. at every double stroke there is a loss of 
 the force of all the steam contained in the passages between the cock and the 
 cylinder. This defect may be avoided by the use of the slide, Fig. 2 and 3. The 
 motion of the slide should terminate with the stroke in the same manner as with a 
 cock ; and in this construction the recoil of the compressed steam is greater, because 
 it has less space of passage to retreat into. Valves may be placed to give similar 
 advantages, but slides or cocks are in my opinion better adapted to high pressure 
 engines. 
 
 365. The modes of giving motion to the cocks, slides, or valves are various : 
 they depend chiefly on the nature of the action the engine is intended for. The 
 same methods are applicable to engines of all species, and therefore are described 
 together. (See Sect, vn.) The power is usually regulated by a throttle valve, but 
 more perfectly by means of Field's valve. (See Sect, vm.) 
 
 366. The Proportion of Parts. The length of the stroke of the steam piston 
 should not, if possible, be less than twice its diameter, (art. 327.) The velocity in 
 feet per minute should be 103 times the square root of the length of the stroke in 
 feet, (art. 337.) And, as 4800 is to the velocity thus found, so is the area of the 
 cylinder to the area of the steam passages, (art. 154.) The strength, proportions, 
 and construction of the parts are given in Sect. vn. and the methods of equalization 
 and regulation in Sect. vm. 
 
 367. The Power of a Noncondensing Engine may be calculated with con- 
 siderable accuracy, from knowing the excess of the force of the steam in the 
 boiler, above the atmospheric pressure, as shown by the steam gauge, the diameter 
 of the cylinder, and the velocity of the piston. The effective pressure on the piston 
 is less than the force in the boiler when that force is represented by unity, 
 
176 OF THE CONSTRUCTION OF [SECT. v. 
 
 1. By the force producing motion of the steam into the 
 
 cylinder, (art. 154.) - '0069 
 
 2. By the cooling in the cylinder and pipes, (art. 158.) '016 
 
 3. By the friction of the piston and waste - '2000 
 
 4. By the force required to expel the steam into the 
 
 atmosphere, (art. 154.) - - -0069 
 
 5. By the force expended in opening valves, and friction 
 
 of the parts of the engine '0622 
 
 6. By the steam being cut off before the termination of 
 
 the stroke, (art. 363.) -1000 
 
 3920 
 
 We may consider this 0'4, and then the effective pressure is 0'6 of the force of the 
 steam in the boiler, diminished by the pressure of the atmosphere ; whence we have 
 the following rule for the power of an engine of this species. 
 
 368. RULE. For noncondensing engines working at full pressure. Multiply 
 six-tenths of the excess of the force of the steam in the boiler, less four-tenths of 
 the pressure of the atmosphere in Ibs. on a circular inch, by the square of the 
 diameter of the cylinder in inches, and by the velocity of the piston in feet per 
 minute ; the product is the power of the engine in Ibs. raised 1 foot high per 
 minute. 1 
 
 To find its equivalent in horse power, divide by 33000. 
 
 Example. Let the diameter of the cylinder be 11 inches, the length of the 
 stroke 2 '5 feet, the number of strokes per minute 33, and the force of the steam in 
 the boiler 24 Ibs. per circular inch above the atmospheric pressure : in this case 
 the velocity is 2 x 2'5 x 33 = 165 feet, and (24 x 0-6 - 11-5 x 0-4) x 121 x 165 
 = 195657 Ibs. raised 1 foot per minute. 
 
 And, 
 
 = 6 horse power nearly. 
 
 369. If the area of the cylinder in feet be multiplied by the velocity of the 
 engine in feet per minute, it will be the volume of steam consumed when of the 
 density of that in the boiler ; and, dividing by the volume of steam which a cubic 
 
 1 Put a = the diameter of the cylinder in inches, t; = the velocity of the piston in feet per 
 minute, and/= the force of the steam in the boiler in inches of mercury; then, 
 
 ^ ~ . x a 2 v = the power in Ibs. raised 1 foot per minute, 
 * o 
 
 2-6 inches of mercury being 1 Ib. per circular inch. 
 
SECT. v.J NONCONDENSING ENGINES. 177 
 
 foot of water forms at the temperature or force in the boiler, (art. 121. or tables 
 at the end,) the result will be the cubic feet of water consumed per minute ; 
 and the quantity of water, and consequently the quantity of fuel, (art. 190.) 
 will be known ; but the supply of water should be a little in excess. 
 
 370. The purposes to which noncondensing engines of this kind have been 
 applied, are to impelling steam carriages, moving materials within deep mines, 
 draining mines in places difficult of access, driving machinery in places where 
 water cannot be obtained at a moderate expense, and in various instances where 
 low pressure steam was equally available ; but for most of these purposes it is 
 inferior to the next species : the sole advantage it possesses being that of uniformity 
 of force in every part of the stroke ; which in some instances is desirable, but in 
 others hurtful. 
 
 NONCONDENSING ENGINES TO WORK BY EXPANSION. 
 
 371. Second Species. The only difference required in the construction of a 
 noncondensing engine to enable us to use the expansive power of the steam, is in 
 the arrangement for opening and closing the steam passages. The steam must be 
 admitted from the boiler only during a part of the stroke, and then shut off, but 
 the passage for the escape of the steam should be open during the whole of the 
 stroke. When the passage from the boiler is shut, the steam acts by expansion, 
 and the power it affords by expansion is wholly in addition to that which is ob- 
 tained by the preceding species ; whence the economy of this method. 
 
 372. The most important question is to determine that point in the length 
 of the stroke at which the steam should be cut off, so that it may afford the 
 greatest quantity of useful effect from a given quantity of steam ; for then a given 
 quantity of fuel produces the greatest useful effect. Now we have shown the 
 resistance from friction, &c. to be nearly, if not exactly, 0*4 of the whole force of 
 the steam in the boiler, (art. 367.) and it is obvious, that when the steam has 
 expanded till its excess of force be equal to this resistance, it will produce no 
 further useful effect ; and also that as far as the expansion exceeds this limit, there 
 must be a decided loss of power. Hence, if we consider the capacity of the cylinder 
 to be 1, the force being inversely as the space the steam occupies, it must be, as 
 the whole force of the steam in the boiler is to 1, so is the whole force on the 
 piston, when it is just equal to the friction, to the portion of the stroke when the 
 steam should be cut off. 1 That is, if the whole force in the boiler be 120 inches 
 
 1 Put/ = the force iu the boiler in inches of mercury, and = the portion of the stroke made 
 before the steam is cut off, then, 
 
178 OF THE CONSTRUCTION OF [SECT. v. 
 
 of mercury, the atmospheric pressure being 30, the resistance is 120 x '4 = 48, 
 the inches equivalent to the friction ; and 30 + 48 = 78, the whole force on the 
 piston, consequently, 
 
 1 
 
 120 : 78 : : 1 : 0-65 = 
 
 1-54 
 
 the portion of the stroke to be made before the steam be cut off, when its force in 
 the boiler is 120 inches, or 90 inches in excess above the atmosphere. 
 
 373. The excess of force in the boiler must be about four-tenths of the 
 pressure of the atmosphere, or twelve inches of mercury, to cause motion at the 
 proper velocity : but the absolute friction being only about half this force, the 
 engine may begin motion with about a force of six inches. 
 
 374. The most common mode of cutting off the communication between the 
 cylinder and boiler, at the proper period of the stroke, is to give a slide two 
 motions ; the first shuts off the steam, and the second motion lets it on at the 
 opposite end, and opens the other to the atmosphere. Such a construction is 
 shown by Plate iv. Fig. 4. the position of the slide being shown when the steam 
 is cut off by its first motion. This construction represents the principle followed 
 by Messrs. Taylor and Martineau ; but they place the axis of the cylinder 
 horizontally, and construct the pistons of the cylinder and of the slides in a 
 rather different manner from those drawn. 
 
 A horizontal piston rod never works well, and the expense of such a frame as 
 enables us to use it in a vertical position can rarely be more than equivalent to 
 this defect ; nevertheless, in mountainous districts, where mines are difficult of 
 access, a horizontal cylinder has the advantage of being very easily fixed. 1 
 
 375. The power of an engine of this kind should be regulated by altering 
 the time of cutting off the steam ; its power may vary from full pressure through 
 the stroke to that obtained by cutting off at the point above determined : the 
 average state that will give the greatest advantage, being to cut off at a mean 
 between the point which gives the maximum of effect, and that which gives the 
 greatest power required for the work ; for a loss of power arises from cutting off 
 sooner than is indicated by the rule, when the right amount of friction is calcu- 
 lated upon. For modes of giving motion to the slide, see art. 478. 
 
 " = . 4/ + 30 ' 
 
 if we disregard the diminution of the pressure due to the fall of temperature in the process of 
 expansion. 
 
 1 Belidor shows a method of constructing a piston for a horizontal cylinder by the addition of 
 friction rollers. Arch. Hydraul. torn. ii. p. 240. 
 
SECT, v.] NONCONDENSING ENGINES. 179 
 
 Oliver Evans made a rude attempt to investigate the advantage of cutting off 
 the steam in high pressure engines, claiming the principle as his own ; but the 
 engine he describes is not arranged for that purpose ; he uses valves for the steam 
 passages: 1 the objection to valves above a certain size is the difficulty of opening 
 them. 
 
 376. The proportions of the parts for expansion engines may be ascertained 
 by the same rules as for full pressure, (art. 366.) excepting that the velocity 
 should be found by the rule, art. 336. 
 
 377. To determine the power of a noncondensing engine working expansively, 
 it will be most useful first to ascertain the mean effective pressure on the piston, 
 and from thence the power. 
 
 To find the mean pressure, let the steam have to be cut off at the part of 
 
 the stroke. Add 1 to 2*3 times the logarithm of n ; divide the sum by n and 
 subtract 0'4 from the result ; then the remainder multiplied by the whole force 
 of the steam in the boiler in Ibs. per circular inch, and 11 '55 subtracted from 
 the product, for the pressure of the atmosphere, the result is the mean effective 
 force of the steam on the piston in Ibs. per circular inch. 2 
 
 To find the power, multiply the mean effective pressure by the square of the 
 diameter of the piston in inches, and by the velocity in feet per minute ; the 
 product is the Ibs. raised 1 foot per minute. 
 
 To find its equivalent in horse power, divide by 33,000. 
 
 378. Example. If an engine work expansively, the steam being cut off at 
 
 1 Steam Engineers' Guide, p. 30 and 67. Philadelphia, no date. 
 
 2 Making b + x = I, and b = , we have, (see art. 306) 
 
 n 
 
 pb(l+ hyp. log. *il ) = Jd. (1 + hyp. log. ) ; 
 
 and therefore the power of a cylinder a inches in diameter, working at a velocity of v feet per 
 minute, is 
 
 (1 + hyp. log. n) friction and resistance of the atmosphere. 
 The latter is -4 pa- v + 11-55 a 2 v ; hence 
 
 a* v | p( l + h yP- lo g- " _ -4\ _ 11-55 j = the Ibs. raised 1 foot per minute. 
 
 The hyperbolic logarithm of n is equal 2-30285 times the common logarithm of ; whence 
 the rule. 
 
 When n is fixed by the rule, art. 372. viz. n = ?- , the formula reduces to the 
 
 4tp + 11-55 
 
 more simple form of, 
 
 a v P (hyp. log. n) = the power in Ibs. raised 1 foot high per minute. 
 
180 OF THE CONSTRUCTION OF [SECT. v. 
 
 the p= P art of the stroke, the cylinder being 12 inches in diameter, the velocity 
 
 160 feet per minute, and the whole force of the steam in the boiler 120 inches of 
 mercury, or 46 Ibs. per circular inch, 
 
 First. 2-3 x log. 1*5 = 0-405 
 Add 1 1- 
 
 Divide by 1-5) 1-405 
 
 0-936 
 Subtract 0-4 the friction and loss. 
 
 0-536 
 Multiply by 46 the pressure of the steam. 
 
 24-656 
 Subtract 11-55 the resistance of the atmosphere. 
 
 And 13-106 Ibs. = the mean effective pressure on each 
 circular inch of the piston. 
 
 Also 12x12= 144 the square of the diameter. 
 Multiply by 160 the velocity, 
 
 23040 
 and again by 13-1 the mean pressure. 
 
 Then 301824 Ibs. = weight raised 1 foot per minute. 
 And m^ =9-15 horse power. 
 
 379. When the steam is cut off at the part of the stroke, the quantity of 
 
 steam consumed in cubic feet per minute will be found by multiplying the area of 
 the cylinder in feet by the velocity in feet per minute, increased by one-tenth, and 
 dividing the product by n. If this result be divided by the volume which a cubic 
 foot of water occupies when in the state of steam of the force in the boiler, (see art. 
 121. or tables,) the quotient will be the quantity of water required per minute, and 
 the equivalent quantity of fuel will be found by art. 190. The actual supply of 
 water, and the power of the boiler should be n times that quantity ; the engine will 
 then either work at full pressure or expansively, as occasion may require. 
 
 380. In an expansive engine the moving force varies from full pressure to 
 
SECT, v.] NONCONDENSING ENGINES. 181 
 
 nothing in the course of the stroke : for some objects this variation is desirable, 
 because the motion of the piston is not accelerated so much towards the end of the 
 stroke. It may be used for any of the purposes to which steam power has been 
 found applicable ; and where water is not easily procurable, it becomes the most. 
 economical species of engine. 
 
 381. Double cylinder expansive engine. An engine of the noncondensing kind 
 may be worked expansively by means of a double cylinder, according to Horn- 
 blower's method, (art. 32.) In Plate iv. Fig. 5. C is the cylinder for the strong 
 steam, and B that in which it acts by expansion. The steam enters at S from the 
 boiler, and passing through the passage t at the top of the small cylinder, forces 
 down the piston ; the steam previously in the cylinder C passes through b, and 
 ascending by the pipe e, enters the large cylinder B at a, and by its expanding 
 force causes the piston to descend, the expanded steam below the piston escaping to 
 the atmosphere by the passage c and through d. The pistons in the passages, 
 being moved by the rods g, ft, to the other sides of the apertures to the cylinders, 
 the pressures are reversed, and the expanded steam escapes to the atmosphere by 
 the passage a, through the aperture /. This construction is not very complex 
 to obtain the motion of both pistons in the same direction ; but it obviously could 
 be done by one slide if the pistons had contrary motions, and I see no sound 
 objection to their motions being contrary; and then the axis of motion should 
 be between them. The effect of this mode of applying steam is the next point of 
 consideration. 
 
 382. Let /be the force in inches of mercury or 0-385 /the force in Ibs. on 
 a circular inch of the small piston, a its area, and / the length of its stroke. Also, 
 let m a be the area of the large piston, and n I the length of its stroke. Then at 
 any portion x of the descent of the piston in the small cylinder, nx = the descent 
 in the large one. The original space of the steam being / a, and its pressure being 
 
 inversely as its bulk ; (I - x) a + m n ax -. I a . . /-. / + (> f _ i) ^ = the elastic force 
 
 of the steam between the pistons. And if "385 /' be the resistance from friction, 
 loss of force, and the resistance of the atmosphere, we have, 
 
 385/ " - ,+(..'-1,. + ,+,,".'-.).) - - 385 - / = 
 
 the forces of both cylinders ; and the differential of the power is, 
 
 / + (m n 1) x 
 Its integral is, 
 
 385/a | x + I hyp. log. (/ + ^HT^l *) j - -385 m n af x, 
 
182 OF THE CONSTRUCTION OF [SECT. v. 
 
 which, corrected, becomes when x = I, 
 
 385fal 1 1 + hyp. log. m n \ -385 m n af I. 
 Or 
 
 385/ a 1 1 1 + hyp. log. mn- mnf ' \ = the power. 
 
 383. The ratio of the capacity of the large cylinder to the small one is 
 dependent on the amount of friction and loss of force. In the small cylinder the 
 loss must be the same as in the cylinder of an engine working at full pressure ; this 
 appears from our mode of inquiry to be 0'4 of the force of the steam in the boiler, 
 (art. 367.) And in the second cylinder the friction of the piston, the cooling of 
 the cylinder, and the excess of force required to expel the steam into the atmo- 
 sphere added together make '016 + -2 + '007 = '223 of the remaining force, or 
 223 x '6 + '4 = -5338 = the whole loss in the two cylinders. Hence, 
 
 5338 / + 30:/:: 1 : m = .5333 y + 3 Q = the capacity of the large cylinder, when 
 
 that of the small one is unity. 
 If/= 120 inches, then, 
 
 5338 f + 30 = 1'28, the relative capacity of the large cylinder. 
 
 And in all cases the value of m n must be less than that of n in the note to 
 art. 377. Also, since -533S/ + 30 =/', we have, from art. 382. 
 
 385/a* (l + hyp. log. m n - ^') = -385 /' v hyp. log. . 
 
 3Q . 
 
 for the power of the engine, of which the velocity of the small piston is v feet per 
 minute, and its diameter a inches, the whole force of the steam being / inches of 
 mercury in the boiler. 
 
 Consequently, the power is less in an engine with a double cylinder, than in one 
 with a single cylinder, in the ratio of, 
 
 the hyperbolic log. of ^SBS to that of T- 
 
 A decrease of power and a more complex arrangement renders the double 
 cylinder engine inferior in every respect, except that of the moving force being 
 more equable than in a single cylinder. 
 
 384. Of the best force for the steam of noncondensing engines. The circum- 
 stances determining the choice of the force of the steam are almost entirely of a 
 practical nature. As far as regards the production of the steam itself, a greater 
 quantity of fuel will be required to generate strong steam, and there will be more 
 
SECT, v.] NONCONDENSING ENGINES. 183 
 
 loss of heat in the operation ; consequently, as far as the generation of the steam is 
 concerned, the lower the force the better. But in the noncondensing engine the 
 steam has to work against the pressure of the atmosphere, and loses so much of its 
 effect ; hence the more its force exceeds the atmospheric pressure, the greater will 
 be the effect of a given quantity of steam in proportion to this loss. On the 
 contrary, when the strength of the steam is considerable, there is much waste by 
 leakage, 1 which with the extra expense of fuel tends to counterbalance the ad- 
 vantage of increasing the force; and considering these circumstances, with the 
 danger of strong steam, it appears to me that steam of four or five atmospheres is 
 about the best force for these engines. 
 
 1 The rate of increase of loss by leakage may be estimated, for it depends jointly on the goodness 
 of the workmanship, and the force tending to separate the parts. Now a good workman may fit 
 the parts so that they would not exceed, under a strain of 1 atmosphere, a continued aperture of 
 the 5000th part of an inch in breadth; and then if/ be the force in inches of mercury, and a the 
 diameter in inches, the magnitude of the joint will be, 
 
 3-1416 a f 3-1416 af 
 
 30 x 5000 = 150000 SqUa 
 
 The velocity of escape will be less than 6-5 V 86-5 (459 + t) or 60 V 459 + t (art. 136.) ; con- 
 sequently, the quantity lost per second cannot exceed, 
 
 3-1416 af y/ 459 + t 
 2500 
 
 If v be the velocity of the piston in feet per second, the steam required in the same time will be 
 7854 a 2 v; hence, the quantity required being unity, the loss will be less than, 
 
 3-1416 af ^459 +1 _ f y/ 459 + t 
 7654 a*v x 2500 625 a t; 
 
 When v = 4, a = 10, /= 133, and t = 300, 
 
 625 a v 
 
SECTION VI. 
 
 OF THE CONSTRUCTION OF CONDENSING ENGINES. 
 
 385. THE distinguishing feature of this class of engines is, that of condensing 
 the steam to the state of water. The moving force is nearly equivalent to the 
 force of the steam, as in the boiler, moving through the difference between the 
 space in the state of steam and that in the state of water. Different systems of 
 construction render the effective or useful power more or less, but I will endeavour 
 to give the general principles in a few words, and then proceed to more minute 
 detail. 
 
 386. The essential parts of a single condensing engine consist of a cylinder 
 having a passage to admit steam at the top, and one from the bottom to convey 
 the steam to another cylinder, called a condenser. The condensing cylinder has 
 a passage from the lower part of it to an air pump ; and both the air pump and 
 the condenser are immersed in a cistern of cold water, a jet of which plays into 
 the condenser. The cylinder has an air-tight piston fixed to a rod, which moves 
 in an air-tight box in the top of the cylinder. Conceive there to be a valve 
 in the piston, which, whenever the piston arrives at the bottom, opens and allows 
 the steam to pass from the upper to the lower side of the piston. Then, let the 
 jet be stopped, and the cylinder and condenser be filled with steam from the 
 boiler, and the piston be raised to the top of the cylinder by a counter weight at 
 the other end of the beam, to which the piston rod is fixed. The cock being open 
 to admit the steam from the boiler to the cylinder, if the jet of cold water be 
 allowed to play into the condenser, nearly the whole of the steam in the condenser, 
 and in that part of the cylinder below the piston, will be reduced to water, and 
 the pressure on the top of the piston being equal to the elastic force of the steam 
 in the boiler, while the elastic force of the vapour remaining below it is very small, 
 the difference of the forces will press down the piston, and, consequently, raise 
 an equivalent weight at the other end of the beam. 
 
SECT, vi.] CONDENSING ENGINES. 185 
 
 When the piston arrives near to the bottom of the cylinder, the passage to the 
 condenser is shut, and the valve in the piston opens ; then the steam above the 
 piston passes through to below it, as the piston rises by the action of the counter 
 weight ; and, being at the top, the valve in the piston closes, and the valve to the 
 condenser opens, and another stroke is made, and so on successively. 
 
 But since a large quantity of water is used at each stroke, and the water con- 
 tains a considerable quantity of air, the condenser would soon become filled with 
 air and water, and the engine would cease to work ; to avoid this the air pump is 
 added, which, being worked by the beam, makes a stroke at each stroke of the 
 steam piston, and clears the condenser of air and water. 
 
 387. In an atmospheric engine with a condenser, the principal difference 
 consists in the steam being let both into and out of the cylinder by passages at the 
 bottom ; and the descent of the piston is caused by the pressure of the atmosphere 
 on its upper surface, which is open to the air. 
 
 388. But in the atmospheric engine, as constructed before Mr. Watt's improve- 
 ment of condensing in a separate vessel, the jet of cold water was thrown into the 
 cylinder itself at each stroke ; and hence the cylinder required to be heated and 
 cooled at each stroke at a great expense both of fuel and cold water. 
 
 The addition of a separate condenser was the most valuable of Mr. Watt's 
 improvements ; his next in importance was the double acting engine. The saving 
 from the concentration of power, which results from these improvements, can be 
 judged of only by those who are intimately acquainted with the employment of 
 mechanical power. To them the merit of his invention must be known and duly 
 appreciated, and by their estimation it must ultimately be valued in public 
 opinion. 
 
 389. The double acting engine, in general construction, resembles the single 
 one described in the preceding article. (Art. 386.) It differs in having a passage 
 from the boiler both to the top and the bottom of the cylinder, and a similar 
 passage from both to the condenser. Hence, it does not require a counter weight 
 to raise the piston, nor that the steam should pass from the upper to the lower 
 side. The force of the steam impels the piston in both directions ; and compared 
 with a single engine of the same size, a double quantity of steam is used, and 
 double power is exerted in the same space and time. 
 
 390. In any of these species, steam may act expansively, whether the 
 atmospheric or steam pressure be used ; but the moving force may be rendered 
 more uniform, by using two cylinders of different sizes : in the smaller of these 
 cylinders the steam acts with all its force throughout the stroke, and in the other 
 it gradually expands as the stroke proceeds, and therefore the moving force is 
 variable : but as the forces on both pistons jointly constitute the moving force, 
 
 2A 
 
186 OF THE CONSTRUCTION OF [SECT. vi. 
 
 it is never less than the force of the steam on the smaller piston. This arrange- 
 ment was devised by Hornblower. (Art. 32.)' The engines may be of either single 
 or double power ; but whether the engine has double or single power, it is, in the 
 usual construction, a complex piece of machinery. 
 
 391. We may now proceed to arrange the different species, and show the 
 proportions adapted to particular cases. 
 
 CONDENSING STEAM ENGINES. 
 
 fl. Atmospheric pressure Newcomen, 1705. 
 
 I. By condensation ( 2 . Steam pressure (Single Watt, 1769. 
 
 I Double Watt, 1782. 
 
 {1. Atmospheric pressure 
 
 f Single Watt, 1782. 
 
 2. Steam pressure < Double Watt, 1782. 
 
 Combined cylinder Hornblower, 1781. 
 
 III. By generation and condensation. 
 
 Cornish engines on Watt's construction, 
 omgie i 
 insion, J 
 
 and condensation 
 
 IV. By generation, expansion, f Dg " I Woolf, 1804. 
 
 I D hi / Cornish engines on Watt's construction. 
 ' I Woolf, 1804. 
 
 OF THE CONSTRUCTION OF ENGINES WORKING BY CONDENSATION. 
 
 392. Of the engines working by condensation alone, two kinds may be 
 distinguished ; in the one kind the moving force is the pressure of the atmosphere, 
 in the other it is the pressure of steam : the former may be further divided into 
 those which condense in the cylinder, and those having separate condensers ; and 
 the latter into single and double acting engines. 
 
 ATMOSPHERIC ENGINES. 
 
 393. The common atmospheric engine. In the atmospheric engine, as it is 
 usually constructed, condensation is effected in the cylinder. The parts required 
 for this object are, a cylinder C, Plate vi. Figs. 1 and 2. close at the bottom and 
 open at the top ; a piston P ; a passage S for the steam from the boiler to the 
 bottom of the cylinder, provided with a valve V, or cock ; a passage for cold water 
 to condense the steam, to inject into the cylinder at I, with a cock D ; and a 
 
SECT, vi.] CONDENSING ENGINES. 187 
 
 passage E for the water used for injection to run out at, provided with a self- 
 acting valve F to prevent it flowing back ; a valve G for the air contained in the 
 water to escape at is also necessary. Mechanism for opening and closing the 
 valves is connected to the engine beam ; and a small supply of water by a pipe 
 is constantly furnished to the top of the piston, to keep the packing saturated, so 
 as to be steam-tight. 
 
 394. The operation is simple : the beam is so balanced that the steam being 
 admitted by the steam valve V below the piston, it rises to the top of the stroke ; 
 the steam valve is then shut, and the injection cock D is opened, and a jet of 
 cold water rises through I, which condenses the steam to a lower degree of 
 elasticity, and the water runs out by the passage E at the valve F ; the pressure 
 of the atmosphere on the piston P being unopposed, it forces it down, and the air 
 extricated by the water is expelled towards the termination of the stroke at the 
 valve G. 
 
 The steam and injection cocks are moved by tappets on a bar moving vertically, 
 and connected to the beam. The steam valve should close and the injection cock 
 open just when the up stroke is completed, and the period of closing the injection 
 cock should be adjusted to the power the engine is to exert ; the steam valve 
 ought to open with the rise of the piston. 
 
 395. The proportions of the parts. The length oi the cylinder should be 
 twice the diameter, art. 329. The velocity in feet per minute should be ninety- 
 eight 1 times the square root of the length of the stroke in feet, (art. 342.) the engine 
 being supposed to be applied to raise water. The area of the steam passages will 
 be found by this proportion, as 4800 is to the velocity in feet per minute, so is 
 the area of the cylinder to the area of the steam passage, art. 154. The tempe- 
 rature for condensation which affords the greatest useful effect will be found by 
 art. 166. If the area of the cylinder in feet be multiplied by half the velocity in 
 feet, and that product by T23 added to 1*4 divided by the diameter in feet, (art. 
 163.) the result divided by 1480 will give the cubic feet of water required for 
 steam per minute. If from 1220 the temperature of condensation be deducted, 
 and the result divided by the difference between the temperature of the cold water 
 and the temperature of condensation, the quotient will be the number of times the 
 quantity of water required for injection must be greater than that required for 
 steam (art. 284.) ; in general it will be about twelve times the quantity, but it had 
 better be a little in defect than excess. The aperture for the injection must be 
 such that the above quantity of water will be injected during the time of the 
 stroke. The moving force in the first instant is only that due to the height of 
 
 1 See note p. 190. 
 
188 OF THE CONSTRUCTION OF [SECT. vi. 
 
 the cistern ; and therefore in order that the injection be sufficiently powerful at 
 first, the head should be about three times the height of the cylinder ; and making 
 the jet apertures square, the area should be the 850th part of the area of the 
 cylinder, or its side should be A of the diameter of the cylinder. The conducting 
 pipe should be about four times the diameter of the jet. 
 
 396. To determine the power of an atmospheric engine. The moving force is 
 the pressure of the atmosphere, from which the whole of the friction and the force 
 of the uncondensed steam is to be deducted. 
 
 The moving force is the pressure of one atmosphere or 1-00 
 
 The loss of force measured in atmospheres consists of, 
 
 1. The uncondensed steam corresponding to the tem- 
 
 perature of condensation (usually about 160) '34 
 
 2. The force to expel it and the air from the cy- 
 
 linder (art. 154.) - - -007 
 
 3. The friction of the piston (art. 474.) - -050 
 
 4. The force required to open and close the valves, 
 
 raise injection water, and overcome the friction of 
 
 the axes - -093 
 
 Making total loss of force O49 
 
 The portion of the pressure of the atmosphere equal the 
 
 effective pressure is - O51 
 
 or 5'9 Ibs. per circular inch. 
 
 397. RULE for the power of the common atmospheric engine. Multiply 
 5 - 9 times the square of the diameter of the cylinder in inches, by half the velocity 
 of the piston in feet per minute ; and the product is the effective power of the 
 engine in Ibs. raised 1 foot high per minute. 
 
 To find the horse power, divide by 33000. 
 
 Example. Let the diameter of the cylinder be 72 inches, and the length of the 
 stroke 9 feet, making 9 strokes per minute : in this case, half the velocity is 
 9x9 = 81 feet per minute ; consequently 5'9 x 72 2 x 81 = 2477433-6 Ibs. 
 raised 1 foot per minute, or 
 
 2477433-6 ,. , 
 
 -33000- = 75 hOTSe P Wer ' 
 
 This example is the size of the Chase Water engine, designed by Smeaton, (see 
 art. 24. p. 23.) His estimate of the equivalent horse power differs from this chiefly 
 through using a different measure of that power ; but he also estimated on con- 
 
SECT, vi.] CONDENSING ENGINES. 189 
 
 densing at a lower temperature than 1 60 : and to estimate correctly, the proper 
 force of the uncondensed steam should be inserted in the causes of loss of force for 
 each particular case. 
 
 398. The engine may be regulated by cutting off the steam before the piston 
 has arrived at the top, and cutting off the injection sooner : further means of 
 regulation are described in Sect. vm. By cutting off the steam it acts expan- 
 sively, and a less quantity produces the effect. Water for the top of the piston, 
 and for the supply of the boiler, should be raised from the hot well. The quantity 
 of water required to supply the boiler being ascertained in cubic feet per minute, 
 (art. 395.) the fuel will be known by referring to art. 190. and the size of the 
 boiler by art. 225 or 229. 
 
 In the case of the Chase Water engine, 
 
 6" x -7854 x 81 /j-oQ + l^N 
 1480 ' \ 6 / 
 
 2'4 feet of water per minute, or 144 cubic feet per hour ; and 8-22 Ibs. of caking 
 coal convert 1 cubic foot of water into steam ; therefore the quantity per hour will 
 
 1183'7 
 be 1183-7 Ibs., or - 75 = 16 Ibs. per hour for each horse power. The boiler 
 
 may be either rectangular or cylindrical, with the steam limited to 1 Ib. on the 
 circular inch. 
 
 399. The atmospheric engine is applicable to raising water in most cases 
 where coals are abundant : the engine is simple in construction and in operation, 
 and does not require that accuracy of workmanship which is necessary for an 
 engine acting by steam pressure. On a small scale it has less advantage ; for 
 when the cylinder is not more than about 2 feet in diameter, the consumption of 
 fuel becomes great in proportion to the effect : the drainage of coal mines, and 
 raising water to supply towns, and for irrigation where fuel is cheap, are its proper 
 objects. 
 
 400. Atmospheric engines with a separate condenser. The manner in which an 
 engine of this kind may be constructed, is shown in Plate vi. Fig. 2., where C is 
 the cylinder with its piston P : the steam comes from the boiler by the pipe S, and 
 by a slide B is let into the cylinder at D, or kept out. A is a pump with a solid 
 piston, to receive the condensed steam, air, and water, and expel it : the injection is 
 made into the pipe E ; and I is the injection cock : F is a cock to let out any air 
 that may collect below the piston p when the engine is at rest. To begin the 
 operation, the slide B must be raised above S, and steam admitted till all the air 
 be blown out at the valve Q ; the pistons being at the top in both the cylinder and 
 pump : then shut off the steam by the slide B, and open the injection ; and, in 
 consequence of the condensation produced by the jet, both the pistons will descend, 
 
190 OF THE CONSTRUCTION OF [SECT. vi. 
 
 and during the first descent the cock F should be open, but afterwards closed : the 
 injection being stopped, and the slide B moved to close the passage to the con- 
 denser, on opening that for the steam the pistons will again ascend, and the air 
 and water of condensation will be expelled at the valve Q : the alternate opening 
 and closing of the passages and the injection cock are required to continue the 
 action. 
 
 401. This engine may be regulated by closing the valve B at any period of 
 the ascent, and the cock I at any period of the descent ; and as the application will 
 be limited to raising water, the velocity in feet per minute should be 98 times ' the 
 square root of the length of the stroke, (art. 342.) ; the length of the cylinder 
 twice its diameter ; the area of the steam passages to the area of the cylinder, as 
 the velocity in feet per minute is to 4800, (art. 154.) The air pump should be 
 one-fourteenth of the capacity of the cylinder, (art. 349. note) ; or making the 
 stroke of the air pump half that of the steam piston, the diameter of the pump 
 should be three-eighths of the diameter of the cylinder. The quantity of steam is 
 found by multiplying the area of the cylinder in feet, by half the velocity in feet, 
 with the addition of one-fifth for loss by cooling and waste (art. 161.) : the result 
 divided by 1480 will give the quantity of water per minute required to supply the 
 boiler, and 24 times that quantity will be that required for injection, (art. 284.) 
 The diameter of the aperture for the injection should be one thirty-sixth of the 
 diameter of the cylinder, and the injection pipe one-ninth. 
 
 402. The power of this atmospheric engine will be the difference between the 
 pressure of the atmosphere on the piston, and the retarding force multiplied by half 
 the velocity. 
 
 The pressure of the atmosphere being - 1 '000 
 The retarding forces are, 
 
 1. The resistance of the uncondensed steam, temperature 125, = '134 
 
 2. The force to expel it through the passages, (art. 154.) - -007 
 
 3. The loss by cooling in the cylinder, &c. (art. 161.) - '067 
 
 4. The friction of the piston, (art. 474.) '050 
 
 5. The force required to open the valve, raise water for injection, 
 
 and overcome the friction of the axes - '100 
 
 6. The force required to work the air pump, (art. 354.) - '100 
 
 Sum of the retarding forces - 0'45S 
 
 Effective pressure in parts of the atmosphere - 0*542 
 
 1 For ordinary pumping engines the velocity should not exceed 40 times the square root of the 
 length of the stroke. (See note p. 167.) ED. 
 
SECT, vi.] CONDENSING ENGINES. 191 
 
 This is equivalent to 6'25 Ibs. on a circular inch : the excess of force of the steam 
 in the boiler is a full compensation for some other causes of loss of power. 
 
 403. RULE. Multiply 6 - 25 times the square of the diameter of the piston, by 
 half the velocity in feet per minute, and the product is the effective power in Ibs. 
 raised 1 foot high per minute. 
 
 Divide by 33000, and the quotient will be the number of horse power. 
 
 Example. If the diameter of a cylinder be 32 inches, and half the velocity be 
 110 feet per minute; then 6-25 x 32 2 x 110 = 704000 Ibs. raised 1 foot per 
 minute, or 
 
 704000 
 
 330QQ- = 21 J horse power. 
 
 404. As the quantity of water required for the boiler is found by art. 401. the 
 quantity of fuel is easily found from art. 190. In the example of the preceding 
 
 H x (4) 2 x -7854 x 110 ,, c 
 
 article we have 1480 " = water per minute, or 29'4 
 
 feet per hour ; consequently 29'4 x 8'22 = 246 Ibs. of caking coal per hour ; or 
 
 -sj- = 11*7 Ibs. per horse power. 
 
 For the proportions of the boiler, see Sect. in. ; and for the beams and other 
 parts, in reference to strength, see Sect. vin. 
 
 405. For raising water this species of atmospheric engine is admirably 
 adapted ; it can be constructed without difficulty by ordinary workmen ; and for 
 water works, drainage, irrigation, canals, and other cases where water is required in 
 considerable quantities, it is an economical mode of obtaining power. 
 
 STEAM PRESSURE ENGINES. 
 
 406. Boulton and Watt's single engine. The essential parts and operation of a 
 single engine having been described, (art. 386.) we have only to show the con- 
 struction as it regards effect. Fig. 4. Plate v. shows a section of the cylinder C, 
 condenser B, and air pump A, of a single engine, arranged as is most convenient 
 for exhibiting the parts. The steam enters from the boiler to the cylinder by the 
 pipe S, through the valve c ; and presses down the piston P, which is supposed to 
 be taken at the time of its descent : the steam below it goes into the condenser, 
 and is condensed by the jet which plays into it. The air pump bucket p is 
 descending in the air and vapour which the pump had received from the condenser 
 during the previous ascent. When the piston is at the bottom of the cylinder, a 
 
192 OF THE CONSTRUCTION OF [SECT. vi. 
 
 motion is given to the rod O, which shuts the valves a and c, and opens the valve 
 b ; there is then a communication open by the pipe E, between the top and bottom 
 of the cylinder, and the pressure of the counter weight must be sufficient to over- 
 come the friction of the piston, and expel the steam from the upper to the lower 
 side of the piston : the action of the counter weight has also to expel the air and 
 water of condensation through the valve Q by means of the air pump. The mode 
 I have shown of placing the valves and moving them by a single motion is not 
 Messrs. Boulton and Watt's, but is one intended to render the motion of the steam 
 from the upper to the under side of the cylinder more quick, by the pipe E being 
 exhausted : the motion of the valves is simple and easily balanced. The valves of 
 Messrs. Boulton and Watt are similar to Fig. 5. but they move them independently 
 of one another ; and this ought to be the case for an engine to work expansively, 
 unless a separate valve acted on by a regulator be used to cut off the steam, (see 
 Sect, vin.) An elevation of Boulton and Watt's single engine is represented in 
 Plate xn. as applied to raising water. 
 
 407. The proportions of the parts. The length of the cylinder should be twice 
 its diameter, (art. 329.) The velocity of the piston in feet per minute should be 98 
 times l the square root of the length of the stroke, (art. 342.) The area of the steam 
 passages should be equal to the area of the cylinder, multiplied by the velocity of 
 the piston in feet per minute, and divided by 4800, (art. 154.) The air pump 
 should be ith of the capacity of the cylinder, or I the diameter and i the 
 length of the stroke of the cylinder, (art. 351.) and the condenser should be of 
 the same capacity. The quantity of steam will be found by multiplying the 
 area of the cylinder in feet, by half the velocity in feet ; with an addition of 
 TVth for cooling and waste (art. 160.) ; and this divided by the column of the 
 steam corresponding to its force in the boiler (art. 121.) gives the quantity of 
 water per minute required for steam, from whence the proportions of the boiler 
 may be determined, (see Sect. in. art. 224 and 227.) At the common pressure 
 of 2 Ibs. per circular inch on the valve, the divisor will be 1497. The quantity 
 of injection water should be 24 times that required for steam, (art. 284.) and 
 the diameter of the injection pipe sVth of the diameter of the cylinder. The 
 valves in the air pump bucket should be as large as they can be made, and 
 the discharge and foot valves not less than the same area. For the proportions 
 of the beams and other parts for strength, see Sect. vn. ; and for the modes of 
 regulation and management, see Sect. vin. 
 
 408. The power of the single engine may be ascertained as follows: 
 
 i See note p. 190. 
 
SECT, vi.] CONDENSING ENGINES. 193 
 
 Let the force in the boiler be denoted by - 1-000 
 
 The effective pressure on the piston is less than the difference 
 
 between the force of the steam in the boiler, and the 
 
 resistance of the uncondensed steam, 
 
 1. By the force producing the motion of the steam into 
 
 the cylinder, (art. 154.) - -007 
 
 2. By the cooling in the cylinder (art. 160.) and pipes, 
 
 (art. 148.) - -038 
 
 3. By the friction of the piston and loss by escape, 
 
 (art. 474.) - -05 
 
 4. By the force necessary to expel the steam through the 
 
 passages - -007 
 
 5. By the force required to open and close the valves, 
 
 raise injection water, and the friction of the axes - '100 
 
 6. By the steam being cut off before the end of the stroke '100 
 
 7. By the power required to work the air pump, (art. 354.) '100 
 
 402 
 
 598 
 
 The force of the steam in the boiler is commonly 35 inches of mercury ; that of 
 the uncondensed steam (temp. 120) is 3'7 inches ; hence, 35 x -598 = 20'93 
 inches, and 20'93 3*7 = 17-23, or 6*65 Ibs. is the mean effective pressure per 
 circular inch on the piston ; and when the steam in the boiler is of any other 
 force, the mean effective pressure may be determined in the same manner. 
 
 409. RULE. Multiply the mean effective pressure on the piston by the 
 square of its diameter in inches, and by half the velocity in feet per minute, and 
 the product is the effective power in Ibs. raised 1 foot high per minute. 
 
 Divide by 33000, and the result is the number of horse power. 
 
 Example. Let the force of the steam in the boiler be 35 inches of mercury, 
 the diameter of the cylinder 48 inches, and half the velocity 135 feet per minute. 
 Then the mean pressure is 6'65 Ibs., and 6'65 x 48 2 x 135 = 2068416 Ibs. 
 raised 1 foot, or 
 
 2068416 
 33000 = 63 horse power. 
 
 The water required would be 
 
 1-1 x 4* x -7854 x 135 , _ , . ,. 
 
 ~1497~~ ~ = cubic feet per minute, or 75 per hour; 
 
 2n 
 
194 OF THE CONSTRUCTION OF [SECT. vi. 
 
 and (by art. 190.) 75 x 8*22 = 616*5 Ibs. of caking coal, 1 or 5 = 9-8 Ibs. 
 
 per hour, for each horse power. 
 
 410. The application of the single engine is limited by the nature of its 
 action, to raising water or other works admitting of an inefficient returning stroke, 
 but for these purposes it has great advantages. I would suggest, as an improve- 
 ment, that the condensation should be effected as described for the atmospheric 
 engine, (art. 400.) and that it should always act more or less by expansion : the full 
 effect of expansion cannot however be obtained, unless the action be equalized by 
 a proper arrangement of the pressures and counter-weight. 
 
 411. Single engine acting expansively. When the single engine acts expan- 
 sively, it is necessary to determine the point of the stroke at which the steam 
 should be cut off. Now the pressure on the piston should never be less than the 
 mean moving force, otherwise it would be overpowered, and the column of water 
 would descend again ; consequently we may adopt this analogy. As the whole 
 force of the steam in the boiler is to unity, so is half the greatest effective force on 
 the piston added to the resistance from friction, &c. to the portion of the stroke at 
 which the steam should be cut off. Thus, if the force in the boiler be 35 inches 
 of mercury, and the resistance of the uncondensed steam 3'7 inches, then 3'7 + 
 35 x '402 = 17'77 inches, the loss of power from friction, &c. (art. 408.) and 
 
 OK _ T7'77 
 
 consequently ^ g - + 17-77 = 26-38, the pressure on the piston at the end of 
 
 the stroke ; therefore 35 : 1 : : 26'38 : -75 = f of the stroke. The steam will 
 
 obviously act expansively in its ascent in the same proportion ; whence a less 
 counter-weight is necessary. 
 
 412. To find the mean pressure on the piston in an expansive engine. Let 
 
 the portion of the stroke made, when the steam is cut off, be > 
 
 Then the th part of the whole force in Ibs. per circular inch, of the steam in the 
 boiler, multiplied by 2-3 times the common logarithm of n, added to -3, is 
 the mean moving force or pressure ; which is to be used in the rule (art. 409.) for 
 finding the power, and also for adjusting the load. 
 
 Example. Suppose the steam to be cut off at three-fourths of the stroke, 
 then - - = I, or n = 1-33, and its logarithm = 0-12516; the whole force being 
 35 inches of mercury, or 13'5 Ibs. per circular inch, we have, 
 
 1 This is equivalent to raising about 17,000,000 Ibs. 1 foot by a bushel of coals, or 192,000 Ibs. 
 by 1 Ib. of coal. 
 
SECT, vi.] CONDENSING ENGINES. 195 
 
 3 x 13-5 x (2-3 x -12516 + -3) no.r c n- n i i e 
 
 j - 5'9o Ibs. per circular inch, for 
 
 the mean pressure. 
 
 413. The velocity should be found by the rule, art. 343. and the quantity 
 of steam will be as much less than that required for an engine working at full 
 pressure, as the portion of the stroke at which the steam is cut off is less than the 
 whole stroke ; and in other respects the quantity of water, fuel, water for con- 
 densation, &c. should be determined by the rules in art. 407. 1 The counter- 
 weight will be less in the same ratio, as the pressure on the piston is less than 
 it is in a common engine. Owing to a larger sized engine being required, the 
 expansive method is not valued as it ought to be, except when the force of the 
 steam in the boiler is increased ; and this I would recommend to the extent of two 
 atmospheres, but not higher. 
 
 414. The double engine of Eoulton and Watt. It has been already shown in 
 what the double engine differs from a single one (art. 389). The parts are 
 shown in Fig. 1. Plate v. where C is the cylinder; the steam enters at S, and 
 passes into the upper part of the cylinder at F, or into the lower part at D, as in 
 Fig. 3. ; Fig. 1. showing the piston in the state of descending, and Fig. 3. as 
 ascending. From the lower part of the cylinder in Fig. 1. the steam escapes 
 through D into the condenser B, where it is condensed by a jet of cold water, 
 which plays into it constantly ; and the uncondensed gases and water pass through 
 the valve G during the ascending stroke, and during the descending one they 
 pass from the lower to the upper side of the pump bucket, through its valves, 
 and are drawn up by the ascending stroke, and expelled at the valve Q into the 
 hot well. When the steam piston P ascends, the steam from the upper part of 
 the cylinder passes through F down the pipe E to the condenser. The steam 
 passages D and F are opened and closed by a D-slide', so called from its plan 
 resembling the letter D ; it is moved by the rod O, by tappets or other methods 
 (see Sect. vn. where the different methods are described). In small engines the 
 steam passages are frequently opened and closed by cocks, in larger ones by 
 valves or slides, the species of which, and the pistons and other parts, are described 
 in Sect. vn. 
 
 415. The proportions of the parts for a double engine acting with full pressure. 
 When the case to which the engine is applied will admit of it, the length of the 
 cylinder should be twice its diameter (art. 329). The velocity of the piston in 
 feet per minute should be found by multiplying the square root of the length of 
 
 1 Taking the example of art. 409. we find 22,000,000 Ibs. may be raised 1 foot by a bushel, 
 or nearly 250,000 Ibs. by 1 Ib. of coal ; and I do not think more has been actually done with low 
 pressure steam by a single engine. 
 
196 OF THE CONSTRUCTION OF [ SEC T. vi. 
 
 the stroke by 103 for machinery, or by 98 1 for raising water (art. 337 and 342). 
 The area of the steam passages should be equal to the area of the cylinder 
 multiplied by the velocity of the piston in feet per minute, and divided by 4800 
 (art. 154). The air pump should be ith of the capacity of the cylinder, or i the 
 diameter, and i the length of the stroke of the cylinders (art. 351), and the con- 
 denser should be of the same capacity. The quantity of steam will be found by 
 multiplying the area of the cylinder in feet by the velocity in feet, with an 
 addition of T*ath for cooling and waste ; and this divided by the volume of the 
 steam corresponding to its force, in the boiler (art. 121.) gives the quantity of 
 water required for steam per minute, from whence the proportions of the boiler 
 may be determined (see Sect. in. art. 224 and 227) : at the common pressure of 
 2 Ibs. per circular inch on the valve, the divisor will be 1497. The quantity of 
 injection water should be 24 times that required for steam (art. 284), and the 
 diameter of the injection pipe ^Vth of the diameter of the cylinder. The valves in 
 the air pump bucket should be as large as they can be made, and the discharge 
 and foot valves not less than the same area. For the proportions of the beams 
 and other parts for strength, see Sect. vii. ; and for the modes of regulation 
 and management, see Sect. vin. 
 
 416. To determine the power of a double acting engine. 
 
 Let the force of the steam in the boiler be denoted by - - 1-000 
 
 Then, besides the loss from uncondensed steam, there is loss, 
 
 1. By the force producing the motion of the steam into 
 
 the cylinder, (art. 154.) -007 
 
 2. By the cooling in the cylinder, (art. 157.) and pipes, 
 
 (art. 148.) - -016 
 
 3. By the friction of the piston and loss, (art. 474.) -125 
 
 4. By the force necessary to expel the steam through the 
 
 passages, (art. 154.) -007 
 
 5. By the force required to open and close the valves, 
 
 raise injection water, and the friction of the axes -063 
 
 6. By the steam being cut off before the end of the stroke -100 
 
 7. By the power required to work the air pump, (art. 
 
 354.) -050 
 
 368 
 
 632 
 1 See note, page 167. 
 
SECT, vi.] CONDENSING ENGINES. 197 
 
 The force of the steam being generally 35 inches of mercury in the boiler, the 
 temperature of the uncondensed steam 120, and its force 3'7 inches ; hence, 
 35 x -632 -- 3 - 7 = 18'42 inches, or 7'1 Ibs. per circular inch, for the mean 
 effective pressure on the piston. l 
 
 417. RULE. Multiply the mean effective pressure on the piston by the 
 square of its diameter in inches, and that product by the velocity in feet per 
 minute, the result will be the effective power in Ibs. raised 1 foot high per 
 minute. 
 
 To find the horse power, divide the result by 33000. 
 
 Example. The diameter of the cylinder of a double engine being 24 inches, 
 the length of the stroke 5 feet, the number of strokes per minute 21|, and the 
 force of the steam in the boiler 35 inches of mercury, or 5 inches above the 
 pressure of the atmosphere ; required its power. 
 
 The velocity is 2 x 5 x 21i = 215 feet per minute, and the mean effective 
 pressure on the piston will be 7*1 Ibs. per circular inch; therefore 7'1 x 24 2 x 215 
 = 879264 Ibs. raised 1 foot high per minute, or 
 
 879264 
 
 330QU = 2o'64 horse power. 
 
 The nominal power of this engine would be only 20 horse power by Boulton and 
 Watt's mode of calculation, but it will be found that the nominal and real power 
 nearly agree when the steam acts expansively (art. 422). 
 The water required for the above engine (art. 415.) will be, 
 
 1-1 X 2 ~ 54 X 215 = ' 50 cubic feet P er minute, or 30 cubic feet per hour ; 
 
 and (art. 190.) 30 x 8'22 = 246'6 Ibs. of caking coal, or ~ = 9'25 Ibs. per hour 
 
 i ) O4 
 
 for each horse power. * 
 
 When an engine is of less than 10 horse power, the consumption of fuel will be 
 greater per horse power about in the ratio given in art. 221. 
 
 418. This engine is applicable to every purpose for which a stationary engine 
 is adapted, and it is only in cases where water is procured with difficulty that it 
 is not applied : it has also lately been brought into use as a moving agent in 
 steam vessels. (See Sect, x.) When the steam acts expansively, the power is 
 obtained with a smaller quantity of fuel, and to save fuel is a great object in 
 every application of steam power. 
 
 1 This is 9-05 Ibs. per square inch. 
 
 2 Mr. Watt states to the effect that 8'7 Ibs. is the quantity equivalent to 1 horse power, but no 
 doubt he means when working expansively. Notes on Robison, vol. ii. p. 145. 
 
198 OF THE CONSTRUCTION OF [SECT. vi. 
 
 419. Double engine acting expansively. The motion of a double engine acting 
 expansively ought to be equalized by a fly or some other method, (see Sect, vui.) 
 otherwise the effect cannot be perfectly obtained. To determine the point of the 
 stroke at which the steam should be cut off, we have this proportion : 
 
 As the whole force of the steam in the boiler is to 1, so is "368 times that force, 
 (art. 416.) added to the resistance of the uncondensed steam, to the part of the 
 stroke to be made before the steam be cut off. 
 
 Thus, if the force in the boiler be 35 inches of mercury, and the resistance of 
 the uncondensed vapour 3 '7 inches, we have 
 
 35 : (35 x -368) + 3-7 : : 1 : -473= -L o f the stroke. 
 
 30*1 
 
 420. To find the mean pressure on the piston of an expansive engine, the 
 part of the stroke at which the steam is cut off being .divide 2-3 times the 
 
 common logarithm of n by n, and multiply the quotient by the whole force of the 
 steam in the boiler in Ibs. per circular inch ; the result will be the mean moving- 
 force on the piston per circular inch. 
 
 Example. Suppose the steam to be cut off at ^ of the stroke, then n = 2'l, 
 and the logarithm of 2-1 is '32222 ; 
 
 ,, 2-3 x -32222 
 consequently, jrrr = ' 
 
 and as the pressure corresponding to this point of cutting off the steam is 35 inches, 
 or 13'5 Ibs. per circular inch, we have 13'5 x '354 = 4-8 Ibs. per circular inch, 
 the mean pressure. 
 
 421. The velocity should be found by art. 336 or 343. and the quantity of 
 
 steam will be - - part of that required when the engine works at full pressure ; 
 therefore the water for steam, the fuel, injection water, will be less in the same 
 proportion in regard to the dimensions of the cylinder ; but the passages, pumps, 
 boiler, and other proportions should be found by the rules in art. 415. in order 
 that the engine may work either at full pressure or expansively, as circumstances 
 may render desirable. 
 
 422. Taking the dimensions and force of steam of the engine given as an 
 example in art. 417. its power as an expansive engine would be 4'8 x 24 2 x 215 
 = 594432 Ibs. raised 1 foot high per minute, or 
 
 594432 
 33Q0Q- =18 horse power. 
 
SECT, vi.] CONDENSING ENGINES. 199 
 
 246 - 6 
 At the full pressure, the fuel was 246'6 Ibs. ; in this case it is -^- =117 Ibs. 1 
 
 117 
 hence -jg- = 6'5 Ibs. per horse power ; the advantage is therefore as 6'5 : 9'2, or 
 
 as 10 : 14. 2 For small engines this quantity requires to be increased in the ratio 
 given in the table, art. 221. 
 
 423. The mode of cutting off the steam by giving two movements to the slide 
 during the stroke is shown in Plate v. : Fig. 2. shows the position of the slide 
 when the piston is descending and the steam cut off, with the passage D to the 
 condenser still open. Slides have the defect of requiring a separate passage to 
 introduce the steam to expel the air from the engine at the time of starting, techni- 
 cally called " blowing through ;" but in other respects they seem to afford the 
 most simple and durable means of opening and closing the passages. 
 
 COMBINED CYLINDER ENGINES. 
 
 424. In Hornblower's engine with two cylinders the steam acts at full pressure 
 in the one, and expansively in the other : as a single engine it is decidedly inferior 
 to Boulton and Watt's construction in every respect, except that of the moving 
 force being more nearly uniform, for there is the additional friction of the small 
 piston ; and it is a singular fact, that a single engine of this kind is more complex 
 than a double one. As mine engines they appear to be nearly abandoned, and 
 therefore it is not necessary to occupy space in describing a species which will be 
 sufficiently understood by imagining two single engines acting on one beam, the 
 one of which works at full pressure, and the steam which propels it acts expan- 
 sively in the other cylinder during the next stroke. In both cylinders the steam 
 has to change from the upper to the lower sides of the piston during the ascent. 
 The ratio of the size of the expansion cylinder to the other should be determined 
 by the same rule as for double engines of this kind (art. 426), and in other 
 respects the proportions should be as for single engines. 
 
 425. The double engine with combined cylinders. This engine will be under- 
 stood most easily with a simple mode of letting on and off the steam. Let C be 
 the small cylinder, Plate vi. Fig. 3. and D the large one, and S the place where 
 the steam enters the pipes. The steam enters the small cylinder at a when the 
 piston descends, and the portion below its piston passes through b, and rising in the 
 
 1 This is the same as raising 27,000,000 Ibs. 1 foot high by 1 bushel of coals. 
 
 2 If we take the mean between 6-5 and 9-2 or 7-85, it is what we may expect to be the ordinary 
 consumption of an engine with a variable resistance, when of the best kind. 
 
200 OF THE CONSTRUCTION OF [SECT. vi. 
 
 passage c, enters the large cylinder at d, while the steam passes to the condenser 
 through e. When the motion is reversed by the slide being moved till the parts 
 are on the other side of the passages, then similar motions take place in the reverse 
 directions, and the vapour passes through / down a pipe to the condenser. Thus 
 the whole apparatus is reduced to a slide box, the rod of which has only one 
 motion for each stroke ; and though it is here shown between the cylinders for 
 convenience, it may be placed in the angle they form when close to each other. 
 
 426. The proportions of combined engines. The smaller cylinder should have 
 the same proportions as for a non-condensing engine working with steam of the 
 same force, (art. 366.) and the loss of force must be the same, that is 0*4 of the 
 force of the steam in the boiler. 
 
 The loss of force at the piston of the large cylinder, when its power is 1 will be, 
 
 1. By the cooling in the cylinder and pipes - -016 
 
 2. By the friction of the piston - -125 
 
 3. By the force necessary to expel the steam through the passages '007 
 
 4. By the power required to work the air pump - -050 
 
 198 
 
 Consequently, '6 x -198 = '1188 = the portion of the whole power, which added to 
 the loss in the small cylinder, the total loss is '1188 -*- -4 = -5188, or -52 nearly. 
 Hence, if / denote the whole force of the steam in the boiler, 3-7 the resistance of 
 the uncondensed steam, and n the times the capacity of the large cylinder is to 
 exceed the small one, we have 
 
 n = 
 
 52 / + 3-7 
 If for example the force of the steam in the boiler be 120 inches of mercury, then 
 
 120 _ 1 .ag. 
 
 (52 x 120) + 3-7 " 
 
 that is, the large cylinder should be 1'82 times the capacity of the small one ; if it 
 be larger, a loss of effect must necessarily ensue. 
 
 427. The power of a combined cylinder engine is easily ascertained from 
 the investigation, art. 382. by substituting the proper constant numbers. The 
 resulting rule for the mean pressure, supposing it to be collected on the surface of 
 the small piston, is 2 - 3 times the common logarithm of the number of times the 
 large cylinder is greater than the smaller one, multiplied by the force of the steam 
 in the boiler on a circular inch. Thus if the force be 120 inches of mercury, then 
 
SECT, vi.] CONDENSING ENGINES. 201 
 
 the capacity of the large cylinder should be 1'82 times the small one ; therefore 
 2'3 x log. 1-82 = '575 : and as each inch of mercury is equivalent to - 385 Ibs. on 
 a circular inch, 120 x -385 = 46'2 Ibs., and 4G'2 x -575 = 26'56 Ibs. on a circular 
 inch, for the mean pressure collected at the small piston. 
 
 428. RULE. The mean pressure being found as above, let it be multiplied by 
 the square of the diameter of the small cylinder in inches, and by the velocity of 
 the small piston in feet per minute, the result will be the power in Ibs. raised 1 
 foot per minute. 
 
 Divide by 33000 for the horse power. 
 
 Example. If the force of the steam be 120 inches of mercury, the diameter of 
 the small cylinder 11 inches, and the velocity of its piston 160 feet per minute, 
 then the mean pressure is 26'56 Ibs. ; and 26'56 x II 2 x 160 = 514200 Ibs. raised 
 1 foot per minute, or 
 
 514200 
 
 33000" = 2 norse P ower - 
 
 429. The quantity of steam required per minute will be equal to the area of 
 the small cylinder in feet multiplied by the velocity ; and the quantity of water 
 will be found by dividing by the volume which the steam from a cubic foot of 
 water occupies, when of the force it is in the boiler, allowing one-tenth for waste. 
 In the above example it is, 
 
 - = -242 cubic feet of water per minute, or 14'52 per hour. 
 
 The fuel will therefore be 14'52 x 8*22 = 119'35 Ibs. of caking coal per hour, or 
 15 =7-7 Ibs. of coal per hour for each horse power. 
 
 Comparing this with art. 422. we find there is no advantage in using two 
 cylinders as regards economy of fuel. 
 
 430. The effects that may be obtained by engines of different species have 
 now been reduced for the first time to definite measures, and their proportions 
 referred to scientific principles. I have in these two sections endeavoured to render 
 assistance to the practical engineer in as condensed and easy a form as possible, and 
 yet with the minute circumstances in detail which are susceptible of variation by 
 improvement in action or construction. He will see that the sum of the particulars 
 must be near the truth, and the circumstances which increase or diminish any one 
 of them must be apparent, or easily known by a reference to the article where it is 
 investigated ; and if he will be careful to distinguish actual practice from preten- 
 sion, he will find that science and practice go hand in hand, the one supporting the 
 conclusions of the other. It is an undeniable proposition, that the ultimate bearing 
 
 2 c 
 
202 OF THE CONSTRUCTION OF CONDENSING ENGINES. [SECT. vi. 
 
 of practice is towards that which is most economically adapted for its object ; arid 
 the proper use of science is to assist in arriving at right conclusions with the least 
 expense in trials : but at the same time that economy of power is considered, I 
 think appropriate forms, good proportions, and excellent workmanship should be 
 attended to in all machinery ; and in many instances it is desirable that they should 
 be beautiful, for a beautiful machine will be so attended to as to produce economy 
 where an inferior one would perish by neglect. 
 
SECTION VII. 
 
 OF THE PROPORTIONS, AND THE CONSTRUCTION, OF THE PARTS OF 
 
 STEAM ENGINES. 
 
 431. THE steam engine has hitherto been studied as a whole ; but in order to 
 become more perfectly acquainted with its nature, we must dissect it, and study it 
 in parts. This forms the object of the present section. Some of these parts have 
 to be considered only as far as strength is concerned, as beams, shafts, cross-heads, 
 &c. ; others in respect to the motions they are to produce, as the parallel motion, 
 the eccentric motion, &c. ; others depend on the combination of moveable parts 
 with accuracy of workmanship, as pistons, valves, &c. besides the modes of con- 
 structing joints, &c. According to the dependence of these parts on one another, it 
 seems desirable to treat them in the order of valves, pistons, stuffing boxes, hand 
 gear, piston guides, parallel motion, strength of parts, (as beams, cranks, wheel- 
 arms, gudgeons, and teeth of wheels, cross-heads and frames, shafts and 
 journals, piston rods, connecting rods, and parallel motion rods, cylinders, pipes, 
 and boilers,) and joining pipes. 
 
 OF COCKS AND VALVES. 
 
 432. Under the head " Cocks and Valves " may be included all those methods 
 which may be found useful for opening and closing passages for steam. It is of 
 some advantage, in discussing their respective merits, to class them ; and the most 
 simple method of doing this seems to be by the motion which opens them. 
 In this way, our arrangement will be as follows : 
 
204 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 Valves 
 
 Reciprocating 
 
 Rising 
 
 Sliding 
 
 On an axis 
 
 Rotary 
 
 Flat valves. 
 
 Conical 
 
 Spherical. 
 
 Flat 
 Cylindrical. 
 
 Throttle valves. 
 Bettancourt's. 
 
 Common. 
 Hornblower's. 
 
 Bramah's. 
 Murray's. 
 Murdoch's. 
 
 {Common. 
 Four-passaged. 
 Bramah's. 
 
 Plate or flat I Regulator. 
 
 433. The office of a valve or cock being to open or to close a passage in the 
 most perfect manner, and either instantly or progressively, as may be proper for 
 the object in view, it is evident that those which offer the least obstruction to the 
 passage, and are opened with the least force, are the best. Hence the convenience 
 of considering them in succession in this place, and referring them to their 
 respective uses. 
 
 434. All the species of valves become more difficult to manage in proportion 
 as the apertures become larger. The area of the passage when open should be 
 rather more than equivalent to that of the narrowest part of the pipe, and by 
 comparing these areas the proportions of the valve boxes or apertures will be 
 easily found for each species. 
 
 435. When valves, cocks, or sliders are to be moved to admit steam to a 
 steam engine, the motion should be as quick as circumstances will permit, so that 
 the passages may be wholly opened or wholly closed at the proper time with the 
 least delay ; for it may be easily shown that a considerable loss of effect arises from 
 valves opening or shutting with a slow motion. 
 
 RISING VALVES. 
 
 436. The common CLACK VALVE is one of the most simple : in its common form 
 it is a plate of leather a little larger than the valve aperture with a part of it fixed 
 
SECT, vii.] STEAM ENGINES. 205 
 
 in the joint as a hinge. The leather is strengthened by a metal plate on each side, 
 the lower one less, and the upper one larger than the valve aperture. It must 
 open to an angle of about 30, to allow a free passage equal to its aperture, and the 
 box should be one and a half times the diameter of the valve aperture. 
 
 Its chief application in the steam engine is for the valve between the condenser 
 and air pump, called the foot valve, and for the blow valve ; but on account of the 
 heat of the water, it is necessary to use metal instead of leather, and to grind the 
 parts to fit. 
 
 The foot valve G, Fig. 1 and Fig. 4. Plate v. is sometimes suspended by a 
 hinge joint to the upper side of the passage, and falls against an inclined seat, the 
 inclination being as much as to cause the weight of the valve to close it, and not 
 more. 
 
 437. A DOUBLE CLACK VALVE consists of two semicircular valves, and is used 
 for pump buckets : the construction of this is similar to the single clack valve, and 
 the valves must rise to the same angle. They have the advantage of being more 
 convenient than single ones for large pistons. The air pump bucket in a steam 
 engine is furnished with metal valves of this species. See Plate v. p, Figs. 1 and 4. 
 
 To afford a greater quantity of passage with less resistance to open the valves, a 
 kind of pyramidical valve, consisting of four triangular pieces, is sometimes used ; 
 but the construction is complex, and without corresponding advantages. 
 
 438. A FLAT METAL PLATE has frequently been recommended for a valve, par- 
 ticularly for a safety valve : it requires a guide sufficient to keep it in its proper 
 seat ; which may be most effectively done by a spindle sliding in holes in cross 
 bars, above and below the valve. The diameter of the box should be to that of the 
 valve as 3:2; and the parts should be ground together with emery, till they fit 
 steam-tight. Its advantage as a safety valve is supposed to consist in its being less 
 liable to stick fast, and with this opinion I perfectly agree : in other respects it 
 differs little from the conical valve. 
 
 439. The CONICAL STEAM VALVE is a plate of metal, with its edge bevelled to fit 
 into a conical seat : it is sometimes called a puppet or T-valve. The steam valves 
 of Watt's engines were at first made of this kind. In this valve the diameter of the 
 box should be to the greater diameter of the valve as 3 : 2 ; and it should rise not 
 less than one-fourth of its greatest diameter when quite open ; but both these pro- 
 portions must be increased if the valve be out of the centre of the box. These 
 valves and seats are often made of brass ; but gun metal is better, the plate and 
 the seat for it being of the same metal. They are turned to fit as nearly as 
 possible ; and afterwards the one is ground into the other with fine emery powder, 
 till it accurately fits the seat. 
 
 The best angle for the valve to fit in its seat is 45, for the pressure is ba- 
 
206 OF THE PARTS OF [SECT. vn. 
 
 lanced by the reaction of the sides. With less taper the valve has a tendency to 
 set fast : with greater it occupies more space. When the conical valve exceeds five 
 or six inches in diameter, it requires great power to open it against the pressure of 
 the steam, and is therefore inconvenient. Mr. Watt applied a piston to the stem 
 of the valve, fitted to a cylinder of the same diameter as the valve, on the opposite 
 side of the passage ; and the steam acting on the valve and piston equally, the 
 difficulty of raising it was much reduced. 
 
 When the valve is to be self-acting, that is, to move as soon as its narrower 
 surface is exposed to a given pressure, then the weight of the valve must be equal 
 to the square of the diameter multiplied by the pressure in Ibs. on a circular inch, 
 
 440. A valve is sometimes made with the seat a portion of a sphere, and the 
 valve either a portion or a complete sphere to fit it. This species, under the name 
 of a CUP VALVE, has been strongly recommended for safety valves ; and by suspend- 
 ing the weight below the valve, it is expected in a steam vessel to be constantly in 
 motion, so as to prevent sticking. See U, Plate xvn. Fig. 1. In other respects 
 the cup valve seems to be inferior to the conical valve. 
 
 441. HORNBLOWER'S VALVE. A common valve must often have to be opened 
 against a pressure depending on its surface : to avoid this, a valve on a different 
 principle was invented by Hornblower. This valve, Fig. 4. Plate vi. is inclosed in 
 a box, and consists of a short cylinder resting on two conical seats, one on the ex- 
 terior of the cylinder, and the other an interior seat at the bottom of it. The valve 
 is raised or depressed by the usual methods applied to the cross bar at the top, and 
 it is guided by the rod which slides in a socket in the lower seat. If there be 
 strong steam on the upper side of the valve, and light vapour below, the pressure 
 tending to keep the valve close is exerted only on the horizontal areas of the two 
 seats, instead of being distributed over the whole surface of the valve. 1 
 
 This reduction of pressing surface is obviously considerable in large valves. The 
 principal passage for the steam is very direct ; and at the lower seat, the steam in 
 its passage going chiefly down through the body of the valve, it is interrupted only 
 by the cross bar at the top. 
 
 442. Improved form for HORNBLOWER'S VALVE. The obvious difficulty of the 
 valve is to make it fit steam-tight on two seats ; but if we make the outside of the 
 cylinder to slide in a stuffing box, or in an elastic packing of metal (see V, Fig. 1. 
 Plate vi.) that difficulty is removed, and the largest valves may be made with no 
 other resistance to being opened, than the pressure on the seat, and the friction 
 of the surface of the cylinder. It is simply the common conical valve inverted, 
 
 1 Professor Robison saw the theoretical advantages of this construction : but why has the account 
 he gave of it been omitted in the reprint of his works ? 
 
SECT, vii.] STEAM ENGINES. 207 
 
 and that which formed the seat in the common valve moves instead of the plate, 
 and should obviously slide in a steam-tight case. 
 
 SLIDING VALVES. 
 
 443. The sluice is the oldest form of this valve, but its advantages for any 
 other than rough work in wood do not appear to have been understood : indeed 
 it was not to be expected that metallic surfaces would slide on each other so closelv 
 as to be tight and durable, unless very truly worked and of a hard metal. 
 
 Mr. Watt endeavoured to employ them at first, but did not succeed, and it was 
 not till about thirty years ago, when more accurate methods of workmanship were 
 introduced, that the slide valve appeared. 
 
 444. BRAMAH'S SLIDE VALVE. This slide valve is extensively used for pipes 
 of water works, breweries, gas works, and various other purposes, and is ex- 
 ceedingly well adapted for steam passages. It consists of a box with a slider at 
 right angles to the passage, moved by a rod passing through a stuffing box. 
 
 The slider is ground to fit accurately against the circumference of the passage 
 with one surface, and is held close by a spring ; it is moved by a handle for small 
 apertures, and for larger ones by a rack and pinion. 
 
 445. The first idea of employing slides for more than one aperture appears 
 to have been to the air pump by Lavoisier or some of his associates, on which 
 Dr. Robison has remarked, that a sliding plate performs the office of four cocks 
 in a very beautiful and simple manner ; he adds, however, " that the best workmen 
 in London thought they would be difficult to execute." The same principle was 
 applied to the steam engine by Murray in 1799, a sliding box answering the 
 purpose of opening and closing four steam passages, to use Dr. Robison's words, 
 " in a beautiful and simple manner." 1 
 
 446. MURRAY'S SLIDE. The apertures all terminate in a steam-tight case, 
 and within this a smaller box slides up and down, so as alternately to open and 
 close the passages. A section of it is shown in Plate vi. Fig. 5. The sliding part 
 is moved by the rod o passing through a stuffing box. The steam from the boiler 
 enters at S, and, when the slide is down, passes through a to the top of the 
 cylinder, while the passage b c from the bottom of the cylinder to the condenser 
 is open through the interior of the slide ; in like manner when the slide is up, 
 the passage b for the steam to the bottom of the cylinder is open, and the passage 
 a c from the top to the condenser is open. 
 
 A small reciprocating motion is obviously sufficient for the motion of the slide ; 
 
 1 Art. Pneumatics. Robison's Mech. Phil. 
 
208 OF THE PARTS OF [SECT. vn. 
 
 its friction from the pressure of the steam against the box is considerable ; but in 
 order to reduce it, the rubbing surfaces should not be too small, and the harder 
 they are the better : for steam boats, gun metal is used ; but where salt water is 
 not to be employed, the sliding parts which apply together may be made of steel, 
 and hardened ; they then act and wear extremely well. 
 
 447. MURDOCH'S SLIDES. In slides formed in the preceding manner there 
 is a loss of steam, in consequence of the apertures being opened and closed at some 
 distance from the places where the steam immediately enters the cylinder. This 
 has been avoided in Messrs. Boulton and Watt's engines, where they have used 
 similar slides invented by Murdoch, in which the strong steam is in the place 
 assigned by Murray to the weak ; and in engines with a long stroke, they make 
 the two sliders separate, and move them by a rod of communication ; because it 
 would be more difficult to fit a long slide, so that there would be a certainty of 
 its rubbing surfaces being in complete contact, as the least deviation of these 
 sliders, whether at the top or bottom of the cylinder, would cause a considerable 
 leakage. Maudslay also, in his later boat engines, has adopted the same arrange- 
 ment of slides as Boulton and Watt. See Fig. 2. Plate iv. l 
 
 448. Slides are getting into considerable repute for many purposes, and even 
 in appearance the intricacy of a double engine is much diminished by using them. 
 The contrivance of the slide to shut off the steam at any portion of the stroke, 
 is a point of some importance. Mr. Millington justly esteems the want of the 
 power to do so a defect, and says it is common to the slide and four-passaged cocks ;* 
 but this objection may be removed in both cases by increasing the quantity of 
 motion of the sliding surfaces one-half. For this purpose the slide should be the 
 depth of the aperture shorter than will cover both the apertures to the cylinder, 
 (see Figs. 1, 2, and 3. Plate v.) and it should be moved twice during the stroke 
 by an adjustable tappet : the first motion shuts off the steam, as in Fig. 2 ; the 
 second opens the passage to the condenser, and admits the steam at the other end. 
 In this case let F and D represent the passages to the cylinder, S the place where 
 the steam enters, and E the passage to the condenser. Suppose the steam to have 
 been admitted to the upper part of the cylinder by the passage F, Fig. 1. and the 
 slide to have been moved its first motion in Fig 2. so as to cover F, and still leave 
 D open to the condenser ; then, at the next movement, Fig. 3. the slide will be 
 at the bottom and admit steam at D, and F will be open to the condenser. The 
 steam should encircle the pipe E ; it then does not increase the friction materially 
 by its pressure. 
 
 1 Messrs. Maudslay and Co., in the first instance, used a four-way cock. 
 Epitome of Natural Philosophy, p. 313. 
 
SECT, vii.] STEAM ENGINES. 209 
 
 449. The chief object of attention in setting out a slide, is to shorten its 
 motion as much as possible, so as not to reduce the area of the passages. The 
 area of the rubbing surface can scarcely be estimated at less than 8 times that of 
 the passages, which will be about Ath of the area of the cylinder, (art. 154.) hence 
 &ths = the pressure ; and taking the maximum pressure to be double the mean 
 pressure, and the friction being supposed ith of the pressure, it will be Aths of the 
 moving force, and it will be, in a short cylinder in action, about ith of the length 
 of the stroke ; whence the loss amounts to about ^Vnd part of the power of the 
 engine. In long cylinders the ratio will be less. 
 
 450. The cylindrical slide of metal, like a piston in a tube, was applied by 
 Edelcrantz to the safety valve, but such a slide would obviously either be subject 
 to stick fast, or allow steam to escape, as it would bear neither wear nor corrosion. 
 Woolf s slide for regulating the quantity of steam passing an aperture is of the 
 same kind, and seems to have no useful application whatever. 1 The attempt has 
 been made to apply the metallic piston as a slide, and there is no doubt that it 
 may be used both for that purpose and for the back of a flat slide : the object 
 must be to construct it so as to be tight, and wear equally when applied to a 
 cylinder. The advantages of such a slide I have endeavoured to show in Plates iv. 
 and vi. 2 
 
 The Box SLIDE, now much in use, is shown in Plate v. Fig. 6. 
 
 451. SEAWARD'S SLIDES. A great improvement has been recently made in 
 the construction and application of slides, by Mr. Samuel Seaward, who took out 
 a patent in 1835. On each of the nosles, or passages to the cylinder, and within 
 the steam pipe, is attached a smooth face of cast iron or other metal, having the 
 smooth part standing from the cylinder. Upon these faces two flat slide valves 
 or shutters are caused to move either conjointly or separately, by means of stalks 
 or spills, each being furnished with a knuckle-joint at its upper or lower end, 
 where it is attached to the stalk so freely, as to easily move from off" the face, 
 independent of the spill or stalk. These slide-valves or shutters will effectually 
 prevent the steam from entering the cylinder, since the pressure of the steam from 
 the boiler will keep them close to the faces upon which they move. For the exit 
 
 1 Philosophical Magazine, vol. xvii. p. 164. 
 
 4 In Fig. 4. Plate iv. I have shown a mode of construction for the piston slide, which would 
 possess some advantages. A ring, cylindrical on the outside and conical in the inside, may be 
 cut into two or more parts, with lap joints, and these parts may be expanded by the pressure of 
 the steam on a conical part made to fit the interior of the ring ; on the opposite side there should 
 be a plate ground to fit the surface of the ring, and between this plate and the bottom of the cone 
 an elastic packing of hemp should be inserted, and the whole held together by nuts upon the 
 piston rod. The steam apertures should be divided so that no single aperture should exceed one- 
 eighth of the circumference. 
 
 2o 
 
210 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 of the steam from the cylinder two similar slide-valves move on faces 
 attached to the eduction pipe, and may also be moved conjointly or separately : 
 but it is not always necessary that there should be two distinct slides and faces 
 within the induction pipe ; in small double action engines the two steam 
 passages may be brought so close, that one steam slide working over both apertures 
 will answer the purpose. By this arrangement, each slide is pressed against the 
 face on which it moves, by the simple pressure of the steam, and thus any water 
 that may accumulate within the cylinder is driven back to the steam pipe, the 
 valves being lifted off their faces by its pressure. The eduction and steam-slides 
 being entirely distinct from each other, although set in motion by one eccentric, 
 and one set of hand-gear, may be adjusted to expand the steam through any 
 portion of the stroke, which is important when high pressure steam is employed. 
 Amongst other advantages of these valves may be mentioned, simplicity of action 
 and management, no trouble of packing and adjustment, and yet perfectly tight 
 with the least possible friction ; also they are so constructed that each slide-valve 
 and face may be easily detached without affecting any one of the other principal 
 valves and faces. l 
 
 The engines of the following steam vessels are fitted with Seaward's patent 
 slide-valves, viz. 
 
 The Volcano 
 Megsera 
 Naslednik 
 Vivid 
 
 Water Witch 
 Emerald 
 Duchess of Kent 
 Ruby 
 Gem 
 Topaz 
 
 City of Kingston 
 Paris 
 
 horse power 
 
 150 
 150 
 190 
 190 
 140 
 130 
 100 
 80 
 70 
 100 
 190 
 
 f Government Packets. 
 Russian Packet. 
 
 " | Hull Packets. 
 ? Ramsgate and Boulogne Packets. 
 
 Gravesend Packets. 
 
 Jamaica Packet. 
 
 Havre and Hamburgh Packet. 
 
 ROTARY VALVES. 
 
 452. Axis VALVES are the most simple of the valves moved by rotary motion. 
 A valve of this kind consists of a plate of metal fixed on an axis in the passage ; 
 the axis crosses the centre of the plate, and is made to pass through an air-tight 
 aperture to the outside : they are extremely useful where perfect tightness is not 
 required, as in the throttle valve, for dampers and the like. Belidor applied an 
 axis valve to pump work, by putting the axis a little to one side of the centre ; 
 
 1 For further description, see the Appendix. 
 
SECT, vii.] STEAM ENGINES. 211 
 
 it then, however, becomes so very difficult to fit, that its use has not been con- 
 tinued ; and this difficulty must always exist in a valve with two seats, otherwise 
 it is easy to simplify Belidor's valve. l 
 
 A species of slide to revolve on an axis was designed by Bettancourt for a double 
 engine : such a slide would not, however, keep in order for any length of time, 
 and does not appear to have been used. * 
 
 453. COCKS are so well known as to need no description ; and on a small 
 scale they are certainly the best adapted for opening and closing pipes of any 
 thing that has yet been proposed. They do not answer so well when they are in 
 constant action ; but even then it is doubtful whether or not they are inferior to 
 other methods, and much depends on their being properly constructed. For a 
 single or common cock the plug should be nearly cylindrical where it has to be 
 exposed to much pressure. The common reduction of the diameter is about one- 
 sixth of the length. 
 
 454. For various purposes a double passage cock is useful, and in some cases 
 one with a triple passage may be required ; but the one most commonly applied 
 to the steam passages of steam engines is of the kind called the four-way cock, 
 and is in fact a rotary slide. Of these we have to consider two kinds : the common 
 one, the application of which was suggested by Leupold, art. 12. and applied by 
 Trevithick ; and Bramah's improved one. 
 
 455. A FOUR-WAY COCK, by its motion round its axis, opens a communication 
 alternately from the boiler and condenser, to the top and bottom of the cylinder 
 of a steam engine; Fig. 1. Plate iv. The simplicity of its action in some degree 
 compensates for its friction, but there is the disadvantage of part of the steam 
 being lost in the pipes at each stroke. Its form should be nearly cylindrical, 
 otherwise its friction and tendency to wear unequally will be increased. When 
 it is ground to fit truly, the pressure of the steam tends to keep the surfaces in 
 contact, and to wear the cavity into an elliptical shape ; hence it is soon necessary 
 to grind it to fit again. 
 
 456. The cock applied in this manner does not admit of the steam being cut 
 off at any portion of the stroke without the use of other valves ; but by dividing 
 the spaces, so that the solid part on each side of the aperture by which the steam 
 passes to the condenser is double the aperture, the cock may be moved at twice, 
 so as to cut off the steam at the first movement, and leave the passage to the 
 condenser open till the second. See Fig. 6 and 7. Plate vi. The cock must move 
 back and forward in this case, but it will be obvious that the disposition of the 
 surfaces is such as will prevent the wear being so destructive as it is in the 
 common form. 
 
 1 Architect. Hydraulique, torn. ii. p. 220. 2 Prony, Architect. Hydraulique, torn. i. p. 572. 
 
212 OF THE PARTS OF [SECT. vn. 
 
 457. BRAMAH'S FOUR-WAY COCK. In the common one the pressure being wholly 
 against the side of the conical plug, its wear is unequal and friction considerable : 
 to remove these, the conic frustrum is formed on a cylindric axis, and the steam 
 is admitted upon its larger end, by which the pressure on the seat is nearly 
 equalized ; and by turning in the same direction constantly, the wear is equalized, 
 notwithstanding the inequality of pressure. 
 
 These cocks, with some deviations, have been very much employed by Mr. 
 Maudslay in small engines ; and an example of their application to his portable 
 engine is shown in Plate xv. and the parts to a larger scale in Plate vm. In the 
 plan, C is the cylinder, I the four-way cock, and E the pipe by which the steam 
 enters. The cock is represented with all the apertures shut ; but the figure above 
 the plan is a section through the cock. The steam enters at E, flows over the top 
 of the cock, and by an aperture G in the top it passes either to the top or to 
 the bottom of the cylinder, according as the aperture in the side of the cone is 
 turned to the one or the other of these passages. 
 
 By comparing the effect of turning the cock to the right or left from the 
 position it has on the plan, the manner of opening and closing the passages will 
 be obvious. The higher passage leads to the condenser, (marked F in the two 
 sections,) the middle one to the top, and the lower one A to the bottom of the 
 cylinder. If the cock be turned to the right, so that the opening in the triangular 
 aperture through which the steam descends from the top is opposite the middle 
 passage, then the steam will pass to the top, and the condensed vapour will have 
 a passage open from the bottom to -the condenser, through the body of the cone. 
 If the cock be turned to the left, the centre of the triangular passage will become 
 opposite the passage to the bottom of the cylinder, and the steam will pass in that 
 direction, and a passage from the top to the condenser will be open through the 
 body of the cock. In this cock the motion is back and forwards. 
 
 The escape of steam at the lower part of the cone is prevented by a packing 
 of hemp round the cylindric part, and the cylindric part of the top is pressed by 
 a spiral spring, with an oil cup H, and screw above it to act on the spring, if 
 occasion requires. 
 
 The pressure and friction of this cock will not be greater than that of a slide, 
 if both be equally well executed. The loss of steam in the passages is an objection, 
 and the steam cannot be shut off without closing the passage to the condenser ; 
 this however is in some degree compensated for by the application of Field's 
 valve. See Plate xv. 
 
 458. FOUR-WAY COCK to cut off the steam at any portion of the stroke. The mode 
 by which this may be done, is to make the cock so much larger that there will 
 be the breadth of two apertures between the middle and each adjoining passage. 
 The diameter will be increased only in the ratio of 8 to 10 ; the rubbing surfaces 
 
SECT. VII.] 
 
 STEAM ENGINES. 
 
 213 
 
 will remain nearly the same, and the cone will be more equally pressed into its 
 socket. 
 
 459. DOUBLE-PASSAGED COCKS. By far the most simple method in practice 
 would be to use two double-passaged cocks : the apparent simplicity of one cock 
 involves more trouble and care, and after all is not so good as two small ones. 
 Two are as easily moved as one when the movements are simultaneous, and more 
 conveniently managed where the steam is to be cut off. 
 
 460. PLATE OR FLAT VALVES. The general nature of these valves may readily 
 be conceived by imagining two flat plates to be ground to fit one another, and 
 one to turn on an axis passing through the other plate ; the plates being both 
 pierced with apertures which coincide in one position of the moveable plate, and 
 are all closed in another position. Valves of this kind, made of hard steel, were 
 resorted to by Perkins for high pressure steam. When accurately made and 
 applied, so that the pressure is tolerably equal on the moving plate, they might 
 be useful. They admit of reducing the quantity of motion to open them in a 
 considerable degree, but not without dividing the passage into small apertures. 
 
 461. REGULATOR. The steam valve is called a regulator in the atmospheric 
 engine ; it is a kind of rotary plate valve, but it is formed wholly on one side of 
 the axis, and hence is more difficult to make work air-tight. Its construction, 
 as designed by Smeaton, is shown in the annexed figure, 
 
 FIG. 17. 
 
 where A B is the under side of the aperture, and C D a section, with the plate P 
 which covers it, and which is turned by a handle applied at E. 
 
 OF PISTONS. 
 
 462. The great desideratum in a piston is, that it should admit of no leakage, 
 and have as little friction as is consistent with this indispensable quality. 
 
214 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 Pistons may be rendered tight by an elastic packing of vegetable or animal 
 matter ; but the latter kind of packing cannot be used for steam, on account of 
 the heat destroying it. 
 
 Pistons may also be made wholly of metal, constructed so as to admit of a 
 certain degree of elasticity. 
 
 After considering some particulars common to all pistons, we will treat of 
 pistons, as below, dividing them into two classes. 
 
 Packed 
 
 Pistons 
 
 Metallic 
 
 Common leathered 
 Atmospheric engine piston. 
 
 Hemp 
 
 Cartwright's 1797. 
 Barton's 1816. 
 Jessop's 1823. 
 
 Perkins' 1823. 
 
 on wood. 
 on metal. 
 
 Common. 
 Woolfs. 
 
 463. When a piston rod is to be pushed as well as drawn, unless it be of a 
 certain thickness in proportion to the diameter, it is liable to stick if there be the 
 slightest inequality in the friction, or in the centring of the rod. If it were a thin 
 plate, nothing but its connexion to the rod would prevent it turning with the 
 slightest inequality of its friction, on being pushed ; and as we make it thicker, 
 the thickness interferes more and more with any tendency to turn. The propor- 
 tions which will secure us from the risk of this evil are not difficult to ascertain. 
 
 Let the pressure on the piston A B move the rod C D. 
 Then, in order that the piston may move steadily, its friction 
 at the circumference multiplied by half the diameter of 
 the piston, should be equivalent to the pressure producing 
 that friction, multiplied by half the thickness of the piston ; 
 consequently, the thickness should be to the diameter, as the 
 friction is to the pressure of the rubbing surfaces. 
 
 The friction of brass on iron is at an average one-eighth 
 of the pressure ; hence the thickness of metallic pistons 
 should not be less than one-eighth of the diameter. 
 
 The friction of hemp packing on iron is about one-sixth of the pressure, hence 
 the thickness of the packing should be one-sixth of the diameter. Practice is 
 
SECT. VII ] 
 
 STEAM ENGINES. 
 
 215 
 
 extremely variable on this point, but the mean appears to be not far distant from 
 the rule. For leather on iron the friction is greater, the average approaching to 
 one-fifth of the pressure. l When the pressure on the piston draws the rod, a 
 thickness not more than four-tenths of that which is required when the rod is 
 pushed will be sufficient. 
 
 It will be evident enough that the central part of the thickness of the piston 
 adds little to the steadiness of its motion, though it increases the friction ; hence 
 that construction of a piston has the advantage which renders the upper and lower 
 part a b tight, without putting a like stress on the intermediate ones at A. 
 
 464. The common position is a double cone of wood (Fig. 19.) having two 
 
 FIG. 19. 
 
 FIG. 20. 
 
 bands of strong leather fastened round it with nails or hoops. The joints in the 
 leather are not seamed, but closed as accurately as possible, and not put opposite 
 to one another. 
 
 465. If the parts be made of metal, a cylinder of brass should be turned to 
 fit the barrel or the cylinder it is to move in, (Fig. 20.) so that it will slide freely 
 without sensible resistance. Then an upper and lower plate, made of sufficient 
 thickness for the piston to be of the depth the diameter requires, confines two 
 cupped leathers C C, with the edges cut to an angle of about 45. 
 
 Both these pistons have the advantage of the friction being at the upper and 
 lower edges ; and bevelling the edges of the leather causes the force of the fluid 
 to spread it against the surface of the pump barrel. This mode of bevelling the 
 leathers seems to have been first used by Mr. Smeaton for a fire engine bucket, 
 and the general principle of construction was first applied in his air pump in 1752. 
 Mr. Bramah applied it to the various parts of his presses, and found its advantage 
 in the application of high pressures. 
 
 i Belidor, who seems to have first applied the solid piston, gives the proportions so that the 
 thickness is nearly equal to the diameter : the friction, with such a proportion, must be greatly 
 increased, as it must be in every part air-tight. His plates in another place show the thickness 
 somewhat less than one-third. Architect. Hydraulique, vol. ii. p. 117 and 223. 
 
216 OF THE PARTS OF [SECT. vn. 
 
 466. The atmospheric engine piston consists of a plate of cast iron, about 
 one-eighth of an inch less in diameter than the cylinder, and about one inch and 
 a half thick, formed with a rim about four inches from the edge. A flat ring 
 corresponding to the part beyond the rim is fitted upon it, and both have holes 
 for bolts to screw them together, which is done after a packing of soft hemp or 
 gasket, saturated with tallow, has been inserted. In order to render it more tight, 
 a portion of water is kept constantly on the upper side of the piston. 
 
 Smeaton had a superior method of constructing the piston for atmospheric engines, 
 which rendered the loss by the condensation of steam much less. The construction 
 of that for the Chase Water engine, with a seventy-two inch cylinder, being given, 
 will show this method. The bottom of the piston was made of wooden planks 
 fastened by bolts to the piston plate, with rings on the under side of the planks 
 to receive the heads of the bolts. The advantage of wood for this purpose, in cases 
 where the injection is made in the cylinder, is obvious. See Fig. 1. Plate vi. 
 
 The plank bottom, of elm or beech, was about two inches and a quarter thick 
 when worked, and was formed by two planks halved together, in the form of a 
 cross, and grooved on the edges with a three-quarter inch groove, to receive the 
 ends of the pieces to fill the corners between the cross, put in so that the pieces 
 may have the grain radiating from the centre : a few rivets to hold the cross 
 planks together were inserted, where they were halved into each other, at their 
 intersection, and the whole being hooped with a good iron hoop half an inch thick 
 and two and a quarter broad, it bound all tight together. The outside diameter of 
 the hoop was a quarter of an inch less than the cylinder. The flat iron rings for the 
 under surface of the piston should be let in flush with the surface of the wood, 
 and the bolt heads counter-sunk : the planking was screwed on with a double 
 thickness of flannel and tar between it and the iron piston plate, and any irregular 
 hollows filled up with additional thicknesses of flannel and tar, so as to exclude the 
 air between the plate and the wood. The bolts were carefully secured so as to 
 make a water-tight joint from above. The plank was covered on the lower side 
 by a lining of deal boards, shot clear of sap, and three quarters of an inch thick, 
 nailed to the planks, with a single thickness of flannel and tar between, so as to 
 exclude the air ; after this the lower surface of the lining was made perfectly flat 
 and smooth. 
 
 467. The HEMP PACKED PISTON is now most commonly employed for steam 
 engines, and the usual mode of construction is as follows : the bottom of the 
 piston b (Plate vn. Fig. 1.) is fitted as accurately to the cylinder as it can be done, 
 to leave it at full liberty to rise and fall through the whole length. The part of 
 the piston immediately above this is from one to two inches, according to the 
 size of the engine, less all round than the cylinder, to leave a circular space into 
 
SECT, vii.] STEAM ENGINES. 217 
 
 which unspun long hemp, or soft rope prepared for the purpose, and called gasket, 
 is wound as evenly and compactly as possible, to form the packing. This packing 
 is compressed together by a plate or cover C, which is put over the top of the 
 piston, having a projecting ring to fit over the lower part, and complete the upper 
 side of the space for the packing, the pressure being produced by screws S S, &c. 
 Both the upper and lower part of the space round the piston, to contain the 
 packing, is a little curved, that the pressure produced by the screws on the 
 packing may force it against the inside surface of the cylinder, into as close 
 contact as possible. 
 
 The screws being tightened when the piston is in the cylinder, the particular 
 form of the piston has the effect of squeezing out the packing, and causing it to 
 press forcibly against the inside of the cylinder at its upper and lower edges. 
 When the packing wears so as to become too small by use, these screws, which 
 are more or less in number according to the size of the piston, are always resorted 
 to for tightening it, as long as they are capable of acting ; and when this is no 
 longer the case, the piston top must be removed, and an additional quantity of 
 new packing introduced. The piston rod is generally attached to the bottom part 
 of the piston, by passing it upwards into a conical hole made to receive it, to 
 which the bottom of the rod is exactly fitted, and a screw nut, or a wedge, between 
 the top and bottom is inserted, which effectually secures it. 
 
 The piston is kept supplied with melted tallow by means of a funnel on the 
 top of the cylinder lid, provided with a cock to prevent the escape of steam. 
 
 468. WOOLF'S PISTON. In the usual method, whenever the piston, by continued 
 working, becomes too small and occasions a waste of steam, it is necessary to take 
 off the top of the cylinder, in order to get at the screws, even when fresh packing 
 is not wanted. This being laborious work, is therefore generally avoided by the 
 person who attends the engine, as long as it can possibly be made to work without 
 taking this trouble ; and the neglect occasions a great and unnecessary waste of 
 steam, and consequently of fuel in proportion. 
 
 The object of Mr. Woolf s improvement is to enable the engine man to tighten 
 the piston, without the necessity of taking off the cover of the cylinder, except 
 when new packing becomes necessary. He accomplishes this by the following 
 methods. 
 
 To the head of each of the screws a small toothed wheel is fixed, so that it may 
 be turned, and therefore tightened, by means of a central toothed wheel, which 
 works upon the piston rod as an axis : if one of the small wheels be turned, it 
 turns the central wheel, and the latter turns the others. The one which is to be 
 turned by the handle is furnished with a projecting square head, which rises up 
 
 2 E 
 
218 OF THE PARTS OF [SECT. vn. 
 
 into a recess in the cover of the cylinder. This recess is surmounted by a plate 
 fixed on with screws, called a cap or bonnet, that can be easily taken off, or put on 
 again in its place. 
 
 The other method is similar in principle, but different in construction. Instead 
 of having several screws all worked down by one motion, there is in this but one 
 screw, and that one is a part of the piston rod, Plate vn. Fig. 2 ; on this is placed 
 a wheel d of a convenient diameter, the hole in the centre of which is a female 
 screw, cut to work into that of the piston rod. The wheel is turned round so as 
 to tighten the piston by means of a pinion a, provided with a square projecting 
 head for that purpose ; rising into a recess in the cylinder cover of the kind already 
 described, and the cover or top plate is prevented from turning with the wheel by 
 means of the pins e e, called steady pins. 
 
 METALLIC PISTONS. 
 
 469. CARTWRIGHT'S PISTON. The idea of employing metal instead of elastic 
 vegetable matter, to render the pistons of steam engines tight, was one part of the 
 patent obtained by Cartwright in 1797. ' It consisted in using six or more solid 
 masses of metal in the place of the usual packing ; these masses being segments of 
 rings, a a, Plate vu. Fig. 3. made to fit the internal surface of the cylinder, with a 
 second series b b, crossing the joints of the other, and both series were pressed 
 against each other and the cylinder by V-springs ; and by having two sets, with 
 the joinings of the rings in the one set, opposite the solid parts of the rings of the 
 other set, the escape of steam at the joints was to be prevented. The upper and 
 lower parts were connected by plates, to which the piston rod was joined. (See the 
 section, Fig. 3.) 
 
 The two exterior rings of brass were made of the full size of the cylinder, and cut 
 into several segments, as shown at a a a, and laid one above the other so as to cross 
 the joints. The joints in the under rings are shown by dotted lines in the figure ; 
 and in like manner are disposed the two interior rings, both being confined to their 
 
 i Mr. Watt tried metallic packings in some of his early engines, but gave them up on account 
 of the practical difficulties in keeping them tight, and from their wearing the cylinders unequally. 
 They are now much employed in the cylinders of sea-going vessels, where opportunities for 
 packing cannot be embraced without considerable inconvenience and loss of time ; but in point 
 of effect, it is questionable whether there be any saving. 
 
 The best description are those manufactured with one or more cast iron or brass rings, the joints 
 of which overlap, with a packing behind : this is preferable to those constructed with springs, 
 which soon lose their elasticity and become useless. 
 
SECT, vii.] STEAM ENGINES. 219 
 
 places by a top and bottom plate, to which the piston rod is fixed. The segments 
 are pushed away from the centre by steel springs, of the form of the letter V. 
 
 Pistons on Cartwright's plan have not been quite successful in practice, when 
 the cylinders have not been truly bored ; and the causes were pointed out very 
 clearly by Mr. W. Nicholson, soon after the invention was brought before the 
 public. 1 The pieces forming the piston having a determinate curvature, and being 
 too strong to be sensibly flexible, cannot be expected to accommodate themselves to 
 any irregularity in the cylinder in different parts of its length, as is done by the 
 elastic stuffing of hemp ; and there is reason to doubt, in applying them, whether 
 the pressure of the rings or pieces together has not been too powerful for the 
 springs to perform their office when applied in this manner. 
 
 As to the actual difference between the friction of metal, and hemp against 
 metal, when the pistons are equally steam-tight, it is undoubtedly in favour of 
 metallic pistons (art. 463). 
 
 470. BARTON'S PISTON. A piston considered superior to Cartwright's was made 
 by Mr. Barton, Plate vn. Fig. 4. It consists of one thick ring E, of brass or cast 
 iron, made very nearly to fit the cylinder, and then cut into three or more equal 
 segments : the equal triangles remaining are used as wedges to expand the seg- 
 ments of rings into a larger circle. The segments, and small triangles or wedges, 
 are secured between a top and bottom plate, as in the piston last described, with 
 spiral springs to press the triangles outwards from the piston rod, making them act 
 as wedges to press the segments against the inside of the cylinder ; and as these 
 wear by use, the points of the wedges themselves protrude, and, being formed of the 
 same metal, still make part of the piston. A piston of this kind, and a true 
 cylinder, has been known to work for some years without requiring any other 
 attention than keeping it properly greased ; but it is easy to prove that the wedges 
 and segments do not expand equally, hence in this state it was not applicable to 
 high pressures ; besides, the imperfection of Cartwright's piston still remained. It 
 has however been recently much improved by Barton, and therefore I propose to 
 describe it more fully in its improved state. 
 
 The piston is represented by a plan and section, Fig. 4. It is composed of a 
 solid cylindrical cast iron body A, having a conical hole B, to receive the enlarged 
 end of the piston rod, to which it is secured by a cross pin D, passing through 
 both. A space or groove is formed round the body of the piston, to receive four 
 brass, cast iron, or cast steel, hardened and tempered segments marked E, which 
 are spread asunder by four triangular wedges G, of the same metal as the 
 
 1 Philosophical Journal. 
 
220 OF THE PARTS OF [SECT. vn. 
 
 segments, acted on by eight spiral springs of tempered steel. These springs are 
 inserted in cylindrical cavities at both ends, in order to render them secure from 
 bending, and yet allow them to play freely. With the same view, each spring has 
 a cylindrical pin of steel within it, a little shorter than the spring. In pistons 
 made for high pressure steam there are three grooves, formed round the exterior 
 part of the segments, as in Fig. 5. ; the middle one a designed to hold oil or grease, 
 to lubricate the rubbing surfaces. The upper and lower grooves, b b, are for hoops 
 of tempered steel, having a forked loose joint, as Fig. 6., at one point in each. 
 These hoops are nicely fitted to the grooves ; and when the piston is placed in the 
 cylinders their jointed ends meet. Each hoop is prevented from turning round in 
 the groove by a pin or stud, in order that the two hoops may not have their joints 
 opposite to each other. These hoops, or rather springs, form an important addi- 
 tion, and assist greatly in preventing the leakage, which otherwise would take place 
 through the unequal expansion of the segments and wedges ; for the point of the 
 wedge will move outwards over n m, Fig. 4., while the segments move only over 
 n o, and consequently would wear the cylinder into grooves, were it not rounded 
 off, and the hoops added, to prevent the escape of steam. 
 
 But by combining hardness and elasticity, Barton has done much to render these 
 pistons tight and durable : they still however depend chiefly on the skill of the 
 workman : when they are done well by a person who understands them, they 
 undoubtedly answer effectively, so long as the springs retain their elasticity. 
 
 471. To avoid the effect which the unequal expansion of the parts of Barton's 
 piston produces, I would recommend the construction shown by Fig. 7., where the 
 wedge-formed pieces do not extend to the surface of the cylinder ; and to prevent 
 there being an aperture at each joint, two series of segments and wedges should be 
 used, as shown in the section : the joints of the lower series are shown by dotted 
 lines in the plan. 
 
 472. It is of importance to remark, that the metallic packing is pressed so as 
 to be steam-tight by the steam itself; and it is essential to their perfect operation 
 that the steam has egress to the cavities in the piston, and that the parts fit 
 perfectly against each other in all the horizontal joints. Let strong steam be on 
 the upper side A, of the piston, Fig. 7. and the lower side B, be open to the con- 
 denser ; then the steam enters at the joints e e, presses the segments close on the 
 lower plates, and fills the interior so as with the assistance of the springs to press 
 the segments outward against the cylinder. Also, when the lower side is open to 
 the steam, and the upper one to the condenser, the steam enters at //, pressing the 
 segments close against the cylinder and upper plate. If this were not so, the 
 springs could not possibly press with sufficient force to keep the joints steam-tight ; 
 
SECT, vii.] STEAM ENGINES. 221 
 
 for a fluid cannot be confined by a force less than its own elastic force ; and hence 
 the pressure producing friction is always greater than the pressure of the steam on 
 the rubbing surface, by that due to the pressure of the springs. 1 
 
 473. JESSOP'S PISTON. A completely different method of applying metal to 
 render pistons steam-tight was invented by Mr. Jessop, and secured by patent in 
 1823. It consists of an expanding coil of metal, which binds round the piston 
 body in a spiral form. Fig. 8. Plate vii. shows a section of a piston of this kind, 
 where A A is the elastic spiral of metal, which, when at liberty and removed from 
 the piston, assumes the form shown in Fig. 9. To form a piston of this kind, a 
 bed of hemp packing, B B, is first prepared, which answers the double purpose of 
 preventing steam passing at the joints, and of supplying a means of pressing the 
 springs against the surface of the cylinder. A small addition of hemp packing is 
 at times necessary to make up for the wear. 
 
 The action of the steam in keeping this piston tight, is by pressure on the top 
 and bottom plates, as in the common hemp-packed pistons. The pressure and 
 wear of these pistons will be more equable than in the other metallic kinds when 
 they are equally well made, and they have been as successful in practice. 2 
 
 474. OF THE FRICTION OF PISTONS. The rubbing surface of a piston must be 
 pressed against the cylinder with a force at least equal to the pressure of the steam 
 it confines, otherwise the surfaces would separate and the steam escape. Now it 
 has been shown (art. 463.) that the thickness of the rubbing surface should be 
 equal to that portion of the diameter which expresses the friction ; therefore, let r 
 be the friction when the pressure is unity, t = the thickness, a = the diameter, and 
 p = pressure of the steam ; then, IT t a p r = the friction ; or since t = r a, it is 
 Tf pa- r 2 = the friction, to which one-tenth may be added for that of the piston rod. 
 
 The moving force is, 
 
 ir pa? 
 
 consequently that part of the moving force equal to the friction is, 
 
 K p tft 
 
 1 So little is known by many mechanicians of the nature of the action of pistons, that it is not 
 unusual to hear them express an opinion on the friction of a piston from the force required to 
 move it in an open cylinder ; and on a level with it is the method of estimating the friction of an 
 engine by the power it requires to move it when it is doing no work. The true state of the fact is, 
 that the friction is as the stress on the parts, and this stress bears a relation nearly in proportion to 
 the work done. 
 
 z An arrangement of the parts of a metallic piston was one of the objects of a patent obtained 
 by Perkins ; but as it is inferior to those already described, it will be sufficient to refer to it. 
 See Repertory of Patents, vol. i. p. 224. 
 
222 OF THE PARTS OF [SECT. vn. 
 
 4'4 
 In double engines with metallic pistons, 4'4 r 2 = gg = '069 of the power. 
 
 4.4 
 In double engines with hemp-packed pistons 4'4 r c = QQ = '1222 of the power. 
 
 1 Tfi 
 
 In single engines with hemp-packed pistons - 4 x 4'4 r z = ^ ^ = '049 of the 
 
 power. 
 
 In high pressure engines the friction is supposed to be in the same ratio ; but 
 the loss of steam past the piston being in respect to the power in the inverse ratio of 
 the diameter of the piston, I have assumed the friction and loss to be two-tenths 
 of the power, and that because it corresponded with observation in two cases where 
 I had a tolerably certain means of comparing the power and effect. Calculation 
 gives the loss a little more. See note to art. 384. 
 
 PISTON ROD COLLARS, OR STUFFING BOXES. 
 
 475. The piston rod collar, or stuffing box, is a contrivance for rendering the 
 place where a smooth rod or plunger passes into a vessel air-tight. This mode of 
 giving motion without admitting air must have been long in use ; we meet with it 
 in various works without an allusion to the time of its invention. It is so similar 
 to the construction of a piston, that a separate detail seems scarcely to be necessary. 
 As in the piston, so in this the effect is produced by elasticity ; and leather, hemp, 
 cotton, cork, and metal, have been used for the purpose. 
 
 Where the heat of steam is not likely to be injurious, leather is generally 
 employed. It was first employed in discs, cut to fit the rod, and pressed together 
 by screws. The next was cupped leathers ; and the first instance of their applica- 
 tion seems to have been at the York Buildings water works, 1 and they were used 
 by Smeaton for his air pump : he also applied them to the piston rods of the 
 blowing machines at Carron, and describes how to form the cups by stamping 
 them into a cylinder of the size of the rod they are intended for. 2 What renders 
 Smeaton's stuffing box for the blowing cylinders more curious, is, that he uses a 
 block of hard wood for the rod to pass through, and the rods it seems were draw- 
 filed. The application of cupped leathers to the plungers of the hydrostatic press 
 by Mr. Bramah, put them to the test on a large scale, under immense pressures. 
 
 476. The stuffing box with the hemp packing is made to fit tight round the 
 piston rod in a manner nearly similar to the piston. A collar with a hole through 
 it, just sufficient to give easy passage to the rod, is screwed down, to confine the 
 
 1 Architecture Hydraulique, vol. ii. p. 62. Description of the Pumps of York Buildings Water 
 Works, London. 
 
 4 Philosophical Transactions, vol. xlvii. p. 415. Reports, vol. i. p. 360. 
 
SECT. VII.] 
 
 STEAM ENGINES. 
 
 22:3 
 
 packing, and cause it to press against the rod ; it is cup-formed at the top to 
 contain tallow to grease the rod. See Plates iv. and v. 
 
 477. Metallic packing was tried for piston rods by Cartwright, and has since 
 been much improved by Barton : it is however a part of so much less importance 
 than the piston, that it will not be very often thought prudent to be at the expense, 
 though the ingenuity of the contrivance renders it desirable to describe it. Bar- 
 ton's metallic substitute for stuffing boxes is shown in the annexed figures ; where 
 D is the piston rod, E the box with a ledge for the cast iron plate F to rest on, and 
 G another above it to receive the cast iron plate H. The cover I of the box is 
 secured by screws in the usual manner, with plates of lead in the joints J and K, 
 
 FIG. 21. 
 
 for the purpose of making the joints closer. The three principal metal blocks L 
 embrace the piston rod D, and three wedging blocks M fill up the spaces between 
 them. Two thin hoops N N of tempered steel, firmly riveted together at their 
 ends, surround the outside of the blocks, binding upon the rounded exterior angles 
 of the blocks, and these angles are left on in the middle to keep the hoops in their 
 places. At each of the exterior angles of the blocks L, there are two spiral springs, 
 fitted to cylindrical holes, and also provided with cylindrical pins, as those of the 
 piston. By these and the elastic hoops the blocks L are strongly pressed towards 
 the piston rod. Two other hoops a a of elastic steel, cut across, are inserted in two 
 grooves to be in contact with the rod, and serve to close the joints more perfectly : 
 they are fixed in a similar manner to the rings round the piston before described. 
 
224 OF THE PARTS OF [SECT. vn. 
 
 The middle groove R is formed between the two others to receive grease ; and a 
 circular cavity S S is also made around the hole in the cover of the cylinder for 
 the same purpose. 1 
 
 In constructing this collar the blocks L should be parallel, otherwise the wear 
 will be irregular, and the springs will soon be ineffective ; the blocks M should not 
 wear unless the piston rod wears ; and perhaps it will be steam-tight, unless 
 assisted by a hemp packing behind the hoops N N. 
 
 MODES OF OPENING VALVES, COCKS, AND SLIDES. 
 
 478. The motion may be given either from the reciprocating or from the 
 rotary parts of an engine. In engines which have no rotary parts, motion is 
 communicated to the valves by a rod or beam, called a PLUG TREE, attached to the 
 engine beam near to the end moved by the piston rod. This plug tree is provided 
 with certain adjustible projections called TAPPETS, which strike the levers or handles 
 of the valves, and thus open and shut them at the proper intervals as the beam 
 ascends or descends. These handles turn on axes, and act as levers to move the 
 valves, slides, or cocks. The most important point is to render the action certain, 
 for the effect of the engine depends on the passages being opened and closed at 
 the proper times. When valves are employed, they are generally opened by 
 weights. (See Plate ix. Fig. 3.) A weight w, sufficient to overcome the friction 
 and open the valve, acts by a short arm a on the axis, which requires to be turned 
 to move the valve ; the weight is kept suspended by a spring catch b while the 
 valve is close, and when the catch is disengaged by the handle c, being moved by 
 the tappet d, the valve opens. If the valve be large, it requires a considerable 
 weight w to open it against the pressure of the steam ; and in that case either the 
 valve described in art. 442, or Watt's mode of relieving the pressure, may be 
 adopted. It will naturally be inquired, why weights are raised to open the valves 
 instead of using the direct power of the beam. The only reason assigned for so 
 doing is, that a weight opens a valve more rapidly, and the loss by closing them 
 slowly was not quite so readily detected ; though the absolute loss is about 
 the same, and the practice is becoming more common to open them by direct 
 action. 
 
 The descent of the weight which opens a valve is regulated by an ingenious 
 method: it either descends into, or forces a piston into a vessel of water, (see 
 C, Fig. 3. Plate ix.) while the aperture by which the water escapes from under 
 it may be increased or diminished at pleasure ; the weight therefore acts with its 
 
 1 Gill's Technical Repository, vol. iv. p. 242. 
 
SECT, vii.] STEAM ENGINES. 225 
 
 full force to open the valve, but as soon as it begins to move, it is retarded by the 
 water, till it be finally stopped. During the ascent, a valve opens inwardly at 
 the bottom of the vessel, and therefore the engine has not more than the weight to 
 raise again. 
 
 In engines for raising water this mode of opening valves has always been fol- 
 lowed. The difficulty of opening large valves was probably the cause of its 
 introduction, and the ingenuity of its mechanism has preserved it in use ; but I 
 think there will be an advantage both in simplicity and effect, to let the motion 
 of the plug tree act directly on the valves, as shown in art. 482 : the tappet by 
 which the steam is shut off should be capable of considerable range, whether for 
 adjusting by hand or by a self-acting apparatus. (See art. 554.) 
 
 479. In an engine having a fly, it is esteemed better to apply an eccentric 
 wheel within a hoop upon the fly-wheel shaft, and this by its evolution alternately 
 pushes and draws a rod connected to the hoop, and thus gives motion to the 
 valves, cocks, or slides. Such an apparatus is shown in Plate xv. Fig. 2. in 
 which N is a cross section of the fly-wheel shaft, and k the eccentric wheel fixed 
 upon and revolving with it ; a circular hoop of metal encompasses the eccentric 
 wheel in such a manner as to permit its turning round, and from this hoop the 
 arm i projects, and it is braced to increase its strength. It terminates in an arm 
 upon a centre, which by a second arm gives motion to the rod /, and causes 
 another axis to move, which, by a pair of bevelled wheels, moves the cock of the 
 engine partly round upon its axis n, and back again. The advantage of an 
 eccentric wheel is the easy changes of motion it makes ; for being constantly 
 moving, it gives no stroke at the times of change ; and in large engines part of 
 the weight of the eccentric apparatus is balanced by a weight, so that there is 
 only a slight pressure on the shaft. (See Plate xix.) 
 
 Let r be the radius of the eccentric circle, and a the distance of its centre from 
 the centre of motion ; then (r + a) (r a) will be the extent of the movement, 
 = 2 a, or twice the eccentricity ; and in any other position the place counted from 
 the centre will be a cos. a where a is the angle between the centres, whose cosine 
 is equal to the horizontal distance. When they are in a vertical line, = 90, 
 and cos. = 0, the distance is 0, and this corresponds to the termination of the 
 stroke. Now we know from the nature of the circle that the cosines increase 
 rapidly at first in departing from the angle of 90 ; but at one-sixth of the stroke 
 counted from either end of it, a valve, slide, or cock, can be only half way 
 opened, and unless its motion be greater than that required to open it, the time 
 it will be about fully open, will be only one-ninth part of the stroke. 
 
 480. Eccentric rollers to raise the valve rods have the same defect ; but the 
 application is ingenious. Conceive the shaft Y, Fig. 1. Plate vm. to be kept in 
 
 2F 
 
226 OF THE PARTS OF [SECT. vn. 
 
 motion by the crank shaft of a double engine, causing the shaft Z to revolve by 
 means of the wheels 7,8; then if on Z two eccentric wheels 4, 4, be fixed under 
 two rods which slide vertically in guides, (see z, z, Fig. 2.) and provided with 
 friction rollers 3, 3, the revolution of the shaft Z will alternately raise and depress 
 the rods, which by the arms 9, 10, 11, 12, raise and depress the valves by their 
 stems. The lever or handle 13 is used to open or close the valves by hand in 
 setting to work, &c. It will be remarked that this construction does not admit of 
 cutting off the steam without also shutting the condenser. 
 
 481. As far as regards opening and closing the passages more rapidly, a 
 good improvement has been made on the eccentric motion, by altering the form 
 of the portion fixed on the shaft so as to act more nearly as a tooth or cam, and 
 by placing adjustible spanners on the eccentric rod ; but why not at once form it 
 as a tooth, or a series of teeth, in the best manner to produce the movements 
 required ? Suppose the object be to cut off the steam at some part of the stroke 
 by a slide or cock, then there must be two motions, the one double the length of 
 the other. Let A B, Fig. 1 and 2. Plate ix. be the first, and B G the second, 
 and from the centre D describe circles through these points ; set off A E for the 
 time to be expended in closing the passage to the condenser, and A F for the 
 time of opening the passage for the steam ; then, that the action may be easy, the 
 curve H G should be drawn, so that each of its parts may be a parabola, the one 
 with its vertex at H, that of the other at G. * To produce the second motion, 
 another wheel should be placed on the same axis, behind the first one, with the 
 curve I K. If these curves have corresponding ones, and act on connected rollers, 
 the motion will be certain, and the range confined, and the motions of the engine 
 may be made to reverse in the case of boat or carriage engines ; for the posi- 
 tion of the slide being changed by hand, the pressure of the steam will impel the 
 crank shaft in the contrary direction, and the toothed wheel will move the slide or 
 cock in the proper directions. 
 
 In order that the steam may be cut off at any period of the stroke, according to 
 the resistance or the work on the engine, the wheel with the curve I K may be 
 made to slide round on its axis, and the curve I K may be placed so that the 
 period of cutting off the steam may be varied from N to O. 
 
 482. If valves are to be opened, the weight of the valves and rods is generally 
 sufficient to close them ; hence the rods do not require to be connected so as both 
 to push and draw, but on the other hand a separate rod for each valve is required 
 for a valve engine to work expansively, 4 and the toothed wheels or cams to move 
 
 1 The best curve for generating motion from rest is the common parabola. See Emerson's 
 Mechanics, 4to ed. prop. 91. case 3. 
 * From the nature of the motions of the valves, slides and cocks being incompatible with the 
 
SECT, vii.] STEAM ENGINES. 227 
 
 the rods will be placed with most advantage under the rods, as on the axis Z, 
 Plate viii. Fig. 1 and 2. 
 
 483. To apply the same principle to a reciprocating engine ; let A B, Fig. 4, 5. 
 Plate ix. be the plug tree, with the curve C D to act on the roller at C, which, 
 as soon as the plug tree descends to C, begins to cause the roller frame to slide, 
 and turn the axis E, so as to depress the slide rod by the arm F. The steam will 
 be shut off by H I on the descending stroke, and by K L in an ascending one. 
 
 484. To regulate the period of cutting off the stroke, the portions containing 
 the curves I H and K L may be made in two parts, to slide side by side by means 
 of a screw ; and if the rod having the screw upon it slides in a wheel acted upon 
 by either a governor or other regulator, the engine will regulate itself. (See 
 art. 554.) 
 
 485. In all cases an axis to be alternately moved in opposite directions should 
 be balanced, and the stress of all heavy parts -should be relieved by counter- 
 balancing them by weights acting on levers. The hand gear should be a power 
 proportioned to the force required to move the slides, cocks, or valves. (See art. 
 449.) 
 
 PISTON GUIDES. 
 
 486. The motion of the piston rod should be in a straight line in the direction 
 of its length, and when the point it acts upon describes the part of a circle, the 
 construction must be such that each may be confined to its proper motion, and 
 yet the piston rod must produce the circular motion with as little oblique action 
 as possible. 
 
 The most simple method is to confine the piston rod to its direction by means 
 of a guide or guides, and to let it act on the part which moves in a circular direc- 
 tion by means of a connecting rod. To reduce the friction of the guides, rollers 
 may be added. A very simple combination of this kind is shown in Plate xv. 
 Fig. 1. A wheel or roller F is fixed on the piston rod D, and is confined to a 
 vertical motion by the guides G G, and the motion is transmitted to the crank I 
 by a connecting rod H H. When the fly is of sufficient power, the whole loss of 
 force in this combination is simply the friction produced by oblique action, and 
 
 employment of the expanding force of steam in the engines of most makers, we infer that, Boulton 
 and Watt's excepted, very few have availed themselves of this great source of economy. The 
 proprietors of engines are too anxious about the power that an engine of a given sized cylinder 
 possesses, forgetting that if an engine work with a minimum quantity, of fuel, it must have a larger 
 cylinder to do the same work. In estimating the comparative economy of engines, nominal power 
 should not be considered, but the effect produced by each pound of fuel. 
 
228 
 
 OF THE PARTS OF 
 
 [SECT. vii. 
 
 is less in proportion as the connecting rod is longer ; provided the stress from 
 weight be not materially increased. l 
 
 CRANKS. 
 
 487. The crank is one of the best contrivances for changing a reciprocating 
 into a rotary motion. There are three different cases : 
 
 1. The moving force may be uniform and in a straight line, 
 
 2. The moving force may be uniform and in a curved line, 
 
 3. In either case the force may be variable. 
 
 I 
 
 A crank increases the velocity of the moving force, and in the usual construction, 
 in the ratio of the circumference of a circle to twice its diameter ; but this ratio 
 is susceptible of variation, as is also the action of the power. This will be evident 
 from the annexed figure ; as if A B be the motion of the piston rod, the crank 
 
 Fig. 22. 
 
 1 The -whole increase of stress required for converting a reciprocating into a rotary motion 
 cannot double the friction on the crank axis in any case, and as double this friction never amounts 
 to a tenth part of the power of an engine, there is no reason to hope for an equal degree either of 
 economy or simplicity by using the rotary action of steam. (See art. 313 317. and the table, 
 art. 487.) 
 
SECT, vii.] STEAM ENGINES. 229 
 
 may be any where in the lune represented by the dotted lines, and drawn from 
 the centres A and B, with radii each equal to the length of the connecting rod. If 
 we sum up the forces acting in the circle, we find them exactly equal to the mecha- 
 nical power in the straight line, the additional friction excepted. 
 
 The following table is calculated for an uniform force acting in a straight line ; 
 the moving force in the straight line is supposed to be unity, and the table shows 
 the pressure it produces in the direction of a tangent to the circle, at the quarters 
 and at every thirty degrees of its path. It will enable the reader to judge of the 
 effect of a variable force ; and where the acting point describes a curve, it is less 
 regular, but not so different nor so important as to require investigation : the last 
 column is added to show the additional stress on the axis above that which would 
 take place if the axis were turned by toothed wheels. 1 
 
 1 When the moving force reciprocates in the straight line A B, and the end D of a connecting 
 rod is moved round in a circle ; let c be the angle D C O which the connecting rod forms with the 
 direction A B of the motion, and a the angle D O E or arc described from E. The force in the 
 direction of the connecting rod is P sec. c, where P is the force when the rod is in the position 
 A E. Also, since C F is parallel to O D, the L O C F = L D O E = a, and consequently the 
 Z.DCF = c + a; therefore the force in the direction F D of the tangent to the circle = P sec. c 
 
 sin. (c + a) = P sec. c (sin. c cos. a + cos. c sin. a) = P [ !_' cos. a + sin. a ). But, when the 
 
 \cos. c / 
 
 connecting rod is n times the length of the crank, sin. a = sin. c, sin. c = Sln ' a , and cos. c 
 
 ' -; therefore, 
 
 [ J = the circular force at D for any 
 
 n 
 
 cos. a 
 
 n 2 sin. 2 a 
 The additional stress on the axis or shaft, and consequently the friction, is as 
 
 P sec. c cos. (c + a) or P ( cos. a sin. 2 a \ 
 
 v // 2 sin. 2 a / 
 
 The additional friction (being about one-eighth of the pressure) is therefore never greater than 
 
 where a is the diameter of the shaft, and r the radius of the crank, both in inches. 
 
 Pa 
 167' 
 
 By construction of the figure the values may be found from a scale of equal parts ; for if C G 
 be the pressure, F D will be the force in the circle, and C F the stress on the axis. 
 
230 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 TABLE OF THE VARIATION OF ROTARY FORCE, WHEN A CRANK is IMPELLED 
 
 BY A CONSTANT FORCE. 
 
 Portion of 
 the stroke 
 described, 
 the whole 
 being 1. 
 
 Portion of 
 circle de- 
 scribed, in 
 degrees 
 from the 
 beginning. 
 
 Length of the connecting rod, the length of the crank being 1. 
 
 Stress on 
 the axis, 
 when the 
 connecting 
 rod is 6 
 times the 
 length of 
 the crank. 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 0-000 
 0-067 
 0-146 
 0-250 
 0-500 
 0-750 
 0-854 
 0-933 
 1-000 
 
 
 30 
 45 
 60 
 90 
 120 
 135 
 150 
 180 
 
 0-00 
 0-72 
 0-97 
 1-10 
 1-00 
 0-62 
 0-43 
 0-27 
 0-00 
 
 0-00 
 0-65 
 0-87 
 1-01 
 1-00 
 0-75 
 0-57 
 0-39 
 / 0-00 
 
 0-00 
 0-61 
 0-83 
 0-98 
 1-00 
 0-75 
 0-57 
 0-39 
 0-00 
 
 0-00 
 0-59 
 0-80 
 0-95 
 1-00 
 0-78 
 0-60 
 0-42 
 0-00 
 
 0-00 
 0-57 
 0-78 
 094 
 1-00 
 079 
 0-62 
 0-43 
 0-00 
 
 0-00 
 0-56 
 0-77 
 0-93 
 1-00 
 0-80 
 0'63 
 0-44 
 0-00 
 
 1-000 
 0-825 
 0-624 
 0-375 
 0-169 
 0-625 
 0-790 
 0-907 
 1-000 
 
 The length of the crank is supposed to be 1 ; and the table applies to any other 
 length of crank, when the connecting rod is 2, 3, 4, 5, 6, or 7 times its length : 
 the columns below these numbers show the rotary force corresponding to the posi- 
 tions indicated in the first and second column. The stress in the last column being 
 greatest at each end, will have a tendency to wear the shaft into the form of an 
 oval, having its longest diameter at right angles with the connecting rod. 
 
 PARALLEL MOTION. 
 
 488. The next method to be described for communicating motion from a 
 piston rod to a beam is that called the ' Parallel Motion.' It was invented by 
 Mr. Watt, who first gave a notice on the subject in ' Robison's Mechanical Philo- 
 sophy ;' and its theory has been since analytically investigated by Prony. We shall, 
 by confining the enquiry to practical conditions, however, be able to treat it more 
 briefly, and show how the best proportions for practice may be obtained. 1 
 
 There are two cases, which for simplicity we shall investigate separately, 
 though they are generally both in use in the same engine. 
 
 489. FIRST CASE. If each of two bars A B, C D, Plates x. (A) and (B) Fig. 4. has 
 an axis at one end, round which it moves, and the other end be connected with a third 
 bar B D, by moveable joints ; then there is a point E in the middle bar which will 
 nearly describe a straight line. The rectilinear movement of the air-pump rod, in 
 
 1 A patent for the protection of the Parallel Motion was taken out by Mr. Watt in 1784, and 
 the invention was in 1787 applied in its most perfect form to the engines of the Albion Mills. 
 
SECT, vii.] STEAM ENGINES. 231 
 
 a steam engine, is often obtained by this method ; and as the motion is not per- 
 fectly rectilinear, it is desirable to determine the point which renders it most 
 nearly so. 
 
 490. In any regulating apparatus of this kind, it is of considerable importance 
 that the strains on the parts should not change their directions during the stroke ; 
 and this condition being premised, we shall have less difficulty in forming them to 
 act with regularity and certainty. The entire arcs described by B and D, in 
 Plate x. (A) have their equal chords in the same vertical line b d ; and since the 
 distance between the upper extremities and between the lower extremities of these 
 chords is in each case equal to the length of the link B D, it is plain that the 
 distance between the middles of these chords is also equal to the link ; that is, if 
 A B, C D, were both horizontal, we should have a D = the link B D, which evi- 
 dently cannot be the case, as the link is in an oblique position at half stroke. The 
 beam A B, and the radius bar C D, will however be both nearly in a horizontal 
 position at the middle of the stroke ; and if the strain is not to change its direc- 
 tion, the connecting bar B D should not pass a vertical position at either termi- 
 nation of the stroke : and to limit it to this condition, we shall in Plate x. (A) suppose 
 the bar, as shown by the dotted lines, to be exactly vertical, or coinciding with the 
 direction of the piston rod at each end of the stroke. 
 
 Let A B and C D, Fig. 4. Plates x. (A) and (B) be the bars, B D the connecting 
 rod, and E the point to which the piston rod is to be attached ; b d being the direc- 
 tion it is to move in. Put AB = ns, CD = ms, B D = /, and the length of the 
 stroke of the piston rod s, which is equal to the chord of the arc described by the 
 bar A B. Make the versed sine of that arc v, and the versed sine of the arc 
 described by the end D of the radius rod = w. Then a B is the sum of these 
 
 versed sines = v + w ; and v + w.v :: I : BE = - -. But, by the properties of 
 
 the circle, we have s (m V m 2 ) = w, and s (n v/ n 2 ^) = v ; therefore, 
 
 BE = -frL-V ' ~ i)!^ 
 
 (w V m 2 ^) + ( <s/ 2 ) 
 
 ^___^^__^ T 1 
 
 But we have very nearly v/ w 2 i = n 5, v/ ? 2 a = m 5 : and there- 
 
 o n o wi 
 
 fore w v/ 2 5 = 5 , m \/ m" i = ^ ; consequently, 
 
 O M O Wl 
 
 BE = OT/ DE = nl 
 
 + m + n 
 
 .-. BE : DE ::::: CD : AB; 
 
 that is, the segments of the link are inversely proportional to the lengths, or radii, of 
 the beams. 
 
232 OF THE PARTS OF [SECT. vn. 
 
 When A B is equal to C D, the point E is in the middle of the length of the 
 bar B D. 
 
 491. RULE i. With any proportion between the lengths of the bars 
 A B and CD; for instance, if A B : C D : : n : m. Then from the number n sub- 
 tract half the square root of four times its square, less one, for a first number. 
 Also from the number m subtract half the square root of four times its square, less 
 one, for a second number. l Divide the first number by the first added to the 
 second, and the quotient multiplied by the length, B D, of the link or bar, will 
 give the distance of the point E from B. 
 
 Example. Let A B be to C D as 2 : 3 ; then 2 x 2 x 4 = 16, and 16 - 1 = 15, 
 of which the square root is 3'873 nearly, and its half is 1*9365 ; and 2 1'9365 
 is -0635 for the first number. Next 3 x 3 x 4 = 36 ; and 36 - 1 = 35, of which 
 the square root is 5-916, and its half is 2'958 ; and 3 - 2'958 = -042, therefore 
 
 0635 
 -0635 + . 042 = : -602 nearly. 
 
 Hence the length of the link or bar B D, multiplied by the decimal '602, is the 
 distance of the point E from B, or B E = -602 B D, when A B is to C D as 2 
 to 3. Or if the point E be given, then B E divided by '602 will give B D, the 
 length of the bar, link, or distance of the point of connexion D from B. The 
 parallel motions of the engines in Plates xi. and xix. are examples. 
 
 The following rule is much easier in its application, and equally good for 
 ordinary purposes. 
 
 RULE ii. Divide the link into two parts, having the same proportion to each 
 other as the beams, placing the greater part next to the shorter beam. 
 
 o 
 
 This rule applied to the preceding example gives B E = a , 3 B D = '600 B D. 
 
 492. SECOND CASE. In this case, to a bar which moves on an axis at A, Fig. 5. 
 Plates x. (A) and (B) conceive three shorter bars to be added to the end, so as 
 to form with a part of the bar the parallelogram B D G F ; and let another bar D C, 
 which moves on a centre at its extremity C, be attached to the lower angle D of 
 the parallelogram which is most distant from the centre C, round which the bar 
 moves. Then the piston rod being attached to the other lower angle G of the 
 parallelogram, its motion will be nearly rectilineal in the direction G H. 
 
 The purpose of rendering the stress in the same direction during the whole of 
 the stroke would determine me to prefer the construction which renders the links 
 B D, F G, vertical at both extremities of the stroke, as in Plate x. (A) : this is not 
 however the usual mode in practice, for the line of motion of the piston rod is 
 
 1 These two numbers are the versed sines of the arcs described by the beam and radius bar, 
 n and m expressing the radii. ED.] 
 
SECT, vii.] STEAM ENGINES. 233 
 
 commonly made to divide the versed sine of the arc, described by the end of the 
 beam, into two equal parts, as in Plate x. (B.) l 
 Let, 
 
 b = the length of the beam from the centre of motion, A F. 
 
 c = the length of the parallel bar D G. 
 
 r = the length of the radius bar C D. 
 
 s = half the length of the stroke. 
 
 v = the versed sine of the angle described by the radius bar. 
 
 a = half the angle described by the beam. 
 
 Assume that the radius bar is horizontal when the beam is horizontal ; this cannot 
 be strictly true, except when the vibration is bisected, but is generally very nearly so. 
 Then, (b c) sin. = V 2 r v 1>* = half the chord of the arc described by the 
 end D of the radius bar. But v = c (1 cos. a) ; and substituting this value of v 
 in the equation and squaring, it becomes 
 
 (b c)" sin. a = 2 r c (1 cos. a) e 2 (1 cos. a)* ; 
 and by reduction, observing that sin. 2 a = (1 cos. a) (1 + cos. a), 
 
 b(b- 2c) . 
 r = -ig- - '- (1 + cos. a) + c, 
 
 which is a convenient formula for the radius bar when the angle is fixed; but 
 when it is not, we have 
 
 = (.- 
 
 the length of the radius bar. 
 
 If the centre C of the radius rod should be fixed by necessity or convenience 
 as in steam packet engines, let h = C G its horizontal distance from the line 
 traversed by the piston ; then c = r h, which substituted in the above, and 
 again solved for r, we get, 
 
 j ft* (1 + cos, a) i&(6 y 
 
 A + b (I + cos. a) H - A + 6 + v/6 e_J - 
 
 in which the former term expresses the parallel bar G D ; and h must be considered 
 
 1 Tredgold has adopted the former construction in Plates xi. xix. and xx. : there can be 
 no doubt, however, that almost every circumstance is in favour of the latter mode of ad- 
 justment, and that manufacturers have shown good judgment in adopting it. The bisection 
 of the vibration certainly causes the strain to change its direction, but this is of little con- 
 sequence, compared with the important advantage of rendering it of the least possible amount. 
 Another advantage in this construction is, that the beam and radius bar are parallel to the horizon 
 at half stroke ; and that the radius bar, like the beam, works equally on both sides of it. ED. 
 
 2 G 
 
234 OF THE PARTS OF [SECT. vn. 
 
 as negative in the calculation, when the radius bar is to be less than the parallel 
 bar. 
 
 This expression, which will be found to be of important use in rectifying and 
 adjusting the motions of old engines, and indeed in all cases where it may be 
 necessary or desirable to have the radius bar to work from a stated centre, was 
 first investigated in the valuable treatise on ' Mechanics for Practical Men,' by 
 Messrs. James Hann and Isaac Dodds, (Newcastle, 1833,) a work in which mathe- 
 matical theory and useful practice are combined throughout, with remarkable 
 clearness and simplicity. 
 
 If the beam from the centre of motion to the point F be one and a half times 
 the length of the stroke or b = 3 s ; then, 
 
 r = +V2 ( 3 *- 2c ) +c = 2-9142 *_(8-8c) + c . 
 
 In any case, except when the radius bar C D, and parallel bar D G are of the 
 same length, the deviation is increased by increasing the quantity of angular 
 motion of the beam. Hence, beams having short parallel bars should be limited 
 in the extent of angular movement ; indeed the motion should not in general 
 exceed 20, and thjs is very nearly the case when the distance of the end F of the 
 beam from its centre of motion A, is to the length of the stroke as 3 : 2 ; in 
 such case the radius bar may be found as follows : 
 
 493. RULE HI. To find the length of the radius bar, when the length of the 
 beam from the centre of motion is to half the length of the stroke, as 3 to 2. 
 From three times half the length of the stroke subtract twice the length of the 
 parallel bar, and multiply the difference first by the half length of the stroke, and 
 then by the number 2-914. Divide the product by the length of the parallel bar, 
 and the quotient added to the length of the parallel bar will be the length of the 
 radius bar. 
 
 Example. Let the length of the stroke be 8 feet, its half 4 feet, and let 
 the length of the parallel bar D G be 3 feet ; then 3x 4 2 x 3 = 6 ; and 
 6 x 4 x 2-914 = 69-936, which divided by 3 gives 23-312 ; add to this the 
 length of the parallel bar 3 feet, and we have 23-312 + 3 = 26-3 12 feet, for the 
 radius bar C D. 
 
 A short parallel bar is assumed in this example, to show the great length of 
 radius bar required in such a case. 
 
 The length of the links D B, G F, are from four to five-tenths of the length of 
 the stroke, depending on convenience and space ; but the longer they can be made, 
 the less oblique strain will take place during the motion. The vertical distance 
 
SECT, vii.] STEAM ENGINES. 235 
 
 between the centres of motion of the beam and the radius bar should be nearly 
 equal to the length of the links. 
 
 494. RULE iv. To find the length of the radius bar when there is no assigned 
 proportion between the length of the stroke and the radius of the beam. 
 
 First, from the length of the radius of the beam, divided by twice the length 
 of the parallel bar, subtract unity. 
 
 Secondly, Find the square root of the difference between the square of the 
 radius of the beam, and the square of the half length of the stroke, and add this 
 root to the radius of the beam. 
 
 Thirdly, Multiply together the numbers so found, and the product added to 
 the length of the parallel bar will be the length of the radius bar. l 
 
 Example. Let the radius of the beam A F be 12 feet, the length of the stroke 
 6 feet, and the length of the parallel bar D G, 5 feet. Then the first opera- 
 tion is, 
 
 12 
 
 2x5 
 
 -1 = 1-2-1 = 0-2. 
 
 By the second operation, the square of 12, less the square of 3, is 144 9 = 
 135, of which the square root is 11-62, and 12 + 11-62 = 23-62. 
 Hence, 
 
 Radius rod = 23-62 x 0-2 + 5 = 9-72 feet. 
 
 This calculation may be much simplified in the following manner. Join A G 
 meeting D B in E ; then since D B, G F, are always parallel during the 
 motion, we have AE:AG:: AB:AF, an invariable ratio ; conse- 
 quently, if E describes a straight line, G will also describe a straight line. 
 But it has been shown that E will very nearly describe a straight line 
 when the segments D E, E B of the link are inversely as the radii C D, 
 A B, or when 
 
 DE:EB::AB:CD. 
 
 But by similar triangles, DE :EB:: D G : A B .-. DG:AB::AB:CD, 
 
 and, 
 
 = . 
 
 1 Where great accuracy of motion is required, diminish in all cases the length of the stroke 
 by its one-sixth part, before it is used in any of the calculations where it is introduced. This 
 preparation will reduce the deviation from a straight line to the least possible amount. ED. 
 
236 OF THE PARTS OF [SECT. vn. 
 
 Hence this rule : 
 
 RULE v. The link divides the beam into two parts : divide the square of the 
 length of the central part by the length of the extreme part, or the length of the 
 parallel bar, and the quotient will be the length of the radius bar. 
 
 7x7 49 
 This rule applied to the preceding example gives the radius bar = g- =-4 = 
 
 9'80 feet, which differs only 0'08 from the other calculation. 
 
 When convenience requires the rod to be attached to some other point between 
 D' and B, as in Fig. 1. it is still only necessary to make the radii inversely as 
 the segments D E, E B of D B, as in the preceding proportion, viz. 
 
 DE:EB::AB:CD, 
 
 since the track of G must be similar to that of E. 
 
 And it may be observed, that as this ratio approaches to a ratio of equality, the 
 more accurate will be the motion, particularly if the beam and bars be fitted 
 parallel at half stroke ; so that the line of the piston rod may bisect the versed 
 sine of the half arc described by the end of the beam, or the horizontal distance 
 through which it vibrates. 
 
 The calculation may be differently conducted by supposing A F to be the 
 radius of the beam, G' F' to be the extreme link or connecting rod, the other 
 link D B to remain unaltered, and supposing the piston to work from the point G'. 
 For on these suppositions the point G' will obviously describe a path exactly similar 
 to that of the point G ; hence we may proceed and calculate the length of the 
 radius bar C D, according to the common rules; and this method has the 
 advantage of taking into account the length of the stroke if required. 
 
 With this arrangement, which is used for boat engines, the parallel bar 
 may be attached from the point D, and as is shown in Plate x. (B), Figs. 10 
 and 11, to which the above reasoning equally applies, the piston rod will then 
 be attached to a point G, in the connecting bar F H produced. In fact, the 
 parallel bar may evidently be fixed to the connecting bars at any distance from 
 the beam, without affecting the motion or the calculation of the parts : strength 
 and convenience are the principal considerations for its regulation. Suppose 
 Fig. 8, the parallel bar G D to be continued to m, so that its length G m may 
 be equal to the radius of the beam ; and the extremity m to be connected to 
 a bar A m equal and parallel to B D and F G. Then it is plain, that during the 
 motion the point m will oscillate over the small arc m n, centre A, of which the 
 horizontal chord m n is equal to the versed sine of the arc, described by the ex- 
 tremity of the beam. Let the combination be now divested of the beam A F, and 
 connecting bars B D, F G ; let the bar A m still work from the fixed centre A, 
 
SECT, vii.] STEAM ENGINES. 237 
 
 and suppose G m now to represent the beam ; then, inverting the figure, we shall 
 have the usual motion by means of the VIBRATING PILLAR, and hence the pre- 
 ceding rules may be applied to the calculation of this motion. 
 
 If A B be retained as a parallel bar, and B D as a connecting bar, the point E 
 may then be employed for a pump rod, as in the particular case of Fig. 9. 
 
 Figs. 12 and 13 exhibit a very simple motion, by which the number of parts 
 is diminished, and two diagrams are given to show that any length of radius bar 
 may be used for such motion, provided the link be properly apportioned. 
 
 495. When the proportions to obtain parallel motion have been found by the 
 preceding rules, the point for the air-pump rod in the link D B is easily found 
 by drawing a line from G to A, as in several figures, and then the rod must be 
 attached to the point of intersection. Its distance from the point B may be 
 calculated by the proportion, 
 
 AF:FG::AB:BE = A B x F G . 
 
 A F 
 
 Thus if A F be 12 feet, F G 3 feet, and A B 7 feet ; then 7 -^ = 175 
 
 Km 
 
 = BE. 
 
 In like manner, for any complex case, as in Woolf s engine with two cylinders, 
 the points of connexion for the piston rods must all be in the line A G, as is shown in 
 some examples in the plates ; or the point for the air-pump rod being found by the 
 rule, (art. 491.) the point for the piston rod may be ascertained by drawing a 
 line through the points A E, Fig. 4. Plate x. (A) till it cuts the line in which 
 the piston rod is to move at G ; then draw G F parallel to the link B D, and G H 
 parallel to the beam, and B F G H are the moveable points of the parallelogram, 
 and G the point to which the piston rod should be connected. The calculation 
 and construction of the parallel motion adopted for steam boat engines, Figs. 1. 
 may be conveniently solved by the methods before described. 
 
 To FIX THE RADIUS BAR. The line of the piston must be first made to 
 bisect the versed sine of the arc described by the end of the beam. Plumb the 
 piston rod when at the top extremity of its stroke ; then the radius bar being 
 moveable about D, with the other end C describe a circular arc. Bring the 
 piston down to the lowest extremity of the stroke, again plumb the piston 
 rod, and in the same manner describe another arc intersecting the former. 
 The point of intersection will evidently be the centre upon which the end 
 C of the radius bar is to move. 
 
 The length as well as position of the radius bar may be similarly ascertained by 
 geometrically finding the positions of the point D respectively at the top extremity, 
 at half stroke, and at the bottom extremity ; and then describing a circle through 
 the three points so found. 
 
238 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 If great accuracy be required, it will be better to take the positions within each 
 extremity by about one-sixth of the half stroke, the note, page 235, being pre- 
 viously followed in the calculation of the parts. 
 
 To FIND THE LENGTH OF THE CONNECTING ROD. Set the beam at half stroke, 
 that is, parallel to the horizon ; then the distance between the centre of the pin on 
 which the connecting rod is to move and the centre of the shaft, is the length of 
 the connecting rod. 
 
 In concluding this part of our subject we may further observe, that a consi- 
 derable increase of accuracy in the motion will be obtained by the adoption of the 
 expedient recommended in the note of page 230, in each calculation where the 
 length of the stroke is taken into account ; and this will be an advantage of some 
 importance in the construction of large engines. According to Rules n. and v., if 
 the beam and radius bar be adjusted parallel to the horizon at half stroke, and the 
 vibration of the beam bisected, the direction of the motion of the point G where the 
 piston is connected will be precisely vertical at half stroke, and its deviation will 
 take place, alternately right and left, towards each extremity of the stroke. By 
 Rules i. and iv. the three principal positions of the point G, viz. at the two extre- 
 mities and at half stroke, will be precisely in a vertical straight line, and its devia- 
 tion will take place, on alternate sides, between the middle and each extremity. 
 Thus in the adjoining diagram, if the beam and radius 
 bar be fixed parallel at half stroke, G G G G, Fig. 1. 
 represents the form of curve described when calculated 
 by Rule n. or v. ; but when the radius bar is properly 
 fixed as directed, the point G will coincide with the 
 line at each extremity, and at another point not ex- 
 actly but nearly at half stroke, and at half stroke the 
 bars will not in this case be exactly parallel. 
 
 Also Fig. 2. shows the curve according to Rule i. or 
 iv. ; but if the half length of the stroke be diminished 
 by its one-sixth part previously to the calculation of the rule, the position of the 
 curve described will be as represented in Fig. 3., in which the intersections 
 occur at the middle and one-sixth of the half stroke from each extremity. 
 These rules will cause the bars to be precisely parallel to the horizon at half 
 stroke, and may be fixed in this way, or, perhaps more conveniently, adjusted by 
 the method before described. 
 
 Fiffl 
 
 fiyi 
 
SECT, vii.] STEAM ENGINES. 239 
 
 OF THE STRENGTH OF THE PARTS OF STEAM ENGINES. 
 
 496. In considering this important branch of my subject, I propose to follow 
 the most simple methods I can devise, and those most readily applied in practice. 
 The foundation of the inquiry must be the power of the steam in the boiler, or 
 rather the greatest power it can possibly acquire without escaping at the safety 
 valve. Now since there is always a risk of the safety valve not being in perfect 
 order, we may in a great degree provide against such risk, by taking the load on 
 the valve at double the actual load upon it. Thus, if the load on the valve be 
 8 Ibs. on a circular inch, consider it 16 Ibs. ; and 16 Ibs. added to 1T5 Ibs., the 
 pressure of the atmosphere, will give 27'5 Ibs. for the strength of the steam, or the 
 pressure which must cause the machine to move backwards. 
 
 497. In the case of steam boats, a greater degree of surplus of strength ought 
 to be provided, because accidents at sea are attended with more serious conse- 
 quences ; and I would recommend all good machinery to be regulated by the fol- 
 lowing rule : it is, to add the load per circular inch on the safety valve to the 
 pressure of the atmosphere, and to take double this quantity as the utmost force of 
 the steam : that is, if the load on the safety valve be 8 Ibs. on a circular inch, let 
 this be added to 11*5, the pressure of atmosphere, the sum is 19*5, and double this 
 is 39 Ibs. per circular inch, for the possible pressure on the piston. 
 
 If the parts be formed to resist this pressure, then, in the case of the machinery 
 being impelled backwards by an excess of resistance, they will not be injured by it, 
 except where the momentum of a heavy fly wheel renders it necessary to provide 
 a resistance to impulsive force. 
 
 498. The datum for the resistance of the material must be the strain it will 
 bear without a permanent derangement of its parts ; and this strain is about one- 
 third of its cohesive force. 1 
 
 499. In respect to the effect of the friction of an engine, it ought to be added 
 to the power in estimating the strength ; because when the resistance is capable of 
 reversing the motion of the engine, it also must have to overcome the friction of 
 the intermediate parts ; but when the force of the steam is considered double its 
 whole pressure, as limited by the safety valve, the friction may be neglected. 
 
 500. The stress on any of the moving parts of a steam engine may be most 
 easily found by comparing the number of revolutions or vibrations it makes for 
 each double stroke of the piston : the stress is inversely as the number of revo- 
 lutions or vibrations multiplied by the diameter of the circle, or the chord of the 
 arc described by the point where the force acts : thus if a wheel 4 feet in diameter 
 makes three revolutions while the piston makes one stroke, and the length of the 
 
 1 See Practical Essay on the Strength of Cast Iron, &c. sect. v. Second edition. 
 
240 OF THE PARTS OF [SECT. vn. 
 
 stroke be 5 feet ; then 4x3:5:: pressure on the piston : stress on the teeth of 
 the wheel, equal five-twelfths of the pressure on the piston. The stress thus found 
 is to be considered as a weight applied at the point to which the motion belongs. 
 
 In like manner, the period of the motion of the working point of any machine 
 may be considered unity ; and by comparing the chords of the arcs described in 
 the same time, and the revolutions in the same period, the stress may be found in 
 terms of the force required to overcome the resistance at the working point. 
 
 501. The method to be followed in determining the strength, is, when there is 
 only one working point to proceed from the engine, taking its power as the measure 
 of the stress at every point, and to make the part so that it shall be sufficiently 
 strong to bear a reversion of the motion ; but if the power of the engine be divided 
 among various trains of machinery, then its power should be the measure of 
 strength only to the point where the trains branch, and for each separate train the 
 greatest possible stress at the working point should be made the measure of the 
 strength of its parts. 
 
 502. The advantage of reasoning by general formulae is so great, that it will 
 be adopted, and the rules as they arise given in words at length with examples. 
 
 Let, 
 
 D = the diameter of the piston in inches, 
 
 L = the length of its stroke in feet, 
 
 P = the double of the whole elastic force of the steam in the boiler, in 
 
 Ibs. per circular inch. 
 
 / = the length from the centre of motion to the centre of stress in feet, 
 a = the depth or diameter, 
 b = the breadth in inches ; 
 
 f = the cohesive force of a square inch at the point of alteration, and 
 R = the radius of any wheel. 
 Then the force on the piston is D 2 P in Ibs. 
 
 503. STRENGTH OF RODS WHERE THE STRAIN is WHOLLY TENSILE. There is in 
 every case of this kind a possibility of the strain deviating one-sixth of the diameter 
 of the rod from the axis, and when it does so the resistance is, 
 
 = : 
 
 consequently, D* P = ^-, or a = D 
 For malleable iron /= 17800, consequently, 
 
 VT: 
 
 This rule applies to rods subject to a tensile strain only : such are piston rods 
 of single acting engines ; pump rods. 
 
SECT. VII .] STEAM ENGINES. 241 
 
 For head links it becomes, 
 
 _ ,/~p~= b t = the breadth multiplied by the thickness in inches. 
 
 o4 
 
 504. RULE. Multiply the diameter of the steam piston in inches, by the 
 square root of twice the elastic force of the steam in the boiler, in Ibs. per circular 
 inch, and the product divided by 84 is the diameter of the rod in inches. 
 
 Example. If the force of the steam be 16 Ibs. per circular inch, and the diameter 
 of the cylinder 54 inches, then the square root of 32 is 5'657, and 
 
 54 X ftT - = 3 ' 6 mcnes > the diameter required. 
 
 OTT 
 
 For the atmospheric pressure it is one-sixteenth of the diameter. 
 
 505. OF THE STRENGTH OF RODS ALTERNATELY EXTENDED AND COMPRESSED. In 
 
 the compression of rods the force increases with the flexure ; but if the length never 
 exceed about thirty-six times the diameter, its error will be very small to assume that 
 degree of flexure ; and by taking in addition the greatest possible deviation, from 
 misfitting, which is half the diameter of the rod, 1 with this simplification we have 
 
 D-P =nearl, or. = 
 
 For cast iron/ = 15300, and a = -^ </~T>. 
 
 For malleable iron /= 17800, and a = ^ 
 
 For tempered steel f= 45000, and a = -70" 
 
 This rule applies to piston rods of double engines, parallel motion rods, air pump 
 and force pump rods, and the like ; and if P be increased in the ratio of the radius 
 to the sine of the greatest angle a connecting rod makes with the direction, it 
 applies to connecting rods. 
 
 506. RULE. Multiply the diameter of the piston in inches by the square root 
 of twice the pressure of the steam in Ibs. on a circular inch, and divide the 
 product by, 
 
 42 for cast iron, 
 45 wrought iron, 
 72 tempered steel ; 
 the quotient will be the diameter in inches. 
 
 Example 1. The force of the steam being 16 Ibs. per circular inch, and the 
 diameter of the piston 80 inches, that of the piston rod should be, for wrought iron, 
 
 80 x */~m 
 jg - = 10-06 inches. 
 
 Example 2. The force of the steam being 4 atmospheres = 46 Ibs. per circular 
 
 1 Practical Essay on Cast Iron, art. 246. 
 2 H 
 
242 OF THE PARTS OF [SECT. vn. 
 
 inch, and the diameter of the cylinder 1 1 inches, the diameter of a piston rod of 
 wrought iron should be, 
 
 11 x v/92 = 2-34 inches. 
 45 
 
 If the rod be of steel, then the diameter should be, 
 
 *.^ = 1'46 inches. 
 7$ 
 
 Example 3. The force of the steam being 16 Ibs. per circular inch, and the 
 diameter of the piston 24 inches, the diameter of a cast iron connecting rod should 
 not be less than, 
 
 24 x /32 j 00 . , 
 T^ = 3'23 inches. 
 
 430 
 
 The middle is commonly expanded into a form of greater lateral strength ; and 
 in all cases should be of larger diameter than the ends, in the proportion of about 
 one-tenth. 
 
 507. For air pump rods, the pressure of the atmosphere and the diameter of 
 the pump must be taken, instead of the force of the steam and the diameter of the 
 cylinder. Parallel motion rods should be three-sevenths of the diameter of the 
 piston rod, except in the case of that for steam boat engines, when there is lateral 
 stress. Connecting rods for giving motion from the cross-head to beams, or to 
 cranks, should be seven-tenths of the diameter of the piston rod. 
 
 508. OF THE STRENGTH OF ARMS OF BEAMS, CRANKS, &c. It may be assumed as 
 a principle, that a beam of uniform thickness should not be of less thickness than one- 
 sixteenth of its depth, otherwise it is liable to overturn ; besides, in cast iron it is 
 not safe to trust the strength of a casting, which is not a sixteenth part of its depth 
 in thickness. Now for the case, when the velocity is the same as that of the piston 
 D 2 P / = 212 b a*, 1 and when 16 b = a, and 12 / = n D, it becomes for cast iron 
 
 P n 
 
 That is, when D = the diameter of the piston in inches, and d = the depth of the 
 beam in inches, the breadth one-sixteenth of that depth, n the number of times the 
 diameter is contained in the length from the centre of motion to the point where 
 the force is applied, and P double the force of the steam in the boiler, in Ibs. per 
 circular inch. The depth at the end should be half the depth at the centre of 
 motion, and the breadth uniform ; and an access of strength may be given by 
 forming the section, so as to increase the thickness at the edges to one-ninth of the 
 depth, or till the parts between be reduced to the thickness of one-sixteenth of their 
 width. 
 
 1 Practical Essay on Strength of Iron, art. 116. 
 
SECT, vii.] STEAM ENGINES. 243 
 
 For wrought iron use 240 instead of 212, and for wood 64. 
 
 509. Example 1. BEAMS. An engine beam is 3 times the diameter of the 
 cylinder, from the centre to the point where the piston rod acts on it, the force of 
 the steam in the boiler is 14 Ibs. per circular inch, its double is 28, and the 
 diameter of the piston is 24 inches. In this case, 
 
 = <"> 
 
 or a = 19-4 inches, and the mean breadth is 1-21 inches, and the breadth at top 
 and bottom 2 - 16 inches. 
 
 If of wrought iron with the same proportions, -78 D = a, and the breadth = one- 
 sixteenth of the depth. . 
 
 Of wood with the same proportions, '78 D = a, but the breadth = one-fourth of 
 the depth. 
 
 510. CRANKS. A crank should embrace a shaft, so that its depth at the shaft 
 should be 1-5 times the diameter of the shaft; hence, if S D be the diameter of 
 the shaft, the depth of the crank must be 1'5 S D, but since (art. 508.) D 2 P / = 
 
 212 b a*, we have 
 
 Pi _ PI 
 b ~ 2-25 S* x 212 "" 477 S* 
 
 Example 2. A crank shaft is equal in diameter to '31 times the diameter of 
 the cylinder, and the force of the steam in the boiler being 14 Ibs. per circular 
 inch, or P = 28 Ibs., required the breadth of the crank at the shaft, its radius 
 being 2'5 feet. In this case, 
 
 and as / = 2'5 feet, it is -6 x 2-5 = 1-5 inches, and the depth is 1-5 x -31 x 30 
 = 14 inches. 
 
 511. WHEEL ARMS. The arms of wheels may be considered in respect to 
 strength only ; and if the rim be of equal strength, then a wheel should have six 
 arms in all cases, when it is of sufficient magnitude to require its strength to be 
 found by rule. With this condition we have 2 D 2 P R = 212 x 6 b a z , or 
 D* P R = 3 x 212 b a*. If we consider the arms to be one-third of the breadth of 
 the wheel, and allow, as excess of strength, that which is added to give it lateral 
 
 strength, then 
 
 D'PR 2 _ ^/ P R 
 
 212 fl2 ' 212T 
 
 When R the radius = 1, and P = 28 = twice the force of the steam in the 
 
 boiler, then 
 
 D 
 
 Q -^- 
 
 as inserted along with the proportions of teeth in the table, art. 513. 
 
'244 
 
 OF THE PARTS OF 
 
 [SECT. vn. 
 
 512. The teeth of wheels will be most conveniently given in a tabular form, 
 with a correction for curvature in determining their breadth, which is not in- 
 cluded in the formula in my treatise on cast iron. The first column shows the 
 stress on the teeth in Ibs. ; the second, the horse power nearly equivalent, 
 when the velocity is three feet per second ; the third column, the pitch ; the fourth, 
 the thickness ; and the fifth, the breadth of the teeth : the sixth column shows the 
 greatest depth of the middle of the arm at the base in the direction of the wheels' 
 motion, when that part is one-third of the breadth of the teeth, and the radius is 
 one foot ; hence, being multiplied by the square root of any other radius in feet, 
 it will be the depth for it ; the seventh column shows the breadth of the rib which 
 strengthens the arm ; and the eighth, the diameter of a cylinder, when the force 
 of the steam is thirty-five inches of mercury in the boiler, and the teeth move at 
 the same velocity as the piston. For any other velocity the stress will be found 
 by art. 500. 
 
 513. A TABLE OF THE STRENGTH, &c. OF TEETH AND ARMS 
 
 FOR WHEEL WORK. 
 
 
 
 Teeth of Wheels. 
 
 Wheel with 6 arms. 
 
 
 
 
 
 
 
 
 
 Diameter of 
 the cylinder for 
 
 Stress 
 in Ibs. 
 
 Horse power 
 at 3 feet per 
 second. 
 
 Pitch 
 in inches. 
 
 Thickness 
 in inches. 
 
 Breadth 
 in inches. 
 
 Depth of arm 
 for 1 foot ra- 
 dius, in inches. 
 
 Breadth of rib 
 in inches. 
 
 low pressure 
 steam, teeth 
 moving at the 
 
 
 
 
 
 
 
 
 same velocity 
 
 
 
 
 
 
 
 
 as the piston, 
 
 
 
 
 
 
 
 
 in inches. 
 
 22 
 
 0-25 
 
 0-25 
 
 0-119 
 
 0-75 
 
 0-87 
 
 0-25 
 
 2-0 
 
 85 
 
 0-5 
 
 0-50 
 
 0-238 
 
 1-25 
 
 1-24 
 
 0-42 
 
 3-7 
 
 191 
 
 1 
 
 0-75 
 
 0-357 
 
 1-75 
 
 1-67 
 
 0-60 
 
 5-5 
 
 337 
 
 2 
 
 1-00 
 
 0-475 
 
 2-50 
 
 1-76 
 
 0-80 
 
 7-4 
 
 520 
 
 3 
 
 1-25 
 
 0-590 
 
 3-00 
 
 2-00 
 
 1-00 
 
 9-2 
 
 800 
 
 4 
 
 1-50 
 
 0-730 
 
 4-00 
 
 2-20 
 
 1-30 
 
 11-3 
 
 1040 
 
 5 
 
 1-75 
 
 0-835 
 
 4-25 
 
 2-40 
 
 1-40 
 
 12-9 
 
 1370 
 
 7 
 
 2-00 
 
 0-955 
 
 5-00 
 
 2-50 
 
 1-70 
 
 14-8 
 
 1720 
 
 9 
 
 2-25 
 
 1-070 
 
 5-50 
 
 2-70 1-80 
 
 16-6 
 
 2100 
 
 10-5 
 
 2-50 
 
 1-190 
 
 6-00 
 
 2-85 
 
 2-00 
 
 18-4 
 
 2560 
 
 13 
 
 2-75 
 
 1-310 
 
 6-75 
 
 3-00 
 
 2-20 
 
 20-3 
 
 3000 
 
 15 
 
 3-00 
 
 1-430 
 
 7-25 
 
 3-20 
 
 2-40 
 
 22-2 
 
 3600 
 
 18 
 
 3-25 
 
 1-550 
 
 8-00 
 
 3-30 
 
 2-60 
 
 24-0 
 
 4150 
 
 21 
 
 3-50 
 
 1-670 
 
 8-50 
 
 3-40 
 
 2-80 
 
 26-0 
 
 4800 
 
 24 
 
 3-75 
 
 1-790 
 
 9-25 
 
 3-50 
 
 2-90 
 
 28-0 
 
 5700 
 
 27-5 
 
 4-00 
 
 1-910 
 
 10-25 3-60 
 
 3-40 
 
 29-5 
 
 6300 
 
 31-5 
 
 4-25 
 
 2-025 
 
 10-50 
 
 3-70 
 
 3-50 
 
 31-5 
 
 6900 
 
 34-5 
 
 4-50 
 
 2-150 
 
 11-00 
 
 3-80 3-70 
 
 33-3 
 
 7700 
 
 38-5 
 
 4-75 
 
 2-270 
 
 11-75 
 
 3-90 
 
 3-90 
 
 35-0 
 
 8500 
 
 42-5 
 
 5-00 
 
 2-390 
 
 12-25 
 
 4-00 
 
 4-00 
 
 37-0 
 
 
 
 
 i 
 
 
 
 
SECT, vii.] STEAM ENGINES. 245 
 
 514. The strength of beam gudgeons may be determined by the rule, 
 P D 2 = 854 a". 1 
 It reduces to, 
 
 30 
 
 and the length should not be less than eight-tenths of the diameter. For low 
 pressure steam, twice its force is 28 Ibs. per circular inch, or P = 28, and 
 therefore in that case one-sixth of the diameter of the cylinder should be that of 
 the gudgeon. For pins for connecting rods where the bearing is double, the 
 stress is reduced one-half, and 
 
 Or in the case of low pressure steam, 
 
 D 
 a=: 8- 
 
 515. THE STRENGTH OF SHAFTS. The shafts are supposed to be supported so as 
 to render the lateral stress as small as possible, then the resistance to twisting 
 alone has to be considered, and as no part of the shaft should be less than the 
 bearings or journals, therefore allowing one-sixth for wear R D z P = 960 a 3 ; * 
 when the shaft revolves in the same time, the piston makes a double stroke, and 
 if the radius R = n D, we have 
 
 a = 
 
 \960 
 for the diameter in inches. 
 
 If it revolve N times while the piston makes a double stroke, then (art. 500.) 
 we have, 
 
 * P 
 
 For wrought iron the divisor should be 1080 instead of 960. 
 
 Example. What should be the diameter of a shaft of cast iron, when the crank 
 arm is equal to the diameter of the cylinder, double the force of the steam in the 
 boiler 28 Ibs. per circular inch, the piston 30 inches in diameter, and one revolu- 
 tion of the shaft made in the same time as a double stroke ? In this case n and N 
 are each = 1, and, 
 
 or a = 0-31 x 30 = 9-3 inches. 
 
 1 Essay on Strength of Iron, art. 139. 
 
 2 Essay on Strength of Iron, art. 224. R being in this case in inches. 
 
246 OF THE PARTS OF [SECT. vn. 
 
 OF THE STRENGTH OF PIPES AND WORKING CYLINDERS. 
 
 516. The thickness for pipes and cylinders of solid metal is more frequently 
 determined by the condition, that the castings may be sound and perfect, than by 
 a regard to strength ; yet it is necessary to show the proportions essential for 
 strength, that a mistake in this respect may not occur. 
 
 The data required are the tensile strain a square inch of the metal will bear 
 without permanent alteration at the proposed temperature, the pressure of the 
 steam on a circular inch including such allowance as is proper for the risk of 
 increase, and the diameter of the cylinder. I advise to take double the whole force 
 of the steam when it escapes at the safety valve of the boiler. 
 
 We may safely consider the cylinder to be of equal resistance throughout its 
 length ; and hence, if we take the stress upon an inch of that length, that stress 
 will be equal to the diameter in inches, multiplied by the greatest possible force on 
 a square inch, and the resistance will be twice the thickness of the cylinder, by 
 one-fourth of the limit of tensile strain of the metal, the tension being considered 
 to be unequal on the resisting part. Thus we have the following rule. 
 
 517. RULE. For the thickness of solid metal, pipes, or cylinders to bear a 
 given stress, the whole being of an equal temperature : 
 
 Multiply 2-54 times the internal diameter of the cylinder, by the greatest 
 force of steam on a circular inch ; divide by the tensile force the metal will bear 
 without permanent alteration, the result is the thickness in inches. 
 
 Example. To determine the thickness of a cast iron cylinder, 60 inches dia- 
 meter, for a pressure not exceeding 3'2 Ibs. per circular inch, in addition to the 
 atmospheric pressure. In this case twice the force is 30 Ibs. on the circular inch, 
 and the resistance of cast iron is 15,000 Ibs. per square inch ; hence, 
 
 *- 0-305 inches. 
 
 518. Were there the direct force alone to consider, we see that a very thin 
 cylinder or pipe is sufficient, but the pressure is often aided by a powerful strain 
 from unequal expansion. If e. be the extension the metal will bear without 
 alteration, and t its thickness, a being the diameter of the pipe, we have 
 
 t 
 _ 
 
 the greatest quantity which the expansion of one side of the pipe should exceed the 
 other, = h t , when h = the excess of heat, and e = the expansion for one degree. 
 
 In cast iron, e = j^ , and = ie-2000 ' h ence > 
 
SECT, vii.] STEAM ENGINES. 247 
 
 270 a 
 
 h= 7- ,. 
 
 the increase which would strain the metal as far as it would bear without per- 
 manent derangement. 
 
 519. Here we suppose the heat to be confined to a single point; but generally, 
 or rather in all cases, a considerable portion of surface is directly affected by the 
 heat : in this case a near approximation will be to double the effect of expansion, 
 or make, 
 
 In the case of pipes and cylinders, the greatest difference of temperature will 
 
 never exceed 300 ; and then, 
 
 300 t 2'2 t 
 the force of cohesion the cylinder loses by unequal expansion = j^g-^ = -^ . 
 
 If this be added to the former, we derive, 
 
 2-54 a P 2-2 1 _ 
 
 ' ' " 
 
 / a \ 
 \a-2-2j ' 
 
 _ 
 15000 a ' "6000 
 
 The effect of irregular expansion is sensible only in small cylinders : in the case 
 of a cylinder of 60 inches diameter we found its thickness -305 inches, and it became 
 only '315 when corrected for expansion. 
 
 For pipes of less than 5 inches diameter, 
 
 t __ ! _ _. 
 - 6000 (1 - 0-116 a) 
 
 For working cylinders both wear and other causes of pressure exist ; the latter 
 will require at least that the thickness should be double, and for wear half an inch 
 may be added, as about the proper quantity of allowance. 
 
 520. RULE. For the thickness of a working cylinder. Multiply four times 
 the elastic force of the steam in Ibs. per circular inch by the diameter in inches, 
 and divide by 6000. The result multiplied by the quotient arising from dividing 
 the diameter by the diameter less 2'2, is the thickness for strength, to which half 
 an inch may be added for wear. 
 
 Example 1 . A cylinder 24 inches in diameter is to be made of cast iron, for 
 steam not exceeding 3^ Ibs. per circular inch on the safety valve, or ITS + 3'5 = 15 
 elastice force, required its thickness. 
 
 We have = '24 ; and l- x -24 = -264 ; 
 
 which, added to half an inch, is '764 inches, the thickness required. 
 
 Example 2. A cast iron cylinder for a high pressure engine being 9 inches 
 in diameter, and for steam 50 Ibs. per circular inch elastic force, required the 
 thickness. 
 
248 OF THE PARTS OF [SECT. vit. 
 
 T ,1 . 4 x 50 x 9 9 
 
 In this case, 6000~~ = ' an ^ 9 _ 3.3 x '3 = '4 ; 
 
 to which adding '5 for wear, it is 0'9 inches. 
 
 521. Of the strength of flat plates to bear the pressure of steam, or other elastic 
 
 fluids. The strength of a plate is limited by the curvature it takes by the strain ; 
 
 and when the length and breadth are equal, the resistance is the same in both 
 
 directions ; but in any other case the two flexures do not correspond, and the 
 
 resistance depends chiefly on the curvature in the shortest direction of support. 
 
 From the laws of deflexion it will be Z 2 : J* :: 1 : -^, the resistance in the Ion- 
 
 7 2 
 
 gitudinal direction ; and 1 + ^ , multiplied by the resistance in the shorter 
 
 direction, gives the whole resistance. 
 
 When a plate is fixed at the edges, the flexure lessens the quantity of strain on 
 the resisting part, but only in a small degree ; and in bending to the new position, 
 the inner part of the matter must be partially compressed, and the resistance to 
 tension will extend only to a little more than half the thickness, and varies as the 
 distance from the neutral line : hence it is only one-fourth oftf, when one-fourth of 
 the thickness is an inch, t being the whole thickness, and / the cohesive force of a 
 square inch ; and allowing for riveted plates, 
 
 t f 3 t f 
 ~4~ x "3" = ~g~ = the resistance in one direction ; 
 
 and 1 1 + ^ J j = t h e wno i e resistance. 
 
 The stress is as the force on a given portion of the curve, resolved into its 
 tendency to split the material. If z be a part of the curve, and r the radius of 
 curvature, 1 we have z : r : : 1-27 p z : 1-27 p r, the stress, p being the pressure 
 
 1 But the curvature is limited by the stretching and bending in the shorter direction ; sup- 
 pose it to be wholly by bending, and we have, 
 
 e : 1 :: "a : r = ^ ; 
 
 therefore in this case, 
 
 / 
 
 T" f 
 
 MO*}/ 
 
 Hence we find, that the resistance of a plate is quite independent of its thickness when it bends 
 
SECT, vii.] STEAM ENGINES. 249 
 
 on a circular inch ; hence, 
 
 '"- 
 
 7-62 
 
 or t = 
 
 '('+*) 
 
 In square or circular plates it becomes 
 
 3-81 p r 
 
 t tm ~; 
 
 For wrought iron, O006 r = t when low pressure steam is to be confined, and 
 both r and t are in inches ; when the length is great compared with the breadth, 
 or the bounding edges are not properly confined in one direction, double the result. 
 
 OF THE EXCESS OF STRENGTH TO RENDER BOILERS SAFE. 
 
 522. The pressure tending to separate a boiler is about proportional to the 
 load on the safety valve ; that to crush it together is equal to the pressure of the 
 atmosphere. In the latter case it cannot exceed that pressure ; in the former a 
 considerable excess may take place if any derangement happens to the valves ; and 
 it is to provide against accident, in the event of the valves being out of order, that 
 an excess of strength in the boiler is necessary. 
 
 It is clearly a matter of opinion, founded on the experience of past accidents, as 
 to the degree of excess required, and it has been almost universally allowed, that 
 three times the pressure on the valve in the working state should be borne by the 
 boiler without injury. 
 
 This degree of excess of power seems to be fully sufficient for the ordinary low 
 pressure steam boilers ; indeed, I should think twice the pressure a proper allow- 
 in this manner, but that the pressure is limited. 
 
 For wrought iron, / = 17800, and e = T^J^ 5 hence ^^y = 3'33 ; and therefore we have, 
 
 3-33 
 
 for the greatest stress in Ibs. on a circular inch that a plate will bear. 
 
 When the plate is either square or circular, it becomes 6-85 Ibs. per circular inch, = 8-5 Ibs. per 
 square inch. When of other proportions, as in the equation, and when the length is very consi- 
 derable, it becomes simply 3-33 Ibs. per circular inch, or 4-25 Ibs. per square inch. 
 
 Copper bears about the same strain. 
 
 This is important, as it shows us that flat surfaces cannot be used with safety to confine high 
 pressure steam. 
 
 2 i 
 
250 OF THE PARTS OF [SECT. VH. 
 
 ance, and were it always provided, there would be little chance of accident if the 
 valves be properly constructed and attended to. 
 
 It becomes insufficient in high pressure boilers, because a common low pressure 
 boiler contains about ten times the volume of steam required for one stroke of the 
 engine, consequently the time of twenty strokes must elapse before the density of 
 the steam could accumulate to three times its working density, supposing the 
 engine to be stopped, and the valve out of order ; but if the boiler contains only as 
 much steam as is required for one stroke, the force will be increased to three times 
 in the time the engine would have made two strokes. This rapidity of the increase 
 of force does not leave the necessary time to examine, nor even to open the valves 
 in this extreme case, and the hazard must be greater in consequence. In all cases 
 the time of accumulating power should not be shorter than it is in the common 
 boiler. Besides, in working an engine where the excess of force increases so fast, 
 the loss of steam would be considerable from any variation of the heat of the fire, 
 even were the valve to act properly, and therefore there is a temptation to load the 
 valve beyond its regular weight. To render the security on the stoppage of the 
 engine equal in all cases, the excess of strength should be inversely as the space 
 allowed for steam. 
 
 It is still more important to consider the subject, in relation to the danger arising 
 from unequal action of the fire ; and for this the excess of strength should be 
 inversely as the contents of the boiler expressed in units of the power. 
 
 Thus, taking the horse power as the measure, if one boiler contains twenty cubic 
 feet for each horse power, and another only ten, the boiler with only ten feet of 
 space should be of twice the strength ; for equal powers require equal fires, and the 
 effect of excess of fire in raising the temperature and force of the steam is inversely 
 as the quantity of matter acted upon ; hence the risk of the dangerous increase of 
 strength is inversely as the quantity of water and steam the boiler contains. 
 
 523. The proportion for excess of strength I shall therefore consider to be two 
 times that which is proper for the working pressure when the boiler contains twenty 
 cubic feet for each horse power ; and containing any other quantity as n cubic feet 
 per horse power, it will be 
 
 40 
 
 . : 20 :: 2 : - . 
 
 The effect of unequal expansion, of improper form and flexure, and of wear, 
 must be included in the calculation of the strength ; for these are not allowances 
 for risk, but actually necessary for security. 
 
 Boilers may fail from strains produced by other causes besides the force of the 
 steam, and these may be noticed to guard against the circumstance which produces 
 them. 
 
SECT, vii.] STEAM ENGINES. 251 
 
 If a boiler flue rise from the fire, and then descend again before it enters the 
 chimney, it will in particular states of the fire be liable to fill with inflammable 
 gas, which takes fire and explodes. The effect of such an explosion in the flues of 
 a boiler must cause an impulsive strain on the boiler, under which it may fail. 
 
 The danger may be avoided by making the flues lead off to the chimney without 
 depression, and constructing the damper so that it cannot be perfectly closed ; and 
 it should either rise so as to close the upper part of the aperture last, or move 
 horizontally. 
 
 Hydrogen gas may be, and frequently is, formed in steam boilers, through the 
 water being in contact with a part of the boiler which is red hot ; and it seems to 
 be regularly produced during the formation of steam at very high temperatures : 
 and though it appears to me that it would not add to the risk of an explosion 
 happening, it undoubtedly would render it more destructive if it should take 
 place. 1 
 
 BOILERS FORMED OF PLATES. 
 
 524. Having determined the resistance of plates of any curvature, it is easy 
 to apply these rules to rectangular boilers ; remarking, that it is indifferent whe- 
 ther the curve be convex or concave to the pressure, provided it have either abut- 
 ments as an arch, or forms a complete circle. I doubt the efficacy of the usual 
 abutments, and I think the fact that boilers fail round the seats is greatly owing to 
 the strain and motion of the parts at every change of force or temperature. 
 
 A rectangular boiler may be considered as a cylinder, taking the greatest dia- 
 gonal line of its section for the diameter ; and for strength the thickness will be, 
 (art. 521.) 
 
 3-81 ap 
 
 t '^ = - ' ^ . 
 
 For wrought iron, f= 17800 Ibs. 
 
 t = ap 
 
 4660' 
 
 1 In a letter I received from Mr. W. Williams, of Cyrfartha Iron Works, he attributes the 
 destructive effects of an accident in that neighbourhood to an accumulation of hydrogen inflaming 
 when the boiler burst. The boiler was constructed of the old spherical form, twenty feet in dia- 
 meter ; the thickness of the plates when new was, top plates a full quarter of an inch, bottom 
 plates half an inch ; load on the safety valve 7 Ibs. per circular inch. Many lives were lost 
 by this explosion ; and the boiler was thrown to a distance of 1 50 feet, to a place 30 feet above the 
 level of its former seat. The upper plates were undoubtedly too weak. 
 
252 OF THE PARTS OF [SECT. vn. 
 
 The excess of strength for risk being - (see art. 523.), we have 
 
 t= ap 
 
 120 n 
 
 For copper, f= 11000 and 
 
 525. RULE for the upper plates of long rectangular and cylindric boilers. 
 Multiply the load in Ibs. per circular inch on the safety valve, by the greatest dia- 
 gonal of the section of the boiler in inches, and for wrought iron divide the product 
 by 120 times the cubic contents of the boiler per horse power ; the result is the 
 thickness in inches. For capper, divide by 72 instead of 120. 
 
 The bottom plates should be as much thicker as will compensate for wear ; 
 usually twice the thickness of the top ones. 
 
 Example 1. In a rectangular boiler the greatest diagonal being 8 feet, and 
 consequently equivalent to a radius of curvature of 96 inches, the load on the valve 
 3^ Ibs. per circular inch, and the space for steam for each horse power 16 feet ; 
 required the thickness for the top plates of wrought iron. 
 
 In this case, 
 
 = ^'175 inches, for the top plates. 
 
 ~16 
 
 The bottom plates should not be less than 2 x -175 = -35 inches. 
 This nearly corresponds with the practice of the best makers. 
 
 526. Example 2. If the boiler be a long cylinder, of which the diameter is 
 60 inches, and the pressure on the safety valve 30 Ibs., the boiler containing 
 20 feet for each horse power of the engine ; then, 
 
 30 x 60 
 
 120^20 = ' 75 mches - 
 
 In practice boilers of this kind are made barely equivalent to the working 
 pressure : can we wonder that they sometimes fail ? 
 
 The same rule applies to internal flues, with addition for the effect of the fire. 
 
 527. OF SPHERICAL BOILERS. A spherical boiler has its dimensions equal, 
 and consequently (art. 521.) its thickness should be, 
 
 _ 3-81 ap 
 
 t - -^j . 
 
 Hence for wrought iron, t = 
 
 and for copper, t = ~~ . 
 RULE for spherical boilers. Multiply the diameter in inches by the pressure on 
 
SECT, vii.] STEAM ENGINES. 253 
 
 the valve in Ibs. per circular inch, and divide by 240 times the cubic contents of 
 boiler for each horse power for malleable iron, or for copper by 144 times instead 
 of 240. 
 
 Example. A boiler is of a spherical form, 20 feet in diameter, with 20 cubic 
 feet to a horse power, and the load on the valve 7 Ibs. per circular inch, what 
 should be its thickness ? The diameter is 240 inches, therefore 
 
 7 x 240 Q _ . , 
 2401T20 =: >35 inches > 
 
 or a little less than three-eighths of an inch. (See note to art. 523.) 
 
 When cylindric boilers have spherical ends, the radius of curvature may be 
 equal to the diameter of the cylinder, and they will be equally strong with the 
 same thickness of metal : flat segments are more convenient in construction, and 
 occupy less space to get the same effect. 
 
 CAST IRON BOILERS. 
 
 528. The preceding rules apply only to boilers of ductile metals : in forming 
 one for brittle ones, the effect of unequal expansion must be considered. For 
 cylindric boilers, 
 
 2-54 a p 40 an . _ n _ , _~ N 
 
 * = --J-* x - = j5^, (art. 517 and 523.) 
 
 and the mode of allowing for expansion was shown in treating of cylinders, 
 art. 519. 
 
 In boilers composed of solid tubes it is possible that in a tube having a diameter 
 of 8 inches or more, the excess of temperature on one of its sides may be 1000, 
 
 and then - - = the loss of force, indicating that in those circumstances a tube 
 
 would ultimately burst, of whatever strength it were made, if 7 - 4 t were made 
 greater than a ; for whenever the quotient is unity, or more than unity, the unequal 
 expansion alone is beyond the power of the material. 
 
 This explains the known fact, that such tubes break without apparent defect, or 
 the use of steam stronger than usual. 
 
 From these principles we derive the following for cast iron boilers : a being 
 
 the diameter, and p the elastic force of the steam, jg^ = the thickness for 
 
 strength ; which, added to a thickness equivalent to the loss of force it may 
 sustain by unequal expansion, is, for boiler cylinders above 8 inches diameter, 
 
 a p 7-4 t 
 
 + 5 whence ' 
 
 t= a<t P 
 
 150 n (a - 7-4) ' 
 
254 OF THE PARTS OF [SECT. vn. 
 
 For boiler tubes, or cylinders under 8 inches iu diameter, 
 
 t 
 
 ~ 
 
 _ 
 
 150 n (1 - 0-116 a) ' 
 
 In either case there is a risk of failure when the diameter is less than 7 - 4 inches 
 in the first, and when O116 times the diameter is greater than one in the second 
 case. If the thickness be much more than the rule gives, the risk from unequal 
 expansion increases ; if it be less, the joint effect of pressure and inequality may 
 cause failure. 
 
 529. RULE for the strength of cast iron tubes exceeding 8 inches in dia- 
 meter. Multiply the square of the diameter by the pressure on the safety valve in 
 Ibs. on a circular inch, and divide the product by 150 times the cubic feet of space 
 in the boiler per horse power, multiplied by the difference between the diameter 
 and 7 '4 inches ; the result is the thickness in inches, which should be increased for 
 wear and tear in proportion to the degree of durability required. 
 
 Example 1. The internal diameter of the tube being 10 inches, the cubic feet 
 of boiler per horse power 10, and the load on the valve 36 Ibs. on the circular inch, 
 what should be its thickness ? In this case, 
 
 10 x 10 x 36_ _ , 
 
 1501TLO (HT-T7-4) " 
 
 Example 2. The internal diameter of a cast iron cylinder for a boiler being 
 3 feet, and the force of the steam to be confined to 5 atmospheres, 58 Ibs. per 
 circular inch on the valve, what should be its thickness, the space of boiler for 
 each horse power being 16 feet? In this case, 
 
 36 x 36 x 58 
 
 150 x 16 x (36 - 7-4) 
 
 = I'l inches. 
 
 OF JOINING PIPES AND OTHER PARTS OF ENGINES. 
 
 530. Joints are generally connected by screw bolts passing through flanches ; 
 between these flanches an elastic material of a durable nature is inserted, or a 
 compound called a cement, which unites and forms one mass with the joined 
 surfaces. 
 
 Iron cement is the most valuable of the latter kind ; it may be compounded as 
 follows : To two ounces of sal-ammoniac, add one ounce of flowers of sulphur, and 
 sixteen ounces of clean cast iron filings or borings ; mix all well together by 
 rubbing them in a mortar, and keep the powder dry. When the cement is wanted 
 for use, take one part of the above powder and twenty parts of clean iron borings 
 or filings, and blend them intimately by grinding them in a mortar. Wet the 
 compound with water, and, when brought to a convenient consistence, apply it to 
 
SECT, vn.] STEAM ENGINES. 255 
 
 the joints and then screw them together. A considerable degree of action and 
 reaction takes place among the ingredients, and between them and the iron sur- 
 faces, which causes the whole to unite as one mass ; the surfaces of the flanches 
 become joined by a species of pyrites, all the parts of which cohere strongly 
 together. Mr. Watt found that the cement is improved by adding some fine 
 sand from the grindstone trough. 
 
 531. For some purposes it is more convenient to join the parts with white lead 
 paint, mixed with a portion of red lead to a proper consistence, and applied on 
 each side of a piece of thick canvas, flannel, or plaited hemp, previously shaped to 
 fit the parts, and then interposed between them before they are screwed together : 
 it makes a close and durable joint, and is generally used for those joints which 
 have occasionally to be opened, and for those which must be separated repeatedly 
 before a proper adjustment is obtained ; and when this is the case, the white lead 
 ought to be predominant in the mixture, as it dries much slower than the red. 
 
 532. There is another cement often used by coppersmiths, to lay over the 
 rivets and edges of the sheets of copper in large boilers, to serve as an additional 
 security to the joinings, and to secure cocks, &c. from leaking. It is formed by 
 mixing pounded quick lime with serum of blood or white of egg into a paste, and 
 must be applied as soon as it is made, for it speedily gets so hard as to be unfit for 
 use. The properties of this cement have been long known to chemists, and it may 
 be found useful for many purposes to which it has never yet been applied : it is 
 cheap and very durable. 
 
 533. Steam-tight joints may also be formed by fitting the parts very accu- 
 rately to a conical aperture, and screwing them close together with bolts of a less 
 expansible metal ; and the same method may be followed where the pressure of the 
 steam tends to close the joint. 
 
 When two flat surfaces are to be joined, they may be made to fit together very 
 accurately, and a single ring of fine copper wire inserted in between them before 
 screwing them close. The pressure of the screws partially flattens the wire, and 
 makes it fit so accurately, as to prevent the escape of even very high pressure 
 steam. 
 
SECTION VIII. 
 
 OF EQUALIZING THE ACTION, REGULATING THE POWER, MEASURING 
 THE USEFUL EFFECT, AND MANAGING THE STEAM ENGINE. 
 
 534. THE action of a steam engine is variable ; consequently, when an equable 
 motion is necessary, its action must be equalized. It may also be employed in 
 one hour to overcome a small resistance, and in another to overcome a conside- 
 rable one ; therefore, the means of regulating the power to the work should be 
 provided : we have also to consider certain methods which may be made sub- 
 servient to ascertaining the useful effect of an engine after it is erected, or, 
 in the language of technical men, its PERFORMANCE ; and, lastly, the mode of 
 managing the generation of steam, and the working of an engine. 
 
 OF EQUALIZING THE ACTION OF STEAM ENGINES. 
 
 535. An equable motion is desirable in almost every kind of machine, it 
 being strained much more by an irregular desultory one, as well as the fabric 
 that supports it, than when the motion is equable. The strength of the machine 
 must be adapted to the greatest strains that occur, but the quantity of work done 
 is equivalent to the mean action only, and more is not performed by a desultory 
 motion, than by one at a mean rate and uniform. There are two modes used 
 for equalizing the action of an engine, which we propose to describe. The one 
 is by ihejly wheel, the other by a counter-weight. 
 
 536. OF THE FLY WHEEL. A fly wheel is a wheel with a heavy rim which 
 absorbs the surplus force at one part of the action, to distribute it again when the 
 action is deficient ; it has been aptly compared by Professor Leslie, to " a reservoir 
 which collects the intermitting currents, and sends forth a regular stream." * To 
 equalize a motion which is subject to variation at each reciprocation in the steam 
 
 1 Natural Philosophy, vol. i. p. 152. 
 
SECT, vin.] OF THE REGULATION, &c. 257 
 
 engine, the fly is used. Its heavy mass of matter must be so shaped, as to balance 
 itself in any position on an axis connected with the machinery, and turning round 
 with a part of it. 
 
 The proportions of the fly wheel must be derived from the laws of rotary motion. 
 They are not often stated very clearly, and rather in too comparative a form for 
 the purpose of application : Dr. Jackson's equation 1 is derived most in unison with 
 my own methods, and adding the time, the radius corresponding to the angular 
 velocity of the exterior ring of the wheel, and comparing with the force of gravity 
 to obtain the coefficient, it is 
 
 32 P a r t 
 
 = n v. 
 
 bx* 
 
 In this equation 
 
 P = the mean quantity the moving force varies in its intensity in excess 
 above the resistance, 
 
 t = the time in which that variation takes place ; 
 
 v = the velocity, 
 
 n v = the greatest variation of velocity, 
 
 a = the leverage the force P acts with, 
 
 r = the radius corresponding to the velocity v, and 
 
 w = the weight of the fly acting at the distance x from the axis. 
 
 It is obvious that the mass of the fly must be sufficient to receive the excess of 
 force during the time it acts, and afford it again to the machine in an equal lapse 
 of time, and so that the velocity shall not vary more than the wth part. The only 
 point, therefore, which depends on practical experience, is what variation of velocity 
 may be allowed. On this point however there is no difficulty, as the practice of 
 different makers is so different, as to show that it may be taken with considerable 
 latitude. 
 
 The weight of the rim may always be considered to be collected at the extremity 
 of the radius ; and then x = r, and the equation becomes, 
 
 32 P at 
 
 = n v. 
 
 w r 
 
 The effect of the arms of the wheel may be neglected, as it is a problem which 
 neither requires nor admits of a very refined solution, in consequence of the un- 
 certainty regarding the precise variation of the intensity of the moving force ; 
 hence it ought not to be rendered complicated. 
 
 537. From this equation it appears, that when the weight or the diameter of 
 
 1 The9retical Mechanics, art. 400 403. 
 2K 
 
258 OF THE REGULATION AND [SECT. vm. 
 
 the rim is considerable, and still more when both are so, it may acquire a great 
 momentum with but little increase of angular velocity, or lose a considerable 
 momentum with little diminution of that velocity. It thus becomes a receptacle 
 for the surplus energy of the power, when it acts with most intensity, or when the 
 resistance is least, and preserves it for future demand. 
 
 By either a diminution of resistance, or an increase of power, the machine 
 would otherwise be considerably accelerated ; the excess of motive force is how- 
 ever, in a great measure, expended upon the fly, in which it generates a pro- 
 portional momentum with little increase of velocity : again, when the resistance 
 is increased, or the moving power diminished, the machinery would be very 
 sensibly retarded if the momentum accumulated in the fly did not continue the 
 motion with little diminution of its own velocity; and other things being the 
 same, the shorter the interval of reciprocation or of unequal resistance, the less 
 will be the change of velocity. 
 
 The greater the angular velocity of the axis of the fly is, the greater will be 
 its dominion or equalizing power, all other things being equal ; for the variation 
 of velocity is inversely as the velocity of the rim. 
 
 Every part of a machine which has either a continuous or pendulous motion, 
 particularly when it is massive, will obviously act as a fly in equalizing the motion 
 of the machine. 
 
 The greater part of these remarks have been made in a less general form by 
 Dr. Robison 1 and Dr. Jackson ; 2 but they also state that when a more perfect 
 equalizer is wanted, we should increase the power of the fly wheel by enlarging 
 the diameter rather than the mass, because we thus produce the same effect with 
 less weight, consequently with less transverse strain upon the axle and supports, 
 and less friction. This must however be carried only to small extent, for a 
 mass of matter with an immense velocity, sustained by arms which must be com- 
 pletely incapable of resisting its impulse, becomes a very dangerous appendage 
 to a machine. Arms of cast iron could not resist a sudden check, with a rim 
 moving at the velocity of eighteen feet per second, and equal to the weight of the 
 arms, 3 consequently such wheels should be of limited diameter. 
 
 538. When it is necessary to exceed a velocity of twelve feet per second at the 
 rim, malleable iron arms should always be used, and a velocity of thirty-three feet 
 per second at the rim is about the extreme limit for a fly, even where the ring is 
 of malleable iron. For cast iron rims, with arms of malleable iron, I should not 
 think a velocity exceeding eighteen feet per second to be safe. 
 
 i Mechanical Philosophy, vol. ii. p. 250. - Theoretical Mechanics, p. 227. 
 
 3 Essay on the Strength of Cast Iron, art. 261. 
 
SECT, viii.] MANAGEMENT OF THE STEAM ENGINE. 259 
 
 With these explanations we may now proceed to form rules from the equation. 
 The equation is 
 
 32 P? 
 
 20 
 
 r n v 
 
 but the dimensions of the rim will be more convenient than the weight ; and the 
 weight w = 2 x 3* 14 16 r A x 3'2 Ibs., for cast iron, = 20 r A, consequently, 
 
 . 1'6 Pat, 
 
 A = , the area ot the section of the nm in inches. 
 
 r* n v 
 
 If the fly wheel shaft makes N revolutions per minute, then in the time t it will 
 _N_ . . 6-2832 t 
 
 60 '" 60 
 
 t N 6-2832 t N r 
 
 make - ' = - - and, 
 
 15 Pa 
 
 ~r*Tir 
 
 539. The next point to be considered is the degree of equalization a machine 
 requires. Its own parts have much effect, and the species of parts which act as 
 flies are most numerous in machines which require the equalizing power of the 
 fly the most. At a mean, perhaps a variation of one-tenth is nearly corresponding 
 with practice, and with this condition the rule is, 
 
 p " 
 
 A = 
 
 540. CASE r. A double engine with a crank. In this case the variation is 
 from the full force of the steam to nothing at each quarter of the stroke ; hence, 
 the mean excess is one-fourth of the greatest force P on the piston, and the rule in 
 the nearest simple expression is, 
 
 A -= 40Pg 
 
 RULE. Multiply forty times the pressure on the piston in Ibs., by the radius 
 of the crank in feet, and divide this product by the cube of the radius of the fly 
 wheel in feet, and by the number of its revolutions per minute, the result is the 
 area of the rim of the fly in inches. 
 
 The number of horse power, multiplied by 200, will be the greatest pressure 
 on the piston, nearly. 
 
 Example. The pressure on the piston of an engine being 4000 Ibs., the 
 radius of the crank 2'5 feet, and the revolutions per minute 22, required the 
 section of the rim of a fly of 9 feet radius. In this case, 
 
 40 
 
 for the area of the section of the rim. 
 
260 OF THE REGULATION AND [SECT. vm. 
 
 541. CASE n. In a single engine with a crank the mean excess is half the 
 moving force ; hence, 
 
 A = 80 P a 
 
 or the rim of the fly wheel should be double that required for a double engine 
 with the same sized cylinder, or of twice the power. x 
 
 542. COUNTER-WEIGHTS. If the beam of a single engine be balanced when at 
 rest, that weight which it is necessary to add or subtract, to cause the piston to 
 rise at the proper speed, is called the counter-weight. The excess of force of the 
 steam overcomes the friction of the parts, and the additional weight ought to be 
 sufficient to cause it to rise and acquire double the velocity of the engine, if it 
 freely accelerated during the whole stroke. If W be the whole weight of matter 
 moved, w = the counter-weight, and / = the length of the stroke, then 
 
 64 ** 
 W + w 
 
 or w = 
 
 But (art. 342.) u s = 2-66 / ; v being for one second : hence, w = 0'2 W ; con- 
 sequently, the counter-weight should, with these proportions, be one-fifth of the 
 mass of matter it has to move, supposing the whole to be collected at the ends 
 of the beam; and it is most easily found by trial. The resistance of the water in 
 the pumps will reduce the accelerated to an uniform motion of half the final 
 velocity it would have acquired with no such resistance. 2 
 
 OF REGULATING THE POWER OF ENGINES. 
 
 543. An engine is frequently applied where the work to be done is not 
 constantly the same ; and when the machinery of a part of it is suddenly stopped, 
 
 1 In single acting atmospheric engines a weight has been applied to the fly wheel, such that 
 its force to turn the shaft should be exactly half the force of the steam to turn it, and placed so 
 as to rise while the piston was descending, and descend during the rise of the piston. To find 
 
 the weight, we have 
 
 Pa 
 
 w being the weight, and P the mean pressure on the piston. It is supposed to be applied to the 
 rim of the fly, and the section of the continued rim should be the same as for a double engine of 
 the same power. This mode is described in ' Fenwick's Essays on Practical Mechanics,' p. 39. 
 Woolf proposed to equalize the motion of an engine by a piston working in a cylinder; this, 
 however, has no other effect than a weight, while the friction and expense of construction are 
 considerably increased. See Nich. Journal, vol. vi. p. 218. and vol. vii. p. 134. 
 
 2 Smeaton arranged his engines to make the returning stroke iu less time than the acting one. 
 (Reports, vol. ii. p. 360.) Watt states it to be generally agreed that the reverse should be the case. 
 (Robison's Mech. Phil. vol. ii. p. 99.) The reasons for making them equal are stated in art. 340. 
 
SECT. viii. J MANAGEMENT OF THE STEAM ENGINE. 261 
 
 or suddenly set on, if the moving power were to remain the same, an alteration 
 of the velocity must take place ; it must move faster or slower. This change of 
 velocity would in most cases be very hurtful to the work, and cause considerable 
 loss ; besides, there is always a velocity at which a machine will act with greater 
 advantage than at any other ; therefore the change of velocity arising from the 
 above cause, is in all cases a disadvantage, and in all delicate operations ex- 
 ceedingly injurious. In a cotton mill, for example, where the power moved the 
 spindles with a given speed, if so much of the work were at once thrown off as 
 to increase the velocity in a considerable degree, a loss of work would immediately 
 take place, and an increase of waste from the breaking of the threads ; on the 
 other hand, there would be much loss of the time of the attendants, if the machinery 
 moved too slow. 
 
 An equally bad effect is observed in raising water, and other species of work. 
 
 544. THE THROTTLE VALVE. The power of a steam engine is usually regu- 
 lated by increasing or diminishing the steam passage, and this is generally per- 
 formed by admitting the steam into the cylinder, more or less freely, by means 
 of what is called a throttle valve : this valve is formed of a circular plate of metal, 
 a, Fig. 1. Plate vm. having a spindle fixed across its diameter. The plate is 
 accurately fitted to an aperture in a metal ring of some thickness, through which 
 the spindle is fitted steam-tight, and the ring is fixed between the flanches of that 
 joint of the steam pipe which is next to the cylinder. A square part is formed 
 on one end of the spindle, to receive an arm or lever b, by which the valve may 
 be turned in either direction. 
 
 545. For many purposes engines are thus regulated by hand at the pleasure 
 of the attendant ; but where a regular velocity is required, means must be applied 
 to open and shut it, without any attention on the part of the person who has the 
 care of the engine. For this purpose Mr. Watt, after trying various methods, 
 fixed upon the conical pendulum, which he called a governor. (See art. 550.) 
 
 An axis valve of this kind has much advantage over a valve of any other form 
 for a circular pipe, because it contracts the aperture without being difficult to move, 
 or presenting more than the necessary obstruction ; but it is by no means an 
 economical mode of varying the power of the steam engine. 
 
 546. To regulate by working more or less by expansion. This may be done by 
 adjusting the motion of the steam valves, so that they may be closed at an earlier 
 or later period of the stroke, according as the engine has less or more work upon it. 
 This method is confined chiefly to regulating by hand, (see art. 481. and Plate ix.) 
 The self-acting regulator in use applies with good effect only to valve engines, as 
 neither the common slide nor cock can be adjusted otherwise than to close the 
 passage to the condenser. (See art. 448. and 456.) 
 
262 OF THE REGULATION AND [SECT. vni. 
 
 547. FIELD'S VALVE. An ingenious mode of cutting off the steam at any period 
 of the stroke has however been discovered by Mr. Joshua Field. 1 It consists of a 
 valve placed in the situation usually assigned to the throttle valve ; that is, near to 
 the place where the steam is admitted to the cylinder. This valve is to be opened 
 at once, at the commencement of the stroke, so as to afford full passage to the 
 steam, and shut at once after a certain part of the stroke is made, that the rest of 
 it may be completed by the expansive power of the steam. This may be done by 
 causing the valve to open by a tooth or cam on a cylinder, on one of the revolving 
 shafts formed to raise the valve, and keep it open till the shaft has made part of its 
 revolution, and then shut it. If the toothed cylinder be made to slide on the shaft, 
 and the form of the tooth be such that as the cylinder is moved in one direction 
 the valve will shut sooner, and in the other direction later, there is then the means 
 of regulating the period the valve shall be open, and consequently of regulating 
 the power of the engine. This may either be done by hand, or by causing the 
 cylinder having the tooth to slide by the governor. Its application to Maudslay's 
 portable engine, where it is moved by the governor, is shown in Plate xv. It was 
 there first applied by way of experiment, which will account for the indirect 
 passages for the steam, and for retaining the throttle valve. The saving of power, 
 according to the experiment, amounted to about 10 per cent. 
 
 548. When atmospheric engines condensing in the cylinder have to work 
 under loads inferior to their whole power, they are regulated by lessening the 
 quantity of injection, or by shutting the injection cock sooner ; but in almost all 
 engines employed for raising water which are regulated by hand, it is necessary to 
 provide the means of warning the attendant of the power being in excess. 
 
 549. SPRING BEAMS. In engines with fly wheels no precaution is necessary to 
 limit the motion of the beam, because this is most effectually done by the length of 
 the crank, while the fly continues the rotary motion so as to prevent strain on the 
 crank shaft ; but in engines where a crank is not used, as in engines for pumping, 
 a very strong piece of timber is bolted across the top of the beam at each end, as 
 shown in Plate xn. each of which strikes against two wooden springs, one placed 
 on each side of the beam, on the two longitudinal beams which support the axis of 
 the engine beam, and which are on this account called the spring beams of the 
 engine. To prevent noise, the springs are covered with cork at the place where 
 
 1 This is an ingenious adaptation of what Mr. Watt practised in the reciprocating engine, viz. 
 shutting off the steam at any required period of the stroke. In the rotative engine the same object 
 has been accomplished since the application of Murdoch's slide valve, in 1799, by increasing the 
 depth of its face to the required expansion in the cylinder, and properly adjusting the motion of 
 the excentric. ED. 
 
SECT. vin.J MANAGEMENT OF THE STEAM ENGINE. 263 
 
 they receive the stroke ; and when they are bent beyond a certain degree they 
 cause a bell to ring, which gives the attendant notice that the engine requires 
 regulation. 
 
 THE CONICAL PENDULUM OR GOVERNOR. 
 
 550. If two or more balls be suspended from a revolving axis so as to revolve 
 with it, the balls will rise when the velocity is increased, and fall when it is dimi- 
 nished ; and by connecting awns to the rods by which the balls are suspended, 
 their rising or falling may be made to move a lever so as to open or close a valve, 
 or the like, on any change taking place in the velocity of the machinery ; and 
 hence it is employed to render an engine the regulator of its own power to the 
 effect it is to produce. 
 
 In the construction of this apparatus it is necessary to consider the place of the 
 balls corresponding to the mean velocity, the range of motion, and the weight and 
 velocity of the balls. 
 
 Different modes of combining the parts are used by different engineers ; one of 
 these is shown in Plate vm. Fig. 1. where g is the revolving axis, /the point of 
 suspension, jj the balls, e e the rods by which the balls are suspended. These rods 
 are connected to the rods i i, and by that means raise or depress the sliding piece 
 h, and with it the lever /, which acts on the throttle valve. The parts marked k k 
 are two rests to receive the balls when the engine is not in motion. 
 
 551. The vertical distance between the point of suspension and the plane 
 in which the centres of the balls revolve, is the same as the length of a pendulum 
 which makes one vibration, forward and back again, in the same time the balls 
 make one revolution. The usual velocity for the axis is 30 revolutions per 
 second, and therefore the height should be the same as the length of the seconds' 
 pendulum, that is, 39'14 inches. To find the height for any other number of 
 revolutions per minute, divide 35226 by the square of the number; thus, for 
 twenty revolutions, 20 x 20 = 400, and 
 
 = 88 '065 inches, the height required. 
 
 552. The range may be settled from considering the greatest change of 
 velocity the machinery may acquire without injurious effect on the work ; and 
 with this range the governor ought to be capable of completely cutting off the 
 acting power. Now the greatest variation should not generally exceed one-tenth 
 of the velocity, that is, one-twentieth on either side of the mean ; and the range 
 of the plane of revolution will, in that case, be nearly one-fifth of the height of 
 
264 OF THE REGULATION AND [SECT. vm. 
 
 the point of suspension above the plane of revolution at the mean velocity. 1 Thus, 
 if the mean height be 39-14 inches, then one-tenth on each side will be 
 
 39-14 + 3-914 = 43-054 
 39-14 - 3-914 = 35-226 
 
 One-fifth of 39- 14 = 7-728, the range. 
 
 Where a throttle valve is acted on by a governor, the steam passage should be 
 fully open at the usual velocity of the engine, and contracted only when it exceeds 
 that velocity, otherwise the steam must be always throttled, except when the 
 engine is working against an unusual resistance. 
 
 553. The balls are made from 30 to 80 Ibs. each ; their effect, however, 
 depends considerably on the angles formed by the combination of bars. In the 
 form in Fig. 1. Plate vm. the force is small, but the quantity of motion is con- 
 siderable ; while that in Fig. 3. Plate xv. has more force and less motion. The 
 angle the ball rods make with the axis, should be about 30 when they are at 
 rest ; and provided the range be sufficient, the angle the connecting rods make 
 with the axis, may be made acute with advantage in point of power. * 
 
 554. The velocity of an engine for raising water has in some instances been 
 regulated by a small cylinder provided with a piston, and fixed on a pipe from 
 the air vessel of the main ; which, when the engine goes too quick, forces water 
 into the lower part of the small cylinder, and raises its piston. The piston is 
 loaded with a weight corresponding to the proper velocity of the engine, and 
 therefore it is only when it goes too rapidly, that, the friction increasing in the 
 
 1 For if v be the mean velocity, and it increases to v + n v = v (1 + n) ; then the height of the 
 plane of revolution will be altered from h to ^ ^ ; or in the ratio of (1 + ) 2 : 1, consequently, 
 
 the change in the velocity will be to the change in the height of the plane of revolution, as 
 1 + n : (1 + n) 2 ; and the increments are as : 2 + *, or as 1 : 2 + n ; and when is a small 
 fraction, it is nearly as 1 : 2. 
 
 From want of attention to this point, the governor has been supposed to be deficient in sensi- 
 bility to the changes of velocity in a nice machine ; and M. Preus has proposed to use a small 
 pump to raise water to a cistern, from whence it escapes by an aperture which can be regulated at 
 pleasure. When the engine moves at a greater speed than the proposed one, the water rises in the 
 cistern, and raises a float which closes the throttle valve. See Phil. Mag. vol. Ixii. p. 298. It is 
 obvious that it cannot exceed the governor in sensibility, while it will require considerable atten- 
 tion to keep it in order. 
 
 * Several trials have been made to apply the governor to boat engines, but it appears to me 
 that the changes are too sudden for this mode of regulation. 
 
SECT, viii.] MANAGEMENT OF THE STEAM ENGINE. 265 
 
 main pipes, the pressure in the air vessel increases also ; and this pressure being 
 also communicated by the small pipe to the regulating cylinder, causes its loaded 
 piston to rise, and the motion is communicated to the top or steam valve by 
 means of spindles and gearing to the regulating screw, so as to regulate the 
 steam; or, on the other hand, if the engine works too slow, the pressure in the 
 air vessel diminishes, and the loaded piston descends and opens the valve. 
 
 In order to prevent the motion of the piston being too great, the load is divided 
 into links like a chain, and, as the piston rises, more links are raised, consequently 
 the load increases ; and also as it descends, the links, by resting on the ground, 
 diminish the load. A spring might be applied to produce a similar effect. 
 
 This plan, however, as it did not regulate the pressure of steam in the 
 boiler, and from the friction did not act promptly, has been some time abandoned. 
 
 555. In some cases the further improvement has been adopted, of using this 
 method to ^adjust the tappets which shut off the steam. For this object, the 
 motion of the small piston is communicated to a wheel which turns a pair of 
 bevelled wheels, the one of which is on the square part of a screw rod attached to 
 the plug tree ; and whenever the motion is too rapid, the rod is turned, and moves 
 the tappet so as to cut off the steam sooner, and the reverse. The square part of 
 the rod slides in the wheel upon it without change, except when that wheel is 
 moved by the regulator piston. 
 
 556. OF THE CATARACT. The power of an engine for raising water may 
 also be regulated by increasing or diminishing the interval between its strokes ; 
 this is done by causing the tappets to disengage a loaded piston, which descends 
 in a small air vessel, expelling the air from it by a pipe, which can be regulated 
 by a cock at pleasure ; the valves are not free to open till this piston be at the 
 end of its stroke. The air vessel is a cylinder of from five to six inches diameter, 
 and twenty inches in length, open at the top with a valve opening inwards at the 
 bottom, that it may ascend without unnecessary resistance. It is provided with 
 a pipe from the bottom, of sufficient diameter to allow the air to escape when the 
 engine is at full speed, which has a cock to regulate the time of discharge. It is 
 also fitted with an air-tight piston, the rod of which is connected with the 
 apparatus which opens the valves. Two air vessels are required for a double 
 
 engine. 
 
 OF THE METHODS OF ASCERTAINING THE STATE AND EFFECTIVE POWER 
 
 OF A STEAM ENGINE. 
 
 557. Certain instruments have been invented which are of great use in 
 ascertaining the state of an engine ; and these ought to be kept in good order, 
 
 2 L 
 
266 OF THE REGULATION AND [SECT. vm. 
 
 so as to be capable of affording the required proof at any time. Mr. Watt has 
 most justly remarked, " it is the interest however of every owner of an engine to 
 see that they, as well as all other parts of the engine, are kept in order." 1 
 
 The instruments consist of a steam gauge, the condenser gauge, and the 
 indicator. 
 
 558. STEAM GAUGE. The steam gauge, Plate vm. Fig. 1, 18. is a short 
 bent tube of iron, nearly half an inch in diameter, with one end fixed into the 
 boiler or the steam pipe, and open to it ; with a portion of mercury in the bent 
 part of the tube. The part joined to the boiler or steam pipe is freely open to 
 the steam, which, pressing on the surface of the mercury in the pipe, raises it in 
 the other leg of the tube, which is open to the air at the upper end, and the height 
 it is raised is measured on a scale, 20, by a slender stem from a light float on 
 the surface of the mercury ; which therefore shows the elastic power of the steam 
 over that of the atmosphere. The scale should be adjusted by allowing the air 
 free access to the mercury on both sides. 
 
 The scale is commonly divided into inches and parts ; each inch corresponds 
 to 2 inches of mercury, and to a pressure of 0'775 Ibs. on a circular inch, or to 
 0-98 Ibs. on a square inch. If each of the divisions of the scale be made 1-3 
 inches, and these each divided into 10 equal parts, the pressure in Ibs. and tenths 
 on a circular inch will be shown by the gauge. Some divide the scale into half 
 inches, then each division represents an inch of mercury. 
 
 Sometimes a cock, 19, is placed between the mercury and the steam, so as to 
 use it or not at pleasure. 
 
 To render the divisions of the gauge larger, Mr. Watt made his gauge pipe of 
 glass, to terminate in a cistern of mercury enclosed in an iron box. The action 
 is then like a common barometer ; the steam having free access to the surface of 
 the mercury in the cistern. 
 
 559. CONDENSER GAUGE. This is sometimes called the barometer gauge, 
 from its resemblance to a barometer. It is made of iron tube in the form of an 
 inverted syphon, Plate vm. Fig. 1,21. with one leg about half the length of the 
 other. To the upper end of the longer leg, 24, a pipe is joined which communi- 
 cates with the condenser, and has a stop cock, 22, to open or close it. When a 
 proper quantity of mercury is poured into the short leg of the syphon, and it is 
 open to the atmosphere at both ends, it naturally stands level in the two legs. 
 A light float with a slender stem is placed in the short leg, and a scale, 25, 
 attached, which is usually divided into half inches ; and as by the exhaustion in 
 
 1 Robison's Median. Phil. vol. ii. p. 156. 
 
SECT, viii.] MANAGEMENT OF THE STEAM ENGINE. 2G7 
 
 the condenser, the mercury rises as much in the long leg as it falls in the short 
 one, these divisions will be equivalent to inches on the common barometer. 
 
 The condenser gauge should indicate the state of the vapour in the condenser, 
 to be capable of sustaining from two to three inches of mercury. While it does 
 not exceed three inches, the condensation may be esteemed very good ; and about 
 two inches is the best I have seen obtained in practice. 
 
 The difference between the elastic force of the vapour in the condenser, and the 
 elastic force of the steam in the boiler, as shown by the gauge, added to the height 
 of the barometer at the time, gives the relative force of the steam to move the 
 engine, but many deductions have to take place before we have the real moving- 
 force ; nevertheless they show the state of two very important parts of the engine. 
 (See Sect. v. and vi.) 
 
 560. THE INDICATOR. The force of the steam and the state of exhaustion 
 in the cylinder, at the different periods of the stroke of the engine, cannot be 
 ascertained by the condenser gauge, and for that purpose it was necessary to form 
 an instrument less subject to vibration ; the instrument in use is called the IN- 
 DICATOR, and is found to answer the end tolerably well. It consists of a cylinder 
 about one inch and three quarters in diameter, and eight inches long, exceedingly 
 truly bored, with a solid piston accurately fitted to it, so as to slide easy by the 
 help of some oil ; the stem of the piston is guided in the direction of the axis of 
 the cylinder, so that it may not be subject to jam or cause friction in any part of 
 its motion. The bottom of this cylinder has a cock and small pipe joined to it ; a 
 flat pillar D, Plate xvi. Figs. 1 and 2. is screwed to the cylinder of the indicator 
 C, and supporting the frame E E, which is twelve inches by seven inches, with 
 the upper and under rail grooved to retain the sliding-board K. 
 
 The piston rod G is about five-eighths of an inch in diameter, and sixteen inches 
 long ; and H is the guide for it screwed to the pillar D, at about six inches above 
 the top of the cylinder C. 
 
 A spiral spring I is attached to the piston at F, and to the guide at H. It 
 should be about seven inches long when at rest, and of such a strength as to allow 
 the piston to descend to within about an inch of the bottom of the cylinder C, 
 when it is loaded with 15 Ibs. upon every square inch of its area ; and the 
 spring should admit of being compressed one inch and a half. 
 
 The board or panel K slides in the grooves of the frame E E, and should be 
 seven inches square ; and a small brass slider L should be set at any height on the 
 piston rod G, by means of a screw. A short pencil is inserted in the other end, 
 with a weak spring to push it against the surface of the board K, which is caused 
 to slide by a weight N, attached to a line passing over a pulley ; the opposite line 
 
208 
 
 OF THE REGULATION AND 
 
 [SECT. vin. 
 
 O being attached to any convenient part of the parallel motion of the engine, so 
 as to cause the board K to traverse a space of about fourteen inches and a half 
 during each half stroke of the engine. 
 
 Operation. By opening the stop cock B, a direct communication is made 
 between the cylinder of the steam engine and the cylinder of the indicator. When 
 the force of the steam in the cylinder is greater than the pressure of the atmosphere, 
 the piston F will rise ; when the force of steam is less than atmospheric pressure, 
 it will sink. The indicator will consequently rise when the upper steam valve 
 opens, and will be at a height proportional to the force of the steam in the cylinder 
 during the stroke of the engine ; and when the eduction valve opens, it will sink, 
 and by the rapidity and quantity of its descent denote the state of the vapour in 
 the condenser. During the motion of the piston F, the sliding-board will move 
 horizontally, and the pencil in the socket in L will trace on the board K, or on 
 a paper on its surface, a figure, P Q R S, resembling those shown on an enlarged 
 scale in the annexed figures. Of this figure, P Q is described during the descent 
 
 FIG. 23. 
 
 of the steam piston ; at Q the condensation takes place, and the indicator is forced 
 down by the pressure of the atmosphere, till it is balanced by the resistance of the 
 spring and the vapour in the cylinder. While the engine makes the ascending- 
 part of the stroke, the line R S is described ; and the line S P is described during 
 a fresh admission of steam by the upper valve. 
 
SECT, viii.] MANAGEMENT OF THE STEAM ENGINE. 269 
 
 The area P Q R S is proportional to the force of steam on the piston during the 
 stroke ; but the steam is not exerting the greatest power in proportion to the quan- 
 tity of fuel when this area is the greatest ; for when the steam acts by expansion, 
 the area described will resemble the figure P Q R S, the steam being cut off at C, 
 and more power will be exerted by a given quantity of steam. In the same engine 
 doing different quantities of work the figures show two cases ; the black lines 
 represent the power when the throttle valve is used for regulation, and the dotted 
 lines when the engine is regulated by cutting off the steam. 
 
 561. Let p be the number of Ibs. on a circular inch of the indicator piston, 
 which causes it to descend a inches, and let m be the length of the line a b, 
 
 measured in inches on the diagram drawn by the indicator, then a : m : : p : , 
 
 the pressure exerted by the steam in Ibs. on a circular inch, at the point a of the 
 descent of the piston. Thus, if by trial 2 Ibs. per circular inch causes the piston to 
 
 descend 1 inch, then T* = - - = 2 m ; or each inch of the indicator would 
 
 correspond to 2 Ibs. per circular inch. 
 
 If the distance the tracer moves horizontally be divided into equal parts, and 
 the vertical distance between the lines P Q and R S be taken at each point of 
 division, and the sum of these distances, less half the distance P S, be taken and 
 divided by the number of divisions, the result will be the mean distance the piston 
 of the indicator moves over ; and calling this mean distance m, it will be, 
 
 ffl D 
 
 = the mean pressure on the steam piston in Ibs. per circular inch. 1 
 
 a 
 
 562. To MEASURE THE USEFUL EFFECT OF AN ENGINE. The preceding 
 methods only give the state of parts, but the useful effect depends on the whole 
 being in order ; and the most simple and convenient mode of measuring the effect 
 is by means of friction. 2 If the rim of a brake wheel on the engine shaft of a 
 known diameter be pressed with a force producing a known degree of friction, 
 which is exactly equal to the effect of the engine at its working speed, then it is 
 clear that if the friction this pressure produces be ascertained, the power of the 
 engine will be equal to the friction multiplied by the velocity of the rubbing 
 surface. 
 
 1 The indicator was invented by Watt, (Robison's Mech. Phil. vol. ii. p. 156.) and the sliding 
 board and tracer were afterwards applied by Mr. Southern. Figures made by the board and 
 tracer, as far back as 1802, are still to be found amongst the archives of Soho. 
 
 2 It is for use in those cases where the work itself is not susceptible of accurate measure ; and 
 almost all engines for impelling machinery are in this class. The power of engines for raising 
 water is easily computed. 
 
270 OF THE REGULATION AND [SECT. vm. 
 
 To apply this, let A B be a lever, with a 
 friction strap that may be tightened upon 
 the cylindrical surface of the shaft or wheel 
 C, and let it be tightened by the screw at B, 
 (the lever being stopped by the stop D,) till 
 the friction be equal to the power of the 
 engine when all other work is thrown off; 
 then, while the engine is still in motion, add 
 such a weight at E as retains the lever in a 
 horizontal position. 
 
 To calculate the power. Multiply together the length F C of the lever in feet, 
 the weight E in Ibs., the number of revolutions of C per minute, and the number 
 6'2832, the result will be the Ibs. raised 1 foot per minute ; and, divided by 33000, 
 it is the horse power. 1 
 
 Thus if a shaft C make 25 revolutions per minute, and the length F C of the 
 lever be 10 feet, and if it be found that a weight of 240 Ibs. is sufficient to retain 
 the lever in a horizontal position, then 6-2832 x 10 x 240 x 25 = 376992 Ibs. 
 raised 1 foot, or 11^ horse power nearly. 
 
 The trial is so easily made, and the result so accurate a test of the qualities of an 
 engine, that I strongly recommend it to the notice of those who are desirous of 
 having good engines. 
 
 563. THE COUNTER. To estimate the saving of fuel by the application of 
 Watt's engines, an apparatus was attached to the beam to ascertain the number of 
 strokes the engine made in a given time : it is called the counter, and consists of a 
 train of wheel-work resembling that of a clock, so arranged that every stroke made 
 by the engine moves one tooth, and the index shows how many strokes have been 
 made between the times of examination. The counter is enclosed in a box and 
 locked, to prevent it being altered during the absence of the observer. If the box 
 be attached to the axis of the beam, the inclination of the beam causes its pendu- 
 lum to vibrate every time the engine makes a stroke, and thus moves the counter 
 round one tooth for every stroke. The box may also be fixed to the supports of 
 the beam, and then at every stroke a small detent is moved one tooth. The 
 
 1 For, let / be the leverage the weight w acts with, and r the radius of the wheel or shaft C ; the 
 
 / MJ 
 
 friction /, the velocity t>, and the revolutions of C per minute n. Thenfv = the power, /= , 
 
 and v = 6-2832 r n ; consequently v f = 6-2832 Iwn, the power in Ibs. raised 1 foot, when / is in 
 feet and w in Ibs. 
 
SECT, viii.] MANAGEMENT OF THE STEAM ENGINE. 271 
 
 counter is still used in Cornwall, in order that the effect of the engines may be 
 reported on by the inspectors ; and it is useful in various instances where a check 
 on the consumption of fuel is desirable. 
 
 OF WORKING STEAM ENGINES. 
 
 564. The first attention should be directed to the qualities of the fuel and the 
 water. The fuel, of whatever kind, should be dry, in small parts, and free from 
 earth, &c. No coals should be above the size of an egg, and they should contain 
 as little pyritical matter as possible. Wood should be in billets not more than a 
 foot long, nor two or three inches diameter. The water used should be pure and 
 soft when it can be had. 
 
 All natural waters contain a quantity of matter, which they derive from the 
 strata through which they flow. The purest springs usually rise in beds of gravel, 
 or in siliceous or argillaceous rocks ; and they contain, for the most part, only a 
 minute portion of saline matter, which is principally common salt. The water of 
 limestone or calcareous districts generally contains a much larger quantity of solid 
 matter, most frequently lime in solution, either carbonate or sulphate of lime, which 
 occasions that peculiar quality in waters commonly known by the name of hard- 
 ness. 1 The waters of mines are still more impure ; they often contain earths, acids, 
 alkalies, and saline compounds. Hence water in its natural state is often unfit for 
 a steam engine. 
 
 Almost the only practicable method of improving water is that of exposing it 
 long to the air in ponds : a more effective one is to use the same water over and 
 over again, with only such addition as compensates for loss ; but even this requires 
 a larger reservoir to allow the water time to cool. Foul river-water may be cleared 
 by filtering through sand or gravel. 
 
 To prevent the sediment from the water adhering to boilers, it is common to put 
 in crushed potato, the refuse of malt, and the like, and change it frequently. 
 
 565. For sea-boat engines sea water must be used, and it deposits salt after 
 the water is saturated. This may be prevented by letting a small quantity of hot 
 water escape constantly from the boiler. One hundred parts of sea water contains 
 three parts of its weight of saline matter ; and is saturated when it contains thirty- 
 
 1 Hard waters do not readily dissolve soap, nor form a good lather with it ; on the contrary, 
 they partially decompose it, and a light flocculent substance is produced, which is insoluble in 
 water. 
 
272 
 
 OF THE REGULATION AND 
 
 [SECT. vin. 
 
 six parts ; l consequently, if the boiler contain one hundred parts of water, and * 
 parts be used for steam, and n parts let out, fix on the degree of saturation, 
 for example, to contain a parts of saline matter ; then if 3 ( s + n) = a n, the 
 quantity of salt entering and the quantity quitting in the same time will be equal ; 
 hence, 
 
 a-3- 
 
 If a = 30, the water in the boiler will not reach to a higher degree of saturation 
 when a ninth part of the quantity used for steam is allowed to escape. Hence, as 
 it requires only about one-sixth of the quantity of fuel to boil water that is required 
 to convert it into steam, the loss of fuel will be $ x $ = one fifty-fourth part. 2 
 
 566. OF WORKING A CONDENSING ENGINE. The engine is supposed to be at 
 rest, the cylinder quite cold, and the condenser partially filled with water, and the 
 piston at the top. When the water in the boiler begins to boil, let steam enter by 
 the valves, or the slide, and the communication which is added when a slide is 
 used ; it will then fill the cylinder and pipes; and the injection cock being shut, it 
 will gradually displace the water in the condenser, 3 by forcing it out at the blow 
 
 1 According to Mr. Faraday's experiments, the deposits take place at the following degrees of 
 saturation and temperature, when 1000 parts of sea water were reduced by evaporation. 
 
 Quantity of sea water. 
 
 Boiling temperature. 
 
 Salt in 100 parts. 
 
 Nature of deposit. 
 
 1000 
 
 299 
 102 
 
 214 
 217 
 
 228 
 
 3 
 10 
 29-5 
 
 None. 
 Sulphate of lime. 
 Common salt. 
 
 - An ingenious combination was formed by Messrs. Maudslay and Field, to avoid this loss, by 
 causing the water entering the boiler to traverse the central parts of the pipe which removed the 
 saturated hot water ; the loss of effect then becomes very small, even when the degree of satura- 
 tion is much less. Now to prevent the deposition of sulphate of lime we must make a = 10, and 
 then three-sevenths of the quantity required for steam must be let out, and one-fourteenth of the 
 effect of the fuel will be lost. It may be necessary to explain, that sulphate of lime does not appear 
 to exist in sea water till a change of combination among its constituents takes place through eva- 
 poration ; also, it requires thirty-six parts of salt to saturate one hundred of water at 226, but it 
 appears that deposit takes place at 228 with only thirty parts. 
 
 3 The best method would be to use a cock to let out the water from the condenser, placed so low 
 as to completely drain it, and the water should be let out in the first instance ; then the steam 
 should be let on, and as soon as steam issues at the cock, it should be closed, till it be evident that 
 the cylinder is as hot as the steam will render it ; then open the cock again till steam has passed 
 out a few seconds, and close it, confining the steam to the top of the piston, and open the injection, 
 when motion will commence if the operation has been properly performed. 
 
SECT, vin.] MANAGEMENT OF THE STEAM ENGINE. 273 
 
 valve, and afterwards the air. When all the air except that mixed with the steam 
 is driven out, which will be known by the sharp cracking noise at the blow valve, 
 this noise must be allowed to continue till it be supposed that there has been time 
 for at least as much steam as fills the engine to run through. Then shut off the 
 steam except to the upper side of the piston, and open the injection cock ; if motion 
 does not commence, the injection cock must be shut, and the blowing through of 
 steam repeated. If the engine have a steam case or jacket, that case must be 
 cleared of air and water, and filled with steam before the operation of blowing 
 through be commenced. 
 
 The noncondensing species of engines require nothing more than to be heated 
 and freed from water, and atmospheric engines condensing in the cylinder to 
 be freed of air. 
 
 567. OF THE MANAGEMENT OF THE FIRE. The chief thing is to obtain as 
 equable a supply of steam as possible ; and the object of the attendant must be to 
 render it so with the least occasion for opening the fire door. He must endeavour 
 to preserve a clear free burning fire, which cannot be done if it be allowed to 
 become foul by clinkers accumulating. Every coal which will not pass a ring of 
 about two inches and a half diameter should be broken ; and either feed frequently, 
 thinly, and equally over the surface of the fire, or adopt the method pointed out in 
 art. 249 ; but in important works Brunton's method should be applied (art. 250). 
 
 568. Great care should be taken to keep the engine and boiler clean and 
 in good order, and for this purpose frequent and steady attention is more effectual 
 than twice the quantity of irregular labour. In work of this kind that which is 
 done well is twice done ; and the most furious zeal is vastly inferior to steady 
 attention, for the one destroys the objects of its care, the other preserves them. 
 
 The best kinds of oil and tallow should be used : for piston grease, tallow is most 
 esteemed ; and when cylinders are new, a small addition of very soft black lead in 
 fine powder improves the effect of the tallow. Oil appears to be improved by the 
 addition of a small quantity of wax. 
 
 2 M 
 
SECTION IX. 
 
 OF THE APPLICATION OF STEAM ENGINES TO DIFFERENT PURPOSES. 
 
 569. THE great variety of objects to which steam power is or may be applied, 
 renders it necessary to confine our attention to the most prominent ones for 
 illustration. These are to raising water ; to impelling machinery for mining, 
 manufacturing, and agricultural purposes; and to land carriage: the application 
 to navigation however is so distinct and important as to require a separate 
 treatment ; and it is therefore reserved for the next section. 
 
 OF RAISING WATER. 
 
 570. Water is generally raised by means of pumps of the lifting or forcing 
 species. The stroke of a pump should not exceed about eight feet, otherwise the 
 air disengaged from the water, the escape by the bucket or piston, and the defect 
 of pressure on the fluid which is rising after the piston, becomes greater than the 
 escape by the valves. The velocity of the piston should not exceed 98 times 
 the square root of the length of the stroke, (art. 342.) l 
 
 571. Owing to the escape at the valves and the disengagement of air, the 
 quantity of water a pump in the best order delivers at one stroke is, 
 
 95 / a 2 x -7854 AACIO 72 v,- e 
 jjl = -00518 / a * cubic feet ; 
 
 where / is the length of the stroke in feet, and a the diameter of the pump in 
 inches ; or substituting half the velocity for /, it gives the cubic feet per minute. 
 
 572. The power required to raise water a given height is found by taking the 
 exact height in feet, from the surface of the water to the point of discharge, adding 
 one foot and a half for each lift, for the force required to give the water the velo- 
 city, and also one-twentieth of the height for the friction of the piston. Call this 
 quantity in feet h ; then -341 h a 2 = the load in Ibs. 
 
 1 See note, page 167. 
 
SECT, ix.] OF THE APPLICATION OF STEAM ENGINES. 275 
 
 Whence, if P = the mean effective force on the steam piston in Ibs. per circular 
 inch, we have 
 
 the diameter of the steam piston in inches. 1 
 
 And as 180 feet per minute is a very good velocity for raising water, if Q 
 be the quantity in cubic feet, 
 
 hence, I 
 
 /-7332AQU 
 : ( P ) 
 
 Example. Suppose it be required to raise 80 cubic feet of water per minute 
 by a single acting engine, the mean effectual pressure of the steam being 11 Ibs. 
 per circular inch, and the lift 149 fathoms in 6 lifts. In this case 149 fathoms = 
 
 (7^S<? v Q48 v 80 \ i i 
 
 - ^- -)' = (5054-171)* 
 
 = 72 inches nearly, for the diameter of the cylinder ; and (2-15 x 80)^ = 13-115 
 inches = the diameter of the pump ; the velocity being 180 feet per minute. 
 Both these diameters ought to be increased 5 per cent, for contingencies. 
 
 DRAINAGE OF MINES. 
 
 573. In this country the drainage of mines is a subject of vast importance. 
 It is mines which supply the means of employing steam power, and also a large 
 proportion of the materials on which that power is expended. To persons accus- 
 tomed to mines, it is seldom necessary to state those principles which should direct 
 them in the choice of engines. The absolute necessity of an economical system of 
 drainage is felt and acted upon ; and it is by comparison of annual expense, and 
 not by a comparison of the effect from a given quantity of fuel, that this economy 
 should be estimated. 
 
 A mine engine should be simple in construction, durable in use, and made with 
 
 1 When a given quantity of water is to be raised ; if Q be that quantity, we have 
 
 2Q PP* 2Q P PS 
 
 : -00518 ' a = : 34O ' ' -00518 v == -341 h ' 
 
 2 P 
 Also, / = -|g- ; an d _ 93 ^ i hence we find, 
 
 P - 
 
276 OF THE APPLICATION [SECT. ix. 
 
 a view to easy repair. When coals are not expensive, the most simple methods 
 are the most economical ; for instance, at the mouth of a coal pit, the extra con- 
 sumption of coals is of less value than the extra wear and tear of a complex 
 engine. 
 
 574. The modes of draining mines are dependent on the nature of the district 
 where they are situated. If it be mountainous, a subterraneous channel or day 
 level drift 1 may be made, from the lowest part of the mine to terminate in the 
 nearest valley, to carry off the water ; and it is only when this method is imprac- 
 ticable that water is raised by power, and even then the water is raised no higher 
 than to where a day level drift can be obtained. But it frequently happens that 
 the flatness of the country renders any other method impracticable, than that of 
 raising the water to the surface. For example, in the coal-field of Northumberland 
 and Durham, many of the large double pits exceed one hundred fathoms in depth, 
 and some are nearly 150 fathoms deep, with no means of drainage by levels. 
 These pits therefore require very powerful engines, and lately they have chiefly 
 erected double engines, some of which are above 100 horse power : the largest 
 I saw there was one on the south side of the Tyne, which was working with 
 160 horse power, and was capable of exerting the power of 200 horses in action 
 at once. In Cornwall they have some larger engines ; but two engines should 
 always be preferred, when the cylinder of one engine would exceed about sixty 
 inches in diameter, for two engines give many advantages. 
 
 575. When double engines are used for lifting water, they generally work 
 one set of pumps by the outward end of the beam, and another set by a diagonal 
 spear from the piston rod end. And in cases where it has not been convenient 
 to divide the pumps into two sets, the ascending motion of the piston has been 
 employed to raise a weight equal to the pressure of half the column of water in 
 the pumps ; but for such cases a single engine should be preferred. 
 
 576. The following table (p. 278.) will give some idea of the work done by a 
 given quantity of fuel, and of the nature of the engines most approved of in Corn- 
 wall ; the results however can be correct only through the different errors of the 
 mode of estimation balancing one another, for the weight of the column of water 
 is less than the resistance, and the counter only registers the strokes, and not the 
 actual quantity of water raised. 8 
 
 1 In Cornwall and Devon it is called an adit, in some other places a sough. 
 
 * In the year 1811, a number of the respectable proprietors of the valuable tin and copper mines 
 in Cornwall resolved that the work which their respective steam engines were performing, should 
 be ascertained, as it was suspected that some of them might not be doing duty adequate to the 
 consumption of fuel; and for the greater certainty of attaining their object, it was agreed that a 
 counter should be attached to each engine, (art. 563.) and all the engines be put under the super- 
 
SECT, ix.] OF STEAM ENGINES. 277 
 
 intendence of some respectable engineer, who should report monthly the following particulars in 
 columns : viz. 
 
 The name of the mine ; 
 
 the size of the working cylinder ; 
 
 whether working single or double ; 
 
 the load per square inch in the cylinder ; 
 
 length of stroke in the cylinder ; 
 
 the number of pump lifts ; 
 
 the depth in fathoms of each lift ; 
 
 diameter of pumps in inches ; 
 
 time worked ; 
 
 consumption of coals in bushels ; 
 
 number of strokes during the time ; 
 
 length of stroke in pump ; 
 
 load in Ibs. ; 
 
 Ibs. lifted one foot high by a bushel of coals ; 
 
 number of strokes per minute ; 
 
 and, lastly, a column for name of engineer and remarks. 
 
 Messrs. Thomas and John Lean were appointed to the general superintendence ; and the 
 different proprietors, as well as the regular engineers of the respective mines, engaged to 
 give them every facility and assistance in their power. The first monthly report was for 
 August 1811. See Phil. Mag. vol. xlvi. p. 116. See also Appendix. 
 
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SECT, ix.] OF THE APPLICATION OF STEAM ENGINES. 279 
 
 The engineers' names are given who plan the construction and superintend the 
 execution and erection of the engines, for which they are paid in proportion to the 
 power ; they also attend to them afterwards, and direct such renewals or repairs 
 as may be necessary, at fixed salaries. The principal manufacturers of engines 
 for the Cornish mines are Messrs. Trevenan, Carne, and Wood ; Messrs. Harvey 
 and Co. ; Messrs. Fox and Co. ; and Messrs. Price and Co. 
 
 577. The depth of the pump shaft of a mine is divided into lifts of not more 
 than twenty-five or thirty fathoms, if it can be avoided, with a cistern at each lift, 
 consequently the water is raised from cistern to cistern. The size of the pumps 
 is seldom greater than sixteen inches in diameter, and it will always be found 
 better to make an additional set than to exceed this size. 
 
 578. The engines most adapted for economy of fuel are described in art. 411 
 and 419 ; those which are most simple, in art. 393 and 400 ; and as it frequently 
 happens that engines have to be removed from place to place, an engine supported 
 by frames of cast iron is shown in Plate xi. 
 
 579. For drawing ores and coals, a double engine of from twenty to thirty 
 horse power is used ; the size of the cylinder should be such, that the power shall 
 be equal to the resistance when the stress is the greatest ; hence, engines for this 
 purpose require more fuel to raise the same quantity of matter a given height, and 
 there is also much loss of effect through stoppages, changes of motion, &c. When 
 1 Ib. of coal raises 70,000 Ibs. of ore, it is about the maximum quantity in irregular 
 work of this kind. The weight of matter drawn at once is from 3 to 7 cwt. 
 The weight of a rope is about -27 c* Ibs. per fathom ; when c is the circum- 
 ference in inches: the greatest stress on a rope should not be more than 700 
 times the weight of a fathom of the rope ; and the stress on the engine should be 
 equalized by the rope winding on to a spiral drum, * like the fusee of a watch, 
 by which the expense of the engine, and the expenditure of fuel would be reduced. 
 The engine should work expansively, (art. 419.) and be equalized by a fly wheel, 
 (art. 540.) and regulated by a governor, (art. 550.) 
 
 When an inclined plane is necessary under ground, a small high pressure engine 
 is sometimes used to draw the coals to the principal shaft, of the kind described 
 in art. 371. 
 
 580. Engines are also employed to break ores by means of stampers, a 
 process which seems capable of much improvement. Double engines are em- 
 ployed to raise the stampers by means of cams ; and as the power of the engine 
 is nearly uniform, the space through which the stamper is raised, should increase 
 
 1 See Encycl. Metho. Diet, de Chimie et Metallurgie, Seconde Partie, Planche 20 ; or Gilpiri's 
 Method, Transactions of the Society of Arts, vol. xxv. p. 76. 
 
280 
 
 OF THE APPLICATION 
 
 [SECT. ix. 
 
 at first in the proportion due to an uniform force ; otherwise the motion will be 
 irregular, and the loss of power considerable. The weight of a stamper is usually 
 made about 190 Ibs., and the height it is raised about 2 feet ; and not less than 
 two-thirds of the stampers should be rising at any instant of time. 
 
 WATER WORKS. 
 
 581. The same formulae apply to water works as to other modes of 
 raising water, when it is raised perpendicularly; but as this is seldom the case, 
 instead of adding 1'5 feet for each lift, as in art. 572, 
 
 add 
 
 140 a 
 
 feet to the vertical height ; 
 
 where v is the velocity in feet per second, L the length of the main in feet, 
 and a its diameter in inches : add also one-tenth of the height for the friction 
 of the piston, and proceed in other respects as in the article referred to. 
 
 582. The supply of a town should be ten cubic feet per day for each house, 
 and for the averaged sized houses this is not more than comfort and cleanliness 
 requires ; or two cubic feet per day for each individual, besides what is required 
 for watering streets, for breweries, engines, and various purposes; and for these 
 purposes two cubic feet more ought to be delivered in summer, making a total of 
 four cubic feet per day for each person, for the greatest quantity : in small and open 
 towns a less quantity of water is required ; but even in these, two cubic feet and a 
 half ought to be calculated upon. 1 In raising water by forcing, the air vessel 
 should always be in the direction of the motion of the fluid, and not to one side 
 of it ; want of attention to this, causes those concussions to take place which tear 
 the joints asunder, break the cranks, and spoil the machinery. Double engines 
 with fly wheels are the most economical when fuel is dear, (art. 419.) and single 
 engines where it is cheap, (art. 411 and 400.) See Plates xn. and xin. 
 
 1 The following table is compiled chiefly from Leslie's Nat. Phil., with some additions, and 
 a more reasonable estimate of the quantity supplied to ancient Rome. 
 
 Towns. 
 
 Inhabitants. 
 
 Supply of water per day. 
 
 Each person per day. 
 
 London 
 Edinburgh (old service) 
 Rome (modern) 
 Rome (ancient) 
 Paris 
 Plymouth 
 
 1,225,694 
 138,235 
 136,000 
 1,200,000 
 713,765 
 21,570 
 
 3,888,000 cubic feet 
 RO (MO 
 
 3'15 cubic feet 
 n.fti 
 
 Ft S05 000 
 
 3Q-0 
 
 1 500 000 
 
 <?-0 
 
 ono nnn 
 
 O/lo 
 
 -n \ oo 
 
 1'5fi 
 
 
 
SECT, ix.] OF STEAM ENGINES. 281 
 
 OF IMPELLING MACHINERY FOR MANUFACTURING PURPOSES. 
 
 583. IRON MANUFACTURE. In this manufacture the steam engine is applied 
 to blowing machines, forge hammers, rolling, flatting, and slitting machines, and 
 various other purposes. 
 
 584. BLOWING MACHINES. The object of this machine is to supply oxygen 
 to furnaces, either for melting or reducing ores to the metallic state ; hence, in 
 order that the effect may be the same, or nearly so, when the same fuel is used, 
 the supply of oxygen should be the same. But in the same bulk of dry air there 
 is nearly 10 per cent less oxygen at 85 than at 32; and 12 per cent less 
 when the air at 85 is saturated with vapour ; consequently, if 1 500 feet per 
 minute be a sufficient supply for a furnace in winter, it may require 1625 feet per 
 minute in summer, to have the same effect ; and the difference ought clearly to 
 be gained partly by the aperture being enlarged, and partly by increasing the 
 intensity of the blast. 
 
 The blast is usually produced by condensing the air, till it will sustain a column 
 of from four to six inches and a half of mercury, (one and a half to two Ibs. 
 per circular inch,) according to the quality of the coal ; and the mean between 
 these is most generally found to answer : the quantity discharged varies from 
 3000 to 1200 feet per minute. 
 
 If v be the velocity of the piston of a blowing cylinder in feet per minute, p the 
 force of compression in Ibs. per circular inch, and a the diameter of the blowing 
 cylinder in inches, then, allowing that the friction increases the power from 1 to 
 1'25, we have 1'25 p v cf = the power in Ibs. raised one foot high per minute, 
 when the stroke is effective in both directions, and half that when in one direction 
 only. l The capacity of the air chest should be proportioned by the principle given 
 in art. 211, and the passages to it should be about one-twentieth of the area of the 
 cylinder. The quantity of air delivered into the chest will be about one-fifth less 
 than the capacity of the cylinder, when taken at atmospheric density, partly 
 through escape by the valves, and by the air not entering till the space within the 
 cylinder is rarefied so as to produce the velocity. 
 
 For this as well as all other parts of iron manufacture, the double acting con- 
 densing engine, prepared to work either expansively or at full power, will be 
 found the best. (See art. 421.) 
 
 1 The rule is only an approximation, but nearly correct for small degrees of compression ; in 
 greater ones the principles of the note to art. 377 should be applied. 
 
 2 N 
 
OF THE APPLICATION [SECT. ix. 
 
 585. COTTON MILLS. The steam engines best adapted for cotton mills are 
 double acting engines working expansively. The mean pressure on the piston of 
 an engine of this kind, using low pressure steam, when working with the greatest 
 advantage, is about five pounds per circular inch, (art. 420.) and each circular 
 inch of the piston may be estimated to drive three spindles of cotton yarn 
 twist with the preparatory machinery. And for mule yarn with its prepa- 
 ration, if 15 be added to the number of the yarn, * and the sum be mul- 
 tiplied by '26, the result will be the number of spindles for each circular inch 
 of the piston. Thus if it be No. 40, then 40 + 15 = 55, and -26 x 55 = 14 
 spindles. 
 
 It is somewhat more accurate to estimate the power of the engine in horse 
 power, and then one horse power will drive 100 spindles with cotton yarn, and 
 the preparatory machinery. And add the number of the yarn to 15, and 
 multiply the sum by 8, and the result will be the spindles that are equivalent 
 to one horse power of mule yarn with preparation. 
 
 One horse power will work twelve power-looms with preparation. 2 
 The day's work, supposing it to be 11 hours, ought to be done with about 
 90 Ibs. of the best caking coal for each horse power. 
 
 586. PAPER MILLS. Steam engines are also used extensively in making 
 paper ; for where the supply of water is regular, it has acquired a value equivalent 
 to steam power, while the latter possesses many advantages. 
 
 A beating machine requires about seven horse power to work it ; the new 
 machines for making paper, from two to two and a half horse power ; and three 
 and a half horse power will prepare one ton of old rope in a week, when the 
 machine works ten hours per day. 3 
 
 OF IMPELLING MACHINERY FOR AGRICULTURAL PURPOSES. 
 
 587. In farming, there are few things that admit of the employment of steam 
 power with economy ; but where it is employed at all, it is an advantage to apply 
 it to as many purposes as possible. 
 
 The species of work to which it is susceptible of application, are thrashing and 
 
 1 The number is the hanks to the Ib. of yarn, and a hank appears to be 120 yards. 
 A spindle produces two hanks per day at an average, and the waste in spinning is about 10 per 
 cent. 
 
 2 Brunton's Compendium, p. 109. 3 Fenwick's Essays, third edition, p. 62. 
 
SECT, ix.] OF STEAM ENGINES. 283 
 
 winnowing grain, chaff-cutting, grinding bones for manure, and to grinding corn 
 for fatting cattle and for family uses. 
 
 The boiler may be further applied to steam food for cattle. No other objects 
 occur to me, except to notice, that for drainage in fenny districts, and for irrigation 
 in others, it is worthy of the landowner's consideration, whether its application 
 would or would not repay the expense. 1 
 
 588. THRASHING. Thrashing machines to be driven by a steam engine are 
 made from four to six horse power ; and the usual proportions are, 
 
 The feeding rollers 35 to 37i revolutions per minute, diameter 3* inches. 
 
 Straw rakes 30 revolutions per minute, diameter 3i feet. 
 
 Drum 300 revolutions per minute, diameter 3| feet. 
 
 The drum has four beaters faced with strong iron plate ; and a cylindric frame 
 with four sets of teeth, five inches long, attached to its circumference, forms the 
 straw rake. 2 
 
 The breadth of the machine, or length of the rollers to receive the feed, is 
 limited by the width to which one feeder can attend in a proper manner, and 
 about from four to five feet is the range: the thickness of the feed cannot be 
 materially altered from that which gives the best effect; and therefore there is 
 only the velocity in which the power can be altered beyond the small change in 
 width. The quantity of wheat thrashed by a machine four feet in breadth varies, 
 according to its quality, from twelve to twenty-four Winchester bushels per hour, 
 and from sixteen to thirty bushels of oats per hour. 
 
 The power required is 100,000 Ibs. raised one foot per minute when for thrash- 
 ing, and 133,000 raised one foot per minute when winnowing machinery is also 
 
 1 By a single engine, (art. 411.) 280,000 cubic feet of water may be raised one foot high by 
 one bushel of coals, and for any other height divide 280,000 by the height in feet. It will require 
 an engine of one horse power to work eleven hours and a half per day, to raise that quantity 
 daily. The expense will be about .8 per annum for each horse power, to return the first cost, 
 and pay for the renewals and repairs of the engine ; the fuel is one bushel of coals per day for 
 each horse power ; and one man and boy will attend an engine of ten or twelve horse power, 
 and also partly to the distribution of the water: the quantity required for an acre would 
 be about 500 cubic feet per day, and therefore an engine of ten horse power would supply 
 560 acres, if it had to be raised ten feet, at a cost which in few cases could exceed ten 
 shillings per acre if continued for six months per year. On proper lands for the purpose, the 
 return would be ample, and a more perfect mode of applying water to land will very probably 
 be discovered. 
 
 2 The straw advances so that each inch receives three strokes of the beaters ; and the stroke 
 should be made with a velocity of about 55 feet per second, or the beater should move at 
 the rate of 3300 feet per minute; these conditions being attended to, the parts may be, in other 
 respects, arranged as the engineer pleases. 
 
284 OF THE APPLICATION [SECT. ix. 
 
 worked ; other sized machines nearly in proportion to their breadth : this supposes 
 the machine to be well made and kept in tolerable order. 
 
 The proper species of engine for farm use is the double engine (art. 414 
 and 419.) with slides, and the whole arranged in the most simple and obvious 
 manner. 1 
 
 589. CORN MILLS. The mean quantity of power required to grind and dress 
 a Winchester bushel of wheat per hour is 31,000 Ibs. raised one foot per minute, 
 and the best velocity for the circumference of a millstone is twenty-three feet per 
 second ; and with this velocity a pair of five feet stones will grind from four to 
 five bushels per hour, according to their condition and the state of the grain : 
 the double expansive engine should be used for this kind of work ; and when 
 working to the best advantage with low pressure steam, it should grind 
 fourteen bushels of wheat for each bushel of coals, and the average should be 
 eleven bushels and a half for one bushel of coals. 2 The same species of engine 
 with strong steam will of course do more work with a given quantity of fuel. 
 (See art. 419.) 
 
 OF THE APPLICATION OF STEAM POWER TO CARRIAGES. 
 
 590. The application of a power within a carriage to move it, is a subject 
 that at an early period engaged the attention of speculative men. Some of their 
 schemes are described by Emerson in his ' Mechanics,' and he gives an example 
 of calculation there (Ex. 20. p. 194.) which seems to be very little understood. 
 The object of it is to determine the power required to move a waggon ; but in fact 
 it simply determines the relation of the forces, the power being the same whether 
 it be in the waggon or out of it, provided it does not add to the weight of the 
 waggon. But power cannot be gained without adding weight; and in steam 
 carriages the whole mass of the engine, with its boiler and fuel and water, has 
 to be moved as well as the load ; and in order to keep the engine as simple and 
 light as possible, and to avoid the weight of water and complexity of a condensing 
 apparatus, high pressure steam is always employed. 
 
 The idea of employing steam as a moving power has been considerably 
 
 1 If an engine be applied for irrigation, it may have the thrashing machine attached when the 
 situation is convenient ; but in that case a double engine should be used. 
 
 2 For 6-5 Ibs. per hour is equal to a horse power, (art. 419.) and a bushel of coals being thirteen 
 times this quantity, it is equal to thirteen horse power per hour ; and 31000 : 33000 : : 13 : 14, 
 nearly. 
 
SECT, ix.] OF STEAM ENGINES. 285 
 
 ridiculed, and some of the schemes for applying it not without reason. As 
 far as railways are concerned, it has however been proved to be applicable, 
 and with as few accidents as in any other of the varied applications of steam 
 power. 1 
 
 591. OF THE APPLICATION OF STEAM POWER TO RAILWAYS. The power of 
 
 steam may be applied by means of a fixed engine, or by a moveable one called 
 a steam carnage. 
 
 FIXED ENGINES have been applied only in the case of inclined planes, and no 
 peculiarity is required in the construction of the engines, more than is wanted in 
 one for impelling a machine. Low pressure engines are generally employed for 
 this purpose ; and they are obviously the most safe and economical for the end, 
 unless when there is not a convenient supply of water. 
 
 The motion of the engine ought to be equalized by a fly wheel, and it should 
 also be provided with a regulating valve. 
 
 To proportion the power of the engine to the effect, the area of the piston 
 in inches, multiplied by the effective pressure on an inch in Ibs., should b e 
 equal to the resistance of the carriages added to the friction of the rope and the 
 engine. 
 
 If A be the ascending, and D the descending load, and q the resistance from 
 friction at the axis, and i the angle of inclination, 
 
 Then A (sin. i + q) D (sin. i - q) = (A D) sin. i + (A + D) q = the re- 
 sistance of the carriages. 
 
 The weight of the rope or chain, and of the moveable parts of the engine, being 
 C, its friction and the stiffness of the rope may be represented by C S, hence, 
 
 1 On common roads there are several circumstances which prevent the application of steam 
 power. The undulations of the road render it necessary to provide a power competent to ascend 
 the greatest inclination, and consequently an immense addition must be made to the weight of 
 the engine, so as to make the engine itself on an ordinary road consume half the power it gene- 
 rates. The resistance of these roads may be reduced by using larger wheels, as it chiefly arises 
 from the wheels sinking into the road ; and larger wheels afford a greater surface without increasing 
 the quantity to be depressed, while broad wheels give very little if any advantage. See my book 
 on ' Rail Roads,' p. 44. It may be proved, that no species of feet can be applied that will require 
 less power than plain wheels. An animal is contrived to move among obstructions, and when we 
 attempt to copy from the beautiful arrangements of our Creator, we should never lose sight of their 
 object. It is their perfect adaptation to the end, and their accomplishment by the most simple 
 means, that excites our admiration ; and the more we study the fine examples of the application of 
 power which nature affords, the more we feel the advantage of knowing the first principles which 
 determine the action of natural forces. 
 
286 OF THE APPLICATION [SECT. ix. 
 
 if a be the diameter of the piston, and p = the pressure on a circular inch, we 
 have, 
 
 a" p = (A - D) sin. i + (A + D) q + C S. 
 From this the diameter of the cylinder is easily found, and in all cases 
 
 where R is the radius of the wheels of the carriage, r that of the axles, and / the 
 friction, when the pressure is 1. 
 Also 
 
 s = iZ 
 x ' 
 
 where X is the diameter of the pulleys, and x that of the axes. When the railway 
 is level, 
 
 a 2 p = (A + D) q + C S. 
 
 In these equations the piston of the engine, and the load, are supposed to move 
 at the same velocity. 
 
 592. STEAM CARRIAGES. The engines of steam carriages are double non- 
 condensing engines, of the kind described in art. 372. They have generally two 
 cylinders. If, 
 
 p be the mean effective pressure on the piston, 
 a the diameter of the cylinders, 
 v the velocity in feet per minute ; 
 i the angle of inclination of the rails of the road, 
 q the friction of all the axes, 
 W the weight of the carriages and their loads, 
 V their velocity in feet per minute, 
 and E the weight of the engine. 
 
 Then, V (W + E) (g + sin. z) = 2 a* p v, in ascending the inclination ; 
 and, V (W + E) (q sin. t) = 2 a z p v, in descending the inclination. 
 
 Also 
 
 E (-08 cos. sin. i) _ -^ 
 q + sin. 
 
 so that the engine may not slide in ascending ; and 
 
 E (-08 cos. i + sin. i) _ w 
 
 - : - : -- W, 
 
 5 sin. t 
 when it will not slide in descending. 
 
SECT, ix.] OF STEAM ENGINES. 287 
 
 In either case, 
 
 when r is the radius of the axle, and R the radius of the wheels. 
 
 The engines should work expansively when moving at the ordinary rate, and 
 upon the mean inclination, with the power of working at full pressure on the 
 steeper ascents. See Sect. v. art. 371 380. 
 
 For further information respecting steam carriages and railways, see the 
 Appendix. 
 
SECTION X. 
 
 OF STEAM NAVIGATION. 
 
 593. ON the value of the application of steam to impel vessels, it has become 
 unnecessary to say more than that its employment is extending rapidly at almost 
 every place on the globe where the trade is considerable, and that its use is limited 
 only by its yet imperfect state. If we had intended to have confined our researches 
 to the mere application of an engine to a vessel already constructed, our labour 
 would have been short, and easily completed : but the construction of vessels is 
 a subject which is capable of improvement ; and while we think there is a power 
 in science to indicate the steps by which it may be improved, it is our duty to 
 submit it to the reader. 
 
 The forms of vessels for stability, speed, capacity, and strength ; the kinds of 
 vessels for different purposes, the resistance, and modes of propulsion ; the nature 
 of the engines adapted for vessels, the strength of their parts, and the species of 
 fuel, and its management to obtain the best effect ; are all objects of importance, 
 and each of these we propose to consider. 
 
 These inquiries are equally applicable to mercantile and to government pur- 
 poses, but there is yet another portion of the subject to which it would be desirable 
 to direct attention. 
 
 In the case of war, steam boats will become a means of attack ; therefore it ought 
 to be considered how far they may become a means of defence, the power of 
 resisting being the best guard against a mode of attack, which will deprive us of 
 many of the advantages of our insular state. Hence, the construction of gun boats 
 for the defence of rivers, and of river navigation, and harbours, would be a proper 
 subject for inquiry, if our limits did not forbid it. 
 
 OF THE FORMS OF VESSELS FOR STABILITY, SPEED, CAPACITY, AND STRENGTH. 
 
 594. In considering the properties of a vessel, the orderly arrangement of our 
 subject requires that we should treat, First, Of stability, or the power a vessel 
 
SECT, x.] OF STEAM NAVIGATION. 289 
 
 has of resisting any change of position when in the water; Secondly, The forms 
 having stability which have the least resistance, and are therefore best adapted for 
 speed ; Thirdly, The different methods of propelling vessels ; and Fourthly, The 
 construction for strength. 
 
 OF THE STABILITY OF VESSELS. 
 
 595. A perfectly spherical ball floating in a fluid has no stability whatever, 
 except that which arises from the friction of the fluid against its sides. On the 
 addition of a small weight to any point of its surface, that point would immediately 
 descend, and become the lowest : such a form would be useless as a vessel. 
 It is obvious, however, that when a weight has been added, and become the lowest 
 point, the sphere possesses a degree of stability depending on the quantity of 
 weight, compared with the weight of the sphere itself. Hence, stability may be 
 given by disposing the weight of a floating body. 
 
 Stability may also be given by the form of the floating body : a spheroid, for 
 example, remains in stable equilibrium when its longer axis is horizontal, and a 
 triangular prism resists change of position with considerable energy from its 
 peculiar form ; so does a thin rectangular prism. 
 
 596. Stability is distinguished by its being longitudinal or lateral; these should 
 be separately considered, and when each is the greatest possible, their joint effect 
 will be a maximum. 
 
 597. For river navigation, the mode of obtaining stability does not appear 
 to be of much importance, but for a sea vessel it must be obtained, so that the 
 vessel may have the least motion possible in consequence of the action of the 
 disturbing forces ; hence, it is necessary to consider that the sea is not a level 
 surface at rest, and that at the time when stability is most important to a vessel, 
 the greatest degree of unevenness occurs. 
 
 598. LONGITUDINAL STABILITY. A vessel at rest would be least disturbed 
 by the motion of the sea, if its surfaces at the water line were vertical ones, and 
 the fore and aft parts of the same figure ; but in motion it is an advantage that 
 the parts should spread above water, both fore and aft, to prevent the vessel 
 burying its head in the wave, or dropping behind as the wave leaves it. The 
 quantity of motion is not increased by this construction, provided the parts produce 
 similar effects ; and the degree of inclination should be proportioned to the velocity 
 the vessel is expected to make. It is also obvious, that the vessel will be more 
 easy in its longitudinal motions, the more gradually it terminates at its extremities. 
 If the vessel be inclined by the action of a lateral force, the longitudinal motions 
 
 2 o 
 
290 OF STEAM NAVIGATION. [SECT. x. 
 
 will be more easy, in proportion as the cross section approaches to that of a solid 
 of revolution. 
 
 599. LATERAL STABILITY. The inequality of the surface of the sea will 
 alone produce considerable lateral motion, if the sides be not sensibly vertical ; 
 hence, in sea vessels lateral stability should not be obtained by form at the surface 
 of the water. The next important point is, that the stability should be equal 
 throughout the length. 
 
 To render it easier to manage the inquiry, we may consider the vessel to be 
 a homogeneous mass of matter, with vertical or circular surfaces at the water 
 lines when at rest ; and that it is of a parabolic form, having the equation p x y", 
 taking the two cases when the ordinate y is the half breadth, and when it is the 
 depth ; for these cases enable us to contrast very opposite forms. 
 
 600. The ordinates being parallel t(^ the depth, we have the difference of the 
 moments of the parabolic parts, when i is the angle the body makes with its 
 position, and B D (Fig. 3. Plate xvi.) coincides with the water line = 
 
 
 and the difference between this quantity and the moment of twice the area of 
 the triangle B C b is the stability. 
 
 2 / b \ s . b s sin. i ., f ., . . i 
 
 cut, -Q ( -5 J sin - * = TO = the moment of the triangles ; 
 
 hence, 
 
 . * ri- ' (v - J>" g * V the stability. 
 12 \ 2 + /' 
 
 The capacity of the section is f^,. 
 
 601. If the negative quantity be less than b z , the body has no stability; hence 
 we see that a certain relation must hold between the breadth and depth, to render 
 a vessel stable. 
 
 602. If the form be a triangle, then n = 1, and putting A = the area, we 
 have, 
 
 Sb sin. i ,, n , a b 
 
 = j_ (6* 2 o), and A = _^-. 
 
 603. If the form be a common parabola, then n = 2, and 
 
 86 sin. t ,, . 2 a b 
 
 = - (6* - 3 a"-), and A = --. 
 
SBCT . x .] OF STEAM NAVIGATION. 291 
 
 604. If the form be a cubic parabola, then n = 3, and 
 
 8 = b s ' m - l (b- - 3-6 *), and A = *JLL. 
 
 605. If the form be a parabola where p x = y*, as in Fig. 3. Plate xvi. then, 
 
 - *' 
 
 (b* - 4-3 a 2 ), and A = 
 
 5 a b 
 
 606. The stability and capacity both increase as the ordinate of the parabola 
 becomes of a higher power, but a greater breadth is necessary in proportion to the 
 depth. 
 
 607. When the ordinates are parallel to the breadth, 
 
 Jy d x ( y - cos. i + (a x) sin. i\ Jy dx [~- cos. * (a x) sin. i J 
 
 r 2 n" a- y sin. i 
 
 = 2 am. ,Jyd* (a -*)-= (ll + 1)2 , +1)' 
 
 and, 
 
 _ b 3 sin, f 2 2 a 2 b sin, i _ bjiin.i f Js _ 12 n 2 o* \ 
 
 12 ' ( + l)(2n + 1) ~~12 \ ~ ( + 1)(2 + !)/' 
 
 The capacity is ~^ as before ; 
 
 and in the case of the triangle we have the same results. 
 
 608. But if the form be a common parabola, or n = 2, then 
 
 S = *^l (b'- - 3-2 a 2 ), and A = ^f* 
 \~ o 
 
 609. If the form of the parabola be p x = y 5 , as in Fig. 4. Plate xvi. then, 
 
 S = ill (J 2 - 4-5 a*), and A = ill. 
 
 610. This species of figure may be easily traced through all the varieties of 
 form, and it is so easy to compute its capacity and to describe it by ordinates, 
 that it is much to be preferred to the elliptical figures which foreign writers have 
 chosen for calculation. * The breadth should be every where in the same ratio 
 to the depth, to render the stability equal throughout the length, or so that the 
 vessel may undergo no strain from change of position. * 
 
 i For a mode of describing curves of this kind, see my ' Principles of Carpentry,' Sect. i. 
 art. 58. 
 
 4 For other methods see Bossut's Hydrodynamique, torn. i. chap. xiii. et xiv ; or Poisson's 
 ait de Mecanique, torn. ii. p. 389. 
 
OF STEAM NAVIGATION. 
 
 [SECT. x. 
 
 OF THE RESISTANCE OF VESSELS. 
 
 611. The resistance of a vessel moving in a fluid increases from the com- 
 mencement of the motion, till it is equal to the moving force, and then the motion 
 becomes uniform. It is the resistance at this uniform motion only, which we have 
 to consider. 
 
 In order to assist in the first steps of the inquiry, let us confine ourselves to 
 a prismatic vessel with flat ends, moving in the direction of its length. 
 
 612. The resistance of such a prism would be nearly equal to the head of 
 water, which would give the water in a canal of the same length, and one and a 
 half times the section of the immersed part of the prism, the same velocity as 
 the prism. 
 
 For let A B be that head ; then the resistance to efflux at D must be equal 
 to the resistance to motion at C, the section being the same ; otherwise the motion 
 would accelerate. But the fluid will rise at C, and fall at D, till the difference 
 be equal to the head due to the velocity of the boat ; and the efflux at D must 
 
 FIG. 25. 
 
 both supply a void with fluid equivalent to the velocity of the boat, and supply 
 a resistance equal to the head pressure. This will be the case when two-thirds 
 of A B is the head corresponding to the velocity. Hence, if v = the velocity, 
 A E = h, and B E = x = the head equivalent to the friction, 
 
 _ 64 (h x) . 
 1-5 
 
 where 64, neglecting a small fraction, is the proper coefficient for the motion of 
 a fluid when free from friction or cohesion ; consequently, 
 
 1-5 v s 
 
SECT, x.] OF STEAM NAVIGATION. 
 
 613. Now if c be the perimeter of the section in contact with the fluid, and 
 a its area, / the length of the vessel, and F = 64 times the friction when the sur- 
 face is 1, we have, 
 
 the head equal to the friction being nearly as the square of the velocity directly, 
 and the area inversely, and the friction being as the surface of the fluid put in 
 motion, or the rubbing surface of the vessel. 
 
 These two values of x must therefore be equal, hence 
 
 , _ 1-5 t> _ /c F v- 
 ~64~ = 64 a ' 
 
 or the whole head is, 
 
 , _ 1-5 t> 2 / c F p 
 ~~ ~~ 
 
 But the resistance being usually estimated in Ibs., we have for sea water 64 ha 
 = that resistance, = t? (1'5 a + /cF) = R, the resisting force; and the power 
 required is as the force and velocity = v 3 (1'5 a + / c F) = the Ibs. raised one 
 foot per second, when F is in Ibs. 
 
 614. For fresh water put 1*45 in the place of 1'5, but the correction is not 
 necessary in practice. The coefficient F is 0*0032 Ibs. found from experiment. 
 
 615. If the body have a simple angular prow, and an after body of the same 
 figure, and a be the angle the prow forms with the direction of its motion, and 3 
 the angle of the after part, then the pressure on its surface depends on the velocity 
 of the surface, in a direction perpendicular to itself. This velocity before is v sin. a ; 
 and behind v sin. ; being to the velocity of the vessel as the sine of the angle 
 is to radius ; and therefore the resistance would be, 
 
 ., 2 /2 a sin. 'a +a8in. a /3 + /cF \ 
 
 The effect of this head in the direction of the motion of the vessel is as the sine 
 of a to radius at the prow, but the quantity of fluid required to fill the void behind 
 is constant for the same angle ; hence the resistance is, 
 
 ^asin.aq + asin.^ + ^^ = R> 
 
 and, 
 v , ^arin.a+gin.0 + / c F ) = the power in Ibs. raised one foot per second. 
 
 This gives the resistance when the vessel is of a wedge shape at both ends, or of 
 any regular pyramidal form, a being the angle the slant side of the pyramid makes 
 
294 OF STEAM NAVIGATION. [SECT. x. 
 
 with the length ; also when the body terminates either in cones or pyramids, the 
 angles being those the slant sides form with the length. 
 
 616. If the section be a triangle, and the ends triangular pyramids, being 
 the angle the side of the triangle forms with the upper surface, then, if q be the 
 product of the sin. , by sin. Q, the resistance will be, 
 
 v3 /a q + q ) + 0-0032 I c \ = the power in Ibs. raised one foot per second. 
 
 The resistance of this figure is less than that of any convex curved solid, but its 
 capacity is also small ; and its stability depending on the form at the water lines, 
 it will be subject to roll at sea. Great capacity cannot be obtained with a 
 minimum of resistance. 
 
 617. If the plan of the water lines be composed of circular arcs, the bottom 
 flat, and the radius be m times the half breadth of the boat, and z be the length 
 of the curved part, r = the radius, and a the depth, which is uniform ; then 3 z 
 = r (4 */ 2 m ^ 2 m z 2 ), and 
 
 V 3 a /3z r(l-m)(3- 4m)./2m' + (2 2 (1 m) \ (1 - m) + 3 m\ r -0032 / c\ _ 
 a V 4 3 a / 
 
 the power in Ibs. raised one foot per second, required to keep the vessel in motion 
 at the velocity v. 
 
 618. In canal boats m = ^ = -125, or the radius is 4 times the breadth, 
 and therefore v 3 ('35 ab + -0032 Ic) = the power in Ibs. raised one foot per 
 second. 
 
 If the radius be equal the breadth, then m = '5, and v 3 ('74 a b + '0032 / c) = 
 the power in Ibs. 
 
 619. Mr. Bevan made some experiments with a canal boat of the form just 
 described, the results of which he has communicated to me for the purpose of 
 comparing theory with practice. 
 
 The length of the boat was 69'57 feet, its width 6'83 feet, its floating depth 
 when tried 0'89 feet ; the bottom was flat, and the sides were parallel to within 
 about 13'75 feet of each end, but the ends were curved, the curves being circles 
 described by a radius of 8 times the half breadth of the boat. The whole 
 surface in contact with the water was 540 feet ; and the weight was 91 tons. 
 Putting these numbers in the equation (art. 618.) we have 
 
 v- (-89 x 6-83 x -35 + -0032 x 540) = 3-8 v* = the resistance. 
 
SECT. X.] 
 
 OF STEAM NAVIGATION. 
 
 295 
 
 Velocity. 
 
 Resistance in Ibs. 
 
 Feet per second. 
 
 Miles per hour. 
 
 By experiment. 
 
 By calculation. 
 
 feet. 
 
 miles. 
 
 Ibs. 
 
 Ibs. 
 
 1-0 
 
 
 
 3-8 
 
 1-31 
 
 0-89 
 
 6-1 
 
 6-5 
 
 1-98 
 
 1-35 
 
 14-0 
 
 14-8 
 
 2-93 
 
 2-00 
 
 28-0 
 
 32-5 
 
 3-666 
 
 2-50 
 
 
 51-0 
 
 4-30 
 
 2-92 
 
 56-0 
 
 70-0 
 
 The agreement is sufficiently near for practical purposes. 
 
 620. The area of the bottom being 4 17 feet, a ton will sink it an inch. The 
 
 fi.QO 
 
 increase of section by adding a ton to the load is therefore ^ = .57 feet ; and 
 
 the increase of surface 12 feet. Adding each ton must therefore increase the 
 resistance about 3'2 Ibs., at the velocity of 2i miles per hour ; therefore the load 
 in tons multiplied by 3'2, added to 51 Ibs. for the boat, will give the force required 
 to draw it. Thus if the load be 20 tons, the force of traction will be 20 x 3*2 + 51 
 = 115 Ibs. 
 
 621. The forms used for vessels are generally curved surfaces of double 
 curvature. To investigate these we may consider them divided into gores, having 
 their bases at the section, and meeting in a point at the water line. A solution on 
 this supposition is fully sufficient for practical objects. Let r be the radius of 
 curvature of the gore, and c its breadth at the base, a being its distance from the 
 axis. Then the differential of the area of the section occupied by the gore 
 will be, 
 
 ex dx 
 
 and, 
 
 c d x 
 
 2 sin. 3 a + sin. 2 a 
 
 = the resistance from pressure. 
 
 By using the approximate equation, 2 r x = y*, we have 
 
 = ? ^- 
 
 d x = ? ^-, and 2- = sin. a, 
 r r 
 
 hence, 
 
 v z c ( JL_ + _L_ -2 ?L_ ) dy = the differential of the resistance. 
 
 \r* 2 r 3 2 r* a 4r*a/ 
 
 Its fluent is, 
 
 - / JL + _J( _ y 8 .} the direct resistance. 
 
 ^5r 8 14r2a 24 r a 
 
296 
 
 OF STEAM NAVIGATION. 
 
 [SECT. x. 
 
 Putting y = N/ 2 r x, and b = 2 x ; j- = a = , and correcting by comparison 
 with particular cases, we have, 
 
 j-(-^2 ' + 0-0833) + -0032 (/ + -29 4 jl + 2 * ) j = the resistance in Ibs. 
 
 V- C 
 
 622. Now, by taking a radius that will describe an arc nearly agreeing with 
 the form, the resistance will be found with tolerable accuracy, even in the most 
 complicated forms ; and in cases where the curve is a circle, it will be very near 
 the truth. To render it more easy to make such calculations, the following table 
 is added, with examples to explain its application. 
 
 Radius of cur- 
 vature in half 
 breadths. 
 
 
 Equations for different radii c 
 
 f curvature. 
 
 1 
 
 t> 2 c (-245 
 
 b + -0032 (I +-54)) 
 
 = resistance 
 
 1-25 
 
 188 
 
 - + , + -545 
 
 = resistance 
 
 1-50 
 
 146 
 
 - + , + '58 
 
 = resistance 
 
 1-75 
 
 120 
 
 - + > + "616 
 
 = resistance 
 
 2 
 
 101 
 
 - + , + -65 
 
 = resistance 
 
 2-25 
 
 086 
 
 - + + "68 
 
 = resistance 
 
 2-5 
 
 075 
 
 - + + '71 
 
 = resistance 
 
 2-75 
 
 067 
 
 - + + -74 
 
 = resistance 
 
 3 
 
 060 
 
 - + + -77 
 
 = resistance 
 
 4 
 
 -041 
 
 - + + -87 
 
 = resistance 
 
 5 
 
 -032 
 
 - + + -955 
 
 = resistance 
 
 6 
 
 -025 
 
 - + +1-05 
 
 = resistance 
 
 7 
 
 -021 
 
 - + +1-13 
 
 = resistance 
 
 8 
 
 ti* c (-018 
 
 b + -0032(7 + 1-2 4)) 
 
 = resistance 
 
 In this table b is the breadth of the vessel at the surface of the water, / the 
 length of the part which is parallel, c the girt from water edge to water edge, 
 of the lower part of the midship section, v the velocity in feet per second, and the 
 result is the resistance in Ibs. To find the power, multiply the resistance again 
 by the velocity ; or use the cube instead of the square of the velocity in the above 
 table, the result is the Ibs. raised one foot per second. 
 
 623. Required the resistance of a vessel of which the breadth is 22 feet, the 
 length of the parallel part 80 feet, and the girt of the midship section 31 feet, 
 when the velocity is 10 feet per second, and the radius of curvature equal 4 half 
 breadths. 
 
 In this case, by the table we have, 
 
 * c (-041 6 + -0032 (/ + -87 4)) = 10" x 31 (-041 x 22 + -0032 (80 + -87 x 22)) = 
 
SECT, x.] OF STEAM NAVIGATION. 297 
 
 3778-9 Ibs. for the resisting force ; consequently the power is 10 x 3778*9 = 37789 
 Ibs. raised one foot per second ; and as 550 Ibs. raised one foot per second is a 
 
 S77SQ 
 
 horse's power, the resistance is equivalent to -ggg- = 68'7 horse power. 
 
 As ten feet per second is six nautical miles per hour, or nearly seven common 
 miles, and the power required is as the cube of the velocity, it is easily ascertained. 1 
 
 OF THE METHODS OF PROPELLING STEAM VESSELS. 
 
 624. Much of the advantage of steam power depends on its being commo- 
 diously and effectively applied to propel vessels. A slight review of these methods 
 will therefore enable us to judge whether or not the most effective and commodious 
 have been resorted to. 
 
 The first and most simple and ancient method of applying a power within a 
 vessel to move it, is by means of oars, and the mode of combining them appears to 
 have been carried to a considerable degree of perfection. Oars, however, are not 
 at all adapted to move a large vessel ; they occupy too much space, and would 
 require too complicated a system of machinery to move them. Second : next in 
 simplicity, and perhaps also next in time, is the method of putting a wheel like a 
 water wheel, with paddle boards on each side of the vessel. This mode is now 
 almost universally followed. Third : an ingenious combination of parts has been 
 proposed, to be constantly under water, and to fold up into a small space when 
 they are moved forward, and spread when striking backward. Fourth : inclined 
 planes placed behind the vessel, and moved with an alternating motion. Fifth : 
 Daniel Bernoulli's method, proposed in 1752, consisting of planes immersed in the 
 water, parallel to the sides of the vessel, which, turning in a collar, were to be moved 
 in a plane, perpendicular to the keel. Sixth : a screw, resembling the water screw, 
 working in a cylinder entirely immersed in the water. 2 Seventh : or two spirals 
 or screws to work in opposite directions without a cylinder. 3 And lastly : a pump 
 
 1 Some recent valuable experiments by John Macneill, Esq., C. E., show that the preceding 
 investigations and formulae for the resistance of vessels, (which are far from being clear,) are not 
 to be depended upon as accurate. See Appendix. ED. 
 
 2 It was proposed by Mr. Scott of Ormiston. Dr. Thomson's Annals of Philosophy, vol. xi. 
 p. 438. 
 
 3 This method was partially tried by Mr. Whytock, (Brewster's Philosophical Journal, vol. ii. 
 p. 39.) and is alluded to by Col. Beaufoy, who states it to have been brought from China ; and he 
 attended to see an experiment on a considerable scale, made in Greenland Dock by Mr. Lyttleton. 
 This gentleman had fixed to the stern-post of a Virginia pilot boat, a frame containing a large 
 copper spiral, which, by a winch turned by two or more men, gave it a rotary motion : the effect 
 was much less than expected, for, notwithstanding the boat was completely empty and considerable 
 exertions used, the progressive velocity did not exceed the rate of two miles per hour. 
 
 2 P 
 
298 OF STEAM NAVIGATION. [SECT. x. 
 
 to raise and propel water out behind the vessel : this mode was proposed by Ber- 
 nouilli, and afterwards by Mr. Linaker. 1 These, with numberless variations, the 
 greater part of which are obviously inferior to the methods in their simple form, 
 have been proposed. Some of the best we propose to notice. Our selection must 
 however be limited, because it must be confined to those which afford sufficient 
 power in a convenient manner, and without being liable to injury by the violence 
 of the waves, or to get out of order. 
 
 625. The species may be divided into two classes ; viz. 1. those in which the 
 action is continuous, or nearly so ; 2. those which act at intervals. To the first 
 class belong the second, sixth, and seventh methods ; to the second, the first, 
 third, fourth, fifth, and eighth. 
 
 Since, when the action is continuous, the area of the surfaces in action, multiplied 
 by their resistance, must be equal to the area of the vessel, by the vessel's resistance 
 when reduced to the same direction, it is obvious that all those which act at inter- 
 vals only, must require to be of greater area than those which act continually. 
 Hence, unless there be some other manifest advantage, this circumstance alone 
 must determine us to reject all except the first class, and of this to take only the 
 second, sixth, and seventh methods. Most of the others would require complicated 
 action, and be inconvenient in practice. The first class also reduces to two ; for 
 the two opposite water screws without a cylinder give about the same effect as one 
 with a cylinder ; and this method, though it has not been used, deserves attention, 
 from the circumstances of its being capable of acting wholly below the surface of 
 the water, and in a direction parallel to the motion of the vessel, and only so far 
 above the centre of resistance as is deemed necessary to stability. I can easily 
 conceive that the trial of an experiment may be the means of condemning a very 
 useful principle, merely through inattention to the proportions and mode of action. 
 
 OF THE SPIRAL PROPELLER OR WATER SCREW. 
 
 626. The acting portion is a spiral surface projecting from a cylindrical axis ; 
 and, in order that it may be at all effective, each point in the surface must revolve 
 so rapidly, that the motion of that point in the direction of the axis must be greater 
 than that of the vessel. Also if the angle of the spiral to the axis be constant, it is 
 obvious, that by having more than one revolution, the rest add little to the effect, 
 perhaps not equivalent to the additional friction. 
 
 1 Buchanan on Propelling Vessels by Steam, p. 40. 
 
SECT. X.] 
 
 OF STEAM NAVIGATION. 
 
 299 
 
 Let B A C = a be the angle which the screw forms with a line A B perpen- 
 dicular to its axis ; then during the time the boat would move from C to B, a point 
 
 FIG. 26. 
 
 in the surface must move from B to A, otherwise it would retard the boat ; and, in 
 order that it may be effective, it must move at some greater velocity. But the 
 velocity of the boat, v, is to that of a point in the surface when no effect is pro- 
 duced, as B C : A B : : v : n A = - - Hence the actual effective velocity 
 
 tan. a 
 
 must be, 
 
 V - 
 
 tan. a 
 
 V tan, a v 
 tan. a 
 
 2 IT x 
 
 Let x be the variable radius of the cylinder, then - - = the length of the 
 
 spiral, and '^- = the differential of its area. Its resistance is therefore, 
 
 v (V tan, a >)* (2 sin, a 3 + sin. aPjxdx 
 
 cos. a tan. * a 
 
 when the vessel is at rest ; and when it is in motion, it increases in the ratio of 
 : v ; hence, 
 
 TT v (V tan. a v) (2 sin. 2 a + sin. a) x d x = the differential of 
 
 V tan. a v 
 tan. a 
 
 the resistance. 
 
 The integral gives, 
 
 |- IT v x 3 (V tan. a v) (2 sin. 2 a + sin. a) the resistance. 
 This resistance is to the effect to impel the boat, as the radius is to tan. a ; 
 hence, 
 
 ^ IT x 3 v (V tan. a vf (2 sin. a" + sin. a) tan. a = the force, 
 and % TT x z v z (V tan. a -- v) (2 sin. 2 a + sin. a) tan. a = the effect, 
 which should be equal to the resistance of the vessel. 
 
 It is a maximum when v s (V tan. a v) = a max. : that is, when V = ~ - 
 
 2 tan. a 
 
 Hence the effect at the maximum is ^ w x~ v 3 (2 sin. 2 a + sin. a) tan. a. 
 
 i ., , , 3 ir x- v 3 (2 sin. 2 a + sin. a) , . , 
 
 But the power to produce it must be, - g - , its velocity being 
 
300 OF STEAM NAVIGATION. [SECT. x. 
 
 V. Consequently, when tan. a = 1, the power is to the effect as 3 to 2, as in the 
 ordinary paddle wheel ; but if tan. a = 1'5, the power and effect are equal : on the 
 contrary, if tan. a = '5, or the angle C A B is about 26, the power is to the effect 
 as 3 : 1. 
 
 Now a little more than one revolution of the spiral would produce this effect, and 
 a second revolution at the same angle could have very little action, because the 
 water would have acquired all the velocity the spiral could communicate. If it be 
 continued, it should therefore be made with a decreasing angle. 
 
 627. In practice the size corresponding to these effects is every thing ; our 
 next object must therefore be to ascertain it. Taking an angle of 60 for the angle 
 CAB, tan. a = 1*732, and sin. a = '866. The effect is in this case, 
 
 1-732 , j* (2 x -8662 + -866) = 0-73 * x- ; 
 
 but JT .r 2 is the area of the end of the cylinder, therefore each foot of surface of the 
 end of the cylinder will act with a force of 0'73 Ibs. for one foot per second. The 
 length of the cylinder would be 2 ic x tan. a = 10 - 8 times its radius, or 5'4 times 
 its diameter. The power required for this effect is, 
 
 3 x- (2 x -866* + -866) _ .g g7 ^ ^ 
 8 
 
 or 0'887 Ibs. for each foot of area of the end of the cylinder, for one foot per 
 second. 
 
 When a = 40, the effective force is only 0'4368 Ibs. per foot, and the power to 
 each foot must be '64 Ibs. The power therefore decreases nearly in the same ratio 
 as the length. 
 
 These calculations are sufficient to show that this method may be used with 
 considerable advantage, the action being under water, and the projection from the 
 side not so great as paddle wheels ; while the smoothness and the uniformity of the 
 motion are circumstances much in its favour. On the other hand, the mode of 
 communicating motion and the resistance the parts will offer that are applied for 
 that purpose, are objections ; for the present I shall therefore content myself with 
 recommending it to the notice of my readers. 
 
 PADDLE WHEELS. 
 
 628. The next inquiry is to ascertain the effect of paddle wheels. Of these 
 the commonest species are plain boards, called paddle boards, fixed to the arms of 
 a wheel ; these arms are as thin as is consistent with strength, and are connected 
 by one or more thin iron rings, to act as braces in giving them firmness ; they are 
 
SECT, x.] OF STEAM NAVIGATION. 301 
 
 sometimes made to slide on the arms, so as to reduce or increase the depth of 
 immersion in the water, according as the vessel is more or less laden. 
 
 629. To determine their power, let V be the velocity of the exterior portion of 
 the wheel, and r its radius ; then the velocity at any distance r x from the centre is 
 
 ( r ~ x > . B u t while the paddle acts on the water, the vessel moves forward, and 
 
 the water recedes only at the rate of the difference between the velocity of the 
 wheel and that of the vessel ; therefore, if v be the velocity of the boat, 
 
 P^ v = the velocity with which the paddle strikes the water. Hence, as 
 
 the quantity of water so struck and put in motion is nearly proportionate to 
 the velocity of the vessel, we have, 
 
 1-5 v - = the resistance to one square foot of the paddle ; 
 
 and, making b = the breadth of the paddle, 
 
 powel , 
 
 The integral is 
 
 1-5 v 2 * (V r x | V ** r v a) . 
 
 . . - _ -- - , 
 
 r 
 and when the depth of the paddle is h, it is 
 
 1-5 b hv* / (r 4A) V-rvj ,. 
 
 _ \ v 2 ' __ / = the direct power, 
 
 r 
 
 which must be equal to the resistance of the vessel. 
 
 The loss by oblique action has to be estimated before the power of the engine 
 can be found, but previously we may proceed to determine the best velocity for the 
 wheels in still water. 
 
 630. Let the equation be freed of all its constant multipliers, except those 
 relating to or connected with its velocities ; then it is v z (V r % V h r v) ; and 
 making v variable, its differential is 2V r v d v V h v dv 3 r v 2 dv = o ; from 
 
 whence we have, 
 
 3 r 2 (r 4 A) , 
 
 V = a^rrTT) and = -SrF- ' v - 
 
 The excess of the velocity of the outer point of the paddle therefore depends in 
 part on its depth compared with the radius ; the greater the depth, the less excess 
 
 is necessary. 1 
 
 t 
 
 1 The above is according to the principles of Tredgold's investigation, but it is not here 
 sanctioned as to its accuracy. Although the quantity of water put in motion may be proportional 
 to the velocity of the vessel, it does not appear that the whole of this water is struck by the paddle, 
 
302 OF STEAM NAVIGATION. [SECT. x. 
 
 631. If this value of V be inserted in the equation for the area of the 
 paddles, then -75 v 3 b h = the effect of the paddles, which must be equal to 
 
 as is assumed at the outset ; on the contrary, a large portion is evidently put in motion by second- 
 ary pressure. The pressure on the paddle must in all cases be nearly proportional to the square 
 of its velocity (V v) through the water, V denoting the velocity of the " centre of pressure," 
 which is near to the centre of the paddle. It should however be observed, that the passage of 
 each paddle leaves a vacuum behind it, and that its repletion causes a temporary stream, which 
 necessarily diminishes the effect of the succeeding paddle. Consequently, if we represent the 
 pressure by c (V v) 2 the coefficient c must be rather less than in the case of the motion of a body 
 through still water ; and it can only be regarded as constant for quick velocities, as the diminu- 
 tion from the cause alluded to will be most considerable when the velocities of the vessel and 
 paddle are slow. 
 
 If we suppose the vessel to be influenced only by the engine and the resistance of the water, 
 and disregard the variations of her immersion, the resistance will obviously be proportioned to v", 
 and, the velocities being uniform, it must be equal to the reaction or pressure against the paddles, 
 in the direction of the motion of the vessel. Let C v 2 denote this pressure, and let k be the distance 
 of the centre of pressure below the axis, or the leverage with which it acts ; then C k v 2 is the 
 effort to turn the wheel. As k t> 2 must therefore be constant under given circumstances, whatever 
 be the dimensions of the wheel and paddle, it is evident that the velocity will be increased by 
 diminishing k, and that in this respect small wheels are preferable to large ones, were it not for 
 the power required to overcome the increased oblique action, and the inconveniences attending it. 
 In strictness k refers to the centre of the entire horizontal pressure against all the paddles im- 
 mersed, and this will be near the middle of that which is most depressed. If we suppose k to be 
 proportional to r, the effort to turn the wheel may be represented by C' r v 3 , and, <u denoting the 
 angular velocity of rotation, C' r <> r 2 = C' V v 2 will then represent the whole power expended by 
 the engine. It hence also appears, that when the engine works with a given power and a given 
 speed, both r v- and w must be constant for all sized wheels, the dimensions of the paddle and 
 the radius of the wheel being properly adapted to each other, for the due consumption of the 
 steam generated in the boilers. 
 
 To put the relations in an analytical form, let the notation be as follows : 
 
 P the pressure on the piston in Ibs. per circular inch, 
 
 a ,, radius of the cylinder, 
 
 / length of stroke, 
 
 n number of strokes per minute, 
 
 a velocity of the piston in feet per second, 
 
 v velocity of the vessel ,, 
 
 V ,, velocity of the centre of pressure of the wheels, 
 
 k the radius of the wheel to the centre of pressure ; 
 
 and let B 2 v- be the pressure or resistance, in Ibs., experienced at the bow of the vessel, and 
 i (V ) 2 that on the paddles, both estimated in the line of motion, so that 
 
 B v = b (V - v) - - (1) 
 
 then B 2 , 4 2 , will be factors proportional to the equivalent resisting surfaces of the boat and 
 the paddles immersed. And since, in respect of the engine, the pressure B 2 v- on the 
 
SECT. X.] 
 
 OF STEAM NAVIGATION. 
 
 303 
 
 the resistance of the vessel ; and the comparison is easily made by means 
 of the equations for the resistance of vessels (art. 622). The power required 
 
 paddles acts with the velocity V, and the pressure P a 2 on the piston acts with the velocity a, 
 we have, neglecting the effects of oblique action, 
 
 P a* u = B 2 v" V - - - (2) 
 We have also, from the mechanical arrangement of the parts, 
 
 V = 
 
 k 
 
 2nl 
 
 "* ~60 
 
 nl 
 
 (4) 
 
 These four equations, which embody the whole theory of paddle wheels, may be easily discussed 
 for any purpose that may be had in view. The following expressions, deduced from them, are the 
 most commonly applicable : 
 
 v = _ 
 
 b 
 B + 
 
 = 
 
 77"' k 3 
 
 B b \ V' 
 
 *_ } 
 
 + b) 
 
 (B + ft) f 3 
 b Pa 2 
 
 30 
 
 () 
 
 K) 
 
 _L X^^ 
 
 r = \ "B-V/ _ * 
 
 V = 
 
 n k 
 
 * -30- 
 B + 6 
 
 Pa 2 / 
 
 * A 
 
 - (V 2 ) 
 
 - (V s ) 
 
 Equations ( 3 ), (V 3 ) show that with given sized paddles and draught of water, the velocities, under 
 all circumstances, will be proportional to the cube root of the quantity of steam consumed per 
 minute. Also equation (tij) shows that more steam may be consumed by either increasing the 
 length of the stroke or diminishing the radius of the wheel, while (t> 5 ), (V 2 ) indicate a corresponding 
 increase of the velocities in the ratio of the cube root of the increased consumption. It is also 
 evident from these last equations, that if the paddle be lessened or b diminished, the velocities 
 u V and consumption of steam will be increased, while v will remain unaltered. 
 
 For any particular vessel the constants B, 6, may be determined from a few good experiments ; 
 the former will be nearly proportional to the square root of the draught of water, and the latter 
 nearly as the square root of the area of one of the paddles. ED. 
 
304 
 
 OF STEAM NAVIGATION. 
 
 [SECT. x. 
 
 to produce the effect is, 
 
 3r 
 
 x -75 .3 bh = 
 
 A somewhat greater power is required, because there is also a loss by oblique 
 action, and this will be expressed with accuracy enough for the object by multiply- 
 ing the power by, 
 
 - h 
 
 where r is the radius C B, and h the depth of the float boards D B. For the 
 
 FIG. 27. 
 
 JF. - 
 
 centre of gravity, a of the immersed part A B D may be considered the actual 
 point where the whole force acts, instead of being distributed over the segment ; 
 and its mean direction will be E F, which is perpendicular to the line A C, drawn 
 from the centre of the wheel through the centre of gravity : and the direction of 
 this line will determine the loss by oblique action, for the power is to the effect 
 as A H : A D, and is nearly given by the multiplier above. 
 
 An example may give a clearer idea of its effect. Let the radius of the wheel 
 be 8 feet, and the depth of the paddles 2 feet, then 
 
 = 1-024, nearly. 
 
 Hence, as it will not exceed one-fortieth part of the whole, it may be neglected. 
 The mean direction of the action is of greater importance to the motion, than the 
 loss of power. 
 
 632. We have supposed the paddles to be of the same breadth every where, 
 
SECT. X.] 
 
 OF STEAM NAVIGATION. 
 
 305 
 
 but this may not be the best form, and therefore let A- : 6 : : *- : ~- = the breadth 
 at any point .r, which substituted for b we have 
 
 1-5 v~ b (V r V x r v) z dx 
 
 Its integral is, 
 
 rh" 
 
 the differential of the power. 
 
 n+l 
 
 n+2 
 
 and when x = /?, it is 
 
 -5 v~ b /r(V v)x V x \ . 
 
 VW \ n + l n +2J ' 
 
 1-5 if- b h I r (V v) VA \ 
 r \~ n + I ~ n + 2/ 
 
 If n = 0, the form of the paddle is a rectangle with the same result as before. 
 
 633. If it be a triangle, n 1, and the result is less than for the rectangle, 
 the velocity and area being the same. 
 
 634. If n = i the form is parabolic, and the result is, 
 
 1-5 pg b h (10 r (V -v)- 6V A) 
 I5~r~ 
 
 There we obviously gain advantage, by getting an equal resistance with 
 less breadth, and by this form the resistance to the paddle is least when it 
 strikes the water obliquely as at A, and increases as its action becomes more 
 
 FIG. 28. 
 
 direct. The velocity for the maximum effect is to the velocity of the vessel as 
 2r l-2A:3r::w:V= ^ . ^W, which is less than for square paddles ; if this 
 
 value of V be inserted in the equation, we have - ^| = the power of the 
 
 paddles when they are of a parabolic form, with the depth h, and breadth b. 
 
 If the form of the exterior edge be more rounded than the vertex of the common 
 
 2 Q 
 
306 
 
 OF STEAM NAVIGATION. 
 
 [SECT. x. 
 
 parabola, the effect again decreases. I was led to examine this point, by observing 
 the form of those fins of fish which are used for impelling in a similar manner. 
 The lines A D E F show the size of a square paddle capable of producing the same 
 effect. It strikes the water at once with its whole breadth, as at G. The parabolic 
 one strikes a little sooner, and gradually acquires its full hold of the water. 
 
 635. The best position for the paddles appears to be in a plane, passing 
 through the axis, as represented in the figure ; if they be in a plane which does 
 not coincide with the axis, they must either strike more obliquely on the fluid on 
 entering, or lift a considerable quantity in quitting it. 
 
 In the direction of the breadth of the paddle, it is evident the form should be 
 such that the resistance to its motion should be the greatest possible, and the 
 pressure behind it the least possible. These conditions appeared to be fulfilled, in 
 a high degree, by making it a plane in this direction also. A flat curve has been 
 used, the concave surface to strike the fluid, and perhaps with a very small increase 
 of power. To set the paddles at any other than a right angle, must obviously be 
 a defect ; for the resistance to motion becomes less when the surface strikes the 
 water obliquely, whereas the greater this resistance, the greater the effect in 
 impelling the vessel. 
 
 636. It is desirable that the action of the paddles should be as equable and 
 continuous as possible. But in attempting to render the action of the paddles 
 equable, their number ought not to be increased more than can be avoided, 
 because the construction is more expensive, and the time for the water to flow 
 between them so as to afford a proper quantity of reaction is reduced ; neither do 
 they clear themselves so well in quitting the water. If we suppose A E to be the 
 line the water would assume when at rest, the most favourable arrangement with 
 the smallest number of paddles appears to be to make a paddle at A, just entering, 
 
 FIG. 29. 
 
 when one at B is in a vertical position, and the one E quitting the water : if a 
 smaller number were employed, there would be a short interval, during which 
 
SECT, x.] OF STEAM NAVIGATION. 307 
 
 none of the paddles would be in full action. A still more equable action will be 
 obtained by dividing the immersed arc into three ; beyond this I do not think the 
 advantage will be worth the extra expense, therefore I propose to give general 
 equations for any proportion, and particular rules for three to be immersed. 
 
 637. To determine the radius of the wheel or the depth of the paddles, when 
 the number of the paddles is given, becomes an easy problem when the preceding 
 conditions are to be adhered to. For, put r = the radius B C, x = the depth 
 B D of the paddles, n their number, and a the number of parts into which the 
 
 immersed arc is divided. Then ' - = the angle A C B, corresponding to half 
 the immersed arc, and 
 
 rcos. i22 =CD, 
 
 
 the cosine of the angle, being the depth from the centre of the wheel to the 
 surface of the water ; and, 
 
 r cos. a } - = r- x; orr (l _ cos. ^ -)-=- BD, the depth of the paddles. 
 And, 
 
 = r = B C, the radius of the wheel. 
 
 T a LoO 
 
 I cos. 
 
 n 
 
 From these equations we have the following rules for the case when three 
 paddles are immersed, or when a = 3. 
 
 638. RULE i. To find the radius of the wheel, when the number and depth 
 of the paddles are given. Divide 540 by the number of paddles, which will give 
 the degrees in the angle contained by half the immersed arc. From unity sub- 
 tract the natural cosine of this angle, and the depth of the paddles divided by the 
 remainder will give the radius of the wheel. 
 
 Or the radius of the wheel multiplied by the remainder will give the depth of 
 the paddles. 
 
 639. RULE u. To find the number of paddles, when the radius of the wheel 
 and the depth of the paddles are given. Divide the depth of the paddles in feet, 
 by the radius of the wheel in feet, and subtract the quotient from unity. Find the 
 angle corresponding to the remainder as a natural cosine, and 540 divided by the 
 degrees in that angle is the number of paddles required. 
 
 If the radius of the wheel be 8 feet, and the depth of the paddles 2 feet, then, 
 
 1 - = -75 which is the cosine of the angle 41 4', 
 
 o 
 
 and rr* =13, the number of paddles. 
 
308 OF STEAM NAVIGATION. [SECT. x. 
 
 640. The size of the wheels depends chiefly on the mode of giving them 
 motion from the engine ; they must be so large as to have the proper speed at the 
 circumference, and where large wheels can be admitted, they have some ad- 
 vantages : they must necessarily be narrower, and they strike the fluid in a 
 favourable direction, and also quit it better ; the paddles having more direct action 
 on the water, they splash it about much less ; the weight of the wheel also renders 
 it more effective, as a regulator of the forces acting upon it. On the other hand, 
 there are some strong practical objections to very large wheels for sea vessels ; 
 they give the momentum of the waves a greater hold on the machinery, they are 
 cumbersome and unsightly, and they raise the point of action too high above the 
 water line. 
 
 641. When the wheels are on the first motion, the radius is determined by 
 the velocity of the engine. Let that velocity be n strokes per minute, then 3' 1 41 6 
 x 2 r = the circumference of the wheel ; r being its radius, and its velocity per 
 minute is 3*1416 x 2 r n : but this is to the velocity of the boat nearly as 
 3 to 2 ; * hence, 
 
 3-1416 x 2 r n = ^ x 3 ". 
 
 B 
 
 or : - = , the number of strokes per minute, when v = the miles per hour. 
 
 Also fixing the number of strokes we have, 
 
 21 v 
 
 = r, the radius of the wheel. 
 
 n 
 
 This therefore reduces to this simple rule : 
 
 RULE. The velocity of the vessel per hour multiplied by 21 is equal to the 
 number of strokes per minute, multiplied by the radius of the wheel. 
 
 From this exceedingly simple rule it can be known at once whether the wheel 
 becomes too large or not, when the simple crank motion is used ; it ought to be 
 used in preference to a second motion, in all cases where it does not involve some 
 other difficulties than merely the size of the wheel. 
 
 For further information on the subject of paddle wheels, the reader is referred 
 to the Appendix. 
 
 MoDIF'CATIONS OF PADDLE WHEELS. 
 
 642. Several methods have been tried or projected for getting rid of certain 
 supposed defects of the paddle wheels. The quantity of force lost by oblique action 
 
 1 This ratio is obtained from art. 630. 
 
SECT, x.j OF STEAM NAVIGATION. 309 
 
 has been greatly overrated, and most of the contrivances are directed to remove it 
 either wholly or in part. The methods proposed are of two kinds. In one a 
 gradual change of position of the paddle is produced by the movement of the 
 wheel ; completely forgetting, that by loss of the velocity, the decrease of force is as 
 the square, while by variation of direction the loss is only in simple proportion. 
 Mr. Oldham, of the Bank of Ireland, proposed a plan for these revolving paddles, 
 to avoid the defects of the fixed paddles commonly used ; and states, that the violent 
 action of the paddles of common wheels, in striking the water in a rough sea, is 
 entirely removed by the use of the revolving paddles, as they enter and rise out of 
 the water with a peculiarly soft and easy motion. We can only regret that so 
 much ease cannot be obtained without a considerable and constant sacrifice of 
 power. 
 
 The other method is to cause the paddles to change at once to a new position at 
 two points in the revolution, by means of proper catches and mechanism. This is 
 a better method for cases where the wheels are to work when deeply immersed in 
 water ; but such wheels require to be made so very strong and powerful, that there 
 appears to be small probability of the machinery keeping in order. 
 
 The plan of making paddles which seems most plausible, is to have a pair of 
 wheels at each side of the vessel, having two endless chains acting on them, with 
 paddles fixed on these chains. As the chain passes in one direction, the paddle 
 boards are immersed in the water, and return in the opposite direction out of the 
 water ; the two wheels around which they pass being partially under water. The 
 whole of the impulse given by these boards from the lower part of one wheel to the 
 lower part of the other, seems as though it would be direct and effectual ; and it is 
 stated, that so far as the plan has been tried on a very small scale, it has been 
 successful. It is said however by Buchanan to have been tried on the Duke of 
 Bridgwater's canal, where it did not give satisfaction ; and the reason not being 
 assigned, we must endeavour to show whether or not the arrangement can have 
 greater effect than the common paddle wheel. 
 
 If a wheel have a sufficient number of paddles to force the whole of the fluid 
 opposed to the area of the paddle into motion, it is obvious that any continuation of 
 "the line of action of the paddles will be only equivalent to the friction of the 
 stream put in motion by their first action on it : and this effect is by far too small 
 to be obtained by a complicated arrangement, which it would be difficult to render 
 durable ; hence the construction is imperfect. 
 
 The subject is further treated in the Appendix. 
 
310 OF STEAM NAVIGATION. [SECT. x. 
 
 OF THE STRENGTH OF VESSELS. 
 
 643. It was not till 1818 that steam vessels were made to perform regular 
 voyages at sea ; and in proportion as they have had experience, the strength of the 
 vessels has been increased. A vessel should be considered as one slightly flexible 
 frame, and the strength determined so that the greatest possible stress, acting with 
 the most disadvantage probable, would not derange the natural elasticity of the 
 parts, nor disturb the connexions. The want of considering the frame as a whole, 
 has often led to weak modes of construction, and improper modes of bracing. 
 A vessel is also to be considered in the condition where hydrostatic pressure 
 contributes least to its support. The strains reduce to those which would take 
 place in a large hollow beam, of which we have to find the neutralaxis, and then 
 the resisting forces are easily measured. 1 When the timbers are filled in between, 
 it must increase the strength, if it be done in a proper manner ; and this increase 
 might perhaps be obtained with less material, and less addition to the weight of 
 the vessel, but the advantage of leaving no hollow cavities is of much importance 
 both to the durability and cleanliness of a vessel. 2 
 
 644. In respect to timber, fir has the advantage of lightness, and for straight 
 timbers it is stronger than a like weight of oak ; but for curved timbers the harder 
 woods which have greater lateral cohesion are better. 
 
 OF THE APPLICATION OF SAILS. 
 
 645. It is found that sails may be effectively combined with steam power, 
 whenever the direction is not within four points of that of the wind. 
 
 But when the force of the wind becomes considerable, and the sea rough, the 
 wheels often revolve without touching the water in the hollows of the waves, and 
 acquire a great increase of velocity, to be reduced, as soon as they meet the wave 
 again, to less than the ordinary speed. To lessen the abruptness of these changes, 
 it is necessary to diminish the supply of steam, and consequently the power of the 
 engine. 
 
 646. It appears to be impossible to apply so much sail as to give a steam 
 vessel the advantage of being used as an effective sailing vessel, in the event of the 
 engines or coals failing. The proper object of sails in a steam vessel is to save fuel 
 
 1 See my ' Elementary Principles of Carpentry,' Sect. 1 and 2 ; and ' Treatise on the Strength 
 of Iron,' art. 85 a. 
 
 2 See Philosophical Transactions for 1820. 
 
SECT, x.] OF STEAM NAVIGATION. 311 
 
 when the wind can be of service, 1 and to do this with economy, the engines should 
 work expansively (see art. 419.) ; hence, the arrangement of the engine should be 
 such as would answer to work at full pressure in a calm. This condition enables 
 us to fix the power of the engine by the rate for still water ; and if the vessel has 
 sails sufficient to maintain the speed with about half the power of the engines, 
 when the wind is fair, it will be as much as can be usefully employed. The 
 greatest attention should be given to keep the centre of effort on the sails as low as 
 possible, and to arrange them so that the angle of the vessel's inclination may be 
 inconsiderable, that the wheels may not dip unequally. 
 
 647. The average speed in still water, beyond which it does not seem to be 
 desirable to go, is ten feet per second ; that is, seven common miles, or six nautical 
 miles per hour : and at this velocity, when the wind is as powerful as it is prudent 
 to carry all the canvas, the direct effect will be only one horse power for each 
 thirty-two yards superficial. 2 
 
 648. A fair wind also contributes to the motion of a vessel, by giving motion 
 to the sea itself; a head wind opposes its motion, and a current has a similar effect. 
 If v be the velocity a vessel is impelled at in still water by the power P, and the 
 velocity of the current be H^ n v, using the upper sign when it is with the vessel, 
 then P (1 +_ nf = the power the boat will require. 
 
 If the stream be in the direction of the vessel's motion, and half its velocity in 
 still water, then n = '5 and P (1 '5) 2 = '25 P ; or the vessel will require only 
 one-fourth of the effective power. 
 
 If the vessel move against the stream, the stream being half its velocity in still 
 water, then P (1 + *5) 2 = 2'25 P ; or the vessel will require 2i times the power to 
 preserve its velocity. 
 
 649. But in ascending a stream the difference must be in the velocity, and it 
 
 1 It is a common notion, that the sails should be used in addition to the steam power, to gain 
 greater velocity ; but this is not desirable, except for post-office packets and the like, because an 
 immense extent of canvas affords only a very small power when the vessel moves at a considerable 
 velocity ; hence, economy directs to saving fuel, rather than increasing speed. 
 
 2 To find the effect of the wind in any other direction, and with any other velocity, let V be the 
 velocity of the wind in feet per second, a = the angle it makes with the direction of the vessel's 
 motion, v = the velocity of the vessel in feet per second, b = the angle a perpendicular to the 
 surface of the sail makes with the direction of the motion of the vessel ; then it is nearly, 
 
 3200 cos. b 
 
 ,-^f - = the yards ot canvas, 
 
 (V cos. (a + b) v cos. 6) 2 
 
 equivalent to a horse power or 550 Ibs. raised one foot per second. 
 
312 OF STEAM NAVIGATION. [SECT. x. 
 
 is generally so also in the descent ; hence, if v be the velocity of the stream, and 
 m v the velocity of the vessel moving in the stream, then 
 
 v- = m (m v + u}-. 
 
 The value of m is not easily separated in this equation, but by assuming that the 
 force of the wheels is invariable, we have v = (m v +_ u) s ; or v +_ u = m v. The 
 upper sign to be used when the vessel moves with the current. 
 
 Hence, if the velocity in still water be 8 miles per hour, and that of the stream 
 3 miles per hour. 
 
 Then down the stream v + M = 8 + 3 = ll miles ; and up the stream v u = 8 
 3 = 5 miles. 
 
 If the velocity of the paddles alter, the power will not be constant ; and if it do 
 not alter, this ratio cannot exactly hold. 
 
 RULE FOR THE POWER OF BOAT ENGINES. 
 
 650. The power of boat engines may be ascertained thus. Let p be the mean 
 pressure on the piston in Ibs., a its diameter in inches, v its velocity in feet per 
 minute, and h = the number of horses equivalent to its power ; then 
 
 a- /"*. 
 33000 
 
 Let the length of the stroke in feet be /, then v = A V I, where A is the 
 multiplier found by art. 336. ; hence, 
 
 A = J>t>a_J>AvT_ k = / 38000 A U 
 
 33000 33000 \ p A ,/// 
 
 In logarithms, log. a = i (log. 33000 + log. h log. p log. A i log. /). 
 For low pressure steam acting at full pressure throughout the stroke we have 
 A = 103, (art. 337-) and p = 7*1. (art. 416.) Hence, in this case the rule becomes 
 
 log. a = i (log. h + 1-66726 - i log. /). 
 Also, 
 
 log. h = 2 log. a + i log. / - 1-66726. 
 
 651. If m times the length of the stroke in feet be the diameter in inches, then 
 
 log. a = f (log. h + 1-66726 + i log. m). 
 
 The most common proportion now used is m = 9, or the length of the stroke 
 four-thirds of the diameter, hence, 
 
 log. a = f (log. h + 2-14438). 
 
SECT . x .] OF STEAM NAVIGATION. 313 
 
 Example. If the resistance be equal to 100 horse power, with two engines 
 
 of 50 eadi ; 
 
 the log. 50 = 1-69897 
 2-14438 
 
 3-84335 
 2 
 
 5) 7-68670 
 log. a = log. 34-5 = 1-53734 
 
 Hence, the diameter should be 34*5 inches, and the length of the stroke 
 34-5 x 4 
 
 OF ARRANGING THE PROPORTION OF PoWER FOR VESSELS. 
 
 652. If we now proceed through a calculation of the proportions, and a 
 statement of the conditions to which we ought to attend in arranging the parts 
 of an engine for a vessel, it will form the best illustration of the use of the 
 preceding rules. 
 
 653. The resistance of the vessel should be ascertained for the average velocity : 
 now without pretending to fix the best average, I will suppose this to be 10 feet 
 per second, or 7 miles per hour in still water. 1 Let the length of the parallel part 
 of the vessel be 72 feet, the mean radius of curvature of the ends be 6 half 
 breadths, the breadth at the midship section 25-7 feet, and the girt of that section 
 in contact with water 38 feet. Then the velocity being 10 feet per second, we 
 have by the table, (art. 622.) 
 
 10 s x 38 (-025 x 25-7 + -0032 (72 + 1-05 x 257) ) = 
 10 3 x 36-5 = 36500 Ibs. raised one foot per second, 
 
 or 36500 divided by 550 = 67 horse power nearly. 2 
 
 654. Now if we were to fix on the area and velocity of the paddles for this 
 velocity, it would not be possible to work with advantage against either wind or 
 
 1 This will be equivalent to an average speed of nine miles per hour, where sailing power is to 
 be used in addition. 
 
 * The coefficient -0032 (see art. 614.) is very likely too high ; it is taken from the experiments 
 made by the Society for the Improvement of Naval Architecture, and agrees with the more recent 
 experiments of Col. Beaufoy ; but I am quite convinced that when water is in motion the friction 
 is less, only the exact measure remains to be determined. 
 
 2 R 
 
314 OF STEAM NAVIGATION. [SECT. x. 
 
 current ; besides there is a disadvantage in large paddles at sea, which is greater 
 than the loss by varying from the maximum. Hence, I would recommend to 
 arrange the paddles for a velocity about one foot per second greater than the 
 average rate. Consequently, (art. 631.) IP x -75 x b h = the power of the 
 paddles; and as the resistance is 36500, we have 
 
 :pp ^H = b h = 36-6 feet, the area of the paddle boards. 
 
 Again, suppose the radius of the wheels to be four times the depth of the 
 paddles, then by the second equation of art. 631. we have, 
 
 2-25rxll 3 xftA 9xll 3 x36-6 O QQ 11, j r 
 
 - 3 - i - = - w - = 62633 Ibs. raised one foot per second, 
 
 fi T A / 
 
 or 62633 divided by 550 =114 horse power nearly. 
 
 655. As the vessel requires 114 horse power, if we have two engines, each will 
 be 57 horse power; and (art. 651.) 
 
 log. 57 = 1-75587 
 2-14438 
 
 3-90025 
 2 
 
 5) 7-80050 
 log. diameter = 1-56010 
 
 or the diameter = 36-32 inches; the length of the stroke four-thirds of the 
 diameter, or 48-43 inches ; and consequently (art. 336.) the number of strokes per 
 minute will be 25|: hence, (art. 641.) corrected for the depth of the paddle, 1 
 we have, when the velocity is 11 feet per second, or 7-5 miles per hour, 
 
 24^ = 24 x 7-5 ? .j f 
 25-5 25-5 
 
 for the radius of the wheels ; and dividing it by 4 gives the depth of the paddles 
 1*8 feet. But in order to reduce the breadth of the wheel, it is better that they be 
 made 2 feet, and the radius of the wheel 7-3 feet ; the paddles will then be 2 feet 
 
 1 For when the depth is one-fourth of the radius, V = 3 r v = ^-^, instead of <LY 
 
 2r d 1 2 ' 
 
 hence, !L : : : 21 : 24. 
 2 7 
 
SECT, x.] OF STEAM NAVIGATION. 315 
 
 by 9-2 feet for each wheel, making an area of 36'8 feet for both, or the breadth of 
 the wheel 9-2 feet. 1 
 
 The other proportions of the engines will be found by the general rule, (art. 415.) 
 except that a somewhat smaller quantity of water produces the steam, owing to its 
 being of a higher temperature, (see art. 90.) but it is only about 2 per cent less, 
 and the fuel required is not sensibly altered ; there is also a slight advantage by 
 the force of the steam being less in the condenser than when pure water is used. 
 (See table, art. 94.) Hence, the cistern of water to contain the condenser is 
 omitted without loss. The engines should be prepared to work expansively, to be 
 adjusted by hand, (see art. 419 and 481.) and the strength of the parts will be 
 found by art. 496 527 : the management of the water is treated of in art. 565. 
 and the parallel motion, art. 488 495. 
 
 656. I think it would be desirable to try the effect of giving a considerable 
 degree of elasticity to the arms of the paddles, and to form the boards in the 
 manner shown in Fig. 28. page 305. The wheels of vessels appear to be kept too 
 forward, so as to keep the fore part of the vessel constantly heaving upwards ; and 
 such an action is unfavourable. A vessel should bear firmly in the direction of its 
 motion to move well ; and that this remark is true in practice as well as theory, 
 may be inferred from the fact, that in the present construction they find an 
 advantage in using the sails to steady, and determine the direction of the vessel's 
 motion. In vessels for towing, 2 this may be adopted with still greater advantage ; 
 and in both cases the proper place for the wheels appears to be behind the centre of 
 gravity of the vessel. 
 
 The following Tables are collected chiefly from the evidence printed in the 
 Reports on the Holyhead Steam Packets, by the committee appointed by the 
 House of Commons ; and will afford a means of comparing the practice of different 
 manufacturers : 
 
 1 The proportions of the vessel in this case are as nearly those of that called the James Watt, as I 
 could ascertain them ; and in the tables which follow, the best information I could procure 
 respecting that vessel is given in order to compare the calculated with the reported effect : the 
 velocity is that in still water, that is, the velocity in the river with that of the current deducted 
 therefrom. 
 
 * The power required for towing a vessel may be estimated by art. 622. 
 
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SECT . x .] OF STEAM NAVIGATION. 319 
 
 The average consumption of coals is that required when the engine is in full 
 action, and including all delays, waste, &c. ; and is to be understood as that which 
 multiplied by the hours it requires for the average passage, would give the quantity 
 consumed for each passage ; and the store ought evidently to be for the longest 
 passage. In the best engines (of this time) it will be found to vary from 12 to 16 
 Ibs. of Newcastle coals per hour for each nominal horse power, and in inferior 
 engines it may extend to 20 Ibs. 
 
 When the consumption is stated at less than it amounts to, at 12 Ibs. per hour 
 for each nominal horse power, it may be fairly esteemed an experimental trial ; and 
 of course the fires are more carefully attended, with every precaution to prevent 
 waste and give effect. The last column of Table HI. will nearly give the fuel 
 required per hour if the nominal power be taken in the first column, (art. 664.) 
 when applied to steam boats. 
 
 The velocity of sea vessels appears to average about ten miles per hour ; their 
 power to face a wind is inconsiderable, because the wind gives the surface of the 
 water so much velocity, that the paddles act with less force in proportion as the 
 velocity of the water approaches to the difference between the velocity of the 
 paddles and that of the vessel ; and when these are equal, the boat will commence 
 moving backward ; and it is also with much reason supposed that the action of the 
 wind itself tends greatly to retard a vessel's motion when it is directly opposed to 
 it : for if a vessel of 100 horse power has a surface of 60 yards above water, 1 and 
 the velocity of the wind be 50 feet per second, (in which vessels are under their 
 courses,) then by the equation, (art. 647, note) 
 
 2500 x 60 ,- i 
 "3200 = 47 horse power, 
 
 for the resistance offered to motion when the vessel is at rest; and as with 
 whatever velocity the vessel moves against the wind, this velocity should be added 
 to that of the wind, the plus sign being the proper one, in the equation for this 
 case it will appear that the power to move forward is extremely limited with so 
 much surface above water. 
 
 The only vessels in the table, art. 657. which have dimensions to enable us to 
 approximate to their speed, are the 'Lightning' and the 'Dee;' and, notwith- 
 standing the great quantity of power to be placed in the ' Dee,' I expect that its 
 velocity in still water will be one-eighteenth less than that of the ' Lightning' in 
 similar circumstances ; and it would require the engines of the ' Dee' to be 230 
 horse nominal power to render them of equal speed. The 'Dee' spreads above 
 water at an angle of about 50 degrees with the water line, to a width of about 
 
 1 This is estimated from a vessel in use, and esteemed. 
 
OF STEAM NAVIGATION. [SECT. x. 
 
 5 feet on each side, in the same manner as in boats for the accommodation of 
 passengers. 
 
 660. Much has been said respecting American steam vessels ; and these 
 vessels as far as excellent workmanship, neatness of fitting up, and convenience is 
 concerned, do appear to be superior to our own. Their best engines however seem 
 to be not more than equal to the British ones, if so good, as many of the reports 
 respecting them carry internal evidence of their inaccuracy. The best I have met 
 with is that of the steam vessel called the ' Chancellor Livingston,' constructed by 
 Mr. Fulton for the Hudson River, from New York to Albany. It is one of their 
 largest vessels : the keel is 154 feet long; deck 165 ; breadth 32 feet ; draught of 
 water about 7 feet 3 inches, and burden 520 tons ; the principal cabin 54 feet long, 
 7 high : ladies' cabin, above the other, 36 feet long, with closets ; the forward 
 cabin 30 feet long, and 7 high. The number of sleeping-berths, in the principal 
 cabin, is 38 ; in the ladies' cabin 24 ; in the fore cabin 56 ; in the captain's cabin 
 on deck 2 ; in the engineers' and pilot's 3 ; in the forecastle 6 ; and for fire- 
 -men, cooks, &c. 6 ; being a total of 135. The engine is of 60 horse power ; 
 the diameter of cylinder 40 inches, length of stroke 5 feet ; the boiler is 28 feet 
 long, 12 broad, with 2 funnels ; the paddle-wheels 17 feet diameter ; paddle- 
 boards 5 feet 10 inches long; they have 2 fly-wheels, each 14 feet diameter, 
 connected by pinions to the crank shaft. The machinery rises 4 feet and a half 
 above the deck. Average rate of sailing is said to be 8 and a half to 8 and three 
 quarter miles an hour. With a strong wind and tide in her favour she has made 
 12, but with wind and tide against her not more than 6 miles per hour. As for 
 low pressure steam the engine is estimated at the greatest power of the cylinder, and 
 it has been imagined that the vessel is moved by less power than the British vessels 
 of equal magnitude. 
 
 The fallacy arises out of erroneous methods of measuring vessels to register 
 their tonnage. 
 
 To ASCERTAIN THE REGISTER TONNAGE OF A STEAM VESSEL. 
 
 661. The breadth is to be taken at the broadest part of the vessel, whether it 
 be above or below the main wales, and is to be from the outside to outside of the 
 plank ; the length is to be the horizontal distance between the back of the main 
 stern post and the fore part of the main stem, under the bowsprit ; and calling this 
 length /, the breadth b, and r = the length of the engine-room, the rule is 
 
 (- jgg-* *) *>* = the tonnage. (Sect. 59th Geo. III. cap. 5.) 
 
SECT, x.] OF STEAM NAVIGATION. 321 
 
 Example. If the breadth be 32 feet, the length 162 feet, and the length of the 
 engine-room 47 feet, 
 
 (102 - 47 - 19-2 )g. = 520 tons. 
 
 The register tonnage is the same whether the draught of water be 7 feet or 14 
 feet ; and it is the same whatever may be the form of the vessel : it is an 
 unpleasant task for an Englishman to mark as fallacious the modes of measuring 
 the capacity of vessels adopted by his government ; it is necessary however for 
 the purposes of science not only that it should be pointed out, but that the 
 error should be corrected. 1 
 
 1 Since the publication of the first edition, the Law of Tonnage has been altered and established 
 by Act of Parliament, William IV., Sept. 9, 1835, of which the following is a summary: 
 
 Divide the length of the upper deck between the after-part of the stem and the fore-part of the 
 stern-post into six EQUAL PARTS, and note the foremost, middle, and aftermost points of division. 
 DEPTHS. At these three points measure in feet and decimal parts of a foot, the depths from the 
 underside of the upper deck to the ceiling at the limber strake, or, in case of a break in the upper 
 deck, from a line stretched in a continuation of the deck. BREADTHS. Divide each depth into five 
 equal parts, and measure the inside breadths ^at the following points, viz., at one-fifth and at 
 four-fifths from the upper deck of the foremost and aftermost depths, and at two-fifths and 
 four-fifths from the upper deck of the midship depth. LENGTH. At half the midship depth 
 measure the length of the vessel from the after-part of the stem to the fore-part of the 
 stern-post. 
 
 CALCULATION. To twice the midship depth add the foremost and aftermost depths for the 
 sum of the depths ; and add together the foremost upper and lower breadths, three times the upper 
 breadth with the lower breadth at the midship, and the upper and twice the lower breadth at the 
 after-division, for the sum of the breadths. 
 
 Then multiply together the sum of the depths, the sum of the breadths, and the length, and divide 
 the product by 3500, which will give the number of tons or register. 
 
 If the vessel have a poop or half deck, or a break in the upper deck, measure the inside mean 
 length, breadth, and height of such part thereof, as may be included within the bulk-head; and 
 multiply these three measurements together, and divide the product by 92'4. The quotient will be 
 the number of tons to be added to the result as above found. 
 
 To ascertain the tonnage of open vessels, the depths are to be taken from the upper edge of the 
 upper strake. 
 
 For STEAM VESSELS, the tonnage due to the engine-room shall be deducted from the total 
 tonnage calculated from the above Rule. To determine this, measure the inside length of the 
 engine-room from the foremost to the aftermost bulk-head; then multiply this length by the 
 midship depth of the vessel, and the product by the inside midship breadth at two-fifths of the 
 depth from the deck, and divide the final product by 92'4. 
 
 2 s 
 
322 
 
 TABLES. 
 
 662. TABLE I. 
 
 Of the Properties of the Steam of Water of different degrees 
 of elastic force. 
 
 Total force of steam. 
 
 Excess of force above 
 
 
 
 
 
 
 
 
 the atmosphere. 
 
 
 
 
 
 
 
 In atmo- 
 spheres. 
 
 In inches 
 of mer- 
 cury. 
 
 In Ibs. per 
 circular 
 inch. 
 
 In Ibs. per 
 circular 
 inch. 
 
 In Ibs. per 
 square inch. 
 
 Tempe- 
 rature, 
 Fahren- 
 heit. 
 
 Volume 
 in cubic 
 feet, the 
 water 
 being 1. 
 
 Weight of 
 a cubic 
 foot in 
 grains. 
 
 Specific 
 gravity, air 
 being 1. 
 
 Velocity 
 into a va- 
 cuum in 
 feet per 
 second. 
 
 Heat of 
 
 conversion 
 from water 
 of 52, to 
 steam. 
 
 0183 
 
 55 
 
 21 
 
 11-33 
 
 14-4 
 
 60 
 
 72190 
 
 6-1 
 
 0115 
 
 1377 
 
 1008 
 
 0333 
 
 1 
 
 385 
 
 11-155 
 
 14-2 
 
 77 
 
 41010 
 
 10-7 
 
 0202 
 
 1400 
 
 1025 
 
 0067 
 
 2 
 
 77 
 
 10-77 
 
 13-7 
 
 98-7 
 
 21400 
 
 20-5 
 
 03S8 
 
 1427 
 
 1047 
 
 1 
 
 3 
 
 1-15 
 
 10-39 
 
 13-2 
 
 112-5 
 
 14570 
 
 30 
 
 0568 
 
 1445 
 
 1061 
 
 133 
 
 4 
 
 1-54 
 
 100 
 
 12-7 
 
 123 
 
 11130 
 
 39 
 
 0744 
 
 1458 
 
 1071 
 
 25 
 
 7-5 
 
 2-88 
 
 8-66 
 
 10-99 
 
 147-6 
 
 6187 
 
 71 
 
 134 
 
 1499 
 
 1096 
 
 5 
 
 15 
 
 5-77 
 
 5-77 
 
 7-33 
 
 178 
 
 3249 
 
 135 
 
 255 
 
 1526 
 
 1126 
 
 75 
 
 22-5 
 
 8-65 
 
 2-89 
 
 3-66 
 
 197-4 
 
 2232 
 
 196 
 
 371 
 
 1549 
 
 1146 
 
 1-00 
 
 30 
 
 11-54 
 
 o- 
 
 0- 
 
 212 
 
 1711 
 
 254-7 
 
 484 
 
 1566 
 
 1160 
 
 1-17 
 
 35 
 
 13-46 
 
 + 1-92 
 
 + 2-44 
 
 220 
 
 1497 
 
 292 
 
 553 
 
 1575 
 
 1168 
 
 1-5 
 
 45 
 
 17-31 
 
 5-77 
 
 7-33 
 
 233-8 
 
 1178 
 
 363 
 
 687 
 
 1591 
 
 1182 
 
 1-75 
 
 52-5 
 
 20-19 
 
 8-65 
 
 10-99 
 
 242-5 
 
 1022 
 
 427 
 
 81 
 
 1601 
 
 1191 
 
 2-0 
 
 60 
 
 23-08 
 
 11-54 
 
 14-65 
 
 250-2 
 
 905 
 
 483 
 
 915 
 
 1610 
 
 1199 
 
 2-5 
 
 75 
 
 28-85 
 
 17-31 
 
 21-98 
 
 263-5 
 
 737 
 
 593 
 
 1-123 
 
 1625 
 
 1212 
 
 3-0 
 
 90 
 
 34-62 
 
 23-08 
 
 29-3 
 
 274-7 
 
 623 
 
 700 
 
 1-33 
 
 1638 
 
 1223 
 
 3-5 
 
 105 
 
 40-39 
 
 28-85 
 
 36-63 
 
 284-5 
 
 542 
 
 810 
 
 1-53 
 
 1649 
 
 1233 
 
 4 
 
 120 
 
 46-16 
 
 34-62 
 
 43-95 
 
 293-1 
 
 479 
 
 910 
 
 1-728 
 
 1658 
 
 1241 
 
 5 
 
 150 
 
 57-7 
 
 46-15 
 
 58-60 
 
 308 
 
 391 
 
 1110 
 
 2-12 
 
 1674 
 
 1256 
 
 6 
 
 180 
 
 69-24 
 
 57-7 
 
 73-25 
 
 320-6 
 
 331 
 
 1317 
 
 2-5 
 
 1688 
 
 1269 
 
 7 
 
 210 
 
 80-78 
 
 69-24 
 
 87-90 
 
 331-5 
 
 288 
 
 1520 
 
 2-88 
 
 1700 
 
 1280 
 
 8 
 
 240 
 
 92-32 
 
 80-78 
 
 102-55 
 
 341-2 
 
 255 
 
 1660 
 
 3-25 
 
 1710 
 
 1289 
 
 9 
 
 270 
 
 103-86 
 
 92-32 
 
 117-20 
 
 350 
 
 229 
 
 1910 
 
 3'61 
 
 1720 
 
 1298 
 
 10 
 
 300 
 
 115-4 
 
 103-86 
 
 131-85 
 
 358 
 
 209 
 
 2100 
 
 3-97 
 
 1729 
 
 1306 
 
 20 
 
 600 
 
 230-8 
 
 219-26 
 
 278'35 
 
 414 
 
 111 
 
 3940 
 
 7-44 
 
 1786 
 
 1302 
 
 30 
 
 900 
 
 346-2 
 
 334-66 
 
 424-85 
 
 450 
 
 77 
 
 5670 
 
 10-75 
 
 1823 
 
 1398 
 
 40 
 
 1200 
 
 461-6 
 
 + 450'06 
 
 +571-35 
 
 477 
 
 60 
 
 7350 
 
 13-88 
 
 1850 
 
 1425 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 The mode of obtaining the first five columns is obvious ; and in the fourth and 
 fifth the negative sign indicates that the force of the steam is less than atmospheric 
 pressure, and the numbers show how much less : the sixth column is calculated 
 by art. 89, the seventh by art. 121, and from it the eighth and ninth: the tenth 
 column is calculated by the equation in the note to art. 136, with the allowance for 
 contraction "of the aperture ; and the last column is obtained in the manner shown 
 in the note to art. 190. 
 
 * The usual force of low pressure steam. 
 
TABLES. 
 
 323 
 
 663. TABLE II. Of the Proportions of Single Acting Steam Engines equivalent to 
 different numbers of horses ; the horse power being 33000 Ibs. raised one foot 
 high per minute, and the elastic force of the steam in the boiler = 35 inches of 
 mercury. 
 
 
 Steam at full pres- 
 
 Steam acting expansively. 
 
 sure throughout the 
 stroke in the same 
 
 
 engine. 
 
 Number 
 of horse 
 power. 
 
 Diameter ol 
 the steam 
 piston. 
 
 Mean pressure 
 on the piston, a 
 5.J Ibs. per cir- 
 cular inch. 
 
 Velocity of 
 the steam 
 piston per 
 minute. 
 
 Length 
 of the 
 stroke. 
 
 Number ol 
 strokes 
 per minute 
 
 Water required 
 per hour to 
 supply the 
 boiler. 
 
 Coals con 
 sumed per 
 hour. 
 
 Number 
 of horse 
 power. 
 
 Coals con- 
 sumed per 
 hour. 
 
 horses. 
 
 inches. 
 
 Ibs. 
 
 feet. 
 
 feet. 
 
 strokes. 
 
 cubic feet. 
 
 Ibs. 
 
 horses. 
 
 Ibs. 
 
 10 
 
 26-4 
 
 3850 
 
 174 
 
 4-4 
 
 19| 
 
 11-1 
 
 114 
 
 11-2 
 
 152 
 
 15 
 
 31-1 
 
 5324 
 
 187 
 
 5-2 
 
 18 
 
 16-7 
 
 164 
 
 16-8 
 
 220 
 
 20 
 
 34-9 
 
 6702 
 
 197 
 
 5-8 
 
 17 
 
 22-3 
 
 213 
 
 22-5 
 
 285 
 
 25 
 
 38-1 
 
 8012 
 
 203 
 
 6-3 
 
 16 
 
 27-7 
 
 257 
 
 28- 
 
 343 
 
 30 
 
 41-1 
 
 9270 
 
 214 
 
 6-8 
 
 15? 
 
 33-3 
 
 307 
 
 33-5 
 
 410 
 
 35 
 
 43-7 
 
 10490 
 
 221 
 
 7-3 
 
 15} 
 
 39- 
 
 356 
 
 39'2 
 
 475 
 
 40 
 
 46-1 
 
 11C70 
 
 227 
 
 7-7 
 
 14$ 
 
 44-5 
 
 401 
 
 45- 
 
 536 
 
 45 
 
 48-3 
 
 12820 
 
 232 
 
 8-0 
 
 14{ 
 
 50- 
 
 450 
 
 50-5 
 
 600 
 
 50 
 
 50-4 
 
 13950 
 
 237 
 
 8-4 
 
 14} 
 
 55-5 
 
 500 
 
 56 
 
 670 
 
 55 
 
 52-3 
 
 15050 
 
 242 
 
 8-7 
 
 14 
 
 61-2 
 
 551 
 
 62 
 
 735 
 
 60 
 
 542 
 
 10140 
 
 246 
 
 9-0 
 
 135 
 
 66-7 
 
 600 
 
 67 
 
 800 
 
 65 
 
 56-0 
 
 17210 
 
 250 
 
 9-3 
 
 13$ 
 
 72-1 
 
 649 
 
 73 
 
 865 
 
 70 
 
 57-6 
 
 18260 
 
 254 
 
 9'6 
 
 13} 
 
 78- 
 
 702 
 
 78 
 
 940 
 
 75 
 
 59-2 
 
 19290 
 
 257 
 
 9-8 
 
 13 
 
 83-3 
 
 750 
 
 84 
 
 1000 
 
 80 
 
 60-8 
 
 20310 
 
 260 
 
 10-1 
 
 13 
 
 89- 
 
 801 
 
 89 
 
 1070 
 
 85 
 
 02-3 
 
 21330 
 
 264 
 
 10-4 
 
 12? 
 
 94-5 
 
 851 
 
 95 
 
 1140 
 
 90 
 
 63-7 
 
 22320 
 
 2G7 
 
 10-6 
 
 12i 
 
 100 
 
 900 
 
 101 
 
 1200 
 
 100 
 
 66-5 
 
 24290 
 
 272 
 
 11-0 
 
 12} 
 
 111 
 
 999 
 
 112 
 
 1330 
 
 120 
 
 71-5 
 
 28 100 
 
 283 
 
 11-9 
 
 12 
 
 133 
 
 1197 
 
 134 
 
 1600 
 
 140 
 
 76-0 
 
 31790 
 
 291 
 
 12-6 
 
 Hi 
 
 156 
 
 1404 
 
 157 
 
 1860 
 
 160 
 
 80-2 
 
 35380 
 
 299 
 
 13-3 
 
 HI 
 
 178 
 
 1602 
 
 179 
 
 2140 
 
 180 
 
 84-1 
 
 38870 
 
 307 
 
 14-0 
 
 11 
 
 200 
 
 1800 
 
 201 
 
 2400 
 
 200 
 
 87-7 
 
 42300 
 
 313 
 
 14-6 
 
 10J 
 
 222 
 
 1998 
 
 224 
 
 2650 
 
 11 |j 
 
 90 
 
 44550 
 
 318 
 
 15-0 
 
 10J 
 
 237 
 
 2133 
 
 265 
 
 2860 
 
324 
 
 TABLES. 
 
 664. TABLE III. Of the Proportions of Double Acting Steam Engines equivalent 
 to different numbers of horses ; the horse power being 33000 Ibs. raised one 
 foot high per minute, and the elastic force of the steam in the boiler = 35 
 inches of mercury. 
 
 
 Steam acting at full 
 
 Steam acting expansively. 
 
 pressure throughout 
 the stroke in the 
 
 
 same engine. 
 
 Number 
 of horse 
 power. 
 
 Diameter 
 of the 
 steam 
 piston. 
 
 Mean pressure 
 on the piston at 
 4-8 Ibs. per cir- 
 cular inch. 
 
 Velocity of 
 the steam 
 piston per 
 minute. 
 
 Length 
 of the 
 stroke. 
 
 Number 
 of strokes 
 per 
 minute. 
 
 Water required 
 per hour to 
 supply the 
 boiler. 
 
 Coals con- 
 sumed per 
 hour. 
 
 Number 
 of horse 
 power. 
 
 Coals con- 
 sumed per 
 hour. 
 
 horses. 
 
 inches. 
 
 Ibs. 
 
 feet. 
 
 feet. 
 
 strokes. 
 
 cubic feet. 
 
 Ibs. 
 
 horses. 
 
 Ibs. 
 
 1 
 
 7-8 
 
 289 
 
 114 
 
 1-3 
 
 44 
 
 0-8 
 
 15 
 
 1-46 
 
 31-5 
 
 2 
 
 10-25 
 
 516 
 
 131 
 
 1-75 
 
 371 
 
 1-37 
 
 23 
 
 2-95 
 
 48 
 
 3 
 
 12-05 
 
 697 
 
 141 
 
 2- 
 
 35 
 
 S>-36 
 
 Ml 
 
 4-4 
 
 64 
 
 4 
 
 13-52 
 
 877 
 
 149 
 
 2-25 
 
 33 
 
 3-13 
 
 38 
 
 5-9 
 
 80 
 
 5 
 
 14-9 
 
 1049 
 
 157 
 
 2-5 
 
 IU 
 
 3-92 
 
 45 
 
 7-4 
 
 94 
 
 6 
 
 15-9 
 
 1214 
 
 162 
 
 2-65 
 
 30.J 
 
 4-7 
 
 53 
 
 8-85 
 
 111 
 
 7 
 
 16-9 
 
 1373 
 
 167 
 
 2-8 
 
 29| 
 
 5-5 
 
 60 
 
 10-3 
 
 126 
 
 8 
 
 17-85 
 
 1527 
 
 171 
 
 2-97 
 
 29 
 
 6-3 
 
 67 
 
 11-8 
 
 140 
 
 9 
 
 18-7 
 
 1678 
 
 175 
 
 3-1 
 
 28J 
 
 7-05 
 
 73 
 
 13-3 
 
 153 
 
 10 
 
 19-5 
 
 1826 
 
 180 
 
 3-25 
 
 2(if 
 
 7-82 
 
 80 
 
 14-6 
 
 168 
 
 12 
 
 20-9 
 
 2113 
 
 186 
 
 3-5 
 
 26J 
 
 9-4 
 
 95 
 
 17-7 
 
 199 
 
 14 
 
 22-3 
 
 2390 
 
 191 
 
 3-7 
 
 MJ 
 
 11-0 
 
 109 
 
 20-7 
 
 230 
 
 16 
 
 23-6 
 
 2659 
 
 196 
 
 3-9 
 
 W 
 
 12-6 
 
 122 
 
 23-6 
 
 256 
 
 18 
 
 24-7 
 
 2922 
 
 201 
 
 4-1 
 
 24J 
 
 14-1 
 
 135 
 
 26-5 
 
 283 
 
 M 
 
 25-75 
 
 3179 
 
 206 
 
 4-3 
 
 24 
 
 15-7 
 
 149 
 
 29-5 
 
 312 
 
 22 
 
 26-75 
 
 3431 
 
 211 
 
 4-5 
 
 23J 
 
 17-3 
 
 163 
 
 32-5 
 
 341 
 
 24 
 
 27-7 
 
 3678 
 
 213 
 
 4-6 
 
 23i 
 
 18-8 
 
 176 
 
 35-5 
 
 370 
 
 26 
 
 28-6 
 
 3922 
 
 216 
 
 4-75 
 
 22J 
 
 20-4 
 
 189 
 
 38-4 
 
 395 
 
 28 
 
 29-45 
 
 4161 
 
 220 
 
 4-9 
 
 22J 
 
 22- 
 
 203 
 
 4V3 
 
 425 
 
 30 
 
 30-27 
 
 4397 
 
 222 
 
 5-04 
 
 22J 
 
 23-5 
 
 216 
 
 44-2 
 
 451 
 
 32 
 
 31-1 
 
 4630 
 
 226 
 
 5-2 
 
 aij 
 
 25-1 
 
 2SO 
 
 47-3 
 
 480 
 
 34 
 
 31-82 
 
 4860 
 
 229 
 
 5-3 
 
 24 
 
 20-7 
 
 243 
 
 50- 
 
 510 
 
 36 
 
 32-56 
 
 5088 
 
 232 
 
 5-43 
 
 2 H 
 
 28-3 
 
 256 
 
 53- 
 
 535 
 
 38 
 
 33-3 
 
 5313 
 
 234 
 
 5-55 
 
 21 
 
 29-7 
 
 269 
 
 56- 
 
 561 
 
 40 
 
 34- 
 
 5535 
 
 237 
 
 5-67 
 
 21 
 
 314 
 
 283 
 
 59- 
 
 596 
 
 42 
 
 34-63 
 
 5756 
 
 239 
 
 6-77 
 
 20f 
 
 33-0 
 
 297 
 
 62- 
 
 624 
 
 44 
 
 35-13 
 
 5919 
 
 241 
 
 5-85 
 
 20| 
 
 34-5 
 
 311 
 
 65- 
 
 (.52 
 
 46 
 
 35-9 
 
 6190 
 
 244 
 
 6-0 
 
 20J 
 
 36-2 
 
 324 
 
 67-5 
 
 6SO 
 
 48 
 
 3G-5 
 
 6404 
 
 246 
 
 6-1 
 
 201 
 
 37-7 
 
 338 
 
 70-5 
 
 709 
 
 50 
 
 37-13 
 
 6617 
 
 248 
 
 6-2 
 
 20 
 
 39-3 
 
 353 
 
 73-5 
 
 739 
 
 52 
 
 37-7 
 
 6828 
 
 250 
 
 6-3 
 
 20 
 
 40-7 
 
 367 
 
 76-4 
 
 768 
 
 54 
 
 38-3 
 
 7036 
 
 252 
 
 6-4 
 
 19| 
 
 42-4 
 
 381 
 
 79-3 
 
 798 
 
 56 
 
 38-85 
 
 7245 
 
 254 
 
 6-49 
 
 19J 
 
 44-0 
 
 396 
 
 82-2 
 
 827 
 
 
 
 
 
 
 
 
 
TABLES. 
 
 3-25 
 
 Table III. continued. 
 
 
 Steam acting at full 
 
 Steam acting expansively. 
 
 pressure throughout 
 the stroke in the 
 
 
 same engine. 
 
 Number 
 of horse 
 power. 
 
 Diameter 
 of the 
 steam 
 piston. 
 
 Mean pressure 
 on the piston, at 
 4'8 Ibs. per cir- 
 cular inch. 
 
 Velocity of 
 the steam 
 piston per 
 minute. 
 
 Length 
 of the 
 stroke. 
 
 Number 
 of strokes 
 per 
 minute. 
 
 Water required 
 per hour to 
 supply the 
 boiler. 
 
 Coals con- 
 sumed per 
 hour. 
 
 Number 
 of horse 
 power. 
 
 Coals con- 
 sumed per 
 hour. 
 
 horses. 
 
 inches. 
 
 Ibs. 
 
 feet. 
 
 feet. 
 
 strokes. 
 
 cubic feet. 
 
 Ibs. 
 
 horses. 
 
 Ibs. 
 
 58 
 
 39-4 
 
 7453 
 
 255 
 
 6-57 
 
 10J 
 
 45-4 
 
 409 
 
 85-1 
 
 850 
 
 60 
 
 39-9 
 
 7656 
 
 257 
 
 6-65 
 
 I9i 
 
 47-0 
 
 423 
 
 88-1 
 
 887 
 
 62 
 
 40-5 
 
 7860 
 
 259 
 
 6-75 
 
 19J 
 
 48-6 
 
 437 
 
 91-0 
 
 916 
 
 64 
 
 41-0 
 
 8062 
 
 260 
 
 6-83 
 
 19 
 
 50-2 
 
 452 
 
 93-9 
 
 946 
 
 66 
 
 41-5 
 
 8263 
 
 2(>1 
 
 6-9 
 
 19 
 
 51-8 ' 
 
 466 
 
 96-8 
 
 975 
 
 68 
 
 42-0 
 
 8462 
 
 263 
 
 7-0 
 
 18? 
 
 53-4 
 
 481 
 
 99-7 
 
 1005 
 
 70 
 
 42-5 
 
 8662 
 
 265 
 
 7-1 
 
 18| 
 
 55-0 
 
 495 
 
 102-7 
 
 1035 
 
 72 
 
 43-0 
 
 8858 
 
 266 
 
 7-17 
 
 18J 
 
 56-6 
 
 509 
 
 105-6 
 
 1064 
 
 74 
 
 43-4 
 
 9013 
 
 268 
 
 7-23 
 
 w 
 
 58-1 
 
 514 
 
 108-5 
 
 1094 
 
 76 
 
 43-9 
 
 9250 
 
 2fi9 
 
 7-3 
 
 lfe| 
 
 59-8 
 
 538 
 
 111-4 
 
 1123 
 
 78 
 
 44-4 
 
 9444 
 
 270 
 
 7-4 
 
 181 
 
 61-5 
 
 554 
 
 114-3 
 
 1153 
 
 80 
 
 44-8 
 
 9637 
 
 272 
 
 7-47 
 
 18J 
 
 62-5 
 
 563 
 
 117-3 
 
 1182 
 
 85 
 
 45-9 
 
 10120 
 
 275 
 
 7-65 
 
 18 
 
 66-5 
 
 599 
 
 124-6 
 
 1256 
 
 90 
 
 46-97 
 
 10590 
 
 279 
 
 7-83 
 
 17? 
 
 70-5 
 
 635 
 
 131-9 
 
 1330 
 
 93 
 
 48-0 
 
 11060 
 
 282 
 
 8-0 
 
 17f 
 
 74-4 
 
 670 
 
 139-2 
 
 1404 
 
 100 
 
 49-0 
 
 115-20 
 
 284 
 
 8-16 
 
 17J 
 
 78-2 
 
 704 
 
 146-0 
 
 1478 
 
 105 
 
 49-95 
 
 11980 
 
 287 
 
 8-32 
 
 175 
 
 82-1 
 
 739 
 
 153-3 
 
 1552 
 
 110 
 
 50-9 
 
 12430 
 
 290 
 
 8-5 
 
 17 
 
 86-0 
 
 774 
 
 161-6 
 
 1626 
 
 115 
 
 51-6 
 
 127 CO 
 
 292 
 
 8-6 
 
 17 
 
 89-9 
 
 809 
 
 167-9 
 
 1700 
 
 120 
 
 52-7 
 
 13330 
 
 294 
 
 8-8 
 
 lif 
 
 93-8 
 
 844 
 
 175-2 
 
 1774 
 
 125 
 
 53-6 
 
 13760 
 
 297 
 
 8-9 
 
 ICf 
 
 97-7 
 
 879 
 
 182-5 
 
 1848 
 
 130 
 
 54-4 
 
 14210 
 
 299 
 
 9-0 
 
 16{ 
 
 101-7 
 
 915 
 
 189-8 
 
 1921 
 
 135 
 
 55-3 
 
 14740 
 
 300 
 
 9-2 
 
 16J 
 
 105-6 
 
 950 
 
 197-1 
 
 1995 
 
 140 
 
 56-1 
 
 15080 
 
 302 
 
 9-35 
 
 16J 
 
 10U-5 
 
 986 
 
 204-4 
 
 2069 
 
 145 
 
 56-84 
 
 15510 
 
 306 
 
 9-47 
 
 16J 
 
 113-4 
 
 1021 
 
 211-7 
 
 2143 
 
 150 
 
 57-6 
 
 15930 
 
 308 
 
 9-6 
 
 16 
 
 117-3 
 
 1055 
 
 219-0 
 
 2217 
 
 155 
 
 58-4 
 
 16360 
 
 310 
 
 9-7 
 
 16 
 
 121-2 
 
 1091 
 
 226-3 
 
 2291 
 
 160 
 
 59-1 
 
 16780 
 
 312 
 
 9-83 
 
 I5J 
 
 125-2 
 
 1127 
 
 233-6 
 
 2364 
 
 175 
 
 61-3 
 
 18030 
 
 318 
 
 10-2 
 
 lij 
 
 129-1 
 
 1162 
 
 210-9 
 
 2438 
 
 180 
 
 62-0 
 
 18440 
 
 320 
 
 10-3 
 
 11 
 
 133-0 
 
 1197 
 
 248-4 
 
 2512 
 
 200 
 
 67-7 
 
 22000 
 
 334 
 
 11-3 
 
 14] 
 
 1504 
 
 1408 
 
 292-0 
 
 2956 
 
EXPLANATION OF THE PLATES; 
 
 WITH REFERENCES 
 
 ARTICLES WHERE THE CONSTRUCTION IS INVESTIGATED. 
 
328 EXPLANATION OF THE PLATES. 
 
 PLATE I. 
 
 Fig. 1. is an isometrical projection of a rectangular steam boiler, (art. 225, 226.) 
 with part of the top plates of the boiler, and part of the brickwork removed to show 
 the internal parts. A is the boiler ; the half of the doorway to the fire is at B, and 
 the fuel rests on the fire-bars G, and against the back F : the flame passes over F, 
 and along under the bottom ; it rises at H, and returns in a flue by the nearest 
 side, passes round the end by the flue I, and along a flue by the further side to the 
 chimney at L; a horizontal damper K regulates the aperture to the chimney. 
 See art. 257. The door to the ash-pit C should shut perfectly close, and the 
 supply of air for the fire should enter by a passage E, the aperture of which is 
 regulated by the force of the steam acting by the chain n, n, (art. 258.) In the 
 figure the air is supposed to enter by the grating at D. The supply of water enters 
 by the pipe M N, the end N being turned along the bottom of the boiler, that the 
 water may acquire heat before it mixes with the rest ; the admission is regulated 
 by the stone float c. (art. 251 253.) The steam passes to the engine by the pipe 
 S, and when it is not required, it goes off by the safety valve V, (art. 260.) and 
 through the pipes T W. The internal valve is on the man-hole plate at a b, 
 (art. 259.) The steam gauge is at h, (art. 558.) the gauge cocks at k, i ; and a 
 cock to clear the boiler of water is at R. Opposite each flue, as at Q, there must 
 be an aperture to clear it out at. 
 
 Fig. 2. shows a method of admitting water to a boiler where high pressure steam 
 is used. The pump forces the water by the pipe D, through the valve aperture A, 
 into the boiler ; but when the quantity is in excess, the copper float F closes the 
 valve, and opens the valve B to the waste pipe C, by which the surplus passes off. 
 The parts must be balanced on the axis by the weight G. (See art. 253.) 
 
 Fig. 3. 4. 5. and 6. are tops for engine chimneys. Fig. 3. is a plain obelisk : the 
 proportions of an Egyptian obelisk are very well adapted for a chimney, and if the 
 faces were stuccoed and covered with sunk figures, it would render them novel and 
 ornamental. Fig. 4. is an octagon top for a square shaft ; Fig. 5. an octagon 
 chimney ; and Fig. 6. a chimney to represent a column. (See art. 274 278.) 
 
EXPLANATION OF THE PLATES. 329 
 
 PLATE II. 
 
 This plate represents a plan and two sections of a cylindrical steam boiler, 
 (art. 227 230.) Fig. 1. is a cross section, Fig. 2. a longitudinal section, and 
 Fig. 3. the plan ; in the last, half of it is the plan above the level of the boiler 
 bottom, and the other half below it. The fuel is put in at the fire-door B, it 
 inflames at D, and the smoke in passing over the hot current of air rising through 
 the red fuel at E is consumed. The ash-pit door is supposed to be provided with a 
 register to regulate the admission of air, but it would be better to make it regulate 
 itself as in the preceding plate. By pushing back the plate k by the handle i, the 
 clinkers are let out behind, (art. 248.) The supply of water is regulated by a 
 hollow copper-ball float, and the supply is continuous, except, when by the water 
 rising, the valve is closed, (art. 254.) To prevent sediment depositing over the 
 fire, I would recommend a division to be placed across the boiler as at O ; the 
 safety pipe T W is recommended instead of the valve, on account of the certainty 
 of its action. The first effect of strong steam is to displace the water down to the 
 level of the mouth of the pipe at T ; this sets the feed pipe into action, and steam 
 and water rise by the pipe T W till the boiler be cooled to its proper temperature, 
 (art. 264 ;) no internal valve is required : S is the steam pipe leading to the 
 engine. The same letters refer to the same parts in all the figures. For the area 
 of the grate, and ash-pit, see art. 197 199; size of the boiler, art. 229; the 
 area of the chimney, art. 274 278 ; and the strength of the boiler, art. 525. 
 
 Note. In Section III. I neglected to remark that the boilers formed of small 
 pipes cannot possibly produce more effect than others, and that every boiler must 
 contain a certain quantity of water and steam, otherwise the slightest neglect of the 
 fire would cause the engine to stop. It has been pretty clearly ascertained that not 
 one of the combinations hitherto proposed, has equalled the kind of boiler above 
 described. 
 
330 EXPLANATION OF THE PLATES. 
 
 PLATE III. 
 
 This plate represents Brunton's apparatus for feeding furnace-fires by means of 
 machinery. The general principles of the method and its advantages have been 
 stated, (art. 250.) and it only remains to describe the parts of the figure. The 
 apparatus was added to two boilers of Boulton and Watt's construction. To the 
 original boilers A A, two additional boilers B B, are attached, which are prepared 
 for the purpose of being over the revolving fire-grate ; the smoke from which 
 passes over and under the bridges d d, and round the boilers A A, by the flue C ; 
 and D D are the flue-doors. The coals, broken to a proper size, are put into the 
 hoppers E E, and fall through the openings F F, and through the top of the 
 boiler to the grate. The door H, to examine or repair the fire-place, is attached to 
 the boiler by a cement joint. The additional boilers are connected to the main 
 boilers by the steam pipes G G. 
 
 To clear the dust away that falls over the edge of the revolving grate, there are 
 doors at I I ; they also admit a small quantity of air to the burning fuel. The 
 axis K of the grate is turned by the pinion and wheel at L, turned by the upright 
 shaft N, which receives its motion by the shaft R from the engine. 
 
 The pivot of the shaft N, and of the spindle K, are in the foundation plate M. 
 The grate bars are surrounded by fire bricks h, and a thin hoop projects below the 
 frame, and moves in sand in a trough /, and prevents air entering by any other 
 passage than through between the bars : a scraper attached to the grate, and 
 consequently moving with it, keeps the channel i clear of dust. 
 
 To regulate the fire, the chains S S are connected to the damper chains, and 
 raise or depress the wedge U by the lever T, and thus increase or diminish the 
 supply of coals according to the force of the steam. (See art. 257.) 
 
 The feed pipe O, with its stone float c and balance /, are as in other boilers, (art. 
 251.) The gauge-cocks are at Z, the man-hole at a, with an internal valve at b; 
 the safety valve is at V, with a pipe Q to convey away the steam ; P is the pipe for 
 conveying steam to the engine, with a self-acting stop valve W, to prevent the 
 steam passing from one boiler to the other when both are in action ; and X Y is a 
 lever handle for closing the aperture when only a small supply of steam is 
 required. 
 
 The construction will admit of considerable variation ; and its advantages in 
 saving fuel, in regularity of action, and in consuming the sooty matter of smoke, 
 render it a desirable addition to a large boiler. 
 
EXPLANATION OF THE PLATES. 331 
 
 PLATE IV. 
 
 Fig. 1 . is a section of the parts of a high pressure engine with a four-passaged 
 cock. The engine is supposed to be partly within the boiler, of which D B is the 
 top plate. P is the steam piston, and R the piston rod, A is the four-passaged 
 cock ; the steam enters from the boiler at S, and passes through t to the top of the 
 piston, and the steam below escapes through the passage b, and pipe a and E, to 
 the atmosphere ; the pipe E is surrounded by water, which the escaping steam 
 warms ready for the boiler. By turning the cock the motions are reversed, but it 
 is obvious we cannot in this engine employ the expanding force of the steam. The 
 motion is regulated by a throttle valve V. See art. 356 361. 
 
 Fig. 2. and 3. show a section and plan of a similar engine, with a D-slide 
 instead of a cock ; the steam enters from the boiler at S, and by the passages being 
 shut and opened close to the extremities of the cylinder, there is no loss by the 
 communicating pipes being filled with strong steam. See art. 364. This engine 
 will not work expansively unless the construction of the slide be altered. See 
 art. 371. Contrary to the usual practice, the packing of the slide is on the sliding 
 part ; the advantage of this plan is obvious, but the practical difficulty of boring 
 a semi-cylinder is incurred. 
 
 Fig. 4. is a simple arrangement of the high pressure engine by which the 
 expanding power of the steam may be used ; it is the invention of Murdoch. The 
 passages are opened and closed by pistons sliding in a pipe : the steam enters this 
 pipe at S, and the steam is supposed to be just shut off by the upper piston, so that 
 by the expansion of that in the cylinder the rest of the stroke is completed, the 
 passage E to the atmosphere being still open. See art. 371 380. The slide 
 would be improved by making it of the form of a D-slide. 
 
 The construction of the pistons of the slide is a suggestion which may perhaps 
 answer better than the common ones, (art. 450. and note.) 
 
 Fig. 5. is an arrangement to illustrate the action of a high pressure engine to 
 work expansively by means of combined cylinders. See art. 381 383. 
 
332 EXPLANATION OF THE PLATES. 
 
 PLATE V. 
 
 Fig. 1. is a section of a double-acting condensing engine, with a slide adapted 
 for working by the expanding force of steam ; the slide being, in Fig. 1., in the 
 position for letting the steam on at the top. Fig. 2. shows the steam shut oft', and 
 the passage to the condenser still open ; and Fig. 3. the position when the steam is 
 let on at the bottom. See art 448. The steam enters at S, and a pipe of com- 
 munication between the steam pipe and the condenser is necessary, to allow steam 
 to enter the condenser when the engine is about to be set to work, (art. 414.) 
 
 Fig. 4. is a section of a single-acting condensing engine, with valves to the 
 passages, (see art. 406.) ; and Fig. 5. a different arrangement of the valves for a 
 single engine. 
 
 Fig. 6. represents the box slide, admitting steam through the upper passage and 
 open below to the eduction passage, or to the condenser. 
 
 In all these figures the same letters indicate the same parts. C is the steam 
 cylinder, P the steam piston, R the piston rod, B the condenser, with a jet of water 
 playing into it from I the injection cock ; A is the air pump, and p its piston ; 
 G is the foot valve between the condenser and air pump ; M the air pump, and 
 Q the discharge valve of the air pump, through which the air and hot water are 
 forced into the hot well K, from whence a part is raised by a small force pump to 
 the boiler feed head, and the rest runs off by a waste pipe. H is the blow valve to 
 the condenser, (art. 566.) The condenser and air pump are placed in a cistern, 
 which is constantly supplied with cold water by a pipe N. 
 
 The jet should be made through a rose on the end of the pipe ; for, to produce 
 speedy and perfect condensation, the cold fluid should present the greatest possible 
 surface to the steam it is to condense, (see art. 280.) ; and it should be impelled 
 into the condenser with greater force than the ordinary head in the cistern 
 admits of. 
 
 In large engines the connecting eduction pipe E, Fig. 1. may be on the outside 
 of the steam pipe S, and the parts of the slide connected only by a rod, as 
 mentioned in art. 447. 
 
EXPLANATION OF THE PLATES. 333 
 
 PLATE VI. 
 
 Fig. 1 . is a section of a common atmospheric steam engine ; C is the cylinder, 
 and the piston is supposed to have a wooden bottom, according to the practice of 
 Smeaton, (art. 466.) ; the steam is let on by a modification of Hornblower's valve, 
 (art. 442.) instead of the common regulator, (art. 461.) For the proportions of the 
 engine, see art. 393399. 
 
 Fig. 2. is a section of an atmospheric engine with a separate condenser "and air 
 pump ; see art. 400 405. An elevation of this engine is shown in Plate xi. 
 
 Fig. 3. is a section of a combined cylinder engine on Hornblower's principle, 
 (art. 32.) where the steam passages are opened and closed by a combination of 
 slides in one pipe. See art. 425 429. Woolf s engines have two cylinders, but 
 the passages are opened by valves. 
 
 Fig. 4. is a section of Hornblower's double-seated valve. See art. 441. 
 
 Fig. 5. represents a section of Murray's slide ; it is a sliding cover which alter- 
 nately covers the passages a c and c b : the disadvantage of this construction is, 
 that the pressure of the steam is nearly three times as great on the moving surfaces, 
 as it is in Murdoch's arrangement shown in the last Plate. See art. 446. 
 
 Fig. 6. and 7. show the mode of forming the apertures of a four-passaged cock, 
 so that the steam may be shut off at any period of the stroke without closing the 
 passages to the condenser. See art. 456. T is the passage to the top, and B that 
 to the bottom of the cylinder ; the steam enters at S, and C is the passage to the 
 condenser. Fig. 6. shows the position of the cock when the steam is entering, and 
 Fig. 7. when it is shut off. 
 
334 EXPLANATION OF THE PLATES. 
 
 PLATE VII. 
 
 This plate is to represent the construction of pistons. 
 
 Fig. 1. represents a section, and part of the plan, of the common packed piston, 
 which is tightened by the screws S when it wears. See art. 467. 
 
 Fig. 2. shows one of Woolfs methods of tightening the whole of the screws at 
 once, and consequently in the most regular manner, without having to take off the 
 cylinder lid. See art. 468. 
 
 Fig. 3. is the plan and section of Cartwright's metallic piston, (art. 43.) as at 
 first executed ; it was afterwards made with spiral and other springs, acting only 
 on the interior segments of rings b b, but it required that the outer ones should be 
 moved ; and this has been done by making the interior segments in short pieces to 
 cover the joints of the outer ones, so as to leave space to insert springs between 
 them, to act directly on the outer segments, by Mr. Lloyd : it has also been done 
 by inserting a short cylindrical piece against each joint of the outer ring, both the 
 cylindrical pieces and the outer segments being pressed outwards by spiral springs : 
 this method is employed by Messrs. Hall. See art. 469. 
 
 Fig. 4. represents Barton's construction of metallic pistons in plan and section. 
 The points of the wedges G expand faster than the segments E in the ratio of m n 
 to o n, and hence wear the cylinder unequally. To prevent this, the points are 
 shortened, and two elastic hoops b b, Fig. 5. are put round, neatly fitted with a 
 loose tongue joint, as shown at Fig. 6. See art. 470. 
 
 Fig. 7. shows a method of avoiding the defect of Barton's piston, by keeping the 
 points of the wedges as much within the segments of the piston as may be necessary 
 for wear, before a change of parts becomes necessary, and making two series to 
 break joints. See art. 471, 472. 
 
 Fig. 8. represents a section of Jessop's piston, and Fig. 9. the expanding coil of 
 metal which rubs against the cylinder. See art. 473. I am of opinion that a 
 more perfect method of pressing the packing against the metal coil, is the only 
 thing wanted to render this decidedly the best kind of piston. 
 
 The friction of pistons is investigated in art. 474. 
 
EXPLANATION OF THE PLATES. 335 
 
 PLATE VIII. 
 
 Fig. 1. represents a section of the steam pipes and valves of Messrs. Fenton 
 and Murray's * double engine, Plate xiv. ; and Fig. 2. the communicating rods. 
 The steam enters by the pipe C, which has a throttle valve at a, to regulate the 
 supply of steam to the engine, (art. 544.) It is regulated by the action of the 
 governor balls on the lever b, by the connecting rod c : the rotary motion is com- 
 municated to the axis of the governor, by means of a band passing from a pulley 
 on the crank shaft to a similar pulley d on the axis of the governor. The governor 
 consists of two bent levers e e, passing through a slit in the middle of the spindle, 
 and turning upon an axis at/. The upper part of the spindle has a slide h, which 
 is connected to the levers by the rods i i, and ascends when the centrifugal force 
 of the governor increases, so as to cause the balls to rise, and descends when it 
 decreases ; and the lever / moves with it, and consequently the valve. When the 
 engine is at rest, the balls jj rest against the arms k k ; the upper end of the 
 levers e e are nearer to each other ; and the rod c is raised so that the throttle 
 valve may be quite in a horizontal direction, and the pipe completely open for the 
 passages of the steam. See art. 550. 
 
 By the pipe D D, the steam passes either to the top or bottom of the cylinder 
 from the throttle valve a, and by the eduction pipe E E the steam from either 
 passes down to the condenser. The valves n o have each a cylindrical tube or 
 spindle passing through the stuffing boxes r s ; the upper end of each of these has 
 a stuffing box, the upper one at t, the other at u, for the rods of the valves p g, 
 which open to the eduction pipe E, so that either the steam or eduction valves may 
 be opened without allowing steam to escape. 
 
 Fig. 2. is a front view of the two sliding rods which give motion to the 
 valves n, o, p, and q. These rods are kept in a perpendicular direction by the 
 pieces z 2, and the guide 1 ; the lower end of the rods have friction rollers 3 3, 
 which are acted upon by the two eccentric pieces 4 4, on the horizontal shaft Z, 
 which derives its motion from a shaft Y, placed at right angles to, and communi- 
 
 * In reference to these nozles and side pipes, Fenton and Murray brought an action against 
 Boulton and Watt for an infringement on their patent for working one valve through the other ; 
 but it was decided that Mr. Boulton's Mint Engine had been working with valves similarly con- 
 structed for a length of time previous to their patent. 
 
336 EXPLANATION OF THE PLATES. 
 
 eating by means of beveled wheels with the crank shaft. Four arms, 9, 10, 11, 
 and 12, are fixed to the rods v v and w w, for the purpose of moving the valves, 
 and a lever or handle (13), turning on a pin screwed on the pipe E, is used to open 
 and shut the steam valves when the engine is first set to work ; (see art. 566 ;) the 
 steam gauge (21) is for measuring the pressure of the steam above that of the 
 atmosphere, (art. 558.) and the condenser gauge (24) is for measuring the force of 
 the vapour in the condenser, (art. 559.) 
 
 Fig. 3. 4. 5. and 6. represent the four-way cock as executed by Maudslay. 
 Fig. 5. is the plan taken at the horizontal line D E, in Fig. 3. and 4., which are 
 sections through the steam cock. In these figures E is the steam pipe, and F the 
 pipe leading to the condenser G. Fig. 4. is the steam cock or cone ground into its 
 seat, and provided with a grease cup H to afford a regular supply. 
 
 Fig. 6. is a plan of the upper side of the steam cone. See art. 457 and 
 Plate xv. 
 
EXPLANATION OF THE PLATES. 337 
 
 PLATE IX. 
 
 The apparatus for opening and closing the steam passages is of more importance 
 to the perfection of the steam engine, than any other part of its mechanism. In the 
 present state of the engine the action is either very complicated or imperfect : my 
 object in this plate is to show how the imperfection of the most simple method may 
 be avoided, and also how it may be applied to reciprocating movements. 
 
 Fig. 1. shows a section, 1 and Fig. '2. a plan, of an apparatus for opening and 
 closing the steam passages by means of the rotary motion of the crank shaft D : 
 the object of the method is to give such a form to a wheel on the shaft D as will 
 move the pin e twice during the stroke, and in the easiest and quickest manner. 
 For this purpose the shaft passes through a rectangular frame which rests in grooves 
 on the shaft to keep it in its place, with liberty to slide backwards and forwards ; 
 and it is provided with two rollers, to be acted on by the curved surfaces of a wheel 
 fixed on the shaft. The curve H G moves the valves at the termination of the 
 stroke, and I K shuts off the steam, that the engine may work expansively the 
 rest of the stroke. In order that there may be the power of varying the time of 
 cutting off the stroke, the curve I K may be on a separate piece M, (Fig. 2.) capable 
 of being moved from N to 0. The apparatus is supposed to move a slide of the 
 kind represented in Plate v. Fig. 1 ; but is equally applicable to move the four- 
 passaged cock, (art. 456 and 458) or valves. For the nature of the curves, see 
 art. 481. 
 
 Fig. 4. and 5. represent the same principle applied to a reciprocating motion. 
 The plug-tree A B is kept in its place by guides on the brackets ; these guides 
 slide in the dark grooves. The curved parts H I, C D, K L, &c. successively 
 move, horizontally, the frame C on four rollers supported by the brackets attached 
 to the engine ; and by the backward and forward motion it turns the axis E, and 
 raises or depresses the lever F, which acts on the rod of the slide. The same move- 
 ment would obviously open valves or turn a cock. By the lever on the right-hand 
 side, the roller frame may be moved by hand ; but by not reversing Fig. 5. it has 
 been shown there on the left. See art. 483. 
 
 Fig. 3. represents the method of opening valves by weights, the plug- tree A B 
 being made a means of raising the weights, and of disengaging them by the 
 tappets/, d. See art. 478. 
 
 1 Fig. 1., as represented in the Plate, is too much limited to allow the motion to be reversed. 
 
 2 u 
 
338 EXPLANATION OF THE PLATES. 
 
 PLATES X. (A) AND (B). 
 
 The figures of these plates are to illustrate the combinations used to produce 
 rectilinear motion, from motion in a circular arc. 
 
 Fig. 1. is the parallel motion used for steam boat engines. The beam A F is 
 below the cylinder ; from G, the end of the cross head, draw a line to A, the centre 
 of the axis of the beam, and it will cut the rod D B in E, and the length of the 
 radius bar C D may be found by art. 492. ; when E B is equal to E D, the length 
 of the bar C D is equal to A B, and this is the best though not always the most 
 convenient form. The rod D' G may be at any height, provided it be parallel to 
 A F ; and B may be at any point in A F, if the position of C is not limited. 
 
 Fig. 2. shows the most common construction for engines with the beam above 
 the cylinder. H is the piston rod connected at G, and C D is the radius bar. 
 The line G A cuts the link B D in E, the proper point for the air pump rod. 
 Fig. 3. shows a plan of the upper side of the beam, where C D, C D are the radius 
 bars ; and the beam is in two parts, as is usual in large engines. 
 
 Fig. 4. is a diagram to illustrate the investigation of the properties of the 
 combination in its most simple form. See art. 489. 
 
 Fig. 5. is a diagram for the apparently more complicated case,- when the rod is 
 fixed to one angle of a parallelogram. See art. 492. 
 
 Fig. 6. shows how to arrange for three piston rods to move parallel, as for 
 Woolf s engine : the points of suspension must be all in the line A G ; and any 
 number of them may be similarly adapted. 
 
 Fig. 7. shows another arrangement for three rods at one end, and two at the 
 other end of the beam. See art. 495. The dotted arcs, Plate x. (B), show how 
 the centre C for the radius bar may be determined geometrically, by drawing a 
 circle through the three positions, D, d, d', of the point of connexion. 
 
 In all the cases the corresponding points are marked by the same letters, and 
 therefore by referring to the investigation of Fig. 4. the relations may be traced : 
 the particular forms of different engine makers will be found by turning the part 
 upside down, altering the place of the parallel bar G D, or altering the proportions 
 of the parts. In every combination where the bar C D is not equal to A B, the 
 variation from rectilinear motion increases with the extent of the angle described. 
 
 Variations of the parallel motion are exhibited in some of the other Plates. 
 Fig. 8. is designed to show that the vibrating pillar motion is exactly the same 
 in principle, and only differs in the particular mode of combination. See art. 494. 
 Fig. 9. is a particular case. 
 
EXPLANATION OF THE PLATES. 339 
 
 Fig. 10. and 11., parallel motions for steam boat engines, show how the point 
 of connexion of the radius rod may be determined by geometrical construction. 
 Thus, having determined the three points, H, //, h', set off h k equal to C h' ; join 
 C k, and bisect it with the straight line n d, meeting k h d in the point required : 
 for since k d = C d, and h k = C h', we have h d = h' d' ; and hence when d arrives 
 at d', h will coincide with h', and the motion will thus be properly adjusted. 
 Fig. 1. may be constructed in this manner. See art. 492. 
 
 Fig. 12. exhibits a simple parallel motion, and is easily constructed geometrically 
 by finding C, the centre of a circle, passing through the three points D D' D''. 
 Fig. 13. shows how a pump rod may be attached to this motion. 
 
 PLATE XI. 
 
 This plate represents a plan and elevation of an atmospheric engine for raising 
 water from a mine. The beam is supported by a frame of cast iron, designed so 
 that it may be taken apart when it is necessary to move the engine to another 
 mine, (art. 578.) The steam comes from the boiler by the steam pipe S, and is 
 admitted to the cylinder C by a sliding piston in B, (see Fig. 2. Plate vi.) and 
 then the piston in the cylinder C rises to the top of the stroke, and the piston rod 
 forces the end / of the beam up with it ; as the beam rises, it draws the rod F G 
 with it, which near the end of the stroke moves the sliding frame H, (art. 483.) 
 and by the rod O the slide in B, so as to shut the steam off, and open the passage 
 to the air pump A : into the passage a jet of water plays at I. The piston then 
 begins to descend by the pressure of the atmosphere and raises the pump rods, and 
 at the end of the stroke the part F of the rod F G moves the slide, and shuts the 
 passage to the air pump, and opens that for the steam. See Plate vi. Fig. 1. 
 
 The parallel motion 1 is guided by the radius rod cd attached to the frame, (art. 
 491. and 495.) and by connecting the rods h i : the same rod does for both ends 
 of the beam. The sliding frame H is supported by a cross bar beneath H, 
 and another at K, and the slide may be moved by hand by the lever M. Cold 
 water for injection is supplied by the pump E, and water is raised from the hot 
 well by the pump D, and passes to the boiler by the pipe Q, with a small branch 
 pipe at P, to give water to the top of the piston. See art. 400 405. 
 
 1 In the parallel motion apparatus, shown in Fig. 1., the vibration of the beam is not bisected. 
 See p. 233, Note. 
 
340 EXPLANATION OF THE PLATES. 
 
 PLATE XII. 
 
 This plate shows an elevation of a single acting engine, as executed by Messrs. 
 Boulton and Watt. The boiler a is inclosed in a case of brickwork, and the steam 
 passes by the steam pipe b, to the cylinder c, which is firmly attached to the floor 
 of the engine room, by the bolts d, d: its upper end is covered by the lid e, 
 through which the piston rod k slides in an air-tight box called a stuffing box. 
 The beam/g- moves on its axis or gudgeon at h; and the bearings in which the 
 gudgeons work are sustained by the floor and wall i. 
 
 The pump rod j, carrying a counter- weight, is suspended at the end g of the 
 beam ; and both it and the piston rod k are connected by a parallel motion appa- 
 ratus to the working beamfg. See art. 492. 
 
 The condensing cistern is at m, and contains the air pump n, the condenser, and 
 hot well o : a continued supply of cold water is procured by the action of the cold 
 water pump p, and the excess is carried off by a waste pipe to the well q ; the 
 whole of the external part of the apparatus being kept by that means at the lowest 
 temperature possible. 
 
 The upper steam valve is at r, and the lower at s, and the exhaustion valve at t. 
 See Fig. 5. Plate v. These valves are moved by the plug tree v, which is furnished 
 with tappets to give motion to the levers acting on the valves r, s, t. See art. 478. 
 
 The pump to raise water from the hot well o, to supply the boiler, is at u, and 
 the water is conveyed by the pipe w w to the small cistern .r on the top of the feed 
 pipe, which is provided with a valve, and acted on by a lever connected by a wire 
 passing down through a stuffing box y, to a stone float in the boiler, which by its 
 descent opens the valve, and allows the admission of an additional supply of water 
 when it is required, (art. 251.) 
 
 In order to prevent concussion, two blocks 1, 2, are fixed across the upper side 
 of the beam, and extend on each side so as to strike on four wooden springs, on 
 the floor which supports the beam. See art. 549. 
 
 For large engines the beam is in two parts, with a space between them, as 
 shown in Fig. 3. Plate x. 
 
 The proportions of the single engines are given in Sect. vi. art. 406 413 ; the 
 application, in art. 572, 573. 582. and 587 ; their effects, art. 576 ; and their power, 
 and consumption of fuel, Table n. art. 663. 
 
EXPLANATION OF THE PLATES. 341 
 
 PLATE XIII. 
 
 This plate represents a double acting steam engine for raising water, (art. 570, 582.) 
 
 The steam from the boiler enters by the steam pipe S, passes through the top 
 valve a, to act on the piston p, and forces it down ; and just before it arrives at the 
 bottom of the cylinder, the plug on the rod R will come in contact with a lever, 
 and shut the valves a b, and open c d, which were shut ; the steam will now 
 continue its course down the pipe S through the valve d, act on the bottom of the 
 piston p, and again force it up to the top of the cylinder, while the steam which 
 forced it down will make its escape to the condenser B, through the valve b, by 
 a pipe which conveys the steam from the valves to the condenser. 
 
 Having described one double stroke of the engine, it is only necessary to remark 
 that its continued motion is made of a repetition of the same thing over again. The 
 steam which passes to the condenser B meets with a jet of cold water from the 
 injection cock I, and the greater part of it is reduced to the state of water, and it 
 is the office of the air pump A to clear it away. The rod R works the air pump 
 which draws out all the injected water, air, and condensed steam, and discharges 
 it through the valve at the top of the air pump into the hot well, where a certain 
 portion of the water is again forced back to the boiler by the force pump L, and 
 the remainder runs to waste : at the same time, to the other end of the great beam 
 is attached the rod of the cold water pump N, which supplies the cistern containing 
 the condenser and air pump with cold water ; and from this source the injection 
 cock has its supply. 
 
 The governor Q is put in motion by beveled wheels on the shaft of the fly 
 wheel P, (art. 54^0.) and regulates the throttle valve in the steam pipe S, so as to 
 close it a little for a less admission of steam when the speed is increasing ; and on 
 the contrary, when the engine relaxes in its speed, the balls will again begin to 
 fall, and open it a little so as to admit more steam ; by this means the work may 
 vary, and yet a uniform motion be kept up by the engine, (art. 550.) 
 
 In the pumping apparatus, the rod M is the pump rod for the purpose of raising 
 water ; when the rod descends, the water will be forced through G into the upper 
 air vessel E, from whence it passes in a continued stream to the reservoir, at a 
 distance and height proportional to the power of the engine. The barrel of the 
 pump will be refilled from F, the source which communicates with the lower air 
 vessel H ; when the rod rises, the opposite valve at the top will open, and the water 
 
342 EXPLANATION OF THE PLATES. 
 
 will be forced through into the air vessel E, and the supply for the descending 
 stroke will rush in by the bottom valve from F, and, as before, be discharged 
 through G. 
 
 For the proportions of this kind of engine (see art. 414 423). I would re- 
 commend the adoption of Field's valve instead of the throttle valve. See 
 art. 547. 
 
 PLATE XIV. 
 
 This plate represents a double acting steam engine, for impelling machinery, as 
 executed by Messrs. Fenton, Murray, and Co., of Leeds. 
 
 The engine is supported by the walls A A A A, part of which form the walls of the 
 engine house. The steam cylinder B is secured to the wall below it by bolts ; it is 
 enclosed in a jacket or casing of cast iron, a little larger than the cylinder, and the 
 space between them is supplied with steam, to keep the temperature of the cylinder 
 as near to the temperature of the steam as possible. (See art. 155.) The steam 
 comes from the boiler by the steam pipe C C, to the valve pipe D D, and passes 
 to the condenser by the eduction pipe E E, leading to the condenser F, which 
 with the air pump G is immersed in the cold water cistern H, supplied through 
 the pipe J. The cold water pump I is worked by the rod O attached to the 
 engine beam. The air pump is worked by the rod N, and delivers the water 
 into the hot well, from whence the hot water pump K, worked by the rod P, the 
 upper part of which is connected with the working beam at Q, raises a quantity of 
 hot water to supply the boiler. 
 
 The working beam Q is supported by the cast iron column R, and is connected 
 to the piston rod L by the parallel motion M M (see art. 188) ; the other end of 
 the beam gives a rotary motion to the crank shaft by means of the connecting rod 
 S, the lower part of which is attached to the crank T ; and a spur wheel U on the 
 crank shaft, working into a pinion on the shaft V, gives motion to it, and to the 
 fly wheel W, (see art. 540.) By means of a train of shafts and beveled wheels 
 X Y Z, moved by the crank shaft, the axis, carrying the eccentric rollers which 
 move the valves, is kept in motion, and the rods a b, which are connected to the 
 valves, are raised and depressed at the proper times, or by hand by the lever e, 
 in the manner more fully described in Plate vui. In some of their engines 
 they use slides nearly of the kind mentioned in art. 447. The injection of cold 
 
EXPLANATION OF THE PLATES. 343 
 
 water to the condenser is regulated by a cock, moved by the handle c on the 
 spindle d. 
 
 The governor g (see art. 550.) is kept in motion by bands from the crank shaft, 
 and opens or closes the throttle valve in the steam pipe C by means of a lever // h. 
 See Plate vnr. Fig. 1. 
 
 The proportion of the parts for a double engine of this kind may be ascertained 
 by art. 414 423. It ought to be made to work expansively, but in this case it 
 has not been done : the saving resulting from causing the engine to work ex- 
 pansively, will be in the ratio of about 10 to 7 to do the same work, (art. 422.) 
 See Table in. art. 664. 
 
 PLATE XV. 
 
 As an example of a portable condensing engine for impelling machinery, I have 
 taken that of Mr. Maudslay, where the beam is omitted, and the crank connected 
 directly with the piston rod. Fig. 1. is a front elevation of an engine ; Fig. 2. 
 a longitudinal section ; and Fig. 3. an end view. The cylinder B is supported by 
 a cast iron frame A, and C is the piston, with the rod D, connected to a cross head 
 at E, and guided by the wheel F, which keeps the piston rod in a vertical direction, 
 by moving in the frame G ; the side rods H H connect the cross head E with the 
 double crank I I, which turns in the plummer blocks or bearings J J, one on 
 each side of the frame, and to which the fly wheel shaft K, carrying a fly wheel M, 
 is connected by a coupling box, or clutch L, at the end next the engine. 
 
 Two eccentric wheels N N, on the crank shaft K, give motion to the levers O 
 and T, by means of the connecting rods P P. The lever O, supported by the 
 bearing Q, works the cold water pump S, by the rod R ; while the beam T, 
 working on the centre V, works the air pump X by the slings v, and the hot 
 water pump Y ; which by the feed pipe Z supplies the boiler with hot water. On 
 the cross rail (a) the guide is fixed to confine the air pump rod to a vertical motion ; 
 the condenser b surrounds the air pump, and is again surrounded by one of the 
 cold water cisterns c ; the two cisterns are connected by a pipe d : the steam from 
 the cylinder passes to the condenser through the eduction pipe e, and the cold 
 water for injection is admitted to the condenser by the cock/. The air and con- 
 densed steam ascends through the foot valve g in the bottom into the air pump. 
 
344 EXPLANATION OF THE PLATES. 
 
 The mechanism for opening and closing the steam passages consists of an 
 eccentric piece k, fixed on the crank shaft, the action of which communicates 
 a reciprocating motion to the rod i, which by a bent lever moves the connecting 
 rod /, and lever m, that is fixed at one extremity of a spindle having a beveled 
 wheel at the other ; which works into another on the spindle n of the steam cock o, 
 by which the steam is admitted from the steam pipe to the cylinder. The engine 
 is worked by hand by means of the handle h. 
 
 A pair of beveled wheels on the fly wheel shaft gives motion to the governor 
 balls, and these raise or depress the piece marked p on the axis, which by its 
 peculiar form acts on a lever, and retains the valve in the steam pipe at g open for 
 a longer or shorter time for the admission of steam according to the velocity of the 
 engine, (see art. 547.) There is also an apparatus for working the throttle valve 
 by the same governor. 
 
 This engine is in a very compact form : it is however a little too complex, and 
 its frame reminds one of an antiquated style of cabinet-work ; but the beauty of 
 the workmanship is unequalled, and is faithfully represented by Mr. Clement's 
 drawings. 
 
 To proportion the parts of an engine of this kind, see art. 419 422. and the 
 articles there referred to ; and Table m. (art. 664.) It is adapted for engines of 
 from 2 to 30 horse power. 
 
EXPLANATION OF THE PLATES. 345 
 
 PLATE XVI. 
 
 Fig. 1. and 2. represent the instrument called the indicator, for measuring the 
 force of the steam in the cylinder of an engine. See art. 560. 
 
 Fig. 3. and 4. are diagrams to illustrate the comparative stability of opposite 
 classes of forms for vessels. See art. 599, 600. 
 
 Fig. 5. If the motion of a vessel were always direct, its sides should be parallel, 
 and one of the section Fig. 3. may be terminated by making both the extremities 
 of the same figure, and formed by circular arcs ; then if the section be similar, so 
 that the stability may be equal throughout the length, (art. 599.) the water 
 lines will increase in curvature towards the keel (they are shown by dotted lines) ; 
 but the actual obliquity of the resisting surface, by which these resistances are 
 measured, decreases in descending. The objection I should make to this mode of 
 forming a vessel is, that it would not have a sufficient tendency to keep in its 
 course ; and I think a better form would be obtained by conceiving the midship 
 section to advance parallel to itself, and also towards the keel, in the same manner 
 as is shown in the next figure. 
 
 Fig. 6. If the section Fig. 4. be the midship section, and the plan of the load- 
 water line be formed by arcs of circles, and the sections be all drawn by the same 
 mould as the midship section, as far as the breadth at the part allows, then the 
 form will be as Fig. 6. ; the water lines would be all of the same curvature, the 
 capacity would be easily measured, and the construction would be simple. 
 
 But it is necessary to remark, that parallel sides are best only for direct motion. 
 In an oblique motion, such as that almost universally produced by wind, the 
 vessel should diminish towards the stern ; the oblique force of the wind then 
 presses its side against the fluid so as to produce an effect similar- to that of an 
 inclined plane, if the sails be properly set, and I think the diminution should 
 commence where the curvature of the fore-part ends. 
 
 It is chiefly for direct motion that a steam vessel is intended, and where it is so, 
 parallel sides have the advantage ; but where sails are to be used with effect in 
 addition to steam power, the direct resistance must be a little increased, or the 
 capacity diminished, to get a clean run when the oblique force of the wind is 
 available. Hence, it appears that a vessel adapted for one mode of action is not 
 the best for another ; and instead of theory being imperfect, it is evident that it 
 only wants to be followed up by analysing the different cases which occur in 
 practice. It is difficult to conceive how much this subject has been neglected, or 
 how much remains to be done. 
 
 2 x 
 
346 EXPLANATION OF THE PLATES. 
 
 PLATE XVII. 
 
 Fig. 1 . is a section of a steam vessel with its boiler in two parts ; the right part 
 is shown in a section across it through one fire-place F, and its flues N, P ; and 
 through the cross flue L of the other fire-place, and through the safety valve U 
 (art. 263.) ; showing the dampers O, R, and the passages of the flues to the 
 chimney. Of the left part the fire-door end is shown with the fire-doors D D, the 
 handles for clearing the clinkers B B, the doors for cleaning the flues at E E E, 
 and the gauge cocks G ; also part of the chimney C, the steam pipe S, and a slide 
 valve V, to shut off" the steam from the engine. There should be as much space 
 between the boiler and the sides of the vessel, as to admit a person to go round to 
 examine it. The floor under the boiler should be rendered as strong as possible, 
 and the boiler should rest on a plate of iron bedded on a layer of bricks or tiles 
 laid over the floor in cement ; in this manner a thin plate of wrought iron ex- 
 tending under the whole, being flexible, and brick a slow conductor of heat, is 
 more secure than a much thicker cast-iron plate. 
 
 Fig. 2. is a plan, showing the arrangement of the two fire-places F F, and their 
 flues. The fire-door is at D, the fire on the grate F, the clinkers fall at H, and 
 the smoke turns at L and returns along the flue N, rises at O, and goes back along 
 a flue P over N. The boilers should be strengthened by internal frames disposed 
 in triangles, and so as to afford supports for the flues. 
 
 Fig. 3. is a longitudinal section through the boiler, and one of the fire-places : l the 
 same letters refer to the same parts in all the figures ; see art. 239 244. : for the 
 fire and flue surface, art. 204. : for the capacity, art. 215 220.; for the area of 
 the chimney, art. 278. ; for safety valves, art. 259 272. ; for the strength of 
 boilers, art. 525. ; and for the management of sea water, art. 565. 
 
 1 In this last figure there is scarcely sufficient space allowed for the action of the slide valve V. 
 
EXPLANATION OF THE PLATES. 347 
 
 PLATE XVIII. 
 
 \ 
 
 To Boulton and Watt steam navigation is indebted for the effective method of 
 working two engines jointly, giving, with other advantages, a more equable motion 
 to the paddle wheel, and, in the event of accident to one of them, enabling the 
 vessel to proceed with the other at about two-thirds of her greatest velocity. 
 
 This plate is an isometrical projection 1 of a steam boat engine, in the manner 
 they were first arranged by Messrs. Boulton and Watt ; and nearly the same 
 general principle of construction is followed by all the best manufacturers. Two 
 small engines connected in this way were adapted to the ' Prince of Orange ' and 
 ' Princess Charlotte,' on the Clyde, by these gentlemen, in 1814. Previous to 
 this, it had been the practice to employ only one engine, ranged by the side of the 
 boiler, having a fly wheel on the paddle axis to assist the engine in passing its 
 centres ; and in such case the occurrence of any accident immediately put an end 
 to the progress of the vessel by steam. 
 
 The steam comes from the boiler by the pipe in the front of the figure, and 
 passes into the steam case and round the cylinder to the slide box, (see art. 146.) ; 
 from whence it is let into the cylinder in a manner which will be more clearly 
 understood by referring to the next plate : from the lower part of the cylinder a 
 trunk proceeds to the condenser, which is below a square cistern ; beyond which 
 a part of the air pump is seen, and to the left of it the hot water pump to supply 
 the boiler. 
 
 The motion of the parts commences at the cylinder : the piston rod is supposed 
 to be descending, and by means of a cross bar (called a cross head) and two side 
 rods, it depresses the ends of the side beams, these side beams moving on axes in 
 the centre ; the other ends rise and force a cross bar upwards, to the middle of 
 which the connecting rod is fixed, by which the crank of the paddle wheel shaft at 
 the upper part of the figure is turned ; and also by the rising of the further end of 
 the side beams, the cross head of the air pump and hot water pump is raised by 
 two side rods. The motion of the piston rod is guided by a combination of rods 
 called the parallel motion, (see art. 495.) and the slide is moved by an eccentric 
 
 1 Some account of this simple and useful mode of drawing, which was invented by Professor 
 Parish, is given in Dr. Gregory's ' Mathematics for Practical Men.' 
 
348 EXPLANATION OF THE PLATES. 
 
 wheel on the crank shaft ; and to reduce the friction its weight would cause, it is 
 balanced by a heavy ball acting on a lever below it. 
 
 Though the figures on the next plate are not a plan and section of this engine, 
 yet the same parts, with the exception of the steam pipe, are nearly in the same 
 places ; and hence, by comparison of the two, the uses and action of the parts may 
 be understood. 
 
 The weight of an engine of this kind is not exactly proportional to its power ; 
 but is nearly so ; and that of a forty horse power engine, with proper duplicate 
 parts, water, and other appendages, is about 100 tons. See Section x. 
 
EXPLANATION OF THE PLATES. 349 
 
 PLATE XIX. 
 
 In this plate, Fig. 1. is a section, and Fig. 2. a plan, of a steam boat engine. 
 A strong frame of cast iron supports the crank shaft I, and connects the parts of 
 the engine ; and the whole is sustained by two strong beams on the floor. The 
 steam pipe S brings the steam from the boiler to the passages of the slide, and 
 from thence to the top or bottom of the cylinder A, and it passes from the 
 slide to the condenser B, where it is condensed by a rose jet playing constantly ; 
 the air pump C expels the air and water into the cistern D, from whence it runs 
 out by a pipe. The motion of the piston is transmitted to the crank by means of 
 the double side beams or levers E F, moving on the axis G ; these are connected to 
 the cross head of the piston L L by two rods called the side rods, and the ends E 
 are connected to the crank by the connecting rod H. The air pump is also worked 
 by side rods from the side beams, and the hot water pump from the same cross 
 head. The parallel motion is guided by the radius rod M N ; see art. 489. : the 
 vibration of the beam is not bisected ; see page 233, note. The slide is on Mur- 
 doch's construction, (art. 447.) and is moved by a wheel on the crank shaft I, 
 with a sliding frame P, (art. 481.) and by hand by the lever T; the slide rod 
 being moved by slings from the arm R. The valve O is used to let steam into 
 the condenser in setting the engine to work, and the air and water are blown out 
 at the discharge valve into the cistern D. 
 
 For the strength of the parts, see art. 496. ; the proportions of the engine, art. 
 419 422. The parts of the slide should be counterbalanced, in order that its 
 resistance may be equal in either direction. 
 
 Each vessel generally has two of these engines, placed parallel to one another, 
 with a passage between them ; and there is room left for working the fires between 
 the cylinder and the boilers. The coals should be kept in iron tanks in the engine- 
 room, each to hold a given weight of coal, with the object of ascertaining with 
 accuracy the consumption for any time ; about four tons is a sufficient quantity to 
 be together, and they should be kept out of the danger of taking fire. 
 
 The proportion of the power to the effect is given in Sect. x. art. 655. 
 
350 EXPLANATION OF THE PLATES. 
 
 PLATE XX. 
 
 Fig. 1. represents a side elevation of a steam carriage, and Fig. 2. part of a 
 cross section to double the scale r 1 the same letters refer to the same parts in both. 
 The steam is generated in a cylindrical boiler A, and the fire and flues surround 
 it ; it is joined to two cylinders H H, of the same diameter, intended as reservoirs 
 for steam, and in these are inserted the engine cylinders G G' : the parts I I 
 form a reservoir of water not exposed to the pressure of the steam, but surrounding 
 the flues and chimney so as to be heated ready for injection into the boiler A by 
 a small force pump. 
 
 In order to distribute the heat of the fuel so as to render it effective on a larger 
 surface, there are two fire-places, with fire-doors at B B', but fed with coals by 
 hoppers from the boxes D D' ; the doors are used only to clear the bars, and 
 should be kept open as little as possible. The fire-flues meet at the middle : the 
 one from the fire B' rises at F', (Fig. 2.) passes along on the upper surface of the 
 cylinder A, round H at M, also round the end of the boiler, and returns on the 
 opposide side, to ascend the chimney in the division E' ; the other proceeds in the 
 same manner in the opposite direction, and ascends at E. There are two apertures 
 for air C C, to each ash-pit, both of which should be provided with registers, so 
 that those may be open which either face a strong wind, or (in ordinary cases) 
 those which face the direction of the motion of the carriage. For a like reason the 
 top of the chimney E should have two apertures, that the motion of the air, or the 
 motion in the air, may assist the draught. 
 
 The engine and boiler are supported by a frame, and this is supported by the 
 axis ; but to prevent the carriage resting on three wheels, there may be four spiral 
 springs in the boxes L L, and the cross heads must be connected to the piston rods 
 by moveable joints, and all the bearings must be formed so as to admit of the 
 motion which would take place by the sinking of one of the wheels in a certain 
 degree. The waste steam passes from the slides to the chimney by the pipes K ; 
 and there should be two safety valves, one locked in a box at J, the other open for 
 the use of the engine-man at J'. See art. 266 273. 
 
 1 This drawing is, through some oversight, not accurately double in all its parts ; and in the 
 parallel motion of Fig. 1. the vibration of the beam is not bisected ; see page 233, note. 
 
EXPLANATION OF THE PLATES. 351 
 
 There will, I think, be some advantage in making the pistons act together, 
 becavise the effect will be as great as by dividing it, supposing both methods to be 
 perfect ; and in acting together, there would be less interference of the motion of 
 the one with that of the other. The slide would be best moved from curved teeth 
 on the beams. See art. 481. 
 
 For the proportions and construction of the boiler, see art. 244, 227, 278, and 
 522 526; for the engines, see art. 271 380; and for the power required, see 
 art. 590. 
 
EXPLANATION OF THE PLATES. 353 
 
 PLATE XXL 
 
 This plate, which represents Kingston's valves, is given by Mr. Dinnen as con- 
 nected with the subject of his valuable paper in the Appendix on steam boilers, and 
 the following is his description, &c. 
 
 I. BLOW-OFF VALVES. 
 
 a, Gun-metal pipe with conical base, passing through the ship's bottom, with the 
 
 conical part outwards and made even with the same. Inboard, the cover of the 
 pipe (forming the gland or stuffing box and the nozle which joins to the stop- 
 cock of the blow-off pipe) is screwed on the upper end of the pipe, down to 
 the ship's floor, on to a chock of wood fitted thereon as requisite, in the manner 
 of a screwed bolt and nut. 
 
 b, The valve, fitted within the cone of the pipe and opening outwards, having a 
 
 copper rod which passes through a stuffing box in the cover. A guard pro- 
 tects the valve beneath. 
 
 c, Cover, which is screwed tightly on the pipe. 
 
 d, Gland or stuffing box. 
 
 e, Handle for lifting the valve. 
 
 f, Nozle, with a flanch for connecting the valve with the stop-cock of the blow-off 
 
 pipe. 
 7, Guard, extending across the base of the pipe, and having no guide spindle passing 
 
 through it ; for the object of allowing the valve to be pressed entirely on one 
 
 side, thereby affording a more ready passage to any matters intruding into the 
 
 pipe from the boilers. 
 x, Planking of the ship's bottom. 
 m, Timbers of the ship's floor. 
 n, Chock, fitted on the timbers to accommodate the required length of the pipe. 
 
 II. INJECTION VALVES. 
 
 a, Gun-metal pipe, passing through the ship's bottom. 
 b', The valve, having a guide spindle below. 
 
 2 Y 
 
354 EXPLANATION OF THE PLATES. 
 
 c, Cover, screwed on the pipe. 
 
 d', Gland, or stuffing box. 
 
 e, Handle of the valve. 
 
 f t Nozle with flanch for connecting the valve with the stop-cock of the injection pipe. 
 
 g', Guard, so constructed as to form a grating, in order to prevent weeds or other 
 substances from being admitted into the condensers ; and having a socket rising 
 from the centre, through which the lower spindle of the valve passes. 
 
 li ft, Two copper standards, screwed into the cover, having mortices or key ways 
 through them, which coincide in direction with a corresponding one in the rod; 
 and are so adjusted, that when the valve is completely open, a key passing 
 through them maintains the valve in its place, and thereby prevents its being 
 closed by the pressure of the water without rushing in to fill up the void in the 
 condensers. 
 
 i, Key, or cutter, for fixing the valve as above. 
 
 nit Ship's timbers. 
 
 x, Planking of the ship's bottom. 
 
 III. HAND-PUMP VALVES. 
 
 These are the same as the Injection, with the exception of the grating. 
 
 MANNER OF FIXING THE VALVES IN THEIR PLACES. 
 
 The situation of the pipes being fixed, a close jacket of fearnought, well covered 
 on both sides with a mixture of white and red lead, is sewn on from the base to the 
 lower part of the screw, and a corresponding hole is formed in the ship's bottom. 
 
 Then the pipe, being set up in its place by shores, is firmly screwed up by the 
 cover, and the space between the cone and a corresponding flanch of copper sheathing 
 (extending two or three inches up between the planking and the cone, to protect the 
 former from the attacks of the worm) is well caulked ; this done, a copper screw is 
 fitted through the lower part of the cone, into the wood, to prevent the possibility of 
 the pipe turning or heaving the cover on or off. 
 
 The cover is now taken off, and the space around the upper part of the pipe is 
 caulked ; then it is finally replaced and screwed down on a copper washer of about 
 \ inch in thickness. 
 
 The chocks are well coated on their under sides with red and white lead. 
 
EXPLANATION OF THE PLATES. 355 
 
 PLATE XXII. 
 
 BOILERS OF H.M. STEAM VESSEL " AFRICAN." 
 See the description of the next plate. 
 
 PLATE XXIII. 
 
 BOILERS OP H.M. STEAM FRIGATE " MEDEA." 
 
 This and the preceding plate are also furnished by Mr. Dinnen in connexion with 
 his paper in the Appendix on steam boilers. The following is his description. 
 
 (The same letters refer to corresponding parts in the several views.) 
 a, Furnaces. 
 
 a, Grate bars. 
 a", Bearer bars. 
 
 b, Ash pits. 
 
 c, Bridges. 
 
 d, Flues. 
 
 e, Smoke-joints,! ., 
 
 / Oi . . > tor connecting the fore with the after boilers. 
 e , Steam-joints, j 
 
 /, Uptake, through which the smoke, &c., passes from the flues to the chimney. 
 
 ff, Chimney. 
 
 h, Air casing, which surrounds the base of the chimney to prevent too great a trans- 
 mission of heat to the deck, or other materials liable to be injured thereby. 
 
 z, Dampers with their levers, for checking the draught of the furnaces. 
 
 j, Water ways between the flues and fireplaces. 
 
 /, Water ways of the bridges, and beneath the flues and fire-places, such that one 
 may enter at the mud hole doors, forward and aft, and pass over the entire 
 bottoms of the boilers, and under the flues. 
 
 k, Mud hole doors, with a similar one on each after boiler. 
 
 /, Furnace doors. 
 
 m, Clinker bars, for supporting the levers employed in clearing the furnace bars. 
 
 n, Feed pipe, with two branches and valve boxes, for supplying the boilers with 
 water. 
 
356 EXPLANATION OF THE PLATES. 
 
 o, Floats, with indexes, for shewing the height of the water in the boilers. 
 
 p, Glass water-gauges, through which the exact height of the water is seen. 
 
 q, Gauge cocks, below which the water is never supposed to descend. 
 
 r, Steam chests. 
 
 *, Safety valve box, containing the two safety valves, with the waste steam pipe 
 
 rising from the same. 
 s, Waste steam pipe. 
 t, Pipes for conveying the water overboard from the safety valve box, and likewise 
 
 that resulting from the condensation of the steam in the globe, or other con- 
 trivance at the head of the waste steam pipe. 
 u, Safety valve levers : accessible*at the front of the boilers, the safety valves being 
 
 lifted by other levers fitted to the same axes, within the steam chest. 
 v, Man holes, with their covers in place. 
 w, Communication valves, having screwed spindles, which are acted on from above 
 
 by two levers, for the purpose of shutting off either boiler from the main steam 
 
 pipe. 
 
 a, Main steam pipe. 
 y, Reverse valves, to prevent the boilers collapsing by the pressure of the atmosphere, 
 
 which, in case of a vacuum being formed, presses the valves inwards to restore 
 
 the equilibrium. 
 z, Vacuum pumps, the rods of which are attached to levers on deck, by working 
 
 which, on charging the boilers with water from the sea, an exhaustion is effected 
 
 which causes the water to rise within, from the pressure of the atmosphere 
 
 without, and thus saves the labour of forcing many tons of water into them. 
 
 The time occupied in fully charging the boilers of the " Medea " by these pumps 
 
 was usually from fifteen to twenty minutes. 
 z, Blow-off pipes, with a nozle to each boiler. 
 
 The same description applies generally to Plate XXII. of the African's boilers, 
 which are fitted with precisely similar appendages, with the exception of the 
 vacuum pumps. 
 
EXPLANATION OF THE PLATES. 357 
 
 PLATE XXIV. 
 
 MORGAN'S PADDLE WHEEL AND SEA WARD'S PADDLE WHEEL. 
 
 This plate relates to Mr. Barlow's paper on " Paddle wheels " given in the Appen- 
 dix, page 40, and a description of the drawings is to be found at pages 41 and 42. 
 
 PLATE XXV. 
 
 POSITIONS OF A FLOAT OF A RADIATING PADDLE WHEEL, AND ALSO OF A 
 VERTICALLY ACTING WHEEL, IN A VESSEL IN MOTION. 
 
 This plate relates to Mr. Barlow's paper on paddle wheels, and is described by 
 him at pages 45 and 49 of the Appendix. 
 
 PLATE XXVI. 
 
 CYCLOIDAL PADDLE WHEEL FITTED TO THE "GREAT WESTERN" STEAM 
 VESSEL, WITH ANOTHER DRAWING REPRESENTING THE POSITIONS OF 
 ONE OF THE FLOATS. 
 
 This plate likewise relates to Mr. Barlow's valuable paper in the Appendix, where 
 it is described by him at page 53. 
 
358 EXPLANATION OF THE PLATES. 
 
 PLATES XXVII. AND XXVIII. 
 
 These plates are designed to illustrate Capt. Oliver's paper on the supposed advan- 
 tages of sail on large SEA-GOING steam vessels under various circumstances of unfavour- 
 able winds. Plate XXVII. represents a scale of different courses from the Cape of 
 Good Hope to the Isle of France, with the several distances marked, and Plate 
 XXVIII. represents four drawings of her Majesty's steam ship Phoenix, in different 
 positions with respect to the wind. 
 
 PLATE XXIX. 
 
 This plate exhibits the various situations of a trial at sailing of her Majesty's steam 
 ship of war Medea with the Caledonia, Vanguard, and Asia. For particulars see 
 the end of Lieut. Baldock's excellent Memoir of the Medea, Appendix, page 100. 
 
 PLATE XXX. 
 
 In 1816 a vessel (Caledonia) was purchased by Messrs. Boulton and Watt, and 
 fitted with two engines of fourteen horses' power, solely for the purpose of making 
 experiments under various circumstances and modifications of paddle wheels. One 
 of these experiments embraced the ascension of the Rhine in the winter of 1817 as 
 high as Coblentz. 
 
 The plate represents a side view of the engines manufactured by Boulton and 
 Watt for the Red Rover and City of Canterbury steam vessels. This form of marine 
 engine adopted by them about this period, say 1817, was fitted on board the Fa- 
 vourite in April 1818, and, with the exception of some slight improvements principally 
 made by themselves, it still remains unchanged. 
 
 In the first edition of this work it was stated in mistake, that they had adopted it 
 from the Clyde. This is incorrect, and we take the present opportunity of stating 
 that this mode of construction is due to Boulton and Watt, and that a preference has 
 been given to the arrangement by several of the best makers who have followed it. 
 
EXPLANATION OF THE PLATES. 3.59 
 
 PLATE XXXI. 
 
 This plate is a longitudinal section of the preceding engine with boiler attached, 
 and the same reference letters apply to both. 
 
 The engines and boiler stand on sleepers of oak X X, African oak from its stiffness 
 being generally employed. And the base of the engine is secured by bolts passing 
 through the sleepers and bottom timbers 1 . The steam pipe S brings the steam from 
 the boiler to the space between the slides, c, and by their movement admits it to top 
 and bottom of cylinder A. At the termination of each stroke it passes to the con- 
 denser B, by the upper and lower eduction pipes, C and D, and is there condensed 
 by a jet of cold water. The air pump E, withdraws the air and water, from the 
 condenser to the hot-water cistern F, which being close at the top forms an air 
 vessel to expel the water from the cistern through the waste water stop- valve pipe G. 
 
 The motion of the piston rod is transmitted to the crank by means of the main levers 
 H, I, moving on the main gudgeon K. These are connected at the cylinder and to 
 the cross bar of the piston by two side rods L L, and the other end, 1 1, to the crank 
 by the connecting rod M. 
 
 The air pump E is also worked by two side rods from the main levers, and the 
 hot water and bilge pumps from the same air-pump cross bar N. 
 
 The piston rod is guided by a parallel motion a a, the slides b b are separate, but 
 connected by a rod similar to their land construction of 1808. These and the upper 
 eduction pipe have been lately applied by Boulton and Watt, and may be considered 
 a great improvement upon the long slide, where the expansion of the metal is liable 
 to twist the face and render them leaky. 
 
 Motion is given to the slide valves by the eccentric circle 0, by means of the ec- 
 centric rod d, connected with the eccentric arm e, from which it may be disengaged 
 with facility when the engines are required to be stopped ; /, the working gear shaft, 
 receiving its action from the eccentric arm. 
 
 P P, Upper and lower blow valves, the former is used before starting the engines 
 to admit steam into the condenser to blow out the air and water by the lower valve, 
 so as to form a partial vacuum in the condenser. 
 
 Q and R, Upper and lower headstock frames which support the engine and paddle 
 
 1 It may not be irrelevant to notice here, that owing to this mode of securing the engines the pro- 
 prietors of the Red Rover were recently enabled to raise that vessel when sunk in forty feet water. 
 The principal chain which lifted her being secured to the frames of the engines, it having given way 
 when fastened to the vessel itself. It is the practice of some makers to bolt only through the sleepers, 
 which we by no means consider so secure. 
 
360 EXPLANATION OF THE PLATES. 
 
 shaft connected with the hot water cistern and cylinder casing, the ribs or webs of 
 which are disposed in the direction of the strain : there are many more fanciful and 
 pleasing forms, but certainly none so mechanical or so well adapted to the purpose. 
 T, Injection pipe through side of vessel, g, bilge injection. To be used in the event 
 of the vessel leaking to any extent, in which case the river injection would be shut 
 off, and the bilge one opened. This is an appendage which has till lately been over- 
 looked by other makers, but a very necessary one, as by such means about four 
 gallons per horse power per minute might be withdrawn by injecting from the 
 vessel. 
 
 U is a longitudinal section of the boiler ; V, the grate ; and W, the flues ; y, safety 
 valves enclosed in safety pipe, and perfectly inaccessible to the engine-man for the 
 purpose of applying extra weight to endanger the boiler. This description of valve 
 was used by them as far back as 1814, in a vessel fitted on the Tyne, consequently 
 three years previous to the examination before the Committee of the House of Com- 
 mons for some such precaution, h k, Blow-out pipes and cocks ; i i i, feed pipes ; It k, 
 &c., hold-down bolts, occasionally cased with brass to prevent corrosion. 
 
 PLATE XXXII. 
 
 This plate represents, with similar reference letters, a transverse section of the same 
 splendid steamers, the Red Rover and City of Canterbury, shewing on the left the 
 cylinder, and on the right the crank end of the engine, with the paddle wheels, main 
 beams for support of paddles, stays, &c., &c. 
 
EXPLANATION OF THE PLATES. 
 
 361 
 
 PLATE XXXIII. 
 
 SIDE ELEVATION OF THE ENGINE OF THE NILE STEAM SHIP. 
 
 a, Boiler. 
 bbbb, Flues. 
 
 c, Fire place. 
 
 d, Steam box. 
 
 e e, Blowing-off valve and pipe. 
 
 f, Air case. 
 
 ff g, Man holes. 
 
 h, Steam pipe. 
 
 i, Cylinder. 
 
 j, Slide valve. 
 
 Jc, Working beam. 
 
 /, Cylinder side rod. 
 
 m, Motion side rod. 
 
 n, Parallel rod. 
 
 o, Working gear. 
 
 p, Counterbalance. 
 
 q, Working gear arm. 
 
 r r, Eccentric and frame. 
 
 s, Gear for starting, &c. 
 
 t, Reverse motion. 
 
 u, Hot water cistern. 
 
 v, Condenser. 
 
 w, Air pump. 
 
 x, Air pump side rod. 
 
 yy, Feed pump and rod. 
 
 0, Connecting rod. 
 
 A, Paddle wheel shaft. 
 
 B, Crank on ditto. 
 
 C, Crank on intermediate shaft. 
 
 D, Drag link. 
 
 E, Paddle wheel. 
 
 F F, Suction for feed, hand pumps, 
 
 and injection cock. 
 G G G, Blowing-out pipes. 
 H H HH, Feed pipes and head. 
 Ill, Pipe for charging boiler by 
 
 hand pump. 
 
 K, Pipe and cock for washing deck. 
 L, Guard rod. 
 
 PLATE XXXIV. 
 
 PLAN OF THE ENGINE OF THE NILE STEAM SHIP. 
 
 a a, Boilers. 
 bbbbb, Flues. 
 c c c c, Fire places. 
 
 d, Steam box. 
 
 e, Blowing-off pipe. 
 , Air case. 
 
 gg, Man holes. 
 h, Steam pipe. 
 ii, Cylinders. 
 jj, Slide valves. 
 kkkk, Working beams. 
 //, Motion cross bars. 
 
 2z 
 
EXPLANATION OF THE PLATES. 
 
 m m, Cross heads to slide valves. 
 
 n n, Cross heads to cylinders. 
 
 o o, Working gear. 
 
 pp, Counterbalance. ' 
 
 q, Working gear arm. 
 
 v r, Eccentric frame and rod. 
 
 *, Gear for starting, &c. 
 
 t, Reverse motion. 
 
 u u, Hot water cisterns. 
 
 v v, Air pump cross heads. 
 
 w w, Air pumps. 
 
 x x, Blow valves. 
 
 y y, Injection cocks. 
 
 z, Connecting rod. 
 
 A, Paddle wheel shaft. 
 
 B, Crank on ditto. 
 
 C, Crank on intermediate shaft. 
 
 D, Drag link. 
 
 E, Paddle wheel. 
 
 F F F, Suction for feed, hand pumps, 
 
 and injection cocks. 
 G G, Hand pumps. 
 H H, Injection pipes. 
 I I I I, Pipes for charging boilers by 
 
 hand pumps. 
 K K, Blowing-out pipes. 
 L L L L, Feed pipes. 
 M M M M, Guard rods. 
 
 PLATES XXXV. AND XXXVI. 
 
 CROSS SECTIONS OF THE ENGINE OF THE NILE STEAM SHIP. 
 
 a a, Boilers. 
 bbbbb, Flues. 
 cccc, Fire places. 
 
 d, Steam box. 
 
 e, Blowing-off valve and pipe. 
 
 f, Air case. 
 yg, Man holes. 
 h, Steam pipe. 
 
 i i, Feed pipe and head. 
 
 j, Waste water pipe. 
 
 kkkkk k, Blowing-out pipes. 
 
 Ill, Gauge cocks. 
 
 m, Cylinder cross head. 
 
 n, Motion cross bar. 
 
 o o, Side rods to slide valve. 
 
 p, Cross head to slide valve. 
 
 g, Working gear. 
 
 r, Working gear arm. 
 
 s s, Side rods to cylinder. 
 t, Cross head to air pump. 
 u u, Side rods to air pump. 
 v, Connecting rod bar. 
 w w, Short links. 
 x, Connecting rod. 
 g, Paddle wheel shaft. 
 z, Crank on ditto. 
 
 A, Drag link. 
 
 B, Crank on intermediate shaft. 
 c c, Plumber blocks. 
 
 D, Paddle wheel. 
 
 E E, Suction pipes, to feed hand 
 
 pumps, and injection cocks. 
 F F, Pipes for charging boilers by 
 
 hand pumps. 
 
 G G, Pipes for washing deck. 
 H H, Air pumps. 
 
EXPLANATION OF THE PLATES. 363 
 
 1 1, Blow valves. 
 
 K K, Hot water cistern. 
 
 L L, Feed pumps, dotted. 
 
 M, Condenser. 
 
 N, Handle of injection cock. 
 
 oooo, Holding down bolts, dotted. 
 
 PLATES XXXVII., XXXVIIL, AND XXXIX. 
 
 ENGINES OF HER MAJESTY'S STEAM FRIGATE PHCENIX. 
 
 These three plates represent a plan, side elevation, and transverse section of the 
 steam engine of her Majesty's steam frigate Phoenix ; they also describe the engines 
 of the Medea, Rhadamanthe, and Salamander, the machinery of these four vessels 
 being identical, and all manufactured by Messrs. Maudslay, Sons, and Field. Plate 
 XXIII. gives a more detailed representation of the boilers of these vessels, and may be 
 referred to for additional information. 
 
 The general arrangement of these engines is on the ordinary side beam construc- 
 tion ; all the working part, except the beam, of wrought iron ; metallic piston ; and the 
 crank pins are so arranged that the wheels may be readily disconnected for sailing. 
 
 The boilers are of iron, in two independent parts, and furnished with valves so 
 contrived that they may be used either separately or both together. 
 
 The wheels are of the ordinary construction, except those of the Medea, which are 
 Morgan's; some of the others have had cycloidal boards applied to the original 
 wheels. 
 
 The proportions of these engines are as follows : 
 The nominal power is . . . 110 each, or 220 H. P. collectively. 
 
 Diameter of cylinder 55^ inches. 
 
 Length of stroke 5 feet. 
 
 Diameter of wheels 21 feet. 8ft. 6 in. wide. 
 
 The Medea, Morgan's . . . . 24 feet. 5 ft. 8 in. 
 Length of engine room . . . . 58 feet. 
 
 The tonnage of the Phoenix, Rhadamanthe, and Salamander is about 800 tons; that 
 of the Medea being 807 tons. They carry two heavy traversing guns, 10 calibre, 
 which throw an 84 pound shot ; one of these guns is placed in the bow and one at 
 the stern; below they carry four 18 pounder carronades, with provisions for 120 men. 
 They can stow from 200 to 300 tons of coal at a draught of water of 14 feet. 
 
 The consumption of coal being 15 tons per day, they can steam from 15 to 20 
 days. 
 
 The scale of the drawings is of an inch to the foot. 
 
364 EXPLANATION OF THE PLATES. 
 
 PLATE XL. 
 
 ENGINES OF THE GRAVESEND PACKET RUBY. 
 
 This celebrated vessel, undoubtedly the fastest in Europe, and perhaps in the world, 
 was built by Mr. Wallis, of Blackwall, near London, in the year 1836, from the de- 
 signs and specifications of Mr. 0. Lang, Jun., of Her Majesty's Dock Yard, Woolwich. 
 The engines were made by Messrs. Seawards and Co., of the Canal Iron Works, near 
 London. 
 
 The very great success of this vessel, she having beaten all competitors from the 
 time of her starting to the present, may be attributed to two principal causes : 
 
 First, to a most judicious arrangement in the form and construction of the vessel, 
 by which the quantity of materials used in the building are brought so to bear upon 
 one another that each piece performs the office assigned to it ; and no more timber 
 is used than what is requisite to give the ship the necessary strength and solidity. 
 From the method of planking which is adopted, consisting of three thicknesses of oak 
 placed diagonally and longitudinally, the vessel is completely trussed from end to end, 
 and at once combines strength and lightness in an eminent manner. The length of the 
 Ruby is 155 feet between the perpendiculars, 19 feet beam, and 9 feet 6 inches 
 depth of hold ; she will carry with ease 800 passengers. When launched she drew 
 about two feet of water. Her after cabin is 33 feet long, and will dine 100 pas- 
 sengers ; the ladies' cabin is about 15 feet long, and the fore cabin 33 feet. 
 
 Secondly, her superiority is attributable to her engines, which consist of two 50 
 horse power engines, (100 horse power the two,) in the making and fixing of which, 
 every care was taken to have them as light and efficient as possible, without endan- 
 gering their stability ; and the calculation of weights and of displacement was so 
 nicely adjusted, that when the whole of the weights were on board, and the vessel 
 equipped for service, her real draught of water, 4 feet fore end and 4 feet 6 
 inches aft, was within a quarter of an inch of the builder's estimate. The weight of 
 the engines complete with the water in the boiler is exactly 90 tons 5 cwt., being 
 about 1 8 cwt. to the horse power ; the diameter of the cylinder is 40 inches, length 
 of stroke 3 feet 6 inches, diameter of outer edge of paddle wheel 17 feet, and 
 length of board 9 feet 2 inches, with a dip of 17 inches with 200 passengers 
 on board ; then the speed of the engines is 30 strokes per minute, the pressure of the 
 steam being only 3-| Ibs. above the atmosphere. The speed of the piston is there- 
 fore 210 feet per minute, the speed of the outer edge of the paddle board is nearly 
 20 miles per hour, and the speed of the vessel through still water by repeated trials 
 is exactly 13^ miles per hour. 
 
EXPLANATION OF THE PLATES. 365 
 
 It is a remarkable fact, that from the first day of trial up to the present time, this 
 boat has not varied her speed T^th of a mile per hour ; she has neither increased nor 
 lost her speed. This is mostly to be attributed to the fact of the engines being in a 
 most perfect state when set to work, but more particularly to the use of the patent 
 slide valves on board of this vessel, and which after two years' working have been 
 found as perfect upon their faces as when first put together ; a further proof of 
 their superior working is evinced by the vacuum in the condensers of the engines 
 having never varied ^th of an inch, remaining constantly between 28^ and 28^. This 
 is ascertained by barometers attached to each engine, which are not affected by the 
 atmosphere and makes the vacuum as perfect as possible, for supposing the waste 
 water as it leaves the condenser to have a temperature of 110, which is equal to 1^ 
 inch of mercury, (see Professor Robinson's experiments,) when added to 28^ it 
 gives 29f , the usual height of the marine barometer in fine weather. 
 
 The safety valves are arranged upon the plan invented and used by Messrs. Boul- 
 ton and Watt a long time since, and now generally adopted by the engineers of 
 London. They are so arranged that no one on board can possibly have access 
 to them ; the engine man can at pleasure open them and let the steam escape, but he 
 has no means by which he can keep them down, beyond the weight placed upon 
 them by the engine maker, which weight is, as before stated, 3^ Ibs. on the inch ; 
 and it is a curious fact, that this boat has attained the great speed named, with this 
 small pressure, while in a variety of instances vessels from different outports, working 
 with high pressure steam, and with the safety valves loaded ad libitum by the en- 
 gineers and captains, have never been able to approach her in speed. This clearly 
 proves, what the late Mr. Watt demonstrated long ago, that the most efficient, safe, 
 and economical mode of working steam engines for marine purposes is at a pressure of 
 from 2^ to 3-g Ibs. on the inch. At the same time, for single acting pumping engines 
 there is no doubt an advantage gained by the judicious use of high pressure steam, 
 say of 30 Ibs. on the inch, working expansively, with boilers properly constructed, 
 but which boilers for many reasons are not at all fit for steam vessels ; in fact, almost 
 all the melancholy accidents that have lately occurred to steam boats by the explo- 
 sion of their boilers, have been caused by the injudicious application of high pressure 
 boilers to marine purposes. 
 
 It is here worthy of remark, that the Americans, who claim to propel their vessels 
 at the high speeds of 15, 16, and in some cases 18 miles per hour, (which, by the 
 by, has been amply contradicted in this work by an able American writer, 
 who states the greatest speed through still water attained by the best American 
 steamers, he believes to be in one instance 14 miles per hour, but that the rest of 
 the New York boats do not come up to this,) state that the principal cause of their 
 
366 EXPLANATION OF THE PLATES. 
 
 alleged triumphs is owing to the use of high pressure steam, used expansively ; 
 the causing the pistons of very long stroke engines to move at the rate of 300, 400, 
 and sometimes 600 feet per minute ; and lastly, to the superior form of the bows 
 of their steamers, which are built so as to glide over the water instead of cutting 
 through it. 
 
 In the case of the Ruby, in all these important matters she is decidedly the re- 
 verse of the Americans; the piston only travels about 210 feet per minute, very low 
 pressure steam is used, the stroke of the engines is very short, being only two inches 
 more than the diameter of the cylinder, and the form of the bow is decidedly that 
 which will cut or divide the water without the least tendency to ride over it, inas- 
 much as this vessel's bow is shaped like a knife, being as long on the keel as at the 
 water's edge within two feet. 
 
 Judging from these facts, it will be seen that high pressure steam, length of stroke, 
 and prow-shaped bows, qualities so loudly extolled by the Americans, are not all 
 necessary for speed, but on the contrary, the first two are positive nuisances ; the 
 length of stroke rendering the vessel an unwieldy, ill-contrived machine, totally use- 
 less for the purposes of sea navigation, as events have proved ; while the high 
 pressure steam system has been the means of filling the journals with those ever- 
 occurring, heart-rending, and sickening details of hundreds and thousands that are 
 being yearly sacrificed to ignorance and prejudice, by attempting to do that by the 
 dangerous use of high pressure steam which can be so well effected by steam of a 
 low pressure, and that too at one half the consumption of fuel. 
 
 The limits of this paper will not permit the writer to digress upon the subject of 
 consumption of fuel, except by stating, that in no instance has the use of high pressure 
 steam applied to an engine for rotary purposes ever been attended with economy of 
 fuel, but the reverse ; and it is not a little singular, that in this age, even in this year, 
 northern engineers are imitating the Americans, by the use of the long stroke and 
 high pressure steam, in the Thames, which one would think might have been spared 
 this pestiferous curse. The results have been, and are, that the short stroke engines 
 are propelling the boats, both sea and river class, faster than the long stroke ones. 
 This length of stroke has been obtained by the placing of one half the machinery 
 upon deck, some 12 or 14 feet high, and thus making the vessel frightfully crank and 
 most unseemly to look at, while in vessels going head to wind, it exposes some 
 hundreds of square feet of surface to be acted upon as a back sail. 
 
 The great danger of high pressure steam will be evident to every one, when it is 
 recollected that within the last three years, three different vessels have had dreadful 
 explosions, viz., two on the Thames and one at Greenock, (besides some less fatal 
 ones in different parts of the north,) by which more lives have been sacrificed to the 
 
EXPLANATION OF THE PLATES. 
 
 367 
 
 Moloch of high pressure steam, than has ever occurred with low pressure steam during 
 the whole progress of steam navigation, extending now almost to a period of 40 years, 
 and in the course of which nearly 3000 steam vessels have been fitted out and suc- 
 cessfully worked. 
 
 REFERENCES. 
 
 A, The cylinder. 
 
 B B, The sway beams. 
 
 C, The cross head. 
 
 D, Main gudgeon. 
 E E, The side rods. 
 
 F, The fork head. 
 
 G, The connecting rod. 
 H H, The cranks. 
 
 I I, The shafts. 
 K K, The side frames. 
 L L L, The condenser, hot well, and 
 foundation plate, all cast in one piece. 
 M, The air pump. 
 N, The feed pump. 
 0, The sleepers. 
 P, The crank pins. 
 
 a a, The steam nozle and valves, 
 b b, The eduction nozle and valves. 
 
 c, The steam pipe. 
 
 d, The throttle valve. 
 
 e, Handle and rod of throttle valve. 
 f, Starting lever. 
 
 </, Spill of steam valve. 
 
 h, Spill of eduction valve. 
 
 i i i i, Levers for working the 
 
 valves. 
 
 k, Rod to connect levers. 
 / 1, Parallel motion. 
 m, Snifting valves. 
 n, Blow through valve. 
 o, Eccentric rod. 
 p, Eccentric beam and balance. 
 
 Speed of the engine 
 Diameter of wheel . 
 Diameter of the float 
 Diameter of cylinder 
 Length of stroke . 
 Weight of engines (two) 
 Dimensions of boiler 
 Length of paddle board . 
 Width of board . 
 Speed through still water 
 
 DIMENSIONS. 
 
 30 strokes. 
 
 17ft. Gin. 
 
 . . . 17 6 
 3 4 
 3 6 
 
 80 tons. 
 18 feet long, 14 feet 2 inches wide, and 7 feet high. 
 
 9 ft. 2 in. 
 
 . . . . 15 inches. 
 
 13-| miles. 
 
 This boat has run four times a day to and from Gravesend six months, making 
 48,600 miles ; a feat never equalled. 
 
 Beats Red Rover ... 10 minutes. 
 
 Star ... . 
 
 Mercury .... 27 
 
368 EXPLANATION OF THE PLATES. 
 
 Beats Vesper . . . . . . 10 minutes. 
 
 Diamond 12 
 
 Gem ....... 5 
 
 Against tide from Gravesend to London all other boats from 30 to 60 minutes. 
 For further information, see description of Plate XCIX. 
 
 PLATE XLI. 
 
 SECTION OF ONE OF THE ENGINES OF THE DON JUAN, PENINSULA 
 
 COMPANY'S PACKET. 
 
 The Don Juan was built by Messrs. Fletcher and Fearnall, of Limehouse, in 1836. 
 She was sailed round to Glasgow, where her engines were put in by Messrs. Claud, 
 Girdwood, and Co., the makers. On her first return voyage from the Mediterranean to 
 London, she unfortunately struck on the Tarifa point and went down in deep water. 
 
 PLATE XLII. 
 
 BOILERS OF HER MAJESTY'S SHIPS HERMES, SPITFIRE, AND FIREFLY. 
 
 The drawings represent a front view and sections of boilers recently constructed 
 by the Butterly Company, who are now making a spare set to be used for any one 
 of the three vessels which may first require them. These boilers are very compact, 
 light, and efficient, and any two of them may be employed in case of accident to 
 one of them, when the vessel is at sea. Each has its own steam-pipe, which can be 
 shut off at pleasure, its safety valve, and a damper, which being closed, as shewn in 
 the transverse section, cuts off the communication with the chimney. A contrivance 
 is effected by which a man can creep into the boiler underneath the flues to clean or 
 repair it, which has been found very useful ; it does not increase the height of the 
 boilers, and adds very little to their weight. The front view of the boilers is placed 
 in a section of the Hermes, to shew " the channels " or passages by which the man 
 has access to the under side of the flues, down between the engine sleepers or 
 foundation timbers. 
 
 The cylinders of the Firefly are 43^ inches in diameter, and the stroke is 4 feet 6 
 inches, which, at 22 revolutions per minute, gives the velocity of piston 198 feet per 
 minute. The area of the piston in square inches is I486'!, and if the effective pres- 
 
 14861 x 198 
 sure be 10 Ibs. per square inch, it would make the horses' power 33000 = ^ 
 
EXPLANATION OF THE PLATES. 369 
 
 horses' power. But the speed of the piston is taken at 185 feet, large allowances are 
 made which the present improved state of workmanship perhaps renders unnecessary, 
 and the engines are estimated at 2 x 70 = 1 40 horses' power. Probably for a sea- 
 going vessel, where the engines often cannot work at their proper speed, we are 
 right in so doing. 
 
 PLATES XLTIL, XLIV., XLV., AND XL VI. 
 
 The drawings in these plates shew an elevation, plan, and two sections of the 
 engine room of those armed Russian steam ships Jason and Colchis, lately built by 
 Messrs. Fletcher and Fearnall, of Limehouse, and fitted with engines by the Butterly 
 Company for the Imperial Government, under the direction of Mr. Glynn. It has 
 been thought unnecessary to give a drawing of the boilers, as they are similar to 
 those made for our own government, and differ only in dimensions. The difference 
 of dimensions is shewn in the general drawing, the internal construction being the 
 same as shewn in the boilers of her Majesty's steamers Hermes, Firefly, and Spitfire, 
 Plate XLII. The Jason and the Colchis are, it may be said, sister ships, but the 
 Colchis being the last built, some slight alterations were made by the constructor, Mr. 
 Fearnall, and the Colchis was his last work as it was his best. This celebrated 
 shipwright died on the 23d of October, 1837 5 and for the construction of steam ships 
 he had no superior. The vessels being expressly designed for the Black Sea, and 
 this being a shallow sea, carried ten days' fuel, and with all their stores and equip- 
 ments drew only 9 feet 6 inches water; yet with only 2 x 60 horse power engines 
 they were propelled through the water at the rate of 10 nautical miles (or about 11-g 
 statute miles) per hour. They each carry one long heavy gun (a 32 pounder) in 
 midships on the quarter deck, besides two bow guns for chasing a flying enemy; also 
 32 pounders, and smaller, guns for signals and salutes. They lie very low on the 
 water, and as war steamers, are formidable antagonists, whilst their capabilities as 
 sea boats have been put to severe trials in the Bay of Biscay in heavy gales of wind. 
 
 3 A 
 
370 EXPLANATION OF THE PLATES. 
 
 PLATES XLVII. AND XL VIII. 
 
 SAMUEL HALL'S IMPROVEMENTS ON STEAM ENGINES. 
 
 Some very important improvements have been made on the steam engine by Mr. 
 Samuel Hall, of Basford, near Nottingham, for which he has obtained letters patent. 
 The principal objects of these improvements are to supply the boilers with pure 
 distilled water (thereby increasing their duration,) to effect an economy of fuel, and to 
 produce an increase of power. These objects, it is stated, are obtained by condensing 
 the steam by the external application of cold water, instead of injecting it into the 
 steam. The improvements have been in successful operation for upwards of four 
 years, having been applied to several land engines and to a considerable number of 
 marine engines, varying from 70 to 320 horse power each pair, and there is every 
 probability that they will generally supersede injection engines. As Mr. Watt 
 attempted to condense steam without injecting cold water into it, and came to the 
 conclusion that it was impossible to effect a sufficiently rapid condensation of steam, 
 for steam engines worked by vacuum, by means of the external application of cold 
 water, and as many other persons have also failed in similar trials, it is desirable to 
 ascertain the means adopted by Mr. Hall, and for this purpose we give the following- 
 extract from the specification of his patent, shewing wherein his invention consists* 
 and the causes of his succeeding in obtaining a desideratum which others have 
 attempted without success. 
 
 EXTRACTS FROM THE SPECIFICATION. 
 
 " The objects of my invention (which invention I confine to steam engines worked 
 by a vacuum produced by condensation) are to condense without injection water 
 (for the purpose of creating as good a vacuum as is obtained and well known in 
 injection engines) the steam which passes through the engine for the working 
 thereof, and also to condense for the most part (if not wholly) that portion of steam 
 which usually escapes into the atmosphere through the safety valves when the 
 pressure of the steam in the boiler is too high during the working of the engine, in 
 order that the water resulting from the condensation of such steam may be returned into 
 the boiler. And also, further to supply so much more distilled water to the boilers 
 of the above mentioned description of engines as is required to supply and replace 
 any waste that may take place in the working thereof, in order to avoid the intro- 
 duction of any water (into the boilers) containing saline or other extraneous matters. 
 
EXPLANATION OF THE PLATES. 371 
 
 "My invention does not consist in the novelty of any one of the five apparatus 
 hereinafter mentioned, but in the combination of the whole five, or at least three out of 
 the five, within proper proportions, (as hereinafter described,) as regards the first three, 
 which I have found by experience to be beneficial, and from the want of knowing 
 and observing which I have reason to believe that all persons who have made 
 former attempts of the same nature have failed. I now proceed to describe the 
 above mentioned five apparatus, consisting of 
 
 " First, a sufficient quantity of metallic surfaces in the form of vessels, channels, 
 passages, or pipes of any convenient form, arrangement, or construction. The extent of 
 such metallic surfaces should be about 2800 square inches for the condensation of 60,000 
 cubic inches of steam per minute. 
 
 " Secondly, a pump or any other proper apparatus for the passing of a sufficient 
 quantity of cold water amongst such above mentioned pipes, not only to condense all 
 the steam of steam engines, but also to cool the water resulting from the condensation 
 thereof, to as low a temperature as (or even lower than) that of the mixture of the 
 condensed steam and injection water, which is discharged from the air pumps of 
 injection engines, in order to produce by such application of cold water, when used 
 in combination with the metallic surfaces, as above stated, and with the air-pump 
 hereinafter mentioned, as good a vacuum as is obtained and well known in such 
 injection engines, if not indeed a still more perfect vacuum. The quantity of cold 
 water which I employ is ten gallons for such condensation of such 60,000 cubic inches 
 per minute. 
 
 " Thirdly, the ordinary air-pump of the capacity hereafter stated to produce, when 
 in conjunction with the before mentioned two apparatus, a sufficiently perfect vacuum, 
 as above defined. 
 
 " Fourthly, an apparatus for distilling water to replace the waste of water that may 
 take place in the working of the engine, in order to avoid, as above mentioned, the 
 introduction of any water into the boilers containing saline or other extraneous 
 matters. 
 
 " Fifthly, an apparatus, which I call the steam saver, for saving the steam that 
 usually escapes into the atmosphere from the safety valves, when it becomes of too 
 high pressure during the working of the engine, the apparatus causing such steam to 
 pass into the condensers to be converted into water and return to the boiler. 
 It may be proper here to remark, that within certain limits which experience will 
 readily suggest, the above mentioned proportions of metallic surfaces of cold water 
 and capacity of the air-pump may be varied in a certain inverse order, that is to say, 
 if the cold water be diminished, the extent of metallic surfaces or the capacity of the 
 air-pump, or both, should be increased ; and on the other hand, if the extent of 
 
372 EXPLANATION OF THE PLATES. 
 
 metallic surfaces be diminished, the quantity of cold water or the capacity of the air- 
 pump, or both, should be increased to produce the same effect. 
 
 " Having now described the five several apparatus the combination of which (within 
 proper proportions as hereinbefore described as regard the first three) constitute my 
 invention, I proceed again to define and explain the extent of my claims. I now 
 therefore state, I do not claim the exclusive use of any one of the five apparatus 
 herein described taken separately, some of them, if not all, having been used before, 
 nor indeed do I claim the use of any two of them, if unaccompanied by any or either 
 of the others, but I do claim as my invention the exclusive use of the threefold 
 combination of the sufficient quantity of metallic surfaces, the sufficient quantity of 
 cold water passing among them, and the sufficiently capacious air-pump as herein- 
 before fully described, whether the said threefold combination be used alone or com- 
 bined with the distilling apparatus and the steam saver, or either of them. I 
 also claim the exclusive right of combining the distilling apparatus and the steam 
 saving apparatus, or either of them, with the above mentioned threefold combination, 
 or even with the two first of them, videlicet, the metallic surfaces and cold water 
 passing among them, should a less air-pump be used. In witness whereof," &c. 
 
 The advantages of Mr. Hall's patent engines over injection engines will perhaps 
 be best understood by his comparative statement of them. 
 
 "COMPARISON BETWEEN INJECTION STEAM ENGINES AND SAMUEL HALL'S 
 
 PATENT STEAM ENGINES. 
 
 " 1. Injection engines, when applied to The patent engines effect a supply of 
 
 steam navigation, comprise of necessity the purest distilled water to the boilers, 
 
 the barbarous practice of supplying dirty by which they are always kept in a 
 
 salt water to the boilers. perfectly clean state. 
 
 2. In injection engines, the water in The patent engines having pure dis- 
 the boilers may become saturated with tilled water in the boilers, it boils at 212 
 salt, in which case it will not boil under or at 13 less temperature than salt water, 
 225 of temperature. and of course requires less fuel to convert 
 
 it into steam. 
 
 3. In injection engines, in order to pre- The boilers of the patent engines never 
 vent the water from becoming saturated require any blowing out, no matter how 
 with salt, a large quantity of boiling long the engines are in uninterrupted 
 water must be pumped out of the boilers, operation. 
 
 or blown off, and replaced with cold water 
 
EXPLANATION OF THE PLATES. 373 
 
 every two or three hours, which cold 
 water, having to be brought up to the 
 boiling point, causes a considerable waste 
 of fuel to take place. 
 
 4. In injection engines, the boilers will, The patent boilers of the engines will 
 after every precaution is taken, become be perfectly clean not only for many 
 coated with hard scale of considerable voyages but for years, and their dura- 
 thickness ; this being a bad conductor of bility will be very much greater than 
 heat prevents the free transmission thereof that of boilers supplied with salt water, 
 from the fires to the water, causes the and a comparatively small consumption 
 boilers to burn and wear out very of fuel will also be the result. 
 
 rapidly, and greatly increases the con- 
 sumption of fuel. 
 
 5. In order to prevent the boilers of In the patent engines, all delays and 
 injection engines from burning and wear- inconveniences arising from the empty- 
 ing out with a rapidity that could not be ing and clearing of boilers are entirely 
 submitted to, it is necessary in long superseded, for by their permanent clean- 
 voyages to suspend the working of the ness, the water they contain entirely de- 
 boilers in order to empty and cool them, fends them from the action of the fire, 
 for the purpose of clearing away and and as no deposit takes place, they are 
 chipping off the scale that firmly adheres not subjected to the injury caused by 
 to them, which operation considerably chipping off scale, as in injection engines, 
 injures the boilers. 
 
 6. In injection engines, the oil which In the patent engines, not a particle of 
 is put into the cylinders, stuffing-boxes, the oil which is given to the internal parts 
 slides, &c., is speedily carried away by of the engine, &c., is washed away into 
 the injection water into the sea ; the time, the sea or lost, but it is all carried into the 
 therefore, of its being in the engines is so boilers, whereby they are protected from 
 short that nine tenths of it is wasted and corrosion, and an ample lubrication of the 
 does but little if any good, and it does not, engines is effected at scarcely any cost, as 
 as in the patent engines, enter the boilers hereafter mentioned. 
 
 and protect them from the corrosive ac- 
 tion of hot salt water. 
 
 7. In injection engines, a portion of the In the patent engines, a portion of oil 
 salt contained in the water is carried over being always, as before stated, introduced 
 mechanically along with the steam into in commixture with the pure water into 
 the working cylinders, slowly corroding the boilers, it passes over mechanically 
 and wearing the slides, valves, and other along with the steam in minute parti- 
 
374 EXPLANATION OF THE PLATES. 
 
 internal parts of the engines, whereby cles into the cylinder, thus, this ample 
 
 they are rendered untrue, and a consider- lubrication actually improves the slides, 
 
 able quantity of steam escapes past them valves, and other internal parts of the en- 
 
 and is wasted. gines instead of injuring them, whereby 
 
 a great saving in their wear and tear is 
 
 effected. 
 
 8. In injection engines, salt water, dirt, In the patent engines, nothing but dis- 
 sand, and other impurities pass through tilled water and oil pass through the 
 the air pumps and thereby render them air pumps, which instead of becoming 
 and their piston rods, &c., very rough and rough are thereby rendered more smooth 
 full of furrows ; in consequence whereof, and polished, and of course brass buckets, 
 great friction in working them and waste piston rods, and linings to the air pumps 
 of power is occasioned. are not necessary, as is the case in injec- 
 tion engines. 
 
 9. In injection engines, a considerable In the patent engines, the air pump has 
 power is required to pump out the injec- only to pump out of the vacuum, the wa- 
 tion water; in engines of 450 horse power, ter resulting from the condensation of the 
 (like those on board the Great Western,) steam, which in a pair of engines of 450 
 2700 gallons of water per minute ha veto horse power is only about 50 gallons per 
 be pumped out of a vacuum, (reckoning minute ; the saving of the power, there- 
 six gallons per horse power per minute,) fore, required to pump out the 2700 gal- 
 and this requires as much power as the Ions per minute of injection water is so 
 pumping of that quantity of water out of much additional effective power gained 
 a well 30 or 32 feet deep. and applicable to the paddle wheels. 
 
 10. In injection engines, in stormy wea- The patent engines, in the roughest 
 ther and heavy seas the condensing water weather and when the greatest power is 
 enters the condensers as rapidly when the required, preserve as perfect a vacuum, and 
 engines are going at a slow as when they consequently as great a power, as in fine 
 are going at a fast speed, and as it is impos- weather, and all the power required in 
 sible to regulate the quantity of injection injection engines to supply the proper 
 water according to the irregularity of the quantity of condensing water is super- 
 speed of the engines, great danger arises seded, and the engineer is relieved from 
 on the one hand of choking the condenser that onerous duty. 
 
 and the air pump, and of even breaking 
 down the engines, by the admission of 
 too much water when they are going 
 slow, or on the other hand, of deducting 
 greatly from the power of the engines by 
 
EXPLANATION OF THE PLATES. 375 
 
 injecting too little water into them when 
 their speed is great, thereby deteriorating 
 the vacuum and reducing the power of 
 the engines, and that at the time when 
 the greatest power is required. 
 
 11. In injection engines, the proper In the patent engines, the boilers are 
 supply of water to the boilers is depend- never liable to be burnt down or injured 
 ent upon and entirely at the mercy of by the water becoming in them, by acci- 
 the engineers, from whose negligence such dent or by the carelessness of engineers, 
 serious accidents arise as those of the ex- too low, for as every cubic foot of water 
 plosion of the two Hull steam vessels, the which is converted into steam is by con- 
 Union and Victoria, and many others, by densation reconverted into precisely the 
 which a most serious loss of life has taken same quantity and returned to the boil- 
 place and great injury has been done to ers, the water is always kept in them at 
 the reputation of steam navigation. exactly the same height without any at- 
 tention on the part of the engineer. 
 
 12. In injection engines, the vacuum is In the patent engines, a superior va- 
 injured by the air which is in mechani- cuum is obtained, owing to no air being 
 cal combination with the injection water introduced into the condensers, and to the 
 being conveyed by it into the condenser, condensation being more perfect than can 
 
 be effected by injection." 
 
 "ADVANTAGES APPERTAINING TO THE PATENT IMPROVEMENTS. 
 
 "First, from the various causes above mentioned, a saving of at least one third part 
 of the fuel is effected in the patent engines, or in other words injection engines con- 
 sume half as much more fuel as the patent engines. 
 
 Second, for every ton of coal that is saved, a ton of profitable freight may be sub- 
 stituted. 
 
 Third, as vessels with engines to which the patent improvements are applied 
 make their passages nearly as quick in stormy as in fine weather, and as they do 
 not require during or at the end of their passages, however numerous, any blowing- 
 out or cleaning of the boilers, to occasion delays, every vessel is capable of making- 
 more passages and of becoming in that ratio more profitable. 
 
 Fourth, as boilers supplied with pure distilled water will endure a much greater 
 length of time than those in which salt water is used, not only is the annual expense 
 of the boilers greatly diminished, but the loss of the time of the profitable use of the 
 vessel during the taking out of old boilers and the replacing them with new ones 
 is also avoided, to say nothing of the breaking up of the decks and other expenses 
 attending the business. 
 
376 EXPLANATION OF THE PLATES. 
 
 Fifth, as the internal parts of the engines are kept so much longer in repair owing 
 to the causes above mentioned, the perpetual expense and time required in repairing 
 such parts is greatly diminished; indeed there is no doubt but the slides, valves, pistons, 
 and all the internal parts of the engines are in much finer condition after having been 
 in operation for years, than they are the first day they are set to work. The 
 circumstance of salt being carried over with the steam into the cylinders (when salt 
 water is used in the boilers) is unquestionable, as well as that it is the cause of the 
 valves and other internal parts of the engines becoming so soon in bad condition, 
 whereby a great waste of steam takes place even long before they become so very 
 much worn as to render it indispensably necessary to give them a thorough repair. 
 
 The regulation of injection water, and of the water to supply the boilers, forms no 
 part of the duty of the engineer, as they are quite superseded by no injection taking 
 place, and the boilers being self-supplied with undeviating accuracy. 
 
 It may also be observed, that the comparative advantages of the patent engines do 
 not appear to be so great on the first starting of new engines, or even during the 
 first month or two, as the boilers and machinery of injection engines, are then as 
 clean and in as good order as those of the patent engines ; but afterwards, when the 
 boilers of the former become thickly coated with scale, the internal parts of the 
 engines are worn and galled, while those of the latter are actually improved, and the 
 comparison should then be made. 
 
 Lastly, it is certain that a vessel with the patent engines of 300 horse power, 
 will effect an increase of economy and advantage of 2500 or 3000 per annum 
 over a vessel having injection engines of that power, and consequently the former 
 will realize so much greater a profit." 
 
 The following engines are now in operation with the improvements applied to them: 
 
 The Sinus steam ship with a pair of engines of 320 horses' power, both included, 
 on the station from London to New York, being the first steam vessel that performed 
 that voyage across the Atlantic and back. This vessel belongs to the St. George 
 Steam Packet Company, and is chartered by the British and American Steam Navi- 
 gation Company. 
 
 The Megcera steam ship with a pair of engines of 140 horses' power, stationed 
 in the Mediterranean, and built by the Lords Commissioners of the Admiralty 
 for her Majesty's navy. Engravings of her engines are given in this work, Plates 
 XLIX., L. 
 
 The Hercules steam vessel with a pair of engines of 180 horses' power, stationed 
 between Glasgow, Dublin, and Cork, belonging to the St. George Steam Packet Com- 
 pany. 
 
 The Sea-horse steam vessel with a pair of engines of 260 horses' power, stationed 
 between Hull and Rotterdam, belonging to the St. George Steam Packet Company. 
 
EXPLANATION OF THE PLATES. 377 
 
 The Juno steam vessel with a pair of engines of 260 horses' power, stationed 
 between London and Cork, belonging to the St. George Steam Packet Company. 
 
 The Vulture steam vessel with a pair of engines of 260 horses' power, stationed 
 between London and Cork, belonging to the St. George Steam Packet Company. 
 
 The Tiger steam vessel with a pair of engines of 300 horses' power, stationed 
 between Hull and Hamburgh, belonging to the St. George Steam Packet Company. 
 
 The pyilberforce steam vessel with engines of 300 horses' power, stationed between 
 London and Hull, belonging to the Humber Union Steam Company. Engravings of 
 the engines of this vessel are given in this work. 
 
 The Kilkenny steam vessel with a pair of engines of 300 horses' power, stationed 
 between London and Waterford, belonging to the Waterford Commercial Steam Navi- 
 gation Company. 
 
 The Windermere steam packet with a pair of engines of 60 horses' power, stationed 
 between Liverpool and Ulverstone, belonging to James Winder, Esq., of Liverpool. 
 
 The Albatross steam packet with a pair of engines of 70 horses' power, stationed 
 between Hull and Yarmouth, belonging to Messrs. Boardman and Harmer, of Nor- 
 wich, and others. 
 
 In addition to the engines above mentioned, a magnificent pair of engines of 500 
 horses' power, on board the British Queen steam ship of 1863 tons, will be, in the 
 course of a short time, in operation between Great Britain and the United States. 
 
 And another pair of engines of 500 horses' power are making for the President, 
 another vessel building for the British and American Steam Navigation Company, of 
 2028 tons, being also for navigation between Great Britain and the United States. 
 
 A pair of engines of 220 horses' power are also now making for the Honourable 
 the East India Company. 
 
 In addition to the above, a considerable number of land engines are in satisfactory 
 operation with Mr. Hall's improvements, but it is not necessary to particularise them. 
 
 The great importance of Mr. Hall's improvements to steam navigation and to land 
 engines, where water containing saline and other extraneous matters only can be pro- 
 cured for the condensation of the steam used in working engines, is strongly illustrated 
 by extensive documentary evidence, corroborating the advantages that have been 
 stated. 
 
 For graphical explanation, see Plates XLIX. and L. 
 
 3-D 
 O 
 
373 
 
 EXPLANATION OF THE PLATES, 
 
 PLATES XLIX. AND L. 
 
 ENGINES OF HER MAJESTY'S STEAM SHIP MEG^ERA. 
 
 Her Majesty's steam ship Megeera is fitted with Messrs. Seaward's engines and 
 Mr. Samuel Hall's condenser. 
 
 Plate XLIX. represents an elevation of the engines. 
 
 Plate L. exhibits a section of the same engines, and comprises a delineation of Sea- 
 ward's Patent Slide Valves, the principle of which has been described in Art. 451. 
 
 The same letters refer to corresponding parts in both Plates. 
 
 A, Is the boiler, of which 
 , Is the furnace door. 
 
 a, Grate bars. 
 a", Furnace. 
 
 b, Bridge. 
 
 c, Flues. 
 
 d, Take-up. 
 
 e, Chimney, which is surrounded with 
 a double casing e, filled with incombusti- 
 ble and non-conducting matters, calcu- 
 lated to intercept the heat and thereby 
 prevent accident from fire. 
 
 f, Water space beneath the flues, suffi- 
 cient to permit a free passage for clean- 
 ing and repairs. 
 
 f, Water space between the flues. 
 9, Steam box, on which are fitted the 
 safety valves g in close iron boxes g". 
 
 h, Is the stop valve, fitted on the 
 upper end of the steam pipe //, so 
 that the steam may be completely 
 shut off from either boiler, and the 
 engines, as found necessary. 
 
 B, The steam cylinder, with its piston 
 B' ; m, m, m", steam slide casing, of 
 which the boxes m, m", contain the 
 steam slides which are connected by 
 the pipe m', with the steam pipe h, 
 leading from the boiler A. 
 
 n, ri, n", Exhaustion slide casing, the 
 boxes n, n", containing the exhaus- 
 tion slides, which are connected 
 with the top chamber of the con- 
 denser L, by the exhaustion pipe ri, 
 and the nozle at n. 
 
 Both the steam and exhaustion slide casings are cast on the cylinders, due con- 
 sideration being paid to the difference in expansion and contraction of the side pipes 
 m, ri, and of the cylinder B. 
 
 By this construction, the usual joints at the nozles, 1, 2, 3, 4, by which the slide 
 casings are attached to the cylinders are dispensed with, and of course the risk of 
 leakage avoided. 
 
 r r, s s, Are the steam slide facings or back plates, through which are apertures 
 corresponding with those of the nozles 1 and 2. 
 
EXPLANATION OF THE PLATES. 379 
 
 it, v v, Are the exhaustion slide facings or back plates, the apertures through which 
 correspond, in like manner, with those of the nozles 3 and 4. 
 
 The four back plates r, s, t, v, are distinct from the casings, and are fixed in the 
 boxes or recesses m, m", n, n of the slide casings, by folding wedges or keys, so that 
 r r, s s have their backs against the cylinder, while 1 1, v v present their faces to the 
 same, their backs being wedged to projections or flanches adapted thereto, in the 
 recesses n, n". 
 
 To insure perfect joints, a plain caulking space is left at the bottom and back of 
 each slide-face, while the edges, which fit the casing at the face, have dovetail 
 portions removed so as to permit the insertion of soft or elastic packing, which, 
 with that beneath and at the back, completely surrounds the aperture and renders 
 all tight. 
 
 Facility is afforded of removing either back plate when requisite, by driving back 
 the folding wedges or keys, which keep them firmly in place, this dovetail form of 
 the edge permitting the facings to be readily detached from the packing after being 
 pressed by the wedges. 
 
 w, #,y, z, Are four slide valves, of rectangular figure, receiving their motion from 
 rods or spills passing through the stuffing boxes 5, 6, 7, 8. 
 
 The valves w, x are the steam slides, having their backs always presented to the 
 steam from the boiler, which maintains them in close contact with the faces of the 
 back plates r r, s s. 
 
 The valves w, x, it will be seen, are connected to their rods or spills by knuckle 
 joints, so as to permit perfect freedom of motion off their facings, independently of 
 the rods. By this contrivance, water carried over from the boilers into the cylinder, 
 is forced back by the piston into the steam pipe ti, till drawn off by cocks fitted at 
 the bottom for such purpose ; thus obviating the risk of accident from its accumulation, 
 and dispensing at the same time with the necessity for escape or discharge valves. 
 
 The backs of the exhaustion valves y, 2, being alternately submitted to the pres- 
 sure of the steam on the descent and ascent of the piston, while their faces are pre- 
 sented to the condenser, it will be observed that perfect contact of the slides with 
 their back plates 1 1, v v will ensue. 
 
 Thus the four slides w, x, y, z are caused to operate without packing, and with- 
 out being submitted to greater friction than that due to the simple pressure of the 
 steam. 
 
EXPLANATION OF THE PLATES. 
 
 ACTION OF THE VALVES. 
 
 The steam passing from the boiler A, by the steam pipe K, is regulated in its ad- 
 mission to the slide valves w, .r, by the throttle valve i, the rodjj, with its lever / 
 and adjusting arc j" being conveniently adapted for the same. 
 
 The engine then, after being cleared of air, &c., through the blow valve I, is put 
 in motion by means of the starting lever p, and causes the eccentric 0, through its 
 rod o, to actuate the lever p, of the exhaustion balance-shaft X, a system of levers 
 q q, affording the means of engaging and disengaging the same, according to the ne- 
 cessity of reversing or stopping the wheels. And the shaft X, being connected with 
 the balance-shaft Y, of the steam slides by the levers u, u, and the rods u", it is clear 
 that both shafts will operate simultaneously on all four slide valves, which are con- 
 nected to the levers u, u', of the said shafts by the side links 9, 10, 11, 12. Now 
 when the lever p, is urged by o, from the condenser L, the steam slides w, x, will be 
 caused to descend, admitting the steam above the piston B', through the passage No. 
 1, while No. 2 will be closed by the slide x. The exhaustion slides y, z, ascending 
 at the same time, will permit the steam from beneath the piston to pass off, through 
 the passage No. 4 and pipe n, into the condenser, the passage 3 being closed by 
 the slide y. 
 
 When the lever p, on the contrary, is drawn towards the condenser L, the exhaus- 
 tion slides will be depressed, while the steam slides are caused to ascend, thereby re- 
 versing the operation of the steam. 
 
 The lever u, moreover, which gives motion to the steam slides is so contrived that, 
 the extremity of the rod " can be moved by an adjusting screw, through a consider- 
 able space in a slot seen at u, thereby lengthening and shortening the leverage, and 
 consequently the stroke of the steam slides. 
 
 The steam is thus caused to act expansively, to such extent as the variable cir- 
 cumstances of the weather at sea may suggest, the advantages of which are shewn 
 in Arts. 422, 451, and elsewhere. 
 
 Hall's condenser is shewn at L, of which 13 is the upper chamber, containing a 
 thin plate 14, completely perforated with small holes, by which the steam from the 
 cylinder B, is distributed in its passage through the pipes 15 15, to the bottom 
 chamber, 16. 
 
 The pipes 15 15, are surrounded with cold water, which is supplied through the 
 pipe R', by the double acting pump R, R', whose motion is derived from the main 
 lever C, through the rods W T, and the lever U, which is supported by the bracket 
 V ; the waste water passing into the sea through the opening S. 
 
EXPLANATION OF THE PLATES. 381 
 
 M, Is the air pump, through which the bucket M' discharges the water resulting 
 from the condensation of the steam from the cylinder, in its passage through the 
 pipes 1515, together with the air and uncondensed vapour, into the hot well Z, through 
 its valve 1 7, whence it is carried forward by the feed pipes into the boiler A. 
 
 Still, in order to meet unavoidable losses of water from the boilers by the waste of 
 steam., &c., a distilling vessel A', of cylindrical figure, is introduced within the boiler, 
 which uniformly maintains the requisite height of water therein, in the following- 
 manner : 
 
 A pipe 1 8, connecting the upper surface of the still A' with the upper or steam 
 chamber 1 3, of the condenser, is furnished with a stop cock 1 9, which when open per- 
 mits the vapour generated in the still to pass over into the condenser, whence it is 
 returned by the feed pipes, in addition to the water resulting from the steam of ex- 
 haustion, into the boilers, and is regulated in quantity by the amount of opening of the 
 stop cock 19. 
 
 The connection with the condenser produces a nearly corresponding vacuum in 
 the still, whence evaporation takes place at a lower temperature and much more ra- 
 pidly than if exposed to the atmosphere at the ordinary boiling point of 212. 
 
 As the evaporation proceeds, and the water in the still becomes lower than the 
 level marked in the drawing, the copper float 20, descends, carrying with it the rod 
 21, of the index 22, and causing the valve 23 to be lifted at the same time. The 
 valve 23, being connected with the supply pipe 24, which is joined at the other ex- 
 tremity with the waste pipe S of the condenser, affords abundance of sea water to 
 pass into the still, until again closed by the float 20 ; the index 22 exhibiting the 
 operation. 
 
 By the frequent repetition of this process, it will be seen that the water in the 
 distilling vessel A', will become saturated with salt, and in that respect the still will 
 be assimilated, with the exception of risk from burning in case of neglect, to ordinary 
 boilers working with sea water ; it is also kept clean by the same rule, thus : 
 
 The pipes, 18 and 24, being first shut off from the still by their respective stop 
 cocks, a communication is opened by the cock 25, with a pipe 26, which descends 
 nearly to the bottom of the still, its other end passing through the ship's side. At 
 the same time, another pipe, (not seen,) also furnished with a stop cock, allows the 
 steam from the boiler to pass into the upper part of the still, whence by its pressure 
 the brine and other impurities are completely driven out into the sea. 
 
 These latter pipes being shut off and the former ones opened, the process of distilla- 
 tion goes on as usual. 
 
 The piston B', acting on the cross head D, gives motion to the side rods E, which 
 are connected at the lower ends with the beams or main levers C, and these vibrat- 
 
382 EXPLANATION OF THE PLATES. 
 
 ing on their axes C', transmit the motion to the connecting rod G, through its side 
 links or forks H, and fork head F. 
 
 The crank I, being impelled by the upper end of the connecting rod, produces a 
 rotary motion about the paddle shaft N, which is supported by the framing K K. 
 
 The air-pump bucket M', receives its motion through the cross head P and side 
 rods Q, which are connected to the beams at Q'. 
 
 To maintain rectilinear motion of the piston rod, a perpendicular rod 27, from the 
 beam C, is caused to act on the radius crank 28, and parallel rods 29, whose action 
 is transmitted to the piston through the side rods E, as in the other parallel motions. 
 
 PLATES LI., LII., LIIL, AND LIV. 
 
 ENGINES OF THE HULL AND LONDON PACKET WILLIAM WILBERFORCE. 
 
 Plate LI. represents a plan of the engines of the Wilberforce Hull and London 
 packet, built by John and Edward Hall, of Dartford, and fitted with Samuel Hall's 
 patent condensers, and Francis Humphrys's patent slides. The mechanical ar- 
 rangement of these engines differ from other marine engines provided with Hall's 
 condensers, as every part of the condensing apparatus is fixed on the foundation 
 plates of the engines, and the cold water pumps receive their motion directly from 
 the great levers, by means of side rods and cross heads, like the air pumps, by which 
 arrangement the parallelism of the several rods employed in working the cold water 
 pumps is preserved, and the pumps themselves firmly and substantially fixed and 
 united with the several other parts comprising the engines ; thus also affording every 
 convenience for ready access to the valves or plungers in case of their requiring re- 
 pairs. 
 
 The slide valves of these engines, as well as the pistons and air pump buckets, are 
 wholly metallic, and their operation have proved them to be quite as efficient as D 
 slide valves in their most perfect condition without requiring any care or attention 
 from the engineer ; and they work with so little friction that one man can when re- 
 quired handle both engines, although the leverage power, as will be seen by inspect- 
 ing the engravings, is little more than as two to one ; this affords a great advantage 
 to a marine engine, particularly in a crowded river like the Thames, through which 
 the Wilberforce has to pass ; but their more important advantage is felt in the 
 steady maintenance of the power of the engines, and in the economy of fuel arising 
 from the total absence of the leakage common to all hemp packed slide valves when 
 neglected by the engine man or not plentifully supplied with melted tallow. 
 
EXPLANATION OF THE PLATES. 383 
 
 The general operation of these engines is like all other marine engines fitted with 
 Hall's condensers, excepting that the water pumped from the condensers by the air 
 pumps is not forced by the air pumps through the feed valves directly into the boilers, 
 but is delivered into a casing or cylindrical jacket surrounding the chimney, and 
 flows out at the upper part of the casing, into a stand pipe, sufficiently high to retain 
 a column of water to overcome the pressure within the boilers, like the usual mode of 
 feeding boilers in an ordinary Boulton and Watt engine. By this means the water ac- 
 quires an additional temperature of about twenty degrees before it enters the boilers, and 
 it is more perfectly separated from any bubbles of air which may arise in admixture 
 with the water, when it leaves the air pumps. 
 
 The nominal power of these engines is 285 horses' ; a very rapid and perfect ex- 
 haustion of the cylinders is effected, as will be seen by diagrams, pgaes 385, 386, 
 taken with great care by a very good indicator adjusted for the occasion. The adran- 
 tage of Samuel Hall's process of condensing by contact instead of by injection, will 
 be very manifest on inspecting the diagram No. 2, taken in a heavy sea while the 
 vessel was rolling and exposed to the effects of half a gale of wind ; yet the vacuum 
 was as perfect as in smooth water, and the exhaustion of the cylinder, proved by ac- 
 tual experiment, amounted to 1 3 Ibs. upon each square inch of its area, which, to- 
 gether with the pressure of the steam, gives a mean force on the piston of 16*54 Ibs. 
 per square inch, and produces an absolute effect of 283'6 horses' power, or 567'2 
 horses' power with both cylinders, after deducting 2 Ibs. per square inch on the pistons 
 for the friction and power expended in working the pumps, &c., leaving an effect of 
 98 per cent, more than the nominal power of the engines ; the diagram No. 1 
 gives a still greater effect than this, being more than 100 per cent, above the nominal 
 power, and the mean effect, as ascertained by the indicator and shewn by the several 
 diagrams, amounts to 96 per cent, more than their nominal power. 
 
 The uniform velocity of the engines in smooth water is 22 revolutions, the pistons 
 moving through 264 feet per minute when the draught of the vessel is 9 feet 6 inches 
 forward and 1 1 feet aft, at which draught the paddle wheels are immersed 3 feet 6 
 inches, measuring from the outer edges of the centre floats to the surface of the water, 
 and the total area of the paddle boards thus immersed, amounts to 102 feet in each 
 w r heel. 
 
 The same letters of reference are employed to denote the same parts in each en- 
 graving, the use and operation of which will be understood on referring to the 
 several plates. 
 
 Plate LII. represents a longitudinal elevation of the engines. 
 
 Plate LIII. represents a cross section shewing the after parts of the engines and the 
 paddle wheels. 
 
384 EXPLANATION OF THE PLATES. 
 
 Plate LIV. shews a longitudinal section of the engines. 
 
 A, Steam pipes. 
 
 B, Throttle valves for regulating the supply of steam to the engines. 
 
 C, Blow valves for clearing the engines of air, by the admission of steam previous 
 to starting. 
 
 D, Inlet sluices and pipes, 1 1 inches' diameter in the clear, for admitting the supply 
 of water to the cold water pumps. 
 
 E, Relief valves for the purpose of affording a ready escape for any accidental ac- 
 cumulation of water within the cylinders, either below or above the pistons. 
 
 F, Humphrys's metallic slides, by which the great pistons are actuated. 
 
 G, The cold water pumps for forcing the water into the condensing cisterns H ; 
 these pumps are 18 inches' diameter having a stroke of 2 feet 8 inches, and supposing 
 their chambers to be quite filled with water at each stroke, will supply at the rate of 
 8 gallons of water per minute per horse power, which is forced round the lower ex- 
 tremities of the condensing pipes and, ascending amongst them with considerable ve- 
 locity, escapes through apertures in the cisterns at their upper extremities, by the 
 pipes marked L. 
 
 H, Condensing cisterns ; each cistern containing 2374 half inch copper pipes, 8 feet 
 long each between the top and bottom plates, in which their ends are fixed, thus 
 giving a total length of 18992 feet of pipe to each condenser exposed to the cold 
 
 18992 x 2 
 water, which is equivalent to OQt ..ru^o = *^ lineal feet of ^ inch pipe per horse 
 
 *vOD 4) JCl A 
 
 power. 
 
 I, Air pumps, 35 inches' diameter and 3 feet stroke, by which the water and air is 
 pumped out of the condensers and conducted by the pipes K to the casing or jacket 
 surrounding the chimney, where it is warmed and perfectly separated from the air 
 and descends through a stand pipe into the boilers by its hydrostatic pressure, as 
 usual in the ordinary mode of feeding low pressure boilers. 
 
 K, The feed pipes, 4 inches' diameter ; each pipe is provided with a stop valve' to 
 prevent the water returning from the casing around the chimney into the air pumps. 
 
 L, Outlet pipes, 11 inches' diameter in the clear, through which the water from the 
 condensing cisterns is conducted outside of the vessel. 
 
 M, Bilge pumps. 
 
 0, Starting handles for working the slide valves. 
 
EXPLANATION OF THE PLATES. 
 
 385 
 
 INDICATOR DIAGRAMS, 
 
 SHEWING THE PERFORMANCE OF THE ENGINES ON BOARD THE WILBERFORCE DURING A VOYAGE 
 BETWEEN LONDON AND HULL, ENGRAVED FROM THE ORIGINAL CARDS. 
 
 DIAGRAM, No. 1. 
 
 15-35-2=13-35; 13 ' 35X2827X252 =288-2 Horses' Power. 
 
 33,000 
 
 !? 
 
 o 2 
 a 3 
 
 n> o 
 
 o= 
 
 t 
 
 V 
 
 W-7 16-8 W8 16-9 
 
 IT- 
 
 W- 
 
 Pressure of Steam in Boilers, 11 inches of Mercury. Revolutions, 21. Condenser 
 
 Gauge, 29-5. 2h. 30m. P.M. 
 
 Taken at the Nore from London to Hull. April 7th, 1838. 
 
 DIAGRAM, No. 2. 
 
 16-54 - 2 = 14-54 ; ^4X2827X228 = 283 . 6 Horses - p ower . 
 33,000 
 
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 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Ol 
 
 __ 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Pressure of Steam in Boilers, 13-5 inches of Mercury. Revolutions, 19. Con- 
 denser Gauge, 29-5. llh. 30m. P.M. Abreast of Winterton. Wind, N.W., blowing 
 very hard. Considerable swell, Vessel rolling, Gib and Fore Sails set. 
 From London to Hull. April 7th, 1 838. 
 
 3 c 
 
386 
 
 EXPLANATION OF THE PLATES. 
 
 DIAGRAM, No. 3. 
 
 15-97 - 2 = 13-97 ; 13 ' 97X28 ~ 7X228 = 272-8 Horses' Power. 
 
 33,000 
 
 !? 
 ^ 
 
 S i 
 
 g 
 
 re o 
 
 -. 5 
 
 X 
 
 1--7 
 
 7-3 17-3 ir-3 
 
 Pressure of Steam in Boilers, 10 inches of Mercury. Taken in the Humber; strong 
 head wind and ebb tide. Revolutions, 19. Condenser Gauge, 29'3. lOh. 30m. A.M. 
 From London to Hull. April 8th, 1838. 
 
 DIAGRAM, No. 4. 
 
 i A A i a 1 o .1 1 12-41 X 2827 X 261 _ . , n 
 14'41 2z= 12'41 ; . =277'4 Horses Power. 
 
 33,000 
 
 Pressure of Steam in Boilers, 12 inches of Mercury. Revolutions, 21 '75. Con- 
 denser Gauge, 29-5. lOh. 30m. A.M. Taken in the River Thames. 
 From Hull to London. April 12th, 1838. 
 
EXPLANATION OF THE PLATES. 387 
 
 MODE OF CALCULATING THE POWER OF AN ENGINE BY THE INDICATOR 
 
 CARDS. 
 
 The mean pressure on the piston, as proved by the indicator in diagram No. 1, is 
 15'35lbs. upon each square inch of its area, and the area of the piston being 2827 
 inches, it follows that the total pressure on the piston is equal to 15' 3 5 multiplied by 
 2827, which amounts to 43394 Ibs., but as an allowance of 2lbs. upon each square 
 inch area is made for the power necessary to overcome the friction of the engine 
 and to work the pumps, the effective pressure on the piston will be represented by 
 multiplying 15'35 2 = 13-35 by 2827, which gives 37740'4 Ibs. ; and as this pres- 
 sure is maintained at a velocity of 252 feet per minute, (the piston making 21 
 double strokes of 6 feet each,) it follows that the power of the engine will be ex- 
 pressed by multiplying 37740-4 Ibs. by 252, the velocity in feet per minute, and 
 then dividing the product by 33,000 for the horses' power. 
 
388 
 
 EXPLANATION OF THE PLATES. 
 
 LM SHIP WILBERFORCE, from LONDON to HULL, 
 
 OBSERVATIONS. 
 
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 Total time occupied from London to Hull, the vessel teing very 
 heavily loaded, with a considerable swell of the sea all the way, 
 and 1 1 hours' gale 27 hours, 55 minutes. 
 
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EXPLANATION OF THE PLATES. 
 
 389 
 
 WILBERFORCE, from HULL to LONDON, 
 
 OBSERVATIONS. 
 
 <>M da i *j 
 
 - N 2 -sfl 
 
 1 I ill 
 
 r. E-M-8 
 
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 HI !1 s 2 P . tf.Hl M 1 
 
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 iu o s fe =[ ot = ''Sio'S^i .s "S 
 
 hrs. min. 
 me occupied from Hull to London . . 24 10 
 
 20 55 
 ccupied from Gravesend to London including ) ^ 
 interruptions arising from a crowded pool \ " 
 
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390 EXPLANATION OF THE PLATES. 
 
 PLATE LV. A. 
 
 This plate represents a longitudinal section of Mr. Francis Humphrys's patent 
 marine engine, of fifty horses' power, as executed by the Messrs. Hall, of Dartford. 
 
 A A, Is the cylinder. 
 
 B B, The working piston. 
 
 C, The crank. 
 
 D D, A steam-tight casing or trunk, of a rectangular form, rounded at each end, 
 which is permanently attached to the piston in such manner that the axis of the 
 one shall correspond exactly with that of the other, and which works up and 
 down with the piston, 
 
 E E, Is the lid or cover of the cylinder A A. 
 
 G G, The stuffing box, which is made to fit the outside of the casing or trunk 
 D D, instead of, as usual, fitting the piston-rod. 
 
 H, Is the connecting rod firmly secured to a cross pin or axis I, working in 
 metallic bearings, one end of which rod is attached to the bottom of the piston, 
 and the other passes up through an aperture in the piston into the casing or 
 trunk D D, and is ultimately connected with the crank C. 
 
 K K, Is a box or cover which encloses the cross-pin or axis I, with its bearings, 
 and is jointed steam tight to the piston. 
 
 L L, A hollow space cast in the cylinder bottom or bed-plate for the reception 
 of the box K K, when the piston is at the bottom of the cylinder. The 
 result of these arrangements is, that on the engine being set to work the motion 
 of the piston is at once communicated by the connecting rod H, to the crank 
 C, and causes it to revolve without the intervention of beams, cross-heads, 
 or other auxiliary appendages, by which diminution in the number of the 
 moving parts of the engine, and consequent simplification of its action, it is 
 greatly reduced in size and weight. 
 
 a a, Slide valves. 
 
 c, Starting handle. 
 
 d, Air-pump rod. 
 
 f, Discharge pipe. 
 
 g, Snifting valve. 
 h, Eccentric rod. 
 
 e, Hot well. 
 
 The same letters of reference are employed to denote the same parts of the engine 
 in each of the engravings, by a reference to which its operation will be better under- 
 stood. 
 
EXPLANATION OF THE PLATES. 391 
 
 PLATE LV. B. 
 
 This plate shews a longitudinal elevation of Humphrys's engine. 
 
 A A, Cylinder and jacket. 
 
 C, The crank. 
 
 D D, The steam-tight casing or trunk, which works up and down with the 
 
 piston. 
 H, The connecting rod, which vibrates freely within the steam-tight casing or 
 
 trunk, as the crank revolves. 
 a a, Slide valve boxes or nozles. 
 
 c, Starting handle. 
 
 d, Air-pump rod. 
 
 e, Hot well. 
 
 f, Discharge pipe. 
 h, Eccentric rod. 
 
 k, Hand pump for supplying the boilers with water when the engine is not working. 
 /, Throttle valve. 
 m, Steam pipe. 
 
 n, Small pipe for supplying the cylinder jacket with steam. 
 u, Bilge pump. 
 
 o, Relief valve connected with the feeding apparatus, by which the water escapes 
 into the hot well when it is shut off from the boiler. 
 
 PLATE LVI. A. 
 
 This plate represents a midship section of the steam packet Dartford, shewing a 
 front elevation of a pair of Humphrys's engines of fifty horses' power each. 
 
 C C, Cranks. 
 
 D, The trunk. 
 
 H H, Connecting rods. 
 
 aaaa, Slide valve boxes or nozles. 
 
 c c, Starting handles. 
 
 d, Air-pump rod. 
 
 e, Hot well. 
 
 ff, Discharge pipes. 
 h h, Eccentric rods. 
 
 k, Hand pump. 
 
 //, Throttle valves. 
 
 m m, Steam pipes. 
 
 pp, Balance weights of slide valves. 
 
 r, Condenser. 
 
 s, Air-pump. 
 
 t, Injection cock. 
 
 x x x, Foundation plate. 
 
392 EXPLANATION OF THE PLATES. 
 
 PLATE LVI. B. 
 
 This plate shews a plan of the engines of the Dartford. 
 
 E E, The cylinder lids or covers. 
 
 C C, The cranks. 
 
 D D, The steam-tight casings or trunks. 
 
 G G, The stuffing boxes. 
 
 H H, The connecting rods. 
 
 a a, Slide valve boxes. 
 
 c c, Starting handles. 
 
 c, Hot well. 
 
 ff, Discharge pipes. 
 
 hh, Eccentric rods. 
 
 s, Air pump. 
 
 k. Hand pump. 
 
 mi, Bilge pumps. 
 
 v v, Feed pumps worked by levers connected with the cross head of the air-pump rod. 
 
 w, Platform on which the engineer stands to start the engines. 
 
 .? x x x, Foundation plate, cast in one piece and firmly secured to the four sleepers. 
 
 yyyy, This plate measures 13 feet 8 inches athwartships, and 8 feet 6 inches fore 
 and aft, which is the space occupied by the two engines. The cylinders are 
 each 42 inches diameter, and the pistons have a stroke of 3 feet 8 inches ; the 
 paddle wheels are 18 feet diameter, and 7 feet wide ; the load water draught 
 of the vessel is 8 feet 9 inches ; the mean revolutions of the engines 26. 
 
 PLATES LVIL, LVIIL, AND LIX. 
 
 FORTY-FIVE HORSE POWER ENGINE CONSTRUCTED BY W. FAIRBAIRN AND CO. 
 
 Plate LVIL J* 1 * ^ Elevation of engine. 
 1 2. Plan of ditto. 
 
 LVIIL 
 
 3. Front elevation. 
 
 4. Back ditto. 
 LIX. 5. Cross section. 
 
 The letters refer to the same parts in all 
 
 the views. 
 
EXPLANATION OF THE PLATES. 
 
 A, Base plate of engine and condenser. 
 
 B, Steam cylinder. 
 
 C, Column and hot well. 
 
 D, Cut-off valve, and steam-pipe from 
 
 boiler. 
 
 E, Slide valve casing. 
 
 F, Slide valve. 
 
 G, Steam passages. 
 H, Metallic piston. 
 
 I, Passage to condenser. 
 
 K, Condenser. 
 
 L, Air-pump. 
 
 M, Foot valve. 
 
 N, Air-pump bucket. 
 
 0, Discharge valve. 
 
 P, Waste water-pipe. 
 
 Q, Injection pipe and regulating valve. 
 
 R, Force pump. 
 
 S, Solid plunger of force-pump. 
 
 T, Beam. 
 
 U, Piston rod. 
 
 V, Air-pump rod. 
 
 W, Force-pump rod. 
 
 X, Connecting rod. 
 
 Y, Crank shaft. 
 
 Z, Toothed fly-wheel, forming first mo- 
 tion wheel. 
 a, Governor wheels. 
 6, Governor. 
 
 c, Wheels for working cut-off valve gear 
 
 ing. 
 
 d, Eccentric rod for working slide valve. 
 
 e, Socket for the starting handle. 
 
 f, Vibrating shaft to work slide valve. 
 
 g, Lever for counterbalance weight. 
 
 h, Boot-leg for giving motion to the slide 
 
 valve. 
 
 i, Slide valve rod. 
 k, K, Counterbalance weight of slide 
 
 valve. 
 I, Stud on small wheel for giving motion 
 
 to the rod m. 
 
 m, Eod for working cut-off valve. 
 n, Vibrating shaft for ditto. 
 o, Lever on shaft for working cut-off 
 
 valve. 
 p, Rod with regulating screw, and levers 
 
 for ditto. 
 
 PLATES LX., LXL, LXIL, AND LXIII. 
 
 TEN HORSE POWER ENGINE CONSTRUCTED BY W. FAIRBAIRN AND CO. 
 
 Plate LX. 
 LXI. 
 
 Fig. 1. Elevation of engine. 
 
 2. Plan of ditto. 
 
 3. Sectional plan. 
 
 4. Cross sectional elevation. 
 
 5. Sectional elevation. 
 
 LXIL 
 
 LXIII. 
 
 A, Engine base. 
 
 B, Column or pillar, to support the end 
 
 of crank shaft. 
 
 The letters refer to the same parts 
 in all the views. 
 
 C, Crank shaft. 
 
 D, Fly wheel. 
 
 E, First motion spur wheel. 
 
 3 D 
 
394 
 
 EXPLANATION OF THE PLATES. 
 
 F, Steam-pipe from boiler. 
 
 G, Stop valve. 
 H, Cylinder. 
 
 I, Belt round the cylinder, to bring the 
 
 steam into the valve case. 
 K, Slide valve. 
 L, Steam ports. 
 M, Piston. 
 N, Eduction pipe. 
 
 0, Feed pump. 
 
 P, Feed pipe. 
 
 Q, Water cock. 
 
 R, Clack valves of feed pump. 
 
 S, Connecting rod. 
 
 T, Eccentric, for working the slide valve. 
 
 U, Eccentric rod for ditto. 
 
 V, Governor wheels. 
 
 W, Governor. 
 
 PLATE LXIV. 
 
 ELEVATION OF LOCOMOTIVE ENGINE, STANHOPE- AND TYNE RAILWAY; CON- 
 STRUCTED BY MESSRS. ROBERT STEPHENSON AND CO., OF NEWCASTLE- 
 UPON-TYNE. 
 
 This plate exhibits a general elevation of the engine without the tender. It 
 should be observed, that the construction of locomotive engines has undergone con- 
 siderable variation in external form and detail since the establishment of the Liver- 
 pool and Manchester railway. The particular form and arrangement of engine 
 represented in the accompanying engraving is such as was adopted on this railway 
 about the year 1834. The following is a general table of the dimensions of the 
 various parts. 
 
 Ft. In. 
 
 Diameter of boiler 36 
 
 Length of ditto ........ 80 
 
 Length of fire-box outside ...... 37 
 
 Breadth ditto . 40 
 
 Depth below boiler 23 
 
 Length of inside fire-box . . . . . . 2 11^ 
 
 Breadth of ditto 3 7 
 
 From top of bars to crown of fire-box .... 3 5f 
 
 Area of fire-grate in square feet . . . . . 10 7 
 Length of smoke-box . . . . . . . 2 If 
 
 Breadth of ditto . 4 1| 
 
 Depth below boiler 25 
 
 Diameter of chimney ....... 12 
 
 Height from rail 140 
 
EXPLANATION OF THE PLATES. 395 
 
 Ft. In. 
 
 Brass tubes, diameter outside If 
 
 Distance of centres ...... 2 2 
 
 Diameter of cylinders 
 
 Length of stroke . ... 
 
 Distance of centres 27 
 
 Steam ports 7 in. x If in. 
 
 Diameter of pumps .... 2 4 
 
 Diameter of wheels (2 pair coupled) . 46 
 
 Ditto wheels, one pair .... . 36 
 
 Distance of centres of coupled wheels ... 46 
 
 Centre of axle from fire-box .... 1 3 
 
 Diameter in middle ....... 05^ 
 
 Diameter of crank pin ... 5f 
 
 Length of ditto .... .03 
 
 Diameter of inside bearings 5f 
 
 Length of ditto two 2f in., and two 3 
 
 Diameter of outside bearings ..... 03^ 
 
 Length of ditto 5f 
 
 Diameter of plain axle, including coupled wheels . 4^ 
 
 Ditto where wheels are on ..... 4 T 3 ff 
 
 Ditto outside bearing ....... 03^ 
 
 Length of ditto . . . . . . . . Si- 
 Distance apart 5 6^ 
 
 Springs' length ........ 2 Q\ 
 
 Breadth ......... 03 
 
 Depth 2| 
 
 Number of plates, 8. 
 
 Plain axle for small wheels, diameter in middle . . 3| 
 
 Diameter where wheels are on .....' 4 
 
 Diameter of bearing ....... 03^ 
 
 Length of ditto 5f 
 
 Length of frame (extreme) 170 
 
 Breadth of ditto 6 3f 
 
 Depth of ditto 07 
 
 Thickness 04 
 
 For description of parts, see Plates LXV., LXVI., LXVII. A., and LXVII. B. 
 
306 EXPLANATION OF THE PLATES. 
 
 PLATE LXV. 
 
 SECTION OF LOCOMOTIVE ENGINE, STANHOPE AND TYNE RAILWAY. 
 
 Plate LXV. is a general section of the engine, divested of its internal apparatus of 
 tubes, &c., in order to prevent unnecessary complication, and to explain more clearly 
 the more important divisions of the engine. 
 
 A locomotive engine is thus shewn to consist of three principal divisions ; namely, 
 A, the external fire-box, containing the internal one in which the fuel is placed ; B, 
 the boiler, of a cylindrical form, containing the brass tubes placed longitudinally from 
 the smoke-box end D, to the fire-box end A ; through these tubes the flame cir- 
 culates, thereby distributing a maximum quantity of heated surface to the water. 
 The boiler contains two or more long stays, E E, extending from the internal plate of 
 the smoke-box end to the external plate of the fire-box end ; the use of these stays 
 is for preventing too great a strain upon the tubes by the expansion of the metal. In 
 the earlier engines considerable inconvenience was experienced by the cylinders be- 
 coming primed, in consequence of water and steam coming over together and entering 
 them, occasioned principally by the motion of the engine. This inconvenience has 
 been obviated by the introduction of the chamber or steam-head C, into which the 
 steam rises ; from the interior of this chamber the steam is conducted by a pipe 
 (not shewn) to the cylinders. The relative position of the cylinders, piston, and 
 guide frame, to preserve the parallelism of the piston-rod is shewn, by the references 
 F, G, and H ; I is the connecting rod attached to the crank J ; K the man-hole for 
 ascertaining the state of the fire-box, and as an entrance for the purpose of cleaning 
 the same. The fire-bars L, it will be seen, are so placed that with a short lever 
 they may be unhooked from their position, and the whole of the fire allowed to fall 
 out when no longer required. M is the fire or furnace door. 
 
 PLATE LXVL 
 
 SAFETY VALVES, STANHOPE AND TYNE RAILWAY LOCOMOTIVE ENGINE. 
 
 This Plate contains drawings to a working size of the two kinds of safety valves 
 usually employed upon locomotive engines. Fig. 1 is a longitudinal section of the 
 lever safety valve, with the application of Salter's improved spring balance at- 
 tached instead of a weight. Fig. 2 is an elevation of the back of the balance, on 
 
EXPLANATION OF THE PLATES. 397 
 
 the line A, fig. 1. The balance terminates with a bent rod, B, somewhat of the 
 curvature of part of the boiler to which it is attached by the screw C. The semi- 
 cylindrical cylinder D contains a strong helical spring, which, by its extension or 
 contraction, (occasioned by the rising or falling of the lever E, fig. 1,) moves a 
 vernier upon the face F of the balance, indicating the power employed in raising 
 or extending the spring. The face upon which the vernier moves is graduated ac- 
 cording to the elasticity of the spring. The metallic circular and mitred valve G, 
 fig. 1, is operated upon its under side by the steam, which rises from the interior of 
 the boiler, passing through the chamber H, fig. 1, and again through a series of 
 holes drilled in the seat of the valve I, fig. 1 ; the valve preserves its parallelism 
 by the spindle K being guided in the tube L. Fig. 3 is a top view or plan of the 
 whole apparatus. 
 
 Fig. 4 represents the construction of the spring safety valve, differing only from 
 that represented above by the pressure of the steam being directly applied to 
 the congeries of springs C C C without the intervention of the lever before described. 
 This valve is usually covered and protected by a trumpet-shaped pipe, so that it 
 may not be improperly loaded or tampered with by any one employed about the 
 engine ; neither are the springs so stiff as those employed in the lever valve, conse- 
 quently any escape of steam from the boiler is first blown off through this valve 
 and gives the requisite notice for checking the intensity of the fire. 
 
 Fig. 5 is a plan of the cap at A, fig. 4. Fig. 6 is a plan of the valve at B, fig. 4. 
 
 PLATE LXVIL A. 
 
 CYLINDER COVER AND CONNECTING RODS, STANHOPE AND TYNE 
 
 LOCOMOTIVE ENGINE. 
 
 Plate V., fig. 1. The cylinder cover of the Stanhope and Tyne engine. A, the 
 brass stuffing through which the piston-rod alternates. B B, brass stuffing piece. 
 
 Fig. 2. Side view of one end of the outside connecting-rods. A, wrought iron 
 strap, secured to the connecting-rod by the gib and key ; the brasses B B are 
 brought to their bearings by tightening the key C. A set screw at A, fig 3, 
 secures it in its position ; the brasses of these connecting rods work on a ball end 
 crank pin, as shewn at B, fig. 3, which is a section of the end of the connecting- 
 rod. 
 
398 EXPLANATION OF THE PLATES. 
 
 PLATE LXVII. B . 
 
 THE CYLINDER AND PISTON AT LARGE; STANHOPE AND TYNE RAILWAY 
 
 LOCOMOTIVE ENGINE. 
 
 This plate represents the form, construction, and dimensions of the cylinder and 
 piston of this engine, and fig. 1, Plate LXVII. A., the cylinder cover, to the same scale. 
 
 The steam from the boiler is admitted into the steam-chest A, fig. 1, from the pipe 
 B, and from thence into the cylinders through the steam ports C, by the alternating 
 action of the slide D ; the exhausting pipe is shewn at E. F is the rod to which the 
 brass slide D is attached ; this rod receives the requisite alternating action by means 
 of an eccentric and driver of the usual construction, placed upon the cranked axle of 
 the engine. 
 
 The piston of this engine is represented in vertical section at fig. 2, and in hori- 
 zontal section at fig. 3. The vertical section shews the piston to consist of two me- 
 tallic rings A A, (brass,) the upper one being grooved to receive the tongue of the lower 
 one. These rings are kept forcibly pressed against the cylinder by the split ring 
 (steel) B B, figs. 2 and 3, in addition to which, are four other steel springs C C C C> 
 fig. 3, which may be adjusted to any further degree of tension by the nut-screws 
 D D D D. The piston cover and bottom are brought up by the screws C C, fig. 2, 
 passing through the holes E E E E, fig. 3, tapped for that purpose. The piston-rod 
 is keyed through, as shewn by the space for the keys at D, fig. 2. 
 
 The following scale of dimensions with respect to the diameters of wheels and 
 piston rods may be found useful. 
 
 WHEEL TYERS FOR LOCOMOTIVES, BY ADMEASUREMENT. 
 
 Diameter of Wheels. Circumference. 
 
 Feet. In. Feet. In. In. In. 
 
 50 . . 16 6 by 5 by If 
 
 46 . . 14 9 do. do. 
 
 40 . . 13 2 do. do. 
 
 36 . . 11 8 do. do. 
 
 30 . . 10 2 do. do. 
 
 28 . . 92 do. do. 
 
 26,. 8 7 do. do. 
 
 DIAMETER OF PISTON-RODS IN LOCOMOTIVE ENGINES, AS USED BY 
 MESSRS. ROBERT STEPHENSON AND CO. 
 
 Diameter of Cylinder, in inches. Diameter of Piston-rod, in inches. 
 
 5 '74 
 
 6 '9 
 
EXPLANATION OF THE PLATES. 399 
 
 Diameter of Cylinder, in inches. Diameter of Piston-rod in inches. 
 
 7 . . 1-04 
 
 8 . . 1.2 
 
 9 . . 1-34 
 
 10 . . 1-5 
 
 11 . . 1-64 
 
 12 . . 1-8 
 
 13 . . 1-94 
 
 14 . . 2-1 
 16 . . 2-375 
 
 For more detailed information on this important subject, see description of Plates 
 LXXXIX XCII. 
 
 PLATE LXVIII. 
 
 This Plate represents a plan and section of boiler seating, for a twenty horse en- 
 gine, at the manufactory of Messrs. Whitworth and Co., Manchester. 
 
 PLATE LXIX. 
 
 This Plate represents Messrs. Hague's double acting cylinder, with slides, &c. 
 
 Fig. 1 is the cylinder, showing the facings for slide ; A is the passage to the top ; 
 B the passage to the bottom ; and C the exhausting passage. 
 
 Fig. 2 is a section of the cylinder and slide in the position for letting in the steam 
 at the top A, and exhausting at the bottom through B C ; D is the slide with the 
 exhausting passage through it ; F is a spring to keep the slide to its face ; and G 
 the steam pipe from the boilers. 
 
 Fig. 3 shows the facings of the slide. 
 
 Fig. 4 shows the side of ditto. 
 
400 
 
 EXPLANATION OF THE PLATES. 
 
 PLATES LXX. A. AND LXX. B. 
 
 SECTIONS OF THE ENGINES OF THE HON. EAST INDIA COMPANY'S ARMED 
 STEAM VESSEL BERENICE, MANUFACTURED BY ROBERT NAPIER, ESQ., OF 
 GLASGOW. 
 
 A A, Boilers. 
 
 B, Steam pipe connected to jacket of 
 cylinder. 
 
 C, Cylinders. 
 
 D, Bed plates of engines, with condenser, 
 hot well, &c., cast in one piece. 
 
 F, Hot well. 
 
 H, Framing. 
 
 I, Steam chest for containing D, slide 
 valve. 
 
 .1 J, Eccentric rod and gearing for con- 
 necting and disconnecting engines. 
 
 K, Piston rod. 
 
 L, Cross heads. 
 
 M, Cylinder side-rods. 
 
 N, Parallel motion. 
 
 0, Side beams (or side levers). 
 
 P, Air pump side rods. 
 
 Q, Connecting rods. 
 
 R, Main cranks. 
 
 S, Intermediate shaft. 
 
 T T, Paddle wheel shafts. 
 
 U, Paddle wheel. 
 
 V, Paddles (or floats). 
 
 W, Plumbing blocks. 
 
 X, Waste pipe from top of hot well. 
 
 Y, Stays for binding engines together. 
 
 Z, Eccentric pulley. 
 
 Nos. 444, Engine bearers. 
 
 5, Keelson. 
 
 6, Keel. 
 
 a a, Safety valves on top and 
 bottom of cylinder. 
 
 b, Stuffing box on cylinder cover. 
 
 c, Valve shaft. 
 
 d, Parallel motion shaft. 
 
 e, Starting shaft. 
 
 f, Hand gear for starting engines. 
 
 g, Expansion valve shaft. 
 
 h h, Gear for working expansion 
 valve. 
 
 i, Side rods for working parallel 
 motion. 
 
 j, Waste water pipe. 
 
 k, Injection pipe. 
 
 I, Waste pipe from feed pump. 
 
 m, Pump for filling boilers, washing 
 decks, or extinguishing fire ; the 
 pump may be worked by the 
 engine or crew. 
 
 n, Steam pipe. 
 
 o, Feed pipes for boilers. 
 
 p, Feed pump. 
 
 q, Cast iron crank hatches. 
 
 r, Malleable iron stays for support- 
 ing ends of paddle beams. 
 
 s, Malleable iron knee and stays for 
 supporting ends of beams. 
 
 t, Handle for working pump on deck. 
 
 u, Funnel. 
 
 f, Steam chest. 
 
EXPLANATION OF THE PLATES. 401 
 
 The engines are 250 horse power, and the following are the principal dimensions : 
 
 Diameter of cylinder . . . 4 ft. 8 in. 
 
 Length of stroke .... 5 6 
 Diameter of wheels . . . .230 
 
 Length of paddle boards ... 8 6 
 
 Breadth of ditto .... 2 1 
 
 Diameter of funnel ... 40 
 
 Length of funnel above deck . . 360 
 
 PLATES LXXI. AND LXXII. 
 
 BEALE'S PATENT ROTATORY ENGINE. 
 
 As many fruitless endeavours have been made at various times to construct 
 engines on the rotatory principle, capable of performing their work regularly and 
 efficiently, as well as economically, we beg to submit the present description of Mr. 
 J. T. Beale's invention to the attention of our readers*. 
 
 The several figures in plates LXXI. and LXXII. represent different views of this 
 engine (of 8 horses' power) and its parts, drawn to a scale of 1 inch to the foot. 
 
 Plate LXXI. Fig. 1 is a plan or horizontal view of the engine complete, show- 
 ing the general arrangement of the whole ; but as very few of the working parts 
 peculiar to this engine can be seen in this or either of the other external views, we 
 shall not particularize any further, until we come to the sections, thinking it rather 
 desirable, in order to preserve simplicity and perspicuity, to confine ourselves in the 
 first instance to the mere citation of the several parts, each with its respective letter 
 of reference, as follows, viz. 
 
 a, Shows the foundation of the engine. 
 
 b, Is the band wheel. 
 
 c, The entrance steam pipe. 
 
 d, The cylinder. 
 
 e, The exit steam pipe. 
 
 f, The cam, or wiper, by which the slides are worked. 
 ff g, The slide rollers. 
 
 * The precise claims to novelty urged by the patentee may be seen on referring to the specifica- 
 tion of his patent, inrolled in the Inrolment Office of her Majesty's High Court of Chancery, August 
 27th, 1835; for although, in the present engine, several of the parts have been modified and im- 
 proved, still the principle is the same. 
 
 3 E 
 
402 EXPLANATION OF THE PLATES. 
 
 h h, Tail pieces connecting the rollers with the slides. 
 
 i i, Springs tending to force the tail pieces with the slides inwards. 
 
 k k, Rods for attaching the tail pieces to the slides. 
 
 /, Bearings for the hollow axle. 
 
 m, Train of gearing communicating with the governor n. 
 
 The connection of the latter with the throttle valve in the entrance steam pipe 
 
 is shown at o. 
 p, Is a wheel taking into the intermediate wheel, m, working a pump for supplying 
 
 water to the boiler. 
 
 A, Is a sluice cock for letting on the steam ; and 
 
 B, A double cock lubricator. 
 
 Fig. 2 is a front elevation, the engine in this figure being supposed to have moved 
 half a turn to the left hand from the position in which the parts are shown in the 
 former figure. 
 
 Plate LXXII. Fig. 1 represents a side elevation of the engine, showing all the 
 parts in similar positions to those represented in the plan or horizontal view. 
 
 Fig. 2 is a longitudinal vertical section taken through the cylinder d, steam stop 
 (or what may be called) piston q, hollow axle r, &c., the connection of the slides s s, 
 with the tail pieces h h, by the rods k k, being also shown in section, in order to 
 render it more evident. The hollow axle r has a partition t, shown in the middle, 
 dividing the entrance from the exit steam way, as may be more clearly seen at 
 figs. 3 and 4. In this figure the entrance steam way is shown in section at u, and 
 the exit v, in dots ; the cam or wiper f, as also the slide race or grooved way, are 
 likewise shown in dots. The piston (marked q in the figure) is composed of several 
 pieces of metal connected together as shown, the manner of fixing it between the 
 hollow axle r and the inside of the cylinder being as follows. A standard piece, 
 as at w, may be cast with the hollow axle r, but is preferred to be screwed firmly 
 to it, to which the blocks of metal x are fastened, also with screws, but which 
 screws, in this case, are passed through slots, in order to allow of a little play ; the 
 connection of the blocks, x, with the pieces y, which fit closely against the internal 
 periphery of the cylinder, is formed by a tongue on the former, fitting into a cor- 
 responding dovetailed groove in the latter, the whole being kept perfectly tight 
 during action by a spring, placed as seen by dots in fig. 3. The rotatory motion of 
 the engine is effected by the elastic pressure of the steam admitted through the 
 axle r, by the aperture M, into the cylinder d, exerted between the stationary steam 
 stop or piston and each slide alternately as they are brought up the groove z into close 
 contact with the axle r, by the action their respective rollers, g, receive in working 
 over the stationary cam or wiper f. In this figure, the dotted line on the right hand 
 
EXPLANATION OF THE PLATES. 403 
 
 is intended to represent the base, the section being taken as looking into the cylinder 
 from the front. 
 
 Fig. 3 shows a detached plan or horizontal view of the hollow axle and piston, 
 with the partition and two steam ways in dots. 
 
 Fig. 4 represents a horizontal section of the above, taken through the centre of 
 the hollow axle, showing the exit steam way v complete, and the partition t in 
 section. 
 
 Fig. 5 is a face view of the side of the piston, fitting against the internal peri- 
 phery of the cylinder ; and fig. 6 exhibits a plan view of one of the slides s, with 
 the tail piece h and roller g shown connected to it. This figure represents, in 
 section, the method of attaching the slide s to the tail piece h, which is done in the 
 following manner: on to the sunken part, 1, of the slide is cast a pin, 2, and over 
 this pin is placed a wrought iron piece or collar, fitting rather loosely, into which 
 the rod k is screwed, as shown in the plate. 
 
 PLATE LXXIII. 
 
 CONTRIVANCE FOR PREVENTING A LOCOMOTIVE ENGINE FROM RUNNING 
 OFF A RAILWAY. BY RICHARD AYRE, ESQ., NEWCASTLE-UPON-TYNE. 
 
 This plate represents one of the ingenious contrivances of Mr. Ayre. 
 
 The figures 1, 2, 3, are different views of the locomotive engine, with the 
 necessary apparatus. In fig. 1, A A A, represents a steel bar descending below 
 the rail in the inside, about an inch below the flange of the wheel. This bar is 
 connected to the frame of the engine by a joint, B, about which it is moveable ; and 
 a roller, E, is attached at the bottom, and a cross bar or brake, G, at the top. It 
 is also connected with the steam valve by means of the chain H H ; C is a joint 
 to enable the bar to move backward or forward ; D is a spring connected to the 
 frame of the engine and, by the chain ED, to the bar A A A, which spring would 
 be pulled down were any thing to come in contact with the bottom of the bar 
 A A A, in the line of railway, and enable the end of the bar to move back and 
 relieve itself. Also FF are two springs to keep the cross bar from the side of the 
 engine, as shown in the cross sections fig. 2 and fig. 3. 
 
 Should there be any tendency to run off the railway, the bottom of the bar 
 A A A, would by the pressure against the rail be driven inwards, and by its action 
 round the joint B, the brake G would be caused to press against the wheels, and 
 thus by the corresponding friction stop the motion ; and at the same time this 
 
404 EXPLANATION OF THE PLATES. 
 
 object would be materially assisted by action of the chain HH, which in con- 
 sequence of the motion of the top of the bar A A A, would regulate the steam 
 valve so as to entirely close it in an extreme case. Fig. 2 shows the positions in 
 an extreme case, when by means of a switch, or pall, which lies upon the cross 
 bar, the parts are effectually prevented from returning to their original positions, 
 and the motion of the engine and train is soon brought to a stand. 
 
 The same arrangement is fitted to the other side of the engine, and, as shown 
 in Figs. 2 and 3, cross chains are fixed from side to side, so as to connect the top 
 of each bar with the bottom of the other, and thereby insure the effect of the 
 brakes against all the four wheels, as shewn in Fig. 2. 
 
 PLATES LXXIV. TO LXXXIII. 
 
 The drawings contained in these plates relate to Mr. Morn ay's valuable paper 
 on " Paddle Wheels," inserted in the appendix, page 117, and their explanations are 
 to be found in that paper. 
 
 PLATES LXXXIV. TO LXXXVIII. 
 
 SIXTY-FIVE INCH CYLINDER ENGINE, ERECTED BY MESSRS. MAUDSLAY, SONS, 
 AND FIELD, AT CHELSEA WATER WORKS, 1837. 
 
 The drawings in these Plates are as follow : 
 
 Plate LXXXIV. Elevation of the engine pumps and air vessel. 
 
 Plate LXXXV. Longitudinal section through the centre of the cylinder, nozles, 
 beam, main pump, &c. 
 
 Plate LXXXVI. Fig. 1. Front elevation of the hand gear, levers, and rods, 
 with expansion tappet, &c. Fig. 2. Transverse section of nozles 
 through centre of valves. Fig. 3. Side elevation of the hand gear, 
 levers and rods, &c., &c. 
 
 Plate LXXXVII. Longitudinal section through the centre of one of the boilers, 
 shewing the steam boxes, feed heads, floats, &c. 
 
 Plate LXXXVIII. Fig. 1. Front elevation of the boilers, shewing the furnace doors, 
 steam boxes, damper pipes, feed heads, &c. Fig. 2. Transverse sec- 
 tion of the boilers, shewing the steam boxes, pipes and stop valves, 
 safety valves and pipes. 
 
EXPLANATION OF THE PLATES. 
 
 405 
 
 REFERENCES TO THE DRAWING, PLATE LXXXIV. 
 
 A, Cylinder. 
 
 B B B, Nozles and valves. 
 
 C C, Condensing cistern. 
 
 D, Air pump. 
 
 E, Eduction pipe to condenser. 
 
 F, Expansion tappet. 
 
 G, Damper barrel for regulating the 
 
 valves. 
 
 H, Main beam. 
 I, Sliding counter weight. 
 K, Hoisting beams. 
 
 L L, Cranes for raising cylinder and 
 
 pump covers. 
 M M, Catch pins. 
 N, Cold water pump. 
 0, Hot water pump and air vessel. 
 P, Pump rod. 
 Q Q, Well. 
 
 R, Working barrel of main pump. 
 S S, Clack barrels. 
 T, Air vessel. 
 V, Main pipe. 
 
 This engine is single acting, the diameter of the cylinder is sixty-five inches, 
 and the length of stroke eight feet ; the diameter of the working barrel of the 
 main pump is twenty-five inches, and the length of the stroke, also eight feet. 
 
 The boilers are six feet wide, eight feet high, and twenty-five feet long. 
 
 The operation of this engine and its appurtenances being nearly similar to the 
 action of other engines before described, it is scarcely necessary to advert to it but 
 for the purpose of explaining that its effective action is only in one direction, viz., 
 during the descent of the cylinder piston. It may be explained as follows : the 
 progress of blowing through * being accomplished, the three valves f shut again, 
 and the injection cock opened, the steam and eduction valves are opened, the 
 former to admit the steam from the boiler into the top of the cylinder, and the 
 latter to permit its egress from the bottom of the cylinder to the condenser. The 
 equilibrium valve remaining shut, the pressure of the steam acting above the 
 piston, with the vacuum underneath it, is sufficient to move the piston, and as it 
 approaches the end of the stroke, or bottom of the cylinder, the hand gear tappets, 
 and catches operate, first, to shut the steam valve, secondly the eduction valve, and 
 lastly, when at the bottom of the stroke, to open the equilibrium, and thus open 
 the communication between the top and bottom of the cylinder, the counterbalance at 
 the outer or pump end of the beam then exerts a force sufficient to move the 
 
 * Opening the valves for the steam to pass from the boiler into the cylinder and through the nozles 
 to the condenser, and thus expel the air, vapour and water through the blow valve and valves of the 
 air pump. 
 
 f Nozles in front of cylinder ; upper steam-valve ; centre equilibrium valve ; lower eduction 
 valve. 
 
406 EXPLANATION OF THE PLATES. 
 
 piston up again, and transfer the steam from the top to the bottom of the cylinder, 
 when the lower tappet shuts the equilibrium valve, and the action of its catch 
 releases the catch of the steam and eduction valves, thereby admitting of their 
 opening as before, and being the means of making the motion of the engine con- 
 tinuous. 
 
 The general construction of this engine is so analogous to that applied for pumping 
 engines in water works of late years, that we think it necessary only to direct 
 attention to those parts which are particularly striking. 
 
 Viewed merely as a machine, it is an admirable specimen of workmanship. The 
 beam, and many of the parts, exhibit great strength, and are fully equal to the 
 application of the expansive principle of working, should the adoption of it at a 
 future period be determined upon. The castings throughout are of a superior 
 description, and the fittings and bright work exhibit an attention to detail that 
 cannot fail to attract the notice of the mechanic ; he will perceive that the lathe 
 and planing machine have lent their aid to all the bearing surfaces, and that every 
 care has been taken to ensure solidity of construction. 
 
 The boilers are of 'wrought iron, upon the marine principle, securely stayed, and 
 fitted with safety valves, feed pipes, and the usual apparatus, with the addition of 
 whistle pipes, that old but effectual mode of making known the deficiency of water 
 in the boilers. 
 
 Arrangements have been made to cover the boilers, steam pipes, and cylinder 
 with non-conducting substances, as soon as the works are proved. 
 
 The structure of this engine admits of its being worked to the various altitudes 
 required for street supplies, the chief means of regulation being the expansion 
 tappet and safety catch, the latter acting when the length of the stroke exceeds 
 the proper limit. The counterweight for adjusting the engine moves between 
 guide strips inside the beam ; it is worked by a long screw, which (the cross 
 handle being moveable) admits of the whole range of the weight between the 
 catch pins when the engine is at work. 
 
 The main pump and clack seats are fixed in a very substantial manner ; they are 
 supported by four strong iron beams, (through which very large holding down bolts 
 pass,) and they are steadied by iron plates fixed above and forced against the masonry. 
 The supporting beams are fixed within four feet of the bottom of the working barrel, 
 and the masses of stone above them are considerable. 
 
 The pump clacks are of gun-metal, fitted with wrought iron plates leathered ; these 
 are of large dimensions compared with the working barrel, and they are fixed in 
 separate chambered seatings and held fast by distinct rods pressed down by set 
 screws. 
 
EXPLANATION OF THE PLATES. 40? 
 
 Duplicates of such of the parts as are liable to derangement are kept in readiness, 
 powerful cranes and hoisting girders are fixed, and the various tools so arranged that 
 the taking to pieces and refixing any part of the engine and pump can be effected 
 without loss of time. 
 
 The engine is calculated to raise 2250 gallons of water per minute. 
 
 PLATES LXXXIX. TO XCII. 
 
 PATENT LOCOMOTIVE ENGINE, 
 
 MADE BY MESSRS. R. STEPHENSON AND CO., NEWCASTLE-ON-TYNE, 
 FOR THE LONDON AND BIRMINGHAM RAILWAY. 
 
 This engine was made in 1836 for Messrs. Cubitt, the contractors for constructing 
 a part of the London and Birmingham Railway near Berkhampstead, and was used 
 by them for carrying the earth excavated in the construction of the line. The engine 
 was employed in this manner for about a year and a half; when, the works being 
 nearly completed, it was no longer required, and was purchased by the Railway 
 Company for the purpose of carrying ballast for repairing the road, and other similar 
 purposes, in which work it is now employed together with other engines. 
 
 Although the original cost of these engines is very considerable, being about l 400 
 each, it is found to be advantageous to use them in executing the earthwork of rail- 
 ways when the earth has to be carried to any considerable distance, as they take the 
 place of so many horses and greatly expedite the work. They are also generally 
 worth a great deal when done with for the particular purpose, as was the case with 
 this engine, which was sold for upwards of two thirds of its original cost. The 
 expense of using them is nearly the same as that of doing the same work by horses, 
 if the saving of time from the greater speed and heavier loads that can be carried are 
 not taken into the account ; but the advantage in these respects is so great that 
 locomotive engines are generally used for the works of railways whenever the earth- 
 work is of any considerable importance. 
 
 A locomotive engine differs considerably from other steam engines in many 
 particulars, as the engine and boiler are combined together in one machine, and have 
 to be carried along at a great velocity, together with the fuel and water required 
 for supplying the boiler. Very considerable modifications in the construction are 
 thus rendered necessary, in order to obtain sufficient lightness and compactness 
 combined with the requisite power. The cylinders are very much smaller than is 
 usual in other engines, the steam used being of very high pressure ; the boiler is also 
 made of small dimensions in proportion to the power, for the sake of portability, 
 
408 STEPHENSON'S PATENT 
 
 requiring therefore a construction affording the means of generating steam very 
 rapidly, or having a great evaporating power, in order to supply the steam in 
 sufficient quantity and of the required pressure. The whole engine has to be very 
 strongly and firmly made and framed together, to enable it to resist the violent strains 
 and shocks produced by the rapid motion of so heavy a mass even upon the com- 
 paratively smooth surface of the rails, and also to meet the accidents to which it is 
 liable, and which are generally ve^ serious. 
 
 The construction of these engines has undergone very great and extensive improve- 
 ment during the last few years, and they have not long arrived at their present 
 state of perfection ; those made before the last ten years were greatly inferior, having 
 not more than a fourteenth of the power of the present ones. 
 
 The engine here described, and shewn in the engravings, contains the latest 
 improvements, and is similar in construction to most of those used on railways in 
 England and on the Continent. 
 
 DESCRIPTION OF THE ENGINE. 
 
 Plate LXXXIX. is a side elevation of the engine and tender. The engraving is 
 highly shaded to show more fully their general appearance. 
 
 Plate XC. a longitudinal section through the centre of the engine and tender, 
 showing their internal construction ; the section below the boiler being taken through 
 the right hand cylinder and crank. 
 
 Plate XCI. Fig. 1, is a plan of the engine #nd tender ; the plan of the engine is 
 taken just below the boiler, in order to show the machinery beneath it, and at the 
 left cylinder the plan is taken a little lower down, showing a section of the steam 
 chest and more of the machinery ; figs. 2, 3, and 4 are detached views of the 
 working gear for the slide valves ; figs. 2 and 3 being side elevations, showing the 
 working gear in different positions, to explain their action ; and fig. 4 a back eleva- 
 tion, showing it in the same position as figs. 1 and 3. The plan of the tender is 
 taken at the top. 
 
 Plate XCII. contains an elevation of each end of the engine, and a cross section 
 through each of the end portions. 
 
 The plates are all drawn to a scale of three quarters of an inch to a foot, or one- 
 sixteenth of the real size, and the same letters of reference are used to denote the 
 same parts in each of the figures. 
 
 The different parts of the engine are shown in detail on a larger scale in the wood 
 cuts accompanying the descriptions, according to the size or importance of the parts. 
 
 The construction and object of the different parts of the engine will be explained 
 in succession, together with the wear to which they are subject, the improve- 
 
LOCOMOTIVE ENGINE. 409 
 
 ments that have been made in them, and the principal variations in construction 
 from other engines. 
 
 The general order of description will be, I. THE BOILER, AND THE MANNER OF 
 GENERATING THE STEAM, with the means of supplying the boiler, of cleaning it out, 
 and of insuring its safety ; also of ascertaining the pressure of the steam, and the 
 quantity of water. 
 
 II. THE CYLINDERS, AND THE MANNER OF USING THE STEAM, with the mode of 
 supplying the cylinders with steam, and working the pistons and slide valves ; and 
 of moving the wheels and propelling the engine. 
 
 III. THE WHEELS, FRAMING, &o, OF THE ENGINE, with the springs, axle boxes, 
 and guides, &c., connected with the frame. 
 
 And IV. THE TENDER, for carrying coke and water to supply the boiler. 
 
 THE BOILER, AND THE MANNER OF GENERATING THE STEAM. 
 
 The boiler consists of several distinct parts ; the cylindrical portion A called 
 peculiarly the boiler, the external fire-box B communicating with it, the internal 
 fire-box C, containing the fire-grate D, and the tubes E communicating between 
 the internal fire-box and the smoke-box F, upon which is fixed the chimney G. 
 
 THE BOILER AA (Plates LXXXIX. and CX.) is a cylinder 7 feet 6 inches long, 
 and 3 feet 6 inches in diameter outside ; it is made of wrought iron plates five-six- 
 teenths of an inch thick, lapping over each other, and joined together by iron 
 rivets seven-eighths of an inch in diameter and If inches apart, as shown at A 
 in fig. 5, which is a section of a joint, half 
 size. The rivets are inserted red hot and 
 contract in cooling, drawing the plates 
 forcibly together, and making a very close 
 joint. 
 
 The boiler is covered with wood aa (Plate XC.) one inch thick, put on in longi- 
 tudinal staves, and bound round by the iron hoops bb, Plates LXXXIX. and CX., 
 which are screwed together at the bottom ; this casing of wood is for the purpose 
 of retaining the heat, and preventing it from being carried off by the air when 
 moving rapidly through it, wood being an imperfect conductor of heat. 
 
 THE EXTERNAL FiRE-Box B B is a box nearly square, 4 feet wide outside, and 
 3 feet TTJ inches long in the direction of the boiler, made of wrought iron plates 
 five- sixteenths of an inch thick, like those of the boiler ; the bottom is 2 feet 1 inch 
 below the boiler, and the upper part is a semi-cylinder, concentric with the boiler, 
 as shown in the cross section, fig. 2, Plate XCII. The fire box is open at the 
 bottom, and has a circular opening cut in the front side, of the same size as 
 
410 
 
 STEPHENSON'S PATENT 
 
 FIG. C. 
 
 the boiler and corresponding to it ; the boiler 
 being fastened to it by means of angle iron 
 cc, (Plate XC.,) as shown in the section, half 
 size, in fig. 6 ; the angle iron ^4 is bent round 
 the boiler at the place of its junction with 
 the fire-box, and riveted to the plates D and C 
 of the boiler and fire-box. The plates compos- 
 ing the front and back of the fire-box are bent 
 inwards at right angles all round as at dd, (Plate 
 XC.,) forming flanches upon which the plates of 
 the sides and top are riveted. 
 
 THE INTERNAL FiRE-Box C C is of similar shape to the external, but flat at the 
 top and closed at all sides except the bottom ; a clear space of 3^ inches is left 
 all round between it and the external fire-box, and on the side next to the boiler 
 the space is 4 inches. The internal fire-box is made of copper plates seven-six- 
 teenths of an inch thick, except the side next the boiler, which is seven-eighths of 
 an inch thick, but all of the plate except the circular portion opposite to the boiler 
 is beaten down until it is only seven-sixteenths of an inch thick, the same as the 
 rest. The roof and sides of the box are formed of one plate, as shown in the section 
 fig. 2, Plate XCIL, and another plate forms the back, corresponding to that in the 
 front next the boiler ; the front and back plates are turned inwards at the edges 
 like those of the external fire-box, and the other plate fixed to them by three-quarter 
 inch copper rivets. The internal fire-box is fastened at the bottom to the 
 external, by setting the plates out until they touch the outer plates, and riveting 
 them together with copper rivets, as shown at ff (Plates XC. and XCIL). The 
 plates are sometimes set out only so as to approach the outer plates within l 
 inch, and a copper ring inserted between them, the rivets being put through the 
 ring, and the joint thoroughly closed by hammering it up underneath ; but it is 
 generally found that the joint keeps watertight best when made by setting the 
 plates together and riveting them : a double row of rivets is generally used. An 
 oval hole, 14 inches wide and 12 inches high, is cut in the back plate of both fire- 
 boxes for the fire-door gg (Plate XC., and fig. 1, Plate XCIL) ; the plate of the 
 internal fire-box is set out all round it to meet the outer plate, and the two are 
 fixed together by a row of copper rivets ; a copper ring is sometimes inserted be- 
 tween the plates here, as well as in the joint at the bottom of the fire-box. The 
 fire-door consists of two wrought iron plates connected together by rivets, leaving 
 a space of half an inch between them ; this protects the outer plate from the fire, 
 and prevents it from getting too hot. 
 
LOCOMOTIVE ENGINE. 411 
 
 The fire-grate D D is fixed 3 feet 2 inches below the roof of the fire-box, and 
 9 inches above the bottom, and is composed of separate loose bars of wrought iron, 2^ 
 inches deep in the middle, and 1 inch thick at the upper side, tapering downwards 
 to allow more free ingress for the air ; the fire-bars are bent down at the ends and 
 drop into holes in a square ring of iron, h k, which runs round the fire-box at a little 
 distance from the side, and is supported by a piece of angle iron, i i, bolted to the 
 front and back plates of the fire-box. The fire-bars are made separate and move- 
 able in order that they may be easily replaced when worn out, which happens very 
 frequently from the great heat to which they are exposed; and also for the facility 
 with which the fire can be extinguished in case danger should be apprehended from 
 any accident; for by lifting them out of the holes with a bent rod, kept for the pur- 
 pose, they can be dropped, together with the whole of the fire, upon the road : this 
 is indeed the manner in which the fire is extinguished when the engine has done 
 working. An ash-pan is fixed under the fire-box in some engines, made of sheet- 
 iron, of the same shape as the external fire-box, and open only in front ; it serves to 
 catch the cinders and prevent their falling on the road, but is rather inconvenient 
 when the fire has to be let out. 
 
 The boiler being cylindrical has an equal strain in all directions from the pressure 
 of the steam; but as the fire-boxes are flat on all sides except the top of the external 
 one, they would have a tendency to be separated from each other by the pressure of 
 the steam if they had not some support. For this purpose they are connected to- 
 gether by a number of three-quarter inch copper bolts, k Jc, which are screwed along 
 their whole length and are passed through holes in both plates, tapped to receive 
 them, and then riveted over at the ends for additional security ; these copper bolts 
 are screwed in about 4 inches apart all over the sides and back of the internal fire- 
 box and that portion of the front that is below the boiler. As the roof of the in- 
 ternal fire-box only requires support, that of the external one being cylindrical, it is 
 strengthened by six wrought iron ribs, II, (Plates XC. and XCII.,) placed parallel to 
 each other and longitudinally upon the roof, and fastened to it by bolts screwed 
 through the roof-plate, and having, in addition, a nut screwed on at the under side ; 
 the ribs are l inch thick, and increased at the bolt holes, and 2^ inches deep at the 
 middle, where the strain is greatest. The ribs //, are cut away on the underside 
 between each of the bolts, so as to touch the roof-plate only where the bolts pass 
 through them, in order that there may be as little mass of metal as possible exposed 
 to the immediate action of the fire ; for when a considerable thickness of metal is 
 interposed between the water in the boiler and the fire, the heat cannot be absorbed 
 by the water with such rapidity as it is supplied, and the metal becomes in conse- 
 quence greatly heated, and is rapidly destroyed. The durability of the internal 
 
412 
 
 STEPHENSON'S PATENT 
 
 FIG. 7. 
 
 fire-box depends very much on the care of the engine man ; with proper use it will 
 last several years, but if the water is allowed to get too low in the boiler, so as to 
 have but little depth over the roof, the plate will be liable to get frequently un- 
 covered, from the motion of the engine, and be rapidly destroyed. To prevent this 
 accident a small plug of lead, m, (Plate XC. and XCII.,) is put through a hole in 
 the centre of the roof of the fire-box, and riveted over on both sides ; when the 
 water gets so low as to uncover this plug it is melted by the heat, and the steam, 
 rushing into the fire-box, extinguishes the fire. The internal fire-box is made some- 
 times of wrought iron, and is generally found to last nearly as long as a copper one ; 
 the iron fire-box costs considerably less, but requires more care in using and is very 
 liable to crack and become leaky at the joints. 
 
 TUBES. The communication between the fire-box and the chimney is made by a 
 number of tubes, E E, (Plate XC. and XCII.,) which are fixed water-tight at one end 
 into the front plate of the fire-box e, and at the other into the plate n, (Plate XC.,) 
 which closes the front end of the boiler ; the tube plate, e, of the fire-box being 
 made thicker where the tubes are inserted, to allow for its being weakened by the 
 holes cut in it. There are 124 of these tubes; they are li inch in diameter 
 outside, and a space of three quarters of an inch is left between them. They are made 
 of the best rolled brass, one thirteenth of an inch thick, 
 (called No. 13. wire-gauge;) the edges of the brass 
 are properly chamfered and lapped over each other 
 and soldered together, the solder being applied inside ; 
 the tubes are then drawn through a circular steel die to 
 make them truly cylindrical. The holes to receive them 
 in the tube plates e and n, (Plate XC.,) are bored quite 
 cylindrical so as to fit the tubes exactly, which are just 
 long enough to come to the outside of both plates : the 
 ends of the tubes are then fixed by driving in a steel 
 hoop or ferrule, made slightly conical, as shewn in Fig. 
 7 ; which is a section full size of the tube A A, the 
 plate of the fire-box B B in which it is inserted, and 
 the ferrule CC; the ferrule is a little larger than the tube, 
 so that, when driven in, it compresses the tube very 
 forcibly against the sides of the hole, and makes the 
 joint completely watertight. The ferrules are sometimes made of wrought iron, but 
 they generally do not last out the tube in that case, and require replacing by new 
 ones before the tubes are worn out ; the steel ferrules are better, as they last nearly 
 twice as long. When a tube or a ferrule requires taking out, the ferrule has to be 
 
LOCOMOTIVE ENGINE. 413 
 
 cut quite through with a chisel and then turned inwards so as to detach it from the 
 tube, which can then be driven out. 
 
 By causing all the flame and heated air to pass through a great number of small 
 tubes surrounded by the water, a very great and rapid means of heating the water 
 is obtained, as a very large heated surface is thus exposed to the water. The first 
 locomotive engines had merely a large flue passing from the fireplace to the chimney; 
 it was bent round at the end and returned again to the back, the chimney being 
 placed at the same end as the fireplace ; the fire was contained in the commence- 
 ment of the flue, which was made larger for the purpose. This is the general prin- 
 ciple of the construction of the boilers for stationary engines where the size and 
 weight of the boiler are not of so much importance, and the flues can be made large 
 enough to get a sufficient area of heated surface in contact with the water. But as 
 in a locomotive engine all the machinery has to be moved at a great velocity, the 
 size and weight of the boiler are obliged to be diminished very much, and some other 
 means has to be adopted to obtain the requisite heating surface. 
 
 The Rocket engine made by Mr. R. Stephenson, which was the engine that gained 
 the prize for the best locomotive, at the opening of the Liverpool and Manchester 
 Railway in 1829, was the first engine made with tubes in this country*. 
 
 The former locomotives with only a flue through the boiler, had never been able 
 to travel faster than about eight miles an hour, as they had not sufficient heating- 
 surface in the boiler to generate the steam for supplying the cylinders more rapidly ; 
 the speed attainable by a locomotive being limited only by the quantity of steam that 
 can be generated in a given time. The introduction of tubes into the boiler is one of 
 the greatest improvements that has been made in the construction of locomotives, and 
 was the cause of the superiority of the Rocket engine to those that competed with it, 
 and to all the former engines. The velocity it attained at the competition trial was 
 29 miles an hour, and the average 14^ miles an hour. 
 
 The tubes of the Rocket engine were 3 inches in diameter, and only twenty-four in 
 number ; in the engines made subsequently, the size was reduced and the number of 
 them doubled and trebled, by which means the heating surface was very much 
 increased and with it the power of the engine. The smaller the tubes are, the 
 greater is the heating surface obtained, as small circles have a much larger 
 circumference in proportion to their area than large ones ; but when the tubes are 
 diminished in size, the total area of passage through them from the fire-box to the 
 chimney is also diminished; and consequently if the diameter of the tubes were much 
 
 * It appears that the merit of the first invention of a boiler with tubes is due to a French engineer, 
 M. Seguin, who had a patent for it in 1828 ; although the application of the principle in the Rocket 
 engine was undoubtedly an independent invention. 
 
414 STEPHENSON'S PATENT 
 
 diminished the draught of the fire would be checked from the passage to the chimney 
 being too small. The heating power of the boiler would thus be injured, although 
 the amount of heating surface exposed to the water was increased, and the abstraction 
 of the heat from the hot air rendered more perfect. The exact size of tubes which 
 produce the best total effect is to be discovered only by experience, and has not yet 
 been completely decided. 
 
 Small tubes have another disadvantage in being liable to choke up very much 
 with the particles of coke which are carried through them in great quantities by the 
 force of the draught, and in their retaining the cinders which are continually blown 
 into them, but which pass clear through larger tubes. The small tubes are often 
 contracted one third in diameter by the deposit of coke on their inner surface during 
 the day's work, and they have to be cleared out every night by passing a rod 
 through them ; the larger tubes never require clearing out. 
 
 The tubes were at first made of copper, and some have been of wrought iron, but 
 the copper tubes were found to wear very fast, generally lasting only three or 
 four months, and were a great source of expense from the necessity of frequently 
 renewing them. Brass tubes were first tried in the locomotives on the Liverpool and 
 Manchester Railway in 1833, at the suggestion of Mr. Dixon, the resident engineer, 
 and were found to be very much superior; they are now universally used for loco- 
 motives. Brass tubes, of the dimensions mentioned above, last about two years, being 
 six or eight times as long as copper tubes of the same dimensions. This increase of 
 durability appears partly caused by their greater hardness, as it has been observed 
 that the soldered joint, which is made with harder brass, wears less than the other 
 parts ; but the whole cause has not yet been satisfactorily ascertained. The tubes are 
 much worn by the friction of the cinders that are blown through them by the force 
 of the draught; but it is very probable that their wear is principally caused by chemical 
 or thermo-electric action. The tubes in the middle and about the fourth row from 
 the bottom are worn out the first, and it is only the ends next the fire-box that are 
 destroyed. 
 
 When the tubes become very thin they are crushed inwards by the force of the 
 steam, and the water is blown out at the ends of the tube into the fire ; when the 
 tubes are getting old, this frequently takes place whilst an engine is running, and it 
 is stopped by the accident. A plug of hard wood is driven into each end of the 
 burst tube, which is preserved from being burnt by the contact of the water inside 
 the tube, and the engine runs on again. When several of the tubes have burst and 
 been plugged up, they are taken out and replaced by new ones ; and if the engine is 
 required to be in constant use, a complete set of new tubes is soon required to avoid the 
 liability of delays from the bursting of the tubes ; they weigh about I61bs. when new, 
 
LOCOMOTIVE ENGINE. 415 
 
 and lose about 6^ Ibs. in the time they are in use. The cost of both the brass and of the 
 copper tubes is about l each, and this makes the expense of repairing an engine very 
 considerable when a complete set of new tubes is required. The tubes being fixed 
 firmly into both ends of the boiler, serve to support and strengthen them ; but for an 
 additional support to the upper part, six wrought iron rods, o o, (Plates XC. and XCII.,) 
 are placed above the internal fire-box, by the side of each other and longitudinally in 
 the boiler ; and the ends are attached by a pin to a piece of wrought iron, called T 
 iron, riveted on to the end plate of the boiler and to the back plate of the fire-box. 
 
 THE SMOKE-BOX F F, is 4 feet wide, like the fire-box, and 2 feet long, and is 
 closed on all sides ; the back of it is formed by the wrought iron plate , half an 
 inch thick, closing the end of the boiler to which it is attached by means of a piece 
 of angle iron riveted to both, like the similar joint at the fire-box. The rest of the 
 smoke-box is made of quarter inch iron plate, the front and back plates being 
 bent in round the edge, and the other plates riveted to them as in the fire-box, 
 except the front plate, which is fixed by screw bolts and nuts, because it is required 
 occasionally to take it off. 
 
 Upon the smoke-box is fixed the chimney G, (Plates LXXXIX., XC. and XCII.) ; 
 it is 15 inches in diameter, and is made of one eighth inch iron plates, riveted 
 together and bound round by hoops, as shewn in the section ; the top is made funnel- 
 shaped to give more free egress to the hot air, and the bottom has a piece of plate 
 riveted to it, forming a flanch all round, by means of which the chimney is bolted 
 down upon the smoke-box. 
 
 In the lower part of the smoke-box are fixed the two cylinders H H, where the 
 steam is used and motion produced; these will be described afterwards. The steam, 
 when it has been used in the cylinder and has performed its work, is no longer wanted, 
 and is let out into the air by the pipe p, (Plates XC. and XCII.) 
 
 The tubes open into the upper part of the smoke-box, and the hot air passes from 
 them up the chimney ; no smoke is produced, except at first lighting the fire, as the 
 fuel used is coke, which does not cause any smoke in burning, but only a light dust. 
 The height of the chimney is obliged to be small, as it can never exceed 14 feet 
 height from the rails ; so that the draught produced by it is not at all sufficient to urge 
 the fire to the intense degree of ignition that is necessary to produce steam at the 
 pressure and in the quantity that is required, and some other more powerful means 
 has, therefore, to be adopted to produce the draught. This is done by making the 
 waste steam issue through the pipe pp, (Plates XC., XCI., and XCII.,) called the 
 blast pipe, which is directed up into the centre of the chimney, and is gradually con- 
 tracted throughout its length to make the steam rush out with more force ; this 
 pipe is made of copper one eighth of an inch thick, and is 3f inches in diameter 
 
416 STEPHENSON'S PATENT 
 
 inside at the bottom where it joins on to the cylinders, and tapers to 2|- inches at 
 the top. 
 
 The waste steam rushes out of the pipe with great force up the chimney, carrying 
 the air with it, and causing a very powerful draught through the tubes and the fire ; 
 a whole cylinder full of steam is let out at each stroke, and the two cylinders deliver 
 their waste steam alternately, so that when the engine is running fast an almost 
 constant current of steam in the chimney is produced, and the interval between the 
 blasts can scarcely be perceived. By this method the fire is not blown, as is usual, 
 by forcing air into it, but by extracting the air from the flues and drawing air 
 through the fire. In the first locomotives no means were used for increasing the 
 draught of the chimney, and their power of generating steam was consequently very 
 limited ; the introduction of the steam blast for urging the fire, and of the tubes for 
 conveying the heated air through the water, are the principal causes of the great 
 power of the present locomotives. 
 
 There is, however, a considerable loss of power attending the use of the blast-pipe, 
 from the obstruction it causes to the egress of the waste steam ; for the waste steam 
 opposes the action of the steam in the cylinders, and should be allowed to escape 
 freely that its pressure might be as small as possible. This causes the greater 
 economy of working in the large stationary and marine engines, where the waste 
 steam is condensed and its opposing pressure is reduced almost to nothing : but in a 
 locomotive engine, on the contrary, its average resistance is not less than 61bs. on the 
 square inch ; and when running very fast, and the issue of waste steam is almost 
 continuous, the whole loss of power amounts to nearly half that of the engine. But 
 the draught must be obtained by an expenditure of some of the power of the engine, 
 whatever means maybe em ployed to produce it; and the plan of producing it by the 
 blast of waste steam is the best, as no power is wasted upon working any machinery 
 for the purpose, and it has the advantage of great simplicity in its application. In 
 some locomotive engines, made by Messrs. Braithwaite and Ericcson, a revolving 
 fan-wheel, worked by the engine, has been used to perform the same operation of 
 drawing the air from the flues ; and in the " Novelty," by the same makers, one of 
 the engines that competed for the prize on the Liverpool and Manchester Railway, 
 air was forced into the fire-box, but that plan was afterwards abandoned from 
 its being found not so advantageous. 
 
 The force of the draught produced by the steam-blast is so great that cinders are 
 drawn through the tubes and even thrown red hot out of the top of the chimney ; 
 sparks are also emitted occasionally, and have sometimes caused accidents. To pre- 
 vent the cinders and sparks from getting out of the chimney, a wire sieve is often 
 fixed on the top of the chimney, but this has a disadvantage in impeding the draught 
 
LOCOMOTIVE ENGINE. 417 
 
 and the exit of the waste steam very considerably ; though it is made convex and 
 larger than the chimney, so as to have a larger surface, and to impede the passage as 
 little as possible. The sieve is, however, but an imperfect remedy, for the cinders 
 are thrown against the sieve with so much force, that the meshes are soon 
 destroyed. A sieve has been tried placed at the bottom of the chimney, 
 so that the blast pipe ran through it, and in this position it afforded much less 
 obstruction to the draught than when placed at the top of the chimney ; for the blast of 
 steam which produces the draught being entirely above it, would not be impeded, and 
 the loss of power from impeding the exit of the waste steam would also be avoided. 
 But the plan was afterwards abandoned, as the sieve was found to be destroyed so 
 quickly as to require constant repair, from being exposed immediately to the air, and 
 to all the cinders, that are drawn through the holes, striking against the front plate 
 of the smoke-box, and rebounding upwards towards the chimney. 
 
 DAMPER. I I, (Plates LXXXIX., XC., and XCII.,) is a damper placed in the chim- 
 ney just below the top of the blast pipe, consisting of a thin iron plate fitting the 
 chimney closely, with a hole cut in its centre just large enough to allow the blast 
 pipe to pass through. A flat bar is bolted on to it to serve as a spindle, and fixed 
 a little out of the centre, in order to clear the blast pipe when the damper is elevated, 
 as shewn in Plate XC. This spindle is made round at each end, and turns in bosses 
 riveted to the outside of the chimney; one end passes quite through, and has a 
 short lever, q, fixed on to it ; the diameter of this end of the spindle is of the same 
 size as the width of the flat part, to allow of the spindle being put into its place 
 through the hole in the boss in which it turns, before it is attached to the damper 
 in the chimney. A long rod, r r, (Plates LXXXIX. and XC.,) is attached to the 
 lever, q, on the spindle, and reaches to the top of the fire-box, terminating in a 
 handle, and resting in an iron fork, s, fixed in the top of the fire-box, in which either 
 of two notches made in the rod can catch; so as to hold the damper either vertical, 
 as in Plate XC., or in a horizontal position, closing up the chimney, as shewn by 
 the dotted lines across the chimney in Plate XC. 
 
 The damper is used to check the draught when a less intense action of the fire is 
 required, such as when the engine is standing still or running down hill, and very 
 little power is wanted ; it causes very little obstruction to the exit of the waste 
 steam, as the blast pipe passes through it. It is a curious circumstance, that whilst 
 the damper is raised, the waste steam passes out of the chimney in an invisible 
 state unless the atmosphere is nearly saturated with moisture, from the increased 
 capacity of the hot air for moisture enabling it to absorb the steam in the chimney. 
 A slight change in the dryness of the atmosphere, or the temperature of the engine 
 fire, causes the steam to be visible ; and hence it is always visible in winter, 
 
 3 G 
 
418 STEPHENSON'S PATENT 
 
 and in summer is invisible only when the hygrometer is high ; its appearance is, 
 indeed, a tolerably correct indication of the hygrometric state of the atmosphere. 
 When the damper is lowered, the steam instantly becomes visible from the want 
 of hot air to absorb it, and it then issues from the chimney in dense white 
 volumes. 
 
 SMOKE-BOX DOORS. A large door, 1 1, (Plates XC. and XCII.,) is made in the 
 front plate of the smoke-box, for the purpose of affording access to the cylinders 
 and the tubes ; there is a ledge fixed inside round the opening, against which the 
 door is closely pressed by four finger nuts, put upon screws fixed in the smoke-box 
 plate, and passing through projecting lugs upon the door. There is also a small 
 door, u, near the bottom of the smoke-box, for the purpose of clearing out the 
 cinders and ashes that collect in it : both doors have to fit closely, that no air may 
 enter at them to impair the draught. 
 
 FEED PUMPS. The boiler is supplied with water by the two feed pumps K K, 
 which are worked by the engine ; their construction will be explained afterwards. 
 One of them is sufficient to supply the necessary quantity of water for the boiler, 
 and the other is thrown out of action ; but two are furnished in the engine, in 
 order that if one should fail from any accident, the other may take its place without 
 any delay being caused. On forcing the water into the boiler, it checks the generation 
 of steam by its coldness, and the effect of the engine is also diminished in consequence 
 of the power required to work the pump ; for this reason the action of the feed-pump 
 is generally suspended when the engine is ascending an inclination, and requires its 
 greatest power, and the supply of water is made up by working both pumps on a 
 succeeding level or descent : this is an additional advantage in having duplicate 
 pumps. A small cock, called the pet cock, is fixed in the pipe leading to the boiler from 
 each pump, and a long handle, v, is fixed to it, extending to within reach of the engine- 
 man, standing behind the engine ; these cocks are opened occasionally to ascertain 
 whether the pumps are working properly, when a stream of water should be forced 
 out at each stroke *. 
 
 * The pet cock was invented by Mr. George Stephenson, to obviate what was for some time an 
 incurable defect in the feed pumps of locomotive engines, the pumps could not be made to keep in 
 action, as they were fixed close to the boiler, and hot water entered from the leaking of the valves, 
 causing them to be filled with steam instead of water at each stroke ; thus preventing them from 
 forcing any water into the boiler, which could, therefore, be used only for a short time, whilst the 
 water in it would last, the boiler having then to be emptied of steam and refilled. The cause of this 
 stoppage of the action was at length discovered, and the pet cock applied, by opening which the steam 
 in the pump was let out, and the action renewed ; the name was given to it playfully, from its petting 
 or coaxing, as it were, the pump to do its duty. It is not now required for this purpose, as the pump 
 is separated from the boiler by a long tube with a valve at each end, and the hot water cannot get into it. 
 
LOCOMOTIVE ENGINE. 
 
 419 
 
 FIG. 8. 
 
 GAUGES. L L, (Plates XC. and XCII.,) is a glass gauge for show- 
 ing the height of the water in the boiler ; it is shewn detached in 
 fig. 8, which is a section through the centre of it to a scale of 2% 
 inches to a foot, or three times the size of the engraving. The 
 gauge consists of a strong glass tube, A, fig. 8, about three quarters 
 of an inch diameter outside, fitted into a brass socket, B B, at top 
 and bottom, the joints being made steam-tight by hemp packing, 
 put round the glass, and compressed against it by the glands C C, 
 which are screwed in round the glass. From each of the socket- 
 pieces B, a tube, D, proceeds with a cock in it and a screw on 
 the end for fixing it into the fire-box ; and the piece E, containing 
 another cock, is screwed into the lower piece, and the plug F into 
 the upper piece, affording the means of putting the glass tube down 
 into its place. When the two cocks in D D are opened, the water 
 of the boiler rises in the glass tube to the same height that it is in 
 the boiler, the upper part of the glass being filled with steam, 
 the height of the water in it shewing always the level of the 
 water in the boiler ; the cocks are for the purpose of stopping 
 the communication, when required, from the gauge being out 
 of order or otherwise. The cock in the piece D is for the purpose of clearing 
 out the gauge, by allowing a stream of water to run through it ; and it is often 
 necessary to open it when examining the gauge, in order to get rid of the bubbles 
 of steam formed by the rapid ebullition of the water, which sometimes render it 
 difficult to ascertain the precise height of the water. The difficulty is also in- 
 creased by the motion of the engine producing oscillation in the water ; but the 
 disturbing effect is much diminished by choking the tube, or making the communica- 
 tion with the boiler through the tube D very small, so as to impede the motion of 
 the water in the tubes. A small plug, G, is screwed in opposite each tube, D, to 
 afford the means of clearing out the tubes D, by passing a wire through them when 
 the plugs G are taken out. 
 
 To afford an additional means of ascertaining the height of the water in the 
 boiler, two gauge cocks, M M, are fixed in the side of the fire-box, one being four 
 inches above the other, and the lower one, one inch above the top of the internal 
 firebox. The boiler is generally filled at starting, until the water runs out at the 
 upper cock ; and during working the water level is kept between the two cocks, 
 and often up to the upper one. The cocks are opened occasionally to try the level, 
 and if steam should ever be found to blow out at the lower cock, showing that there 
 is not more than one inch of water over the roof of the internal fire-box, instant 
 attention has to be paid to the feed-pumps, and the fire damped if necessary, to 
 
420 
 
 STEPHENSON'S PATENT 
 
 FIG. 8. 
 
 prevent the roof of the fire-box being uncovered and getting burnt. The glass tube 
 is, however, the more certain guide, being less affected by the oscillations of the 
 water than the gauge cocks. 
 
 THE LEAD PLUG, m, (Plates XC. and XCII.,) described before, is an additional 
 security against any accident arising from the water being suffered to get too low 
 in the boiler. 
 
 SAFETY VALVES. The pressure of steam in the boiler is regulated by the safety 
 valve N, (Plates LXXXIX., XC., and XCII.,) the construction of which is shewn in 
 fig. 9 and 10, drawn to a scale of 2^ inches to a foot, or three times the size of the 
 engraving. Fig. 9, is a longitudinal section through the valve, and fig. 10, a plan of 
 the valve-seat with the valve removed. The valve A is made of brass ; it is 
 conical round the edge, or mitred at an angle of 45, and has 
 a spindle or stalk, B, cast on it in the middle. The seat 
 C of the valve is also of brass, and is cast with a flange 
 at the bottom, to bolt it on to the boiler ; and the valve 
 is ground into the upper part, so as to fit it steam-tight. 
 The opening in the valve seat, C, is 2ij inches diameter, 
 and across it is cast a thin piece D, extending to the 
 bottom, and having a longitudinal hole through it, in 
 which the spindle J3 of the valve works ; this is to hold 
 the valve steady when it is raised, and to guide it into its 
 seat again. A projecting lug, E, is cast on the valve 
 seat, in which is fixed the standard, F ; this is forked at 
 the top, and receives the end of the lever G, which turns in it upon a centre pin ; a 
 rod, H, is jointed to the lever by another pin, at 3 inches from the former one, and 
 bears directly upon the valve. 
 
 At the other end of the lever, and at a length of 3 feet from the fulcrum, is 
 attached by a finger nut, the rod of a common spring balance, w, (Plates LXXXIX. 
 and XCII.,) the bottom of which is fixed on to the fire-box ; this spring balance is 
 screwed up by the finger nut on the valve lever, until the required pressure on the 
 valve is produced, which is generally 50 Ibs. on the square inch above the at- 
 mosphere; and the valve, on rising to let out the surplus steam, has to raise the 
 spring balance, which acts upon it with twelve times the leverage. 
 
 In stationary engines, the safety valve is kept down by a weight hanging on the 
 lever, and shifted to different positions to alter the pressure on the valve ; but in a 
 locomotive engine a weight could not be used, because the motion of the engine 
 would cause it to jolt up and down, and the valve would be continually letting off 
 steam. There is one disadvantage attending the use of the spring balance that the 
 other plan is free from ; namely, that any opening of the valve by raising the lever, 
 
 FIG. 10. 
 
LOCOMOTIVE ENGINE. 421 
 
 compresses the spring in the balance more, and increases the pressure upon the 
 valve, so that the free egress of the surplus steam is checked, and the pressure of 
 the steam is allowed to become greater than that indicated by the balance when the 
 valve is shut ; the longer the lever is, the greater is this difference of pressure, and 
 it is sometimes as much as 10 Ibs. per square inch. 
 
 In observing the pressure on the safety valve, allowance must also be made for 
 the effect of the mitre, or conical part of the valve ; for when it is raised, the steam 
 acts on the conical part as well as on the bottom of the valve, and has therefore a 
 greater power in lifting the valve ; and this diminution of the pressure on the valve 
 varies with the extent of the mitre and with the degree that the valve is opened. 
 
 These different circumstances render the safety valve but an imperfect means of 
 ascertaining the pressure of the steam in the boiler. In stationary engines, which are 
 generally w r orked at a much lower pressure, a mercurial gauge is often used to 
 indicate the pressure of the steam ; but this instrument cannot be used in a loco- 
 motive, as a tube of great size, and not less than twelve feet high would be re- 
 quired ; it has, however, been used as a means of testing the accuracy of the in- 
 dications of the safety valve by a temporary connection with the engine. 
 
 0, (Plates LXXXIX. and XC.,) is the lock-up safety valve, enclosed in a case, to 
 prevent access to it so as to increase the pressure to a dangerous degree. The 
 valve is exactly similar in construction to the other safety valve, but instead of 
 being held down by a lever and spring balance, several small elliptical springs, x x, 
 (Plate XC.,) about six inches long, are placed one above another and over the valve, 
 and pressed down by a screw at the top in the frame y y, fixed into the valve seat. 
 By turning this screw, the pressure on the valve can be adjusted to any required 
 degree ; and when the case is fixed on, the valve is effectually protected from having 
 the pressure altered. The lock-up valve is loaded rather more heavily than the 
 ordinary working pressure, 50 Ibs. ; so that it does not blow except when the pres- 
 sure has exceeded that limit, as in performing work requiring more power than 
 usual. 
 
 A large spiral spring is used in some engines to press upon the valve, being fixed 
 in a similar manner to the elliptical springs ; it is rather more compact, but is not quite 
 so free in its action, as the pressure increases more rapidly on the using of the valve. 
 
 MAN HOLE. P, (Plates LXXXIX. and XC.) is a circular opening into the boiler, 
 called the man hole ; it is 1 6 inches in diameter, and surrounded by a ring, z, (Plate 
 XC.,) bolted on to the boiler, having a flanch at the top for fixing on the cover. 
 This opening is large enough for a man to enter, and affords access to the interior of 
 the boiler for making repairs in it, or for cleaning it out. 
 
 MUD HOLES. These are two small openings, Q Q, in both sides of the fire-box at 
 the bottom, closed by plates bolted upon the outside, and are for the purpose of 
 
422 STEPHENSON'S PATENT 
 
 cleaning out the fire-box and removing the sediment that is deposited from the water. 
 Two mud holes, at opposite corners of the fire-box, are usually opened twice a 
 week, and the deposit washed out by directing a stream of water into them ; each 
 pair of opposite holes being opened alternately. The boiler does not often require 
 cleaning, but it is occasionally washed out by putting the water hose in at the man 
 hole, and washing all the sediment into the fire-box ; this is found to be quite suf- 
 ficient to keep it clean. 
 
 BLOW-OFF COCKS. R R are two cocks, one inch in diameter, fixed one in each 
 side of the fire-box, close to the bottom, for the purpose of emptying the boiler ; 
 this is called blowing off", as it is done just after the engine has left work, and the 
 water is blown out with great force by the pressure of the steam. This blowing 
 off serves to cleanse the boiler, and the whole water has to be thus emptied out 
 two or three times a week when the engine is in full work, as it gets foul after 
 remaining in the boiler for some time. 
 
 FIRE AND HEATING POWER. The fuel used is coke, and is that most generally 
 used in locomotives ; coal was employed in the first ones, and is now made use of 
 on railways in the collieries and where passengers are not carried ; but on the 
 large public railways it is inadmissible on account of the smoke that is produced. 
 Coke has an advantage over coal in being very light in substance and not caking 
 together, but allowing the draught of air to pass freely through the fire ; it is also 
 capable of attaining a very intense degree of ignition ; but its lightness renders it more 
 liable to be drawn through the tubes by the draught, and the fine dust or ashes, pro- 
 duced by its combustion, is very annoying to outside passengers. The coke used is 
 of the best quality ; and the operation of coking the coal is performed only with a 
 view to the abstraction of the volatile parts, as the hydrogen, and the losing as little 
 as possible of the carbon ; gas coke or the remains of the coal used in gas works is 
 very inferior, being overburnt and having lost a good deal of its carbon to form the 
 gas, carburetted hydrogen ; it also contains a good deal of sulphur, which is very in- 
 jurious to the metal of the boilers ; this causes also the principal objection to the 
 use of coal. The coke used in the locomotives on the London and Birmingham 
 Railway is made upon the works, and is very nearly pure carbon. Welsh stone 
 coal or anthracite has been also tried ; it produces no smoke or flame, being almost 
 pure carbon, like coke ; but it appears to be not suited to locomotives, from its den- 
 sity and flying into small pieces, so as to form a close mass on the fire-grate, and not 
 allow a sufficiently free passage for the air through the fire. 
 
 The fuel is carried in the tender behind the engine and immediately contiguous to 
 the fire-door, so that it can be readily shovelled into the fire when required ; it is sup- 
 plied on an average in quantities of about half a cwt. at intervals of from five to ten 
 minutes. The heating the water in the boiler and getting up the steam takes about 
 
LOCOMOTIVE ENGINE. 423 
 
 an hour and three quarters on an average, and requires the consumption of about one 
 and a half or two cwt. of coke ; in some places the boiler and tender are supplied 
 with hot water by means of a stationary boiler, in order to expedite the getting up of 
 the steam, and also as a means of economy. 
 
 The area of the fire-grate is 9^ square feet; it is 18 inches below the bottom of 
 the lowest tubes, and the space for the fire when quite filled up to the tubes is 14 
 cubic feet, and holds about 2^ cwt. of coke ; but the fire-box is not always filled so 
 full as this, and usually contains about one and a half or two cwt. 
 
 The surface of water exposed to the heat directly radiated from the fire is the 
 whole surface of the internal fire-box, deducting the fire-door and the tubes, and is 
 equal to 50 square feet ; and that exposed to the current of hot air, or conducted heat, 
 is the interior surface of the tubes, and is equal to 432 square feet. The surface 
 exposed to radiated heat is considerably more efficacious in generating steam than 
 that exposed to conducted heat only, as the supply of heat is more copious, and the 
 proportion was found to be about three times in an experiment tried by Mr. Stephen- 
 son, which is the only one that has been made upon the subject ; the experiment was 
 made with an old engine and the proportion may be somewhat different in the mo- 
 dern engines. 
 
 The area of passage for the heated air from the fire-box to the chimney is the 
 sectional area of all the tubes inside the ferrules ; the ferrules are three eighths of an 
 inch less than the outside of the tubes, and are therefore an inch and a quarter in diame- 
 ter inside; and the sectional area of them all, (124 in number,) is T06 square feet. 
 The area of the passage through the chimney is rather more, or T23 feet. 
 
 In the Rocket engine the area of passage through the tubes was '90 square feet or 
 nearly the same as in this engine, though the fire-grate was but half the size ; but 
 the heating surface of the tubes was only one third, from the large size and small 
 number of the tubes ; the heating surface of the fire-box was also only three quarters 
 of that of the present engine. 
 
 In the old engines before the Rocket, the area of passage through the flue was 
 two and a half times the size, but the heating surface was only one thirteenth of 
 that in the present engine; the fire-box had also only one fifth of the heating surface; 
 the fire-grate was three quarters of the size. 
 
 THE CYLINDERS AND THE MANNER OF USING THE STEAM. 
 
 STEAM PIPE. SS, (Plates XC. and XCII.,) is the steam pipe for conveying the 
 steam from the boiler to the cylinder where it is to be used ; it is made of copper 
 three sixteenths of an inch thick, and the part within the boiler is 5 inches' diameter in- 
 side ; it passes through the tube plate of the smoke-box and is bolted to it by a flanch. 
 The pipe then divides into two smaller ones, 3| inches in diameter, which pass down 
 
424 STEPHENSON'S PATENT 
 
 on each side of the smoke-box to the cylinders, as shown in Plate XCII. Fig. 4 ; they 
 are turned on one side in order to keep them clear of the tubes, so as to allow access 
 to all the tubes, that they may be taken out when necessary through the smoke- 
 box door. It is also necessary to protect the steam pipes from the immediate action 
 of the hot air issuing from the tubes, which is nearly hot enough to melt copper. In 
 the first engines, the steam pipes were brought straight down to the cylinders across 
 the ends of the tubes, but they were found to be very rapidly destroyed. 
 
 The area of the large steam pipe is 19'6 square inches, and is equal to the areas of 
 both the small ones, which are 9'6 square inches each. 
 
 The other end of the steam pipe is connected to the box a, (Plate XC.,) by means 
 of the stuffing box b', containing packing made of loose spun hemp, called gasket, com- 
 pressed against the steam pipe by the brass gland c, which is bolted to a flanch on 
 the stuffing box b'. This stuffing box is necessary because iron expands by heat only 
 two thirds as much as copper, so that when the boiler and its contents are heated, 
 the wrought iron increases in length less than the copper pipe, and the pipe would 
 be very much strained if it were rigidly fixed at both ends, and the joint would soon 
 become defective by the repetition of the action ; but the stuffing-box allows the end 
 of the pipe to slide through it, and still keeps the joint steam-tight, preventing all 
 injurious action*. 
 
 The steam enters through the funnel-shaped copper pipe d', (Plate XC.,) which is 
 fixed upon the top of the box a, and this pipe rises nearly to the top of the steam dome 
 T, which is made of brass, cast three eighths of an inch thick, and is 1 5 inches in 
 diameter and 2 feet high, and bolted down by a flanch on to the fire-box. The 
 object of this steam dome, and of carrying the steam pipe up to the top of it, is to 
 obtain the steam as pure and dry as possible, by taking it at a distance from the 
 water ; because from the great agitation of the water in the boiler, and the rapid 
 emission of the steam to the cylinders, some of the water gets mixed up with the steam 
 in a finely divided state, and is liable to pass over with the steam into the cylinders. 
 This effect is called priming, and is very injurious when it takes place to any extent, for 
 all the water carried over into the cylinder is wasted and occupies the place of steam, and 
 thus diminishes the power of the engine ; but principally because it accumulates in the 
 cylinder and sometimes remains in it, being unable to escape with the waste steam ; 
 and in that case, from being so incompressible, it causes the breaking of some part 
 of the engine. By carrying the steam pipe up into the dome, the quantity of 
 water taken with the steam is very much diminished, as it has time to separate, and the 
 expanded end of the steam pipe nearly filling the dome, serves to catch the water and 
 prevent its entering the steam pipe. 
 
 * The brass tubes of the boiler are liable to the same action, but as they are small and very firmly 
 fixed at the ends, the expansion is immaterial, the tubes allowing for it by bending slightly. 
 
LOCOMOTIVE ENGINE. 
 
 425 
 
 Fie. 11. 
 
 The priming is much increased when the water in the boiler is not clean or pure ; 
 and an engine that does not prime perceptibly with good water may prime very much 
 if supplied with impure or hard water. When priming, the water is thrown out in a 
 shower from the chimney at each blast, and the power of the engine is very much 
 impaired, as the violence of the ebullition of the water is thereby greatly increased. 
 The prevention of the priming was found to be a very great difficulty in the first 
 locomotives, and several contrivances were made use of for the purpose ; such as 
 making the steam pass through a plate pierced with holes before entering the steam 
 pipe, or dividing the dome by a plate over which the steam had to pass to the steam 
 pipe. But it has been observed that the priming has been gradually diminished by 
 increasing the steam room or space in the boiler occupied only by steam ; for this 
 renders the generating of the steam more uniform, as the abstraction of the successive 
 cylinders full of steam is less felt and causes less agitation when the total quantity 
 of steam is greater. In the first locomotives very little steam room was afforded, but 
 in this engine the steam room is generally about 44 cubic feet, and there is no per- 
 ceptible priming under ordinary circumstances. 
 
 REGULATOR. In the box a (Plates XC. and XCII.,) is placed the 
 regulator e, extending across the box so that all the steam must pass 
 through it before it can enter the steam pipe S ; and by means of this 
 the steam is either shut off or allowed to enter the steam pipe in greater 
 or less quantities. The regulator is shewn in figs. 11, 12, and 13, 
 to a scale of double the size of the engravings, or 1^ inch to a foot. 
 The box is made of cast iron half an inch thick, and has a plate, A, 
 extending across it, with two openings BB, of nearly a quadrant each; the diameter of 
 the opening is 8^ inches, and that of the solid part in the centre separating them, 2 
 inches. The brass plate C, placed against this plate, fits 
 exactly the space between the openings B B, and if turned 
 round and placed over the openings would project beyond or 
 overlap them three quarters of an inch on each side, as they 
 are three quarters of an inch smaller than a complete quadrant. 
 The spindle D passes through a boss in the centre of the plate 
 C, turning at its end in a socket in the plate A, but without 
 touching the bottom of the socket, and a small pin is fixed 
 into the spindle fitting into a notch, E, in the centre boss, 
 to enable the spindle to turn round the regulator plate C, 
 and yet allow it to be withdrawn a little without draw- 
 ing the regulator plate away from the other plate. The 
 plates are held together by the pressure of the steam; and by 
 
 3 H 
 
 FIG. 12. 
 
426 STEPHENSON'S PATENT 
 
 forming the connection with the spindle in this manner, they are enabled to keep in 
 close contact, although the position of the spindle should be altered ; and the regulator 
 plate is still made to turn with the spindle. 
 
 The two plates are ground together, so that when the regulator plate is turned round 
 and covers the openings, the passage is closed completely steam-tight ; the under 
 side of the regulator plate, and the solid space between the openings in the other 
 plate, are both hollowed a little in the middle, as shewn in the section through the 
 centre of each, in fig. 13, so that they touch only for a space of three quarters of an 
 inch round the edge. This diminishes the labour of grinding them, as there is so 
 much less surface to grind, and also ensures their fitting round the edges, where 
 alone it is required ; for the little steam that will pass through the hollow between 
 the plates when the regulator is partially open, is of no consequence, as it will only 
 slightly increase the quantity of steam passing through. 
 
 The other end of the box a, (Plate XC.,) is fixed by a flanch to the back plate 
 of the fire-box ; and an opening is cut in the plate corresponding to the inside of 
 the box, which is closed by a plate, having the stuffing-box/', fixed on to its 
 inside with its gland g. The spindle of the regulator turns steam-tight in 
 this stuffing-box, a collar on the spindle resting against the end of it ; and the 
 handle, //, is fixed on the end of the spindle, moving between two brass arcs, z", 
 (Plate XC., and fig. 1, Plate XCII.,) which are connected together at the ends, and 
 bolted on to the fire-box : these arcs serve as guides for the handle when moved, 
 and stop it at each side. In fig. 1, Plate XC., the regulator is shewn quite open; 
 but if it were made to turn round, it would immediately begin to contract the pas- 
 sage for the steam, and when turned a quarter round, the passage would be com- 
 pletely closed. The motion of the handle is therefore through a quarter of a circle, 
 or half a quadrant on each side of the vertical position. When the handle is put 
 down on the right hand side, the regulator is shut, and when down on the left side, 
 it is full open ; and in intermediate positions the regulator is proportionally open, 
 except for the small distance at each end along which it is passing over the over- 
 lap. The area of passage through the regulator when full open, is 21 '9 square 
 inches, or a little more than the area of the steam pipe, which is 19'6 square inches. 
 
 This is the form of regulator that is most frequently used, as it is simple in its 
 construction and not liable to get out of order, and particularly as it is very 
 uniform and regular in its action ; and excepting the small overlap, the degree of 
 opening is exactly proportionate to the amount of motion of the handle. Another 
 contrivance that is also used for the purpose, consists of a conical valve like a 
 safety valve, which closes the end of the steam pipe; and is drawn away gra- 
 dually from its seat, when turned round with the handle, by means of a fixed pin 
 
LOCOMOTIVE ENGINE. 427 
 
 fitting in a spiral groove on the spindle, similar to a screw ; only that the groove 
 makes but a quarter of a turn round the spindle, and is very much inclined to it, 
 so as to cause the valve to be sufficiently drawn back by a quarter turn of the 
 handle. This regulator is very efficient, and acts a little more uniformly than the 
 other, but the friction in it is greater from the spiral motion, and it is more liable 
 than the other to get out of order and stick fast. 
 
 STEAM CHESTS. The steam chests or slide valve boxes U U, (Plates XC., XCL, and 
 fig. 4, Plate XCII.,) are made of cast iron half an inch thick; and are bolted down upon 
 the top of each cylinder, and to the front plate of the smoke box, in which holes are cut 
 of the same size as the steam chests, and closed by cast iron plates termed bonnets 
 bolted on the outside. The steam chests have the two branches of the steam pipe 
 fixed upon them at the back, and opening into them ; and a stuffing box, k', is cast upon 
 the end of each, passing through the tube plate n, the joints being completely and 
 firmly closed by running melted lead into it all round. 
 
 SLIDE VALVES. In the steam chests are placed the slide valves, V V, shown in section 
 longitudinally and across in Plate XC., and fig. 4, Plate XCII. They are brass boxes 
 lij inch deep inside and three eighths of an inch thick, having flanches five eighths of 
 an inch thick all round them at the bottom. The slide valves are made to move 
 backwards and forwards by the spindles /', which have each a cross piece at the end 
 that fits into a notch in the back of the valve ; the spindle is generally connected to 
 the valve by means of a rectangular wrought iron frame, called a bridle, dropped 
 over the valve and having the spindle screwed into it. The bridle has an advan- 
 tage in holding the valve very steady, and yet allowing it to drop through readily 
 as it is worn by friction, and thus keep always in contact with the surface that 
 it slides upon. The valve spindle t moves steam-tight through the stuffing box k' at 
 the inner end of the steam chest. 
 
 CYLINDERS AND PISTON. The cylinders, HH, where motion is produced by 
 the pressure of the steam, are made of cast iron, five eighths of an inch thick 
 and 12 inches diameter inside, and are bored out perfectly smooth and cylindrical. 
 A box is cast on the top of each cylinder, running along its whole length and flat 
 on the upper side, containing two hollow rectangular passages m, ri, and another 
 passage d, between them; these are separated from each other, and the ends 
 of them are shown coming to the outside and opening into the steam chest at the 
 leit cylinder, (Plate XCI.) The two outer passages m, ri, are the steam ports; they 
 are eight inches long and one inch wide, and open one into each extremity of the 
 cylinder, for the purpose of conveying steam to and from the cylinders ; their area 
 is 8 square inches, or rather less than the area of the steam pipes. The other pas- 
 sage o, is the waste steam port, of the same length, and one inch and a half wide on the 
 face ; expanding inside, as shown in Plate XC., occupying all the space between the 
 
428 STEPHENSON'S PATENT 
 
 steam ports, and passing round the cylinder (as in fig. 4, Plate XCII.) until it clears the 
 steam chest and comes to the outside again opposite to the other cylinder ; having 
 gradually assumed a circular form three inches and three quarters in diameter, as 
 shown by the dotted lines in Plate XC. The cross area of this passage is made of 
 such dimensions that although it alters in shape, it is in all parts equal to the area at 
 the end, that of a circle three inches and three quarters diameter or 1 1 inches area. 
 On the outside of this opening in each cylinder are fixed the two ends of the branch- 
 ing copper pipe p, of the same diameter, termed a breeches piece, and having the blast 
 pipe P bolted on to it. The piece p is fixed on to the cylinders by screws put into holes 
 tapped to receive them in the solid metal, as there is no place for nuts. The steam chest 
 is also fixed on to the cylinder at the hinder end in the same manner. The flanches are 
 made rather thicker to allow for being weakened by the holes in them, and those of the 
 copper pipes are three eighths of an inch thick, and made of brass soldered on to the 
 pipe ; the pipes are made of one eighth of an inch sheet copper lapped and soldered at 
 the edges. A layer of canvas or of gasket, like that used for packing, covered with red 
 lead and oil, is placed between the flanches of the pipes and under the flanch of the 
 steam chest, and in all other similar joints, in order to make them steam-tight. 
 
 The face of the ports that the slide valve moves upon is made quite even and 
 true by a planing machine, and the valve Is ground upon the face to make it fit 
 steam-tight ; the face is sunk down round the ports beyond that part over which 
 the slide moves, in order to diminish the surface to be planed and ground. The 
 spaces between each of the steam ports and the waste port, called the bars, are one 
 inch wide. A section of the slide valve, quarter size, is shown in fig. 14, where 
 A and B are the back and front steam ports, 
 
 * 
 
 C is the waste port, and DD the bars. The 
 width of the slide inside is the same as the 
 ports, as shown in fig. 4 (Plate XCII.); the 
 length E, (fig. 14,) is one-eighth of an inch 
 less than the distance between the ports, and 
 the flanches F and Cf are one-eighth of an inch wider than the ports ; so that when 
 the slide is in a central position, as shown by the dotted lines, the flanches F and 
 G lie exactly over their respective steam ports, and overlap them one-sixteenth of 
 an inch on each side. This overlap is for the purpose of ensuring that one port is 
 completely closed before the other is opened, in order that they may never com- 
 municate with each other under the slide during its motion, nor the steam be 
 allowed to enter both ports at the same time. 
 
 The slide valve is moved backwards and forwards a distance of 3 inches, or 1-^ 
 inch on each side of the central position, and is carried beyond the inner edge of 
 each steam port alternately, a distance of nearly half of an inch, as shown in 
 
LOCOMOTIVE ENGINE. 429 
 
 fig. 14, before its motion is changed and it begins to move back again; this dis- 
 tance that the slide moves beyond the port is called the travel. The waste port 
 is always covered by the slide, as the travel is less than the width of the bars, 
 so that the steam is always prevented from entering the waste port from the 
 steam chest. During the reciprocating motion of the slide, each of the steam 
 ports is alternately uncovered, and the steam allowed to enter and flow into the 
 cylinder ; the port is than covered again by the slide, and when the flanch has 
 passed over, communicates through the inside of the slide with the waste steam 
 port, allowing the steam which has performed its duty in the cylinder to escape 
 by the port at which it had entered, into the waste port and out at the blast pipe ; 
 this action is called the eduction. The slide valve is held upon the face of the 
 ports only by the pressure of the steam upon it, which is quite sufficient to keep it 
 always steam-tight whilst moving; as all the inside of the slide is open to the air 
 through the waste port, and the flanches fit air-tight upon the face of the ports, so 
 that the whole pressure of the steam upon the slide is effective in keeping it down ; 
 the area of the slide being 55 square inches, the pressure upon it is about 
 l-if tons. In large stationary engines the steam is admitted under the slides, as 
 the pressure of the steam upon the slides would be more than is necessary to keep 
 them tight, and would cause very great friction ; the slides have, in this case, to be 
 held down by other means, as packing or springs upon the back of them. At the 
 extreme position of the slide, as in fig. 14, the inner edge of the flanch G ap- 
 proaches the opposite bar, thus contracting the opening of the waste port to the 
 size of the port out of which the steam is escaping ; if contracted more, the free 
 exit of the steam would be obstructed. 
 
 The front end of each of the cylinders is closed by a cast iron cover W, seven 
 eighths of an inch thick, let into it; the cylinder runs through the plate of the smoke 
 box, projecting beyond it, and having a flanch resting against the inside of the plate, 
 and fixed to it by bolts, which are screwed through the plate into the flanch. The 
 cylinder cover W is of the same size as this flanch, and is held on to the cylinder 
 by the same bolts that fix the cylinder to the smoke box plate ; the heads of the 
 bolts are made thin to clear the cover, and the bolts are prolonged beyond their 
 head to pass through the cover, and have nuts screwed upon them on the 
 outside. The other end of the cylinder has also a flanch, by which it is bolted to the 
 inside of the tube plate; this is shewn on a larger -scale in figs. 15 and 16, 
 which are a longitudinal and a cross section of the cylinder to a scale of 2 inches 
 to a foot, or three times the engravings. is a section of the cylinder; P P 
 the back steam port leading into the end of the cylinder ; Q Q is the tube plate 
 or back plate of the smoke box; and R the flanch upon the cylinder, similar to that 
 at the other end. The cylinder runs through the plate, and comes flush with 
 
430 
 
 STEPHENSON'S PATENT 
 
 FIG. 1C. 
 
 the outside ; the joints and the space between the flanch and the plate are run with 
 lead all round to make the cylinder quite firm and steady, as the hole in the plate 
 does not accurately fit the cylinder ; the joint at the other end of the cylinder is also 
 run flush with lead for the same reason. The flanch is fixed to the plate by six three- 
 quarter inch bolts, which are screwed into the flanch from the outside, in order that 
 they may fit closely to the holes in the flanch and the plate, and hold the cylinder quite 
 steady. A flanch SS is cast on the inside of the end of the cylinder, projecting 
 into the cylinder, and the cover T is bolted to the outside of this flanch, 
 having a projection in the centre that fills up the opening, and makes the end of 
 the cylinder even or flush inside ; the cover is fixed on by six bolts, screwed into 
 the flanch of the cylinder, and having nuts on them on the outside ; the bolts are 
 made square where they pass through the cover, to prevent their turning when the 
 nuts are screwed on. It is not required to have ready access to this end of the 
 'cylinder ; but at the other end it is necessary that there should be no obstruction, as 
 the cylinder is required to be completely opened occasionally to get the piston in and 
 out. X (Plate XC.) is one of the pistons ; there is one in each cylinder, fitting the cy- 
 linders accurately, so as not to let any steam escape between them and the cylin- 
 ders when they are moved backwards and forwards. The piston is made entirely of 
 brass, and consists of a plate, A, (figs. 15 and 16,) five-eighths of an inch thick, 
 having a boss, B, cast on the centre, with three arms, CCC, three quarters of an inch 
 thick, also cast upon it, radiating from the centre and equidistant from each other. 
 
LOCOMOTIVE ENGINE. 431 
 
 These arms and the centre boss stand up 2^ inches from the plate A, and another 
 plate, D, of the same thickness as the first, is put upon them, making the whole thick- 
 ness of the piston 3f inches. The plate D is held steady in its place by a projection 
 on the centre boss passing through it, and is fixed by screws CC, tapped into the 
 bosses at the ends of the arms C, the heads of the screws CG being countersunk 
 into the plate D. The plates A and D are turned so as to be just capable of 
 moving in the cylinder without touching it, and three brass rings FF are placed 
 between them. The inner ring is three-eighths of an inch thick, and is the same 
 width as the space between the plates ; the two outer rings are half an inch thick, 
 and of half the width ; and one of them has a projecting ring or rebate upon its 
 edge, fitting into a corresponding groove in the other to keep them steady. The 
 rings are turned exactly to fit the cylinder and each other, and cut through in one 
 part, having been first hammered a little all round on the inside, which gives them 
 a tendency to expand, and causes them to fly open on being cut ; when, therefore, 
 they are put in their places in the cylinder, they press against the cylinder by their 
 elasticity, and keep in close contact with it, so as to make a steam-tight joint during 
 the motion of the piston. The divisions in the rings are placed in opposite positions, 
 or break joint, in order to prevent the escape of steam through them ; for if they 
 were to coincide, a passage would be left for the steam through the piston. 
 
 The elasticity of these rings is found to be quite sufficient to keep the piston steam- 
 tight when moved in the cylinder, and it continues so for a long time ; when, however, 
 the rings become so much worn by the friction as to have expanded nearly to the ut- 
 most, some other means is necessary to press them against the cylinder. For this pur- 
 pose the three steel springs OGG are placed in the piston; they are of the same 
 width as the inside ring, against which they bear, and one-eighth of an inch thick in 
 the middle, and a pin is put through each of them, having a collar bearing against 
 the spring, and screwed at the other end into the centre boss of the piston ; by un- 
 screwing the pin a little the spring can be made to press harder against the ring 
 when required, and the pin is then fixed by screwing up the set-nut upon it against 
 the boss. When the piston is first made and the rings are new, these springs are 
 not required, and they are set so as only to touch the rings ; but as the rings wear 
 and become too loose in the cylinder, the springs are screwed up more and more, 
 and made to press harder against the rings ; and when they are very much worn 
 they are kept tight to the cylinder by the springs only, as they have expanded to 
 their utmost. Access is readily obtained, when necessary, to the inside of the 
 piston, by taking off the front cylinder cover and unscrewing the front plate D of 
 the piston. 
 
 The pistons are often made upon different modifications of Barton's prin- 
 
432 STEPHENSON'S PATENT 
 
 ciple ; with two or more rings of cast iron or brass, about an inch thick, cut into 
 three or four segments, and having wedges inserted between them, which are con- 
 stantly pressed outwards by springs, so as to keep the segments always tight to 
 the cylinder ; the springs are either spiral or flat springs like those in the engrav- 
 ing, or a circular steel hoop, a little larger than a circle touching the ends of the 
 wedges, is forced in so as to bear against them. These pistons are liable to a de- 
 fect from which the other with the spring rings is free ; that of wearing grooves in 
 the cylinder where;! the points of the wedges rub against it, as the wedges have to 
 wear down faster than the segments ; the plan shown in the engravings is very 
 efficient, and appears on the whole to be the best. The hemp packing used some- 
 times in stationary engines is now generally superseded by metallic packing, as 
 it requires frequent renewal, and is unequal in its pressure, the piston having to be 
 packed very tight at first, in order to keep tight for any considerable time ; in 
 a locomotive, where the motion of the piston is very rapid, it would be quite in- 
 admissible. 
 
 H H, or Y, (Plates XC. and XCI.,) is the piston-rod ; it is If inches diameter, 
 and is made conical at the end, being increased to 2-| inches diameter in the centre 
 boss of the piston, which is fitted upon it very exactly, and fixed by the cotter or 
 key I, half an inch thick, and tapered slightly from 1-J inches wide; the piston rod 
 has to be fixed very firmly, and is split at the end, to prevent its getting loose. 
 The other end of the piston rod passes through the stuffing box K, (figs. 15 and 16,) 
 in the cylinder cover ; it is made of steel, and turned truly cylindrical, to move 
 through the stuffing box with as little friction as possible. The stuffing box 
 has a half inch space round the piston rod for the packing, which rests against the 
 brass ring or bush L, fitted on to a small flanch at the end of the stuffing box, 
 and is compressed by the brass gland M, which leaves about three inches for the 
 packing. The gland has two projections on the outer end, making an oval shape, 
 and is held by bolts passing through these projections and screwed into correspond- 
 ing projections on the stuffing box. 
 
 The piston is impelled by moving the slide valve from its central position, so as to 
 admit the steam from the steam-chest into the cylinder through one of the ports, as 
 in Plate XC., where the front port n is shewn open ; and the steam pressing against 
 the front of the piston impels it to the back end of the cylinder. The slide is then 
 moved to the opposite position, covering over the front port n, and opening the back 
 port m, to admit the steam behind the piston and impel it back again to the fore 
 end of the cylinder ; at the same time allowing the steam in front of the piston, 
 which had impelled it before to the back of the cylinder, and is now waste steam, 
 to escape by the inside of the slide and the waste port d, into the blast pipe, rushing 
 
LOCOMOTIVE ENGINE. 433 
 
 out thence up the chimney. At the end of this fore stroke the position of the slide 
 valve is again reversed to admit the steam in front of the piston and impel it to the 
 back of the cylinder, or make the back stroke ; the waste steam behind the piston 
 escaping through the back port and the inside of the slide into the waste ports as be- 
 fore : and on repeating the forward motion of the slide, another fore stroke is produced. 
 The steam is thus made to produce a reciprocating motion of the piston from one end 
 of the cylinder to the other ; by moving the slide backwards and forwards from one 
 extreme position, when one port is opened to the steam, to the other extreme, when 
 that port is closed and the other opened. The motion of the slide is in the same 
 direction as that of the piston, but precedes it, as it must take place before 
 the stroke of the piston ; and it is produced by the machinery, as will be ex- 
 plained afterwards. The amount of motion, or length of stroke of the piston, is 
 1 8 inches, and it moves to within half an inch of each of the cylinder covers. In 
 stationary engines, the action of the steam in the cylinder is exactly similar ; but the 
 cylinders are vertical instead of horizontal, and the strokes of the piston are up and 
 down instead of fore and back. The horizontal position of the cylinders is disad- 
 vantageous in causing an unequal wear of the pistons and cylinders, from the weight of 
 the pistons and piston rods acting always on one side ; and in also producing a strain 
 on the piston rod from the wearing of the piston. However, in locomotives, where 
 the pistons are very small and light, this unequal wear is quite imperceptible, 
 though in large stationary engines, whose pistons are several feet in diameter, the 
 action would be very injurious ; and many small stationary engines are also made 
 with horizontal cylinders, as the arrangement has several advantages in simplifying 
 and strengthening the machinery. 
 
 When the waste steam is let out at the end of each stroke, there is also let out the 
 steam occupying the space of half an inch at the end of the cylinder beyond 
 the stroke of the piston, and the quantity required to fill the ports, which are both lost 
 as they are expended without producing any effect. The steam lost at the ends 
 of the cylinder cannot be avoided, as some clearance must be allowed for the piston 
 to prevent the chance of its striking against the cylinder covers; and also to 
 allow space for the escape of water that may accumulate in the cylinder, either 
 from priming or from condensation of steam. To let out this accumulated water, a 
 cock, q, (Plate XC.,) fixed in a boss in the centre of each cylinder cover, is opened 
 occasionally. A small pipe, r, (Plates XC. and XCII.,) with a cock in it, is also 
 fixed into the lower part of the blast pipe, passing through the bottom of the smoke-box 
 for the purpose of letting out any water that may accumulate there. The steam 
 lost in the ports can be diminished by shortening them, and for this purpose double 
 slide valves have been used ; the ports were carried directly up from the cylinder at 
 
 3 I 
 
434 
 
 STEPHENSON'S PATENT 
 
 each end, a branch from the waste port being brought up alongside of them corre- 
 sponding in size and distance with the present one, and a separate slide placed over 
 each port. The action of the steam in this arrangement was exactly the same as in 
 the present one, but the quantity of steam wasted in the ports was much diminished. 
 Double slides were used in several of the first locomotives, but they have since been 
 abandoned ; as the quantity of steam contained in the ports is but small compared 
 with the contents of the cylinder, and the arrangement added considerably to the 
 friction and the complexity of the machine. However, in all stationary engines, ex- 
 cept some of the smallest, double slides are used, but they are generally of a different 
 construction and made together in one piece. 
 
 CROSS-HEADS AND GUIDES The outer, end of the piston rod Y is attached to 
 the cross head Z, (Plates XC., and XCI.,) shewn on a large scale in figs. 1 7, 1 8, 
 and 1 9, which are drawn three times larger than the engraving, or to a scale of 2^ 
 
 FIG. 17. FIG. 19. 
 
 Fie. 18. 
 
 inches to a foot. Fig. 17, is a plan ; one side being shewn broken off, as it is exactly 
 like the other side; fig. 18, is a longitudinal section through the centre; and fig- 
 1 9, a cross section shown complete on both sides. The end of the piston-rod A A 
 is turned down smaller, and fitted into the wrought iron socket B B by the key or 
 cotter and gib C and D ; the gib D being tapered like the key, making their outer 
 edges parallel. Two arms, E E, project from the end of the socket B, parallel to 
 
LOCOMOTIVE ENGINE. 435 
 
 each other, having a semicircular notch at the end fitted exactly to the cross head F, 
 which is a turned iron pin, one inch and three-quarters in diameter. The cross head F 
 is attached to the arms E E, of the socket B B, by wrought iron straps, G G, fitted 
 on to both, and fixed by the keys and gibs H and /; the gibs being required to 
 prevent the ends of the straps being sprung open by driving the keys. A small pro- 
 jection upon the cross head is fitted into a notch in one of the arms, D, in order to 
 prevent its turning round. 
 
 The ends of the cross head K K are inserted into two guide blocks, L L, 6 inches 
 long and if inch thick, with flanches on the inner side ; these are made of steel and 
 are grooved on the sides to save metal. Each of these guide blocks is placed be- 
 tween two steel bars, M N, 2| inches wide, fixed firmly to the frame of the engine, 
 and shewn at A' A', in Plates XC. and XCI. The guide blocks and bars are 
 ground together and fitted accurately, enabling the blocks to slide steadily and easily 
 between the bars ; the upper bar, M, is five-eighths of an inch thick, and the 
 lower one, N, one inch thick in the middle, and five-eighths of an inch at the ends ; 
 the two being connected firmly together by small pillars, c, (Plate XC.,) fixed 
 into them at each end. The lower bar, N, is required to be stronger than the upper 
 one, as it is only supported at the ends. The upper bar, M, is fixed to a piece of 
 angle iron, 0, (fig. 19,) by bolts P, with countersunk heads, ground down flush 
 with the bar ; small pieces of brass, Q, being interposed between the bar and the 
 angle iron at each of the bolts, affording the means of adjusting the bars accurately 
 level when the angle iron is fixed on to the engine framing R. The bars M N 
 are adjusted exactly parallel to each other, and to the axis of the cylinder, so as to 
 allow the blocks, L, to slide behind them without any strain when moved by the 
 piston rod and cross head ; and they serve the purpose of guiding the end of the- 
 piston rod, and causing it to move always exactly in the line of the axis of the 
 cylinder. 
 
 CONNECTING RODS. The connecting rods B'B', (Plates XC. and XCI.,) are 
 fixed at one end to the cross heads, and at the other end to cranks on the axle, C' C', 
 of the large wheels, D' D', of the engine ; they are of wrought iron, two inches 
 diameter in the middle, and taper down to one inch and five-eighths towards the ends. 
 The manner of fixing them to the cross heads, is shewn in figs. 17, 18, and 19, S 
 being the end of the connecting rod, enlarged at TT to three inches wide, and made 
 square and flat at the end. The brass bearing, U, is fitted to the end, and has 
 another brass piece, V, upon it, made octagonal on the back ; the two brasses are two 
 inches wide, and have flanches upon them at the sides, as shewn by the dotted lines 
 in fig. 18, that of the end brass V being semicircular. 
 
 The brasses are fitted accurately on to a spherical ball, W, that is turned upon.the- 
 
436 
 
 STEPHENSON'S PATENT 
 
 middle of the cross head, and are held upon the end of the connecting rod, T, by 
 the iron strap, X, fitted between the flanches of the brasses and fixed to the connecting 
 rod by the key and gib Y, so as to hold them firmly and steadily together. The 
 key Z is put through the connecting rod and strap close to the inner brass U; the 
 holes in the strap being made larger than the key at the outer end, so that the key 
 bears against the brass U, and forces it against the brass on the cross head. The 
 connecting rod moves upon the cross head, and the friction causes the brasses 
 to wear, so that they require tightening up occasionally by driving in the key 
 Z farther, and bringing them nearer together ; a little space is left between the 
 brasses to allow for this. Small screws are inserted opposite to each of the keys, 
 and are screwed against them when they are driven into their places to prevent 
 their jolting loose. 
 
 The construction of the other end of the connecting rod is shewn on the same 
 scale in figs. 20 and 21, which are a plan and a longitudinal section of it. 
 
 FIG. 20. 
 
 FIG. 21. 
 
 A is the end of the connecting rod, which is enlarged at B B to five inches and 
 three quarters wide, and cut out to an octagonal shape at the end, fitting the brass bear- 
 ing C. The other brass, D, is similar to it, and they are both three inches wide, with 
 
LOCOMOTIVE ENGINE. 437 
 
 
 
 semicircular flanches on the outside to hold them steady; and are fitted on to the crank 
 pin, which is cylindrical, and five inches' diameter, as shewn by the dotted lines in fig. 
 20, and rounded out to a shoulder on each side. The brasses are held by the strap E, 
 which is fixed on to the end of the connecting rod by the key jPand gib G ; the key 
 terminates at the bottom in a screw passing through the prolonged end, H, of the 
 gib, and held by nuts. These nuts are screwed up against the end of the gib, when 
 the key is driven into its place ; and effectually prevent its jolting loose ; the hole for 
 the screw being made oblong, to allow for the side motion of the key. The holes 
 in the strap E, for the key, are made rather longer outwards than the key, and the 
 key- way in the connecting rod is as much longer at the inner end ; causing the key 
 to bear only against the connecting rod, and the gib against the strap : the strap is 
 thus drawn farther on the connecting rod by driving the key, and the brasses are 
 brought nearer together, and tightened up on the crank pin as they are worn by 
 friction. This end of the connecting rod is shortened as much as the brasses wear^ 
 as the outer brass is drawn inwards by the key ; but the other end of the con- 
 necting rod is lengthened by the wear of the brasses, because the outer brass is 
 fixed, and the inner one is pressed against it by the key. The total length of the 
 connecting rod is thus kept always nearly the same, as the wear of one set of 
 brasses compensates for that of the other. If this were not the case, the piston 
 would be brought nearer to one end of the cylinder than the other by the wear of the 
 brasses, and would require more clearance, to prevent it striking the cylinder cover. 
 
 CRANKED AXLE. The axle C' of the large wheels D', (Plate XC. and XCI.,) is 
 called the cranked axle, from its having two cranks in it, to which the connecting 
 rods from the two pistons are attached. It is drawn to a scale of an inch to a foot, 
 or one third larger than the engravings in figs. 22 and 23, and it is shewn in the 
 same position as in the Plates. It is made all in one piece and of the best wrought 
 iron, termed back-barrow, or scrap-iron, and is 6^ feet long, and 5 inches in diameter. 
 The axle is cylindrical at the centre part, A, (fig. 22,) and is increased to five and a 
 quarter inches at C C, where the cranks are formed. The two cranks, R and L, for 
 the right and left hand cylinders, are exactly at right angles to each other, as shewn 
 in fig. 23, which is a section through the axle at E ; the sides of the cranks D D are 
 four inches thick. The crank pins B B are five inches diameter and three inches 
 long, the same dimensions as the brasses in the ends of the connecting rods, which 
 are fixed upon them ; and the length of the cranks from the centre of the axle 
 to the centre of the crank pin is nine inches, which is exactly half of the stroke 
 of the piston. Upon the parts F F, which are seven and a half inches long, the wheels 
 are firmly fixed, so as to prevent their turning or shaking upon the axle ; and 
 outside the wheels, at G G, the axle is reduced to three inches and an eighth diameter 
 
438 
 
 STEPHENSON'S PATENT 
 
 FIG. 22. 
 
 for five inches in length, having a collar at the end ; these parts, G G, turn in 
 brasses, which are fixed in the outside frame of 
 the engine, and have the weight of the engine 
 resting upon them. The axle is all turned in 
 a lathe, and each of the crank pins is also 
 turned by suspending the axle on centres cor- 
 responding with the centre of the crank pins ; 
 and made in strong cast iron arms, that are 
 firmly fixed on the ends of the axle, and pro- 
 ject beyond the cranks, so as to balance the 
 axle, and enable it to turn round on the centre 
 line of the crank pin. The axle is by this means 
 made very true, and the cranks are made of 
 exactly the proper length, and at right angles to 
 each other. The corners of the cranks are 
 champered off, as shewn in the figure, and the 
 ends of the smaller cylindrical parts well 
 rounded out. 
 
 The crank R of the right hand cylinder 
 is shewn vertically, and in its lowest position ; 
 and the piston in the cylinder is shewn in the 
 middle of its stroke, or at half stroke. (See 
 Plate XC.) If the piston be now made to 
 move backwards, by admitting the steam to 
 the front of it, it will press against the crank 
 pin by means of the piston rod and connecting 
 rod, with a force equal to the pressure of the 
 steam upon it ; and as the piston is twelve inches 
 diameter, or 113 square inches area, this force 
 upon the crank will be 2^ tons, when the 
 steam is at the usual pressure of 50 Ibs. per 
 square inch. And as the cylinder and cranked 
 axle are firmly connected together by the frame- Flo . 23 _ 
 
 work of the engine, they cannot be separated by this force upon the crank ; 
 the crank therefore gives way by turning round, making the axle and wheels 
 upon it revolve in the direction of the arrow, until it is brought to its farthest 
 position and becomes horizontal, as the left hand cylinder is shewn in Plates XC,. 
 and XCI., and the piston has arrived at the end of its stroke. 
 
LOCOMOTIVE ENGINE. 439 
 
 On reversing the slide valve to admit the steam behind the piston, and produce a 
 fore stroke, the piston has no power to move the crank, as it is pulling directly in a 
 line with the centre of the axle, and only tending to break the axle; and the crank has 
 therefore to be moved on, so as to rise a little above the centre line, when the piston is 
 able to move it, and pulls it round to the opposite position, or the side next the 
 cylinder, and the piston arrives at the end of its stroke. On the commencement of 
 a back stroke the piston has also no power to move the crank, it being again on the 
 centre, and requiring to be assisted on a little, to enable the piston to act upon it and 
 push it round to the opposite side again. The crank requires assisting over these 
 two centres, or dead points, in order that continued rotation may be produced by the 
 reciprocation of the piston ; and for this purpose the two cranks upon the axle, 
 which are worked by the two pistons, are placed at right angles to each other : for 
 when one of the cranks is on the centre, and the piston connected with it has no 
 power to make it revolve, as is the case with the left hand crank in Plates XC. and 
 XCL, the other is at half stroke, and its piston has the greatest power upon it, so 
 that it moves the axle round and makes the other crank pass the centre. In a 
 similar manner, when they have made a quarter revolution, the right hand crank 
 comes to the centre, but the piston of the left crank is then in full action, and this 
 continues throughout the revolution, one crank being always in full action, when 
 the other comes to the centre and ceases to propel the axle. 
 
 The power of the piston to propel the crank is greatest at half stroke, when the con- 
 necting rod is at right angles to the crank, and acts with the leverage of the full length 
 of the crank ; but as the piston advances to the end of the stroke, the angle that the 
 connecting rod forms with the crank is continually diminishing, and with it the leverage 
 and power to propel the crank, until at the end of the stroke the crank comes to 
 the centre, and the connecting rod ceases to have any power to move it ; the mean 
 leverage throughout the stroke being only about two thirds of the length of the crank. 
 This would cause therefore the motion to be very irregular if there were only one 
 crank ; but with two cranks placed at right angles to each other, the irregularity 
 is very nearly corrected ; as at half stroke the power of one piston only is effective, 
 and at quarter stroke the power of both pistons together, though acting with equal 
 advantage, very little exceeds the full power of the one alone. In stationary engines 
 which have only one cylinder, the irregularity of the action of the crank is com- 
 pensated for by the use of a large and heavy fly-wheel; which when once set 
 moving, has sufficient momentum to bring the crank over the centre, and to render 
 the velocity of the motion very uniform, as there is not time to accelerate its ve- 
 locity perceptibly in the middle of the stroke, or to diminish it at the ends. Marine 
 
440 STEPHENSON'S PATENT 
 
 engines which have no fly-wheels are always in pairs, like locomotives, except in 
 some of the smallest vessels. 
 
 The connecting rod being inclined below the piston rod during the back stroke, 
 and above it in the fore stroke, requires a moving joint at the end which takes hold 
 of the cross head ; and the cross head is made spherical at that part, to prevent any 
 lateral strain that might arise during the motion from the crank not being accurately 
 in the line of the piston rod, or the axle at right angles to it. The varying 
 position of the connecting rod also renders the guides for the piston rod necessary to 
 resist the great oblique strain upon it caused by the inclined positions of the con- 
 necting rod tending to force it upwards in the back stroke, and in the opposite 
 direction during the fore stroke. This oblique strain is diminished by increasing 
 the length of the connecting rod ; which is therefore made as long as possible, in 
 order to diminish the friction of the guide blocks, leaving only a small clearance beyond 
 the crank and head of the piston rod at their extreme positions. Other modifications 
 of the plan are also used to preserve the parallel motion of the piston rod, such as a 
 single square bar placed on each side with the edges at top, termed diamond guides, 
 and having sockets on the ends of the cross heads sliding upon them ; but the other 
 plan is found to be most advantageous ; in small stationary engines similar plans 
 are also sometimes adopted. But in stationary and marine engines generally, the 
 motion of the piston is maintained in a straight line by various combinations of 
 rods, forming a parallel motion, which has less friction than guides, and is more 
 convenient in those cases. The strain is also diminished by the piston rod being 
 connected with the end of a beam instead of directly with the connecting rod, which 
 has a much less irregular motion. 
 
 The two cranks are thus made to revolve uniformly by the action of the steam 
 upon the pistons in the cylinders, and move with them the axle and the wheels 
 fixed upon it. The wheels are made to revolve in the same direction that they 
 would turn if the engine were running forward ; and they cannot turn round without 
 either slipping round upon the rails, or rolling forward upon them and moving the 
 engine with them. If the adhesion of the wheels upon the rails is greater than the 
 resistance of the engine to being moved, and the pressure of the steam be sufficient, 
 the wheels will roll forward upon the rails ; and the engine will be propelled, and 
 be able to draw after it a load, the resistance of which is equal to the excess of the 
 adhesion of the wheels upon the rails above what is required for moving the engine 
 itself. The adhesion of the wheels is not always the same ; it is the greatest when 
 the rails are most clean, and are either quite dry or quite wet ; and it is least 
 when the rails are dirty, and greasy with being partially wetted. For this 
 
LOCOMOTIVE ENGINE. 441 
 
 reason an engine, which is not loaded so much as the full adhesion of the 
 wheels upon the rails, will often slip, and let the wheels turn round quicker 
 than the engine is running, on passing a station, or any part of the line where 
 the rails are liable to be dirtied by the traffic of persons across them. 
 
 The adhesion of the wheels is found to be about one fifth of the weight upon them 
 when the rails are in a good state, and it varies between that and one tenth or twelfth. 
 The weight upon the driving wheels as they are termed, is six tons, and the adhesion 
 is therefore sufficient for drawing a load of 280 tons besides the engine upon a level. 
 When the first locomotives were made, it was thought that the adhesion of the wheels 
 upon the rails could not be sufficient to draw any load besides the engine, if it were 
 enough for that ; and various contrivances were resorted to, in order to obtain the 
 necessary fulcrum from which to move the engine. Levers were first tried which 
 resembled a horse's legs, and were thrust against the ground by the piston rods ; a chain 
 was also tried lying on the ground between the rails and taken hold of by a wheel 
 in the engine ; also a rack was fixed inside the rails and a toothed wheel turned 
 by the engine worked in it. Locomotives which are intended for conveying heavy 
 goods have their adhesion upon the rails generally increased by coupling four wheels 
 together so as to make them all turn together, and thus obtaining the adhesion of all the 
 four to assist in drawing the load. The power of the engine can then be increased 
 as the increased adhesion will enable it to be exerted ; for the power of engines 
 with only two driving wheels cannot exceed a certain limit, or it will be greater than 
 the adhesion of the wheels and the excess will be useless. The wheels that are 
 coupled together are of the same diameter, and have connecting rods attached to 
 cranks, which are fixed on the axles outside of the wheels. Some of the old engines 
 had their wheels coupled by a pair of cog wheels ; and also by an endless chain 
 passed round a pulley on each axle. 
 
 The plan of driving the wheels of a locomotive by means of cranks upon the axle, 
 is attended by the disadvantages that the axle is weakened very much by the cranks 
 in it, and the power is applied at some distance from the wheels where it is wanted. 
 The action of the pistons upon the cranks, alternately pulling and pushing them, and 
 the great weight that the cranked axle has to carry, make it necessary that it should 
 be made very strong in order to stand its work ; they are therefore very heavy and 
 expensive, costing about 50 each. They, are very seldom broken, though they some- 
 times get bent by the engine running off the line ; but the older locomotives had their 
 cranked axles broken more frequently, as they were not made so strong at first. 
 Several plans have been tried for obviating the necessity for a cranked axle, but they 
 do not appear to be any of them so good upon the whole. The Rocket, and some of 
 the first locomot ives upon the Liverpool and Manchester Railway, had their cylinders 
 
 3 K 
 
442 
 
 STEPHENSON'S PATENT 
 
 placed outside and fixed above the wheels; and the connecting rods took hold of crank 
 pins outside of the wheels and fixed into them, so as to drive them directly. But 
 it was found better afterwards to place the cylinders in the smoke box, where 
 they were protected from the air, which cooled them very much before; and 
 the machinery could then be fixed more conveniently; some engines, however, 
 are still made on that construction. Engines have also been made with vertical 
 cylinders, which worked cranks outside the wheels by means of bell cranks and 
 connecting rods. 
 
 ECCENTRICS. Upon the cranked axle C', (Plates XC. and XCI.,) are fixed the four 
 eccentrics E', E", F', F", for the purpose of working the slide valves. The construction 
 of one of the eccentrics is shewn to double the scale in figs. 24 and 25, which are 
 drawn to a scale of an inch FI. 25. 
 and a half to a foot. Fig. 24 
 is a side elevation of an ec- 
 centric, and fig. 25 a section 
 through the centre of it. A 
 is a portion of the cranked 
 axle, five inches diameter; B 
 andC'are two cast iron pieces, 
 two inches and a quarter 
 wide, forming the eccentric, 
 and each fitted half round 
 the axle ; the smaller one, C, 
 being one inch thick in the middle, and the two pieces forming together a circle of ten 
 inches diameter. They have a projection of a quarter of an inch running round both 
 sides of the outer edge, and the piece B has two openings, D D, east in it to diminish 
 the metal, leaving a thickness of an inch on each side. A rebate, E, projects from the 
 straight edge of the piece C, fitting into a groove in B to hold them steadily on each 
 other ; and the two pieces B and C are fixed together by the pins F F, which are 
 firmly screwed into the piece (7, and passing through corresponding holes in the other 
 piece into the openings D D, are fixed by keys driven through them ; the whole eccen- 
 tric is then fixed upon the axle, so as to make them turn round together by driving the 
 key G into a groove in both. The brass ring H H, one inch thick in the middle, is put 
 in the groove round the eccentric; being made in two pieces in order to enable it to be 
 put into the groove, and the ends connected by flanches 1 1. KKis the eccentric rod, 
 forked at the end ; the ends of the fork being three-quarter inch screws, which pass 
 through the flanches of the brass rings H, and hold them together by nuts upon the 
 screws. The other ends of the eccentric rods e" e'" and/"/", (Plates XC. and XCI.,) 
 
LOCOMOTIVE ENGINE. 443 
 
 are carried on towards the smoke box; and when the axle si revolves, the eccentric 
 B C revolving with it, turns round inside of the brass ring H H, which is prevented 
 from revolving by the eccentric rod that is fixed to it. The groove of the eccentric and 
 the brass ring are both turned exactly to fit, allowing the eccentric to turn freely and 
 steadily within the ring. As the eccentric projects from the axle more on one side 
 than the other, the ring is pushed out farther from the axle on that side ; and hi re- 
 volving with the axle, the ring is pushed out from the axle on each side in succession, 
 causing the eccentric rod to be moved in each direction from its central position as much 
 as the projection or the eccentricity, which is an inch and a half, or three inches total 
 motion or throw. 
 
 The action of the eccentric is precisely similar to that of a crank an inch 
 and a half long ; and the eccentric is in fact a crank with a very large crank 
 pin, this pin being ten inches in diameter, and reaching beyond the axle 
 itself; and the eccentrics are used instead of cranks, to avoid the necessity of 
 making so many small cranks in the axle, though there is considerable loss of 
 power attending the use of them from the friction being increased by their 
 large size. Eccentrics are used for working the slide valves in almost all steam 
 engines, because of their convenience and steady action ; they are also readily 
 capable of adjustment, by altering the position in which they are keyed on the axle. 
 They cannot be cast in one piece as the cranks are forged with the axle, and the ec- 
 centrics have, therefore, to be put on in two halves. 
 
 SLIDE-VALVE GEAR. A side elevation of the eccentric rods and levers for working 
 the slides is shewn detached in figs. 2 and 3, (Plate XCI.,) in two different positions, 
 with a cross section through the eccentric rods, shewing a back elevation of the levers, 
 &c., in fig. 4 ; and a plan of them is given in Plate XCI., in their position in the en- 
 gine. The two eccentrics E' and E", are, for working the slides when the engine is 
 running forward ; E' being for the slide of the right hand cylinder, andE" for that of 
 the left cylinder, and the ends of the eccentric rods, e" e", are formed into large ver- 
 tical forks, g" g", having a notch in the bottom of each ; the section in fig. 4 (Plate 
 XCI.) is taken through the notches. These notches take hold of steel pins, with 
 shoulders to hold the eccentric rod steadily, which are fixed into the lower ends of the 
 levers h" Ji", by means of nuts screwed on at the other side. The levers h" h!" are keyed 
 on to the ends of the horizontal shafts or weigh-bars i" i'", turning in brass carriages, 
 W k'", fixed on to the frame of the engine, and made in two pieces, the upper part being 
 loose and held down upon the weigh-bar by bolts, allowing it to be tightened up as it 
 wears. Upon the weigh-bars i" i'", and standing above, are fixed the levers I" F, of the 
 same length as the bottom levers, h" Ji" ; and two horizontal links, m" m", are attached 
 
444 STEPHENSON'S PATENT 
 
 to the ends of each of these levers by a steel pin passed through them, with a 
 small pin and washer at the end, to prevent its getting loose ; the other ends 
 of the links m" m" , being attached in a similar manner to a socket on the valve 
 spindle I ', which is guided at its end by an eye in a small pillar fixed on to the boiler. 
 
 The eccentric rods d' d", taking hold of the bottom levers h" h'", make them move 
 backwards and forwards with the eccentrics; and the top levers I" I'", connected with 
 them by the weigh-bars i" i'", communicate the motion to the valve spindles 
 by means of the links, m" m"' ; the levers h" and I" being of the same 
 length, the motion of the slide valves is the same as the throw of the eccentrics, 
 or three inches, as before stated. The links allow for the oblique action 
 of the top levers which move in an arc of a circle, instead of a straight 
 line as the valve spindle. The pins and eyes of the levers are all of steel, to 
 diminish .the wear, and are fitted very accurately, so as not to allow any shake 
 when the motion is rapidly reversed at the end of each stroke, and that the slide 
 may be moved the full three inches. The eccentrics E' and E" are placed at right 
 angles to each other, that they may be both in the same relative position to the 
 respective cranks ; and they are fixed in such a position with regard to the crank, 
 that the port is full open, or the slide at the end of its motion, when the piston is 
 at half stroke, as shewn in Plate XC. The eccentrics are therefore at right angles 
 to their respective cranks, and they have to be fixed a quarter of a revolution 
 behind the cranks, in order to move the slides as much in advance of the pistons ; 
 because the levers h" and I" reverse the motion, so that when the slide has to be 
 pulled back, the eccentric rod must be pushed forward. 
 
 REVERSING GEAR. The eccentrics, E' E", are placed so as to work the engine for- 
 ward ; and when the crank is down, as in Plate XC., to cause the piston to be pushed 
 back, and pulled forward when above the axle, and thus cause the wheels to turn 
 round in the direction of the arrow, and propel the engine forward. In order to 
 make the engine run in the opposite direction, two other eccentrics, F' and F", are 
 necessary, which are placed exactly in opposite directions to the former ones, or 
 at the extreme back position when the former ones are at their greatest throw 
 forward ; their rods, f'f", have forks at the ends, similar to the other eccentric 
 rods, and levers, n" n", corresponding to them are fixed on the other ends of the weigh- 
 bars i" i'", exactly like the levers h" h'". The four eccentric rods have pins fixed 
 into them below the forks, and attached to the suspending rods, o"o", o'"o"; the 
 two middle rods, o" o", for the working eccentrics, E' E', being connected at the 
 top to a cross head at the end of the horizontal lever p", and the other two, d" o", 
 for the reversing eccentrics, forked at the top, and attached to the levers p" p", 
 
LOCOMOTIVE ENGINE. 445 
 
 which extend in the opposite direction to the lever p". The lever, p", is keyed upon 
 the cross shaft (/', and the other two, p'" p", upon another shaft q", both extending 
 to the side of the engine, and turning in carriages, like the weigh bars i" i'", and 
 having the vertical levers r" r" fixed upon their outer ends. The levers r" r" are 
 connected by the link / attached to both ; and one of them, r", extends above the 
 joint, and is attached to the end of the long bar t", extending to the back of the engine, 
 and connected to a similar lever, u", upon a short shaft, v", which is fixed on the 
 frame at the side of the fire-box. On the outer end of this shaft, v", and close to 
 the hand railing of the engine, is fixed the long handle w", which moves between 
 guide plates attached to the hand rail ; the outer guide having a notch in the middle 
 to hold the lever w" in a vertical position, and another at each extremity of the passage 
 between the guide plates. 
 
 In Plates LXXXIX., XC., and figs. 1, 3, and 4, Plate XCI., the lever w" is shewn 
 pushed over into the forward notch, pulling the levers r" r" forward also, by the 
 bar t" and link a" ; causing the lever p" to be raised by the means of the cross shaft 
 q, and to pull up the ends of the eccentric rods e" e'", by the suspending rods o" o", 
 making the notches in them take hold of the pins in the bottom levers, /*" h", of the 
 weigh-bar. The two forward working eccentrics, E' E", are thus put into gear, 
 and made to work the slides of the two cylinders, and cause the engine to be pro- 
 pelled forwards. The other two lifting levers, p" p", are at the same time lowered 
 by the lever r" being pulled forward, letting down the rods f f" of the reversing 
 eccentrics by the suspending rods o" o", so that their forks clear entirely the pins 
 in the levers, n" n" ; leaving them free to move with the weigh-bar, and in exactly 
 opposite directions to the eccentric rodsf'f" below them. 
 
 When the hand lever w" is placed in the centre notch of the guides, or in a 
 vertical position, as shown in fig. 2, (Plate XCI.,) the side levers r" r'" are brought 
 upright, and the lifting levers p" p" p" made horizontal ; so that the ends of the 
 middle eccentric rods are let down, and the notches in them escape from the pins in 
 the bottom levers of the weigh-bars : and the outside eccentric rods, ff, are only 
 raised into a similar position, and are still not in contact with the levers of the weigh- 
 bars. The slides will therefore cease to be worked, although the eccentric rods 
 continue moving, and the engine will not be propelled any more, as the steam con- 
 tinues pressing upon the same side of the pistons. 
 
 But when the hand lever w" is pulled quite over into the back notch of the 
 guides, the positions of the eccentric rods are reversed ; the outside lifting levers, 
 p"p", being raised into the same position that the other lever, p, had before, and 
 drawing up the ends of the rods f" f" of the reversing eccentrics F' F", to catch 
 the pins in the levers n n" of the weigh-bar upon one of the inclined planes of 
 
446 STEPHENSON'S PATENT 
 
 their forks, and force them into the notches in the bottom of the forks. The re- 
 versing eccentrics, F' F", are thus brought into gear, and made to work the slides, 
 causing the motion of the pistons to be reversed by the steam being admitted on the 
 opposite side of them, and making the engine run in the opposite direction to its 
 former course ; the middle eccentric rods, e e", are at the same time lowered, as the 
 outside ones were before, allowing the forks upon them to clear the pins of the levers 
 ft" h'". The engine can then be propelled forward again by putting the hand lever 
 over into its front position ; dropping the rods of the outer reversing eccentrics out of 
 gear, and drawing up the inner rods of the forward working eccentrics to force the 
 levers of the weigh-bars into the opposite positions by their forks, and take hold of 
 the pins in them. 
 
 The engine can thus be made to run either forward or backward, by merely 
 pulling the hand lever w" forward or back ; and the handle is placed close to the 
 engine man, who stands behind the fire-box, so as to be readily moved ; it is fixed 
 so as to drop into the notches, and requires pulling out of them to shift its position, 
 in order to prevent its jolting loose. The suspending rods, o" d", that support the 
 ends of the eccentric rods, have to be moved with the eccentric rods in working, 
 causing some friction to the engine ; those rods that are in gear have to be held close 
 up to the pins on the levers of the weigh-bars, that they may not get out of the 
 notches in the eccentric rods ; and their motion does not exactly correspond with 
 that of the pins in the levers of the weigh-bars, from the suspending rods 
 taking hold below the notches of the eccentric rods, and moving in an arc of a rather 
 larger circle, causing a little additional friction from the sliding of the pins in the 
 notches, though the amount of it is very small. To obviate this, the eccentric rods 
 are placed in some engines above the pins in the levers of the weigh-bars, with the 
 forks and notches inverted, so as to drop down upon the pins and rest upon them 
 when in gear ; allowing the suspending rods to have a loose hold of them, as they 
 do not require support. This plan is liable to the objection, that if the eccentric 
 rods should accidentally get loose by the pins jolting out, they would all fall into 
 gear and cause the breaking of the machinery, as they move in opposite directions ; 
 but with the other arrangement the eccentric rods would in this case merely fall 
 upon a rod that is fixed under them across the engine. 
 
 This plan of reversing has been but lately introduced, having been first used 
 by Messrs. Stephenson, and since adopted with different modifications by other 
 makers. The plan in many locomotives is, to have the four eccentric rods 
 suspended above the levers of the weigh-bars in a similar manner to the last, but 
 with notches only in their under side, so that they cannot take hold of the lever 
 pins until they have moved along, and the notches coincide with the pins ; the 
 
LOCOMOTIVE ENGINE. 44? 
 
 slides and levers being moved to the right position by means of two starting handles 
 fixed on to the fire-box, and connected by rods and levers with the two weigh- 
 bars, and these starting levers are always moving with the slides. This plan 
 is inferior to the other with the forked eccentric rods, as the slides have to be 
 set by the starting handles, as well as the eccentrics reversed, in order to reverse the 
 engine : though when the engine is running, the first is not required, but a con- 
 siderable strain is then caused by the eccentric rods suddenly catching hold of the pins 
 and bringing them into motion. The starting handles are used to enable the engine 
 to be moved very steadily or for a small distance by working the slides by hand, 
 the eccentrics being thrown out of gear ; but a good regulator renders them un- 
 necessary for this purpose, as the steam can be admitted very gradually to the 
 cylinders. Considerable friction is also caused by their being continually in motion 
 with the slides, and to avoid this, another handle has been added in some cases, 
 by means of which they can be thrown out of gear when not required ; but that 
 adds to the complexity. 
 
 The plan of driving the slides that has hitherto been most universally adopted, 
 and is still much used, is by means of two eccentrics only, fixed together at right 
 angles to each other, and placed loose upon the centre of the cranked axle ; their 
 rods being connected with the weigh-bars, as in the other plans ; and a driver with a 
 projecting stud is fixed on the axle on each side, just clearing the eccentrics, a hole 
 being made in each side of the eccentrics to fit the studs. The eccentrics can be 
 shifted along the axle to either side by means of a lever, to make the stud in the 
 driver on that side drop into the hole in the eccentric when it comes opposite to it 
 in revolving, and cause the eccentric to turn with the axle and work the slides. 
 The stud of the other driver is put on the opposite side of the axle to the corre- 
 sponding hole in the eccentric ; so that when the eccentrics are shifted to the other 
 side by the lever, they have to stop for half a revolution before that driver catches 
 hold of them, and are then fixed exactly opposite to their former position, and 
 reverse the engine ; in their intermediate position, when they touch neither of the 
 drivers, they are stationary and cease to work the slides. This plan is inferior to 
 those with four eccentrics, as it is not so certain in its action, and does not keep in. 
 order so well. 
 
 WORKING OF SLIDES AND PISTON. As the slides are worked by eccentrics, they 
 are not suddenly reversed in position at the end of each stroke, in order to let the 
 steam on to the other side of the piston, and keep the steam port full open 
 throughout the stroke ; but are always in motion, and commence returning as soon 
 as they have arrived at the end of their stroke- From this cause they are obliged 
 
448 STEPHENSON'S PATENT 
 
 to have some travel, in order that the port may be full open for some time ; and 
 after having fully uncovered the port, the slides move or travel a little farther, not 
 beginning to close the port again until they have returned over the travel. The 
 motion is very varying as the eccentric drives the slide most quickly at the middle 
 of its stroke ; corresponding to the ends of the strokes of the piston, where the 
 quickest motion is wanted, to admit the steam for the next stroke ; the velocity of 
 the slide diminishing rapidly towards the ends of its stroke, where it stops and 
 retrogrades. Many contrivances have been tried in stationary engines for working 
 the slides more suddenly, either by striking the spindle with tappets or projections 
 on a moving rod, or by means of different kinds of cams or eccentrics of irregular 
 shapes ; with these plans travel of the slide would not be necessary, the port 
 being full open nearly all the stroke. But in a locomotive no plan can well be 
 adopted for working the slides which has a more Sudden or irregular motion than 
 an eccentric, because of the very great rapidity with which the strokes have to be 
 made ; which would soon cause the machinery to be deranged. 
 
 The piston and slides make two reciprocations or changes of motion during one 
 revolution of the driving wheels, and as these are five feet in diameter, they make 
 nearly 4 reciprocations per second when the engine is running at the rate of 20 
 miles an hour, and 8 reciprocations in a second when running at a little more than 
 40 miles an hour ; the ordinary rate of working is about five reciprocations per second. 
 This extreme rapidity causes every change of motion to produce a violent blow to 
 the machinery, requiring that all the parts should be very well made and fitted to- 
 gether, in order that they may stand the work ; the greatest strain is produced upon 
 the fixing of the piston rod into the piston, and upon the joints of the piston rod 
 and connecting rod. The brasses in the crank end of the connecting rod are 
 not keyed up quite tight, but a very little play is left, allowing them just to shake 
 when worked backwards and forwards ; in order to prevent their heating by the 
 great rapidity of the motion, and expanding by the heat together with the crank 
 pin, making the joint very tight ; they have sometimes expanded so much from the 
 heating in consequence of being keyed too tight, that the engine has been nearly 
 stopped by the great friction occasioned, and the brasses have been broken to 
 pieces. 
 
 All the moving parts require a constant supply of oil to diminish the friction ; and 
 oil cups are fixed for this purpose upon all the principal moving parts, stich as on - 
 the ends of the connecting rods over the bearings, on each of the piston rod 
 -guides, and over the piston rod and the slide valve spindle ; the piston is oiled 
 by pouring oil into the cylinder by the cock in the cylinder cover, the bent end of 
 
LOCOMOTIVE ENGINE. 
 
 449 
 
 IG. 28. 
 
 the cock turning round for the purpose. An oil cup is shown one quarter the full 
 size in figs. 26, 27, and 28. Fig. 26 is a side elevation FIG. 26. FIG. 27. 
 
 of it; fig. 27, a section through the centre; and fig. 28, 
 a plan of the top. The cup A is made of brass, and 
 the cover B has a piece projecting from it turning upon a 
 pin in a socket C at the side of the cup A, and square at 
 the end, resting upon a small spring at the bottom of the 
 socket to hold it either open or shut. An iron tube D, 
 is fixed into the foot of the cup, extending to the top, and 
 projecting through the bottom, where it is screwed, for 
 the purpose of fixing the cup on to the part which has to 
 be oiled. The hole into which the cup is screwed runs through to the rub- 
 bing surface ; and some cotton thread is put through the tube, dipping into the 
 oil in the cup, and the other end touching the moving part; the thread acts as 
 a syphon, and continually drops the oil upon the rubbing surface. The oil cups 
 were made at first without the tube or cotton thread, but the oil was found to run 
 out too quickly, and could not be kept supplied ; loose cotton was then put into 
 the cup to prevent the oil running out so fast, but the syphon cup acts much better 
 as it supplies the oil uniformly and gradually. The oil cup on the crank end of the 
 connecting rod has so violent a motion, that it is almost impossible to keep the cover 
 shut without the spring is very strong ; the covers are sometimes detached and screwed 
 on, but they are then very liable to be lost ; and the best cup for that purpose is one 
 without a loose cover, but with only a small hole in the top to pour in the oil, and 
 made funnel-shape inside to prevent the oil jolting out of the hole. 
 
 The faces of the slide valves and the outside piston rings are subject to considerable 
 wear, from the pressure upon them and the rapidity of their motion ; but the wear is 
 very much increased when the boiler is supplied with dirty water, priming much 
 in consequence ; as the water which gets over into the cylinder carries particles of 
 sand with it, which grind the rubbing faces very quickly. The slides in the engine 
 shewn in the engravings have just been removed, having lasted two years ; the old 
 ones were worn down to less than a quarter of an inch thickness of flanch. The 
 piston rings are not yet worn out ; they usually last about three years. In another 
 engine that had run upon a part of the works where the water was very bad and 
 sandy, the piston rings were worn down to one eighth of an inch thick in four 
 months. The cylinders get worn uneven in time by the friction of the pistons, and 
 require reboring ; about one eighth of an inch is taken off by the boring, and they are 
 bored out generally two or three times before they are worn out ; they wear usually 
 
 3 L 
 
450 STEPHENSON'S PATENT 
 
 for four years, before requiring to be rebored, but the time varies much with the 
 quality of the metal, it being necessary sometimes much sooner. 
 
 A larger passage for the entrance of the steam is required in a locomotive than in 
 a stationary engine, in proportion to the size of the cylinders ; as the piston moves 
 quicker, and the steam has to be admitted proportionally quicker. The best velocity 
 for the piston of a steam engine is given by Watt as 220 feet per minute ; and the 
 area of the steam port, so as to admit the steam to move the piston at that velocity 
 with its full pressure, he gave as one twenty-fifth of the area of the cylinder. In this 
 locomotive, the velocity of the piston when the engine is running at 20 miles an hour 
 is 350 feet per minute nearly, and at 40 miles an hour, nearly 700 feet per minute ; 
 the usual velocity being about 440, or double of the velocity in stationary engines. The 
 size of the ports is one fourteenth of the cylinder, or rather less than Watt's proportion, 
 which would be one twelfth and a half, as the piston moves twice as fast ; the steam 
 ports hi some locomotives are made as large as one eleventh, and in others only one 
 seventeenth of the cylinder, but one fourteenth appears to be a very good pro- 
 portion. 
 
 The slide begins to open the steam port a little before the commencement of the 
 stroke of the piston, so that the steam is shut off from the piston and let on to the 
 opposite side for the commencement of the next stroke, a little before the end of 
 each stroke ; acting for this interval in opposition to the motion of the piston. 
 This is called the lead of the slide, and it is made generally about a quarter of an 
 inch, being produced by fixing the eccentrics a little in advance of the position 
 at right angles to the cranks. It is found necessary to let the steam on to the opposite 
 side of the piston before the end of the stroke, in order to bring it up gradually 
 to a stop, and diminish the violent jerk that is caused by its motion being changed so 
 very rapidly as five times in a second. The steam, let into the end of the cylinder 
 before the piston arrives at it, acts as a spring cushion to assist in changing its motion, 
 and if it were not applied, the piston could not be kept tight upon the piston rod. 
 A little lead of the slide is also necessary that the steam may be admitted through the 
 port into the cylinder, and be completely ready to begin the next stroke when the piston 
 is at the end of the cylinder ; but so much is not necessary for this. 
 
 The principal advantage gained by giving lead to the slide is in beginning to get rid 
 of the waste steam before the commencement of the stroke ; so that when the piston 
 commences its stroke there is but little waste steam before it to resist its progress, the 
 steam beginning to be let out of the cylinder before it has driven the piston to the 
 end of the stroke. This is a very important point in a locomotive, as the resistance 
 at negative pressure of the waste steam upon the piston is very considerable ; from 
 
LOCOMOTIVE ENGINE. 451 
 
 the rapidity of the motion, which allows very little time for it to escape, and from the 
 use of the blast pipe, which obstructs its passage. The area of the extremity of the blast 
 pipe is only five square inches, while that of the steam port is eight square inches, re- 
 quiring the velocity of the steam in the blast pipe to be considerably greater than in the 
 cylinder. The average negative pressure of the waste steam throughout the stroke is 
 6 Ibs. per square inch when running at the usual rate of 25 to 28 miles an hour ; and at 
 greater velocities the negative pressure has been found to increase to double that amount 
 and even more. The effective pressure of the steam upon the piston at such high 
 velocities is considerably below the full pressure of the steam in the boiler ; as the 
 steam cannot be supplied to follow up the piston so quickly with the full pressure, 
 and the regulator has to be only partially opened, so as to throttle the steam and check 
 its passage into the cylinders ; which diminishes its pressure, as it has still to occupy 
 the same space. The negative pressure of the waste steam amounts, for this reason, 
 to 30 or 40 per cent, of the positive pressure of the steam upon the piston when the 
 engine is running very fast, and the power of the engine is diminished nearly one half. 
 
 For this reason an advantage is obtained by letting out the steam before the end 
 of the stroke ; and the steam still exerts a very considerable pressure on the piston 
 to the end of the stroke, so that the whole power during the stroke is very little 
 diminished though the steam begins to be let out before the end, and the resistance 
 of this pressure of the waste steam during the next stroke is saved ; the lead 
 given to the letting out the steam, or the eduction lead, is often made greater than 
 the steam lead, to increase this effect. The steam is shut off a little before the end of 
 the stroke in consequence of the lead of the slide, and acts expansively for that por- 
 tion, saving so much of the steam, but diminishing the total power a little ; the 
 extent of this action is, however, very limited, as the piston is less than a quarter of 
 an inch from the end of its stroke when the steam is shut off. In stationary and marine 
 condensing engines the steam has usually very little or no lead ; but it is shut off 
 at two- thirds or three-quarters of the stroke, giving a great amount of expansive 
 action ; and the eduction has a great deal of lead, the port being nearly full open 
 at the commencement of each stroke. 
 
 FEED PUMPS. The feed pumps, K K, (Plates LXXXIX., XC., and XCI.,) are 
 fixed by means of flanches to plates which are bolted on to the frame of the engine ; 
 they are fixed on the outside of, and a little below the piston rods, and exactly parallel 
 to them. Each pump is worked by an arm, G G, fixed on to the piston rod ; it has a 
 socket at the end, fitted on the piston rod, and fixed by a small pointed screw tapped 
 into it and bearing against the piston rod ; the arm is inclined obliquely downwards, so 
 as to clear the guides of the piston rod as it is moved backwards and forwards by the 
 
452 
 
 STEPHENSON'S PATENT 
 
 piston rod, and attached at the outer end to the plunger of the pump. One of the 
 pumps is shewn in section in fig. 29, to three times the scale of the engraving, or 2^ 
 inches to a foot. The barrel of the pump, A A, is made of cast-iron, If inches in 
 
 FIG. 29. 
 Vi 
 
 FIG. 30. 
 
 FIG. 31. 
 
 diameter inside, and three-eighths of an inch thick. B B, is the plunger, If inches in 
 diameter, and made of a wrought iron tube for the sake of lightness, plugged up at the 
 inner end, and having a short rod keyed into the other end, which is fixed into the 
 socket in the driving arm by a nut screwed on the end. The plunger B, passes 
 through a stuffing box, C, at the end of the pump barrel A, with a brass gland, D, 
 attached by screws, E E, to the flanch of the stuffing box. The plunger is turned 
 truly cylindrical, to move water-tight through the stuffing box, but the inside of the 
 barrel of the pump is not bored, as the plunger does not touch it. 
 
 A plug, F, is screwed into the other end of the pump to afford a passage quite 
 through for the convenience of fixing. Two short pipes, G O, are cast upon the end 
 of the barrel A, to the lower one of which is bolted the tube L, having the piece 
 / fixed below it ; both are of brass, and the piece / has a short tube cast on its side, 
 with a screw made upon its outer end. H is the copper suction pipe, having a brass 
 
LOCOMOTIVE ENGINE. 453 
 
 collar soldered upon it with a thin conical end, which is fitted into the tube /, and 
 held water-tight by the socket K, screwed on to the tube and bearing against 
 the collar of the suction pipe. 
 
 The piece M, which is bolted upon the upper pipe G, is closed at the top by a 
 cap, P, screwed upon it, and has a tube cast on it like the bottom piece, 7, into 
 which the end of the delivery pipe, -N, is fixed by the screwed socket 0, exactly 
 similar to the suction pipe, H. The delivery pipe is bent round backwards, as shewn 
 in Plate LXXXIX., extending to the fire box, where it is fixed into a valve 
 box, in the same manner as the other end is fixed ; the pipe has to be bent in 
 this way that the ends may be turned in the same direction to allow them both to 
 be screwed into the sockets instead of having the screws at the two ends pulling 
 against each other. This box contains another valve like those in the pump, 
 and is fixed on to the fire box, communicating with the inside. The suction pipes, 
 K'K', (Plates LXXXIX., XC., XCI., and XC1I.,) pass under the fire box, and are 
 connected at the end to the pipes that bring the water from the tender, being sus- 
 pended by stays, s s, from the fire box. 
 
 In the pieces L and M, are fixed the valves Q and R, which are shewn to 
 double the scale in figs. 30, and 31, where T is the valve seat, made conical and 
 with a groove outside to hold packing for fitting it water-tight when driven into its 
 place in the pump. The valve S is a ball, turned and ground truly spherical, 
 fitting water-tight into its seat in every position ; it is guided by the piece U U, 
 screwed upon the valve seat, and cut into four bars to allow passage for the water. A 
 pin, V, is screwed through the cap P, bearing upon the guide of the valve R, and 
 fixed by a set nut, W, to hold down the valve seat and prevent its being raised 
 out of its place by the force of the pump ; the lower valve seat does not require 
 holding, as the pressure is above it. 
 
 The plunger B, fig. 29, is worked in and out of the barrel of the pump A, a dis- 
 tance of 18 inches, by the piston rod at each stroke; leaving a space behind it when 
 drawn out equal to its bulk, which is supplied with water through the suction pipe 
 and lower valve, and the water again forced out through the upper valve and delivery 
 pipe into the boiler when the plunger is pushed in. The internal diameter of the 
 suction and delivery pipes, and of the water way in the valve seats, is one inch. The 
 pump would force a quantity of water into the boiler at each stroke equal to the 
 bulk of the plunger for 1 8 inches in length, if the suction pipes were kept open ; but 
 the quantity is regulated according to circumstances by means of the cocks t' t' 
 fixed in the suction pipes, the handles of which extend upwards through the foot 
 board on which the engine man stands so as to be within his reach ; and the closing 
 these cocks causes the plunger to leave a partial vacuum behind it, and as the 
 
454 STEPHENSON'S PATENT 
 
 water cannot enter to fill it up, so much less water is forced into the boiler. In small 
 force pumps a plunger is preferable to a piston, because the barrel does not require 
 boring out, as would be the case if a piston were used ; and the packing of the stuff- 
 ing box upon the plunger is much more easily kept in order than the packing of a 
 piston. 
 
 The additional valve in the delivery pipe acts in a similar manner to the upper valve 
 of the pump, and it is used as a security in case the other valve should get out of order 
 from any dirt getting on its seat and preventing its closing. The valves first used for 
 the feed pumps were mitre valves similar to the safety valves; but ball valves are now 
 used instead, and are found to be much superior, as they are more free and certain 
 in their action from requiring no spindle to guide them, and keep in better order. 
 The plungers of the feed pumps are sometimes attached to the cross heads, which 
 are prolonged outside of the guide blocks for the purpose, instead of being worked by 
 an arm fixed on the piston rod ; but in both plans a considerable strain is caused as 
 the pumps are so much on one side of the piston rod. To prevent this strain they 
 have been worked by eccentrics fixed upon the axle in some large engines ; in which 
 plan additional friction is produced by the eccentric, but the friction caused by the 
 strain is quite avoided, and perhaps more than compensates for it. 
 
 THE WHEELS, FRAMING, ETC., OF THE ENGINE. 
 
 WHEELS. The wheels are of two kinds; the two driving wheels, D ' D', which are 
 fixed on the crank axle C', are 5 feet diameter and are flat on the edge; the other four 
 wheels L'M', two of them, L', placed towards the front just behind the smoke box, 
 and the other two, M ', at the back behind the fire box, are 3 feet 6 inches diameter, 
 and have a projecting rim or flanch upon their edges which runs against the inner side 
 of the rails. Each pair of the small wheels is fixed upon an axle, L" M", as well as 
 the large wheels ; they are three inches and five eighths diameter, and the outer ends 
 project beyond the wheels, turning in brasses in the frame of the engine. Upon these 
 brasses the whole weight of the engine rests through the medium of the springs above 
 them ; and all the weight is thus suspended by springs except that of the wheels and 
 axles themselves, for the purpose of deadening the shocks that are caused by the 
 rapid motion of the engine. It is necessary for all wheels of railway carriages 
 to be fixed upon the axles and have the axles turn with them, instead of turning 
 loose upon the axles as in carriages upon common roads, in order that they may be 
 held quite steady and upright ; for if they were to get nearer together they would 
 run off the rails, though in common carriages it would be of no consequence, as they 
 would still have as firm a bearing. Also when the wheels are fixed upon the axle 
 
LOCOMOTIVE ENGINE. 
 
 455 
 
 there is the leverage of the whole length of the axle to keep them upright, but when 
 they are loose there is only the hold of the thickness of the nave. 
 
 The construction of the wheels is shewn in figs. 32, 33, 34, and 35, to a scale of an 
 
 Fia. 32. FIG. 34. 
 
 FIG. 35. FIG. 3& 
 
 inch and a half to a foot, or double the size of the engravings. Fig. 32 is a section 
 through the centre of one of the small wheels, and fig. 33, is a cross section through 
 
456 STEPHENSON'S PATENT 
 
 the axle and nave ; figs. 34 and 35, being similar sections of one of the driving wheels. 
 ^4 ^4 is the axle of each wheel, the large one is 5^ inches diameter inside the 
 wheel, and the small one is enlarged to 4 inches ; the outside bearing, B, of both, 
 are of the same size. C C are the naves of the wheels, made of cast iron ; the large 
 one is 18 inches diameter and the small one 13 inches ; the length of both in 
 the centre where they are fixed to the axle is 7-g inches, and they are fixed 
 by four keys, E E, each, driven into grooves cut in the axles and inside the 
 naves. The wheels are entirely supported and held by these keys, as the naves do 
 not touch the axle; and by this means a firm and uniform bearing can be obtained, 
 and the wheels can also be fixed truly at right angles to the axle and at the proper 
 distance from each other. Hollows, E E, are cast in the naves between each of the 
 keys to diminish the metal. 
 
 The rims of the wheels, F F, are of cast iron, four inches and a half wide and two 
 inches and a half deep ; they are cast with a groove round them on the outer side to 
 diminish the weight; bosses, G G, are cast on the inner side, where the spokes are in- 
 serted. The spokes, H H, are wrought iron tubes one quarter of an inch thick and 
 tapering from two inches and a quarter to two inches in diameter, and they are cast in 
 the nave and rim. The spokes are inclined to the plane of the wheel, so as to come 
 nearly to one face of the nave and the opposite face of the rim ; and they are inclined 
 alternately in opposite directions, as shewn in the figure, for the purpose of increasing 
 the lateral strength of the wheels, and preventing their bending and getting out of the 
 vertical position with the great strains to which they are subjected. The spokes are 
 laid in the moulds in which the wheels are cast, and the metal cast round them, the 
 ends of the spokes being first plugged up ; and the spokes are covered at the ends with 
 a composition of borax, which causes them to partially melt when the metal is poured 
 in, forming so close and firm a joint that they never get loose. The rims of the 
 wheels are cast first, and allowed to remain for about three quarters of an hour 
 before the naves are cast, because they contract much more in cooling than the 
 naves, being of a much larger diameter, tending to force the spokes nearer to the 
 centre ; and if the naves were cast at the same time, the spokes would be prevented 
 from approaching the centre, and there would consequently be a very great 
 strain upon them, and the metal in the rims would not set firm from cooling in a 
 state of tension, and would be liable to break with any blow ; but by allowing the 
 rims to set before the naves are cast, this action is prevented. 
 
 / / are the tires of the wheels ; they are made of wrought iron rolled into the 
 required shape, with the ends welded together ; the plain one for the driving wheels 
 is 5| inches wide, and the flanch tire for the small wheels 4^ inches wide. Sections 
 
LOCOMOTIVE ENGINE. 
 
 457 
 
 FIG. 37. 
 
 of the two tires are given in figs. 36 and FlG - 3G - 
 
 37) half of the real size ; they are both 
 
 made slightly conical, being tapered 
 
 from If inch to 1-| inch thick ; and the 
 
 flanch projects one inch and a quarter, 
 
 and is three quarters of an inch thick 
 
 at the edge and an inch thick at the base. 
 
 The rims and tires are both turned, and 
 
 the tires are heated when put on, and 
 
 contract on cooling so as to hold firmly on 
 
 the wheel; great care is required in 
 
 fitting them, that they may not be 
 
 loose upon the wheels nor shrunk too 
 
 tight, so as to injure their texture. 
 
 They are held in their places by three bolts with countersunk heads in the tires 
 
 and nuts screwed on against the inner side of the rims. The tires are turned when 
 
 fixed on the wheels to make them truly circular, and to make the two in each pair 
 
 exactly alike. 
 
 The flanch wheels, like the wheels of all railway carriages, require to be made a 
 little conical, in order to prevent the flanches being continually in contact with the 
 rails and rubbing against them, which would cause a great deal of friction ; as a 
 wheel, when running towards one side and bringing the flanch in contact with the 
 rail, will bear upon a larger circumference than the other wheel, and will tend to run 
 towards the opposite side and make the wheels central again ; the flanches are 
 thus hardly required on a straight line, and only necessary upon sharp curves to 
 keep the wheels from running off the line. The rails are laid inclined a little, so as 
 to fit the conical wheels, and for this reason the driving wheels have to be made 
 also conical, although they have no flanch. The driving wheels are made without 
 flanches that they may always have firm hold on the rails, as a flanch on the inner 
 one, when the engine is turning round a curve, would be forced against the inner 
 rail, and would interfere with the bearing of the wheel and cause friction ; and 
 flanches upon the front and hind wheels are sufficient to keep the engine upon the 
 rails. For the improvement of making the middle driving wheels without flanches, 
 Mr. Stephenson has a patent. 
 
 The wheels of the first engines were made entirely of cast iron, but it was found 
 difficult to make them sound in consequence of the unequal contraction in cooling, 
 and they were too brittle to bear the shocks produced in running fast ; the cast iron 
 was also found to be too soft and to wear in a groove on the edge with running on the 
 
 3 M 
 
458 STEPHENSON'S PATENT 
 
 rail, and the driving wheels could not be case-hardened, as the others were, from its 
 diminishing the adhesion upon the rails. Wheels with wooden spokes and rims and 
 wrought iron tires, were tried on the Liverpool and Manchester Railway, and found 
 to wear better, being more elastic ; and flat wrought iron spokes were then tried. 
 The wheels with tubular spokes, and cast iron rims with wrought tires, are now 
 very generally used, and wear very well, lasting two or three years ; the driving 
 wheels being subject to the most wear, in consequence of the slipping to which they 
 are liable. The tires squeeze out at the sides as they wear, and when worn out are 
 replaced by new ones ; they are now made wider, the flanch tires being six inches, 
 and those of the driving wheels seven inches, in order to prevent squeezing out at the 
 sides, which is the greatest cause of their wearing out. The cast iron rims are rather 
 objectionable from their brittleness, as they have to run with so great a velocity; and to 
 obviate this, some engines have wheels with wrought iron rims, to which the spokes 
 are fixed by rivets, having the tires shrunk upon them ; this construction is con- 
 siderably more expensive, though very durable. 
 
 All the earlier locomotives on the Liverpool Railway, and many of the present 
 ones, have been made with only four wheels, D' L' ; the third pair of wheels, M', 
 placed behind the fire box, has been added but lately ; but six-wheeled engines are now 
 coming into more general use, and on several railways none others are used. In the 
 earlier engines the fire-box was considerably smaller than the present size, and that 
 end of the engine behind the crank axle was but little heavier than the other end 
 before the front axle, so that the engine was nearly balanced upon the axles and ran 
 steadily along. But the weight of the hind end of the engine has been so much in- 
 creased, by increasing the fire-box, that it has a considerable preponderance, and the 
 present engines are far from balanced ; in the engine shown in the engravings, the 
 weights at the wheels, D'L', supposing the hind wheels, M', removed, are six tons at 
 the large wheels, D', and only four tons at the front wheels, L', including the weights 
 of the wheels. This excess of weight behind the wheels causes in the four-wheeled 
 engines a pitching motion, which makes them rise on the springs of the front axle, 
 and is considered dangerous when running very fast. The pitching of the engine 
 causes also great injury to the rails, as the wheels are made continually to strike upon 
 them with very great force. 
 
 The hind wheels in the six-wheeled engines support the fire-box, and prevent this 
 action ; the springs over their axle are hung very light, so that in the ordinary state of 
 the engine they only just bear against the frame, and take scarcely any weight away 
 from the driving wheels ; but they serve to catch the weight in the oscillations of 
 the engine, and prevent that overbalancing which causes the pitching motion. The 
 weight on the rails at these wheels is therefore only that of the wheels and axle, or 
 
LOCOMOTIVE ENGINE. 459 
 
 about a ton and a quarter, when the engine is empty ; and when filled for working, 
 the weight is about two tons, making the total weight of the engine twelve tons 
 when full. The weight of the engine when empty is ten tons ; and that of the 
 driving wheels and axle is about a ton and three quarters, of which the cranked 
 axle has nearly a quarter of a ton. 
 
 When an engine is required for heavy work, as for carrying goods, and the 
 adhesion of four wheels must be made use of for propelling it, the front wheels, L', 
 are made of the same size as the driving wheels, and coupled with them. The 
 cylinders have then to be placed lower, and inclined upwards towards the cranked 
 axle, in order that the piston rods and guides may clear the front axle, L", as that 
 is raised up to a level with the cranked axle C' and the former position of the 
 piston rod, by the wheels D' and L' being of equal size. The driving wheels are 
 in this case sometimes made less than five feet, in order to increase the power of the 
 engine, as the diminishing of the diameter of the wheels diminishes the leverage of 
 the load upon the engine, or increases the leverage of the engine in moving the 
 load. But the speed of the engine is diminished in the same proportion, as 
 the smaller wheels will advance a less distance than the larger ones in the same 
 number of revolutions ; but this is not material in the carrying of heavy goods, as so 
 great a speed is not required for them. In order to enable the engines to run faster 
 without having to make more strokes in the same time, the size of the wheels has 
 been increased, and a great many are now making with six feet driving wheels ; the 
 size of the cylinders has also to be increased to supply the increased power that is 
 required, and they are made 13 inches diameter with the same stroke, 18 inches. 
 Wheels have been tried lately of double the size, or ten feet diameter, and even 
 larger in some instances, for the purpose of still more reducing the velocity of the 
 piston, and diminishing the loss of power from the resistance of the waste steam, 
 which is the great difficulty in locomotive engines. But it appears very question- 
 able, whether the disadvantages arising from the use of such large wheels do not 
 more than compensate for their advantages in diminishing the velocity of the piston; 
 as there is a serious objection to them in their great weight, which, together with 
 that of the cranked axle, also proportionally increased, is necessarily unsupported by 
 the springs, and therefore the violent shocks produced by the rapid motion cannot 
 be eased by them. A certain velocity of the piston is also required for the effective 
 operation of the blast, and the velocity should for this reason be, probably, not less 
 than 300 feet per minute. Cog wheels, worked by the connecting rods, have also 
 been tried, doubling or trebling the velocity of the driving wheels ; but they are 
 objectionable, from their jarring action with so rapid a motion. 
 
 OUTSIDE FRAMING, &c. The principal or outside frame, N'O'P', (Plates LXXXIX., 
 XC., XCI.,and XCII.,) is placed along the sides of the engine outside the wheels, and 
 
460 STEPHENSON'S PATENT 
 
 across the ends, serving to support the whole engine, which is firmly fixed to it. It is 
 made of good tough ash plank, the side pieces N ' N ' are three inches thick and seven 
 inches deep, and covered on both sides with sound wrought iron plates, a quarter 
 of an inch thick, fixed on by a number of iron bolts ; the best plates are termed 
 Low Moor plates. The side pieces are morticed into the end pieces, 0' P', of the 
 frame ; that in front of the engine, 0', being five inches thick, and thirteen deep ; 
 angle pieces of iron are bolted on to strengthen the corners inside and out. The 
 outside length of the frame is 17 feet, and the width 6 feet 4 inches. The boiler, 
 fire-box, and smoke-box, are fixed to the side frames, N'N', by strong wrought 
 iron stays, u v', four inches and a half wide and half an inch thick. The stays, 
 u'u, for the smoke-box and fire-box, consist of a horizontal piece, (see Plate 
 XCII.,) bent downwards at right angles at the inner end, and riveted to the 
 side plate of the fire-box or smoke-box, and resting at the other end upon the side 
 frame ; the other inclined piece is welded on to it at the outer end, the two being 
 bolted down to the frame, and it is riveted like the other piece at the upper end to 
 the plate ; the inner ends of both that are riveted to the fire-box and smoke-box 
 are made T shaped and twelve inches wide. The stays, v' v, for the boiler are made 
 and fixed in a similar manner; they are longer, as shewn by the dotted lines in fig. 4, 
 (Plate XCII.,) in order to reach the boiler, and have a ring of the same sized iron 
 inserted in them, touching the horizontal and inclined pieces of the stays and the 
 sides of the boiler, and riveted to each of them. 
 
 Q' Q' Q' are wrought iron plates, seven-sixteenths of an inch thick, bolted on to each 
 side of the frame at the axles, and called the axle guides ; serving to hold steadily the 
 boxes that contain the brasses bearing on the axles, and to guide them when they 
 slide up and down from the play of the springs. A piece 4^ inches wide is cut out 
 in the middle of each for the axle box to slide in. These axle guides have to resist 
 all the strain of the wheels, and those of the driving wheels have to bear the whole 
 force of the engine, which is moved along by the axle of the wheels. They are there- 
 fore strengthened by 1 ^ inch rods, w' w', fixed between each of them, with sockets 
 across their ends, fitting between the two axle guide plates, and fixed to them by 
 bolts passed through both ; the extreme rods are fixed to the end frames of the 
 engine, as in Plates LXXXIX. and XC. ; the axle guides for the small wheels have 
 also bolts fixed through the bottom. 
 
 R' R' R' are the axle boxes in which the axles turn ; they are all alike, and are 
 shewn to three times the scale, or 2^ inches to a foot, in figs. 38, 39, and 40. 
 Fig. 38 is a section along the centre of one of them ; fig. 39 is a cross section ; and 
 fig. 40, a plan of the top. A A is a cast iron box, open at the bottom and 
 the inner side, and 4j inches wide, so as to fit into the opening in the axle guides. 
 A hollow, B JB, is cast in the top of the box A A, for the purpose of holding oil to 
 
LOCOMOTIVE ENGINE. 
 
 461 
 
 supply the bearing, and in it is cast the socket C, in which the end of the spindle 
 attached to the spring rests. The inside of the box is octagonal at the top, as shewn 
 in fig. 39, and has the brass 
 piece D D fitted into it ; which 
 is turned out in the inside to 
 fit the end of the axle, reaching 
 down to the centre, and having 
 a small projection, E, on each 
 side, which fits ^nto a corre- 
 sponding notch in the sides of 
 the box A A, and serves to hold 
 the brass steadily. Two thin 
 brass tubes, F F, are screwed 
 into the brass, and pass through 
 holes in the top of the box A, 
 projecting up into the hollow 
 B, containing oil ; and cotton 
 thread is put into them, dipping FIO. 40. 
 
 into the oil and touching the axle at the other end, acting like a syphon in furnishing 
 a constant supply of oil to the axle, as in the oil cups before described. The bottom is 
 closed by the cast iron piece G Cr, made tapering to fit closely to the sides of the 
 axle box, and held in by the bolts H ; and hollowed in the inside so as to clear the 
 axle, the position of which is shewn by the dotted lines. A piece, //, is cast on each 
 side of the box, projecting half an inch, which fits exactly between the two axle 
 guide plates, and slides between them; as shewn in the plan, fig. 40, where K K is 
 a horizontal section of the axle guides ; L L are pieces of iron plate bent so as to 
 fit accurately between the plates K K, and bolted to them, as shewn in Plate XCII. ; 
 the faces of the pieces // bear against them, and they are both made true and 
 smooth^ so as to allow the axle box to slide up and down easily and without shaking. 
 The top of the box is covered by a piece of sheet iron, with a hole in it for the 
 spindle of the spring, in order to protect the oil. 
 
 S' S' S' are the springs, made as usual of separate steel plates ; those for the driving 
 wheels, D', are the strongest, consisting of thirteen plates, 4 inches wide, and five 
 sixteenths of an inch thick ; the other springs are 3 inches wide, the front ones having 
 twelve plates and the hind ones eight. The four small springs are placed under the 
 outside frame, and their ends rest in sockets x V, fixed to the frame, and are kept 
 in by bolts put through the sockets. The larger springs are turned over at the 
 ends and take hold of short bolts, having the links y y fixed on them ; the lower ends 
 
462 STEPHENSON'S PATENT 
 
 of which are fixed to cross heads on bolts, which are put down through holes in the 
 side frame and fixed by nuts underneath. A square iron socket is fitted on to the centre 
 of each spring, and has a steel pin z, I ^ inch in diameter, fixed into its under side, 
 the lower end of which rests in the socket on the top of the axle boxes, (C, figs. 38, 
 39, and 40,) and thus the frame N'N', which bears the whole weight of the 
 engine, is supported by the ends of the springs, which rest at their centres upon the 
 axles of the wheels. The bearing pins z of the middle springs pass through holes in 
 the side frame, which serve to steady them when playing up and down ; other pins 
 are fixed in the upper side of the sockets on the other springs, which pass through 
 holes in the frame above for the same purpose. 
 
 At the ends of the part of the frame 0', in front of the engine, are fixed the buffers 
 T'T'; they are strong leather cushions stuffed with horse-hair, and are placed 
 there for the purpose of deadening the shock of any collision with another carriage. 
 Buffers are fixed upon each end of carriages of every description that run upon a 
 railway, being all fixed at the same height and distance apart, in order that they 
 may be the only parts of the carriages that ever touch each other ; those on the 
 engines are sometimes made with a large spiral spring inside, that their action 
 may be more perfect. In the centre of the end frame 0', is fixed a strong chain 
 and hook, a", for attaching the train of carriages when the engine is running back- 
 wards ; a small iron plate being placed on each side of the frame for the bolt 
 that holds the chain to be fixed against. A strong staple is also fixed into the frame 
 on each side of the chain, as an additional means for attaching the train. The foot- 
 board U', upon which the engine man stands, rests upon cross pieces of wood that 
 are fixed to the piece of the outside frame P', at the back of the engine, and sup- 
 ported at the other end by the plate ft'; a hand-rail is fixed on each side of the foot- 
 board as a guard, and to one of these the guides for the hand lever w" are attached. 
 6" b" are two pieces of iron plate placed across the back of the fire-box, and bent 
 at right angles along one side, forming a flanch which is riveted to the back plate 
 of the fire-box ; they are also fixed at the ends to plates which are riveted on to the 
 sides of the fire-box. Through the centre of the plates b" b" is put the draw-pin V, 
 1 ^ inch diameter, resting by its head on the top plate, and held by a key put 
 through it under the bottom one ; a socket is fitted on to it having a pin projecting 
 from it on each side, on which is fixed one of the links W'W, which are 
 attached in a similar manner at the other end to another socket, connected to 
 iron bars fixed on the tender by a pin, X', passed through them all ; this pin is 
 held by a key underneath, and is taken out when the tender is required to be dis- 
 connected from the engine. The socket on the draw-pin V is supported by a small 
 ring fixed by a set nut ; and the link W can by this means be readily adjusted level, 
 
LOCOMOTIVE ENGINE. 463 
 
 so as to pull without side strain when the height is altered from the use of another 
 tender or other cause. The draw links W W are left free to move in any direction, 
 in order to allow for the play of the springs of the engine and tender, and the oblique 
 direction of the pulling round a curve ; when they are disconnected from the tender 
 they can also drop down upon the edge of the plate b". The draw-pin V is re- 
 quired to be strong to resist the great strain to which it is subjected ; it is most 
 strained when running down a considerable inclination, as the engine is not then 
 constantly pulling, but the train often pushes against it, and a continued succession of 
 violent jerks on the pin are produced in opposite directions ; instances have occurred 
 of the draw-pin breaking under these circumstances in engines where it was not 
 made strong enough for its length. 
 
 Splashers, d" d", are fixed over each of the wheels to catch the dirt thrown up by 
 them ; those for the middle wheels are of brass and are ornamented, the others of 
 sheet iron, and they are fixed by small stays on to the boiler and the outside 
 frame. 
 
 INSIDE FRAMES. Four wrought iron frames, Y' Y', (Plates XC. and XCI.,) are 
 fixed between the smoke-box and fire-box ; to afford additional strength to the engine 
 by securing firmly the back plate of the smoke-box, in which the cylinders are fixed, 
 and which has to bear the whole strain of the working of the engine. These inside 
 frames have also bearings in them for the cranked axle, and hold it steadily against 
 the action of the connecting rods, by which it is strained alternately in opposite 
 directions. The frames Y' Y' are 3^ inches deep, and three quarters of an inch 
 thick ; they are attached to the smoke-box and fire-box by means of T shaped pieces 
 of iron, which are riveted on to their inner and side plates, and are bolted to the 
 ends of the frames ; the two middle frames are made to approach each other, and are 
 welded together at the back end, so that there are only three bearings on the cranked 
 axle. On to the four frames are fixed the piston rod guides, A' A', by means of 
 pieces of angle iron, as before explained. The frames have to be inclined upwards 
 towards the fire-box, in order to pass above the cranked axle. 
 
 The construction of the inside bearings of the cranked axle is shown in figs. 41, 
 42, 43, and 44, to double the scale, or 1-| inch to the foot. Figs. 41 and 42 are 
 side and end elevations ; fig. 43 is a horizontal section through the centre of the 
 bearing ; and fig. 44, a plan of the top. The frame, A A, is increased at the bearing 
 to 2^ inches thick, the upper part, B, is 11^ inches wide, and the lower part is 
 formed into a fork, CC, 10 inches long, the sides tapering an inch and a quarter in 
 width. A tube, D D, is fitted between them, having a bolt passed through it by 
 means of which the two sides of the fork are held firmly together. Two iron 
 wedges, E E, are fitted accurately to the sides, so that their inner faces are parallel 
 
464 
 
 STEPHENSON'S PATENT 
 
 to each other, and will remain parallel when moved up and down. Each side, 
 CC, has a small projection on its inner side, fitting into a corresponding groove 
 in each wedge, as shown in fig. 41, to guide it when moved; and a bolt, F, 
 is carried upwards from each of the wedges E, through the upper piece B, having 
 a nut screwed upon it at the top ; the holes for the bolts are made oblong to 
 allow for the lateral motion of the wedges FIG. 41. FJC. 4-2. 
 
 when they are screwed up. The two 
 brass bearings, G G, are inserted be- r~ 
 tween the wedges, having flanches on 
 each side fitted on the faces of the 
 wedges ; they are three inches wide, 
 and bored out to five inches diameter, to 
 fit the cranked axle. One of the brasses, 
 G, overlaps the other, which is fitted 
 steadily into it, but not quite touching 
 at the ends. They are made to close 
 upon the axle by screwing up the two 
 wedges E E, thereby forcing the two 
 brasses nearer together; and they are 
 then free to slide up and down between 
 the wedges to allow for the play of the 
 springs, which affects the engine only 
 and not the axle ; and are readily tight- 
 ened up as they wear from friction, by 
 screwing up the wedges farther. 
 
 The cranked axle is thus steadied against the horizontal force of the connect- 
 ing rods, which is the greatest strain that it is subjected to ; but it can have no 
 vertical support in consequence of the play of the springs. A shoulder is made 
 on the bottom of the nuts on the bolts F, and cut into teeth, as shewn in the 
 plan, fig. 44, which catch the ends of a small spring H, fixed by a screw in the 
 middle. This prevents the nuts from turning round and getting loose with the great 
 jolting to which they are subject, the spring having to be forced out from each 
 tooth in succession to let the nut turn ; and though this does not impede the 
 screwing up of the nuts, it is sufficient to prevent their getting loose. The same 
 contrivance is applied to all the nuts in the engine that are used for the adjustment 
 of some moveable part, as those in the glands of the piston rod and slide valve 
 spindle ; as these nuts are not screwed hard up so as to keep them fast. 
 
 Some engines with four wheels are made without the outside frame, and also 
 
 H 
 
 FIGS. 43 and 44. 
 
LOCOMOTIVE ENGINE. 
 
 465 
 
 FIG. 46. 
 
 FIG. 46. 
 
 have not the inner ones ; and instead of them a strong iron frame is placed imme- 
 diately within the wheels, bearing upon the axles, and having the whole engine 
 resting upon it ; this gives the engine a lighter appearance, as the wheels are quite 
 on the outside. But the outside frame adds considerably to the stiffness of the engine, 
 and is of great utility in that respect, particularly when the engine gets thrown off 
 the line, as happens occasionally; when the outside frame serves materially to 
 protect the machinery. It has also an advantage in enabling the engine man to 
 have access to any part of the engine whilst it is working, as the wheels and the 
 space between them are covered over by the splashers, and can be readily passed over; 
 this is very useful, as the working parts frequently require examining and replenish- 
 ing with oil whilst running. The friction is less when there is no outside frame, as 
 there are but two bearings on the cranked axle instead of five ; but they have to 
 be the full size of the axle, as they are inside the wheels, which much increases the 
 friction of each, and renders the whole but little less than in the other plan ; the axle 
 is also not held so steadily as with the middle inside bearings. 
 
 WHISTLE. Z' (Plates LXXXIX., XC.,and XCII.,) is a steam whistle used for the 
 purpose of giving warning of the approach of the engine when running ; the con- 
 struction of it is shewn to one quarter size, or four times the scale of the engravings., 
 in figs. 45 and 46. It is all of 
 brass, and the foot, A, is cast 
 hollow, with a flanch, B, at the 
 bottom to bolt it upon the fire- 
 box ; it has a cock, C, placed in 
 it, with the handle D, and screw 
 E, to keep it tight, the handle 
 projecting out to allow firm hold 
 to be taken of it. The cup F, is 
 fixed upon the foot A, by screw- 
 ing the piece G, upon it, and both 
 are turned truly at their outer edges, 
 leaving a very narrow passage, //, 
 four inches diameter, between them all round. The piece G is hollow, having 
 holes, H, in its sides ; and a pillar, K, stands upon its centre, on which is screwed 
 the bell L L, the thin edge of which is brought just over the opening /, and half an 
 inch above it. When the cock is opened, the steam enters the cup F, through 
 the holes H, and rushes out at the narrow slit /, striking the thin edge of the bell L, 
 in a similar manner to the action in organ pipes, and producing an exceedingly shrill 
 sound ; some holes, M, are made in the top of the bell, to allow the steam to pass 
 
 3 N 
 
466 STEPHENSON'S PATENT 
 
 freely through, which improves the sound considerably. The cock is required to be 
 steadily opened to adjust the quantity of steam, so as to produce the clearest sound. 
 The steam whistle is very effective, and its sound can be heard at a great distance. 
 
 THE TENDER. 
 
 The tender is attached behind the engine and close to it ; it contains a tank of 
 water for supplying the boiler, and has a space in the middle filled with coke for 
 feeding the fire. A side elevation of it is shewn in Plate LXXXIX., a longi- 
 tudinal section in Plate XC., and a plan in Plate XCII. 
 
 FRAMING. The side frames, A" A", are made double, with diagonal bracing pieces 
 inside them, and are connected by strong pieces at the ends. The floor is supported 
 by diagonal and cross pieces, dotted in the plan, which are fixed into the sides and 
 ends ; and the joints of these pieces are strengthened by iron plates ; the plate in the 
 centre is shewn at at", extending along each of them. An iron bar, B" B", is fixed upon 
 the bottom along the centre, and another bar bolted to it underneath at the front, the 
 two projecting beyond the front, and having holes in their ends through which the pin 
 X ' is passed to connect the socket at the end of the drawing links W of the engine. 
 A chain and hook, y", is fixed on to the other end of the draw bar B", for the 
 purpose of attaching the train of carriages ; in this end of the bar a large square 
 socket is made, and is fitted upon the middle of the long spring C". D" D" are the 
 ufters faced with leather cushions, and fixed upon iron spindles which pass through 
 holes in the centre of two blocks of wood, z" z", that are bolted upon the end of the 
 frame ; and the spindles have sockets in the outer ends in which the ends of the 
 spring C" rest, and when the buffers strike against those of another carriage they 
 press against the spring C", which yields and reduces the shock of the collision. 
 
 WHEELS. The tender runs upon four wheels, G" G", three feet diameter, which 
 turn in the space between the pieces of the side frames ; they are made with flanches, 
 and are similar to the small wheels of the engine. The wheels are keyed upon 
 the axles, which are 3^ inches diameter, and turn at, their outer extremities in 
 axle boxes similar in principle to those of the engine ; the axle guides consist only 
 of a single plate, each three quarters of an inch thick, bolted on to the inside of the 
 outer pieces of the frame, and the axle boxes have grooves cast in their sides, into 
 which the edges of the axle guides are fitted. The springs H" H" are fixed down 
 upon the top of the axle boxes by two bolts made each into a large eye at the upper 
 end, which fits upon the spring, and the ends of the springs rest in sockets fixed upon 
 the under side of the outer piece of the frame. The tenders for the largest engines 
 are often placed upon six wheels, to diminish the weight upon each wheel. 
 
LOCOMOTIVE ENGINE. 46? 
 
 TANK. I" I" is the water tank, made of wrought iron plates one-eighth of an 
 inch thick, riveted together and joined at the corners by angle iron ; it is 
 of a horse-shoe shape, 9 feet long, 6| feet wide, and 2 feet deep. It is sup- 
 ported upon the side and end frames and a cross piece in the middle, and is 
 held in its place by pieces of strong angle iron fixed on to the frame and 
 standing up to hold the front and back ends. The top of the tank is covered with 
 the board K", having sides of iron plate fixed upon it ; and a raised part, N", is made 
 at the back, divided into three portions, covered with lids on hinges ; the middle one 
 containing an opening, 0", into the tank, twelve inches square, surrounded by iron plate 
 brought up to the top, for the purpose- of supplying the tender with water. The other 
 spaces on each side are used as tool boxes for holding the different articles that are 
 constantly in requisition in the engine. A copper pipe, P", is fixed underneath each 
 end of the tank, communicating with it, and passing through the floor, having 
 a cock in it to close the pipe when disconnected from the engine. The hose 
 pipes Q" Q", that are attached to the suction pipes K' K', for the feed pumps of 
 the engine, are connected with them by screwed sockets or union joints, which can 
 be readily unfastened when the tender has to be separated from the engine. The 
 hose pipes are made of leather or Indian rubber cloth, with a spiral spring inside to 
 keep them open like the suction pipes of fire-engines ; a flexible pipe being necessary 
 to allow for the variations of motion between the engine and tender. There is used 
 sometimes, instead of the flexible hose, a metal pipe with a double ball and socket 
 and a sliding joint, to allow motion in every direction ; this has the advantage of not 
 requiring repairs so often as the hose. 
 
 COKE. The middle space of the tender, R" R" R", is occupied with coke, the front 
 end being made level with the foot-board of the engine, and a board, S", fixed 
 inclining from thence down to the floor, for the convenience of taking up the coke 
 with a shovel to throw it upon the fire ; the bottom and sides are covered with 
 sheet iron. 
 
 The BRAKE for stopping the wheels is shewn in Plate LXXXIX., and consists of 
 two wrought iron frames hung by pins from the side frame of the tender, and 
 having blocks of wood fixed on to them, that are cut to fit the circumference of 
 the wheels. A flat iron wedge fits into grooves in the two frames and is con- 
 tinued up by a rod to the top of the tender, passing through a strong iron piece, W", 
 and having the double handle X" screwed upon it. By screwing down the handle 
 the wedge is drawn gradually up, and the two brakes are separated from 
 each other, pressing the wood of each very forcibly against the wheels until they 
 are stopped, if necessary. This brake is used to stop the engine and train quickly, 
 and others are also used on the wheels of some of the carriages in the train ; 
 
468 STEPHENSON'S PATENT 
 
 the brakes are of many different constructions, but this one is very simple and con- 
 venient and has great power. A step and a handle are fixed on to the tender 
 on each side for the convenience of getting upon it or upon the engine. 
 
 The tender weighs, when empty, 3^ tons, and about 7 tons when filled with 
 water and coke. The tank holds about 700 gallons of water, and the quantity of 
 coke that is carried is about 8 cwt. ; these are sufficient to supply the engine for run- 
 ning from thirty to forty miles, according to the load taken ; but the tender is seldom 
 run farther than twenty miles without being refilled. 
 
 The power of a locomotive engine cannot readily be estimated in the same manner 
 as that of other engines, by taking the actual force upon the piston, and the velocity 
 of its motion ; for it is very difficult to ascertain the effective pressure of the steam 
 upon the piston, in consequence of its differing often very considerably from that of 
 the steam in the boiler, and because of the large amount of the resistance of the 
 waste steam, owing to the great velocity with which the piston moves. The 
 power is also different at different velocities, as these circumstances vary with the 
 velocity. The only correct means therefore, of ascertaining the power of a loco- 
 motive, is by deducing it from the work that it is capable of performing. 
 
 This engine has drawn a load up an inclined plane that was equivalent to 220 
 tons gross weight upon a level, (including engine and tender,) at a velocity of 14 miles 
 an hour ; which appeared to be about the extent of the power of the engine with 
 the steam at the usual pressure of 50 Ibs. on the square inch, in the boiler. The force 
 required to perform this, is about 2050 Ibs. moving at that velocity ; which is equal 
 to 77 horse power. The effective pressure on the piston, or the actual force with 
 which it was propelled, must therefore have been 47^ Ibs. per square inch, instead of 
 50 Ibs., which was the pressure of the steam in the boiler ; the difference being the 
 power that was lost by the resistance of the waste steam, and by the diminution of 
 the pressure of the steam, in consequence of the throttling or wire drawing that takes 
 place in passing through the ports of the cylinders, and which was in this instance 
 very inconsiderable. 
 
 The horse power of an engine is less when drawing a lighter load at a greater ve- 
 locity, as the loss of power from the throttling and the waste steam is then increased ; 
 and it would cease altogether at a certain speed, varying according to the proportions of 
 the engine, when the velocity of the piston became as great as that with which the steam 
 can enter into the cylinder, or the waste steam escape. This engine has drawn 40 tons 
 at 35 miles an hour, which is equivalent to 40 horse power ; in which case the ef- 
 
LOCOMOTIVE ENGINE. 469 
 
 fective pressure on the piston must have been only lOlbs. on the square inch, or 
 but one fifth of that of the steam in the boiler. This shews the great loss of 
 power in working the engine so quickly ; the loss at 1 4 miles an hour having been 
 very little. This loss of power is lessened by making the wheels larger, the velo- 
 city of the piston being by that means diminished ; and they are consequently made 
 as large as is practicable. 
 
 The power of a locomotive engine is limited only by the evaporating power of the 
 boiler, or the number of cylinders' full of steam that can be supplied in a given time, by 
 which the velocity of the piston is determined ; while in other steam engines the size 
 of the cylinders is the limit to the power, as a sufficient quantity of steam to supply 
 them can be readily obtained by increasing the size or number of the boilers, which 
 cannot be done in a locomotive. This engine is capable of evaporating 77 cubic feet 
 of water per hour, or eight gallons in a minute ; and the large amount of this power 
 causes its great superiority to the old locomotives, which could evaporate only about 
 16 cubic feet per hour. 
 
 The consumption of fuel per mile for every ton of the gross load is about a quarter 
 of a lb., and that of the water is rather less than a quarter of a gallon ; the con- 
 sumption increasing to nearly one half, according as the engine is less fully loaded, 
 being proportionally greater with a light load ; the consumption of water, when 
 working with a full load, is a cubic foot per hour for each horse power, which is 
 also the usual proportion in stationary engines although they condense the steam. 
 About 8 Ibs. of fuel is required to evaporate a cubic foot of water, being nearly 
 the same as in stationary engines; but in the old locomotives as much as 18 Ibs. 
 was required, in consequence of their having so small a heating surface, which was 
 only about two and a half square feet for each foot of water evaporated per hour ; 
 the proportion in the present one being five and a half square feet, and in stationary 
 engines as much as eight. 
 
 The great perfection of the present locomotives, and their superiority to the old 
 ones, is caused not so much by the application of new inventions to them, as by the 
 combination of many former ones, and the uniting together several plans which, sepa- 
 rately, would be but of small value. Their great power and velocity, for example, 
 could not have been obtained without the rapid means of generating steam afforded 
 by the use of the tubes ; and the tubes would have been useless, without the 
 powerful draught produced by the blast, which increases in intensity with the 
 velocity, and with the necessity for its increased action. 
 
470 EXPLANATION OF THE PLATES. 
 
 PLATE XCIII. 
 
 This plate contains drawings of the Comet, the first steam boat in Europe, con- 
 structed by Mr. Henry Bell, of Glasgow, for the Clyde River. To some of our 
 readers the following circular respecting this boat may be interesting. 
 
 " STEAM PASSAGE BOAT, THE COMET, BETWEEN GLASGOW, GREENOCK, AND 
 HELENSBURGH, FOR PASSENGERS ONLY. 
 
 " THE subscriber having, at much expense, fitted up a handsome vessel to ply upon 
 the river Clyde, between Glasgow and Greenock, to sail by the power of wind, air, 
 and steam, he intends that the vessel shall leave the Broomielaw on Tuesdays, 
 -Thursdays, and Saturdays, about mid-day, or at such hour thereafter as may answer 
 from the state of the tide; and to leave Greenock on Mondays, Wednesdays, and 
 Fridays, in the morning, to suit the tide. 
 
 " The elegance, comfort, safety, and speed of this vessel require only to be proved, 
 to meet the approbation of the public ; and the proprietor is determined to do every- 
 thing in his power to merit public encouragement. 
 
 " The terms are, for the present, fixed at four shillings for the best cabin, and 
 three shillings the second ; but beyond these rates, nothing is to be allowed to ser- 
 vants or any other person employed about the vessel. 
 
 " The subscriber continues his establishment at Helensburgh Baths, the same as for 
 years past, and a vessel will be in readiness to convey passengers in the Comet from 
 Greenock to Helensburgh. 
 
 " Passengers by the Comet will receive information of the hours of sailing, by apply- 
 ing at Mr. Housten's office, Broomielaw; or Mr. Thomas Blackney's, East Quay 
 Head, Greenock. 
 
 " Helensburgh Baths, " HENRY BELL." 
 
 " Aug. 5, 1812." 
 
 Mr. Bell presented this new method of navigation to the British government at 
 three different times, viz., in 1800, 1803, and 1813, when, after all his exertions, it 
 was thought to be of no utility to government. After it was denied him in 1803, he 
 thought it very hard that such a discovery should lie dormant, and on that account 
 he sent a description of the method of applying steam, in propelling vessels against 
 wind and tide, to all the emperors and crowned heads in Europe, and also to 
 America, which last government put it in practice in the year 1806. 
 
EXPLANATION OF THE PLATES. 
 
 471 
 
 PLATE XCIV. 
 
 VIEW OF THE PACHA'S STEAM VESSEL OF WAR, THE NILE, AT SEA, 
 
 IN THE NILE. 
 
 The construction of this vessel is shewn in Plates CIV. to CVII., and full parti- 
 culars respecting her will be found in the description of those plates. 
 
 PLATES XCV. AND XCVI. 
 
 THE HONOURABLE EAST INDIA COMPANY'S STEAM VESSEL BERENICE. 
 
 This beautiful vessel, which is of 680 tons, was built in the Clyde by Messrs. 
 Wood ; and her engines, 230 horse power, were manufactured by Mr. Robert Napier, 
 of Glasgow. 
 
 Prom the log of her voyage from Falmouth to Bombay by the Cape of Good Hope, 
 performed between the middle of March and the middle of June 1837, the results 
 expressed in the following Table have been derived : 
 
 
 Distance in 
 nautical miles. 
 
 Time 
 
 Rate per hour 
 in miles. 
 
 Coal expended. 
 
 n 
 
 . 
 
 ajs 
 
 s s 
 
 Voyage performed. 
 
 
 occupied, in 
 days and 
 hours. 
 
 
 
 I!! 
 
 11 
 
 a g 
 
 s's'S 
 ! 
 s.s 
 
 Mea- 
 sured. 
 
 By log. 
 
 Meas. 
 (list. 
 
 Log. 
 dist. 
 
 tons. 
 
 cwts. per 
 hour. 
 
 
 
 
 d. h. 
 
 
 
 
 
 
 
 
 Falmouth to Tene. ? 
 
 1430 
 
 1572 
 
 7 7 
 
 8-2 
 
 8-9 
 
 127 
 
 14-5 
 
 124 
 
 380 
 
 11-2 
 
 Teneriffe to Mayo ) 
 B. Vista ) 
 
 840 
 
 952 
 
 4 9 
 
 8-0 
 
 9-0 
 
 84 
 
 16-2 
 
 17 
 
 240 
 
 10-0 
 
 Mayo B. Vista to > 
 Fern. Po y 
 
 2180 
 
 2272 
 
 11 5 
 
 8-1 
 
 8-4 
 
 155 
 
 11-4 
 
 39 
 
 1770 
 
 14-1 
 
 
 
 
 
 
 
 
 
 
 
 
 Fernando Po to > 
 Cape Good Hope. J 
 
 2340 
 
 2594 
 
 14 6 
 
 6-8 
 
 7'6 
 
 267 
 
 15-6 
 
 52 
 
 1614 
 
 8-1 
 
 Cape Good Hope to 7 
 Mauritius \ 
 
 2290 
 
 2692 
 
 1* 
 
 73 
 
 86 
 
 246 
 
 16-2 
 
 48 
 
 578 
 
 9.3 
 
 Mauritius to Bom- ) 
 bay . . \ 
 
 2520 
 
 2847 
 
 13 18 
 
 7-6 
 
 8-6 
 
 197 
 
 11-9 
 
 55 
 
 
 
 14-4 . 
 
 
 The boilers are three in number and of copper ; they are blown out every two 
 hours. There is no gauge on the steam-chest, or for the steam ; and there are nine 
 
472 EXPLANATION OF THE PLATES. 
 
 fires. The wheels, which are of the common kind, are about 22 or 23 feet in dia- 
 meter, and the boards 9 feet wide. The cylinder is 56 inches, and the stroke 5 feet 
 6 inches. 
 
 Plate XCV. presents a view of the vessel at sea, off Bombay ; and Plate XCVI. 
 shews the sheer draught, lines of bottom, &c. 
 
 GENERAL OBSERVATIONS UPON THE CONSTRUCTION OF STEAMERS. 
 
 The construction of the draught should be made with very strict attention to the 
 weight of the hull, fittings, stores, engines, coals and cargo, (if required to take goods,) 
 reducing as much as possible the component parts of the hull, and giving that form 
 which is best adapted for velocity. 
 
 It should be particularly considered, as stated by Sir Robert Seppings, that the 
 strength of any fabric consists in the disposition of the materials, (in the connection and 
 security of its several parts,) and that " the strength of a vessel, let its construction be what 
 it may, can never exceed that of its weakest part ;" or that " union is strength," i. e. 
 giving the required strength with the least quantity of wood, copper, iron, &c. ; 
 keeping every part of the fabric as tight as is consistent with safety, equal to contend 
 with the violent action and impulse it will be subject to at sea. The fastenings 
 recommended, (and which have been so extensively introduced,) are those laid 
 down in " The New Principle of Ship Building," by Sir Robert Seppings ; a system of 
 trussing and diagonal ties of iron. (Vide the Philosophical Transactions.) 
 
 The form should be, in midships, nearly a square with the corners rounded off, 
 or " a long, flat floor" gradually rising to an acute angle at the extremes, or fore and 
 after bodies, similar to the water lines or horizontal sections of those renowned and 
 celebrated schooners of America called " Clippers." The dead wood or extreme 
 fineness abaft being done away, as shewn in the following diagram : 
 
 A, The water or horizontal load line. 
 
 B, The new line of keel, the dead wood shewn by the shaded part to be done 
 away with. 
 
 C, The old line of keel. 
 
EXPLANATION OF THE PLATES. 473 
 
 D, The new line of post, with the rake taken out and brought perpendicular to the 
 new line of keel, B. 
 
 E. The stem to have a flare or flam to correspond with the bow. 
 
 To prevent rolling as much as possible and falling to leeward, two deep bilge 
 keels to be fastened to the bottom plank, with bolts clinched on the inside. (These 
 keels have been well tested in certain vessels belonging to the Honourable East India 
 Company, in Bengal.) 
 
 The fore and after bodies of the American schooners (applied as just described) 
 have been proved to be the best suited for velocity, the sharp flaming bow dividing 
 the fluid with the greatest facility, and the fineness of the run allowing it to pass to 
 the stern with the utmost rapidity. 
 
 This improved form is obtained by giving a great proportion of length to breadth, 
 which has been so successfully adopted in the construction of all recently con- 
 structed steamers (particularly those built by private companies or individuals). 
 It is recorded in the translation of Chapman's celebrated work by Dr. Inman : 
 " Care must be taken to shape the fore and after bodies, the former so that the 
 fluid may be cloven with facility, and at the same time the displaced fluid dis- 
 persed and transmitted towards the stern with as much ease as possible." Velocity 
 in steam vessels is, therefore, obtained by a light draught of water, and keeping the 
 fore and after bodies sharp, and giving the least proportion of length to breadth with 
 reference to the required stability, viz. for sea-going steamers, six times the breadth 
 for the length at the load water line ; in vessels for inland or river navigation, the 
 length has been carried to ten times the breadth in some of the American boats. Vide 
 Stephenson's late work on American Engineering. 
 
 PLATE XCVII. 
 
 DRAUGHT OF THE FORBES STEAMER, CONSTRUCTED AT CALCUTTA, 
 BY ALEXANDER HENDERSON, ESQ.; CHINESE RIGGED. 
 
 This plate presents a sketch of the masts and sails of the steamer Forbes, as fitted 
 when she towed a ship of 380 tons from Bengal to China against the monsoon in 1830, 
 with the fore-sail and main-sail; the plan of the Chinese sail was adopted as best suited to 
 the purposes of a steamer, giving the greatest spread of canvas, with the least weight 
 of mast and rigging ; the stretchers or yards in the body of the sail, by dividing the 
 strain on the mast, are useful to reduce the weight aloft and require little rigging ; 
 
 3 o 
 
474 EXPLANATION OF THE PLATES. 
 
 besides facilitating the working and reefing of the sail. These sails act best sailing 
 by the wind ; and there being no depot of coals in China, to return to Singapore 
 with a fair wind, a fourth mast was fitted in an iron step or trunk immediately in 
 front of the boilers ; with a square-sail, top-sail and topgallant-sail, with their 
 studding-sails. While steam power was used, this mast was lowered fore and aft, 
 as shewn by the ticked lines. 
 
 PLATE XCVIII. 
 
 HERNE BAY STEAM PACKET RED ROVER. 
 
 The engines, two 60 horse power, are by Messrs. Boulton and Watt, and the 
 vessel was built by Messrs. Fletcher, Son, and Fearnall, London ; launched 28th March, 
 1835, for the Herne Bay Steam Packet Company. 
 
 PRINCIPAL DIMENSIONS OF THE HULL. 
 
 Ft. In. 
 
 Length between the perpendiculars . . . 154 
 
 Breadth to the outside of the bottom plank . . . 22 4 
 
 Depth at shaft from top of floor timber to the under side 
 
 of deck 10 4 
 
 Burthen in tons, 376$-j (builders' measurement). 
 
 This vessel was constructed for the conveyance of passengers and luggage to and 
 from London to Herne Bay with the greatest possible dispatch, and comparing her 
 displacement and power with other similar vessels, was and continues the fastest 
 running out of the Thames. This superiority of speed was chiefly effected by a 
 novel mode of building, a mode combining the fourfold advantages of increased 
 buoyancy, a more uniform diffusion of strength, prevention of rot by exclusion of 
 surfaces, and affording the greatest possible facility to repairing. 
 
 The bottom, or that part of it on which the engines and boiler were fixed, was 
 composed of stout floor timbers going from bilge to bilge, placed close together and 
 dowelled and bolted to each other, and planked externally with the best well 
 seasoned four-inch Dantzic deals, fastened in the usual manner ; but above, before, 
 and abaft this part of the bottom so wrought, the timbers of the frame used in 
 common were omitted, and the plank continued of the same thickness to the top of 
 
EXPLANATION OF THE PLATES. 475 
 
 the sides, having the edges grooved and tongued, and secured to each other by f bolts 
 driven through the edges in a diagonal direction at about 1 5 inches apart ; in addition 
 to which, long diagonal iron plates, 4 inches broad by f ths of an inch thick, placed at 
 an angle of 65, and 2 feet 6 inches from each other, were worked each on a 
 Dantzic fir plank ^,\ inches thick and 9 inches broad, the whole secured by a through 
 bolt in each outside strake, having a screw point and nut setting up on the diagonal 
 plate inside the vessel. 
 
 It must be obvious to all persons acquainted with the nature of shipbuilding, that 
 the hull of a vessel so built would offer the greatest advantages to the caulking, 
 requiring but half the usual quantity of oakum, and that stopped from being driven 
 through the seams by a strong oak tongue bedded in white-lead uniting the edges 
 of the planks. The uniform strength of the entire hull has very far exceeded all 
 expectation, and in the opinion of those acquainted with its nature this method is 
 admitted to be superior to any yet practised. 
 
 PLATE XCIX. 
 
 DIAMOND COMPANY'S STEAM PACKET RUBY. 
 
 This plate represents a drawing of the Ruby steamer, which belongs to the 
 "Diamond" Company, plying between London and Gravesend, and is unquestionably 
 the fastest boat on the Thames. We do not make this assertion upon mere hearsay, 
 having had frequent opportunities of satisfying ourselves of the fact. It would be 
 entering too much into detail to give a statement of the progressively improving 
 character of the various steam boats which have plied between London and 
 Gravesend during the last ten years ; it is enough for our present purpose to state 
 that the "Diamond" and "Star" Companies keep up an establishment, upon an 
 average, of a dozen boats, of a very superior description, every thing connected with 
 their appointments being upon a most liberal scale. The vessels belonging to the 
 " Diamond " Company are, the Diamond, Pearl, Gem, Brilliant, Topaz, and Ruby ; 
 and those belonging to the " Star " Company are the Mercury, Star, Comet, Planet, 
 and Vesper, one of the boats, Medway, having been burnt by accident during the 
 summer of 1837. Until the beginning of the year 1837 (at which time the Ruby 
 was placed on the station) the Star was considered to be equal in speed to any of 
 the above ; indeed it may be said that no vessel that navigated the Thames could 
 
476 EXPLANATION OF THE PLATES. 
 
 equal her, except perhaps the Diamond, and the City of Canterbury, (running from 
 London to Herne Bay and Margate ;) with these exceptions it is admitted that in 
 velocity the Star was unrivalled. 
 
 Vessels of the greatest speed will always command a decided preference ; hence 
 it is to the interest of proprietors to apply to the most skilful naval architects 
 and engineers, to procure vessels which shall combine speed with strength and 
 durability. 
 
 The Ruby built by the " Diamond " Company, at Mr. Wallis's ship yard, 
 Black wall, in the early part of the summer of the year 1837, possesses the above es- 
 sential qualities in an eminent degree, which has induced us to solicit the favour 
 of her plans for publication. 
 
 Mr. 0. W. Lang, who designed the Ruby, has obligingly presented us with the 
 lines, and put us in possession of many particulars respecting her. 
 
 Her length is 155 feet between the perpendiculars ; 141 feet 9| inches on the keel 
 for tonnage ; breadth for tonnage 19 feet, moulded 18 feet 5^ inches; depth in hold 10 
 feet 2 inches ; and burthen 272 tons. She is propelled by two engines of 5 horse power 
 each, made by Messrs. Seaward and Company, of which the following are some of the 
 most important particulars : diameter of cylinder 40 inches ; length of stroke 3 feet 6 
 inches ; number of strokes per minute 30 ; diameter of paddle wheel 1 7 feet 6 inches ; 
 length of paddle board 9 feet 2 inches, and depth 15 inches; dip or immersion 15 
 inches. The practical construction of the vessel is upon a principle recommended 
 by Mr. 0. W. Lang, and invented many years since by Mr. Johns, a clever practical 
 officer of Plymouth Dock-yard. It consists of an outer surface of plank, placed 
 horizontally in the usual manner, but of an inch and a quarter only in thickness, the 
 timbers being substituted by two other thicknesses of plank, laid diagonally to the 
 keel, but at right angles to each other, with felt introduced between the layers, the 
 whole three being fastened together by nailing, in the same manner as a clench work 
 boat. Vessels built in this manner have been found to be far less expensive (at least 
 20 per cent.) than vessels built in the usual way ; they also possess greater strength, 
 and judging from the trials that have been made of ships' launches and other large 
 boats for the Navy *, for several years past, there can be no doubt of their durability. 
 The comparative lightness of vessels built in this manner is also a great recommenda- 
 tion. The Ruby, when launched, was found to displace only 65 tons of water. Her 
 draught, with her engines and fuel on board, complete in all respects, was only 4 feet 
 8 inches abaft, and 4 feet 1 inch forward ; her displacement 1 70 tons, and the area 
 
 * The boats built for the Navy are only of two thicknesses, the outer (fore and aft) planking being 
 deemed unnecessary. They are well known as Mr. Johns' double bottomed diagonal built boats, and 
 are held in high estimation. 
 
EXPLANATION OF THE PLATES. 477 
 
 of her midship section 63.2 feet ; under these circumstances her speed through the 
 water has been ascertained by careful trials to be 13.5 miles per hour, no other 
 vessel having yet exceeded the rate of 12.7- 
 
 PLATES C. TO GUI. 
 
 DESCRIPTION OF HER MAJESTY'S STEAM VESSEL OF WAR MEDEA, CON- 
 STRUCTED AND BUILT BY OLIVER LANG, ESQ., MASTER SHIPWRIGHT, 
 ROYAL DOCK YARD WOOLWICH; 
 
 Shewing the mode of putting her frame together so as to obtain and produce the 
 greatest combination of strength in connecting the various parts of the ship, and dis- 
 tributing the fastenings equally throughout the fabric. 
 
 Light. Deep. 
 
 Feet. In. Feet. In. 
 
 , f afore 70 13 10 
 
 Draught of water < ... 
 
 (.abaft 91 14 6 
 
 Displacement in tons ...... 502'81 1230 
 
 Area of midship section 168'84 354 
 
 The keel was made secure on his principle of the " safety keels ;" the inner or 
 solid one, fitted to the floor timbers in midships, and to the deadwood afore and 
 abaft, with dowels on the upper or faying part, connecting the floors, deadwood and 
 keel together ; the under side of the keel projecting a few inches only beyond the 
 bottom, protected by a longitudinal piece of timber, fitted all fore and aft on each side, 
 substituting the chocks usually brought on the heels of the timbers, to fashion them 
 at that place, and of sufficient size not only to make good the said chocks, but like- 
 wise the plank of the bottom (commonly called the garboard) in one solid substance ; 
 those pieces are placed one on each side of the inner keel, with felt between the 
 faying surfaces, dowelled and connected together by bolts, driven athwartships 
 through all and clenched on a ring at the outer sides of the longitudinal pieces, and 
 likewise in an up and down direction, through the frame timbers, similarly clenched ; 
 the inner or solid keel as before described, is previously dowelled and bolted in a ver- 
 tical direction through the floors, deadwood and keelson, in addition to those lon- 
 gitudinal pieces or side keels, the ends of the bolts being well clenched on rings, thus 
 
478 EXPLANATION OF THE PLATES. 
 
 making the base of the fabric perfectly secure and strengthening the most important 
 part of the ship. Vide section, Plate CII. 
 
 The timbers composing the frame of the lower part of the ship, are strengthened 
 by solid fillings caulked and made water-tight from the keel to about four feet above 
 the turn of the bilge, so that if the vessel should by accident at any time take the 
 ground, and disturb the outer or false keel with such part of the planking on the 
 lower part of the bottom as might by any possibility come in contact with the rocks, 
 yet she would be perfectly safe, as the inner or solid keel could not be removed but 
 only ground away in such places as bore against the shore, it being firmly attached 
 to the fabric. 
 
 The lower part of the stern post (vide Plate C.) is united to the after end of the 
 solid keel, by a knee piece scarphed and grooved at the after end, and scarphed and 
 dowelled at the fore end, bolted through and securely clenched on a ring at the end 
 of each bolt, instead of the old method, a mortice and tenon, as generally adopted by 
 shipbuilders in this and all other countries, which insufficient mode has caused the 
 loss of many vessels. The lower piece of stem is scarphed to the foremost piece of 
 keel horizontally, and not with a vertical or side scarph in a square boxing, that 
 dangerous system so long practised in vessels of all descriptions, but on the con- 
 trary, forming no projecting butt, to the fore end of the keel ; should the gripe be car- 
 ried away by the ship striking the rocks, the remaining surface of the keel and bottom 
 would offer no resistance to the cable after such an accident, but would retain a 
 similar shape to the original form of the ship when in its perfect state. 
 
 The whole frame is connected together by iron braces on the inside, placed in a 
 diagonal direction, let into the timbers about half their thickness, and having one bolt 
 passing through every timber for their security, and a wood trussing of four-inch 
 plank in the opposite direction, to prevent the hull of the vessel from hogging or 
 altering her form ; between the wood trussing, the timbers are covered by board of 
 one inch and a half thick, secured at the ends on a cant two inches square, so that 
 the board may bear only on the cants, and allow a current of air to pass throughout 
 the ship. 
 
 The upper deck beams are secured to a shelf or thick clamp, which extends all 
 fore and aft on both sides of the ship and embraces every timber ; the beams are 
 dowelled and bolted to the said clamp, their ends extending without over the top- 
 side to connect the sponcing, being scored and let into the sponcing timbers, dovetailed, 
 and bolted in a fore and aft direction ; a thick strake is then worked on the outside 
 on the ends of the beams against the timbers forming a sheer strake, scored half way 
 between the said timbers to meet the thick water-way, which is scored in like man- 
 
EXPLANATION OF THE PLATES. 479 
 
 ner to meet the sheer strake from inside ; felt is placed between the joint vertically, 
 the whole bolted together with bolts driven horizontally and well clenched on a ring 
 at each end ; the under side of the water-way is scored dovetail about one inch and a 
 half over the beam ; on the upper part of the sheer strake and water-way, felt is laid, 
 and on that a plan sheer or gunwale placed, which is bolted through the water-way 
 and plan sheer in a vertical direction and clenched with a ring on each end of the 
 bolt to keep it down and make it firm. The sponcing timbers run up to the rough 
 tree rail, their heels stepping on a thick strake worked in the side of the vessel 
 and well bolted, forming a rabbet which receives the planking, making a secure 
 artificial topside in addition to the common topside of the ship. Vide section, 
 Plate GIL 
 
 The engine bearers are dowelled and bolted firmly through the bottom, scored on 
 the under part to receive the nuts for securing the hold down bolts which prevent 
 their passing through the outside plank and creating danger. 
 
 Plate CI. shews the plans of the upper and lower decks, under which there is a 
 fore and after platform, exclusive of her store-rooms and magazine ; on these platforms 
 there is provision made for berthing in hammocks 145 men in addition to her ship's 
 company, which are berthed in like manner on the lower deck, the fore side of the 
 engine-room ; on the aft side the officers' cabins are shewn ; the planks of the lower 
 decks, both afore and abaft, are laid athwartships, rabbeted into the sides of the 
 beams, which are considerably less in number than if the deck were laid in a fore 
 and aft direction on beams as usually done ; the beams are secured to the side by iron 
 knees. 
 
 The upper deck is laid in a fore and aft direction on substantial beams, made par- 
 ticularly strong on the fore and aft parts with carlings well pillared under the deck 
 in wake of the great guns, which are both of ten inches calibre, and worked on a 
 carriage and slide with pivots, which admits of their being turned in any direction 
 that may be required ; the bulwarks above the plan sheer are light, the fore and aft 
 parts fitted to drop in several pieces by iron stanchions, forming a hinge, so that the 
 whole or any part required can be let down clear to admit of the guns being 
 run well out, that their muzzles may not interfere with the side of the ship when 
 firing. 
 
 Her tiller is under the upper deck that it may not obstruct the working of the guns; 
 an iron plate is attached to the head of the rudder, with three holes, one in the centre 
 and one on each quarter ; an iron plate is fitted on the head of the stern-post, and 
 when the rudder is required to be secured in midships, a pin is dropped into the 
 centre hole of the plate on the rudder, which passing through this and the plate on 
 the post, fixes the rudder immediately in midships ; the same may be done by re- 
 
480 EXPLANATION OF THE PLATES. 
 
 moving the pin to one of the other holes, when the rudder may be placed on the 
 quarter on either side if at any time it may be required to lay the ship to, to shift 
 the tiller, or to reeve new ropes to the wheel. The heel of the mainmast is fitted 
 in an iron crutch with a strong pillar, in order to bring the mast nearer its proper 
 position for sailing, which otherwise would be prevented by the boilers. 
 
 In corroboration of the foregoing facts we shall here state a most extraordinary 
 circumstance. Her Majesty's frigate, the Pique, of thirty-six guns, built with Mr. 
 Lang's safety keels, had the misfortune to run on the rocks near the strait of Belle 
 Isle, on the 22d of September, 1835, and tore off her false, and likewise her outer 
 main keel all the way fore and aft, and ground away, in four different places, the 
 inner or solid keel, and the longitudinal pieces at those parts forming the garboard 
 connected thereto, which being so firmly attached to the ship bore the violent fric- 
 tion of such ponderous weight, the frigate with her guns, stores, &c., in contact 
 with the rocks without being displaced, and the vessel was got off, preserved from 
 shipwreck, and brought to England in safety, although encountering very severe 
 gales of wind on her passage. Several instances have occurred of other ships fitted 
 with the safety keels getting off the rocks without admitting any water. We shall 
 now mention two cases, not only to prove the safety of vessels fitted with the keels in 
 question, but to shew the strength of the fabric of ships built like the Medea ; those 
 alluded to are the Lightning and Flamer steamers, constructed by Mr. Lang, and 
 built under his superintendence. The former vessel, the Lightning, on her first pro- 
 ceeding to sea, ran ashore a little below Sheerness, on the Spaniard shoal, fell over 
 on her side where she lay dry at low water ; she floated again at high water, and it 
 was found she had sustained no damage. As she was entering Dover harbour, soon 
 after, she ran full speed against the pier and struck her fore-foot or gripe, knocking it 
 over on one side, but made no water ; on being docked at Portsmouth after this, her 
 gripe was replaced and no other injury appeared. The next important occurrence 
 happened when at Jersey : being aground alongside the pier, and a rope made fast to 
 her mast-head, secured to the shore to keep her upright, the water having left her 
 dry above one hundred and fifty feet, the rope broke and she fell violently down on 
 her side ; this shock was severely felt in the engine-room, but she sustained no injury 
 in the hull nor machinery by the fall ; at high water she righted again and sailed 
 across the Channel to the Downs, where she was run into, just abaft the starboard 
 paddle-box, by a loaded collier, which did the Lightning but little harm in her top- 
 side and sponcing, but the collier, by the concussion, stove in her bows, ran on shore 
 to save her from sinking, and became a wreck. 
 
 In the heavy gale of wind in February, 1833, the Lightning was in the Irish 
 Channel on her way to Dublin, with the Erin, a large steam vessel, when the latter 
 
EXPLANATION OF THE PLATES. 481 
 
 foundered in the gale, and the Lightning had the misfortune to run on shore, but was 
 got off with the loss of part of her keel and gripe ; notwithstanding, she made the 
 voyage in safety, continued at sea for two months after the accident, and did not 
 leak in any part, was taken into dock, her keels and gripe replaced, and damages 
 made good. 
 
 In the month of December following the Lightning sailed from Falmouth on the 
 same day as her Majesty's steamer Columbia ; in the course of the day she passed 
 her, the wind blew very hard and increased to one of the most tempestuous gales 
 that had been known for several seasons ; so severe was the wind that the Columbia 
 was obliged to put back, and from the situation in which she left the Lightning, 
 considered the latter had foundered ; but the Lightning proceeded on till she arrived 
 at Corunna, and from thence to Lisbon. On her way to the latter place, when 
 about forty miles distant from it, she discovered a vessel in distress under the rock 
 firing guns, being on a lee shore ; the Lightning immediately went to her assistance, 
 and found her to be H. M. brig Plover, of ten guns, which had sailed from Fal- 
 mouth eight days before the Lightning ; she towed her off from the land, and leaving 
 her with a good offing continued on for Lisbon, there delivered her dispatches to the 
 admiral, and returning to the Plover, again took her in tow and conducted her 
 safely into port. 
 
 In October, 1834, the Lightning ran over the Coal Rock, near Elsinore, going 
 between eight and nine knots ; this had about a foot less water over it than her 
 draught, but she was brought up against and hung by the middle upon another 
 rock, where she remained ten hours, dropping and rising head and stern succes- 
 sively. The consequence was that her gripe, part of the fore piece of keel, and 
 midship piece, by which she was hung on the rocks, were carried away, the whole 
 of her keel all fore and aft about two or three inches from the under side against the 
 rocks ; after getting off in this injured state, she experienced a heavy gale of wind, 
 which lasted four days, and from which she sought shelter at Heligoland, but there 
 she parted both her cables and was driven to sea ; although the sea was running 
 as high as her funnel, she shipped nothing but spray ; at the same time the Superb, 
 a common built steamer, was lost. It was observed by those on board the Light- 
 ning, that while on the rocks and in the gale she did not work or strain in any 
 part ; not a seam or a butt opened, nor was even the pitch broken in any place ; no 
 sign whatever of altering her form but remained perfectly tight. On repairing the 
 keel it was found, on removing the damaged part, that it was quite dry within, 
 and no water had penetrated into the hull of the vessel ; the calking of the seams 
 and wood ends, notwithstanding the heavy shock in dislodging the gripe and keel, 
 was hard and sound and not started in the least, thus proving the strength of the 
 
 3 P 
 
482 EXPLANATION OF THE PLATES. 
 
 fabric ; since which she has been on shore on the coast of Spain, while employed 
 on that service in January 1837, rubbed off the copper from her keel, and in Fe- 
 bruary 1838, at Holyhead, she had the misfortune to run on the rocks, and struck off 
 her gripe and foremost piece of keel, immediately after which she encountered a very 
 severe gale of wind for three days, and did not strain or leak in the smallest degree. 
 This vessel has also performed many difficult voyages in various parts of the world, 
 viz., Mediterranean, Spain, Portugal, France, Holland, Denmark, Sweden, Russia, 
 Scotland, Ireland, &c., and experienced very bad weather. She was at the battle 
 of Algiers, and was very useful in towing and placing the ships in order of battle, 
 and towing from under the batteries such vessels as drifted within the reach of the 
 enemy's guns. 
 
 The Flamer went on share on the rocks at Zante in the Mediterranean, going 
 nine knots, and ran up two feet less than her draught of water ; she remained on 
 shore twenty-two hours, carried away her fore piece of keel and gripe, tore off the 
 copper from her bilge, and injured the plank of her bottom ; she was lightened and 
 got off, came to England safely ; previously she was run into by a Spanish ship just 
 abaft the paddle box, which stove in the sponcing at that place without affecting 
 the Flamer in any other part ; the Spaniard received much damage in running 
 foul, and on getting clear left the knee of her head behind, which was broken off in 
 the Flamer and brought home. When taken into dock about six weeks after, the 
 calking was found hard and sound, even close to those parts of the keel that were 
 carried away, and the ship shewed no appearance of straining, or having suffered 
 in her fabric by the violence of the blows she sustained in running on shore, or by 
 being struck by the Spaniard. On this principle of strength Mr. Lang commenced 
 the construction of sea-going steamers, having designed and built the first for sea 
 service, an experiment at that time considered impracticable. 
 
 The steam vessels he has constructed for her Majesty's service are the Comet, 
 237 tons, engines 80 horse power, for towing men-of-war from one port to another ; 
 Advice (late Vixen), 185 tons, engines 80 horse power, for the Post Office service 
 between Holyhead and Dublin ; Lightning and Meteor, 296 tons each, engines 100 
 horse power, for towing ships and any sea service required; Pluto, 365 tons, 100 
 horse power, for the suppression of the pirates on the Bahama Banks, armed with 
 two long eighteen pounder guns, one afore and one abaft, on a carriage and slide to 
 traverse on a sweep; Flamer, 492 tons, 120 horse power; Firebrand, 492 tons, 
 engines 120 horse power, Mediterranean packets; the Firebrand has since become 
 the Admiralty yacht ; Medea, 843 tons, engines 220 horse power, war steamer ; 
 Firefly, 549 tons, engines 140 horse power, and Spitfire, 553 tons, engines 140 
 torse power, Mediterranean packets ; and Ionia, 263 tons, engines 90 horse power,, 
 
EXPLANATION OF THE PLATES. 483 
 
 packet for the Ionian Islands ; all which are built on the same mode of security as 
 the Medea, and have proved to be excellent sea boats, possessing speed, ease, and 
 comfort combined with superior strength of fabric. 
 
 PLATES CIV. TO CVII. 
 
 CONSTRUCTION OF THE NILE STEAM SHIP, BUILT FOR THE 
 BASHAW OF EGYPT. 
 
 That steam vessels will become of more and more importance, as well in a 
 commercial point of view as in warfare, is a point now generally admitted ; and 
 though they may never entirely supersede the vessel impelled with sails, it is likely 
 they will ultimately be employed in all services for which sailing vessels are now 
 used except that of the service for which ships of the line are employed. In 
 carrying on experiments for the general improvement of steam navigation, there 
 must necessarily be failures ; but the advantages and particular interest the intro- 
 duction of an extensive steam navigation involves, must ultimately engage the 
 energies of every nation at all interested in maritime pursuits, and desirous of the 
 benefits that an extensive application offers. 
 
 The use that these vessels are found to be in towing ships in and out of harbours, 
 and carrying mails, is now evident ; and the advantages proposed by them in 
 warfare are too great to suffer the neglect of any experiment that may bear any 
 evidence of improvement. With a proper rig, they may be rendered effective for 
 almost every purpose for which sailing vessels are employed ; while their dis- 
 advantages on comparison are small. The liability of their machinery to be 
 destroyed by shot, and the space and weight of machinery required for impelling 
 the vessel, are the greatest objections that can be urged against them : and may 
 be particular objects for the attention of engineers. 
 
 In the construction of the Nile these were subjects particularly attended to, 
 without speculating beyond what was warranted by experiment : to reduce the 
 consumption of fuel by her engines, bad conductors of heat were placed over her 
 boilers, &c., such as felt and cement ; and from their construction and position, a 
 greater space than common was obtained for the coals. To ensure, as far as 
 possible, the protection of the engines in the event of her being engaged in warfare, 
 
484 EXPLANATION OF THE PLATES. 
 
 wings were formed on both sides that might be filled with such light substances as 
 would resist shots when required as cork, bags of flax, &c., or if required, the 
 seamen and soldiers' beds. With the protection that may thus be afforded, the 
 Nile could be rendered quite as efficient in every respect as a sailing vessel ; for 
 with the security thus obtained, the only parts unprotected would be the paddle 
 wheels and chimney, which probably would not offer more exposure to shot than 
 the masts and yards of sailing vessels : while with the paddles and chimney in- 
 jured, the Nile has still her masts and yards, which are equal for the performance 
 of a voyage. This was clearly proved on her taking troops from Syria to Alex- 
 andria ; when from the number of troops on board, and delays occasioned by 
 them, the fuel was exhausted, and the only resource left was her sails. 
 
 This vessel was rigged with three masts as a brigantine or ketch forwards, and 
 two masts as a schooner abaft, as may be seen by reference to Plate XCIV. ; added 
 to which, when not steaming, several large staysails were set flying from the main to 
 the foremast, so that she could be impelled in strong winds, when close hauled, 
 from eight to nine knots, and off the wind, from ten to eleven knots. When 
 steaming head to wind, the yards could be lowered one on the other pointed to the 
 wind, as low as that when the foremost gun was required to be fired, the explosion 
 would not affect them ; and the topmast was then lowered to the deck, being of a 
 length, that when struck, it could be lashed between the trestle-trees, on the fore 
 side of the foremast, so that her mast and yards did not oppose any great resist- 
 ance when steaming head to wind. 
 
EXPLANATION OF THE PLATES. 
 
 483 
 
 NILE STEAM SHIP. 
 
 DIMENSIONS OF SAILS. 
 
 DIMENSIONS OF MASTS AND YARDS. 
 
 I 
 
 i 
 
 Middle. 
 
 JS 
 
 3 > 
 
 fS O 
 
 
 
 tl 
 
 9 
 
 1 
 
 Ft. In. 
 
 Jib i 
 
 Ft. In. 
 
 35 
 30 
 36 
 68 
 59 6 
 39 6 
 48 
 43 
 38 
 44 
 29 
 
 Ft. In. 
 
 40 
 37 
 19 
 
 Ft. In. 
 
 62 
 48 
 36 
 44 
 37 
 21 
 64 
 73 
 41 
 54 
 32 
 
 Ft. In. 
 
 84 
 60 
 53 
 
 38 
 53 
 56 
 40 
 40 
 
 Main mast Hounded 
 
 Feet. In. 
 
 84 
 14 
 52 
 10 
 70 
 14 
 40 
 19 
 8 
 68 
 10 
 38 
 7 
 43 
 41 
 63 6 
 2 
 53 6 
 7 
 33 
 1 6 
 60 
 1 6 
 38 
 1 6 
 42 6 
 2 6 
 37 6 
 2 6 
 32 
 4 
 47 6 
 2 6 
 28 
 25 
 21 
 
 Inches. 
 
 24 
 
 251 
 
 14 
 
 20 
 10 
 
 
 Headed 
 Main topmast Hounded 
 
 
 Fore course 58 
 
 Pole 
 Fore mast Hounded 
 
 
 Fore top gallant sail... 29 
 
 Head 
 
 
 Fore top gallant mast to do 
 
 
 Sky sail 
 
 
 Mizen gaff topsail 10 
 
 Head 
 
 
 Pole 
 
 AREAS OF SAILS. 
 
 
 
 Arms 
 
 101 
 
 7| 
 10 
 
 8 
 10 
 9 
 
 Arms 
 
 Arms 
 
 
 Square feet. 
 
 Arms 
 Main topsail yard 
 
 Jib 
 
 1036-8 
 7296 
 693-0 
 2566-24 
 1823-58 
 684-86 
 2136-72 
 2303-62 
 1107-2 
 1617-2 
 640-52 
 
 Arms 
 
 
 Without the cleats 
 
 
 
 Without the cleats 
 Mizen ffaff . 
 
 
 
 Without the cleats 
 
 
 
 Without the cleats 
 
 
 
 Main storm ffaff 
 
 
 
 
 
 
486 
 
 EXPLANATION OF THE PLATES. 
 
 MOMENTS OF SAILS. 
 
 SPECIES OF SAILS. 
 
 Jib 
 
 Second jib 
 
 Fore staysail 
 
 Fore course , 
 
 Fore topsail , 
 
 Fore top gallant sail. 
 
 Fore gaff sail 
 
 Main gaff sail 
 
 Main gaff topsail 
 
 Mizen gaff sail 
 
 Mizen gaff topsail .... 
 
 In relation to the load water line. 
 
 Height of 
 
 the centre of 
 
 gravity. 
 
 1036-8 X 
 
 729-6 X 
 
 693-0 X 
 
 2566-24 X 
 
 1823-58 x 
 
 684-86 X 
 
 2136-72 X 
 
 2303-62 X 
 
 1107-2 X 
 
 1617-2 X 
 
 640-52 X 
 
 15339-34 
 
 50'Oz 
 39-2: 
 32-4: 
 37-2: 
 76-4: 
 108-0: 
 40-8= 
 47-Oz 
 98-0: 
 37-8i 
 75-2: 
 
 Moments. 
 
 51840-0 
 
 28600-32 
 
 22453-2 
 
 95464-12 
 
 139321-51 
 
 73964-88 
 
 87178-17 
 
 108273-14 
 
 108505-6 
 
 61130-16 
 
 48167-1 
 
 824898-20 
 
 In relation to a section passing through the 
 middle of the water line. 
 
 Distance 
 from the 
 middle. 
 
 108-0 
 92-6 
 68-6 
 51-4 
 50-8 
 50-4 
 26-6 
 53-2 
 47-6 
 91-2 
 85-2 
 
 Moments before. 
 
 Moments abaft. 
 
 111974-4 
 
 
 67560-96 
 
 
 47539-8 
 
 
 131904-73 
 
 
 92637-86 
 
 
 34516-94 
 
 
 56836-75 
 
 
 
 122552-58 
 
 
 52702-72 
 
 
 147488-64 
 
 
 54572-3 
 
 542971-44 
 
 377316-24 
 
 Height of the Centre of Effort ? 
 
 15339 
 
 Distance of the Centre of Effort before 1 542971 '377316 
 the middle of the Water Line 3 15339 
 
 = 53-77 
 
 = 10-7 
 
 DIMENSIONS OF RIGGING, ANCHORS, &c. 
 
 Inches. 
 
 Fore shrouds, 5 pair 8 
 
 Pore stay '<''. 
 
 Fore bob stay 6 
 
 Fore topmast shrouds !.' 
 
 Fore topmast stay 5 
 
 Fore dead eyes, diameter 11 
 
 Main shrouds chain, 4 pair f 
 
 Main stay chain, short link ^-f 
 
 Main topmast stay J 
 
 Main dead eyes, diameter 11 
 
 i i . Inches. 
 
 Mizen shrouds, 3 pair 5 
 
 Mizen dead eyes, diameter 8 
 
 cwu. 
 
 Anchors 1 Bovvers 19 
 
 Iron stock 5 Stream 12 
 
 Kedge , 5 
 
 Inches. 
 
 Cables, bower, 3 N., 100 fathoms each 1 
 
 Stream, 75 fathoms ^ 
 
 The armament of the Nile consisted of two guns of large calibre and long 
 range, with a view to choose a proper position to windward, so as to be effective 
 
EXPLANATION OF THE PLATES. 48? 
 
 while without the reach of the enemies' guns ; and in the event of being disabled, 
 or at close quarters, twenty short guns of large calibre could be mounted, to offer a 
 proper defence ; and to produce effect when landing troops may be required, she 
 was made to carry on her platform 500 troops. 
 
 In the construction of the Nile, every care was taken to give a suitable degree 
 of strength, and she was built in every respect equal, both in the quality of the 
 materials and in the scantling and dimensions given to her timbers, to any of the 
 armed steam ships heretofore built ; while in the equipment of this vessel, every 
 thing was done that skill and experience could devise or expense accomplish, 
 towards making her as effective as possible. 
 
 The engines of the Nile were by Boulton and Watt: two of 110 horse power 
 each, and which appear to have been most effective, from the manner in which this 
 vessel made her passage out to Alexandria ; and acted when contending against 
 a strong gale and a heavy head sea. From the size of this vessel it might for the 
 sake of velocity have been considered proper to give greater power ; but in deter- 
 mining them, the power given was considered the best suited for making a voyage, 
 when the consumption of fuel must be an object of the first consideration : and the 
 experiment proved, that to accomplish a voyage and to gain the greatest distance 
 in the shortest time, her power was properly proportioned. 
 
 The disposition and particulars of her engines will be best explained by reference 
 to the Plates. 
 
 In determining the elements, and giving the principal dimensions of the Nile, for 
 her construction, the dimensions, &c., of several fast steam vessels were taken to 
 compare with ; but as it was considered of the first importance in the construction 
 of this vessel, that she should be able to carry sufficient sail to keep company with 
 convoys when not steaming, and to make a reserve of her coals whenever practi- 
 cable, it was thought desirable to give a greater breadth than common, so that her 
 length was about 5-5 of her breadth instead of from 5'8 to 6'8, the breadth as given 
 to some of the fast boats ; and the proportion of the area of the load water section 
 to the circumscribing parallelogram formed by the length and breadth was consider- 
 ably more than is commonly given, keeping the area of the greatest transverse 
 section about the same in relation to the circumscribing parallelogram formed by the 
 draught of water and the breadth ; as it was found impossible to reduce this element 
 much, on account of the displacement required being more than common, from the 
 great weights she was intended to carry. Something might have been obtained, as 
 to displacement, and possibly in the area of the midship section, by making the rise 
 of the floor something less ; but in doing this the resistance occasioned by the 
 adhesion of the fluid would have been considerably increased ; probably more than 
 
488 EXPLANATION OF THE PLATES. 
 
 could possibly have been obtained in the direct resistance, by this alteration of the 
 form of the body. 
 
 In giving the general form to the body, she was not so sharp forward as to be 
 according to the opinion of the day ; but the form and adjustment of the body were 
 such as to ensure her being easy against a heavy head sea, and with it as little 
 direct resistance as could be obtained without endangering other essential qualities 
 on which the general efficiency of the vessel depends. 
 
 To determine the elements that relate to the form, and are essential to the 
 resistance the body will meet in passing through the water, considerable difficulty is 
 involved, and it yet remains for the progress of knowledge to develope ; and in a 
 great degree this subject must rest on mere opinion, as the theories laid down do 
 not notice clearly the different forces that materially affect the motion of bodies ; as 
 the pressure on the anterior part of the body, the minus pressure on the posterior 
 part, with the resistance that arises from friction, as well as the adhesion of the 
 fluid. The writings of several authors on this subject, as Bouguer, Euler, &c., we 
 find the theory is laid down by Newton, and applied by them to the motion of ships 
 is of little practical utility. Euler has, however, given his theory in a very general 
 manner, without enforcing the correctness of his conclusions in practice. M. Romme, 
 in his Art de la Marine, gives some interesting experiments, as made by himself at 
 Rochfort ; and with a general expression for the resistance of ships drawn from 
 these experiments, and from the Newtonian theory ; but we find the Academy of 
 Science did not consider his experiments sufficiently numerous, or on a scale suf- 
 ficiently large to be conclusive. And the experiments made by the British Society 
 for the Encouragement of Naval Architecture have, in a degree, set aside his 
 conclusions ; especially on one material point, viz., that while the midship section 
 remained unaltered, the form forward and abaft would not greatly affect the velocity, 
 which appeared not to be the case ; only that this element materially influenced the 
 resistance of the body. 
 
 In the theory, as laid down by Chapman, the Swedish ship-builder, an expression 
 has been investigated on small parts of the surface, partly by the Newtonian theory, 
 and partly frorn^experiments of his own ; and which he applied in calculating the 
 resistance applied to a vessel ; which method, although the results may not be 
 strictly true, is still very useful, as giving the relative plane of direct resistance very 
 nearly, and was used in constructing the Nile ; and is, in most cases, as the form of 
 steam boats varies in terms of the area of the midships, applicable in comparing their 
 direct resistance, instead of the area of midship section, which is now often taken by 
 constructors of steam boats to determine the velocity likely to be obtained by any 
 power given. 
 
EXPLANATION OF THE PLATES. 489 
 
 The direct resistance, as obtained for the Nile, was estimated according to the 
 rule given by Chapman in his slrcliitectura Navalis, Inman's Translation, Chapter IV., 
 was found equal to the resistance of a plane of sixty-two square feet moving perpen- 
 dicularly through the fluid. This quantity, when examined with power and speed, 
 appears to give results more satisfactory than in taking the area of the midship 
 section ; and we find by taking this quantity in relation to the midship section, and 
 comparing it with the results of steam boats, it in general agreed better with the 
 experiments than taking the whole area of the midship section, and would appear 
 sufficiently near for all practical purposes. In some cases, when the plane of direct 
 resistance was obtained for different boats, as for the Nile, they only varied from 
 124 to '132 of the area of this section. It may, however, be proper to observe, 
 that in any case it can only be an element by which to determine nearly the power 
 required for different steam vessels ; as from the friction and adhesive influence of 
 water, the loss of power by the paddle wheels, &c., it would be impossible, with 
 our present knowledge, to give a correct rule ; and we have no experiment that will 
 shew how the resistance varies in different degrees of velocity, only that it is in a 
 higher power than the square of the velocity when the velocity is great. 
 The following are some of the principal elements of construction : 
 
 Length on the range of deck, 180 feet. 
 
 Breadth, extreme, 33 feet. 
 
 Draught of water, afore, 13 feet; abaft, 14 feet 
 
 Weight of hull, 530 tons. 
 Weight of machinery, water in boilers, coal, &c., as follows : 
 
 Tons. cwt. qrs. Ibs. 
 
 Weight of engine ..... 135 3 1 
 
 Ditto of boilers 65 7 3 13 
 
 Ditto of coal boxes .... 10000 
 
 Ditto of water 44 11 1 14 
 
 Ditto of coal 320 
 
 Total 575 
 
 Weight of mast, rigging, ordnance stores, provisions, &c., 347 tons. 
 
 Total displacement, 1452 tons. 
 
 Area of load water line, 5086 square feet. 
 
 Area of the greatest transverse section, 360 square feet. 
 
 Distance of the centre of gravity of displacement before the middle of the 
 
 length on the water line, taken from the fore part of the stem to the 
 
 after part of the stern post, 3 feet. 
 
 3 Q 
 
490 
 
 EXPLANATION OF THE PLATES. 
 
 Depth of centre of gravity of displacement below the load water line, 5 
 feet 25 inches. 
 
 
 Number of 
 strokes per 
 minute. 
 
 Velocity of 
 vessel. 
 
 Velocity of 
 wheels. 
 
 Multiple 
 of the speed 
 of vessel equal 
 that of the 
 wheel. 
 
 
 In a moderate breeze, going free, with half the sails set .... 
 
 Number. 
 
 22 
 
 18 
 16 
 12 
 9 
 
 Miles per hour 
 
 12 
 
 9-75 
 8*25 
 5-5 
 4-25 
 
 Miles per hour 
 
 18 
 14-7 
 
 1-5 
 1-5 
 1-6 
 1-G6 
 1-71 
 
 
 
 9-18 
 7-3 
 
 
 
 Feet. Inches. 
 
 Diameter of cylinder 5 
 
 Length of stroke 5 2 
 
 Diameter of air pump 3 
 
 Length of stroke 3 
 
 Diameter of paddle wheel 22 
 
 Breadth of ditto . 9 7 
 
 Average consumption of coals, 1 8 cwt. per hour. 
 
 It would be impossible to deduce any rule to shew the exact relation between 
 the velocity of the vessel and that of the wheel, for the want of some instrument 
 that would mark accurately the speed of the vessel. With this multiple, however, 
 we may determine nearly the relative perfection of different steam vessels, when 
 the surface and position of other floats are in the same relation to each other ; and 
 by a proper register of these numbers, the relative perfection of paddles on the 
 same vessel may be determined by bringing her under the same circumstance as to 
 draught of water, &c. 
 
 SCANTLINGS, ETC. 
 
 
 c 
 
 
 
 1 i 
 
 
 6 
 s. 
 
 i 1 
 
 S 
 
 KEEL. Elm. Moulded 
 
 
 I 3 
 
 
 
 5 
 
 
 
 1 2 
 
 
 8 
 
 1 
 
 
 
 10] 
 
 FALSE KEEL. Elm. Thick 
 
 
 4 
 
 (Aft 
 
 
 10} 
 
 
 
 1 3 
 
 
 
 11 
 
 Moulded 
 
 
 1 2J 
 
 
 
 
 
 
 
EXPLANATION OF THE PLATES. 
 
 491 
 
 SCANTLINGS. CONTINUED. 
 
 Scarph, long 
 
 Bolts, copper 
 
 STERN POST. Oak. Square at the head 
 
 Inner post, fore and aft, at the keel 
 
 Ditto, at the' head 
 
 DEADWOOD. Oak. Sided 
 
 FRAME. Oak, except top timbers and timbers 
 forward and aft ; are of Riga fir where curve 
 would admit. 
 CROSS TIMBER. Sided midships 
 
 Forward and aft 
 
 Moulded at the cutting down 
 
 Moulded at the head 
 
 HALF FLOORS. Oak. Sided midships 
 
 Forward and aft 
 
 Moulded at head 
 
 FIRST FUTTOCKS. Oak. Sided midships .... 
 
 Forward and aft 
 
 Moulded at the head 
 
 SECOND FUTTOCKS. Sided in midships 
 
 Forward and aft 
 
 Moulded 
 
 THIRD FUTTOCKS, and TOP TIMBERS. ) 
 Sided in midships i 
 
 Forward and aft 
 
 Moulded 
 
 TOP TIMBERS. Riga fir, excepting wake of) 
 
 paddles, oak. Sided in midships J 
 
 Forward and aft 
 
 Moulded at the deck 
 
 Roughtree 
 
 FLOORS made of Oak, with crosstrees and two } 
 half floors. Circular coaks in each floor ... \ 
 
 Bolts ditto 
 
 KEELSON. Oak. Square in midships 
 
 Forward and aft 
 
 Bolts, copper, one through each floor 
 
 S T E M so N. Oak. Square at the upper part .... 
 Bolts, copper from 18 to 20 inches apart .... 
 
 STERNSON. Oak. Square at the head 
 
 Bolts, copper, from 18 to 20 inches apart 
 THICKNESS of PLANK. Wales (oak). Thick, ? 
 
 three strakes \ 
 
 DIMINISHING PLANK. Four strakes of oak, ) 
 
 upper edge of upper strake J 
 
 Lower edge of lower strake 
 
 PLANK of BOTTOM. English oak to light? 
 
 water mark, thick $ 
 
 Oak strake above the wale, lower edge thick 
 
 Upper edge thick 
 
 SHEER STRAKE. Oak. Thick 
 
 TOPSIDE (Uiga fir). Thick above the wale .... 
 Thick under sheer strake 
 
 PL AN SHEER 
 
 TOFSIDES, size above these strakes 
 
 ROUGIITREE RAIL. Deep 
 
 Broad 
 
 INSIDE PLANKING. Clamps, oak in two j 
 strakes, upper strake thick ) 
 
 Lower ditto, ditto 
 
 I 
 
 3 5 
 
 1 
 
 1 2 
 1 3 
 
 9 
 
 1 3 
 
 11 
 
 10 
 
 1 1 
 111 
 11 
 10 
 10 
 
 o 9; 
 
 9 
 
 9 
 
 9 
 
 8 
 
 71 
 
 8} 
 
 71 
 6| 
 
 8 
 
 o 74 
 
 6 
 4 
 
 3 
 
 1 
 
 1 2 
 11 
 
 
 11 
 
 o n: 
 o ii\ 
 Uj 
 
 6 
 
 6 
 
 4 
 4 
 
 5| 
 
 5 
 
 4 
 
 41 
 
 3 
 
 4 
 
 2 
 
 6 
 
 6 
 
 6 
 5 
 
 THICK STRAKE on the floor-heads (of African} 
 
 oak, in midships) thick C 
 
 FIRST FUTTOCKS (African oak, in midships), I 
 
 thick $ 
 
 SECOND ditto ditto 
 
 THIRD ditto ditto 
 
 TRUSSES (African oak, in midships), thick 
 
 Fore and aft, fir, thick 
 
 Broad 
 
 FILLINGS between timbers. Oak. Thick 
 
 [RON PLATES for trusses. Thick 
 
 Broad 
 
 IRCULAR COAK in each strake opposite the) 
 
 abutment of each truss ) 
 
 SHELF PIECES. Upper deck oak. Deep 
 
 ii" i V Forward 
 
 Wlde Uft 
 
 Scarphs, long 
 
 Circular coaks in ditto 
 
 BOLTS, six inches from the side of each beam, } 
 
 or from 18 to 20 inches apart \ 
 
 BEAMS. Oak sided 
 
 Moulded 
 
 Roundup 
 
 Secured to the shelf with one circular coak... 
 
 And two bolts 
 
 IRON KNEES in wake of engine-room, and 
 three aft and two forward (see Section). 
 
 BOLTS in up and down arm 
 
 DITTO, in beam arm 
 
 PADDLE, or main beams. Sided 
 
 Moulded at the middle 
 
 DECK and BREAST HOOKS. Wood. Sided.... 
 
 Long 
 
 Bolted copper 
 
 HOOK below, iron. Long 
 
 Bolted 
 
 CRUTCHES 
 
 Long 
 
 Bolted, copper 
 
 CROSS BOLTS in keelson to pass through the 1 
 double futtocks, and two between each hook V 
 
 and crutch j 
 
 FLAT of DECK. Prussia deals. Thickness 
 
 DITTO, platform forward and aft. Thick 
 
 SHELF. Deep , 
 
 Broad 
 
 BEAMS. Moulded 
 
 Sided 
 
 BOLTS, copper through side and shelf 
 
 WATERWAY to upper deck. Thick 
 
 Broad 
 
 WINDLASS BITTS. Knees 
 
 CARRICK BITTS. Thick 
 
 RUDDER. Pintles 
 
 Braces 
 
 COUNTER, STERN, and QUARTERS. Oak. 1 
 Lower counter, thick ) 
 
 Backing of stern 
 
 10 
 
 10 
 
 10 
 
 I I 
 
 5 
 
 4 
 
 4 
 
 3 
 
 4 
 
 3 
 
 9 
 
 24 
 
 o 04 
 
 !> 
 
 24 
 
 8 
 
 1 1 
 101 
 
 4 i; 
 
 2 
 
 1 
 
 9 
 
 8 
 
 o 74 
 
 o 24 
 
 o 05 
 
 o o] 
 
 oj 
 
 1 5 
 1 8 
 
 8 
 
 13 
 
 1 
 
 12 
 
 1 
 
 10 
 
 1 
 
 1 
 
 4 
 
 o 24 
 
 7 
 
 10 
 
 7 
 
 81 
 
 01 
 
 10 
 
 1 1 
 
 81 
 
 4 
 
 21 
 
492 
 
 EXPLANATION OF THE PLATES. 
 
 PLATES CVIIL, CIX., AND CX. 
 
 HIS IMPERIAL MAJESTY'S ARMED STEAM VESSEL COLCHIS. 
 
 This vessel, and likewise the Jason, was built for the Russian Government by 
 Messrs. Joseph Fletcher and William Fearnall, and was principally designed by the 
 latter gentleman. The plan of construction, with the various dimensions and descrip- 
 tions of material, are exhibited in the following specification appended to the original 
 contract, from which it has been carefully extracted : 
 
 THE SCHEDULE OR SPECIFICATION REFERRED TO BY THE 
 FOREGOING CONTRACT. 
 
 " DIMENSIONS. 
 
 Length from the part of the stem to the aft part of the stern post, at the rebate of the keel 156 
 
 Breadth, extreme 24 
 
 Moulded 23 6 
 
 Depth in hold 13 g 
 
 Burthen in tons '. 433 ^ 
 
 " SCANTLINGS, ETC. 
 
 
 
 Ft. In. 
 
 Material. 
 
 Diameter of 
 bolts. 
 
 sided 
 ditto 
 deep 
 long 
 
 11 
 
 11 
 3 6 
 
 4 
 
 2| 
 101 
 
 9 1 
 
 English elm 
 
 
 
 
 
 
 
 
 Bolted with 6 bolts of. 
 
 
 I 
 
 To be below the rebate 
 
 
 
 
 deep 
 sided 
 
 
 
 English oak, or 
 African 
 
 
 
 At the keel 
 
 
 moulded 
 
 1 1 
 6 
 3 6 
 
 8 
 91 
 8 
 101 
 1 6 
 7 
 1 
 
 
 
 
 
 
 long 
 
 
 "i" 
 
 Bolted with 6 bolts of 
 
 
 
 moulded 
 square 
 ditto 
 
 
 STEMSON, scarphed upon the fore end of the keelson... 
 
 
 
 
 
 
 
 
 Abaft the rebate at wing transom ... 
 
 
 
 
 
 
 1 
 
 
 
 
EXPLANATION OF THE PLATES. 
 
 493 
 
 SCHEDULE continued. 
 
 
 
 Ft. In. 
 
 Material. 
 
 Diameter of 
 bolts. 
 
 INNER POST, to run up to the under part of the wing 
 
 
 7 
 
 
 
 
 
 1 
 
 
 
 
 sided 
 
 9 
 
 
 
 
 moulded 
 
 1 3 
 
 
 
 , Secured at each end with an iron knee the fore 
 and aft arm to have four bolts, and thwartship 
 
 
 
 
 1 
 
 The stern post to be bolted through the transom 
 
 
 
 
 1 
 
 Not to have any transoms below the wing, but all 
 the timbers to be dowelled at their heads to the 
 under side of the wing transom, and bolted at 
 their heels through each other across the dead- 
 
 
 
 
 1 
 
 DEADWOOD, to be sided same as keel, and wrought 
 sufficiently high for the security of the heels o\ 
 the cant timbers, and bolted at every two feet 
 
 
 
 
 I 
 
 
 
 
 elm 
 
 
 
 
 
 English oak 
 
 
 
 square 
 
 101 
 
 African 
 
 
 
 
 9 1 
 
 
 
 
 loner 
 
 4 4 
 
 
 
 And to be 6 feet clear of the masts and scarphs o1 
 the keel. 
 To be bolted through every floor and the keel, with 
 
 
 
 
 11 
 
 FASHION PIECES, to be double the foremast, one to run 
 
 
 2 6 
 
 
 ' 8 
 
 
 sided 
 
 8 J 
 
 
 
 And to be dowelled to its end ; the after one to run 
 up to the under part of the wing transom, and 
 to be dowelled into it. 
 
 
 " "2 
 10 1 
 
 
 
 
 
 
 
 7 
 
 
 sided 
 
 10 
 
 
 5 
 
 To run up to within 1 foot of top of knighthead, 
 the hawse holes to be fitted with cast iron 
 
 diameter 
 
 9 
 
 
 
 ROOM AND SPACE, to be the whole length of engine! 
 
 5 
 
 2 
 
 
 
 
 \ 
 
 2 2 
 
 
 
 
 
 2 3 
 
 
 
 
 
 2 4 
 
 
 
 CROSS PIECES, or short floors, in engine room 
 
 sided 
 
 10 
 
 
 
 
 ditto 
 
 9 
 
 
 
 
 moulded 
 
 11 
 
 
 
 At the head 
 
 ditto 
 
 9 
 
 
 
 HALF FLOORS, in engine room 
 
 sided 
 
 9 
 
 
 
 
 ditto 
 
 83 
 
 
 
 
 
 8 
 
 
 
 
 
 8J 
 
 
 
 
 ditto 
 
 7' 
 
 
 
 
 
 7 
 
 
 
 
 
 
 
 
494 
 
 EXPLANATION OF THE PLATES. 
 
 SCHEDULE continued. 
 
 
 
 Ft. In. 
 
 Material. 
 
 Diameter of 
 bolts. 
 
 SECOND FUTTOCKS, and Top Timbers, in engine room 
 
 sided 
 sided 
 moulded 
 
 7i 
 
 
 
 7 
 
 4\ 
 
 
 
 
 
 
 
 2 3 
 
 5 
 4 
 9 
 4 
 1 6 
 3 
 4 
 
 I 3 
 
 3 
 
 4 
 
 2 1 
 
 English oak, or 
 African 
 
 1 
 
 The timbers to be put together, close joints up to 
 the lower futtock head, with dowels uniting their 
 heads and heels, and bolted together sidewise 
 with 2 bolts * 
 
 
 In each scarph, and all the openings, to be fitted 
 
 
 English oak 
 
 English or 
 African 
 
 From the keel to 2 feet above the turn of the bilge, 
 and to be calked ; adhesive felt to be put in 
 between the faying parts of both timbers and 
 fittings. 
 
 broad 
 
 thick 
 thick 
 broad 
 thick 
 broad 
 thick 
 thick 
 
 broad 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 English oak 
 African, or 
 English oak 
 
 
 ...... 
 
 Together 
 
 BOTTOM PLANK, from the garboard strake to the turn 
 
 American elm 
 Oak, or Dantzic 
 American elm 
 
 
 thick 
 ditto 
 
 
 I 
 
 To be bolted through the keel and opposite strake, 
 and up and down through the bottom at every 
 
 All the bolts through the butts 
 
 
 
 
 
 
 
 thick 
 thick 
 
 ARD. 
 
 thick 
 broad 
 thick 
 broad 
 
 
 
 2 
 3i 
 
 4 
 9 
 3 
 9 
 
 4 6 
 1 
 
 African 
 
 WITHINBO 
 
 
 
 
 1 
 
 
 
 
 African 
 Copper 
 
 To have two on each side, well dowelled into the 
 timbers, and bolted, the length of engine room, 
 
 
 
 
 
 long 
 sided 
 
 
 
 
 And deep as may be required by the engineer. 
 
 
EXPLANATION OF THE PLATES. 
 
 495 
 
 SCHEDULE continued. 
 
 
 
 Ft. in. 
 
 Material. 
 
 Diameter of 
 bolts. 
 
 SHELF PIECES, to receive the ends of the beams, of size 
 as per margin, not to be dowelled, but 
 
 
 4 
 1 6 
 4 
 
 01 
 
 3 
 
 2J 
 
 
 1 
 
 s \ scored over every timber, and bolted 
 
 
 thick 
 broad 
 broad 
 thick 
 
 African or Eng. 
 
 
 12 in. 
 
 
 DIAGONAL IRON PLATES, to be laid at an angle of 70... 
 Scored into the timbers their whole thickness, to 
 
 
 
 
 
 
 I 
 
 And in length from the under part of the shelf- 
 piece to the outside of the outer bearers to be 
 
 
 
 In the middle they are to cross each other. 
 
 thick 
 broad 
 
 Oak or African 
 
 
 10 
 2 6 
 3 
 
 6 
 2 
 
 1 1 
 1 4 
 1 1 
 
 5 
 3 10 
 3| 
 
 31 
 \l 
 
 
 
 3 
 4 
 
 
 
 
 All the fastenings of the bottom to be driven 
 through and additional bolts added where re- 
 quired, and between the planks to be fitted in 
 with l deal flush with the diagonal plank, all 
 fore and aft. 
 
 square 
 
 Baltic fir, or 
 red pine 
 
 Secured to the side by an angular shelf with 1 
 
 
 thick 
 
 sided 
 moulded 
 
 Fir 
 African 
 
 To build a magazine and such store rooms as may 
 be required under and upon the platforms. 
 
 ...... 
 
 
 
 
 
 IRON KNEES to PADDLE BEAMS, withinboard, Side 
 
 long 
 ditto 
 broad 
 thick 
 ditto 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 50 
 5 
 3 1 
 
 
 i* 
 
 
 long 
 ditto 
 broad 
 thick 
 
 
 
 
 
 
 
 
 31 
 
 H 
 
 03 
 
 10 
 
 
 "ij" 
 
 
 
 
 
 
 
 diagonal 
 sided 
 
 
 
 Oak or African 
 
 And deep as may be required. 
 PADDLE CASES, to be properly framed and covered 
 with good seasoned deal of two thicknesses, to 
 be rebated, the lower one half an inch thick, 
 wrought fore and aft, the upper one an inch 
 and a half thick. The hinges to the flaps to 
 
496 
 
 SCHEDULE continued. 
 
 EXPLANATION OF THE PLATES. 
 
 
 
 Ft. in. 
 
 Material. 
 
 Diameter of 
 bolts. 
 
 be of copper or mixed metal. A bridge board 
 to be fitted for a gang-way between the paddle 
 boxes. 
 UPPER DECK BEAMS, to round in 4 feet 
 
 
 () 1 
 
 
 
 The hatchway and mast beams 
 
 
 8\ 
 
 '. f . 
 
 
 
 moulded 
 
 7 
 
 
 
 The remainder 
 
 
 ORi 
 
 R j 
 
 
 
 moulded 
 
 7 
 
 
 
 WATERWAY 
 
 
 10 
 
 j* fi 
 
 
 
 thick 
 
 4 
 
 
 
 DECK. Flat 
 
 ditto 
 
 3 
 
 T\ t- ' A 1 
 
 
 ROUGHTREE TIMBERS, at the gunwale 
 
 sided 
 
 7 
 
 
 
 
 moulded 
 
 4 
 
 
 
 
 
 5 
 
 
 
 
 deep 
 
 4 
 
 
 
 Height from upper side of deck to top of rail 
 
 
 4 2 
 
 
 
 
 thick 
 
 I 1 
 
 
 
 
 sided 
 
 *2 
 
 1 
 
 
 
 
 moulded 
 
 7 
 
 
 
 
 
 7 
 
 
 
 One between that and platform to be 
 
 
 3^ 
 
 
 
 
 thick 
 
 3 1 
 
 
 
 
 ditto 
 
 1 1 
 
 
 
 
 
 11 
 
 
 
 
 
 7 
 
 
 
 
 
 
 
 11 
 
 
 
 3 1 
 
 
 *8 
 
 
 thick 
 
 3 
 
 
 
 
 
 ditto 
 
 I 1 
 
 
 
 
 
 J 4 
 
 10 
 
 
 
 CRUTCH. Abaft, one of iron for the security of the 
 heels of the timbers, of size and bolted the 
 same as lower hook. 
 WINDLASS. To have a patent one of African or 
 English oak, fitted with wheel pinion and 
 winch handles, and to receive chain cables .... 
 
 diameter 
 
 I 3 
 
 10 
 
 African 
 
 
 
 
 6 
 
 
 
 
 
 9 
 
 
 
 
 moulded 
 
 8 
 
 
 
 
 
 
 
 
 DAVITS. To have proper ones for the boats of iron, two on each side. 
 
 ROTHER. To be fitted with metal braces and pintles, Lihour's patent. 
 
 PUMPS. To find and fix two cast iron pumps with gear complete. 
 
 HEAD, STERN, AND QUARTER GALLERIES. To be built and elegantly finished, with suitable mouldings, 
 
 carved works, etc. 
 MAST AND BOWSPRIT, PARTNERS, COMINGS, COMPANIONS, AND SKYLIGHTS. To be properly fitted, as 
 
 may be shewn in the profile and plans. 
 STEERING-WHEEL, TILLER, OR YOKE. The wheel to be handsomely wrought with brass plates; the 
 
 tiller to be of iron, and fitted as may be directed. 
 CHAIN CABLE LOCKERS. To fit lockers for the reception of chain cables, and a box on wheels on 
 
 deck for the stream cable, as may be directed. 
 ENGINE ROOM BULK-HEADS. At the after part of the engine room to be double of lg inch, rebated 
 
 deal on each side of a 4 inch stanchion, at the fore part to have a single bulk-head ; to fit a bench 
 
 and cupboards or lockers for the engineer. 
 
EXPLANATION OF THE PLATES. 497 
 
 COPPER. The vessel to be docked, and the bottom coppered with 32, 28, and 24 oz. 
 
 CALKING. The whole of the calking to be done in a proper manner, the oakum to be good and 
 sound. The bottom to be plyed over with tar, and well prepared to receive the copper. 
 
 JOINER'S WORK. To emboss the vessel within and without board in a proper manner ; build all ac- 
 commodations for passengers in the saloon under the main deck ; the doors to be mahogany, and 
 the sides of the cabins to be panelled with mahogany. To build accommodation on the fore 
 platform with deal as may be directed by the plans designed for that purpose. 
 
 PLUMBERS, GLAZIERS, PAINTING. To lead the taffrail under the quarter galleries, cheeks of the head, 
 and all air scuttles ; fix all scuppers ; find and fit two of Downton's water-closets abaft, and one 
 common hopper on deck ; the skylights, scuttles, and lights in the stern to be glazed with the 
 best crown glass. The whole of the weather work and under part of the deck to have three 
 coats of good oil colours ; the fore cabin to be painted in common colour. 
 
 MASTS, YARDS, BLOCKS, &c., &c. To supply and fit all masts, yards, and blocks, one suit of sails, 
 and bend them to the yards, two best bower anchors, one stream anchor, one kedge, and one 
 grapnel, two one and one sixteenth chain cables, 90 fathoms each ; one seven-eighths stream 
 cable, 90 fathoms. Supply and fit all chain rigging, stays and cordage, necessary to rig the 
 vessel, fit tarpaulings to the hatchways, awning stanchions, and one awning to quarter-deck ; 
 supply a buoy and buoy-rope ; two boats with one set of oars, and a canvass cover. Supply a 
 fire-hearth to cook for 100 men ; iron tanks to contain about 2,000 gallons of water ; a patent bin- 
 nacle, and a double lamp in the saloon. 
 
 SPONCINGS. To be two inches thick, of Baltic fir ; the timbers of English oak sided 6 inches, and bolted 
 in the heel through the side, with one bolt of three quarters of an inch in diameter. A thick strake 
 of Baltic fir let on one half of the moulding of the sponcing timber to meet the water-way, a 
 piece of felt being first placed in the joint, and bolted through each other, with one bolt between 
 every timber five-eighths diameter, with a ring well clinched on each end ; the beam ends 
 secured to the strake by a drawtort dog bolt secured with a bolt and one nail. 
 
 For a Description of the Engines, see Plates XLIII. to XL VI. 
 
 PLATES CXL, AND CXI. A. 
 
 ENGINES OF THE STEAM SHIP TIGER. 
 
 The engines of this vessel were manufactured by Edward Bury,Esq., and fitted with 
 Hall's patent condensers, and the description of the parts will be understood by 
 reference to that of the engines of her Majesty's steam ship Mageera, Plates 
 XLIX. and L. 
 
 The Tiger is a Hull built vessel, and belongs to the St. George Steam Packet 
 Company ; her burthen is 800 tons ; her engines are of 300 horse power ; she is at 
 present stationed between Hull and Hamburgh ; and her equipment, in every respect 
 does the highest credit to the port of Hull and to the owners. The following 
 extracts from Captain Knocker's journal will show the leading points of her 
 passages : 
 
 3 R 
 
EXPLANATION OF THE PLATES. 
 
 EXTRACT from the Journal of the St. George Steam Packet Company's steam ship the Tiger, from 
 HULL to HAMBURGH Draught of water 13 feet 3 inches aft, 11 feet 10 inches forward. 100 tons 
 coals ; 15,000 feet measurement goods. 
 
 DEPARTURE. 
 
 HE.MABKS. 
 
 July 14. Weighed from Hull Roads. 
 
 H. M. 
 
 9 30 P.M. 
 
 15. Passed new Sand Light. 
 Passed Borkum 
 
 16. Passed Elbe Light , 
 
 Cuxhaven 
 
 Arrived at Hamburgh.. 
 
 SW. 
 
 sw. 
 
 1 5 A.M. 
 10 P.M. 
 
 3 57 A.M. SW. 
 5 20 
 10 10 Hull time. 
 
 Strong wind and rain ; detained 
 by the pilot, going down the 
 H umber full an hour. 
 
 Fresh wind and plenty of sea. 
 
 Fine weather. 
 Squally, with rain. 
 
 The passage from river to river Humber to Elbe was performed in 26 hours 50 minutes : the 
 distance run being about 300 miles. The whole passage from Hull Roads to Hamburgh, including 
 a delay of an hour in the Humber, was made in thirty-six hours and a half. 
 
 FROM HAMBURGH TO HULL. 
 
 DEPARTUBE. 
 
 TIME. 
 
 WINDS. 
 
 REMARKS. 
 
 July 22. Started from Hamburgh 
 
 H. M. 
 
 2 40 A.M. 
 8 40 
 11 30 
 
 1 50 P.M. 
 
 10 P.M. 
 1 A.M. 
 
 4 
 
 i9 hours thr 
 ort, and the fi 
 /erage passagi 
 
 NW. 
 N NW. 
 
 N. 
 NE. 
 
 ee of whi< 
 rst-class s 
 : by ten h( 
 
 Strong gales and heavy rains. 
 Continued gales, and heavy rain. 
 Left the French steamer for 
 Havre, wind bound. 
 
 Strong gales and clear. Thick, 
 with heavy rain. 
 Strong gales and clear. 
 
 :h at anchor ; the weather being so 
 team ships from London to Hull 
 mrs. 
 
 
 Heligoland NNE 
 
 23. Anchored in 6 fathoms water 
 
 
 The voyage home was performed in 
 bad that the French steamer kept her p 
 even the Wilberforce exceeded their a 
 
 PLATE CXII. 
 
 THE ADMIRALTY YACHT FIREBRAND. 
 
 We shall have occasion to say but little of this vessel, as her qualifications are 
 comprehended in what has been already said of the Medea. The Firebrand is on the 
 
EXPLANATION OF THE PLATES. 499 
 
 same principle, with the exception of the fittings for war, being armed with only 10 
 brass swivels, one pounders ; she was constructed by Mr. Lang for the packet ser- 
 vice between Falmouth and Malta, and built under his superintendence by Messrs. 
 Curling and Young ; was employed in that service at first, about nine months, under 
 the command of Lieutenant Baldock ; she was afterwards fitted as a yacht for the 
 Marquis of Anglesea, at Dublin, since which, on the Marquis leaving Dublin, she 
 has been employed as the yacht for the Lords Commissioners of the Admiralty to 
 perform their sea duties ; her dimensions are as follow : 
 
 Feet. Inches. 
 
 Length between the perpendiculars . . . . 155 
 
 Ditto on the keel for tonnage . . t . . 136 9^ 
 
 Breadth, extreme . . . . . . . 26 1 
 
 Ditto, moulded .... . 25 7 
 
 Depth in engine-room . . . . . 14 9f 
 
 Burthen in tons 494ft 
 
 LIGHT. LOAD. 
 Feet. Inches. Feet. Inches. 
 
 (Forward .... 6 6 10 2 
 
 Draught of water | Aft .... 7 10 11 
 
 Displacement in tons .... 288'9 642*0 
 
 Area of midship section, in square feet . . 117'64 215'0 
 
 Her two engines are 60 horse power each, made by Messrs. Maudslay ; her pad- 
 dle-wheels by Mr. Morgan ; her performance is considered to be superior to any 
 vessel of her size in proportion to the power of her engines, which are very small for 
 a vessel of such dimensions ; her velocity has been proved in several instances where 
 she has beaten her opponents ; one vessel of 237 tons, two engines of 50 horse 
 power each * ; one vessel of 400 tons, two engines of 90 horse power each f ; an- 
 other, 700 tons, two engines 150 horse power each \ ; one of 237 tons, two engines 
 of 50 horse power each $, &c. She behaves well at sea in bad weather, and is a good 
 sea-boat under canvass alone ; she is rigged with three masts, similar to the Medea. 
 Nothing further need be said by way of description of the vessel, as her form, method 
 of fastenings, fittings, &c., are all exhibited in the drawings. Vide the Plate. 
 
 * Escape, of Holyhead. t Victory, of Bristol. 
 
 J City of Aberdeen. Dragon, of Holyhead. 
 
500 EXPLANATION OF THE PLATES. 
 
 PLATE CXIII. 
 
 PORTRAIT OF THE LATE MR. WATT, THE CELEBRATED INVENTOR AND 
 IMPROVER OF THE STEAM ENGINE. 
 
 PLATE CXIV. 
 
 PORTRAIT OF THE LATE MR. TREDGOLD. 
 
 PLATES CXV., CXVII., AND CXVIII*. 
 
 These drawings are designed to illustrate the state of steam navigation in America, 
 in reference to Professor Renwick's paper on that subject, inserted in the Appendix, 
 page 101. 
 
 * Plate CXVI unfortunately not having reached us, we have reluctantly been compelled to 
 abandon it. 
 
APPENDIX. 
 
 L O N MARINE BOILERS. 
 BY MR. J. DINNEN, 
 
 ASSISTANT ENGINEER, HER MAJESTY'S DOCKYARD, WOOLWICH. 
 
 1. THE paucity of information connected with steam navigation, a subject, it must be 
 allowed, of great national importance, and which has assumed a prominent feature in her 
 Majesty's naval service, suggested the investigations from which the following practical 
 essay on marine boilers has resulted. The incrusted state of the boilers of all steam vessels 
 returning from the Mediterranean with mails, in the early stage of their employment, was 
 calculated to impress the observer with the impracticability of making such voyages without 
 submitting to like effects ; no experiment having been made, or correct data furnished, at that 
 period, to counteract the notion, so universally entertained, that the water of the Mediterra- 
 nean holds more marine deposit in solution than that of the Channel. It is probable that 
 Dr. Halley's experiments on the evaporation of water from the surface of the sea assisted 
 materially in the formation of this general opinion. 
 
 It is calculated that the Mediterranean evaporates no less than 5,280,000,000 tons daily : 
 and this quantity far exceeds that evaporated from any other surface of equal extent, 
 being entirely encircled by land ; but it does not follow from this that the water is salter. 
 Whoever has been in the Mediterranean is aware that the dews there are exceedingly heavy, 
 and that they begin to descend some time before the sun has set : in still evenings indeed 
 the dew descends where it has arisen ; and no doubt much is precipitated on the land ; but it 
 must be borne in mind, that land gives forth exhalations at all temperatures, as well as the 
 sea. Again, the visible current always runs into the Mediterranean, in addition to the great 
 rivers Nile, Danube, Rhone, &c., to supply that portion of water which the land may carry 
 off. Experiments do not show the specific gravity to exceed that of other waters ; and hence 
 the general opinion alluded to must have been conjectural, and not founded on the result 
 of investigation. 
 
 2. It cannot be too generally known that the thermometer is a good practical test of the 
 concentration of a boiling solution of salt ; of which the following is offered in illustration. 
 
2 APPENDIX. 
 
 Some years since, experiments were tried by Messrs. Maudslay and Field, and an appa- 
 ratus adapted to marine boilers, the purpose of which was, that the water of the boilers 
 should at all times be maintained at the same temperature and at the same degree of con- 
 centration ; and I am not aware of any experiments for such an object prior to these. It 
 resulted from their investigations, that sea water boiling under a pressure of 1\ Ibs. on the 
 square inch, (the usual low pressure standard,) will arrive at 226 Fahrenheit in 24 hours, 
 at 230 in 48 hours, and 232 in 60 hours, Sic. ; at which period it will contain ^ of 
 its bulk of salt. At 232 saturation takes place, and salt (muriate of soda) will be crystal- 
 lized and deposited ; the concentration having progressed from 222, the temperature exhi- 
 bited at the commencement of the experiment. The boilers of course receive only the 
 necessary supply of water for evaporation ; in the above instance 16 gallons per minute. 
 These experiments I have frequently repeated under varied circumstances with correspond- 
 ing results. 
 
 Sea water containing -fa of its bulk of salt, and the quantity evaporated being entirely 
 fresh or distilled water, it is evident that all the salt injected remains in the boilers : the 
 specific gravity of the water is thus constantly increased, and the salt, now more tenacious 
 of its water of solution, requires an increase of heat to separate it ; so that with an uniform 
 heat evaporation would proceed proportionally slower ; but the necessities of the engines 
 requiring that it should proceed at all times equably, the fires must be urged accordingly. 
 The temperature thus increasing (under the same pressure) with the saturation, a thermo- 
 meter becomes a practical register of the density of the water ; of the waste of fuel, to a 
 certain extent ; and a certain index of the danger to which the furnaces are exposed. 
 
 3. A particular arrangement was adopted in the above experiments : a thermometer was 
 applied to the front of the boilers, ranging from 210 to 250 or 300 Fahrenheit, the bulb of 
 which was immersed in mercury, contained in an iron box, protruding into the water of the 
 boilers through the front thereof, so as invariably to partake of the same temperature ; and so 
 that its state could always be known by inspection. To apply the thermometer to boilers 
 generally, it would be necessary to graduate it to suit the particular pressure on the safety 
 valve, the boiling point varying accordingly. An objection may be offered, that the thermo- 
 meters thus applied are very liable to get out of order. To prevent errors of this kind, a 
 common Fahrenheit's thermometer may be employed without reference to the pressure on the 
 safety valve, by immersion in water drawn from the boilers at regular intervals, and boiling 
 under the pressure of the atmosphere ; which, if possible, should be noted when nice 
 observations are required. 
 
 Now, as muriate of soda is an exception to the general law of the solution of salts in 
 water, as scarcely any more is taken up at a boiling heat than at a moderate temperature, 
 it is clear that this boiling in the air exhibits the exact state of the brine, whether from a high 
 or a low pressure boiler ; the thermometer alike showing its specific gravity, and of course 
 acting near enough for this purpose as a hydrometer. In this way the experiments referred 
 to in this paper have been made. 
 
 4. An essential part of the apparatus alluded to for equalizing the concentration of salt 
 in the boilers, was a pump, technically called a brine pump, the particular office of which 
 was to extract from the lowest part of the boilers, at each stroke, a certain aliquot part of the 
 water supplied by the feed pump. One-fifth of the quantity injected was found to be that 
 
ON MARINE BOILERS. 3 
 
 necessary to be withdrawn, four-fifths being the amount required to be evaporated for the 
 supply of the engines. It having been before observed that the water evaporated is fresh or 
 distilled water, that remaining being specifically heavier than sea water in proportion to the 
 quantity evaporated, it is evident that without a change the saturation would increase till the 
 boiler became a common salt pan. The operation of the brine pump however maintained 
 the water uniformly at about 226, at 2| Ibs. pressure per square inch ; at which temperature 
 it contained -/^ of its bulk of salt : hence, as much salt was extracted by the pump, in a 
 gallon of brine, at -/$ concentration, as was injected by the feed pump in 5 gallons of sea water 
 containing ^ salt : thus maintaining the condition required, which being within the prescribed 
 limits of saturation, viz. 232, sulphate of lime only could be deposited ; but at this period 
 the deposition of muriate of soda was the evil sought to be averted, and this arrangement 
 did it effectually. The lime remains to be considered, of which more hereafter. The brine 
 pump has given place to the indefinite operation of blowing out ; but, from my knowledge 
 of its advantages at sea, I should recommend its use in all land engines where fresh water 
 cannot be obtained ; an opportunity being afforded of recovering nearly all the heat abstracted 
 from the boilers with the water thus withdrawn. 
 
 5. The incrusted state of the boilers, to which I have referred, appeared at variance with 
 observations made by me in the North Sea, Channel, &c. on the influence of sea water on the 
 interior of marine boilers. To determine the fact, I carefully noted the degree of saturation 
 of the water of the boilers at various periods each day, as indicated by Fahrenheit's thermo- 
 meter immersed in a portion drawn therefrom, and boiling under the pressure of the atmo- 
 sphere, on my first voyage, in 1831, from Falmouth to the Mediterranean and back; the 
 result of which was, that having blown out a portion of water from the boilers (which were of 
 copper) every two hours during the passage, they were on each successive examination found 
 perfectly clean and free from marine deposit, with the exception of a slight film ; the thermo- 
 meter being at 215, and not having varied in excess throughout the voyage. This circum- 
 stance was without precedent ; no mud-plate having been removed, or men employed in the 
 boilers during the voyage. 
 
 From extensive experiments of Dr. Davy, (brother to Sir Humphrey,) to ascertain the 
 relative saltness of the sea in various situations, its specific gravity was found to vary very 
 little, except when influenced by the influx of large rivers ; and this conclusion is corro- 
 borated by other scientific men, with whom I have conversed on the subject, in the 
 Mediterranean. 
 
 From the coincidence of the above experiments, therefore, it may be inferred that the 
 water of the Mediterranean is not, in its effect, salter than that of the Bay of Biscay or the 
 Channel, that boilers hitherto incrusted must have contained a solution saturated to a much 
 higher degree than that exhibited in the case alluded to, and that marine boilers are not 
 more subject to incrustation during a voyage to the Mediterranean, than on any other voyage 
 of similar duration. Also from recent examinations of boilers returned from the West Indies, 
 and the reports from the ' Atalanta ' and ' Berenice ' steam ships sent out by the East India 
 Company, I am led to the same conclusion as regards the waters of the Tropics. 
 
 t>. The specific gravity of the water of the boilers, as indicated by the thermometer 
 remaining uniformly at 215, and its not having indicated a higher degree of concentration on 
 either passage, the delay of blowing completely out on the voyage became unnecessary, and 
 
4 APPENDIX. 
 
 this was justified on each arrival ; hence no time was thus wastefully consumed. The order 
 for laying-to every three or four days, to blow the boilers entirely out, at sea, is still in force 
 in the navy, and forms part of the instructions to officers commanding her Majesty's steam 
 vessels ; but how far this is necessary, the fact of having never blown off entirely at sea will 
 explain : I believe the practice is now rarely resorted to, although some are still inclined 
 to think it necessary. 
 
 7. I am also decidedly of opinion, that it is unnecessary to prescribe any specifics for the 
 prevention of deposit or chemical action in copper boilers affixed to marine engines, such as 
 the introduction of large masses of iron, &c. ; the same effects exhibiting themselves in iron 
 as well as copper boilers, when submitted to the influence of a highly concentrated solution 
 of saline matter, 8cc. in a constantly boiling state, viz. deposition of the salts, 8cc. and 
 ultimate destruction of the boilers. As a proof of the fallacy of such applications, the incision 
 I made in a copper boiler with a chisel was not obliterated or sensibly diminished by the 
 action of the water alone, at the end of three years ; the boilers, during the time, being 
 employed in the North Sea and Channel, and free from incrustation, except a film with which 
 the tubes were whitened. After the experiments before alluded to, the boilers were con- 
 stantly employed in the Mediterranean, and on the Lisbon service ; and were not in any way 
 submitted to the form of cleaning out, till the expiration of the third year : a very slight 
 scale was then removed, leaving the surfaces scaled, precisely as when rolled. 
 
 8. The remarkable preserving influence these calcareous matters possess over copper 
 and other metals has recently been exhibited in the bronze guns, raised by the enterprising 
 Mr. Deane from the Royal George at Spithead ; which properties, if generally known, 
 might be available for some useful purpose. I give the notice extracted from the ' Mechanic's 
 Magazine :' " The guns are incrusted with a coat of lime about the twentieth of an inch 
 thick, to which several oysters have attached themselves ; but these, as well as the calcareous 
 coating, separate very easily from the metal, leaving the gun perfectly clean and sharp in 
 its castings." It observes also, "that the rings of wrought iron attached to the breech 
 were totally decayed, the cast iron shots and wads being in a perfect state of preservation." 
 The preservation of the shot is easily accounted for, being pent up by its wad ; but the 
 galvanic agency of the iron, exposed to the water, neutralized its destructive effects on the 
 gun ; and hence the calcareous formation, which, when the existence of the iron should 
 totally cease, would certainly defend the bronze from all attacks of the sea. The adhesion 
 of oysters favours this view of the circumstance. 
 
 Since noting the above in the Mediterranean, I have seen in the arsenal at Woolwich 
 
 O 
 
 several of the guns alluded to, which in every respect confirm what is stated in the 
 extract. The condition of these guns is a fair specimen of the interior of a boiler 
 after a few voyages to sea, except that in the case of the boiler the surfaces are incrusted 
 more uniformly : the coating however in both instances equally protects the surfaces from the 
 destructive attacks of the sea water ; but the causes of deposition are different : in one case 
 it is effected by galvanic influence ; in the other by depriving the water of a component part, 
 by the simple operation of boiling. 
 
 9. The experiments of Davy on copper sheathing induced many to attempt the applica- 
 tion of the principle to other purposes, and marine boilers (copper) proved to be a failure 
 of this description ; for the electric action which was induced by the application of cast iron, 
 
ON MARINE BOILERS. 5 
 
 zinc, &c. to copper sheathing, favoured marine vegetation, and the adhesion of shell-fish, 
 lime, &c. to the ship's bottom ; a disadvantage greater than the evil it was intended to obviate. 
 Iron placed in a copper boiler, for the object alluded to, was speedily decayed, without appa- 
 rent effect : in fact, it was treating the boilers for a distemper which existed only in imagi- 
 nation. Hence no calculable diminution of weight is sustained in copper boilers, from the 
 action of salts, Sec. when held in solution, at sea : but when the interior becomes incrusted 
 with laminae of insoluble calcareous matter, which firmly adheres to the surfaces of 
 the flues, and fire places, and thus certainly protects them from chemical action, and 
 frequently fills the interstices or water-ways of the boilers, it requires violent mechanical 
 means to extract it. In removing these masses, the boilers are much injured ; quantities of 
 rivet heads imbedded in the deposit, and portions of the metal, being alike separated by the 
 instruments used for the purpose. These facts obtain alike in iron and copper boilers. 
 
 10. An evil, however, most sedulously to be avoided, is the accumulation of soot, 
 salt, &c. in the flues ; the chemical action of which is very destructive to boilers. Water, 
 whether cold or boiling, filters through numerous apertures insignificant in dimensions, and 
 almost inseparable from the intricacy of the construction, and mixes with the soot, forming 
 a combination which corrodes the material very rapidly. The heat of the boilers, when 
 employed, evaporates the water, and leaves the salt, 8tc. in a concrete state ; which, when 
 cold, is again dissolved, and recommences its action more formidably. 
 
 On a voyage to the Mediterranean in the months of September and October, 1835, the 
 stay at Malta, on the passage to Corfu, being too short to clean out the flues or to inspect 
 the interior of the boilers, these duties were necessarily delayed till the arrival t Corfu 
 out, and thence to Gibraltar home ; and in both instances there appeared an unusual quantity 
 of soot, &c. in the flues. The congeries of salt, soot, and water was thrown out upon the 
 iron plates of the engine room flooring, where in both instances it remained for nearly two 
 days (the time occupied in properly sweeping) ; when removed and the plates well washed, 
 a pretty and novel phenomenon was exhibited. The iron plates had precipitated the copper 
 from the solution which covered them, exhibiting a permanent metallic surface of copper. 
 This is a valuable practical corroborative of the observation just made concerning the great 
 transmission of the metal, when such solvents are not removed at frequent intervals. I was 
 first attracted to the fact at the above period, have had many opportunities of seeino- it 
 repeated since, and have collected the water, to amuse others by the experiment of the 
 precipitation of copper by iron, from an acid having a greater affinity for the latter. 
 
 The leaks whence the salt resulted, on careful examination, were found so unimportant, 
 that the usual measures to stanch them could not be attempted without the risk of increas- 
 ing the evil ; particularly as this voyage immediately succeeded a general caulking of 
 the flues in parts requiring it, when numbers of screwed rivets were substituted for de- 
 fective ones. 
 
 11. Now, as the defects exist exclusively in the angle pieces and rivets of the bottom 
 of the flues, the top and sides being invariably tight, I have applied a fillet of Parker's or 
 Roman cement in these cases, so as to completely inclose the angle pieces, with their defects, 
 and have thus succeeded in checking the destructive effects of these otherwise trivial, but 
 numerous and incorrigible channels. I have recommended its adoption in other steam vessels, 
 
6 APPENDIX. 
 
 with equal success and satisfaction ; and from three years' experience of its advantages, when 
 applied to the cleaned surfaces of the defective parts, I suggest its use under similar circum- 
 stances in iron boilers ; although inconveniences here alluded to are less frequent and more 
 easily checked in these boilers, by the usual method of chincing, &,c. It must be understood 
 that I here confine myself entirely to cases where mechanical skill is found to be ineffectual ; 
 the cement need be resorted to only when every other means has failed. 
 
 I also conceive that copper boilers experience more deterioration than iron from these 
 deposits ; the bottom flue plates of a copper boiler, upwards of f of an inch in thickness, 
 (where water was present, as before described,) being totally decayed in twelve months ; 
 the side of the plate exposed to the action of the salt water alone being unimpaired ; 
 a fact which I never witnessed in an iron boiler under similar circumstances. Hence the 
 rapid decay of boilers if these deposits are allowed to remain in the flues an unwarrant- 
 able space of time. The only mode, of course, to obviate this, is to sweep the flues as often 
 as convenient ; and the boilers, it should be provided, are to be kept perfectly dry when 
 not employed. 
 
 12. To keep those parts of the boilers clean which are exposed to the influence of the 
 boiling salt water, it appears to be absolutely necessary to hold the salts in solution, since 
 deposits are separated from the water some considerable time before salt is formed, and at 
 a much lower temperature ; 220 having been esteemed a limit (under the pressure of the 
 atmosphere) at which a boiler begins to incrust, while my experiments have shown that 
 215 should be the maximum. Professor Faraday's experiments on sea water appear to con- 
 firm these observations : 1000 parts of sea water being evaporated, 825 parts of steam could 
 be drawn off before any deposition commenced ; but then the sulphate of lime was deposited ; 
 and proceeding till 110 parts remained, the common salt began to crystallize and deposit 
 till 35 parts remained only ; when the muriatic acid, from the decomposition of the muriate 
 of magnesia, began to separate. About f ths of the water may be raised in steam before the 
 salt is deposited. 
 
 13. To obtain the required condition, I recommend that the practice of blowing-out should 
 be periodically and promptly attended to in the Channel as well as at sea, so as to effectually 
 expel the earthy matters while agitated, and prevent induration. I also suggest the expediency 
 of engineers strictly examining their boilers prior to a long voyage, in order to ascertain that 
 their blow-out cocks and pipes are in perfect order. A due circulation of the water in the 
 respective boilers should likewise be attended to, that the blowing-out may equally influence 
 the whole ; and blow-out cocks especially should be so arranged and adjusted, that their 
 use may be quite practicable on all occasions at sea ; as the due performance of the 
 boilers, and consequently the certainty of a passage, materially depends on attention to 
 these particulars. 
 
 14. The construction and arrangement of the blow-off cocks and pipes of most vessels in 
 her Majesty's service were formerly very defective : in some instances, four or five men were 
 summoned to attend when the boilers were blown off, in order to shut the cocks, which 
 were often jammed by expansion ; in other instances, the boilers were blown off through 
 the hand pump, to obviate the risk of the cocks jamming. The boilers, in consequence, were 
 insufficiently attended to ; the construction not admitting these duties to be performed at all 
 
ON MARINE BOILERS. 7 
 
 times with safety. Independently of these difficulties, the pipes through the ship's bottom 
 were frequently of cast iron, and were often severely attacked by bilge water between the 
 cocks and the sea ; and thus the safety of the vessel depended on the slightest tenure. 
 These remarks still apply to existing arrangements on board many vessels. 
 
 15. The safety valve and pipe lately invented by Mr. John Kingston is so constructed 
 that a conical valve, fitted in the pipe which is introduced through the bottom of the vessel, 
 opens outwards to the sea, and is attached to a copper rod under the control of the engineer : 
 thus, in case of any difficulty arising with the blow-out cocks, the valve can be immediately 
 closed ; and being entirely within the thickness of the ship's bottom, is always protected 
 from accident ; while in case the pipe within the vessel were broken, the pressure of the 
 sea would maintain the valve firmly in its place. 
 
 It is not generally known, except to those practically acquainted with engineering, that 
 a steam vessel's bottom is perforated with many large holes, each equal to sink a ship in a 
 very short space of time, particularly when it is understood that they are for the most part 
 pierced close to the keel, where the pressure of water is greatest. It would give additional 
 confidence to every one crossing the seas by steam, if all these holes were rendered as secure 
 as the blow-out pipes now are by Kingston's safety valve : and from the necessity of 
 frequently examining and grinding the sea cocks, the adoption of valves would obviate the 
 necessity of docking for these purposes alone, and is a strong inducement to their general 
 employment in every steam vessel not confined to the limits of river navigation. 
 
 16. Instances are not rare of boilers being permanently injured, and sometimes totally 
 ruined, in a first voyage, whether iron or copper ; occasioned alone by neglect of proper 
 precautions. Incrustation, which is certain, strongly opposes the efforts of the men to 
 generate steam, the combustible portion of the fuel being consumed in heating the plates of 
 the boiler ; and the heat must necessarily pass through strata of stone, (if I may be allowed the 
 comparison,) a very bad conductor of heat, before it is given out to the water; which being 
 highly saturated, requires an additional, instead of a diminished, supply of caloric, to sepa- 
 rate its aqueous and volatile portions from those that are fixed, which are constantly subsiding 
 on the tubes. It requires no argument to show that the fire places and flues thus subjected 
 to intense heat, become nearly red hot, and consequently expand much beyond their usual 
 limits ; while the stay bolts and other ties, holding them with immense force, either break or 
 cause the plates to crack in the weakest place, which is generally in the wake of the stays, 
 joints, or bends, parts, of course, the most heated from the increase of mass; sometimes 
 even the tubes collapse, the powers of expansion resisting all opposition. 
 
 Serious delays and many inconveniences arise from the evils here described, since in 
 most cases immediate repair is absolutely necessary, and can only be effected at the expense 
 of great physical exertion. In fact, from observations on sea water, and its effects on marine 
 boilers, for many years, I am convinced that it is absurd to expect to make a voyage with 
 success if blow-out pipes are choked or otherwise disordered ; or even that at the end of 
 three days, without a change of water, the boilers will not be incrusted to a considerable 
 extent. 
 
 17. The injury sustained by some boilers, either from the above cause or from the 
 neglect of blowing-off uniformly at sea, has by some been erroneously attributed to the 
 
8 APPENDIX. 
 
 intensity of the draught, which they supposed to cause incrustation by burning the material. 
 A tolerable draught appears however to be preferable, and not injurious to a boiler, being 
 always under control ; moreover, I have invariably observed, that boilers with insufficient 
 draught expend more coals, with a considerable addition of labour, than others adapted to 
 engines of equal power where the draught is capable of extracting the whole of the combus- 
 tible matter of the coal, and vitrifying the residue ; for a great waste attends the former, from 
 the constant necessity of clearing the bars. I am also of opinion, that no serious deposit can 
 be formed, if change of water is duly attended to and the evaporation constantly supplied ; 
 and that the sound plates will not experience injury if water alone is in immediate contact 
 and the essentials of construction properly observed : for when the fires are in a state of 
 active combustion, the iron or copper rapidly absorbs the caloric from the fuel, and as 
 speedily transfers it to the water, which is accordingly in a greater or less state of ebullition, 
 and not of incrustation, the temperature of the plates not very much exceeding that of the 
 water. 
 
 18. In iron boilers it is difficult to insure the duration of the plates, for various reasons. 
 Boiler plates are often on inspection apparently sound and of good quality ; but when 
 submitted to the heat of the furnaces, films of the metal opposed to the fire, where adhe- 
 sion was not perfect, become separated in the form of blisters or cracks, (according to 
 the nature and situation of the latent defects,) which are on examination frequently found to 
 exist through the whole plate, to an extent often exceeding- half its thickness. On testing 
 plates of various kinds for experiment, by heat, punching, breaking, &c., those of the most 
 perfect exterior were often found to be much laminated ; and those parts of boilers which 
 have been previously heated and bent to form the bridges, and on which (when con- 
 structed) the tire incessantly impinges, will, if defective, most readily afford opportunity of 
 detection. I have known boilers to run for- some months on occasional service in the 
 Channel during the existence of defects, which did not exhibit themselves till the plates 
 were overheated ; no doubt, through partial incrustation, experienced on a voyage to the 
 Mediterranean, immediately succeeding. 
 
 19. Instances seldom occur of copper plates cracking, unless from causes already 
 described ; a material difference existing between the manufacture of copper and iron plate, 
 which renders it incompatible that they should display similar effects from the cause of heat 
 alone. The former, after certain refining processes, is cast in open iron vessels, forming con- 
 venient cakes, and of course solid and free from air and extraneous matters, prior to being 
 heated and rolled ; while the latter, in masses prepared from scraps, or slaps, is raised to a 
 welding heat, with its heterogeneous accompaniments, then submitted to pressure under the 
 rolls; on the judicious observance of which processes a perfect union of the parts and con- 
 sequent solidity mainly depends. 
 
ADDITIONAL OBSERVATIONS AND GENERAL REMARKS. 
 
 20. ENOUGH has been stated to show that muriate of soda is crystallised subsequently 
 to the deposition of the sulphate of lime ; and from further observations, I conclude that the 
 sulphate of lime will deposit and indurate at any temperature from 212 upwards, and at any 
 degree of concentration ; the more limited this is, of course the less deposit ; so that a person 
 having the care of marine engines on a station cannot be too much on the alert to meet the various 
 mechanical difficulties which may interfere with prescribed arrangements for the good conduct 
 of the boilers ; which arrangements are not always disposed so as to effect the desired 
 purpose, particularly when boilers are composed of many parts. Engineers do not give that 
 attention, at all times, to the due circulation of the water in the respective boilers, which their 
 necessities require : not unfrequently I have known three or more boilers communicating 
 freely above the furnaces, and by side pipes beneath : the pipes often become choked ; 
 consequently in blowing off the front boiler, the water equally descends in the whole, the 
 after-boilers yielding their quota from the surface, (where they communicate freely,) while the 
 earthy matters, and common salt even, are permitted to subside in receptacles whence they 
 cannot be removed. 
 
 If there were even three or more cocks in such case, it would not be possible, day and night, 
 nor would it be safe, to open all at the same time ; and if one boiler is blown off at the end 
 of two hours, as recommended, each boiler remains six hours before the operation is repeated. 
 The descent of the water should be equal and simultaneous from all the joining boilers 
 if possible; which, if not effected, will often permit one boiler to be perfectly clean, whilst its 
 neighbour is thickly incrusted. Very recent examples of the neglect of proper arrangements 
 for circulation of the water in the respective boilers, and of injury thereby sustained, have 
 induced me rather to enlarge on this matter; but still I fear that nothing but the use of 
 distilled water will ever thoroughly obviate the evils to which marine boilers are subject on 
 very long voyages, although at the end of five or six years in active employ a copper boiler 
 may not be liable to injury if properly attended to; while it is notorious that the fire-places 
 of iron boilers of similar construction, employed between Falmouth and Corfu, require repair, 
 almost invariably, at the conclusion of every voyage. I believe that four voyages to the 
 Straits are the most that have been made prior to a general repair of the boilers. 
 
 I have stated that the African was three years employed before it was deemed necessary to 
 detach the scales : on the sides this is extremely difficult to manage, the waterways seldom 
 exceeding four inches, and rarely being so wide. 
 
 I was led to imagine, from the appearance of the boilers after the first voyage, that they 
 could have been employed indefinitely without any considerable scale ; but experience has 
 shown, that to a certain extent it must be expected : in the sixth year, the vessel being 
 actively employed in the Mediterranean, the boilers were scaled about once in three months ; 
 the number of entire days at sea in that time being from sixty to seventy. The tops of 
 the tubes were not always cleaned, attention being paid to remove all scales that might be 
 partially detached from the sides : no time was wasted in removing the scales by scraping or 
 chiselling them in minute portions, the loose or easily detached pieces only being attended to. 
 
 The sides of the fire-places have seldom more than patches adhering to them here and 
 
 b 
 
10 APPENDIX. 
 
 t 
 
 there, and of course are easily cleaned. By the above operation it will be readily seen that 
 the surfaces of the flues would be constantly approaching their original state; that is, each 
 scale of five or six years' formation leaves the copper bare; and the more frequently the 
 boilers are scaled, the greater opportunity is afforded the parts to detach themselves. 
 
 I should recommend that boilers employed beyond a limited period, regulated by the 
 incrustations, should be scaled once a month while actively employed ; the operation would 
 then be simple, and would not occupy above two or three days to do it effectually : no violent 
 measures need be adopted, for reasons already given ; and, the matter removed always 
 exceeding that deposited, the condition of the flues, as before observed, would be constantly 
 improving, as regards the parts which are exposed to the water. 
 
 ON THE CONSTRUCTION OF COPPER BOILERS. 
 
 21. Copper boilers, to a certain extent, have fallen into disrepute, three or four sets having 
 been cut up after employment in the government steam vessels. The fire-places were ex- 
 ceedingly good, as well as the top and side plates of the flues, except in some instances where 
 permanent injury was sustained by incrustation, the result of negligence. 
 
 Now, in every instance the destruction of the bottom plates of the flues was the prominent 
 cause of their disuse. Hence, after much inquiry and observation, I suggest that more care 
 and attention, than that usually paid in the construction of iron boilers, should be observed in 
 fitting the bottom of the flues and shell of copper boilers ; in fact, too much pains cannot be 
 taken in the first place, as it is amply repaid in the sequel. The rivet holes through the 
 lower " angle irons" and plates should exactly coincide, and the rivets properly fit them. One 
 of the greatest present nuisances is the defects of rivets ; many of them actually bend in the 
 disfigured holes in the act of clenching ; they certainly cannot fill a hole of a different figure. 
 The riveting merely swells the point, and not the body to any extent, as I have witnessed in 
 many instances : the result is, that water arrives at the clench of the rivet immediately, which, 
 if not well worked, seldom prevents the water from oozing through. The rivets should, in 
 these places, be well worked in the style observed by coppersmiths. The junctions of the 
 " angle irons" should be carefully fitted ; for neglect of this is almost irremediable : and the 
 caulking or chincing should be eventually executed with the greatest nicety, as no opportunity 
 is afforded, after construction, of properly making good any defects consequent on neglect, or 
 want of sufficient care in this stage of the manufacture. 
 
 22. In IRON BOILERS, when water is first admitted after construction, hundreds of "weeps" 
 or channels in the plates and rivets, whence water oozes, are totally disregarded ; the most 
 important only being stopped mechanically; the rest are stanched merely by the rust the water 
 has formed in its passage, and the bulk of the oxide being greater than that of the original metal, 
 lingers where it is formed, and thus becomes a perfect iron cement, and the boilers are tight : 
 not so the COPPER BOILERS ; for the water, attacking the metal in its passage through, forms 
 the carbonate of copper, a clear transparent solution, which is not crystallised till deposited on 
 and spread over the bottom of the flues, where it continues its work of destruction. The 
 track of the water, as exhibited in defective rivets, precisely resembles the tortuous operation 
 of the worm in fruits or wood ; being partly in the plates and partly in the rivets, so as in 
 almost every case to require the hole to be much enlarged, in order to remove the defect prior 
 
ON COPPER BOILERS. 11 
 
 to the substitution of screwed rivets, which at the best are a poor substitute for a rivet of the 
 original kind. 
 
 I have found, that when sufficiently acted on chemically, the above observations equally 
 apply to the joints of the plates with the "angle irons," the apertures formed between them 
 being sometimes entirely in the plate, which is thus decayed so as to receive copper pins of 
 considerable size. This is the worst state of the evil ; for the water by its pressure, in addition 
 to that of the steam, acts mechanically as well as chemically in forcing its passage, which, 
 if not timely stopped, will certainly eat transversely through the plate. It is also worthy of 
 note, that the flues are found perfectly tight over-head and along the sides ; the lower parts 
 and the " angle iron " of the bottoms only, and that in spots difficult of construction, yielding 
 to the action. 
 
 After a lapse of six years of active employment, 1 can safely pronounce the parts above the 
 bottom of the flues and fire-places, exposed to the constant action of the fire and water, to 
 retain nearly their original thickness ; I say nearly, because the deficit cannot be actually 
 observed or estimated unless by weight. From the line, however, which the usual length of 
 voyage permitted the salt to accumulate downwards to the bottom of the flues, that is, to the 
 extent of thickness of salt deposited, corrosion has evidently taken place, so much as to 
 threaten the security of parts originally well manufactured, even in the face of caulking, &c. 
 This evil necessarily continued in action for some months in the Mediterranean, when 
 employed between Malta, Egypt, and Syria, on an average of twenty to twenty-four days per 
 month at sea, in the total absence of Roman cement ; which, when procured, again kept the 
 flues tight and dry. The advantages of the cement, here exhibited, suggest its use not only 
 when a boiler is defective, but when perfectly new. 
 
 I should propose, that when tried and found perfect, the flues should be well cleaned, and 
 a flooring of cement applied by proper persons, so as to include the "angle irons;" tiles 
 should then be imbedded nicely, forming a perfect surface from the chimney to the furnace, 
 or, which was the method I adopted, a fillet should be applied all round the "angle irons," 
 with a flooring beneath the funnel. Thus the water from the chimney, impregnated with the 
 matters of the soot, would be entirely prevented, in the beginning, from acting on the bottoms 
 of the tubes ; and any spot beneath, being disposed to " weep," would be prevented till it had 
 been permanently filled with sulphate of lime or other matter, which, on the contrary, would 
 be forced onwards into the bottoms of the flues if water could freely pass. It would have 
 another advantage, it would afford facility in sweeping the flues, and would occupy the 
 intricate parts, from which the soot is never thoroughly cleaned. No very material loss of 
 heat would be sustained by this application, the fires not being calculated to reverberate 
 downwards to a great extent: on the contrary, I have often sent wood into the flues, which 
 has been withdrawn, merely charred; a proof that the bottoms of the flues, those leading 
 directly from the furnaces excepted, contribute little to steam generation, even before any 
 deposition of soot has taken place. 
 
 I think it probable, that "weeps " in the tops and sides of the flues, before alluded to, are 
 first checked by the intensity of the fire acting on the water as it oozes, when the lime subsides 
 and hardens to cement ; for there is no reason why " weeps " should not have existed in 
 equal abundance in these places, as well as in the bottoms ; but it is certain that none have 
 been exhibited. 
 
12 APPENDIX. 
 
 The bottom and lower parts of the shell of the boiler should be treated with as much care 
 in construction, as it has been suggested to pay to the bottom of the flues ; and the chimneys 
 should invariably be made of iron, to step on a cast-iron ring fitted to the top of the boilers. 
 The cast-iron ring does not seem to be affected by the copper ; its situation accounts for it. 
 
 23. COPPER FUNNELS have beenacomplete failure, in every instance of their adoption ; 
 they are rapidly corroded within the air casing, so as in one or two instances to have been 
 crushed by the effects of a gale of wind. IRON FUNNELS decay principally in the parts on 
 which the waste steam operates, and these plates require renewal more frequently than the 
 rest ; therefore it is better to carry the waste-pipe level with the top of the funnel : coal tar, or 
 red lead, or a mixture of both, is the best varnish I have known to be adopted for funnels, 
 which with care may last five or six years. 
 
 In conclusion, I confidently express my opinion that COPPER BOILERS are very far 
 superior to Iron for marine purposes ; and that if the necessary precautions in construction be 
 observed, they will run for a considerable time without giving trouble of any kind. Tinning 
 the bottom plates, lately observed by Messrs. Maudslay and Field, I should certainly 
 recommend ; it will remove the chance of decay to a certain extent. Large pieces of iron 
 have frequently been sent into the flues by me, which have been completely decayed in a 
 short time; no doubt with some good effect to the copper, but without the possibility of being 
 estimated. If the cause be removed by attention to the suggestions on construction, a patch 
 will seldom be required ; consequently delays will be seldom experienced on account of the 
 boilers. The original cost is nearly as three to one on the iron ; this ought not to deter 
 companies, or the proprietors of foreign steam vessels, where the means of repair is not at 
 hand : besides, when unfit for further use, they will always make a good return as old 
 copper; an old iron boiler being, in general, worth little more than the cutting up. Copper, 
 again, is a better conductor of heat than iron ; and if the advantages of incasing marine 
 boilers with non-conducting matter were properly considered and availed of, boilers might be 
 reduced in capacity, weight, and expense, to the obvious account of the proprietor, and to the 
 increased stowage of fuel. More might be said, but the above, coupled with the fact that 
 the shell will scarcely ever be injured or decayed, will be sufficiently demonstrative ; when 
 iron boilers frequently require extensive repairs of the shell or casing, either from water 
 passing by the funnel on the top of the boiler, or from the unavoidable leaks of the deck and 
 comings around the steam-chest ; also the shell is decayed, from the salt, 8cc. on the line of 
 stoke-hole plates or flooring, as well as in the neighbourhood of most of the stay-bolts on 
 the back and sides, the bottoms being often totally decayed ; and these are parts which, 
 from their situation, cannot be attended to conveniently. The above facts are notorious in 
 iron boilers, when in many instances no other defect has existed ; indeed, copper boilers 
 appear to be almost invulnerable in those situations where in iron boilers, whether employed 
 or not, the work of decay is constantly going on. Many cases of delay and incapacity 
 could be mentioned from these causes alone, when important public service was most 
 urgent, not to mention that of individuals. 
 
 It is a common practice in many vessels to throw water into the ash-holes, to cool the 
 cinders prior to sending them up ; the salt, which adheres to the ash-pit in consequence, has 
 sometimes destroyed the bottom plates, when every other part of the boiler was sound. I 
 have seen some instances recently, where the water discharged from the gauge cocks is 
 
CIRCULATING PIPES, DAMPERS, &c. 13 
 
 conducted there by tubes : the men avoid being scalded by this arrangement, at the risk of 
 the destruction of the ash-pits by the brine there deposited. Water in ash-pits has a cooling 
 and draught-exciting property on account of the evaporation ; but it ought on no account to 
 occupy the ash-place of an iron boiler, unless a cistern, constructed for that purpose, was 
 appropriated for its use. In copper boilers I have disregarded the water arising from 
 " weeps " in the ash-pits, no chemical action taking place here, when employed at sea, on 
 account of the frequent removal of their contents. The intrusion, however, of sea-water into 
 the ash-holes, no matter from what cause, ought by no means in any boiler to be encouraged. 
 My object having been to show by comparison the advantages of copper over iron boilers 
 for marine purposes, and to set in a proper point of view the deposition of salts, their effects, 
 and the means of avoiding the same in boilers, as now adapted and arranged, I think that for 
 the future, as regards these matters, all vague speculation, with practical men, may be laid 
 aside ; the evils complained of having been shown to arise, in all cases, both from want of 
 sufficient care in construction, and in the ultimate management. 
 
 CIRCULATING PIPES, DAMPERS, &c. 
 
 24. Circulating pipes, that is, pipes of communication between boilers when more than one 
 is used, are generally fitted with a small bonnet for the purpose of cleansing. The situation of 
 these pipes generally is such as to deprive the engineer of examining them at all times : the 
 pipes on the sides are concealed by the coal-boxes ; those abaft and forward being usually at 
 hand. 
 
 Now, in many instances, the feed, or water for the supply of evaporation, is injected into 
 the front boiler or boilers, those abaft depending mainly on the condition of these pipes, 
 through which they are intended to be supplied. Instances occur where the flues have been 
 much burnt and injured from incrustation, while the fire-places situated in the front boilers 
 were in perfect order. The pipes have been choked, and of course a sufficient supply could 
 not be maintained in the after boilers; hence the deposit and permanent injury. The coal- 
 boxes, therefore, and other obstructions, should be so modified and cut, as to afford 
 convenience for examination ; which should take place at least on the return from every 
 voyage, the small bonnet being removed from each pipe, and its condition strictly looked into. 
 If duties be ever so pressing, commanders should always afford time for, and engineers strictly 
 fulfil, this most important one. 
 
 Circulation of the water through all the boilers should never depend entirely upon the 
 pipes, but should be maintained moreover by free communication above the flues; and these 
 communications should be cut as near the surface of the flues as possible, in order that the 
 blowing off one boiler may to a certain extent affect the condition of the water in the rest. 
 The ' Flamer ' and some other of the government steam vessels have lately been fitted with 
 two tiers of connecting pipes, the upper ones three inches below the level of the flues, and 
 thereby favoring the circulation desired. Cutting the passages through the joining 
 boilers, for sea-going vessels, sixteen or eighteen inches above the flues, has been deemed 
 necessary to prevent the water from leaving the flues of the side boilers when rolling : 
 experience shows this precaution to be unnecessary, the temporary inclination of the 
 ship never exposing the flues to injury, when rolling simply ; and no extraordinary angle is to 
 
14 APPENDIX. 
 
 be anticipated, such as canvass would effect, it being sufficiently understood by commanders 
 who have the least acquaintance with steam vessels, that the sails are a disadvantage when 
 they give the lee-wheel too much depression. A single boiler may be at least eight feet wide 
 without any risk, with the ordinary quantity of water above the tubes ; indeed nearly twice this 
 width may be trusted safely, as instanced in front boilers containing four fire-places of 
 considerable size. A wash plate fitted into the middle of the after boiler, fore and aft, upon 
 the flues as high as the water line, would answer every purpose of preventing the water from 
 entirely leaving the wing flues, on taking a lurch : the same arrangement may be adopted in 
 a front boiler ; but it is not absolutely necessary, the water above the tubes having a greater 
 depth, generally, than that of the other boilers. 
 
 25. Boilers for steam vessels of great or considerable power are necessarily constructed in 
 two, three, or more parts : these parts are best arranged when they are the entire length of the 
 boiler fore and aft, their ends forming the front and back of the whole : thus the longitudinal 
 boiler precludes the inconvenience liable to connecting pipes in the coal-boxes, and to the 
 heavy rolling of the vessel causing the water to recede from above the flues. Each boiler 
 can then be entirely distinct from its neighbour, having its own feed and blow off pipes, and 
 containing its own fire-places and flues ; the smoke and heated air arriving at the upper 
 surface of the boiler, to the chimney, before it mixes with that from the other boiler or 
 boilers. The base of the chimney in the case of three boilers, placed side by side, may be of 
 an elliptical or oblong, instead of cylindrical figure, covering the mouths of the flues, which 
 should each be furnished with a damper, fitted directly on the boiler, and quite distinct from 
 the funnel ; having a communication by levers with the engine-room in front of the boilers, 
 and thus being at all times under the control of those below. 
 
 When a DAMPER is fitted in the chimney, it will inevitably be carried away with it in case 
 of accident, and the ship exposed to fire: a recent instance occurred in the 'Thames' Irish 
 steamer, in the Channel, where the vessel was nearly on fire from the sudden loss of the funnel 
 by a ship running on board her in the night. I have seen funnels carried away in harbours, 
 by getting athwart hawse of other vessels. Accidents are not uncommon at sea, particularly 
 when the funnels are of copper, which, decaying rapidly within the air casing, is less calculated 
 to resist a gale than iron. I have frequently been surprised that funnels stand so well as they 
 do ; preventer stays are often necessary : therefore, fitting dampers in the chimney should by 
 no means be adopted. 
 
 To complete the arrangement, each steam pipe should have a COMMUNICATION VALVE ; or 
 a valve should be fitted on top of the steam chest of each boiler, where they join the common 
 steam pipe; so that either of the boilers may be employed, without at all depending on its 
 neighbour ; the safety valves, as usual, having one common waste steam pipe. The advantage 
 of this mode of construction is obvious, when it is understood that in a gale of wind, or in the 
 case of a ship of war cruising with a squadron by steam, not half the power can be 
 employed with effect j then one boiler or two can be dispensed with, according to necessity, 
 with a saving of fuel, almost in a ratio to the consumption of the boilers unemployed ; I say 
 almost, because a certain portion of heat will be lost by radiation, and by the absorption of the 
 contiguous boiler. In going head to wind the above advantages are most felt ; for the number 
 of revolutions at full speed, of sea-going steam vessels, varying from thirty to twenty-two 
 per minute in smooth water, within the limits of 80 and 200 horse power inclusive, and 
 when contending with a strong gale ahead, the speed being reduced to eight or nine 
 
CIRCULATING PIPES, DAMPERS, &c. 15 
 
 revolutions per minute in most cases, it will be seen that the demand for steam is wonderfully 
 less in the latter, than in the former case. There being two engines employed, and each 
 making two strokes to effect a revolution of the wheel, four cylinders full of steam are consumed 
 in the same time, though of a pressure less than that on the safety-valve : independently of 
 expansion, the pressure of the steam is diminished by condensation in the passage through the 
 steam pipes and jackets, which, by the bye, is very considerable in those vessels fitted with 
 the cylinders forward. Now, the loss of heat by radiation from the steam pipes, cylinders, 
 and slide casings being constant at all speeds, the saving, by dispensing with the use of one 
 or more furnaces, will fall short of the expectations raised by their temporary disuse, 
 inasmuch as the remaining furnaces require to be urged. A furnace cannot be thrown out of 
 use with economy, when the fuel contained in the remainder must be disturbed often before 
 it is fairly consumed ; and this must be the case, unless the mouth of the furnace unemployed 
 be closely covered in, the in-draught of cold air through the same being a great drawback on 
 the effect of the other furnaces : hence the greatest effect will be produced when an entire 
 boiler is thrown out of use. When one furnace only of a boiler could be dispensed with, I have 
 often found it most economical to burn the ashes of the rest therein, mixed with a little coal ; 
 and when too dirty, or the draught too much impeded by clinker, another furnace performed 
 the same office, while it was thoroughly cleared out, and became an active furnace ; and so on 
 in turn with the rest. 
 
 26. Since it has been shown that the consumption of fuel, on principle, should be expected 
 to be in proportion to the revolutions of the wheel, but that in practice it is found to be much 
 greater, the masses of the boilers, cylinders, pistons, &.c. &c. having at all speeds to be 
 maintained by the steam at its own temperature, it follows that the less these parts are 
 exposed, the better ; and if radiation were prevented by completely covering the boilers, steam- 
 pipes, and cylinders with non-conducting materials, the saving of coals only would soon amply 
 return the cost, particularly in sea-going vessels, where gain cannot at all times be effected 
 by bearing up for a port, but where the gale must be struggled with for many days together, 
 not to mention the constant injury sustained by bulk-heads, comings, and decks, by the 
 overpowering heat to which they are submitted. The frequent repairs and renewals of these 
 parts only, amount to no small cost per annum in Her Majesty's steam vessels on foreign stations. 
 Economy of fuel on long voyages has not, I am prepared to say, met with the attention it 
 deserves: stokers consult their own convenience ; and as long as they keep plenty of steam 
 flying off to waste, they are seldom called to account : as to myself, I have found the greatest 
 difficulty in obliging them to keep the fires uniformly. In a gale of wind, and then only, when 
 the labour was little on the fires, and when it became a consideration with every one, both on 
 deck and below, to eke out the means of arriving at the destined port in safety, the fires were 
 minutely attended to, and the fullest effect obtained at the least possible expense : a few 
 clinkers only, and no ashes, which should never, in iron boilers, be allowed to remain 
 longer than two hours in the ash-pits, or in contact with the boilers on the stoke-hole 
 plates, were thrown overboard twice in twenty-four hours, when such discipline was 
 observed, and this with the Welch coal. How much greater would the gain be at all times, if 
 the oppressive heat, which drives the fireman from his quarters now, were removed, so as 
 to permit him to dispose a less portion of fuel to a wonderfully increased advantage ? These 
 considerations are by no means visionary ; the people in Cornwall understand them well, and 
 
16 APPENDIX. 
 
 profit thereby to a considerable amount. I have, on a summer's day, found it sensibly 
 cooler in an engine-house closed, containing a cylinder eighty inches in diameter, and ten 
 feet stroke, while the steam-gauge indicated thirty-four Ibs. per square inch on the 
 safety-valve, than I experienced without : the boiler-house nearly the same. Is not economy 
 in fuel as loudly called for in marine engines, without reference to stowage, health, and the 
 labour and dirt of shipment ? 
 
 The advantages above proposed are now carried into effect to a certain extent in Her 
 Majesty's steam vessels, by coating the boilers, whether of iron or copper, with "felt," laid 
 on a thick covering of a mixture of white and red lead ; the same treatment has been observed 
 with regard to the sides of the respective boilers where they come together, when smoke-joints 
 do not interfere : the advantage of this does not consist only in the preservation of these 
 sides, so liable to decay from the water which descends there leaving its salt adhering to the 
 plates, but it operates to prevent the heat of one boiler from being transmitted to another 
 when not employed ; indeed, the practice of coating boilers of marine engines was observed as 
 far back as 1818 in the ' Caledonia,' Mr. Watt's private steam vessel, and also in the ' James 
 Watt' in 1823: the cylinders of the former were also coated in the same manner and 
 covered with reeded mahogany. By combining the arrangements before mentioned, so as to 
 have the respective boilers and flues distinct, smoke-joints may be entirely dispensed with : 
 these are generally dangerous, although often unavoidable, both from the size to which the 
 boilers are required to be carried, to meet the power of the engines, and from the necessity 
 which sometimes exists of adapting them to the peculiar construction of the vessels. 
 
 27. From the frequent necessity of opening the furnace doors, when under weigh, to re- 
 plenish and arrange the fires, a large portion of cold air is allowed to pass through the flues ; this 
 ready passage for the air checks its entrance through the bars of the adjoining furnace or fur- 
 naces, and in most instances throws them for the time nearly out of use : thus the boilers are not 
 only deprived of the effect of the open furnace, but, to a great extent, of all others connected 
 with the common flue : this is so certain, that boilers having four furnaces joining in one flue, 
 as formerly fitted to vessels of 100 horse power and upwards, have been supplanted by others 
 in which two furnaces only discharge their fire into a flue which meets that of the other 
 two furnaces at the chimney, having traversed the water separately before they meet. The 
 former plan of boiler is always remarkable for a bad or indifferent draught; it requires more 
 area of heated surface to generate sufficient steam, occupies of course more space, contains 
 a larger quantity of water, and is, in addition, considerably heavier than the latter style 
 of boiler, which is distinguished for its power in producing steam, and for the ease of working 
 it. Hence it follows that the more distinctly furnaces perform their work, the greater the 
 effect obtained ; but this has its limits ; for if a flue is too direct, a great portion of heat passes 
 up the chimney without effect, the fire not having traversed sufficiently through the water to 
 be absorbed by it. In land engines this defect is not experienced, the fire passing around as 
 well as through the boiler ; while in vessels the fire must be entirely confined to the flues, which 
 are surrounded with water. 
 
 Some of the best judges of the construction and working of marine boilers recommend that 
 the fire should be divided by as many furnaces as possible within certain limits, in order that 
 the feeding a fire should not occupy too much time, and that it might be performed more 
 frequently, and in consequence more regularly; and, it is presumed, with better effect, on 
 
CIRCULATING PIPES, DAMPERS, &c. 17 
 
 account of a less portion of cold air being permitted to pass through the flue at a time. When 
 three such furnaces are employed instead of two, (for it has been observed that four are 
 decidedly objectionable,) which communicate with a common flue, it is evident that there are 
 always two furnaces in action, while the third is being entirely cleared out ; an operation which 
 at sea must be performed at least, in turn, once in two hours, the fire-door being open during 
 the operation, and a considerable quantity of cold air afterwards passing through the grate 
 until the relay of coals is in a proper state of combustion. Here the three furnaces have 
 a decided advantage over two of the same area collectively, in maintaining the power of the 
 engines during the disuse of one of the number : but if the two furnaces be managed properly, 
 want of steam during the above operation will rarely be felt. Of course these observations are 
 referred to vessels of such power, as to have, at least, two distinct boilers, or two distinct sets 
 of furnaces and flues in the same boiler, so that you have the full effect of one or more boilers 
 or sets of furnaces, without any drawback, at all times. From the necessities of construction, 
 three furnaces cannot directly discharge their fire into a flue, whose width is less than that of 
 either of the furnaces individually : the fire having, in one furnace at least, to cross, to a certain 
 extent, that of another before it can enter the flue, this furnace is least active when either of the 
 other furnace-doors are open, the cold air directly entering the flue retarding its effect : the fire 
 of this furnace moreover, when all are in full force, acts directly on the side plates of the cross 
 flue opposite, before it passes with that of the other furnaces into the common flue ; the con- 
 sequence is, that if the boilers are partially incrusted, these plates must be the first to give out, 
 next to those of the furnaces, of which there are many instances. Hence when three furnaces 
 are employed, the flue should be deflected as much as possible, to accommodate each of them. 
 28. From an extensive examination of the boilers of long sea voyage, I am led to the 
 opinion that the fires act more destructively on the sides of narrow furnaces, than of those under 
 similar circumstances of greater width ; it may arise in a great measure from the fuel being 
 heaped up more thickly in the former than the latter : the air not being able to penetrate the 
 mass well in the middle, then passes up the sides, urging an intense flame to act thereon ; this 
 cannot take place so effectually in a wider furnace. A furnace that is very long cannot 
 be properly managed by the firemen at sea : it has every chance of being overcharged, more 
 particularly if the boilers keep steam easily, because then they require less attention, and are 
 charged so as to last as long as possible for the accommodation of the man ; and this practice 
 cannot well be overruled night and day, unless engineers neglect other duties ; for it would be 
 necessary to be constantly in a stoke-room for the purpose. I should say, that if a furnace be 
 six feet in length, it should not be much less than three feet in breadth, to afford a fair chance 
 for firing with as little injury to the side plates as possible, and with the means of keeping the 
 fires in the required condition for the greatest effect : furnaces should not be carried beyond 
 this length more than can be avoided ; it is not necessary that they should ever be wider than 
 three feet, indeed it would be inconvenient : but the nearer it is approached in width for 
 various powers, I think, the better. By adopting short and wide furnaces, short firing-tools 
 become necessary, and of course short stoking-room, thereby gaining on the entire section of 
 the ship for the stowage of coals abaft. The crowns of the furnaces, whether of iron or copper, 
 never decay, and rarely alter their figure, if arched, unless the water is allowed to descend below 
 them. In some of the most neglected and most injured boilers that I have seen, the crowns of 
 the fire-places have remained perfect, when every other part has been attacked by the fire : it 
 
18 APPENDIX. 
 
 can be accounted for by the ready transmission of the heat, which is obstructed more on the 
 sides, from the accumulation of scales and the increased difficulty of removing them. 
 
 29. In the arrangement of plates in the furnaces, perpendicular seams are bad, and in long 
 voyages are certain of injury from the fire; the quantity of inetal at the joinings or seams 
 causing an unequal expansion, and retarding the transmission of heat. Plates the entire 
 length of fire-place may be employed, having their seams beneath and in the direction of 
 the bars ; the upper seam, when the furnaces are large, being as much above the fire 
 as possible ; but, on this subject, opinions are divided, some still preferring the former 
 method of construction. Plates of copper may be manufactured with certainty of the 
 entire size required for the sides, in 50 horse boilers; but iron plates of such dimen- 
 sions could not be depended on. Iron plate for furnaces should be manufactured of 
 the best material that can be obtained ; additional expense for such would be amply 
 repaid. The plate used for furnaces mostly owes its premature destruction to the 
 great thickness usually employed: it thus conducts heat more slowly, and is neces- 
 sarily more heated than thinner plate; besides it is much less likely to be sound than 
 the latter, although of an excellent exterior, which conceals the defects of manufacture. I 
 some time since examined, in a foreign port, an excellently constructed boiler of a 200 horse 
 marine engine, and of the very best material, which had been comparatively seldom employed 
 during eighteen months after construction : the interior of the boilers evidenced the greatest 
 care and attention, but the side plates of the fire-places, from the bars upwards, required to be 
 replaced, from no other cause than that of being too thick. These cases are very common, as 
 before observed, in Her Majesty's steam vessels between Falmouth and the Mediterranean, 
 as likewise those employed on other stations, which need repairs in these places several times 
 before the boilers are required to be taken out, from actual decay. 
 
 Many have been formerly misled as to the cause of injured boilers. I have witnessed 
 ingenious expedients of negligent persons to account for the same, in the presence of eminent 
 engineers, who, not having an opportunity of watching proceedings on a long sea voyage, were 
 obliged, to a great extent, to take plausible reasons as their guide ; viz. saltness of the Medi- 
 terranean, 8tc. : allowing water to become too low in the boilers is too frequently the real 
 cause, which, if copper, will soon exhibit the consequence. Thicker plate has been adopted, 
 probably to resist the tendency to bend, but it only increases the evil. Plates for the sides of 
 fire-places then should not, in the largest boilers above the bars, be more than three-eighths 
 of an inch thick ; and in smaller boilers a less thickness would be preferable, as no oxidation 
 takes place here, or even throughout the flues, of any consequence, above the mass of soot 
 therein deposited. This fact is decidedly opposed to the notion generally propagated, that the 
 iron rapidly imbibes oxygen from the cold air admitted, when the fire-doors are opened to 
 replenish fuel : no more injury is experienced practically from this cause, than that found to 
 be sustained by the exterior of a common culinary boiler, the plates not being sufficiently 
 heated to imbibe a destructive portion of oxygen. 
 
 The lower part of the sides, and the bottom of the fire-place, should be thicker in all cases, the 
 better to bear up against oxidation, which here takes place to a great extent, as likewise along 
 the bottom and lower part of the flues ; and the bottom of the boiler, and the lower portion of 
 the sides, should be stouter than the crown, particularly in the wake of the stoke hole flooring, 
 where, as has been before observed, decay very rapidly takes place. 
 
CIRCULATING PIPES, DAMPERS, &c. 19 
 
 It has sometimes occurred that boilers of good construction have suddenly failed in 
 generating the necessary quantity of steam for the engines, although the fires have been urged 
 as usual : this unaccountable circumstance, after the strictest investigation, has been cleared 
 up by the appearance of steam at the top of the chimney, instead of at the waste steam head. 
 The UPTAKE, or portion of the flue which rises through the water of the boilers to join 
 the chimney, has been found defective, so that the steam escaped above the water line, through 
 the rent it made, directly into the funnel or chimney, the boilers in every other respect 
 performing their duty properly : the uptake, therefore, should be thicker than the other 
 portion of the flue, and should at frequent opportunities be perfectly cleaned and coated 
 with some anti-corrosive : coal tar mixed with red lead, and applied hot, I should 
 recommend. 
 
 The SHELL OR CROWN of the boiler, and STEAM CHEST, suffer most from accumulation of 
 dirt, and leakage from above. Steam vessels are necessarily much more subject to be extremely 
 dirty than other vessels ; in fact, it is periodical every sixth or seventh day on foreign service, 
 and sometimes oftener, to be completely covered with coal dust in every part exposed. Water is, 
 and can never be entirely prevented from being, thrown over every part of the ship : it is this, 
 and the every-day work of dashing water over the decks, that achieves the destruction of the 
 parts above mentioned, more than any other cause ; the rain and spray certainly assist. Hence 
 too much care cannot be taken in rendering every part of the deck, or other covering of the 
 boilers, as tight as possible. Waste and feed pipes rather interfere ; but they can be, and are 
 generally fitted now, beneath the deck, so as to be entirely out of the way of accident, in case 
 the funnel be carried away. 
 
 The AIR CASING around the base of the funnel, in most vessels in Her Majesty's service, has 
 been surmounted by a hood water-tight, so as to prevent the water passing in that direction com- 
 pletely, the flanch of the casing being made tight on deck; and the bottom cants of the coal- 
 boxes are fixed two or three inches clear of the sides of the boilers, so as to permit dirt, which 
 may not be intercepted by the pieces of wood, fitted between the crown and the coal-boxes fore 
 and aft for that purpose, to be washed into the ship's bottom, whence it can be removed, thus 
 preventing its accumulation between the coal-boxes and the boiler sides. If it could be 
 afforded, sufficient space should be allowed for a passage around the boilers, by which they 
 may be kept perfectly clean. 
 
 As little wood as possible should be used around the upper parts of boilers, in addition to 
 the covering of the deck. Thin sheet iron, properly riveted and chinced, should take the place 
 of comings, &c. which, with the carlines which support them, are frequently set on fire. Coals 
 and wood, not directly in contact with the air casing, have often been fired in a very short 
 space of time on deck when exposed, as likewise when contained in bags in the same situation. 
 More than one air casing should invariably be fitted around the funnels of sea-going steam 
 vessels, the air freely passing between them, so as not only to remove the risk of fire in a great 
 measure, but also the oppressive heat which is experienced in still weather in warm climates, 
 when passing or standing in the neighbourhood of the same. The outer casing, whenever the 
 construction of boiler will permit, should have a large flanch fitted on deck, which should be 
 cut round as far as possible from the casing, the flanch being made perfectly tight, which can 
 never be attained by the pitch and oakum joints of comings, or the hatches or platforms they 
 support. Corrugated iron, is a neat substitute for wood to surround the parts of boilers 
 
20 APPENDIX. 
 
 projecting above the decks, in vessels which cannot conceal them beneath ; but when the deck 
 is sufficiently above the boilers, projections of hatches and scuttles should be avoided, the 
 deck being more easily kept tight by being often wet, and occasionally caulked. 
 
 WATER-WAYS of marine boilers, to economise space, are often made much too narrow; so 
 that the crust, in falling from the sides of the flues, is intercepted with other matters left in the 
 boilers by oversight or neglect ; thus forming convenient shelves on which the calcareous 
 matters repose and continue to accumulate. It is then inevitable, that the side plates will be 
 "drawn" or bent towards each other by the fire, in its passage through the flues: not 
 unfrequently, in such cases, the flues are so obstructed as to become impassable. The fire in 
 its zig-zag course now attacks the bends or extremities of water-ways, which turn its direction 
 into the joining flues ; cracks and openings are soon made, through which the water and non- 
 conductors are forced; in these places, patches are with difficulty fitted, and, from their 
 situation, are exposed to be speedily injured from the increase of mass. Water-ways in no 
 instance should be less than four or five inches wide, and in those between the fire-places some- 
 thing more ; the ebullition being so rapid here, that the water is more likely to be repelled, and 
 the plates exposed to injury, which a sufficient quantity of water would obviate to a certain 
 extent. If it be found convenient to make the spaces six, seven, or even eight inches, which 
 is more than necessary in the largest boilers, no increased expense of fuel will be felt in 
 practice, after the bulk of water is once heated: this fact is quite established. Too much space 
 beneath the flues, in the lower class of vessels having little depth of hold, is not necessary; it 
 ta.kes away from the room above, requisite for scaling, and adds to the gross weight un- 
 necessarily, by the increased stowage of water. A rectangular trunk or trough, extending the 
 entire length of the bottom of each boiler, with a man-hole at both ends, is the plan most 
 desirable ; and being fitted between the sleepers, it descends beneath the other portion of the 
 bottom, and becomes a receptacle for all the scales which may fall from the tubes. From 
 the bottoms of these trunks the blow-off pipes, well protected by a grating, should proceed : 
 thus the necessary space is gained, without too great an increase of weight or height. 
 
 Boilers that have been much incrusted, and the water-ways in many places choked, have in 
 some instances, when blowing off could at all be effected, been perfectly clear beneath the flues ; 
 that is, the scales have not combined into a mass : therefore, the space in addition to the trunk 
 need not be much more than that pointed out for the water-ways between the flues, except in 
 large vessels, where a space beneath the entire bottom of the flues is desirable for repair ; 
 and for the purpose of affording means of keeping the bottom of the shell perfectly dry when 
 not employed, a very necessary precaution on a foreign station. The accumulation between 
 the tubes is much to be guarded against; to meet which a sufficient number of 'man-holes 
 should be cut through the upper parts of the boilers, so as to permit a due ventilation for the 
 men employed in scaling the boilers, (a material object in a warm climate,) 1 as well as 
 to afford convenience of repairing fire-places, and removing the scale, which I am persuaded 
 has been often negligently permitted to fall between the tubes, by the people employed in 
 scaling, to avoid the increased labour imposed by neglect of proper arrangements for removing 
 the same, it not being at all times in the power of engineers to look after them : much time 
 will be gained, as well in repairs as in cleaning, by anticipating these difficulties. 
 
 1 Keeping the safety-valves open greatly assists in cooling the boilers. 
 
CIRCULATING PIPES, DAMPERS, &c. 21 
 
 The great preparation necessary for cleaning and scaling a boiler, and the number of hands 
 required to attend with buckets, &c. to remove the crust, frequently prevent an engineer from 
 entering willingly on the task, unless he can calculate on sufficient time for the same ; it is 
 in proportion to the convenience afforded, that these duties may be expected to be fulfilled. 
 
 FLUES need never be wider than to allow convenience for repair and sweeping, without 
 reference to the magnitude of the boiler, so that much gain may be obtained in heated 
 surface in large boilers by the introduction of an additional flue, when the breadth will 
 permit ; that is, the increased horizontal surface due to the dimension of a boiler for large 
 engines over that of smaller ones will, with nearly the same water-ways, afford sufficient space 
 for the flue as above, instead of increasing the width of the others to occupy the said space ; 
 thus the surface of two additional sides is gained for steam generation. Fifteen or sixteen 
 inches may be taken as a good standard for width ; it ought not to be much less, and need 
 not be much greater. 
 
 30. As the safety of boilers must always be entrusted to the engineers, whose duty requires 
 them to blow off a part of the water therein contained every two hours, it has often occurred, 
 that from neglect, or from having their attention suddenly withdrawn from this momentous 
 operation, the water has been allowed to descend below the flues and fire-places ; this, though 
 rarely, might happen from a defect in the feeding-pump or some of its apparatus : the burning 
 of fire-places and flues is inevitable, and almost immediate, HO notice being given till the injury 
 is effected ; and much greater mischief might take place, under the circumstances, from 
 explosion even, when the water of the feeding-pump is violently repelled, and flashed 
 into steam of a high degree of expansibility, by the red-hot metal on which it is injected. 
 The above neglect, and its partial consequences, I have witnessed several times ; and it will 
 and must be expected to occur again unless some arrangement is made, in order that the 
 blow-off cocks or valves shall be closed, and the blowing off cease, when the water has 
 descended to a certain limit consistent with the safety of the flues. In fact, I have considered 
 blowing off, at all times, so important and dangerous an operation, that I never permitted 
 it to be performed without the attendance of one fireman at least, with the engineer of the 
 watch, whose undivided attention was directed to trying the gauges, till the moment prescribed 
 for shutting the cocks : so valuable a part of the machine as the boiler should not be left 
 entirely to the discretion of men who may or may not look properly after it. 
 
 A "DETECTOR PIPE," as now fitted in some of Her Majesty's steam vessels, will effectually 
 give notice of the approach of danger, in case the water is allowed to become low, as well as in 
 cases where the action of the safety-valves becomes obstructed from any cause whatever, of 
 which we have lately had alarming instances. This pipe is bent like a syphon ; one leg of 
 which, two inches in diameter, to avoid becoming foul, descends beneath the water of the 
 boilers to a point above the flues, where they are perfectly safe. From the bend, the height 
 of which should be above that due to the pressure of steam in the boilers, a smaller leg 
 descends to the engine-room ; the bottom being directed towards the ash-holes, with stop- 
 cocks at hand, to be used when the boilers are entirely blown off" on arrival, and so arranged 
 that the cocks must always be open when the levers or spanners are removed. A hole is 
 made, or a tube inserted, in the upper part of the bend, so as to prevent the " detector" on 
 the inclination of the ship, or otherwise, from acting as a syphon. The steam rushing 
 
22 APPENDIX. 
 
 violently through the apertures into the engine-room, when the water is below the mouth of 
 the pipe, will not only arouse the attention of those below, but will alarm the people who 
 are at all times on watch on deck : there could then be no false account of the neglect, 
 which would thus be publicly made known. Time will thus be afforded either to shut the 
 valves or cocks, or to haul out the fires, when the boilers will be safe. 
 
 Instances have often occurred of cocks being re-opened by the engineer instead of shut : 
 now in vessels, as fitted by some engineers, cocks may be shut when turned half round, and 
 by others, with the common two-way cocks, which are shut only when turned one quarter of a 
 circle ; thus, by force of habit, a person may inadvertently, in a strange vessel, re-open 
 instead of shut a cock, and think all secure ; it is the work of a moment, and this I 
 have seen take place. 
 
 Mr. Kingston, by a very simple contrivance, applicable to any of the ordinary blow-off 
 cocks, entirely prevents this occurrence. A fork, or two horns, are fitted to the bottom of the 
 common socket-spanner, which project so as to meet the pipe or shell of the cock, when it must 
 be either open or shut, an opening of the figure of the socket and its horns being made in a plate 
 which covers the cock, for that purpose. When the cock is open, the horns are beneath the 
 plate, and of course the spanner cannot be withdrawn ; so that a general order being given by the 
 chief engineer to every person connected with the engine-room, that the spanner is on no account 
 to be left in its place, it is clear that any one removing it must leave the boilers safe ; and its 
 situation being generally in the middle of the stoke-hole, if an engineer's attention by day or 
 night should happen to be called off, a fireman will, on observing it, be aware that all is not 
 right, and will act accordingly. By adopting these precautions, which should be general in 
 sea-going vessels, and are attainable at little cost, accidents which they are immediately 
 intended to ward off will rarely be heard of; they scarcely could occur without the grossest 
 neglect under such arrangements. 
 
 Glass water-gauges are useful, to show by inspection the height of the water in the boilers ; 
 but unless treated with great care, they will get out of order, and cease to be of service. 
 Copper floats are much to be recommended, with an index to each appearing in the front of 
 the boilers, the oscillation of which can be well observed night and day by every one below, 
 and generally from the deck as well : floats seldom get out of order if properly made and 
 attended to. Many boilers have owed their safety to the timely warning of the floats when 
 feeding-pumps have ceased to act, and I am not acquainted with any real practical objection 
 to their general use. I have known the feed to be regulated for days together, at sea, by 
 floats, with great nicety; but this office I should not recommend, the levers requiring to be 
 adjusted according to the varying state of the weather and speed of the engines. These 
 ostensible indicators of the quantity of water in the boilers should be fitted to every vessel 
 without exception ; their just performance depends entirely on the care of the engineers. 
 
 Reverse valves, for the admission of air into the boilers when the vapour has less force than 
 the atmospheric pressure, should never be less than four inches in diameter, and should be 
 carefully cleaned and set in order prior to each voyage ; as (for they are rarely tight) the dirt 
 and salt congeal around the spindles and gear to such an extent as to soon render them useless 
 in case of need : I have never seen them act spontaneously, even when the steam-gauge has 
 been an inch below zero ; and recent injury, to a great extent, by the collapsing of a boiler 
 
CIRCULATING PIPES, DAMPERS, &c. 23 
 
 from this inefficiency of the valves, points out the necessity of observing the above precautions 
 strictly, and not ofjijci>ig them to their places, which has been done occasionally, to avoid the 
 nuisance of leakage, by those not duly estimating their probable utility. 
 
 31. Ultimately, the fixing of boilers in their places requires particular attention, the 
 bottoms often giving out before any other part of the shell. All copper bolts, securing 
 the sleepers to the ship's bottom, should be clenched beneath the surface of the 
 sleepers, and then covered with wood let in flush with the same : or plank may be brought 
 on each of the sleepers, when fixed, of the entire length of boilers, and secured with iron 
 nails ; for, if a copper bolt-head comes in contact with any part of the bottom of an iron 
 boiler, a hole will inevitably be eaten through in a short time in that spot, the most difficult 
 of any to be repaired in place. 
 
 When the angle iron projects beyond the bottom of the boiler, in the manner of Messrs. 
 Boulton and Watt, it is customary to fill the space inclosed, with wood nicely fitted and coated 
 with white lead ; so that, when in place, the bottom is well supported and protected from 
 corrosion : but this method does not so well apply to other constructions of boiler ; in 
 bedding which, platforms laid across the sleepers should cautiously be employed. If a leak 
 should exist in any part of the bottom, which is almost certain, the water, not being able to 
 make its escape, flows beneath the bottom of the boilers, covering the surface of the platform, 
 which supports them at the seams or stays only : this water is imbibed by the wood, which is 
 thereby speedily rotted, the salt remaining in contact with the boilers, to effect their 
 destruction. Boilers then, when not too near the bottom, may rest on the sleepers only, which 
 should be thickly covered with some anti-corrosive, such as white and red lead ; and when 
 fixed in their proper places, some one should be sent beneath, to fill up spaces in such parts as 
 the irregularity of the bottom has prevented from coming in contact. The vapour arising from 
 the bilge-water does not at all affect the parts of the bottom exposed to its influence. Boilers 
 that have been in use for some years, placed as above, (the application of red lead excepted,) 
 have, when taken out, been found decayed in such parts of the bottom only as rested on the 
 sleepers, with the exception of a few defects arising from bad workmanship or straining; the 
 common lead-coloured paint remaining on the plates exposed, as when first applied by the manu- 
 facturer. But when the boilers by necessity are placed too near the wash of the bilge-water, 
 their bottoms, which are soon covered entirely with salt, are rapidly and completely decayed : 
 here platforms well covered with white and red lead must be resorted to. 
 
 32. The most important parts of marine boilers, and those on which opinions have not gene- 
 rally agreed, having been considered, from the facts, apparent on a strict examination of their 
 details, when employed, and when totally dismembered after service, I have to observe, that if 
 the boilers be constructed distinctly from each other, or so as to permit each series of flues to 
 act on distinct bulks of water, the steam of each being under control, they will not only have 
 all the advantages before described, but, as the efficiency of our steam marine is of paramount 
 importance, and steam vessels are essentially ships, and liable to encounter the thousand 
 casualties to which all ships are exposed, a shot through one boiler would then by no means, 
 after the escape of steam or water, prevent a vessel from continuing her way from an enemy, 
 in the case of a merchant-ship ; and if a steam-frigate, there would still be an opportunity 
 afforded to manreuvre, while a single shot meeting boilers which are not distinct, would leave 
 the ship a certain prize to the enemy. These considerations are not trifling, when it is 
 recollected that steam vessels have already been extensively engaged for warfaring purposes in 
 
24 APPENDIX. 
 
 Portugal, Spain, and elsewhere ; and although no shot has yet penetrated a boiler, the paddle- 
 boxes and other parts have borne strong testimony of the risk to which they are liable. 
 
 The increase of expense to effect all suggested, is not worth mentioning as an item in the 
 value of a steam-engine. 
 
 To illustrate the construction of marine boilers those of the ' Medea' and 'African' steam 
 ships are represented in Plate xxn. 
 
 REMARKS ON ATLANTIC STEAM NAVIGATION. 
 
 33. In Atlantic steam navigation the fullest effect should be brought out with the engines 
 and boilers as now constructed, the necessities being greater than that of any other effort of 
 steam as a propeller. 
 
 WASTE OF FUEL FROM CYLINDERS. I have alluded to the advantages of non- 
 conductors ; this should be carried as far as possible in these ships. Cylinders, slide casings, 
 as well as boilers, should be completely incased. The following facts will remove all question 
 of the propriety. 
 
 In the ' African ' the cylinders are about 5 feet 3 inches distant from the boilers : there 
 are no hatches immediately over them, and the short steam-pipes are covered with fear- 
 nought, &c. The quantity of distilled water produced from the belts of 50 feet square surface 
 which girt the cylinders (there are no jackets surrounding them) in the Mediterranean, was 
 constantly about 270 gallons in 24 hours ; that is, a quantity of fuel was lost by radiation 
 from the belts of the cylinders in 24 hours, equal to that which would raise 270 gallons of 
 water, at a boiling temperature, into steam. 1 
 
 From experiments made on board the 'African' in December, 1831, moored in still 
 water, without the influence of tides, 306 cubic feet of fresh water (measured) were required 
 to maintain the engines at an uniform velocity of 12 revolutions per minute for 6 hours, 
 at an expense of 24 cwt. of Heaton Main coal ; one boiler or two furnaces only being 
 employed ; a certain portion of heat being abstracted by the joining boiler, which was in all 
 respects distinct from that employed : now 270 gallons = about 44 cubic feet of water pro- 
 duced in 24 hours from the belts of the cylinders; and 306 cubic feet x 4 == 1224 cubic feet 
 of water evaporated in 24 hours by 24 cwt. x 4 = 96 cwt. of coals, according to the 
 experiment above noted. 
 
 Hence 96 cwt. x 44 cubic feet = 3 . 45 f coa , s &s ft dead 
 
 1224 cubic feet 
 required in 24 hours to maintain the temperature of the belts alone. 
 
 Here the tops and other portions of two cylinders of 38 inches in diameter only, and slide 
 casings, are not at all taken into consideration. The loss here recorded is rather under than 
 over rated. The water thus procured was constantly appropriated to the use of passengers 
 and the ship's company ; and, when on the Alexandrian station, no other water was made use 
 of in the ship, 10 tons only excepted, being the greatest quantity received at Malta, the 
 absence from which port being never less than 18 days. 
 
 In the steam frigates, the quantity of distilled water produced at sea in 24 hours, by the 
 
 1 The steam pipes, although covered, no doubt contributed in some measure to the loss above stated. 
 
ON ATLANTIC STEAM NAVIGATION. 25 
 
 jackets of the cylinders, of 162 feet square surface, amounts to upwards of 4 tons! equal to 
 
 143-36 cubic feet. 
 
 Now, according to the foregoing, 
 
 143-36 cubic feet x 96 cwt. = n>24 cwt> of coalg in 24 hourS; to meef . the radiation of heat 
 1224 cubic feet 
 
 from the jackets of the cylinders ; and when they are placed forward, and at a considerable 
 
 distance from the boilers, the expense is much greater. 
 
 The saving of fuel and comfort in the engine-room would be, on the whole, very con- 
 siderable, particularly in 400 horse engines, were the loss, before estimated, prevented by 
 clothing. 
 
 34. WASTE OF HEAT FROM BOILER. As to the waste of heat from the boilers, from 
 experiments I made in the coal-boxes, I found that when the thermometer ranged from 50 
 to 59 on deck during five days, it increased to 116 in the boxes, the thermometer being 
 suspended from the beams in the neighbourhood of scuttles, which were left open more or 
 less night and day, and through which the heated air was constantly escaping from the 
 coal-boxes ; this heat was radiated through a space of 6 or 7 inches, at which the coal-boxes 
 were distant from the boilers, a large hatch directly over the boilers being at the same time 
 kept open for ventilation. The thermometer, when the bulb was applied to the coal-box 
 plates, two-thirds of their depth from the deck, varied from 138 to 148 ; and when applied 
 to the front plates of the boilers, the temperature indicated was 169, not very greatly 
 exceeding that of the coal-box plates. 
 
 One important fact was elicited on these experiments, that when the surface of the coals 
 was removed, and the thermometer introduced amongst the lower portion, it was raised 36 
 above the temperature of the air in the boxes, vapour being given out from the surface 
 exposed ; that coal which was immediately in contact with the coal-box plates appearing as if 
 dry distilled. From this I was led to judge, that the lower portion of the coal being pressed 
 upon by the superincumbent mass, and constantly receiving heat from the moment of getting 
 the steam up, maintained this heat embodied in the form of vapour ; which, not being able 
 to escape through the mass, assisted in extracting the gaseous portion of the coal, tending to 
 produce spontaneous combustion ; which I have witnessed in several instances, although these 
 consequences are mostly found to be brought about by defective smoke-joints. The injurious 
 effect of this heat on the constitution of the coal trimmers, and the great amount of fuel 
 wasted by this channel, clearly demand every attention from those interested in the Atlantic 
 voyage. 
 
 From the data furnished by the loss of fuel from the jackets of the cylinders, all other 
 circumstances being the same, an approximation may be arrived at of the waste by radiation 
 from the boilers ; thus, the entire external surface of the boilers and steam-chests of the 
 ' African ' amounts to 855 feet square ; and the area of the belts being 50 feet square, effecting 
 
 a loss of 3-45 cwt. of coals per day, we have, 3 ' 45 cwt ' x ** 5 sq " ft ' = 58-99 cwt., or 2-95 
 
 50 sq. it. 
 
 tons of coals required in 24 hours to meet the loss from radiation in these comparatively small 
 boilers : in this calculation, the surface of the bottoms of the boilers is included ; the loss 
 from which, it should be observed, is trifling when shielded, by platforms, from exposure to the 
 bilge water. 
 
 d 
 
26 APPENDIX. 
 
 The boilers, on the whole, are certainly less exposed than the cylinders, but, from their 
 greatly reduced thickness, they transmit the heat more readily. 
 
 When one boiler only is employed, the side next its neighbour, by giving out heat 
 thereto, is another source of loss. The side of either of the ' African's' boilers has 123 feet 
 
 square surface. Then, as before, 3 ' 4 cw r t- x 123 S( *- f< " = 8'48 cwt. of coals expended 
 
 oU sq. tt. 
 
 in maintaining the temperature of the contiguous boiler. I think this falls short of the 
 actual waste by this channel in 24 hours. 
 
 ' Dee ' steam-frigate, 200 horse power ; area of jackets, 162 feet square ; external surface of 
 boilers and steam-chests, 1783 square feet. Now, the actual waste by her jackets per day, 1 
 
 as before estimated, is 11'24 cwt. of coals; and U ' 24cwt - x 1783 sq. ft. = 123 . ? cwt Qr 
 
 lb'2 sq. ft. 
 
 6'18 tons of coals loss in 24 hours by radiation from the exposed surface of the boilers; 
 the surface of the bottoms being included. 
 
 Again, the area of the sides of one set of boilers opposed to their neighbours in the same 
 
 vessel amounts to 263 feet square. And H ' 24 cwt ' x 2 3 8q ' ft ' =a 18-25 cwt. of coals 
 
 162 sq. ft. 
 
 loss in 24 hours from absorption, when one set of boilers alone is employed. If the above is 
 considered as a fair estimate of the loss from radiation in 200 horse vessels, it must of course 
 be proportionally greater in vessels of double the power. 
 
 35. ECONOMY IN THE EXPENDITURE OF COALS. In order to obtain a correct idea of 
 the number of days' fuel which a vessel can carry, an important consideration in vessels of long 
 voyage, it should be estimated what amount the boilers consume at full speed in still 
 water, (the greatest expenditure takes place under these circumstances,) making allowances 
 for clearing out fires alternately, after having been some time under weigh : under every other 
 circumstance, the consumption is rather less than greater. During strong gales the con- 
 sumption may be very considerably reduced : I have seen seven days' fuel protracted to 
 eleven, by working such of the furnaces only as were adequate to the wants of the 
 engines. 
 
 I subjoin one or two extracts from my journal of a Mediterranean voyage, which will show 
 to a certain extent the advantages of this practice, labouring under the drawbacks of radiation 
 before detailed. 
 
 1st Experiment. 10 hours with Welch coal. Consumption, 9^ bushels per hour with 4 fires. 
 Revolutions, 25 per minute. Speed of vessel, 7 knots per hour by log. Vessel deep ; smooth 
 water. 
 
 2nd. Strong winds a-head. Put out one fire, and closed the furnace-mouth. Consumption, 
 8 bushels per hour with 3 fires. Revolutions, 18| per minute. Speed of vessel, 5 knots. 
 
 3rd. Strong gales a-head. 2 furnaces, or one boiler only employed (being robbed now by 
 that in disuse). Consumption, 6 bushels per hour. Revolutions, 11 per minute. Speed of 
 vessel, 4 knots. 
 
 These extracts of actual work will give the best idea of what might be further gained by 
 a better arrangement than sea-going steam vessels are usually prepared with. 
 
 36. SWEEPING FLUES, &c. Persons not practically acquainted with the working of 
 
 1 The steam pipes were clothed. 
 
ON ATLANTIC STEAM NAVIGATION. 27 
 
 marine boilers on long voyages, are liable to form erroneous notions of the accumulation of soot 
 and its consequences. In the first place, soot cannot exist in the furnaces, when the plates 
 of which they are formed, with the best management, are constantly giving out from the 
 intense heat they sustain. The accumulation in the flues is principally on the bottoms, as will 
 presently be shown. The chimney or funnel never absolutely requires to be swept, even in 
 the worst cases of draught. In some vessels the practice is resorted to simply as a matter of 
 course : in the 'African' it was never done, except to prevent the dust from falling on those 
 repairing the flues immediately beneath, when it was previously beaten only on the outside for 
 that purpose : again, the vessels in the Mediterranean packet service are never detained on 
 their voyage of 1000 miles, no matter how long the time occupied thereon, to sweep 
 the flues. 
 
 The 'African' eight or nine years since, when in the colonial service, made the passage from 
 England to Malta direct, nearly 2000 miles. On the third day after her departure a fair wind 
 sprang up, the wheels were unconnected, and the vessel put under canvass : it was thought a 
 favourable opportunity of setting the machinery in order; the flues were swept at the same 
 time, in order to profit by any advantage arising therefrom : after having sailed two days, they 
 proceeded by steam at full power and fine weather for the nine succeeding days, at the end of 
 which time no lack of steam was apparent. And recently she went from Malta to Alexandria, 
 820 miles, thence to Beyrout, 320 miles, back to Alexandria, and thence to Malta, without 
 sweeping the flues, a distance of 2200 miles ; the necessity of arriving at Malta with the 
 Indian mails, preventing the vessel from remaining a sufficient time at either of the posts for 
 the purpose of sweeping the flues. 
 
 The sweeping of the flues consists simply in removing the soot and burnt fuel carried over 
 by the draught from the lower part of the flues ; the upper portions, which are available for 
 steam generation, having merely a thin coating of soot, which by no means amounts to 
 a formidable non-conductor. 
 
 After the long voyage of the 'African' above alluded to, I was curious to know the condition 
 of the flues, more particularly as the steam was generated in abundance, without any apparent 
 increase either of labour or fuel, immediately before arrival ; a blue lambent flame (carbonic 
 oxide) constantly appearing some feet above the chimney, as was usual after being a day or 
 two under weigh : it appeared that the flame had reverberated downwards, so as to act on the 
 lower parts of the first or main flue of each boiler : the soot was deposited on the bottoms of 
 the other flues to a greater extent ; and beneath the chimney, the soot was swept, so as to leave 
 an opening about one foot clear, out of 4 feet 6 inches, the entire depth of flue ; the voyage 
 having occupied, with stoppages at Alexandria and Beyrout, about twenty days. 
 
 Shortly afterwards, a voyage was made from Malta to Corfu, of between four and five days; 
 the flues were then swept, and, to my surprise, as much soot was withdrawn as on the occasion 
 last described : it then became quite evident, that after a certain quantity of fine cinder and 
 soot had been carried over and deposited, the surface, being swept by the flame and heated 
 air, was rendered so light as to be carried up the chimney, and driven away at the same rate 
 as its formation ; and this conclusion was confirmed by the quantity of burnt soot which was 
 strewed over the decks, at night in particular, after the awnings were furled, being sensibly 
 crushed by the feet on pacing the decks. Again, having examined the flues of the same vessel, 
 after being employed on experiments, &c. for twenty-five days, during the months of June and 
 
28 APPENDIX. 
 
 July, 1837, (coals used principally, West Hartly,) the steam was generated abundantly at 
 the conclusion, and the flues contained far less soot than I had calculated, which I attribute to 
 less urgent firing : the sides and tops of the interior of the flues were comparatively clean. 
 From this it may be inferred, that were sufficient coals on board, a vessel with boilers of good 
 construction might continue to steam for an indefinite time or distance, so far as the accumu- 
 lation of soot is concerned. It should be observed, that the coal employed in the two former 
 cases was not all Welch coal ; a quantity of Newcastle and Beyrout coal having been 
 procured at Alexandria. 
 
 The flues of marine boilers are rarely on fire ; I never saw but one instance, when the 
 ignited soot was carried through the chimney in a shower which lasted nearly an hour, on 
 board a merchant steam vessel which had only made the voyage from Ireland to St. Andero, 
 and back to Falmouth. I have questioned several engineers of long experience at sea, who 
 have never witnessed any other appearance than that which is common to all steam vessels 
 after being some days at sea ; viz. the flame of carbonic oxide flickering at the top of the 
 chimney, and perceived only at night. The burning of a vast quantity of smoke, and its 
 consequent soot, is to be referred to the great admixture with the air introduced through the 
 fire-doors during the operation of feeding : this has been often exemplified by leaving the 
 doors slightly a-jar, when the smoke is most completely consumed. 
 
 37. FRESH WATER. Charging ordinary boilers with fresh water, prior to starting for 
 a long voyage, is certainly to be recommended ; it cannot be too frequently done, if at no 
 very great expense and labour of a ship's company. I think, however, its advantages have 
 been generally too highly rated : it was rarely done in the 'African;' but from its probable 
 tendency to loosen scale, as well as to prevent the formation of the same to a certain extent, 
 till totally displaced by the salt water, it has its advantages. 
 
 From experiments before detailed, the engines of the 'African' were maintained at twelve 
 revolutions per minute, with an evaporation of 306 cubic feet of fresh water in six hours, by 
 two furnaces, or one boiler, a certain portion of heat being abstracted by the adjoining boiler : 
 now with both boilers in use, the engines are abundantly supplied with steam at twenty-eight 
 or thirty revolutions, a surplus flying to waste ; so that we may reckon that at all times 
 double the above quantity will be evaporated with both boilers. 
 
 That is, 306 cubic feet x 2 boilers = 612 cubic feet evaporated in 6 hours ; and 612x4 
 = 2448 cubic feet = 68'3 tons of fresh water required in 24 hours to meet the necessities of 
 the engines at full speed ; and this is more than treble the contents of both boilers when 
 charged : so that during twenty-four hours the fresh water will have been displaced by more 
 than treble its quantity of salt water : therefore the advantages of fresh water are limited, 
 and a boiler may keep at sea for a considerable time, exclusive of accident, depending alone 
 on the system of change usually adopted in vessels of long voyage. 
 
 Hence the only question of a vessel's continuance at sea, for any consistent period of time, 
 is the fitness of the engines, the conduct of the boilers, and the quantity of fuel which she 
 can stow, compared with her consumption. Consequently the probable capacity of a steam 
 vessel for the Atlantic or any other voyage, so far as her machinery is concerned, may be 
 fairly estimated before she finally sets out for her destination ; the contingencies of weather on 
 the particular service being duly considered. 
 
PADDLE WHEELS. 29 
 
 PADDLE WHEELS. 
 
 38. The arms, segments, and bolts of paddle wheels immersed below and in the neigh- 
 bourhood of the water line, in the Mediterranean and between the Tropics, are found 
 to decay very rapidly, much more so than I ever observed in the Channel or North 
 Sea. Having to remove several segments, arms, and bolts at Malta, in order to substitute 
 new in their places, after having been a long time in use, the oxidation exhibited in twenty-four 
 hours on those new ones which were turned unprotected into the water was astonishing : large 
 blotches of rust were distributed over the surfaces of the iron, which, when rubbed off, left 
 corresponding holes, eaten to a considerable depth. On strict examination, I was led to 
 attribute it mainly to the effect of the wash or spray dashing on the wheels when in harbour, a 
 ripple or ground swell being generally felt in the finest weather, causing them alternately to 
 dip into the water : the great heat of the sun speedily evaporating a portion of the water, 
 which I have often taken at 81 Fahrenheit, leaves either brine or crystals of salt adhering 
 to them, which of course becomes powerfully corrosive. 
 
 We must look, however, to another agent as the principal cause of destruction, when under 
 weigh as well as in harbour. Some months after the above, I observed in the mole at 
 Gibraltar, where the water is so clear that the bottom of the ship can be distinctly seen from 
 alongside, that marine vegetation, barnacles, and lime were existing in great abundance in the 
 neighbourhood of the paddle wheels, while every other part of the bottom was comparatively 
 clean : this I pointed out to a friend, who immediately crossed with me to examine the 
 opposite side, where the same appearances were presented, no part of the wheel being nearer 
 than a foot or eighteen inches to the ship's side. 
 
 Hence I concluded, that to the galvanic influence of the copper sheathing was this effect 
 owing, which became thus protected at the expense of the various parts of the paddle wheels : 
 this influence has before been suspected, allusion being made to it in the instructions for Her 
 Majesty's steam vessels ; but its effects, I believe, had never been demonstratively exhibited 
 hitherto. The circumstance was rendered still more remarkable, from the fact of the vessel 
 having just arrived from a voyage of eight days; the water in this particular place being 
 agitated more, and driven with a greater velocity, than on any other part of the bottom. 
 
 It was remarked often in the Mediterranean, by persons in the paddle wheels, which were 
 the constant bathing-machines in harbour, that the ship's bottom must be very foul ; in which 
 opinion I was a party : to this was attributed any falling off in the speed of the vessel ; and a 
 " hog," or cleansing machine, was obtained to clear the same : but the bottom, when the 
 vessel was taken into dock at Woolwich, was found, as before noted, to be kept sufficiently 
 clean by constant employment at sea, no weeds or barnacles being found, except in the 
 vicinity of the wheels. 
 
 Since the above observations, I have examined at Woolwich the wheels and bottoms of all 
 Her Majesty's steam vessels that have returned from the Mediterranean and West India 
 station ; the bottoms being clean, except the parts immediately abreast the wheels, which 
 were thickly covered with large barnacles, &c. ; and in one instance in particular, the teredo 
 worm had nearly bored his way through the ship's side in this spot only ; the copper sheathing 
 
30 APPENDIX. 
 
 not being carried sufficiently above the load water line : thus placing the inference beyond a 
 doubt ; the activity of employment by no means interfering with the chemical action induced. 
 The wheels and sides of those vessels employed in the Channel only do not exhibit the 
 above effects to such an extent as those employed in the Mediterranean and Tropics. 
 
 Since the accumulation of matters on the ship's side abreast the wheels must be submitted to, 
 I suggest that protectors, on Sir H. Davy's principle, be applied to all steam vessels in this 
 particular place, in order to prevent the wheels operating as such. 
 
 Thus it is probable that the influence of the sea water only will have to be encountered with. 
 I have found coal tar, heated by a shot plunged in to drive off the naphtha, when applied to 
 such parts as were chafed, or otherwise left unprotected, to be a very good varnish for paddle 
 wheels; the wheels being examined, and covered in such places on the arrival from every 
 voyage : by this treatment, a paddle wheel may resist the action of the sea water for several 
 years. 
 
 Wood floats, as usually applied, directly on the arms, are constantly becoming more com- 
 pressed thereon ; so that in a short time they are cut partly through, and of course are much 
 weakened in these places : this is not all ; the portion of the arms impressed are eaten away 
 by the moisture retained by the wood, long before any other part of the arm is decayed. 
 From these causes, the bolts, which secure the floats to the arms, are constantly getting loose 
 at sea, and are frequently lost before an opportunity is afforded to secure them ; the boards in 
 consequence become slack on the arms, to the imminent risk of other parts of the wheels : 
 to remedy this, iron plates not less than three or four inches broad, and three-eighths to half 
 an inch thick, may be advantageously applied above and beneath the boards, across the entire 
 breadth, in order to compress the board between the two. When the plates are defective, they 
 may be thrown aside, and new ones substituted, the arms remaining perfect, and the bolts less 
 liable to be lost : indeed in the Mediterranean packet service from Falmouth to Corfu, 
 bolts are required to be replaced or secured at the end of each trip of six or seven days, 
 in the common paddle wheels. 
 
 Boards, if possible, should never be carried out beyond the inner edge of the segments, or 
 extreme ring of the wheel ; for no protecting coat can be applied within the slot made in the 
 board ; and, of course, the board being always moist on both sides of the segments, they are 
 eaten through in a very short time, while apparently in very good condition. Segments thus 
 decayed often give way at one end, being whirled about the other in a flail-like manner, 
 cutting the beams which carry the wheels, very destructively. In a sea-way this can rarely 
 be remedied, and they must consequently be permitted, in such case, to come in collision till 
 completely broken adrift. 
 
II. A FORM OF STEAM JOURNAL, 
 
 REMARKS ON THE NECESSITY OF KEEPING A PROPER RECORD OF THE OPERATIONS 
 OF THE ENGINES IN ALL STEAM VESSELS, 
 
 AND DIRECTIONS FOR MARKING THE STEAM JOURNAL, 
 
 &c. &c. &c. 
 
 BY THOMAS BALDOCK, LIEUT. R.N., K.T.S. 
 
 IN order to obtain any USEFUL information of the comparative working of steam engines, it 
 is indispensable to ascertain the positive resistance which has been overcome, or the weight 
 that has been lifted ; but as this is a quantity which is ever varying when the engine is 
 employed in propelling ships, it is absolutely necessary to obtain a just estimate of the 
 retarding causes, and their occasional fluctuations. 
 
 The action of a steam vessel's engines, supposing them in good order, will be found to 
 be diminished, and the speed of the ship retarded, according to the influence ; first, of the 
 wind ; secondly, of the waves ; and thirdly, according to the immersion of the ship in the 
 water, from her lading : if therefore a scale be formed of the proportionate power of these 
 obstructing causes, and a just record of their influence duly kept, together with an account 
 of the coal used, a tolerably correct estimate may be obtained of the comparative duty per- 
 formed, in proportion to the fuel consumed. 
 
 To effect this object, and to afford a permanent record of the operations of the engines, it 
 is proposed, independent of the usual ship's log, to keep a steam journal ruled after the 
 annexed form, in which the force of the wind may be expressed by numbers, according 
 to a scale invented by Captain Beaufort, and intended for adoption in the navy, a copy of 
 which will be found attached to the directions for marking the steam journal. It is also 
 proposed, that the height of the wave above the trough of the sea may be estimated and 
 marked in yards, with occasional letters to express whether it be a long and easy, or a short 
 
32 APPENDIX. 
 
 and chopping sea; thus, 1, waves under one yard high; 2, waves under two yards high, 8cc. 
 Ch, chopping ; L, long ; R, rough cross sea ; S, smooth water ; Sw, swell. The draught of 
 water should be observed on all possible occasions. Draught or float gauges for this purpose 
 were formerly in use in the British navy, but have long since been discarded ; though it is 
 believed that all French ships of war are still fitted with them, and their use fully acknow- 
 ledged. The usual form of float gauges consisted of tubes communicating with holes 
 through the bottom ; one near the stem, another near the stern post ; the water flowing to the 
 same height in these tubes as outside the ship, and thus indicating her degree of immersion : 
 but as it is very inconvenient to increase the number of holes through the bottom, of which 
 there are unavoidably so many in steam vessels, it is recommended that two horizontal pipes 
 of small dimensions should be inserted, one in the bow, the other in the stern, about a foot 
 below the light draught water line, and at a few feet from the stem and stern post, choosing 
 some convenient spot on the round of the bow, directly over or vertical to the scarf of the 
 stem, for the foremost hole, and placing the after one over the mortice of the stern 
 post ; each of the pipes to be fitted with a cock, and communicating in some place easy of 
 access with a glass vertical tube, the tubes having graduated scales corresponding with the 
 ship's draught marks. On either cock being turned, it is evident the water will flow to the 
 same height inside as out ; and the ship's immersion may, in a tolerably smooth sea, be 
 read off with great facility and correctness, making it a rule always to stop the vessel 
 a few minutes for the observation : and when it is recollected the frequent slight stoppages 
 which a steam vessel makes on a long voyage, for the purposes of adjusting screws in the 
 machinery, paddles, &c. &c., which may always be seized as opportunities of observing 
 the immersion, the delay will hardly be objected to; 1 at all events, whether the gauge is 
 used or not, the draught of water should be observed on all possible occasions, and marked in 
 the journal, with the addition of the letters F or E, to denote the boilers being full or empty: 
 and as a very little experience will soon inculcate an adequate knowledge of the effect on 
 the ship's trim, produced by the consumption of fuel and provisions, the draught may be esti- 
 mated when it cannot be observed, and entered each day at noon in the proper column. 
 
 This habit of continually inserting the immersion, and observing the effects pro- 
 duced as the draught varies, will draw the attention of the officer to the important 
 necessity of keeping his vessel in trim, by the judicious arrangement of coals or other 
 weights, and tend to make him familiar with her qualities; the judgment necessary to 
 be exercised, in applying the proper symbols to express the state of the wind and sea, 
 recording at the same time the rate of the engine, and the vessel's progress under every 
 variety of circumstance, will engender a large portion of useful practical knowledge ; and the 
 steam journal will become a valuable record of incalculable use, in promoting the science of 
 steam navigation. 
 
 A table has been calculated, showing the rotary length of the path formed by the extremity, 
 
 1 The plane of flotation of a vessel at rest, and the same vessel in rapid motion, is very different, even though the 
 sea be quite smooth ; it is consequently impossible to obtain the statical immersion of any ship when sailing or 
 steaming, either by actual observation or the use of any description of float-gauge ; though the immersion so 
 obtained, if it could be observed, would have more immediate reference to the actual resistance experienced by the 
 vessel in passing through the water. 
 
FORM OF STEAM JOURNAL. 33 
 
 or any defined spot on the radii of the paddle wheel, with the object of pointing out 
 the difference between the velocity of the paddle, which by its reaction on the water 
 propels the ship ; and the speed of the vessel thereby produced. As it would be unreasonable 
 to use for this purpose the extreme periphery of the wheel, which is so much immersed, 
 so also it is not deemed proper to take that point on the radii which corresponds with the 
 water line ; but it is proposed that the velocity of the paddle shall be understood to mean 
 the velocity due to the rotation of the wheel, of that point on the paddle about which all the 
 propelling force is concentrated in the various positions it assumes, from its entering to 
 its leaving the water, which may be called " the Mean Centre of Effort." The variable 
 immersion of the paddle in each rotation of the wheel, together with other conditions that 
 should be taken into consideration, render it extremely difficult to ascertain the exact 
 distance, from the outer edge of the paddle, where the mean horizontal effort is collected, 
 and the question involves the most abstruse mathematical investigation ; it is however near 
 the centre of percussion ; and, as an approximation, we may, for practical purposes, assume it 
 to be in Morgan's wheel at the centre of the paddle, and in the radial or old wheel at one- 
 third of the board from its outer edge : thus in the latter case, supposing a wheel of 16 feet 
 diameter, having boards 18 inches wide, the centre of effort may be assumed to be 7 feet 
 6 inches from the axis ; and on reference to the table, we shall find that if a wheel of the 
 above dimensions be making 21 revolutions per minute, the centre of effort is, in reference 
 to the revolution of the wheel, travelling at the rate of 9f miles an hour ; the difference 
 between which and the speed of the vessel would be uniform, if the resistance was unvaried. 
 It is proposed to note hourly, in a column next the " Knots," the rotary progress of " the 
 Centre of Effort" in miles, derived from inspection of the table. 
 
 It is necessary to make a few observations with reference to the throttle-valve, which, as 
 its use is to controul the admission of steam to the cylinders, is supposed by most steam 
 seamen to do this so effectually, that a record of its partial closing or opening forms a just 
 estimate, in all cases, of the power acting on the engine ; but that this is not the case, may 
 be exemplified by the two following hypotheses. First, supposing the ship in good trim, the 
 weather calm, and the sea smooth, the throttle-valve being quite open, the engines will 
 attain the maximum velocity, which may be assumed at 22 revolutions per minute, and the 
 speed of the ship at 10 knots an hour. Secondly, the vessel's trim may be the same, the valve 
 still open, but the violence of the wind and the sea may have so increased, that the rate of 
 the engine is reduced to 11 revolutions a minute, and the speed of the ship to 4 or 5 knots 
 an hour : it is now evident that the consumption of steam in equal times is about half what 
 it was in the former case ; it would be exactly half, except for the additional waste in the 
 cylinder, and other slight causes. It is also evident, that if the valve be half closed, it 
 would not diminish the quantity of steam used in the cylinder, or the power of the engine ; 
 thus, supposing a repetition of the first case when the ship is at full speed, it will be 
 found that the valve must be nearly closed to effect any material reduction of the velocity. 1 
 
 > When an engine meets with any sudden increase of resistance, the steam will at first be spent at a higher 
 pressure and greater density, even if the safety valve acts freely ; but as on the occurrence of such cases at sea, the 
 draught is always diminished by the damper, and the fires slackened, this effect must soon cease, and it will not be 
 
 e 
 
34 APPENDIX. 
 
 It is however expedient to keep a statement of its operations, the benefit of which will be, 
 that the officer will gain a practical knowledge of the effect produced by the partial opening 
 or closing of the valves, when, in a high sea, the ship maybe overpressed with steam power, 
 a consideration of the utmost importance; which, if leading to judicious management, may 
 prevent incalculable mischief in the rapid deterioration of the hull and machinery, besides 
 the possibility of immediate danger. The steam journal will form a permanent record of the 
 way this duty has been attended to. 
 
 The course of the ship, her progress, and the direction of the wind, should also be entered 
 in the journal, as the angle between the first and third will indicate the proportionate degree of 
 resistance which the wind affords ; while the numerical symbol in the column of " Force " 
 marks its power, and the variation in the rate of progress forms the estimate of the effect. 
 
 If the table before described is used, a column should be ruled next the " Knots" for the 
 purpose of marking the progress of the " Centre of Effort," the variations between which and 
 the vessel's speed will form the basis of considerations most useful in estimating the effective 
 duty of the engine. As the measure of USEFUL effect or duty of the marine engine is, in fact, 
 the rate at which the vessel, under given circumstances, is moved through the water, the 
 area of the paddle should be such as to displace the fluid (when acted upon by the maxi- 
 mum speed of the engine in still water at the mean trim of the ship) at that rate most 
 favourable to propulsion by its reaction. A few experiments in each vessel would decide 
 the proportion which the speed of the ship should bear to that of the " Centre of Effort ;" 
 these experiments of course being made under circumstances of known and unvaried re- 
 sistance, in considering which particular reference should be had to the ship's immersion 
 in the water. In closing this subject, it is necessary distinctly to state, that the position 
 previously given for the " Centre of Effort," and also stated at the foot of the table, is 
 only to be considered as an approximation, which may indeed be too far from the truth to 
 admit of that appellation ; still it is presumed that for practical purposes it is sufficient, 
 though by no means meant as an absolute datum. 
 
 found materially to alter the assumption offered above ; neither can it affect the principle, that the power is not 
 lessened in the same proportion as the aperture of the throttle is diminished; although it still affords the means, if nearly 
 closed, of using steam of low pressure in the cylinder when it is desirable to decrease the power. 
 
STEAM JOURNAL. 
 
 1 
 
 B 
 
 
 c 
 
 
 
 Course. 
 
 Wind. 
 
 X 
 
 2 
 1 
 
 Immer 
 sion. 
 
 Throttle valve. 
 
 i 
 
 a; 
 
 Revolutions. 
 
 ai 
 
 z. 
 -p 
 
 pq 
 
 =: 
 
 i 
 
 u 
 
 Mean Height o 
 
 Boilers. 
 
 Initials of Engineers. 
 
 Report and General Remarks 
 of Engineer, the of IS 
 
 i 
 
 r 
 C 
 
 | 
 
 1 
 03 
 
 Baro- 
 meters. 
 
 i 
 | Thermometer. 
 
 d 
 I 
 
 I 
 
 1 
 
 < 
 
 Forward. 
 
 1. 
 
 2. 
 
 I 
 
 ] 
 
 :i. 4. 
 
 J 
 
 a! 
 
 A.M.I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 > 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 7 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 8 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 10 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 12 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Remains of 
 Coal the 
 
 Total used to day 
 Remains 
 
 f; 
 
 J 
 
 3 
 
 Tallow. 
 
 1 
 
 Oil. 
 
 4 
 
 c 
 
 a 
 
 Oakum. 
 
 J 
 
 Coal used raising 
 Steam bushels. 
 
 ?or other purposes , 
 bushels. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 P.M.I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 
 
 
 3 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 5 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 7 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 8 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 10 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 11 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 12 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
36 APPENDIX. 
 
 DIRECTIONS FOR MARKING THE STEAM JOURNAL. 
 
 In the column of "Winds," the strength will be expressed in the figures invented by 
 Captain Beaufort to denote its force. 
 
 In the column marked " Waves," the height of the wave above the trough of the sea is to be 
 estimated and expressed in yards, with occasional figures, to denote whether it be a long and 
 easy, a short and chopping, or a cross confused sea : thus, 1, waves under one yard high ; 
 2, under two yards, &c. ; Ch, chopping ; L, long ; R, rough confused sea ; S, smooth 
 water ; Sw, swell. 
 
 The draught of water is to be taken on all possible occasions, particularly at noon each 
 day, and marked in the column of " Immersion," with the addition of the letter F or E, 
 to denote the boilers being full or empty : when circumstances will not admit its being 
 measured, it is to be estimated. 
 
 The operations of the throttle valve are to be noted thus : S signifies it is shut ; 1 that it 
 is J open ; 2, its being j open ; 3, that J of the apertures are open ; and O, that it is quite 
 open. 
 
 The column " Sail " will show, by the insertion of the letter S or N, whether or not sail 
 be set. 
 
 The average number of revolutions per minute for each hour, and the consumption of coals 
 during the same period, are to be entered in the proper columns. 
 
 In addition to the mean height of the engine barometers, that of a thermometer is to be 
 registered each hour : the latter should be permanently fixed in some part of the engine 
 room where it cannot receive the radiated heat from the fire-places. 
 
 .The sub-divisions of the general column relating to the " Boilers" will apply to the several 
 boilers on board ; and a note should be made in the first page of the journal, stating which 
 boiler is expressed in each particular column. The partial blowing-off should be done at the 
 discretion of the engineer, as the water approaches saturation ; but in all voyages extending 
 beyond one day, a portion should be blown off at least every two hours : the letter P will 
 indicate that this duty has been performed, and the letter W will show when the whole is 
 blown out. 
 
 The column of " Remarks " is to contain an account of every particular occurrence ; as, 
 when the fires are lighted (noting the minute at which the steam is raised), when extinguished, 
 when banked up, &c. ; also, any variation in the number of fires, when the engines or boilers 
 are connected or unconnected, stopped, or set at work, &c. An entry is also to be made of 
 every particular operation performed on the boilers or engine, noting when the flues are 
 swept, boilers chipped, stating the quantity of soot taken from the former, and the weight 
 of calcareous or other matter from the latter ; also when the connecting parts of the engine 
 are examined, the wheels turned in harbour, or the paddles reefed ; and prefixing to each 
 day's remarks the description of coal then in use, noting any change thereof. The 
 engineer is also to state the number of artificers employed in effecting repairs which may 
 be beyond the power of the ship's engineers, particularly noting what work they are upon. 
 
 At noon each day a calculation is to be made of the expenditure of coals, oil, tallow, and 
 
FORM OF STEAM JOURNAL. 
 
 37 
 
 oakum, noting the remains ; an entry is also to be made of the coal used in raising the steam, 
 as well as what is consumed for other purposes in the ship ; but the whole is to be included 
 in the total stated to be used on that day. Although the coal is supplied in tons measure- 
 ment, it is more convenient that the hourly expenditure should be calculated in bushels ; and, 
 it can easily be transferred to tons on totalling the account. 
 
 It would be interesting if an account was kept of the temperature of the hot-well, and of 
 the quantity of water distilled from the cylinder jacket ; but it is not indispensable. 
 
 It 
 
 Calm. 
 
 1 
 
 Light Air 
 
 2 
 
 Light Breeze . . ^ 
 
 3 
 
 Gentle Breeze 
 
 4 - 
 
 Moderate Breeze . _, 
 
 5 - 
 
 Fresh Breeze . 
 
 6 
 
 Strong Breeze 
 
 7 - 
 
 Moderate Gale . j 
 
 8 
 
 Fresh Gale 
 
 9 
 
 Strong Gale . 
 
 10 - 
 
 Whole Gale . 
 
 11 
 
 Storm 
 
 12 
 
 Hurricane 
 
 FIGURES TO DENOTE THE FORCE OF THE WIND. 
 
 Or just sufficient to give steerage way. 
 
 li-f 1 
 
 all 
 
 to 
 
 IOr that in which a well-condi- 
 tioned man-of-war, with all j A t , 
 c 11 1,1 s to 4 > knots, 
 
 sail set, and clean lull, would j 
 
 go in smooth water, from 5 t 6 
 
 Or that to which she could just 
 * carry in chase, full and by < 
 
 Royals, &c. 
 
 Single-reefed topsails and top- 
 gallant sails. 
 Double-reefed topsails, jib, &c. 
 
 Triple-reefed topsails, &c. 
 _ Close-reefed topsails and courses. 
 
 Or that with which she could scarcely bear close-reefed main top- 
 sail and reefed foresail. 
 
 Or that which would reduce her to storm stay-sails. 
 Or that which no canvas could withstand. 
 
 F. B. 
 
A Table showing the Velocity of the Centre of Effort of Steam Vessels' Paddle 
 meters and at various velocities ; intended, by comparing the results with th 
 
 
 
 Number of revolutions per minute 
 
 
 
 Number of revolutions per minut 
 
 
 
 and corresponding miles per hour. 
 
 
 
 and corresponding miles per houi 
 
 Distance of the 
 centre of effort 
 
 Number of revo- 
 lutions required 
 
 
 Velocity of 
 
 Distance of the 
 centre of effort 
 
 Number of revo- 
 lutions required 
 
 
 Velocity of 
 
 from axis of 
 
 to make a geo- 
 
 Revolutions 
 
 centre of effort 
 
 from axis of 
 
 to make a geo- 
 
 Revolutions 
 
 centre of effor 
 
 wheel, in feet 
 and inches. 
 
 graphical mile. 
 
 per minute. 
 
 in miles per 
 hour. 
 
 wheel, in feet 
 and inches. 
 
 graphical mile. 
 
 per minute. 
 
 in miles per 
 hour. 
 
 Feet. Inches. 
 
 
 
 -10 
 
 6-35 
 
 Feet. Inches. 
 
 
 "10 
 
 5-89- 
 
 
 
 
 11 
 
 6-99 
 
 
 
 
 11 
 
 6-48 
 
 
 
 
 12 
 
 7-63 
 
 
 
 
 12 
 
 7-07 
 
 
 
 
 13 
 
 8-27 
 
 
 
 
 13 
 
 7-06 
 
 
 
 
 14 
 
 8-90 
 
 
 
 
 14 
 
 8-25 
 
 
 
 
 15 
 
 9-53 
 
 
 
 
 15 
 
 8-83 
 
 
 
 
 16 
 
 10-17 
 
 
 
 
 16 
 
 9-42 
 
 
 
 
 17 
 
 10-80 
 
 
 
 
 17 
 
 10-01 
 
 10 3 
 
 94-41 
 
 < 
 
 18 
 
 11-44 
 
 9 6 
 
 101-86 
 
 < 
 
 18 
 
 10-60 
 
 
 
 
 19 
 
 12-08 
 
 
 
 
 19 
 
 11-19 
 
 
 
 
 20 
 
 12-71 
 
 
 
 
 20 
 
 11-78 
 
 
 
 
 21 
 
 13-35 
 
 
 
 
 21 
 
 12-37 
 
 
 
 
 22 
 
 13-98 
 
 
 
 
 22 
 
 12-96 
 
 
 
 
 23 
 
 14-62 
 
 
 
 
 23 
 
 13-55 
 
 
 
 
 24 
 
 15-25 
 
 
 
 
 24 
 
 14-14 
 
 
 
 
 _25 
 
 15-89 
 
 
 
 
 J 88 
 
 14-72 
 
 
 
 
 "10 
 
 6-20 
 
 
 
 
 "10 
 
 5-73 
 
 
 
 
 11 
 
 6-82 
 
 
 
 
 11 
 
 6-31 
 
 
 
 
 12 
 
 7-44 
 
 
 
 
 12 
 
 6-88 
 
 
 
 
 13 
 
 8-06 
 
 
 
 
 13 
 
 7-46 
 
 - 
 
 
 
 14 
 
 8-68 
 
 
 
 
 14 
 
 8-03 
 
 
 
 
 15 
 
 9-30 
 
 
 
 
 15 
 
 8-60 
 
 
 
 
 16 
 
 9-92 
 
 
 
 
 16 
 
 9-18 
 
 
 
 
 17 
 
 10-54 
 
 
 
 
 17 
 
 9-75 
 
 10 
 
 96-77 
 
 < 
 
 18 
 
 11-16 
 
 9 3 
 
 104-62 
 
 < 
 
 18 
 
 10-32 
 
 
 
 
 19 
 
 11-78 
 
 
 
 19 
 
 10-90 
 
 
 
 
 20 
 
 12-40 
 
 
 
 
 20 
 
 11-47 
 
 
 
 
 21 
 
 13-02 
 
 
 
 
 21 
 
 12-04 
 
 
 
 
 22 
 
 13-64 
 
 
 
 
 22 
 
 12-62 
 
 
 
 
 23 
 
 14-26 
 
 
 
 
 23 
 
 13-19 
 
 
 
 
 24 
 
 14-88 
 
 
 
 
 24 
 
 13-76 
 
 
 
 
 J* 
 
 15-50 
 
 
 
 
 J 25 
 
 14-34 
 
 
 
 
 "10 
 
 6-04 
 
 
 
 
 "10 
 
 5-58 
 
 
 
 
 11 
 
 665 
 
 
 
 
 11 
 
 6-14 
 
 
 
 
 12 
 
 7-25 
 
 
 
 
 12 
 
 6-70 
 
 
 
 
 13 
 
 7-86 
 
 
 
 
 13 
 
 7-25 
 
 
 
 
 14 
 
 8-46 
 
 
 
 
 14 
 
 7-81 
 
 
 
 
 15 
 
 9-07 
 
 
 
 
 15 
 
 8-37 
 
 
 
 
 16 
 
 9-67 
 
 
 
 
 16 
 
 8-93 
 
 
 
 
 17 
 
 10-28 
 
 
 
 
 17 
 
 9-49 
 
 9 9 
 
 99-25 
 
 < 
 
 18 
 
 10-88 
 
 9 
 
 107-52 
 
 < 
 
 18 
 
 10-04 
 
 
 
 
 19 
 
 11-48 
 
 
 
 
 19 
 
 10-60 
 
 
 
 
 20 
 
 12-09 
 
 
 
 
 20 
 
 11-16 
 
 
 
 
 21 
 
 12-69 
 
 
 
 
 21 
 
 11-72 
 
 
 
 
 22 
 
 13-30 
 
 
 
 
 22 
 
 12-28 
 
 
 
 
 23 
 
 13-90 
 
 
 
 
 23 
 
 12-83 
 
 
 
 
 24 
 
 14-51 
 
 
 
 
 24 
 
 13-39 
 
 
 
 
 25 
 
 15-11 
 
 
 
 
 25 
 
 13-95 
 
 N.B. The centre of effort in the radial wheel is about one-third of the paddle from its outer edge, 
 and in the vertical wheel it is about the centre of the paddle. 
 
iccording to the number of revolutions ; calculated for wheels of different dia- 
 'essel's speed and fuel consumed, to show the proportionate duty performed. 
 
 Distance of the 
 centre of effort 
 from axis of 
 wheel, in feet 
 and inches. 
 
 Number of revo- 
 lutions required 
 to make a geo- 
 graphical mile. 
 
 Number of revolutions per minute 
 and corresponding miles per hour. 
 
 Distance of the 
 centre of effort 
 from axis of 
 wheel, in feet 
 and inches. 
 
 Number of revo- 
 lutions required 
 to make a geo- 
 graphical mile. 
 
 Number of revolutions per minute 
 and corresponding miles per hour. 
 
 Velocity of 
 Revolutions | centre of effort 
 per minute. in miles per 
 hour. 
 
 Revolutions 
 per minute. 
 
 Velocity of 
 centre of effort 
 in miles per 
 hour. 
 
 Feet. Inches. 
 
 
 
 flO 5-43 
 
 Feet. Inches. 
 
 
 
 "10 
 
 4-96 
 
 
 
 
 11 
 
 5-97 
 
 
 
 
 11 
 
 5-46 
 
 
 
 
 12 
 
 6-51 
 
 
 
 
 12 
 
 5-95 
 
 
 
 
 13 
 
 7-05 
 
 
 
 
 13 
 
 6-45 
 
 
 
 
 14 
 
 7-60 
 
 
 
 
 14 
 
 6-94 
 
 
 
 
 15 
 
 8-14 
 
 
 
 
 15 
 
 7-44 
 
 
 
 
 16 
 
 8-68 
 
 
 
 
 16 
 
 7-94 
 
 
 
 
 17 
 
 9-22 
 
 
 
 
 17 
 
 8-43 
 
 8 9 
 
 110-25 
 
 < 
 
 18 
 
 9-76 
 
 8 
 
 120-96 
 
 <; is 
 
 8-93 
 
 
 
 
 19 
 
 10-31 
 
 
 
 
 19 
 
 9-42 
 
 
 
 
 20 
 
 10-85 
 
 
 
 
 20 
 
 9-92 
 
 
 
 
 21 
 
 11-39 
 
 
 
 
 21 
 
 10-42 
 
 
 
 
 22 
 
 11-94 
 
 
 
 
 22 
 
 10-91 
 
 
 
 
 23 
 
 12-48 
 
 
 
 
 23 
 
 11-41 
 
 
 
 
 24 
 
 13-02 
 
 
 
 
 24 
 
 11-91 
 
 
 
 
 25 
 
 13-56 
 
 
 
 
 J 86 
 
 12-40 
 
 
 
 flO 
 
 5-27 
 
 
 
 
 flO 
 
 4-80 
 
 
 
 
 
 11 
 
 5-80 
 
 
 
 
 11 
 
 5-29 
 
 
 
 
 12 
 
 6-33 
 
 
 
 
 12 
 
 5-77 
 
 
 
 
 13 
 
 6-85 
 
 
 
 
 13 
 
 6-25 
 
 
 
 
 14 
 
 7-38 
 
 
 
 
 14 
 
 6-73 
 
 
 
 
 15 
 
 7-91 
 
 
 
 
 15 
 
 7-21 
 
 
 
 
 16 
 
 8-43 
 
 
 
 
 16 
 
 7-69 
 
 
 
 
 17 
 
 8-96 
 
 
 
 
 17 
 
 8-17 
 
 8 6 
 
 113-85 
 
 < 
 
 18 
 
 9-49 
 
 7 9 
 
 124-87 
 
 
 
 18 
 
 8-65 
 
 
 
 
 19 
 
 10-01 
 
 
 
 
 19 
 
 9-14 
 
 
 
 
 20 
 
 1054 
 
 
 
 
 20 
 
 961 
 
 
 
 
 21 
 
 11-07 
 
 
 
 
 21 
 
 10-09 
 
 
 
 
 22 
 
 11-59 
 
 
 
 
 22 
 
 10-57 
 
 
 
 
 23 
 
 12-12 
 
 
 
 
 23 
 
 11-05 
 
 
 
 
 24 
 
 12-65 
 
 
 
 
 24 
 
 11-53 
 
 
 
 
 .25 
 
 13-18 
 
 
 
 
 ^25 
 
 12-01 
 
 
 
 
 riQ 
 
 5-11 
 
 
 
 
 r io 
 
 4-65 
 
 
 
 
 11 
 
 5-63 
 
 
 
 
 11 
 
 5-12 
 
 
 
 
 12 
 
 6-14 
 
 
 
 
 12 
 
 5-58 
 
 
 
 
 13 
 
 6-65 
 
 
 
 
 13 
 
 6-05 
 
 
 
 
 14 
 
 7-16 
 
 
 
 
 14 
 
 6-51 
 
 
 
 
 15 
 
 7-67 
 
 
 
 
 15 
 
 6-97 
 
 
 
 
 16 
 
 8-18 
 
 
 
 
 16 
 
 7-44 
 
 
 
 17 
 
 8-70 
 
 
 
 
 17 
 
 7-91 
 
 8 3 
 
 117-30 
 
 <| 18 
 
 9-21 
 
 7 6 
 
 12903 
 
 < 
 
 18 
 
 8-37 
 
 
 
 19 
 
 9-72 
 
 
 
 19 
 
 8-84 
 
 
 
 
 20 
 
 10-23 
 
 
 
 
 20 
 
 9-30 
 
 
 
 
 21 
 
 10-74 
 
 
 
 
 21 
 
 9-76 
 
 
 
 
 22 
 
 11-25 
 
 
 
 
 22 
 
 10-23 
 
 
 
 
 23 
 
 11-76 
 
 
 
 
 23 
 
 10-69 
 
 
 
 
 24 
 
 12-28 
 
 
 
 
 24 
 
 11-16 
 
 
 
 
 25 
 
 12-79 
 
 
 
 
 25 
 
 11-62 
 
 November, 1836. 
 
 THOMAS BALDOCK. 
 
III. ON THE MOTION OF STEAM VESSELS. 
 BY P. W. BARLOW, ESQ., CIVIL ENGINEER. 
 
 
 THE benefits which this country has derived from the application of steam power to navigation 
 by its certainty and rapidity, as well as safety of communication, must be too generally felt 
 to require any remark in this place. In fact, the success which has in every instance 
 attended the employment of steam power is such, that its extent is rapidly increasing, and 
 voyages of much greater length are now about to be performed, among which may be 
 mentioned those to America and to the East Indies. 
 
 The circumstances under which steam vessels are rendered available as a means of commu- 
 nication differ widely from each other ; some being employed in river navigation, others at 
 sea : in some, the voyages are of great length, and exposed to tempestuous and adverse 
 weather ; and in others, comparatively short and free from these disadvantages : in some, 
 speed is the principal object to be attained ; in others, great length of voyage. Under each of 
 these circumstances, vessels of a particular construction, power, and tonnage, are best adapted 
 to attain the specific object in view ; and it is very desirable to ascertain as near as possible 
 what these should be, which we think can be in a great measure accomplished by the 
 examination and comparison of the results of what has already been attained. 
 
 Impressed with the general importance of the subject, and the advantages which may be 
 derived from such inquiries, and my former residence at Woolwich having afforded me the 
 opportunity of attending many experiments and collecting much information on the subject, 
 I beg to offer to the public the following pages on the motion of steam vessels, in the hope 
 that they may prove of utility to those interested in the progress of steam navigation. 
 
 The power of the steam engine, when employed in propelling vessels, being applied through 
 the medium of a fluid by the reaction of the paddle wheel, there results an unavoidable loss 
 of a large portion of the power of the engine. To construct a wheel by which this loss will 
 be reduced as much as possible, is an important point to be aimed at, and many inventions 
 have appeared with the view of effecting this object. We therefore propose, in the first place, 
 to enter into a comparison of such of these wheels as have come into general use, and 
 to endeavour to illustrate the nature of their action. 
 
 ON PADDLE WHEELS. 
 
 The construction of the ordinary paddle wheel is so simple as scarcely to need description : 
 it consists of a circular framework of iron, supporting paddles at equal distances round 
 the rim, and radiating from the centre : these wheels are attached to a strong shaft pass- 
 ing through the vessel, to which the motion of the 'engine is conveyed by cranks placed 
 
ON PADDLE WHEELS. 41 
 
 at right angles to each other : the revolution of the floats or paddles in the water creates a 
 resistance upon them, and the corresponding reaction on the main shafts produces the force 
 by which the vessel is propelled. 
 
 It is evident, that in this construction of wheel two kinds of lost power must exist : first, by 
 the action of the paddle being oblique, or at an angle with the horizontal direction of the vessel 
 in every position except the vertical one, by which of course only a portion of the power 
 exerted on the paddle becomes effective ; and secondly, by -the receding of the wheel in the 
 water necessary to create a resistance equal to the force applied by the engine. This may 
 perhaps be best illustrated by the case of a locomotive engine : if the friction between the 
 wheel and the rail be such that the former does not slip, the motion of the carriage will be the 
 same as that of the circumference of the wheel ; the whole power of the engine is employed 
 in propelling the carriage, and consequently there is no lost power : but if the friction be not 
 sufficient, the wheel will slip back some quantity ; the same steam will be consumed in the 
 revolution of the wheel, but the carriage will not be advanced as before, and there will be a 
 loss of power proportional to the skidding or receding of the wheel : so also in a steam 
 vessel all that the centre of pressure actually goes back in the water, or all that its circum- 
 ferential velocity exceeds that of the vessel, is comparatively lost power ; the expense of the 
 steam being proportional to the former, and the effect to the latter. 
 
 This source of lost power must of course exist in all paddle wheels, whatever their con- 
 struction, from the resistance being created in a fluid ; but that kind first described being 
 owing entirely to the radiation of the paddles, a great number of inventions have been pro- 
 posed to remedy the evil, by causing them to keep a vertical position by the aid of machinery 
 during their progress through the water. These wheels, although they possess much supe- 
 riority over the ordinary construction in a sea, or where the wheel is deeply immersed, by 
 obviating the loss of power from the obliquity of action and back water, are subject to evils of 
 another description ; and it is a question of doubt, whether the common radiating wheel does 
 not admit of a construction, which, in average of weather and circumstances attending a sea 
 voyage, might lead to as little loss of power as the vertical wheel, and at the same time 
 possess the advantage of less liability to derangement. 
 
 The first vertically acting wheel which has been employed to any extent in this country is 
 that commonly known as Morgan's Wheel. The original patent for this construction was 
 granted to Elijah Galloway, and sold by him to Mr. William Morgan ; but has since that 
 time undergone considerable improvements in its structure and arrangement, and is now 
 extensively adopted by Government in the Admiralty steamers. 
 
 Fig. 1. and 2. are a plan and elevation of the improved wheel : a a a a are paddles, which 
 turn upon spindles having a bearing on the framework, c c c, and of the wheel, which is of a 
 polygonal figure, having as many sides as it is required to have paddles. The inside frame or 
 polygon is alone attached to the shaft of the engine, which does not continue beyond the side 
 of the vessel ; and the outer one has an independent bearing on a centre attached to the paddle 
 box, so that it derives its motion entirely from the arms or angles of the polygon ; the space be- 
 tween the two frames of the wheels being left quite free. A is a crank fixed to the paddle box, 
 upon which the outer polygon revolves ; it projects in an inclined direction in the open space 
 between the sides of the wheel, but to a point considerably excentric with it. Each paddle 
 has a crank attached to it at an angle of about 70, and arms a a, 8tc. connect the extremity 
 
4-2 APPENDIX. 
 
 of the cranks with a moveable boss, which revolves upon the fixed centre A. One of these 
 arms is fixed to the boss, and is termed the dividing arm. 
 
 It will thus be seen, that in consequence of the point A being situated out of the centre, the 
 paddles will assume different positions during the revolution of the wheel, which positions 
 can be so arranged as to differ very little from the vertical wheel, while passing the lower part 
 of the revolution, or that part where the action of the paddle takes place. 
 
 In the year 1837, Messrs. Seawards fitted a vertically acting wheel to the ' Levant' steam 
 boat, in which the positions of the paddles are similar to the above, but are brought about by 
 a different arrangement of machinery. This wheel formed the subject of a charge of piracy, 
 on the grounds of being a colourable evasion of the patent of Elijah Galloway. The Vice- 
 Chancellor having given judgment against granting an injunction, the parties tried an action 
 at law, in which they were also unsuccessful ; and Messrs. Seawards have now the privilege of 
 making these wheels. 
 
 Fig. 3. and 4. is a representation of Seawards' wheels. A A is the shaft of the engine, 
 to which the two frames or polygons B B, C C are attached. D D D D are the paddles, 
 which revolve in bearing in the two frames. E E is an enlarged axle fixed to the side of 
 the vessel excentrically with the shaft, and answers the same purpose in giving the requisite 
 positions to the paddles as the cranked axis A in Morgan's wheel. F F is a rim of iron, 
 which is caused to revolve on the enlarged axle by an arm G attached to the inner polygon of 
 the wheel : from this rim proceed arms or rods H H H, to the bent cranks III, attached to 
 the paddle boards. 
 
 It will here be seen, that the paddles will in like manner, by the motion of the wheel, take 
 up positions similar to those of Morgan's, entering and leaving the water nearly in a vertical 
 position. The main difference in the construction of the two is the excentric, which by 
 being fixed at the side of the vessel, instead of in the centre of the wheel, is less adapted to 
 giving motion to the paddles, from acting at one end of them, but has the advantage of 
 allowing the shafts to be continued through the wheel, which certainly adds to its strength. 
 
 EXPERIMENTS ON PADDLE WHEELS. 
 
 For the purpose of instituting a comparison and explaining the action of these wheels, I 
 have given the following set of experiments on her Majesty's vessels, fitted out at Woolwich, 
 some of which are provided with Morgan's wheels, and others with the radiating wheel. 
 Each vessel is submitted to accurate experiment, sometimes when light, and sometimes laden. 
 The exact amounts of their cargoes are known, their registered and actual tonnage, area of 
 paddle, and every other particular which can serve as a guide to such an inquiry. 
 
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44 APPENDIX. 
 
 With the aid of these experiments, and the data given with them, I have been enabled to 
 calculate in each case the relative velocity of the wheel and vessel, the actual pressure upon 
 the vertical paddle, the area of paddle per horse power, and other facts; by the comparison of 
 which with the velocity, tonnage, &c., a just conception may be formed, not only of the action 
 of each paddle wheel, and the manner in which the power of the engine is expended, but also 
 the amount of surface, proportion of the paddles, dip of immersion, &c., which are required 
 to enable an engine to produce the greatest useful effect. 
 
 The manner of obtaining these calculated results will be at once evident from the heads of 
 the columns, except the last five, which relate to the velocity of the vessel as compared to the 
 wheel, and the amount of pressure exerted by the engine on the vertical paddle. 
 
 As the resistance opposed to the paddle is distributed over a considerable depth of paddle 
 board, it is necessary, in comparing the relative velocity of the wheel and vessel, to find that 
 point in which, if all the resistances were concentrated, they would have equal effect in pro- 
 pelling the vessel : this point is termed the centre of pressure, and its exact position becomes 
 a question of very intricate calculation, as it changes according to the depth of immersion, the 
 diameter of the wheel, and other circumstances, which vary in different boats. It was 
 necessary therefore to assume a point which would meet the ordinary cases; and this has 
 been decided upon from the following considerations. 
 
 ON THE CENTRE OF PRESSURE OF A PADDLE. 
 
 It is very evident, that in every case the resistance upon different parts of the paddle is as 
 the square of the distance from the centre of motion, because the resistance of a fluid varies as 
 the square of the velocity : this ratio is however always increased more or less in consequence 
 of the extremity acting for a greater length of time than the inner part. 
 
 In the case of a wheel in motion in a vessel at rest, if the length of the arc described by 
 the outer extremity of the paddle exceed that described by the inner edge, in the ratio of the 
 larger radius to the smaller, the resistance upon any part of the paddle would vary exactly as 
 the square of the radius ; but this can only occur when the wheel is either totally immersed, 
 or up to the centre of motion : in every other circumstance it is evident that the arc described 
 by the extremity will exceed that of the inner edge in a greater ratio, depending upon the 
 degree of immersion, radius of wheel, See. ; consequently, the resistance upon any part of the 
 paddle will increase in a greater ratio than the square of the distance from the centre of 
 motion. It is moreover evident, that the position of the centre of pressure will not only vary 
 with every change of immersion, but will continue to ascend from the moment the paddle 
 enters the water until it is immersed below the surface, when it becomes constant, and 
 continues so until the upper part of the paddle again leaves the water. 
 
 As these experiments are made entirely with vessels in motion, it is not necessary to enter 
 into a calculation of this precise point ; the above case being alluded to merely with a view of 
 facilitating the investigation of the more complicated question of the centre of pressure of the 
 paddle when the vessel is in motion. 
 
 Here it will be seen, that as the revolution of the paddle resembles a circle rolling on a plane, 
 every part of it will describe a cycloid. That point whose rotary velocity is equal to that of 
 the vessel will move through a simple cycloid ; points within that circle, in prolate cycloids ; 
 
ON THE CENTRE OF PRESSURE OF A PADDLE. 45 
 
 and points without, in curtate or contracted cycloids. In Fig. 5. is represented the posi- 
 tion of the float of a paddle wheel in different parts of its revolution. The circumference, 
 whose velocity is equal to that of the vessel, is here equal to two-thirds of that which passes 
 through the extremity of the paddle, which is about a medium case in practice. 
 
 It will be readily seen, that the effect of the vessel being in motion will be to roll the circle 
 abed on the line ef, so that the inner edge of every paddle will move through the cycloid 
 g h i, whilst the extremity moves through the cycloid klmno, as shown by the dotted lines 
 in the figure. 
 
 As the centre of pressure varies at every angle of the paddle, in order to come at the true 
 position it becomes necessary to find the relative velocity of the two extremes of the floats, or 
 the distance moved in the two cycloids, at every instant of time : this would, however, lead 
 to a calculation of greater labour than the nature of the present investigation demands ; and 
 as the circumstances upon which such calculations would be founded vary in every experi- 
 ment, according to the diameter of the wheel, depth of immersion, 8cc., two points have been 
 assumed, one of which is intended to meet the ordinary cases of slightly immersed, and the 
 other that of deeply immersed paddles. It appears, again, referring to the figure, that whilst 
 the extremity of the paddle is moving through the part of the curtate cycloid below the level 
 of the water, a point P in the radius of the wheel, which is situated in the circumference of 
 the rolling circle, has scarcely moved in the simple cycloid apr. The difference of the 
 curves during the lower part of the motion amounts nearly to what is due to an arc described 
 with a radius equal to the difference of the extreme radius of the wheel, and that of the circle 
 of equal velocity with the ship. 
 
 It therefore appears, that the resistance on any part of the float varies nearly as the square 
 of its distance from the rolling circle ; and having at the same time taken into consideration 
 the greater length of time of the action of the extremity than of the inner edge of the paddle, 
 I find, from the examination of several experiments, that in the case of slight immersion 
 the assumption of the resistance on any point varying as the cube of the distance from the 
 rolling circle, and in deep immersions as the 2'5 power, will approximate very nearly to 
 the truth. 
 
 Having thus assumed the law of resistance with respect to the radius, we readily find the 
 position of the centre of pressure by the following equation. 
 
 Let r be the difference of the radius of the rolling circle and that of the wheel, n the power 
 of the resistance in relation to the radius, b the depth of the paddle, x any variable distance 
 from its upper edge, and y the distance of the mean centre of pressure, also from the upper 
 edge ; then the integral of (r + x) n d x will be the sum of all the resistances, and (r + y) b 
 the expression to which it is to be equal. 
 
 We have therefore, when x = b, 
 
 which, when = 3, gives 
 
 and, when n=2'5, 
 
 (2 (r + 6)3 \4 
 -TI ) - * 
 
46 APPENDIX. 
 
 From these equations the diameters to the centre of pressure of the common wheel (given 
 in column 16 of the following table) have been calculated. 
 
 In the new wheel the centre of pressure will be nearly in the centre of gravity, when the 
 paddle is totally immersed, the motion of the paddle being nearly vertical ; but in con- 
 sequence of the lower part coming sooner into and continuing longer in action, it must be 
 taken some distance below the centre of gravity. 
 
 It is not easy to determine this by calculation ; but by a comparison of all circumstances 
 bearing upon this question, an allowance of one-eighth of the paddle has been made on this 
 account. 
 
 It may be proper to observe, that in these wheels there is no relation between the diameter 
 of the polygon and the diameter to the centre of pressure, the paddles being differently hung 
 and differently shaped in the several vessels, particulars it has not been thought necessary 
 to .introduce into the table. 
 
 The diameter to the centre of pressure, or effective diameter of the wheel, being known, we 
 at once deduce the excess of the velocity of the wheel over that of the vessel, or that at which 
 it recedes in the water to produce the resistance necessary for propelling the vessel. The rule 
 for ascertaining the amount of this resistance or pressure on the vertical paddle, is to multiply 
 the square of this velocity by the area of the paddle board and by G2| (the weight of a cubic 
 foot of water in Ibs.), and divide by 64J- ; the pressure upon a surface moving in a fluid being 
 equal to the weight of a column of water whose base is the area of the surface, and alti- 
 tude that through which a body must fall to acquire the velocity. This number, multiplied 
 by the velocity of the wheel, will express the power expended on the vertical paddles ; and 
 this divided by the whole power of the engine, will give the proportion consumed on the 
 vertical paddle given in column 18. 
 
 In estimating the parts of the power of the engine exerted in any case, the number of 
 strokes made in a minute is compared with the actual number of strokes which ought to be 
 made for the engine to perform its whole duty. 
 
EB 
 
 - 
 
 B 
 
 W 
 
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48 APPENDIX. 
 
 DEDUCTIONS FROM THE TABULAR NUMBERS. 
 
 The amount of resistance on the vertical paddle, and proportion of the power of the engine 
 expended upon them, will be found to differ considerably in the different cases given in the 
 table, and might, if unexplained, throw an appearance of doubt upon the accuracy of the 
 experiments. These discrepancies are evidently attributable to the result depending upon 
 the square of the difference of two velocities ; so that the slightest inaccuracy in either of the 
 observations is greatly magnified. There is no doubt, however, with so many experiments 
 made at different times and under different circumstances, that the means obtained in the 
 table are sufficiently near the truth for all practical purposes. 
 
 In examining column 18, a striking difference is seen in the proportion of the power of the 
 engine expended on the vertical paddle in Morgan's wheel and in the common wheels, the 
 mean of the former being -546, and of the latter '151 and -197. The difference arises from 
 the nature of the action : in the new wheel the vertical position is the most effective in propelling 
 the vessel, and in the common wheels the least so , a fact which, although little known among 
 the projectors of paddle wheels, and even among engineers, who are constantly witnessing 
 their daily performance, it is very essential should be understood before any calculation or 
 judgment can be formed of the construction and proportion of wheels best adapted to steam 
 vessels, under the different circumstances and various kinds of duties in which they are 
 employed : we beg therefore to call the attention of the reader particularly to this point. 
 
 The difference of action which caused this unexpected result will be understood by exa- 
 mining Fig. 5., which exhibits the positions of each paddle, at equal intervals of time, in a 
 vessel in motion : it will there be seen, that the progress made through the water bv the 
 radiating paddle, while passing the vertical position, is considerably less than in the preceding 
 equal interval of time. After first entering the water, and as the resistance opposed varies as 
 the square of the velocity or space passed through, it is evident that the resistance in passing 
 from A to B will greatly exceed that of passing from B to C ; and it may be readily demon- 
 strated, that in ordinary cases it exceeds it so much, that the portion of it which when 
 resolved is in a horizontal direction, or effective in propelling the vessel, is greater than the 
 whole action at the vertical position, although this latter is attended with no loss from oblique 
 action. This effect will be illustrated very clearly by assuming the extreme case of the 
 paddle wheel being immersed to the axle : here the floats will enter the water at the whole 
 velocity of the wheel ; but this velocity will diminish until they arrive at the vertical position, 
 when it will be only the difference of the velocity of the wheel and vessel, which is generally 
 not more than one quarter of the whole. 
 
 On the contrary, if we examine the position of the vertically acting paddles of the new wheel 
 in the same equal intervals of time, we find that the space B C, in passing the vertical posi- 
 tion or bottom of tlie arc, greatly exceeds that of the preceding interval of time A B : in fact, 
 the motion of the vertical paddle in entering the water is scarcely perceptible, but it gradually 
 increases until it has passed the bottom of the arc ; and hence arises one of the greatest 
 advantages of this construction of wheel, by totally avoiding the shock or blow on the paddle 
 entering the water, which is experienced in the common construction, and which is not only 
 injurious to the engine and unpleasant to the passengers, but. productive of a serious loss of 
 power, particularly at sea, or when the vessel is deeply immersed. 
 
ON THE CENTRE OF PRESSURE OF A PADDLE. 49 
 
 The actual amount of effective pressure at any angle may be ascertained in the following 
 manner. Let A B, Plate xx v. Fig. 7., be any position of the paddle board of a vessel in motion ; 
 V being the velocity of the wheel, and v that of the vessel, and <f> the angle of inclination of 
 the paddle board with a vertical line. Let C D represent the velocity V at right angles to the 
 paddle, and E C that of the vessel in a horizontal direction. Then it is evident, that C F, 
 which is the resultant of these velocities, will represent the velocity and direction of motion of 
 the paddle with respect to still water. Resolve F C into the two velocities F G, C G, one at 
 right angles to, and the other in the direction of, the paddle ; of which the latter is lost, while 
 the former will represent the velocity with which the paddle meets the water in a direction at 
 right angles to its face : then CG or HF = EF EH = V v cos. <p ; consequently, 
 (V v cos. <p) J will represent the whole resistance which the paddle opposes to the engine at 
 any angle <f. 
 
 In order to get an expression for the resistance in a horizontal direction, or that part which 
 is effective in propelling the vessel, C G must be resolved into the two resistances C T, GT, 
 one in a horizontal, and the other in a vertical direction. GT or the effective propelling 
 force will therefore be (V v cos. p) 1 cos. <p : and it will be found in all cases which occur 
 in practice, that the velocities V and v are such that this expression is greater than (V 1>)% 
 or that of the resistance on the vertical paddle. 
 
 In the case of the new or vertical wheel at any angle <f of the paddle rod, the resistance 
 will be (V cos. <p r) 2 ; so that in this wheel, when the angle is such that V cos. if is equal 
 to v, no resistance is opposed to the engine ; and when it is less, (a case I have witnessed in 
 practice,) it opposes a resistance in a contrary direction, or is a direct impediment to the 
 motion of the boat when first entering the water. It is, however, sufficiently obvious, that 
 the resistance opposed to the engine in this case is less than when in its lowest position, while 
 in the old wheel it is every where greater : it will also be readily seen, with such velocities 
 V and v, as usually occur in practice, that not only is the resistance to the engine greater 
 in the oblique paddle, but that more effect is produced by them in propelling the vessel, 
 unless the immersion of the wheel is very great, as is sometimes the case in stormy weather, 
 when of course the angle may be such that the resistance is almost entirely in a vertical 
 direction. The angle when the effective resistance is the greatest may be found as follows : 
 
 (V v cos. ip) 1 cos. <p is the maximum when 
 
 V 1 d cos. $ 4 V D cos. if d cos. <p + 3 v 1 cos. Q 1 d cos. $ = ; 
 
 4 Vcos.<t V 2 
 
 whence cos. <* 5 = .-, j ; 
 
 3 v dv 1 - 
 
 V 
 
 and cos. <J> = .-. ; 
 3 v ' 
 
 hence, with the velocities such as form the limit of practice, viz. 
 
 V = 5, v = 4, <p, or angle of greatest effect, is . . 65 33' 
 
 4 3 63 37 
 
 3 2 60 
 
 It should be stated, however, that although an increased propelling power is obtained at 
 the above angles, it is not to be understood that so great an angle is practically advan- 
 
 S 
 
50 APPENDIX. 
 
 tageous : the amount of vertical resistance or lost power is here increased to a considerable 
 amount, and the shock by the paddles striking the water at so great an angle is highly 
 injurious. 
 
 EXPLANATION OF THE MANNER IN WHICH THE POWER OF THE ENGINE IS 
 EXPENDED IN THE TWO WHEELS. 
 
 As the preceding formulae enable us to calculate the degree of resistance on the paddles at 
 any angle of inclination, we may readily find the whole power exerted by the engine, either 
 by obtaining the sum of all the resistances of one paddle in passing through the water, and 
 multiplying by the number ; or by finding the mean resistance of one paddle while in action, 
 and multiplying by the number acting at the same time, and the circumference passed through 
 by the centre of pressure. This latter mode is preferable, being arrived at by a less com- 
 plicated calculation, and as it represents more truly the real action of the resisting medium, 
 which, from there being several paddles in the water at the same time, is in fact equivalent 
 to that of an uniform weight acting at the distance and velocity of the centre of pressure. 
 
 Not having the dip of immersion in all the experiments in the table, a separate calculation 
 is not given for each, but a dip of 3ft. '6 in,, equivalent to an entrance angle for the centre 
 of pressure of 44, is assumed as the average in the first class, which, from the experiments 
 being generally made after the engines were fitted, and before the vessel had taken in her 
 cargo of coals, must be very nearly the truth. 
 
 The general expression for the tangential resistance with the COMMON WHEEL is (V 
 v cos. if) 1 ; the mean resistance will therefore be the integral of (V v cos. <p)* d <p divided by 
 p ; or it may be obtained sufficiently near, arithmetically, by calculating the resistance at 
 equal intervals or angles, and dividing their sum by the number, for the mean. 
 
 Assuming V = 4 and v = 3, which is very nearly the mean ratio of the velocity of the 
 common wheel and vessel, we find the mean resistance of the paddle passing through the 
 whole arc to be to the resistance of the vertical one as 1'75 to 1. Now, as the whole circum- 
 ference contains sixteen paddles, and the arc passed through is 88, three paddles and a half 
 may be considered to be acting : this will make the whole resistance to the engine to be 6-12 
 times that opposed by the vertical paddle, or the proportion of the power of the engine 
 exerted on the vertical paddle to be = '163, while the mean obtained from the experiments 
 is -151. 
 
 In the second class, the paddle wheels, though smaller, being proportionally immersed, will 
 enter the water at the same angle of inclination, so that the same mean resistance will result 
 from it, viz. 1-75. The number of paddles, however, being less in the small wheels, there are 
 not more than three of them effective ; which gives the proportion of the power of the engine 
 exerted on the lower or vertical paddle -190, the mean obtained from the experiments being 
 193. We are thus able to account in the radiating wheel for a power exerted on the paddles 
 equal to the whole nominal power of the engine, which not only speaks strongly as to the 
 accuracy of the principles adopted in the preceding calculations, but also that the supposed 
 loss from back water cannot be much. 
 
 It now remains to account for the power of the engine in the NEW WHEEL, where we have 
 found the horizontal resistance to the paddle to be (V cos. <p v) 1 . The power of the engine 
 
LOST POWER IN VERTICAL AND IN COMMON WHEELS. 51 
 
 necessary to overcome this resistance will be (V cos. $ t;) 1 cos. <p, as may be shown as 
 follows : 
 
 Let G B, Plate xxv. Fig. 8., represent the horizontal resistance or force on the paddle ; it is 
 to be ascertained what force in the direction F B will overcome it. Resolve G B into the two 
 forces H G, H B, one at right angles to, and one in the direction of, the radius rod. The effect 
 to turn the line A B about the point A will be the force H B alone ; the force G H, which is in 
 the direction of the line A B, having no power to turn it, its whole action being on the axle of 
 the wheel. It therefore follows, that the force F B at right angles to the radius rod required 
 to retain the point B in equilibrio, or to exert a force in a horizontal direction equal to G B, 
 is G B cos. <p (because the angle G B H = B A I) and consequently equal to (V cos. <}> vY 
 cos. <f>, as already stated. 
 
 Having assumed in this case the same angle of 44 when the paddle begins to act, the 
 mean of the horizontal resistances on the paddle, viz. (V cos. <p v) 1 = G B will be '547, 
 and the mean of the forces necessary to create these resistances or (V cos. $ t-) I cos..ip 
 will be '522 (the force on the lower paddle being 1) ; which, multiplied by 2|, the number of 
 paddles acting, makes the whole power of the engine employed 1'436 times that exerted 
 on the vertical paddle ; or the proportion of the power of the engine employed on the lower 
 paddle '696 ; the mean given by the experiments being '546 : there is therefore a deficiency 
 of -150 of the power of the engine to account for, which I suppose partly due to the greater 
 friction of this wheel, and partly to the paddles not being quite perpendicular in every 
 position in the water, as has been assumed in the preceding calculations. 
 
 COMPARISON OF THE LOST POWER IN THE VERTICAL AND IN THE 
 
 COMMON WHEEL. 
 
 In the action of the common wheel there arises, as we have before described, two kinds of 
 lost power, one from the retrograding of the wheel, and the other from the oblique action of 
 the paddles ; and we are now enabled to estimate the amount of each of them with con- 
 siderable accuracy, and thus draw a comparison of the efficiency of the two constructions of 
 wheel in different states of immersion. 
 
 The expression (V v cos. <J>) 1 represents the whole mean pressure exerted on the paddle ; 
 this, multiplied by the velocity or space passed through by the centre of pressure in a given 
 time, will express the whole power of the engine. In the same way, by the expression 
 (V v cos. <$Y cos. <p, the resolved horizontal resistance, we may obtain the mean effective 
 pressure acting on the vessel ; which, multiplied by its velocity, will express in the same 
 manner the proportion of the whole power which is useful in propelling the vessel. These 
 numbers are computed and arranged within all practical limits in the following table, the 
 original engine power in each case being assumed to be 1. 
 
 In the vertical paddle wheel, as there results no loss of power from oblique action, the ratio 
 of the useful to the whole effect will be that of the velocities of the wheel and vessel : ' this 
 ratio, as will be seen from the experiments, is 3 to 2, or the proportion of effective power is 
 666 of the whole power. 
 
 1 See the note at the end of this paper. 
 
5-2 
 
 APPENDIX. 
 
 TABLE III. 
 
 
 
 
 
 Mean effective 
 
 Mean resistance 
 
 
 Angle at 
 which the 
 centre of 
 pressure of 
 
 Proportion 
 immersed 
 of the 
 
 Effective power, 
 that of the engine 
 being 1. 
 
 Lost power, 
 that of the engine 
 being 1. 
 
 resistance, the 
 resistance of 
 the vertical paddle 
 being 1. 
 
 opposed to the 
 engine, that of 
 the vertical paddle 
 being 1. 
 
 Remarks. 
 
 entered the 
 
 the wheel. 
 
 Common 
 
 Morgan's 
 
 Common 
 
 Morgan's 
 
 Common 
 
 Morgan's 
 
 Common Morgan's 
 
 
 water. 
 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 wheel. 
 
 
 
 
 
 
 
 
 
 
 
 
 f Vessel very light, 
 
 35 
 
 252 
 
 660 
 
 666 
 
 310 
 
 333 
 
 1-298 
 
 702 
 
 1-457 
 
 674 
 
 J the immersion to 
 } the top of ihe 
 (. paddle. 
 
 44 
 
 350 
 
 045 
 
 666 
 
 355 
 
 333 
 
 1-510 
 
 547 
 
 1-750 
 
 522 
 
 { Mean immersion 
 \ of experiments. 
 
 50 
 
 430 
 
 620 
 
 666 
 
 380 
 
 333 
 
 1-C28 
 
 504 
 
 1-971 
 
 482 
 
 
 60 
 
 550 
 
 553 
 
 606 
 
 447 
 
 333 
 
 1-850 
 
 425 
 
 2-510 
 
 404 
 
 I Very deep im- 
 
 
 
 
 
 
 
 
 
 
 
 
 From an examination of the above table, we arrive at several important conclusions. In the 
 first place it is seen that when the wheel is slightly immersed, little or no advantage is gained 
 from the vertically acting paddle, the loss from the additional velocity required to obtain the 
 necessary resistance or receding of the wheel being fully equal to that of oblique action in the 
 common wheel. The only remedy for such an evil is the increase of the number and dimen- 
 sions of the paddles, both of which are difficult to accomplish in Morgan's wheel : we may 
 therefore very fairly conclude, that in the navigation of rivers or smooth water, where generally 
 little variation is required in the degree of immersion of the vessel, the common wheel, if pro- 
 perly proportioned, is preferable to the vertically acting wheel, in consequence of its admitting 
 of a larger surface of paddle board. 
 
 In the case of deep immersion the effect is very different : here the loss from oblique 
 action in the common wheel becomes very serious, so that the total loss of the engine 
 amounts 'to '447 of that expended, while the loss from Morgan's wheel remains nearly 
 the same. It therefore appears, that the latter has great advantages over the common 
 wheel for sea purposes or long voyages, where the immersion of the vessel is constantly 
 diminishing by the exhaustion of the coals and other stores required at the com- 
 mencement of the voyage. The loss from the oblique action of the paddles must also 
 be very great in rough weather, from the degree of immersion to which the wheel is 
 subject; in addition to which, the paddles entering the water with so great a velocity, 
 receive a reaction or blow which has the effect of nearly bringing up the engine, and 
 there in consequence results a loss, in addition to that of oblique action, from the power 
 required to put the mass of machinery again in motion. The advantages which the common 
 wheel possesses in still water, of presenting a larger surface of paddle board, does not now 
 exist, as a large surface has a tendency to bring up the engine, and throw all the work on the 
 oblique paddle, which is in every case disadvantageous. In fact, the desideratum that has to 
 be aimed at in every wheel, is to throw as much work as possible on the vertical paddles, 
 where there is no loss from oblique action, which can be accomplished in the ordinary con- 
 struction when the immersion does not exceed one-fourth of the radius, and a large surface of 
 paddle board taken advantage of; but at sea it can only be effected by reducing the number 
 
ON CYCLOIDAL WHEELS. 53 
 
 and surface of board, which is at a great sacrifice of speed when the vessel is in still water, 
 a condition to which the same vessel is of course liable ; and hence arises the disadvantages 
 and loss of power of the ordinary wheel for sea purposes. 
 
 CYCLOIDAL WHEELS. 
 
 The vertical wheel, although possessing in its action the advantages we have pointed out, is 
 however attended with several serious practical objections. To effect the vertical position of 
 the paddles, considerable complication is necessary in the construction, and a great number 
 of moving parts are required, which are not only attended in the commencement with a great 
 outlay, but require continual repairs, and are liable to derangement. 
 
 These objections have led to attempts to improve the action of the common wheel by a 
 different arrangement of the paddle boards, which have been so far successful in the cycloidal 
 wheel, that its use is very likely to become general and supersede that of Morgan, from its 
 superior strength and simplicity, while it does away with most of the evils to which the com- 
 mon wheel is subject. A patent for a cycloidal wheel was first taken out by Mr. Galloway, 
 in August, 1835 ; but as it appears that a similar wheel was employed by Mr. Field, in a 
 vessel on the Thames, in the year 1833, and a model of a cycloidal wheel exhibited to the 
 Lords of the Admiralty in the same year, (see ' London Journal,' December, 1835,) we 
 conceive that the credit of the invention rests with the latter gentleman. 
 
 The principle of this contrivance consists in dividing the paddle into a number of parts, 
 which are placed upon the wheel in the curve of a cycloid, so that they enter the water at the 
 same spot, and follow one another so rapidly as to cause little resistance to the engine on 
 entering the water ; and afterwards separate, so as to afford full scope for their action in passing 
 the centre, and in coming out allow the water to escape readily from them. A drawing of the 
 cycloidal wheel, fitted by Messrs. Maudslay and Field to the Great Western steam ship, is given 
 in Plate xxvi. Fig. 9. The dotted circle is that which I have termed in the preceding investi- 
 gation the rolling circle, the velocity of its circumference being equal to that of the vessel : the 
 action of the paddles will be truly represented by the motion of this circle on the horizontal 
 line. The paddles are placed in the direction of the curve A B, which is a portion of a simple 
 cycloid described by the point A in the circumference, or by a fixed point at B during the 
 rolling of the circle along the line, and must therefore enter the water at the same spot. 
 When immersed, they no longer follow a common direction of motion, but gradually separate, 
 so that in passing the vertical position they do not in any way interfere with each other's 
 action, and resembler so many small radiating paddles. After passing the centre, they still 
 continue to separate in their direction of motion, and consequently leave the water very freely, 
 and without the back water to which the common wheel is subject. To enable the reader 
 to understand the beautiful action of this wheel, we have drawn the positions of the paddles 
 in a vessel in motion, at equal intervals of time, (Fig. 10.) as has already been shown in the 
 common wheel, from which will be seen its great superiority both in entering and leaving the 
 water : it enables an engine in any weather to make a greater number of strokes, by throwing 
 more work on the bottom paddles ; and reduces considerably the shock on entering the water, 
 which is not only productive of a loss of power, but is very unpleasant to the passengers. 
 
54 APPENDIX. 
 
 In river navigation, where there does not exist the necessity of deeply immersing the wheels, 
 and the common paddles can be made much broader without inconvenience, the advantages of 
 this construction will not be so much felt : at the same time, it may always be employed 
 beneficially, and will occasion less lost power than the common wheel. 
 
 ADDITIONAL EXPERIMENTS ON PADDLE WHEELS. 
 
 The results of the preceding investigations have been fully borne out by a very interesting 
 and complete set of experiments made by Mr. Field, (most of which I attended,) with the 
 view of comparing the effect of the cycloidal and Morgan's wheel with the common one, with 
 different proportions, number, and arrangements of paddles. 
 
 The apparatus, by which the experiments were made, consisted of a vertical shaft, which 
 was hung so as to revolve freely in the centre of a circular reservoir. The wheel was 
 suspended in a horizontal arm attached to this shaft, and was put in motion by a descending 
 weight, which caused the wheel to revolve and carry the horizontal arm, with a small plate 
 attached to it to represent the resistance or vessel, round the reservoir. The weight was 
 wound up to the same height at each experiment, to cause the wheel to make an equal 
 number of revolutions ; and the time employed by the weight in descending, and the number 
 of circuits made, were accurately observed. The different states of immersion of the wheel 
 were produced by altering the level of the water in the reservoir. The column describing 
 the effect is calculated by multiplying the square of the velocity by the number of circuits 
 and the area of resistance. 
 
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50 APPENDIX. 
 
 DEDUCTIONS FROM THE PRECEDING EXPERIMENTS. 
 
 \ 
 
 In experiments such as the preceding, made on a small scale, there frequently arises a 
 difference of action, and consequent effect, at variance with the true practical results : it 
 therefore becomes important, before drawing conclusions from such experiments, to examine 
 into the causes, which will operate differently on the large and small scale. In the model of 
 Morgan's wheel the friction will be proportionally greater than in the actual wheel : the 
 model was however made so perfect, that it could not have been much greater, although 
 some allowance should be made. 
 
 The cycloidal wheels lost much of their effect from being on the small scale : the intervals 
 between the paddles were so small, that the water could not escape, owing to its natural 
 adhesion, which would have no sensible effect in practice : the loss from this was evidently 
 so great, as could be seen by examining the motion of the wheel, that no just comparison can 
 be made of its effect as compared with the others. These considerations will not, however, 
 affect the comparison of the same wheel in different states of immersion, from which we learn 
 the nature of its action ; nor will it affect the comparison with the common wheel with different 
 number and surface of paddles ; so that many conclusions of practical utility may be derived 
 by an examination of the preceding table of experiments. 
 
 The most direct comparison of the action of Morgan's with the radiating wheel, is with the 
 last experiment, No. 10., which is in fact the same wheel with the paddles fixed radiating. 
 Here, in the small immersions, the effect of Morgan's wheel is less than the radiating, the 
 mean of the three first immersions of the former being 6990, and of the latter 7156 ; which is 
 owing to loss, as we have before pointed out, from the additional receding of the wheel : this 
 is rendered strikingly evident from the velocity (in the experiments) on Morgan's wheel being 
 at the same time greater than in the other. 
 
 In the deep immersion, Morgan's wheel has considerably the advantage, not only in velo- 
 city, but in effect, the mean of the three last observations on the former being 6790, and the 
 latter 5003 ; the loss from oblique action operating in this case very much against the com- 
 mon wheel. 
 
 In examining the other experiments, we find that a less deep paddle with a greater number 
 of boards gives a better effect throughout. In comparing the best radiating wheel with Mor- 
 gan's, we find it is completely superior in the small immersions, and continues to be so until a 
 greater proportion than '235 of the diameter of the wheel is immersed. In the experiments 
 an allowance should be made for the loss of effect from the greater friction of the model ; at 
 the same time, there is little doubt that a well-proportioned common wheel will be superior to 
 Morgan's in small immersions. 
 
 The experiments on the cycloidal wheels were not so satisfactory as could have been 
 wished, from the loss of effect evidently produced by the adhesion of the water in coming 
 out, a difficulty that could not exist on the large scale : they however show a greater 
 equality of effect throughout the different states of immersion than any of the wheels ; arid, in 
 fact, in the deep immersions are superior to most of the wheels ; which ar,e important points 
 in favour of this construction, and leave little doubt that the deficiency in the light dips, 
 from the cause above named, was very great. 
 
EXPERIMENTS OF FIXING THE PADDLE-BOARDS, &c. 57 
 
 These experiments also very satisfactorily confirm the preceding calculations of the lost power 
 with different immersions of the radiating wheel. The effective power in the calculated table with 
 the immersion '252 of the radius is 660, and with the immersion -550 of the radius it is 553. In 
 the experiments with immersion '123 of diameter or '246 of radius, the effect is 9086, (radi- 
 ating wheel, No. II.); and with immersion -273 of diameter or -540 of radius, the effect is 
 7466, which will be found to have nearly the same ratio as the two calculated numbers ; and 
 the same will hold good with all the experiments in the table. 
 
 EXPERIMENTS TO ASCERTAIN THE EFFECT OF FIXING THE PADDLE-BOARDS 
 AT AN ANGLE WITH THE RADIUS OF THE WHEEL. 
 
 In the radiating wheel as commonly constructed, the arms radiate to the centre, and the 
 floats being attached to the faces of them, make an angle with the true radius, which has 
 the effect of causing the paddles to enter the water more obliquely, and thereby in- 
 creasing the concussion. To obviate this, Messrs. Maudslay and Field have constructed 
 wheels, so that the arms radiate to points at such a distance from the centre, that the faces 
 of the floats are in the true line of the radius, which is found to have a beneficial effect. 
 
 The object of the following experiments was to ascertain how far an advantage would be 
 gained by giving the floats an angle in a contrary direction, (viz. so that they radiate when 
 entering the water to a point forward of the centre of the wheel,) and thereby causing them 
 to enter less obliquely. 
 
 The experiments were made with the same apparatus as the preceding ; and they were 
 repeated in some immersions with the wheel inverted, so that the motion was in a contrary 
 direction, to represent the effect of angling the paddles aft of the centre. The remaining four 
 columns of each division of the table represent, 1st, The number of circuits or revolutions 
 made in the reservoir ; 2nd, The time of the experiment in seconds ; 3rd, The relative 
 velocity obtained by dividing the circuits by the time ; and 4th, The useful effect cal- 
 culated, as we have before described, by multiplying the square of the velocity by the 
 circuits, which is doubled for the double area. 
 

 
 
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ON THE RELATION BETWEEN THE DIAMETER, &c. 59 
 
 ON THE RELATION BETWEEN THE DIAMETER OF THE WHEEL, AREA OF THE PADDLE, 
 
 AND THE VELOCITY OF THE VESSEL. 
 
 When the area of the float of a paddle-wheel is so adjusted to any given diameter that the 
 engine is capable of performing its whole duty, it is evident that the same duty might also 
 be performed with a less paddle and larger wheel, or with a smaller wheel and larger 
 paddle, but the velocity of the vessel will not be the same in the two cases ; and the 
 question therefore is, to determine what change must be made in the area of the paddle, and 
 what change would take place in the speed of the vessel, with a given change in the 
 diameter of the wheel, so that the engine in both cases may perform its whole duty. 
 
 Let d = diameter of the first wheel, 
 
 V = its circumferential velocity, 
 
 a = the area of paddle, 
 
 v = the velocity of vessel, 
 r d = the diameter of the second wheel, 
 r V the circumferential velocity, 
 
 a' = the required area of paddle, 
 
 v' = the new resulting velocity of the vessel, 
 
 all of which quantities are given except ' and v', which may be determined from the 
 following considerations, viz. 
 
 1st, That the whole duty of the engine is exerted in both cases, consequently, 
 
 (V-v) 2 Va = (r V i/) 2 r Va'. 
 
 2nd, That the resistance on the paddle in each case is equal to that of the vessel, and 
 therefore proportional to the squares of the two velocities, v' and v, that is, 
 
 ( V - i') 2 a : (r Vv')* a : : * : i'' 2 . 
 From these two equations we find 
 
 , v , (V vY 
 v = . and a = x a. 
 
 From the first it appears that the two velocities are to each other inversely as the square 
 roots of the radii. And by the second, the new area of paddle will be found to increase and 
 decrease so rapidly, that generally little practical advantage can be taken of the condition of 
 the first equation. 
 
 It appears from the above, that there are two different diameters of wheel, with dependent 
 area of paddles, that will allow the full power of the engine to be developed. And when 
 from circumstances of loading, &c., the whole power of the engine cannot develope itself- 
 there are two ways in which this effect can be insured ; the one by reducing the paddle 
 and the other by reducing the diameter of the wheel : by the former it will be seen that 
 the speed of the vessel will remain the same, but by the latter it will be increased as the 
 cube root of the power developed in the two cases. 
 
 We have seen that (Vv) *V a expresses the whole amount of the power exerted, 
 which, in the case we are now supposing, is less than the engine is capable of exerting. 
 
60 APPENDIX. 
 
 Let the power, or, which amounts to the same thing, the number of strokes made in the 
 two cases be as 1 to m. 
 
 Now supposing, in the first place, the diameter to remain the same, the velocity V will 
 become m V ; and we may find a and the resulting velocity v from the equations, 
 
 (V - r) 2 Fa : (m V - v')* m V a : : 1 : m, 
 
 and 
 
 ( V - )* a : (m V ')* a : : v* : v' 2 
 
 that is, by making the whole power in the two cases as 1 to m, and the resistances on the 
 paddles as v 2 to v' 2 . 
 
 From these equations it appears that v' = v, or that no increase of velocity will be given 
 to the vessel by reducing the paddle, so as to bring out the full power of the engine. 
 
 But if the diameter of the wheel be changed, the paddle remaining the same, both the 
 velocities Fand v will be changed. Let the former become p V, and the latter n v; our 
 equations are therefore, 
 
 (F - )* V a : (p V - nvf p Va : : 1 : m, 
 (V - v) 2 a : (p V - n v) s a : : 1 : w 2 , 
 
 which reduced, give p = n, and each equal to the ^/^ ; that is, the velocity of the 
 vessel will be increased in the ratio of the cube root of the powers expended. 
 
 We see, therefore, that when an engine is not able to perform its whole duty, the diameter 
 of the wheel ought to be reduced, and not, as is usually done, the area of the paddle; for in 
 the former case the velocity is increased in the ratio of the cube roots of the number of 
 strokes, while in the former it remains the same as when the less power was developed. 
 
 To find the change in the diameter required to produce this effect, we know the circum- 
 ferential velocities are V ': V ^^m, or as 1 : &/ m ; we know also that these velocities 
 are as the number of strokes multiplied by the radii of the wheels ; putting therefore r and r' 
 for the two radii, the velocities are as r : m r', or r : m r' : : 1 : v*/ m , whence 
 
 .' r 
 
 mi' 
 the required radius of the paddle. 
 
 In the case of the Salamander, from the great immersion of the paddles, the engine could 
 only make 15 strokes instead of 20, its full duty. 
 
 We may now find what increase of speed would have been given to the vessel by reducing 
 the wheel so as to allow the engine to perform its whole duty. 
 
 We have m = 1-33, whence r' = -8264 r ; and n v = I'lOO v ; if therefore the diameter 
 of the wheel of the Salamander had been reduced in the ratio of 1 to -8264, the speed of 
 the vessel would have been increased in the ratio of 1 to I'lOO; that is, by reefing each 
 paddle about 19 inches, the speed of the vessel would have been increased about |ths 
 of a mile. 
 
 In these calculations a similar action of the paddles has been assumed, with every variation 
 of diameter, which in reality is not strictly true, as every change of the position of the floats 
 will vary the angle at which the centre of pressure enters the water. This variation will 
 
ON REEFING PADDLES. 61 
 
 however be so small in the greatest extent of reefing ever required, that it is not necessary 
 to introduce it into the calculation. As far as its effect extends, it is favourable to the 
 reefing, as thereby the obliquity of action is diminished, and consequently the loss of power. 
 
 ON REEFING PADDLES. 
 
 In the commencement of a long voyage, a steam vessel is necessarily very deep in the 
 water, from the quantity of coals required for the consumption of the engine. This would 
 have the effect of diminishing the speed in a small degree, were the engine capable of exerting 
 its full power ; but from the wheel being also necessarily more immersed, there results a great 
 loss of the power of the engine, not only from the increased oblique action, but from the 
 number of strokes being reduced ; and having at the same time to combat with a greater 
 resistance, a very considerable loss of speed is the consequence. 
 
 In the experiments given in Table I, the speed of two of the vessels is given both when 
 light and laden, from which the great amount of this loss will be seen. The first is the 
 Messenger with common wheels of 730 tons burden, and 200 horse power. Her speed with 
 60 tons of coals on board is 9'75 miles, and with 130 tons 8'00 miles an hour. 
 
 Her sectional area of resistance could not have been increased in a greater ratio than 6 to 7, 
 so that the speed, if the whole power of the engine was brought out in the two cases, 
 ought not to have been reduced in a greater ratio than the cube root of these numbers, or 
 from 9'75 to 9 '25 miles per hour; hence there is a loss of 1*25 miles an hour from the bad 
 action of the wheels, and from the engine not being able to make its full number of strokes. 
 
 The second experiment alluded to is the Flamer of 494 tonnage, and 120 horse power, 
 fitted with Morgan's wheels. Her speed with 15 tons of coals was 10'9, and 112 tons, 9'57 
 miles per hour ; the section of resistance would not be increased more than as 4 to 5, 
 so that the speed should not have been reduced to less than 10-12 miles; the remaining 
 loss of 0'55 miles per hour is therefore due to the diminished power of the engine, which, 
 although much less than in the common wheel, is still very serious. 
 
 A similar comparison can be made between the Phoenix and the Salamander, which are 
 vessels of the same tonnage and horse power, and have nearly the same speed under similar 
 circumstances. The speed of the Phoenix light was 11 -7, and the Salamander laden 8-15. 
 Allowing a difference of section in the ratio of 11 to 15, which is the extreme between 
 a light and laden vessel, the reduced speed ought to have been 10'55, and there is there- 
 fore a loss from the combined effect of the bad action of the wheel and reduction of the 
 strokes of the engine, of 2'4 miles per hour. 
 
 This serious loss of speed in a laden vessel, although greatly reduced by the use of Morgan's 
 wheels, as seen from the second experiment, as I have no doubt it will be in nearly an equal 
 degree by the cycloidal wheel, would be more effectually saved by reefing the paddles, by 
 which the whole power of the engine might be brought out, and the loss from oblique 
 action very much reduced. 
 
 A ready method of reefing appears at present to be attended with some practical difficulties, 
 from the alterations that are made being required while the vessel is at sea. The advantages 
 which would be derived from it, particularly where speed is of importance, are evidently so 
 great, that I hope still to see it accomplished ; but should it ultimately be found im- 
 
(i-2 
 
 APPENDIX. 
 
 practicable, the best remedy is the use of the vertically acting or cycloidal wheel, and keeping 
 the diameter as large as possible, by increasing the length of the stroke of the engine, so 
 that more or less immersion will make comparatively less difference in the action of the 
 wheel ; the larger the vessel the less will be the loss, because the diameter of the wheel 
 increases in a greater ratio than the degree of immersion. In the Victoria, which is fitted 
 with the cycloidal wheels, it is proposed to remove the outer paddles before starting, and 
 to replace them during the voyage when the vessel is sufficiently light, which, if it can be 
 effected, will be attended with considerable advantage ; but much less than if a ready 
 method of reefing could be devised, so that the surface of the paddle-board should be at the 
 constant command of the engineer. 
 
 EXPERIMENTS TO ASCERTAIN THE RATIO OF THE SPEED OF A STEAM BOAT 
 
 TO THE POWER. 
 
 By the preceding investigations we learn, that the speed of a vessel varies theoretically as the 
 cube root of the power effectively developed. In vessels destined for long voyages, where a 
 great number of miles has to be travelled before a fresh supply of coals can be taken on 
 board, it becomes of importance to ascertain by experiment how far this law is consistent with 
 practice. The attention of Professor Barlow, as one of the Commissioners appointed by 
 Government to report upon the communication to America by steam boats from Valentia, 
 was directed to this subject, and he obtained the permission of the Admiralty to make some 
 experiments on her Majesty's ships Echo and Lightning, the results of which, with the 
 reports accompanying them, are as follows. 
 
 TABLE VI. Experiments on her Majesty's ship Lightning, to ascertain the dif- 
 ference of speed due to different amounts of steam power ; taken in successive 
 hours by Massey's Patent Logs, between 8 h. A. M. and 3 P. M., November 15th, 
 1836. 
 
 Time of heaving 
 the log. 
 
 Three Patent Logs. 
 
 Mean velocity. 
 
 Pressure by 
 Steam Gauge. 
 
 State of 
 the vacuum. 
 
 Larboard, 
 No. 4529. 
 
 Midship, 
 No. 4530. 
 
 Starboard, 
 No. 4532. 
 
 
 
 
 Full steaiu. 
 
 
 
 
 H. m. s. 
 9 18 56 
 Taken up, 
 10 18 56 
 
 Miles. 
 000 
 
 8-19 
 
 000 
 
 000 
 8-34 
 
 Miles. 
 8-26 
 
 Lbs. 
 31 
 
 Inches. 
 27 
 
 
 
 
 Reduced steam. 
 
 
 
 
 10 45 
 
 Taken up, 
 11 45 
 
 000 
 
 8-03 
 
 000 
 
 000 
 8-05 
 
 8-04 
 
 1 
 
 27j 
 
 11 53 
 12 53 
 
 000 
 7-44 
 
 Head 
 000 
 7-42 
 
 lo wind, reduced 
 000 
 7-63 
 
 steam. 
 | 7-58 
 
 1 
 
 27J 
 
 
 
 
 Full steam. 
 
 
 
 
 1 4 
 240 
 
 000 
 
 7-92 
 
 000 
 7-91 
 
 000 
 7-90 
 
 | 7-91 
 
 3J 
 
 27 
 
RATIO OF SPEED OF A STEAM BOAT TO THE POWER. 03 
 
 Mean of number of strokes, full steam . 24j Mean speed . 8'08 miles. 
 
 Do. do. reduced steam 23 Mean do. . 7-78 
 
 Difference . 0-3 
 
 Steam used at full pressure. Reduced steam. 
 
 Atmosphere . 14| Ibs. Atmosphere . 14J Ibs. 
 
 Above do. . 3j Above do. . 1 
 
 Total .18 15| 
 
 Number of strokes 24 J Number of strokes 23 
 
 Products . 441 362 
 
 Powers employed nearly as 11 to 9, speed 25 to 24. 
 
 FIRST REPORT ACCOMPANYING THE EXPERIMENTS ADDRESSED TO 
 
 SIR JOHN BARROW. 
 
 " SIR ; Woolwich, Nov. 15, 1836. 
 
 " On the next page I have given the result of my experiments yesterday, 
 on his Majesty's steamer Lightning, from which it will appear, that reducing the steam 
 pressure from 3^ to 1 lb., makes a difference in the speed, when going with the wind, of only 
 about |th of a mile per hour ; and with her head to the wind, of less than fths mile per hour ; 
 at a medium -j^ths mile per hour ; the reduction of the steam power being between ^th and 
 |th : that is, by allowing a reduction of less than ^rd of a mile per hour, or 8 miles per day, 
 a vessel which can now carry only ten days' fuel, would, with this reduction of speed, carry 
 twelve days' fuel, and perform a voyage longer by nearly 330 miles, i. e., 2330 miles, 
 instead of 2000. 
 
 " There are different ways in which this reduction may be effected ; viz. either by reducing 
 the pressure, as I have done, by using an engine of less power, or by causing the steam to 
 act more expansively : which will be the best is a question for the decision of an engineer, 
 all I intended to show by the experiments was, that the questions of going quickest and going 
 farthest were different. 
 
 " I beg to return my best thanks to my Lords Commissioners of the Admiralty for the 
 facilities they have afforded me of confirming by experiment a result which is perfectly 
 consistent with theory. 
 
 " I have the honour to be, Sir, your obedient servant, 
 
 (Signed) " PETER BARLOW." 
 
 SECOND REPORT, ADDRESSED TO CHARLES WOOD, ESQ. 
 
 " SIR ; Woolwich, March 2nd, 1837. 
 
 " In compliance with the request of Sir Charles Adam, I beg to forward 
 a. concise abstract of my experiments on his Majesty's steamers Echo and Lightning, and the 
 conclusions I draw from them, although perhaps they require to be confirmed by one or two 
 other experiments. 
 
64 
 
 APPENDIX. 
 
 " It is well known, that the resistance of water to a body moving in it increases much more 
 rapidly than in the proportion of the velocity, and therefore, that the quantity of fuel requisite 
 to increase the speed from any given velocity, as for example, from 9 miles to 9| miles, 
 would be much more than in the latter proportion : in fact, by being content with the former 
 speed, the same fuel would in some cases carry the vessel 100 or 200 miles farther than with 
 the latter. 
 
 " This was my theoretical view of the subject ; and by permission of the Lords Commis- 
 sioners I put it to the test of experiment in the two vessels above named ; and the result was, 
 that by reducing the power, and therefore the expenditure of fuel, one-sixth, the speed was 
 reduced only one twenty-fourth : and this result is in a great measure confirmed by the prior 
 experiments of Captain Oliver on his Majesty's steamer Dee. 
 
 " I consider, therefore, that, it would be desirable, that the captains in command of his 
 Majesty's steam vessels should be made acquainted with the facts, and that they should be 
 recommended, when their vessels are employed in services which do not require the greatest 
 speed (at all cost), and when wind and weather are favourable, to work with their steam 
 gauge at a less pressure above the atmosphere than at present. 
 
 " This may be done by allowing their fires to act with less energy, without requiring any 
 other change ; and the full power will be always at command if any circumstance should 
 require it. 
 
 " There can, I think, be no doubt, that this practice in such cases as I have supposed, 
 would allow the same distance to be run at 9 miles per hour, with ith less fuel, than if the 
 speed were forced all the voyage to 9^ or 9i miles per hour. 
 
 " I have the honour to be, Sir, your obedient servant, 
 
 (Signed) "PETER BARLOW." 
 
 The experiments on her Majesty's ship Dee, alluded to in this Report as confirming those 
 on the Echo and Lightning, are as follows. 
 
 TABLE VII. Experiments on relative speed and power of his Majesty's ship Dee, 
 on her passage from Portsmouth to the Downs. Tonnage, 705 ; power, 200 ; 
 boilers, iron ; pressure on the safety valve, 3^ Ibs. ; wheels, radiating ; manu- 
 facturers, Maudslay and Co. 
 
 . 
 
 
 
 Winds. 
 
 
 Immersion. 
 
 
 
 
 Coals. 
 
 S . 
 
 Barometer. 
 
 
 1 
 
 
 
 
 
 
 
 
 5 
 
 
 i 
 
 g 
 
 
 <c be 
 
 
 
 Remarks. 
 
 
 
 *2 
 
 i 
 
 o 
 
 
 
 
 
 
 
 t* 
 
 
 
 o 
 
 | 
 
 . 
 
 *= E 
 
 
 
 
 
 8 
 
 3 
 
 o 
 U 
 
 
 1 
 
 
 i 
 
 i 
 
 o 
 
 ! 
 
 & 
 
 'o 
 1 
 
 o. 
 
 1 
 
 1 a 
 
 s ^ 
 
 L. 
 
 s. 
 
 Boilers in two sets ; six fire- 
 places, three in each. 
 
 
 
 
 
 Q 
 
 
 
 
 A 
 
 H 
 
 
 
 O 
 
 01 
 
 g M 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Bush". 
 
 . 
 
 
 
 
 
 
 1832 
 
 8 
 
 
 calm 
 
 
 - 
 
 13-4 
 
 12-2 
 
 
 
 If 
 
 16 
 
 20 
 
 3 
 
 6 
 
 ft 
 
 28 
 
 2fc 
 
 Full power, six firrs. 
 
 
 7-2 
 
 
 
 1 
 
 - 
 
 II 
 
 ,, 
 
 H 
 
 
 
 16 
 
 15 
 
 
 4 
 
 2J 
 
 M 
 
 i. 
 
 f Fires in each boiler, banked 
 
 
 6-4 
 
 _ 
 
 head 
 
 4 
 
 . 
 
 1* 
 
 
 
 
 14 
 
 15 
 
 1 
 
 4 
 
 __ 
 
 
 
 
 ^ up. 
 
 
 6-2 
 
 - 
 
 
 4 
 
 - 
 
 M 
 
 it 
 
 II 
 
 
 
 12J 
 
 10 
 
 i 
 
 3 
 
 2i 
 
 
 
 ,, 
 
 { Half power, one Bet of fires, 
 ( banked up. 
 
 - 
 
RATIO OF SPEED OF A STEAM BOAT TO THE POWER. 
 
 G5 
 
 Maximum speed, full power 8'2 knots. 
 
 One fire banked up under each boiler ....... 8'0 ,, 
 
 The same, with more head wind, and fires banked up under one set, and full 
 
 fires under the other 6'2 
 
 Thus, | speed with fuel ; ship deep. 
 
 TABLE VIII. Her Majesty's ship Phoenix. Tonnage, 815 ; power, 220 ; boilers, 
 iron ; pressure on the valve, 3^ Ibs. ; wheels, radiating. 
 
 
 
 
 Winds. 
 
 
 Immersion. 
 
 
 
 Coals. 
 
 i 
 
 Barometer. 
 
 
 
 
 
 
 
 
 
 
 
 tn 
 
 a 
 
 c 
 
 
 
 
 
 
 Remarks. 
 
 
 
 
 
 
 
 
 
 
 o 
 
 o 
 
 
 
 
 
 
 jj 
 
 3 
 
 1 
 M 
 
 
 
 O 
 
 | 
 
 V 
 
 | 
 
 1 
 
 
 
 1 
 
 1 
 
 "3 
 
 > 
 u 
 
 B, 
 
 J5 
 
 C 
 
 1 
 
 
 
 L. 
 
 S. 
 
 Boilers in two sets ; 
 six fire-places, 
 
 
 
 
 3 
 
 
 
 
 1 
 
 
 PS 
 
 1 
 O 
 
 1 fc 
 
 a 
 
 3 
 f, 
 
 
 
 three in each. 
 
 1S31 
 
 
 
 
 
 
 
 
 
 
 Bush''. 
 
 
 
 
 
 
 Julv 
 
 8-4 
 
 
 head 
 
 1 
 
 
 
 
 
 16J 
 
 15 
 
 
 6 
 
 28 
 
 28 
 
 
 25 
 
 8-6 
 
 
 
 4 
 
 
 
 
 
 17 
 
 17 
 
 
 
 
 
 
 May 28 
 
 8-6 
 
 W. to N. 
 
 W.E. 
 
 5 
 
 
 
 
 17 
 
 15 
 
 
 4 
 
 
 
 
 24 
 
 9- 
 
 N.W. 
 
 N.E. 
 
 5 
 
 
 
 
 sail 16 
 
 15 
 
 
 
 
 
 
 
 25 
 
 9-2 
 
 W. by N. 
 
 East 
 
 G 
 
 
 
 
 18 
 
 15 
 
 
 
 
 
 
 
 27 
 
 3-6 
 5-6 
 
 E. by S. 
 E.S.E. 
 
 E. by S. 
 S.E. 
 
 G 
 G 
 
 chop 
 
 
 
 10 
 
 15 
 14 
 
 00 
 
 fi 
 G 
 
 
 
 
 29 
 
 8-2 
 
 E. by N. 
 
 N.E. 
 
 4 
 
 
 
 
 16 
 
 15 
 
 a 
 
 4 
 
 
 
 
 June 20 
 
 M 
 
 9-2 
 9- 
 
 
 
 
 smooth 
 calm 
 
 
 
 sail 
 
 18 
 
 15 
 
 c 
 
 
 s 
 
 G 
 
 
 
 ( Royal George 
 ( yacht in tow. 
 
 July 6 
 
 7-2 
 
 E. by S. 
 
 E.S.E. 
 
 4 
 
 chop 
 
 13-9 
 
 13-2 
 
 
 15 
 
 15 
 
 
 G 
 
 
 
 
 9 
 
 Aug. 15 
 18 
 
 6-2 
 
 4-6 
 8-4 
 
 W. by N. 
 W. by N. 
 
 W. by N. 
 head 
 N.E. 
 
 5 
 
 G 
 
 
 
 
 sail 
 
 15 
 12 
 17 
 
 16J 
 16* 
 
 
 6 
 
 G 
 G 
 
 
 
 {Royal George 
 yacht in tow. 
 
 With full power 8-4 8'6, 
 
 Reduced 8-2 8'6, 
 
 Sails set 9-0 9-2, 
 
 Full power 3'6 5-6, 
 
 Full power 9'2 knots, 
 7-2 
 4-6 
 
 6 fires, 
 
 15, 17 bushels. 
 
 4 
 
 15 
 
 4 
 
 15 
 
 6 
 
 14, 15 
 
 YACHT IN TOW. 
 6 fires, 15 bushels, 
 
 6 
 6 
 
 15 
 15 
 
 Moderate, and fine weather. 
 
 Fresh, and strong head wind. 
 
 Sails set, five. 
 
 Head wind, moderate. 
 
 Do. do., fresh. 
 
 No satisfactory record of speed by one boiler alone. Welsh coal a saving of Jth over 
 Scotch, though not the best quality. Two revolutions approximate to the knot ; and the 
 table formed on propositions of Lieut. T. Baldock. 
 
 (Signed) ROBERT OLIVER. 
 
 * 
 
 The results of these experiments, although they do not sufficiently coincide to establish the 
 exact law of the ratio of speed to the effective power, agree in showing, that the last mile or 
 half mile of velocity is obtained at a very great expense of fuel, and that in circumstances 
 
66 APPENDIX. 
 
 where from the length of a voyage there is a difficulty in carrying a sufficient supply of fuel, 
 great economy will be effected by the sacrifice of some speed. 
 
 This, perhaps, with the present engines, cannot be more effectively done than by the mode 
 adopted by Mr. Barlow, in his experiments on the Lightning ; viz. working the steam at a 
 very little pressure above the atmosphere : this, in fair weather, when the engine can make 
 nearly its full number of strokes, will produce a very small diminution of speed ; and in 
 circumstances when any additional power may be required for the safety and management 
 of the vessel, it can be at once effected by the addition of a weight to the safety valve. 
 
 By referring to the experiments on the Lightning, it will be seen, that the increase of speed 
 by the additional pressure of steam in the boiler is much less in proportion to the fuel con- 
 sumed, than the theoretical law would give it, chiefly owing, probably, to the vacuum in the 
 condenser being so much less perfect in this case, so that the effective power is less than in 
 the proportion of the consumption of steam : this is an additional argument in favour of 
 working at a low pressure in sea boats ; and there will be, besides, less wear of the engine 
 and less liability to get out of order. 
 
 It is however a very commonly received opinion, totally at variance with the above results, 
 that by increasing the power in proportion to the tonnage, less fuel would be consumed in a 
 voyage of a given length. In fact, Dr. Lardner, in his work on the Steam Engine, states, 
 " that the results pf experience obtained in the steam navigation of our channels, and parti- 
 cularly in the case of the Post Office packets on the Liverpool station, have clearly established 
 the fact, that by increasing the ratio of the power to the tonnage, an actual saving of fuel in a 
 given distance is effected ;" which anomaly he accounts for by the diminution of the draught 
 of water produced by the additional speed. 
 
 The question of the most economical ratio of the power to the tonnage being one of the 
 highest importance in vessels destined for long voyages, we have endeavoured to obtain as many 
 facts and experiments as possible, of the times of making sea voyages of various vessels, with 
 the tonnage and hors'e power ; and, it is found, in every instance, that the consumption of fuel 
 is less the smaller the power in proportion to the tonnage. 
 
 To illustrate the above, we give the following table, from the Parliamentary Reports on 
 Steam Navigation to India, of the times of the voyages of Her Majesty's Admiralty steamers 
 to Corfu and Patras, and back, a distance of 5200 miles, made by nine different vessels, 
 varying in tonnage and horse power. These voyages being so extensive, and made in every 
 variety of weather, we have chosen them as furnishing the best possible data by which to 
 ascertain the truth of the above question. 
 
 The columns of the table, 1, 2, 3, 4, 5, and 7, are abstracted from the Parliamentary Report 
 as thev stand ; the remaining columns are calculated. Column 6 is the number of tons per 
 horse power, obtained by dividing the measured tonnage by the nominal horse power. Co- 
 lumn 8 is the time of steaming in each voyage, obtained from column 7 by subtracting the 
 time of stoppages from that of the whole, voyage. Column 9 gives the means of the preceding. 
 Column 10 is the actual consumption of coals during the voyage, calculated at the rate of 
 8 Ibs. per horse power per hour ; which (as stated by Mr. Field in his examination) is found 
 to be very nearly the average of all engines. Column 1 1 is obtained by dividing the whole 
 consumption by the tonnage, and gives the weight per ton consumed during the voyage, and 
 consequently expressing the relative economy of each vessel. 
 
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68 
 
 APPENDIX. 
 
 In examining this table, it will be seen that vessels with similar wheels, whose tonnage is 
 large in proportion to the horse power, in every case consume less fuel per ton during the 
 voyage : for instance, in the Hermes, which has the largest proportional tonnage, viz. 5'21, 
 the consumption per ton is 1544 Ibs. ; being less than half that of the Alban, viz. 3722, the 
 tonnage of which is the least (viz. 2'94) per horse power. 
 
 In the vessels with Morgan's wheels the largest proportional tonnage is the Flamer, being 
 4 1 13 per horse power ; the consumption per ton is 1477. In the Columbia, the tonnage per 
 horse power is 3'60, and the consumption per ton 1833. 
 
 The most direct comparison in the table is between the Hermes and the Messenger, being 
 vessels of equal tonnage and similar wheels, but with different power, the former being 140, 
 and the latter 220 horse. The consumption of the Hermes is not more than frds that of the 
 Messenger. 
 
 As an additional confirmation of these results, I have given the following table of the mean 
 time of performing several voyages, between Liverpool and Kingstown, of Her Majesty's Post 
 Office packets, Comet, Etna, Thetis, and Dolphin, between January and June, 1837 ; with 
 the quantity of coals consumed, and the same calculated columns as in the preceding table. 
 
 TABLE X. Performances of Her Majesty's Post Office Packets 
 between Liverpool and Kingstown. 
 
 
 
 
 
 
 
 
 
 Coals per 
 
 
 
 
 
 Tons per 
 
 
 
 Consump- 
 
 Consump- 
 
 ton con- 
 
 
 Name of 
 
 Tonnage. 
 
 Horse 
 
 horse 
 
 Mean. 
 
 Mean 
 
 tion of 
 
 tion of coals 
 
 sumed 
 
 Remarks. 
 
 the vessel. 
 
 
 power. 
 
 power. 
 
 
 speed. 
 
 coals per 
 
 during the 
 
 duringthe 
 
 
 
 
 
 
 
 
 hour. 
 
 voyage. 
 
 voyage. 
 
 
 
 
 
 
 Hours. Min. 
 
 Miles. 
 
 Lbs. 
 
 Lbs. 
 
 Lbs. 
 
 
 Comet 
 
 437 
 
 190 
 
 2-3 
 
 13 :;-". 
 
 8-86 
 
 2632 
 
 35,640 
 
 81-5 
 
 < Mean of six voyages 
 ( each way. 
 
 Etna . . 
 
 365 
 
 ISO 
 
 2-43 
 
 14 26 
 
 8-31 
 
 1904 
 
 27,480 
 
 75-3 
 
 Do. do. 
 
 Thetis 
 
 391 
 
 160 
 
 2-47 
 
 12 47 
 
 9-38 
 
 2000 
 
 25,560 
 
 65-4 
 
 Do. do. 
 
 Dolphin . 
 
 331 
 
 166 
 
 2-00 
 
 12 18 
 
 9-75 
 
 2285 
 
 28,105 
 
 64-9 
 
 SMean of two voyages 
 each way. 
 
 These results, it will be seen, confirm those of the Mediterranean packets ; the con- 
 sumption being less per ton during the voyage, when the tonnage of the vessel is largest in 
 proportion to the horse power. 
 
 We may therefore fairly conclude, that the idea of a saving of fuel being effected by 
 increasing the power of a vessel is erroneous. Under particular circumstances it may happen, 
 that an additional power may effect a saving ; but, generally speaking, it may be assumed, 
 that a great economy of fuel will be obtained by diminishing the power of the vessel as much 
 as possible, provided there is sufficient at command for the safety and management of the 
 vessel, should circumstances require it. 
 
ON STEAM VESSELS ADAPTED TO LONG VOYAGES. 69 
 
 ON THE POWER AND TONNAGE OF STEAM VESSELS BEST ADAPTED TO 
 
 LONG VOYAGES. 
 
 The proposed employment of steam communication in voyages of greater length than has 
 hitherto been accomplished, and particularly in the voyage to America, a distance of 3000 
 miles, renders the question of the vessel best adapted to such purpose of great interest, both 
 in this country as well as in America. In fact, a voyage of such length has been hitherto 
 considered beyond what can be obtained by steam power alone, from the difficulty of carrying 
 a sufficient quantity of coal for the consumption of the engine : the improvements, however, 
 which have gradually been introduced, and the success which has attended what has yet been 
 attempted, have given confidence to a sufficient number of individuals to embark in this 
 undertaking, and vessels for the purpose are now being constructed both at London and at 
 Bristol, 1 which will be ready to launch in a few months. 
 
 The voyages which have already been performed, not being of such length that the supply 
 of coals for the engine has been a matter of difficulty, the attention of engineers has been 
 directed rather in giving the greatest speed, than in the greatest capabilities for distance : 
 such vessels must therefore not be looked upon as a criterion of what may be performed : 
 their consumption, speed, &c., will however serve as data by which we may estimate the 
 capabilities of vessels of tonnage and power better adapted to the purpose. 
 
 The larger the vessel, every thing being in proportion, the greater will be her capabilities 
 both for speed and length of voyage : this I will illustrate in a few words theoretically, and 
 then compare it with the practical results. 
 
 The means of stowage of any vessel (which is proportional to the tonnage) will increase as 
 the cube of the linear dimensions, but the sectional area or resistance will increase only as the 
 square ; consequently, if the power be made proportional to the tonnage, an increased speed 
 will be given to the vessel, and consequently the consumption of fuel in a voyage of a given 
 length will be decreased, or length of voyage increased, in the same ratio. 
 
 If the power of the engine be only increased proportionally to the resistance, or immersed 
 section, or the same velocity given to the vessel, the consumption of coals per hour being 
 increased in a less proportion than the means of stowage, it is obvious the fuel will last much 
 longer, and the length of the voyage, both in time and distance, will be proportionally 
 increased. 
 
 To ascertain numerically the amount of the saving in the two cases, let the contents, power, 
 sectional area, and velocity, of any existing vessel, be represented by c, p, a, and v ; and let 
 it be required to find the velocity of a vessel, c, whose power, sectional area, and velocity, we 
 will call p, a, and v. 
 
 Assuming the case of the powers being in the ratio of the tonnage, 
 
 p' = 7- p ; 
 
 and as the section is increased as the square of the linear dimensions, and the tonnage as the 
 cube, we have 
 
 1 This vessel (The Great Western) is now launched, and is arrived in the Thames. 
 
70 APPENDIX. 
 
 Again, the resistance in the two cases being as the area into the square of the velocity, 
 we have 
 
 / c' N g 
 r : r :: (~) s aV* : at,- 
 
 but the power expended and overcome in a given time is as the resistance into the velocity ; 
 therefore the power expended is as 
 
 ' 2 
 
 c \2 
 Y av ' : v! ; 
 
 but the force expended by the engine in a given time is a representation of its power ; 
 therefore, 
 
 / c \i 
 p : p : : c : c : : ( J 3 t> J :t>', 
 
 or, c' 3 : c 3 : : u' ! : t> ! , 
 
 whence, v' = v ^ J ? . 
 
 Then, if we take c' = 2c, or double tonnage, we find the ratio of the areas 1 : 2s, or 1 : 1-587 ; 
 and the ratio of the velocities 1 : 2-^, or 1 : 1'08 : or a decrease of about j^th in the time of 
 
 making a given voyage, and of course a corresponding increase in the capability of the vessel for 
 distance. 
 
 If, instead of increasing the power in proportion to the tonnage, it is only increased in pro- 
 portion to the resistance, or the same speed is given to the vessel, then the power required 
 will be as the section, or as 1 to 1'587, or not much more than half as much again ; and, 
 consequently, a voyage of more than one-and-half times greater length can be performed, 
 while the spare room for cargo will be in the same ratio as the increase of the vessel, or as 
 1 to 2 ; and the vessel will have the same power to contend with adverse weather, as the smaller 
 one with the larger proportion of power. 
 
 These results may be said to be theoretical, but the examination of our present voyages 
 show that they are perfectly consistent with practice. Referring to the performances of Her 
 Majesty's Mediterranean packets, it will be seen, that in the smaller vessels, where the power 
 is large in proportion to the tonnage, and consumption of coals large per ton, the speed of the 
 vessel is generally less than in the larger vessels with a smaller proportion of power, and 
 consequently small consumption of coals per ton. 
 
 It may also be seen to obtain throughout the experiments on Her Majesty's steam vessels 
 at Woolwich, where the larger vessel generally gives a greater speed, although the pro- 
 portion of power is less than in the small ones. 
 
 To exhibit the difference more fully, I have given the following table of the average speed 
 and consumption of coals of nine of the most recently constructed of Her Majesty's steam 
 vessels, and have calculated what speed the largest, viz. the Medea, should make, by the 
 rules given above from each of the other vessels, having Morgan's wheels. I have compared 
 those with the radiating wheels with the largest of that class, viz. the Dee. 
 
ON STEAM VESSELS ADAPTED TO LONG VOYAGES. 
 
 71 
 
 TABLE XI. Giving the Speed and Consumption of Coals of nine of the most 
 recently constructed of Her Majesty's Steam Vessels. 
 
 
 
 
 
 
 
 
 Speed of the 
 
 Speed of the 
 
 
 
 
 
 
 Average 
 
 Number 
 
 Medea, calcu- 
 
 Dee, calcu- 
 
 
 Tonnage, 
 
 
 Description 
 
 Average 
 
 consumption 
 
 of hours 
 
 lated from 
 
 lated from 
 
 Name. 
 
 new re- 
 
 Horse 
 
 of paddle 
 
 speed 
 
 of coals 
 
 steaming the 
 
 each of the 
 
 each of the 
 
 
 gister. 
 
 power. 
 
 wheel. 
 
 in nautical 
 
 per hour 
 
 average is 
 
 vessels having 
 
 vessels having 
 
 
 
 
 
 miles. 
 
 per horse 
 
 deduced from. 
 
 Morgan's 
 
 the common 
 
 
 
 
 
 
 power. 
 
 
 wheels. 
 
 wheel. 
 
 
 
 
 
 
 Lbs. 
 
 
 
 
 Medea 
 
 807 
 
 220 
 
 Morgan's 
 
 7-8 
 
 8-3 
 
 1176 
 
 7-8 
 
 
 Flamer 
 
 414 
 
 120 
 
 Do. 
 
 6-0 
 
 10-7 
 
 780 
 
 7-3 
 
 
 Blazer 
 
 410 
 
 100 
 
 Do. 
 
 6-9 
 
 10-3 
 
 1045 
 
 7-7 
 
 
 Tartarus 
 
 410 
 
 100 
 
 Do. 
 
 5-5 
 
 10-7 
 
 914 
 
 6-15 
 
 
 Pluto 
 
 295 
 
 100 
 
 1)0. 
 
 6-5 
 
 9-7 
 
 986 
 
 6-8 
 
 
 Confiance 
 
 240 
 
 100 
 
 Do. 
 
 C-2 
 
 10- 
 
 2279 
 
 6-2 
 
 
 Dee 
 
 G30 
 
 200 
 
 Radiating 
 
 6-5 
 
 8-3 
 
 1161 
 
 
 6'5 
 
 Firefly 
 
 473 
 
 140 
 
 Do. 
 
 6-25 
 
 10-7 
 
 2206 
 
 
 6-5 
 
 African 
 
 246 
 
 90 
 
 Do. 
 
 5-13 
 
 10-9 
 
 3695 
 
 
 5-5 
 
 It will here be seen, that the speed both of the Medea and the Dee exceeds that obtained 
 from the smaller vessels ; which clearly shows that the advantages of increased tonnage are 
 even greater than the theory gives it : the consumption of coals per horse power is also less 
 in these vessels ; which shows that there are several practical advantages in their favour, 
 which are not embraced in the theoretical view of the case. One of which is, that the 
 diameter of the wheel increases in a greater proportion than the variation of immersion of the 
 vessel, and is consequently proportionally less buried in the water when the vessel is laden, 
 which is a cause of great loss of the power of the engine, as we shall explain more parti- 
 cularly in another part of this article. 
 
 There is another advantage in a large engine, from its increased momentum, which causes 
 it to act as a fly wheel, and is, I am satisfied, of more importance than is generally supposed. 
 One often hears of the motion of the vessel acting as a fly wheel to the engine ; which is quite 
 an erroneous idea, as the action of a fly wheel is that of a reservoir of power, receiving it at 
 one time from the engine, and exerting it at another on the machinery to be put in motion : 
 now as the paddle wheel is always exerting a force, although a variable one, on the water, 
 it cannot possibly receive any assistance from the motion of the boat, which therefore cannot 
 act as a fly wheel to it. It certainly so far assists it, as by its velocity through the water to 
 allow the engine to make a greater number of strokes, and increases the momentum produced 
 by its weight; but this is all it does, and this effect is greatly increased by giving more 
 weight to the paddle wheels. 
 
 The above observations are given merely to show, that the advantages of the increased 
 tonnage of steam vessels, which have been calculated theoretically, are fully borne out in 
 practice. I shall now proceed to calculate with the data, which the performances of some of our 
 sea-going vessels afford, what may be accomplished by others, whose power and tonnage 
 are better adapted to making a long voyage. 
 
 The Medea, the largest of Her Majesty's steamers, is 835 tons' burden, and has engines of 
 inches cylinder, and 220 nominal horse power. The average speed at sea is 7-8 nautical 
 
72 APPENDIX. 
 
 miles per hour, and she consumes 8'3 bushels of coals per horse power per hour, or about 
 20 tons per day. She is capable of carrying 360 tons of coals, or sufficient for 18 days, and 
 consequently of making a voyage of 3370 miles. 
 
 Let us inquire what will be the capabilities of another vessel of the same model, and of 
 1670 tons in point of distance ; supposing, 1st, her power to be increased proportionally to 
 tonnage ; and 2ndly, that it is increased proportionally to the sectional area or resistance. 
 
 To double the tonnage of a vessel preserving the same model, her linear dimensions will 
 be increased as - 100 to 126 
 
 Consequently, her section or area of resistance - 100 to 158 
 
 And her stowage as 1 00 to 200. 
 
 Now, in the first case, the power being as 200, and the resistance to which it is opposed 
 being only as 158, the increased force per square foot of the section will be as 158 to 200, 
 and the resistance being as the cube of the velocity, the speed will be increased in the ratio 
 of 158-J- to 200i, of 1 to 1'08, or, which is the same thing, 1 to 2^ ; and the capabilities of 
 the vessel for distance will be increased in the same proportion, viz. from 3370 to 3640 
 miles. 
 
 In the second case, viz. increasing the power of the engine only in proportion to the 
 section, the velocity will remain the same as in the former vessel ; but proportional consump- 
 tion of coal will be less in the ratio of 200 to 158, and consequently the length of the voyage 
 will be increased as 158 to 200, or from 3370 to 4266 miles. 
 
 The splendid steam ship, Victoria, now being built by Messrs. Curling, Young, and Co., 
 for the American voyage, is 1825 tons' burden, and has engines of 76 inches cylinders, or 
 nominal power of 412 horses. The speed of this vessel, if the engines bore the same pro- 
 portion to the tonnage as the Medea's, viz. 481 horse power, would be increased in the ratio of 
 
 1 to ( -ggg- \i, or 1 to 1-091, or from 7 ! 8 to 8'5 knots per hour ; but as the engines are but of 
 
 412 horse power, her actual speed will be reduced in the ratio of the cube root of 481 to 
 the cube root of 412, or from 8'5 to 8'08, being an actual increase of velocity above the Medea 
 from 7-8 to 8-08 knots. 
 
 Or we may arrive at the speed differently, as follows : to give the Victoria the same speed 
 
 as the Medea, the power must be increased as 1 to ( V, or 1 to 1' 684, or from 220 to 370 
 
 \ 835 ' 
 
 horse power ; but as the actual power is 412, the speed will be increased above the Medea 
 as the cube root of 370 to cube root of 412, or from 7-8 to 8'08 knots per hour, the same 
 as before. 
 
 The Victoria is estimated to carry 750 tons of coals in addition to her cargo : allowing 
 8-3 Ibs. per horse power per hour, or 36| tons per day, to be her consumption of fuel, she 
 is well able to perform a voyage of 20| days, and traverse a distance of 3960 miles without 
 a fresh supply of coals. Now as the voyage from Cork does not exceed 3000 miles, and 
 will be accomplished in average weather in eighteen days, she will have above 2^ days' fuel 
 to spare. 
 
 In this calculation I have assumed the same consumption of fuel per horse power as in the 
 Medea, making no allowance for the economy of the larger engines ; besides which the Victoria 
 
ON STEAM VESSELS ADAPTED TO LONG VOYAGES. 73 
 
 is fitted up with Hall's Patent Condenser, which is stated upon good authority to produce a 
 saving of at least one pound per horse power per hour. Allowing the consumption to be 
 reduced to 7 Ibs. from this cause, and from the greater economy of the larger engines, the 
 voyage will be made with a consumption of 565 tons, being 185 tons less than the 
 vessel is capable of carrying ; and she will perform a voyage of 4690 miles. 
 
 There is no doubt, therefore, that this vessel will, in average weather, accomplish the 
 voyage with facility : and I should expect, with the power she possesses, under the most 
 unfavourable circumstances ; for although in a very severe gale ofw ind the most powerful 
 steamers will make little headway, yet such gales are never of sufficient duration to effect in 
 a great degree the time of a voyage, if we may judge from the voyages of the Mediterranean, 
 Liverpool and Kingstown Post-Office Packets, 8cc., which, although comparatively small ves- 
 sels, the time of their voyages rarely exceeds one-fifth of the average time. This in the Victoria 
 will still leave spare fuel for two days, supposing the engines to work at full power the 
 whole time ; which need not be the case in adverse weather, for as the engine does not make 
 its full number of strokes, it does not require its full allowance of steam. 
 
 We have hitherto spoken of a vessel as a steamer only, but it is to be presumed she will 
 gain much by the power of her sails. Captain Austin states, that the sailing rate of the 
 Medea, when on a wind in a strong single-reefed topsail breeze, and smooth water, is 8 knots 
 per hour, and in a moderate quarterly gale, 11^ knots. Her tacking may be depended upon 
 in strong breezes in a sea way fully equal to a sailing vessel of war, and in light winds when 
 she has steerage way. He also states, that while cruising with the squadron, in treble-reefed 
 topsail breezes, he has found her to weather considerably upon them ; showing the advantage 
 of the great quantity of canvas spread in the fore and aft sails. 
 
 Should it therefore happen that the fuel is exhausted in the outward American passage, 
 or any accident happen to the machinery, which, if ever, will be a rare occurrence, re- 
 course may be had to the sails, and she will still be upon a par or nearly so with the sailing 
 packets : in fact, a vessel properly constructed and rigged, may, under many circumstances, 
 derive great benefit in the use of sails, not only in the economy of fuel, but in saving the 
 wear and tear of the machinery. 
 
 If the Victoria had been fitted with engines of power only in proportion to the increased 
 section, viz. 373 horse power, she would have the same speed and power to contend with 
 a gale of wind as the Medea ; and calculating the same consumption of 7 Ibs. per horse 
 power per hour, she would carry twenty-eight days' coal, and would perform a voyage of 
 5240 miles, without allowing for the weight saved of the engine, which would carry her 
 300 miles further, or 5540 miles, being a voyage of 850 miles longer than she is now able 
 to perform. There is no doubt, however, that she is able, with her present engines, to 
 accomplish the voyage ; and if the proportion of tonnage assigned for merchandise is as much 
 as is required, the additional power will certainly give greater security and manage- 
 ment to the vessel. It appears, moreover, that her engines (which are building by Mr. Na- 
 pier) are constructed so as to work with five pound steam more or less expansively ; 
 and as a great economy of fuel is obtained with a small diminution of speed, it is strongly 
 advisable not to urge her, when circumstances permit, to the utmost of her speed. In voyages 
 when the quantity of coals required does not form a large proportion of the tonnage of the 
 
 k 
 
74 APPENDIX. 
 
 vessel, the advantages of such economy is not felt ; the more particularly- as passengers are 
 chiefly what is conveyed, the competition of other vessels renders speed of such value, as to 
 be obtained at any cost. On the contrary, with vessels destined for long voyages as that of 
 America, the greater portion of the vessel must be devoted to coals, and the less mer- 
 chandise can be carried, when it will probably form a more important consideration. The 
 speed will be bought at greater expense, although less valuable ; and when it becomes the 
 interests of commanders to increase the capability of their vessels for distance, instead of 
 giving them the greatest possible speed, much will be effected by the management of the 
 working power of the engine, combined with the use of sails in the varied circumstances 
 a vessel must have to contend with, in a voyage of such length. 
 
 The above calculations of the length of voyage, that may be performed by a vessel of 
 large power and tonnage, are founded upon the performances of Her Majesty's ship Medea, 
 which I have preferred, from this vessel being of the largest class, and from its speed, 
 consumption of fuel, &c. being accurately recorded, but more particularly from its having 
 been employed by Dr. Lardner as data in similar calculations ; by which he appears to 
 demonstrate the impracticability of making a longer voyage than 2000 miles. 
 
 The more recent private vessels built expressly for the purpose of making a long voyage, 
 give results completely superior to the Medea, as may be seen particularly in the voyages 
 of the Honourable East India Company's steamers Atalanta and Berenice to Bombay, by 
 the Cape of Good Hope. 
 
 Th Atalanta is of 630 tonnage and 210 horse power ; she made the voyage from Falmouth 
 to the Cape of Good Hope, a distance by the log of 6935 miles, having much adverse 
 weather to contend with, in 37 days 16 hours, steaming, at an average speed of 7'67 miles 
 per hour ; her consumption of coals being 14 tons 1 1 cwt. per day, or at the rate of less 
 than 6^ Ibs. per horse power per hour : she performed the voyage from Fernandez Po to the 
 Cape of Good Hope, a distance by log of 2373 miles, in one stage in 14 days 10 hours, 
 with a consumption of 213 tons of coals. 
 
 The Berenice, which is of 680 tons and 230 horse power, made the voyage from Falmouth 
 to Fernandez Po, 4796 miles in 22 days 22 hours, or at an average rate of 8'72 miles per 
 hour, and at an average consumption of coals of 16 tons 3 cwt. per day, or 6'56 Ibs. per horse 
 power per hour. She is able to carry 330 tons of coals, and therefore, if steaming, a distance 
 of 4290 miles. In fact she performed the voyage from Bonavista to Fernandez Po, a distance 
 by log of 2272 miles, and consumed less than half her cargo of coals. 
 
 The results of these voyages are indeed so favourable, as to set the question at rest as to 
 the practicability of the American voyage : the consumption of fuel has been so reduced 
 by the superior construction of manner of working the engines, that these vessels, although 
 comparatively small, are enabled to perform a voyage much exceeding that to New York ; 
 and consequently the American Steam Company's vessels, whose capabilities for distance 
 are greater in the ratio of 7 to 9, from the superior tonnage and power, must perform the 
 voyage under any circumstances, with the greatest facility. 
 
 ON IRON STEAM BOATS. 
 
 It is necessary to mention, among the improvements which are likely to add to the capa- 
 bilities of steam vessels for making long voyages, the introduction of iron as the material 
 
RESISTANCE OF STEAM VESSEL WITH PLANE SURFACE. 75 
 
 of construction, the use of which has been attended with complete success, in every instance 
 in which it has been tried. The advantages of iron vessels are stated to be, that they do not 
 weigh one-half that of a timber sea-going vessel, and they therefore draw considerably less 
 water, and give a greater speed with equal power ; greater safety, in consequence of being di- 
 vided into water-tight compartments by iron bulkheads ; and greater economy, as they do not 
 require so many repairs. The capacity is also increased for passengers and goods : a wooden 
 vessel of 30 feet beam is only 27 feet 6 inches inside, while an iron vessel would be 29 feet 
 6 inches ; consequently a saving of two feet is produced throughout the whole length 
 of the vessels. 
 
 They besides possess the advantage in hot climates, of being cooler, more free from 
 vermin, and in consequence more healthy. In fact, the advantages seem to be generally ac- 
 knowledged. The only difficulty that has at present stood in the way of their employment, 
 in sea voyages, has been the effect of the iron on the compass : and this has been suc- 
 cessfully overcome in the late voyage of L'Egyptien to Alexandria ; in which the compass 
 was fixed under the direction of Professor Barlow, and has been found to work with the 
 same accuracy as in an ordinary vessel. 
 
 We have no doubt, therefore, that iron vessels will in a short time become very general, 
 and add greatly to the facilities and extension of steam navigation. 
 
 COMPARISON OF THE RESISTANCE OF A STEAM VESSEL WITH THAT 
 
 OF A PLANE SURFACE. 
 
 The resistance of vessels being a subject which has of late much engaged the attention of 
 engineers, we have been induced to add the following comparison of the resistance of a steam 
 vessel with that of the paddles, a calculation which can be arrived at with the aid of the 
 preceding experiments and investigations with considerable accuracy. 
 
 Let V the velocity of the wheel, that of the vessel, s its sectional area immersed, and a 
 the area of a paddle whose action is horizontal and effect equal to the sum of all the paddles : 
 the resistance being as the square of the velocity, (V x>) 2 a will express the resistance on 
 the paddle, and i) 2 s would be the resistance of the vessel if it were a plane surface ; but the 
 real resistance being (V v)- a, the fraction of the resistance compared with a plane will be 
 (V vY a 
 v- s 
 
 The value of a has been obtained by knowiag the depth of immersion, so as to ascertain the 
 angle at which the centre of pressure entered the water, and thence the number of times the 
 whole effective action exceeds that of the vertical paddle : this, multiplied into the area of the 
 paddle, gives the whole surface above denoted by a. 
 
 In the following table is given the effective pressure exerted by the engines in every expe- 
 riment where the dip or immersion of the paddle is given ; but the comparison of the 
 resistance of the vessel with a plane is of course limited to those experiments only in which 
 the area of the immersed section could be ascertained. 
 
APPENDIX. 
 
 TABLE XII. 
 
 
 
 
 
 
 Velocity of 
 
 
 
 
 Ratio of the 
 
 
 
 
 Effective 
 
 Velocity of 
 
 the vertical 
 
 
 Area of 
 
 
 resistance of 
 
 
 
 
 pressure 
 
 the vessel, 
 
 paddles 
 
 Area of 
 
 a vertical 
 
 Immersed 
 
 the vessel 
 
 Name of 
 the vessel. 
 
 Tonnage. 
 
 Horse 
 power. 
 
 exerted 
 by the 
 
 that of the 
 wheel 
 
 through the 
 water, that of 
 
 the paddle 
 board. 
 
 paddle sectional 
 equal in ! area of 
 
 to that of a 
 plane surface 
 
 
 
 
 engine. 
 
 being 1. 
 
 the wheel 
 
 
 effect to all the vessel. 
 
 of the same 
 
 
 
 
 
 
 being 1. 
 
 
 the paddles. 
 
 
 section. 
 
 
 
 
 Lbs. 
 
 
 
 Feet. In. 
 
 
 
 
 Medea 
 
 835 
 
 220 
 
 4536 
 
 627 
 
 373 
 
 19 
 
 54-00 
 
 263 
 
 J,~\ 
 
 Flamer 
 
 401 
 
 120 
 
 2814 
 
 683 
 
 317 
 
 16 
 
 52-44 
 
 174 
 
 IS 1 
 T>5 
 
 Flamer 
 
 494 
 
 120 
 
 2593 
 
 674 
 
 326 
 
 16 
 
 5760 
 
 218 
 
 J. 
 
 Firebrand 
 
 494 
 
 120 
 
 2J72 
 
 6(i7 
 
 333 
 
 12 9 
 
 38-56 
 
 200 
 
 ? 
 
 Firebrand 
 
 404 
 
 120 
 
 2527 
 
 666 
 
 334 
 
 12 9 
 
 42-00 
 
 214 
 
 T9 
 
 A 
 
 Columbia 
 
 360 
 
 100 
 
 1807 
 
 654 
 
 346 
 
 12 
 
 4:!- 10 
 
 202 
 
 H 1 
 
 JL } A 
 
 Salamander 
 
 820 
 
 220 
 
 2150 
 
 833 
 
 167 
 
 22 6 
 
 398-70 
 
 359 
 
 IS I 17 
 
 A 
 
 Dee 
 
 710 
 
 200 
 
 2531 
 
 732 
 
 268 
 
 20 
 
 69-00 
 
 209 
 
 X 
 
 Firefly 
 
 550 
 
 140 
 
 3808 
 
 733 
 
 207 
 
 18 
 
 201-00 
 
 275 
 
 19 
 
 A 
 
 Firebrand 
 
 494 
 
 140 
 
 2474 
 
 772 
 
 228 
 
 18 
 
 128-61 
 
 200 
 
 
 Pluto 
 
 365 
 
 100 
 
 985 
 
 823 
 
 117 
 
 16 6 
 
 105-23 
 
 1IC 
 
 
 Monarch 
 
 872 
 
 200 
 
 7167 
 
 748 
 
 252 
 
 20 
 
 
 
 . 
 
 Monarch 
 
 872 
 
 200 
 
 6976 
 
 746 
 
 254 
 
 20 
 
 
 
 
 VIonarch 
 
 872 
 
 200 
 
 7002 
 
 756 
 
 244 
 
 20 
 
 
 
 
 Magnet 
 
 360 
 
 140 
 
 3G72 
 
 763 
 
 237 
 
 15 
 
 
 
 
 Meteor 
 
 29G 
 
 100 
 
 4320 
 
 671 
 
 229 
 
 13 6 
 
 
 
 
 Carron 
 
 294 
 
 100 
 
 1731 
 
 777 
 
 323 
 
 13 6 
 
 
 
 
 1. 
 
 2. 
 
 3. 
 
 4. 
 
 5. 
 
 6. 
 
 7. 
 
 8. 
 
 9. 
 
 10. 
 
 It thus appears contrary to the results of all experiments hitherto made on the small scale, 
 that the resistance of a well-shaped vessel does not exceed -j^th part that of a plane of the 
 same sectional area. 
 
 The above mean, being founded on several experiments, must be very near the truth ; 
 although in each so much error may exist, from the want of minute attention to the number 
 of strokes of the engine, as to afford no test of the best shaped vessel. 
 
 As, however, the results are very extraordinary, it may be well to submit them to a totally 
 independent mode of estimation. In the above investigation, the mean number of acting 
 paddles, with their corresponding velocities and areas, are compared with the sectional area of 
 the vessel and its velocity ; but we might have made the calculation in another way, that is, 
 by comparing the force necessary to urge a plane section equal to that of the vessel with the 
 velocity at which it passes through the water, with the actual power of the engine employed 
 to propel the vessel, which ought to give nearly the same fraction as the other method. 
 
 Of the whole power of the engine, we have seen that with the vertically acting paddle one- 
 third is lost by the retrograding of the wheel : in the Medea, therefore, the power employed 
 in propelling the vessel is two-thirds of 220 = 146 horse power: now the velocity of the 
 vessel having been 11-33 English miles per hour, or 16-62 feet per second, the resistance in 
 
 feet of water is 
 
 and in Ibs. rrr. x 62J, on each square foot. The number of 
 
 64i (341 
 
 feet in the section is 263, and the velocity in feet per minute is 997 ; the whole force, there- 
 fore, expended in a minute, is 70,796,970, which, divided by 33,000, gives 2150 horse power 
 for the force necessary to urge a plane section of 263 feet through the water at the rate of 
 1 1-33 miles per hour : but the vessel itself is urged with that velocity by the power of 146 
 horses ; the resistance to a vessel is therefore to that of a plane section of the same area as 
 
RESISTANCE OF STEAM VESSEL WITH PLANE SURFACE. 77 
 
 146 to 2150, or as I to 15 very nearly, which exactly agrees with the number given in the 
 table. The agreement is equally close in the Flamer ; and the mean obtained this way from 
 the whole set of experiments is very nearly the same as that given in the above table. 
 
 In this calculation the actual power of the engine is assumed equal to the nominal power ; 
 but it may slightly exceed it, but the degree will not be much when the loss from the air, 
 friction, 8tc., are deducted. 
 
 The valuable experiments on resistances made by the late celebrated Colonel Beaufoy, and 
 presented to his scientific countrymen, in a truly liberal manner, by his son, Henry Beaufoy, 
 Esq., enable us to put a third test upon the accuracy of the preceding deductions; 
 and it is very satisfactory to be able to confirm those extraordinary results on the authority 
 of his tables. 
 
 It has been found above, that to urge a plane section 263 feet area at the rate of 11 '33 
 English miles, or 9'84 nautical miles, per hour, through still water, would require 2150 horse 
 power. According to Colonel Beaufoy's results, it would require a power of 2444 horses, 
 which would give a still less fraction than a fifteenth ; but compared with a cylinder with flat 
 ends, the number of horses power is 2275, and the fraction greater than one-sixteenth, but less 
 than one-fifteenth, a confirmation which one could scarcely have hoped to have obtained. 
 
 These results are deduced as below. According to Colonel Beaufoy's experiments, 
 (Table 1. Part in.,) it requires a force of 203'79 Ibs. to urge a plane of one square foot 
 through still water at the rate of eight nautical miles per hour, or 810 feet per minute : now 
 the Medea moved with a velocity of 11-33 miles per hour, or 966 feet per minute ; it would 
 therefore require, according to Colonel Beaufoy, (the resistance being as the square of the 
 velocity,) 
 
 810* : 996 2 :: 203-79 Ibs. : 308 Ibs. 
 
 Now the section being 263 feet, the resistance per foot 308 Ibs., and the velocity 996 feet 
 per minute, 
 
 308 x 996 x 263 
 
 33,000 = 2444 ' 
 
 the number of horse power requisite to urge a plane section of this area at the given rate : 
 but if, instead of a mere plane, we take Colonel Beaufoy's experiments for a cylinder with 
 flat ends, we obtain the number of horse power 2275, as above stated. 
 
 If the results of Colonel Beaufoy's experiments had been made use of throughout the pre- 
 ceding investigations, the numbers in column 17. of Table II., and in column 4. of Table XII., 
 would have been increased by about one-seventh ; and in estimating the power exerted on the 
 paddles it would have been found to exceed the nominal power of the engines, which proves 
 that engines work above the nominal power. 
 
 [NOTE. In the paragraph at the foot of page 51, the author of this excellent paper appears to have disregarded the 
 inclination of the paddle-board with the radius, as far as it affects the power developed by the engine, and this will 
 have some degree of influence on several of his results. This was suggested to the author when the sheet was in the press, 
 and some explanatory remarks are appended at his request. If the tangential resistance to the motion of the wheel were 
 equal to the resistance to the transmission of the vessel, the ratio of the useful to the whole effect, would be precisely 
 that of the velocities of the vessel and wheel. But the resistance on the vessel is equal to the lateral pressure on the 
 wheel, and the tangential force by which the engine overcomes it, as the author shows at the top of the same page, 
 
78 APPENDIX. 
 
 is of less magnitude in the proportion of the cosine of the inclination (<f>) of the radius with the vertical ; so that the 
 power employed is less than of the effective power, or, which is the same, the effective power is more than jj of the 
 whole power. 
 
 To state the ease in symbols, we have the pressure of the engine necessary to overcome resistance = cos <f> ( V cos <f> 
 v) 3 , as stated in pages 50 and 51 ; and hence the whole power employed = 5 V cos. $ ( V cos # of = V 2 cos <f> 
 ( V cos <t> )*> where 2 is supposed to include the same expression for each of the paddles immersed at the same 
 time. But the horizontal pressure on the paddles = 2 ( F cos <p u) 2 , which being also the resistance on the vessel, 
 the effective power is v 2 ( Kcos <t> y) 2 . It therefore follows that the proportion of the effective power is, 
 
 effective power v 2 ( V cos <j> ) 2 
 
 whole power V 2 cos. <t> ( V cos <t> )" ' 
 
 which is necessarily greater than 
 Instead of the terms under 2, we may substitute the equivalent mean pressures for one paddle, viz. 
 
 effective power _ v , f d $ (V cos <J> c) a 
 whole power V f~d <J> cos <f> ( F cos <p ) 
 
 If we assume v = V, as stated in the paragraph referred to, the proportions of effective power at the four immer- 
 sions of Table III., page 52, calculated accurately in this way, come out -696, -701, -701, '690 ; Mr. B. gives them 
 
 all -666. When the immersion of the wheel is so much as to cause cos <t> to become less than -=> which occurs in the 
 
 two latter cases, it should be particularly remarked in taking the integrals, or calculating in any way from these 
 formulae, that the factor ( V cos <t> v)* should be accounted negative, as long as Kcos ^> t; is so, since under such 
 circumstances the paddle retards both the wheel and the vessel. EDITOR.] 
 
 IV. TIME AND TRAVERSE TABLE, 
 
 Calculated to show the advantage of sail on large SEA-GOING steam-vessels in 
 extended voyages, masted and rigged on the principle of spreading the 
 greatest quantity of canvas with the least possible resistance from masts 
 and yards when steaming. 
 
 BY CAPTAIN ROBERT OLIVER, R. N. 
 
 In well proportioned steam-vessels, under steam and sail, (being capable of making a 
 4 point course good, and from that to 5J points, acccording to the extent and force of the sea,) 
 the rate of speed is very considerably increased by sail, and great relief is thereby given to 
 the engines and vessel. 
 
TIME AND TRAVERSE TABLE. 
 
 79 
 
 It therefore becomes a consideration, when reduced to low rates under steam alone, by the 
 resistance of wind and sea, if by the assistance of sail and consequent increase of speed a 
 given point to windward cannot be made in equal or less time. For example, if the speed 
 from the above causes, in a direct distance of 2300 miles, be reduced to 3 knots per hour, 
 767 hours will be occupied in the performance ; but by making sail and a 4 point course, 
 (thus increasing the speed to 4| knots,) the same position will be gained in 723 hours, running 
 over a traverse distance of 3253 miles. 
 
 Again, should the wind enable the vessel to lay up 2 points from the direct course, at the 
 same increase of speed, it will be accomplished in 668 hours, running over a traverse distance 
 of 3005 miles. 
 
 Other speeds also afford relative advantages in the same manner ; and with the use of the 
 following table, they may be roughly estimated by inspection. 
 
 It being decidedly ascertained that H. M. steam-vessels of war, with wheels disconnected, 
 can work within 1 1 points of the wind, making 8 knots, consequently a 6 point course becomes 
 a free wind. When at and beyond that, the sails will frequently impel the vessel beyond her 
 maximum engine speed, whereby the whole expenditure of fuel, wear and tear, can be 
 saved. 
 
 These advantages are more applicable to long runs, where the wind is rarely right 
 ahead for any considerable distance, but veers so as to enable a long line to be made on one 
 tack or the other. For illustrations, see Plates XXVII. and XXVIII. 
 
 TRAVERSE TIME TABLE, for the purpose of showing the comparative advantage 
 obtained with a steam-vessel when upon an oblique course and assisted with 
 canvas, over the same vessel upon a direct course, without canvas, and with a 
 diminished velocity. 
 
 
 Distance 
 per log 
 run 
 through 
 
 Rate per hour in nautical miles. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 upon the 
 course. 
 
 3 
 
 i 
 
 4 
 
 44 
 
 5 
 
 51 
 
 6 
 
 q 
 
 7 
 
 71 
 
 8 
 
 8J 
 
 9 
 
 i 
 
 10 
 
 
 Miles. 
 
 
 
 
 
 
 
 Hours. 
 
 
 
 
 
 
 
 Direct distance . . 
 
 2300 
 
 767 
 
 057 
 
 575 
 
 511 
 
 460 
 
 418 
 
 383 
 
 354 
 
 328 
 
 307 
 
 287 
 
 271 
 
 256 
 
 242 
 
 230 
 
 1 point from the course 
 
 2705 
 
 902 
 
 773 
 
 676 
 
 601 
 
 541 
 
 492 
 
 451 
 
 416 
 
 386 
 
 361 
 
 338 
 
 318 
 
 301 
 
 285 
 
 270 
 
 2 
 
 3005 
 
 1002 
 
 858 
 
 751 
 
 6fi8 
 
 601 
 
 546 
 
 501 
 
 46? 
 
 4?P 
 
 401 
 
 376 
 
 354 
 
 334 
 
 116 
 
 300 
 
 3 . . .... 
 
 3190 
 
 1063 
 
 911 
 
 7Q7 
 
 709 
 
 638 
 
 A 80 
 
 53? 
 
 4<11 
 
 456 
 
 .m 
 
 fl< 
 
 S75 
 
 T>f> 
 
 136 
 
 319 
 
 4 
 
 3253 
 
 1084 
 
 P?0 
 
 HI; 
 
 Tf,"\ 
 
 651 
 
 iPl 
 
 542 
 
 501 
 
 465 
 
 41*1 
 
 407 
 
 SRI 
 
 361 
 
 34? 
 
 325 
 
 
 4140 
 
 1380 
 
 1183 
 
 1035 
 
 920 
 
 828 
 
 753 
 
 690 
 
 6^37 
 
 591 
 
 552 
 
 517 
 
 487 
 
 460 
 
 436 
 
 414 
 
 
V. MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA, 
 
 DURING A SERVICE OF NEARLY FOUR YEARS. 
 
 BY THOMAS BALDOCK, LIEUT. R.N., K.T.S. 
 
 HAVING been enabled to lay before our readers a set of plan drawings of the splendid steam 
 ship of war Medea, we annex a brief memoir of facts connected with that vessel, and her perform- 
 ance under a variety of circumstances, which may we trust be interesting to those who take into 
 consideration the extraordinary revolution which the steam engine is accomplishing in nautical 
 affairs ; not only in abridging time and space, and thus bringing distant nations into close com- 
 munion with each other, but in its scarcely less important application, when allied to our fleets 
 as a powerful auxiliary in war : and although the philanthropist will not view these con- 
 sequences with the same complacency, that attends the contemplation of the benefits which 
 the agency of steam confers upon mankind, yet this subject may be favourably considered, 
 under the conviction, that the most effectual way of preserving peace, is to be prepared at all 
 times for war. The change, therefore, which the steam engine must effect, in the tactics of 
 naval warfare, cannot be viewed with indifference in a country whose " best bulwarks are her 
 wooden walls." 
 
 Previous to the year 1 830 the Government only possessed a few small steamers, which were 
 principally employed for the purpose of towing ships in and out of harbour, and other trifling 
 services on the coast, with an occasional voyage to Lisbon or Gibraltar. These vessels were 
 built very strong ; and although it became necessary, in the first instance, to employ them 
 in the conveyance of the Mediterranean mails, on the adoption of steamers for that service, 
 they were removed to other duty as soon as more competent vessels could be built expressly 
 as packets. 
 
 About the year before mentioned, the Admiralty having judiciously determined to add a 
 small squadron of steam cruizers to the navy, gave directions for the construction of a steam 
 ship of war, at each of the king's dockyards, the form, scantling, and internal arrangements, 
 being left in a great measure to the judgment and skill of the master shipwright of the yard 
 at which each vessel was designed and built ; well considering, that although many private 
 steamers then existed, even of the size suitable for war purposes, which vessels, from the ex- 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 81 
 
 cellence of their performance, appeared to realize the perfection of what we may call the art of 
 steam navigation in its then state of advancement, yet that the necessary qualifications for an 
 armed ship of any sort, particularly for distant cruizing and extended voyages, with a power- 
 ful armament and large crew, differed so essentially from those of a merchant vessel, as to 
 render it extremely dangerous to follow without variation even the most approved plan 
 of any commercial steamers, whose sole object was the conveyance of passengers and 
 cargo on coasting voyages, never at that time extending beyond four or five hundred 
 miles, and throughout the whole of which route, they generally had some port of refuge, 
 to which they might have recourse, either in extremely bad weather, or for a supply of fuel if 
 necessary. 
 
 In carrying into effect this plan of building a few war steamers, it became important that 
 they should be so constructed as to be able to cruize, and make long passages under sail 
 alone ; it being obvious that if a war steamer is to be dependent on the power of her engines 
 for every movement, she will in all probability exhaust her resources, before arrival at her 
 scene of action. To accomplish this end, therefore, became of vital importance, and it was 
 considered unavailing for them to possess good steaming qualities, without they were in all 
 respects quite competent to act as sailing ships of war. 
 
 Although it is unnecessary to state here all the particulars in which the construction of 
 ships of war differs from that of merchant vessels, there are some important features which so 
 much affect steamers, and have so great an influence on their character as such for velocity, 
 when competing with passenger vessels or packets, that we deem it necessary to advert to 
 them here. 
 
 The war steamers being armed with the heaviest description of guns, one of which, weighing, 
 together with its carriage, more than six tons, is placed at each extremity of the vessel, with 
 others of somewhat less weight on the sides, it becomes necessary to afford the proper support, 
 not only when steaming in an upright position, with the centre of gravity of the displacement 
 in the plane of the keel, but perhaps engaging when under sail, with a considerable inclination, 
 and the whole weight of ordnance probably on the lee or depressed side. It is necessary, we say, 
 from these considerations, and others connected with the ponderous appurtenances of war ships, 
 among which may also be named the additional number and weight of the anchors, which are 
 always carried on the ship's side, that all the superstructure, or the whole fabric above the 
 water, should be very much stronger, and therefore heavier, than is required in any steam 
 vessel carrying passengers, or even a heavy description of cargo, which being always stowed 
 below, admits of the upper works being slight. It is also indispensable that the war vessel 
 should have a high and strong bulwark or " berthing," to afford shelter to the crew in time 
 of action : and, above all, it is necessaiy that the form of the ship should vary considerably 
 from that most calculated to insure velocity, when, as in the case of steamers, it is derived 
 from a self-contained motor, instead of being dependent on the influence ol' the wind, on sails 
 attached to the lofty and weighty masts, &c. of a sailing vessel, the oblique action of which 
 in most instances tends as much to depress the ship, as to propel her on the line of keel. Thus, 
 any vessel intended to act either as a sailing ship or steamer, must, to insure her being a 
 good sea boat, have greater stability, and more breadth of beam, than is required for one 
 
 I 
 
82 APPENDIX. 
 
 dependent entirely upon the engines. It is scarcely necessary to add the conclusions to 
 which this argument leads, or to state that these important essentials must considerably 
 diminish the steaming speed of a war steamer. 
 
 We should not have thought it requisite here to refer to these peculiarities of construction, 
 were it not for the many aspersions which have been cast upon what we may presume to call 
 the architectural qualities of the Government steam marine, by those who apparently have 
 never taken into account the matter to which we have alluded, and who have generally been in 
 the habit of estimating the qualities of steamers entirely from the rate at which they would, in 
 an upright position, be propelled by the engines, omitting in a great degree the consideration, 
 that the sharp narrow vessels in which the greatest steaming speed is obtained, are not well 
 adapted for general ocean navigation, and that although they may succeed for a long time 
 in making favourable passages, they must, in the event of any failure of the engine, or the 
 supply of coals in a gale of wind, become unmanageable logs on the water. We need not 
 advert to facts in verification of this opinion, which must be allowed by all seamen ; though 
 we are quite prepared to prove that the case to which we have just adverted, has occurred to 
 some of the best and fastest commercial steam vessels, and yet to admit that they have been 
 and are likely to be of rare occurrence, as in such vessels the engines are examined, and, if 
 necessary, refitted at the termination of every passage they make ; and thus incipient defects 
 are checked or remedied, and their frequent access to a depot for coal renders the failure of 
 fuel improbable. Thus their plan of construction may be proper for the service to be performed, 
 however unfit it is for steam ships of war. 
 
 In pursuance of the Admiralty arrangement to which we have referred, the Dee, Phoenix, 
 Salamander, Rhadamanthus, and Medea, were constructed. The first-named four vessels 
 appear to have answered well ; but there is no doubt that the Medea, designed and built 
 by Mr. Lang of Woolwich dockyard, is the most perfect of this flotilla, not only having 
 evinced admirable qualities when impelled by steam, (under which circumstances she is 
 equal to the best sea-going steamers,) but shown her capability under sail, to keep com- 
 pany with any squadron of Her Majesty's ships, either in blockading an enemy's port or 
 making a passage across the ocean, being thus enabled to convey her energies unimpaired 
 to the most distant part of the world, and always ready to put forth that giant force, which 
 the agency of steam affords, when occasion may require it. 
 
 Few seamen would believe, when looking at a steamer, with her lumbering paddle-boxes, 
 wheels, and apparently jury-rigging, that this can be the case. We have, however, ample 
 proof, that the Medea has, under sail alone, with the wheels revolving loosely in the 
 water, beat several of our best ships of war. 
 
 The Medea fell under the control of an officer (commander, H. Austen) whose talent 
 and perseverance have rendered evident all those good qualities of the ship, which under 
 less able management might not have been so obvious; and has proved, that the naval 
 superiority this country so justly boasts, is not likely to suffer either in the construction or 
 tactics of our steam marine. 
 
 This ship was launched at Woolwich in September, 1833, and immediately fitted with two 
 engines of 110 horse power each, by Messrs. Maudslay and Field, who had supplied those 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 83 
 
 to the other four war steamers, and who had succeeded by their adaption of boilers, 8tc. in 
 producing the best possible effects with the least proportion of fuel then known ; the wheels 
 being according to the plan of Mr. Morgan, with the revolving vertically acting paddle, of 
 which a full description is given in another part of this work. 
 
 The masts, sails, and rigging, as well as the internal fittings, were principally propor- 
 tioned by the constructor, assisted by such modifications as the skill and experience of Capt. 
 Austen, and Mr. Peacock, the able master of the vessel, suggested. It will not be uninte- 
 resting to our nautical readers to state, that the Medea has three masts, the foremast being 
 rigged nearly as that of a brigantine ; the mainmast and mizenmast having each a lower 
 gaff- sail and gaff- topsail ; the arrangement of the standing and running rigging being so 
 adapted, that the upper masts, yards, &c., may be lowered to the deck with the greatest 
 facility, and again reinstated with little labour, thus affording the least possible resistance 
 when steaming head to wind, and yet spreading a large quantity of canvas, when under sail, 
 and all the gear in its place. 
 
 The armament consists of two guns of great calibre, capable of carrying heavy shot fur- 
 ther than the range of the largest guns in use in sailing ships of war, and also calculated 
 to throw shells : besides these heavy pieces of ordnance, which are mounted on pivots, 
 one before the foremast, and the other abaft the mizenmast, she has less guns of con- 
 siderable weight, intended to be " transported" about the deck as occasion may require, 
 with a full proportion of small arms for a crew of 120 men, for the purpose of repelling 
 boarders, should unforeseen and improbable circumstances place her in close contact with a 
 heavy vessel of war, the obvious tactics of a war steamer being to keep out of range of an 
 enemy's guns, which she may always do by maintaining a position in the wind's eye of an 
 opponent, and assailing her adversary with very little chance of receiving any damage in 
 return, a good steamer having no difficulty in keeping to windward of the best sailing ships, 
 even in strong winds : and it is quite evident that in a calm the steam vessel may take any 
 position she pleases. 
 
 By the seaman this will be well understood and admitted ; but we may be excused in 
 digressing to inform those less acquainted with nautical affairs, that, during the late wars, 
 particularly in the Baltic and Straits of Gibraltar, much serious damage was done to some of 
 our largest ships of war by the attacks of gun-boats during calms ; and the writer of this 
 article was once in a corvette, mounting eighteen guns, that was assailed, in a moderate 
 breeze, by a small schooner with only one long gun, which vessel being enabled by her supe- 
 rior sailing to keep out of range of the corvette's carronades, maintained for some hours a most 
 destructive action, in which the latter lost a lieutenant and twelve seamen, without having the 
 power of inflicting the slightest punishment on her pigmy and audacious opponent. 
 
 Previous to entering into any particulars connected with the performance of the Medea, we 
 shall give the dimensions of the ship and engines, together with the immersion or draught 
 of water, the proportion of fuel carried and consumed in given times and distances, and such 
 other facts as appear to have reference thereto. 
 
84 APPENDIX. 
 
 DIMENSIONS OF H. M. STEAM FRIGATE MEDEA. 
 
 Feet. Inches. 
 
 Length extreme 206 
 
 ,, between perpendiculars ...... 
 
 ,, of keel for tonnage ...... . . 157 OJ 
 
 Breadth extreme over paddle boxes . 46 
 
 ,, inside ,, ,, . . 31 11 
 
 ,, ,, including sponsons ........ 42 
 
 Burthen, old measurement, 835 tons. 
 new 807 . 
 
 Breadth of engine room, including boilers, but exclusive of coal bunkers . . 22 
 Length of engine room, including boilers . . . . . . . . 61 9 
 
 Quantity of coals stowed in the bunkers within this length . 200 tons. 
 ,, ,, in coal room forward . . 35 ,, 
 
 ,, ,, ,, aft . . . . 40 ,, 
 
 bags on orlop docks . . . . 45 ,, 
 
 With the armament complete, 320 tons of coal, 18 tons of water, and three 
 
 months' provisions for 120 men, the immersion is, forward . . . . 13 10 
 
 abaft . . 14 6 
 
 The upper part of the boilers are then above water line . . . . .26 
 
 The upper part of the steam chest is ..69 
 
 The centre of paddle shaft is ,, 67 
 
 The summit of the water in boilers is 09 
 
 The dip of the paddle floats with the above immersion is .... 5 8 
 
 THE ENGINES AND BOILERS. 
 Power, 220 horse. 
 Diameter of cylinder ... ..... 4 6 
 
 Length of stroke 50 
 
 Diameter of the wheels 24 6 
 
 Length of the paddle boards ... ... . . 5 7J 
 
 Breadth ,, ,, ..... -...46 
 
 Minor diameter of elliptical funnel ......... 4 
 
 Length of funnel above the deck 32 
 
 Weight of the engines 165 tons. 
 
 >t boilers ...... . . 35 ,, 
 
 water required in boilers 45 
 
 good water distilled daily from cylinder jackets or casings . 4 ,, 
 Maximum number of revolutions made by the engines per minute, 22. 
 Average consumption of good coal for each horse power per hour, 8 Ibs. * 
 
 per day, working at full power, 18 tons 17 cwt. 
 
 Number of days' coal carried in the vessel, with the armament on board, supposing her work- 
 ing at full power the whole time, 17. 
 
 1 With the best coal 7 Ib. per horse power each hour, was sufficient. 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 85 
 
 Expence in money, (English prices,) of coals and engine stores, (say tallow, &c.) . s. d. 
 
 24 hours' steaming 16 12 
 
 ,, per mile, about . 1 1\ 
 
 ,, ,, (Malta prices,) 24 hours . . 24 10 
 
 ,, per mile, about . 2 4| 
 
 Rate of steaming, with 320 tons of coal and war equipment on board, in a calm, 8J- knots per hour. 
 ,, ,, when lightened by the expenditure of one-third the fuel 9|- ,, ,, 
 
 ., ,. of two-thirds 10 ,, ,, 
 
 She will therefore go at 8' knots an hour about 1190 
 ,, ,, at 9 knots an hour ,, 1258 
 
 at 10 knots an hour 1360 
 
 Thus accomplishing the distance of 3808 knots, or geographical miles. 
 
 Each rate being attained by a gradual progression, as the ship lightens from the expenditure 
 of coals, and as the latter part of the distance may be at a speed even above ten knots ; some 
 addition should be made to the gross amount above stated : it must however be observed, 
 that the experiments from which the foregoing data are taken, were all made in calm 
 weather; but, as the consumption of fuel is by a judicious arrangement of the dampers, and 
 by slackening the fires, considerably lessened as the speed is diminished from the violence of 
 the wind or sea, we may safely state, that the Medea is competent to undertake any voyage 
 of at least 3000 miles, except a westerly passage across the North Atlantic in the winter 
 season ; at which period of the year the ocean between England and America is swept with 
 scarce an intermission by violent westerly gales, creating waves which, even supposing the 
 temporary cessation of the wind, must oppose an effectual barrier to the favourable operations 
 of any steamer. We by no means presume to state that the voyage cannot be made, or these 
 difficulties safely overcome, by a powerful vessel with a large supply of fuel ; but her progress 
 at times must be very slow ; and though, no doubt, in such a case she might cross the 
 Atlantic in much less time than a sailing ship under similar circumstances, it would be at a 
 speed far below the usual rate of steaming voyages. 
 
 It is proper to state, with reference to the coal carried by the Medea, that the weight of 
 the armament and war materiel is quite equal to 50 tons, and consequently, that if disarmed, 
 she could carry fuel without being further immersed in the water, or her progress thereby 
 impeded, sufficient for a voyage the extent of which may be at least 500 miles more than the 
 distance before stated : she might therefore be sent to the West Indies with despatches, or 
 even troops, at a few hours' notice, almost with a certainty of reaching Barbadoes, or any 
 other of the windward islands, in nineteen, or at most twenty, days, under the average 
 circumstances of weather usually experienced in that voyage. 
 
 Speed of the Medea with the wheels detached from the engine, and revolving by the reaction 
 
 of the water as the ship is impelled by the influence of the wind on her sails. 
 Blowing strong, smooth water, close hauled " within " 6 points . . 8 knots 
 Blowing strong wind on the quarter ....... 
 
 1 Including cost of conveyance to, and stoppage at, Malta. 
 
86 APPENDIX. 
 
 f 
 
 Before entering into any particulars of this vessel's service, from the time she was first 
 
 commissioned in February, 1834, until she was dismantled in October, 1837, we think it 
 important to state, that during the three years of this time which were spent in the Medi- 
 terranean, neither the engines nor boilers underwent any other repairs than such slight work as 
 was effected by the engineers of the ship, without any extraneous assistance whatever : and 
 moreover, that on her being paid off, as before referred to, (having been in commission rather 
 a longer time than is usual for ships of war in peace,) the machinery and boilers were found in 
 such excellent condition as to require very little refitting, a circumstance not less creditable 
 to the original constructors than to the engineers on board, and to the able system and 
 management of the commander and officers, who thus maintained the vessel on a distant 
 station for a long space of time always ready, and frequently performing important services, 
 though left entirely to their own resources. 
 
 During the early part and summer of 1834, she was principally employed on various duties 
 on the coast of England, and in performing one voyage to Bilboa and Corunna. On the 5th 
 of October of that year the Medea left Plymouth to join the squadron in the Levant, and 
 accomplished the voyage out to Malta in ten days and five hours, the wind being generally 
 contrary during the passage, and for two days having to contend against a fresh gale ahead, 
 the other eight days being for the most part moderate. On this occasion five hours were 
 lost by a stoppage to effect certain adjustments in the engines and boilers, and two hours from 
 circumstances unconnected with the engines or vessel. The distance of 2100 miles from Ply- 
 mouth to Malta was thus effected at the average rate of 8'82 geographical miles per hour, 
 under circumstances by no means favourable, the ship having coals enough on board at the 
 termination of this run for a voyage of 1000 miles additional ; fully corroborating the state- 
 ment we have before made, of her ability, with a full armament on board, to steam at least 
 3000 miles under ordinary circumstances without any additional supply of fuel. 
 
 After completing the coal at Malta, the Medea proceeded to join the fleet under Sir Josias 
 Rowley, then assembled at Vourla Bay, in the neighbourhood of Smyrna, and at once took 
 her place as a cruizing ship in the squadron, performing under sail all the evolutions usual to 
 ships of war, either when proceeding from place to place, or cruizing, and maintaining a posi- 
 tion as in front of an enemy's port. To effect this object, and yet to enable the vessel to 
 resume her service as a steamer at short notice, it became necessary that the engineers and 
 their assistants should be well exercised in the duty of connecting, and detaching the paddle- 
 shaft, in order that the wheels should be free to revolve when the ship was under the influence 
 of sail alone, and speedily re-attached if necessary. The particular arrangement by which 
 the cranks are united to the machinery in the engines constructed by Messrs. Maudslay and 
 Field, rendered this operation more facile than where a different modification is adapted ; 
 and after some practice on board the Medea, it was found, that the wheels could be detached 
 under favourable circumstances in five minutes, and united again to the engines in a scarcely 
 longer time. 
 
 We should however observe, with reference to this part of our subject, that the wheels 
 with the paddle-boards in place, must tend in a great degree, in light winds particularly, 
 to lessen the speed at which the vessel would attain under canvas, if the boards were displaced, 
 besides effecting the concomitant evil of considerable wear, and consequent deterioration, 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 87 
 
 more especially to the machinery of the vertical paddle ; and although the experiment 
 of this vessel fully proved, that the resistance which the paddle-boards afforded, did not prevent 
 her from keeping company with the squadron, and, in some instances beating them, yet it is 
 evident, in making long passages under sail, that it is desirable at least the lower float 
 boards should be removed ; and we have the authority of Captain Ramsay, 1 late commanding 
 Her Majesty's steam vessel Dee, (which vessel is fitted with the old radial wheel,) for stating, 
 that "in common weather the paddle-boards could be shipped in about an hour, and un- 
 shipped or detached in half that time." It was found in the Dee that under canvas, with 
 the paddle-boards removed, her best point of sailing, as compared with other ships, was during 
 light winds ; whereas in the case of the Medea, with the boards in place, the velo- 
 city of the ship in very light airs, being insufficient to overcome the friction of the wheels, 
 they did not revolve, and consequently in most such instances, she was in the rear of 
 the squadron. 
 
 We have no reason to believe, that the floats of Mr. Morgan's vertically acting paddle require 
 a very much longer time for removal, than those of the old construction ; although it is proper 
 to observe, that, if removed, the heavy iron work composing the revolving apparatus would 
 oppose a greater resistance to the ship's progress, than the naked framing of the radial 
 wheel. Still as the Medea's disparity of rate was so small with the boards in place, it is 
 most probable that if they had been removed, she would have been quite as equal to sailing 
 ships in light airs, as she evidently was, (even with their obstruction,) in fresh winds. And 
 as the steam could never be raised from cold water in so short a time as that stated by 
 Captain Ramsay, to be occupied in unshipping the paddle-boards, we might from these 
 premises come to the conclusion, that in all cases when a steam vessel is required to act 
 under sail, the paddles ought to be removed. We are, however, very doubtful, that it would 
 be proper to establish this as a general rule under all circumstances, particularly when the 
 service of the ship is such that she may be required, at the shortest possible notice, to resume 
 her steaming duties. It must be quite obvious to the seaman, that cases may occur in which 
 it would be extremely difficult, if not absolutely impossible, to re-attach the boards ; and 
 whenever the ship has any considerable motion from the waves, it must always be done at 
 some degree of risk to the men employed on the duty; whereas, under similar circumstances, 
 the wheels can always be connected with the engine, in less time than would be occupied in 
 getting up the steam. 
 
 As the vertical paddle is more effectual in propelling, so also it does not offer so much 
 resistance when revolving freely in the water, being easily set in motion when the ship's 
 movement, under the influence of the wind, opposes its surface to the fluid. As the ad- 
 vantages, therefore, of detaching the boards from these wheels, is less than in the old ones, 
 and the difficulties of doing so (though in a very slight degree) greater, 1 the propriety of 
 their removal in all cases becomes more doubtful ; and we are quite sure that the plan would 
 
 1 Vide Nautical Magazine, Jan. 1838, page 49. 
 
 * Captain Ramsay states, in the paper above referred to, that " the Medea, having Morgan's wheels, the removal 
 of the paddle-boards was almost out of the question, as the iron work left would have produced nearly as much 
 resistance." We are induced to attribute his objection as much to the difficulty he conceives attendant on their 
 removal, as to the resistance the iron work affords; it being quite evident, that as the iron work cannot obstruct the 
 
88 APPENDIX. 
 
 have been adopted in the Medea, had its benefits been commensurate with the in- 
 convenience. 
 
 The first trial of sailing after the Medea joined the squadron was on the 3rd of 
 November, in company with Her Majesty's ships Scout, Childers, and Columbine. These 
 vessels being ordered on some detached service, it was considered a good opportunity, as the 
 wind blew directly into the Bay of Smyrna, for the steamer to test her qualities of " beating" 
 to windward with such fast-sailing ships ; and we accordingly find that, although labouring 
 under all the disadvantages of a first experiment, which the seamen will not fully appreciate, 
 she was, with wheels revolving loosely in the water, nearly equal to both the first-named 
 vessels, and only beaten in any very decided degree by the Columbine, built by Sir William 
 Symonds, the present Surveyor of the Navy. Having gained the outside of the bay, the ships 
 proceeded towards their destination, and the Medea remained for some hours exercising the 
 crew, in performing the evolution of " tacking," and in developing such modifications as might 
 be applicable in the performance of her duties as a sailing ship of war, of which she had 
 hitherto had no practice. It was ascertained that, with the moderate breeze then blowing, 
 she made nearly a straight course at five points from the wind, and meeting with two Greek 
 polaccas, well known to be fast vessels, she joined company, beat them both " on a wind," 
 and returned to the anchorage at Vourla. 
 
 Several trials of sailing were afterwards made in company with the squadron, and on the 
 20th of November and 16th of December the Medea beat through the narrow entrance of 
 Smyrna harbour, against a strong wind in both cases ; in the first instance alone, and on the 
 second occasion, in company with Her Majesty's ships Beacon and Mastiff, both of which she 
 considerably outsailed, and " weathered" upon. 
 
 On the 8th of January, 1835, the whole squadron left Vourla, and gained the open sea by 
 " tacking" out of the bay, and on that day the following entry appears in the steamer's 
 log-book : "Tacked occasionally find we both 'weather' and 'fore-reach' on every ship in 
 the squadron," the wind at the time being moderate. During the passage to Malta it was 
 thought necessary, in order to preserve her exact position in the order of sailing, in light 
 winds particularly, to use the steam from one boiler, with one wheel occasionally. The 
 connecting and disconnecting of the paddle-shaft with the machinery occupied in no 
 instance more than twenty minutes, and on some occasions as little as five ; the expense of 
 coal when at work being somewhat less than three bushels an hour, and while the fires were 
 " banked up," (t. e. sufficient fire retained under the boiler to keep the water nearly at boiling 
 heat, ready to generate steam at short notice,) half a bushel per hour sufficed. The whole 
 quantity of coals expended during this voyage of eleven days was sixteen tons, about one- 
 third of which quantity was used in keeping the water warm while the steam was not in 
 operation. 
 
 ship's progress, so much as the boards would do, their being displaced must therefore, to a certain extent, be 
 beneficial ; yet it is but fair to state, on the authority of Mr. Morgan, that " it will occupy about the same time 
 for the removal of each board from the patent wheel, as the common one ; and as the patent wheel has fewer paddles, 
 they can of course be sooner removed." To the above we may add the opinion of Captain Austen : " The radius rods 
 and principal working machinery of Morgan's wheel may be displaced or reinstated with great ease ;" in which case 
 the bare skeleton would afford less resistance than the naked framing of the common wheel. 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 89 
 
 It was found that in adopting this clever expedient of working only one wheel with such an 
 insignificant expenditure of fuel, very little inclination of the helm was required to preserve 
 the line of the ship's course. In steady breezes on this passage she frequently, under sail 
 alone, beat the large ships "on a wind;" and during a moderate gale on the "quarter," 
 without any assistance from the steam, she averaged ten knots for twenty-four successive 
 hours, the only vessel having an advantage over her being the Columbine, which ship 
 out-sailed her in a slight degree. On arriving near Malta on the J8th of January, the fleet 
 were becalmed about ten or twelve miles from the port, when the Medea, having "got the 
 steam up," took the ships successively in tow and brought them into the harbour, towing the 
 Caledonia at the rate of three and a half, and the two-decked ships four miles an hour, the 
 speed being much impeded by a heavy north-west swell. We may here state that in a calm, 
 with smooth water, the Medea could tow a line-of-battle ship at the rate of six miles an hour; 
 but the influence of the slightest wave on the hull of a large ship caused a more than 
 corresponding diminution of progress. 
 
 The squadron now remained at Malta until the 8th of February, when intelligence arrived 
 from the Levant of such a nature as to render it expedient that the fleet should forthwith 
 proceed to sea. The wind, which had been violent from the north-east, was still blowing 
 freshly up the harbour, and the heavy swell, which, rolling in from the Mediterranean, spread 
 over the whole surface of the narrow entrance, rendered it impracticable for the ships to 
 " beat" through. Thus if an enemy's force had been outside the port, it would have been 
 impossible for the most able officer or skilful tactician to have suggested any means by which 
 the British fleet could have been extricated from their land-locked position, and they must of 
 necessity have been idle spectators of any devastation, which a squadron, possibly of inferior force, 
 might have been committing outside the harbour. Here then an important -case occurred, in 
 which was to be proved how far the agency of steam would be effectual, in rendering 
 assistance to large ships of war under some of those peculiar circumstances, to which, by 
 casualties, or the nature of their service, they are not unfrequently exposed. 
 
 It was nothing new for steam-vessels to tow ships in and out of port under ordinary 
 circumstances, and most naval officers had contemplated the advantages that a fleet would 
 derive in a general action, from the co-operation of a few steamers ; still it was doubtful if it 
 would be possible to tow a first-rate ship against any considerable force of wind and wave, or 
 that it would have been in the power of any steam-vessels to have prevented the calamitous 
 wrecks which occurred after the battle of Trafalgar. The facts, however, we have now to state 
 fully prove that, had three or four such ships as the Medea been attached to Lord Nelson's 
 fleet, most of those prizes which in their dismantled state were either wrecked in the neighbour- 
 hood of Cadiz, or recaptured by drifting within its bay, would have reached a British port as 
 proud trophies of that eventful day. All required was the removal of the disabled hulks to 
 such a distance from the land as to place them in safety during a temporary refitment, and to 
 afford time for rigging jury-masts, &c. ; which service might therefore have been effectually 
 rendered to three or four ships successively, by one steamer. 
 
 In thus referring to the co-operation of steam-vessels in a sea-fight, we have supposed them 
 to be kept aloof during the action, prepared only to give assistance afterwards, either by 
 securing prizes or rendering aid to disabled ships ; but the history of our naval warfare affords 
 many instances in which the presence of a few steamers might have changed the whole tide 
 
90 APPENDIX. 
 
 of battle, for instance in light winds, as in the action of Trafalgar, by bringing up the 
 sternmost vessels of the fleet, or afterwards, during the continuance of the engagement, 
 removing a disabled ship from a perilous position. Thus had a steamer been lashed alongside 
 the Prince, of 98 guns, she might have been brought up to the fight, in which she could, 
 from the lightness of the wind, unfortunately take but little part ; and the same facility being 
 rendered to the other sternmost ships, they might, in a greater degree, have participated in that 
 glorious day, whilst the steamer, being sheltered by the larger hull of a line-of-battle ship, 
 would have been in little danger. The statement we have thus made, however, includes but 
 a small portion of the beneficial co-operation of steam power in such instances; and it would 
 be foreign to our purpose to enter upon the subject at large ; although we are induced to 
 allude to the case of the Belleisle and Bellerophon in that great sea-fight, particularly the 
 former vessel, which, after she was dismasted, lay an unmanageable log upon the water, for 
 some time exposed to the attack of four ships, each her superior in force ; and though, in the 
 service of extricating this ship from the position in which she was so nobly defended, the 
 steamer would have been- in a situation of greater peril, yet the intrepidity of British seamen 
 would not have failed to accomplish it. 
 
 The squadron, assembled at Malta on the 8th of February, and which it was deemed 
 necessary should at once proceed to sea, consisted of one first-rate and five eighty-gun ships. 
 The Medea, having been rapidly prepared and the steam " raised," was attached to the 
 Caledonia of 120 guns, and the ship cast loose from her moorings : the sea at this time was 
 beating nearly over the turreted battlements of St. Elmo, and throwing its spray into the 
 opposite fortress of Ricassoli ; while further up the harbour the half-spent surge rolled into the 
 embrasures of the low batteries of St. Angelo, causing the ships to ride uneasy even at their 
 secure and sheltered moorings. Expectation was raised to its highest pitch, and the enthusiastic 
 population of La Valette flocked to its ramparts as they were wont to do, when, in the olden 
 time, the proud soldiers of the Cross proceeded forth in their galleys, arrayed in all the panoply 
 of war, to chastise the marauding infidel. Many were the doubts raised as to the possibility of 
 the Medea towing this immense fabric against the fresh wind and beating sea which opposed 
 her egress, particularly when, on reaching the narrow part of the entrance, the Caledonia was 
 seen to pitch heavily, as she encountered the full force of the wave, which rolled in from the 
 open Mediterranean. Still they kept on at a rate never less than two miles and a half an 
 hour; and in seventy minutes from the time that this heavy vessel was loosened from her 
 moorings, the steamer cast off', and, having thus left her sufficiently distant from the land to 
 be safely navigated under sail, returned into harbour for another ship. In this manner all 
 the fleet were taken out, the whole being effected in four hours and ten minutes, after which 
 the fires were extinguished on board the Medea, and she pursued her course as a sailing 
 vessel in company with the squadron ; the whole cost of coals and other engine stores 
 expended on this occasion amounting only to 3. 6s. 1 
 
 1 Although it is not our purpose to give a history of the Government steam marine, we are induced to record another 
 instance in which the efficiency of an Admiralty steamer was fully tested. 
 
 In March, 1832, on the first alarm of cholera in this country, the transport-ship, William Forbes, of 600 tons, left the 
 river with convicts to proceed to New South Wales, and put into Plymouth Sound, in consequence of some cases of 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. ' 91 
 
 The ships now proceeded towards Vourla, where they arrived on the 14th of February, 
 the steam not being used on board the Medea during the passage, she having sailed 
 186 miles in one day, for 19 hours of which a straight course was made within 6 points from 
 the wind. 
 
 It is worthy of observation, that on the crew becoming expert in " working " the ship, and 
 as the various modifications incidental to her new character as a sailing ship were adopted by 
 the skill of the commander and officers, she improved in all points ; and thus we find, on this, 
 her second passage of any length with the sailing ships, it was not found necessary to light 
 the fires at all, although they met with every variety of weather from a calm to near a gale, 
 and contrary as well as fair winds were experienced. 
 
 During the return voyage with the admiral to Malta, which occupied from the 7th to the 
 20th of March, an attempt was made to navigate the ship with the lower paddles removed, 
 without unconnecting the shaft; and in light winds some advantage was perceptible. They were, 
 however, re-attached before the end of the passage, and the wheels allowed to revolve as 
 heretofore. 
 
 On the 12th of May the fleet again left Malta and proceeded to Salamis. During the light 
 winds that occurred on this route, the Medea was not able to keep up with the sailing ships, 
 and at times lost sight of them, the "way " of the vessel being insufficient in several instances, 
 from the faintness of the wind, to cause the revolution of the wheels. On this occasion, as also 
 on many others, she went to sea with her full complement of coals and stores on board, and 
 was consequently much immersed in the water, which would considerably influence her 
 sailing qualities, particularly in light winds. It appears that her best sailing trim was, (as in 
 the trial of the 6th July, 1837, to which we shall afterwards refer,) when about 100 tons 
 short ; and if we consider how easily this or even a much larger quantity of coals would, 
 without inconvenience, be carried in bags distributed among the large ships of a squadron, it 
 will hardly be said she is unable to accompany a fleet on distant service without using steam. 
 Thus, for instance, she certainly might have attended Lord Nelson on his celebrated chase to 
 
 that epidemic appearing on board. Immediately on the arrival of the ship being known, she was ordered by the 
 authorities to proceed to the lazaretto either at Standgate Creek or Milford, it being contrary to law, for any vessel 
 having a malignant disease on board, to remain in a port unprovided with such an establishment. The wind was 
 blowing so strong from the south-west, and causing such a high sea, that it was impossible for the ship to " beat" out 
 of the Sound for the purpose of proceeding to either of the above-mentioned places ; but the inhabitants of the town 
 and neighbourhood were so much alarmed that the port-admiral was requested to afford a steamer, in order that, if 
 possible, she might be towed to sea, though the force of the wind and waves rendered the experiment extremely 
 doubtful. The only government steam-vessel at that time in Plymouth harbour was the Firebrand, a new Medi- 
 terranean packet ; and although this vessel was at the time undergoing some refitment at the dock -yard, the case was 
 considered of such importance, that she was immediately prepared for service, the fires were lighted, and in a very short 
 time she was anchored in the Sound about half a cables' length a-head of the transport's buoy, the sea at that time 
 making a fair breach over the bows of the latter vessel. The steamer having been veered tolerably near to the ship, 
 proper ropes were attached, and the paddles being set in motion, she was thus assisted up to her anchor; both vessels 
 weighed at the same time, and though the progress was at first so slow that near an hour elapsed before the breakwater 
 was passed, yet in little more than four hours the ship was towed a sufficient distance from the land to enable her to 
 prosecute her voyage under sail alone, and the steamer returned into port. It is proper to state that the Firebrand is 
 a vessel of 550 tons, and had at that time engines of only 140 horse power, constructed by the Butterly Company, 
 and was then fitted with the old radial wheel, which is certainly not so well adapted for towing ships as the verti- 
 cally-acting paddle invented by Mr. Morgan. 
 
02 APPENDIX. 
 
 and from the West Indies without occasioning any delay, and would always have been ready, at 
 short notice, to have been detached to the distance of at least 3000 miles, and have 
 required only an hour and a half's preparation, to render her powerful assistance on the day 
 of battle. 
 
 On the 28th of May the Medea went into the Piraeus, received the King of Greece on board, 
 and conveyed him to the French, Russian, and English squadrons, then at anchor in the 
 Gulf of Salamis, returned with his Majesty to the Piraeus, and again rejoined the admiral, 
 with whom and the rest of the ships she proceeded on the 6th of June to Naussa, in the island 
 of Paros, and on this occasion beat most of the squadron. 
 
 After cruizing for about a month in the Archipelago and visiting many of the islands, the 
 steamer was detached on the 1st of July to Zante, with despatches. When the signal was made 
 to the Medea, at 5h. 30m. P.M., " prepare to steam," she was carrying a press of sail going eight 
 knots. The fires were lighted, and the ship still kept on her course until 6h. 55m., when she 
 was hove-to, the wheels connected in 17 minutes, and the engine " put on" at full power. 
 Here, then, is an instance fully corroborating what we have before said of this war steamer's 
 ability to keep company under sail with a fleet proceeding to distant service, and of the short 
 notice required to make her steaming qualities available. We find the weather stated as 
 " fresh winds and squally; " therefore, as the situation of the ship was such that she had no 
 shelter from the land, she was exposed to the full force of the waves, which a wind 
 that would drive the whole squadron, as well as herself, eight knots an hour, must occasion ; 
 proving that the shaft could in the worst of weather always be connected with the 
 machinery in far less time than would be required to " get the steam up :" as we find in the 
 foregoing case, the course was continued under sail for 1 hour and 25 minutes after lighting 
 the fires, and they were only hove-to for 17 minutes. 
 
 After leaving Zante, the Medea, under sail, rejoined the admiral on the 7th of July, at the 
 gulf of Kalamata in the Morea, and started for Malta on the following day with the fleet in 
 company. On the 10th of July the wind being very light, this vessel, still without steam, beat 
 the whole squadron in an extraordinary degree, which (to use the words of the log-book) 
 " is accounted for by the Medea not feeling the short ' swell' in the same proportion of dis- 
 advantage as the shorter and heavier vessels." We are, however, inclined to attribute this 
 success in some degree to her being without her usual full quantity of coals, as the resistance 
 which the paddles afforded in light winds must greatly have impeded her progress. Still the 
 fact is most extraordinary ; and as she had upwards of 200 tons of coal on board, it cannot be 
 said that her efficiency as a steamer was in any considerable degree impaired by her being 
 thus rendered more perfect as a sailing vessel. 
 
 We next find the Medea visiting the Ionian Islands, and cruizing for nearly two months 
 under sail with the fleet in the neighbouring seas and on the coast of the Morea : in all the 
 various evolutions incidental thereto, she acquitted herself well. 
 
 On the 10th of October the squadron proceeded on their return to Malta, and encountered 
 during a considerable part of the passage from Cephalonia strong contrary winds. The 
 first day the steamer under canvass " fore-reached " and " weathered " so much upon the 
 whole of the ships, that towards the evening it was judged necessary to shorten sail in order 
 to keep company with the Admiral. Still, however, the means that were thus taken to ensure 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 93 
 
 her remaining with the fleet did not prevent her outsailing them in the night, and the next 
 morning they were out of sight. The vessel now prosecuted her voyage alone, and reached 
 Malta on the 14th, two days before the rest of the ships. We have said that the wind was 
 strong and contrary during a considerable part of the route : the fact is therefore extraordinary 
 that a steamer should thus, under sail, with paddles revolving loosely in the water, beat a 
 fleet of good sailing ships of war two days out of a passage of only six, over a distance of little 
 more than 300 miles ; and although from her light draught of water the former had a slight 
 advantage in being able to "tack" closer into the Italian shore than the large vessels would 
 venture, yet in the open sea, on which the greater part of the voyage was made, this was 
 against her; and the performance is altogether so extraordinary that nothing short of the 
 testimony before us would give it the character of truth. Nor can the success of the Medea 
 be attributed to her having got into a different vein of wind than that encountered by the 
 squadron, as we find, on the first day, the steamer shortened sail to keep company, and only 
 lost sight of the ships by her superior sailing on a dark night. It is fair to add, that on this 
 occasion she had not above 150 tons of coal on board, which, however, was sufficient to work 
 the engine for eight days, and might have carried her over 1600 miles of a steaming 
 voyage. 
 
 We now proceed to give an account of the most interesting cruize performed by this ship 
 during her services in the Mediterranean. 
 
 The king of Bavaria, having contemplated a visit to his son Otho, who occupied the throne 
 of Greece, and had recently removed the seat of government from Nauplia de Romania to 
 Athens, requested fit means of transport on board an English vessel of war from Ancona to the 
 shores of Attica. In order to show as much honour as possible to the father of the young 
 sovereign, whom the British power had been so mainly instrumental in raising to his eminent 
 yet difficult position, the Portland, of 52 guns, was directed to proceed to the coast of 
 Italy to receive the King on board, and the Medea was ordered to the same destination to 
 attend the frigate in the performance of this service. 
 
 The Portland, being at Corfu, received the directions of the Admiralty, by an over-land 
 despatch, sufficiently early to enable her to leave that island two days before the Medea could 
 proceed from Malta, to which place her orders were conveyed by steam-packet from England, 
 yet, although the voyage was of double length, she reached Ancona three days before the 
 frigate, having steamed the whole distance against a continued contrary wind at the rate of 
 eight miles an hour. The King of Bavaria at once determined on making the passage in the 
 steamer ; but being aware that the Portland had been despatched on purpose to receive him, 
 awaited her arrival, and on the evening of the 3rd of December embarked on board that ship, 
 thus affording a better opportunity for a display of the pomp and ceremony usual on such 
 occasions. The Medea, having taken the frigate in tow, proceeded out of the harbour, and 
 immediately both ships were clear of the land the King removed into the steamer, which then 
 prosecuted her voyage alone. 
 
 The mild autumnal weather which so frequently prevails in the Levant, then shed its 
 influence over the whole of that region, and scarce a ripple disturbed the surface of the 
 Adriatic or jEgean seas. 
 
 The first and second night, and also the intermediate day, were passed on the broad waters 
 
94 APPENDIX. 
 
 of the Adriatic, with an occasional glimpse of the coasts of Italy and Dalmatia on either 
 side, as the steamer gallantly pursued her rapid course towards the Acroceraunian pro- 
 montory, the thunder-riven mount of ancient lore, which, like another Calpe, projects its bold 
 front into the wave between the Adriatic and Ionian seas. 
 
 " Morn dawns, and with it stern Albania's hills," 
 
 and at noon on the 5th of December the ship entered the narrow strait between the ancient 
 cities of Buthrotum and Cassiopea, and passed into that magnificent sheet of water, which, 
 like some great inland sea, extends in a south direction for more than thirty miles, bounded to the 
 west by the contiguous islands of Corfu and Paxo, and opposite by the Albanian hills, indented 
 all around by many a fair and tranquil bay, fringed on the Ionian side with olives and the 
 clustering grape ; while, on the more rugged coasts of the main land, " dark Suli's rocks," 
 the mountains rise abruptly from the sea-shore towards the summits of the Pindean range, 
 which, clothed in the snow of ages, terminate the prospect eastward. 
 
 The Medea glided over these placid waters at a rate never less than ten miles an hour, and 
 shortly arrived in front of the sea-girt fortress and town of Parga. The dark and bitter 
 Acheron, " bleak Pindus and Acherusia's lake," were next passed ; and another hour's 
 steaming brought the ship in front of the Ambracian estuary. 
 
 Pursuing their rapid course, and passing between Ithaca and Cephalonia, in front 
 of the Corinthian Gulf, the vessel skirted the fair and fertile coasts of Zante ; and 
 early on the 5th of December entered the harbour of Navarino. Having made a 
 circuit of its bay among the wrecks, which still remain as sad mementos of the 
 Moslem's fate, she pursued her navigation close to the Morea, reached the promontory of 
 St. Angelo, and entered the ^Egean sea. The passage to the Isles of Hydra was soon effected, 
 and the next morning's dawn showed them " Colonna's neighbouring height," Egina, 
 Hymettus, and the shores of Attica ; and in eighty-two hours from the time of leaving 
 Ancona, they were safely anchored in the Piraeus ; having thus accomplished the distance of 
 760 miles at an average rate of nine and a quarter geographical miles per hour. 
 
 We have already digressed too much to admit of our tracing, however briefly, the various 
 cruizes and excursions made by the Medea with the royal guest on board, during the four 
 months she remained in attendance on the King of Bavaria : it will suffice to say, that they 
 visited most of the places of note on the coast of Asia Minor, and nearly all the Grecian 
 islands in the Archipelago, having, from the time King Louis first embarked at Ancona on the 
 3rd of December, until he ultimately arrived at the same place on the 31st of March, 1836, 
 gone over a distance of 3000 miles, at an average rate of more than nine knots an hour, 
 though the wind in many cases was strong and contrary ; indeed we have the authority of 
 Mr. Peacock, the master of the Medea, for stating, that "during the last cruize, which lasted 
 fifteen days the Medea averaged ten knots an hour the whole cruize, though strong head 
 winds were experienced most of the time." * We presume, however, she had but few coals on 
 board, and was consequently in better trim than when complete ; such, however, was not the 
 case on the passage from Ancona, which, as before stated, was at the rate of nine and a quarter 
 miles an hour. 
 
 ' Nautical Magazine, page 305. May, 1836. 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 95 
 
 After landing King Louis of Bavaria, the Medea returned to the Piraeus, and on the 10th of 
 May received the king of Greece on board, to convey him to Ancona, where His Majesty 
 proceeded to meet his bride, and ultimately returned to Athens in H. M. S. Portland. 
 
 In prosecuting this voyage the Medea conveyed the Grecian King close along the shores of 
 such parts of his dominions as bordered on the sea, and thus made a circuit of the whole 
 Peloponnesus, from the Gulf of Egina to that of Lepanto, stopping at every place of note, 
 at all of which the young sovereign of this resuscitated state was most enthusiastically re- 
 ceived by his Hellenic subjects. 
 
 From the gulf of Lepanto, near the entrance of which the King landed, at the ancient 
 town of Patrse, now the commercial emporium of Greece, they proceeded to Missolonghi, 
 and viewed the sad memorial of him who devoted his best talents and his latest energies 
 in the cause of Grecian independence, and fell a victim at the shrine of that liberty he loved 
 so well. 
 
 From Corfu, where the steamer stopped a few hours, the voyage was continued to Ancona, 
 at the rate of ten knots an hour, though the wind was mostly contrary, and for the last 100 
 miles fresh against her. 
 
 Thus ended these most interesting yachting cruizes of the Medea, throughout the whole of 
 which she acquitted herself to the admiration of all, and worthy of that country whose 
 standard was borne in unison with the royal banners, either of Bavaria or Greece. 
 
 The ship now returned to Malta, and steamed the whole distance from Ancona at the rate 
 of nine and a half knots per hour, the wind being ahead, with occasional fresh breezes for 
 one-third the passage. On the 10th of June she rejoined the fleet at Corfu, to which place 
 she was navigated under sail ; and having cruized about the Ionian Islands, and off the coast 
 of the Peloponnesus, anchored with the rest of the ships close to the shore of Attica, imme- 
 diately in front of the old Athenian havens of Phaleron and Munychia. 
 
 Leaving the squadron at this anchorage on the 10th of August, the Medea sailed round to 
 Zante to meet the English packet, and beat up the west coast of the Morea at the rate of six 
 and a half knots an hour, against a fresh north-westerly breeze, making nearly a straight 
 course at five points from the wind. From Zante she returned to the JEgean sea under 
 steam, and on the 21st rejoined the admiral, then at anchor off the island of Syra, 
 after a passage of thirty hours ; thus accomplishing this circuitous and intricate navigation of 
 290 miles at an average of nine and two-thirds knots per hour, the wind having been directly 
 ahead, but moderate during the first half of the run : and although for the latter part it was 
 mostly on the " beam " and " quarter," the waves which it created were by no means 
 favourable to her progress. On the 26th a Turkish ship of war was driven in a gale of wind 
 close to the rocks on the windward side of the island Gutherize, near Syra, and obliged to 
 anchor close to the reefs. The Medea proceeded to her assistance, and extricated her from 
 her perilous position by towing her off-shore against the gale. On the 28th she again pro- 
 ceeded to Zante with the admiral's despatches, and arrived in twenty-seven hours, at a mean 
 rate of more than ten and a half miles each hour. 
 
 There being no necessity of expedition on her return to the fleet, the passage was made, in 
 accordance with her usual custom on such occasions, without the aid of steam. It is 
 worthy of remark, with reference to the Medea's frequent voyages under sail, that she inva- 
 riably beat the trading vessels which were met with ; and it is well known that the commerce 
 
96 APPENDIX. 
 
 of the Mediterranean, particularly the Levant, is pursued generally in ships second in their 
 sailing qualities to the mercantile marine of no country in the world. 
 
 After rejoining the admiral and fleet in Vourla Bay, she was despatched on the llth of 
 September again to Zante for the mails from the English packet, and made the voyage under 
 canvass in six days, encountering light winds throughout, principally in a direction contrary 
 to her course ; and on this occasion she beat an Austrian ship of war. The return 
 to Vourla under steam was at an average rate of eight and a half miles an hour, the 
 wind being contrary during the whole passage, and for more than half of it very strong. 
 
 On the 7th of October the ship returned to Malta, and from thence she proceeded by steam 
 on the 20th towards Constantinople, with a messenger and despatches for the British 
 minister ; but not being allowed to enter the Dardanelles, she remained at anchor in Basika 
 Bay, on the coast of Asia Minor, close to the plains of Troy. On the 2nd of November, when 
 returning, they experienced in the neighbourhood of Lemnos a heavy gale of wind, in which 
 the vessel behaved remarkably well and suffered no damage, except the loss of a few sails 
 (it being always expedient, when the steam is used in a gale of wind, to set as much sail as 
 may conveniently be carried, in order to steady the ship). As the wind was very strong 
 ahead on nearly all the route to Malta, the passage was made at a slower rate than usual, 
 the speed being in some instances, during the height of the gale with a heavy swell, reduced 
 as low as three and a half knots ; yet, even under these untoward circumstances, the average 
 rate was six knots an hour. 
 
 The next voyage was on the 26th of December, from Malta to and from Zante, Patras, 
 Cephalonia, and Corfu ; in this instance performing the duty of a packet. The run to Corfu 
 was at a mean rate of near nine miles an hour, the wind being variable, and having ex- 
 perienced as far as the islands a heavy swell, of course always unfavourable to the progress of 
 a steamer. On the 2nd of January, 1837, she left Corfu, at 4 P. M. again called at the 
 places above-mentioned, (being detained eight hours at Patras,) and reached Valette at 
 6 P. M. on the 5th, making the whole distance at an average of nine miles an hour, though the 
 wind was mostly contrary, and in some instances strong ahead. 
 
 After this voyage the Medea remained at Malta until the 20th of March, when she started 
 for Toulon with some important despatches, and also to receive on board Sir Charles 
 Vaughan, lately appointed Ambassador Extraordinary to the Porte. This passage was effected 
 by steam in four days, at a mean rate of seven and a half knots, having for more than twenty- 
 four hours of this time experienced a heavy gale of wind from the westward, with a tremendous 
 sea, so high that at one time the ship was nearly thrown on her "beam-ends," the lee 
 paddle-box immersed, and a boat which was secured to " davits " far above the " gunwale" 
 much damaged. 
 
 As the wind still continued westerly, it was favorable for the return passage so far as the 
 straits of Bonifacio, and the rate was nine and a quarter miles an hour, though the coals 
 were so bad as to make it difficult to keep the steam up, and the ship's motion, from the 
 waves, was very unfavorable to her progress. On the coast of Sardinia the wind changed to 
 south, with a continued high sea ; yet her speed against it was not below nine knots, and she 
 continued on the remainder of the route to Malta, with an incessant breeze ahead, at nearly 
 the same average, and reached the port on the 30th of March. 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 97 
 
 Having received a full supply of coal on board, she again departed, with an officer of the 
 diplomatic corps on board, on the evening of the 1st of April, reached Basika bay in 
 ninety-two hours ; and, after remaining eight days, returned to Malta, where she arrived on 
 the 16th of April. During this voyage more than one gale was experienced, and the first 400 
 miles, being the passage between Valette and Cape Matapan, was against a strong Levanter^ 
 besides which she encountered contrary winds both going up and coming down the Archipelago ; 
 yet the average rate of steaming, from leaving until the return to Malta, was near eight miles 
 an hour. 
 
 Nothing extraordinary occurred in this vessel's service till she was ordered, early in June, 
 to convey Sir Charles Vaughan from Malta to Venice, and she accordingly left the former 
 place on the evening of the 18th. Although some part of the passage was against a violent 
 head-wind, the speed was never reduced below five knots and a half, and the average rate of 
 the whole was above eight. Towards the close of day on the 22nd, the Medea passed the 
 Lido, entered the narrow canals of Venice, and moored to the quay opposite the Bazilica of 
 St. Mark, precisely in the spot once occupied by the far-famed Bucentaur, fit palace for a 
 sovereign whose chief dominion was the wave, who was wont, in the by-gone days of 
 Venetian glory, to receive in these his floating halls the honoured great who flocked from 
 distant lands to view the wealth of Adria's Queen ; and which served to convey him, on the 
 magnificent ceremony of Ascension-Day, to the bridal of that wave over which his empire has 
 passed away. 
 
 The Medea also visited Trieste, Pola in Istria, and Ancona, making a rapid passage 
 between each place, and on the 1st of July reached Malta; the steaming rate from leaving 
 the last-named place being nine knots and three-quarters. 
 
 On the 4th of July she proceeded on a cruize under canvass in company with the squadron, 
 and succeeded on all occasions in keeping her station in the " order of sailing " without diffi- 
 culty. On the 6th of July the trial of sailing was made, of which we publish a delineation in 
 a diagram, when it appeared that she was equal in speed to all, except the new ship Van- 
 guard, of 80 guns, (built by Sir William Symonds,) and that she gained much to windward of 
 the Caledonia. We also find that during this cruize, which lasted till the 15th, the 
 steamer had frequently to bear up and run to leeward into her station in consequence of her 
 very extraordinary " weatherly " qualities ; and that in no one instance did the ships shorten 
 sail for her. 
 
 Being detached from the fleet on the last-named day, the Medea ''beat" into Malta 
 harbour against a fresh wind ; and having received a few coals, she quitted Malta for the last 
 time, rejoined the admiral, received despatches, and forthwith proceeded towards Gibraltar; 
 where she arrived in 113 hours, being at a rate of nine knots, having encountered about an 
 equal proportion of fair and contrary winds during the passage. 
 
 Between the time of her arrival at Gibraltar and the day she reached England, in September, 
 she made two passages to and from Port Mahon, and on one occasion towed the Princess 
 Charlotte, of 120 guns, and the Vanguard, to sea against a light breeze. She also visited Valencia 
 and Barcelona on the coast of Spain, and Tetuan in Africa ; and being at Gibraltar at the time 
 the Don Juan steam-packet was wrecked at Tariffa, the Medea proceeded at once to the 
 spot, where she was mainly instrumental in saving much property and stores, and afterwards 
 
98 APPENDIX. 
 
 carried the mails to England. During this time, namely, from the 20th of July until her 
 arrival at Falmouth on the 24th of September, she steamed 3660 miles, of course ex- 
 periencing great varieties of weather, at an average rate of more than nine miles an hour. 
 
 The novelty of navigating a steamer under sail would naturally suggest to intelligent 
 officers such modifications of marine tactics as might appear suited in the particular cases of 
 steam-vessels to the varied and ever-changing circumstances which the seaman encounters in 
 the prosecution of his eventful duties ; and we have now to advert to a contrivance adopted 
 on board the Medea, which, though productive of very beneficial consequences during the 
 services of that ship, and worthy of imitation in all war-steamers, would be quite inapplicable 
 to commercial vessels, and worse than useless if attempted. 
 
 Our naval readers are well aware of the inconvenience that sometimes arises to a cruizing 
 squadron, generally sailing in " close order" or "line of battle," when in calm weather the 
 ships involuntarily approximate each other, and the consequent labour of towing by boats to 
 prevent accidents by collision. The Medea, when acting as a sailing vessel, was of course 
 liable to be placed in these circumstances ; and as it was impossible by boats to produce 
 velocity enough to set the wheels in motion, that usual resource, if not quite unavailing, was, 
 from the resistance which the paddles afforded, attended with as much labour; and as much 
 force was required as to tow the largest ship of war. To light the fires and " get the steam 
 up" at once put an end to the difficulty; but this caused an expenditure of coal, and the 
 great object was to perform all the duties of cruizing without invading those resources on 
 which her great power and efficacy depended. 
 
 Much inconvenience had also been experienced during the varied services of this vessel from 
 the difficulty of changing her position in harbour when required to move towards a coal 
 depot; and it was found, as before stated, that as many boats were required to move her even 
 a short distance as would suffice to " transport" a first-rate ship of war, and the obstacles 
 to effecting the same object by using "warps " were of equal magnitude. Although the fuel 
 could generally be renewed in cases similar to the above, yet, if the steam was used, an ex- 
 pense would be incurred even in the performance of such insignificant duties, particularly 
 when occurring on a foreign station to which the coals are conveyed at a considerable cost ; 
 and the boilers, 8cc. would undergo some deterioration, however slight it might be. The small 
 quantity of coal consumed on board this ship, although she steamed full 30,000 miles, and 
 the excellent state of her machinery and boilers after a service of nearly four years, fully prove 
 how excellent was the system which led to such results. 
 
 "To obviate the difficulties attending the removal to a short distance," writes Mr. Peacock, 
 the master of the Medea, l " I hit upon the following simple contrivances, which were fitted to 
 the Medea's wheels by our own resources: To the inner side of the inner arms, between the 
 outer polygons, a set of iron lugs, shaped like the letter V, are riveted on, large enough to 
 take a three -and-a-half inch hawser. Two iron fair-leaders, with rollers in them a foot apart, 
 project from the inside the paddle-box immediately over the shaft, and are of such a height 
 and distance from the side as to insure the lugs alternately catching the hawser, and prevent 
 
 1 Vide Nautical Magazine, p. 731, November, 1837., to which we would refer our readers for a more elaborate 
 description of this contrivance, and its probable benefits, of which those only who tried the experiment can be 
 competent judges. 
 
MEMOIR OF HER MAJESTY'S STEAM SHIP THE MEDEA. 99 
 
 the possibility of the arms or lugs coming in contact with them when the wheel springs in a 
 sea way steaming, which every steam-vessel's wheels are more or less liable to. A hole two 
 inches in diameter, nicely leaded, is bored in one of the steps at the fore and after part of 
 the paddle-box, through to the inside, at a convenient height for a man to pull from, in a 
 horizontal position, and at an angle sufficient to prevent the inner end of the paddle-boards 
 picking up the bight of the hawser in its rotatory progress ; which angle also guides the posi- 
 tion for the two leading blocks, one of which hooks on to a timber-head on the forecastle, 
 and the other at any convenient length abaft the wheel, according to the number of men who 
 are to clap on the hawser, which is a three-and-a-half cable, cut to a convenient length, and 
 has an ' Elliott eye' spliced on each end. This hawser is rove as follows : one end is first 
 passed through the after-hole, then through the foremost fair-leader over the iron lugs alter- 
 nately, then through the aftermost fair-leader, (crossing the feeding part between the fair- 
 leaders,) and brought out through the foremost hole, where it is lashed with small line to the 
 other end, which in the mean time has been rove through the after and foremost leading 
 blocks, and brought to the foremost hole in readiness. When the lashing is secured, the after 
 leading block is braced taught with a jigger the larboard and starboard watches man their 
 respective messengers, the band strikes up, and ofFshe goes." 
 
 It may perhaps to our non-professional readers simplify the description thus given by 
 the inventor of the plan, if we state, that the wheels were set in motion by a rope acting, and 
 resting on certain fixtures attached to the radii at a regulated distance from the periphery ; 
 and that this endless rope, being extended to and passed over fixed pulleys near each ex- 
 tremity of the vessel, presented to the crew a continuous line on which their labour could be 
 expended as they walked or ran along the deck, and produced the rotatory action much in 
 the same way as distant machinery receives its impulse by a band connected with some 
 steam-engine or other prime-mover. 
 
 Thus the Medea was occasionally moved, when the shortness of the distance, or other circum- 
 stances rendered it inconvenient to use steam, and in one instance proceeded through the 
 entrance of Malta harbour against a light breeze, at the rate of two knots an hour. 
 
 We have now laid before our readers such facts connected with this vessel, (the only 
 government steamer that has been for a lengthened period on a foreign station, or extensively 
 employed as a sailing vessel,) as we think may be interesting to those who would form a 
 correct estimate of the means which have been adopted for the benefit of the public service in 
 thus creating a novel description of war vessel, to accord with a new era in navigation. 
 
 T. B. 
 
 2 
 
100 
 
 Trial of Sailing between H. M. Ships Caledonia, Asia, Vanguard, and Medea, 
 
 made on 6th July, 1837, off Malta. 
 
 At 10 h 15 A. M. commenced to try rate of sailing; close hauled on the larboard tack; a fresh 
 breeze and little head sea ; ships under courses, single-reefed topsails, top gallant sails, jib and spanker, 
 being as much as each could well carry. Wind W. by N., Caledonia's rate, 5 knots. Vanguard 
 passed under Asia's stern, and soon shot ahead of her ; and upon her weather bow passing to 
 windward of Medea, (which latter bore up to enable her to do so) 30. At the time of commence- 
 ment 10 15, the respective ships bore from Caledonia as follows : 
 At 10 15 Vanguard S.S.W. i, W. J-mile : Asia S.S.W.i, W. f andl20fms: Medea W. by S. i', 
 
 175 fms. from 10 15 to 11 Caledonia averaged a north course 4i knots, wind from W. by N. 
 
 to N. W. by W. 
 At 11, Vanguard W. by S. | S. l' : Asia S. W. f , S. 1* 20 fathoms : Medea S. W. |, W. l'|, 
 
 125 fms ; from 11 to 12 Caledonia averaged a N. by E. - E. course, 4 knots 4 fms. 
 At 12, Vanguard N. W. i, W. S'i, 172 fms : Asia W. by S. >, S. 2'i, 31 fms : Medea W. by S. J, 
 
 S. 2', 220 fms. At noon the wind freshened, Asia and Vanguard took in royals and F. Jib. 
 
 at 12 30, came up to N. by W. Average course from 12 to 1, N. by W. -'-, W. 4 knots. 
 At 1, Vanguard N. W. , N 4'|, 110 fms : Asia W. S. W. 2^, 50 fms : Medea W. by S. 2'$, 200 
 
 fms. Trial continued from 1015 A. M. to 1 p. M., being 2 h. 45' course made good by Cale- 
 donia, N. 13', in which time each ship gained as follows : 
 
 To windward. Fore-reaelud. To windward, Fore-reachfJ. 
 
 Vanguard of Asia, 2'-J 4' 184 fms. Asia of Caledonia, 1' -J 
 
 of Caledonia, 4' 135 fms. 3{ of Medea, 75 125 fms. 
 
 of Medea, 2 185 fms. 4 Caledonia of Asia, i 209 fms. 
 
 Medea of Caledonia, 1| 180 fms. of Medea, 1' 150 
 
 N. B. During this as well as former trials, Vanguard has done exceedingly well, and again 
 proved her great superiority, both in speed and stability ; and had the wind remained steady, she 
 would have shown it still more, as the changes were always to her disadvantage. The Medea 
 also (considering her small spread of canvas) has again proved her superiority in going to wind- 
 ward, having beaten Caledonia considerably, and kept away with Asia during the whole time 
 of trial. 
 
 (Signed) C. P. BELLAMY, 
 
 Master H. M. S. Caledonia. 
 
 See Plate XXIX. 
 
VI. ON THE STEAM BOATS OF THE UNITED STATES OF AMERICA. 
 
 BY JAMES RENWICK, LL.D. 
 
 PROFESSOR OF NATURAL EXPERIMENTAL PHILOSOPHY AND CHEMISTRY IN COLUMBIA COLLEGE, 
 
 NEW YORK. 
 
 THE application of the steam engine to the purposes of navigation attracted the attention of 
 many persons in the United States at an early period. No sooner had Watt's improvements 
 become known, than the circumstances of the population of that country, and its very geo- 
 graphical character, pointed out the propulsion of vessels, as the most important of the 
 many uses to which that powerful agent may be made subservient. The Atlantic coast, 
 with the exception of the extreme north eastern part, is either intersected by deep bays, or 
 covered by islands. By these means a navigation parallel to the coast might, at small ex- 
 pense, be extended from New York to the southern limit of Georgia; and in the opposite 
 direction, the Hudson River and Lake Champlain pointed out the means of extending the 
 water communication to the frontiers of Canada. These natural advantages have been im- 
 proved by artificial means, and at the present moment, an internal navigation exists from the 
 boundary of the British possessions to the sounds which line the coast of North Carolina. 
 
 The parts of this navigation which have required no artificial improvement, are large and 
 deep rivers, lakes, sounds, and arms of the sea. In these, although transportation was secure 
 from the storms and waves which affect the open sea, yet this very security was gained at the 
 expense of time, so long as the currents of the atmosphere were the only power which could 
 be applied. 
 
 The accession of the vast territory known under the collective name of Louisiana, but now 
 divided among many states and territories, opened a still wider field for navigation by steam. 
 The Mississipi and its innumerable branches comprise navigable waters of many thousands of 
 miles in extent, but which, from the rapidity of their currents, are almost inaccessible from 
 the Gulf of Mexico, either by sails or oars. The population of the territories traversed by 
 these streams is sparse and scattered, almost wholly devoted to agricultural pursuits, and yet 
 feeling the wants, and desiring the luxuries of the highest civilization. To supply these wants, 
 and furnish these luxuries, rapid methods of transportation, as well as great foreign importa- 
 tions, are demanded ; and there are no means yet discovered by which these purposes could 
 have been effected, except by the steam boat. 
 
 Influenced by such considerations, attempts to apply steam to the purposes of navigation 
 were made in the United States, even before Watt had succeeded in giving a double action to 
 his engine. The earliest enterprises of this sort were those of Fitch and Rumsey, which both 
 bear the date of 1783. Both were founded upon the original form of Watt's engine, and both 
 
 o 
 
102 ON THE STEAM BOATS OF 
 
 failed, rather from the inherent defects of that instrument, in its power of general application, 
 than from any want of ingenuity or mechanical skill in the projectors themselves. 
 
 John Stevens, of Hoboken, commenced his experiments on steam navigation in 1791? and 
 for sixteen years devoted much time, labour, and money, to this object. In this pursuit he 
 sometimes acted alone, at other times had the aid of associates. Among these may be named 
 Chancellor Livingston, and Roosevelt. This association, among other persons, called to their 
 aid Brunei, since celebrated as the engineer of the tunnel beneath the river Thames. The 
 appointment of Chancellor Livingston to the post of minister to the consular government of 
 France, dissolved this association, at a moment when hopes of at least partial success might 
 reasonably have been entertained. 
 
 In the year 1801, a remarkable experiment was performed at Philadelphia, by Evans. This 
 engineer had been employed by the corporation of that city, to construct a dredging machine, 
 for the purpose of removing obstructions in the Delaware river. He proposed to work the 
 dredging apparatus by the high pressure engine, which he had invented some years before. 
 Constructing the vessel and engine at his shops, distant a mile and a half from the water, he 
 mounted the whole upon wheels, to which he gave motion by the engine, and thus exhibited 
 the earliest instance of locomotion. The vessel being thus transported to the water, and 
 launched, he next placed a paddle wheel at the stern, and connecting it with the engine, made 
 it the means of conveying the vessel to the place where the work of dredging was to be per- 
 formed. 
 
 Livingston, on reaching Paris, became acquainted with Fulton, and discovered that he had 
 also studied in what way the steam engine might be applied to the purposes of navigation. 
 Struck with the soundness of his views, Livingston induced him to enter into a course of 
 experiments, for the purpose of testing them practically. These experiments were performed 
 at Plombieres, and were subsequently repeated on a larger scale, upon the Seine, near Paris. 
 
 The results of these experiments were so satisfactory, that Livingston forthwith undertook 
 to provide the funds for building and equipping a steam boat of large size, in the United 
 States. As the workshops of that country could not, at that time, be depended upon for fur- 
 nishing an engine of good construction, it was agreed that those of Watt and Bolton should 
 be resorted to. From a variety of circumstances, delays were not to be avoided, and the 
 engine constructed by Watt and Bolton did not reach New York until 1806, nor could the 
 vessel be prepared to receive it before the summer of 1807- 
 
 The engine which was used in this final and successful experiment, and which was con- 
 structed from the draughts made by Fulton, in France, in the year 1803, had a marked influ- 
 ence upon the forms of those subsequently constructed for this purpose, both in England and 
 the United States. The cold water cistern of Watt's engine was dispensed with, and in order 
 to supply its place the diameter of the condenser was doubled ; its capacity thus became half 
 that of the cylinder, instead of one-eighth, as had before been customary. The water of injec- 
 tion was supplied by a pipe passing through the bottom of the vessel. A parallel motion 
 seems to have been sent out as a part of the engine, but for reasons which cannot now be 
 discovered, a cross head, adapted for another purpose to the piston rod, was made to work in 
 guides. This cross head was added for the purpose of bearing two connecting rods or straps, 
 by which two working beams were, as it were, suspended. The working beams were neces- 
 sarily two in number, in order to include the cylinder between them ; and Fulton being aware 
 
THE UNITED STATES OF. AMERICA. 103 
 
 of the difficulty which would exist in uniting an engine constructed at one place with a vessel 
 built at another, had a double provision for uniting the beams to the cranks. The former 
 were therefore made of the form of an inverted j, j giving him the choice of taking off the 
 motion either from the horizontal or the vertical branch. The latter was found most expedient, 
 and thus the working beam became, in its primitive use, a bell-crank. The connecting rod 
 was therefore extended horizontally to meet the crank. 
 
 We may here state that this very form of engine, with the exception that the beams had the 
 usual shape, and the motion was taken off by a connecting rod directed upwards, was adopted 
 by Bell in the vessel which he constructed upon the Clyde in 1812; and that from this latter, 
 as the original model, all the engines used in the British steam boats have been derived. 
 
 The paddle wheels of Fulton's first steam boat were attached to the axles of the cranks, and 
 the latter also bore spur wheels which drove pinions ; upon the axles of the pinions was placed 
 a heavy fly wheel. The latter was of essential use, so long as the velocity of the paddle 
 wheels themselves was not great ; but, at the speed which is now customary, they cease to be 
 of value, as the paddle wheels themselves act as regulators. Fly wheels are, in consequence, 
 no longer to be seen in American steam boats. 
 
 The object proposed by Fulton, in the mode we have described, of connecting his water 
 wheels with the engine, was unquestionably that of enabling him to change their diameter, 
 and to raise and lower their axis of motion, until he should, by experiment, ascertain the size 
 and position most advantageous in practice. In conformity with this view of the subject, it is 
 known that the position of the axis was more than once changed ; and it is believed that the 
 diameter of the wheel was also altered, before the first steam boat was considered by him as 
 completed. In constructing his second steam boat, ' The Car of Neptune,' Fulton, being no 
 longer compelled to feel his way by experiment, made very important changes in the form of 
 his engine. The piston rod was still directed by a cross head, moving in guides, but the 
 working beams were suppressed altogether, and two cranks, adapted to two separate axles, 
 were attached directly to the cross head by connecting rods. A fly wheel was still used, 
 driven by wheels and pinions, and in the slow rate of motion to which he restricted himself, 
 was found of great value. This form of engine is still much used, with the omission, however, 
 of the fly wheel. Two views of such an engine, with a boiler of a favourite form, are given 
 in Plate cxv. 
 
 In his first steam boat, Fulton was satisfied with endeavouring to attain the speed of four 
 miles per hour, which had been made the condition of his obtaining an exclusive right to 
 navigate the waters of the state of New York, by an Act of the Legislature of that state. By 
 alterations suggested in the experiments of the first summer, and which consisted principally 
 in raising the axle and increasing the diameter of the water wheels, the velocity of the first 
 successful steam boat was carried up to six miles per hour. 
 
 The first voyage of Fulton upon the Hudson was performed in the summer of the year 
 1807; and in the year 1808, the same vessel, much improved in convenience, began to ply as 
 a passage boat between the cities of New York and Albany. 
 
 In his subsequently constructed steam boats, Fulton aimed at, and succeeded in attaining, 
 a greater degree of speed ; but, even in the last which he constructed, he limited himself to 
 nine miles per hour, which, by the application of theory, derived from the best published 
 experiments, he considered as the greatest velocity which could be advantageous. 
 
104 ON THE STEAM BOATS OF 
 
 Three steam boats were constructed by Fulton for the navigation of the Hudson. These 
 were all flat bottomed. He also constructed a vessel intended for the navigation of Long 
 Island Sound. This had a keel, and although of little depth of hold, approached in figure, in 
 other respects, to the usual form of a fast sailing ship. He also drew the plan of another, 
 which was left unfinished at his death, and which was intended for the navigation of the 
 ocean. 
 
 The success which attended the vessel intended for the navigation of the Sound, but which, 
 in consequence of the presence of an enemy's fleet, had been restricted to the Hudson, seems 
 to have caused Fulton to doubt the propriety of the first model which he had adopted ; and, 
 in consequence, the last vessel which he planned for the navigation of the Hudson, and which 
 was also left unfinished at his death, had a keel. It is, however, a remarkable fact, that after 
 innumerable trials, the present model of the most rapid steam boats has returned nearly to 
 the proportions originally adopted by Fulton. They have a keel indeed, but the floor timbers 
 have but a few inches of dead rise, and thus the bottom is nearly flat. Besides vessels intended 
 for the conveyance of travellers upon the Sound and the Hudson, Fulton constructed several 
 ferry boats, intended for the transportation of loaded carriages, and a formidable ship of war. 
 He also furnished plans for vessels intended for the mixed purposes of carrying freight and 
 passengers upon the Mississipi. 
 
 The elder Stevens of Hoboken, whom we have mentioned as having made experiments on 
 steam navigation, resumed his attempts at the very moment that Fulton was about to put his 
 plan in operation ; and it was only a few weeks after the first successful voyage of the latter, 
 that he also had a steam boat in motion. The speed of this was at least equal to that of the 
 first steam boat of Fulton. It plied for a time as a ferry boat from New York to Hoboken, 
 and, when excluded from the navigation of the Hudson by the exclusive grant to Fulton, 
 Stevens sent this boat round to the Delaware by sea, and was in consequence the first to 
 navigate the ocean by steam. 
 
 The form of engine adopted by Stevens differed less from the original form of that of Watt, 
 than the form chosen by Fulton. The parallel motion and working beam were both retained 
 in their usual form and proportions ; the connecting rod was increased somewhat in length, 
 and the axle of the crank produced on both sides, in order to form the axle of the paddle 
 wheels ; the enlarged conductor, as a substitute for the cold water cistern, was also used 
 by him. 
 
 These forms of engines, thus brought into use by Fulton and Stevens, have directed the 
 practice of American engineers. The fly wheel used by Fulton has been laid aside as 
 unnecessary at high speeds ; the parallel motion has been superseded even in the engine with 
 a lever beam by a cross head and slides. Upon the Mississipi, and in a few instances in 
 the Atlantic States, horizontal engines have been employed ; and the description of engine 
 called high pressure, in contradistinction to condensing, is much used in the Western waters. 
 
 New York and its vicinity may still be considered as furnishing the most successful instances 
 of steam navigation. WTien the monopoly granted to Fulton by the state of New York was 
 decided to be unconstitutional by the Supreme Court of the United States, the navigation of 
 the Hudson was thrown open to competition. The number of passengers then conveyed upon 
 that river had already become enormous, and presented inducements of the most powerful 
 kind to the proprietors of steam boats. The boats of Fulton's Company had performed the 
 
THE UNITED STATES OF AMERICA. 105 
 
 passage between New York and Albany, axdistance once estimated at 160, but not exceeding 
 145 miles, in fifteen or sixteen hours; but, for all useful purposes, a whole day might be 
 considered as expended in this voyage. It was now attempted to perform the passage between 
 sunrise and sunset. A vessel called the ' Sun ' was the first to undertake this, but was not 
 able to make her average passages in less than fourteen hours, and thus could fulfil the desired 
 object only during the longest days of summer. The engine of the ' Sun' was on the plan of 
 Woolf, having two cylinders, in one of which the steam acted by its pressure, in the other 
 expansively, and was condensed on leaving the second. The boilers were cylindrical, and as 
 there were no return flues, and the fuel employed was pine wood, a great loss of heat ensued. 
 Flame, in fact, issued from the chimnies, to the distance of six or eight feet. 
 
 It was at this moment that Robert L. Stevens, the son of the Stevens who had devoted so 
 much time and labour to the early experiments on steam navigation, placed upon the Hudson 
 a vessel which he had constructed for the navigation of the Delaware, on which river an active 
 competition had been kept up, while all opposition had been excluded from the former river 
 by the exclusive grant to Fulton. This vessel far exceeded the ' Sun ' in speed, and made the 
 passage easily in twelve hours. 
 
 The possibility of leaving New York after sunrise, and reaching Albany before sunset, for 
 the greater part of the season in which navigation is practicable, being thus established, several 
 other vessels were immediately constructed to fulfil the same object; and the steam boats 
 planned by Fulton himself, or constructed in direct imitation of them, were driven from the 
 river, or applied to the purpose of towing barges. 
 
 Among the vessels which replaced them a strong rivalry existed, and contests of speed took 
 place daily. These contests involved more than mere reputation ; for the way passengers, who 
 often form the majority, were in the habit of entering the vessel which first reached their place 
 of embarkation. It thus happened that vessels which were frequently defeated were sure to 
 be losing speculations ; and even some of great speed, but which were not backed by a sufficient 
 capital, were also withdrawn, in consequence of the unprofitable prices at which the passages 
 were often given. 
 
 In the course of these contests, changes were made in existing vessels, and these changes 
 were copied in the construction of new ones. These changes consisted principally in an in- 
 crease of the stroke of the piston, and therefore in the length of the crank, and in cutting off 
 the steam at half stroke. The first object was accomplished, in existing vessels, by adding an 
 additional piece to the cylinder. Even some of the older vessels were improved in these 
 respects, and again replaced upon the navigation, and competed, with tolerable success, with 
 those of the improved description. The old vessels, thus improved, took their places in what 
 is called the night-line. The transportation of passengers on the Hudson is adapted to two 
 distinct classes, those who travel for business, and those who travel for pleasure. The former 
 are best accommodated by vessels performing their passage during the night ; for thus business 
 may be transacted in New York on one day, and in Albany the next. No real advantage is 
 gained to these passengers by reducing the time of transit below twelve hours ; and the old 
 boats, thus improved, were enabled to effect this. On the other hand, every minute saved in 
 the passage by day light was considered of advantage. 
 
 It appears probable that the use of a valve, cutting off the steam at half stroke, had at first 
 no other object in view than a saving of fuel. The person who first ascertained, as a practical 
 
106 ON THE STEAM BOATS OF 
 
 result, that a greater speed might be attained ia a given vessel by using steam expansively, 
 was Adam Hall, at that time the director of the workshops of the West Point Foundry As- 
 sociation. He, at all events, entered very fully into the practical investigation of this subject, 
 and drew up a paper exhibiting his views, which was communicated to the writer of this 
 essay. The same views had been previously exhibited theoretically by the writer in a public 
 course of lectures delivered in February and March, 1830. These were soon after made 
 public in a treatise on the steam engine, which it is believed had some influence in the im- 
 provements that have since been made in navigation by steam. It was therein demonstrated, 
 that the power of a given engine might be doubled by loading the safety valve with 5 7 IDS. per 
 square inch, and cutting off the steam when one-eighth of the cylinder had been filled, and a 
 saving of two-fifths of the fuel effected at the same time. 
 
 In the subsequent improvements of which we shall hereafter speak, the excellent work- 
 manship of the West Point Foundry, with which, however, Mr. Hall ceased to be connected, 
 and the high scientific attainments of the Messrs. Kemble, its president and agent, had a very 
 important influence. 
 
 While the contests of which we have spoken were going on, Stevens was busily engaged in 
 building a new steam boat, to which he gave the name of the ' North America.' As this vessel 
 embodied all the improvements either in the original structure, or derived from experience in 
 his former steam boat, we shall give a concise description of her form and arrangements. 
 The dimensions of the 'North America' were as follow : 
 
 Beam ..... 30 feet. 
 Draught of water ... 5 feet. 
 
 Diameter of water wheel . . 21 feet. 
 
 Length of bucket . . .13 feet. 
 
 Depth of ditto .... 2 feet, 6 inches. 
 
 The engines were two in number, and with the boilers, were placed upon the wheel guards, 
 thus leaving the deck free from incumbrance from stem to stern. The cabins beneath could 
 also be opened, so as to afford a clear view from the sternpost to the cutwater. The engines 
 worked with beams, and had the following dimensions : 
 
 Diameter .... 44-^ inches. 
 
 Length of stroke ... 8 feet. 
 
 Strokes per minute . . .24 
 
 The steam was usually raised to a tension, over and above an atmosphere, of lOtbs. per inch, 
 and was cut off at half stroke. The velocity through the water, as ascertained from the 
 average of a great number of passages, was 19'8 feet per second, or about 13 1 English miles 
 per hour. The relative velocity of the outer circumference of the wheel was 6*6 feet per 
 second. 
 
 Another vessel, intended for a different navigation, namely, that from New York to New- 
 port R. I., was built shortly after the ' North America,' and was considered as successful an 
 application, taking the difference of circumstances into account, as that steam boat. In this 
 navigation it is necessary not only to pass the wide and often stormy sestuary, known as Long 
 Island Sound, but to enter the open ocean. It was therefore considered expedient to sacrifice 
 speed, for the purpose of rendering the vessel more fit for the navigation of agitated and tem- 
 pestuous waters. 
 
THE UNITED STATES OF AMERICA. 107 
 
 This vessel was called the ' President ;' the particulars of her structure, &c. were as follow : 
 Breadth of beam .... 32^feet. 
 
 Draught of water .... 9 feet. 
 
 Diameter of water wheels . . . 22 feet. 
 
 Length of bucket . . . .10 feet. 
 
 Depth of ditto . . . . 3| feet. 
 
 Engines, in number, ... 2 
 
 Diameter of cylinders ... 4 feet. 
 
 Length of stroke .... 7 feet. 
 
 Number of revolutions . . . 21 per minute. 
 
 The average velocity was 17'6 feet per second, or about 12 English miles per hour, and 
 the relative velocity of the circumference of the wheel was 6 1 feet per second. 
 
 On one occasion it became necessary for the ( President' to make a passage with only one 
 of her wheels and engines in action. In this passage the velocity of the boat was diminished 
 to 13*8 feet per second, but the relative velocity of the wheel fell but little short of that 
 acquired when both wheels were used, being 6'3 feet per second. The constancy which thus 
 appeared to exist in the relative velocity of the circumference of the wheel, in two boats of 
 very different form and structure, and in the same boat, when propelled by forces, differing as 
 much as in the ratio of 2 : 1, is a remarkable fact, and appears wholly irreconcilable with the 
 ordinary mathematical expression of the relation between the two velocities of the wheel and 
 the vessel. It had been deduced by a course of reasoning, which has been received without 
 question, that the velocity of the vessel bears a constant proportion to that of the wheel, while 
 in the instances we have cited they differ by a constant quantity. 
 
 Without attempting to question the skill in analysis of the distinguished mathematicians, 
 both French and English, who have investigated this problem, we may venture to state that 
 this appears to be a case in which the formula of Parent is applicable, and that the velocity of 
 the circumference of the paddle wheel through the water ought to be constant, and equal to 
 one-third of the greatest velocity at which a flat surface can be propelled through that fluid, 
 in a direction perpendicular to its plane. Assuming this to be twelve nautical, or 13'8 English 
 miles per hour, we have for the proper constant relative velocity of the circumference of a 
 paddle wheel 6J feet per second. On examination of the performance of a great number of 
 American steam boats, some of which we shall hereafter cite, it has been found that the 
 relative velocity of their paddle wheels has always been nearly this quantity. This fact is 
 thrown out for the present, for the purpose of drawing the attention of the scientific world to 
 it ; and should it be found to be universal, it will probably furnish a basis for the mathematical 
 theory of steam boats, whose results will be more applicable to the cases which occur in 
 practice, than those which are now set forth, but which are of little or no use to the engineer 
 or ship builder. 
 
 As the speed which has been stated for one of the vessels, which, from their having been 
 long attentively observed by the writer, have been chosen as instances, is far beyond that 
 which has been attained in Europe, it may be well that we should cite the facts whence this 
 statement .has been derived. The distance from New York to Albany has been measured 
 by the late Surveyor-General of the State of New York, in straight lines joining the extreme 
 points of the several reaches of the river, and amounts to 145 miles. The average passages of 
 
108 ON THE STEAM BOATS OF 
 
 the ' North America,' before the further improvements we shall mention, were performed in 
 lOlirs. 48min., after deducting stoppages. 
 
 The circumstances of the tide in the river caused the curious result, that among the passages 
 whence the above average was deduced, those which were performed in the shortest time were 
 upwards, or in opposition to the fall of the stream. The Hudson is affected by the tide 
 beyond Albany, but in the higher parts the flood is rarely attended by a strong current, and 
 at times no other effect is produced by it than a variation in the velocity. But the wave 
 which causes the tide reaches Albany in about eighteen hours ; and thus, a vessel leaving 
 New York soon after low water carries the flood tide with it, and if it perform the passage in 
 ten or twelve hours, feels its full influence for the whole of the way. In descending, the vessel 
 meets at least two successive waves, and thus has the tide alternately favourable and un- 
 favourable. 
 
 At New York the water of the Hudson at high water is usually nearly as salt as that of the 
 ocean ; but there have been two or three instances within the memory of man, when it was so 
 fresh at low water that outward-bound ships have rilled their supply of water from it. At a 
 distance of seventy-five miles from New York the water is always perfectly fresh, and is rarely 
 perceptibly brackish above the highlands, which are fifty miles from New York. For the latter 
 distance the channel for the largest ships is never less than 1000 yards in width, and is in many 
 places seventy feet in depth. Ships drawing fifteen feet water have a good beating channel 
 at all times of tide as high as the city of Hudson, 120 miles from New York : the remaining 
 twenty-four miles are comparatively shallow and narrow. 
 
 The writer made in the ' New Philadelphia' one of the most remarkable passages ever 
 performed. Leaving New York at five o'clock P.M. with the first of the flood, he landed 
 at Catskill, distant 111 miles, a quarter of an hour before midnight. As passengers were 
 landed and taken in at seven intermediate points, the rate at which the passage was per- 
 formed was not less than eighteen English miles per hour. Now, as the current in no case 
 exceeds four miles per hour, the absolute velocity through the water must have been at least 
 fourteen miles. 
 
 It may be here remarked, that the demonstration which attempts to prove that the absolute 
 velocity of a vessel propelled by steam in a current differs when the direction of the motion 
 is with the stream, from that with which it may be moved against the stream, is at variance 
 with the facts. Upon examination, this demonstration will be found to rest upon false premises : 
 the conditions laid down are not those which actually exist. In order to view the subject 
 in a proper light, let us suppose that a steam boat is abandoned to the current : in this case 
 it must speedily acquire the velocity of the stream, and be at rest in relation to the water on 
 which it floats. 1 When the machinery begins to act, no difference of circumstances can arise 
 from the direction in which the prow of the boat is turned, and all the motions in reference 
 to the mass of fluid will be performed exactly as if that mass were not in motion. In 
 moving with the current, then, the rate of progress by the land will be the sum of the ordinary 
 rate of the boat's motion, and the velocity of the stream ; in moving against the current, the 
 rate of progress will be the difference between these two velocities. 
 
 In obtaining these velocities of thirteen miles and upwards per hour, it does not appear 
 
 1 Here the particles of the fluid are supposed to move in parallel straight lines, and with the same velocity at all depths. ED. 
 
THE UNITED STATES OF AMERICA. 109 
 
 that the force of the engines employed exceeded that which had been used in some American 
 vessels which had far less speed. Neither was the relation of the power of the engine, estimated 
 in the usual manner, to the tonnage of the vessel, greater than that found in European 
 steamers, whose velocity does not appear, at that time, to have exceeded ten miles per hour. 
 Besides, it cannot be denied that the advantage in the finish and workmanship of the engines 
 was on the side of the European vessels. We may therefore inquire to what circumstances it 
 was owing, that a rate of speed, which a high British authority has very recently declared to be 
 incredible, should be actually obtained. We ascribe this chiefly to the great difference in the 
 principles which governed the structure of the engines in the two different countries. In the 
 modifications of the original form of the engine of Fulton, the English engineers, whose efforts 
 were principally directed to the navigation of stormy seas, thought it indispensable that the 
 machinery should be included beneath the deck of the vessel. The stroke of the piston and 
 the length of the crank were therefore diminished below the proportion originally chosen by 
 Watt. In America, the vessels being principally intended for the navigation of rivers, no 
 such change occurred; and when it became necessary to make the 'New Philadelphia' compete 
 with vessels driven by more powerful engines, Stevens increased the length of the stroke and of 
 the crank. The new relation between the diameter and length of the cylinder thus obtained, 
 was followed, or even exceeded, in all subsequent engines. No change was made in the 
 dimensions of the boiler, but the additional force was obtained by causing the steam to act 
 expansively. The latter method was attended by an anomaly, which is however readily 
 explained, when it is considered that the relative velocity of the circumference of the wheel is 
 constant. It was not found that the steam, although cut off, at first at half stroke, was much 
 increased in tension. The most obvious effect of the method was an increase in the velocity 
 of the piston, by which the steam was prevented from accumulating. 
 
 When we consider the wheel as a body revolving on an axis, and which meets with a 
 resistance, whose resultant is applied to a point at no great distance from its circumference, 
 it will be obvious that there will be a point, to which, if the crank be applied, the whole force 
 of the engine will be exerted to overcome the resistance ; but if the crank be applied to any 
 other point, a part of the force will be wasted upon the axle itself. Now, even in the long 
 stroke usual in the modern American engines, it does not appear that the crank extends as 
 far as this most favourable point ; but in the short stroke of the English engines a large 
 proportion of the whole power is lost. 1 This advantage is, however, at present less sensible 
 in the American steam boats ; for the principle of using cylinders of great length having been 
 introduced, the next step was to increase the diameters of the wheels. The object intended 
 to be gained by the latter change was an increase in the velocity of the circumference of the 
 wheel, for the constructors of steam boats seem to have reached the conclusion that every 
 addition to this velocity would add as much to that of the vessel. In one instance the 
 diameter of the water wheels has been increased to thirty feet, and the stroke of the piston to 
 twelve feet. 
 
 As an additional means of obtaining high velocities in the piston, the dimensions of the 
 valves and steam pipes of the American engines have been increased beyond the proportion 
 used by Watt. The flow of the steam from the boiler is thus rendered more rapid, and the 
 
 1 The author must here allude to the friction caused by the pressure on the shaft : no loss of power can otherwise result 
 from the mechanical arrangement. ED. 
 
 P 
 
110 ON THE STEAM BOATS OF 
 
 velocity of the piston increased in like degree. We have already stated that the steam is 
 cut off, and thus caused to act expansively : the advantage thus obtained is analogous to that 
 derived from the same method in the pumping engines of Cornwall. 
 
 As an accessory, and one of no little importance, we may mention the form of paddle wheel 
 originally introduced by the younger Stevens, but now universally adopted. The form of 
 this may be readily understood, by supposing a common paddle wheel to be cut into three 
 parts, by planes perpendicular to its axis ; that one of these being supposed to remain at rest, 
 the second is moved through one-third, and the third part through two-thirds of the space 
 intervening between two contiguous paddles. 
 
 It seems to be conclusively shown by the researches of Barlow, that the modifications 
 of paddle which have been tried in Great Britain, are, upon the whole, inferior to the common 
 paddle wheel. The triple wheel of Stevens does away the principal objection which can be 
 opposed to the latter, namely, the long interval between the successive strokes of the wheel 
 against the water, and their violence. 
 
 In vessels of small dimensions the same principle is applied, but the wheel is only double, 
 instead of being triple. 
 
 The velocity of the pistons of engines used for manufacturing purposes is about 200 feet 
 per second. In the ' North America' this velocity was carried up to 384 feet, and the rate is 
 now exceeded in many of the newer vessels. Thus, in the steam frigate ' Fulton,' the velocity 
 of the piston is 450 feet, and in the ' Cornelius Vanderbitt ' and ' Highlander,' as much as 
 600 feet per second. 
 
 We have enlarged upon the performances of the ' North America,' not from their being 
 unsurpassed, but in consequence of their forming an era in the history of steam navigation. It 
 was easily seen that the important part of the resistance, and which in fact seemed to oppose 
 an absolute barrier to all velocities beyond a certain limit, arose from the wave raised in front 
 of a vessel in rapid motion. 
 
 Don George Juan estimates, that this cause of resistance increases with the fourth power 
 of the velocity. It was attempted to lessen this part of the resistance, by altering the form of 
 prows. False prows were therefore adapted to the vessels in use ; and, as the cavity left 
 behind the sternpost causes a similar resistance, false sterns have also been applied. These 
 attempts have been eminently successful, and in some instances no visible wave appears on 
 the water, before the entrance of the extreme breadth of the vessel. This is remarkably the 
 case in some of the newer steam vessels, in which the form has been derived from that 
 obtained experimentally by the addition of false prows and sterns. The latest model of this 
 description is that adopted in the new steam frigate ' Fulton,' a draught of whose water lines 
 accompanies this paper. (PI. cxvi.) 
 
 A section of a vessel (the ' North Carolina,' PI. cxvu.) of similar form, but of less draught 
 of water, is also appended ; with a view of a third intended for sea navigation. 
 
 In the models of this new class of vessels, although built with keels, there is only a few 
 inches dead rise in the midship section, and the floor extends, horizontally, nearly the whole 
 length of the keel. This form will be better understood from the draught of the steam frigate 
 Fulton.' 
 
 A long flat floor had been used before in the ' North America,' ' Dewitt Clinton,' and 
 several other vessels, but differed from that of the new models in being nearly rectangular, so that 
 
THE UNITED STATES OF AMERICA. in 
 
 the prow and stern resembled conoids applied to a parallelepiped. In the new models all the 
 water lines are continuous curves, except at the place where the water wheels are applied, 
 where the sides of the vessel are vertical. The prows of the new models are wedges with 
 curved surfaces, instead of being conoidal, and the general character of their models appears 
 to Ije borrowed from the fast rowing boats, used by the Whitehall boatmen, in the harbour of 
 New York. 
 
 The first steam boat in which the new structure was adopted, was the ' Lexington.' This 
 vessel was planned by Captain Vanderbitt, a very enterprising and intelligent owner, and 
 commander of steam boats. The undertaking, considering the circumstances, was one of great 
 boldness, for this vessel was at once placed upon Long Island Sound, where it was exposed 
 occasionally to high waves. The experiment was so successful, that the passage to New Port 
 and Providence, R. I., was attempted ; and from the rapidity with which the voyages of the 
 'Lexington' were performed, the proprietors of the old class of vessels were compelled to with- 
 draw them, and substitute others designed upon the new model. So far as this particular 
 passage is concerned, the greater part of which is inland, and within reach of safe and con- 
 venient harbours, the experiment, although bold, is not to be considered as involving any 
 notable danger. But it has unluckily happened, that this apparent success has led to the 
 attempt to navigate the ocean in vessels of the same species of model. We cannot believe 
 that these vessels are to be considered as perfectly safe. Their length is as much as eight 
 times their breadth of beam, and the form of their prows and sterns extremely acute : hence the 
 tendency to hog, and break their backs is great ; and one instance has already occurred, where 
 a new vessel has gone to pieces by mere stress of weather. It may be possible, by trussing, 
 or by diagonal ceilings, to lessen the danger arising from this source ; but vessels of this 
 model will be still exposed to being washed from stem to stern by the waves. 
 
 We do not class among the objections to steam boats of the new model as sea-going 
 vessels, the fact that the cylinder is wholly raised above the level of ,the deck. It might at 
 first sight appear that the vessel would in this way be rendered, in nautical language, too 
 crank. But when we consider that the heavy masts and sails with which ships are 
 loaded, are dispensed with altogether in steam boats intended for the navigation of rivers, 
 and may be replaced in those intended for the navigation of the sea by spars of the lightest 
 description, we shall see that the centre of gravity in the latter case, need not be more elevated 
 than it is in ships. Now it is a well known principle in the stowage of ships, that stability is 
 increased for a time by raising the centre of gravity ; nay, that were it so low as to coincide 
 with the centre of the part immersed, the condition of equilibrium would be indifferent. 1 It 
 is also a well known fact, that a ship may be rendered more easy, and therefore more safe at 
 sea, by raising the centre of gravity beyond the point at which the greatest degree of stability 
 is attained. May we not, then, question whether the anxiety of the British engineers to keep 
 the weight low has been founded upon correct principles ? At any rate, although the American 
 engineers may perhaps have erred on the other extreme, their practice is not as inconsistent 
 with safety as some of their own countrymen have imagined. 
 
 One prominent mistake, however, appears to have been committed in the vessels recently 
 constructed for the navigation of the ocean in the United States. Departing from the practice, 
 
 1 We cannot assent to this principle. ED. 
 
112 ON THE STEAM BOATS OF 
 
 which had become sanctioned by successful usage, of employing two engines placed upon the 
 wheel guards, a single one has been substituted. This being necessarily placed in the plane 
 of the keel, the rolling of the vessel is rendered more rapid, and more likely to be injurious. 
 It is indeed another well known principle in the stowage of vessels, that the rolling is to be 
 rendered less violent by placing the weights at the greatest possible distance from the plane 
 of the keel, as well as at the greatest height which is consistent with stability. 
 
 The use of a single vertical engine of long stroke is attended with another difficulty, namely, 
 that it requires a large opening to be left in the deck of the vessel, which cannot be suffi- 
 ciently defended from the influx of the sea ; for the bulkheads which surround it, cannot be 
 rendered strong enough to resist a violent wave. 
 
 After all, the main objection to the present model of American steam boats, when con- 
 sidered in their fitness for the navigation of the ocean, is the weakness inherent in the great 
 proportion which their length bears to their breadth and depth. To remedy this defect is not 
 beyond the power of a skilful application of the principles of carpentry. We have already 
 indicated the most obvious method which these principles would suggest, namely, the adoption 
 of the diagonal framing of Seppings, either in the form of trusses, or in the ceiling planks. 
 
 This defect being overcome, no doubt can exist that vessels combining great safety with an 
 average speed of at least twelve nautical miles per hour, can be constructed. Such vessels 
 might make the passage from New York to Liverpool in less than twelve days ; and with 
 such a speed there can be no reason to doubt that they might carry, in the form of coal, more 
 than a sufficient supply of fuel. A direct passage will be absolutely indispensable to success ; 
 for should it be found necessary to make intermediate ports, as for instance, Valentia, or 
 Cork, Halifax, or the Western Islands, the delay consequent on making a harbour, and in taking 
 in fuel, will prevent the passage being performed in a time much less than the average passages 
 of good ships. As the expense of the steam boats will be vastly the greatest, they would not 
 be able to compete with the existing packet ships. On the other hand, in a direct passage 
 performed with the speed of the American steam boats, the saving in time will more than 
 compensate the excess of the daily expense of steam navigation. 
 
 Since the preceding paragraphs were written, an experiment has been made with the British 
 steamer, the 'Great Western,' which renders the successful navigation of the Atlantic, 
 between New York and England, without stopping at an intermediate port, no longer a matter 
 of inference, but a fact established by experience. This vessel has carried more than a suffi- 
 cient supply of coals for the passage ; and although having an average speed of no more than 
 nine nautical miles per hour, has been no more than fifteen days in making her harbour. On 
 examining this vessel, and comparing her performance with that of American steam boats, it is 
 easy to perceive that her speed might be very materially increased without making any 
 important change in her engines, and probably with a saving of fuel. It would be necessary to 
 modify the boilers so as to convert a less quantity of water than they now do into steam, but 
 to furnish it of a tension of 20 or SOffis, instead of 3 L, which they now carry. Nor, when the 
 boiler is of sufficient strength, need any increase of danger be apprehended from using steam 
 of this medium pressure. It is now well established that the mere pressure of the steam is 
 among the least important causes of danger, and that such as are most to be apprehended are 
 as likely to occur in using steam of a single atmosphere as that of ten or twelve. 
 
 The arrival of the ' Great Western ' in New York was preceded by that of the ' Sirius,' 
 
THE UNITED STATES OF AMERICA. 113 
 
 although only by a few hours. The competition for the honour of successfully accomplishing 
 this voyage, between the respective owners and commanders of these vessels, involves less of 
 reputation than is generally believed. It is nearly twenty years since the ' Savannah/ a steam 
 boat built and equipped in the port of New York, made a voyage to Europe and returned. If 
 then new honours are to be awarded, it is to the parties concerned in the ' Great Western ' that 
 they are due ; for the mere practicability of the enterprise is not the point on which well 
 informed persons have ever hesitated ; but the doubt has been whether it can be made certain 
 within given limits of time, and whether these limits will be less than the average passage of 
 packet ships. This point, which the arrival of the ' Sirius' would have left in doubt, is decided 
 by the voyage of the ' Great Western.' The question of the relation between the cost of the 
 enterprise, and the freight, is still undecided. We do not doubt, however, that this will be 
 such as to yield a profit. 
 
 The ' Savannah ' proceeded from New York to Liverpool without stopping at any inter- 
 mediate port ; from Liverpool to St. Petersburgh, touching at Copenhagen. In returning 
 thence this vessel entered the port of Arendal in Norway, and then crossed the Atlantic a 
 second time to New York, without making any intermediate port. Steam, however, was not 
 used during the whole voyage, but the use of the engine was intermitted whenever the wind 
 was such as to enable the vessel to lay her course without deviation. No record appears to 
 remain of the time in which steam alone was used, but the two passages across the Atlantic 
 were each made in twenty-five days. 
 
 A year or two after the voyage of the ' Savannah' a splendid vessel was built in New York, 
 intended as a packet between that city and New Orleans. This vessel was 600 tons burthen, 
 rigged as a ship, and propelled by a powerful steam engine. Several voyages were performed 
 successfully by this vessel, but the number of passengers was not found sufficient to defray 
 the expenses, and the vessel was laid up. This vessel had sufficient burthen to have carried 
 fuel for an entire passage to Europe,-but the public mind was not prepared for the- experiment. 
 The navigation between New York and Charleston S. C. has been for some years partially 
 carried on in steam vessels. These have generally been of small size, and the engines of 
 inferior workmanship to those used upon the Hudson and Long Island Sound. The first 
 attempt to introduce a vessel of larger dimensions and greater cost was unfortunate. The 
 vessel was so weak, in consequence of her extreme length, and the desire to render her 
 buoyant, that in the second voyage she became a perfect wreck at sea, and was with difficulty 
 brought to the land. This was an unfortunate enterprise, not only in the loss of life with 
 which the wreck was attended, but in the check it gave to the spirit of enterprise which was 
 about to be directed to the navigation of the Atlantic. 
 
 For three years past, steam packets have plied regularly between Norfolk in Virginia and 
 Charleston S. C., passing the most dangerous part of the southern coast of the United States, 
 the shoals of Cape Hatteras. 
 
 At the present time, and for some months back, a steam vessel called the ' North Carolina,' 
 has been employed in the conveyance of passengers between Charleston S. C., and Wilmington 
 N. C. A gentleman who recently travelled by this route informs us that the passage occupied 
 15^- hours. The distance by sea is 120 nautical miles, to which is to be added the distance of 
 the two places from the ocean. 
 
 The performances of some of the American vessels of the new model have been very 
 
114 ON THE STEAM BOATS OF 
 
 extraordinary. The following facts, in relation to two of them, have been derived from a com- 
 munication of Mr. Haswell, an engineer in the service of the United States, to whom the 
 construction of the machinery of the steam frigate ' Fulton ' was confided. 
 
 Steam Boat ' Cleopatra' 
 
 Diameter of wheel . . 23 feet. 
 
 Length of bucket . . 11^ feet. 
 
 Breadth of do. 2 feet, 8 inches. 
 
 Revolutions per minute . . 24 
 
 Velocity of wheel per second . 28'8 feet. 
 
 of vessel . . 22-6 feet. 
 
 Relative velocity of wheel . 6'2 
 
 Steam Boat 'Lexington.' 
 
 Diameter of wheel . . 24 feet. 
 
 Length of bucket . . 11 feet. 
 
 Breadth of do. . . 2 feet, 8 inches. 
 
 Revolutions per minute . 23 
 
 Velocity of wheel per second . 28'8 
 
 of vessel . . 22'5 
 
 Relative velocity of wheel . 6 - 3 
 
 These velocities would carry up the speed of the vessels to 15 English miles per hour, and 
 it appears that in many instances such a rate has been attained for a short time. But we 
 have no evidence to adduce that the ordinary average performances of the most recently con- 
 structed boats have amounted to more than fourteen English miles per hour. The average 
 passages between New York and Albany do not yet fall much short of eleven hours ; and if 
 we allow no more than half an hour for stoppages, the rate is less than fourteen miles. 
 
 A speed almost equal is attained in the passage between New York and Providence, Rhode 
 Island. This passage, as we have partly stated, is performed upon the arm of the sea, called 
 at New York the East River, and for its greater extent, Long Island Sound. On leaving 
 this, the open sea is entered, and the voyage, after passing through an open and wide bay, 
 terminates in a narrow river. In its circumstances of alternate shelter and exposure, it may 
 be likened to the passage from London to Calais. The distance, as measured on a good chart, 
 is 160 nautical or 184*3 English miles. We have obtained the records of a voyage performed 
 between the two places, by the steam boat ' Massachusetts,' the circumstances derived from 
 which, with the dimensions of the vessel, are given beneath : 
 
 Length of vessel . . 200 feet. 
 
 Breadth of beam . . 29^ feet. 
 
 Draught of water . . 8 feet, 5 inches. 
 
 Diameter of wheel . . 22 feet. 
 
 Length of bucket . . 10 feet. 
 
 Depth of do. . . 2 feet, 4 inches. 
 
 Diameter of cylinder . . 3 feet, 8 inches. 
 
 Length of stroke . . 8 feet. 
 
THE UNITED STATES OF AMERICA. 115 
 
 Number of revolutions . . 26 
 
 Velocity of vessel per second . 19'95 feet. 
 
 Relative velocity of wheel per second 6'3 feet. 
 
 Whole velocity of wheel . 26-25 feet. 
 
 The passage whence the above data were derived, was performed in thirteen hours and a 
 half, and does not differ materially from the average of those now usually performed. 
 
 It would thus appear that no very great increase of speed has been gained in the steam 
 boats used in river navigation since the construction of the ' North America.' As to those 
 which navigate the Sound, the improvement in velocity is considerable, but seems to be 
 attended with a loss of good qualities in other respects. But we are not to estimate the value 
 of the new models from speed alone. It is in the duty of the engines, or the effect produced 
 by a given quantity of fuel, that the newly constructed vessels manifest their superiority. 
 Not only is the size and nominal power of the engines used in boats of given dimensions 
 lessened, but the fuel Consumed in the passages is diminished in a still greater ratio. Thus 
 the ' Erie ' and ' Champlain,' boats of a newer construction than the ' North America/ but 
 modelled after her, have each two engines 44 inches in diameter, and 10 feet stroke ; while the 
 ' Rochester,' 20 feet longer than either, and of two feet less beam, has no more than one 
 engine of the'same dimensions. In comparative speed the ' Rochester 3 has the advantage over 
 the others. The two vessels belonging to the Port of New York, which have the highest 
 reputation for speed, are the ' Passair,' and ' Cornelius Vanderbitt.' The former was con- 
 structed by the younger Stevens, and the latter is said to be as near a copy of her dimensions 
 and model, as could be constructed without direct reference to the original moulds. The ' Pas- 
 sair' has not come into direct competition with the vessels which navigate the Hudson, but 
 the ' Cornelius Vanderbitt' exceeds them all in speed. The superiority of this vessel, how- 
 ever, rather consists in the capacity of arriving first at the several landings, in the case of a trial 
 of speed, than in any great reduction of the average time of passage. In fact, to gain several 
 miles in the course of a passage amounts to no more than a saving of a very few minutes of 
 time. 
 
 Our view of the subject would be incomplete, did we not refer to a vessel which has been 
 for some months in preparation in the port of New York, for the purpose of running between 
 that city and Liverpool. In this vessel a new form of boiler has been introduced, the prin- 
 ciple of whose action is, that the combustion shall be maintained by air forced into a furnace 
 without a chimney, and that the air, after acquiring, by the joint effect of compression and 
 elevated temperature, a tension equal to that of the steam, shall open a valve by which it may 
 join the steam in its passage to the valves of the engine. A sufficient number of experiments 
 have been performed with this boiler, to show that it will produce a given effect at a vast 
 saving of fuel, but various practical difficulties seem to oppose its perfect success. 
 
 In conclusion it may be stated, that in respect to speed the steam boats of the Hudson 
 exceed any others, have attained a velocity which is hardly believed to be possible in 
 Europe, and are for the navigation of rivers unequalled. The same principles, modified 
 according to the circumstances of the case, may be applied to give a greater velocity to vessels 
 intended for the navigation of the ocean than has yet been attained by the English steamers. 
 On the other hand, the vessels constructed in the United States for speed, want some of the 
 essential properties of good sea boats. In the competition and honourable rivalry between 
 the engineers and naval architects of the two countries, which the voyage of the 'Great 
 
116 
 
 ON AMERICAN STEAM BOATS. 
 
 Western ' is likely to call forth, the advantages of the methods which difference of circum- 
 stances has brought into use in England and the United States will probably be combined. 
 We may therefore hope to see the rapid motion of the American vessels planned for river 
 navigations, united with the strength, safety, and seaworthy qualities of the British steamers. 
 By such an union the ports of the British channels, and the mouth of the Hudson, will be 
 brought within twelve days' passage of each other, and the time of transit diminished one half. 
 It is difficult to appreciate the advantages which will be mutually derived from such speedy 
 and easy communication, not only to the ports between which it shall be carried on, but to 
 both nations. 
 
 LIST OF STEAM VESSELS OF THE LATEST CONSTRUCTION BELONGING TO THE 
 
 PORT OF NEW YORK. 
 
 Names of 
 vessels. 
 
 Length 
 on 
 deck. 
 
 Breadth 
 of 
 beam. 
 
 Draught 
 of 
 water. 
 
 Diameter 
 of 
 wheel. 
 
 Length 
 of 
 bucket. 
 
 Depth 
 of 
 bucket. 
 
 No. of 
 engines. 
 
 Diameter 
 of 
 cylinder. 
 
 Stroke. 
 
 Number 
 of revo- 
 lutions. 
 
 Feet. 
 
 Feet. 
 
 Feet. 
 
 Feet. 
 
 Feet. 
 
 Inches. 
 
 
 Inches. 
 
 
 
 Steam Frigate Fulton* 
 
 181-5 
 
 34-5 
 
 10 
 
 22-4 
 
 11-5 
 
 36 
 
 2 
 
 50 
 
 9 
 
 25 
 
 Massachusetts 
 
 200- 
 
 29-5 
 
 81 
 
 22 
 
 10 
 
 28 
 
 2 
 
 44 
 
 8 
 
 26 
 
 Narragausett 
 
 
 
 
 25 
 
 11 
 
 30 
 
 1 
 
 60 
 
 12 
 
 
 Swallow 
 
 232-8 
 
 22-5 
 
 H 
 
 24-2 
 
 11 
 
 30 
 
 1 
 
 46 
 
 
 27 
 
 Rochester 
 
 200- 
 
 25 
 
 3J 
 
 23-5 
 
 10 
 
 24 
 
 1 
 
 43 
 
 10 
 
 28 
 
 Utica 
 
 200 
 
 21 
 
 31 
 
 22 
 
 91 
 
 24 
 
 1 
 
 .39 
 
 10 
 
 
 N. Cobb 
 
 176 
 
 18 
 
 4 
 
 20 
 
 10 
 
 22 
 
 2 
 
 35 
 
 6 
 
 
 Clifton 
 
 135 
 
 18 
 
 3J 
 
 18-7 
 
 7 
 
 24 
 
 1 
 
 25 
 
 9 
 
 25 
 
 Erie \ 
 Champlain 
 
 180 
 
 27 
 
 51 
 
 22 
 
 15 
 
 34 
 
 2 
 
 44 
 
 10 
 
 271 
 
 Belle 
 
 190 
 
 26 
 
 41 
 
 24-5 
 
 11 
 
 26 
 
 1 
 
 50 
 
 10 
 
 25 
 
 New York 
 
 230 
 
 22 
 
 4 
 
 24 
 
 11 
 
 30 
 
 1 
 
 50 
 
 10 
 
 
 Boston 
 
 150 
 
 28 
 
 71 
 
 19 
 
 9 
 
 30 
 
 I 
 
 40 
 
 7 
 
 23 
 
 Highlander 
 
 181 
 
 24 
 
 4-3 
 
 20 
 
 10 
 
 30 
 
 1 
 
 41 
 
 10 
 
 30 
 
 Dewitt Clinton 
 
 230 
 
 28 
 
 5-5 
 
 21 
 
 13-7 
 
 36 
 
 1 
 
 65 
 
 10 
 
 29 
 
 Olive Branch, \ 
 (Ferry boat), J 
 
 90 
 
 23 
 
 *f 
 
 15-3 
 
 6 
 
 22 
 
 1 
 
 25 
 
 8 
 
 30 
 
 Arrow 
 
 160 
 
 21 
 
 4-3 
 
 22 
 
 8 
 
 22 
 
 1 
 
 31 
 
 11 
 
 27 
 
 Bolivar 
 
 120 
 
 24 
 
 4 
 
 15 
 
 5-5 
 
 22 
 
 1 
 
 30 
 
 4 
 
 30 
 
 Fulton, (Ferry boat), 
 
 95 
 
 25 
 
 4-7 
 
 15 
 
 7 
 
 24 
 
 1 
 
 30 
 
 8 
 
 25 
 
 Neptune, (Charles- "1 
 ton packet), J 
 
 220-7 
 
 25 
 
 7-5 
 
 25 
 
 9-4 
 
 36 
 
 1 
 
 50 
 
 11-5 
 
 
 Home, (lost on the") 
 
 
 
 
 
 
 
 
 
 
 
 coast of North I 
 
 212 
 
 22 
 
 6-5 
 
 25 
 
 10 
 
 24 
 
 1 
 
 56 
 
 9 
 
 25 
 
 Carolina 
 
 
 
 
 
 
 
 
 
 
 
 Echo 
 
 117 
 
 15 
 
 3 
 
 15 
 
 6-5 
 
 16 
 
 1 
 
 20 
 
 6 
 
 32 
 
 Cornelius Vanderbitt 
 
 175 
 
 24 
 
 5-3 
 
 22-2 
 
 10 
 
 24 
 
 1 
 
 41 
 
 10 
 
 30 
 
 We are indebted to Lieut. Lynch, of the United States frigate ' Fulton,' for the following additional particulars : 
 
 Tonnage of the United States steam frigate ' Fulton' 875 American tons. 
 
 Depth of hold ........... 12ft. 
 
 Power of engine (mean average of steam) 500 H. P. 
 
 (Made by Mr. Kemble, agent for the West Point Foundry Association.) 
 
 The cylinders are laid nearly horizontal, with a very slight upward inclination. ED. 
 
ON PADDLE WHEELS. 117 
 
 VII. ON PADDLE WHEELS. 
 
 BY ARISTIDES A. MORNAY, ESQ. 
 
 UNTIL within the last few years the construction of paddle wheels, although by no means 
 an unimportant part of the machinery of steam vessels, met with little or no attention from 
 men capable of investigating the action and estimating the qualities of this description of 
 machinery ; and even now we have but few works on this subject, and those generally of a 
 superficial character, by far the most complete being Mr. P. W. Barlow's paper On the Motion 
 of Steam Vessels, published in the Philosophical Transactions for 1834; which, with some 
 important additions, is inserted in another part of this work. 
 
 It is well knoM'n that the common paddle wheel, which has been almost universally used 
 from the time when the steam engine was first applied to the purpose of propelling vessels, is 
 very defective in its action, owing to the great obliquity of the floats ; the immediate conse- 
 quence of wh'ch is the loss of a considerable portion of the power applied, from the reaction of 
 the water not taking place in the direction in which the useful effect is produced. This is 
 what is understood by oblique action. Another disadvantage arising from the above cause is 
 the shock received by each float on entering the water, the resistance being the greatest at 
 that instant, when also the smallest proportion of it is beneficially employed, the obliquity of the 
 floats being greater at the beginning and end than at any other part of the stroke. The rapid 
 succession of shocks so produced causes an unpleasant tremulous motion in the vessel, and 
 occasions a further loss of power by checking the motion of the wheel, and thus impairing its 
 effect as a fly wheel. Another bad effect of the great obliquity of the floats is the back water, 
 or the water thrown up by the floats as they leave the water, and projected towards the stern 
 of the vessel. 
 
 To remedy these defects many different plans have been devised, but few of them have 
 attracted serious attention ; the greater number having been erroneous in principle, and fre- 
 quently extremely inconvenient in practice. 
 
 One of the earliest of these inventions is that of Mr. Robertson Buchanan, for which he 
 took out a patent in the year 1813. In his wheel the floats are made to maintain the vertical 
 position during the whole revolution, and consequently there is no oblique action ; but during 
 the first and last portions of the stroke the floats impinge upon the water with their front 
 surfaces, thus opposing an additional resistance to the progress of the vessel. For this reason 
 Buchanan's wheel has not come into use, although not very complicated in its construction. 
 This wheel, with a very slight modification, was again patented in 1828 by Mr. A. Bernhard. 
 
 Several wheels were so contrived that each float entered the water edgewise, and was then 
 made to turn on an axis radiating from the centre of the wheel until it took the same position as a 
 
118 APPENDIX. 
 
 float of the common wheel, and so passed the middle of the stroke ; after which it was again 
 made to turn on the same radial axis, so as to come out of the water in the same manner as it 
 went in. In these the shock and back water are, no doubt, in a great measure avoided, but 
 the loss of power from oblique action is still greater than in the common wheel; the con- 
 trivances also for causing the floats to take the required positions are all very objectionable in a 
 mechanical point of view ; so that no advantage has been found to result from the use of 
 wheels constructed on this principle. A wheel of this description was patented in the year 
 1828 by Messrs. W. and J. Stead, another by Messrs. W. and A. Symington in 1834, and a 
 third was invented in 1829 by Mr. A. Heilbronn, of New York. 
 
 In the wheel invented by Lieutenant Skene, R.N., in the year 1828, each float was 
 suspended on a horizontal axis, and its lower part loaded with metal, so as to cause it to 
 enter the water in a vertical position ; by the time it had reached the middle of the stroke, 
 a projection on each side had come in contact with the arm of the wheel, causing it then to 
 act precisely as a common radial float to the end of the stroke. It was tried on the ' Sons of 
 Commerce' Gravesend steam boat, and the performance was found to be better when the floats 
 were lashed to the arms, than when free to act as intended by the inventor. 
 
 In some wheels the floats have been fixed obliquely, so as to enter and leave the water 
 more gradually, in order to diminish the shock and back water ; but the action is more oblique 
 than that of the common wheel. A patent was obtained by Mr. S. Hall in 1836 for a 
 wheel of this description. Mr. J. Perkins proposed to place both the floats and the shafts 
 obliquely ; and other arrangements, too numerous to be detailed here, have been proposed, 
 mostly with the object of reducing the shock and back water, without regard to the oblique 
 action. 
 
 In 1827, Mr. J. Oldham took out a patent for a very ingenious method of giving each float 
 exactly half the inclination of the radius passing through its centre. By this means the shock 
 and back water, as well as the loss of power from oblique action, were very much reduced ; but 
 the objection in practice to the use of spur wheels, by means of which the feathering of 
 the floats was effected, has prevented this wheel from being generally adopted. Several other 
 modes of producing the same effect have been contrived, but similar objections apply to 
 them all. 
 
 A wheel which has been employed to a considerable extent is that generally known as 
 Morgan's wheel. In this the floats may be made to enter and leave the water at any required 
 angle, which is therefore regulated in each wheel according to the relative velocities of the 
 wheel and the vessel ; and the machinery for this purpose does not appear to have been attended 
 with any serious inconvenience in practice. Since 1829, the date of the patent, a consider- 
 able number of government and private steam vessels, both English and foreign, have been 
 fitted with wheels of this construction. In the year 1829, Mr. Poole took out a patent for a 
 wheel in which the action of the floats is the same as in Morgan's wheel; this effect is 
 however produced by means of a very different contrivance, which is attended with several 
 disadvantages. Another wheel, very similar to Morgan's, was invented by Mr. Cave, engineer 
 at Paris, in 1827, but the action of the floats was much less uniform in consequence of a 
 difference in its construction. 
 
 A modification of the common wheel was tried in the year 1833 by Mr. Jos. Field, the 
 object of which was to reduce the shock and back water, without impairing the effect of the 
 
ON PADDLE WHEELS. 119 
 
 wheel ; but it does not appear to have answered Mr. Field's expectations at that time, for it 
 did not come into public notice until 1835, when Mr. E. Galloway, ignorant of what had been 
 previously done by Mr. Field, took out a patent for the same arrangement, since which time 
 it has been applied to a considerable number of private steamers and to a few government 
 vessels ; but the experiments hitherto made have not established its superiority over the other 
 kinds of wheel with which it has been compared. 
 
 In order to facilitate the following investigation, we will divide the different kinds of paddle 
 wheels into two classes : 
 
 I. Paddle wheels with fixed floats. 
 
 II. Paddle wheels with feathering floats. 
 
 Before, however, proceeding to the examination of each kind of wheel in particular, 
 we will offer some preliminary observations on the motion and action of paddle wheels in 
 general. 
 
 ON THE MOTION OF PADDLE WHEELS. 
 
 If the paddle wheels of a steam vessel be made to revolve, the vessel being at rest, which is 
 always the case at first starting, any given point of one of the wheels (if of the first class) 
 will describe a circle ; but as soon as the vessel has acquired a certain velocity, its path will be 
 lengthened out into a curve, which has been called a curtate cycloid; this continues to lengthen 
 as the vessel gains velocity, and becomes the common cycloid when the velocity of the vessel is 
 equal to the circumferential velocity of the given point. If the speed of the vessel go on 
 increasing, the given point will describe a curve called a prolate cycloid, 
 
 By circumferential velocity is understood the velocity of any point of the wheel relative to 
 the centre of the shaft, or, in other words, what its absolute velocity would be if, the centre 
 being stationary, the wheel made the same number of revolutions in the same time. 
 
 It is evident that when the vessel has attained her maximum speed, there will be a series 
 of points in each wheel, situated at an equal distance from its axis, which will describe common 
 cycloids : the projection of these points on a plane perpendicular to the axis of the wheel is 
 called the rolling circle. All points situated within the circumference of the rolling circle 
 describe prolate, and all those without the same curtate cycloids. 
 
 To illustrate the motion of paddle wheels, we will refer to Plate LXXIV, where Fig. 1 is a 
 diagram of the common wheel as fitted to Her Majesty's steam vessels 'Phoenix' and 'Sala- 
 mander.' C is the centre of the shaft ; r, r, r, represent the arms ; and A B, A B, A B, the 
 floats. L L is the water line at the light immersion of the ' Phcenix,' and L 1 L 1 at the deep 
 immersion of the ' Salamander.' The extreme radius C A is 10 ft. 6 in.; the depth of the floats 
 2 feet 6 in. ; their breadth 9 ft., 1 and number 16. The floats are here drawn radiating from the 
 centre, which is not strictly the case in practice, as they are generally fixed on one side of the 
 arms of the wheel ; the deviation is, however, so trifling, that it is of no importance. Fig. 2 
 is intended to show the path of one of the floats according to the result of the mile trial of 
 the 'Phcenix' made at Woolwich to ascertain her speed. The number of strokes per minute 
 
 ' We have since learned that the breadth of the floats of the ' Salamander's ' wheels is only 8 ft. 9 in. 
 
120 
 
 APPENDIX. 
 
 made by the engines is stated to have been 21, the speed of the vessel 11*7 statute miles per 
 hour, and the greatest immersion of the floats 2 ft. 6 in., or exactly their own depth. L L 
 (Fig. 2) is the water line, C the centre of the shaft, D D D the circumference of the rolling 
 circle, A B the float, and C A the radius, at the commencement of a revolution of the wheel ; 
 C C 1 is the line described by the centre during one revolution, which is equal to the distance 
 traversed by the vessel during the same time; D 1 D 1 D 1 is the position of the rolling circle, 
 and A" B" that of the float at the end of the revolution. The curtate cycloid A A 1 A 11 is the 
 line described by the outer edge of the float, and B B 1 B 11 that described by its inner edge; 
 and the various positions of the float are shown at intervals of one sixteenth of a revolution. 
 In order to render the motion of the float through the water more distinct, the node has been 
 drawn on an enlarged scale in Fig. 3, where Aa 1 A 11 is a part of the curve described by the 
 outer edge of the float, and B6 1 B 11 a part of that described by its inner edge, L L the water 
 line, a b the position of the float at the instant of entering the water, a b its position soon 
 after the immersion of the lower edge, being the end of one of the intervals mentioned above, 
 a 1 b 1 at the end of the next interval, a 1 6 1 in the middle of the stroke, and so on, a 11 6" being 
 its position at the instant of leaving the water. Figs. 4 and 5 relate to the performance of 
 the ' Salamander' at the mile trial, when the greatest immersion of the floats is stated to have 
 been 5ft. 6 in., the number of revolutions 15, and the speed 8'15 statute miles per hour. 
 
 It has already been observed, that every point of a common paddle wheel situated on the 
 circumference of the rolling circle describes a common cycloid : let C A in the annexed 
 diagram represent a radius of the wheel, intersecting the circumference of the rolling circle at 
 the point B, and let D E be the vertical diameter of the rolling circle. On C D as a diameter 
 describe a circle intersecting the radius C A at the point F. The arc F D of this circle is 
 equal to the arc B D of the rolling circle, being the measure of twice the angle measured by 
 the latter in a circle of half the radius ; therefore if the two circles E B D, C F D, roll simul- 
 taneously along the horizontal straight line H K, so as to preserve the same relative positions, 
 the points B and F will coincide at some point G on that line, and will describe two cycloidal 
 
 arcs, to the latter of which the radius C A, or its production on the opposite side of the 
 centre, will always be tangent at its intersection F with the circumference C F D ; this point 
 
ON PADDLE WHEELS. 121 
 
 is, therefore, in any given position of the radius moving in the direction of the radius itself, 
 which consequently lias no angular velocity at this point. The whole jadius may thus be 
 conceived to move in its own direction, and at the same time to revolve about the point F. 
 If we call p the radius of the rolling circle, and < the angle A C D contained between the 
 given radius and the vertical, the distance C F is equal to p cos. < . 
 
 ON THE ACTION OF PADDLE WHEELS. 
 
 Every paddle wheel may be regarded as a series of levers, coming successively into action. 
 Each lever is represented by one of the arms of the wheels, at the extremity of which a float 
 is attached : the fulcrum is obtained by means of the reaction of the water on the paddle 
 board; the resistance to be overcome is that of the water to the motion of the vessel 
 acting at the centre of the wheel and in the direction of the vessel's course ; and the power 
 is that of the engine, applied at the extremity of the crank, which thus forms a bent lever 
 with each arm of the wheel. Now, since the fulcrum is obtained, as above stated, by means 
 of the reaction of the water on the float, and there can be no reaction unless the surface of 
 the float move through the water, it follows that the true fulcrum is situated at that point, on 
 which, if immersed, there would be no reaction. This is the point F found above ; for, as it 
 moves in the direction of the surface of the float, it can meet with no resistance from the 
 water. A certain expenditure of power is therefore necessary to force the floats through the 
 water, in addition to that required to propel the vessel. 
 
 It is evident that the mean horizontal pressure on the floats of a steam vessel must be equal 
 
 to the resistance opposed to the motion of the vessel ; therefore the 
 motive power must be equal to the mean product of the total pres- 
 sure on the floats by their velocity perpendicular to their surface, 
 plus the product of the mean horizontal pressure by the velocity of 
 the vessel. This sum in the common wheel is equal to the mean 
 product of the total pressure on the floats by their circumferential 
 velocity ; for let C A in the annexed figure represent a radius of 
 the wheel, C D a vertical line, and A a point of the surface of the 
 float ; also let A B, perpendicular to C A, represent the circum- 
 ferential velocity of the given point, and the horizontal line B G the 
 velocity of the vessel. Join A G, and draw G E parallel to 
 C A. The motion of the given point is in the direction of the 
 line A G, the length of which represents its velocity. Let p be 
 the pressure on the point A in the direction B A, perpendicular to the surface of the float ; 
 the pressure in the direction G A will be p sin. AGE, and the power required to overcome 
 that resistance at the velocity A G will be p sin. AGE x A G = p xAE. The horizontal 
 
 T> -p 
 
 pressure is equal to p cos. A B G = p x -p, which, multiplied into the velocity of the 
 
122 APPENDIX. 
 
 vessel, gives p x B E for the propelling effect. The sum of these two quantities is p [A E + B E] 
 = p x A B, whiclj is the product of the total pressure on the given point by its circum- 
 ferential velocity, as was to be proved. 
 
 This is true only for wheels with radiating floats : in all other cases the velocity perpendicular 
 to the surface of the float which the given point would have if the axis of the wheel were 
 stationary, must be substituted for the circumferential velocity, and, as in the common wheel 
 the motion of each float is perpendicular to its surface when the axis is at rest, these two 
 velocities are identical. 
 
 In order to be able to calculate the absolute amount of power required to produce a given 
 effect, it is necessary to be acquainted with the laws which govern the resistance of fluids to the 
 motion of solid bodies in them, which are generally admitted to be based on the following 
 theorem. Prop. 1. If a plane surface move at a given velocity through a fluid at rest in a 
 direction perpendicular to itself, the resistance is proportional to the density of the fluid and 
 to the square of the velocity of the plane, or it is equal to the weight of a column of the fluid, 
 whose base is equal to the area of the surface, and altitude equal to the height through which 
 a body must fall by the force of gravity to acquire the given velocity ; which, if v denote the 
 A'elocity of the surface in feet per second, a its area in square feet, and w the weight of a cubic 
 
 v 2 v 2 
 
 foot of the fluid, is equal to a w , the altitude due to the velocity v being. 
 
 2/ *2ff 
 
 It is assumed that the resistance to a plane moving in a fluid at rest is equal to the pressure 
 of the fluid on the plane at rest, the fluid moving at the same velocity and in the contrary 
 direction to that of the plane in the former case; on which hypothesis the ratio of the square of 
 the velocity is explained in two very different ways. The first is, that " the resistance must 
 " vary as the number of particles which strike the plane in a given time, multiplied into the 
 " force of each against the plane ; but both the number and the force are as the velocity, and 
 " consequently the resistance is as the square of the velocity." The second explanation is, that 
 " the force of the fluid in motion must be equal to the weight or pressure which generates 
 " that motion, which, it is known, is equal to the weight of a column of the fluid, whose base 
 " is equal to the area of the surface, and altitude the height through which a body must fall 
 " to acquire the given velocity." 
 
 These explanations are extracted from Dr. Gregory's Treatise on Mechanics, in which he 
 states that they are founded on the hypothesis that " the particles of the fluid move freely 
 " without disturbing each other's motions, and that it flows in behind as fast as a plane body 
 " moves forward, so that the pressure on every part of the body is the same as if the body 
 " were at rest," which is well known to be incompatible with the nature of any fluid with 
 which we are acquainted. 
 
 In what precedes, only one plane has been mentioned, namely, that which strikes the fluid, 
 the after surface of a body being supposed, by the hypothesis, to have no influence on the 
 resistance ; but we know that the pressure on the after surface must decrease as the velocity 
 increases, for if the body were suddenly abstracted, so as to leave a void, the water which had 
 been pressing on the after surface could only move to fill it with the velocity due to its depth 
 below the surface of the fluid ; so that, if the body moved forward with a greater velocity, the 
 fluid would cease to be in contact with it, and could not therefore exert any pressure upon it, 
 
ON PADDLE WHEELS. 
 
 123 
 
 much less the same as if the body were at rest. We have not yet met with any explanation 
 of the law according to which this pressure decreases, but we suggest the following. 
 
 Let A be a reservoir of fluid, which we will suppose to be water, but the reasoning will 
 apply as well to any other fluid, and let B C be a bent tube 
 communicating with the reservoir by means of the aperture a, 
 at a depth d below the level of the water in the reservoir, 
 which is supposed to be maintained constant, the part B 
 being horizontal, and the part C vertical and open at the 
 extremity c, which is situated at a height h above the level 
 of the aperture a. It is evident that, neglecting the effect of 
 friction, the water will issue from the orifice c with the 
 velocity due to the head d h, or, calling v the velocity of 
 the water, v= ^ 2 g (d h) ; and, if the sectional area of the tube B be equal to the area of the 
 orifice c, the water in it will have the same velocity ; so that, if a solid piston were fitted into the 
 tube B, and made to move forward towards the branch C with the above velocity, the pressure 
 on both sides of the piston would be equal, or if the branch C were removed, the pressure of 
 the water in the reservoir on the after surface of the piston would be equal to the weight of a 
 
 v 3 
 column of water, whose altitude is equal to h or d . Or it may be explained other- 
 
 i/ 
 
 wise, thus : Let a solid body, terminated by a plane at its stern end, move through water in 
 a direction perpendicular to that plane with a given velocity v. The water in immediate 
 contact with the surface must evidently have the same velocity if it remains in contact with 
 it ; to generate which velocity in the water a pressure is required equal to the weight of a 
 
 v 2 
 column, whose altitude is ; this pressure cannot produce any effect on the surface, its 
 
 *9 
 
 force being already expended in producing the motion of the water, and must therefore be 
 deducted from the weight of the total column of water pressing upon the surface when 
 at rest. 
 
 Applying this to the case of a prismatic body terminated at both ends by planes perpen- 
 dicular to its axis, moving through water in the direction of its axis, which is supposed to be 
 horizontal, with a certain velocity v, we find for the pressure on an indefinitely small portion 
 
 v 2 
 
 e of its after surface, situated at a depth d below the level of the water, e \d ] ; so that 
 
 * ff 
 
 if we suppose the pressure on the head end of the body to be the same as if the body were at 
 rest, i. e. e d on an element of the front surface equal and opposite to that on the after surface, 
 
 v* v 2 
 
 the excess of pressure on the former will be e [d (d 5)] or e ., which is equal to the 
 
 y * & 
 
 whole resistance as generally assumed. There seems to be no reason to suppose the head 
 pressure to increase with the velocity ; so that the only addition to be made to the above 
 resistance would be that produced by the cohesion of the particles of water. 
 
 Another theorem, founded on the preceding, and applicable to paddle wheels, is the 
 following : 
 
 Prop. 2. If a plane surface move with a given velocity through a fluid in a direction not 
 perpendicular to itself, the resistance is equal to the weight of a column of the fluid, whose 
 
124 APPENDIX. 
 
 base is equal to the area of the surface, and height that due to the given velocity, multiplied 
 
 into the cube of the natural sine of the angle of incidence. 
 
 Let A B in the annexed figure be the horizontal projection of the given plane, which we 
 A. suppose to be vertical, and moving in the direction, and with the 
 velocity B C ; and draw C D perpendicular to A B. The pressure on 
 the given surface is by the former theorem proportional to the square 
 of its velocity through the fluid in a direction perpendicular to itself: 
 this velocity is here represented by the line C D, for the pressure is 
 
 precisely the same as it would be if the surface moved in the direction of that line, and with a 
 
 velocity equal to its length. Thus, calling v the velocity B C, i the angle of incidence ABC, 
 
 t) ^ sin / ^ 
 
 andjo the pressure on the surface perpendicular to its plane, p = a - , and the resistance 
 
 2 9 
 
 in the direction C B, which is equal to p sin. i, = a 
 
 The power required to overcome this resistance with the velocity v, being equal to the 
 
 77 " Sill t '* 
 
 moment of the resistance or the pressure multiplied into the velocity, is a - v or 
 
 y 
 
 v ^ sin / '' 
 ^ , which is the same as if the surface moved perpendicularly to itself with the 
 
 velocity v sin. i. This may therefore be called the effective velocity of the surface. 
 
 These two propositions form the basis of all the calculations contained in the present 
 paper. 
 
 CLASS I. PADDLE WHEELS WITH FIXED FLOATS. 
 
 1. The Common Wheel. 
 
 The construction of this wheel is so simple and so well known, that a description of it here 
 would be superfluous, having already referred to the diagram PL LXXIV. Fig. 1, which is 
 sufficient for our present purpose ; we shall therefore proceed at once to investigate the action 
 of the floats (which, for the sake of simplicity, we shall suppose to be perfectly radial) during 
 their motion through the water. 
 
 Let R be the extreme radius of the wheel, r the radius to the inner edge of the floats, a the 
 height of the axis above the level of the water, < the angle which the surface of one of the 
 floats makes with the vertical at any given instant, x the distance of a given point .of the 
 surface from the axis, V its circumferential velocity, and v the velocity of the vessel, all the 
 measurements being given in feet, and the velocities in feet per second. The velocity of the 
 given point through the water in a direction perpendicular to the surface of the float, which we 
 have called its effective velocity, is equal to V v cos. $ ; for, in the figure page 121, A being 
 the given point, its effective velocity is A E ; and, the angle A B G being equal to A C D 
 which is equal to $ , and A B being equal to V and B G to v, we have 
 
 AE=AB-BE =V-vcos. <f> . 
 
ON PADDLE WHEELS. 125 
 
 Let n be the number of revolutions of the wheel per minute, and p the radius of the rolling 
 
 circle; the distance travelled by the vessel in a minute = 60 v = 2 TT p n, whence v = - . 
 
 30 
 
 In like manner V = - These values being substituted in the expression of the effective 
 
 velocity, it becomes 
 
 TT n r 
 
 [at-pcoB. +]. 
 
 The factor x p cos. <f> is the distance of the given point from the point F (V. Fig. page 120). 
 
 Let b be the breadth of the float, then b.dx will be the area of an element of its surface 
 extending from one side to the other, and the resistance opposed to its motion, according to 
 the theory already laid down, will be equal to 
 
 w being the weight of a cubic foot of water. 
 
 If we multiply this expression into the circumferential velocity of the element of surface, we 
 have already shown that the product will be the power expended upon it, or the differential of 
 the power expended upon the surface of the float while in the given position. We have 
 therefore, calling^ this latter quantity, 
 
 27000 x2y . 
 
 and supposing the upper edge of the float not to be immersed below the surface of the water, 
 in which case the limits of the values of x are R and 
 
 27000 x 
 
 COS. <f> 
 
 /R 
 [x p cos. </>] 2 x. dx 
 3 
 
 cos. <t> 
 1 n 3 bw i 1 2 _ 1 la 4 
 
 27000 x2 ff 
 
 If we call P the mean power expended on the float during a whole revolution, on the 
 supposition that it is never immersed above its upper edge, and a. the angle at which it enters 
 and leaves the water, we shall have 
 
 7r 2 w 3 6w " a 
 
 p = _ / [3fl<-8#>cos.</> + 6flVcos.</> 2 - ~^~ + ^-^ - 6V] rf^. 
 
 324000 x 2c/ J L cos.</> 4 cos.^> 2 
 
 By integration we find, after simplifying, 
 
 _ 7T 2 W 3 AW 
 
 In cases where the upper edge of the float is immersed during a part of the stroke to a 
 certain depth below the surface of the water, the above value of P includes the power which 
 would be expended on a paddle-board extending from the upper edge of the actual float to 
 the surface of the water at the deepest immersion of the radius. This quantity, which is to 
 be deducted from the former, is found by substituting in the value of P, r for R, and /3 for , 
 
 r 
 
126 APPENDIX. 
 
 /3 being the angle at which the upper edge of the float enters and leaves the water. The 
 difference multiplied by 2 m, the number of floats in the two wheels, will express the power 
 expended upon them in ffis. raised one foot per second, which is reduced to horse powers by 
 multiplying by 60, the number of seconds in a minute., and dividing by 33000. We find thus 
 for the general expression of the power of the engines of a steam vessel transmitted to the 
 paddle wheels, 
 
 . . (1) 
 
 To find the portion of this power which is effective in propelling the vessel, we must first 
 find the mean horizontal pressure on the floats, which, multiplied into the velocity of the 
 vessel, will be equal to the effective power required. 
 
 The horizontal pressure on one of the floats in any given position is equal to the product 
 of the total pressure by the cosine of its inclination, or 
 
 R 
 jr'ri'bw 
 
 900 x 2ff 
 
 I [xp cos. $] 2 cos. $ dx. 
 \J 
 
 COS. <p 
 
 This is equal to 
 
 TJ- + a?p a p 2 cos. 
 
 the mean value of which during an entire revolution is, 
 
 2700x20,7 V cos.<f> 
 
 
 
 Integrating and simplifying, we find the mean horizontal pressure on one of the floats, 
 supposed to extend to the surface of the water, to be equal to 
 
 7TW 2 bw ( i \ I \1 
 
 ,,-.. r { 6a?p3R'p3ap i ) .+ (2R 3 + 4Rp 2 3 Rap 2Ra? ap 2 cos.a) sin. >. 
 5400 x2y l\ / v / J 
 
 The quantity to be deducted in cases where the float is immersed above its upper edge, 
 is found in the same manner as it was done for the total power, and the remainder, which 
 then expresses in Ibs. the mean horizontal pressure on one of the floats, multiplied into the 
 velocity of the vessel, which is equal to 2 ir p n, in feet per minute, will give the propelling 
 effect due to the float in tbs. raised one foot per minute. We have thus, 
 
 sn. a 
 
 sin. /3 
 
 Multiplying by 2 m, and dividing by 33000, we find, for the general expression of the effective 
 power, or that portion of the power of the engines which is employed in propelling the 
 vessel, 
 
ON PADDLE WHEELS. 
 
 127 
 
 ) 2 3 rap 2ra? ap*cos. /3 j sin. ft j . . (2) 
 
 The mode of applying these formulae will be illustrated by the following example : 
 The wheels of Her Majesty's steam frigate 'Salamander' are 21 ft. in diameter, the paddle- 
 boards 8 ft. 9 in. broad, and 2 ft. 6 in. deep, and there are sixteen on each wheel. Thus 
 R = 10-5, r = 8, b = 8'75, and m = 16. When tried at Woolwich, the greatest immersion 
 of the floats was 5 ft. 6 in., the number of strokes made by the engines was 15, and the speed 
 8'15 statute miles per hour. We have therefore a = the height of the axis of the wheel 
 
 88 x 8-15 
 above the surface of the water = 5, n = 15, and p = 
 
 2 TT n 
 
 . The angles a. and 
 
 TT n 
 
 j8 and their sines are easily found in tables of logarithms, knowing that cos. a = -=- and 
 cos. /3 = 
 
 a 
 
 r 
 
 Log. TT=O- 4971499 
 Log. n = 1 1 760913 
 Log. b =0-9420081 
 Log. m= 1-2041 200 
 
 We will first apply the formula (1) to find the total power transmitted to the wheels, which 
 is most conveniently done by means of logarithms. We find, 
 
 Log. R= 1-0211893 
 
 Log. r = 0- 9030900 
 
 Log. 0=0-6989700 
 
 Log. p =0-8813691 
 
 We have assumed w= 64- 125, which is the weight of a cubic foot of sea water, and 2 g, which 
 is the velocity of a falling body at the end of the first second, is equal to 64-38. We find 
 therefore, 
 
 Log. w =1-8070274, 
 Log. 2^=1-8087510, 
 
 Log. cos. = Log. a Log. R= 1-6777807, and the corresponding angle given in the table 
 of sines and cosines is 61 33'47""2, and the logarithm of the sine of this angle is found to be 
 equal to 1-9441579. The length of the arc a is equal to 1-074479, radius being taken as 
 unity, and its logarithm is consequently 0-0311979. In the same manner we find by sub- 
 tracting log. r from log. a, cos. /3= 1-7958800, whence =5119' 4"- 14 = 0-8956649, and 
 log. /3= 1-9521455, also log. sin. /9= 1-8924424. We shall first find the value of the sum 
 of the terms included between the brackets, and then perform the multiplication, by means of 
 logarithms. 
 
 Log. 
 
 3 = 
 
 Ctr 
 
 0-47712 
 4-08476 
 0-03120 
 
 Log. 
 
 a = 
 
 3-93883 
 0-03120 
 
 3fl 4 a 
 3 
 
 = 4-59308 3B 4 a 
 
 = 39181 
 
 6aV = 3-97003 
 
 6 a 2 p 2 
 
 =9333 
 
 ,2 
 
 0-47712 
 2-04238 
 1-76274 
 0-03120 
 
 8 
 R* 
 
 P 
 sin. a 
 
 = 0-90309 
 = 3-06357 
 = 0-88137 
 = -1-94416 
 
 = 4-31344 
 
 =20580 
 
 8 .R 3 p sin. a = 4-79219 8.R 3 psin. a =61970 
 
128 
 
 Log. 3 
 R 
 a 
 
 / 
 ,, sin. a 
 
 3 R a p 2 sin. 
 
 8 
 R 
 
 a 2 
 p 
 sin. a 
 
 6 
 a 2 
 p 3 
 P 
 
 6a 2 p 2 8 
 
 8 
 r 3 
 
 /> 
 ,, sin. ft 
 
 8 r 3 p sin. 8 
 
 r 3 
 a 
 sin. 8 
 
 r 3 a sin. 8 
 
 2 
 r 
 
 a 3 
 sin. 8 
 
 " ra 3 sin 8 
 
 = 0-47712 
 = 1-02119 
 = 0-69897 
 1-76274 
 
 APPENDIX. 
 
 Log. R 3 
 a 
 ,, sin. a. 
 
 ,, R 3 a sin 
 
 a =8020 2 
 R 
 a 3 
 ,, sin. a, 
 
 2 R a 3 sin 
 
 3 
 a= 14052 r 4 
 
 > P 
 
 3^8 
 
 3 
 
 r 2 
 = 7780 - p2 
 ft 
 
 3 r 2 p 2 8 
 
 3 
 r 
 = 24332 a 
 
 P" 
 
 sin. 8 
 ,, 3 r a p 2 sin. 
 
 = 1998 8 
 r 
 a 2 
 p 
 sin. 8 
 
 8 ra 2 psin. 
 1561 
 
 = 3-06357 
 = 0-69897 
 = -1-94416 
 
 =5090 
 
 = 2308 
 = 11006 
 
 = 9958 
 =5425 
 
 = -1-94416 
 
 . a= 3-70670 R 3 a sin. a 
 
 a= 3-90418 3 .Rap 2 sin. 
 
 = 0-30103 
 
 = 0-90309 
 = 1-02119 
 1-39794 
 
 U2119 
 
 = 2-09691 
 = 1-94416 
 
 = 0-88137 
 1-94416 
 
 . a = 3-36329 2 .R a 3 sin. a 
 
 
 
 a= 4-14775 8#a 2 psin. 
 
 4/712 
 = 3-61236 
 
 0-77815 
 
 1"95215 
 
 = 1-39794 
 1-76274 
 
 = 4-04163 3r*ft 
 
 = 1-95215 
 
 = 0-47712 
 
 = 3-89098 6a 2 P 2 ft 
 
 oUolo 
 - 1-76274 
 
 0-90309 
 
 ao2lo 
 
 = 2-70927 
 0-88137 
 
 = 3-99819 3rV/3 
 
 = -1-89244 
 
 = 0-47712 
 
 = 4-38617 Sr'psin.S 
 
 9Uo09 
 = 0-69897 
 
 = 2-70927 
 Q-69897 
 
 76274 
 = 1-89244 
 
 = -1-89244 
 
 8= 3-73436 3rap 2 sin. ft 
 
 = 3-30068 r 3 a sin. 8 
 
 = 0-90309 
 
 = 0-30103 
 = 0-90309 
 = 2-09691 
 1-89244 
 
 = 1-39794 
 = 0-88137 
 = 1-89244 
 
 
 
 3-19347 2 ra 3 sin ft 
 
 
 9505 
 
 
 
 c 
 
 114595 
 117504 
 
 Sum of positive terms = 
 
 117504 
 
 Sum of positive terms = 
 
 2909 
 
ON PADDLE WHEELS. 
 
 129 
 
 Log. 
 
 2909 = 
 
 3-46377 
 
 > 
 
 JT 2 = 
 
 0-99430 
 
 It 
 
 n s = 
 
 3-52827 
 
 ft 
 
 b = 
 
 0-94201 
 
 ,, 
 
 w = 
 
 1-80703 
 
 >J 
 
 m = 
 
 1-20412 
 
 
 1 _ 
 
 -8-05012 
 
 
 89100000 
 
 
 1 
 
 -9-1 91 M 
 
 Log. H.P. = 2-18087 H.P. = 151-66. 
 
 The nominal power of the engines is 220 h. p. at 22 revolutions per minute, therefore the 
 nominal power with only 15 revolutions is 150 h. p., so that in this case the calculated power 
 surpasses the nominal power by very little more than one per cent. In this calculation some 
 of the resistance has been neglected, viz., that on the arms and the edges of the floats, to 
 which should also be added the effect of the back water and the shock, the amount of which 
 we cannot at present estimate ; but as the engines are supposed to work above their nominal 
 power, and it is not known by how much, the above result may be very near the truth. 
 
 The following is the calculation of the effective power according to the formula (2). 
 
 Log. 
 
 6 
 a 2 
 
 P 
 at. 
 
 0-77815 
 1-39794 
 0-88137 
 0-03120 
 
 6a 2 pa = 3-08866 6 a 2 p a. =1226'5 
 
 2 
 R* 
 
 sin. a 
 
 0.30103 
 
 3-06357 
 
 -1-94416 
 
 2# 3 sin. a = 3'30876 2.R 3 sin. a =2035'9 
 
 4 
 R 
 
 sin. a =- 
 
 0-60206 
 
 1-02119 
 
 1-76274 
 
 -1-94416 
 
 4R P 2 sm. a, = 3-33015 4Rp 2 sin. a=2138'7 
 
 3 
 
 r 2 
 
 P 
 ft 
 
 = 0-47712 
 = 1-80618 
 = 0-88137 
 =1-95215 
 
 = 3-11682 
 
 Log. 
 
 q 
 
 P 
 
 ct, zzz 
 
 0-47712 
 2-04238 
 0-88137 
 0-03120 
 
 3.R 2 pa = 3-43207 3 R z p a =2704-4 
 
 3 = 0-47712 
 
 a = 0-69897 
 
 p 2 = 1-76274 
 
 a = 0-03120 
 
 Sap 2 a, = 2-97003 
 
 Sap 2 a, 
 
 = 933-3 
 
 3 
 R 
 
 a 
 
 P 
 sin. a 
 
 0-47712 
 1-02119 
 0-69897 
 0-88137 
 -1-94416 
 
 3 flap sin. a= 3'02281 3 JZapsin.a=1053-9 
 
 2 
 R 
 
 a 2 
 sin. a 
 
 0-30103 
 
 1-02119 
 
 1-39794 
 
 -1-94416 
 
 =1308'6 
 
 2.Ra 2 sin.a= 2-66432 2.Ra 2 sin.a= 461-7 
 
130 
 
 Log. 
 
 3 
 r 
 a 
 
 P 
 sin. |3 
 
 = 0-47712 
 = 0-69897 
 = 1-76274 
 = -1-95215 
 
 = 2-'89098 
 
 = 0-47712 
 = 0-90309 
 = 0-69897 
 = 0-88137 
 = -1-89244 
 
 APPENDIX. 
 
 Logr. 
 
 3 rap sin. /3 = 2'85299 3 rap sin. 0= 712'8 
 
 2 
 
 r 
 
 = 0-30103 
 = 0-90309 
 a 2 = 1-39794 
 
 sin. /3 =-1-89244 
 
 2ra 2 sin.0 = 2-49450 2 r a 2 sin. = 312-2 
 
 a 
 
 P 2 
 cos. /3 
 
 sin. 8 
 
 = 0.69897 
 = 1-76274 
 = 1-79588 
 = 1-89244 
 
 ap 2 cos./3sin. /3= 2-15003 ap 2 cos./3sin.j3=141'3 
 
 Sum of positive terms 
 
 = 8654-0 
 
 cos. a 
 sin. a 
 
 = 0-69897 
 = 1-76274 
 = -1-67778 
 = -1-94416 
 
 = 778-0 ap 2 cos.a sin.a= 2-08365 a/> 2 cos.asin.a=121-2 
 
 6 
 a 2 
 P 
 
 = 0-77815 
 = 1-39794 
 = 0-88137 
 = -1-95215 
 
 6n 2 p/3 = 3-00961 6<z 2 p/3 = 1022-4 
 2 
 
 sn. 
 
 = 0-30103 
 = 2-70927 
 = -1-89244 
 
 2 r 3 sin. /3 = 2-90274 2 r 3 sin. = 799'4 
 
 r 
 
 P 2 
 sin. /3 
 
 = 0-60206 
 = 0-90309 
 = 1-76274 
 = -1-89244 
 
 4r P 2 sin.j3 = 3' 16033 4 r p 2 sin. =1446-5 
 
 Sum of negative terms . . 
 Sum of positive terms . . 
 
 = 8542-8 
 = 8654-0 
 
 111-2 
 
 Log. 
 
 111-2 
 w* 
 
 n 3 
 b 
 
 w 
 
 P 
 m 
 1 
 
 44550000 
 
 \_ 
 
 2> 
 
 = 2-04610 
 
 = 0-99430 
 
 = 3-52827 
 
 = 0-94201 
 
 = 1-80703 
 
 = 0-88137 
 
 = 1-20412 
 
 = -8-35115 
 
 =-2-19125 
 
 Log. H.P.E. = 1-94560 
 
 H.P.E. = 88-23. 
 
ON PADDLE WHEELS. 131 
 
 Thus a power of 88'23 horses is sufficient, if applied immediately to the vessel; but 151-66 
 horse powers are required to be applied to the wheels to produce the same propelling effect, 
 the proportion of the effective to the total power being as 0-582 to 1. This shows the loss of 
 power at deep immersions to be very great, even without considering the effects of the shock and 
 back water: it amounts in the above example to more than 63 h. p., or about 41-8 per cent, 
 of the whole power transmitted to the wheels. 
 
 It is obvious, that at light immersions, when the upper edge of the float is never under 
 water, all the terms in which /3 or sin. /3 enters as a factor disappear, and only one-half of the 
 number of terms remain ; and even if the float is immersed a few inches above its upper edge 
 at the middle of the stroke, the amount of those terms is so small, that they may be neglected 
 
 15 7 
 without causing any material error in the result. For example, if a= rand p= r, the 
 
 16 8 
 
 error is about one per cent.; but if p=a, then the error is only about one-third per cent. 
 Thus, the diameter of the wheel being 20 ft., the depth of the floats 2 ft., and their greatest 
 immersion 2 ft. 6 in., or 6 inches above their upper edge, the resistance would not be more 
 than one per cent, less than if the floats were made 2 ft. 6 in. in depth, so as to reach the 
 surface of the water. We here suppose the radius of the rolling circle to be 7 ft. ; if it were 
 only 6 ft. the error would be a little more considerable, but not much, for if the immersion 
 were 3 ft. and the radius of the rolling circle 6 ft., the error would not exceed 2 per cent. 
 
 If we calculate the power of the ' Phoenix ' from the data which we possess, which coincide 
 exactly with those given in Mr. Barlow's tables, except in the diameter of the wheels, which 
 is 21 ft., and not 20 ft. 4 in. as he has there given it, we shall find but 110 h. p. for the power 
 of the engines, or not much more than one-half of the nominal power. It is however very 
 probable that there were some slight errors in the observations ; for the dip of the floats is 
 measured before starting, when it is generally not the same as when the vessel is in motion : 
 there is a wave on each side of the vessel, travelling along with it, caused by the displacement 
 of the water, and varying in its position according to the form of the bows : this is sometimes 
 situated directly under the paddle shaft, and then naturally increases the dip of the floats. 
 The mean speed may be a little too great, a difference of a few seconds in the time of running 
 a mile making a difference of half a mile an hour in the speed; it is also next to impossible 
 to know the exact mean number of revolutions made by the wheels in a minute without 
 counting the whole number made during the run. If, during the trial of the ' Phoenix,' the 
 immersion of the floats was 2-8 ft. instead of 2- 5 ft., the mean speed 11-23 miles, instead of 
 ir7, and the mean number of revolutions 21 instead of 21, we should find for the power 
 of the engines 203 f h. p., which is about 6 per cent, below their nominal power, and it is 
 probable that the dip of the floats was still more considerable. 
 
 We have been informed by a gentleman who cannot well be mistaken, that no copy of the 
 official account of the mile trials of Her Majesty's steam vessels at Woolwich has hitherto 
 been published, and we know that some of the dimensions in Mr. Barlow's table are incorrect, 
 so that we cannot rely upon the other figures contained in it, although they coincide with a 
 table which we have obtained from another quarter. Wishing to have authentic data to 
 reason upon, we applied to the Lords Commissioners of the Admiralty for permission to 
 obtain a copy of the official returns, but their lordships declined acceding to our request, and 
 no information is to be obtained at Woolwich dock-yard on this subject. We are at a loss to 
 
132 APPENDIX. 
 
 conceive the object of so much secresy : it can hardly answer any useful end, whereas it 
 would be a certain benefit to the nation if the public were made acquainted with all facts 
 relating to steam navigation. We have ascertained the diameters of the following paddle 
 wheels, which differ from those given in Mr. Barlow's table : ' Messenger's,' 20 ft. ; ' Dee's,' 
 20 ft.; ' Rhadamanthus,' 'Salamander,' and 'Phoenix,' each 21 ft. ; ' Firefly's,' most probably 
 18 ft., and the depth of the floats of ' Medea's' wheels, 3 ft. 8 in. 
 
 The power expended on the wheels of a steam vessel would be found much more readily 
 if we knew the position of the centre of pressure, but we are not aware of any direct method 
 of finding that point. 
 
 By centre of pressure is understood a point on the surface of the paddle-board at such a 
 distance from the axis of the wheel, that if the whole surface of the board were concentrated 
 in that point, or in the horizontal line passing through it, the mean resistance would not be 
 affected by the change ; it does not however follow that the effective resistance would remain 
 unaltered, so that this point is only the centre of total pressure, and not of effective pressure ; 
 nor is it the centre of pressure of the float in any given position, but the mean for all the 
 positions taken by the float during its passage through the water, and should therefore, 
 strictly speaking, be called the mean centre of pressure ; but as it is already known as the 
 centre of pressure, we will retain this expression for the sake of brevity. The position of 
 this point being known, we can find the power in the following manner. 
 
 Let y be the distance of the centre of pressure from the axis of the wheel, 8 the angle at 
 which it enters and leaves the water, a, b, p, n and m, the same as in the former calculations, 
 and /the depth of the float. The pressure on the float at any angle </> is equal to the product 
 of its area bf, by the square of its effective velocity and the weight of a cubic foot of water, 
 divided by 2 g. The effective velocity of the float is equal to 
 
 irn r ,-, 
 
 [y-pcos.0], 
 
 2 2 ft y* 
 
 so that the pressure is equal to ^ [y pcos. <] 2 , 
 
 900 x 2 ff 
 
 and the moment of the resistance to ^-^ ^- [yp cos. <f>]* y. 
 
 ^ \y\j\j x // 
 
 The mean value of this expression is equal to the definite integral 
 
 A 
 
 f* , ,-,, 
 
 If -** 
 
 27000X2 
 which is 
 
 which is slooox^l [2y 3 + ^ 2 ]a+[p 2 -4y 2 rf 
 
 This multiplied by 2 m, and reduced to horse powers, becomes, 
 
 (3) 
 
 The first member of this equation being equal to the second member of the equation (1) 
 (page 126), it is evident that the sum of the terms between the brackets in the former, multi- 
 plied by 6/ must be equal to the sum of the terms between brackets in the latter, or, calling 
 S that sum in formula (1), and S" the sum in formula (3), we must have 
 
ON PADDLE WHEELS. 
 
 133 
 
 Having first found the value of S, and assumed a value of y not very far from the truth, 
 we can prove it with very little trouble by the above formula. If we find too great a value 
 for S", we take off a little from our assumed value of y, and if the second result differ still 
 from the true value of S", we make a proportion of the differences ; the third result will be 
 as near as can be desired, if the differences are small. In this manner the following tables 
 were calculated, in which the extreme radius of the wheel has been assumed equal to 10, or, 
 which is the same thing, one-tenth of the radius has been taken as unity. The immersion 
 is given in the upper line, and the radius of the rolling circle in the first column on the left : 
 the decimal fraction corresponding to the given immersion and radius of the rolling circle, 
 expresses the portion of the depth of the float included between its upper edge and its centre 
 of pressure. Thus, if the immersion be 4, and the radius of the rolling circle 7'4 (see 
 Table I.), the centre of pressure will be situated at a distance of 0'557 of the depth of the 
 float from its upper edge. 
 
 TABLE I. Extreme radius = 10 ; Depth of float = 2. 
 
 
 
 T2 ' 
 t- 
 
 'o5 
 
 '2. in 
 
 J; ^ 
 
 DIP OF THE FLOAT. 
 
 2-00 
 
 2-25 
 
 2-50 
 
 2-75 
 
 3-00 
 
 3-25 
 
 3-50 
 
 3-75 
 
 4-00 
 
 4-25 
 
 4-50 
 
 4-75 
 
 5-00 
 
 5-25 
 
 5-50 
 
 8-0 
 
 0-607 
 
 0-599 
 
 0-593 
 
 0-587 
 
 0-582 
 
 0-577 
 
 0-573 
 
 0-569 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-557 
 
 0-555 
 
 0-552 
 
 0-550 
 
 7-9 
 
 0-603 
 
 0-596 
 
 0-590 
 
 0-584 
 
 0-579 
 
 0-575 
 
 0-571 
 
 0-567 
 
 0-564 
 
 0-561 
 
 0-559 
 
 0-556 
 
 0-554 
 
 0-551 
 
 0-549 
 
 7-8 
 
 0-599 
 
 0-593 
 
 0-587 
 
 0-582 
 
 0-577 
 
 0-573 
 
 0-569 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-550 
 
 0-548 
 
 7-7 
 
 0-595 
 
 0-589 
 
 0-584 
 
 0-579 
 
 0-574 
 
 0-570 
 
 0-567 
 
 0-564 
 
 0-561 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-549 
 
 0-547 
 
 7-6 
 
 0-592 
 
 0-586 
 
 0-581 
 
 0-576 
 
 0-572 
 
 0-568 
 
 0-565 
 
 0-562 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-548 
 
 0-546 
 
 7'5 
 
 0-588 
 
 0-583 
 
 0-578 
 
 0-574 
 
 0-570 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-546 
 
 7-4 
 
 0-585 
 
 0-580 
 
 0-576 
 
 0-572 
 
 0-568 
 
 0-565 
 
 0-562 
 
 0-559 
 
 0-557 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-549 
 
 0-547 
 
 0-545 
 
 7-3 
 
 0-582 
 
 0-578 
 
 0-574 
 
 0-570 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0.551 
 
 0-549 
 
 0-548 
 
 0-546 
 
 0-544 
 
 7-2 
 
 0-580 
 
 0-575 
 
 0-571 
 
 0-567 
 
 0-564 
 
 0-561 
 
 0-559 
 
 0556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-547 
 
 0-545 
 
 0-544 
 
 7-1 
 
 0-577 
 
 0-573 
 
 0-569 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-546 
 
 0-544 
 
 0-543 
 
 7-0 
 
 0-574 
 
 0-570 
 
 0-567 
 
 0-564 
 
 0-561 
 
 0-559 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-545 
 
 0-544 
 
 0-542 
 
 6-9 
 
 0-572 
 
 0-568 
 
 0-565 
 
 0-562 
 
 0-560 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-544 
 
 0-543 
 
 0-541 
 
 6-8 
 
 0-570 
 
 0-566 
 
 0-563 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-545 
 
 0-543 
 
 0-542 
 
 0-540 
 
 6-7 
 
 0-568 
 
 0-564 
 
 5-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-544 
 
 0-543 
 
 0-541 
 
 0-540 
 
 6-6 
 
 0-565 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-543 
 
 0-542 
 
 0-540 
 
 0-539 
 
 6-5 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-544 
 
 0-542 
 
 0-541 
 
 0-540 
 
 0-538 
 
 6-4 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-545 
 
 0-543 
 
 0-542 
 
 0-541 
 
 0-539 
 
 0-538 
 
 6-3 
 
 0.559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-552 
 
 0-550 
 
 0-549 
 
 0-547 
 
 0-546 
 
 0-544 
 
 0-543 
 
 0-541 
 
 0-540 
 
 0-538 
 
 0-537 
 
 6-2 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-551 
 
 0-549 
 
 0-548 
 
 0-546 
 
 0-545 
 
 0-543 
 
 0-542 
 
 0-540 
 
 0-539 
 
 0-538 
 
 0-536 
 
 6-1 
 
 0-556 
 
 0-554 
 
 0-553 
 
 0-551 
 
 0-550 
 
 0-548 
 
 0-547 
 
 0-545 
 
 0.544 
 
 0-542 
 
 0-541 
 
 0-540 
 
 0-539 
 
 0-537 
 
 0-535 
 
 6-0 
 
 0-554 
 
 0-553 
 
 0-551 
 
 0-550 
 
 0-549 
 
 0-547 
 
 0-546 
 
 0-544 
 
 0-543 
 
 0-542 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-536 
 
 0-535 
 
134 
 
 APPENDIX. 
 TABLE II. Extreme radius = 10 ; Depth of float = 2-5. 
 
 OJ 
 
 "2 
 
 'oC 
 
 g 60 
 
 DIP OF THE FLOAT. 
 
 = := 
 
 51 
 
 2-50 
 
 2-75 
 
 3-00 
 
 3-25 
 
 3-50 
 
 3-75 
 
 4-00 
 
 4-25 
 
 4-50 
 
 4-75 
 
 5-00 
 
 5-25 
 
 5-50 
 
 7-5 
 
 0-607 
 
 0-601 
 
 0-596 
 
 0-591 
 
 0-587 
 
 0-583 
 
 0-579 
 
 0-576 
 
 0-573 
 
 0-570 
 
 0-567 
 
 0-564 
 
 0-562 
 
 7-4 
 
 0-004 
 
 0-599 
 
 0-594 
 
 0-589 
 
 0-585 
 
 0-581 
 
 0-577 
 
 0-574 
 
 0-571 
 
 0-568 
 
 0-565 
 
 0-563 
 
 0-561 
 
 7-3 
 
 0-601 
 
 0-596 
 
 0-591 
 
 0-587 
 
 0-583 
 
 0-579 
 
 0-576 
 
 0-572 
 
 0-569 
 
 0-566 
 
 0-564 
 
 0-562 
 
 0-560 
 
 7-2 
 
 0-598 
 
 0-593 
 
 0-589 
 
 0-585 
 
 0-581 
 
 0-578 
 
 0-574 
 
 0-571 
 
 0-568 
 
 0-565 
 
 0-563 
 
 0-561 
 
 0-559 
 
 7-1 
 
 0-595 
 
 0-590 
 
 0-586 
 
 0-582 
 
 0-579 
 
 0-576 
 
 0-573 
 
 0-570 
 
 0-567 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 7-0 
 
 0-592 
 
 0-588 
 
 0-584 
 
 0-581 
 
 0-578 
 
 0-574 
 
 0-571 
 
 0-568 
 
 0-566 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 6-9 
 
 0-590 
 
 0-586 
 
 0-582 
 
 0-579 
 
 0-576 
 
 0-573 
 
 0-570 
 
 0-567 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-556 
 
 6-8 
 
 0-587 
 
 0-583 
 
 0-580 
 
 0-577 
 
 0-574 
 
 0-571 
 
 0-568 
 
 0-565 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 6-7 
 
 0-585 
 
 0-581 
 
 0-578 
 
 0-575 
 
 0-572 
 
 0-569 
 
 0-567 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 6-6 
 
 0-583 
 
 0-579 
 
 0-576 
 
 0-573 
 
 0-570 
 
 0-568 
 
 0-565 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 6-5 
 
 0-580 
 
 0-577 
 
 0-574 
 
 0-571 
 
 0-569 
 
 0-566 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 6-4 
 
 0-578 
 
 0-575 
 
 0-572 
 
 0-570 
 
 0-567 
 
 0-565 
 
 0-563 
 
 0-560 
 
 0-558 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 6-3 
 
 0-576 
 
 0-573 
 
 0-570 
 
 0-568 
 
 0-566 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-554 
 
 0-552 
 
 0-551 
 
 6-2 
 
 0-574 
 
 0-571 
 
 0-569 
 
 0-566 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-553 
 
 0-551 
 
 0-550 
 
 6-1 
 
 0-572 
 
 0-569 
 
 0-567 
 
 0-565 
 
 0-563 
 
 0-561 
 
 0-559 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-552 
 
 0-550 
 
 0-549 
 
 6-0 
 
 0-570 
 
 0-568 
 
 0-566 
 
 0-563 
 
 0-561 
 
 0-560 
 
 0-558 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-551 
 
 0-549 
 
 0-548 
 
 5-9 
 
 0-568 
 
 0-566 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-558 
 
 0-557 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-550 
 
 0-548 
 
 0-547 
 
 5-8 
 
 0-566 
 
 0-564 
 
 0-562 
 
 0-560 
 
 0-559 
 
 0-557 
 
 0-556 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-549 
 
 0-548 
 
 0-546 
 
 5-7 
 
 0-564 
 
 0-562 
 
 0-561 
 
 0-559 
 
 0-558 
 
 0-556 
 
 0-555 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-548 
 
 0-547 
 
 0-546 
 
 5-6 
 
 0-563 
 
 0-561 
 
 0-560 
 
 0-558 
 
 0-557 
 
 0-555 
 
 0-554 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-547 
 
 0-546 
 
 0-545 
 
 5-5 
 
 0-562 
 
 0-560 
 
 0-559 
 
 0-557 
 
 0-556 
 
 0-554 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-546 
 
 0-546 
 
 0-545 
 
 The following is a type of the calculation of the power by means of the centre of pressure. 
 Let it be required to find the power exerted by the engines of the ' Salamander ' in the case 
 proposed at page 127. 
 
 The radius of the paddle wheels being 10ft. Gin., the position of the centre of pressure 
 cannot be found immediately by referring to either of the preceding tables, in which the radius 
 is assumed equal to 10 ; we must therefore first find the numbers which represent in the tables 
 the depth and immersion of the floats, and the radius of the rolling circle. The depth of the 
 float is represented by the number 2*38, the immersion by the number 5'238, and the radiiis 
 of the rolling circle by 7'247. The depth of the float being intermediate between those 
 assumed in the tables, we must first enter Table I. ; and in the column under the immersion 
 5'25, and opposite to the numbers 7'2 and 7'3, in the first column on the left, we find the 
 numbers 0'545, 0'546, of which we take the mean, 0'5455 ; then in Table II. we do the same, 
 
ON PADDLE WHEELS. 135 
 
 and find 0'561 and 0*562, of which we take the mean, 0-5615. The difference between 0-5455 
 and 0*5615, or 0'016, corresponding to a difference of 0*5 in the depth of the float,, we find 
 the difference corresponding to 0'38 by the proportion 0'5 : 0'016 : : 0*38 : 0*012, sufficiently 
 near for our purpose, and this added to 0*5455 gives 0'5575 for the proportion of the depth of 
 the float contained between its upper edge and the centre of pressure : the distance of this 
 point from the axis of the wheel, or y, is therefore equal to 9*3937 ft. 
 
 Log. a = 0-6989700 
 p = 0-8813691 
 y 0-9728367 
 
 6 = 0-0041126 
 
 sin. = - 1-9276647 ' 
 Whence, 
 
 Log. 2 y 3 6 = 3-2236527 2 y 3 6 = 1673-60 
 
 (? y 6 = 2-7396875 p 2 y = 549-15 
 
 ap 2 sin. 6 = 2-3893729 ap 2 sin. 6 = 245-12 
 
 2467-87 
 ,,4py 2 sin. 6= 3-3567672 4pfs\n. 6= 2273-88 
 
 S" = 193-99 
 
 Log. S" = 2-2877771 
 
 7T 2 = 0-9942998 
 
 n 3 = 3-5282738 
 
 b = 0-9420081 
 
 / 0-3979400 
 
 w = 1-8070274 
 
 m 1-2041200 
 
 27 = - 2-1912490 
 
 -148^000 = - 8-8282735 
 
 Log. H.P. = 2*1809687 
 
 H.P. = 151*69. 
 
 The calculation of the effective power would be abridged in the same manner by means of 
 an analogous point, which we would call the centre of propelling effect. This point is so 
 situated, that, if the whole surface of the float were concentrated there, the propelling effect 
 would remain the same ; so that, calling z the distance of this point from the axis of the 
 wheel, and the inclination of the float when its centre of propelling effect enters and leaves 
 the water, the propelling effect of a pair of wheels may be found in the following manner : 
 We know the total pressure on one of the floats at the angle $ to be equal to 
 
 7T 2 n 2 bfw I ^ 
 
 900 x 2ff 
 
 > 
 
136 APPENDIX. 
 
 whence the horizontal or effective pressure is equal to 
 
 7T 2 2 bfw 
 
 900 x2 -P cos - * cos - 
 
 the mean value of which is 
 
 7T W 2 b fw C r 
 
 900 x 2g o > 
 
 or, 
 
 > *' + 2 * + * cos " f 2 - 3 
 
 The mean effective pressure on the two wheels, which is equal to the resistance opposed to 
 the motion of the vessel, is therefore 
 tr w 2 bfwm ( 
 
 COS< f ~ 
 
 I * 
 
 Multiplying this by -^r-j the velocity of the vessel in feet per second, we find the pro- 
 oU 
 
 pelling power in Ifes. moved through one foot in a second to be equal to 
 
 COS< f2 ~ 
 
 2 
 
 which, reduced to horse powers, becomes 
 Tr 2 n 3 b fw m o 
 
 22275000 x2ff < ~ > ~ = H - P - E ..... (4) 
 
 The first member of this equation being equal to the second member of the equation (2) 
 (page 127), the sum of the terms between the brackets in the former, multiplied by If, is 
 equal to the sum of the terms between brackets in the latter ; or, calling S' that sum in the 
 equation (2), and S'" that in the equation (4), we have 
 
 Q'" _ ^' 
 
 ' 2?' 
 
 The following tables were constructed, like the two former, by assuming values for z until 
 the equations (2) and (4) gave the same value of S'". 
 
ON PADDLE WHEELS. 
 
 137 
 
 TABLE III. Extreme radius = 10; Depth of float = 2. 
 
 -_ - 
 
 - 
 "So 
 
 2 *> 
 
 IMMERSION. 
 
 II 
 
 2-00 
 
 2-25 
 
 2-50 
 
 2-75 
 
 3-00 
 
 3-25 
 
 3-50 
 
 3-75 
 
 4-00 
 
 4-25 
 
 4-50 
 
 4-75 
 
 5-00 
 
 5-25 
 
 5-50 
 
 8-0 
 
 0-595 
 
 0-586 
 
 0-579 
 
 0-573 
 
 0-568 
 
 0-564 
 
 0-560 
 
 0-556 
 
 0-553 
 
 0-550 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 7-9 
 
 0-590 
 
 0-582 
 
 0-576 
 
 0-570 
 
 0-565 
 
 0-561 
 
 0-557 
 
 0-554 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 7-8 
 
 0-586 
 
 0-578 
 
 0-573 
 
 0-568 
 
 0-563 
 
 0-559 
 
 0-555 
 
 0-552 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-537 
 
 7-7 
 
 0-582 
 
 0-575 
 
 0-570 
 
 0-565 
 
 0-560 
 
 0-556 
 
 0-553 
 
 0-550 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-536 
 
 7-6 
 
 0-578 
 
 0-572 
 
 0-567 
 
 0-563 
 
 0-558 
 
 0-554 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-536 
 
 0-535 
 
 7-5 
 
 0-574 
 
 0-569 
 
 0-565 
 
 0-560 
 
 0-556 
 
 0-552 
 
 0-549 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-534 
 
 7-4 
 
 0-571 
 
 0-567 
 
 0-562 
 
 0-558 
 
 0-554 
 
 0-550 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0-533 
 
 7-3 
 
 0-568 
 
 0-564 
 
 0-559 
 
 0-555 
 
 0-552 
 
 0-549 
 
 0-546 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-535 
 
 0-533 
 
 0.532 
 
 7-2 
 
 0-565 
 
 0-561 
 
 0-557 
 
 0-553 
 
 0-550 
 
 0-547 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-536 
 
 0-535 
 
 0-534 
 
 0-532 
 
 0-531 
 
 7-1 
 
 0-562 
 
 0-558 
 
 0-555 
 
 0-551 
 
 0-548 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-535 
 
 0-534 
 
 0-533 
 
 0-531 
 
 0-530 
 
 7-0 
 
 0-559 
 
 0-556 
 
 0-552 
 
 0-549 
 
 0-546 
 
 0-544 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0.533 
 
 0-532 
 
 0-531 
 
 0-530 
 
 69 
 
 0-557 
 
 0-553 
 
 0-550 
 
 0-547 
 
 0-545 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-536 
 
 0-535 
 
 0-533 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 6-8 
 
 0-554 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-535 
 
 0-534 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 6-7 
 
 0-552 
 
 0-549 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-536 
 
 0-534 
 
 0-533 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-528 
 
 6-6 
 
 0-550 
 
 0-547 
 
 0-545 
 
 0-542 
 
 0-540 
 
 0-539 
 
 0-537 
 
 0-535 
 
 0-533 
 
 0-532 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-528 
 
 0-527 
 
 6-5 
 
 0-548 
 
 0-546 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-536 
 
 0-534 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-527 
 
 0-527 
 
 6-4 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-533 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-527 
 
 0-526 
 
 0-526 
 
 6-3 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0-532 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-527 
 
 0-526 
 
 0-526 
 
 0-525 
 
 6-2 
 
 0.542 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-535 
 
 0-533 
 
 0531 
 
 0-529 
 
 0-528 
 
 0-527 
 
 0-526 
 
 0-526 
 
 0-525 
 
 0-525 
 
 6-1 
 
 0-540 
 
 0-539 
 
 0-538 
 
 0-536 
 
 0-535 
 
 0-534 
 
 0-532 
 
 0-530 
 
 0-529 
 
 0-528 
 
 0-527 
 
 0-526 
 
 0-525 
 
 0-525 
 
 0-524 
 
 6-0 
 
 0-539 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-534 
 
 0-533 
 
 0-531 
 
 0-530 
 
 0-528 
 
 0-527 
 
 0-526 
 
 0-525 
 
 0-525 
 
 0-524 
 
 0-524 
 
138 
 
 APPENDIX. 
 
 TABLE IV. Extreme radius = 10; Depth of float = 2*5. 
 
 i) <U 
 
 5 
 
 "3 3 
 a P 
 
 11 
 
 IMMERSION. 
 
 2-50 
 
 2-75 
 
 3-00 
 
 3-25 
 
 3-50 
 
 3-75 
 
 4-00 
 
 4-25 
 
 4-50 
 
 4-75 
 
 5-00 
 
 5-25 
 
 5-50 
 
 7-5 
 
 0-592 
 
 0-585 
 
 0-579 
 
 0-574 
 
 0-569 
 
 0-565 
 
 0-562 
 
 0-559 
 
 0-556 
 
 0-553 
 
 0-551 
 
 0-549 
 
 0-547 
 
 7-4 
 
 0-588 
 
 0-582 
 
 0-576 
 
 0-571 
 
 0-567 
 
 0-563 
 
 0-560 
 
 0-557 
 
 0-554 
 
 0-552 
 
 0-549 
 
 0-547 
 
 0-545 
 
 7-3 
 
 0-585 
 
 0-579 
 
 0-573 
 
 0-569 
 
 0-564 
 
 0-561 
 
 0-558 
 
 0-555 
 
 0-552 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-544 
 
 7-2 
 
 0-581 
 
 0-576 
 
 0-571 
 
 0-566 
 
 0-562 
 
 0-559 
 
 0-556 
 
 0-553 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-543 
 
 7-1 
 
 0-578 
 
 0-573 
 
 0-568 
 
 0-564 
 
 0-560 
 
 0-557 
 
 0.554 
 
 0-551 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 7-0 
 
 0-575 
 
 0-570 
 
 0-566 
 
 0-561 
 
 0-558 
 
 0-555 
 
 0-552 
 
 0-550 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-542 
 
 0-540 
 
 6-9 
 
 0-572 
 
 0-568 
 
 0-563 
 
 0-559 
 
 0-556 
 
 0-553 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-539 
 
 6-8 
 
 0-569 
 
 0-565 
 
 0-561 
 
 0-557 
 
 0-554 
 
 0-552 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 6-7 
 
 0-567 
 
 0-563 
 
 0-559 
 
 0-555 
 
 0-553 
 
 0-550 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-537 
 
 6-6 
 
 0-564 
 
 0-560 
 
 0-557 
 
 0-554 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-541 
 
 0-539 
 
 0-537 
 
 0-536 
 
 6-5 
 
 0-562 
 
 0-558 
 
 0-555 
 
 0-552 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-549 
 
 0-538 
 
 0-536 
 
 0-535 
 
 6-4 
 
 0-559 
 
 0-556 
 
 0-553 
 
 0-550 
 
 0-548 
 
 0-545 
 
 0-543 
 
 0-542 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-534 
 
 6-3 
 
 0-557 
 
 0-554 
 
 0-551 
 
 0-549 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0-533 
 
 6-2 
 
 0-555 
 
 0-552 
 
 0-549 
 
 0-547 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-536 
 
 0-535 
 
 0-533 
 
 0-532 
 
 6-1 
 
 0-553 
 
 0-550 
 
 0-548 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-534 
 
 0-532 
 
 0-531 
 
 6-0 
 
 0-551 
 
 0-548 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-540 
 
 0-539 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0-533 
 
 0-532 
 
 0-531 
 
 5-9 
 
 0-549 
 
 0-546 
 
 0-544 
 
 0-542 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-536 
 
 0-535 
 
 0-533 
 
 0-532 
 
 0-531 
 
 0-530 
 
 5-8 
 
 0-547 
 
 0-545 
 
 0-542 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-537 
 
 0-535 
 
 0-534 
 
 0-533 
 
 0-531 
 
 0-530 
 
 0-529 
 
 5-7 
 
 0-545 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-537 
 
 0-536 
 
 0-534 
 
 0-533 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 5-6 
 
 0-543 
 
 0-541 
 
 0-539 
 
 0-538 
 
 0-537 
 
 0-536 
 
 0-535 
 
 0-534 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 5-5 
 
 0-541 
 
 0-540 
 
 0-538 
 
 0-537 
 
 0-536 
 
 0-535 
 
 0-534 
 
 0-533 
 
 0-532 
 
 0-531 
 
 0-530 
 
 0-529 
 
 0-528 
 
 Let us now apply these tables to the case of the e Salamander,' for which the calculation by 
 the other method is given in pages 129 and 130. The depth of the floats, reduced to the 
 scale of the tables, becomes 2*38, the immersion 5*238, and the radius of the rolling circle 
 7*247, as at page 134. In Table III., under the immersion 5*25, and opposite to the numbers 
 7*2 and 7*3 in the first column on the left, we find 0*532 and 0-533, of which we take the 
 mean 0-5325, and in Table IV. we find the numbers 0'544 and 0'546, of which the mean is 
 0*545. The difference being 0*0125, we make the proportion 0*5 : 0*0125 :: 0*38 : 0*0095, 
 which, added to 0*5325, gives 0*542 for the proportion of the depth of the float contained 
 between its upper edge and the centre of propelling effect, so that the distance of this point 
 from the axis of the wheel, or z, is equal to 9*355 ft. We have thus, 
 
ON PADDLE WHEELS. 139 
 
 Whence, 
 
 Log. 3 z 2 sin. f 
 2 p 2 sin. f 
 p 2 cos. f 2 sin. 
 
 Log. a = 
 
 0-6989700 
 
 
 P = 
 
 0-8813691 
 
 
 z = 
 
 0-9710438 
 
 
 C = 
 
 0-0029913 
 
 
 sin. f = - 
 
 1-9269519 
 
 
 cos. f = 
 
 1-7279262 
 
 
 = 2-3461608 
 
 3 z 2 sin. f 
 
 = 221-902 
 
 = 1-9907201 
 
 2 p 2 sin. f 
 
 = 97-886 
 
 t= 1-1455425 
 
 p 2 cos. 2 sin. 
 
 = 13-981 
 
 Sum of positive terms =333-769 
 
 Zap sin. f = 1-9844123 3 ap sin. f = 96'474 
 3pzt =2-3325255 3 p z =215-043 
 
 Sum of negative terms =311-517 
 
 S'" = 22-252 
 
 Log. S"' = 1-3473691 
 
 Tr 2 = 0-9942998 
 
 n 3 = 3-5282738 
 
 b = 0-9420081 
 
 / = 0-3979400 
 
 w = 1-8070274 
 
 m = 1-2041200 
 
 p = 0-8813691 
 
 -^ =-2-1912490 
 1 
 
 " 22275000 
 
 Log. H.P.E. = 1-9458386 
 
 H.P.E. = 88-275. 
 
 When a steamer is heavily laden, the wheels, from their excessive immersion, act less 
 advantageously, besides reducing the number of strokes of the engines by the great number 
 of floats immersed at once, and their great obliquity, which increases the resistance. Under 
 these circumstances the speed of the vessel-is naturally diminished, and it may in some cases 
 be desirable to bring out the full power of the engines, as it is called ; that is, to enable them 
 to make the full number of strokes they were calculated for, in order to prevent so great a 
 loss of speed. We know but one mode of effecting this, and that is by reefing the floats, or 
 shifting them from the circumference nearer to the shaft. This method is attended at present 
 with too much difficulty and danger to allow of its being put into general practice ; but we 
 
140 APPENDIX. 
 
 do not presume to say that a means may not be found to facilitate the operation, so as to 
 render it practicable. 
 
 It is very clear that the desired effect could not be produced by reducing the size of the 
 paddle boards, except inasmuch as the centre of pressure is thereby brought nearer to the 
 axis of the wheel : suppose, for example, that a piece has been cut off from the end of each 
 board ; the consequence will naturally be that the circumferential velocity of the wheel will be 
 increased, until the mean pressure on the floats becomes equal to what it was before they were 
 reduced. The pressure being restored, the horizontal pressure will be so too, but cannot 
 surpass what it was before, since the ratio of the horizontal to the total pressure is independent 
 of the breadth of the floats. The speed of the vessel must therefore remain the same, 
 although the expenditure of fuel is increased in the ratio of the increased velocity of the 
 engines. If, on the other hand, we suppose the floats to be reefed, then the engines will not 
 only move so much faster that the floats shall experience the same resistance, but their 
 velocity will increase until the mean pressure on the floats is to the former mean pressure as 
 the former radius to the centre of pressure is to the new one. The total pressure being thus 
 increased, the horizontal pressure will be so in a greater proportion, because, the angles of 
 the floats being less oblique, the ratio of the horizontal to the total pressure will be greater ; 
 consequently the vessel will go faster. We can only come to this general conclusion at 
 present, as there is no method yet known of finding the precise effect of reefing the floats. 
 
 2. Field's Paddle Wheel. 
 
 This is what Mr. Field calls the Cycloidal Wheel ; but as we do not consider that appellation 
 at all suitable, we prefer that adopted at the head of this chapter, Mr. Field having been, to 
 the best of our knowledge, the first inventor of this variety of paddle wheel. It was tried on 
 the ' Endeavour,' a passage steamer, in the year 1 833, but was abandoned immediately. 
 
 The construction of this wheel is thus explained by Mr. Field in the 'London Journal' for 
 December, 1835 : 
 
 " Each board is divided into several parts, or narrower boards, and arranged in, or nearly, 
 such cycloidal curves, that they all enter the water at the same place in immediate succession, 
 thus avoiding the shock produced by the entrance of the common board, so unpleasant to 
 passengers, injurious to the vessel, and wasteful of the power. As the acting face of each 
 board is radiating, it propels while passing under the centre in the ordinary way, and when it 
 emerges, the water escapes simultaneously from each narrow board, and consequently cannot 
 lop-up." 
 
 Mr. Galloway describes his invention to be exactly the same thing, but goes into geometrical 
 details, which are not mathematically correct. 
 
 Fig. 1. Plate LXXV. is a diagram intended to elucidate the construction of this kind of 
 wheel. Not having any data at the time this plate was engraved, we contented ourselves with 
 the same dimensions as those of the common wheel in Plate LXXIV., and supposing the same 
 performances as with the latter, merely with the view of comparing their modes of action. 
 Each board is divided into four narrow boards, a, b, c, d, respectively, six, seven, eight, and 
 nine inches in depth. Figs. 2 and 4 show the path of one set of boards at the light and load 
 draught, and Figs. 3 and 5 the nodes, enlarged to four times the scale on account of the 
 complication resulting from the number of boards in the set. On inspecting the two latter 
 
ON PADDLE WHEELS. 141 
 
 figures, the peculiarity of action arising from this disposition of the paddle boards becomes 
 evident, but more particularly in Fig. 5, where the floats are immersed for a longer time. 
 One set of floats is there seen entering the water at a, b, c, d, the position of which is shown 
 at a', b', c", d', after an interval of one-sixteenth of a revolution ; and it is apparent that, while 
 the outer board, a, is moving to the position a', the next board, b, almost follows the track of 
 the former to arrive at b' ; in the same manner the third follows the second, and the fourth 
 the third, until they arrive at the middle of the stroke, when they diverge so as to perform 
 the last half of the stroke independent of each other's motions, and emerge from the water at 
 such a distance from each other, that the water which is not thrown off with violence can run 
 off more readily than from the broad float of the common wheel. It thus appears that very 
 little more effect is produced during the first half of the stroke of one set of boards than would 
 be produced by the outer board alone, and during the second half the effect is about equal to 
 that of a common float equal in size to the sum of those which form a set. We conclude, 
 therefore, that the shock received by the floats on entering the water must be reduced nearly 
 to that of the outer board, but that this advantage is gained at the expense of a considerable 
 portion of the effect, in consequence of which the wheels must require a greater surface of 
 paddle board than common wheels. There may also be a little advantage in the manner the 
 floats leave the water, but that, if any, must be very trifling. It is evident that no theoretical 
 calculation can be made of the effect of this wheel, its action being precisely similar to that of 
 the common wheel, except that all but the outer boards move during a considerable part of 
 their stroke in troubled water, whereby a loss of resistance is sustained, the amount of which 
 cannot be computed. It remains, therefore, to be decided by experience whether the dis- 
 advantages of this wheel are overbalanced by the advantages which it seems to possess. 
 
 It is remarkable that since the adoption of this wheel, when Mr. Galloway made them with 
 six or seven bars in each set instead of the ordinary paddle boards, this number has been very 
 much reduced : those now used in Her Majesty's service have only two boards in a set, every 
 reduction having been found to be attended with advantage ; they cannot, however, carry their 
 improvements any farther without annihilating the principle of the wheel altogether, and 
 returning to the common wheel. 
 
 It should here be observed, that in the summer of the year 1837, before these wheels were 
 adopted in Her Majesty's service, a numerous series of experiments were made at Woolwich 
 on Her Majesty's steamer 'African,' under the superintendence of Mr. Ewart, inspector of 
 steam machinery, some with the common wheel, and some with Field's, in order to ascertain 
 the comparative merits of the two wheels. The results of these experiments were not allowed 
 to be publicly known, because they were not complete ; but Mr. Ewart was so well satisfied 
 with the success of the trials, that Her Majesty's steam vessels ' Rhadamanthus,' ' Dee,' 
 'Tartarus,' and 'Meteor/ were immediately fitted with Field's wheels, each with two boards 
 in a set. From what we have been able to learn from persons who were present at the 
 experiments alluded to, some very anomalous results were obtained, such as less velocity of 
 the engines and greater speed of the vessel ivith less float, all other circumstances being the 
 same. 1 
 
 1 This is a proof that the accuracy of the mile trials cannot be implicitly relied on, at least as they have been made till 
 now ; perhaps they might be made more practically useful, if greater attention were paid to the various circumstances which 
 affect the results. 
 
 t 
 
142 APPENDIX. 
 
 A few trials were subsequently made with Her Majesty's steam vessel 'Tartarus,' which may 
 throw some light on the relative qualities of the wheel under consideration, and Morgan's 
 wheel. This vessel formerly had a pair of the latter wheels with two fifty horse engines ; she 
 has now a pair of wheels with the divided floats, which have been made to go into the old 
 paddle boxes, and two seventy horse engines. When she was tried with the former, she was 
 ready for sea, drawing 12ft. 2 in. mean, and having an immersed midship section of about 
 254 square ft. ; the steam pressure in the boiler was 2f IDS., and the vacuum 27 inches. Under 
 these circumstances a mean speed of 8'508 statute miles was obtained, the wheels making 
 22 revolutions per minute. When tried in February, 1838, with Field's wheels, the mean 
 draught was 9 ft. 11 in., making her immersed midship section about 176 square ft.; the 
 steam pressure was 5 ffis., and vacuum 28 inches. The mean speed was 11-11 statute miles, 
 with 32 revolutions per minute. 
 
 She was tried again on the 1 1th of March, with her lower masts and shrouds, having provisions 
 and 130 tons of coal on board; she drew about 11 ft. 8 in., and the speed obtained was 8'44 
 miles, with 24 revolutions : the radius of the rolling circle was consequently 4ft. 11 in., the 
 extreme radius of the wheels being 8 ft. 5 in., so that the slipping through of the floats on both 
 these trials was quite extraordinary, and can only be accounted for by the loss of resistance 
 in the first half of the stroke, and the want of a sufficient surface of paddle board, which 
 cannot be given without far surpassing the dimensions required by Morgan's wheels. 
 
 Plate LXXXIII. represents the performance on the February trial : it has been drawn on a 
 very large scale, in order to make it less confused than it would otherwise have been ; but 
 there have been too many lines inserted that were not absolutely necessary, so that it is still 
 not so distinct as we could have wished. C is the centre of the wheel, of which a part is 
 shown on the right of the plate, as well as a part D D D of the rolling circle, at the commence- 
 ment of a revolution ; A A' A" is the curve described by the extreme edge of the outer board, 
 and B B' B" that described by the inner edge of the inner board of one set, and C C' the 
 distance travelled by the vessel, during a revolution ; at the termination of which the rolling 
 circle has arrived at the position D' D' D'. The radius C D of the rolling circle is about 4 ft. 
 1(H in., so that the distance C C' is about 30ft. 6| in. Towards the middle of the plate part 
 of the wheel has been drawn, showing the floats which are immersed at the same time with 
 the nodes of their respective cycloids, in order to give a more perfect idea of the action. The 
 set 1, 1, which is that of which the whole cycloid is given, is near leaving the water; of the 
 next set 2, 2, which has just passed the middle of the stroke, the outer board is about 
 to enter the path which the first set has just traversed, and the inner board has just left 
 the path of the outer one ; and of the third and fourth sets the inner boards are following in 
 the very track of the outer ones. It is obvious that the resistance to the floats must be very 
 much diminished by the naturally disturbed state of the water in which they move. Plate 
 LXXXII. b represents the above-mentioned performance with Morgan's wheel ; it has been 
 drawn on the same scale as the former, for the purpose of comparing the two. It will there 
 be seen that no one of the floats ever enters the path of another, and that the water in which 
 they move cannot be so much troubled as in the former case. The radius of the rolling 
 circle is 5 ft. 5 in., and the distance travelled in one revolution of the wheels consequently 
 34 ft. The quantity of steam consumed was nearly in the ratio of 5 to 7? and the body to be 
 propelled through the water more considerable, the draught of water being greater, so that 
 
ON PADDLE WHEELS. 143 
 
 more work was done at much less expense with Morgan's wheels than with the new ones. 
 The dip of the floats in the former case was 5 ft. 8| in., and the height of the axis above the 
 water only 3 ft. 1 in.; in the latter case the dip was 3 ft. and the height of the axis above 
 the water 5 ft. 5 in. 
 
 The new steam frigate ' Gorgon,' of 1100 tons, has lately been fitted with a pair of Field's 
 wheels, and was tried a short time ago without her masts, drawing 13ft. 6 in. mean. The 
 wheels made 20J revolutions per minute, and a mean speed of nearly lOf miles was obtained, 
 which gives about 7 ft. 4 in. for the radius of the rolling circle, the extreme radius of the wheel 
 being 13 ft. 3 in. The paddle boxes here were also made for Morgan's wheels, so that 
 sufficient width could not be given to those afterwards made for the vessel. This disadvantage 
 must, of course, be taken into account in estimating the value of a wheel. This wheel being 
 now very extensively employed, experience will soon show whether there is any advantage 
 in it or not. Among the principal vessels fitted with these wheels, besides those already 
 named, are the 'Great Western' and the 'British Queen' American packets, and the 'Hermes,' 
 a government steamer of 730 tons. 
 
 3. Paddle Wheels with oblique floats. 
 
 Such wheels have been tried at various times and under various forms, some of which have 
 been patented. Among these may be named, as the most simple, that for which Mr. Samuel 
 Hall obtained a patent in June, 1836. In this wheel the paddle boards, instead of standing 
 at right angles to the rims and parallel to the axis of the wheel, as in wheels of the ordinary 
 construction, are placed obliquely to the rims and to the axis of the wheel. The subject of 
 the patent is not, however, the use of oblique floats, but the making of one-half of them to 
 enter the water in one diagonal direction, and the other half to enter it in the reverse diagonal 
 direction, or in large paddle wheels, making the boards change their direction of entering the 
 water four times instead of twice. We do not think that any effect can be produced by 
 giving the floats different positions, but that the action would be about the same as that of 
 the ordinary paddle wheel with oblique floats, in which they all incline the same way ; and it 
 has been found by experience that this requires a greater surface of paddle board than the 
 common wheel to produce the same effect, which can also be demonstrated theoretically in 
 the following manner : 
 
 The circumferential velocity of any given point of a float of the common wheel being V, 
 and the velocity of the vessel v, we have already seen that its effective velocity is V v cos. $, 
 and that the pressure upon it is proportional to [V v cos. ] 2 ; but, with the same given 
 velocities, the effective velocity of a point of an oblique float, situated on the radius which 
 passes through the middle of the float, and at the same distance from the axis as the given 
 point in the common wheel, is only [V v cos. </>] cos. , if a is the angle which the surface 
 of the float makes with the axis of the wheel. The corresponding pressure is therefore 
 proportional to [V v cos. </>] 2 cos. a 2 ; and, the width of the wheels being the same in both 
 cases, the ratio of the tangential pressure on the oblique float to that on the common float is 
 
 POS Q? 
 
 - , supposing the whole of the former to radiate from the axis, which is only true for 
 the middle part ; but that will not affect the reasoning, as it might easily be shown that there 
 
144 APPENDIX. 
 
 t 
 
 is rather a disadvantage than otherwise in the float not being radial. The effective pressure in 
 the common wheel is proportional to [ V v cos. 0] 2 cos. <f>, and in the other to [ V v cos. $] 2 
 cos. a? cos. <f>. Thus the resistance overcome, and power required to overcome it with the 
 oblique floats, are to the resistance and power required with the common wheel (the dimensions 
 of the wheels and velocities being the same, except that the quantity of float in the former is 
 to that in the latter as 1 to cos. a) nearly in the ratio of cos. a 2 to 1. But if it be required to 
 determine what circumferential velocity would be necessary to give the same vessel the same 
 speed as with the common wheel and the circumferential velocity V, let V be the required 
 velocity ; then we must have 
 
 [F" - V COS. <] 2 COS. a 2 = \VV COS. <] a , 
 
 or [ V' v cos. $] cos. a = V v cos. <f>, 
 
 ..-, V V COS. <& (1 COS. a) 
 
 whence V = e - i 
 
 cos. a 
 
 It will be at once observed that this is not a rigorous calculation, and that the above result 
 is not yet determined, as it contains the variable quantity cos. <f>, for which we ought to 
 substitute its average value. Assuming this to be -fc, a probable value, and cos. a = -f-, which 
 makes the obliquity less than that preferred by Mr. Hall, viz., 45, the value of V becomes 
 
 , V ' ~ & . 50 V ~ 9 v 
 4- 40 
 
 Assuming v to be equal to f of the mean value of V, we find by substitution, 
 
 V' = ttV, 
 
 and, as the resistance overcome is now equal to that overcome with the common wheel at the 
 velocity V, it follows that the former requires about -fa more power than the latter to produce 
 the same effect. 
 
 We repeat that the above calculation is not rigorous, but it is obvious that whatever 
 probable values are substituted for a, <, and v, V' will always be found greater than V, which 
 is a sufficient indication of the inferiority of this wheel. 
 
 It is superfluous to add, that the same effect would be produced, without altering the velocity 
 of the wheels, by increasing their breadth in the ratio of cos. a? to 1, but that would nearly 
 double the weight of the wheels under the circumstances assumed above. 
 
 It is evident that, whichever method be adopted, the shock cannot be very much reduced, 
 and, the loss of power from oblique action being greater than with the common wheel, the 
 oblique floats are not likely to supersede the ordinary ones. 
 
 We shall now briefly notice a modification of this wheel invented by Mr. Jacob Perkins, 
 which we will therefore call Perkins's paddle wheel. 
 
 4. Perkins's Paddle Wheel. 
 
 Mr. Perkins took out a patent for this wheel in the year 1829: it differs materially from 
 all others, although the floats are fixed, as in the preceding, at an angle with the shaft ; but 
 that angle is essentially 45, and the shafts, instead of traversing the vessel in the usual 
 manner, are carried in a sloping direction towards the stern, and meet in the plane of the keel, 
 making with it an angle of 45, and with each other a right angle. On the extremities of the 
 
ON PADDLE WHEELS. 145 
 
 shafts farthest from the paddle wheels are fixed bevel wheels, which act upon each other, or 
 are both acted upon by an intermediate bevel wheel in connexion with the steam engine or 
 first mover. 
 
 By this arrangement the surface of each float when under the centre is perpendicular to 
 the vessel's course, so that the whole pressure is at that moment effective, and, when over the 
 centre, it is parallel to the course of the vessel, so as to cause the least possible useless 
 resistance. 
 
 The circumferential velocity of any given point of a float being V, and the velocity of the 
 
 V 
 vessel v, the effective velocity of the given point when under the centre is v, which 
 
 shows that the upper edge of the float would back water in the middle of the stroke, if the 
 ratio of the velocity of the vessel to the circumferential velocity of the inner edges of the floats 
 
 exceeded 
 
 It is already well established that the more the circumferential velocity of the floats of a 
 paddle wheel exceeds the speed of the vessel, the greater is the waste of power ; and Perkins's 
 wheel requires a rather large excess, so that this quality, together with the great weight of 
 the wheels compared with that of common wheels of equal effect, the use of bevel wheels to 
 turn the shafts, which must be longer than they usually are, and the inconvenient position of 
 the wheels, which makes it very difficult to support them, and exposes them very much to 
 the action of the winds and waves ; all these circumstances are so conclusive of the disadvan- 
 tage of the system, that it is unnecessary to carry the investigation any farther. An additional 
 argument against the utility of this wheel is, that it has not been adopted in practice. 
 
 Several other varieties of paddle wheels with oblique floats have been invented and tried, 
 but without success, and, as there is neither ingenuity nor novelty of invention in any of 
 them, we shall pass them over. 
 
 CLASS II. PADDLE WHEELS WITH FEATHERING FLOATS. 
 
 This class may be subdivided into, 
 
 A. Paddle wheels with floats turning on radial axes, and 
 
 B. Paddle wheels with floats turning on horizontal axes or spindles. 
 
 A. Paddle Wheels with floats turning on radial axes. 
 
 Of these very little need be said, as they have not yet been, and are not likely ever to be, 
 adopted. The action of all of them is nearly the same : the floats either enter or leave the 
 water, or both, in the direction of their surface, or at a very acute angle with it. The action 
 is therefore generally very oblique ; besides which, the mode of feathering the floats is so 
 objectionable, that that alone would be sufficient to condemn the system. The floats are 
 fixed to spindles radiating from the axis of the wheel, each of which is furnished with a crank 
 at its inner extremity, through the medium of which the spindle is made to turn by means of 
 
146 APPENDIX. 
 
 a groove or other guide fixed to the side of the vessel (as in Symington's wheel), or in the 
 interior of the wheel itself (as in Steed's, &c.). Time will not permit us to give a full 
 description of any of these wheels, nor to enter into any calculation of their effect, which 
 must, however, be quite unnecessary ; for a machine tried under such favourable circumstances 
 as Symington's wheel must certainly have been adopted, if it had any claim to preference. 
 A wheel, on a similar principle, with the paddle cranks guided by cams in the interior of the 
 wheel, was tried some years ago in a small boat on the Thames ; but the friction was so great, 
 that three or four men could scarcely prevent the boat from being carried down by the tide, 
 although they could easily have rowed her at a moderate speed. The friction of the feathering 
 machinery must in all cases be very considerable ; so that, however beautifully it may work at 
 the beginning, there is no doubt that its action would soon be impaired by wear, and it would, 
 perhaps, not require a long time to be entirely destroyed. 
 
 B. Paddle Wheels with floats turning on horizontal axes or spindles. 
 1. Buchanan's Wheel. 
 
 The principle of this wheel is described by the patentee in his specification in the following 
 manner : 
 
 " In the first place, my said invention is established upon a mathematical theorem, which 
 " may be enumerated in the words here underlined, namely : If two equal rings or circular 
 " lines be conceived to revolve, each upon its respective centre in its own. plane, with one and the 
 " same uniform velocity, and in the same direction with regard to parts of the lines or rings alike 
 " situated, and any point be taken in one of the rings or lines, and a right line be drawn from 
 " that point parallel to a line supposed to join the centres, until it meets the other line or circle, 
 " then I say the right line so drawn will be equal to the line of distance between the centres, and 
 " will continue equal and parallel to that line of distance during the whole of every revolution 
 " so made." 
 
 Fig. 1. PI. LXXVI. is a diagram of Buchanan's wheel, which has been drawn of the same 
 dimensions, and with the same number of floats as those of the ' Phoenix' and ' Salamander.' 
 From the centre of a framing similar to that of the common wheel, and called by the patentee 
 the Pitch wheel, r, r, r, are the radii or arms ; S, S, S, spindles, working in bearings in the cir- 
 cumference of the Pitch wheel ; each spindle is attached to a float, represented in the diagram 
 by the straight line A B, which is divided into two equal parts by the spindle, one end of 
 which passes through the Pitch wheel, and is furnished with a lever or crank S G. The ex- 
 tremity G of this lever is bent at right angles to S G, and works in a bearing on the circum- 
 ference of a flat wheel or frame G G G, called by the patentee the Connexion wheel, which 
 turns on an axle fixed to the ship's side, excentrically with respect to the Pitch wheel, its 
 centre being situated at a different point. This axle is made sufficiently large to admit of the 
 shaft passing through it. The crank S G is equal in length, and constantly parallel to the 
 line that joins the two centres. 
 
 The float, being fixed to the crank, must evidently remain constantly parallel to a fixed 
 straight line during the whole of each revolution of the wheel, nor can any alteration in the 
 
ON PADDLE WHEELS. 
 
 147 
 
 proportions of the parts cause it to change its position ; indeed it would be impossible to 
 make the wheel revolve, if any other length or position were given to the crank or lever S G. 
 This essential property of Buchanan's wheel is amply sufficient to distinguish it from another, 
 known by the name of Morgan's wheel, which we shall treat of in a future part of this paper. 
 We mention this because some persons have confounded these two wheels together from 
 ignorance of their respective properties, although they are widely different both in principle 
 and construction. 
 
 Fig. 2. PL LXXVI. shows the path of one of the floats of the wheel represented in Fig. 1, 
 under the same circumstances as those of the ' Phoenix' in Fig. 2. PL LXXIV. Fig. 3 is the 
 enlarged node. Figs. 4 and 5 correspond with Figs. 4 and 5, PL LXXIV., which relate to the 
 trial of the ' Salamander.' In both these cases the floats back water, or move forward in the 
 same direction as the vessel, but most considerably at the deep immersion. We will not, 
 however, investigate the action of the wheel under such circumstances, but suppose the 
 velocity of the wheel to be such that the floats, at their immersion and emersion, shall move in 
 a vertical direction. 
 
 In the adjoining figure let C S represent the radius, A B the float, and S the spindle, at 
 the instant the lower edge of the float enters the water, C D a vertical line, A D the water 
 line, and S H a horizontal line, passing through 
 the spindle S and intersecting the line C D 
 at the point H. Let C S = R, C H = a, A B =/, 
 and the breadth of the float = b ; let $ = the in- 
 clination of the radius at any given instant, and 
 its inclination at the instant its lower edge enters 
 the water, or the angle S C D, = a ; also let S E, 
 perpendicular to the radius C S, = the circum- 
 ferential velocity of the float, = V, and v = the 
 velocity of the vessel. 
 
 In order that the above-mentioned condition 
 may be satisfied, it is evident that there must 
 exist the following relation between v and V, 
 
 V V COS. a. ; 
 
 for v must be equal to A E, which is equal to S E 
 cos. SEA; but the angle S E A = the angle 
 S C D = a. ; therefore v = V cos. a ; and p, the 
 radius of the rolling circle, = R cos. a = a. 
 
 The effective velocity of the float in any given position is V cos. $ v. For let A' B' be 
 the given position of the float, the angle S' C D being equal to 0, and let S' E', perpendicular 
 to the radius C S', = V, and the portion E' G of the horizontal line E' F, which intersects 
 A' B' at the point F, = v ; the straight line S' G will represent the motion of the float both 
 in direction and velocity, and F G, which is perpendicular to its surface, will be equal to its 
 effective velocity. Now we have E' F = S' E' cos. S' E' F = V cos. 0, and E' G = v, there- 
 fore effect, vel. = F G = E' F E' G = V cos. <f> v, or, substituting for V and v their 
 
 respective values, viz., V= 
 
 r Rn 
 30 
 
 and v = Fcos. a = 
 
 rRn 
 30 
 
 cos. a = 
 
 TT a n 
 
 ~sd~' 
 
148 APPENDIX. 
 
 Effect. veL = [R cos. < - a], 
 30 
 
 The corresponding pressure on the float (which is all effective) is equal to the product of its 
 immersed area by the square of its effective velocity and the fraction . The immersed 
 
 w t/ 
 
 area, supposing the float to extend to the surface of the water, is equal to the product of its 
 dip, B' A', by its breadth b, and the dip is, in general, equal to R cos. <f> a ; therefore the 
 pressure is 
 
 7T 2 M 2 W b r-f, -I, 
 
 p = [R cos. A a] 3 . 
 
 900 x 2 g L 
 
 The moment of resistance due to the given float, being equal to the sum of the products of 
 p by the effect, vel. of the float, and by the velocity of the vessel respectively, is equal to 
 p [F G + G E'] p. F E' =p V cos. <f>, or substituting forp and V their values, 
 
 n 3 R n 3 w b rr) -,,, 
 
 R cos. <z> a 3 cos. <p. 
 
 27000 x 2ff L 
 
 The mean value of this expression for the whole revolution of the wheel is equal to the 
 definite integral 
 
 a 
 n 2 R n 3 w b 
 
 27000 x 2y 
 
 o 
 which is 
 
 / [R cos. cf> a] 3 cos. (f>. d $, 
 
 -([3 R 3 + 12 R a 2 ] a - [13 R? a + 2 a 3 ] sin. a ). 
 
 216000 x 2 r\ 
 
 This is on the supposition that the float extends to the surface of the water during the 
 whole stroke. If otherwise, let A' B' be the position of the float at the instant its upper 
 edge enters the water, and let the inclination S' C D = /3 ; we shall then have R cos. 
 /3 = a + f, which for simplicity we will call k. Let A" B" (see the figure) be one of the 
 positions of the float, in which its upper edge is immersed to a certain depth I B" below the 
 surface of the water. In this case we must deduct from the above resistance the portion due 
 to an area of float, whose length is equal to b, and breadth to I B". Now I B" = R cos. < k, 
 so that the required area is equal to b [R cos. <f> k], and the moment of resistance due to 
 this area is 
 
 7T 3 Rn 3 W b rTS lorn 
 
 \R cos. <6 a] 2 |K cos. <p k] cos. <t>. 
 
 27000 x 2ff L 
 
 Its mean value is equal to the definite integral 
 
 ^ 
 Tr 2 R n 3 w b 
 
 /f-R cos. <4 a] 2 T.R cos. rf> k~\ cos. <f>. ? <f>, 
 L V J L V J V V, 
 
 27000 x 2^r 
 
 o 
 
 which, after integrating and substituting for cos. /3 its value , becomes 
 
 R 
 
 HT* ft n^ in hi \ 
 
 ( [9 # 3 + 12 7? 2 + 24 .R a /t] ^- [32 R* a + 7 fl 2 k+ 12 a 2 /t-8 a F + 2 P] sin. ft). 
 648000 x 2 y\ L I 
 
ON PADDLE WHEELS. 149 
 
 The general expression of the moment of resistance due to one of the floats is therefore 
 
 P = ^ Rn3wb { rg pa + 3 6 ft 02] a _ r- 39 jR2 a + 6 a s] sin a 
 648000 x 2ffl l 
 
 -[9R 3 + 12 Ra* + 24 R ak~\ /3 + [32 R* a + 7 R 1 k+I2 a* k 8ak*+2 k 3 ] sin. j, 
 
 and the number of horse powers exerted through the medium of the two wheels with m floats 
 on each, 
 
 H. P. = -^-^^A- ( [9 /? 3 + 36 /{ a 2 ] - [39 J? a + 6 a 3 ] sin. a 
 178200000 x 2ff\ L 
 
 The effective pressure being in this wheel equal to the total pressure on the floats, or p, 
 and the moment of effective resistance being equal to the product of this quantity by v or 
 
 ^-?, the moment of effective resistance due to one of the floats in any given position, its 
 
 upper edge not being immersed, is equal to 
 
 Tr 3 a n 3 w b 
 
 27000 x 2ff 
 the mean value of which is equal to 
 
 [R cos. <j> a] 3 , 
 
 a 
 1 a n 3 w b 
 
 27000 x 2ff< 
 o 
 
 /[TZcos. <f> a] 3 .d<j>, 
 
 or 
 
 ! n 3 w b 
 
 162000 x 2ff 
 
 The quantity to be deducted for the over-immersion of the float is 
 
 ft 
 
 /[R cos. < a] 2 [_R cos. < A] . d <f>, 
 
 a w 3 w b 
 
 27000 x 2 ff, 
 o 
 
 or 
 
 Tr 2 a n 3 w b 
 
 162000 x 2ff 
 so that the general expression of the moment of effective resistance due to one of the floats is 
 
 E.P.= ~- n 3 wb_f - [9 fl 2 a + 6 a 3 ] + [4 E 3 + 11 jRa 2 ] sin. a 
 162000 x 2ff \ 
 
 sin./9J; 
 
 and the number of horse powers effectively employed, or the propelling effect of the two 
 wheels, 
 
 H. P. E. = ** n * W b m ( - [9 R* a + 6 a 3 ] a + [4 R 3 + 11 R a 2 ] sin. 
 44550000 x2^l 
 
 [4 R 3 + 6Ra? + 6Ra k-RP~\ sin. . . (2). 
 To find the formula for the centre of pressure, let x be the distance of that point from the 
 
150 APPENDIX. 
 
 lower edge of the float, and 6 the inclination of the radius when it enters the water ; we shall 
 have 
 
 The moment of resistance due to the float in any given position is found by substituting, 
 in its former value, the depth of the float /, for the immersion R cos. <f> a, which gives for 
 
 its mean value 
 
 6 
 Tr 2 Rn 3 w b f f r 
 
 -27060^ J [#-?***. 
 
 o 
 and, after integrating and substituting for cos. 6 its value, we get 
 
 which, multiplied by 2 m and reduced to horse powers, becomes 
 
 The moment of effective resistance is found in the same manner as above ; and if we call z 
 the distance of the centre of propelling effect from the lower edge of the float, and the 
 inclination of the radius when that point enters the water, its mean value is 
 
 
 
 7i 3 an s wbff* rTt -11 j i 
 
 -- ^ / \R cos. <f> a] 2 , ad), 
 27000 x2ffj 
 o 
 
 which, after integrating and substituting for cos. f its value, --_, becomes 
 
 This gives for the number of horse powers effective, or propelling effect, 
 
 H.P.E.= 7r [P? + 2a*]{-[SRa-Rz]sm.{ ....(4) 
 
 14850000 x 2ff I L / 
 
 We regret not having the time to construct tables for these two points, although they 
 would be more interesting than useful, as Buchanan's wheel is not used ; we will, however, 
 apply the two first equations to a case that will serve in a measure as a comparison of this 
 with the common wheel. 
 
 Let it be required to find the breadth of the floats, and the power of the engines necessary 
 to give the ' Salamander' the same speed under the same circumstances, as on the trial with 
 the common wheels alluded to in a former part of this paper : the extreme diameter of the 
 wheels, the depth of float, and the height of the shaft above the water, being the same ; the 
 radius of the rolling circle, however, being limited by the condition explained above, the 
 number of revolutions is thereby fixed. All the necessary data will be found at page 127. 
 
 The condition that the same effect is to be produced, requires that the value of H. P. E. 
 should be equal to 88-23, as found, page 130, for the common wheel ; and, b being the only 
 quantity not yet determined, its value may be found by substituting the value of H. P. E. in 
 the equation (2), which we will now proceed to solve with the assistance of logarithms. 
 
ON PADDLE WHEELS. 
 
 151 
 
 6-25 
 
 We have R = 9-25 ft., a = 3'75, cos. = ^ , k = 6-25, cos. /3 = - r , and, since p = a, 
 
 9-25 
 
 we have n = 30-439. 
 Log. 
 
 55 
 
 R = 0-96614 
 a = 0-57403" 
 a = 0-06197 
 sin. a =1-96101 
 
 Substituting these values, we find, 
 
 Log. 4 R 3 sin. a = 3-46149 
 11 Ra?sm. a= 3-11660 
 6 R? a /3 = 3-20297 
 3 R 2 k /3 = 3-12379 
 6 a 2 k /3 = 2-64060 
 fl/Psin. /3 = 2-42548 
 
 Log. 9 # 2 a a = 3-52252 
 
 6 a 3 a = 2-56221 
 
 4 I? 3 sin. /3 = 3-36806 
 
 6 R a 2 sin. /3 = 2*75993 
 
 6 Raksin./3= 2-98178 
 
 9-25 
 
 Log. A = 0-79588 
 
 /3 =-1-91851 
 
 sin. ,8 =-1-86758 
 
 4 fl 3 sin. a 
 1 1 .R a 2 sin. a. 
 6.R 2 a/3 
 3/Z a /t/3 
 6 a 2 k 13 
 R /t 2 sin. /3 
 
 2893-9 
 
 1308-0 
 
 1595-8 
 
 1329-8 
 
 437-1 
 
 266-4 
 
 Sum of positive terms = 7831-0 
 
 9 R* aa. 
 
 6 a 3 a 
 4 R 3 sin. /3 
 6 1? a 2 sin. /3 
 6 R a k sin. /3 
 
 Sum of negative terms 
 Sum of positive terms 
 
 3330-6 
 364-9 
 
 2333-8 
 575-4 
 
 958-8 
 
 7563-5 
 7831-0 
 
 267-5 
 
 Log. 
 
 267-5 
 TT 3 an 3 w m 
 
 = 2-42732 
 = -l-572l7 
 
 JJ 44 
 
 55 
 55 
 
 [550000 x2g 
 H.P.E. 
 
 1-99949 
 
 b 
 H.P.E. 
 
 = 1-94560 
 
 b -1-94611 
 
 b = 0-8833 ft. = 10-6 inches. 
 
 The other question to be solved is, what is the power necessary to produce the required 
 effect. This is found by substituting, in formula (1), the value of b just obtained, as well as 
 those of all the other quantities which enter into it. This operation is in substance as 
 follows : 
 
152 
 
 APPENDIX. 
 
 Log. 9 R 3 a. = 3-91463 
 36 R a? a. = 3-73247 
 32 R 3 a sin. 0= 3-87904 
 7 R 3 k sin. /3 = 3-44084 
 12 a 2 A sin. /3= 2-89070 
 2 k 3 sin. /3 = 2-55625 
 
 Log. 39 fl 2 a sin. a = 4-05838 
 
 6 a 3 sin. a = 2-46125 
 
 9/Z 3 /8 = 3-77117 
 
 12 Ra* /3 = 3-11189 
 
 24 Rakft = 3-63477 
 
 8 A 2 sin. /3 = 2*93646 
 
 
 
 
 
 
 
 
 9 R 3 a = 8215-4 
 
 36 R a 1 a = 5401-0 
 
 32 R 2 a sin. /3 = 7569-0 
 
 7 R 3 k sin. /S = 2759-6 
 
 12 a 2 & sin. /3 = 777'5 
 
 2 A 3 sin. /9 = 360-0 
 
 Sum of positive terms = 25082-5 
 
 
 39 R 3 a sin. a = 
 
 11438-8 
 
 
 6 a 3 sin. a = 
 
 289-2 
 
 
 9E 3 /3 = 
 
 5904-3 
 
 Sum 
 Sum 
 
 12#a 2 /9 = 
 24Rakj3 = 
 8 a k 3 sin. J3 = 
 
 of negative terms = 
 of positive terms = 
 
 1293-9 
 4312-9 
 863-9 
 
 24103-0 
 25082-5 
 
 979-5 
 
 Log. 979-5 
 
 7T 2 Rn 3 w b m 
 " 178200000 x 2y 
 
 H.P. 
 
 2-99100 
 - 1-30853 
 
 2-29953 
 
 H.P. 
 
 = 199-31. 
 
 In this example the ratio of the effective to the total power is only 0-443, which shows that 
 the principle of vertical paddles is in this case fallacious. We do not think it necessary here 
 to enter into the practical objections that may be raised against this wheel, but proceed at 
 once to the next kind that claims our attention, which is, 
 
 2. Oldham's Paddle Wheel. 
 
 The principle of this wheel will be perfectly understood by conceiving the axis of the 
 excentric in Buchanan's to revolve round the main shaft in the same direction as the latter, 
 and with half its angular velocity. This is effected by fixing a spur wheel on the shaft close 
 to the vessel's side ; another on an independent axis fixed to the vessel's side, working in the 
 former ; a third on the same axis as the second, and fixed to it, but of a different size ; and a 
 fourth fixed to the excentric, or guiding frame, concentrically with the main shaft, working 
 in the third ; the dimensions of all being so proportioned that the last shall make one revolu- 
 tion to every two of the first. It follows from this, that as each paddle-crank or lever must 
 of necessity be constantly parallel to the imaginary line which joins the two centres, and as 
 
ON PADDLE WHEELS. 
 
 153 
 
 this line is constantly changing its position, the cranks must be set at different angles with 
 the surface of their respective floats, in order that the latter may all have the same inclination 
 when at the same point of the circumference. Fig. 1. PI. LXXVII. will explain this arrange- 
 ment : C is the centre of the wheel, and E that of the guiding frame, r r r the radii or arms ; 
 the polygon, or outer frame of the wheel, F F F, is made sufficiently large to include the whole 
 of the floats, in order to have a bearing for cross-stays, which traverse the wheel from one 
 side to the other at the points F F F, &c. ; S, S, S, &c., are the spindles with the cranks 
 S G, S G, S G, &c., exactly as in Buchanan's wheel, except that each crank, S G, makes an 
 angle with its float, differing from that of the next on either side by half the angle included 
 between the respective arms of the wheel ; ff,g,ff, &c., are the arms, and G, G, G, the periphery 
 of the guiding frame. The positions of the paddle-cranks are easily found by drawing the 
 wheel without the floats with the guiding frame in any arbitrary position (in the figure its 
 centre is immediately over the shaft, but any other position would do as well) ; the line C E 
 being given, all the cranks must be parallel to it, and the floats radiate from the highest point 
 of the circumference which passes through the spindles ; each float being then fixed to its 
 crank, will evidently radiate from the same point during the whole of every revolution of the 
 wheel, and its inclination will consequently always be half that of the radius. 
 
 The action of this wheel is theoretically very good, the pressure on the floats being nearly 
 uniform throughout the stroke ; but the great friction, liability to get out of order, and other 
 difficulties attending its construction, have hitherto overbalanced its theoretical advantages. 
 The wheel represented in the figure is of the same dimensions as those in the preceding plates, 
 and the same speed and number of revolutions in each of the Figures 2 and 4, as in the 
 corresponding figures in the other plates. In 
 comparing the nodes, Figs. 3 and 5, with those 
 of the other wheels shown in Plates LXXIV., 
 LXXV., LXXVI., the superiority of Oldham's 
 wheels is manifest : the float strikes the water, 
 on entering, less violently than that of the 
 common wheel, having at that moment less 
 effective velocity, and there is throughout less 
 loss from oblique action, from its inclination 
 being always less : the whole immersed surface 
 of the float is always effective, which gives it 
 another advantage over the divided float of 
 Field's wheel; and the radius of the rolling 
 circle is not limited, as with Buchanan's, which 
 causes a great proportion of the power to be 
 spent simply in turning the wheels. 
 
 To investigate the action of the floats, let 
 L L be the water line, C the centre of the 
 wheel, S' S" its vertical diameter, C S one of 
 the radii, A B the float, and S the spindle. 
 Let R = the radius C S ; / = AS, the half 
 depth of the float. Produce A B until it meet 
 
 r 
 
154 APPENDIX. 
 
 the vertical diameter at the point S', and let 8 = the angle S S' S" contained between 
 the surface of the float and the vertical. Let S E, perpendicular to C S = the circum- 
 ferential velocity of the spindle = V, and the horizontal line S G = the velocity of the 
 vessel = v. Through the point S draw a straight line F H perpendicular to A B, and 
 from the points E and G draw E F and G H perpendicular to F H, and meeting it at 
 the points F and H ; the difference between F S and S H will be the effective velocity of 
 the spindle. Now, the angle E S F being equal to the angle S S' S" or 8, we have F S = 
 V cos. 8, and, because the angle G S H = 8, we have also S H = v cos. 8 ; therefore, the 
 effective velocity of the spindle = ( V v) cos. 8, which is always positive, for the speed 
 of the vessel is always less than the circumferential velocity of the spindle. Through 
 the points S' and F draw a straight line S' K, and from any point A of the line A B draw 
 another straight line A K parallel to S F, and intersecting the former at the point K ; 
 A K S H will be the effective velocity of the point A : for, since the float always radiates 
 from S', we may consider that point as the centre of revolution, in which case S F would 
 represent the circumferential velocity of the spindle, and consequently A K that of the point 
 A. Now, if we combine this with the horizontal velocity S G, and resolve the resultant into 
 two others, one perpendicular and the other parallel to A B, the former, which is the effective 
 velocity of the given point, will be found to be equal to A K S H. Let z = the distance 
 of the given point from the spindle, taken positively towards the lower edge of the float, and 
 negatively towards its upper edge ; then we shall have 
 
 AK : SF :: AS' : S S', 
 or, 
 
 A K : V cos. 8 : : 2 R cos. 8 + z : 2 R cos. 8, 
 whence, 
 
 A K = JL [2 R cos. 8 + z] , 
 and, deducting S H, we shall find the effective velocity to be 
 
 - [2 R cos. 8 + z] v cos. 8, 
 2 H 
 
 or, putting for V and v their values, 
 
 Effective velocity = 2L^L [2 (R - p) cos. * + z] . 
 60 
 
 From this equation it appears that the difference between the effective velocities of any two 
 points on the surface of the float is constant during the whole of the stroke, and that the 
 effective velocity of the spindle increases in the same ratio as cos. 8, therefore the effective 
 velocity of any point, and consequently the pressure upon it, increases from the moment it enters 
 the water until it arrives at the middle of the stroke, and then decreases again until it leaves 
 the water. This property causes the shock to be much less than with the common wheel, of 
 which the floats experience the greatest resistance at the beginning and end of the stroke. 
 
 A curious property of this wheel is that the effective resistance is always equal to the tan- 
 gential resistance at the spindle, which is the resistance to be overcome by the engines ; so 
 that the propelling effect is to the power employed as the radius of the rolling circle, or p, is to 
 the radius of the wheel R, which ratio has not been attained by any of the foregoing varieties 
 of wheel. To demonstrate this property, let/? = the pressure on any float A B perpendicular 
 
ON PADDLE WHEELS. 155 
 
 to its surface, that is, in the direction F S; the tangential pressure, which is of course in the 
 direction E S perpendicular to C S, is equal to p cos. 8, since the angle E S F = 8, and the 
 moment of resistance due to the given float is equal to the product of this pressure by the 
 circumferential velocity of the spindle, or p V cos. 8. Now the angle G S H being also equal 
 to 8, we have also the effective pressure = p cos. 8, and p v cos. 8 = the moment of effective 
 resistance due to the given float ; therefore, since in any position of the float the effective is to 
 the total resistance as v is to V, or as p to R, the same proportion must hold good for the 
 sum of all the resistances on the different floats through the whole revolution of the wheels. 
 
 The ratio of the speed of the vessel to that of the wheel is even less limited than with the 
 common wheel, or, what is still better, the floats may be made of a greater depth without the 
 upper edge backing water ; for it is evident that when the upper edge of a float enters the 
 water, as at B, if the velocity of the vessel be to that of the spindle as B M to S E, or as S' B 
 to S' S, or putting for the two latter their values, as 2 R cos. 8 f : 2 R cos. 8, the upper edge 
 of the float will move in the direction of its surface, and will consequently have no effective 
 velocity until it has passed that position. Assuming this ratio of velocities, we have 
 
 p: R:: 2 R cos. 8 /: 2 R cos. 8, 
 whence, 
 
 p = R - 9~r h > or /= 2 ( R - ?) cos - 8 - 
 
 COS. O 
 
 If the dip of the float in the middle of the stroke be equal to its depth, cos. 8=1, and we 
 may have 
 
 p = R-L, OT f=2(R-p), 
 
 in which case the rolling circle would extend to J the depth of the float ; and if the velocity of 
 the vessel were to the circumferential velocity of the spindles as 11 to 12, we should have 
 
 R 
 
 7 ' ' ~6 ' 
 
 or the depth of the float one-third of the radius of the wheel. If at the immersion of the 
 upper edge of the float cos. 8 = f , which requires a very great immersion, we should have 
 
 Assuming again p - R, we find 
 
 
 or the depth of the float = one-fourth of the radius of the wheel. 
 
 Thus, in principle, Oldham's wheel is very superior, but in a practical point of view so 
 exceptionable, that unless some much better method of carrying the principle into execution 
 be devised, it never can be made to succeed. It is, however, perfectly useless to attempt the 
 improvement of this wheel, since the one we are about to describe possesses the same 
 theoretical advantages in a still higher degree, and is as simple in construction as can 
 reasonably be expected. 
 
156 APPENDIX. 
 
 3. Morgan's Paddle Wheel. 
 
 This wheel being of some importance on account of the extent to which it has already 
 been employed and its decided superiority over all others that have hitherto been used, and 
 having been very much misrepresented, we feel it necessary to be explicit in showing its 
 peculiarities of principle and construction. The Plates LXXXII. and LXXXII. a, are the plan 
 and elevations of the wheel of Her Majesty's steam frigate ' Medea,' of which the principal 
 dimensions are indicated ; but, as there are no letters of reference in these plates, we will refer 
 to Fig. 1. PI. LXXVIII., which is a diagram of Morgan's wheel intended merely to explain 
 its principle, and as a comparison with the other kinds of wheel of which similar diagrams 
 are contained in the preceding plates. The proportions of the parts are not such as are 
 given them by the manufacturer, Mr. William Morgan, being the same as those of the 
 common wheels in PI. LXXIV. The elevations of the 'Medea's' wheel will give the best 
 notion of Morgan's wheel, as made at present. 
 
 This wheel is composed of the following parts : an iron frame-work, forming each side of 
 the wheel, consisting of a boss, represented in Fig. 1. PI. LXXVIII. by the larger of the two 
 circles described with the centre C, (the smaller one is the section of the shaft,) in the 
 circumference of which are keyed the arms, represented by the radial lines r, r, &c., and 
 these are united at their outer extremities by a polygon, S S S, made of round iron for the 
 sake of lightness ; there is also a smaller polygon, which is indicated in the figure but without 
 letters, and in large wheels two smaller polygons, as in ' Medea's * wheel ; these serve to 
 render the frames more compact and firm. The two frames are united together at the angles 
 of the outer polygons, as at S, by means of spindles firmly keyed to the frames, and by 
 diagonal stays of iron from the alternate angles of the smaller polygons, in small wheels, to 
 points situated on the opposite arms between the two polygons, so that, if one diagonal stay 
 departs from one of the angles of the polygon in the outer frame, and joins the inner frame 
 at a point between the two polygons, the next shall depart from the next angle of the 
 polygon in the inner frame, and meet the outer frame at a point on the opposite arm between 
 the two polygons, and so on alternately. In large wheels, where there are three polygons in 
 each frame, the diagonal stays are made in the form of a cross, joining all the angles of the four 
 smaller polygons two by two diagonally, as is seen in the plan of 'Medea's' wheel, PI. LXXXII. a. 
 Each paddle-board is bolted to a kind of frame of iron, called the stem (originally the bent 
 stem), of which the lever S G forms a part, and which is furnished with two steel bushes, 
 made to turn on steel collars fixed on the spindle, which are accurately turned and polished. 
 The stem-lever S G is fixed at any angle with the surface of the float which may be most 
 convenient, that, as well as its length, having very little influence on the motion of the float, 
 and none at all, within certain limits, on its inclination as it enters and leaves the water. In 
 order to leave room in the interior of the wheel for the machinery which is to guide the 
 floats, the shaft is only fixed to the boss of the inner frame, and does not pass through as in 
 other wheels ; this does not, however, much affect the solidity of the wheel, for the diagonal 
 stays make it nearly as strong, if not equally so, with no more weight of metal than there 
 would be in the piece of shaft which is dispensed with : in practice, at least, no deficiency of 
 strength has been experienced on that account. The guiding machinery consists of a crank, 
 
ON PADDLE WHEELS. 157 
 
 whose axis is fixed to the spring beam in a line with the main shaft, and passes through the 
 centre of the outer boss of the wheel ; the crank head is shown at E, abaft the axis of the 
 wheel, and slightly elevated above it ; on this revolves a collar, round the circumference of 
 which are pin-jointed the guide rods, h, h, h, &c., each of which is pin-jointed at its other end 
 to the extremity G, of one of the stem levers. One of the guide rods, g, is an exception, being 
 keyed, and not pin-jointed, as the others are, to the revolving collar, and is called the driving 
 rod, because by its means the collar is driven, or made to revolve at the same time as the 
 wheel. It acts upon one of the floats in the same manner as the other guide rods. 
 
 The object of this combination is evidently to regulate the inclination of the floats by 
 alternately increasing and diminishing the distance between the spindles and the excentric 
 centre E, to obtain which centre is the sole intention of the crank ; but, as it was found im- 
 practicable to make all the guide rods as well as the driving rod radiate from that centre, the 
 revolving collar was added in order to obtain excentric centres for the rest of the guide rods, 
 and this collar ought to be as small as it can conveniently be made, for a large one would cause 
 a variation in the action of the different floats. 
 
 There is a great advantage in the mode of hanging the floats in this wheel, which cannot 
 be applied to Buchanan's or Oldham's, viz., that the spindles, being fixed in the frames of 
 the wheel, contribute greatly to its solidity, and the stem levers, being situated in the centre 
 of the floats, to which they are firmly fixed, are much more efficient instruments to guide the 
 floats than the cranks in the two other wheels, which, besides being on one side and at a 
 considerable distance from the floats, have very weak bases in consequence of their axes 
 having to turn in bearings in the framing of the wheel, and are thus very liable to ring, which 
 must be very injurious to the action of the wheel, as all the floats are guided by one single 
 piece. 
 
 It is astonishing that Morgan's wheel should ever have been for a moment confounded with 
 Buchanan's, the principle and construction of the two differing from each other so widely as 
 they do. The difference of principle has been already pointed out (see page 147), and in 
 construction they differ materially : in Buchanan's wheel the pin-jointed guide rods are entirely 
 wanting, and the revolving collar is enlarged to the size of the principal framing of the wheel ; 
 the levers by means of which the floats are feathered must be equal in length, in Buchanan's 
 wheel, to the distance between the centre of the wheel and that of the excentric, while in 
 Morgan's they never are ; in Buchanan's wheel the spindles revolve uniformly in their bearings, 
 for which reason the cranks must be outside the wheel, as otherwise they could not pass, 
 while in Morgan's the floats vibrate on their spindles, which motion allows of the stem levers 
 being situated in the interior of the wheel. 
 
 Oldham's wheel is still more distinct from Morgan's in construction, by reason of the gear 
 for causing the excentric axis to revolve ; it resembles it, however, much more in effect, as 
 the floats are constantly changing their inclination, but the fixed law, that this must always be 
 exactly half that of the radius, allows of no deviation, while in Morgan's wheel there exists no 
 fixed relation between the inclination of the float and that of the radius. 
 
 We shall presently have to describe another wheel, which has been declared to be the same 
 as Morgan's, which it resembles very much ; namely, that invented by M. Cave, engineer, at 
 Paris, to whose kindness we are indebted for a drawing of his wheel. In this all the guide- 
 
 x 
 
158 APPENDIX. 
 
 rods are pin-jointed, the revolving collar being driven by a different instrument from the 
 driving-rod, g, in Morgan's wheel, which is not so uniform in its action. 
 
 We feel called upon here to correct a statement in Mr. P. W. Barlow's paper " On the motion 
 of Steam Vessels," page 42 of this Appendix, relating to the case of Morgan and another, 
 versus Seaward and others. Mr. Barlow states that " The Vice-Chancellor having given 
 " judgment against granting an injunction, the parties tried an action at law, in which they 
 " were also unsuccessful ; and Messrs. Seaward have now the privilege of making these 
 " wheels." Now, the state of the case is this. It is necessary before an injunction can be 
 granted that the validity of the patent should be established by an action at law. To this, 
 therefore, the plaintiffs had recourse, in full confidence of success, and they obtained a verdict 
 on the following heads : 
 
 1. That defendants' wheels were only a colourable evasion of plaintiffs' patent, and the 
 
 former were therefore guilty of infringement ; 
 
 2. That the specification was sufficient ; 
 
 3. That the invention was novel and useful ; 
 
 4. That the wheel was an improvement, but that the engine, which was coupled with it in 
 
 the same patent, although new, was useless. 
 
 The jury, however, under the judge's direction, found for defendants on the ground of 
 previous sale ; but it was afterwards decided by the judges in Banco that the alleged sale was 
 no sale at all ; nevertheless, as the jury had found that the engine was useless, the judgment 
 must be for defendants, because plaintiffs had coupled in one patent two distinct things, and 
 had therefore committed a fraud on the Crown, 1 thus imposing on them the necessity of pro- 
 nouncing the patent inoperative. They added, however, that " they had the satisfaction of 
 " knowing that this decision would not destroy the patent, as it might be rendered valid by 
 " disclaiming the engine before the Attorney-General." We understand that steps are about 
 being taken to effect this object. 
 
 Figs. 2 and 4, PI. LXXVIII., show the path of one of the floats of the wheel represented by 
 Fig. 1, with the same relative velocities as those relating to the common wheel in PI. LXXIV. 
 Figs. 3 and 5 are the nodes enlarged. It will be seen at once that both the upper and lower 
 edges of the float are nearly tangent to their respective cycloids at the time of entering the 
 water, so that there can be no perceptible resistance at that time, and consequently no shock ; 
 at its emersion the float is also nearly tangent to its course, so that there is no back water : 
 the float only raises as much water as adheres to its surface. We have observed, when on 
 board a vessel with Morgan's wheels, which did not act exactly as they ought to have done 
 on account of the draught of water being greater than was intended, that each float, as it left 
 the water, could be easily distinguished through the spray, which must therefore have been 
 very inconsiderable, and that the surface of the water behind the wheels was perfectly level. 
 Whoever has seen the common wheels in action cannot fail to have observed the hillocks or 
 waves formed by the back water, which make it sometimes dangerous for little boats to be 
 brought up along side without stopping the engines, and show at the same time that a 
 
 1 Query ? Are there no other patents in which two distinct things are included ? If there are, have the patentees com- 
 mitted a fraud on the Crown ? and if so, why are patents granted in such cases ? 
 
ON PADDLE WHEELS. 159 
 
 considerable amount of power must be spent in raising water. In the vessel alluded to there 
 was also no vibration whatever, so that a gentleman sitting in the cabin was quite surprised 
 to hear that she was not stopping, but going at full speed. Thus the defects, so much com- 
 plained of in the common wheel, are here quite obviated ; nor is it necessary for this, as it is 
 with Buchanan's wheel, to give the wheels an unusually great excess of velocity over that of 
 the vessel : indeed, the inclination of the floats may be regulated to suit any required ratio of 
 velocities. It is to be remembered that the proportions of the parts in the figure referred to 
 above are not such as would be chosen by the manufacturer : there would be fewer floats, but 
 they would have a greater depth, as may be seen in the elevation of ' Medea's' wheel, PI. 
 LXXXII., and in the diagram of the Trinity yacht ' Vestal's ' wheel, Fig. 1, PI. LXXIX. 
 
 Fig. 2 represents a performance of that vessel, from data furnished by the engineer on board. 
 The wheels made 2.3 revolutions per minute, and the speed was 12' 16 statute miles an hour; 
 one revolution, therefore, carried the vessel forward 46 ft. 6^ in., and the diameter of the 
 rolling circle was 14 ft. 9-J in., or nearly eight-ninths of that of the wheel between the spindles. 
 
 It will be observed that the floats are not vertical, as Mr. Barlow repeatedly calls them, 
 notwithstanding that he himself has made a drawing of one (see Fig. 2, PI. xxiv.), which we 
 presume to be that of His Sardinian Majesty's steam vessel ' Gulnare," from its resemblance 
 to a lithograph we have seen of that wheel, and in which the floats are evidently not vertical. 
 But Mr. Barlow not only calls them vertically acting floats, but calculates the proportion of 
 effective power as if they were really so, and, even on that supposition, his calculation would not 
 be correct, as the Editor has shown in a- note at the end of the paper. In Buchanan's wheel the 
 floats are essentially vertical, which we have shown to be rather detrimental to their action than 
 otherwise, particularly at deep immersions, when the loss of power is excessive ; and this dis- 
 tinction constitutes the principal advantage which Morgan's wheel possesses over Buchanan's. 
 
 But, although the floats are not perfectly vertical, they approach nearer to that position 
 than those of Oldham's wheel ; therefore a rather greater proportion of the pressure is effective, 
 and a smaller proportion re-acts upon the arms of the wheel, the former being proportional to 
 the cosine of the angle included between the float and the vertical, and the latter to the cosine 
 of the angle between the float and the radius ; therefore the propelling effect bears -a greater 
 proportion to the power applied than the velocity of the vessel to the circumferential velocity 
 of the spindles, which is about the proportion of effective power with Oldham's wheel. Thus 
 
 1 The following particulars relating to this vessel, which we have from an authentic source, may not be uninteresting to 
 the reader. She left Blackwall in the month of April, 1835, and steamed to Sheerness in 3 hours 15 minutes, or at a speed 
 of about 13-5 miles an hour, then proceeded, against a rather strong head wind, to Falmouth, where she arrived after a 
 voyage of 36 hours 30 minutes, making sometimes 10J knots, and generally from 9j to 10 knots an hour, the speed of the 
 engines being maintained between 25 and 27 revolutions per minute. She made the voyage from Falmouth to Lisbon in 75 
 hours 40 minutes, the sea being so rough that she had almost constantly one of her wheels immersed to the shaft, and the 
 other scarcely touching the water. In the following year she towed a 60 gun frigate, without any assistance, at the rate of 
 6 knots an hour, her engines making 18 revolutions per minute. Her usual speed was from 10 to 10-5 knots, and the 
 number of revolutions between 28 and 29. In February, 1838, after nearly three years of hard service, we learn that they 
 were repairing the wheels at Genoa, with some improvements, which had been introduced in the construction since the 
 ' Gulnare ' left this country. 
 
 The diameter of the wheels between the spindles is 15 ft., and if we take 9~75 knots as the mean speed between Sheerness 
 and Falmouth, and 26 as the number of revolutions, we find the diameter of the rolling circle to have been 12 ft. 2 in., or a 
 little more than fmtr-fifths of the diameter of the wheel, which must be rather below than above the ratio of the effective to 
 the total power, exclusive of friction. 
 
160 APPENDIX. 
 
 in the example of the ' Vestal,' quoted above, more than eight-ninths of the power developed 
 by the engines (exclusive of friction) appears to have been effectively employed. 
 
 The superiority of Morgan's over the common wheel is shown in a striking manner by the 
 14th and 21st experiments in Mr. Barlow's table, page 47 of the Appendix. They were both 
 made with Her Majesty's steamer ' Firebrand,' the former with the old wheels, and a pair of 
 70 horse engines, the latter with Morgan's wheels and a pair of sixties, both light. In the 
 former case her speed was 10'15 miles, and in the latter 10'55, being improved by four-tenths 
 of a mile with one seventh less power. The common wheels had each 14 floats of 18 square 
 ft. area, and Morgan's only 9 floats of less than 13 square ft. area, which proves that the latter 
 kind of wheel does not require so much float as is given to the former, to produce an equal 
 effect. The economy of fuel arising from the use of Morgan's wheels is also proved by Mr. 
 Barlow's table, page 67, which is merely intended to show the economy of using little power 
 in proportion to the tonnage. This economy exists certainly with the same kind of wheels, 
 but if we compare Morgan's with the common wheel, we find an exception in favour of the 
 former. For example, of the ' Flamer ' and ' Hermes,' the latter ought to consume the 
 smallest quantity of coal per ton during the voyage, for two reasons : 1st, because she has 
 much less poM'er in proportion to her tonnage than the former ; and 2ndly, because, being a 
 much larger vessel, even with the same ratio of power to tonnage, she ought to consume less 
 fuel per ton by going faster ; the reverse is, however, the case, as is shown by the numbers 
 in column 11. As another example, we may compare the 'Columbia' (Morgan's wheels) 
 with the ' Messenger ' (common wheels) ; here the difference ought to be more than in the 
 foregoing example in favour of the common wheels, whereas it is still more in favour of 
 Morgan's. 
 
 The superiority of Morgan's over Field's wheel with divided floats, as the latter has hitherto 
 been used in the Royal Navy, is demonstrated by the trials of the 'Tartarus' (see page 142, 
 and the diagrams, PI. LXXII. b, and LXXIII). 
 
 We have now before us a pamphlet published in 1834, containing testimonials of the beauti- 
 ful action, strength, and durability of Morgan's wheels, as well as the increased safety, economy 
 and comfort, attending their use, signed by most of the officers who had at that time com- 
 manded government steamers fitted with them, as well as by Admiral Sir T. Byam Martin, 
 Vice-Admiral Sir George Cockburn, O. W. Lang, Esq. of Woolwich Dock Yard, and by 
 Charles Russell, Esq., as chairman of the Committee of the Trieste and Venice Steam Naviga- 
 tion Company. Examples of economy are afforded by the experiments on the ' Firebrand ' 
 quoted above, and by the voyages of the ' Columbia ' and ' Flamer ' (see the last mentioned 
 table, page 67). We have also received a letter from Captain Austin, who commanded Her 
 Majesty's steam frigate ' Medea ' during her late service of nearly four years. 1 He states that 
 
 1 For the particulars of her performances during that period, see the interesting memoir of Lieut. Baldock, R.N., page 80 
 of this Appendix, particularly page 86, where her average speed from Plymouth to Malta is shown to have been 8-82 knots 
 an hour, under circumstances by no means favourable, which compare with her average speed as stated by Mr. Barlow, page 
 71, page 90, respecting her towing the squadron out of Malta harbour; compare also the speed of 9-25 to 10 knots, page 94, 
 and 9-5 knots from Ancona to Malta (against a head wind), page 95, &c. Lastly, see the end of the last paragraph but one 
 in page 98, where the author speaks of the excellence of the machinery, which must apply in a great measure to the wheels, 
 as the engines are no better than in many other steam vessels. The author of this memoir has adopted Mr. Barlow's error of 
 calling the paddles of ' Medea's ' wheels " vertically acting paddles." 
 
ON PADDLE WHEELS. 161 
 
 whether at light or load draught, in smooth water or high sea, he found the action of her 
 wheels to be uniform, causing but very little, if any tremulous motion in the vessel, or jerk to 
 the engines. As regards their durability, he considers that a vessel, if stationed abroad, taking 
 with her a small proportion of " spare spindles," as now fitted, with a spare set of " steel 
 collars " for the spindles, and " bushes " for the stems, she would be fully equal to continue 
 her service for any period (with the mechanical powers they might possess in the engine 
 department) that her engines might enable her to do. He states that owing to the twisting of 
 the spring beams, the crank head in the wheel lowered considerably, and altered the angles of 
 the floats ; but that was of course not to be attributed to any want of solidity in the wheels 
 themselves, nor did it do them any injury. There was no twist owing to the break in the 
 shaft, as has been supposed to be the case, on account of the inner frame only being immedi- 
 ately driven by the engine, for the paint was not disturbed in the joints where the spindles are 
 united to the frames, which must otherwise have been the case. In conclusion, Captain 
 Austin expresses his opinion that if the part of the vessel alluded to (the spring beams) were 
 properly secured, Morgan's wheels would be, as sea propellers, most valuable and perfect. 
 
 4. Cave's Paddle Wheel. 
 
 Plate LXXXI. Fig. 1., is an elevation of the first wheel made by M. Cave on his improved 
 construction : it is reduced from a drawing on a larger scale, which that gentleman had the 
 kindness to send from Paris, with a note stating it to be the drawing of the wheels fitted by 
 him in the year 1827, to the iron steam boat ' La Seine.' P, P, P, &c. is thepolyyon; r, r, &c. 
 the arms ; C the shaft in the centre of the boss ; A, A, &c. are the floats ; D, D, &c. the 
 stems ; h, h, &c. the guide rods ; B the excentric axis fixed to the side of the vessel, of which 
 the centre is at E, and which is sufficiently large to allow the shaft C to pass through it ; F 
 the revolving collar, turning on the excentric B ; and g the driving rod, fixed to the revolving 
 collar, and passing between two friction rollers k, k, attached to the polygon ; L L is the water 
 line. Now, since the point of contact between the roller and the driving rod must move 
 nearly in the circumference of the dotted circle, which is sometimes nearer and sometimes 
 farther from the excentric centre E, there results a difference in the velocity with which the 
 revolving collar is driven round : in the wheel represented in the figure the maximum velocity 
 is nearly double the minimum. This causes the great variations in the position of the different 
 floats and their guide rods, shown by the dotted lines in the figure : the floats are numbered 
 on the outer ring of the revolving collar, close to the pins by which their respective guide rods 
 are jointed to it; the numbers on the excentric axis show the positions which the cor- 
 responding pins take, and those at the extremities of the lower floats, the positions of the 
 respective floats when their spindles arrive at the same positions. These variations must 
 cause a great irregularity in the action of the floats, and it is evident that only one or two can 
 take approximately the required positions during their motion through the water. Fig. 2. 
 represents a wheel on Morgan's construction of the same dimensions as the former, in which 
 it was attempted to show, as in the other, the various positions of the different floats, but it 
 was found to be impracticable, the only variation sensible on this scale being that of the guide 
 rod Number 4, of which the positions are shown by dotted lines passing through the three 
 lower guide rods; the variations of the float were, however, imperceptible. The only 
 
162 APPENDIX. 
 
 difference which has been made in the dimensions, in order to convert Cave's wheel into 
 Morgan's, is that the excentric collar F has been made much smaller than it was possible 
 according to the other construction, and this diminution tends to equalize the motion of the 
 floats ; but what equalizes it still more is that a driving rod of a constant, and always greater 
 length, has been substituted for one which was always varying. Another difference, which 
 could not appear in the figures, and which, in our opinion, operates in favor of Morgan's 
 wheel, is that the excentric in Cave's is outside, and in Morgan's inside the framing of the 
 wheel. 
 
 Some remarks on Mr. P. W. Barlow's calculations, &c. 
 
 Very little can be said regarding his mode of determining the centre of pressure of floats, 
 since he has assumed, and not calculated its position ; or rather, he has assumed an empirical 
 rule (see page 45), which facilitates the calculation very.much, but clearly cannot suit all cases. 
 In the following page he assumes the centre of pressure in Morgan's wheel to be situated at 
 one-eighth of the depth of the float below its centre. We think he allows too much for the 
 lower part acting during a longer period than the upper ; for until the point which he con- 
 siders as the centre of pressure enters the water, the power expended on the immersed portion 
 has amounted to scarcely any thing. This trifling quantity being neglected, the resistance in 
 the ensuing portion of the stroke is increased materially, being considered as equal to what it 
 would be if the whole surface of the float were acting at the centre of pressure, while at first 
 only three-eighths of it are actually immersed ; and as the difference between the effective 
 velocities of different parts of the float is not great, it appears that much more resistance is 
 added after the centre of pressure has entered the water, than was neglected at the commence- 
 ment of the stroke. We do not, indeed, deem it improbable that the centre of pressure is 
 situated as high, or even higher than the centre of the float. 
 
 The method of finding the whole power exerted by the engines adopted, (page 50), can 
 seldom, if ever, give a correct result ; for the number of floats acting at one time varies very 
 much in different wheels, and in the same wheels at different immersions ; that is, the mean 
 number varies, for there may be in two cases sometimes three, and sometimes four in the 
 water at the same time, and yet the mean number may be different : in one case it may be 3^ 
 and in the other 3| ; and, as Mr. Barlow assumes it either at 3 \ or 4, the error may be -fe or 
 -fij. of the true power exerted, of which the mean number of floats acting at the same time is a 
 factor. Such an error cannot surely be considered of no consequence, particularly as errors of 
 observation are inevitable in such experiments as those made to ascertain the speed of steam 
 vessels. A fact which proves Mr. Barlow's calculations of power to be inaccurate, is that the 
 proportion of the power expended on the vertical paddle in the experiment of the ' Sala- 
 mander,' differs from the calculated proportion by more than 72 per cent. This is the very 
 example we have worked out (page 127), and found the calculated to agree with the nominal 
 power in a remarkable degree, although calculated according to the same theory as that 
 adopted by Mr. Barlow, but without any arbitrary assumptions, which are probably in a 
 great measure the cause of the discrepancies observed by him, and of his being unable to 
 account for the whole power with Morgan's wheel, though this is, perhaps, principally to be 
 attributed to his confounding it with Buchanan's. 
 
ON PADDLE WHEELS. 163 
 
 The experiments, of which the details are given in Table IV., page 55, having been made 
 with small models, it is impossible to place any confidence in the results, or of course in 
 any conclusions drawn from them. 
 
 In the second paragraph, page 7l> we presume that the word "engine" has been used 
 for "paddle wheels;" for the engine itself cannot act as a fly wheel, since its momentum 
 is destroyed at the end of every stroke ; but the paddle wheels are allowed by the motion 
 of the vessel to act as such, as they retain their momentum as long as the engines continue 
 in action. 
 
 In comparing a steam ship of war, such as the ' Medea,' with others, whose destination is 
 either to carry goods or passengers, it should be remembered that the latter are susceptible of 
 much greater capabilities for speed than the former for the reasons assigned by Lieutenant 
 Baldock, page 81. Besides this, the power of the ' Berenice' being greater, and her tonnage 
 less, than that of the ' Medea,' it would not be at all surprising if the speed of the former 
 were greater than that of the latter, as it appears in page 74 ; but experience shows ' Medea's' 
 mean speed to be much more than 7'8 knots ; indeed, from Lieutenant Baldock's Memoir, 
 her mean speed in all weathers, principally with adverse winds, seems to have been about 9 
 knots an hour. Her rate of steaming with 320 tons of coal, and war equipment 50 tons 
 more, most probably also water and provisions for 120 men for 4 months, on board, in a calm 
 is (page 85) 8| knots, and with one-third the quantity of fuel, 10 knots. 
 
 We have now investigated the action of the principal kinds of paddle wheels which have 
 been seriously expected to supersede the common wheel, and we find Morgan's wheel to 
 excel the others in all points except simplicity, in which, of course, it must cede to all 
 those with fixed floats, but it is not more complicated than is absolutely necessary to produce 
 the desired effect ; for what can be more simple for a feathering float than the float itself 
 suspended on a spindle in the circumference of the wheel, with an arm or lever fixed to it, 
 and a simple link connecting the extremity of the lever with an excentric centre, which has 
 merely a ring or collar revolving on it in order to receive the extremities of all the connecting 
 links, or guide rods, one of which is connected immediately to the excentric centre itself, 
 being fixed in the revolving collar. We are fully justified in this opinion both by theory 
 and experience, and we sincerely hope, as well for the benefit of the public as for that of the 
 patentee, to whose talent and perseverance are due the great improvements which have been 
 made in the construction of the wheel since the date of the patent, that the eyes of the public 
 will at length be opened to the advantages which Steam Navigation will receive (and has 
 received as far as experience has gone) from the increased safety, economy, and comfort attending 
 the use of Morgan's wheels. 
 
 Some persons have been deterred from using Morgan's wheels on account of the prime 
 cost being so much greater than that of the common wheels ; but that argument, when 
 examined into, falls to the ground, the difference in the cost of the engines, which with 
 Morgan's wheels may be considerably less than with the common wheels, being an ample 
 compensation for the difference in the cost of the wheels ; besides which, the constant economy 
 of fuel and the increased stowage are advantages not to be despised. 
 
164 
 
 APPENDIX. 
 
 Note 1. In illustration of what is observed in the first paragraph on the motion of paddle 
 wheels (page 119), the author of this paper has been prevailed upon by some of his friends to 
 consent to the insertion of Fig. 4, Plate LXXIX., which was drawn merely as a curiosity, and 
 not with any intention of having it engraved. The largest of the concentric circles in the 
 centre of the figure represents that described by one of the points of a paddle wheel, before 
 the vessel has any velocity, and the curves extending farther and farther on both sides represent 
 the curtate cycloids described by the same point, when the vessel has acquired the respective 
 velocities represented by the dotted horizontal lines extending from the middle of one node of 
 the curve to that of the next, the last being the. simple cycloid described when the velocity of 
 the vessel is equal to the circumferential velocity of the point ; the first-mentioned circle is 
 then the rolling circle, and the dotted circles those corresponding to the respective curtate 
 cycloids, the largest circle, considered as a curtate cycloid, having, of course, no rolling circle. 
 
 Note 2. We have omitted to mention the six figures in Plate LXXX., which are intended to 
 show the distance between the nodes of successive floats in the different kinds of wheel. 
 Fig. 1 refers to the deep trial of the ' Salamander' with the common wheel, Fig. 2 to Field's 
 cycloidal wheel, Fig. 3 to Buchanan's, Fig. 4 to Oldham's, and Fig. 5 to Morgan's wheel, (all 
 these corresponding to Fig. 4 in the Plates LXXIV. to LXXVIII. inclusive), and Fig. 6 to the 
 performance of the ' Vestal,' Fig. 2, Plate LXXIX. In these figures it will be observed that 
 the distances between the nodes of the feathering floats are always greater than with fixed floats, 
 particularly those of the cycloidal wheel ; and that the nodes are most distant with Morgan's 
 wheel, as actually made, is seen in Fig. 6, although the wheel is much smaller than the others. 
 
 
 *#* We have been favoured with a sketch of what we consider to be a very desirable im- 
 provement in the mode of connecting Morgan's wheel with the engine. 
 
 To appreciate the improvement it must be borne in mind that the wheel, as hitherto con- 
 structed, has three main bearings in which it revolves, viz., one on the engine frame, one on 
 the ship's side, and the third on the spring beam. Experience has proved the great difficulty 
 of maintaining three bearings in a right line ; and has also shown a great increase in friction, 
 and in wear and tear, where any one of the three bearings has got, as workmen express it, 
 " much out of truth." 
 
ON PADDLE WHEELS. 
 
 165 
 
 The accompanying diagrams represent, 
 
 A. A part of the outer crank-shaft of a pair of marine engines. 
 
 B. The journal, bearing on the ship's side. 
 
 y 
 
166 APPENDIX. 
 
 C. A portion of a sphere, forged on the shaft and turned to truth. 
 
 D. The end of the shaft projecting into the wheel. 
 
 E E. Part of the wheel centre, or nave, made in two parts, o and n, truly faced, bolted to 
 each other, and turned to fit the sphere on the shaft : the part n is again constructed in 
 two parts, for the convenience of removal when needful, and joined together by bolts 
 through two flanches across the nave. The radii of the wheel are clipped between o and 
 n, in recesses purposely cast for them. 
 
 F F. Two crank-pins with spherical ends. 
 
 G G. A double driving arm fixed on D. 
 
 H H. Two crank-pins, also with spherical ends, and respectively connected by drag-links, 
 with the pins in the nave, in the same manner as Boulton and Watt have usually con- 
 nected their marine engine cranks. 
 
 This arrangement obviously acts as a universal joint, and admits a deviation in the line 
 of bearings much beyond the limits of any thing required in practice. 
 
 It is due to J. B. Humphreys, C.E., who has applied it to an IRON VESSEL constructed by 
 him for the Rio Doce Navigation Company, to state that our attention is attracted to his 
 practice by our knowledge of his long experience in these matters, he being well known as 
 the founder of steam navigation in Prussia so early as the year 1814. ED. 
 
ON THE INDICATOR. 167 
 
 V 1 1 I. O N THE INDICATOR. 
 
 BY JOSEPH GLYNN, ESQ., C.E., F.R.S., &c. 
 
 ALTHOUGH the construction and application of the indicator has been described in such a 
 manner that most persons conversant with the mechanical contrivances of the time, and 
 with the steam engine as now manufactured, have a general idea of its form and use, yet it 
 seems to have been regarded rather as an ingenious invention, among many others, of the 
 late Mr. Watt fitted more for the philosophical lecturer than for the practical engineer ; as 
 a curious instrument by means of which the action of the steam in the cylinder, and that of 
 the vacuum or atmospheric pressure upon the piston, might be delineated, and its varying 
 force represented by a curve, as it was at one time the fashion to represent every thing ; even 
 the arguments and statements of the political economist were drawn out in curved lines and 
 figured in a diagram. 
 
 But the indicator shows not only the relative action of the vacuum and pressure of the 
 steam upon the piston of an engine, but their absolute force and effect ; it shows how much 
 of that force is taken to overcome the friction of the machine, and produce the change of 
 motion in its parts, and how much is available for useful purposes ; it exhibits, if we may so 
 say, the disposable force of the steam engine, and the perfection or imperfection of its con- 
 struction or condition at the time of making the trials. The indicator, in its most simple and 
 best form, is shown in the engraving (see PL xvi). The cylinder, or tube of the instrument, 
 should be truly bored, and the piston ground into it, so that the workmanship should be as far 
 as possible perfectly accurate. The piston should fit the tube without packing, so that it may 
 be made air-tight by pouring olive oil upon it when it is in use. Its area should be exactly 
 lj HJ 1^9 lf> or two square inches, and a loop or an eye should be fixed in the under side of 
 it, so that by means of a cord and weights attached to it, the extension of the spiral spring 
 with each ft. upon the square inch may be proved, and a scale of extension formed, up to 
 14lbs., ruling parallel lines for each B5. from the line of rest, which may be marked with a 
 cipher. The compression of the spring from the line of rest may also be tried, by attaching 
 the cord to the loop at the top of the piston rod which holds the tracing pencil, and hanging 
 the weights over a pulley. To insure accurate observations, it is best to prove the spring of 
 the indicator every time the instrument is used, and form the scales for the occasion : it is 
 almost needless to say that it should be cleaned and oiled afresh for each trial ; but unless this 
 be done, it may cause great discrepancy in the results, and much time may be wasted in trying 
 to reconcile apparent differences arising only from a little stiffened oil. These observations 
 
168 APPENDIX. 
 
 may seem minute and trifling, but serious errors may occur from the neglect of them, when 
 from a piston of 1^ inches area and 3 inches stroke, we judge of another of 3 feet in diameter 
 and 8 feet stroke. 
 
 Those manufacturers who use the indicator have the lower part of the stop-cock formed into 
 a plug, which can be unscrewed at pleasure, and made to fit in the place of the plug or barrel 
 of the grease cock on the cylinder cover. It is to be presumed that in most engines of the 
 best makers, the action on both sides of the piston is the same ; but if this be matter of doubt, 
 it is easy by means of a pipe bent at right angles, and screwed into the cylinder at the bottom, 
 to apply the indicator there also. The apparatus being fixed, and the stop-cock closed, the 
 point of the tracing pencil should be carefully adjusted on the line of rest. The sliding table 
 carrying the ruled paper may then be put in motion by attaching the cord to it, which has 
 already been fastened to some convenient moving point of the engine ; then, observing that 
 the pencil makes its mark on the line of rest, open the stop-cock, and so set the piston of the 
 indicator in motion. The pistons of the instrument and the steam engine now move simul- 
 taneously, but in opposite directions, the force of the steam driving them asunder, and the 
 vacuum bringing them, as it were, together, at the same time that the horizontal motion of 
 the sliding table represents the vertical motion of the larger piston ; consequently, on the 
 indicator, the horizontal motion shows the stroke of the steam engine piston, and the vertical 
 motion shows the pressure upon it. The preceding explanation is requisite to enable the 
 general reader to understand the annexed diagram of a trial which we made on a steam 
 engine applied to drive a rolling mill for the manufacture of iron. This engine had a cylinder 
 of 36 inches in diameter, and a stroke of 7 feet, making 16 strokes per minute (that is to say, 
 16 revolutions of the crank shaft) ; the fly wheel, as in most rolling mill engines, was on the 
 second motion making 64'6 revolutions per minute ; it was 20 feet in diameter, and weighed 
 about 25 tons, serving to accumulate the engine power, as well as to regulate its motion, and 
 thereby overcome any sudden resistance, as the passing a mass of iron between the rolls of 
 the mill. Such irregular application of power made this engine peculiarly eligible for exhibiting 
 the use of the indicator in delineating its varying action. The instrument being fixed as before 
 stated, and the steam engine in its usual order having been at work for some hours before 
 the experiment was made, it was stopped, and all the machinery detached; the condenser 
 was cleared of air and water by blowing the steam through it, and the engine started in the 
 usual manner, when the pencil of the indicator described the curvilinear figure marked A 
 (see the annexed figure), showing the force required to put the engine into motion from a state 
 of rest. This figure gradually diminished until the engine acquired a uniform speed, which 
 was maintained and regulated by the governor at the proper rate of going, namely, 16 revolu- 
 tions per minute, for a considerable time, and the pencil of the indicator continued to trace 
 the curve marked B, showing the force expended in overcoming the constant friction of the 
 engine, in changing the motion of its parts, and in working the air-pump, &c. The principal 
 machinery of the rolling mill was now attached to the engine, and set in motion ; it consisted 
 of a pair of rollers for the puddled iron, a pair of boiler plate rollers, a pair of rolls for making 
 small bars, a pair of shears for cutting them to the proper length, and a large lathe used for 
 turning the rollers. The above machinery in motion, but without performing any work, pro- 
 duced the figure C on the tablet of the indicator. When this had been continued for some 
 time, the small rolls were kept at work making bars (small squares), and the figure D was 
 
ON THE INDICATOR. 
 
 169 
 
 Steam. 
 
 Q 
 
 < 
 
 a 
 
 s 
 So 
 
 1 
 
 o 
 
 1 
 
 ti 
 
 8 
 
 S 
 
 o 
 
 u 
 
 *j 
 
 e 
 
 S 
 
 g -ff 
 
 * -a 
 3 S 
 
 ft 
 iu 
 
 o 
 
 C 
 
 o 
 
 
 i 
 
 * 
 
 u 
 
 P be 
 'o 'S 
 
 .S - 
 
 OJ o 
 
 13 
 t 0) 
 
 r 
 
 
 . 
 
 ft 60 
 at <a 
 
 s f 
 
 S JJ 
 
 O *C 
 
 U * 
 
 a -2 
 I 
 
 t o 
 
 If 
 
 S S 
 I 
 
 
 s 
 
 s-s 
 
170 APPENDIX. 
 
 described ; the lathe was then applied to turn a case-hardened roller for rolling boiler plates, 
 and the pencil traced the figure E. The merchant-bar rolls were now set in motion, in 
 addition to the above (these rolls are for making the ordinary square and round bar iron), but 
 they were not employed in rolling it : the additional power required to keep them going 
 increased the figure to F. The puddled ball rolls, the small rolls, the heavy lathe, and the 
 shears were kept in full work, and the engine being fully loaded, the figure G was delineated. 
 The diagram shows that the engine was doing its duty, and it was proved that an engine 
 of larger power must be employed if the merchant rolls and the plate rolls be required to be 
 kept in work, rolling iron at the same time with the other machinery. During this experiment 
 the safety valve of the boiler was loaded at 3 ffis. upon the square inch above the pressure 
 of the atmosphere ; and it will be seen by the diagram, which is an exact copy of that actually 
 made by the instrument, what mechanical force was taken in each case, and at each point of 
 the piston's course. It has been noticed that the stroke was 7 feet ; the steam was cut off 
 about 9 inches from the end of the stroke, as the diagram shows ; and the action of the 
 governor may be discerned, as regulating the supply of steam, a little farther from the cylinder 
 top every time the engine's load is increased. The effective or disposable force of the engine 
 will be found to be about 10 tfes. on each square inch of the piston, the area of which is 
 101 7'8 inches, which makes the actual power of the engine about 69 horses, reckoning 33,000 
 ffis. raised one foot high in a minute each horse power ; whereas, the nominal power of the 
 engine was only 55 horses, as indeed it would be called by most of the engine-makers. 
 
HOWARD'S METHOD OF VAPORISATION. 171 
 
 IX. HOWARD'S METHOD OF VAPORISATION. 
 
 THE principle of Mr. Howard's apparatus, which is of recent date, may be gathered from the 
 following description, which is abstracted from the specification of his patent. 
 
 In the ordinary method of generating steam by means of boilers, a body of water is exposed 
 to a large surface of metal, presenting to it a comparatively low degree of heat ; and the tem- 
 perature of the water bearing a constant relation to the density or pressure of the steam, the 
 rapidity of evaporation is limited thereby. In my process of VAPORISATION the power of the 
 engine is derived from the vaporisation of the least possible quantity of water on a small 
 surface, heated to and maintained at such temperature (about 400 Fahrenheit) as will vaporise 
 the water with the utmost rapidity ; the steam so formed having a high temperature, but 
 relatively a low density or pressure. And by the interposition of mercury, or other medium 
 of the like effect, the surface exposed to the fire is preserved from the injury that would 
 otherwise arise from a strong local heat ; and the deposit of salts or other impurities on the 
 vaporising surface is prevented by the continued use of the same water. And in my engine 
 other liquids, as alcohol for instance, may be substituted for water. 
 
 A circular, or otherwise formed wrought-iron plate, is fixed horizontally over a fire con- 
 structed to burn coke, anthracite coal, or other fuel of the like nature, and urged by a blowing 
 machine subject to regulation. The area of the grate is about a fifth of a square foot per 
 horse power of the engine. The area of the plate exposed to the action of the fire need not 
 exceed three-fourths of a square f :ot per horse power. A second plate is fixed above this, 
 and has securely fitted into it, and throughout its surface, a number of thin wrought-iron cups 
 or short cylinders, about two inches in diameter, closed at bottom, and reaching to within a 
 little distance of the interior of the lower plate, by which means the upper surface is increased 
 to about four times the lower. Both plates are slightly curved downwards. A true and 
 secure joint is formed at the circumference of the plates, by bolting them to a strong ring 
 about three inches deep, and which fixes them at a corresponding distance apart. The inter- 
 mediate space (being under and around the cups) is entirely filled with mercury or a soft 
 amalgam. A small box of iron communicates with it to allow of its expansion when heated, 
 and the steam being admitted to this portion of the mercury, the pressure is equalized above 
 and below the upper plate and cups. A thermometer indicates the temperature of the mer- 
 cury, which must never be permitted to rise much above five hundred degrees Fahrenheit, 
 nor should it be allowed, while the engine is at work, to fall below three hundred and fifty 
 degrees, the fire, or the quantity of water injected (as presently described) being regulated 
 accordingly. A nosle or rose, constructed to disperse the water as equally as possible, is 
 fixed above the upper plate, and, by means of a pump, throwing at intervals, a small quantity 
 
172 APPENDIX. 
 
 of water is withdrawn from the condenser, or hot-water cistern, and projected through the 
 nosle over the upper plate and cups, when it is instantly and completely vaporised. The 
 pump has a cock or valve by which to adjust the supply of water, and a hand-pump is pro- 
 vided to start the engine, and increase the facility of commanding it. Before arriving at the 
 nosle the water is heated, in a pipe or vessel exposed partially to the fire, in order that it may 
 not diminish the elasticity of the steam already formed, and that it may more readily vaporise. 
 The heat from the fuel that has not been absorbed by the mercury passes around a steam 
 chamber, by which means the steam is heated and expanded considerably after its formation, 
 and thence proceeds from the upper part of the chamber to the cylinder valves in the usual 
 manner. This exterior or flue casing is covered by a non-conducting substance, as are also 
 the steam pipes, cylinder, &c. The above construction is expressly intended for working the 
 steam expansively, the pressure being in general about ten fts. per square inch above the 
 atmosphere, and the steam cut off from the cylinder at about a third of the stroke. The 
 acting machinery of the engine is on the ordinary construction, and the packing of the piston 
 and valves are metallic. 
 
 The process of CONDENSATION consists in abstracting the heat from the water of injection, 
 by bringing it in contact with a sufficient surface of metal, exposed externally to cold water in 
 any efficient manner, and re-injecting the water thus cooled amidst the steam. 
 
 The air-pump withdraws the warm water from the condenser into the hot cistern in the 
 usual manner, and the water is passed from thence by the pressure of the atmosphere (a partial 
 vacuum existing in the condenser) into a copper pipe or worm, exposed to cold water in a 
 cistern constantly supplied by a pump or otherwise. The refrigerating pipe terminates 
 within the condenser, and the water having been previously cooled by its gradual progress 
 through it, enters into immediate contact with the steam, and instantly reduces it to the liquid 
 state. A valve is placed at the end of this pipe within the condenser, and is connected by a 
 rod and lever to a float in the hot cistern, which prevents all the water from being drawn out 
 of the latter at any time, and which valve also serves to disperse the water amidst the steam. 
 It is further adjustable by hand. Before starting the engine, a sufficient quantity of water is 
 provided to ensure the circulation, by entirely filling the refrigerating pipe and part of the hot 
 water cistern. The surface of this pipe (or other vessel substituted for it), when the condenser 
 is employed with the vaporiser before described, and the steam worked expansively, should 
 be about four square feet per horse power. 
 
 A still is provided to furnish a supply of pure water, to replace any loss by leakages, and is 
 attached to the flue of the vaporiser, in which latter the use of water containing salt or other 
 impurities is inadmissible. 
 
 This process of condensation is equally applicable to the ordinary engine with boilers. 
 
173 
 
 X. ON THE GENERAL THEORY OF THE STEAM ENGINE. 
 
 BY THE EDITOR. 
 
 THE mechanical relations of the steam engine, or the principles upon which the power is 
 transmitted from the cylinder, are of a simple and elementary nature. To discuss them it is 
 only necessary to have recourse to the properties of the crank and the well understood 
 mechanical powers, the lever, the wheel and axle, and the inclined plane. In every combina- 
 tion of the ordinary mechanical powers, supposed to be divested of friction, the transmission 
 of force follows the well-known law that the efficient power is of precisely the same value at 
 each point, understanding the efficient power to be the force of resistance multiplied into the 
 velocity. Thus the effect produced, or the effective power, is measured by the weight moved, 
 or resistance overcome, multiplied by its velocity : the moving power is similarly measured 
 by its force multiplied by its velocity ; and these powers would in all cases be equal, were it 
 not for the effects of friction. To preserve distinctness, we shall designate the pressure by the 
 term pressure or force, and the effect produced, or the force multiplied into the velocity, by 
 the term power ; the former of these may likewise be called the statical, and the latter the 
 dynamical value of the force. These terms being agreed upon, it follows that in every machine 
 composed of the ordinary mechanical powers, the quantity of power developed, or the dyna- 
 mical effect of the force, would be the same at all points ; that the power, by such arrange- 
 ment, is transmitted without any change in its value, except it be such as is caused by the 
 loss resulting from friction. It would be easy to show that this principle is universal, or, in 
 other words, that it applies to every possible combination of machinery ; but this is quite 
 unnecessary for our present object, though it may perhaps not be out of place to make a few 
 observations on the nature of the crank, in addition to what has been stated in the present 
 work at page 228. 
 
 I. ACTION OF THE CRANK. 
 
 In the annexed figure let C D = r be the 
 length of the connecting rod; O D = p the 
 radius of the crank; the angle (D O E) de- 
 scribed = a ; the velocity at C = v ; the velocity 
 of D = v', and the distance (A C) described 
 = x. Then, the perpendicular D G = p sin. a ; 
 
 C G = ^/ r 2 p 2 sin. 2 a ; O G = p cos. a ; C O = >/ r 3 p 2 sin. 2 a + p cos. a ; A O = r + p, 
 and therefore the value of A C, or A O C O, is 
 
 x = r + p (>/r 2 p 2 sin. 2 + p cos. a) 
 
 = p (1 - cos. a) + (r - V r* - p 2 sin. 2 ) (1). 
 
 z 
 
174 APPENDIX. 
 
 By differentiating this expression of the distance traversed by C, we obtain the velocity of the 
 extremity C, viz. : 
 
 dx odd i p cos. a \ 
 
 -r-. j-T- sin. a I ' .== + 1 ) 5 that is, 
 
 * v v r* p 2 sin. 2 
 
 / p COS. a v 
 
 v = v sin. a ( . -L i ) (2). 
 
 \ \A^- p 2 sin. 2 a 
 
 But if P denote the moving force acting at C, in the direction C B, P' the effective force of D, 
 and r = n p, it has been shown at page 229 of the present work, by means of the resolution 
 
 of the forces, that P' = P sin. a ( / ' . = +1 ) or, replacing n by -, 
 
 \ V w 2 sin. 2 * J p' 
 
 P' = Psin. a ( /2 PC S ; g . . + 
 
 \ > r * _ 2 sm> 2 a 
 
 p/ 
 
 Equation (2) hence reduces to v v' , and therefore 
 
 that is, the moving power at C is always equal to the effective power at D. 
 
 The moving force P being nearly uniform, the force P* expressed by the equation (3) will 
 be materially different at different positions of the crank, and the velocity of the engine will, 
 in consequence, be subject to small fluctuations in the course of each revolution. To 
 ascertain the law of these variations, it will be necessary to have recourse to the usual equation 
 of rotatory motion. Let R denote the real moment of the resistance, including friction, 
 reduced to the point D, or the force which uniformly applied along the circumference E D 
 would just suffice to preserve the mean velocity of the engine without any variation. Then 
 being the force actually applied, the effective accelerating force, or the part tending to pro- 
 
 d a. 
 duce acceleration, will be P 7 R ; and where this is negative, the velocity - must be re- 
 
 '' / 
 
 tarded instead of accelerated. If we now multiply the force P' R by p, the leverage at 
 which it acts, the product p (F R) is its moment or tendency to generate angular motion. 
 Hence, if M designate the moment of the inertia to be overcome, and if we neglect, as com- 
 paratively insignificant, the slight variations of the resistance R due to the small changes of 
 velocity, and suppose it to continue uniform, we shall have, 
 
 M ? = P ( P/ ~ R )' 
 
 Multiply by -1, and 
 
 M " = 2 P' p - 2 R p 
 
 dt 3 v dt v dt 
 
 2 PV - 2 R p 
 
 f dt 
 
 2Pv - 2Rp p. 
 
 (' > 
 
 n -T. dx n r, da. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 175 
 
 Consequently, by integration, 
 
 M 
 
 
 
 Now, the engine being supposed to have acquired her permanent speed, there can be no 
 progressive acceleration ; the same velocity must recur at the period of each revolution. The 
 velocity at E is obtained by putting x = o, a = o, and is, 
 
 ( 
 
 Also, the velocity at His obtained by putting x = 2 p, a. = tr (= 3-14159), and is, 
 
 Again, it is to be observed that the preceding investigation equally applies to the returning 
 motion along H D, provided, in that case, the symbol a. represents the angle H o D, and x' ', 
 which is accentuated for distinction, the retrograde distance B C. If therefore, x' being 
 each nought, the velocity at H be, 
 
 when a = TT, x' = 2 p, the recurring velocity at E will be, 
 
 r). ..... (d). 
 
 Thus it appears that the squares of the three velocities ( ^ )' ( ^ )" ( ^ )'" are 
 
 in arithmetical progression, and that this progression would go on indefinitely if the resistance 
 R did not augment so as to destroy the common difference 2 P p R p IT, and cause the 
 same velocity to recur at each period. It hence follows that so long as the smallness of R 
 renders 2 P p R pv, or2P RTT, positive, the engine will be acquiring additional speed ; 
 and that when R becomes such that 2 P R TT = o, the power will just be capable of main- 
 taining unaltered the periodical movement, and the general speed will not admit of any further 
 increase. For permanent speed we must therefore have, 
 
 R = - P ...... (6). 
 
 7T 
 
 This result shows that the general effect of the moving force P acting obliquely on O D at D 
 
 o 
 is the same as if " P, or very nearly -fa P, were always applied perpendicularly at the same 
 
 77 
 
 point ; and this again is the same as if the force P itself were continually applied perpendi- 
 cularly at a distance of -fa ths of the radius p. This last distance is therefore the effective 
 leverage of the crank. 
 
 It is not to be inferred from this that the effect of any portion of the power is lost. The 
 quantity of power developed by a constant force is measured by the force multiplied into the 
 
176 
 
 APPENDIX. 
 
 distance through which it has acted. In a semi -revolution, the power developed by P is 
 hence P x 2 p ; that expended by R would similarly be R x TT p ; and, according to the equa- 
 tion (6), it appears that the expenditure would be the same in both cases, and that no loss 
 is sustained through the obliquity of the action of the crank, except that which arises from 
 the additional friction caused by the stress on the shaft. 
 
 Substitute the value of R by (6) in (5), and, for permanent speed, the angular velocity of 
 the shaft of the engine at any period of the stroke is, 
 
 (7); 
 
 and for any position D from E to H, if /8 denote the angle E O D, this becomes, 
 
 - cos. /3 ) - f 
 
 - p 2 sin. 2 /3 ) ...... (8). 
 
 For a point D in the returning half stroke from H to E, if /3 denote the angle H O D, the 
 value of A C' is obtained by substituting TT ft for a in the value of x expressed by equation 
 (1), and is therefore, 
 
 A C = p (1 + cos. /3) + (r - 
 
 (9). 
 
 -/> 2 sin. 2 /3); 
 
 and, if we deduct this from the whole distance A B = 2 p, we get the expression for B C or 
 x', viz. 
 
 af = p(l- cos. /3) - (r - A 
 Therefore by equation (7) the velocity at D is, 
 
 /TV 
 
 -p 3 sin. 2 /3) 
 
 M 
 
 ( c + p (1 cos. /3) ft (r 
 
 \ IT 
 
 - 2 sn. 2 
 
 ) 
 
 (10). 
 
 The velocities w <*>" at D' D" will now be determined by substituting TT /3 for ft in equations 
 (10) and (8) ; thus we find, 
 
 /T 
 
 r 
 
 JVL 
 
 ~ cos - 
 
 *JL ft -fa- 
 ir 
 
 - 2 
 
 p 2 sin. 2 /3) (H), 
 
 o>" = V 4r- ( c ~ P ( l ~ cos - #) + & + ( r ~ V ^ - P 2 sin. 2 /3) ) . , . (12). 
 
 M v 7T / 
 
 To put these in a more simple form for comparison, let (<) denote the velocity at E, as 
 expressed by equation (a), and assume, 
 
 2 
 
 7T 
 
 h = r - 
 
 A = p ( - ft - 1 + cos. 
 
 \ 7T 
 
 (13) 
 
 r 3 p 2 sin. 2 /9 
 Then, the angular velocities at any four corresponding points D D D' D" are, 
 
 = V W 2 - 
 
 (A + h) 
 
 , = ()+ 
 
 (A-*) 
 
 (14); 
 
 <o" = V (a,) 2 + 
 
 (A + A) 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 177 
 
 which are here arranged respectively in the order of their magnitudes, that at D being the 
 least, and that at D" the greatest. 
 
 These expressions may be put in a more convenient form by neglecting the higher powers 
 of the small variations. We shall then have, 
 
 = () - J^_ (A + h}, 
 P (A - h), 
 
 MH 
 ' = () + ^JL (A - A), 
 
 -" = () + JT-T ( A + *) 
 
 But for h we may now substitute ^ sin. 2 /3 ; therefore, 
 
 = (,) - .J^_ (A + P- sin. 2 /3 ) 
 M (a,) V 2r I 
 
 p / * 
 
 M (>) 
 
 _ sin. 2 /3 ) 
 9.r ' 
 
 L_ f A - P 
 
 - sin. 2 /3 ) 
 2 r / 
 
 ( A 
 
 sin/ 
 
 (15); 
 
 M() V 2r 
 
 in which the values of A in parts of p are by (13) found to be as follows : 
 
 ft A 13 A ft A, 
 
 0-0000 30+ -1994 60+ '1667 
 
 5 + -0518 35 '2080 65 -1448 
 
 10 -0959 40 -2105 70 -1198 
 
 15 -1326 45 '2071 75 -0922 
 
 20 -1619 50 '1984 80 '0625 
 
 25 -1841 55 '1847 85 + '0316 
 
 30 + -1994 60 + -1667 90 0-0000 
 
 From these last expressions we conclude that the velocity M which occurs at E and H is the 
 mean velocity, and that the greatest and least velocities occur in the quadrants of D" and D, 
 
 o 2 2 p 
 
 at the points where A + sin. 2 /3, or ft + cos. ft + -. - sin. 2 /8, attains its maximum 
 
 2 r TT 2 r 
 
 value. If we assume these points to be in the middle of the respective quadrants, so that 
 /3 = 45, which will be very nearly the case with all the proportions observed in practice, and 
 cannot sensibly affect the accuracy of the results, the greatest and least velocities will be 
 
 M + , , x ( - + 0-207 ) and the deviation from the mean value will be, 
 " M M * r 
 
 fL ( -- +0-207). 
 
 M M v 4 r ' 
 
178 APPENDIX. 
 
 Again, by substituting the values of F, R, the force V - R, which at each position tends to 
 accelerate the motion, is found to be, 
 
 TV T r. f 1 P COS. a \ 2 i 
 
 F - R = P \ sin. a ( J + 1 ) I (16). 
 
 I v v r* (r sm. 2 a TT J 
 
 It hence appears that the motion is, 
 
 accelerated T CQS> a ("greater 1 2 
 
 >when sin. a I r . + 1 is < > than - or 0'63. 
 
 retarded J ^ r ~ P sin - [less J "" 
 
 Values of this expression are shown in the table given at page 230 of the present work. 
 
 In the preceding investigation we have only considered the action of a single crank ; but it 
 will be found to apply, with a slight modification, when the rotary force of the shaft is main- 
 tained by the action of any number of cranks making given angles with each other. We have 
 only to substitute, in place of P', in the right-hand member of the equation of motion, the sum 
 of the forces F arising from the several cranks ; and, by following out the same process, the 
 equation (5) will become, 
 
 in which 2 (P x) includes the same term for each crank. Let (<>) denote the value of this 
 angular velocity when x = o, a. = o, and the expression, for any other position, will hence be, 
 
 (17). 
 
 By attending to the nature of the integration, it is evident that this equation applies generally 
 from any assigned position throughout the entire period of each revolution of the shaft, if we 
 give to the symbols x a. the following signification, viz. 
 
 x, the entire distance travelled over by the^ 
 
 extremity C, for each crank ; I each being estimated from that position in 
 
 a, the angle described by the revolution of j which the velocity was (<a). 
 the shaft ; 
 
 Let us take the practical case, in which the revolution of the shaft is maintained by a pair 
 of equal engines, and in which the equal arms of the two cranks are placed at right angles, so 
 that each of them may be in full action when the other is " on the centre." If we suppose 
 one entire revolution to be performed, the distances x traversed by the extremity of each con- 
 necting rod will be 4 p, the angle a described will be 2 tr, and the velocity will become 
 
 . = V (o,) 2 + ^ (4PP + 4PP-2RP-7T) = V ()" +^(4P-R7r). When the 
 
 engines have attained their regular speed, this velocity must correspond with (), since precisely 
 the same motions must recur in successive revolutions ; we must hence have 4 P R TT = o, 
 
 .-. R = 1 P ..... (18). 
 
 7T 
 
 2 
 This value is the same as (2 P) in which 2 P is now the moving power, and we observe 
 
 IT 
 
 that it corresponds with the expression (6) for the single crank. 
 
 To find a more convenient expression for the velocity at any position, let x be the distance 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 
 
 1/9 
 
 traversed by the connecting rod of that crank which takes the lead in the direction of rota- 
 tion, and y the corresponding distance traversed by the connecting rod of the other crank 
 which follows it. Then, substituting the value of R, &c., in (17), we have, 
 
 = v W 2 + ^ ( + v - ^ ) 
 
 Now, referring to the figure on page 2, we shall suppose the advancing crank to proceed 
 from the point E with the angular velocity (<>), and to pass over to the four successive 
 positions D, D", D, D', equidistant from the diameter E H. The other crank will proceed 
 
 from the point F, and always be 90 or behind the former. Let ft denote the arc E D or 
 
 H D", and assume, 
 
 h = r - 
 
 - p 2 sin. 2 /? 
 
 k = r - V r* - p* cos. 2 /3 
 
 m = r - 
 
 ---- (20). 
 
 Then we shall have, for the point D, x = p (1 cos. ft) + h, 
 
 y = p + m p (I sin. ft) k; for the point D", x = p (1 + cos. ft) + h, 
 y = p + m + p(l sin. ft) + k; for the point D, x = 4 p p (I + cos. ft) h, 
 y = p + m + p(l + sin. ft) + k; and for the point D', x = 4 p p(l cos. ft) h, 
 y = p + m + 4:p p (I + sin. ft) k. Hence the sum of the distances x + y takes 
 
 the following values, 
 
 at D, x 4- y = p (1 cos. ft + sin. ft) + m + h k, 
 
 D", ' = p (3 + cos. ft sin. ft) + m + h + k, 
 
 D, = p (5 - cos. ft + sin. ft) + m - h + k, 
 
 D', = p (7 + cos. ft sin. ft) + m h k. 
 
 Also, for these four points the angles described are respectively ft, IT ft, tr + ft, and 2 IT ft, 
 which must likewise be severally substituted for a in (19). Performing these substitutions, 
 and making, 
 
 A = p(i/8-l+ cos. ft - sin. ft } (21), 
 
 * IT ' 
 
 we find, for the four respective points just enumerated, 
 
 = ,/ (a,) 2 + --(m- 
 
 JV1 
 
 *) 
 
 = V (a,) 2 
 
 
 (22). 
 
 These expressions may be considerably simplified by disregarding the powers of the small 
 variations above the first. In the first place we immediately obtain, 
 
180 
 
 APPENDIX. 
 
 < ==()+ (i A + h K), 
 
 " = (,) + *L ( m + A + h + k), 
 
 M. (<a) 
 
 > = () + T^T ( ~ A - h + k), 
 
 ,' = () + ^ ( m + A - A - k). 
 
 2 o 
 
 But the values of h k m in (20) will now become h = sin. 2 /3, A = cos. 2 $ and * = 
 
 -2 
 
 jE_. We have finally, therefore, 
 
 - V 
 
 cos 
 
 . 2 /3 - A ) 
 
 (23). 
 
 M \ r 
 ' = () + _L_ (A) 
 
 The expression (21) gives to A the following values in parts of p for every fifth degree ofthe 
 arc /3 : 
 
 ft A. A 
 
 0-0000 30 + -0327 
 
 5 + -0201 35 -0234 
 
 10 -0334 40 + -0121 
 
 15 -0404 45 -0000 
 
 20 -0421 50 - -0121 
 
 25 -0393 55 -0234 
 
 30 + -032? 60 - -0327 
 
 On examining the values (23) we observe that the greatest velocity takes place in the 
 
 quadrant of D", and at the point where A attains its greatest positive value, viz., at 19 from 
 
 H ; we also perceive that the least velocity occurs in the quadrant of D' and at the point 
 
 where A attains its greatest negative value, viz., at 71 from E; and that the mean angular 
 
 ft 
 
 A 
 
 
 60 
 
 - -0327 
 
 
 65 
 
 0393 
 
 
 70 
 
 0421 
 
 maxima 
 
 75 
 
 0404 
 
 + 0-0422 
 
 80 
 
 0334 
 
 - 0-0422 
 
 85 
 
 0201 
 
 
 90 
 
 o-oooo 
 
 
 velocity is (o>) + 
 
 M 
 
 o 
 
 . - . We have therefore, 
 2r 
 
 Position when the velocity is greatest. 
 
 Maximum 1 
 
 Vvalue of <a = ' 
 Minimum I 
 
 Greatest deviations "l 
 from mean value J 
 
 "(.) + 1 r r r ( ^ +0-042) 
 M V r 
 
 ._ 
 M () \ 2 r 
 
 Position when the velocity is least. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 181 
 
 and these occur in the positions represented in the figures annexed. For only one engine 
 and crank we have before found the greatest deviation from the mean angular velocity to be 
 
 _ ( -B + 0'207 ) in which, for the moment, M r e accentuate the symbol P, because in this 
 
 M () \ 4 r * 
 
 case it represents the entire acting power, whereas in (25) it represents only the power of one 
 of the two engines ; and, under like circumstances, we have P' = 2 P, so that the latter ex- 
 pression becomes ^ ( - + 0'414 j. Comparing this with (25) it appears that the 
 variation of velocity with a single engine and one crank, and the variation of velocity with a 
 
 pair of engines and two cranks, are to each other in the ratio of - + 0-818 to - + 0-082, 
 
 r r 
 
 which ratio varies from about 3 to 1 up to that of 10 to 1. 
 
 These results are of much value in pointing out the effects to be produced by varying the 
 radius of the crank, the length of the stroke, and the diameter of the cylinder. All other 
 circumstances being the same, the values P p, M, (to) will be constant ; and therefore the 
 
 extreme variation of velocity will always be proportional to + 0'828 for one crank, or 
 
 P + 0-084 for two cranks acting alternately in the usual way. Hence it follows, that by 
 r 
 
 diminishing the radius of the crank and increasing the length of the connecting rod, the 
 irregularity of the movement will be materially diminished, more particularly when two 
 engines are employed. It is on this account highly desirable to have as long a connecting 
 rod as convenient, in proportion to the radius of the crank ; while, on the other hand, it adds 
 another to many important objections 1 against the adoption of the American proportions 
 recommended by Professor Renwick at page 109, viz., to employ a crank of large radius and 
 a long cylinder, since the disagreeable and destructive jolting, experienced in the working of 
 engines, is principally due to the irregularity of action here alluded to. 
 
 We have gone thus far into an investigation of the motion of the crank, as it forms one of 
 the most important instruments of the steam engine, and has hitherto met with very little 
 attention from scientific writers. It is, doubtless, the most simple, and perhaps the most 
 efficient, contrivance that can be devised to convert a reciprocating action into a rotatory 
 motion ; and in this respect we cannot be surprised that it has not been superseded by any 
 one of the numerous inventions that have been proposed with the view of dispensing with it. 
 We are compelled, however, at the same time, to admit that this beautiful simplicity is 
 accompanied by corresponding inconveniences in the inequalities of motion, pressure, friction, 
 and consequent wear. The mechanical defects of engines constructed on the rotatory 
 principle appear to be of greater magnitude, and the disadvantages and difficulties that stand 
 in the way of their application to the most important uses, are of a very formidable nature. 
 This is much to be regretted, as we conceive a perfectly equable motion to be a great deside- 
 ratum in the steam engine, and the only hope we can have of succeeding in obtaining it is in 
 the exclusive employment of rotary action. On this head we may refer our readers to an 
 instructive paper, entitled " On the Fallacies of the Rotatory Steam Engine," by John Scott 
 
 
 
 1 See pages 365, 366, of the present work. 
 2 a 
 
182 APPENDIX. 
 
 Russell, Esq., a gentleman to whom practical science is much indebted. One of the leading 
 objects of this paper, which is printed in the Edinburgh New Philosophical Journal for 
 January 1838, is to show that no loss of power is sustained by the intervention of the crank; 
 but, in doing this, it should be remarked, that the author has throughout his paper discussed 
 only the particular case in which the moving power acts on the crank in parallel lines, or in 
 which the connecting rod is supposed to be of infinite length ; and that this necessarily 
 reduces many of his statements into mere approximations, when the subject is generally con- 
 sidered. Mr. Russell has, however, handled the subject with considerable power, and his 
 remarks are, perhaps, sufficiently precise for the object he had in view, viz., to dispel the 
 delusion under which many practical men labour with respect to the nature of the crank, that 
 it is attended with a loss of nearly one-third of the power. It is well known that persons are 
 to be found who have been the subjects of this delusion, as well as inventors who have been 
 its victims, but we cannot concur with Mr. Russell that " some eminent standard writers on 
 the steam engine have advanced the same doctrines." Most writers who are accustomed to 
 treat these matters scientifically have doubtless considered that no reasonable dispute could 
 possibly be entertained, and have thought it unnecessary to make any declaration on the 
 point in question. We may, however, be allowed to refer to one exception. At page 137 of 
 " Hann and Dodd's Mechanics for Practical Men," the very question is taken up, and com- 
 prehensively disposed of, in the following paragraph : 
 
 " In the crank, as applied in the steam engine, the effect which is produced, is to the effect, 
 " were the force to act perpendicularly on the crank all the way round, as twice the diameter 
 " of a circle is to the circumference ; in consequence of which, many practical men have 
 " considered that there is a corresponding loss of power by using a crank ; without ever 
 " considering that the piston, or moving power, only moves through twice the diameter of the 
 " crank's orbit, while the crank moves through its whole circumference. For here the same 
 " principle holds good as in all other mechanical contrivances, viz., the power multiplied by 
 " the space which it passes over, is equal to the weight or resistance multiplied by the space 
 " which it passes over." 
 
 These statements have since found their way into other mechanical works of more recent 
 date ; and it is certainly of some moment that practical men who have not the means of 
 following out theoretical investigations of these subjects, should be thus guarded from an error 
 by which many of them have been so widely misled. That no power is gained or lost by the 
 use of the crank has already been established on dynamical principles at the commencement 
 of this paper. We are not, however, to conclude that this principle is at all peculiar to the 
 crank. It is well known to apply to every combination of the five elementary powers, and by 
 the principle of virtual velocities it may easily be shown that it is an universal property of 
 mechanical arrangement, that with every possible mechanical combination, no power can be 
 gained or lost, if we except the resistances occasioned by friction. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 183 
 
 II. PRINCIPLE OF LIVING FORCES. 
 
 The quantity of power expended in the production or maintenance of any effect is, how- 
 ever, most simply determined by the general principle of living forces. This principle, which 
 is immediately deducible from that of virtual velocities, is applicable to every possible motion 
 of terrestrial bodies, and may be enumerated as follows : 
 
 At any instant let each particle of the system be multiplied into the square of its velocity, 
 and the product will be the living force of the particle. The aggregate of all these products 
 will measure the total amount of impetus or living force of the system. 
 
 Let each force CJ, acting at a particular point, be multiplied into the small distance dq tra- 
 versed by that point, in the direction of the line in which the force acts, during an elementary 
 instant of time dt, and the product will measure the expenditure of power during that instant. 
 In this measurement, the forces or pressures arising from the connexion of the parts will be 
 neglected, because no motion can at any instant be produced in the direction of such press- 
 ures, and they consequently can have no share in the generation or consumption of living 
 force ; but the resistances of friction, which are proportional to the pressures on the parts, 
 and act in the direction of the motion, must be regarded. In the cases where the point 
 moves in the direction of the force, the effect will be to increase the living force ; but in the 
 cases where the point moves in the contrary direction, the effect will be to diminish the 
 living force, and all resistances are of this latter description. 
 
 Now, if from double the total expenditure towards the increase of the living force we 
 deduct double the total expenditure towards its diminution, each being so estimated, the 
 difference will always accurately express the variation that takes place, during the instant dt, 
 in the above-defined value of the living force of the system. 
 
 The sum of the variations through successive instants will express the total variation that 
 takes place in a finite time. When the forces are variable, this summation must be effected 
 by tne integral calculus ; but when the forces are constant, it will only be necessary to mul- 
 tiply each into the whole distance traversed by its point of application in the direction of its 
 action, to get its effect in any given time or space. 
 
 When the motion is permanent and the velocities recur at stated periods, the whole vari- 
 ation of living force through the extent of each period must evidently be zero ; and hence in 
 this case the expenditure of the moving powers must be precisely equal to that of the 
 resistances throughout an entire period. 
 
 This principle, though exceedingly general, is of very easy application, and it will readily 
 be perceived how the preceding theories of the action of the crank, or indeed of any other 
 action, may be immediately deduced from it. 
 
 It may be here worthy of remark, that in the case of steam employed at a given temperature, 
 the density being inversely as the pressure, the expenditure of the moving power of the 
 piston will be proportional to the quantity of steam consumed or the effective quantity of 
 water evaporated. 
 
184 APPENDIX. 
 
 III. TRANSMISSION OF EFFECT FROM THE CYLINDER. 
 
 The principle that no power can be gained or lost in its transmission by means of 
 mechanism, enables us without much difficulty to trace the effective working of an engine due 
 to a given pressure in the cylinder. 
 
 Let a denote the diameter of the cylinder in inches. 
 I the length of the stroke in feet. 
 T the temperature of the steam in the cylinders. 
 P its mean pressure in ffis. per square inch. 
 F the entire friction, estimated on the pistons, in fl5s. per square inch. 
 
 For high pressure engines this must include the pressure of the 
 
 atmosphere. 
 R the resistance, in ffis., overcome at the extremity of the two wheels con- 
 
 nected with the shaft. 
 
 n the number of strokes per minute. 
 u the velocity of the piston in feet per minute. 
 V the velocity of the circumference of the wheel in feet per minute. 
 TT 3-14159, &c. 
 Then if 1 denote the force on the pistons which would just overcome the resistance R, we 
 
 V 
 
 shall have, equating their powers, Q, u = R V ; and therefore Q = - - R. The area of the 
 
 two pistons being a 2 square inches, the pressure per inch just sufficient to overcome the 
 
 m 
 
 resistance will be a = - = -= 5 R. To this add the friction F, and the entire 
 TT 2 TO TT a* u 
 
 2 
 pressure per square inch on the pistons is hence, 
 
 But since V passes through TT D, a circumference of the wheel, and u passes through 2 I, 
 twice the length of the stroke, in each revolution, - - = y ; and this being substituted 
 
 U ' 
 
 in (A) we get, 
 
 P = ^R + F....(B); 
 
 and hence, 
 
 F=P--$-R ..... (C), 
 
 2 Z 
 
 R = ^(P-F) ...(D); 
 
 which express the relations amongst the mean forces or pressures P, F, R. 
 
 The velocities of the parts of the engine depend on the number of strokes, that of the 
 piston being, 
 
 u = 2 n I ...... (E). 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 165 
 
 Also the number of horses' power on two cylinders, according to Tredgold's general rule, page 
 197, is found to be, 
 
 -a 2 P x 2 n I 
 
 33000 
 
 . .(F). 
 
 33000 
 
 The numerator of this expression represents the quantity of steam (IT n a 2 /) consumed per 
 minute multiplied into the pressure (P) at which it is supplied to the cylinder : and, the tem- 
 perature T being supposed to be preserved, this product, in fact, expresses the evaporating 
 power of the boiler, including, of course, the necessary reductions for the unavoidable losses 
 by the passage of the steam through the steam pipe, the clearance of the cylinder, &c. ; and 
 it hence also appears that the effective evaporating power of an engine is proportional to the 
 number of horses' power. 
 The equation (F) gives also, 
 
 n p = 33000 H _ _ (G) 
 TT a 3 1 
 
 Thus it appears, that when the engine is working at a given power, the number (n) of strokes 
 per minute will vary inversely as the mean pressure P on the piston, which is a principle 
 particularly applicable to the motion of Locomotive Engines, where the forces P, R, are 
 subject to considerable variations. 
 
 The special relations of the motion of locomotive engines have been ably treated by the 
 Chevalier G. De Pambour, in a valuable treatise recently published by Mr. Weale, which 
 contains much valuable practical information on the subject. From numerous experiments 
 with different engines on the Liverpool and Manchester Railway, made under the author's 
 inspection, with the view of ascertaining the amount of friction, he has arrived at the following 
 useful conclusions, respecting the resistance to traction, which may be regarded as approxi- 
 mate estimations for locomotive engines as at present constructed, viz. 
 
 1. That the average tractive friction of the carriages, without the engine and tender, may 
 be reckoned at 8 fts. per ton of the entire weight of the carriages and load. (Page 116). 
 
 2. That the average friction or resistance to traction of well-constructed locomotive engines, 
 in good order, is about 15 fts. per ton of their weight. (Page 136). 
 
 3. That the tractive friction of the engine is increased by the load at an average of about 1 ft. 
 per ton. (Page 157). 
 
 We may hence add, 
 
 4. That the friction of the wheels alone of an engine, by the first estimation, being 8 fts. 
 per ton of its own weight, the friction due to its own weight as a load being 1 ft. per ton, 
 and the whole resistance being 15 fts. per ton, it follows, that the friction of the engine gear 
 alone, independently of any connexion with the rails, is, on the average, about 6 fts. per ton 
 of the weight of the engine applied at the circumference of the wheel. 
 
 5. That the entire resistance to an engine and train may be estimated at 9 fts. per ton on 
 the gross weight of the engine, tender, carriages, and load, increased by 6 fts. per ton on the 
 weight of the engine alone. 
 
186 APPENDIX. 
 
 IV. TRANSMISSION FROM THE BOILER TO THE CYLINDER. 
 
 M. Pambour professes to determine the velocities on considerations of a novel nature, which 
 may be briefly explained, thus : If the evaporating power of the boiler be capable of supplying 
 a greater quantity of steam, at the required pressure, than is consumed at the successive 
 strokes of the piston, it is evident that the pressure of the steam in the boiler will gradually 
 increase, provided no portion is supposed to escape through the safety valve or otherwise. 
 This increasing pressure will gradually accelerate the velocity ; and finally, when the engine 
 attains her permanent speed, the quantity of steam consumed in the cylinder and supplied 
 through the steam pipe, must evidently correspond with the quantity evaporated by the 
 boiler. Thus he pretends to introduce a new element into the calculation, viz., the evapo- 
 rating power of the boiler, which again is to be estimated by the quantity of fire surface ; and, 
 the density of steam at a given temperature being, according to the law of Boyle and Mariotte, 
 proportional to the pressure and inversely as the volume, as in the case of gases, the evapo- 
 rating power is measured by the volume of steam, generated in a given time, multiplied into 
 its pressure. We submit, however, that M. Pambour is mistaken if he supposes such a mode 
 of proceeding to involve any new doctrine, or any principle that had not already been laid 
 down by Mr. Tredgold in the first edition of this work. In support of this statement we 
 need only refer to the equations (F), (G), which are founded on Tredgold's well-known rule for 
 calculating the power of an engine, and from which it will appear that he measures the power 
 by the quantity of steam effectively consumed in the cylinder per minute, multiplied into its 
 pressure. Indeed, the preceding equations (A), (B), (C), (D), (E), (F), (G), which are strictly 
 in accordance with the principles laid down by Tredgold, constitute the whole of our scientific 
 information on the power of the steam engine that has hitherto been established on theoretical 
 principles. No scientific theorist or experimentalist has yet satisfactorily ascertained the laws 
 which regulate the transmission of the steam from the boiler to the cylinder, 1 and we cannot, 
 therefore, be surprised that Tredgold has treated this part of the subject in a very slight and 
 imperfect manner. We here allude to Art. 396, which has especially been objected to by the 
 Chev. de Pambour, in a Memoir on the Steam Engine, just published in the form of a 
 pamphlet by Mr. Weale. With this we may include Articles 402, 408, 416, and 426 ; and we 
 
 1 It is impossible that this difficulty can ever he properly surmounted until we first determine either the specific heat of 
 steam, or the whole quantity of heat contained in a given volume of steam at a given temperature and pressure. A decisive 
 step towards the solution of this most important problem has been effected by E. Clapeyron, in a Memoir inserted in the 
 ' Journal de 1'Ecole Royale Fob/technique,' vol. xiv. page 153. The investigation is conducted on a principle which to all 
 appearance is deserving of credit, viz., that no power can possibly be created or generated without the transmission of a 
 portion of heat, and that the amount of power must be wholly independent of the nature of the medium of transmission. 
 The latter condition depends on the former ; for if the power developed varied with the nature of the medium, a quantity of 
 heat being transmitted by one medium and returned by another, a portion of power might be so gained or lost without any 
 resulting or effective transmission. In this principle it is of course assumed that no loss of power or vis viva is occasioned by 
 contact of bodies of different temperatures. The application of it is very ingenious, and leads to the following expression for 
 the whole quantity (Q) of heat contained in a volume (B) of steam at the pressure (p), viz., 
 
 Q =/0> ) - F (p . ) hyp. log. JB, 
 
 in whichy (p . ), F (/).) denote functions of the product (p . ) of the pressure and volume, the nature of which functions 
 still remain to be determined before the solution can be considered to be complete. It is found by experiments, that the latter 
 function increases gradually with the temperature. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 187 
 
 have every reason to suppose that they were all of them approximate estimations for the work 
 of such engines as Mr. Tredgold had access to for his experience, which, in reference to engines 
 now constructed, were no doubt of very limited dimensions and power, and of comparatively 
 inferior workmanship. There can be no doubt that estimations of this kind, where a fixed 
 proportion of the whole power is taken, are not to be depended upon. It cannot, however, 
 be overlooked that M. Pambour, in throwing discredit on what he terms the ordinary theory, 
 has unfairly applied the principle of constant coefficients in such a way as had never been 
 contemplated by Tredgold or any one else ; besides, it should be observed, that M. Pambour 
 has only evaded the difficulty in another way : he has estimated the friction and losses in a 
 manner more in accordance with the nature of the steam engine, but, nevertheless, equally as 
 empirical as that of Tredgold ; and the state of the problem remains nearly the same as it did 
 before. For instance, in his Treatise on Locomotive Engines, page 184, he takes the effective 
 evaporation through the cylinders at three-fourths of the total evaporation in the boiler, viz., 
 the effective evaporating power O3 cubic foot, and the total evaporating power 0'4 cubic foot 
 of water, for each square foot of surface exposed to the fire. On the whole, we are compelled 
 to conclude that such estimations are not to be relied upon as general rules ; that where 
 accuracy is really wanted, the actual amount of loss, &c., is only to be estimated by having 
 recourse to the experience of each individual description of engine under given circumstances ; 
 and that the correct value of the effective power of an engine is only to be found in the mean 
 pressure on the piston, and the velocity with which it moves, according to the old rule. 
 
 There is one more point in M. Tambour's strictures on Tredgold's principles which it may 
 be necessary to notice, being one on which he has, by some sort of inattention, allowed 
 himself to be grossly deceived. The point in question, which, on being misrepresented, might 
 possibly mislead others, is involved in the following extract from page 9 of his Memoir on the 
 Steam Engine : 
 
 " Tredgold, in his Treatise on Steam Engines (Art. 127 and following), undertakes to 
 " calculate the velocity of the piston from considerations deduced from the velocity of the 
 " flowing of a gas, supposed under a pressure equal to that of the boiler, into a gas supposed 
 " at the pressure of the resistance. He concludes from thence, that the velocity of the piston 
 " would be expressed by this formula, 
 
 V = 6-5 \Th, 
 
 " in which V is the velocity in feet per second, and h stands for the difference between the heights 
 " of two homogeneous columns of vapour, one representing the pressure in the boiler, the other 
 " that of the resistance. But it is easily seen, that this calculation supposes the boiler filled with 
 " an inexhaustible quantity of vapour, since the effluent gas is supposed to rush into the other 
 " with all the velocity it is susceptible of acquiring, in consequence of the difference of pressure. 
 " Now such an effect cannot be produced, unless the boiler be capable of supplying the expendi- 
 " ture, however enormous it might be. This amounts consequently to supposing that the produc- 
 " tion of steam in the boiler is unlimited. But, in reality, this is far from being the case. It is 
 " evident that the velocity of the piston will soon be limited by the quantity of steam pro- 
 " ducible by the boiler in a minute. If that production suffice to fill the cylinder 200 times 
 " in a minute, there will be 200 strokes of the piston per minute ; if it suffice to fill it 300 
 " times, there will be 300 strokes. It is then the vaporization of the boiler which must 
 
188 APPENDIX. 
 
 " regulate the velocity, and no calculation which shall exclude that element can possibly lead 
 " to the true result ; consequently the preceding formula cannot be exact. 
 
 " This is why, in applying this formula to the case of an ordinary locomotive engine of the 
 " Liverpool Railway with a train of 100 tons, the velocity the engine ought to assume is found 
 " to be 734 feet per second, instead of twenty miles an hour, or 30 feet per second, which is 
 " its real velocity." 
 
 On reference to the article alluded to, it will at once be perceived that these remarks are 
 based entirely on M. Pambour's own misconception of what Tredgold has really given. The 
 formula in question has no reference whatever to the velocity of the piston. It will be 
 observed, that instead of the velocity of the piston, it is distinctly given as the velocity of the 
 steam through the steam pipe, and that the sole object of Tredgold's inquiry is no velocity at 
 all, but merely the determination of the requisite aperture of the steam pipe ! This sufficiently 
 accounts for M. Pambour having puzzled himself with the case of the Liverpool Railway 
 locomotive engine, and leaves us with the full assurance that Tredgold was too well acquainted 
 with the nature of his subject to allow himself to wander so immeasurably from the truth as 
 M. Pambour had supposed. 
 
 We have not made the preceding remarks with any view to the disparagement of what the 
 Chev. de Pambour has done towards our knowledge of the steam engine, which we by no 
 means hold to be unimportant: he is evidently well versed in the practical nature of its 
 action ; he has, doubtless, furnished the best set of experiments on locomotive engines, and 
 his general remarks embody much sound and valuable information on that subject. We 
 cannot, however, admit that he has made any important advance in the mathematical 
 theory of the steam engine, much less that he has brought it to absolute perfection ; and so 
 long as the theory remains incomplete, we must continue to make certain estimations by 
 assumed and approximate rules. It is fortunate, however, that the theory of transmission 
 from the boiler to the cylinder ' and other points, which Tredgold left untouched, and which 
 are still open for future investigation, are matters that may be practically dispensed with. 
 
 V. PADDLE WHEELS. 
 
 It was originally our intention to have. entered rather fully into the theory of the action of 
 paddle wheels ; but this has been rendered almost wholly unnecessary by the valuable con- 
 tributions of Mr. Barlow and Mr. Mornay, who have each discussed the subject with great 
 ability and at considerable length. Mr. Barlow's paper is interspersed with numerous ex- 
 perimental results arranged in the convenient form of tables, and he has successfully applied 
 these results to the solution of various practical questions of great importance. Mr. Mornay 
 has classified the various kinds of wheel, and treated the subject of their capabilities and 
 relative merits with an attention to mathematical precision much to be desired, but which we 
 think, in some cases, unfortunately, to be beyond the practical nature of the inquiry, since 
 the action of the floats must always be affected, in some degree, by the disturbance of the 
 fluid through which they have to pass, more particularly when the velocity of the vessel is 
 
 1 It would be highly desirable to have a series of well-conducted experiments on this point. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 189 
 
 slow. This disturbance has already been partially alluded to in the foot-note at page 311 of 
 this work, and it will no doubt, to a certain extent, vitiate any calculation of the power of an 
 engine which does not include its influence, however exact it may be in other respects. Be- 
 sides, independently of this disturbance, the assumed law that the resistance varies as the 
 square of the velocity, cannot be regarded as satisfactorily established, since another agent, 
 of considerable influence, is to be found in the waves produced by the action of the vessel on 
 the fluid. For these reasons we are inclined to doubt whether, to practical men in particular, 
 the general accuracy of the calculations can reach that degree of minuteness which will com- 
 pensate the labour incurred by the complexity of Mr. Mornay's analytical expressions. His 
 investigations cannot fail, however, to be highly esteemed by such of our scientific readers 
 as may be desirous of thoroughly examining the theory of this interesting and important 
 subject. 
 
 We here propose, in the first place, to explain precisely how the power of the engine is 
 distributed in the general production of effect ; then to show how the determination of the 
 power of a wheel, by means of the centre of pressure, may be materially simplified for prac- 
 tical calculation ; after which we shall add a few remarks on the resistance of fluids. 
 
 Suppose a force Q to intervene between any two objects A, B, tending to their separation, 
 and to act simultaneously upon both of them in the opposite directions, according to the 
 property of action and reaction. Then, if da, db, denote the indefinitely small distances 
 described in an element of time, and c the mutual distance of A and B, by the principle of 
 living forces the quantity of power expended on A will be GL da, that expended on B will be 
 Q, db, and the entire expenditure of power will be Q da + Q, db = Q dc. In this manner we 
 shall find no difficulty in resolving the action of a paddle wheel into its distinct effects on the 
 vessel and the fluid. 
 
 In the annexed diagram let C be the centre of the wheel ; A D B 
 the arc which passes through the centres of pressure of the paddles, 
 and m n any position of one of them when immersed in the fluid. 
 
 Let V denote the circumferential velocity of the point A round the centre C, in feet per 
 
 second. 
 
 v the velocity of the vessel in feet per second. 
 
 k C A, the radius of the wheel to the centre of pressure, and estimated in feet, 
 a the height of C above the surface of the fluid, and estimated in feet. 
 <f> the angle A C D of the radius, with the vertical. 
 the value of <f> when the point A enters or quits the fluid, 
 e the angle re A C of the paddle with the radius. 
 m the number of paddles on each wheel. 
 s the surface of each paddle, in square feet. 
 S the surface of the m paddles on each wheel, = m s.' 
 p the pressure on the paddle, in fes., supposed to be concentrated at A. 
 
 Then, the angle of the float with the vertical = < e ; the velocity V resolved in the direc- 
 tion perpendicular to the surface of the paddle = V cos. e ; that of v = v cos. (<f> e) in the 
 opposite direction ; and therefore the effective velocity of the paddle through the water per- 
 
 2 b 
 
190 APPENDIX. 
 
 pendicularly to its plane is V cos. e v cos. (<j> e). Consequently, adopting the same law 
 of resistance as that followed by Mr. Mornay, we have, 
 
 p = I V cos. e v cos. ((f> e) 1 2 . . . . (a). 
 2ff {. 
 
 By putting the effective velocity of the paddle equal to zero, we have V cos. e - 
 v cos. (c e) = o, which gives, 
 
 V v cos. <f> ,, N 
 
 tan. e = : _-r (b) ; 
 
 v sin. <p 
 
 and this determines the position in which the paddle would pass through the water edgewise, 
 without producing any effect. 
 
 The pressure p being resolved tangentially, horizontally, and vertically, gives, 
 
 Tangential pressure = p cos. e, 
 Horizontal pressure = p cos. (< e), 
 Vertical pressure = p sin. (0 e). 
 In an elementary instant dt of time, the distances traversed by the point A are, 
 
 Tangential distance = V . dt "l , .. , ,, T, 
 
 \ relatively to the Engine ; 
 
 Horizontal distance = V cos. <f> . d t i 
 also, 
 
 Horizontal distance = (V cos. <f> v) . dt "l , ,- , ,, m i 
 
 V relatively to the Fluid ; 
 Vertical distance = V sin. < . dt i 
 
 and the horizontal distance traversed by the vessel = v . dt, 
 
 By multiplying the tangential pressure into the tangential distance relatively to the engine, 
 we have, 
 
 Power developed by the engine =pV cos. e . dt. 
 
 By multiplying the horizontal pressure into the horizontal distance traversed relatively to 
 the engine, we have, 
 
 Power developed horizontally = p V cos. <f> cos. (cf> e) . dt. 
 
 By multiplying the vertical pressure into the distance traversed vertically, we have, 
 Power developed vertically = p V sin. <j> sin. (<f> e) . dt. 
 
 By multiplying the horizontal pressure by the horizontal distance traversed with respect 
 to the fluid, we have, 
 
 Power expended horizontally on the water = p (V cos. <f> v) cos. (< e) . dt. 
 
 Lastly, by multiplying the horizontal pressure by the horizontal distance traversed by the 
 vessel, we have, 
 
 Power expended horizontally on the vessel = p v cos. (<f> e) . dt. 
 These results may be conveniently classified thus : 
 
 rby the Engine = p V cos. e . dt ~\ 
 
 I. Entire power 
 
 . < on the Fluid = p ] V cos. e v cos. (6 e) } . dt > . . . . (c). 
 
 expended 
 
 "- on the Vessel = p v cos. (0 e) . dt 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 191 
 
 II. Power ex- ("by the Engine p V cos. </> cos. (<f> e) . dt ~] 
 
 pended hori- J on the Fluid = p (V cos. <j> v) cos. (</> e) . dt > . . . . (d). 
 
 zontally [_on the Vessel =p v cos. (<f> e) . dt 
 
 III. Power ex- fby the Engine i 
 
 i-u -c-i j f = P V sin. <f> sin. (<i e) . o# 
 pended verti- < on the Fluid J V . . . . (e). 
 
 cally Ion the Vessel = o 
 
 In each case it will be observed that the power expended by the engine is made up of the 
 powers expended on the fluid and on the vessel ; it will also be observed that the entire 
 expenditure is made up of the horizontal and vertical expenditures. 
 
 The whole power expended by the engine being p V cos. e . dt, and the useful power, or 
 that expended horizontally on the vessel, being p v cos. (0 e) . dt, the proportion of the 
 
 power that is effective is ^- -, which evidently increases with the angle e. It attains 
 
 V cos. e 
 
 the value of unity when e attains the value according to the equation (b), or when the paddle 
 moves through the water edgewise, and produces no effect. If e be taken greater than the 
 value so determined, the effective velocity will become negative, and the paddle will act in the 
 contrary direction and retard the vessel. It is wrong, however, to suppose, as is sometimes 
 done, that the misdirected action of the vertical paddle in such a case constitutes a dead loss 
 of power, since it is plain that when the paddle ceases to propel the vessel, it will at the same 
 instant cease to put the engine to any expense of power ; and when it impedes the vessel, it 
 will, at the same time, assist the efforts of the engine, and thereby increase the action of the 
 other paddles. 
 
 By integrating the preceding expressions (c) (d) (e), we shall obtain the respective amounts 
 of power developed by one paddle during any finite time, or throughout any proposed finite 
 
 a 
 
 distance. For conciseness let N dt denote any one of them. Then / N dt will give the 
 
 o 
 power expended during each half revolution of the wheel, supposing the motion of the paddle 
 
 to begin or end at the lowest point D ; or since dt = ^ , 
 
 a. 
 Power expended by one paddle in each "i k /* -^ , , 
 
 half revolution / V J 
 
 
 
 a. 
 
 Power expended by all the paddles in "l _ 2 m k f* ^ , , 
 each half revolution / V J 
 
 
 
 Now, the circumferential distance traversed by the centre of pressure, in half a revolution, 
 being IT k, and the velocity per minute being 60 V, the number of minutes elapsed will be 
 
 -. Therefore, dividing the last expression by this number, we have, 
 60 V 
 
 a 
 Power expended per minute by "1 120m /* ,. , ., 
 
 both wheels J TT J 
 
192 
 
 APPENDIX. 
 
 Hence, dividing this by the amount expended per minute by one horse's power 
 = 33000 x 1 = 33000, we get, 
 
 a. 
 Horse power expended by both 1 m i* 
 
 wheels / " 275^ J 
 
 o 
 
 In the values of N given in equations (c), (d), (e), restore the value of p by equation () ; 
 assume 
 
 1000 w 
 
 c = 
 
 275 TT 2 ff 
 and we deduce the following general formulae : 
 
 = 1-15291 .... (g), 
 
 by the Engine 
 on the Fluid 
 on the Vessel 
 
 I. HORSES' POWER expended ENTIRE, 
 
 
 V / cos. e | V cos. e v cos. ($ e) \ ' 
 
 cS 
 1000 
 
 a, 
 I | 
 
 Vcos. e v cos. 
 
 e)\ 3 d<f> 
 
 by the Engine 
 
 on the Fluid 
 
 on the Vessel 
 
 M, 
 
 vj cos. (<f> e) | Vcos. e t>cos.(c e) \ 2 d<l> 
 
 o * 
 
 II. HORSES' POWER expended HORIZONTALLY, 
 
 a 
 y cos. cos. (< - e) | V cos. e - v cos. (0 - e) j 
 
 ..(A) 
 
 cS 
 1000 
 
 x < 
 
 J (V cos. $ v) cos. (0 - e) I V cos. e-v cos. (<f>- e) ] 2 
 o 
 
 a 
 
 v J cos. (0 - e) I V cos. e - v cos. (<f> - e) I *dcf> 
 
 n * 
 
 III. HORSES' POWER expended VERTICALLY, 
 
 by the Engine I c S ,, /* . 
 
 ontheFluid f : = looo" X V Sm ^ ^ ^ ~ 
 
 J 
 
 >'(*) 
 
 o I 
 
 on the Vessel = o 
 
 To effect the integration of these expressions, the mechanical properties of the wheel will give 
 e a function of <f> ; and in this way they will evidently apply to every possible description of 
 wheel. 
 
 By way of examples we shall apply the formulae (A) to Oldham's wheel, the common wheel, 
 and the vertically acting wheel. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 193 
 
 1. OLDHAM'S WHEEL. Here e = $-, and hence, the number of horses' power ex- 
 
 pended, 
 
 by the Engine 
 
 on the Fluid 
 
 on the Vessel 
 
 cS 
 1000 
 
 x -< 
 
 , 
 
 (V - vY C 
 o 
 a. 
 
 (v - ) r 
 
 cos. 3 
 
 In which 
 
 /J.L s $ _ o / 1 2 a i ^ \ a _ 5 + cos. a . a. _ 5+ cos. a /I cos. a 
 cos. ^ - cos. - - J - - 3 1- 2 ~ 3 2 
 
 o 
 
 = i \/ 1 may be very readily calculated. 
 
 3 2 
 
 The respective proportions of the whole power expended on the Fluid and Vessel are therefore 
 
 2. THE COMMON WHEEL. Here e = o, and the number of horses' power expended, 
 
 Co. 
 
 by the Engine 
 on the Fluid 
 on the Vessel 
 
 1000 
 
 x < 
 
 V (V - v cos. 
 
 4>) 3 d4>. 
 
 a, 
 C (V - v cos. 
 
 a 
 / cos. <j> (V v cos. <f>} 2 d<f>. 
 
 3. THE VERTICALLY ACTING WHEEL. Here e = <f>, and the number of horses' power 
 expended, 
 
 by the Engine 
 on the Fluid 
 
 on the Vessel 
 
 cS 
 1000 
 
 / cos. 
 
 (Vcos. <f>-v) 3 d<j>. 
 
 , 
 v C (V cos. < - t)) 2 <fy>. 
 
194 
 Assume now, 
 
 A 
 
 APPENDIX. 
 
 A = c C d<f> = 1-15921 () 
 
 o 
 a 
 
 B = c C d<}, (cos. <f>) 
 
 o 
 a 
 
 A' = cC d<j> (cos. 3 <) = 1-15921 ( 3 s ' a + 
 
 = 1-15921 (sin. a) 
 
 3 sin. a sin. 3 a \ 
 
 12 
 
 B' = c d<f> (cos. 2 <) = 1-15921 + 
 
 and we shall have, 
 
 With the COMMON WHEEL, 
 
 f expended by the Engine 
 Horses' Powers 
 
 L effective on the Vessel 
 
 1000 
 
 V(AV 2 -2BV0+ BVn 
 
 . .(m); 
 
 With the VERTICALLY ACTING WHEEL, 
 
 ("expended by the Engine 
 Horses' Powers 
 
 L effective on the Vessel 
 
 (A'V 2 -2B'Vt>+ 
 
 } 
 
 (*). 
 
 These last expressions afford great facility in the solution of any questions concerning the 
 working of paddle wheels, as they give the most simple relations amongst the four leading 
 quantities, viz., the proportionate immersion, the power, and the two velocities, and enable us 
 to determine any one of these when the other three are known. 
 
 For convenience of calculation the values of the coefficients A, B, A', B', which depend on 
 the immersion of the centre of pressure, are exhibited in the following table. They are given 
 for every hundredth of immersion as far as eight-tenths of the radius of the wheel, which will 
 take in every possible case in practice ; and the smaller figures inserted at the right hand of each 
 column are the respective differences of the two values between which they stand, and serve to 
 expedite the interpolation of any intermediate value falling between those in the table, for 
 which simple proportion will be quite sufficient. 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 
 
 195 
 
 CO-EFFICIENTS FOR CALCULATING THE ACTION OF PADDLE WHEELS. 
 
 [The first column contains the greatest immersion of the centre of pressure in parts of the radius drawn 
 
 to that centre.] 
 
 Dip of 
 centre of 
 pressure. 
 
 A 
 
 B 
 
 A' 
 
 B' 
 
 o-oo 
 
 o-oooo 
 
 o-oooo 
 
 o-oooo 
 
 o-oooo 
 
 
 1632 
 
 1626 
 
 1616 
 
 1621 
 
 o-oi 
 
 0-1632 6 . 8 
 
 0-1626 66g 
 
 0-1616 64g 
 
 0-1621 fi , 8 
 
 0-02 
 
 0-2310 ' 
 
 0-2294 509 
 
 0-2264 484 
 
 0-2279 qfi 
 
 0-03 
 
 0-2831 
 
 0-2803 
 
 0-2748 , 
 
 0-2775 * 
 
 0-04 
 0-05 
 
 0-3272 389 
 0-3661 d 
 
 0-3228 1:1 
 0-3600 U 
 
 0-3144 
 0-3483 *' 
 
 0-3185 
 0-3540 * 
 
 
 353 
 
 333 
 
 298 
 
 316 
 
 0-06 
 
 0-4014 325 
 
 0-3933 . 
 
 0-3781 ,,. 
 
 0-3856 2S , 
 
 0-07 
 
 0-4339 HI 
 
 0-4238 . 
 
 0-4047 , 
 
 0-4140 * 
 
 0-08 
 
 0-4643 , 
 
 0-4518 , 
 
 0-4287 * 
 
 0-4400 ,. 
 
 0-09 
 
 0-4929 2 ,, 
 
 0-4780 
 
 0-4506 * 
 
 0-4639 
 
 o-io 
 
 0-5200 7 
 
 0-5026 2 ' 
 
 0-4707 201 
 
 0-4861 2 
 
 
 258 
 
 231 
 
 185 
 
 208 
 
 0-11 
 
 0-5458 
 
 0-5257 21q 
 
 0-4892 ,., 
 
 0-5069 
 
 0-12 
 
 0-5706 2 ; 
 
 0-5476 " 
 
 o-5064 :* 
 
 0-5263 * 
 
 0-13 
 
 0-5944 2l 
 
 0-5684 
 
 0-5224 ) 
 
 0-5445 ,., 
 
 0-14 
 
 0-6174 2 ' 
 
 0-5883 
 
 0-5373 | 
 
 0-5617 .'" 
 
 0-15 
 
 0-6396 222 
 
 0-6074 Ic 
 
 0-5512 ' 
 
 0-5779 
 
 
 216 
 
 182 
 
 130 
 
 154 
 
 0-16 
 0-17 
 
 0-6612 
 0-6822 2 
 
 0-6256 ... 
 0-6431 ! 
 
 0-5642 
 0-5764 J: 
 
 0-5933 ... 
 0-6079 f! 
 
 0-18 
 
 0-7026 204 
 
 0-6599 , 
 
 0-5878 J 
 
 0-6218 ,, 
 
 0-19 
 
 0-7225 199 
 
 0-6761 }' 
 
 0-5986 1( 
 
 0-6350 1; 
 
 0-20 
 
 0-7419 1! 
 
 0-6917 1; 
 
 0-6087 * 
 
 0-6476 1: 
 
 
 190 
 
 151 
 
 96 
 
 120 
 
 0-21 
 
 0-7609 
 
 0-7068 
 
 0-6183 
 
 0-6596 ... 
 
 0-22 
 
 0-7795 I! 
 
 0-7215 ; * 
 
 0-6273 ; 
 
 0-6711 
 
 0-23 
 
 0-7978 1! 
 
 0-7356 ' l *; 
 
 0-6358 
 
 0-6821 1 
 
 0-24 
 
 0-8157 179 
 
 0-7493 |; 
 
 0-6438 ' 
 
 0-6926 l 
 
 0-25 
 
 0-8333 176 
 
 0-7626 133 
 
 0-6514 76 
 
 0-7026 1( 
 
 
 172 
 
 129 
 
 71 
 
 96 
 
 0-26 
 
 0-8505 
 
 0-7755 
 
 0-6585 
 
 0-7122 , 
 
 0-27 
 
 0-8675 r 
 
 0-7880 * 
 
 0-6653 ' 
 
 0-7214 
 
 0-28 
 
 0-8843 1( 
 
 0-8001 ' 
 
 0-6717 ' 
 
 0-7302 ! 
 
 0-29 
 
 0-9008 165 
 
 0-8119 r 
 
 0-6777 ' 
 
 0-7386 ! 
 
 0-30 
 
 0-9170 162 
 
 0-8233 114 
 
 0-6834 57 
 
 0-7467 '' 
 
 
 161 
 
 111 
 
 53 
 
 78 
 
 0-31 
 
 0-9331 
 
 0-8344 
 
 0-6887 
 
 0-7545 
 
 0-32 
 
 0-9489 L 
 
 0-8453 , 
 
 0-6938 ' 
 
 0-7619 
 
 0-33 
 
 0-9645 I! 
 
 0-8559 !l 
 
 0-6986 ; 
 
 0-7690 ' 
 
 0-34 
 
 0-9800 155 
 
 0-8661 x 
 
 0-7032 ' 
 
 0-7758 ( 
 
 0-35 
 
 0-9952 152 
 
 0-8761 10 
 
 0-7075 43 
 
 0-7823 65 
 
 
 151 
 
 98 
 
 40 
 
 63 
 
 0-36 
 
 1-0103 
 
 0-8859 
 
 0-7115 
 
 0-7886 , 
 
 0-37 
 
 1-0252 l '' 
 
 0-8953 ; 
 
 0-7154 ; 
 
 0-7946 ; 
 
 0-38 
 
 1-0400 *' 
 
 0-9046 ' 
 
 0-7190 ' 
 
 0-8004 ' 
 
 0-39 
 
 1-0546 l> 
 
 0-9136 ' 
 
 0-7224 : 
 
 0-8059 ' 
 
 0-40 
 
 1-0691 145 
 
 0-9223 87 
 
 0-7256 32 
 
 0-8112 53 
 
196 
 
 APPENDIX. 
 
 Dip of 
 centre of 
 pressure. 
 
 A 
 
 B 
 
 A' 
 
 B' 
 
 0-40 
 0-41 
 0-42 
 
 1-0691 
 1-0835 
 1-0977 , 
 
 0-9223 , 
 0-9309 1 
 0-9392 * 
 
 0-7256 
 0-7286 
 0-7314 * 
 
 0-8112 
 0-8163 " 
 0-8212 
 
 0-43 
 
 i-iii8 |; 
 
 0-9473 ' 
 
 0-7341 a 
 
 0-8259 
 
 0-44 
 
 1-1257 lda 
 
 0-9552 7I 
 
 0-7366 2: 
 
 0-8303 
 
 0-45 
 
 1-1396 139 
 
 0-9629 77 ' 
 
 0-7390 24 
 
 0-8346 43 
 
 
 137 
 
 75 
 
 22 
 
 41 
 
 0-46 
 
 1-1533 
 
 0-9704 ., 
 
 0-7412 2 
 
 0-8387 , Q 
 
 0-47 
 
 1-1670 HI 
 
 0-9777 ', 
 
 0-7433 
 
 0-8426 
 
 0-48 
 
 i-isos ;; 
 
 0-9848 '* 
 
 0-7453 , 
 
 0-8463 ,' 
 
 0-49 
 
 1-1939 J 
 
 0-9917 . 
 
 0-7471 J 
 
 0-8499 * 
 
 0-50 
 
 1-2073 v 
 
 0-9985 bl 
 
 0-7488 17 
 
 0-8533 
 
 
 133 
 
 65 
 
 16 
 
 32 
 
 0-51 
 
 1-2206 132 
 
 1-0050 6 , 
 
 0-7504 j. 
 
 0-8565 31 
 
 0-52 
 
 1-2338 131 
 
 1-0114 62 
 
 0-7519 v 
 
 0-8596 30 
 
 0-53 
 
 1-2469 
 
 1-0176 ' 
 
 0-7534 .I 
 
 0-8626 28 
 
 0-54 
 
 1-2599 
 
 1-0237 
 
 0-7547 ; 
 
 0-8654 ,. 
 
 0-55 
 
 1-2728 
 
 1-0296 
 
 0-7559 
 
 0-8681 
 
 
 129 
 
 57 
 
 11 
 
 25 
 
 0-56 
 
 1-2857 , 28 
 
 1-0353 56 
 
 0-7570 
 
 0-8706 24 
 
 0-57 
 
 1-2985 
 
 1-0409 
 
 0-7581 }* 
 
 0-8730 2 , 
 
 0-58 
 
 1-3113 
 
 1-0463 
 
 0-7591 ^ 
 
 0-8753 ' 
 
 0-59 
 
 1-3239 J 2 f 
 
 1-0516 * 
 
 0-7600 ' 
 
 0-8775 I! 
 
 0-60 
 
 1-3365 126 
 
 1-0567 5 
 
 0-7608 ' 
 
 21 
 
 0-8796 
 
 
 126 
 
 49 
 
 8 
 
 20 
 
 0-61 
 
 1-3491 
 
 1-0616 
 
 0-7616 
 
 0-8816 
 
 0-62 
 
 1-3616 , 
 
 1-0664 * 
 
 0-7623 ' 
 
 0-8834 
 
 0-63 
 
 1-3740 124 
 
 1-0711 4 
 
 0-7629 ' 
 
 0-8852 I 
 
 0-64 
 
 1-3864 L 
 
 1-0756 4 ' 
 
 0-7635 ' 
 
 0-8868 
 
 0-65 
 
 1-3987 123 
 
 1-0800 4 ' 
 
 0-7641 ' 
 
 IK 
 
 0-8883 l ~ 
 
 
 123 
 
 42 
 
 5 
 
 15 
 
 0-66 
 
 1-4110 19* 
 
 1-0842 
 
 0-7646 
 
 0.8898 , 
 
 0-67 
 
 1-4233 J" 
 
 1-0883 4 
 
 0-7651 
 
 1 4 
 
 0-8912 ,. 
 
 0-68 
 
 1-4355 J.; 
 
 1-0923 4( 
 
 0-7655 ' 
 
 1 Q 
 
 0-8925 
 
 0-69 
 
 1-4476 *' 
 
 1-0961 3 
 
 0-7659 ' 
 
 0-8937 
 
 0-70 
 
 1-4597 1; 
 
 1-0998 37 
 
 0-7662 3 
 
 0-8948 l] 
 
 
 121 
 
 36 
 
 3 
 
 11 
 
 0-71 
 
 1-4718 
 
 1-1034 
 
 0-7665 
 
 0-8959 ln 
 
 0-72 
 
 1-4838 HI 
 
 1-1068 ,* 
 
 0-7668 ! 
 
 0-8969 " 
 
 0-73 
 
 1-4958 j 
 
 1-1101 * 
 
 0-7671 
 
 0-8978 ; 
 
 0-74 
 
 1-5078 
 
 1-1133 * 
 
 0-7673 ' 
 
 0-8986 
 
 0-75 
 
 1-5197 l 
 
 1-1163 30 
 
 0-7675 ' 
 
 0-8994 
 
 
 119 
 
 29 
 
 1 
 
 7 
 
 0-76 
 
 1-5316 llg 
 
 1-1192 9fi 
 
 0-7676 2 
 
 0-9001 6 
 
 0-77 
 
 1-5435 , 
 
 1-1220 2" 
 
 0-7678 
 
 0-9007 
 
 0-78 
 
 1-5553 
 
 1-1247 ' 
 
 0-7679 : 
 
 0-9013 
 
 0-79 
 
 1-5671 1 
 
 1-1272 2< 
 
 0-7680 
 
 0-9019 
 
 0-80 
 
 1-5788 l 
 
 1-1296 2 
 
 0-7681 
 
 0-9024 
 
 We have so far considered V, v, as arbitrary quantities ; but it is evident that, with a given 
 vessel, the dimensions and immersion of the wheel and paddles being given, the communication 
 of any proposed velocity to the wheel must determine that of the vessel, and this will evidently 
 depend on the nature and dimensions of the resisting surface she presents to the fluid. The 
 resistance of the vessel may be estimated by that of a plane surface moving through the fluid 
 perpendicularly to itself with the same velocity, and this may appropriately be termed the 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 197 
 
 effective surface of resistance. Denote this surface by S', and the force of resistance in Its. 
 
 will be - S' v 3 . Multiply by 60 v, the speed per minute, divide by 33000, and we obtain the 
 2 ff 
 
 number of horses' power effectively developed on the vessel, h = . S' v 3 = <7r c S' v 3 . 
 
 550 2 g 2000 
 
 Hence, 
 
 c , 2000 h , N 
 
 o = . (). 
 
 7TC V 3 
 
 This expression will serve to calculate the surface of resistance in any experiment ; and by 
 substituting the preceding value of h for any particular wheel we shall express the necessary 
 relation between the velocities for a given vessel at a given immersion ; and this relation will, 
 in fact, express a constant ratio between the velocities. For the common wheel, for instance, 
 this relation is, 
 
 7T C 
 
 A'-2B' + B 
 
 V IT 
 
 V . 
 
 and the ratio is determined by the positive root of quadratic equation, 
 
 - .. 
 
 v v 3 2 S 
 
 EXAMPLES. Take the case of the 'Salamander' calculated by Mr. Mornay, at pages 127 
 and 135. The radius to the centre of pressure for the whole power is by Mr. Mornay 
 denoted by y, and, in page 135, is 9'3937 feet ; and that for the effective power is, page 138, 
 z = 9'355 feet ; also the paddles are 16 in number, depth 2 feet 6 inches, and breadth 8 feet 
 9 inches, making a surface of 350 square feet. 
 
 1. COMMON WHEEL. 
 
 For the calculation of the POWER OF THE ENGINE we have therefore a = 5, k = 9'3937, 
 speed of the engine re = 15 strokes per minute, speed of the vessel 8' 15 miles per hour, and 
 the surface of paddle on each wheel S = 350 square feet. Hence, 
 
 log. a 
 k 
 
 0-69897 
 0-97284 
 
 flog- 
 
 9-72613 
 
 I 
 
 0-5323 
 1-0000 
 
 Immersion 
 
 Hence A = 
 B = 
 B'= 
 
 0-4677 
 
 1-1638 
 0-9760 
 0-8417 
 
 log. n 
 
 1-17609 
 0-97284 
 
 const. 9-02003 
 30 
 
 log. V 1-16896 
 
 log. V 2 2-33792 
 
 A 0-06588 
 
 SV 
 
 1000 
 
 3-11683 
 
 1308-7 
 
 log. 8-15 0-91116 
 
 99 
 
 const. _ 0-16633 
 15 
 
 0-71303 - 
 
 log. v 1-07749 
 
 V 1-16896 
 
 log. VD 2-24645 
 
 B 9-98945 
 
 - - - 0-71303 
 
 2-94893 
 
 889-06 
 
 log. S 
 , V 
 
 2-54407 
 1-16896 
 
 SV 
 1000 
 
 0-71303 
 
 log. v 2 2-15498 
 B' 9-92516 
 - - - 0-71303 
 
 2-79317 
 
 621-1 
 1308-7 
 
 1929-8 
 1778-1 
 
 Horse Power 151-7 
 
 2 c 
 
198 
 
 APPENDIX. 
 
 The result of Mr. Mornay's calculation is 151-69 horse power. 
 
 For the calculation of the EFFECTIVE POWER we have a = 5, k = 9-355, n = 15, speed of 
 the vessel = 8-15 miles per hour, and S = 350, with which we proceed as follows : 
 
 log. S 2-54407 
 v 1-07749 
 
 log. 
 Hog- 
 
 a 
 
 k 
 
 0-69897 
 0-97104 
 
 log. 
 const. , 
 
 log- 
 log. 
 
 n 
 
 1- 
 () 
 
 9- 
 
 17609 
 97104 
 02003 
 
 log. 8-15 
 const. ,, 
 
 
 
 
 
 91116 
 16633 
 
 
 9-72793 
 
 log. v 
 
 v 
 
 i 
 1 
 
 07749 
 16716 
 
 V 
 
 1- 
 
 16716 
 
 
 0-5345 
 1-0000 
 
 A' 
 Sv 
 
 2- 
 
 9- 
 
 o- 
 
 15498 
 87064 
 
 62156 
 
 log. V v 
 
 B' 
 
 2 
 
 
 
 24465 
 92469 
 62156 
 
 Immersion 
 
 0-4655 
 
 1000 
 
 
 Hence 
 
 A! 
 
 0-7424 
 0-8408 
 0-9744 
 
 B' = 
 B 
 
 f 
 
 2' 
 
 64718 
 
 / 
 
 2 
 
 79090 
 
 
 1 443-79 I 
 
 617-87 
 
 Sv 
 1000 
 
 0-62156 
 
 log. V 2 2-33432 
 B 9.98874 
 0-62156 0-62156 
 
 2-94462 
 
 880-28 
 443-79 
 
 1324-07 
 1235-74 
 
 Effective horse power 88'33 
 
 Mr. Mornay makes it 88-275 horse power. 
 
 For the EFFECTIVE SURFACE OF RESISTANCE, we have, according to equation (p), 
 
 log. 88-33 1-94611 
 v 3 3-23247 
 
 const. 
 
 [_ S' = 28-56 square feet of resisting surface, which is 
 about -rhrths of the immersed sectional area of the vessel. 
 
 Mr. Barlow, page 76, estimates the resisting surface at -Jyth o f the sectional area. 
 
 The PROPORTION OF THE POWER THAT is EFFECTIVE, when the common wheel is em- 
 
 ploved, is . A. P 3 2B V + B V 2 if x <} eno te JL the ratio of the velocities, we 
 
 V A V 2 2BVw+Br V 
 
 have, 
 
 2000 
 
 8-71364 
 
 2-74208 
 
 TTC 
 
 [log- 
 
 1-45572 
 
 Proportion of power effective = x 
 
 2B 
 
 P 
 
 A 2Bx + B x 2 
 
 the factor z may be taken out roughly from the following table : 
 
 = xz, where the value of 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 
 
 Values of z* 
 
 199 
 
 Immer- 
 sion. 
 
 X 
 
 30 
 
 40 
 
 50 
 
 60 
 
 70 
 
 80 
 
 90 
 
 o-io 
 
 0-97 
 
 0-97 
 
 0-97 
 
 0-97 
 
 0-97 
 
 0-97 
 
 0-98 
 
 20 
 
 93 
 
 93 
 
 93 
 
 92 
 
 92 
 
 91 
 
 89 
 
 30 
 
 89 
 
 89 
 
 88 
 
 88 
 
 87 
 
 85 
 
 82 
 
 40 
 
 85 
 
 84 
 
 84 
 
 83 
 
 81 
 
 79 
 
 75 
 
 50 
 
 81 
 
 80 
 
 79 
 
 77 
 
 75 
 
 72 
 
 68 
 
 60 
 
 0-76 
 
 0-75 
 
 0-73 
 
 0-71 
 
 0-69 
 
 0-65 
 
 0-61 
 
 In the foregoing example we have x = - - = 0'8 ; immersion = 0*47 ; hence z = 0*74, and 
 
 proportion of power effective = x z = 0*59. In this way a tolerably good estimation of the 
 relative effect of a wheel can be made almost at sight. 
 
 2. VERTICALLY ACTING WHEEL. 
 
 Take the hypothetical case worked by Mr. Mornay, at page 151, for the vertically acting 
 paddles, and suppose the centre of pressure to be in the middle of each paddle, which is 
 always nearly the case when the velocity of the paddle bears a high proportion with that of 
 the vessel. 
 
 First, to calculate the requisite quantity of PADDLE SURFACE (S) we have a = 5, k = 9'25, 
 n = 30-439, speed of the vessel = 8'15 miles per hour, and the effective horse power = 88'33 ; 
 hence, 
 
 log. a 
 
 k 
 
 0-69897 
 0-96614 
 
 log. n 
 const, 
 log. V 
 
 log. v 2 
 A 
 
 V 
 
 " 1000 
 
 1-48343 
 - 0-96614 
 9-02003 
 
 log. 8-15 
 const. 
 
 log. v 
 
 v 
 
 log. V v 
 B 
 
 0-91116 
 0-16633 
 
 log. V 2 2-93920 
 B' 9-92350 
 8-07749 
 
 /log- 
 
 9-73283 
 
 1-07749 
 1-46960 
 
 1-46960 
 
 I 
 
 0-54054 
 1-00000 
 
 2-15498 
 0-06168 
 
 8-07749 
 
 2-54709 
 9-98677 
 8-07749 
 
 Immersion 
 
 0-45946 
 
 Hence A = 
 
 1-1526 
 0-9700 
 0-7411 
 0-8385 
 
 {0-61135 
 
 f 0-94019 
 
 B 
 
 f 0-29415 
 
 A' 
 
 4-0865 
 
 \ 8-7134 
 1-9686 
 
 TV 
 
 1 1-9686 
 
 10-6820 
 8-1730 
 
 Effective Power 88-33 log. 1-94611 
 2-5090 0-39950 
 
 2-5090 
 
 log. 1-54661 
 
 S . . 35 "205 square feet of paddle surface. 
 
200 
 
 APPENDIX. 
 
 The same depth and number of paddles being taken as before, this amount of surface gives 
 a breadth of 10'56 inches. Mr. Mornay calculates it 10'6 inches. 
 The requisite POWER OF THE ENGINE may now be found as follows : 
 
 log. 
 
 log. V 2 
 
 A' 
 
 SV 
 
 " 1000 
 
 2-93920 
 9-86988 
 
 0-01621 
 
 2-82529 
 668-79 
 
 log. Vt> 2-54709 
 
 B' 9-92350 
 
 0-01621 
 
 2-48680 
 
 306-76 
 
 Mr. Mornay's calculation is 199'31 horse power. 
 
 B 
 
 2-15498 
 9-98677 
 0-01621 
 
 2-15796 
 
 143-87 
 668-79 
 
 812-66 
 613-52 
 
 Horsepower 199"14 
 
 3. OLDHAM'S WHEEL. 
 
 Taking the same data as in the first example, let it be required to determine the requisite 
 amount of PADDLE SURFACE (S) on each wheel. 
 
 log. a 0-69897 V = 14-530 
 
 =. 0-54054 
 
 k 
 
 0-96614 
 
 - 9-73283 
 
 v = 11-953 
 
 V-t>= 2-577 
 
 - ^ 0-45946 
 
 ;- 5-54054 
 
 (V - ) 
 v 
 
 i ditto 
 log. 
 
 log. 
 
 9-66225 
 
 9-83113 
 0-74355 
 
 9-43416 
 
 0-00884 
 0-82222 
 1-07749 
 
 1-90855 
 
 Effective 1 
 
 VT c \ 88-33 log. 
 Power / 
 
 1-94611 
 1-90855 
 
 0-03756 
 
 1000 
 
 .-. S = 1090-3 feet. 
 
 This wheel, therefore, requires a much larger surface of paddle than the common wheel. 
 Indeed, under any given circumstances, the common wheel may be said to possess the advan- 
 tages of requiring the least surface of paddle to produce a given effect, and of encumbering the 
 action with the least possible amount of friction and strain on the bearings, which are recom- 
 mendations of a very strong character. 
 
 VI. ON THE ACTUAL RESISTANCE OF BOATS ON CANALS. 
 
 The experiments alluded to in the foot-note, page 297, were made by John Mac- 
 neill, Esq., C.E., &c., in July 1834, on two canals in Scotland, with the boats actually used 
 in the traffic on those canals ; and from a scientific gentleman of such universally acknowledged 
 ability and experience, they are deserving of the greatest reliance. The experiments, which 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 
 
 201 
 
 are very numerous and of a varied character, were conducted with great care ; and an interesting 
 description of the circumstances under which they were made, and a well-arranged table 
 showing the results observed, are given in detail in vol. i. of the Transactions of the Institution 
 of Civil Engineers, to which we refer such of our readers as may wish for minute information. 
 A few extracts will be sufficient to show that the theory which considered the resistance of a 
 vessel moving on a canal to be as the square of the velocity, can no longer be maintained. 
 
 The canals upon which Mr. Macneill made his experiments were of very different sizes. 
 This circumstance alone had the unexpected effect of destroying the universality of the 
 application of the ordinary rule. On neither canal did the resistance vary precisely as the 
 square of the velocity : and it is remarkable that the increase was not the same in the wide 
 and deep canal as it was in the narrow and shallow one. An extensive field of enquiry is thus 
 opened, which will require much time and numerous observers to collect the harvest of 
 interesting and important facts which it contains. 
 
 We have thrown our extracts into Tables, for more convenient reference and comparison. 
 Table I. contains the experiments on the larger canal: Table II. those on the smaller; and 
 it will be observed that the resistance on this canal was less at velocities of 9 and 10 miles 
 per hour, than of those of 7 and 8 ! The velocities marked * were taken as the standards of 
 comparison. 
 
 TABIE I. EXTRACT. EXPERIMENTS MADE UPON THE FORTH AND CLYDE CANAL. 
 
 No. of ex- 
 periment in 
 the series. 
 
 Total weight moved. 
 
 Velocity in 
 miles per 
 hour. 
 
 Resistance 
 in hours 
 avoided. 
 
 Power of the velo- 
 city according to 
 which the resist- 
 ance varies. 
 
 Name of boat. 
 
 56 
 
 ton. cwt. qr. Ib. 
 8 3 21 
 
 3-4* 
 
 51 
 
 
 
 49 
 62 
 
 
 9-9 
 7-62 
 
 435 
 363 
 
 2-01 
 2-43 
 
 Rapid. 
 
 59 
 
 
 8-08 
 
 395 
 
 2-37 
 
 
 97 
 
 3 12 6 
 
 4-22* 
 
 40-5 
 
 
 
 95 
 
 
 9-33 
 
 225-4 
 
 2-16 
 
 
 94 
 
 
 12-33 
 
 362-8 
 
 2-04 
 
 
 101 
 
 3 18 6 
 
 4-12* 
 
 42-95 
 
 
 
 100 
 
 
 7-34 
 
 153-8 
 
 2-21 
 
 
 99 
 
 
 9-28 
 
 233-7 
 
 2-09 
 
 
 98 
 
 
 12-08 
 
 367-5 
 
 2-00 
 
 
 106 
 
 5 11 6 
 
 4-04* 
 
 50-4 
 
 
 
 109 
 108 
 
 
 8-41 
 11-69 
 
 281-45 
 427-5 
 
 2-35 
 2-01 
 
 Zephyr. 
 
 113 
 
 6 17 6 
 
 4-29* 
 
 59-97 
 
 
 
 112 
 
 
 8-11 
 
 331-1 
 
 2-68 
 
 
 111 
 
 
 10-72 
 
 422-3 
 
 2-13 
 
 
 116 
 
 4506 
 
 4-73* 
 
 59-9 
 
 
 
 115 
 
 
 10-00 
 
 274-7 
 
 2-04 
 
 
 114 
 
 
 12-18 
 
 383-3 
 
 1-96 
 
 
 118 
 
 
 12-17 
 
 386-2 
 
 1-97 
 
 
 128 
 
 3 12 3 5 
 
 4-39* 
 
 55-9 
 
 
 
 127 
 
 
 9-28 
 
 257-8 
 
 2-04 
 
 
 126 
 
 
 11-38 
 
 348-9 
 
 1-92 
 
 
 132 
 
 3 17 3 5 
 
 4-26* 
 
 44-1 
 
 
 Lark. 
 
 131 
 
 
 9-63 
 
 266-8 
 
 2-21 
 
 
 130 
 
 
 11-57 
 
 375-0 
 
 2-14 
 
 
 Dimensions of the Section of the Forth and Clyde Canal. 
 
202 
 
 APPENDIX. 
 
 TABLE II. EXTRACT. EXPERIMENTS MADE UPON THE MONKLAND CANAL. 
 
 No. of ex- 
 periment in 
 the series. 
 
 Total weight moved. 
 
 Velocity in 
 miles per 
 hour. 
 
 Resistance 
 in hours 
 avoided. 
 
 Power of the velo- 
 city according to 
 which the resist- 
 ance varies. 
 
 Remarks, and 
 Name of boat. 
 
 266 
 
 ton. cwt. qr. Ih. 
 4 18 20 
 
 3-70* 
 
 42 
 
 
 
 267 
 
 
 6-00 
 
 135 
 
 2-41 
 
 
 264 
 263 
 
 
 6-17 
 9-39 
 
 168 
 358 
 
 2-71 
 2-30 
 
 Rapid. 
 
 262 
 
 
 10-97 
 
 383 
 
 2-03 
 
 
 261 
 
 
 10-98 
 
 406 
 
 2-08 
 
 
 260 
 
 
 6-73 
 
 323 
 
 3-41 
 
 
 269 
 270 
 270 
 271 
 
 
 8.03 
 9-00 
 9-38 
 7-26 
 
 385 
 318 
 359 
 362 
 
 2-86 
 2-27 
 2-31 
 3-19 
 
 Heavy swell. 
 Light swell. 
 Light swell. 
 
 271 
 
 
 7-38 
 
 431 
 
 3-36 
 
 
 274 
 
 
 10-71 
 
 471 
 
 2-27 
 
 
 275 
 
 
 9-57 
 
 271 
 
 1-96 
 
 
 Dimensions of the Section of the Monkland Canal. 
 
 From the observations made upon the spot by Mr. Macneill we select the following 
 interesting and important conclusions. 
 
 " That in the wide and deep canal the resistance was observed to increase with the velocity, 
 " but not in any uniform ratio. 
 
 " That in the shallow and narrow canal the resistance had a limit at a certain velocity, and 
 " under certain circumstances even decreased with the increase of velocity. 
 
 " That there existed a relation between the resistance and the inclination of the keel ; the 
 " resistance diminishing and increasing in some ratio or other, as the angle it made with an 
 " horizontal line diminished or increased. 
 
 " That the boat absolutely rises during its motion. This fact was most satisfactorily de- 
 a monstrated by the apparatus designed for the purpose. In some of the experiments, the 
 " mean of the several rises, indicated by the four slips, was about 4 inches, the bow being, in 
 " every case, more elevated than the middle and stern." 
 
 The subject of this last observation has excited considerable interest amongst scientific 
 men, but it does not appear to have met with a satisfactory explanation. It has been par- 
 ticularly noticed by Mr. Russell of Edinburgh, the same gentleman we alluded to at page 182, 
 who has, in furtherance of the objects of the British Association for the Advancement of Science, 
 devoted much time and labour to the experimental investigation of the progression and nature 
 of the waves produced on canals and rivers. Mr. Russell's experiments have proved very 
 successful, and in his reports he has developed many valuable and interesting facts relative to 
 the phenomena of waves, which promise to have an important bearing on the prosecution of 
 future hydrodynamical researches ; but, in our view, he has, in some instances, jumped rather 
 hastily to his general conclusions, and in his endeavours to investigate, or rather to induce, 
 the laws of dynamical and statical emersions, we conceive he has proceeded on sup- 
 
ON THE GENERAL THEORY OF THE STEAM ENGINE. 203 
 
 positions that are not altogether in accordance with universally received principles. For 
 instance, in the first section of his researches, printed in vol. xiv. of the Transactions of the 
 Royal Society of Edinburgh, after having stated that the resistance of a small unit of surface 
 to a fluid, when either the fluid is in motion, or the surface itself is equal to the statical 
 pressure of a column of fluid having for its height the height due by gravity to that velocity, 
 he asserts that " this statical quantity being the measure of the pressure of the fluid upon the 
 " anterior surface of the immersed solid, will also be the measure of the quaquaversus pressure 
 " of the fluid in every direction, and therefore will measure the pressure of the water upon 
 " the vessel causing its emersion." This assumed hypothesis is obviously inconsistent with 
 the mode in which the action and reaction takes place between the vessel and the fluid ; and 
 its random nature, independently of other misapplications of mathematical principles, to 
 which it is not necessary to advert, is amply sufficient to account for the startling nature of 
 the conclusion to which it leads, viz., that the vessel rises with every increase of velocity, and 
 that "at 43'8 miles an hour, the floating body emerges wholly from the fluid and skims the 
 " surface." By what mysterious action of forces the vessel is thus elevated or suspended in 
 the air, is, of course, left for the reader to find out, but we trust it will not long exercise his 
 ingenuity. 
 
 The principal feature of Mr. Russell's observations is the propagation of the great solitary 
 wave of displacement, which appears to act an important part in the modification of the 
 resistance to the vessel ; and Mr. Russell's beautiful illustrations of its mechanism and 
 properties are very interesting and important. It is remarkable that the velocity of the 
 generating body does not in any way affect the velocity of this wave ; a wave, for example, 
 of 8 miles an hour being produced alike from bodies moved at the rate of 2, 5, 6, and 12 miles 
 an hour. The velocity appears to depend chiefly on the depth of the fluid, and Mr. Russell, 
 in his experiments on canals, has found that in each case it does not differ sensibly from that 
 which is acquired by a heavy body in falling freely by gravity through a space equal to the 
 depth of the centre of gravity of a cross section of the fluid, below the surface. It is not 
 difficult to conceive how this wave exercises its influence and the changes that must take 
 place in the resistance, accordingly as the vessel falls behind the wave, mounts upon it, or 
 passes over it. 
 
 The only rational explanation of the phenomenon of the vessel rising out of the fluid, 
 appears to depend on the form of its construction. Thus, the action of the fluid, excepting 
 the slight influence of friction, must, at each point, always be directed perpendicularly to the 
 surface of the vessel ; and hence, when in motion, the increase of head pressure must tend to 
 elevate the head of the vessel, whilst the loss of stern pressure will cause the stern to lose a 
 portion of its statical support, and so sink deeper into the fluid. And if we simply consider 
 that the elevated position of the keel of the vessel, so acquired, has a direct tendency to 
 increase the elevating action of the fluid at the head of the vessel, and to retrieve the loss of 
 stern support, the partial rising out of the fluid becomes an immediate consequence of the 
 resolved forces ; and it is evident that the vessel cannot, under any circumstances, emerge 
 wholly out of the fluid. The truth or error of this explanation might easily be tested by 
 employing a floating body of a rectangular form : if it be correct, the tendency ought to be 
 to bury itself in the fluid instead of rising out of it. 
 
 Mr. Mornay (page 123) appears to be of the opinion that in the motion of a body through 
 
204 APPENDIX. 
 
 a fluid we have no reason to suppose that the head pressure is at all changed. That it is so, 
 is clearly made out by the valuable experiments of the late Colonel Beaufoy, in which bodies 
 of various mathematical forms are employed, and which distinctly point out the separate 
 effects produced by altering the velocity, the figure of the head, and the figure of the stern. 
 A volume of these experiments, elegantly executed, has recently been presented, in the most 
 liberal and handsome manner, to his scientific countrymen, by Henry Beaufoy. At page xxxix 
 of the Introduction, the different forces which act upon a body moving through a fluid are 
 clearly defined as follows : l 
 
 " By HEAD PRESSURE, is meant the total pressure which exists against the head end, or 
 " foremost part, of a body immersed, either wholly or in part, in any given fluid when such 
 " body is at rest. 
 
 " By STERN PRESSURE, is meant the total pressure which exists against the stern end, or 
 " hindermost part of a body, immersed, either wholly or in part, in any given fluid when such 
 " body is at rest. 
 
 " By PLUS PRESSURE, is meant the additional pressure which is sustained by the head 
 " end, or foremost part of a body, moved through a fluid ; which additional pressure is over 
 " and above what we have termed the Head Pressure, and arises from the fluid being obliged 
 " to be displaced in order to permit the moving body to pass through it. 
 
 " By MINUS PRESSURE, is meant a subtraction of pressure from the stern pressure, and 
 " which subtraction is occasioned by the fluid not pressing so strongly against the stern end, 
 " or hindermost parts of a body, when such body is in motion through the fluid, as when the 
 " body is at rest. 
 
 " By FRICTION, (as relating to this subject,) is meant that sort of resistance to a body 
 " moved through a fluid, which arises either from the adhesion of the particles of the fluid to 
 " the surface of the moving body, or from the roughness of the body ; or from both these 
 " causes united. 
 
 " By TOTAL RESISTANCE, is meant the sum total of the plus pressure, the minus pressure 
 " and friction united." 
 
 To complete the forces which act on the body we should introduce two other classes, viz., 
 those which arise from the destruction of the equilibrium of pressure caused by the dis- 
 placement and consequent unevenness of the fluid, and those which arise from the inclination 
 of the axis of the moving body : these may probably account for many of the discrepancies 
 observed in the results of the experiments. 
 
 Colonel Beaufoy's extensive experiments, taken in connexion with those of Macneill and 
 Russell, supply various important data for the sciences of hydraulics and naval architecture. 
 These subjects have, unfortunately, been but little cultivated by British mathematicians, 
 notwithstanding their peculiar importance to this country ; and we regret that time will not 
 allow us to enter here into any discussion of what has already been done. We trust, however, 
 that the theories of waves and naval architecture will shortly be taken up by some enterprising 
 and able analyst, who may allow his attention to be drawn to such pursuits by their vast 
 utility and importance. 
 
 1 These definitions were drawn out by the late Earl Stanhope. 
 
RULES FOR CALCULATING THE STEAM ENGINE. 205 
 
 XL PRACTICAL RULES FOR CALCULATING THE STEAM ENGINE. 
 
 [The number inserted at the end of each rule refers to the page of the book where information respecting it 
 
 is to be found.] 
 
 PROPERTIES OF STEAM. 
 
 THE additional heat required for the formation of steam may be estimated at 1000 Fahr., the 
 heat of conversion from liquid to vapour. 
 
 1. To find the elastic force of steam when in contact with the liquid from which it is 
 formed, the temperature being given. 
 
 Tredgold's Rule. 
 
 RULE i. Add 100 to the temperature, in degrees, and from the logarithm of this sum 
 subtract 2-24797 j then multiply by 6, and the product will be the logarithm of the force in 
 inches of mercury. (59.) 
 
 Example. Let the proposed temperature be 250 Fahr. 
 
 Temperature 250 
 Add 100 
 
 350 - - - log. 2,54407 ' 
 
 Subtract by the Rule 2,24797 
 
 Difference 0,29610 
 Multiply by 6 
 
 Log. 59-8 1,77660 
 The required force is therefore 59'8 inches of mercury. 
 
 Southern's Rule. 
 
 RULE ii. Add 51'3 to the temperature, and multiply the logarithm of the sum by 5'13 ; 
 from the product deduct 10'94123 and find the natural number answering to the remainder as 
 a logarithm; this number increased by O'l will express the required pressure in inches of 
 mercury. (58.) 
 
 1 When the water is salt, refer to the last column of the table, page 61, for this logarithm. 
 
 Id 
 
206 APPENDIX. 
 
 Example. Take the same as before. 
 
 Temperature 250 
 Add 51-3 
 
 301-3 log. 2.47900 
 
 Multiply by 5'13 
 
 743700 
 247900 
 1239500 
 
 12-7172700 
 10-94123 
 
 Corresponding number 5 9- 7 1 '77604 
 
 To be increased by 0*1 
 
 Required force 59-8 inches of mercury. 
 This Rule appears to be preferable for high temperatures. 
 
 The force in inches of mercury may be reduced to ffis. on the square inch by dividing 
 successively by 2, 6, and 9, and subtracting the third quotient from the first, thus : 
 
 2) 59'8 inches of mercury, 
 
 6) 29-9 
 
 9) 4-98 
 
 0-55 
 29-35 ffis. per square inch. 
 
 2. To find the volume or space the steam of a cubic foot of water occupies, when the steam 
 is of a given elastic force and temperature, and separated from the liquid from which it is 
 generated. 
 
 RULE. To the temperature, in degrees, add 459 and multiply the sum by 76-5 ; divide the 
 product by the force of the steam in inches of mercury, and the result will express the space 
 in cubic feet which the steam of a cubic foot of water will occupy. (84.) 
 
 Example. Let the force be 4 atmospheres, or 120 inches of mercury, and the tem- 
 perature 295. 
 
 Temperature 295 
 Add 459 
 
 754 
 Multiply by 76-5 
 
 3770 
 4524 
 
 5278 
 
 57681-0 
 
RULES FOR CALCULATING THE STEAM ENGINE. 207 
 
 Force in inches of mercury 120) 57681'Q (481 cubic feet, the volume of the steam 
 
 480 from a cubic foot of water. 
 
 968 
 960 
 
 81 
 
 RULE ii. To the temperature, in degrees, add 459, and multiply the sum by 38; divide 
 the product by the pressure in Its. per square inch. (84). 
 
 Same Example. 
 Temperature 295 
 Add 459 
 
 754 
 Multiply by 38 
 
 6032 
 2262 
 
 fts. per inch 59) 28652(486 cubic feet. 
 236 
 
 505 
 472 
 
 332 
 
 BOILERS. 
 3. To find the dimensions of a boiler for a given power. 
 
 I. Rectangular or Watt's Boiler, when it has no internal flues. 
 
 RULE. The bottom surface should be about 5 feet for each horse power. (124). Take the 
 capacity of the boiler for water, and divide it by the quantity of bottom surface, and the 
 quotient will be the depth of water. 
 
 Divide twice the capacity for water less the area of the bottom surface by the side 
 surface for fire and flue, and the result will be one of the dimensions of the bottom. Divide 
 the bottom surface by this dimension, and it gives the other. (125.) 
 
 Example. To find the proportions of a boiler for an engine of 12 horse power, the capacity 
 for water being 12'2 cubic feet for each horse power. 
 
 Horse power 12 Cubic feet per horse power 12'2 
 
 Table, page 124, 5 Horse power 12 
 
 Bottom surface 60 Capacity 146*4 
 
 Horsepower 12 6,0) 14,6'4 capacity 
 
 Table, page 124, 4-9 
 
 Side surface 58'8 or 59. 
 
 2'44 depth of water. 
 
208 APPENDIX. 
 
 Double the capacity 292-8 
 
 Subtract bottom surface GOO 
 
 Divide by side surface 59 ) 232-8 (4 feet, one of the dimensions 
 
 236 of the bottom. 
 
 4 ) 60 (15 feet, the other dimension. 
 
 N.B. It cannot be of much importance that the dimensions should be in the proportion of 
 4 to 15, so long as the quantity of bottom surface is 60 square feet. 
 
 II. Cylindrical Boilers, with the fire applied externally. 
 
 RULE. Let the capacity for water and for steam be added together, and also the quantities 
 of fire surface ; then divide twice the capacity by the quantity of fire surface, and the result 
 will be the diameter. (126.) 
 
 Also 1-27 times the capacity divided by the square of the diameter will give the length. 
 
 Example. Required the dimensions of a cylindrical boiler for a 12 horse power, the whole 
 capacity being 293 cubic feet. 
 
 m , , , n . c f Bottom surface 5'0 
 
 Table, page 124, for 4 r 
 
 I Side surface 4'9 
 
 9-9 
 Horse power 12 
 
 Fire surface 118-8 or 119. 
 Capacity 293 
 
 2 
 
 Fire surface 119) 586 (5 feet, the diameter. 
 Capacity 293 
 1-27 
 
 2051 
 586 
 293 
 
 Square of diameter = 25 ) 372-11 ( 14-9 or 15 feet, the length. 
 
 25 
 
 122 
 100 
 
 221 
 225 
 
 4. To find the requisite thickness for a rectangular or cylindric boiler. 
 
 RULE. Multiply the load in Its. per square inch on the safety valve, by the greatest 
 diagonal of the section of the boiler in inches, and divide the product by, 
 
RULES FOR CALCULATING THE STEAM ENGINE. 209 
 
 1 j times the cubic feet of boiler per horse power, for ( wrou S ht iron 
 i J I copper ; 
 
 150" 
 
 the result will be the thickness of the upper plates in inches. 
 
 The bottom plates should be as much thicker as will compensate for wear ; usually twice 
 the thickness of the top ones. (252.) 
 
 Example. In a rectangular boiler, the greatest diagonal being 8 feet 2 inches = 98 inches, 
 the load on the valve 6 Ins. per square inch, and the space for steam for each horse power 
 18 cubic feet ; required the thickness of the top plates, to be made of wrought iron. 
 
 18 cubic feet 98 inches 
 
 150 6 ffis. 
 
 900 27|00) 5|88 (0'218 of an inch for the top plates. 
 
 18 54 
 
 2700 48 
 
 27 
 
 210 
 The bottom plates should be the double of 0'218 or 0'436 of an inch. 
 
 5. To find the requisite thickness of a spherical boiler. 
 
 RULE. Multiply the diameter in inches by the pressure on the valve in ffis. per square 
 inch, and divide by 
 
 n f times the cubic feet of boiler per horse power, for \ v 
 1 ou J I. copper y 
 
 the result will be the thickness in inches. (252.) 
 
 Example, A spherical wrought iron boiler, 18 feet 8 inches = 224 inches diameter, with 
 20 cubic feet to each horse power, and the load on the valve being 8 Ibs. per square 
 inch ; required its thickness. 
 
 20 cubic feet 224 inches 
 
 300 8 IDS. 
 
 6000 6|000) 1|792 
 
 0'3 of an inch thickness. 
 
 6. To find the height of a column of water to supply a boiler against any proposed pressure 
 of steam. 
 
 RULE. Multiply the pressure in ffis. per square inch by 2'44, and the product will express 
 the required height in feet. (141.) 
 
 Example. Required the length of feed pipe capable of supplying a boiler when the pressure 
 
 is 5 ffis. per square inch. 
 
 2-44 
 
 5 
 
 12-20 
 
 12'2 or 12 feet 3 inches above the surface of the 
 water in the boiler. 
 
210 APPENDIX. 
 
 SAFETY VALVE. 
 7. To find the aperture of a safety valve, suited to any given pressure. 
 
 RULE. Divide the area of the fire surface by the excess of the pressure above the atmo- 
 sphere, expressed in tbs. per square inch, and the quotient will be the square of the diameter 
 of the narrowest part of the valve in inches. (142.) 
 
 Example. Required the aperture of a safety valve for a boiler with 60 feet of fire surface, 
 
 the pressure being 5 tbs. per square inch above the pressure of the atmosphere. 
 The feet of fire surface (60) divided by the tbs. per square inch (5) gives 12 for the square 
 of the diameter. Hence, by finding the square root, the diameter of the narrowest aperture 
 of the valve should be 3*46, or about 3 \ inches. The aperture should be made rather in excess 
 than defect. 
 
 STEAM PASSAGES. 
 
 
 
 8. To find the diameter of the steam pipe. 
 
 RULE. Multiply the length of the stroke in feet by the number of strokes per minute, and 
 divide the product by 6 ; take the square root of the quotient, multiply it by the diameter of 
 the cylinder, and then divide by 20. The result will be the diameter of the pipe in inches. 
 (95.) 
 
 Example. To find the diameter for the steam pipe of an engine, of which the diameter of 
 the cylinder is 2 feet, the length of stroke 2'5 feet, and the number of strokes per minute 38. 
 
 Length of stroke 2'5 
 Number per minute 38 
 
 200 
 75 
 
 Divide by 6) 95-0 
 
 16, nearly 
 
 Square root 4 
 
 Diameter cylinder 24 inches 
 
 Divide by 20) 96 
 
 4'8 inches. 
 
 The diameter of the pipe should therefore be about 5 inches. 
 The same rule applies to the steam passages, and the passages to the condenser. 
 
 FIRE GRATING. 
 
 9. To find the area of the grating. 
 
 RULE. Divide twice the square root of the height, in feet, from the bottom of the ash pit 
 to the bottom of the chimney by the said height, and multiply the quotient by the number of 
 horse power. The result will be the area of the grating expressed in square feet. (116.) 
 
RULES FOR CALCULATING THE STEAM ENGINE. 211 
 
 Example. Let the height be 5 feet, and the number of horses' power 96. 
 
 Square root of 5 = 2-28 
 2 
 
 Divide by 5) 4-56 
 
 0-91 
 Horse power 96 
 
 546 
 819 
 
 87'36 square feet for the grating. 
 
 CHIMNEY. 
 
 10. To find the area of a chimney for a steam engine. 
 RULE. For engines of 10 horse power and upwards the area of the chimney, in square 
 inches, should be 112 times the horse power divided by the square root of its height. (145.) 
 
 Example. Required the area of a chimney for an engine of 40 horse power, the height 
 being 70 feet. 
 
 Horse power 40 
 112 
 
 Square root of 70 = 8'4) 4480,0 (533 inches 
 
 420 
 
 280 
 252 
 
 280 
 252 
 
 28 
 The area should therefore be 533 square inches. 
 
 CYLINDER. 
 
 11. To find the requisite thickness of a working cylinder. 
 
 RULE. To the diameter of the cylinder in inches add 2'5 ; multiply the sum by the total 
 pressure of steam in Ifcs. per square inch in the boiler, and divide the product by 1900. The 
 result will express the thickness for strength, and half an inch may be added for wear. (247). 
 
 Example. A cast iron cylinder 24 inches diameter is to be made for steam not exceeding 
 5 Ifes. per square inch on the safety valve ; required its thickness. 
 
212 APPENDIX. 
 
 Diameter 24 inches Safety valve 5 Ifcs. 
 Add 2-5 Atmosphere 14'7 
 
 26-5 Total pressure 197 
 
 26-5 
 
 19iOO) 5J22-05 (0-275 inches 
 38 0-5 for wear 
 
 142 0-775 inches, the re- 
 133 quired thickness. 
 
 90 
 
 PISTON ROD, &c. 
 
 12. To find the diameter of the piston rod, &c. 
 
 RULE. Multiply the square root of the pressure of the steam per square inch in the boiler 
 by the diameter of the cylinder in inches, and divide the product by 
 
 33 for cast iron, 
 36 wrought iron, 
 57 tempered steel ; 
 
 and the quotient will be the diameter of the rod in inches, for a double-acting engine. For a 
 single-acting engine one-half of the result will be sufficient. (24 1 .) 
 
 Example. The force of the steam being 20 fts. per square inch, and the diameter of the 
 cylinder 38 inches ; required the diameter of the piston rod, the material being wrought 
 iron. 
 
 Square root of 20 4-47 
 
 38 
 
 3576 
 1341 
 
 36)169-86(4-7 inches diameter. 
 144 
 
 258 
 252 
 
 Thus, for a double-acting engine the diameter should be about 4| inches ; and for a single- 
 acting engine 2| inches. 
 
 Parallel motion rods should be about half the diameter of the piston rod ; and connecting 
 rods should be about seven-tenths of the diameter of the piston rod. (242.) 
 
RULES FOR CALCULATING THE STEAM ENGINE. 213 
 
 THE CONICAL PENDULUM OR GOVERNOR. 
 
 The vertical distance between the point of suspension and the plane in which the balls 
 revolve is the height of the governor. 
 
 13. To find the height for any proposed number of revolutions per minute. 
 
 RULE. Divide the number 375 by twice the number of revolutions per minute, and the 
 square of the quotient will be the required height of the governor in inches. (263.) 
 
 Example. What ought to be the height of the governor so that the number of revolutions 
 may be 42 per minute ? 
 
 42 
 
 2 
 
 84) 375 (4-46 
 
 336 4-46 
 
 4-46 
 390 
 
 336 2676 
 
 1784 
 540 1784 
 
 19-8916 
 Height 19-9 inches. 
 
 14. The height being known, it is required to find the number of revolutions per minute. 
 RULE. Divide 375 by twice the square root of the height in inches, and the quotient will 
 be the number of revolutions per minute. (263.) 
 
 Example. Take the same example and let the height be 19-9 inches, to find the revolutions 
 per minute. 
 
 Square root of 19'90 = 4-46 
 
 2 
 
 8-92 
 8-92) 375-00 (42 revolutions per minute. 
 
 3568 
 
 1820 
 1784 
 
 36 
 
 ECCENTRIC. 
 
 15. The length of the levers being given, to find the requisite throw of the eccentric. 
 
 RULE. Multiply the length of the stroke of the valve by the length of the lever on the 
 weight shaft for the eccentric rod, and divide the product by the length of the lever which 
 works the valve, and the quotient will be the throw required. 
 
 2 e 
 
214 APPENDIX. 
 
 Example. The stroke of the valve is 5 inches, the lever for working it 10 inches, and the 
 lever for the eccentric rod 8 inches ; required the throw of the eccentric. 
 
 Stroke 5 
 
 8 
 
 10)40 
 
 4 inches throw. 
 
 The throw of the eccentric is the distance between the circumferences of the eccentric circle 
 and the shaft, or it is the difference of their diameters. 
 
 For calculating the proportions in any other way it will only be necessary to make the 
 throw of the eccentric and the eccentric lever, in the same proportion to each other as the 
 stroke of the valve and the valve lever. 
 
 PUMPS. 
 
 16. To find the number of cubic feet in the volume of a given cylinder. 
 
 RULE. Multiply the square of the diameter in inches by half the length in inches, or 6 
 times the length in feet ; then, cutting off two figures from the right hand, divide the product 
 by 11, and the result will express the required volume in cubic feet. 
 
 Example. What is the volume of a cylinder whose diameter is 36 inches and length 32 
 inches ? 
 
 Diameter 36 inches 
 36 
 
 216 
 108 
 
 Square of diameter 1296 
 
 Half length 16 inches 
 
 7776 
 1296 
 
 11) 207,36 
 
 Volume 18'85 cubic feet. 
 
 17. To find the power requisite to raise water to any proposed height. 
 
 RULE. Multiply the square of the diameter of the pump, in inches, by the perpendicular 
 height of the water in feet, and by the velocity also in feet per minute, and, cutting off three 
 figures from the right hand, divide by 96. The result will express the number of horse 
 power necessary to raise the water. (274.) 
 
 It is customary to increase the result by a -|-th part, for friction and waste. 
 
 Example. To find the power requisite to raise a column of water 16 inches diameter, 86 
 feet high, at the velocity of 128 feet per minute. 
 
RULES FOR CALCULATING THE STEAM ENGINE. 215 
 
 Diameter 16 inches 
 16 
 
 96 
 16 
 
 256 
 Height 86 feet 
 
 1536 
 
 2048 
 
 22016 
 Velocity 128 feet 
 
 176128 
 44032 
 22016 
 
 96) 2818]048 (29'35 
 
 192 5-87 one-fifth 
 
 898 35'2 horse power. 
 864 
 
 340 
 
 288 
 
 524 
 
 The addition of one-fifth for friction and waste appears to be too much for large engines. We 
 would recommend, as more preferable, to multiply by the velocity increased by 20 feet, and 
 then to make no addition afterwards. The work, in the above example, would stand thus : 
 
 22016 
 148 
 
 176128 
 88064 
 22016 
 
 96) 3258|368 (33*94 or 34 horse power. 
 
 288 
 
 378 
 288 
 
 903 
 864 
 
 396 
 
216 APPENDIX. 
 
 18. To find the velocity necessary to discharge a given quantity of water. 
 
 RULE. Multiply the number of cubic feet discharged per minute by 1100, and divide the 
 product by 6 times the square of the pump's diameter in inches. The result will express the 
 velocity of the discharge in feet per minute. 
 
 Example. The diameter of the pump being 16 inches, and the discharge 179 cubic feet per 
 minute, required the velocity. 
 
 16 inches 179 cubic feet 
 
 16 1100 
 
 96 1536) 196900 (128 feet velocity 
 
 16 1536 per minute. 
 
 256 4330 
 
 6 3072 
 
 1536 12580 
 
 12288 
 
 292 
 
 19. To find the diameter of the pump necessary to discharge a given quantity of water. 
 
 RULE. Multiply the number of cubic feet to be discharged per minute by 1100, divide the 
 product by 6 times the velocity in feet per minute, and the square root of the quotient will be 
 the diameter of the pump in inches. 
 
 Example. The velocity being 32 strokes per minute, the length of stroke 4 feet, and the 
 discharge 1 79 cubic feet per minute, required the diameter of the pump. 
 
 32 179 
 
 4 1100 
 
 128 feetper minute 768) 196900 (256; square root of 256 = 
 6 1536 16 inches, the re- 
 
 quired diameter. 
 
 768 4330 
 
 3840 
 
 4900 
 
 PARALLEL MOTION. 
 
 20. The lengths of the beam, radius bar, and link, as in Fig. 4, Plate x. (B) being given, 
 together with the length of the stroke, to find the point E in the link where the piston rod 
 must be attached. 
 
 RULE. Divide the lengths of the beam and radius bar, measured from their centres of 
 motion, by half the length of the stroke. From the square of each of the two quotients 
 subtract unity ; find the square roots of the remainders, and subtract them respectively from 
 the preceding quotients. The numbers so deduced will express the relative proportion 
 between the segments of the link ; and if we multiply each of them by the length of the link 
 
RULES FOR CALCULATING THE STEAM ENGINE. 
 
 217 
 
 and divide the product by the sum of the two numbers, we shall get the respective distances 
 of the required point from the beam and radius bar. (231.) 
 
 Example. The radius of the beam is 7 feet, the length of the radius bar 4 feet, the link 
 2 feet, and the length of the stroke 5 feet ; required the point of connexion of the 
 piston rod. 
 
 Half length of stroke = 2-5 feet. 
 2-5)7-0(2-8 2-5)4-0(1-6 
 
 5-0 25 
 
 200 
 200 
 
 Quotients 2'8 
 
 2-8 
 
 224 
 56 
 
 150 
 150 
 
 Squares 7'84 
 Subtract 1 
 
 6-84 
 
 Square roots 2-6153 
 Subtracted from quotients -1847 
 
 1-6 
 1-6 
 
 96 
 16 
 
 2-56 
 1 
 
 1-56 
 1-2490 
 
 3510 
 
 Numbers/' 1847 
 I -3510 
 
 1847 
 Link 2 
 
 Sum -5357 
 
 535 7) -3694,0 (0-69 
 32142 
 
 47980 
 
 3510 
 Link 2 
 
 5357)7020(1-31 
 5357 
 
 16630 
 16071 
 
 5590 
 
 The distance of the required point from the end of the beam is therefore 0-69 feet or 8-28 
 inches, and the distance from the end of the radius bar is 1-31 feet or 1 foot 3- 72 inches. 
 
 N.B. As a check against any gross blunder, the distances multiplied by the respective lengths 
 of the beam and radius bar ought to give nearly equal results. In the present case 
 
218 APPENDIX. 
 
 they give 4'83 and 5-24. For short strokes, however, they ought to come much 
 nearer. 
 
 21. To find the length of the radius bar. 
 
 I. When the radius bar and piston rod are attached to the links at the same distance 
 from the beam. 
 
 RULE. First, From the radius of the beam, divided by twice the length of the parallel bar, 
 subtract unity. 
 
 Secondly, Find the square root of the difference between the square of the radius of the 
 beam, and the square of the half length of the stroke, and add this root to the radius of the 
 beam. 
 
 Thirdly, Multiply together the numbers so found, and the product added to the length of 
 the parallel bar will give the length of the radius bar. (235.) 
 
 Example. Let the radius of the beam be 11 feet, the length of stroke 5, and the length of 
 the parallel bar 4 feet. 
 
 First operation. 
 
 Parallel bar 4 feet 
 2 
 
 8 
 
 Second operation. 
 Stroke 5 feet 
 
 Half 2-5 
 2-5 
 
 8)11 
 
 1-375 
 Subtract 1 
 
 375 > 
 
 Beam 11 feet 
 11 
 
 121 
 
 125 
 50 
 
 6-25 6-25 
 
 114-75 
 
 Square root 10'7l 
 Beam 11 
 
 21-71 
 
 1 This difference may sometimes be negative ; in that case the final product must be subtracted from the length of the 
 parallel bar (see next Example). 
 
RULES FOR CALCULATING THE STEAM ENGINE. 219 
 
 Third operation. 21'7l 
 
 375 
 
 10855 
 15197 
 6513 
 
 8-14125 
 Parallel bar 4 
 
 Radius bar 12-14 feet. 
 
 II. When the radius bar and piston rod are attached to the links at different distances 
 from the beam. 
 
 RULE. Multiply the radius of the beam by the distance of the radius bar, and divide the 
 product by the distance of the piston rod or cross head, for the prepared length of the beam. 
 
 Also, multiply the length of the stroke by the distance of the radius bar, and divide the 
 product by the distance of the piston rod, for the prepared length of stroke. 
 
 And to the length of the parallel bar add the prepared length of the beam, and subtract 
 its true length, for the prepared length of the parallel bar. 
 
 The values thus deduced will then be the lengths of the beam, stroke, and parallel bar, 
 prepared for the calculation of the length of the radius, according to Rule I. (236.) 
 
 Example. Let the radius of the beam be 64 inches, the parallel bar 50 inches, the stroke 
 42 inches, the radius bar connected 68 inches from the beam, and the piston rod con- 
 nected 84 inches from the beam. 
 
 Beam 64 Stroke 42 
 
 68 68 
 
 512 336 
 
 384 252 
 
 84) 4352 (51-81, 84) 2856 (34, prepared stroke. 
 420 prepared beam 252 
 
 152 336 
 
 84 336 
 
 680 * 
 
 672 
 
 80 51-81 
 
 Parallel bar 50-00 
 
 101-81 
 Beam 64-00 
 
 37*81 prepared parallel bar. 
 2 
 
 75-62 
 
220 
 
 APPENDIX. 
 
 75-62) 51-810 ( 0-6851 
 453/2 1-0000 
 
 Beam 51-81 
 51-81 
 
 Half stroke 
 
 64380 -3149 
 60496 
 
 38840 
 37810 
 
 10300 
 
 5181 
 41448 
 5181 
 25905 
 
 2684-2761 
 
 289- 
 
 2395-2761 (48-94 
 
 16 51-81 beam 
 
 17 
 
 119 
 
 17 
 
 289 
 
 881795 
 704 
 
 969|9127 
 
 8721 
 
 9784|40661 
 
 100-75 
 -31 49 
 
 100-75 
 
 90675 
 40300 
 10075 
 30225 
 
 -31-726175 
 Parallel bar 37'8l 
 
 Radius bar 6-08 inches. 
 
 22. To find the lengths of the parallel bar and radius bar, when the latter works from a 
 stated centre, as is generally the case for marine engines. 
 
 RULE. Prepare the lengths of the beam and stroke as directed in the last rule, and then 
 proceed as follows : 
 
 From the square of the radius of the beam subtract the square of half the length of stroke, 
 and take the square root of the remainder. 
 
 To this square root add the horizontal distance between the centres of the beam and radius 
 bar ; to the same root add the radius of the beam. 
 
 Multiply the latter of these into half the radius of the beam, and divide by the former ; 
 then the quotient subtracted from the radius of the beam will give the distance of the con- 
 necting bar from the centre of the beam. 
 
 By subtracting this distance from the true radius of the beam, we get the length of the 
 
RULES FOR CALCULATING THE STEAM ENGINE. 221 
 
 parallel bar ; and by subtracting it from the horizontal distance of the centres we get the 
 length of the radius rod. (233.) 
 
 Example. Taking the same case as that of the preceding rule, we shall have the radius of 
 the beam 64 inches, the length of stroke 42 inches, the radius rod connected 68 inches 
 from the beam, the piston rod connected 84 inches from the beam, and the horizontal 
 distance between the centres of the radius bar and beam 20-08 inches, to find the 
 suitable lengths of the parallel bar and radius bar. 
 
 Beam 64 Stroke 42 
 
 68 68 
 
 512 336 
 
 384 252 
 
 84) 4352 (51-81, prepared beam 84) 2856 (34, prepared stroke. 
 420 252 
 
 152 336 
 
 84 336 
 
 680 * 
 
 672 
 
 80 
 
 Beam 51-81 Half stroke 17 
 
 51-81 17 
 
 5181 119 
 
 41448 17 
 
 5181 
 25905 
 
 2684-2761 
 289 
 
 2395-2761 ( 48-94 - ... 48'94 
 
 16 Hor. dist. I OA AQ Beam 51-81 
 
 centres / 2( 
 
 881795 100-75 
 
 4 Half beam 25-9 
 
 90675 
 8721 50375 
 
 9784 I 40661 2015 
 
 2609-425 
 
222 APPENDIX. 
 
 69-02)2609-425 (37'81 
 20706 
 
 53882 
 48314 
 
 55685 
 55216 
 
 4690 
 
 Beam 51*81 
 Subtract 37'81 
 
 14'00 connecting bar from centre of beam. 
 
 True radius of beam 64 Hor. dist. of centres 20-08 
 14 14 
 
 Parallel bar 50 inches. Radius bar 6-08 inches. 
 These results exactly correspond with the original data. 
 
 Note 1. For marine engines, the distance from the beam at which the radius bar is con- 
 nected, is the perpendicular height of the centre of the radius bar above the axis of the beam 
 when horizontal ; and the distance at which the piston rod is connected is the perpendicular 
 height of the cross head above the axis of the beam at half stroke, and may be found by 
 taking the height of the lowest position of the cross head, and increasing it by half the length 
 of the stroke. 
 
 Also, the length of the connecting rod which works the crank is the perpendicular distance 
 between the centre of the shaft and the centre of the beam. 
 
 Note 2. Calculations of parallel motions will be rather more accurate if the length of stroke 
 be diminished by its one-sixth part, before it is used ; and in fitting them they should be 
 adjusted at one-sixth of the half stroke from each end, instead of the top and bottom of the 
 stroke. 
 
 PRESSURE ON THE PISTON. 
 
 23. To find the mean pressure of the steam on the piston when it is worked expansively. 
 
 RULE. Divide the length of the stroke by the distance the piston moves before the steam 
 is shut off, and the quotient will express the relative expansion it undergoes. With this 
 number take out the multiplier from the annexed table, and multiply it into the full pressure 
 per square inch of the steam on entering the cylinder. The product will be the mean pressure 
 per inch, or that pressure which, continued uniformly throughout the whole length of the 
 stroke, would produce the same effect. (155.) 
 
RULES FOR CALCULATING THE STEAM ENGINE. 
 
 223 
 
 MULTIPLIER for MEAN PRESSURE of Steam worked EXPANSIVELY. 
 
 Relative 
 Expansion. 
 
 Multiplier. 
 
 Relative 
 Expansion. 
 
 Multiplier. 
 
 Relative 
 Expansion. 
 
 Multiplier. 
 
 Relative 
 Expansion. 
 
 Multiplier. 
 
 1-000 
 
 i-oooo 43 
 
 2-000 
 
 0-8466 ... 
 
 3-000 
 
 0.6995 120 
 
 4-000 
 
 0-5966 g g 
 
 1-100 
 
 0-9957 104 
 
 2-100 
 
 8295 
 
 3-100 
 
 6875 
 
 4-100 
 
 5880 , 
 
 1-200 
 
 9853 
 
 2-200 
 
 8129 
 
 3-200 
 
 676 2 
 
 4-200 
 
 5798 ' 
 
 1-300 
 
 9710 " 
 
 2-300 
 
 7968 J 
 
 3-300 
 
 6648 I 12 
 
 4-300 
 
 5718 ." 
 
 1-400 
 
 9546 : 
 
 2-400 
 
 7814 J 
 
 3-400 
 
 6540 1( 
 
 4-400 
 
 5640 " 
 
 1-500 
 
 9370 l '* 
 
 2-500 
 
 7665 149 
 
 3-500 
 
 6436 J 
 
 4-500 
 
 5564 'I 
 
 1-600 
 
 9188 1! 
 
 2-600 
 
 7521 ! 
 
 3-600 
 
 6336 1( 
 
 4-600 
 
 5491 7 
 
 1-700 
 
 9004 1( 
 
 2-700 
 
 7382 l ~ 
 
 3-700 
 
 6239 97 
 
 4-700 
 
 5420 71 
 
 1-800 
 
 8821 183 
 
 2-800 
 
 7249 133 
 
 3-800 
 
 6145 94 
 
 4-800 
 
 5351 69 
 
 1-900 
 
 8641 18 
 
 2-900 
 
 7120 129 
 
 3-900 
 
 6054 91 
 
 4-900 
 
 5284 67 
 
 2-000 
 
 0-8466 l75 
 
 3-000 
 
 0-6995 125 
 
 4-000 
 
 0-5966 88 
 
 5-000 
 
 0-5219 65 
 
 Example. Suppose the steam to enter the cylinders at a pressure of 50 fts. on the square 
 inch, and to be shut off after the piston has moved 16 inches ; and let the length of 
 stroke be 4 feet 6 inches or 54 inches. 
 
 16) 54 (3-375, relative expansion. 
 
 48 
 
 60 
 
 48 
 
 120 
 
 112 
 
 80 
 80 
 
 The relative expansion falls between 3'3 and 3'4. Referring to the table, the multiplier for 
 3'3 is 0*6648 ; and in passing to 3'4 we see that it decreases by the printed difference 108. 
 Hence, multiplying 108 by '75 and subtracting the product 81 from 0'6648, the remainder 
 0-6567 is the multiplier answering to 3'375. Therefore, multiply 0-6567 by 50 16s. and we 
 have 32-83 Ibs. per square inch, the mean pressure required. 
 
 In practice a small extra portion of steam will occupy the clearance of the cylinder. The 
 power of this portion is obviously lost at the beginning of the stroke, but when the steam is 
 shut off, it will evidently afford some slight assistance in the expansion, since a greater volume 
 of steam must lose less pressure in expanding through the same distance. The additional aid 
 thus derived is, however, extremely small in respect of the portion of steam expended ; and as 
 the quantity of clearance is generally very small (the smaller the better) the effect of it is dis- 
 regarded in the above rule. It would be of little avail to include the effect of the clearance of 
 the cylinder, when .the influence of other causes, such as friction, waste, &c., which vary in 
 different engines, can be but imperfectly estimated. In cases, if there be any, where the 
 accuracy of information on these points is such as to be relied upon, the following rule may be 
 adopted. 
 
 RULE. To the distance moved by the piston before the steam is cut off, and to the actual 
 
224 APPENDIX. 
 
 length of the stroke of the piston, add the length of the clearance, and call the sums the 
 increased distance and the increased stroke. Divide the increased stroke by the increased 
 distance, and the quotient will express the true relative expansion of the steam. With this 
 number take out the multiplier from the table, and multiply it into the increased stroke ; the 
 product will represent the entire effort of the steam. From this subtract the length of clear- 
 ance, and the remainder will be the actual effort. Lastly, multiply the actual effort by the 
 full pressure per square inch in the cylinder, and divide the product by the actual length of 
 stroke, and the result will be the mean pressure of the steam exercised upon each square inch 
 of the piston. 
 
 The latter part of the rule may be more simply performed thus : having taken out the 
 multiplier, subtract it from 1-0000, multiply the remainder by the length of the clearance, and 
 divide the product by the true length of stroke. Subtract the quotient from the multiplier, 
 and the remainder will be the corrected multiplier, to be multiplied into the full pressure to 
 get the mean pressure. 
 
 Example. Take the preceding example, and suppose the clearance of the cylinder to be one 
 inch at each end. 
 
 Distance 16 inches Stroke 54 inches 
 
 Clearance 1 Clearance 1 
 
 17 55 
 
 17) 55 (3-235, relative expansion 
 51 
 
 40 
 34 
 
 60 
 51 
 
 90 
 
 With 3-235 we find multiplier, from table, 0-6721. 
 1-0000 
 0-6721 0-6721 
 
 0-3279 
 Clearance 1 
 
 Stroke 54) -3279 (61 - - - Subtract 61 
 324 
 0-6660 
 
 39 Pressure 50 tfes. 
 
 Mean pressure 33-300 tbs. per square inch. 
 
 The former rule, which supposes no clearance, gave 32-83. It hence appears that the addi- 
 tional -f^th'of the quantity of steam used only increases the mean pressure by 0*47, or about 
 \ Tb. on each square inch. 
 
RULES FOR CALCULATING THE STEAM ENGINE. 225 
 
 The preceding rules determine the mean pressure, which is equivalent to the entire action 
 of the steam. To get the mean effective pressure it must be diminished by an estimated 
 amount of the resistance and friction of the parts of the engine ; and for condensing engines 
 an addition of about 13 Tbs. per square inch must be added as the pressure acquired by the 
 partial vacuum. 
 
 POWER. 
 
 24. To find the power of an engine. 
 
 -f 
 RULE. Multiply double the length of stroke by the number of strokes per minute, and we 
 
 get the velocity of the piston per minute. 
 
 If the engine works expansively, find the mean effective pressure by the foregoing rules. 
 
 Multiply the square of the cylinder's diameter in inches by the mean effective pressure on 
 the piston in Tbs. per square inch, and by the velocity of the piston ; point off three figures 
 and divide the product by 42, and the quotient will express the number of horses' power. (197.) 
 
 Example. Let the diameter of the cylinder be 36 inches, the length of stroke 4 feet, the 
 number of strokes per minute 24, and the mean effective pressure on the piston 4 Tbs. 
 per square inch. 
 
 8 feet x 24 = 192 feet per minute 
 Diameter 36 inches 
 36 
 
 216 
 108 
 
 1296 
 Mean pressure 4 Tbs. 
 
 5184 
 Velocity 192 feet 
 
 10368 
 46656 
 
 5184 
 
 42) 995)328 (23'7 horse power. 
 
 84 
 
 155 
 
 126 
 
 293 
 
 25. To find the quantity of water required for steam. 
 
 RULE. Find the volume of steam from a cubic foot of water by rule No. 2. 
 
 Multiply the square of the diameter of the cylinder in inches by half the velocity of the 
 piston in inches, or six times the velocity in feet per minute ; cut off two figures from the 
 right hand, divide by 11, and the quotient will express the cubic feet of steam effectively 
 
226 APPENDIX. 
 
 expended per minute. Divide this by the volume from a cubic foot of water, and we get the 
 cubic feet of water required per minute. 
 
 Example. Let the diameter of the cylinder be 30 inches, the velocity of the piston 120 feet 
 per minute, the temperature of the steam 250, and its elastic force 29 Ibs. on the 
 square inch. 
 
 250 
 Add 459 
 
 709 
 Multiply by 38 
 
 5672 
 
 2127 
 
 Elastic force 29) 26942 (929 cubic feet of steam 
 261 from 1 cubic foot of 
 
 water. 
 
 58 
 
 262 
 
 Diameter 30 inches 
 30 
 
 900 
 6 x 120 = 720 
 
 Divide by 11) 6480|00 
 
 589 cubic feet of steam per minute. 
 
 929) 589-0 (0-634 cubic foot of water 
 
 5574 required per minute. 
 
 3160 
 
 2787 
 
 3730 
 
 Some addition should be made to the result for clearance of the cylinder, escape through the 
 valves, and waste. 
 
 The quantity of water required serves to determine the dimensions of the hot water pump. 
 
 About 12 times the quantity is necessary for condensation. 
 
 LOCOMOTIVE ENGINES. 
 
 26. To find the effective force of gravity when an engine and train are running"upon an in- 
 clined plane. 
 
 RULE. Multiply the gross load in tons by 2240 and divide the product by the length of 
 
RULES FOR CALCULATING THE STEAM ENGINE. 227 
 
 the plane corresponding to an ascent or descent of unity. The quotient will be the force in 
 fts. acting down the plane. 
 
 Example. Let the engine be 12 tons, the tender 7 tons, and the carriages and load 105 
 tons; and suppose the inclination of the railway to be 1 in 128. 
 
 Engine 12 tons. 
 Tender 7 
 Train 105 
 
 Gross load 124 
 Multiply by 2240 
 
 4960 
 248 
 248 . 
 
 128) 277760 (2170 tfcs., the force required. 
 256 
 
 217 
 128 
 
 896 
 896 
 
 27. To find the tension on the circumference of the driving wheels, or the resistance to 
 traction. 
 
 RULE. Multiply the gross load, expressed in tons, by 8, and the product will be the 
 number of tfcs. resistance if the engine and train move horizontally : for ascending an inclined 
 plane the effect of gravity, calculated by the last rule, must be added; and for descending an 
 inclined plane the effect of gravity must be subtracted. 
 
 Example. Take the same case as before. 
 
 Engine 12 tons. 
 Tender 7 
 Train 105 
 
 124 
 
 8 
 
 992 fts. traction on a horizontal line of railway. 
 
 If the engine and train be ascending an incline of 1 in 128, we have by the example of 
 last rule, 
 
 Effect of gravity 2 1 70 Ibs. 
 Add 992 
 
 3162 Ibs. traction up the plane. 
 
228 
 
 APPENDIX. 
 
 28. To find the pressure of the steam in the cylinder. 
 
 RULE. Determine the resistance to traction by the last rule; add to it an eighth part for 
 the additional friction it causes on the engine, and 6 Its. per ton of the weight of the engine 
 for its own separate friction. The sum will express the whole force or resistance to be 
 . overcome by the engine. Multiply this resistance at the circumference of the wheel by its 
 diameter in inches, and then divide by the product of the square of the diameter of the 
 cylinder into the length of the stroke. The quotient will express the effective pressure on 
 the piston in fts. per square inch ; and, adding 14*7 ft>s. for the pressure of the atmosphere, 
 the result will be the pressure of the steam in Tbs. per square inch. 
 
 Example 1. The weight of the engine is 12 tons, the tender 7 tons, the train 50 tons, the 
 diameter of the driving wheels 54 inches, the diameter of the cylinder 12 inches, and the 
 length of the stroke 18 inches. It is required to find the pressure of steam in the cylinder to 
 sustain an uniform velocity up an incline of 1 in 140. 
 
 tons. Gross load 69 
 
 2240 
 
 Engine 
 
 12 
 
 Tender 
 
 7 
 
 Train 
 
 50 
 
 Gross load 
 
 69 
 
 
 8 
 
 Horizontal traction 552 Its. 
 
 20160 
 13440 
 
 140) 154560 (1104 Its. effect of gravity. 
 140 
 
 145 
 140 
 
 560 
 560 
 
 Gravity 1104 Ibs. 
 Horizontal traction 552 
 
 Diameter 
 cylinder / 
 
 Inclined traction 1656 up the plane. 
 Additional friction 207 one-eighth. 
 Engine 72 
 
 12 
 12 
 
 Resistance 1935 
 Wheel 54 
 
 144 
 Stroke 18 
 
 1152 
 144 
 
 2592) 104490 ( 40-3 fl5s. effective pressure. 
 10368 14'7 atmospheric 
 
 Divisor 2592 
 
 8100 
 7776 
 
 324 
 
 55'0 Ibs. pressure of steam per square 
 inch. 
 
 The consumption of water may hence be calculated by No. 25. 
 
RULES FOR CALCULATING THE STEAM ENGINE. 229 
 
 *#* The two preceding rules are founded on the Chev. de Tambour's estimation of the 
 resistances experienced by locomotive engines, stated at the foot of page 185 ; which are, 
 doubtless, good approximations to the truth with the usual proportions and velocities of 
 locomotives ; but it should be observed, that in the determination of these resistances, the 
 experimental data are all necessarily affected by the resistance of the atmosphere, which varies 
 nearly as the square of the velocity. It is evident that the results must involve an average 
 value of the atmospheric resistance for the experiments adopted, and that no material cor- 
 rection will therefore be required, on account of the atmosphere, with ordinary velocities, 
 though some additional resistance should be added for very high velocities. It may also be 
 a question whether the resistance of the carriages, &c., would at all be affected by altering 
 the diameters of the running wheels. 
 
 29. To determine the power of a locomotive engine. 
 
 RULE. Find the effective pressure on the piston by the last rule, and thence the power ^ , 
 by the rule of No. 24. 
 
 The following method, however, will be found to be more convenient and useful in practice. 
 
 Calculate the resistance by the last rule ; multiply by 8 times the velocity in miles per 
 hour ; point off 3 figures from the right hand, and divide by 3. The result will express the 
 number of horses' power. 
 
 Example. Take the last case, and suppose the velocity to be 12 miles an hour. 
 The resistance has already been calculated, 1935 Tbs. 
 
 Resistance 1935 tfes. 
 
 8 times speed 96 miles. 
 
 11610 
 
 17415 
 
 3) 185-760 
 
 61-92 horse power. 
 
 30. The power of a locomotive engine being known, it is required to determine the speed 
 under any given circumstances of load, inclination of railway, &c. 
 
 RULE. Find the whole resistance in ffis. overcome, by the rule of No. 28 ; multiply the 
 number of horses' power by 375, and the product will be a constant number to be divided by 
 the resistance to obtain the velocity in miles per hour. 
 
 Example. Taking the same case as before, we have, 
 
 Horse power 61-92 
 375 
 
 30960 
 43344 
 18576 
 
 Constant number 23220-00 
 
230 APPENDIX. 
 
 Resistance 1935) 23220 (12 miles per hour in ascending the plane. 
 1935 
 
 38/0 
 
 3870 
 
 * 
 For the velocity when the railway is horizontal, we have, 
 
 Horizontal traction 552 Tbs. 
 Additional friction 69 
 Engine 72 
 
 Resistance 693) 23220 (33-5 miles per hour. 
 2079 
 
 2430 
 2079 
 
 351 
 
 The force arising from gravity being greater than the horizontal traction, in this example, 
 the carriages would of themselves run down the inclined plane with an accelerated velocity ; 
 and this would be the case on all inclinations greater than 1 in 280. 
 
 Example 2. To find the greatest uniform velocity of the same engine and train down an 
 inclination of 1 in 600. 
 
 Engine 12 tons. Gross load 69 
 
 Tender 7 224 
 
 Train 
 
 Gross load 69 13440 
 
 _ 6,00) 1545,60 
 
 Horizontal traction 552 Ifes. 
 
 257-6 IDS. erlect of gravity. 
 
 Horizontal traction 552-0 ffis. 
 Gravity 257'6 
 
 Inclined traction 294*4 down the plane. 
 Additional friction 36-8 one-eighth. 
 Engine 72'0 
 
 Resistance 403-2 
 
 403-2) 23220-0 (57'6 miles per hour. 
 20160 
 
 30600 
 
 28224 
 
 2376 
 
RULES FOR CALCULATING THE STEAM ENGINE. 231 
 
 The velocity would, therefore, be about 57i miles per hour; but this is sure to be in 
 excess, since at such high velocities the resistance offered by the atmosphere must be very 
 considerable. 
 
 For any particular engine the constant number, which forms the dividend, when once 
 prepared, will be ready for general application. 
 
 In the calculation of the average speed, the distances traversed, or the times of transit, due 
 allowances should be made for the intervals spent in the generation of motion. Nearly 
 one-half of the time elapsed, or one-half of the distances passed over, in the gradual pro- 
 duction and annihilation of the velocities, may be considered as lost. 
 
 FORMULAE for calculating the effects of the SCREW PROPELLER, when applied to 
 
 steam vessels. 
 
 r = the radius of the screw in feet. 
 
 h = the pitch, also in feet. 
 
 TT = 3-14159 log. TT = 0-49715. 
 
 log. c =7-75506. 
 
 2 ff 550 
 
 log. 2 IT - 0-79818. 
 
 2 7T 
 
 v = the velocity of the vessel in feet per second, or the velocity in miles per hour mul- 
 tiplied into if. 
 
 u = the velocity of a point in the screw at the distance k from the axis. 
 S = the effective resisting surface of the vessel. 
 
 Number of revolutions per second = . 
 
 h 
 
 Horse power of engine = c A (u v) 2 . u 
 Horse power effective = c A (u v) 2 . v 
 
 In the absence of better information, the value of S may be roughly estimated at about 
 one-fifth or one-sixth of (tonnage)T, according to the construction of the vessel. 
 
 The larger the diameter and the less the pitch of the screw, the greater will be the pro- 
 portion of effective power on the vessel. 
 
ERRATA, &c. 
 
 Page 155 line 3 from bottom, omit = at the end. 
 
 158 Tredgold has made use of the moment of the pressure of the steam instead of the actual 
 pressure on the parts. 
 
 The force at the distance x from E is/y d x, which multiplied into 2 it (r + x), the space 
 described, gives Ifnydx (r + x) ; and the integral is fir a y (2 r + a), the power expended 
 on each revolution. It is hence plain that no power is lost, the factor n a y (2 r + a) being 
 
 the volume of steam employed at the pressure/. 
 1641 
 
 jgg | Arts. 333, 342, foot-notes and other parts depending on the same, are incorrect in principle. 
 
 The greatest effect is generally produced with the least velocity ; the effect being the 
 effective force multiplied into the space through which it is exerted. 
 ,, 263 line 11 from bottom, for second read minute. 
 ,, 393 lines 4 and 5 from bottom, transpose LXII. and LXIII. 
 
 APPENDIX. 
 
 Page 128 at the bottom on the left, for r a 3 sin. ft read 2 r a 3 sin. /3. 
 
 Plate xi. The adjustment of the parallel motion is wrong ; the same radius bar will not do for both 
 ends of the beam. In the plate, the motions for the cylinders and air pump are correct; but 
 the pump rods on the left cannot move in straight lines with such an arrangement. 
 
 We are indebted to Professor Willis, of Cambridge, for a notice of this error. 
 
INDEX. 
 
 A. 
 
 ' ABORTION of the Young Steam Engineer's 
 
 Guide' . . .43 
 
 Achard . . .30 
 
 Agricultural purposes, engines for . 282 
 
 Air . . . .86 
 
 and steam mixed . . 84, 86 
 
 engine . . .8 
 
 motion of . .87 
 - pump . 24, 25, 86, 167, 170, 190 
 
 proportion of . 167 170 
 
 power required to work 170 172 
 
 rods . . 242 
 
 -for fires . . 119, 120 
 
 flues . . .134 
 
 regulator . . .138 
 Alcohol vapour, force of . 30, 32, 39, 72 
 
 engine . . .34 
 
 latent heat of . . 53, 55 
 
 effect as fuel . .109 
 
 Ammonia . . 55, 79, 82 
 
 Amonton's engine . 8, 16 
 
 Apparatus for boilers . .135 
 
 Arsberger's, Professor, experiments on high 
 
 pressure steam . . 71, 72 
 
 Ash pit . . . .115 
 
 Atlantic steam navigation . App. 101 
 
 remarks on App. 24 
 
 Atmosphere, pressure of . . 80, 89 
 
 Atmospheric engine 9, 10, 23, 24, 36, 96, 149, 185 
 
 effect of . 33, 34, 36 
 
 improved . 40, 189 
 
 piston . . 216 
 
 Austen, Capt. Horatio . App. 82 
 
 Ayre's, Richard, contrivance for preventing 
 
 engines from running off a railway 403 
 
 B. 
 
 PAGE 
 
 Banks, John . . .33 
 
 Baldock, Lieut., his form of steam journal 
 
 App. 3139 
 's memoir of H. M. steam ship the 
 
 Medea . . App. 80 100 
 
 Barlow, P., of the Royal Military Academy, his 
 
 reports of experiments on steam vessels 
 
 App. 63, 64 
 
 Barlow, P. W., on steam vessels App. 40 
 
 Barton's piston . . .219 
 
 stuffing boxes . . 222 
 
 Beale, J., his rotary engine (Plates 71, 72) 401 
 Beam, working . . . 10, 20 
 
 angular movement of limited . 24 1 
 
 strength of . . 242 
 
 Beauty essential to perfect engines . 202 
 Beighton, Henry . . .12 
 
 Behdor, Bernard . .15,210,211,215 
 
 Bell, Henry . . . 44, 45 
 
 steam navigation in Britain success- 
 fully introduced by .45 
 Berenice, Hon. East India Company's vessel 
 
 (Plates 70 A, 70-B, 95, 96) 400, 471 
 
 Bettancourt . . 32, 63, 211 
 
 Bevan, B., experiment by . . 294 
 
 Black, Dr. Joseph . . . 21, 49 
 
 's definition of latent heat . 21, 48 
 
 capacity for heat . 21 
 
 Blake, Francis . . .18 
 
 Blakey, John . . . 24, 128 
 
 Blowing through . . .199 
 
 machines . . . 281 
 
 Boats, steam . . 14,31,313,316 
 
 steam engines for . 312, 313 
 
 canal 294 
 
234 
 
 INDEX. 
 
 Boiler with internal flue 
 
 tube 
 
 Boilers, cast iron 
 
 formed of plates 
 
 copper 
 
 construction of copper 
 
 PAOE 
 
 . 21, 22 
 
 25 
 
 253 
 
 251, App. 8 
 
 . App. 4 
 
 App. 10 
 
 of the African steam vessel of war, 
 
 description of (Plate 22) 
 of the Medea steam vessel of war, 
 
 description of (Plate 23) 
 
 surface for fire 
 
 space for steam and water in 
 
 power of low pressure 
 
 number of . 
 
 form of 
 
 355 
 
 - Watt's . 
 
 strength of 
 
 size of 
 
 cylindrical 
 
 roles for . 
 
 spherical . 
 
 tubular 
 
 Rumford's 
 
 - Woolf's . 
 
 with internal fires 
 
 steam carriage 
 
 supply 
 
 steam boat 
 
 high pressure 
 
 portable 
 
 apparatus for 
 
 116 
 
 120, 122 
 123 
 124 
 ibid 
 125 
 
 249, 251, 252 
 
 126, 133 
 
 126, 260 
 
 125, 126 
 
 253 
 
 254 
 
 128 
 
 129 
 
 130 
 
 130, 132 
 
 130, 135, 136, 143 
 131 
 136 
 132 
 135 
 
 supply of with water . 135, 136 
 
 practical roles for . App. 207 
 
 marine . . . App. 1 
 
 uses of roman cement for App. 5,11 
 
 coating for . App. 1 6 
 
 incrustation of not greater in 
 
 a voyage to the Mediterranean, than on 
 any other voyage of similar duration App. 3 
 ^ circulating pipes and dampers 
 for . . . . App. 13 
 
 brine pump for App. 2, 3 
 
 Maudslay and Field's, expe- 
 riments on . . App. 2 
 
 bio wing- off cocks . App. 6 
 
 Kingston's safety valve for App. 7 
 
 PAGE 
 Boilers, marine, water ways of . App. 20 
 
 flues of . . App. 21 
 
 detector pipe for . App. 21 
 
 glass water gauges and cop- 
 
 per floats for . 
 reverse valves for 
 
 App. 22 
 App. 22 
 
 60 
 , 32, 291 
 
 29 
 
 Boiling point of solutions 
 
 Bossut . 
 
 Boulton 
 
 Boulton and Watt . 
 
 . 24, 163, 170, 192, 195, 208, 218 
 Bramah, Joseph . . 32, 40, 215, 222 
 
 Bramah and Dickinson's rotary engine . 32 
 
 's slide valve . . 207 
 
 's four-way cock . . 212 
 
 Brindley . . '.21 
 
 Brunei . . . .81 
 
 Brunton's fire place . .134 
 
 Bucket, air pump . . . 205 
 
 Bury, Edward, of Liverpool (Plates of the 
 
 Tiger's marine engines 111, and 111 A) 497 
 
 C. 
 
 Cagniard de la Tour, experiments by 71,73,75,78 
 Canal, Table I. of experiments made on the 
 
 Forth and Clyde . App. 201 
 
 Table II. Monkland . . ibid 
 
 Canal boats . . . 294 
 
 Carbon, effect as fuel . .107 
 
 Carbonic acid . . . 80, 81 
 
 Carburet of sulphur . . 77 
 
 Carriage, steam (Plate 20) . 
 
 42, 119, 120, 132, 284, 403, 407 
 Cartwright, Dr. Edmund . 34, 218, 223 
 
 's engines . . 35 
 
 's piston . 34, 35, 218 
 
 Cataract . . 23, 265 
 
 Cements . . . 254 
 
 iron . . . ibid 
 
 Centre of pressure of a paddle App. 44 
 investigation 
 
 of . . . App. 45 
 
 Charcoal, effect of . . .107 
 
 Chase water engine . 23, 188, 216 
 
 Chelsea water-works engine (Plates 84, 85, 
 
 86, 87, 88) . . . 404 
 
IXDEX. 
 
 235 
 
 Chimney, ascent of smoke in . 
 
 areas 
 
 tops 
 
 practical rule for 
 
 Christian, experiments by 
 
 Clack valve 
 
 Clement, M. 
 
 Clinkers 
 
 Coal, effect of 
 
 engines for drawing 
 
 PAGE 
 100 
 145 
 146 
 
 App. 211 
 72 
 
 204, 205 
 71 
 
 133, 134 
 
 17, 112, 113 
 
 279 
 
 Cock, four- way, to cut off steam at any 
 
 portion of the stroke . 13,40,211,212 
 
 double passaged . . 213 
 
 Cocks . . . 203, 211 
 
 construction of . . 211 
 
 Coke . . . 112, 115 
 
 Colchis and Jason, Russian steam ships of 
 war (Plates of engines and vessels 43, 
 44, 45, 46, 108, 109, 110) 369, 492 
 
 Combined engines 29, 181, 185, 186, 199 
 
 Combustion and combustibles 105, 114 
 
 Combustion, process of . . 114 
 
 Comet, first steam boat in Europe (Plate 93) 470 
 Condensation . . 6, 25, 34, 146 
 
 principles of . 146, 150 
 
 Condensers . 26, 27, 34, 86, 169 
 
 Condenser gauge . . . 266 
 
 Condensing engines, nature of .184 
 
 construction of . 186 
 
 proportion of parts 
 
 187, 190, 192, 195 
 
 power of 
 
 188, 190, 191, 196, 198, 201 
 
 application of 189, 191, 197 
 
 Conical valves . . . 205 
 
 pendulum . . 261, 263 
 
 practical rules for App. 213 
 
 Connecting rod . . 229, 230, 242 
 
 to find the length of . 238 
 
 Contractions in pipes, effect of . 88 
 
 Copper, precipitation of, by iron -App. 5 
 
 funnels, failure of . -App. 12 
 
 boilers, advantages of . ibid 
 
 Corn mills . . .284 
 
 Cornish reports . . 276, 277, 278 
 
 Cooling, loss of force by . . 92, 95 
 
 PAGE 
 
 Cotton mills . . .282 
 
 Counter . . . 270 
 
 Counter weight . . 10, 194, 256, 260 
 
 Crampton, T., his drawings of Hague's 
 
 slides (Plate 69) 
 Crank . . 27, 228 
 
 strength of . . . 243 
 
 table of the variation of rotary force of 230 
 
 action of . . App. 1 73 
 
 expression for effective leverage of App. 1 75 
 
 expressions for angular velocity of for 
 
 one engine . . App. 177 
 expression for deviation from mean 
 
 value of angular velocity . ibid 
 expressions for angular velocity of, 
 
 for a pair of engines . -^pp. 180 
 expressions for greatest deviation from 
 
 mean value . . . ibid 
 
 position of, when velocity is greatest 
 
 App. 180 
 
 is least 
 
 Crawford, Dr. 21 , 
 
 311, 
 
 Creighton, W. 
 
 experiments by 
 
 Curr, John 
 
 Currents, resistance of 
 Cylinder, cooling in 
 
 ratio between length of stroke and 
 
 diameter of 
 proportions of 
 
 ibid 
 107, 108 
 51, 56 
 69 
 36 
 312 
 95 
 
 161 
 ibid 
 
 Cylinders, double, ratio of 
 practical rules for 
 
 182, 192 
 App. 211 
 
 Cycloidal paddle wheel of the Great West- 
 ern steam vessel (Plate 26) App. 53 
 
 D. 
 
 Dalton, John 
 
 40 
 
 experiments by 
 
 64, 65, 66, 74, 76; 79, 107, 108, 167 
 
 's mode of experimenting : 65 
 
 tables of experiments on the force 
 
 of steam of temperatures from 32 to 
 212 . . 66 
 
 Damper, regulated . . 37, 251 
 
 self regulating . . 137 
 
 Davy, Sir H. . . . 80, 114 
 
236 
 
 INDEX. 
 
 Davy, C. (Plates 64, 65, 66, 67 A, 67 B) 
 Dead plate . . .132 
 
 D slide . . . .195 
 
 Density of steam . . .16,83 
 
 Desaguliers, J. T. . . . 14 
 
 Dickinson's and Bramah's engine 32 
 
 Dinnen, J., assistant engineer, Woolwich 
 
 Dock-yard, on marine boilers . App. 1 
 
 Ditchburn, T. J., (Plates of the Red Rover, 
 
 30, 31, 32) 
 Don Juan, engines of, Peninsula Company 
 
 (Plate 41) . . .368 
 
 Double acting engine . 27, 185, 195 
 
 for mines . 276 
 
 Drainage of mines . 275 
 
 Dupin, Baron . . .29 
 
 total extent of steam power 
 
 applied in Great Britain estimated by 46 
 
 E. 
 
 Eccentric motion 
 
 practical rule for 
 
 225 
 App. 213 
 
 Edward Anthony, United States' boat en- 
 gine (Plate 115) 
 
 Edelcrantz . . 141, 209 
 
 Eduction pipe . . .11 
 
 Effect, useful, how to measure . 269 
 
 Elastic fluids and vapours, motion of . 87 
 
 Elastic force of vapours . . 56 89 
 
 separated from the 
 
 liquids from which they were generated 82 
 of steam or vapour produced by 
 
 increased temperature does not follow 
 the same law, when it is not in contact 
 with the fluid from which it is gene- 
 rated, as when in contact . 58, 82 
 
 of steam . . 56, 89 
 
 rules for . . 58, 59 
 
 Electric fluid . . .45 
 
 Emerson, William . . 20, 226, 284 
 
 Engine, Amonton's . 8, 16 
 
 atmospheric . . 9, 10 
 
 improved . 40, 189 
 
 Cartwright's . . 35 
 
 condensing . .184 
 
 Dickinson's . 32 
 
 PAGE 
 Engine, double cylinder expansive . 181 
 
 expansive 
 
 27, 29, 33, 43, 167, 177, 194, 198 
 
 fire . . .25 
 
 Hornblower's . . 29 
 
 Newcomen's . 10,11,23 
 
 noncondensing . 1 73, 1 74 
 
 Papin's . . .8 
 
 portable . . .22 
 
 - rotary . 27, 28, 30, 32, 36, 40 
 
 Savery's . 5, 6, 17, 24, 36, 37 
 
 Stephensons" patent locomotive 407 469 
 
 water- commanding . . 2 
 
 Watt's . . 25, 26, 27, 28 
 
 Woolf's . . .94, 237 
 
 Worcester's, Marquis of . 3 
 
 Eohpile . . 1,2 
 
 Equalization of the motion of engines . 256 
 
 by a fly . . ibid 
 
 by counter weights . 260 
 
 Equilibrium of heat . . 47 
 
 Ether, sulphuric . . .75 
 
 latent heat of . . 54, 55 
 
 elastic force of . 75 
 
 Evans, Oliver . . 43,131,179 
 
 Expanding power of steam . 152,226 
 
 Expansive engine . 
 
 27, 29, 33, 43, 167, 177, 194, 198 
 
 double cylinder . . 181 
 
 Experiments, Arsberger's, on high pressure 
 
 steam . . .71 
 
 Cagniard de la Tour's on ether 75 
 
 Dalton's on the force of steam 66 
 
 on ether . . 76 
 
 Macneill's on canals App. 200, 201 
 
 Payne's on steam . 16,17 
 
 Robison's on the force of steam 64 
 
 Roy's on air and steam . 86 
 
 Rumford's on steam 52, 53, 54 
 
 Southern's on the force and 
 
 heat of steam . . 5 1 , 70 
 
 Taylor's on steam . 70 
 
 Ure's on vapour of alcohol . 74 
 
 ether . . 76 
 
 petroleum . 79 
 
 . force of steam . 69 
 
INDEX. 
 
 237 
 
 Experiments, Watt's on steam from salt water 62 
 from pure water ibid 
 
 on paddle wheels App. 42, 43, 47 
 
 additional, on paddle wheels App. 55 
 
 deductions from 56 
 
 description of, to ascertain the 
 
 effect of fixing the paddle boards at an 
 angle with the radius of the wheel 57 
 to ascertain the ratio of the 
 
 84 
 90 
 
 speed of a steam boat to the pressure 62 
 on H. M. ship Lightning ibid 
 
 - Dee - 64 
 
 - Phoenix 65 
 
 Explanation of plates . . 327 
 
 Expressions for the heat of conversion into 
 
 steam . . .50 
 
 finding the volume steam 
 
 will occupy under any compressive 
 force not exceeding 60 atmospheres 
 
 area of steam passages 
 
 loss of velocity of steam from 
 
 bends or obstructions in the pipes . 91 
 
 loss of force of steam by cool- 
 ing in passing through the steam pipe 92 
 
 loss by cooling cylinder . 99 
 
 area of chimneys 102, 103 
 
 fire surface . . 117 
 
 quantity of water for con- 
 densation . . . 147 
 
 power of the steam of a cubic 
 
 foot of water . . .155 
 
 power of steam of a cubic foot 
 
 of water when acting expansively . ibid 
 the greatest quantity of me- 
 
 chanical power the steam of a cubic 
 foot of water will give when acting 
 expansively . . .156 
 
 proportion of length of cy- 
 linder to diameter . 1 62 
 
 best velocity for the engine 
 
 to work with . . .164 
 
 capacity of air pump . 1 69 
 
 power required to work air 
 
 pump . . .171 
 
 friction of pistons 221, 222 
 
 circular force of crank . 229 
 
 Expressions for stress on the axis or shaft 229 
 
 length of radius rods for 
 
 parallel motion . 231, 233, 234, 235 
 
 - strength of rods subjected to 
 
 tensile strain . . . 240 
 
 piston rods . 241 
 
 cranks . 243 
 
 wheel arms . ibid 
 
 beams . . ibid 
 
 shafts . . 245 
 beam gudgeons . ibid 
 
 pipes and cylinders 247 
 
 flat plates to bear the 
 pressure of steam . 248 
 
 the greatest stress in tts. on 
 
 a circular inch a plate will bear . 249 
 
 strength of boilers formed of 
 plates . 251, 252 
 
 cast iron boilers . 253 
 
 fly wheels . . 259 
 
 counter weights . 260 
 
 paddle wheels . 303, 304 
 
 the angle when the effective 
 resistance of the paddle is greatest App. 49 
 
 effective leverage of crank 175 
 
 angular velocities of crank 
 
 for one engine . 177 
 
 deviation from mean value of 
 
 angular velocities . . ibid 
 
 angular velocities of a crank 
 
 for a pan- of engines . 1 80 
 
 the screw propeller applied 
 
 to steam vessels 231 
 
 F. 
 
 Fairbairn, W., of Manchester 392, 393 
 
 Faraday, Michael . 56, 60, 80, 81, App. 6 
 
 Feedpipe . . .135 
 
 Fenwick, Thomas . . . 40, 260 
 
 Field, Joshua . . 262, 272 
 
 'a valve . . . 262 
 
 Fincham, J., master shipwright, Sheerness 
 
 Dock-yard, (Plates 33, 34, 35, 36, 94, 
 
 104, 105, 106, 107) 
 Fire, management of . . 273 
 
 2 h 
 
238 
 
 INDEX. 
 
 PAGE 
 
 Fire grating, supply of air and area of . 115 
 
 rule for . App. 210 
 
 engine . . .25 
 
 - places . . .132 
 
 Watt's . . . ibid 
 
 Roberton's . .133 
 
 Brunton's . .134 
 
 regulation of . . . 137 
 
 Fitzgerald, Keane . . .20 
 
 Float . . . .135 
 
 Flues . . . .251 
 
 internal . . .125 
 
 Fluids . . . .47, 109 
 
 resistance of . . 292308 
 
 Flywheel . . 20, 163, 256 
 
 velocity of . .258 
 
 danger of . . ibid 
 
 rules for . . 259 
 
 Formula for the heat of conversion into 
 
 steam . . .50 
 
 finding the volume steam will 
 
 occupy under any compressive force 
 not exceeding 60 atmospheres 
 
 area of steam passages 
 
 loss of velocity of steam from 
 
 bends or obstructions in the pipes . 91 
 loss of force of steam by cool- 
 ing in passing through the steam pipe 92 
 
 loss by cooling cylinder 99 
 
 area of chimneys 102, 103 
 
 fire surface . . 117 
 
 quantity of water for conden- 
 sation . . . 147 
 
 power of the steam of a cubic 
 
 foot of water . . .155 
 
 power of steam of a cubic foot 
 
 of water when acting expansively . ibid 
 the greatest quantity of me- 
 
 84 
 90 
 
 chanical power the steam of a cubic 
 foot of water will give when acting 
 expansively . . . . 156 
 
 proportion of length of cy- 
 linder to diameter . .162 
 
 best velocity for the engine 
 
 to work with . . .164 
 
 capacity of air pump . 1 69 
 
 PAGE 
 Formula for power required to work air 
 
 pump . . .171 
 
 friction of pistons 221, 222 
 circular force of crank . 229 
 
 stress on the axis or shaft ibid 
 
 length of radius rods for pa- 
 rallel motion . 231,233,234,235 
 
 strength of rods subjected to 
 tensile strain . . . 240 
 
 piston rods . 241 
 
 cranks . .243 
 
 wheel arms . ibid 
 
 beams . . ibid 
 
 shafts . . 245 
 
 beam gudgeons . ibid 
 
 pipes and cylinders 247 
 flat plates to bear the 
 
 pressure of steam . .248 
 
 the greatest stress in B>s. on a 
 
 circular inch a plate will bear . 249 
 
 strength of boilers formed of 
 
 plates . . 251, 252 
 
 cast iron boilers . 253 
 
 fly wheels . .259 
 
 counter weights . 260 
 
 paddle wheels . 303, 304 
 
 the angle when the effective 
 
 resistance of the paddle is greatest App. 49 
 
 effective leverage of crank 175 
 
 angular velocities of crank for 
 
 one engine . . 177 
 deviation from mean value of 
 
 angular velocities . . ibid 
 angular velocities of a crank 
 
 for a pair of engines . 1 80 
 the screw propeller applied to 
 
 steam vessels . 23 1 
 
 Foot valve . . . 205 
 
 Friction of engines . . 40 
 
 of bodies . . . 215 
 
 of fluids . . 293,313 
 
 of pistons . . 221, 222 
 
 of slides . . . 209 
 
 Fuel, effect of . . 22, 194, 195, 201 
 
 nature of . .105 
 
 measure of effect of . . 107 
 
INDEX. 
 
 239 
 
 Fuel, table of effect of 
 Fulton . 
 Furnace, Roberton's 
 Fusible plug 
 
 G. 
 
 Gases, properties of 
 
 PAGE 
 
 109 
 44 
 133 
 142, 143 
 
 47, 82, 83 
 80, 81, 85 
 216 
 7 
 . 28, 266 
 28, 34, 266 
 . 17, 105 
 151 
 18 
 101, 145 
 45 
 App. 167 
 263, 264 
 App. 213 
 , 135, 210 
 284 
 
 334 
 the steam 
 370, 371 
 224, 226, 227 
 107 
 21, 47, 49 
 21, 48, 49 
 . 21, 48 
 ibid 
 214 
 216 
 cutta . 473 
 13. 27, 41, 152 
 rf . 174 
 133 
 8, 153, 186, 199 
 30 
 206 
 . 22, 23 
 11 
 . 14 
 
 PAGE 
 
 Hull's method of converting a reciprocating 
 motion into a rotary one . . 14, 15 
 Humphrys, F., Dartford, (Plates 51, 52, 
 53, 54, 55 A, 55 B, 56 A, 56 B) 382, 390 
 Humphreys, J. B. . App. 166 
 Hydrogen, effect of, in fuel . 107, 108 
 
 I. 
 
 Inclined planes . . 279, 285 
 Indicator . . .28, 267 
 
 Gasket . 
 Gauge cocks 
 
 
 
 Generation of steam 
 
 
 by the indicator cards . . 387 
 Injection . . 9, 146, 147, 187 
 
 Gensanne 
 Gilbert, Mr. 
 Glasgow, number of engines in 
 Glynn, J., on the indicator 
 Governor 
 
 
 . water, quantity of . 146, 147 
 Inspection of engines . 276, 277 
 Irrigation . . 189, 283 
 Irvine, Dr. . . .21 
 Ivory, James . . . 71, 72 
 
 J. 
 
 Jacket, steam . . . 93, 95 
 
 Grate bars, area of 115, 116, 134 
 Grinding corn 
 
 H. 
 
 Hall's piston 
 Hall, Samuel, his improvements in 
 engine 
 Hand gear 
 Hassenfratz 
 Heat, specific 
 
 Jackson, Dr. . . 257, 258 
 Jessop's piston . . .221 
 Jet for condensing . . 147 
 Joining pipes . . . 254 
 Jouffroy, Marquis de . .31 
 
 K. 
 
 Kier's engine, effect of .36 
 Kingston's valves . . 353, 354 
 
 L. 
 
 Lang, Oliver, master shipwright, Woolwich 
 Dock-yard, (Plates 100, 101, 102, 103, 
 112) . . 477,499 
 Lang, James Henry, Woolwich Dock-yard ibid 
 Lang, Oliver, Jun., Plymouth Dock-yard 
 (Plate 99) . . . 476 
 Latent heat . . . 21, 48 
 
 
 
 Hemp, friction of . 
 
 Henderson, Capt. Andrew, of Cal 
 High pressure engine 
 
 Hopper . 
 Hornblower, Jonathan 28, 29, \A 
 
 
 Horse power 
 Hot well 
 Hulls, Jonathan 
 
240 
 
 INDEX. 
 
 PAGE 
 
 Latent heat, measure of .49 
 Lavoisier . .107, 108, 207 
 Leslie, Professor . . 42,117,256 
 
 Leupold . . . 13, 211 
 
 Limit of steam power . . 156 
 
 Links . . . .231 
 
 Living forces, principle of . App. 183 
 
 Lloyd's piston . . . 334 
 
 Locomotive engine, parts of . . 407 
 
 blast pipe . . 415 
 
 blow off cocks . 422 
 
 boiler and manner of ge- 
 nerating steam . . 409 
 
 brake . . 467 
 
 coke . . 467 
 
 connecting rods . 425 
 
 cranked axle . 437 
 
 cross heads and guides 434 
 
 cylinders and manner of 
 
 using steam . . . 423 
 
 cylinders and piston 427 
 
 damper . .417 
 
 eccentrics . . 442 
 
 action of ._ 443 
 
 external fire box . 409 
 
 feed pumps 418, 451 
 
 fire and heating power 422 
 
 gauges . . 419 
 
 inside frames . 463 
 
 internal fire box . 410 
 
 lead plug . . 420 
 
 manhole . .421 
 
 mud holes . . ibid 
 
 oil cup . . 449 
 
 outside framing . 459 
 
 pet cock . .418 
 
 piston . . 430 
 
 regulator . . 425 
 
 reversing gear . 444 
 
 safety valve . 420 
 
 lock-up . 421 
 
 slide valves . . 427 
 
 form of . 428 
 
 . gear of . 443 
 
 smoke box . .415 
 
 doors . 418 
 
 PAGB 
 
 Locomotive engine, splashers . . 463 
 
 -- steam chest . 427 
 
 - pipe . 423 
 
 - area of . 424 
 
 tank . . 467 
 
 tender . . 466 
 
 wheels for 
 
 tubes . . 412 
 
 wheels, framing, &c. . 454 
 working of piston and slides 447 
 practical rules for App. 226 
 
 M. 
 
 MacneiU's experiments on canals 
 Manufacture, engines for 
 
 iron 
 
 cotton 
 
 paper . 
 
 App. 200 
 281 
 ibid 
 282 
 ibid 
 
 32, 163, 212 
 335, 336 
 
 Maudslay 
 
 'a four-way cock, (Plate 8) 
 
 and Field's experiments on marine 
 
 boilers . . . App. 2 
 
 and Co. . . 272,316 
 
 Maximum of useful effect . . 33, 163 
 
 equalized by a fly . .163 
 
 Medea, H. M. steam ship, memoir of App. 80 
 
 power of engines . . 82 
 
 rigging and internal fitting . 83 
 
 dimensions of . . 84 
 
 engines of . . 85 
 
 Mediterranean, daily evaporation of . 1 
 Mercurial gauge . . 142, 266 
 
 safety gauge . . 142 
 
 Metallic piston . . 34,35,218 
 
 Metallic packing for rods . . 223 
 
 Miller, Patrick . . .31 
 
 Millington, John . 119,120,208 
 
 Mines, engines for . 178,189,275 
 
 depth of . . . 276 
 
 Morgan, W. App. 41, 42, 43, 48, 52, 53, 55, 56, 
 61, 71, 83, 87, 88, 118, 156, 157, 158, 159, 
 
 160, 162 
 Morland, Sir Samuel . . 4 
 
 's table of force of vapour . ibid 
 
 Mornay, A. A., on paddle wheels App. 117 
 
INDEX. 
 
 241 
 
 Motion of air and vapour 
 
 PAGE 
 
 87 
 308 
 18 
 38 
 208 
 37 
 , 208 
 37 
 38 
 
 37 
 471 
 , 288 
 9 
 1, 23 
 
 9 
 9 
 
 11 
 140 
 55 
 
 174 
 179 
 177 
 179 
 180 
 183 
 
 297 
 273 
 80 
 212 
 
 , 78 
 279 
 
 216 
 300 
 
 121 
 
 PAGE 
 
 Paddle wheels, motion of . App. 119 
 
 Moura, De, M. 
 Murdoch, William 
 
 's slide 
 
 centre of pressure of 44 
 
 with fixed floats . j>>4 
 
 with feathering floats 145 
 
 Murray, Matthew . 
 
 floats turning on radial axes ibid 
 
 - horizontal axes 
 146 
 
 *s damper 
 
 *s portable engine 
 
 oblique floats 143 
 
 N. 
 
 Nancarrow, John . 
 Napier, Robert, Glasgow 
 Navigation, steam 14, 31, 44, 45, 46 
 
 Newcomen, Thomas 
 
 improved mode of connecting 
 Morgan's wheel to engine App. 164, 165 
 
 cycloidal, invention of, due to 
 Mr. Field . _ 53> 140 
 
 description of, as ap- 
 plied to the Great Western App. 53 
 
 coefficients for calculating the 
 
 action of . jgg 
 
 
 hoises power expended on 
 entire . . jgg 
 
 side of the cylinder for condensing the 
 steam of 
 
 hori- 
 
 zontaiiy . . ibid 
 
 by accident 
 
 Oil, 
 
 vertically . j^2 
 
 closing valves invented . 
 Nimmo, Alexander 
 Nitric acid 
 Noncondensing engines . 173, 
 
 i - 
 
 
 
 - By jr. w . .Barlow 40 
 
 by A. A. Mornay 117 
 
 Cave's ifii 
 
 
 fuel and water for 105, 
 
 
 common wheel . App. 124, 193 
 
 
 Field's j4Q 
 
 
 best force of steam 182, 
 
 0. 
 
 Oars 
 Oil 
 Oil gas vapour 
 Oil cup . 
 Oliver, Capt. . . App. 65 
 Ores, engines for drawing 
 
 P. 
 
 Packing 
 Paddle wheels 
 
 Tiff . 
 
 Morgan s . 155 
 
 Oldham s 152,193 
 
 
 
 
 table of velocity of centre of 
 effort 38, 39 
 
 experiments on Admi- 
 ralty steamers . 43 
 
 experiments exhibiting 
 the ratio of the velocity of the wheel 
 and vessel . . 47 
 
 comparison of the lost 
 power in the vertical and the common 
 wheel . . 52 
 
 
242 
 
 INDEX. 
 
 PAGE 
 
 Paddle wheels, table of experiments on, made 
 
 at Maudslay and Field's manufactory App. 55 
 
 experiments to ascer- 
 tain the effect of fixing the paddle 
 boards at an angle with the radius of 
 the wheel . . 58 
 
 experiments on Her 
 
 Majesty's ship Lightning, to ascertain 
 the difference of speed due to different 
 amounts of power . 62 
 
 do. Dee . 64 
 
 do. Phoenix 65 
 
 ratio of speed of a steam 
 
 boat to the power . 67 
 
 performances of Her 
 
 Majesty's Post Office steam packets 68 
 
 speed and consumption 
 
 of coals of nine of the most recently 
 constructed of Her Majesty's steam 
 vessels . . 71 
 comparison of the re- 
 sistance of a steam vessel with that of 
 a plane surface . 76 
 Paddles . 301, 302, 308, 309, 314, 315 
 
 number of . . . 307 
 
 power of . 302, 303, 304, 314 
 
 modification of . 308, 309 
 
 reefing of . 61 
 
 Papin, Dr. . 5, 7, 9, 16, 25, 31, 139 
 's suggestion of employing the expan- 
 sion and contraction of steam tinder a 
 piston to form a vacuum . . 5 
 
 's suggestion of a steam engine being 
 
 applicable to impel machinery . 8 
 
 's engine . . . ibid 
 
 Parabola . . .226 
 
 Parabolic paddles . . . 305 
 
 Parallel motion . . 28, 33, 35, 230 
 
 Case I. Where two beams 
 
 are connected by a link, the segments 
 of the link are inversely proportional to 
 the radii of the beams . .231 
 
 Rule I. . . 232 
 
 -Rule II. . . ibid 
 
 Case II. When a beam is 
 
 fitted with a full motion . ibid 
 
 PAGE 
 
 Parallel motion, formula for . . 233 
 
 when radius rod 
 
 works from a stated centre . ibid 
 
 Rule III. . . 234 
 proportion of links . ibid 
 
 - Rule IV. , . 235 
 
 -RuleV. . . 236 
 
 for steam boat engines . ibid 
 
 point for the air pump rod 
 
 to be attached . .237 
 
 to fix the radius bar . ibid 
 
 form of curve described by 
 
 the piston rod . . 238 
 
 rules for . 232, 234 
 
 practical rules for App. 216 
 
 Passages, steam, area of .94 
 Payne, John . . .16 
 's experiment to determine the den- 
 sity of steam . . . 1 6, 1 7 
 
 's disperser . . 17 
 
 Peacock, G., master of the Medea 
 
 . App. 83, 94, 98 
 
 Pendulum, conical . . . 263 
 
 Perkins, Jacob . . 214, 221 
 
 Perronet . . .31 
 
 Petroleum .. . . 55, 79 
 
 Phosphorus, effect of as fuel . .108 
 
 Pipes . . . .254 
 
 Pistons . . . .10, 213 
 
 Barton's . . .219 
 Cartwright's . . 218 
 
 Jessop's . . .221 
 
 Hall's . . . 334 
 
 Lloyd's . . .334 
 
 Smeaton's . . .216 
 
 Woolf's . . .217 
 
 metallic . . 34, 214, 218 
 principles of action . 221 
 
 pressure on . . 23, 36 
 rules for . . App. 222 
 
 slide . . .209 
 
 construction of . . 214 
 
 arrangement of . . ibid 
 
 thickness of . . ibid 
 
 leather . . .215 
 atmospheric engine . . 216 
 
INDEX. 
 
 243 
 
 Pistons, hemp packed 
 
 friction of . 
 
 Piston rod 
 
 PAGE 
 216 
 221 
 214 
 
 collars . . .222 
 
 guides . . .227 
 
 -strength of . 241, App. 212 
 
 diameters of, for locomotive en- 
 gines, as used by Messrs. Stephenson 
 and Co. . . . 399 
 
 Plates, explanation of > . 327 
 
 Plate 1. Isometrical projection of a rectan- 
 gular steam boiler . . 328 
 
 Plate 2. Two sections of a cylindrical steam 
 
 boiler . . .329 
 
 Plate 3. Brunton's apparatus for feeding 
 
 furnaces by machinery . . 330 
 
 Plate 4. High pressure engine with four- 
 passaged cock . . 331 
 
 Plate 5. Section of a double acting conden- 
 sing engine for working expansively 332 
 
 Plate 6. Section of an atmospheric engine 333 
 
 Plate 7. Represents the construction of 
 
 pistons . . . 334 
 
 Plate 8. Fenton and Murray's double engine 335 
 
 Plate 9. Apparatus for opening and closing 
 
 steam passages . . 337 
 
 Plate 10. (A and B) Combinations used to 
 produce rectilinear motion from motion 
 in a circular arc . . 338 
 
 Plate 1 1 . Plan and elevation of an atmos- 
 pheric pumping engine for raising water 
 from a mine . . . 339 
 
 Plate 12. Boulton and Watt's single acting 
 
 engine . . . 340 
 
 Plate 13. Double acting engine for raising 
 
 water . . .341 
 
 Plate 14. for impelling 
 
 machinery . . . 342 
 
 Plate 15. Maudslay's portable engine . 343 
 
 Plate 16. Indicator for measuring the force 
 
 of steam in the cylinder . . 345 
 
 Diagrams to illustrate the com- 
 parative stability of opposite classes of 
 vessels . . . 345 
 
 Plate 17. Section of a steam vessel with its 
 
 boiler in two parts . .346 
 
 Plate 18. Isometrical projection of a steam 
 boat engine as first arranged by Boul- 
 ton and Watt . . . 347 
 
 Plate 19. Steam boat engine . . 349 
 
 Plate 20. Side elevation and cross section 
 
 of a steam carriage . . 350 
 
 Plate 21. Kingston's valves . . 353 
 
 blow off valves . . ibid 
 
 hand pump valves . . 354 
 
 injection valves . . 353 
 
 manner of fixing the valves . 354 
 
 Plate 22. Boiler of H. M. steam vessel 
 
 African . . . 355 
 
 Plate 23. Boilers of H. M. steam frigate 
 
 Medea . . . ibid 
 
 Plate 24. Paddle wheels of Morgan and 
 
 Seaward . . .357 
 
 Plate 25. Positions of a float of a radiating 
 wheel, and also of a vertical acting 
 wheel, in a vessel in motion . ibid 
 
 Plate 26. Cycloidal paddle wheel fitted to 
 
 the Great Western " . . ibid 
 
 Plates 27, 28. To illustrate Capt. Oliver's 
 
 paper . . . 358 
 
 Plate 29. Exhibits the various situations of 
 a trial at sailing of the Medea, with the 
 Caledonia, Vanguard, and Asia . ibid 
 
 Plate 30. Side view of the engines of the 
 Red Rover, and City of Canterbury, 
 steam vessels . . . ibid 
 
 Plate 31. Longitudinal section of the Red 
 
 Rover's engine . . 359 
 
 Plate 32. Cross section of engines of the 
 
 Red Rover . . . 360 
 
 Plate 33. Side elevation of the engine of the 
 
 Nile steam ship . . 361 
 
 Plate 34. Plan of the engine of the Nile ibid 
 
 Plate 35, 36. Cross sections of engines of 
 
 the Nile . . . 362 
 
 Plates 37, 38, 39. Engines of H. M. steam 
 
 frigate Phoenix . . 363 
 
 Plate 40. Engines of the Ruby Gravesend 
 
 packet . . . 364 
 
 Dimensions and speed of . 367 
 
 Plate 41. Section of one of the engines of 
 
 the Don Juan 368 
 
244 
 
 INDEX. 
 
 Plate 42. Betters of H. M. ships Hermes, 
 
 Spitfire, and Firefly . . 368 
 
 Plates 43, 44, 45, 46. Elevation, plan, and 
 two sections of the engine room of the 
 armed Russian steam ships Jason and 
 Colchis . . . 369 
 
 Plates 47, 48. Hall's improvements on 
 
 steam engines . .370 
 
 Extracts from his specifica- 
 tion . . . ibid 
 
 Plates 49, 50. Engines of H. M. steam ship 
 
 Megaera . . . 378 
 
 Action of the valves . 380 
 
 Plates 51, 52, 53, 54. Engines of the Hull 
 and London steam packet William Wil- 
 herforce . . . 382 
 
 Plate 55 (A). Longitudinal section of Hum- 
 
 phrys's patent marine engine . 390 
 
 Plate 55 (B). Longitudinal elevation of 
 
 Humphrys's engine . .391 
 
 Plate 56 (A). Midship section of the steam 
 packet Dartford, showing a front 
 elevation of a pair of Humphrys's 
 engines . . . ibid 
 
 Plate 56 (B). Plan of the engines of the 
 
 Dartford . . .392 
 
 Plates 57, 58, 59. Forty-five-horse power 
 engine, constructed by W. Fairbairn 
 and Co. . . . ibid 
 
 Plates 60, 61, 62, 63. Ten-horse power en- 
 gine, constructed by W. Fairbairn 
 and Co. . . . ibid 
 
 Plate 64. Elevation of a locomotive engine. 
 Stanhope and Tyne Railway ; con- 
 structed by Messrs. R. Stephenson 
 and Co., of Newcastle-upon-Tyne 394 
 
 Plate 65. Section of ditto . .396 
 
 Plate 66. Safety valves of ditto . ibid 
 
 Plate 67 (A). Cylinder cover and connect- 
 ing rods of ditto . . 397 
 
 Plates 67 (B). Cylinder and piston at large 
 
 of ditto . . .398 
 
 Plate 68. Plan and section of boiler seating 
 for a twenty-horse engine, at the ma- 
 nufactory of Messrs. Whitworth and 
 Co., Manchester 399 
 
 PAGE 
 
 Plate 69. Messrs. Hague's double acting 
 
 cylinder with slides . . 399 
 
 Plates 70 A, 70 B. Sections of the engines 
 
 of the Berenice steam vessel . 400 
 
 Plates 71, 72. Beale's patent rotatory en- 
 gine . . . 401 
 
 Plate 73. Mr. Ayre's contrivance for pre- 
 venting a locomotive engine from run- 
 ning off a railway . . 403 
 
 Plates 74 to 83. Relate to Mr. Mornay's 
 
 paper on paddle wheels . App. 117 
 
 Plates 84 to 88. Sixty-five inch cylinder 
 engine, erected by Messrs. Maudslay, 
 Sons and Field, at Chelsea water- works 
 
 404 
 
 Plates 89 to 92. Patent locomotive engine, 
 made by Messrs. R. Stephenson and 
 Co. for the London and Birmingham 
 Railway . . .407 
 
 Plate 93. Drawings of the Comet, the first 
 
 steam boat in Europe . .470 
 
 Plate 94. The Pacha's steam vessel of war, 
 
 the Nile . . .471 
 
 Plates 95, 96. The Hon. East India Com- 
 pany's steam vessel Berenice . ibid 
 
 Plate 97. Draught of the Forbes steamer 473 
 
 Plate 98. Herne Bay steam packet Red 
 
 Rover . . . 474 
 
 Plate 99. Diamond Company's steam packet 
 
 Ruby . . .475 
 
 Plates 100 to 103. Her Majesty's steam 
 
 vessel of war Medea . . 477 
 
 Plates 104 to 107. Construction of the Nile 
 
 steam ship, built for the Pacha of Egypt 483 
 
 Plates 108, 109, 110. His Imperial Ma- 
 jesty's armed steam vessel Colchis 492 
 
 Plates 111, 111 (A). Engines of the steam 
 
 ship Tiger . . .497 
 
 Plate 112. The Admiralty yacht Firebrand 498 
 
 Plate 1 13. Portrait of the late Mr. Watt 500 
 
 Plate 114. Portrait of fee late Mr. Tredgold ibid 
 
 Plates 115, 117, 118. Illustrate the state of 
 
 steam navigation in America . ibid 
 
 Plug tree . . .224 
 
 Poisson . . . . 86, 291 
 
 Portable engine . . . 22, 28, 38 
 
INDEX. 
 
 245 
 
 PAGE 
 11 
 
 150, 153 
 150 
 151 
 
 151, 152 
 App. 225 
 
 157 
 160 
 
 306, 313, 314 
 313, 325 
 33, 120, 230 
 297 
 
 App. 231 
 168 
 274 
 Pumps, rule for finding the volume of App. 214 
 
 finding the power requisite 
 
 to discharge a given quantity of water ibid 
 finding the velocity neces- 
 sary to discharge a given quantity of 
 water . . App. 216 
 finding the diameter of, 
 
 Potter, Humphrey 
 Power of steam 
 
 by condensation 
 
 generation . 
 
 expansion . 
 
 practical rule for 
 
 rotary 
 
 modes of applying 
 
 paddles . 301, 
 
 for vessels 
 
 Prony, R. 
 Propelling vessels . 
 
 screw 
 
 Pumping expels air from water 
 water 
 
 to discharge a given quantity of water 
 
 - brine 
 
 ibid 
 App. 2 
 
 R. 
 
 Radius bar 
 
 Rail road 
 
 Raising water, engines for 
 
 Reciprocating engine 
 
 Rectilinear motion of steam 
 
 Regulating by cataract 
 
 injection 
 
 expansion 
 
 production of steam 
 of the fire 
 
 Regulation of power 
 
 by pump 
 
 Regulator 
 
 Renwick, Dr. J. 
 Resistance of parts 
 of fluids 
 
 231 
 285 
 
 165, 274 
 
 227 
 
 153 
 
 23 
 
 . 23, 189 
 
 . 27, 261 
 
 37 
 
 137 
 
 260 
 
 264 
 
 9, 213, 264 
 138 
 
 App. 101 
 239 
 292 
 
 PAGE 
 
 Resistance of vessels . 292,313 
 
 Roberton's furnace or fire-place . 39, 133 
 
 Robison, Dr. John . 38, 206, 207, 258 
 
 experiment by . 63, 64, 74 
 
 Rotary motion, methods of producing . 
 
 15, 20, 26, 37, 227 
 engines . 27, 28, 30, 32, 36, 40 
 
 power of steam 
 valves 
 
 Roy, General . . 
 
 Ruby, Gravesend packet, engines of . 
 Rule for conversion of heat into steam . 
 - for the quantity a gas or vapour ex- 
 pands under a constant pressure . 
 
 157 
 210 
 
 85, 86 
 364 
 50 
 
 82 
 207 
 
 Rules, practical, for BOILERS . 
 
 - the dimensions of, for 
 
 any given power when rectangular ibid 
 
 - when cylindrical 208 
 
 - the requisite thickness 
 
 of plates for . App. 208, 209 
 
 - the height of a column 
 
 of water to supply a boiler against any 
 
 proposed pressure . 209 
 
 cylinders, requisite 
 
 thickness of . . 211 
 
 chimney, area of . ibid 
 
 eccentric 213 
 
 fire grating 210 
 
 governor . ibid 
 
 PARALLEL MOTION 216 
 
 the point in 
 
 the link where the piston rod must be 
 attached . . . ibid 
 
 the length of 
 
 the radius bar 
 
 218 
 
 the length of 
 
 radius bar when it and the piston rod 
 are attached to the links at different 
 distances . . 219 
 
 the lengths of 
 
 parallel bar and radius bar, when the 
 latter works from a stated centre 220 
 
 piston rod.diameter of 212 
 
 PUMPS the number of 
 
 cubic feet in the volume of a cylinder 214 
 the power re- 
 
 2 i 
 
246 
 
 INDEX. 
 
 PAGE 
 
 quisite to raise water to any proposed 
 height . . App. 214 
 
 Rules, practical, for pumps the velocity 
 necessary to discharge a given quantity 
 of water . - . 216 
 
 the diameter 
 
 of, necessary to discharge a given 
 quantity of water . . ibid 
 
 LOCOMOTIVE ENGINES 226 
 
 the power 229 
 
 .the ef- 
 
 fective force of gravity when an en- 
 gine and train are running upon an 
 inclined plane . 226 
 -the speed 
 
 under any given circumstances of load, 
 inclination of railway, &c. . 229 
 the ten- 
 
 sion on the circumference of the driving 
 wheels, or what is termed the resistance 
 to traction . . 227 
 
 the quantity of water 
 
 required for steam . 225 
 
 the pressure of steam 
 
 in the cylinder . 228 
 
 properties of steam 205 
 
 steam pipe, diameter of 210 
 
 the elastic force of 
 
 steam when in contact with the liquid 
 from which it is generated 205 
 the mean pressure on 
 
 the piston, when worked expansively 222 
 table of multipliers for 
 
 mean pressure, acting expansively 223 
 
 the power 225 
 
 the aperture of a safety 
 
 valve for any given pressure 210 
 the space the steam of 
 
 a cuhic foot of water occupies when of 
 a given elastic force and temperature, 
 and separated from the liquid from 
 which it is generated . 206 
 Rumble, F. (Plates 8488) 
 Rumford's, Count, boilers 42, 106, 107, 128 
 experiments on latent heat . 52 
 
 PAGE 
 
 S. 
 
 Sadler . 32 
 
 Safety valve . . 7, 103, 139, 206 
 
 rule for area of . App. 210 
 
 escape of steam at .103 
 
 pipes . . 140, 141, 142 
 
 rules for . . 142 
 
 Sailing, trial of between H. M. ships Asia, 
 
 Caledonia, Medea, and Vanguard App. 100 
 Sails, power of . .310 
 
 Savery, Thomas . . 5, 7, 16 
 
 's Miner's Friend . . 5 
 
 engine simplified . . 7 
 
 first effective steam engine by . ibid 
 
 engine . 5, 6, 17, 24, 36, 37 
 
 Schmidt's experiments on heat . 51, 70 
 
 Screw propeller applied to steam vessels App. 231 
 Seaward's slides . . . 209 
 
 Sea water, elastic force of steam of . 60 
 
 analysis of . 61, 271, 272 
 
 boiling point of . . 272 
 
 Shafts, strength of . . 245 
 
 Ships, resistance of . 296, 313 
 
 Side rods, strength of . . 242 
 
 Simpson, J., Chelsea water-works 404, 405 
 
 Single acting engine . . 191 
 
 expansive . 1 94 
 
 Sleek, effect of . . . 36, 113 
 
 Slide . . 38, 174, 175, 199. 207 
 
 construction of . .207 
 
 unproved . . . 208 
 
 friction of . .209 
 
 cylindrical . . . ibid 
 
 modes of opening by . . 225 
 
 Murray's . . .207 
 
 Bramah's . . . ibid 
 
 Murdoch's . . .208 
 
 Seaward's . . .209 
 
 Smeaton, John 18, 21, 22. 23, 24, 118, 119, 215 
 
 's piston . . .219 
 
 Smoke, ascent of . . 100, 145 
 
 quantity of . . 115 
 
 Snifting valve . 1 1 
 
 Southern, John . . 44, 56, 57 
 
INDEX. 
 
 247 
 
 Southern's mode of experimenting on high 
 
 pressure steam . . 69 
 
 experiments by . . 51, 70 
 
 on the force of steam . 70 
 
 Speed of vessels . 311,313 
 Spring beams . . . 262 
 Stability of vessels . . 289 
 Stamping engines . . . 279 
 Steam, density of, directly as the pressure 52 
 condensation of . . 146 
 
 - elastic force of . 51, 56, 62, 64, 70 
 rules for 58, 59, 82, 83 
 
 App. 205 
 
 - volume of . . 12, 16, 52, 83, 84 
 inversely as the pressure 52 
 
 rules for . 84, App. 206 
 
 expansion of . .83 
 
 temperature . . 58 
 
 capacity of, for heat greater than 
 
 that of water . . .48 
 Robison's apparatus for determin- 
 ing the force of . .63 
 generation and condensation of . 105 
 
 - heat to produce 49, 51, 52, 55, 56, 113 
 power of . . . 150 
 
 to produce rectilinear motion 153 
 
 modes of applying the power of 160 
 
 power, rotary . . 157 
 
 latent heat of . 48,56,112 
 mixture of air and . 84 
 
 312 
 103, 143 
 
 motion of, in an engine 
 
 effect of 
 
 escape of, at valves . 
 
 quantity of, for engines 
 
 176, 180, 181, 187, 190, 192, 196 
 
 force of . . 32, 41, 5684 
 
 Steam vessels . . 14, 41, 288 
 
 - Red Rover . 358, 474 
 
 - City of Canterbury . 358 
 Medea . App. 100 
 
 African , . 355 
 
 Caledonia . App. 100 
 
 Asia . . . ibid 
 
 Vanguard . . ibid 
 
 -Nile . . 361,483 
 Phoenix 363 
 
 PAGE 
 Steam vessels, Rhadamanthus, Salamander 
 
 (Plates 38, 39) . . 363 
 
 Ruby . . 364, 475 
 
 Don Juan . . 368 
 
 Hermes, Spitfire, Firefly . ibid 
 
 Jason and Colchis . 369 
 
 enumeration of, fitted with 
 
 Hall's improvements . . 376 
 
 - Megaera . . 378 
 
 - William Wilberforce . 382 
 -Dartford . . 391 
 
 Comet . . 470 
 
 Forbes . . 473 
 
 Berenice . 400,471 
 
 - Colchis . . 492 
 -Tiger . . 497 
 
 Firebrand . . 498 
 
 Great Western . .357 
 
 Car of Neptune (U. S.) App. 103 
 
 - Sun (U. S.) . - 105 
 
 - North America (U. S.) 106 
 
 - President (U. S.) 107 
 
 - New Philadelphia (U. S.) - 108 
 -Fulton (U. S.) . 110 
 
 - North Carolina (U. S.) . ibid 
 
 Cornelius Vanderbitt (U. S.) ibid 
 
 Highlander (U. S.) . ibid 
 Lexington, dimensions (U. S.) Ill 
 
 - Dewitt Clinton (U. S.) 110 
 -Savannah (U. S.) - 113 
 
 - Cleopatra (U. S.) - 114 
 Massachusetts (U. S.) . ibid 
 
 register tonnage of . 320 
 
 - navigation of 14,31,41,288,360 
 
 engines of . . 314 
 
 pressure engines . 25,175,191 
 
 case . , 38, 92, 93, 95 
 
 gauge . . .266 
 
 cylinder . . .161 
 
 indicator . . . 267 
 
 engine, invention and improvement 
 
 of . . . . 1 46 
 
 general theory of, by Editor 
 
 App. 173 
 
 Dickinson's . . 32 
 
 Hornblower's 29 
 
248 
 
 INDEX. 
 
 PAGE 
 
 Steam engine, Newcomen's . 10, 11, 23 
 
 Papin's . . 8 
 
 Savery's 5, 6, 17, 24, 36, 37 
 
 Stephensons' patent locomotive 407 
 
 Watt's . 25, 26, 27, 28 
 
 Woolf s . . 94, 237 
 
 Worcester's, Marquis of . 3 
 
 equalizing the action of . 256 
 
 -atmospheric . 96,98,99,187 
 
 maximum effect of . 99, 100 
 
 of useful effect in 1 63 
 
 for, when equal- 
 ized by a fly . . .163 
 
 of useful effect for 
 
 raising water . 1 65 
 
 atmospheric improved . 1 89 
 
 single acting . 184, 191 
 
 - double acting . 185, 195, 199 
 
 combined cylinder . 199 
 
 high pressure 152,173 
 
 noncondensing . 173 
 
 proportion of parts and 
 
 power of . .175 
 
 at full power . .176 
 
 by expansion . . 177 
 
 classification . 150, 161 
 
 condensing . 184 212 
 
 double cylinder expansive 
 
 best force for the steam of 
 
 noncondensing . 182, 183 
 
 regulating the power of . 260 
 
 methods of ascertaining the 
 
 state and effect of . . 265 
 measuring the useful effect 
 
 of ... 269 
 
 working of . . 271 
 
 motion of steam in . 88 
 
 : loss of force by cooling 
 
 92, 95, 97, 99 
 
 length of stroke . 161 
 
 velocity of mean effect 163 
 
 for expansion . 1 65 
 
 air pumps and condenser 
 
 proportions . . .167 
 
 power required for working 
 
 air pump . . 1 70 
 
 PAGB 
 
 Steam engine, force of steam for 183, 194, 195 
 
 loss of steam . .183 
 
 Steam passages . . .187 
 
 rules for . . 94 
 
 Steam pipes, cooling in .92 
 
 journal, form of . App. 31 
 
 Stephensons' patent locomotive engine 407 
 
 Strength, effect of expansion on 247, 253 
 
 Strength of parts of engines . 239 255 
 
 rods . . 240, 241 
 
 beams . . 243 
 
 cranks . . ibid 
 
 wheel arms . . ibid 
 
 teeth of wheels, table of . 244 
 
 - shafts . . 245 
 
 pipes and cylinders . 246 
 
 plates . .248 
 
 boilers . . 249 
 
 vessels . . 310 
 
 Stress on the parts of engines . 239 
 
 Stroke, length of . . . 161 
 cutoff 178,179,194,198 
 
 Stuffing boxes . . . 222 
 
 Sulphuret of carbon, force of .77 
 
 Sun and planet wheels . . 27 
 
 Symington, William . . 31, 41 
 
 T. 
 
 Table of Southern's experiments on the 
 
 bulk and heat of steam . . 51 
 
 Rumford's, on heat of steam . 53, 54 
 
 Ure's, on heat of steam . 54, 55 
 
 boiling points of solutions . 60, 61 
 
 expansion of water . . 58 
 
 constant numbers for sea water 61 
 
 Watt's experiments on the steam 
 from salt water . . 62 
 
 Watt's experiments on pure water ibid 
 
 Robison's experiments on pure water 64 
 
 on the force of steam . ibid 
 
 Dalton's experiments on the force 
 
 of steam . . .66, 67 
 
 Ure's experiments on the force of 
 
 steam . 69 
 
INDEX. 
 
 249 
 
 Table of Southern's experiments on the 
 
 force of steam . . 70 
 
 Taylor's experiments on pure water ibid 
 
 scale of force of steam ibid 
 
 Arsberger's experiments on high 
 
 pressure steam . 71 
 
 Ivory's calculations . . 71, 72 
 
 force of alcohol vapour . 72, 74 
 
 Cagniard's, de la Tour, experiments 
 
 on ether . . .75 
 
 force of ether vapour . 75, 76 
 
 Ure's and Dalton's experiments on 
 
 ether 
 force of vapour from sulphuret of 
 
 carbon 
 Cagniard's, de la 
 
 76 
 77 
 
 78 
 79 
 ibid 
 82 
 
 Tour, experiments on 
 
 force of petroleum 
 
 force of turpentine 
 
 mechanical power of gases 
 
 various substances where one vo- 
 lume of water is shown to produce 
 more vapour than an equal volume of 
 any other substance in the list . 83 
 
 Roy's experiments on air and steam 86 
 
 effect of contractions . . 88 
 
 the effect of combustibles 109, 1 10, 111 
 
 - the effect of fuel . 112,113 
 
 quantity of smoke from fuel . 115 
 
 quantity of fire surface for boilers 118 
 
 experiments on boilers 119,120 
 
 power of boilers . 1 23, 1 24 
 
 - for calculating safety valves 142, 143 
 
 - of the power of cranks 228 230 
 
 the teeth of wheels . . 244 
 
 the effect of engines . . 278 
 
 the supply of towns with water 280 
 
 experiments on canal boats 294, 295 
 
 for calculating the resistance of ves- 
 sels . . . 296 
 of steam vessels . 316,317,318 
 
 the properties of steam . 322 
 
 the proportions of single engines 323 
 
 the proportions of double engines 
 
 324, 325 
 Tappets . . 187,224;265 
 
 PAGE 
 
 Taylor's, Philip, scale of the force of steam 70, 178 
 
 Taylor and Martineau . . 178 
 
 Teeth of wheels . . .244 
 
 Thomson, Dr. T. . 110, 114 
 
 Thrashing machines . . 283 
 
 Throttle valve . 27, 210, 261 
 
 Tonnage of a steam vessel . . 320 
 
 Towing boats . . .41, 315 
 
 Towns, supply of water for . . 280 
 
 Trevithick and Vivian . .41,141 
 
 Turpentine vapour . . 55, 79 
 
 U. 
 
 Ure, Dr. 44 
 
 's mode of experimenting . 54, 67 
 
 tables of experiments on the force of 
 
 steam . . .69 
 
 experiments by 54, 74, 76, 79, 168 
 
 Useful effect, mode of measuring . 269 
 
 V. 
 
 Valves 
 
 safety 
 
 rule for 
 
 throttle 
 
 Kingston's 
 arrangement of 
 
 principles of construction 
 
 boxes 
 rising 
 clack 
 foot 
 flat 
 
 Bramah's slide 
 conical 
 Field's 
 
 Hornblower's 
 sliding 
 rotary 
 
 plate 
 
 modes of opening 
 
 Vapour, force of 
 
 175, 203 
 139 
 
 App. 210 
 261 
 353 
 204 
 ibid 
 ibid 
 204 
 205 
 ibid 
 ibid 
 207 
 205 
 262 
 206 
 207 
 210 
 213 
 224 
 
 . 56,57 
 
250 
 
 Vapour, elastic force of, separated from the 
 liquids from which it is generated 
 - bulk of 
 
 nature of . 
 
 Velocity of elastic fluids 
 engines 
 
 vessels . 
 
 paddles . 
 
 spiral propellers 
 
 Vessels, strength of 
 
 arranging the proportion of power 
 
 for 
 
 Vinegar 
 
 W. 
 
 Water . 
 wheel 
 
 air in 
 
 raising 
 
 screw 
 
 works 
 
 modulus of . 
 
 expansion of 
 
 Watt, Dr. James . 
 
 25, 49, 98, 99, 125, 132, 
 207, 208, 230 
 
 experiments of 
 
 Watt's boilers 
 engine 
 
 expansive engine 
 
 
 INDEX. 
 
 
 
 PAGE 
 
 
 PAGE 
 
 rom 
 
 the 
 
 Watt's fire-place . 
 
 132 
 
 ited 
 
 82 
 
 n*n T.*PT*n nr "tpiTn c"i i IO*P t*t 
 
 mdenser 
 
 & ' CLCrtlll i^aUiiC, C' 
 
 
 4, 12, 51 
 
 gauge, and indicator 
 
 28 
 
 
 47 
 
 , - n i .rt*i.~~ 
 
 . 28, 230 
 
 
 
 87 
 
 , . .+ 41 
 
 O7 
 
 
 . CJ / 
 
 163 
 
 
 27 
 
 
 311 
 
 , 313, 317 
 
 Wheels . 
 
 243 
 
 301 
 
 , 302, 313 
 
 ,j,_ 
 
 319 
 
 ' pauuie . . 
 
 298 
 
 , App. 231 
 
 Wheel tyers for locomotives . 
 
 398 
 
 
 310 
 
 Whim engines 
 
 279 
 
 }f power 
 
 Williams, W. 
 
 251 
 
 
 313 
 
 Wind, force of 
 
 310, 319 
 
 
 55 
 
 Wood, Nicholas 
 
 119 
 
 
 
 Woolf, Arthur . 42, 133, 
 
 152, 209, 260 
 
 
 
 
 
 . 94, 237 
 
 
 
 
 * li il t* 
 
 1 9Q 
 
 
 271 
 
 
 . l ~. 
 
 217 
 
 
 
 . 24, 87 
 
 'n , .. . , 1 1. nf --T^eirtvi 
 
 rf steam 
 
 
 
 167 
 
 shown to be false 
 
 43 
 
 
 194, 274 
 
 Worcester, Marquis of 
 
 2 
 
 
 298 
 
 .- iri ti 
 
 3 
 
 
 
 280 
 
 Working of engines 
 
 271 
 
 
 57 
 
 
 
 
 58 
 
 
 
 
 
 Y. 
 
 
 48, 
 
 153, 206, 
 
 
 
 255 
 
 , 261, 262 
 
 Young, Dr. 
 
 120 
 
 
 49, 60, 62 
 
 
 
 
 125 
 
 Z. 
 
 
 25, 
 
 26, 27, 28 
 
 
 
 
 27 
 
 Zeigler, J. T. 
 
 29 
 
 THE END. 
 
LONDON : 
 
 PRINTED BY W. HUGHES, (SUCCESSOR TO MR. VALPV,) 
 KING'S HEAD COURT, GOUGH SQUARE. 
 

 
 
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