JHB9i xey ^^ti^vtVa &&&&$&$^P 'J* .*!-;* , UNIVERSITY OF CALIFORNIA IB*. ANDREW SMITH HALLIDIE: / THE GLASGOW MODEL OF NEWCOMEN'S STEAM ENGINE. NOTE. In working to repair the model here represented, James Watt, in 1765, made the discovery of a separate condenser, which has identified his name with the steam engine. TEXT-BOOK ON THE STEAM ENGINE WITH A SUPPLEMENT ON GAS ENGINES AND PART II. ON HEAT ENGINES BY T. M. GOODEVE, M.A. BARRISTER-AT-LAW FORMERLY PROFESSOR OF MECHANICS AT THE ROYAL COLLEGE OF SCIENCR, LONDON AUTHOR OF 'THE PRINCIPLES OF MECHANICS' 'THE ELEMENTS OF MECHANISM* ( AN ABSTRACT OF PATENT CASES* ETC. FOURTEENTH EDITION LONDON CROSBY LOCKWOOD AND SON 7' STATIONERS' HALL COURT, LUDGATE HILL 1898 [A/I rights reserved} , BY THE SAME AUTHOR. The ELEMENTS of MECHANISM, designed for Students of Applied Mechanics. New Edition, rewritten and enlarged, with 357 Woodcuts. Crown 8vo. 360 pp. Price 6s. CONTENTS : I. Introductory. V. On the Teeth of Wheels. II. On the Conversion of Circular VI. On the Use of Wheels in Trains. into Reciprocating Motion. . VII. Aggregate Motion. III. On Linkwork. VIII. On the Truth of Surface and the IV. On the Conversion of Recipro- Power of Measurement, eating into Circular Motion. IX. Miscellaneous Contrivances. Appendix. The PRINCIPLES of MECHANICS. New Edition re-written and enlarged. With 253 Woodcuts. Crown Svo. price 6s. In this volume an endeavour has been made to present a comprehensive view of the science of mechanics, to point out the necessity of continually referring to practice and experience, and above all to show that the relation of the theory of heat to mechanics should be approached by the student, in his earliest inquiries, with the same careful thought with which he will regard it when his knowledge has become more extended. A MANUAL OF MECHANICS : an Elementary Text- Book for Students of Applied Mechanics. With 138 Illustrations and Diagrams, and 188 Examples taken from the Science Department Examination Papers, with Answers. Fcp. 8vo. Price 2s. 6d. London: LONGMANS, GREEN, & CO. 39 Paternoster Row. SUPPLEMENT on GAS ENGINES. Reprinted, with some Additions from the 'Text-Book on the Steam Engine.' Crown 8vo. Price 2s. 6d. London : CROSBY LOCKWOOD & SON, 7 Stationers'-Hall Court, Ludgate Hill. An ABSTRACT of REPORTED CASES relating to LETTERS PATENT for INVENTIONS. Vol. I. A New and Enlarged Edition, containing the cases befoie the Privy Council and other applications relating to Patents, and bringing down the Reports to the end of the year 1883. Svo. pp. 634. Price 30^. PATENT PRACTICE BEFORE the COMPTROLLER and the LAW OFFICERS, with an ABSTRACT of REPORTED CASES. With an APPENDIX bringing the Cases down to the end of 1892. Svo. pp. 143. Price 6s. The APPENDIX is sold separately, price 2s. 6J. London: SWEET & MAXWELL, Ltd. 3 Chancery Lane. ri PREFACE TO THE ELEVENTH EDITION. THE plan of this book is the following : The first chapter contains a sketch of the steam engine as it existed in the time of Watt, together with an account of the ideas then prevalent as to the nature of heat, and concludes with a summary of some physical properties of steam. The second and third chapters are occupied by an investigation of the principles of the modern theory of heat in its appli- cation to the steam engine. Then comes a chapter on the conversion of motion, which deals with certain salient points in the mechanism of an engine. The fifth chapter is mainly devoted to the expansion of steam, to the action of valves, and to the application of Watt's indicator. The sixth chapter treats of boilers and the consumption of fuel. The seventh chapter is on compound cylinder engines, ,and is illustrated by some drawings of the engines con- structed by Messrs. Maudslay, Sons, and Field for the White Star line of mail steamers making the voyage be- tween Liverpool and New York. Finally, there is a chapter on miscellaneous details, such as steam-engine governors, Giffard's injector, the link motion, modern valve gears, and valve diagrams. The part relating to the steam engine contains also an Appendix, with a series of examination questions and answers. There is in the present edition a Supplement on Gas Engines, and Part II., on Heat Engines. T. M. GOODEVE. 5, CROWN OFFICE Row, TEMPLE: November, 1890. 141875 CONTENTS. CHAPTER I. THE STEAM ENGINE AS VIEWED UNDER A KNOWLEDGE OF THE DOCTRINE OF LATENT HEAT. PAGB Black's Doctrine of Latent Heat. Material Theory of Heat. Arts. 13. Savery's Engine. , 4 8. Newcomen's Atmospheric Engine. 9. Watt's Experiments while repairing the Glasgow Model. 10 14. Watt's Patent of 1 769. Single-acting Pumping Engine. 15. The Expansion of Steam. Watt's Patent of 1782. 16. Boyle's Law. 17. Boyle's Law represented by a Curve. 18 19. Diagram of Energy. 20. Double-acting Engine. 21. Hornblower's Engine. 22. The Indica- tor. 23 24. The Properties of a Vapour. 25. Isothermal Line for a Vapour. 26 28. Determination of Vapour Pressure. 29. Regnault's Experiments ... ....... I CHAPTER II. HEAT IS NOT A MATERIAL SUBSTANCE. Art. 30. Introductory. 31. Rumford's Experiment. 32. Davy's Ex- periment. 33. Modern Theory of Heat. 34. Work and Heat. 35. Joule's Experiments. 36. Kinetic Theory of Gases. 37 38. Gay- Lussac's Law. 39. Air Thermometer. 4041. Fall in Temperature of Gas while doing Work. 42. First Law of Thermodynamics. 43 44. Specific Heat. 45. Latent Heat of Steam. 46. Absolute Zero of Temperature. 47 52. Adiabatic Curves 51 CHAPTER III. ON HEAT ENGINES. Art. 53. Introductory. 54. Diagram of Work. 55. Cycle. 56. Further Diagrams. 5759- Heat Engine. 60. Carnot's Principle. 61. Second Law of Thermodynamics. 62. Use of High-pressure Steam. 6364. The Invention of a Regenerator. 6567. Stirling's Engine .... ...... Si CHAPTER IV. THE CONVERSION OF MOTION. Arts. 6870. Analysis of Circular Motion. 72. Sun and Planet Wheels. 73. Crank and Connecting Rod. 74 76. Watt's Parallel Motion. Contents. vii PAGF 77. Scott Russell's Straight-line Motion. 79. Grasshopper Engines. 80 8 1. Peaucellier's Exact Straight-line Motion. 82. Duplicate Straight-line Motions . 101 CHAPTER V. THE INDICATOR, AND DETAILS OF CONSTRUCTION. Arts. 8385. Th. Horse Power and Duty of a Steam Engine. 86. Richard's Indicator. 8788. Diagram of Expansion of Saturated Steam. 89. The Cataract. Valve Motion of Single-acting Engine. 90. Cylinder, and Parts connected therewith. 91 93, Murdoch's Valve. Other Valves. 94 95. Piston and Packing Rmgs. 96 97. Balanced Valves. Gridiron Valve. 98 99. Eccentric Circle. 100. Direct-acting Engine. 101. Cam Motion. 102 106. Lap of a Valve. 107. Lead of a Valve. 108 in. Diagrams of Work done. 112 113. Expansive Working. 114 117. Indicator Diagrams. Af. mospheric, Single-acting, and Double-acting Engines. 118119. Wire-drawing and Clearance. 120. Expansion Valves. 121 123. Further Indicator Diagrams. 124. Steam Jacket. 125 126. Re- marks on Diagrams. 127128. Connecting-rod Ends . , .123 CHAPTER VI. ON BOILERS. Arts. 129 130. Forms of Boilers. 131132. Strength of Tubes. 133. Effect of Heat. 134135. Stays and Tie Rods. Tubular Flues. 136. Fittings for a Boiler. Pressure and other Gauges. 137 140. Safety Valves. Ramsbottom's Valve. 141 143. Heat of Combustion. Waste of Fuel. 144146. The Locomotive Boiler. 147. The Marine Boiler. 148. Fire-Grate and Heating Surfaces . . .190 CHAPTER VII. COMPOUND CYLINDER ENGINES. Art. 149. Woolfs Engine. 150151. Engines of Sims and McNaught. 152 154. Double-cylinder Pumping Engines. 155. Factory Engine. 156. Indicator Diagram. 157 158. Calculation of Work done. 159. Point of Cut-off. 160161. Cranks at Right Angles. 162. Intermediate Receiver. 163. Milner's Engine. 164. Adamson's En- gine. 165. Four-cylinder Compound Marine Engines (Maudslay & ^.o.). 1 66. Surface Condensers. Indicator Diagrams . . . 232 CHAPTER VIII. MISCELLANEOUS DETAILS. Arts. 167173. The Pendulum Governor. Watt's Governor. Head's Governor. 174. Siemens' Governor. 175. Donkey Engine. 176. Giffard's Injector. 177. Link Motion. 178. Other Reversing Valve Gear. 179. Principle of Construction. 180 181. Hackworth's Gear. 182. Marshall's Gear. 183 184. Joy's Valve Gear. 185 186. Valve Diagrams. 187. Zeuner's Valve Diagram . . , . , 262 viii Contents. SUPPLEMENT ON GAS ENGINES. PAGE Art. I. Invention of Gas Engine. 2 3. Explosive Mixtures of Gas and Air. 4. Explosion in a Closed Vessel. 56. Dugald Clerk's Experi- ments. 7. Comparison between Early and Modern Rifled GUPS. 8. The Lenoir Engine. 9. Indicator Diagram. 10. The Otto and Langen Engine. II. Indicator Diagram 303 THE OTTO ENGINE. Arts. 1214. The New Principle of Action. 15. Charging with Gas and Air. 16. Firing the Charge. 17. The Exhaust. 18. Regulator for Supply of Gas. 19. Working of the Engine. 20. Plan View of the Otto Engine. 21. Indicator Diagram of the Otto Engine. 22. Fittings of the Engine ......... 3*9 APPENDIX. The Appendix contains Examples, with Answers, taken chiefly from papers set in the Science Examinations .....,, 340 PART II. THEORY OF HEAT ENGINES. Art. I. The Relation between Heat and Work. 2. External Work done during the Expansion of Volume. 3. Cyclical Process. 4. Relation be- tween the Temperature and Pressure of Saturated Steam. 5. Specific Volume. 6. Heat Expended in the Evaporation of Water. 7 10. In- ternal and External Work. II 13. Specific Heat. 14. Internal and External Work done in Heating Air. 15. Specific Heat of Steam. 16. Expansion Curves of Air and Steam. 17. Area of the Expansion Curve, jg 19. Work done during the Expansion of a Gas. 20-22. Internal and External Work done during the Expansion of Air. 2324. Absolute Scale of Temperature. 25 26. Comparison of Densities. 27. Calcula- tion of the Density of Steam. 28 29. Trials of Engines. Tables [At -end ELEMENTARY TREATISE ON THE STEAM-ENGINE. CHAPTER I. THE STEAM-ENGINE AS VIEWED UNDER A KNOWLEDGE OF THE DOCTRINE OF LATENT HEAT. THIS treatise is intended to prepare the way for a complete and extended study both of the theory and practice of the steam- engine. We premise that there is much introductory matter which the student should consider and arrange in his mind before he can hope to grapple successfully with the difficult questions which occur in practice ; and the mode of treatment herein adopted is to be taken, not as something sufficient in itself, but rather as an indication of the points wherein existing books on the subject may with advantage be supplemented. The nature of the work will soon become apparent to those who take it as a guide in this particular branch of study. It is only within the last thirty years that p. knowledge of the principles of the mechanical theory of heat has influenced the practice of those who are engaged in improving the construction of the steam-engine, and in seeking to obtain from it a larger amount of useful work with a given expenditure of fuel. The student of mechanics will do well to look backward into the history of scientific discovery, and he should endeavour to trace the pro- gress which has accompanied each successive step in our compre- hension of the real nature of that origin of force which we call heat 2 The Steam-Engine. Living at the present day, he finds himself face to face with a novel conception, which has struggled into life by slow and almost insensible degrees, but which appears to be accepted with the same degree of confidence as that accorded to Newton's theory of universal gravitation. True it is that the new doctrine, which is recognised under the name of the dynamical theory of heat, has not come upon scientific men in the complete and startling manner in which Newton announced his great discovery ; but al- though its development has been gradual, its applications are almost universal, and we are ever finding it a guide to valuable results which would probably have remained undiscovered were it not that a new impulse had been given to our thoughts. This chapter is devoted to an account of the progress of the steam-engine, under a perception of the doctrine of latent heat, and extends only to the period of Newcomen and Watt, when the state- ment that heat was a material substance was almost universally accepted as being true. In pursuing still further, through sub- sequent chapters, the progress of improvement and discovery, we shall gradually develop the application of that mechanical theory which has displaced all others, and has become the foundation on which the whole fabric of physical knowledge is built up. It appears that in the year 1757 Black commenced a course of lectures in the University of Glasgow, and at that date the ac- cepted opinion on the subject of the liquefaction of any substance (say, for example, ice) by the agency of heat was the following : A certain quantity of heat being competent to raise the tem- perature of a mass of ice from 31 F. to 32 F., the same quantity of heat would be competent to melt the ice completely and to produce an equal weight of water at 33 F. In other words, the rise of the thermometer revealed the entrance of heat into the melting body, and gave an exact measure of the quantity so entering and combining with its substance. This was the statement propounded in the schools at the time referred to ; and, in respect of congelation, it was supposed that the inverse process was a simple undoing of that which had been done before, whereby water lost no more heat when passing into ice than that indicated by the fall of the thermometer. Black was, however of opinion that when a solid substance Doctrine of Latent Heat. 3 sucli as ice, changed into a liquid, it received a much greater quantity of heat than that perceptible immediately afterwards by the application of a thermometer ; and he performed an experi- ment which not only established his conclusion, but also .gave him a measure of the excess of heat required to cause liquefaction in a solid substance. BLACK'S DOCTRINE OF LATENT HEAT. The object being to estimate the amount of absorption of heat into melting ice, and the concealment of it in water, Black selected two thin globular glasses, A and B, each about 4 inches in diameter, and very nearly of the same weight. Into A he poured 5 ounces of pure water, which he congealed by a freezing mixture of snow and salt, and after allowing the glass to stand for a few minutes until the ice inside was beginning to melt and the temperature of the surface had risen (in his estimation} to 33 F., he suspended A by a slender wire in a large empty hall, the air of which remained at a uniform temperature of about 47 F. through- out the experiment. In like manner he poured into B exactly 5 ounces of water previously cooled as nearly as possible to 33 F., and after placing a very delicate thermometer therein, he suspended this latter vessel at a distance of 18 inches from A. At the end of one half-hour the water in B rose to 40 F., but it was not until a lapse of ten and a half hours that the water in A irrived at the same temperature, and that the whole of the ice became practically melted, the residue being a very small spongy mass which was disregarded. Black reasoned, according to the scientific language of that day, somewhat as follows : The external heat is entering the water-glass with a certain celerity whereby it* has received 40-33 or 7 degrees of heat in one half-hour ; the external heat is entering the ice-glass under similar circumstances, and the heat received by the ice-glass in twenty-one half-hours is 21 x (40-33) or 147 degrees. This is a quantity of heat which, had it been added to the liquid water, would have directly raised its temperature by a correspond- ing amount. No part of this heat, however, appears in the water except, at the utmost, 40-32 or 8 degrees, and the inference is B 2 4 The Steam-Engine. that the remaining 139 or 140 degrees have been absorbed by the melting ice and are concealed in the water into which it has been changed. The expression ' a degree of heat ' was here used as meaning that which is properly called a 'unit of heat,' and which cannot be defined until the theory of heat is explained. The student will find the whole matter set forth in the second chapter ; at present he should regard heat as something measurable as to quantity, although not a material substance, a thing apparently impossible at first sight, but hereafter shown to be entirely reasonable. At this stage he should be careful to avoid the use of the word ' degree ' except as applied to temperature. As a general rule, it is wrong to estimate quantities of heat by degrees of temperature. For a definition of temperature we refer to Mr. Maxwell. DEF : The temperature of a body is its thermal state con- sidered with reference to its power of communicating heat to othe? bodies. For a definition of latent heat take the following : DEF : Latent heat is the quantity of heat which must be com- municated to a body in one given state in order to convert it into another state without changing its temperature. In like manner it was taken for granted that after a body is heated up to its vaporific point, nothing further was necessary than the addition of a little more heat in order to change it into vapour, but Black disproved this notion by a series of experiments, whereof one is recorded as having been made on October 4, 1762.- Into each of two flat-bottomed tin-plate vessels, about 4 or 5 inches in diameter, he poured the same quantity of water at a tem- perature of 50. The vessels were placed on an iron plate, nearly red-hot, under which a fire was burning, and the water in each began to boil after an interval of four minutes. In twenty minutes more the whole of the water had boiled away ; and since it had gained (in the imperfect language of that day) 162 degrees in the first four minutes, or 40^ degrees in one minute, and since the tem- perature of the steam was no higher than that of the boiling water, the experiment showed that 20x40^ or 810 degrees of heat had been absorbed by the water and carried off by the steam. This result is not accurate, for the sources of error are numerous, but Doctrine of Latent Heat. 5 the experiment induced more careful investigation, and it is now generally taken that 966-6 units of heat become latent when one pound of boiling water is converted into steam. Another illustration is thus described by Black : ' I have put a lump of ice into an equal quantity of water heated to the temperature of 176 F., and the result was that the fluid was no hotter than water just ready to freeze.' Assuming this to mean that the ice in melting cools the hot water down to a temperature of 33 F., we should have 176-33 or 143 as the number of units of heat on the Fahrenheit scale which became latent during the liquefaction of one pound of ice at 32 F. This number expresses the latent heat of liquefaction in the case of ice. Even at the present day the writers on heat are not in agree- ment as to the measure of the latent heat of the liquefaction of ice. Tyndall assigns the number 143, Balfour Stewart adopts 142, and Maxwell 144, as the number of units of heat on the Fahrenheit scale which become latent in the passage of i Ib of ice at 32 F. into water at the same temperature. It appears, therefore, that heat becomes latent when a sub- stance undergoes a change of consistence, that is, when it passes from a solid into a liquid state, or from a liquid state into one of vapour. Hence we speak of the latent heat of fusion, and of the latent heat of evaporation. But heat disappears under other conditions, as will be explained, and accordingly it becomes neces- sary to refer to the disappearance of heat during expansion as well as during certain chemical changes. The doctrine of latent heat, so far as it is material at present, relates only to the cases of liquefaction and evaporation. THEORY OF HEAT AT THE TIME OF BLACK. In order to prepare the way for the first great discovery in the steam-engine, we should carefully consider the view which Black himself entertained as to the nature of this thing called heat which became latent during the conversion of ice into water or of water into steam. To us. at the present day, while profiting by the light of the 6 The Steam-Engine. knowledge everywhere existing, it seems incredible that anyone who thought on the subject could have seriously entertained any doubt but that something capable of being measured as to its quantity was really passing from the furnace into the boiler of an engine during the whole time that the water was being converted into steam. Any such erroneous notion as the measurement of quantities of heat by a thermometer was swept away at once and for ever by Black's experiments ; but nevertheless it is a remark- able thing to find that the very men who became the leaders in a new advance of scientific research should have embraced theo- retical views as to the agency of heat which in their turn barred the way to all true progress. The doctrine of latent heat was made transparently clear by the facts just referred to, but the question as to what heat really was received a most unsatisfactory solution. For the present pur- pose it is unnecessary to refer to the arguments by which the so- called material theory of heat, or the doctrine of caloric, was sup- ported. It may here suffice to state the view entertained by Black and those who followed in his steps, viz., that heat is a stibtle elastic fluid termed caloric, which surrounds, as by an atmosphere, the grosser particles of all material bodies ; the atoms of caloric being so much smaller than those of matter, that each material particle may be conceived to be surrounded by a large number of them. Further, the atoms of caloric have a strong repulsion for each other at the same time that they attract the particles of matter. In other words, heat is an indestructible, elastic, gaseous fluid, which weighs nothing, which insinuates itself into the pores of bodies, causing them to expand and dilate, which combines with bodies so as to become latent when they pass from a solid to a liquid state, or from a liquid into a vapour, and which reappears when the passage is reversed. Just as certain gases are absorbed and become fixed in bodies, so this subtle fluid of heat enters into every form of matter, and causes repulsion by reason of the property that its own particles are self-repulsive and not attrac- tive. In this way the repulsion due to the heat fluid separates the particles of ice till it becomes water, and still further drives asunder the particles of water till it passes off as steam or vapour. Savery's Engine. y At the time of Watt, when the advantage of using high-pressure steam came to be discussed, the absorption of heat in generating steam was thus regarded, and it was said : ' Highly elastic steam requires as much more heat for its formation as it is more elastic ; for it is, in fact, only a greater quantity of heat and water crowded into a smaller space. Hence, any greater power that it possesses will be obtained by a proportionately greater expenditure of heat.' The conception that heat was a fluid received all possible adornment at the hands of mathematicians, as in Kelland's theory of heat, A.D. 1837, which was a text-book at Cambridge down to the year 1849, or even later. In this work the statement on the first page is that ' the popular (probably the correct) idea attached to heat or caloric is that of a subtle fluid emanating from hot bodies and entering between the particles of colder ones/ SAVERY'S ENGINE. ART. i. We pass on to review the invention of steam-engines as preceding and accompanying the discovery of the doctrine of latent heat, and we prefer to begin with an account of the invention of a steam-engine which was the subject of letters patent, bearing date July 25, 1698, and granted to Thomas Savery. An account of this ' engine to raise water by fire ' was set forth by the inventor in a treatise called ' The Miner's Friend.' A cheap reprint of the paper, together with facsimile copies of Savery's drawings, can be obtained at the Patent Office. In a letter addressed to the ' Gentlemen Adventurers in the Mines of England ' the patentee says that he should never have pretended to any invention by the old causes of motion, but that he ' had happily found out this new, but yet much Stronger and cheaper, force or cause of motion than any before made use of.' Then he points out the advantages of the new method, and makes one observation which gives an idea of mechanical construction at that time : ' As for pump-making, that part of the trade will be much improved by my engine, for I must use board and timber for pipes, and have considerable employment for pump makers and carpenters for timber used about my engine. . . . For my design is not in the least to prejudice the artificers, or, indeed, any other 8 The Steam-Engine. sort of people by this invention, \vhich on the contrary is intended for the benefit and advantage of mankind in general.' Coming after the discovery of the law of atmospheric pressure, Savery's engine was based on the principle of the barometer, the action being that water was forced upwards into an empty receiver by atmospheric pressure, and was afterwards carried to an ad- ditional height by the pressure of steam. The arrangement and operation of its working parts will be understood from an inspection of fig. i, which is a diagram show- ing the principle of the engine without giving the details of its construction. Steam is generated in a boiler A, and passes into a receiver B, which communicates with a pipe H K leading from some water below the level of the apparatus to a reservoir overhead. At E and D are two clack valves, each opening upwards, and F is a tap for throwing cold water on the receiver. FIG. i. The action is the following : The stopcock c, which admits steam from the boiler into the receiver, is opened, and the rush of steam expels the air from B by driving it upwards through E. Then F is opened and c closed, while a jet of cold water is allowed to play upon the outside of B, thereby condensing the steam to a extent and lowering the pressure of the vapour in B. Savery's Engine. 9 pressure of the external air at H presently forces a quantity of water up the pipe H and through the valve D, whereby the receiver becomes nearly rilled with water. Steam is again admitted into the receiver and forces out its contents through the valve E. The tap F is opened with the same result as before, and the action is renewed. A drawing which shows the general appearance of the engine and the mode of applying it to the draining of a mine, is to be found in * The Miner's Friend/ There are two receivers, each similar to B, the object being to force water out of one vessel while the other is being rilled, and thus to render the flow con tinuous. The boilers and receivers stand upon a stage which ap- pears to be some 20 or 25 feet above the level of the water, while the height of the overflow may be 30 or 40 feet above the boilers. A trial of Savery's engine, as made at Manchester in 1774, is recorded by Smeaton. The receiver was a cylinder, 2 feet in diameter and 7 feet high. The engine delivered water at a height of 1 9 feet above the surface of a well, and made 7^ strokes per minute, each stroke filling the receiver to a height of 6 feet. The work done was the raising of i8| cubic feet of water per stroke through a height of 19 feet, which was equivalent to raising 136 cubic feet per minute to the same height. The consumption of coal was 32 cwt. in 24 hours, or about i j bushels of 84 Ibs. per hour. Each bushel of coals would therefore raise about 5^ millions of pounds through one foot. This is less than one-tenth part of the work performed by a modern pumping-engine. The loss of heat was enormous. First, there was the conden- sation of a quantity of steam, consequent upon its coming in contact with the cold water about to be driven out by it. No doubt this action would speedily come to an end, because a layer at a boiling temperature would form upon* the surface, and the bad conducting power of water would prevent this layer from extending to any depth, but in the mean time a considerable waste of heat took place. And secondly, during the expulsion of the contents of the receiver additional surfaces of cold metal would be continually presented which would cause condensation, the neat so absorbed being entirely wasted. The principal defect, qamelv. the alternate heating and cooling of the receiver, remained io The Steam-Engine. tmcorreeted and clung to the engine through all subsequent stages of modification and improvement until the invention of a separate condenser in the year 1769. THE PRESSURE OF STEAM FROM WATER BOILING IN THE OPEN AIR IS EQUAL TO THE PRESSURE OF THE ATMOSPHERE. 2. There are many simple experiments ' for showing that the pressure of steam from water boiling in an open vessel is equal to the pressure of the atmosphere. i. A cylindrical vessel with flat ends, made of tin-plate, say 5 inches in diameter and io inches long, has a stopcock fitted at the top. A small quantity of water is poured into the cylinder, and made to boil by the heat of a lamp. As soon as steam issues freely from the stopcock, the tap is closed and the vessel is ex- posed to a jet of cold water ; this condenses the steam, whereby a partial vacuum is formed within the vessel, and the atmospheric pressure causes its sides to collapse and to flatten together with considerable violence. The explanation is that the steam displaces and drives out the air just as it cleared the air from the receiver B in the Savery engine but supplies a pressure undistinguishable from that of the atmosphere, which pressure continues until conden- sation takes place. 2. Another experiment, very easy of performance, gives the young student an insight into some fundamental properties of steam. A glass flask, A, about 4 inches in diameter, is partly filled with water and placed over the flame of a lamp. c D is a bent glass tube, one leg of which is open and passes through a cork in the neck of the vessel, while the other terminates in a fine orifice and dips into a beaker of cold water. First, let the open end of the tube in A be raised above the level of the water. On applying heat, bubbles of air continue to escape into B ; this shows the expansion of air by heat as well as the displacement of it by the vapour of Pressure of Steam* 1 1 water. The bubbling of the air in B goes on until the water has been boiling some little time, the steam which is carried over with the air being condensed in the tube itself ; but presently no more air escapes and a loud cracking noise indicates the escape and condensation of the steam at the orifice. The next thing to be noticed is the rise of temperature of the water in B. It may easily be arranged that the water in B shall be caused to boil by the condensation of the issuing steam, and then we have the water boiling in both vessels. This result was observed by Watt and caused him to consult with his friend Dr. Black as to the correct explanation of it. Secondly, press the tube further into A until the end dips below the level of the water, and remove the beaker. It will now be seen that the water rises up the tube and begins to travel along c D. By withdrawing the lamp and again applying it, the end of the column of water may be made to move to and fro along c V, thereby indicating the delicacy of balance between the pressure of the steam in A and the pressure of the atmosphere outside the vessel. Finally, replace the beaker, and the water can be passed from B to A or from A to B at pleasure. SAVERY'S ENGINE INADEQUATE FOR DRAINING MINES. 3. In considering the practical working of Savery's engine it is necessary to remember that although water could be raised through a height of 20 feet or thereabouts into the receiver by simple atmospheric pressure, there would still remain the task of forcing it to the top of the mine, and for this purpose a supply of steam would be required at a pressure proportionate to the height of the column of water lifted, every additional 33 feet of water demand- ing an increased pressure of 15 Ibs. on the square inch, which again would require to be supplemented to the amount of 3 or 4 Ibs. in the boiler in order to overcome loss by cooling, condensation, and friction. The main obstacle to the application of the apparatus on a large scale would be found in the boiler. How was a vessel to be constructed which should support with, safety an internal burst- 12 The S team-Engine. ing pressure some two or three times greater than that of the atmosphere ? The practical difficulties connected with the con- struction and form of boilers will be discussed in a separate chapter, and here it may suffice to refer to Mr. Bramwell (' Lectures on the Steam-Engine '), who remarks : ' It is by no means surprising that the mechanical skill and appliances of that time were unable to cope with the demands made upon them, and that pipes, joints, and cocks leaked and gave way/ whereby it became impossible to make a good working engine for mines. A pumping apparatus on Savery's principle was thus inadequate to the wants of mining engineers, and the problem of adapting the power of steam to the lifting of water through considerable heights yet remained open for solution. It was speedily mastered by the inventive genius of Newcomen, whose engine, improved and altered and remodelled by Watt, has yet remained to the present day as the representative type of a single-acting pumping engine. NEWCOMEN'S INVENTION OF THE ATMOSPHERIC ENGINE. 4. It appears that about the year 1710, Thomas Newcomen, ironmonger, and John Cawley, glazier, of Dartmouth, in the county of Devonshire, (whose names are associated as the makers of the first engine which worked a pump), made several experiments in private, and in the year 1712 put up at Wolverhampton an engine which acted successfully. The progress made was very rapid, and it is recorded that in the year 1737 there was a pumping engine of the Newcomen construction working a succession of pumps each 7 inches in diameter and 24 feet apart, and making 6 feet strokes at the rate of 15 per minute, whereby water was pumped from cistern to cistern throughout the whole length of a shaft 267- feet deep, by steam at or near the atmospheric pressure. Nothing can show more clearly the remarkable character of Newcomen's invention than a statement of these numbers, but it remains to set forth the exact principle as discovered and applied. It would seem that improvements connected with the steam- engine have followed closely upon those made in connection with enquiries into the nature and properties of air. As pointed out by Mr. Scott Russell in his excellent work on the steam-engine, Newcomers Engine. \ 3 Savery's idea was nothing more than an application of the discovery of the law of atmospheric pressure; and in like manner Newcomen might well have been a pupil of Otto von Guericke, and might have claimed merely to have put to a practical use one of the earliest experiments on the power of an air-pump. As a matter of fact it is very probable that Newcomen worked out the problem quite independently of any previous knowledge of what had been done by Otto von Guericke, but in collating the history of inven- tions it is impossible to lose sight of the various steps made in one common direction. The most striking early experiment with the air-pump was the cohesion of two hemispheres known as the Magdeburg hemispheres, but there was another illustration nearly as remarkable, which was the following : A vessel of copper made truly cylindrical was fitted with a piston 8 inches in diameter, which allowed no air to leak round it. The piston was attached to a rope passing over a pulley above the cylinder and carried on one side so as to run over a second pulley before being attached to a heavy weight. When the trial began the weight was on the ground, and the piston was at the top of the cylinder. A boy then pumped out the air from the bottom of the cylinder by means of an air-pump, and the result was that the pressure of the external atmosphere on the movable piston forced it down and lifted the weight. The work here done by the air-pump could be accomplished equally well by steam. The exhaustion of the cylinder might be effected by a jet of steam, which would displace the air within, and supply a pressure equal to that of the atmosphere. Upon condensing the steam the cylinder would be exhausted even more completely than by the mechanical action of an air-pump, and the piston would be forced down just as in the previous experiment. Instead, however, of lifting a weight by a chain passing over a pulley, Newcomen employed a beam and gave us the type of modern beam engines. The object in view was to pump water out of a mine, and the arrangement for doing it was to hang the pump rods at one end of a strong beam centred on its middle point, and to hang the piston of a steam cylinder at the other end of the beam. The condensation of steam in the space below the piston produced a vacuum, and the piston was forced downwards 14 The Steam-Engine. by the pressure of the atmosphere. The descent of the piston at one end of the beam caused the rise of the pump rods at the other end, and thus the atmosphere was continually exerting a mighty force in pulling down one end of the beam against the drag of the pump rods. As soon as steam was readmitted under the piston the pressures on its upper and under surfaces were balanced, whereby the weight of the pump rods caused them to descend and carried the piston to the top of the cylinder. This was the general plan of the engine, and it is said that a beam was indispensable, for there was at that time no special machinery for boring out cylinders, and the packing of a piston so as to make it steam-tight was most easily effected by a layer of water lying on the top thereof. In order to use this water-packing the cylinder was of necessity vertical, and the pumps did their work as the piston de- scended. It will be seen that the leakage would be trifling during the ascent of the piston, at which time the pressure of the steam balanced that of the atmosphere, and that on the descent of the piston or during the condensation, the leakage might be consider- able, but it would do no harm but rather good, as the water passing into the cylinder would help to condense the steam. A story is told to the effect that in putting up his first engine, Newcomen in- tended to condense the steam by dashing cold water on the out- side of the cylinder, and was surprised to find the engine make several strokes and very quick together; on searching he found that the piston leaked so much as to allow a quantity of cold water to pass to the inside of the cylinder, and thereby to condense the steam. This led to the use of a jet condenser as it is called, that is, a jet of cold water thrown in a spray into the interior of the cylinder itself. DESCRIPTION OF NEWCOMEN 's ENGINE. 5. The general arrangement of Newcomen's engine is shown in the diagram. A piston p, movable in the steam cylinder A, was attached by a chain to one segmental end of the working beam, the pump rods R being hung by a chain at the other end. The boiler B was directly under the cylinder, and a plate or regulator valve K admitted the steam thereto. Towards the Newcomerts Engine. 15 bottom of the cylinder was a small pipe terminating in a clack valve n, called a smiting valve, which opened upwards. A pipe E F leading to a cistern of water overhead was fitted with an injection-cock E, and there was an eduction or waste pipe L M ter- minating in a small cistern, and having at its end a clack valve M immersed in water and opening upwards. The drawing also FIG. 3. shows a vertical rod H G, called a plug rod, which was employed for working the valves, but no attempt is made to indicate the manner in which the connections were made. There was also a small pump T which raised water into the cistern above F, the pipe connecting T with the cistern not being shown. The weight of the pump rods was greater than that of the piston, and acted as a counterpoise to keep it at the top of the 1 6 The Steam-Engine. cylinder unless brought down by external pressure. In order to work the engine, the pressure of the steam in the boiler should be at least i Ib. per square inch in excess of that of the atmosphere, and the reservoir should be several feet (usually 10 to 12) above the bottom of the cylinder, whereby a strong jet of injection water would be thrown in. The piston being, as above stated, at the top of the cylinder, the steam regulator K was opened and the entering steam cleared out all air from the space A, and drove it through the valve D. The injection-cock E was then opened, whereby the injeclion water entered the cylinder, slowly at first, but with great force afterwards, as the condensation went on and the pressure of the enclosed vapour was reduced to ^ or ^ that of the air outside. The injection-cock was provided with a hammer weight to ensure its opening quickly. The condensation of the steam took away the pressure from the lower surface of the piston, and there being nothing to balance the pressure of the atmosphere on its upper surface, the piston descended and lifted the pump rods together with the column of water resting upon the buckets. In this way the down stroke of the piston, technically called the ' indoor stroke] was completed. The ascent of the piston in making the return or ' outdoor ' stroke was effected by closing the injection-cock E, and opening the regulator K so as to admit a fresh supply of steam. The waste injection water at the bottom of the cylinder would cause some loss of the entering steam, but it would soon be expelled through the eduction pipe. The pressure on the lower surface ot the piston would be at first a little greater, and afterwards about equal to that of the atmosphere, and hence the weight of the purnp rods would carry the piston to the top of the cylinder. The injection-cock would then be opened and the action would go on as before. 6. The following example of the working of a small Newco- mcn's engine is given by Farey, and demonstrates its superiority over Savery's contrivance. It is said that the original engine put up at Wolverhampton had a cylinder 23 inches in diameter with a 6 feet stroke, and made 15 strokes per minute when worked by hand, or 12 strokes when made self-acting, and the dimensions now about to be given are nearly identical with these. Newcomers Engine, 17 EXAMPLE. Diameter of cylinder=24 inches, area=452 square inches. Pressure of atmosphere=i4j Ibs. Pressure of residual vapour in cylinder at temperature of 140 F. to 1 60 F.=4 Ibs. suppose. .. effective pressure on piston =i of Ibs. Here the pump was of 8-inch bore, and the lift 54 yards in perpendicular height, whence weight of column of water =3, 535 Ibs. Taking the pressure on piston at 7-8 Ibs., we have 452 x 7-8 =3,525, and therefore a pressure of 7*8 Ibs. will about balance the weight of the water lifted, leaving the difference to raise the counterpoise and overcome the friction of the engine. Let the stroke of the piston be 5 feet, and the number of strokes 15 per minute. /. Work done=3535 x 75 foot-pounds =2 65, 125 foot-pounds. Adopting Watt's estimate that a horse can raise 33,000 Ibs. through one foot in one minute, we have the horse-power of the engine = 265,125 = 8 nearl 33,000 Also the quantity of water raised per minute is equal to 26*1 cubic feet, which is 1,566 cubic feet per hour. 7. A singular fact is observed in the working of the engine, namely, that at the beginning of the ' indoor ' stroke the cylinder is heaved upwards with a jerk. In a large engine the weight of the cylinder will not counterpoise this upward action, and accord- ingly massive beams are built into the wall of the engine-house in order to hold the cylinder securely in position. The lifting of the cylinder is caused by the immediate con- densation of steam when the injection water is^rst admitted, and affords a remarkable illustration of the rapidity with which the steam loses its elastic force in the presence of a colder body. The pressure is instantaneously relieved, but there is a small interval of time, probably from to \ a second, before the inertia of the pump rods and of the water column is overcome, and the piston begins to move. During that interval the pressure of the atmosphere on the piston and on the base of the cylinder tends to bring them together, and whichever can move first will do so. c 1 8 The Steam Engine. Usually it is the piston which moves, but during the small interval while the piston is held immovable by the inertia of the pump rods, the cylinder would be pressed up to meet the piston unless it were restrained, and hence the necessity of the precaution rtferred to. As regards the height of the cistern for the supply of injection water, it was usually 12 feet for an engine of 6 feet stroke, but was raised, in some of the largest engines, to 24 or 36 feet. 8. The construction of the Newcomen engine was greatly improved by Smeaton, who designed and erected an engine for the Chase-Water mine, in Cornwall, which had a cylinder of 72 inches in diameter, with a 9 feet stroke, and worked up to 76 horse-power. The whole structure was on an unexampled scale at that time, and it may be interesting to point to one or two masters of detail. Thus the cylinder weighed 4 tons 16 cwt., and was ioj feet long. The piston was in the form of a flat circular dish 66 inches in dia- meter and i \ inch thick, the edge of the dish being raised so as to form a vertical rim 5 inches high. Underneath the iron dish was a planking of wood 2\ inches thick, bolted on by a number of bolts, and forming the actual steamtight packing. The planking was surrounded by a hoop of iron \ inch thick and 2 j- inches broad. There were three columns of pumps, each i6| inches in diameter, and 17 fathoms in length, making a total lift of 51 fathoms. The weight of the column of water in the pumps was estimated at 14 tons. The load on the piston was 7| Ibs. per square inch. The great beam was 27 feet in length, and was made up by bolting together 20 balks of timber, the four nearest the central line being 1 2 inches square, and the remainder being 6 by 12 inches. There were three boilers, each 15 feet in dia- meter. This was the last effort on a system then about to pass away. The engine was set up in 1775, no less than six years after the date of Watt's patent ; and we are told that ' when erected it was the most powerful machine in existence. It worked for a few years, and was then altered by Mr. Watt to his improved system, which soon after superseded all the atmospheric engines in Cornwall, where fuel is very expensive, and the mines very deep.' Watts Experiments. 19 WATT'S EXPERIMENTS WHILE REPAIRING THE GLASGOW MODEL, 9. It now becomes necessary to enter upon a brief account of the great invention connected with the steam engine, and in doing so it may be convenient to refer to the illustration in the frontispiece. The engraving is from a photograph showing the present condition of the celebrated model of Newcomen's engine, which forms one of the principal mechanical treasures preserved in Scotland, and which was exhibited at South Kensington in the Loan Collection of 1876, with the following label attached to it : l In 1765, James Watt, in working to repair this model belonging to the Natural Philosophy class in the University of Glasgow, made the discovery of a separate condenser which has identified his name with the steam-engine.' We have an account of the progress of the discovery to which the mind of Watt was now directed in the language of the inventoi himself, and a very brief abstract is here given, partly in his own words. Watt says : ' I set about repairing the engine as a mere mechanician, and when that was done and it was set to work, I was surprised to find that the boiler could not supply it with steam, though apparently quite large enough ; the cylinder of the model being 2 inches in diameter and 6 inches stroke, and the boiler about 9 inches in diameter.' Such small models of engines often work very indifferently, and Watt's next observation was that the engine required an enormous quantity of injection water, though but lightly loaded by the column of water in the pump. He considered that the waste of steam was caused by the fact that the little cylinder exposed a greater surface for condensation in proportion to its contents than would be found in the cylinder of a large engine. Then he thought that "the cylinder of the model, being of brass, would conduct heat much better than the cast-iron cylinders of large engines (generally covered on the inside with a strong crust), and that considerable advantage could be gained by making the cylinders of some substance that would receive and give out heat slowly.' He next tried a wooden cylinder, well soaked in oil and baked to diyness, but it soon became apparent that the material was C 2 2O The Steam Engine. unsuitable, and that the proportion of steam condensed on ad- mission into the cylinder still exceeded that observable in large engines. He found also that any attempt to produce a better exhaustion by throwing in more injection water caused only a greater waste of steam. On reflection, he attributed some part of the difficulty to the boiling of water in vacuo at low heats, a dis- covery then recently made by Dr. Cullen, whereby the water in the cylinder would produce a steam, capable in part, of resisting the pressure of the atmosphere. Watt was then led to experiment as to the temperature of water boiling under pressures greater than that of the atmosphere, from which it appeared ' that when the heats proceeded in an arithmetical, the elasticities proceeded in some geometrical ratio.' Being now led to examine the bulk of steam which could be obtained from a given quantity of water boiling under atmospheric pressure. Watt made the following experiment : ' Into a Florence flask capable of holding 17! oz. of water, he poured i oz. of distilled water, and fitted a glass tube into the flask by a steam- tight joint made by packthread and putty.' He goes on to say : 'When the flask was set upright, the end of the tube reached nearly to the surface of the water, and in that position the whole was placed in a tin reflecting oven befo r e a fire, until the water was wholly evaporated, which happened in about an hour, and might have been done sooner had I not wished the heat not much to exceed that of boiling water. As the air in the iiask was heavier than the steam, the latter ascended to the top, and expelled the air through the tube. When the water was all evaporated, the oven and flask were removed and a blast of cold air was directed against one side of the flask to collect the condensed steam in one place.' Then he weighed the flask with these con- densed globules in it, again heated the flask and dried it by blow- ing air into it with a bellows, and found the weight of the water to be rather more than 4 grains (estimated at 4^ grains). Also the flask held lyj oz. of water, or 8,220 grains. From these numbers it was apparent that the volume of steam was about 1,900 times that of the boiling water from which it was generated. Allowing for sources of error in the estimation, Watt appears to have considered that i cubic inch of water at 212 F. formed Watt's Experiments. 21 i cubic foot of steam at 212 R, and at the atmospheric pressure. Both estimates are too large, and Mr. Maxwell gives 1,650 as representing approximately the number of cubic inches of steam at 212 F. obtained from i cubic inch of water at its temperature of greatest density, viz., 39*1 F. The next experiment was of great practical value : A glass tube being bent at a right angle, one end was inserted horizontally into the spout of a tea-kettle and the other end was turned down- wards into a vessel containing a known quantity of cold water taken from a well. The temperature of the water is not re- corded. Steam from the kettle was passed into the water until it began to boil, and the weight which it had then gained was found to be part of the original weight. Watt inferred that water when converted into steam can heat about 6 times its own weight of well-water to 212 F., or till it can condense no more steam, and he goes on to say : ' Being struck with this remarkable fact, and not understanding the reason for it, I mentioned the matter to my friend Dr. Black, who then first explained to me the doctrine of latent heat. On reflecting further, I perceived that, in order to make the best use of steam, it was necessary first that the cylinder should be maintained always as hot as the steam which entered it ; and secondly, that when the steam was condensed, the water of which it was composed, and the injection itself, should be cooled down to 100 F., or lower, where that was possible. The means of accomplishing these points did not im- mediately present themselves; but early in 1765 it occurred to me that if a communication were opened between a cylinder containing steam and another vessel which was exhausted of air and other fluids, the steam, as an elastic fluid^ would immediately rush into the empty vessel, and continue so to do until it had established an equilibrium ; and that if that vessel were kept very cool by an injection or otherwise, more steam would continue to enter until the whole was condensed.' Then Watt proposed to employ a pump to extract both the air and the water from this second vessel, which formed the separate condenser of the improved steam-engine. Other improvements ' followed as corollaries in quick succes- 22 The Steam Engine. sion.' Thus water packing was inadmissible, for if any watei entei ed into a partially exhausted and hot cylinder, it would boil and prevent the production of a vacuum. This defect he proposed to remedy by employing wax, tallow, or other grease to lubricate and keep the piston tight. Then he saw that the open mouth of the cylinder would admit air and cool the interior thereof, and he therefore proposed to ' put an air-tight cover upon the cylinder with a hole and stuffing box for the piston to slide through, and to admit steam above the piston to act upon it instead of the atmosphere.' There still remained the cooling of the cylinder by the external air, and this he remedied by the use of an external cylinder containing steam (now called a steam-jacket] surrounded by another of wood, or of some other non-conducting substance. WATT'S PATENT OF 1769 10. Having thus pursued the train of thought developed in carrying out the invention of a separate condenser, it may be use- ful to turn to the specification of the patent granted -on January 5 1769 to James Watt (No. 913) for 'a new invented method of lessening the consumption of steam and fuel in fire-engines.' The document commences with an unfortunate sentence, viz. : ' My method of lessening the consumption of steam, and con- sequently fuel, in fire engines consists in the following principles' Now it is a maxim of the law that there cannot be a patent for a principle, and accordingly the property in an invention which revolutionised the mechanical industry of the whole world was nearly shipwrecked on the technical objection that the method claimed was a principle and not a manufacture ; and it was only after a long struggle that the question was determined in favour of the inventor. The Court of Common Pleas was unable to arrive at any decision, but the objection was finally disposed of by the strong common sense of Lord Kenyon, C.J., who observed : ' I have no doubt in saying that this is a patent for a manufacture, which I understand to be something made by the hands of man.' An account of the proceedings in Boulton and Watt v. Bull, and in Hornblower v. Boulton, is given in an * Abstract of Patent Cases,' by the author of the present treatise. Watt's First Patent. 2$ The specification goes on to describe the invention of the separat^eondenser, and shows the sense in which the word principle has been employed, 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 which enters it. ' i. By enclosing it in a case of wood or other materials they transmit heat slowly. * 2. By surrounding it with steam or other heated bodies. ' 3. By suffering neither water nor any other substance colder than steam to enter or touch it during that time. ' Secondly. In those engines that are to be worked wholly or partially by condensation of steam, the steam is to be condensed in vessels distinct from the cylinders, though occasionally com- municating with them. These vessels I call condensers, and whilst the engines are working they ought to be kept as cool as the air in the neighbourhood by the application of water or other cold bodies. ' Thirdly. Whatever air or other elastic vapour is not condensed by the cold of the condenser is to be drawn out of the steam vessels or condensers by means of pumps wrought by the engines themselves or otherwise.' The remainder of the specification is not important for the present purpose except towards the end, where the patentee states : ' 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 or other metals in their fluid state.' There was no drawing annexed to the specification, and in this respect the description was imperfect. ii. It appears that in Watt's first experimental model the con- denser consisted of two small pipes of thin tin-plate, each about 12 inches long, connected at their upper ends with the steam cylinder and at their lower ends with a common suction pump ; the tubes and pump being wnolly immersed in a vessel of cold water. This would now be called surface condensation. It further appears that the pipe condenser was afterwards 24 The Steam Engine. changed for an empty vessel, generally of a cylindrical shape, into which an injection of cold water played in the form of a jet, and the air-pump was enlarged in consequence of there being more water and air to extract. This is &jet condenser. Watt says that ' the change was made because, in order to procure a surface sufficiently extensive to condense the steam of a large engine, the pipe condenser would require to be very volumi- nous, and because the bad water with which engines are frequently supplied would crust over the thin plates and prevent their con- veying the heat sufficiently quickly.' Portions of some such apparatus as that here referred to are to be found among the collection of Watt's models now preserved at South Kensington. 12. The annexed drawing approaches closely to the form of one of the early pumping engines with a separate condenser, and it is introduced in order to show that a steam-jacket was an essential portion of the steam cylinder. Here, as in Newcomen's engine, the piston and pump rods were suspended by chains from the working beam, and the work done by the steam was that of lifting a weight. When the engine was at rest the piston remained at the top of the cylinder. The drawing shows a steam pipe s opening into a jacket or steam casing which surrounds the cylinder A, and which provides that a supply of steam shall always press down upon the upper surface of the piston p. The cylinder is now completely closed in, and accordingly the piston rod passes through a steam-tight box and packing at K, the construction of which will be explained in Chapter V., to which we refer for all such details. At the bottom of the cylinder is an eduction pipe leading into the condenser c, and there are two valves, E and D, the valve E opening into the eduction passage from the steam casing and the valve D being in the pipe itself. There is also an injection orifice for admitting cold water into the condenser, a foot valve R for preventing the return of any water or air after it has been drawn out therefrom, and an air-pump Q for removing from the condenser the water and air which are continually accumulating. At the top of the air-pump chamber there is a valve N (called a delivery valve), which opens into a reservoir or hot well, intended to receive the water that Early Engine by Watt. 25 has been warmed by condensation of the steam, and from which the supply for the boiler is continually being drawn. There is also a blow-off valve L, or valve opening outwards from the condenser, which corresponds to the snifting valve in Newcomen's engine. In setting the engine in motion the first thing to be done is to clear all the air from the lower part of the steam cylinder and con- denser, which is effected by allowing the steam to pass freely through FIG. 4. the condenser and to escape at the blow-off valve. The air being expelled, the engine can begin to move. The equilibrium valve E is closed, the eduction valve D remains open, and the injection cock is opened \ a jet of cold water now rushes into the condenser and creates a partial vacuum, the steam from below the piston flows into the condenser and is converted into water, whereupon the pres- sure of the boiler steam on the upper surface of the piston carries it down and raises the pump rods. When the piston reaches the 26 The Steam Engine. bottom of the cylinder the eduction valve is closed as well as the injection orifice, and the equilibrium valve is opened, thereby per- mitting the steam from the boiler to flow freely into the space below the piston. This equalises the pressure on both surfaces, and the weight of the counterpoise or of the pump rods carries the piston again to the top of the cylinder just as in the case of Newcomen's engine. All this time the air-pump is at work, removing water or air from the condenser, and sending it through the delivery valve into the hot well. The principle being that nothing colder than steam shall enter the cylinder during the working of the engine, the air which pressed down the piston in the atmospheric engine is replaced by steam at a pressure equal to or a little above that of the atmosphere. The function of the equilibrium valve is to allow steam to -pass underneath the piston, and the condensation takes place in a separate vessel, The early commentators on Watt's engine (Dr. Robison, for example), speak with interest of the fact that ' the cylinder may be allowed to remain hot ; nay, boiling hot, and yet the condensation may be completely performed.' The reason that this happens will be better understood when the properties of a vapour are discussed, but the instantaneous fall of pressure in the steam can hardly be accounted for without reference to the modern theory of the constitution of gases. 13. In the form above described, the engine should be regarded as a Newcomen's engine with steam instead of air acting upon the piston, and provided with a separate condenser. But a material change was soon introduced, for it was seen that many advantages would arise from cutting off the free communication between the boiler and the top of the piston by means of a third valve capable of regulating both the periods of admission and cut off of the steam in the upper part of the cylinder. At the present time three valves, viz. a steam valve, an equilibrium valve, and an eduction valve, are always to be found in a single-acting pumping engine of Watt's construction, and as a matter of precaution a fourth valve, or steam regulator, is interposed just on the boiler side of the steam valve, being kept permanently open while the engine is at work. The drawing shows the arrangement of the three principal Single-acting Engine. 27 valves in a single-acting engine of the early construction ; s is the trteam valve which admits steam from the boiler, E the equilibrium valve, D the eduction valve which opens or closes the passage to the condenser. The action is the following : As before, the piston being at the top of the cylinder, and the air being blown out of the cylinder, condenser, and steam passages, the valves s and D are opened, and E is closed. At the same time a jet of cold water is admitted into the condenser, whereby the steam which has displaced the air in the interior of the engine is condensed and a partial vacuum is formed below the piston, the result being that the steam above the piston forces it down and raises the pump rods. When the piston reaches the bottom of the cylinder s and D are closed and E is opened, whereupon the steam which drove the piston down circulates freely on both sides of it, neither assisting nor retarding its motion, and the weight of the pump rods or counterpoise drags the piston to the top of the cylinder. The double movement is thus completed, and it FIG. $. will be seen that s is an independent valve which can be closed at any period of the stroke. It should be noted that the method of representing the valves is conventional, the object being to indicate their operation, but not their construction. GENERAL ARRANGEMENT OF THE WORKING PARTS IN WATT'S SINGLE-ACTING PUMPING ENGINE. 14. The drawing on p. 28 is inserted in order that the general arrangement of the engine may be placed before the student. It is taken from one of the series of lecture diagrams published by Messrs. Chapman and Hall in connection with the Science and Art Department, and gives a fair idea of the respective work- ing parts. The beam is the first thing to notice as an example 28 The Steam Engine. FIG. 6. WATT'S SINGLE-ACTING PUMPING ENGINE. of construction, for it is put together with a due regard to me- chanical principles, and presents a striking contrast to the beam which appears in early drawings of Newcomen's engine. Single-acting Engine. 29 The beam of a modern pumping engine is, of course, no longer a trussed wooden beam, but it is made either of cast or wrought iron. By way of comparison we may refer to an example to be found in a pumping engine at the Clay Cross Colliery, which has a cylinder 84 inches in diameter, with a stroke of 10 feet, and raises water from a depth of 420 feet. Here the beam is of wrought iron, formed by two massive slabs placed side by side, each 2 inches thick, and 7 feet i inch deep at the middle, but tapering to 3 feet 4 inches at each end. The full length of the beam is 36^ feet, and when the several parts are all put together, with a strong cast-iron centre piece for supporting the gudgeons, ft weighs about 33 tons. In our drawing the pump terminates suddenly in a cistern of water, but the intention is not to follow out what is done literally, and the pumps at Clay Cross are combined lifting and forcing pumps, the water being lifted through 150 feet, and forced up the remaining 270 feet by a plunger. The valves in Watt's engine are worked by toothed sectors engaging with racks, a method which is represented in a drawing given in Chapter V. The operation of the valves is the same now as formerly, their construction being the only thing that has been varied ; and at Clay Cross the steam valve is 14 inches in diameter, while the equilibrium and eduction valves are re- spectively 12 and 1 8 inches in diameter. Except in matters of detail there is no essential difference between an early example of Watt's single-acting engine and the Cornish pumping engine of the present day. THE EXPANSION OF STEAM. WATT'S PATENT OF 1782. 15. Referring back to Article 13, where it Is stated that s is an independent valve which can be closed at any period of the stroke of the piston, we have now to consider the consequences of closing the valve s when some portion only, say \ or \ of the stroke, has been completed. Under such circumstances the engine is said to work expansively. There was no such thing as the expansion of steam, either in Newcomen's engine or in Watt's earliest engine with a steam- 30 The Steam Engine. jacket fully open to the cylinder. In the atmospheric engine the function of the steam' was merely to oppose a force which should continuously balance the pressure of the external air, and the work was done while the steam was being exhausted and not while it was in action. In the engine with a separate condenser the case was different, for the steam did the work and everything was ready for expansion as soon as provision was made for it by the introduction of a separate valve. But without a cut-off valve there would of course be no expansive woi king. It appears that as early as 1776 Watt made experiments on the expansion of steam, and about that time he altered an engine at the Soho Works so as to test the result of an early cut-off. Other trials succeeded, but it was not until the year 1782 that Watt took out his patent for ' certain new improvements upon steam or fire- engines for raising water, and other mechanical purposes/ and gave a demonstration of the economy due to expansion. The specification (No. 1,321) stated: ' My first new improvement in steam or fire-engines consists in admitting steam into the cylinders or steam vessels of the engine only during some part or portion of the descent or ascent of the piston of the said cylinder, and using the elastic forces wherewith the said steam expands itself in proceeding to occupy larger spaces as the acting powers on the piston through the other parts or portions of the length of the stroke of the said piston.' In other words, the steam- valve remains open until some definite portion of the stroke of the piston has been completed, and is closed during the remainder of the stroke. In order to comprehend the effect produced we must refer to a law discovered by Robert Boyle in 1662, and subsequently veri- fied by Marriotte. It is known as Boyle's or Marriotte's law, and is often termed the first law of the expansion of gases. BOYLE'S LAW. 1 6. The law may be stated as follows : The pressure ol a portion of gas at a constant temperature varies inversely as the space it occupies. In order to verify this statement roughly by experiment we Boyle's Law. 31 refer to a simple apparatus consisting of two pieces of strong glass tube A B, CD, each about inch internal diameter, and having their ends secured in a small metal box, F, provided with a stopcock. The tube AB is open at the top, and is a little more than 35 inches in length, while the shorter leg is somewhat over 10 inches long, and is provided with a cap closed by a screw-plug. A board having a scale graduated to inches carries the tubes, the zero of the scale being a little above the box, and the graduation for 10 inches marking the bottom of the plug, so that the space from o to 10 is a definite measured length of the tube c D. The plug at D being unscrewed so that air can enter, a little mercury is poured in at B, and the cock F serves to withdraw any excess and to bring the level of the mercury to the zero of the scale. Then D is closed and mercury is introduced slowly at B until the level in A B is 30 inches in excess of that in c D. Supposing the barometer to mark 30 inches at the time of the experiment, it will now be found that the level of the mercury in CD is 5 inches. That is, the air in c D is compressed into half its volume by a pressure of two atmospheres. In this way the law may be approximately verified ; and the important thing to be noticed is that it does not hold unless the temperature of the enclosed air remains unchanged. This is an imperative condition. Note. Since the pressure of a portion of gas at a constant temperature varies inversely as its volume, and since the density of the same portion also varies inversely as its volume, it follows that the pressure of a portion of gas varies directly as its density. It is stated by Mr. Maxwell that this law 4 ' is not perfectly fulfilled by any actual gas. It is very nearly fulfilled by those gases which we are not able to con- dense into liquids ; ' and moreover, that when a gas is about to pass by condensation into a liquid form ' the density increases more rapidly than the pressure.' In the year 1829 MM. Dulong and Arago carried the experi- ment above described to an extreme degree, for the tube A B was 32 The Steam Engine. elongated until the pressure of the compressed ah reached 27 atmospheres. These experimenters failed to detect any deviation from the law laid down by Boyle and Marriotte. BOYLE'S LAW REPRESENTED BY A CURVE. 1 7. The application of Boyle's law to the expansive working of steam will be made more clear if we deal with a substance, such as air, having the same elastic properties, but which does not pass into liquid in the same manner. Suppose the case of a cylinder with a circular base, partly filled with compressed air, and having a piston capable of moving along it without friction. Take o x 9 oy at right angles to each other, and let o x represent a line along which volumes are measured, called a line of volumes, and oy a line along which pressures are measured, or a line of pressures. Starting with a vo- lume of air enclosed in the space E A, it is evident that the travel of the pis- ton represents the increase of volume of the enclosed air. Also, if A R be the pressure of the air in E A, the line B s will represent the pressure in E B, under the condition that B s vol. E A _ o A A R vol. E B OB If a sufficient number of lines corresponding to B s be drawn the curve R s may be set out, and will present to the eye a series of changes of pressure and volume made in accordance with Boyle's law. But since the pressure of the enclosed air varies inversely as its volume, it follows that the product of the numbers repre- senting its volume and pressure is a constant quantity. That is, if o A = z>, A R = p. we have the equation p v = a constant, as an analytical representation of Boyle's law. It is known that , A ! i R \* k T 1 * 2 94> ' 2 77> <262 > ^So- Then each of these numbers representing the steam pressures at the respective points i, 2, 3 . . . 20, is supposed to remain constant during the passage from one division to the next in order, and is multiplied into the number i representing the space tra- velled over by the piston, and in that way a series of rectangles are obtained, each of which is an area representing work done. The addition of all the rectangles would give an area a very little less than that of the true diagram of work, that is, of the diagram set out, one side of which is the curved line in the sketch. The sum of all the 20 numbers enumerated is 11-562, which, divided by 20, gives '578, or approximately '57, as the mean pressure of the steam during the stroke. But ^5- is greater than , and the conclusion follows in these words : ' Whereby it appears that only J of the steam necessary to fill the whole cylinder is employed, and that the effect produced is equal to more than ^ of the effect which would have been produced by one whole cylinder full of steam, if it had been permitted to enter freely above the piston during the whole length of its descent.' By this explanation Watt showed conclusively that the direct result of expansive working was to obtain an increased amount of work by the consumption of a given quantity of steam. But the principle cannot be carried to any extreme degree, for the increase in the size of the cylinder, and the inequality in the pressure on the piston would soon present formidable difficul- ties. It will be necessary to recur to this subject after some preliminary enquiry into the principle of heat engines. Not only is expansive working a source of direct economy, but it is valuable also as a regulator, that is to say, it enables an engine to put forth variable amounts of power without the necessity of a permanent alteration in the pressure of the boiler steam. D 2 36 The Steam Engine. It is important to observe that in the drawing of the specifica- tion the cylinder has a steam-jacket surrounding its ends as well as its sides. The proposition in the original patent was that the cylinder should be kept as hot as the steam which entered it, and Watt was too good an engineer to enter upon a discussion as to the behaviour of steam when admitted into the cylinder at a total pressure of 14 Ibs. per square inch, and at the same time to show the cylinder entirely unprotected from the cold of surrounding bodies. The true value of the steam-jacket will be understood after the next two chapters have been examined, but it may be permitted to say that it is unfortunate that the teaching of the great master should have been so soon disregarded by those who came after him for example, Tredgold, in his large work on the steam-engine, enters into an elaborate attack upon the steam- jacket, which he sums up as follows : ' I hope this will be suffi- cient to establish the truth, that the steam-case is a useless addi- tion to the expense of an engine.' This was before practical men had taken account of the conversion of heat into work. THE DOUBLE-ACTING ENGINE. WATTES PATENT OF 1782 (continued]. 20. In order to adapt the steam-engine for driving machinery much yet remains to be done. Something must be known of the first principles of the conversion of motion before the problem can be fully grasped, and at present it may suffice to refer to a double-acting engine as set forth in the patent (No. 1321). Watt says : ' My second improvement upon steam or fire- engines consists in employing the elastic power of the steam to force the piston upwards, and also to press it downwards alter nately, by making a vacuum above or below the piston respectively, and at the same time employing the steam to act upon the piston in that end, or exerted upon the piston only in one direction, whether upwards or downwards.' The object here is to allow the steam to enter on one side of the piston, while the other side is in free communication with the condenser. For this purpose there are four valve chests, viz. at A, c, B, and F. In each chest there is a valve opening upwards, and between the valves A and c there is a passage leading to the Double-acting Engine. 37 top of the cylinder, while between B and F there is a passage leading to the bottom of the cylinder. The steam-pipe K A D B A 1 TUl FIG. 10. enables steam to enter either the top or bottom of the cylinder, according as the valve A or the valve B is lifted from its seat. In like manner by opening the valve c, the top of the cylinder is freely open to the condenser by means of the pipe c E F H ; and by opening F the bottom of the cylinder also opens to the exhaust. Thus, in the working of the engine A is opened for steam and F for exhaust, whereupon the piston descends ; other- wise B is opened for steam and c for exhaust, and the piston rises. HORNBLOWER'S PATENT OF 178:1. 21. There can be no question as to the fact that Watt invented the expansive working of steam, but, technically, he does not stand first in the records of the Patent Office, for he was antici- pated by a patent of Hornblower for a single-acting pumping engine which dates from the year 1781. The specification of this patent (No. 1,298) is a mere statement of what is to be done, and rather publishes an idea than an in- vention. The patentee says : 38 The Steam Engine. ' i. I use two vessels, in which the steam is to act, and which in other steam-engines are generally called cylinders. ' 2. I employ the steam after it has acted in the first vessel, to operate a second time in the other, by permitting it to expand itself, which I do by connecting the vessels together, and forming proper channels and apertures, whereby the steam shall occasion- ally go in and out of the said vessels. '3. I condense the steam by causing it to pass in contact with metalline surfaces while water is applied to the opposite side.' We can obtain no further information from the specification, FIG. ii. and the mode of carrying out the improvement is therefore taken from other sources, the sketch given being a mere lecture diagram. The engine is single-acting, and works with a separate con- denser, after the method invented by Watt The valves A, c, and E are open while B and D are closed, whereby steam from the boiler is entering the small cylinder H, and is also escaping from below the piston into the larger cylinder K, while steam from below K is passing into the condenser. The result is that both pistons descend together. When they arrive at the end of their respective strokes the valves A, c, and E are closed while the equilibrium valves B and D are opened, and the pressure of the steam is thus equalised on both surfaces of each piston, which is all that is required for performing the up stroke. It will be noticed that the cylinders are of unequal length, the Watt *s Invention of the Indicator. 39 reason being that the piston rods are attached to the same work- ing beam, and that the small, or high-pressure cylinder, is nearer to the centre of motion of the beam. WATT'S INVENTION OF THE INDICATOR. 22. In giving evidence before a parliamentary committee in 1829, Mr. Farey mentioned that Watt had been the first to invent and apply to steam-engines an instrument called an indicator, with the object of determining the amount of plenum and vacuum formed on either side of the piston of an engine during the work, and further that Watt himself had kept the invention in the com- plete and perfect form which was essential to its successful use a profound secret for many years. Mr. Farey also said : ' An instrument fell into my hands in Russia, where it had been made by some of the people sent out from England with Mr. Watt's steam- engines. On my return to England I made one, and also showed several other engineers how to make such for themselves, and since that time every one of those persons has very greatly improved his practice by the light it has enabled him to throw upon the operation of steam in an engine.' In an appendix by Mr. Watt to Dr. Robison's ' Mechanical Philosophy/ it is stated that although a barometer serves very well for ascertaining the degree of exhaustion in the condenser of an engine, it is quite unsuited for testing the degree of pressure or exhaustion in the steam cylinder on account of the vibrations to which the mercury would be subjected by the rapid fluctuations which take place. Then Watt proceeds to describe his invention of an indicator, or instrument for observing the changes of pressure of the steam or vapour in the cylinder of an engine. A cylinder, about i inch in diameter and 6 inches long, ex- ceedingly truly bored, has a solid piston accurately fitted to it, so as to slide easily by the help of some oil ; the stem of the piston being 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, which, having a conical end, may be inserted in a hole drilled in the cylinder of the engine near one of its ends, so that The Engine. by opening the cock a communication may be effected between the inside of the cylinder and the indicator. There is also a frame with a steel spring attached to it by one end, the other end being fastened to the piston. The cylinder is open to the atmosphere at the top, and the piston remains at rest when the steam pressure is equal to that of the atmosphere, but rises or falls as the pressure becomes greater or less than the air pressure. The amount of the rise or fall will be determined by the strength of the spring, which must be tested, and a graduated scale together with an index at the end of the piston serves for measuring pressures. The account here set forth appears to be all that Watt made public, and it leaves the instrument in an unfinished state. If, how ever, the index at the end of the piston be replaced by a pencil, and a board carrying a sheet of paper be caused to move to and fro underneath the pencil with a motion identical withi that of the piston of the engine but on a diminished scale, the direction ( of motion of the pencil being vertical and that of the board being horizontal, it will be found that the pencil traces upon the paper a closed curve, which is Watt's diagram of work. The instrument is shown in the drawing, which is copied from a sketch of early date, and is noi very correct in proportion. It is screwed into an opening made in the cylinder at one end, where- by the steam passes through the cock K into the lower end of the cylinder, and presses upwards against the piston P. The piston rod carries a pencil R which traces out the diagram on a board mo- ving to and fro horizontally in the frame AB CD. When the pressure of the steam balances that of the external atmosphere the piston is at rest, the spring being in its normal position and FIG. 12. exerting no force to resist either extension or compression. If, in this state of things, the sliding The Indicator. 41 board be moved to and fro, the pencil will trace the horizontal line E F, technically called the atmospheric line. Whereas, if the pressure of the steam (or uncondensed vapour below the piston) be either greater or less than that of the atmosphere the pencil will rise or fall, and the curve (which is a rough copy of the diagram of work) will be the result of combining the motion of the pencil with the to and fro movement of the board. The string passing upwards round the pulley on AD is attached to some moving part of the mechanism in such a manner that the motion of the board shall reproduce that of the main piston, but reduced until the travel is limited to the breadth E F. A weight is fastened to a second string in order to produce the return movement of the board. Hereafter it will be explained that the curve traced out by the indicator pencil gives more than a mere measure of the actual per- formance of the engine, and that it enables us to clear up many obscure points connected with the construction and action of the working parts. THE PROPERTIES OF A VAPOUR. 23. It is difficult, in writing a book of this kind, to treat every subject in a perfectly logical order. Strictly speaking we ought to begin with a complete series of definitions and experiments, and suppose nothing to be known until it has been explained in due course. If this method were adopted the chapters might gain in methodical arrangement but they would be intolerably dull, and it seems preferable to assume a general acquaintance with things which every reader would know, and to enter upon a more complete examination at any particular stage, where it would be useful. Recurring to the properties of the vapour of water, we remark that water gives off vapour at all temperatures, whether in a liquid or frozen state, and that the vapour, being a gas, has that property of indefinite expansion which characterises gases. It follows that if a small quantity of vapour be formed in a closed vessel, however large, it will at once expand so as to fill the whole of it, and will exert a pressure against the enclosing surface. 42 The Steam Engine. There are two cases to be considered 1. When the vapour is, in contact with the generating liquid. 2. When it is entirely separated therefrom. A simple experiment may be arranged for giving some insight into the behaviour of vapour when in contact with the generating liquid. i. Take a barometer tube, say about 33 inches long, and closed at one end. Fill it with clean mercury, which may be done by pouring in mercury nearly to the level of the open end, closing the end with the finger and then passing the large bubble of air two or three times up and down the tube. This removes all the minute bubbles of air which adhere to the glass, and mercury may be added up to about \ an inch from the open end ; then fill this empty space with bisulphide of carbon (a very volatile liquid), and invert the tube in a deep well of clean mercury, as shown in the diagram. The bisulphide of carbon will rise to the top of the tube, vapour will form in the empty space above the mercury, and will, by its pressure, drive down the column of mercury so as to shorten it considerably as compared with the column in an ordinary mercurial barometer. We have accordingly a small layer of liquid lying on the top of the mercury and several inches of apparently empty space above the liquid. A singular result may now be exhibited. Depress the tube by the finger so as to sink it in the well, or cause it to rise higher, when it will be found that the height of the column A p remains absolutely constant. If the tube be raised quickly the liquid begins to boil, fresh vapour is formed instantly, and the pressure is kept at a constant intensity. On the other hand, a portion of the vapour passes into the liquid state when the space which it fills is contracted, and nothing will alter permanently the height of the mercurial column except a permanent change in the temperature of the liquid and of the tube. Another experiment is instructive, as illustrating the action of vapour in the condenser of an engine. A glass receiver, H, from 4 to 5 inches in diameter, with a wide neck, has a cork fitted into it, through which three small tubes are passed. One tube, ABC, FIG. 13. Properties of Vapour. 43 pump is a bent barometer tube about 36 inches long and dipping into a vessel of mercury at c. Another is a tube, fitted with a stopcock, and terminating in a small glass cap, D. The third tube, E F, is connected with an air-pump. On pumping out air from the receiver we have an illustration of the barometer gauge of a condenser. The pressure of Toazrt the air in H is diminished in the same proportion as that in which the mercury rises in B c, and by comparison with an ordinary barometer the exact degree of exhaustion can be estimated. Thus, if the top of the scale was marked 30 inches and the mercury stood at 25 inches, it would be said that the pressure of the air in H was competent to support 5 inches of mercury. In common parlance that is called a vacuum of 5 inches, a phrase not very correctly adopted. Pour now some ether into D, and open the stopcock just enough to allow the pressure of the ex- ternal air to force a little of the liquid into the receiver. In an instant vapour is formed and the mercury drops through several inches. The vapour of ether may be then pumped out, and the mercury will rise as before, but it may be again as suddenly depressed by the admission of a fresh supply of ether. The rapidity with which vapour forms in vacuo is strikingly shown by these experiments, the results o which are in strict accordance with the known laws which regulate the behaviour of a vapour when in contact with the generating liquid, viz. : 1. Vapour exerts pressure. 2. Vapour forms with great rapidity in an empty space, though slowly in air. 3. The pressure of a vapour rises as you exalt its temperature 4. The further formation of vapour is arrested by the pressure of the vapour already formed. FlG< 44 The Steam Engine. 5. If the temperature be given, reduction of \olume causes liquefaction, leaving the pressure unaltered. 6. If the volume be given, reduction of temperature causes liquefaction. 24. When a vapour is formed in a closed space, and is in contact with the generating liquid, it is said to be saturated. That is the technical word for expressing its physical condition when just ready to yield some portion of liquid on the smallest increase of pressure or reduction of temperature. Thus steam at 212 F exerts a pressure equal to that of the atmosphere, and is called saturated steam, the condition being that it is taken direct from the boiler without being separated at a lower temperature and heated up to 212 F. by subsequent treatment. If it were so heated it would approach the condition of a permanent gas, and would be called superheated steam. The two extreme cases are those of a saturated vapour and a so-called permanent gas. The experiment gives an example of the former ; thus the vapour of bisulphide of carbon becomes in part liquefied rather than support an additional pressure of one or two inches of mercury. There is one gas which is ordinarily permanent, but may be liquefied by pressure without difficulty, viz., carbonic acid, and its properties have been investigated in a systematic manner by Dr. Andrews. ISOTHERMAL LINE FOR A VAPOUR. 25. The behaviour of a vapour when near the point of saturation may be studied by the aid of a diagram. Conceive that a mass of vapour exists at a volume o N, and pressure R N, its temperature being above that at which condensation would begin. Conceive also that its temperature remains constant ir()l during any changes of volume M NX and pressure through which it is FIG. IS- about to pass. According to Boyle's law the expansion or contraction of the vapour, so long The Pressure of a Vapour. 45 as it possesses the properties of a gas, will be given by the curved line P R. Suppose, further, that when the pressure is increased to p M liquefaction begins. At this point reduction of volume may go on, but the pressure cannot be increased, and the way to express that fact geometrically is to carry the line P s in a direction parallel to o x ; the vesult being that the ' isothermal ' is no longer curved throughout, but suddenly passes into a straight line at the point of saturation. EXPERIMENTAL DETERMINATION OF VAPOUR PRESSURE. 26. Let us now examine the methods adopted for ascertaining the pressure of the vapour of water at different temperatures, both above and below 212 F. The earliest accepted authority on this subject is Dalton, who published his results in the l Memoirs ' of the Lit. and Phil. Soc., Manchester, in 1802 (vol. v. page 551). It appears, however, that Watt had obtained approximate results as to the vapour pressure of water while working out his discovery, and that his mode of experimenting was substantially that adopted by Dalton. The paper in the Manchester * Memoirs ' begins with some prefatory observations on the remarkable increase observed in the elastic force of a vapour when heat is applied directly to the generating liquid : ' By increasing the temperature of any gas a proportionate increase of elasticity ensues ; but when the temperature of a liquid is increased the force of vapour from it is increased with amazing rapidity, the increments of elasticity forming a kind of geometrical progression to the arithmetical increments of heat. Thus the ratio of the elastic force of atmospheric air a>t 32 to that at 212 is nearly 5 to 7, but the ratio of the force of aqueous vapour proceeding from water of 32 and 212 is as i to 150 nearly.' This striking fact being pointed out, Dalton goes on to describe his experiments, and states that he introduced a very little water into the inside of a barometer filled with mercury, leaving a layer of or ^ inch of water upon the top of the mercurial column. The upper part of the tube was then enclosed io a larger glass tube, 2 inches in diameter and 14 inches long, by 46 The Steam Engine. means of two perforated corks which formed the top and bottom of a water chamber or hot bath enveloping the whole of the upper portion of the barometer tube, and wherein the water was maintained at a fixed temperature by means of a lamp. The vapour enclosed in the top of the barometer as well as the generating layer of liquid thus became heated at a constant tem- perature, and the depression of the column of mercury as com- pared with the column in a standard barometer showed the amount of pressure exerted by the saturated vapour. In this way Dalton had ' water as high as 155 F.' surround- ing the vapour tube. For higher temperatures up to 212 F. he modified the apparatus, and employed a tin tube 4 inches in diameter as a casing for the bath ; also the observation was made with a siphon barometer having two parallel legs, whereof one was enclosed in the bath, and the reading of the mercury in the leg outside the tin tube gave the required depression of the column as due to the pressure of the vapour. 27. Dr. W. A. Miller gives the following table of the pressures of the vapours of several liquids estimated in inches of mercury. Thus it appears that at 50 F. the vapour of bisulphide of carbon will depress the mercurial column through 7-846 inches, a fact which is apparent when trying the experiment described in Art. 23. Tempera- ture F. Ether Bisulphide of carbon Water Alcohol Oil of turpentine 4 H 2725 4-3S6 3'IIQ 036 082 131 256 32 7-146 5-008 182 501 082 50 U-278 7-8 4 6 361 948 090 68 I7-II7 11-740 686 1-732 168 104 35-971 24-310 2-168 5-159 460 140 68-121 43*71 5-874 I3-776 1-058 176 116-03 79-94 13-998 32-00 2 408 212 193-72 I30-75 30-00 66-33 5-310 We have seen that the condenser of a steam-engine has for its object the complete discharge of all steam from the working cylinder after it has done its work in propelling the piston. The degree of completeness with which this is effected will depend entirely on the temperature of the water after condensation, and The Pressure of Steam. 47 the table of pressures of the vapour of water shows at a glance what may be done. If ice at 32 F. were converted by the waste steam into water at 32 F. the pressure of the vapour left in the cylinder would fall to \ inch of mercury. The temperature of the condensing water is, however, commonly 110 F., giving off vapour capable of supporting a pressure of z\ inches of mercury. If a smaller quantity of condensing water be used it will be raised to a proportionately higher temperature, and a less perfect con- densation will be effected. At 212 F. the object of the condenser would be entirely frustrated. THE TEMPERATURE OF HIGH PRESSURE STEAM RISES WITH ITS PRESSURE. 28. It is well known that when water is confined in a closed vessel and heated, the pressure of the vapour formed therein con- tinually increases. The precise temperature of the vapour which corresponds with any assigned pressure has been a subject of care- ful enquiry, and an apparatus called a Marcet's boiler has been designed for exhibiting the relation to a class. It is n in a form which forbids any exact determination, but the student may contrast it with the arrangement employed by Regnault, and described in Art. 29. The apparatus consists of a small boiler, provided with a thermometer and a mercurial pressure gauge. The drawing shows the boiler containing a small quantity of mercury covered by a layer of water rest- ing upon it. The mercury is intended for filling the pressure gauge, which is a piece of barometer tube, c D, open at both ends, and passing down nearly to the bottom of the boiler. EF is a thermometer about 20 inches in length, whose graduations begin at 130 and go on to 250. A large thermometer is chosen, in order that its graduations may be seen at a distance. H is a pipe provided with a stopcock. On applying heat to the boiler by a Bunsen burner or a spirit lamp the temperature soon rises above 212 F., and some mercury will ascend the tube, by reason that the pressure of the enclosed vapour becomes greater than that of the external air FIG. 1 6. 48 The Steam Engine. The height of the column of mercury denotes the pressure of the vapour, and the corresponding temperature given by the thermometer may be observed ; thus at 230 F. we should find the column at a height of about \2\ ins., and so on. The effect of opening the stopcock should be noticed ; for, with a little care, it is easy to keep a small jet of steam blowing off without any fall in temperature or pressure, just as in the case of the boiler of a working engine, whereas, if the stopcock be fully and suddenly opened, the pressure and temperature drop at once, and the mer- cury in the thermometer very quickly falls to 212 F. REGNAULT'S EXPERIMENTS FOR DETERMINING THE PRESSURE OF THE VAPOUR OF WATER. 29. The methods above described have been improved upon by Regnault, who has published a complete series of observations of the pressure of the vapour of water, ranging from 32 C. as far as 230 C. For temperatures below o C. a special ap- paratus is required, a description of which is beyond the scope of this book, while for tem- peratures ranging from o C. to 50 C. the apparatus shown in fig. 17, which closely re- sembles that of Dalton, has sufficed. Two barometer tubes, corresponding to those of Dalton, stand side by side in the same vessel of mercury. The tube A is a common barometer, and the tube B is also a barometer, but with a small layer of water resting on the top of the mercury. The upper portions of both tubes are enclosed in a metal cylindrical vessel, filled with water, and provided with a glass window. The water in this vessel is heated by a lamp, and is agitated so as to keep the tempera- ture uniform throughout, while the depression of the mercury in B is noted by comparison with the ^column in A, the difference in altitude of the two columns giving the amount of vapour pressure at the temperature of the observation. For temperatures above 50 C. an apparatus has been con- The Pressure of Steam. 49 trived involving a special principle. The idea carried out has been to subject the water to the pressure of an artificial atmo- sphere capable of being regulated and measured with extreme nicety. The mercurial gauge no longer dips into the boiler, but a separate receiver connected with a pump is employed for produc- ing an artificial pressure on the surface of the heated water. FIG. 1 8. 1. There is a boiler, A, placed over a furnace, and fitted with four thermometers for ascertaining the temperature. 2. A condensing tube, B, is inclined upwards at an angle, and is surrounded by an envelope of cold water. Any steam issuing from the boiler would condense in this tube and drain back again. 3. A globular reservoir of air, c, is enclosed in a vessel of cold water, and is maintained at a constant pressure, either greater or less than that of the external air, by means of >a compressing or exhausting pump. This reservoir has a free passage through B into the boiler, and forms the atmosphere under the pressure of which the vapour is generated. 4. A measuring instrument of special construction is used for determining the pressure of the air in c, and is capable of being read to a pressure of twenty-seven atmospheres. In the drawing a mercurial siphon gauge serves to exhibit the nature of the measure- 5O The Steam Engine. ment, which is the same in principle to whatever extent it may be carried. By this apparatus Regnault was enabled to measure accurately the temperature of the vapour, and at the same time to preserve a nearly constant artificial pressure upon the surface of the water in the boiler. Note. Hitherto the term ' pressure' has been used in its ordinary sense, but the word has a technical meaning, and is used to denote the pressure in pounds on a square inch of surface. When we say that the pressure of steam, in a boiler is thirty pounds, we mean that the pressure of the enclosed gas on each square inch of the surface of the shell is thirty pounds. We append a few results of the pressures of the vapour of water estimated in inches of mercury at the sea level at different temperatures on Fahrenheit's scale, the place of observation being in latitude 53 21'. Our authority is Mr. Balfour Stewart, and the numbers are, no doubt, of a high degree of accuracy : Temperature Fahrenheit Pressure in inches of mercury Temperature Fahrenheit Pressure in inches of mercury 32 1810 215 3173 40 2475 220 34-98 3607 5178 225 2 3 38-50 42-30 g 7327 I -0227 240 250 50-85 6076 100 I-9I7 270 8530 120 3-423 300 136-72 150 7-540 350 274-78 200 212 23'435 29-898 4OO 430 503-90 698-58 CHAPTER II. HEAT IS NOT A MATERIAL SUBSTANCE. 30. WE pass on to describe two principal attacks made upon the theory that heat is a material substance, and shall give some details of Joule's experiment for determining the numerical measure of work done by the expenditure of heat. The sketch will be very brief, inasmuch as the subject matter is only introductory to the purpose of this volume. It is worthy of notice that the conception that heat was in some way caused by motion had been entertained before the time of Black, as to which it is customary to quote the following passage from Locke's writings, where it is stated : ' Heat is a very brisk agitation of the insensible parts of the object, which produces in us that sensation from whence we denominate the object hot ; so what in our sensation is heat, in the object is nothing but motion.' This idea did not find favour with Black, who argued against the possibility of accounting for the phenomena of latent heat on any such hypothesis (' Lectures,' p. 125), in the following terms : 'Some persons may perhaps imagine that the heat which thus disappears does not truly enter into the melting ice or become combined with that into which it is changed. This heat is perhaps entirely ex- tinguished and destroyed. As heat has been supposed by some to consist in a rapid tremor or motion of the particles of bodies, or of some subtle matter that is intermixed with them, those who choose to adopt this opinion may imagine that motion may meet with friction and resistance in the ice, and that a part of it maybe thus destroyed or the moving parts brought to rest.' Then he combats the idea thus set up by showing experimentally that ' while water is congealing it is constantly imparting heat to the air with- out becoming cooler itself,' and he considers that this heat must 2 52 The Steam Engine. have been previously absorbed or concealed in the water on the last occasion of its becoming liquefied by the melting of ice. The mistake here made consisted in adopting a belief that the motion of heat could be destroyed. At the time of Newton it was supposed that the motion arrested by fricton was absolutely lost and put out of existence. Any such idea is now entirely abandoned, and Black's reasoning has no application. By way of contrast to the erroneous statement thus laid down, it may be useful to lead up concisely to the modern views enter- tained as to the nature of heat COUNT RUMFORD'S EXPERIMENT ON THE PRODUCTION OF HEAT BY FRICTION. 31. A first overwhelming blow to the doctrine of caloric was ^iven by Count Rumford's experiment of causing water to boil by the agency of mechanical force, and the following details are extracted from a paper read before the Royal Society in 1798. In casting guns it is usual to leave a cylindrical head of metal at the muzzle end so as to ensure soundness of structure, the mould being placed in a vertical position with the muzzle end upwards. FIG. 19. The drawing shows the end of a six-pounder brass gun, having a cylindrical neck of solid metal, A, 2 -2 inches in diameter, and 3-8 inches in length. Beyond the neck the waste portion of metal forming the head for the casting was shaped into a cylinder c, 7-15 inches in diameter and 9-8 inches in length, having a cylindrical cavity bored out for the reception of a hard steel blunt borer. The borer was made from a plate of steel 3-5 inches wide Heat and Friction. 53 and -63 inch thick ; it is marked D in the figures, being shown both when turned edgeways and also when presenting its flat side. The cavity of the cylinder is given in section, with the borer in situ, the piece marked E being a rectangular iron bar terminated in a cylindrical plug and holding the borer D. The borer was firmly held at rest and was pressed against the base of the cavity by means of a screw, the estimated pressure being 10,000 Ibs. The gun itselt was rotated by horses, the number of revolutions being 32 per minute. The cylinder was enclosed within a deal box shown in section in the diagram. The box was 11*5 inches long, 9^4 inches wide, 96 inches deep, and it contained 1877 Ibs. of water. The square bar E, and the cylindrical stem A passed through packed water- tight openings in the sides of the box. The temperature of the water at the commencement of the experiment was 60 F. The rotation of the gun under a pressure of 10,000 Ibs. caused a considerable evolution of heat, traceable to the friction of the rubbing surfaces, and the heat so generated was but slowly con- ducted away by the comparatively slender neck of the cylinder. The result was that the temperature of the water rose as the trial went on, and at the end of one hour a thermometer placed in the water marked 107 F. At the end of the next half-hour the temperature had risen to 142 F., then in another half-hour to 178 F., and, finally, at the end of two and a half hours, the water boiled. In describing this result, Rumford breaks out into an enthusiastic recital of the effect upon those who witnessed it, and exclaims : * It would be difficult to describe the surprise and astonishment expressed in the countenances of the bystanders on seeing so large a quantity of water heated and actually made to boil without any fire.' He goes on to say : '- 1 By meditating on the results of these experiments, we are naturally brought to that great question which has so often been the subject of speculation, namely, What is heat? Is there any such thing as an igneous fluid ? Is there anything that, with propriety, can be called caloric ? ' The conclusion which he draws is full of sound philosophy, and is a statement which the student should examine carefully and carry in his mind through the enquiries here presented : 54 The Steam Engine. 1 In reasoning on this subject we must not forget to consider that the source of heat generated by friction in these experiments ap- peared evidently to be inexhaustible. ' It is hardly necessary to add that anything which an insulated body or system of bodies can continue to furnish without limita- tion cannot possibly be a material substance ; and it appears to me to be extremely difficult, if not impossible, to form any distinct idea of anything capable of being excited and communicated in the manner heat was excited and communicated in these experi- ments except it be motion.' DAVY'S EXPERIMENT ON THE MELTING OF ICE BY FRICTION. 32. On the recommendation of Count Rumford^ Davy was appointed to a lecturership at the Royal Institution in 1802. His experiment in refutation of the doctrine of caloric is regarded as conclusive. In an atmosphere at a temperature of 29 F. he rubbed to- gether two small slabs of ice, each 6 inches long, 2 inches wide, and f inch thick. The slabs were attached by wires to iron bars, and the friction was continued for several minutes. The result was that the ice melted at the surfaces of contact, producing water at a temperature of 35 F. Now a mass of water is known to contain an absolute quantity of heat far greater than that contained in an equal mass of ice, and it is therefore impossible to account for the presence of this heat on the assumption that heat is a material substance. Davy's conclusion is a wonderful example of clear insight into the nature of heat, and we shall adopt it as the guiding statement in considering the working of heat engines. It is expressed in the following sentence : ' The immediate cause of the phenomenon of heat is motion, and the laws of its communication are precisely the same as the laws of the communication of motion.' It follows that the three laws of motion laid down by Newton, together with the principles applicable to the measurement of the action of force, should be studied most diligently by anyone who desires to understand the theory of heat. Heat and Friction. 5 5 HEAT IS PRODUCED BY THE AGITATION OF THE MOLECULES OF BODIES. 33. After the experiments of Rumfordand Davy, the belief that heat was a material substance necessarily languished and died away, and the time has now come for stating more precisely the modern theory according to which the particles of all bodies by which we are surrounded are to be regarded as in a state of rapid and never ceasing agitation. In order to present to the mind a ' sense-image ' of the nature of heat, we begin by regarding all bodies as made up of assemblages of parts called molecules. A molecule may be of a complex character, consisting of distinct portions of matter held together by chemical bonds (as in the case of water, where a molecule is made up of separate parts of oxygen and hydrogen), and whatever may occur in the disposition of these separate parts or portions of matter, as to which we say nothing, it is agreed to call each whole collected mass a molecule, so long as its different portions do not break up and part company. Heat is produced by the agitation or motion of the molecules of bodies. But the motion of heat is too minute to be recognised in any way by the senses, and cannot be detected by direct obser- vation. It is evident, therefore, that very cogent evidence ought to be adduced before the new proposition is accepted. The doctrine of caloric may be untenable, and may have been de- molished by experiment, but the student should nevertheless distinctly set before himself the question How is a theory to be established which appeals for its support entirely to facts of ob- servation, and which yet starts with the assumption that the thing to be made manifest to the mental vision exists in a region where no direct observation has ever yet penetrated ? Without doubt there is an enormous difference between the work of demolition and the work of construction. The former is comparatively easy, but the latter can only be arrived at by a slow and tedious process. Two decisive experiments abolished at once and for ever the theory supported by Black, but not one, nor two, nor one hundred isolated experiments can be appealed to as con- clusively establishing Davy's proposition, and it is only by passing 56 The Steam Engine. ovei the whole domain of physical research that we meet with an aggregate of facts reconcilable with the one theory and irrecon- cilable with any other, and thus gradually yield to a conviction which it becomes impossible to resist. Mr. Maxwell tells us (' Theory of Heat,' p. 306) : ' The mole- cules of all bodies are in a state of continual agitation. The hotter a body is, the more violently are its molecules agitated. In solid bodies a molecule, though in continual motion, never gets beyond a certain very small distance from its original position in the body. The path which it describes is confined within a very small region of space. ' In fluids, on the other hand, there is no restriction to the ex- cursions of a molecule. Hence in fluids the path of a molecule is not confined within a limited region, as in the case of solids, but may penetrate to any part of the space occupied by the fluid. 'A gaseous body is supposed to consist of a great number of molecules moving with a great velocity. ' The actual phenomena of diffusion both in liquids and in gases furnish the strongest evidence that these bodies consist of molecules in a state of continual agitation.' THE CONVERSION OF WORK INTO HEAT. 34. In the year 1843 Mr. Joule made the following observation : 'When we consider heat, not as a substancej&tf. as a state of vibra- tion, there appears to be no reason why it should not be induced by an action of a simple mechanical character, such, for instance, as is presented by the revolution of a coil of wire before the poles of a permanent magnet.' Some striking experiments followed upon this suggestion, and it was shown that heat was actually in- duced in the manner anticipated. It is, however, not within the scope of this book to describe more than one illustration which has grown out of that originally suggested by Mr. Joule, and which powerfully confirms the belief that heat is caused by vibration. In order to perform the experiment which we are about to describe, it is necessary to be provided with a very powerful electro- magnet and a whirling table, the arrangement being to bring the axis pf the whirling table between the poles of the magnet and to Heat and Work. 57 rotate at a high speed a small copper tube containing an alloy of metal which fuses at a low temperature. After three or four minutes of rotation the alloy melts, and may be poured as a liquid out of the tube. The question then arises, what agency has been at work to fuse the metal. The heat is not traceable to direct friction, for the tube rotates in the empty space between the poles of the magnet and does not rub against anything. The effect must be in some way due to magnetism, for it is found that unless a battery current is sent through the coil of the magnet the rotation of the tube may go on as rapidly and as long as we please without producing any effect whatever. The tube remains perfectly cool, and there is no appearance of any heating action. The connection between heat and work becomes apparent upon testing the increased exertion necessary for rotating the spindle of the whirling table while the metal is being heated. Before the magnetism is set up, a certain amount of effort is necessary in order to overcome the friction and inertia of the moving parts and to keep up the rotation. But the moment the magnetism is called forth, an increased resistance is felt, and a greater effort must be made in order to sustain the speed of the whirling tube. The additional work so demanded is passed in the form of heat into the tube. The conversion of work into heat is direct and pal- pable, but the precise nature of the molecular changes presents great difficulties. It will suffice here to point out that the experi- ment is based on an observed fact, viz., that when a flat blade or strip of copper is passed between the poles of an excited electro- magnet a resistance is felt, and if the blade be moved to and fro the sensation experienced is not that of moving through free air but rather of cutting through some viscous substance which clings upon the knife. It appears that the magnetism sets up an electric current in the strip of copper when its opposite ends are brought into contact, as they would be if the strip were bent round into a tube, and that new sets of particles come into action during the rotation. The resistance felt is exactly like that due to friction, but it is here not traceable to the rubbing of any material sub- stances but rather to the indisposition of the metal to receive new currents of electricity induced by magnetic action and involving 58 The Steam Engine. sets of particles in which a new molecular motion is continually being set up, the disturbance caused thereby coming out as heat, and the work done being the increased effort made by the arm of the operator. The effect has been called by Dr. Tyndall ' friction against space.' JOULE'S DETERMINATION OF THE MECHANICAL EQUIVALENT OF HEAT. 35. In a paper read before the Royal Society in 1849, Mr. Joule Stated : ' From the explanation given by Count Rumford of the heat arising from the friction of solids, one might have anticipated as a matter of course that the evolution of heat would also be detected in the friction of liquid and gaseous bodies. Moreover there are many facts, such as, for instance, the warmth of the sea after a few days of stormy weather, which had long beeri commonly attributed to fluid friction. The first mention, so far as I am aware, of experiments in which the evolution of heat from fluid friction is asserted was in 1842 by M. Mayer, who states that he has raised the temperature of water from 1 2 C. to 13 C. by agitating it, without, however, indicating the quantity of force employed or the precautions taken to secure a correct result.' And he further said that he considered it of the highest importance to obtain the relation between force and heat with accuracy, and proceeded to describe the apparatus employed for that purpose as well as the mode of using it. The apparatus employed for producing the friction of water consisted of a brass paddle-wheel furnished with eight sets of arms working between four sets of stationary screens attached to the in- side of a copper cylinder, 7 J inches in diameter and 8 inches deep. A facsimile model of the paddle and cylinder is deposited at South Kensington. The cylinder was covered by a lid having two necks a and b, the latter for the insertion of a thermometer, and the former being an opening for the axis of the paddle to revolve in without contact. The general arrangement will be apparent from the sketch. The weights which rotated the paddle were each 29 Ibs. (more ac- curately, 203,066 grains and 203,086 grains), and they fell through 63 inches at a rate of about 2-43 inches per second. Each weight Joule's Experiment. 59 was attached by pieces of thin twine to a wooden roller A B, 2 inches in diameter, as shown, the roller being supported by steel axles \ inch in diameter, and running upon friction wheels. A wooden pulley, E, 12 inches in diameter and 2 inches' thick, was also carried FIG. 20. by the roller and was connected by a string to the small roller/ on the axis of the paddle. The roller / could be fixed to the paddle axis by a pin/, or be disconnected at pleasure. While the friction was going on the paddle and roller revolved together, but they were disconnected by taking out the pin / as soon as the weights reached the ground, the roller being then supported in a movable frame while the weights were wound up ready for another descent. The manner in which the friction of the water was set up will be apparent from fig. 21, which is a sectional elevation of the cylinder and paddle. The dark crossbars, two of which have square ends, are the paddles, and there is only just room for them to pass between cor- responding openings in the fixed plate CD. A second plate, similar to CD, stands at right IG angles to it, and there are in all eight sets of paddles, whereby the drag upon the motion becomes very con- siderable. The plate c D is 7^ inches wide and 7 inches deep. 6o The Steam Engine. The laboratory was a spacious cellar, the temperature of which preserved a remarkable uniformity. The copper cylinder rested on a wooden stool, or rather grating, supported at some distance from the ground, and there was a wooden screen to protect the cylinder against any radiation of heat from the person of the operator. Each experiment lasted 35 minutes, during which time the weights were allowed to fall twenty times in succession. Two thermometers of extreme delicacy were employed, one, A, for reading the temperature of the water in the cylinder, and the other, B, for reading that of the air in the room. The space of i F. was subdivided into 12-951 divisions in thermometer A, and into 9-829 divisions in thermometer B, whereby Mr. Joule con- sidered that he could estimate the temperatures to two-hundredths of a degree. There were two classes of observations, viz. : (i) a frictional observation, wherein the total fall of the weights was recorded, as well as the temperatures of the water in the cylinder before the rotation of the paddle began and after it Had ended. Thermo- meter B was also read at the beginning and end of the trial. (2) There was a so-called radiation experiment, intended to furnish an estimate of the probable passage of heat to or from the apparatus during the time of the frictional experiment The nature of the observation is well given by Mr. Joule, who says : ' Previously to and immediately after, each of the experiments, I made a trial of the effect of radiation and conduction of heat to or from the atmosphere, in depressing or raising the temperature of the fric- tional apparatus. In these trials the position of the apparatus, the quantity of water contained in it, the time occupied, the method of observing the thermometers, the position of the experimenter ; in short, everything with the exception of the apparatus being at rest, was the same as in the experiments in which the effect of friction was observed.' Taking the fourth experiment as an example of what was done we find a tabulated result which is perfectly intelligible. The total fall in inches is recorded, and the word friction refers to the time when the paddle was in action, while the word radiation refers to the observations made in the next thirty-five minutes by starting at the temperature in the top line of column 6, Joule's Experiment. 61 Total fall in inches Mean tempera- ture of air Difference between mean of cols. 5 and 6 and col. 3. Tempera- ture when experiment began Tempera- ture when experiment ended Gain or loss Friction 125274 6 1 -ooi I-IIO 59-592 60-191 '599 gain Radiation . 60-890 0-684 60-191 60-222 031 gain i 2 3 4 5 6 7 From a comparison of forty trials Mr. Joule deduced the numerical measure of the work done as being 6,067*1 14 foot-pounds, and inferred that the total rise of temperature in the water and copper was equivalent to a rise of '563209 F. in 97,470*2 grains of water, or to i F. in 7-842299 ]bs. of water. But 7-842299 Hence he deduced the mechanical equivalent of heat, as shown by the friction of water, viz. 773*64 foot-pounds in air, or 772-692 foot-pounds if the experiment had been conducted in a space freed from atmospheric air. There were other experiments on the friction of mercury and cast iron, giving remarkable approximations to the above result, and Mr. Joule's paper ends with the following observations : 1. 'The quantity of heat produced by the friction of bodies, whether solid or liquid, is always proportional to the quantity of force expended. 2. ' The quantity of heat capable of increasing the temperature of i Ib. of water (weighed in vacuo, and taken at between 55 F. and 60 F ) by i F. requires for its evolution* the expenditure of a mechanical force represented by the fall of 772 Ibs. througli the space of one foot/ THE KINETIC THEORY OF GASES. 36. Here it may be convenient to refer to the kinetic theory of gases, viz., the theory that a gas consists of a numbci of molecules, flying in straight lines, and impinging like little pro- 62 The Steam Engine. jectiles not only on one another, but also on the sides of the vessel holding the gas. It is well known that a quantity of gas, however small, will expand and fill the whole of a vessel, however large ; and further that it will exert some pressure upon its sides. Also, gases of every kind will diffuse into each other a striking fact which may be illustrated by the following experiment. Fill two glass vessels, one with chlorine gas and the othei with hydrogen gas, and connect them by a glass tube so that the hydrogen is uppermost. Chlorine gas is thirty-six times as heavy as hydrogen, yet in a few hours the gases will have diffused through both vessels, which will be filled with equal parts of chlorine and hydrogen. The expansion and diffusion of gases are accounted for at once by the kinetic theory, and so is the law of Boyle, as well as a second fundamental law presently to be examined, and known as the second law of gaseous expansion. According to .this theory the molecules should be pictured to the mind as endued with velocities somewhat greater than that of a rifle bullet, and thereby competent to rush into and fill an empty space with great rapidity. Also, by continually rebounding from the sides of the vessel and from each other they keep up an incessant cannonade, and the aggregate of these minute blows is felt as a sensible pressure on the surface subjected to them. A bladder partly filled with air looks shrivelled, but when held before a fire it becomes hard and tense. The heat of the fire has given increased velocity to the molecules, and has enabled them to do more work. They dis- charge themselves with greater impetus against the inner surface of the bladder and overpower the bombardment from without. Presently their power becomes weakened by the increase of the area to be supported, and the bladder ceases to enlarge. As the air cools down the motion partially dies away and the bladder shrinks back to its original dimensions. It is thought that the velocity of a molecule of hydrogen at 32 F., and at the atmo- spheric pressure, is 6,097 feet per second. We have to take this theory with us to the consideration of the loss of heat experienced by a gas when doing work, and there can be no question that it enables the mind to grasp the fact with clearness. Add to which, that a general statement of the ideas now prevailing amongst certain writers is, at any rate, serviceable to the student, Law of Charles. 63 THE SECOND LAW OF THE EXPANSION OF GASES: CHARLES'S, OR GAY LUSSAC'S LAW. 37. The expansion of gases under the action of heat is now to be discussed. Whatever view may be adopted to account for gaseous pressure, the fact of its dependence on temperature is thoroughly established, and such an illustration as that of the shrivelled bladder when partially filled with air becoming tense under the action of heat, is to be connected with a particular law known as the second law of the expansion of gases, and which was discovered by Charles, a professor of physics in Paris, some fourteen years before it was made public. It was published by Dalton in England in 1801, and by Gay Lussac in Paris in 1802, and is often called Gay Lussac 's law. The method of experimenting adopted by Gay Lussac will be understood from the annexed diagram. FIG. 22. A certain volume of air, freed from moisture by passing it through chloride of calcium, was introduced into a thermometer tube having an enlarged bulb. A drop of mercury served both as an index and a valve, marking the expansion and separating the air within the tube from the external atmosphere. This air ther- mometer A B was then introduced into an iron vessel containing water and placed over a source of heat. Thtf liquid was agitated, and two thermometers, c and D, marked the temperature. The drop of mercury p indicated by its position the volume of the enclosed air, both when the experiment began and when it termi- nated, the tube B A being drawn out through a water-tight collar and pushed in when necessary, so as to keep the mercurial index just outside the vessel. The conclusions arrived at were the following : 64 The Steam Engine. 1. All gases expand at one uniform rate as the temperature increases. 2. The expansion of air between 32 F. and 212 F, is -375 of its volume at 32 F. 3. The law of expansion is the same at all pressures, whether great or small. The number expressing the amount of expansion, viz., '375 has been modified by subsequent observers, and Regnault assigns the fraction '3665 in place of '375. 38. It is believed that Gay Lussac's method failed in two parti- culars ; that is to say, (i) the mercurial index allowed a minute quantity of air to pass by it, (2) the air enclosed in the tube was not sufficiently freed from the vapour of water. It appears, as the result of observations of extreme delicacy, that the laws of gaseous expansion are not absolutely -verified, and hence a distinction is drawn between perfect and imperfect gases. Rankine defines a perfect gas as a substance in which the tendency of any small portion to expand and diffuse itself through a given space is a property independent of the presence of other gases within the same space. He further states that every gas approxi- mates more closely to the condition of a perfect gas the more highly it is heated and rarefied, and he admits that air is sufficiently near to the condition of a perfect gas for thermometric purposes. Another mode of defining a perfect gas is the following : DEF. A perfect gas is one which satisfies the condition that the addition of equal quantities of heat shall cause equal accessions of pressure when the volume remains constant, or shall cause equal additions of volume when the pressure remains un- changed. The student will readily infer that all vapours, when separated from the generating liquid and highly heated, approach to the qualities of a perfect gas ; whereas, when the vapour is near the point of condensation, it differs therefrom in a marked degree. THE AIR THERMOMETER. 39. An air thermometer may be any vessel containing air, and the principle of the instrument is well exhibited by means of a bent thermometer tube, such as B P A. Some air is enclosed in The Air Thermometer. 65 the bulb A and is separated from the air outside by a drop of mer- cury p, which acts as an index, and ^.^ is prevented from falling out by the ^^ p (f=( j-A. bends in the tube. The touch of the finger on the bulb A will cause a sudden and rapid movement of the index, due to the expansion of the air in the bulb. For scientific researches an air thermometer may be a small globe with a tubular mouthpiece drawn out to a convenient length. The weight of the air in the globe is carefully ascertained in the first instance. At the close of the experiment the tubular end is sealed by the flame of a blowpipe, and a comparison is made between the weights of air enclosed in the vessel under the two conditions. Instead of air Regnault has used the vapour of mercury for estimating high temperatures. His apparatus consists of a cylin- drical 01 spherical vessel made of porcelain and closed by a plate with a small aperture. A little mercury being poured into the vessel, its vapour displaces the air, and becomes more rare as the temperature rises. The weight of mercury left in the vessel after condensation reveals the temperature. The value of air as a thermometric measurer is very great The uniformity which characterises its expansion between freezing and boiling points, obtains, it is believed, alike at the highest and the lowest recorded temperatures. The measure given by air is equally reliable whether we are observing the fusing of platinum or the congealing of mercury. So far as we know, and disregarding minute differences which are practically inappreciable, air has never failed as a measurer of temperature. THE LOWERING OF THE TEMPERATURE OF A GAS WHILE DOING EXTERNAL WORK. 40. In discussing the invention of the expansive working of steam we obtained the curve of the expansion of steam according to Boyle's law, assuming, as a matter of course, that the temperature remained constant. We have now to enter upon a new enquiry, which follows as a consequence of the mechanical theory of heat, F 66 The Steam Engine. and shall endeavo ir to show that a mass of air may have its temperature lowered, not by the escape of heat according to the usual processes of conduction or radiation or convection, but in a totally different manner, namely, by allowing it to perform external work. If we accept Davy's belief * that the immediate cause of the phenomenon of heat is motion, and that the laws of its communi- cation are precisely the same as the laws of the communication of motion/ there should be no hesitation in applying Newton's law that ' action and reaction are equal and opposite.' In doing so the result arrived at is no doubt startling. Granted that 772 Ibs., (about of a ton) would, by falling through i foot, develop an amount of heat sufficient to raise i Ib. of water through i F., it follows from the above law that the converse proposition should also be true, and that the heat necessary to raise the ^ temperature of i Ib. of water by i F. should be competent to lift 772 Ibs. through a height of i foot. It does not appear that any direct experiment has ever established such a result, and it is difficult even to conjecture that it could be accomplished. Nevertheless our theory accepts the conclusion, and the failure is traced to practical difficulties. The student should therefore set before him- self, as a model, an apparatus capable of converting heat into work according to the numerical result above stated, and should contrast the imperfect performance of actual practice with the imaginative working of an ideal engine where all imperfections or impossibilities of construction are supposed to be eliminated. By noting the degree in which the conclusions of theory exceed those actually reached, he will be working in a path which is continually leading to some improvement. Already important changes have taken place in the ideas which formerly prevailed among engineers as to the directions in which greater economy of fuel may be prac- ticable. 41. We propose, in the first instance, to consider the perform- ance of an ideal engine, where the material is such that no external heat can enter the working cylinder and no internal heat can pass away by the ordinary processes of conduction or radiation, and where the piston moves without any friction. Introduce now into the cylinder a mass of air at a high pressure and at a given Heat and Work. 67 temperature, and allow it to expand doing work. Although the air enclosed can lose no heat by conduction or radiation, yet its temperature will rapidly fall as the expansion goes on. The walls of the cylinder present an impassable barrier to the transfer of heat according to the ordinary processes by which heat passes, but the engine is at work and there is no obstacle to the transfer of motion. If heat be motion, the machinery outside the cylinder cannot start into action unless the air within loses an exact mechanical equiva- lent in the agitation of its molecules, and it would be futile to expect that Boyle's law should be strictly fulfilled. It is remarkable that Watt, in his patent of 1782, showed a working cylinder surrounded by a hot steam jacket, the direct ten- dency of which would be to preserve a constant temperature within, and to cause the expansion to follow the precise law laid down in his description of the invention. In order to understand the matter more thoroughly it may be well to refer to some facts which have been observed in the appli- cation of compressed air engines. Taking the case of a compressed air engine set up at the Govan Colliery near Glasgow in 1 849, it appears that a steam-engine was employed to compress air to a pressure of 20 to 30 Ibs. per square inch. The air was then con- veyed down a shaft 176 yards deep, and along a road through a further distance of 700 yards. The first difficulty arose from the heating of the compressed air in the cylinders of the compressing pumps, and layers of water covered the series of balls forming the piston and delivery valves, and thereby absorbed a quantity of heat as soon as it was generated. In recent engines, the flooding of the valves is not practised, but a horizontal compressing air cylinder has a water jacket open at the top in order to keep down its tem- perature. According to the old theory it was believed that the heat fluid, or caloric, was squeezed out of a mass of air by sudden compres- sion, and in this way the lighting of a piece of German tinder at the bottom of an air syringe by the sudden forcing down of the piston was commonly explained. The development of heat by the act of compression being thus rendered apparent, we have to point out what takes place at the bottom of the mine where the compressed air does work in ex- F 2 63 Tit* Steam Engine. panding. The air engine referred to was an old high-pressure engine with a cylinder of 10 inches in diameter and 18 inches stroke, making about 25 revolutions per minute ; and the next practical difficulty arose from the disappearance of heat in the working cylinder, whereby, on some occasions, the formation of ice in the cylinder and exhaust pipe clogged the working parts. In order to meet the difficulty various suggestions have been made, and Mr. Siemens has pointed out that according to theory the better course would be to inject cold water, in the form of spiay, into the compressing cylinder in sufficient quantity to keep the temperature practically uniform throughout the stroke ; and afterwards, if such a thing were practicable, to take the very same water which had become heated in the compressing cylinder, and inject it again into the expanding cylinder, so that the heat taken from the air during the compression should be restored to it during the expansion. UNIT OF HEAT AND FIRST LAW OF THERMODYNAMICS. 42. Adopting the belief that a quantity of heat means a quantity of molecular motion, the unit of measurement is the following : DEFINITION. A unit of heat is the quantity of heat required for raising the temperature of i Ib. of water, at or near its tem- perature of greatest density (39*1 F.) through i F. The 'pound' here spoken of is the unit of mass, viz., the standard pound avoirdupois. FIRST LAW. Heat and mechanical energy are mutually con- vertible, and heat requires for its production, or produces by its disappearance, mechanical energy in the proportion of 772 foot- pounds for each unit of heat. The number 772 is usually denoted by the letter J, in token of Mr. Joule's experiment, and the temperature of the water referred to in denning a unit of heat is taken at 39-1 F. instead of lying between 55 F. and 60 F., as in the original experiment. ON SPECIFIC HEAT. 43. The term ' specific heat ' is used in a technical sense, for the word * heat* signifies quantity of heat, and specific means Specific Pleat. 69 peculiar to the substance. There must be some standard of reference in the measurement of specific heat, and the substance selected for this purpose is water at or near 39'! F. DEF. The specific heat of any solid or liquid substance is the ratio of the quantity of heat required to raise the tempera- ture of a given weight of the substance through i F., to the quantity of heat required to raise the temperature of an equal weight of water at 39*1 F. through i F. Water is selected as a standard, because it opposes a greater resistance to a change of temperature than any other liquid or solid substance, and it follows that the specific heats of all solids or liquids are registered as fractions less than unity. The specific heat of water is not absolutely constant, the specific heat of boiling water becoming increased by a minute fraction, and a progressive increase continuing at still higher tem- peratures. In symbolical language it may be said that if q be the quantity of heat required to change the temperature of a given mass M from / to T, we should infer that ^varies as (T-/) when M is given, and that q varies as M when (T - /) is given. Hence q varies as M (T - /), or = c M (T - /), where the constant c is called the specific heat of the substance, and is the measure of the quantity of heat which will raise the unit of mass through one degree. 44. In estimating the specific heat of a gas it is necessary to bear in mind the fact that the temperature of a gas is lowered by causing it to do work. 1. If a portion of gas be enclosed in a rigid vessel whose form is unalterable, and be heated, it does no external work, and its specific heat would be assigned just as in the case of a solid or liquid, that is, by comparison with water whose specific heat is unity. The specific heat of air at a constant volume is '169. 2. If a portion of gas be enclosed in a vessel in such a manner that it can expand under a constant pressure, and if it be subjected to the action of heat, it will increase in volume, and will push any external air which presses upon it, thereby doing work. 7O The Steam Engine. The result is that it absorbs more heat in rising through a given number of degrees of temperature than it would do if no heat were converted into work. The specific heat of air at a constant pressure is -238. The next step is to apply symbols to these results, and to certain calculations about to be given. Let k be the specific heat of air at a constant pressure. c constant volume. k Then - = 1-408 = y suppose. The ratio - is of such frequent occurrence that it has been usual to designate it by a Greek letter y. The velocity of sound (in feet per second) in air, at the tem- perature 32 F. may be proved to be N/J^H, where g is 32-2 feet, and H is 26,214 feet, the height, as it is called, of the homogeneous atmosphere at 32 F. The measured velocity of sound hence gives y=i '408. The value of k has been found by experiment, and (as stated) is equal to '238, but the value of c cannot be ascertained by direct experiment, and is therefore deduced from the equation k -218 , c = 2- = -169. i '408 i '408 THE LATENT HEAT OF STEAM. 45. The principle successfully carried out in determining the temperature of high-pressure steam, has been also applied for determining the latent heat of steam. The apparatus employed by Regnault (whose results are of the first authority) was too complex to admit of explanation here. A lull account of it, together with an engraving of the several parts, is to be found in Jamin's ' Cours de Physique.' Steam was generated in a boiler containing some 30 to 40 gallons of water, and was passed through a coiled pipe in the interior thereof before it was led away, the result being that any water adhering to the issuing steam was vaporised, and that the supply consisted of dry saturated steam. The pressure of the Latent Heat of Steaw. 71 vapour thus generated was determined by an artificial atmospheie, and was measured as in the previous case. There were two vessels, technically known as calorimeters, through each of which the steam passed twice for a few minutes, and wherein its latent heat was given up to a measured quantity of water. The annexed drawing shows the construe- tion of one of the calorimeters employed. Steam enters the copper reservoir, c, which opens into a second reservoir, B. There is also a worm pipe passing from B, and twisted in a spiral round the inside of the calorimeter, but terminating in a pipe, D, leading to the receiver which regulates FlG - 2 4- the pressure of the artificial atmosphere. A thermometer, T, gives the temperature of the water in the calorimeter. In order to preserve a continuous flow of steam through the apparatus at a time when the measurement is not proceeding, there is a condenser, into which the supply is turned at pleasure ; also the pipe which leads from the boiler to the calorimeters is steam-jacketed throughout. The results were, of course, given in graduations of the centi- grade thermometer, and were as follows : 1. The latent heat of steam produced at atmospheric pressure, or at a temperature 100 C., was represented by the number 537. 2. Taking the temperature of the steam at T degrees centi- grade, it appeared that the quantity of heat necessary to raise a unit of weight of water from o to x and to transform it into vapour at a temperature T was equal to 606-5 + '305 T Since 537 C. = 966-6 F., we estimate that 966-6 units of heat become latent in the conversion of one pound of water at 2 1 2 F into one pound of steam at the same temperature. Adopting now the graduations of the Fahrenheit thermometer, and remembering that i C. is equivalent to f F, let L re- present the latent heat of steam, and let H be its total heat. The designation ' total heat ' is conventional, and is taken to express 72 The Steam Engine. the heat required to raise i Ib. of water from 32 F. to the tem- perature of evaporation and afterwards to convert it into vapour, then H = 10917 +'305 (/ 32) L = I09I7--695 (/-32) = 1092 .7 (/ 32) approximately ; or = 966 7 (/ 212). Watt experimented on the latent heat of steam, and in 1781 estimated it by the number 950, but subsequently he put the numerical value a little higher, viz., at 960. Also, using the term ' free heat ' to indicate the amount of sensible heat above 32 F. as measured by a thermometer, he enunciated the law that in steam at any given temperature Latent heat + free heat = a constant quantity. For ex- ample : Units. One pound of steam at 212 F. . f 180 sensible heat, condensed at 32 F. gives out . I 966-6 latent amounting together to . 1146 '6 Again Units. One pound of steam at 250 F. . f 218 sensible heat, condensed at 32 F. gives out . \ 928*6 latent still amounting together to 1146-6 But Regnault showed a variation from this law, and his formula gives 1158-2 as the total heat of steam at 250 F., instead of 1146-6. It will be necessary to recur to this subject in the Appendix, where numerical examples and questions set in the Science and Art examination papers are brought together. THE ABSOLUTE ZERO OF TEMPERATURE. 46. If air be adopted as a thermometric substance we com- mence our researches upon temperature in a very advantageous manner, for it is easy to conceive that the law of expansion of air is carried on indefinitely at increasing temperatures, and that the law of its contraction pursues an undeviating course as far as the point at which the whole of the heat contained in a mass of Absolute Zero of Temperature. 73 air has been taken away from it. Then arises the question : What is the real zero of an air thermometer, or the indication which it would give if the air were deprived of all its heat ? In order to make the matter clear, let us take the case of air enclosed in a cylindrical tube of indefinite length, and separated from the atmosphere by a small globule of liquid which does not evaporate sensibly. Let the tube A P be 6o# inches long, and conceive 212- that when the index is at B, marking 32 F., the length, A B, is 30 a inches. At 212 F, the index will rise to E, where A E is 32, 410 inches. Let x be the number of graduations in B p, when the index rises to P, such that A P = 600. Then B p : B E = x : 180 or 300 : na = x : 180 -2 .Mi* = 5,400 x 491 very nearly. Hence 300 inches is added to the tube of air by an increase of temperature of 491; and, in like manner, 30^ inches would be cut off by a fall of temperature of 491. But that is the whole length of the tube, and FlG * 25 * it follows that the air cannot contract more than by a fall of 491, or that the zero of the scale is 491 below B. Hence DA = 491 32 = 459. The true value of the expansion is taken, however, to be "3665, and not -3666..., and consequently this number is slightly altered ; so that whereas the bottom of the tube would be marked correctly at 45 9. 1 3 F., it is usual to assign the number 460 F. as the zero of the scale. This number indicates what is termed the absolute zero of temperature, and if the reading could be observed at the bottom of the tube it would imply that the volume of the air had been reduced to nothing. Mr. Maxwell says : ' If it were possible to extract from a substance all the heat it contains, it would probably still remain an extended substance, and would occupy a certain volume. Such an abstraction of all its heat from a body ha^s 74 The Steam Engine. never been effected, so that we know nothing about the tempera- ture which would be indicated by an air thermometer placed in contact with a body absolutely devoid of heat.' If we agree to adopt the absolute zero of the air thermo- meter as the point at which the readings commence, and adhere to Fahrenheit's scale, we shall estimate freezing point, not as 32, but as 32 -(- 460 or 492. And like alterations for other tempera- tures. On pausing to consider the amount of progress which has been made in travelling down the tube of an air thermometer to- wards the limit of the absolute zero, we shall find that hitherto the best results have been obtained by combining chemical with mechanical action. Thus Faraday obtained carbonic acid snow by allowing the substance when liquefied under pressure to escape into a small box, and the snow so formed could be wetted with ether, so as to produce a sort of paste having a temperature of 1 06 F. By accelerating the evaporation of the ether from this paste under the exhausted receiver of an air-pump the tempera- ture was reduced to 166 F. Natterer has obtained a still more intense degree of cold, by mixing liquid protoxide of nitrogen with bisulphide of carbon, and placing the bath in an exhausted receiver. By this process he has lowered the reading of a thermometer to 220 F. The two laws of the expansion of gases, namely, the laws of Boyle and Charles, are connected together in a very simple manner under the view now suggested. Thus if /, v, t represent the pressure, volume, and absolute temperature of a quantity of gas, then while / is constant, the pro- duct/ v is for this gas invariable. This is Boyle's law. When /varies, pv varies as /, or/ v = Rt, R being constant This is the expression of the law of Charles or Gav-Lussac, which- ever it may be called. THE PROPERTIES OF AN ADIABATIC CURVE. 47. Another point for explanation is that there is a special curve which represents the expansion of a gas when confined in a vessel which possesses the imaginary property of not suffering any Adiabatic Curves 75 heat to pass through its substance, and where the gas is doing external work during its expansion. In such a case the curve of expansion will not follow Boyle's law, by reason that the temperature of the air will be affected through the interaction between heat and work. For example, if the expanding gas does work, its temperature will fall by the conversion of the molecular motion of heat into the sensible motion of the mass upon which the work is done, and, since the pressure of a portion of gas is influenced by its temperature, the reduction of pressure will be greater than that exhibited by Boyle's law. The curve of expansion is now called an adiabatic curve (from two Greek words, signifying not to pass through), and the name is intended to express the conditions under which expansion takes place, viz., that no heat passes out of the gas either by conduction or radiation. The calculations necessary for determining the form of an adiabatic curve will now be given ; but the processes cannot be made intelligible to students who are not conversant with mathematics, and the explanations in the next chapter are so framed that those who are unable to follow the symbolical reason- ing may nevertheless take the results here investigated and apply them as required. 48. PROP. To find the relations between the pressure, tem- perature, and volume of a portion of gas when it is expanded or compressed without addition or subtraction of heat. Let/ be the pressure, v the volume, and / the temperature of a given portion of gas. Then/ v Rt. .: pdv + vdp = Rdi. (i) As before, let k be the specific heat of the gas at a constant pressure, then the quantity of heat necessary to be given to a unit of weight of the gas without change of pressure, in order to increase its volume by d v is * " * dv and if f. be the specific heat at a constant volume, the quantity of 76 The Steam Engine. heat required to increase the pressure of the same portion by dp without change of volume is If the variations of volume and pressure occur together, we adopt the principle that small increments from different causes may be superposed without interference, and the whole quantity of heat so required will be k..dv + c. d 'dp. dv dp But, taking the equation pv = Rt, and differentiating, (i) when p is constant, (2) when v is constant, we have = v , = L dp R p' .'. quantity of heat = . dv + d p = o by hypothesis, since there is no addition or subtraction of heat. k d v _ _ c dp ~ ' ~Y' Substituting in (i) we have pdv -^ .dv = Rdt =^-d(. or -f y - I ^ = ^/ | since \ J v t r =lo/+ C. Taking/ , V Q , as values of the pressure and volume correspond- ing to a temperature / we have /"My- 1 * \v) 'o " P v Adiabatic Curves. whence = / ^ ]7 or/z> 7 = a constant, A \*v A which is the equation to the adiabatic curve. Also the relations between the temperature, pressure, and volume of the enclosed gas are given by the equations 7-1 7 ( 2 ) \ " / Y/'O ' COR. If y = i, the adiabatic curve passes into the curve p V = constant, which is the curve of Boyle's law. DIAGRAM OF AN ADIABATIC CURVE. 49. It is instructive to set out an adiabatic curve in a diagram, and to compare it with an isothermal curve, which follows the law of Boyle. Let o M represent the volume, v Qy and P M the pressure, / , of a portion of gas at a temperature / - If tne g as De compressed at a constant temperature / , we shall have R N representing the pressure at a volume o N and heat will escape. Whereas, if it be compressed to a volume o N without escape of heat, the pressure will be represented by Q N, as assigned by the previous cal- culation, and it is easy to see that Q N is greater than R N. Also the temperature will rise from / to /, as determined by the FIG. 26. formula. The conclusion is that air resists compression with greater power when the action is sudden, and the heat has no time to escape, than when it is gradual and the heat insensibly passes away. It is often said that a gas has two elasticities, viz., (i) the the elasticity at a constant temperature, (2) the elasticity when no heat escapes, and that we lose sight of the latter, which is the true elasticity, because it so rarely influences any observed result. Tlie Steam Engine. A remarkable illustration is afforded byreseaiches on the velo- city of the propagation of sound. The sound-waves compress and rarefy air suddenly. As stated by Mr. Maxwell : * The changes of pressure and density may succeed one another several hundred times in a second, whereby the heat developed by compression in one part of the air has no time to travel by conduction to parts cooled by expansion, even if air were as good a conductor as copper is. But we know that air is really a very bad conductor of heat, so that in the propagation of sound we may be quite certain that the changes of volume take place without any appreci- able communication of heat, and therefore the elasticity, as de- duced from measurement of the velocity of sound, is that corre- sponding to the condition of no thermal communication.' Newton calculated the velocity of sound by assuming that the elasticity of air followed Boyle's law, and made it less by one- sixth part than the observed result. The error was subsequently pointed out and corrected by Laplace. 1 The ratio of the elasticities in the case of air, as deduced from experiments on the velocity of sound, is 1*408, which is also the ratio of the specific heat at constant pressure to the specific heat at constant volume.' 50. It may here be useful to point out one or two applica- tions of the formulae obtained. Let a mass of air at volume 12, pressure 15 Ibs., and tempera- ture 60 F., be compressed with- out addition or subtraction of heat till its pressure rises to 30 Ibs., the increase of temperature will be given by the formula, " /-i But 7 = 1 '408 /. Here / n = 6o c 7 + = -29 460 12 VOL FIG. 27. = 520, and / = 15, whence tempera- ture at pressure 30 pounds = 520 I 3 29 = x suppose. Adiabatic Curves. 79 .'. log. x = log 520 + '29 x log. 2. = 27160033 + -0872987 = 2-8033020 = log. 63577 /. temperature = 63577 460 = 176?. In like manner the temperatures corresponding to pressures of 45 Ibs. and 60 Ibs. will be 255 F. and 318 F. respectively, the results being marked down in the annexed diagram. 51. To find the work done by a gas while expanding we proceed as follows : Adopting the previous notation, let w be the work done, and remembering that p d v expresses the work performed in passing from v to v + dv, or is represented by the rectangle s m referred to in Art. 18, we have to find the sum of all such rectangles analytically, which is done by integration, whence w =. But/-/. (J) _ A?0 / j _ /^C y i 1 vz/ y-i This formula may also assume the following shapes : 7-1 52. A comparison is often instituted between the relative advantages of compressed air or of water under pressure as a medium for the transmission of power to a distance. Those who advocate the use of compressed air, which is of great practical value in many cases, should nevertheless understand the penalty tfO The Steam Engine. which must be paid for the use of it. We are now in a position to calculate the loss of work due to the cooling of compressed air after it has been heated by the action of the compressing pumps. Let a mass of air of volume z' and pressure / be compressed to a pressure /, the work expended during its compression will be 7-1 (L\\ -lJ 7 / The temperature of the mass of air will Be raised by this com- pression, and the simplest way of looking at the question will be to conceive that the air is allowed to cool at a constant pressure /, but contracting to a volume v. Then / V Q = pv by Boyle's law ; and work restored by the air when expanding behind a working piston work expended _ ' * v Y work restored \A>/ ^ Ex. Let/ = 3/0, or let the air be compressed to three times its original pressure, . work expended _ (3P\ '29 _ '29 work restored ~ \ p ) But 3 ' 29 = 1-375, .*. work restored = I00 x work expended, 1375 = 73 x work expended. That is to say, before any useful work is obtained from the com- pressed air, as much as 27 per cent, of the power has been thrown away. In tunnelling through the Alps, where the boring machines were worked by engines supplied from a reservoir of air at a pres- sure of six atmospheres, the loss by cooling amounted to about 40 per cent, of the power expended during compression. 81 CHAFFER III. ON HEAT ENGINES. 53. A HEAT ENGINE, in the sense adopted in this book, is an apparatus for converting heat into mechanical work. We purpose to discuss, in the first instance, the performance of an ideal heat engine, such that the curve of expansion of the working substance shall be an adiabatic curve. On this hypothesis the working substance is a perfect gas, say air, enclosed in a cylinder provided with a piston capable of moving without friction. When the air is doing work, the material of the cylinder should be such that no heat can pass out of it and none can warm it. At other times it may be necessary for the air within the cylinder to accept or reject heat. The condi- tions for working are therefore contradictory, and accordingly, in the books on heat engines it is supposed that the piston, and the whole of the cylinder except its base, are perfect non-conductors of heat, while the base of the cylinder is a perfect conductor of heat, but yet has no capacity for heat, i.e. the amount of heat required to alter its temperature may be left out of consideration. Then there are two bodies A and B kept at different fixed tempera- tures, and there is a stand with a non-conducting surface on which the working cylinder can be placed when required. The engine is supposed to be placed on A when it takes in heat, to be carried to B when it gives out heat, and to rest on the stand when it works with the heat bound up in the enclosed gas. What is to become of the mechanism is not stated. Under these circumstances it appears to be a waste of time to go through the formulary of supposing the engine to be actually ai work, and shifted about during its performance. The whole G 82 The Steaw Engine. tiling is the creation of the mind, and we shall disregard these details of supposed practice which clear up nothing, and shall merely conceive that everything takes place as required, so that the engine performs work in the manner intended. Having thus settled the qualities which a heat engine should possess, we have next to ascertain what can be done with it. The hypothesis being that a given mass of air is enclosed in the cylinder of an engine behind the working piston, it has been shown that if the air expands, doing work, its temperature will fall, not by conduction or radiation, but by reason of the conver- sion of heat into external work. The air inside the cylinder gives up part of its motion to the piston, and the fall of temperature is an interchange of motion and of nothing else. DIAGRAM TO REPRESENT THE WHOLE WORK STORED UP IN A HEATED GAS. 54. Starting then with a mass of air at a volume V Q , a pressure /> , and a temperature / , we observe that although it is impossible to predict anything as to its physical condition when ap- proaching the temperature zero, yet we may assume that its pres- sure and temperature fall during the expansion of its volume ac- cording to the laws already dis- cussed, whereby the shaded area bounded on one side by the adiabatic curve P Q, represents the whole work capable of being yielded up during an indefinite expansion which finally depresses the temperature to the absolute zero. Further the line o x is an asymptote to the adiabatic curve P Q, wherefore it becomes impossible to obtain the whole work theo- retically bound up in the mass of air in question without carrying on the expansion till P Q meets o x, or until the volume becomes infinite. When that takes place, and not until then, will / become equal to zero. At present we are engaged on a work of the imagination, anj Diagram of Heat or Work. 3 have divested the problem of all practical difficulties, but it is nevertheless important to remember that an expansion down to 460 below zero in the Fahrenheit scale would be required in order to compel a mass of heated gas to yield up the whole of its molecular motion in the form of work. It is a common thing for people to say that i Ib. of carbon, in burning, gives out heat enough to do the work of raising 772 x 14,500 Ibs. through one foot, and they are apt to disregard the primary condition under which this performance would be possible. That condition is as hopelessly removed from our reach as if it were to be grasped only in some distant planet, and therefore it is better not to give any prominence to this mode of estimating the work stored up in fuel, but rather to think of it as a conception of the mind, and as something quite unreal. MEANING OF THE TERM 'CYCLE/ 55. At this stage it will be convenient to introduce a technical word, namely, a cycle, and to explain the use made of it. DEF. A series of successive states of the volume and pressure of a working gas, which may be represented by a continuous line returning into itself, is called a cycle. A cycle is reversible when the series of changes of volume and pressure can be passed through indifferently in either direction. It should be understood that a cycle is the bounding line of some definite area, and the important consideration connected with it is that the area so enclosed represents either the external work done during the series of transformations by the enclosed gas ; or, if not, it represents the work done .upon the gas while carrying through these transformations in a reverse order. Furthermore, by the first law of thermodynamics, heat and work are convertible the one into the other, whence it follows that the area enclosed by the cycle represents also the amount of heat expended in doing the work in question. This is universally true. If an area represents an amount of work done, it must also represent the quantity of heat expended in doing that work. Referring to the diagram where the axes are the lines of a 2 8 4 The Steam Engine. pressure and volume as in the previous cases, let the point s, whose position indicates the pressure and volume of a given quantity of gas at a given temperature, trace out the closed curve A p B p'. That curve will record the corresponding values of the pressure and volume of the gas at any instant, and is called a cycle. Also the area M A p B N represents the positive work done in passing through A P B, while the area M A p' B N represents the negative work done in passing through B P' A, the difference A p B p 7 being the work done by the substance in undergoing the series of transformations. The same area might also represent the work done upon the substance under altered conditions, and it necessarily represents the heat expended in the first case, or that absorbed on the alternative supposition, viz., that work is done upon the substance. DIAGRAM OF HEAT ABSORBED OR REJECTED BY A PORTION OF GAS IN PASSING FROM ONE TEMPERATURE TO ANOTHER. 56. Let o 27, v T represent the volume z', and pressure p of a portion of a gas (say air), at a given absolute temperature T, and draw the adiabatic curve T T' R. Let the air expand doing work, to a pressure v' T' and temperature T'. Then lower its tempera- ture at a constant volume o ?>', till its pressure falls to t' z/, and its temperature to f. Compress the air to its original volume o v, as shown by the adiabatic curve f t. when its temperature will rise to / (suppose), and finally heat the air at a constant volume o 7>, till its temperature rises again to the original value T. This will form a complete cycle of operations, and, according to the principle laid down, the work done by the air during tho cycle will be represented by the area T T' f t. Referring to the diagram where o x represents the line of volumes, and o y the line of pressures, we observe that the two adiabatic curves approach indefinitely near to the line o x as the expansion goes on, and therefore also they approach indefinitely Diagram of Heal or Work. 85 near to each other. But the air gains heat in passing from / to T, and loses heat in passing from T' to /', and it is apparent that as the expansion goes on this lost heat is continually be- coming less and less and finally vanishes, wherefore the whole heat absorbed in passing from / to T is represented by the in- definitely prolonged area T R s /, FIG. 30. bounded by T / and the two adiabatic curves T R, / s. This conclusion follows, indeed, as a corollary to Art. 54. In like manner if the volume and pressure be caused to vary in any arbitrary manner between the points A and B, as shown by the curve A D B, and the adiabatic lines B R, A s, be drawn as before, the shaded area ADBRS will represent the mechanical equi- valent of the heat absorbed or given out by the substance in passing from the state A to the state B, or conversely. HEAT ENGINE WORKING BETWEEN TWO FIXED TEMPERATURES. 57. It is the property of an engine that it must continually get back to a starting-point, and go through all its operations over again, and of course it becomes necessary at once to abandon all idea of obtaining the work represented by the indefinitely pro- longed strip A B R s. A heat engine can only operate in a closed cycle such that the working substance reverts continually to the volume, pressure, and temperature which it had at starting. All that we can hope for is to obtain as large a slice of the strip A B R s as may be practicable under the conditions of expansion which the construction of the engine will permit. The method will be to travel a certain distance down the adiabatic curve T R, then to cross over to another adiabatic curve s /, to pursue an upward path through a certain space, and finally to return in some con- venient manner to the starting-point. Our hypothesis shall be 86 The Steam Engine. that the engine works between two fixed temperatures T and / (T being the greater), and that the working substance, say air, takes in a quantity of heat H at the higher temperature T, and rejects a quantity h at the lower temperature /, and performs external work under these conditions. The cycle of operations will be the following : Starting from the point T in the adiabatic curve c s, the air expands through T T according to Boyle's law, remaining at a fixed temperature T and vot & FIG. 32. taking in a quantity of heat H. It then expands through T / along the adiabatic curve A R, doing work, and falling from a tempera- ture T to /. It is next compressed along // at a constant tempera- ture /, giving out the quantity of heat ^, and finally it is compressed along the adiabatic curve s c from / to T, and returns to its original volume, temperature, and pressure. The enclosed shaded area is the indicator diagram of the engine, and gives a measure of the work done, or equally, of the heat converted into work. In truth, the heat taken in along the curve T T is represented by the indefinitely prolonged area T T R s, while that rejected along //is given by //RS, the difference between the two areas marking the conversion of heat into work. The problem now in view is to find some relation between (H, ti] on the one hand, and (T, /) on the other hand. Let it be granted, as there is no reason to doubt, that if the absolute temperature of any uniformly hot substance, such as the Diagram of Heat or Work. 87 working gas or air, be divided into an indefinitely large number of equal parts, the effect of each of those parts in causing work to be performed will be the same; and it will follow that if /T be made very small at any temperature /, however selected, the area T Ttf will always bear to the whole area / / R s the same propor- tion which T t bears to /. In other words if q be the quantity of heat represented by the area //R s, and dq that represented by T T tt, the alteration from / to T being represented by dt, we shall have dq___dt_ ? : : > ' or q = A /, where A is a constant. That is the same thing as saying that H _ h T ~ /' a fundamental relation which is of the greatest possible use in this theory, and which has been shadowed forth throughout the reason- ing of the previous pages. It is material to comprehend the exact agency of the heat consumed in the operations, and we note that the heat H is taken in while expanding according to Boyle's law, and that the heat // is given out during a like compression. In order to estimate the work done we proceed as follows : Let j represent Joule's equivalent, or 772 foot-pounds. The quantity of heat H is capable of doing the work j H, and in like manner the quantity of heat h can do the work j h. .'. work done by the engine = j (H h) j H fi -\ But * = _', H T /. work done = J H f I -H -=JH ( - V Conceive that an ideal engine worked with an heated up to 300 F. and cooled down to 50 F., we should have T = 460 -f 300 = 760, / = 460 + 50 = 510. .*. work done = j H f^ 6o ~5 IQ \ = J ; H> very nea rly. V 760 J 3 88 The Steam Engine. That is to say, our ideal engine, which is absolutely faultless in construction, and therefore unattainable, cannot reproduce, under the assigned differences of temperature, so much as ^ of the work which is stored up in the mass of heated air. A practical mechanic who is concerned at the statement that the modern steam- engine is full of glaring defects, may derive some consola- tion from an accurate definition of the limits within which im- provement is possible. It is hardly necessary to point out that the cycle of operations is reversible.. Thus we may start from the point T in the line c s, travel down T t doing work, cross over through 1 1 taking in a quantity of heat h, then rise through / T doing work upon the air, and pass through T T giving out a quantity of heat H. The work done upon the enclosed air would therefore be represented by j (H - /i). 58. As an example of a cycle which is not reversible, take the indicator diagram of an ordinary condensing engine as given by theory. The steam is supplied at a uniform pressure along A B, it expands and does work along B c, its temperature and pressure fall suddenly as shown at c D, and its pressure re- mains constant through D E. In the reverse operation the steam and condensed water should be com- o ~vol pressed till its pressure rises through FIG. 33. D c, and the water into which the steam has been condensed should be reconverted by pressure into steam at the temperature at which the expansion during the direct working came to an end. This is an impossibility, and an ordinary condensing engine is therefore non-reversible. ELEMENTARY HEAT ENGINE. 59. It is convenient to distinguish by a particular designation an engine which works under the three conditions now to be enu- merated, viz. ; that Carnot' s Principle. 89 1. All the heat is taken in at a higher constant temperature T. 2. All the heat is rejected at a lower constant temperature /. 3. The cycle is reversible. When an engine fulfils these conditions, it is termed an elementary heat engine, and enjoys the property that it cannot be surpassed in efficiency by any other engine working between the same temperatures ; it is, in fact, an ideal perfect engine, and is the model instituted for mental comparison in viewing the per- formance of real engines. CA KNOT'S PRINCIPLE. 60. At this stage we propose to discuss the principle laid down by Sadi Carnot in 1814. Carnot, who was a French officer, and son of the celebrated Minister of War under Napoleon, founded his theory of heat engines on the erroneous supposition that heat was a substance, but his errors were those of a man of genius, and the principle which he enunciated is a fundamental truth according to the dynamical theory. Writers on the subject of heat tell us exactly where Carnot was right, and where he was in error, and they distinguish and analyse his statements. In the present treatise we shall not attempt to follow them, and shall merely refer the student to other sources, such as Maxwell on ' Heat,' for in- formation on this point. Carnot's book was entitled ' Reflexions sur la puissance motrice du feu, et sur les machines propres a developper cette puissance,' and the idea firmly fixed in the mind of the writer was that the performance of work should be attributed solely and absolutely to the agency of heat. The principle of Carnot may be stated as follows : The amount of work done by a reversible heat engine depends only on the constant temperatures at which heat is received and at which it is rejected, and is independent of the nature of the in- termediary agent (such as steam, air, &c.). This principle involves two propositions which are sufficiently striking, and the first is that the elementary heat engine heretofore disc ussed, and which took in heat at one constant temperature and 9O The Steam Engine. rejected it at another temperature also constant, is really and truly, and in virtue of being reversible, a perfect engine. That is to say, no other engine working between the same temperatures can do more work than that performed by this particular engine. The second proposition relates to the part played by the work- ing substance, and, when rightly understood, may serve to dispel a number of erroneous notions which are commonly entertained on the subject of steam and vapour engines. The fundamental con ception being that the whole work done by a heat engine is traceable to the disappearance of heat, and to that alone, it follows that a heat engine is entirely independent of the nature of the substance under which it performs its functions. Whether the apparatus is a steam, air, or ether-vapour engine is of no consequence what- ever. That is the correct view, but nevertheless many would hesitate to compare the economic advantages 6f saturated steam at a pressure of 10 atmospheres with a temperature of 358 F., and steam at a pressure of (say) two atmospheres, when superheated to the same temperature. They would conclude, as a matter of course, that the steam at the higher pressure was the better working substance. And yet we submit that, irrespective of any practical con- siderations in the application of steam to working engines, such an inference is entirely fallacious. The heat consumed does the work, and nothing else is of any avail ; the substance which takes in or gives out the heat is like the casing of the cylinder, it is matter which must be interposed, but it is not the agent. The quantity of heat contained in the substance which fills the cylinder is that which alone becomes important, it is that alone which is the vera causa of the efficiency of the engine; and we need to look only to the temperatures of the source of heat and of the re- frigerator in order to discover the work that should be performed. Taking the reversible heat engine already discussed and calling it A, let it be supposed that some other engine, which works by taking in the quantity of heat H at a fixed temperature T and giving out a like quantity of heat h at another lower temperature / is more efficient, either by some difference of construction or by working with some more effective agent such as ether vapour, for example, instead of air. Call the second engine B, and let it be Garnet's Principle. 91 coupled to A and drive it in the reverse direction, thereby doing work upon, instead of deriving work from, the intermediary agent. The engine B takes in a quantity of heat H at each stroke and gives up the portion h to the refrigerator, and A would do precisely the same if it were allowed to work in the ordinary manner. But since B works A in the reverse direction, the heat consumed in a stroke of B is restored to the source again by A, and the coupled engine is therefore automatic. Since the source of heat loses nothing it is clear that the action would go on for ever, but then an anomaly arises, for B being more powerful than A, we can suppose B to do some surplus work over and above the work done upon A. This excess of work done continually accumulates, and how is it to be accounted for ? It cannot come from the source of heat, since that neither loses nor gains anything, and therefore it must either be (i) created out of nothing, or (2) it must be taken from the refrigerator. 61. We reject both alternatives : for the first law of thermo- dynamics denies the creation of heat, and we announce a second law to express the absurdity of the second alternative, viz. : SECOND LAW OF THERMODYNAMICS. SECOND LAW. It is impossible for a self-acting machine un- aided by any external agency to convey heat from one body to another at a higher temperature. THE USE OF HIGH-PRESSURE STEAM. 62. We are now in a position to form an adequate idea of the advantages to be derived from the use of high-pressure steam, working expansively, and with condensation. As to high pressure and condensation, we may say that a steam- engine is a heat engine. It cannot be worked as a perfect engine, and the approach to perfection is aimed at in a somewhat rude manner, but the great gain exhibited by theory rests solely upon a difference of temperatures, and the wider this difference, the greater is the amount of. work which can be done. As to expaa- 92 The Steam Engine. sion, that passes without any contest, the whole theory of heat engines is based upon expansive working. And here it may be instructive to review the progress made by engineers in the use of high-pressure steam without reference to the doctrine that heat alone is the agent which does the work. It has been stated in Art. 21 that Hornblower invented the double or compound cylinder engine for expansive working, and that he intended, as did Watt in his patent of 1782, to employ steam at or near the atmospheric pressure. The economy resulting from the expansion of steam at a high-pressure was, however, first in- sisted upon by A. Woolf, a Cornish man, who converted Horn- blower's double cylinder engine into a form suitable for driving machinery (see Chapter VII.), and erected a so-called Woolfs engine working with high-pressure steam and condensation at Meux's Brewery in 1806. Woolf entertained the most fanciful and erroneous ideas as to the power of high-pressure steam when ex- panded, but, although quite wrong in his theory, he persevered in the construction of his engines, and erected several which worked with steam at a pressure of from 40 to 60 pounds above the atmospheric pressure. Down to the year 1814 the pressure of the steam in Cornish engines never much exceeded that of the atmosphere, and at this low initial pressure there was practically but little economy resulting from expansive working, whereby it appears that after Watt's immediate connection with the mining district ceased, expansion fell rapidly into neglect. Then it was that R. Trevethick and Woolf both advocated in Cornwall the economy of high-pressure steam with expansion, a mode of work- ing which was applied by the former in Watt's single cylinder engine and by the latter in the double cylinder engine. It was indeed proved that, by the new method, it was possible to raise the duty of an engine (see Chapter V.) from 20 millions of foot pounds for one bushel of coal (94 Ibs.), at which Watt had left it, to 50 or 60 millions of foot pounds. This was an extraordinary result, and the only question that arose related to the manner in which the principle should be carried out. At the present day there are often long discussions as to the comparative value of one or two cylinders for expansive working, but in Cornwall the practice soon settled down into that which has been maintained High Pressure Steam. 93 ever since, viz., the use of a single cylinder engine with steam at a pressure of some 30 Ibs. above the atmosphere, and cut off at th or th of the stroke. Note. In practice, steam at 30 Ibs. pressure means 30 Ibs. above the atmosphere, unless the contrary be expressed. In theory, it means 30 Ibs. actual or absolute pressure, giving an effective pressure of 15 Ibs. approximately. 1. It is now worth while to apply our conclusions as to the effici- ency of a heat engine to the case of expansive working, under Watt in the first instance, and afterwards under Woolf or Trevethick. Watt used steam at atmospheric pressure and condensed at a temperature of 100 F. He expanded it (say) four times. At that time there was no numerical measure of the conversion of heat into work, and the idea of regarding the higher temperature of denser steam as entering at all into the question of its economy as an agent was not entertained by any engineers. It was enough to be satisfied that additional work was obtained from the steam before it was thrown away. Theoretically, in a heat engine, the working substance should expand from the temperature of the source of heat to that of the refrigerator, in this case the condenser. That would require, for steam falling from 212 F. to 100 F. an expansion to about fifteen times the original volume, which of course was impracticable. Taking that expansion as accomplished, we should have r = 212 4- 460 = 672, and / = 100 + 460 = 560. .*. greatest work possible = JH H^ = JH x - . . (j) 672 6 2. Taking a WoolPs engine working with steam at 45 Ibs. actual pressure, i.e. at a temperature of 274 F., and condensing at 100 F., as before. The expansion should now go on to about 45 times, and if that were possible we should have work done = JH (1345} = JH x 4 nearly . ( 2 ) \ 734 / 17 Referring to Chapter V., we find that with ordinary coal j H represents a consumption of \ Ib. of coal per H.P. per hour ; hence the above results are (i) \\ Ibs. of coal per H.P. per hour ; and (2) i^g Ibs. of coal per H.P. per hour. 94 The Steam Engine. These examples show unmistakably that theory soon leaves practice far behind. They are inserted solely with the intention of exhibiting the subject from a modern point of view. After reviewing the theory of heat engines it must appear to be a remarkable tiling that the progress in the use of high -pressure steam with expansive working and condensation should have gone on so slowly. In the year 1817 marine engines were worked at a pressure 3 to 5 Ibs. above the atmosphere. In that year an engineer giving evidence before a Select Committee on Steamboats took it for granted that cylindrical boilers would not be used in steamboats, because, as he put it, the most convenient form of the boiler was one adapted to the shape of the boat, and the safety depended upon the strength of the metal and not upon the form. The committee had been appointed in consequence of the explosion of a boiler using high -pressure steam on board a vesseL at Yarmouth ; the boiler was cylindrical, with a flat cast-iron end, which gave way. Other engineers who were examined were of opinion that the steam-pressure in a boiler should not exceed 6 Ibs. above the atmosphere, and further, that there was no saving to be effected by employing a higher pressure. When screw ships were adopted in the navy, one of the first of the new series of vessels, the ' Arrogant,' was designed to work at 6 Ibs. steam pressure ; but the ship was deep in the water, and the boiler would not blow ofT under 7 Ibs. It appears that Mr. Penn soon went to TO Ibs. and then to 14 Ibs. But boilers for 14 Ibs. nominal pressure were capable of supporting 20 Ibs., and the usual average of pressure came to be about 16 to 17 Ibs. Within the last 15 years, however, a great change has occurred in the construction of marine engines, and it is shown from the tabulated results furnished by Mr. Bramwell in a paper on the pro- gress effected in economy of fuel in steam navigation, which is particularly referred to in Chapter VII., that the advantage of using steam at a high pressure, with an early cut-off, and as perfect con- densation as can be obtained, is now thoroughly recognised. Mr. Bramwell gives the experience of 19 engines of ocean steamers, with high and low pressure cylinders, working at a steam pressure of from 45 to 60 pounds in the boiler with a consumption of coal Stirling's Engine. 95 certainly less than one half that which commonly prevailed in the days of single cylinder engines with low-pressure steam and very moderate expansion. In like manner the practice with stationary engines has improved, so that it is common to hear of engines with compound cylinders using steam at 70 to 80 Ibs. pressure, and consuming J or ^ less coal than was formerly required for ob- taining the same amount of work. ON AIR ENGINES WORKING WITH A REGENERATOR. 63. Having investigated the conditions under which an ideal heat engine exhibits the greatest efficiency, whereof one is that all changes in temperature of the enclosed air shall be caused solely by compression or expansion, we may remark that, in the present state of knowledge, no method has been proposed whereby the conclusions of theory can be successfully carried out, the enormous dimensions which the cylinders would assume presenting insuperable difficulties. But although the practical obstacles which stand in the way cannot be overcome, they may be evaded by a method which per- mits of a deposition and a taking up of heat within the interior of the engine itself, so that none is lost, the result obtained being much better than would probably have been anticipated. The artifice consists in the use of a so-called regenerator (said to have been invented by the Rev. R. Stirling), which is an apparatus employed in various forms, and which was described by J. & R. Stirling in the specification of a patent (A.D. 1827, No. 5,456), for improvements in air engines for working machinery. The principle of a regenerator is perhaps most readily exhibited by the safety-lamp of Sir H. Davy. It is well known that if a piece of wire gauze be brought down upon 'the flame of a candle the flame will be cut off at the part where it touches the gauze. The explanation is that the meshes of the metal wire have robbed the gases of so much heat as to lower their temperature below the point at which ignition is possible. They are not otherwise affected, and may be at once rekindled on presenting a flame at the upper surface of the gauze. In its earliest form the Davy lamp was an ordinary lamp, 96 The Steam Engine. having the flame encased in a cylindrical covered chimney of wirt gauze. By multiplication of the layers the effect is heightened, and we arrive at a respirator for filtering out heat from a warm current of air, and heating up a current of colder air sent through in the opposite direction. The principle here set forth has also been applied in the construction of furnaces, where a regenerator is composed of a number of open fire-bricks, exposing a large surface for the absorption of heat. In such a case the products of combustion from the furnace gradually deposit their heat before escaping into the chimney, and the end of the regenerator nearest to the furnace reaches a very high temperature, while the chimney end remains comparatively cool. The direction of the draught is now re- versed, and the air for supplying combustion in the furnace is drawn through the heated regenerator, while the waste gases are led into a second cool regenerator, in order to yield up their heat in the manner already described. By alternating the current between the two regenerators a great saving of fuel is effected, for the furnace is supplied with heated air, and the escaping gases deposit a large amount of heat, which is carried back to the fuel instead of being wasted. The regenerator of a Stirling engine was intended to raise and lower very rapidly the temperature of a mass of air, and the substance employed for the purpose was the thinnest sheet-iron. The area of surface exposed was very large, amounting to as much as 3,200 square feet in an air engine of 45 horse power. A number of strips of sheet-iron, each 38 inches long and i| inches broad, and of a thickness of -^ inch, were arranged side by side at intervals of -^ inch. The narrow passages between the strips formed channels through which the air passed in alternate direc- tions. If a regenerator were formed of sheets of wire gauze placed parallel to each other and separated by non-conducting material, it would be easy to conceive that each plate might preserve its proper temperature, but where the air passed through continuous metal channels it might be thought difficult to maintain one end hot while the other was cold. With one engine making about 30 strokes per minute, it did not appear that the loss by conduction was serious, but the specification of a subsequent Stirling 's Engine. 97 patent of 1840 (No. 8,652) for an improved air engine described the plates as divided into four or more portions, the object being ' to diminish their effect in conducting heat from the hot to the cold part of the plate box.' 64. Two engines have been constructed on Stirling's principle, and have worked with considerable success. The first had a cylinder 12 inches in diameter, with a 2 feet stroke, making 40 revolutions per minute, and giving out 21 H.P. The consump- tion of coal was 2\ Ibs. per H.P. per hour. Subsequently an engine of 45 H.P. was set up at the Dundee Foundry, and drove all the machinery of the works for a period of three years. The cylinder was 16 inches in diameter, with a 4 feet .stroke, and the number of revolutions was about 28 per minute. The heating vessels, however, caused so much difficulty that the method was given up. DESCRIPTION OF STIRLING'S AIR ENGINE. 65. Stirling's engine is supplied with compressed air; that is an essential condition, for otherwise the power developed would be insufficient to move the working parts. In one example the pressure of the air varied from 160 Ibs. to 240 Ibs. per sq. inch, the temperature rising to 650 F. on one side of the regenerator, and falling to 160 F. on the other side. The appearance of the engine is that of an ordinary steam engine, the usual steam cylinder being converted into an air cylinder. Two cylindrical air vessels are connected with the working cylinder, one at each end thereof, and they perform the double office of a slide valve and boiler. They are of considerable size, being more than five times as large as the' working cylinder ; and it is stated that f of each air vessel is occupied by its plunger, which is a hollow vessel, also cylindrical, turned so as to fit the interior of the air vessel quite closely, but without friction, and having a quantity of brickdust or other slow conductor of heat at its base. The drawing shows a section of the air vessel A B, with its plunger K H j both are formed of cast iron, and the object is to obtain a very close fit between the plunger and the cylindrical 98 The Steam Engine. casing, so as to prevent as far as possible any leakage of air along its sides. The bottom of the plunger is lined with brickdust, and a pipe leads from the space K B to a box E F, containing the regenerator. Two-thirds of this box is filled with plates of sheet-iron, and the remainder is filled with a number of copper pipes \ inch internal diameter, and y 1 ^ inch thick, through which cold water circulates. The pipes are at a distance of -^ inch apart, and form a refrigerator for removing any heat which has not been previously ex- tracted by the cold end of the re- generator. Any empty space round the pipes may be filled with blocks of iron or brass. The plate box ter- minates in an open pipe E M leading to the working cylinder. A fire is kept burning under the bottom of the air vessel, which is of increased thick- FlGt 34- ness at the base. There is a compress- ing pump for supplying any waste of air by leakage, the usual pressure of the enclosed cold air being ten atmospheres. When the plunger is raised it sends a quantity of air from the top of the air-vessel through the regenerator into the space K B. The air in K B is heated not only by passing through the hot end of the regenerator, which is at its base, but also by the heat of the fire ; its preseure rises, and it expands so as to produce an in- creased pressure along the passage R, which is at once felt upon one side of the piston in the working cylinder. On the other side of this piston is a second similar air-vessel, with its plunger de- pressed, whereby heated air has been forced through the re- generator into the space corresponding to A H, and has been cooled to a lower temperature and pressure, thereby causing the pressure on its side of the piston to fall, and the result is that we have air at, say, 240 Ibs. pressure on one side of the piston, but at 150 Ibs. pressure on the other side, and that there is an ample amount of working power. The peculiarity of the engine is Stirling } s Engine. 99 that the enclosed mass of compressed air is divided into two distinct portions, A and B, which are in some sense separate, although an open passage leads always from one to the other. The mass of air A nils the air vessel and passes to and fro through the regenerator. It is heated and cooled alternately, and the changes in its temperature give rise to the work done. The mass of air B is in contact with the piston of the engine ; and since B and A open freely to each other, the pressure of the mass B rises or falls with the pressure of the mass A. But that is all, for B is a mere carrier of pressure to the piston of the engine, and its temperature is comparatively unaffected. As to the mechanism of the engine, that is the same as for an ordinary steam engine. The only point to be noticed is that the plungers of the two air vessels are first worked by hand, in the same manner as the valves of a steam engine, and that after the engine is fairly started the motion is continued by an eccentric on the fly-wheel ^haft. 66. It may be useful to give the type of the diagram of energy in Stirling's engine, although the subject demands much more space than is available in order to examine it thoroughly. Starting from the point s, with a mass of air at volume o M, and pressure s M, and remembering that we are not now dealing with the working cylinder for the primary effect is modified by the cushion of air, so that the diagram in the cylinder would be some- what as if that now to be exhibited were drawn on an elastic sheet of indiarubbe and pulled out at two opposite corners we proceed as follows : 1. The air takes up heat in passing through the regenerator, and its pressure rises to P M. 2. The air expands along the isothermal curve P Q, for the loss of heat in doing work is at once repaired. 3. The air deposits heat in the regenerator, and its pressure falls from Q N to R N. 4. The air is compressed along the isothermal curve R s, for the heat given out in compression is at once absorbed. H2 IM FIG. 35. ioo The Steam Engine. The shaded area P Q R s is the diagram of energy, and we see that by the artifice employed the engine works approximately according to the figure given above, but only approximately, for the heating or cooling does not take place exactly at a constant volume, and does not affect more than a poition of the enclosed air, nor do the expansion and compression occur exactly at con- stant temperatures. It does not appear that a heated air engine with a regenerator has ever taken root, but the principle is established, and accordingly the reversible quality of such an engine has been successfully applied to that which is somewhat misnamed by its advocates, viz., the so-called ' mechanical production of cold/ 67. In a reversed Stirling's engine the working cylinder is converted into a pump driven by external force, and the cool end of each air vessel receives a substance from which lieat is to be abstracted. Referring to fig. 35 we find that 1. The air is compressed through Q P, and its temperature rises. 2. Heat is then abstracted by a refrigerator cooled by a cur- rent of cold water, and further by a regenerator, the pressure falling to s M. 3. The air expands through s R doing work, losing temperature, and taking up heat from the substance to be cooled. 4. It is passed through the regenerator, becoming warmed, and its pressure rises to Q N. This cycle is continued., and at each double stroke of the pump a portion of heat is taken from the substances in each air vessel which are undergoing the cooling process, and is deposited in the regenerator, and this goes on until such a difference of temperature is set up between the hot and cold ends of the absorbing surfaces that the heat taken away from the substances is continually restored by conduction through the material of the regenerator. In a working engine it has been found that this result takes place at a temperature of 50 to 60 below the zero on the Fahrenheit scale, 1C! CHAPTER IV. ON THE CONVERSION OF MOTION. 68. Ji ST as it is necessary to know something of the theory of heat in order to understand the philosophy of the steam engine, so also it is essential to pass through some training in the elements of the conversion of motion in order to comprehend the mechanism of the moving parts. We propose in the present chapter to give a brief outline of certain fundamental propositions which will be useful. The belief held by the ancients as to the nature of cir- cular motion was fanciful in conception, and was obviously unten- able. It was said that motion in a circle was simple, in the sense that it was a primary movement, and not made up by putting together other separate movements. We, on the other hand, hold that the only case of simple motion is that of a point describing a straight line with a uniform velocity. Whenever a point deviates from a rectilinear path it is, or may be, the subject of two in- dependent movements in lines at right angles to each other. It is upon this idea that the whole learning of analytical geo- metry is built up. If we wish to repre- sent a curve by means of a relation be- tween symbols, called an equation to the curve^ we begin by drawing two lines, x o #', y o y, at right angles to each other, and employing them as lines of refer- ence. For example, let the curve be a circle whose centre is the point o. Take P. any point in the curve, and FlG - ? 6 - chaw P N perpendicular to o x. Let o N = x t N p = y, o p 102 The Steam Engine. Then o N 2 + N p 2 = o p 2 ; or x* + y* = a\ a relation between x, y, a which is satisfied by points situated in the circular curve A p, and by none other, and which is there- fore called the equation to the curve. The lines x, y are the co-ordinates of the point P, and the axes x o x', y oy' are the axes of co-ordinates. Also the signs + and are employed to indicate the position of P in any particular quadrant ; thus, if P were situated anywhere in the quadrant as? oy' the corresponding values of x and y would both be negative. It is to be observed that when P starts from A and travels round the circle, the point N follows this movement and makes an excursion from A to B and back again from B to A (see fig. 38). In other words, N makes a complete double oscillation in the line A B, while P describes the circumference of the circle. In like manner if we draw P M perpendicular to o y, we shall find that M makes a complete double oscillation in the line yy f , while P describes the circumference beginning at A and ending there again. And yet there is a marked dissimilarity, as well as a resemblance, between the movements of N and M, which should now be made clear. 69. Referring to the drawing, which is sketched from a model intended to exhibit simultaneously the motions of the points M and N, the framework being left out, we have a pin P passing through the grooved bars RS and T v, which overlap each other, and are con- nected by slender rods sliding between guides. Also x and y are small balls or index fingers traversing over a gra- duated scale, and indi- FIG. 37. eating the movements of the respective bars. As the pin P travels round a circular groove A P B E formed in a board, it is apparent that x will oscillate to and fro with a motion identical with that of N, and that^ reproduces the movement of M, Circular Motion. 103 Also everything depends on properly timing the rectilinear movements. In order to describe a circle, x starts from rest when y is at the middle of its swing. This is the essential condition ; and it is worth notice that if the board with a circular groove be replaced by another having a straight line groove inclined at 45" to o x, the two balls will start together from rest, and after preserv- ing identical movements throughout will come to rest at the same instant, the difference between the times of starting giving a circle in one case and a straight line in the other. ANALYSIS OF CIRCULAR MOTION. 70. To express analytically the relation between the move- ments of the points N and P we proceed as follows : Let A N = #, N P = JJ>, O P = 0, P O N = 0, then A. N = o A o N = a a cos 0, or x = a (i cos 6) . . . (i) whence the position of N is known from that of P. In comparing the velocities of the same points it is usual to refer to the calculus and differentiate, when we have : FIG. 38. dx and remembering that velocity of N = -, and velocity of p = a J A T , it is apparent that vel. of N vel. of P = sin 6 ... (2) Equations (i) and (2) contain the whole theory of the subject, the first defining the law according to which the point N travels along A B, and the second indicating the velocity with which it moves at any instant. That velocity being variable, its value may be most readily assigned by a process in the differential T IO4 The Steam Engine. calculus, but it may also be deduced by geometrical reasoning, and the student would probably be able to solve the problem for him- self, now that the answer has been given. THE MOTION OF AN INDICATOR PENCIL. 71. The model serves extremely well to exhibit the combina- tion of movements which occur in tracing an indicator diagram. For this purpose replace the board with a circular groove by another having an indicator diagram traced upon it. As the pin p travels round the outline of the diagram it is ap- parent that the index y will rise or fall with the fluctuations of the steam pressure, while the ball x moves to and fro hori- zontally with a motion de- rived from that of the piston of the engine, though on a F diminished scale. Watt's first idea was to observe only the motion of y, but the invention was completed by com- bining therewith the reciprocation derived from the piston. The model presents an image of this combination of motions in a manner which renders it perfectly intelligible. THE SUN AND PLANET WHEELS. 72. The sun and planet wheels, as used in the early rotative steam engines, were invented by Watt, and were employed for converting the reciprocating motion of the working beam of an engine into the circular motion of the fly-wheel. They involve a distinct principle in mechanism, which is applied in the construc- tion of some governors of steam engines. In a note upon this invention Watt says : ' Having made my reciprocating engines very regular in their movements, I con- sidered how to produce rotative motions from them in the best manner ; and, amidst various schemes which were subjected to Irial or which passed through my mind, none appeared so likely The Sun and Planet Wheels. 105 to answer the purpose as the application of the crank in the manner of the common turning lathe.' He goes on to say : * I proceeded to make a model of my method, which answered my expectations ; but having neglected to take out a patent, the in- vention was communicated by a workman employed to make the model to some of the people about Mr. Wasbrough's engine, and a patent was taken out by them for the application of the crank to steam engines. In these circumstances I thought it better to endeavour to accomplish the same end by other means. Accord- ingly, in 1781 I invented and took out a patent for several methods of producing rotative motions from reciprocating ones, amongst which was the method of sun and planet wheels.' It appears that in 1780 a patent (No. 1,263) was granted to J. Pickard, of Birmingham, for a ' new invented method of apply- ing steam engines to the turning of wheels.' In the specification it is stated that a lever, commonly called a crank, is fixed to the shaft or arbor of a great wheel, the pin of the crank being inserted into one end of a spear or carrier, the other end of which spear is connected by a moving joint with the regulating or great work- ing beam, and in some cases to the piston, of the fire engine cylinder. This is precisely the mode of connection now ordinarily adopted. The drawing shows Watt's invention as specified in a patent of 1781 (No. 1,306). c B is the working beam, and AB is the spear or connecting rod ; E is a wheel fixed upon the end of the shaft or axis F, which receives the rotatory motion which is com- municated to it by a second wheel, firmly fixed to A B in such a manner that it cannot rotate. Behind E B there is a heavy wheel, G G, having a groove or circular channel around its circumference, into which a pin at the back of A enters. The wheels A and E are thus kept in gear, and some such precaution is indispensable, but instead of the wheel with the groove and pin there may be a link connecting A and F. The construction having been described, the specification states that in the working of the engine the connecting rod pulls the wheel A up and down; and since its teeth are locked in the wheel E and it cannot turn upon its own axis, it cannot rise or fall without causing E to turn upon the axis F. When the two wheels A and E have equal numbers of teeth the io6 The Steam Engine. wheel E makes two revolutions on its axis for each stroke of the engine. In proving this result we shall assume that an imaginary arm connects the centres of the wheels A and E. Let E make x revolutions in one double stroke of the piston; then the arm makes one revolution in the same time, and the wheel A remains practically at rest. Therefore E makes x i revolutions relatively to the arm, while A makes o i relatively to the same FIG. 40. arm ; also E and A are two equal wheels in gear, and consequently their relative rotations are equal in amount and opposite in sign. It follows that o i x i i = i, or x 2. That is, the wheel E makes two revolutions Avhile the wheel A is carried once round it. The Crank and Connecting Rod. 107 After explaining the contrivance Watt makes one most impor- tant observation : ' And in order that the motion may be more regular I fix to or upon the shaft or axis F, or to or upon some other wheel or shaft to which it gives motion, a heavy wheel or flyer, to receive or continue the motion communicated to it by the primary movement.' And further, that in the cases to which this method may be applied, ' a flyer or heavy rotative motion should be applied in order to equalise the motion/ The heavy wheel or flyer is the fly-wheel which gives smooth- ness and regularity to the motion of the shafting employed for driving the machinery of mills. THE CRANK AND CONNECTING ROD. 73. We pass on to analyse the conversion of circular into reciprocating motion by means of a crank and connecting rod. A crank being a lever or bar movable about a centre at one end, the connecting rod may be a bar attached to a sliding piece moving between guides, as in an ordinary direct acting engine. FIG. 41. Let c P represent an arm or crank centred at c, and attached by means of the connecting rod P Q with a point Q constrained to move in the straight line c D. Draw p N J_ r to c Q, and let c P = a, P Q = , p c A = 0, p Q A = 0. Then CQ = CN + NQ = a cos 6 + b cos 0. But 4 = f /. sin f = sin 0, sin 6 b b whence cos ^ = \ f i ^. sin* 0, IO8 The Steam Engine. .-. c Q = a cos 6 + ,/ & z a* sin 2 0, which gives the relative positions of Q and P at any instant. Cor. i. Let = o .*. c D = a + b, = TT .*. CE= a + by whence DE = CD CE 2a. The length D E is called the throw of the crank. Cor. 2. If we refer the motion of Q to the point D we have D Q = c D c Q = # + a cos b cos 0, or D Q = a (i cos 6) + b (i cos (-0603074) = -2010247. Or a represents an angle of n 31'. /. sin $ = sin 20 + f (i cos 11 31') = -3420201 + f (-0201333) = -3541001. .*.

+ kT 2 .*. ** V* C P 2 -f 2X X C P C P (C P + 2X) =- C P X C Q. Peaucellier's Invention. 1 19 When the rods are in the normal position, as shown in fig. 49, let Q be at the point F. Join F Q and P D. Then by parity of reasoning we have CD X C F = 26 4>ooo _ 28o<7 it appears t h a t the per- 33,000 formance would be to that of an engine burning i Ib. of coal per H.P. per hour as 2807 : 60, which is somewhat greater than 4 to i. We have seen in the third chapter the true meaning which is to be attached to such observations. A pound of coal can only do work by the operation of a heat engine, its function being to store up heat in a gas which does work by expanding between two given temperatures. Let the pound of coal supply without any loss steam at 300 Ibs. pressure to a perfect engine where the condenser is at a tempera- ture of iooF. The temperature of the steam will be 417 F. Thus, work done = 8? 7 8 7 y 56 JH = 77 JH = ^ J H ' Now, JH represents , ' H.P. for i Ib. of coal. -^ JH re- 60 TI presents 17 H.P. for i Ib. of coal. Also 2\ Ibs. of coal for i H.P. is the same as i Ib. of coal for - H.P. Hence the comparison lies between i Ib. of coal for 17 H.P., and i Ib. of coal for '4 H.P., 126 The Steam Engine. which numbers are as 17: 4, being a little more than 4 to i, in stead of 10 to i. In truth, we begin by throwing away JL of the whole heat, ii which passes into the condenser and is lost ; and indeed we are constrained to work between temperatures which lie within mode- rate limits of difference, for which reason it becomes hopeless to refer to the whole heat as a standard. IMPROVEMENTS IN THE INDICATOR. 86. The indicator, as originally constructed, was not in a form convenient for use, and it has been modified and improved by FIG. 55. /arious makers. The first obvious change has been to replace the flat- board by a cylinder enclosing a spring. The cylinder is caused to reciprocate through one turn by the pull of a string attached to some piece whose motion is identical with that of the Richards'* Indicator. 127 piston, and it returns with a corresponding movement, whereby a diagram is traced upon a sheet of paper wrapped round the cylinder, just as in the former case. Another improvement consists in reducing the motion of the piston, and magnifying that of the pencil. It is manifest that when steam at a high pressure is suddenly admitted into the cylinder of the instrument the pencil will rise with a jerk, and will oscillate with a tremulous motion during the time that it ought to be descending smoothly according to the curve of expansion. The result will be a wavy line instead of a regular curve, being the very defect which Watt said was sure to occur when the steam pressure was read by a mercurial gauge. The jumping up and down of the pencil has proved a source of great annoyance in practice, so that thoroughly good diagrams could scarcely be obtained from fast-going engines. However, Mr. Richards has overcome the difficulty by diminishing, the piston-stroke and multiplying the travel of the indicator pencil, so as to bring it up to the original standard. He supplies a stronger and shorter spring than that used in an ordinary instrument, and the vibrations become incon- siderable. The drawing shows the improvement, and furnishes an illustration of a useful adaptation of Watt's parallel motion : FIG. 56. Two equal bars A B and c D are connected by a link D B carry- ing a pencil p at its middle point P. The piston rod E R is attached by a link R s to a point s in c D, such that c s = J c D. Also when A B and c D are in the position of rest, as in the sketch, it will be found that R s is parallel to D B, and that c R P is a straight line. It follows that, just as in the duplicate straight line motion of Peaucellier, the pantograph exists in a disguised form. Thus the f 28 The Steam Engine. points R and p necessarily both describe straight lines, which are similar paths ; and s R and D p, being parallel at starting, must remain so throughout the motion. They would be kept parallel to each other if the pantograph were constructed, and they remain parallel in virtue of the motion, which is that due to a pantograph, and not to be distinguished from it. Hence, travel of p : travel of R = c D : c s. In the indicator, as constructed, the movement of R is magni- fied about/our times. It should be understood that the frame carrying the parallel motion bars is attached to a collar which can be rotated on the cylinder, whereby the pencil is readily brought up to the paper or removed from it DIAGRAM EXHIBITING THE RELATION BETWEEN THE PRESSURE AND VOLUME OF SATURATED STEAM. 87. Hitherto we have spoken of the expansion of air either according to Boyle's law or in an adiabatic curve, but in ap- plying the results of experiments on the expansion of steam to a practical use it becomes important to regard the behaviour of that particular substance from another point of view. It has been shown that the pressure and temperature of satu- rated steam rise conjointly, though not in the same degree, and tables have been formed expressing the relation between the pressure, volume, and temperature of saturated steam. It will be borne in mind that steam in contact with the water from which it is generated is called saturated steam ; and further, that when saturated steam at a high pressure expands while doing work its temperature falls, and a portion of the steam is re-converted into water. Furthermore, if we operate with saturated steam at a given temperature and endeavour to compress it, we may reduce its volume, but we cannot increase its pressure. Each temperature has its own corresponding pressure, which cannot be varied ; and, as we have sufficiently shown in the first chapter, if the volume be diminished while the temperature remains constant, the only result will be that more and more of the steam will be reconverted into water, the pressure remaining unchanged, Diagram of Expansion. 129 If the relations between the pressure and volume be mapped out for any given weight of steam, we have a curve, which is of great value in interpreting the diagrams given by an indicator. It differs from Boyle's curve of expansion, it differs from the curve of expansion of superheated steam, which would be that of a perfect gas ; it is a curve furnished by experimental data, and expresses the conditions which obtain when saturated steam changes its state of pressure, volume, and temperature without ceasing to be saturated. The table generally relied on is deduced from Regnault's ex- periments, but as a matter of illustration we refer to the results of experiments made by Fairbairn and Tate. The substance being saturated steam, those numbers only are selected which are re- quired for the present example : Pressure in Ibs. per sq. inch Temperature Fahrenheit Specific volume II 19777 2167-4 12 xoi -96 1994-0 147 212 1641-5 25 240 984-8 9 259-65 260-83 7I3-4 694'5 By ' specific volume,' or, as it is sometimes termed, 'relative volume/ is meant the volume of the steam as compared with that of the water from which it is generated; and since the numbers are large it is common to reduce them by increasing the unit of volume fifty times. Conceive now that we deal with a given weight of saturated steam at a pressure of 36 Ibs. and a volume 694*5, and allow it to expand doing work. Since 3 x 694*5 = 2083.5, ft i apparent that if the expansion be carried to three times the original volume the pressure will become less than 12 Ibs., whereas, according to Boyle's law, it should be exactly 12 Ibs. There is, therefore, asmal! deviation from Boyle's law in the form of the curve. The point to be noticed is that the curve, when obtained, repre- sents a theoretical indicator diagram. In the present example, setting out a number of intermediate points for pressures at 34 K * 3 The Steam Engine. 33, &c. Ibs. and registering the corresponding volumes, also calling 694*5 unity, we have the annexed diagram, where all vertical lines represent lines of pressure, and all horizontal lines refer to volumes, and where the steam is maintained in its hypothetical state by a supply of heat from without J6 FIG. 57. Let the horizontal line terminating at D represent the travel of the piston of an engine which is supplied with saturated steam at 36 Ibs. pressure, and let the pressure be continued constant during of the stroke, as indicated by H s. The steam now ex- pands along the curved line s R and its pressure falls to R D, which is a little under 1 2 Ibs. A full opening is then made to the exhaust \ and if the condensation of the steam were instantaneous and perfect the pressure would fall to zero, and would remain so during the return stroke. Assume that the condensation is instantaneous, but that the pressure falls only to 4 Ibs., repre- sented by B D, and remains constant till the piston reaches the end of its stroke. The area H s R B A will represent the whole work done in the double stroke, and is contrasted with the area H s E A, which re- presents the work which would have been performed by the same weight of steam if there had been condensation without expansion, Expansion of Saturated Steam. 131 In 1849 Mr. C. Cowper published a complete diagram of the expansion of saturated steam, ranging from a pressure of 2 Ibs. per square inch up to 120 Ibs. He stated that the diagram was 'in- tended to facilitate the calculation of the amount of power ob- tained by different methods of employing steam/ There were two divided scales, viz., (i) a vertical scale of pressures from zero up to 120 Ibs. (2) a horizontal scale of volumes, giving the volume of the same weight of steam at each different pressure as com- pared with the water from which it was generated, one division on the scale representing 50 units of volume. The general character of the diagram is shown in fig. 58, each little square being further subdivided into 25 squares in the pub- lished card. A dotted line represents the curve of expansion from the top of the figure according to Boyle's law. The dimen- sions are the following : Line of volumes = 1 1 inches, line of pressures = 6 inches. 140 _ FIG. 58. 88. Having employed this expansion curve for obtaining the normal or theoretical form of an indicator diagram, which closely resembles that given by Watt, we refer to fig. 58, where five small sketches are appended, which, when rightly understood, present a summary of successive improvements in the steam-engine, the horizontal dark line being the line of atmospheric pressure throughout : i. The shaded rectangle is the diagram of work done by a given weight of steam when employed in a condensing engine. K2 132 The Steam Engine. The rectangle cut away at the base represents the loss by imperfect condensation, 2. The diagram of work when steam at the atmospheric pres- sure is expanded 2\ times with condensation, as in Watt's early engines, before the employment of high pressure steam. 3. This figure represents the work done by an equal weight of steam at a pressure of 60 Ibs., without expansion and without condensation. 4. Then comes moderate expansion of steam at 60 Ibs. pressure, without condensation. It is apparent that the curve is taken in every case from the normal diagram, and here the expansion is carried to three volumes. The rectangle cut away represents, in each case, the loss by back pressure. 5. The same case repeated, except that the expansion is con- tinued to 9 volumes, and we have the theoretical indicator diagram of an engine working according to a more economical method. The indicator being a measuring instrument attached to the cylinder, and intended particularly to inform us as to the action of the valves connected therewith, it will be essential to give some sketch of these working parts before discussing the peculi- arities of the outline traced out by the pencil. It is not within the purpose of this book to present that full information which is to be found in large works crowded with working drawings, and it must suffice to point out enough for a fair explanation of the matter before us. VALVE MOTION OF A SINGLE-ACTING ENGINE. THE HYDRAULIC GOVERNOR, OR CATARACT. 89. To begin with the valve motion of a single-acting engine. It will be remembered that there are three principal valves con- nected with the cylinder, viz. (i) the steam valve, (2) the equili- brium valve, (3) the exhaust valve. Originally these valves were simple discs covering the respective openings, but at the present time they are balanced valves, usually of the Cornish double-beat or crown-valve construction, to be presently described. There is no rotating shaft or fly-wheel connected with a pumping engine for mines, and hence the motion available for rendering the The Cataract. 133 mechanism self-acting is not continuous but intermittent. The exact period of opening each valve will determine the number of strokes made per minute, and is the first thing to be provided for. It is evident that some independent agent must be at work to open the valves, and when that is effected the motion of the beam may be utilised for closing them at the right instant. The independent agent referred to takes the name of a cataract^ probably from the original form of the apparatus, which, in the early days of steam engines, was that of a vessel into which water was poured at a definite rate through a partly- opened tap. The vessel was lop sided and tilted over, so as to discharge its contents in a sort of cataract as soon as the water had risen to a certain height. The falling over of the vessel determined the period of opening the valve with which it was connected. After a sufficient time the same valve was closed by a lever actuated by a projection or tappet on the plug rod, of which mention was made in the account of Newcomen's engine. The principle of the cataract in its modern form will be under- stood from the annexed sketch. Inside a cistern partly filled with water there is placed a plunger pump P, connected with a valve o, opening upwards into the chamber of the pump, and having a tap A, capable of being regulated by a lever A d and a rod d e. The plunger P is loaded, so that after being raised it will force out water through the tap A. The valve o is fully open when the plunger rises, and closes as soon as it begins to FIG. 59. descend, and the only escape remaining for "the water is through the partly open tap, the regulation of which determines the rate at which P descends. Up to this point the cataract is a simple plunger pump, with a partly open tap in place of the usual delivery valve. The next drawing, on p. 134, will show the external form of the cataract as well as its connection with the valves of the engine. And here we may point out that there are commonly two cataracts 134 The Steam Engine. TOP STEAM ARBOR (Q>^\) \ FIG. 60. employed, the function of one being to open the steam and exhaust valves, and that of the other being to open the equilibrium valve. In the drawing the cataract is represented as acting upon the steam Valve Motion of Single-acting Engini and exhaust valves. The plunger p is a hollow cylinder, closed at the bottom but open at the top, and called a trunk ; it is attached by a rod to the lever N o M, which is centred at o, and is raised when the tappet or projection shown at / on the plug rod comes in contact with the tail of the curved lever-arm springing from w, which lever-arm is a handle for rotating the small chain-wheel. The result is that the chain is wound up to some extent, and P is raised. The weight hung at N now causes the plunger to sink, and water is forced out at the partly open tap, the cataract rod rising until eventually its extreme end lifts the lever at the top steam arbor (that is, axis) and liberates the catch. The regulation of the descent of the plunger being effected by opening the waste tap at d more or less, there is a separate bar de connected with the short lever attached at d, which has a screwed portion, as shown, and by rotating the knob e at the upper end of the bar the tap may be opened or closed. In order to complete the explanation it is necessary to turn to fig. 6 1, which exhibits the mechanism employed for opening and vv FIG. 61. closing the steam valve s. A catch rod r s holds the catch i, which has a fixed centre at E. As soon as i is liberated w descends and s opens. The left-hand sketch shows the cataract rod ascending and just about to raise the end r of the catch rod r s. The tail/ of the lever /E b will then move upward into the position shown in the second sketch, and it should be understood that the only part of the plug rod which interferes with the freedom of motion of/ is the dark-shaded piece marked H. 136 The Steam Engine. When the valve s is raised the piston descends and pulls down one end of the working beam; this brings down also the plug rod, and causes the part H to strike the tail /of the lever b E/; and to depress it into a position ready for being locked by the catch rod s r as soon as that rod is set free by the sinking of the cataract rod. When once locked the valve s must remain closed until it is liberated by the cataract or by hand, for of course the valves may be worked by hand if desired. The period, or rather the portion of the length of stroke, during which the steam valve remains open is regulated by adjusting the position of the piece H, and determines the amount of expansion. In a powerful pumping engine, such as is employed at waterworks, where a weight of 30 or 40 tons is lifted some eight times in a minute, it is most remarkable to watch the steam valve lever and to note the short space of time which elapses between the opening and closing of the passage for steam. CYLINDER, SLIDE-VALVE, AND PISTON. 90. We pass on to the cylinder, piston, and slide-valve of a locomotive engine. Several drawings would be required for exhibit- ing these respective parts completely, but there is not space for FIG. 62. more than a longitudinal section of the cylinder, together with the piston and valve for distributing the steam. Murdoch's Slide-valve. 137 The cylinder is 16 inches in diameter and J- inch thick ; it is made of cast iron, and is bored out in a lathe. The thickness of a steam cylinder depends, of course, upon the diameter and the intended pressure of the steam. One cover is movable, in order to admit the piston, but the other cover is often a part of the casting. The openings into the cylinder are called steam-ports, being rectangular in shape and bounded by a plane surface scraped up so as to approximate to a so-called true plane. The ports lead into passages shown in the sketch through which the steam enters into or escapes from the cylinder. MURDOCK'S SLIDE-VALVE. The most important element of the combination is the slide- valve, which is in a form derived from the original invention of W. Murdock, who, in 1799, obtained a patent (No. 2,340) for an im- proved construction of the steam valves in Watt's double-acting engine. 91. Murdock's valve, technically called a D valve, consists of a hollow pipe A, usually semicircular in form, and attached to a rod as shown. Upon the flat side of the pipe are two plane rectangular faces which slide upon correspond- ing plane surfaces having rectangular openings called ports, which form passages into the cylinder and convey the steam to either side of the piston. The sliding faces are scraped so as to be as nearly as possible true planes and work upon a corresponding plane surface, the object being to render the valve steam-tight on the plane side. The valve is cylin- drical at the back, and is kept steam-tight by packing at D and E. It will be understood that the^ sketch is a mere lecture diagram, and does not show the con- struction of the several parts ; thus, the packing at D and E is not carried with the valve, but is pressed against it through openings in the back of the slide-case. Any steam which enters the central portion by the FlG - 6 3 passage indicated will circulate freely round the pipe, while the space below the valve is permanently open to the condenser. In the drawing steam is entering below the piston p, and is 138 The Steam Engine. driving it upwards, while the steam above P escapes through the upper port, passes down the hollow pipe, and enters the condenser. Upon raising the slide-valve .the reverse takes place, for steam enters at the upper port and escapes through the lower port directly into the condenser. Each end of the pipe may be regarded as a separate valve, and accordingly in Murdock's account of his invention it is stated that the upper and lower valves are worked by one rod or spindle, the stem or tube which connects them being hollow, * so as to serve for an eduction pipe to the upper end of the cylinder, by which means two valves are made to answer the purpose of the four used in Mr. Watt's double engine.' It will be remembered that a dia- gram showing the arrangement of the four valves in Watt's early engine has been already set out at page 37. OTHER SLIDE VALVES. 92. Another form of valve derived from the above is called a box valve, being a sort of box with plane faces and containing a passage along the back of it. Here the packing d& may be dispensed with, but a third port becomes "psli I necessary, so that in one sense the contrivance is less |rv\ simple. It is sketched in fig. 64, where A is the upper steam port, B the lower steam port, and c the eduction port. The drawing shows steam entering above the piston at A, and escaping through B into c, and so to the condenser ; whereas, by lowering the I valve, steam would pass into the space below the piston at B, and would escape from the upper part of the cylinder into the passage formed by the valve, p * i which would now lead directly into the condenser. 1 nr it will be readily seen that the flat portions of the I T IJj L valve are in steam-tight contact with the faces on FIG. 64. which they work. 93. If the ports be interchanged, so that c lies between A and B, the construction of the valve is greatly simplified, and it is no longer necessary that it should assume the form of a pipe, for it may be a simple box with flat faces. Such a valve is applied in engines of every class, but is of universal use in locomotive Slide-valves. 1 39 engines, and is distinguished as a locomotive D valve, or three- ported valve. It is the valve shown in the section of a cylinder and its appendages which has led to this discussion about valves, and may be conveniently studied in the following example, which Is taken from an oscillating engine working in one of the boats on the Thames. The annexed diagram shows the steam ports A and B, together with the eduction port c, and a passage s leading to the boiler. The valve and ports are covered by a rectangular box or casing, seen in section in fig. 66. The metal surface abed surrounding the ports, including the intermediate bars m , is carefully planed in the first instance, and is usually scraped afterwards, according to the method originated by Sir J. Whitworth, so as to be as nearly as possible a true plane surface. In the year 1840, when slide-valves scraped up to a standard FIG. 65. surface plate first came into use, and were tried against others prepared on the old plan by grind- ing with emery, it was stated by the Superintendent of the Manchester and Liverpool Railway, in answer to a letter from Mr. Whitworth : * I have this day taken out a pair of valves got up with emery that have been in constant wear five months, and I find them grooved in the usual way. The deep grooves are J inch deep, and the whole surface, which is 8 inches broad, is ^ hollow or out of truth. Those that are scraped are perfectly true, and likely to wear five months longer.' The grooving action which here arose, probably from the emery- powder which adhered to the metal, has in some form or other always been a source of difficulty, and is also traceable to the inequality of wear due to the open faces of the ports as compared with the sides. Mr. Webb has accordingly patented a circular slide-valve which is free to rotate in the buckle that holds it ; 'so that if the valve should have a tendency to seize in any one part of the sliding surface, which would put more friction on that 140 The Steam Engine. particular side, it will immediately begin to revolve, and so rectify itself by bringing different portions of the surfaces to bear.' The steam ports are annular segments on this construction, the exhaust port being circular. A pair of valves exhibited at a meeting of the Institution of Mechanical Engineers in 1877 had run 20,000 miles on the North- Western Railway, and the surfaces were polished by wear, but appeared to be perfectly true. FIG. 66. The next drawing shows (i) an outside casing D D, which forms a receiver into which the steam enters on its way from the boiler ; (2) the valve E and its spindle ; (3) a stuffing-box and gland at H, forming a steam-tight collar through which the spindle passes ; (4) the steam passages marked A and B respectively, and the eduction passage c which leads directly into the condenser. Two sections are given of the valve and the slide case, one a longitudinal section through the valve spindle, the other a cross section through the middle of the slide case, showing the breadth of the valve. Taken with the plan of the ports, these sketches make the construction of the whole apparatus sufficiently clear. Also it is apparent that when the valve moves to the left suf- ficiently to uncover the port A, there will be an escape for steam from B into the condenser, the arch of the valve forming a passage from B to c. On moving the valve sufficiently to uncover the port B to the steam there will be an escape through A into the condenser. The action is, therefore, precisely the same as in Murdock's valve. The Piston. 141 THE PISTON AND ITS PACKING RINGS. 94. We come now to the piston and the method of packing it so as to prevent any steam from passing from one side to the other by leakage. The drawing (fig. 62) shows the piston wrought in one solid piece, and dished out so as to form a deep surface of contact with the sides of the cylinder. Here the depth of the guiding surface of the piston is 4 inches, and the three grooves shown in section are intended for the reception of metallic pack- ing rings, as applied by Mr. Ramsbottom about 1854, and which form the simplest method that has been devised for keeping the piston steam-tight under the high pressure employed in locomo- tive engines. The contrivance is thus described in a paper on an improved piston for steam-engines : ' Three separate grooves, each J inch wide, \ inch apart, and ^ inch deep, are turned in the circumference of the piston, and these grooves are fitted with elastic packing rings. These rings, which may be of brass, steel, or iron, are drawn of a suitable section to fit the grooves in the piston, and are bent in rollers to the proper curvature, the dia- meter of the circle to which they are bent being about -nyth larger than the cylinder. They are placed in the grooves in a com- pressed state, and along with the body of the piston are thus put into the cylinder, care being taken to block the steam-port. The rings are therefore forced outwards by their own elasticity, which is found quite sufficient to keep them steam-tight.' Of course the rings are put on so as to break joint. One object in the con- struction of this particular piston has been to reduce as much as possible the amount of rubbing surface. It is a maxim in books on mechanics that the amount of friction is independent of the extent of surfaces in contact, but that rule only applies where the surface is directly supporting a pressure, and it has nothing to do with the friction of a piston, where an increase of surface un- doubtedly increases the friction. Here the lightness of the piston reduces the friction, and so also does the small amount of elastic surface pressed against the interior of the cylinder. As to the amount of bearing surface, it appears that for an 1 8-inch piston it would come to about 42 sq. inches, whereas in a 142 The Steam Engine. piston of the same diameter with 2\ inch packing rings the area of rubbing surface would be 141 sq. inches. The simplicity of construction is also an advantage, the only workmanship expended on the piston being that of turning its rim and forming its centre. The packing rings are drawn as ordinary wire, and are afterwards bent into shape, the cost of production being very small. The mode of attaching the piston rod is apparent from the sketch. There is a shoulder, and the rod terminates in a coned end, the whole being screwed up tight by a nut. The cylinder covers are copies of the configuration of the piston, thereby avoid- ing a waste of steam. PISTON OF AN OSCILLATING CYLINDER. 95. In contrast with the locomotive piston, 28 inches in dia- meter, take a piston for an oscillating cylinder of a large paddle- wheel steamer, the work done by which is 300 nominal H.P., but is really much greater. In the present example the piston is made of cast iron, and is 88 inches in diameter. It has to support the enormous driving pressure of the steam, which at 13 Ibs. per square inch would amount to 35 tons, and is constructed of two plates of iron of great strength, increasing from \\ inch in thickness near the cir- FIG. 67. cumference to if inch near the piston rod, being further strength- ened by six ribs of iron, indicated in the sketch, each of which is \\ inch thick. The depth of the piston is 7 inches at the Balanced Valves. 143 packing ring, and increases to about 13 inches near the centre, whereby every vertical radial section presents an analogy to a cantilever or beam supported at one end. There is one large metallic packing ring, made of cast iron, 5 inches deep, and f inch thick. It is turned in the lathe, and then cut through and jointed with a tongue, so as to be the exact size of the cylinder, an outward elastic pressure being maintained by junk packing, which is wound round the piston behind the ring in the empty space #, and is held down and compressed as well as forced outwards by a ring with a shoulder. This ring is tightened on by a series of bolts, whereof one is seen in the drawing, having square heads to prevent their becoming loose, and being retained in position by one tight encircling ring, c. The piston rod is 10 inches in diameter, coned at one end, and secured by a nut 16 inches in diameter. The nut is tightened up by a long lever, which has a forked end, terminating in two pins, which enter the recesses shown in the nut BALANCED VALVES. 96. The next point to be considered is an improved construc- tion of valve which will permit of an opening being made with but little effort in a space exposed to the full pressure of steam. The subject-matter for alteration is the old disc valve em- ployed by Watt, and shown in the annexed drawing, as being lifted by a rack and segmental pinion. The steam pipe opens into the box or casing above the valve, and the steam FlG - therefore presses with its full force upon the surface of the disc, which cannot be raised until that force is overcome. It is, how- ever, easy to vary the construction so as to remedy this defect, and the method adopted is to balance the fluid pressure by subject- ing two equal areas to equal pressures in opposite directions. The applications of this principle are the following : i. The Throttle Valve. This valve was introduced by Watt, and consists of a circular plate turning on a spindle which coincides with a diameter of the 144 The Steam Engine. plate. It is shown in section in fig. 69, the seats being indicated at/, h, and the point o being the axis of rotation of the valve. The pressureofthe steam on one half of the valve viz. o b is, of course, balanced by that on the other half o a, and there is equilibrium in FIG. 69. all positions. The valve is a sort of door swinging on a central line in its own plane, and is actuated by the rod m acting on a crank or lever handle. 2. The Double Beat Valve. This valve consists of two circular discs A B and c D, threaded on the same spindle E H. The principle here relied on is again the opposition of fluid pressure on two surfaces, but the mode of application is different. Steam is supposed to be on its way to the cylinder and to have passed a regulator viz. the throttle valve so as to be entering the space between the discs. It is manifest that the tendency of the steam pressure is to lift A B upwards and to press c D downwards ; and if the areas of the two discs be equal these opposing forces will balance, and the valve may be lifted with a very small exertion of fcrce. The same thing is done in organs, where it is an object to open and close passages for the supply of compressed air with compara- tively little effort ; but in that case the valves are discs attached to the opposite ends of a lever whose fulcrum is supported at a poiit raised a little above the general plane of the discs. Also the discs themselves are on opposite sides of a partition, so that one moves outwards in the direction of the air pressure, and the other inwards against that pressure, the result being the same as in the stearc valve, but arrived at by a different mode of construction. The Crown Valve. 145 In the left-hand sketch the steam is entering between the discs, but it may come upon them from the outside, as in the adjoining diagram, and it is manifest that the principle of the opposition of fluid pressure applies equally in this case. 3. The Cornish Double Beat or Crown Valve. This is a valve very extensively used, and consists of a hood or cover resting upon two seats. It matters not whether the steam passes through the valve from above downwards or in the reverse direc- tion, and for the purpose of explana- tion we will assume that it is passing upwards, as shown by the arrows. The pipe H is permanently closed at the top by a fixed plate A B. The only thing movable is the part E c D, which forms a casing to the open sides of the pipe just below A B. The seats are shown in the diagram ; FlG> 7 * and inasmuch as the resultant vertical pressure on the inside of the curved portion c D is zero, the valve is in equilibrium when on its seat, although exposed to the full pressure of the steam. The construction of the valve is indicated in the annexed sketch, which shows an ordinary steam or eduction valve suitable for a pumping engine. An important advantage attaches to a double-beat valve in respect of the area of opening for the passage of steam under a given amount of lift. The question is one of geometry. Let 2 r be the internal diameter of a pipe covered at one end by a disc of the same diameter. When the valve is raised kt x be the linear motion of the disc along the axis of the pipe, and we have area of opening = 2 ?r r x x. But if the pipe be fully open, area of opening = area of pipe. Or 2 TT r x = TT r 2 . Which proves a well-known rule, viz., that a pipe, closed by an 146 The Steam Engine. ordinary plate valve, is fully open when the lift of the valve is one- fourth trie diameter of the pipe. 97. As a mechanical device for effecting the object in view viz., the opening of a closed pipe against fluid pressure, with a small expenditure of force the double-beat valve is a perfect apparatus. An ordinary slide-valve, such as the locomotive valve, occupies a sort of intermediate position between the simple disc and the double-beat valves. It is a great deal better than one and worse than the other. If a passage be opened by the sliding of a plate over an orifice the pressure of the steam exerts no direct influence to oppose the motion, but indirectly it causes friction, which in the case of the large D valves of marine engines becomes very serious, and accordingly slide-valves are converted into so-called balanced valves by first boring a hole through the valve and then attaching a packing ring at the back thereof, which ring comes in close contact with the slide case and takes off the pressure from the area so encircled. The drawing, taken from a marine engine, illustrates this ar- rangement. The valve and the packing ring are shown in section, and it will be noted that the back of the slide case is strengthened by arched ribs, so as to avoid any warping under pressure. The inside surface is faced, and a circular packing ring cuts off the steam pressure from the whole area which it encloses. It would be right to show this ring in plan, but there is not any great necessity for doing so, as the drawing in plan is easily supplied. Gridiron Valve. 147 There are small packing rings, like Ramsbottom's rings in a locomotive piston, which keep the principal ring steam-tight as far as the annular portion in contact with the valve is concerned ; and the upper plane surface which is in contact with the back of the slide case is pressed against it by the action of the steam on the projecting edge. A slide-valve having been thus improved by diminishing the friction which impedes its working, the next step is to cause a FIG. 72. large area to be set open for the passage of steam by means of a comparatively small movement of the valve. For this purpose a distinct principle has been brought into play, which is well known in its application to the ventilators of a railway carnage, and which consists in the multiplication of a single valve several times over. Valves of this kind are distinguished as gridiron valves, and there is an example in the expansion valve of the marine engine, to which the former valve belongs. Steam is admitted by the pipe s into a small chamber with a grating at the base, which is, in fact, the valve and its seat. There are eight rectangular openings for the passage of steam in the bottom of the chamber, and attached to the rod above is a plate or grating having eight corresponding rectangular slots cut in it. Supposing the valve to be so placed as just to cover all the openings, it is obvious that a motion of \ inch would cause each of the eight valves to open by J inch, or would give the same result as with a single valve L 2 148 the Steam Engine. moving through 8 half-inches. In other words, the area opened is multiplied without any increase of linear motion. The reason for the peculiar form of the slide-valve of the engine, shown in fig 7i s will now be understood. The outside shell of the valve forms an ordinary D slide-valve, but the two inner pieces, a, , are passages through which the steam circulates. There is, therefore, a pair of steam ports communicating with the top of the cylinder, and another communicating with the bottom of it, and the length of stroke of the valve is halved with the same effective opening. This result may be of great value in powerful screw-propeller engines. THE ECCENTRIC CIRCLE. 98. Before proceeding further it will be convenient to explain the use of an eccentric circle in actuating the slide valve of an engine. For this purpose we refer back to Art. 73, where the contrivance of the crank and connecting rod has been discussed ; and, beginning with the conversion of circular into reciprocating motion in its simplest form, it will be remembered that if the con- necting rod could be prolonged until it became infinite the line P Q would always remain parallel to itself, and the travel of the point Q would be represented by the equation D Q = a (i cos. 0). A crank with a connecting rod of infinite length is an imaginary creation, but there are simple combinations which will give the motion, and which have been commonly used. 1. Let a pin P, fixed in the face of a circular plate whose centre is c, move in a horizontal groove R s attached to a vertical rod passing between guides, as shown. It has been proved that this motion causes a reciprocation in the point B, which is that of a crank with an infinite link. 2. Let a circular plate centred at c rotate in a vertical plane under a horizontal bar R s which is attached to a vertical bar E D, constrained by guides and pointing towards c, as in the previous case. Taking P, the centre of the plate, draw P B parallel to c D, then the point of contact of R s and the plate remains in a vertical line through P during the motion. But the point P describes a The Eccentric Circle. 149 circle round c, and therefore c P is in effect a crank of fixed length ; also since P B remains parallel to itself, the motion is the same as FIG. 73. if the connecting rod between P and the piece moved by it were infinite. Thus the motion is that of a crank with an infinite link. 3. A new form, of the greatest possible utility, and giving the motion of a crank and connecting rod of any length within certain limits, is deducible at once from that last examined. Conceive that the bar R s is wrapped round the plate so as to encircle one-half of it, and let the end B of the rod B D be con- strained to move in a line pointing to c. As the circle revolves the crank c P remains constant, and the connecting rod is now P B, which may be extended at pleasure beyond the limits of the circular plate. The combination is a mechanical equivalent for the crank and connecting rod. The form usually adopted in practice is derived from the arrangement just described. A circular plate, is completely en- circled by a hoop to which a bar (always pointing to the centre of the plate) is attached, the object of the complete hoop being to cause a reciprocation of B in both directions. If there were only a half-hoop, as in our sketch, the eccentric circle would drive B upwards, but it would not necessarily return, and might require the force of a spring or the action of a weight to assist in completing the double oscillation. As before, the throw of the eccentric is the same as that of the 150 The Steam Engine. crank, viz., a space equal to the diameter of the circle whose radius is c P. 99. Having thus explained the principle of construction adopted in the eccentric, it remains to give a sketch showing the contrivance as made and applied in an engine. Usually the eccentric occupies so much space in a drawing that it is difficult to find an example suitable for insertion in the small page of this book. The annexed diagram, however, may suffice, the eccentric rod being very short, as in a small oscillating engine, from which the sketch is taken. The circle c represents a section oi the crank shaft, c being its centre. Upon the crank are fitted two circular half-pulleys of cast iron, which are bolted together, and have a centre at p. Two half-hoops of brass, tinted in the sketch, and united together by bolts and double nuts at E and H, carry the eccentric bar, which actuates a pin at B connected with the valve lever. The engine being designed for a river boat, and therefore requiring to be reversed at pleasure, there is a strap a b, to prevent the ec- centric rod from falling away from the pin while the valve is being moved by hand. Also, in this case, the eccentric pulley rides loose upon the shaft within certain limits defined by stops, and there is consequently a disc D, forming a counterbalance to the weight of the pulley, which prevents it from falling out of position during the disengagement of the pin at B. It should be noted that p, the centre of the pulley, may be brought as near as we please to the centre of the shaft, and that the throw of the eccentric may be reduced accordingly ; but that we are limited in the other direc- tion, for the shaft must be kept within the boundary of the plate, and the plate itself must not be inconveniently large considera- tions which are sufficient to prevent any great increase in c p. FIG. 74. Crank and Connecting Rod. DIRECT-ACTING ENGINE. ioo. The general arrangement of a direct-acting engine in its simplest form may be made clear by the lecture diagram, fig. 75, which is taken from Dr. Anderson's collection, as published for the Science and Art Department, and represents a small vertical engine driving some light machinery. The steam cylinder is marked c, and H is the slide case, the piston rod being connected with the crank pin by the connecting rod PR. The slide valve is worked by an eccentric, shown at E, and the eccentric rod attached to the valve spindle is marked E D. It is apparent that the use of a crank in the position shown in the drawing entails the division of the shaft A B, in order to leave an empty space which the connecting rod may sweep over. This necessarily hap- pens unless the crank is at one end of the shaft ; and the great value of the eccentric arises from the circum- stance that it enables us to derive the motion which would be given by a crank and connecting rod from any part of the shaft, whether at the end or not, without forging a crank upon it or subdividing it. The main object of the sketch is to make this matter clear, and to show the conversion of the reciprocating motion of the piston into the rotation of the shafting in the first instance ; and further the re-conversion of that circular motion, so set up, into the reciproca- tion of the slide valve. We shall presently refer to the construction of the ends of a connecting rod and the mode of fitting the brasses- As to the cranks, it is enough to say that they are frequently forged FIG. 75. 152 The Steam Engine. in one solid mass upon the shaft, and are shaped afterwards by the machinery of the workshop. Where the crank shaft is of great size, as in some marine engines, a special machine tool is adapted for turning the crank pin while the shaft itself is at rest. VALVES LIFTED BY CAMS. 10 1. It often happens that the steam and exhaust valves of an engine are lifted directly by cams. The term ' cam ' is applied to a curved plate or groove which communicates motion to another piece by the action of its curved edge. In general mechanism the particular curve which determines the nature of the movement communicated has every possible variety of form according to circumstances, but in the application of a cam-plate to the actuation of a valve all that is required is to lift the valve rapidly, then hold it raised for a certain proportion of the stroke and allow it to come down again upon its seat. It is apparent that in a simple movement of this kind, where one end of a lever is to be raised, held up, and allowed to drop, it will suffice to surround the shaft by a plate or cylinder having a circular portion ef> on which the end of the valve lever rests when the valve is closed, and a raised portion, A B, also circular, upon which the valve lever runs when the valve is to be opened, and which holds it open until the end of the lever runs down a slope and comes upon the lower circular portion corresponding to ef. For some pur- poses, as where steam is to be worked expan- FIG 76 sively, the raised portions are of different lengths, as A B, A c, A D, arranged in successive steps, one behind the other, whereby the valve may be held open for different periods. Also it is manifest that the cam may be on the face of the plate, instead of being part of its edge, and that in effect two portions of flat plates rotating about a common axis perpendicular to each, and raised one above the other, with a sloping surface connecting them, would be a mechanical equivalent for the cam described. Such a cam -plate was used by Sir W. Fairbairn. The Working of a Valve. 153 THE LAP OF A VALVE, 102. A peculiarity in the construction of the valve described In Art. 93 could hardly escape notice, even if it were passed by without comment. Referring to fig. 66, it is seen that the arch of the valve exactly bridges over the interval between the inner edges of the steam ports A and B, but that the faces of the valve considerably overlap the ports on the outside edges. The valve is placed symmetrically with regard to the ports, and is therefore in the middle of its stroke. In the annexed diagram there are three vertical lines intersect- ing a horizontal dotted line at the points o, N, and D. The space o N denotes the extent to which the face of the valve overlaps the port A, and is technically distinguished as the ' lap ' of the valve. The space N D indicates the extent to which the port A is opened for steam, and is often less than the whole breadth of the opening, the reason being that the same passage serves both for the entrance O N FIG. 77. and exit of the steam, and that a larger opening is required for the rapid passage of steam into the condenser than for its admission into the cylinder. The circle on the right hand may be taken to represent the path of the centre of the eccentric pulley which actuates the slide- valve. The diameter H D is the whole travel of the valve, and P is the point which the centre of the pulley occupies when the piston is at the end of the stroke. Draw P N R perpendicular to H D, and we have (neglecting obliquity of eccentric rod^ ON = lap of valve, ND = opening of steam port. Since o H represents the direction of the crank of the engine when the stroke is commencing, the first thing we observe is, that the 154 The Steam Engine. centre of the eccentric pulley has been set back through an angle EOF, such that o N = lap of valve, and that if there were no lap the line o P would be at right angles to o H. The importance of putting lap upon a slide-valve will be better understood by noting what would happen without it, If there were no lap the opening for steam would be represented by o D, and the result would be that the steam port could only be perfectly closed at the precise instant when the valve was in the middle of its stroke, at which time it would be moving most rapidly. It is apparent that a valve of this kind is unsuitable for an engine, the better plan being that the steam should be compressed or cushioned on one side of the piston, so as to assist in bringing it to rest, and that the driving pressure on the opposite side should be relieved by opening a passage to the exhaust or releasing the steam, as it is termed, just before the stroke terminates. This precaution prevents the violent jerk and strain which would come upon the crank-pin if the piston were thrown with full force upon the crank at the dead points. 103. The value of an indicator diagram in interpreting the RELEASE:, FIG. 78. action of a slide-valve should now be made clear. The drawing will give an idea of the action of a model belonging to the Schoo : Lap of a Valve. 155 of Mines, and intended to illustrate the relative motion of the slide- valve and piston in a direct-acting engine. The moving parts are attached to a board carrying a sheet of paper on which the circles described by the crank-pin and centre of the eccentric are marked. Below this is a space for tracing the indicator diagram. The crank and connecting rod which actuate the piston are at the back of the board, but an index arm, o H, is placed in front and moves with the crank, thereby trans- ferring its apparent motion to the part where it can be seen. The eccentric is represented by an actual crank, o/?, whose extreme end describes the smaller circle, and the rod p L carries on the motion to the valve. The point p can be shifted along the arm o T, thereby varying the amount of travel of slide, and the length of the rod / L can also be adjusted. In this way the effect pro- duced by any deviation from the proper length of the eccentric rod can be studied. We are at present in a position to trace out the diagram as given by an indicator. The crank being horizontal, with the piston at the end of its stroke, the first thing to be done is to place the valve in the correct position for admitting steam by setting back o/ until the lap is allowed for. The valve then opens ; and if the pressure of the steam is sufficiently maintained, the indicator pencil will trace the horizontal line ab. When the crank gets to the end of the first dotted line, A is closed, so that expansion begins, the pressure falls, and we have the curve b c. At the point marked ' release ' the valve is moved so far to the left as to open a passage from A to c, and the release, as it is termed, begins. The pressure falls from c to /, and continues very low till the point marked ' compression,' when B is closed, and the steam in the corresponding end of the cylinder is cushioned so as to increase its pressure, the pencil rising from m to a when the double stroke has been completed. 104. The effect of putting lap upon a slide is thus to produce a fixed amount of expansive working, and it is easy to calcu- late the amount of lap which should be assigned in order that the steam may be cut off at any part of the stroke. Let the larger circle represent the motion of the crank-pin in a direct-acting engine, and let the smaller circle be the path of r S 6 The Steam Engine. the centre of the eccentric. When the crank is in the position o H, and centre of the eccentric at /, steam is just beginning to enter the cylinder. Draw pnr perpendicular to o d, then r must be the centre of the eccentric when the steam is shut off, at which time let OP be the position of the crank of the engine. Draw p N perpen- dicular to o D. Let o P N = a,p o d=do r=0. Then angle H o/ = angle por, /. 180 = 6 + 90 a, FIG. 79. or d = 45 + o' whence the position of op can be calculated. Ex. Let the steam be cut off at \ of the stroke from the ex- tieme end. Then ND = ^HD = I o P. 6 3 or or i sin a = -, o .*. sn a = .. 3 Referring to a table of natural sines, we find that Sin 41 48' = '66653 /. a = 41 48' approximately /. H o/ = 135 -20 54' = 114 6'. o n But = cos H Qp = sin 24 6', o/ and sin 24 6' = '4083 by the tables, /. o n = '408 x op = '204 x travel of slide. In like manner the amounts of lap in order to cut off at cjis- Compression and Release. I $7 tances of ^, J, of the stroke from the end thereof are -289, -250, 177 of the travel of valve. 105. An inspection of fig. 78 shows that the four principal points in the valve motion are (i) the admission of steam, (2) the cut-off, (3) the release or opening to the exhaust, (4) the compres- sion or cushioning of steam behind the piston. We have shown how to arrange for expansive working, and it remains to consider the causes which determine the periods of compression and release. Just as expansion begins when the outside edge of the valve face comes upon the outer edge of the port A, so compression begins when the inside edge of the arch of the valve comes upon the inner edge of the port A, and it is easy to draw a figure and repeat the calculation for the compression. When the point of compression is determined it is only ne- cessary to cross over in a diameter of the circle to the opposite circumference, and the point of release is obtained, which is as far from D as the point of compression is from H. Thus a first general idea of the motion is arrived at. 1 06. Before going further two points may be noticed : 1. A single indicator diagram does not give an accurate measure of the work done, for the line abcf records the steam pressure at one end of the cylinder, and the linefma records the amount of condensation and compression at the same end, but does not combine the steam pressure above the piston with the vacuum pressure below it, or conversely. In order to effect this object, which is what is really wanted, two diagrams are required, which should be taken consecutively (usually on the same piece of paper) at the top and bottom of the cylinder. An inspection and measurement of the pair of cards will give, a complete opportunity of estimating the work done. It is common, however, to regard a single diagram as indicating sufficiently the general character of the performance of the engine. 2. The measurement of pressures is made from the atmospheric line, taken before steam is admitted into the cylinder of the in- dicator, and not from the zero line of pressures, as in the case of the theoretical diagram. This is simply a matter of convenience as it is perfectly evident that if the point ;//, for example, is at a 1 58 The Steam Engine, perpendicular depth below the atmospheric line which would give a reading of 1 1 Ibs. on the indicator spring, that informs us that the zero line is 14-7 11 below the point m, and that the back pressure is 37 Ibs. ; and it is, in fact, easier to look only to the number n, and not to go through a process of subtraction, in order to arrive at the same result. Of course, in any case, subtraction will be necessary when two bounding lines of the curve pass along upon the same side of the atmospheric line. The average pressure of the atmosphere is taken to be : 147 ..... Ibs. per sq. inch. 2116*4 . . . . . Ibs. sq. foot. 29-922 inches of mercury. THE LEAD OF A VALVE. 107. In a previous article we have spoken of the indicatoi pencil as being carried up to the highest point of steam pressure simply by compression, but it is obvious that such a movement would seldom occur in practice unless assisted from without. Accordingly, it is the rule to open the steam port, so as to admit fresh steam into the space where the cushioning is going on, just before the piston comes to the end of the cylinder. In such a case the valve is said to anticipate or lead the motion of the piston ; and the ' lead of a valve ' may be denned as the width of opening of the steam port when the piston is at the end of its stroke. By giving lead to a valve a strong pressure is brought against the piston just as it is reaching the end of its motion in one direction, and the strain upon the crank-pin is correspondingly relieved. The more rapid the motion of the piston the greater the necessity for giving lead, and accordingly we find that the lead in a locomotive engine is very considerable. Thus Mr. Clark, in his book on locomotives, gives 4^ inches as the travel of a Stephenson's slide-valve, the outside lead being ^ inch. The lead of which mention has been made is outside lead ; that is, it relates to the admission of steam ; but of course lead can be given on the exhaust side of the valve, and in that case it would be called inside lead. In the case of Stephenson's valve the inside lead amounts to i-^r inches. Pressut e on the Crank Pin. 1 59 DIAGRAM OF WORK DONE IN ROTATING THE CRANK. 108. The indicator gives a measure of the mean effective pressure on the piston during a stroke ; and, supposing that pressure to be known, there yet remains the problem of investigating its transmission to the crank shaft. It is common to set out a diagram of work done in rotating the crank shaft, and to trace thereby the fluctuations of driving pressure as due to the position of the crank and the obliquity of the connecting rod. Such a diagram may be viewed under different conditions. First, the pressure on the piston may be taken as constant ; that is, as having its mean value throughout a stroke, in which case the diagram of work done upon the crank is symmetrical, or nearly so. But, secondly, there is another way of looking at the question which is more complete and accurate, and that is, to trace the outline of the diagram of work on the supposition that the actual pressure of the steam on the piston is transmitted at each point of the diagram. This second method involves accurate drawing and measurement, and the student can easily set out such a diagram after comprehending the principle on which it is constructed. To begin with an old proposition in applied mechanics which may be solved analytically as an exercise. 109. PROP. To find the work done upon the crank in a direct-acting engine, friction being neglected. Here a force P, which we assume to be constant, pulls the end D of the connecting rod D B, and turns the crank c B. Except at the dead points the line D B is inclined to D P, and it may be said tha*. there is a force Q pulling against P in the line D B. This force FIG. 80. produces a reaction R perpendicular to one of the guides (friction being neglected), and R itself may be resolved into components, 160 The Steam Engine. one in B D, and the other perpendicular to it, whereof the formet acts against o Hence, if B D c = 0, B c D = 0, we have Q = p cos + R sin 0, also P sin = R cos 0, p ... Q = P ( I cos cos J cos This result may be obtained more easily, but with less appre ciation of the precise action which takes place, by resolving Q in directions parallel and perpendicular to D R , when Q cos = P, p or Q = - . COS (j) Let c B = a, D B = b, then moment of force to turn the crank p#sin cos /. work done while c B moves through an angle d p a sin (0 + 0) , fl = ^ '-La 6, COS 11 i /' sin (0 + 0) in whole work = P a I * " a 0, ./ COS = p a I (sin + cos . tan 0) d *.' But sin | . sin .*. cos = .'. whole work = P a = P X 2 , tlie integral being taken between the limits = o, = a . It is well known that this result might have been arrived at directly, and without any calculation, as an application of the Work Done upon the Crank. 161 principle of work. For, adopting the notation of the previous proportion, P x 2 a is the work done upon the piston in one stroke, and P x 2 a is also the work done upon the crank- pin in half a revolution from one dead point to the other. It may, indeed, be said that no amount of symbolical reasoning can establish the proposition more conclusively than the simple state- ment that it follows as a deduction from the principle of work. no. The diagram of work done in rotating the crank, in the case where friction is entirely left out of consideration, may be set out as follows : i. Let the obliquity of the connecting rod B D be neglected, or let B D be supposed to remain always parallel to D c. Then and P sin (0 + 0) perpend i cular to c B cos <(> we can infer the pull or push along c B at any instant of the stroke as well as the pressure acting perpendicularly to c B and tending to produce rotation. The diagram of work sets out the latter pressures, and a corresponding diagram may be constructed for the pressures in c B without difficulty. ESTIMATE OF WORK DONE WHEN STEAM IS EXPANDED IN THE CYLINDER. 112. Having discussed the general character of an indicator diagram, as taken from a double-acting condensing engine, the next step is to estimate the area of the enclosed space. In the case of a theoretical diagram, where the curve of ex- pansion is that given by Watt, the true area can only be ascertained by a mathematical process. The calculation is now given, and those who are unable to follow it may * take the result as established. To find the work done in each stroke of an engine where the steam is supposed to expand according to Boyle's law : Let c H represent the steam cylinder of an engine, p R being its piston. Also, let c D = /, c E = a, or the space described by the piston before the steam is cut off. C P = x, A = area of piston, / = pressure of steam. M 2 164 The Steam Engine. Then work done through c E = A/ a. Also pressure of steam on piston at P = ^?? .*. work done through space d x = JL^rfx. 00 Whole work = Kp a I from x = a, to x = I = A/ a log. - a .'. Whole work in one stroke = A/ a < i + log. - > . (ij This is the theoretical expression for the work done by the steam on one side of the piston, and no account is taken of the back pressure from uncondensed vapour on the other side. In practice the mean back pressure should be subtracted from the mean forward pressure, viz., y (* + 1S- -), and the result will be the mean effective pressure during one K stroke. Cor. i. To find the horse-power, or the work H done on the supposition that 33,000 foot-pounds FIG. 83. per minute is the unit of work, we multiply ex- pression (i) by the number of strokes (say ri) per minute, and divide by 33,000. Thus, A/ na { i + log. - j Horse-power = E-- 33,000 It is a common thing to ascertain the mean pressure of the steam per stroke by measurement, much as Watt found it, and in such a case : , T Area of piston in sq. inches x mean press, x nl Horse-power = - 33,000 Cor. 2. If - = E, or the steam be expanded E times, we have a work done = ^ < i -f log. E j Diagram of Energy. 1 65 Cor. 3. In practice there is a vacant space between the cylinder cover and piston at the beginning of the stroke, and also there is a definite space occupied by the passages leading to the valve ; taking the whole content so regarded as equivalent to the volume cut off from the cylinder by a plane parallel to its base, and at a distance c from it, we have then work done = A/ a f A/ (a + c) C + (a + e) log. 44 the limits being / + c, and a + c, instead of / and a. In applying these formula it must be noted that the symbol 1 log.' represents the Napierian logarithm, and not the logarithm to base 10. The two kinds of logarithms are connected by the equations Log. n to base 10 = '434294819 x Nap. log. n, Or, Nap. log. n = 2-3025851 x log. n to base 10. The following results for Napierian logarithms are useful : Log. 2 = '6931472 Log. 3 = 1-0986123 Log. 4= 1-3862944 Log. 5 = 1-6094379 Log. 6 =.17917595 Log. 7 = 1-9459101 Log. 8 = 2-0794415 Log. 9 = 2-1972246 Log. 10 = 2-3025851 113. It will be instructive to recur to the theoretical diagram set out in Art. 19, and to find its area according to Watt's method, as well as by theory. Divide the stroke of the piston into twenty equal parts, and conceive that the steam pressure remains constant throughout each division, having (i) its value at the end of each respective division, and (2) its value at the commencement thereof. Then multiply each assumed value of the steam pressure into the distance between two consecutive divisions, and we shall obtain a series of rectangles representing work done, and lying within the curved line on one hypothesis, but overlapping it on the other. Let these be dis- tinguished as inside and outside rectangles respectively. The pressures up to 5 are all equal, and each interval is unity, whence the pressures are as follows : 166 The Steam Engine. 1 . 2 . 3 - 4 5 6 = 7 = Press, at i . . = r Press, at n = T B T = '4545 r 12 = & = -4167 i' 13 = A = "3846 i' 14 = T$ = '357i r 15 = A = '3333 8333 i6 = A='3 I 25 7143 17 = T 5 T = -2941 625 18 = A = '2778 9 = t = '5556 19 = A = '2632 10 = ^ = '5 20 = T/V = -25 Hence area with inside rectangles =11-572 . . (i) Also sum of pressures from 6 to 19 = 6.322. .*. area with outside rectangles =12-322 . . (2) But the true value of the area is, by the formula, 5 +,5 log. 4. And log. 4 = 1-3862944 .'. 5 log. 4 = 6-9315 whence true value of area = 11*9315 . . (3) The mean pressure of the steam in each case is deduced bj dividing these respective areas by 20. Hence on ist supposition, mean press, of steam = '5786. 2nd =-6161. 3 rd = '59 6 5- Thus Watt's estimate, the little inaccuracies in Art. 19 having been corrected, gives '5786 as the mean value of the steam pres- sure, while the theoretical true value is "5965. This shows what may be done by taking pains and subdividing sufficiently, so as to estimate by small rectangles. Watt's method is commonly followed in practice, as it is very simple and easily carried out. Further, we remark that the difference of pressure between any two consecutive divisions continually diminishes. This fact is pre- sented to the eye by the form of the curve, which continually tends to become more nearly parallel to the line of volumes. The differences between the pressures at 5 and 6, and 6 and 7, and so on through the series, are : 1667, -119, -089, -0694, -0556, -0455, '378, -0321 0275, ' 02 38j '0208, '0184, '0163, '0146, '0132 Whereof the last difference is about -Ar of the first. Indicator Diagrams. 167 INDICATOR DIAGRAM OF ATMOSPHERIC ENGINE. 114, We pass on to discuss the performance of an engine by teference to an indicator diagram taken from it, and shall com- mence with an atmospheric engine. The card is taken from the collection of steam diagrams. A scale of pressures, showing the strength of the spring of the instrument, should always be marked or recorded on the diagram, and is here rioted on the vertical line at the left hand of the sketch. Also we require to know the diameter of the cylinder, the length of stroke, and the number of strokes made per minute. The product of the number of square inches in the area of the piston and the length of stroke, when divided by 33,000, forms what may be called the piston constant for the engine, and the horse-power is then obtained by multiplying the piston constant by the mean pressure of the steam and the number of strokes per minute. 425 5- 9 9 9-25 Q 875 8-25 7 ^-- in - FIG. 84. In the present example the steam pressure never rises above o, which here marks the atmospheric line, and, as before, horizontal lines represent volumes occupied by steam in the cylinder, or otherwise the amount of travel of the piston, for one measure is identical with the other. The diagram is intersected by ten vertical lines at equal distances, dividing the length of stroke into ten equal parts, and the first thing to be done is to determine the mean pressure of the steam in each of these divisions. An estimate of this kind is to some extent uncertain, and the results are marked on the diagram, in order that the student may verify the conclusions for himself. In doing so he should remember that the outlines of the curves cannot be copied with any great accuracy, and that some corrections may appear desirable. 1 68 The Steam Engine. Referring to the diagram, the action of the steam is quite intelligible. The pressure is maintained during the upward stroke, but there is a loss at the commencement due to the injection abater which remains in the cylinder. On the downward stroke the condensation is imperfect at first, but improves afterwards, and the pressure of vapour in the cylinder never falls quite so low as 5 Ibs., which would be called 10 Ibs. vacuum according to the usual mode of estimating it. Adopting the numbers as printed and adding them together, we find that their sum is 73*5, which, when divided by 10, gives 7-35 as the mean effective working pressure on the piston in pounds per sq. inch during a stroke. The dimensions of the engine and the rate at which the piston moves are now to be taken into account. In our example the diameter of the cylinder is 72 inches, the length of the stroke is 8 feet, and the number of strokes per minute is 10 ; hence Area of piston = 4071-5 sq. inches. Travel of piston per minute = 8 x 10 feet. Indicated horse-power = 7'35 x 4071*5 x 8 x 10 33,000 INDICATOR DIAGRAM OF SINGLE-ACTING ENGINE. 115. In the single-acting engine two diagrams must be taken, one from the top and the other from the bottom of the cylinder. These diagrams are quite unlike in form, for the action during the down stroke is not repeated during the up stroke, as in a double- acting engine, and our first task will be to comprehend the reasons of the particular conformation observed. For this purpose re- ference is made to a diagram taken from a Cornish pumping engine, having a cylinder 70 inches in diameter, and making 4 strokes per minute, under a mean pressure of 15-1 Ibs. per sq. inch. The figure is reduced from one on a larger scale, so that the indicator spring would extend one inch on the reduced diagram for a steam pressure of 40 Ibs. per sq. inch. One card is taken from the top and the other from the bottom of the cylinder, and each must be interpreted in its turn, Indicator Diagrams 169 As far as the upper card is concerned that figure indicates the admission and cut-off of steam, together with the opening of the equilibrium valve, which corresponds to imperfect condensation in our normal diagram. The lower card has reference to the state of things below the piston, where the equilibrium and exhaust valves are opened consecutively. FIG. 85. Beginning at the point A, with the piston at rest at the top of the cylinder, we note that the pressure rises until the down stroke commences when the steam line B c D is traced out. The portion B c is horizontal, and the cut off takes place at c. It is common for the steam line B c to drop considerably before the cut off begins, especially in large engines. The line D E indicates that the equilibrium valve is opened, and that the steam pressure has fallen somewhat during the circulation which takes place. At the point E the equilibrium valve is closed, and compression or cushioning begins, just as in a double-acting engine. At the point A the piston is coming to rest, and there is a drop in the curve, which is often much more marked than in the present example and which indicates loss of pressure before the down stroke begins. Such loss would be due to leakage of the compressed steam round the circumference of the piston or perhaps to loss of heat. As to the lower card, the nearly horizontal line b a shows that the equilibrium valve is opened. When compression begins at E, above the piston, expansion will also begin to much less extent below it, and there will be a slight drop towards the end of b a. Otherwise the lines D E and b a nearly coincide, and would do so absolutely, if there were no disturbing causes at work ; but the diagram shows some difference of pressure at the two ends of the cylinder when the equilibrium valve is open. The Steam Engine. With regard to work done, the piston is driven down by the steam from above it, as opposed to the back pressure of the exhausted space underneath, and that part of the action is fully determined by comparison of the lines BCD and dc. But the whole work done by the steam in the double stroke is, according to our principles, obtained by a careful measurement of the areas of the enclosed figures. At first sight the student might imagine that the horse-power may be calculated by simply noting the pressures indicated by the steam and exhaust lines, the cutting away of any part of the intermediate area as by compression, or by want of coincidence of the lines D E and b a affecting only the up stroke when the weight of the pump rods is the moving force. But a little consideration will show that such a notion is erroneous, and that the compression of steam in the up stroke and the resistance to the motion of the piston due to inequality of pressure when the equilibrium valve is open must be deducted from the total efficiency. The steam opposes the piston in its ascent to some degree, and this gives rise to negative work, which must be deducted from the positive work accomplished in the down stroke. In other words, during the down stroke the steam does the work, and during the up stroke work is done upon the steam. It follows, therefore, that the portion of unoccupied space between the two intermediate horizontal lines is a veritable sub traction from the efficiency of the agent ir 6. We pass on to calculate the horse-power in the case of FIG. 86. a single acting pumping engine, having a cylinder 112 inches in Indicator Diagrams. 171 diameter, with a stroke 9-166 feet, and making 7-5 strokes pei minute. Referring to the diagram where the steam pressures are noted > and taking each group of numbers in order, there is, above the atmospheric line, a series amounting in all to 56-5. Below the at- mospheric line the first series amounts to 48*5, and the second series gives 39-3. Hence mean pressure of steam =-f$ (56-5 + 48-5 + 39*3)= 14*43 H P = T 4'43 x 3'i4i59 x 56 x 56 x 9-166 x 7-5 33,000 = 296-5. In an example of this kind the answer is very readily obtained by the use of a table of logarithms. DOUBLE-ACTING ENGINE. 117. In illustration of the mode of estimating the work done by a double-acting engine we go back some thirty years to an example from a powerful oscillating cylinder of a marine engine, which may give an idea of the performance commonly accepted before the days of compound cylinder engines with high pressure and expansion. The engine was composed of two cylinders, each 82^ inches in diameter, with a stroke of 6 feet, making 14^ revolutions per T FIG. 87. minute. It would be described as a pair of 250*5, meaning that each cylinder was of 250 H.P., according to a nominal scale then adopted, but now almost, if not quite, obsolete. The scale is not marked on the diagram, but the student will infer it approximately from the values of the steam pressures 1/2 The Steam Engine. above the atmospheric line at the respective divisions, which are 4'5> 4'5> 4'45i 4'35 4'3> 4'3, 4*i, 27, '6, stopping at the ninth division. The so-called vacuum pressures are estimated as follows : 8-8, 10-8, n-2, 11-3, 11-3, 11-4, 11-4, 11-4, 11-5, 10. Hence the sum of pressures = 109-1 + 33*8 = 142-9 ; mean pressure = 14*29. It is recorded on the card that the steam was blowing off, and that the barometer gauge of the condenser stood at 26^. WIRE-DRAWING AND CLEARANCE. 1 1 8. Among the causes which deteriorate from the perfection of an indicator diagram one is that of wire-drawing. This term is intended to convey the idea that the pressure of the steam is attenuated by obstacles which impede its passage. The effect of wire-drawing is to cause a gradual decline or subsidence of the steam line. It is commonly seen in the indi- cator diagram of a large Cornish pumping engine. The cubic content to be filled by the steam increases so rapidly as the piston descends that the steam pressure can hardly be maintained. Again, it will have been noticed that the definite well-marked angle at the point where the curve of expansion leaves the hori- zontal line of steam pressure is seldom to be noticed in an actual diagram, or certainly not in an engine worked by a slide-valve and eccentric. In such a case the valve closes gradually, and the out- line becomes rounded at the point of cut-off. This rounding at the point where expansion begins is also marked in diagrams where the FIG. 88. valves are lifted by cams, as in the annexed figure, which is taken from an engine by Fairbairn & Sons, having the following particulars : Wire-drawing. 173 Diameter of cylinder . . 40 inches. Length of stroke .... 6 feet. Number of revolutions . . . 25 per minute. Steam is. admitted a little after the crank-pin has passed the dead centre, and is cut off at -45 of the stroke. The lead of the exhaust is f inch. The valves are double-beat or balanced valves, and the exhaust is kept open during the whole stroke. Here, therefore, there is no compression; and to obviate the sudden strain on the crank-shaft from admitting steam while the piston is at the exact end of its stroke, the curve is cut away along the bounding vertical line, instead of before reaching it, as in the case of the locomotive engine. The diagram tells at once what is happening by the little tail at the point A. Then comes the rise of steam pressure and a small jump of the pencil at B. There is also, to a small extent, wire-drawing, as shown by the gradual drop of the steam line between B and c ; and there is a small rounding at the extreme end of the upper steam line, showing the lead of the exhaust. According to a scale of the strength of the indicator spring the mean effective pressure on the piston is 11-5 Ibs., the vacuum being 13 Ibs. 119. Hitherto it has been assumed that the travel of the piston is exactly equal to the length of the cylinder, but in practice the piston does not come home to the cylinder cover'at the end of a stroke, and a certain empty space or clearance is left between their respective surfaces. Also the steam passages leading from the valve to the cylinder increase this ineffective space, which must be filled with steam before any work can be done. The cubic content thus occupied, which causesAvaste when the steam is perfectly exhausted, but forms no part of the real working cylinder, is called the clearance. It may be estimated in terms of the content of the cylinder by assigning a length thereof (say c) which determines its volume. Thus, let A be the area of the piston, then A c is the clearance. But for simplicity it is common to call (c) the * clearance,' especially in analytical calculations of work done. The tendency of compression or cushioning is to eliminate the waste due to clearance. The steam compressed at the end of the J- OF 1 UNIVERSITY J 174 The Steam Engine, stroke behaves like an elastic spring and gives out during ex- pansion the work expended in compressing it, whereby it obviates^ as far as it will go, the waste of boiler steam. The effect of clearance on the indicator diagram is to lift the curve of expansion in some degree. Thus, let AN be the travel of a piston, OA the clearance, where o is the real zero from which volumes are measured. Neglecting clearance, we should assume that the volume A D expanded accord- ing to Boyle's law, and on this sup- position B P R would represent the lines of pressure, whereby ifAD = DM = MN we should have P M = , N R = 2 , 3 ' But since OD is the true volume of steam undergoing expansion, it is evident that tne true pressures at M and N are somewhat greater than before, and are in fact represented by/M, rN, such that / M : r N : B D : : ^ : ^ : L_ . VOl. O M VOl. ON VOl.OD In other words, let vol. A D = v, vol. o A = z', and let/ be the pressure at B. If there be no clearance, pressure at M = But with clearance, pressure at M = 2 v = |f 2V The amount of clearance which is to be allowed for in prac- tice may be set out upon an indicator diagram by drawing a vertical line similar to the dotted line in fig. 97, and regarding it as a zero line from which volumes are to be measured. Clearance. 175 The indicator diagrams in fig, 90 are intended to give an idea of the effect now referred to. They are taken from a blast engine, having a cylinder 42 inches in diameter, with a stroke of 8 feet 3 inches, working at 14 .strokes per minute. The smaller diagram, with the less perfect vacuum line, was taken when there was an excessive amount of clearance, the cut-off valve being placed in the steam-pipe, whereby the steam contained in a side 1 . pipe or steam-chest expanded after the valve was closed. The effect of clearance has been to raise the expansion curve in the manner pointed out in the previous investigation. That such is the case will be rendered more certain by reference to the second diagram, which is the card taken when the two valves viz., the steam and cut-off valve were replaced by a single valve lifted by a cam and placed close to the cylinder. The expansion curve falls at once by reason of the diminution of clearance. It must be noted that the pressure of the steam is not the same at the beginning of the stroke in the respective diagrams, nor is the point of cut-off exactly the same, so that the comparison is not perfect ; but we see that clearance must be allowed for in estimating the expansion curve of an indicator diagram, and that otherwise the information given is entirely deceptive. Another point is, that excessive clearance diminishes the excellence of the vacuum, by reason that the condensation is less perfect when a portion of steam is lodged in the passages. This is apparent from the diagrams, the vacuum having improved from 9 Ibs. in the first card to 10*9 Ibs. in the second, solely from the lessening of the amount of clearance. EXPANSIVE WORKING OF STEAM. 1 20. This example suggests a connection between the subject of clearance and that of expansive working as carried out by seperate The Steam Engine. /alves. It will be understood that expansion o steam may be provided for : 1. By putting lap on a slide valve, whereby a fixed rate of expansion is secured. 2. By employing four independent valves lifted by cams, viz., two steam and two exhaust valves. Here the expansion can be regulated without any difficulty, all that is required being; to change the cam-steps for different grades of expansion. 3. By employing a separate expansion valve, placed behind the ordinary slide valve. This method will be understood by referring back to fig. 69, where a double-beat valve, actirig as an expansion valve, is shown in combination with a slide valve. The latter has scarcely any lap, and contributes nothing to expansive working,, its function being merely to distribute the steam on its way from the slide case to the exhaust. The double-beat valve would probably be lifted by a cam, and would regulate the passage towards the slide valve, being opened or closed at will, and at any desired period of the stroke. It does all that is required for cutting off the supply of steam, but it labours under the defect that it causes a sensible addition to the amount of clearance which is inherent to the use of a slide valve. The waste of steam now commences a step further back, and is reckoned from the valve A B c D, instead of from the slide valve. It has consequently been a common practice to retain four valves for distributing the steam in a double-acting engine, according to the method originally practised by Watt Each of these valves may be opened and closed by cams at any period of the stroke, and they give a power of carrying out expan- sive working with great facility. If, on the other hand, a combination of a slide valve with a separate expansion valve be employed, it is essential that the latter should be placed as close as possible to the former, or indeed should form part of it, as in the following instance, which illustrates an excellent mode of providing expansion, viz., by a back cut-off valve. Such a valve is shown in the drawing, and is marked H. We have here the cylinder, with its steam ports and eduction ports, as in the repeated examples. Instead of an ordinary D Expansion Valve. 177 slide valve there is a box with steam passages and an arch fot bridging over the interval between the steam and eduction ports. It is apparent that on lowering both this box and the supplemen- tary block behind it, marked H, the steam will enter the top of the FIG. 91. cylinder, and will escape from the bottom of it in the manner pre- viously described. Whereas on raising the block H no more steam can enter the upper port, and an effectual cut-off is the result. The back of the valve as well as the face of it will be plane surfaces, and, by properly adjusting two eccentrics connected with the valve and with H respectively, it is possible to provide for a cut-off at any part of the stroke, and to do so with scarcely any waste of steam other or greater than that which would occur with a single D valve. N The Steam Engine. The effect of expanding in different degrees is marked on the diagram by way of illustration, and requires no special explana- tion after the previous remarks, but it is necessary to notice the stuffing box and gland for keeping the piston rod steam-tight. This is an improvement upon Watt's method, which is drawn in fig. 9, as it appeared in his patent of 1782. The stuffing box, marked E E, is provided with a brass bush at the bottom of it, which is bored to fit the piston rod. An empty space is left for packing, and a gland, D D, with a brass lining, is screwed down, so as to compress the packing and tighten it round the piston. The top of the gland is formed into a cup for oil, and this completes the arrangement. FURTHER INDICATOR DIAGRAMb. , i2i. In a diagram taken from a locomotive engine the periods of expansion, compression, and release are often well marked, as confirmed by the following example, which exhibits successive FIG. 92. stages in tiie modification of the indicator figure. The engine Indicator Diagrams. 179 being non- condensing, the atmospheric line is below the whole enclosed area. 1. Here the diagram is intersected by three vertical lines at equal distances, and represents a species of theoretical curve. The steam line is maintained during the first third of the stroke ; then come expansion, release, exhaust, and compression in the order and to the extent marked. 2. This is a tolerable copy of an actual diagram given to the writer, where the boiler pressure was 128 Ibs., the diameter of the cylinder 17 inches, with a stroke of 2 feet. The train was de- scribed as consisting of fifteen carriages, and was just starting. The three periods in question are extremely well defined. 3. Here the three periods are still defined, but the greatei speed of the engine causes them to lose much of their distinctive character. The boiler pressure is still 128 Ibs., but the speed is 28 miles per hour. 4. The boiler pressure is marked at 123 Ibs., but the speed of the piston has quite swept out the characteristics of the steam line. The train is now running on a level line at 58 miles per hour, and the principal effect to be seen is the jump of the indicator pencil ; but, taking the dotted line as an approximate mean, it is appa- rent that cut-off, expansion, and release are hopelessly blended together. 122. As an illustration of the necessity of providing in the design of an engine for effective condensation of steam, we refer to a simple illustration. Some thirty years ago, in the iron district of South Stafford- m FIG. 93. shire, an indicator diagram taken from a mill engine of nearly 200 N 2 i8o The Stectm Engine. H.P., having a cylinder 42 inches in diameter, with a 7 feet stroke, gave the result shown in fig. 93. The engine took steam at about 19^ Ibs. pressure, which was maintained nearly uniform to the middle of the stroke, falling only to about 17^ Ibs., and was then reduced by wire-drawing to 6 Ibs. The average vacuum was 2f Ibs. below the atmospheric line, the lowest point attained being 5 Ibs. This is made very clear by the outline of the diagram. Of course such a performance was most defective, and accordingly a careful examination was made into the construction of the engine, when it was seen that the steam and eduction valves, as well as the thoroughfares or passages, were on too small a scale. The con- denser B D was of insufficient size, and water was admitted into it by a simple opening, A, without any pipe or rose for throwing out a divided stream. The conclusion arrived at was to remodel the valves and steam thoroughfares as well as the condenser. The engine was worked by four Cornish valves, so that it was easy to supply others on a L FIG. 94. larger scale, and accordingly the steam and eduction valves were enlarged from 7 inches to 12 inches in diameter, and the pipe marked E was similarly altered. The condenser was improved by the addition of a supplemental chamber, c, and an injection pipe with a rose, P, was introduced. Otherwise the construction of the engine was undisturbed. The altered form of the indicator diagram at once shows the gain of power. The largest portion of the area of work done is below the atmospheric line, instead of being above it, the vacuum averaging a very little over 10 Ibs., instead of only 2| Ibs. The Indicator Diagrams. 181 steam pressure commences at 8 Ibs., and averages 5*4 Ibs. through- out the stroke. It is instructive to note the gain of work under the new conditions, and we can form a general idea at once from the increase of effective pressure below the atmospheric line. In the first case it was found that a mean effective pressure of 19 Ibs. from steam and vacuum combined gave 190 horse-power; and in the second case there was a gain of 7*43 Ibs. from conden- sation alone; whence it followed that the actual gain was to 190 H.P. as 7-43 to 19; that is, or 123. As an additional illustration two indicator diagrams are appended, which were taken from a direct-acting horizontal engine at Woolwich. In the one diagram the engine was working much FlG. Qi). in its ordinary manner, and the curve of expansion is well marked ; but in the other the condenser was leaky; and in order to keep the machinery in action it was necessary to maintain the steam pressure nearly to the end of the stroke, the contrast between the two diagrams being here greater than in the example first com- mented on. PROTECTION OF THE CYLINDER. 1 24. There are three conditions of the steam cylinder in the working of an engine : (i) it may be entirely unprotected by any covering ; (2) it may be coated with felt and wood or some non- conducting material: (3) it may be stearn-jacketed, the jacket itself being covered with a non-conducting material. 182 The Steam Engine. 1. It seems clear that the first mode of working is wrong. But in order to impress this view upon the student we refer tc the annexed diagram, which shows the expansion curve of steam in an imperfectly pro- tected cylinder, as contrasted with the true theoretical curve which would have corre- sponded with the weight of steam found in the cylinder is J ! at the end of the stroke. In FIG. 96. the diagram ABC represents ihe actual expansion curve of the steam, and D c that which should have been the expansion curve if the walls of the cylinder had de- tracted nothing from the work done. The steam loses pressure on its entrance by the chilling of the colder metal, and there is an immediate drain upon the molecular motion within the cylinder, on which we rely for the movement of the machinery outside. The escape of heat, from whatever cause it may arise, is a direct subtraction from the efficiency of the working substance, and at the present day it can scarcely be necessary to marshal all the reasons to be urged against such a practice. 2. The second case is where the cylinder is coated with some non-conducting material, and here it is essential to remember that steam cannot expand and do work behind a piston without a fall in temperature. If the steam enters the cylinder direct from the boiler, as is commonly the case, it will be saturated, and reduction of temperature will cause partial condensation. As the expansion goes on it appears that the temperature of the steam will fall below that of the surface surrounding it, and towards the end of the stroke the heated metal will boil off the water de- posited and send it out as steam into the condenser. By such an action steam will have passed through the cylinder without doing work. A c}linder of metal may be covered with a non-conducting casing, but it remains a large metallic mass, and it is impossible to reason about it as if it were not alternately heated and cooled during the working of the engine. It was this alternate heating The Steam Jacket. and cooling which Watt strove to eliminate by a separate con- denser and a steam-jacket, In the last diagram the curve of expan sion appears to rise more than is usual towards the end of the stroke, and this indicates, as clearly as if the thing were spoken in words, that the steam which has been condensed by chilling is evaporated by the walls of the cylinder towards the close of the stroke. Adopting a view similar to that now referred to, Mr. Cowpei has pointed out that, with high expansion and a marked difference in temperature at the beginning and end of the stroke, the cylinder acts somewhat as a condenser to the entering steam, and as a boiler just before it escapes. That this is so became apparent from an experimental trial, where a glass tube closed at one end was fitted to the non-jacketed cylinder of a high-pressure engine working expansively. Mr. Cowper found that the steam condensed in a cloud inside the tube at the beginning of each stroke and re- evaporated before its conclusion. He then brought a shovel of hot coals near the tube, and the heat of the fuel effectually pre- vented condensation, for it acted as a steam-jacket The point is, that no covering to the cylinder would raise its temperature permanently to that of the entering steam, for the heat deposited on condensation would not remain, but would be carried away afterwards, during the re-evaporation. 3. The last case is that where the cylinder is covered both at its ends and sides by a steam-jacket, the external casing being also protected by a covering of non-conducting material. Under these circumstances the walls of the cylinder may be kept nearly as hot as the entering steam, and the chilling effect of the metal surface is to a great extent eliminated. Enough has been stated in the dis- cussion on heat engines to demon- strate the serious waste of heat which is inevitable with even the best- constructed engines, and it is a clear advantage to get the FlG greatest possible amount of work nut of the steam just at the precise instant when it is in action. 1 84 The Steam Engine. There is no known material which is insensible to the action of heat ; that is, which cannot be warmed or cooled, and which will not conduct or radiate heat. Of necessity a cylinder is made of metal, a material peculiarly sensitive to changes of temperature, and possessing every quality, except strength, which we should prefer not to find in it. It would, therefore, appear that the most reasonable course would be to enclose the cylinder in a hot envelope, which may serve to maintain its temperature at a high level and to supply the heat which is otherwise escaping. Mr. Cowper has brought before the Iron and Steel Institute several valuable observations on the utility of a steam-jacket, and he has illustrated his remarks by reference to indicator dia- grams taken from cylinders with and without steam-jackets. The card (fig. 97) was from an engine with a steam-jacket over the ends and sides, and the curve of expansion was nearly that given by theory. Towards the end of the expansion the true curve is represented by the dotted line, and it appears that the actual expansion rises above it, showing that the steam was a little super- heated by the hot casing. Several diagrams were adduced, which came pretty much to a repetition of that given above, the point being that the greater the amount of expansion the greater was the loss of work from the absence of a steam-jacket. DIAGRAM FROM A CORLISS ENGINE. 125. A form of engine was introduced some thirty years ago by Mr. Corliss in the United States, and has worked successfully, although the arrangements for actuating the valves are somewhat complicated. The only point to which reference is made is the form of the indicator diagram, as taken from engines of this type. Without attempting to de- scribe the engine, we may say that it works with two steam and two exhaust valves. FIG. 98. The steam valves are ex- tremely rapid in their action ; they are opened, when under the Indicator Diagrams. 185 control of springs, like the hammer of a gun, and they move suddenly into the position of being fully open. They are closed in like manner and are, as it were, shot round from the position of being fully opened to that of being fully closed, or conversely. The valves are cylindrical slides working in the arc of a circle. It is remarkable that liberating gear for disengaging a valve which was lifted by the action of a falling weight was introduced by Watt, and is therefore as old as the condensing engine; but here the valves are not lifted, but rotated, and they are actuated by springs, and not by weights. Another point is that in engines of this class the governor acts directly on the steam valves, so as to cut off the steam earlier, instead of actuating a throttle valve, as in Watt's arrangement. FURTHER REMARKS ON INDICATOR DIAGRAMS. 126. It is hoped that enough has been said to present a general view of the application and use of the indicator, and before leaving this branch of our inquiries it may be useful to append a few general remarks. Rankine, in his book on the steam-engine, discusses several causes which influence the form of the indicator diagram. i. It appears that the steam pressure undergoes some fall during the passage from the boiler to the cylinder. The amount of such fall varies greatly in different engines, but the general result is, that the highest average indicated steam pressure before expansion begins is some two or three pounds less than the boilei pressure. Among the points to be noticed are (i) the resistance of the steam pipe through which the steam passes, (2) the resistance of the regulator or throttle valve, (3) the resistance due to the ports and steam passages ; and here also the bends or sharp angles as well as the imperfect coating of the steam pipe must be taken into account. Rankine says that in the present state of our knowledge it is im- possible to calculate separately the losses of pressure due to these causes, and if it were possible the resulting formulae would be too complicated to be of much use. An observation of this kind has 1 86 The Steam Engine. a wide application. It may be pointed out that steam which has been lowered in pressure by the resistance of passages, or has been wire-drawn, as we have termed it, is to some extent superheated by the friction of its molecules, the tendency of all friction being to produce heat. 2. There is in practice a rounding of the angle at which the expansion curve begins in the theoretical diagram. This is called wire-drawing at cut-off. It is always to be seen where a slide valve, closing gradually, is employed, and is reduced to a mini- mum in a well-formed diagram of a Corliss engine. Speaking generally, it may be said that the steam begins, as it were, to work expansively a little before the valve is completely closed, or that the energy exerted is nearly the same as if the valve had closed instantaneously at a somewhat earlier point of the stroke, which point may be termed the ' effective cut-off,' Such a point is easily obtained by carrying the expansion curve a little higher, and by prolonging the probable steam line to meet it. 3. There is a rounding of the expansion curve when release begins before the end of the stroke, and it is recommended that the point of release should be so adjusted that one-half of the fall of pressure takes place at the end of the forward stroke, and the other half at the beginning of the return stroke. Where the release is small the expansion curve is continued to the end of the dia- gram, as may be seen in fig. 98, and in such a case the exhaust line slopes gradually downwards as the piston returns instead of being nearly horizontal. 4. The general effect of water in the cylinder, from whatever cause produced, but which we will suppose to be present in some degree throughout the stroke, is to lower the steam line in the first portion of the stroke and to raise it in the latter portion. On this subject it is very easy to propound theories ; but the subject- matter lies so much within the region of experiment that any theoretical deductions, which are nearly all that we can be said to have at present, may indeed be interesting, but would perhaps admit of being classed among ' conclusions in which nothing is concluded.' 5. There is also the conduction of heat to or from the walls of the cylinder, the general effect of which is that in the last case. Indicator Diagrams. 187 6. Clearance will modify the form of the expansion curve of steam, by removing backwards through a small space the zero line of volumes. And, as we have seen, if the steam be completely exhausted from the cylinder during the return stroke the effect of clearance is to waste a quantity of steam during the double stroke. But, inasmuch as it is possible to compress a portion of steam in the cylinder during the return stroke, the loss above referred to may be greatly or perhaps wholly eliminated. On this subject Rankine recommends that the point of compression should be adjusted in such a manner that the quantity of steam confined or cushioned should be just sufficient to fill the clearance with steam at the initial pressure when the piston comes to rest. In such a case the work expended in compression is restored again during expansion, and the steam spring is continually reproduced without waste. CONNECTING ROD ENDS. 127. Two principal methods of forming the ends of connect- ing rods will be apparent from the sketches, which are copied from the collection of lecture diagrams. In Fig. 99 we have an elevation and side-view of a con- necting-rod with a forked end, showing the combination known as a strap, gib, and cotter. A pin to which the rod is at- tached is encircled by brasses made in two halves, as indi- cated by the tinted pieces while the brasses themselves are bound round by the strap cc, and held together by the gib, marked a, and the cotter (sometimes called 'cutter') marked d. This part of the contrivance affords a good illustration of the use of FIG. 99. wedges in combination with a tightening screw. As the brasses wear the oblique surfaces of a and d slide uoon each other, and 188 The Steam Engine, the thick end of the cotter is continually advanced by the screw, while the surfaces which abut against the brasses on the one side, and the connecting-rod on the other, remain parallel, as at first. The key-way, which is cut through the strap and connecting rod for the insertion of the gib and cotter, is shown in the side-view, and spaces are left to allow for the screwing up of d as the bearing wears. Also the connecting rod is enlarged towards the middle, as indicated by the broken piece which marks the increase in size. 128. Another construction for the end of a connecting rod is simple in its details, and is much used in marine engines, as in the compound cylinder engine by Messrs. Maudslay (see fig. 127). Here a brass block is divided into two parts, and is bored through for the reception of two holding bolts, each screwed at one end. The connecting rod terminates in a T-piece marked it is apparent that 2 TT r e Cor. Let x=y=i. .'. P =-?, Q =/ r, whence Q -= 2 p, or the strain on a longitudinal section (per linear inch for any thickness) is twice that on a transverse section. O 2 The Steam Engine. 132. The strain on a longitudinal section per linear inch of the material of a cylindrical boiler may also be found by a simple application of a law of fluid pressure. Let D E H B A represent a portion of a cylindrical boiler, D E A, C H B being two planes perpendicular to its axis, and D c B A being a plane containing its axis. The pro- B 3 perty of fluid pressure relied on is that the whole bursting strain on the metal strips A B and D c is the same as the pressure of the enclosed fluid on the area D c B A. Let A B = #, DA=2r, and let IG. 103. ^ b e the pressure of the fluid or steam. Further, let t be the thickness of the shell (a section at A B being really represented by Kab B, where A a Kb = . If the steam had expanded in a single cylinder of sectional area B, and the cut-off had occurred when the piston had traversed a space y, the expansion 'being finally in the ratio ?, we should have had j> = ; and, applying the formula of Art. 112, it would B be found that r R i work done = ^>py < i + log. V . (2). But Kpy = A/ /, and therefore the expressions (i) and (2) are identical, which proves the proposition. Cor. The form of equation (i) may be altered. Thus, let the steam expand E times, so that E = , A /. work done = 5^ < i -f log. E I . So, also, equation (2) becomes, (since y = - I , work done = ^- < i -f log. E I . POINT OF CUT-OFF IN SMALL CYLINDER. 159. Mr. Pole proved, in 1851, that in the case of expansion with compound cylinders there is one particular point of the stroke where the steam may be most advantageously cut off, so far as the initial pressure on the pistons is concerned, and that such pressure Point of Cut-off. 243 may be reduced to a minimum value dependent on the degree of expansion. The investigation is the following : Let / represent the length of each cylinder, r the length of stroke in the small cylinder before the cut-off, A, B the areas of the pistons of the small and large cylinders respectively, B being constant, while A and r vary. / the pressure of the steam on admission into the smaller cylinder, whence ^ is its pressure on admission into the large cylinder. Then initial pressure =/A + 'B A)^*. B / But the whole expansion = x. -= E suppose. Let r r = z, then we have p A ? I EZ .*. initial pressure = ^-? + B p z * = a minimum, E Z E *.0= 9 + I, E* 2 \'E or / = r\/E Which determines the point of cut-off when the initial pressure of the steam on the two pistons is the least possible. "ft TC 'fy R Also, initial pressure = * h B/0 ^ , E Z Ex. i. LetE~io, .*. r= == N/ IO = /( 32) nearly. V TO TO Also A = r== N/ 10 = B (-32) nearly. v E Io Initial pressure =/B( 2 L^ 1^1 M =/B x "532. V 10 / 10 R 2 244 The Steam Engine. Ex.2. L And v/2 = = 8, .-. r=-L = = , \/8 2x/2 4 = *- nearly, .*. r = ' = 25 5 20 100 ENGINES WITH CRANKS AT RIGHT ANGLES. 1 60. For many purposes it is enough to have an engine with a single steam cylinder, or the equivalent Woolf s engine, with a pair of cylinders acting as one only ; but, on the other hand, there are numerous instances where two engines should be placed side by side and work cranks at right angles to each other. This is particularly the case in applying steam-power to flour mills or to cotton mills, where it is of consequence to preserve the rotative pressure on the crank as nearly uniform as possible, and to maintain a smooth and even motion. Or, again, in marine engines, for convenience of starting in any position, the same rule would hold ; and before proceeding further it may be useful to point out the reason for the greater uniformity of rotative pressure which is a consequence of working with a pair of cranks at right angles. It has been shown in Art. no that the variations of tangential pressure on the crank of a direct-acting engine are represented by the vertical lines on a diagram similar to that shown by the dotted curve /in the annexed sketch. Putting a series of such curves end to end, we obtain a graphical indication of the fluctuations of FIG. 121. tangential pressure during the working of an engine with one cylinder. The force is zero at a dead point, and rises to />, its greatest value, after which it sinks again to zero. But if there be a pair of cranks at right angles, a second series of diagrams of rotative pressures must be superposed upon the first series, as shown by the second set of dotted curves, whereof one portion te Cranks at Right Angles. 245 marked b e, and the final result is exhibited by the upper line, not dotted, which is obtained by adding together the pairs of ordinates at each point; for example : nm-\-mr=ms, The greater uniformity of rotative force is apparent, and it would be improved by cutting off at half-stroke in each cylinder, for then the curve b e would be hollowed out and reduced, while the part bf would be unaffected, and the upper resultant wavy line would become more nearly horizontal. By proceeding in this manner it is easy to set out a diagram of the rotative pressure upon the cranks of any pair of engines working under given conditions. 1 6 1. In applying Horn blower's principle to direct-acting engines, where two cranks at right angles are to be connected with the cylinders, there are different methods for adoption, each of which has its advocates. One plan very commonly met with has been to place the high and low pressure cylinders in pairs, with their axes in the same straight line, so that one piston rod serves for both. Thus, in marine engines, with the cylinders vertical, there may be 1. The high-pressure cylinder above the low-pressure cylinder. 2. The low-pressure cylinder at the top. 3. The low-pressure cylinder encasing the high-pressure cylinder. But in each of these cases, as also in compound cylinder horizontal engines, it is usual to confine the expansion to one pair of cylinders, although there is an example, to which reference will shortly be made, in which the steam is carried in succession through four cylinders. THE USE OF AN INTERMEDIATE RECEIVER. 162. In another class of compound cylinder engines there are two cranks at right angles, but only one cylinder connected with each crank. Here each cylinder forms, as it were, an engine complete in itself; the cylinders (called A and B, as before) are placed side by side, and are of equal length, and the point to be 246 The Steam Engine. noticed is, that the pistons in A and B no longer move together, but that one leads the other by half a stroke. It is clear that Hornblower's mode of exhausting at once from A into B is no longer applicable, and that some special method of distributing the steam, different from anything that we have yet seen, must be arranged. The difficulty arises from the fact that the directions of motion of the pistons cross each other, whereby, for example, when the piston in A is at the end of its stroke and about to ascend, that in B is in its middle position and is descending. In order to get over this obstacle Mr. Cowper has proposed to place an intermediate receiver between the cylinders A and B, which shall act as an exhaust reservoir for the steam coming from A, and as a boiler for the steam going into B. It appears that engines with a receiver have worked well in practice, but it seerps difficult to justify the use of this arrangement by a strict reference to the principles of the theory of heat. A general idea of the arrangement of the engine proposed by Mr. Cowper may be gathered from the sketch, where the cylinders FIG. 122. A and B are placed side by side, and the high-pressure cylinder A is enveloped in a steam receiver or reservoir, marked c, the content of which is perhaps three times that of A. In a working engine on this plan steam (say at 70 Ibs. pressure) would enter A and be cut off at half-stroke ; it would then expand and finally exhaust itself into the receiver, where the pressure would vary from, say, 10 Ibs. to 14 Ibs. The receiver would supply steam for the low-pressure cylinder B, just as if it were the boiler of an ordinary engine, and the pressure of the steam in c would fall to 10 Ibs. when the demand upon it was made, but would rise to 14 Ibs. when fresh steam entered it from A. The temperature of the steam in the jacket surrounding A is, therefore, much below that of the entering steam, which is so far a departure from Watt's practice. Milnefs Engine. 247 MILNER'S COMPOUND CYLINDER ENGINE. 163. A mode of working a compound cylinder engine with two cranks at right angles, and without an intermediate receiver, was patented by J. Milner in 1853, No. 2,281. It does not ap- pear that the engine has ever come into use, but it is referred to as an exercise for the student. The specification describes the engine as having two working cylinders, with pistons connected to two cranks placed at right angles to each other on the same shaft, one of the cylinders being of greater capacity than the other. The valves are worked by cams or eccentrics, and it is ' arranged that steam may be admitted from a boiler into the top of the smaller cylinder until the piston has made half its stroke, and then be shut off. A communication is next made between the top of the first cylinder and the top of the second one, whose piston is then at the top of its stroke.' The part of the sketch marked (i) shows the piston of the smaller cylinder A descending, the steam being just shut off, while the piston in the larger cylinder B is at the top of its stroke, and is on the point of descending, as marked by r. .'. w 2 r 2 h = gr 1 or w 2 h = g. But h = / cos D c B = / cos 6 suppose .'. w 2 / cos = r, and cos 6 = -^. /W 4 If w be increased, cos 6 is diminished, and is increased, whereby D moves up into a higher position. 170. There is another observed result which will carry us on iq 266 The Steam Engine. the investigation, viz., that if a cylindrical vessel partly filled with water be whirled round a vertical axis coinciding with the axis of the vessel, and at a uniform velocity, the water will be hollowed out into the form of a cup, the particular surface exhibited being that known as a paraboloid of revolution. In other words, if A be the vertex of the cup, c A being the axis of rotation, any section of the surface, such as D A, made by a plane through the axis, is a parabola. Note. The curve called a parabola is frequently met with in studying me- chanics; it is, very approximately, the path described by a ball when thrown obliquely into the air, and may be the curve formed by the section of a right cone as made by a plane parallel to a generating line, or slant side, as it is commonly called. By reason of the mobility of the particles of water it is a property of this FIG. 133. substance, in common with other liquids, that the pressure at all points of a surface formed upon it when at rest is the same. If it were not so the particles would move along the surface. But the water in the vessel is permanently rotating with a uniform velocity, and is, therefore, in an artificial state of equilibrium. Hence a particle at D will remain at rest just as much as a particle at d. Draw D c, d c perpendicular to the surface of the water at the points D and d respectively. Then D and d move with the same angular velocity round the axis c A. Let this angular velocity be u>, and we have w 2 x c B = g. , w 2 x c b = g, whence c B = c b. It is a property of a parabola that the subnormal is constant, and the term ' subnormal ' is merely a technical name for the line c B, being the part of the axis intercepted between any two lines, such as D c, D B, whereof D c is perpendicular to the curve and D B is perpendicular to the axis A c. As soon as we knew that the section of the fluid cup was a parabola it became possible to predict that property of the curve which is now referred to. 171. The investigation of the property of a parabolic curve as The Pendulum Governor. 267 applied tD a conical pendulum will have prepared the student foi understanding the so-called parabolic governor. It appears that in 1851 a governor was brought over from Vienna where the pendulum balls rode on guides having the form of a parabola. This governor had, as we might anticipate, the fault of being too sensitive. The balls rose to the highest point or fell to the lowest on the smallest variations of speed, and it became necessary to diminish this extreme sensitiveness by attaching to the sliding collar of the governor an air cylinder or cataract, whereby in rising or falling the balls were made to suck in or force out air through a a small adjustable aperture in the top of the cylinder. 172. It may now be convenient to refer to some working models, deposited by Mr. Head in the Museum at South Kensing- ton, which are intended to illustrate (i) the common pendulum governor, (2) Watt's governor, and (3) an approximate parabolic governor ; and we should premise that in applying the conical pendulum to an engine the chief point to notice is that the number of revolutions made per minute depends upon the height of the cone, viz., CB, in fig. 134. i. The common method of con- structing the governor has been that shown in the sketch. The balls are suspended at the points E and H, a little on either side of the central vertical spindle c B. Each arm, as H D, is connected by a link to a sliding block s T. As the rate of rotation increases the balls fly out, s T rises, and in doing so actuates a lever which controls a steam valve and diminishes the supply of steam. . The effect of placing E and H at a little distance from the axis c B is to cause the variation in the height of the cone to become greater for any given rise of the balls, and thereby to render the governor less sensitive. Thus the heights of the cone in the two positions shown sure c B and cb respectively, the variation being equal to ct + B b. TO VALVE FIG. 134. 268 The Steam Engine. TO VALVE 2. In the governor as made by Watt, of which there is an example at the Patent Museum, the variation in height of the cone was much reduced. The centre of suspension was set in the ver- tical axis, and a jointed parallelo- gram c E was attached to the sus- pending rods, the angles DCP, F c Q being rigid and invariable. It followed that as D moved up into the position d the vertex E would descend to e, and the variation in the height of the cone would be B b> which is certainly less than in the previous construction. The valve lever was actuated from the point E, instead of from B, and on the whole a considerable rise and fall in the FlG> I3 $- point E was secured by an extremely small change of height in the described cone. The governor was driven by a cord passing over a grooved pulley at H. It is stated that Watt's original governor would begin to rise at 36 revolu- tions, and would reach its maximum height at 38, corresponding to a variation of only 5 J per cent, in the speed of the engine. 3. The approximate parabolic governor was designed by Mr. Head, and is shown in fig. 136. It will be seen that the points of suspension are on opposite sides of the central vertical line round which the balls rotate. The apparatus is, therefore, termed a * crossed arm ' governor, and the peculiarity consists in this, viz., that by properly adjusting the centres E and H to the lengths of the arms it can be provided that the arc D d, in which either ball moves, shall be approximately an arc of a parabola. The following construction may be taken for setting out the governor : The balls, being on a level d b t and revolving in a cone whose altitude is c b, are required to make a certain number of revolutions per minute, as shown by the formula. Draw d t perpendicular to H d and bisect b t in a, then a will be the vertex of a parabola passing through d. The rise from b to B for a higher velocity is then assigned according to any proportion which Head's Governor. 269 FIG. 136. may be thought desirable ; and by a property of the curve we have D B : d b '.'. \/a E : \f ab. This determines the point D, and other points in the curve may be assigned in like manner j after which it is only necessary to select a centre H which shall give a circular arc passing approximately through the points so determined. A comparison of the three modes of construction is given by the model, wherein the different governors are connected with the same driving wheel and move at the same rate. On setting them in motion the first to open out fully is the crossed arm governor, then follows that of Watt ; and the least sensitive apparatus is the common governor. On reducing the speed the balls fall in the reverse order, viz., (i) the common governor, (2) Watt's governor, (3) the crossed arm governor. In practice the last apparatus would be too sensitive, and accordingly a spiral spring is placed upon the spindle, as indi- cated in the sketch, the object being to retard the balls during their ascent. The spring is under no compression when the balls are in their lowest position, but offers a slight and increasing resistance as they rise ; and the governor is thus rendered a practical instrument, instead of being a mere mathematical ab- straction. For example, at the Newport rolling mills, Middles- borough, this governor has been applied to a large single cylinder horizontal engine driving two plate-mills. The engine makes about 40 revolutions per minute ; and wheri nothing is passing through the rolls the balls remain in their highest position, but when the plates are passing through the rolls the arms collapse, admit full steam, and rise again as soon as the work has been done. 1 73. The weighted pendulum governor is a form frequently used, and is shown in fig. 117. It consists of two small pendu- lum balls, weighing from 2 Ibs. to 3 Ibs. each, and attached by links passing downwards to a collar on the driving spindle, which 270 The Steam Engine. carries a weight varying from 50 Ibs. to 300 Ibs., according to the size of the governor. The balls revolve at a high speed, making from 200 to 300 revolutions per minute. Suppose that the rods carrying the balls are equal in length to the links connected with the suspended weight w, then it is clear that for any small dis- placement the vertical rise of w is twice that of either ball. Let P be the sum of the weights of the two balls, and let there be a small increase of velocity ; then the centrifugal force is the same as in an ordinary governor, but the weight raised is different, for when P rises through a small vertical space w is raised, by the arrangement of linkwork, through twice that space. It follows that the height of the cone is to that of an ordinary pendulum as p + 2 w : p, and that the sensitiveness is increased in the propor- tion of P to P + 2 w. SIEMENS' CHRONOMETRIC OR DIFFERENTIAL GOVERNOR. 174. If the governor of an engine were absolutely perfect it would regulate the velocity of the machine to one uniform, unde- viating speed, and would not suffer any departure from that defi- nite rate of motion. Such a governor would adjust the supply of steam exactly to the demands made upon it, and would in effect cause the machinery to move at one constant rate. The governor by Watt makes no pretension to realise this ideal perfection, and does nothing more than moderate the inequali- ties to which a steam engine is liable under varying conditions of load. So far from being perfect it is subject to two principal defects, which are well known to exist, but which do not detract from its general utility as the most effective of any simple apparatus for regulating the speed of an engine which has yet been devised. i. Watt's governor cannot prevent a permanent change in the speed of the engine when a permanent change is made in the load ; that is evident ; for suppose that the load were diminished, and that the speed were required to remain constant, such a result could only be obtained by reducing the supply cf steam, whereas the governor fails to reduce the supply unless the balls open out more widely, or unless a correspondingly higher rate of motion is maintained. Siemens' Governor. 2/1 In order to retain one uniform speed two things appear to be necessary, viz., first, that the pendulum constituting the governor should be driven by a constant force, in which case its rate of motion could be prescribed definitely beforehand, and would remain in- variable ; and, secondly, the engine should be compelled to adapt its own motion to that of the invariable pendulum by some mechanical contrivance which should forbid any deviation. Mr. Siemens has endeavoured to carry out the conception stated above : he drives the pendulum by a raised weight, and pours into it a little excess of maintaining power, which excess is absorbed by friction. The pendulum, therefore, revolves at a constant speed, and the apparatus for tying down the engine to the rate of the pendulum is a differential train of wheels, which will be described immediately. 2. The second defect is that the governor does not begin to act until a sensible change has occured in the speed of the engine ; for the balls do not open out more widely until after the velocity has increased, nor can they rise until an additional store of energy sufficient to overcome the friction or inertia of the moving parts has been accumulated. Mr. Siemens' invention is directed also against this second defect, for by the operation of the differential motion it results that the whole energy stored up in the revolving balls is ready to act upon the steam-valve at the first instant that the engine attempts to deviate from the pendulum ; whereas in the ordinary governor the additional energy stored up in the balls by increased velocity of rotation is the power available to control the valve. One action is slow and comparatively feeble, the other is instantaneous, and cannot be resisted. The annexed sketch shows an elevation of Siemens' governor partly in section, together with a plan of the levers between the train of wheels and the raised weight. The differential motion is made up of the mitre wheels A, B, B, and c, whereof A is keyed to the vertical spindle, and is driven by the engine, while c rides loose upon the same spindle, and is connected directly with a heavy conical pendulum enclosed in a casing d, d. B, B are two separate wheels, carried on a hollow spindle, through which the driving spindle passes, and in gear with both A and c. The dif- 272 The Steam Engine. ferential motion is made up of the three wheels A, B, and c> the fourth wheel being merely put in to equalise the driving pressure on the two sides of the vertical spindle ; and it is well known that where three equal bevel wheels, as A, B, c, are in gear the velocities of A and c are equal and in opposite directions. Also as long as the velocities of A and c remain equal and opposite B will rotate on its axis but will not shift its position ; whereas on the smallest difference between the motions of A and c the wheel B must begin to run round them, and it is only by so running round that a difference in the velocities of A and c becomes possible. It further remains to connect the weight w and the throttle FIG. 137. valve with the differential train of wheels. This is done by attaching w to the end of one arm of a bell crank lever whose fulcrum is at/, the other arm moving in a different vertical plane, and being connected by a link e to a short projecting rod which acts as a handle to shift the wheels B, B round A or c. The axis of the valve spindle passes also through /, whereby, on turning the bell-crank lever, a throttle valve is more or less opened and the supply of steam is regulated. A model of this governor is deposited in the Museum of the Patent Office. The wheel A is driven by hand, and on examining the apparatus it becomes easy to comprehend the action of the weight w. First, move the handle suddenly, when A runs round, but the inertia of the pendulum prevents c from responding, and the consequence is that w is jerked upwards. Next, turn the handle Chronometric Governor. 273 slowly, when all the wheels rotate on their respective axes, but w remains at rest. On gradually increasing the velocity we find that there is one particular speed at which w is just raised, and that it can be maintained in higher and higher positions by further accele- rating the motion until it reaches a stop which defines the limit at which the governor ceases to act. As to the pendulum, that is, in fact, a small fly-wheel divided into segments, and carrying a sort of friction brake, which is pressed outwards against the casing by springs. So long as w is raised it tends to accelerate the motion of c, and, according to the phraseology of mechanics, it is the driver of c, and we have here an example of a conical pendulum driven by a raised weight, and therefore moving at a constant velocity. Also it follows that the engine must accommo- date itself to the speed of the governor, for otherwise B would run round and the throttle valve would be acted upon. It is furthei evident that the whole energy accumulated in the pendulum would be thrown upon the valve if the velocity of A varied from that of f. In the year 1866 Mr. Siemens brought to the notice of the Institution of Mechanical Engineers a new form of this governor, in which the conical pendulum was replaced by a cup of parabolic shape, open at both ends and dipping into water. In the modi- fied apparatus the cup rotates about a vertical axis, and as it revolves the water rises in a parabolic surface and may flow over the rim. At a sufficient velocity a continual stream of water is raised, which is projected over the edge, caught upon fixed vanes, and deflected back against other vanes attached to the outside of the cup and rotating with it Work is, therefore, continually done and a resistance is opposed whereby the velocity of rotation of the cup remains practically constant. As before, the cup is driven by a raised weight, and the only difference con- sists in the substitution of the liquid and the rotating cup for the ordinary conical pendulum. DONKEY ENGINE. 175. The greater number of the diagrams on the steam engine which have been published by Messrs Chapman & Hall have been reproduced in this book, and we purpose now to describe the T 274 The Steam Engine. arrangement of a small pumping engine, which has been photo- graphed on wood from the large diagram. The method here adopted of placing the pump in a line with the steam cylinder is in common use, and if the engine were of larger dimensions and placed horizontally it would represent the type of engine employed for forcing water into a full-sized ac- cumulator. The upper part of the drawing requires no special explanation ; the throttle valve, the slide valve, the ports, and the exhaust passage are sufficiently indicated, but there is a peculiarity in the mode of actuating the slide and of obtaining the rotation of the fly-wheel which should be made clear. Supposing the fly-wheel to rotate upon the axis F L it is appa- rent that the end a of the crank D a will describe a small circle round the central point of the extremity L, and that the slide s will be driven by the motion of a in a circle, just as if an ordinary eccentric had been constructed. The rotation of the crank L H is obtained by a movement which can hardly be recommended as being good of its kind, and which is the converse of the motion shown in fig. 37. Instead of the pin causing the slit bar to reciprocate, we have the reciproca- tion of the bar R s causing the rotation of the crank L H. The example is interesting as showing one of the devices used by mechanics in the conversion of motion, as well as the utility of a fly-wheel for carrying the crank over the dead points. As to the pump, it is unnecessary to say more than that the action is that of a common force-pump, with a suction valve at n and a delivery valve at m. GIFFARD'S INJECTOR. 176. The invention of the injector for supplying feed-water to the boiler of an engine is principally remarkable as presenting an illustration of the direct conversion of heat into work. Before describing the apparatus it will be necessary to explain the mean- ing of the term * induced current.' Looking back historically it appears that in 1719 Hawksbee, the inventor of a double cylinder air-pump, showed that when a current of air was sent through a small box entering by an opening Donkey Engine. 276 The Steam Engine. at one side near the top and escaping by a corresponding opening at the opposite side the effect was to rarefy the air within the box rather than to compress it. It is an old experiment to suck up and drive a jet of spray out of a bottle by blowing through a horizontal tube with a contracted nozzle whose end is placed just over a vertical tube dipping into water contained in the bottle. The current of air passing over the open mouth of the vertical tube carries away some of the air from inside the tube, whereby the water rises to the top and is dispersed in a jet of spray. According to theoretical definitions the particles of gases repel one another and have no coherent action among themselves. In practice this is not the case ; and if a definite current of air be set up in a mass of air at rest, .as when a jet escapes from the mouth of a tube, the air in motion will drag a number of the quiescent particles with it and will extend considerably the di- mensions of the original current. It will, in technical language, induce a current also in the surrounding air. The application of an induced current, with which we are now concerned, is exhibited in the annexed sketch. The globular ves- sel represents a boiler in which high-pressure steam is generated, and from which it escapes at an orifice E. The steam is discharged just inside a conical casing or nozzle, the object of which is to provide a means for setting up an induced current of air which will speedily exhaust the tube. The water, forced up by atmo- spheric pressure to supply the loss of air, will, therefore, issue from E, and we shall have made the first step towards the construction of an injector, viz., the discharge through E of a mixed jet of steam and water (see fig. 139). In fig. 140, which shows a Giffard's injector as constructed by Messrs Sharp, Stewart & Co., there is a pipe marked ' steam,' which terminates in a vertical conical nozzle, having within it a solid rod or needle capable of contracting in any degree the amount of the issuing jet. On the opposite side of the apparatus is a pipe marked f water,' which corresponds to A B in the ele- mentary diagram, and by turning the wheel marked ' water regu- lator' the tinted sliding tube is brought up or down, so as to regulate the supply of water which is sucked up by the inducing action of the steam. There is here, therefore, precisely the ap- GiffarcTs Injector. 277 paiatus already described, together with mechanical means for regulating (i) the supply of steam and (2) the supply of water. Near the bottom of the injector is a valve opening downwards and leading to the flanged end, marked ' delivery/ which is in direct communication with the boiler. The valve in question is STEAM REGULATOR STOW WATER**-* OVERFLOW FIG. 139. FIG. 140. shown open in the drawing, but it is closed by the pressure within the boiler when the injector is not at work. Recurring to the elementary diagram, which is intended to show the action in its most simple form, we may point out that M. Giffard discovered that a mixed jet of steam and water issuing from E under the circumstances above stated is competent to overpower and drive back a simple jet of water issuing from the opening D, and that a supply of feed-water may be forced back into a boiler by the steam generated therein without the inter- vention of any pumping apparatus whatever. 278 The Steam Engine. Since action and reaction are equal and opposite it is abun- dantly clear that a simple jet of high-pressure steam issuing from E could never drive back a jet of water issuing from D under the same pressure. It was a great step in science to conceive the idea that the absorption of heat which took place at E could furnish a source of energy directly available for doing work. There has been no parallel to this discovery in any analogous direction, and it is difficult to account for the action, On the steam side there is the kinetic motion of the molecules of steam, and on the water side there is the motion of translation of a quantity of water, and the problem is to show a possible method of passing from the one to the other. Now, the steam issuing at E has a velocity many times greater than that of the water forced out at D. The instant that steam is liberated and escapes, the kinetic motion of its particles appears 'under a new form, viz., as a motion of translation, and the velocity of an issuing jet of steam is many times greater than that of a jet of water forced out by the same pressure. If, therefore, the jet of steam could be condensed by an indefinite source of cold after it had fairly got clear of the orifice it would be converted into a fine liquid line, and the velocity with which its molecules were rushing out would not be changed. The motion of heat would be diminished, but the onward motion would remain unimpaired. This liquid line would be moving at such a high velocity that it would pierce any jet of water coming towards it from the boiler, very much as if it were a steel wire forcing its way through the mass. We know of no source of cold competent to produce this result, but what really happens is the same in character though less in degree. The steam, liquefied at E, retains to some extent the higher velocity which it possessed as steam, and on the whole the aggregate energy of the water globules flowing onward at E is greater than that of the water jet coming towards them from D. The latter jet is overpowered and driven back, and a quantity of water from the cistern at A is continually forced into the boiler. As to the velocities with which we have to deal, it appears that if the steam had an actual pressure of six atmospheres the water would issue at a velocity of about 101 feet per second, and the steam at a velocity of about 1,800 feet per second. GiffarcTs Injector. 279 FIG. 141. In dwelling on this subject ttiere is an experiment, easy of performance, which exhibits the effect of fluid pressure in forcing out a jet of liquid, and which recalls the cer- tainty that without the direct agency of heat, the injector would be powerless. The appa- ratus consists of a brass tube, say 4 feet long having a glass beaker at the top. There is a stopcock at the base of the tube, and directly opposite to it is a small open nozzle of the same bore as the stopcock which leads into the base of a glass tube about an inch in diameter. The water in A is maintained at a constant height, and it is found that the water rises in the glass tube until it reaches a level B, which ap- proaches closely to the level of the water in A. The difference depends on the loss of energy by friction and also upon imperfections of the apparatus and the difficulty of adjusting the openings for the water so as to cause the stream which comes from A to corres- pond with that coming from B. Referring again to fig. 140, it will be seen that a pipe marked ' overflow ' leads out from the centre of the instrument ; this pipe communicates with a small chamber in the central channel just below the level of the pinion, and is intended to allow the escape of any surplus water. When the supply of steam is properly ad- justed to the amount of water sucked into the instrument no over- flow takes place, whereas an excess of water or steam will at once give rise to a discharge at the overflow. In the one case the energy imparted to the water is insufficient and part recoils, while in the other case too great a condensation of steam will occur and energy will be dissipated. It is, however, easy to adjust the steam and water regulators so as to avoid any waste. The rise in temperature of the feed-water shows the amount of energy available for doing work, and it is found that the quan- tity of water delivered into the boiler increases as the feed-water itself is supplied in a colder state. Thus, in one case, the tempera- ture of the feed-water before entering the injector was 60, 90, 120, and the number of gallons of water delivered per hour was 280 The Steam Engine. 972, 786, 486 respectively. Tt is a confirmation of the expla- nation that steam at a given pressure will force water into a boiler against a still higher pressure. Thus, steam at 27 Ibs. pres- sure forced water into a boiler where the steam was at 52 Ibs. pressure, the temperature of the feed- water being raised from 92 to 170 during the operation. LINK MOTION FOR REVERSING AN ENGINE. 177. When the piston is near the middle of its stroke in a direct-acting engine the slide-valve will have moved over the steam ports in the manner pointed out in 'fig. 142. The large and small circles represent respectively the paths traced out by the centre of the crank pin and the centre of the eccentric which works the valve; and inasmuch as the slide would not be seen in a sectional drawing it is repeated in a supplemental diagram, where its position in relation to the steam ports is indi cated. The method of reversal is the following : FIG. 142. In the upper diagram the piston is moving to the right and the valve to the left, the piston having advanced so far in its stroke that the valve is returning to cut off the steam. In order, there- fore, to change the motion it is necessary to drive the piston back Link Motion. 281 by admitting steam on the opposite side and by letting out that portion of the steam which is urging it forward. Hence the valve must be moved into the position shown in the lower diagram, which is equivalent to shifting the centre of the eccentric from the position marked A to that marked B. The piston will then return before it has reached the end of the cylinder, or in other words the motion of the engine will have been reversed. It will be seen that the imaginary crank which works the slide is inclined at an angle somewhat greater than 90 to the crank which is connected with the piston, as must be the case where lap and lead are given to the valve. Further, it is appa- rent that the crank of the slide rod is in advance of, or leads, the larger crank in its journey round. The explanation shows that in reversing an engine we must either shift the centre of the eccentric from the position A to the position B, or else we must employ two eccentrics and provide some means of connecting each in turn with the slide-valve. The method of reversal by shifting the eccentric from the position A into the position B was at one time largely employed in marine engines, but it has gradually given place to the reversal by a link motion. That apparatus for reversing an engine has grown with the locomotive engine, and is so convenient and rapid in its action that no other can compare with it The link motion appears under three forms : there is (i) the shifting link, having its concave side towards the axle or crank shaft ; (2) the stationary link, where the curvature is in the opposite direction ; (3) the straight link, which is derived from a com- bination of the two former contrivances. 1. In the shifting link motion two eccentrics are keyed upon the shaft in the positions which we have agreed to call A and B ; the link is an open slotted circular piece, struck with a radius equal to the effective length of each eccentric rod, and having, as before stated, its concavity turned towards the axle or shaft of the engine. The slide rod is connected with a block which moves in the slotted link, whereby the end of the rod is actuated by either of the eccentrics at will. This construction was adopted at an early period, and is known as ' Stephenson's link motion.' 2. The stationary link, which is that shown in the drawing, was 282 The Steam Engine* Locomotive Link Motion. 283 invented by Mr. Gooch, of the Great Western Railway. It will be seen that the link R s is here suspended by an arm b c, so as to be stationary so far as any up-and-down movement is concerned, and that it is circular in form, being struck by a radius equal to D R, whereby also its concavity lies towards the cylinder and away from the axle or shaft of the engine. In the sketch the for- ward eccentric is in operation, and the motion is readily traced from the axle to the slide, which is shown as having partly un- covered the steam port marked A. On pulling the rod H which is in connection with the starting lever, or its equivalent, the bell crank K e L is moved, and the jointed rod D R is brought down by the pull of L M into a lower position, whereby it imparts to the slide the motion due to the back eccentric, and the engine is consequently reversed. 3. A third method is Allan's straight link motion, in which \he link and the valve rod are both shifted in opposite directions at the same time. When the link is shifted it must of necessity be curved towards the eccentric rods, and when the slide rod is jointed as at D and shifted up or down the curvature of the link must be towards the slide, from which it follows that if both the link and the slide rod shift in a vertical plane the concavity and convexity may neutralise each other and a straight link may serve to give the motion. Link motions prove to be rather complicated pieces of mechanism when any attempt is made to analyse them thoroughly, and therefore it may suffice to say that with a stationary link the lead of the slide is maintained constant under all changes in the position of the sliding block, whereas with the shifting link the lead increases a little towards the central position. One advantage of the contrivance consists in the power which it gives to the engineer of regulating the supply of steam admitted into the cylinder. By moving the starting lever or its equivalent into intermediate positions the amount of travel of the valve is reduced at pleasure, for it is evident that no steam can enter the cylinder when the lever is half-way between its extreme positions, and that varying amounts of opening of the steam ports, increasing to the maximum value, will occur when the lever is pushed over by successive steps. We pass on to describe other arrangements of reversing gear 284 The Steam Engine. which are now of considerable practical value, and shall confine the inquiry to certain principal forms, commencing with that patented by/. W. Hackworth, A.D. 1859, No. 2,448. OTHER REVERSING VALVE GEAR. 178. It will be remembered that in working a slide valve by a simple eccentric, the motion is equivalent to that of a crank c P and connecting-rod P Q, the end P being carried round in a circle while the slide s reciprocates in a straight line. FIG. 144. It is clear that a sufficient motion of the valve might be ob- tained if the point P were constrained to move in an inclined oval curve as shown in the diagram, the longer axis of the oval, viz. p/, making an angle with the line c Q. This idea has been at the foundation of the class of inventions now to be considered, for it will be seen that there are many ways of getting such an oval, each of which has its advocates and is well worthy of consideration. 179. It is an elementary fact in geometry that, in the ordi- nary combination of a crank and connecting rod, as used in a direct-acting engine, any point in the connecting rod P Q will, as the crank revolves, describe an oval curve in the plane c P Q. This curve resembles a section of an egg, being rather more pointed at one end than the other, and is approximately an ellipse. In fig. (i) of the annexed diagram, the end Q of the connecting rod P Q is constrained to move along the line A B, pointing to c, Valve Gear. 28 5 and a point R in the connecting rod, selected at pleasure, will de- scribe an oval as shown by the dotted curve. Taking the position of the connecting rod p Q when p c Q is a right angle, it appears that if A B be turned about the point Q so as to take the position L M, or N T, the point Q will, as c P revolves, move up and down the lines L M or N T, as the case may be, and the point R will describe an inclined oval curve such as that which we are seeking to obtain. It appears also that the direction of the longer axis of the ova depends on the direction of the guiding slot in which the point Q moves. It only remains to connect one end of the valve rod with the point describing an oval, taking care that the other end moves in FIG. 145. a straight line perpendicular to c Q, and we shall have a conve- niently arranged valve motion which can be reversed by changing the direction of the guide as in figs. (2) and (3). 1 80. Having premised these introductory observations, we turn to Hackworth's specification, which states that on the main shaft of the engine and side by side with the driving crank there is placed an eccentric pulley, the extreme throw of which is directly opposite the extreme throw of the driving crank, while the throw of the eccentric must exceed the traverse of the valve. 286 The Steam Engine. 1 1 / !/' z ^^->^ I **<. / ^ FIG. 146. Valve Gear. 287 The annexed lecture diagram is taken substantially from that in the specification, c P being the crank which is the equivalent of the eccentric pulley, P Q the eccentric rod, the end Q being con- strained to move in the vertical line c Q, and the steam cylinder being horizontal. c B is the crank of the engine, terminating in the crank pin B, while B D is the connecting rod. The piston is now at one end of its stroke, and it will be seen that c B and c P point in opposite directions in a horizontal line. The valve, with its strap or spindle, is connected with a hori- zontal valve rod T R, jointed to the eccentric rod at the point R, which is preferably chosen so that Q R = -J Q P, or nearly so. When the crank is on the dead centre, as in the diagram, the valve is thrown back by a space on the opposite side of c Q, which is equal to the lap plus the lead. In whatever position the bar A Q may be held it is always capable of oscillating about the end A, and it follows that if c P be rotated about c, the end Q of the eccentric rod P Q will describe a small arc of the circle whose centre is A and radius A Q, which is practically the same as if Q were constrained to move in a straight slot pointing to c. In this state of things the port will not open any farther for steam, but when c P and c B have each made half a revolution the valve will be moved back upon the other steam port by an amount equal to the lap plus the lead, and neither port will open for steam by a greater amount than that due to the lead of the valve. There are different contrivances for shifting the lever A Q, as to which it is easy to arrange a convenient mechanism, and we shall now suppose that A Q is shifted into the position L Q, being still free to oscillate about the end L, which is the new position of A. It follows that during each revolution of c P the point Q will oscillate in the dotted line lm, which is approximately a straight line corresponding to L M in fig. 145, and as this line is inclined to c Q the point R will describe an oval whose longer axis is simi- larly inclined to c Q. In order to make this clear the lever A Q is shown in three positions in a separate diagram, and the corresponding oscillations of the point Q are indicated by the dotted circular arcs. 288 The Steam Engine. It is evident, from what has been premised, that a valve motion is obtained by setting A Q in the position L Q, and it remains for us to show that the engine will be reversed by placing the lever in the position N Q, which is equivalent to causing the point Q to oscillate in the line n t instead of the line Im. Whether / m and n t be actually straight lines, formed by a slot in a block riding on a stud or pin, or whether they be approximate straight lines formed by small arcs of a circle, as in the main dia- gram, is only a question of construction. Both methods are fully set out in the specification, and we shall therefore assume that Im and n t are straight lines. The main diagram shows the piston at the end of its stroke, and the present diagram is intended to show that the crank pin B has moved from B to B' in the forward stroke, at which time the piston will be near its middle position, the valve being open for steam and the piston moving to the right. Conceive now that the line //, in which Q moves, is shifted into the position n t by changing the position of the reversing lever from L Q to N Q. The effect of doing this will be at once to carry the slide to the left hand, thereby opening the team port on the opposite side Valve Gear. 289 of the piston and reversing its motion. In truth the joint of the valve rod marked T in the main diagram will be shifted from ef to e. Inasmuch as the valve is set back by an amount equal to the lap plus the lead when B c P is horizontal, and no motion is im- parted to the valve by shifting the lever A Q into the positions L Q or N Q, it is apparent that the lead remains constant for every position of A Q, whether in the direction marked forward or in that marked backward, and hence, as stated by the inventor, the lead never varies. This is a prominent advantage secured by the forms of valve gear now under consideration. 181. In order to appreciate from a general point of view the value of an oval curve in working a slide valve, the student should refer back to Arts. 103 and 104, where the crank of the eccentric, marked o/ in figs. 78 and 79, is set back so as to make an obtuse angle HO/ with the line of centres, in order to allow for the lap and lead. It follows that when the main crank arrives at a dead point the slide valve will have completed the most rapid part of its motion (which occurs when H op is a right angle), and its velocity will have begun to diminish. But it is just at this moment that the steam port is opening for the entrance of steam into the cylinder, when it is an advantage to quicken the motion of the valve instead of retarding it. It will be found, on applying the oval motion, that the point R, to which the valve rod is attached, is near the apex of the oval when steam is admitted, and that in passing round this apex the valve is shifted rapidly so as to complete the full opening for steam. It is one of the advantages claimed by the inventor that the valve opens quickly when the crank is passing a dead point, or when the engine is on the centre, as engineers express it. It is fully explained in the Elements of Mechanism that an oval curve is the result of combining in a regular manner two motions at right angles to one another, which are of proper amount and properly timed. It is further apparent that the point R is the recipient of two simultaneous movements at right angles to one another, the result of the combination being shown by the form of the oval. Taking one of these movements as occurring in c Q, and the other at right angles to c Q, it will be easy to trace the effect of V 290 The Steam Engine, each upon the valve and to find out when they tend to corroborate or when to neutralise each other. In this manner the valve motion may be subjected to a com- plete analysis. 182. When the principle of a movement, such as that now under discussion, is well understood there will be no difficulty in suggesting modifications of construction. FIG. 148. For example, it is obvious that if the point R in fig. 145 were to reside in p Q produced, as in the annexed diagram, there would be no material change in the character of the ovals traced out by the point R. In fact, the principal difference consists in the power of obtaining an enlarged curve without increasing the length of the crank. As before, let the point Q in the connecting rod p Q be guided in the straight slots marked A B, L M, and N T, when a point R in p Q produced will, as required, trace out the ovals ab, fm, or nt. In a patent of 1876, No. 4,246, Messrs.^ W. and A. Hack- worth described such a modification, and their specification states that by attaching the valve rod to the overhanging end of the eccentric rod there is obtained the advantage of giving a greater travel of the valve with either a smaller eccentric or less amount Valve Gear. 291 of inclination of the changeable path, which has been called / m or n t in the description given above. Indeed, \hefirst claim of invention was obtaining ' increased expansion of steam through connecting the valve to the extreme end of the connecting rod.' It was further claimed that there was an admission ' of a more equal charge of steam at both ends of the cylinder at all grades of expansion.' It is further apparent that the virtual crank of the eccentric may coincide with the main crank instead of being opposed to it, regard being had to the necessary motion of the valve, and we refer to a diagram taken from the specification of a patent granted to \ \ FIG. 149. Mr. F. C. Marshall, the well-known engineer, in 1880, No. 4,185, where such a construction is set forth. The student may also refer to the specification of a patent granted in 1879, No. 2,138, to F. C. Marshall, on the same subject-matter. U 2 292 The Steam Engine. The sketch is taken from the specification No. 4,185, and shows the eccentric rod p Q R having the intermediate point Q attached to the reversing lever A Q, whereby the point Q moves in the small arc of a circle centred at A. The direction of this arc being inclined to the line c Q, and the valve rod being attached to a point R in c Q produced, it follows that the end of the valve rod will describe a small inclined oval curve such as is set out in the diagram. The specification No. 2,138 states that the valve used with the gear therein described { is made dissimilar ended when connected direct to the eccentric rod, having, in the case of a valve with single exhaust opening, two steam openings at the end opposite the gear and one steam opening at that other end, and in the case of a valve with double exhaust openings three or four openings for steam on that end opposite to the gear, and two only at the other end.' This is a combination of an ordinary valve at one end and a gridiron valve at the other end. JOY'S VALVE GEAR. 183. In Joy's valve gear, which has been adopted in some engines on the London and North-Western Railway and elsewhere, and is a most valuable invention, there is no eccentric, but the oval curve is derived from a single combination of linkwork, the direction of the longer axis of the oval being varied by changing the direction of a slotted guide. The first patent was granted in 1879, No. 929, and there have been other subsequent patents. The nature of the invention will be apparent from the diagram, which shows its application in a locomotive engine, c being the centre of the crank shaft, and B the crank pin. The end Q of the connecting rod B Q is constrained to move in the line c Q, while R E is a link jointed at R to the connecting rod, and attached at the end E to an arm or lever D E having a fixed centre of motion at D. Another link s T is jointed at s to R E, and carries at the point N a small sliding block which travels up and down in the curved slotted block / m. The valve rod T v is jointed at T to a point in s T, and at v it Valve Gear. 293 is further attached to the valve spindle. There is provision made for changing the direction of Im when it is required to reverse the engine. The precise arrangement of the working parts will be explained in the next article, the present description being merely introduc- tory. The three principal ovals are marked out by dotted lines. There is first an oval described by the point R, then there is an oval described by the point s, which shows a peculiarity often FIG. 150. observed in the final curve on which we rely, viz. that one half is flatter than the other half. There is finally the curve described by T, which gives the re- quired valve motion. 184. In order to set out Joy's valve gear we proceed according to the rules stated in a short pamphlet written by the inventor, and to which the reader is referred for a more detailed account. Let P Q c be the central line of the cylinder, c B the crank, B Q the connecting rod, P Q the piston rod, cb, cb' the positions of the crank, and b e, b'e those of the connecting rod, when the piston is at half-stroke. Select a point on the connecting rod such that its vertical vibration between the positions be and b'e (which is marked cd on 294 The Steam Engine. Valve Diagrams. 295 the diagram) shall be about equal to c B, being preferably a little in excess of the length of the crank. Let R and z be the extreme pDsitions of the point so selected when the crank is on the dead centres. Produce the vertical cd in both directions, and take a point E in cd produced such that the angle R EZ shall not be in excess of a right angle, being pre- ferably a little less. The link R E connects the points R and E as shown, and the link E D has a fixed centre of motion D at some convenient point in the framework of the engine. Taking the direction of the valve spindle line VT, which is horizontal on the diagram, mark off upon it a space v T on one side of the vertical line dc produced upwards, which is equal to the required lap plus lead. On R E measure R s= cd, and join T s cutting dcv in N. The point N will be the centre of oscillation of a curved link, which, by assuming different inclinations to dcv, causes the reversal of the engine. As the crank goes round, and the connecting rod oscillates, the point N travels up and down the curved link already referred to in the last article, and T describes the oval curve for which we have been seeking. The curved link or slot in which the pin N travels to and fro is indicated by dotted lines in the diagram which correspond to / m and n t in the Hackworth diagram. The curve of the link is a circular arc having T v as a radius. In the diagram the radius of the curve is marked by the line N o, which is equal and parallel to T v, and Mr. Joy states that the opening of the port beyond the amount given as lead is dependent on the amount of angular motion imparted to the curved link. Also "that in this gear the * leads ' and * cuts off' for both ends of the cylinder and for back- ward and forward going will be practically equal, the opening of the ports being also as near as possible equal. VALVE DIAGRAMS. 185. There is yet another matter connected with valves which should not be passed over, and that is the graphical method of representing the motion of a valve, as laid down by Zeuner, who 296 The Steam Engine. has written an elaborate treatise on the subject. We shall confine the inquiry to an elementary explanation of the so-called valve diagram. When the slide valve of an engine is worked by an ordinary eccentric, the motion of the valve is that due to a crank and con- necting rod ; but in practice the length of the eccentric rod is so much greater than that of the crank that we may, as a first approximation, conceive that the eccentric rod remains parallel to itself during the motion. On this supposition the position of the valve during each instant of the stroke may be set out in a simple form of diagram, giving the so-called curve of position of the valve. For example, let c be the centre of the circle AD BE, described by P, the centre of an eccentric pulley. Draw the diameter ACB, and let AB represent the whole travel of the valve. Draw PN perpendicular to AB ; then as P goes round in the circle the position of N will indicate the position of the valve. On AC describe a circle cutting c P in R, and join R A. Then in the triangles c R A, c N p we have c P=C A, FIG. 152. and angle c R A = angle c N p, each being a right angle ; also the angle R c N is common to both triangles, therefore CR=CN. Hence if c P represent the crank of the eccentric pulley, and the construction in the figure be completed, the curve ARC will give the position of N relatively to P at any instant. It follows that as P travels round the circumference of the circle A D B E the two small circles drawn upon A c, B c as dia- meters are the curves of position of the slide valve. Thus when p comes to P' the line c R' represents the distance of the valve from its central position, or more accurately the distance of any point in the valve from the central position of the point in question. If the obliquity of the eccentric rod be taken into account, the curve of position of the valve can be set out in the manner following. Let c P be the crank of the eccentric, and P Q the eccentric Valve Diagrams. 297 lud at any instant. With centre Q and radius Q P describe the circular arc PR, and with centre c and radius CR describe the circular arc R s, cutting c P in s. Then the curve of position of the valve will be ascertained by setting out a sufficient number of points, such as s. It is given roughly by the dotted lines in the FIG. 153. diagram, the small circles indicating, as before, the curve of posi- tion when the obliquity of the eccentric rod is neglected. The student will note that the dotted curve lies inside one small circle and outside the other. There is also a peculiarity in the shape of the curve near the point c, which cannot be shown on the scale of the diagram. 1 86. So much being premised, we pass on to consider the method of setting out in a single diagram the movement of the valve corresponding to any given position of the main crank of the engine. Taking the case of a direct-acting engine, let x x' represent the centre line of the cylinder, and let B c A be the travel of the valve, the small circles being the curves of position as found in Art. 185. Disregard the lead of the valve, and let G E be the direction of the crank of the eccentric, when c B x is that of the main crank. Then c R is the movement of the valve from its central position, and is therefore equal to the lap of the valve. With centre c and radius c R describe the circular arc R Q s ; then c R E is the direction of the crank of the eccentric at admis- sion^ and c s e is the same at cut-off. Also, if any line c Q P be drawn from c it will represent the whole movement of the valve from its middle position, when the crank of the eccentric takes The Steam Engine. the direction c P, and since c Q is equal to the lap of the valve it follows that Q P is the opening of the steam port for the admission of steam. In like manner, while the crank of the eccentric moves through dLD we can set put the points of release and compression. Thus let cr be the inside lap of the valve; then the circular arc rq cor- responds to R Q, and just as P Q shows the opening for steam so/ q shows the opening for exhaust, the lines CL, c/ indicating the direc- tions of the eccentric at the periods of release and compression respectively. As yet nothing has been said about the lead, the object being to explain the principle of construction of the diagram in its sim- plest form, but in the next article the lead will be taken into account. 187. It remains to modify the diagram, so as to make it more convenient for the solution of problems, leaving its general cha- Valve Diagrams. 299 racter untouched. What is really wanted is a method of i ecording the motion of the crank and the travel of the valve in a single diagram. As before, let x x' be the central line of the cylinder, and A B the travel of the valve, and let A B, D d be at right angles. Let c R = lap of valve, RT = lead of valve. Draw TM at right angles to CA and join CM. Then, upon com- parison of this diagram with that in the last article, it is clear that M Compression FIG. 155. the angle MOD represents the angle by which the crank of the eccentric is advanced to allow for the lap and the lead. Hence angle M c D = angle of advance. .Upon CM as diameter describe a circle which which will be one valve circle of the diagram. With centre c and radius c R describe the circular arc m R s. Join c m and produce it to a \ then a is the position of the main crank at admission. Also join c s and produce it to e ; then e is the position of the crank at cut-off. 300 The Steam Engine. In like manner we may deal with the points of release and compression, and trace the period during which the exhaust of steam is continued. For this purpose draw the second valve circle on c N, and with centre c and radius c r, equal to the inside lap, draw the circular arc rqs ; then L is the position of the crank at release and / the same at compression. The respective openings for steam and exhaust at any time are represented by lines such as p Q and / q. The steam port is always large enough to give the full opening as marked, but it often happens that the exhaust port is more contracted relatively, whereby the actual opening may be somewhat less than that set out in the diagram. Ex. i. If the travel of a slide be 4^ inches, outside lap = i inch, inside lap= inch, angle of advance=3o, find the positions of the crank at admission, cut-off, release, and compres- sion. Referring to diagram (i) in fig. 156, we have CD=2j inches FIG. 156. and angle MCD= 30, also CR=I inch, whence the point m is found, and cm a, cse can be drawn. Also cr=J inch, whence c r L, c s I can be drawn, and it will be found that angle AC a 3 36' 44", angle AC e= 123 36' 44", angle A c L = 156 22' 46", angle A c/ = 36 22' 46". Ex. 2. Given outside lap=i inch, lead=-^ inch, and greatest Valve Diagrams. 301 opening of port to steam=i-i^ inch, show that angle of advance =35 9', travel of valve=4| inches, and that cut-off takes place when crank has described an angle 115 51', or at 718 of stroke. Referring to diagram (2), draw a valve circle whose diameter is CQ + MQ = i + ITS = 2 jV inches. With radius c Q = i inch describe the arc m Q s. Draw c R T A such that R T = ^ ; then A is the position of the crank when on the line of centres. Draw c D at right angles to c A ; then M c D is the angle of advance = 35 9' by measurement. Draw c s *, which gives , the position of the crank at the point of compression, and if et be drawn perpendicular to AC produced we have A/=7i8 of the stroke, and angle AC =115 51'. Here it will be necessary to quit our subject for the present. The object of the writer has been to point out the influence which the modern theory of heat has exercised on the practical construction of the steam engine, and to contrast the views entertained under the old and new doctrines. No one can be said to have a knowledge of the principles of mechanics who has not grasped to some extent the philosophy of the dynamical theory of heat, and an endeavour has accordingly been made to put forward, in a simple manner, many elementary propositions which are essential for the comprehending of that ideal heat engine which an engineer should always keep in view as some- thing to be aimed at though it can never be reached. The mechanism and construction of the engine have been touched upon in many important particulars ; the drawings have been collected from various sources, and in particular from dia- grams prepared for the Science and Art Department by C. P. B. Shelley, C.E., and the Author ; and it only remains for the latter to express a hope that the book now completed may prove to some extent useful as a guide to his younger fellow-workers. Examples on Valve Diagrams. Ex. i. The travel of a slide valve is 8| inches, the angle of advance is 35, the outside lap is 2\ inches, and the in- side lap is % inch. Find greatest opening to steam, lead, and point of cut-off. Ans. Greatest opening = 2^ inches ; lead = inch ; cut-off at ^ of stroke. 302 The Steam Engine. Ex. 2. Given travel of valve = 5 inches, outside lap = f inch, inside lap = \ inch, angle of advance = 20, prove that the position of crank is at admission 2 30' before line of centres cut-off 142 30 after release 167 40 ,, compression 332 20 ,, Ex. 3. An engine has steam and exhaust ports each 3 inches wide, also inside lap = \ inch, outside lap = f inch. Find travel of valve when the porl just opens fully to exhaust ; find also the angle of advance when lead = inch. Ans. Travel = 6| inches ; angle of advance =15 37'. Ex. 4. Given width of steam port = 2 '5, opening to steam =i '5, outside lead ='25, opening to exhaust = 2 -5, travel of valve = 5, no inside lap, find outside lap and angle of advance, all the measurements being in inches. Ans. Lap = I inch, angle of advance = 30. Ex. 5. Given travel of valve = 4 inches, angle of admission = 3^, cut-off at f stroke, release at '95 of stroke, prove that lead = ^ inch, angle of advance = 39 30', outside lap= 1*176 inch, inside lap= '4728 inch ; also that angle of crank at cut-off = 104 29' release = 154 10 ,, .compression = 306 49 Ex. 6. Given travel of valve = 4 inches, outside lap = i|- inch, inside lap = f inch, angle of advance= 40, prove that lead= -16 inch, also that angle of crank at admission... = 5 46', period of stroke = '0025 cut-off = 105 46 ='6359 release = 150 48 = -9364 ,, ,, compression = 309 12 ,, ='1839 Ex. 7. Given travel of valve = 4 '6 inches, cut-off at of stroke, exhaust opens when piston is 2 V from end of stroke, angle of advance 30, prove that outside lap = '903 inch outside lead = '247 inch inside lap = '277 inch inside lead = -873 inch Ex. 8. Given cut-off at ^ stroke, outside lap=i inch, lead=^ inch, prove that angle of advance = 36 35' 21", travel of valve = 4 inches. Ex. 9. Given cut-off at '6 of stroke, compression at '85 of stroke, angle of admission = 4, width of steam port=i inch, and greatest opening of steam ports = | their area, prove that travel of valve = 4^ inches, angle of advance = 41^, lead ='128 inch, outside lap =1-438 inch, inside lap = -17 inch, angle of release= 143, angle of compression = 45^ or 134^, period of stroke at release = '9, period of stroke at admission = '0013. SUPPLEMENT ON GAS ENGINES. I. THERE are two numerical results connected with the theory of heat which are of the highest practical value. They are given in the Text Book, and are the following : (1) By an expenditure of 772 foot-pounds of mechanical work one thermal unit of heat is produced. (2) In converting a quantity of heat into work the greatest amount of work which can by any possibility be obtained from a heat engine T ~ x total heat, where T and / are the temperatures on Fahrenheit's scale between which the heat engine (supposed to be perfect) is working. In applying these laws in the construction and management of heat engines, we begin by increasing the elasticity or pressure of a quantity of gas, such as air or steam, by heating it. Such heated gas is then passed into a cylinder and is expanded so as to do work. After a portion of its heat has been converted into work, the residue is expelled from the cylinder at a lower temperature. The first operation, then, is to obtain a supply of heated gas, and here we encounter losses at every stage. Thus in burning coal for the generation of steam there is a continual escape of heat by reason of the imperfections of the furnace, and by the discharge of heated products up the chimney. Again, there are difficulties to be overcome in forcing heat 304 Gas Engines. through the shell of the boiler, and in conveying it into each individual particle of the water or steam. It would appear then to be a manifest advantage if the heat could be applied directly to the elastic gas without the intervention of any furnace or boiler. An idea or suggestion so obvious as this can hardly have failed to attract those who are in search of improvements, and, accordingly, numerous attempts have been made from time to time, in order to obtain an elastic agent by setting fire to a mixture of coal gas and air within the very cylin- der in which the piston of an engine is working. The neat deve- loped in the gas during the act of burning would be thus compelled to supply a source of energy in the closest contact with the moving piece to which such energy is to be transferred. No action can be more direct than this, and, in truth, it is the very thing which for centuries past has been done in a gun. When gunpowder is fired in a closed chamber the temperature of the gases rises to a little above 2,000 C., and in the case of guncotton the temperature of the gases is about twice that of gun- powder (Noble). The enclosed gases at these temperatures exert an enormous pressure, amounting in the case of guncotton of specific gravity 55 to as much as 70 tons per square inch, whereas with gun- powder of specific gravity i and fired in a closed vessel, the pressure would reach 43 tons per square inch (Noble). Pressures such as these, generated suddenly in a closed vessel, cannot be dealt with in the present state of our knowledge, except for the discharge of projectiles. They are not suitable for driving the piston of an engine. In order to adapt heated gas to the performance of useful work in an engine, we require (i) that its pressure shall not rise too suddenly, (2) that the intensity of the pressure shall be kept within reasonable limits. These conditions can be fulfilled during the burning of coal gas or of some form of carburetted hydrogen when mixed with air. 2. Explosive mixtures of gas and air. Simple hydrogen explodes when mixed with oxygen in sufficient proportions. Thus 2 volumes hydrogen \ give a louder explosion than any other I volume oxygen j proportionate Explosive Mixtures. 305 It is a fundamental fact in chemistry that water is composed of hydrogen and oxygen in the above proportion. For the purposes of an engine coal gas or some form of car- buretted hydrogen is preferable to pure hydrogen, and we may p Difference for 9 = 8-8 1 7=-? x 8-81=6-852. Whence pressure at 300 F. = 60-39 I DS - + 6-852 Ibs. = 67*24 Ibs. per sq. in. Ex. 2. Find the temperature of saturated steam at a pressure of 150 Ibs. per square inch. Here a pressure of 145-8 Ibs. indicates 356 F. 163-3 365 F. Difference for 17-5 9 F. 4-2 2-16 F. or, temperature at 150 Ibs. = 35 6+ 2-16 F. = 358-I6 F. Ex. 3. Steam is blowing off at a pressure of 75 Ibs. by the gauge ; the barometer stands at ,29-5 in. What is the tempera- ture in the boiler ? Taking the weight of a cubic inch of mercury at ordinary temperatures as -49 Ibs., we have weight of 29-5 in. of mercury = 14*455 Ibs. and absolute pressure of steam = 89-455 Ibs. Whence it is easy to show that required temperature = 31 9*65 F. Ex. 4. The temperature of the condenser is 110 F. The vacuum is 25-3 in. by the gauge ; the barometer stands at 29 in. What part of the pressure in the condenser is due to the presence of air? Ans. -539 Ibs. Specific Volume. 7 5. Specific volume. In the Text-book the term specific whtmevfas employed as synonymous with relative volume, that is, the ratio of the volume of a quantity of steam to that of the water from which it is generated. This was done because reference was then being made to some experiments of Fairbairn wherein that parti- cular meaning was assigned to the term in question. In the present chapter the volume of one unit of weight of any substance under consideration, whether water, air, or steam, will be called the specific volume of the substance, and will be represented by the symbol v. And inasmuch as the volume depends on the external pressure/ supported by each unit of surface, and also on the temperature /, we have or the specific volume is in general a function of the temperature and pressure. It is to be noted that in the present article t is expressed in absolute measure. For example, in the case of air, which is treated as a perfect gas, the fundamental equation is pv = Rt. In the case of steam, by which we shall always intend dry saturated steam, unless the contrary be expressed, there is no simple fundamental relation between/, /andz> ; and it is necessary there- fore to have recourse to empirical formulae, or to tables which give experimental results. 6. Heat expended in the evaporation of water. We have now to examine the expenditure of heat when converting water into steam, as well as the measure of the external and internal work done during the operation. As to the heat expended in changing .water into steam, there are two cases to be considered. (1) The water may be converted into dry saturated steam. (2) The steam generated may be moist steam, or may contain a definite amount of water in the form of fine globules mechanically suspended. For case (i). There is the formula by Regnault, viz. H = 1 09 1 7 4- '305 (/- 32) = a + mt, suppose, 8 The Steam Engine. where / is expressed in Fahrenheit's scale, and H and L are expressed in British thermal units. The formula for H is fundamental, and the student may refer to Table L, where he will find a column of values of H in thermal units, for intervals of temperature marking 9 F. Another column gives values of h' , where h' is the heat expended in raising i Ib. of water from 32 to /. We take the values in this column from a table calculated by Rankine, the results being adapted for thermal units. Another column gives the values of L for intervals of 9 F. It appears also from the definitions of H, L, and h 1 that we have the fundamental equations : H = L + h', or, L = H h'. It will be understood that the values of L are deduced imme- diately from those for H and h'. Thus, if it be required to find the heat expended in evaporating water at a temperature / mt dry saturated steam at a tem- perature / : Let h Q be the heat required to raise ilb. of water from 32 F. to /o, Then, total heat of formation=H h . Ex. i. The absolute pressure of steam in a boiler is 95 Ibs. per square inch ; find the total heat of formation from water at 32 F. By Table L Pressure 101-9 l s - corresponds to 329 F. 89-88 320 F. Difference for 12/02 Ibs. is 9 F. .'. 5 'i 2 Ibs. corresponds to 3*83 F. or, /= 323-53; whence, H = 1091-7 + -305 (323-83 32) = 1180-71 the answer being expressed in British thermal units, or B.T.TJ. as it is often written. In case (2). Let the steam be moist, so that for each i Ib. of Examples. 9 water raised to temperature /, only x Ibs. have been evaporated, we have Total heat of formation h' + XL where h' is the heat required to raise ilb. of water from 32 F to /. If the water be originally at temperature / we have Total heat of formation = h' h Q + x L. Ex. 2. The absolute pressure of steam in a boiler being 95 Ibs. per square inch, and the steam containing 10 per cent, of water, find the total heat of evaporation from water at 110 F. By Ex. i we see that Total heat of formation from noF. = 118071 (no 32) = 110271 Latent heat of evaporation 110271 (323-83 no) = 888-88 /. heat required = 213-83 + ^ x 888-88 = 1013-82 B.T.U. Ex. 3. Dry steam is generated in a boiler at 90 Ibs. absolute pressure from water at 65 F. What percentage of heat will be saved by a feed-water heater which raises the temperature of the water to 200 F. ? Here temperature of steam = 320-09 F. (by table). Heat of formation = 1091-7 + -305 (320*09 32; 33 = 1146-57 B.T.U. Here the heater saves 200 65, or 135 thermal units, and, required percentage = -?- x 100 = 1178 Ex. 4. One pound of coal (A) evaporated 9 Ibs. of water at 324 F. from water at 60 F., while i Ib. of coal (B) evaporated 8^ Ibs. of water at 350 F. from water at 104 F. The steam produced by coal (A) had 10 per cent, of water, while that from coal (B) had 5 per cent, of water : compare the evaporative powers of (A) a d (B) under these conditions. IO The Steam Engine. 9. 10 = 1063-89 B.T.U. For (A), heat of formation = 26*4 + x 115276 For (B), heat of formation = - (350 104) + x 1116-69 IOO IOO = 1073-16 B.T.U. o x io6r8o Required ratio = 8 . 5XI073 - l6 = i'49 or, (A) is nearly 5 per cent, more effective than (B). Ex. 5. In a trial of an engine making 20 revolutions per minute, and indicating 75-H.R, the absolute pressure in the boiler was 62 Ibs. per square inch ; the weight of steam and water passing into the cylinder per stroke was '52 lb., of which -013 Ib. was priming water; the weight of steam condensed in the jackets was *o6 lb. per stroke ; and the temperature of the feed-water was 85-5 F. Find the number of thermal units taken from the boiler per stroke, and the efficiency of the engine, neglecting any change in the specific heat of water. Temperature of steam at 62 Ibs. = 294-64 H = 1091-7 + -305 (294-64 - 32) - 53-5 = 1118*31 B.T.U. L = 966 "J (294-64 212) = 908*15 B.T.U. # = 294*64 85*5 = 209-14 B.T.U. Weight of steam passing into the cylinder per stroke = -52 - -013 = -507 lb. Total heat per stroke = "507 H + -06 L -f -013 h' = 624*19 B.T.U. Useful work per stroke = 75 X 33 = 80-14 Efficiency = ^ =-1284. 7. Internal and external work. The next point is to measure the internal and external work done during the total or partial evaporation of a mass of water into steam. Internal and External Work. II It has been explained that in the case of a perfect gas there exists the relation Where, however, the substance is found in two physical states in the same space, as in a mixture of steam and water, the pressure p will depend on the temperature, and we shall have / = * CO- In such a case, it will be necessary to introduce a new variable in order to determine v. Thus, let a- = volume of ilb. of water = '016 cub. ft. very nearly, v = specific volume of dry steam, v' = volume of a mixture of steam and water. Also, let the mixture in question contain x parts of steam and (i x) parts of water. Then v' = vx + = =2o*qc;lbs. per pound of steam J 10454 Pounds of condensation water 1 _ 33-24 per H.P. per minute J ~ :0 ' 55 X 60 = 11-39 IDS - n. Specific heat. It has been stated that quantities of heat are measured either in thermal units or \VL foot-pounds and that the specific heat of water at its maximum density = i, in thermal units, or = 772, in foot-pounds. In the former treatise we found that Specific heat of air at a constant pressure = "238 = k. constant volume = -169 = c. In this case the unit is a thermal unit, and we shall adopt the notation c f and c v to express the specific heat of gas, such as air or steam, at a constant pressure and constant volume respectively, when expressed in foot-pounds. Thus, for air, c> = 772 x -238 = 183-7 foot-pounds. c v = 772 x -169 = 130-4 foot-pounds. 12. We may deduce the values of c f and c v from the general equation, as follows : Let a quantity of air have a pressure /, temperature /, and volume v, and let dp, dt^ dv be the corresponding increments of /, /, v when the air receives a small increase of heat, viz. dq. Taking the general equation dq ^u + 2 > A E =/ Then, external work done = p (# 2 v^ = area AD. /. External work done = R (/ 2 /,) = 53'2(>2- Also internal work = c v (/ 2 /i) = area E F, suppose. . , internal work _ (c, R) (/ 2 -^) external work R (/ 2 /j) Fio. 4- = SL=5 R = 2-45 nearly, _ area A D "~ area E F* 15. Specific heat of steam. Let dry saturated steam be superheated and expand as a perfect gas. For air p v = R /. For steam p ?/ = R' / ; R But^r = -622 v' f _. R _ 53' 2 _Q 622 '622 Also experiments give Cp = 370*56 foot-pounds, whence c v = 285-03 foot-pounds. It follows that ^ = 1-3, whence the adiabatic curve for the expansion of superheated steam is 1 6. Expansion curves of air and steam. At this stage it may be convenient to examine with some particularity the expansion curves of air and steam under different conditions. There are certain primary forms, which obtain more or less Expansion Curves. 2 1 approximately in practice, and which are important as giving the curved outline of one side of the diagram of work done in a heat engine. At present we only point out what would happen if such diagrams were obtainable. As to the notation employed, let v be the volume of a unit of weight of the substance at the pressure /. The unit of pressure is always taken to be one pound, unless the contrary be expressed, and c has different values in the several cases. (1) There is hyberbolic expansion, given by the equation pv = c, which follows from Boyle's law, and was assumed by Watt as regulating approximately the expansion of steam in an engine. As we have seen, this equation represents a hyperbola whose asymptotes are at right angles. (2) In the case of heated air doing work behind the piston of an air engine, there is the curve of adiabatic expansion, following from the laws of Boyle and Charles and given by the equation This curve has been drawn out roughly in the Text-book, and resembles the hyperbola in its general character. (3) In the case of superheated steam raised to such a tem- perature that it does not fall to the point of saturation during the expansion we have the curve / v^ = c. (4) In the case of dry saturated steam, supposed to vary its heat so as to remain always dry and saturated, an approximate form of the curve of expansion is given by an equation adopted by Rankine, viz. p v* =f. It will be understood that this equation for the expansion curve is empirical. It is not deducible from any general law, but is the result of laborious computation. (5) The curve of adiabatic expansion of saturated steam is considered to be given approximately by the equation 22 The Steam Engine. Ex. 6. The volume of i Ib. of saturated steam at a pressure of 60 -4 Ibs. per sq. in. is 6-992 cubic feet. Find its pressure after expanding five times : (i) According to the law of expansion of saturated steam ; (2) according to the adiabatic law ; (3) accord- ing to the law for a perfect gas. (i) Here ^ == i' and ^ 1 =60-4 .\/ 2 = 12-08 (i) * =10-924 \j/ (2) / 2 * a i'i = t l v l / 2 \ '135 \vhence / 2 = 1 2-08 ( J = 9-7218 (3) \, whence / 2 = 60-4 Qj = 7-4534. 17. Area of the expansion curve. Inasmuch as all the above formulae are comprised in the general equation P p v n when x = a, Then/! a = ra'- n , *>, .*. area = cb 1 ~ ". n i . If n = i, the formula fails, and in that case, = f^ = area = { Taking the integral between the limits x = a, and x = b, we have Area = c{ log b log a] =c log -. 1 8. Work done during the expansion of a gas. It remains to find an expression for the work done in a heat engine where the * expansion proceeds according to the =C. Let the piston move through OM = a, under the constant pressure / b and suppose the gas to expand ac- cording to the above law along the curve A B. Let o M = a, o N = b, MA =/!, N B =/ 2 > Then work done =/i a + M FIG. 6. n i n i b n i Let = I ; then work done = J ( /** . - -A_ I . ^ r I r( i) n i J w = mean pressure, we have work done =-p m b ; In the particular case of hyperbolic expansion, where the general formula fails, we have, 24 The Steam Engine. Work done =jp l a + c log -, an a .*. Work done pia < i+ log - I be the mean pressure, then work done p m b ; orp m = *( i + log rj. In applying these formula, it may be convenient to adopt the notation that a gas whose pressure is p Y and volume, v l expands to a pressure / 2 an< 3 volume # 2 . In such a case work done = / 2 ?; 2 I 1 +lg ^}i Referring to the Text-book, we find work done in hyperbolic expansion of steam This is the same formula as that investigated above, for b = /, /!, = - = r, and A /is the same as v l =z^ E. /. Work done =^ lZ/lE | i +log E j It must be borne in mind that a back pressure (which ca usually detracts from the efficiency of the engine. Then work lost by back pressure =/^ 2 = x p^v.^ /2 .'. Work done=/2^2 S I 4 log r ^ I , L /a J or =/ t ^ (i+logr-^j. L /a J Expansion Curves. 25 19. In applying the formula in the last article to the hyper- bolic expansion of steam, the successive steps in the calculation are brought together, and we shall verify the figures in the first line of the following table, leaving the rest as an exercise for the student. Data. Initial pressure of steam = 100 Ibs. per sq. in. (absolute). Back pressure = 3 Ibs. Temperature of feed- water = 104 F. Steam supposed to be dry at end of stroke. In complete expansion the steam expands to back pressure. Effective Pounds of steam per H.P. per hour Heat ex- Rate of expansion work per Ib. steam in B.T.U. Cylinder Jacket Equivalent steam from feed -water Total pended per H.P. per minute Efficiency r = 3 155-3 16-5 1-18 94 I7H4 322-S I 3 2 r = 6 194-2 13-2 1-49 1-19 I4-39 266-1 161 r = 9 2I3-8 12 'O 1-64 1-31 !3'3i 245-9 174 r - 12 219-8 117 173 i'38 13-08 241-4 177 Complete 23I-3 II'I 2-19 174 12-84 237-4 180 In the case of jacket steam it is to be remembered that the steam after condensation is taken as returned to the boiler in the form of water at boiler temperature. It follows that the heat expended in the jacket is less than the total heat of formation by the amount of heat required to raise the temperature of the feed- water to that of the boiler. Hence the amount of steam con- sumed in the jacket must be reduced so as to correspond with the amount which would have been produced from the heat given up in the jacket, if the same had been supplied directly to the feed- water. As before (Art. 10) the letter P will indicate pressure in pounds per square foot. Taking the formula, work done = P 2 v*n A> Vf b *2> be the initial and final values of/, v, t. Then external work done in expansion = Pi v i~P\ v \ ^ i n =R/ 2 , /,>, zsR/! ; R ~~ * /. External work= i n Also, internal work = c v (/ 2 A)* * 7 ~ i, then I is negative. If I be positive, we infer that additional heat must be supplied, in order that internal work may be done upon the air, whereas ii c c 23 The Steam Engine. 1 be negative, we infer that the internal work is in excess, and that a demand of some sort may be made upon it. In order to obtain a clear insight into the matter, it will be convenient to refer to the following diagrams, where A A' is the boundary line of the diagram of external work, and D D' is the boundary line of the diagram of internal work, whereby A A' B' B represents external work done, and D D' B' B represents internal work. FIG. 7. (1) Let n be < i, then I is positive, and must be added to E, whence the shaded area A A' D' D in diagram (i) represents the whole heat required in order to obtain the expansion curve pv n = C. (2) Let n be > i, but < y. Then - is negative, and is a proper fraction ; E or, the external work is greater than the internal work, /.*., the area A A' B B' is greater than the area D D' B' B, whence the shaded area in diagram (2) represents the amount of heat which must be supplied to produce the expansion curve. (3) Let n be > i and > y. Then - is negative, and is an improper fraction. E It follows that the shaded area in diagram (3) now represents an amount of heat, which must be taken away in order to pro- duce the expansion curve. Expansion Curves. 29 (4) If n = y = i '408, we have E = I, which is the well- known case of adiabatic expansion, where the external work is derived from the intrinsic energy of the air, and no heat passes in or out by the ordinary processes of conduction or radiation. 21. We are now in a position to determine generally whether heat must be imparted or taken away in order to produce any given expansion curve of air. In the diagram let P A represent the curve of isothermal or hyperbolic expansion, and P B the adiabatic curve. For PA we have/z/ = which in this case is the adiabatic curve for the mixture. This appears to show that combustion goes on during expansion. c c 2 go The Steam Engine. 22. We may put the heat expended in another form without the aid of a diagram, as follows : Internal work = c v (/ 2 A) y-l Then heat imparted = internal work + external work = A *a-/i p i + external work. y-i If heat imparted = o, we have External work= P\ V \~P* V * , y-l which accords with the formula in Art. 17. 23. Absolute scale of temperature. Hitherto, in all ther- mometers for measuring temperature, the nature of the substance employed, such as alcohol, mercury, or air, necessitates different scales for each degree of temperature one scale for alcohol, another for mercury, and so on. It is, however, possible to suggest a method of graduation of a thermometer which shall be inde- pendent of the substance employed, and this was first done by Sir W. Thomson. It happens that the scale so selected is very nearly coincident with that of an ordinary air thermometer, but it is proper to point out that in the present state of our knowledge it is not practically available. Referring to the diagram of energy in a heat engine, let o N = v, N A =/, and let x be the temperature of the gas at the point A. Let A s, B R be two adiabatics, A B, D c two isothermals. Also let H = heat taken in expanding through A B at tempera- ture T, h = heat rejected in compressing through c D at tem- perature /. Absolute Temperature. Then 5 = * (Art. 57, Text-book.) Also area A BCD = H h = u (i -Y If T / = i, we have area A B c D= ?. T TT That is to say, - represents the y work done in a perfect engine work- ing between the temperatures T and T i, and taking in a quantity of heat H at the temperature T. In like manner, if we draw another isothermal E F, and take D c E F to represent the diagram of energy in a perfect engine work- ing between the temperatures / and t i, we have area DCEF =-. FIG. 9. - ; hence if A D, D F, &c., each But it has been shown that ? T correspond to intervals of i degree of absolute temperature, the respective amounts of work done, or the areas A B c D, DCEF, &c., will be severally equal to each other. The equation j- = also shows that the colder the refrigerator the greater the proportion of the heat, H, which the engine can convert into work. It is only when the temperature of the re- frigerator sinks to the zero point that the engine can convert the whole heat into work, and it thus becomes evident that the abso- lute zero of temperature may be defined with reference to the performance of a perfect engine capable of converting all the heat existing in a substance into work. In the Text-book we obtained the zero of so-called ' absolute temperature ' by supposing that the law of contraction of gases by 32 The Steam Engine. cooling obtained until the limit when the gas was deprived of the whole of its heat. We are now, as stated by Mr. Maxwell, enabled to reckon temperature from a zero point defined on thermodynamic principles independently of the properties of a selected substance. What we say is that in a reversible or perfect engine the ratio of the heat received to the heat rejected is that of the numbers expressing on an absolute scale the temperatures of the source of heat and of the refrigerator, or in other words : The absolute values of two temperatures are to one another in the proportion of the heat taken in to the heat rejected in a perfect engine working with a source of heat at the higher temperature, and a refrigerator at the lower temperature. An absolute scale so selected differs but slightly from that of the ordinary air thermometer. 24. Whatever be the temperature of a substance, it can always be brought to a temperature / by adiabatic expansion or com- pression, and can then be brought to a state represented by the position of D by taking in or giving out heat at a temperature /, and if this operation be performed the ratio _ will be constant for every position of D in the curve A s. The ratio - is termed the entropy of the substance, because it indicates a quality of the substance with reference to the transformation of heat into work, and the word isentropic is used as synonomous with adiabatic. It is usual to represent the entropy of a substance by the symbol <. Where < is constant the transformation of heat into work can only occur in one way viz., by adiabatic expansion. Also when a substance has completed a reversible cycle d = o, or the entropy is the same as it was originally. We pass on to discuss the method of tabulating the volume of a given weight (say, one pound) of steam at any given tem- perature and pressure, and it may be useful in the first instance to call attention to the manner in which the density of gas is estimated. 25. Comparison of densities. In comparing the densities Density of Steam. 33 of gases, we take the density of dry air at a given pressure and tem- perature as unity, and proceed as follows, adopting the well-known formulae p = pp (i -i- at) for dry air, / = p p' (i + a/) for gas (A). Then = /'. = - = D, suppose P P Thus the density of dry air = i oxygen =.1-1056 hydrogen = -0692 nitrogen = -9713 chlorine = 2*4502 and so for other gases. According to this measure, we have Density of dry saturated steam = "622. The density of dry saturated steam may also be determined from the following empirical formulae, the first of which is due to Fairbairn : 389 w =* '41 + (Fairbairn) where / is given in pounds per sq. inch. Clausius has obtained a formula for computing the density of steam at different temperatures, from which the following results are arrived at : o C. 50 C. 100 C. 150 C. 200 C. D 622 631 645 666 698 26. We proceed to apply the principles laid down in previous articles in order to calculate the density of saturated steam at a given volume and pressure. In the case of saturated steam, the isothermal lines are horizontal, and the quantity of heat required 34 The Steam Engine. to evaporate ilb. of water into steam at a given temperature is known from Regnault's formula. 27. Calculation of the density of steam. Let L be the latent heat of evaporation at temperature t. Also, let tr cubic feet of water become v cubic feet of steam at a pressure/ and temperature /. Let o x, oy be lines of volume and pressure such that o N=V, A N =/. Draw A B, DC, two isothermals, at temperatures / and t dt, re- spectively. Further, draw the adiabatics A s, B R through A and B. Let q be the quantity of heat absorbed in passing from A to B ; then AB is horizontal and repre- sents the increase of volume in passing from A to B. It follows that FIG. 10. v-I 307-5 + 460 = 2 341 753'5 = -311 Whence the actual efficiency is 48 per cent of the theoretical efficiency, the more accurate result being 48-4 per cent. There remains a comparison between the amount of steam as shown by the indicator diagrams and that already estimated as having passed through the engine during each stroke. The mean indicator diagram is set out in fig. n, and we pur- pose examining the high pressure diagram with a view of estimating the quantity of steam which has been condensed into water at admission, so far as the data at our disposal enable us to infer this amount. Take the point B where the steam is cut off, and where p 64 Ibs. The volume of steam at this point is taken to be 2*961 cubic Trials of Engines. 39 feet, this number being deduced from the dimensions of the high pressure cylinder, and of the clearance space. PRESS. IN BOILER 76 IBS. SCALE FIG. ii. Then weight of i cubic foot of dry saturated steam at pressure 64 Ibs. = "1506 Ibs. by the table. /. weight of 2-961 cubic feet dry steam = 2-961 x '1506 = -4392 Ibs. Let M C = weight of steam existing in the cylinder and clear- ance space when compression begins. The diagram shows that, when exhaust commences, the pressure of steam = 15-2 Ibs. ; whereas, when compression com- mences, the pressure of steam =15 Ibs., and its volume is ^ of the volume when exhaust begins. Hence we have, very approximately, P +M C ), assuming that the steam re- mains in the same condition during exhaust 40 The Steam Engine. (1672-150)= 150 = 150 x -60768 g = 150 x -60768 lb 1522 Hence ^ + M P + M C = -60768 + '0599 = -6675 Ibs. It follows that the weight of dry saturated steam in the cylinder at the part of the stroke corresponding to B, as revealed by the indicator diagram, = -4392 Ibs., whereas the weight of dry saturated steam in the cylinder, as deduced from the air pump discharge, = -6675 Ibs. The inference is that ('6675 -4392) or -2283 Ibs. of steam have somehow disappeared as steam, and can, therefore, only exist as water. It is usual to employ the expression ' dryness fraction ' to indicate the ratio of the amount of dry saturated steam to the amount of steam and water in any given quantity of wet steam. In the present example we have dryness fraction = - = "66 6675 Drawing the horizontal line AB, produce it to c such that AB : AC =4392 : 6675 j tnen A "R = dryness fraction AC = 66 Or A B = 2 B C, which result, as given by the data on which the estimation has proceeded, exhibits a very important deficiency of working steam. It must, however, be remembered that there already exists in the form of water M, + water in clearance space. Trials of Engines. 41 But M P = -02430 water in clearance space = M C '02995 or M p + water in clearance space = -02430 + -02995 = -05425 Hence weight of steam not accounted for after admission = -2283 --0543 = -1740 Ibs. It is also inferred that Indicated work per stroke in high 1 = S3 . 49 thermal units pressure cylinder J Same in low pressure cylinder = 60*06 Total work per stroke = 113*55 Consumption of steam per I.H.P. per hour = 14-84 Ibs. 29. The most recent recorded trial has been that carried out by a committee of the Inst Mech. Eng., an account of which is published in the Proceedings for May, 1889. The vessel was the ss. 'Meteor,' of about 2,000 tons, and 2,000 H.P. The engines were triple expansion. The object of the trial was to measure the coal consumed, the water converted into steam, and the indicated horse-power, and so far the trial was interesting, although the observations afforded little scope for theoretical conclusions. Data. Voyage from Leith to London : Time occupied by trial = 17 hrs. 6 mins. Mean speed of vessel =14-6 knots per hr. No. of revolutions = 73,650 No. per minute =71-78 Mean temperature of boiler steam =.^363 F. Mean pressure = 145*2 Ibs. (absolute) Mean admission pressure = 134*4 Ibs. Mean atmospheric pressure =14-9 Ibs. Supply of feed- water = 5 12,150 Ibs. Supply per hour = 29,860 Ibs. Supply per revolution = 6 -93 Ibs. Temperature of feed = 163*1 F. 42 The Steam Engine. Quantity of feed-water per I.H.P. per hour = 14-98 Ibs. Heat given to feed-water per I.H.P. per minute = 265-6 thermal units. The temperature of water in hot well was not observed, but it was estimated that the temperature of the condensed steam was 120 F., and the feed- water was heated up to 163 F. after leaving the hot well. There were two boilers, each double ended, the total number of furnaces being 12. The boilers were of steel, and had a length of 16 ft, with a diameter of 13^ ft. The calorific value of the coal was estimated at 12,790 thermal units per Ib. The coal used amounted to 68,693 Ibs. Actual consumption per hour = 4,005 Ibg. Consumption per I.H.P. per hour = 2-01 Ibs. Temperature of waste gases = 791 F. Pressure shown by water gauge = $ inch. The rate of evaporation was 7-46 Ibs. water per i Ib. coal, from feed-water at 163 F. to steam at 363 F. The mean effective pressures in the different cylinders (in pounds per square inch) were the following : Cylinder Top Bottom Mean High pressure . Intermediate . . Low pressure . 6o'io 20-47 I2'22 56-82 18-54 12-55 58-46 19-50 12-38 The corresponding indicated horse-powers being High pressure = 662 Intermediate = 507 Low pressure =825 Total I.H.P. = 1,994 The actual heat received by the feed-water per minute was estimated at 528,700 thermal units, which is 62 per cent, of the total nominal calorific value of the fuel burnt per minute viz., 853,900 thermal units. Trials of Engines. 43 Taking the engine as perfect, and working between the 363 F. and 120 F., we have Theoretical efficiency = |43 = 295 But heat received by feed- water per minute = 528,700 thermal units. .'. Theoretical work done = 150,9665* thermal units. Heat converted into work = 85,240 Actual efficiency = -161, or actual efficiency = 54/6 per cent, of that given out by a perfect engine working between the same temperatures. By careful measurement of the indicator diagrams the follow- ing results have been obtained : Weight of steam per revolution Percentage of total feed Percentage in jackets or not accounted for High pressure cylinder after cut off 5*31 77-1 22'9 Intermediate cylinder, 22 Ibs. above atmo- sphere 5- 5 6 80'2 I9-8 Low pressure cylinder, 4 Ibs. below atmo- sphere 5 '22 75'3 217 In the discussion on the paper the President called attention to the fact that the table showed more steam in the second cylinder than there had been in the first, and asked for an ex- planation, but none could be given. It appeared, however, that in the high-pressure diagram the steam was measured at about 57 per cent, of the stroke, and in the other two cylinders at about 82 per cent, thereof. D D 44 The Steam Engine. TABLE I. From Dixorfs table (in inches of mercury)^ true for latitude of Dublin. Temp. F. Press, in Ibs. per sq. in. dp H L h' Thermal units Thermal units Thermal units 32 0889 00416 1091-7 1091*7 41 1263 00490 1094-4 1085-4 9 5 1771 00662 1097-2 1079-2 18 59 2455 00883 1099-9 1073-0 27 68 336l 01164 1102*7 10-367 36 77 4551 01520 1105-4 1060*4 45 86 6097 01963 IIO8'2 1054-2 54-o 95 8084 . 02507 1 1 10*9 1047-9 63*0 104 i -06 1 03176 1113-7 1041-6 72*0 H3 1-380 03983 1116*4 1035-4 8ro 122 1-778 04944 1119-1 1029*1 90*1 J 3i 2-270 06100 1 1 2 I '9 I022'8 99*1 140 2-876 0745 6 IT 24*6 1016*5 108*1 149 3-612 09044 1127-4 IOIO*2 117*1 158 4"54 10906 1130-1 1004*0 126*2 I6 7 5-575 13050 1132*9 9977 135-2 I 7 6 6-853 I55H H35' 6 991*4 I44-3 I8 5 8-367 18317 1138*4 985-1 153-3 194 10-15 21572 1141-1 978*7 162*4 203 12*25 25222 ii43'9 972*4 i7i-5 212 14-69 29278 1146*6 966*1 180*5 221 i7'52 33833 i *49'3 959-7 189*6 Tables. 45 Temp. F. Press, in Ibs. per sq. in. dp H Thermal units L h' Thermal units Thermal units 198*7 230 2078 38944 1152*1 953'4 239 24*53 44611 1154-8 947*0 207-8 248 28-81 50944 1157-6 940*7 216*9 257 3370 57889 1 160*3 934*3 226*0 266 39'23 65444 1163*1 927*9 235*2 275 45'48 73778 1165*8 921-5 244*3 284 52*5I 82833 1168-6 915-0 253*5 293 60-39 92722 1171-3 908-6 2627 302 69*20 1-03389 1174*1 902*2 271*9 3H 79-00 1-14889 1176-8 8957 281-1 320 89-88 1*27222 1179*5 889-3 290*3 329 101*9 1-40667 1182-3 882-8 299'5 338 115-2 1*55000 1185*0 876-3 308-8 347 129-8 1*70000 1187*8 869-8 318-0 356 145*8 1*86111 1190-5 863-2 3273 365 I 63'3 2-03889 U93'3 8567 336-6 374 182-5 2*22222 1196*0 850*1 345*9 383 203-3 2-4IIII 1198-8 843-5 355*2 392 225-9 2'6lIII 1201*5 837-0 364*5 401 250*3 2-82778 1204*2 830-4 373*9 410 276-8 3'0555 6 1207*0 823-7 383*3 419 305'3 3-28889 1209*7 817*1 392*6 428 336*o 3*41111 1212-5 810-4 402*0 N.B. The entries in Dixon are multiplied by '4912, to convert inches of mercury into pressure in Ibs. per sq. inch, i.e. by the weight of a cubic inch of mercury at 32 F. 4(3 The Steam Engine. "5" ^ 00 vo to o CO VO VO ON VO M VO CO 00 CO O VO i CO M M 4>. *^h ON ^f. ON co O O to t^ CO vo co .f^ to oo vo VO O t> P-. M ON vo vO vo CO vo to CO to to Tl- M CO ^t- co IO M M M vo VO vo VO vo vo VO vo VO VO vo vo 00 oo vo vo VO to \o Cv| oo M to CO ON 00 to O & ON 04 M oo to N oo oo t-^ N PH 00 ON to CO M % ON to CO oo to Th VO CO OO t>. CO J> r^. .I s -* VO Tf CO M 0* VO vo vo VO VO vo vo vo vo vo SO vo CO M M ON M Tf ON O ON S; vo ON to ON co to oo CO ON 00 rj- N CO CO VO !> ON i>. w , O !>. vo vo VO CO CO N J 1 .-3 O CO VO CO vo VO t>. to &> ON VO 00 M OJ ^J- to 10 VO vo co ^"j C3 *sj" to ON ^t" CO ^^ 00 co IO M 3 ^ CO ^ to vo 00 N to ON to co oo O N CO O to co *^i ri- ^ ^ CO CO H 00 10 O to CO t^ "^3 O r^ M O 00 VO CO M ON VO CO M CO CO CO CO a N CJ M H M M M . CO CO to CO t^ ^ Tf to CO ON ON to Tf VO to a p CO CO 10 to 10 M to O g M '^(. ^ ON Q M M OO rj- T^ O H CO * M * ON CO 00 CO CO to T}- co CO 04 O) CO CO la g to to to o to O to O w to C-J o to o x^^ to N O ON |i CO CO CO 04 N M M M M M Tables. 47 VO vo 00 N M ^ Os vo M N M 00 ? vo ON 00 M vo vo o CO M vo OO to O M VO to to ON VO N M t^. OO Os t^. to VO 00 M to VO CO to o OO CO 8" vo Tt- cf N ON 'o ON to VO ON ON t^. ON CO VO to o M M M O ON 00 vo vo vo to N M o ON oo vo VO VO VO vo vo vo vo VO VO VO VO vo vo Ti- M Os to VO Os oo 00 vo M t^ VO ON oo CO g. to N VO to vo 04 Tj- vo oo TJ- rj- rj- vo ON H T^- 00 M vo n VO VO ON to CO ^ Os M ON J^. ^ o ^. '-4. 00 T^ to VO to VO ON ON vo oo to CO to oo vo M VO to to ON o o VO OO ON ON VO M t-l I * O ON 00 vo vo vo to O) M o ON oo vo vo vo vo vo vo vo VO VO VO vo VO VO vo M 00 M ON M o vo vo CO rt- to VO oo ON s M to VO M M OO t-i M vo O oo to o vo M CT vo M < o M 8 M rf vo ON rf M M oo ON ^ to ^ 2. vo O oo M o vo o ON OO M J^ ON oo H vo M a 1 M vo to Tj- to vo ON r^- oo t-^ CO OO CO o VO If) VO 1^ 00 to Os VO vo f^. vo M ON f^. M to H M M N e* CO vo 00 M CO hi CO VO 00 o O vo o *-f- VO vo VO M d vO co CO vo ^- ON VO O ON ON vo VO M vo to Os ON M M M M CO M 8" o VO M o M M vo VO H ON to to ON vo o o M to o to CO O r^ CO o oo vo oo vo 00 ON N CJ\ M vo N ON H ON & vo* vo N to M M to ON 00 to VO 5. vo M o 8 vo T o to M VO M M O M 00 VO n- CO M H 48 Ttie Steam Engine* TABLE III. Temp. F. k k r 400 8748 4*373 375 9-130 4'i37 350 9'504 3-888 325 9^49 3-652 300 10-440 3-416 275 i'933 3-164 250 11-456 2-904 225 12*082 2-648 200 12-690 2-366 175 13-381 2-076 150 14-138 1-772 125 1 5 '3o 1-432 IOO 15-881 1-099 PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE LONDON BY THE SAME AUTHOR. THE ELEMENTS OF MECHANISM, DESIGNED FOR STUDENTS OF APPLIED MECHANICS. New Edition, re-written and enlarged, with 342 Woodcuts. Crown 8vo. 340 pp. Price 6s. THE PRINCIPLES OF MECHANICS. New Edition, re written and enlarged. With 253 Woodcuts. Crown 8vo. Price 6s. A MANUAL OF MECHANICS: AN ELEMENTARY TEXT-BOOK FOR STUDENTS OF APPLIED MECHANICS. With 138 Illustrations and Diagrams, and 141 Examples taken from the Science Department Examination Papers, with Answers. Fcp. 8vo. Price 2s. 6d. London: LONGMANS, GREEN, & CO. 39 Paternoster Row. SUPPLEMENT ON GAS ENGINES. Reprinted, with some Additions from the ' Text-Book on the Steam Engine.' Crown 8vo. Price 2s. 6d. London: CROSBY LOCKWOOD & SON, 7 Stationers' Hall Court, Ludgate Hill. AN ABSTRACT OF REPORTED CASES RELATING TO LETTERS PATENT FOR INVENTIONS. Vol. I. A New and enlarged Edition, containing the cases before the Privy Council and other applications relating to Patents, and bringing down the Reports to the end of the year 1883. 8vo. pp. 634. Price 30^. PATENT PRACTICE BEFORE THE COMPTROLLER & THE LAW OFFICERS, With an ABSTRACT OF REPORTED CASES, brought down to July 1889. 8vo. pp. 88. Price 4^. Also, APPENDIX I., with Cases to end of 1892. Price 2s. 6d. London : SWEET & MAXWELL, 3 Chancery Lane. PRACTICAL BOOKS FOR ENGINEERS. THE PRACTICAL ENGINEER'S HANDBOOK. Com- prising a Treatise on Modern Engines and Boilers, Marine, Loco- motive and Stationary. And containing a large collection of Rules and Practical Data relating to recent Practice in Designing and Con- structing all kinds of Engines, Boilers, and other Engineering work. By WALTER S. HUTTON, Civil and Mechanical Engineer, Author of "The Works' Manager's Hand-book for Engineers," &c. With upwards of 370 Illustrations. Fourth Edition, Revised with Addi- tions. Medium 8vo, nearly 500 pp., price i8s. Strongly bound. " We have kept it at hand for several weeks, referring to it as occasion arose, and we have not on a single occasion consulted its pages without finding the information of which we were in quest." Athenaeum. THE WORKS' MANAGER'S HANDBOOK OF MO- DERN RULES, TABLES, AND DATA. For Engineers, Millwrights, and Boiler Makers ; Tool Makers, Machinists, and Metal Worker, ; Iron and Brass Founders, &c. By W. S. HUTTON, Civil and Mechanical Engineer, Author of " The Practical Engineer's Handbook." Fifth Edition, carefully Revised, with Additions. In one handsome Volume, medium 8vo, price 155. Strongly bound. "The author treats every subject from the point of view of one who has collected Engineer* STEAM BOILER CONSTRUCTION. A Practical Hand- book for Engineers, Boiler- Makers, and Steam Users. Containing a large Collection of Rules and Data relating to Recent Practice in the Design, Construction, and Working of all Kinds of Stationary, Loco- motive, and Marine Steam-Boilers. By WALTER S. HUTTON, C.E., Author of " The Works' Manager's Handbook " &c. With upwards of 300 Illustrations. Second Edition, medium 8vo. i8s. cloth. "There has long been room for a modern handbook on steam boilers ; there is not thnt room now, because Mr. Hutton has filled it. It is a thoroughly practical book for those who are occupied in the construction, design, selection, or use of boilers." Engineer. THE PRACTICAL MECHANIC'S WORKSHOP COM- PANION. Comprising a great variety of the most useful Rules and Formulae in Mechanical Science, with numerous Tables of Prac- tical Data and Calculated Results for Facilitating Mechanical Opera- tions. By WILLIAM TEMPLETON. Seventeenth Edition, Revised, Modernised, and considerably Enlarged by WALTER S. HUTTON, C.E., Author of "The Works' Manager's Handbook." Fcp. 8vo. nearly 500 pp. , with 8 Plates and upwards of 250 Illustrative Dia- grams. Price 6s. Strongly bound. "In its modernised form Hutton's ' Templeton ' should have a wide sale, for it contains much valuable information which the mechanic will often find of use, and not a few tables and notes which he might look for in vain in other works." English Mechanic. _ CROSBY LOCKWOOD & SON, 7 Stationers' Hall Court, London, E.G. STATIONERS' HALL COURT, LONDON, E.G. CROSBY LOCKWOOD & SON'S Catalans of ^F Scientific, Technical and Industrial Books. PAGE MECHANICAL ENGINEERING . 1 CIVIL ENGINEERING .... 10 MARINE ENGINEERING. Ac. . 17 MINING & METALLURGY . . 19 COLLIERY WORKING. &c. . . 21 ELECTRICITY 28 ARCHITECTURE & BUILDING . 26 SANITATION & WATER SUPPLY 28 PAGE CARPENTRY A TIMBER . . 29 DECORATIVE ARTS 31 NATURAL SCIENCE 83 CHEMICAL MANUFACTURES . 34 INDUSTRIAL ARTS 38 COMMERCE. TABLES. Ac. . . 41 AGRICULTURE A GARDENING- 43 AUCTIONEERING. VALUING. Ao. 46 LAW A MISCELLANEOUS. . . 47 MECHANICAL ENGINEERING, ETC. THE MECHANICAL ENGINEER'S POCKET-BOOK. Comprising Tables, Formulae, Rules, and Data : A Handy Book of Reference for Daily Use in Engineering Practice. By D. KINNEAR CLARK, M. Inst. C.E., Fifth Edition, thoroughly Revised and Enlarged. By H. H. P. POWLES, A.M.I C.E., M.I.M.E. Small 8vo, 700 pp., bound in flexible Leather Cover, rounded corners. [Just Published. Net 6/O SUMMARY OF CONTENTS : MATHEMATICAL TABLES. MEASUREMENT OF SURFACES AND SOLIDS. ENGLISH WEIGHTS AND MEASURES. FRENCH METRIC WEIGHTS AND MEASURES. FOREIGN WEIGHTS AND MEASURES. MONEYS. SPECIFIC GRAVITY, WEIGHT, AND VOLUME. MANUFACTURED METALS. STEEL PIPES. BOLTS AND NUTS. SUNDRY ARTICLES IN WROUGHT AND CAST IRON, COPPER, BRASS, LEAD, TIN, ZINC. STRENGTH OF MATERIALS. STRENGTH OF TIMBER, STRENGTH OF CAST IRON. STRENGTH OF WROUGHT IRON. STRENGTH OF STEEL. TENSILE STRENGTH OF COPPER, LEAD, &c. RESISTANCE OF STONES AND OTHER BUILDING MATERIALS. RIVETED JOINTS IN BOILER PLATES. BOILER SHELLS. WIRE ROPES AND HEMP ROPES. CHAINS AND CHAIN CABLES. FRAMING. HARDNESS OF METALS, ALLOYS, AND STONES. LABOUR OF ANIMALS. MECHANICAL PRINCIPLES. GRAVITY AND FALL OF BODIES. ACCELERATING AND RETARDING FORCES. MILL GEARING, SHAFTING, &c. TRANSMISSION OF MOTIVE POWER. HEAT. COMBUSTION : FUELS. w ARMING, VENTILATION, COOKING STOVES. STEAM. STEAM ENGINES AND BOILERS. RAILWAYS. TRAMWAYS. STEAM SHIPS. PUMPING STEAM ENGINES AND PUMPS. COAL GAS, GAS ENGINES, &c. AIR IN MOTION. COMPRESSED AIR, HOT AIR ENGINES. WATER POWER. SPEED OF CUTTING TOOLS. COLOURS. ELECTRICAL ENGINEERING. " Mr. Clark manifests what is an innate perception of what Is likely to be useful In a pocket- book, and he is really unrivalled in the art of condensation. It is very difficult to hit upon any mechanical engineering subject concerning which this work supplies no information, and the excellent index at the end adds to its utility. In one word, it is an exceedingly handy and efficient tool, possessed of which the engineer will be saved many a wearisome calculation, or yet more wearisome hunt through various text-books and treatises, and, as such, we can heartily recommend It to our readers." The Engineer, " It would be found difficult to compress more matter within a similar compass, or produce a book of 700 pages which should be more compact or convenient for pocket reference. . . . Will be appreciated by mechanical engineers of all classes," Prattical Engineer. CROSBY LOCK WOOD & SON'S CATALOGUE. MR. MUTTON'S PRACTICAL HANDBOOKS. THE WORKS' MANAGER'S HANDBOOK, Comprising Modern Rules, Tables, and Data. For Engineers, Millwrights, and Boiler Makers ; Tool Makers, Machinists, and Metal Workers ; Iron and Brass Founders, &c. By W. S. MUTTON, Civil and Mechanical Engineer, Author of "The Practical Engineer's Handbook." Sixth Edition, carefully Revised, and Enlarged. In One handsome Volume, medium 8vo, strongly bound ............. 15/0 The A uthor having compiled Rules and Data for his own use in a great variety of modern engineering work, and having found his notes extremely useful, decided to publish them revised to date believing that a practical work, suited to the DAILY REQUIREMENTS OF MODERN ENGINEERS, would be favourably received. " The author treats every subject from the point of view of one who has collected workshop notes for application in workshop practice, rather than from the theoretical or literary aspect. The volume contains a great deal of that kind of information which is gained only by practical experience, and is seldom written in books." The Engineer, June 5, 1885. " Of this edition we may repeat the appreciative remarks we made upon the first and third. Since the appearance of the latter very considerable modifications have been made, although the total number of pages remains almost the same. It is a very useful rollfction nf rules, tables, and workshop and drawing office data." The Engineer, May 10, 1895. (Second/Notice.) " The volume Is an exceedingly useful one, brimful with engineer's notes, memoranda, and rules, and well worthy of being on every mechanical engineer's bookshelf." Mechanical World. " The information is precisely that likely to be required in practice. . . . The work forms a desirable addition to the library not only of the works' manager, but of any one connected with general engineering." Mining Journal. " Brimful of useful information, stated In a concise form, Mr. Hutton's books have met a pressing want among engineers. The book must prove extremely useful to every practical man possessing a copy." Practical Engineer. THE PRACTICAL ENGINEER'S HANDBOOK. Comprising a Treatise on Modern Engines and Boilers, Marine, Locomotive, and Stationary. And containing a large collection of Rules and Practical Data relating to Recent Practice in Designing and Constructing all kinds of Engines, Boilers, and other Engineering work. The whole constituting a com- prehensive Key to the Board of Trade and other Examinations for Certificates of Competency in Modern Mechanical Engineering. By WALTER S. HUTTON, Civil and Mechanical Engineer, Author of " The Works' Manager's Handbook for Engineers," &c. With upwards of 420 Illustrations. Sixth Edition. Revised and Enlarged. Medium 8vo, nearly 560 pp., strongly bound. 18/O 9GT~ This Work is designed as a companion to the Author's "WORKS' MANAGER'S HANDBOOK." It possesses many new and original features, and con- tains, like its predecessor, a quantity of matter not originally intended for publication but collected by the A uthor for his own use in the construction of a great variety of MODERN ENGINEERING WORK. The information is given in a condensed and concise form, and is illustrated by upwards of 420 Engravings ; and comprises a quantity of tabulated matter of great value to all engaged in designing, constructing, or estimating for ENGINES, BOILERS, and OTHER ENGINEERING WORK. "We have kept it at handler several weeks, referring to it as occasion arose, and we have not on a single occasion consulted its pages without finding the information of which we were in quest." Athenaum. " A thoroughly good practical handbook, which no engineer can go through without learning something that will be of service to him." Marine Engineer. " An excellent hook of reference for engineers, and a valuable text-book for students of engineering. " Scotsman. "This valuable manual embodies the results and experience of the leading authorities on mechanical engineering." Building News. "The author has collected together a surprising quantity of rules and practical data, and has shown much judgment in the selections he has made. . . . There is no doubt that this book is one of the most useful of its kind published, and will be a very popular compendium." Engineer. " A mass of information set down in simple language, and in such a form that it can be easily referred to at anv time. The matter is uniformly good and well chosen, and is greatly elucidated by the illusTations. The book will find its way on to most engineers' shelves, where it will rank s one of the most useful books of reference." Practical Engineer. " Full of useful information, and should be found on the office shelf of all practical engineer! English Mechanic. MECHANICAL ENGINEERING, MR. HUTTON S PRACTICAL 5TEAM BOILER CONSTRUCTION, A Practical Handbook for Engineers, Boiler-Makers, and Steam Users. Containing a large Collection of Rules and Data relating to Recent Practice in the Design, Construction, and Working of all Kinds of Stationary, Loco- motive, and Marine Steam-Boilers. By WALTER S. HUTTON, Civil and Mechanical Engineer, Author of " The Works' Manager's Handbook," "The Practical Engineer's Handbook," &c. With upwards of 500 Illustrations. Fourth Edition, carefully Revised, and Enlarged. Medium 8vo, over 680 pages, cloth, strongly bound. [Just Published. 1 8/O B^F* THIS WORK is issued in continuation of the Series of Handbooks written by the Author, viz. .-"THE WORKS' MANAGER'S HANDBOOK " and " THE PRACTICAL ENGINEER'S HANDBOOK," which are so highly appreciated by engineers for the practical nature of their information ; and is consequently written in the same style as those works. The Author believes that the concentration, in a convenient form for easy reference, of such a large amount of thoroughly practical information on Steam- Boilers, will be of considerable service to these for whom it is intended, and he trusts the book may be deemed worthy of as favourable a reception as has been accorded to its predecessors. "One of the best, If not the best, books on boilers that has ever been published. The Infor- mation is of the right kind, in a simple and accessible form. So far as generation is concerned, this Is, undoubtedly, the standard book on steam practice." Electrical Review. " Every detail, both in boiler design and management, is clearly laid before the reader. The volume shows that boiler construction has been reduced to the condition of one of the most exact sciences ; and such a book is of the utmost value to the fin de siecle Engineer and Works Manager." Marine Engineer. " There has long been room for a modem handbook on steam boilers ; there is not that room now, because Mr. Huttpn has filled it. It is a thoroughly practical book for those who are occupied ia the construction, design, selection, or use of boilers." Engineer. " The book is of so important and comprehensive a character that it must find its way into the libraries of every one interested in boiler using or boiler manufacture if they wish to be thoroughly informed. We strongly recommend the book for the intrinsic value of its contents." Machinery Market. PRACTICAL MECHANICS' WORKSHOP COMPANION. Comprising a great variety of the most useful Rules and Formulae in Mechanical Science, with numerous Tables of Practical Data and Calculated Results for Facilitating Mechanical Operations. By WILLIAM TEMPLETON, Author of " The Engineer's Practical Assistant," &c., &c. Eighteenth Edition, Revised* Modernised, and considerably Enlarged by WALTER S. HUTTON, C.E., Author of "The Works' Manager's Handbook," "The Practical Engineer's Hand- book," &c. Fcap. 8vo, nearly 500 pp., with 8 Plates and upwards of 250 Illus- trative Diagrams, strongly bound for workshop or pocket wear and tear . 6/O " In its modernised form Hutton's ' Templeton ' should have a wide sale, for it contains much valuable information which the mechanic will often find of use, and not a few tables and notes which he might look for in vain in other works. This modernised edition will be appreciated by all who have learned to value the original editions of 'Templeton.'" English Mechanic. " It has met with great success in the engineering workshop, as we can testify ; and there are a great many men who, in a great measure, owe their rise in life to this little book." Building News. " This familiar text-bookwell known to all mechanics and engineers Is of essential service to the every-day requirements of engineers, millwrights, and the various trades connected with engineering and budding. The new modernised edition is worth its weight in gold."uitdine News. (Second Notice.) " This well-known and largely-used book contains information, brought up to date, of the sort so useful to the foreman and draughtsman. So much fresh information has been introduced as to constitute it practically a new book. It will be largely used in the office and workshop." Mechanical World. "The publishers wisely entrusted the task of revision of this popular, valuable, and useful. book to Mr. Hutton, than whom a more competent man they could not have found." Iron. ENGINEER'S AND MILLWRIGHT'S ASSISTANT, A Collection of Useful Tables, Rules, and Data. By WILLIAM TEMPLETON Eighth Edition, with Additions. i8mo, cloth ..... 2/8 "Occupies a foremost place among books of this kind. A more suitable presen apprentice to any of the mechanical trades could not possibly be made." Building News. " A deservedly popular work. It should be in the ' drawer ' of every mechanic."-. of every mechanic."-.ge^A 4 CROSBY LOCK WOOD * SON'S CATALOGUE. THE MECHANICAL ENGINEER'S REFERENCE BOOK, For Machine and Boiler Construction. In Two Parts. Part I. GENERAL ENGINEERING DATA. Part II. BOILER CONSTRUCTION. With 51 Plates and numerous Illustrations. By NELSON FOLEY, M.I.N.A. Second Edition, Revised throughout and much Enlarged. Folio, half-bound . Net 3 3s. PART I. MEASURES. CIRCUMFERENCES AND AREAS, &c., SQUARES, CUBES, FOURTH POWERS. SQUARE AND CUBE ROOTS. SURFACE OF TUBES. RECIPROCALS. LOGARITHMS. MENSURATION. SPECIFIC GRAVITIES AND WEIGHTS. WORK AND POWER. HEAT. COMBUSTION. EXPANSION AND CONTRACTION. EXPANSION OF GASES. STEAM. STATIC FORCES. GRAVITATION AND ATTRACTION. MOTION AND COMPUTATION OF RESULTING FORCES. ACCUMULATED WORK. CENTRE AND RADIUS OF GYRATION. MOMENT OF INERTIA. CENTRE OF OSCILLATION. ELECTRICITY. STRENGTH OF MATERIALS. ELASTICITY. TEST SHEETS OF METALS. FRICTION. TRANSMISSION OF POWER. FLOW OF LIQUIDS. FLOW OF GASES. AIR PUMPS, SURFACE CONDENSERS, &c. SPEED OF STEAMSHIPS. PROPELLERS. CUTTING TOOLS. FLANGES. COPPER SHEETS AND TUBES. SCREWS, NUTS, BOLT HEADS, &c. VARIOUS RECIPES AND MISCELLANEOUS MATTER. WITH DIAGRAMS FOR VALVE-GEAR, BELTING AND ROPES, DISCHARGE AND SUCTION PIPES, SCREW PROPELLERS, AND COPPER PIPES. PART II. TREATING OF POWER OF BOILERS. USEFUL RATIOS. NOTES ON CONSTRUCTION. CYLINDRICAL BOILER SHELLS. CIRCULAR FURNACES. FLAT PLATES. STAYS. GIRDERS. SCREWS. HYDRAULIC TESTS. RIVETING. BOILER SETTING, CHIMNEYS, AND MOUNTINGS. FUELS, &c. EXAMPLES OF BOILERS AND SPEEDS OF STEAMSHIPS. NOMINAL AND NORMAL HORSE POWER. WITH DIAGRAMS FOR ALL BOILER CALCULATIONS AND DRAWINGS OF MANY VARIETIES OF BOILERS. " Mr. Foley is well fitted to compile such a work. The diagrams are a great feature of the work. It may be stated that Mr. Fpley has produced a volume which will undoubtedly fulfil the desire of the author and become indispensable to all mechanical engineers." Marine Engineer. " We have carefully examined this work, and pronounce it a most excellent reference book for the use of marine engineers." Journal of American Society of Naval Engineers. TEXT-BOOK ON THE STEAM ENGINE. With a Supplement on GAS ENGINES and PART II. on HEAT ENGINES. By T. M. GOODEVE, M.A., Barrister-at-Law, Professor of Mechanics at the Royal College of Science, London ; Author of " The Principles of Mechanics," " The Elements of Mechanism, "&c. Fourteenth Edition. Crown 8vo, cloth . 6/O " Professor Goodeve has given us a treatise on the steam engine, which will bear comparison with anything written by Huxley or Maxwell, and we can awaid it no higher praise." Engineer. " Mr. Goodeve's text-book is a work of which every young engineer should possess himself." Mining journal. ON GAS ENGINES, With Appendix describing a Recent Engine with Tube Igniter. By T. M. GOODEVE, M.A. Crown 8vo, cloth 2/6 " Like all Mr. Goodeve's writings, the present is no exception in point of general excellence. It is a valuable little volume." Mechanical World. GAS AND OIL ENGINE MANAGEMENT. A Practical Guide for Users and Attendants, being Notes on Selection, Construction, and Management. By M. Powis BALE, M.I M.E., A.M.I.C.E. Author of " Woodworking Machinery," &c. Crown 8vo, cloth. [Just Published. Net 3/6 THE GAS-ENGINE HANDBOOK. A Manual of Useful Information for the Designer and the Engineer. By E. W. ROBERTS, M.E. With Forty Full-page Engravings. Small Fcap. 8vo, leather. Net 8/6 A TREATISE ON STEAM BOILERS. Their Strength, Construction, and Economical Working. By R. WILSON, C.E. Fifth Edition. i2mo, cloth 6/O "The best treatise that has ever been published on steam boilers." Engineer. THE MECHANICAL ENGINEER'S COMPANION. Of Areas, Circumferences, Decimal Equivalents, in inches and feet, millimetres, squares, cubes, roots, &c. ; Strength of Bolts, Weight of Iron, &c. ; Weights, Measures, and other Data. Also Practical Rules for Engine Proportions. By R. EDWARDS, M.Inst.C.E. Fcap. 8vo, cloth. 3/6 "A very useful little volume. It contains many tables, classified data and memoranda generally useful to engineers." Engineer. "What it professes to be, ' a handy office companion,' giving In a succinct form a variety of information likely to be required by mechanical engineers in their everyday office woik."Na(me. MECHANICAL ENGINEERING, A HANDBOOK ON THE STEAM ENGINE. With especial Reference to Small and Medium-sized Engines. For the Use of Engine Makers, Mechanical Draughtsmen, Engineering Students, and users of Steam Power. By HERMAN HAEDER, C.E. Translated from the German with additions and alterations, by H, H. P. POWLES, A.M.I.C.E., M.I.M.E. Third Edition. Revised. With nearly 1,100 Illustrations. Crown 8vo, cloth Net 7/6 " A perfect encyclopaedia of the steam engine and its details, and one which must take a per- manent place in English drawing-offices and workshops." A Foreman Pattern-maker. " This is an excellent book, and should be in the hands of all who are interested In the con- struction and design of medium-sized stationary engines. ... A careful study of its contents and the arrangement of the sections leads to the conclusion that there is probably no other book like It in this country. The volume aims at showing the results of practical experience, and it certainly may claim a complete achievement of this idea." Nature. ' There can be no question as to its value. We cordially commend it to all concerned in the design and construction of the steam engine." Mechanical World. BOILER AND FACTORY CHIMNEYS. Their Draught-Power and Stability. With a chapter on Lightning Conductors. By ROBERT WILSON, A.I.C.E., Author of " A Treatise on Steam Boilers," &c. Crown 8vo, cloth 3/6 " A valuable contribution to the literature of scientific building." The Builder. BOILER MAKER'S READY RECKONER & ASSISTANT. With Examples of Practical Geometry and Templating, for the Use of Platers, Smiths, and Riveters. By JOHN COURTNEY, Edited by D. K. CLARK, M.I. C.E. Fourth Edition, 480 pp., with 140 Illustrations. Fcap. 8vo, half- bound 7/O " No workman or apprentice should be without this book." Iron Trade Circular, REFRIGERATION, COLD STORAGE, & ICE-MAKING: A Practical Treatise on the Art and Science of Refrigeration. By A. J. WALLIS-TAYLER, A.M.Inst.C.E., Author of " Refrigerating and Ice- Making Machinery." 600 pp., with 360 Illustrations. Medium 8vo, cloth. Net "J 5/O "The author has to be congratulated on the completion and production of such an impor- tant work and it cannot fail to have a large body of readers, for it leaves out nothing that would in any way be of value to those interested in the subject." Steamship " No one whose duty it is to handle the mammoth preservi can afford to be without this valuable book." Glasgow Herald. . . oth preserving installations of these latter days THE POCKET BOOK OF REFRIGERATION AND ICE- MAKINQ. By A. J. WALLIS-TAYLER, A.M.Inst.C.E. Author of " Refrigerating and Ice- making Machinery," &c. Third Edition, Enlarged. Small Crown 8vo, cloth. [Just Published. Net 3/6 REFRIGERATING & ICE-MAKING MACHINERY. A Descriptive Treatise for the Use of Persons Employing Refrigerating and Ice-Making Installations, and others. By A. J. WALLIS-TAYLER, A.-M. Inst. C.E. Third Edition, Enlarged. Crown 8vo, cloth . . 7/6 "Practical, explicit, and profusely illustrated." Glasgow Herald. " We recommend the book, which gives the cost of various systems and illustrations showing details of parts of machinery and general arrangements of complete in-jtallations." Builder. " May be recommended as a useful description of the machinery, the processes, and of the facts, figures, and tabulated physics of refrigerating. It is one of the best compilations on the subject. "Engineer. ENGINEERING ESTIMATES, COSTS, AND ACCOUNTS. A Guide to Commercial Engineering. With numerous examples of Estimates and Costs of Millwright Work, Miscellaneous Productions, Steam Engines and Steam Boilers ; and a Section on the Preparation of Costs Accounts. By A GENERAL MANAGER. Second Edition. 8vo, cloth ..... 1 2/O " This is an excellent and very useful book, covering subject-matter In constant requisition In every factory and workshop. . . . The book is invaluable, not only to the young engineer, but also to the estimate department of every works." Builder. " We accord the work unqualified praise. The Information Is given In a plain, straightforward manner, and bears throughout evidence of the Intimate practical acquaintance of the author with every phase of commercial engineering." Mechanical World. 6 CROSBY LOCKWOOD & SON'S CATALOGUE. THE MECHANICAL HANDLING OF MATERIALS. A Comprehensive Treatise on Lifting and Conveying Machinery and Appliances. By G. F. ZIMMEK, Consulting Engineer. Super Royal 8vo, with over 200 Illustrations. [/ the Press. Price about 25/O net. HOISTING MACHINERY. An Elementary Treatise on. Including the Elements of Crane Construction and Descriptions of the Various Types of Cranes in Use. By JOSEPH HORNER, A.M I.M.E., Author of ''Pattern-Making," and other Works. Crown 8vo, with 215 Illustrations, including Folding Plates, cloth. Net 716 AERIAL OR WIRE-ROPE TRAMWAYS. Their Construction and Management. By A. J.WALLIS-TAYLER, A.M.Inst.C.E. With 81 Illustrations. Crown 8vo, cloth 7/6 " An excellent volume, and a very good exposition of the various systems of rope transmission n use, and gives as well not a little valuable information about their working, repair, and manage ment We can safely recommend it as a useful general treatise on the subject." Engineer. MOTOR CARS OR POWER-CARRIAGES FOR COMMON ROADS. By A. J. WALLIS-TAYLER, A.M.Inst.C.E. 212 pp., with 76 Illustrations. Crown 8vo, cloth 4/6 " A work that an engineer thinking of turning his attention to motor-carriage work, would do well to read as a preliminary to starting operations." Engineering. PLATING AND BOILER MAKING. A Practical Handbook for Workshop Operations. By JOSEPH G. HORNER, A.M.I.M.E. 380 pp. with 338 Illustrations. Crown 8vo, cloth . . 7/6 " This work is characterised by that evidence of close acquaintance with workshop methods which will render the book exceedingly acceptable to the practical hand. We have no hesitation in commending the work as a serviceable and practical handbook on a subject which has not hitherto received much attention from those qualified to deal with it in a satisfactory manner." Mechanical World. PATTERN MAKING. Embracing the .Main Types ot Engineering Construction, and including Gearing, Engine Work, Sheaves and Pulleys, Pipes and Columns, Screws, Machine Parts, Pumps and Cocks, the Moulding of Patterns in Loam and Greensand, Weight of Castings, &c. By J. G. HORNER, A.M.I.M.E. Third Edition, Enlarged. With 486 Illustrations. Crown 8vo, cloth. . Net 7/6 " A well-written technical guide, evidently written by a man who understands and has prac- tised what he has written about. . . . We cordially recommend it to engineering students, young ourneymen, and others desirous of being initiated into the mysteries of pattern-making." Builder. "An excellent -vade mecum for the apprentice who desires to become master of his trade." English Mechanic, MECHANICAL ENGINEERING TERMS (Lockwood's Dictionary of). Embracing those current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turning, Smiths', and Boiler Shops, &c. Com- prising upwards of 6,000 Definitions. Edited by J. G. HORNER, A.M.I.M.E. Third Edition, Revised, with Additions. Crown 8vo, cloth . . Net 7/6 "Just the sort of handy dictionary required by the various trades engaged in mechanical en- 'Ineering. The practical engineering pupil will find the book of great value in his studies, and every I'jreman engineer and mechanic should have a copy." Building News. TOOTHED GEARING. A Practical Handbook for Offices and Workshops. By J. HORNER, A.M.I.M.E. Second Edition, with a new Chapter on Recent Practice. With 184 Illustra- tions. Crown 8vo, cloth. [Just Published. 6/O " We give the book our unqualified praise for its thoroughness ot treatment, and recommend to all interested as the most practical book on the subject yet written." Mechanical World. FIRES, FIRE-ENGINES, AND FIRE BRIGADES. With a History of Fire-Engines, their Construction, Use, and Manage- ment ; Foreign Fire Systems ; Hints on Fire-Brigades, &c. By C. F. T. YOUNG, C.E. 8vo, cloth 1 4. " To such of our readers as are Interested In the subject of fires and fire apparatus we can most heartily commend this book." hnifineertng . MECHANICAL ENGINEERING, &-c. AERIAL NAVIGATION. A Practical Handbook on the Construction of Dirigible Balloons, Aerostats, Aeroplanes, and Aeromotors. By FREDERICK WALKER, C.E., Associate Member of the Aeronautic Institute. With 104 Illustrations. Large Crown 8vo, cloth Net 7/6 STONE-WORKING MACHINERY. A Manual dealing with the Rapid and Economical Conversion of Stone. With Hints on the Arrangement and Management of Stone Works. By M. Powis BALE, M.I. M.E. Second Edition, enlarged. Crown 8vo, cloth . . 9/Q " The book should be in the hands of every mason or student of stonework." Clliery Guardian. " A capital handbook for all who manipulate stone for building or ornamental purposes." Machinery Market. PUMPS AND PUMPING. A Handbook for Pump Users. Being Notes on Selection, Construction, and Management. By M. Powis BALE, M.I. M.E. Fourth Edition. Crown 8vo, cloth 3/6 "The matter is set forth as concisely as possible. In fact, condensation rather than ditiuse- ness has been the author's aim throughout ; yet he does not seem to have omitted anything likely to be of use." Journal oj Gas Lighting. " Thoroughly practical and clearly written." Glasgow Herald. MILLING MACHINES AND PROCESSES. A Practical Treatise on Shaping Metals by Rotary Cutters. Including Information on Making and Grinding the Cutters. By PAUL N. HASLUCK, Author of ' ' Lathe- Work. " With upwards of 300 Engravings. Large crown 8vo, cloth 12/6 " A new departure in engineering literature. . . . We can recommend this work to all in- terested in milling machines ; it is what it professes to be a practical treatise." Engineer. " A capital and reliable book which will no doubt be of considerable service both to those who are already acquainted with the process as well as to those who contemplate its adoption." Industries. LATHE-WORK. A Practical Treatise on the Tools, Appliances, and Processes employed in the Art of Turning. By PAUL N. HASLUCK. Eighth Edition. Crown 8vo, cloth 5/O " Written by a man who knows not only how work ought to be done, but who also knows how to do It, and how to convey his knowledge to others. To all turners this book would be valuable." Engineering. " We can safely recommend the work to young engineers. To the amateur It will simply be invaluable. To the student it will convey a great deal of useful Information." 2mi'ttr. SCREW-THREADS, And Methods of Producing Them. With numerous Tables and complete Directions for using Screw-Cutting Lathes. By PAUL N. HASLUCK, Author of " Lathe- Work," &c. Sixth Edition. Waistcoat-pocket size . .1/6 " Full of useful information, hints and practical criticism. Taps, dies, and screwing tools generally are illustrated and their action described." Mechanical World. " It is a complete compendium of all the details of the screw -cutting lathe ; In fact, a ntultum- in-parvo on all the subjects it treats upon." Carpenter and Builder. TABLES AND MEMORANDA FOR ENGINEERS, MECHANICS, ARCHITECTS, BUILDERS, &c. Selected and Arranged by FRANCIS SMITH. Seventh Edition, Revised, including ELECTRICAL TABLES, FORMULA, and MEMORANDA. Waistcoat-pocket size, limp leather. [Just Published. 1/6 " It would, perhaps, be as difficult to make a small pocket-book selection of notes and formulae to suit ALL engineers as it would be to make a universal medicine ; but Mr. Smith's waistcoat- pocket collection may be looked upon as a successful attempt." Engineer. " The best example we have ever seen of 270 pages of useful matter packed into the dimen- sions of a card-case." Building News. " A veritable pocket treasury of knowledge." Iron. POCKET GLOSSARY OF TECHNICAL TERMS. English-French, French-English ; with Tables suitable for the Architectural, Engineering, Manufacturing, and Nautical Professions. By JOHN JAMES FLETCHER. Third Edition, aoo pp. Waistcoat-pocket size, limp leather 1 /6 " It is a very great advantage for readers and correspondents In France and England to have so large a number of the words relating to engineering and manufactures collected in a liliputian volume. The little book will be useful both to students and travellers." Architect. " The glossary of terms is very complete, and many of the Tables are new and well arranged. We cordially commend the book." Mechanical World. CROSBY LOCKWOOD < SON'S CATALOGUE. THE ENGINEER'S YEAR BOOK FOR 1905. Office, London, Author of "A Handbook of Electrical Testing," "The Electrical Engineer's Pocket-Book," &c. With 1,000 Illustrations, specially Engraved for the work. Crown 8vo, 924 pp., leather. [Just Published. 8/O "Kempe's Year B >ok really requires no commendation. Its sphere of usefulness is widely known, and it is used by engineers tne world over." The bngineer. "The volume Is distinctly In advance of most similar publications in this country." Engineering. " This valuable and well-designed book of reference meets the demands of all descriptions of engineers." Saturday Review. " Teems with up-to-date information in every branch of engineering and construction." BuiMing- News. " The needs of the engineering profession could hardly be supplied in a more admirable, complete and convenient form. To say that it more than sustains all comparisons is praise of the highest sort, and that may justly be said of it." Mining- Journal, " There is certainly room for the new comer, which supplies explanations and directions., as well as formulae and tables. It deserves to become one of the most successful of the technical annuals." Architect. " Brings together with great skill all the technical information which an engineer has to use day by day. It is in every way admirably equipped, and is sure to prove successful." Scotsman. " The up-to-dateness of Mr. Kempe's compilation is a quality that will not be lost on the busy people for whom the work is intended." Glasgow Herald. THE PORTABLE ENGINE. A Practical Manual on its Construction and Management. For the use of Owners and Users of Steam Engines generally. By WILLIAM DYSON WANSBROUGH. Crown 8vo, cloth 3/6 " This is a work of value to those who use steam machinery. . . . Should be read by every one who has a steam engine, on a farm or elsewhere." Mark Lane Express. IRON AND STEEL. A Work for the Forge, Foundry, Factory, and Office. Containing ready, useful, and trustworthy Information for Ironmasters and their Stock-takers ; Managers of Bar, Rail, Plate, and Sheet Rolling Mills ; Iron and Metal Founders ; Iron Ship and Bridge Builders ; Mechanical, Mining, and Con- sulting Engineers ; Architects, Contractors, Builders, &c. By CHARLES HOARE, Author of "The Slide Rule," &c. Ninth Edition. 32010, leather . 6/O CONDENSED MECHANICS. A Selection of Formulae, Rules, Tables, and Data for the Use of Engineering Students, &c. By W. G. C. HUGHES, A.M.I. C.E. Crown 8vo, cloth . 2/6 " The book is well fitted for those who are preparing for examination and wish to refresh their knowledge by going through their formulae again." Marine Engineer. THE SAFE USE OF STEAM. Containing Rules for Unprofessional Steam Users. By an ENGINEER. Eighth Edition. Sewed 60. " If steam-users would but learn this little book by heart, boiler explosions would become sensations by their rarity." English Mechanic. THE CARE AND MANAGEMENT OF STATIONARY ENGINES. A Practical Handbook for Men-in-charge. By C. HURST. Crown 8vo. Net 1 JQ THE LOCOMOTIVE ENGINE. The Autobiography of an Old Locomotive Engine. By ROBERT WEATHER- BURN, MJ.M.E. With Illustrations and Portraits of GEORGE and ROBERT STEPHENSON. Crown 8vo, cloth. Net 2/6 THE LOCOMOTIVE ENGINE AND ITS DEVELOPMENT, A Popular Treatise on the Gradual Improvements made in Railway Engines between 1803 and 1903, By CLEMENT E. STRETTON, C.E. Sixth Edition, Revised and Enlarged. Crown 8vo, cloth. [Just Published. Net 4/6 " Students of railway history and all who are interested in the evolution of the modem 'emotive vill find m ich to attract and entertain In this volume." The Times, MECHANICAL ENGINEERING, TOOLS FOR ENGINEERS AND WOODWORKERS. A Practical Treatise including Instruments of Measurement. By JOSEPH HORNEK, A.M.Inst.M.E., Author of "Pattern Making," "Hoisting Machinery," &c. Demy Svo, with 450 Illustrations. [/ the Press. Price about 9/Q net. MODERN MACHINE SHOP TOOLS. A Practical Treatise describing in every detail the Construction, Operation and Manipulation of both Hand and Machine I ools ; being a work of Practical Instruction in all Classes of Machine Shop Practice, including Chapters on Filing, Fitting and Scraping Surfaces ; on Drills, Reamers, Taps and Dies ; the Lathe and its Tools ; Planers, Shapers and their Tools ; Milling Machines and Cutters ; Gear Cutters and Gear Cutting ; Drilling Machines and Drill Work; Grinding Machines and their Work; Hardening and Tempering, Gearing, Belting, and Transmission Machinery; Useful Data and Tables. By WILLIAM H. VAN DERVOORT, M.E. Fourth Edition. Illustrated by 673 Engravings of Latest Tools and Methods, all of which are fully described. Medium Svo, cloth. [Just Published. Net 21 /O LOCOMOTIVE ENGINE DRIVING. A Practical Manual for Engineers in Charge of Locomotive Engines. By MICHAEL REYNOLDS, formerly Locomotive Inspector, L. B. & S. C. R. Eleventh Edition. Including a KEY TO THE LOCOMOTIVE ENGINE. Crown Svo, cloth 4/6 " Mr. Reynolds has supplied a want, and has supplied it welL We can confidently recom- mend the book not only to the practical driver, but to everyone who takes an interest in the performance of locomotive engines." The Engineer. "Mr. Reynolds has opened a new chapter in the literature of the day. This admirable practical treatise, of the practical utility of which we have to speak in terms of warm commendation." Athenaeum. THE MODEL LOCOMOTIVE ENGINEER, Fireman, and Engine-Boy. Comprising a Historical Notice of the Pioneer Locomotive Engines and their Inventors. By MICHAEL REYNOLDS. Second Edition, with Revised Appendix. Crown Svo, cloth 4/6 " We should be glad to see this book in the possession of everyone in the kingdom who has ever laid, or is to lay, hands on a locomotive engine." Iron. CONTINUOUS RAILWAY BRAKES. A Practical Treatise on the several Systems in Use in the United Kingdom : their Construction and Performance. By M. REYNOLDS. Svo, cloth 9/0 " A popular explanation of the different brakes. It will be of great assistance in forming public opinion, and will be studied with benefit by those who take an interest in the brake." English Mechanic. STATIONARY ENGINE DRIVING. A Practical Manual for Engineers in Charge of Stationary Engines. By MICHAEL REYNOLDS. Sixth Edition. With Plates and Woodcuts. Crown Svo, cloth 4/6 " The author's advice on the various points treated is clear and practical." Engineering. " Our author leaves no stone unturned. He is determined that his readers shall not only know something about the stationary engine, but all about it." Engineer. ENGINE-DRIVING LIFE. Stirring Adventures and Incidents in the Lives of Locomotive Engine- Drivers. By MICHAEL REYNOLDS. Third Edition. Crown Svo, cloth . 1/6 " From first to last perfectly fascinating. Wilkie Collins's most thrilling conceptions are thrown into the shade by true incidents, endless in their variety, related in every page." North British Mail. THE ENGINEMAN'S POCKET COMPANION, And Practical Educator for Enginemen, Boiler Attendants, and Mechanics. By MICHAEL REYNOLDS. With 45 Illustrations and numerous Diagrams Fourth Edition, Revised. Royal iSmo, strongly bound for pocket wear. 3/6 " A most meritorious work, giving in a succinct and practical form all the Information an engine-minder desirous of mastering the scientific principles of his daily calling would requiie." The Miller. io CROSBY LOCKWOOD & SON'S CATAlOGVS. CIVIL ENGINEERING, SURVEYING, ETC. PIONEER IRRIGATION. A Manual of Information for Farmers in the Colonies. By E. O. MAWSON, M.Inst.C.E., Executive Engineer, Public Works Department, Bombay. With Additional Chapters on Light Railways by E. R. CALTHKOP, M.Inst.C.E., M.I.M.E. Illustrated by Numerous Plates and Diagrams. Demy 8vo, cloth. [ Just Published. Aet 1 Q/ 6 SUMMARY OF CONTENTS : VALUE OF IRRIGATION, AND SOURCES OF WATER SUPPLY. DAMS AND WEIRS. CANALS. UNDERGROUND WATER.- METHODS OF IRRI- GATION. SEWAGE IRRIGATION. IMPERIAL AUTOMATIC SLUICE GATES. THE CULTI- VATION OF IRRIGATED CROPS, VHGETABLES, AND FRUIT TREES. LIGHT RAILWAYS FOR HEAVY TRAFFIC. USEFUL MEMORANDA AND DATA. TUNNELLING. A Practical Treatise. By CHARLES PRELINI, C.E. With additions by CHARLES S. HILL, C.E. With 150 Diagrams and Illustrations. Royal 8vo, cloth Net 1 6/O PRACTICAL TUNNELLING. Explaining in detail Setting-out the Works, Shaft-sinking, and Heading-driving, Ranging the Lines and Levelling underground, Sub-Excavating, Timbering and the Construction of the Brickwork of Tunnels. By F. W. SIMMS, M. Inst. C.E. Fourth Edition, Revised and Further Extended, including the most recent (1895) Examples of Sub-aqueous and other Tunnels, by D. KINNEAR CLARK, M. Inst. C.E. With 34 Folding Plates. Imperial 8vo, cloth 2 2s. "The present (i896Vedition has been brought right up to date, and is a work to *luch civil engineers should have ready access, and engineers WHO have construction work can hardly afford to be without, but which to the younger members of the profession is invaluable, as from its pages they can learn the state to which the science of tunnelling has attained." Rail-way News. THE WATER SUPPLY OF TOWNS AND THE CON- STRUCTION OP WATER-WORKS. A Practical Treatise for the Use of Engineers and Students of Engineering. By W. K. BURTON, A.M. Inst. C.E., Consulting Engineer to the Tokyo Water-works. Second Edition, Revised and Extended. With numerous Plates and Illustrations. Super-royal 8vo, buckram 25/O I. INTRODUCTORY. II. DIFFERENT QUALITIES OF WATER. III. QUANTITY OF WATER TO BE PROVIDED. IV. ON ASCERTAINING WHETHER A PROPOSED SOURCE OF SUPPLY is SUFFICIENT. V. ON ESTIMATING THE STORAGE CAPACITY REQUIRED TO BE PROVIDED. VI. CLASSIFICATION OF WATER-WORKS. VII. IMPOUNDING RESER- VOIRS. VIII. EARTHWORK DAMS. IX. MASONRY DAMS. X. THE PURIFICATION OF WATER. XI. SETTLING RESERVOIRS. XII. SAND FILTRATION. XIII. PURIFICATION OF WATER BY ACTION OF IRON, SOFTENING OF WATER BY ACTION OF LIME, NATURAL FILTRATION. XIV. SERVICE OR CLEAN WATER RESERVOIRS WATER TOWERS STAND PIPES. XV. THE CONNECTION OF SETTLING RESERVOIRS, FILTER BEDS AND SERVICE RESERVOIRS. XVI. PUMPING MACHINERY. XVII. FLOW OF WATER IN CONDUITS- PIPES AND OPEN CHANNELS. XVIII. DISTRIBUTION SYSTEMS. XIX. SPECIAL PRO- VISIONS FOR THE EXTINCTION OF FIRE. XX. PIPES FOR WATER-WORKS. xxi. PRE- VENTION OF WASTE OF WATER. XXII. VARIOUS APPLIANCES USED IN CONNECTION WITH WATER-WORKS. APPENDIX I. By PROF. JOHN MILNE, F.R.S. CONSIDERATIONS CONCERNING THE PROBABL.E EFFECTS OF EARTHQUAKES ON WATER-WORKS, AND THE SPECIAL PRE- CAUTIONS TO BE TAKEN IN EARTHQUAKE COUNTRIES. APPENDIX II. By JOHN DE RIJKE. C.E. ON SAND DUNES AND DUNE SAND AS A SOURCE OF WATER SUPPLY. " The chapter upon nitration of water is very complete, and the details of construction well Illustrated. . . . The work should be specially valuable to civil engineers engaged in work in Japan, but the interest is by no means confined to that locality." Engineer. " We congratulate the author upon the practical commonsense shown in the preparation of this work. . . . The plates and diagrams have evidently been prepared with great care, and cannot fail to be of great assistance to the student." Builder. RURAL WATER SUPPLY. A Practical Handbook on the Supply of Water and Construction of Water- works for small Country Districts. By ALLAN GREENWELL, A.M.I.C.E., and W. T. CURRY, A.M.I. C.E., F.G.S. With Illustrations. Second Edition, Revised. Crown 8vo, cloth 6/O "We conscientiously recommend it as a very useful book for those concerned in obtaining water for small districts, giving a great deal of practical information in a small compass." Builder. " The volume contains valuable information upon all matters connected with water supply. , . . It is full of details on points which are continually before water-works engineers." Nature. CIVIL ENGINEERING, SURVEYING, & SON'S CATALOGUE. PUBLICATIONS OF THE ENGINEERING STANDARDS COMMITTEE. THE ENGINEERING STANDARDS COMMITTEE is the outcome of a Committee appointed by the Institution of Civil Engineers at the instance of Sir John Wolfe Barry, K.C.B., to inquire into the advisability of Standardising Rolled Iron and Steel Sections. The Committee is supported by the Institution of Civil Engineers, the Institution of Mechanical Engineers, the Institution of Naval Architects, the Iron and Steel Institute, and the Institution of Electrical Engineers ; and the value and importance of its labours has been emphatically recognised by his Majesty's Government, who have made a liberal grant from the Public Funds by way of contribution to the financial resources of the Committee. The subjects already dealt with, or under consideration by the Committee, include not only Rolled Iron and Steel Sections, but Tests for Iron and Steel Material used in the Construction of Ships and their Machinery, Bridges and General Building Construction, Railway Rolling Stock Underframes, Component Parts of Locomotives, Railway and Tramway Rails, Electrical Plant, Insulating Materials, Screw Threads and Limit Gauges, Pipe Flanges, Cement, &c. Reports already Published : 1. BRITISH STANDARD SECTIONS. List i. EQUAL ANGLES. List 2. UNEQUAL ANGLES. Lists- BULB ANGLES. List 4. BULB TEES. List 5. BULB PLATES. List 7. CHANNELS. List 8. BEAMS, F'cap. folio, sewed. [Just Published. Net I/O 2. BRITISH STANDARD TRAMWAY RAILS AND FISH PLATES: STANDARD SECTIONS AND SPECIFICATION. F'cap. folio, sewed. [Just Published. Net 21 /O 3- REPORT ON THE INFLUENCE OF GAUGE LENGTH AND SECTION OF TEST BAR ON THE PERCENTAGE OF ELONGATION. By Professor W. C. UNWIN, F.R.S. F'cap. folio, sewed. [Just Published. Net 2/6 4. PROPERTIES OF STANDARD BEAMS. Demy 8vo, sewed. [Just Published. Net 1 /Q 6. PROPERTIES OF BRITISH STANDARD SECTIONS. Embracing Diagrams, Definitions, Tables, and Formulae. Demy Svo, cloth. [Just Published. Net 5/Q 7. BRITISH STANDARD TABLES FOR COPPER CON- DUCTORS AND THICKNESSES OF DIELECTRIC. F'cap. folio, sewed. [Just Published. Net 2/6 8. BRITISH STANDARD SPECIFICATION FOR TUBU- LAR TRAMWAY POLES. F'cap. folio, sewed. [Just Published. Net 5/O 9. BRITISH STANDARD SPECIFICATION AND SEC- TIONS FOR BuLL HEADED RAILWAY RAILS. F'cap. folio, sewed. [Just Published. Net 1Q6 BRITISH ENGINEERING STANDARDS CODED LIST. Rolled Sections for Constructional Iron and Steel Tram Rails. Compiled by ROBERT ATKINSON. 476 pp., 410, cloth, Net 21 /O MARINE ENGINEERING, NAVIGATION, &c. i? MARINE ENGINEERING, SHIPBUILDING, NAVIGATION, ETC. MARINE ENGINES AND BOILERS. Their Design and Construction. A Handbook for the Use of Students, Engineers, and Naval Constructors. Based on the Work " Eercchnung u:;d Konstruktion der Schiffsmaschinen und Kessel," by L)r. G. BAUER, Engmetr- in-Chief of the Vulcan Shipbuilding Yard, Stettin. Translated from the Second German Edition by E. M. DONKIN, and S. BRYAN DONKIN, A.M.I.C.E. Edited by LESLIE S. ROBERTSON, Secretary to the Engineering Standards Committee, M.I.C.E., M.I.M.E., M.I.N.A..&C. With numerous Illustrations and Tables. Medium Svo, cloth . [Nearly Ready, Price abo*t 32/- &t't. SUMMARY OF CONTENTS: PAK.T I. MAIN ENGINES. DETERMINATION OF CYLIN- DER DIMENSIONS. THE UTILISATION OF STEAM IN THE ENGINE. STROKE OF PISTON. NUMBER OF REVOLUTION^ TURNING MOMENT. BALANCING OF THE MOVING PART?. ARRANGEMENT OF MAIN ENGINES. DETAILS OF MAIN ENGINES. T h V CYLINDER. VALVES. VARIOUS KINDS OF VALVE GEAR. -PISTON RODS. PISTON?. CONNJ CTING ROD AND CROhbHEAD. VALVE GEAR ROD?. -BED PLATES. ENGINE COLIMNJ, REVERSING AND TURNING GEAR. PART II. PUMPS. AIR, CIR> \ LATINO FEED, AND AUXILIARY P( MPS. PART III.-SHAFTING, KES1STANCE OF SHIPS, PROPELLEKS. THRUST SHAFT AND THPU?T BLOCK. TUNNEI SHAFTS AND >LUMMER BLOCK?. SHAFT COUPLINGS. STEI-N TUBE. THF. SCRRW PI.OPFLLER. CONST RUCTION OF THE SCREW. PART IV. PIPES AND CONNECTIONS.-GENBRAL REMARKS, FLANGf S, VALVES, &c. UNDE* WATER FITTINGS. MAIN bTEAM, AUXILIARY S>TFAM, /M;> EXHALST PIPJNGFFED WATER, BILGE, BALLA?T AND CIRCULATING PIPES. PART V STEAM BOILERS.- FIRING AND THE GENERATION OF STEAM. CYLINDRICAL con LX?. LOCOMOTIVE BOILERS. WATER-! UBE Bon ERS. SMALL TUBE WATER-TUBE BOILERS. 5 MOKE Box. FUNNFL A>D Bun ER LAGGING. FOOTED DRAUGHT. BOILER FiTTiNr.s AND MOUNTINGS. PART VI. MEASURING INSTRUMENTS. PART VII. VARIOUS DETAILS. BOLTS, NUTS, SCREW THREADS &c.- PLATFORMS, GRATINGS, LADDER?. FOUND ^TION=. BEATINGS. LUBRICATION VF-NTII ATJON OF ENGINE, ROOMS.- RULES FOR SPARE GEAR, PART VIII. ADDITIONAL TABLES. THE NAVAL ARCHITECT'S AND SHIPBUILDER'S POCKET-BOOK Of Formulae, Rules, and Tables, and Marine Engineer's and Surveyor Handy Book of Reference. By CLEMENT MACKROW, M.I.N.A. Eighth Edition, carefully Revised and Enlarged. Fcap., leather . . . Net 1 2/6 SUMMARY OF CONTENTS : SIGNS AND SYMBOLS, DECIMAL FRACTIONS. TRIGO- NOMETRY. PRACTICAL GEOMETRY. MENSURATION. CENTRES AND MOMENTS OF FIGURES. MOMENTS OF INERTIA AND RADII GYRATION. ALGEBRAICAL EXPRESSIONS FOR SIMPSON'S RULES. MECHANICAL PRINCIPLES. CENTRE OF GRAVITY. LAWS OF MOTION. -DISPLACEMENT, CENTRE OF BUOYANCY. CENTRE OF GRAVITY OF SHIP'S HULL. STABILITY CURVES AND METACENTRES. SEA AND SHALLOW-WATER WAVES. ROLLING OF SHIPS. PROPULSION AND RESISTANCE OF VESSELS. SPEED TRIALS. SAILING, CENTRE OF EFFORT. DISTANCES DOWN RIVERS, COAST LINES. STEERING AND RUDDERS OF VESSELS. LAUNCHING CALCULATIONS AND VELOCITIES. WEIGHT OF MATERIAL AND GEAR. GUN PARTICULARS AND WEIGHT. STANDARD GAUGES. RIVETED JOINTS AND RIVETING. STRENGTH AND TESTS OF MATERIALS. BINDING AND SHEARING STRESSES. STRENGTH OF SHAFTING, PILLARS, WHEELS, &c. HYDRAULIC DATA, &c. CONIC SECTIONS, CATENARIAN CURVES. MECHANICAL POWERS, WORK. BOARD OF TRADE REGULATIONS FOR BOILERS AND ENGINES. BOARD OF TRADE REGULATIONS FOR SHIPS. LLOYD'S RULES FOR BOILERS. LLOYD'S WEIGHT OF CHAINS. LLOYD'S SCANTLINGS FOR SHIPS. DATA OF ENGINES AND VESSELS. SHIPS' FITTINGS AND TESTS. SEASONING PRESERVING TIMBER. MEASUREMENT OF TIMBER. ALLOYS, PAINTS, VARNISHES. DATA FOR STOWAGE. ADMIRALTY TRANS- PORT REGULATIONS. RULES FOR HORSE-POWER, SCREW PROPELLERS, &c. PER- CENTAGES FOR BUTT STRAPS. PARTICULARS OF YACHTS. MASTING AND RIGGING. DISTANCES OF FOREIGN PORTS. TONNAGE TABLES. VOCABULARY OF FRENCH AND ENGLISH TERMS. ENGLISH WEIGHTS AND MEASURES. FOREIGN WEIGHTS AND MEA- SURES. DECIMAL EQUIVALENTS. USEFUL NUMBERS. CIRCULAR MEASURES. AREAS OF AND CIRCUMFERENCES OF CIRCLES.- AREAS OF SEGMENTS OF CIRCLES. TABLES OF SQUARES AND CUBES AND ROOTS OF NUMBERS. TABLES OF LOGARITHMS OF NUM- BERS. TABLES OF HYPERBOLIC LOGARITHMS. TABLES OF NATURAL SINES, TANGENT?, TABLES OF LOGARITHMIC SINES, TANGENTS. &c. " In these days of advanced knowledge a werk like this Is of the greatest value. It contains a vast amount of information. We unhesitatingly say that it is the most valuable compilation for its specific purpose that has ever been printed. No naval architect, engineer, surveyor, seaman, wood or iron shipbuilder, can afford to be without this work." Nautical Magazine. " Should be used by all who are engaged in the construction or design of vessels. . . . Will be found to contain the most useful tables and formulae required by shipbuilders, collected from the best authorities, and put together in a popular and simple form. It is of jxceptional merit." Enginttr. " A pocket-book of this description must be a necessity in the shipbuildir-g trade. It con- tains a mass of useful information clearly expressed and presented in a hanay I'orni. ' Marine Engineer. 1 8 CkuSBY LoCKfrOOt) * SON'S CATALOGUE W ANNAN'S MARINE ENGINEER'S GUIDE To Board of Trade Examinations for Certificates of Competency. Containing all Latest Questions to Date, with Simple, Clear, and Correct Solutions ; 302 Elementary Questions with Illustrated Answers, and Verbal Questions and Answers ; complete Set of Drawings with Statements completed. By A. C. W ANN AN, C.E., Consulting Engineer, and E. W. I. WANNAN, M.I.M.E., Certificated First Class Marine Engineer. With numerous Engravings. Third Editiohj Enlarged. 50*0 pages. Large crown 8vo, cloth . . Net 1 0/6 " The book is clearly and plainly written and avoids unnecessary explanations and formulas, arid we consider it a valuable book for students of marine engineering." Nautical Magazine. WANNAN'S MARINE ENQINEER'5 POCKET-BOOK. Containing Latest Board of Trade Rules and Data for Marine Engineers. By A. C. WANNAN. Third Edition, Revised, Enlarged, and Brought up to Date. Square i8mo, with thumb Index, leather 5/O " There is a great deal of useful information in this little pocket-book. It is of the rule-of- thumb order, and is, on that account, well adapted to the uses of the sea-going engineer." Engineer. THE SHIPBUILDING INDUSTRY OF GERMANY. Compiled and Edited by G. LEHMANN-FELSKOWSKI. With Coloured Prints, Art Supplements, and numerous Illustrations throughout the text. Super- royal 410, cloth. [Just Publistiea. Net 1O/6 5EA TERMS, PHRASES, AND WORDS (Technical Dictionary of) used in the English and French Languages (English- French, French-English). For the Use of Seamen, Engineers, Pilots, Shipbuilders, Shipowners, and Ship-brokers. Compiled by W. PIRRIE, late ot the African Steamship Company. Fcap. 8vo, cloth limp . . . QjQ "This volume will be highly appreciated by seamen, engineers, pilots, shipbuilders and ship- owners. It will be found wonderfully accurate and complete.' Scotsman. MARINE ENGINEER'S POCKET-BOOK. Consisting of useful Tables and Formulae. By FRANK PROCTOR, A.I. N.A. Third Edition. Royal samo, leather 4/O " We recommend it to our readers as going far to supply a long-felt want." Naval Science. " A most useful companion to all marine engineers." United Service Gazette. ELEMENTARY MARINE ENGINEERING. A Manual for Young Marine Engineers and Apprentices. By J. S. BREWER. Crown 8vo, cloth "|/g PRACTICAL NAVIGATION. Consisting of THE SAILOR'S SEA-BOOK, by J. GREENWOOD and W. H. ROSSER ; with Mathematical and Nautical Tables for Working the Problems, by H. LAW, C.E., and Professor J. R. YOUNG. i2mo, half-bound . 7/Q THE ART AND SCIENCE OF SAILMAKING. By SAMUEL B. SADLER, Practical Sailmaker, late in the employment of Messrs. Ratsey and Lapthorne, of Cowes and Gosport. Plates. 410, cloth. 12/6 " This extremely practical work gives a complete education in all the branches of the manu- f acture, cutting out, roping, seaming, and goring. It is copiously illustrated, and will form a nrst- rate text-book and guide." Portsmouth Times. CHAIN CABLES AND CHAINS. Comprising Sizes and Curves of Links, Studs, &c., Iron for Cables and Chains, Chain Cable and Chain Making, Forming and Welding Links, Strength of Cables and Chains, Certificates for Cables, Marking Cables, Prices of Chain Cables and Chains, Historical Notes, Acts of Parliament, Statutory Tests, Charges for Testing, List of Manufacturers of Cables, &c., &c. By THOMAS W. TRAILL, F.E.R.N., M.Inst.C.E., Engineer-Surveypr-in-Chief, Board of Trade, Inspector of Chain Cable and Anchor Proving Establishments, and General Superintendent, Lloyd's Committee on Proving Establishments. With numerous Tables, Illustrations, and Lithographic Drawings. Folio. cloth 2 2. " It contains a vast amount of valuable information. Nothing seems to be wanting to make it a complete and standard work of reference on the subject." Nautical Magazine. . M&lALLVRGY, &> COLLIERY WORKING. 19 MINING, METALLURGY, AND COLLIERY WORKING. THE OIL FIELDS OF RUSSIA AND THE RUSSIAN PETROLEUM INDUSTRY. A Practical Handbook on the Exploration, Exploitation, and Management of Russian Oil Properties, including Notes on the Origin of Petroleum in Russia, a Description of the Theory and Practice of Liquid Fuel, and a Translation of the Rules and Regulations concerning Russian Oil Properties. By A. BEEBY THOMPSON, A.M.I.M.E., late Chief Engineer and Manager of the European Petroleum Company's Russian Oil Properties. About 500 pp. With numerous Illustrations and Photographic Plates, and a Map of the Balakhany-Saboontchy-Romany Oil Field. Super-royal 8vo, cloth. [Just Published. Net 3 3 S . MACHINERY FOR METALLIFEROUS MINES. A Practical Treatise for Mining Engineers, Metallurgists, and Managers of Mines. By E. HENRY DAVIES, M.E., F.G.S. 600 pp. With Folding Plates and other Illustrations. Medium 8vo, Cloth .... Net 25/O " Deals exhaustively with the many and complex details which go to make up the sum total of machinery and other requirements for the successful working of metalliferous mines, and as a book of ready reference is of the highest value to mine managers and directors." Mining Journal. THE DEEP LEVEL MINES OF THE RAND, And their Future Development, considered from the Commercial Point of View. By G. A. DENNY (of Johannesburg), M.N.E.I.M.E., Consulting Engineer to the General Mining and Finance Corporation, Ltd., of London, Berlin, Paris, and Johannesburg. Fully Illustrated with Diagrams and Folding Plates. Royal 8vo, buckram ......... Net 25/O " Mr. Denny by confining himself to the consideration of the future of the deep-level mines of the Rand breaks new ground, and by dealing with the subject rather from a commercial stand- point than from a scientific one, appeals to a wide circle of readers. The book cannot fail to prove PROSPECTING FOR GOLD. A Handbook of Practical Information and Hints for Prospectors based on Personal Experience. By DANIEL J. RANKIN, F.R.S.G.S , M.R.A S , formerly Manager of the Central African Company, and Leader of African Gold Pros- pecting Expeditions. With Illustrations specially Drawn and Engraved for the Work. Fcap. 8vo, leather ........ Net 7/6 "This well-compiled book contains a collection of the richest gems of useful knowledge for the prospector's benefit. A special table is given to accelerate the spotting at a glance of minerals associated with gold." Mining Journal. THE METALLURGY OF GOLD. A Practical Treatise on the Metallurgical Treatment of Gold-bearing Ores. Including the Assaying, Melting, and Refining of Gold. By M. EISSLER, M, Inst. M.M. Fifth Edition, Enlarged. With over 300 Illustrations and numerous Folding Plates. Medium 8vo, cloth .... ^VJe^21/O " This book thoroughly deserves its title of a ' Practical Treatise.' The whole process of gold mining, from the breaking of the quartz to the assay of the bullion, is described in clear and orderly narrative and with much, but not too much, fulness of detail." Saturday Review. THE CYANIDE PROCESS OF GOLD EXTRACTION. And its Practical Application on the Witwatersrand Gold Fields and elsewhere. By M. EISSLER, M. Inst. M.M. With Diagrams and Working Drawings. Thiid Edition, Revised and Enlarged. 8vo, cloth .... Net 7/6 "This book is just what was needed to acquaint mining men with the actual working of a process which is not only the most popular, but is, as a general rule, the most successful for the extraction of gold from tailings." Mining Journal. DIAMOND DRILLING FOR GOLD & OTHER MINERALS. A Practical Handbook on the Use of Modern Diamond Core Drills in Pro- specting and Exploiting Mineral-Bearing Properties, including Particulars of the Costs of Apparatus and Working. By G. A. DENNY, M.N.E. Inst. M.E., M Inst. M.M. Medium 8vo, 168 pp., with Illustrative Diagrams . 12/6 " There is certainly scope for a work on diamond drilling, and Mr. Denny deserves grateful cognition for supplying a decided want." Mining Journal. CRGS8Y LQCRWOOD & SON'S CATALOGUE. GOLD ASSAYING. A Practical Handbook, giving the Modus Operandi for the Accurate Assay of Auriferous Ores and Bullion, and the Chemical Tests required in the Processes of Extraction by Amalgamation, Cyanidation, and Chlorination. With an Appendix of Tables and Statistics. By H. JOSHUA PHILLIPS, F.I.C., F.C.S., Assoc.Inst.C.E., Author of " Engineering Chenrstry," etc. With Numerous Illustrations. Large Crown 8vo, cloth. {Just Published, Net 7/6 FIELD TESTING FOR GOLD AND SILVER. A Practical Manual for Prospectors and Miners. By W. H. MERRITT, M.N.E. Inst. M.E., A.R.S.M., &c. With Photographic Plates and other Illustrations. Fcap. 8vo, leather Net 5/O "As an instructor of prospectors' classes Mr. Merritt has the advantage of knowing exactly the information likely to be most valuable to the miner in the field. The contents cover all the details of sampling and testing gold and silver ores. A useful addition to a prospector's kit." Mining Journal. THE PROSPECTOR'S HANDBOOK. A Guide for the Prospector and Traveller in search of Metal-Bearing or other Valuable Minerals. By J. W. ANDERSON, M.A. (Camb.), F.R.G.S. Tenth Edition. Small crown 8vo, 3/6 cloth ; or, leather .... 4/6 " Will supply a much-felt want, especially among Colonists, in whose way are so often thrown many mineralogical specimens the value of which it is difficult to determine." Engineer. " How to find commercial minerals, and how to identify them when they are found, are the leading points to which attention Is directed." Mining Journal. THE METALLURGY OF SILVER. A Practical Treatise on the Amalgamation, Roasting, and Lixiviation of Silver Ores. Including the Assaying, Melting, and Refining of Silver Bullion. By M. EISSLER, M. Inst.M.M. Third Edition. Crown 8vo, cloth . 1Q/6 " A practical treatise, and a technical work which we are convinced will supply a long-felt want amongst practical men, and at the same time be of value to students and others indirectly connected with the industries." Mining Journal. THE HYDRO=METALLURGY OF COPPER. Being an Account of Processes Adopted in the Hydro-Metallurgical Treat- ment of Cupriferous Ores, Including the Manufacture of Copper Vitriol, with Chapters on the Sources of Su pply of Copper and the Roasting of Copper Ores. By M. EISSLER, M. Inst. M.M. 8vo, cloth .... JVtf*1 2/6 " In this volume the various processes for the extraction of copper by wet methods are fully detailed. Costs are given when available, and a great deal of useful informal! n about the copper industry of the world is presented in an interesting and attractive manner." Minim? Journal. THE METALLURGY OF ARGENTIFEROUS LEAD. A Practical Treatise on the Smelting of Silver-Lead Ores and the Refining or Lead Bullion. Including Reports on various Smelting Establishments and Descriptions of Modern Smelting Furnaces and Plants in Europe and America. By M. EISSLER, M. Inst. M.M. Crown 8vo, cloth .... 12/6 " The numerous metallurgical processes, which are fully and extensively treated of, embrace all the stages experienced in the passage of the lead from the various natural states to its issue from the refinery as an article of commerce.' Practical Engineer. METALLIFEROUS MINERALS AND MINING. By D. C. DAVIES, F.G.S. Sixth Edition, thoroughly Revised and much Enlarged by his Son, E. HENRY DAVIES, M.E., F.G.S. 600 pp., with 173 Illustrations. Large crown 8vo, cloth Net 1 2/6 " Neither the practical miner nor the general reader, interested in mines, can have a better book for his companion and his guide." Mining Journal. EARTHY AND OTHER MINERALS AND MINING. By D. C. DAVIES, F.G.S., Author of " Metalliferous Minerals," &c. Third Edition, Revised and Enlarged by his Son, E. HENRY DAVIBS, M.E., F.G.S. With about 100 Illustrations. Crown 8vo, cloth 1 2/6 " We do not remember to have met with any English work on mining matters that contains the same amount of information packed in equally convenient icr*\.."~Acaatmy, BRITISH MINING. A 1 realise on the History, Discovery, Practical Development, and Future Prospects of Metalliferous Mines in the Uiaieti Kingdom. By ROBERT HUNT, F.R.S., late Keeper of Mining Rccordb. Upwards of 950 pp., with 230 Illustrations. Second Edition, Revised. Super-royal 8vo, cloth 2 2s. MINING, METALLURGY, &> COLLIERY WORKING. 21 POCKET-BOOK FOR MINERS AND METALLURGISTS. Comprising Rules, Formula;, Tables, and Notes for Use in Field and Office Work. By F. DANVERS POWER, F.G.S., M.E. Second Edition, Corrected. Fcap. 8vo, leather 9/O " This excellent book is an admirable example of its kind, and ought to find a arge sale amongst English-speaking prospectors and mining engineers. " Engineering. THE MINER'S HANDBOOK. A Handy Book of Reference on the subjects of Mineral Deposits, Mining Operations, Ore Dressing, &c. For the Use of Students and others interested in Mining Matters. Compiled by JOHN MILNE, F.R.S., Professor of Mining in the Imperial University of Japan. Third Edition. Fcap. 8vo, leather "7/6 " Professor Milne's handbook is sure to be received with favour by all connected with mining, and will be extremely popular among students." Athenaeum IRON ORES of GREAT BRITAIN and IRELAND. Their Mode of Occurrence, Age and Origin, and the Methods of Searching for and Working Them. With a Notice of some of the Iron Ores of Spain. By J. D. KENDALL, F.G.S., Mining Engineer. Crown 8vo, cloth . . 1 6/O MINE DRAINAGE. A Complete Practical Treatise on Direct-Acting Underground Steam Pumping Machinery. By STEPHEN MICHELL. Second Edition, Re-written and Enlarged. With 250 Illustrations. Royal 8vo, cloth . Net 25/O HORIZONTAL PUMPING ENGINES. ROTARY AND NON-ROTARY HORIZONTAL ENGINES. SIMPLE AND COMPOUND STEAM PUMPS. VERTICAL PUMPING ENGINES. ROTARY AND NON-ROTARY VERTICAL ENGINES. SIMPLE AND COMPOUND STEAM PUMPS. TRIPLE-EXPANSION STEAM PUMPS. PULSATING STEAM PUMPS. PUMP VALVES. SINKING PUMPS, &c., &c. " This volume contains an immense amount of important and interesting new matter. The book should undoubtedly prove of great use to all who wish for information on the sub- ect." The Engineer. ELECTRICITY AS APPLIED TO MINING. By ARNOLD LUI-TON, M.Inst.C.E., M.I.M.E., M.I.E.E., late Professor 01 Coal Mining at the Yorkshire College, Victoria University, Mining Engineer and Colliery Manager; G. D. ASPINALL PARR, M.I.E.E., A.M.I. M.E., Associate of the Central Technical College, City and Guilds of London, Head of the Electrical Engineering Department, Yorkshire College, Victoria University ; and HERBERT PERKIN, M.I.M.E.. Certificated Colliery Manager, Assistant Lecturer in the Mining Department of the Yorkshire College, Victoria University. With about 170 Illustrations. Medium 8vo, cloth. Net 9/O For SUMMARY OF CONTENTS, see page 23.) THE COLLIERY MANAGER'S HANDBOOK. A Comprehensive Treatise on the Laying-out and Working of Collieries, Designed as a Book of Reference for Colliery Managers, and for the Use of Coal- Mining Students preparing for First-class Certificates. By CALEB PAMELY, Mining Engineer and Surveyor ; Member of the North of England Institute of Mining and Mechanical Engineers ; and Member of the South Wales Institute of Mining Engineers. With over 1,000 Diagrams, Plans, and other Illustra- tions. Fifth Edition, Carefully Revised and Greatly Enlarged. 1,2.0 pp. Medium 8vo, cloth. [Just Published. Net 1 5s. GEOLOGY. SEARCH FOR COAL. MINERAL LEASES AND OTHER HOLDINGS. SHAFT SINKING. FITTING UP THE SHAFT AND SURFACE ARRANGEMENTS. STEAM BOILERS AND THEIR FITTINGS. TIMBERING AND WALLING.- NARROW WORK AND METHODS OF WORKING. UNDERGROUND CONVEYANCE. - DRAINAGE. THE GASES MET WITH IN MINES ; VENTILATION. ON THE FRICTION OF AIR IN MINES. THE PRIESTMAN OIL ENGINE ; PETROLEUM AND NATURAL GAS. SURVEYING AND PLANNING. SAFETY LAMPS AND FIREDAMP DETECTORS. SUNDRY AND INCIDENTAL OPERATIONS AND APPLIANCES. COLLIERY EXPLOSIONS. MISCELLANEOUS QUESTIONS AND ANSWERS. Appendix: SUMMARY OF REPORT OF H.M. COMMISSIONERS ON ACCIDENTS IN MINES. " Mr. Pamely's work is eminently suited to the purpose or which it is intended, being clear. Interesting, exhaustive, rich in detail, and up to date, giving descriptions of the latest machines in every department. A mining engineer could scarcely go wrong who followed this work." Colliery Guardian. " Mr. Pamely has not only given us a comprehensive reference book of a very high order suitable to the requirements of mining engineers and colliery managers, but has also provided mining students with a class-book that is as interesting as it is instructive." Colliery Manager. "This is the most complete 'all-round' worn on coal -mining published in the English language. . . . No library of coal-mining books is complete without It." Colliery Engines Scranton, Pa., U.S.A.). 22 CROSBY LOCK WOOD * SON'S CATALOGUE. PRACTICAL COAL MINING. An Elementary Class-Book for the Use of Students attending Classes in Pre- paration for the Board of Education and County Council Examinations, or Qualifying for First or Second Class Colliery Managers' Certificates. By T. H. COCKIN, Member of the Institution of Mining Engineers, Certificated Colliery Manager, Lecturer on Coal-Mining at Sheffield University ollege. With Map of the British Coal-fields and over 200 Illustrations specially Drawn and Engraved for the Work. Crown 8vo, 440 pp. [Just Published. Net 46 COLLIERY WOXKINQ A.ND /VlAiN AUGMENT. CnmiM-King tne Duties of a Colliery Manager, the Oversight and Arrange- mcru _f Labour and Wages, and the different Systems of Working Coal Seams. By H. F. BULMAN and R. A. S. REDMAVNE. 350 pp., with 28 Plates and other Illustrations, including Underground Photographs. Medium 8vo, cloth. 1 5/Q " This is, indeed, an admirable Handbook for Colliery Managers, in fact it is an Indispensable adjunct to a Colliery Manager's education, as well as being a most useful and interesting work on the subject for all who in any way have to do with coal mining. The underground photographs are an attractive feature of the work, being very lifelike and necessarily true representations of the scenes they depict." Colliery Guardian. " Mr. Bulman and Mr. Redmayne, are to be congratulated on having supplied an authorita- tive work dealing with a side of the subject of coal mining which has hitherto received but scant treatment. The illustrations are excellent." Nature. COAL AND COAL MINING. By the late Sir WARINGTON W. SMYTH, M.A., F.R.S. Eighth Edition, Revised and Extended by T. FORSTER BROWN, Chief Inspector of the Mines of the Crown and of the Duchy of Cornwall. Crown 8vo, cloth. . 3/6 " As an outline is given of every known coal-field in this and other countries, as well as of the principal methods of working, the book will doubtless interest a very large number of readers." Mining yournal. NOTE5 AND FORMULA FOR MINING STUDENTS. By JOHN HERMAN MERIVALE, M.A., Late Professor of Mining in the Durham College of Science, Newcastle-upon-Tyne. Fourth Edition, Revised and Enlarged. By H. F. BULMAN, A.M.Inst.C.E. Small crown 8vo, cloth. 2/6 "The author has done his work in a creditable manner, and has produced a book that will be of service to students and those who are practically engaged in mining operations." Engineer. INFLAMMABLE GAS AND VAPOUR IN THE AIR (The Detection and Measurement of). By FRANK CLOWES, D.Sc., Lond., F.I.C. With a Chapter on THE DETECTION AND MEASUREMENT OF PETRO- LEUM VAPOUR, by BOVERTON REDWOOD, F.R.S.E. Crown 8vo, cloth. Net fi/O " Professor Clowes has given us a volume on a subject of much industrial importance . . . Those interested in these matters may be recommended to study this book, which is easy of compre- hension and contains many good things." The Engineer. COAL & IRON INDUSTRIES of the UNITED KINGDOM. Comprising a Description of the Coal Fields, and of the Principal Seams of Coal, with Returns of their Produce and its Distribution, and Analyses of Special Varieties. Also, an Account of the Occurrence of Iron Ores in Veins cr Seams ; Analyses of each Variety ; and a History of the Rise and Progress cf Pig Iron Manufacture. By RICHARD MEADE. 8vo, cloth . . 1 8s. " A book of reference which no one engaged in the iron or coal trades should omit from his library." Iron and Coal Trades Review. ASBESTOS AND ASBESTIC. Their Properties, Occurrence, and Use. By ROBERT H. JONES, F.S.A., Mineralogist, Hon. Mem. Asbestos Club, Black Lake, Canada. With Ten Collotype Plates and other Illustrations. Demy 8vo, cloth. . 1 6/O " An interesting and Invaluable work." Colliery Guardian. GRANITES AND OUR GRANITE INDUSTRIES. By GEORGE F. HARRIS, F.G.S. With Illustrations. Crown 8vo, cloth 2/6 TRAVERSE TABLES. For use in Mine Surveying. By WILLIAM LINTERN, C.E. With two plates. Small crown 3vo, cloth . Net /Q ELECTRICITY. ELECTRICAL ENGINEERING, frc. 23 ELECTRICITY, ELECTRICAL ENGINEERING, ETC. THE ELEMENTS OF ELECTRICAL ENGINEERING. A First Year's Course for Students. By TYSON SEWELL, A.I.E.E., Assistant Lecturer and Demonstrator in Electrical Engineering at the Polytechnic, Regent Street, London. Second Edition, Revised, with Additional Chapters on Alternating Current Working, ami Appendix of Questions and Answers. 450 pages, with 274 Illustrations. Demy 8vo, cloth. [Just Published. Net 7/6 OHM'S LAW. UNITS EMPLOYED IN ELECTRICAL ENGINEERING. -SERIES AND PARALLEL CIRCUITS ; CURRENT DENSITY AND POTENTIAL DROP IN THE CIRCUIT. THE HEATING EFFECT OF THE ELECTRIC CURRENT. THE MAGNETIC EFFECT OF AN ELECTRIC CURRENT. THE MAGNETISATION OF IRON. ELECTRO-CHEMISTRY ; PRIMARY BATTERIES. ACCUMULATORS. INDICATING INSTRUMENTS; AMMETERS, VOLTMETERS, OHMMETERS. ELECTRICITY SUPPLY METERS. MEASURING INSTRUMENTS, AND THE MEASUREMENT OF ELECTRICAL RESISTANCE. MEASUREMENT OF POTENTIAL DIF. FERENCE, CAPACITY, CURRENT STRENGTH, AND PERMEABILITY. ARC LAMPS. INCAN- DESCENT LAMPS; MANUFACTURE AND INSTALLATION; PHOTOMETRY. THE CON- TINUOUS CURRENT DYNAMO. DIRECT CURRENT MOTORS. ALTERNATING CURRENTS. TRANSFORMERS, ALTERNATORS, SYNCHRONOUS MOTORS. POLYPHASE WORKING. APPENDIX OF QUESTIONS AND ANSWERS. "An excellent treatise for students of the elementary facts connected with electrica engineering." The Electrician. " One of the best books for those commencing the study of electrical engineering. Every- thing is explained in simple language which even a beginner cannot fail to understand." Engineer. " One welcomes this book, which is sound in its treatment, and admirably calculated to give students the knowledge and information they most require." Nature. THE ELECTRICAL TRANSMISSION OF ENERGY. A Manual for the Design of Electrical Circuits. By ARTHUR VAUGHAN ABROTT, C.E., Member American Institute of Electrical Engineers, Member A.merican Institute of Mining Engineers, Member American Society of Civil Engineers, Member American Society of Mechanical Engineers, &c. With I en Folding Diagrams and Sixteen Full-page Engravings. Fourth Edition, entirely Re- Written and Enlarged. Royal 8vo. cloth. [Just Published. Net 3O O CONDUCTORS FOR ELECTRICAL DISTRIBUTION. Their Materials and Manufacture, The Calculation of Circuits, Pola-Line Construction, Underground Working, and other Uses. By F. A.C. PERKINE, A.M., D.Sc. ; formerly Professor of Electrical Engineering, Leland Stanford, Jr., University ; M.Amer.I.E.E. 8vo, cloth .... Net 201- CONDUCTOR MATERIALS ALLOYED CONDUCTORS MANUFACTURE OF WIRE WIRE-FINISHINGWIRE INSULATION CABLES CALCULATION OF CIRCUITS KELVIN'S LAW OF ECONOMY IN CONDUCTORS MULTIPLE ARC DISTRIBUTION ALTERNATING CURRENT CALCULATION OVERHEAD LINES POLE LINE LINE INSULATORS UNDFR. GROUND CONDUCTORS. WIRELESS TELEGRAPHY; Its Origins, Development, Inventions, and Apparatus. By CHARLES HENRY SKWALL. With 85 Diagrams and Illustrations. Demy 8vo, cloth. [Just Published. Net 1Q/6 ELECTRICITY AS APPLIED TO MINING. By ARNOLD LUPTON, M.Inst C.E., M.I M.E., M.I.E E., late Professor ot Coal Mining at tht Yorkshire College, Victoria University, Mining Engineer and Colliery Manager; G. D. ASPINALL PARR, M.I.E.E., A M.I.M.E., Associate of the Central Technical College, City and Guilds of London, Head of the Electrical Engineering Department, Yorkshire College, Victoria University; and HERBERT PKRKIN, M.I.M E., Certificated Colliery Manager, Assistant Lectuier in the Mining Department of the Yorkshire College, Victoria University. With about 170 lllustratiuns. Medium 8vo, cloth. Net Ql INTRODUCTORY. DYNAMIC ELECTRICITY. DRIVING OF THE DYNAMO. THB STEAM TURBINE. DISTRIBUTION OF ELECTRICAL ENERGY. STARTING AND STOPPING ELECTRICAL GENERATORS AND MOTORS. ELECT RIC CABLES. CENTRAL ELECTRICAL PLANTS. ELECTRICITY APPLIED TO PUMPING AND HAULING. ELECTRICITY APPLIED TO COAL-CUTTING. TYPICAL ELECTRIC PLANTS RECENTLY ERECTED. ELECTRIC LIGHTING BY ARC AND GLOW LAMPS MISCELLANEOUS APPLICATIONS OF ELECTRICITY ELECTRICITY AS COMPARED WITH OTHER MOOES OF TRANSMITTING POWER. PANQERS OF ELECTRICITY, 24 CROSBY LOCKWOOD & SON'S CATALOGUE. DYNAMO, MOTOR AND SWITCHBOARD CIRCUIT5 FOR ELECTklCAL ENGINEERS. A Practical Book dealing with the subject of D'rect, Alternating and Poly- phase Currents. By WIT.LIAM R. BOWKF.R, C.E., M.E., E.E., Consuming Tramway Engineer. 8vo, cloth. [Just Published. Net Q/Q DYNAMO ELECTRIC MACHINERY: its CONSTRUC- TION, DESIGN, and OPERATION. By SAMUEL SHELDON, A M., Ph.D , Professor of Physics and Electrical Engineering at the Polytechnic Institute of Brooklyn, assisted by HOHART MASON, B S In two volumes, sold separately, as follows : Vol. I.-DIRECT CURRENT MACHINES Fifth Edition, Revised. Large crown 8vo. 280 pages, with 200 Illustrations . . Net "\ 2/O Vol. II.-ALTERN \TING CURRENT MACHINES. Large crown 8vo. 260 pages, with 184 Illustrations Net 1 2/O Designed as Text-books for use in Technical Educational Institutions, and by Engineers whose work includes the handline of Direct and Alternating Current Machines respectively, and for Students proficient in mathematics. ARMATURE WINDINGS OF DIRECT CURRENT OYNAMOS. Fx-^nsion and Application of a General Winding Rule. By E ARNOLD, Engineer. As-nstait Professor in Eiectrotechnics and Machine Design at the Ri.a Polytechnic School Translated from the Original G-yman by FRANCIS B. DE GRKSS, M.E.. Chief of Testing Department, Crocker-Wheeler Com- pany Wich 146 Illustrations. Medium 8vo, cloth . . . Net 12/- ELECTRICAL AND MAGNETIC CALCULATIONS. Fnr the Use of Electrical Engineers and Artisans, Teachers. Students, and all others interested in the Theory and Application of Electricity and Magnetism. By A. A. ATKINSON, Professor of Electricity in Ohio University. Crown 8vo. cloth Net 9/O "To tenchers and those who already possess a fair knowledge of their subject we can recom mend this hook as being useful to consult when requiring data or formulae which it is neither con- venient nor necessary to retain by memory." The Electrician. SUBMARINE TELEGRAPHS. Their History, Construction, and Working. Founded in part on W(JNSCHEN- DORFF'S " Traite de Telegraphic Sous-Marine," and Compiled from Authorita- tive and Exclusive Sources. ByCHARLES BRIGHT, F.R.S.E., A.M.Inst.C.E., M.I E.E. 780 pp., fully Illustrated, including Maps and Folding Plates. Royal 8vo, cloth . Net 3 3 8 . "There are few, if any, persons more fitted to write a treatise on submarine telegraphy than Mr. Charles Bright. He has done his work admirably, and has written in a way which will appeal as much to the layman as to the engineer. This admirable volume must, for many years to come, hold the position of the English classic on submarine telegraphy." Engineer. "This book is full of information. It makes a book of reference which should be in every engineer's library." Nature. THE ELECTRICAL ENGINEER'S POCKET-BOOK. Consisting of Rules, Formulae, Tables, and Data. By H. R. KEMPE, M I.E.E.. A.M.Inst.C.E., Technical Officer Postal Telegraphs, Author of "A Handbook of Electrical Testing," &c. Second Edition, thoroughly Revised, with Additions. With numerous Illustrations. 32mo, leather 5/O " It is the best book of its kind." Electrical En^neer. " The Electrical Engineers Pocket-Book is a good one." Electrician. " Strongly recommended to those engaged in the electrical industries." Electrical Review. POWER TRANSMITTED BY ELECTRICITY. And applied by the Electric Motor, including Electric Railway Construction. P.- P \TKTNSON \.M.. Ph.D. Third Edition, Fully Revised, and New Matter added. With 04 Illustrations. Crown 8vo, cloth . . Net QIQ DYNAMIC ELECTRICITY AND MAGNETISM. By PHILIP ATKINSON, A.M., Ph.D., Author of "Elements of Static !crricity," &c. Crown 8vo, 417 pp., with 120 Illustrations, cloth . 1O/6 ELECTRICITY, ELECTRICAL ENGINEERING, &c. 25 THE MANAGEMENT OF DYNAMOS. A Handybook of Theory and Practice for the Use of Mechanics, Engineers, Students, and others in Charge of Dynamos. By G. W. LUMMIS-PATERSON. Third Edition, Revised Crown 8vo, cloth 4/6 " The subiect is tre.uea ii. a manner which any intelligent man who is fit to be entrusted with charge of an engine should be able to understand. It is a useful book to all who make, tend, or employ electric machinery ." Architect. HANDBOOK FOR THE USE OF ELECTRICIANS. In the Operation and Care of Electrical Machinery a^d Apparatu- of the U. S. Sea-Coast Defences. By GEO. L. ANDERSON, A.M., Captain U. S. Artillery. Prepared under the direction of the Lieutenant-General Commanding the U. S. Army. Royal 8vo. cloth . . . Net 21 /O THE STANDARD ELECTRICAL DICTIONARY. A Popular Encyclopaedia of Words and Terms Used in me Practice of Electrical Engineering. Containing upwards of 3,000 definitions. By T. O'CoNOR SLOANE, A.M., Ph.D. Third Edition, with Appendix. Crown 8vo, 6go pp., 390 Illustrations, cloth Net 7/6 " The work has many attractive features in It. and Is, beyond doubt, a well put together and useful publication. The amount of ground covered may be gathered from the fact that in the index about 5,000 references will be found." Electrical Review. ELECTRIC LIGHT FITTING. A Handbook for Working Electrical Engineers, embodying Practical Notes on Installation Management. By J. W. URQUHART. With numerous Illustra- tions. Fourth Edition, Revised. Crown 8vo, cloth .... 5/O " This volume deals with the mechanics ot electric lighting, and Is addressed to men who are already engaged in the work, or are training for it. The work traverses a great deal of ground, and may be read as a sequel to the author's useful work on 'Electric Light.'" Electrician. ELECTRIC LIGHT. Its Production and Use, Embodying Plain Directions for the Treatment of Dynamo-Electric Machines, Batteries, Accumulators, and Electric Lamps. By J. W. URQUHART, C.E. Sixth Edition. Crown 8vo, cloth . . 7/6 " The whole ground of electric lighting is more or less covered and explained In a very clear and concise manner, " Electrical Review, DYNAMO CONSTRUCTION. A Practical Handbook for the Use of Engineer -Constructors and Electricians- in -Charge. Embracing Framework Building, Field Magnet and Armature Winding and Grouping, Compounding, &c. By J. W. URQUHART. Second Edition, Enlarged, with 114 Illustrations. Crown 8vo, cloth . . 7/6 " Mr. Urquhart's book is the first one which deals with these matters In such a way that the ensrineering student can understand them The book is very readable, and the author leads his rea 1ers up to difficult subjects by reasonably simple tests." Engineering Review. ELECTRIC SHIP-LIGHTING. A Handbook on the Practical Fitting and Running of Ships' Electrical Plant. For the Use of Shipowners and Builders, Marine Electricians, and Seagoing Engineers-in-Charge. By J. W. URQUHART, C.E. Second Edition, Revised and Extended. With 88 Illustrations. Crown 8vc, cloth . . . 7/6 "Mr. Urquhart is to be highly complimented for placing such a valuable work at the service of marine electricians. "The Steamship. ELECTRIC LIGHTING (ELEMENTARY PRINCIPLES OF). By ALAN A. CAMPBELL SWINTON, M.Inst.C.E., M.I.E.E. Fifth Edition. With 16 Illustrations. Crown 8vo, cloth 1/6 ELECTRIC LIGHT FOR COUNTRY HOUSES. A Practical Handbook on the Erection and Running of Small Installations, with Particulars of the Cost of Plant and Working. By J. H. KNIGHT. Third Edition, Revised. Crown 8vo, wrapper 1 /O HOW TO MAKE A DYNAMO. A Practical Treatise for Amateurs. Containing Illustrations and Detailed Instructions for Constructing a Small Dynamo to Produce the Electric Light. By ALFRED CROFTS. Sixth Edition, Revised. Crown 8vo, cloth . 2/O THE STUDENT'S TEXT-BOOK OF ELECTRICITY. By H. M. NQAP. F.R.S. 650 pp., with 470 Illustrations. Crown 8vo, cloth. 9/0 26 CROSBY LOCKWOOD * SON'S CATALOGUE. ARCHITECTURE, BUILDING, ETC. SPECIFICATIONS IN DETAIL. By FRANK W. MACEY, Architect, Author of "Conditions of Contract. Second Edition, Revised and Enlarged, containing 644 pp., and 2,000 Illustra- tions. Royal 8vo, cloth. [just Published. Net 21 /O SUMMARY OF CONTENTS: GENERAL NOTES (INCLUDING POINTS IN SPECIFICATION WRITING, THE ORDER OF A SPECIFICATION, AND NOTES ON ITEMS OFTEN OMITTED FROM A SPECIFICATION). FORM OF OUTSIDE COVER TO A SPECIFICATION. SPECIFICA- TION CF WORKS AND LIST OF GENERAL CONDITIONS. PRELIMINARY ITEMS (INCLUDING SHORING AND HOUSE BREAKER). DRAINAGE (INCLUDTNG RAIN-WATER WELLS AND REPORTS). EXCAVATOR (INCLUDING CONCRETE FLOORS, ROOFS, STAIRS, AND WALLSI. PAVIOR. BRICKLAYER (INCLUDING FLINTWORK, RIVER AND OTHER WALLING, SPRING- WATER WELLS, STORAGE TANKS, FOUNTAINS, FILTERS, TERRA COTTA AND FAIENCE). MASON. CARPENTER, JOINER AND IOONMONGER (INCLUDING FENCING AND PILING. SMITH AND FOUNDER (INCLUDING HEATING, FTRB HYDRANTS, STABLE AND COW-HOUSE FITTINGS!. SLATER (INCLUDING SLATE MASON). TILER. STONE TILER.- SHINGLER. THATCHER. PLUMBER (INCLUDING HOT-WATER WORK). ZINCWORKER. COPPER- SMITH. PLASTERER. GASFITTER. BELLHANGER. GLAZIER. PAINTER. PAPER- HANGER. GENERAL REPAIRS AND ALTERATIONS. VENTILATION. ROAD-MAKING ELECIRIC LIGHTING. INDEX. PRACTICAL BUILDING CONSTRUCTION. A Handbook for Students Preparing for Examinations, and a Book of Reference for Persons Engaged in Building. By JOHN PARNELL ALLEN, the Surveyor, Lecturer on Building Construction at the Durham College of Science, Newcastle-on-Tyne. Fourth Edition, Revised and Enlarged. Medium 8vo, 570 pp., with over 1,000 Illustrations, cloth. [Just Published. Net 7/6 " The most complete exposition of building construction we have seen. It contains all that is necessary to prepare students for the various examinations in building construction." Buildinf News. " The author depends nearly as much on his diagrams as on his type. The pages suggest the hand of a man of experience in building operations and the volume must be a blessing to many teachers as well as to students." The Architect. PRACTICAL MASONRY. A Guide to the Art of Stone Cutting. Comprising the Construction, Setting Out, and Working of Stairs, Circular Work, Arches, Niches, Domes, Penden- tives. Vaults, Tracery Windows, &c. ; to which are added Supplements relating to Masonry Estimating and Quantity Surveying, and to Building Stones and Ma'bles, and a Glossary of Terms. For the Use of Students, Masons, and Craftsmen. By WILLIAM R. PURCHASE, Building Inspector to the Borough of Hove. Fifth Edition, Enlarged. Royal 8vo, 226 pp., with 52 Lithographic Plates, comprising over 400 Diagrams, cloth. [Just Published. Net 7/6 The book Is a practical treatise on the subject, the author himself having commenced as an operative mason, and afterwards acted as foreman mason on many large and important buildings prior to the attainment of his present position. Most of the examples given are from actual wort carried out. It should be found of general utility to architectural students and others, as well as to those to whom it is specially addressed." Journal of the Royal Institute of British Architects. MODERN PLUMBING, STEAM AND HOT WATER HEATING. HEATING BY HOT WATER, VENTILATION AND HOT WATER SUPPLY. By WALTER TONES M.I.M.E. 360 pages, with 140 Illustrations. Medium 8vo, cloth. [Just Published. Net 6/O CONCRETE : ITS NATURE AND USES. A Book for Architects, Builders, Contractors, and Clerks of Works. By GEORGE L. SUTCLIFFE, A.R.I.B.A. Second Edition, thoroughly Revised and Enlarged. 39 6 pp., with Illustrations. Crowu^dot^ ^ ^ " The author treats a difficult subject In a lucid manner. The manual nils a long-felt gap. It Is careful and exhaustive ; equally useful as a student's guide and an architects boojc pf reference." Journal of the Royal Institute of British Architects, ARCHITECTURE, BUILDING, &c. 27 LOCKWOOD'S BUILDER'S PRICE BOOK for 1905. A Comprehensive Handbook of the Latest Prices and Data for Builders, Architects, Engineers, and Contractors. Re-constructed, Re-written, and Greatly Enlarged. By FRANCIS T. W. MILLER. 800 closely-printed pages, crown 8vo, cloth. [Just Published 4/0 " This book is a very useful one, and should find a place in every English office connected with the building 1 and engineering professions." Industries. " An excellent book of reference." Architect, " Compre aenstve, reliable, well arranged, legible, and well bound.'' British Architect. MEASURING AND VALUING ARTIFICERS' WORK (The Student's Guide to the Practice of). Containing Directions for taking Dimensions, Abstracting the same, and bringing the Quantities into Bill, with Tables of Constants for Valuation of Labour, and for the Calculation of Areas and Solidities. Originally edited by E. DOBSON, Architect. With Additions by E. W. TARN, M.A. Seventh Edition, Revised. Crown 8vo, cloth. 7/6 "The most complete treatise on the principles of measuring and valuing artificers' work.' Buildinp News. TECHNICAL GUIDE, MEASURER, AND ESTIMATOR. For Builders and Surveyors. Containing Technical Directions for Measuring Work in all the Building Trades, Complete Specifications for Houses, Roads, and Drains, and an Easy Method of Estimating the parts of a Building collectively. By A. C. BEATON. Ninth Edition. Waistcoat-pocket size. 1/6 " No builder, architect, surveyor, or valuer should be without his ' Beaton. ' "Building News. THE HOUSE-OWNER'S ESTIMATOR. Or, What will it Cost to Build, Alter, or Repair ? A Price Book for Un- professional People as well as the Architectural Surveyor and Builder. By J. D. SIMON. Edited by F. T. W. MILLER, A.R.I.B.A. Fifth Edition. Carefully Revised. Crown 8vo, cloth Net 3/6 " In two years it will repay its cost a hundred times over." Field. SPECIFICATIONS FOR PRACTICAL ARCHITECTURE. A Guide to the Architect, Engineer, Surveyor, and Builder. Upon the Basis of the Work by A BARTHOLOMEW, Revised, Corrected, and greatly added to by F. ROGERS, Architect. Third Edition. 8vo, cloth ... 1 5/Q " one of the books with which every young architect must be equipped." Architect. ARCHITECTURAL PERSPECTIVE. The whole Course and Operations of the Draughtsman in Drawing a Large House in Linear Perspective. Illustrated by 43 Folding Plates. By F. () FERGUSON. Third Edition. 8vo, boards 3Q " It is the most intelligible of the treatises on this ill-treated subject that I have met with E. INGRESS BELL, ESQ., in the R.I.B.A. Journal. PRACTICAL RULES ON DRAWING. For the Builder and Young Student in Architecture. By G. PYNE. 410. 3/6 THE MECHANICS OF ARCHITECTURE. A Treatise on Applied Mechanics, especially Adapted to the Use of Architects. By E. W. TARN, M.A., Author of "The Science of Building," &c. Second Edition, Enlarged. Illustrated with 125 Diagrams. Crown 8vo, cloth 7/6 " The book is a very useful and helpful manual of architectural mechanics." Builder. A HANDY BOOK OF VILLA ARCHITECTURE. Being a Series of Designs for Villa Residences in various Styles. With Outline Specifications and Estimates. By C. WICKES, Architect, Author of "The Spires and Towers of England," &c. 61 Plates, 410, half-morocco, gilt edges ... 1 11s. 60. DECORATIVE PART OF CIVIL ARCHITECTURE. By Sir WILLIAM CHAMBERS, F.R.S. With Portrait, Illustrations, Notes, and an EXAMINATION OF GRECIAN ARCHITECTURE, by JOSEPH GWILT, F.S.A. Revised and Edited by W. H. LEEDS. 66 Plates, 410, cloth . . 21/O THE ARCHITECT'S GUIDE. Being a Text-book of Useful Information for Architects, Engineers, Surveyors, Contractors, Clerks of Works, &c. By F. ROGERS. Crown 8vo. . 3/6 30 CROSBY LOCK WOOD * SON'S CATALOGUE. HANDRAILINQ COMPLETE IN EIGHT LESSONS. On the Square-Cut System. By J. S. GOLDTHORP, Teacher of Geometry and Building Construction at the Halifax Mechanics' Institute. With Eight Plates and over 150 Practical Exercises. 410, cloth .... 36 " Likely to be of considerable value to joiners and others who take a pride in good work. The arrangement of the book is excellent. We heartily commend it to teachers and students." Timber Trades Journal, TIMBER MERCHANT'S and BUILDER'S COMPANION. Containing New and Copious Tables of the Reduced Weight and Measure- ment of Deals and Battens, of all sizes, and other Useful Tables for the use of Timber Merchants and Builders. By WILLIAM DOWSING. Fourth Edition, Revised and Corrected. Crown 8vo, cloth 3/O " We are glad to see a fourth edition of these admirable tables, which for correctness and simplicity of arrangement leave nothing to be desired." Timber Trades Journal, THE PRACTICAL TIMBER MERCHANT. Being a Guide for the Use of Building Contractors, Surveyors, Builders, &c., comprising useful Tables for all purposes connected with the Timber Trade. Marks of Wood, Essay on the Strength of Timber, Remarks on the Growth of Timber, &c. By W. RICHARDSON. Second Edition. Fcap. 8vo, cloth . 3/6 " This handy manual contains much valuable information for the use of timber merchants, builders, foresters, and all others connected with the growth, sale, and manufacture of timber." Journal of Forestry. PACKING-CASE TABLES. Showing the number of Superficial Feet in Boxes or Packing-Cases, from six inches square and upwards. By W. RICHARDSON, Timber Broker. Third Edition. Oblong 4to, cloth 3/6 " Invaluable labour-saving tables." Ironmonger. " Will save much labour and calculation." Grocer. GUIDE TO SUPERFICIAL MEASUREMENT. Tables calculated from i to 200 inches in length by i to 108 inches in breadth. For the use of Architects, Surveyors, Engineers, Timber Merchants, Builders, &c. By JAMES HAWKINGS. Fifth Edition. Fcap., cloth. 3/6 " These tables will be found of great assistance to all who require to make calculations of superficial measurement." English Mechanic. PRACTICAL FORESTRY. And its Bearing on the Improvement of Estates. By CHARLES E. CURTIS, F.S.I., Professor of Forestry, Field Engineering, and General Estate Management, at the College of Agriculture, Downton. Second Edition, Revised. Crown 8vo, cloth 3/6 PREFATORY REMARKS. OBJECTS OF PLANTING. CHOICE OF A FORESTER. CHOICE OF SOIL AND SITE. LAYING OUT OF LAND FOR PLANTATIONS. PREPARATION OF THE GROUND FOR PLANTING. DRAINAGE. PLANTING. DISTANCES AND DISTRI- BUTION OF TREES IN PLANTATIONS. TREES AND GROUND GAME. ATTENTION AFTER PLANTING. THINNING OF PLANTATIONS PRUNING OF FOREST TREES. REALIZATION. METHODS OF SALE. MEASUREMENT OF TIMBER. MEASUREMENT AND VALUATION OF LARCH PLANTATION. FIRE LINES. COST OF PLANTING. " Mr. Curtis has in the course of a series of short pithy chapters afforded much informa- tion of a useful and practical character on the planting and subsequent treatment of trees." Illustrated Carpenter and Builder. THE ELEMENTS OF FORESTRY. Designed to afford Information concerning the Planting and Care of Forest Trees for Ornament or Profit, with suggestions upon the Creation and Care of Woodlands. By F. B. HOUGH. Large crown 8vo, cloth ... 1 0/O TIMBER IMPORTER'S, TIMBER MERCHANT'S, AND BUILDER'S STANDARD GUIDE. By RICHARD E. GRANDY. Comprising : An Analysis of Deal Standards, Home and Foreign, with Comparative Values and Tabular Arrangements for fixing Net Landed Cost on Baltic and North American Deals, including all intermediate Expenses, Freight, Insurance, &c., &c ; together with copious Information for the Retailer and Builder. Thrd Edition, Revised 121110, cloth 2 C " Everything it pretends to be: built up gradually, it leads one from a forest to a treenail, and throws in, as a makeweight, a host of material concerning bricks, columns, cisterns, &c." English Mechanic. DECORATIVE ARTS. &c. 31 DECORATIVE ARTS, ETC. SCHOOL OF PAINTING FOR THE IMITATION OF WOODS AND MARBLES. As Taught and Practised by A. R. VAN DER BURG and P. VAN DER BURG, Directors of the Rotterdam Painting Institution. Royal folio, i8J by 12^ in., Illustrated with 24 full-size Coloured Plates ; also 12 plain Plates, comprising 154 Figures. Fourth Edition cloth Net 1 5s. LIST OF PLATES. i. VARIOUS TOOLS REQUIRED FOR WOOD PAINTING. a, 3. WALNUT ; PRELIMINARY STAGES OF GRAINING AND FINISHED SPECIMEN. 4. TOOLS USED FOR MARBLE PAINTING AND METHOD OF MANIPULATION. 5, 6. ST. REMI MARBLE; EARLIER OPERATIONS AND FINISHED SPECIMEN. 7. METHODS OF SKETCHING DIFFERENT GRAINS, KNOTS, &c. 8, 9. ASH: PRELIMINARY STAGES AND FINISHED SPECI- MEN 10. METHODS OF SKETCHING MARBLE GRAINS. n, 12. BRECHE MARBLE ; PRELIMINARY STAGES OF WORKING AND FINISHED SPECIMEN. 13. MAPLE ; METHODS OF PRODUCING THE DIFFERENT GRAINS. 14, 15. BIRD'S-EYE MAPLE; PRELIMINARY STAGES AND FINISHED SPECIMEN. 16. METHODS OF SKETCHING THE DIFFERENT SPECIES OF WHITE MARBLE. 17, 18. WHITE MARBLE ; PRELIMINARY STAGES OF PROCESS AND FINISHED SPECIMEN. 19. MAHOGANY; SPECIMENS OF VARIOUS GRAINS AND METHODS OF MANIPULATION. ao, ai. MAHOGANY ; EARLIER STAGES AND FINISHED SPECIMEN. 22, 23, 24. SIENNA MARBLE; VARIETIES OF GRAIN, PRELIMINARY STAGES AND FINISHED SPECIMEN. 25, 26, 27. JUNIPER WOOD; METHODS OF PRO- DUCING GRAIN, &c. ; PRELIMINARY STAGES AND FINISHED SPECIMEN. 28, 29, 30. VERT DE MER MARBLE; VARIETIES OF GRAIN AND METHODS OF WORKING, UNFINISHED AND FINISHED SPECIMENS. 31, 32, 33. OAK ; VARIETIES OF GRAIN, TOOLS EMPLOYED AND METHODS OF MANIPULATION, PRELIMINARY STAGES AND FINISHED SPECIMEN. 34. 35. 36- WAULSORT MARBLE; VARIETIES OF GRAIN, UNFINISHED AND FINISHED SPECIMENS. " Those who desire to attain skill in the art of painting woods and marbles will find advantage In consulting this book. . . . Some of the Working Men's Clubs should give their young men the opportunity to study it." Builder. " A comprehensive guide to the art. The explanations of the processes, the manipulation and management of the colours, and the beautifully executed plates will not be the least valuable to the student who aims at making his work a faithful transcript of nature." Building- News. " Students and novices are fortunate who are able to become the possessors of so noble a work." The Architect. ELEMENTARY DECORATION. A Guide to the Simpler Forms of Everyday Art. Together with PRACTICAL HOUSE DECORATION. By JAMES W. FACEY. With numerous Illus- trations. In One Vol., strongly half-bound 5/O HOUSE PAINTING, GRAINING, MARBLING, AND S1QN WRITING. A Practical Manual of. By ELLIS A. DAVIDSON. Eighth Edition. With Coloured Plates and Wood Engravings. Crown 8vo, cloth . . . 6/O "A mass of information of use to the amateur and of value to the practical man." English Mechanic, THE DECORATOR'S ASSISTANT. A Modern Guide for Decorative Artists and Amateurs, Painters, Writers, Gilders, &c. Containing upwards of 600 Receipts, Rules, and Instructions ; with a variety of Information for General Work connected with every Class of Interior and Exterior Decorations, &c. Eighth Edition. Cr. 8vo . 1 /O " Full of receipts of value to decorators, painters, gilders, &c. The book contains the gist of larger treatises on colour and technical processes. It would be difficult to meet with a work so full 01 varied information on the painter's art." Building News. MARBLE DECORATION And the Terminology of British and Foreign Marbles. A Handbook for Students. By GEORGE H. BLAGROVB, Author of " Shoring and its Applica- tion," &c. With ?8 Illustrations. Crown 8vo, cloth .... 3/6 " This most usetui ana much wanted handbook should be in the hand:- ui every architect and builder, "a-uiuiing ri or la. "A careiully and usefully written treatise ; the work is essentially prdctical." Scotsman, CkOSSY LOCRWOOb SON'S CATALOGUE. DELAMOTTE S WORKS ON ILLUMINATION AND ALPHABETS. ORNAMENTAL ALPHABETS, ANCIENT & MEDIAEVAL. From the Eighth Century, with Numerals; including Gothic, Church-Text, large and small, German, Italian, Arabesque, Initials for Illumination. Monograms, Crosses, &c.. for the use of Architectural and Engineering Draughtsmen, Missal Painters, Masons, Decorative Painters, Lithographers, Engravers, Carvers, &c., &c. Collected and Engraved bv F. DELAMOTTE, and printed in Colours. New and Cheaper Edition. Royal 8vo, oblong. ornamental boards 2/6 " For those who insert enamelled sentences round gilded chalices, who blazon shop legends over shop-doors, who letter church walls with pithy sentences from the Decalogue, this book will b useful. " Athenemm.. MODERN ALPHABETS, PLAIN AND ORNAMENTAL. Including German, Old English, Saxon, Italic, Perspective, Greek. Hebrew. Court Hand, Engrossing, Tuscan, Riband, Gothic, Rustic, and Arabesque ; with several Original Designs, and an Analysis of the Roman and Old English Alphabets, large and small, and Numerals, for the use of Draughtsmen, Surveyors, Masons, Decorative Painters, Lithographers, Engravers, Carvers. &c. Collected and Engraved by F. DELAMOTTE, and printed in Colours. New and Cheaper Edition. Royal 8vo, oblong, ornamental boards . 2/6 " There is comprised in it every possible shape into which the letters of the alphabet and numerals can be formed, and the talent which has been expended in the conception of the various plain and ornamental letters is wonderful. " Standard. MEDIEVAL ALPHABETS AND INITIALS. By F. G. DELAMOTTE. Containing 21 Plates and Illuminated Title, printed in Gold and Colours. With an Introduction by J. WILLIS BROOKS. Fifth Edition. Small 410, ornamental boards Net 5/Q "A volume in which the letters of the alphabet come forth glorified In gilding and all the colours of the prism interwoven and intertwined and intermingled." Sun, A PRIMER OF THE ART OF ILLUMINATION. For the Use of Beginners ; with a Rudimentary Treatise on the Art, Practical Directions for its Exercise, and Examples taken from Illuminated MSS., printed in Gold and Colours. By F. DELAMOTTE. New and Cheaper Edition. Small 410, ornamental boards 6/O "The examples of ancient MSS. recommended to the student, which, with much good sense, the author chooses from collections accessible to all, are selected with judgment and knowledge as well as taste." Athenaum.. THE EMBROIDERER'S BOOK OF DESIGN. Containing Initials, Emblems, Cyphers, Monograms, Ornamental Borders, Ecclesiastical Devices, Mediaeval and Modern Alphabets, and National Emblems. Collected by F. DELAMOTTE, and printed in Colours. Oblong royal 8vo, ornamental wrapper Net 2,O " The book will be of great assistance to ladies and young children who are endowed with the art of plying the needle in this most ornamental and useful pretty work." East Anglian Times. WOOD-CARVING FOR AMATEURS. With Hints on Design. By A LADY. With 10 Plates. New and Cheaper Edition. Crown 8vo, in emblematic wrapper 2/0 " The handicraft of the wood-carver, so well as a book can impart it, may be learnt from ' A Lady's ' publication." Athenaum. PAINTING POPULARLY EXPLAINED. By THOMAS JOHN GULLICK, Painter, and JOHN TIMBS, F.S.A. Including Fresco, Oil, Mosaic, Water-Colour, Water-Glass, Tempera, Encaustic. Miniature. Painting on Ivory, Vellum, Pottery, Enamel, Glass, &c. Fifth Edition Crown 8vo, cloth 6/0 * t * Adopted as a Prize Book at South Kensington. " Much may be learned, even by ihose who fancy they do nor require to be taught, .rcffl the careful perusal of ihii unpretending but coaiprehent-ive ireatise 'Art Journal. NATURAL SCIENCE, &c. 33 NATURAL SCIENCE, ETC. THE VISIBLE UNIVERSE. Chapters on the Origin and Construction of the Heavens. By J. E. GORE, F.R.A.S., Author of " Star Groups," &c. Illustrated by 6 Stellar Photographs and 12 Plates. Demy 8vo, cloth 1 6/O STAR GROUPS. A Student's Guide to the Constellations. By J. ELLARD GORE, F.R.A.S., M.R.I.A., &c., Author of "The Visible Universe," "The Scenery of the Heavens," &c. With 30 Maps. Small 410, cloth 6/O AN ASTRONOMICAL GLOSSARY. Or, Dictionary of Terms used in Astronomy. With Tables of Data and Lists of Remarkable and Interesting Celestial Objects. By J. ELLARD GORE, F.R.A.S., Author of " The Visible Universe," &c. Small crown 8vo, cloth. 2/6 THE MICROSCOPE. Its Construction and Management. Including Technique, Photo-micrography, and the Past and Future of the Microscope. By Dr. HENRI VAN HEURCK. Re-Edited and Augmented from the Fourth French Edition, and Translated by WYNNE E. BAXTER, F.G.S. Imp. 8vo, cloth .... 18/O A MANUAL OF THE MOLLUSCA. A Treatise on Recent and Fossil Shells. By S. P. WOODWARD, A.L.S., F.G.S. With an Appendix on RECENT AND FOSSIL CONCHOLOGICAL DISCOVERIES, by RALPH TATE, A.L.S., F.G.S. With 23 Plates and upwards of 300 Woodcuts. Reprint of Fourth Edition (1880). Crown 8vo, cloth 7/6 THE TWIN RECORDS OF CREATION. Or, Geology and Genesis, their Perfect Harmony and Wonderful Concord. By G. W. V. LK VAUX. 8vo, cloth . 5/O LARDNER'S HANDBOOKS OF SCIENCE. HANDBOOK OF MECHANICS. Enlarged and re-written by B. LOEWY, F.R.A.S. Post 8vo, cloth . 6/O HANDBOOK OF HYDROSTATICS AND PNEUMATICS. Revised and Enlarged by B. LOEWY, F.R.A.S. Post 8vo, cloth . 5/O- HANDBOOK OF HEAT. Edited and re-written by B. LOEWY, F.R.A.S. Post 8vo, cloth . 6/O HANDBOOK OF OPTICS. New Edition. Edited by T. OLVER HARDING, B.A. Small 8vo, cloth 5/O ELECTRICITY, MAGNETISM, AND ACOUSTICS. Edited by GEO. C. FOSTER, B.A. Small 8vo, clo*,h .... 6/O HANDBOOK OF ASTRONOMY. Revised and Edited by EDWIN DUNKIN, F.R.A.S. 8vo, cloth . . 9/6 MUSEUM OF SCIENCE AND ART. With upwards of 1,200 Engravings. In Six Double Volumes, j1 1 9. Cloth, or half-morocco 1 11s. 60. NATURAL PHILOSOPHY FOR SCHOOLS . . 3/6 ANIMAL PHYSIOLOGY FOR SCHOOLS . . 3/6 THE ELECTRIC TELEGRAPH. Revised by E. B. BRIGHT, F.R.A.S. Fcap. 8vc, cloth . . . 2/6 34 CROSBY LOCK WOOD & SON'S CATALOGUE. CHEMICAL MANUFACTURES, CHEMISTRY, ETC. THE OIL FIELDS OF RUSSIA AND THE RUSSIAN PETROLEUM INDUSTRY. A Practical Handbook on the Exploration, Exploitation, and Management of Prussian Oil Properties, including Notes on the Origin of Petroleum in Russia, a Description of the Theory and Practice of Liquid Fuel, and a Translation of the Rules and Regulations concerning Russian Oil Properties. By A. BEEBY THOMPSON, A.M.I. M.E., late Chief Engineer and Manager of the European Petroleum Company's Russian Oil Properties. About 500 pp., with numerous Illustrations and Photographic Plates, and a Map of the Balakhany- Saboontchy-Romany Oil Field. Super-royal 8vo, cloth. [Just Published. Net 3 3 S . THE ANALYSIS OF OILS AND ALLIED SUBSTANCES. By A. C. WRIGHT, M.A.Oxon., B.Sc.Lond., formerly Assistant Lecturer in Chemistry at the Yorkshire College, Leeds, and Lecturer in Chemistry at the Hull Technical School. Demy 8vo, cloth ...... Net QQ THE GAS ENGINEER'S POCKET-BOOK. Comprising Tables, Notes and Memoranda relating to the Manufacture, Distribution and Use of Coal Gas and the Construction of Gas Works. By H. O'CONNOR, A.M. Inst.C.E. Second Edition, Revised. 470 pp., crown 8vo, fully Illustrated, leather .......... 1 Q/6 "The book contains a vast amount of information. The author goes consecutively through the engineering details and practical methods involved in each of the different processes or parts of a gas-works. He has certainly succeeded in making a compilation of hard matters of fact " absolutely interestine to read." Gas W "The volume contains a great quantity of specialised information, compiled, we believe, from trustworthy sources, which should make it of considerable value to those for whom it is specifically produced. Engineer. LIGHTING BY ACETYLENE Generators, Burners, and Electric Furnaces. By WILLIAM E. GIBBS, M.E. With 66 Illustrations. Crown 8vo, cloth ....... TIG ENGINEERING CHEMISTRY. A Practical Treatise for the Use of Analytical Chemists, Engineers, Iron Masters, Iron Founders, Students and others. Comprising Methods of Analysis and Valuation of the Principal Materials used in Engineering Work, with numerous Analyses, Examples and Suggestions. By H. JOSHUA PHILLIPS, F.I.C., F.C.S. Third Edition, Revised and Enlarged. Crown 8vo, 420 pp., with Plates and other Illustrations, cloth. .... Net "I 0/Q "In this work the author has rendered no small service to a numerous body of practical dnen. . . . The analytical methods may be pronounced most satisfactory, being as accurate as the despatch required of engineering chemists permits." Chemical News. " The analytical methods given are, as a whole, such as are likely to give rapid and trust- worthy results in experienced hands. . . . There is much excellent descriptive matter in the work, the chapter on ' Oils and Lubrication ' being specially noticeable in this respect." Engineer. NITRO-EXPLOSIVES. A Practical Treatise concerning the Properties, Manufacture, and Analysis of Nitrated Substances, including the Fulminates, Smokeless Powders, and Celluloid. By P. GERALD SANFORD, F.I.C., Consulting Chemist to the Cotton Powder Company, Limited, &c. With Illustrations. Crown 8vo, cloth. 9/O "One of the very few text-books in which can be found just what is wanted. Mr. Sanfprd goes steadily through the whole list of explosives commonly used, he names any given explosive, and tells us of what it is composed and how it is manufactured. The book is excellent." Engineer. A HANDBOOK ON MODERN EXPLOSIVES. A Practical Treatise on the Manufacture and Use of Dynamite, Gun-Cotton, Nitro-Glycerine and other Explosive Compounds, including Collodion-Cotton. With Chapters on Explosives in Practical Application. By M. EISSLSR. M E. Second Edition, Enlarged. Crown 8vo, cloth 1 2/6 " A veritable mine of in r ormiti>n on the subject of explosives employed for military, mining and blasting purposes." Army and Navy Gazette. CHEMICAL MANUFACTURES, CHEMISTRY, &-c. 35 A MANUAL OF THE ALKALI TRADE. Including the Manufacture of Sulphuric Acid, Sulphate of Soda, and Bleaching Powder. By JOHN LOMAS, Alkali Manufacturer. With 232 Illustrations and Working Drawings. Second Edition, with Additions. Super-royal 8vo, cloth 1 10s. " We find not merely a sound and luminous explanation of the chemical principles of the trade, but a notice of numerous matters which have a most important bearing on the successful conduct of alkali works, but which are generally overlooked by even experienced technological authors." Chemical Review, DANGEROUS GOODS. Their Sources and Properties, Modes of Storage and Transport. With Notes and Comments on Accidents arising therefrom. A Guide for the Use of Government and Railway Officials, Steamship Owners, &c. By H. JOSHUA PHILLIPS, F.I.C., F.C.S. Crown 8vo, 374 pp., cloth .... 9/Q " Merits a wide circulation, and an intelligent, appreciative study." Chemical News. THE BLOWPIPE IN CHEMISTRY, MINERALOGY, Etc. Containing all known Methods of Anhydrous Analysis, many Working Examples, and Instructions for Making Apparatus. By Lieut. -Colonel W. A. Ross, R.A., F.G.S. Second Edition, Enlarged. Crown 8vo, cloth . 5/O " The student who goes conscientiously through the course of experimentation here aid down will gain a better insight into inorganic chemistry and mineralogy than if he had ' got up ' any of the best text-books of the day, and passed any number of examinations in their contents. " Chemical News. THE MANUAL OF COLOURS AND DYE-WARES. Their Properties, Applications, Valuations, Impurities and Sophistications. For the Use of Dyers, Printers, Drysalters, Brokers, &c. By J. W. SLATER. Second Edition, Revised and greatly Enlarged. Crown 8vo, cloth . "7/6 " There Is no other work which covers precisely the same ground. To students preparing for examinations in dyeing and printing it will prove exceedingly useful." Chemical News. A HANDYBOOK FOR BREWERS. Being a Practical Guide to the Art of Brewing and Malting. Embracing the Conclusions of Modern Research which bear upon the Practice of Brewing. By HERBERT EDWARDS WRIGHT, M.A. Second Edition, Enlarged. Crown 8vo, 530 pp., cloth ... ... ... 1 2/6 " May be consulted with advantage by the student who is preparing himself for examinationa tests, while the scientific brewer will find in it a resume" of all the most important discoveries of modem times. The work is written throughout in a clear and concise manner, and the author takes great care to discriminate between vague theories and well-established facts " Brewers' Journal. " We have great pleasure In recommending this handy book, and have no hesitation In saying that It is one of the best if not the best which has yet been written on the subject of beer-brewing In this country ; it should have a place on the shelves of every brewer's library." Brewers' Guardian. FUELS: SOLID, LIQUID, AND GASEOUS. Their Analysis and Valuation. For the Use of Chemists and Engineers. By H. J. PHILLIPS, F.C.S., formerly Analytical and Consulting Chemist to the G.E. Rlwy. Fourth Edition. Crown 8vo, cloth 2/O " Ought to have its place in the laboratory of every metallurgical establishment and wherever fuel Is used on a large scale." Chemical News. THE ARTISTS' MANUAL OF PIGMENTS. Showing their Composition, Conditions of Permanency, Non-Permanency, and Adulterations, &c., with Tests of Purity. By H. C. STANDAGE. Third Edition. Crown 8vo, cloth ... 2/6 " This work is indeed multum-in-parvo, and we can, with good conscience, recommend it to all who come in contact with pigments, whether as makers, dealers, or users." Chemical Review. A POCKET-BOOK OF MENSURATION AND GAUGING. Containing Tables, Rules, and Memoranda for Revenue Officers, Brewers, Spirit Merchants, &c. By J. B. MANT, Inland Revenue. Second Edition, Revised. i8mo, leather 4/O Should be in the hands of every practical brewer." Brewers journal. 36 CROSBY LOCK WOOD * SON'S CATALOGUE. INDUSTRIAL ARTS, TRADES, AND MANUFACTURES. THE CULTIVATION AND PREPARATION OF PARA RUBBER. By W. H. JOHNSON, F.L.S., F R.H.S., Director of Agriculture, Gold Coast Colony, West Africa, Commissioned by Government in 1902 to visit Ceylon to Study the Methods employed there in the Cultivation and Preparation of Para Rubber and other Agricultural Staples for Market, with a view to Intro- duce them into West Africa. Demy 8vo, cloth. [Just Published- Net 716 SUMMARY OF CONTENTS: INTRODUCTORY. THE PARA RUBBER TREE (Htiea trasiliensts) AT HOME AND ABROAD. CULTIVATION OF THE TREE : PROPAGATION. SITE FOR PLANTATION. DISTANCE APART TO PLANT THE TREES. TRANSPLANTING. CULTIVATION. INSECT PESTS AND FUNGOID DISEASES. COLLECTING THE RUBBER: VARIOUS METHODS EMPLOYED IN TAPPING RUBBER TREES. FLOW OF LATEX INCREASED BY WOUNDING THE TREE. How TO TAP. THE PREPARATION OF RUBBER FROM THE LATEX: LATEX. VARIOUS METHODS EMPLOYFD IN THR PREPARATION OF RUBBER. SUGGESTED METHOD FOR PREPARING RUBBER. SCRAP RUBBER. YIELD OK PARA RUBBER FROM CULTIVATED TREES : CEYLON. MALAY PENINSULA. GOLD COAST, WEST AFRICA. ESTABLISHMENT AND MAINTENANCE OF A PARA>RU H BER PLANTATION : CEYLON. MALAY PENINSULA. COMMERCIAL VALUE OF THE OIL IN HEVEA SEEDS. TEA MACHINERY AND TEA FACTORIES. A Descriptive Treatise on the Mechanical Appliances required in the Cultivation of the Tea Plant and the Preparation of Tea for the Market. By A. J. WALLIS-TAYLER, A.M. Inst. C.E. Medium 8vo, 468 pp. With ai3 Illustrations Net 25/O SUMMARY OF CONTENTS. MECHANICAL CULTIVATION OR TILLAGE OF THE SOIL. PLUCKING OR GATHERING THE LEAF. TEA FACTORIES. THE DRESSING, MANUFACTURE, OR PREPARATION OF TEA BY MECHANICAL MEANS. ARTIFICIAL WITHERING OF THE LEAF. MACHINES FOR ROLLING OR CURLING THE LEAF. FERMENTING PROCESS. MACHINES FOR THE AUTOMATIC DRYING OR FIRING OF THE LEAF. MACHINES FOR NON-AUTOMATIC DRYING OR FIRING OF THE LEAF. DRYING OR FIRING MACHINES. BREAKING OR CUTTING, AND SORTING MACHINES. PACKING THE TEA. MEANS OF TRANSPORT ON TEA PLANTATIONS. MISCELLANEOUS MACHINERY AND APPARATUS. FINAL TREATMENT OF THE TEA. TABLES AND MEMORANDA. "The subject of tea machinery is now one of the first interest to a large class of people, to whom we strongly commend the volume." Chamber of Commerce Journal. "Contains a very full account of the machinery necessary for the proper outfit of a factory, and also a description of the processes best carried out by this machinery." Journal Society of Arts. FLOUR MANUFACTURE. A Treatise on Milling Science and Practice. By FRIEDRICH KICK, Imperial Regierungsrath, Professor of Mechanical Technology in the Imperial German Polytechnic Institute, Prague. Translated from the Second Enlarged and Revised Edition. By H. H. P. POWLES, A.M. Inst. C.E. 400 pp , with 28 Folding Plates, and 167 Woodcuts. Royal 8vo, cloth . . fil 5s, " This invaluable work is, and will remain, the standard authority on the science of milling. . . . The miller who has read and digested this work will have laid the foundation, so to speak, of a successful career ; he will have acquired a number of general principles which he can proceed to apply. In this handsome volume we at last have the accepted text-book of modern milling In good, sound English, which has little, if any, trace of the German idiom." The Miller " The appearance of this celebrated work in English is very opportune, and British millers will, we are sure, not be slow in availing themselves of its pages." Millers' Gazette. COTTON MANUFACTURE. A Manual of Practical Instruction of the Processes of Opening, Carding, Combing, Drawing, Doubling and Spinning of Cotton, the Methods of Dyeing, &c. For the Use of Operatives, Overlookers, and Manufacturers. By JOHN LISTER, Technical Instructor, Pendleton. 6vo, cloth . . 776 " A distinct advance in the literature of cotton manufacture." Machinery. " It is thoroughly reliable, fulfilling nearly all the requirements desired." Glas^-cw Herald. MODERN CYCLES. A Practical Handbook on their Construction and Repair. By A. J. WALLIS- TAYLER, A. M. Inst. C. E., Author of " Refrigerating Machinery," &c. With upwards of 300 Illustrations. Crown 8vo, cloth . .... "1 O/6 "The book will prove a valuable guide for all those who aspire to the manufacture or repair of their own machines." The Field. "A very useful book, which is quite entitled to rank as a standard work for students of cycle construction. Wheeling. MOTOR CARS OR POWER CARRIAGES FOR COMMON ROADS. By A J. WALLIS-TAYLER, A.M. Inst. C.E. Crown 8vo, cloth . . 4/6 "A work that an engineer, thinking of turning his attention to motor-carriage wrk, would do well to read as a preliminary to starting operations." Engineering. INDUSTRIAL AND USEFUL ARTS. 37 PRACTICAL TANNING. A Handbook of Modern Procesess, Receipts, and Suggestions for the Treatment of Hides, Skins, and Pelts of every Description. By L. A. FLEMMING, American Tanner. 472 pages. 8vo, cloth. [Just Publistud. Net 25/O THE ART OF LEATHER MANUFACTURE. Being a Practical Handbook, in which the Operations of Tanning, Currying, and Leather Dressing are fully Described, and the Principles of Tanning Explained, and many Recent Processes Introduced ; as also Methods for the Estimation of Tannin, and a Description of the Arts of Glue Boiling, Gut Dressing, &c. By ALEXANDER WATT. Fourth Edition. Crown 8vo. cloth. 9/O "A sound, comprehensive treatise on tanning and its accessories. The book is an eminently valuable production, which redounds to the credit of both author and publishers." Chemical Review. THE ART OF SOAP-MAKING. A Practical Handbook of the Manufacture of Hard and Soft Soaps, Toilet Soaps, &c. Including many New Processes, and a Chapter on the Recovery of Glycerine from Waste Leys. By ALEXANDER WATT. Sixth Edition, including an Appendix on Modern Candlemaking. Crown 8vo, cloth . 7/6 " A thoroughly practical treatise. We congratulate the author on the success of his endeavour to fill a void in English technical literature." Nature. "The work will prove very useful, not merely to the technological student, but to the practical soap boiler who wishes to understand the theory of his art." Chemical News. PRACTICAL PAPER-MAKING. A Manual for Paper-Makers and Owners and Managers of Paper-Mills. With Tables, Calculations, &c. By G. CLAPPERTON, Paper-Maker. With Illus- trations of Fibres from Micro-Photographs. Crown 8vo, cloth . . 6/0 " The author caters for the requirements of responsible mill hands, apprentices, &c., whilst his manual will be found of great service to students of technology, as well as to veteran paper- snakers and mill owners. The illustrations form an excellent feature." The World's Paper Tradt Review. THE ART OF PAPER-MAKING. A Practical Handbook of the Manufacture of Paper from Rags, Esparto, Straw, and other Fibrous Materials. Including the Manufacture of Pulp from Wood Fibre, with a Description of the Machinery and Appliances used. To which are added Details of Processes for Recovering Soda from Waste Liquors. By ALEXANDER WATT. With Illustrations. Crown Svo, cloth . . 7IQ " It may be regarded as the standard work on the subject. The book is full of valuable information, The 'Art of Paper-Making' is in every respect a model of a text-book, either for a technical class, or for the private student." Paper and Printing Trades Journal. A TREATISE ON PAPER. For Printers and Stationers. With an Outline of Paper Manufacture ; Complete Tables of Sizes, and Specimens of Different Kinds of Paper. By RICHARD PARKINSON, late of the Manchester Technical School. Demy 8vo, cloth 3/6 CEMENTS, PASTES, GLUES, AND GUMS- A Practical Guide to the Manufacture and Application of the various Aggluti- nants required in the Building, Metal-Working, Wood-Working, and Leather- Working Trades, and for Workshop and Office Us^. With upwards of ooo Recipes. By H. C. STANDAGE. Third Edition. Crown Svo, cloth . 2/O "We have pleasure In speaking favourably of this volume. So far as we have had experience, which is not inconsiderable, this manual is trustworthy." Athenaunt, THE CABINET-MAKER'S GUIDE TO THE ENTIRE CONSTRUCTION OF CABINET WORK. Including Veneering, Marquetrie, Buhlwork, Mosaic, Inlaying, &c. _ By RICHARD BITMEAD. Illustrated with Plans, Sections, and Working Drawings. Small crown Svo, cloth 2/6 FRENCH POLISHING AND ENAMELLING. A Practical Work of Instruction. Including Numerous Recipes for making Polishes, Varnishes, Glaze-Lacquers, Revivejs, &c. By RICHARD BITMEAD, Author of " The Cabinet-Maker's Gu" " 38 CROSBY LOCK WOOD 6- SON'S CATALOGUE. WATCH REPAIRING, CLEANING, AND ADJUSTING. A Practical Handbook dealing with the Materials and Tools Used, and the Methods of Repairing, Cleaning, Altering, and Adjusting all kinds of English and Foreign Watches, Repeaters, Chronographs, and Marine Chronometers. By F. J. GARRARD, Springer and Adjuster of Marine Chronometers and Deck Watches for the Admiralty. With over 200 Illustrations. Crown 8vo, cloth. {Just Published. Net 4/6 MODERN HOROLOGY, IN THEORY AND PRACTICE. Translated from the French of CLAUDIUS SAUNIER, ex-Director of the School of Horology at Mecon, by JULIEN TRIPPLIN, F.R.A.S., Besan9on Watch Manufacturer, and EDWARD RIGG, M.A., Assayer in the Royal Mint. With Seventy-eight Woodcuts and Twenty-two Coloured Copper Plates. Second Edition. Super-royal 8vo, 2 2s. cloth ; half-calf . . . 2 1Osi "There is no horological work in the English language at all to be compared to this produc- tion of M. Saunier's for clearness and completeness. It is alike good as a guide for the student and as a reference for the experienced horologist and skilled workman." Horological Journal, " The latest, the most complete, and the most reliable of those literary productions to which continental watchmakers are indebted for the mechanical superiority over their English brethren hi fact, the Book of Books is M. Saunier's ' Treatise.' " Watchmaker, Jeweller, and Silversmith. THE WATCH ADJUSTER'S MANUAL. A Practical Guide for the Watch and Chronometer Adjuster in Making, Springing, Timing and Adjusting for Isochronism, Positions and Temperatures. By C. E. FRITTS. 370 pp., with Illustrations, 8vo, cloth . . . 16/O THE WATCHMAKER'S HANDBOOK. Intended as a Workshop Companion for those engaged in Watchmaking and the Allied Mechanical Arts. Translated from the French of CLAUDIUS SAUNIER, and enlarged by JULIEN TRIPPLIN, F.R.A.S., and EDWARD RIGG, M.A., Assayer in the Royal Mint. Third Edition. Cr. 8vo, cloth. . 9/Q 11 Each part is truly a treatise in itself. The arrangement is good and the language Is clear and concise. It is an admirable guide for the young watchmaker." Engineering. HISTORY OF WATCHES & OTHER TIMEKEEPERS. By JAMES F. KENDAL, M.B.H. Inst. 1/6 boards ; or cloth, gilt . 2/6 "The best which has yet appeared on this subject in the English language." Industries. " Open the book where you may, there is interesting matter ir> it concerning the ingenious devices of the ancient or modem horologer." Saturday Review. . ELECTRO^PLATING&ELECTRO^REFININGOFMETALS. Being a new edition of ALEXANDER WATT'S " ELECTRO-DEPOSITION." Re- vised and Largely Rewritten by ARNOLD PHILIP, B.Sc., A.I.E.E., Principal Assistant to the Admiralty Chemist. Large Crown 8vo, cloth. . Net 1 2/6 "Altogether the woik can be highly recorrmended to every electro-plater, and is of un- doubted interest to every electro-metallurgist." Electrical Reiiie-w. "Eminently a book for the practical worker in electro-deposition. It contains practical -lescriptions of methods, processes and materials, as actually pursued and used in the workshop," Engineer. ELECTRO-METALLURGY, Practically Treated.lBy ALEXANDER WATT. Tenth Edition, including the most recent Processes. i2mo, cloth 3/6 " From this book both amateur and artisan may learn everything necessary for the successful prosecution of electroplating." Iron. JEWELLER'S ASSISTANT IN WORKING IN GOLD. A Practical Treatise for Masters and Workmen, Compiled from the Experience of Thirty Years' Workshop Practice. By GEORGE E. GEE. Crown 8vo. 7/6 " This manual of technical education is apparently destined to be a valuable auxiliary to a- handicraft which is certainly capable of great Improvement." The Times. ELECTROPLATING. A Practical Handbook on the Deposition of Copper, Silver, Nickel, Gold, Aluminium, Brass, Platinum, &c., &c. By J. W. URQUHART, C.E. Fourth Edition, Revised. Crown 8vo, cloth; 5/O " An excellent practical manual." Engineering. " An excellent work, giving the newest information." Horological Journal. INDUSTRIAL AND USEFUL ARTS. 39 ELECTROTYPING. The Reproduction and Multiplication of Printing Surfaces and Works of ^\rt by the Electro-Deposition of Metals. By J. W. URQUHART, C.E. Crown 8vo, cloth 6/O ' The book is thoroughly practical ; the reader Is, therefore, conducted through the leading irough the metals used by electrotypers, the apparatus, and laws of electricity, then through the metals used by electrotypers, the apparatus, and the depositing processes, up to the final preparation of the work." Art Journal, GOLDSMITH'S HANDBOOK. By GEORGE E. GEE, Jeweller, &c. Fifth Edition. 12010, cloth , 3 O "A good, sound educator." aorological Journal. SILVERSMITH'S HANDBOOK. By GEORGE E. GEE, Jeweller, &c. Third Edition, with numerous Illustra- tions, izmo, cloth . . 3/O "The chief merit of the work is its practical character. . . . The workers In the trade will speedily discover its merits when they sit down to study it." English Mechanic. *** The above two works together, strongly half*bound, price 7s. SHEET METAL WORKER'S INSTRUCTOR. Comprising a Selection of Geometrical Problems and Practical Rules for Describing the Various Patterns Required by Zinc, Sheet-Iron, Copper, and Tin-Plate Workers. By REUBEN HENRY WARN, Practical Tin-Plate Worker. New Edition, Revised and greatly Enlarged by JOSEPH G. HORNER, A.M.I.M.E. Crown 8vo, 254 pp., with 430 Illustrations, cloth . . 7/6 SAVOURIES AND SWEETS Suitable for Luncheons and Dinners. By M'ss M. L. ALLEN (Mrs. A. MACAIRE), Author of " Breakfast Dishes," &c. Twenty-ninth Edition. F'cap Svo, sewed 1 /O BREAKFAST DISHES For Every Morning of Tbrte Mor th. By Miss ALLEN (Mrs A. MACAIRE), Author of "Savouries and Sweets," &c. Twenty-second Edition. F'cap Svo, sewed 1/O BREAD & BISCUIT BAKER'S & SUGAR-BOILER'S ASSISTANT. Including a large variety of Modern Recipes. With Remarks on the Art of Bread-making. By ROBERT WELLS. Third Edition. Crown Svo, c'.oth . 1 /O " A large number of wrinkles for the ordinary cook, as well as the baker." Saturday Review. PASTRYCOOK & CONFECTIONER'S GUIDE. For Hotels, Restaurants, and the Trade in general, adapted also for Family Use. By R. WELLS, Author of " The Bread and Biscuit Baker " . . 1 /O " We cannot speak too highly of this really excellent work. In these days of keen competition our readers cannot do better than purchase this book." Baker's Times. ORNAMENTAL CONFECTIONERY. A Guide for Bakers, Confectioners and Pastrycooks ; including a variety of Modern Recipes, and Remarks on Decorative and Coloured Work. With 129 Original Designs. By ROBERT WELLS. Crown Svo,- cloth . . . 6/O " A valuable work, practical, and should be in the hands of every baker and confectioner. The Illustrative designs are worth treble the amount charged for the work." Baker's Times. MODERN FLOUR CONFECTIONER. Containing a large Collection of Recipes for Cheap Cakes, Biscuits, &c. With remarks on the Ingredients Used in their Manufacture. By R. WELLS. 1,Q " The work is of a decidedly practical character, and in every recipe regard is had to economical wofUng." North British Daily Mail. RUBBER HAND STAMPS And the Manipulation of Rubber. A Practical Treatise on the Manufacture of Indiarubber Hand Stamps, Small Articles of Indiarubber, The Hektograph, Special Inks, Cements, and Allied Subjects. By T. O'CoNOR Sc OANH, A.M., Ph.D. With numerous Illustrations. Square Svo, cloth. , . . 5/O 40 CROSBY LOCKWOOD & SON'S CATALOGUE. HANDYBOOK8 FOR HANDICRAFTS. BY PAUL N. HASLUCK. Editor of " Work " (New Series), Author of " Lathe Work," " Milling Machines," &c. Crown 8vo, 144 pp., price is. each. fSTThest HANDYBOOKS have been written to supply information for WORKMEN, STUDENTS, and AMATEURS in the several Handicrafts, on the actual PRACTICE of the WORKSHOP, and are intended to convey in plain language TECHNICAL KNOW- LEDGE of the several CRAFTS. In describing the processes employed, and the manipu- lation of material, workshop terms are used ; workshop practice is fully explained ; and the text is freely illustrated with drawings of modern tools, appliances, and processes. METAL TURNER'S HANDYBOOK. A Practical Manual for Workers at the Foot-Lathe. With 100 Illustrations. I/O " The book will be of service alike to the amateur and the artisan turner. It displays thorough knowledge of the subject." Scotsman.. WOOD TURNER'S HANDYBOOK. A Practical Manual for Workers at the Lathe. With over 100 Illustrations. 1/O " We recommend the book to young turners and amateurs. A multitude of workmen have hitherto sought in vain for a manual of this special industry." Mechanical World. WATCH JOBBER'S HANDYBOOK. A Practical Manual on Cleaning, Repairing, and Adjusting. With upwards of 100 Illustrations I/O " We strongly advise all young persons connected with the watch trade to acquire and Study this Inexpensive vtor]s.."Clerkenwell Chronicle. PATTERN MAKER'S HANDYBOOK. A Practical Manual on the Construction of Patterns for Founders. With upwards of 100 Illustrations 1/O "A most valuable, if not indispensable, manual for the pattern maker." Knowledge. MECHANIC'S WORKSHOP HANDYBOOK. A Practical Manual on Mechanical Manipulation, embracing Information on various Handicraft Processes. With Useful Notes and Miscellaneous Memoranda. Comprising about 200 Subjects 1 /O " A very clever and useful book, which should be found in every workshop ; and It should certainly find a place in all technical schools." Saturday Review. MODEL ENGINEER'S HANDYBOOK. A Practical Manual on the Construction of Model Steam Engines. With upwards of 100 Illustrations. ......... "JO " Mr. Hasluck has produced a very good little book." Builder. CLOCK JOBBER'S HANDYBOOK. A Practical Manual on Cleaning, Repairing, and Adjusting. With upwards of 100 Illustrations "I/O " It is of inestimable service to those commencing the trade." Coventry Standard. CABINET WORKER'S HANDYBOOK. A Practical Manual on the Tools, Materials, Appliances, and Processes employed in Cabinet Work. With upwards of 100 Illustrations . . 1/O " Mr. Hasluck's thorough-going little Handybook is amongst the most practical guides we have seen for beginners in cabinet-work." Saturday Review. WOODWORKER'S HANDYBOOK. Embracing Information on the Tools, Materials, Appliances and Processes Employed in Woodworking. With 104 Illustrations 1/O " Written by a man who knows, not only how work ought to be done, but how to do It, and bow to convey his knowledge to others. " Engineering. " Mr. Hasluck writes admirably, and gives complete instructions." Engineer. " Mr. Hasluck combines the experience of a practical teacher with the manipulative skill and scientific knowledge of processes of the trained mechanician, and the manuals are marvels of what can be produced at a popular price." Schoolmaster. " Helpful to workmen of all ages and degrees of experience." Daily CkronicU. " Concise, clear, and practical." Saturday Review. COMMERCE, COUNTING-HOUSE WORK, TABLES, &c. 41 COMMERCE, COUNTING-HOUSE WORK, TABLES, ETC. LESSONS IN COMMERCE. By Professor R. GAMBARO, of the Royal High Commercial School at Genoa. Edited and Revised by JAMES GAULT, Professor of Commerce and Commercial Law in King's College, London. Fourth Edition. Crown 8vo, cloth . 3/6 " The publishers of this work have rendered considerable service to the cause of commercial education by the opportune production of this volume. . . . The work is peculiarly acceptable to English readers and an admirable addition to existing class books. In a phrase, we think the work attains its object in furnishing a brief account of those laws and customs of British trade with which the commercial man interested therein should be familiar." Chamber of Commerce Journal. " An invaluable guide in the hands of those who are preparing for a commercial career, and, n fact, the information it contains on matters of business should be impressed on every one." Counting House, THE FOREIGN COMMERCIAL CORRESPONDENT. Being Aids to Commercial Correspondence in Five Languages English, French, German, Italian, and Spanish. By CONRAD E. BAKER. Third Edition, Carefully Revised Throughout. Crown 8vo, cloth . . . 4/6 " Whoever wishes to correspond in all the languages mentioned by Mr. Baker cannot do better than study this work, the materials of which are excellent and conveniently arranged. They consist not of entire specimen letters, but what are far more useful short passages, sentences, or phrases expressing the same general idea in various forms." Athenaum. " A careful examination has convinced us that it is unusually complete, well arranged and reliable. The book is a thoroughly good one. "Schoolmaster , FACTORY ACCOUNTS: their PRINCIPLES & PRACTICE. A Handbook for Accountants and Manufacturers, with Appendices on the Nomenclature of Machine Details ; the Income Tax Acts ; the Rating of Factories; Fire and Boiler Insurance; the Factory and Workshop Acts, &c. , including also a Glossary of Terms and a large number of Specimen Rulings. By EMILE GARCKE and J. M. FELLS. Fifth Edition, Revised and Enlarged. Demy 8vo, cloth 7/6 " A very interesting description of the requirements of Factory Accounts. . . . The principle of assimilating the Factory Accounts to the general commercial books is one which we thoroughly agree with." Accountants' Journal. " Characterised by extreme thoroughness. There are few owners of factories who would net -derive great benefit from the perusal of this most admirable work." Local Government Chronicle. MODERN METROLOGY. A Manual of the Metrical Units and Systems of the present Century. With an Appendix ', containing a proposed English System. By Lowis D A. JACKSON, A. M. Inst. C. E., Author of " Aid to Survey Practice," &c. Large crown 8vo, cloth 1 2/6 "We recommend the work to all Interested in the practical reform of our weights and measures. "Nature. A SERIES OF METRIC TABLES. In which the British Standard Measures and Weights are compared with those of the Metric System at present in Use on the Continent. By C. H. DOWLING, C.E. 8vo, cloth 1O/8 " Mr. Dowling's Tables are well put together as a ready reckoner for the conversion of one system into the other." Athenceum. IRON AND METAL TRADES' COMPANION. For Expeditiously Ascertaining the Value of any Goods bought or sold by Weight, from is. per cwt. to 112$. per cwt., and from one farthing per pound to one shilling per pound. By THOMAS DOWNIE. Strongly bound in leather, 396 PP 9/O " A most useful set of tables, nothing like them before existed." Building News. " Although specially adapted to the iron and metal trades, the tables will be found useful in very other business in which merchandise is bought and sold by weight." Rail-way Nevis. 42 CROSBY LOCKWOOD < SON'S CATALOGUE. NUMBER, WEIGHT, AND FRACTIONAL CALCULATOR. Containing upwards of 250,000 Separate Calculations, showing at a Glance the Value at 422 Different Rates, ranging from yg-gth of a Penny to 20$. each, or per cwt., and .20 per ton, of any number of articles consecutively, from i to 470. Any number of cwts., qrs., and Ibs., from i cwt. to 470 cwts. Any number of tons,_ cwts., qrs., and Ibs., from i to 1,000 tons. By WILLIAM CHADWICK, Public Accountant. Fouith Edition. Revised and Improved. 8vo, strongly bound ............. 18/O " It is as easy of reference for any answer or any number of answers as a dictionary. For making up accounts or estimates the book must prove invaluable to all who have any considerable quantity of calculations involving price and measure in any combination to do." Engineer. "The most perfect work of the kind yet prepared." Glasgow Herald. THE WEIGHT CALCULATOR. Being a Series of Tables upon a New and Comprehensive Plan, exhibiting afc one Reference the exact Value of any Weight from i Ib. to 15 tons, at 300 Progressive Rates, from id. to i68s. per cwt., and containing 186,000 Direct Answers, which, with their Combinations, consisting of a single addition (mostly to be performed at sight), will afford an aggregate of 10,266,000 Answers ; the whole being calculated and designed to ensure correctness and promote despatch. By HENRY HARBEN, Accountant. Sixth Edition, carefully Corrected. Royal 8vo, strongly half-bound. {Just Published. 1 6s.. " A practical and useful work of reference for men of business generally." Ironmonger. "Of priceless value to business men. It is a necessary book in all mercantile offices." Sheffield Independent. THE DISCOUNT GUIDE. Comprising several Series of Tables for the Use of Merchants, Manufacturers, Ironmongers, and Others, by which may be ascertained the Exact Profit arising from any mode of using Discounts, either in the Purchase or Sale of Goods, and the method of either Altering a Rate of Discount, or Advancing a Price, so as to produce, by one operation, a sum that will realise any required Profit after allowing one or more Discounts : to which are added Tables of Profit or Advance from ij to 90 per cent., Tables of Discount from ij to g8| per cent., and Tables of Commission, &c., from J to 10 per cent. By HENRY HARBEN, Accountant. New Edition, Corrected. Demy 8vo, half-bound . 1 5s.. " A book such as this can only be appreciated by business men, to whom the saving of time means saving of money. The work must prove of great value to merchants, manufacturers, an* general traders." British Trade Journal. TABLES OF WAGES. At 54, 52, 50 and 48 Hours per Week. Showing the Amounts of Wages from. One quarter of an hour to Sixty-four hours, in each case at Rates of Wages- advancing by One Shilling from 45. to 555. per week. By THOS. GARBUTT, Accountant. Square crown 8vo, half-bound ...... 6/O IRON-PLATE WEIGHT TABLES. For Iron Shipbuilders, Engineers, and Iron Merchants. Containing the Calculated Weights of upwards of 150,000 different sizes of Iron Plates from i foot by 6 in. by J in. to 10 feet by 5 feet by i in. Worked out on the Basis of 40 Ibs. to the square foot of Iron of i inch in thickness. By H. BURLINSON and W. H. SIMPSON. 410, half-bound ...... 1 5s. ORIENTAL MANUALS AND TEXT-BOOKS. Notice, Messrs. Crosby Lockwood & Son will forward on application a New and Revised List of Text-books and Manuals for Students in Oriental Languages, many of which are used as Text-books for the Examinations for the Indian Civil Service and the Indian Staff Corps; also as Class Books iu Colleges and Schools in India, AGRICULTURE, FARMING, GARDENING, &>c. 43 AGRICULTURE, FARMING, GARDENING, ETC. THE COMPLETE GRAZIER AND FARMER'S AND CATTLE BREEDER'S ASSISTANT. A Compendium of Husbandry. Originally Written by WILLIAM YOOATT. Fourteenth Edition, entirely Re-written, considerably Enlarged, and brought up to Present Requirements, by WILLIAM FREAM, LL.D., Assistant Com- missioner, Royal Commission on Agriculture, Author of " The Elements of Agriculture," &c. Royal 8vo, 1,100 pp., 450 Illustrations, handsomely bound. 1 11s. 60. BOOK I. ON THE VARIETIES. BREEDING, \ BOOK VII. ON THE BREEDING, REARING, REARING, FATTENING AND MANAGE- MENT OF CATTLE. BOOK II. ON THE ECONOMY AND MAN- AGEMENT OF THE DAIRY. BOOK III. ON THE BREEDING, REARING, AND MANAGEMENT OF HORSES. BOOK IV. ON THE BREEDING, REARING, AND MANAGEMENT OF POULTRY. BOOK Vlll. ON FARM OFFICES AND- IMPLEMENTS OF HUSBANDRY. BOOK IX. ON THE CULTURE AND MAN- AGEMENT OF GRASS LANDS. BOOK x. ON THE CULTIVATION AND APPLICATION OF GRASSES, PULSE AND- AND FATTENING OF SHEEP. ROOTS. BOOK V. ON THE BREEDING, REARING, BOOK XI. ON MANURES AND THEIR AND FATTENING OF SWINE. APPLICATION TO GRASS LAND AND BOOK VI. ON THE DISEASES OF LIVE i CROPS. STOCK. BOOK XII. MONTHLY CALENDARS OF FARMWORK. " Dr. Fream is to be congratulated on the successful attempt he has made to give us a work which will at once become the standard classic of the fann practice of the country. We believe that It will be found that it has no compeer among the many works at present in existence. . . . The Illustrations are admirable, while the frontispiece, which represents the well-known bull,. New Year's Gift, bred by the Queen, is a work of art. " The Times. " The book must be recognised as occupying the proud position of the most exhaustive work of reference in the English language on the subject with which it deals." Athenaum. " The most comprehensive guide to modern farm practice that exists in the English language to-day, . . . The book is one that ought to be on every farm and in the library of every land owner." Mark Lane Express. " In point of exhaustiveness and accuracy the work will certainly hold a pre-eminent and. unique position among books dealing with scientific agricultural practice. It is, in fact, an agricul- tural library of itself." North British Agriculturist. FARM LIVE STOCK OF GREAT BRITAIN. BY ROBERT WALLACE, F.L.S., F.R.S.E., &c., Professor of Agriculture and Rural Economy in the University of Edinburgh. Third Edition, thoroughly Revised and considerably Enlarged. With over 120 Phototypes of Prize Stock. Demy 8vo, 384 pp., with 79 Plates and Maps, cloth. . . 1 2/S " A really complete work on the history, breeds, and management of the farm stock of Great Britain, and one which is likely to find its way to the shelves of every country gentleman's library." The Times. " The ' Farm Live Stock of Great Britain ' Is a production to be proud of, and its Issue not the least of the services which its author has rendered to agricultural science." Scottish Farmer. NOTE-BOOK OF AGRICULTURAL FACT5 & FIGURES FOR FARMERS AND FARM STUDENTS. By PRIMROSE McCoNNELL, B.Sc., Fellow of the Highland and Agricultural Society, Author of " Elements of Farming." Sixth Edition, Re-written, Revised, and greatly Enlarged. Fcap. 8vo, 480 pp., leather, gilt edges . . 6/O CONTENTS : SURVEYING AND LEVELLING. WEIGHTS AND MEASURES. MACHINERY AND BUILDINGS. LABOUR. OPERATIONS. DRAINING. - EMBANKING. GEOLOGICAL MEMORANDA. SOILS. MANURES. CROPPING. CROPS.-^ROTATIONS. WEEDS. FEEDING. DAIRYING. LIVE STOCK. HORSES. CATTLE. SHEEP. PIGS. POULTRY. FORESTRY. HORTICULTURE. MISCELLANEOUS. " No farmer, and certainly no agricultural student, ought to be without this multum-in-parvo manual of all subjects connected with the farm." North British Agriculturist. " This little pocket-book contains a large amount of useful information upon all kinds oi agricultural subjects. Something of the kind has long been wanted." Mark Lane Exf) ess. " The amount of Information It contains Is most surprising ; the arrangement of the matter is so methodical although so compressed as to be Intelligible to everyone who takes a glance through Its pages. They teem with information." Farm and Home. THE ELEMENTS OF AGRICULTURAL GEOLOGY. A Scientific Aid to Practical Farming. By PRIMROSE McCoNNELL. Author of "Note-Book of Agricultural Facts and Figures," c. Royal 8vo, cloth. NetZllQ ' On every page the work bears the impress of a masterly knowledge of the subject dealt with, and we have nothing but unstinted praise to offer." Field. 44 CROSBY LOCKWOOD * SON'S CATALOGUE. BRITISH DAIRYING. Revised. Crown 8vo, cloth "... 2/6 "Confidently recommended as a useful text-book on dairy fanning." Agricultural Gazette. " Probably the best half-crown manual on dairy work that has yet been produced." North British Agriculturist. " It is the soundest little work we have yet seen on the subject." The Times. MILK, CHEESE, AND BUTTER. A Practical Handbook on their Properties and the Processes of their Produc- tion. Including a Chapter on Cream and the Methods of its Separation from Milk. By JOHN OLIVER, late Principal of the Western Dairy Institute, Berkeley. With Coloured Plates and 200 Illustrations. Crown 8vo. cloth. 7/6 " An exhaustive and masterly production. It may be cordially recommended to all students and practitioners of dairy science. North British Agriculturist. " We recommend this very comprehensive and carefully-written book to dairy-farmers and students of dairying. It is a distinct acquisition to the library of the agriculturist." Agritultui al Gazette. SYSTEMATIC SMALL FARMING. Or, The Lessons of My Farm. Being an Introduction to Modern Farm Practice for Small Farmers. By R. SCOTT BURN, Author of " Outlines of Modern Farming," &c. Crown 8vo, cloth. ...... 6/O " This is the completes! book of its class we have seen, and one which every amateur farmer will read with pleasure, and accept as a guide." Field. OUTLINES OF MODERN FARMING. By R. SCOTT BURN. Soils, Manures, and Crops Farming and Farming Economy Cattle, Sheep, and Horses Management of Dairy, Pigs, and Poultry Utilisation of Town-Sewage, Irrigation, &c. Sixth Edition. In One Vol., 1,250 pp., half-bound, profusely Illustrated 1 2/O FARM ENGINEERING, The COMPLETE TEXT-BOOK of. Comprising Draining and Embanking ; Irrigation and Water Supply ; Farm Roads, Fences and Gates ; Farm Buildings ; Barn Implements and Machines ; Field Implements and Machines ; Agricultural Surveying, &c. By Professor JOHN SCOTT. In One Vol., 1,150 pp., half-bound, with over 600 Illustrations. 12/O " Written with great care, as well as with knowledge and ability. The author has done his Vork well ; we have found him a very trustworthy guide wherever we have tested his statements. The volume will be of great value to agricultural students." Mark Lane Express. THE FIELDS OF GREAT BRITAIN. A Text-Book of Agriculture. Adapted to the Syllabus of the Science and Art Department. For Elementary and Advanced Students. By HUGH CLEMENTS (Board of Trade). Second Edition, Revised, with Additions. i8mo, cloth 2/6 " It is a long time since we have seen a book which has pleased us more, or which contains such a vast and useful fund of knowledge." Educational Times. TABLES and MEMORANDA for FARMERS, GRAZIERS, AGRICULTURAL STUDENTS, SURVEYORS, LAND AGENTS, AUCTIONEERS, &c. With a New System of Farm Book-keeping. By SIDNEY FRANCIS. Fifth Edition. 272 pp., waistcoat-pocket size, limp leather . . . .1/6 " Weighing less than i oz., and occupying no more space than a match-box, it contains amass of facts and calculations which has never before, in such handy form, been obtainable. Every operation on the farm is dealt with. The work may be taken as thoroughly accurate, the whole of the tables having been revised by Dr. Fream. We cordially recommend H."Beirs Weekly Messenger. THE ROTHAMSTED EXPERIMENTS AND THEIR PRACTICAL LESSONS FOR FARMERS. Part I. STOCK. Part II. CROPS. By C. J. R. TIPPER. Crown 8vo, cloth. 3/6 " We have no doubt that the book will be welcomed by a large class of fanners aad other* interested In agri.ulture." Standai -d. AGRICULTURE, FARMING, GARDENING, *. 45 FERTILISERS AND FEEDING STUFFS. Their Properties and Uses. A Handbook for the Practical Farmer. By BERNARD DYER, D.Sc. (Lond.). With the Text of the Fertilisers and Feeding Stuffs Act of 1893, The Regulations and Forms of the Board of Agriculture, and Notes on the Act by A. J. DAVID, B.A., LL.M. Fourth Edition, Revised. Crown 8vo, cloth. [Just Published. 1/Q "This Kttle book is precisely what it professes to be 'A Handbook for the Practical Farmer.' Dr. Dyer has done fanners good service in placing at their disposal so much useful Information in so intelligible a form." The Times, BEES FOR PLEASURE AND PROFIT. A Guide to the Manipulation of Bees, the Production of Honey, and the General Management of the Apiary. By G. GORDON SAMSON. With numerous Illustrations. Crown 8vo, wrapper "I/O BOOK-KEEPING for FARMERS and ESTATE OWNERS. A Practical Treatise, presenting, in Three Plans, a System adapted for all Classes of Farms. By JOHNSON M. WOODMAN, Chartered Accountant. Fourth Edition. Crown 8vo, cloth. [Just Published. 2/6 " The volume is a capital study of a most important subject." Agricultural Gazette. WOODMAN'S YEARLY FARM ACCOUNT BOOK. Giving Weekly Labour Account and Diary, and showing the Income and Expenditure under each Department of Crops, Live Stock, Dairy, &c., &c. With Valuation, Profit and Loss Account, and Balance Sheet at the End ot the Year. By JOHNSON M. WOODMAN, Chartered Accountant. Second Edition. Folio, half-bound Net 7/6 " Contains every requisite for keeping farm accounts readily and accurately." Agriculture. THE FORCING GARDEN. Or, How to Grow Early Fruits, Flowers and Vegetables. With Plans and Estimates for Building Glasshouses, Pits and Frames. With Illustrations. By SAMUEL WOOD. Crown 8vo, cloth 3/6 " A good book, containing a great deal of valuable teaching." Gardeners' Magazine. A PLAIN GUIDE TO GOOD GARDENING. Or, How to Grow Vegetables, Fruits, and Flowers. By S. WOOD. Fourth Edition, with considerable Additions, and numerous Illustrations. Crown 8vo, cloth 3/6 "A very good book, and one to be highly recommended as a practical guide. The practical directions are excellent." Athenaum. MULTUM-IN-PARVO GARDENING. Or, How to Make One Acre of Land produce .620 a year, by the Cultivation of Fruits and Vegetables ; also, How to Grow Flowers in Three Glass Houses, so as to realise 176 per annum clear Profit. By SAMUEL WOOD, Author of "Good Gardening, "&c. Sixth Edition, Crown 8vo, sewed . . . 1/O THE LADIES' MULTUM-IN-PARVO FLOWER GARDEN. And Amateur's Complete Guide. By S. WOOD. Crown 8vo, cloth . 3/6 POTATOES: HOW TO GROW AND SHOW THEM. A Practical Guide to the Cultivation and General Treatment of the Potato. By J. PINK. Crown 8vo 2/O MARKET AND KITCHEN GARDENING. By C. W. SHAW, late Editor of "Gardening Illustrated." Crown 8vo, clotb. 46 CROSBY LOCK WOOD SON'S CATALOGUE. AUCTIONEERING, VALUING, LAND SURVEYING, ESTATE AGENCY, ETC. INWOOD'S TABLES FOR PURCHASING ESTATES AND FOR THE VALUATION OF PROPERTIES, Including Advowsons, Assurance Policies, Copyholds, Deferred Annuities, Freeholds, Ground Rents, Immediate Annuities, Leaseholds, Life Interests, Mortgages, Perpetuities, Renewals of Leases, Reversions, Sinking Funds, &c., &c. 2yth Edition, Revised and Extended by WILLIAM SCHOOLING, F.R.A.S., with Logarithms of Natural Numbers and THOMAN'S Logarithmic Interest and Annuity Tables. 360 pp., Demy 8vo, cloth. [Just Published. Net 8/O " Those Interested In the purchase and sale of estates, and in the adjustment of compensation cases, as well as in transactions in annuities, life insurances, &c., will find the present edition of eminent service." Engineering. " This valuable book has been considerably enlarged and improved by the labours of Mr. Schooling, and is now very complete indeed." Economist. " Altogether this edition will prove of extreme value to many classes of professional men in saving them many long and tedious calculations." Investors' Revie-w. THE APPRAISER, AUCTIONEER, BROKER, HOUSE AND E5TATE AGENT AND VALUER'S POCKET ASSISTANT. For the Valuation for Purchase, Sale, or Renewal of Leases, Annuities, and Reversions, and of Property generally; with Prices for Inventories, &c. By JOHN WHEELER, Valuer, &c. Sixth Edition, Re-written and greatly Extended by C. NORRIS. Royal 32mo, cloth fi/Q " A neat and concise book of reference, containing an admirable and clearly-arranged list of prices for inventories, and a very practical guide to determine the value of furniture, &c." Standard. "Contains a large quantity of varied and useful information as to the valuation for purchase, sale, or renewal of leases, annuities and reversions, and of property generally, with prices for Inventories, and a guide to determine the value of interior fittings and other effects." Builder. AUCTIONEERS: THEIR DUTIES AND LIABILITIES. A Manual of Instruction and Counsel for the Young Auctioneer. By ROBERT SQUIBBS, Auctioneer. Second Edition, Revised. Demy 8vo, cloth . 12/6 "The work is one of general excellent character, and gives much information In a com- pendious and satisfactory form." Builder. "May be recommended as giving a great deal of Information on the law relating to auctioneers, in a very readable form." Law Journal. THE AGRICULTURAL VALUER'S ASSISTANT. A Practical Handbook on the Valuation of Landed Estates ; including Example of a Detailed Report on Management and Realisation ; Forms of Valuations of Tenant Right ; Lists of Local Agricultural Customs ; Scales of Compensation under the Agricultural Holdings Act, and a Brief Treatise on Compensation under the Lands Clauses Acts, &c. By TOM BRIGHT, Agricul- tural Valuer. Author of "The Agricultural Surveyor and Estate Agent's Handbook." Fourth Edition, Revised, with Appendix containing a Digest of the Agricultural Holdings Acts, 1883 1900. Crown 8vo, cloth . Net 6/O " Full of tables and examples in connection with the valuation of tenant-right, estates, labour, contents and weights of timber, and farm produce of all kinds." Agricultural Gazette. " An eminently practical handbook, full of practical tables and data of undoubted interest and value to surveyors and auctioneers in preparing valuations of all kinds." Partner. POLE PLANTATIONS AND UNDERWOODS. A Practical Handbook on Estimating the Cost of Forming, Renovating, Improving, and Grubbing Plantations and Underwoods, their Valuation for Purposes of Transfer, Rental, Sale or Assessment. By TOM BRIGHT. Crown 8vo, cloth 3/6 "To valuers, foresters and agents it will be a welcome aid." North British Agriculturist. " Well calculated to assist the valuer in the discharge of his duties, and of undoubted interest and use both to surveyors and auctioneers in preparing valuations of all kinds." Kent Herald. AUCTIONEERING, VALUING, LAND SURVEYING, &c. 47 AGRICULTURAL SURVEYOR AND ESTATE AGENT'S HANDBOOK. Of Practical Rules, Formulae, Tables, and Data. A Comprehensive Manual for the Use of Surveyors, Agents, Landowners, and others interested in the Equipment, the Management, or the Valuation of Landed Estates. By TOM BRIGHT, Agricultural Surveyor and Valuer, Author of " The Agri- cultural Valuer's Assistant," &c. With Illustrations. Fcap. 8vo, Leather. Net 7/6 "An exceedingly useful book, the contents of which are admirably chosen. The classes for whom the work is intended will find it convenient to have this comprehensive handbook accessible for reference." Live Stock Journal. "It is a singularly compact and well informed compendium of the facts and figures likely to be required in estate work, and is certain to prove of much service to those to whom it is i." Scotsman. THE LAND VALUER'S BEST ASSISTANT* Being Tables on a very much Improved Plan, for Calculating the Value of Estates. With Tables for reducing Scotch, Irish, and Provincial Customary Acres to Statute Measure, &c. By R. HUDSON, C.E. New Edition. Royal samo, leather, elastic band 4/O " Of incalculable value to the country gentleman and professional man. "Farmers' Journal. THE LAND IMPROVER'S POCKET-BOOK. Comprising Formulae, Tables, and Memoranda required in any Computation relating to the Permanent Improvement of Landed Property. By JOHN EWART, Surveyor. Second Edition, Revised. Royal 32010, oblong, leather . 4/O " A compendious and handy littl volume." Spectator, THE LAND VALUER'S COMPLETE POCKET-BOOK. Being the above Two Works bound together. Leather .... 7/6 HANDBOOK OF HOUSE PROPERTY. A Popular and Practical Guide to the Purchase, Tenancy, and Com- pulsory Sale of Houses and Land, including Dilapidations and Fixtures : with Examples of all kinds of Valuations, Information on Building and on the right use of Decorative Art. By E. L. TARBUCK, Architect and Surveyor. Seventh Edition. i2mo, cloth [Just Published, g/Q "The advice is thoroughly practical." Law Journal. " For all who have dealings with house property, this is an Indispensable guide." Decoration. " Carefully brought up to date, and much improved by the addition of a division on Fine Art. A well-written and thoughtful work." Land Agents' Record. LAW AND MISCELLANEOUS. MODERN JOURNALISM. A Handbook of Instruction and Counsel for the Young Journalist. By JOHN B. MACKIE, Fellow of the Institute of Journalists. Crown 8vo, cloth . 2/O " This invaluable guide to journalism is a work which all aspirants to a journalistic career will read with advantage." Journalist. HANDBOOK FOR SOLICITORS AND ENGINEERS Engaged in Promoting Private Acts of Parliament and Provisional Orders for the Authorisation of Railways, Tramways, Gas and Water Works, &c. By L. L MACASSEY, of the Middle Temple, Barrister-at-Law, M.I. C.E. 8vo, cloth 1 gs. PATENTS for INVENTIONS, HOW to PROCURE THEM. Compiled for the Use of Inventors, Patentees and others. By G. G. M. HARDINGHAM, Assoc. Mem. Inst. C.E., &c. Demy 8vo, cloth . .1/6 CONCILIATION* ARBITRATION in LABOUR DISPUTES. A Historical Sketch and Brief Statement of the Present Position of the Question at Home and Abroad. By J. S. JEANS. Crown 8vo, 200 pp., cloth . 2/6 CROSBY LOCKWOOD & SON'S CATALOGUE. EVERY MAN'S OWN LAWYER. A Handy-Book of the Principles of Law and Equity. With a CONCISK DICTIONARY OF LEGAL TERMS. By A BARRISTER. Forty-second Edition, carefully Revised, and comprising New Acts of Parliament, including the Prevention of Cruelty to Children Act, 1904 ; Weights and Measures Act, 1904 ; Licensing Act, 1904; Shop Hours Act, 1904; as well as the Motor Car Act, 1903; Employment of Children Act, 1903; Poor Prisoners' Defence Act, 1903, &c. Judicial Decisions pronounced durng the year have also been duly noted. Crown 8vo, 800 pp., strongly bound in cloth. [Just Published. QIQ. *** This Standard Work of Reference forms A COMPLETE EPITOME OF THE LAWS OF ENGLAND, comprising (amongst other matter) ; THE RIGHTS AND WRONGS OF INDIVIDUALS LANDLORD AND TENANT VENDORS AND PURCHASERS LEASES AND MORTGAGES JOINT-STOCK COMPANIES MASTERS, SERVANTS AND WORKMEN CONTRACTS AND AGREEMENTS MONEY-LENDING, SURETISHIP PARTNERSHIP, SHIPPING LAW SALE AND PURCHASE OF GOODS CHEQUES, BILLS AND NOTES BILLS OF SALE, BANKRUPTCY LIFE, FIRE, AND MARINE INSURANCE LIBEL AND SLANDER i CRIMINAL LAW PARLIAMENTARY ELECTIONS ' COUNTY COUNCILS DISTRICT AND PARISH COUNCILS j BOROUGH CORPORATIONS i TRUSTEES AND EXECUTORS I CLERGY AND CHURCHWARDENS ! COPYRIGHT. PATENTS, TRADE MARKS ' HUSBAND AND WIFE, DIVORCE I INFANCY, CUSTODY OF CHILDREN | PUBLIC HEALTH AND NUISANCES i GAME LAWS, GAMING, INNKEEPERS i TAXES AND DEATH DUTIES FORMS OF WILLS, AGREEMENTS, NOTICES, &c. W*" The object of this -work is to enable those -who consult it to help themselves to the law ; and thereby to dispense, as far as possible, -with professional assistance and advice. There aye many -wrongs and grievances -which persons submit to front time to time through not knowing how or -where to apply for redress ; and many persons have as great a dread of a lawyer's office as of a lion's den. With this book at hand it is believed that many a SlX-AND- ElGHTPENCE may be saved ; many a -wrong redressed ; many a right reclaimed ; many a law suit avoided ; and many an evil abated. The work has established itself as the standard legal adviser of all classes, and has also made a reputation for itself as a useful book of reference for lawyers residing at at distance from law libraries, who are glad to have at hand a work embodying recent decisions and enactments. *** OPINIONS OF THE PRESS. " The amount of information given in the volume is simply wonderful. The continued popularity of the work shows that it fulfils a useful purpose." Law Journal. " As a book of reference this volume is without a rival." Pall Mall Gazette. " No Englishman ought to be without this book." Engineer. "Ought to be in every business establishment and in all libraries." Sheffield Post. " The ' Concise Dictionary ' adds considerably to its value." Westminster Gazette. " It Is a complete code of English Law written in plain language, which all can understand . . . Should be in the bands of every business man, and all who wish to abolish lawyers' bills." Weekly Times. "A useful and concise epitome of the law, compiled with considerable care." Law Magazine. " A complete digest of the most useful facts which constitute English law." Globe. "Admirably done, admirably arranged, and admirably cheap." Leeds Mercury. " A concise, cheap, and complete epitome of the English law. So plainly written that he whc runs may read, and he who reads may understand." Figaro. " A dictionary of legal facts well put together. The book is a very useful one." Spectator. LABOUR CONTRACTS. A Popular Handbook on the Law of Contracts for Works and Services. By DAVID GIBBONS. Fourth Edition, with Appendix of Statutes by T. F. UTTLEY, Solicitor. Fcap. 8vo, cloth 3/6 BRADI'URY, AGKEVV, & CO. LD., PRINTERS, LONDON AND TONBRIDGE. WEALE'S SERIES OF SCIENTIFIC AND TECHNICAL WORKS. " It is not too much to say that no books have ever proved more popular with or more useful to young engineers and others than the excellent treatises comprised in WEALE'S SERIES." Engineer. Jlefo Classifbtr list. PAGE CIVIL ENGINEERING AND SURVEYING 2 MINING AND METALLURGY . . . . 8 MECHANICAL ENGINEERING .... 4 NAVIGATION, SHIPBUILDING. ETC. . 5 ARCHITECTURE AND BUILDING . . 6 INDUSTRIAL AND USEFUL ARTS. . O AGRICULTURE, GARDENING, ETC. . 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