•x^ SHIP-BUILDING IN IRON AND WOOD ANDREW MURRAY ME31EEK OF THE IXSTITUTIOX OF CIVIL ENGINEEES, AND OF THE ISSTITDTION OP NAVAL ARCHITECTS. AND CHIEF ENGINEER AND INSPECTOR OF MACHINERY OF H. M. DOCKYARD, PORTSMOUTH ^VND STEAM- SHIPS ROBERT MURRAY, C.E. ENGINEER SURVEYOR TO THE BOARD OF TRADE, AND GOVERNMENT EXAMINEE OF ENGINEERS FOR THE MERCANTILE MARINE SECOND EDITION EDINBURGH ADAM AND CHARLES BLACK JIDCCCLXIII [2%e riyht of Trandation is reserv«d.\ Library YAi PREFACE. The proprietors of the Encyclopa3dia Britannica having determined ou printing as a separate treatise, in a somewhat enlarged form, the article Ship-Building as prepared for the eighth edition of that work, and a second edition of the separate treatise being now called for, it is proposed to say a few words explanatory of the tenor and scope of the original article. The article in the previous edition of the Encyclopaedia was written by Mr Creuze, a member of the School of Naval Architecture which existed at Ports- mouth under the late Dr Inman. Mr Creuze's death at a comparatively early age, while it Avas a source of great regret to a numerous circle of friends, was at the same time a serious loss to the profession of which he formed so distinguished an ornament. His work was received with the greatest favour, as a valuable addition to the works on Ship-building in the English language ; but since it was written, great changes have taken place. The researches of Canon Moseley, and the still more important researches and woT'ks of the Rev. Dr Woolley, have added to the theoretical knowledge of the sub- ject ; and the rapid extension of Steam-Shipping, the general increase in the size of vessels, the introduction, or perhaps, to speak more correctly, the now general adoption of Iron as a material for the construction of Ships, and latterly the use of a casing of thick armour-plates of iron for the protection of men-of-war, all called for special notice, and for a revisal, and in some respects a renewal, of the article. To follow Mr Creuze was felt to be assuming no light responsibility ; but, as it was specially desired to produce a work which should be of a nature to be useful to the practical ship-builders of the day, and as the use of Iron in the construction of ships had assumed so important a position in the country, it was considered desirable that the work should be undertaken by one possessed of as much experience and practical knowledge of this branch of the subject as possible ; the more so as it was felt that the previous article by Mr Creuze afforded so good a groundwork for the portion on wooden IV PREFACE. ship-building which would still be required. The writer was therefore applied to by the proprietors to undertake this task. He had been employed by Mr Fairbairn of Man- chester, in 1834, upon two iron steamers constructed to run upon the Humber between Selby and Hull; in 1836 he entered into partnership with Mr Fairbairn, for the purpose of commencing Iron Ship-building on the Thames, and works for this purpose were erected at Millwall, where he was for some years the sole and resident partner, actively engaged in superintending the construction, both theoretically and practically, of the iron vessels built there. In 1843 he entered the service of the Admiralty, and since then he has carefully watched the progress of iron vessels, and, while he has been in a position to do so, he has at the same time also had opportunities of seeing the construc- tion of some of the finest specimens of wooden ships that the world has ever seen, or probably now will ever see. The history of naval architecture, as given by Mr Creuze, has been retained with but little change ; and from the period up to which his treatise carried the subject, a mere outline has been given in continuation up to the present time, the article Steam-Ships supplying the deficiency. The chief alterations which are taking place in ship-building in the present day are confined to those in the Royal Navy, in consequence of the intro- duction of the coating of armour-plates on the sides of ships of the ordinary form, and the new class of vessels created by Captain Coles's invention of revolving shot-proof turrets. Of the former class, the " Warrior" and the "Black Prince," of 6109 tons and 40 guns, and "The Defence" and "The Resistance," of 3668 tons and 18 guns, have proved themselves to be ships excelling in all respects in sea-worthy qualities. The weU-known principles enunciated by scientific research, as well as by practical experience, that weights at the sides of a ship, and not too low down, will tend to slow and easy rolling, and that heavy w^eights at the extremities, especially of long ships, are to be avoided as producing violence of motion in pitching and 'scending, have been carried out in these ships, and these results have shown the value of knowing how to apply scientific knowledge to the regulating the disposition of weights in the design and construction of ships. These vessels have therefore demonstrated in the fullest manner the correct- ness of the views adopted by the Board of Admiralty and the Controller of the Navy, who decided upon vessels of such a class being added to the British Navy ; and their performances, now that they have been fully tested, have shown how well the intentions of the Board have been carried out by those who designed their lines and determined on their details. PREFACE. V The question, however, whether ships with broadside guns, or ships with Captain Coles's revolving turrets, are to be preferred, still remains unsettled. It will perhaps be found that each of these classes will prove useful in a sphere of its own, and that what- ever success may attend Captain Coles's ships, a considerable, if not the largest portion of our future fleet, must still consist of ships with broadside guns. It has been assumed by the advocates of turret ships, in their arguments in their favour, that in revolving turrets alone can guns of very large calibre be used ; but it is submitted that this is not necessarily the case if the guns in the broadside of a ship be placed on a traversing platform worked by mechanical appliances ; and it may be remarked, that though guns worked on board ship in the way here suggested might not each have individually the same extent of angular traverse as the guns in revolving turrets, yet as all screw ships have to some degree, by judicious management of the helm and the screw, the power of revolving almost on their own axis without going ahead, this objection is very much obviated. It must not be forgotten, also, that the ship to carry a turret, to prevent her being sunk or set on fire, must be as thoroughly protected as the ship to carry broadside guns ; and though possibly she may be built with her sides of a less height out of the water, yet for a sea-going vessel this advantage has many counter- balancing evils. After completing the history, the theory of naval ai'chitecture was treated of by Mr Creuze, and the same arrangement has been continued. This portion of the present article has been rewritten, and is entirely the production of Mr Robinson, Head- master of the school for apprentices in Chatham Dockyard. The writer believes that he could not have obtained the assistance of any one more competent to do justice to the subject, knowing that Mr Robinson's knowledge and acquirements in this respect have been highly considered by both Canon Moseley and Dr Woolley, the two highest authorities of the pi'esent day upon this branch of mathematical research. For the investigations respecting the effects of the forces which act upon a ship when in motion, and the strains to which she is liable under different circumstances, the writer is himself answerable, as well as for the portions upon the materials used in ship-building, upon the forms and the construction of the bodies of ships, and upon the practical operations required therein. On all these points, occasional remarks from Mr Creuze's previous work, which was placed by the proprietors at the disposal of the writer, have been introduced ; but they are so mixed up with the general reasoning, that it was found impossible to separate them, or to give them entire as extracts from vi PREFACE. his work, without hurting tlie continuity of the argument, and rendering the illustrations aimed at obscure. The desire throughout has been, to produce, in the simplest possible form, a work which may be useful to the practical ship-builders of this country. To naval officers, it is at the same time believed that much of the article will be found useful ; because, while it must be beneficial to them to understand the principles on which the ships in which they are serving are constructed, they ought also, certainly, to understand those principles which regulate the strains to which their ships are exposed under different circumstances, and how these may be modified and lessened by their management. In conclusion, the writer desires to express his thanks to the managing Directors of the Peninsular and Oriental Company, and to the Practical Builders to whom he applied; and who, in the most kind and ready manner, furnished him with the valuaV)lo specimens of their works which appear in the plates. PoRTSMOCTii, March 1863. CONTENTS. SHIP-BUILDING. History : — page Eise and Progress of Naval Arcliitecture, . . 2 Ancient Floats and Vessels, .... 2 Venetian Shipping, 3 Ancient Exglish Shipping : — First Epoch : Galleys and Vessels propelled by Oars alone, ....... 4 Second Epoch, a.d. 1327 : Introduction of larger Ships, 6 Fleet of Henry V., Caxracks, Barges, &c.. Mercan- tile Shipping, " The Henri Grace a Dieu," &c., 7 Third Epoch — commencing with the reign of Henry VIIL, 11 Spanish Armada, 12 Phineas and Peter Pett as Ship-lmilders, . . 13 Sir Walter Ealeigh on Ship-building, . . 13 Subsequent History of Ship-building in England, 14 Derrick's jNIemoirs of the Eoyal Navy, iind Dimensions of Ships at various periods, . 17 Dimensions of French Ships in 1786, . .18 Efforts at Improvements in Naval Architecture, 18 Extent and Disposition of British Naval Force in 1813, 20 Sir Wm. Symonds' Sui"veyorship of the Navy, 21 Dimensions of English Ships of War, . .21 of French Ships of W;ir in 1837, . 21 Introduction of Steam-Vessels, . . .21 „ of Iron Ships, . . . .22 „ of Screw Propidsion, . . .22 PAGE Sir B. Walker appointed Surveyor of the Navy, 22 British Navy in 1859, 23 Navy of other Nations in 1859, . .23 First Experiments with Sliot on Iron, . . 23 First Iron-cased Ships 24 Capt. ]Moorsoni on Iron-cased Ships, . . 25 The Warrior ordered to be built, . . .25 Advantages of the Bows and Sterns being left improtected, ...... 25 Vessels Designed by !Mr Eeed, . . .25 Cupola Ships on Capt. Coles's Plans, . . 26 La Gloire, The Warrior, and Black Prince, . 26 Timber Backing beliind Armour Plates, . ■ 28 The ^lerrimac and jNIonitor, . . . .28 British ^Mercantile Shipping, . . . .28 Influence of Yacht Clubs, . . . .29 The America and Titania Yachts, . . .29 Eowing and Eacing Boats, . . . .29 The Great Eastern, 29 The Theory of Ship-building : — Preliminary Eemarks, 30 ilethod of Finding the Areas of CurN-ilinear Figures. Eules by Atwood, Simpson, Weddle, &c., with Demonstrations to these Eules, . 30 Examples illustrative of the foregoing Eules ; some Examples worked out, and others for Practice, 32 On the Methods of Finding the " Displacement" of Vessels. Eules by Simpson, Dr Woolley, &c., with Demonstrations, . . . .34 Vlll CONTENTS. Theory oi' yiiir-iaiLiiiNG — continued. page On the ]\Iethod of Fimliug Centres of Gravity of Areas, Volumes, &c., Mith Demonstrations to the Eulcs ; Displacements — Guililin's Ihile, . 3G Examples on the above llules, some Worked out, others for Practice, 37 Method of Finding the Eadius of Gyration, PIGMENTS OF IXERTU, &C., OF BODIES, — with Examples, Definitions of Staticvl and Dvnamic.vl Sta- bility, &c., Tlieorem rcj^arding the Line joining the Centres of Buoyancy in any two positions of the Vessel, and the Line joining the Centres of Gravity of the Immersed and Emerged A^olumes, Theorem regarding the Tangent Plane to the Sur- face traced out hy the Centre of Buoyancy, . On the Metacentre, Centre of Curvature, Meta- centric Curve, &c., ..... Kule for finding the Metacentre, &c., Tlieorems relating to the different kmds of Equi- lilivimii of Floating Bodies, viz. : — Stable, Unstal)lc, and Indifferent, .... On the Centre of Gravity of the Plane of Flotation, Method of Determining the Line of Intersection of the Upright Water Section with the Inclined Water Section, New and Simple Eule foii Detekjiining the Volumes of Immersion and Emersion, as well as for Finding the Moments required IN Statical AND Dvn.vmical Stability, &c., 47-58 Measure of Statical Stability, as given by Atwood, 47 Methods of Finding the Centre of Gravity of the Ship by Chapman and Abethell, . . .47 Method of Calculating the Statical and Dyna- mical Stability by IMr Barnes, . . .47 Theory of Dynamical Stability, as Propoimded by Canon Moseley, 40 Times of Oscillation of a Simple and Com- pound Pendulum investujated : — " Time of EoUing," as given by Dr WooUey, Canon Moseley, Mr Froude, Dr Eankine, &c. 50 Tables sho^atnt; the Method of Calculating THE Displacement, Centre ok BuoViVNCY, TklETACENTRE, VOLUMES OF IMMERSION, STA- BILITY, Time of Kolling, &c., of the Yacht "TiTANIA." 54 42 43 45 4G 4G The Theory of Siiip-buildlnc — continued. pagk EeSULTS DEDUCED FROM TllEORY AS APPLICABLE TO Ship-building, 56 The Forces which Act on a Ship in IMotion — as they influence her General Dimensions, l'"()rm, and Qualities, ..... 58 Laws of Eesistance, 58 Proi)ulsion of A^essels by Sails, . . . ()2 Weather-helm and Lee-helm, . . . . G3 Pitching and Eolling, 63 Metacentre familiarly explained, . . .64 Centre of Gravity of a Ship, obtained by Cal- culation or by Experiment after her com- pletion, ....... 64 Centre of Gravity of a Ship should remain with as little alteration as possible in Eolling, or in Pitching and 'Scending, . . . .65 Influence of Form as comprised in Length, Breadth, and Depth, 66 Influence of Consumption of Stores or Discharge of Cargo, ....... 66 Advantages of an increased Drauglit of Water Abaft, 67 Designing of Vessels, 67 Tonnage, ....... 68 Description of Pl<vtes, 68 The Schomberg. Plate III. Clipper Sailing Ship by Messrs Hall of Aberdeen, . . 69 The Lord of the Isles. Plate IV. Iron Sailing Ship by Messrs J. Scott & Co., (Jreen- ock, 69 Titan lA and America Yachts. Plates V., V^, and VI., 69 The Delta, Clipper Paddle Steamer, belonging to Peninsular and Oriental Company. Plate VII., 69 The Great Eastern. Profile, Horizontal Sec- tions, and Deck Plan. Plate VIII., . . 69 The Great Eastern. Vertical Sections and Scale of Displacements. Plate IX., . .69 The Bremen, Screw Steam-Ship. Plate X., . 6!» Her Performances, . . . . .69 The Pera. Plate XL, 70 The Nubia. Plate XII., . . . .70 Her Performances, . . . . .70 The Ceylon. Plate XIII., . . . . 70 Inboard Works. Plate XIV.. . 70 CONTEXTS. IX PAGE Materials used in Shipbuilding, . . 71 TiMBEE, its Durability and Preservation, . - . 71 „ its Strength, 70 Supply of Timber, . . . . . .77 Weight of Timber, 78 Materials used in combination with Timber, . 79 Sheatliing of Timber Vessels, . . . .79 Iron for Ship-building : — Cohesive Strength of Plate and Bar Iron, . 79 Force required to Shear and Punch Iron, . 81 Strength of Piivetted Joints and Proportions of Eivets for Joints, . . . . .82 Transverse Strength of Iron, . . . .83 Power of Iron to resist Compression, . . 83 Forms of Iron Beams : Eules for their Strength, 83 Strength of Iron Columns, . . . .8-4 Durability and Fouling, &c., of Iron, . . 84 "Weight of Iron, 85 Practical Buildkg : — Strains to which a Ship is liable at Eest and in Motion, ....... 85 A Ship considered as a Beam, . . . .85 Hogging and Arching 86 Importance of Strength in Upper Works, . 86 Sagging, 86 Diagonal Trussing, 87 Comparison of Iron and Wooden Ships, . 88 Practical BurLDmo — continued. Water-tight Bulkheads, 89 Advantage of a Keel, 89 Practical Operations, .... 89 Principal Plans, 90 Square and Cant Bodies, . . . .90 Diagonal Lines, expanding the Body, &c., . 91 Timber Ships : — Section of a 3-decker Man-of-War, . . 93 Experiments on the Strength of Fastenings, . 9-i Seppiugs' System of Diagonal Tnxssing, . . 96 System of Biulding adopted by Messrs HaU of Aberdeen, 98 Details of Iron Ships : — Keel and Keelson, . . . . .100 Beams and General Strength of the Ship, . 101 Section of an Iron Vessel by Mr Bowman, . 102 Mode of attaching Water-tight Bulkheads, . 103 Specification of an Iron Screw-Ship for the Peninsular and Oriental Steam Company, with Sketches of Details, . . .103 Specification of The Australasian, . . ,106 Taylerson's Diagonal Framing, . . .110 Armand's Mixed System of Wood and Iron, . 110 Effects on Shipbuilding of Lloyd's Eegu- lations, 110 Launching, m STEAM-SHIPS. History of the Invention of Steam Navt- gation : — Paddle- Wheels used by the Ancients, Blasco de Garay suggests the first Steamer in 1543, Dr Papiu describes a possible Steamer in 1681, Newcomen completes his Atmospheric Engine in 1705, Jonathan Hulls projects a Steam-Vessel in 1736, James Watt improves the Steam-Engine, 1780, Mdler, Taylor, and Symington construct the first Steam-boat on Dalswinton Loch, Dumfries- shire, in 1788, 113 113 113 113 113 114 114 The first "practical" Steamer, the "Charlotte Dundas," is set to work on the Forth and Clyde Canal in 1801, 114 Fidton's experiments in France and America in 1803-7, 115 The Clermont, the first Steamer launclied in America, 1807, 115 Stevens, an American, takes the fii-st Steamer to Sea, from the Hudson Eiver to the Delaware, in 1808, 115 The Comet begins running on the Clyde, being the first regular Passenger Steamer, in 1^12, 115 b CONTENTS. The first Steamer in tlie Itoyal Na\7, also called The Comet, is built in 1819, . . .115 David Napier introduces Coasting Steamers in 1818, lie The "James Watt" and "United Iviugdom," 1822-26, lie The " Savannah," Auxiliary Steamer, crosses the Atlantic from New York to Liverpool in twenty-six days, 1819, . . . . IIG The Sirius crosses the Atlantic from London to New York in seventeen days, and the Great Western from Bristol to New York in fifteen days, April 1838, .... IIG The Screw Propeller introduced in 1837, . 116 The Archimedes (1840) and the Eattler (1842), 116 Statistical Table, showing the Progress of Steam Navigation in the British Empire, . .117 Comparative Sizes of Five remarkable Steamers, 118 The Marine Engine — its pecvdiarities, . .118 Side-Lever Engines, 118 Direct-acting Engines for Paddle "WTieels, . 118 „ „ for Screw Propellers, . 120 Oscillating Engines in Great Eastern, . .120 Screw-Engines in the Royal Navy, . . .120 Nominal Horse-power, 121 Indicated Horse-power, 121 Description of the Indicator, .... 121 Indicator Diagrams, to calculate, . . . 122 The Dynamometer, 122 Velocity of Piston in Marine Engines, . . 122 Long and Short Stroke Engines, . . 123 Long and Short Connecting-Eods, . . . 123 Expanding the Steam in the Cylinder, . . 124 Steam-jackets, 124 Combined-cylinder Engines, . . . .124 Single-cylinder Engines considered equally effective, 125 Marine Boilers : Management of the Fires, . 125 Admission of Air to the Furnaces, . . . 125 Kate of Combustion of the Fuel, . . . 126 Nature of the Heating-surface, . . . 126 Salt Water in Marine Boilers, . . . .126 Blowing off, 126 Proper Saturation of Water in Boiler, . .126 Feed-water Heaters, 127 " Priming " of Boilers, 127 Wet Steam, . Superheating Apparatus, Economy of the Process, The Common Tubular Boiler, The Vertical Tube Boiler, The Sheet-flue Boiler, Explosions of Boilers — Causes and necessary Precautions, ..... Merchant Sbippuig Acts of 1854 and 1862, Coal — the Qualities most desirable for Steamers, Admiralty Table of Experiments on Fuel for the Iloyal Navy, Average Properties of Coal, Evaporative Power of Coal, Anthracite and Welsh Coal, . Bituminous Coal, Treatment in the Furnace, Patent Fuels, Marine Engines, Proportion and Management of, ... . Marine Governor, . Expansion Valve, . Slide Valves, . Condenser, Surface Condensers, Air-Pump, Simplicity of the Machinery should be Studied, Large Bearings necessary for Efficiency . Deterioration of Padtlle and Screw Shafts, Lubrication of the Machinery, Form for Engineer's Log, PADDLE-WHEELS, Common and Feathering, Slip of the Paddle- Wheel, Screw Propeller — Definition, Pitch of the Screw, Slip of the Screw, Form for Screw-Blades, .... Effect of the Screw in Propelling, . Woodcroft's " Increasing Pitch" Screw, . Smith's Screw, Lowe's Screw-Blades, .... Griflith's Screw, Feathering Screw Resistance of the Screw while SaiUng, Hoisting Screw, Effect of Variations in the Pitch of the Screw, „ „ Diameter, 127 127 128 129 129 129 129 129 130 130 131 131 131 131 131 131 131 132 132 132 132 133 133 133 133 133 134 135 135 135 135 135 136 136 136 136 136 136 137 137 137 CONTENTS. XI Effect of Variations in the Area and Length, Slip of the Screw, " Negative Slip" of the Screw Trials of Screw Propeller in the Eattler, . Flying Fish, Doris, . Screws with Two, Three, and Four Blades, Official Explanation of Admiralty Tables Trials of Screw-Ships, .... Euthven's Water-Jet Peopellee, The Enterprise, Comparison between the Paddle and Screw, Resistances offered to a Steamer's Progress, Direct Eesistance of the "Water, Influence of Form, Frictional Eesistance, .... Effect of Increased Length, Law of Gross Eesistances, Eelation of Power to Speed, . Practical Examples, .... of PAGE 137 137 137 137 138 138 138 138 139 139 139 140 140 140 140 141 141 141 141 PAGE Value of the terra " Efficiency." . . . 141 Modes of comparing Steamers, . , . 141 Formulae for Determining Steamsuip Per- formance, . . • 142 Proportion of Horse-Power to Tonnage, . . 142 Main Elements of Steam-ship Economy, . . 142 Proportions of Length, Breadth, and Depth, . 142 Management of a Steamer at Sea, . . . 142 Details and Particulars of Eighteen Eepre- sentative steamers, 143 List of Spare Gear for a Sea-going Paddle Steamer, ....... 145 List of Spare Gear for a Sea-going Screw Steamer, 145 Table of Weights of Steam Machinery in Eoyal Navy, 145 Description of the Plates, . . . .146 Table of Particulars of Seventy-two 2*Ierchant Steamers, 147 Table of Particulars of Fifty-six Screw Steamers in the Eoyal Navry, 148 TIMBER. Definition of the Term, 151 Growth of the Tree, 151 Early Authorities on Timber, . . .151 Mr Knight's Experiments on the Physiology of Trees, 151 Manner of Increase, 151 Hardening of the Sap-wood, .... 151 Nature of the Circulation of the Sap, . ,152 Functions of the Leaves of a Tree, . . . 152 Formation of the Annual Eings, . . .152 Influence of Situation on Trees, . . . 152 Mineral Constituents of Timber, . . . 152 Influence of Soil on Trees, .... 152 Deseases and Accidents to whidi Trees are liable, 152 Effects of a Marshy Soil, .... 153 Growth of the Oak, . . . . .153 Connection between the Eoots and the Branches, 153 Depth of Soil required for Timber Trees, . 153 The Properties of the Soil must be studied, . 154 Properties of the Best Oak Timber, . . 154 Dimensions of the Largest Oaks on record, . 154 Different Species of Oak, . . .154 Proportion between Sap-wood and Heart-wood in different Trees, 154 Eate of Increase of Oak Timber, . . . 155 Value of Oak Timber upon an Estate, . . 155 Hardwood Plantations, ..... 155 Proper Time for Planting, .... 155 Drainage of the Ground, .... 155 Thinning the Woods, 155 Best Season for FeUing Timber, . . . 155 Ebn Timber, 156 Chestnut, Beech, and Ash, .... 156 Fir Timber, viz. : — Eiga, Scotch Fir, Yellow Pine, Spruce, and Cedar, .... 156 Defects in Fir Timber, ..... 157 Cultivation of Larch Timber, .... 158 Foreign Timbers : as Teak, Saul, Mahogany, Greenlieart, &c., .... 158 xu CONTENTS. Classification of Timbers at Lloyd's, Supply of Colonial Timber, Timber Trees of Minor Importance, Strength of Timber, PAGE PAGE 159 Preservation of Timber by Ai-tificial Means, . 161 160 Thorough Ventilation necessary for Preserving 160 1 Timber, 161 161 Measurement of Timber, .... 162 TONNAGE. Signification of the Term, . . . .163 Importance of good Toimage Laws, . . 163 Principles on which Tonnage should be computed, 163 Scales of Displacement or Tonnage, . . 163 " Builder's Old Measurement," . . .163 Tonnage Law of 1836, 164 Difficulty of Framing a perfect Tonnage Law, 16-4 New Tonnnge Law of 185-4, . . . .164 Practical Working of the present Law, . .166 Modification of it introduced in 1860, . . 166 SHlP-BUILDINa. To a people whose power is essentially maritime it is not necessary to use any arguments in proof of the importance of ship-builtling. Without pausing to dwell on the various struggles by which England has maintained her position amongst nations, it must be seen by all who study her his- tory, that it has been by keeping invaders from her shores, by means of her wooden bulwarks, that she has withstood the repeated attacks of the powerful nations of the con- tinent. And whilst the navy must be looked upon as the proper means of defence to this sea-girt land, who can visit the docks of London, Liverpool, the Clyde, or any of her other commercial ports, and not feel that her very heart's strength lies in those forests of masts which bring wealth to her merchants and manufacturers, and the means of employment to her artisans, forming, at the same time, a nursery and a reserve of seamen, who will be ready in the hour of need to vindicate her claim to pre-eminence on the ocean ? Who, it may also be asked, can look upon the changes effected by her instrumentality in all quarters of the globe, and not own that her winged messengers have, under God's blessing, been the means of spreading civilization and truth through a large portion of the world ? The love of a sailor's life, common to all ranks amongst her sons, owes perhaps its origin to their Norman fore- fathers ; but, however begotten, and however fostered, Eng- land owes much to it, and to the spirit of adventure which it has engendered amongst them. Individual enterprise has led to national achievements, till the name and power of Great Britain have been so extended that the sun never sets upon her possessions. In an age when science is lending its mighty aid to every peaceful and warlike art, when mighty armies may be sud- denly concentrated by railroads, and a nation's fate may hang on the electric wire, England must not trust in the multitude alone of her ships. Every fresh struggle for wealth or power proves that it is the amount of mind and intellect put forth in that struggle, and the amount of energy, and of means used to effect the end desired, which, humanly speaking, ensure success ; and, as knowledge is always increasing, nations or individuals must not rest upon what has been done, if they desire to keep pace with the world in its eager rush of advancement and improve- ment. With regard to ship-building, not only must in- genuity and skill be brought to bear to assist the artisan in the practical construction of the fabric, but men of science must lend their aid, and use their powers of investigation, to assist in designing a complete whole, adapted to meet the ever-increasing competition for mastership on that ele- ment on which not only the welfare of England but of the whole world seems to hang. The limits of a treatise of this nature are such that a very general view only of the many branches of inquiry in- volved in this important subject can be given. It could not, however, be considered complete without a short out- line of the rise and progress of the art, or without some re- ference to the authors from whose works further information may be obtained. It is always interesting and instructive in every art to trace the various stages it has gone through before arriving at its existing state. The retrospect of the art of ship-building shows that there has been no standing still in its course without corresponding injury to the pros- perity and power of the nation which has neglected it, and tliat there must be no relaxation of exertion to meet the demands of a commercial and warlike people. A SHir-BUILDING. History. Marine architect ture di- vided into epochs by C'harDOck. The Aik. RISE AND PROGRESS OF NAVAL ARCHITECTURE. In tracing the progress of naval arcliitecture among the nations of antiquity, in order to connect it with its advance in more modorn times, the chronological divisions adopted by that indctlitisrable investigator, Charnock, in his valuable History of Marine Architecture, present a very succinct idea of the probable rise, progress, decline, and revival of the art, and therefore offer a valuable guide for investiga- tion. It would not be consistent with the purpose of this article to enter into the detail that would be necessary to ascertain the state of naval architecture during the periods embraced in each of the sections he has assigned to this subject. Some few facts only will be collected from various aulliors in illustration of the probable size and nature of the shipping of the ancient world, with an outline of what little is known of the rude vessels which, during the darkness ot the middle ages, bore the marauders of the northern nations on their predatory excursions. Charnock divides maritime history into seven sections. The first comprehends the time previous to the foundation of Home, until which he considers that all history is founded on surmise. The second section comprises a period somewhat less obscure, in which the collateral testimony of various authors maybe examined and compared ; and therefore there certainly appears less difficulty in ascertaining facts. It extends from the foundation of Rome to the destruction of her rival, Carthage. The termination of the third is at the conver- sion of the Republic into an empire. The death of Charle- magne ends the fourth epoch. The fifth extends from this period to the discovery of the mariner's compass. The sixth ends with the discovery of cannon, and with their adaptation to naval warfare commences the seventh epoch. The first vessel of which we have any description is the ark as built bv Noah under the directions of the Almisrhtv. Its proportions possess some interest, because, though not intended for a voyage, it may be inferred that it was con- structed to float with as little motion as possible, consider- ing that it " went upon the face of the waters" for about five months. It was no do\d)t exposed to the action of the winds and waves during that' period, for before it rested "a wind was made to pass on the earth, and the waters asswaged." Assuming a cubit to be about 18 inches of our measure, its length was about 450 feet, its breadth about 75 feet, and its depth about 45 feet, with an arch or round-up of the upper deck of about 18 inches. Its draught of water must have varied greatly during the period of its occupation, as twelve months' provisions must liave formed a very large proportion of the original weight, and these must have been grailually consumed. Its length is thus seen to have been six times its breadth, and it is per- haps curious that ship-builders should not sooner have given this, or a greater proportion of length to their vessels ; seeing that these were intended for locomotion, with as much speed as possible, and consequently that an increase of length must have been proportionally advantageous to them, by giving them a finer fijrm. The rememljrance of this huge vessel, or floating house, would remain long on the minds of Noah's posterity ; but it was not likely to influence them in the construction of petty floating vessels, to meet any of their limited requirements. Wickerwork frames of rushes, or reeds, or of the rind of the papyrus, smeared with mud or pitch, similar to the ark in which Moses was exposed, appear to have been at a very early age brought into use, and basketwork, covered with skin, has continued in con- stant use among many nations, even up to the present time. They are still in use in some parts of this and other countries under the name of coracles. Canoes, formed out of the trunk of a tree, require tools or implements for their construction, and were, therefore, no doubt of later intro- duction. As early authentic records on the subject of ship-build- ing, the paintings and sculptures of Upper and Lower Egypt may be referred to. These show regularly formed boats, constructed of sawn planks of timber, propelled by numerous rowers, and also by sails. Some are represented as formed with inclined planes, forward and aft in the same manner as the barges on the Thames, and in this respect are more correct in theory and in reality as to ease of pro- pulsion than many canal-boats of the present day, con- structed of a wedge-like form. The Hebrews in the time of Solomon must have possessed vessels of considerable size, as mention is made, in the sacred writings of that date, of " stately ships" and of voyages made to bring trees of considerable size to be used in the building of the temple. In addition to the trade in the Mediterranean from Joppa and Tarshish, it is also recorded that Solomon despatched a navy of ships from the Red Sea to fetch gold from Ophir, the position of which, though disputed, was probably on the east coast of Africa. The Phoenicians were connected with the Hebrews in their maritime expeditions, and this people appear to have been the most enterprizing in navigation of all the nations of antiquity. There can be no doubt from the accounts given by thatmost pains-taking andcareful historian, Herodo- tus, that an expedition fitted out by this people sailed round the Cape of Good I lope. They started from the Red Sea, and after passing Ophir, if situated, as previously supposed, on the east coast of Africa, and to which they were in the habit of trading, they rounded the Cape, and keeping by the shore they entered the Mediterranean through the pillars of Hercules, or Straits of Gibraltar, and arrived in Egypt in the third year of their expedition. Vessels capable of per- forming such a voyage must have been of considerable size. The Phoenicians were also engaged, in concert with other nations, in wars with the Greeks; and it was from them that the latter nation learned in their wars what they knew of ships and of navigation. Amongst the Grecian states, the Corinthians appear to have most distinguished themselves by improving the forms of the galleys, and in- creasing their size. The people of Tuscany and the Car- thaginians also became important maritime powers about this time. The Romans in the earlier stage of their history paid little attention to navigation, until it was forced upon them by the necessity of com|)etiiig with their great rivals the Carthagenians. The galleys of this period ranged from a single bank up to the quinquireme of five banks of oars. The oars in these large galleys being arranged in sets or banks, the number of these could be increased to any extent by giving additional length to the galley. The trireme, or three-banked galley, appears to have been gene- rally open in the middle where the rowers sat, with decks or platforms at both ends for the soldiers ; but this was not always the case, as in the representation of a trireme found at Pompeii, it is decked over for its whole length, and with a house or inclosed space at the stern. The galleys of greater size than the triremes appear to have been always deckeil-vessels, and the u[)per or fourth and fifth oars of each bank were probably pulled from the deck, in the same manner as the long oars of the present day, called sweeps, while the three lower oars were pulled through port-holes by men seated below the deck. The chief information on the vessels of this period is gathered from the accounts of naval expeditions and en- gagements as recorded in the histories of the Peloponne- sian war by Thucidydes ; the wars of Alexander the Great, especially the siege of Tyre, by Curtius and Arrian ; the Ilistory. Vessels of Ancient Egypt. Phoenician shipping. G recian shipping. Roman shipping B.C. SHIP-BUILDING. battle between Demetrius and Ptolemy, by Diodorus Sicu- lus; the first Punic war, by Polybius, in which a very minute account is given of the ensragement between the Romans and the Carthaginians; and of the battle of Actium, by Dionysius Cassius. Csesar, in his Commentaries, also gives an account of the vessels used in the invasion of Britain, which seem to have been of greater draught of water than common at that period, as lie considers it worthy of record- ing, that the men on disembarking were breast-high in the water, and that at last the galleys were ordered in between these larger vessels and the shore, to protect the disem- barkation. The Roman ships were divided into three classes : the naves longre, or ships of war ; the naves oneraria, or ships of burthen ; and the naves liburnce, which were ships built expressly for great velocity, and may be supposed to have been used as despatch-boats, and for making passages with important personages. There is repeated evidence to prove that these vessels were invariably built of pine, cedar, or other light woods, excepting that the bows ol thuse for wai- were of oak, strongly clamped and strengthened with iron or brass, in order to withstand the shock of opposing ves- sels ; the tactics comprisintr the attempt to sink or dare^age the enemy's vessel, by violently propelling this armed bow against the weaker broadside of the enemy, or else endea- vouring to break and cripple the oars. Oak was first ap- plied to ship-building by the Veneti, on the testimony • of Cssar in his treatise De Sella Gallico, lib. iii. cap. 13. Copper or brass was introduced for fastenings, in con- sequence of the quick corrosion of the iron, about the time of Nero. This is stated on the authority of Vege- tius, and also of Athenaeus ; and Pliny mentions that flax was used for the purpose of caulking the seams of the plank. The following quotation is from Locke's History of Navi- gation : — •" Sheathing of ships is a thing in appearance so absolutely new, that scarce any will doubt to assert it alto- gether a modern invention ; yet how vain this notion is, w ill soon appear. Leo Baptisti Albert!, in his book oi Archi- tecture (lib. v. cap. 12), has these words : But Trajan's ship weighed out of the lake of Riccia at this time, w hile I was compiling this work, where it had lain, s>mk and neglected, for above 1300 years ; I observed that the pine and cypress of it had lasted most remarkably. On the outside it was built with double planks, daubed over with Greek pitch, caulked with linen rags ; and over all a sheet of lead fastened on with little copper nails. Raphael Volaterranus, in his Geography, says this ship was weighed by the order of Cardinal Prospero Colonna. Here we have caulking and sheathing together above 1600 years ago; for I sup- dose no man can doubt that the sheet of lead nailed over the outside with copper nails was sheathing, and that in great perfection, the copper nails being used rather than iron, which, when once rusted in the water, with the working of the ship, soon lose their hold and drop out." During the dark ages which followed the downfall of Rome, little progress was made in navigation, and but little is known of the vessels in which the nortnern hordes made their predatory and conquering excursions. The investigations of the Royal Society of Northern Antiquarians at Copenhagen have thrown considerable light on the subject of this early navigation, and of the discoveries of the Scandinavians in the west ; and it cannot be sup- posed that it was in coracles that frequent voyages were made to Newfoundland, and colonies established there, which, it appears jjroved, were in existence as early as the tenth century. But to recur to the description given by Caesar of the ships of the Guidish Veneti. " Their bottoms were somewhat flatter than ours, their prows were History. very high and erect, as likewise their stern?, to bear the hugeness of the billows and the violence of the tempests. The body of the vessel was entirely of oak. The benches of the rowers were made of strong beams about a foot in breadth, and fastened with iron nails an inch thick. In- stead of cables, they secured their anchors with chains of iron ; and made use of skins and a sort of thin pliant leather, by way of sails, probably because they imagined that canvas sails were not so proper to bear the violence of tempests, the rage and fury of the winds, and to govern ships of that bulk and burthen Neither could our ships injure them with their beaks, so great was their strength and firmness, nor could we easily throw our darts, because of their height above us, w hich albO was the reason that we found it extremely difficult to grapple the enemy and bring him to close fight." And again, speaking of the manner in which these ships were eventually taken posses- sion of: " They," the Romans, " had provided themselves with long poles, armed with long scythes ; with these they laid hold of the enemies' tackle, and drawing off the galley by the extreme force of oars, cut asunder the ropes that fastened the sailyards to the masts ; these giving way, the sailyards came down, insomuch that, as all the hopes and expectations of the Gauls depended entirely on their sails and rigging, by depriving them of this resource, we at the same time rendered their vessels wholly unservice- able." The account proceeds to state, that many attempted to escape from this unforeseen means of aggression ; but that the wind falling, and a perfect calm coming on, they were obliged to remain inactive on the water, and were taken possession of, one after the other, by the simultaneous at- tack of several Roman galleys. It would appear from this that they were vessels only intended for sailing, and that, since oars were used, from the mention made of seats for the rowers, they could have been as very partial accessories to the sails, or probably even only for steering. Another fact is mentioned by Casar, that the Veneti sailed from their port to meet the Roman fleet, and several of the vessels escaped to their port from the fleet. This, though not conclusive of the fact of sailing on a wind, is worthy of notice. It is probable that it was ships such as these which brought Hengiet Hengist and Horsa to England about the middle of the fifth a°<l Horsa. century, since it is recorded that their force, which con- *""• sisted of 1500 men, found accommodation in only three ves- sels. It is hardly to be imagined that the coracles, or skin- boats of the northern nations, were ever of sufficient dimen- sions to accommodate a force of 500 men, with arras and means of active aggression. The earlier irruptions of the northern barbarians into Rise of Italy had desolated the Roman province of Venetia, and Venice driven a remnant of its inhabitints to the refuge aflbrded by the small marshy islands at the extremity of the .Adri- atic. There they are described by Cassiodorus, who assimi- lates them to water-fowl, as subsisting on fish, and steeped in poverty, their only manufacture and their only com- merce being salt. From such humble beginnings arose the state destined to connect the old world with the new, and to lead the van of modern commercial and maritime enterprise. The mercantile prosperity of Venice diffused its influence throughout the shores of the Mediterranean, which thus became once again the nursery of civilization For many centuries Venice was the great school of the arts connected with navigation, and her shipwrights and seamen were long the most instructed in Europe. While the north- ern seas were navigated by the Scandinavian sea-kings, in their rude and frail boats, in quest of plunder or of a home, ships floated on the waters of the Mediterranean bearing the banner of St Mark, which, it is said, were, even as early SIIIP-BUILDING. Jlistory. Mediterra- nean gal- ley. Alfred. A.D. 871. Ilia ships. Reasons for tiieir intro- ilaction. Their suc- re^s. Sixon rule as the tenth century, of the burthen of 1200 up to 2000 tons. The vessels, however, generally ailopted by the Me- diterranean states were either copies or modifications of tiie ancient galley. It is a fact worth notice, that while the continuation of the use of this species of vessel in the comparatively tranquil waters of the Mediterranean fostered the arts of commerce and navigation, its introduction into the northern seas, to which it was ill adapted, appears to have checked, in a most remarkable degree, the maritime enterprise wiiich liad hitherto so characterized the population ot their coasts. It is even probable that the barrier thus opposed to commerce entailed on the states of Northern and Western Europe centuries of comparative barbarism. Alfred was the first ruler of England wlio clearly under- stood that the policy of Britain was rather to prevent than to resist invasion ; and the bygone history of liis country told him plainly that its military strength was not only insufficient to awe invaders from its shores, but that all the military resources at his command were inadequate to pre- serve the liberties of his people. He therefore turned the energies of his mighty mind to the task of creating a naval force, which should be more powerful than that of his untiring persecutors the Danes. In this he succeeded ; and at length, under the protection of the fleets which his genius had created, he was enabled to estiiblish that frame- work of internal policy and government, from the wisdom of which England has even to this day benefited. It is historically certain that Alfred himself superintended the formation of his fleet, and that he gave the design of vessels to be superior to those of the Danes. These vessels were galleys, generally rowed with forty oars, some even with sixty, on each side ; and they were twice as long, deeper, nimbler, and less " wavy" or rolling, than the ships of the Danes. The information on this subject is obtained by Selden from a Saxon chronicle of the time of .\lfred, which is in the Cottonian Library. It should be remembered, that when .Alfred thus intro- duced the Mediterranean galley into these northern seas, his object was not so much to form a vessel adapted for the purpose of navigating those seas, as to obtain one which would afford space for a large force of fighting men. For this the galley was admirably qualified; and indeed it main- tained its place as the appropriate ship for the purposes of war until the invention of cannon rendered other arrange- ments necessary. The immunity which it insured from the attacks of the Danish marauders caused its general adoption along the coasts hitherto open to their incursions, on all of which it thus superseded the sailing vessels that have been already described ; and voyages which, until its introduction, were boldly and successfully achieved, became of rare occurrence and of hazardous issue during the subsequent ages, until the galleys once again gave place to sailing vessels. It also gradually checked the enterprise of the Northmen, by the cuib wh'ch it placed upon their successes. It is not proposed to give more than a slight sketch of the naval history of Britain through the line of her Saxon princes; for little data can be found on which to base any speculation even, as to the progress of naval architec- ture during these ages. The galley of the Mediterranean continued to be used for the defence of the coasts ; and the policy of Alfred appears to have been well understood by many of his successors — that England only enjoyed peace from invasion when her fleets were powerful enough to repel it from her shores. It is also to be inferred that the use of sailing vessels was not wholly abandoned; for in the reign of Athelstan, the third in descent from Alfred, as recorded by Hackluyt, it was decreed, that " if a raar- cliant so thrived, that he passed thrise over the wide seas of his owne crafte, he was thenceforth a Thein's right worthie." This est.ablishes two rather interesting facts : one is, that at so early a period there were merchants of importance enough to engage in such a traffic ; and the other is, that from the richness of the reward held out to successful enter- prise, the difficulty of the task assigned nmst have been esti- mated as great. It may be assumed that these long voyages were made in ships more adapted fortiie purpose than galleys; in fact, in the vessels which the galleys had been intended to supersede. But the spirit of maritime enterprise had, as before observed, evidently received a ciieck, since one of the highest rewards in the power of the monarch to bestow was held out to the merchant as an incitement to an adventure, which the vague hope of |)lunder would alone have been sufficient to induce that merchant's progenitors to attempt and successfully perform. However, it is probable that at no time was the art of navigating vessels, which depended principally, although perhaps not wholly, ujjon their sails, lost in the northern seas. Gibbon says, that at the early crusades the vessels of the " Northmanni et Gothi" (the Norwegians and Danes) differed from those of the other powers, among all of whom tlie ships partook of the charac- ter of the Mediterranean galley. These nortliern crusaders are described by him as navigating " ttavibus rotundis — that is to say, ships infinitely shorter in proportion to their length than galleys." This was not later than the beginning of the twelfth century, and therefore not so far removed from the periods in question as to render the inference proposed to be deduced from it erroneous, particularly when referring to times of such slow improvement as the middle ages. The " mighty" fleets maintained by Edgar afford no in- formation on the subject of this article, excepting that the facts connected with that monarch's annual circumnaviga- tion of his territories prove them to have consisted of row- galleys. They must, however, have formed comparatively a " mighty" fleet ; for, from a grant of land made by Edgar to Worcester cathedral, it is found that heassunud to him- self the title of '' Supreme Lord and (Jovernor of the Ocean lying round about Britain." That they were but of slight construction may be inferred from the low state of the navy so shortly after the death of Edgar as the reign of Ethelred, who, in order to re-establish it, instituted a regular lax fiir providing and maintaining a navy. It was enacted, accord- ing to Selden, that whoever possessed "310 hides of land was charged with the building of one ship or galley ; and owners of more or less hides, or part of one hide, were rated proportionally" — the hide being, according to the best authorities, as nnich ground as a man could turn up with one plough in a year. But this tax appears to have been inadeijuatc to the purpose of providing a sufficient fleet, for all the exertions of Ethelred could not preserve Britain from again being ravaged by the Danes, and, after the short reign of his son Edmund Iroll^idcs, England was ruled by Danish nionarchs. From the known talent of Canute, the first of these princes, and from the crowns of Denmark, Norway, and Britain being united in his person, it may be presumed that the naval affairs of England were not suffered to retrograde. There is, indeed, a record of their advance during this second Danish rule. It may also be inferred from the present which was made by Earl Godwin to Ilardicanute, the third Danish sovereign, of a galley, sumptuously gilt, and rowed by fourscore men, each of whom »vore on his arm a bracelet of gold weighing sixteen ounces ; not that the mere gorgeousness of the gift would prove any advance in the art of ship-building, but it may be supposed, from its nature, that naval aftairs found favour in the sight of this monarch. Of this there is also otiier historical evidence, as Hartlicanute raised L.11,0-1S, History. Mercantile shipping. Decline of naval en- terprise. Edgar. Ethelred. Canute. A.D. 1016 SHIP-BUILDING. History, in the first two years of his reign, for the purpose of build- ^^■^^/^-^ infj thirty- two ships; and the taxes he levied for the support of his navy were so grievous that, Florentius says, scarcely any man was able to pay them. The marine of England seems to have been maintained on a comparatively powerful footing up to the period of the Norman conquest ; and from the naval resources at the command of Harold the Saxon, in comparison with the in- significance of the shipping which brouglit William and his Normans across the channel, there can be no doubt that had Harold relied upon his naval strength, the conquest of England would never have been achieved ; but, by some fatality, his fleet, wliich had been long stationed off the Isle of Wight, was dispersed, in consequence of a report that William iiad abandoned his enterprise. Tlie flotilla of William the Conqueror is variously stated ; by some at 900, by others at 3000 vessels. Either num- ber proves their insignificance, as the invading force con- sisted of about 60,000 troops, which would give in the one case about 66 men to each vessel, in the other 20 men only (figs. 1 and 2). fig. 1. The conquest of England being completed, the shores on either side of the narrow seas between England and Probable size of 6hips. Normandy were under the same rule. William, therefore, claimed sovereignty over them, which right was maintained by his successors. There can be no doubt that the con- stant intercourse between the two portions of the empire, which continued throughout the Norman sway, and indeed for a period of upwards of three centuries, must have dune much towards fostering a maritime spirit among the popu- lation of England, and accustoming it to consider that fame and fortune « ere the rewards of nautical adventure. There is but slight evidence as to the state of naval architecture during the early period subsequent to the Con- quest. There are a few (acts scattered among the records of these times, from which some vague coiKlu>ions as to the probable size and nature of the vessels used may be History, drawn. When Prince VV'illiam, son to Henry I., was '-^^— >* drowned, by the loss of the vessel in which he was cross- a.d. lloo. ing from France to England, it is recorded that 300 souls perished with him. As of this number a large portion, his- torians say 140, were men of rank, a: id as there were many ladies, since the |irince was accompanied by his sister, the vessel must have been of considerable burthen. A similar event, namely, a shipwreck, that occurred during the reign of Henry H., by whicii nearly the same number of persons perished, tends to prove that such was about the extent of the accommodation affurded by the shipping of this period. Galleys still continued to be used for the purposes of war ; but as commerce began to be extended, it became nects- sary to recur to the use of sails, and they were therefore gradually recovering their importance, and superseding oars. Indeed, it is difficult to conceive commerce to be profitably engaged in when attended with the immense expense of the crews necessary to propel the larger galleys. This must have had an imjiortant influence in the improve- State of ment of navigation and of naval architecture, for the com- trade, mercial intercourse between the portions of the empire on either side of the channel must have been considerable. There is constant reference in the early chronicles to the great extent of the wine trade, and of the commerce in wool and woollen cloths. The introduction of vessels propelled by sails for the pur- poses of commerce would necessarily cause a change in the constitution of the fleets assembled for the services of war; and this will be found to have been the case. The expedition of Richard Cceur de Lion, in 1190, to Kichard join the crusade to the Holy Land, consisted of nine ships, Cttur de ahich are described as being of extraordinary size, 150 '"'"";, g^ others of inferior dimensions, and only 38 galleys. Alter the reduction of Cyprus, and the addition of the vessels captured there, with others which he had hired at Mar- seilles and in Sicily, his armament consisted of 254 " tall shippes, and about three score galliots." The increase was, therefore, almost wholly in the ships. This, together with the recorded fact, that he captured a Saracenic vessel of such size as to be capable of containing loOO Saracens, and a large quantity of military stores, destined lor the relief of Achon, tends to prove that the progress of naval architec- ture, under the influence of the commercial powers of the Mediterranean, had been more rapid than in these northern seas, where the commerce was much more confined in its nature, and the nations bordering on which were in con- stant warfare with each other. The Norman monarchs appear to have been very tena- Sovepfign- cious of their claim to the sovereignty of the narrow seas; tyof the and not only their claim, but their power to maintain their "•'*'• ri^ht, is admitted by the Ficnch historians. The Pere Daniel sanctions the claim of Henry II. to this sovereignty. In the reign of .lohn the fleets of England were of such John, importance that the claim was extendeil ; tor it was then*-"- ^'^^• enacted, that if the masters ol" foreign ships should refuse to strike their coloms, and thus pay homage to the English fla<_', such ships should be considered as lawful prizes. This monarch most carefully fostered the naval power of Eng- land ; and it is in the records of the thirteenth year of this reign that mention is first made of any public naval estab- lishment. There is in the close rolls, published by the Early ori- Kecord Commission, an order, which is dated the 29th oi'f^"°^ Mux 1212, from the king to the shcrift" of the county of ^"""J^ Southampton, in which he is directed without delay to cause dockya.d. the king's docks at Portsmouth to be enclosed by a good and strong wall, in order to protect the king's galleys and ship's; and also to build storehouses against this wall, for the preservation of the fittings and equipment of the said vessels ; all of which works .are to be performed under the direction of William, arcl'deacon of Taunton, and the SHIP-BUILDING. Sove- reignty of thenea held by Kng- land, and spontane- ously aban- doned. ni»torT. greatest dilijicnce is to bo used, in order that the whole may ^~mm^/'^m^ bc completcd during tlic siunmer. Edward I. 1"''c naval power of England ai)pcars to have continued i.D. 1272. sufficient to maintain the sovereignty assumed by John. For the occurrence of predatory excursions by some Genoese, during the reign of Ldward I., caused ail the nations of Europe, bordering on the sea, to appeal to the kings of England, whom they acknowledged to be in peaceable pos- session of the " Sovereign Lordship and Dominion of the Seas of England, and Islands of the same ;" which proves that tlieir claim was generally acknowledged. This docu- ment, Evelyn says, was still extant in his time, in the archives of the Tower. The right to the absolute sove- reignty of the seas was maintained up to (lie reign of James I. Queen Elizabeth insisted on and maintained her power to refuse or grant passage through the narrow seas, accord- ing to her i)leasure. In 1634 C'harlef ' asserted his right to their sovereignty; and in 1654 the Dutch were com- pelled, after a severe struggle, to submit to it, and consent to " strike their flags and lower their top-sails on meeting any ship of the English navy on the British seas ;" which iiomage the commanders of English men-of-war were in- structed to exact from all foreign vessels \mtil so lately as the close of the last war, when it was judiciously aban- doned, for the following reasons, as given by Sir John Barrow. In his Life of Howe, with reference to Traflilgar, he says, " That battle, moreover, having so completely humbled the naval powers of France and Spain, suggested to the consideration of the Board of Admiralty, with the approbation of the government, the omission of that arbi- trary and offensive article which requircil naval officers to demand the striking of the flag and lowering of the top-sail from every foreign ship they might fall in with. That in- vidious assumption of a right, though submitted to generally by foreigners for some centuries, could not probably have been maintained nuich longer, except at the cannon's mouth ; and it was considered, therefore, that the proper time had come when it might, both morally and politically, be spontaneously abandoned." It is generally supposed that ships intended onlv for sail- ing were first built by the Genoese, and that not until the beginning of the fourteenth century. It is perhaps more probable, that in tlie Mediterranean they date from an earlier period than this ; and that although the general adoption of the galley in Western Europe had much checked the art of navigation by means of sails, it had never been wholly lost, but that saihng vessels, though probably very few in number, and imperfect in rig, had been constantly in use. To judge from the few hints handed down to us by history, they were probably luggers, and were adopted for mercan- tile purposes along the coast of the Channel and the Bay of Biscay. In the north of Europe sails had never been dis- continued, but the more warlike galleys of England and France prevented the incursions of the northern nations with such vessels into these more southern seas. The beginning of the fourteenth century is decidedly an epoch in the histories both of navigation and of naval archi- tecture, and from it may be dated the general introduction of sails and many other appliances. It is generally supposed that the " large ships" mentioned in the enumeration of the fleets of this period, were ships built only for sailing, and intended for those long voyages which the invention ot' the compass by Flavio Gioio, a Neapolitan, about the year 1300, had rendered of comparatively easy pertormance. Msriner'3 It has been surmised that the compass was brought to compass. Europe from the East about forty years previous to this date, by Paulus Venetus. It is certain that the Portuguese found the knowledge of the magnetic needle generally and -ong diffused among the eastern navies. Evelyn says, that '■ it was, near eighty years after its discovery, unknown in Britain." This is not improbable, for there does not re- Error re- specting the ute of mailing ves- sels. main miich record of maritime affairs in the interval be- nistory. tween the reigns of John and Edward III. ^— ^ r— ^ The reign of this latter monarch, however, was, after a Kdward most severe struggle with France for supremacy on the '"• seas, the era of a series of naval tri\miphs, and both navi- *'^ 1327. gation and naval areliitecture made most decided advances. In an engagement which took place in 1340, the French Naval force amoimted to 400 vessels, of which 120 were " large *'*'"*• ships," these being principally Genoese mercenaries. Ed- ward III. conmianded the English fleet in person, wliich consisted of but 260 sail. The French are variously re- ported to have lost 20,000 and 30,000 men, and 200 vessels are said to have been captured. The loss to the English was only 4000 men. Two facts are elicited by the ac- counts of this engagement ; one is, that there is no mention of galleys as forming any part of the fleets ; the other is, that in the James of Dieppe, which was captured by the Earl of Huntingdoti, 400 persons were found slain ; consequently the size of the vessel must have been very considerable. In 1344 Edward sununoned commissioners from all the Royal fleet ports, to meet in the metropolis, provided with the state of their " navies." The roll of this fleet is inserted in the first volume of Hackluyt, from a copy in the Cottoiiian Library. The total numbers were 710 ships, and 14,151 mariners; and there were 38 foreign ships, with 815 mariners. From this roll it « ill be seen that it was about this time that gal- leys ceased to be used by England for war or commerce, as neither among the king's ships nor among those furnished by merchants is there any mention of them. This fleet was that engaged in the celebrated siege of Calais, and it Use of can- was probably at this time that cannon were first em])loyed "on- by the English. Camden, in his Remains, says, " Certain it is, that Kins; Edward III. used them at the siege of Calais in 1347." Although from the fact of there being a royal dock-yard Sizes of at Portsmouth so early as the reign of John, it is probable Edward's that the kings of England were possessed of a navy almost *"'?'■ from the conquest ; yet this roll of Edward's fleet contains the first enumeration of ships belonging to the sovereign, and employed in the service of the state, which occurs in English history ; and consequently it is from the reign of Edward III. that the formation of a royal navy must be dated. The king's shi|)s were 25 in number, and were manned by 419 mariners. It appears that the vessels be- longing to the sovereign were inferior in force to many of those which were su|)plied by subjects ; for the average number of the crews of the king's ships were 17 men to each vessel, while the average of the fleet was rather above 20. Of course these numbers only include the mariners employed in navigating the vessels, and not the soldiers to bc afterwards embarked on board them. Considering the sim|)licity of the rig of these ships, in comparison to the wilderness of canvas and cordage covering the tall masts of a modern merchantman, there is more reason to be astonished at the large number of hands employed, than at the smallness of the averages, 17 and 20. There is good reason to suppose that the addition of the bowsprit to the rig of ships dates no farther back than late in the reign of Edward III., which is alone quite sufficient to prove the very imperfect state of the navigation at that period, and also to excite astonishment that, with such ap- parently inadequate means, so much was effected ; lor history would almost lead us to supoose that, lor all the pur- poses ot war and conunerce, fleets as proudly or as in- dustriously ploughed the main then as now. " with all appliances and means to boot." In the year 1331, the fourth of the reign of Richard II., Hichard the first navigation act was passed in England, for the en- 'J- courasement of the naval interest and the augmentation of 'f? ""^I' ° ■ . , ,■ ■ 1 " 1 . gation act. our maritime power, by discountenancing tlie employment of foreign shipping. It enacted, "That tor increasing the SHIP-BUILDING. niatory. A.D. 1381. Royal ships hired by uerchaots. shipping of England, of late much diminished, none of the king's subjects shall hereafter ship any kind of merchandize, either outward or homeward, but only in ships of the king's subjects, on forfeiture of shi[)s and merchandize, in which ships also the greater part of the crews shall be of the king's subjects." This act was not, however, enforced, permis- sion being given to hire foreign shipping when there were no English ships in readiness. It has been remarked above, that the royal navy of Eng- land must date from the reign of Edward III. There is proof that it continued to be customary tor the sovereign to possess ships ; they were, however, used both for war and commerce. This practice, which does not at all militate against the existence of a royal navy, appears to have commenced when " large ships" were substituted for the galleys as vessels for war ; and it long continued to be usual for merchants to hire shipping from the sovereign for com- mercial voyages. The proceedings of the privy council, which have been printed by the Record Commission, show that in June of the year 1400, Henry IV. ordered his '" new ship," together with such others as were in the port of London, to proceed against the enemy. There is also a letter in the Cottonian Library, which has been printed in Ellis's Collection of Letters, from John Alcetre to King Henry V., concerning a ship building for tliat monarch at Bayonne. The letter is of the date of 1419 ; and as it contains more minute details than niigiit be expected to have descended to us from such an early period, we give the following extract : — " At the makyng of this letter yt was in this estate, that ys, to wetyng xxxvj. strakys in hyth y bordyd, on the weche strakys hyth y layde xj. bemys ; the mast heme ys yn leynthe xlvj. comyn fete, and the beme of the hameron afore ys in leynthe xxxix. fete, and the beme of the hameron by hynde is in leynthe xxxiij.fete ; fro the onemost ende of the stemme in to the post by hynde ys in leynthe a hondryd iij"'and vj. fete ; and the stemme ys in hithe iiij"' and xvj. fete; and the post xlviij. fete; and the kele y in leynthe a hondryd and xij. fete ; but he is y rotyt, and must be chaungyd." We have also evidence of the existence of ships which belonged to the monarch, in contradistinction to ships which belonged to the "commons," in the quaint rhymes of an anonymous author of the year 1433, which have been preserved by Hackluyt, termed The Prologue of the pro- cesse of the Libel of English policie, exhorting all England to keepe the sea, and namely, the narroice sea, shotting what profile commeth thereof, and also uhat worship and saluation to England, and to all Englishmen. "And if I should conclude all by the king Henrie the Fift, what was his purposing, "Whan at Hampton he made the great dromons, "Which passed other great ships of all the commons ; The Trinitie, the Grace de Dieu, Holy Ghost, And other raoe, which as nowe bee lost. What hope ye was the king's great intent Of ihoo shippes, and what in minde hee meant : It was not ellis ; but that hee cast to be Lorde round about environ of the sea." The terra dromond is the corruption of a Levantine term, dromones, imported probably by the crusaders. The dro- monds were long row-galleys, but the adopted term dro- mond was applied generally to all large ships. There is a list of Henry's vessels in the fourth year of his reign preserved in the proceedings of the privy council. His navy then consisted of three " large ships," or " grantls niefs," three " carracks," eight barges, and ten balingers. In 1417 it was augmented to three " large ships," eight " car- racks," six other ships, one barge, and nine balingers. Again, in a letter preserved among the Cottonian manu- scripts, and printed in Eliis's collection, it is stated that the Spaniards offered Henry V. two carracks for sale, one of which is described as of a tonnage equal to 1400, and the other to 1000 butts. So energetical was Henry V. in all History, things relating to his navy, and the consequent increase in ^^^^^/>-mm^ the number of the royal ships during his reign was so great, as to have led to the error that before his time the sove- reigns of England were not possessed of vessels, but relied wholly upon the aid to be gathered from the different ports of England, or to be hired from foreigners. This is evi- dently incorrect. On the death of Henry V. a different line of policy ap- Neglect of pears to have been adopted; for in May 1423 the king's tbe navy, ships were all sold at Southampton, under a restriction that no foreigner could be a purchaser of them. But it appears that a long period did not elapse before the depressed state of the naval resources of the kingdom, consequent on this injudicious measure, attracted the attention of parliament. The following interesting quotation from the preface of the fifth volume of the Proceedings of the Prii-y Council, printed by the Record Commission, refers to this event: — "In 1443 the attention of parliament was directed to this im- portant part of the national defence (the naval force), and a liighly curious ordinance was made for the safeguard of the sea. From February to November eight ships with fore- stages, or, as they were sometimes called then, as now, forecastles, armed with 150 men each, were to be constantly at sea. Every large ship was to be attended by a barge of 80 men, and a balinger of 40 men. There were also to be 'awaiting and attendant upon them* lour 'spynes' or ' spinaces,' with 25 men each. The whole number of men in these 24 ships was 2240." There is also in the same preface an account of the va- rious kinds of ships which formed the navies of this period, a part of which we shall quote, and by the addition of some further information of the same nature, derived from Frois- sart, Monstrelet, and other sources, the reader will be en- abled to form a tolerably correct opinion as to the state of naval architecture in England previous to and during the fifteenth century. Ships. " The burthen of the largest ships at that period Ship*, probably did not exceed 600 tons, though some of them were certainly very large," as, lor instance, the vessel built at Bayonne for Henry V., already mentioned. " One which belonged to Hull was released from arrest" (she having been pressed into the king's service), " because she drew so much water that she could not approach within two miles of the coast of Guienne, where the Duke of Somer- set's army intended to disembark;" and several notices occur of ships of 300 and 400 tons and upwards. Some had three and others only two masts, with short topmasts, and a '' forestage " or " forecastle," consisting of a raised platform or stage, which obtained the name of castle from its con- taining soldiers, and probably from its having bulwarks. In this part of the ship it appears business was transacted ; and in the reign of Edward III., if not afterwards, ships had sometimes one of these stages at each end, as ships " ore ehastiel devant et derere' are then spoken of. Lydgate, describing the fleet with which King Henry V. went to France alter the battle of Agincourt, says, " Fifteen hundred ships ready there be found, AVtth rich sails and high topcastle.*' This is a confusion of terras. The " topcastles" were not the forecastles, but were castellated enclosures at the mast- heads, in which the pages to the officers were stationed during an engagement, in order to annoy the enemy with darts and other missiles ; as is frequently mentioned in Froissart, and is represented in the illuminations to his work. Carracks " were vessels of considerable burthen, and Cairacka. were next in size to great ships, in which class they indeed were sometimes included. Their tonnage may be estimated by their being in some instances capable of carrying 1400 butts ; and the sail of one afforded Chaucer a strange simile expressive of magnitude, 8 History. SlIIP-BUILDING. ' And now halh Sitlianas, daith he, a ta)l Broiler than of o carrike is the sayl.' Tliouch occasionally armed and employed against tlieencmy, they were more generally used in foreign trade." Cliarnock says tliat the first carrack which was built in England was built for a merchant, John Tavenier of Hull, who was consequently honoured by Hein-y VI. with distin- guished favour; and she was licensed in 1449 with parti- cular privileges to trade through the Straits of Morocco. The king also ordered her to be called the '• Grace Dieu ("arrack." The license states her to have been built " by the help of God and some of the king's subjects." Barges. Barges " were a smaller kind of vessel and of different construction from ships, though, like them, they sometimes had forecastles. 'I'hose appointed to protect the seas in 1415 were of 100 tons burthen, and contained forty mari- ners, ten men-at-arms, and ten archers ; whilst the ships employed on the same occasion were of 120 tons, and had forty-eight mariners, twenty-six men at arms, and twenty- six archers each. Four large barges and two balingers were capable of holding 120 men-at-arms and 480 archers and sailors." Balingers. Balingers "were still smaller than b.irges, had no fore- castle, and sometimes contained about fiirty sailors, ten men-at-arms, and ten archers." Froissart makes frequent mention of" balniers," '■ balleniers," which he describes " as drawing little water, and being sent in advance to seek adventures, in the same manner as knights and squires, mounted on the fleetest horses, are ordered to scour in front of an enemy, to see if there be any ambuscades." Monstrelet speaks of one vessel that was em[)loyed by Louis XI. to abduct the Count dc Charolais, by the two names ballenier and balayer. It is not improbable that the name is derived from the French word baleine, and that its origm was similar to that of our English name whaler. The whale- fishery in Biscay was of a very early date. (iuUeys. Galleys " are frequently mentioned at a very early period; and in the oth Rich. II., 1.381, the Commons complained that no measures had been taken to resist the enemy, who had attacked the English at sea with their barges, galleys, and other vessels. In 1405 Henry IV. directed his council to apply to the King of Portug:U to lend him his galleys to assist the English navy against the French." In Sir Grenville Temple's Travels in Greece and Turkey the following description of a Maltese galley, or, more cor- rectly, galleas, made from an old model preserved there, will be found: — " These galleys meas\ired 169 feet 1 inch in length, and 39 feet 6 inches in breadth. They had three masts with latine sails, and were propelled by forty-nine oars, each 44 feet 5 inches long. Tiieir armament con- sisted of 1 thirty-six pounder, 2 of twenty-four, and 4 of six, all on the forecastle, which in those days had in reality some appearance of a castle. On each side of the vessel, aft of the forecastle, were 4 six-pounders." The total crew, including galley-slaves, consisted of 549 persons. Galleas. The (Salleas and the Galleon appear to have been suc- cessive improvements on the original galley, rendered ne- cessary by the introduction of cannon into naval warfare. The artillery introducetl on board the early galleys was placed either before or abaft the rowers, and to fire in the direction of the length. In the galleas, a description of vessel first used at the battle of Lepanto, guns were also placed between the rowers, to fiie from the broadside. Evelyn describes the galleases he saw^ at Venice (1645) as being "vessels to rowe of almost 150 foote long and 30 wide, not counting prow or poop, and contain twenty-eight banks of eares, each seven men, and to carry 1300 men, with three masts." In the galkon the oars ceased to be the principal means of propulsion, and if used at all, were only so as occasional aids. The galley and galleas had overhanging topsides for the accommodation of the oars, nistorr. In the galleon, on the contrary, the topsides " tumbled ^»— v/.^^ home" to so extraordinary an extent, that the breadth !>t the water was twice that at the topsitle, a fashion which has conlimied, hut in a much less degree, to the present time. Sp;/)ies or spi/naces, " now called pinnaces, seem to haveSpynesor been large boats, capable of holding twenty-five men, and'!'?"*"'- were probably used for swiftness. To these must be added crayers, l)ulks, gaharres or gabbars, a kind of flat-bottomed boat, used in shallow rivers." The French still continue to apply the term " gabarre" to store-ships. " Playtes, cogships, whence perhaps cogs and coggles are Playtcs derived; farecrofts, passagers, which were perhaps boats *"'• """»"" used between England and France ; and cock-boats, a small ^'**"'*' boat which attended upon all kinds of ships. The whole of these vessels were employed in conveying goods or pas- sengers, and most of them on rivers or in the coasting traile. The ships, carracks, barges, balingers, and galleys, were employed equally for commerce or for war. When sent against the enemy, soldiers were put on board of them ; and it is most likely tliey were at all times partly manned by soldiers. In foreign voyages they usually sailed in con- voys ; and it was a very ancient custom for the masters and sailors to elect their own admiral." In Burchett's account of the unfortunate action in the Foists or Bay of Conquet, in 1513, in which the Lord High Admiral, f"ys»». Sir Edward Howard, lost his life, ihuv foists are mentioned as forming a part of the French force. They were proba- bly vessels of a similar character with the galley, but smaller in size. About the beginning of the seventeenth centurv, " carracks," " galleons," and " tall shippes," a])pear to have become synonymous terms. The term hulk originally was applied in a different sense Hulks, from that which is stated in the part of the foregoing remarks which we have quoted from the preface to the proceedings of the privy co\mcil. Frequent allusion is made to hulks in documents of the fifteenth and sixteenth centuries. In a letter from Sir Thomas Seymour to the privy council, dated the 13th of November 1544, when in command of the " shipes whyche was a poyntede to kepe the Narrow Sees," vindicating himself for putting back on account of a storm, there is the following passage, from which it might almost be inferred that hulk was a general name synonymous with shij)s: — " Thre holkes that come after me colde nott gett syght thereof (the ' Eylle of Wyght') tyll they warre in a bay on the est syde of the Eylle, of the whyche Mr Strowd, Bramston, and Battersebe of the garde, God rest their sowles, was in on of them, whyche holke brake all her ankeres and cabelles, and she brake all to peses on the shorr, and but 41 of 300 saved a lyve. The other two rode out the storme, whyche lasted all that nyght and the next day. My brother (Sir Hy Sey- mour) and John Robcrds of the garde, tryde the sees all the furst nyght, and the next day cam into Dartemouth haven, wharre my brothers holke strake on a roke and brest all to peses ; but God be praysede, all the men warre savede, savying thre ; and a nother new holke that tryde the sees that nyght brake thre of her hemes, and with moche ado came into the Wyght." Again, in a letter from Lord Viscount Lisle, Baron Malpas, the Lord High Admiral of England, to Henry VIII., there is an announcement, that " their is cum into the Downes 30 sayle of hulkses, whereof sum be tall shipes." And again, in a letter from the same to the Lord Chamberlain, Lord St John, he speaks of having detained "3 grate hulkes bound, as they say, for Lusshborne, the leste of y" 500 tunnes." And again, from the same to the same, he speaks of his former letter and the "goodly hulkes," and says, " sithens that tyme I have stayed other too, which in beautye and w ell appoynting are beyond the others. That I have last stayed ys a shipe of 600 at the least, and hath SHIP-BUILDING. History. A.D. 1450. State of mercantile shipping. William C'anyne. Doubts as to accuracy in estimat- ing size of ships. Henry ^'II .5 toppcs, and s.he ys of tlie town of Dansick, and ladon in Flanders for Lusshbourne." The importance of the mercantile shipping of England during the fifteenth century must have been considerable. About the middle of it flourished the celebrated William Canynge, a merchant of Bristol, who built the church of St Marv's, Redcliff. in that city, in which church he was buried in 1474. This man appears to have been much in advance of the rude times in which he lived. His mercantile trans- actions were on so extensive a scale, and carried on in ves- sels of such large size, that they must have had an important influence in improving the navies of the period. The in- formation which has descended to us respecting him is therefore not only a fact of much historical interest, but is one which is intimately connected with, and most materially affects, our subject. He was a great patron of the arts, a friend and protector of genius, and eminent for his virtue and piety. From an inscription upon his tomb, a tradition has become current, that Edward IV. took 2470 tons of shippins: from him, he having " forfeited the king's peace ;" and for the obtaining of which again, it is stated that Ed- ward accepted these ships instead of a fine of 3000 marks. The Itinerary of William of Worcester, preserved in the library of Bennett College, Cambridge, gives the names of Canvn^e's vessels, among which are the Mary and John of 900 tons, Mary Redcliff of 500 tons, and Mary Canynge of 400 tons. The same authority gives the names and ton- nage of other large ships belonging to Bristol merchants, among which are the John of oil tons, and the Mary Grace of 300 tons. If there be any truth in the tradition of the confiscation of the shipping, it is probable that the inscrip- tion on the tomb may refer to some act of Canynge's in favour of the house of Lancaster, as he appears to have enjoyed the favourable opinion of Henry \T. Another account, which, it is said, is authenticated by the original instrument in the Exchequer, states that this Canynge assisted Edward IV. with a loan, and received in return a license to liave 2470 tons of shipping free of imposts. In Corry's History of Bristol it is said, " the commerce and manufactures of Bristol appear to have made considerable progress during the fifteenth century, about the middle of which flourislied the celebrated Canynge. This extraordi- nary man employed 2So3 tons of shipping, and 800 ma- riners, during eight years. Two recommendatory letters were written by Henry VI. in 1449, one to the master- general of Prussia, and the other to the magistrates of Dantzic, in which the king styles Canynge his beloved eminent merchant of Bristol." Some doubt must always remain as to the actual size of the shipping of this remote period, as we cannot ascertain the bulk that was then considered as equivalent to a ton. It is probable that the tonnage was estimated according to the number of butts of w ine that a vessel could carry. For we find references to ships sometimes by tonnage, and sometimes by the "portage" of so many butts. This, however, is only a question as to exactness of size. In whatever way measured, Canynse's ships must have been iif very considerable dimensions. It is rather extraordinary, that at the unsettled period in question Bristol should have enjoyed such a st.ate of commercial prosperity as the owner- ship of such shipping as that enumerated by William of Worcester necessarily involves. Bristol, for many centuries, was only second in mercantile importance to London ; but the civil wars which distracted the kingdom during a great part of the fifteenth century must have much retarded the increase both of the military and the mercantile navy of England ; and only when order was again re-established by the accession of Henry VII. to the throne, in 1485, could men's minds revert fiom the internal excitement of party strife to external affairs. In this interval, in which England was torn by the wars of the houses of York and Lancaster, naval science had History made more rapid strides than in any previous period of ^-.m^^-L^ similar duration. The compass was not only known but Progress of was generally adopted. Navigators could take observations naval im- by the use of an instrument called the astrolabe, invented provement. by the Portuguese. The Spaniards and Portuguese were Compass, sufficiently advanced in the art of navigation to sail on a Astrolabe, wind, and their smaller vessels, at least, were adapted for this manoeuvre. New maritime states had started into existence. The Netherlands, until then scarcely known, Xether- was, under the Duke of Burgundy, the most formidable l»°<ls. naval power in the north of Europe. " His navy," says Philip de Commines, " was so mighty and strong, that no man durst stir in those narrow seas for fear of it, making war upon the king of France's subjects, and threatening them everywhere ; his navy being stronger than that of France anti the Earl of Warwick joined together." Ve- Venice, nice, in 1420, according to Denina, in his Revolulion.i of Italy, supported 3000 merchant-ships, on board of which were 17,000 seamen. They employed 300 sail of superior force, manned by 8000 seamen ; had forty-five carracks, with 11,000 men to navigate them; and her arsenals em- ployed 16,000 carpenters. Portugal had pushed her dis- coveries round the Cape, and Spain had added America to the world. The progress of discovery by the Portuguese to the south Portugal, and east, and by the Spaniards to the west, in the voyages Spain, of Columbus, with the consequent rapid increase in the importance of these two powers, and the influence of their discoveries on the state of Europe, renders the fifteenth century probably the most important of modern history. In it w-as given the death-blow to the increase of the Saracenic power, and to that of the Mediterranean states. The Turk, the Venetian, and the Genoese, had hitherto been the monopolizers of the commerce of the east. The dis- covery of the passage round the Cape of Good Hope Passage opened this trade to all nations. The commercial sceptre, round the and consequently the military sceptre, hitherto shared by „*P^ fy the Turk, passed wholly from the infidel to the believer. ^ The crescent sank before the cross. There can be no doubt, also, that the " tormentas" of the ^^ influ- " grao Cabo de boa Espera^a," were a means of great ira- *°'=« o" provement in naval architecture; for, in consequence of the ^|jjjg|,j|J^ representations of Bartholomew Diaz, John II. of Portugal ordered ships to be constructed for the especial purpose of contending with the stormy seas of the Cape of Good Hope. The shi|)s were built to form the squadron of Vasco de Gama, and were of small tonnage, from the very proper idea that small vessels were more adapted to prosecute re- searches in unknown seas than those of a large size, and consequent increased drauglit of water. The squadron of Vasco de Gama consisted of three ships Squadron and a caravella. One of the shi|)s was of the burthen of °f Vasco 200 tons, another 120, and the third 100; the caravella was*** ^*°"'- of 50 tons. The largest of the ships was a victualler; the smallest was intended to prosecute discovery up creeks and shallows ; and the other was for a display of force. As it is evident that it was not increase of dimensions which was to be the object in designing new vessels, the direction of im- provement must have been towards perfecting their forms, strengthening their frames, and adding to the efficiency of their materiel. Portugal by these means became the most advanced state of Europe in knowledge of the art of ship- building ; for it was long supposed that the passage to India required ships such as the Portuguese alone could build. Spain, in her career of discovery, conquest, and coloniza- tion across the mighty waters of the Atlantic, as if to assimilate the means to the vastness of her achievements, ra[)idly acquired the art of constructing ships of very large dimensions ; and as long as she possessed a marine, her ships maintained this superioritv. 10 History. A.D. 15U0 State of naval af- fairs in England. SHIP-BUILDING. Henri Grace a Uieu. Early ori- gin of na- val terms. There is a curious instance of the light in which naval ' enterprises were considcreil in England at this time, not- withstanding the e-irnest desire of the monarch to re- estabiisl) his navy, which h.id necessarily suffered from the long civil wars. A letter from Henry ^'II. to the I'ope is preserved in the Cottonian Lilirury, excusing himself from sending succour against the Turk, from which the following is a quotation : — "' The Galees conmiying from Vennest o England be commonly vij. monethes sailying, and some- times more ;" and again, " it should be May or they should be ready to saill, and it shall be the last end of September or the said shippes shuld passe the Streits of Marrok ; and grete difficultie to fynde any Maryncrs liable to take the rule and governance of the said shippes sallying intoso jeo- pardous and ferre parties." There is a drawing extant in the Pepysian Library in Magdalen College, Cambridge, of the Henri Grace d Dieu, built by the order of Henry VII., which Charnock has engraved in his I/iston/ of 31 urine Architecture, and argues as to the general authenticity of the representation. He says, " this vessel may be termed the parent of the British navy. This celebrated structure, the existence of which is recorded in many of the ancient chronicles, cost the king, by report, nearly 14,000 pounds." From this drawing may be traced the derivation of one or two names which have been jireserved even to the pre- sent hour ; as, for instance, the '" yard-arm," no doubt from the ends of the yards being armed with an iron hook. The castellated work from which has arisen the term " forecastle" is earlier than this ; and tlie buckler-ports are most probably derived from a yet earlier period, when the bucklers of the knights were ranged along the sides of the ship, as they are represented in the illustrations of Froissart, and of the early chroniclers, and even in the Baycux Tapestry. " The masts were five in number, inclusive of the bow- sprit, an usage which continued in the first-rates without alteration till nearly the end of the reign of King Charles I.; they were without division, in conformity with those which had been in imiinproved use from the earliest ages. This inconvenience it was very soon found indispensably neces- sary to remedy, by the introduction of separate joints, or top-masts, which could be lowered in case of need." The drawing shows two tiers of ports. The introduction of port-holes is said to be an improvement due to a French ship-builder of Brest, named Descharges, in the reign of Louis XII., and about the year J 500. If the drawing be authentic, the correctness of this appropriation of the merit of the introduction of port-holes may be questionable. Again, if the drawing be a correct representation of the vessel, she would have been in danger of upsetting, ex- cepting in calm weather, and when her course was with the wind. In fact, as yet the large ships of war of England were not at all adapted to sail on a wind, and were very ill provided with such sails as would enable them to do so ; they had therefore nothing to fear from the result of a measure which could not be put into execution. The fleets of war seldom ventured out of port excepting in the summer months, and then only when the wind was favour- able to their intended course. But very shortly after the date of the building of the Henri Grace a Dieu, great improvement took place, and in the reign of Henry VHI. there is evidence to prove that sailing on a wind formed one of the qualities of the vessels composing his fleets. This fact appears to throw some doubt upon the correct- ness of the drawing, for it must have required ships widely different from any of which that would at all give an idea, to have performed the evolution of tacking or wearing ; and as the Henri Grace a Dieu was in all probability the same ship that on the accession of Henry VIII. was called the Regent, she must have formed one in fleets which were capable of performing these mancEuvres. It is true that she may have been altered to adapt her to these new require- History, nients of an improved system of seamanship ; and it must ^■«»v^-».'' also be said, that she wiis burned in an action with the & d. 151? French fleet, which occurred as early as the fourth year of the reign of Henry VIII. Though it is out of the question that ships with tlie Henry enormous top-hamper which, on the evidence of all the ^'"I- drawings extant, still continued to be the fashion, could ■*"'''"(( <"> have made much progress in s.ailing on a wind, the letters* "">''• of the time extant corroborate the statement made ; for they begin to contain references to this improvement in navigation. In a letter from Sir Edward Howard, " Lord Admiral," to King Henry VHI., upon the state of the fleet, A.D. 1.513, jireserved in the Cottonian Librarv, and published in Ellis's collection, the following passage oc- curs : — "Ye commanded me to send your grace word hoiv every shipp dyd sail ; and this same was the best tryal that cowd be, for we went both slakyng and by a bowlyn, and a cool acros and abouet in such wyse that few shippes lakkyd no water in over the lee wales." The Lord High Admiral Lisle, in one of his letters (1545), says the small vessels of his fleet could " lye best by a wynde ;" and in 1567 we have conclusive proof that there were "fore and aft," indeed " cutter-rigged" vessels on the British seas ; as in a map of Ireland of that date, published in the state- papers, two such vessels are represented, for the purpose, apparently, of indicating regular packets from England to Ireland. It has been very generally supposed, on the authority of Sir Walter Raleigh, that the " knowledge of the bowline" was a discovery in navigation made shortly before his time; but is is probable that there were, even from the time of the Northmen, craft so rigged as to be capable of sailing on a wind. Froissart mentions, in several instances, "a Vessel called a Lin, which sails with all winds, and without danger;" and again, "a vessel called a Lin, which keeps nearer the w ind than any other." Boats w ith a rig adapted tor this manoeuvre are also represented in engravings of a very early date. In the ()lates of Breydenbach's Voyage to Palestine, which was published in 1483, boats and small vessels are represented with lateen sails ; and in Braun's Civitates Orbis Terrarum, published in 1572, sprit-sails are met with. It is quite certain, however, that sailing on a wind was by no means a general quality possessed by the ships of war, or to any extent even by the greater portion of the larger shipping, until about the reign of Henry VIII. One other instance may be adduced in the account of the loss of the Mari Rose, a ship of the " portage of 500 tons," not so much to corroborate the fact of sailing on, a wind as to show that the two innovations, the intro- duction of port-holes and the " knowledge of the bow- line," were in advance of the qualities of the large ships of war of the time. Sir Walter Raleigh says that, "in King Henry VIII. 's time, at Portsmouth, the Mari Rose, by a little sway of the ship in easting about, her ports being within sixteen inches of thq water, was overset and lost." The loss of this ship has been the means of giving Loss of the another interesting insight into the comparatively low state ^'^ri Kose. of nautical skill in Eiigland at this period, namely, the middle of tlie sixteenth century. In a letter among the state-[)apers published under the direction of the Record Commission, addressed by the Duke of Suffolk to Sir William Pagett, " chief secretary to the kinge's highnes," dated the 23d of July 1545, and containing a schedule of things necessary to be had for the raising of the Mari Rose, one item is " fifty Venyzian maryners and one ^ cnyzian carpenter ;" the next item is " sixty Englisshe maryners to attende upon them." It would also appear that the attempt was to be made under the direction of an Italian, as the conclusion of the schedule is, " Item, Symond, petrone and master in the Foyst, doth aggrie that all thyngs must be SHIP-BUILDING. 11 Minutiae of ship-build- ing at this period. History, had for the purpose aforesaid." The attempts, however, all — »^^»^ failed ; the wreck of the Mari Rose remains to this day at Spithead, and so lately as August 1836, several of her brass cannon, of most exquisite workmanship, were re- covered from the sea by the enterprise and ability of an Englishman of the name of Deane. Some idea of the detail of ship-building rather before this period may be obtained from an account of a vessel built by James IV. of Scotland, at the close of the fifteenth or the beginning of the sixteenth century. The extract is from Charnock, but he has not mentioned his authority. " The king of Scotland rigged a great ship, called the Great Michael, which was the largest and of superior strength to any that had sailed from England or France ; for this ship was of so great stature, and took so much timber, that, except Falkland, she wasted all the woods in Fife which were oakwood, with all timber that was gotten out of Norway ; for she was so strong, and of so great length and breadth, all the wrights of Scotland, yea, and many other strangers, were at her device by the king's command, who wrought very busily in her ; but it was a year and a day ere she was completed. To wit, she was twelve score feet of length, and thirty-six foot within the sides ; she was ten foot thick in the wall and boards, on every side so slack and so thick that no cannon could go through her. This great ship cumbered Scotland to get her to sea. From that time that she was afloat, and her masts and sails complete, with anchors offering thereto, she was counted to the king to be thirty thousand pounds ex- pense, by her artillery, which was very great and costly to the king, by all the rest of her orders. To wit, she bare many cannon, six on every side, with three great bassils, two behind in her dock and one before, with three hundred shot of small artillery, that is to say, myand and batterd talcon, and quarter falcon, flings, pestilent serpentens, and double dogs, with hagtor and culvering, corsbows and liandbows. She had three hundred manners to sail her, she had six score of gunners to use her artillery, and had a thousand men of war, by her captains, shippers, and quarter-masters." Several of the writers of this period mention the fact of a Swedish ship of extraordinary dimensions being built in the middle of the sixteenth century, and which was burned in an action between the Swedes and Danes in 1564. Chapman has given an estimate of the dimensions of this vessel. She was called the Makalos (by Charnock, Megala). According to Chapman, she was 168 English feet in length and 43 English feet in breadth, an immense vessel for that period. Her armament was 173 guns, 67 only of which could be considered as cannon, the remainder being merely swivels. Henry VIII. was deeply sensible of the necessity of a permanent and powerful naval force, and established the navy office, and also several dockyards tor building and repairing the ships of the royal navy. Among these were Woolwich, Deptford, and Chatham. He also greatly added to and improved the dockyard at Portsmouth. He invited from foreign countries, particularly from Italy, the com- mercial cities of which were still in advance of the rest of Europe in the maritime arts, as many skilful foreigners as he could allure, either by the hope of gain or by the honours and distinguished countenance he paid to them. The following extract is from a report made to James I. in the year 1618, and published in the Archaologia. It was made in answer to a commission issued by that mon- arch to the several master-builders. The minority of Edward VI., and the civil and religious strife which distracted the kingdom during the reign of Mary, depressed the resources of the state, and evidently much checked the progress of its maritime strength. The report says, " In former times our kings have enlarged their dominions rather by land than sea forces, whereat History, even strangers have marvelled, considering the many ad- '^.^/«^ vantages of a navy ; but since the change of weapons and ^.d. 1547 fight, Henry VIII., making use of Italian shipwrights, and Keport of encouraging his own people to build strong ships of war, to of mastnr carry great oidnance, by that means established a puissant ^•^''"^^'^ navy, which in the end of his reign consisted of 70 vessels, whereof 30 were ships of burthen, and contained in all lO.ooO tons, and 2 galleys. The rest were small barques and row-barges, from 80 tons downwards to 15 tons, which served in rivers and for landing of men. Edward VI., in the sixth year of his reign, had but 53 ships, containing in all 11,005 tons, with 7995 men, whereof only 28 vessels were above 80 tons each. Queen Mary had but 46 of all sorts." There is one peculiarity of ships of war up to this time, Peculiar which exemplifies the defects of their design in a remark- "lef«<=' "f able feature. It is, that the ships built for the royal ^'''^ °^^ navy appear only to have been adapted for the lodgment of ^[^^3 period, the soldiers and mariners, with their implements of war, and the necessary stores for navigation. The provisions were carried in an attendant vessel, called a " victualler," of which there was one attached to each of the large ships of war in the fleet, or to several of the smaller size. The hold appears to have been principally occupied by the " cook-room," the inconvenience of which arrangement, though much complained of, was general when Sir Walter Raleigh, in his Discourse on the Royal Navy and Sea Service, recommended that it should be removed to the forecastle ; and even so lately as 1715, several men of war had " cook-rooms" in their holds. There is also no doubt that the enormous quantity of ballast which was rendered necessary by the immense top-hamper of these ships, and the space which it occupied, from being shingle, left but little room for the stowage of any quantity of provisions. In the ships built for commerce, this defect does not appear to have existed, as in fleets composed of the king's and of private shipping, those ships only which belonged to the royal navy had these attendant victuallers. The cook- rooms in the merchant shipping were under the forecastle ; and they had less top-hamper, as less accommodation was required for officers. Although the comparative inefficiency of the vessels may Epoch in be commented on, it will be apparent that that period in the najal ar- history of naval architecture and of navigation has now been cnitecture. entered on in which, though still in their infancy, these arts may be considered as perfect in all but the maturity to be acquired by the experience of years. The mariners com- jjass was known ; the theory of taking observations was understood, and the practice of it iu the course of being perfected ; and therefore the longest voyages could be undertaken with comparative certainty and safety. Besides this, the ships, though still imperfect, were becoming gradu- ally manageable machines, and had ceased to be the cum- brous masses of the preceding ages, which, with few ex- ceptions, were capable of little more than of being driven before the wind. If the contents of the foregoing pages be considered, Three there will appear to be three epochs in the maritime history epochs in of England ; the first commencing with the introduction of* * ^^\ galleys by Alfred, and ending with the reign of Edward ^^ ^f III., before whose time these galleys and vessels, propelled England, by oars, were the chief instruments of navigation ; the second ending with the reign of Henry VII., during which period, though sailing vessels were used for the purposes both of war and commerce, they were comparatively at the mercy of the winds, and, speaking generally, could sail only when they blew both fairly and gently ; the third epoch has been already noticed. From the extract of the report of the builders, the state of the navy during the reigns of Edward VI. and of Mary 12 SIIIP-BUILDING. TTistorv. Actionwitli ^^pani8h Arinudn. Three- decked 6bii>s. will be seen. It is known, tlierefore, tliat wlien Elizabetli ascended tiie tlirone, the marine of Enfjlaiul, both military and mcreanlile, was in a very depressed state. The suc- cessful enterprise of Drake, aiul the fear of the Spanish Armada, aroused the eneriries of the country, and the force collected to resist the invasion amounted to 197 vessels of various descriptions, of the a<r<,'resate burthen of nearly 30,000 tons, 34 of which, measurini; together 12,600 tons, composed the royal navy. It is true, that by far the larger portion were of small fi)rcc. One only, the Triumph, was of ] 100 tons ; another, the White Bear, was of 1000 tons ; two were of 800 Ions, 3 of 600, si.x of 500, and five of 400; sixty-six were under 100 tons; and fifieen were victuallers, of which the tonnage is not mentioned. There are also seven other vessels included in the 197 which have no tonnage assigned them ; but they must have been of small size, the number of mariners on board the whole seven being only 474. We have very conclusive means of comparing the Spanish with the English ships, and also of judging how very little naval arrangements were then understood, from their imperfect state even on board a fleet which had occupied the whole attention of the Spanish authorities for a space of three years, exemplified in the following anecdote. ]5urchett, in his account of the action of the 23d of July 1588, says, "The great guns on both sides thundered with extraordinary tury, but the shot from the high-built Spanish ships flew over the heads of the English without doing any execution ; one Mr Cock being the only Englishman who fell, while he was bravely fight- ing against the enemy in a small vessel of his own." The Spaniards appear to have been the first to introduce a third tier of guns, the earliest mention of a three-decker being the Philip, a Spanish ship engaged in the action off the Azores in 1591, with the Revenge, commanded bv Sir Richard Greenvil. The following armament of the Philip is extracted from a most spirit-stirring account of this tremendous action, which was written by Sir Walter Raleigh, and has been preserved by Hackluyt. " The Philip carried three tire of ordnance on a side, and eleven pieces in euerie tire. She shot eight forth right out of her chase, besides those of her stern portes." The English do not appear to have followed the example set by the Spaniards ; for, iluring the long reign of Eliza- beth, the ships of the royal navy were not much, if at all, increased in their dimensions, which was probably owing to the triumphant successes of her fleets, though they were composed of ships generally m\ich smaller in size than those opposed to them. Prom the list of the royal navy at the time of her death, in 1603, given by Sir William Monson io his tracts, of 42 ships composing the navy, there were then only two ships of 101)0 tons, three of 900, three of 800, two of 700, four of 600, four of 500, and there were eight under 100 tons burthen. Two of these ships, the Triumph and the White Bear, are rated in this list each at lOQ tons less burthen than in the list of the fleet in the year 1588, already noticed. The mercantile marine was also greatly improved and incrcised during the reign of Elizabeth. This wise monarch did all in her power to encourage foreign trade ; and she honoured Drake by knighting him on board his own vessel at Deptford, after his return from circumnavigating the globe. The celebrated Sir Walter Raleigh, luidcr a charter granted by her in 1584, commenced trading with America, and his successes, with those of others, in trade, as well as in the capture of richly laden Spanish merchantmen, prove the superiority of the English ships of this period. In 1600 the East India Company obtained their charter from Eliza- beth, and merchant-ships, which proved the precursors of a fleet of the finest merchantmen, were immediately built by them for this distant traiEc. Shortly after the accession of James to the throne, several commissions were appointed to inquire into the state of the History. navy. Prom that of the year 1618 a very vohmiinous ^>— >y-^-^ ref)ort einanated, of which the following is an extract, that a.d. 1603. aflbrds an example of the state of knowledge on naval arclii- James 1. tecture at that time : — " 1 he next consideration is the ^ep*""' "f manner of buildinLT, which in shipps of warr is of greatest •^l'""""*" , ■ , . -111. I- 1 6ioa uuportance, because therem consists botli tlieir saylmg and force. The shipps that can saile best can take or leave (as they say), and use all advantages the winds and seas does afford; and their mould, in the judgment of men of best skill, both dead and alive, should have the length treble to the breadth, and breadth in like proportion to the depth, but not to tlraw above 16 fbote water, because deeper shipps are seldom good saylers, and ever unsafe for our rivers, and for the shallow harbours, and all coasts of ours, or other seas. Besides, they must bee somewhat snugg built, without double gallarys, and too lofty upper workes, which overcharge many shipps, and make them coeme faire, but not worke well at sea. "And for the strengthening the shipps, wee subscribe to the manner of building a|)proved by the late worthy prince, the lord adm"., and the oHicers of the navy (as wee are in- formed), on those points. "1. In makeiiig 3 orlopes, whereof the lowest being placed 2 fiiote under water, both strengtheneth the shipp, and though her sides bee shott through, keepeth it from bildgeing by shott, and giveth easier meanes to finde and stopp the leakes. "2. In carrying their orlopes whole floored throughout from end to cud, without fall or cutting oft"y* wast, which only to make faire cabbins, hath decayed many shipps. "3. In laying the second orlope at such convenient height that the portes may beare out the whole fire of ordinance in all seas and weathers. " 4. In placeing the cooke roomes in the forecastle, as othcrr war shipps doe, because being in the midshipps, and in the holds, the smoake and heate soe search every corner and seame, that they make the okani spew out, and the shipps leaky, and soone decay ; besides, the best roonie for stowage of victualling is thereby soe taken up, that trans- porters must be hyred for every voyage of any time ; and, which is worst, when all the weight must bee cast bel()re and abaft, and the shipps are left empty and light in the midst, it makes them apt to sway in the back, as the Guard- land and (livers others have done." This commission was followed by several others during this and the succeeding reign, and from their reports arose many regvilations tending much to the improvement of the navy, although the expenses incurred were, ostensibly at least, in part the means of causing the subsequent revo- lution. In the early part of the reign of James I. the mercantile Mercantile navy of England was reduced to a very low state, most of shippinq o< the commerce being carried on in foreign bottoms. The "."' l'"' incitement offered by the advantageous trade which the Dutch had long engaged in to India at length aroused the nation, and the formation of the East India Company, whicn was the act of Jaiues, was followed by the building of the largest ship that had yet been constructed for the purposes of commerce, at least in England. The king dined on board Trade's In- of her, and gave her the name of the Trade's Increase, crease. She is reported to have been of the burthen of 1200 tons. The impetus once given, before the end of the reign of James an important mercantile navy was owned by British merchants. Another interesting fact connected with this reign is the Ship- founding of the Shipwrights' Company, in the year 1605, wrights' and which was incorporated by a charter granted to the Company "Master, Warden, and Commonality of the Art or Mys- tery of Shipwrights," in May 1612. Mr Phineas Pett was the first master. The draughts for the ships of the royal SHIP-BUILDING. 13 History. A.D. 1610. Draught of ships of royal navy. Jfoyal I'rince. I'hineas Pett. The Petts. First fri- gate. I'eter Pett. First three- decker. navy were subsequently ordered to be submitted to this company tor approval previously to being built from. Tiiey also had jurisdiction over all builders, whether of the royal navy or of merchant-shipping. In 1610 the Royal I'rince was launched; she was the largest ship which at that time had been built in England, and was also a most decided improvement in naval archi- tecture. The great projection of the prow, a remnant of the old galley, was for the first time discontinued, and the stern and quarters assimilated more to those of a modern sliij) than to any which had preceded her. She is thus de- scribed in Stow's Chronicles: — "A most goodly ship for warre, the keel whereof was 114 feet in length, and the cross-beam was 44 feet in length ; she will carry 64 pieces of ordnance, and is of the burthen of 1 400 tons. The great workmaster in building this ship was Master Phineas Pett, Gentleman, some time master of arts at Emanuel College, Cambridge." The same gentleman, Mr Phineas Pett, continued the principal engineer of the navy during the reign of Charles. The family of the Petts were the great instruments in the improvement of the navy, and, if the term may be allowed, of modernizing it, by divesting the ships of much of the cumbrous top-hamper entailed on them from the castel- lated defences which had been necessary in, and which yet remained from, the hand-to-hand encounters of the middle ages ; and it is probable that, but for the taste for gorgeous decoration which prevailed during the seventeenth century, this ingenious family would have been able to efiect much more ; as it was, they decidedly rendered England pre- eminently the school for naval architecture during the time they constructed its fleets. This family can be traced as principal engineers for the navy tiom about the middle of the fitteenlh century to the end of the reign of William III. Evelyn, in his Diary, relating a conversation, says, " Sir Anthony Deane mentioned what exceeding advan- tage we of this nation had by being the first who built frigates, the first of which ever built was that vessell which was alterwards called the Constant Warwick (built in 1646), and was the work of Pet of Chatham, for a trial of making a vessell that would sail swiftly. It was built with low decks, the guns lying near the water, and was so light and swift of sailing, that in a short time she had, ere the Dutch war was ended, taken as much money from privateers as would have laden her." The dimensions of this vessel are given in Pepys's Miscellanies as follows : length of the keel 85 feet, breadth 26 feet 5 inches, depth 13 feet 2 inches, and 315 tons burthen; her highest number of guns" 32, and of crew 140. Peter Pett, who built the Constant Warwick, was tlie son of Phineas Pett. He caused the fact of his being the in- ventor of the frigate to be recorded on his tomb. He was also the builder of the Sovereign of the Seas, in 1637, which was the first three-decker built in England. Her length over all is stated to have been 232 feet, her length of keel 128 feet, her main breadth 48 feet, and her tonnage 1637. Heywood describes her in the following terms : — " She hatli three flush dcckes and a forecastle, an halfe decke.a quarter decke, and a round-house. Her lower tyre hath thirty ports, which are to be furnished with demi-cannon and whole cannon throughout, being able to beare them. Her middle tyre hath also thirty ports for demi-culverin and whole culverin. Her third tyre hath twentie-sixe ports lor other ordnance. Her forecastle hath twelve ports, and her halfe decke hath fourteene ports. She hath thirtcene or foufeteene ports more within board for murdering peeces, besides a great many loope-holes out of the cabins tor musket shot. She carrieth, moreover, ten peeces of chase ord- nance in her right forward, and ten right aff ; that is, ac- cording to land service, in the front and the reare. She carrieth eleaven anchors, one of them weighing foure thou- nistorv. sand foure hundred, &c. ; and according to these are her cables, mastcs, sayles, cordage, which, considered together, ^^^^^^^m^ seeing Majesty is at this infinite charge, both lor the honour a.d. 1637. of his nation, and the security of his kingdome, it should bee a spur and encouragement to all liis faithful and lovintr subjects to bee liberall and willing contributaries towards the ship money." Of this ship. Fuller, in his Worlfiies, says, "The Great Sovereign, built at Woolwich, a leiger ship for state, is the greatest ship our island ever saw ; but great medals are made for some grand solemnity, while lesser coin are more current and passable in payment." She was afterwards cut down one deck, and remained in the service, with the character of the best man-of-war in the world, until the year 1696, when she was accidentally burnt at Chatham. About this time, 16o0, appeared the first work connected Sir Walter with naval improvement ever written in this country, and Raleigh's by no less celebrated an author than Sir Weaker Raleigh, works : It is very probable that his two discourses, the one on the ?c^„'"" Invention of Shipping, the other Concerning the Royal f„. . (•(,„. Nary and Sea-Service, had great influence in creating the ceming the interest which was evidently taken about this period in the Royal Xavy improvement of the navy. Sir Walter says, " Whosoever ""<' ^"^• were the inventors, we find that every age had added some- ^"■""• what to ships and to all things else. And in my owne time the shape of our English ships hath been greatly bettered. It is not long since the striking of the top-mast (a wonder- fully great ease to great ships both at sea and harbour) hath been devised. Together with the chaine-pumpe, which takes up twice as much water as the ordinary did, we have lately added the bonnett and the drabler. To the courses we- have devised studding-sayles, top-gallant-sayles, sprit- sayles, top-savles. The weighing of anchors by the cap- stane is also new. W'e have fallen into consideration of the length of cables, and by it we resist the malice of the greatest winds that can blow ; witnesse our small Milbroke men of Cornewall, that ride it out at anchor half seas over betweene England and Ireland all the winter quarter ; and witnesse the Hollanders that were wont to ride before Dun- kirke with the wind at north-west, making a lee-shore in all weathers ; for true it is that the length of the cable is the life of the ship in all extremities ; and the reason is, because it makes so many bendings and waves as the ship riding at that length is not able to stretch it, and nothing breaks that is not stretched. In extremity, we carry our ordnance better than we were wont, because our nether- overloops are raised conmionly from the water, to wit, be- tweene the lower part of the port and the sea. We have also raised our second decks, and given more vent thereby to o\ir ordnance lying in our nether-overloope. " We have added crosse pillars in our royall ships to strengthen them, which being fastened from the kelson to the beames of the second decke, keep them from settling jr from giving away in all distresses. " We have given longer floares to our ships than in elder times, and better bearing under water, whereby they never fall into the sea after the head, and shake the whole body, nor sinck sterne, nor stoope upon a wind, by which the breaking loose of our ordnance, or the not use of them, with many other discommodities, are avoided. And to say the truth, a miserable shame and dishonour it were for our shipwrights, if they did not exceed all other in die setting up of our royall ships, the errors of other nations being farre more excusable than ours. For the kings of England have for many years been at the charge to build and furnish a navy of powcrfuU ships for their owne defence, and tor the wars only ; whereas the French, the Spainards, the Portu- galls, and the Hollanders (till of late), have had no proper fleete belonging to their princes or states. " Only the Venetians for a long time have mamtained their arsenal of gallycs, and the kings of Denmark and 14 Hiitory. A D. 1650. SHIP-BUILDING. EJiips of royal navy inferior to merchant- ships. Sweden liave had good sliips for these last fifty years. I say that the forenamed kings, especially the Spainards and Portugalls, have ships of great hiilko, but fitter for the mer- chant than the man of ivarre, for burthen then for battaile. .... Although we have not at this time 135 ships belong- ing to the subjects of 500 tuns each shi[i, as it is said we had in the 24th vcare of Queen Elizabeth, at which time also, u|)on a generall view and muster, there were foimd in EnglantI, of all men fit to beare arms, tleaven hundred and seventy-two thousand ; yet are our merchants' ships now farre more warlike and better appointed than they were, and the royal navy double as strong as then it was We have not, therefore, lesse force than we had, the fashion and furnishing of our ships considered ; for there arc in England at this time 400 saile of merchants fit for the wars, which the Spainards woulii call gallions ; to which we may add 200 saile of crumsters or hoyes, of Newcastle, which each of them will heare six demi-culverins, and four sakers, need- ing no other addition of building than a slight spar-decke (ore and afte, as the seamen call it, w liich is a slight decke throughout. The 200 which may be chosen out of 400, by reason of their ready staying and turning, by reason of their windwardnessc. and by reason of their drawing of little water, and they are of extreame vantage neere the shoare, and in all bayes and rivers to turn in and out ; these, I say, alone, well manned and well conducted, would trouble the greatest prince in Europe to encounter in our seas ; for they stay and turn so readily as, ordering them into small squadrons, three of them at once may give their broad-sides upon any one great ship, or u|)on any angle or side of an enemy's fleet. They shall be able to continue a pt rpetuall volley of demi- culverins without intermission, and either sink or slaughter the men, or utterly disoriler any fleete of crosse sailes with which they encounter. " I say, then, if a vanguard be ordained of these hoyes, who will easily recover the wind of any other ships, with a battaile of 400 other warlike ships, and a reare of thirty of his majestie's ships to sustaine, relieve, and countenance the rest (if God beat them not), I know not what strength can be gathered in all Europe to beat them. And if it be ob- jected that the states can furnish a farre greater number, I answer, that his majestie's forty ships, added to 600 before named, are of incomparable greater force than all that Hol- land and Zeeland can furnish for wars." In the foregoing extract there is strong evidence that the ships of the royal navy w ere generally inferior to those employed by the merchant-service, in the essential qualifi- cations of being weatherly. This is exactly the conclusion that might be arrived at from the consideration, that a pri- vate individual would dispense w ith all that superabundance of top-hamper which was entailed on the ships of the royal navy, by the accommodation required for the numerous officers and gentlemen generally embarked on board them, and also by the mania lor gorgeous decorations. This mania is well exemplified by the fact, that of the Sovereign of the Seas it is stated, " She beareth five lanthornes, the biggest of which will hold ten persons to stand upright, and without shouldering one another." Sir Walter Raleigh, in iiis Discourse on the Royal Navy and Sea-Service, adverts to the same subject. He says, " We find by experience, that the greatest ships are lesse serviceable, goe very deep to water, and of marvellous charge and fearefull cumber, our channells decaying every yeare. Besides, they are lesse nimble, lesse maineable, and very seldome imployed. Grande navio, grande fatica, saith the Spainard ; a ship of 600 tons will carry as good ordnance as a ship of 1200 tons; and though the greater have double the number, the lesser will turn her broad- sides twice before the greater can wend once ; and so no advantage in that overplus of ordnance. And in the build- ing of all ships, these six things are principally required : — 1. First, that she be strong built; 2. Secondly, that she be History, swift ; 3. Thirdly, that she be stout sideil ; 4. Fourthly, v^.^-^ that she carry out her guns all weather ; 5. Fifthly, that ,g«(, she hull and try well, which we call a good sea ship ; 6. Sixthly, that she stay well when bourding and turning on a wind is required. " 1. To make her strong, consisteth in the truth of the workeman and the care of the officers. " 2. To make her saylc well, is to give a long run forward, and so afterward done by art and just jiroportion. For, as in laying out of her bows before, and qu.iriers behind, she neither sinck into nor hang in the water, but lye cleare off and above it ; and that the shipwrights be not deceived herein (as for the most part they have ever been), they must be sure that the ship sinck no deeper into the water than they promise, for otherwise the bow and quarter w ill utterly spoile her sayling. " 3. That she be stout, the same is provided and performed by a long bearing floore, and by sharing off above water even from the lower edge of the ports. " 4. To carry out her ordnance all weather, this long bearing floore, and sharing off from above the ports, is a chiefe cause, provided alwayesthat your lowest tyre of ord- nance must lye foure foot cleare above water when all loading is in, or else those your best pieces will be of small use at the same in any growne weather that makes the billoe to rise, for then you shall be enforced to take in all your lower ports, or else hazard the ship. " 5. To make her a good sea ship, that is to hull and trye well, there are two things specially to be observed ; the one that she have a good draught of water, the other that she be not overcharged, which commonly the king's ships are, and therefore in them we are forced to lye at trye with our niaine course and missen, which, with a deep keel and standing streake, she will performe. " 6. The hinderance to stay well is the extreame length of a ship, especially if she be floaty and want sharpnesse of way i()rwards ; and it is most true, that those over-long ships are fitter for our seas than for the ocean ; but one hundred foot long, and five and thirty foot broad, is a good proportion for a great ship. It is a speciall observation, that all ships sharpe before, that want a long floore, w ill tall roughly into the sea, and take in water over head and ears. "So will all narrow quartered ships sinck alter the tayle. The high charging of ships is it that brings them all ill qualities, makes them extreame leewarti, makes them sinck deep into the water, makes them labour, and makes them overset. Men may not expect the ease of many cabbins, and safety at once, in sea-service. Tw-o decks and a half is sufficient to yield shelter and lodging for men and mariners, aud no more charging at .ill higher, but only one low cabbin for the master. But our marriners will say, that a ship will beare more charging aloft for cabbins, and that is true, if none but ordinary marryners were to serve in them, w ho are able to endure, and are used to, the tumbling and rowl- ing of ships from side to side when the sea is never so little growne; but men of better sort and better breeding would be glad to find more steadinesse and lesse tottering cadge work. And albeit, the marriners doe covet store of cabbins, yet indeed they are but sluttish dens, that bread sicknesse in peace, serving to cover stealths, and in fight are danger- ous to teare men with their splinters." In Fuller's Worthies, there is also a short summary of pyii^p', the comparative qualities of the ships of difierent nations in Wonhiei. the middle of the seventeenth century. It is as follows : " First, for the Portugal, his cavils and carracts, whereof few now remain (the charges of maintaining them far ex- ceeding the profit they bring in) ; they were the veriest drones on the sea, the rather because formerly their seeling was dam'd up with a certain kind of mortar to dead the shot, a fashion now- by them disused. SHIP-BUILDING. li " The French, however dexterous in land-battles, are left-handed in sea-fights, whose best ships are of Dutch , building. The Dutch build their ships so floaty and buoyant, they have little hold in the water in comparison to ours, which keep the better winde, and so outsail them. " The Spanish pride hath infected their ships with lofti- ness, which makes them but the fairer markes to cur shot. Besides the winde hath so much power of them in bad weather, so that it drives them two leagues for one of ours to the leeward, which is very dangerous upon a lee- shore. " Indeed the Turkish frigots, especially some thirty-six of Algier, formed and built much nearer the English mode, and manned by renegadoes, many of them English, being already too nimble heel'd for the Dutch, may hereafter prove mischievous to us, if not seasonably prevented." During the early part of the seventeenth century, the Dutch navy rapidly increased in importance. Their suc- cess in having wrested from the Portuguese a share of the commerce of the east, emboldened them, in the then de- pressed state of the Spanish marine, to make a similar at- tempt on the west, and endeavour to establish settlements in South America. The wars with Spain, in which they were consequently engaged, had such an important effect in establishing their maritime power, that in 1650 their navy consisted of 120 vessels fitted for war, seventy of which had two tiers of guns ; and their fleet was in all respects the most efficient in Europe. Evelyn, in his tract on Navigation and Commerce, speak- ing of the fisheries, says " Holland ami Zeeland alone should, from a few despicable boats, be able to set forth above 20,000 vessels of all sorts, fit tor the rude seas, of which more than 7000 are yearly employed upon this oc- casion. 'Tis evident that by this particular trade they are able to breed above 40,000 fishermen and 116,000 mari- ners, as the census (1639) has been accurately calculated." The tremendous struggle in which they were enabled by these means to engage with us shortly after this period, in consequence of the injurious operation of the navigation act on their commerce, had a most influential effect on the improvement of our navy, which at the commencement of the contest was very unequal to that of the Dutch ; and it is probable that this war was the means of enabling us to contend triumphantly against the immense and unexpected attempts of Louis XIV. to wrest the sceptre of the seas from our grasp. The sovereigns of the house of Stuart, without excep- tion, appear to have devoted much attention to the improve- ment of the navy. Charles I. may be almost said to have lost both crown and life in consequence of these efforts ; nor would it be doing justice to Cromwell to omit mention of the energy with which he took advantage of the all but despotic power which he possessed to increase his naval force. For this purpose not only many ships were built during the protectorate, but numbers of merchant-vessels were bought for the service of the state. After the Restoration, Charles II. paid great personal attention even to the minutiae of his navy, as shown by the following curious extract fiom a letter of his to Prince Rupert, preserved in the state-papers, and also by con- tinual references to his naval predilections in Evelyn's and Pepys's memoirs and writings. The letter is dated 4th August 1673. It says, " I am very glad the Charles does so well ; a gerdeling this winter when she comes in will make her the best ship in England ; next summer, I believe, if you try the two sloops that were builtc at Woolidge that have my invention in them, they will outsail any of the French sloops. Sir Samuel Mooreland has now another fancy about weighing anchors ; and the resident of Venice has made a model also to the same purpose. We have not yet consulted them with Mr Tippet nor Mr Deane ; Ilistory. but hope when they are well considered, we may find one ^>-^^-^ out of them that will be good." ^ j,. 1666. In Pepys's Diary, 19th May 1666, there is the following Sir Antho- notice relating to one of the gentlemen mentioned in the "y Deane. above letter : — " Mr Deane and I did discourse about his ship the Rupert, which succeeds so well, as he has got great honor by it, and I some by recommending him. The king, duke, and everybody, say it is the best ship that was ever built. And then he fell to explain to me his manner of casting the draught of water which a ship will draw before- hand, which is a secret the king and all admire in him ; and he is the first that hath come to any certainty beforehand of foretelhng the draught of water of a ship before she be First ap- launched." This gentleman appears therefore to have been plication of the first who applied mathematical science to naval archi- mathema- tecture in this country. Pepys also says, " another great *"^f' calcu- step and improvement to our navy, put in practice by Sir '''"°° *" Anthony Deane," was effected in the Warspight and chitecture. Defiance, which were " to carry six months' provisions, and their guns to lie 4j feet from the water." This was in 1665. The foregoing extract probably indicates the date of the first practical application to a useful purpose in this country of the famous discovery of Archimedes. It is well known that he was called upon by his king to test the purity or the adulteration of the gold of the royal crown, and the dis- placement of the water of his bath by his own immersion therein suggested to his mind the means of solving the problem. He saw that a body immersed in water displaced its own bulKofwater, and that by immersing the crown, which was correct in weight, and measuring the water displaced by it, the increased bulk necessary to make up the weight, if the gold had been adulterated by any lighter metal, could be detected. After this the knowledge followed that a body floating in a fluid displaced its own weight of that fluid. In this historical sketch the probability that the mer- sir Robert chant-shipping of England were superior in their sea-going Slingeby. qualities to those composing the royal navy, has been ad- verted to in a Discourse touching the Past and Present Slate oftheNavj/, by Sir Robert Slingeby, knight-baronet, and comptroller of the navy, dated 1669, there is the following interesting statement, which points to a reason why this superiority of the merchant-shipping may have existed. '• But since these late distractions began at home" Decay of (the Commonwealth), " forraigne trade decayed, and mer- mercantile chants so discouraged from building, that there hath been navy dur- scarce one good merchant-ship built these twenty years past, ""g ^^e and of what were then in being, either by decayes or acci- ^"""."J""' dent, there are very few or none remaining. The merchants have foimd their private conveniences in being convoyed att the publick charge ; they take noe care of making defence for themselves if a warr should happen." Yet he its sub«e- says, in the time of Charles I., " the merchants continued quent im- their trade during the wars with France and Spain, if there provement. could but two or three consort together, not caring who they met," they being little inferior in strength or burthen to the ships of the royal navy. About 16S4 Sir Richard Haddock, comptroller of the sir Rich- navy, adopted the recommendation of Mr, afterwards SirardHid- Anthony Deane, at that time surveyor of the navy, and Jock, directed an inquiry to be made as to "the number of cube pj^jj g„,. feet that are contained in the bodyes of several draughts ijsis of the to their main water-line, when all niaterialls are on board royal navy, fitt for saileing." The result of this inquiry was a very voluminous statement of the weights which made up the whole displacement of the fourth, fifth, and sixth rate ships, including minute details of their masts, yarns, armament. &c., .iccompanied by perfect drawings of each ship. The following table contains the dimensions and displacements. &c., of each class : — STIIP-BUILDING. Tiihle of Dimensions, from a Manuscript dated 1684. History. A First Fourth- rato ncir tho largest ilimon- sions. A Si-rom! Fourthrato | A Fifth-rato near Iho tlimcn ot the liirtest sions or the Ad-I dniionaiuiis. venture. Length on the gun-deck from therabbiit 1 of the stem to the rnl>bittof the post ( Maine brendlh to the outside of tho I outbonrd phinke J Depth in hold from the seeling to the ) uppir side of the beanie J Breadth at the afte side of the maine ) transome ( Height on the gun-deck from plankc toplunke The center of the. f fore .... ^ ' ter I . < maine.. V I mizion. J {afore..., miiiship abafle . mast from the rubbitt of the stern Draft of water [''[°"- \ abuft .. Number of tuns, tunage Number of men (in warr) Number of guns Cube feet in the several draughts to 1 their main water line J Weight of each ship's hull, and all man- 1 ner of materials on board J Karh ship's hull at first launching Burtlicn in tuns, what she will really 1 carry J No. of months' provisions and water Feet. In. 121 6 U 21 Feet. In. 116 6 32 9 13 2 18 4 5 9 G I! 6 G 6 6 3 13 G 12 9 69 62 02 96 9 U 6 13 6 15 10 15 885 580 2G0 180 SO 44 29,814 Tfl. cwt. qr. 851 16 2 418 433 16 2 8.324 4 ! 22,346 Ts. cwt. qr. lb. 638 9 314 Feet. In. 103 9 28 8 11 4 18 5 9 7 10 6 16377 0160 6 6 9 54 84 12 13 3! 2 135 34 13,195 Ts. cwt. qr. A First Sixth- rate. Feet. In. 87 8 23 6 10 9 14 5 7 6 3 7 6 45 71 9 8 10 8 85 24 A Second Sixth- rate. Fcvt. In. 70 21 6 9 10 13 5 6 36 57 8 6 9 6 70 18 16216 89u6 6790 lb. Ts. cwt. qr. Hi. Ts. cwt. qr. lb. 3 254 9 16|l94 120 98 134 9 16 2 2 A Sixth rale of tho lurgedt di- monaiond. Feet. In. 92 6 23 6 11 9 14 10 50 73 10 11 230 90 22 A Sixth- riito of Ih.. old liuiliiun. 135 Feet. In. 93 22 9 10 15 9 6 49 6 74 8 9 220 29 24 T». 130 The Re- volution James 1(. James II., from Iiavins; so long and so gloriously filled the office of Lord High Admiral «liile Duke of York, was perfectly aware of the requirements of the navy ; and during his short reign lie paid great attention to increasing its effi- ciency. He also especially directed inquiries into the question of the duraliility of timber for the construction of it, and careliilly accumulated both materials and stores for its maintenance. It is not a little curious that it was pro- bably the attention which the manarchs of the line of Stuart had bestowed on the naval service, which enabled it so triumphantly to resist the persevering attempts of Louis XIV. to recover for them the throne of their an- cestors. Though England was at the Revolution possessed of an efficient fleet, manned by experienced seamen, who had all the confidence arising fi-om a series of naval triumph,-;, it must be remembered that (or a long period no opposition to hernaval superiority had been aiitici|)atedfrom any other power than Holland ; and consequently the fleets of England were composed of ships which had many of them been built to adapt them to this service, for «hith small dimensions and light draughts of water were essential qualifications, on account of the shoalness of the Dutch coast. William was too catitious a monarch to have neglected so important a means of national defence as was the navy, «hen engaged with such an ambitious and energetic oppo- nent as Louis XIV.; and «e find that the naval force was considerably increased, both numerically and in dimensions, during his reign. But the triumphs of our armies under Marlborough havingfor a time diverted the attention of the nation from naval affairs, it fell into decay during the reign of his successor. When Louis XIV. determined to dispute with England the sovereignty of the seas, he was not only without a navy, but without the means of forming one. The military and commercial marine of Fiance had ceased to exist. The sanguine temperament of the monarch, and the wisdom of his minister Colbert, removed all obstacles; commerce began to flourish on the quays, merchant-vessels to crowd William 111. 1 iouis XIV. the ports ; dockyards, harbours, and shipping appeared Rise of siuuiltancously to start into existence; and the nation, ''"''•'"<^'' """ which almost for centuries had been essentially military, ^"' P""*^""- felt constrained to turn its energies to commerce and to the sea. A navy which, in 1661, consisted of some four or five small vessels, in little more than ten years bearded and baffled the combined fleets of Holland and of Spain, and asserted the sovereignty of the Mediterranean. In 1681 her fleets consisted of 11.5 line-of-battle ships, manned by 36,4-40 men, with 179 smaller ships, the crews of which amounted to 3037 men ; and in 1690 a fleet of eighty-tour vessels of war, out of which three were of a hundred guns anti ujiwards, and ten others were above eighty-four guns, with twenty-two fire shij)S, was cruising in the British seas. It is true that these mighty annamciits failed in fulfilling the ambitious designs of Louis. But the severity of the struggle, which at length ended in the annihilation of his hopes, and in our triumphant assertion of our naval supe- riority, must always serve as an example of the danger we may incur by too great confidence in that superiority. The following comparison between the Trench and Bri- Oompnri- tish ships of about this period, is from an official contem- so" •'s- porary paper, by a gentleman of the name of Gibson : — *"'^*'? '• Our "uns beiuiT for the nio>t part shorter, are made to '"F,',^ , carry more shott than a French gunn of like weight, there- giii,,j_ fore the French guns reach further, and ours make a bigger hole. By this the French has the advantage to fight at a distance and wee yard-arm to yard-arm. The like advan- tage wee have over them in shipping; although they are broader and carry a better saile, our sides are thicker, and better able to receive their shott; by this they are more subject to be sunk by gunn shott than wee." The paper also complains much of the injudicious "I'l" jnjuj-.- nagement of our shipping, by which it says, " many a fastn]„„g„g. sayling shipp have come to loose that property, by beingmcnt of over-masted, over-rigged, over-gunned (as the Constant rojal navy. Warwick, from twenty-six gunns, and an incomparable sayler, to forty-six gtinns and a slugg), over-manned (vide all the old shipps built in the parliament time now left), SIIIP-BUILDING. over-built (ride the Ruby and Assurance), and haveing great lafFciills, gallarys, &c., to the making many formerly a stiff, now a tender-sided shipp, bringing thereby their head and tuck to lye too low in the water, and by it takeing away their former good property, in steering, sayling, &c. The French by this delect of ours make war with the sword (by sending no small shipps of warr to sea, but clean), and wee, by cruseing in fleetes, or single shipps foule, with bare threates." of practical men, so that the forms and dimensions of the previous century passed down, in many instances, into the succeeding one, and justice was not done to the ship- building knowledge of the surveyors. The French system of improvement was followed by the Spaniards, and the capture of the Princessa, in ] 740, of 70 guns, 165 feet in length, and 49 feet 8 inches in breadth, when our ships of the same force then building were only 1.51 feet long and 43 feet 6 inches broad, caused an In a letter from Sir George (afterwards Lord) Rodney, appeal to be made by the Admiralty to Admiral Sir John dated the .Slst May 1780, to Mr Stejihens, the secretary of Norris. The surveyors of the navy of that date who had suc- the Admiralty, is a passage which goes to prove the truth of the above statement. " Nothing could induce them (the French fleet) to risk a general action, though it was in tlieir power daily. They made, at different times, motions which indicated a desire of engaging, but their resolution failed them when they drew near ; and as they sailed far better than his majesty's fleet, they with ease could gain what dis- tance they pleased to windward.' ceeded Sir A. Deane were men of no note, because no op- portunity of showing their powers had been allowed them. In consequence of the inquiries then made, the several master-shipwrights of the dockyards were directed to send in proposals for the future established dimensions of the navy; and, in 1745, Sir Jacob Attwood being surveyor of the navy, the Admiralty issued a new establishment for the dimensions of the several ratines of ships. The foUowinsj A.D. 1745. French system fol- lowed by Spain. Improve- ments at- tempted by the Ad- miralty. One great cause of the inferiority of our ships arose from table, taken from Derricks Memoirs of the Royal Navy, the practice which prevailed during the first half of the contains the various established alterations from time to eighteenth century, through a mistaken idea of economy, time, from the reign of Charles II. to this of 1745, which of "rebuilding" old ships, without reference to the opinions was the last: — An Account showing the Dimensions established, or proposed to be established, at different times, for Building of Ships. E.rtracted from Derrick's Memoirs of the Royal Navy. Ships of 100 Guns. Length on the pun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 90. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 80. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 70. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 60. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 60. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 40. Length on the gun-deck Length of the keel, for tonnage.. Breadth, extreme Depth in hold Burthen in tons 20. Length on the gun-deck Length of the keel, for tonnage. Breadth, extreme Dpptli in hold llnnhen in tons Establishment of Ft. 165 137 46 19 In. 8 2 1550 158 44 18 2 1307 150 39 8 17 1013 156 41 17 4 1100 144 37 6 15 8 900 1706. Ft. In. 162 132 47 18 6 1.551 156 127 6 43 6 17 8 1283 1.50 122 41 17 4 1069 144 119 38 15 8 914 130 108 35 14 704 118 97 6 32 13 6 531 1719. Ft. In. 174 140 7 50 20 1869 164 132 5 47 2 18 10 1566 158 128 2 44 6 18 2 1350 151 123 2 41 6 17 4 1128 144 117 7 39 16 5 951 134 109 8 36 15 2 755 124 101 8 33 2 14 594 106 87 28 9 374 Proposed in 1733. Ft. In. 174 140 7 60 20 6 1869 166 134 1 47 9 19 6 1623 158 127 8 45 5 18 7 1400 17«. 151 122 43 5 17 9 1224 144 116 4 41 5 16 11 1068 134 108 3 38 6 15 9 853 124 100 35 8 14 6 678 106 85 8 30 6 9 .■> 421 Ft. In. 175 142 4 50 21 1892 168 137 48 20 2 1679 161 130 10 46 19 4 1472 154 125 5 44 18 11 1291 147 I 119 ! 42 I 18 1123 140 113 9 40 17 2i 968 126 102 6 36 15 5J 706 112 91 6 33 11 498 Establish- ment of 1745. Ft. In. 178 144 6J 51 21 6 2000 170 138 4 48 6 20 6 1730 165 134 10{ 47 20 1585 160 131 4 45 19 4 1414 150 123 Oj 42 8 18 6 1191 144 117 8J 41 17 8 1052 133 108 10 37 6 16 814 113 93 4 32 11 508 Sn IP-BUILDING. Royal Oeorge, Triumph and Va> littot. The sliips built after tlic establishment of 1745 are re- porteil to have been stiff, and to have carried their guns well, but were still interior to those of" the French ; and, consequently, about ten years afterwards an alteration was made in the draughts for the several ratings, and the di- mensions were also slightly increased. It may not be un- interesting to remark, that the proportional breadths in the establibhment of 1745 considerably exceeded those of more modern ships. Their length varied from 3'49 to 3'85 of their breadth ; while tlie lengths of most of our line-of-battle ships, built shortly afterwards, are within the limits of 3"61 and 3-83 of their breadths. The Royal George was the first ship built on the in- creased dimensions, which were the result of the before- mentioned inquiry. She was laid down in 1746, and launched in 1756; and rather more than ten years after- wards, that is, in 1758, Thomas .Slade and William Bateley being the surveyors of the navy, the Triumph and Valiant of 74 guns were built on the lines of the Invincible, a French 74 gun-ship, captured in 1747. The dimensions of these ships are given below, as they were manifestations of an improved system, which, however, was not persevered in; for, with the exception of occasion- ally building after a French or Spanish model, the English ships were scarcely altered from those built at the com- mencement of the century. Length on the gun-deck Iicngth of the keel, for tunnoge Breadth, extreme Depth in hold Burthen in tons Rotal Feet. tn. 178 143 &i 51 9i 21 6 2047 Triumph and Valiant. Fppt. In. 171 3 138 8 49 9 21 3 1826 There was still a very essential distinction between the navy of England and of either France or Spain, which was this, that until after 17()3 neither of these nations had any three-deckers in their fleets. Their largest armament ajjpears to have been eighty-four gims on two decks, while we had third-rates which were three-deckers, as the Cam- bridge and I'rincess .Amelia, launched in 1754 and 1757, and carrying only eighty-four guns, our naval officers of that [jcriod having advocated a high battery, and the naval architects having designed some very fine ships of this new class. The capture of the Foudroyant, a French eighly-foiu' on two decks, in 1758, caused a change in this respect, by furnishing the English with a model tor a very superior class of men-of-war, which was adopted. Derrick, in his Memoirs of the lioi/al Nan/, says, that " no eighty-gun ship with three decks was built after the year 1757, no seventy-gun ship after 1766, nor any sixty-gun ship after 1759." During the peace that preceded the war with America, which commenced in the year 1 768, the French had in- troduced three-deckers into their fleets, having found their eighty-fours on two decks to be no match for the more powerful of our three-deckers. Their first-rates were at this time generally of 110 g\ms on three decks. The Bre- tagne, one of these shijis, was, according to Charnock, 196 feet 3 inches long on the water-line ; and her moulded breadth was 53 feet 4 inches. Her displacement, it is stated in Sewell's Collection of Papers on Naval Archi- tecture, was 4640 English tons. In 1786 the establishment of the French fleet was fixed by an ordinance of the government, as according to the fol- lowing table, which is extracted liom Charnock, and some very fine vessels of each class were built upon these dimen- sions : — Ilistor A.D. 1763. tirand dis- tinction be- tween Kng- lish and foreign navies. Prench- liuilt ttirea* deckers. Establish- ment of French fleete. Lenj^th from head to stern Ureadih from outside to out- 1 side of the frame j Depth in hold Draught of water abaft when 1 light ] Draught of water forward \ when light J Draught of water abaft when 1 laden j Draught of water forward \ when laden j Total weight of the ship and stores when victualled and furnished for a six months' cruise Weight of the hull and masts... Ships of 120 Guns. Feet. In. 196 6 50 2.'") 17 6 14 2'j 22 8 T..ns. .■5246 2600 Ships of 110 Cruns. Fiu-t. 186 — 185 49 6 in 24 6 17 4 13 8 24 8 22 2 Tons. 4910 2100 Ships of 80 (juns. Ffct. 184—180 48 in, 23 9 17 12 21 Tons. 3825 1804 Ships of 74 Guns. Feet. In. 170 44 6 22 15 8 10 10 21 6 19 10 Tons, 3548J 1437 Shins nffti Fricatcs Guns ",?'■'•>""« '8 ^'""- Pounders. Fwt. In. 156 41 20 14 6 11 1 19 9 18 9 Tons. 2300 1120 Feet. In. 144 36 6 18 12 6 8 7 16 15 2 Tons. 1479 665 Fripates carrying 12 Pounders. Corvettes of 20 Guns, Feet. In. 136 34 6 17 6 11 3 8 6 15 4 13 9 Tons. 1162 583 Advioe- boats, oar- ryini; four 4 Founders, Feet, In. 112 28 4 14 4 9 6 8 5 13 3 11 9 Tons, 546 266 Feet. In. 80 24 12 8 4 8 11 6 10 Tons. 266 141 George III. '^^^ ships of England continued throughout the wars of and George the reign of George III. inferior to those of France and IV. Spain. The skill of our conmianders, and the indomitable courage of our seamen, eventually succeeded in these, as in all former contests, in annihilating opposition, and in triumphantly asserting our naval supremacy. It cannot be denied that their task would have been comparatively easy, accompanied with less loss of life and expenditure of treasure, had their ships been more upon a par with those of their opponents. The French officers, however, after the war, to save their vanity, attributed our successes at sea to the superiority of our ships, and they commenced building after our models. Although so much attention appears to have been directed at various times to the improvement of the navy, not only by the servants of the crown officially connected with it. Reasons for but by the sovereigns themselves, we have seen that an the con- inferiority of our ships in sailing to those of our op|)oneiits ''"."^'l '"' has been repeatedly asserted on undoubted testimony. The °'"'"'""y °' 1 11 1 ■ 1 1 1 /■ 1 1 • British reason that all the attention thus bestowed failed in pro-gijippj^^ ducing a corresponding beneficial effect appears to have been that in England the speculative ideas of men, un- doubtedly of sense and judgment, as may be seen from the quotations of their opinions which have been given, but men uninformed as to principles, were taken as the rules for guidance. In F'rance, on the contrary, the aid of science was called in, and some of the greatest mathema- ticians of the time turned their attention to the improve- ment of the shipping of that country, and worked harmoni- ously with the naval officers who were to use the ships, as S II I P - B U I L D 1 N G. 19 [nstanceo ignorance. Razee of the Anson. iniprove- nents in laval ar- ihitpcture n this Jountry. well as with the practical men who were to construct them, modifying their theories by the practice and experience of the otiiers. Colbert employed an engineer of the name of Renau d'Elisagary, a protege of the Count de Verman- dois, whose first essay was in the adaptation of ships to carry bombs, to be used in the then projected armament against the piratical states of the Mediterranean. Under the enlightened direction of Colbert, the French ships which, by the ordinance of 1688, were much restricted in dimen- sions, were increased nearly one-fourth in size, and every means taken which the then state of knowledge could sug- gest to insure a proportionate improvement in their qua- hties ; while a corresponding increase in size was not made in English ships till the commencement of the energetic surveyorship of Sir William Symonds in 1830. Kenau was, we believe, the first French author who wrote on the theory of ships. He was followed by the Bernoullis, by Pere La Hoste, by Bouguer, Euler, Don Jorje Juan, Romme, and a host of others, the effects of whose writings may be traced in the progress of the improvements intro- duced into the navies of France and Spain, and which the navy of England was forced to imitate. The only English treatise of that period on ship-building that can lay any claim to a scientific character was published by Mungo Murray in 1754 ; and he, though his conduct was irreproachable, lived and died a working shipwright in Deptford dock-yard, f A palpable instance of the ignorance or neglect of all the principles of naval architecture among the authorities who were charged with designing our royal navy, even up to the close of the last century, may be quoted from an arti- cle in the Papers on Naval Architecture, as given by Mr Wilson then of the Admiralty. Mr Wilson, speaking of the cutting down of the Anson, a sixty-four-gun ship, to a frigate of thirty-eight guns, says, " she was cut down in the year 1794 ; and although in all other maritime states the science of naval construction was well imderstood, yet so culpably ignorant were the English constructors, that this operation, so well calculated, when properly conducted, to produce a good ship, was a complete failure. Seven feet of the upper part of the top sides, to- gether with a deck and guns, making about 160 tons, were removed, by which her stability was greatly increased ; but, by a complete absurdity, the sails were reduced one-sixth in area. In her first voyage the rolling was so excessive that she sprung several sets of top-masts. To mitigate this evil, in 1795, her masts and yards were increased to their original size ; but as there were no decrease of ballast, she was still a very uneasy ship, and, as a necessary result, her wear and tear were excessive. " Other sixty-fours were cut down, masted, and ballasted in exactly the same manner, and, it need scarcely be added, experienced similar misfortunes ; and although they were improved by enlarging their masts and yards, they were still bad ships. Had their transformations been scienti- fically conducted, a class of frigates would have been con- tinued in the navy, capable, from their size, of coping with the large American frigates ; and thus the disasters we experienced in the late war, from the superior force ot that nation, would, without doubt, have been not merely avoided, but turned into occurrences of a quite opposite character." The subject, however, of the improvement of ship-building was by no means lost sight of in this country at that period. The investigations and experiments which were made were, as usual in England in comparison with France and other continental nations, more of a practical than of a theoretical nature. Attwood's papers, read before the Royal Society in 1796 and 1798, form almost a solitary exception to this remark. In 1785, and subsequent years, Mr Miller of Dalswinton, in Dumfriesshire, made many experiments, ex- History, pending as much as L. 30,000 of his own private fortune for '- » .^ -._ ■> the advancement of naval architecture. In 178S he was ^ j,. 1800. induced, by a Mr Taylor, to allow Symington, a working- engineer, to place a steam-engine on board a pleasure-boat on his lake at Dalswinton, for the purpose of propelling it by a paddle-wheel, and he thus became the originator of steam-navigation.' In 1791, " a Society for the Improvement of Naval Beaufoy's Architecture" was instituted, mainly by the exertions of «='P«''i- Colonel Beaufoy. This society numbered amongst its ™^°''- members the then Duke of Clarence, afterwards William IV., and many noblemen and gentlemen of great influence. They conducted a most valuable series of experiments be- tween 1793 and 1798, but a first report only of the results was ever published by the society. The funds at their disposal became exhausted, and the experiments were thus terminated, the interest of the public having flagged on account of the necessarily tedious nature of the proceedings. A detailed account of the whole of the experiments was subsequently published, in a most patriotic spirit, by Mr Henry Beaufoy, at his own private expense, and presented gratuitously to scientific societies and parties connected with naval architecture. Some valuable practical results were deduced from them, and these will be discussed here- after, when treating of the resistances and other qualities of differently formed vessels. At the commencement of the present century the mer- Increase of chant-shipping of this coiuitry had increased to such an merchant- extent as to be of great importance. From the returns 6'i'PP'"g- prepared by the Registrar-General of the Board of Trade, the total number of British merchant-vessels in the vear 1801 was 19,711, with an aggregate registered tonnage of 2,038,253 tons, employing 149,766 men. In 1811 the total number of merchant-vessels was 24,106, with an aggregate registered tonnage of 2,474,784 tons, employing 162,547 men. In the Honourable East India Company's service there East India were at this period 67 ships, each carrying 30 to 38 guns, Company s 31 ships of 20 to 28 guns, and 52 ships of 10 to 19 guns, ^'''PP"'^- thus forming a powerful addition to the warlike resources of the country. Additional attention was also attracted to the subject of ship-building in the early part of this century by the institution of the Royal Yacht Club. It was joined by many influential and wealthy noblemen and gentlemen, and they gave much encouragement to the production of sujierior fast-sailing yachts. Another important effort to improve the scientific know- School of ledge of naval architecture, was tlie establishment, in 1811, ^^'^''l ^^ of a school for naval architecture in Her Majesty's Dockyard ^, n„.^., at Portsmouth. This school was the result of the state- mouth, ments and recommendations contained in the report of a commission of naval revision, appointed in 1806, to examine into the management of the dockyards. The commissioners found that the practice of permitting the master shipwrights and their assistants to take private apprentices, receiving high fees with them, had been at that time disallowed and discontinued. By this system young men of superior early education, and of superior standing to the ordinary ship- wright apprentices, had been trained in the higher branches of the profession, and their further scientific and theoretical education had been attended to, while at the same time they had acquired a knowledge of practical shipbuilding by being employed amongst the workmen. The commis- sioners therefore considered it expedient that some means should be adopted to supply the future demand for such men to fill those higher civil situations in which scientific knowledge is indispensable for the due performance of the duties. The school was accordingly instituted, but upon ' Skttch of the Origin and Progress of Steam A^avigalion, Bennet Woodcroft, 184S. 20 Hiitory. A.I>. 1813. SHIP-BUILDING. so lariie a scale, ami nitli so little consideration of the real reqniremciils of the service, that in a very few years 42 students were educated there, while the whole number of places in the Adniirahy service, requirin;: such education and training;, did not exceed 25 or 26. The necessary result of this was, that they were put into inferior positions for which their previous standina; and training had not adapted them, they failed in the duties of men required in these positions, and the school was considered to have been a failure. Much increase, however, of sound scientific know- ledge resulted from the labours of the principal of the school, the late Dr Inman, thoufrli he confined his labours to too Ilistory. limited a sphere, and did not follow out the investifiations of ^~^^/— ' the French mathematicians. Many valuable pa[>ers on a.d. 1832. naval arcliitecture have also been published by different members of the school, and the article Sliip-building. in the previous edition of this work, and from which much of the present article is taken, was written by the late Mr Creuze, one of its most talented and distinguished members. The following table, taken from the navy list of 181.3, will show the force of the royal navy at that period, distin- guishing the number of ships in each class : — Extent and Disposition of the British Naval Force in 1813. Downs North Sea and lialtic English Channel and coast of France... Irish station Jersey, Guernsey, &c Spain, Portugal, and Gibraltar Mediterranean and on passage Coast of Africa Halifax, Newfoundland, &c _. . ,. f Leeward Islands Hest indies | Jamaica and on passage South America Cape of (iood Hope and southward East Indies and on passage Total at sea In port and fitting Guard-ships llospital ships, prison ships, &c Total in commission Ordinary, and repairing for service Building Totals Line. 5I)-M Frigates. Sloons nnil Yaclils. Bombs, Firo- sliips. Brigs. Cutters. Srhooncrs, Guu-rei*., Lug., iiC. Tot.lI. 4 1 4 20 5 6 40 12 o 8 5 3 50 11 9 100 15 16 15 23 7 13 89 5 3 5 1 7 21 1 2 2 2 7 15 11 6 2 14 4 1 53 27 5 33 10 2 2d 1 2 106 1 1 9 2 23 13 23 1 6 77 2 1 10 8 6 2 4 33 6 1 11 7 8 32 4 1 8 7 4 2 24 1 3 3 2 9 4 16 3 ^ 27 619 98 12 146 85 7 187 34 52 24 9 24 21 25 9 9 121 5 1 4 5 15 32 1 3 2 38 159 23 177 111 7 212 43 Gl 793 72 11 80 37 4 12 1 3 220 28 4 25 9 7 73 259 38 282 157 11 231 44 64 1086 Abolitioa In 1832 the Navy Board was abolished, and it was de- of Navy termined to ])lace the construction of ships under one Boird and j,ga(j_ continuing the name of surveyor of the navy, but appoint altering the nature of the office by the appointment of a William na^'al officer instead of a naval architect and ship-builder. Symondsas Captain (afterwards Rear-Ailmiral Sir) William Symonds surveyor, was the officer selected. He had early distinguished him- self amongst his brother-officers by the attention he had paid to the sailing pro|)erties of boats and vessels. It was said of him that he could take any one of the boats in turn, of the vessel to which he was attached, and make her beat any of the others. His habit of observing the peculiarities of the different ships, whose properties he had an oppor- tunity of witnessing, led him to draw certain conclusions respecting the forms of vessels ; and, while holding a civil appointment in Malta, he built a yacht called the Nancy Dawson, in accordance with these preconceived views. The great speed of this yacht gained him notoriety, and procured for him the patronage and support of several in- fluential and patriotic noblemen. Through their influence he obtained tlie sanction of the Board of Admiralty to build a corvette, the Columbine, and as this vessel was very favourably reported of, his character as a designer was proportionally raised. These successes led to his appoint- ment as surveyor of the navy. It is not proposed here to discuss the propriety or otherwise of this office being filled by a naval officer, though in Sir William Symonds' case it led to important changes in the construction of the ships of the royal navy, and to much acrimony of feeling on the part of the shipwright officers of the service. One point is quite certain, that no man can be qualified to control the different forms of the various classes of ships, more espe- cially of new classes that may be required in the navy, without long and careful study of tlie subject of naval architecture, both practically and theoretically. It is equally certiiin that a naval officer of experience is the most com- petent judge of the general proportions and qualities of the ships that will be most useful in the service, and that he is best able to point out the faults at sea of any ships that have been so tested. Sir William Symonds was the first constructor of the English navy whose standing enabled him to claim the power legitimately due to Ids position, that he should be left unrestricted as to dmiensions, and he was consiqiiently en- abled to introduce into the service ships wliich undoubtedly bore very high characters as men-of-war. He also practically demonstrated the possibility of ships of war obtaining suf- ficient stability without the aid ol ballast— a very important advantage, and one which has been productive of much benefit. He was in error, however, as to the true |)rinciples on which the stability of floating bodies is dependent, in order to secure as great freedom from rolling and as great ease of motion as possible. His ships had great statical stability, and therefore great power of carrying sail, and hence were gene- rally very successtiil in trials of speed in sailing. But this ad- vantage was not obtained without, in many instances, in- curring a compensating disadvantage from uneasiness of motion. This appears to have been a very general fault in ships of his construction, some of them being marked ex- amples of the unea-iiness attendant on a stability which depends almost wholly on breadth at the load-water section and above it, to the' neglect of the form of the solids of SHIP-BUILDING. 21 History, immersion and emersion. His ships, however, were very '^— ^^^-^ general favourites in the service amongst the officers in A.D. 1832. command of them, who in their reports made liglit of any faults, and bore any personal inconvenience and want of comfort cheerfully and willingly, on account of the speed of their ships and their success in the sailing matches. The country is much indebted to Sir William Symonds for many miprovements which he introduced into the navy, especially at the commencement of his tenure of office. He failed, however, to keep pace with the improvements of his time, his want of scientific education and of enlarged \iews rendering him unable to go beyond or apply to History, steamers, or any new class of vessels, the ideas whicli he ^^•v^-^./ had imbibed in his earlier years, and to which he adhered a.d. 1837 with a pertinacity amounting to obstinacy. 'I'he following table contains the dimensions of the Dimensiong various classes of ships wli'ch Sir William Symonds in- "f ships of troduced into the British navy, as well as of one or two '','** I'ojal other English ships built to compete with those of his ^**'y- construction. The dimensions accordmg to which the ships of the French navy were at that time built are also given : — Dimensions of English Ships of War at the period ichen Sir W. Si/nionds vas Survei/or of the Xari/. Names of Ships and of their Designers . Queen Vanguard . Boscawen ., First Rate. Second Rate. Third Rate. Vernon . Pique ... Fourth Rate. Fifth Rate. Sixth Rate. Vestal Carysfort.. Rover... Calypso. Corvettes. Brigs. Columbine Serpent Racer \ Pantaloon London 1 I Sir Robert Seppings.... Castor J Inconstant, Admiral Hayes Moiieste, Admiral Hon. G. Elliot. Sapphire 1 r. /• i Q *1 > Professor Inman 110 on 1 3 decks j 80 on 2 1 decks. J 70 on 2 1 decks. J 50 36 26 26 18 18 16 16 16 16 92 on 2 deck 36 36 18 28 18 ■..^! Lengtii of Gun-Deck. Feet. Inch. 204 190 180 176 160 130 130 113 120 105 102 100 91 10 205 6 0} 5 8 159 166 120 119 109 11 Keel for Tonnage. Feet. Inch. 166 5 155 146 8 144 131 105 9 106 10 90 99 1| 5i 84 79 10 78 9i 71 170 133 133 98 100 4 4 7 H 7 'l Extreme Breadth. Depth in Hold. Borden in Tons. Feet. Inch. 60 56 9 54 52 8J 48 8 92 lOi 40 40 35 37 33 32 32 29 54 4 43 45 5 32 9 33 8 30 6 5 6 6i 3 H 4 Feet. Inch. 23 9 23 17 14 10 10 16 18 7 15 6 6 9 11 14 10 12 8 23 13 13 7 8 7 2 6 7 11 6 3099 2589 2212 2082 1622 913 911 590 731 492 434 431 323 2598 1283 1422 562 605 459 Dimensions of French Ships of War, as built in 1837. Number of Guns Length on gun*deck between rabbets Moulded breadth C forward Draught of water, <. aft \ mean Load, displacement in tons Line-ofBattle. 11 Feet. inch. 209 5 55 33 24 11} 26 8J 25 lOi 4Sy40 100 Feet. Inch. 205 OJ 54 Hi 23 10} 26 OJ 24 11} 4393 90 FePt. Inch. 198 6 53 I 23 ■ 25 ■ 24 . 4013 Frigates. 60 Feet. Inch. 178 IJ 47 7 19 11} 21 3} 20 7i 2542 52 Feet. Inch. 172 1 45 2} 20 8 2267 Corvettes. 32 Feet. Inch. 138 7} 36 OJ 14 9 16 ; 15 ( 999 24 Feet. Inch. 125 4 32 7i 13 6} 14 10 14 2i 738 Dimension! of ships of the French Navy. The introduction of vessels propelled by steam for practical purposes dates its origin in the year 1812, when Henry Bell started the Comet steara-vessel on the Clyde, for the con- vex ance of passengers. In 1815 there were 10 steamers in existence in this country, with a registered tonnage of 1633 tons. In 1825 this number had increased to 168, with an agirretrate tonnage of 20.287 tons, and in 1835 the number n as 538, with an aggregate tonnage of 80.520. Some very interesting experiments were made about 1832, by Mr Scott Kussell, on the Forth and Clyde Canal, with a view to introduce steam on canals. These were not suc- cessful in their object, but a class of very loni; and finely- formed boats lor cpiick passenger traffic on canals were introduced at this time. These were drawn by two horses, and were expected to travel at the rate of 9 or 10 miles per hour, but it was found that if they were not at once put to this speed, but started sluggishly or gradually, a wave was formed in front of them, and continued to pre- cede, washing over the banks of the canal and over the tow- ing-path. Under these circumstances the horses were much distressed with the labour which they had to perform. If, on the other hand, they were urged into a speed of 9 or 10 miles an hour at once upon starting, no wave was formed, and the boat seemed to rise on the surface of the water and to be propelled with comparative ease so long as that speed was maintained ; but if they flagged, and their rate of travel- ling fell to 6 or 7 miles an hour, the wave was formed, and it then became necessary to reduce their speed to a walk. 22 SHIP-BUILDING. New Ton- nage Act. In trod ac- tion of iron. Introduc- tion of Bcrfw pro- pulsion. till it tlisappcarcil, and llicn to start tliein .nfjain at once into the liiphtT spceil. This petiiliar resuh «as no ilouht mainly tauseii hy the confined space of the canal, but no scientific investigalion to account t()r it iias yet been j;ivcn. The lines of these boats were called wave-lines by Mr Scolt Russell, and for ease of propulsion in smooth water they are undoubtedly beneficial. Lines of a similar cha- racter were also useti about the same time by Mr Fcarnall in last-passenfrer steamers on the Thames. Their advan- tage was made very apparent by the construction of the Vesper in 1837, a passenger-boat from London Bridge to (Iravesend. This boat went through the water at a spee'd of about 12 miles an hour, with scarcely any wave or even a ripple at her bows, wiiile her competitors were carrying a heavy wave and swell before them. Other vessels with lines of a similar character were built subse- quently by Messrs Fletcher and Learnall, by Mr Dilch- biun, who had been in their employment, and also by others. Up to 1836 the mercantile marine had laboured under the disadvantage of a t<innage law tor the charging of dues, which, by the mode of measurement enacted, held out a premium tor the construction of inferior ships. In this year a new ;ict was pa>setl, and a better system introduced. IJy this act the internal capacity of a ship became the mea- sure of her tdiuiage, and the serious objections to the former law were obviated. It was about this period that iron began to be used to any great extent as a material for ship-building. Its merits for tills purpose will be discussed hereafter, when treating of the practical construction of ships. Mr Manby, Mr Laird of Liverpool, and Mr Fairhairn of Manchester, were the first constructors of vessels of any size of this material. Mr Fairhairn, in 1833 and 1834, built two passenger- steamers of iron to ply on the Humber, between Sclby and Hull, and in 1836 he commenced the business of iron ship-building, in company with others, with the writer as the resident managing partner, at Millwall,on the Thames. In 1837 Mr Laird built an iron steam-vessel, the Rain- bow, for the (ieneral Steam Navigation Comjiany at Deptford, and from that time the use of iron has rapidly increased. The next important step in the history of ship-building was the introduction of the screw-propeller. Many pro- posals had been made, and |)atents taken out, for propellers of this nature ; but a small vessel fitted with a |)ropeller, patented by Ericsson, was the first brought into practical use. A small experimental vessel called the F. 15. Ogdon was built in 1837, and fitted by Ericsson with one of bis propellers, and the Lords Commissioners of the Admiralty, attended by their surveyor. Sir William Symoiids, took a trip in her in tliat year. They, however, failed to see the advantage of such an invention to men-of-war, and refused to entertain any proposal f()r its introduction into the navy. Mr F. P. Smith also built a small experimental vessel during this year, and fitted her with a screw propeller. Ericsson, on receiving no encouragement from the Rritish government, took steps to bring his invention before the Americans, and a small vessel, the Robert F. Stockton, was built by him in 1838, in this country, with this view, and made the voyage safely to America. Mr Smith, in the meantime, induced a number of influential men to form a company to carry out his invention, and in 1839 the Archimedes was built by them, to test and demonstrate its value. The success of this vessel was such, and the ad- vantages likely to accrue to men-of-war from the introduc- tion of the screw were so apparent, that the Rattler was then ordered to be built in one of the government yards. This vessel was on the same lines as one of the Admiralty paddle-wheel steamers, but its stern was lengthened to fit it to receive the screw propeller. Her success was un- deniable, but the progress of the screw in the navy was Ilistory. very slow for many years, owing to the ojipositiou of Sir v^p^/— »> M'llliam Symonds, and to the frequent clianges of the ^.b. ib46. ISoard of Admiralty. Some i)rogress, however, was made in the introduction of screw-ships into the navy, several small vessels being built to the designs of Mr I'incham, the master-shipwright of Portsmouth yard. This officer was in favour of its introduction, as were all the officers of the engineering department under the Board of Adinir.ilty, and they were supported by the Right Hon. Mr Corry, the secretary of the Admiralty at that time. The Arrogant and Daimtless, two screw frigates, were afterwards built by Mr Fincham ; and, at the same time, the Termagant, also a screw-frigate, was built by Mr White of Cowes. Alter this time, the growing dissatisfaction with the ex- Sir B. cessive rolling of Sir William Symonds' ships, his obstl- Walker nate adherence to his own forms of construction, together I'lii'ointc with his unwillingness to co-operate in the introduction of ^"'''"■>"' screw-steam ships into the navy, led the Hoard of Admi- Ko^y. ralty, of that date, to order that a committee of reference should be constituted, to whom all designs fiir ships should be submitted before they were laiil down. This led to Sir W'illiam Symonds resigning his office, and Sir Baldwin Walker, a naval officer distinguished for bis seamanship, was appointed as his successor. Sir Baldwin Walker had not given his attention to the study of naval arcliitectme theoretically, and the Board of Admiralty announced that they should not expect him to originate the lines of the vessels to be built, but that these should be designed by naval architects attached to his office. The construction of the ships of the royal navy was thus |)laced on a proper footing; and if this arrangement had been carried out, and the naval architects had had full power given to them, and been at the same lime com- petent men, the country ought to have reaped the benefit of so judicious an arrangement. With respect to the class of ships ordered to be bnilt at Sailing this period in the dockyards, no change in accordance with ■"^ini"' co the advancing state of screw prO|mlsion took place. The """' ' naval members of the Board of Aiimiralty were men who ." ^ had long looked upon the noble line of battle-ships of the navy as not to be surpassed, and they could not apparently make up their minds to desecrate tlicm, as they seemed to consider it, by the introduction of steam-power. The re- sult of this somewhat romantic feeling was, that early in Sir Baldwin Walker's administration a number ol sailing three-deckers were laid down, in opposition to the expressed opinion of the leading civil professional officers attached to the Admiralty. Not one of these vessels, as had been pre- Sub«e- dicted, was ever launched as a sailing vessel. They were qucntly converted into screw-slii|)s by being lenuthencd in midshiris, ^°"^^rt( II 11 A ■- -i-i" 'nto Scr at the bows, and also at the sterns. J he greater pro[)orti(in §!,;„,_ of the other sailing three-deckers were also cut down and converted into two-decked screw-ships, their sterns only being altered. These important changes on the last men- tioned vessels were all carried out at much additional expense, while two of the members of the late School of Naval Architecture were the assistant surveyors; and a repetition of the errors committed at the end of the last century, on the occasion of a similar operation upon several ships, has thus been avoided. The errors committed at that time have been described by Mr Wilson, as previously quoted, and are ascribed by him to a want of sufficient scientific knowledge; but as this is not the case at the present time, the coimtry may now expect a very fine class of vessels to be t"rc result of any new proposals. It may also be remarked, that the introduction of the system of distilling the necessary supply of fresh-water on board the ships, and thus obviating the necessity of carry- ing so great a weight of fresh-water, materially facilitated the ari-angenients for these alterations. SHIP-BUILDING. 23 The following is a table of the Rrilisli Navy as it existed in ly59, extracted from tiie iS'avy List of October 1809 : — Table of the British Navy, extracted from the Navy List, Octobtr 1«59. Class. o c Guns. c o 1 1 C a §1 a'St |2 to c n 8 11 56 35 42 82 50 6.5 64 Ki 22 12 53 29 8 547 160 4 711 Three-decked ships... Do. do Two-decked ships .. Do. do Screw Sails Screw Sails Screw SaUs Screw Sails Paddle Screw Screw Screw Paddle Sails Screw Screw 110 to 131 110 to 120 60 to 100 72 to 84 36 to 50 40 to 50 4 to 21 14 to 26 3 to 22 2 to 4 2 to 4 ... 16 2 2 9 34 12 19 12 29 20 46 7 16 8 37 12 4 1 12 23 18 70 11 45 18 3 4 3 16 17 8 "l 2 10 5 id 2 1 Do Corvettes and sloops Do. do Frigate and sloops ... Despatch vessels G un and other vessels Yachts, tups, &c Do., andothervessels Floating batteries ... Total Gun-boats Frigates, iron-cased, \ not yet in Navy \ List — building . Grand total Austria 135 Portugal 37 Sardinia 28 Prussia 55 Greece 26 Turkey 49 Brazil 27 Peru 15 Chili 5 Mexico 9 Navy of By a let mn piiblished during 1859, it appears that the other (Qtal number of ships of all classes belonging to the navies nations in j- m|,^ kingdoms was then as follows :- France 448 Russia 164 Sweden — principally 1 oi i small vessels j Norway 143 Denmark 120 United States 79 Holland 139 Belgium 7 Spain 82 The Two Sicilies 121 In the foregoing list it will be observed, that a new class of vessels called gun-boats are, for the first time, included as forming a portion of the naval strength of the nation. These gun-boats are of three classes, varying sliL'htly in size and horse-power. Tlie greater proportion are 106 feet long between the perpendiculars, 22 feet beam and 8 feet deep, and are fitted with engines of sixty horse-power. They are of 233 tons burden, and their draught of water, when ready for sea, is about 6 feet. The importance of this class of vessels as a protection against invasion cannot be overrated. The introduction of steam as a mechanical agent for the propulsion of vessels, independent of wind and tide, brings us back to a state of things similar to that which existed when hostile fleets were composed of rowing galleys. The supremacy on the ocean which this country has so long held, by means of the experience of such a large proportion of her population as seamen, must now de[)end on other sources of strength, and it behoves the nation to make arrangements suitable to meet the altered circumstances. If our fleet were to sutler any reverse, and thus leave the sea free to an enemy ; or if an enemy came to a determination to try and evade our fleet, and land an army on our shores, that army might be •^".ibarked at many different points, and, with steam as an agent, the different portions of it might, with almost perfect certainty, meet at any appointed time at any spot. When History, once upon our coasts, tliey could move along them with a '^>^^/-»^ raj)idity which would make it difficult lor any troops on a.d. 1859, shore to follow them, if they were confined to the ordinary means of transport. If, however, our coasts were iron- bound by coast-lines of railroads, so that troops could be moved along them and concentrated rapidly at any spot, with the assistance of the electric telegraph, our power ot resisting the landing of any foreign force would be im- measurably increased. The art of war has been said by the highest authorities, to he mainly in the power of sud- denly concentrating men on any one point ; and if our rail- roads and telegraphic communication are made available for this purpose, the importance of keeping up a large and effective force of steam gun-boats, lying at the time of an expected invasion in every bay and creek of our indented shores, prepared to act in concert with other and more powerful vessels, is evident. For the construction of a fleet of such vessels, iron is fortunately the most valuable mate- rial, as the evils attending its use in large men-of-war will not militate against its use in these vessels. If they should be struck by shot, the men will be above the splinters, and by building thtm with extra frames very far apart, and with a strong inner and outer sheathing, both water-tight, on these frames, they may be made almost unsinkaijle. The chief advantage, however, of iron for such vessels is its durability, if moderate care be taken to construct them in such a manner that all the parts may be kept painted, and then that they be periodically cleaned and painted. Iron vessels so constructed and hauled up on shore, and so cared for, might be considered as aJraost tree from decay. The applicability for purposes of war, of iron vessels Experi- constructed in the ordinary way, early engaged the attention ""en's "''''» of the writer, and in 1845, in concert with the late Major- ^''*'' .°" General, then Colonel Dundas of the Royal Artillery, one ig^g'" of the officers of the arsenal at Woolwich, he arranged some experiments to test the effects of shot on such vessels. So little importance, however, was at that time atiached to the subject by the authorities, that at first no official notice was taken by the Admiralty of these experiments, the targets, representing a portion of the side of an iron vessel, being constructed in the dockyard at Woolwich under merely verbal sanction from the Captain Superintendent o( that yard. By these experiments it was at once shown, that iron plates of ^-incli or gth-inch thick were easily pene- trated by solid 32-pounder shot, that the hole made was no greater than the size of the shot, and that the injury was merely local and easily repairable. These experiments also proved that the shot, in striking plates of this thickness, was frequently, though not invariably broken, and that the portion of plate taken out by the shot was broken into a number of small and most dangerous splinters. Targets made of plates of the best Low Moor Iron were tried in comparison with targets made of common boiler plates; but the ditterence of the quality of these two kinds of iron made no difference whatever in the splintering or in the general effect. To guard against the risk of a ship being sunk by the clean hole thus shown to be made through the iron by a shot, the parasol shot-plug was introduced at this time by the military officers. This plug is composed of trimmed sail-cloth, or of India-rubber cloth, in the form of an um- brella or parasol with a long handle, and is intended to be pushedout through the shot-hole, and then opened and drawn back on the hole so as to cover it and prevent the entrance 01 water. Layers of timber varying in thickness from 3 and 4 inches up to 15 and 18 inches, placed behind the iron, were then tried, with a view of collecting and stopping the splinters. It was found that this was not effected with less than about 14 inches of thickness. Wadding and packing of various SHIP-BUILDING. kinds were tried with an inner sl)eathin<; of plate on tlie ribs to sustain it, but no bcMiitiiial rL■^ull was ii)iinil to be ob- tained from any course of tbis kind. A layer of a mixture of saw-dust and Indian rubber was sul)sequently tried, and 24 HUtory. A.D. 1859. Experi- monts with (|,j^ „.jy (bund to answer well, but it required to be of Shot on nearly as iireat thickness as the solid wood. An experiment Jron in ■, ^ , . , , , it, 1845. "'^* "'*'' niadi- with a target placed at an anfjle with the line of (ire ; but the thickness of plate of w Inch these targets were composeil was found not to be sufficient to make a 32- pounder shot glance. When fired Ironi a distance of 200 yards with the ordmary cliarge tor short ranges, the sh>)t Btrui k l)etween t\vo ribs, and kept its course, making a long slot or elongated hole. To test the ert'ect of a spent shot, a .Uiot was merely pitched against the target trom a gun brought within a bhort range, and fired with the smallest possible quantity of gunpowder ; the shot was not broken, and it went through the target, making, as in other cases, a hole no larger than itself, but the edges of the plate round the periphery of the hole were bent backwards with rugged radiating points. The inside of the target was also fired at, to represent the effect of a shot passing tlirongh a ship and strikuig tlie olT-side ; the effect was the same as before, except that the rivets within a circle of about 2 feet to 3 feet radius, which attached the plates to the ribs, were loosened, and the heads of some of them were broken off. In 1845 and 18-16, the Admiralty of the day, with a view of testing the efficiency of iron ibr men-of-war, after having had " The Dover" packet, built of iron, Ibr some years in their service, and subsequently the Birkenhead iron paddle-wheel steamer, ordered the Minx, 2 guns and of 303 tons, and Sliarpshoi ter, 8 guns andof 503 tons, and several frigates, to be built of iron. Of these latter, the Simoom, of 19y0 tons, built by Mr Robert Napier of Glasgow, is always quoted as the type. The Ministry of the country, however, having changed, and with it the Board of .•\diniialty, before the completion of these frigates, they were ordered to be converted into troop-ships, and the views of their original proposers unfortunately were not carried out with them, nor, still more unfortunately, with the smaller class of vessels. If the foresight of Sir George Cockburn, and Sir Charles Adam, and those asso- ciated with him at this time at the Admiralty, in attein))ting the construction of these small screw steamers, had been followed up, the country would not have been without them at the beginning of the Russian war, wlien they were so much wanted, and when a fleet of them had to be constructed w iihoiit experience as to the best form and size, in great haste, and with much loss, both of money and of credit, to the country. The experiments at Woolwich in 1845 having shown the necessity of guarding against splinters, the sides of the iron frigate between the main and upper deck, opposite where the men were fighting, and w here the guns would be chiefly collected in the time of action, were ordered to be lined with wood, whilst the other portions were intended to be left un- protected, as splinters from them would be of less impor- tance. This, however, did not satisfy the new Board of Admiralty, and with the view of confirming the correctness of their decision in ordering these frigates to be converted into troop-ships, a further set of experiments were ordered to be made in 1848 from the Excellent at Portsmouth, by firing against targets made to represent portions of the Simoom. These experiments corroborated all the results previously obtained from the experiments at Woolwich arsenal, and seem to have further proved an important fact, which did not then suggest itself, and was not tested, that plates of |th inch thick prevented any shells then known from passing through and exploding inside the ship. This lact, however, was not made known to the House of Com- mons or to the public generally, and the tide of public nistory. opinion was then strongly directed again>t the use of iron ^"^^.''~' ships for purpo>es of war, by the amount of information on a.d. 1839. the subject officially promulgated. Sonic years previous to 1848, other experiments against Other Ex- iron had been tried with a totally different obji ct in vitw, perimenl* but from which results of much imporiance to ships of war "''[' ^'"'' have followed. These ex|)criments were made at Ports-"" ™°' mouth, a'jainst a target composed of 14 thicknesses of iiiuli boiitr jilates, boiled together so as to form a mass of 7 inches thick. This was found practically to be siiffi. icnt to sto)i 32-p()under >liot. A much more im|)ortaiit and elabo- rate series of experiments on this subject were made at this time in America, and from these it was found that a thickness of 6-inch solid hammered iron was practically iiuulnerable against the power of any ordnance then in use. Alter these experiments Na[ioleon 111., who has paid great P'rst attention to the subject of artillery, conceived the idea o('ron-cascd encasing a ship in thick plates of iron as in armour, to re- '' sist shot. In 1853 this idea seems to have been publicly broached by him, and in 1854 the Governments of England and France constructed vessels on this principle to be brought into action against Russia, They were called floating batteries, as they are mere barges built for the pur- pose of carrying their guns and their armour plates with a small amount of steam power, sufficient to give them a low rate of speed, and enable them to put themselves into position in the field of action. They vary from 1535 to 1954 tons burthen, and carry 14 to 16 of the heaviest guns ; their draught of water iloes not exceed 9 feet, so as to enable them to afiproach the forts more nearly against which tliey were intended to act. Those built in France having been completed at an Iron-cased earlier date than those built in England, one of the French Shijis of batteries was brought into action against the Russian lort I,'* """^ of Kiiiburn, and with the most complete success. Upon this the Emperor of the French immediately set about carrying out the idea to a greater extent and in more per- fect ships. He selected an able naval architect, M. Dupiiis de Lome, and, as stated by Mr Scott Russell from personal knowledge,' " One of the first acts which the imperial designer and his own naval architect undertook together, was the reconstruction of the French Navy. They soon saw that it must be reconstructed as a whole, not in parts merely; that it must consist of ships of the line, frigates, despatch-boats, and gun-boats, similar in some degree to the various arms of the existing fleet ; and they forthwith set about the design, and constructed a pattern of every one of those classes. Thus it was that, so far back as 1857, the Emperor and his naval architect had not only frankly ac- cepted the new state of things, but had formed a syste- matic design, and commenced the methodical execution of a navy of iron-sides, the I'rench Fleet of the future." In England the subject was at the same time pressed upon Iron-cased the consideration of the Board of Admiralty. In 1835 Mr Ships for Scott Russell laid plans and a model respecting a shot-proof "'^ liritisl iron vessel before Sir Baldwin Walker, the surveyor of the ^^^y* navy, as he informs us in the pamphlet before quoted. He also says, " He expressed to the Admiralty his belief that an entirely new class of shot-proof ship could be constructed, which should possess all the qualities of a good sea-going ship, which should possess speed as well as power, which should carry a shot-proof battery, and which should belong to the corvette class or frigate, or a single covered deck. He proposed that this vessel should be entirely of iron ; that it should be constructed on the longitudinal system of structure, like the Great Eastern ; that it should be built with a shelf or recess on the outside of the iron skin of the ship, which should receive wooden barking and iron armour in 1 The Fleet of the Future in 1862. By J. Scott Russell, Esq., C.E., F.U.S. SHIP-BUILDING. >tam orsom Iron- id Ships. the manner subsequently carried out in the Warrior ; and lie accompanied liis proposal with a large size model, show- ing the practical arrangements by which this was to be carried into effect. This was the first design of what we call the " Warrior class of ship." The attention of the Admiralty was also directed to iron- cased ships of war by the late Captain Moorsom, R.N., C.B., a very talented and valuable officer, who in 1857 printed a j)amphlet entitled, " Remarks on the Construction of Ships of War and the Composition of War Fleets." In this pamphlet he proved the feasibility of taking the two upper decks and tiers of guns off the three-decked ships of the fleet, and converting them into iron-cased frigates, protect- ing the remaining lower deck with a covering of iron-plates 4 inches thick. He advocated, however, the construction of new and superior ships on this design. He said, " Our present line-of-battle ships should be replaced by iron-cased ships, carrying one tier of heavy guns, from 15 to 18, on the broadside. If intended to act against mere wooden ships, they should be armed with shell guns ; but of course other nations would soon adopt iron-cased ships, and conse- quently all ships would be armed in chief with the heaviest solid shot-guns. Our 95 cwt. 68-paunder is probably about as heavy a gun as can be worked with facility on board of ship ; but speaking generally, I should say the guns for a ship's armament should weigh about 100 cwt., and throw a missile of about 60 or 70 lb. weight if a solid shot, as that may be handled by one ordinary man ; or of about 100 lb. weight if a shell, as this can be handled by two men. As guns of this size would require spacious platforms, the ships should not have less than 50 or 55 feet beam, and it would of course be necessary to make them long in proportion to their beam, in order to obtain speed under steam. The difficulty of applying iron-casing or armour, which must of course extend considerably under water, to copper-bottomed ships, would be overcome ; but possibly, for other reasons, it might be found desirable to construct the frames of such ships as I have indicated of iron instead of wood." " With regard to the class of frigates, it would be more difficult to furnish them with armour, and probably frigates would resume their legitimate place of scouts or attendants on the ships of the line, instead of as at present, rivalling them in size and power ; but perhaps it would be found that a ship carrying a very fevi heavy guns protected by iron parapets, would be a more valuable vessel than our present first-class frigates." " With regard to corvettes, gun, and mortar vessels, they would remain as they are, and trust to distance for impunity, or to local advantages to be of service ; but the ship of the line must command the ocean." He did not receive any immediate encouragement; but in the year 1858 the first Lord of the Admiralty, Sir John Pakington, and the Secretary of the Board, the Right Honourable H. Corry, succeeded in obtaining a decision in favour of building a large vessel on the design submitted by Mr Scott Russell in 1855, for a smaller vessel ; this vessel is " The Warrior." Though a change of Ministry shortly thereafter caused a change at the Board of Admiralty, this order was soon followed by one to construct two similar vessels, but of less power and tonnage — " The Defence" and " The Resistance." A second Warrior, "The Black Prince," was also shortly afterwards commenced. The success of all these vessels has been almost beyond expectation. The Warrior, when fully weighted, realized on the race-course at Spithead a speed of 14'354 knots per hour. The Black Prince made rather less speed ; she was equally stored for sea, but she carried somewhat greater weight, being a few inches more deeply immersed. This must have arisen either from the plates and angle iron of her hull being in a trifling degree tliicker, or from the mode of her construe- 25 History. tion causing greater weight. She is clinker built, that is, the plates of her bottom below the armour-plates overlap each other at the edges, instead of being carvel-built, that a.d. 1862. is, with the plates laid edge to edge and made flush, as in The Warrior. The Resistance at the race-course made a speed of The Re- 1 1'832 knots per hour, a speed far above that of merchant sistance. ships engaged in ordinary traffic ; and in her late cruise in the Baltic she proved herself to be very easy in her motions in a sea-way. The whole of these vessels are iron-built ships, divided Advantage' into many water-tight compartments, both horizontally and °^ leaving vertically, especially fbnvard and aft, where also they are ^ °^^ divided longitudinally. A portion of their length, at the without bows and at the sterns, are not protected by armour-plates, armour- but are built with frames and sheathing similar to a strong plates, well-constructed merchant ship. The whole of the space amidships is protected by a casing of 4|-inch armour-plating, with athwartship bulkheads of armour-plating before and abaft the unprotected portions of the bow and the stern. The importance of saving weight in the extremities of a ship both as regards the strain brought upon the material by the want of a due apportioning of the weights to the dis- placement that is to support them, and also as regards the performances of the vessel at sea in pitching and scending, as will be pointed out hereafter, is very great. If the rudder be protected, or other means, protected from shot, be pro- vided for steering the ship, in case of the ordinary rudder being earned away or injured by shot, no bad consequences can possibly follow to endanger any iron ship such as those under consideration, however much their bows and their sterns may be battered. The true way of looking at these portions of ships so constructed, is to consider them an assemblage of moderate-sized iron water-tanks, with the exterior tanks made to the forms of the bow and the stern. All the guns in use, and all the men in time of action, should be within the armour-plating. Other large iron-cased vessels are also now under con- struction, completely encased in armour from the bow to the stern. If the views previously expressed are correct, this is to be regretted, as tending to weaken the ships, and to make them uneasy in their pitching and scending at sea, and also as being an expenditure on parts which it is argued may be looked upon merely as a false bow and a false stern, to enable the ship to pass through the water with the least resistance that we know how to obtain. This may be illustrated by what was done by Mr David Napier, an engineer who has originated many brilliant conceptions, many years ago on the Clyde. When a steamer brought out by him did not realize the speed he expected, carrying a heavy wave at her bow, and was beaten by her rival, he added a false bow of thin iron plate outside the bow of his wooden steamer, scarcely reaching above the water and being finished at the extremity in the form of a dolphin. This bow answered the desired purpose in every respect ; and it is considered that the unprotected bows and sterns of our iron-cased iron ships, with their water-tight shot-proof bulkheads, may be looked upon in the same light, wherever such bows and sterns are attached. The dockyards are at present engaged in cutting down Wooden two and three decked ships of wood, and coating then, with Ships iron- armour-plates, as proposed in 1857 by Captain Moorsom,*^** and so as to form vessels similar to those which are being constructed by the French. Another anda smaller class of protected vessels are also Of asmallei now being constructed of wood, with the armour-plates class, made thinner at the extremities, al^er a design produced by Mr E. J. Reed. The importance of this class of vessels is obvious ; and it is to be hoped that they may realize all the expectations formed of them by their designer. Ships are also being cut down and coated with arraour- D 26 SHIP-BUILDING. History, plafc and prepared to receive turrets or shields according to ^^-v— ^ the design of Captain Cowpur Piiipps Coles. He places one A.D. 1862. or more guns on a turn-table similar to thoseuscd on railways, with a perpendicular wall of .armour-plate, with wood backing Cupola rising from the circumference of this turn-table, protecting Shipi. the guns and the men working them, and revolving as may be desired. The turn-tables are worked by machinery, and the heaviest shields yet proposed will revolve with facility with 8 men at the handles. This promises to be a most important invention ; and it may be considered that by it Captain Coles has solved the problem of how to work the lieaviest guns on board ship or on forts with the greatest ease, and with protection to the men, so as to give them confidence, witho\U which there will be no effective firing against a powerful enemy in action. The French took active measures for the construction of a fleet of iron-cased ships at an earlier date than the British Admiralty. The views entertained by them were the same as those enunciated in this country in 1857 by Captain Moorsom. Their first vessel was La Gloire, a first-class Hislor frigate. She is built of wood, and is stated by Mr Scott *—- ^^- Kiissell to have been constructed on the type of the well a.d. 186 known and very successful French screw ship of the line, !"» Gloii the Napoleon ; but on taking as his type the Napoleon cut down, the naval constructor made all the chiinges in the design which the altered circumstances required, and the (jloire is even faster than the Napoleon. She is 252 feet 6 inches long between the pcr|)endiculars, and 55 feet beam, draws upwards of 27 feet of water, and has obtained a speed of 1 Ij knots per hour under steam. She carries her ports about 6 feet 6 inches out of water, and her armour at present is said to consist of 34 rifled guns, 54-pounders, and two shell guns. Being of wood, she is armour-plated from stem to stern. She is built with an upright or rather receding stem, prepared for nmning down an opponent. The annexed wood-cut is made from a hand-sketch of her, made by Mr Cimningliam on the spot, after she had been tried. Her engines are of 900 horse-power. The Warri From the sketch, it will be observed that the foremast is lier rolling. The rigging is carried very far aft, probably very far aft, and that the mizenmast is very far forward, for the purpose of supporting the masts, in the event of the The position of these masts, therefore, will tend to ease the ship running stem on against an opponent, and having her ship very much in pitching and scending; and the moderate way stopped, height of the roasts, and their simple rig, will tend to ease The Warrior and the Black Prince, the English iron- SHIP-BUILDING. 27 cased first-class Trigates, are built of iron, as before stated. 'They are 380 feet long between the perpendiculars, and about 420 feet long over all, 58 feet beam, and 41 1 feet deep from the spar deck, and of 6173 tons burden. The armour-plates with which they are sheathed are 4| inches thick. They are not laid directly on the iron sheathing of the ship, but teak, 1 8 inches thick, is interposed between them and the sheathing, with a view of supporting the armour- plates by the elasticity of the wood behind them, and also to prevent the bolts of the sheathing from being started by the concussion when the plates are struck by shot. The con- struction will be understood by the annexed section of the Black Prince, and by the explanation of the mode of con- structing iron ships, as given in the portion of this article devoted to practical shipbuilding. The engines of these frigates are of 1250 nominal horse-power. Section of Black Prince. They are constructed to carry 40 guns, 34 on the main deck, all 68-pounders, and on the upper deck 2 pivot guns, 68- pounders, and 4 Armstrong guns. The ports are about History. 9 feet above the water when the ship is ready for sea, with ^■^^/■""^ everything on board. The thick armour-plating does not a.d. 1862. extend (or the whole length from stem to stern, but for aT*ie War- length of about 213 feet in the middle, and for a height of"°'' *"'* 22 feet vertically, 16 feet above the water-line, and 6 feetp^-^^^ below it ; 26 guns are protected by this extent of armour. Near where tlie arraoui'-plating ceases, and a short distance H ithin it, water-tight bulkheads, protected by similar armour- plates, are carried across the ship. The finely formed portions of the bow and the stern are constructed in the same manner as those of any strongly-built iron vessel, as explained hereafter, when treating of practical building. They are divided into a great number of water-tight com- partments, the bulkheads or divisions running fore and aft and athwartships and horizontally. On a minute examina- tion of all the details, great credit will be found to be due to the designers for the way in which the safety of the ship, and all the varied requirements of a man-of-war, have been pro- vided for, and also for the way in which the many contin- gencies to which such ships are subject have been provided against. It is quite evident that every one, conversant with the subject of naval architecture, and the various con- tending influences that have to be met, who will examine into the details of the Warrior or the Black Prince, must be satisfied that great thought and consideration have been given to the subject, and that, on the whole, the conclusions arrived at have been judicious. Though these vessels are Their not specially prepared for it, they are equally able with La P°"*r of Gloire to run down an opponent, if a desirable opportunity j""""!? to do so should present itself. It is argued by some, that opponent, the English ships are too long for this purpose, and that they will therefore take too long a time, and too much room to turn, to be able to run down any vessel that sees their in- tention beforehand ; but the difference between them and La Gloire in this respect is not so great; and if they are not fit, neither is La Gloire. Any one who has ever been present at a boat regatta, and has seen a duck or punt hunt, will know well, that a sharp and fast man-of-war's gig, be it a little longer or a little shorter, is not the class of boat that will catch the duck ; and no more would La Gloire, under similar circumstances, get a chance of running doxvn our gun-boats, if we were to surround her with the number that might be built for the sum of money that such a vessel as she is must cost. Frigates, corvettes, and gun-boats, might be constructed at very moderate cost, of plates sufBciently thick to make them safe against all known shell, and there- fore against fire ; and with sufficient divisions to make them almost unsinkable by any number of solid shot likely to strike them ; and they might be armed with guns, or rifled mortars, or carronades of extraordinary calibre, with both guns and crew safe within Captain Coles's shields, in the larger vessels at least. Gim-boats so constructed and so armed would be serious opponents to these huge mail-clad ships. They could also be supplied with buoys carrying pieces of rope or chain, prepared to foul the screw pro- peller of their great opponents, and which, if thus deprived of their power of motion, would be very much at their mercy. The stems of the Defence and Resistance below water project forward beyond the line of the knee of the head, which forms an exterior or false stem beyond the real stem, which latter rises up perpendicularly in the interior, and is supported by a fore-and-aft bulkhead. They are therefore eijually prepared with La Gloire to run stem on into an adversary. It is not to be supposed, that in the event of a general close .iction of two fleets, such vessels would "run a muck" at full speed into the enemy's fleet, armed, as of course every vessel would be, with at least one or more guns, capable of injuring them in their weakest points, which would no doubt be known ; and if the fleets once came to close action, and the ships were with- 28 SIIIP-BUILDINO. Iliitorv. A.P. 1862. Timber backing. British Jlerchant Shipping. out way, all chance of running each other down would for the time be at an end. It is not the lcf,ntiniate purpose of tliis article to discuss naval tactics, but these few remarks will perhaps be |)ardoned, as bearing \ipon tlie question so important at this time, as to what class of vessel it is most judicious for this country to build, in addition to a sufficient number of mail-clad ships, to meet tlie extraordinary, and (as at least one high authority' thinks) perhajis the passing circumstance of the construction of a certain number of ships of tills class by the present Emperor of the French. It is not proposed here to discuss the disputed question of the relative value of the system of interposing a mass of timber between the armour-plates and the sheathing of the ship, compared with making the armo\ir-plates themselves thicker, or using the weight rendered available by dispensing with the wooden sheathing in adding to the strength of the hull of the ship. It is evident that the introduction of this element of decay is much to be deprecated, if it can possibly be avoided, and the fact, true by mathematical deduction, and corroborated by the experiments at Shoeburyness, that the resistance of iron plates is increased in proportion to the squares of their depths, seems to indicate that increasing the thickness would be the proper course to pursue. On a ship clothed as the Warrior, armour-plates of 6 inches thick could thus be used, if the timber backing were dis- pensed with, without any increase of weight, and the resist- ance, as compared witli that of a 4^-inch plate, without, however, reckoning anytiiing for the timber backing, would be nearly double. Mr Fairbairn of Manchester had a target constructed to test this principle ; but the bolts seem to have given way from the want of any elastic medium to take off the vibra- tion caused by the force of the blow of the shot. Mr Scott Russell also had a target of this kind constructed, which re- sisted all the attempts to penetrate it with any of the guns in use in the spring of 1862. Twenty-eight shots, some of them of 150 ami IGO lbs. weight, fired with charges up to 50 lbs. of poHikr, some of them steel bolts with square heails, and also every ordinary description of missile, have been fired from the short distance of 200 yards, and have failed to pass through it. Mr Whitworth's new bolts and gun have not yet been tried against it. Mr Russell is understood from the first to have been the consistent advocate of excluding wood from the structure of armour-plated vessels, and his target carries that principle into effect. The armour-plates are themselves only 4\ inches thick ; all the rest of the structure is of iron-plating, incorporated with, and contributing the whole of its strength to, the structure of the ship, so that no weight of material is wasted in mere backing. The structure of the ship here consists of two plates of an inch thirkncss, together with the Extract from Return of British Merchant- Shijiping by the Ref/istrar-General of tlie Board of Trade. layer of " continuous riveting," which forms another char- History, acteristic of the plan. This " continuous riveting" of a j)re- '^«»,^^,.».. pared edge on one plate over the edge of the adjoining pl;>teji.D, 1862. has the effect of binding the armour-plates so firmly in ihtir place, that though they may be siiaitered by shot, the parts do not fall away. There is, however, a strong feeling, in con- sequence of the effect produced by the 300-pounder Whit- worth gun lately tried ( 1 862), that a wooden backing to pre- vent the splinters going into the ship cannot be dispensed with. The present year(l 862) will be noted inthehistoryofships of wax, as the year in which iron-[)lated ships were fn-st brought into actu.al engagement, as has been the case in the course of the American war now raging. The Southern States having possession of a very fine frigate, the Merrimae, tp|,g of upwards ot 3000 tons burden, cut her down and coated her American sides with iron, and built upon her at a sloping angle so as frigate to resemble the roof of a house, using such bars of iron as Merrimae. they could most readily obtain. Though protected in this rude manner only, she was tbimd comparatively invulner- able by the guns then in use in the American navy, and she destroyed in a very short time two fine wooden vessels, the Cumberland and the Congress.belonging to the Northern States. She destroyed the former by running into her, and the latter by firing shell into her, creating the most dread- ful carnage and destruction. She was, however, soon met by a formidable opponent, the Monitor. This vessel 'Sxhe M„ni. composed of two rafts or vessels constructed of iron, the one tor. laid upon the top of the other, and projecting over it so as to protect the sides of the lower vessel from injury. On the deck or surface of the raft is placed one of Capt. Coles' revolving shields, as before explained carrying two, evidently from their effects, very heavy and powerful guns. Her sides were not above one foot above the water when brought into action ; and the advantage of having great facility in turning, so as to be able to choose her position, was very evident according to the account given of the engagement. The dimensions of this vessel are as follow : — Length of upper vessel, .... Beam of do. do. . • • . Depth of do. do. . Length of lower vessel, .... Beam of lower vessel at junction with upper vessel, Beam at bottom, ..... Depth of lower vessel, .... Diameter of turret inside, . . . Height of turret, . .... Diameter of pilot-house, .... Height above deck, . . . ■ >^ » It will now be necessary to return to the mercantile ma- rine, and notice shortly the progress made therein within the last few years, leaving this part of the subject, however, to be more largely treated of under the head of " Steam-Ships." 172 feet 41J 5 124 34 18 a 20 9 6 Year. IJ limber and Tonnage of New Vessels Utiiltand Registered in the British Empire in each Year. Total Number of Registered Merchant- Vessels belonging to the British Empire in each Y'ear. Men. Sailing Vesselfl. 1 Steamers. S.iiling Vessels. Steamers. Total. Nami er. Tons, Namlter. Tons. Number. Tons. Number. Tone. Number. Tons. 1840 1845 1850 1855 1904 1183 1381 1319 285,289 154,783 229,603 305,113 77 73 81 263 10,639 11,9.50 15,527 84,862 28,138 30,805 32,938 33,782 3,215,731 3,582,859 4,045,331 4,842,263 824 1012 1350 1910 95,807 131,202 187,631 408,290 28.962 31,817 34,288 35,692 3,311,538 3,714,061 4,232.962 5,250,553 201,340 224,900 239,283 261,194 Progress of In the merchant-service, the screw, for some time after Screw- the trials of the Archimedes and the Rattler, though they were generally looked upon as prognosticating success, made but little progress. A company trading to Rotterdam, Messrs Laming and Company, were amongst the first to Ships in Merchant Shipping. adopt it ; and the mercantile marine owes much to their enterprising spirit in this respect. Their vessels were very successful, and attracted much attention from the time of their first introduction ; and doubtless much of their immediate success may be attributed to men of high stand- 1 The late Sir Howard Douglas e.vpressed this opinion in a letter addressed to the Institution of Naval Architects, and in which the writer is inclined to agree with him, though differing from him in his opinion in favour of wooden ships. SHIP-BUILDING. 29 History, ing in their respective professions of ship-biiilders and ^>— vy— -^ engineers being employed in their construction, and being A.D. 1862. 'sft unfettered to worlc out the end that was desired. From that time screw-vessels, constructed of iron, began rapidly to supersede paddle-wheel steamers and sailing vessels, especially for the conveyance of perishable merchandize, such as fruit and provisions ; and the great capability of combining sailing and steaming which the screw affords, is causing a contin\ied and rapid increase of auxiliary steamers. The preceding table of the merchant-shi('ping of the country shows the extent to which the substitution of steamers for sailing vessels is taking place. Reference has been previously made to the beneficial influence of the yacht clubs throughout the country. The English yachts were supposed to be unrivalled in speed ; and in 1851 a challenge cup was given, open to the whole world for competition. A yacht from America, however, came over to this country, and carried off the prize. She soon showed such great superiority that the favourite English yachts at once gave up the contest, and it appeared likely that she would be allowed to walk over the course. To prevent this the late Mr Robert Stephenson entered his yacht, the Titania, built by Mr Scott Russell, to com- History, pete with her, and thus give her an opportunity of showing ^^— v, — ' the extent of her superiority, and on what [loints that supe- a.d. 1862. riority was greatest. Representations of these t«o yachts are given in Plates V-^. & VI., and their relative performances and qualities will be examined hereafter. Though the intro- duction of steam has done much to lessen the interest taken in yachting, yet it is to be hoped that the valuable encour- agement given to naval architects, and to the maritime predilections of the country by yachting clubs will be con- tinued, and that many will follow the example already set by a few spirited men, of placing a small amount of auxi- liary steam-power in their yachts with screw-propellers. This is done without impairing their beauty, and renders them certain in their movements when desired. In connection with this subject, and as a means of form- Ro*ing ing a taste for it, the rowing and racing boats of the youths Kacing at public schools, and of the young men at the universities Boats, and elsewhere, may be mentioned. The following may be taken as the average performances of such boats at the pre- sent day. The drawings and the dimensions are from boats built by Messrs Searle and Sons of Lambeth, London : — Randan Gio, 28 Feet Long. APleasare Boat for three Pairs of ScuUs; or for a Pair of Scalls in the middle, and with a single Oar or S«nU forward and aft in addition when desired. ^><PI A ScDLLiNO OCTBiGGEB, 30 Feet Lon^. New Style for Racing ia Smooth Water. -z^ Eigbt-Oabed Octtbigges, fiO Feet Long. New Style for Racing in Smooth Water, _^ ^ ^i!N=_ _^lk_ =^^ A _>l\_ _.ik. Eight-Oabed Cctteh, 60 Feet Long. The Old Style of Racing Boat, or for Water for which the Outrigger i3 considered of too slight a Bnild. Description of Boat. Length. Breadth. Depth. Weight. Maximum speed per hour in still water. Outrigger Racing Boats- Feet. 32 3-t 42 to 45 50 to 54 57 to 65 30 32 40 to 42 45 to §0 54 to 58 23 to 25 27 to 30 40 to 42 55 to 48 54 to 58 Ft. 1 1 2 2 3 3 3 3 3 3 3 3 3 3 In. Ft. 10 to 1 3 tol 10 to 2 to2 2 to 2 4 to 3 4 to 3 6 to 3 6 to 3 6 to3 6 to3 6 to 3 4 to 3 4 to 3 2 to 3 In. o 6 3 4 4 6 6 8 8 8 8 8 6 6 4 8i in. 9 to 11 in. 1 foot. 1 .. 1 » Ft. In. Ft. In. 1 Otol 2 1 to 1 3 1 1 tol 3 1 1 to 1 3 1 1 to 1 3 1 foot 4 in. 1 ,, 4 „ 1 „ 3 „ 1 „ 3 „ 1 ,. 2 „ lb. 30 to 40 45 to 55 100 to 112 150 to 190 280 to 330 55 to 60 100 to 140 224 to 280 336 to 376 520 to 600 180 to 200 200 to 224 250 to 300 350 to 400 560 to 620 Miles. 6 6} to 7 8J to 9 9 to 9J 9J to 10 6 7i to 8 8 8^0 9 4 to 41 5 6ito 7 7 7J Racing Boats of the old style — Sculling boat Randan wherrv Six-oared cutter Kight-oared cutter The lighter kind of Pleasure Boats — Eicht-oared ciff To pass from these diminutive but beautiful specimens of naval architecture, the last great work which requires to be noticed in this brief outline of the history of the rise and progress of ship-building is the construction of the Great Eastern, Plate VIII. The dimensions of this vessel, as given on the plate, are so far beyond those of ordinary vessels, that it is necessary to draw particular attention to them. Her performances will be discussed hereafter, but the results predicted by science as to her speed, with a given amount of steam-power, appear to have been realized ; and this being the case, it is evident that her success or failure commercially must depend entirely on the profits, reckoned on the proper cost for the construction of such a vessel, and on proper eco.ioray of management. 30 SIIIP-BUILDING. Cklcala- tloDS inci- dental to designing a Ship. marks OD Tlitory. DESCUimON OP THE MAKSER OF PFRFOUMING THE CALCU- LATIONS IKCIDESTAL TO DESKIMNG A SniT, WITH INVES- TIGATIONS OF SOME OF THE PRINCIPAL ELEilENTS OF THE DESIGN. The labours of the numerous men of science who have devoted either the whole or a |)ortion of their attention to the various problems embraced in the theory of ships, have left but few of its alistract principles uninvestigated ; most of the proportions of a ship have been examined, and the la"S on «hicli they de[)end clearly defined, either by the aid of mathematical demonstration, or by experimental in- duction. '1 "here are, however, some (iiiistions which, though sound in theory, still depend on the results of physical experiments for perfecting their practical applica- tion. Many of the elements of naval cnnstruction are dependent on the known laws of nature ; and it may now be said that the principal difficulties of these are surmounted, and are familiar to the instructed naval architect. These are of themselves sufficient to insure the attaiiunent of a certain and considerable degree of excellency in a ship, to give it a preponderance of any given qiiality, to discover the causes of anv bad quality, and to |)ointout the means of providing a remedy for the faults discovered. The forces which act upon a ship in motion, in a fluid, even though the fluid be at rest, are as yet but imperlectly defined by mathematicians; and the elements of naval con- struction dependent on the laws regulating them are, there- fore, less known and less certain in their application. The form of a ship's body need not, however, remain imperfect, because the curve of the solid of least resistance is uncer- tain, since enough has resulted from the consideration of the nature of that solid to prove its inap])licability to vessels in general; and theoretic perfection ot the science in this particular would, therefore, be of no practical utility. A very unphilosophic mode of reasoning is frequently applied to the question of the application of the exact sciences to naval architecture. It has been argued, that because men without any great amount of scientific know- ledge have produced good ships, therefore the exact sciences are not necessary for the advancement of naval architecture. In such instances the success has resulted in some cases from chance, in others from induction after a succession of failures, but more frequently from the results of observa- tions on other good ships ; and in all these cases, wherever the changes from a foregoing example have been of any inoment, the result has been a matter of dmibt until tested by trial after completion. It is true that the scientific naval architect cannot effect, by any mathematical process, the synthetical composition of a perfect ship, but he ma}', by the application of the ])rinciples fully established and known to him, produce one with a full confiiience of its possessing a preponderance of those qualities which he has considered it desirable that it should possess. The mistake .is in the assumption that men of science consider that the theory of naval architecture is already perfected, and is a definite science, whereas this is far from being the case ; and it can only be advanced gradually to a greater degree of perfection by an analysis of the actual performances of ships at sea, collected and registered, and the abstract sciences then brought to bear upon them. In every science a perfect theory is the result of the perfection of the science. The time is gone by, when a theory was first formed, and facts were then warped or twisted to suit the pre-con- ceived theory. It is now proposed to proceed to show, in as concise a man- ner as possible, the method of perUirming the calculations necessary to determine the essential elements of the design of a ship's body, and which are required in the course of pre- paring the original draught or di-awing. The rules to find the areas of plane figures, bounded by straight lines and Calcnla- curves, will first be given ; and afterwards those for finding *'"■>" '°ci- the volumes of solids, bounded by planes and curvilinear ^*')'''', *" ^ ' desitrniniF »i"»ces. „ s^hip." To find the area of a plane area, bounded by straight lines and a curve. AllT. 1. If the area is symmetrical in regard to the line .A, A„. S'T'on'a thttt is, if a line A, A, can be found to divide the area into two rules for equal parts, as A, o, and A, 6, ; — finding the Divide this line (or axis) into a convenient number of equal areas of parts, taking care to have an tven number of such parts, then draw plane sur- tho lines A, a,, Aj a,, A, dj. &c., A, a, at right angles to the line faces. A, A„, through the points Ap A.^, A3, Ac, A„, and meeting the curve in the points a,, a,, a^, &c., a,, these lines being called ordinates ; The second, Aj Oj, fourth, Aj a^, &c., are called the even ordi- nates. The third A3 a^, fifth A^ a^ &c., are called the ODD ordi- nates (the first and last being omitted). Then, if these ordinates be measured on the same scale as the equal distances A, A„, A^ A3, &c., the following rules will give the area of the figure : — Rule I. — To the sum of the first and last ordinates addRaie I., four times the sum of all the even ordinates, and twice the<:omnv>n\j sum of all the ddd ordinates (omitting the first and last) ; known as^ multqih) this final sum by the common distance between the l"'"^',^"" * ordinates, divide by 3, and the result will be the area {nearly). Note 1. — The following is the usual demonstration given to this First de- rule, which is due to Thomas Simpson, who was Professor of Mathe- monstra- matics at Woolwich, about the middle of the last century : — tion to ,1^ n -■ "Simpson's Rule " for finding the area of a curvilinear figure. i'i. Referring to fig. 3, i'ut A, a, =«!,, A^ "3 = "a- *<'•> A, a„ = o.) ■h Oj =: a.,, A3 A| Aj ^ .Aj A3 := A3 A^ We suppose a parabolic curve, the equation to which is y = A 4- B X -)- C i2 (1) to pass through the three points Oj, a^, a^ ; for since (1) contains three arbitrary constants A, li, C, we can, as is well known, make the curve (1) jmss through three given points. Now, since (1) passes through a^, we know (if A, be taken as origin) that y = «, when X z= ; when x ^ A, y ^ o^ ^= A^ a^, and y ^^ a^ = A3 a^ when x = 2h; hence we have the following equations :— «, = A . . (2) o, = <t, -h B i -(- C A2 . . (3) «^ = Oj + 2 B A -H 4 CA^ . . (4^ between (3J and (4) we readily determine B and C, viz.: — B_. *«a- *»-3' c=: 2A 2A' (0) (6) Introducing these values into (1), we obtain y = «i + i'-i-'^-^' 2A ix-H tc, — 2 «, + a, But by the Integral Calculus we know that the area of a curve ia represented by f'y dx, taken between proper limits. In the present case thesa / limits are and 2A. , area of A, a,, or y^%.x = 2.,A+(to_-^-),. SHIP-BUILDING. 31 Calcula- tions inci- dental to designing a Ship. («.J-2«2^^^, \ Ti / , , \ f, ordinate) ; muhiplif this final sum hy three times the com- Calcula- "^ — ST. l/i', or area of A, a, =— I a,+«, + 4a., I, after ,■ ' , ' .,■' ,. , •',, ... , ... . . 6A« y ' ' 3 y ^ i J ' -y jiiQii (lislanee between the ordinates, dti-ide the product by tions inci- 8, and the result will give the area (nearly). j— --i •- a little reduction. Again, by making a parabola of the same form as (1) pass through the three points a^, a^, a^, we obtain a result precisely similar to we suppose a parabola, the equation to which is dental to designing Note 2. — To obtain what naval architects call the " Second Rule," a Ship. the above, that is, area A, "6=3(''3 + '«S + ^°'4"'>'""^ area A^ a, =- («5 + «.-|-4«^), area A, _2 1,= - (a, _ I + «, + 4«, -J ). Adding these areas we find (I.) Area A,a,=:-2 | <'i + », + 4 (aj + a, -l-«6-l-&c., a,.,) + 2(«3 + «5,&C.,«,^l)} It ought to be observed that in the application of this, and the following rules, an odd number of ordinates are always to be taken, and the nearer the ordinates are taken, that is, the less the common interval, the more nearly will the final result approach the true area of the figure. Second de- For those who are not familiar g, monstra- with the Integral Calculus, another tion to demonstration may be obtained, aa "Simpson's follows : — Rule," Through the point Uj, drawa tan- without gent to the parabola which passes the aid of through a^ a^, a^, and produce A, the *' Inte- a^, Ag 03, to meet this tangent in gral Calcu- the points c and d ; join a^ a^ ; in- lus." tersecting Aj a^ in 6 ; through a, and c draw c e and aj /parallel to A, A3, then it is shown in all works on Conic Sections that a^ a^ is pa- rallel toed. Hence by Euc. 1. 35 — Paral™ a, rf = paral?^ cf, because they are on the same base and between the same parallels A^ c^, A3 d. Now, Aj 6 = — ! — '—^ — 3 — ? and A, a^ = ctj 2 2 .•. area of parabola a, ba^ a^ o, := ^paral? a, d = ^paral? e/i o 3 = |( "2 - "'"t,"-* ) X2A, since AiA3 = a/=2/i. Also area of trapezoid A, Oj a^ A3 = f — ' ' ^ ^ I -^1 -"^s Adding these two areas, we obtain that of the whole figure = 3- I «i + ^«2 + "3- } By repeating this process for the area of the figures A3 a^ a^ <jj "2 A, Fig- 4. f Aj !, = A + B. + Cx» + Dx> (1) p^^„„. to pass through the four points a,, a,, a, a^ (fig. 3), the four con- stration to stants being determined by these conditions ; that is, when x takes " Second the successive values o, A, 2A, 3A; y becomes «,, a,^, oj, and a^; Rule." hence the following equations : «i=A (-)'•' whenj:= o y = «, «.,-«, =BA-t-CA= -I- D/i' (3) •.• when X = 4, y = «, «;,-«,=2BA + 4CA»-|-8DA' . . . (4) V when « = 2A, y = a, «,-<t, = 3BA-)-9CA='-f 27DA^ . . (5; •.- when* = 34, y = a, (4)-(3)x2 gives 03 -2«,j-f«, = 2CA»+6DA' (6) (5) + (3)-(4)x2gives<i.,-2«3-H«jZ=2CA»-f 12DA» (7) (7)-(6)gives6DA3 = «,-3=3-f3«j-a, (s) From (6) and(8)2CA2 = a, H- 4*3 - 5*, -^ 2«, (9) From (3), (8) and (9) 6BA = 2«,-9«3 + 18«2- lU, . . . (10) But area, or/ ydx=/ [a + Bx + Cx' + Dx= j dx (we write the limits of x, and 3A, because at A, , i is o, and at A„ X is 3A). *^ .■. Area A 3A I 8A + 12BA4-24CA=-f54DA». I e a' Introducing the values of A, B, C, and D, given by the above equations, we find, after some obvious reductions, Area A In like manner, by making a curve similar to (1) pass through the points a^, a^, a^.. ct^, we have Area A Area A, 3A / „ „ 1 7"io=g |^ + «io + 3o!„-f 303 j '3h j+a«-l-3o:,_„ + 3a Adding equations (11), (12), (13), &c., (N), we get -)- a, -1- 3 (a, -I- 013 -f ttj -f «j -t- if. (II.)AreaA,a. = ^|{ (12.) (13.) + «.- '1 It will be seen from the foregoing method that we may mako a Method of curve of the form obtaining y = A + Bjr-(-Ci«-fDx3.)-Ej:*+&c., Kr„., otherrules. pass through n points, taking care that the equation shall contain n arbitrary constants, to be determined by the conditions that the curve may pass through a,, Oj, 03, a^. &c., a„ (fig. 3, page 30), when Aj, &c., cic, and adding the results, we obtain for the whole area * """^ V ^^e respectively a: = o, x = k, x = 2 k, &c., *:= (n-l) A, Aj a„ the same result as before. If «2 were less than Wj, the parabola would be convex towards A, A3 ; but the same rule would still apply, for A^ft would then be " Second,' or " Jth Kule." y = «„ y = «2, y = aj, &c., y = «„, "p «2' '«3' *<=■> *"<' *) having the same interpretation as before ; the ordinates being taken at equrl distances apart, as on this hypothesis the calculation of the area is much simplified. Rules obtained after this manner for any given number of ordi- nates will, in general, give us the area of the figure more correctly than if we employed the preceding rules, because in the latter case we suppose a continuous curve to pass through the given points, whereas, in the former cases, we have a stri« 0/ curr« passing Rule II. — To the sum of the first and last ordinates, add through the given points, and the curvilinear boundary is itself THREE TIMES the sum of the second, third, fifth, sixth, eiahfh, ^'.'PPO^«d '<> be a continuous curve. Such rules (for many ordinates) 7linth, &-C., ordinates, and T-SVICE the sum of the fourth, ^^ZTJ''J'. f r'/""'. "f !«!'«'"• '". obtaining them and entaU .1 . .L .1- . .1 « J- . I ■[.■ .1 , ' almost as much labour in their application. In the latter case, seventh, tenth, thirteenth, S)C., ordinates (omitti?ig the last moreover, logarithms will assist us to some extent, and in the former, equal to —„— — »j, and this introduced into the form for finding the area of the parabola, leads to the same result as that already obtained. Another demonstration, on different principles, will be given in Note (3.) • The equation to a parabola being y- = 4 m i, or y = 2 mj rf Area, or/"y dx = 2m} C' xi dx=^ = l^by (1) ixu 2 .•. area =: -—. ^ - circumscribed parallelogram, 00 (1) 32 SIIIP-BU CalcaU- there are some remarkable properties of the natural numbers con- tions inci- necteil with the determination of the arbitrary constants, and on dental to which perhaps more light may hereafter be thrown. I have re- iesigning marlted some curious properties of the squares, cubes, &c., of num- a Ship, bers connected with the eliminations. There can be no doubt that i_ / niany other rules of a very simple kind may be obtained on the ^ condition that any number of the constants may disappear from the general equation, » liich is equivalent to as many conditions. Rules for Emerson, in his Arithmetic of Infinite), published by Nourse in different the year 1767, gives the following formula;, obtained by the fore- numbers of going processes— from one up to nine ordinates. ordinatet. Area = A«i for one ordinate. ^z— (a +«2) for two ordinates, (1)= ^ («, + «3 + 4«.j) for three ordinates. (2) = ^/.., + «j + 3(«j + «.j)| . . . . for four ordinates. (3) = ^|7(«i + «4) + 32(«, + ccji + 12o3| for five ordinates. (4)=^ {l9 («, + «,)+ 75 (<^ + «j) + 50 (», + <.,)] six do. (5) =z — - I 41 («, + «,) + 216 (., + «,) + 27 («3+«5)+272 .. } for seven ordinates. (6)= Sh- f 751 (., + «.) + 3577(«j+«,) + 1323(«j+«5)+2989 ((ij + B,) I for eight ordinates. ^7) = _li_/ 989(«, + «3) + 5888C«, + «„)-928(«3 + a,) +10496 (a^ + a5)-4540«5, I for nine ordinates. Where extreme accuracy is required, these may be combined in inch a way as to give the area. For instance, if there were fif- teen ordinates in a figure, (5) and (7) may be combined, remember- jng that the last ordinate of (5) becomes the first in (7), Sc, &c. When seven ordinates are considered sufficient, the following elegant rule, due to the late Mr Thomas Weddle, of the Military College, Sandhurst, may be employed : — Kule ITI., Rule III. — Wien seven ordinates are employed.^ To jive orMrWcd- times the sum of the kvkn ordinates. add the fourth, or die's Uule. middle ordinate^ and all the odd ordinates ; multipli/ this sum by thkee tisies the common distance between the ordi- nates, divide by 10, and the result irill give the area (nearly).' Note 3.— The Calculus of Finite Differences may be advanta- geously employed to approximate to the areas of surfaces, lengths of curves, volumes of solids, centres of gravity, moments of inertia, 4c. For triple integrals may generally be reduced to integrals of the form I udx Applica- vphereu represents a function of i, or /(i), as it is usually written, tion of the and x^, x^ represent the limits of the integral. Calculus of Now, if we suppose a: to vary by the constant difi'erence Ar, we Finite Dif- x , .. ^ v »i. i <■ ferences to may suppose * = — • and if «i, "j, «3, &c., «„ be the values of u the method ^j^^^ x = o, 1, 2, 3, ic, n, we have, by Taylor's theorem, of finding , theareasof ^, ^^ +..(,_l)^_+,^,_l)(,_2)^+&c.,..(l.) curvilinear i ■ > '1-2 l .^ •> figures. jjuj ^ hypothesis Ai is constant, and according to the* notation X we have previously employed, we may suppose it = A .-. — =r,and — = dz. Multiplying each side of (I) by these differentials, and . integrating, we have A»« 1-2-3 ILDING. (r»_6r« llj» Gf\ A*«, /:J 10«« 38j« 60x» o 4 ■*■ 3 ~ 2 y l-2-3-4"^ \^6 ~ 6 4 ~ 3 24 .-A A"«, ('^ 15 <» 85 1' 225 1« 274 1« 120j^\ A"., ^ \7 6 ■*■ 6 ~ 4 "^ ~3 2~y r6~" /'£^_ 21j7^ 175*» 735 1«, 1624 »* 1764 r * 720.A ■^ Vs 7 ■*■ 6 ^S""*"^ 3~'*^~2~/ Calcula- tions inci- dental to designing a Ship. /'i»_2_8i» 322£_1960£« V,9 i""*" 7 6 ■*■ 5040^2 \ a"«, - 2 jlX /-•i»_ 362; yw 9 6769 1» 13132t* 13068 f» « 546 i» _ 4536 t'' 22449 t» 67284 «» 118124 1* 109584 1^ 40320 1- "*" i 3~"*' 2 .-A A^. 45 2"> 870 f» 9450 1» 6327 3 z' 269325 z« + s li H s ;; 10 7236802* 1172700Z* 1026576 z3 362880 z''' ■*■ 6 ~ 4 ■*■ A>»c., ITo- ) (.•"_ 55t" 12 IF 1320 .-10 18150 2° 157773 z» 902055x7 10 ~ 9 ■*■ 8 7 3416930 z« 8409500 x' 12753576 f* 10628640 z» "*" 6 6 + 4 3 3628800 j2 )\JL (zl3 66 2" 19252" 32670 z"> l3""iT'*' 11 10 ■* 3574232»_ 2637568^ 9 8 1333954527 459957302 ° ^ 1052588762 * _ 150917976a* 7 6 120543840 2^ 35916800 2^ ■^"'1 + &c., &c.. . (2.) The coefficients in each of these terms are readily obtained by multiplying (p-l) (j>-2) (p - 3) {p - i) (p-5), &c. (p - n) to- gether. If we take this integral between the limits z ^ and ; = 2, which correspond to * =: and x = 2A, after multiplying by A, /2A ^ , , 1 . 1.1 udx = A {2a, +2i^, + j u<iai = A{2«, +2i^, + jA'a.-^A'a, -|- -^ A»«, — 37 gygpA'a, +&C.} But by the principles of the Calculus of Finite Differences : A«, = «, - «, A»«, = «, - 2« + «. .y2A„^, = ij., + 4., + 2«, - IjA... +i A.a. - 37 1260 A"a, + &c.} Now, if we add similar expressions for the area included between e = 2A and j: = 4A ; x = ik and x = 6A, &c. x = (n — 2) A and a = nA (n being an even number). 1 Seven, thirteen, nineteen. *c., ordinates, may be employed on the same hypothesis, as is mentioned hereafter. ^ The fourth ordinate is considered among the eren ordinates. SHIP-BUILDING. 33 ns inci- / 3 \ Calcula- tion dental to designing + 2 («, + a^ + «, + &c. + a„_i} i (", + «,+«„ + .Ic. + , a Ship. Simpson's Kule de- duced when small quan- tities are omitted. — gg (A'a, + A<aj+ A'«. 4-&C. A'«._,). -f — (A'oc, + A<«2 + ii'a^ + &C. A'«,_,). 37 1260 + &C. &c. &c. 1 &c. &c. (3.) The first line corresponds to the Rale we have already obtained (I.) by supposing a parabola to pass through the extremities of the ordinates a^, «,, ccg ; and another through a^, ot^, a^, &c. The following terms are the correction of the first line ; hence, when great accuracy is required, the following results may be taken into account. Demon- To obtain Rule (IH.), we only have to suppose the integral (1) stration of taken between the limits r = and z ^ 6, or ar = and x = 6A, Mr Wed- as was done by Mr Weddle in his demonstration, given in the die's Hole. Dublin and Cambrtd^je Mathematical Journal for February 1856, which is similar to this : j: udx =z k [6«^ + 18 Aa^ + 27 A*«^ + 24 A=»a, + ^^ ( 33 J.1 + 10^'"' + no^'". + &-=} ^^-^ And we may suppose tixth differences constant^ and then all the 41 42 terms after A^a, in (4) will vanish ; but j-— differs from ^77; by 1 41 42 the small fraction ^t^! hence, instead of =— tt we may write t-tt 140 140 140 3 or — without material error. Replacing Aa, by «, — «j. A'«i by «3 — 2«c^ + aj, A^x^ by a^ — 3*^ + 3«2 — ft^ &c.j after some obvious reductions (4^ becomes pGh ^ 3A f / "'^* = 10 \ "i + *3 + "5 + 'V + 5 '■"■J + "i) + ^'t} 3h 3k ( = Jo I «i + «j + "1 + «5 + «7 + 5 r<«o + + "e) 1 (5-) ^ ' From the foregoing investigation, it is clear, that formula (5.) gives the exact area, when fifth differences are constant, while it differs (in excess) from the true value by ^^7; A'«iWhen tixth, or even seventh, differences are constant. In other cases it will give the area very nearly, providing the differences, beginning at the sisth, are small." ^ As many rules as we please may be obtained by integrating (1.) from z=:Otor = l, i = 0toz^2, z = 0tor = 3, z = 0to » = 4, &c. : from j = to « ^ n, and, neglecting small quantities, as has been done by Mr Weddle, and by supposing the (n — 1^^ order of differences constant. 2 Rule (II.) may be obtained by integrating equations (1.) from « = to « = 3, which will be the same as supposing a series of parabolas to pass through the extremities of «,, (tj, 03, a^ ; i^, m^. «,, cLjy &c., as was the case in formula (3). Ordinates. 1 Ist ord. 1 last do. By Rule (I.) Eren Ordinates. 4 4 2 sum of 1st and last ord. 2 48 four times sum of even do. — Odd Ordinates. 3 5 3 Calcula- tions inci- dental to designing a snip. 22 twice sum of odd do. 72 1:= J common distance. 72=area. 11 sum of odd ord. 12 sum of even ord. 4 48 — four times do. 22 twice sum of do. By RuU (11.) Ordinates. Ordinates. 1 first ord. 2 second ord. 1 last do. 3 third do. 5 fifth do. 2 sum of 1st and last ord. 4 sixth do. ,„ f —thrice sum of 2d, 2 eight do. \ 3d, 5th, 6th, &c. — 14twicesumof 4th, 7 th. 16 sum of do. — 3 64 — 9 := 3 times com. dist. 48 three times sum of do Ordinat«s. 4 fourth ord. 3 seventh do. 7 sum of do. 2 14 twice sum of do. 8)576 72 = area, which agrees exactly with the area obtained by Rule (I.) (2.) Find the area of a fifrure where the ordinates are 10, 12, 13, 14, 13, 12, and 10 feet, respectively, and the common distance 2 feet. By Rule (I.) Area = | | 10 -t- 10 + 4 (12 -1- 14 + 12) + 2 (13 + 13)} = 149i feet. By Rule (II.) Area — ?-^ ( 10 -|- 10 -I- 3 (12 -F 13 -(- 13 + 12) + 2 X 14} = 148J feet. By Rule (III.) Area = ?-^ | 10 + 13 -(- 14 + 13 + 10 + 5 (12 + 14 -H 12)} = 150 feet. (3.) Find the area where the ordinates are 2075, 21 '78, 22-56, 23-79, 22-64, 21-51 ; and 21-51, the common dis- tance being 6 feet. By Rule (I.) Area = || 2075 + 21-51 + 4 (21-78 + 23-79 + 21-51) + 2 (22-56 + 22-64)} = 801-96 feet. By Rule (II.) Area = — g— | 20-75 -t- 21-51 + 3 (21-78 + 22-56 -f 22-64 + 21-51) + 2 X 23-79} = 799-4475. By Rule (III.) Area = 6x3 10 20-75 + 22-56 + 23 79 +22-64 + 21-51 + 5 (21-78 + 23-79 -f- 21-51)} = 803-97. As is stated in Not* (3.), Rule (III.) can only be applied to obtain a very near . approximation to the true area when the In these rules, if the curve passes througli A, or A„, the sixth and seventh ordinates are alike, or first or last ordinate must be considered 0. differ by a very small quantity. Examples Some examples will now be given on the application of on the fore- the preceding rules. By applying these rules to find going rales. Test of the accuracy of the differ- ent rules. the area of the quadrant A, a?, the (1.) Find the area of a figure, bounded by right lines and radius of which is 6 feet, it will be a curve, the ordinates of w hich are taken at 3 feet apart, seen how much the results differ A^ A:; Aj .\^. A^ a. Ay and measure 1, 2, 3, 4, 0, 4, 3, 2, and I feet respectively. fi-om the true area. rig. 6. ' The Duh. and C. Math. Journal, Feb. 1854. ' The coefficients of the various orders of differences have been extended, in order that the reader may obtain some of the^e rules for liimself. E 34 SHIP-BUILDING. Calcula- tions inci- dental to designing a Ship. Divide the radius A, A, into six equal parts (l''ig. 5), and erect the ordinates A, a,, A, Oj, &c. observing that A, o, = 0. A„ a„ = V(A,aj)''-(A,A^)' = V6'-6' = %/lT= 3-3163 A, a, = ^'(A, a3)»-(A, A,)' = Vii^l' = Vm = 4-4721 A, a^ = V(J»-3» — \^27'= 5-1961 Aj flj = V6'-2' = n/37"= 5 6568 A, a, = VO'-I* = V'35'= 5-9160 Ay Oj =6 The area found by Rule (I.) = 279901 feet. (11.) =27-9285 „ „ (111.) = 280401 „ Apply formula (5.) given at the end of Note (1 ) Area = jJq ( ^1 («, + «7 + 216 («., + «») + 27 («-, -f «j^ 4- 272 .J- Where k = 6, «; = 0, «.j = 3-3163, a, = 44721, &c. And area = 2805 feet. 6« X 3-3 416 Examples for prac- tice. Displace- ment Flane of flotation. But true area of quadrant = — = 28-2744, 60 that Rule (III.) and formula (5.), in the present case, give the area almost accurately. (4.) The ordinate? of a curve taken 6 feet apart are, 20, 22, 24, 25 ; 24, 23, and 21 feet, respectively : find the area o!' the figure. By Rule (I.) Area = || 20 -H 21 -^ 4 (22 + 25 -|- 23) -|- 2 (24 + 24)} = 834 feet. By Rule (II.) Area = —^ I 20 -I- 21 + 3 (22 -|- 24 -|- 24 -1- 23) + 2 X 25} = 832-5 feet. By Rule (III.) Area = ^^^' | 20 -(- 24 + 25 +21 -f 5 (22 -t- 2.i -I- 23} = 835-2 feet. By forn-ul. (5.) Arei. = ^^ | 20 -1- 21 + 216 (22 + 23) + 27 (£4 + 24j + 272 X 25} =: 835-5 feet. (5.) Find the area, when the ordinates, taken 4 feet apart measure 0, 2-275, 3-476, 4-567, 5-673, 6-451, 5-341, 4-236, 3*254, 3-065, 2-784, 1-876, and 0, respectively. By Rule (I.) Area = 174-6293. (6.) Find the area by Rules (II.) and (HI.) when the ordinates, taken 1 foot apart, measmc, 0, 1-7684, 2-3457, 8-4567, 3-214, 2-97654, and 2-8543 feet, respectively. By Rule (II.) Area = 15-2556, &c. By Rule (III.) Area = 15-86367 AnT. 2. Def. — By the i3/.«p/ace;«fn< of a ship is meant the volume of water which the ship displaces when floating on its surface. Now, by the princii)!cs of Hydrostatics, it is well known that the weight of a body floating in water, or any other fluid, is equal to the weight of the water or fluid displaced. Hence, after obtaining the displacement of a body, it is only necessary to multiply the volume (say in cubic feet) of the displaced fluid, by the weight of a cubic foot of the fluid, in order to obtain the weight of the floating body. Def. — Bi/ a plane of flotation is meant that section of the vessel, in any position, made by the surface of the water. Several general rules have been given to determine the displace- ment of ships, which can be but approximations to the true re- sults, since the outlines of ships differ so widely, and it is there- fore not considered necessary to give them. In order to find the displacement, the ship is supposed to be di- vided by any number of cqui-distant horizontal planes, that is, planes taken parallel to the load-water lino, and also by any con- venient number of oqui-distant vertical planes, intersecting, of course, the former series of horizontal planes at right angles. These planes are genenilly projected by the draughtsman on the three plans of the vessel, viz., the body plan, the sheer plan, and half-breadth plan. (.See Plate I.) As is seen in the half-breadth plan, the ship is divided into two equal portions by a vertical plane, running from stem to stern ; and the perpcridicular distances measured on each horizontal plane, froni their intersection with this plane to the ship's side, are con- sidered as ordinates. Thus, in the half-breadth plan (Plate I.), F 7 is the projection of the vertical plane which divides the ship into two equal parts, and Vf Ke are the ordinates in the horizontal plane, F, 7„, any number of these liorizontal planes may be taken, and for tlie pur- poses of calculation they may bo numbered 1, 2, 3, 4, &c. ; and A . B.C. &c. The small portions, fore and aft, are usually calculated separately, the horizontal and vertical planes being taken mucli nearer to each other in consequence of the greater curvature of the vessel at these parts. The calculation of the displacement may bo proceeded with in two ways :— 1st, By finding the areas of all the horizontal sections, and em- ploying these as ordinates in Rule (I.) or (II.) 2d, By finding the areas of all the vertical sections, and U8li.g these as ordinates in the same rules. These two results ought to agree. Or, the rule may be enunciated as follows, ordinates on the half-breadth plan being imderstood : — Rule IV. To the sum of the fikst and last horizontal sectional areas, add Fouit times the sum of all the even horizontal areas, andrwiCK t/ie sum of all the odd horizon- tal areas ; multiply this final sum by ONE-TniUD the common distance between these horizontal planes, and this result gives one-half the displacement. We could not, from what has already been done, A priori, con- clude that " Simpson's Rule " would enable us to find the volume of a solid, bouP-ded by planes and a curvilinear surface. The fol- lowing demonstration, however, proves that it holds true. iVule 4. — Let A, Cj represent a portion of such a body, bounded by the planes A, Cj,C, a„ A, a,, C, a,,Ci e,,and by the surface o, e,, we take the planes A, a^. A, c,, and A, o,, as the three planes of reference, viz., (x y), (y z), and (i j), respectively. Calcula- tions inci dental to designing a Ship. First RuIb for finding the " bit- place- ment." T'. <: ::; /C p '^~~: ^^ K T>s c. ■^ ''. '^1 a^ 1^: ^J /5- ''\ A, l„ Aj Bt ^\ ^^ \ Bi V ^^--^^Sx. \ Fig. 6. Bisect A, A„ A, C,, C, 0,, A, C„ in the points A„ B„Cj, and B,, respectively; join A^ Cj, and B, B, ; through these right lines let planes A, Cj, B^ 6,, be drawn at right angles to the plane A, C„ then AssumeA, A, = A, A, = B, B, = BjB3 = C, €3 = 0,03 = * A,B, =B, C, =A,B2=B3C, = A3,B3 = B,C, = * A, a, = «,, B, 6, = /3., C, e, = y, A, Oj = «,, Bj 6j = Pj, Cj Cj = j-j ■A3 "3 = "3> 1^3 ^3 = ^S' *^3 «3 = 73 ■We may then imagine a surface of the form (1.) to pass through the nine points, a,, a,, a^, 6,, h^, 63, c„ c^, C3. J =: A + Bi + Cx« + B,j( -f C,y« -H Dxy + E*»y -f Exy« -h C:c'y», (I.) SHIP-BUILDING. 35 Calcula- ' Since it contains nine arbitrary constants, A, B, C, B,, C,, &c., By making similar paraboloidal surfaces pass throngh e,, e^, e^, Calcula- tions inci- observing that the ot are measured along A, A,, the ys along A, C„ a°d six other points, &c. we have tions inci- dtUnin", """^ '"^ " "*^ ^' "'• ^' "»• ^^ "- ''• *" ^" '""""' ""^ ''" Volume A3 c. ue.t portion = | CA3 + 4 A. + AJ. ,t';^„\„*° a Ship. "''^ follo"'"? equations :- ^ ■^ ^ Ihip," V^.^^—^ (1.) «, =:A whena: = 0, y= 0,j = «,...by (I.) " >• - 1 (a^ + 4 A^ + A,). 's-.y^ (2.)«5-<u, = BA + Ci« a: = A, y = 0, s = A^ a, = b, (3.)<.,-«, =2BA + 4a» x = 2A,y= 0,^ = A3a, =.3 __ last portion = | (A._2 + 4 A._i + A.). (4.) /3,-«, = B,jI + C]i2 iri=0, y= i,2 = B, 6, =,5, 3 (5.)y,-«, = 2Bii + .ICi-t' z = 0, y = 2.t,i = C, e, = 7, Adding these— (6.) 0j - itj-/3i + «, = DAi + E7.2i + Eii= + Gh^k"...by (2.) and Total volume = | ( Aj + A, + 4 ( A, + A, + A, + &c. + (4.) x = A, y = J-. J = B^ft„ = /5, -^i (7.) (!3-«3-Pi + «, = 2DAi + 4EA=A + 2Eii2 + 4GA2i-2...by (3.) A,_ j + 2 (A, + Aj + &c. + A,_2)} (IV.) and (4.) j: = 2A, y = i, z=B3ft3=f53 k We might have regarded :^ («i + 4 0, + y,) as the area of the (8.) r„-aj-'>'j + Kj =2DAi + 2EA»jfc + 4EW + 4GA«i»...by '' *" 3 w --I ^-w (2.) and (5.) x = h, y = 2k,z = C, e, = y, section Ai c,, or B,, as we shall denote it,- («2 + 4/32 + yj) ">»' (9.) ^3-^-^, +«,=4DAt + 8EA^i + 8EAi»+16GA=i=...by of A^ .2- &c., or B,, &c., and then (3.)and|0.) x = 2A,y = 2i-,j = C3e3 = y3 ^ Now, B, C, B, and C, are readily determined from equations Volume = - | B, + B, + 4 (Bj + Bj + &c. + B._i) + (2), (3), (4), and (5), and D, E, F, and G, from equations (6), (7), g (B3 + B, + &c. B._y}. Multiplying these volumes by 2, we (8;, and (9) ; their values are- ^^^ ^^^ ^^^^j displacement of the ship. ' A Rule similar to that of (II.) Note (2) may be found by making How the _ 4o!2 — Skj — Oj a surface, the equation to wliich is of the form r z= A + Bj; + "Second or ~ 2A ■ Cx2 + Da:3 4. B,y + C^y- + Djya + Exy + Ei^y + Gjry2 + fthe Rule" _ «,-2«,, + «.j. H:tV + l-c^y + Kxyi + Lx3y2 + il^y^ + Nx^yS pass through "?yj* "'*" ^ — 0I2 ' sixteen points, since the equation contains this number of arbitrary * constants, which are determined as before, and the integrations are _ 4S,-3a, — y ,_ taken from a; =: to a; = 3A, and y = to y = 3A-. We shall leave 1 2k this work for the student, and proceed at once to a^ _ 2;Sj + 7, Observe that vertical areas may be employed in the place • ~ 2p of horizontal areas, and care must be taken to omit the first ir/! 1 o . "3 J Q j_ 1.1 10/1 Ar A and last areas from the oc?rf ones in each case. D = tog - + 9«i + 3» 3 + 3y , + 73- 1 J»;-lgg_, - 453-4^ 3^ ^^'' Rule (II.) might have been employed ; but the following A nevr 6aj + 4/3, + 41S3 + 2j,2-3«, -3«3-8/32-y,-y3. is the neatest, most concise, and at the same time siiffi-R"le by Dr "~ ihik ciently accurate, that has yet been given. It is by the Rev. ^^ ooUi^y- J _L Ra _L on -i_ J •? 0,1 o Joseph Woollev, M.A., LL.D., Her JNIajesty's Inspector of F =; —' i ihi? — Schools, to whom naval architects are under great obliga- tions tor the attention he has given to this branch of _ «, + »3 + 4g. + y. + y3-2a;-2ff,-2y.-2g3 _ science :— 4A-yl- Rdle v. (1.) Add together all the even ordinates in Ip order to find the volume of a solid, we must integrate the ^^^ ^^^^ ^^^ ^^^ horizontal planes. equation ///rfx dy dz. as shown in most works on the Differential ,^. ^^^ j^^ ^^ ^^^ ^^.^^ ordinates in the 3d, 5th, and Integral Calculus, or, what amounts to the same thing, ffz dx ^^^^ . sections, omitting the FIBST and LAST, and multiply dy, where s is given by the equation to the surface, and the inte- .7 ^,.», ^,. 9 crations in regard to x and y are to be determined by the condi- ,„ , ^77. .1 71 jj „j , j- m j- tt . „ ^ ' (3.) Add toaelher all the rmsT and hA.ST ordinates <ff alt tions of the question. It is evident that, in tho present case, the .; 1 • , 7 ; .,„ ^ ) 1 > ff^g EVEN horizontal planes. limiting values of X are and 2A, those of y being and 2i. Hence ,.\ m 7 ^7 i 11^7. j- ^ ■,.■ ° ' s fe ^^_^_ Take T^viCE tlie sum oj all the ordinates, omitting r-lh r-lk r-lh r-lk ,,,,,„ ,n-,n , the m^^l and -Lk^-i of all the y.^-^.^ horizontal planes. I I zdxdy = / / (?x rfy ( A -1- Bx + Cx- + B,y + , , , ^ ,.-, ,^^ ,„, J, J, J,J^ Thm, add together the results of (I), {2), {i), {A), and ^j. (• multiply this final sum by two-thirds of the product of Cjy2 + Dxy + Ex-y + Exy= + G:<?y-) = - | 36 A + 3G BA + 4S fj^^ common distances between the horizontal and vertic'il CA2 + 36 B,A + 48 C.i^ + 36 DAit + 48 EA^* + 48 EA^ + 64 P^«""'' °'"^ '''"" result gives the displacement. GA2A2}. Introducing the values of A, B, C, &c. already found, we ^.^"^ 5— Not having seen the demonstration by Dr WooUey to •' ° ) • , "• J -^" . = jjjj^ rule, the editors beg to offer the following, which must be . -. . . ... , . hk ! , somewhat similar in principle. get, after obvious reductions, volume A,f3 = — aj + 4a.> + Uj ^ ■^ ^ " Dr WooUey supposes fig. 6 to be divided into two portions by a + 4 (/3, + 4 /5j -1- /Sj) + y^ + 4 yj -I- yj } (II.) plane passing through Cj Bj A3 Oj b^ Cj, and the equation to the h surface passing through o, I, e, 60 "■> "% ™*y ^^ assumed as On examining the equations, we perceive that — (*, + i G, + =1 -• 3 '■ ' ^ ' - ^ r = A + Bx -l- Cx2 + B,y + Ciy2 + Dxy .... (I.) tg) represents the area of the section A, a, {Vide Equation I., p. ^^^ ^^^^ li^^itg are x = and x = 2A, and since. A, C, = 2t, at 35),:and | (;3, + 4 /B^ + d,) represents the area B^ I, ; also, ^ (y, „„y ^^.^^ ^^ ^., „^^^, ^ave y = Q^-\ + 4 y2 + ya) that of Cj Cj. Writing for the area of Aj Oj. Aj ; i . tbr that of Bi 6„ Aj ; for C. c,, A3 (Equation II.) becomes /T2A /^(,2A-x) ^ p>hr(2h-x) ^ .•.I I I dxdy ^ j I dzdy{K + Bs -h Vol«meA,e3 = |(A,4-4A2 + A3) (III.) ^,//b,, + 0.,= -H Dxy) ° ° 36 ralculu designing a ^hip. SIIIP-BU I'aicum- ^^ ^„, jlnairininrr *^ B|I-/4A'-4Aj ; + j' \ , City 8A» - \2h^x + 6Aj^ - j-'' \ + 2 ^^ A^ yl „ . L. . 4B/.2A . 4CA3k ^ 4B,Ai' ^ 4r',Ji» ^ 20*2*2 = 2AAt+ -3- +^p- + — L_ + _L_ + ___(II.) Now, since the surface (I.) passes through the sin points already mentioned, we readily determine A, B, I',, &c., as in the last note Their values are A := «) 2BA = 4«t, - otj - 3a, 2CA2 = «i - 2«2 + "a 2B,t = 43, - n - 3»| 2C,k2 = «, - 2/3i + ^, DA* = «i + p, - "ij - ^, Writing these values in (II.) it reduces to "hk I 1 Volume = -g- I oj + Ai + Sj I In the same way, we find the volume of the figure C| Cj fcg ^3 '^3 2hk f 1 = -^\y2 + h + h] Adding these results, we find for the whole volume .A, c^ ?^ I «2 + /3, + 2/32 + /Sj + ^2 I With similar expressions for the other portions of the ship, .-. Whole volume = ?^ | |3i + /3. + 2(li^ + /Sj + <;, + &c ) + ("J + yj + «, + o-, + &c.) + 2(;32 + f>i + l^i + a^ + &c.} Tiijind the Centres of Gravity of Bodies. Art. 3. As a knowledge of the centres of gravity of bodies is of so much importance in the calculation of sta- bility, it has been thought advisable to introduce the sub- ject here at some length. Various definitions have been given of the centre of gravity of a body. It is shown in almost every work on Statics, that there is a point in (sometimes without) every body such, that if the particles of the body be acted on by parallel forces, and the point already mentioned be fixed or supported, the body will remain in equilibrium, no matter in what position it is placed ;^ and when the forces herein mentioned are replaced by the weights of the elementary portions of the body, or bodies, this point is known as the centre of gravity of the body or bodies.' Gravity, or the force which attracts all bodies towards the earth's centre, is supposed to act on every particle of the body in parallel and vertical directions. This force is supposed to be constant at the earth's surface, and there- fore attracts all bodies with an equal intensity. The reader will readily perceive that this hypothesis cannot differ ma- terially from the truth when he compares the earth's nidius with the dimensions of all bodies at its surface, and re- members that this attr.active force varies inversely as the Centres of gravity. Definition, I L D I N G. square of the distance. Under these circumstances, then, Oaleuls- tlie centres ofgravily of bodies are calculated. This point tions inci- cannot be obtained, however, without the aid of the Inlegial dental to Calculus, except in the case of a few plane surfaces and "="K"'"8 .■I 11.111 1 1 11 1 * Ship, solids. We shall premise tliat when boilies are nomogene- y - , _ ' ous, or of the same density throughout their parts, — that is, ~ ^ ~ having equal weights, comprised under equal volumes, — we may then re[)lace weights by masses, and conversely. Thus, if M represent the mass of a body, d the density of a unit of the body, V the volume, W ihe weight, then M = dxV (1.) 'W=gxdxy=gM (2.)' When a body is not homogeneous throughout its parts, the determination of the centre of gravity becomes some- what more difticult. To find the Centre of Gravity of an Area similar to fig. 3. Art. 4. — Rule VI. Multiply the ordinales, beginning CentTa of at the first by 0, 1, 2, 3, 4, ^c, respectively, and employ S"^'''^^^ "^ these as ordinates in Rule (I.) ; multiply the result thus "^^• obtained by one-third of the common interval squared, divide by the area of the curve, and the result gives the distance we are to measure along A, A^ — i.e., A, jr.* Having obtained the distance Aj^, we may obtain the length of the perpendicular G^ (G being the centre of gravity of the figure, and ^ the point where the perpendicular drawn from G intersects A.A".) by Rule VII. To the sum of the squares of the first and LAST ordinates, add four times the sum of the squares of all the EVEN ordinates, twice the sum of the squares of all the ODD ordinates ; miUliply by one-third the common inter- val, a7id divide this result by twice the area, the quotient gives the perpendicular height of the centre of gravity above the axis A, A„.' Similar rules apply for finding the centres of gravity of the displacement of a ship. Art. 5. To find the centre of gravity of the displacement of a ship floating in the water, and in a state of equilibrium — The horizontal sections are taken at equal distances apart and parallel to the plane of flotation. The vertical sections are also taken at equal distances apart and parallel to the midship section. The ship is then cut into two equal portions by a plane running fore and aft, and at right angles to the two planes just mentioned. In the following rules, half areat and halfvolumtt are to be under- stood. Rule VIII. Fi?id the areas of all the horizontal sections Centre of [such as those shown in the half-breadth plan) and multiply gl'^^'^ these, beginning from thejirst, or plane of flotation, by the "''^^'if '„ consecutive numbers 0, 1, 2, 3, 4, Sfc, respectively ; intra- fo^n^ duce these products as ordinales into " Simpsons Rule ;' multiply this result by one-third of the square of common distance between the sections, divide by the volume, and the quotient gives the distance of the centre of gravity below t/te plane of flotation.^ Rule IX. Find the areas of all the vertical sections^ multiply these, beginning from thefirsf by the consecutive numbers 0, 1,2, 3, 4, !^c., respectively, and work as in the last rule ; the result thus obtained gives the distatice (f the centre of gravity from the first vertical plane. ' Pratt's Mechanical PhUoiophy, 2d edit., pp. 18 and 19. ' The centre of gravity has also been defined as that point within or without the body, from which, if the body be conceived to be sus- pended, it will remain in equilibrium in any position. ^ " <7, or ' the accelerating force of gravity,' is uniform, and is the same for all substances, and in the latitude of London := 32'18 fcct>" (Esrnshaw's Dynamics, 3d edit,, p. 42.) * Care must be taken not to multiply by one-third of the common distance, as is mentioned in Rule I. ^ The last ordinate must not be reckoned amonp the odd ordinates in these and the following rules. ^ Either the first vertical section of the main body nearest the bow or stern may be taken as th*' first. SHIP-BUILDING. 37 Cslcula- tions inci- dental to designing a Ship. Centre of gravity. Centre of gravity of displace- ment when the small portions " fc re and aft" are taken into account. releldin'a Rule. Nfathema- tical prin- ciples of centres of gravity of bodies. These two distances fix the position of the centre of gravity of the main body. Since a ship is symmetrical in regard to the plane which divides it, fore and aft, into two equal parts, we know that the centre of gravity must lie in this plane. No account is here taken of the small portions at the stem, stern, and that between the keel and last horizontal section. These are usually calculated separately, and in the same way as the main body. Having obtained the centres of gravity of all these por- tions, we readily obtain the centre of gravity of the total displace- ment by the rule which follows, observing, that if we consider the first vertical plane to be that nearest the bow, the volume of the small portion forward multiplied by the distance of its centre of gravity from the plane just mentioned must be subtracted. Or, in other words, if we consider all horizontal distances, measured in the opposite direction (from the first vertical plane) to the centre of gravity of the main body as netjative,^ui all distances measured in the same direction as positive, we have then only to add the products algehraically, and this is to be understood in the following rule (one product being always negative in Rule XI.) All results will be posi- tive in finding the distance of the centre of gravity helow the plane of flotation. Rule X. Multiply each of the volumes by the perpen- dicular distance of its centre of gravity from the plane of flotation, and add the products ; divide this result by the sum of all the volumes, and the quotient is the distance of the centre of gravity of the total displacement below the plane of flotation. Also, Rule XI. Multiply each of the volumes by the per- pendicular distance of its centre of gravity from the first vertical plane, and add algebraically {observing that one result will be negative), divide this result by the sum of all the volumes, and the quotient is the distance of the centre of gravity of the total displacement from the flrst vertical plane. One of the properties of Guldinus is also of great use in finding centres of gravity when the necessary data are supphed. Rule XII. Any solid of revolution is equal to the area of the surface which generates this solid, multiplied by the circumference, which is described by the centre of gravity of the latter. Without attempting to demonstrate formulae (1.) of this article, since a demonstration may be found in almost every work on Statics, we proceed to lay before the mathematical reader the principles on which the centres of gravity are calculated. J\ot« 6. — If we consider, in the first place, a system of material points having weight, and connected in an invariable manner, the weights of these points may be considered as so many vertical forces acting in parallel directions. If, moreover, we take three fixed planes.mutually at right angles to each other, their point of intersec- tion being the origin (as is done in Geometry of three dimensions) let a/j be the weight of the first material point, and its co-ordinates x,, y,, j|, measured along the three co-ordinate axes : oj. ij, t/j, s^, the weight and co-ordinates of the second point, &c. &c. ; also, let X, y, z represent the co-ordinates of the centre of gravity of the system of weights measured along the same axes, then we have -_ 3(iiXi + ».^2 -^ .,,.T, + &c.) ' 2(o<l -f <»2 + "3 + &"=• &"^-) — _ S (mi»i + <»2y2 + "sVj + &"■) S (<U[ -t- uj -f 0,3 -H iic) — S i^»i|g, + i»2-2 + "'3-3 + &C.) (1) 2 |a<j + «i2 -i- •13 -H (St-.) Remark. — These formulae would be equally true if we suppose <i;,, «2> "i' &«• to represent the weights of any bodies whatever, and connected in an invariable manner, providing we suppose these weights to act at their respective centres of gravity, and x^, j/j, z,, d'c, to be the co-ordinates of these centres of gravity. Next, if we suppose the density of the bodies to be uniform throughout, we can re- place the weiL'hts by their respective volumes v^, V2, v^, &c. since g X d appears both in numerator and denominator. tion is also true for areas. area8 Therefore, if A, The proposi- &c. represent + v^x^ + &c.) \ 2 ("1 -t- l'2 + "3 + &c.) 2 (Aj -f Aj -h Aj H- &c.) 2 ("iV l + ''2-"2 + ".^Vs + &"•) 2(vi + v^ + v^ + &.C.) > or 7 = ? (^lyi + A2y2 + ^3.1/ 3 + &f.) 2(Ai -h Aj -h A3 -H &c.) -_ 2 (vyZi + v^Zj + V3Z3 -f &c.) &c.) , + &c.] Calcula- tions inci- dental to designing a Ship. 2 (p, + V2 + "3 + "_ ^ (-^I'l + ^2 (2.) 2 (A, -(- Aj -t- A3 -h iic.) J If the centres of gravity of the weights, volumes, or area"!, as the case may be, range in a right line, the first equation gives the distance of their common centre of gravity from the origin. If the weights, or areas, &c., are in the same plane, the four former equations are all that are necessary to determine the centre of gravity. Premising that the centre of gravity of a ball, or sphere, is at the centre of the body, we shall proceed to give two or three examples on these formulae. (1.) Four cannon-balls have their centres in the same right line at 2, 3, and 4 feet, respectivelv, apart, and weigh 68, 32, 12, and 8 lbs. respectively ; that is, the "32 " is 2 feet from the « 68," the " 12 " is 3 feet from the " 32," &c. Find the distance of the common centre of gravity from the centre of the " 68 " (supposing their centres to be in the same horizontal line). Taking the origin at the centre of the " 68," we have x, =^ 0, «2 = 2, 13 = 2-1-3 = 5, X. = 2-t-3-^4 = 9 feet. Examples of finding the centrei of gravity of bodies. (1.) X = 68xO-H32x2-H2x5-4-8x9 68 -h 32 + 12 -h 8 = 1-63 feet. That is. if the balls were connected by an indefinitely fine rigid rod, without weight, passing through the centres of the balls, the whole might be suspended, and remain in equilibrium, at a point distant 1'63 feet from the centre of the " 68." (2.) Five cannon-balls, whose weights are 2, 8, 12, 32, and 68 lbs., lie on the floor of a room, at the respective per- pendicular distances 3, 4, 5, 6, and 7 feet from the side, and 1, 2, 3, 4, and 5 feet from one end of the room ; find their common centre of gravity from that corner of the room where the side and end (from which these distances are measured) intersect, supposing the centres of the balls to lie in the plane ot the floor. Here x ■■ x3 + 8x4-4-12x5 + 32 x6 -I- 68 x7 y = But distance from corner 2 -t- 8 -t- 12 -t- 32 -H 68 6-28 feet nearly. 2x1-1-8x2-1- 12 X3 + 32x4x68x5 2 -f 8 -f 4-28 feet nearly. V x^ + y2 12 -f 32 -h 68 = V(6-28)2 + (4-28y2 = 76 feet nearly. (3.) Four cannon-balls, whose weights are 1, 8, 32, and 68 lbs., are suspended in a room (of the form of a parallel- opipedon), their vertical heights from tlie floor being 2. 4, 6, and 5 feet, respectively, and their perpendicular distances, from an end and side of the room, are 2, 4, 5, 6 feet, .ind 3, 5, 6, 7 feet, respectively ; find the distance of the centre of gravity of the balls, from that corner of the room where the side and end, herein mentioned, intersect. 38 SHIP-BUILDING. Calcula- tions inci- dental Co designing a Shi)). ITerc the side, end, and floor of the room am the planes of refer- ence, and tlie origin at the corner, mentioned in the question, the line where the siJe intersects the floor may bo taken as the axis of X, and the intersection of the end and floor as the axis of y, or, vice vend, the intersections of the end and side being the axis of i. - Ix2 + 8x4-l-5x32 + 6x68_ 1 .(. 8 -h 32 -h 68 = 6-523 ft. nearly. -2 + ^2 = V(5 323)2 + (G-523)- + (5-ll'2)2 = - _ lx3-^-8x5-^32x6-^68x7 _ y - 1-1-8-1-32 + 1)8 " " -_ 1 x 2-HSx4 + 32x6 + 68x5 _ ' - 1 -I- 8 -1- 32 -I- 68 ^' Again, it is easily shown that the distance of a point x, y, from the origin is — 10 feet nearly. For if XOY be the plane of the floor, XOZ the side, and YOZ the end of the room, G the centre of gravity. Draw GZ _[_ to the plane XOY ; and from Z draw ZX and ZY respectively, _|_ to OX and OY; then OX = x^OY = t^ GZ = z in the above equations, and since the triangles OXZ, OZG are right- angled, OG* = OZ^-1- GZ^= OX'^ + XZ2-l-GZ2,andXZ= = 0Y2. Fie-5. /W4- OG = \^0.\2 + OY2-HGZ2 C^ W3 Formulae for the cen- tre of gra- vity when the density ii variable. Hence x ^ / // z dx dtt dz ; M M These equations are to bo taken between proper limits, and if Calcula- the body is homogeneous, i will appear in both numerators and de- tions inci- Dominators, and the equations may then be written : V = /// dx dy dz. (2) {.7 = /// X dx dy dz — f f f v dx du dz — V • " ~ '~~^ '' ' ' '' dental to designing a Ship. /// z dx dy dz V We may obtain a clearer idea of these integrals from the follow- ing considerations. Let us take the first of the latter set of equa- tions, and integrate, first, in regard to z, and next in regard to y, observing that in these integrations x is constant, we may then AVe might have determined the centre of gravity of any system of material points, or balls, not situ- ated in the same line, or plane, Fig. C and rigidly connected in the fol- lowing manner: \Y,, Vf^, W'j, &c. representing these material points and their positions, join W, \Yo, and let G, be their common centre of gravity, then these two points will act in the same man- ner as if their weights were collected at the point G|. Join Gj W,, and let Gj be the centre of gravity of Wp \\'2< acting at G,, and "f \\'^ ; then W^, Wj, AVj, may be conceived to act at Gj. Join Go W,, &c. &c. Nnte 7. — The principles made use of in equations (1.) may readily be extended to any body, or system of bodies ; for, suppose the body referred to three co-ordinate i)lane9 mutually at right angles to each other, their common point of intersection being the origin, and Xj, T/,, 2p Jhe co-ordinates of any point in the body ; then it is shown, in most works on the " Calculus," that the volume of an infinitesimal parallelopipedon, at that point, is represented by .ix^ X Ay, X A?,.' Also, if 5|repre9ents the density of a unit of volume at that point, the mass of the particle is 3, . ^^ . Av, . ^^p and its weight is *;3j :ix^ .it/, at,. But as ^ is constant, it follows that we may either employ the weights or masses of the body in finding its centre of gravity, and 11 = 2 (3, jx, . Jy, . .iZ2 -^ Jj ^ ^Vi ^2 + &''■ '^'''•) — 2 (j, S[ xt^ Ay, ^., + X, ?2 .1.1X2 -^."2 .5^2 + &"•) * ~ ' if " " — a (y, i, AX, Ay, a;, -t- y; ^2 -^2 ^Vl ^2 + &") "" M — 2 (z, >, A*, Ay, jz, -1- Zj J2 ^''" ^"■i ^''■> + A""-) ' - Ai " Bat at the limit Ax,, Ay,, ^i become dx,, <fy,, rfz,, and dropping the suffixes, and ext^-nding the summation, or rather integration, to all the elements of the body, we obtain (1.) M = /// dx dy dz . J. Where i is given by an equation of the form 5 = / (x, y, r). — /// X dx dy dz .i -_ / / f y dx dy dz i — _ J\fdyjz V dx. Where the quantity within the brackets represents the product of » by the area, A, of a plane section of the figure, perpendicular to the axis of x, and at a distance x from the plane of zy. — [A xdx V -, and similar expressions may be obtained for y (3.) \ — ff X dx dy J'xy dx — ff y dx dy y = If it be required to find the centre of gravity of any area, &c, we hove only to 6U2)pose it to lie in the plane of xy and formula) (2) reduce to A ■^fj dx dy = f y dx (if we integrate in regard to y) ,/."■■' "i" Jiemark. — In many cases it is convenient to employ polar co- Polar for- ordinatet to find centres of gravity, and we have for the transfor- mulse. roation x^:^ r sin 6 cos ^, y -z^ r sin 6 sin ^, z ^ r cos (J, Formulae (2.) become ,—_ /// r3 sin • 't cos <pdr.dt .dp SSS ""^ si" ldr.dS.d(p ' ]— f ff T^ sin •-( sin -p ilr didf Jff r- sin ■ I dr dt dip ' {i-)\y- fff r* sin • ^ cos I dr dl df /// r^ sin ■ t dr dl df ' where /// r^ sin • f dr dS df between proper limits gives the volume. We shall at once proceed to show by formul.T! (3.) how to find the centre of gravity of an area, similar to the horizontal or verti- cal sections of a ship, premising that the notation is the same as that employed above (p. 30, 31 &c.) Kote 8. — To find the centre of gravity of the portion A, Bj, the Remon- cquation to the parabola passing through a,, a,, (13, being (A the stration o( common interval). Rule V^I., — Art 4 &c y = A + B X + Cx~, Xj denoting A, j, and y,, G, j,. ' ' - _S ^y ^^ _y f ^ (A » Jy dx rih 7r2k a a: (A + Bx -t- Cx-) dx r{ 6A + SBA + 12C7< y^2A „ (A + Bx -1- Cx-} dx ^ / GA -1- 8V,h + 12C&' \ - { 6A + 615A -^ 8CA2 I 1 6A + 6iJA H- SCA^ J But by Note (1), formulae (2, 5, and G) A = «,, B = -1?-^ w^~ ~' and C ^ "^ ~ 'J^ r^ !. Writing these in the above, wc got - ^ 2h (2,2 + -s) ' "1 + «3 + ■1«2' e centre of gravity ol e ^^"^ = 'H+aXta - ■■■ ^^1 "2 = ^^' ^■•' + -V-- •'= = -* + "3 + '5 + *"l In the same w.ay, the centre of gravity of A3 Aj, along the line A, A, is found to be X,, ^y^, AZ[, represent the respective increments of x,, y,, Zj. SHIP-BUILDING. 39 Cftlcula- tions inci- dental to desi;Tning a Ship. 2A («j + «,) or if ^2 ^ A, .72, ^3 = ■A2?.ii &c. <«3 + «5 + 4.CJ ^ " «3 + "S + ■^"4 «3 + "s + •*"* 2/. (2«e + « ;) _ 2A (2«, + lOgg + 3«.) 4A + + «7 + 401 + «;-(- 4a5 And if ^ be the distance along the line Aj A„ of the centre of gravity of the whole figure, we have by formula (2), since the areas may be supposed to be collected at their respective centres of gravity, Gj, Gg, Go. &c. Ag or X Area AiOjX AjTj + areaA3<j5 X A,^;, + area A^o, X Ajj;3 + Area Aj a^ + area A3 a^ + area Ag a^ + &c. &c. A, Xi + A2?-2 + A3 r, + &c. + A„ Xn Ai + A2 + A, + &c. + An Introducing the values of Aj, Aj, A3, &c. x,, x^, x^, &c. already found, this reduces to (I.) l — h {0 + (»-1)«n + 4(^2 + Sct^ + £«e + ra^ + &c. "i + «» + 4 («2 + '«4 + |«6 + "a + ^''■) + 2(2«3+4«g + 6«, + &c.)} + 2(a3 + aj + aj + &c.) ' Next, to find Gg, or y, we have /^ 2A /^ 2A t/ ^ I dx Demon- stration of Kule Vll. Demon- stration of Rules Via., IS., &o. But y2 = (A + Bx + Cx")' ; and this integration, added to the work connected with the substitution into the form - _ A.yi + A^yg + &c - " A, -1- A2 + &c. • would lead to an immense amount of labour, which may be avoided by observing that the integral J y- dx may be taken to represent the area of a curve, the ordinates of which are the squares of those at given points of the curve, as a^, o^, k^, &e. With this under- standing, we readily find, by employing " Simpson's Rule," + »." + 4 {^} + «,^ + «6^ + &c.) + «! + a^ + 4 (ko + o, + aj + &c.) -|- 2 («,2 ^. .2 ^ -2 .J. ^c.) ' , — ■ — —, — s — c- ; whence the centre of gravity of the 2 ("I + «5 + a? + &<:•) curve is completely determined. Note 9. — We next proceed to show how the centre of gravity of the volume of a figure similar to fig. 6, page 34, may be found, its equation being z — A + 'Bx + Qx- + 'B^y + V^y- + T>xy + lix- y + Exf + By formula: 2 if we integrate in regard to z, (II ) y - i o{- %y t-/ -_ f fxz drdy _ f zdxdy 2k xdxdy (A -H Bz + Cx^- + E,y + C^ y^ + Bxy + r-2h n2k »/o Jo dxdy (A -t- Bx + Cat^ + B,?/ + Cj!/- + Vtxy -(- Y-xhj + Ezxf- + Gz- y-) Ex2y -1- Ery2 + Ga;V) Ajfc f -^ I 36 AA + 48 BA2 + 72 CA3 -i- 36 B, Ait + 48 Ci Ai2 + -i-' I 36 A + 3tJ BA -I- 48 CA^ + 3G Bji + 48 C, i- -f 48 DA'ifc + 72 EA3t -f- 64 FA^/fcZ -f 96 Glv'l " } 36 DA* + 48 EA=i + 48 FAX;= -(- 64 Gi'-'i=] " But A B = 4 a, 3a, 2A ^,C = ' Calcula- -s,.; ^, &c. .. . . aA-' tions inci- as was shown on page 30. Introducing these values, we find — -^^ 2 (2«2 + gj) + 8 (2/3; + g,) + 2 (2^, + y^ ■ «! + 4«2 + 03 -1- 4(^1 + 4/52 + /Sj) + n + 4 >'2 + ^3 dental to designing a Ship. JJ^dxdy t/ 0/0 2i rfj^y y(A -f Bg -t- Ca:^ + '&^g '2k dxdy (A + Bi + Cx= + B,y -H Ciy^ + Dzy + Ez^y + Ezy^ + Ga:-y') + C'l y^ + Dxy + Ya' y + Fxy' + Gx^ y^)' + Ciy- - + C'l y^ + hk < -g- j 3G AA + 36 Bhk + 48 CA^ k + i8Bik' + 72 C, *» ~ hk I -g- I 36 A + 36 BA -H 48 CA2 + 36 Bj i + 48 C, i» -(- 48 DAi2 + 64 EA2A2 + 72 FAi^ + 96 GA^ A 1 ,.. ,^ , . + 36 DA* + 48 KA^' k + 48 FAA^ + 64 GA^ t 1 ' ^'^"'^' ^"" """ troducing the values of the constant, and reducing, becomes y^k. f 2 (2gi + n) + 8 (2g2 4- 72) + 2 (2g3 -f >.3) 1 I "1 + -^"2+ "3 + 4((3i + 4/52 + ''a) + ri + ^72 + rs J " Also, yy z dxdy ' But, as before, we avoid the labour of integrations, &c., if we consider the expression J"/ 2- dxdy as the volume of a figure, the squares of the areas' of which may be introduced into " Simpson's Rule." We should obtain similar expressions for the centres of gravity of the volumes of the other solids, and by introducing the resulta into the formula — • - V, ^ -f Vg ^ + V3 ^ + &c - "" "" Vj -i- ^2 + V3 + &C. - Vi y. + Voy. +y3y3 + &'= - y - Vi -f V2 + V3 -t- &c we obtain the rule, in common use among naval architects, namely : — If A,, Aj, a,, &c., represent the areas of half the horizontal sec- tions, or the sections shown by the half-breadth plan, and A the com- mon interval between those sections, weknow that the centres of gra- vity of the whole horizontal sections in question lie in the planes of these areas at distances 0,A, 2A, 3A, &c., respectively, from the origin. /T,r^ - A, X -f («-l) hA, + 4A (A, -f 3A^ -f- gA, + ("'•) ■■■ " Aj + A.-f 4(A2-f A,-f 6A, -1- &.^) -f 2A (2A3 + 4A, -f 6A, -f- &c.) . A,-f &c.)-f2(A3-l-A,-f A,-|-ic.) ' (« - 1) A. -)- 4 (A 2 -f 3A, -I- 5A, -f &c.) + + A. -I- 4 (A2 + A, + A, + &c.) -f- =-r^ 2 (2A3 + 4A, + &c.) I 2 (A3 -I- A, + Aj + &c. In like manner, if Aj', A2', A3', &c. represent the half are»s of the vertical section, and k the common interval between them. (IV.) Then F = M ^r']^itl^i:^t\V^f^\^ + 2 (2A3' + 4A/ + &c.) I > 2(A3'-f A,'-f &c.) /• Hence the centre of gravity of the displacement is determined; for we know that it will lie somewhere in the plane which cuts the vessel into two equal parts, and the value of « gives its distance below the load-water plane, y gives its distance from the origin. 40 Calcula- which may bo taken for convenience at the point of intersection of tiona inci- ti,e loiid-water plane, tlio plane just mentioned, and the first vcrti- dental to ^^j ||iu„g next the bow, or stern (as the calculator pleases). Wo a siiiu "■'" 8"PP™« the former, and that the centres of gravity of the small t , , ' portions, fore and aft, and below the last horizontal plane, ore not taken into account. Let Vy, V„ V*, be their volumes, */, x„ Xk, y/. y«. 7t. the distances of their centres of gravity from the origin. Therefore, for the whole ship, V representing the volume between file first and last vertical sections, - V J + Vt at + V.X. - V,~%f V + V* + V. + Vj. V + V* + V. + V/ Observe that V/.ry has a negative sign because it is in the oppo- ■ite side of the origin to the other quantities, that is, X/ is negative. Note 10. — The mathematical reader will at once perceive that these are not the only rules which might be obtained to calculate the centre of gravity of a vessel. As has been remarked before, the Calculus of Finite Difference again comes to our aid ; and, by neglecting small orders of ditferences, we may obtain any number of ruk'S we please. As an instance, let us take tlie case given by Mr Weddle for a curve passing through seven points, and suppose sixth differences constant. We have for z, using the same notation 08 in Note 3, — ^Tx^^^x fjjjgQ between proper limits ; and^ := a -f- ^ •^" + A SIIIP-BUILDING. Introducing these values, and reducing /xxj dx='^ I 36 «j + 9 «., + 136 «, + 18 «, -f 180 «, + 61 «,) | 28 «, + 5 aZ, » (» — 1) n^- + &c. ; where - = ^• ads ■ I?' I have X or 77 /-fy dx =^ I la sd: + (z-: Multiplying this by zdz z=. d^.-^ + hc. I = -^+- Aa+ (^T--3) T2 + T 4+3)l'-3"^(ir 5+4 3J A* «^ , / f_ _ 10^° I 35£5 _ 50z<_ 24^ \ a' a 2-34"^ (7 6 "^ 5 4 "'' 3)2-3-4-6 "*■ ( 8 7 "* 6~ 5 ' 4 3~ ) ^ 1-2-3-4-5-6 -j- &c. &c. Taking this integral from j =: to » = 6, or a =r to i ^ 6A, and multiplying by A^, we find, after considerable reductions, ftydx = h.^ {18a + 72 A« + 126 a2 « + ?!?^ .^3 g 1 551 ^4 „ 1 5 ' 10 ^ 639 . , 123 . , -35-^'"+70-" -}• W" might obtain a tenth rule by neglecting small quantities ; ' ■ . li simply write down the total result, leaving the reader ' "-in any other rules be may think proper. Aa = *2 — ''i A-a = «3 — 2a2 + a, &c. &c. — _ 9A» • ^— TOX Calcula- tions inci- dental to designing a Ship. j;:L^aL^+.,(,^+3a, + 5a,)+(a,+ 2a,+ 4a,)} ; which will give a result much more accurate than that ob- tained by " Simpson's Kule." The result for y may be obtained by " Simpson's Uule," or by squaring the value of y, given above, and neglecting the squares and products of higher order of differ- ences. Nou 11. — The reader will have no difficulty in obtaining for Property of any plane surface ' Uuldinus. " fydz ' or y X A ^ J / (Y,^ — ^,,2) dx; if A represent the area of the surface, and Y, Y„ denote the limits of y. Multiply both sides by 2«-. .-. A X 2a- y = x/ Yj- Jx — rf Y„- dx. The left hand side is the area of the surface multiplied by the cir- cumference described by its centre of gravity, and tlie right hand side denotes the difference of the volumes of revolution described by the plane surfaces comprised between the axis of x, the extreme onliiiates, and the curve which terminates the generating sur- faco." (1.) Find the centre of gravity of an area, similar to fig. Examples. (3.) page 30. tlie equidistant ordinates measuring 2"5, 3, 3'5, 4, 5, 6, 5-5, 5, 4, 3, 2, 1'5 and 1 feet, respectively, the common interval being 2 feet. \st, To find the Area by " Simpson's liuU." Ordinates. 2*5 first ordinate. 1-0 last „ 3*5 sum of first and last ord. Ordinate^). 3 second ord. 4 fourth „ 6 sixth „ eighth „ tenth „ Ordinates. 3'5 third ordinate. 5 fifth „ 0-5 seventh „ 4'0 ninth „ 20 eleventh „ 20 sum of odd ord. 1-5 twelfth „ 22-5 sum of „ 2 4 40 twice sum of otA, 90'0 four times sum of ordinate. 40'0 twice sum of odd „ 3'5 sum of first and last „ 133-5 2 common interval. 3)267 89 ^ area. 2d, Tojlnd the Distance of the Centre of Gravity from A,. Ist, 2-5 X = \ 2d, 3 X 1 = 3 3d, 3-5 X 2=7 4th, 4 X 3 = 12 5th, 5 X 4 = 20 6th, 6 X 5 = 30 7th, 5-5 X 6 = 33 8th, 5 X 7 = 35 9th, 4 X 8 = 32 10th, 3 X 9 = 27 11th, 2 X 10 = 20 12th, 1-3 X 11 = 16-5 13th, 1 X 12 = 12 J \ ordinates multiplied by 0, 1, 2, 3, &C. ^ This and other properties are due to Pappus, and were published by Guldinus, a Jesuit, who was Professor of Mathematics at Roma, In the middle of the seventeenth century. ' See any work on the Calculus for the interpretation of the expressions on the right hand side. SHIP-BUILDING. 41 Results. first result. 12 last „ 12 Bum of ,, By " Simpson's liuk.^' KeSQlts. second result fourth ,, sixth „ eighth ,, tenth „ 3 12 30 35 27 16-5 twelfth 123-5 sumofaven results, 4 Results. 7 third result. 20 fifth „ 33 seventh „ 32 ninth „ 20 eleventh „ 112 sum of odd results. 2 224 494 224 12 730 2 four times „ two times ,, first and last ,, common interval. 3)1460 486-66 2 common interval. 973- 3 .". Distance of centre of gravity from A[ = 12-25 25-00 30-25 1600 4-00 973-3 ~89^ = 12-4344. (2-5 j2= 6-25 6-00 3» = 9-00 16-00 (3-5)2 = 12-25 36-00 4» =16 00 25 00 52 =25-00 9-00 62 =3600 2-25 (5-5)2 _ 30-25 52 = 25-00 97-25 42 = 16-00 4 3« = 900 22 = 4-00 389 i (1-5)2= 2-25 12 = 1 6-25 1 87- 175 twice sum of odd ord. sqd. four times sum of even ord. squared. 7-25 sum of first and last ordinates squared. 389-00 175-00 571-25 By last process, we have 571 -"5 V ' .: Perpendicular Gg=—^ — —^= 2-139, i- .' '^ -^ 267 X 5 (2.) Find the centre of gravity of a figure similar to the above, when the ordinates are taken 3 feet apart and mea- sure 1-25, 2-35, 4-56, 7-87, 8-97, 9-65, 10-o4, 9-97, 8-65, 7-54, 6-34, 7-43, 5-42, 4-53, 4-23 feet respectively. Distance along the axis from A, = 20-82. Distance above the axis at the above point = 3945. (3.) Find the same, as in tlie last example, when the equidistant ordinates measure 20, 20-5, 21, 22, 22-5, 23, 24-5, 25, 26 ; 25, 24, 23 ; 23, 22-5, 2 1 , 20 ; 19, 1 8, and 17 feet, respectively, and are taken at 6 feet apart. Distance along the axis from A, An from A, = 52-82. Perpendicular distance above ditto at the above point =: 11-18. (4.) Find the same, as in the former examples, when the ordinates are 0, 2, 3, 3-5, 4-5, 5, 6, 7-5, 8, 8-5, 9, 8, 7, 6, 5"o, 4-0, 4, 3'5, 3, 2"5, and 2 feet, and their distance apart is 2 feet. Distance along Aj An from A, = 20 feet nearly. Distance above Aj A„ at the above point = 30506. (5.) Find the same when the equidistant ordinates mea- sure 17, 18, 18-5, 19, 19-5, 20, 20-5, 21, 22, 23, 22, 21-5, 20, 19, and 18 feet, their distance apart being 4 feet Distance along A, An from A, = 28605. Distance above Aj An at the above point = 10-134. Examples on the Calcuhition of the Centre of Gravity of CalcuU- DisplacemeTit. Half Horizontal Areas in equare feet, ftund by Simpson's Kule. ,289-2.5 300-0.5 3-.'5 00 _ 400-2.5 o 40.5-2.5 S 4.50-i;5 g 470-7.5 3 490 00 D 49.5 -J.5 S" 500 00 3 "I 487 fi.5 =■ 470-6.5 ^ 460fi.5 S- 450-7.5 ^ 435-2.5 40016 39000 375-25 ,350-00 7643-23 = X X X X X X X e X 7 X 8 X 9 X 10 X 11 X 12 X 13 X 14 X15 X 16 X 17 X 18 Half Areas Half-vertical Half- Areas multiplied byO, 1,2.&<:. respectively. multiplied by 0,1,2,3, Areas in square feet. ,49-75 X = 000 -00 00000 9 49 95 X 1 ^ 49-95 300O5 q 5200 X 2 ^ 104 (JO 6.50 -no H 54-25 X 3 = 162-75 120075 66-45 X 4 = 225 80 1021-00 7S4.-i X 5 ^ 392 15 2253-25 60-00 X 6 = 360-00 2824 60 h 55-25 X 7 = 386-75 3430-00 48-65 X 3 ^ 389 2D 39f.2-00 ^ 47 00 X 9 = iam 460000 45-75 X 10 ^ 457-50 487f;-50 5-: 43 50 X 11 = 47850 617605 42 23 X 12 ^ 50676 6527 80 !* 40-22 X 13 = 622-86 6869-75 ^ 38-21 X 14 = 634 94 6093-50 Volume by Simpson sRule = 7643 2.1 6002-25 nearly. 6240 00 6379-25 630000 tions inci- dental to designing a Sliip. volome by Simpson's Bole. 1st, Beginning with the results in the right-hand column of the horizontal section : — Results. 0000-000 6300-000 Result.'. 300-05 1200-75 2253-25 6300-000 sura of 1st and last 343000 4500-00 6176-05 5859-75 600225 637925 Results. 650-00 1621-00 2824-50 3962-00 4876-50 5527-80 6093-50 6240-00 [results. [results. 31795-30sumof odc{ 35101-35 sum of eren 4 140405-4 63590-6 63000 210296 1 3)210296 63590-6 twice do. four times do. twice sum of odd do. sum of first and last do. common interval. 70098-6 result obtained by ' Rule." Simpson's Therefore, distance of centre of gravity of main body heUnu the plane of flotation ^^ 7C098-6 70098-6 = 9-17 feet. volume 7643-23 ' 2d, Taking the results in the right-hand column of the vertical section : — Results. Results. 49-95 104-00 162-75 22580 392-15 360-00 386-75 389-20 423-00 457-50 478-50 506-76 522-86 [resulta. [results. 2043-26 sum of odd 2415-96 sum of <r«n 2 Results. 000-00 first result. 534-94 last do. 534-94 sum of do. 4086-52 twice do. 9663-84 four times do. 4086-52 twice sum of odd do. 534-94 sum of first and last. 14285-30 10-56 common distance. 857118 714265 1428530 3;150852-768 ^ The calculator will ahvajs have a check on his w-ork by observing the length of the axis A, A„, and observing also whether or not the ordinates near the beginning ditfer widely from those at the end. If the ordinates do not differ widely in this sense, the centre of gravity will be determined by a line perpendicular to the axis near its middle point. If the ordinates are greater near the beginning than at the end, the centre of gravity determined along A, A„ will be nearer the first ordinate than the laft, and cicc vend. SHIP-BUILDING. 50284-256 result obtnirieil by 10-56 common distance. 301705536 251421280 602842560 531001-74336 , distance of centre of gravity from first vertical section ■ Simpson's [liule." 53100174 7643-:;3 5 to be that nearest = 69-47 feet. We shall suppose the first vertical section 49- the bow, and 234 25 cubic feet, to be the volume of the portion below the Inst horizontal section, or the portion just above the keel. 22-5 feet, the distance of its centre of gravity below the plane of notation. 70- ,, from the first vertical plane. 324-76 cubic fuet, the volume of the portion bf/ore the first verti- cal plane, or betvreen this plane and the bow. 10 and 7 feet, the respective distance.i of the centre of gravity from the same pliine.s as above. 57600 cubic feet, the volume of the portion aft of the lost verti- cal plane, or lying between this plane and the stern. 8 and 160 feet, the respective distances of the centre of gravity from the planes already mentioned. Then, if d/, <J„ be the distances of the centre of gravity of the total displacement from the planes of flotation and first vertical, we have _ 7643-23 X 917 + 234-25 x 22-5 + 324-75 X 10 -t- 576 x 8 ^~ 7643-23 + 234-25 + 32475 + 576 = 9-48 feet below the plane of flotation. 7643-23 X 69-47 + 234-25 x 70 + 576 X 160 — 324-75 x 7 d.= 7643-23 + 234-25 + 576 + 324-75 = 71 8 nearly. The reader will perceive that all the quantities are added in obtaininsj the former result, and that the last one is sub- tracted in the latter case. The reason for this i.s, that in the latter c.ise, the portion forward lies on the opposite side of the first vertical plane to all the rest, or is measured, what we iiave called barkicurds. Now, if we had considered the first vertical section, -19-75, as bein<; taken at the stern, then 324-75 X 7 would have been added, and 57G x 160 sub- tracted, in consequence of the portion aft lying, in this case, on the opposite side of the first vertical plane to the other portions. In the first result, all the portions lie below the plane of flotation. We also perceive that the centre of gravity lies between the sixth and seventh vertical sections inasnnich as their common distance is 10*56, and 10"56 x 6 = 63-36; also, 10-56 x 7=73-92 ; therefore 71-8-63-36 = 8-44 feet abaft the sixth section. MOMENTS OF INERTIA, &C. Moment of Ai!T. 6. — As the calculation of Moments of Inertia are inertia and of the greatest importance in the determination of the stability of a vessel, we proceed to furnish the reader with a short sketch of the subject. Def. (1.) — Tlie sum of the products of the mass of each particle of awj si/slcin into the square of its distance from any straiyht line is named the Moment OF Ineutia of that System about the given line. Def. (II.) — Jf k be a quantity such that the moment of inerlia = Mk\ then h, the distance at wliich we may sup- pose the whole mass, M of the body, collected so as tiot to alter the moment of inertia, receives the name of the Radius OF Gyration. Thus, if m,, nij, njj, &c., be the nmsRes of the particles, and r,, rj, rj, &c., their respective distances from a line about which the 1 )dy or system revolves, radiuii of gyration. „,. , 2 _ m, r' + ni; r^' + m^ r.,'-f &c. 3 (m r-) '"l-f'nj-l-'ns-f &c. ^iv*) _f/fe^^_dxd^d$ ~ JfJidxdyd: ( representing the density, and x, y, x, the co-ordinates of any point of the body or system. In the calculation of the motion of a ripid body, or system of bodies invariably connected, we meet with the following expressions; — 2mx, 2'nj/, Imt Z'xxt/, 2f».r7, "iiniiz 2/uj:-, ^my-, 2m;^ Now if M represent the total mass of the body, or system, of which m represents a particle, x, y, z, the co-ordinates of the centre of gravity, then Mx = 2mx, My ^ 2niy, ils := 2m Note 6, p. 37. If we select a plane passing through the centre of gravity for one of the planes of reference, that of xy for instance, then Mz = o .-. 2nir ^ o. If we select for the axis of z, a line through the centre of gravity, and take the origin of co-ordinates at that centre, then we have simultaneously X =: 0, y = 0, 2 =: 0, and therefore 2m.r = o, 2my = o, 2niz = o. In general for any body, or system of bodies, the axe> of co-ordi- nates may be so selected that Smxy, Sm.rr, and 2my: become separately = o. Def. (III.) — Axes so chosen are called the Principal Axes of the body at the point which is taken as origin. Prop. (I.) — The moment of in- ertia of any system about any axis is equal to the moment of inertia about an axis Ihrour/h the centre of gravity parallel to the former ; plus the product tf (/ the mass of the system into the square of the distance between the two axes. For, let p be a particle whose mass is m, and A and G be the traces of two lines (passini; through ;> at ri^'ht angles to each other) on a plane, the latter one being drawn through the centre of gravity G of the body. Draw pp' _I_ to .-X G, or A G produced and join pA, pi}. Thon p\- = ;)G2-HAC2-h2AG . G;/ (Euclid, II. 13), And 2(m . /lA-) = 2(m .pG-)+2(m . AG2;-|-S(2m . AG . Gp'). liut as above, 2mfjp' ^ o .". S (2mAG . G;)') ^ o. And 2 (m . pA^) = 2 (m . pCi^) + 2{m . AG^). If A be the distance between the two axes here mentioned, and k the rodius of gyration about an axis through G, the moment of inertia about the axis in question ^ M (h^ + k-) and V/i--hi- is generally named the radius of gyration about the given axis. Pkoi". (II.) — The moment of inertia of any plane area about a perpendicular axis is equal to the sum of the moments of inertia about any two lines at right angles to each other in the plane of the area passing through the point in which the axis meets the area. Keferring to the figure in the last article where Aji is at right angles to Ap', and p>/ perpendicular to Ay. .-. 2 (m . Ap-) = 2 {m . pq-)+2 (m . pp'^) Which establishes the proposition. Def. (IV.) — The moments of inertia of a body about its principal axes at any point are called its principal moments at that point. If we take the principal axes for the co-ordinate axes and repre- sent the principal moments by A, B, 0, then if 1' be the moment of inertia about an axis whoso direction cosines are *, ^, y, then where «- + ^'- + y'' = l .-. (A-p)«=-i-(B-P)p=-(-(c-rjr=o Principal axis of bodies. First im- portant itule for finding the moment of inertia of bodies. Second im- portant Uule for finding the moment of inertia of bodies. SHIP-BUILDING. 43 then one ofthe quantities A-P,B-P,orC-P must have a negative sign, and therefore P must lie between the greatest and least of the quantities A, B, and C. Hence, of all moments of inertia about axes through a given point, the moment of inertia about one of the principal axes is greatest, and about another the least.' (1.) Find the radius of gyration of an indefinitely thin rod about an axis in its own plane at right angles to its length and passing through an extremity. Let X be the distance of any point p from the axis, t the indefi- nitely small thickness of the rod, and ; its density, supposed uni- form, then ri<.'ht angles to the axis ; 2d, about the axis ; 3d, about a Stability line through its vertex at right angles to its plane. of Floating Then y- •=. ^mx. 1st, .•. rad. of gyration about line through vertex at right angles to axis and in the plane of parabola *J :2 dx-=.^ "- where a is the length But M^^Ta (2.) Find the radius of gyra- tion of a circle about an axis in its own plane passing through its A B the diameter or axis about which we wish to fiud the moment of ul inertia. Take a lamina p^ parallel to the given axis Cr=Ar, i>r-=zt/. Then, aJ! + j,2=:a2 .... (I) where a = radius is the equation to the circle. If r be the very small thickness of the circle, j its density, we have for the mass of the lamina 2^Tudx. 2^1- I ydx y. x^ I c^ydx J.i:-d.tVa?~x^ i^TJiidx lydx IdWu-— 1~ a? {d- — x^) J O"^^ ~ W a^ — x^ + ^- s\n. — Take this between the limits a: = a and x = — a and k- = — . ■i (3.) Find the radius of gyration of a circular area about a straigiit line parallel to its plane at a distance c from its centre. i2 = ^ + c2 (Prop. I.) (4.) Show that the radius of gyration of an ellipse about its major and mmor axes are -r and -7- respectively. (5). The radius of gyration of a circle perpendicular to its own plane and passing through its centre = —, and about a similar axis for the ellipse = -(a- -f- 6"). . . (Prop. II.) (6.) The radius of gyration of a triangle about an axis perpendictdar to its plane and passing through its centre of gravity = ^ (cr- + 6--(-c"), and about an axis at right angles to its plane and passing through one of its angular points = Y^ (3a- + 3i- — c") where c is the side opposite the angle through which the axis passes. (7.) Find the radius of gyration of a parabolic area, 1st, about a line atid its plane jiassing through the vertex at Bodies. l^Tix'ydx 2m- ix^dx -=■ . 2srlydx ..f -+c dx Take this from ^ := to x = a and the result is ^ a* 2J, If 26 be the double ordinate, a the abscissa, Rad. of gyration about axis = 2{T/(a-x) y-du j( a-j— li'^'iy fcZ (rl(a-x)dy 20 am«2- 3.1,5 60 amy — 10 y^ + C. But m =: — and if we take the integral between the limits y = b ia " and y =. — }) we obtain rad. of gyration about the axis : 1 62 3d, rad. of gyration about an axis through vertex, at right angles 3 1 to the plane of parabolas- a2+ — 62 .... (Prop. II.) (8.) Find the radius of gyration of the parabolic area 7/ = A -f !5.r + C3?, bounded by the double ordinates 2a, 20,. Note 1, p. 30. About the axis Aj Xj also about an axis parallel to the former at a distance c ; hence, deduce the moment of in- ertia of the plane of flotation about its longitudinal and transverse axes through its centre of gravity. STABILITY OF FLOATING BODIES. Art. 7. — Various definitions have been given of the stability of floating bodies. The reader w ill probably com- prehend the term from the explanation and definitions which follow. Euler, in his Theory of the Construction of Vessels, &c^ as translated by Colonel Watson, observes, that, " As soon as a vessel becomes ever so little inclined, or displaced from its state of equilibrium, three consequences may liappen : — 1st, Either the vessel remains in the inclined state ; or, 2t/ly, It re-establishes itself in its preceding situation, when its equilibrium will be permanent, or rather, it will be endowed with a stability which may be great or little according to circumstances ; or, Sdly, The vessel, after this inclination, will be completely overturned. This equilibrium is calkd unstable, or reatiy to fall. We can see, evidently, that neither this last case nor the first can have place in vessels ; and with respect to the second case, a sufficient stability is absolutely necessary."^ The last remarks here made are not altogether true when a vessel is inclined through considerable angles by impulsive forces, ^^'e shall therefore proceed to investi- gate the different kinds of stability. Def. (1.) — Statical 'Stabiltix is de/iiied to be the mo- ment o/" force {or effort), by which a floating body endea- vours to regain i/s xiprighl or vertical position, after having been deflected from that position. Def. (II.) — Dynamical Stability is defined to be the amount of work' done on any body, in order to deflect it through any angle from its upright position. As has already been stated, it is shown in books on Hy- drostatics, that when a body floats in equilibrium, the fi'l- low ing conditions must be fulfilled : Stability. General principles. Statical Stability. Def. Dynamicf Stability. Def. ' Griffin's Dynamics of a Bigid Body, p. 9. See also Koulh's liitjid Dynamia. 2 Vide chap, iv., sect. 22. of the work here mentioned. ^ By the amount of work here alluded to, is meant the weight of the body, in pounds avoirdupois, multiplied by the vertical height, in feet, of the sum or difference of displacements of the centres of gravity of the body and of the water which it displaci-s. 44 stability SIIir-BUILDING. \st, .''e iV,i ^ ;)Ar, or Bini|)ly {Vj = M, of Floating where M represcms tiie mnss of the flouting body, V^ the volume Bodies, of wotcr displaced, ; the density of a cubic unit (say a cubic foot) V , / of water, and <; the accelerating force of gravity. ' 2il, The centres of gravity of the body, and of the water which it displaces, must lie in the same vertical line — that is, in a line at right angles to the plane of flotation. From the first condition, namely Vj^ — , it is at once manifest, { that in many bodies, such as some of the solids of revolution, this will furnish us with an infinite number of positions of equilibrium, for all of which the second condition will be fulfilled. When a body is inclined through any angle from its upright position, the plane of flotation will differ in position from the plane of flotation in the former case ; and for every plane of floata- tion the centres of gravity of the vessel and its displacement will in general have different positions. If we suppose the vessel to roll and pitck' uniformly through any finite an^'les. the centre of gravity of displacement tij, or centre of buoyancy, as this point is sometimes called, will describe a portion of a surface in the interior of the vessel. It will readily be comprehended by the reader, that a vessel may possess a great amount of both kinds of stabilitij specified in the definitions up to a certain point, that is, through a given angle from its upright position, and then instantaneously become un- stable. Sufficient attention has not been paid to this fact, inas- much as writers on stability, as applied to ships, generally neglect to discuss the case of unstable equilibrium. It is a well-known fact, tliat ships have been capsized through unforeseen impulsive forces, as in the case of the lloyal George.^ When the vessel has been inclined through any angle, it has been always customary to assume that the volume of the portion which is emerged is equal to that which is immersed. This is not accurately true, on account of the inertia of the vessel and the water, as well as on account of the effect of the wind on the sail.s, « hich may tend to increase the total displacement. Property Art. 8. Theorem I. — The line joining the centres of common to ijravily of the displacement of the body in any two positions all bodies jg parallel to the line joining the centres of gravity of the " -" ■"- tpiiiigj-scil and emerged portions due to these positions. For, let FKIi' represent a transverse section of the body, made by the plane of the p^iper, and Gj, G'j the projections of the centre of gravity of displacement in the two positions,^,, <7; the projec- tions of the centres of gravity of the emerged and immersed volumes due to the two positions. Then the immersed portion of the body in the two positions will have the common part (the section of which is shown by F'PLK), where « represents the volume of the part emerged or immersed. Let 0' be the projection of the centre of gravity of the volume Vd — v on the plane of the paper, then by the principles which have been already enunciated (Art. -4, p. 36, &c.), the centre of gravity Gj is determined from Ojy,xv = GjO'x(Vj-v) (1.) and the centre of gravity G'j, in like manner from g,G'dXv = G'jO'yi(\\-v) (2.) Hy (1.) and (2.) a, Gj x G'^O' = <7i G'^^G^ 0'; or, g.Gj-.GjO'-.-.giG'y.G'jO; hence Gj G'j is parallel to ^, jj. (Euclid, vi, 2.) Next, if we consider the volumes immersed and emerged to be infinitely small, or, in other words, the two planes of flotation, of which FL, F'Li', are the projections, to be indefinitely near, the centres of gravity of these two volumes may be considered as situ- ated in the plane of flotation (FL). In this case Gj G'j becomes parallel to FL, that is, Gj G'j becomes a tangent at Gj, to the c«rc« traced out by the latter point in the plane of the paper. This is rigorously true at the limit, no matter in which direction we sup- pose the body to revolve (through an infinitely small angle) : it fnl- Stability lows, therefore, that all the tangent4> drawn through Gj are parallel of Floating to the plane of flotation ; hence liodiea. Theorem II. — 77/e tangent plane,' drawn through the ^■^/■"^ centre o) gravity of displacemoit in any position to the iur- Tangent face traced out by this point during the rolling and pitch- p'*'"-" ""o ing of the vessel, is pnralhl to the plane (f flotation cor- V,^*- ° responding to that position. Art. 9. — If G (fig. 7) denote the centre of gravity of the float- when in- clined through a given angle. Fig. 7. ing body, and Gj that of the water displaced, then in positions of equilibrium Gj G is a normal* to the surface described by the latter points. For, by the second condition of equilibrium, given in .\rt. 7, G^ G, is necessarily perpendicular to the plane of flota- tion, and is therefore perpendicular to the tangent-plane at the point Gj, since the latter plane is parallel to the former. Let us suppose the surface traced out by Gj to be actually described, then if from G, the centre of gravity of the body, we draw all the normals which it is possible to do from this point to the sur- face, we shall determine as many portions of Gj as there are nor- mals, and consequently as many planes of flotation, for all of which there will be equilibrium of one kind or the other^that is, 3tabU or unstable. A rolling motion will be suflScient to establish the following principles : — Let us suppose the plane of the paper to be that transverse vertical section of the vessel which contains the centres of gravity of the vessel and its displacement when floating at rest. Next let the body be made to roll through any angle, and the point Gd will describe a curve in the same plane, which is represented by AGjB. Let G</, G'j (fig. 7) be two consecutive positions of the centre of The Met«- gravity of displacement (that is, two positions indefinitely near to centre or each other) ; draw normals through these two points to the curve centre of AGiB. ami let them intersect in M, the latter point in geometry curvature. and analysis receives the name of the centre of curvature ; but in regard to the floating body it was named by Bouguer the meta- etntre, and the circle described through Gj with radius MGj is called the circle of curvature, or sometimes the osculating circle. The curve described by the centre of gravity of displacement Metacen- (centre of buoyancy) has been named the metacentric curve. Mr trie curve. Head, late master-shipwright of II. M. Dockyard, Sheerness, pro- ' By a rolling motion is understood a motion about a longitudinal axis, or from stem to stern. By a pitching motion is to be under- stood the motion of the vessel about an axis at right angles to the former axis, or about an axis which lies in a transverse vertical section. During a rolling motion only, the centre of gravity of the vessel will remain in the same transverse section ; and during a {'itching motion only, the centre of gravity will remain in a vertical section at right angles to the former. When the motion is due to rolling and pitching combined, the vessel will revolve about an inilantaneout axis, which may be determined, 2 And in all probability many other vessels.- " By a tangent-plane is here meant a plane which touches the surface described by G** at a given point, and which, if produced, does not intersect this surface. For the general definition of a tangent-plane and its properties, see llymer's and Gregory, and Walton's Geometry of Three Vimenrions. * By a normal to a surface at a given point is meant the line drawn at right angles to the tangent-plane at that point. SHIP-BUILDING. 45 Stability poseil to call it the mrtacrntric involute, and the curve described by )f floating SI the metacentric erolute} which terms are strictly in accordance Bodies, with mathematical theory. V ^. / It will he seen hereafter that the position of the metacentre is ^ of the greatest importance in the determination of the stability and times of oscillation of vessels. Its heiijht above the centre of gravity of displacement may be determined as follows — ' Art. 10.— The notation and figure remaining the same as in the previous article ; the ordinates measured on the half-breadth plan at the load-water line being employed. Rnr.E XIV. — Ciche the ordinates measured on the half- hreadth plan, introduce tliese CTBES as orditmtes in Rule /., p. 30, and proceed as therein stated ; divide the result thus ohtained hi/ the volume of tvatcr displaced, and two- thirds of the quotient gives the distance of the metacentre from the centre of gravity of displacement. Let the vessel be slightly inclined from its upright position, we may consider the areas FPF' and LPL' to be two equal sectors of the same circle ;- then g, £f„ the line joining their centres of gravity, will bisect this angle. Draw (f, jJj, J;?] perpendicular to F'L', and Grfll perpendicular to MG'j. Let r = FP = F'P = LP = L'P, and it is well known that the centres of gravity are determined by „ „ 2r.chordFF' 2r.chordl,L' 3 arc FF' 3 arc LL' 4 r sin ^ " 3 (( ^ being = <; FPF' But area of sector FPF' or PLL'=- And PPl = P?l = P3'«-co4= Pi'' 4 r sin r COS V 3 p li r sin ( 3^ Also moment of sector FPF', or sector LPL', ^ area FPF' x Ppj = area LPL' X P?, = — r^ X — ^. ' 2 6 ip r ^ Pin ip (I-) Now, since the solids emerged and immersed are supposed to be equal, and that these solids may be conceived to be collected at their respective centres of gravity, it is clear that the centre of gravity of the volume of water emerged has been moved from p, to q^ in the direction F'L', while the total volume of water dis- placed by the vessel has been transferred from G,2 to R in a parallel direction. Hence taking moments, we have, by elementary nieclianical principles, GdRx jx Vci = ;)j7i X J X c. . . ... (11.) Or, GdR . Vd =: p, 7, . V. But the angle FPF' = angle GaMO'j between two consecutive normals .-. MGd sin <p = GdU From (II.) MGd = ^,L?'.— (III.) ' Yd sm f * ' Kow, if we imagine a plane drawn parallel to the plane of the paper, or to the section shown in the figure, and at the infini- tesimal distance a«, the moments of the volumes of the solids emerged and immersed will be represented by -~ S r3 A X, from (I.), or —^ I r^dx; by employing the notation of the Integral tjalculus, observing that the integral here given must be taken from stem to stern. MG<i=- hP'-- \ d Sin ((J from (III.) , . (IV.) The integral /^ , . , . . , Stability r^dx IS sometimes named the moment of intrtia or^j. Floatiiia the load-water section FL, about a horizontal a-tis through the ^ ' ^ centre of gravity. ^^^/"^^ It ought to be observed that, though we have here obtained the position of the metacentre of the vessel when in a vertical position, this point may in like manner be obtained, by employing the same rule, when the vessel is inclined through any an;/le, providing we substitute the ordinates of the inclined load-water section for those of the load-water section of the vessel when in an upright position. Art. 1 1 — Having obtained the position of the metacentre, we are now in a position to determine the nature of the equilibrium when a vessel is in any position ; for, if we call the lengths of the lines drawn from G, perpendicular to the curve described by Gj, NORMALS, then Theorem III. — Positions of stable equilibrium cor- Stable and respond to miniiiu.^i 7iormals, and positions of unstable unstable equilibrium correspond to MAxniuM normals : also these ^l"'"' normals ivill have alternutdij maximum and minimum values.* Various demonstrations ef this theorem have been given in books on Hydrostatics, and the reader will find the subject dis- cussed in the Mechanic's Magazine, a periodical which contains many valuable papers on shipbuilding. The following exposition of the principle may be found sufficient for the mathematical reader. If (fig. 7) M be the centre of curvature corresponding to Gd, and situated at first above G, the osculating circle at Gd will lie both within and without the curve AG^B in the immediate neighbour- hood of G,;, and the circle described from G as a centre, with radius GGd< will lie entirely within the curve in the vicinity of Gd, and the normal GG^ will be a minimum among all those drawn from G to the points of the curve in the neighbourhood of Gd ; that is, GGd will be less than GG'd and GG "d. If M lie below G, we learn by the same reasoning that GGj is greater than GG'd and GG"d, since the circle described from G with radius GGd lies en- tirely without the curve AGdU; that is, the contact is of the third order. ^ These normals are alternately maxima and minima, since be- tween two maximum values there is a minimum, and a maximum between two minima. There are as many maximum as minimum values; hence the number of positions of equilibrium, neglecting the kind, is even. Moreover, Theorem I V\ — When the metacentre lies above ^^e Condition centre of gravity of the vessel, the equilibrium is stable, for stable equili- For, if we incline the vessel in such a manner that Gd shall be jj^jy^, at G'd, indefinitely near to Gd. the normal at G'd will pass through II (since the latter point is the intersection of two consecutive normals); then the weight of the water displaced applied at G'd will be parallel to MGd and will act upwards, whilst the wei^lht of the body at G' will act downwards in the direction parallel to MGd and it is evident tliat the effect of these two forces will be to bring the points M and G'd into their original position.^ Theorem V. — TV/ien the metacentre lies beloav the centre of gravity of the vessel, the iqiiiltbrium is UNST.MiLE. For, inclining the vessel as before, through an indefinitely small angle, the effect of the two forces just mentioned will bo to bring G' and M into a vertical position; and since G is above AI, the vessel will be capsized.^ Theorem VI. — When the metacentre coincides with the centre of gravity, the equilibrium is said to be indifferent or Jicutral ; that is, the vessel will rest in the position in which it is then placed. Art. 12. — Having obtained the kind of stability, we may Condition for un- stable equi- librium. Condition for indif- ferent or neutral equili- brium. 1 The metacentric curve is that made by any plane (a transverse vertical one in the present cose) with the metacentric surface. * It is not necessary to consider the sectors as equal, providing we bisect the angle FPF'; and with centre P and radii PC, PC, we describe arcs of circles intersecting the two planes of flotation (the projections of which are FL and F'L'), the same result as is obtained below may be shown to hold true. " Because 2 sin J' cos ^ sin f. » See Hall's Cakulus, p. 200. * Maximum and minimum mean greatest and least values. ° Tlic axis about which the vessel rolls is here not supposed to pass through the centre of gravity. 46 SIIIP-BUILDING. 8tal/ility nt once obtain tlic analytical condition for the natiual of Floating STABILITV of a boily after liavinj; proved tlie followinj; :— Bodies. V.-v/'^-' Theorem VII. — Tlie centre of gravity of a plane offlo- Centre of '"'""' ^"'•' "" t/ie line of its intersection, with a plane ofjlo- gravity of t"l'on iitdejinitely near to the former plane. plane of jjet pQ represent tlie intcrsuction of the two planes here nion- flolation. tioned, <7,</', the centres of gravity of the areas F.PQ , ^, and LPQ, the areas being denoted by A and A'. Now, the centre of gra- vity of FPI>Q is obtained by dividing g y' into two parts reciprocally propor- tional to those areas. Ijet, then, ^ bo the infinitely small angle between lh<> two planes of flotation, I and I' the perpendicular distances of <j, g\ from rtj. As the wedge-like portions emerged and im- mersed are exceedingly Fig. 8. Biiiall, we may apply the principle of Guldlnus, gUen at page 37, viz. : — 1 Volume F'FPQ = A/f, and volume LL'PQ = AY^; and since these volumes are equal .-. Alp = AVip or M = A'V ; that is, / : r : : A' : A (1) From the similar triangles ghO, g'h'O, we have, l-.V ■.-.gO-.gO (2) hence by (1) and (2), gO : ^'0 : : A' : A ; that is, is the centre of gravity of the plane of flotation. It is clear that the point will trace out a curve in the plane of the paper, provided the body be made to revolve through a finite angle in this direction, and F'L' is a tangent at to this curve. Moreover, the vessel might be made to revolve in any direction, and the point would then trace out what is called the surface of flotation. From the manner in which we have obtained the result just given, we arrive at Kuler's theorem, viz., — The point of contact of the plane of flotation with the turface of flotation it the centre of gravity of that plane. Moreover, if we conceive (.iA,) to represent an elemental portion of the plane FPQF, and r, the distance of this element from PQ, then p (.iA,) r, will represent the corresponding volume of the portion FPtJF', assuming it to be a solid of revolution, and the total volume is got from v=f {(aA,) r, + (,iA2)rj-KAA3) r, + &c.} = $2 (.iA)r. We know from the formula for determining the centre of gravity of bodies ( p. 37 ), that ^Q ^ ^ {(.^A^)r^2 + (:,A,y,^ + (^A^)r^^ + kc.} f{(AA,)r,-l-(AA2)r2-^(.iA3)r3-^-&c. } ~f2{.^A)r pfdA.r by employing the notation of the Integral Calculus, and bearing In n<ind that these integrals arc to betaken between projier limits: — Now, fdA . r^ is called the moment of inertia of the plane I'QF in regard to the axis PQ, the density being unity .(See Art G.) .gO = ' . ki representing this moment of inertia; also, .**i g'O ^^—i, where k. represents the moment of inertia of the o plane LPQ, in regard to the same axis. But gg' = gO + g'O = ^— ' — =: — , k being the moment of inertia of the plane FPLQ in regard to PQ. Returning again to fig. 7, where ge, <7i, represent the centres of gravity of the inde- finitely small volumes emerged and immersed, we have shown that gt Si is parallel to Gd G'd. GdG'4 _ \'4 _ pk _ Stability ■*■ 9e:ii ~ « ~Vd'' of Floating and f being the angle between two consecutive normals, then ""d'*'- Mf!<j^ -! = — ' , since p is exceedingly small, and the 6in p f sine may be taken equal to the arc, and ge gi >s the same os the value of gg' (given above) at the limit; henee "«-f. = ^ We have seen that the condition of italU equilibrium >Gl.:j; so that if A denote the distance GGj, the condition is v^>*>-S>* ("•) Theorkm V'III. — The moment of inertia of the plane of Condition flotation must be greater titan the product of the volume of for stable ivater displaced, and the distance between the centres o/'''1"''' gravity of the body and its displacement. The value of k may be found by Art. 6. brium. From (I.) GdM = GGj-t- CM = '- ,GM=e^. GGd (HI.) Art. 13. — To determine the line of intersection of the plane of flotation of the vessel, tc/ien in a vertical position ivith the plane of flotation, tchcn the vessel has been inclined through any angle ; or to lietcrniiiie tile point V (tig. 7) of the intersection of FL and F'L'. Through (fig. 7), the middle point of FL, draw/;, making the angle K0/= LOi =: given angle p. Let the volumes, of which FU/and \jOI are sections, be represented by Vj and V^ respec- tively; also, letrj and r^ represent the volumes of which EPO/aitd fj'POl are sections, and p = volume emerged or immersed ; then Vj = V + v.^ ; and Vj ^ w — V| ••• V2 — V, = 1/1 + ^2 = area of plane/Z x OE (nearly) where 03 is drawn perpendicular to F'L'. But OE = OP sin p V _v ... OP = l3__Li___ (I.) area plane// sin ^ ^ ' Various methods have been recommended for the calculation of the solids V2 and V^, as well as for the volume r, all three of which are obtained in the same way. The following plan will guide the reader to find v: — lit. Join FF' and LL', and the areas of the triangles FPF'j Ti'I> ' - - or LPL' = FP.F'Psina LP.L'Psina 2 ■°' 2 2nd. The curves FCF' and LCL' may be considered as parab- olas, and the areas lying between FF' or LL' and the curves are equal to 2 FF . X perpendicular height of segment F(JF' and 2 LL' X perpendicular height of segment LCL' , — — ; or we may employ Zrd instead of 2nd to find the areas of the segments just mentioned. , 3rrf. When p is very large, ordinates may be measured at right angles to FF' and LL' (seven will always be sufficient), and at equal distances apart, and the area found by Itule (III.) Art, I. (or by Kule I.) ilk. Having found the arias FPF' and LPL' made by each ver- tjral section, introduce these as ordinates in Rule (I.), and proceed as therein stated. Rtmark. — Several writers have proposed to draw the ordinates, mentioned in (3), parallel to the plane of flotation. There is, how- ever, little labour saved by such a plan. For a very large number of vessels, which are full below the load-water plane, the following method may be applied, and will, it is believed, be found almost as accurate as those just recom- mended. Bisect the angle FPF' by the line CC", and with radii PL', PC', describe the arcs IICH' and NTS'; then the sectors will, in general, be very nearly equal in area to the portions FPF' and LPL'. If CP = r, and C'P = », then the area of the sector UPU' = :^, and area NP.N'= 'p. Summing these areas (by Rule * We here suppose that the volumes emerged and immersed are soHds of revolution, that is, solids described by the revolution of th« planes FPQ and LPQ round PQ. This assumption will be accurate enough when the angle p is very small, as we have assumed it to be. SHIP-BUILDING. 47 Stability I) from stem to stern, and writing r, , r^ , r,, Ac, for the Ist, 2d, 3d, of Floating &c., radii, with similar expressions for », &c., we have ,^f^^^ Volame emerged = -| | r,2 + r2„ + 4 (r.,' + r/ + &c.) + 2 (r^s + '-6= + *<=■;} Volume immersed = -^- | !,- + -'„" + 4 ('2' + 'i' + *<'■)+ - (.'i + '5' + *0} New rule Calling the lines CP, C'P, measured on each vertical section, for finding ordinates, we have the following approximate rule to find the the vol- volumes of the solids emerged or immersed : — umes of , r, 1 /^ J 1 i immersion RcLE XV. — To the sum of the squares of the first and last and emer- ordinates add four times the sum of the squares of all the sion. f^.f.,1 ordinates, and twice the sum of the squares of all the odd ordinates ; multiply this result by the common distance 3-1416^ and by the circular measure — Joq" ' <^o''^^^onding to the angle through which the ship has rolled — divide by 6. and ice o^it'iin the vnlnme required {nearly). Art. 14. — Returning to Art. 8, and referring to fig. 7, Draw GT parallel toMGrfand GG' parallel to G jR. Then, GjR . 5 . Vj =p,7, . 5 . w ; And GG' = G<iR— GdT Vilx ■ ? ■ Measure of jtaticalsta- sUity. r^ GG': -Pill ■ e • •GG<isin{). t)-GG^. {. VjSin^; ^avitydue o Chap nan Or, W . GG' = (;>,?1 .«; — GGi.Wsinp) . . . (I.) «/ representing the weight of water emerged or immersed; For- mula (I.) measures the itatkai stabilitu, Def. (I.) of a vessel as given by Atwood in his paper published in the Transactions of the Royal Society for the year 1796. ilethod of Art. 15. — The rule most frequently used by naval archi- inding the tects to determine the centre of gravity of a vessel, when lentre of {n\\y equipped for sea, is due to Chapman, and is as follows : — Suppose any weight ''or weights) W,, either on the upper deck or els«where, to be moved from its position at Wi(fig. 7 ) to another posi- tion, as ^V'',. and that by this change of position the ship has been in- clined through the angle (p. From W'j (the centre of gravity of the weight or weights) draw \V',E parallel to F'L', and W,E perpendicu- lar to\\",E; then WiE:=\V[W, cos ip^c cos f; ifWj\V'j=:c. So long as the disturbing weight "Wj remains in its new po3i[ion Wj, the vessel will remain in equilibrium, and therefore its centre of gravity must lie in the line G'^M by the second condition of equi- librium. Hence it has been transferred a distance GG' parallel to the plane of flotation F'L', while W| has been moved through a distance \V',E in a parallel direction. Taking moments, we have W . GG' = Wi, ccos f. From Equation I. of last article — PP>_ Pi ?l"'-GGj. W sin (p W Writing this latter value of GG' in the former equation, we get W sin f which determines the centre of gravity of the ship, when the centre of gravity of displacement has been determined. Mr Abethell, master-shipwright of H.M. Dockyard, Ports- mouth, proposed thefollowing method, in the second volume of the Papers on Xaval Architecture: — " It is applicable whenever a ship is taken into dock with the under side of her keel deviating from parallelism with the upper surface of the blocks. This is almost always the case ; and it also not unfrequently occurs that ships are docked 'all standing,' and with so large a portion of their armament and stores on board, that the correction necessary to be made to the result which would be obtained by the experiment and investigation about to be described, in order to make that result agree with the circumstances of any additional armament and equipment, would bo comparatively easy. We will now quote from the article in question. inotber lethod ue to Mr Ibethell. " ' We will suppose, by the falling of the tide in the dock, the Stability after e-ictreniity of the keel to come first in contact with the blocks; of pioating then, as the tide continues to fall, the after-body is gradually for- Bodies, saken by the water, and the fore-body further immersed, a constant v. ^ / equilibrium being maintained between the total weight of the ship ^ and the p'-essure of the water against the immersed part of the body, until the ship is aground fore and aft. At any intermediate instant the ship may be considered as a lever of the second kind, of which the fulcrum is the transverse line or point of contact of the keel and after-block, and the power and weight, the weight of the immersed volume and that of the ship respectively, each acting in the vertical line passing through its centre of gravity. As we can, by mensuration and calculation from the draught of the ship, easily find its weight, that of the immersed volume, and the perpendicular distance of the line of pressure from the fulcrum : in the equation of the moments, the distance of the vertical line passing through the centre of gravity of the ship is the only unknown quantity, which is therefore readily deterniined. AN (fig. 9} represents the Fig. 9. water-line corresponding to the floating position of the ship, and KL the observed water-line just previously to the fore-part of the keel touching the blocks. The line PBO, perpendicular to AV, passes through the centre of gravity of the displaced volume AFMN, and consequently through that of the ship. Draw QH through the centre of gravity of the volume KFML, perpendicular to KL, and FG through the fulcrum F, parallel to QH. Then, putting the total displacement AFMX = V, KFML = v, and GU= b; if the line SEO, parallel to Qll, be drawn at the distance GE from G equal to -rj, it will, as well as PBO, pass through the centre of gravity of the ship, which will be in 0, the point of their inter- section. " ' To obtain from these considerations a general expression for the perpendicular distance of the point from the water-line AX, draw AD perpendicular to EG, and meeting it, when produced, in D ; and having calculated the values of AB and GE, put AB = a, DE or DG-|-G£^d, and the angle of inclination between the (d \ 1 <V>a 1 ; cos / tan A which must be set off upon the perpendicular PBO, above or below AN, according as • is greater or less than a.' " Since the publication of the first edition of tliis book, two interesting and valuable papers have made their ap- pearance in "The Transactions of the Institution of Naval Architects," for the year 1861. One of these papers was read by Mr Barnes, the other was given in an extemporary addiess by Mr Fronde. It is first proposed to give an outline of Mr Barnes's SlrBarnes'g paper, entitled "A m.w method of Calculating the Stability method of of a Ship." As the originality consists in finding the calculating volumes, centres of gravity, Sec. of the portions of immersion and emersion, the following remarks are confined to tiiat portion of the paper : — The method seems to have been suggested by Rule XV. of the present work.' At all events, the advantage of employing the section of a circle for approximating to the true volume is there clearly pointed out. But, whereas, in that rule, each transverse section SL'L, is considered as a section of the same circle of which tiie radius equals the line drawn from S to the middle point of the arc LL', Mr Barnes, in his paper, supposes the arc LL' to be divided into any convenient number of equal parts, and by joining stability. ^ This was published in the first udiliou of this article, some months before Mr Barnes read his paper. 48 SIIIP-BUILDING. Stability the parts of ilivision to II, he obtains a series of elementary sectors. of Floating Generalising his \ie«s :^ Bodies. ir I R l-if. 10. If IIR represent the line in which the plnne of flotation, corre- sponding to the upright position of the vessel, intersects the plane of flotation when the vessel has been inclined through a given angle ^, Mr Barnes divides II K into any number, say m equal parts; also the angle Llllj' is divided into any number of equal parts, say n ; then, through the points of division, transverse planes, IILI/, Ac, are drawn parallel to each other, and radial planes, H.MZR, are drawn inclined to the plane of flotation II K, at equal angles 1., n Then since area of sector Hb'M= '"ad x length of arc ^ ± -^nW 2, 2 2n multiplying this by the breadth III, we obtain for the volume of the small wedge UN, -1 UL'» x HI. 2n Similarly the wedge IP _ t 10- III. A line equal to II K is now taken and divided into m equal parts, and ordinates are drawn at right angles to this line, and equal in value to IIl^, 10', &c. Mr Barnes next considers a series of para- bolic arcs to pass througli the extremities of those ordinates, as is done in obtaining Simj)son's Rule, and he works by that rule for the area of the figure. Multiplying the result thus found by ^- (circular measure, i.e., 180° corresponding to 31416, ~- will corre- 31416 x« spond to - 30On -), which gives the volume of the thin wedge HZ. Lastlv, Mr Barnes takes a line at pleasure to represent the mag- nitude of ^, and divides this line into ii equal parts, and erects ordinates at right angles to the given line. On these ordinates he sets off the numerical values of the thin wedges HZ, Ac, already found, and tiirough the extremities of these ordinates he again passes a series of parabolic arcs, and works as in Simpson's Uule. By a similar process the centres of gravity of these wedges are determined.^ Method of *'■■ Barnes next proceeds to find the value of the expression /)|7| finding the ^ "'• alluded to in Formula I., Art. 14, p. 47. This he does in valueof the 'he following manner :— expression The centre of gravity of the wedge DN lies in the line bisecting Pill ><■ *" the angle L'H.M, and at a distance 5- IIL' from the axis HR, and o therefore its distance from lilt, measured in the direction IIL'= 2 , « =-UL' cos -^■ 3 2n Now the volume of this wedge has been shown to its moment about IIR =z -— cos -f- 3n 2n be equal to .|- X HI X HL'^, . * 2n HI X HL'3 ; and as — cos -r- HI will be the same for all the wedges 3n 2n in the slice HZ, Mr Barnes again refers to the line which was taken equal to IIR, and draws ordinates at right angles to it (through the m + I points of division) and equal respectively to IIL'', 10'', Ac, works again by " Simpson's Rule," and multiplies the curvilinear area thus obtained by ^ cos i (HI, being used as the common interval, is not to be multiplied into this result again). He treats the slices similar to HZ in a like manner, except that he multiplies respectively by ; 3; ip Of &c., and thus Mr Barnes lastly refers to the line which was taken equal tu the Stability angle ^,and sets off ordinates at right angles to it (through the n + 1 of Flouting jioints of division) equal to the moment of each slice, similar to Bodies. HZ, and again works by *' Simpson's Rule" for the moment of the ■ , , . whole wedge-like solid of iirmersion or emersion, which, of course, gives the numerical value of ;i|7. X ti/ ; the statical stability ia then readily obtained by Formula 1., p. 47. a It ought tu be observed that, instead of taking — slices similar to HZ, Mr Barnes takes three dices only, — viz., one adjacent to the upright water section, another adjacent to the inclined water section, and a third midway between the other two, so that his method approaches still nearer to the one indicated at the top of p. 47 tlian was at first imagined. Mr Barnes employs the same method for finding the moments w (/'i ?« + 1\9i)> t''^ method given on p. 47 readily gives the moments just alluded to, for 2 2 « 2 a l"!/' = 3^1 •■• ^P\ = J""! <^»s ^ and Ty, = j '1 cus - (employing the notation there used) .•. moment of first section similar to EPE' (fig. 7; about longitudinal r, -^ 2 ^ ^ , ^ axis through P = },- ** 3 ''l *^°' 5 ~ 3 ' "* ^ ' Moment of second section similar to EPE' (fig. 7) about longitudinal axis through P = J— *^ X ^ rj cos ~ : .'. by Simpson's Rule, A{ If cos 3 - f fr,'- + r„2 + 4 (r,3 + r^^ + r„2 + , Jfcc.)! -\ + 2(r32 + r/+,&c.) t hfi; obtains the moments of the several slices. Vg, X to = — when f represents the weight of a cubic unit of water, and A the common distance of the sections. Similarly, PjTi xvi—hfif cos ;, J ,j= + J,- + 4 (t,- + s^- + /^- + , ic.J I + 2(v + V +.*■:■) j 7, + P?;) w, or p, g, X w = , cos ^ I""'' + '■"' + ^ ^•'i" + '•i" + ■ *<=■) + 2 ('■3' + '-6= +. &c-)"l ~3 \'r + ',' + ii'-i' + 'i- +.*<=•) + 2('3' + 's' +.&<:.)/ A method very easy of application, and which will be found suflSciently accurate for a large number of ships when the angle ^ is small. Should this method be deemed not sufBcicntly accurate, that of Mr Barnes will also deviate, though in a less degree from the correct result; and, in this case, the use of Mr Weddle's Rule, given at p. 32, is strongly recommended. For vessels, as they are now constructed of such great length as compared with the breadth of beam, it would perhaps be advisable to employ " Simpson's Rule'' for finding the volume and moment of each of the slices situil;tr to HZ ; but if the arc LL' were divided into 5t> equal portions instead of three, and the volumes and moments of each of these slices introduced into Air Weddle's Rule, very little more labour would be required, and very accurate results obtained. Dynamical Stability. Art. 16. — Wlien a vessel is inclined tlirougli any angle Dynamical by a force acting parallel to the surface of tlie water, the Stability, centre of gravity of the body and its centre of buoyancy will generally, as has already been stated, receive vertical disjilacements. If during the motion we use the same con- vention in regard to signs as is done in the determination of Virtual Velocities, our results will be attended with greater simplicity. That is, if the point of application of any force is moved in the same direction as that in which this force acts, then the distance through which the point of a|>plication has been moved must be consklered positive ; where;is, if the point of application is moved in the opposite direction to that in which the force acts, the distance this point has been moved during the motion must be considered tirgatire. Let h and ; be the absolute vertical displacements of the centre of gravity of the vessel, and its centre of buoyancy respectively, after the ship has been heeled through a given angle, then ' For a large class of ships rolling through moderately small angles, the method indicated iu this work will be found suiEciently correct, and will save an immense amount of labour, even if we adopt Mr Barnes's method. SHIP-BUILDING. 49 stability * ^^'^ '^ '^® work done on the vessel due to its weight, the upper f Ploatintr ^iy" being tal^en when the centre of gravity descends, and the lower Bodies, sign when the centre of gravity ascends. Ijiitewise, db Wi is the worli done by the upward pressure of the water, the upper sign being talten when tlie centre of buoyancy, ascends, and the lower sign wlien it descends. Consequently, the total work done in heeling the vessel through the given angle, = W (± h ± I), the signs depending upon the directions of the motions of the centre of gravity and the centre of buoyancy. Make the same construction as in fig. 7, and draw GX and GjY perpendicular to fl, meeting l'"'L' in x and y respectively ; through G',i draw G'.jZ, parallel to F'L', inter.secting YG',i, produced in Z. Here it is easily seen, that while W, the weight of the water displaced, has been moved through the distance G'dli, the weight of that portion of the water emenjed has been moved through a distance OfPl+Oi'^l in the same direction.- Taking moments, G'dll. \V = w(cr,p,+(7i7i)= w-^. (''■-= 3<?'i+?-?i) • (^O Then, in the case in which GO is greater than Gx, we have GO-Gx =GO-(GX-Xx) = GO-GO cos f + Xx If GO be less than Gx, then G.r-GO= GO cos ^-GO-Xa: Hence db (GO vers if + Xx) (2.) is the vertical distance through which the centre of gravity has been moved. Also, when G'dU is greater than GjO, G'rfU - GjO = Gjv + GrfZ - GjO = G'uK + Gji,-Xx-GjO = G'jl{ + Grf() C0SIP-G0-X.T = G'jU-G vers <p-Xx And when G'dU is less than G^O GjO-G'jU = GjO vers?)4-X^-G'dR I GUli- (GO vers f + X.v) (3.) 18 the vertical distance through which the centre of buoyancy has been moved. Hence the total work done on the vessel is, where Vd represents the dynamical stability, Ud=W ± (GO vers. ^ + Xx)± | G'dR-(GjO vers. ^-|-Xi) j {^■) Suppose the centre of gravity of the vessel to ascend, and the centre of buoyancy to descend, then Ud=W (GGj vers ^^-G'<,R) by taking the sign -1- in the first and — in the second member of the right-hand side, and if we take the contrary signs Ui = \V (G'jR-GGiVers f) = \y I (ff,Pi+9ilO^ -GGi vers ? | = tw-W.GGrfvers^ (.5.) "We may re.idily obtain a relation between the dynamical and Hutical stability, for by Kqua. 1, Art. 14, the statical stability U, = W.GG' = fpiJi.«/-GGi.Wsin. f) GGd=:—rr; — : — W sin If And if we employ Equa. 5, and write this value of GGj therein -cos ^) sin ip xT,^,^_(?'i?i"'-tJ.)a- = zif — J'l'/iW tan -^ + U, tan -^ Ud — U, tan -^ ^ :w — l-'^q^w tan -^ (6.) Canon Moseley, in his paper on Dynamical Stability, gives U, (f, n) ■ ■ W GGdVers, f + w; BB the vessel's stability in regard to rolling or pitching. He takes a prismatic element of the emerged volume, the base of which = rf.c di/ cos <p, and height ^ y sin ^ ; then w.g,py, in respect to the element just mentioned, = -^ i/- sin^ ip cos f dx dy, and in re- gard to the whole space represented by the sections E'I'Q, and J/i'Q', by i: ./ If cos ip I y- dx dy Time of performing an Oscilla- tion. ^ J f sin^ (p cos ip I Where I represents the moment of inertia of the inclined load- ^^^^/"^ water plane, about an axis through I', and inclined at the angles " ""i^ TT"" '° ""^ principal a.\es of that plane, where n denotes the inclination of line through P (in which the planes FL and V'li' intersects), to that line about which the plane F'L' is sym- metrical. If A = the perpendicular distance of the line through P from the centre of gravity of the plane F'L', and A and B de- note the moments of inertia of the same plane about its principal axes. A' = area of this plane, and -^ the value of wz in regard to the spaces FQF', L'Q'L «f^ ^ -^ I sin- (p cos ^ + ^^ where I = A cos- » -(- B sin^ , + X'h- •'• ^\(p. ^) = * '^V-GGi vers ,p + -|-(A cos-' , + B Bin= , 4- A' A^) . sin^ ip cos ip + yp (7.) the minus sign being taken when GO is greater than 0^0. Time of Performing an Oscillation. Art. 17. — There is nuicli difficulty attending the investi- Time of gation of the times of rolling and |)itchingof vessels through rolling or large angles, inasmuch as the a.ris about which the motion P'":'>'"g- takes place is instantaneous. This axis can, however, be de- termined at any instant, providing the direction in wliich the ship is rolling or pitching be giren.' All methods hitherto given are incomplete, yet all tend to show, that no matter what may be the amplitudes (the angles through wliich the vessel revolves, providing the position of the ballast, cargo, and other weights retain their original positions), the time of performing a complete oscillation, in smooth waters, is the same. Writers on Hydrostatics, in investigating the time of an oscillation, have usually considered the plane of flotation as constant throughout tlie motion. The Rev. Canon Moseley, in his paper already quoted, endeavoured to obtain new results for the time of performing an oscillation, as well as for the dynamical stability of the vessel. Notwithstand- ing that several corrections have been made in the pa[)er, as published in his second edition of T/ie Mcrlianicnl Prin- ciples of Engineering arid Architecture, the results are still open to the same objection, since tliey are made to depend upon the moment of inertia of the plane of flotation. which is itself a variable quantity throughout the motion. It would seem that the Calculus of Variations might be ad- vantageously applied to the question, or, at all events. Canon Moselcy's paper might be made available, providing we tcere to calculate the amount of prohaile error in assuming the plane of flotation constant icilhin given limits. The centre of gravity of displacement is frequently called the centre of buoyancy. * See iloseley's Mechanics of Engineering, 2d Edit. ' G 50 SHIP-BUILDING. Time of performing an Oscilla- tion. Simple pendulum. AnT. 18. — As we sliall have to refer to the motion of a simple peiiilulum, we shall liere lay before tlie reader the nic- tliocl by which the time of a com|)iete oscillation is obtained. In the case of a simple pendulum oscillatinfr in vacuo, we imagine a heavy particle suspended from a fixed point bv means of an inextensible string without weight. Let (■ (fip. 11) be the lowest position of the particle, GM ver- tical, 0' the initial position of the particle from which it sets out with the velocity v„, ti" its position after any time t, MG ^ /, ^ GMG' = «, <:GMG" = «, arc G'G'' = ». Then the tangential component of the accelerating force is expressed by — j , both in regard to magnitude and sign, the sign + referring to the case where s increases, and — to the case where t decreases. ds df Soyr,, = l(»-f).:--=-l dt dt and -,-.,= — /—-f, and the tan- di^' di^ ' gential component of the weight being g sin f, we have d-f g . ^ — f- = —4 sin f. dt- I * Multiply by 2 -^, and integrate But when ^ = a = 2 y COS f -I- C. 2? h- COS «, t-'f And dt=- - (cos ^ — COS «) Idf Vv'o + 2gl (COB f - COS «) or, if we suppose the initial velocity zero, dt df 29 V, cos a — cos a dip 9V' '.■ cos f ^1 —2 sin . ■mall. gVa'-- 1 , when the angles « and f are very dp =^/: -1 , -+c, ,0=0 Time of os- cillation of Q simple pendulum. when, t ^ 0, ^ = a, ""^ '-2- ff- which gives the time for a semi-oscillation. .•.T = V^ (T.) Though the amplitudes hnve been here considered small, it ia not absolutely necessary to make this assumption, as the integral may be found approximately for given values of ^, from tables inserted in Ijegendre's Traiti des Fonctiona £lliptiqtiet j the result of the integration in a series is — But, 0-4) , 1 . a 1-3 . 2« ^ = ^+2°"'2+2l"''2+*'=- Hence we perceive that the terms which enter into t ore the squares of the latter terms, and we can thus conclude that the expression for « is a convergent series. Jtemark. — The only Tantochronous curve, or the curve in which the times are all equal, whatever may be the amplitudes, gravity only acting, is the cycloid, whose equation from the lowest point is y = V2ax — X-+ a vers — . a Compound Penditlum. — When a rigid body oscillates about a fixed horizontal axis, not passing through the centre of gravity, the time of an oscillation is determined as fol- io n's : Let CAD (6g. 12) be a section of the body made by the plane of Time of perform! n( an Oscilla- tion. the paper, which is supposed to pass through the centre of gravity G, and intersecting the axes of rotation at right angles on A. L^t I' be the projection of any particle on this section, Ax vertical, AG =:A, AP^r, <GA4: ^ ^. PAa;=f', then, by well known prin- ciples, d'f moment of forces dt^ moment of inertia If Mi^ be the moment of inertia about an axis through G, and parallel to the given one, then i<l(li' + k'-) (Art. 6, prop, i.) is the moment of inertia of the body about the axis through A, and the moment of the forces about the axis ^ W'h sin (f ^ Mgh sin f ; dt^' ^\gh sin ^ ' M(li- + k-)' g sin 9 if 1 = h^ + k^ ,df ilultiply by 2 -- , and integrate (?)■ - cos f + C, and if -p^ =. 0, when « = a, dt dp dt" (cos f — cos a) =yi( =^/ 2 sin-;- 2 sin 4 .= a/ - (a- — f-), when X and f are small. (I-) Whence we conclude that the oscillations of such a body are per- formed in the same manner as if the body were a material particle, and oscillating at a distance, I =: — 7 — from the axis. Now, if AO = — r — • , then A is the centre of tuijieniion, and the centre of oscillation. If L = length of the simple isochronous yendulum, — that is, the simple pendulum which oscillates in the same time, — Time of os dilation o a com- pound pen dulum. then, L ^ t^-l-OG' OU - _^ ' l-k _lk-h- '' l-h + l-h i-' + A2 z=zl + l-k = l; whence we conclude that the centres of suspension and oscillation are reciprocal, — that is, if the body be conceived to oscillate about an axis through 0, and parallel to the former axis, then A becomes the centre of oscillation. The following manner of obtaining the time of an oscillation of a vessel in rolling is due to the Kev. Dr Woolley, and will be the most intelligible to the practical man ; and if the times of rolling through dilTcrcnt amjilitudes be nearly isochronous, as l)r Woolley states, the result is exceedingly simple: — r^ 314159, &c. " Suppose GG' to be an arc described by the centre of gravity, corresponding to the half-angle through which the vessel rolls, and let M, M', be the limits within which the normals to the curve cut, G M, the former corresponding to the upright position of the ves- sel, G the centre of gravity of the vessel, then the time of rolling, supposing M to be fixed during the motion, is too great ; and if M' were the point of suspension, the time would be too small ; but taking intermediate points, and calculating the time for each, sup- posed fixed, let T be the true time, bj, kj, itj, 4c., the errors, (,, tj, („ &c., the calculated times, then — Dr Wool- ley's me- thod of finding the time of rol- ling. SHIP-BUILDING. 51 Time of erforming m Oscilla- tion. 'I T + «3 = ,T = «1 + (2 + '3 + 4c. + (It a, + a^ + «:t + ' <■ + . W{-t2 + (n,-R)2 8in '"'<>} (57) where IIj representa the depth of the centre of gravity in a ver- tical position of the ship. And from the principle of Via viva, \V(IIi-Il2)(cos p-cos ^,)-t- |-A (cos 2j-cos -f ,) = W{^^-^ (IIi-R)=sin=,}^;-^?y Where IIj is the depth of the centre of buoyancy when the ship is in an upright position, dip -co:-^,) ... .(,.) ^ If + ^' / ^!+(Hi^K)!sin_ i/ -fi ^ (II,_H,)+|_;(c08f + C0Sf, ) (cos f If COS ^ + cos ^p^ , or ^ and f^ be small, , ^_ 1 /•<-^p / A-'-Kll,-K)s!n2*. <i^' — Yal J 71 rf» i/-f, N (iii-n2)-i-|^(cos,-cvK,,) tif,) Time of v., ... „ ^ , fA A ■^'' /*''-t-(H,-R)28in2,. P^forming V.V(U,_ig + f_y_^^ V vers,,- vers / '^>i ^ O"""" Now, since some of these errors are negative and some positive, we may make this result as email as we please, by taking n suffi- ciently great, .'. T = -i * — ^ , very nearly. "When the distance between M and M' is very small, aa ia the case in most vessels for a moderate amplitude, then the question is reduced to the case of a simple pendulum, the length of which ia GM. Therefore K being the radius of gyration of the ship round a longitudinal axis through its centre of gravity. T = -^ ([.) K ia obtained by multiplying each of the elementary weights of the vessel by the square of its distance from the horizontal axis through the centre of gravity, and extending the sumraatian tliroughout *he whole ship. Divide this result by the total weight of the ship when ready for sea, and extract the square root of the quotient, which gives K. We see from (I.), that the time of a natural oscillation varies directly as the radius of gyration, and inversely as the square root of the- distance between the centre of gravity of the vessel and its raetacentre. Hence, by increasing K, which may be done by moving the weights on board further from the axis about which the ship revolves, the time of oscillation is increased ; also K re- maining constant, if GM be diminished, T is also increased, and vice ven^d. l)r Woolley here supposes the centre of suspension to move in a straight line, but a more accurate way of considering the question is as follows : — Suppose the metacentric evolute to be found, and the curve de- scribed by the centre of gravity is Icnown, we have then to calculate the time of an oscillation of a simple pendulum, whose centre of gravity moves on the metacentric evolute the length of the inexten- sible thread, which has a material particle at its other extremity, varying between given limits. The general solution of this question is attended with great diffi- culties ; but, in particular cases, the time of an oscillation may be accurately obtained. The following is a very similar question, except as far as the re- action of the curve and string is concerned : — An inextensible flexible thread, of given length, and without weight, is fixed at a given point on the arc of a given curve, which lies in a vertical plane, and to the other extremity is attached a heavy particle ; find the time of an oscillation, the particles being acted on by gravity only. The following is the method given by the Rev. Canon Moseley to find the time of an oscillation when the body is rolling. Let D (fig. 7) be the projection of the axes about which the ship is roll- ing, and O' the centre of curvature of the surface traced out by the planes of flotation at the point where the plane F' L' touches this surface. Assume R = this radius of curvature, then since the axis about which the ship is rolling is perpendicular to the plane of the paper, its moment of inertia is and if R be supposed constant between the limits — ,, and pj, we gel ^(iii And since sin -~ is small, Kfi) ■■ <rk V ("t-".+^^). and the oscillations are nearly tantochronous. Throughout these investigations, j = weight of cubic unit of water. But Uj^ — GO, and IIj : ■■ (idO, also L- ; : GjM by form (III). rk rh Theorem VIII. p. 155 ; . , , Tk ■■'*>■ ~v'(GO-GdO + GdM)y~V'(GdM-GdG)j'~Vj7GM' which agrees exactly with the result obtained by Dr Woolley ; and since t is independent of the angle, we are thus led to the tanto- chronism of the oscillations which he has assumed. Mr Froude, in his very valuable paper, assumes for the time of a ^f"" ship's rolling in still water the equation, T= -7^= (that is to say, he supposes for a given vessel the oscillations are isochronous); when T represents the time ; g the moment of inertia of the vessel about an axis passing through the centre of gravity ; M the mass; and g the accelerating force of gravity. Now all experiments tend to show that this equation nearly agrees with observed results, but it ought to be observed that the vessel really rolls about on an instantaneous axis, — as has been ob- served by Canon Moseley in his paper already alluded to ; and hence the value of g on this latter hypothesis leads to almost in- superable difficulties in its calculation. Mr Froude next takes into account the action of the waves on the vessel, and observes that '• the curve of sines" represents approxi- mately the vertical section of large and uniformly recurring waves, though he thinks that some cycloidai or trochoidal surfaces would be nearer the truth. Adopting Mr Froude's notation, he finds, — " H ^ height of wave, L = its length from bottom to crest, T' ^ period of wave, or the time occupied by it in traversing the space L ; then at any intermediate period t, the generating point will have F roude'a method. traversed an arc 6, the value of which is T' Calling the space the traversed by the wave, and the height to which it has risen in time, t, I, and A respectively, we have Z = L-,and-=-, A = ^(^l-cos-|and^=^.sln.,p dh 2 II . Tt l"°t^ dh when ^ = tan I', l' being the slope of the wave, or its inclination di rpf ^ to the horizon. This is a maximum when t = -^, and sin — = 1 ; hence, — . y- is the steepest slope of the wave which occurs at the middle height, and the middle distance of the ascending or descend- ing side." "In proceeding from the case of the ship oscillating in still water, to that of the ship oscillating in undulating water, it is necessary to remind the reader that it has been shown that the momentary efibrt of the ship is to place her masts at right angles to the surface of the wave when she floats ; and that for a given ship, occupying at any moment an angle of inclination diflfering from this, the measure of the effort is the same as that by which she would endeavour to assume a vertical position, if occupying for the moment, in still water, an inclined one, with an angle equal to the difference. Hence, if I' be the inclination of the wave- Burface, just as the eflTort of stability in still water was resolved into the expression y^ =— fhj '. so it follows that an undulating ware is expressed by the equation 572 = — mVS C — ')) which will 52 Time of S II IP-BUILDING. B?9urae a form more suitable for integration if #' be eliminated in terms of (, 6o as to express the changes of inclination of the wave- surface; and the elimination could be performed riporously, if the true equation of an oscillating wove were certainly known.'' Assuming tan (' = (', as is done by Mr Froudc, the equation becomes. Or writing it as is done by Mr Froudc, — ^'' + n=#-DBint{ = (2.) at" He goes a long way round to integrate this well-known equation. We have. ^ - n nW — k'J Again, let < = «, when t = o; .". C (3) « = (■' 15 . ^ .. . ^ i=f(^\- + n-\ Bsinit; Hence t = ;_ ,^ sin kc+ 1. ( But„=^-,B=J and - =- n .. • ". / rl 1 ••'-.- -L ^ T: (sin ~-j cos ^ r sin it 4- a COS nt. » n 1 ' - k- 1- < = B 2-42 sin kt + C sin nt + C cos nt (3.) the last two terms being the complementary functions due to the operating factor m'-'i (See Gregory's ExampUt on iht Differential and Jntrgral C'ahulut, p. 29').) Or equation (2) mny be integrated thus : — Differentiating twice in regard to t, and eliminating sin kt, we obtain 5?+("^ + i=) + n- k-l = (»•) assuming t := Ci sidiary equation mt, and writing in equation (4), we get as the sub- Mr Proude then goes on to observe, " Now, in discussing the simple oscillations of a ship in still water, in the earlier part of tlio p:iper, we found that if U be her angular velocity, and « her angle of position, when t^o, ^ UT . «■« , ,1 * = — Bin — + « cos ^ And if the expression be compared with the two final terms in the precndinj; equation, which expresses the value of t for a ship rolling in waves, it will be seen to be identical with the two final terms of the latter. And, on the other hand, if the constants U and K vanish, — that is to say, if we assume that the ship was stationary and upright when the waves reached her, — she will undergo a series of movements defined by the expression » II 1 « = .„4 + („? + il>) rn- = - n- i". The roots of which are m = ± kj — I and ± nJ — \. Writing these values in rf = ci"'' and reducing by well known forms, we get C = C, (cos kt + B,) + Cj (cos n! + B.^) (See Boolr't Dif. Equations, p. 306), when C, C'.j"U, B, are constants, two of which are independent. Keturning to equation (3) to determine C and C we have on differentiating, di lik , „ r^, ■ . . cos kt + Cn cos nt — C ii sin nt. - • - • 7^, /" ■ ■rt T . !r( \ 2 ^ l.^X""'F-^""'^i") Let dt dt ■ n-— i= : U, when t ^ ; .*. U = ■ Bt + Cn; Which series, though its results have to be combined with those of the series expressing the ship's proper oscillations due to a previ- ously existing velocity and position, when such are assumed to have existed, maintains, nevertheless, its independent vitality and integrity ; each series, in fact, thus retaining iti complete indivi- duality, in a manner analogous to what may be observed to happen when independent sets of wave oscillations in the water surface in- tersect or overtake each other. It would be impossible to enter more fully into the whole of Mr Fronde's theory, which is certainly one of the most original and valuable that has been propounded in the present day. Wo therefore recommend the careful perusal of the paper in question to those who desire to obtain further information on this matter. Table I.—Calculalion of the Displacement of a Yacht similar to the Titania. (See Plate V.) M.\IN BODY. SMALL POP.TION AT THE BOW. I ■-■■ II iJ! > — — ^ Horizontal Ordinates taken at 5-8125 feet apart Vertical Ordinates taken at 2 feet apart. H.Mi- zuntal Areas. g C 1 Y U Q M H D X 4 8 1 12 16 20 24 1-4 •75 •0 ■0 2 75 19 ■8 ■5 •0 4-5 23 1-7 •8 •5 6-3 60 25 1-2 ■8 •8 6 5 3 5 1-4 ■9 9 4 10-2 8 6- 2- 14 10-75 97 5-5 2-0 14 10 75 9-7 5-5 2 14 10-75 9 5 6-3 175 10 10-4 8-5 4 4 1-5 -9 95 7-75 2 75 1-2 ■8 7-75 4-0 l-.'5 10 ■75 4-6 1-4 -3 •0 -0 -6 •2 -0 -0 ■0 621744 4.S5 828 ■2.J0.'il9 96 875 61419 Vertical itreos. ......... 1 346 9-3 13 86 246 31-6 37 86 410G 40-63 46 63 449 40 06 34 4 19-6 713 -86 Vdlninc = 2343-3 II . .' .* Horizontal and Ver- IS "■^ ■cal Ordinates, each -:- ■< is taken 1 foot apart. = ■3 ii 2 3 •5 -9 14 2 46 s 05 -1 -4 7 10 1683 -00 -05 -2 ■6 -76 1110 O -0 -0 -05 -2 •6 •45 - •0 -0 •0 -0 -2 -0 Vertical Volume areas 13o 2.5 1 -90 1-86 3 03 = 4 45 SM.VLL POr.TIOX AT THE STEItN'. li = tT p. Horizontal and Ver- tical Areas, eacli takea at 1 foot apart. it "3 •5 2 •0 ■0 ■0 .25 .1 .0 .0 .0 •1 •05 •0 •0 ■0 ■0 •0 ■0 ■0 -0 ■0 ■0 •0 •0 ■0 •63 •216 ■0 •0 ■0 Vertical areas..... -43 216 •1 -0 •0 Volume = 464 2343 3 = half volume of main body. 19 45 = volume of small portion at the bow, including knee, Ac. 20464 = volume of small portion at the stem, inclufliiig rudder-post, ic 100 -000 = volume of small portion above the keel, including the keeL 2483i214 = half Tolome of water displaced. 2 4906428 = displacement 64 = lbs. weight of 1 cubic foot of Bea-water. Number of lbs. In 1 ton = 2240)318363 392(142 = floats at the load-water line. : nomber of tons of water di^laced = weight of resscl as she Kemark. — The reader will haro no difficulty in understanding the aboTc calculations, and the manner in which ordinates are measured on the plan of the horizontal water-lines given in Plate V. The sectional areas ara found by Rule L page 23, and these areas are introduced into Rule IV. page 3X * Transactions of the Institution of Naval Architects for 1861, pp. 192 and 183. ^ In a paper read at a meeting of the members of the Institution of Naval Architects, on 28th March 18G2, Mr Crossland gives -T-jj = — ^sin(^ — ^') X ( 1 ± - ) sec. ^', as the angular acceleration ; and Ur J. W. M. JJankine furnishes the following, on the hypo- thesis that the wave surface is a trochoidal one: — ;r2 + ^ I ^^^ ^ + — sin (i — ^ f \ = o, where T' = 2^ of Mr Froude*8 equa- tion, X = 2L, and 2r = U. SHIP-BUILDING. Table II. — Calculation of the Centre of Buoyancy. MAIN UODY. 53 245 672 last 24S-67: Horizontal Areas mnlti- Func- plied by 0, 1, 2, 3, &c. tiona. 621-744 X = 000-000 485-828 X 1=485-828 250-519 X 2 = 501-308 96-875 X 3 = 290-625 61-418 X 4 = 245-672 unction. function. 485-828 2d f do. 290-625 4th do. of 1st and last. 776-453 sum 4 of even functions. 501-038 3d function. 1002076 twice oddio. 3105-812 four times even do. 1002-076 two do. odd do. 245-672 first and last 4353-560 4^(common intervalj". 3)17414-240 Vortiral Areas niiiUip ieil by Fnnc- O.I, 2.; ,■1, tc. tions. 3-46 X = •ooo""! 9-30 X 1 z^z 9-300 13-86 X 2 =z 27-732 24-60 X 3 :^ 73 800 31-60 X 4 = 126-640 37 86X 5 =r 189-300 4106 X 6 = 246-360 46-63 X 7 = 326-410 46-63 X 8 = 373040 44 90x 9 — 404-100 40-06 x 10 ^ 400-600 34-40 X 11 := 378-400 19 60X 12 nr 235-200 7-13 X 13 z= 92-690 •86 X 14 = 12 040 J Displacement of main body =2343-4) 5804-746 (2-47 Calculating the centres of gravity of the small portions at the how, stern, and near the keel in the same way, we obtain Horizontal distance of main body from the section marl^ed No. 24 ^ These functions in- introduced into Rule VIII. art. 5, page 35, bearing in mind tliat the common in- terval ie 5-8125 and ^ volume of water displaced = 23433 gives 42 feet nearly for the distance of the centre of gravity of the displacements of the main body from the first vertical section, marked No, 24, at the bow. 42 feet. = 85 :-3 60 at the bow Horizontal distance of portion at the stern, includ- ing rudder, port, &c Horizontal distance of portion at the bow, including knee, &c Horizontal distance of portion above the keel, includ- ing keel Vertical distance of centre of gravity of main body below load- ■ water section = 2 47 Vertical distance of centre of gravity of portion at stern, including rudder, &c := 5-00 Vertical distance of centre of gravity of portion at bow, including knee, &c = 3 00 Vertical distance of centre of gravity of portion above keel, including keel, &c := 9-40 . = 42 7 ft. : 2343-3 X 42 -I- 20-464 X 85 + 100 x 60 — 19-45 x 3 2483214 Distance of centre of gravity of displacement from first section at bow. 2343 X 2-47+20-464 X 5+100 x 9-4 -^ 19-45 x 3 _ „ -, , _ 2483-214 '' "^^ " Vertical distance of centre of gravity of displacement below the load-water section. Table III. — Calculations necessary to determine the Point P (See Fig. 7.) To find tl e volume Vi, Art 13, p. 45 To find the volume Vj, Art. 13, p. 45 To tind the area of the plane/ i. a 1° <S <Q c o S .S o '?£ 1° 1° O C (so £ ca u Eo c 'u 1 1 u &4 i S o O . s| si «e 11 c •3 o o O . « c tl o ■o h O o O o •§.- (- .J - c £. ^ ^E o S "5 W M 1 a. o 1 i li •5 o 1 o . ii c o o E O 3 . S = ^ o 1 c u •8 ■7 -3 -00 ■096 ■000 ■096 ■8 •8 ■2 ■00 •109 ■000 •109 •8 ■7 13 1-5 1-3 ■5 ■00 •334 •000 •334 1-5 1-7 ■6 ■05 •436 •020 •456 1-7 1-3 30 2-1 17 -6 •00 ■611 •000 ■611 21 2^6 1-0 ■05 •934 ■033 •967 2-6 1-7 1 4-3 3-0 2-4 1-0 ■00 1^231 ■000 r231 3-0 3^6 1-4 •10 1^846 -093 1.939 3-6 2^4 6^0 3-8 3-2 1-4 ■05 2079 ■047 2^126 3-8 4-8 r7 ■15 3119 -170 3^289 4-8 32 8^0 4-8 3-7 1-6 ■05 3^037 ■053 3^090 4-8 5-9 2^1 •16 4-843 •224 5-067 5-9 3^7 9-6 6-6 45 2-0 •05 4-310 ,067 4-377 5-6 69 2^5 •17 6-008 •283 6-891 69 4o 114 6-5 5-2 24 ■06 5-780 ■096 5-876 6^5 7-9 27 •18 8-780 •324 9-104 7-9 5^2 13-1 ..i 7-4 5-6 2-7 ■06 7^086 •108 7194 7^4 8-7 3 1 ■18 11-009 •372 11-381 8-7 5-6 143 £ 83 6-3 3-2 •06 8-941 ■128 9^079 8^3 9-4 3-2 ■20 13-341 ■427 13-768 9-4 6-3 15-7 e 00 89 6-7 3-5 ■08 10^199 •187 10-386 89 98 34 ■20 14-915 •453 15-368 9-8 6-7 16-5 9-5 7-2 37 •10 11^696 •247 11-943 9-5 10-2 3-5 ■20 16-570 •466 17-036 10^2 7-2 17-4 . II 100 7-5 39 •10 12^825 ■260 13-085 10-0 10-6 3-6 ■25 18-126 •504 18-630 10-6 7-5 18-1 > =:.« !5 105 7-7 4-1 •10 13-825 ■273 14-098 10-5 10-8 37 ■25 19-391 ■617 20-008 10-8 7-7 18-5 1 ?s cp 1075 8.0 4-2 ■20 14-706 •560 15-266 10-75 10-9 3-8 •30 20-037 •760 20-797 109 8-0 18-9 s. a^ X 1075 8-2 42 ■20 15-074 ■560 15-634 10-75 10-9 3-8 ■35 20-037 ■887 20-924 10-9 8-2 191 - 1 10-50 7-8 4-1 ■20 14-005 ■547 14 552 10^50 10-8 37 ■40 19-391 •987 20-378 10-8 7-8 18-6 Zi 00 10-20 7-5 4-1 ■30 13-082 ■820 13 902 10-20 10^7 3-6 ■50 18-662 ^267 19-929 10-7 7-5 18-2 =) ^' ^ 9 80 7-0 4-1 .30 11^731 ■820 12-551 9-80 10-5 3-6 ■35 17-696 1-483 19 179 10-5 7-0 17-5 1 1 1 9-00 6-4 4-0 ■20 9-850 ■533 10383 9-00 10-2 3.6 ■30 15-698 •680 16-378 10-2 6-4 16.6 O 8 60 5-8 3-6 ■20 8-531 .480 9011 8-60 9-9 3-6 ■25 14-559 ■567 15-126 9-9 5-8 15-7 7-70 5-2 3-4 ■10 6-487 -227 7-074 7-70 96 35 ■20 12-640 -467 13107 9-6 5-2 14-8 » 6-80 44 3-0 ■08 5-116 ■160 5-276 6-8U 9^2 3-5 ■15 10-698 350 11-048 9-2 44 13-6 5-70 3-6 3-5 •00 3-509 ■000 3-509 5-70 8^4 36 ■14 8-178 •336 8-523 8-4 3^6 12-0 4-40 2-5 2-2 —•2 1^881 —■293 l-5i<8 4-40 7-4 3-9 ■10 5-368 •2'!0 5-828 7-4 2-5 99 1-80 1-4 -7 — 1 •431 — 046 -385 1^80 6-1 3-8 •05 1-878 ■126 2-004 6-1 14 7-5 ■6 •4 -2 •0 ■410 ■000 •410 •6 ■' - -2 ■00 •872 •000 •072 ,T •4 1-1 1 Ordinates tak en at 3- 3 feet ap art. Volume =6365 cubic ft. 1 Ordinates taken it 3-3 feet apart. V, = 9S0 cubic ft. Area 1142-2 of/; = square ft. SHIP-BUILDING. 54 Table IV. — Calculation of the Metacentre when the Vessel is in an Upright Position, also when the Vessel has been inclined through an aiii/lc of 20°. UPnnHT POSITION. inci.inkd position. Tabls I. OrdinAtos on tho Ilalt- CuhoorOrdi- Drca.Hh Plan nates ti» Two at tlu' Lo.-i(l- Pl&ces of Deci- iT.ilt>r Lin« mals. taken at &'M11'5 feet ul>.irt. H 2-7« l'-7j 20-80 4-5 9113 6.8 2.'iOU5 RO 51200 114 SSJOO 1(1.' liii;ii-oo )()7.'j VM-y.m 111-;.'. 1 ■.')■.' 30 1II7S i'.')2;o HUD ir.'ii-oo VM w.ioo 7-75 it\i ta IM 11113 •50 •13 Tabll 11. Onlinatcs mea- sured from P Cnbesof Ordi- on the inclined nates to two Plane of Flota- PlaceM of Ueci- tion, taken at maU. 3-3 feet apart. •7 ■M 1-9 I'l'i^i 30 81(10 4-4 8.V18 S2 mini G-2 23833 7-1 8-->7^91 7-8 47155 8-2 6.J1-37 8^7 658-50 91 75357 9-4 830-58 »•♦ 830-58 9-2 778-B9 8^7 65H-50 8-5 614-12 8-2 551-37 7-5 421^87 7^0 nana 6-0 2ii;-oo 50 12'r00 30 •.'7110 Table 111. Ordinatos mea- sured from I" Cnbosof Ordi- on the inclined naten to Two Plane of Flota- Places of Deci- tion, taken at mals. 3 3 foot apart. ■6 -13 14 2-74 2-2 10-i:5 80 27(10 4-5 aii2 i-a 1)7-34 68 V.IVU 6-8 31443 70 31 ;-oo 7-4 4iia-:'2 8-7 658 50 90 7:".' no 9^2 778 li9 9 4 8 '.0-.'i8 9^0 7:':i no 8-8 681-47 88 (i3(l-(Ni 8-2 651-37 80 6rj-00 70 8t3-(M) 60 2li;ui) 6-0 l-j:.-00 4-1) 64-00 Calculatioo of the Me- tucentro. The cubes of the oi-Jinates given in the first of these tables in- troduced into Simpson's rule, (jives 44800 81 ; this result multi- plied by §, and divided by ^483-2, or half the displacement, give8 12 3 feet nearly for the distance between the metacentre and centre of buoyancy. (See iiule XIV. p. 45.) It has been more convenient to take the ordinates at 3-3 feet apart in the second and third of these tables. The cubes of the ordinates in Table II. introduced into Rule I. p. 30, gives 28829-58. The cubes of the ordinates in Table 111 rule gives 2731G-95. £8829 -58 -4-27310-95 = 56146 53 = the moment of inertia of the inclined plane of flotation. Hence, 2x56146 53 2x56146-53 3x4 displacement 3 x 4966-428 = 7^53, height of mcta- introduced into the same centre above the centre of buoyancy when the ship has been inclined through an angle of 20°. The latter centre must be calculated in the same way as was done in Table II. ; whence the position of tiie metacentre in the inclined state of the vessel becomes completely determined. T.Mii.K V. — Calculation of the Volume nf Immersion v'hen the Ship is inclined through an angle of 20° Volume of Nat. Sin 20° = ■342— Ordinates at S'Sfret apart. immersion. 1. 2. o. «• 5. c. 7. 8. 9. 10. 11. 1-2. 13. 14. 15. ii;. = .2 1 It .J ll O b 3 1; M o a a ■& i£ - = g & o rt lis c B 3 Hi ©CO 1- a Is S2 11 s O U n i ° s ►. £2 o o rt III J s :^ o s o SI- III -Is- si's OS 1. a £S-5i: + B D £ II- 1 3 i| El B 3 3 -] X 5 '' Q H a. &; E-i < < -<! o o u o •6 •7 •2 •00 •4 •60 •072 •000 •072 •000 029 •000 ■029 •40 ■379 •027 14 1^9 •8 •05 11 1-7 •455 •027 •482 •482 •501 •046 •547 1^13 1-072 •517 2-3 3-0 1-2 •10 1-7 3-0 I^ISO •080 r260 2-520 2^006 •240 2^246 1^78 1-688 2127 33 4-4 1-7 •10 2^4 4^0 2-483 •113 2^596 7-788 5^959 ■452 6411 £•47 2-343 6^882 4-2 5-2 2 1 ■10 3-0 4-9 3-735 •140 3875 15500 11^205 •686 11891 307 2912 12-284 5-2 6-2 2.5 •10 3-7 5-6 5-513 .167 6-680 28400 20^398 •935 21-333 3-75 3-557 20-204 58 7-1 2-7 •10 4-4 7.0 7-042 •180 7-220 43-320 30-985 1^260 32-245 4-46 4-230 30-540 67 7-8 2-8 •20 4-8 7-3 8-936 ■373 9-3ii9 6.5-163 42-893 2-723 45 616 4-90 4-647 43-2-59 7-5 8-2 30 •20 5-2 7-9 10-516 •400 10.916 87-328 54-683 3-160 57-843 5-30 5026 54-864 8.0 8-7 3-0 •22 5-5 8-3 11-902 •440 12-342 111-078 65-461 3^652 69^113 5-61 5-321 65-671 8^5 9-1 3-2 •30 5^8 8-8 13-227 •640 13-867 138-670 76-716 5^632 82-348 5-94 5633 78-113 89 9-4 3-3 •30 61 9.3 14-306 •660 14-966 164-626 87-267 6^1.38 9.'}-405 6-24 5-918 88-369 9-3 94 3-4 •30 fr3 9-4 14-949 •680 15-629 187 548 94-179 6-392 100-571 6-43 6-098 95 306 9-4 9-2 3-5 •40 60 - 9-2 14-788 •933 15-713 204-352 88-728 8.584 97-312 619 5-871 92-251 91 8-7 3-4 •30 6^0 9-1 13-478 •680 14-158 198-212 * 80-868 6188 87-056 6-14 5-823 82-442 8-7 8-5 3-3 •30 58 8^8 12-645 •660 13-303 199.575 73 341 5 81)8 79149 5-95 5-643 75-OSO 85 82 3-2 •40 5^7 8-7 n-909 .853 12-772 204-352 67-881 7-421 75-302 5-90 5-626 71-853 7-5 7-5 3-2 •50 5^4 84 9-619 1^067 9^686 164-662 51-943 8 963 60-9U6 6-28 5-956 57-690 70 7-0 31 •50 4^6 7-2 8-379 1^033 9-412 169-416 38-543 7^4:!8 45 981 4-88 4-628 43-559 6-0 60 3-1 ■50 4-0 6-3 6156 1.033 7-189 136-591 24^62i 65U8 31-132 433 4-107 29-525 5-0 5-0 3-2 •40 3-4 5-3 4275 •8.i3 5 128 102-560 14-535 4-521 19^056 3-71 3-519 18065 40 3-0 3-1 •30 2-4 37 2-051 •620 2 671 56-091 4-922 2 294 7^216 2-70 2.561 6-840 2-5 2-5 3-1 •20 1^7 2^6 1-069 •413 1,482 32-608 1^817 1-074 2-S91 1-90 1-802 2-670 Distance of Volume im- mersed =6-2-i-84 centre of gra- vity from Ist '^'"■'' -5-15ft. vertical Sect. tun. = 401 feet. SHIP-BUILDING. 55 Ta BLE VI.- -Calculation of the Volume of Emersion, 1. 2. 3. 4. 1 5. 6. 7. 1 8. 9. 10. 11. \-l. 13. 14. 1 I.-,. 1 W. c ii 2 . O " 1: O O o .2 'S u a of tl ° i n ■w ^ "S.2 O o o Hi a i Z 1 I [0 .X I'* c 1 1 1 c o o "1 Is Ii Is II p g u d 11 i Ii t- d O si ^ a> Itl 5 = i s ? 9 II J i "3 £^ ^■^ c o E 9 3 3 O X o Q H 0. H H f^ a •s. 5 u 5 •6 •5 •3 ■00 ■4 •60 •051 •000 ■051 •000 ■020 ■000 •020 •39 •370 ■019 1-4 1-4 •8 •05 ■9 1^42 •335 •027 •362 •3ti2 •302 ■038 •340 •94 •892 •323 2-3 22 1-3 •10 1-4 214 ■865 •087 ■952 1^904 1-211 •186 1-397 1^46 1-385 1^219 3-3 30 1-4 •10 20 304 1-693 •093 1-786 5-358 3-386 •283 3-669 2 05 1944 3452 4-2 4-5 1-5 •10 28 4-24 3-232 •100 3^332 13-328 9050 •424 9-474 2-84 2-093 8-973 5-2 4-6 2-0 •12 32 4-85 4090 •160 4^250 21-250 130S8 ■776 13 864 3-26 3^092 13-141 58 5-8 2-5 •12 38 5-75 5-752 •200 5-952 35712 21-858 1^150 23-008 3-87 3670 21-844 6-7 6-8 30 •14 44 6^66 7-791 •280 8071 66-497 34-276 1^865 36-141 4-47 4^239 34-213 7-5 7-0 30 •16 4-8 7-26 8-978 •320 9-298 74-384 43-094 2-323 45-417 4-88 4-628 43-031 80 7-4 30 •18 5-2 7^87 10123 •360 10-483 94-347 52 640 2-833 55-473 5-29 5017 52-593 8-5 8-7 3-2 ■20 58 8^78 12 645 •427 13072 130-720 73-311 3749 77090 5-90 5596 73-151 8-9 9-0 34 •20 60 904 13-697 •453 14-150 155-650 82-182 4-095 86-277 6-09 5-776 8V730 9-3 9-2 3-4 •30 6-2 942 14-631 •680 15-311 183 732 90-712 6-406 97-118 6-34 6-013 92-065 9-4 9-4 4-0 •30 6-2 9-42 15-110 •800 15-910 206830 93-682 7-536 101-218 6-36 6-032 95-969 9-1 90 4-0 •30 60 9^12 14004 •800 14-804 207-256 84-024 7 296 91320 617 5-852 86-633 8-7 8-8 38 •20 5-8 8-78 13-092 •507 13599 203-985 75-934 4^451 80385 5 91 5^604 76^209 8-5 8-6 3-7 ■20 56 8^48 12-500 •493 12-993 207-888 70-000 4^181 74-181 5-71 5415 70^357 7-5 8-2 3-6 •20 5^0 7^58 10-520 •480 11-000 187-000 52-600 3-638 56-238 511 4-846 53706 70 80 30 ■15 50 7^56 9-576 ■300 9873 177-768 47-880 2-208 50148 5-08 4-818 47^583 60 70 2'0 ■12 4-4 6.65 7-182 ■160 7-342 139498 31-601 1-064 32-665 4-45 4-221 30-991 50 6-0 2-0 ■10 38 5-74 5130 ■133 5-263 105-200 19-.194 •763 20-257 3-85 3052 19122 -10 50 1-5 •10 3-2 4-84 3420 •100 3-620 73920 10 944 •484 11-428 3-24 3^073 10-817 'J 5 4-0 1-0 •00 2 300 1-710 000 1-710 37-620 3-420 •000 3-420 2-60 1^897 3-244 Volume by Distance of 3018W45 Simpson^s li'ule centre of £rra- i;ou = aiO feet «'8 = vity from a ver- _ = 5'03 feet. 17"1 tons. tical section = 41-t; feet. Obserra- tions on the preced- ing Tables. Observations on the ■preceding Tables. It ought to be remarked, tliat in the foregoing tables extreme accuracy has not been aimed at, cither in taking off the lines of the yacht, or the multiplications, &c.: the re>ults are offered to the practical man, merely as illustrations of the rules already given. No remaiks are needed on tables I. and II., except that in the latter, the centres of gravity of displacement of the small portions near the bow, stern, and keel, have been assumed instead of calculated ; but it will be (iaimd that the distances given therein are very nearly correct. Table III. determines the position of the point P {vide Art. 12, p. 46). The reader will under- stand how the necessary data are obtained from the obser- vations appended to Table V. Having determined P, set off a distance OP' = OP {vide fig. 7), and through ihe points P and P' draw the lines on and on respectively, making angles of 20° with the line FL., then referring to Table V. The first column is obtained by measuring, on tlic same scale, the ordinates Pa, Py8, P-y, &e. up to PL, and then by measuring P'F, P'^, P'o, PV, up to P'o. Column (2) is obtained by measuring the ordinates Pa, Vb, Pc, &c., up to P«, and then P'o, Vp, kc, up to Vz. Column (3) is got by measuring the right lines aa, /36, cy. Sec, up to 7/L, and then FO, ^p. Sec. Column (4) is obtained by measuring the perpendicular heights of the small parabolic segments, aa, bfi, kc. Column (5) is got by bisecting the right line joining \,n, joining the point of bisection to P, and measuring all the bisectors of the triangles Pao, Vb(i, and by taking two- thirds of these results from stern to stern, as was done in columns (3), (4), since the centre of gravity of a triangle lies in the bi>cctor of a side at a distance of two-thirds of the length of the bisector from the vertex. In column (6), it has been assumed that the centres of gravity of the parabolic and triangular areas lie in the same right lines, namely, the bisector of the bases of the triangles (produced for the paraboloe). This supposition will be very near the truth. If, then, we add the length of each bisec- tor to two-fifths of the height of each corresponding para* 56 SIIir-BUILDING. Observa. tions on the preced ing Table.' bola, wc obtain the results contained in tlii-s column. The centre of jiravity ol' a parabola, it oui;lit to be ol)serveii, is at tliree-fitths ot the Uiij;lli of the axis from the vertix, a 1, consiqucntly, at tuo-fifths of the lenixtli of the axis mini (lie point wlierc the liimble orilinate cuts the axis. Cohniin (7) is obtained by taking the product of the cor- responding iioiizontal numbers, given in columns (1) and (2), and multiplying the result by i the natural sine ol 20° = ■342 ■ ='171. Because the area of a triangle = J the pro- duct of any two sides, multiplied by the natural sine of the included angle. Column (8) is got by multiplying together the corre- sponding numbers in the horizontal rows of columns (3) and (4), and then taking two-thirds of the products, since the area of a parabola = two-thirds of the circumscribed rectangle. Column (9) is obtained by adding together the corre- sponding areas in columns (7) and (8). These areas are introduced into Rule I. for the volume. The results in column (10) are obtained by multiplying the results of cohunn (9), by the niniibers 0, 1, 2, .", 4, &'c., and these numbers are introduced into Rule VIII., in order to obtain 40" I feet for the distance of the centre of gravity of the immersed wedge-like portion from the first section at the bow. The results of column (11) are the areas of the triangles multiplied by the distances of their respective centres of gravity from the axis passing through P. The results of column (12) are the moments of the para- bolic areas about the same axis. The results of column (13) are obtained by adding to- gether those of columns (II) and (12), that is, ni^x^ + »i.,x^ where ni„ m., represent the areas of the triangle and para- bola res[)ectively, and x^, a-j the distances of their centres of gravity from the axis. The results given in column (14) are obtained from the /H X ^" Jtt OC formula x= — — ' ^— -, where m,, m, represent tlie areas OTl + ZHj i' 2 I of the triangle and parabola respectively, and ar,, x., the re- spective distances of their centres of gravity from the axis, and X the distance of the centre of gravity of the whole area from the same axis. The results given in column (15) furnish \is with the distance of the centre of gravity of each mixtilinear area measured along the inclined plane of flotation Pa. Column (IG) gives us the moment of each of these areas in regard to the same plane of flotation, and these results introduced into Uide (I.), and divided by the wedge of im- mersion, gives o'lo feet, the distance of the centre of gravity of the whole volume of the wedge of immersion mcastired from the axis along the inclined plane of flota- tion P«, that is the distance ;>, (/,. In Table VT. the same methods are ptustied as in Table (V.), the ordinates Po', I'b, Sec; PV, V'j)', Sec, being taken. The reader will readily perceive how the work in co- lumns (lo) and (16) may be curtailed, since each horizon- tal row is multiplied by the common factor '9484. He will now have no difficulty in calculating the dynamical stability of the vessel w hen inclined through the same angle. The results of such calculations are too laborious and lengthy to introduce into the present work after what has already been given. Adding the results given at the bottom of Tables (V.) and (VI.) Colunm (16) we obtain p, 7,= 10-18 feet. We have next to ascertain the exact position of G, the centre of gravity of the ship, as she floats at the load-water line, for in the present case all our calculations have been Ohserva- based on this assumption. tions on " The position of the vessel's centre of gravity G de- f"* precpii- pcnds partly on the construction and partly tipon the dis- "'*>' '''"I''''*- tiibution of the lading and ballast, which ci.X'umstaiices ^"V"*"^ therelore determine the distance GGj, or the distance be- tween the centre of gravity of the vessel and that of the displaced volume." ' The centre of gravity may be found by the method eniimerated in Art. (4) ; but as the centre of gravity ought to lie in or a little below the load-water section, we shall assume it to be one foot below that section. Then, since MGj= 12-3 feet, vide Table IV. Static:.! and OG = 2-7 „ „ Table II. stability .-. MO = 9-6 „ and MG = 9 6 -H = 10-6 feet. ^°"""'- and GGrf = 2-7 - 1 = 1-7 feet. It will readily be seen, from these residts, that cqu.ations (I.), (II.), (III.), Art. 11, are satisfied, and hence the ves- sel is in a stable [josition of equilibrium after she has been inclined through an angle of 20°. Atwood, in the paper just quoted, takes GG'as the mea- sure of stability; hence, by Equation (I.), Art. 4, — /»! 7, w — GG^ . W sin <^ GG'=' W _ lOiSx 17-6 142 ■ GGd sin <f> - 1-7 X -342, where 17-6 tons is taken for w, — that is, the mean value of the weight of the volumes of water emerged and immersed, .-. GG'=l-2638--5814 = -6S24 feet. If we multiply this result by the weight of the vessel, we obtain the moment of the vessel's stability. Atwood states that, in some vessels built in his time, the distance between the points G and G<i= Jth of the greatest breadth at the load-water line.' The determination of the stability herein given refers to the rolling motion only of the vessel, though, generally speaking, when a vessel is in a sea-way, there will be both a pitching and rolling motion. " The force, or measure of stability here given, is en- tirely independent of the water's resistance, which co- operates with the vessel's stability only while it is inclining, and wholly ceases as soon as the vessel has attained to the greatest inclination, at which it is supposed permanently to remain in a state of equilibrium ; the inclining force being exactly balanced by the force of stability."'' The time of an oscillation may readily be obtained from Tlmeofrol- Equation fl.). Art. 18. ling found. For T = -j^L^ -/ff.GM = 3-14I6xA \/32-2 X 10-6' when k may be calculated when the position of the weights on board arc known, inasmuch as the axis about which the vessel is rolling is supposed to be known. Akt. 19. — Naval architects em|)l(iy a method for deline- ating the immersed portion of a ship by means of a curve of vertical sectional areas, as well as for determining the position of the centre of buoyancy, &c. The principles employed are those enunciated in Rules I., II., VIII., IX., &e., where the areas, moments, &c., are set off at their re- spective distances on the base-line, — that is, the load-water 1 Atwood's " Disquisition on the Stability of Ships," Phil. Tram, of 1798. « Ibid., p. 296. 3 Ibid., p. 305. SHIP-BUILDING. 57 line, divided by a constant quantify corresponding to the away the masts &c., in ore 1 1 i'.i 1 „ „f„atr.r Hiinlirpfl times of oscillating would depth of the volume ot water dibplacecl. ,..,,, . ., _ , r^„ ru„ „.k. Thus the displacement is considered as divided longi- tudinally into two equal portions, which is equivalent to dividing the base-line of the sectional areas into two equal portions. Thus, if FL (fig. 10) be the load-water line, which is bisected in A, F JB L A F is taken to represent liall'the displacement. If we set off tlie vertical areas as ordinates at equal distances apart, the curve F B L, passing through their extremities, will be that of the curve of sec- tional areas, and the centre of buoyancy may be deter- mined by the usual methods. See Peake's Kudimentary Treatise on Shiiibuilding ; London, John Weale. Conclusions deduced from Theory applicable to Ship- Huilding. order to case the ship, since their Ccncln- not synchronize with those of eions de- the vessel. On the other hand, when the weights are duced from placed at a greater distance from the axis of rotation, the Theory, moment of inertia, and therefore the time, is, cateris pari- ^-""v"*^ bus, increased. Generally speaking, the rolling under these circumstances will be easier than in the former case, as the times of oscillation of tlie masts, &c., will more nearly syn- chronize with those of the vessel. (See below.) Much, too, depends upon the draught of water of vessels, Draught for a vessel with too great a draught of water must neces- sarily meet with great resistance from the pressure of the water on the low er part of the bottom, especially on a wind, and she will therefore tack and wear w ith difficulty and un- certainty. A greater draught is generally given at the stei n than at the bow, since a finer run is thus obtained, and the rudder becomes more deeply immersed in the water. More- over, in sailing-vessels, the effect of the w ind on the sails will generally be to immerse the fore-body more deeply than the after-body, and thus to counterbalance the increased draiisrht of water aft. Having assumed a length, breadth, and draught of water, the constructor must in the next place determine the posi- tion and form of the greatest transverse or midship section. Every naval architect will adhere to his own opinions in regard to the position of this section ; but as the vessel has Before a naval architect lays down the lines of a ves- to cleave her way through the water, the position and form sel, he is aware of the purposes for which she is in tended ; he knows the armament, cargo, Ssc., which it is intended she should carry. These being known, as well as her weight at launching, since the specific gravity of the materials of which she is composed is known, the first re- quirement is to make the total weight and corresponding (iisplacement, when ready for sea, agree with the required draught of water. We know that the displacement de- pends on the product of the three dimensions, length, breadth, and depth ; the naval architect therefore proceeds to form a rough design, probably in comparison with some well-known ship of the same class, and he will then pro- ceed to adapt this design, as far as practicable, to his own calculations, at least as far as is necessary. One of the first dimensions he ought to fix on is the length; but g' cat care is here required, as one of the dimensions camot be determined, without, to some extent, determining the others also, in order that the requisite sta- bility may He secured. When the length is too great, there is a grca: difficulty to be overcome in steering, owing to the effect of the winds and water on the bow, stern, and hull generally. If care is required in fixing the length, still greater cau- of this section, as well as the form of the fore and after bodies, ought to be such as to transmit the displaced fluid with the greatest facility to the right, left, or to the stern. Mr Scot* It was with this object in view that Mr Scott Russell pro- Kussell's posed his " Wave-Line Theory," by which plan he endea- '' .^^ "* voured to throw each particle of water, as it came in contact ^^^^^ with the vessel, just far enough to the right or left, so as to admit of the midship section of the vessel passing through without the same particles of water again coming in contact with her sides. A vessel ought to be so constructed, that when it is made to roll through small angles, all the centres of gravity of the planes of flotation should lie in the midsliip section ; which section should also contain the centre of gra- vity of the ship, and that of the displaced fluid ; for, if these conditions be not fulfilled, the vessel will not roll about an axis parallel to its length ; and then for every rolling motion there will also be a corresponding pitching motion.' As has already been remarked, the straining of a vessel depends upon the oscillations of the various portions of the vessel synchronizing with each other, and upon the times of rolling or pitching. Cateris paribus, the more slowly a vessel rolls, the less strain w ill there be on the masts and timbers ; because in quick rolling the masts, on account of tion is required in fixing the breadth, inasmuch as, to a their inertia, are not put in motion at the same time as the great extent, though not entirely, her stability during a rolling motion depends on this dimension. Dr Inman, in his notes appended to Chapman's Architectnra Novalis Mercatoria, pp. 273, 274. says that " a straight of breadth, extending as far as possible tore and aft, and above and be- low the load-water line, is no doubt the most advantageous to the stability at any finite angles of heeling," and also that the vessel ought to be stiff at a small angle, and neither increase too rapitlly nor too slowly in the resistance to heeling at larger angles. If the breadth is not sufficiently great, the weights on board could not be removed sufficiently far from the axis passing through the centre of gravity, and, during a rolling motion, the time would thus be diminished, inasmuch as the moment of inertia of the vessel about the same axis would be diminished, other things remaining the same. (See Equation I., art. I*^.) In consequence ot this uneasy ship ; and by the time the vessel begins to roll back again the masts are still being carried forward, so that this cause will often account for the masts and yards being carried overbo.ard in a heavy storm. In order to make a vessel roll more slowly, the' weights ought to be removed to a "reater distance from the axis about which she rolls — by running up the yards, for instance ; and the more quickly will she roll when the weights are brought nearer to the axis, as when the guns are run back in a heavy sea.' We see by Equation, Art. IS, that the time of rolling dc Time of pends on the moment of inertia of the ship, and the dis- rolling, tance between the metacentre and centre of gravity of the ship. This time varies directly as the former, and in- versely as the square root of the latter. Four cases will thus present themselves when the same vessel is immersed to the same draught fore and aft : — (1.) "The time of natural oscillation maybe increased rolling, it might become necessary in a heavy sea to cut both by reason of the increase of K, Equation (I.), p. 51 See iluseley's Pa^'er on Dynamiad Stab lily. '' Ibid. 58 SHIP-BUILDING. Concln- anil ilie raising of the weights of the ship. Tliis can scarcely dions de- be t'xpcctcii except in tlie case of a very broad vessel with dureil frnmj.o,„p;,r;itiveiy liisili masts and yards. Theory. ^.j.) The time of a natural oscillation may be dimin- ^"^"^j"^^ ished by the diminution of K, and increased by raising the weights of the ship, and in that case tliere may result little or no change in the time. (3.) It may be increased by the increase of K, and di- minislied by tlie lovvering of (i, the centre of gravity. Here, again, there may be little or no cliange in tlie time of oscillation. (-4.) It may be dimiiii.-hed both by the diminution of K, and by the lowering of the centre of gravity. A ship laden with a very heavy cargo — iron or copper, for instance — will roll more rapidly on both these accounts, if the iron or copper be placed in the hold near the kelson than if raised on a stage ; and if it be stowed near the sides of the ship, this circumstance will tenil still further to make the vessel roll more slowly. If G is fixed, it is evident that G Ga will be smallest in those vessels wliich are full about the water-line and lean below ; such ships must therefore, cateris paribus, be quick rollers. If G Gj be increased by lowering G<j — i.e., by making the vessel comparatively full below, and therefore of less depth — M G will be diminished, and the time of oscillation is increased. It is hence eviilent that the form of a vessel below the water-line must naturally affect its rolling qualities."' Canon Moseley remarks,'' " That form of vessel in which the surfaces subject to immersion and emersion, when intersected by planes perpendicular to the vessel's length, have circular sectinits, having their centres in a common axis, is, cateris paribus, eminently a stable form ; because, in a vessel of such a form, the centre of gravity of the portion of the dis|)laced fluid which is included Hitliin the solid of revolution formed by all these circular sections, does not in the act of rolling rise. " If it be not practicable to give to the vessel, throughout its whole length, a form subject to these conditions, this is practicable with regard to the midship section, n hich is the governing section." On the whole, as might have been expected, vessels with paddles may be built of less breadth than those fitted with the screw, as the paddle-wheels will tend to increase the stability when inclined through a finite angle. This remark ought, however, to be received with some caution. There cannot be a doubt that, as far as speed goes, the best form of vessel has not yet been obtained, though daily experience seems to show that naval architects are gra- dually advancing in this respect. To prove this we need only instance the performances of the new Dublin and Holyhead, and Dover and Calais steam-packets, as well as the performances of other fine vessels, as given hereafter in this article, and also in the article Steam Ships. Some further remarks on these points will be fbund when treating of tlie forces acting on a ship in motion. The Forces which act upon a Ship in motion, as they in- Jiuetice her general dimensions, form, and qualities. Forces The methods by which the displacement of a ship is affecting a foimd, and those by which the positions of her centres of Ship in gravity are determined, having been described, and the ° '°°' principles on which her stal)ility depends having been pointed out, it is now proposed to consider the forces which afiect her speed through the water. Laws of It ^as at a very early period pointed out by mathema- """*"*'^^- ticians, that the velocity with which water will run 'out through a small orifice in the bottom of a vessel is the same as that which would be acquired by a body falling from a height equal to tlie depth from the surface of the water to Forces the orifice. The truth of this has been at various times «ff''i'tins tested by many experiments, and has been confirmeil by all ^'"'IJ '" that have been made. Euler, in his work, Theorie Com- ™°"'"'' ptette de la Construction det Vaisseauj; took this as the ^^/^ basis of his investigations of the theory of the resistances l'e8'«'="i>: which solid bodies moving in a fluid have to overcome. A pas- as the squares o sage in the English transltaion of his work is giventhus : — ■ ti'g yeig. " We know, both from theory and experience, that the wiitor cities, by contained in a vessel, whose height is ^ h, will run out through a theory, hole in the bottom with the same velocity that a body falling from the same height, A, would acquire. And if the letter g denotes the height through which a body falls in one second, we also know the velocity will be such that it would run through a distance = ^^Jyh in the same time. Since, therefore, this velocity is su)!- posed = c, or SVg^rrc, and, by taking the square, 4^A = c-; whence we have the height sought, hz= — ; consequently, the force of the resistance which a supposed plane surface =/." will experience by moving in water, with the velocity c, will be = — - — : and by this force the surface will be acted on, in a direc- tion contrary to its motion. Hence, we see that this resistance is always proportioned to the square of the velocity, and also propor- tional to the area of the surface itself, so that by this means the resistance is perfectly determined."' The truth of this fact may also be made apparent by ordi- byordinai nary reasoning. For if a body be moved in water with a reasoning velocity of 1 foot per second, a column of water having the same area for its base as the direct surface or midship sec- tion of the body in motion will be moved out of the way, or impelled with a velocity of 1 foot per second, and the weight of this quantity of water will be the measure of the resistance ; but if the body be moved with a velocity of 2 feet per second, the column of water will not only be 2 feet long, but each foot in length of fluid must now be moved in half a second, as each particle is moved with double the former velocity. The measure of the resistance therefore is first doubled on account of the doubled velo- citv, and is again doubled or made tburfnld, that is squared, on account of each particle, or the whole of the double quantity, having to be moved at this doubled velocity. The resistance, thertforc, which with a velocity of 1 foot |)er second was=l, will with a velocity of 2 feet be equal to 4, or the square of the velocity. In the same manner, if the velocity be increased from 1 foot to J feet per second, the amount of water to be displaced in one second will be four times the quantity ; and, again, each particle of water must be moved with four times the original velocity. The measure of the resistance in this case, therefore, will be = 16, which again is the square of the velocity ; and thus it may be shown, that to whatever degree the velocity may be increased, the resistance will always be increased in the ratio of the square of this velocity. In all these cases, as the columns of water to be moved Resistanc always have for their bases the same areas as the areas of are direct the direct surfaces of the moving bodies, so the resistances *' "'"'ni which are res|)ectively represented by the weights of these columns of water will always be proportional to the areas of the surfaces, or midship sections of' the bodies. If the resistance to the motion of a vessel through the Amount o water were not lessened and modified by her form, the de- resistance gree of it, by the foregoing considerations, would be ascer- ". "I'"!'? tained by finding the weight of a column of water "hose Jl'^^J - ' base is equal to her midship section, and whose height is body, equal to that from which a body must fall to acquire the velocity at which she is propelled ; and the resistances of similar vessels, when moved with the same velocity, would be proportional to their midship sections. The direct resistance, however, to any plane surface will be diminislied by placing a triangular or other form of body before and 1 From a paper by Dr Woolley. 2 Jloseley's Paper, &c., p. 621. SHIP-BUILDING. 59 Forces behind it. Many experiments have been made on the forms .ffeciin^a to be added in this manner, witli a view to discover the law Ship in of the diminution of this resistance, and thus to be able to motion, approximate to the form of least resistance. All attempts ^'^'^^^'"^ to reconcile the theory of tiie resistances on plane surfaces, as established by experiments, with those on obhque surfaces ])resented to a fluid, have as yet failed. Bossut' was the first to give the theoretical resolution of the resistances on the sides of a wedge-shaped body, wliich he did as follows. Let ADB (fig. 12.) be an isoBcclea triangle, moving in a fluid of Infinite extent in the direction of its height QD. The face AD is subject, according to theory, to a resistance in the direction FK perpendicular to itself, such thiit in calling r the perpen- dicular and direct resistance experienced by the half-base AQ. AV hen moved with the same velo- city as the triangle, we have forca AUx^sinADQ£ _ ADx AQ 2 "''^AQx AD2 AQ , . = IT X -r-pr ; and in a simi- lar manner we have, for the other BQ BD force BD, force e^ t y. AQ AU" Fig. U. Resolving each of the two eqaal forces FE and fe = :rX into the two others, FH, FK and/A/i, the one perpendicular and the other parallel to the base AD of the triangle, it is evident that the two forces equal and directly opposed to each other, FK and fk, destroy each other, and that the triangle is simply acted on in AO the direction QD by one force = FH + /A = 2 FH = 2 FE x ^ AQ-2 AU r X vivv. Hence, if we call this force 2 FH =/), and call the „ ^ perpendicular and direct force which acts upon the base AB, when moved with the same velocity as the triangle = P, we have AQ2 7) ^ P X rK2- Comparing this formula with his experiments, Bossut found the following results in four instances of experiments with different models: — [iesistances Distinguishing No. of Model Experimented npon. Angle of Incidence. ■\^alQe of p in Marcs. By Experiment. By Theory. 9 10 11 12 45° 33° 41' 26° 34' 21° 49' 12-96 nearly. 10-80 „ 8-39 „ 8-32 „ 12 7-38 nearly. 4-80 3-31 nearly. He then showed that this is found by experiment not to be true with respect to bodies with sharp ends moving in water, these dif- From the above it is seen that the results of theory differ fer in further and further from those of experiment, the smaller ;h«ory and jj^^ angle of incidence, that is, the finer the angle of en- inprac ice, jj.^j,pg of a ship, is made. Further experiments have been made with a view to discover the law of this branch of the theory of resistances, but as yet without any results such as will enable any calculation to be made to determine be- forehand, with any accuracy, the extent to which the resist- ance of a body of any given form will be diminished from that due to the base or midship section of the body. Even if a law were discovered for different angles of incidence, the difficulty of the investigation would still be great, when it is considered how constantly this angle varies on every portion of the fore-body of a ship. Every one conversant with the practice of naval architecture is well aware, that if a model of a vessel be made in wood, a very slight amount of paring away at the bows will make a very mate- rial alteration in the speed, while the alteration upon the angles of incidence would be so small as not to affect, in anv Forces material degree, anycalculations based upon them as awhole. affecting a Theory therefore fails, by any abstract calculations ^^'V '" /, , , , f /» . ■ 1 1 u motion, founded on the angles of mciuence, to give any rule oy , ^ ^ / which to ascertain the resistance of a vessel of any given liirm, and consequently to ascertain the velocity that she Accuracy will obtain by the exertion of any given amount of power ^^' ^"^ to propel her; and the naval architect is thus driven to^^^ j_' ascertain these points by comparison with the results ob-Q,entson tained from vessels of known form and power. plane sur- It has already been shown, that the resistances, expe- faces, rienced by the same body when moved at different velo- cities, vary as the squares of the velocities, and that the resistances of vessels similar in form, but of different mag- nitudes, when moved at the same velocity, are proportional to the areas of their midship sections. Many experiments have been made to test the accordance or otherwise of these theoretical deductions with the actual results ob- tained in practice. M. Bossut reported, as the result of the experiments conducted for the Royal Academy of Sciences at Paris in the year 1776, that the resistances of the same surface, moved w ith different velocities through a fluid infinite in extent, follow nearly the proportion of the squares of the velocities, and also that the perpendicular and direct resistances of several plane surfaces, moved with the same velocity, are very nearly proportional to the areas of the surfaces ; and, consequently, that experiment and theory may be said to agree on these points. The experi- ments made in 1796 and 1798 in this country by the So- ciety for the Improvement of Naval Architecture, and con- ducted by Colonel Beaufoy, lead to the same conclusion. These latter experiments were made with bodies of va- On bodic rious forms, and at velocities varying from 1 to 8 nautical of variom miles per hour. The relative proportion or degree in w hich forms, the resistances and velocities varied in bodies of different forms, differed comparatively slightly, being in some cases above the square or second power, and in other cases below it ; in one instance it reached as high as the power of 2'2061, and in another instance as low as 1'7914, but the average of the results obtained from these experiments may safely be taken as corroborative of the theory, and as evidence that it is sufficiently accurate for all practical pur- poses, and is applicable to vessels of the different forms used in practice by naval architects. Exception has been taken by some to the results of these experiments, because the bodies were entirely sub- merged ; but the reasons for so conducting them appear to be stronger than those for conducting a series of experi- ments on bodies only partially submerged, and then sulyect to other influences than the action of the water through which they are passing. Deductions based upon the grounds thus established, as furnishing correct data on the subject of resistances, are of great practical value to the naval archi- tect, though the actual or absolute resistances per square foot of surface or of midship section remains undetermined on account of the ever-varying forms given to the bodies of ships before and abaft the midship section. The direct resistances to which any body is subject while The rcla- moving at different velocities have been shown to be as thetion of squares of the velocities ; that is, if K represent the resist- po^'^"" to ante at one velocity called V, and r represent the resist-^ "'^* ance at another velocity called t', then B : r : : V2 : r3 The power expended to overcome any resistance for any definite distance, or, what is the same thing, the amount of work done within any given time, may be represented by the product of the resistance overcome, multiplied into the velocity, or by the product of the weight representing the resistance, multiplied into the distance passed over by it- ' Xouvelks Expiriencu tur la Retistance des Fiuidei. Paris, 1777. 60 Forces affecting a Ship ia motion. SHIP-BUILDING. Examples, Compari- eon of ves- sels of dif- ferent sizes and powers. Such com- parisons are inathe- niHticully correct. If R then be multiplied by V and r by i', the prodiiets will respectively represent the powers employed in each case, and KV = P wiiilst rv=p. llevertinjj to the I'orinula — U : r : : V2 : «2 it is evident tlut by multiplying both sides by the propor- tional V : V, we obtain UV : rp : : V3 : v\ and by equality of ratios, and the substitution of the above equals P : p : : V^ : r'. In cale\ilations respecting the speed of vessels, the poner taken is generally the indicated horse-power, or the gross power exerted in the cylinders; and to denote this, IHP is generally used instead of P. This will make the formula stand tlms : — inP:iAp:: V^ : v\ From this it will be seen that the horse-powers vary as the cubes of the velocities, or the velocities vary as the cube roots of the powers required to produce them. If the velocity, therefore, of any vessel with any given amount of horse-power is known, the velocity she will attain with any other amount of power, or any other velocity being assumed, the power necessary to drive her at that velocity niav be computed. E.r/iiiiple. — A vessel having been proved to have a speed of 8'32b knots per hour, with 813 indicated horse-power, it is desired to know what velocity she would attain with 2000 indicated horse-power ; the vessel being supposed in every case to have the same draught of water, so that there is always the same body to be propelled, the formula would stand thus : — 813 : 2000 : : 8-328» : t/». V, the required speed, is thus found to be equal to 11 '20 knots. Or, with the same vessel it is desired to know what indi- cated horse-power would be required to give her a velocity of 1 1 •25 knots — 8-3283: 11-253: :813:iA^; i/ip, the reqifired indicated horse-power, is thus found to be 2000 horses. The speed or the power thus obtained, even though in practice it may be impossible to carry out the conditions, will be a mathematical truth, and will afford perfectly sound grounds from which to draw conclusions with respect to other vessels in which these conditions will be possible. For instance, in theoretical calculations, a large amount of power may be supposed to be put into a vessel of so small a size that she could not carry it, but the velocity found by calculation as due to this small vessel with this large amoimt of power may be used as a ground of comparison, if it be desired to compare her performance with the per- formance of a vessel of sufficient capacity to carry this power. A comparison in this way may even be carried so far that the performances of H. M. yacht Fairy, of 312 tons measurement, may be used to predict the speed at- tainable by a vessel of the size of the Great Eastern if built xvith a midship section, and with lines of the same character, so as to be as near as may be mathematically similar. This mode of comparison has been most success- fully carried out by Mr Atherton, who has investigated the subject of comparative steam-ship capability at great length, and in a most able and valuable manner.' The mathematical correctness of the comparisons be- tween similar vessels, though of different sizes and pro- pelled by engines of different powers, may be demonstrated by reverting to the fact that the resistances of two differ- ent areas are directly as these areas when both are moved Porcei at the same velocity ; and that the velocities of the same "C'lg on vessel, or of two vessels of the same size and similar in all * '^'".1' '° respects, are as the cube roots of the powers, the areas or ^ ^ ""* '""'^ midship sections of the two vessels being the same, and '^ "" therefore ecpial. When the areas or midship sections are not equal, it is evident that the cubes of the velocities will be to each other as the ratios of the powers to their re- spective areas, thus : — and therefore, V3 : „3 . . V : eS : : P - p A Pa : j)A, or In using this formula, a coefficient C may be introduced A coefE- thus — <;'«'" raay V^ X A _ , „ 1/3 X a l« em- — g — = CandC= ployed. for the purpose of saving labour in the calculations. The velocity, area of midship section, and horse power of any vessel being known, the coefficient for tiiat vessel may thus be found ; and if it be proposed to build a larger vessel, similar in proi)ortions to the existing vessel, of which all the particulars are known, and which is called the type of the larger one, then the coefficient, the area of midship section and the horse-power of the pro|)osed vessel being known, the speed she will attain is found as above. In [iractice a ratio of the displacement of ships to be A ratio of compared is frequently used in preference to the ratio ofdisplace- tlieir midship sections, because it is considered that there ""'"' """y is likely to be a nearer approach to a mathematical siini- ^ "t^ ,'"' , • .' ^, . ,,, ' ' , r 1 ir 11 stead of larity m tins case. It two vessels of ditterent displacements, niijghip D and d, and different midship sections, A and o, be mathe- Beciion. matically similar, then the displacements vary as the cubes of any one of their like dimensions, — their breadths, tor in- stance; whereas, the areas of the midship sections vary as the squares of the same dimensions ; that is, if 15 and b denote the breadths of two similar vessels at the load-water line, : : A : a. :: U2 : : A3 ; :: D2; ::DS; the lengths or the depths— The principles here made use of are generally stated thus: — The volumes of similar solids are as the cubes of their like dimensions, and tlio areas of similar figures are to each other as ttie squares of their like dimensions. Hence, then, D*, or V D- may be used instead of the areas of the uidbhip section, and the formula V xA V X mid. sec. ("'' , IIP ■ , 8« it is generally written), may be substi- and B2 : b^ }K-nce, 1J« : (.« and B8 : b^ therefore, A^ : a^ and A : a Any other dimensions — viz,, mij;ht have been employed. ■ d\ ■.di. lUP tutcd by the formula V^x DJ 1 HP = C. As an example of the practical use of this formula, let it Example be supposed that there is a vessel in existence whose velo- of 'he ap- city is 8-328 knots, with the exertion of 813 indicated horse- 1^^^^°^ " power, and whose displacement is 3080 tons. The coeffi- nmi,, cient for this vessel is therefore found thus. 8-328" X 3080 i 813 = C = 150-4.2 It is now desired to find what will be the speed of a ves- sel similar in form to this vessel, but so much larger as to have a displacement of 5760 tons, and with an indicated horse-poH er of 2000 horses. In this case 1 Sttamihip Capabiiilu, by C. Atherton, Grant, Woolwich, 1854. * In Jlr Atherton's work, previou.sly quoted, tables of the cubes of the velocities, or v', and of the cube roots of the squares of the displacements, or 1)1, otherwise written V D-, will be found, which will materially lessen the labour of these calculations. SHIP-BUILDING. 61 Forces acting on a Ship in mutioD. V 3 X 576 0? 2000 : 150-4 V 2000 : iJ 150-4 X „-v— = 9-78 knots. 2000^ 576iis Ilogue and These figures are not imaginary, tiie results given as Dulie of those of the smaller vessel are the results which were ob- ^^ '^""'6*"" tained from H.M. ship Hogue, on trial at the measured cri'or^'o '^"'" '" Stokes Bay, at Portsmouth, and the particulars of completion 'he larger vessel are those which were a>sumed for H.M. of the lat- ship Duke of Wellington in 1852, before she or any vessel ter. of her class had been fitted or tried with a screw propeller and stiam power. On actual trial in 1853 the Duke of Wellington realised a speed of 9891 knots, with a displace- ment of 5829 tons, and an indicated horse-power of 1G99'2 horses. The coincidence of the actual results with the speed, as calculated by the formula, is remarkable; but many in- stances of similar correctness might be quoted. In using For correct the t()rmula, however, it must never be forgotten that the compari- vessels, though of different sizes, must be mathematically similar, in order that the results may be true, and that otherwise the results must only be looked upon as approxi- mations nearer or liarther Irom the truth, as this condition is more or less nearly fulfilled, care being taken that the propelling power in both cases is applied with equal effici- ency. It is scarcely necessary to remark, after what has been said, that the higher the coefficient or index number of any vessel is, the better is her relative performance, taking into account her size, power, and speed. It has before been shown that calculations founded on the angles of incidence at the bows of a ship to determine the exact resistances, do not correspond with the results determine, obtained by experimental researches or with practice. At- tempts are still being made to determine the exact resist- ances to ships of different forms, moving at different velo- cities, and valuable additions to our knowledge, in this respect, may yet be looked for ; but tlie subject is one Theamount which is beset with many difficulties. The state of the of friction- surface of the immersed body will always affect this ques- al resist- jiof, greatly ; and, after the utmost care, it is most diffi- ance influ- ^,^]|. ^^ ensure that two vessels brought together for rigid comparison, or that two or more results obtained from the same vessel at different periods of time, shall be equally affected in this way. The speed of a vessel has been found by observation to be reduced as much as 20 per cent, by the fotilness of the bottom. It must be observed, how- ever, that whilst this last-mentioned fact proves the extent of the influence which the friction of the water upon the surface of the vessel exercises upon her speed, it in no way invalidates the foregoing calculations, because similar ves- sels, with their surfaces in a similar state, no matter what that state may be, whilst within the limits of roughness or foulness fiiund in practice, will still have their speeds to vary as the cube roots of the powers. The following formula: were submitted to the Institution founded on of Civil Engineers in 1857, as the results of some experi- " °"" °° ments instituted by Mr Hawksley, and as the results of ex- perience up to that time on the subject : — son, ves- sels must be mathe- matically similar. Actual re- sistances per fo"t difficult to enced by state of surface. Vormulae the angles at bow and stern, and on friction of surface. " H = V3 I (jy^sm-^-xsm^ V = 2: H 144 oi(sin -— 4- sin ' -5- \ ■•■2512.1 J No. 1. No. 2. In which H was the effective horse-power, and equal about jths of the indicated horse-power, and a the area of the midship section in square feet, ^ the angle of the bow lines, (' the angle of the stern lines, and s the immersed or wetted surface of the vessel in square feet. The value of the coefficient of s had been ascertained from numerous experiments made to determine the friction of water passing through pipes, and, from the consis-tency of the results, might be regarded as practically correct for surfaces of iron. At a velocity of 15 feet per second, the resistance of water amounted to iJo ounces per foot superficial. The precise value of the coefficient of « was somewhat less cer- Forces tain, inasmuch as the theoretical and experimental results were not nctine on altogether coincident, or in perfect agr'-einent amongst themselves, ^ Rhiu in and it was therefore proposed to institute a further cour-e of ex- motion periments, which would, in due time, be laid before the Institution. ^ j In their present form, however, the equations would give a near '' ~ approximation to actual experience; for instance, when applied to the Atrato, a large steamer having upwards of 3000 indicated horse-power on board, the formula gave a speed of 15 miles per hour, while, upon the measured mile, the actual speed appeared to be 16 miles per hour. It was quite useless to attempt equations for curved forms, nor was it necessary to do so, as by dividing the im- mersed solid into four parts, by five equidistant planes taken par- allel to the load-water line, and calculating each part by three or more angles, formed by the intersection of tangents to the respec- tive curves of the bow and the stern lines, any required degree of exactitude might be obtained. In general, with regard to sharp vessels, a single calculation would be sufficient for ordinary prac- tical purposes, and especially after a little experience had been gained, in estimating the angles at the bead and stern, capable of approximating to the results of curves." It is believed, however, that the resvdts before shown as Compari- being so easily obtained by comparison with the known ™° "'■''' » perf()rmances of any known vessel, even though she raay'^f P"' not be in all respects an exact type of the pro|Hised vessel, will still be tijund in practice to be a safer guide than any calculations founded on such assumed amounts of actual resistance and friction, when it is desired to obtain the speed, or any other element of performance, to be expected from any hypothetical vessel. Another elensent affecting the correctness of the resulst Ratio of of all these calculations to determine the speed due to any '"dicated vessel, is the difference between the indicated horse-power, co-effectiva or the gross power exerted in the cyliiider of a steam-en- ""*" gine, and the net horse-power really effective in propelling „g-ects the the vessel — that is, the power left for thi s purpose after results of deducting the amount expended in the friction, and in foregoing working the parts of the engine itself. Engineers jiave '^''^"'*" not, as yet, succeeded in devising any ready and satisfactory '""'^' method by which the amount of effective horse-power in any ship may be measured separately from the gross horse- power as shown by the indicator to be exerted in the cylinder. Dynamometers have been fitted to some ships, but their action has been so irregular and anomalous that no reliance can be placed on the results obtained from them. A very beautilul instrument as a dynamoiueter f<)r this purpose was fixed in the dockyard at Woolwich, designed by Professor Collation of Geneva, and some valuable results have been obtained from it, showing a mnch greater dif- ference between the indicated and effective horse-power than thatassimied by Jlr Hawkesley in the formula by him, as pre- viously quoted. It is usual, however, to assume that the ratio between the indicated and the effective horse-power, what- ever that ratio may be, remains constant, and is the same in all cases ; and the gross indicated horse-powers are therefore taken as proportional to, and a measure of", the effective powers. In many cases this assumption is no doubt correct, but in many others its correctness may be questioned ; and the results, therefore, which are obtained with the indicated horse-power as the measure of the propelling power, must not be argued upon .as definite, or as anything more than an approximation sufficiently accurate tor most practical purposes. The form of the engines and boilers to be used in the Naval ar- propulsion of a vessel is generally left by the navd archi- chitects tect to be determined by the engineers ; but at the same ^'^^ *"• time, the amotmt of power to be placed in the vessel, the^'"*^" . - . , It . . c I i» -11 must work weight ana the positions of the centres of gravity, both ,o(,eti,g, vertically and longitudinally, of the machinery, must be duly considered and determined in concert with the naval architect. The form of the vessel at the place where the paddle-wheels or where the screw are to act, also requires special consideration on the part of the naval architect, otherwise the jiower exerted by the engine may be wasted, C2 S II IP-BUILDING. Forces as it formerly was in churninp; the water when llie paddle- acting on wlictls were boxed up in sponsuns. a Ship in motion. \^m..y^-^ Propulsion of Vessels by Sails. Resultants Tlie arrangements for the propulsion of vessels by the of lorces agency of the wind come within the province of tiie naval aciuig on a iirj.i,it,.(.t, and niucli consideration has been given to tiie ' NVhen tiie siiip is luider sail, there are two forces acting on it — the one, the force of the wind on the sails, to propel the ship ; and the other, tiie resistance ot the water to op- pose her motion. These forces, immediately the ship has acquired the velocity due to the strength of the wind, are e(|ual, and, as is the case with all forces, may cacli be reasoned on as if acting only on one point of the surface and centres over which its effect is diffused. This point is that in of effort, which, if the whole force were to be concentrated, its effect would be the same as when dispersed over the whole area: it is usual to call these concentrated forces " resultants of forces," and the points on which they are supposed to act, " centres of effort." From what has been before said, the resultant of the force of the wind on the sails, and the resultant of the force of the water on the hull, are equal ; the one acting on the on the'hu'll weather-side of the ship, in the direction into which the force of the wind resolves itself, and the other opposed to it, acting on the lee-side, in the direction into which the force of the water resolves itself. The action of the wind upon a ship will be understood from the annexed figure. Action of wind on tlie sails, and water Fig. 00. to propel Let A B be the centre line of the ship, and let D C rcpre- tt ship, sent the direction of the wind, and EF the sail. If the length of G C is taken to represent the Itirce exerted by the wind, the force upon the sail will be represented by the line L C at right angles to it, the length of L C having been found by completing the parallelogram L C M G ; the force M C being in the direction of the sail is lost. The force L C may now be resolved into the two forces L P and L Q, or Q C and P C ; the one acting to propel the vessel in the line of her keel, and the other at right angles to it. It is evident that the motion of the ship resulting from these two forces will not be in the direction L C, on account of the body of the ship, from its form, offering much less re- sistance to the force Q C than to the lateral force P C. Tlie relative degree of this resistance cannot be deter- mined by calculations,' though attempts to do so have been made. If, however, the relative resistances be supposed to be such that the motion from A towards B may be taken to be represented by C S, while the motion away from the wind or to leeward is represented by C r, then the motion of the ship will be along the diagonal C t. The course of the ship will thus be represented by the line a b, and the angle i C B is called the angle of lee-way. The direction of the wind may be more ahead of the ship than shown in the figure ; the position or trim of the sail would then be Forces altered, and its force may be resolved in the same manner acting on as before. It is evident that the more acute the angles ° '''■'l' '" B C F or B C D are made, the less will be the propelling vj])^'^ power longitudinally, and ilie greater will be the lateral ^"^ effect. The effect of the resultant of the force of the wind on to turn a the sails and of the water on the hull, is necessarily in pro- '■''il) f>e>m portion to their distances from the centre of gravity. If they ^" course, an; equally ilislant they will destroy each other, and the ship will remain at rest with respect to the line of its course ; if the resultant of the resistance of the water passes before the resultant of the wind, the sliij) will turn to the wind ; but if the resultant of the wind passes before that of the water, the effect will be the contrary, and the ship will fall off" from the wind. In either of these cases, in order that the ship may be made to keep her course, it will be necessary to equalize these forces by the action of the water on the rudder, on its lee-side to bring the re- sultant of the water more aft, and on its weather-side to destroy a part of the effect of the wind. This is the prin- ciple of the action of the wind on the sails, and of that of the water on the hull, with res])ect to the course of the ship through the water; and it is on these considerations only that the various alterations can be regulated, which it may from time to time be necessary to make in the trim either of the sails or of the ship ; and hence the accurate determination of the positions and directions of these two forces is a ])oint of great importance in naval archi- tecture. The position of the centre of effort of the wind on the sails may be found under certain reservations ; and that being known, enough is determined to lead to correct conclusions on the other circumstances attendant on the subject. The centre of effort of the wind is always placed Centre of some distance before the centre of gravity of the ship ; '^|T'"'' "'^ and in order to find this distance in any ship, the mo- "^'^" ^^^^^^ nient of each sail is calculated by multiplying its area „f „^,jyi^y by the horizontal distance of its centre of gravity from of ship, that of the ship ; the sum of the negative moments, or those abaft the centre of gravity of the ship, is then subtracted from the sum of the positive moments, or those before the centre of gravity of the ship; the remainder is then divided by the total area of the sails, and the result gives the required dis- tance of the centre of effort of the wind on the sails determines before the centre of gravity of the ship. The situation of positions of this point with respect to the length of the vessel must ""'sts. determine in a considerable degree the positions of the masts ; for experience has proved that it is among the most essentially requisite good qualities of a ship that she shall carry a weather-helm. With respect to ships carrying a weather-helm, Mr Creuze Effect and assumed that the particles of water have a motion at tjie l'""'''"" o*" stern of the vessel, the direction of which forms an acute the rudder during angle (A xy, fig. 00) with the middle line of the ship pro- gg„tj„^g,,j duced afl, which angle will evidently be dependent on the motion, fulness or the fineness of the after-part of the boily, and on the angle which the line of the ship's course, or that of the lee-way, makes with the middle line of the ship ; conse- qtiently, the inactive position of the rudder will be when it forms this angle with the middle line of the shi|), that is, when the rudder is to leeward, and, consequently, the helm a-weather. And this position should be the theoretic limit of the degree of weather-helm a ship should carry, as in any other position there must be a force acting on the rudder, which must increase the resistance the ship experiences in her passage through the water. It may perhaps tend to illustrate these views further, if it be supposed that the ship is at rest, and that tlie water 1 See article Seamansuip (Eney. Brit.), where this subject will be found treated at length. SHIP-BUILDING. 63 ■Weather- helm. Ships with lee-helm leewardly. Effect mis- taken for cause. Disadvan- tage of lee- helm. Sails as- sumed to be plane eurfaces, Strikes lier in tlie direction of her true course, A B, fig. 00, incliuiing tiie lee-way ; and then as tile anj;les of incidence and reflexion are equal, the particles of water which strike the ship at an angle varying with the angle of lee-way will be reflected off the lee-side at the same angle, and this angle will be that of the inactive position of the rudder. A practical confirmation of the correctness of the view, that the advantageous position of the rudder is a-lee of the middle line of the ship, may be drawn from the common observation, that when a ship is in good trim, the helm being a-weather, and the ship keeping her course steadily, the helm has a very perceptible trenmlous motion, which must arise from the rudder being in a position in which it is not acted upon on either side by any constant force. This method of considering the direction of the flow of the water to the rudder considerably diminishes the estimate of the excess of its effect on the lee-side of the rudder over that on the weather. But there are several other consi- derations which operate in increasing the effect of tlie weather-helm. From the direction in which the water flows past the ship, there will be a much greater reduction of pressure on the weather-side of the rudder when the helm is to windward, and therelbre a greater positive pres- sure on its lee-side to turn the ship, than will occur under the opposite circumstances, or when the helm is a-lee. Also, the broken and disturbed state of the water on the after- part of the weather-side of the ship, arising from the water having to acquire a motion to leeward to fill up the void made by the ship as she goes ahead and to leeward, and the consequent various degrees of resistance it opposes must lessen its effect when the helm is a-"iee. It has been said to be proved by [iractice, that ships which carry lee-helms cannot be vveatherly; that is, will fall faster to leeward than those which carry weather-helms. But though the fact is correct, the reason assigned is in some degree mistaking the effect for the cause. It has before been said, that a part of the force of the wind acts in driving a ship bodily to leeward ; of course its effect will be greater or less in proportion to the lateral resistance opposed to it, and the ship which opposes less lateral and greater longitudinal resistance to the water than another, will in the same period of time have fallen furthest to lee- ward, and the line of her course will have made a larger angle with her middle line, by which the effect of the water on the after-part of the lee-side is increased, while that on the fore-part, l)oth of the lee and weather sides, is diminished, and the helm must consequently be kept less a-w eatlier. A practical proof of the correctness of this rea- soning may be drawn from the (iractice of the older class of merchant vessels, which are generally, from form, more lee- wardly than men-of-war. They have their foremast placed much nearer the centre of the ship than is usual in sharper and finer formed bodies. This has evidently arisen from the operations of the cause above mentioned, which has shown that they require the resultant of the effort of the wind on the sails to be proportionately farther aft to ensure their carrying a weather-helm. There is another disadvantage arising from a ship's car- rying a lee-helm, which is, that the action of the water on the weather-side of the rudder acts in conjunction with the force of the w ind in forcing the ship bodily to leeward ; while, on the contrary, while the helm is a-weather, the action of the water on the rudder is in opposition to the force of the wind. The ardency of a ship, which is her tendency to fly to the wind, depends on the relative positions of the resultant of the effort of the wind on the sails, and the resultant of the resistance of the water on the hull. The position of the centre of effort of the wind on the sails is calculated under the su|)position that the sails are plane surfaces, and equally disposed witli regard to the lon- gitudinal axis of the ship; but when a ship is on a wind, as the force of the wind acts in a direction oblique to the Forces surface of the sails, a greater proportion of the sail is car- acting on ried to leeward of this axis, and the whole sail assumes a * ^'''P '" curved surface, the curvature of which increases from the ""''o"- weather to the lee-side. From these circumstances, the '^~V~^ centre of effort is in fact carried gradually farther aft as Effect of the action of the wind takes place on the sails. Also, as their cur- the force of the wind inclines the ship, the centre of effort ^'"""'e' of the wind on the sails is carried, by this inclination, over to the lee-side, by which, as also by the effect produced on the resultant of the water, which has been before men- tioned, the distance between them is farther increased. It therefore appears that, the quantity and dis[)osition of the sail set remaining the same, the ardency will increase asOfincreafo the force of the wind increases, and diminish as that force of wind, diminishes. The defect of a vessel carrying a lee-helm may be lessened by those means of trimming either the sails or the ship, which will tend to increase the distance of the restdtant of the water before the centre of effort of the wind. Great caution is necessary before altering the posi- tion of the masts, with a view to remedy this defect, be- cause her working quickly depends on the proportion of sail before and abaft the axis of rotation, and not on the position of the centre of effort of the whole surface of the sails. Up to the year 1852 the topsails of ships were reefed and unreefed by the seamen going aloft and out on the yards. About this period Henry D. P. Cunningham, an officer of Her Majesty's navy, invented a plan for reefing and unreefing the topsails, and other square sails of shi|)s, from the deck, without sending any one aloft. He accom- plished this by using the yards as rollers, fitting them to turn round in their different fastenings, and so rolled up and unrolled the sails upon them, employing the gravita- tion of the yards as the motive power for turning them, thus also greatly economising labour, as well as giving security to life. This new method is now in extensive use in the mercantile marine and troop ships of Her Majesty's navy, and is rapidly superseding the old. The limits of this article will not permit the subjects of masting, or rigging, or sailmaking, to be gone into ; much valuable information on the subject of the pro|)ulsion of vessels by sails will, however, he found in the article Sea- MANSUIP, in Ency. Brit., 8th Edit. Motions of a Ship under other Influences. The motion of pitching and scending is generally the most violent action to w hich a ship is subjected, and the most injurious to her structure and her velocity. It is the longitudinal motion caused by the variable support afforded to the body by the waves as the vessel meets and passes over them ; pitching being dipping of the bows into the water, and scending the dipping of the stern. To obtain ease of motion in this respect, Rlr Henwood advocated, in 3 paper piiijlished in the Papers on Naval Architecture, that the after-part of the ship, or that part abaft the centre of gravity, should be constructed so as to have precisely the same cubic contents as the fore-body, and that its centre of gravity should be at the same distance from the centre of gravity of the ship as that of the fore-body. The disposition of the weights, and especially of the masts, in- fluences this motion in a powerful degree ; because, though the weights in the fore and after bodies may balance each other while at rest — a greater w eight, perhaps at a less dis- tance, balancing a less weight at a greater distance — yet, when the ship is set in motion the balance will no longer hold, because the moments of the weights in motion will be according to the squares of their distances from the com- mon centres of gravity. If a vessel pitches heavily, the moments of the weights forw.ards are too great, and the contrary if she scends heavily abaft. An tnieasy motion in pitching is much more common than in scending, and this Pitrhing and scend- ing. Jfoments of weights are as the tquares of the dis- tances of their com- mon centres of gravity 64 SHIP-BUILDING. Forces acting on a Ship ID KoUing. Modes of correcting. Definition of raeta- ceatre no doubt arises from tlic ecncrally very forward position of the tbre-inast, especially in men-of-war. Tlie importance ol a little attention to tiiis subject on tlie part of naval men will be at once apparent, when it is consiilereil that the I fleet of moving or placing 5 tons at a distance of 120 feet from the centre of gravity of the ship is represented by the number 72.000 = 120- x 5, while it would be necessary to move 720 tons to a distance of 10 feet on theop|)osite side of the centre of gravity to produce the same effect on the pitching and scending motions of a ship. The rolling motion of a ship is caused more by the mulu- lations of the waves than by the shock oi a wave striking tlie side of a ship. The princii)les on which the rolling ol' a vessel depends liave been already investigated, and a few practical remarks will only be added here. The remark is common, and it is trtie, that the crank ship is the easy ship — that is, the more readily a vessel rolls, the easier will be her motion in rolling. Mr Wilson, late of the Admiralty Of- fice, in an able article on the Pa/)crs on Naval Architec- ture, says, " If stability is too great, the most efficacious way of dindnishing the rolling is to bring up the ballast, because it raises the centre of gravity, and it increases the distance of the centre of oscillation from the axis of rota- lion. The ballast removed from near the keelson to the wings, even if placed as high as the deck, is as far from the metacentre as when it was in the hold, and consequently, its weight nndtiplied into the s-quare of that distance is the same as before ; the rollings, therefore, will be slower." The cables, shot, stores, &c., in any shi|), if jilaced near the side, while this will not affect the stability, will increase the distance between them and the axis of rotation, and will consequently lengthen the time of vibration. Mr Wilson proceeds to say, that it is by no nn ans a difficidt task to reduce a ship of extraordinary stability, which is always an uneasy one, to a state of easy rolling by increasing the masts and yards, and increasing the weights above and put- ting them in the wings, and removing some ballast, if she has any on board. The stability and the rolling of a ship were fully treated of when considering the theory of ship-lniikiing. It was there demonstrated, that if a ship be forcibly inclined to a given position, it is necessary, in order that she may regain her upright position, that her centre of gravity be below a definite point in the vertical centre line of the transverse midship section. This point is called the metacentre-, and it was shown how its position coidd be determined, mathe- matically, for any ship. Its position may be familiarly explained by referring to the fact, that the supporting or buoyant power of the water in keeping a ship afloat is concentrated in the centre of gravity of the mass of water displaced by her body, which is hence called the "centre of buoyancy," or "centre of iumiersion," as well as the " centre oi the displacement." The buoyant power or up- wartl pressure of the water is therefore equivalent to a force acting upwards in the vertical line which passes through the centre of the dis|)laccment, with its effect concentrated on the ship wherever this line may intersect it. When a vessel is inclined, the centre of gravity of her displacement will be removed to a vertical line difierent from that which it occupied when the ship was vertical ; and looking at the ship in this inclined position, it will be evident that the keel will be forced up and the vessel upset, if her centre of gravity be so situated that the line of the upward pressure of the water comes between it and the keel. If, on the contrary, her centre of gravity be so low that this line of uuward pressure comes above it, she will evidently right herself; and the greater its lateral distance from the line of upward pressure towards the keel, the greater will be her tendency to do so, or her stability; and a measure of her stability is thus obtained. There must then be a spot for the centre of gravity of the ship between these two sup- posed positions, so situated, that when she is inclined, the Forcet line of upward pressure will pass exactly through it, and the "e'ing "n ship will have no tendency either to upset or to right her- * *'"!' '" self'. This point is calleil her metacentre, and its distance ^ "'o """.^ from, that is its height above, the centre of gravity of the ' v"^ ship is a measure of her stability. it is diliicult to determine the position of the "centre of Centre of gravity of the ship," by which is always meant the centre ofprnvity of gravity of the hull and fittings, if the ship be empty, or of "'"P """> tlio slnp and cargo combined, if she be loaded, bv any direct "i^'Br- 1 , ' - p ., ■ 1 . 1 ,1 ■ .- ' ..nnncd bv calculation of the weis;lits and (luir respective centres of , , • ..,,..{ . , culculn- giavity, but an approximation sufhciently accurate for the tjon- purposes of forming the general design ot a ship and a|)proximating to the position of the metacentre, can easily be made even for a novel design. Immediately after a vessel is launched, her stability or her want of it, is made apparent, and if any correction is re- quired, her fittings and equipment are completed in such a manner as to meet her condition in this respect, the practi- cal knowledge and experience of the builder guiding his juilgment after seeing the effect produced by weights placed on board the ship. The instances in which the by expert centre of gravity of the ship and her weights, light or loaded, mcnt nfier liave been obtained correctly, by experiment, after she has ''e'"K been completed afloat, and which have been publicly re- '*""'-''"'°- corded, are not numerous. The details of the manner in w hich it was obtained, proceeding upon the principles given in Art. 15, ])age 47, were recorded fiir two ships by Mr Crcuze in the first edition of this work; and the details for several other ships, as obtained by Mr Barnes, will be found in the volume of Transactions of the Institution of Karal Architects for 1860. Supposing the centre of gravity IlIustrnMi.r of the ship and her weights to have been found, and that ofthcefffcti it lies in the point G, fig. 7. page 44, if a piece of transpa- pruduced rent tracing-paper is taken and placed over the fiirure and . ^ '"<:'■"- the outline of tlie liody of the vessel, of the form as deline- ' atcd tlure for the sake of better illustration, F/'K L /' be traced ipo i it, also the lines FL,//, MK, and MG d' pro- duced, and a compass point or pin be now placed and held on the centre of gravity G, and the piece of tracing-paper be made to revolve on this centre till the YiweJ'l becomes horizontal and parallel to the line FL of the original figure underneath the tracing-paper, it will at once be evident to the eye that the space /oK on one side of the keel is much less than the space on the other side, oKL, and that the water displaced on the Ibrnier side is therefore greater, and the centre of gravity of the displacement must be on that side, and the ship will right herself, as it was before stated would be the case under such circumstances. From this illustration it will also be evident, that the Alteration centre of gravity of the ship will rise vertically before the '" *'■« new water-line//, due to the inclined position, will coincide '"''g''' of with the original water-line FL, and give the amount of'J*''^"f™ displacement required for the flotation of the ship ; and it^f f jhin must be remembered, in designing a ship, that such altera- when rol'l- tions of level in the centre of gravity of a ship, when she is ing. to be inclined, are to be carefully avoided, as this is the point avoided; round which the ship revolves, and her easy rolling is much affected thereby. With reference to a change of the position of the centre also when of gravity of displacement of a ship when pitching, Mr P'tchi'ig- Barnes, in his pajier on A New Method of CaLxdating the tSla/iilitj/ of a ,Shi/i, puhWfhed in the Transactions of the Institution of xiaval Architects for 1861, amongst other diductions of great value to the practical builder, says, "It is usual when making the calculations for the stability of a ship, to ascertain the positions of the centres of gravity of the wedges of immersion and emersion in a fore and aft direction, with a view to making the ship of such a form in the neighbourhood of the water-line that these centres of gravity should be situated in the same transverse plane. S H I P - B U I L D 1 N G. 65 ;hip TO- SS round centre gravity pitching [rolling, L also in Ding. )ude on rolling ibips. soley's narks on 3ude's ws. A ship of tliis form, when inclineil about a fore and aft hori- zontal axis, will make no effort to cliange tlie axis of rota- tion ; the ship will, in fact, under these conditions, roll only. If a ship be of such a form that the centres of gravity of tliese wedges are not in the same transverse plane, but the centre of gravity of the immersed wedge, for instance, be abaft that of the emerged wedge, then the centre of buoy- ancy moves aft by the inclination, and the ship has a tendency to depress the bow and elevate the stern, — th;it is, the motion will be compounded of rolling and pitching." In the same manner as a ship revolves transversely in a rolling motion, and longitudinally in a pitching motion round her centre of gravity, so will she revolve horizon- tally round the same centre by the action of the rudder, or that of any other disturbing force acting horizontally upon her body. In the paper by Mr Froude, published in the same volume of Transactions, the subject of The Rolling of Ships is treated in a very ingenious, novel, antl masterly manner, and the consideration of the synchronism of the oscillations of the waves and of vessels, or their keeping time together, is likely, in the opinion of Canon Mosely, as ex|)ressed by him, to have an important bearing hereafter upon the construction of ships, as well as to be of inestim- able value in the theory of Ship-building. In his remaiks on Mr Froude's paper, he proceeded to say, " I allude par- ticularly to the way in which the repetition of the ini])ulses exerted upon the body is made to modify the oscillations. If when a vessel first rolls, and then rolls back at the instant it has got to the extreme roll back, you apply a second impulse, you very considerably increase the amount of the succeeding oscillation ; and if you wait till the third extreme roll, and then a|)ply a third impulse, you impel her tin-ough a still further angle ; and so you may go on apply- ing such impulses at these particular periods. The effect of such accumulation of motion is displayed in the case of sus- pension bridges, some of which have been brought down by the steady marching of a body of troops, owing to the f ict of the steps of the troops synchronising with the oscillations of the bridge. The view of the subject which has been taken by Mr Froude is one that could only be taken by a person who is familiar with mathematical questions of this kind, and it shows that a great harvest of valuable results is to be reaped from the mathematical discussion of the more pro- found problems of ship-building science. Whether the action of water upon a ship is like the action of water upon a little float, is, I think, a qtiestion which admits of consi- derable doubt. The relation there may be between the motion of a great ship in reference to the waves which rock it, and that of the little float mentioned by Mr Froude, is a subject to which I would direct the attention of those who are interested in these matters. There is this to be borne in mind, in discussing the question of the stability of a sliip as dependent upon the position of the centre of gravity of the ship, we must remember that the rolling depends partly upon the centre of gravity of immersion. We may nieasiu'e the work required to incline a shi[) from the up- right position down upon her side by the wind or the waves. This work may be measured by calculating the number of pounds lifted one foot high which would be requisite to lift the whole ship bodily up through a space equal to the dif- ference between the heights through whicli the centre of gravity of immersion and the centre of gravity of the ship itself, would respectively rise during the inclination. Take the difference between tlie elevations of the two centres, then the work required to lift the ship through a height equal to that is the work that must be done upon the side of the ship to bring her over to the proper angle, — that is, going upon the supposition that the ship is in still water, and that the water remains still when she has been deflected and is left to return. Tlie great merit of this investigation is, that it takes into account the influences of the fluid in which the vessel is floating. But this is to be borne in mind, that the expression of the time of oscillation has reference to the slabiliti/ of the ship as well as to this ivork. To what extent these two elements separately influence the motion of the ship, remains for further discussion. I would add, that the influence of the motion communicated to the fluid in the act of rolling was perfectly ap[>arent in the experi- ments made at Portsmouth by Mr Fincham. Experiments Were made with models of circular sections and triangular sections. With the circidar, the body moved the water round it but very little, and in that respect theory agreed with experiment ; but wlien we took up the triangular model, then the water was displaced by the triangle of im- mersion, and there was great discrepancy between the actual results of experiments and the results of theory." As deductions drawn by Mr Froude, we may quote the following paragraphs from his paper, referring the reader to the paper itself, if he wishes to follow up the subject. " We' see, then, that though the effect of stability of any given ship depends primarily on her mass, and the position of her metacentre and her centre of gravity, the rate at which she will acquire or lose velocity under given circumstances of inclination and angular velocity, and the position she will assume at any |)criod, may be wholly expressed in terms of her Aperiodic time.' " In making this statement I do not forget that the oscil- lations of a ship are performed in a resisting medium, and that the scale of resistance is so high that when a ship of whatever form has been set rolling in still water, the range of each successive oscillation becomes sensibly less than that of its predecessor." " In proceeding from the case of the ship oscillating in still water to that of a ship oscillating in undulating water, it is necessary to remind the reader that it has been shown thai the momentary effort of the ship is to place her masts at right angles to the surface of the wave where she floats ; and for a given ship occupying at any mo- ment an angle of inclination differing from this, the measure of the effort is the same as that by which she would en- deavour to assume a vertical position if occupying for the moment in still water an inclined one, with an angle equal to that difference." He also ^tates, " that, on the whole, ir appears there are no circumstances under which material advantage can be practically gained by quickening the period of a ship, while there are many under which very material advantage can be gained by rendering it slow. Also that the surest and readiest method of giving a ship a long periodic time is by lessening her stability under can- vas. The effort of stability is the lever by which a wave forces a ship into motion ; if a ship were destitute of this stability, no wave that the ocean produces would serve to put her in motion." "But though, of course," Mr Froude proceeds, "some such stability is essential, I believe that most large ships possess it in excess, e.g., slow as is the period of The Great Eastern, I believe she could with much advantage part with a considerable portion of her stability. Let us see how the account stanils : When she is loaded to about 22,000 tons, her metacentre is about 8'7 feet above her centre of gravity, so that when she is forcibly inclined at an angle of 10° from her position of rest, the effort of sta- bilitvmay be expressed by 22,000 tons x S'T x 10° = 22,00.) X 1-52 = 33,400 X 1 = 334 x 100 ; that is to say, if a spar were rig^fed out from her side till its end was 100 feet from her centre line, 334 tons suspended on it would only incline her 10'. Now, with the ' Duke of Wellington ' {Z-dechtr first-rate line-of-battlc screw ship), only 50 tons suspended Forces acting on a Ship in motion. Ded'jctions from Froude's views. 1 Pn-c 102. G6 SIIIP-BUILDING. Forcei octing on B Ship in motion. Motion as influenceJ by general dimensions or form. Length. on sucli a lever would create the same inclination. Or if tlic nieiisiire be ba«cil on tlie ship's own dinunsions, tlie Great Eastern would carry 800 tons at the extreme width of her own beam wiili an inclination of 10°, while the Duke of Wellington will carry only 170 tons similarly placed with the same inclinaticm. Yet the masts and spars of the Great Kastern are in effect scarcely double those of the Duke of Wellington ; ami the contrast will be intensi- fied, and its bad results increased, by every step taken in the reduction of top hamper, which a mistaken policy or theory may suggest. 15ut exclusive of masts and spars, on which, when bare, the i ffect of the wind is trivial (the strongest head w ind, when the sea is smooth, scarcely taking 5 per cent, off lier speed), the effect of a very strong wind on her lol'ty sidi.- ought to be taken account of. If she has stability enough to bear the stress of a hurricane (broadside on), on this, with a moderate inclination, no more need be required of her. Her side may be taken as 35 x 700, and if we put 100 ll>. per foot as the force of a hurricane, the total pressure will be about 1100 tons ; and as the centre of effort for this force is about 30 feet above the centre of lateral resistance, the whole force may be considered as delivered at a leverage of 30 feet ; and this, according to the scale of stability just given, would incline her only 987°. Or if the ship were robbed of half her stability, were that possible, by stowing her cargo high, she would still bear the force of the hurri- cane on her broadside with an inclination of only 19"7 l'. But were her stability thus reduced, her period would be enlarged in the ratio of V 2 : 1, and would be 8'5" instead of 6''; and we have no reason to believe th it waves of such period are ever formed." " The neces-ity of attending to the question of periodic time in reference to wave action is of far greater importance to large ships than to smaller ones, partly because in such ships the disuse of an external keel becomes almost a necessity, and although bilge pieces may be succe.ssfully substituted tor a keel as a means of enhancing resistance to rolling motion, and thus limiting the accumulation of angle, their application, if on a scale suffi- cient for the purpose, involves structural difficulty and |>ractical inconvenience ; so (hat thus such ships are the more capable of the development of cumulative rolling motion, and partly because the larger the ship the greater is, caleris paribus, the stress called into play by motions she impresses on the weights she carries." Fincham, in his History of Sliip-Building, gives a re- markable instance of tlie extent to which the qualities of a ship may be influenced by other circumstances than htr form. " The Mutine, an experimental brig, built to coiii- pc'e with others, was beaten on the first experimental cruise, but she afterwards beat the others, alterations hav- ing been made in the trim of her sails and in her stowage. Alter the alterations, instead of rolling the shot out of the raiks and the wind out of the sails, as before, she rolled little, and neither deep nor quick. At first her weights were carried too low down." 'Jhe motions of a vessel are much affected by the pro- portions which the general dimensions bear to each other. .\n increase of length gives an increase of displacement, or if this is not desired, it allows of finer lines forward and aft, and it also increases the stability and the resistance to lee- way. The power of turning, tacking, wearing, or making any other change in her course, is lessened by an increase of length ; but this effect may be much modified by dimi- nishing the amount of forefoot, or of dead-wood forward, which will alter the position of the resultant of the action of the waier, and wili consequently also require a corespond- ing alteration in the aniomit or position of the forward and aft sails ; and as all weights are multiplied by the squares of their distances from the centre of gravity of the ship lor their moments, the effects of weights forward and aft become much greater in long ships. The friction ujon the sides of a vessel upon any addi- tional len'jih of parallel body amitlship". .tnpenrs tn be very Poroes trifling, if we may judge from the results of ca-es " iiere a<^^'nK on vessels have been cut in midships, and lengthened, Hitlumt * ^'".1' '" any other alteration in their form having been made. The v""* ' ""', following is a statement of the results obtained by lengthen- "" ^ ing the Canada, a vessel belonging to the Peninsular and Oriental Company, by putting 35 feet into her amidships :— l^raft forward „ aft „ mean Area midship section.. Displacement Noniinal horse-power.. Indicated horse-power, Itevolutions I*ressure Vacuum Speed I'itch of screw Diameter of ditto Blades Trial First trial Second trial before being after being after lieinir 1oni;tbene<l, lenptlicneH, lenc b" neH, .May 31, 1S.VV Aug. s, 1807. Aug. 1:', |H.',7. 18 ft. 6 in. 18 ft. 2 in. 18 ft. 2 J in 18 ft. 6 in. 19 ft. 5 in. 19 ft. 7 in. 18 ft. 6 in. 18 ft. 9i in. 18 ft. 11 in 536 feet. 551 feet. 556 feet 2,435 tons 3,036 tons 3.069 tons 450 450 450 1,415 1,250 about 1,400 34i to 37 31 33 22 1b. 16 1b, 20 1b. 26} 26 26i 12.651 11.675 12.443 20 feet 21ft. 21 feet 15 ft. 6 in. 15 ft. 6 in. 15 ft. 6 in. 3 3 3 By increasing the breadth aniieiships, as well as the Breadth. average breadth throughout the whole length of the vessel, while the length and depth are kept the same as before, the stability, which varies as the cube of the breadth, is increased. As the angular momenta of the weights, esti- Effect mated from the axis of rotation, vary as the squares of their '''ereof on distances from that axis, and the momentum of the action!.,'."'"'. ,. . . II ■ \ 1' bility of a of a wave is increased in the same proportion, tlierefore jhip the increase of stability is accomjianied by increased vio- lence in the motions, and consequent increased strain l on the combinations and materials of the structure, and 1 thereby danger to the masts, by which the safety of the vessel may be compromi>ed. The stability of a ship of war, being the quality on which the efficiency of her arma- ment is essentially dependent, and which also, by enabling her to carry a press of sail in circumstances of danger, as on a lee-shore, or before a superior enemy, requires special attention ; the only limit to its increase is involved in the consideration of easiness of motion. But if this considera- tion be neglected, and the breadth be such that the moment of stal)ility in proportion to the moment of sail is so large, or of such sudden increase, that the masts are endangered or the combinations of the structure prematurely destroyed, the object for which a large moment of stability was desir- able is frustrated. The breadth, therefore, is limited by easiness of motion. The best mode of ensuring stability is to give a large area and great fulness and similarity of form immediately above and below the average water-line, as by this means the centre of gravity of the displacement will be kept ai as short a distance as j)ossible below the surface of the water, that is as high as possible. The depth of a ship, or her draught of water, may vary Depth, according to local circumstances, or the objects for which she is to be employed, or by a judicious arrangement of her other proportions and of her form, and the positions of the centre of gravity. Good ships may be produced varying con- siderably in the proportions of their depth to their breadth. An important consideration connected with the forming Alteration the design of a ship is involved in the gradual alteration of of seat in tiie vessel's seat in the water from the consumption of***" '^""' stores. It is not only essential that a ship should be pos- ^"gj 'J,^'*' sessed of stability combined with easiness of motion, be stores, weatherly and quick in manoeuvring when she is stored and completed for foreign service as a ship of war, or fully laden as a merchant-ship, but it is equally essential that she should be possessed of these qualities towards the ex|)ira- tion of her cruise, or on her return light from her voyage. The loss of stability which results from the diminution of S II IP-BUILDING. 67 'esigning if Vessels. msing iminutiOD f stabi- ty, and icreased □easiness. liffprence r draught f water. dvan- .ges of peater naught of ater at le stern. )esigning f vessels. ciraiijlit of wntcr cannot be compensated by a proportion- ate arrangement ot'#ail, without inc\irring otlier evil conse- quences. If tile quantity of sail, which at all times is com- paratively small in a merchant-ship, be lessened, the wind on the increased hull might so counterbalance its eft'tct that she would be utterly unable to beat oS' a lee-shore, or make any way on a wind. A ship is not only subject to a loss in stability when lightened, but becomes laboursome, on account of top- hamper: her rolling motion is more violent as her dimi- nished depth in the water decreases the resistance which is opposed to the inclination, and she also generally becomes more leewardly, owing to the difference made in the result- ant of the resistance, the diminution of the lateral resistance, and of her power of carrying sail. It is almost a universal custom in all vessels to give a greater draught of water abaft than forward. In steam- vessels this is not necessar\% and in sailing-vessels occa- sional attempts have been made to discontinue this [)rac- tice, as involving a supposed unnecessary increase in the water required for floating a ship ; but the increased draught of water tor the after-body has been reverted to as essen- tially requisite in practice, in this class of vessels. There are several minor advantages which result from this arrangement ; such as the more easy and unchecked flow of the water to the rudder, and its consequent increased effect in governing the motions of the ship ; also the dimi- nution of the negative resistance which the vessel would otherwise experience from the greater difficulty with which the flow of water would fill the vacuity caused by the pas- sage of the vessel, if the fulness of the after-body were such as would be required to preserve an even draught of water ; and again, the adjustment of the resultant of the resistance of the water to that position of the masts which experience has determined to be requisite for the facility of manoeuvring the sails. But the principal reason for the inequality in the draught of water appears to be the advantage which results from it to the more easy regula- tion of the motion of the vessel by an adjustment of the resultant of the resistance of the water on the lee-side when on a wind. DESIGNING OF VESSELS. The considerations which lead to a settlement of the general dimensions of a vessel, and which must vary greatly according to the purpose for which she is intended, having been touched upon, it is proposed to give an outline of the course pursued in designing the form, or making the co7i- strtictive drawing, as it is termed, of any vessel. Three plans are required in all designs of vessels — the body-plan, the sheer-plan, and the half-breadth plan (see Plate III.) The form of the midship section, or a vertical cross-section at the point of greatest breadth, is generally the first por- tion of a ship that is designed ; the outline of the sheer- plan may then be delineated, and after that the half-breadth plan may be begun. The vessel is supposed to be divided into a certain number of horizontal sections, and these are represented by the lines on the sheer-plan, marked 1st, 2d, 3il, 4th, and 5th water-line. The sheer-plan is either a Vertical longitudinal section, or a side-plan of the ship, and on it may be delineated any point in her length or height. On the half-breadth plan are delineated the outlines of the horizontal sections previously referred to, and marked water-lines. These horizontal sections may either be pa- rallel to the keel or to the intendeil water-line of the vessel, if she is intended to draw more water abaft than forward. When parallel with the keel, they are sometimes called level-lines. The midship section is not necessarily in the middle of the length ; it is called dead-flat, and is always marked as shown on the plate. The length of the vessel is divided into any desired number of sections, and these sec- tions are marked forward and aft from dead-flat w itii dis- tinguishing letters and figures. The water-lines being also ncsipning draw n upon the midship section or body-plan, the form of ot Vessels, the body at each section in the half-breadth jilan is ob- '*'"^~v^^ tained by finding the distance from the centre-line at each water-line, and transferring it to the body-plan, showing the sections of the fore-body and of the after-body on dii- ferent sides of the middle line. In addition to these lines, the vessel is supposed to be cut into various longitudinal sections, at given distances from the centre-line; these lines of section are shown on the half-breadth and body- plans ; and the form of the body where these cut the exte- rior surface of the ship are shown on the sheer-plan ; they are marked Iv, 2v, 3v, on all the plans. The sections represented on all these plans must be fair and of easy cur- vature, and many little alterations will probably require to be made by the draughtsman, to get them to coincide. The constructor or designer is now in a position to test his work by making the necessary calculations. These will be comprised in ascertaining the area of the midship section, the area of the load-water section, the displace- ment, the positions of the centres of gravity of these two sections, and also the position of the centre of gravity of the displacement. The areas of the two sections, and the positions of their respective centres of gravity, are required to be determined, on account of the influence of these areas and their posi- tions on the content of the displacement, and the position of its centre of gravity, and also in consequence of their influence on the stability of the ship. If the results of these calculations do not accord with the intentions of the con- structor, or are inadequate to the development of his design, he must make such alterations in his curves or in his dimen- sions as he may consider necessary, before proceeding fur- ther with his design ; and if he shall have sufficiently informed himself on the theory of ships, he will be enabled to do so with considerable confidence at this stage of his progress, as to the final result of his work. These calculations are no doubt laborious, but they have been previously explained, and there is no difficulty in them, and any moderately educated assistant may soon be taught the readiest method of working them out The labour will be greatly facilitated by tabular forms, and further examples will be found in Mr Peake's work on Ship-building, and in one of a series of articles on Ship- building in the London Mechanics' Magazine for 1859. Before the design can be considered complete, it is ne- cessary to ascertain the w eight of the hull and of the whole of the proposed contents of the ship, and compare these with the calculated displacement. It is seldom that these weights can be obtained with perfect accuracy, and it is therefore scarcely necessary in practice to go to any undue labour to bring out results to fractions. It is usual to delineate the results of the calculations of Scsleof the displacement in the form shown in Plate IV'., — the displace- curved line representing the displacement of the ship at ment. any draught. As a guide in commencing a design, it is also usual, and very useful, to know what proportion the -1°^^ '"" circumscribing parallelopipedon will bear to the body of gpribing the shi[) — that is, to multiply the intended length, breadth, parallelo- and draught of water of the ship together, and deduct such pipedon. portion as will leave a body of the desired fineness. The amount to be deducted, or the decimal fraction by which the parallelopipedon is to be multiplied, varies, of course, for every class of ship. The form of the midship section, and of the other sections Influence near it and therefore influenced by it, affects the question °^ '^""■"' *^' of rolling, by affecting the position of the centres of gravity of the displacement and of the ship and her weights; but there is no doubt but that if it were possible to keep these centres of gravity relatively in the same position with dif- ferent forms of bodies, the rapidity and extent of rolling would still be influenced by the form, and be diflerent. rolling. 68 SHIP-BUILDING. Form and Tonnage of Vessels. Forms of water- lines. Vertical lines. Tonnage. BuilJer's measure- ment. No niles can be laid down definitely on tliis subject; but ships with a form of niidsiiip section a|)proacliin!j a semi- circle liave a bad reputation for roliin;; ; as also those with a very rising floor, if accompanied with i;reat beam, or such beam that the half-breadth exceeds the draught of water by more than 1 or 2 feet. A flat floor is also injurious, as tending to keep the centre of gravity of the displacement too low. Some good midship-sections of ships of various classes will be I'ound in Fincham's Oulliius of Ship-builil- iiig ; but the great length now given to the fore and alter bodies of sliijis renders the etfeet of the Ibrm of the mid- ship-section nnich less influential on the general properties of a vessel than formerly, when the pro|)ortion of length to breadth wxs so much less. For the water-lines of vessels no definite instructions have been attempted to be laid down that have been of ai".y practical \alMC. A few general remarks maybe made, to the effect that certain degrees of sharpness seem suited for ditterent degrees of speed — the f;ister the vessel the finer are the lines required ; and if a moderate amount of power only be applied to a vessel, so that her speed cannot be great, it will be of little avail to give her finer lines than those suited to her actual speed. Hollow-water lines below the surface of the water seem to be beneficial for high velo- cities, but not at the water-line or above it, as the waves seem then to dash into the hollow and obstruct the vessel's way, by their being confined and not passing freely away. In all the plates given with this article, vertical lines are shown. The Ibrm of vessels, in respect of the sections shown by these lines, would appear to have been too much neglected by naval architects. It is considered that the form of vessels at the bows or at the stern may be looked upon as made up of lines representing a wedge with its face vertical, and dividing the water sideways, combined with other lines re- presenting an inclined plane, as in the Thames barges. Bodiesof a wedge form were experimented upon by Colonel Beaufoy, as also others, w ith an inclined plane forward and aft to compare with them, and the results were decidedly in favour of the inclined plane ; the inclined plane in the after- body having been proved decidedly superior.' The bodies which gave these results were those designated m, b, m, and p, b,p, and the experiments were conducted at the surface, and not with the bodies totally submerged. The tonnage of a shi|) is her assumed capacity for carrying cargo of any description. The capacity of space required for a ton of iron being very different from that required for a ton of light goods, a certain number of cubic feet are necessarily taken as the measure of a vessel's tonnage. An empirical rule, founded ujion obsolete ])roportions of a ves- sel's dimensions, continued in use for many years, serving as a measurement, not only of builder's tonnage, but also of the register tonnage for regulating the dues payable by the ship. This rule is still continued by builders as the measure by which ships are bought and sold ; but as the price per ton may be varied in the same proportion as the dimensions, and are known at the time of purchase or sale, no evil re- sults arise from this adherence to the old rule, however far the measurement may be from the truth. This rule for old or builder's measurement was estab- lished by act of Parliament in the reign of Geo. III. It enacted, that " the length shall be taken in a straight line along the rabbet of the keel of the ship, from the back of the main stern-post to a perpendicular line from the fore-parts of the main-stem under the bowsprit. The breadth also shall be taken from the outside of the outside plank, in the broadest part of the ship, either above or below the main wales, exclusive of all manner of doubling planks that may be wrought upon the sides of the ship." If the ship be afloat, the directions are, " to drop a plumb-line over the stern of the ship, and measure the distance between such line and the after part of the stern-post, at the load water-mark ; then Tonnage measure from the top of the said plumb-line, in a parallel »•"! Uc- direction with the water, to a perpendicular point imme- '<='"'l'''<"' <>< diately over the load water-mark at the lijre-part of the \ ' i main-stem ; subtracting from such admeasurement the ^ ^ above distance, the remainder will be the ship's extreme length, from which is to be deducted .3 inches for every foot of the load draft of water for the rake abaft ; from the length, taken in either of the ways above mentioned, sub- tract f ths of the breadth taken as above, the remainder is esteemed the just length of the keel to find the tonnage; then multi|)ly this length by the breadth, and that |)roduct by half the breadth, and, dividing by 94, the quotient is deemed the true contents of the lading." The existing act for ascertaining the tonnage is a great Existing improvement upon the above, and its directions are as fbl-rule for low: — Divide the length of the upper- deck, between the "*""'"''* after-part of the stem and the foremost part of the stern- "1°" post, into six equal parts. Depth, — at the foremost, middle, and aftermost of these points of division, mea^mc in feet, and decimal parts of a foot, the depths from the under-side of the upper-deck to the ceiling at the limber-strakc. In case of a break in the upper-deck, the depths are to be measured from a line stretched in a continuation of the deck. Breadths, — divide each of these three depths into five equal parts, and measure the inside breadths at the following points ; viz., at Jtli and at f tlis from the upper- deck of the foremost and aftermost depths, and at fihs and Jths from the upper-deck of the midshi|) depth. Length, — at half the midship depth, measure the length of the vessel from the after-part of the stem to the foremost part of the stern-post ; then to twice the midship depth add the fore- most and aftermost depths for the sum of the depth ; add together the upper and lower breadths at the foremost division, three times the upper breadths and the lower breadth at the midship division, and the upper and twice the lower breadth at the after-division, lor the sum of breadths ; then multiply the sum of breadths by the sum of the depths, and this product by the length, and divide the final product by 3500, which will give the nimiber of tons for register. If the vessel have a poop, or half-deck, or a break in the upper-deck, measure the inside mean length, breadth, and height of such part thereof as may be included within the bulkhead. Multiply these three mea- surements together, and dividing the product by 92"4, the quotient will be the number of tons to be added to the result as above found. In order to ascertain the tonnage of open vessels, the depths are to be measured from the upper edge of the upper strake. In vessels propelled by steam, the ton- nage due to the cubical contents of the engine-room is to bt dctlucted from the gross tonnage thus found. It is enacted that the tonnage due to the cubical contents of the engine- room shall be determined in the following manner : that is to say, measure the inside length of the engine-room in feet, and decimal parts of a foot, from the foremost to the after- most bulkhead, then multiply the said length by the depth of the ship or vessel at the midship division aforesaid, and the product by the inside breadth at the same division, at two- fifths of the depth from the deck, taken as aforesaid, and divide the last product by 92-4, and the quotient will be deemed the tonnage due to the cubical contents of the engine-room. DESCUIPTION OF PLATES. Among the plates will bo found vessels of the highest character of the present ilay. The Pera of thf I'l ninsular and (Jrient:il Com- piny's fleet is a well-known vessel, undone whose results are looked u[ion as of the highest character; and if the form of her body, as shown by the vertical lines on the sheer plan, be examined and compared with those of any of the other vessels, it will be seen that she excels in this particular. The kindness of the different owners and builders in permitting the lines of their different vessels to be * Ceaufoy's Nautical and Hydraulic Experiments, lutroductiun, p. 43. S H I r-B U I L D I N G. 69 Description of I'lates and Perfor- mances. Sohomberg, Plate III. Lord of the Lsles, Plate IV. Plates V ind VI. published, has been great ; and it is to be hoped that so much public spirit as is now manifested in this respect may be rewarded by still further improvements upon the forms of vessels. The dipper sailing-ship Schomberg, represented in Plate III., is a specimen of a first-class Aberdeen clipper, built by Jlessrs Hall of Aberdeen. The Lord of the Isles is a very fine iron vessel, built by Jlessrs Jn. Scott and Company of Cartsdyke, near Greenock. Although a sharp ship, she carries a good cargo of weight and measurement goods combined. On her first voyage from Clyde to Sydney she had 1300 tons of weight and measurement cargo on board, and made the passage in 70 days — a passage which, it is believed, has not yet been surpassed. Her register tonnage is 691-i^;,'i; tons; and her tonnage, by builders' measurement, is 770 tons. She also made a passage from Shanghae to London in 87 days, with 1030 tons of ti^a on board. On one voyage she averaged 320 mutical miles for five consecutive days; and on her last voyage to China, in crossing the ^.E. trades, her average way was over 12 knots. Yachts Plates V*. and VI. represent the rival yachts Titania (row Titania and Themis) and America, the prize having been carried off from all America England by the latter. The sections of the vertical lines are shown upon the drawings of both of these yachts ; and if the vertici.1 lines on the sheer-plan of the one are traced and laid upon those of the other, a marked difference in favour of the America will be appa- rent. The original Titania which ran against the America was subsequently burnt; but being of iron her hull was saved, and was restored under the name of Themis. A new Titania of larger dimensions was then built (Plate V.); and a marked improvement in her lines as a whole is evident, though the America still excels her in the easy slope of the lines of the vertical sections at the bow and at the stern. Delta, Plate Plate VII. is a representation of a paddle-steamer, the Delta. V'U, The engines in this vessel were taken out of a vessel of 500 tons, and put into the Delta, of nearly four times this tonnage, and the result is a specimen of what may be achieved by fine lin^ s with a judicious application of po« er ; the larger vessel having nearly a knot more speed. Great East- Plates VIII. and IX. represent the Great Eastern. Her success 5rn, Plates theoretically as a specimen of naval architecture has now been VIII. and fully established. Plate X. is a representation of the Bremen, a vessel whnsa per- formances have been such as to attract special attention, and to lead the Committee appointed by the British Association for the Advancement of Science to make the following report concerning her : — " This Committee are assured, on authority which they believe to be unquestionable, that a certain vessel, the Bremen,^ of 3440 tons displacement at the time of trial, propelled by engines work- ing up to 1624 indicated horse-power, attained the speed of 1315 nautical miles per hour. Now, if we estimate the dynamic duty V^ Dl thus performed by the formula-^ — ; = C, we shall hav the "^ Ind. H.P. ' (1315)3 X (3440^1 2274 x 227 83 1624 1624 = 319, and this co-efficient of dynamic duty, resulting from the mutual relation of displacement, speed, and power, appears, from the statements which have been communicated to this Committee, nearly 50 per cent, higher than that realised by the average performance of the steamships of the present day. The following are the co-efficients of dynamic duty deduced by the foregoing rule from the perform- ances of mercantile steamers of high repute, of which the trial data have been communicated to this committee, viz. 325, 294, 291, 28S, 259, 248, 231, 230, and 204, and many others below 200. " This Committee, therefore, regard the Bremen as being a feli- citous eiemplification of naval architecture as respects type of form adapted for easy propulsion ; and as we conceive that the promulgation of some of the constructive elements of this vessel may be of public importance, we are happy in being authorised and enabled, by Messrs Caird and Company, of Greenock, the con- structors of the ship and of the cngines,'to communicate to the British Association the following statistical data as to the elements of construction of the Bremen : — Length between perpendiculars of stem and rud- 1 derpost / 318 feet. Breadth of beam 40 [X [iremen, Plate X. co-efficient, C : Depth of hold Mean draught of water at the time of trial Displacement (D) at trial draught Area of maximum immersed section (A) at the trial draught Distance of maximum section (A) measuring from the stem Constructors' load draught | ^^j"""^"" Displacement at constructors' load draught Uate of ships' displacement at constructors' load draught 26 feet. 18 ft. 6 in. 3440 tuns. I 606 sq. ft. 1 159 feet. 18 feet. 19 „ 3440 tons. I 25 tons per I inch. o o tczi C > Area of immersed vertical section at the \ distance of J length measuring from I 256'5 sq. ft, stem j Do. i do. do. 486 „ Do. i do. do. 606 „ Do. J do. do. 489 „ Do. } do. do. 253-5 „ Displacement at draught of i' TJ", being ] J load draught J Displacement at draught of 9' 3", being J 1 load draught J Displacement at draught of 13' lOJ", being ] f load draught Displacement at draught of 18' 6", or load 1 draught J 300 tons. 1165 „ ooift — -iv ,f 3440 „ " The foregoing data afford all the particulars required for the construction of Peake's curve of vertical sections, whence may be deduced the position of the vertical line passing through the centre of gravity o<' displacement, and also the positions of the centre of gravity of the fore and aft bodies respectively. " It will be observed, from the foregoing data of the construc- tive elements of the Bremen, that the maximum immersed section is at the middle of the length, and that the vertical sections are in such ratio to eaoh other, with reference to their respective posi- tions, that the curve of vertical sections will be a close approxi- mation to a parabola. " The ratios deducible from the foregoing particulars of con- structive data, combining Peake's curve of immersed vertical sec- tions with the curve of displacement, will give a close approxima- tion to the type of form of the immersed huU. " The engines of the Bremen consist of two direct-acting inverted cylinders, 90 inches diameter and 3 feet 6 inches stroke, fitted with expansion-valves capable of working expansively to a high degree. All parts of the engines are felted and lagged with wood wherever practicable, the lower 16 feet of the funnel being surrounded by a casing forming a superheating chamber, the steam entering at the lower end, and passing off at the top into the steam-pipes leading to the cylinders. " On the important question as to the extent to which the ordi- nary smooth-water trial of a steamer affords a criterion of the general average performance that may be expected of the vessel at sea, this committee has not been able to obtain such an extent of returns of the comparative smooth -water trials and sea perform- ances of the same ships as enable them fully to respond to this part of the inquiry, and they refrain from expressing any speculative opinion, because they have adopted the principle which they desire to recummend to the notice of the British Association, that shipping improvement is to be discovered by statistical record and analysis of the constructive elements of ships that have practically shown themselves to possess good sea properties, rather than by assuming the mere theories of opinionative speculation, from whatever source such opinions may emanate; in short, that experience of actual performances at sea, statistically recorded and utilized by being made the basis of comparison, is the most reliable base on which to construct an inductive system of progressive improvement in naval architecture and marine-engine construction. This commit- tee, however, have much satisfaction in being enabled to commence this inquiry by recording the sea performance of the before-men- tioned vessel Bremen, on a passage from Bremen Haven to New York and back, during the months of June and July last, during the whole of which passages indicator-cards were frequently taken, and the indicated working power of the engines ascertained. On the out-passage the mean displacement was 2878 tons, the mean indicated horse-power was 1078, and the mean speed 10 28 knots per hour, giving a coefficient by the formula referred to^ 204 ; but on the return-passage the mean displacement was 2990, the 1 The Bremen is referred to as being the vessel which gave the highest co-efficient of dynamic performance of any vessel which was Drought before the Committee, and of which the statistical data of construction were also given in a complete form. Sn IP-BUILDING. moan imlicatod horse-powor 1010 nnd the mean spoed at tlio riito of 11'92 knots por hour, jjivinij a co-efiicicnt= 348. Honce. the m.^Hii co-rfficient of the out and home pa^pape ^ '27G, beinj; about 13 ppr Cfnt. below the co-efficient (;U9) dbtnined on the Rmooth- water test-triiil of the ship. The state of the weather and the sea WHS also recorded daily ; it appears to have been adverse on the out passage, but favourable on the home passage. The committee are therefore of opinion, that by following up this course of sta- tistical record of the smooth-water trial and subsequent sea per- formances of ships respectively, a tabular statement might be com- piled, showing the probable ratios of the coefficients of smooth- water and sea performance, corresponding to the various rat* s of speed for which steamers may be respectively powered, whence the smooth- water test-trials of ships may be made available as approxi- mately indicative of the sea service capabilities of ships as respects their dynamic properties. *' Such are the statistical data of the constructive elements and dynamic capabilities of the Bremen ; and if all steam- vessels engaged in the mercantile transport service of Itritain were equally effec- tive as respects the mutual relations of displacement, speed, and power ; that is, capable of producing a coefficient of dynamic cnpa- Lility = 319, by the formula referred to, it is probable thut the prime cost expenses of steamship transport per ton weight of cargo conveyed on lc)ng passages would, on the aggregate of the foreign trade of Britain, be reduced not less than 25 per cent, as compared with the prim© cost expenses incurred by Btcam-vcsscls of the average dynamic capability in present use." 'I'abulatcd restilts of tlie pcrfoniianccs of many vessels will l)L" f'uiind in tlie article Stkam Navigation; but the Collowing results of the trials in smooth water of four of the vessels, whose lines and dimensions are given in the plates, may be (piotctl here: — Name of ship. Draui.'ht of water. Indicated Speoil Id Delta ft. in. 15 18 6 18 3^ 17 3 1612 2054 1373 1422 14-609 13-340 12-633 12149 Ceylon Pera Nubia PlatesXI., XII., XIII., and XIV. are specimens of very IVra, I'lnte fine vessels in the fleet of tlie Peiiinsiilaiaiul Oriental Com- ^l. pany. The Pera is especially celehrateii tor iier perlorin- ances, as also the Ceylon. Tlie f'ollowinf; table is interest- ing as showing the performances of tlie Nubia on lieractnal voyages at sea: — S.S. KtWA.—Ciilriida to Suez. Voyage. Under Weigh. Under Steam. Aver. "ipeed. Coal Consump tion. 1 Sandheads to Madras. COi Miles. Madras to I'oint de Gallc, 643 Mile.'. Point de Gallo to Aden, •21M Miles. Aden (o Suez, 1308 .Miles. Sandheads to .Slier., 4(U0 .Miles. Calcutta to Suez, 4757 .Miles. Sandheads to Suez. Calcatta to Suez por Time. Speed. Time. Speed. Time. Speed. Time. Speed. Voyatre. Hour. Mile. No. 4 5 6 7 8 9 u. u. 52 25 66 65 67 5 54 55 56 59 40 K. F. 12 5 9 7 9 7 12 11 7 U 1 B. H. 43 8 52 30 56 5 46 30 42 20 57 K. P. 12 5 10 3 9 6 11 6 12 7 9 4 R. u. 178 55 201 27 244 55 193 48 166 28 176 60 K. r. 11 7 10 5 8 6 11 12 6 12 1 u. H. 114 20 112 45 124 30 118 113 58 124 40 E. F. 11 4 11 5 10 4 11 1 11 4 10 4 n. M. 388 48 433 37 492 35 413 13 378 43 418 10 II. u. 431 464 530 474 411 441 K. 12 10 9 11 12 U F. 6 4 2 2 1 Tons. 974 1140 1194 1058 1046 1090 c. qr. lb. 45 22 49 15 45 6 44 2 16 50 3 17 49 1 23 o.qr. lb. 4 11 4 3 5 5 2 4 1 22 4 1 16 4 2 9 Under weigh, 27,900 miles ' Under steara, 28,542 *. les . Total 2525 6 420 61 2751 458 30 11 6502 10831 47 1 2 4 2 6 Suez to Calcutta. Point do Calle to Madras, 515 .Miles. Madras to Sandheads, 6C3 Miles. Under Weigh. Under Steam. Aver. Speed. Coal Consumption. 1 Voyage. Snez to Aden, 130S Milos. Aden to Point de (ialle, il3t Miles. Siiei to Sandheads, 4GJU .Miles. - Suez to Calcutta, 4757 Miles. Suez to Sandheads. Suez to Calcu per tta Time. Speed. Time. Speed. Time. Speed. Time. Speed. Voyasc. Hour. Mile. No. *3 5 6 7 8 9 n. M. 112 15 108 10 112 122 10 129 40 118 15 K. P. U 5 12 1 11 5 10 5 10 1 11 n. u. 178 174 40 190 55 206 30 194 15 192 10 K. F. 12 12 2 11 1 10 3 11 11 1 n. M. 51 15 44 50 48 50 63 47 25 47 20 K. F. 10 5 12 1 11 1 10 2 11 4 11 4 B. M. 55 30 50 45 52 30 65 25 55 15 47 45 K. F. 12 13 0} 12 5 10 1 12 13 7 11. M. 397 378 25 404 15 447 5 426 35 405 30 D. H. 431 433 443 478 454 434 K. 11 12 11 10 10 11 F. 6 2 4 3 7 4 Tons. 1060 1092 1048 1176 1174 1082 c. qr. 11.. 49 21 50 1 21 47 1 7 49 23 51 2 24 49 3 12 c. qr. lb. 4 1 23 4 2 10 4 1 18 4 3 22 4 3 23 4 2 5 Under weigh, 27,900 miles Total 245S 50 409 52 2C73 445 30 11 3 6632 1105J 49 2 14 4 2 16 Under steam, 28,542 miles ] AveraiT Under weigh, 65,800 miles 1 „ , Under steam, 57,084 miles J ^''""'^ Averog Total 4983 66 5424 11 1.1 13134 48 1 20 4 2 11 e Distance in calculating speed taken from Sandheads ; but, in ca taken. — Coal account not avi * Instead of Voyace 4, on ^ Iculating consu lilable for othe rliich iron shaft mption of cc r distances. *as liroken. al, the whol e distan ce to Calcu tta is Nubia, I'latc XII., iiTid Ceylon, l'late».\lll. and XIV. SHIP-BUILDING. 71 Materials used in Ship- Uuildins. MATERIALS USED EM SmP-BUILDING. Import- ance of knowledire Nothing can be more important to the naval architect than a thorough knowledge of the properties of tlie mate- rials with which he has to deal. He requires this to enable him to dispose them to the greatest advantage, and with the least pos^ible expenditure; and thus to produce a well- of the'pro" proportioned structure of great and uniform strength. The pprties of introduction of iron as a material for ship-building has en- materials, larged this field of inquiry, and has led to much discussion as to its merits in comparison with those of timber. Timber. The properties of timber will be first considered. A lengthened examination into the nature and qualities of the different varieties used in ship-building cannot, however, be attempted here, as the space which can be allotted to the subject will not admit of more than a few practical observations. Deterioration and decay, in timber-built Durability, ships, may result either from the decay to which timber itself is subject, in common with all organic matter, and which may be hastened or retarded according as destruc- tive or preservative influences are brought into action ; or they may be the consequences of an injudicious combina- tion of destructive agents with the inorganic compounds of he timber, thus inducing not only premature but unnatural Jecay. All large masses of timber in close contact are subject to deteriorating influences, such as a high degree of temperature, an increase of moisture, or a want of free circulation of air. These and other agencies, by promot- ing fermentation, lead to the first stage of decomposition, whereas the reverse of these conditions would in like man- ner retard its progress. Moisture as well as heat is neces- sary to produce fermentation, but when heat and the other agencies are at work, moisture will generally be found to exist, either left in the timber itself, or absorbed by it from the atmosphere. Dry-rot. Decay of timber, when accompanied by the growth of finigi upon its surface, has received the name of drt/-rot. This term was probably applied to it in consequence of tlie peculiarity, that wood so decomposed becomes a dry friable mass without fibrous tenacity, the parasitical fungi robbing the timber of its substance to support their own grow ih. In general, decay, when it takes place in this particular form, may be traced to imperfectly seasoned material, and the inference may be drawn with a considerable degree of probability, that the natural juices of the timber are neces- sary to the growth of fungi, and consequently that if these juices could be entirely abstracted or destroyed, this species of decay might be prevented. It does not fuUow that the presence of any of these juices will necessarily produce dry- rot, should the circumstances in which the timber is placed be such as to tend to their dispersion, or to their remaining in a dormant state. But as they do undoubtedly remain in much timber that is considered seasoned, any alteration of circumstances to prevent a free circulation of air, to lead to a deposition of additional moisture, and at the same time to an increased temperature, will in all probability induce the growth of fungi, and cause the destruction of the timber. In ships, the frequent presence of these injurious ele- ments must necessarily tend to produce fermentation. But though these facts are perfectly well known, it is remark- able how little attention has been paid to the necessity of a free circulation of air upon the timber of such parts of a shi|) as are below the surface of the water. This may be effected in various ways, though it is doubtful whether in all cases the current of air produced by natural causes would induce a sufficiently rajiid circulation. This sub- ject was forcibly broiight before the Admiralty by Mr Creuze in 1827, but was not taken up or acted upon. In the navy, the decrease of expense which would be occa- sioned by any increase of durability in ships, laid up in Ship- BuUding. ordinary, would be great ; and in reality, with proper care JratcrlaU and arrangements, there is no reason why the timbers of a "^«d in ship so situated should not be almost as durable as the same wood employed in houses and other structures. The ex- pense caused by decay is even greater in ships than in ^"^^" houses, yet the attention paid to the subject has been in an inverse ratio. The same facilities for the prevention of decay are not available for ships in commission, and if their timbers should have been unseasoned, or have had much of the natural sap left in them, dry-rot must almost necessarily ensue. It may be especially looked for in ships sent to a warm climate immediately after their construction, and ex- posed to a high temperature, and of its attacking these, many instances have occurred even w ithin the last few years. The same evils exist to a greater degree in merchant- vessels. Private ship-builders are unable to keep their capital locked up in a large stock of the different classes of timber fit for the different ships they may be called upon to build, and as the purchaser ordinarily requires a speedy execution of his order, the use of unseasoned timber is the necessary consequence. No better arrangements for the prevention of decay seem to be made on board of merchant- men, after they are built, than on board of men-of-war. Lloyd's register of shipping may be said to have an injuri- ous influence on this question. The register is kept bv a joint-stock company, and a committee of their body com- posed of ship-o» ners, merchants, and underwriters, w ith a staff of professional surveyors, have laid down a code of rules for the construction of ships as a guide to their classi- fication on survey. By these rules, a ship built of the very best species of timber, thoroughly seasoned, can be classed as a first-class ship for twelve years only ; a renewal for eight years may be obtained, but not without much trouble and expense ; and further extension asain of four years involves another expensive survey. Sufficient inducements are apparently, therefore, not held out for increasing the durability of ships. Many teak-built ships have lasted longer than these assigned limits, and yet no attempts have been made to rival them, thus leading to the belief that Lloyd's rules have had the effect of rendering builders and owners satisfied with existin? results. It has been argued that, to season a ship after she is built, by a free circulation of air, will cause shrinkage, and thus injure the good fit- ting and the strength of the fabric, and that it w ill strain the fastenings, and admit damp, and thus cause the decay it was intended to obviate. In reply to this it may be urged, that shrinkage could never be produced to this extent on the timbers of a ship by the circulation of air, had they not been in such an unseasoned state as to be totally unfit for use ; and that even in such a case, it would be far better to take the chance of less certain mischief, than to leave the ship to inevitable destruction by dry-rot. These remarks show the importance of well-seasoned timber for ship- building, and have been insisted upon here, not from any supposed want of general knowledge of the fact, but to show the importance of applying the means which exist to remedy the evil. It must be evident that when timber is to be closely jointed to other timber, to form a compact mass, the whole should not be wet with rain, or water-soaked when put in place. The im|)ortance of this is recognised by Lloyd's rules allowing one year to be added to the prescribed period of durability of any ship built under a roof. All vessels laid down in royal dockyards have this advantage. Different .species of timber are possessed of very different Different qualities, both as regards their durability and their strength. qualities in Oaks and other hard close-grained w oods, being the most different durable, are chiefly used for the frames of ships. The*P*''l"° juices of the oak are of an acid nature, and besides the ligneous, which it has in common with other woods, it con- tains the Gallic acid peculiar to itself. Oak when used in 72 SIIIP-BU Materials an iinscasniied state is extremely liable to ilry-rot, wliieli used ID in some cases lias been f'ouiul to destroy it in the space oF I'P' a few montiis. Teak is a very valuable timber for slii|)- ^ ""£) buiUiinsr, but like other woods it varies much in qiiality """ according to the soil in which it is grown, and consequently requires great care in its selection. Morning saul, green heart, morra, and iron-bark, are also valuable woods. Like teak they are extremely din-able, and are more oily and resinous in their nature than oak. The whole of the fore- going are classed together by Lloyd's committee as supe- rior woods, and are adniilted for the construction of ships classed for a durability of twelve years. The general classitication of woods by this committee is as follows : — Mahogany of hard texture, Cuba Sebicu, and pencil 1 -ia . cedar, Adriatic, .Spanish, and French atik J ^ Red cedar, AngcUy, and Vcnatica; other continentiil ^ white oaks, Spanish cbesnut, stringy barli, and blue > 9 ,, green J North American white oak, and American sweet chosiiut 8 ,, Larch, hackmatack, tamarac and juniper, pitch pine ] - and English ash J " C'owdic, American rock elm 6 „ Ilaltic and American red pine, European and American 1 , grey elm, black birch, spruce fir, English beech J " Hemlock 4 ,, There are some slight variations in the durability as- signed to these when used for other parts of the ship than the ribs or frames. Elm, which decays very rapidly when alternately wet and dry, is very durable if kept constantly submerged in water. On this account, as well as for its q\ialities of strength and toughness, it is well adapted for the keels of vessels. Other woods will be mentioned here- after when the sources of the su|)ply of timber ibr ship- building are considered. Means of The difficulty of obtaining jiroperly seasoned timber preserving whenever it may be wanted, and the great expense attend- timber. jp^, ji,g g^,.|y j^.g-jy ^f unseasoned timber, have led to various means being proponeil for its preservation. Satu- rating the timber with various chemical compounds, has been the method generally suggested for its accomplish- ment. In India, Machonochie, by steaming his timber, and then condensing the steam in the tank, and producing a partial vactunn, endeavoured to dissolve and carry off the juices of the timber, and he then submerged it in an oil Steaming obtained from the chips and sawdust of teak. Steaming or and pick- stoving timber has always been considered advantageous ling tim- (or wood used in a green state. Exposing it to the action **"• of water has been advocated with the same view, and this certainly tends to shorten the tiine required tor weather seasoning thereafter. About 40 years ago the timber used in the royal dockyards was ordered to be submerged in salt water ibr some time, and then stamped with the «ord "salt." Pieces of sound timber with this mark are found in Corrosive men-of-war up to the present day. Mr Kyan patented a Bublimate. process for preserving timber, by saturating it with corrosive sublimate ; and Sir W. Burnett, late Medical Director- Chloride of General of the Navy, patented the use of cliloride of zinc, 2inc. but „iti, neither of these processes is the effect in all ciises Creojote. certain. Creozote appears to preserve timber «ith greater certainty than any other chemical material yet used. The timber is put into a close tank, the air is abstracted, and the vacuum is kept up for two or three hours by continued pumping, to allow the air to escape from the pores of the wood. The creozote is then introduced, and is forced into the tank, until a pressure of about 150 lb. to a square inch is obtained. This pressure is kept up by continued pump- ing during successive days for forty-eight hours, or for as long as may be required to make the timber absorb the requisite amount. 'I'his process is chiefly used for pine tim- ber. Yellow pine should absorb about 1 1 lb. to the cubic foot, and Riga pine about 8 lb. The timber is weighed before it is put into the tank, aiul again after it is taken Ship- Building. I L D I N G. out, to ascertain the amount absorbed. Should this prove Materials less than the amount required, it is returned to the tank used in for a repetition of the process. Creosoted timber has hitherto been chiefly used by civil engineers in land and sea works. The objections to its use ^'^''V"™ in ship-building are its offensive smell and its great inflam- mability. Its |)ower of protecting timber from natural decay, and of resisting the lorcdo ?iovalis, or any of the other worms to whose ravages ship's timber is subject, if it be not thoroughly covered with copper sheathing, appear to render it peculiarly fit for such a purpose as doubling upon a ship. If (bund to answer, it might be used in thin boards as a sheathing instead of co|i[)er. Another process w hich is applicable to the preservation of Dr Boa- certain descriptions of straight-grained and porous timber, cherie'a has been patented by Dr IJoucherie, a French chemist of 1'™"=*" note, and been brought forward in this country by a com- ^^''^ ' pany formed tor the maintenance of the permanent way of' railways. They have publi>hed the following inlormation respecting it. Instead of using great pressure, as before explained, to imijregnate the tree, a moderate [iressure only is applied to one enil of it ; the efl'ect is to expel the sa|), and fill the tubes or pores of the timber with the preserving liquor. The tubular structure of trees has been long known, and Dr Houcherie's process shows that no connec- tion exists between the lubes laterally. Colouring liquiil applied in the form of a letter or word at one end of the tree a|)pears in the same shape at the other. The fluid used by Dr Boucherie is a solution coiTi|)osed of one part of sidphate of copper to one Imndred parts of water by weight. The specific gravity of the solution, when ot ]iroper strength, at GO" Eahr., is I'OOG, or nearly so. A water-tight cap is placed on one end of the tree which is to be saturated, and the solution is introduced within it by a flexible tube. The pressure re(|uired not being more than from lo to 20 lb. on the square inch, it luay be obtained in a very simple way, by raising the tank which contains the solution 30 or 40 feet from the ground. When the pres- siue is applied the sa|) runs in a stream from the opposite end of the tree; and a ready means exists of discovering when it is exhausted and the whole length of the tree penetrated, by rubbing the end with a piece of prussiate of potash, which will leave a dee|) brown mark when brought into contact with the cop|)er ot' the solution. The sap and surplus solution, should any pass through the tree, may be pum|)cd back into the reservoir, the sap being a better solvent of the sulphate of copper than water, if it should happen to be impregnated with lime or other im])urities. There are certain kinds of timber which are iiupcnetrable by the solution applied in the manner described. It answers best with trees that are the least costly, as beech, birch, larch, Scotch fir, alder, elm, poplar, &c. Trees felled any lime between November and .May may be prepared in the latter month. But when they are cut down in May or any month between then and November, they should be prei)ared "ithin throe weeks of the time of felling. It has been found, in the preparation by this system of vast quan- tities of timber for the French navy and railways, that the time necessary for the operation depends both on the length of the tree and on the description of timber. Trees of 40 feet in length, prepared at Fontainbleau for the French navy, required from eight to ten days to become sufficiently im|)regnated ; whereas for lengths of 9 feet only, the pro- cess was accomplished in twenty-four hours. A summary of experiments made in Derby with this process is given in the following table. It will be observed from the facts there stated, that the pores of the poplar are more pervious than those of other woods ; and the rapid and large absorp- tion of the fluid by the memel timber shows, that the pores of fir timber, when the natural juices are dried up, still afford a continuous channel Ibr its flow : — Uaterialfl used in Ship- Juilding. SHIF-BUILDING. Summary of Experiments. 73 Total No. Amount of pure .Sap forced out Amount of Time Amount of Solu- Time .\mount of Solution use<l per cube foot. £![- Date. Description of When cnt down. Length. Averace Diameter. Cobic Con- .Solution used to ttfect in forcing pur*-. Sap tion run out of of Opera- pen- meiiU Wood. tent. Solution perceptible. this. out. Tank during opera- tion. tion. Feet. Inches. Feet. Quarts. Quarts. Hours. Quarts. Quarts. 1 April 29, 1836 Beech January, 1856 18 12i Hi 33 64 4 104 8J 704 2 May 1, 1856 .Spruce Fir April 23, 1856 18 Hi m 27 50 5 95 12 700 3 .May 5, 18.56 Poplar April 1, 1856 m Hi V.ils Copper perceptible from commencement. 130 11 9-60 i May 7, 18.56 Elm Dec. 1855 18 Hi m — — — 156 23 11-52 6 May 9, 1856 Alder Feb. 1856 18 11 12 43 58 14 176 31 14-64 6 May 10, 18.56 ftlemel — 18i 11 by 11 15i Copper perceptible from commencement. 230 50 1508 7 May 22, 1856 Birch May 21, 1856 18 l-'i m 32 34 25 minutes. 184 ^ 12 00 8 May 23, 1836 Scotch Fir — 18 l-'i m 35 47 130 58 8-80 Materials used in Ship- Building. 'eather asooing. One great advantage attentling this niethotl, and which is likely to render its application very general, is the inex- pensive nature of the apparatus required. Seasoning timber, by e.\posing it for a lengthened period without subjecting it to any other process, has received much attention, and much controversy has arisen upon tlie best mode of carrying it into effect. It may perhaps be stated as the general opinion, that rough timber may be improved in this country by stacking it off the ground, that it may not be injured by damp. Sided timber, thick stuff, and plank, should always be stowed under sheds, and these must be airy and well ventilated, without partial draught which could affect the ends or any one portion of required to season these descriptions of timber to a mode- rate degree only. Mast spars are best protected when submerged under water, antl if buried in mud they are still more effectuullly preserved. Boards of mahogany or fir are well seasoned by being stacked on end in the open air without covering, but raised a little from the ground to avoid damp. In the royal yards it was formerly the custom to allow ships to stand in frame for various periods before they were planked, but tlie necessity of building ships rapidly has of late years precluded the possibility of doing this; and the evil effects have been too apparent. The fol- lowing tables show tlie results of weather se.isoning, as collected by Mr Fincham, and published in his work on the Outlines of Ship- Building : — ibie of irinkage f weather asoning. the timber more than another. Two or three years are A Table of the Shrinkage and Loss of Weight in Seasoning, of the principal Timbers used in Ship-huilding period of seasoning was ten gears. the Species of Timber. English Oak , African Oak . Italian Larch Scotch Larch . Cuba Cedar . New South Wales Cedar |- butt I top . 1 butt V top . /- butt I top. I butt ^ top . butt top . butt top . {butt top. butt top . f butt I top \ butt V top . butt top . butt top . Dimens. Weight. 6 by 6 lb. oz. 7 8 7 10 8 4 2 6 12 4 15 15 1 8 10 5 12 3 14 10 OJ 12 6 5 Dimensions. Weight. 6 5; J 5U 5i# 51 J 5\i 5\i 5!J 51J 5U 5iJ 5U 6 5U 5U 5U 5\i 5U in. by 5H =, 5i* ., 5] J ., 5il ., ^n ,. °\i 5i* 5U 51 S 5U 5U 5U 5U 5\i m 5\i 5i* 6 6 5U 5\i 5H 5U lb. oz. 6 6 6 6 8 7 7 6 10 4 8 4 9 4 9} 4 11 4 2i 4 1 4 3 7 3 12 3 12J 3 3 5 3 10 3 6} 3 8 3 9 Relative shrinkatje and loss of weight. Dimens. Weight. 1-000 1-010 1-010 1-000 1-068 1066 1-033 1-010 1-000 1-021 1-021 1-021 1-021 1-000 1010 1-021 1-000 1-010 0-979 0-989 1-010 1-000 1-000 1-021 1-000 1-176 1-588 1-176 1-059 1176 0-588 0-588 0411 0-354 0-384 0-354 0-323 0-530 0-300 0-300 0235 0-411 0823 0-300 0-382 0-323 0823 0-706 Weight of a cubic foot. Green. Seasoned. lb. 60 61 64 58 73 67 62 58 39J 3.'i 40 40i 36 37 34J 30 32 33} 31 29 32i 30 35 34} lb. 51} 51 50} 48 64 57 57 53 36 36} 363 37} 33i 32} 32 27} 30 80i 24 26} 29 27i 28 28} A Table of the Transverse Shrinkage in Seasoning of Board, 12 inches square and half-an-inch thick : the period of seasoning was thirteen years. Species of Timber. English Oak .... { African Oak.., Kiga Fir Dantzic Fir... Virginia Pine Shrunk in Seasoning, butt .j'j the breadth. I top T>3 „ (butt 5V l'"P 51 ,. fb"" -i, I top 5'j f butt ,V 1 top s-i ( butt sV I top ,'ff Species of Timber. Yellow Pine.. butt., top... Larch I''""- \ top... butt.. Shrunk in Seasoning. ^g the breadth, 1 5F )» ■ !T English Elm.. Canada Elm.. Cowdio . I top... I butt.. • 1 top... f butt., ttop... 74 SniP-BUlLDING. Materials used in Ship. Building. Seasoning timber by di-sicca- tion. Seasoninsr timber by exposing it to a current of heated air at a higlier velocity than is cnj,'endereil by natural causes, was introduced by Mr Davison. Tiie desiccating process, as he terms it, and as explained by him to tlie institution of civil engineers in 1853, consists in impelling rapid currents of air through a chamber or chambers con- taining the wood ; spaces being left between the ranges or tiers of timber for the heated air to act uniformly upon all its sides. The moisture, as soon as it is cooled, passes in- stantly away through an opening in the roof of the chamber, and this appears to be a distinguishing and essential feature in the process. Tlie wood remains in the chamber until by weighing a sample from time to time, the whole aqueous matter had been expelled from its pores. Charring wood in a sand-bath was practised in the beginning of the last century, and apparently with some success ; but the heat must have been much greater than that employed by Davi- son, and the process probably was nnich more rapid. In car- rying out the desiccating system, attention nnist be paid to the following points : — Different woods and different thick- nesses of wood, require different degrees of heat ; hard woods and thick logs of wood require a moderate degree of heat, from 90° to 100° Fahr. 'I'lie softer woods, such as pine, may be safely exposed to 120°, or even to a still higher temperature ; and when cut extremely thin and well clamped, 1S0° or 200° have been found rather to harden the fibre and to increase its strength. Honduras mahogany in boards of one inch in thickness may be exposed with advantage as regards colour, beauty, and strength, to a heat as great as 280° or 300° Fahr. A slab of Honduras mahogany 1 J inch thick, cut fresh from the log, was wholly deprived of its moisture, amounting to 36 per cent, by exposure to the temperature of 300° for fifty consecutive hours. In practice, however, it is found that from 115° to 120° of temperature brings almost every kind of timber in slabs or boards of moderate thickness, safely and steadily towards complete desiccation in a comparatively short space of time. For bo.irds up to 4 inches thick, one week is suf- ficient for every inch of thickness, thus one week for 1 inch thick, and four weeks for 4 inches thick, but beyond this thickness the proportions require to be increased. For 6 inches thick, seven weeks should be allowed ; for 8 inches ten weeks, and so on. 'J'hese periods are fixed on the supposition, that the rapid forced current of heated air will be kept up only during the day of twelve hours, and that the chamber will then be closed till the following morning, that being the customary mode of working. English oak requires more than ordinary care when thus prepared. It should never be exposed under any circum- stances for any length of time to a higher temperature than 105° ; more intense heat has been found to act u|)on the Gallic acid, or on the fibres in some peculiar way, so as to produce internal fissures. Mr Davison also stated, that still heat like that of an oven had an effect upon wood totally different from that produced by a current of heated air. In the one case the fibre is rendered short, brittle, and weak ; in the other, all that is valueless is driven awav, and the albumen becomes solidified or coagulated into a hard compact substance, and the fibres gain a great increa;e of strength and rigidity. Seasoning under ordinary de- grees of temperature has a completely diflerent effect on the albumen, which, if not previously dissolved or washed out by any of the processes previously referred to, remains, when dried, in a soft spongy state, ready to become an absorbent of moisture. It has been found by experience that 100 feet per second is the best velocity for the current of heated air, and with a proportionate area of inlet-pipe, a sufficient quantity should be delivered into the chamber to cause a complete displacement of the air and moisture in three niinutes. If a desiccating chamber contains 30,000 cubic feet of air, 10,000 cubic feet ought therefore to be pro- pelled into it per minute, care being at the same time taken that the area of the outlet or outlets for the escipe of the moisture exceed the area of the inlet-pipe, and that they be so arranged as to avoid a direct current between them. The Board of Ordnance adopted this system tor gun- stocks in 1840. Previous to its introduction, about 400,000 stocks were undergoing regularly a course of sea- soning, each requiring to be turned once or twice every year to avoid the ravages of worms or decay. In a report from Mr Lovell, then her Majesty's inspector of fire- arms, he states respecting some gun-stocks subjected to the process : — " One half of the number were quite fresh cut and green wood, the other moiety had been about twelve months in store ; the total weight before the pro- cess was 536 lb. 9 oz.; and after sixteen davs' exposure to a current of air heated to 110", or 114° Fahr., that weight was reduced to 413 lb. 14Joz. ; that is to say, 122 lb. lOJ oz. of moisture had been driven off. Some of the stocks had been purposely selected with seen cracks in the butts and other faults, for I expected that those cracks and faults would be exaggerated by the heat of the cham- ber. But the result was not so ; on the contrary, they were closed considerably behind the marks that had been stamped upon the ends of them before they were put in, and the whole number of stocks came out in good condi- tion, and fit for immediate use." He proceeds to say, — " The wood is better seasoned than when dried in the open air ; Isl, Because the albumen being dried on the pores and in the capillary tubes, renders the fibre stronger and less liable to absorb moisture ; 2d, The wood is stronger, tougher, and, of course, more capable of withstanding the effects of violent vibration from the laternal adhesion of the fibre being better preserved ; 3(1, It works smoother and more waxy under the chisel, and has less tendency to speel and crumble away, which is generally the great fault of steam-dried timber. I have now worked nearly 30,000 desiccated stocks, none of which had been under the pro- cess more than twenty-one days ; and my opinion is very tiecided, that the wood is more thoroughly seasoned, and with niuch greater certainty, than if it had been merely exposed to the open air in the usual way for three or four years. 'J'he desiccating chamber created in the royal manufactory at Enfield continues in full activity. The heat is kept down to a medium degree, between 90° and 100°; and at this temperature it delivers the stocks per- fectly seasoned in fourteen to sixteen days, accoriling to the quality of wood, whether of sap or heart ; and I pro|)ose to subject the whole of the stocks to it in future, whether they have been air-dried previously or not, in order to make sure that the whole shall have been equally seasoned." Some bearers of Riga |)ine and American elm, after they had been in use for about six years, and exposed for that length of time to a temperature of 115° or 120° of heat, at which the chamber invariably stood, were examined, and were found to be perfectly sound and in excellent condi- tion; thus proving that the process, even though continued for so long a period, did not injure in the slightest degree the fibre or the strength of the wood. It is difficult to understand how the timber subjected to this process can be rendered more capable of sustaining a tensile strain, if this be the case, but it is natural that the albumen, when hardened in the pores, should render it more incompressible, and therefore more capable of resisting any strain when the strength depends on this property. For hard woods, to which Dr Bouclierie's process is not appli- cable, desiccation seems to be admirably adapted, Mr Lovell's experience with the walnut-tree gun-stocks appear- ing conclusive. The following table is interesting, giving the results of experiments made by Mr Davison : — tfaterlala used In Ship- Builuing. Seasoning by desicca tion, con- tinued. SHIP-BUILDING. io iterials bed in Ship- lilding. General Results of Desiccation, showinr/ the Percentage lost by four kinds of Timl/er of different dimensions, seasoned hy the Desiccating Process ; the Number of Days in which the Seasoning was effected ; and the Ratio of Time in which equal degrees of Seasoning were produced, upon duplicate Specimens by the arlijicial and by the ordinary processes. ilaterialg used in Sbip- Building, les of \ £.LLow Pine. Mahoqaht. RlOA PiME. Ekgliso Oak. | ilts on c ber Ratio of time Ratio of time Ratio of time Ratio of time oned by -2 in which in which in which in which a. Dimen- Ave- equal degrees Ave- eqoal degrees Ave- equal degrees of desiccation Ave- equal degree! ^ &ians. Average ra-^e Vo. of desiccation Average rasTo No. of desiccation Average rage Xo. Average rage Xo. of desiccation s Percenl- of Days were effected Percent- of Days were effected Percent- of Days were effected Percent- of Days were effected a by the natn- age lost. desic- by the natu- age lost. by the natu- age lost. by the natu- eating. ral and arti- ficial pro- cesses. cating. ral and arti- ficial pro- cesses. eating. ral and arti- ficial pro- cesses. eating. ral and arti- ficial pro- cesses. Inch. •a f 1 20-76 21 25-8 26 6:1 ^ 'i 18- 26 n I li 1415 26 36:1 24-0 37 16: 1 Mean results J 17-63 24-3 36: 1 249 31-5 11 :1 Inch. r 2 35- 42 6:1 21-2 37 15 : 1 14-61 343 62: 1 32-36 47 20:1 3 23-43 47 9:1 19-69 44 71 :1 19-48 46-66 36 : 1 28-43 58 36 : 1 a . 4 27-79 49 9: 1 18-7 47 20:1 1359 47- 42:1 28-98 58 20 : 1 Kt .5 24-1 63 6 :1 1392 47 20: 1 15-69 52- 18 : 1 29-69 58 36:1 6 21-9 63 7 :1 19-24 51 20 :1 17-2 49- 59:1 26-51 58 36 :1 Mean 1 results J 26-44 52-8 7-4 :1 18-55 45-2 29-4 : 1 16-11 45-79 43-4 : 1 2919 55-8 29-6 : 1 Sq. inch. 1 1719 7 28 : 1 13-97 7 71 : 1 13-46 7 71 : 1 22-72 12 16 : 1 IJ 19-35 13 44:1 1594 14 71 : 1 10-92 7 71 :1 23-36 21 10 : 6 Mean 1 results J 18-27 10 36 : 1 14-95 10} 71 :1 24-38 7 71 : 1 23-04 16-5 13 : 1 Sq. inch. ' 2 37-19 23 6 : 1 17-56 23 71 :1 1205 12-33 71:1 29-38 37 20:1 a 3 25-6 35 4:1 8-64 26 71 : 1 12-33 24-33 71 :1 24-26 42 10: 1 •^ 4 13-27 35 20: 1 17-81 40 16 : 1 10-94 35-66 59:1 1936 40 16:1 a 5 28-57 47 8: 1 17-61 37 36 : 1 11-95 41-33 71 : 1 22-95 74 20:1 A L 6 22-48 47 7:1 16-93 47 36: 1 15-95 43-66 53 : 1 16-13 86 36 : 1 Mean 1 26-2 9: 1 15-7 34-6 46:1 12-64 3211 65:1 22-57 55-8 20-4 : 1 results 1 Comparative Strength and Deflection of Desiccated Specimens and their Duplicates, denominated Woolwich Specimens. Description. Yellow Pine. Mahogant. Riga Pi.se. English Oak. Dimen- sions. Broke with Deflec- tion. Dimen- sions. Broke with Deflec- tion. Dimen- sions. Broke with Deflec- tion. Dimen- sions. Broke with Deflec- tion. Desiccated specimens Woolwich , Desiccated „ Woolwich , Desiccated , Woolwich , Desiccated Woolwich , Desiccated , Woolwich Sq. inch. 1 li 2 2 3 3 4 1 4 lbs. 45} 40} 138 107 237 282 884 716 Were not broken inch. 6 11 6 4 4 33 3J 4} T li Sq.inch. 1 li IJ 2 2 3 lbs. 70} 62} 185} 156 436 394 1514 1318 inch. 9} 8i 6| 6J 5i Si 4i H Sq.inch. 1 li li 2 o 3 3 4 4 lbs. 46 48} 100 127 345 363 996 793 Were not broken inch. 8i 8? n 5J ii 4i 3J 4} i 1 Sq.inch. 1 1 li 1} o 2 lbs. 54} 47i 84} 128} 385 327 inch. 9i 11} 4i 7 4} 4J The weights were applied at one end of the piece, at a distance of 3 feet from the fulcrums. Tlie slow progress made in the introduction of this pro- cess has doubtless arisen partly from a fear that so speedy a method of drying or seasoning is likely to warp and rend the timber. Though this result does ensue from exposing it to draughts in covered sheds, yet as the evil in this case arises from the partial action of the currents of air on the log or piece of timber, it need not be feared where the temperature and the current are equally diffused, as in the desiccating chamber. The expense of the apparatus is, however, a serious drawback to its introduction, except in works where a very large quantity of timber is used. The best season for felling timber has been a subject of Season uf some discussion ; but the evidence that has been collected felling seems to be in f:ivour of that which is winter-felled. Its timber. specific gravity is less than if summer-felled ; and it is na- tural to suppose that the less amount of sap in the tree will render it more readily and easily seasoned. The relative value of the various woods must also de- 4 O Materials used in Ship- Ruildinfj. STIIP-BUILDING. Cohesive ■trength of timber. Power to rosist a crushing force. pond upon their stretisith as well .is upon tlicir durability. Tiie colic>ive strcn;,'tli per square-incli, or power of resist- ing' a tensile strain to te.ir the p.nrlicles asuniler, v.irics in dilt'erent species. Professor ]5arlo\v, in his work on the streiii,'tli and stress of timber, gives it as under for the fol- lowing kinds of wood : — Cohesive atrenirth Species of Timber. per i«qtiaro incli in lbs. Ash 17,000 Teak 15,000 Fir 12,000 Beech 11,500 Oak 10,000 Pear 9,800 Mahogany 8,000 These being the breaking weights, it will not be safe in practice to expose timber to nioie than about one-half of them. Professor Hodgkinson h.is investigated tlie powers of different species of timber to resist a direct crushing force, and the results which he obtained show that this power varied greatly according to the state of seasoning. He f()und that timber, wlien in a wet and unseasoned state, cindd be crushed by a force less than one-half of tiiat which would be required to crush it when properly seasoned, the moisture acting as a lubricating medium to allow the particles to slide upon each other more easily. The following, however, may be taken as the crushing weights of the different species named, in an ordinary state as regards their degree of seasoning: — Specific Gravity Specimen. Species of Timber. Resistance per eqnare incti in lbs. •560 Yellow Pine 5376 6674 5748 6402 7082 8198 8683 9509 9771 •540 ■580 Red deal •640 Birch •660. . •753 Spanish mahogany.. Ash •780 •700 Dry English oak.... Box •980 No satisfactory rules have yet been promulgated to deter- mine the weights which may be placed with safety upon wooden columns of diflereiU diameters and different lengths. It is not unusual in practice to confine the load to 500 lb. per square inch of section on a column of oak, and when required to carry this load per sq. inch, the length is gene- rally limited to fifteen times the diameter. But, however short the column may be, it shoidd never be loaded to a greater degree than one-third of the weights in the fore- going table, and the length should never exceed twenty, or at the utmost twenty-five, times the diameter without a great diminution of the load proposed above. The strength of similar columns varies inversely as the squares of their lengths. Thus, if the weight which a coluiun of oak of 5 inches diameter and 6 feet long will support with safety be taken at 9800 lb., a column of oak of 5 inches diameter, and 10 feet long, will support only 2-150 lb., with an equal degree of safety, because by the proportion mentioned above 10': 5-:: 9800: 2450. Transverse The annexed table of data is given by Professor Barlow, "If"^** °^ '" ^'^ work, for determining the weights w hich the different woods enumerated will respectively carry, when exposed to a transverse strain, and the rules which follow lor its practical application are also taken from the same autho- rity: — timber. Teak 2402 English Oak 1672 Canadian, ditto 1766 Dantzic, ditto 1457 Adriatic, ditto 1383 Ash 2026 Beech 15.56 Material! used in 8liili- Building, Elm 1013 Pitch Pino K.32 IJed Pine 1341 New England Fir 1102 Kiga Fir 1108 Mar Koreat Fir 1262 Larch 1127 To find the ultimate strength of any rcctangidar piece Rules for of timber fi.\ed at one end and loaded at the other: — strength o Rli.f..— Multiply the value given in the table of data by '"'"'"8 of the breadth and square of the depth, both in inches, and ''"''""'• divide the product by the length, also in inches ; the quo- tient will be the breaking weights in pounds. Example 1. — What weights will a beam of English oak sustain before it breaks, when the breadth is 8 inches, the depth 12 inches, and the length 10 feet from the point of support? The relative strength of English oak, as given in the table, is 1672. Then 1672x8x12* = 16,051 lb., or 7-255 tons. 120 Example 2. — What weight will a beam of larch sustain before it breaks, when the breadth is 4 inches, the deptli 6 inches, and the length 5 feet fi-om the point of support ? .Answer— 2704 lb. To find the ultimate tr.ansverse strength of any rectan- gular beaiTi, when supported at both ends and loaded in the centre : — Rule. — Midtiply the value given in the table of data by four tiiues the breadth and square of the depth in inches, and divide that product by the length, also in inches, for tlie weight. Example 1. — What weight will be necessary to break a beam of teak, the breadth being 10 inches, the depth 14 inches, supported at each end, and the distance between the faces of the supports being 20 feet, the beam being loaded in the middle ? For teak, the value given in the table is 2462. „, 2462x4x10x14' ^^ ... ,, „,_^, ^ Then wjtz = 80,42j lb., or 3o-904 tons. Example 2. — What weight will a beam of English oak carry bel()re it breaks, the breadth being 8, the depth 12 inches ; the beam being loaded in the middle, antl sup- ported at each end, and the distance between the faces of the supports being 15 feet? Answer — 42,803 lb., or 19'153 tons. If the dimensions of a beam be required so as to support a given weight, the following rule must be used: — Rule. — Multiply the weight in pounds by the length in inches ; and this product, divided by the tabular value, will give the product of lour times the breadth and square of the depth ; then the breadth being known, we can find the depth ; or the dejith being known, we can find the breadth. Example 1. — What must he the dimensions of a beam of English oak to carry a weight of 5 tons in the middle, where the distance between the supports is 20 feet? The tabular value for English oak is 1672, — " __ = 1607, which is the square of the depth multiplied by four times the breadth. Let the breadth be 6 inches ; then 6x 4=24, or four times the breadth. ^v- =66.96 = the square of the depth, Then- and ^/ci6•96= 8*18 inches, or 8Jth inches nearly. Or, if we take the depth at 8 inches, then 8^=64 and ^-^ = 25-1, O-i SHIP-BUILDING. 77 used in ^"'^ '~J~~^~'^' °^ ^ ''"'^ more than GJth inches = the T'hy' breadth. . _^"/ Example 2. — What must be the dimensions of a beam of red pine to carry a weight of 15 tons in tiie middle, when Eules for the distance between the supports is 30 feet ? Answer — 10 strength of inclies in breadth by 15 incites deep nearly. .. . If a beam be supported at both ends, and the load be timberjCon- ., ,■ , , ' ' • , i ■ -n l tinued. equally distributed over its length, it will carry twice the Weight ; that is, the result obtained by the foregoing rule must be doubled. If the beam be firmly fixed at both ends, so as to prevent the ends from rising, when the weight is applied in the middle, the result will be increased by its half; that is, a weight of 10 tons may be increased to 15 tons. If the beam be fixed at both ends and loaded uniformly throughout its leniith, the result must be multiplied by 3 ; that is, a beam which w ill cany 10 tons in the middle when it is laid loosely upon its supports, will carry 30 tons when fixed at both ends, and the load distributed uniformly over its length. It must always be remembered, in applying these rules to practice, that the weights found by them are the break- ing weights. The proportion of the breaking weight with wliich it is considered safe to load a beam in actual use varies according to the nature of the material. In the case of cast-iron, which breaks without giving any warning, it is not considired safe to place more than one-third of the breaking weight upon it. In wrought iron and timber, which both sliow symptoms of being overstrained before they break, by becoming crippled, or by an amount of flexure so great as to be very observable to the eye, the load in practice may be one-half of the breaking weight, as found by the rules. Experiments on the strength of materials are alwa5-s valuable to practical men, as adding to the store of know- ledge, and acting as a check on any rules which may be in use. A series of experiments on timber were made by Colonel Fowke, of the Royal Engineers, at Paris, during the universal exhibition held there in 1855, and the results were published at great length in the report upon that exhibition. Mr Fincham made some experiments, with great care, on the transverse strength of timber, and the following table, showing the results, is extracted from his work on ship-building : — A Table of a Series of Experiments on the Strength of the undermentioned species of Timber. In each case the piece was three inches square and four feet long between the supports, and the weights were placed in the middle. Species of Timber and No. of Experiments. Specific Gravity. English oak, the mean of 8 experiments Italian oak, the mean of 4 experiments Dantzic oak, the mean of 4 experiments African oak, the mean of 4 e.tpcriraents Malabar teak, the mean of 4 experiments... Moulmein teak, the mean of 4 experiments... Riga fir, the mean of 4 experiments Dantzic fir, the mean of 4 experiments Italian larch, the mean of 4 experiments.... Scotch larch, the mean of 4 experiments Hackmatack larch, the mean of 4 expert- I ments J Cowdie, the mean of 4 experiments Bermuda cedar Cuba cedar, the mean of 4 experiments Van Dieman's Land cedar Mahogany, the mean of 4 experiments New South Wales mahogany, the mean 1 of 4 experiments J Cwts. •791 10-7 •704 1021 •724 •909 •576 •708 •645 •661 ■708 •614 •932 •524 •616 •636 1-382 Weight at wbich the piece broke 32-973 38-792 39-732 59-897 43723 34-292 35-558 36-718 40047 27-750 37-886 33^317 36-776 24348 18^303 30093 36777 Rigidity, or the opposite of elasticity, is the power of Materials resisting deflection or bending, when a weight is placed upon •"«<' "> a beam, or when a side pressure is brought to bear at'ainst „^.^l?' it. This power is increased in a much more rapid ratio " '°^^ than tlie power to sustain loads without fracture; thus, in •■ "" order that a beam may bear 10 tons with the same degree ■f'"'*^''? "' of deflection as one bearing 5 tons, much less increase of dimensions will be required than will be necessary for a beam whose breaking weight is to be 10 tons, in compari- son with one whose breaking weight is 5 tons. The pos- session of rigidity in a lateral direction is necessary to every beam to a certain extent, to prevent its bending side-wise and becoming crippled, and hence beams must not be too much reduced in their breadth relatively to their depth. In practice, the proportions of 2 for the breadth to 3 for the depth, and also of 3 for the breadth to 5 for the depth, are very common ; but in joists of floors, and in other situ- ations, where side props, or supports to prevent flexure, can be introduced, the depth is often made in a greater propor- tion, with the advantage of a saving of material, to carry the same weight. The supply of timber for ship-building purposes is a sub- Supply of ject that has at various periods attracted much attei.' ion, timber both as regards the species grown in this country and those which are imported from abroad. Some valuable remarks on foreign woods were lately made by Mr Leonard Wray, in a paper read before the Society of Arts, and published in their journal of 6th May 1859. He called attention to the fact, that before forests of the finest timber can be brought into beneficial tise, a popula- tion is required to fell and trim the trees, as well as a good shipping |)ort, and the cheapest possible means of bringing the timber from its native forests to the port of shipment. Honduras has long had its organised bands of wood- from Hon- cutters, and has long been one of the most important timber- duras, exporting countries. It now- exports about 25,000 tons of mahogany and 6000 tons of logwood annually, and the woodsmen in pursuit of these two staple products continu- ally pass and repass other species of the finest quality ot timber in the world. Amongst many other fine trees found there, Mr Wray specially enumerated the following : — The green heart, the live oak (Bignonia), and other oaks; the niahoc, the bullet-tree, the Neesberry bullet-tree, the iron- wood, the locust, used for ships' planking and treenails ; the dogwood, the red pine, the pitch pine (much superior to that of Carolina and the other southern states of America), the cedar (Cedrela odorata), a light and durable wood, not liable to dry-rot, nor subject to the attack of insects, and of which the trunk is 70 or 80 feet long, with a diame- ter of from 4 to 7 feet. The morra is described by Mr Wray as a most valuable timber, the trees often attaining a height of from 100 to 150 feet, the lowest branches being 60 feet from the ground. The wood is extremely tough, close, and cross-grained, so that it is difficult to split, and not liable to splinter, which renders it particularly adapted for ship-building, more espe- cially in the royal navy. The trunk makes admirable keel.s, timbers, and beams ; and the branches having a natural crookedness of growth, are unsurp^sed as knees. Sir R. Schomburgk, referring to this tree, states that it grows abundantly in Guiana, on the banks of the river Btrima, which is navigable lor vessels drawing 12 feet of water, so that they might load close to the spot where the trees are cut down. Mr \\'ray also mentions many other fine timber trees as the growth of Guiana, and Assam, Tenassarim, and the provinces and settlements in the neighbourhood of the Straits of Malacca. He states that a quantity of teak has for many years been exported fi-om Moulmein, and other parts along the coast, but that the field which this healthy and must pleasant country still presents is so inexhaustible SHir-BUILDING. Materials tliat he considers it to stand unrivalled as a timber-pro- used in dticinsr country. Hitherto teait alone has been exported, ^•"P" but there are others which are consideretl quite equal, and Building, p^,^^^ superior to it. He gives the fbllowing list of sonic of ^"^^/"^ the best timber woods, which will serve to give an idea of Moulmein the capabilities of these neglected provinces: — Timbers. Anan. — One of the hardest and most compact woods known. Ahnaun. — Strong and very durable ; used in ship-building. Ktoun-lac (Kottlera). — KxccUent for rudders. Kat-uat-na (C'edrela). — Large timber, 40 to 70 feet long ; used for ship-building. Ka-nyeng-kyaungkhyay. — For ship-builders; cootains an aro- matic oil, and is not attacked by insects. Eyeat-yo. — Similar to teak. Kud-doot-alaiu. — A large tree ; used in ship-building. Kunnazoo. — A very large tree; very hard and durable timber. May-Mayka. — Used in ship-building. May-raug. — Said to be very durable. May-tobek. — Used for the bottoms of ships, considered preferable to teak. ilayam. — An indestructible, strong, heavy, dark-red wood. Podauk. — A beautiful, compact, and hard wood, sometimes called rosewood. Penjadoh. — Strong and durable. Fienmahne. — Yields very strong knee-timber. Pvau-ga-deau. — Hard, dense, and durable; called iron-wood. Soondra. — A very tough, elastic wood; said to be the strongest of all tlie Indian woods. Tkab-bau. — Fine solid timber, sometimes 70 feet long ; used for boats. Thau-kya. — .\ species of wood similar to Saul. 2Via-riot. — A kind of grey teak. Tha-nat. — .More resembling Saul. Thau-That.— A capital wood, like .Saul. Theet-ya-hau. — A species of teak ; close grained. Theug-gau (Ilopea od(>rata). — An enormous tree of the Saul tribe ; yields a strong, compact, and excellent timber, considered superior to teak ; also a quantity of good dammer or resin. Insects never attack this wood, nor is it liable to rot. Tirhbac (Quercus Amhersliana). — An oak; large tree; used in boat-building. Thnnnsauja. — A large tree ; used in boat-building. Thinijnn kyaust. — Close grained, strong, heavy wood; used in ship. building. Thubbae (Mimusops). — Used in ship-building. Thubbor (Uvaria). — A large tree; used in boat-building. Toungbytng. — A kind of red Saul. Thym-bro. — A good, strong, durable wood ; used in boat-building. Malacca Of the Malacca woods Mr Wray gives a long list, and of timbers. these he describes the following t'rom his own experience while resident in the straits : — Mitrbouw. — Very strong, hard, and heavy; used in shipping; not attacked by insects ; will last 100 years. Binlaugoor. — Valuable wood for ship-building, especially for planks, mast, spars, &c. It grows in great abundance, especially near Singapore, and is largely exported to Mauritius, California, &c. Vamerlaut. — Uard, tough, and very durable. Qihnm. — A pale yellow wood, close grained, hard, elastic, very durable, and generally used in boat-building. Tampauu. — Used for house-building; hard, and exceedingly durable. Tamboosu. — House beams ; considered very durable. _,?, "* \ — Hard, tough, elastic ; used in boats. MarauUe. — Very large; light resinous wood, much used for planking, and in building boats. AastmUan Australia is the next country to which he directed at- timber. tention ; and though distant, it may yet become an im- portant timber-exporting country, the timber being brought here as a home freight in return for our large exports. The trees of this country which are mentioned are the iron-bark, the tuart, the jarrah blue-gum, and morrell. The tuart is especially mentioned as adapted for ship- building, as it is most difficult to split, and not liable to splinter. The jarrah, whose stems average 65 feet long, nearly parallel, and without a branch or knot, is also a most im- portant tree of this colony. It is not attacked by insects of Material! any kind, nor has it any tendency to dry-rot. used in 'I'here are forests of this wood, almost unmixed with Ship- other trees, in Western Australia, of more than 4 miles in ^ "^^ depth, and which are known to extend for a length of 150 ^"V""^ miles. Planks may be obtained I'rom it 10 feet wiile if desired. It is not only valuable as a ship-building timber, but also for furniture, being foimd of various shades of colour, and of almost every variety of grain. A ship may therefore be loaded very advantageously with this timber after proper sawing-machinery has been erected in the country, as it may be converted into scantling and other pieces for furniture, which may be stowed along with the balk timber of any size that may be desired. Some very fine specimens of pine have likewise been im- ported lately from Vancouver's Island, of immense size, of great strength, and very durable. Specimens of foreign woods may be found in the collec- List of coi- tions at Kew ; at the Kensington Museum ; East India lections of House ; Somerset House, Admiralty branch ; and at the '!"'<:'"'«'" Crystal Palace. timber ^" Since the |)ublication of this paper, containing so mtich valuable information, and so liiierally contributed by Mr Wray to the Transaclions of the Society of Arts, and from which the foregoing extracts have been so copiously taken, contracts have been made by the government for green-heart Tuart and Jarrah timber. It is to be hoped that this is a i)relude to timber from our own colonies being hereafter used in the royal dockyards in larger quantities. The importance of ship-building timber for the merchant service is undoubtedly decreasing, on account of the in- creasing use of iron ; and it therefore behoves the govern- ment to make its own arrangements to originate and foster this trade in those districts pointed out by Mr Wray. Though insignificant in comparison with these magnifi- cent trees of foreign growth, the increasing quantity of larch now grown in this country deserves attention. The larch {Pinus Larix) now so much grown in Eng- land as well as in Scotland, is frequently called Scotch fir, thus being mistaken for the " Scotch fir" as so called in Scotland (Piiius si/lvestris), which has a dark-coloured foliage. The latter is considered superior lor the purposes of architecture, but larch is better adapted for ship-building purposes whenever its size is sufficient. Like most other woods, it varies extremely, according to the soil on which it is grown, and care must therefore be taken in its selec- tion and use. It stands exposure to wet and dry better than most timber, and is hence much used for pit-props in coal mines. The late Duke of Atholl induced the government to build a vessel of larch from his forest. She was called the Atholl ; and though her durability has been very great, no further attention appears to have been as yet paid to the subject by the authorities. A knowledge of the weight of the different species of Weight of timber is necessary to the naval architect, to enable him to timber, compute or estimate the iveight of the hull of the vessel which he is designing or constructing. Mr Edye, the late assistant-surveyor of Somerset House, published an elaborate work containing tables of the weights and the dis|)lacements of the different classes of men-of-war of his day, but now rendered comparatively valueless by the in- troduction of steam-vessels and the great changes in the proportion of ships. The following table, containing the weight of a cubic foot of timber in a green and seasoned state, is extracted from this work ; and if the weights of the different timbers be compared with their strengths as previously given, it will be seen that the heavier timbers may be used without increasing the weight of the vessel, as their scantling may be reduced, and the same strength be retained, and with advantage, also, as to durability : — , SHIP-BUILDING. 79 Namo of Timbers. English oak , Dantzic oak , African teak Indian teak, green or sea- eoned, about the Bame. . . Mai abar* Kangoon* Indian mast peon Cedar Larch Riga fir New England fir Elm Beech Ash Green. lb. oz. 71 10 49 14 63 12 48 32 45 48 12 44 12 66 60 58 Seasoned. lb. oz. 43 8 36 60 10 52 15 26 36 28 34 35 30 37 53 50 4 4 4 8 11 5 6 * Malabar teak is the heaviest^ and Rangoon the lightest of all the Indian teaks imported. Special care is required in the selection of materials to be \ised in combination with timber, in order that no che- mical or other action, which may tend to premature decay, may take place between them and tiie timber. Great care is required in the use of iron for fastenings on account of the great affinity which exists between this metal and oxygen. The oxidation of the iron not only destroys the fastening itself, but has an injurious effect upon the timber surrounding it. If the nature of the wood be such that a supply of oxygen from the atmosphere can be kept tip through its pores, the oxidation and destruction of tlie iron will be very rapid. The use of iron in combination with oak is particularly objectionable on account of the acid na- ture of this wood, and the quantity of oxygen which it con- tains. In oily and resinous woods the surface of the bolt, when driven, receives a coating of this matter, and is thus niideied less liable to oxidation. Such woods are also more impervious to the passage of a continued supply of oxygen. Iron fastenings, under copper sheathing, are also liable to be destroyed by the galvanic action which takes place between these metals. Many attempts have been made to prevent this action by driving tlie bolt so far into the wood that a cement of some kind could be put over the head of it, so as to break the connection between the metals, but no important results of any system of this kind are as yet known to have obtained. Copper is therefore used largely for the fastenings of ships. This metal is liable to a very slight oxidation only upon its surface, and when this has taken ])lace, all fur- ther oxidation ceases, and the metal is not destroyed, as is the case with iron. Copper, however, is not possessed of the same strength as iron, and is soft and ductile in com- parison with it. It is therefore fiir from being so good a fastening, especially when driven through iron-knees and iron- riders. It is liable to be bent and crushed, or crippled at the neck, by the iron through which it has passed, if the ship be severely strained and work in any degree. Some valuable experiments were made on the tensile strength of bolts of dockyard copper, Grenfell's copper, and Muntz's yellow metal, by Mr Jn. Kingston, of Woolwich dockyard. The results are shown in the follow ing table : — Description of bolt. '"'"t^.:^^.'-" Dockyard copper, average of 12 ex- 1 49,490 lb., or 23 tons periments J very nearly. Grenfell's copper, average of 11 ex- 1 46,592 lb., or 20} tons periments J nearly. or 221 tons Muntz's yellow metal, average of 11 1 49,945 lb., experiments J nearly. Copper, from its ductile nature, is quite unfit to be used for any purpose where a cross-strain has to be resisted. used in Ship- Building. A late invention, by which a coating of copper is put upon Materials iron, in the same manner that iron-plates are coated with tin, promises to be very valuable. Fastenings of this kind will then combine all the good qualities of both metals, and w ill tend materially to strengthen the general fabric of the ship. Treenails of timber, equal in quality to that through which they are to be driven, make excellent fastenings, but their strength and their |)ower of holding are not such that they can be used to the entire exclusion of metal fastenings. The materials used for the sheathing of ships to pro- Sheathing, tect them from fouling, and from the attacks of the teredo tiavalis, and other destructive worms, are chiefly copper and Muntz's metal. These metals are kept clean by the sea-water acting slightly upon them as a solvent, or by oxidation ; and a gradual waste is therefore taking place continuously from their surface, thus preventing the adhe- rence of any animal or vegetable matter. With a view to obviate this gradual wearing away, Sir H. Davy proposed to induce a galvanic action u|)on the sheathing by attaching protectors of iron on its surface. He succeeded to some extent ; but in proportion as the iron was eaten away and the copper preserved, it became foul with sea-weed and shell-fish, so that his proposal was abandoned. Iron for Shlp-huildmg. The use of iron having now become common in the con- struction of ships instead of timber, a thorough knowledge of its properties is thus rendered necessary to the naval architect. The properties of wrought or malleable iron, as a material for the construction of the component parts of ships, will first be considered in a general point of view. The strength of rolled iron varies with its quality ; the Cohesive results given will be those due to an average quality, such strength. as ought to be used in sliip-building. The cohesive strength of bar-iron, or its power to resist a tensile strain, may be Bar-iron. safely taken at 25 tons, or 56,000 lb. per square inch of section. Messrs Robert Napier and Sons of Glasgow have made some valuable experiments on the cohesive strength of wrought-iron, and steel bars and plates, which have been publishetl in the Transac/ioiis of the Institution of En- gineers in Scotland, vol. ii., 1859, and the results, along w ith others, by Mr Fairbairn of Manchester, on iron-plates, are given here by their kind permission. Table of the average Strength of Steel-bars, as found hij Messrs Napier and Sons. Steel-bai-3. Strengrth per sq. inch ot section. Cast-steel for rivets 106,950 lb. Homogeneous metal for rivets 90,647 „ Puddled steel-forged bars 71,486 „ „ „ rolled bars 70,166 „ The average cohesive strength of rolled bars of York- shire iron was found by Messrs Napier to be 61,505 lb. per square-inch, this being the mean of twenty experiments on bars varying from ^^th inch diameter, up to 1 inch square. And the average strength of bars manufactured by nine different makers in different parts of the country, and pur- chased promiscuously in the market, was 59,276 lb. ; this being the mean of 1 10 experiments on bars varying trom ^Jth up to Ijth inch diameter, and it is most satisfactory to find that the experiments showed a remarkable unifor- mity of results. Mr Fairbairn of Manchester directed his attention, at a Experi- very early date, to the subject of iron for ship-building, ™^°** °" commencing his operations by the construction of various jjj. pair- small vessels for canal navigation. In 1830 and 1831 he built bairo. three iron steam-vessels for the Fortli and Clyde Canal Com- pany, and to be employed as co;isting traders to Grange- mouth. These vessels made the voyage from Liverpool to Glasgow, and showed such symptoms of strength as to in- duce Mr Fairbairn to enter more largely into the business. 80 SHIP-BUILDING. Materials used in Ship- Building. Witliin tlie next four years he constructed a vos^cl for tlie Lake of Zurich, and two river-steamers of about 170 tons for the navi'jation of tlie Huniher; and in 1836 lie com- menced the liuilihnt: of iron-ships atMilluall, on llieThames, in company with otiiers. With a view to the introihiction of correct principles into what was tlien a new line of manu- facture, he made some valuable experiments at Manchester in 1838, to test the strength of iron-pLitcs and of riveted joints. The results were communicated to the Philosophi- cal Society of that town, and have since been repiibli-,hed by him.' The results which he obtained were as ibilow :^ Cohesive strength of plktes. Species or Iron. Mean break- in(i Weigbt in the Direction of the ril>re, in tcma per eq. inch. Moan br^-ak- injj Weiclit across tiio Fibre, in tons per sq. iiicb. 2.5-770 22-760 27-490 26037 1 Jlean 2-1-205 26-7fi3 Derbyshire plates Shropshire plate.'? 21-680 22826 19-563 18-650 22-000 21010 21-350 20-553 The plates experimented <ipoii were as nearly ^ inch thick as could be obtained ; due allowance being made, in calculating the results, for any excess or deficiency in thick- ness in the ditfei-ent specimens. The section through A 13 was 2 inches wide. The plate having been made narrower there to ensure its breaking at that part. Plates were riveted on each side of the ends to stiffen them. The holes O (fig- 1-1) were bored through the TT "I h Fig.13. J. o o o ^ y O (>-®-0- O h c- VJ/ (J O < >, Messrs Na- pier's ex- perimeute. «_...._ B Fig. 14. ends at right angles to the plates, with their centres in a direct line along the centre line of the part AB; and the apparatus for tearing the plates asunder was attached by bolts passing through these holes. Iron-plates are supposed to be fibrous lengthwise, or in the direction in which they are rolleii ; but their cohesive strength ought to be nearly equal, whether the strain be ap- plied with the fibres or across it. This unilbrmity of strength is attained by the shingles, or piles from which the jilates are rolled, being composed of layers of bars carefully selected and laid at right angles to each other. When plates are very inferior in this respect, they may be sup- posed to have been manufactured from masses or blooms made up of irons and ores of different qualities, and these not sufficiently worked to amalgamate them properly. In testing iron-plates, it is therefore important to test their strength in both directions. The very extensive series of experiments on the strength of iroii-plates by Messrs Napier have fully corroborated the results previously obtained by Mr Fairbairn. The strengths per square inch of sections were as follow : — Yorkshire Plates. Lengthwise 65.433 lb. Crosswise 50,462 „ Mean strength 52,947 „ This result being obtained from 45 experiments upon plates varying in thickness from ^ inch up to f inch. Ordinary best, and best best boilcr-filatis, as manufac- tured by ten different makers in different parts of the country, and purchased promiscuously in the market — Lengthwise 60.2t2 lb. Croiisw-ise 45,986 „ Mean strength 48,114 „ This result being obtained from ninety-three experiments a|K)n plates varying iu thickness from |-inch up to j-iuch. Glasgow Ship Plates. Lengthwise 47.773 lb. Crosswise 44,355 „ Mean strength 46,064 „ This result being obtained from twelve experiments on plates, varying in thickness from -i^jy-inch up to J-inch. Messrs Napier made some experiments upon steel-plates also, with a view to test their value fiir the construction of light boats for river navigation, or for any portion of iron- ships generally. The results were as follow : — The Mersey Company^ s Steel-plates, for Ships. Per sq. in. or ^o^-tion. Lengthwise 101.450 lb. Crosswise 84,968 „ Mean strength 93,209 „ Steel-plates for Ships— Puddled Steel— " Jlild"— by the same makers. Lengthwise 71,532 lb. per sq. id. Crosswise not recorded. Slochairn Boiler-plates — Puddled .Steel. Per sq. in. of section. Lengthwise 96,320 lb, Cros,«wise 73,699 „ Mean strength 85,010 „ Homogeneous Metal. Per flq. in. of si-ction. Lengthwise 96,280 lb. Crosswise 97,150 „ Mean strength 96,715 „ Same Metal — Second Quality. Per eq. in. of section. Lengthwise 72,408 lb. Crosswise 73,580 „ Mean strength 72,994 „ The portions of the plates tested by Messrs Napier and Sons were made of a similar form to those tested by Mr Fairbairn. As the result of these experiments, it may fairly be assumed, that iron-plates of good average quality should stand a strain of 56,000 lb., or 21 tons, as their breaking weight per square inch of section. The results from the Yorkshire plates have been kept separate, because their quality and their price are such as to preclude their general use in ship-building. In boiler- making they are only used for furnaces, and those parts which require especial care. Some valuable experiments have been made for the pur- Force re- pose of ascertaining the relative resistance of wrought iron I'l'red to to shearing in different thicknesses and proportions of w idth ^^^'^^ ""'' to thickness, by Mr Little at the works of Mr Eastwood, with P""*^'' "'"'^ a hydraulic shearing-press ; tliis plan of press affording the opportunity of measuring the force actually employed at the moment of cutting, by the pressure upon the hydraulic ram ; the results are published in the Transactio7isof the Institution ' Useful Information for Evjineert, London, Longman & Co., 18S6. SHIP-BUILDING. 81 faterials used in Ship- uildin?. of Mechanical Engineers. Tlie pressure was measured, as tlie most eligible method available, by hanging weights at the end of a long hand lever for working the force pumj), the dis- tance from the fiilcrnm to the pump being 3J inclies, and from weight to fulcrum 78 inches, or 24 to 1 ; the area of the ram being lll-J times that of the pumps, the total ratio of the actual pressure on the cutters to the load em- , ployed was 2682 times. All the experiments were made with hammered scrap iron of uniform quality, and the fol- lowing general results were obtained. Punching a 1 inch hole through \ inch and 1-inch bars required 36 and 69 tons respectively, or a mean of 22"5 tons per square inch of sectional area cut, as measured by the circumference of the bole multiplied by the thickness (ex- periments Nos. 1 and 2). Punching a hole 2 inches diameter through 4 inch, 1 inch, and l-J- inch bars succes- sively required 65, 132, and 186 tons respectively, giving a mean of 19'4 tons per square inch of the sectional area cut, or 14 per cent, less in punching the 2-inch holes than in the 1-inch holes (Nos. 3 to 6). TABLE. Experimenh on P unching. ^i Sectional Ai-ea Cut. C 1.. Pressure on punch. d 'H E S Thickness n Tons Remarks. iSo and Circum- ference, Area. 1 2G82 times load. Total. per in. of area cut. Ins. Ina Ins. .Sq.Ins. Lbs. Lbs. Tons. Tons. 1 1 0-51 X 3-14 l-(iO 2H-9 80IH2 35 -S 2^-4 \ 22-5 mean 2 1 0-98 X 3-14 3-08 57 9 1552SS 69-3 22-6 s 2 0-52 X 6-28 3-27 49-9 133832 .59-7 lS-3 \ 4 '2 0-57 X 6-28 3-.'i8 ."iS-W 157970 70-5 19-7 V19-4 nicau .5 2 l-0fcix6-28 6 -(it) 1109 2:17434 1.32-8 19-9 6 2 l-52x6-2S 9-55 155-9 418124 lStJ-7 19-5 j Experiments on Shearing. ■^ Direc- Sectional .\rea Cut Pressure on cutters. tion 3 . of = s Tons Remarks. A 6. Shear- Thickness 2G82 perm. M mg. and Area. times Total. of area Breadth. .-) load. cut. Ins. Ins. Sq.Ins. Lbs. Lbs. Tons. Tons. 7 Flat 0-,50x3-00 1-50 27-9 74S28 ,33-4 22-3 1 22-7 mean | 8 Eilse 0-50x300 1-50 28-9 77510 34-6 23-1 9 Fiat 100x3-00 3-00 57-9 155288 69-2 23-1 V 21 -5 mean % 10 Edge 100x300 3 00 .56-9 152606 68-1 22-7 11 Flat 1-00x3-02 3-02 49-9 133832 .59-7 19-8 12 Edge 1-00x3 02 3-02 51 -9 139196 62-1 20-6 ) 1 13 Edge 180x5-00 10-20 175-9 471764 210.6 20-6 Flanged tjTe. (£ 14 Flat 0-56x3-00 1-68 17-7 47471 21-2 12-6 ( °^ 15 Edge'0-56x3-00 1-68 27-7 74291 33-2 19-7 1(5 Flat !0-90x 3.37 3-03 22-9 61418 27-4 9-0 rH 17 Edge 0-87x3-32 2-89 47-9 128468 .'i7-4 19-8 IS i Flat 11-06x3-02 3-20 41-9 112376 .50-2 15-7 1 P 19 i Edge 1-06x3-02 3-20 56-4 151265 67-5 21-1 20 I'lat l-52x3-03 4-61 69-9 187472 83-7 18-2 } 1 21 Edge 1-53x3-03 4-64 77-9 208928 93-3 20-1 22 Flat 1-39x4-50 6-25 74-9 200882 89-7 14-3 J" » 23 Edge 1-38x4-50 6-21 92-9 249158 111-2 17-9 24 Flat 1-73x5-30 917 127.9 34302S 1.53-1 16-7 a. 25 Edge 1-73x5-30 9-17 172-9 46371S 207 22-6 26 Flat 1-56x6-00 9-36 116-9 31.3526 140 15-0 27 Edge 1-56x0-00 9.36 143-9 385940 172-3 18-4 28 Sqre. 3-10 x 3-10 9-61 137-9 369848165-1 17.2 Hammered Iron. 29 Sqre. 3-10x3-10 9-61 129-9 348392 155-5 16-2 Rolled Iron. 30 Flat 1-80x5-00 10-20 82-9 2223381 99-3 9-7 Flanged tvre. 31 Edge 1-80x5-00 10-20 154-9 415442185-5 18-2 iFlanged tvre. 32 Edge 1-70x5-25 10-57 149-9 402032jl79-5 17-0 .Fliinged tyre. Shearing flat bars was tried with sections 3 inches by \ Material inch and 3 inches by 1 inch ; and the results gave a mean ^^^^, '" of 22'7 and 21-o tons per square inch of sectional area cut, t,^!'!!'" the difference being inconsiderable between the two direc- y j tions of shearing, flatways or edgeways (Nos. 7 to 12). ' In comparing the shearing of these sections, 3 inches ^"f*^* "' by J- inch and 3 inches by 1 inch, with the punching of ag^earand 1-inch hole through ^ inch and 1 inch bars, the result is punch iron nearly the same in both cases with the h inch thickness, contioued. and with the 1 inch thickness about 5 per cent, less in ~ shearing than in punching, the area of section cut thiough being about the same in the cases of shearing as in those of pimching. In the above experiments of shearing, cutters with parallel edges were used ; but when the ordinary cutters with edges inclined to one another at an angle of 1 in 8 were emploved, the force required in shearing was dimini^hed, and consider- ably so in the case of the thinner sections when sheared flatways ; and as bars are usually sheared flatways, a decided advantage is shown in favour of inclined over parallel cutters. The force in tons per square inch of section cut with the bars Flatways. Tons. 3 X 1^ incli was 18-2 44 X 1| 14-3 3x1 15-7 5^ X 1| 16-7 6 X 14 Edgeways Tons. and 20-1 or 10 per cent, less flatways. 17-9 20 21-1 26 22-6 26 15-0 18-4 18 A trial was also made of the force required to shear some hard railway tyres 1^^ inch thick, and the result was 185 tons total edgeways, and 99 tons flatways (Nos. 30 and 31). A 3-inch square bar of rolled iron was also tried, and the force required was 155 tons total, against a total of 165 tons required for a hammered bar of the same section (Nos. 28 and 29). Diawings of the fracture of the bars in the experiments Nos. 20 and 21, 26 and 27, are given in the original paper. In the accompanying Table are given the details of the several experiments. Mr E. Jones had also made a set of experiments on the foice required for punching different sized holes in different thicknesses of plates, up to 1 inch diameter and 1 inch thickness ; the force was applied by means of dead weights with a pair of levers giving a total leverage of 60 to \, so that 1 cwt. in the scale gave a pressure of 3 tons on the punch ; the weights were added gradually by a few lbs. at a time until the hole was pimched. The following results were obtained, which appeared to corroborate generally the experiments given in the paper with larger sizes : — Diametci Thickness Sectional area Total pressure I'rciwurc per of hole. of plate. cut through. on punch. square mch of area cut. Inch. Inch. Sq. Ins. Tons. Tons. 0-250 0-437 0344 8-384 24-4 0-500 0-G25 0-982 26-078 27-2 0-750 0-G25 1-472 34-708 23-6 0-875 0-875 2-405 55-500 23-1 1-000 1-000 3142 77-170 24-6 The strength oi' rivets and of riveted joints, to connect Strength o( plates in various ways, was made the subject of experiment rivets aud by Mr Fairbairn in 1838 ; and as no subsequent expcri- f'veted ments appear to have thrown any further light upon the J°'°'^' subject in its bearing upon ship-building, the results obtained at that time will be given. The experiments were conducted in the same manner as those to test the strength of plates. 82 SIIIP-BUILDING. Materials used in Ship- lluildin'7. In liip-joints with a single line of rivets, the edges are made to lap over each other, tlius — Strength of rivets and rivetied joints, con- tinued. Fig. 16. When the strain is applied to a joint of this kind, the edges of the jilates turn up, and the plates tliemselves bend till they take the direct line of the strain, as indicated by the dotted line, a b. a.. 3 Fig. 16. Plates may also be united by bringing their edges to- gether to make a flush or butt-joint, ()utting an extra piece of plate behind the joint to whicli botii |)lates are riveted by single lines of rivets, thus — ';:n\k:</. .'6. Fir.n. This joint also gives way by the plates bending and taking the line of strain ; and no material difference of strength was found between this and the preceding joint. Trcdgold lias shown that when tlie line of strain is not in the axis or centre of the material, the strength decreases with the divergence in a much more rapid ratio than the direct distance of the divergence. It is therefore evident that this evil is greatest in thick plates, and that the strength of thick plates will not be proportioned to that of thin plates, though the sections of each tiirough the rivet-holes may bear tiie same relative proportion to the sections through the solid plates.' Double-riveted lap-joints are those in which a second line of rivets is introduced. The edges are overlapped as in single riveting, but to a greater breadth, thus — Fig. 18: The line of rivets nearest the edge keeps it from rising. In this joint the strength is much increased, but the plates bend as before, and take the line of tension wiien a direct tensile strain is brought upon them. The edges may also be brought together flush, with a broader piece of plate behind the joints, and a double line of rivets, thus — In this joint, also, the plates bend before they give way, and the strength is similar to that of ilie preceding double- riveted joint. The relative strength of these joints, in comparison with the strength of the body of the plate, was found to be as follow : — Materials used in 8hi|>- Building. Strength of the plate 100 Douhie-rivctcd joints 70 Single do. do 56 Countersinking the rivets, or making the heads flush on the outside, was not found to make any a|)preciabie diffe- ^""^z^"' rence of strength. Strength o The strongest mode of jointing plates is by bringing a •■'*«"• ""il lapping piece of plate upon each side, and passing tlie ?''ye">:<l rivets on each side of tlie joint through tlie three tliiik-''?'""'i*°°' nesses. In the experiments of 1838 upon this joint, double- '°'" * riveting only was tested ; but in subsequent experiments suggested by Mr Fairbairn, and carried out in tlie con- struction of tiie Menai tubular bridge, four lines of rivets were used, thus — "" '^ '^ '^ '^ '^ "'^ h Fig. 20. ^o o o o c T o o o o o o ( O o o iO O y O O \ o o io o O ( Fig. 21. Tn this joint a tensile strain is directly in the line of the joint, and the material is therefore in the best position for exerting its full strength. This joint, however, is not applicable to the sheathing of ships, on account of the necessity of keeping the exterior surface flush and smooth. But no other joint should be used in uniting plates in the construction of beams, or other parts, in the interior of a sliip. \ complete system of two thicknesses of plates, for the whole surface of the plating, has been occasionally used, so as to break joint where a large flat surface of great strength has been desired, with a lapping piece on each joint, thus — Fig. yj. The evil, however, which results from the line of the strain not being in the centre line of the joint affects this system of double plating, and the full strength attainable from the material is not secured. The only advantage gained is, that in the event of one plate being defective, a partial re- medy will thus be supplied by the second [ilate. By the same series of experiments in 1838, the diameter and distance apart of the rivets, and the proper amount of la|) fiir plates, up to f inch thick, were very accurately as- certained, and the following table was formed: — Table exhihidng the strongest forms and best proportioTuPToper in of Riveted Joints, as deduced from Experiments arac/'""-''^'' of aclmtl Practice. ''""^ ""^ distunces between them. Thickness of Plates in inches. Diameter of Kivets in inches. Length of K. vols from the Head in inches. Distance of Kivels from Centre to Centre in inches. Quantity of lap in Sinirle Joints in inches. (Inantity of lap in Double Riveted Joints in inches. ■19 = -,»j •25 = ,V ■31 = A ■38 = A •50= A •63 = U ■75 = iJ 38 > ■50 L •63 f- ■75 > •811 ■94 \ 1-5 113 J •88\ 113 1-38 1 63 45 225 2 75 3^25/ 125 „ 1-50 1 ^ 1-75 ) S 200 ^ 2^50 4 300 J 125 \ 1-50 U r88j 2'(10 5-5 2^25 \ 275 l4^5 3^25j For the double-ri- veted joint add §d« of the depth of the single lap. This subject has also been ably investigated in a pamphlet and report on W. Bertram's patent welding process, by Mr Renton, C.E. SHIP-BUILDING. The fiRuros 2, 1-5, 4-5, 6, 5, &c., in the preceding table, are multipliers tiir tlie diameter, lenjith, and distance of rivets, also for tlie quantity of lap allowed for the single and double joints. These muhipliers may be considered as proportionals of the thicknesses of plates to the diameter, length, distance of rivets, &c. For example, suppose we take I plates, and require the proportionate parts of the strongest form of joint, it will be •375x2 = '"SO diameter of rivet, J inch. •375 X 4J =: 1-688 lengtli of rivets, IJ inch. •375 X 5 =: 1-875 distance between rivets, Ij inches. •375 X SJ = 2-063 quantity of lap, 2-^ inches. •375 X 8 := 3-438 quantity of lap, for double joints, 3J inch. In practice plates and rivets of certain thicknesses and diameters only are obtainable in the market, and for these the table would stand thus : — Thickness of Plates in inches. Diameter of Rivets in incht'S. Length of Rivets from tbe Ht'ads in inches. Distance of Kivets from Centre to Centre in inches. Quantity of lap in Single Joint in inches. Quantity of lap in Double- Riveted Joints in inches. i S 4 f 1 w i f « if if n T n n If 2i 2J 3i li H If li 2 2i 3 li li n 2iV 2i 2} 3i 2,V 2J 3i 3J 3i 4iV 5A By using these proportions, it will be found that the rivets will not be sheared in two by the plates when a strain is brought on them, and tiiat efficient joints will be made for all vessels wliich require to be steam or water tight. When this is not required, soiue additional strength may be ob- tained by enlarging the rivets and increasing the distance between them. lachine In forming the hull of a ship, the riveting is at present iveting. entirelv performed by manual labour; but in the construc- tion of beams, or any such se[)arate parts, considerable advantage, both as regards strength and economy, will be ol)tained by riveting them by machine. The rivet by the latter process is more compressed, and thus made to fill the hole ; and the operation being completed while the rivet is still hot, its shrinkage in cooling draws the plates together. This adds to the strength of the joint by caus- ing friction, when a strain is applied to pull it asunder. The extent, however, of the advantage so obtained is neces- sarily very variable, depending on the amount of compres- sion by the machine in forming the head of the rivet, and on tlie temperature of the rivet when closed, Mr Fairbairn does not attach much importance to it, and as it certainly does not exist to any important extent in iiand-riveted work, it is safest to disregard it when any calculations of strength are being made, tiilidity of The liability of plate to yield by flexure depends upon ilate. its thickness, and upon the amount of lateral support given to it, compared with the area of its surface. To give to different plates an equal capability to resist flexure, the unsupported lengths sliould vary as the thickness.^ Vansverse The transverse strength of iron equally requires the trength of attention of the iron ship-builder. It is necessary to bear ron. constantly in mind, that in supporting a load, or resisting a transverse strain, the upper portion of a beam, wliich is supported at botii ends, is subjected to compression, while the lower portion is in a state of tension. The line be- tween the particles exposed to these opposite forces is called the neutral axis ; but its position and direction, whether straight or curved, has not yet been definitely or mathematically determined. If the material of which a beam is composed be better able to resist compression tlian extension, it is evident that there may be less material in the upper than in the lower portion of the beam. The power to resist fracture is therefore looked upon as mainly concentrated in these portions; and wliile the duty of the centre portion, called the plate or the web of the beam, has not yet been brought clearly under the rigid laws of mathematics, its chief duty may be said to be to keej) the top and bottom fianches separate from each other, and in their relative positions. The power of iron to resist compression is generally taken at 3 1 J tons, or 70,000 lb. per square inch. It is one of tiie advantages of iron over wood that it can be made of any form, and that the foregoing prin- ciples, in as far as they are known, can be brought into actitm. The accompanying sections may be taken as represent- ing the sections of tlie beams in general use at the present day. 83 Materials U5ed in Ship- Building. Power to resist cora- pressiun. Advan- tageous Fig. 26. Fig. 27. The proper proportions of iron-beams, and the consequent Diff rent rules for their strengths, have been much discussed. forms of Box-girders (Fig^ 27), were used for paddle beams ofJ'™.™«»"'l vessels at Millwall liy RIessrs Fairbairn and Co. as early as^^^.^^ jjj_ 1840. They are stronger than any of the forms of plate- beams given above ; and for long spans on board ship, plate- beams should not be used on account of their want of lateral stiffness, unless they are supported by trimmers or fore and aft carlines. The ordinary rule for the strength of iron-beams, as given by Mr Fairbairn, is applicable to all the foregoing forms, the number 80 being u?ed as the constant to represent the strength of the box-beam, and 75 that of the plate-beam. Let W represent the breaking weight in tons, a the area of the bottom flanche, d the depth of the beam, and I the length of the beam, C representing the con- stant as usual. Then the area of the bottom flanche nuiltiplied by the depth of the beam, and by 80 tor a box- beam, and 7o for a plate-bcam, and the product divided by the length of the beam (all these dimensions being * See Proceedings C. E Inst., vol. xv., p. 176 ; and the subject will be found further investigated, vols, xi., xiv., and xvi. 84 SHIP-BUILDING. Materials (alien in indies), will give the breaking-weight in tons — ■ used in Ship- or BuilJing. \v= a d c It will be observed that the top flnnche is not an element f.'. -in this formula. Its correctness, tlicrefore, is dependent' ! „ i^„~. upon the maintenance of certain relative and definite pro- irnn beams, ' . . i • . !• i i i ' r- continued, portions in the parts, and it is not applicable to beams ot indefinite forms or proportions. For beams of the ordinary length used in ships, the top and bottom flanclies may bb made of equal sectional area, and the greater tlie length of the beam the greater sliould be the cmnparativc sectional area given to the top flange, to prevent its buckling or bending. It has been argued that one-half the area of the centre web or plate should be added to the sectional areas of the top and bottom flanclies, so as to include its strength as one of the elements of the (orniula, and a new formula be then deduced, but the rule, as given, is more simple, and may be relied upon. From the nature of the material it is considered that wrought-iron beams may be loaded up to one-half of their breaking weight, though with cast-iron this limit is not per- mitted to exceed one-third. The following arc given as examples of the rule : — (1.) What is the breaking weight of a box-beam 60 feet long, between the supports IS inches deep, and the area of the section of the bottom flanche being 16 inches ? W = 16 X 18x80 720 = 32 tons. (2.) What is the breaking weight of a plate-beam .30 feet long, between the supports 10 inches deep, and the area of the section of the bottom flanche being 5 inches? W = 5 X 10 X 75 360 = 10-41 tons. Power of •wrought- iron to re sist a crushing force. iron columns. The crushing force which malleable iron is capable of sustaining has been stated to be 70,000 lb. per square inch, but it could only sustain this great load when the force applied is so truly in the axis of the material, and when the specimen under pressure is so short that no de- flection is produced. Wrought-iron, however, is very liable from its nature to give way by bending or buckling when the length bears too great a jiroportion to the area of the cross-section. This was previously mentioned when the relative sections of the area of the top flanclies of beams which are exposed to a crushing force were recommended to be increased. Ptrengthof It has been found by experiment that wrought-iron is wrought- crippled, and its power of resistance destroyed by a weight of 130,000 to 40,000 lb. per square inch, whenever the length is such as to permit of its bending. The load, therefore, which it may be considered safe to put upon it in practice mav be assumed at GOOO to 8000 lb. per square inch for columns of ordinary proportions. With this load the length of the column should not exceed ten times its diameter, and however short the column may be ni.ade, the load should never exceed 10,000 lb. per square inch of section. The strength of similar columns of wrought-iron, as before stated to be the case with wooden columns, varies as the squares of their lengths inversely. In .all columns it is most important that the pressure should be applied in the line of the axis of the material. By Hodgkinson's v.aluable experiments on the subject must be in of columns, it was found that the strength of a column line of axis rounded at both ends, in comparison with one whose ends were flat, was as one to three. This result no doubt arose mainly from the strain not being correctly conveyed and kept in the axis of the material. If the strain on a column be in any degree greater on one side than on the other, this side will be unduly compressed, while the other Pressure of material. side will be extended, and fracture or crippling will take Mnterinia |)lace with a very small proportion of the load which the ""^d '" column ought otherwise to have sustained. „®.''''.'' Dr Yoinig was the first to investigate this subject pro- >"" '"^j oerly, and his work may still be consulted with advanta'je by '' "" any one who is desirous of tiillowing up this inquiry. When treating of the strength of riveted joints, the iuiportanee of attending to the line of the strain, when the material was exposed to a tensile force, was dwelt ujion, and it is evi- dent, from what has now been said, that this is still more important when it is exposed to a crushing force. In the latter case, if the column be in the least digree curved, the strain increases the deflection, whereas in the former any curvature will be diminished, the tendency being to pull the material into a straight line. Hence, it is of the greatest importance to place columns directly under the weight which they snp|)ort, and to avoid Unequal strains on the sides, whether they be round or square. With wrought-iron columns it is also very evi- .strenctli of dent, that by using a hollow column much greater strength wrouj;lit- is obtained from the same quantity of metal, great si ifi- iron tubes ness being obtained by the increased dimensions. Hollow °^ columns, wrought-iron tubes, such as those used by engineers in boiler-making, may therefore be used with great advantage. They may be rolled to almost any diameter and length likely to be required in shipbuilding. No experiments appear yet to have been made on the power of such tubes to resist a direct crushing force, but the following experi- ments were lately made at Portsmouth Dockyard, by Mr Lynn of that yard, to test their power of resistance when used at an angle, as a pair of sheer-legs, to raise screw- propellers on board ships. The tubes were \ inch thick, 4 inches external diameter, and 12 feet long. They were fitted with wrought-iron ends, the lower ends being pre- pared to rest on a step on the deck, and the upper ends had a double and single eye to fit into each other, and re- ceive a pin for the shackle to carry the weight. The length was thus increased, from step to eye, to J 2 feet 5 inches. At 9 feet spread at the base, one of the tubes which had been annealed in the fire for the purpose of straighten- ing it, as it was slightly curved when received from the maker, deflected -j inch when the weight reached 26 tons. On removal of the weight it returned fth inch, leaving a permanent set of fth inch. At 7 feet spread at the base, the same tube yielded w hen the weight reached 29i tons, the other tube remaining uninjured. i'he durability of iron is entirely dependent upon the Durabilitj state in w hich its surface is kept. Under ordinary circuni- "f "on stances there is probably no better preservative than good paint; but in the interior of iron-vessels it tends materially to their preservation, if the snrfiice be coated with asphalte, or cement sufficiently thickly to cover tli« heads of the rivets. In some cases it is even desirable, especially in the sharp run of a shi|) fore and aft, in the position of the dead-wood in a wooden vessel, to fill up the entire spaces between the fiames, and f()rm a flush surface. The ex- terior also of an iron-vessel is easily maintained in good condition by frequent painting. Below the water-line, where the surface cannot be reached by heeling the ship to a moderate degree, the iron is not apt to corrode. There is no chemical action by sea-water upon malleable iron, and there is not sufficient oxygen present below the surface to induce oxidation. In every instance in which an iron- vessel has been rapidly destroyed, it has been by corrosion on the interior surface. Great injury has in some cases re- sulted from acids leaking from certain cargoes, such as sugar, and also in parts where the leakage of brine from provision casks has been allowed to lie upon the plates. For gun-boats or vessels, which it may be desired to lay lip or preserve fiir any lengthened time, iron is peculiarly ai'apted, as, under such circumstances, the whole of the SHIP-BUILDING. 85 Different sections of a ship not equally supported by the ■water. s\irfaces can always be attended to both externally and in- ternally. Malleable- iron, when submerged in salt-water, rapidly becomes foul by sea-weed and sliell-fii-h adhering to its surface ; but these do not cause decay ; they may rather be said to form a coating to protect the iron from decay of any kind as long as it is submerged. The decay of iron externally on ships' bottoms has, how- ever, been observed to take place in the neighbourhood of copper-pipes. This is caused by a galvanic action which takes place between the copper and the iron, tending to the preservation of the former and the destruction of the latter, on the sameprincijileas that proposed to be brought into action by the use of Sir Huni])hrey Davy's protectors for the preservation of copper sheathing. A layer of zinc at the point of junction, to separate the copper from the iron, will protect the iron, but as the zinc will then be raj)idly eaten away, care must be taken that it is not used in such a manner that a leak would ensue in consequence. The ready fouling of iron in sea-water is still a great drawback to its use. Many applications for this purjiose have been proposed, but none seem yet to have been so thoroughly successful as to require any special mention as deserving of any decided preference. The weight of a cubic foot of wrought-iron is 480 lb. The weight of a square foot of plate |th inch thick, is therefore 10 lb., and this gives a ready and easily remem- bered standard for calculating the weight of any surfaces of iron of different thicknesses. PRACnCAI, BUILDING. There is, perhaps, no structure exposed to a greater variety of strains tlian a ship, and none in which greater risks of life and property are incurred. A consideration of the disturbing forces in action, either to injure or destroy the several combinations embraced in its structure, is therefore most important. And a thorough knowledge of their action is necessary to a practical builder to enable him to guard against them, in whatever form they may present themselves, and to dis])ose and arrange the materials at his command, accordingly, in the most judi- cious manner. Some of these forces are always in action vihether the ship be at rest or in motion. She may be at rest floating in still water, and will be at rest if cast on shore ; and « hen there, — she may he resting on her keel as a continuous bearing, with a support from a portion of her side, — she may be supported in the niiddle"only, with both ends for a greater or less length of her body left wholly unsupported, — or she may be resting on the ends with the miildle unsupported, — or under any other modifi- cation of these circumstances; and under all these the strains will vary in their direction and in their intensity. If the ship be in motion, the same disturbing forces may still be in action, with others in addition, which are pro- duced by, and belong only to, a state of motion. AVhen a ship is at rest in still water, it has been before explained, that the upward pressure of the water upon its boiiy is equal to the total weight of the ship, but it does not neces- sarily follow that the weight of every portion of the vessel will be equal to the upward pressure of that portion of the water directly beneath it, and acting ujion it ; on the con- trary, the shape of the body is such that their weights and pressures are very unequal. If the vessel be sup[)osed to be divided into a number of lamina; of equal thickness, and all perpendicular to the vertical longitiulinal section, it is evident that the after laminae comjirised in the overhanging stern above water, and the fore lamina; comprised in the projecting head also above water, earniot be supported by any upward pressure from the fluid, but their weight umst be wholly sustained by their connection with the supported p.arts of the ship. Practical The laminae towards each extremity immediatelycontiguous Building, to these can evidently derive only a very small portion of ^^"v/^^ their support from the water, whilst toward the middle of the ship's length a greater proportionate bulk is immersed, and the upward pressure of the water is increased. At some certain station from the middle of the length in Certain each body, fore and aft, the upward pressure will therefore s^c"""* be equal to the weight of the superincumbent lamirise, and ^"PI"'" all the lamina; composing that portion of the body between these two stations will be subjected to an excess of pres- sure above their weight, tending to force them upward ; which upward pressure will be the greatest at the lamins having the greatest transverse area of section. Now, as the total pressure upward is equal to the total weight of the vessel, this excess of upward pressure to which the midship part of the body is subjected, must be equal to the excess of weight over the upward pressure in the parts of the vessel before and abaft those laminae at which the pressure and weight have been supposed to be in equilibrio. A ship, when at sea, is subjected to severer strains than Strensth when floating at rest, and it cast on shore it may be sub- must be jected to still greater strains. Its strength, therefore, as a ^qual fabric, should be considered with reference to the severest ..,.„.„.► trial of strength which may be required of it under any strjing. circumstances. A ship floating at rest under the view just taken of the relative displacement of different portions of the body, if A ship at the weights on board are not distributed so that the difierent ''^*' """y laminae may be supported by the upward pressure beneath ^,''° I them as equally as possible, may be supposed to be in the ^ beam, position of a beam supported at two points in its length at some distance from the centre, and with an excess of weight at each extremity. At sea it would be exposed to the same strain; and if also when supported on two waves, w hose crests were so far apart that *' ***• they left the centre and ends couifiaratively imsupported, the degree of this strain would be much increased. The strain would be still more severe if the vessel got aground, and rested on two isolated points situated in the supposed positions in her length. Under these circumstances, however, the strain would depend upon w hether the weights in the middle or in the ends preponderated. The latter is the usual case ; and then the whole of the upper portion of the vessel will be subjected to a tensile strain from the tendency of the ends to droop. The more these two points of support approach each other, or if they come so near each other that the vessel may be looked upon as supported on one wave, or on one point only in the middle of her length, the greater will be the tensile strain on the upper portion, and the crushing strain on the lower portion of the fabric of the ship. The importance, therefore, of so forming the deck and Impnrtance the iqijierworks that they may afford an efficient tie is °f "I'l""'' apparent; and it is to be feared that this has been too much ^.^^ neglected, especially in many iron-ships. If a vessel be weak in this respect, and touch the ground in the middle of lier length, the consequences will neces- sarily be most disastrous, as she will open at perhaps more than one place, and her sides will tear dow n instantaneously after the tie of the deck and upperworks is gone. These results appear to accord with the accounts given of the manner in which several iron-vessels have broken up on their being cast ashore. A vessel whose weights and displacements are so dis- Hocrging posed as to render her subject to a strain of this kind be- f"** "'^^ yond w hat the strength of her upperw orks will enable her '"°" to bear, will assume a curved form. The centre is curved upwards by the excess of the pres- sure beneath it, and the euds drop, producing what is called 86 SIIIP-BUILDING. Upper works must be stronj; to resist tun- (ion : rr»ctlcal " hngijinj;." The main remedy for tlicse evils, as before BuilJing. ftatcii, is in tlie strength of tlie deck and iiii|)erw<)rks, and V^.*^,-.-' tluir power to resist a tensile strain. There is seldom a want of snfficient strenj;th in the lower parts of the vessel to resist the ^■r^^^hin;.r or compressing force to which it is subjected. The decks of vessels should not, therefore, he too ranch cut up by broad hatchways; and care should be taken to preserve entire as many strakus of the deck as possible. The tensile strength of iron can be brought to bear most beneficially in this respect, and some conliimous strakes of it laid upon the toi)s of the beams and below the (leck-plank would add materially to the strength of all ships. Dick-planking has been sometimes laid diagonally at an angle across a ship, but it will be evident, from these re- marks, that the value of the longitudinal tie is thereby much lessened, and there is no sufficient corresponding benefit of any other kind to justify the whole deck being laid in this manner. Too much Great sheer, or rising of the deck, fore and aft, is ob- Bheer ob- jectionable, from its lessening the strength of the longitu- J*"'° duial tie, though it is much practised, as it gives a lively appearance to a ship, and hides the defects of hogging if it should occur. In the whole of the upper parts of a ship, as well as in the deck, every means should be taken to increase the power of resisting tension. In a wooden ship the upper part of the frame shoidd be cliain-holted wherever the con- tinuous range of bolts can be placed so as not to interfere with the in and out fastenings; and the shifts of the different wales, and other parts, which act as longitudinal ties, should be carefully attended to. The waterway-planks and shelf- pieces are also most important, and their continuity should be maintained throughout the length of the vessel, w ith as little diminution of strength as possible, at the junction of the different lengths, particular- In iron-vessels the parts corresponding to these are par- ly in iroQ ticniarly important, as the plating exposes a very weak edge vessels. ^j jj^^ j^^p^ ^^i^^j j^ \[^\)\^. t,, be torn down if this edge be not Well guarded and supported. To enable the lower part of the ship to resist the compression to which it is subject, the spaces between the frames in the best built wooden vessels are filled in solid, so as to make, as far as possible, an incompressible mass. The various abutments of this part of the body should be as closely fayed or fitted as pos- sible. In iron-vessels, as the spaces between the frames cannot be filled in solid, the keel.-ons should be of great strength. The power of wrought-iron to resist compression, « hen it is prevented from buckling, is here of great value, as the fastening of the keelson to every frame as it passes gives stiffness and rigidity to it, and consequently great power to resist compression. Though these are the strains to which a ship is most likely to be exposed, it by no means follows that there are , .no circumstances under whicli strains of the directly oppo- l^ site tendency, when pitching and tossing, or otherwise, may be brought by recoil to act upon the parts. The weights themselves in the centre of the ship may be so great that they may have a tendency to give a hollow cur- vature to the form, and it is therefore equally necessary to guard against this evil. When this occurs, the vessel is Bagging, technically said to be " sagged," in distinction to the con- trary or opposite change of form by being hogged. The weight of machinery in a steam-vessel, or the weight or undue setting up of the main-mast, will sometimes produce sagging. The introduction of additional keelsons tended to lessen this evd, by giving great additional strength to the bottom, enabling it to resist extension, to which, under such circumstances, it became liable ; and as the strain upon the deck and uppernorks becomes changed at the same time, they are then called upon to resist compression. In iron-vessels, the waterway- planks and shelf-pieces are Opposite strains lUOSC al:jO be atteD again, in this case, very important to aid in resisting this Prarfieal strain. The deck-planks may become shortened bv the Buildinf;. del k assuming a curved form in the middle of the length ^"^"v^^ of the ship, the beams yiehiing anil working with them ; and a crushing strain is then brought to bear upon the plating of the topsides, which they are not calculated to sustain. Some light flat-bottomed river-steamers of iron with very full lines forward and aft, have given way from this cause. The best practical lesson upon the subject, and the most direct proof of the want of strength of iron- vessels at the top;>ides, if constructed without additional strengthening there, was given by the Nemesis when her topsides opened, as so well described by Captain Hall in his account of her voyage to India, and when he so judi- ciously strengthened her by attaching balks of timber longi- tudinally to the two sides. A corres|xmdiiig action to that described as hogging A vessel takes place in relation to the breadth of the vessel, but """y "'""" more particularly in the case of men-of-war, on account of '"'.'" the weight of the ordnance concentrated along the sides. ^^^■ The central portion of the body is subjected to an undue upward pressure, while the outer portions are strongly acted upon by the weight there tending to depress and immerse them. The effects of this action may be greatly modified by the form of the vessel ; longitmlinally, it pro- duces the upward curvature previously referred to ; and transversely, it tends to separation of the sides, except in three-decked or very lofty ships, in which, if the tumbling home be very great, the tendency is to produce a separa- tion at the main breadth and below it, and a collapsing of the sides above it. Another force tending to alter the form of a vessel Horizontal arises from the horizontal pressure of the water on the sides prossure of of the vessel. The sides are compressed or forced together, '''6 water. and the tendency produced is to add to the curvature of the deck amidshi()s, and increase the hogging both longi- tudinally and transversely. When a ship is in motion, if the surface of the sea be Other very uneven, so that her passage will be over the waves, forces the sup|)orts become very variable, and the opposing ^'"'^'' 'f' forces of upward pressure and gravitation w ill have a ten feet a ship dency to produce corresponding changes in the form of the body; and if the motion of the ship be violent, and thus produce any sudden shuck or jerk, the strain upon the ma- terials and upon the fastenings will become immeasurably increased. Wlien the ship is on a wind, the lee-side is subjected to Force of a series of shocks from the waves, the violence of w Inch the waves, may be imagined from the effects they sometimes produce in destroying the bulwarks, tearing away the channels, &c. The lee-side is also subjected to an excess of hydro- static [iressure over that ujion the weather side, resulting from the accumulation of the waves as they rise against the obstruction offered by it to their free passage. These forces tend in part to produce lateral curvature. When in this inclined position, the forces which tend to produce hogging when she is upright also contributes to produce this lateral curvature. By experiments made on her Ma- jesty's ship Genoa, in 1823, by Mr Moorsom, a member of the late school of naval architecture, he ascertained that this lateral curvature amounted to 1^ inch on each tack, making an alteration of form to the extent of 3 inches from being on one tack to being on the other. The strain from the tension of the rigging on the wea- Tension of ther side when the ship is much inclined is so great as the rigging frequently to cause working in the topsides, and sometimes even to break the timbers on which the channels are placed. Additional strength ought therefore to be given to the sides of the ship at this place; and in order to keep them apart, the beams ought to be increased in strength in coi:ij)arison with the beams at any other part of the ship. SHIP-BUILDING. 87 Practical It Iias been proposed to introduce tic-rods from the chan- Buililing. nels to the step of the mast, so as to render each mast and '^""V^^ its supports a combination of struts and ties with tiie strains seH'-contained. This may be explained by the an- nexed figure. Let AB represent the deck-beam, or beams of the ship at the channels, CD the mast, and AC and CB the shroiids. Now, if the ties AD and BD be introduced, it is evident that any additional strain brought upon AC or CB will be transferred to AD or BD, and resisted independently of any strength in the sides of the ship, so long as AB the beam, and CD the mast, are rigid and do not bend. By this system, also, any excessive strain is prevented from being brought upon the step of the mast at D, producing sagging, by setting up the rigging unduly. Though the ties AD and BD cannot conveniently be introduced in ships in direct lines, as shown in the woodcuts, the princi- ple proposed may yet be brought into play by curved ties of sufficient stiffness not to straighten under the tensile strain to which they will be exposed. General re- The foregoing are tile principal distm-bing forces to which narks on the fabric of a ship is subjected ; and it must be borne in disturbing ,iii„(( that some of these are in almost constant activity orces. jy destroy tiie connection between tiie several parts. Whenever any motion or working is produced by their operation between two parts, which ought to be united in a fixed or firm manner, the evil will soon increase, because the disruption of tlie close connection between these parts admits an increased momentum in their action on each otiier, and the destruction proceeds with an accelerated progression. This is soon followed by the admission of damp, and the unavoidable accimiulation of dirt, and these then generate fermentation and decay. To make a ship strong, therefore, is at the same time to make her durable, both in reference to the wear and tear of service and the decay of materials. It is evident from the Ibregoing re- marks, that the disturbing influences which cause " hoeg- Practical ing," commence their action at the moment of launching Building, the ship, and are thenceforward in constant operation. As "^"^v"^^ this curvature can only take place by the com|)ression of the materials composing the lower parts of the ship, and the extension of those composing the upper parts as more particularly explained when treating of the strength of beams, the im[)ortance of preparing these separate parts with an especial view to withstand the forces to which they are each to be subjected cannot be overrated by the prac- tical builder. The side of a ship is, however, in a some- what different position from the plate or web of an ordi- nary plate-beam, or the sides of a box-beam, on account of the horizontal pressure of the water against it ; and because in deep ships, with one or more intermediate decks, some of the strain is brought upon it in the middle of its depth. The position of the neutral axis or line between those [)ar- ticles exposed to a crushing and those exposed to a tensile strain, is therefore very difficult to determine ; but from a consideration of the circumstances just mentioned, it must be higher in a ship than theory would place it if the ship were considered in the light of an ordinary beam exposed to strains brought upon it in the ordinary way. The importance of the system of diagonal trussing and Diagonal bracing in ship-building appears to have been firstfully *■""'*'"?'" appreciated by Sir Robert Seppings, and the principle on * '"''*''=' "^ which it should be introduced to have been first explained strains'^ by him. It is obvious that if four pieces of timber bo put together, so as to form a square, or a rectangular parallelo- gram, with their ends coimected by a round pin only at each corner, they may assume the form of any other ()aral- lelogram whose sides are of the same length, but that in so doing the length of the two diagonal lines will be altered ; thus — In both of the annexed figures, the sides are of the same length, but the dia- gonal AC of fig. 29 is shortened intoac in fig. 30, and BD of fig. 29 is lengthened into bd in fig. 30. The intro- duction, therefore, of diagonals of a fixed or unalterabie length into any piece of frame- work will tend to prevent alteration of form, and it will be d^ perceived that the duty required of the two diagonals in resisting any change is dif- ferent, the one being required to resist extension, and the other to resist compression. One diagonal only is sometimes considered sufficient, but in this case care must be taken that the material of which it is composed, and the man- ner in which it is applied, be such that it may be fit to resist either extension or compression, if the (rame-work is liable to be alternately strained in either direction. In any piece of frame-work, however large, a straight wrought-iron bar is excellent as a tie, but as a strut it would be nearly useless on account of its liability to bend. Wrought-iron, however, is the material chiefly used in diagonal bracing ; and it may be used with propriety for both diagonals, wherever on account of lial)ility to a strain in both direc- tions two are used, because each in its turn will resist ex- tension, and that diagonal which is exposed to compres- sion will be protected from injury by the resistance of the other to extension. The siiies of a ship may be supposed to be divided into a numl)er of pieces of frame-work of imaginary outlines or dimensions. Those embraced in the midship body may be supposed liable to be strained in both directions ; but the upper portions of those composin-j Fig. 29. Fig. SO. 88 SIIIP-BUILDING. Practical Jluihlinj;. Diagonal tlUMing; not so ne- cessary in iron slilps. Compan- ion of iron with wood- en vessels. the fore and after bodies will be inclined to fall forward and ait rcspcclivily ; and it this tendency only is to be guarded against, the tics must be placed in difterent direc- tions in the two bodies sloping up from below from amid- ships forward and aft in paralKI lines, extension being the force wliich they will be called upon to resist. The system is not so much required in the bottom of a ship. In the dfcks diagonal trussing, placed diagonally across a ship, is advantageous as tending to prevent the ship working, by one side advancing or receding alternately with the other, and here the diagonals should be made to cross each other and lie in both directions. Diagonal trussing, as used by Sir Robert Seppings, w.is introduced into some ships as a series of frame-work along the centre of the ship, from pillar to pillar, from the keelson to the decks, and he arranged these on the principle of depending upon struts and not upon ties. Wrought-iron was then much less used than in the present day, and tim- ber forms an excellent material for a strut, weight for weight, in comparison with solid iron-bars, on account of its dimensions giving it stiffness. Struts are also conve- nient because tliey require comparatively little attention to the fastening of their ends. They abut against a surface, or into a corner, and their ends are easily prevented from shifting. With ties this is very different ; their ends must be made sufficiently secure to resist a strain equal to their whole strength. Before the introduction of this system, it was no uncom- mon thing to find ships hogged to the extent of from two to three lieet. An instance is quoted in Portsmouth dock- yard of an old ship, whose keel was curved upwards to tiie extent of two feet or more, and which was grounded in drv- dock on a set of blocks laid level. She straightened as she settled upon them, and diagonal trussing being then intro- duced, it was found to support her in a remarkable degree, whfn she was again floated. In this case the trussing was applied chiefly in midships, from pillar to pillar, from the keelson to the deck-beams. In iron-ships diagonals are not so much reqtiired on the sides of the ship, because the plating being a connected surface of equal or nearly equal strength in all directions, it is incapable of motion in its parts, and the line of any sup- posed diagonal is incapable of extension otherwise than by a force sufficient to tear the plating asunder. A general consideration of all the strains to which ships are subjected naturally leads to the question of selecting the material which is best adapted to resist them. In treating of the materials used in ship-building, especial reference was had to the various qualities possessed by each, which rendered them more or less valuable individually or collectively. It may perhaps be expected, that before leaving this part of the subject a more direct comparison shouKl be drawn than has yet been done between the rela- tive merits of wood and iron vessels, and that the points in their structure, in which they chiefly differ in strength and safety, should be pointed out. The advocates of either sys- tem will, no doubt, discover many errors and omissions in tlie remarks on this subject, which have been made, or which may now be made ; but they are given as the results of close observation and experience for a period of upwards of twenty-five years of practical connection with both classes of vessels. It may at the same time be stated with respect to this treatise, that while the increaseof steam-vessels, and the great alterations in the forms of slii|)s since the publi- cation of the previous edition of the EiicyclopcBdia Britan- nica, had to be considered, much of the alteration from the previous very able article on this subject, by the late Mr Creuze, is caused by the necessity of now treating of iron- ships equally w ith tliose of wood. An endeavour has been made to introduce as much information respecting iron- vessels, in addition to as full information respecting wooden vessels, as the assigned limits would permit ; and the sub- Practical stance of the article by Mr Creuze has been retained in B"il<li")?- many points, and free use has been made of it w herevcr '^"^"v""' desired, so as to form, as far as may be, a concise and con- secutive treatise. If strength alone were to be assumed as the basis of com- Basis of parison, w ithout reference to weight or cost, it would pro- compari- hably be conceded that a stronger vessel could l)e built of ""'■ iron than it would be possible to construct by any combi- nation of wood. It will, however, be more praeticallv use- ful to compare vessels of about equal weight, or equal cost or strength. An individvial frame in an iron-vessel is formed with ^""""• more continuity of strength throughout its length, than is the case in a wooden vessel, and greater opportunity is given of obtaining strength, no matter what may be the form of the body. By the variety of form into which iron can be rolled by the manufacturer, opportunity is also given to obtain the desired strength with less useless material. In the sheathing, whether internal or external, much Sheathing, greater difference exists. In wooden vessels the planks are laid side by side, and with few exceptions are not fastened or connected with each other ; indeed they are forced asunder by the caulking required to make the joints between them water-tight. Their only connection there- fore is by means of the fastenings which unite them to the frames. The plating of an iron-vessel, on the contrary, is made into one completely connected surface, and even if all the frames were removed, it would remain in shape, and would still form a vessel of great strength and stiffness. The fastenings, also, to the frames will not bear compari- son, the power of iron to resist shearing across being so much greater than that of treenails or copper-bolts. The power of iron-plates to resist a force similar to that Resistance to which they would be subjected if an iron-vessel took '" ''"'b'ing the ground on a hard bottom, with some projectinsr points . "* ' of rock or stones, was also experimented on by Mr Fair- bairn. The plates were placed upon a frame, leaving a space of 1 foot square, unsup|)orted, and on the centre of this a bar of iron, 3 inches diameter, with its end rounded, was brought to bear. Plate ^ inch thick was burst with a force of 1G,7"9 lb., and a plate \ inch thick, bore a strain of 37,723. The plate of double the thickness, therefore, bears more than double the pressure. The power of lira- ^y t'^ter- her to bear a similar strain was tested at the same time. Oak planks, 3 inches thick, were burst with a force of 17,933 lb., or only a little more than was required to burst the same surface of a plate ^ inch thick. Oak [)lanks, of H inch thick, were burst with 4406 lb. A plank of double the thickness, therefore, bore much more than double the pressure, the proportion being as the squares nearly. Beams of iron are applicable to both classes of vessels, Ecams. and their superiority is now becoming so generally acknow- ledged, that they are being largely used in wooden vessels in the merchant-service and in the French navy. It is, General however, to the results of the combination of these mate- "'rength. rials as a whole that consideration must chiefly be given. Unfortunately there are no want of instances of both species of vessels going to pieces suddenly w hen cast on shore on rocks ; and until iron-vessels are double-plated with an interior water-tight sheathing, wooden vessels, with solid bottoms of floors and futtocks, will probably give greater security in such a position f<)r a short period of time if the sea be rough, and for a greater period if it be smooth ; on a flat beach, however, iron-vessels seem undoubtedly to have the advantage. The Great Britain, lying for a whole winter on the coast of Ireland, and the Vanguard, lying ashore for several days on a rocky beach, are two notable instances of iron-vessels having come off comparatively un- injured, after having been exposed to strains which it is believed no wooden vessels could have undergone. There SHIP-BUILDING. 89 Practical Building. Safety of ron- essels in sea-way. dvantage " water- ght bulk- ;ads. are, at least, no such instances on record with regard to tliem. As another direct comparison, tlie Demerara may be mentioned as a wooden vessel w liich, after being launched, grounded in the river at Bristol wliile being brought down, and she was so much injured that she was condemned ; whereas the Australia, an iron-vessel, on first coming down the Clyde grounded in a similar manner, lying right across the river in one of its narrowest parts, but she came off quite uninjured. Another instance of strength, such as no wooden vessel has ever exhibited, may be quoted in the case of an iron-vessel which, on the occasion of her being launched, stuck on the ways which were upon a high wharf above the water, and more than one-third of the whole length of the vessel was left totally unsupported, overhanging the w harf, and yet she did not break or receive any damage The same elements of strength which enabled these vessels, especially the Great Britain and the Vanguard, to withstand the strain to which they were exposed, will also be efficacious in preventing a vessel straining at sea in a heavy sea-way, so as to become leaky and foimder at sea from this cause. From a consideration of such facts as the foregoing, the general opinion appears to be, that iron-ves- sels, as a whole, are not only stronger than wooden vessels, generally speaking, but that they may be made of greater or equal strength, with considerably less weight of hull. The extent to which this saving of weight may be carried, without impairing the strength to an improper or unsafe degree, will always be a subject of inquiry to the iron ship- builder ; but if he err in jtidgment and produce too weak a ship, the error must be attributed to him, and the mate- rial must not be considered to be in fault. The power of fitting water-tight bulkheads to iron-ves- sels is also a great advantage, and will be a source of much greater secm-ity hereafter, when vessels are better built than they have hitherto been. Their importance, and the great additional safety which they impart, are evident, and the principle may be carried o\it to any extent, and this longi- tudinally as well as athwartship. In the after part of screw- ships, the passage alon<;side of the shaft to the propeller may be made water-tight, and communication with the engine-room may be cut off, if it be desired, and if proper arrangements be made for this purpose. These bulkheads also form a good protection against the very rapid spread- ing of fire, and in the case of any vessels particularly liable to this danger they might be made double, and water be admitted between them. The mode of attaching them to the ship's side also re- quires special attention, so that the ship may not be weakened by a continuous line of rivet-holes too close to- gether, extending down the sides and across the bottom. To obviate this difficulty, a practice has lately been intro- duced by Mr Bowman of London, to double upon the plates of the sheathing wherever a water-tight bulkhead was to be situated, by a line of plates sufficiently wide to take the two adjacent frames of the ship on each side of the bulkhead frame. Indeed, it would be far better that the rivets should be placed so far apart, that a slight leakage should be likely to take place past the bulkhead, between it and the sheathing of the ship, especially high up the side, and still more so at the shear strakc, rather than that she should be so weakened as to endanger her breaking across at the line of attachment. The number of such bulkheads to be put into any ship must necessarily depend on the services on which she is to be employed ; but miless special circumstances prevent it, there ought in every ship to be one immediately abaft the stern, and another immediately before the stern-post. In no case should the compartments be so large that any two, exclusive of the two small compartinents forward and aft just mentioned, being filled with water, would sink the ship ; and if the requirements of the ship rendered a communi- cation necessary between any two of the compartments, Practical the means of opening and shutting the water-tight doors Building, ought to be from the upper or w eather deck, and not below ; -^»^»»ir/ and the communication itself ought to be made as high up from the keel as possible, in order that after the ship begins to fill from the leak, there may be as much time as possible to close '" Another point for the consideration of the practical The pro- builder has been raised with reference to iron sl)ips, byprietyof the " Great Eastern" and other large vessels having been .'""''^'"S built without a keel. The propriety of this seems very^™"V doubtful, as many wooden vessels are believed to have been without a saved by their false keels, and there seems to be no sound keel doubt- reason for alleging that equal advantages would not accrue ful. imder similar circumstances in the case of iron vessels. Instances may have occurred where a sharp and thin iron keel has cut into the bottom of a ship ; but this may have resulted from the keel having been improperly formed, or from its being improperly attached to the sheathing with- out proper internal support. With a keel formed as in fig. 41, no such evil results would be likely to accrue ; nor have they been found with keels formed as required by the specifications for an iron screw ship for the Peninsular and Oriental Company, figs. 51 and 52, or as shown in the section of a vessel by Mr Bowman, fig. 48. A keel may also, in some cases, be of material benefit in preventing a ship running so far agroimd as she would have done if she had been constructed without a keel, and thus cause her to be more easily got off. An internal water-tight ceiling of iron plates is also a Advantage most important advantage in iron ships, and one whichof anin- should certainly be adopted in all large vessels. The ex-*""^. tent to which this may be carried up the bilire, or on the j 11° . , , . , ■' ,. '. ■ ' , or double sides, may be varietl accoiUing to circumstances, — always bottom, bearing in mind the importance of being able to get to the interior spaces, to keep them free from corrosion and decay. Care must also be taken that this ceiling is sufficiently strong to resist the great pressure of water that will be brought upon it. The benefit of the system has been most fully illustrated in the case of the " Great Eastern." The durability of iron-ships has been already referred to, Facility for as far as regards ordinary tear and wear ; but their superi- repair in oiity in the event of injury by collision, or by being on '''"°' shore, is still more marked. If a few frames or floors are ^^^*^''* broken in a wooden vessel, the amount of work required to be entered into to replace them is very great, a large portion of the plank in the neighbourhood requiring to be ripped off. In an iron-vessel, on the contrary, a new piece of frame can be introduced to replace the injured part, and the whole made as strong as before, by lapping pieces. And in the sheathing, an injured plate, or a piece of a plate, can be cut out and replaced without disturbing any of the other work. rUACTICAL OPERATIOXS. After the cursory view which has been taken of the CommeT.ffr. strains to which ships are liable, and the general remarks ™^ot of w hich have been made on the points to be attended to in ?■'»<'•";" their construction, it is now proposed to give a short outline P "" ' " • of the proceedings in the actual building of the vessel. The term " laying off" is applied to the operation of Laying o9. transferring to the mould loft-floor those designs and gene- ral proportions of a ship which have been drawn on paper, and which have been previously referred to, and from which all the preliminary calculations have been made and the form decided. The lines of the ship, and exact representa- tions of many of the parts of which it is to be composed, are to be delineated there to their full size, or the actual or real dimensions, in order that moulds or skeleton outlines may be made from them for the guidance of the workmen. M 90 SIIIP-BUILDING. Itiiililiiig. Principal Pore and ttfttT budic9. Midship budy. Bqunre &ihI cunt bodies. 'I'liese working clraHinrrs are made by projection, and are not views of the p.irts as they appear to tiie eye. In a projected chawing the eye is supposed to tnove and lie directly opposite to each hne, as it, in its turn, is represented by tlie drani;htsnian. Separate draHin;_'s nnist, therefore, be made tor the different faces ot" any object whicii are at right angles to each other. The delineation in this manner of solids of a complicated form is of itself a science, and one which is now attracting much more attention than tiirnieily. It is very ahly treated by the llev. Dr WooUey in a work entitled Descriptive Cieometry. Before the publication of this work the efforts in this direction in this country hail been chiefly made by practical men, each showing the mode of tldineating the more difficult objects in his own art. Architectural works showed tlie mode of delineating the nioidilings and details of the columns of the seven orders of architecture. Books on carpentry showed the mode of working and laying off a geometrical or winding staircase, and works on ship-build- ing included, at great length, the modes of laying off com- plicated and irregularly formed parts. To show the mode of delineating not only the frames, but all the pieces of varying form which are required in the bows or sterns of ships, would be fiir beyond the limits of this treatise. It is impossible to include either a complete treatise on draw- ing or a complete set of delineations of the modes of com- bining the whole of the various minute parts of which all classes of vessels of wood and of iron are composed. A proper knowledge of the minutia; of construction and of workman^hip can only be obtained by practical experi- ence upon the work itself; and the tiirm and combinalion of the parts will continually vary with the variations in the fiiriu and outline of the bodies and of the heads and sterns ot the ships. The principal |)lans of a ship are the sheer plan, the body plan, anil the half-breadth plan, and these have been already fully discussed, and their u>es ex[)lained. In addi- tion to the^e plans it is customary to furnish the architect with a profile of the inboard works, showing the dis- position or distance apart, and the appearance of the tim- bers which constitute the frame, also the length or the heads and heels, and general arrangement of the floors and futtocks, the midship section, on which is described the moulding or athwartship size of the timbers, the thickness of the exterior and interior planking, the connec- tion of the beams to the side, the dimensions of the water- ways and shelf-pieces, and the fiirms and fiistenings of the knees, &c. These, with a scheme of scantlings containing the dimensions and other jiarticulars of the principal pieces which enter into the construction of the liibric, constitute all the preparatory intormation required by the builder. In private contracts very full information on all these points is generally included in the specification. A ship is generally spoken of as divided into fore and after bodies, and these combined constitute the v\hole of the ship ; they are supposed to be separated by an ima- ginary athwartship section at the widest part of the ship, called the midshi|) section or dead-flat. The midship body is a term applied to an indefinite length of the middle part of a ship longitudinally, includ- ing a portion of the fore-body and of the after-body. It is not necessarily parallel or of tlie same form for its whole length. Those portions of a ship which are termed the square and cant bodies may be considered as subdivisions of the fure and aft bodies. There is a square fore-body and a square after-body towards the middle of the ship, and a cant fore-body and a cant after-body at the two ends. In the square body the sides ol the frames are square to the line of the keel, and are athuartship, vertical planes. In the cant bodies the side'- of the frames are not square to the line of the keel, but are inclined aft in the fore-body, and foi«ard in the after-body. The reasons lor the frames in these portions of a wooden ship being canted, is that, in these parts of the ship, the timber would be too much cut away on account of the finenos of the angle formed between an athrtart ship plane and the outline or water-lines ot tlie ship. The timber is therefore turned partially round till the outside lace coincides nearly with the desired outline, and it is by this movement that the side of a frame in the cant fore-body is made to point aft, and in the cant aftbody to p( lilt forward. This will be best understood by the an- nexe I figure, showing an exaggerated horizontal section of a frai.ie in the fore cant-body, the dotted line representing the e tent to which the timber would have been cut away if it iiad been placed square to the line of keel, and if the Practirftl Ituildin^'. Fig. 31. side ab had not been "canted" aft, turning on the point or edge a. In wooden ships the term " timbers" is sometimes ap- plied to the frames only, but more generally to all large pieces of timber used in the construction. Timbers, when combined together to form an athwartship outline of the bodv of a ship, are technically called frames, and some- times ribs. In iron-ships the frames are comjiosed of iron- bars of various forms. The terms moulding and siding are nearly synonymous Mouldinc; with thickness and breadth, observing that the moulding ot ""J siding a piece of timber is the dimension of the side on which the mould is ajiplied for determining its shape or curvature. For instance, the moulding of a beam is its length and thickness ; its siding is its fore and aft dimension or breadth. Hooui and sp.ice is a certain distance determined by the Room and fore and aft dimensions, or the siding of two adjacent tini- space, bers, together with the opening between them. It is gene- rally detined as the distance from centre to centre of the frames, or from centre to centre of the spaces between them. The centre line between two adjacent frames is called the joint. Shift in its general sense is applied to a certain arrange- Sliift. ment among the component parts of a ship. Thus a shift of deadwood, or a shift of plank, means the disposition of the huts of the timber or plank with reference to the longi- tudinal distiince of one joint from another, and this with respect both to strength and economy. The bevelling of a timber is the angle contained be- Bevellings. tween two of its adjacent sides. Bevellings are either acute angles, right angles, or obtuse angles. 'Jhese three sepa- rate cases are denominated under bevellings, square bevel- lings, and standing bevellings. Sirmarks are certain points or stations marked on the Sirmarks. mould of the timbers, at which the bevellings are applied, in order to cut the timber to the bevelling required at that spot. These sirmarks are determined, and their positions denoted in the body plan, by the various diagonal lines. Water-lines in the sheer plan, are lines drawn parallel Water- to the surface of the water (Plate III.) Level-lines are lines and similar to water-lines, except that they are drawn parallel level-lines, to the keel instead of to the water (Plates V. and VI.) In the hall-breadth plans, the water-lines or level-lines show the outline of the form of the ship at sections at the corre- sponding heights in the sheer and body plans. Diagonal lines, as shown in the body plan and half- Dli^onal breadth plan (Plate 111.), and marked 'l D, 2 D, 3 U ''"<=»■ SHIP-BUILDING. 91 Diaj^nnals on sheer plan. Diarxonal on hiilf- breadtil plan. Every form to be drau n on the floor, and its beveling obtained. Expanding Ihe body. sliow the boundaries of various sections which are oblique to the vertical longitudinal plane, and which intersect that lane in strai<;lit lines parallel to the keel. In wooden ships, the position of the diagonal lines drawn in the body plan is not arbitrary, because it has reference to the differ- ent timbers of which the frame is composed, and also to the station of the ribands and har|)ins. The number of dia- gonals is increased in the deeper class of vessels. They are drawn to show the lengths of the floors and futtocks, together witli the heights of their heads and heels above the keel, and are marked floor-head, &c. Diagonals, marked as 1st sirmark, 2d sirmark, Sd sirmark, &c., or 1 D, 2 D, 3 D, on the body plan (Plate III.), show the heights and situation of the harpins and ribands which are used to give support to the ship whilst in frame. In wooden ships they are always placed between the heads of the respective timbers. The following is the mode of setting off the diagonals in the sheer plan : — Take the perpendicular heights in the body plan, that is, the heights square to the upper edge of the keel of the intersection of the diagonal with each of the transverse sections, and transfer these heights to the corresponding section in the sheer plan. Through the points thus obtained draw a curve, which will be the line required. To transfer the diagonals to the half-breadth plan : ob- serve the point of intersection of the diagonal on the body jjlan with each transverse section, and take the horizontal distance of each of these points from the middle line, and transfer it to the corresponding section in the half-breadth plan. Through the points thus obtained draw a curved hne, which will represent the horizontal line of the diagonal. After these lines have been added to the sheer, body, and half-breadth plans on paper, the transference to the floor, where the ship is to be delineated to the full size, is easy. It is the duty of the draughtsman on the mould-loft floor to fair the body, if any of the curves shown by the lines previously drawn on the paper do not appear of easy and good tbrms, when represented of their full size. On the mould-loft floor it is necessary, in iron-ships, to draw out every frame, so as to be able to give the particu- lars to the workmen ; and it is not only necessary to give them the outline of the frame, but also the beveling or the angle which the outer surface makes with the side at each spot or sirmark. This is obtained from the half-breadth plan at the various points where the different level lines or diagonal lines cross each frame. A variety of modes are practised by different builders of iron-ships to convey this information from the niould-loft to the workmen, instead of using moulds, as almost universally practised by builders of wooden ships. Great accuracy in this respect is re- quired in iron-ships, as in them no dubbing off or pairing the body by the adze is practicable. Expanding the body so as to represent the whole of the planking or outer skin or surface of a ship, is another |)ro- cess connected with laying off; and it is particularly im- portant to the iron ship-builder, as it enables him to obtain the necessary iron-plates from the rolling-mills of the exact widths and lengths that will be required. This is done by drawing a line, to represent the line where the plates meet the keel and stern-po>ts. On this line the station of any number of frames that may be necessary to give the de- sired degree of accuracy must be set off, and at these stations lines must be drawn of a length equal to the girt or outline of the frame at that station ; this length will be obtained from the body plan. The number of strakes to be used in planking or sheathing the shi[) must next be determined and be set oft" accordingly, on the lines repre- senting the different frames ; and great art is necessary in this operation, as upon these lines much of the beauty of a sliip depends to please the eye of a connoisseur. The shift or the distances between the ends of the different plates Practical may also be determined and marked in this plan, and thus Building, the length, width, and breadth of every plate maybe accu- —"V"^ rately ascertained. Tlie circumference of the bottom being greater at the midship part than toward the extremities— that is, at the bow and buttock — the lines of the strakes taper as they recede from midships. They also acquire an upward curve, called " Sny," which renders it difficult to work the plank. "Sny." When the sny becomes too great, a strake is ended short of the others, and this is termed a " stealer," as it dimi- nishes the sny for the succeeding strakes. Under the buttock it is often necessary to work some of the after- plank wider at the after-end, and this has the same effect of diminishing the sny of the following strakes. " Hang" is the exact reverse of " sny." It mostly occurs in work- ing plank on the inner surface of the timbers, and outside above the main breadth. With regard to the practical operations in building a ship, nothing more can be attempted here than a few general observations on the principal parts of a ship, and the mode of putting them together, to resist the various strains to which each part w ill be subjected. The practice in her Majesty's yard will be found very fully explained in Fincham's outlines of shipbuilding, and in a very excel- lent treatise by Mr Peake, now master-shipwright at Devon- port. Some details of wooden ships of the ordinary system of construction w ill be first described. The keel of a ship built in this country is generally com- The keel posed of elm, on account of its toughness, and from its not being liable to split if the ship should take the ground, though pierced in all directions by the nuinerous fastenings passing through it. It is generally composed of as long pieces as can be obtained, united to each other by hori- zontal scarphs. These scarphs are made sloping; up from the bottom to the upper surlace, on which the floors rest. But the strain to which a keel is subjected has a tendency to curve it up or down, and not sideways. These scarphs should, therefore, be made vertical, in the same manner as scar[)hs of the beams, as there can be no doubt that the vertical scarph will give the greatest strength to resist a strain in this direction. The rabbet of the keel is an ang\ilar recess cut into the Rabbet of side to receive the edge of the planks on each side of it. ^""^ ''^el- In the government service this rabbet is made of greater breadth vertically, so that the plank to fill it is required to be of such great thickness that it altogether loses the cha- racter of a plank, and becomes a stout massive piece of timber. This arrangement was introduced by Mr Lang, and has been denominated Lang's safety keel. It gives great additional strength to the bottom of a ship, and great lateral support to the keel, when the ship takes the ground and rests on the edge, as tiie leverage to displace it side- ways is thus reduced. in the merchant service the rabbet is seldom carried so low down on the side, and the garboard strake or strakes are not so thick. The keel forward is connected to the stem by a scarph, sometimes called the boxing scarph, and aft to the stern-post, by mortice and tenon. The apron is fayed or fitted to the after-side of the stem, and is intended to give shift to its scarphs, the lower end scarphs to the deadwood. The keelson is an internal line of timbers fayed upon the inside of the floors directly over the keel, the floors being thus confined between it and the keel. Its use is to secure the frames and to give shift to the scarphs of the keel, and thus give strength to the ship to resist extension length- ways, and to prevent her hogging or sagging. The fore- most end of the keelson scarphs to the stemson, which is intended to give shift to the scarphs connecting the stem and keel. The frames or ribs are composed of the strong- est and most durable timber obtainable. By Lloyd's rules 92 SIIIP-BUILDING. yioors. Practiciil a durability of twelve years is assigned to frames composed of Uuilding. Kiijrlish, African, and live oak, East India tcik, Morninij Said ^^"V^^ f;rcenlieart, morra or iron-bark ; of ten years to mahofjany of hard texture, Cuba, sabicu, and pencil cedar ; of ten years for floors and first fultock, and nine years for second and tiiird futtoeks and top timbers, to Adriatic, Spanish, and French oak ; of nine years to red cedar, ansjelly and Venatica ; of nine years for floors and first futtoeks, and seven years to second and third futtoeks and top tiudiers of other continental wliile oaks, Spanish chestnut, stringy bark, and blue gum ; of eight years and seven years re- spectively, as betbre, for North American vvliite oak and American sweet chestnut ; of seven years for larch, hack- iiiatac, tamarac and juniper, and pitch-pines. The floors in the goveriuiient service arc carried across the keel with a short and long arm on cither side alter- nately, so as to break joint, and between the frames the space is filled in solid. Longitudinal pieces of timber are worked roiuid the interior of a ship for the purpose of receiving the ends of the beams of the several decks; they are called shelves, and are of the greatest importance, not only for this purpose, but also as longitudinal ties and struts. In any system of diagonal bracing, properly carried out, they should form one side of the parallelogram or of the triangle, and those other timbers, or iron-bars, which form the diagonals or the other sides of the parallelogram or triangle ought to be firmly secured to them. A thick strake of plank used for- merly to be worked between the shelf and the timbers or frames, but now it is generally worked home upon them. The shelf is generally supported by some thick strakes of plank worked immediately under it, and formerly it was also sometimes supported by chocks or triangular pieces, like brackets on the ship's side, brouirht out to be flush with the inner edge of the shelf, and on tlie lace of this an iron- knee. This chock is now generully dispensed with, and the lower side of the shelf is bevelled off towards the ship's side, and the iron-knee is forged to fit under it acconlingly. These fastenings will be referred to when treating of the means of securing the ends of the beams. The other fast- enings of shelf-pieces are by nimicrous through-bolts. Timbers which are fiiyed to the inside of the frame, or upon the inside of the plank, longitudinally or diagonally, solely for the purpose of supporting the frame, are called riders. The beams. The beams of a ship prevent the sides froni collapsing, and at the same time carry the decks. The beams are spaced, and their scantling settled upon, according to the strength required to be given to the decks, and to suit the positions of the masts and hatchways, and other arrange- ments connected with the economy of the ship. All beams have a curve upwards towards the middle of the ship called the round up. This is lor the purpose of strength, and for the convenience of the nm of the water to the scuppers. Wooden beams are single piece, two, three, or four piece beams according to the number of pieces of timber of which they are composed. The several pieces are scarphed to- gether,anddowelled i:fy:B,a,n. bolted, the 5 ' and scarphs being al- ways vertical. A Fig. 32. scarph now very generally adopted was introduced by Mr Edge, late master-shipwright of Dcvonport dockyard, and is represented in the annexed figure. The beams of ships being supported at both ends, and one of the strains to which they are chiefly subjected being a downward pres- sure, the upper part of the beams will then be compressed, and the lower parts extended. It is therefore desirable that the lower part of the beams should not be wounded so as to cut the fibres across in that part. An incision above the line of the vertical axis is of less moment, and if an in- cision be made there for the purpose of introducing a carling, for instance, and if this be well fitted, and be of as Practical hard wood as the beam, the strength of the beam will not Building, be iinj)aired, but may even be increased. '*"^/'"~' The connection of the ends of the beams to the sides of Connection the ship have been made in various ways. The points to"*^"'" be considered, with reference to this connection, are, that ''^"'n' to the beam is required to act as a shore or strut, to l""L'vent,|j^ j'J."' the sides of the ship from collapsing, and also as a tie to prevent their falling apart ; that the beam shall not rise (iom its seat, and that it shall not work in a lore and aft direction ; that the beam may be an effective shore, no- thing more is necessary than that the abutment of the end against the ship's side may be perfect. In order that it may act as a tie between the two sides, it is generally dowelled to the upper surfiice of the shelf on which it rests ; and the under surface of the water-way plank which lies upon it is sometimes dowelled into it. These dowels, therefore, connect it with the slielf and the waterway, and through this means it is thus connected with the sides of the ship. There is, also, in the ships of the royal navy, a plank called a side-binding strake, scored down over and into the beam-ends at some distance Irom the side, and bolted through the side between the beams. The scoring into the beams coiuiects the in and out fastenings of this strake with the longitudinal tie of the beams, but the advantage does not seem to be connnen- surate with the labour. The beams are also supported by knees below them. Knees to Wooden knees are chiefly used in America; and it is beams, argued that they give a better support to the beam from their greater surface, and fiom their stiffness in the throat, or angle of the knee. The iron-knees used in the royal navy vary in form ; they are made not only to support the beam from below, but sometimes with horns to clasj) it side- ways at a short distance from the side of the ship. The lower arms of these knees are so formed as to fit round the slielf; or sometimes, with a view to prevent the necessity of working the iron into this form, and at the same time afford additional support to the shelf, a chock is fitted under the shelf to receive the face of the knee. While the knee is instrmnental in supporting the beam, it is also upon it that dependence is mainly |)laced to prevent the beam rising, or working in an U])ward direction. In these fastenings there appears a want of any very efficient means to prevent the beam straining in a fore and aft direction, or working upon the end as upon a pivot. From the short outline previously given of the disturb- Strains ing forces acting on a ship, it will be seen that the strain wliich a on the ends of tlie beams to destroy their connection with '^''.'" "'"■' the side and loosen the fastenings, must be very great when the ship is under sail, either on a wind or before it — that is, either inclined or rolling. The principal action of these forces is to alter the vertical angle made by the beam and the ship's side — that is, to raise or de|>ress the beam, and so alter the angle between it and the side of the ship above or bekny it. On the lee-side the weight of the weather side of the ship and all connected with it, and of the decks and everything upon it, as well as the u|)ward pressure of the water, all tend to diminish the angle made by the beam nntl the ship's side below it, and consequently increase the angle made between them above it. The contrary effect is produced on the weather side, where the tendency is to close the angle above the beam and open that below it. If the beam when subjected to these strains, be considered as a lever, it will be evident that the fastenings to prevent its rising ought to be as far fiom the side as is consistent with the convenience or accommodation of the ship; and that while the support should also be extended inwards, the fastening to keep down the beam-end should be as close to the end of the beam, and consequently to the ship-side, as it can be placed. SHIP-BUILDING. 93 Practical Building. Elalf- beaois. The annexed section of the s'ule of a three-decked ship of the royal navy shows some of the modes that have been adopted for securing j.^ theendsof the beams. Cl_____^-..^., , Beams wliich do ^^^^=^?^^~^=^ * «-iis-^ not extend from one side of the ship to Quarkr.i,. the otiier are called half- beams. They are introduced when- ever the hatches or openings in tlie mid- dle of the ship are such as to require the whole or unbroken beams to be so wide apart that the deck ^^ requires support be- tween them. Their ends, towards the midships, are receiv- ed by fore and aft jiieces called carl- ings, which go from beam to beam ; and any intermediate athwartship pieces between the carlings and ledges, are called ledges. „ , The two sides of Hooks. , , . ,1 the snip at the bows are connected by hooks, which are either of timber or of iron. It is im- portant to remember that the hooks above, and those below the Carlings Fig. 33. surface of the water, are subjected to an opposite strain. The tendency of the pressure of the water on the bow is to make the sides collapse, and therefore the hooks be- Practical low the water's surface should not only act as ties to the Building, bow while the ship is groiuided— as, for instance, when in ^'■^"v"^'^ dock — but should be formed more especially to resist the pressure of the water when she is afloat. Those hooks which are above the surface of the water act principally as ties, the rake of the bow and the weight of its parts tending to separate the two sides of the ship. The plank, or skin, or sheathing of a ship, both externa! Planking, and internal, is of various thicknesses. A strake of plank- ing is a range of planks abvitting against each other, and generally extending the whole length of the ship. A thick strake, or a combination of several thick strakes are worked wherever it is supposed that the frame requires particidar support — for instance, internally over the heads and heels of tlie timbers; both externally and internally in men-of-war vessels between the ranges of ports ; and internally to sup- port the connection of the beams with the sides, and at the same time form a longitudinal tie. The upper strakes of plank, or assemblages of external planks, are called the sheer-strakes. The strakes between the several ranges of ports, beginning from under the upper-deck ports of a three-decked ship in the royal navy, are called the channel wale, the middle wale, and the main wale. The strake inmiediately above the main wale is called the black strake. The strakes below the main wale diminish from the thick- ness of the main wale to the thickness of the plank of the bottom, and are therefore called the diminishing strakes. The lowest strake of the plank of the bottom, and whose edge fits into the rabbet of the keel, is called the garboard strake. Plank is either worked in parallel strakes, when it is called " straight edged," or in combination of two strakes, so that every alternate seam is parallel. There are two methods of working these combinations, one of which is called " anchor stock," and the other " top and butt." The difference will be best shown by the annexed figure. The difference in the intention is, that in the method of work- ing two strakes anchor-stock fashion, the narrowest part of one strake always occurs opposite to the widest part of the syi'iwUjt other strake, and consequently the least possible sudden interrujition of longitudinal fibre, arising from the abut- ment, is obtained. This description, therefore, of plank- ing is used where strength is especially desirable. In top and butt strakes the intention is, by having a wide end and a narrow end in each plank, to approximate to the growth of the tree, and to dimini.-h the difficulty of procuring the plank. When the planking is looked upon as a longitu- dinal tie, the advantage of these edges being, as it were, imbedded into each other is apparent, all elongation by one edge sliding upon the other being thus prevented. The shift of plank is the manner of arranging the butts of the several strakes. In the ships of the royal navy the butts are not allowed to occur in the same vertical line, or on the same timber, without the intervention of three whole strakes between them. Of the internal planking the lowest strake, or combina- Limber- tion of strakes, in the hold, is called the limber-strake. A strike- limber is a passage for water, of which there is one through- out the length of the ship, on each side of the keelson, in order that any leakage may find its way to the pumps. The whole of the plank in the hold is called the ceiling. Ceiling and Those strakes which come over the heads and heels of the internal timbers are worked thicker than the general thickness of planking, the ceiling, and arc distinguished as the thick strakes over the several heads. The strakes under the ends of the beams 94 SHIP-BUILDING. pluuks. rrsctiral of the diffiTent decks in a man-of-war, and down to tlie Building, ports ol' tile deck lieloiv, if there be any ports, are called the *^-^~V^^ clamps of the particular decks, to the beams of which they are tlie support, as the <,'un-dick clamps, the middle-deck clamps, &x. The sirakes which work up to the sills of the ports of the several decks are called the spirkettin<j of those decks — as gun-deck spirkettinj^, upper-dtck spirkettin;:, &c. Fastenings The fastening of the plank is either " single," by which of the is meant one fastening only in each strake, as it passes each timber or frame ; or it may be " double," that is, with two fastenings into each frame which it crosses ; or, again, the fastenings maybe "double and single," meaning that the fastenings are double and single alternately in the frames as thev cross them. The fastenings of planks consist generally either of nails or treenails, excepting at the butts, which are secured by bolts. Several other bolts ought to be driven in each shift of plank as additional security. Holts which are required to pass through the timbers as securities to the shelf, water-way, knees, &c., should be taken advan- tage of to supply the place of the regular fastening of the plank, not onlv for the sake of economy, but also for the sake of avoiding unnecessarily wounding the timbers. The planking in the royal yards is not visually fastened permanently till some time after it is trimmed and brought on to the bottom of a ship. It is thus allowed to season and shrink ; and one strake in eight or ten is left out for the purpose of allowing ventilation, and to make good the shrinkage, and also to allow the strakes to be refayed. Without the latter provision there would be such an altera- tion of edge as would throw the holes made for the tem- porary securities out of the range of the strakes; but with this precaution it is very seldom that the alteration of edge is such as to re(iuire new holes, especially as the iron screw-eye bolts used for this temporary (astening are of much smaller diameter than the [lermanent treenail fastening, and there- fore the holes for them through the plank can still be made good holes for the treenails. This method of securing the planks bv a first or temporary fastening, to be afterwards substituted by a treenail, is also of advantage in enabling them to be brought into close contact with the timbers, in the saving of bolt fastenings, and in causing a good and regular seam to be given for the caulking. The advantages and disadvantages of iron as a fastening for planking have been already discussed. The strength of treenails to resist a cross-sheering strain, as found by Mr Parsons, late of H.M. Dockyard Service, is shown in the following table : — Experi- " Table of the Transverse Strength of Treenails of English nients on Q„;, ^^^^ ^^ Jasteiiing for Planks of 3 and of 6 incites fastenings. ^.^ thickness, and subjected to a Cross Slriiin. Nnmlwr of the Eiperi- Diameter of the Treenails. llnch 1 U Inch. lilncb. li Inch. meDt. Thickness of th » Plank. 3 In. 6 In. 8 In. 6 In. 8 T. n. C. 6 In. 8 In. 6 In. T. C. T. C. T. C. T. C. T. C. T. C. T. C. 1 1 8 1 7 1 14 2 8 2 3 12 3 5 10 o 1 7 1 15 2 2 2 2 2 6 2 10 2 10 3 13 3 I 2 1 8 1 17 2 19 2 15 2 10 4 4 4 1 5^ 1 8 2 2 2 2 2 4 3 12 2 8 3 8 S 2 12 1 3 2 2 1 15 2 18 2 5 3 10 4 6 2 o 1 7 2 9 2 10 2 6 2 5 3 10 5 8 7 o 4 1 10 2 8 2 10 3 7 2 5 3 5 3 12 8 1 6 2 3 2 7 2 2 5 3 3 5 3 13 9 1 8 1 8 2 12 2 10 3 4 4 6 4 13 10 1 2 2 3 2 10 2 15 3 4 10 3 8 4 11 o 2 2 7 2 3 9 2 18 4 3 8 12 1 8 1 7 2 10 2 4 2 3 4 10 5 13 Average 1 16 2 8 2 17 2 3 2 3 18 4 2 5 5 1 U ll 13 2 6j2 6 2 16 3 2 3 10 4 6 " In all these experiments on treenails, when the tree- nails were evidently good, they gave way gradually. In some of the rejected experiments, however, the treenails certainly did break off suddenly, but then they were evi- dently, on examination, either of bad or over-seasoned ma- terial. It h;is been asserted that the treenails made from the Sussex oak are much stronger than those made from the New Forest limber, or any other English oak. To ascertain the truth of this assertion, some experiments were made with Sussex and New Forest treenails of all sizes ; and the result was, that there was not the least difference in them, the New Forest were, on experiment, quite as strong as the Sussex. In the experiments on treenails, the plank generally moved about half an inch previous to the fracture of the treenail." The following useful tables were also drawn up by Mr Parsons from a scries of valuable experiments carefully made by him, and show the longitudinal holding jiower of treenails. 'I'lie first of these tables exhibits the adhesion of iron and copper bolts, driven into sound oak, with the usual drift, not clenched, and subject to a direct tensile strain. By drift is meant the allowance made to insure suffi- cient tightness in a fastening ; it is therefore the quantity by which the diameter of a fastening exceeds the diameter of the hole bored for its reception. " Table of the Adhesion of Iron and Copper Bolts driven into sound Oak with the usual Drift, nut clenched, and subjected to a direct Tensile Strain. T-rartiral Building. Iron. Copper. 1 Diameter i>l the Holt. of the Kx[»eri- lueiit. Lengrli of the Bolt driven into the Wood. Fonr Six Fonr Six Inches. Inches. Inches. Inches. Inches. Tons. C»t. Tons. Cwt. Tons. (*wt. Tons. Cwt. f 1 1 13 ... 18i '■ 2 2 18 ... 3 2 2 19 I 4 1 13 18 f 1 2 6 2 12 1 7 2 2 ' i 2 2 4 2 11 1 8 2 2 s.< 3 2 4 2 16 1 10 2 2 I 4 2 2 10 1 13 2 ( 1 3 2 3 12 2 10 2 15 .. 2 3 4 4 1 17 3 10 3 3 4 2 2 3 1 l 4 2 10 4 2 6 2 15 ( 1 3 2 5 5 3 4 5 ' 2 3 4 8 3 6 3 18 3 3 1 4 8 3 6 3 16 I 4 3 1 5 2 9 3 5 "1 1 3 3 6 3 10 5 6 2 3 2 6 3 10 5 5 3 3 10 6 3 10 5 8 ( 4 3 10 6 3 18 4 18 f 1 4 10 6 2 4 4 13 >.. 2 5 12 6 10 4 4 13 3 3 10 6 11 4 6 4 19 I 4 4 10 6 4 4 2 4 19 ( 1 5 7 2 4 2 5 19 ,... 2 4 7 8 1 4 8 5 3 4 11 6 5 3 15 6 5 I i 4 7 4 in " In liiga fir the adhesion was, on an average, about one- third of that in oak, and in good sound Canada elm it was about three-fourths of that in oak. The following table exhibits the strength of clenches and of forelocks as securities to iron and co|)per bolts, driven six inches, without drift, into sound oak, either clenched or Ibrelocked on rings, and subjecttd to a direct tensile strain. It gives the diameter of the bolt on which the experiment was made, as well as the number of the experiment : — SHIP-BUILDING. 95 Practical " Table of the Strength of Clenches and of Forelocks, as BuilJing. securities to Iron and Cupper Bolls, driven six inches, ■^-V"— ^ uutkout Drift, into sound Oak. either clenched or fore- locked on Rings, and subjected to a direct Tensile Strain. Diani(*ter of the Bolt. Nomber of the Hxpcri- Iron. Copper. ment. Clench. Forelock. Clench. Forelock. 1 Inch. Tons. Cwt. Tons. Cwt. Tons .Cwt. Tons. Cwt. ( 1 1 16 16 1 8 ,.\ 2 1 13 14 19 8 3 1 9 20 1 7 I 4 1 9 18 1 6 f 1 3 1 15 2 10 4 ,... 2 3 1 8 2 10 3 2 16 1 9 2 5 2 I 4 2 15 1 14 2 9 4 ( 1 4 15 2 11 3 10 18 .... 2 4 10 2 15 3 15 18 3 4 5 2 10 4 2 4 I 4 4 12 2 12 4 10 1 16 t 1 5 18 3 15 6 2 13 .... 2 6 8 3 6 5 15 2 10 3 6 8 3 6 5 2 16 I 4 6 3 7 5 10 2 10 ( 1 7 10 3 10 J.... 2 7 10 3 15 3 8 3 10 5 . 4 S 15 3 15 8 c 1 11 11 5 1 16 >.. 2 11 15 5 10 16 3 8 11 4 6 12 I 4 8 6 4 15 5 ( 1 12 S 18 1 .... 2 12 3 6 18 1 3 11 3 5 12 14 I 4 11 1 5 2 8 14 " In the experiments on the clenches, the clenches always t;ave way ; but "itli the forelocks it as frequently occurreil that the forelock was cut off as that the bolt broke ; and in the eases of the bolt breaking, it was invariably across the forelock hole. According to the tables, the security of a forelock is about half that of a clench. " It a|)pears an anomaly that the strensth of a clench on copper should be equal to that of one on iron. But, in consequence of the greater ductility of copper, a better clench is formed on it than on iron. Generally the thick- ness of the fractured clench in the copper was double that in the iron. With rings of the usual width tor the clenches, the wood will break away under the ring, and the ring be imbedded for two or more inches before the clench will give Hay. " With the inch copper-bolts, all the rings under the clenches turned up into the sha()e of the frustum of a cone, and allowed the clench to slip through at the weights specified. " Experiments with ring-bolts were made to ascertain the strength of the rings in comparison with the clenches. The rings were of the usual size, viz., the iron of the ring one-eighth inch less in diameter than that of the bolt. It was found that the rings always carried away the clenches, but that they were drawn into the form of a link with per- fectly straight sides. The rings bore, before any change of torm took place, not quite one-half the weight which tore off the clenches. It appears that the rings are well proportioned to the strength of the clenches." From these tables it will be seen how much the strength of a clenched or fore-locked holt falls short of the strength due to the full diameter of the bolt where a tensile strain only is applied to it; and »lun exposed to a cross strain, it is also well known how much tiie strens;th is diminished when the ends are not lastened and held securely in posi- tion. An increased use of screw-bolts «ith nuts and larger plates or rings under the heads and under the nuts would therefore give great additional strength ; and if a sufficient Practical length of the bolt were screwed at the end to allow of as Bailding. much as an inch being cut off when too long, the supply ^■^~v^~' of sizes necessary to be kept in store would not be large. Economy also would be likely to result from the greater accuracy in the length required to be given for the bolt about to be drawn from the store lor use. Screw-treenails of the annexed form have lately been introduced by Messrs Hall, the well known builders of the Aberdeen clipper-ships, and whose modes of construction will be more particularly referred to hereafter. The in- creased holding power of such treenails to prevent planks from starting needs no demonstration. W<^^M^ <NM><>^^f*«*^*^sj^<^*<wl-<f. i7VA,WW WVAXAV The decks of a ship, as has before been stated, must not Hecks. be considered merely as platforms, but must be regarded as performing an important part towards the general strength of the whole fabric. They are generally laid in a longi- tudinal direction only, and are then useful as a tie to resist extension, or as a strut to resist compression. The outer strakes of decks at the sides of the ship are generally hard wood, and of greater thickness than the deck itself; they are called the water-way jilanks, and are sometimes dowelled to the upper surface of each beam. Their rigidity and strength is of great importance, and great attention should be paid to them, and care taken that their scarphs are well secured by through bolts, and that there is a proper shift between their scarphs and the scarphs of the shelf. When the decks are considered as a tie, the importance of keeping as many strakes as possible entire lor the whole length of the ship must be evident ; and it has already been stated that acontinuousstrakeof wrought-iron plates beneath the decks is of great value in this respect. The straighter the deck, or the less the sheer or upward curvature at the ends that may be given to it, the less liable will it be to any alteration of length, and the stronger will it be. The ends of the different planks forming one strake are made to butt on one beam, and as the fastenings are then driven close to the ends, they do not possess much strength to resist being torn out. The shifts of the butts, therefore, of the differen strakes require great attention, because the transference oi the longitudinal strength of the deck from one plank to an- other is thus made by means of the fastenings to the beams, the strakes not being united to each other sideways. These fastenings have also to withstand the strain dur- Strain in ing the process of caulking, which has a tendency to force caulking t< the planks sideways from the seam; and as the edges of planks resisted, of hard ivood will be less crushed or compressed than those of soft wood when acted on by the caulking-iron, the strain to open the seam between them to receive the caulking will be greater than with planks of sorter wood, and will require more secure fastenings to resist it. It may also be remarked that the quantity of fastenings should increase with the thickness of the plank which is to be secured, for the set of the oakum in caulking will have the greater mechani- cal effect the thicker the ed>;e. A deck, laid in a diagonal direction only, involves a great r>iag"nally loss of strength longitudinally, and the advantages are not'*''' Jecks. such as to compensate for this loss, and tor the other in- conveniences as to wear and tear, which residt from such a system. Mackonochie proposed to lay decks in three lavers, one diagonally from starboard to port, another from port to starboard, and an upper layer fore and aft. He also proposed a somewhat similar system for the outside planking, and vessels have been built on different modifica- tions of this plan both in this country and in America. 96 SHIP-BUILDING. Pmcfical Buililini;. Import- ance of se- curing the decks at the extre- mities. Dowelling and scoring down. Partners. Steps. Coamings and head ledges. Caulking. Marine glue. At the two ends of a ship it is important that the strengtii of the tie of the deck shoulii be maintained there, and while tlie continuation and connection of tile shclf-|)ieces and waterway-planks are duly attended to, with any neces- sary hooks and crutclies, additional strengtii to sustain the projecting bows and raking sterns may be obtiincd by a judicious connection of several beams to the extreme ends. This may be done by long bolts passed through the beams and secured by nuts and screws at their ends, or by pieces of timber fore and aft, underneath the beams, and bolted to them. These beams should have several ranges of carlings let down between them to diffuse the strain. In all such connections of wood with wood, dowelling is much to be preferred to scoring down. The latter is ob- jectionable on account of its wounding and weakening the parts in a greater degree, and the joint is subject to become loose or open by the shrinkage of the materials, and it also requires much more care and skill on the part of the work- man for its perfect execution. It should therefore be dis- continued wherever practicable. The frame-work of timbers w'hich is formed round the mast-holes in each deck is called the mast partners. " Part- ners" generally arc the principal timbers in a framing formed for the support of anything passing through a deck, as tlie masts and capstands. The pieces of timber to receive the heels of the several masts are called steps, as the main, fore, or niizen steps. Coamings are pieces generally faying on carlings, and rising higher than the flat of the deck, to form the fore and aft sides or boundaries of o|)enings, such as hatch or ladder- ways ; head ledges forming the athwartship boundaries to the same openings. When tlie planks are fastened, the seams or the inter- vals between the edges of the strakes are filled with oakum, and this is beaten in or cauiked with such care and force that the oakum, while undisburbed, is almost as hard as the plank itself. If the openings of the seam were of equal widths throughout their depth between the planks, it would be impossible to make the caulking sufiiciently compact to resist the water. At the bottom edges of the seams the planks should be in contact throughout their length, and from this contact they should gradually open upwards, so that, at the outer edge of a plank 10 inches thick, the space sliould be about ^Jth of an inch, that is, about tV''' "^ ^" inch open for every inch of thickness. It will hence be seen that if the edges of the planks are so prepared that when laid they fit closely for their whole thickness, the force required to compress the outer edge by driving the caulk- ing-iron into the seams, to open them sufficiently, must be very great, and the fastenings of the planks must be such as to be able to resist it. Bad caulking is very injurious in every way, as leading to leakage and to the rotting of the planks themselves at their edges. It frequently happens, however, that the caulking is blamed when the leakage and the attendant evils have been caused by the edges of the planks sliding upon each other through the working of the deck or of the ship. Instead of pitch for closing the seams above the oakum, Mr Jeffery introduced a mixture of shellac and caoutchouc, combined witli naphtha. This is at first more expensive, but its decided superiority ami greater durability, prevent- ing the necessity of so frequently re-caulking, will counter- balance this in due time, so as to be to the advantage of the ship-owner, though this will not make it economical to the ship-builder who builds and completes a vessel by con- tract. It is insoluble in water, and impervious to it; it is also clastic, and yet of sufficient solidity to fill up the joint and give strength ; and it is also powerfully adhesive, so as to connect the planks together at their edges. The mode of applying diagonal trussing to strengthen the side of a ship constructed in accordance witli the foregomg Practical outline, will next be considered. Buildir^. In the system of building which was superseded by that ^^-"^.'""^ termed the di.igonal system, the whole of the interior sur- Diagonal face of the frame was planked, and a second series of internal trussing, frames was worked upon this planking, agreeing in direc- tion with the timbers of the ship. Riders were also intro- duced in various parts, but not diagonally, and those in the hold were no doubt necessary when it was the custom to " ground" ships on a beach for repair ; a large quantity of timber was thus massed together, having the appearance of great strength; but, in (act, from its weight, injudicious combination, disposition and fastening, much of it was, if not injurious, at least useless. The idea of diagonal trussing was not an entire novelty at the time when Sir Robert Seppings introduced it as a system. There is evidence, in the representation of a vessel under repair in the fifteenth cen- tury, of some pieces of timber having been u-ed diagonally in her construction, as also in some other isolated instances. The credit, however, of calling the attention of ship-builders to the principles on which the advantages of diagonal trussing depend, is entirely due to Sir Robert Seppings, and no ship is now ever built without the principle being brought into action in a greater or less degree. lie described his system in a paper communicated by him to the Royal Society, and which is printed in their Transactions for the year 1814. In that paper, after sup- posing the frames for a two-decked 74 gun-ship to be in place, and the spaces between the frames tilled-in solid, he proceeds as follows : — " In this state the diagonal timbers are introduced, inter- secting the timbers of the frame at about the angle of 45°, and so disposed as that the direction in the fore is contrary to that in the after part of the ship, and their distance asunder from 6 to 7 feet or more ; their upper ends abutting against the horizontal hoop or shelf-piece of the gun-deck beams, and the lower ends against the limber strakes, ex- cept in the midships, where they come against two pieces of timber placed on each side of the keelson (called addi- tional keelsons), for the purpose of taking olf the partial pressure of the main-mast, which always causes a sagging down of tlie keel, and sometimes to an alarming degree. These pieces of timber are nearly as square as the keelson, and fixed at such a distance from it that the main step may rest upon them. They may be of oak or pitch-pine, and as long as can be conveniently procured. Pieces of timber are next placed in a fore and alt direction over the joints of the frame-timbers, at the floor and first futtock-heads ; their ends in close contact with, and coaked or dowelled to, the sides of the diagonal timbers. In this state the frame-work in the hold presents various compartments, each representing the figure of a rhomboid. " A truss-timber is then introduced into each rhomboid, with an inclination opposite to that of the diagonal timbers, thereby dividing it into two parts. The truss-pieces so introduced into the rhomboid are to the diagonal frame what the key-stone is to the arch ; for no weight or pres- sure on the fabric can alter its position in a longitudinal direction, till compression takes place at the abutments, and extension of the various ties. " This arch-like property of the diagonal frame not only opposes an alteration of position in a longitudinal direction, but also resists external pressure on the bottom, either from grounding or any other cause, because no impression can be made in its figure in these directions without forcing the several parts of which it is composed into a shorter space." The trussing here proposed for the hold of the ship was undoubtedly with the intention of introducing the principle of tlie inverted arch or dome ; and it must be remembered, that the general Ibrm of the vessels to which Sir Robert SHIP-BUILDING. 97 'ractical Seppings was accustomed approached that of a hemisphere tuilding. at their midship section, and was very different from the ^•-y^ comparatively flat or plain surfaces now common. Any lower ranges of riders and trusses brought on the floors and first futtotks could have little effect in preventing arching beyond that which arises from the additional re- sistance they offer to deflexion by their rigidity. In men- of-war with several decks above the lower deck, the object aimed at seems to have been to obtain a firm base on which to ground a new and upper series of diagonal ties and struts. It will be evident from these remarks, that it is not considered that the bottom of a ship, if filled-in solid, and made as little compressible as possible by this means, and by the introduction of additional or sister keelsons, requires any great expenditure of material or labour, in order to adapt a system of diagonal trussing to it. The position for its most beneficial application is undoubtedly the sides of the vessel, but whether struts or ties be used, there must be a proper starting point for their ends. In wooden vessels of ordinary construction, this would, per- haps, be found to be in the sister keelson, nearest the wing, or in the thick strakes or riders brought on at the head and heels ot the floors and first futtocks. The im- portance of these last in resisting any strain, if the ship takes the ground and rests on her bilge, is also evident ; and it would therefore be advantageous to increase their strength with this view, even if there existed no other reason. Having determined a base or starting point for the lower ends of the diagonals, the next point to be at- tended to is to determine a strong line of work to which to attach their upper ends. Where intermediate decks occur the diagonals must either be carried past them in one continued line, or a new system be commenced and Practical carried on from that line. In this case the strain on the Building, parts may become such that the direction of the ties and "^•-v^-' struts may require to be changed. While diagonals are useful as a means of firmly connecting the adjacent pieces of timber, it must be remembered that this is a small por- tion of their value, and that full advantage will not be ensured from them without due consideration being given to keep up an imbroken system of sides and of diagonals, with their ends firmly united. It is immaterial whether parallelograms or triangles be used, if the last side of the one be always made the first side of the next. A triangle is a valuable form in structures of this kind, because it is a figure which admits of no alteration in its form ; its angles are invariable as long as the sides remain the same, that is, as long as they are neither elongated nor shortened. These principles are becoming more and more appre- ciated every day, and the strength of ships is consequently becoming much increased. In the government service the diagonals, which extend Diagonal over the surfiice of the side of the ship, are of iron-bars, trussing io varying according to the size of the ship, and also of wood, m"^!"^"' The annexed wood-cuts represent and shoiv portions of the vessels, side of a two-decked ship, the diagonal riders of iron passing up between the ports (figs. 36 and 37). They com- mence under the thick strakes over the first and lower fut- tock-heads, and run up unbroken to the shelf of the upper- deck. On the turn of the bilge, where it is most rounding, and where the ship would rest if she took the ground, there is a system of wooden trusses introduced to stiffen the vessel at that ?pot, which has before been stated to be so desirable an iihject. Fig. 36. In other vessels the iron-bars are laid upon, and sunk into, the frames in one direction, while a series of wooden diagonal riders are placed upon the surface of the internal sheathing, crossing them in the other direction. In the fabric, as a whole, there appears a want, to the eye of an engineer, of a due consideration to the fact, that the strength of a box-girder, or tubular bridge, to wliicli the mind natu- Rilly reverts as the simplest form of a long body to sustaia 08 SHIP-BUILDING. Trnetical sucli weights and strains as those to wliicli a sliip is liable. Building, lies mainly in tlie top and bottom, and not in individual ^"^^v"— ' portions of the sides. A lattice, or trellis girder, is noUiing Details of 8bip Schora- bcrg, by ilcssrs Hall and Co., of Aberdeeo. Sheathing. Beams. Fig. W. without the top and bottom bars unitinj; the lattice or trellis works. If a weif;ht is to be supported by ties, there must be something to carry their upper ends without yielding; and if it is to be supported by struts, there must be a sound and unyielding foundation for them to rest upon, and from which they may rise. Messrs Hall and Co., of Aberdeen, carry out the prin- ciple to a great extent in the vessels built by them. The following is a general description of the Schora- berg (Plate III.), as built by them, in 1854, for James Baines and Co., of Liverpool, and many valuable hints may be gained from the practice of these eminent builders. She was expressly designed for an Australian passenger- ship, and every attention was paid to render her ventilation complete : — Her register measurement was 2400 tons; her frames were of British oak, 4^ feet from centre to centre, close- jointed and bolted, and her sheathing consisted of four thicknesses of 2J inch Scotch larch, first two courses worked diagon.ally at an angle of 4o° passing under the bottom of inside keel, and up the opposite side ; the third course also passed under the keel, and was laid on transversely, same as the frames; there was a similar course worked inside be- tween the frames, each course having a layer of felt, and a coat of Archangel tar, between them. The outside lon- gitudinal planking averaged 6 inches in thickness, and the whole mass was combined by screw treenails of African oak. If inches diameter, put through the whole, there being one treenail at every foot in each strake of plank. She had three tiers of malleable iron-beams, there being one attached to each frame on each side of the three decks, as shown in the transverse section (PI. III.) These beams were laid on pitch pine stringers, which were in two depths, Practical and were attached to the sides by iron staple knees, a piece Building, of plate-iron passing betwixt the beam end and the frame, *^-»v"-' and these plates being connected with the knees by the throat-bolts passing through them, and thus forming a lodgment for the iron beam ends. There was also a malleable iron-plate, 16 x J inches, riveted to the top angle-irons on the beams ; to this plate the water-ways were secured, besides being bolted horizontally. The sizes of the beams were : — Upper declc, 7xJ width, 2Jx2^ inches in single iron, tliiiillc deck, 8x^ 3 inches angle iron. Luwer deck, do. do. do. The beams were in one length ; the lower edge with a bulb, and upper edge with angle-irons, back to back. Tliey were supported by three tiers of iron stanchions, riveted to the beams, and bolted to the keelson and sister-keelsons. For ventilation, the spaces, 3 feet wide, between the frames, were boarded up, and formed excellent ventilators from the various decks and hold, leading up to a space im- mediately imder the main rail, which was fitted all round with Venetians. She was also fitted with large funnels, and with a fanner for forcing the air down to the keel, be- sides scuttles on every six feet on the middle deck. The saloon was on the upper deck, and was fitted with a double roof for causing a current of air, with orifices all round under the cornice outside. The vessel having a great rise of floor, it was levelled off inside to the 5 feet water-line, by having a fourth deck laid from end to end, and under this deck tanks were fitted to hold 300 tons of fresh water. Along the upper deck, from saloon forward, there was a range of houses for live stock, cook-house, and accommodation for the crew. This vessel sailed from Liverpool for Australia in 1854, drawing 21' 6" flirward and 24' 6" aft, and on the eighty-fourth day was lost on Cape Otway, on a fine moonlight night. No favourable opportunity occurred during the passage to test her speed for any continued length of time; but she attained, on one occasion, a speed of sixteen knots for a ihw hours. This ship, complete, cost L.45,000. The annexed figures are further illustrations of the de- tails of construction adopted by the same builders. fl{.88a. Fig. 38 b. A section of a clipper ship, of 700 tons burthen. The Vision, of Liverpool, built in 1854, is given in fig. 39. The larboard side represents the bolting in the frames, SHIP-BUILDING. 99 Practical which are 4J feet asunder from centre to centre. The in connecting the various layers of plank, which consist of Practical Buildiog. starboard side shows the application of the screw-treenails two thlclmesses of 2-inch larch worked diagonally, as shown BuUdiDg. Fig. 89. in figs. 39 a and 38 i, one thickness of larch worked vcrti- worked longitudinally, the slicer-strakes of East India teak, cally, and one outsiue, of an average thickness of A^ inches, top sides Dantzic red pine, Wales, and to light water-line of FU.«. Dantzic imported plank, from thence to the keel-strakes between the planks, which are all coated with vegetable of Diintzic red pine, with two complete layers of hair felt tar. 100 Practical Building. SHIP-BUILDING. Details of Iron ships. Keel. Fij. 38 a represents an outside longitudinal section of the side planking fastened w itli screw-treenails ; and fivr. 38 b represents a vertical section of the same, with the I'elt be- tween and the metal bolting in the frames. Fig. 40 represents the mode of laying the diagonal plank- ing of the deck under the longitudinal upper-deck planks. inoN snirs. A cursory view will now be taken of a few of the leading features in the construction of iron ships, and of the mode of forming and uniting some of the principal parts ; and the specifications, in full, to which two first-class steamships have been built, will then be given. The keel is sometimes formed of a single bar, with the floors crossing above it, and united to the floors by being riveted to the garboard strakc. It is more frequently formed of a plate, sufficiently deep to form both the keel and the centre plate of the keelson, or of a box form. Specimens of these forms of keel will be found in the engravings. A box-keel may also be made thus (fig. 41): — in the section of that vessel at HH. There docs not ap- Practical pear to be any particular advantage gained by the floor Building, being made continuous across the bottom of the vessel ; ^-^w"^ and as additional height is occupied by placing the keelson above them, there does not appear to be sufficient grounds for adopting this system in preference to the other. With any side or sister keelsons this is dift'erent, as it Side or would be inconvenient to break the floors or frames again, sister keel- In cases where such sister-keelsons are to be used as """■ engine or boiler bearers, it would much improve tiieir strength, and they would be better fitted to receive any such weights to be bedded upon them, if the plates were double, and they were brought up above the top of the floors, and formed into a box-keelson, thus (fig. 42). The Fi(;.4I. 'i'he points, in addition to general strength, which require attention, are, that if the keel be injured by the vessel taking the ground, it shall cause as little damage as possible to the vessel itself. A keel should also be capable of being varied in strength, so that it may be made stronger at the heel of the stern-post, where the bottom of the rudder is attached to it. It will be observed that this latter point is parti- cularly attended to in the vessel for the Peninsular and Oriental Company. In the keel, according to the above sketch, it will he observed that the plating is carried right across it, so that it might be very much injured, and probably even torn away in parts, without causing any leak into the ship, its edge being made purposely weaker than the bottom plate to which it is attached. Cross-plates with flanges, or with angle-iron, may be riveted across it, at any distance that may be desired, so as to stiffen it ; and the plates can be made thicker, or additional strengthening plates may be added inside or outside the side-plates, at the stern-post, or at the forefoot. The keelson is generally formed in one or other of the manners shown on the sections ; and the floors may be carried across the bottom of the vessel, and the keelson be placed upon the top of the floors, following the same ar- rangement as in wooden vessels. In the latter case the side-plates of the keelson should be the w hole depth of the floors, in addition to the height of the keelson above them, a space for each frame being cut out of the lower part of the plate to allow it to pass down between the frames, and be attached to the bottom by short pieces of angle-iron, as specified for the side keelsons of the Australasian, and shown Fie. «?- angle-irons of the keelson lying on the floors, and attached to them as they pass, stiffen them, and will tend to prevent their buckling or bending sideways when a great strain from the outside is brought upon them. Where the floors abut on each side of the centre keelson, there is no reason why they should be the same height as the top of the keelson ; and if the top or covering plate of the keelson be put on with external angle-iron (as shown in the above sketch) for a sister-keelson, great facilities are given for taking off the plate at any time for repair, or to renew any of the rivets. Indeed, there is no reason why different lengths of the covering plate should not be put on with screw-bolts, care being taken that the bolts fill the holes correctly. The floors are generally composed of an angle-iron, to Floors, which the external plating is attached, and a plate of any depth that may be desired, with single or double angle- iron on the inner edge of this plate. For the frames two angle-irons riveted back to back are generally sufficient. A T-shaped iron is also sometimes used, and if made with the centre web very deep, so as to be similar to the bulb- iron used for deck-beams, it would be suitable for vessels of great strength, and, in some cases, for the floors with a single or double angle-iron on its inner edge. Some of the forms of beams have already been described. Beams. Beams formed of bulb-iron, with two angle-irons, are de- cidedly the most convenient, as there is no difficulty in welding them up in a common smith's fire to any length that may be required ; and the top edge may be cut so as to vary the depth, and this even in the same beam if desired. By doing this the lower edge of the beam might be made straight, so as not to follow the round-u|5 of the deck and of the upper edge ; and thus any slight elongation of the beam, when brought down or straightened by any weight or strain, and the pressure to force out the sides of a ship consequent upon this, as dreaded by some, would be obviated. The forms of bulb-iron, as generally rolled, do not give nearly so large a proportion of iron in the bulb as would be desirable. It is not consistent with the proper proportion of the flanches of beams, in reference to their depths, as laid down by Mr Fairbairn and other authorities on the subject. SHIP-BUILDING. Practical For beams 8, 12, 18, and 24 inches deep, proportions Building, ^lay be adopted according to the annexed four figures. The L.....-7 Fig. 46. breaking weights of these beams, at the distances of 10 feet, 15 feet, 20 feet, and 30 feet between the supp irts, are re- spectively 10, 15 J, 21, and 22 tons. The thickness of the webs may be considered by many to be too tliin, but a beam of tlie annexed figure (fig. 47) is given by Mr Fairlwirn as one much used by him, with a distance of 30 feet between the supports, and it may therefore be taken as a standard pattern. VViiere a saving of dejitli is a great object, the pro- portions may be varied. Tlie relative strengths and weights of such beams, in comparison witii ordinary wood beams, may be easily obtained by the rules whicli liave been given. Of tlie desirability of introducing iron beams into wooden vessels tliere can be no doubt. Their durability alone ought to be a sufficient inducement. Beams are now being welded up to any lengths by a process patented by Mr Bertram, late of Woolwich dock- yard. The edges to be welded are brought together, and two jets of gas are made to play upon both sides at the same time till the iron is brought to a welding heat, when it is united in a most perfect and satisfactory manner. Shcathin!; An increase of thickness in the plates of iron-vessels or plating, adds to the safety and general strength of the vessel in a much more important degree than putting the same addi- tional weight into the frames would do. A large surface of unequal strength in different parts is objectionable ; it will be sure to yield at tlie line where the weak and the strong parts meet, and probably a rupture may take place along 101 Practical Building. RivetiDg. that line ; but if the surface be all of nearly equal strength, and a pressure be then applied, as may be the case on the exterior .. of a vessel, it may yield, and the in- ''"'' dentation may be extensive with- out any rupture. The subject of riveting has al- ready been fully treated, when giving the details of Mr Fairbairn's experiments on the strength of riveted joints. Mr Bertram's pro- cess, as adapted for the welding of beams, and by which one or more experimental boilers have already been constructed, is also proposed for the purpose of unit- ing the plates of iron ships, and there do not appear to be any reasons to prevent it from becom- ing available after more experi- ence in its use has been obtained. The same remarks, with regard to decks, apply to iron ships as to wooden ships ; but iron has been i .v.-j more used as diagonal and longi- tudinal stringers under the deck- Fi?. *^■ planks in the former than in the latter class of vessels. In the accompanying sections of a vessel constructed to the design of Mr Bowman of London (fig. 48), the iron plating below the deck-planks is shown, and it is laid com- plete over the whole surface beneath the deck-planks. The water-ways, or pieces for forming the run of the water at the sides to the scuppers, it will also be observed, are of iron, which is an important improvement, and a step in the right direction of greater dock-strength, and which is also practised by Messrs Laird and sons of Birkenliead, who make the waterway an open trough prepared to receive the water from the deck, and form a run for it. At the risk of its being considered a repetition, reference Vessels is again made here to the importance of this point. As ""'s' be has been before observed, the severest strain to which a .^ ^ 1®' vessel is likely to be exposed is when it is supported in the "■ ^"^'o" middle of its length, while the two ends are left unsup- pression in ported. As a familiar illustration of the mode of dealing the dccli with this subject, a vessel in this position may be looked and in the upon as a beam supported at the middle, and weighted at bottom, the two-ends, or, which is tlie same thing, as a beam p\ished up in the middle and prevented from rising by the weights, or by being fixed at the two ends. And if this beam be now supposed to be turned upside down, or reversed, and then to be subjected to the same strains upon it as before, it becomes equivalent to a beam sup- ported at the two ends and weighted at the middle, and all the calculations for beams or tubular bridges so weighted immediately become applicable. It will thus be seen that the bottom of the ship has to bear a strain of compression as due to the top, or top Hanche of the tubular bridge, and the deck has to bear a strain of extension as due to the bottom or bottom flanche. The keel and keelsons, and the internal and external plates of the bottom, supported, or rather stiffened and kept in the direct line of the strain, by being attached at such short intervals to the floors, duly meet the case of the top flanche, and give the requisite strength ; and the deck of the ship, and the strengthening pieces con- nected with it, must be made equal to meet the strain of extension, to which the bottom flanche of the beam is sub- jected. Let a vessel be supposed to be of the length of 300 feet, with a depth of 30 feet, and the weight of fittings, niacliinery, and everything wliich she has to carry, to be 1500 tons, which may be assumed to be nearly correct for a passenger screw steam-ship of this length, — and let it be 102 SHIP-BUILDING. Practical Building. >^ Practical J Building, Section of a Vessel by Mr Bowman. Flg.Ul SHIP-BU Practical further supposed that the weights are equally distributed Building, over her length, then the strain would require to be the '*«"V"»^ same as for a tubular bridge, or girder, to carry a weight of 750 tons at the middle. Now, if the ordinary rules be applied, it will be found that the sectional area of the bottom flanche of a box-girder of these dimensions, and whose breaking weight is 730 tons, would be 94 square inches ; and doubling this for the excess of strength necessary in practice, will give an area of 1 88, or say 200 square inches of iron. The strength of the deck, therefore, at the middle, should be equal to the strength of iron-bars or plates of this iectional area, and towards the ends it may be diminished [0 about two-thirds of this strength, on the same principle and in the same manner as the flanches of a beam may be diminished. . An ex[)lanation of the theory of the strength of girders is not within the province of this article. It will be found very fully treated in the works of Tredgold, Hodgkinson, Barlow, Fairbairn, Latham and others, as also in some papers in the Transactions of the Institution of Civil Engi- neers, and in a paper in the Transactions of the Royal So- ciety, by Mr Barlow, " On the position of the Neutral Axis." Water- While the advantages of iron water-tight bulkheads are tight bulk- unquestionable, nothing can be worse than that the sheath- heads, jj^g should be weakened in one direct transverse line by a series of rivets, placed so close together as to lessen the strength of the plates in an undue degree at that line. The Board of Trade insist upon the bulkheads being attached to two frames (figs. 49 and 50), but it is not apparent how the difficulty is got over by this means alone, because on one or other of these frames the rivets must be sufficiently close to make the joint water-tight. This would be advantageous if the bulkhead were made to run home to the side of the ship, and be made water-tight there by an additional angle- iron, while the two frames on either side are united together by means of a thick plate laid upon the sheathing, sufficiently wiile to go past and take the two frames on each side of the bulkhead. This is the mode practised by Mr Bowman of London, and appears to secure the requisite strength to pre- vent the vessel separating along the line of the water-tight attachment of the bulkliead to the ship's side. Specifica- The following is a specification of an iron screw-steam- tion of a ship for the Peninsular and Oriental Steam Navigation Peninsular Company :— and Orien- d • • , n- tal screw- '^ eteam-ship Length between the perpendiculars 335 feet. T ^1- ^ xu 1 T /• * f To be accordincT to the Length of the keel for tonnage { j j ■ ° I approved design. Breadth, extreme 39 feet. Depth amidships (from top of keel) 31 „ Burthen in tons, Nos 2520. {i o. M. Keel.— To be formed of plates, as shown in figs. 51 and 52, the centre through-piece to be 3 feet 6 inches deep from bottom of keel to top of floors, and U thick right fore and aft. The plate on each side to be 10 inches deep by IJ inches thick. The fore and aft plate shown on top of floors to be | in. thick, and 2 feet 6 inches wide, worked so as to fit on top of floors, and connected to centre through-piece by two angle-irons 4 X 4 x A- The after- end of keel to have an angle-iron 6 X 4 on each side, and a plate ^ in. thick on the bottom, to run for 50 feet from the aftermost etern-post. Seem. — To be made of plate in exactly the same manner as the keel, the plate on eaeli side the centre through-piece to gradually taper to yj inches deep at the top, and all the bow-frames to be riveted to it. Breast-hooks. — As may be required. Stern-posts. — 15 inches broad by 7 inches thick, and a heel left on the after-side to bear the rudder, with eyes for the pintles, and turned so as to form a knee forward on the keel. The screw-port to be forged in one piece to suit the drawing, or as the engineer may require. Frames. — Of angle-iron, SJ x 4 x { J, and 20 inches from centre to centre. In engine and boiler spaces, the frames to be doubled in the bottom, and a reverse angle-iron on every frame, 4 x 3 X iV, from floor to gunwale, the whole length of the vessel. ILDING. 103 Plates. — Garboard-strake, |J plates, as broad as can be procured. Practical or worked ; bottom-plates -J J, next plates up to the wales -if, from Building the wales to gunwale |g-, except two plates, 2 feet 6 inches wide, ^^ I J thick, or one plate equal to this to form the wales; the sheer * v ^ Specifica- tion of a Peninsular and Orien- tal screw- steam-ship, continued. Fig. 52. strake, \^ thick, to be doubled right fore and aft, and butt-straps inside, as in single plates, all double riveted from keel to gunwale, and all butts to be flush ; the upper or sheer-strake to go 12 inches above top of water-way, as per sketch. All spaces formed by the projections of the plates to be fitted with liners, so as to avoid small 104 SHIP-BUILDING. Tractical BuilJiDg. Specifica- tion of a Peninsular and Orien- tal fcrcw- Bteam-ship, coutiuuetl. pieces and rings being nsed, except in the case of tne sheer and upper wale-strakes, which will be doubled, and the inner strake will necessarily form the liner. The butts to be perfectly close «a well as the seams, as no pieces will be allowed to be put in and caulked over. The counter-sinking to be carefully done and all rivets to be full ond smooth outside plates, and to be chipped down while hot. The greatest care to be taken in the punching, to pre- vent unfair holes. Floors. — 30 inches deep in engine and boiler spaces of }} plato, with angle-iron, 4} x 3 X I'j. O" «»<='• '"'^i o" '"I' "^ every floor, to run from 1-1 to 16 feet up the turn of bilge. The floors in after- h.jld, 30 inches deep, \i thick, with single angle-iron on top, 4} x 3 X tV- The floor-plates to run 6 feet up the turn of bilge on each side of frames in one piece. Kteltons. — As may be required, and to suit the engineer's draw- ings, to ran right fore and aft as far aa the form of vessel will allow. Pillart. — In holds between keelsons and beams, to be SJ inches in diameter amidships, tapering to 2J at the ends. One on every beam, or as may be directed. Pillars on main-deck, one on every other beam, arranged so as to suit the cabin plan. liulkheadi. — Water-tight; one in fore-peak, two before the en- gine, one abaft the boilers, and one in after-hold; to be in accord- ance with the Board of Trade regulations in every respect. To have iron-bulkheads, or floors, on every frame from stern-post for 40 feet, and o<i every frame from stem for 20 feet, the after ones } inch thick, the foremost \ inch. Those abaft the aftermost water- these bulkheads, aa well as the water-way forming part of the Practical deck. I'roper man-holes, cut through each floor above the shaft. Building, and sufficient water-tight man-hole doors, fltted to the holes in the ^ ^ j iron-deck. The floors before the water-tight bulkhead to run up ^^ .^ as far above the shaft as may be required. Every other bulkhead, .'' . the lencth of screw-shaft, to have a forged iron-rim, 3 inches wide, ,1 ". , 1 • u .1 • 1 • . J I'eninsulap 1 inch thick, riveted round shaft-space. The Flit 54. tight bulkhead to run up to the lower-deck water-way plate, and an angle-iron on the top of each, with a water-tight deck, riveted to the same. The loweiwdeck water-way plate will run throagi hole for shaft to be drilled from after-end through all these by the engineers. All wa- ter-tiglTt bulkheads to be fitted with approv- ed brass sluice-valves. The space below the screw-shaft, abaft the aitermost water-tight hulkhcad, to be fiUed- iii solid with bricks acd cement. Iron-tie bulk- heads to be placed, as directed, between main and spar-decks, about 20 feet apart. Beams. — Of plate, 10 X iV> with two angle- irons on top, 3^ X 2} X -Jg. Beams not to be turned at the ends, but to have a vertical and horizontal plate, rivet- ed to under side of beams and side- frames, with an angle-iron in the angle, and to be finished on the lower edge, with half-round iron, as may be requir- ed. An angle-iron on each alternate frame, for main and lower decks, with as many in the engine and boiler spaces as the position of the machinery will allow. To have orlop- beams and a deck to allowof such accommo- dation for stores as nmy be required (fig. 53). Engine-beams as the engineers may direct. Eight of the foremost beams to be made of an elliptical shape, turned down 2 feet 6 inches to strengthen the bow, and likewise for the hawse-pipes to pass through. The plate to be twice the thickness of the other beams. Stringers. — An angle-iron, 6x4, all round the gunwale, with two covering plates, the outside one 18 X J 8, the inside one 24x 18, riveted to gunwale stringer, and upper side of deck-beams, and 6 inches apart, to allow for pipes or scuppers to pass through the first plank from water-way, which is to be East India teak (figs. 54 and 55). The same on main and lower decks. The lower-deck plates to run right thnmgh engine-room ond boiler space, and to have in that space an angle-iron top and bottom, and to be from the foremost to the aftermost midship water-tight bulkhead in engine-room ^J. Two midship deck-plates, of the same dimensions as the inside gunwale stringer, to run right fore and aft, full length of vessel, on each side of engine-room sky- light, and riveted to upper side of deck beams. To have at lea't 6 diagonal spar-deck plates, 12 x }, riveted on top of all these stringers, to tie the sides of the vessel together, to be placed as may be required (fig. 56). The butts of all these fore and aft stringers to be placed so that the whole of them come on beams, and to have a butt-strap to each butt 12 inches in width, and a row of rivets on each side of the edge of the beams. A vertical stringer, 2 feet 2 inches wide, \% thick, to run round the main-deck at back of epirketting, and to be connected to side deck-plate, or horizontal stringer, by and Orien- tal screw- steam-sbip, continued. Fig 55. SHIP-BUILDING. 105 Practicfil Building. Bpecifi ca- tion of a Peninsular and Orien- tal screw- Bteani->hip, continued. an anpU-iron, 6 X 4 X U- All thftse fore and aft stringers and deck-plates to run fore and aft, and not to be disconnected or cut throu^'h anywhere, and all water-tight bulkhpads, beams, or any ath" artship work to be cut round them, and all to terminate at each end in plate-breasthooks of \ in. thicker plate than the stringers, and to run out as far from either end as may be required. A bilge-stringer, formed of two angle-iron!^, 6 X 4 x U- ^ith a plate at back 18 x -[%, fas- tened to frames to run right fore and aft the ship. All stringers, vertical and hori- zontal, water-way plates, &c., to be doubled for 30 feet in way of cargo gangways. Riveting. — The vessel to be all double riveted with J rivets, except in keel and stern-post, which must be Jth inch thicker than the plates they pa-s through. Other Iron Work. — Iron casing round boiler space and Btoke-hole, between main and upper-decks, likewise all coal- bunker bulk-heads (except what forms part of the en- gineer's contract). Coal-shoots and deck-plates for them, flat in bunker-bottoms, casing of bunkers, engine-beams, screw- tunnel, iron gratings over stoke-hole on upper deck, ash- bucket pipe from stoke-hole to spar-deck, with revolving cap on top, to be furnished by the contractors. A water-tight slide, at foremost end of screw- tunnel, to be fitted in accord- ance with the Board of Trade regulations. Preparation to be made for a lifting-screw on the most approved principles. The engineer to furnish all slides and lifting a[)paratu3. Topgallant Forecastle. — To be in accordance with thedraw- ing given both in length and height, to be plated up from sheer-strake to top with | iron- plates, and to be fitted up in- side as may be directed. A manger, 3 feet deep, to be fitted forward, with 4 hawse- pipes, bucklers, plates, and all complete, as may be required by the company. The deck to be 3 inches thick, with iron- stancheons, and rails round the top-beams, 8 x ^g, bulb-iron, *^'^* * with 2 angle-irons on top, 3 x 3 X iV* -^ water-closet on each side, the aftermost end outside, with pumps, and all complete for the crew. Inside Cement. — The vessel to be filled up solid to the limber- holes with Portland cement. Quality of Iron. — GarboarJ-strake, sheer-strake, and longitudi- nal stringers, of Stafford>hire B. B., of an approved maker, all the other plates of Stafi'ordshire B., except curves, which are to be the best Lowmoor, or of iron made from best picked scrap equal to this. Wood Work and General Outfit, Upper or Spar Deck. — East India teak 3J inches thick, secured to beams by two J-inch galvanized iron bolts and nuts, let in ^ths of an inch below the surface, and dowelled with wood. The mid- ship's deck-strakes to be 1 inch thicker, and to run fore and aft, or as may be required. Main Deck. — Yellow pine 6x5, caulked and secured with iron bolts and nuts as upper deck. Lower Deck, — Yellow pine 9 X 3J, caulked and secured with iron bolts and nuts as above. Stancheons. — Teak or British oak 6x5. Stern timbers of the same 7x6, and to run well down, to give strength to the stern. PrsctioAl All the other stancheons to run down on top of spar-deck, wat^r- Building, way plate through covering-board, and the space between under- ^ -^ > side of covering-board, and top of water-way to be filled in polid and caulked, and a piece of teak-spirketting inside of stancheon, "p^C'iica- bolted through and through, from outside of iron «-heer-strake, *^*^" **' * except in those stancheons which come in way of boats' davits, Peninsular which will have an angle iron knee to turn under water-way, in- ^^^ Urien- side of bulwarks, well riveted to water-way pl'ite. Oak or teak ^' screw- spirketting 18 X 9, to run right round themain^deck inside, on top steam-ship, of water-ways. continued. Awning Stancheons. — Of iron, all round the vessel. Water-ways. — Upper or spar deck, and main deck, to be East India teak 18 X 9, and, if required, to be fitted over the angle-iron stancheons. Ceiling of Hold. — Flat of floor laid with 3-inch American elm, and from that to be ceiled with jellow pine, room and space to the main deck beams. The remainder to be :?-inch close futline, caulked, payed, and beaded over seams, as will be pointed out. Bulwarks. — Yellow pine 3 X 2J thick, and to have a panel grooved in the centre. Main-Hails. — Teak, 12 x 4 J ; to have copper or yellow metal along the edge outside, fere and aft. Gangways. — To be where shown on plan — viz. four cargo-gang- way ports with all doors, brass scuttles, banging platform to turn outside or inside as m^v be required, between main and upper decks, lined in sill and edi^es, with twenty ounces copper or yel- low metal. Two passenger gangways on upper deck, fitted with the most approved accommodation-ladders complete, with all neces- sary fittings. Four coaling gangways on upper dtck, fitted with doors complete; also hanging brackets rivett-d on s-hip's s-ide, to carry stage when required. The ends of rough-tree-rail and gang- ways to be capped with a casting of brass. Catheads. — British or African oak, 18x16, mounted with all stoppers, cleats, &c,, as may be required. Bitts, — Of British or African oak, 22 X 22, stepped on keelson. Towing bitts, t'tpsail-sheet bitts, belaying pin-rack':, cleats, eye- bolts, timber-heads, &c., to be fitted as and where required. Bridge. — To be 5 feet 6 inches wide, to be supported with suf- ficient iron stancheons, and fitted with ladders, lamp-boxes, hand- rails, and all complete, as may be required. Masts. — Lower mast and bowsprit of iron or steel as may be ap- proved, and a provision to be made for cutting them away if req lired, the other masts and spars to be of black spruce or red pine, to be rigged according to plan. Rnging. — Standing rigging of wire-rope, the rest of best hemp, with ill requisite blocks. All blocks to be brass bushed, or patent leathtr bushes, as may be preferred ; all dead eyes, both upper and lower, to be made of lignum vita:; if required the vessel to be fitted vith Cunningham's patent self-reefing topsails. Stonn- House. — To be built at after-end of upper deck, with two two-be. -th cabins on each side of w heel, w ith a water-closet in each, and fitted up inside in every respect as first-class cabins. The top of this liouse, as well as those of all other cabins and offices on the upper deck, to be double; the upper one teak, the lower one pine, covered with canvass. Comp^tnions and Skylights. — To be built according to plan. The tops of all of them on the upper deck to be made of East India teak. Boats -To be in accordance with the Board of Trade regula- tions, aid to be fitted complete, with nia.-t5, sails, oars, boat-hooks, breakers, gratings, davits for ship's sides, and all necessary fittings as mav le lequired ; brass rowlocks to mail-boat; lift:-boa;s to be accordinj; to Lamb and While's plan. Fowl-Cooj s. — Twelve ; 12 feet by 2 feet 4 inches high. Sheep JVra.— To hold forty sheep. Scuppe~-s. —Eight on each side on each deck, to be placed where shown. Fish- D frits.— Tot fishing anchors to be fitted, as will be shown. Anchors and Chain Cables.— In proportion to tonnage of vessel, the anchoi-s to be patent, or as required by the Board of Trade re- gulations. Winches. — Two; if steam, the difference in price to be paid by the company. Sails, — One suit of sails complete. Tarpaulins, — One for each hatch and scuttle. Awnings. — A complete set, fore and aft. Bumps. — One copper chambered pump 8 inches in diameter, with brass bucket and lead pipe, tilted in every compartment, and a 7 inch and a 5-inch i)ownion, fitted as may be directed. Wheeh. — Two of mahogany, brass-mounted, hide-rope, fitted with patent steering gear complete. Fenders. — With chains, &c., complete. Porij.— Of East India teak, 21 inches square, with a o-inch brass O 106 SHIP-BUILDING. Practical BuiMing. Specifica- tion of a Peninsular and Orien- tal screw- steam-ship, CODtiDued. Bcuttlo fitted in the centre of each, hung with strong iron hinges, brass-bushed, ami copper pins, except where shown round in plan, as in water-closets or other tleclc-oirices, where scuttles must bo 6tted, 7 inches in diameter, of the best manufacture. WctUr-Closets. — Tylor's of Newgate Street to be fitted whore shown on plan, with cisterns, pipes, valves, and all necessary fittings. Baths. — ITot, cold, and shower, lo be fitted where shown on plan. Tanks. — For 12,000 gallons of water, with all requisite cocks, pumps, pipes, and all necessary fittings. BinnacUs. — Two, with adju5.tod compasses and lamps complete. Brass Bdl. — 18 inches in diameter, with vessel's name engraved thereon. Cook'IIouses. — Two of iron, with all necessary fittings complete. Cooking and Baking Apparatus — With all necessary utensils complete, as may be required to be furnished by the company. Colours.— A complete set as may be required. Life-Buoys. — Six of such description as may be required. Lanterns. — Signal-lanterns and fittings to be fitted where re- quired — viz., 2 bridge, 1 mast-head. Buckets. — Twelve wash-deck and twelve leather buckets, with the company's crest and sliip's name painted tliereon. Hose. — Leather fire-hose and canvass-hose fur washing decks, with the necessary couplings complete. Capstans. — Two; the foremost, or main capstan, to be one of Brown's patent double-headed capstans, to work on top of topgal- lant forecastle, with all the bitts, stoppers, &c., fitted complete on spar-deck. The after one to be Brown's patent double-power cap- stan for warping the ship, and to be fitted complete. Meat-Safe and Vegetable Locker. — One of each to be made and fitted, as will be shown. Butcher's Shop. — To be where shown on plan, slate-tanks, and all complete. Cabins. — To be fitted acconUng to plans furnished by the company, arranged generally as the '' Pera"' and " Candia."' The contractors to find everything complete, except saloon and fore- cabin tables, seats, chairs, sideboards, sofas, bed and sofa mattresses, curtains, cump-stools, gl;is?, earthenware, plated goods and cutlery ; cabin-lamps and looking-glasses; pantrj*, steward's and store- keeper's utensils ; but the contractor will find all the furniture and fittings for all the cabins and ofTices in the ship, including first and second class passengers, otiicer's, engineer's, steward's, and any other cabin in the ship, such as chests of drawers, washstands with marble tops, tables, toilet-shelves, or any other fittings that may be required ; likewise all the different offices on deck, as shown in plan, to be fitted complete, such as surgery, lamp-room, baker's shops, scullery, or any other office not named here, but shown on plan. All the cabins in the ship to be fitted with Robinson's patent ventilating bulkheads, as per elevation. Painting. — All the wood- work to have four coats. The main- deck cabins, from the main hatch forward, to be grained oak in the very best style. The main saloon to have at least six coats of paint and two of best varnish, and the whole of the gilding to be of the very best quality. Mail'Room. — To be where shown on plan. Space for sixty tons of mjiil, and to be lined with zinc all over, q^he bottom to have ledges of wood, 3 x -J-, 1- inches apart, secured to deck. Sail-lioom. — To be where shown on plan, and to be covered over with zinc. Purser s Store-Hooms. — To be where shown on plan, and to be fitted up inside as may be directed. Boatswain and Carpenter s Store. — To be where shown on plan, and to be fitted up as shall be directed. Ihnally. — The whole of the material and workmanship to be of the very best quality, and the vessel (with the foregoing excep- tions) to be entirely fitted and ready for sea at the cost of the contractors, notwithstanding any omission in this specification, and subject to the approval of the managing directors, or of such fiurveyor or surveyors as they may appoint to inspect the work. ' The tollowing is a copy of tlic specification of an iron screw steamship, built for the European and Austrahan Royal Mail Company, the Australasian, buih m 1857, by Messrs J. and G. Thompson ol"Glasi;o\v, under the in- spection of Mr Bowman, of London, wlio has kindly per- mil:ted its publieation here. The strength of tliis vessel, and the soundness of the principles on which she is con- structed, were well proved bv her ^ronndinj; in the Clyde, on her first passing down the river after being latmched, when she came off, as before stated, quite uninjured. Specification of an Iron Screw-steamship to he built for Practical the European and Australian Royal Mail Company. liuilding. Principal Dimensions, ^ -^ Ft. In. ^Pecifica- Tjcngth of keel 310 ^'"" °'' **'*-' IJicdthof beam 42 " ^"stral- Deplh of hold to spar-deck 29 9 ***'""■ To have three decks, with full poop and full topgal- ) Ian t- forecastle J Height of poop 8 „ topgallant- forecastle 6 3 „ from main to spar-deck 8 6 Keel and KeeUon. — The keel to be formed of three thicknesses of plate; the centre plate to be 1 inch thick, and 45 inches deep; forming, at same time, the main keelson and centre of keel ; these plates to be in as long lengths as possible, to be put together, butt- jointed, with straps of same thickness, and double-riveted above that part which forms a portion of the keel ; the plates to run the entire length of the vessel, and for 10 feet up the stem. The keel side-plates to be 12 inches x 1^ inch; to be in as long lengths as can possibly be obtained ; to be all scarphed on to each other scarphs 6 inches long ; these three thicknesses of plate, to be par- tially riveted together before the garboard-strake is fitted on; the garboard-strakea to be double- riveted to the keel with \\y\\ inch rivets; all the holes to be runneled out perfectly true before rivet- ing ; the butt of the keel-plates and garboard-strakes to be care- fully shifted and caulked, and made water-tight. (Section AU, fig. 69.) Stern-post, — To be of best hammered scrap-iron in one piece, the after-post to be 12 X 5 inches, the inner-post to be 12x7 inches ; the lower portion, uniting the two posts, to be 12x8 inches; and to have about 8 feet of keel attached to it, and with correspond- ing Fcarph for riveting to keel. The keel portion to be planed out into a groove, 1 inch wide and 6 inches deep, into which the keel- son plate is to be worked, and double-riveted through and through. The end of the keelson-plate to be secured to the inner post by two vertical bars of angle-iron secured to it by rivets, and to the post by tapped bolts (fig. 57). The inner post, at the line of the lower "^^ lC\\\\'^'^'-X^ Pig. S7. Frtr.Sft. deck-stringer, to have a palm welded to it, which Is to be firmly riveted to the stringer, so as to give security to the post (fig. 58^, To be formed in the same way as the keel, from iron of tlie same dimensions, and riveted together in the same way ; the keel, keelson, floors, stem, ond stern-post to be according to sketch to be fur- nished. Frames. — To be spaced throughout the vessel 18 inches apart from centre to centre, of angle-iron, 4 X 3J x gth inch, to have a reverse angle-iron on every frame, 4J x 3J x i inch, riveted along the top of the floor-plates, and up the frames, to the height of the uj)per deck-beams, by Jth inch rivets, 6 inches apart (every alter- nate frame from main-deck may be left without reverse iron, a piece beins put in underneath the clamp-plate). Where desired, in wake of boilers and engines, the frames and reverse bars to bo worked double. Floors. — The floor-plates at keelson or amidships to be 33 inches deep X §th inch thick ; to be carried up past the turn of bilge, say to the 6 feet water-line, and riveted to the frames and reverse angle-irons. The end of each floor, which butts against the keel- son, to have a vertical angle-iron, 5 x 3 x J inch, riveted to the floors and to the centre keelson, (section CD, fig. 59). Along each side of the top of keelson-plate there will be angle-iron 5 xo x gibs. riveted on a level with the top edge of kedson-plate and floors. A SHIP-BUILDING. 107 Practical Buililin;:'. Practical BuiMiu^f. Fig. 50 , 108 rrnctical Iluilding. Specificn- tiun uf thi •' Au8trul' asiau.'' S H 1 r - B u plate 3R X Jlli inch in enpinp-mnm, nnii 36 X IJlhs at ends of vessel, in long li-ngih^, will run the whole I'ngih of the ve«sel, nnil be riveted to the nncle-iron on top of keelson, and to the reverse nnple-ironii of the floor!) ; these plates to be built jointed, and double riveted, section GtJ. Keelioni — To have two side and two bilge keelsons, to be formed of plates 30 inches broad X JIh inch, riveted to the reverse frames. On the centre of these plates there will be double Rnpleiron 6 X 3J X {th, riveted back to back, and to the plates. Krom be- twixt these angle-irons tliere w-ill pass down to the skin-plate jjth inch thick, the breadth regulated by the distance apart of the frames and reverse ungle-irons ; these jdates to be riveted at the foot to short pieces of angle-iron, secured to the skin, and at the top, be- twixt the floor angle-irons, section H. 11.. &c., &c. ; to have inter- mediate keelsons for about 150 feet amidships, to be double angle- iron 6 X 3J X }th inch, riveted back to back, and to the reverse angle-irons on the floors, and to be connected to the outer skin, same as the other keelsons, section II. II. The whole of the stringers, main, bilge, and otiier keelsons, to pass unbroken through the bulkheads, and to be made water-tight by strong brackets, riveted to them, and to the bulkheads. „ , son foot , ,, f^''- Mi.l. *"• Plating. — Garboard-strcke tobe fit- 1 , , j^ j j^^ ted close up to the frames J * Next strake to garboard (to gar- 1 , , - board) 1 * » * Thence to bilge.... \i J H Bilge-strake U i 'ih Thence to wales iV J & iV i AVales in two strakes Ill Thence to sheer-strake ■,'„ \ iV Sheer-strake at least 36 in. broad i ^ i The plating from keel to gunwale to be laj>-jointed horizontally with vertical flush-buits, with an internal strap of corresponding thickness to the respective plates, 8 inches wide. The butt-straps of the fheer, wale, or garboard strakes to be cut across the thread of the iron from plates, and to be I'yth thicker than the plates to which they are respectively fitted. All the plates which end on screw-frames, and the next adjoining them on every strake, to be not less than { Jths thick, and double riveted, with very great care, to the stern-frame. Riveting. — The keel, stem, stern-post, and all the longitudinal seams of the plates, uj) to the spar-deck, to be double riveted. All the butts throughout the ship to be double riveted. Double rivet- ing to have about eight rivets to the foot. The bar-rivets, through frames and plates, to be spaced 6 inches apart, and the plating to be wrought out and in fashion ; the space between each alternate strake, and the frame being filled with a solid sliver-piece closely fitted ; all the rivets of keel, stem, and stern-post, to be IJth inch diameter ; those passing through inch plates to be 1 inch ; through {th plates, to be {fths; through {tb plates, {th inch; remainder, |th inch. Caulking. — The whole of the seams and butts to be caulked in the most careful manner, and made perfectly water-tight ; and on no account is any canvass, or red-lead, or like substance, to be in- serted in the seams, but all to be caulked throughout, metal to metal. Beams. — Main-deck beams, of patent bulb-iron, 10 x Jth inch ; upper and lower deck-beams, of patent bulb-iron, 9 X i inch, all to be Bi)aced on alternate frames ; the upper, main, and lower deck- beams to have double, 3 x 3 X } inch ani.'le-iron, securely riveted on top edge, with rivets 8 inches apart ; all the beam* to have suit- able knees, solid, 18 inches deep, for securing them to the frames, formed by bending round the ends of the beams. Siringert. — On the upper-deck, of plate, 42 X |lhs amidships, and i^ths at end, with angle-iron 3 x3i X Jth incti riveted to it, and to the deck-beams, and double riveted to the sheer-strake on the main and lower deck, of plate 36 X jth« amidships, and iV'hs at end with angle-iron, 5 X 3 x jth inch, firmly riveted to the main and lower deck-beams, and reversed angle-irons, 2 feet below the main and upper deck-beams, to have a clanip-plate 18 X jth inch, running the whole length of the vessel, and securely riveted to the reverse angle-irons on the frames, by riveta spaced 4 inches apart. All the butts to be double riveted. Deck Trussing. — On the upper and main deck, on each side of the hatches, to have a plate 24j inches, carried right fore and aft, worked in lengths of 15 feet, with doubie-riveted butts, the whole rivetfd to the beam anglc-iions with ten rivets in each ; the whole space from the outside edge of this to the inside edge of gunwale stringer on the upper-deck to be filled in with plate, wrought in long lengths, not less than 18 inches broad and a J-inch thick (these plates may be f inch, and cover a space equal in weight to those plates specified). .Austral- I L D I N G. All butt-jninted Inngitudinnl Rtraps sinplp riveted, thwurt ulrnp* PracHcoi double riveted : the whole riveted to the beam anglc-iruna with Building, rivet8 ppnced 4 inches apart. v^ ^ , > Hold Stanch<ou$. — From keehon to lower deck beam* to have 31 c .^ • u I • * I. ■ . J 1 « .1 1 I 1 ^pecifica- imhos round iron stanrhcon'*. riveted securely to the knelKnn-nlnie .■ -. .. 1 .1. i i. .u r 1 J 1 . ■ 1 . . . *'*'" O' Iho and the benniB ; above these from lower deck to mam uerk to have ,, 3 inchfs round iron fitancheons, firmlv secured to both tiers of . . •' asian. beams where necessary Sulkheads.— To have the number of water-tipht bulkheadfl that may be required by the company, fitted between double frames and over keeNon and ptrinfjers. supported by suitable ban* of angle- iron 4 X 3 X }. spnccd 30 inches apurt. Bulkheads to be carried to main deck, and to be fitted in every respect in accordance with the Board of Trade regulntiitns. Be- tween the aftermost bulkhead, to which Bcrew-|ir(ipeller pipe is attached, and the stern-post, to have fitted on every frame, up lo the hrij^ht of lower-deck beams, a series of bulkheads formed of J-inch plate, and firmly riveted to the frames, and secured on the top w ith double an{,;le-iri)n ; at this line breasi-ho* ks, Rpecifind iifler- wards, are to be worked forwards to the pipe bulkhead, so as to form an iron deck above these bulkheads specified, and to be riveted to the double angle-iron on them. The hole for passing stern-pipe through to be carefully arranged, so that no more than necessary space is cut. Rudder. — The stock to be 7J inches diameter, with turned pintles, of best hammered scrup-iron, in one piece with the frames, and plated with gths plate. Breasihooks and Crutches. — To be fitted at each deck, fore and aft the ship, at the junction of the stringer plates ; bilge and side keelson formed by riveting triangular plates about 9 fe«*i long to these fore and aft ties, so as to firmly unite the two sides of the ship. MaMt' Partners. — On the various decks to be formed of materials similar to the beams, and to bo securely riveted to them. Gunwale Moulding. — To be formed of G-inch half-rnund iron in b'ngth, securely riveted to the upper edge of walo struke by rivets about 8 inches apart. Water-tvays.^On main and lower deck of red pine 4J inches thick, and on the upper deck of Kast India tpak 18 inches broad by 9 inches thick, both securely bolted to the stiinger plates by two rows of bolts and nuts. Decks. — To have three decks. Upper deck throughout where exposed to be of best East India te:ik 3 J inches thii k, to be secured to the beams by bolts and nuts at evety third beam, and with a wood screw of best form on both sides of the alternate beams, the whole to be planed true on the edges, top, and bottom before being laid, and thoroughly caulk<d and payed with resin or pitch, as may be directed by the company, and made perfectly wat^r-tight ; main-deck to be of best seasoned Quebec yellow pine 3J inches thick, thoroughly secured to the beams by wood screws with bolts in the butts, thoroughly caulked, payed and made water-tight ; lower-deck of 3 inches yellow pine to be similarly fitted. Rails. — The rails to be of best East India teak of suitable breadth, firmly bolted to stancheons, to be covered on the outside and inside edge with 18 oz. yellow metal, firmly nailed ; to have a netting all round of best cordage, firmly secured to galvanised iron rods on rail and water-way. Bxtlwark Staiicheons. — To be of East India teak, and to be fitted into sockets formed of angle-iron, 7 X 3 X J ; these to be riveted to the stringer plates at proper intervals for the stuncheons, one bolt through each socket and stancheon. Hatch Coaminys. — On main, upper, and lower decks, of East India teak, of dimensions to suit the size of the hatches, and securely bolted to the iron carlines ; to be protected by iron plates on sides and top, and fitted wiih iron battens, cleats, and cutbands; on upper decks to have teak skylights on the hatches. Ceilinfj. — In flit of tloor in hold? of 2J-inch elm, thence to hold beams of 2-inch red pine from hold beams to main-deck beams, and cabins and store-rooms of 1-inch yellow pine close sratned ; the ceilings to be bolted to reverbe angle-irons with galvanised screw-bolts. Ports. — To have four gun-ports on each side, with flaps properly arranged in netting, and fitted with ring-and-eye bolts as required. Capstands. — To have one of Brawn's patent capstands of suit- able size, placed forward, with patent chain-stoppers, and four riding bitts complete for working cable ; in addition, to havea cast- iron working capstand, with brass top on quarter-deck poop, both complete, with all necessary bars. Catheads. — Of British oak, with anchor stoppers, and all usual fittings. Jiitts. — To have at least five cast-iron mooring timber-heads on each side, of suitable strength, properly bolted through waier-waya and stringer jdates, with heavy chocks of hard «ood limber below, Jiawsc'^i^et. — To have a strong cast-iron hawse-pipe on each bow, SHIP-BUILDING. 109 of size to suit chains, firmly eccured to the skin of the ship ; also stern and side mooring pipes of cast-iron where required, and firmly secured. Chain- Lockers, — To be built of wood where required. Anchors and Chains. — To have anchors and chains; the chain cables of best best iron, and to be tested to the government test. Uemp-warps according to Lloyd's rules. Anchor- Davits. — To have two strong anchor-davits, with blocks and fills complete for lifting anchors. Pumps. — To have a pair of 6-inch Redpath's patent pumps in each compartment, with lead-pipes and roses, and all the necessary iron gearing for working. Scuppers. — To have sufl5cient lead scuppers on upper and main deck, well secured to ship's side and water-ways. Tanks. — To have suitable iron tanks made of quarter plates, cap- able of containing 10.000 gallons of water, with two fixed copper pumps with brass boxes, lead pipes, and iron gearing complete for working, and placed where required. Masts and Spars. — To be rigged as a ship, with one complete set of masts and spars according to plan ; lower masts and bow- sprit of yellow, red, or pitch pine in one stick, or built and hooped if neces:>ary ; topmasts, liwer and topsail yard?, and jibboom to be of red or pitch pine, the remainder of black spruce; to be all ac- cording to plan, and complete with all usual iron work of best quality. Hifjgina. — All the standinfj rigging to be of galvanised wire, the running rigging to be of the best St Petersburg or Manilla hemp and chain where required, chain of best best iron. Blocks. — To have a complete set of iron and rope stropped blocks of suitable sizes, the lower and topsail yards brace blocks, topsail peak and throat haulyards, catblocks, &c. ; to have Dalton's patent roller bushes in the sheaves, the standing rigging to be set upon lignum vitae dead eyes of proper size ; to have all nrcessary snatch blocks, catblocks, watch-tackles, and belay ing-pina of greenheart. Sails. — To have one complete suit of sails, the topsails to be fitted with Cunningham's patent reefing api)aratus according to plan, of Gonvock extra canvass, with suitable Nos. complete, ready for bending with sail covers as required. Iron Work. — All the small iron work of the hull to be furnished complete of the best quality. Bouts. — To have at least six boats, according to Act of Parlia- ment, complete with strong iron davits, tackle falls, &c., as usual. The boats to be supplied with ash oars, rudders, tillers, and boat- hooks, and the four largest to have raasis and sails. All the boats to be supplied with canvass covers and gripes as required ; the four midship boats to be carried inboard on beams of proper strength, and properly supported on iron stancheons from the rail, and to be fitted with patent lowering apparatus to a plan to be furnished. Gangways. — To have properly-fitted gangways opposite to each hatch for receiving cargo; to have on each side a passenger-gang- way, with suitable accommodation-ladders, davits for lilting, iron railings, and man-ropes. Coaling- Ports. — To have fitted along ship's side, between upper and main decks, the number of coaling-ports that may be afterwards found necessary, properly hinged, so as to be perfectly water- tight when closed, and fitted with strong iron shoots inside, com- municating, by grated openings, with the upper-decks and with coal-boxes. Painting. — The outside of the ship to receive throe coats of the best oil paint, the inside two coats, except the bottom, which is to be coated with patent cement. The wcdwork on deck to receive three coats, and to be grained in imitation oak. Masts and spars to receive two coats of paint or varnish. Cabins and internal fit- tings to be painted in the best manner, as may be afterwards directed. Winches. — To have three double-power cargo winches, with der- ricks and chains complete, for working cargo. Side Lights. — 'Vo have two brass side lights in each state-room on main-deck and spar-deck, uU securely riveted to ship's side, and made water-tight. Bells. — To have a ship's bell and belfry, with name engraved on it, and binnacle-bell. Binnacles. — To have two brass and one mahogany binnacle, with lamps. Figurehead. — To have a hamlsome full-length figurehead, with trail-boards, stern and quarter ciirving, as may be required to suit name, nil handsomely relieved with gilding. Flags. — To have one ensign, one burgee, one union-jack, one blue-peter, one private signal, and one set of Marryatt's signals with chest and hook. Signal Lmtems. — To have complete set of Admiralty signal lanterns (brass, of large size). Guns. — To have two brass 4-pounder, and fear iron 9-pounder Practical guns, with breecbings, rammers, and sponge complete, with all the Building, usual complement of muskets, pistols, and cutlasses. y »- .. -w^ Steering Apparatus. — To have a handsome double-steering wheel ^ ~ of E. I, teak, fitted with right and left handed screw-steering gear, Specifica- brass nuts, malleable iron crosshead, connecting-rods, and screw, tiun of the To have two portable tillers fitted to rudder-stock ; wheel to be *' Austral- covered by a substantial house, with glass front. asian." Cook-House. — To have a spacious galley of iron fitted on main or spar-deck, near funnel, with the most improved form of cooking apparatus and baking ovens fur crew and passengers; the wood- work of the galley to be lined with 5Ib. lead and felt, and the floor to be covered with fire-tiles, and to have proper ventilators on sides and top. Poop. — To have a poop to extend from after-part of vessel to after-part of after-hatch, about 90 feet long; in forming the poop, every alternate frame of the vessel to be carried up, to which are to be joined the beams of the poop, same size of iron as the frames. The sides and after-end of the poop to be rounded over and plated with § plates, the poop-deck to have teak water-ways, 12x5; teak decks, 3" X 5". The whole fastened to the beams with bolts and screws, every butt to have a screw-bolt. Stancheons of gal- vanised iron to be carried round the poop, with a teak rail on top. The poop to be fitted with suitable skylights, made of teak, fitted in the best style for light and ventilation ; also to have round or square side lights in state-rooms, as may be required ; to have side stairs, with brass rails, from the upper deck. The inside of poop to be fitted up in fiist style for passenger accommodation, and in accordance with a plan to be approved; to have two bath-rooms; also a water-closet for every eight passengers, side state-rooms, ladies' sitting cabin, captain's cabin and steward's pantry, with all the necessary furniture and fi tings; the whole of the very best description of workmanship and material, as usual in large pas- senger steamers of the first-class. Main-Beck, — On the main-deck a dining-room, to be entered by a spacious stair, either from inside of poop or from upper-deck, to be fitted with all the necessary furniture; a full set of dining- tables, sofas, settees, and chairs covered with morocco; to have mirrors, carpets, sideboards, stoves, lamps, swinging trays, A:c., &c., and to have side state-rooms for first-class passengers, with carpets, curtains, sofas, wash-stands, &c., the whole arranged to a plan to be approved of. Second-Class Accommodation. — To be fitted on main-deck forward for 100 passengers, with a water-closet for every 12 passengers, bath-room, &c. Saloon under spar-deck, of polished E.I. teak, with tables, settees, &c. The steward's bar and other conveniences all in the best manner. Deck-IIouse. — To have a strongly-fitted deck-house, as large aa possible, consistent with other deck arrangements ; to be constructed with iron-frames and beams, made fast to strong teak coamings, bolted to the deck-beams. The deck of the house to be of 2J inches yellow pine, with a side covering board to form moulding, of E. I. teak ; the sides and ends to be of IJ inch yellow pine, half checked or feathered, and grooved ; the house to be fitted according to a plan to be arranged and approved. Officers' Accommodation, — To liave accommodation for the oflScers, engineers, stokers, and stewards, with a sufficient number of wuter- closets and other conveniences, fitted on main-deck, between the first and second-class cabins, with separate ladder-ways, all as may be afterwards arranged. Topgallant Forecastle. — To extend from the back of the figurehead of vessel to the fore side of the fore-hatch, being about 68 feet in length, and in height about 6 feet to 6 feet 6 inches ; every alternate frame of the vessel at forecastle to be carried up to deck of fore- castle, with reverse angle-irons, 4x3x4 inches, by piecing the pre- sent frames ; to have an angle-iron stringer, 4x4x4 incites, with plates 18 X j inches. The beams to be of bulb-iron, 7 x J, placed on every frame ; these beams to be turned down at ends, to form knees, same as the other beams of the vesst 1 ; the beams to have an angle- iron, 2J X 2t X I inches, riveted on each side, for fastening down decks; to have two beam-ties riveted on top of plates, 12 x J ; and that part of the forecastle deck where rap>.tan comes through, to be all plated between the beam-ties ; same to extend a sufficient length for strengthening that part of capstan ; plating to be iV^hs thick, and to extend from gunwale of vessel to top of forecastle, and the whole length of forecastle «ith double riveted butt-joint**. The decks to be of teak, 5J x 3 inches, with teak water-ways. 12 X 4j, well fastened down, caulked, and made water-tight; the part of deck at capstands to be well fastened and strengthened with teak planks, of increased thickness to those on deck; the top of fore- castle to be fitted with all the necessary chocks. &c., required for a vessel of this class. The capstand for anchors to be double, and wrought on topgallant forecastle; but the stopper and riding-bitts to remain on spar-deck, as originally intended. The front of fore- no SHIP-BUILDING. Prncticnl castle to be neatly cIo?e>l in and panellej, equal to bulwarks of Building, vessel. The interior to be fittcil up for crew, as may be directed V ^ , ^ by owners, with suitable bra-8 aide lights for ventilation. Fartcattle. — The crew to bo accommodated in forecastle, under epar-deok, with berths^ mess tables, Ac, as may be required. Lower-Dtck Fittings. — The lower-deck, forward and aft, to be fitted with bullion-room, mail-room, wine-cellar, store-rooms^ &c., as miy be ilirecteil. all in the most approved manner. On the main-deck, forward of second-class cabin, the remainin^^ space to be fitted with butcher's shop, cabin for petty officers, and other necessary fittings, as may be directed. Stulitihlt. — The second-class cabin to be lighted and ventilated by 8kyli;;hts, fitted on cargo hatches, with suitable gratings, and other particulars as required. Sundriit, — All the lucks, hinges, hat-hooks, ftc, to be of brass, and fitted as required, and of the best description; to have com- plete sets of lamps for all the cabins, locks and bars for all the hatches and store-rooms ; hen-coops, sheepfold, pig-sty, sets of Fig. 60. sapstand bars for both capstands; four 60-gal1on water-casks foar harness-casks, twenty -four buckets, twenty-four mess kids; four water-funnels, six breakers, four deck-tubs, and four tar-buckets; awnings for quarter-deck, with iron stancheons, binnacles, and bell- covers ; skylight-covers and tarpaulines as required ; iron bell- mouthed ventilators, and windsails for engine-rooms where re- quired. TaTierson's Me?srs Taylcrson and Company, of Port-Glasgow, have diagonal patented a diajional arran<;ement of the frames of iron framing, vessels. Tliev siibstiliite diagonal framing in the place of the ordinary vertical framing, or interspe^^e diagonal witli vertical frames. The annexed figure shows the latter sys- tem of arrangement. No addition of strength, however, to the side of a ship will obviate the necessity for strength in the bottom and in the deck. If rupture were to lake place at the top edge of the side, it may be doubted whether the diagonal frame would do more than divert the line of rupture into the sloping line between itself and the next frame. The same builders use a remarkably strong form of keel and keelson (fig. 61) ; and a representation of this is annexed, showing at the same time their mode of attaching the water-tight bulkheads ; they introduce a piece of timber at each bulkhead, where it is attached to the ship's side, and fasten this by screws from the outside, with a view of lessening the number of rivet-holes. This most desirable object is no doubt attained, but great care must be taken that corrosion of the fastenings does not take place. Arman's Mr L. Arman, of Bourdiaux, has constructed ships with mixed sys. diagonal iron framing inside a framing of wood of very l*""ilrj'"'''S scantling, the sheathing of the ship being of wood. Inside the vessel, and attached to the iron frames, he in- troduced a scries of horizontal stringers of [)late-iron at intervals from the deck to the keelson, which is also of iron. This system imparts great strength to the frame- work of the vessel, and it is believed that it has, upon the whole, been very successful. Altogether the combination of wood with iron has been carried much further in France and iron. than in this country. Iron beams are being much used in Practical their vessels, and iron riidder- pieces, the latter being very Building, advantageous in men-of-war, from their smaller size. ''-^^/"^ IJefore closing these remarks, the influence or effects KfTects of exerci.<ed upon the practical construction of ships by the Moyd's rules of Lloyd's register require to be noticed, as they '■cB'"'*'" '■> form a code of instructions to which all merchant-builders? ''*' of this country are compelled to adhere. These rules are called compulsory, because if a builder deviates from them, or ventures to differ in any point from the opinions of the surveyor, his vessel loses caste, either by being excluded altogether from the first class, or by being put on it for a less term of years. This does not suit the purchaser, and as there is no appeal from the decision of the surveyor, the builders must submit. In the first place, o o o o o o o o o O J OO o o o o OO O O GO fc\ 9 o o o o o o o q yn\ Fig. a. it may be remarked, that to have but one table of scant- lings, &c., for ships of the same tonnage, while it is evident that the same rules as to scantling, &c., cannot be cor- rect for the sharp long ship intended for carrying light cargoes, such as tea, wool, &c., and also for those which are intended for heavy dead-weights. Nor is any differ- ence permitted in tlie scantlings of the timbers at the bow and at the stern of full or sharp ships. The rules do not directly interfere with the forms of ships, but in some re- spects they have imdoubtedly indirectly militated against the production of fast-sailing vessels. The supporters of Lloyd's register claim to themselves the credit of having improved the British mercantile ma- rine ; but, in the o[)inion of many experienced persons, its effect has been to produce a dead and spiritless mediocrity. That the construction of many very bad ships is greatly prevented is true, but there is no actually compulsory law to force every ship to be inspected and classed at Lloyd's, and many ships are sailed independent of any such inspec- tion : its action in this respect, therefore, is not complete. On the other hand, it is equally true, that men of skill and talent are restrained from introducing improvements in the combination of materials. That this is the effect produced is well known ; and as an instance, it may be mentioned, that on the first proposal being made to introduce iron beams into a wooden vessel, leave was refused unless the vessel was put into a lower class ; and this improvement. SHIP-BUILDING. Ill which is now fully admitted by Lloyd's, was kept hack for . many years. It is natural that the general feeling of ser- ' vants of the government, or of large public or joint-stock companies, should be against taking responsibility upon themselves by introducing or permitting changes; but it is much to be deplored if this spirit is brought into such a position as to be a drag upon the talent and energies of the whole nation. Shipowners who are not themselves practi- cally acquainted with ship-building, take the natural course of adopting Lloyd's register as their statidard. They con- tract for a ship to be built in such a manner that she may be put into the first class at Lloyd's, and tluy thus declare themselves ready to pay the cost of the builder's adherence to Lloyd's rules. The ship-builder knows, perhaps, that he could introduce improvements, but he is unwilling to subject himself to the risk of a refusal by Lloyd's surveyors, and as the purcliaser for whom he is working is satisfied, he builds accordingly. The want of encouragement by Lloyd's rules to increase the durability of ships has been before noticed. Under the existing rules, then, there seems to be reason to fear that the tendency of Lloyd's register has been to some ex- tent to cause increased expenditure, to restrain improve- ment, and to uphold a dead and stagnant mediocrity. It Practical is to be hoped that care will be taken to guard against Buildinj^. the possible existence of such evils for the future. ^^^/""-^ On Launching. Ships are generally built on blocks which are laid at a I'auncliing declivity of about f ths of an inch to a foot. This is for the facility of launching them. The inclined plane or sliding plank on which they are launched has ratlier more inclina- tion, or about f ths of an inch to the foot for large ships, and a slight increase on this for smaller vessels. This in- clination will, however, in some measure, depend upon the depth of water into which the ship is to be launched. While a ship is in progress of being built, her weight is partly supported by her keel on the blocks, and partly by shores. In order to launch her, the weight must be taken off these supports, and transferred to a movable base ; and a platform must be erected for the movable base to slide on. This platform must not only be laid at the necessary inclination, but must be of sufficient height to enable the ship to be water-borne, and to preserve her from striking the ground when she arrives at the end of the ways. For this pinpose, an inclined plane, a, a (figs. 62 and 63), purposely left unplaned to diminish the adhesion, is laid on each side the keel, and at about one-sixth the breadth of the Fig. 03. vessel distant from it, and firmly secured on blocks fast- ened in the slipway. Tliis inclined plane is called the sliding-plank. A long timber, called a bilgeway, b, b, with a smooth under surface, is laid upon this plane ; and upon this timber, as a base, a teni[)orory frame-work of shores, c, c, called " poppets," is erected to reach from the bilge- way to the shi[). The upper part of this frame-work abuts against a plank, d, temporarily fastened to the bottom of the ship, and firmly cleated by cleats, e, e, also temporarily secured to the bottom. When it is all in place, and the sliding- f)lank and under side of the bilgeway finally greased witii tallow, soft soap, and oil, the whole framing is set close up to the bottom, and down on the sliding -I'lank, by wedges, f, f, technically called slivers or slices, by which means the ship's weight is brought upon the " launch" or cradle. When the launch is thus fitted, the ship may be said to have three keels, two of «bich are temporary, and are se- cured under her bilge. In consequence of this width of support, all the shores may he safely taken away. This being done, the blocks on which the ship was built, except- ing a fi;w, according to the size of the ship, under the fore- most end of the keel, are gradually taken from under her as the tide rises, and her weight is then transferred to the two temporary keels, or the launch ; the bottom of which launch is formed by the bilgeways, resting on the well greased inclined planes. The only [ireventive now to the laimch- ing of the ship is a short shore, called a dog-shore (g). on each side, with its heel firmly cleated on the immovable platform or sliding-plank, and its head abutting against a cleat (A), secured to the bilgeway, or base of the movable part of the launch. Consequently, when this shore is re- moved, the ship is free to move, and her weight forces her down the inclined plane to the water. To prevent her running out of her straight course, two ribands are secured on the sliding-plank, and strongly shored. Should the ship not move when the dog-shore is knocked down, the blocks remaining under the fore part of her keel must be consecutively removed, luitil her weight overcomes the adhesion, or until the action of a screw against her fore- foot forces her off. A much less expensive mode of launching is now much I'sanching practised in the merchant-yards of this countrv, and has"" ■'"'''^*'' been long in use in the French dockyards, allowing the keel to take the entire weight of the vessel. The annexed Fig. 64. figure represents this method (fig. 64). The two pieces (a a), which are shown in the figure as being secured to the ship's bottom, are the only [lieces which need be pre- 112 SHIP-BUILDING. Prnrtical pared acconlinff to tliis svstpm for cacli sliip, the wliole of Building. t|,j. rciiiaiiultr bi'ii)!; available fur tvery linincli. A space ^— /^"^ of about li.ilf an inili is left bctwicn tlu'iii and tlie balk timber |ilacc(l Ijciuatli tliem, as it is not iiiteiulcd that llic ship sluiuld bear on these balk timbers in laiinchini;, bvit merely be supported bv them in the event oF her heeling over. The shi|), tlurelore, is lannehed wholly on the slidinp-plaiik (e). fitted inider the keel. Messrs Hall of Aberdeen launched a vessel of 2C00 tons in this manner witlioiit a sinple cleat npon her bottom or riband of any kind, and avoided all the niaking-np of the side-ways, e.xcept tor about 60 feet in mid^hips for keeping the ship upright. The centre- "ay v\as liollowed, and a round sliding-way fitted in it, and tlie keel Avas thus sujiported from end to end. This may therefore l)e considered to be the safest, cheapest, and easiest mode of launching long sharp sliips. If a ship is coppered before launching, so that putting her into a dry-dock for that pm-posc becomes unnecessaty, it is then desirable that she should be launched without any cleats attached to lier bottom. This method of fitting the Practical launch, as represented in figure Co, is then adopted for this liuiUi'ig. j)iirpose. The two sides of the cradle are pieventeil biing ^"V^^ forced apart when the weight ot the ship is brought upon them by eliains ])assing under the keel. Each portion of frame" (irk com|)Osing the launch has two or more of these chains attached to it, and eacli cliain is brought lUKJer the keel, to a bolt a, which passes slackly through one of the poppets, and is secured by a long fore lock li, with an iron liandle (c), readiing above the water-line, so that when the ship is afloat it may be drawn out ol the bolt. The chain tlien draws the bolt a, and in falling trips the cradle from under the bottom. There should be at least two chains on each side seemed to the fore-poppets, two on each side secured to the after-poppets, and two on each side to the stopping up, and this only (or the huineh of a small ship: in larger shifis the nimiber will necessarily be increased according to the "eight of the vessel and the tendency that she may have, according to her form, to separate the bilge- ways. This tendency on the part of a sharp ship by a rising floor, or by her wedge-shaped form in the fore and after bodies, is great, but there is not much |)robability of a ship heeling over to one side or the other. It is recorded that upon one occasion of our sailors hav- ing taken posession of an enemy's arsenal, and finding a vessel on the stocks nearly compleleti, they removed the shores from one side, and tried to upset her by wedging up the shores on the other side, but were unilile to do so. There appears, therel<)re, to be no valid objection to the chea|)er and more ready method of launcliing on the keel. (a. M— T.) 113 STEAM SHIPS. steam Na vigatioo. addle- 'hoels u^eJ y the an- ients. lasco de aray, U3. 'p Papin, S81. Op the various triumphs of man's ingenuity for which tliis aire is so remarkable, none, perliaps, has conduced more to the weilbeing and happiness of the human race tlian the art of Steam Navigation. This is apparent wlien we consider the vastly extended means of co[nmunication wliich we now enjoy with the most distant parts of tlie globe; the fresh impulse given to commercial undertakings by the rapidity, the safety, and the certainty of steamships, as compared with sailing-vessels; and the increasing spread of civiliza- tion and Christianity attendant upon onr intercourse with distant and semi-barbarous nations. It is not wonderful, therefore, that the merit of having invented an art so preg- nant with interest to mankind should be claimed for many different individuals; and we accordingly find the names of ingenious men of all countries associated, more or lesS; with its origin.' The use of paddle-wheels, propelled by manual or animal power, dates back to a very remote period, these having been employed by the Romans, and other na- tions of antiquity, for propelling their war-galleys ; but it is doubtful whether any advantage was thus obtained in economy of labour, as compared with the use of oars. It is not, therefore, until the gradual development of the steam-engine, and its introduction as a motive power, that we can hope to find any advancement in the long- sought-for art of navigating ships against adverse winds and currents. The first historical notice we meet with of such a combination — a steam-engine placed on board a vessel to act as the propelling agent — occurs in the year lo43, when we are informed that Blasco de Garay, a sea- captain in the service of Charles V. of Spain, succeeded in propelling a ship of 200 tons burthen in the harbour of Barcelona, at the rate of a league (or three miles) an hour. No information is afforded us of the nature of his apparatus, except that it comprehended a boiler, which, it is stated, was liable to burst ; that the power was transmitted through paddle-wheels, and that the vessel could be turned with much facility by means of the apparatus. We can only speculate as to the nature of this mysterious engine, but it seems probable that it owed its efficacy to the reaction of a jet ot high-pressure steam, on the same principle as that famous classical toy, the iEolipile of Hero, invented B.C. 120. Notwithstanding that the scheme was commended by the emperor and his ministry, and its author promoted, we do not read of any second experiment being made, or of any further notice being taken of the invention. We may assume, therefore, that in this case the propelling power was found to be insufficient and unsatisfactory, and the experiment was worthless in its result. In the year 1630, David Ramsey, "page of the king's bed-chamber," obtained a patent " To make boats, ships, and barges goe against the wind and tyde," but we do not hear ot any experiments having been made by him. The patent office contains records of various similar suggestions made between the years 1630 and 1681, but nothing of any practical value appears to have been effected. At the latter date the ingenious Dr Papin, a Frenchman, de- scribed a method of propelling a vessel by steam. The only engine then known, however, being itself very crude and imperlect, the doctor experienced so much difficulty in reducing his scheme to practice, that it is believed no actual trial of it ever took place. His principal difficulty lay in obtaining the required rotatory motion from the re- Steam Na- ciprocating one of the piston, for which pur])0se he proposed vigiition. to employ two cylinders, the piston of one of which should "^-"v*"^ be ascending, while that of the other should be descending, the continuous rotative motion being obtained by means of racks attached to the extremities of the piston-rods, work- ing altfrnatehj into a pinion on the paddle shaft. Although Dr Papin's schemes can only be viewed in the light of theoretical suggestions, he still deserves much credit both for his idea of the atmospheric engine, and for his proposal to employ it for working the paddles of a boat. Savery, on the other hand (who published his Miner's Friend in the year 1698), although a great actual improver of the steam-engine, and famous in his day as a clever mechani- cian, appears to have doubted the applicability of his engine to the propulsion of ships, since he only alludes cursorily to the possibility of such a thing. In the year 1705 Newcomen, having adopted Papin's Newcomen, suggestions of the cylinder and piston, and Savery's method 1705. of condensation, first completed the atmospheric engine, and made it capable of becoming, in practical hands, an efficient propelling power; and it is worthy of remark, that even at the present day, we have several excellent paddle- wheel steamers which are most satisfactorily propelled by modern atmospheric engines, constructed by the late Mr Seaward. The great engineering difficulty at this period was how to convert the reciprocating motion of the piston into the rotary motion of the shaft; for although, to our eyes, the crank may appear a very simple and almost self- evident expedient for this purpose, it was not till long afterwards that we find it introduced. In the year 1730, Dr John Allen proposed to propel a vessel by the re-action of a jet of water forcibly expelled from the stern — a scheme which has been repeatedly re- vived since his time, and which has recently been attended with a considerable amount of success in the hands of Mr Ruthven of Leith. Six years after Dr Allen's proposal, Jonathan Hulls obtained a patent for his " Invention of a machine for carrying ships and vessels out of or into any harbour or river against wind and tide, or in a calm." His idea of a steam-boat was as follows ; and however we may now be inclined to smile at his rude mechanism, in compa- rison with the beautiful machinery of a steamship of our own times, Jonathan Hulls undoubtedly deserves much Jonatlian ^ credit for his ingenuity. In his boat two paddle-wheels ^'^'^'^'•'^ were suspended in a frame projecting from the stern. In the body of the boat were two steam cylinders, whose pistons acted on the atmospheric principle; that is to say, they were impelled in one direction only, by the pressure of the atmosphere acting against a vacuum. To each piston one end of a rope was fastened ; the rope was then carried round a grooved wheel or pulley on the correspond- ing paddle-wheel, the other end of the rope being allowed to hang free, with a weight attached to it. When one of the pistons descended in its cylinder by the pressure of the atmosphere, it pulled its rope, and consequently moved the paddle-wheel round in a degree due to the length of the stroke and the diameter of the pulley. While the piston was ascending in the cylinder, on the re-aduiission of the steam, the counter-balan<;e weight at the end of the rope dragged the pulley round in the contrary direction ; but the pulley being attached to the paddie-wheel by 1 The historical portion of this article is indebted to Professor B. Woodcroft's Sketch of the Origin and Progress of Steam Navigation C)r some valuable facts. 114 Steam Na- vigation. STEAM SniPS. James WBtt,l780. MiUer of Dalswin- ton, Taylor, and Sy- mington, 1788. ratchet-work, it was so arranfjed that the pailtlle-wheel rc'm;iincil stationary (iurin;; the rctrognule motion of the )iiikv. There biin;; two cyhnders ami two piuidle-whccls in the boat, one would be in motion whilst the other was stationary, and tlnis a continuous progressive movement was given to the boat. It is uncertain whether this plan was ever put in practice. We now arrive at the era of James Watt, whose inven- tive genius removed most of the obstacles whicli had hitherto prevented the steam-engine from being effectively employed for propelling vessels. His main improvement, after his invention of the separate condenser, was the sub- stitution of the double-acting in place of the single-acting or atmospheric engine, by which means the power of an engine of given size and weight was at once doubled, while the motion was at the same time rendered more uniform. About this time also (1780) the crank and fly-wheel were first patented by James Pickard. Although Watt's improve- ments rapidly paved the way for the successful adaptation of the steam-engine to the purposes of navigation, we do not Hnd that he himself devoted much attention at first to this subject, confining his views to perfecting the rotatory- engine, and increasing its economy. Accordingly, we fincl that it was not till after the expiry of their patent in 1800 that Boulton and Watt's engines were applied to tliis use. In the year 1781, the Marquis de Jouffroy constructed a steamboat at Lyons of the following dimensions : — 140 feet long, 15 feet beam, and 3'2 feet draught of water. His experiments, which were made in the river Soane, were probably unsuccessful, as the subject was allowed to drop. Leaving undiscribed some abortive schemes of Ramsay and Fitch in America, and Serrati in Italy, which were attended with no practical result, we pass on to the first really successful attempts at steam navigation, which were made in 1788 by a Scottish gentleman, Patrick Miller of D.dswinston, in Dumfriesshire. Having previously ex[)e- rimented with boats propelled by the power of men and horses applied to paddle-wheels, he resolved to make the steam-engine do this work ; but neither he nor Mr James Taylor, who resided in his family as tutor, and assisted him in his experiments, could devise a plan for apply- ing the engine. In this dilemma Taylor suggested that they should call to their assistance an old schoolfellow of his, Mr William Symington, an engineer, at that time employed in endeavouring to adapt the steam-engine to wheeled carriages. Mr Miller accordingly saw Symington in Edinburgh, and, after examining the model of his loco- motive carriage, was convinced of the perfect applicability of a similar engine to drive the paddle-wheels of a boat, and gave orders for one to be made under the direction of Symington and Taylor. This engine was accordingly made in Edinburgh, sent to Dalswinton, and put together by them in October 1788. The engine, in a strong oak frame, was placed on one side of a twin, or double pleasure- boat, on Dalswinton loch ; the boiler was placed on the opposite side, and the paddle-wheels in the middle. In the same month of October the machine was put in mo- tion, and the inventors had the gratification of witnessing the perfect success of their efforts. Although the cylin- ders of their engine were but 4 inches in diameter, this first steambo.1t attained a speed of 5 miles an hour on the waters of the lake. Mr Miller, being now desirous of trying the experiment on a larger scale, commissioned Mr Symington to purchase one of the canal-boats employed on the Forth and Clyde Canal, and to have suitable engines constructed for her at Carron Ironworks. When this new machinery was ready, a trial took place on a straight reach of the canal of about 4 miles in length, on the 26th of December 1789, when the vessel moved at the rate of about 7 miles an hour. Many other experiments followed with a similar result, Stcnm No- as will be seen by the following notice of them sent (by vigaiiun. Lord Cullen) to several of the Edinburgh newspa])ers : — ^^V"~^ " Tt is with great pleasure I inform you that the experiment which some time ago wa sinude upon the great canal here by Mr Milli>r of Dalswinion, for a^c rtiiining tie powers of the steam- engine when applied to sailing, has lately 1 ei n repeated with great success. Although these exppriments have be^n rep atrd under a variety of disadvantaj^es, and »iih a ves-el built formerly for a different purpose, yet the velocity acquired was no less than from 6J to 7 miles an hour. This sufficiently shows that, with vessels pro- ] erly constructed, a velocity of even 8, 9, or even 10 miles an hour, may be easily accomplished, and the advantages of so great a velo- city in rivers, straits, Ac, and in cases of eToeigency, will be suffi- ciently evident, as there can be few winds, tides, or currents, which can easily impede or resist it; and it must be evident that, even with slower motion, the utmost advuDt ges must result to inland navigation." Although these expeiiments were thus partially .success- ful, and their value well understood and appreciated, we find that Mr Miller's boat was soon afterwards disuianlled and laid up at Carron, and nothing further was at that time attempted. This apparent apathy can only be ac- cotmted for by the fact (which was afterwards acknow- ledged by Mr Miller himself), that Symington's machinery was not equal to the task of propelling a boat with the degree of certainty anil regularity necessary to ensure com- mercial success. Hence, although the great principle of the possibility of steam navigation was thus apparently settled by Mr Miller's experiments in 1788 and 1789, it was not till the year 1801 that a really practical steamboat was first produced in Scotland. In this year Thomas Lord Dundas, who was well acquainted with Miller's experi- ments, and who was a large proprietor in the Forth and Clyde Canal, eng:»gcd Mr Symington to tindertake a (resh stries of experiments on this subject, with the view of em- ploying steamboats for towing on the canal in place of horses. The result was the production of the Charlotte Dundas, The Char- named alter his lordship's daughter, and which, fi-om the lotto Don- simplicity and practical nature of its machinery, may be dasi 1801. justly considerctl as the " first practical steamboat." The superiority of this boat over its predecessors lay in Syming- ton's more judicious arrangement of the machinery, which consisted of Watt's double-acting engine, working a con- necting-rod and crank, which turned a single paddle-wheel, revolving in a well-hole near the stern of the vessel. This engine had one horizontal cylinder, 22 inches in diameter and 4 feet stroke. In March 1802 Lord Dundas, Mr Speirs of Eldcrslie, and several other gentlemen, being on board, the Charlotte Dundas " took in drag," says Mr Sym- ington, " two loaded vessels, each upwards of 70 tons bur- then, and with great ease carried them through the Long Reach of the Forth and Clyde Canal to Port-Dundas, a distance of 19 J miles, in six hours (being at the rate of .3^ miles per hour), although it blew so strong a gale right ahead that no other vessel on the canal that day attempted to move to windward." Notwithstanding this favourable result, the scheme was doomed a second time to disappoint- ment, in consequence of some of the proprietors of the canal becoming alarmed at the destructive effects of the wash of the steamboat upon the banks. The boat was therefore laid up in a creek of the canal, where it remained as an object of curiosity for several years. It may be remarked, that this production of Symington's possessed every necessary qualification which is considered requisite, even at the present day, to make a good and useful steamer ; and in proof of the confidence it inspired in its own time, we may observe that the Duke of Bridgewater actually ordered eight steamers from Symington lor use on the Bridgewater Canal, to be built on the model of the Char- hitte Dundas. His grace dying, however, shortly after- wards, this order was never executed. STEAM SHIPS. 115 ;eam Ka- We now arrive at the period when American enter- •igation. prise stepped in to avail itself of the painful and laborious — ^r~^ results of these costly experiments, which although made and perfected in this country, had not yet been turned to good account. About a year after Symington's ex- nlton, periment with the Charlotte Dundas, Fukon, the Ame- 103. rican engineer, made a similar though less successful ex- periment on the Seine, for the weight of his engine broke the vessel in two, and the whole went to the bottom. He persevered, however, and in August 1803 completed an- other vessel with its machinery. This boat was 66 fett long and 8 feet wide, but moved so slowly that his experi- ment is described as having been a failure. He afterwards came to Scotland, and saw Symington's steamboat on the Forth and Clyde Canal, his visit being thus recorded by Mr Symington : — " When engaged in these experiments I was called upon by Mr Fulton, who told me he was lately from North America, and in- tended returning thither in a few months, but having heard of our Bteamboat operations, could not think of leaving this country with- out first waiting upon me, in expectation of seeing the boat, and procuring such information regarding it as I might be pleased to lommunicate, observing that, however advantageous such an in- vention might be to Great Britain, it would be still more valuable in .America, where there were so many great navigable rivers. In compliance with his earnest request, therefore, I caused the engine- fire to be lighted up, and, in a short time thereafter, put the steam- boat in motion, and carried him 4 miles west on the canal, return- ing again to the point from which we started in one hour and twenty minutes (being at the rate of 6 miles an hour), to the great astonishment of ilr Fulton and several gentlemen, who, at our out- set, chanced to come on board. During the trip Mr Fulton asked if 1 had any objection to his taking notes regarding the steamboat, to which I made no objection, as I considered the more publicity that was given to any discovery, intended for general good, so much the better; and, having the privilege secured by letters- patent, I was not afraid of his making any encroachment upon my right in the British dominions, though in the United States I was Well aware I had no power of control. In consequence, he pulled out a memorandum-book, and. after putting several pointed ques- tions respecting the general construction and effect of the machine, which I answered in a most explicit manner, he jotted down parti- cularly every thing then described, with his own observations upon the boat during the trip." Fulton having thus obtained what information he could, returned shortly afterwards to America, and, in coiijunc- tion with Mr Livingstone, obtained a patent securing to them the prospective advantages of steam navigation in America, by what they were pleased to call " their inven- tion of steamboats." They very wisely got all their ma- chinery from England; so that in the year 1807 the first steamboat in America was launched, and fitted with a pair of engines constructed by Boulton and Watt. Phe Cler- This vessel, called the Clermont, though probably fitted nont, 1807. ^.jji, superior machinery to tliat in Symington's boat, was barely so fust, making less than five miles an hour. Her dimensions were 130 feet long, 16^ feet beam, and 7 feet deep ; the boiler 20 teet long, 7 feet deep, and 8 feet broad ; the steam-cylinder (one only) was 24 inches in diameter, and 4 feet stroke ; burthen 160 tons. Her paddle shaft was of cast-iron, with no outer support be- yond the sides of the ship. The diameter of the paddle- wheels was 15 feet, the boards being 4 feet long, and dipping two feet in the water. She was subsequently lengthened to the extent of 140 feet keel. In the begin- ning of the year 1808 the Clermont was placed for regular work on the Hudson River, between New York and Al- bany, a distance ot 125 geographical miles, and was crowded w ith j)assengers, her sfieed after the alteration being at the rate of 5 miles an hour. This was, therefore, the first steamboat that ever ran continuously for the accommoda- tion of passengers, and the first that ever remunerated her owiurs, and to this the AmericariS may justly lay claim ; but that Fulton was the "inventor" of the present system of steam navigation, as asserted by some American authors. Steam 5r»- cannot be admitted ; nor, indeed, did he " invent" any vigation. single improvement in the construction either of the ma- ^^/^~^ chinery or the vessel. The success of their first steamer induced Messrs Fulton and Livingstone to build two other vessels, the Car of Neptune, of 300 tons, and the Para- gon, of 350 tons, also supplied with Boulton and Watt's engines. The first person who ever took a steamer to sea was also Steven*, an American, R. L. Stevens of Hoboken, who had been 1808. associated with Livingstone previously to the connection of the latter with Fulton, and had brought his experiments to a successful issue nearly as soon. As Fulton, however, had secured to himself the exclusive privilege of navigating by steam in the state of New York, Stevens boldly took his vessel round by sea from the Hudson to the Delaware. To him are due many of the present peculiarities of Ame- rican steamers. He it was who first adopted the long stroke ; the upright guides for the piston-rod ; the beam overhead, raised on a high framework of wood, working above the deck ; and the connecting-rod, descending thence to the paddle-shaft, all characteristic of American steamers to the present time. He also improved the form of the American boats, by substituting a fine entrance and run for the old bluff bow and stem, as well as by increasing their relative length to eight or ten times the beam. Stevens is believed to liave been the first engineer who constructed a " tubular" boiler, though these did not come into general use till long alter his time. Although steam navigation had been thus early intro- duced on the -American waters, it was not till the year 1812 that the first regular passenger-steamer made its appearance in this country, on the Clyde. This was the Comet, built Tomet, for Mr Henry Bell, the proprietor of the Helensburgh 1**12. Baths on the Clyde, and who had long been a most zealous advocate of steam propulsion. This little vessel was 40 feet long on the keel, and 10 feet 6 inches beam, propelled by a steam-engine of three or four horse-power, with a ver- tical cylinder, and working on the bell-crank principle — the engine being placed on one side of the vessel, and the boiler (of wrought iron) on the other. The Comet made her first voyage in January 1812, and continued to ply re- gularly between Glasgow and Greenock, at a speed of about 5 miles an hour. She was propelled by two small paddle- wheels on each side, each wheel having four boards only. She was afterwards transferred to the Forth, where she ran for many years between the extremity of the Forth and Clyde Canal and Newhaven, near Edinburgh. The dis- tance is 27 miles, which is stated by Mr Bell to have been performed, on the average, in 3J hours, being at the rate of above 7J miles an hour. Mr Bell had on several occasions brought his projects for Henry steam navigation under the notice of the British govern- Bell, ment, but always without success ; and it was not till the year 1819 that the admiralty of the day became impressed with the importance of steam-power for towing men-of-war, chiefly through the representations of Lord Melville and Sir George Cockburn. The first steam-vessel in the royal navy was then built, and was also named the Comet- She is still in existence, and measures 1 15 feet in length, 21 feet in breadth, and draws 9 feet water, being propelled by a pair of engines, by Boulton and Watt, of 40 horse- power each. But to return to Mr Bell's steamers on the Clyde. The Comet was so successful, that two other steamers, of in- creased size and power, were constnicted ; and, in 1814, Mr Cook, of Glasgow, built a fourth, called the " Glasgow," which, in point of power and efficiency, became the standard at that time for river-steamers. The marine engines hitherto constructed hud all been applied siiiyly in the ves- sel i but in 1814 Messrs Boulton and Watt first applied two IIG Steam Na- vigation. STEAM SHIPS. Pnvid Na- pier, 1818. The Jamee ■NVntt, Ac, as2a. The Sa- vannah, 1819. coiulcnsins engines, connected by cranks set at right-angles on tlie sliaCr, to propel a steamer on the Clyde. This was found to be a j;ieat improvement, and tliciiceforward almost all steamers have been fitted with two engines. In tlie year 1815 a small vessel, with a side lever-engine of 14 liorsc-powcr, by Cook of Glasgow, made a voyage from Glasgow to Dublin, and thence round the Land's End to London. It then ran with passengers between London and Margate with some success, though encountering great opposition from the Thames watermen. In 1818 Mr David Napier, to whom we owe the intro- duction of British coasiing steamers, as well as of steam- packets for our post-office service, first established between Greenock and Belfast a regular steam communication by means of the Rob Roy, a vessel of about 90 tons burthen and 30 horse-power, built by Mr William Denny of Dum- barton. For two winters she pUed with great regidarity and success between these ports, and was sJ'terwards trans- ferred to the English Channel, to serve as a packet-boat between Dover and Calais. Soon after this Mr Napier liad the Talbot built for him by Messrs Wood. She was 120 tons burthen ; and when fitted with two of Mr Napier's engines, of 30 horse-power each, this vessel was in all re- spects the most perfect of her day. She was the first steamer that ran between Holyhead and Dublin. About the same time, also, he established the line of steamships between Liverpool, Greenock, and Glasgow, for v.liich traffic he built the Robert Bruce, of 150 tons, with two engines, of 30 horse-power each ; the Superb, of 240 tons, with two engines of 35 horse-power each ; and the Eclipse, of 240 tons, with two engines of 30 horse-power each. All these were established as regular coasting traders belore the year 1822. In the latter year the steamer James Watt was built by Messrs Wood, to |)ly between Leith and London. She was the largest steamer that had yet been built, being 448 tons measurement, and fitted with two engines of 50 horse- power each, by Messrs Boulton and Watt. The Soho followed on the same line, and was equally successful. The next great advance made was in 1826, when the United Kingdom was constructed, this vessel having been regarded in her day with as much wonder and interest, from her (so-called) gigantic proportions, as were afterwards the Great Western, the Great Britain, and, more recently, the Great Eastern. The United Kingdom was 160 feet long, 26i feet beam, and 200 horse-power; the ship being built by Mr Steele of Greenock, and the machinery by Mr David Napier. Prior to this time many improvements had been made in the arrangement and construction of the marine engine by Boulton and Watt, Maudslay and Field, Penn, and others of our eminent mechanical engineers ; the ex- pansive action of steam in the cylinder having already been taken advantage of by Messrs Maudslay and Field in their engines, which were also fitted with escape-valves on the cylinders, and other imiirovements. The first steamer which crossed the Atlantic was the "Savannah," an American vessel of 300 tons burthen. which arrived at Liverpool in the year 1819, direct from the United States, in 26 days, partly steaming and partly sailing. Being tittedwith engines of small power, and the vessel beingotlier- Avise unsuited for ocean navigation, this must be regarded rather as a bold experiment (and not a very successful one) than as establishing the practicability of a rapid and regular steam communication between this country and America ; for it is only in the combination of these two qualities of speed and regularity that the steamship excels the sailing vessel. In 1829 the Cura9oa, an English built vessel, of 350 tons and 100 horse-pow er, made several successful runs between Holland and the Dutch West Indies. In the mean time Dr Lardner and other theorists attempted to demon- strate, that the navigation of the Atlantic by steain-power alone was impracticable; and it was not till the Sirius and the Stflam Na- Great Western had shown the fallacy of their reasoning, that vigaiion. the public mind was disabused of this idea. The Sirius '^■""^r~~^ «'as not built expressly for transatlantic navigation ; she The Sirius belonged to the St George Steam-Packet Company, and ""d Great had run with a good reputation between London and Cork. ,„^q''"'' Her tonnage was alxmt TOO tons, and her horse-power 320. She started from London on the morning of the 4th of .^pril 1838, with 94 passengers. Though first in the race, she was only three days in advance ; (()ron the 7th of the same month the Great Western, built and fitted at Bristol expressly for the purpose, (ollowed her. The Sirius arrived at New York on the 22il, being 17 days clear on the passage, and the Great Western (sailing from Bristol) on the 23d, being 15 days. The Sirius again sailed on her homeward passageon the 1st of May, and the Great Western on the 7th of May, and they arrived, the first on the KStli, and the second on the 22d, being 16 .and 13.\ days respec- tively. The average speed of the Great Western on this voyage was thus 8"2 knots on her ontw,ird passage, and nearlv 9 knots on her homew.ard, reckoning the distance at 3125 knots for the one, and 3192 for the other. She con- sumed 655 tons of coal going out, having still 205 tons re- maining in her coal-boxes upon her arrival at New York. Coming home her consumption was 392, having 178 tons remaining on her arrival at Bristol. Her average daily consumption varied from 27 tons, with expansive gear in action, to 32 tons without it. As the Great Western pos- sesses considerable historical interest, some of her principal dimensions are here subjoined. She was designed and built by Mr Paterson of Bristol, and fitted with machinery by Messrs Maud>lay, Sons, and Field of London. She is . 212 feet long between the perpendiculars, 35 feet 6 inches beam, and 23 feet 3 inches depth of hold, drawing from 16 ' to 18 feet of water. Her tonnage is 1340 (builders' O.M.), and her engines (on the side-lever construction) are 440 horse-power. Her cylinders are 73J inches in diameter, and 7 feet stroke, making 12 to 15 revolutions per miiuitc. Her complete success was doubtless mainly attributable to the fact, that she was especially fortunate both in her de- signer and in her engineers, w ho are still, perhaps, the most eminent of the present day in their respective departme.its. The practicability of transatlantic steam navigation being thus triumphantly established, the Briti>h Queen, the Pre- sident, and other large steamships, were built in rapid suc- cession, as well as many steam-vessels of war. Up to this time the paddle-wheel was the only propelling The screw agent employed ; but in 1837 the rival system of propelling propeller ships by means of the screw-propeller first came prominently '_n'''f'<l'"«<l| into notice, through the successful experiments of Captain Ericsson and Mr F. P. Smith. Captain Ericsson's small vessel, of 45 feet in length, 8 feet beam, and but 2 feet 3 inches draught of water, towed the American ship Toronto, of 630 tons, on the Thames, on the 25th of May 1837, at the rate of 4]t knots an hour, against the tide, as authenti- cated by the pilot; and also towed the admiralty barge, w ith their lordships on board, from Somerset House to Black- wall and back, at the rate of about 10 miles an hour. Later in the same year Mr Smith made some very success- ful trips with his small boat and screw-propeller between Margate and Rainsgate. The next screw-vessel was the Robert Stockton, built in 1839 by Messrs Laird for an American gentleman, who had witnessed Captain Ericsson's experiments. This boat was also perfectly successful ; but the Board of Admiralty still failed to recognise the peculiar applicability of this means of propulsion for vessels of war. The next year, however, in 1840, Mr F. P. Smith, having obtained the support of some influential mercantile men, brought out the Archimedes, a screw-vessel of 232 tons The Archi- burthen and 80 horse-power. The success of this vessel modes, was so complete, that the Admiralty were at length induced ^^*''' STEAM SHIPS. 117 Btcam Na- to make a trial of tlie screw in the royal navy, and the vigation. i{.it[igr Has ordered to be built on the same lines as the ^"^/""^ Aiecto paddle-wheel steamer, and to be fitted with en- gine< of the same nominal power. The next screw-steamer worthy of notice was the Dove, an iron boat, constructed under Mr Smith's direction. Her speed, however, proved so unsatisfactory to her owners, that they ordered her to be changed into a paddle-wheel boat ; and as it happened that she had been built with very fine after-lines, her constructor, Mr Smith, unfortunately charged her deficiency of speed to this circumstance, and adopted the theory that full stern- lines »ere the most advantageous for the action of the screw. The Rattler was now tried ; and her trials having fully satisfied the Board of Admiralty, they ordered the construction of several screw-vessels, which were all built with full sterns. This idea having at length been proved, by further experiment, to be erroneous, and that, on the contrary, fine after-lines were absolutely required for the proper efficiency of the screw-propeller, so as to allow of a ready access and escape of the water, tlie whole of these vessels Here deficient in speed, and some of them were altered at great cost. The sciew had meanwhile advanced rapidly into favour as an auxiliary power for fast sailing vessels in the merchant service; and more recently it has been extensively em- ployed for full powered steamers of the very largest class St<?am Na (in preference to the paddle-wheel) by several of our great vigation. mail-packet companies, the Peninsular and Oriental Com- ''"-^^-^ pany taking the lead in this respect. The requirements of the great navigable rivers of Ame- rica have naturally led to the supremacy of that nation in the art of river navigation. The description of the large American river-steamer, The New World, given in another part of this article, as a type of her class, will be found both novel and interesting. This rapid sketch of the rise and progress of steam navi- gation would not be complete without referring specially to the wonderful development it has lately received in the construction of the Great Eastern, which, notwithstanding a few minor defects, has undoubtedly proved herself to be a most efficient steamship. In addition to the interest natu- rally excited by the immense size of this vessel (whose pro- portions and performance will be given hereafter), she is destined to solve another problem in marine engineering, namely, the desirability of combining screw-propeller and paddle-wheels in the same steamship. A statistical table is subjoined, showing the progress of steam navigation in the British Empire, from its first intro- duction in 1814, down to the most recent times for which returns have been received. Table shoicing the progress of Steam Navigation in the British Empire, by the Heyistrar-General of the Board of Trade. Eiitish Merchant-Steamers built and i-egistered each year. Total number of Mercliant- Stetiiners belongicE to the British Empire in each year. British Merchaiit-Steameni built and registered each year. Total number of Merchant- Steamers belonging to ttie British Empire in each year. Steamers. Eeg. Tons. Steamers. Reg. Tons. Year. Steamers. Eeg. Tons. Steamers. Reg. Ton.1. 1814 6 672 •> 456 1838 87 9.857 722 82,716 1815 10 1,394 10 1,633 1839 65 6,522 770 86.731 1816 9 1,238 15 2.<;i2 1840 77 10,639 824 95.807 1817 10 2,054 19 3,950 1841 54 12.391 856 104 845 1818 9 2,538 27 6.441 1842 67 14.931 906 118,930 1819 4 342 32 6,657 1843 53 6,739 942 121,455 1820 9 771 43 7,243 1844 73 6.930 9b8 125,675 1821 23 3,2G6 69 10534 1845 73 11.9.0O 1012 131,202 1822 28 2,634 96 13,125 1846 88 17,172 1070 144,784 1823 20 2,521 111 14,153 1847 115 17,333 1154 146,557 1824 17 2,234 126 15,739 1848 128 16,476 1253 158,078 1825 29 4,192 168 20,287 1849 80 13,480 1296 167,310 1826 76 9,042 248 28,958 1850 81 15,527 1350 187,631 1827 30 3,784 275 32,490 1851 88 23,527 1386 £04,654 1828 31 2.285 293 32,032 1852 112 31,792 1414 223,616 1829 16 1,751 304 32,283 1853 162 49,008 1534 264,336 1830 19 2,226 315 33.444 1854 189 66,446 1708 326,452 1831 36 4,436 447 37,445 1855 263 84,862 1910 408,290 1832 38 4,090 380 41,669 18c6 245 58,621 1950 417.717 1833 36 3.945 415 45,017 1857 237 53,898 2132 453,966 1834 39 5,756 462 60,735 1858 168 55,844 2239 488,415 1835 88 11.281 538 60,520 18.59 158 39,071 2239 472764 1836 69 9.700 600 67.969 1860 211 55,742 2337 500.144 1837 82 12,147 6C8 78,288 It shotild be observed that the "register" tonnage here given is exclusive of the tonnage of the engine-room, which in a well-powered steamer generally amounts to one-half, or more of the regi-^tered tonnage. An addition of one-half should therefore be added lor the gross tonnage of this table. To take an example. The Shannon, West India mail packet, has Register tonnriir.^ 2187 2t \ Eiigiae-room d 1284-57 I n. 775. Gross io 3471 81 J The horse-power (nominal) averages about one-third of the register tonnage ; so it may be fairly assumed that this country now possesses (in 1860) a fleet of 2150 merchant- steamers, having an aggregate gross tonnage ol 670,000 tons, and a nominal horse-power of 165,000 horses. The steam navy of this country consists at present of aoout 468 vessels, having an aggregate tonnage of 470,000 tons, and a nominal horse-power of 1 10,000 horses. Steamships aHoat (18-59). Building or I x„.-i Convening, j T"'*'" Ships of the Line Screw. 33 19 9 4 38 3 26 161 8 4 13 1 Paddle. 9 35 24 38 2 4 Screw. 16 6 9 1 49 34 9 4 82 27 26 162 8 42 15 -<; Block Ships Mortar Ships Corvet tes and Sloops .. Floating Batteries.... Tenders, &c Troops & Score Ships . Yachts Total - 1 319 112 32 463 118 Stouni Na- vij'ation. STEAM SHIPS. 8t«am Na- vigntiori. The Great W«»ttnr U3S - '-Tht Great Britbia.r -ISM ^ThtFtrsiar iliiS r — , n n TheGrcnf P.a5tcm..-^rr Fig. 1.~Coinpnrutivc S121O0 In constructing a steam- vessel three things require to l)e specially considered, each of which is a sufficiently com- plex study in itself; namely, the ship, the engines and boilers, and the propeller. ']"o combine these in such a maimer as to produce a perfect whole is one of the most difficult problems of modern engineering, demanding at once the theoretical attaimnents of the natural philosopher, and the laboriously acquired knowledge and shrewd saga- city of the practical mechanii ian. As the limits of this article must preclude the pursuit of theoretical investiga- tion, it is proposed to confine it almost exclusively to the |)ractical part of the subject, and to a record of the results of actual and approved performance. The marine The marine steam-engine, altliough acting on the very engiue. same principles as the ordinary laud condcnsing-engine, and providid with the same integral parts, ditt'urs from it essentially in the particulars of weight and f()rm, being ne- cessarily made as light, and as com|)act, as possible. These requirements throw many obstacles in the vvay of the ma- rine engineer which are not encountered on shore, both as regards the engines and boilers ; and his difficulties are increased by the stern necessity which exists on board ship for the utmost economy in the consumption of fuel, the value of which is there immensely enhanced. The oldest type of the marine-engine is the side-lever variety, which, till within the last ten or twelve years, was almost universally employed in steamers ; and which is, in- deed, still preferred for paddle-wheel steamers by at least two large mail-packet companies — viz: Cunard's and the West India Mail Company (fig. 2). There are several Si(l«»-lever engines. of Ihu abuvo Steiimurs. the crank to be kept in the most advantageous position for giving |)rompt motion to the shaft immediately that the engine is started. Direct-acting engines are often very troublesome in this respect. Another advantage of the parts being nicely l)alanced is, that the engine works with little friction, and consequently less strain, and wear and tear of the brasses and moving parts of the machinery. Hence the side-lever engine is very economical in main- tenance and repairs, as well as in the quantity of oil and tallow required for lubrication, no mean item in the ex- penditure of some engines. Again, this form of engine admits of a good long stroke and connecting-rod, by which means the steam may be u>ed to best advantage in the cylinder, while, at the same time, the thrust of tlie piston is transmitted to the crank in the most equable and ett'ect- ive mariner. Many pairs of side-lever engines are still doing their work well, after more tlian twenty years' ser- vice, and have cost less for repairs than most direct-acting varieties in half that time. But although it may lie quite true that side-lever engines Direct- arc thus economical in tluir working, it does not necessa- acting rily follow that they are the best form of engine (or pas- engineg senger-steamers. On the contrary, when we consider the Fiit. 2. Side-levcr Engine. pood reasons why this form of engine should be thus favoured. In the first place, the working parts are well balanced on either side of the main centre (c, fig. 2 ), so that the engine will stand in any position without the piston liaving a tendency to fall by its own weight, thus enabling Flu. 3. Direct-acting Engines in Gorgon, &c (Seaward.) value of space and weight in a first-class merchant-steamer, it appears probable that they are really more expensive STEAM SHIPS. 119 Steim Na- than the lighter and more compact forms of direct acting- Fig. 4. Direct-acting Engines in Vultare,&c. (Fairbairn.) engines which have now so generally come into use, and by Fig. 5. Direct-acting Engines for shallow draught. (Maudslay and Field.) employing which we may save at least 20 feet in the length of the engine-room, and 100 tons of displacement, in engines of 500 nominal horse- power. Direct-acting engines, being susceptible of great va- riety of form, have assumed as many different shapes as there are manufacturing engineers ready to invent, adapt, or distort them, as the case may be ; and the now very general use of the screw- |)ropeller has, of course, varitd and modified these forms still more, In the merchant service, the height of the machinery is not of much moment, provided only that it does not raise the centre of gravity of the vessel too high ; but in the steam- navy it is considered essential that the whole of the engines and boilers should (if pos- steam Xa- sibie) lie kept under tiie water-line of tiie ship, as a protec- vigntion. tion from shot; which, in the case of screw-vessels, is now V^-v^.^-/ generally accomplished (see fig. lo). Direct-acting |)addle-wheel engines may be classed under Varieties, four iieads ; namely, those Hhich preserve the parallelism of the piston-rod by means of the system of jointed rods called a parallel motion (figs. 3 and 4) ; those which use guides or sliding surfaces for this purpose (figs. 5 and 7) ; os- cillating engines (fig. 6), in which the cylinders are hung upon pivots, and follow the oscillations of the crank ; and Fig. 7. Direct Doable-cylinder Engines, snitable for large power. (Mandplay.) those denominated "trunk-engines" (fig. 8), in which a hollow cylindrical trunk is att;iched to the piston, and passes, steam-tight, through the cylinder cover. Several of these va- rieties have their distinctive appellations, being known as the " steeple-tngine" (which is a favourite form on the Clyde); Maudslay's double-cylinder engine (fi;j. 7); the animlar-piston engine (with two piston-rods) ; the atmospheric en^'ine ; the combined-cylinder engine (Plates XXI. and XXII.) ; and several others. As verbal description is of little value in making these forms intelligible to the reader, sketches of the more charac- teristic of them are subjoined, as well as detailed plates of approved examples (see Plates). These engines are generally »•»■ ■ made with two cylinders, but in the case of screw-engines there are sometimes three, and sometimes four cylinders Fift. 6.— Oscillating Faddte-wheel Engines in the Great Eastern. (J. Scott Russen.) 120 Steam Na- vigation. Scrow- •ngiDCB. STEAM SHIPS. placed in all possible positions ; being found upright, in- verted, liorizontai, and inclined. ScTew-en;:ines are made either with or without gearinij. Tile use of geared wheels intervening between the engine and the propeller admits of a slow S[)eed of piston with a high veloeity of screw, and is so liir beneficial, but in prac- tice there are several disadvantages attending it. noise, from which there is no escape on board-ship. In Steam Na- stcain-vessels of war it is difRcidt to keep the top of the vigation. large wheel sufficiently low, while at the same time their ^"^"v""^ drauglit of water admits of the use of a screw of great diameter and pitch, by which means the necessary speed may be obtained for the ship without unduly increasing the velocity of the piston. Hence there are comparatively few geared screw-engines in the Royal Navy. In the case of full-powered screw-engines in the merchant service, the use of gearing is generally found to be necessary (fig. 10)^ m^ I Fig. 9. Horizontal Screw-engine (Direct), adapted for tlic Royal Xavy, 4c. ^'E- 10. rpi J • ■ 11* "1 1 1 Vertical Sorow-engine (Geared), adapted for the Merchant SerTlee. I he driving-whecl is necessarily very large and cum- » i. ^. i- brous, while the wooden teeth with vliieh it is fitted are but it may be advantageously dispensed with wherever the subject to uneciiul wear, and are liable to be " stripped," power of the engines is not calculated to give a very high <.r broken off, by a sudden stroke of the sea upon the screw, speed to the ship. The velocity of fiiston in actual use in Their revolution is also attended with a loud rumbling different classes of steamers will be hereafter noted. The follotcirtg {Figs. W to 16) are other examples of Screw-engines : — fig. 11.—'* Trunk '* Screw-engine, Direct. Fij. II.— Horizontal Cylindsr Sorev-cngine, Geared. Fig. 1:;.— Oscillating-Cylindcr Screw-engine, Direct. Fig. 13. — Doable Piston-rod Screw-engine, l^irect. Fig. 15.— Screw-engines in the Royal Nary, Direct. STEAM SHIPS. 121 Steam N'a- vigalion. The cylinder of the steam-engine, being that portion of the machine in which the poner is developed, must be considered as its principal member. Upon its dimensions depend, in some degree, the size of all the otiier parts of the engine, as well as its reputed powers, being called an engine of 100 or of 200 horse-power according to the dia- meter of the cylinder, modified to a small extent by the length of the stroke. This, called the nominal horse-power, is obtained by the formula — Area of cylinder x effective pressure X speed of piston ■~ 33,000. In this formula the area of the cylinder is taken in square inches; the "effective pressure" is assumed at 7 lb. (by some makers at 7i lb.) to the square inch ; and the speed of the piston (according to the arbitrary rule adopted by the admiralty), is presumed to vary with the length of stroke, as shown in the following table : — stroke. Speed of piston. Stroke. Speed of piston. Ft. In. Ft. per rain. Ft In. Ft. pt-r min. 3 180 6 221 3 6 188 6 6 £26 4 196 7 231 4 6 204 7 6 236 5 210 8 240 5 6 216 9 243 It is at once apparent that the power thus calculated cannot be the real power of the engine, since it is wholly irrespective of the pressure of steam in the boiler, the per- fection of the vacuum in the condenser, the actual number of reciprocations of the piston, and the varying loss by friction depending upon good or bad workraansiiip, and the general plan of tlie engine. For the sake of convenience, however, the nominal horse-power is still retained, since it defines, with tolerable accuracy, the actual size of the engine, and its commercial value, in so far as the latter is dependent upftn the dimensions of the cylinder. To re- medy, in some degree, the uncertainty attending the use of this term, it is now becoming usual for the purchaser of a steam-engine to insert a clause in his contract, binding the manufacturer to show a certaia specified amount of indi- cated horse-power. Fig. 16.— Screw-engines in the Royal NaTy, Geared. The indicated horse-power of an engine is obtained by Indicated the aid of a valuable little instrument called an indicator,'"'"^ consisting mainly of a small cylinder placed in connection P° with the cylinder of the engine, both above and below the piston. This little cylinder is open at the top, and is fitted Pescrip- with a piston which presses aMinst a spiral s:)ring. The ''°" " ' * 111 II- 11 'i- 1 r .1 indicator, cock which connects the indicator with the cylinder or tne engine being opened, steam is admitted under the piston of the indicator during the one stroke, and vacuum during the other, precisely as in the large cylinders ; thus causing the little piston to push and pull alternately against the spiral spring. If the pressure were imifbrm throughout the stroke, the indicator-piston would start at once from top to bottom, and vice versd, remaining stationary until acted upon by the opposite pressure; but since the pressure within the cylinder of a steam-engine is constantly varying during every portion of the stroke, it follows that the pres- sure on the spiral spring of the indicator, and the corre- sponding movement of the indicator-piston, must be variable too. If a pencil be fixed to the piston-rod ot the instrument, it will register the fluctuations of pressure upon a piece of paper held close to it ; but unless some provi- sion be made for allowing the pencil a clear space on the paper at each successive instant of time, it will only move up and down in the same vertical line, and the markings due to fluctuation of pressure will be undistinguishable. To obviate this, the paper receives a circular motion in one direction during the down-stroke of the piston, and a re- versed circular motion during the return-stroke, the result being that, as the pencil moves vertically up and down, a continuous curved or sloiiing line is traced on the paper. By this line an oblong space is inclosed, called the indi- cator-figure, card, or diagram, the vertical ordinatcs of which will then represent the ettective pressures at the cor- responding portions of the stroke, and their mean length will therelbre indicate the average pressure in the cylinder during the whole period of the struke. To find the indicated horse-power, therefore, we must Indicated take the area of the cylinder in square inches, multiply it "." effec- by the average pressure .as found from the indicator-figure, _.„., and again by the actual number of feet through which the piston is travelling per minute ; when the product, divided by 33,000, is tlie indicator or gross horse-power of the ]22 STEAM SUIPS. Stoam Na- cnpinc. This must not be confounded, however, with the vigation. c/fntire power of" the engine, or tiiat actually available for ^^"y-^^ tile purpose for wliicli the engine is used. To ol)tain this, a considerable deduction (about 25 per cent., it is believed) must be made for the friction of the niovinj; parts, and for the power required to work the valves, air-puni]), feed and bilge piuiip, &c. ; but as this would be nearly alike for all well-constructed engines of equal power, and no ready means exist for testing it, the gross or indicated horse- power is taken us iJie measure of the power in all ordinary cases. An example of a set of indicator-diagrams (fig. IT) is sub- Steam Nv joined, to show the manner in which they are usually worked vigatiu:. out ; and it will be seen that, in this instance, a |)air ol'engines ^-^/-'-^ of 500 nominal horse-power were actually exerting an in- Proportiim dicaled horse-power of more than 2000 horses, or four times of indicated the nominal. This may be taken as the usual proportion '" "ommal now existing between nominal and indicated horse-power °"*' in modern engines by the best makers, while using steam ^ of from 15 to 20 lb. pressure ; but the average perlbrmance of existing engines is still very nuich below this, not ex- ceeding from 2 to 2'5 times thi,' nominal horse-power. Indicator- Diagrams taken from Scrcw-engincs of 500 korse-powcr, by liavenhill, Salkeld, arid Company. (Steam ia Boilers 20 lb.) to c '~"^~~~V^ 15-5 [hjy ^^8"i5'«^ <^J 15.2 i^}) \\ J4.9 Jh.4) «...■ ■■')-/.<? (/a.tf) /0.9(8.7)\ 1.0. S (9-4) 1 i0.9{9-6) \ /jjy4.3 {15-2) 10-3 {loi) \ / \/.3-8 {17 -4) 9-9 (/0-9) j \ j \i-9 in-c) 9-0 (/i-4) / t \\ eNt (/8-2J ;/ 5-9 (ihq) 8-6(ll-4) 1 7-9 (ll-5)l •!::'.'.V.,....^ V. a ' e-i (7s:.j---'' f a "»C ^^ " .•*'' -41 >\ is \ 1 ' ''^ "^ / \ % 2 w 03 ^{ \ Co "6? 1 1 ;-. _ i ^ to c- .•1 o • 1 " 1 .._; P? ..S. -^ ^■■■' Fig. 17. Calculation for tindiiig Ind. U. P. Steam 11-7 Vacuum 9'2 (13-5) 9-2 ( 9-8) (13-5) Ind. B. r. of both tiiciiifS. = 1001-248 n. r. X 2 = 2U0:;-40t>. Itulicated liiirpe- jiower depends mriinly on the boiler. Top Btroke 209 Bottom (233) Diameter of Cylinder 71 inches. Length of stroke 3 feet. Indicated pressure (mean of 6 experiments) 21'904 lb. Meun number of revolutions per minute 63}. The size of the boiler is obviously a very important ele- ment in determining the indicated horse-power of an engine, inasmuch as the sjieed of the piston (or the number of revo- lutions per miiuite) depends mainly upon the supply of steam from the boiler. The power of an engine may thus always be increased by adding to the sizeof the boiler, pro- vided the steam-passages are large enough to admit of the increased flow of steam without its becoming throttled or "wire-drawn." A large boiler, however, implies a large consumption of coal as a necessary attendant upon any in- crease of power in the engines, or velocity in tlio ship ; so that in practice it is generally found inconvenient for sea- going steamers to urge their engines to the utmost duty of which they are capable, as teiuling to limit the distance which it is possible to run with a definite weight of coals. Hence it follows, that while vessels making short runs (such as the Holyhead packets) will show an indicated horse-power of four, or even five times their nominal, a transatlantic steamer cannot afford to do so, although her engines may be equally efficient. The dynamometer is an instrument used to measure the force actually expended in propelling the vessel ; or, in other words, for showing the effective horse-power ol' the 3959 2014 x3 81x2 1 904 33,000 Speed of the vessel at a mean draught of 24 ft. OJ in.... 10 897 knots. Mean of forward engine 221 lb. „ after engine 22-4 „ Mean of both engines 22^ lb. engines. It is fitted occasionally on board of a screw- steamer, the thrust of the propeller being transmitted through a series of levers to a Salter's spring-balance ; but it is difficult to obtain true indications from this instrument, which is liable to many disturbing influences. There is a fixed dynamometer at some of 11. M. dockyards, by means of which the pull of any steamer, whether paddle or screw, may be obtained in tons. It will be understood, from what has been already said, Velocity o| that the speed at which marine engines are driven is very piston, various, and also that it is liable to vary (even in the same vessel) according to circumstances; such as the steaming capacity of the boilers, the necessity for economizing fuel, and the dimensions of the paddles or screw. A[)art from the proper or "calculated" speed, there is of com-se the additional consideration of the variable trim of the vessel, and the undulations of the sea, which affect the speed of the engines by throwing more or less work u|)on them, in pro- portion as the propelling agent is deeply or lightly im- mersed. The subjoined tables w ill convey some idea of the velocity at which pistons are driven (under the most favour- able circumstances of trim) by some of the principal marine engineers of the day : — STEAM SHIPS. Speed of Pistons in Merchant- Steamers {Paddle and Screw). 123 Steam Na- vigation. Name of VesseL Great Eastern... IMta Great Eastern... Shannon Mersey Ceyliin CoKmibo Atrato Pera Oneida Taniar Prince Consort . Makers of the Machinery. Diameter of cylinder. Length of stroke. Watt Penn Scott RiLssell R. Napier Maui'islay and Field Huniphrys R. Napier Caird Rennie Inglis Peim Scoit KusscU jn'^lies. 84 72 74 97 60 72 72 96 75 82 72 30 ft. in. 4 7 14 9 5 3 5 9 4 4 7 2 Revolo- tions per Revols. 80 25 12 18 30 50 2';j 15 32 26 lej 45 Speed of piston in ft. per min. Feet. 400 350 336 326 300 300 29l-£ 270 256 234 231 225 Hoir propelled. Speed of Pistons in Government Screw- Steamers. Agamemnon Mohawli Esk Arrogant Princess-Royal Simoom Conflict Duke of Wellington . Highflyer Dauntless Fairy Shnrpshooter Rifleman Rattler Penn Humphrys Scott Russell Penn Maudslay and Field ., Watt Seaward R. Napier Maudslay and Field ., R. Napier Penn Miller and Ravenhill . Ravenhill Maudslay and Field . 70? 3 6 60 42i 2 2 88 50 2 9 68 55 3 61 64 3 68 43f 3 55 46i 2 70 94 4 6 30 55i 2 6 53 84 4 31 42 3 40 46 3 38 34 2 9 36 40J 4 25i 420 381 374 366 348 330 280 270 265 248 240 228 198 204 Screw, dirf'Ct. Paddle, feathering floats. Do. common. Do. Do. Screw, direct. Do. geared. Paddle, feathering. Screw, geared. Do. do. Paddle, feathering. Do. do. Trunk, direct. Horizontal, direct. Oscillating, direct. Trunk, direct. Horizontal, direct. Oscillating, direct. Horizontal, direct. Horizontal, geared. Horizontal, direct. Horizontal, geared. Oscillating, geared. Horizontal, geared. Oscillating, geared. Double cylinder, geared. All the merchant-steamers in this table have a speed of above 13 knots, and the government steamers of 10 knots. Some of these speeds are nearly tn ice as great as would be sanctioned by the table previou.<Iy quoted as embodying the practice of James Watt ; and although, theoretically speaking, there may be no objection to such high velocities, tliev are inconvenient in practice, from the tendency of the working parts to heat by the friction, from the rapid wear of the parts, and their increased hability to accident or de- rangement. Although engineers are perfectly agreed as to the supe- rior advantages of a long stroke for their engines, it will be seen by the preceding table how rarely in the case of screw- engines this desirable object can be accomplished. The cause of this is, that the pitch of the screw-propeller (by which term is implied the linear advance made by the screw during one complete revolution, supposing it to be working in a solid), cannot be effectively increased beyond a certain proportion, depending \ipon the diameter of the screw; and as the latter is necessarily limited by the draught of water, it follows that the only available means for aug- menting the linear advance of the screw is by increasing the number of revolutions. For each revolution of the screw two journeys of the piston (in a direct engine) are required, ami to enable this to be done within the required time, the strokes must be short. The chief disadvantages attending a short stroke are the more frequent recurrence of the " dead points" of the crank (when the piston arrives at tlie top and bottom of the cylinder), at which times much of the mo- mentum of the moving parts is destroyed, and a jerk ensues in the engine ; and the loss of a certain quantity of steam contained within the cylinder ports or passages at each stroke, which does not exert a direct pressure on the piston. It is natural to suppose, also, that short-stroke engines do not derive so much benefit from expanding in the cylinders as those having longer strokes. Another desideratum for all kinds of steam-engines is a long connecting-rod, as tending to diminish the angular strain thrown upon the main crank, and thus avoid the loss Long and of power arising from unnecessary friction. This action is short con- necting- rods. Fig. IS. made apparent by the accompanying sketch (fig. 18), in which a b represents a long connecting-rod, and aba. Awrt one, their relative efficiency varying as the angles a, b, c, and a, 6, c. The defects of a short connecting-rod be- come sensible in practice by greater liability of the bearings to heat, by an increased wear of "brasses" and packings, and a larger consumption of oil for lubricating. The cylinder of a steam-engine is never allowed a full Tutting off measure of steam from the boiler, this being shut off at some ![|'^j^'g' ""^ part of the stroke according to the power it may be desira- J"^^^^/'" ble to exert. A certain quantity of steam, varying gene- rally from |- to ^ of the contents of the cylinder, is always excluded by the slide-valve, which is made to close the steam-port before the end of the stroke. In most engines a further amount of steam is excluded by means of a sepa- rate valve, called the expansion-valve, which is so arranged that it mav " cut off ".the steam, or prevent a further supply, at any desired point, according as it may be wished to econo- mize fuel, more or less, at the expense of velocity. Thus, some engines are worked with J of a cylinder full of steam to each stroke, some with i, and others with only ^ ; or the same engine may be worked successively at the different " grades of expansion " corresponding to these quantities. Tills is called " working ex|)ansively," because the portion of steam thus shut in continues to exp.and in volume, and to give out elastic force, to tlie end of tlie stroke. ]24 STEAM SHIPS. Steam Na' vigation. Advan- tages of expanding 8team in the cylin- ders. Two advantascs arise from cuttin<; off the steam in tliis way. Fitstly, it allows tlie stroke to be completed iiiuler a ilimiiii.-lied pressure, so that the piston comes s;ei\tly to rest at the top and bottom of the cylinder, without impart- inj; a destructive jar to the machinery; and, secondly, it is economical of power (or, which is the same thing, of fuel), since it is found that the force actually exerted upon the piston by tlie isolated steam, during its expansion into the increased volume as the piston descends in the cylin- der, is considerably greater than that due to the simple pressure of the same weight of steam acting at a imilorm density. It is found bv calculation that when the steam is cut off at J stroke, seven-ti iiths of the power already exerted in the cylinder is added by the subsequent ex))ansion of the steam; when cut oft" at ^, 2"1 times the j)ower is addtd; and when cut oH'at J, 24 times marly. According to the usually-received natural law regulating the pressure and elasticity of steam, it is assumed that the pressm-e is in- versely proportional to the volume of the steam after it has expanded into the increased bulk, or, in other words, that when the steam has expanded to twice its original volume its pressure will be reduced one-half; when it lias expanded four times its volume, the pres^ure will be Jih, anil so on. The ])umping-engines in Cornwall, which do their work so very etonomiially, use steam of about -10 lb. pressure, cutting it ort' in the cylinder after ^tli or even ^th part of the stroke has been made, the remaining |^ths being performed wholly by expansion. Expansion It is very seldom, Iiowever, and that only when special Clin be means are provided for this pui pose, that the ])rinciple of rarely expansion can be beneficially carried out in marine engines pushed to jg jji^ extent nearly approaching that just mentioned. It Its extreme. ,. . J i i o j /i ■ i . limits '^ * well-known property oi all gaseous tluiUs, steam included, that any expansion of volume is necessarily accompanied with the loss of sensible heat, which is taken up in the latent form by the expanded gas or vapour. Hence, when the steam expands muier ordinary circum- stances within the cylinder of a steam-engine, a portion of it is compelled to part with its latent heat, to enable the rest to retain the gaseous form. This portion of steam, therefore, condenses into water of the same temperature, which forms a thin film over the interior surface of the cylinder. When the return stroke begins, and the watery lining of the cylinder is brought into connection with the condenser, it rapidly evaporates into steam of low tension. This steam, besides vitiating the vacuum, acts still more injuriously by robbing the cylinder of the heat which it required for evaporation ; when the metal of the cylinder, being thus lowered in temperature, condenses the steam, upon its re-admission, to a serious extent. Thus it happens that the principle of expansion, when carried out to any great extent in cylinders which are only "clothed" in the usual way, hi\s so freq\iently failed to realize the expected economy of fuel ; and this has been most unjustly charged to a delect in the principle of expansion. In the case of the Cornish engines already mentioned, where the steam is expanded to eight times its volume w ith known advantage, tlie cylinder is invariably surrounded with a "jacket" kept well supplied with dense hot steam from the boiler, by which means it is retained at a high and nearly uniform temperature during the entire stroke ; and to this steam-jacket it is mainly due that so remarkable an economy attends the use of expansion in Cornwall. The cylinders of a marine engine, on the other hand, are pro- tected from radiation by a clothing of felt and wood only ; but in the few instances where a steam-jacket has been Advan- applied, tlie most beneficial results have followed. ^'P" Another mode by which the expanded steam may be inc the protected from condensation in the cylinder is by previously •team. imparting to it an extra dose of heat beyond that due to its Advan- tage of a Bteam- jackec pressure, or, in other words, by "stipcrheating" it. It is Steam Wa- apparent that this extra heat becomes available for the vigation. supply of the latent heat demanded by the expanding steam, ^■^"v^"' which is thus saved from premature condensation. In order to derive the utmost benefit of which the prin- Conditions ciple of ex])ansion is capable, it is necessary that the initial under pressure of the steam should be considerable, that it should T'?."^.'' '*"!. -' - - ..'... full benefit have plenty of space to ex|)and into, and that the cylinder of expnn- should be maintained at a high temperature. These con- ,]„„„,„„ i,« ditions would seem to imply the use of a large jacketed obtained, cylinder of sufficient strength to bear the high initial pres- sine. As such a cylinder, however, wouKl be very heavy and cumbrous, the plan has been occasionally adopted of using tivo cylinders in which to utilize the steam, namely, a large and a small one. In this case the high-pressed steana from the boiler is admitteil into the small cylinder oiily, and after expanding in that to twice or three times its volume (by which its pressure is reduced to one-half, or one-third), it is then admitted from the small cylinder into the large one, where the expansive process is finally com- pleted under the most favourable circumstances. This combination, called the combined-cylinder engine, Combined- lias of late been brought prominently forward by the en- cylinder gineering firm of Kandolph Elder and Co., of Glasgow.*"8'°**- Plates XXI. and XXII. represent the engines of the steamers Callao, Liin.a, and Bogota, made on this principle, and which have attracted much notice by their remarkable economy of fuel. Their principle dimensions will be after- wards given with the description of the plates. They were thus described by Mr Elder at the late meetings of the Hritish Association — " These engines are constructed with the view of getting the greatest amoiuit of power from a given quantity of steam at a given pressure, with less total weight of engines, boilers, and water, and occupying less total space than is found in the ordinary class of steam- engines on board of steamships. To accomplish these objects the following construction of engine has been adopted: — The cylinder capacity is so great as to admit of the steam being expanded to within 2 lb. of the pressure in the condenser at the end of the stroke, while the engines are working full jiower. In order to reduce the violent shock of steam at 42 lb. pressure on such a large piston, a cylinder with a piston one-third of the size is placed beside it. This small cylinder receives the steam direct from the boiler during one-third of its stroke, alter which it is cut off. This steam is consequently reduced to one-third of its original (iressure, or to 14 lb., at the end of the stroke, and it then enters the second or larger cylinder. Here it is exjianded three times more, or down to 4| lb. Thus, the steam at 42 lb. is expanded to 14 lb. in the first cylinder, at which pressure it enters the second cylinder, and is further expanded down to 4J lb. ; but as the second piston has three times the area of the first, the load will be the same on both pistons, and the |)iston-rods, cross-heads, and connecting-rods may be the duplicates of each other." The steam is superheated in the boilers to about 3()0°, and the cylinders are steam -jacketed and clothed with felt and wood. The feed-water is heated before entering the boilers. It is stated that, although the engines worked with superheated steam, this was found inadequate to prevent condensation in the cylinders without the use of the steam- jackets in addition, the indicator diagrams taken from these engines showing a marked increase of power resulting from a free use of the steam-jackets, the supply of steam to which may be modified at pleasure. These vessels have all shown a minimum consumption of Economy from 2 to 2J lb. of best Welsh coal per indicated horse- of *""«• ■" power per hour, their speed being at the same time I2| '" ^^*'& 13 knots, which must be considered a very satisfactory ^° result. Their consumption of coal at their usual working trim is about 3 lb. per indicated horse-power, the vessel STEAM SHIPS. 125 Fwo cylin- icrs not jonsidered requisite. Bteam Na- making 1 1 knots ; whereas the more usual consumption of vigation. modern marine engines varies frdm 4 to 5 lb. per indicated ^-'^/^•^ horse-power per iioiir, and the average consumption of all classes cannot be less than 6 lb. It is not contended, however, that the system of expand- ing in two cylinders is essentially requisite towards the attainment of a great economy in the consumf)tion of fuel, and there are many instances of single-cylinder engines in wliich the same beneficial results have followed a like judi- cious combination of means and appliances for this purpose. A case in point is sup|)lied by the recent performances of the steamship Thunder, a vessel fitted with macliinery of much the usual kind, by Messrs Dudgeon of London. Although supplied with steam of only 14 lb. pressure, her engines do not consume more than 2J lb. of coal per indi- cated horse-power per hour, the ves5el muking 13 knots. Her machinery is represented by Plates XIX. and XX., and will be found fully described at [lage 140. An indi- cator-diagram from her engines is here subjoined (fig. 19). / Steam ^■Itmosphrric Steam Lint ITaruum Fig. 19. Screw-steamer Tliur.der. — 3d Nov. IS-'JG. Forward J^mjine. — With super-heated tteam and expansion. Steam in boiler 13 lb. Pyrometer on superheater 350 deg. Jsuraberof revolutions 50 Diameter of cylinder 55 inches. Stroke 36 „ Indicated horse-power, eacfi cylinder, with expansion ^ 348 It may be stated that a consumption of 2J lb. of coal per indicated horse-power per hour would represent in Corn- wall a " duty" of about 90,000,000 of pounds raised 1 fool high in an hour by a bushel (or 94 lb.) of coal, which is considered economical working even for a Cornish engine. The success achieved in the case of the Thunder appears to be due to the conjunction of the following good qualities in the machinery — viz., a perfect command of steam in the boilers, the superheating and expanding the steam in "belted" or jacketed cylinders, and the allowance of an unusually large inlet and outlet for the steam by the main valves. Another example of unusual economy in the consumption of fuel has been recently shown in the auxiliary screw- steamer Omeo, fitted with engines of 100 nominal horse- power, by Messrs Morrison of Newcastle. These engines use steam at 60 lb. pressure, which is expanded to a large extent in single cylinders, and afterwards condensed in the usual way, the cylinders being stuTounded with steam- jackets. The engines work up to 426 indicated horse- power, while driving the ship at 9 knots, and burning only 2'4 lb. of coal per indicated horse-power per hour. As the use of high pressure steam necessarily implies a boiler of Steam Na- coiresponding strength, the Omco's boilers are cylindrical, vigation. with "coned" furnaces and upright "coned flues," fitted ^""v"^^ w ith a superheating chamber on the top. The employment of steam of this high tension, however, is not to be recom- mended for passenger-steamers. The question of economy of fuel is of vital importance Importance even in a national point of view, as affecting the mainten-of '*'«<1"<'»- ance and extension of some of our great postal lines of ocean "°" t*^' ... . . II r- .. .• nomy of Steamers, and it is now receiving a large share of attention f^gl both from steamship owners and engineers. The subject naturally divides itself into two heads — the production of steam in the boiler, and its subsequent employment in the engine. 1st, The Boiler. — It is a material point towards economi- The boiler, cal working that the boiler should be large enough to ensure a constant command of steam without the necessity for Forcingtha "forcing" the fires, or continually stirring them up. This fires is ex- acts prejudicially in more ways than one. In the first peisive of place, each time that the fire-door is opened the cold air ^®^ rushes in through it, and mixing with the hot gases in the furnace, checks their perfect combustion, at the same time that it robs the interior of the boiler of much valuable heat. Again, if the boiler be deficient in heating surface, the fires must be kept thin, to promote rapid combustion ; and as these fires are specially liable to " burn into holes," a quantity of cold air enters the furnace through them, and the same cooling effect is produced in the flues and passages. It may be also remarked that, however desirable it may be Smoke- to "burn smoke" by admitting air into the furnace above '"""°'"g the bars, it is seldom an economical process, and if""' ^^°'^'^ not managed with great caution, is apt to become very much the reverse. The best practice seems to be to admit a definite small quanity of air to the fires through perforated fire-doors of the common construction ; those complicated doors fitted with Venetians, or other contrivances, for open- ing and closing the apertures, requiring too much attention from the firemen to be practically useful, besides adding to the weight and expense of the doors. Again, the natural consequence of stirring the fire too much is, that a large quantity of small coal and cinder falls through the bars into the ash-pit, and as the boilers cannot supply the constant demand for steam unless the fires are kept bright and active, these cinders cannot be re-burned, for fear of check- ing the formation of steam. They are thrown overboard, therefore, with the ashes, and a heavy expense is incurred. It may be thought by some persons that stoking is a Stoking is mere mechanical operation, easily acquired by the com- not a mere monest labourer ; but this is a great and vital error, which mechanical generally costs steamship owners many thousand pounds " before they find it out. The stokers, in fact, may be wast- ing coals by the ton at the furnaces of the boilers lor want of proper supervision, while the engineer is straining every nerve to save a few pounds weight by economizing steam in the engines, and possibly congratulatmg himself, at the same time, upon his able management. It is no unusual case for a difference of 20 per cent, in the consumption of fuel to arise simply from good or bad stoking, by which is meant the whole management of the fires and the draught. The quality of the coals is another important item in esti- mating the consumption per horse-pow er, and some remarks on this subject w ill be made hereafter. In large ships the mere labour of passing the coals along to the front of the fires is very severe, and some contrivance of slides or rails to enable the buckets to be easily run down the firing stage is recommended. The stoker's duty is, at the best, The com- a most irksome one, and it is found in practice that any fort of the contrivance which adds to his comfort or convenience, *'*'''^r9 w hether it be bv reducing the heat of the stoke-place, sup- *'>o"'f '>f 1 ■ 1 ■ -1 1- 1 1 1- .11 1 1 ■ 1 consulted, plying him with a taj) of cold distilled water, tic, is amply repaid by the increased attention bestowed on the fires. 126 STEAM S II I r S. Stpam Na- A marked reduction in the Iicat of the stoke-place in many vigation. of hiT Maji'stv's ships lias atlciided tlie use of tiie douliie "^■•"V"*^ Bmoke-bux doors, sliown in tlie subjoined sketch (tig. 20), O QOOO OoOOOO DiomcUr of lwl«$,lim. . ^^ntvlatmg SmoVcloac Door. FlK. 50. which are kept cool by a rurrciit of air passing between the Prnn^ht to double rminL;s. It is very inipoitant, botli as rei^ards the the fires, eoolness of the stoke place and the steaming poxver of the boilers, tiiat the draught of air to tlie fires should be en- couraged as much as possible by means of large hatches, wind-sails, and air-tubes. It is found preferable, where rapid combustion is required, to allow two or more funnels to the boilers, if by this means the draught may be made more direct ; tor the question here is not merely how to generate steam with the least possible consumption of fuel, but how to do this in the least possible time, and "itii a boiler of the least possible weight and capacity. It is com- paratively an easy matter to evaporate water economically in a Corni.^h boiler, for instance, but a very difficult and complex one vuuier the conilitions imposed upon the marine Rapidity of engineeer. The ordinary rate of combustion in the fur- combus- naces of marine boilers is about 15 lb. of coal burned on *""'■ each square toot of grate-bar surface per hour; and the ratio existing between the absorbent or "heating surface" of the boiler and the grate-bar surface varies from 15 to 25 of the former to 1 of the latter. The furnace-bars are frequently matle so thick as unnecessarily to impede the admission of air to the fires. They should not exceed J of an inch for wrought-iron, or 1 inch for cast iron, on the upper edge, and should have an air-space of from y'^ths to ^ inch between them, while burning Welsh coal. Henting The nature and arrangement of the heating surface in a surface. boiler is very material, the chief points to be considered being, that the sieani may have a ready escape from every part of the heated surface, that every portion of the interior of the boiler should be accessible for " scaling," or remov- ing the crust of insoluble matter which forms upon the plates and tubes, and that soot and ashes should not collect in any of the flues or passages. A large and high furnace is very desirable for facilitating the proper admixture of the combustible gases with the oxygen of the air. Brass tubes are much preferable to iron for rapidity of evapora- tion, as might be expected from their relative powers of conducting heat. Some recent experiments have shown, that the evaporative power of clean brass tubes is, to that of iron, as 125 : 100 ; and copper tubes as 150 : 100, nearly. Vs'-nfsalt Salt-water being necessarily used in the boilers of sea- wntcr in going steamers, this is liable to become more and more saturated with salt and earthy impurities in proportion as the steam passes off to the engines. A twof()ld evil thus arises. The super-salted water, as it increases in density, demands more heat belore it will part with its steam ; and the insoluble ingredients it contains (chiefly the carbonates of lime and magnesia, and the sulphate of lime), gaining strength with the abstraction of the steam, are deposited inside the boiler, thus forming a non-conducting skin, which greatly impairs its efficacy, and subjects the plates to risk of injury from the fire. To remedy tliis, a certain portion of the water in the boiler is " blown off" into the sea, its place being supplied by the feed-pumps with a corresponding portion of the hot water, which results from the condensa- tion of the stcaui by a jet of sea-water. As the tempera- nanne boilers. ture of the "feed," however, does not exceed 100", wliile Steam Na- that of the brine it replaces is probably about 230°, it is vig""""- evident that much heat is thus lost, more especially as a ^^^V"^ good deal of steam is believe<l to escape with the water that is blown off. Notwithstanding this, however, it is more economical of heat to keep the water in the boiler tolerably fresh by a copious admission of feed, which pre- vents in a great measure the formation of scale, and con- duces to the longevity of the boiler at the same time. According to Dr Ure's experiments, the largest propor- Constl- tion of salt held in solution in the open sea is 3M parts in '"ems of 1000 by weight, and the smallest 32. In a specimen ""■""*'• brought from the Hed Sea, 43 parts were found, the specific gravity of the water being 1'035. The Mediterranean contains about 3S parts in 1000, the British Channel 35-5, the Arctic Ocean 28-5, the Black Sea about 21, and the Baltic only 6'6. The same authority states, that deep sea-water from the ocean (from whatever h)cality) holds nearly the same- in- gredients in solution, containing, on an average, in 1000 pans — 25'0 Ctiloride of sodium or common salt. 6 3 Sulphate of magnesia. 3*5 <_'hlori<le of magnesium. 0-2 Carbonates of lime and magnesia. 1 Sulphate of lime. 341 Also a little sulphate and miniate of potash, iodide of sodium, and bromide of magnesium. It is now a common practice to " blow off" the requisite "Blowing- quantity of brine continuously, in the proper |)roponion to off-" the amount of feed admitted, so as to keep the water in the boiler at a certain regular degree of saturation, at which it is found by experience that little or no deposition of "scale" Surface will take place. Till within the last fiew years, boilers were •''""■''"• always blown-off from the boliom only, it being not un- naturally supposed that the heaviest and most saturated water would be found there ; but experience has now proved that the greater portion of the impurities from which the scale is formed are to be found on the surface of the water of the boiler (being carried upwards by the steam), and should be abstracted from tlicnce. Mr Lamb, the superintending engineer of the Peninsular and Oriental Steam Navigation Company, was the first to introduce " surface blow-off," which is now very generally used in adilition to blovving-off from the bottom, and is attended with a considerable improvement in the condition of the boiler surfaces. The rule adopted by this company is, that Proper the feed and blow-off shall be so regulated, the one to the •'"K"®."*' other, that the water in the boiler may be alwavs at tiigSa''"'''''"'" Or WfltPr in degree of saturation marked 17 on the scale of their hydro- (,^1^^ meter, which represents a saturation of between ^^ and j'j parts of salt, pure water being represented by zero, common J sea-water by g>j, and fully saturated sea-water by ^J. I The followmg table shows the boiling point and specific gravity of sea-water (at 60° Fahr.) of different degrees of saturation, expressed in parts of salt cont. lined therein, the barometer indicating 30 inches of mercury :— Saltncss. Boili Sp. gr. Pure water 212° 1- Common fiea-«ater.... 3', 213-2'' 1 029 Up to this point but A 214-4° 1-058 little deposit will be ^, 215 5° 1-087 formed -» ^, 216-7° 1116 •f, 217-9° 1-145 /, 219-1° 1-174 ,', 220-3° 1-203 ^, 221-5° 1232 /, 222-7° 1-261 i5 223 8° 1-290 iJ 2250° 1-319 if 226-1° 1-348 saturated foliition. STEAM SHIPS. 127 team Na- As a general rale, the atmospheric boilinsr point of tlie igution. jvater sliould never be aTiowed to exceed 216°, when the ""V"~^ baioiueter stands at 30 inches. The temperature nnist be ascertained by drawing off a small quantity of tlie brine, and boiling it in a deep copper vessel in the engine-room, a coirection being made, as nearly as possible, for the state of tiie barometer. Tiic following table shows tlie heiglit of the boiling point of pure water at different heights of the barometer: — Barometer, Inches. 27 27i 28 Boiling Point 206-96° 207-84° 208 69° 28} 29 209.55° 210 3»° Barometer. Inches. 29i 30 30J 31 Boiling Point. 211-20° 212° 212 79° 213 57° 'rncess of scaling." In testing brine by the hydrometer, care must be taken that it has the particular temperature for which the hydro- meter-scale was calculated. This is usually 200° Falir. About 3° of temperature make a difference of "0001 of the spccifii: gravity, or •036 of the usual hydrometer degree, or •0036 of the density of sea- water. The steam raised from salt-water and fresh is precisely the same in every respect ; but it has been found by experiment that water of the density which it usually acquires in marine boilers, demands about one-tenth more of heat to convert it into steam than if it were fresh-water, its "capacity for heat" being greater to this extent. It is needless to say, that salt itself will not be deposited until the brine arrives at its point of greatest saturation, or three times tlie density which the water should ever be allowed to acquire ; but what the engineer has to guard against is, the deposition of a solid stone-hke incrus- tation, composed of the sulphate and carbonate of lime, and the carbonate of magnesia. These are at first held in solu- tion by the water, but are subsequently rendered insoluble, and become dejiosited on the plates and tubes of the boiler, partly fiom the free carbonic acid being expelled by the boiling of the water, and partly by its continued saturation. Many, though hitherto unsuccessful, attempts have been made to obviate the necessity for this expensive process of blowing off. The only effectual remedy is the employment of fresh water in place of salt in the boilers; but this can only be accomplished by the adoption of "surface conden- sation." By this term is understood the condensation of the steam by contact with a large extent of cold metallic surface, instead of the usual method of condensing by a jet of sea- water. This principle, though occasionally adopted, has generally proved more or less inefficient, and the in- vention of a really effective method of surface condensation is still a problem in marine engineering. It is believed that an economy of about 15 per cent, in consumption of fuel, results from the use of fresh-water in the boilers of marine engines, with a longer duration of the boiler, and the saving of much valuable time consumed in cleaning. The average duration of boilers using salt-water does not exceed six years, while those using fresh-water last eight or nine; but the life of a boiler is very uncertain, depending so much on the care and attention bestowed ujion it. The process of "scaling" a boiler, or removing the de- posit fiom the internal surfiices, is a very tedious and troul)lesome one, the scale being detached by hammers and chisels, alter being loosened as much as possible by lighting fires in the furnaces of the empty boiler. In some recent experiments on this subject made at Portsmouth by Mr Lindjay, the boiler was filled with hot air at a temperature of 400°, which acted most successfully in detaching the scale by the rapid expansion induced. The boiler was afterwards filled lor service, and so soon as a pressure of steam was obtained, the bottom blow-off cocks were opened, and most of tlie scale previously detached was " blown off"" into the sea. Almost all boilers are now fitted with an auxiliary or " donkey" engine, for the purpose of keeping up the re- Steam Na- quisite supply of feed, while the regular feed-pumps attached vigation. to the large engines are not working. The " donkey " is *^— ^/-"^ also made useful for pumping water either from the sea or Donltey- the bilge, and is an invaluable aid in ca-ie of fire. engine. In many steamers the feed-water is heated to a point Feed-water considerably above the temperature of the condenser, by he^'i-'". means of the waste heat of the boiler itself; being brought into contact either with the brine which is blown off, or with the hot air at the foot of the chimney. By this means its temperature may be raised from about 100° to 180° or 2(X)''; and as modern practice shows the advantage of freshening the boiler by a plentiful admission of feed, it is very de- sirable that its temperature should be thus previously raised. Various modes of effecting this will be found mentioned in the descriptions to the plates accomiianying this article. The feed-water heater of the Great Eastern has acquired an unfortunate notoriety from the sad consequences attend- ing its explosion, though there is no inherent danger in the arrangement there adopted, which has been safely and suc- cessfully applied in many other vessels. When the ebullition inside a boiler is so rapid and violent "Priming." that the water rises with the steam in considerable quan- tity, and is carried over with it to the engines, or is blown up the waste steam-pi|)e, the boiler is then said to " prime." This is one of the most dangerous and troublesome pro|)en- sities to which a boiler can be subject, as it may occasion a break-down in the engines by the shock of the piston upon the incompressible fluid (if escape-valves of sufficient capa- city are not fitted), and in all cases it entails a great loss of heat carried off by the hot water which boils over. Prim- Causes of ing may arise from a variety of causes, but the prevalent priming', one, more especially in the government service, is a too contracted steam space over the water of the boiler. For where the reservoir of steam from which the engines are supplied is very small, there must be constant pulsations of pressure in the boiler ; and each time that the surface of the boiling water is relieved of a certain amount of pres- sure by the rapid withdrawal of a cylinder full of steam, it boils up with great violence, and possibly overflows into the steam-pipe. The only remedy for this is an addition to the size of the steam-chest, and an increased height above the surface of the water to the steam-pipe orifice. Priming, however, is frequently the result of accidental causes, apart from the construction of the boiler. Water charged with mud or mucilage, which forms a viscid scum on the sur- face, is sure to induce it ; also while the ship is passing from fresh-water into salt, and vice versd. A new boiler w ith clean " raw " surfaces, is more liable to prime than after it has contracted a coating of scale, in consequence of the brisker ebullition going on, as well as from the dirt and grease left in a new boiler by the workmen. It is a usual practice to put tallow in a boiler as a preventive of priming, but this is not always attended with the desired effect. When the boiler primes very much, it is necessary to slow the fires, so as to prevent the too rapid formation of steam. All boilers are subject to the loss of a certain quantity " Wet" of water, which rises with the steam in the shape of fine steam, spray, and passes over with it into the cylinders of the engines. When much of this is present, the steam is said to be " vvet ;" but it is believed that all steam raised in the ordinary way is more or less charged with water in a stale of fine subdivision. To evaporate and utilize this water is one of the principal incentives to the use of surcharged or " superheated " steam. The other advantage arising from its use, namely, the prevention of condensation in the cylinders, has been already referred to while treating of expansive working. The steam in the boiler may be superheated in a variety Superlieat- of ways, but those methods seem preferable which use fbringaiipam- tliis purpose the spare heat at the bottom of the chimney, tus. 123 Steam Na- vigation. STEAM SHIPS. which would otherwise be ahnost entirely lost. The ac- couii)anying sketch (fig. 21) explains the method which has ELEVATION. Fie. 21. Laml) and Snmmot:.' S.iiHMlioatin? Apparatus. The saving of fuel in the steamships of the Peninsular Steam Ne- aiid Oriental Company, by the use of this apparatus, is vigation. .slated to vary from lo to 30 per cent., witliout any inju- ^-^^/-^ rious effects resulting to the piston-packings, &c. By this A high simple and inexpensive process the whole steam given offt'^n't'era- by the boiler is "superheated" from the temperature due*"".""' to its pressure (which for steam of 1.5 pounds pressure"*^ W(udd be 250") to a temperature of from 320° to 350°, which has been proved to be amply sufficient lor ohtainiu'^ all the benefit derivable from the process. That much of the heat of superheated steam is really employed in evapo- rating the particles of water held in suspension seems to be proved by this fact, that its temperature will fall as much as 25 or 30 degrees, in some cases, during its passage from the boiler to the engine, though there is no perceptible escape of heat by radiation from the surface of the well- protected steam-pipe. The heat thus apparently lost is undoubtedly taken up (in the latent form) by the steam resulting from the vaporization of these watery particles, by which means the heat already contained in the water is turned to good account, and the evaporative power of the boiler is virtually increased. A great many experiments have been made to test the Economy actual economy of the process by comparison with the ex- of the j>ro- isting consumption of coal before the superheating appara- <=«'»■ tus was fitted, and in every instance there has been a per- ceptible improvement. This sometimes takes the shajie of increased speed in the engines and vessel, sometimes a saving of fuel alone is effected, and in other instances both of these are combined in the same vessel in variable pro- portions. Where the speed of the vessel has been kept a constant quantity, there would appear to be an actual sav- ing of from 10 to 20 per cent, of fuel, according to the been already largely employed in tlie steamships of the nature and qualities of the boiler to which the process has Peninsular and Oriental Steam Navigation Coini)any, those been ap|)lied, ami the amount of ex])ansion in the cylinders, of the Union Steam Packet Company (carrying the Cape The high rates of economy are naturally shown by those mails) and many others at Southampton, and which has boilers which were previously the worst to keep steam been attended with the most undoubted success. It will with, and which required very hard firing to do so. Those be observed that the steam, in its way from the boilers to addicted to priming and wet steam rank next in apparent the engines, passes through the superheating chest A, at economy, while those boilers which show the least were the foot of the chimney, the steam occupying the narrow originally the best specimens of their class. There is no spaces between the sheet-Hues through whidi the smoke question, however, but that the process is beneficial in all and hot air pass. cases, though not equally so; and that it enables the steam BB are stop-valves for admitting the steam to the appara- to be raised in the boilers without " hard firing" being re- tus, or excluding it if necessary. CCC are stop-valves for passing the steam direct from the boilers to the engines without going through the ap- paratus. sorted to, being in this respect a great boon to the stokers. It is believed that no advantage over the ordinary me- Wethcred'n thods of superheating the steam is due to Mr Wethered's mi.rc<i ru- system of mixing superheated and ordinary steam together I'^rheated -. .i._ __• . ...1. .._ .1 .i,„ . ..,].. „ ;..„i.„. T„ .!,;_. steam. DD are stop-valves for admitting the superheated steam at the point where they enter the valve-jacket. To this to the enn-ines, or shutting it off when common steam only gentleman's patent, however, we owe, in a great measure, is used. the general awakening of marine engineers to the un- EE is a square casing enclosing the apparatus, and form- doubted advantages of the process, which have been ti inf the foot of the chimney, the smoke and hot air of which entirely siuTOund the superheating chest. Other casings of thin iron are fitted outside this, to prevent the radiation of heat. F is a door for getting into the chimney, and examining the flues of the apparatus, now so unaccountably overlooked. The plan adopted by Conscrva- the government of contracting for their steam machinery tism in with only a few favoured and old-established houses, though "lar'ne perhaps justifiable in other respects, has undoubtedly tended *"B'°«'- to promote conservatism in marine engines, and to repress innovations and improvements, the wholesome though often The chimney is not rigidly fastened to the square casing, unpalatable principle of competition being scarcely roused but ships over the projecting part HH, the space between into action. These lordly manuficturers have nothing to beinf filled with clay. This mode of carrying the chimney gain, in fact, by breaking new ground, being well assured is adopted, so that, in the evi?nt of collision, the loss of the of their accustomed orders from the Admiralty, and not chimney should not entad the destruction of the apparatus caring, perhaps, to raise the question whether their beauti- and its connexions. fully constructed machinery might not possibly content it- It is found, from experience, that a heating surface of self with a more moderate allowance ot fuel. In the case about 4 square feet per nominal horse-power of boiler is of those nianul'acturers, however, who have not the enir&e required to superheat the steam under ordinary circum- at Whitehall, but who are dependent upon the custom of stances. The temperature of the steam, when issuing from the great steam shipping companies, and other private this apparatus, is generally found to bo about 320° to 360°; owners of steam-vessels, who have a strong interest in this and in the slide-jacket, from 20° to 30° less, according to question, there exists an active competition, and conse- the leu"th of the steam-pipe. quently a powerful inducement to improve upon the econo- STEAM SHIPS. 129 klarine toilers. Steam Na- mical performance of their machinery. We find, acconl- vigation. ingly, that it is this class who have taken the lead in the '— ^r^-' steam reformation which has recently set in. Tiiere are three principal kinds of marine boilers in use in this country, namely, the rectanf;ular-flne boiler (which is now very generally discarded) ; the nuiltitubular boiler, or, as it is more usually called, the tubular boiler; and the ?hptubular sheet-flue boiler. The tubular boiler (as shown in Plates loiler. XIX. and XX.) is that in most general use. This con- struction enables a very large quantity of heating surface to be crowded into comparatively small s])ace ; while the form of the tubes, which vary from 2i to 4 in. in diameter, affords great strength, at the same time that the thinness of the metal composing them offers little impediment to the conduction of heat. They are attended with this inconve- nience, however, that the fl.uiie arising fiom the comb\is- tion of the inflammable gases in the furnace is prematurely extinguished by the minute subdivision and rapid reduction of temperature to which it is exposed in passing through these small tubes. It is well known that flame requires a very high tempe- rature for its maintenance, and is easily extinguished by contact with a comparatively cool surface; as for instance, in passing through the wire-gauze of the miner's safety- lamp. A precisely similar efl'ect is produced by the boiler- tubes, whose temperature, from their being surrounded with water, must be considered low when compared with that of tlie flame and hot gases passing througli them. ''ertical- The Americans have adopted a dift'erent form of tubular ube boiler, boiler (as shown in the accompanying wood-cut, fig. 22), Fig. 22. American iipriglit-tube Boiler. in which the tubes are disposed vertically, the smoke and flame passing round the outside of the tubes, and tlie water being contained inside. These vertical-tube boilers are very effective in generating steam, and partly for this reason, that the flame reaches further amongst their tubes than in the case of a horizontal boiler, in consequence of the greater space outside the tubes in which the flame may develop itself. The importance of this, while using the bituminous faming coal of the northern coal-fields, is very great. The absorbent surface of the vertical-tube boilers is, of course, greater than that of the horizontal in proportion as the external diameter of the tubes exceeds their internal diameter, and the weight of water it is necessary to carry is much less. Sheet-fluo Sheet-flue boilers are constructed with numerous flat, boiler. narrow water-spaces, alternating with flues of the same form in place of tubes. The width of the water-spaces in "Lamb and Summei's' patent sheet-flue boilers" varies from 1^ to 2 inches, and the flues from 2J to 3 inches. They are extensively used in the steamers of the Penin- s\ilar and Oriental Company, where they give much satis- Steam Na- faction from their durability, and economy in repairs. vigation. When a marine boiler explodes, the presumption is, '^-^•^/"^^ either that the boiler has been originally weak in one par- Explosions ticular place, w here it has given way under a pressure but "f boilers, slightlv exceeding that at which it is usually worked : or, ^"''"**'' secondly, that the safety-valve has not acted properly, or has been over-weighted, and the boiler lias burst simply from excess of pressure: or, thirdly, that the water has been allowed to fall too low, and thus expose the tops of the flues or furnaces, or the boiler-tubes, which, getting red-hot by the action of the flame, have suddenly generated such a rush of steam, upon the re-admission of the feed, as to cause a rupture of the weakened plates. Explosions most frequently hap|)en at the moment of opening or shut- ting a safety-valve or communication-valve, which shows that so long as the steam remains undistvirbed within the boiler, it will sustain a very high pressure w ithout bursting ; but should a wave or pulsation be carried through it, the equilibrium is instantly destroyed, and a rupture takes place. The very act of suddenly opening a safety-valve, or a communication-valve to the engines, would cause the water to boil up with great violence, and an immense volume of steam to be instantly liberated, in consequence of the water being relieved fiom a certain amount of pres- sure. In the event, therefore, of the discovery being made precau- that any portion of the boiler has become overheated from tions, &c. want of water, the engineer should neither open the safi»ty- valve nor admit the feed, but throw open the fire-doors, close the dampers, and draw the fires, after which the safety-valves may be cautiously relieved, and the feed gradually admitted, until the overheated surfaces are covered with water. In those parts of the boiler where the heat is most intense (as at the backs of the furnaces) the plates will gradually become oxidated and weakened by the fire, even although kept constantly in contact with water. This is probably owing to the rapid disengagement of steam from the surface, which interposes a non-conducting film of steam between the iron and the water, and thus permits the former to get overheated. Thick jilates, or overlapped joints, in such a position, "burn out" quicker than thin ones, from the imperfect conduction of the heat through the metal, and this is of course much aggravated when the plates are coated with scale. Plenty of steam room is a safeguard to a boiler, as tending to diffuse and neutralize any dangerous oscillation or sudilen accession of steam. The immense rush of steam which always follows an ex- plosion is satisfactorily explained, when we consider tli.it the instant the water contained in the boiler is relieved of pressure it throws off steam with great rapidity, and con- tinues to do so until the whole mass of the water is reduced to the atmospheric condition of 212° Fahr. To make matters worse, the steam-chests of all the boilers are usually in communic.ition. It is gratifying to find that explosions occur so rarely as Ttnrity of they do on board of steam vessels in this couniry — a result e^plns'ons which is doubtless to be attributed, in a great measure, to '" ''**'''^"- the supervision of the Board of Trade: and it is worthy of remark that the majority of such accidents have happened to tug-boats, which, from not carrying passengers, are exempt from Government interference. By the Merchant Require- Shipping Acts of ISd4 and 1862 the Board of Trade may '"^"" of enforce certain provisions of eouipment of the vessel and I"^ "'. 1 I • 1 • , I 1- r .\ chant bhip. Iier macliinery, conducive to the safety oi the Passengers jji^^.^' and ship. The points to which attention is directed by this act are, that the masters, mates, and engineers of steamers shall have proper certificates of competency ; that the hull and machinery generally shall be of sufficient strength ; that the number of passengers carried shall be in proportion to the accommodation ; that a sufficient number of boats be 130 Stenm Nil- vigation. STEAM SHIPS. QuMities of Cuul. carried ; tliat pmpcr watcr-ti<rlit biilklieacis be fitted, as well as inuiips, lire-|)imi|>s and hose, life-buoys, lifjlits, com- passes, &c., &e. Eacli boiler is required to iiave one sal'cty- valve, and reconiniended for further security to liave two, the »-ei',dils upon which liavc been sanctioned by tlie Board through their surveyor. One of these valves (called the government safety-valve) is to be kept locked beyond the control of the enuineer of the boat, the key being placed under the master's charge. Every passenger-steauicr is re(|uired by this act to renew her certificate of efficiency or sea-Horthiness twice a-year, after periodical surveys have been held upon her hull and machinery; and if such cer- tificate is not granted, she is debarred from carrying passengers until the required provisions are complied with. It will now be desirable to convey some practical infor- mation reiiarding the coals used in steam-vessels. The qualities it vs most ue.sirable for otcaai coals tc possess may be siunmed up as follows: — 1. They should have a highStpnm Na- evajKirative power, or, in other words, they i-hould be viguiion. capable of converting much water into steam with a small '""^"^/'^^ consumption of fuel. 2. They should not be highly bitu- minous, as such coals produce a dense black smoke uhicii it is difficult to consume in the furnace, and the soot and tarry matter evolved are lound to clog the tubes and Hues, and detract from the evaporative power of the boiler. 3. The coal should light quickly, and be capable of a rapid combustion. 4. It should be sufficiently cohesive in its nature to bear the constant attrition it is subjected to with- out becoming broken into small fragments. 5. It should combine a considerable density with such a mechanical structure as may admit of its being stowed in thi; smallest possible space, this involving a dirt'erence of 20 per cent, between coals of diffi.rent kinds. 6. It should be as free as possible irom sulphur, which induces progressive decay and spontaneous combustion. Table, showing an Adstrnct of ihe Principal Results obtained frotn the Best Coals of the United Kingdom, collated from the Admirulli/ Reports on Coals suited to the Steam Nary. f«arao of Fuel. Kvaporativo puwt-r or Nii.oflbs.of \V liter con- verted into Steam l»y 1 lb. of Coal. WciKht of cubic foot in lbs. Sparo occupied by 1 toll hi cubic feet. CotlOHlTO Power per- eciitage of large Coals. Ernporative Power after dediictinc for Coinbustiblo Mutter in residua. Eraporativo Power per Hour per Squ.-ire Foot of Grate Burfaco. Lbs. of Clinker per ton. 9-35 9-46 636 10-14 8-94 9-40 994 8-86 8 72 9 52 8-8-1 8-70 8-42 9-53 7-47 9-79 10-21 7-53 800 9-38 9-19 7-68 9-73 10-16 996 9-75 9-85 7-08 8-46 7-40 7-37 8 23 7-71 7-57 7-77 8-16 6-82 7-42 929 7-48 7-61 679 7-44 7-90 632 8-92 8-53 10-36 9 58 11-03 60-17 58-25 66-17 5322 50-92 57-43 57-08 56-93 57 72 56 33 56 39 55-28 56-00 6866 55-70 50-50 53.30 5330 53 00 69-30 53 30 65-00 4930 53-00 51-70 51 20 62 80 49-8 54-6 54-25 520 50 5 47-8 491 48-5 52 49 1 504 61-6 49 5 47-7 47-9 51-1 50-8 51-6 65-08 65-3 6905 61-10 67-0 37-23 38 45 33-85 42 09 4399 39-0 39-24 3934 3880 3976 39-72 40-52 40 00 38 19 40-22 44-32 42-26 42-02 4226 37-77 4202 40-72 45 43 4226 43-32 4374 35-66 44-98 41-02 40-13 4307 4435 46 86 45-62 46-18 43-07 45 62 44-44 4.-241 45-25 46 96 4676 43 83 44-13 4341 3441 34-30 3244 3666 33-43 493 68-5 527 56-2 57-7 465 51-2 53-5 46-5 637 52 7 72-5 55-7 35-0 57-50 54-00 45-00 62-00 62-00 60-00 6.V-5 74-5 57-5 645 64-0 74-0 85 7 64-0 69-7 795 78-5 77-5 60-0 75-5 85-5 800 63-5 68-5 795 76-5 74-0 70-0 80-0 82-0 87-5 966 9-7 7-4 11-8 10-6 10-3 9-2 8-98 10-59 9 35 882 10-44 8-04 9-99 1064 7-75 834 965 9-58 7-88 10-27 10-72 10-70 10-18 10-49 7-10 8-67 791 7-48 865 8-13 7-72 7-96 871 698 7-66 10-73 7-85 7-83 7-02 7-58 8-23 6-62 9 74 8-65 1060 977 11-40 40 6 698 71-0 87-8 61-5 79-6 88-3 71-3 71-4 550 90-5 90-5 77-3 75-7 1160 89-0 91-0 92-4 lU-8 102-6 1198 84-5 630 910 714 90-0 62 84-6 940 104-0 74-8 106-5 95 96-5 61-0 965 84-0 935 79-0 80-5 72-4 91-5 965 930 127-4 30-6 22-7 64-5 68-6 80- 2 591 428 408 23-7 20-9 25-2 93 270 39 5 192 36-0 38-0 9-8 39 5-7 7-5 180 62-2 146 164 82 170 50 78 1-7 144 101 28 3 11-6 98 2-1 37 223 26-4 34-4 61-6 76-1 29-7 38-7 24-6 Ebbw Vale Coleshill Npath Abbev Hill's Plyinoulh Works WalUend El"in Der went water's Hartley HasweH's Coal Company's Steamboat... Johnson and Wirthington's Sir John... Wylam's Patent Fuel iJell's „ , Admiralty experi- monts on con Is for tlie Uoyal Kavv. Lteam Na- vigiition. Average iroperties if coal. ivapora- ,ive power )f coal. Anthracite Welsh ccal Treatnipnt of bitumi- nous coals. STEAM Average of Properties. Seventepn S.-unplea Six Samples of NVelsh. of Newcastle, lb. lb. Theoretical evaporative power 15-785 14 208 Specific gravity i;!25 1-259 Coke 86-87 661 Moisture 088 507 Fratigibility, large 792 850 small 208 15 Average Chemical Analysis of 100 parts of Dried Coal. Ash 2-21 4-32 Carbon 89 13 78-45 Hydrogen 4-23 5'11 Nitrogen 127 1.79 Sulphur 1-01 1-36 Oxygen 212 897 In the foregoing tables the " theoretical evaporative power" is deduced from the composition of each coal as determined by chemical analysis. It gives the maxinmm amount of heat which each coal could produce, calculated in terms of the number of pounds of water at 212°, which would be converted into steam at 212° by the complete combustion of lib. of each variety of co.^1. lib. of pure carbon (according to the most accurate experiments) emits, by its combustion, an amomt of heat sufficient to evaporate 14'88 lb. of water at 212° into steam at 212°; and lib. of hydrogen, when burned, emits heat enough to convert 63o61b. water at 212" into steam of tlie same temperature. It is found experimentally that the quantity of water capable of being evaporated by any coal is (as nearly as possible) directly as the quantity of coke which can be produced from that coal ; the fact being, that in the case of bituminous coals, as burned in an ordinary furnace, as much heat is required for liberating the volatile products of the coal as is afterwards produced by the com- bustion of these volatile products, taking into account the cooling effect of the air admitted to maintain their combus- ' tion. Hence the very high evaporative power of anthracite coal, which, unfortunately, has certain countervailing disad- vantages, that preclude its use in the boilers of a steam-vessel uiuler ordinary circumstances. It is not only very difficult to light, but when lighted can be maintained in active combus- tion only by the aid of artificial draught, when the heat evolved is so intense as rajiidly to >""^ destroy the fire-bars, as well as the material of the boiler itself. Welsh coal, which holds an intermediate rank as to its evaporative power • between anthracite and the bituminous coals of the northern district, is considered the most suitable for steamers in general, and is much more easily stoked than bituminous coal. As Newcastle and other bituminous coals demand careful and peculiar treatment in the furnace, it may not be out of place here to give some directions for stoking it. The fires should be kept at a uniform thickness of from 12 to 14 inches. When the furnaces of one boiler are being charged, the fresh coal should be thrown upon the right-hand half of each fire in succession for one charge, and then upon the left-hand half of each fire during the next charge, and so on alternately, so that the whole fire may never be covered with "green" coals at once. The green coal is to be thrown upon the tVont half of the fire only, and never at the back of the fire, but when necessary the red burning fuel must be pushed back by the shovel, to keep >ip the proper thickness of the fires at the bridge. Where no means are provided for .admitting air through the fire-doors, these must be left slightly open, after charging with fresh coal. By a due observance of the three last directions, the formation of black smoke with north country coal may be prevented. The cinders, as they lall through the spaces SHIPS. 131 between the fire-bars, are to be raked forward in the ash- Steam Na- pits, and at every fresh charge a portion of them is to be vigation. thrown upon the fires after the green coal, so that nothing ^— "v^^ is removed from the stoke-hole but clinkers and ashes. The spaces between the fire-bars are at all times to be kept clear of clinkers and ashes, so that the air may have free access to the burning fuel. When the coals cake on the bars, the poker must be gently used to raise and open them for the admission of air to the mass of the burn- ing fuel. Some of the " patent fuels" have a very high evaporative Patent power, but they are all, more or less, difficult to manage in fuels, the furnace, and should never be used where the stokers are unaccustomed to their peculiarities. They are very valuable in special cases, from the compactness with which they may be stowed. We shall now advert to a (evi particulars having refer- Marine ence to the general construction and management of the engines. Engines of steam-vessels. The first vaWe through which the steam passes after leaving the boiler is the throttle- valve, by means of which the flow of steam to the engines is regulated or shut off entirely by hand. In the event of a ship pitching very much in a heavy sea, it is often neces- sary to station a man at the throttle-valve to shut off the steam from the engine whenever it begins to " race," or fly off at a high velocity, according as the resistance is removed bv the propeller becoming raised out of the water. Both paddle and screw engines are subject to this dangerous action, but particularly the latter, on account of the screw being, from its position in the ship, more exposed to sudden variations of "dip" or immersion. To mitigate this (in some measure), the contrivance called a " governor" has Marine been successfully applied in many cases of screw-steamers, governor, whose consumption of fuel in bad weather has been thereby much diminished, as well as the working of the machinery rendered more regular. Indeed, the commander ofa screw- steamer has often found it practicable, after this little in- strument had been fitted to his machinery, to keep his vessel head to wind in such weather as would have formerly necessitated his laying to. The annexed figure (23) represents the best, and indeed ^^5^^ Silver's Marine English Governor. ly, species of marine governor that has (we believe) V™ °^ uccessfullv applied. It is called " Silver's momentum- '!„....„ the onl been successlully .apj wheel governor," constructed by Jlessrs J. Hamilton and Company of Glasgow, who have purchased the patent. " It consists of a momentum-wheel A, fixed on the boss of a pinion B, which works loosely on tlie spindle C, and gears into the two-toothed sectors DD. These two sec- tors, being supported on a crosshcad E, made fast to and carried with the spindle C, work in opposite directions on the pinion 15; and as they are linked by the rods FF to the sliding collar (i, which receives and works the forked lever H, communicate motion to the throttle-valve T. MM are vanes, and N is a spiral spring, both of which are adjustable." Pescrip- tion of s governor. 132 STEAM SHIPS. Steam \a- "The action of the above instrument is as follows: — vi^utiuii. ^Vhcii the spindle of the governor is tiiriieil b)' the eii<;ine "^""^""^ to which it is attaiheii. the two-toothed sectors, which are curried on the lixed crosshead, being geared into the pinion on the momentum-wheel, have the tendency to turn round on this pinion ; bnt as they are linked to the sliding collar, they necessarily pull inwards this collar, and so compress the spiral spring, and this spring reacting on the collar, and consequently on the toothed sectors, serves to turn round the momentum-wheel, while the vanes on the momentum- wheel balance the action of this spring by the resistance the atmosphere offers to their progress through it. As the leverage action of the toothed sectors upon the momentimi- wheel pinion increases (as the spring becomes distended, and vice versa), it will be seen that the re.tction of the spring in propelling the niomentum-wluel will at all times be uniforju, and as much only is rtquiied as will carry round the monientuni-wheel with its vanes at its proper speed, and overcome the (riction of working the throttle- valve and throttle-valve connection*. When the momen- tum-wheel is in motion, it vvdl rotate with the engine to which it is attached at a velocity proportioned to that at which it is fixed by the connecting gear; and while the engine, from the usual causes, may attempt to vary this velocity, it caiuiot affect the momentnm-wiieel, but leaves it free to act upon the sliding collar, and consequently upon the throttle-valve — at one time closing the throttle- valve by its action in resisting any increase of velocity, and at another time opening the throttle-valve by its action in resisting any decrease of velocity on the part of the engine. A momentum-wheel of 2 feet 8 inches in diaineter, and 2 inches breadth of periphery, running at a speed of 180 revolutions per minute, is fourul to be sufficient to work with promptness and ease the largest throttle-valve." The same engineers have also introduced, for this pur- pose, an ingenious modification of the ordinary Watt's cen- trifugal governor, called " Silver's four-ball governor," in which the action of a spiral-spring is substituted for that of gravity, and the whole apparatus (like the preceding one) is balanced, so as to remain undisturbed in its action by the pitching or rolling of the vessel. The [)erl'ormance of the four-ball governor, however, is not nearly so satisfactory as that of the one previon>ly described. Expansion- The steam, after passing the throttle-valve, next enters valve. the expansion-valve, where it is cut off at any desired [)ortion of the stroke, by the action of an eccentric, or cam, on the main shaft. Such an arrangement is shown in Plate XV'. The valve usually employed tor this purpose is the "equilibrium" or "double-beat" valve, as shown in the annexed engraving. This kind of valve has the advantage „ of being opened X I and shut with great facility, since, from its construction, the ' |)ressure of the steam has no tendency to jam it against its seat, F'B-'^*- the objection to which all single flat valves are subject. It is also apparent that a slight rise of this valve gives a large opening for the steam to pass. In the engraving, the valves a a are made of brass, and the valve- box, and the spindles connecting the valves, are of iron. In this instance the valves are purposely connected by iron spindles, in order that the linear expansion of the sides of the box containing the valves, and of the spintlle connecting them, may be equal in amount, and therefore have no tendency to raise the upper valve off its seat, which would certainly ensue were the valves connected by a brass spindle, in consequence of the greater expansion of that metal by heat. This arrangement of tlie nictals stcam Nu- will be seen to be of special importance when superheated vigution. steam is used, and the temperature thereby increased. v^-^^^*/ Having passed the expansion-valves, the steam now enters silil.'. the jacket of the cylinder slide-valres. These are usually valves, so c(mstructed an<l arranged as to fulfil the following con- ditions for the admission and exclusion of the steam, iiule- ptndently of the action of the expansion-valves : — \st, The steam is shut off a little bef()re the end of the stroke, by the valve prematurely closing the steam-port ai)erture. The use of this is to check the velocity of the pisKm, by causing it to finish the stroke by the expansiim of the enclosed steam only. This is effected by giving " lap" to the valve. 2d, The eduction-port, or the passage to the condenser, is closed a little beibre the end of the stroke, which is called cusliioniny the piston, because it then completes the stroke aganst an elastic cu.«/iio/i of va|)our shut up between it and the top or bottom of the cylinder. .3(/, The port is opened for the admission of steam to the cylinder a very little beibre the piston begins the return-stroke, in order that the steam may have filled the passages and the " clearance " of the pis- ton, and have acquired its full pressure, by the time that the crank shall have turned the centre. This is effected by giving what is called " lead" to the valve. Ath, The com- munication with the condenser is opened a little before the end of the stroke, so as to have a vacuum ready made in the cylinder so soon as the return-sUoke begins. In this way each operation which takes place in the cylinder is slightly anticipated by the mode of setting the valves. In the case of screw-engines especially (which run at a high velocity), it is of the greatest im[)ortance that the steam- passages and valves should be of amj)le size, and those valves only should be used which give a large opening fur the steam, with a short " travel" of the valve. As the nature and limits of this article preclude a mi- nute description of the details of the marine engine (which indeed are very similar to those of the stationary condens- ing engine, already given in the article Sticam-Exgine in Ency. liril.), we will not attempt this, hut at once lidlow the steam from the cylinder into the condenser. The conden- Condenser sation of the steam is usually effected by the dispersion of a jet of cold sea-water amongst it, »hich is the most effectual means yet known lor producing that instantaneous conden- sation, tipon which the efficacy of the process is entirely dependent. Many attempts have been made, as we have before stated, to condense the steam by contact with cold metallic surfaces without the use ol the water jet, bnt they have for the most part failed to give permanent satisliiction. Although a good vacuum may undoubtedly be thus ob- tained when the apparatus is clean and in good working Surface- order, it has been too frequently found in practice that coudeuscra. any apparent advantages are more than counterbalanced by the additional cost, weight, and complexity of the apparatus, and its consequent liability to derangement. In most stirf"ac€-condensers the steam is passed through a great many small copper pipes, contained in a cistern of cold water, through which a current from the sea is made to flow by means of a force-pump. As the cop- per pipes are liable to become furred on the outside from impurities in the water, as well as choked in the inside by grease and dirt carried into them with priming from the boiler, it is recommended that these should never be made less than about one inch in diameter, and that means be provided for frequently flushing or clean- ing out the chest containing the tubes. VVhcre sur- face-condensers are used, the loss of water arising from leakage, or from blowing-off at the valves, is compensated to the boiler by employing a small apparatus to distil sea- water, by the aid of which the boilers are kept constantly supplied with fresh water. A close connection exists be- tween tile temperature of tlie condenser and the vacuum, STEAM SHIPS. 133 Super- heated steam con denies freely. Contents o; the con- denser. The air. purap. Xfririne en^'inea should be eiitiple. the latter beinj of cntirse more complete as the tempe- ratvire is reduced. There is a hniit, hnwever, beyond «iiicii any fm-ther reduction of temperature, by injecting more sea-water, is attended by a loss of power. It is foiuid in practice, tiiat a temperature of from 95° to 105° (depend- ins; upon the [iressure of the steam), is the most economi- cal, with w liich a vacuum of from '27^ to 26 Indies of mer- cury Is obtained when the weather barometer stands at 295 inches, tlie standard of this country. It is a curious fact, and contrary to what mijjht at first sight have been anticipitated, that a better vacuum, and a lower temperature of the condenser, is obtained with superheated steam, than with common steam, being probably owing to the move perfect condensation of the steam, when not mixed with particles of hot water held in mechanical suspension. This fact appears also to Indicate, that the extra dose of heat contained in the superheated steam has been all previously and usefully expended In the cylinder (by stipplving the expanding steam with latent heat), and that no portion of it survives to enter the condenser. Whatever tiie cause may be, the result Is, that considerably less injection-water is required when superheated steam is used, much to the surprise of the engineer in charge. f According to Dr Ure's experiments, uncondensed watery vapour at a temperatiu'e of 100° balances 1'86 Inch of mer- ctiry; at 110°, 2-45 inches; at 120, 3-3 Inches; at 130°, 4-366 inches ; at 140°, 5-77 inches ; and at 150°, 7-53 inches of mercury, or exerts a pressure of 3^ pounds per square Inch. In addition to the uncondensed vapour, a consider- able quantity of atmospheric air is always present In the condenser, having entered it in combination with the con- densing water. The contents of the condenser, therefore, are sea-water used for condensation, condensed steam, un- condensed watery vapour, and atmospheric air. To remove these Is the duty of the air-pump. It has a cajiacity of about fths of that of the cylinder, and is furnished with a " bucket " and valves, « hich are now usually formed of stout circular discs of vulcanised India.rubber. The air- pump draws Its contents from the condenser through the foot-valve, and then passes them on through the delivery- valre and the discliarge-pipe Into the sea, a small portion of the hot water being abstracted by the feed-pumps to supply the boilers. The very remarkable and ingenious apparatus, known as Giftard's patent Injector, although per- ha{)s well suited to take the place of the ordinary feed- pumps In stationary or locomotive-engines, does not appear to have given satisfaction in the case of the i'ew marine- engines w lure it has been tried in this country ; its action being imquestlonably rendered capricious, if not altogether stopped, by the use of hot water for the feed. The machinery of a sea-going steamer should be as simple in design, anil possess as few moving parts, as possible. In all vessels designed for long voyages, as well as in those which are intended for foreign stations, it Is inuch better to dispense with new and Ingenious contrivances for saving infi- nitesimal qti-mtities of fuel, than to run any risk of derange- ment. During a long run, as from Aden to Australia, fur instance, the chances of derangement of the machinery are much increased by the mere inability to make the usual atljustments demanded by ordinary wear and tear; and it Is surely wise to avoid the additional risk attentling a great multiplicity of parts, the failure of any of which may cause the stoppage of the eng'nes. When we consider that a larire pair of engines may very possibly have five lunidred different centres all in motion at once, and that each of these parts is making a thousand rotations, or double oscil- lations, each half hour, for twenty days consecutivtlv, it can scarcely be wondered at that accidents should occasionally happen. But allowing that everything goes well w ith this complicated machinery. It is not by the use of such finical refinements of mechanism that any great saving of fuel can be effected (for this is the main point aimed at), but rather St^am Xa. by the careful and judicious management of the boilers and vigation. engines. The fortunate selection of a good chlel-engineer ^-^V""^ tor the vessel will generally effect more saving in fuel than the most ingenious and expensive ''modern itiiprovements." Tliese remarks are not intended to apply to the obvious advantages obtained by superheating the steam, large ex- pansion, careful clothing (or jacketing) of the cylinders and steam-pipes, &c., which do not add much to the complexity of the engines. The tendency of modern practice is to run the pistons Large of steam-engines at a much higher speed than formerly, bearings This Is more especially the case with screw-engines, whose necessary, pistons frequently rim at the rate of 400 feet per minute, in place of Watt's old rule of 220 as a maximum. Althoui;h theory does not iiupose larger dimensions on the moving parts of a machine on this account, It is found In prac- tice that the shafts of screw-engines running at a high velocity must be considerably increased in size to avoid accident. This arises partly from the increased momentum of the parts in motion ; partly from the greater tendency of the bearings to heat from friction ; and partly from the more ra|)id wear and tear of the brasses and sockets, by which the accurate fitting of the parts is destroyed, and these are consequently svibjected to unecjual jerks and strains. The simple remedy (or such disorders is to en- large the main shafts and bearings, the latter being also made unusually long, so as to diminish the effects of fric- tion and wear and tear. The iron shafts of marine engines revolve In sockets or Linings o( bearings lined with brass or gun-metal. These give rise bearings. to little friction, but as their wear is rapid, they require frequent attention to keep the lining screwed up to the neck of the shaft, and they must be renewed when much w orn. In the case of screw-ships, where the bearings of the screw-shaft are not readily accessible, this ra]iid wear occa- sions much Inconvenience, and can only be cotmteracted by largely increasing the bearing surfaces. Bearings lined with lignum vita: are found to be subject to exceedingly little wear or friction. A plan has been therefore adopted of fitting these bearings with rings o( lignum vita: alternating with rings of gun-metal, which answers very satisfiictorily. Before leaving the subject of shafts, it may be remarked Deteriora- that these, whether paddle or screw, appear liable to dete- tion of riorate by continuetl use, and finally to give wav, some- shafts, times suddenly, but oftener gradually. It is contended by some that the iron of which they are formed has a tendency to lose Its toughness, and assume a crystalline texture, from long ex|)osure to the shocks and vibrations to which all such shafts are subject. Having had very many oppor- tunities of observing broken shafts, the author does not hold with this theory, but thinks the following explanation to be more probable. It is allowed to be a difficult operation to make large shafts perfectly sound In the centre, where the bars of Iron of which they are built up are not alwavs thoroughly welded Into one homogeneous mass. These imperfections, when they exist, are of course not visible on the outside, nor do they seriously affect the strength of the shaft at first ; but as the continued jarring and tw Isting goes on from year to year, they become more and more devel- oped, and the shaft becomes loose in the centre, acquiring a '•reedy" structure, which gradually extends to the surlace. \ fracture then takes place, if the crack be not observed anil the shaft renewed. The efficient lubrication of the bearings and other work- T.nbri^-a- ing parts of the engine with oil or melted tallow is a ma tion of thf terial point to be attended to, both as regards the smooth machinery working of the machinery and Its preservation from Injury. From want of this simple precaution the bearings get strongly heated by the friction, and may either be damased by the consequent expansion which takes place, or else STEAM SHIPS. cracked by the cold water which is usually poured on them from a hose, to cool them down aj^ain. Self-lubricating ai)|)aratiis is preferable for this purpose, wherever it can be applied, as it is both more economical of oil and more cer- tain in its operation. Allliou!;h compactness in an engine is desirable within certain limits, this should never be car- ried to such an excess that tlie engineer is unable to get conveniently about his engine while it is at work, in order Steam Na- to lubricate the parts, and tighten brasses and packings. vigntion. Every chief engineer of asteam-slii|)should be furnished '^""^/^^ with a printed form of Engineer's Log to be filled up by Kngineer's the engineer in charge during each watch of f()ur luiurs. 'jog- It should be arranged in a manner somewhat similar to the annexed form : — Steamer ENGINE-ROOM REGISTER. Proceeding from To 6 Q o Hour 4> be 3 a M e d to t. a S 0, S s c i t 1 3 '5 > « a <2 1 O o c o a. B c 1 i C s E o 6 B '5 c M o a, i f '£ t o a < c a a i 1 « 1 o c Q i « o £ a h S. B 1 o O e o ■5 o» P. e Total Expenditure per '2i Lours. Itemarltfl on the Sta and Wind, to of the Sea iLO. Coals. Stores. For Engines. For Ship. Oil. 1 Si Lb. No. Lb. In. In. In. De2. Deg. Dog. Tons.jCwl. Tons.jCwt. Galls. Lb. Lb. 1 N <te. — Indicator-diaj^rains to be taken occasionally. Pnddle- wheel ; appnrent than real, Steam-vessels are propelled either by paddle-wheels or screws. 1. Paddle- Wheels. — There are two kinds of paddle- wheels in general use in this country, namely, the common wheel, and that with feathering floats. The common pad- dle-wheel, notwithstanding many attcmfits to supersede it, still maintains a high place as a simple and eliicient pro- pelling agent ; the faults which have been attributcil to it its defects being, it is believed, more apparent than real. When a arc more steam-vessel is moored in a liarbour and prevented from moving, or when first commencing motion after having been at rest, the defects of the common paddle-wheel ap- pear to be very great. The paddle-boards, on entering the water, press obliquely down into it, tending to raise or lilt the vessel tip out of the water with a force w hich produces no useful eHect. Again, when the [ladiile-boartl is leaving the water, it seems to do little more than raise or drive the water ujjwards in the form of back-water. It is only, there- fore, in the middle of its path that the pro- pulsion of the paddle seems to be exerted in forwarding the boat, and that only for a short time. A large ^ part of the force of the steam - engine seems ended cal conditions of a paddle moving forwards and in a circle at Its actual the same time renders this plain. The paths described by motion, the boards are frachoidal curves, being of the family of the cycloid ; and from the study of the motion actually per- formed by the padille-board of the common wheel, it is seen, first, that the board is inserted into the water in an angular position resembling closely the entrance of an oar into the water; scciuully, that it is then made to act horizontally on the water during a short interval ; and thirdly, that it is withdrawn from the water edgeways, with an easy and graceful movement. When the paddle-wheel is either badly proportioned. Feathering immersed too deep in the water, or attached to a very I'aJ'l'e slow boat, its action becomes much impaired or impedeti. ^v"^"- Hence much attention has been devoted to the construc- tion of a paddle that shoidd be more effective in these un- favourable circumstances than the common wheel. Some of the contrivances invented for this purpose have failed for want of perception of the precise motion it was neces- sary to give to the paddle-board ; others fiom the con)j)lexity of the mechanism employed. In the year 1829 a patent was granted to Elijah Galloway for a paddle-wheel with mov- able boards, which patent was purchased by Mr William Morgan, who made some unimportant alterations in the F.g.25. The Common Taddlc-i rheel. thvis to be expended .ne,.o™.„>., .....^ ...^.. in raising the vessel, and in elevating the back-water, and onlv a siiiall portion in carrying the ship forward. this is the case of a vessel at rest, or not in rapid motion ; but the phenomena of a paddle-wheel revolving when the vessel is in motion differ essentially from the phenomena of a wheel revolving on a vessel at rest. \\ hen it is just startin<T or as yet moving very slowly, the evils here men- tioned'tlo in some degree take place ; but by the motion of the vessel forwards (which is the result of the revolution of the paddles), the faults complained of are at once remedied, and the puddle-float of a common wheel in a quick vesse is virtually " feathered" as perfectly as the most practised rower cou'ld feather his oar. A little study of the geometn- Featberin? I'addlo-wbCfl. mechanism. This, called the feathering paddle-wheel, is represented by the above wood-engraving (fig. 26), by STEAM SHIPS. Slip of the [laddle. IVant of Sxplana- ,iun. Steam Na- inspecting which it will be seen tliat a distinct feathering vigation. movement is imparted to the boards on entering and leaving ^^^y.m^ the water. Tliis movement, it will be observed, is derived from the excentric motion of the periphery of the second paddle-centre, to which are hinged the long rods that com- nmnicate the desired movement to the boards turning on pivots. Wheels made on this principle, though consider- ably heavier and more expensive than the common paddle- wheels are very frequently preferred for sea-going steamers subject to much variation of draught. They have been known to improve the average speed of a steamer by more than a knot an hour, and they are always accompanied with less vibration than the common paddles. The "slip" of the paddle-wheel, by which is meant the excess of its velocity above that of the vessel, may be gene- rally taken at Jth (or IGg^ per cent.) of the vessel's speed when the wheel is well proportioned, and the vessel toler- ably fast. Feathering wheels have less slip. 'i'he captains of steamers are frequently both surprised lower in a and disappointed to find how powerless their vessel is to iteamer to jj-^g ^ stranded ship off the shore, even when the whole 1 ar a oa ■ p^^.g^ pC [i^ejr engines is exerted for this purpose. A slight consideration of the subject will show that the requirements of such a case are very unfavourable to the proper develop- ment of the power of a steamer. We will suppose a vessel fitted with a pair of paddle-wheel engines of 500 horse- power collectively. The diameter of each cylinder will then be, say, 80 inches, and the stroke 6 feet. The length of the crank will therefore be 3 feet, driving a paddle-wheel of, we will suppose, 28 feet effective diameter, reckoned at one-third of the depth of the boards from their extreme edge. W^hen the piston of each engine alternately arrives at the top or bottom of its stroke, that engine is then power- less, and the whole of the work devolves upon the other engine, which is then at half-stroke, with the crank nearly at right angles to the thrust, and therefore in the most advan- tageous position for transferring the power. By bringing the pistons of both engines to f stroke, we obviously im- prove upon this, for now both engines are assisting to turn the shaft, though acting at a reduced leverage in the pro- portion of 3 feet to 215 feet nearly. By calculating the pres- sure upon the two pistons, we find the statical power exerted by the engines (the one pushing anA the oihcr pulling); but as the thrust thus found is transmitted by a lever of the second order, the short arm of which is the crank, and the long arm the radius of the paddle-wheel, it is necessarily re- duced in the inverse ratio which these bear to each other, or as 14 : 2" 15. The calculation would then be as follows : — 50^6"5 (area of cyl.) X 22 ( '''VVO^^^ f -"ive press. | ^ '' ' \ per sq. inch of piston.. J cylinders) = 22M66 lb. = 98-75 toas total pressure on pistons. Then as 14 : 2-15 : : 98 75 : lo-16 tons. X 2 (for both This being further reduced by 20 or 25 per cent, for the friction of the machinery, working the air-jiumps, &c., leaves scarcely eleven tons of thrust available (or ^tarting a weight, or dragging a stranded vessel off the shore, by a steamer of 500 nominal horse-power. A similar calculation made for screw-engines shows a like result. Definition 2. Screic-Propeller. — A screw as used for propelling of a screw, vessels may be de- fined as a metal [)late wound, edge- ways, round a cylin- der or spindle, as shown in the accom- panying sketch (fig. 27 a), which repre- sents one full turn of thecommon screw. Fig. 27 o. This would be a single-threaded screw, but it is evident that two, three, or more threads, if kept uniformly parallel to each other, may in the same way be wound round the spindle without interfering with each other. We should thus have a two-threaded or a three-threaded screw, the former being chiefly used for propelling in the navy, and the latter in the merchant service. The whole length of one complete turn of the screw, measured in a straight line along the spindle, is called the pitch of the screw. In the preceding engraving, therefore, the pitch is measured by the length of the Fij. 27 6. spindle (fig. 27 a), since the thread makes one complete turn upon it. It is also apparent, that if this screw were turned once round in a piece of soft wood (in the same manner as a carpenter's screw), it would advance through the wood the exact distance between the cut ends of the thread, which (we have seen) is the pitch. Hence, by the pitch of a screw, we understand always its linear progres- sion for one revolution, and the speed of the screw is mea- sured by multiplying the pitch into the number of revolu- tions. If the screw were working in a solid, the speed thus found would give its actual linear advance ; but as it revolves in water, which is a yielding medium, the water gives way to some extent, and the screw does not advance the full amount of its pitch, this deficiency in its progress being called the slip of the screw. Now, if the screw represented by fig. 27 a be cut into several portions by planes passing across it at right angles to the axis, each of these sections woidd have the appear- ance of the vane of a windmill. If the screw were two- threaded, the vanes or " blades," as they are called, would be exactly opposite each other, as shown in fig. 27 6, or as in the annexed sketch, fig 28 b, which repre- sents a two-bladed screw as used in propelling. The 135 Steam Na- vigation. Slip of the screw. Form of the screw- propeller. Fig. 28 a, fig. -.'St. screw here represented is abotit one-sixth part only of the whole length, or pitch, of the full turn of the screw shown by fig. 27 a, this small fraction of the pitch being found sufficient to absorb the whole power of the engines, so that any greater length of screw would only be hurtful by causing unnecessary friction, as well as by increasing the size of the aperture in which it works. By the length of the screw, therefore, is meant the traction of the pitch employed, measured along the axis of the screw. By the DIAMETER of the screw is meant the diameter of the circle described by the extremities of the blades during their revolution. The effect produced in propelling the ship will be best Action of understood by supposing the screw represented by fig. 27 a, J*"^ screw to be revolving rapidly in a trough lull of water. It would jP P^P^'" then send the water away from it with great force ; but as action and reaction are equal, it would be itself, at the same time, urged in the opposite direction with exactly the same degree of force. If we suppose it, then, to be fixed in a ship, the ship will be pushed forward with the same force that is exerted by the screw in pushing back against the water. If the screw is made to revolve in the opposite direction, the converse of this takes place, and the ship is then pushed backwards by the reaction of the screw. 136 3team Na- The screw-propeller lias been subjected by would-be in- vigation. vcnlors to an endless variety of form ; but these have gene STEAM SHIPS. Different firms of screws. Wood- croft's pro- peller. Smith's screw. Lowe's screw- blades. rally shown themselves more or less inefficient accordmfj as they may have departed from the principle of the tine screw. The first patent of any interest connected with this subject is that of Mr B. WooDCI!0^■T, taken out in 1832, for an "increasing pitch" screw-propeller. His specifica- tion describes " A spiral worni-blade or screw coiled round a shaft or cylinder cf any convenient length and diameter, in such form that the angle of inclination which the worm makes with the axis of the cylinder continually increases, and the pitch or distance between the coils or revolutions of the spiral continually increases throughout the whole length of the shaft or cylinder upon which the spiral is formed." Mr Woodcroft's idea, that the after-part of the screw would thus be made to act with increased efficiency upon the water which had been previously acted upon by the fore- most part, is undoubtedly correct in jirinciple, and had a full turn of the thread been found necessary for propelling (as was at first thought), this plan would probably have been found practically ailvantageous ; but when the length of the screw was cut down by Lowe to one-sixth part of the pitch, very little scope was afforded for Mr Woodcroft's refinement, and it has proved to be really of little or no value. Mr F. P. Smith's patent was secured in 1836 for "a sort of screw or worm made to revolve rapidly under water in a recess or open space formed in that part of the after- part of the vessel commonly called the dead rising or dead- wood of the run." Mr Smith's original drawings showed a screw with two whole turns of the thread, which was after- wards altered in 1839 to one whole turn. Mr .Iamks Lowe obtained a patent in 1838 for a screw- propeller formed of " curved blades, each a portion of a curve, which, if continued, would form a screw." The drawings attached to his specification show a shaft with one blade, a shaft with two blades, and a shaft with four blades. The screw-propeller now generally used (see fig. 27 6, and fig. 28 (/), may be considered as a combination of Smith's screw and Lowe's blades, its present form having been in a great measure determined by the series of experiments with the Rattler in 1844. (See page 132) Griffith's screw-|)ropeller, first patented in 1849, is propeller, probably the best modification of the common screw which has yet been produced. Its principal feature consists in the employment of alarge sphere occupyingthe central portion of the screw. The second peculiarity of CJriffith's screw consists in the peculiar form of the blades, which, unlike those of the common screw, are larger towards the centre, and taperin" towards the extremities. The extremities of the blades are curved from the front or propelling side towards the vessel, which causes the screw to take a greater hold of the water, and drive it towards the inner or central portion, which, in Griffith's screw, is the most effective part. This propeller is represented in its simplest form by the wood-engraving (fig. 28 a), and as recently improved by the annexed engraving (fig. 29.) It will be seen that this propeller consists of three main parts, viz., the boss which is keyed on to the screw-shaft in the usual manner ; and tlie two blades, w hich have turned shanks fitting into bored recesses in the boss. Each blade is retained in its position by a key, which is adjusted into its place after the blade has been inserted and turned in its socket about ninety degrees, or until the arrow marked on the flange points to the pitch n hich it is desired the screw shall have, of w hich several have been previously measured, and marked upon the screw. When Griffith's screw was first introduced, it was ex- pected that great advantages would result from an arrange- ment in its construction (Hhich it shared with Maudslay's feathering screw), by which the pitch or angle of the blades could witli facility either be increased, diminished, or " fea- thered" during the voyage, to suit the varying exigencies Griffith's Descrip tion. of a steam- vessel at sea. Experience, fiowevcr, hasStenmNa- proved that the ri>k of derangement incident to the ma- vijjntiiir,. chinery requisite for this purpose is too great to admit of *^— ^/— -^ Feather- ing-screws not Buctcss ful. Vie. S9. Grifnth's Improved Patent Screw-propeller. practical success, and also that the advantages to be ob- tained by such an arrangement are far less than was sup- posed. The use of screws to feather at sea has, therefore, been very generally abandoned. It will be observed, byAdvan- looking at the engraving, that the blades of Griffith's screw tBges of are quite distinct from the boss, into which they arc in- ^'"'*B'''> serted and keyed in such a manner that their angle or pitch '"""• may be altered and fixed before the voyage, though not at sea. The use of this arrangement is. that the engineer may find out experimentally the particular pitch of his screw which is most suitable to the engines and ship, experience liaving shown how very difficult a thing it is to hit upon the right [)itch by previous calculati<m alone. Another ad- vantage resulting from this arrangement is, that when a blade is accidentally broken, it can be re[>laced without having to remove the centre part, which in Griffith's fcirm of screw is tolerably safe from injury. It is unnecessary, therefore, to carry a spare screw, but only a couple of blades. When the ship is placed under canvass alone, the screw is brought into a position with the blades vertical, in a line with the stern-post, when little resistance is offered to the water. Although Giiffith's screw cannot be said to have shown any very decided superiority in speed over a common screw of the best form, it is certainly not inferior in this respect, while it is attended with less vihration, is less affected by a rough sea, and is more manageable under canvass from offering less resistance to the water, and less obstruction to the free action of the rudder. When the common screw is employed in merchant- Common steamers, a three-bladed screw is usually preferred, since screw, this causes less vibration, and gives a steadier motion in a rough sea than the two-bla<led screw. The resistance jjp,.j„jg„gg which such a screw occasions to the vessel, when sailing to sailing, under canvass alone, is very serious, in addition to the diffi- culty ex|)erienced in steering ; and it is found in practice, that but little advantage is gained by disconnecting the screw from the engines, and letting it revolve in its bear- STEAM SHIPS. 137 Iteam Na- vigation. foisting :rew. l^'^ escnp- ■ ir."-:, in prePercnce to dragging it through the water. Hence, in the case of steamships which depend much upon their canvass, one of three remedies must be adopted : namely, the screw musteitiier be hoisted bodily out of the water; it must be feathered ; or, thirdly, such a form must be employed (as Griffith's two-bladed screw, for instance), which will not interfere much with the sailing and steeriuL,' of the ship, when the blades are placed vertical, and the screw left down in its place. The lioisfmg screw has been adopted gene- rally for war-steamers, wliich are supposed to make great use of their sails, and which have a Iar<rer number of men available for quickly hoist- ing and lowering it. The annexed engraving shows the manner in which this is effected in the royal navy. A is the screw (of gun-metal) ; B is the hoisting-frame (also of gun-metal)which lifts the screw, with its bearings, bodily out of the stern- frame of the ship ; C is a gun-metal rack, to hold the hoisting-frame at any portion of its ascent ; D is the chain and pulley used in hoisting ; E is a clutch upon the screw- shaft, to enable the screw to be disconnected, and rise when brought into g a vertical position ; F is the gun-metal lining of fig- so. the screw-shaft, which passes water-tight through the inner stern-post I ; G is the iron screw-shaft ; H is the outer stern-post ; K is the " trunk" through which the screw is raised to the main-deck, when the blades are brought ver- tical. Having now seen what are the principal forms of screw- propellers in general use in this country, let us briefly ex- amine some of the qualities inherent in the screw itself. 1. Pitch. The question between the relative values of the pitch fine and coarsely pitched screws still remains, in a great a screw, nieasure, undecided. In fact, our experience hitherto has only tended to show, that nothing but actual trial of dif- ferent pitches can satisfactorily establish the best pitch of screw for any particular vessel. The points to be con- sidered in reference to this inq\iiry are so numerous and complicated in their bearings upon each other, that they utterly defy previous calculation of their effects ; some vessels giving the best results with coarsely-pitched screws running at a low speed, while other vessels, not very dis- similar, attain their hiijhest velocity with a finely-pitched screw running fast. It is generally acknowledged, how- ever, that a coarsely-pitched screw is the best for a vessel with fine after-lines, and a finely-pitched screw for vessels with full sterns. The form of the after-lines has un- doubtedly a very great influence on the most advantageous pitch of screw for that particular ship, depending on the amount of " back-water" in which the screw works, and the velocity with which it follows the ship. It is by no means an uncommon thing for one vessel to gain a knot an hour by an alteration of the pitch ; while in the case of another vessel, perhaps, no improvement is effected by a sin)ilar alteration. inctions 2. Diameter. This is made simply as great as the draught Steam Ka- of water will admit. In sea-going steamers the top of the vigation. screw should be submerged about 18 inches or 2 feet at ^""^/'^^ the average trim, to allow for the undulations of the sea. Diameter. 3. Area and Length. By the area of the screw is gene- Area and rally understood the |)lane projection of the resisting sur- length, face of the blades. In the experiments made with the Dwarf, it was found that the speed of the vessel remained almost a constant quantity, although the length of her screw was successively diminished from 2 feet 6 inches to 1 foot, the area corresponding to each of these lengths being respectively 222 and 8'96 square feet. The slight improvement which did take place in the speed of the boat attended the diminished area. It seems at first sight ex- traordinary that so great a variation in the resisting surface should cause so little disturbance either in the speed of the engines or of the vessel, thus showing plainly how small a segment of the whole pitch is required to absorb all the power which the reaction of the watei is capable of im- porting, any extra length of screw beyond this point only retarding by friction. The Rattler's experiments were in the same way commenced with a screw 5 feet 9 inches long, which was gradually shortened until it reached its point of maximum effect at 15 inches only. It is now a common practice to make the length of the screw ^th of the pitch. 4. Slip. The apparent slip of the screw depends upon a Slip, great variety of circumstances. It is modified by the dia- meter and by the speed, being generally found to diminish as these increase. Thus, the diameter of the Rattler's screw, during her experiments, was 10 feet, and her ave- rage slip lo per cent. ; while the Dwarf and Fairj-, with screws of 5 or 6 feet diameter, show an average slip of about 35 per cent. The form of the after-lines of the vessel has a very notable effect on the apparent slip of the screw, which must not be regarded as a measure of the efficiency with which the propeller is acting. On the contrary, many vessels whose lines are most unfavourable for speed show an exceedingly small slip of the propeller ; and in some instances of this kind there is not only no slip apparent, but the screw has actually what is called negative slip, which implies that the vessel is going faster than the rate at which the screw which propels it would advance if working in a solid. This curious and paradoxical result is due to the Negative current w hich all ships, more or less, but especially those slip- with full sterns, carry in their wake ; and since the screw acts in this current, the apparent slip will be positive or negative in proportion as the real slip, or the velocity of the current, may preponderate ; but in every case the screw must have some slip relatively to the water in which it acts. Suppose, for instance, that a badly formed ship h;is a current of water following in its wake, and closing in upon the screw at a velocity of 4 miles an hour, while the real slip of the screw is but 3 miles an hour, the result will be that the screw will show an apparent negative slip of 1 mile an hour. It must not be supposed that in such a case the power of the engines is economically applied, for, in fact, much power is uselessly consumed in dragging this current of water after the ship. The same apparent dimi- nution of slip is always found when the vessel is advancing with a tide or current. Anomalies of this kind most fre- quently occur in auxiliary screw-steamers, where the vessel, after attaining a high velocity by sails alone, still continues to receive a propelling thrust from the screw, even after the .speed of the latter appears to be less than that of the vessel. In order to give the reader some perception of what Trials of really are the conditions of the screw most conducive to screws in speed in the vessel, I have selected the trials of twelve *''*^*"^" different screws made in the same vessel, the Rattler, arranging tliem in the order of their relative efficiency, beginning with the lowest. S 138 STEAM SHIPS. atpam Na- '• With a four-threadcd Woodcroft's increasing pitch screw, vigation. 9 '>^''' ilinnipter. 1 foot 7 inches long, and the pitch varying from V / 11 feet to 11 feet 6 inches (mean 11-275), the speed of the vessel ' was 8-159 knots ; the engines making 2415 revolutions per minute, anil the screw 96 — slip, 23-5 per cent. 2. With a three-threaded common screw, 9 feet diameter, 3 feet long and 11 feet pitch, the speed of the vejsel was 8-23 knots ; the en^'ines making 24-2 revolutions, and the screw 94-3— slip 1966 per cent, 3. With Sunderland's propeller, 8 feet in diameter, the speed of the ship was 8-38 knots ; the engines making 17-49 revolutions, and the screw-shaft 69-97. 4. With the same screw as Xo. 2, reduced in length to 1 foot 7J inches, the speed of the vessel was 8-57 knots; the engines making 248 revolutions, and the screw 984 — slip, 197 per cent. 5. With the same screw as No. 1, but with two of the blades cut off, the vessel's speed advanced to 8-63 knots; the engines making 27-07 revolutions, and the screw 107-5 — slip, 2597 per cent. 6. With a two-threaded common screw, 10 feet diameter, 3 feet long, and 11 feet pitch, the speed of the vessel was 8 958 knots; the engines making 21 revolutions, and the screw 95 — slip, 13 8 per cent. 7. With a four-threaded common screw, 9 feet diameter, 1 foot 7 inches long, and 11 feet pitch, the S])eed of the vessel was 9-18 knots : the engines making 26 3 revolutions, and the screw 104-4— slip, 27-7 per cent. 8. With a two-threaded common screw, 9 feet diameter, 3 feet long, and 11 feet pitch, the speed of the vessel was 925 knots; the engines making 26-8 revolution.% and the scraw 106 — slip, 195 per cent. 9. With the same screw as No. 6, shortened to 2 feet, the vessel's speed increased to 9-448 knots; the engines making 25-5 revolu- tions, and the screw 107 — slip, 13-5 per cent. 10. With the same screw as No. 6 further reduced in length to 1 foot 6 inches, the speed of the vessel was 9-811 knots ; the engines making 2792 revolutions, and the screw 1107 — slip, 18-3 per cent. 11. With the same screw as No. 2 further reduced in length to 1 foot 2 inches, the speed of the vessel was 988 knots; the engines making 27-39 revolutions, and the screw 108'4 — slip, 15-97 per cent. 12. With the same screw as No. 6 further reduced in length to 1 foot 3 inches, the speed of the vessel increased to 10-74 knots; the engines making 26-19 revolutions, and the screw 103 97 — slip, 1042 per cent. Trials made trith her Majesty's Steamer Fli/ing Fish. SCEEW. Indicated liorso- powor of Engine^. Speed of Sliip. Description of Screw. Diame- ter. Pitch. Ileroln- tiona of. Speed of. Slip p.ct. Common Screw, GrifBt>'8 Screw withfea- ■ thering blades. Ft. in. 11 11 13 2 13 2 13 li 13 1} 13 1} 13 li 13 1} 13 U Ft. in, 21 4 21 4 20 20 19 17 16 15 18 17 No, 82 79} 75 74i 71} 77i 77i 83 75} 77} Knots, 17-263 16-737 14-802 14-704 1.3-406 13-00 12-197 12-286 13411 13-00 321 32} 20J 21 15? 10} 4t 3i 14} n,p. 1302-26 1154-86 1166-76 1160-60 1198-56 1287-00 1265-00 1358-80 1226-20 1265-80 Knots. 11-585 11-298 11-736 11-603 11-284 U-640 11.568 11-832 11461 11-552 Trials of A very intorcsting series of ex|)erimcnts has been re- screws in ceiitly made with llie screw-fi-igate Doris, to determine the the Doris, niost suitable form of screw-propeller for our steam-vessels of war. 'I'lie following is a resume of the principal lesults arrived at, the first five trials having iieen made with the common or admiralty screw, and the last three with Grif- fith's propeller. The engines of the Doris (by Messrs J. Penn and Son) are of bOO nominal horse-power. The draught of water while under trial was kept constant at about 19 ft, 6 in. forward and 21 ft, 9 in. aft — exact mean, 20 ft. 6 in.; giving an immersed midship-section of 7421 s-quare feet. Pressure of steam in boilers, 20 lbs. ; indicated horse-power, about ."5000. The first trial with the admiralty (;crew was with a diameter of 18 feet, the vessel's speed being 1 1-823 knots. On the second trial, with the diameter increased to 20 feet, the speed realized was 11-826 knots, with a great increase of vibration ; steering imperfect. On Steam Ne the third trial, the " leading" corner of each blade was cut vigation off, and in this form the common screw attained its gi-eatest '^-^V" speed, giving a result of 12-032 knots, with 50 revolutions of engines per minute, and 2S84 indicated horse-power; vibration reduced, and steering good. On the fourth trial, both the corners of each bh-idewere cut oft' so as to assimi- late the blades to Griffith's Ibrm, when, with a greater num- ber of revolutions, the speed fell off" to 12-012 knots. In the filth trial, with the "following" corner of each blade cut off, but the screw restoicd to its perfect form in every other respect, a result of 11-815 knots was obtained. The common screw was then removed, and the next trial was made with Griffith's propeller, 20 feet diameter and 32 feet pitch; this gave a result of 11-931 knots, there being scarcely any vibration, and the ship steering well. Tlie second trial, with the same Griffith's propeller, having the bhitles set at 26 ft. 6 in. pitch, gave a speed of 12-269 knots, being the highest of the series ; steering perfect, and no vibration perceptible; indicated horse-power, 3091. The third trial of Griftith's 20-feet screw, with the blades set at a medium pitch of 30 feet, gave 12-158 knots. Several important points connected with the screw-pro- Results o peller seem to have been proved by these trials — \st. That I^ori"'" the leading edge of the screw is the part that luostly affects '"»''• the steering of the sliip, and also causes the greater part of the vibration ; 2d, That increased diameter of the screw is better than increased pitch for reducing the sjiced of the engines, but it considerably increases the vibration with the common screw ; whereas with Griffith's it did not produce that effect, in consequence of its chief pi-opelling surface being towards the centre. The common screw, when its blades are cut to the form of Griffith's, is not so effective as when the centre sphere is applied to them. The power re(]uired to obtain the same speed was very much the same lor both screws. The latest experiments also prove the superiority of screws with thice or four blades over those having two only, both as regards speed and vibration. Now that the engines and boilers of a steam-vessel of war may be rendered practically invulncra'-le by armour- ])laling, it becomes a matter of the greatest importance that the propeller also should be adequately protected from an enemy's shot. To effect this with the ordinary screw-|)ro- peller is, I fear, an itupossibility, since any shield or covering of thick iron plates, which coi.l I form a real protection, would materially interfere with the progress of the ship through the water ; nor could the screw revolve in a well without a serious loss of power. The only availalile ex])cdient is therefore to submerge it as much as possible by reducing its diameter. In tliis dilemma it seems at least worthy of a trial whether the water-jet proiieller (as hereafter described) might not be found suitable for some of our armour-plated ships, since this propeller can not only be completely protected, but would also become available for steering the ship in case of the rudder being disabled. Official explanation of the Table of " Results of Trials made in her Mujesti/s Screw-ships," pages (\A2, 143J ** The numbers in the last two figure-columns of the table show approximately the relative excellence, in respect of speed, of the forms of the various vessels, conjointly with the relative efficiency of tlie propeller, as adapted to e.ach of them, " The formula: by which the calculations are made are founded on the assumption that the resistance of a vessel varies as the square of her velocity, and, therefore, that the power required to produce that velocity varies as the cube, and that the usual efft-ct of the engine — that is, the efTect which remains after deducting the power absorbed in overcoming friction, working air-pumps, &c, — bears a constant ratio to the power developed in the cylinder, known by the term ' Indicated horse -powei-,' The resistance is, in the first of these columns, assumed to vary, cceterit paribtt*, as the area of the midship-section, and in the last column as the square of the cube-root of the displacement. STEAM SHIPS. 139 ■am Na- igation. thven's ter-jet )peller. 6 Enter- se. " JToDe of these assumptions, however, more especially the last two, are absolutely correct, but probably they are not so far from the truth as to render useless and uninteresting a comparison, of which they are the basis, made between the performances of any two screw-vessels; while between two vessels which do not mate- rially differ in engines and displacement, or in the area of their midship-sections, such a comparison is not only highly interesting, but it may prove of great value in pointing out the forms of ves- sels and proportion of propellers which ought to be adopted. In some striking cases it is scarcely necessary to make any other comparison than that of speed. For example, as may be seen in the table printed in 1850, the Teazer, after her form had been im- proved, went above a knot an hour faster with 40-horse engines than she had previously gone with engines of 100 horse-power. Again, these engines of 100 horse, when transferred to the Kifle- man — a vessel approaching to double the tonnage — drove her, after her form had been altered, as fast as she was previously driven by engines of double the power, and nearly two knots faster than the same engines drove the smaller vessel before the alter- ation of her after-body. — Admiralty, August 1856." The only other mode of steam-propulsion which has been attended with any considerable success is that known as Ruthven's water-jet system, in which the propelling power is derived from the reaction, or recoil, of two jets of water projected, at a high velocity, from nozzles at the ship's side. The first experimental vessel on this principle was built by Messrs. Ruthven, of Edinburgh, in ib43, and was tried on the Firth of Forth, when it attained a speed of from 6J to 7 miles an hour. This was an iron-boat, 40 feet long. ilore recently, in 185.3, the Enterprise was constructed on Ruthven's princijile, for deep-sea fishing, a preference being given to the jet propeller in this case, from its being less likely to interfere with the fishing-nets than the screw or the paddles. The dimensions of the Enterprise are as follow : — length of deck, 95 feet ; length on the water-line, 87 feet ; breadth of beam, 16 feet; depth, 8 feet; draught at load-line, 4 feet; burthen, 100 tons. The propelling power is derived from two pairs of horizontal oscillating cylinders, each 12 inches in diameter, and 24 inches stroke (condensing), working a vertical shaft. There is one cy- lindrical boiler, 6 feet in diameter, and 5 feet long, with two fire-tubes running through it, each 22 inches diameter, and 105 return flue-tubes, each 5 feet long, and 2 inches internal diameter. The propeller consists of a fan-n heel, or centrifugal pump, 7 feet in diameter, with curved blades, keyed on the lower end of the vertical crank-shaft ; this revolves horizontally in a water-tight casing into which the water from the sea flows (along a covered passage), through crescent-shaped openings in the bottom of the hull. The water is expelled laterally, from the fan-wheel, in two con- tinuous streams, through curved pipes with nozzles, 10 inches in diameter, protruding from the sides of the hull. The nozzles turn in collars fixed to the ship's side, so that they can be pointed a-stern or a-head, as required, for for- ward or backward motion, or downwards, when the vessel is to remain at rest. These changes can be made rapidly md easily from the deck, since the nozzles alone require to be operated upon, while the engine continues to work at full speed. Again, by setting the nozzles in opposite di- rections, one pointing a-head and the other a-stern, the vessel can be turned on the spot, swinging on her beam without the aid of the rudder ; and she could thus be steered by the nozzles in case of the rudder being lost or disabled, the manoeuvring of the vessel being entirely in the hands of the officers on deck. The vessel progressed very smoothly, without tremulous motion. In a trial trip with the Enterprise on the 16th of January 1854, from Granton to Kirkcaldy, in the Firth of Forth, and back, a distance of lOJ miles each way, the speeds ob- tained were 9'69 statute miles per hour going, and 9 miles per hour returning, giving an average of 9'35 miles per hour — the engine making 50 revolutions per minute. On another occasion, she is stated to have made a considerably higher speed, the engine making 65 revolutions per minute. Steam Na- Tlie draught of the vessel, during the trial, was 3 fett 2 vigation. inches; and the immersed midship-section, 40'5 square feet. ^""^/""^ The indicated horse-power of the engine was not known, no indicator-diagrams having been taken. In such an arrangement, much power is necessarily lost in communi- cating to the water which enters the propeller a velocity equal to that of the ship, besides a considerable loss from friction, eddies, &c.; but upon the whole, the power of the engine seems to be applied to considerable advantage. Even allowing that the speed attained does not equal that Advan- from paddles or screw, the jet-propeller possesses other un- tagesof the doubted advantages which recommend it for special cases, *'*'*''"J^' as for instance, in the Government floating-batteries and P'"?® steam-rams, where the screw and the rudder are particu- larly liable to be fouled by wreck and cordage. It would also be preferable to the screw in cases of river-steamers of very light draught, where the paddle might not be ap- plicable. Several of the large floating Sre-engines on the Thames have been fitted with this propeller, the water being ejected by the powerful steam-pumps with which these vessels are fitted. The speed, however, has in these cases not proved satisfactory. A steamer, called the Albert, propelled on this principle, was placed on the Rhine, as a passenger-boat, a few years since, but did not attain a speed proportional to her power or consumption of fuel. It is frequently asked. Whether is the paddle-wheel or Paddle the screw the most efficient propeller ? This question may and screw now be safely answered, by asserting, that when both are compared, in their best trim, and both are equally well proportioned to the engines and vessel, they are, as nearly as possible, equally efficient. It follows, therefore, that the preference for one or the other, in any particular case, depends entirely upon the class of vessel and the nature of her service. The objections to the paddle, as compared with the screw, may be thus briefly stated, namely, the unequal immersion of the wheels, according as the vessel swims light or deep ; the obstruction to the sailing of the ship caused by the resistance of the paddle-boxes to the wind; and the dragging of the paddle-boards through the water when the engine power is not used, and the wheels are not disconnected ; and, in the case of steam-vessels of war, the exposure of the wheels and machinery to an enemy's shot. The advantages of the paddles, on the other hand, are, that they are not so much affected by the pitching motion of the ship, when steaming head to wind, as the screw is ; that they do not require such a speed of engine (or else gearing) ; and tliat, from the disposition of the weights in respect to the centre of gravity of displacement, the movements of the vessel are easier than those of a screw -steamer, a matter of conside- rable interest to the passengers at least. With regard to the screw, its efficiency is but little impaired by variations of trim in the ship, but it is most injuriously affected by the pitching motion. Its advantages in facilitating the sailing of the ship are self-evident, and have been already alluded to. In fine, the superiority of the screw for sea-going steamers appears to amount to this, that it retains its efficacy as a propelling agent under a greater variety of conditions of sea, weather, and trim, than the paddles, and that it admits of more use being made of the sails and a greater display of seamanship in the navigation of the vessel. Under proper management, therefore, it a|)pears to be more economical of steam-power than the paddle-w heels ; and this, it may be remarked, is the actual experience of the Peninsular and Oriental Company, whose steam fleet is composed of vessels on both principles. Having thus briefly considered, firstly, the engine-power of the steamship, and secondlj', the immediate propelling agents employed to produce locomotion, it will now be nccess.iry to view her as a completed whole, and to ex- HO Steam Na- vigtktion. Resistances offered to a ■teamer. STEAM SHIPS. Direct re- eistancc. Inflaence of form. amine some of tlie general properties and q\i;ilifications in- herent in, or dcmaiuled by, tliis complicati'cl structure, as well as tlie relations they severally hear to each other. The construction ol'ihe steamer's liiill will be found amply detailed under SiiH'-BuiLDiNG, so this need not be here adverted to. When a steamer is once set in motion, the motion is, of course, continued by iier momentum, and she would then evidently continue to advance at a unilbrni speed, without any more force being applied to her, were it not for the opposition of external causes. These external forces which she encounters, and which are constjintly at work to destroy her momentum, and bring iier to a state of rest, are the resistance of the water to her hull, and the resistance of the air to her upper works and rigging; the impetus of the waves and the winds being exerted sometimes in her favour, and at other times against her. The power of the steam-machinery is therefore applied to counteract these retarding forces, and to maintain a certain amount of progressive motion in the ship, depending upon the resistance on the one hand, and the power of the engines on the other. The resistance ofllred by the water to the passage of the luiU must be divided into two parts; firstly, that due to the dividing and displacing of the water, to make room for the hull of the ship to pass through, which (according to Mr Scott Russell) is analogous to scooping out a long trough or canal, of the full breadth of the ship ; and, secondly, the resistance arising from the friction of the water upon the sides and bottom of the vessel. Of these resistances, the first is by much the more serious, altlioush the second must not be overlooked. The resistance offered to the passage of the hull depends mainly upon the area of the immersed midship- section of the ship (or its greatest cross-section), but also very materially upon the form of the vessel's lines under the water. There is considerable discrepancy ot opinion as to the re- lative value of these two fiinctions of the ship ; one naval constructor relying for speed upon a small immersed midship- section, while another holds that fine lines for dividing and closing the water are still more essential. The lines of a ship undoubtedly exert a great influence upon her speed, as lias been shown experimentally in numerous instances. In the case of the Government disp.itch-boat. Flying Fish, (.•\lready referred to at Jiage 13-), this vessel, of 1050 tons displacement, attained a speed of only ll'VS knots, with 1166 indicated horse-power. That performance did not equal the expectations of the Admiralty authorities ; and without making any variation in the other parts of the vessel, they ailded, not a 7iew bow, but an elongated bow, 18 feet in length, in advance ot the original one, to divide the water more freely. The resiilt was, that with the same draught of water, the velocity of the vessel increased from 11"73 knots to 12'5o knots an ho\n\ Mr J. Scott Russell, in the course of a discussion on this subject at the Institution of Civil Engineers,' has given some very interesting results of experiments, all tending to show that the shape of the vessel has a very decided in- fluence upon her speed, irrespective of her engine-power. He relates that he had, on one occasion, the control of four timber ships of the same dimensions, the same displace- ment, and the same horse-power ; but each had different lines, being constructed by different shipbuilders. The engines were all alike, being made by the same firm. The result was that, upon a run of 16 miles, their several speeds were 12i, 12, under 11, and between 10 and 11 miles an hour. In another instance, a steamer, constructed to go both ways, but built « ith one end finer than the other as an experiment, went fully a knot faster one way than the other, although the midship section and the horse-power were necessarily identical at all times. A third case was the followin'^: — Two vessels were built of the respective Steam Nn- lengths of 190 feet and 1 86 feet, their breadths being equal, vigation. The engines were the same in each, the cylinders being ^""v^^ 48 inches diameter and 4 feet 6 inches in stroke, making 39 revolutions per minute. The speed attained by the first vessel, however, was lo'03 knots, while that of the second was but 11'32 knots. Tlie difference in the two vessels consisted mainly in the shape, the other and minor elements being much in favour of the slower vessel. For insUmce, the faster vessel had 124 t'cet of midship-section, whilst the slower vessel had but 71 feet of midship-section to drag through the water. The faster vessel drew 6 feet 8 inches of water, whilst the slower vessel drew only 2 feet 10 inches. The dilfeiencc in length was only 4 feet, yet a radical difference in shape thus reduced the velocity, with equal power, from 15 knots to 11 knots per hour. Colonel Beaufby's experiments determined the resist- ance of the water to a ship with a square head only, and it has since been found that a semicircular or ronnil head offers two-thirds of the resistance derived from his formula I R = aw—- j , and an eliptical head considerably less.- By making the bow still finer, the resistance had been gra- dually reduced to one-sixth, and one-eighth, of that given by the formula ; and Mr Scott Russell believes that the engine-power required to drive a large vessel through the water has now, in some cases, been reduced as low as one- twelfth. We learn from the same authority (the highest, indeed, which it is possible to adduce on this subject), that with a vessel of proper form, measuring about 1500 tons, the resistance of a ship can be reduced to 50 lb. per square foot of immersed midship section, while steaming at the rate of 10 knots an hour. This is the direct resistance of the water upon the hull, and Mr Scott Russell .asserts that he has thus been enabled to calculate confidently, to within a quarter of a knot, the amount of steam-power necessary to propel a given ship at a given speed, basing the calculation upon his own peculiar form of " wave-line," there being necessarily a shape for every speed. For instance, when a speed of 10 knots an hour was desired, he provided engine- power for 50lb. per square foot of immersed midship- section (exclusive of the resistance of the machinery, which brought it up to 65 lb. per square foot), for a vessel of about 1500 tons, built on the " wave-line" construction. These figures, 50 lb. and 65 lb., are gross resistances, and include friction of skin. With regard to the absorption of power by the friction ofFrictional the skin, it is a difficult matter to estimate this correctly, but"''"*""^*- that it must be very considerable is sufficiently proved by our every day's experience of how much a vessel will fall off in speed by even a slight fouling of her bottom. This often amounts to a loss of one-filili of her original speed, the engine-power exerted remaining the same ; so that, under j these circumstances, double the power would be reipiired to attain the same speed as before. An iron steamer has been known to fall off a knot an hour by her bottom be- coming only so rough as the skin of a walnut. The total immersed surface of the Rattler's hull has been calculated at 7000 square feet, and according to Beaufoy's experi- ments on tlie friction of immersed surfaces, the resistance thus arising would be eight-tenths of a pound per square foot for a speed of 10 knots an hour, and nearly 1 lb. per square foot at 1 1 knots. At the speed and friction first named, the power absorbed would be equivalent to nearly 170 i.n.r., the total i.n.p. of the engines amounting to 428 n.r. onlj'. In the case of the Himalaya, an im- mersed surface of about 18,000 square feet is exposed, the friction from which, at a velocity of 13 knots an lujur, 1 See Traniactions of ImtituU of Civil Engineert, Session 1856-57. 2 In the formula in the above sentence a represents the mirlship section in square feet, v the velocity of the vessel in linear feet per eecon J, g the accelerating force of gravity = 32^, and w the weight of a cubic foot of sca-water at 64J lb. avoirdupois. STEAM SHIPS. 141 Effect of increased length. Steam Na- would absorb about 650 I.H.P., supposing the bottom to vigation. be perfectly clean. """"^/'^^ The consideration of frictional resistance, of course, places a limit to increase of length in a steamer, although many instances have occurred in which the vessel has gone as fast, or very nearly as last, with the same engines, and on the same draught of water, after some 30 or 40 feet have been added in midships. The Candia is a remarkable instance of this, as will be seen by the following comparison of her speed when originally built, and after she was lengthened in midships by 33 J feet, her load displacement being thereby increased about 470 tons : — ^ •c — t-' . Sn .-■^ °£ 2e s . k n "o^ Date or trial. a g 11 Q 11 P Oh z; Ft. Ft. Tons Tons' No. U>. III. p. Ft. Knots. ^ray31, 1S54... IS-G 281 2-520 G50 36i 22 1672; 20 2 12-651 Aug. 12, 1857.. 19-0 314-fi, 3 090,1000 33 III 20 1462 21 t 1 3 12-443 Law of re Eistance. Although in this instance, from some unexplained cause (owing possibly to improved trim, or circumstances of wind and sea), it would appear from the trial trips that a con- siderable increase of length has been obtained without any corresponding absorption of power, there must necessarily be a limit where further extension of length is more than neutralized by increased frictional resistance. It is universally admitted that the gross resistances (direct and frictional) to which a vessel is subject increase as the square of the velocity, and therefore, as a necessary conse- quence, the power expended in producing tiiis velocity varies as the cube of the velocity. For instance, if the resistance to one square foot of midship-section propelled through the water at 5 miles an hour be 5 lb., then the resistance at 10 miles an hour would be four times 5, or 20 lb. But the latter resistance has acted over double the space, so that the result must be again doubled for the Relation of measure of the power expended; and hence it follows power to that tl)e power exerted must always be in the ratio of the cube of the velocity. This rule cannot be expected to hold strictly good in all steamers alike, looking to the great diversity of form and displacement which exists, but in the great majority of cases it is fully borne out in practice. Thus, in H.M. screw-steamer Desperate, the following relation between power and speed was found to obtain : — velocity Indicated Horse- power. Knots. Coal nei I.H.P. p. hour. 80589 57932 363-87 169-32 9-15 8-25 7-35 5-98 lbs. 4-61 5-13 5-58 5-89 With 3 boilers anj 4 cylinders, work- 1 ing expansively J With 2 boilers and 4 cylinders, do. ... With I boiler and 2 cylinders, do. ... Practical examples. The Retribution, paddle-wheel steamer, had a speed of 10-4 knots with 1092 i.h.p., and a speed of 6'22 knots with 226 i.n.r. The Onyx, with 2 boilers and 533 i.h.p., realized a speed of 13"1G knots, whilst with one boiler and 158 I.H.P. the speed was 8'6 knots. The Minx, with 234 I.H.P., made 9'14 knots, and with 3r6 I.H.P. 4'51 knots. These, and many other instances, are all in accordance with the rule, that the power and consumption of fuel vary as the cube of the velocity. The [jractical value of this rule will be made apparent by the following examples : — 1. If it be wished to find the speed corresponding to a diminished consumption of fuel for any particular steam-vessel, the calculation will be effected thus; — The vessel, we will suppose, has engines which propel her at the rate of 12 knots, with a consumption of 35 V3. tons of coal per diem, and we wish to find tbe speed correeponding Steam Ka- to a consumption of 25 tons per diem ; then — vigation. 35 : 25 : : 12' : V^ (cube of required velocity). ^^"V^^ AVhen reduced, 7:5:: 1728 : V^ As an equation, 5 x 1728 = 7 V-*; or, 8640 ., ^ '' And V 1234 = V' 10 726 knots = V, the required velocity. It is thus seen, that by reducing the consumption of fuel by 10 tons per diem, we lose in this instance about ij knot per hour. 2. If it be wished to increase the speed of the vessel, on the other hand, from 9 to 11 knots, and we desire to know the increased con- sumption attending the increase of speed, this will be in the propor- tion of 93 to 11', or as the numbers 729 : 1331, or as 1 : 1-825. All we have to do, therefore, is to multiply the present consump- tion by this latter number. 3. If a certain steamer consumes, say 220 tons of coal, during a run of 1600 miles, performed at the average speed of 11 knots per hour, and we wi-^h to find her probable consumption of coal for a longer voyage of 2400 miles, at a reduced speed of 9 miles, the calculation will then he as follows : — 220 tons coal : C (required consumption) : : 11- knots X 1600 : 92 knots X 2400 miles. Then C x 121 x IGOO = 220 x 81 x 2400; or, C X 193,600 = 42,768,000. 427 680 Reduced toC = — ilJl^" ^^ 220-9 tons, required consumption. It is thus seen that the consumption of fuel is almost exactly equal in these two cases, showing that the same vessel would steam 1600 miles at 11 knots, or 2400 miles at 9 knots, with the same quantity of coals. 4. Supposing that we have a steamer with stowage-rrtom for only 460 tons of coal, which she has nearly e.\peniied during a trip of 1800 miles, while steaming at the speed of 11-5 knots an hour, and we wioh to place her upon another station, where she must run 2500 miles w-ithout coaling, it is required to find at what reduced speed she must steam so as not to run short of coals ? tons. knots. knots. tons, knots. 460 X 11-5- X 1800 = 460 X 2511O X V2 required velocity; or, 460 X 132 25 x 1800 = 460 x 2500 x V2; reduced to 109-503 = 1150 V^; ,,, 109503 Therefore, V = %/95-04 = 975 knots, required velocity ■We thus find that the same vessel which ran 1800 miles at a speed of 11-5 knots, and with a consumption of 460 tons of coal, must re- duce her speed to 9j knots, to enable her to run 2500 miles with the same constimption. The preceding examples all show that an increase of speed Efficiency is obtained only by the expenditure of a very great increase "^ * of power. Hence, to draw even the most superficial com- steamer, parison between the efficiency of different steam-vessels, their speeds must first be reduced to a common standard, and the relation must then be found between the consump- tion of fuel at the standard speed, and the size or tonnage of the vessel, tlie maximum speed of each bemg treated as a separate question. Tlie value of the term efficienci/ also varies so much for different classes of vessels, that steamers of the same class only can be justly compared together. The number of tons displacement that 100 gross or indicated horse-power will propel, at the rate of 10 knots an hour, has been proposed as a standard of comparison between different steamers. A vessel, for instance, is known to have a speed of 12 Modes of knots an hour, the engines exerting 1620 indicated horse- '^"^"'P'"''' power, at a displacement of 2240 tons. '°°' Then, as 12 knots : 10 knots : : ',^1620 h.p. : 3^lnd. H.p. required; or, 1728 : 1000 : : 1620 : 937-5 ; and 937-5 : 2240 : : 100 : 23!;-9 = tons displacement propelled by 100 l.ll.r., at 10 knots an hour. By making similar calculations for other vessels, their rela- tive efficiency may be, to a certain extent, comparcil one with the other. It is found, in practice, however, that the form of the vessel influences the ratio existing, theoreti- cally, between the power exerted and the resulting speed. 142 Steam Na' vtgatioD. STEAM SHIPS. Kormulm for deter- mining steamship perform- ances. ■Thus, in tlie Flyint: Fish, before slic was altired, an in- crease of only i'6H knots in the spccil of the sliip was obtained by douhUnj; the indicated horse-power ; but after a fine bow'was fitted, slie gained 2-452 knots by doubhn<; the power, the latter increase of speed bein<; just propor- tional to tlie cube of the extra power exerted. A formula frequently employed in comparing the relative merits of vessels '9 V^ I> ^- ^ is thus expressed in words :— The cube of I.1I.P. ' ' the speed in knots, multiplied by the square of the cube-root of the displacement, and diviiled by tlie indicated horse-power. The ri'sultant number is culled the co-officient of dynamic duty for that particular steamer, an<l forms a criterion of tlie cost at which she performs her work, the higher the coefficient the greater being the economy. In a steamer of good average perl'ormunce, the co- efficient, as calculated by this rule, should lie between 200 and 320, or thereabouts. As the preceding formula does not take note of the area of im- mersed midship-section, the following is also useful as a means of V X I afct ton. comparison : — jflTp The two formula! next to be given are used indiscriminately for estimating the probable speed of a steamer, viz. — No. 1. V3 : yii.i'. X 0. Hi ; or, when expressed in words, the cube of the velocity equals the square-root of the nominal horse-power, multiplied by the diameter of the cylinder in inches, divided by the square of the cube-root of the displacement. jI.H.P. X 100 No. V2=- mid. sect. Proportion of horse- power to tonnage. Main ele- ments of steamship economy. The speed of the Candia, when measured by the first of these rules, is 11-38 knots, and by the second, 11'28 knots; while her actual speed, under the same conditions of di.-^placement, &c., is 11-93 knots. In the same way the speed of the Pcra, by the first rule, is 11-22; by the second, 11-28; and actual, 12-55 knots. The actual speed, in both of these cases, is therefore in excess of that calculated by the formulae. In proportioning the horse-power of a steamer, tlie fact must be borne in mind that the effective power of the engines increases in a higher ratio than simply as the ton- nage, since the resistance varies as the square of the cube root of the tonnage. Thus, if a vessel of 1200 tons and 400 horse-power have a speed of 12 knots, a similarly con- structed vessel of 1650 tons and 550 horse-power (with the same proportion of power to tonnage), ought to have a considerably higher speed, since the square of the cube root of 1200 being 112-78, and the square of the cube root of 1650 being 139-47, the proportion will then be 112-78 : ■400 : : 139-47 : 494-6 horse-power, instead of 550 horse- power. The proportion of horse-power to tonnage recommended for different classes of ocean steamships may be stated as follows : — For full-powered passenger paddle-steamers of from 500 to 1200 tons (builders' o.m.), 1 horse-power to 3 tons; for ditto, of from 1200 to 3000 tons, 1 horse- power to 4 tons ; for full-powered passenger screw-steamers of from 500 to 1 200 tons, 1 iiorse-power to 4 tons ; for ditto, of from 1200 to 3000 tons, 1 horse-power to 5 tons; for auxiliary screw-steamers, I horse-power to 6, 7, or 8 tons, according to size. It must not be supposed that a steamer can, or ever will be constructed by the sole aid of " forniul»," which are themselves, for the most part, empirical. They serve, how- ever, to assist in estimating the value and tendency of the several proportions and attributes of the structure, a wide margin being left for the cxcicise of practical sagacity and experience on the part of the constructor. To sum up, in a few words, the main elements upon which economy in steam navigation seems to depend, these are — a fine form, a moderate speed, considerable magnitude, a clean bottom, and a high ratio of length to breadth ; to which may be added, effective engines, and a properly proportioned pro- peller. Again, after the naval constiuctor and engineer liave each done their best, much still remains for the skill of the commander and ofUcers of the ship. With regard to the relative proportions of the hull, our fastest and most successful ocean merchant-steamers of the [iresent day liave their length and breadth as 7, 7'5, or even 8 to 1 for iron screw-steamers, wooden hulls being generally confined to 6-5 and 7 times the beam. The pro- portion of depth varies very nuich, but this should never exceed eight-tenths of the breadth, and is better limited to six-tenths. A very deep steamer is always tinweatherly and tmmanageable, and often dangerous. The proportions in actual tise will be seen by inspecting the tables of steamers in the royal navy, and the table of merchant- steamers, at pages 141, 142, 14;!, With reference to the management of steamers at sea, a full-powered |)assenger-stcanier is generally so tied to time that she cannot afford to disuse any portion of her steam- power, contenting herself with expanding more or less in the cylinders, according as the wind and sea are propitious or otherwise. Every opportunity of a fair winil, however, should be eagerly seized for hoisting sail, which, in the case of a screw-steamer especially, affords a great addition to the power of the engines. Steam-vessels of war, on the other hand, are expressly designed to sail well, in addition to their steaming powers; and in estimating the ])trlor- niance of a Government steamer, we should rather look to the direct distance run by the combined action of steam and sails, at a moderate but iminterrupted speed, and with a small consumption of fuel, than to the attainment of a high velocity, which is seldom wanted in war-steamers. In steaming against a strong head wind, with a paddle-wheel steamer of moderate steam-power, it is found preferable to keep the vessel in a direct course as long as jjossible ; but, so soon as her head begins to fall off for want of good steerage way, the fore and aft sails should be set, and the vessel tacked, the engines being kept working. Iti the screw-steamer, on the other hand, there is no economy in keeping a direct com-se against a head wind and sea, after her speed is reduced to three or four knots an hour, since the engines keep up their usual number of revolutions, and the steam is mostly wasted in slip, or during the "racing" of the machinery. In such a case, tlierefbre, the ship's course should be altered, and the sails set to assist the screw, so soon as the speed falls to this amount. In paddle-wheel engines, the waste of steam is not so great while going head to wind, since the revolutions decrease with the speed of the vessel. When a vessel is steaming against an ojjposing stream or tide, it is found that her engine-power is most economically applied when she goes half as fast again as the velocity of the stream. Notwithstanding the many undoubted improvements which have been recently introduced in the application of the screw propeller, and the extended experience we have now liad of its operation in different classes of ships, and under every variety of trial, the position which it holds in the merchant service, either as an antagonist to the paddle-wheel in full-powered Steam Na- vigation. Propor- tions of length, breadth, and depth. Manage- ment of a steamer at sea. Fig. 32. Paddle-steamer for the rivcre of India Steamers, or as an auxiliary to tlie sails in sailing ships, is still far fiom being well defined. STEAM SHIPS. 143 steam Na- Before bringing this article to a close, it is proposed to vigation. gjyg ^ few examples of steam-vessels which have either ^'^■^l'"~^ proved unusually successful, and may, therefore, stand as types of their class, or have some peculiarity of structure which seems to point them out for special notice. 1. Duke of Wellington, 131 guns, steamship of the line, is 240 feet 6 inches long between jjcrpcndicuhirs, and 60 feet broad. Tonnage, 3826, builders' o.M. Has two horizontal, geared, screw- engines. Diameter of cylinders, 94J inches, and 4 feet 6 inches stroke. Nominal H.P., 780 ; indicated do., 2500. Machioery by Robert Napier & Sons, of Glasgow. Has 4 tubular boilers, each containing 5 furnaces of the following dimensions, viz. — 7 feet 4 inches long + 2 f^et 9J inches wide ; the total space occupied by the machinery being 70 feet in length. The diameter of the screw shaft ne.xt the engines is 12J inches. The screw itself is double threaded, 18 feet diameter, 16 feet 3 inches pitch, and 3 feet 4 inches long. The driving-wheel of screw-gearing is 10 feet 6 inches diameter, worlting into a pinion (with wooden cogs), 4 feet 6 inches diameter, and 4 feet 5 inches broad. The speed of the vessel at her trial trip was 10-2 knots. 2. AlEIisiiV, 40 guns, screw steam-frigate, is SCO feet long be- tween perpendiculars, and 52 feet beam. Tonnage, 3726 ; nominal H.P., 1000 ; indicated n. P. ,4000. Makers of the machinery, .1. Penn and Son. Pressure of steam, 20 lb. ; mean number of revolutions of engines (direct), 55^. Screw, diameter, 20 feet ; pitch, 29 feet ; immersion at trial, 6 inches; revolutions of screw, 55J. Draught of water of ship, forward, 20 feet 8 inches ; aft, 22 feet 7 inches. Coals on board, 850 tons ; consumption of fuel at full speed, about 140 tons per day of 24 hours. Number of furnaces, 32 ; length of stoke-hole, 68 feet lOinches; breadth of ditto, 10 feet; temperature of ditto, 100° Fahr. The tops of the boUers are 4 feet under the water-line ; fitted with three auxiliary engines, two of which supply the boilers, and the third acts as a steam fire-engine. Weight of shot fired by one broadside, 1652 lb. Speed at trial, 13-29 knots. 3. Rattler, screw-sloop, 179 feet 6 inches long between per- pendiculars ; 32 feet 8^ inches beam ; 888 tons builders' O.M. ; 13 feet 6 inches mean draught of water at trial ; area of immersed midship-section, 330 square feet ; displacement at trial, 1078 tons ; nominal n.P., 200 ; ditto, indicated, 436 ; diameter of cylinders, four of 40J inches each ; length of stroke, 4 feet. Revolutions dur- ing trial, 27. Diameter of screw, 10 feet; pitch, 11 feet; length, 1 foot 3 inches ; multiple of gearing, 4:1; revolutions of screw per minute, 107'9; slip per cent., 17'67. Description of engines, vertical geared. Makers of the machinery, Maudslay, Sons, and Field. Alasimum speed of the vessel at trial, 10 knots. 4. Growler, screw gun-boat. Length between perpendiculars, 100 feet ; breadth, 22 feet ; draught of water, mean, 6 feet lOJ inches ; immersed midship-section at this draught, 130 square feet; horse-power — nominal, 60; indicated, 200 ; high pressure engines working direct, with 2 cylinders, each 151 inches in diameter, and 18 inches stroke. Makers of the machinery, Maudslay, Sons, and Field. Pressure of steam, 50 to 60 lb. ; weight of engines, 8 tons 14 cwt. Boilers, 3 in number, are cylindrical, with internal tubes. Length of boilers, 15 feet 4 inches X 4 feet diameter, with one furnace in each, 2 feet 2 inches broad x 4 feet 6 inches long. Each boiler contains 82 iron tubes, 2 inches in diameter and 8 feet long. Total grate-bar surface in the three boilers, 29'25 square feet; weight of the three boilers complete, 13 tons 1 cwt. ; weight of water in the three boilers, 9 tons. Screw, tw^o-lhreaded, 6 feet diameter ; 8 feet pitch; 16 inches long; weight, 840 lb. Total weight of the machinery with spare gear, 32J tons. Coals carried in bunkers, 28 tons. Speed at above immersion, 8'38 knots ; speed of engines and screw, 154 revolutions per minute; slip, 31 per cent. 5. Warrior, iron-cased steam-frigate, is built of iron ; extreme length, 380 feet ; breadth, 58 feet ; depth, 41 feet 6 inches ; tonnage, 6177. Weight of hull, about 5700 tons ; fitted with engines of 1250 nominal horse-power, weighing 950 tons. Builders of the ship, the Thames Iron Co. ; makers of the machinery, J. Penn & Son. She will carry 950 tons of coal, and the weight of armament, masts, stores, &c., will amount to about 1200 tons. The total weight at sea will thus be about 9000 tons. Sheathed with wrought-iron armour-plates 4^ inches thick from 5 feet below the water-line to the level of the upper deck for 220 feet of the broadside, each plate being 15 feet long by 4 feet broad. Behind the iron armour-plates there is a thickness of 24 inches of teak, protecting all the fighting portion of the vessel. The bow and stern are not thus sheatned, being merely plated with thick iron plates in the usual way, and crossed by several water-tight bulkheads. Armament will consist of Armstrong guns, each capable of throwing a 100 lb. shot a dis- tance of 5 miles. The total cost of each frigate will be about L. 320,000. Estimated speed, 14 knots an hour. 6. ViOTOniA AND Albert, H.M. steam-yacht. Is built of tlm-gteam Na- ber, and has the following dimensions: — Length between the per- \i|ration pendiculars, 200 feet 1 inch; breadth of beam, 33 feet: depth ', of hold, 23 feet 9 inches; burthen in tons, builders' o.M. 2343; ' ■*■ horse-power, noninal, 600; horse-power, indicated, at trial 2980. Propelled by paddle-wheels. Has oscillating engines by J. Penn and Son, with two cylinders, each 88 inches in diameter and 7 feet stroke, the total weight of her machinery being 401^ tons. Her draught of water when complete for sea, with stores and coals on board, is 15 feet forward and 15 feet 9 inches aft. Revolutions of engines at this draught, 22 ; displacement at medium load-draught, 2120 tons. Has four tubular boilers, containing in all 3024 brass tubes, each 6 feet 5 inches long by 2j inches external diameter. The boilers have altogether, 24 furnaces, each 7 feet long by 3 feet w-ide, fired from two stoke-holes. The pressure of steam on the safety-valves is 20 lb. The steam is superheated ; has two funnels, each 5 feet 6 inches diameter, and 40 feet 3 inches high from top of boiler. The coal-boxes contain 410 tons of coal. The paddle- wheels are feathering, 29 feet extreme diameter, 14 boards to each wheel, each board 11 feet 6 inches by 4 feet 2 inches. The wheels can be disconnected by a friction-disc and break. Speed at trial trip, 17-022 knots. 7. Fairy, H.M.'s screw steam-yacht, is built of iron, and has the following dimensions : — Length between the perpendiculars, 144 feet 8 inches; breadth extreme, 21 feet IJ inches; mean draught of water at trial, 4 feet 10 inches ; area of immersed mid- ship-section, 715 square feet ; mean displacement at trial, 168 tons. Tonnage, builder's o.M., 312 ; nominal horse-power, 128 ; indicated horse-power, 364. Builders, Mare & Co.; machinery by J. Penn & Son. Diameter of screw, 5 feet 4 inches ; pitch, 8 feet; length, 1 foot. Revolutions of screw at trial, 258 per minute ; slip of the screw, 34 per cent. Has two vertical, oscillating, geared engines, the cylinders 42 inches diameter, and 3 feet stroke, making 51 J re- volutions per minute. Speed of the vessel at trial, 13'324 knots. 8. Himalaya, steam troop-ship, propelled by the screw, is built of iron, and has the following dimensions: — Length between the perpendiculars, 341 feet; breadth, extreme, 46 feet 4 inches; depth of hold, 35 feet; tonnage, 3560^; horse-power, nominal, 700. Has horizontal direct engines, with cylinders 84f inches diameter, and 3 feet 6 inches stroke, making 59 revolutions per minute. Boilers on Lamb and Summer's sheet-flue principle. Pressure of steam, 14 lb. She can stow 1000 tons of coal ; her daily consump- tion, at full speed, being 70J tons. Fitted with the common 3-bladed screw, 18 feet diameter, by 28 feet pitch, making 59 revolutions per minute. Speed at trial, 13 9 knots. This steamer has proved eminently successful, having made the trip from Eng- land to Alexandria, on several occasions, at an average speed of 12 knots an hour ; and with a favourable breeze, she has been known to run 16 knots within the hour. 9. Troop River-steamers for India. These are now being built for Government of the following proportions: — Iiength on the water-line, 350 feet ; length over all, 375 feet ; breadth, 46 feet. Built of steel-plates, weighing about 5 lb. per superficial foot, with the exception of the keel-strakes, which are 7 lb., and the girder-strakes 15 lb. per square foot. They are flat-bottomed, to draw only 2 feet of water, with machinery, fuel, stores, and 800 troops on board. The bulls are estimated to weigh only 370 tons. They are to be propelled by paddle-wheel engines of 200 horse-power. They will be steered by two large patent steering- blades. The hull is stiffened by two iron girders, rising above the deck, and running for 300 feet of the length, from which vertical and diagonal trusses are carried. They will be sent to India in parts, after being put together and tried in this country. Esti- mated speed, 12 miles an hour. 10. Great Eastern, of iron. Length between the perpendiculars, 680feet; length on deck, 691 feet; breadth, extreme, 83 feet ; depth of side, 68 feet; draught of water, from 20 to 30 feet. Gross tonnage, 22.500. Nominal horse-power, 2600. Builder, J. Scott Russell. Her screw-engines of 1600 horse-power, by James Watt and Company ; and paddle-engines of 1000 horse-power, by J. Scott Russell. The screw-engines are horizontal direct, with 4 cylinders, each 84 inches diameter, by 4 ft. stroke, making 43 strokes per minute ; with tu- bular boilers, carrying 25 lb. pressure. The screw is of the common construction, with four blades, 24 ft. diameter, with a pitch of 44 It. The paddle-wheel engines are oscillating, with 4 cylinders, each 74 in. diameter, by 14 ft. stroke. Boilers, tubular, 25 lb. pressure. Paddle- wheels are of the common construction, 50 ft. diameter, 13 ft. leng;h of floats, and 3 ft. depth. Total coals carried, 10,000 tons. Coals burnt per hour, 12 to 13 tons. Speed about 15 knots. Her ship- draught is shown in the plates illustrating article SiiiP-BciLDINO. 11. Persia, transatlantic mail-steamsbip, of iron, has the fol- lowing dimensions : — Length between the perpendiculars, 360 feet; breadth of beam, 45 feet ; depth of hold, 29 feet 8 inches. Medium load-draught of water, 215 feet. Displacement at this draught, 144 STEAM SHIPS. Stt-nm Na- 5285 tons. Area of immersed midship-section, 818 square feet. vi"ation. Tonnage, builders' CM., 3J86. Ituilders of vessel and makers of \ . ^ . , / the machinery, Robert Napier and Sons. The bottom plates of the ^ hull are 4| inch thick, tapering to J inch at the load water-line, and above this \i inch, except round the gunwale, where they are { inch. The hull is divided into 7 water-tight compartments, and has a double-iron bottom for a considerable portion of her length. The launching weight of the iron hull was 2200 tons, her displacement with machinery, coals, ond stores on board being about 5400 tons, on a draught of 23 feet. Accommodation Is pro- vided for 250 passengers (besides a crew of 150 persons), and stowage room is found for 1200 tons measurement goods. Coals carried are 1400 tons. The engines are on the side-lever construc- tion, with 2 cylinders, each lOOJ inches diameter, and 10 feet stroke, 850 nominal horse-power, and about 3000 indicated horse- power. Diameter of i)addle-shaft, 23J inches. There are 8 tubular boilers, containing, in all, 40 furnaces, each 7 feet long by 2 feet 9 inches wide. Total length occupied by the machinery is 107 feet 6 inches. The paildle-whcels arc of the common construction, 38 feet 6 Inches diameter to extremity of boards, which are 10 feet 8 Inches long, 2 feet 1 inch broad, on 28 arms. On the occasion of the Persia's trial trip from (Jla^gow to Liverpool, slie ran 175 knots In 10 hours 43 minutes ; thus accom[>lishing nn average speed of IG knots, or nearly 19 British statute miles an hour. 12. Peiia, Alexandria mail screw-steamship, is of iron, and has the following dimensions : — Length between the perpendiculars, 303 feet 7 inches ; breadth extreme, 42 feet 3 inches ; depth of bold, 27 feet 2 inches; gro.«s tonnage, 2613; nominal horse-power, 450 ; indicated horse-iwwcr, 1500. Builders of the vessel, JIare and Company ; makers of the machinery, Messrs Itennie. She has vertical trunk-engines, geared, with 2 cylinders each "Oj inches diameter (trunk 30 Indies diameter), and 4 feet length of stroke. Strokes of engine per minute, 294. There are fi)ur sheet-flue boilers; pressure of steam IC lb., superheated. 700 tons of coal are carried in boxes ; coals burned per day of 24 li nirs, 44 tons (in place of 56 before superheating apparatus was fitted). Screw propeller has 3 blades, is 15 feet G inches diameter, 21 feet pitch, making 60 revolutions per minute. Speed at trial trip, 12-5 knots. The Pera has made some very remarkable passages. Thus, in the month of July 1859, she ran from Southampton to Gibraltar, 1000 miles, in 3 days 21 hours (being at the rote of lOj knots per hour) ; thence to Malta, another 1000 miles, in 3 days 12 hour3(ll-9 knots per hour); and from Malta to Alexandria, 1000 miles, in 2 days 19 hours (14-92 knots per hour). The Pera's lines are shown in the plates of article Ship-Biiildino. 13. Lkinster, Ulster, Munster, Connacoht, new Holyhead mail-packets, are of iron, and propelled by paddle wheels. They have the following dimensions : — Length extreme, 350 feet ; breadth, 35 feet; depth, 20 feet; draught of water, 12 to 13 feet; builder's tonnage, 2000 ; nominal horse-power, 700 ; indicated horse power (estimated), 3500. Average speed contracted for, 20 miles an hour. The engines are oscillating, and the p:iddle-wheels have feathering floats. Three of the vessels are built by Messrs Laird, and one by Messrs Samuda ; and the machinery is by Messrs Kavenhill, Salkeld, and Company, and Messrs James Watt and Company. They are rijiged very lightly, for fore and aft sails only, their great engine-power making them independent of the wind. They have 9 water-tight bulkheads, extending to the upper deck, one of which divides the engine and boiler rooms ; this latter bulkhead constituting an important element of safety and strength, which might be advantageously introduced Into iron steamers much more frequently than it is. The cabins are 9 feet 6 inches high ; the principal saloon being GO feet long. We are enabled to give the following additional particulars of the Leinster through the kindness of her constructor, Mr Samuda: — Length between the perpendiculars, 328 feet; length on deck, 346 feet ; breadth of beam, extreme, 35 feet ; depth in engine-room. 21 feet; burthen in tons, builders' old measurement. 2 00. Draft of water at oflicial trial at Stokes Bay, 26th July 1860 — forward, 12 feet 2} inches ; aft, 13 feet 2 J inches (12 feet 8} inches mean). Area of midship section at this draft := 336 square feet. Displacement at same draft = 1880 tons. Area of horizontal water-line section at the same draft = 7974 square feet. The form of the Leinster mid- ship section may be thus described : A round bilge, having a radius of about 8 feet, joining the straight of the side at the 11 J feet water- line, and sloping down with an easy sweep to the keel, which It meets at an angle of about 12 degrees from the horizontal line. Her mean speedat the measured mileat Stokes Bay, as above, was 17797 knots, or 20-502 English statute miles ; mean revolutions of engines, 26i per minute. The engines (oscillating) are by Messrs Ilavenhill, Silkeld, and Company, and have the following dimensions : — Diameter of cylinders, 98 inches ; length of stroke, 6 feet 6 inches; revolutions per minute, 26 ; nominal horse-power, 700 ; indi- cated horse power at trial, 4200 ; i)ressure of steam in the boilers, (tubular), 25 lbs. ; consumption of fuel during trial trip, at the Steam Na- rate of 7 tons per hour ; coals on board during the trial (on start- vication ing), 30 tons; stowoge for coids in bunkers, 90 tons; estimated ^ '/ consumjition while at regular work, 6 tons per hour. Feathering ^ ~ wheels, 27 feet diameter to centre of axis of floats. The excep- tional character of the Holyhead packets is made further apparent by the following statement of the oflicial tonnage of Leinster: — Gross tonnage, 1382 ; engine-room tonnage, 997 ; leaving only 385 for the register tonnage, 14. Brkmf.n, screw-cJipper steamship, is built of iron, and has tlie following dimensions : — Length between the per[)endiculars, 31 8 feet ; breadth of beam, 40 feet ; depth of hold, 26 feet ; mean draught of water at trial, 18 feet 6 Inches. Displacement at this draught, 3440 tons. Area of immersed midship section, 606 square, feet. Kate of displacement at load draught, 25 tons per square inch. Builders of the ship and makers of the machinery, Messrs Caird and Company. The engines of the Bremen consist of two direct-acting Inverted cylinders, each 90 Inches diameter and 3 feet 6 inches stroke. Nominal horse-power, 500 ; indicated horse- power at trial, 1624. Speed at trial trip, 1315 knots per hour. The average performance at sea. between Bremen and New York, with a mean displacement of 2950 tons, was found to be 11-05 knots, the engine showing a mean indicated horse-power of 1045. The superiority shown by the Bremen is believed to be principally due to her fine form of body, and judicious proportions. Her ship-draught will be found amongst the plates illustrating Sliip- BUILDINO. 15. Windsor Castle, Clyde river-steamer, propelled by paddle- wheels, is built of steel-plates, and has the following dimensions: — Length, 190 feet; breadth, 20 feet; depth, 7 feet 6 inches; tonnage, gross, 190 ; register, 93. Mean draught at trial, 3 feet 1 inch. Immersed midship-section at this draught, 52 square foet. Average number of revolutions, 43. Nominal horse-power, 115. Indicated horse-power at trial, 620. Pressure of steam in the boilers, 40 lb. Builders of the vessel and makers of the machinery, Messrs Caird and Company. The cylinders are placed diagonally ; they are 40 inches in diameter and 5 feet stroke, cutting off steam after 12 inches. The steam Is supplied by an upright tubular boiler, and is superheated In the funnel to a temperature of 375° Fahr. before entering the cylinders. The boilers have 76 square feet of fire-grate surface, and 1526 square feet of total heating surface, consuming about 20 cwt. of coal per hour. The paddle-wheels are feathering, 15 feet diameter, each having 10 boards, 8 feet long by 2 feet 3 inches broad. Speed at trial trip, 17083 knots, or 19 679 British statute miles an hour. In this steamer weight is economised in every possible way, and only 10 tons of coal are carried. 16. Tacht.\LIa, river-steamer for shallow navigation, is built of iron, and has the following dimensions: — Length, 150 feet; breadth, 20 feet ; draught of water, with machinery and pa.ssengers on board, 12J inches. Builders of the vessel and makers of the machinery, Messrs J. and A. BIyth. She is propelled by 4 conden- sing engines, of the collective power of 40 horses, acting through 4 paddle-wheels, each 6 feet in diameter and 6 feet wide ; the forward engines making 87 revolutions and the after-engines 96 revolutions per minute, and the speed through still water being about 11 miles per hour. The bull is formed of very thin plates, stiffened by frequent transverse bulkheads, and webs of plate sur- rounding the vessel internally. By employing 2 pairs of paddle- wheels, each pair driven by a distinct pair of steam-engines, not only are the weights of the machinery, water, and coals diffused over the vessel, but the propelling power is also widely distributed over the structure. The use of i paddle wheels in place of 2 greatly Improves the steering of the vessel, always a matter of much difliculty with boats of shallow draught running on swift rivers. Lightness of machinery in this vessel is promoted by the substitu- tion of gun-metal for cast-iron In the condensers, &c., and of cast- steel and wrought-iron for the framing of the engines. The boilers are constructed of Lowmoor plates throughout, without angle-irons, to save w-eight. Vessels of this class are well adapted for the rivers of India. A representation of the Tacbtalia is giveu at page 136. 17. Screw-steamer for the rivers of India, built of iron. Length, 70 feet ; breadth, 7 feet G inches ; depth, 3 feet 6 inches; draught of water, 2 feet. Boat and machinery constructed by Messrs G. Rennie and Sons. Propelled by two screws, one on each quarter (see annexed wood engraving, fig. 33) ; diameter of the screws, 2 feet 2 inches; pitch, 4 feet. Driven by a pair of disc engines acting direct. Speed of the engines and screws, 260 revo- lutions per minute. Speed of the boat, 10 knots per hour. Weight of the boat, 3 tons 8 cwt. ; weight of the machinery, 3 tons. Con- sumption of coal, per hour, 100 lb. Power of traction, at slow speed, 250 tons. Cost of trackage, J of Id. per ton per mile. 18. American Steamboats (by a correspondent of The En- gineer). — " Going aboard at a late hour in the evening, the scene STEAM SHIPS. 145 Na- which presented itself to our eyes was novel in the highest degree, ion. Painted a pure white, as nearly all American river-steamboats are Screw-Bteamer for tte rivers of India. (for the anthracite coal burned under their boilers makes no smoke whatever), the enormous mass of the vessel rose like a giant iceberg above the water. Hurrying over the broad gangway, we found ourselves in a crowd of nearly 700 passengers, more than one-third of whom were ladies. We were upon the main-deck, although under a lofty ceiling, over which was a grand saloon of palatial propor- tions and magnificence. Looking aft, a broad entrance, flanked with gilded columns and luxurious drapery, opened to the ladies' saloon — a sanctum sanctorum not to be profaned by the footsteps of a bachelor, although steamboat etiquette was not so strict, nor steamboat regu- lations so inflexible, as to forbid the momentary presence there of gentlemen accompanying their wives, or other fair charges, to be intrusted to the care of the stewardess. On either side of this en- trance were broad staircases descending to an immense lower cabin, along the sides of which were more than 400 berths. The supper tables were then set out with a degree of splendour for which an English traveller would be altogether unprepared. Nearly amid- ships, on the main-deck, a grand staircase, sweeping both to the right and left, conducted to the great saloon, or state-room hall, nearly 300 feet in length, several yards in width, and having an upper gallery, with a second story of state-rooms — a lofty arched ceiling, glazed with ground and coloured glass, and supported by richly-carved columns, covering the whole. In its construction, this steamboat (the New World) is totally unlike anything ever seen in British waters. It is of enormous size. Originnlly 376 feet long, it was afterwards lengthened to 468 feet over all. With a breadth of beam of -50 feet, the main deck is extended by means of plat- forms, or " guards," projecting over the water to the full width across the paddle-boxes, 85 feet, being thus wider than the main- deck of the Great Eastern. Yet the vessel, which is flat-bottomed, with bilges nearly or quite square, draws only 5i feet of water, the whole displacement being about 2500 tons, and the immersed mid- section 275 square feet. All American boats have wooden hulls, and how to stiffen such a vast and shallow craft, flat-bottomed as Noah's Ark ? There are no tubular cells, no ' double skins,' nor is there a hundredweight of boiler-plate, excepting in the boilers themselves, in the whole structure. As if to increase the strain' Steam Na- the boilers, weighing, with water, 75 tons each, are placed upon vi<ration. the " guards " outside the hull, and of course several feet above the '^ ^ ,_ ' load-line. To make the whole as rigid aa a tubular girder, two enormous arched trusses, placed one over each side of the hull, ex- tend over nearly 350 feet of the length of the boat. These great bows, like the arches of a bow-string bridge, are connected to king- posts and queen posts, and strapped and fastened, so that the whole is as stiff as a man of war. Then there are four or five large king- posts, or masts, stepped upon the keel, and carrying the weight of the projecting ' guards' by long diagonal tension rods. These masts carry no spars, booms, or rigging of any kind, all of which would be so much top hamper, worse than useless, at a speed of 20 miles an hour. These posts, like nearly all the rest of the wood-work, are painted a dazzling white, and surmounted by gilded balls. The lines of the hull are very sharp, and at 22 statute miles an hour, a speed not unfrequently attained, there is only a thin spurt of water breaking into spray to mark the keen entrance of the cutwater." We subjoin a list of those parts which are considered most necessary to be carried as spare geak for sea-going PADDLE-WHEEL ENGINES of a large class : — 100 bolts and nuts for paddle-wheels ; 50 bolts and nuts for paddle-floats ; 6 paddle-floats ; 2 sets of gearing for paddle-floats (feathering-wheels) ; 1 connecting-rod for ditto, ditto ; 1 driving- arm for ditto, ditto ; 4 large pins and 2 small for brackets, ditto; 2 radius boss pins for ditto, ditto ; 2 bushes fur ditto, ditto ; 8 brass washers for gearing, ditto; 4 bolts and nuts for radius-boss, ditto; 4 segments of paddle-centres; 4 arms for paddle-wheels; 18 iron washer- plates ; 2 brass linings for outer-bearings; 120 brushes for boiler-tubes ; 36 stoking-irons ; 60 scrapers, circular and forked ; 1 set of stocks, taps, and dies, from J to 1} inch ; 1 air-pump rod and nut; 1 cylinder-cover, bush, and gland; 1 piston and rod; 1 piston-rod cap, complete ; 2 complete sets of all India-rubber valves ; J set of fire-bars ; 1 set of bearing-bars for one furnace ; boiler- plate, about 6 or 8 cwt. ; 60 boiler-tubes; 300 ferules for boiler- tubes ; 8 handles for boiler-tube brushes ; 24 drifts (short and long) for tubing; 12 mandrils for ditto; 1 crank-pin for engine; 1 eccentric-band, complete ; I feed-pump rod, complete ; 1 bilge- pump rod; 1 gross iron washers of various sizes; 120 bolts aud nuts; 8 glass gauge-tubes for boilers ; 2 glass tubes for barometers. The following is a list of spare-geab for SCREW-EN- GINES of a large class : — 1 Cylinder-cover, complete ; 1 connecting-rod ; 1 centre-bonnet, for cylinder ; 1 air-pump rod ; 1 piston and rod, complete ; 1 feed- pump rod ; 1 bilge-pump rod ; 1 slide-rod, complete ; 1 eccentric strap, complete ; 1 spiral-spring, for escape-valve ; 1 cross head ; 1 guide-block and brass (if so made), complete; 1 cap for thrust- block, fitted with white metal ; 2 screws for thrust-block ; soft metal bearings, various ; 2 complete sets of Intlia-rubber valves ; 1 wrench for piston-rod nuts; 1 set of taps and dies, complete; 50 bolts, assorted (iron and metal); 80 bolts and nuts (assorted) ; 40 spanners, various; J set of firebars ; 60 fire-irons, assorted ; 110 scrapers (50 circular and 60 forked); 3 bearing-bars; 100 boiler- tubes ; 300 ferules for boiler-tubes ; 40 drifts and mandrils for boiler-tubes; 200 tube-brushes, and 4 handles,- 140 washers for boiler-tubes; 3 boiler-plates; 16 glass gauge-tubes, and 60 India- rubber rings. Actual Weights of Steam 3Iac/tineri/ in the Royal Navy • Name of the Vessel. Nominal Horse- power. Encines completf. Boilers and apparatus. PropeHer and gear. Coal- boxes. Sundries. ^ machinery. Water in boilers. Grand Tot.-iI. H.P. KlOO 600 COO 450 200 800 800 600 Tons. 213-4 84- 78-9 128-4 18-8 200-9 210-7 183-2 Tons. 263-7 128-6 135-9 1692 45-4 211-8 2107 170-4 Tons. 659 51-2 48-9 46-9 1 . 3 3.5-9 21-2 *73-3 Tons. 173 8-1 93 12-7 4-7 14-8 11-6 15-0 Tons. 25-8 15- 23-8 13-5 9-6 37- 26- 317 Tons. 43-7 21-8 13-7 '4-7 26-4 24-8 260 Tons. 629-8 308-7 310-5 370-8 97-5 5268 505-8 499-6 Tons. 136 85 30 112 112 Tons. 765-8 4558 127-5 638-8 617 8 Shannon Cornwallis Koyal Sovereign Victoria and Albert ... • Puddles. 146 Steam Xa- vigation. STEAM SHIPS. SESCaiPTlON OP THE PLATES. The pressure of steam in the boilers is 19 lb., the steam being cut Steam ] off in the cylinders (when working most expansively) after one- vigutic Plate XV. represents the usual type of the side-lever marine- fourth of the stroke. v - engine. The principal parts are — A the cylinder, B the valve- The letters of reference, previously given, indicate tbo same chest, C the condenser, D the hot vrell, K the air-pump, F the feed portions of the machinery for this and all the remaining plates, and bilge pumps, GG the great lever, G' its main gudgeon, II the The boilers are tubular, two in number, with four furnaces, and cylin'ier side-rods, I the cross-head, K the piston-rod, LI; the pa- ore fired from each end. Each boiler has 360 tubes, SJ inches rallel motion, M the air-pump cross-head, N the air-pump side-rods, external diameter, and 7 feet long. The boilers are fitted with O the air-pump piston-rod, P the connecting-rod cross-tail links, superheating apparatus (A), on Mr Beardmore's plan; each eon- Q the cross-tail, R the connectir.g-rod, S the crank, U the eccentric sists of two steam-chambers, placed one on each side of the chim- puUey or cam, u u u the eccentric rod, V the valve-shaft, WW the ney, connected by 172 tubes in each, each tube being 2 inches in valve-lever and counterbalance lever. diameter. The lower end of the chimney is expanded so as to The apparatus for working the valves expansively is distinctly encase the tubes, through which all the steam from the boilers shown. On the crank-axle, T, is placed a series of cams 1 1 1, which passes on its way to the cylinders. These boilers generate steam Oct upon the roller of the expansion- valve tumbler. Y j/yy are with much focility. The advantage of having two funnels in this the expansion-valve connecting-rods and levers. Z is the valve- case is, that the draught thus becomes more direct, and therefore chest, and the valve is of the kind called equilibrium-valves, or sharper than it would be with one large funnel. The temperature crown-valves. of the superheated steam is about 320°. Plates XVI., XVII., and XVIII., represent a pair of direct These engines have exhibited a very remarkable economy of screw-engines of 500 horse- power (nominal), as constructed by fuel, the consumption, under favourable circumstances, not exceed- llessrs Kavenhill, Salkeld, and Company, for various ships in the jng IJ lb. per I.H.r. per hour; and when the vessel was deeply royal navy. The following vessels have been fitted with machinery laden, this did not exceed from 2 to 2J lb. during a ten days' voyage on this plan, vix.— the Waterloo and Nelson, 98 guns, 500 h.p. ; at sea. The Thunder ran from Plymouth to St Vincent in 9 days the Undaunted, Glasgow, and Newcastle, 50-gun frigates, and 600 14 hours, the chief engineer writing thus from the latter place: — H.P. ; the Narcissus, 50 guns, and the Jason, 21 guns, each of 400 " We have run 285 miles during the last 24 hours; and our ave- B.P. These engines have given much satisfaction, being at once rage speed has been throughout the voyage 11 knots per hour, on compact, and at the same time easy of access to all the working a consumption of 15 tons of coal per 24 hours. Pressure of steam parts. 10 1b.; 44 revolutions per minute. Temperature of steam in super- The following are the principal dimensions of the 500-horse heaters, 310°." This is equal to a consumption of about 12 cwt. of screw-engines: — coal per hour while steaming at the rate of 11 knots, which, for a displacement of 2000 tons, is an extraordinary result. Whilst on piamclcrofthe cylinders (two) " '"'^•'«»- her trial trip her displacement was only half the above, when, Leii(nh of stroke 8 feet. ... "^ . y. '^., . u • . .u . r Revolutions of engines and screw-shaft, per min SO under the most favourable circumstances, she went at the rote of Pressure of steam in the boilers per sq. Inch 20 ll>. 14 knots on a consumption of 8 cwt. per hour. Mameter of the screw 18 feet Plates XXV., XXVI., and XXVII., represent six varieties of Pitch of do. mean 20 feet . ' . . 1 i »t \i . , c, 1 r-- 1 1 Description of screw GrIfHth's. marine engines, constructed by SIcssrs Aiaudsley, Sons, ond I tela Mean draught of the ship (ILM.S. Nelson) 24 n. 94 in. — namely, oscillating-cylinder marine engines for paddle-wheels. Speed at the measured mile '"PA"""- double-cylinder encines for paddle-wheels, annular-cylinder en- Indlcated horse-power 2150bor8ca. ^ ' , ,, , ■ '^, ,• ■ • r t. gines for paddle-wheels, annular-cylinder engines for the screw- The various parts of the engines will be recognised by reference propeller, horizontal direct engines for the screw-propeller, and to the following letters:— AA are the cylinders; B the piston- steeple-engines for river-navigation. rods, of which there are two to each cylinder; C the connecting- Plates XXI. and XXII. represent a pair of "combined-cylinder" rods, working between the guiding surfaces DD, and giving motion paddle-wheel engines of 320 horse-power collectively (nominal), as to the main cranks EE ; F is the screw-shaft ; G the thrust-block, constructed by Messrs Randolph, Elder, and Company, of Glosgow, on which the thrust of the screw is taken ; H the coupling for dis- '" ">' steam-ships Callao, Lima, ond Bogota. connecting the shaft; I a worm-wheel for turning the engines by "^^"^^ vessels arc 245 feet long, 36 feet broad, and 23 feet deep, hand; K the steam-pipe from the boilers; L the throttle-valve; and are designed with lines favourable for speed. Their tonnage N the expansion-valves; N the cylinder slide-valves; the ex- is 1650 tons ; draught of water, 11 feet forward, 12 feet aft; fitted haust-passages ; P the condenser ; Q the air-pump-rods, which work "'"' feathering wheels 25 feet 2 inches diameter, direct from the piston, passing steam-tight through the cylinder "^^^ cylinders are four in number, viz., two of 52 inches diame- covers like small piston-rods. The air-pumps themselves cannot '^■'' ^"^ '"° °^ ^^ '°<^''«^ diameter, and 5 feet stroke. It wUl be be seen, being concealed by the condenser. K the discharge-pipes ; observed that they lie diagonally to each other. During the S the feed and bilge plunger pumps ; eccentrics and gear for work- ""'"^ ""'P^ *''® engines made from 23 to 26 revolutions per minute, ing the slide-valves. *■"' indicated from 1000 to 1300 horse-power, the pressure of Plates XIX. and XX. represent the engines and boilers of the ^'^'"" '"='"5 -^ ^^- ^"^ '*"= ^P^^^ °^ ""^ ^'''P' <"■■<"" ^-i '° 13 screw steamship Thunder, which are possessed of several interesting ''"°'» V"^ ^°'"- The boilers are tubular, ond superheat the peculiarities and appliances for economizing fuel ond steam. The *'<''"° '" ""^ steam-chests by contact with the ui)-takes only, vessel (built by Messrs Lungley of London) is of iron, 240 feet "''^° ^^'^"S purposely divided and prolonged with this view, long, 30 feet beam, 22 feet 6 inches deep, and 1062 tons B.O.M. ^he cylinders are further provided with "jackets" kept well Her draught of water is 13 feet 8 inches aft, and 10 feet 8 inches s"PP''«d with hot steam, to guard against condensation within forward. The engines are constructed by Messrs Dudgeon, of ' cylinders. Millwall, London, and have the following dimensions:— These engines have also been attended with a remarkable eco- nomy of fuel. The Bogoti lately ran from Glasgow to St Vincent, Diameter of cylinders (two) 5S inches. * distance of 2470 nautical miles, in 9 days 21 hours, on a con- Length of stroke 36 „ sumption of 232 tons of coal, thus civinc an averatre speed of Revolutions of engines and screw per min 68 „ in.t.ii *„ «„ „ ^ «....-,,.,*; r lo -„.* Jl v. mu Diameter of screw .„. , 15 feel 10-42 knots, on a consumption of 19 cwt. per hour. The average Pltcli of screw ...!'...!....!!.!!.!!.!!"!"!..".."."...".""".'...'.... SDJ „ i.h.p. being 950, this gives an average of 2i lb. of coal per I.H. per Nominal horse-power 210 horses. hour. Indicated horse-power with full steam BiO to lOTO „ !>,..«« •vvttt -..«.»...«..«.. - •- -r v_ j _!■ j Da, with expansion when cutting off after 1th 696 ", PLATE XXIII. represents a pair of combined-cylinder engine* Speed, with an immersed midship-section of 312 s<iuare feet of the same description as shown in the preceding plates, and by anddisplncemcntof 1175 tons, the engines making Mrevo- the same makers, but designed for driving the screw-proiieller tions per minute, and cutting off steam after 1th of the frK«^« j^ ..,;ii i.„ «i .1 ^ .. a - ■ a ■ • ,u Uroke. .7. r. .. 14knots. 'Ihesc, it will be observed, ore geared engines, driving the screw- Maximum speed at trial witii full power ......'.."...."!!!!!!!!."!! is „ shaft by means of internal gearing. The nature and presumed advantages of ''combined-cylinder" Thecylindersof these engines are inverted, and are fixed directly engines have been already explained. It maybe here repeated, over the crank-shaft. They have separate expansion-slides, and however, that the steam is first admitted into the small cylinder double-port steam-slides. The exhaust is carried round the cylinders for about one-third of the stroke; and after expanding during the by broad belts (see O, Plate XIX.) into the condenser P, the belts remainder of the stroke in the small cylinder, it enters the large thus acting as steam-jackets to the cylinders to preserve their tem- one, and completes its work there by further expanding to the end peroture. The condensers themselves form part of the framing on of its stroke. which the cylinders stand. The shaft is forged with solid cranks, Plate XXIV. is a section of inboard works of the paddle- and the thrust of the screw is taken by the long collared bearing steamer Delta, carrying the Indian mails from Southampton to at C, which is supnorted independently of the engine framing. Alexandria. (b. m T.) STEAM SHIPS. 147 _ o o - = »? = w ^ (- d ■ESi^a^ S-il^.S":; <<3 = = i "5 >- rSS £■ 77 ?» So-= u :^ s 11 1" — =S 3 — o -■< ^ - ;:: -.. 1^^ n » o I i3 s a - d 111" = = 3 5" >- ?^ =""~"" S r^ — — ' §£■; = '■ >-2 S- oS 2f:r: s:^ = o !• «3 2 6S JO ajossaj^j 5-.S ►• P «i-t -^ 3 §-2-SJ2| J-lll o "" O O O X => '-'O ^ lO rj ^-^-,t~ -J o — -< 7< -• r« ^o^-o?*w iQ — r— t-- ri S M ^ ;^ i-": O O K5 3 iS ^ O X '-3 o?*Mrt3;'^o;30io«ortoox»r^ior*» ■«?*c^-«M e-*^- :autSu3 jo'Sia^ •aTlo«s JO q^Sua^ , •-»■ CO w-^sio oowo5ioxoo«t»!00 ciosooooooow«»ts»»«oooooooo«otooo:s«aoo ooo^o o»oo»ooo««o»« ^■r»?^«^*^<M ?*?^«c>t?*T«5*NC*5^s*e«?*w?^c*r*^ c^?*c»mh ?*?*?»?*?»?* *»?*«e*nc^e*?«?« B i^ — -H OOJiMtO?* C* — - * r< -H ra c^ - cc ;t r* 90 -^ ^ O 'J « « X M !■ -n" r< X ?» -^ ^ -< so X -f — ' ^«:- cirsx^ «rt-«-^ ;-o^i*0"0?ssb^of»x>-'5xoi^?^xr50-i'xio«-i e*»3iw uaj5i3aH Jad qjJuai eo M la T» a ,7 X t^i-zi Ti •-~ -f -^ t- o •» M Si t; weir-x o — ^ f» lb o«s o ■?» -^ — — OT rt — 3o w sss — ^- — OCT-^**I^5 coeew — coxx- a 1 *poo^\\ JO aojj ooooooooooooo ut.ht.bt> occccccccccccccoBoccccecos ococ oooooooooooooooooooooo fc.t.t.i:.i:i:;:.l:-i: ;:.--■--£:■->- » i: i: -i: .i i i: ^h, . e s c . s c = o o s ooocooooi U >. O » CO •as . Ifl • a .30 J-r Ji — ^ =^ rf a s-;-;h £^ .0,. ,^S iit^ 11^ s-;oo ■»Xinq nanAv irt -jor-o X ^2 ^2'-'^ " '^ T ^ r~'.'30i~o» cv :c x -J o f ■•• ri^~ x ^ -»■ ji ci ■*-»w-*e»»£Sgoio w 5*» t; 45 Ci o r^ »a i: ;^ rs ■* r^ tr "f x n -y r o s - o a o = c o c P.d d 2.(3 Sfi.rt£."icada.s.cs ; ^ - ?^t^ ■ri :; ? - ti J N^ cc -^ X X X — -3 X -— sl.s.w a. : o ? 2 t. p.- - a. , X C ~ X J ^ U3 ^^X' n ®t. u~A ^uu^j; t..a — = ";-=■-; = c r ■- ■- o o ■- o ^ o EcE o o -fl-a. aa. sa 53 (« 2 aa 222 3 3 : O O '. cnxa *2 » uo. a. a. gESstSaE = 33 SCO a.a.a E)eEEE d o d a a f|||| ': X O '^ X o 35 : : : : m z : : : : :o 3 : : : : I-SH ; iiiisii ••;.:< a : s ; J :^ "< o a =: M M 3 - .00 >• w :b : : -O :^ £ S J S : M z ' ■< M : y < H H (£ -< „ .J < U £. Z M Ci U a a h D < =3 ei ■< ' 5 o s s: H f- ; O C ] : < a 1 = 5^ MO? 5 Z O' H D ^ S £: < < J J a » ,:: = *- =.'*t^.' — X IX X — ^ P 148 STEAM SHIPS. TABLE OF SCREW-STEAMERS IN THE ROYAL NAVY, ENGINES. NaiiI. Tin. Knts, AOAUEMMOX Mli 11 20ot. IMS Xoro Ditlo 'Wi 11-243 3 Mav 1S.-.1 StottoB nay Aloicbs :i-H7 I IJiniolh-M I'lvninnth AhbooanT 1^7-' 8-640] 11 July !«,; St.iki-s l!ay Arrow 1 477; 11 yli Auf*. 18-'>4 Spitliea<I .. AssoiANCl C7U 11-143 lij Juno ISOU Stokes Bay C-CSAB Colossus Conflict Ditto Ditto Ditto Ditto Ditto Ditto Ditto CoNQUERoa COQDETTB .27171 10-2:41 3 Mar. 1S"4 Stokes Hay . -aw 'j-;ir.' ii; oi-t, is.'>i .sioki-s liay . iMjs s-s:l7 li; July ls,'.:l.Si<.ki-» Huy .|lo;;s 'j-l-.'.-. -.'2 Auc. 1>^>V. Stokes Hay .IIOIS ll-4.'4 -.'3 AiiclK-W Stokes Hay .locks' U772,21 Sopt.lW-JS.Stokes Bay .1038' 94-2s'30Sept. .'.Wis 9-!M3 180ct. .'IDltt 9.'.71| 2 Nov 1U38| a-772 7No>- 3-.'.'4 lO-SUi; ICJuno OTOi 109U2il9 May COIACOA Dauntless... Ditto Desperate.. Ditto D.opWellino Encocntbe ... Ditto Ditto Fairt Ditto Ditto Ditto Ditto Ditto Ditto Ditto Ditto Fltino Fiso .... Ditto Ditto Forth Glatton, iJaf.. Hannibal 1571 10-7D3 2r, Sept. 1J7.J lOOlii 12 .Sept. IWi ll)-13:112 0ct. 1037 10-71^ IK July 1037 9-S<; 111 Mar. ton 37 j'J 10-15 1 1 1 Apr. lR.WStokcs Bay IS.-)-. Stokes Bay IH.'. ( stokes Bay 18)3 Stokes Bay lS.JO|Plynioatb lS5«.Stokc3 Bay 18.->4 Stokes Bay IK'iO Stokes Bay IS-'iO Stokes Bay 1^50 Noro 18.72 Plymouth 18J3,Stoke3 Bay ft. in. •230 30 218 7 -.W ICO 180 ft. in. M 4 SS CO DranfElitor Water. ft, in. ft, in. sq- ft. 7 120 1 |23 24 fi 23 4 I 8ie 8 'imW 11063 43 ^ 19 It '20 -i C15 ■240 4 GJ 6J 64 34 C}j»4 6134 6(34 Ci3( 6i»4 00 28 953' 10699 10 JonolS-W'Stokes Day 190 11691 9-439 3 Jan. IS-iijISIokesBay ;192 1169' 9219 R Jan. lSo.)'stoke3 B.iy 1192 312 11-309 laSopt, ls-,3Stokes Bay jl44 312 12-20 24DCC. lW3'stokesBayll44 312 12-137 -27 Dec. ISjS'Stokes Bay 1144 312 812 312 312 312 312 8S3' 808' SOS; 1-228 15351 8136 11-699 29 ll-fi4S,28 13-033 24 13-27 111 13-2-.'9|14 13-216 17 11-&M13 11736 20 11-003; 3 9-3S4 16 4-5 4 86 12 Dec. 1S.M Stokes Bay .Mar. 185l',Stokes Bay JiinolS-'illStokes Kay July 1^)1 Stokes Hay Apr. Kij Stoke? Bay- Apr. ISoo Stokes Bay May 18i6 Stokes Bay Junel8.V:>Stokcs Bay July IS.16, Stokes Bay .May IS.-i6 Stokes Bi-y July 18551 Nore Apr. l854lNor HlOHFLlER 1153 9-399 10 Apr. 185-ii Thames ... Hoooe 1846 7-80;)|13 Dee. IS.')0|Stok.-s Bay Ditto 1846 83-.'8JI8 Dec. 1S.J0 Stokes Bay Horatio 1090 8-855 17 J one IS.JO Noro lurERiEOSE 2355, 10-073 11 Jan. 1853 Noro James Watt 3083 9-361 30 .Mar. 1855 Stokes Bay r.APWlso 6701 Il-02l|->7 .May IR-Vl'stokes Bay .MAHLBOR0I7GII ... 40ou: ll-Hi;o 12 .May IS.)*: Stokes Bay .Meo.t.ra !l39')! 10-241128 Mar. 1S.')0 Thames 141 144 1 144 jll4 144 144 200 200 200 '139 172 217 192 184 184 in 212 230 .Meteob. Batter]/ 1409; .Mibanoa 10391 10- MoBA«c 670l 10-721 Oriow , Pearl Ditto Pioneer Plduper Princess Kotal. Ptlades Rattler RlFLEM.IN Ringdove RoTAL Albert.. Kotal tiEoROE.. St Jean D'Acbe. Sans Pareil Satelli re Seahorse Shannon Sharpshooter.. Simoom Ditto sparbowuawk .. Surprise Terhaqant Ditto 16 May 18.V'i;Thamos ... 2 July 18531 Nore 4 J une 1856 Stokes Bay 19 5 -22 8 •23 2 25 7 15 91'17 *i ill 4 11 16 9 15 9 15 10 15 9 15 9 15 10 15 9 '24 3 10 1 17 3 17 5 17 4 0il4 9 16 9 16 41113 4114 23 43 36 36 21 21 1 1 21 21 21 21 1 30 30 30 42 45 48 36 4 2U3 3 15 3 17 6 16 10 71 10 14 10 15 9 24 3 472 470 472 472 471 471 472 471 ll-.'2 238 467 512 570 8Sg 424 988 3S2 470 470 86 86 86 6 17 1 4 9i 7 3i 4 10 4 10 4 Hi 5 1 44121 2 2i'12 1 16 • 48 4i 20 10 48 " 40 50 55 6 {23 3 33 4 10 2 61 2*21 1 37 10 11 4 172 6 143 U 6 196 0)34 1 180 '28 4 10 xar. 11-44C 2 May la'.r. Stokes Bay 298 1402' 11-313 -JO .May lAV. Stokes Bay 2'Hl 141^2 10-109 j7 .May l.l-jO Stokes Bay -200 SOSI ll-3i;*i!20 .May 18.5o.stoke» Bay ;'200 490 7-218 -21 July I853Stoko8 Bay Il40 U29| ll-03l| 2 Nor. 1853 Stokes Bay :217 31 Mar.lM.j'stokes Bay 192 9 3129 1 1278 10-119 9-77 7-13 10-824 10 9-375 486 670 37-20 1-2616 SSept. l.t'il :5 Nov.l,s-,J ■211 .May 1S.30 21 Nov. 18.H 13 Dec 1851 riiames ...|176 6 32 Thames ... 150 26 Stokes Bay 180 |28 At Sea 232 9 61 Noro 205 7 54 '■3'>00 11-1991 3 Dee. 1S<>3 Stokes Bay 238 .'339 9-3 12 Aug. IMJ.Vt Sea '200 ISJunel-i'iO Plymouth 2')0 16 .May 1850 Stokes Bay ,159 5 JoneI8.Vt'Stokes Bay '.'■35 9 Nov. 1S52 .Stokes Bay 150 Tribune Victor Viper Wandeebb.... 1402 11'4 12121 9'29S -.'651' 11-807 I 503] 9-327 19S0' 8 747 8 Feb. 1851 Stokes Bay 1980 10-647 16 Oct, ls55!stoke3 Bay 670 11-065 10 Junel-^Vi'Stokes Bay 67'i 11-H9 14 July ls30 Stokes Bay 1547' 8-781; 2 Sept. 1^)2 Stokes Bay 1547. 9-593 9 OcU 18o4|Stokes Bay 1570 10-418 9NoT.la53;Stokes Bay 851 ll-383!l2 May 1856 Stokes Bay 477 11-86 127 Sept 18.54 Noro 670 10-733 13 May 1856 Stokes Bay 65 4 62 8 40 4 41 10 50 -26 7J 4 4 4 11-20 2j 5 10 84 10 11 7 111 3 4 9 2 24 8 6i22 10 Tn.i. 3750 5080 4730 '2615 58.5 781 3250 atoi 1702 1740 17.52 1752 1746 174<; 1752 1746 5665 72 1735 l.'iO '2480 1393 1645 5080 1459 1757 1757 210 210 210 Horizontal, Trnnk John Penn and Son Horizontal, Trunk John Penn and Son Horizontal Kairbairn and Sons Horizontal, Trunk ijohn Penn and Son Horizontal Hunipbryi*, Tennant, ^Co. Horizontal j.Millor, Itavenhill, and Co. 23 6 22 8 12 8 17 18 II 43 30 2 26 4 '23 4 7 1 7 1 7 01 7 1 12 3 12 11 12 11 18 9 8 8 20 7 17 4 23 10 23 10 18 8 18 3 23 10 11 6 22 10 15 3 8 12 C 11 6 26 10 19 9 19 9 12 ii?} 19 12 li 11 10 11 3 27 4 23 10 23 25 7; 16 4 18 9 19 10 9 17 10 19 2 18 8 19 4 12 12 U 5 85-4 84 84 85 86 281 272 •277 616 379 777 476 799 805 391 524 1040 240 928 ■.t3 310 336 ■242 9S2 640 644 273 194 805 522 206 233 ■223 1100 945 Cylinders. Dceoription of Engines. Name of Manufactarer. Horizontal, Trunk . Horizontal, Trunk . Horizontal Horizontal Horizontal Horizontal Horizontal Horizontal Hor.zontal Horizontal Horizontal, Trunk . Horizontal Horizontal Horizontal, Geared Horizontal, Geared Horizontal, Geared Horizontal, Geared Horizontal, Geared Horizontal, Trunk Inclined, Oscillating Inclined, Oseillatine Vertical, OsciUg., Geared Vertical, Oscillg., Geared Vertical, Oscillg., Geared John Penn and Son .lohn Penn and Son Seaward andCapol Seaw.ird and Capel Seaward and Capel Seaward and Capel , Seaward and Capel Seaward and Capel Seaward and Capel «.. Seaward and Capel John Penn and Son .Miller, HaTonhill, and Co. Mandslav, Sons, and Field Robert Napier and Sons ... Robert Napier and Sons ... Maudslay, Sons, and Field - Maadslay, Sons, and Field 4 Robert Napier and Sons . ** John Penn and Son J. Soott Rnssell and Co. . J. Scott Russell and Co. . John Penn and Son John Penn and Son John Penn and Son inrhos. 1067 9»4 404 613 6-26 237^5 656 678 240 244 562 653 578 264 215 231 1090 10.50 1072 1792 HAD 3300 1775 3051 3081 1175 2'2^25 4950 781 4510 1,'kM 1316 1350 785 5070 2115 2130 10)6 610 81(10 1956 810 678 714 5571 4110 5340 3800 1500 1799 294« C53 2700 2830 781 790 2270 2230 2220 1019 COO 745 210 Vertical, Oscillg., Geared John Penn and Son •2074 Vertical, Oscillg., Geared John Penn and Son ■203 ■■ " . - - .- •203 205 210 Vertical, Oscillg., Geared John Penn and Son Vertical, Oscillg., Geared .loliti Penn and Son Vertical, Oscillg., Geared'Jolin Penn and Son Vertical, Oscillg., Geared John Penn and Son Horizontal Horizontal Horizontal llorizontal, Tk., High Pre, Horizontal, High Press Horizontal, Geared Horizontal Horizontal Horizontal Horizontal, Geared Horizontal, Trunk HoriEontal Horizontal » llorizontal Horizontal Horizontal, High Press Horizontal, Geared Horizontal Horizontal, Trunk Holizontal, Trunk Horizontal, Trunk Horizontal Vertical, Oscillating, Grd Horizontal Maudslay, Sons, and Field Maudslay, Sons, and Field .Maudslay, Sons, and Field John Penn and Son .Miller, Karenhill, and Co. Scott, Sinclair, and Co .Maudslay, Sons, and Field Seaward and Capel Seaward and Capel Seaward and Capel John Penn and Son James Watt and Co Miller, Ravcnhill, and Co. Maudslay, .Sous, and Field George and John Rennie.., Slaudslay, Suns, and Field Robert Napier Humphrys, Tennant, &Co. John Penn and Son John Penn and Son Jolin Penn and Son .Milter. Karenhill, and Co. Miller, Karenhill, and Co. Maudslay, Sons, and Field Horizont.al, Trunk .... Vertical, Dbl. Cjlrs., Vertical, Oscillating, Horizontal Horizontal, Trunk .... Horizontal, Trunk .... 461 -^ c & 2 55 3-16 2 .lohn Ponn and Son Gr<l. .MaiifJalay, Sons, and Field '■ ' .\1i1Ut, Kav(riiliiU,and Co. Miller. Karenhill, and Co. John Fenn and Son John Penn and Son Horizontal, Trunk John Penn and Son 2 Horizontal James Walt and Co Horizontal, Trunk John Penn and Son Horizontal, Tk^ High Prs. John Penn and Son I 2 Horizontal, Trunk |John Penn and Sod Horizontal, Goarcd iMillcr, HaTcnhiU, and Co. HorizoBtal , Oseillatiog.. Horizontal Horizontal Horizontal Horizontal, Geared Horizontal BouUon and Watt 4 Portfmth. Yard (refitted) 2 Humphry?, Tennant, ii Co. Miller, Kavcnhill, and Co. Seaward and Cajiel Portdmtb. Yard (refitted) Horizontal Mandslay, Sone, and Field Horizontal iMillcr, Kavenhill, and Co. Horizontal „ Maudslay, Son a, and Field UorizoDtal '.Maadfilay, Sods, and Field 3 3 62 6Jh 62l 400 400 , 200 &m 2uu STEAM SHIPS. COMPILED BY THE STEAM DEPARTMENT OF THE ADMIRALTY. 149 PROPELLER. RATIO OF Dimensions. 1 .1 s o .a Slip. .a •a (3 £ o s .« » u Indicated Power. Si a. e h 9 Ii g A i S o O c . c X X ^0 i REMARKS. u <aM o'^ PS-= i B 2 A ja .2 % .- % i 03 i HI c Ii S p. o a & bo § s. P. 01 ^.2 ■=-2 is 1 •ft. CO ■5 1 w ^ S 5 a 1 a > 2 en •a ft. in. ft. in. ft. in. ft. in. ft. in. knta. knt.'i. la 20 6 3 4 11 5 8 11 60 12-133 1-133 9-34 4-16 1-14 3-21 2-25 7-62 590-7 174-7 Weather not favonrable. 18 20 6 3 4 11 5 12 3 63 12-739 1-49G 11-74 4-lG 1-14 4-17 2-14 7-G7 664-2 183-2 Weather very favourable. 17 14 2 4 11 9 13 10 69-12 9-315 0-545 5-71 3-65 0-80 4-64 1-06 8-96 6.S7-2 183-9 Speed by common log. 18 6J IS 2i 2 5 10 1 10 11 GI 9-163 0-517 5-64 4-37 0-93 3-24 1-26 4-03 513-5 158-5 Slide-valve of forward engine defective. U Oi 13 2 a 7 1 4 7 93 11-926 0-926 7-7G G-32 1-18 2-18 2-85 3-48 468-3 166-9 Speed by patent log. U 0' 16 2 6 7 1 4 3 87 13-731 2-589 18-86 6 35 1-45 2-53 3-10 8-78 446-3 167-5 Calm. 17 U 18 103 2 lU 11 3 U 5 60 11-183 0909 8-13 3-70 I-IO 2-16 1-96 6-47 654-5 1G7-G Wind No. 1. 17 IJilS 5i 13 5i]15 2 2 lOi 11 4 14 3 GO 10-924 1-612 14-76 3-33 1-08 3-87 1-63 G-10 494-0 132-3 Wind No. 3toXo. 4. 2 G* 8 10 8 61 73 10-921 2-084 19-08 5-61 1-13 3-31 1-593 5-174 433-2 133-4 Sparo propeller (cut). Wind No. 5. 13 5j!i5 2 2 eji 8 10 8 5 77 11-520 2-094 18-18 5-61 1-13 3-29 1-6G3 5-419 501-9 154-5 Spare propeller, with wooden sphere attached to boss. Calm. 13 5} 15 2 2 GJ 8 10 8 7 75-75 11-333 1-909 1684 5-61 1-13 3-31 1-720 5-537 48G-3 149-8 Same propeller as on the trial of the 16th July 1853. 13 8 19 lOJ 2 7 8 10 8 6 Gl-5 12-063 2-291 18-99 561 1-4G 3-22 1-G44 5-34 567-6 174-3 Common propeller (uncut). Calm. [to No. 4. Common propeller. I foot cut off each comer of each blade. Wind No. 3 13 8 19 lOJ 2 7 8 10 8 6 G2-5 12-259 2-831 23-09 5-61 1-46 3-21 1-639 5-324 511-3 157-4 13 7 20 1 2 103 8 10 8 G 67-25 13-322 3-409 25-59 5-61 1-48 3-25 1-696 5-51 574-2 176-3 Bomerang propeller. Wind No. L {No. 3 to No. 5. 13 8 19 103 2 6 8 10 8 6 6G 12-946 3-375 26-07 5-61 1-46 322 1-661 5 395 527-3 162-5 Common propeller, surface reduced to that of Bomerang propeller. Wind 13 8 19 lOj 2 6 8 10 8 G 66-5 13-044 3-272 25-08 5-61 1-46 3-21 1-614 5-242 578-3 178-0 Common propeller, and edges of blades bevelled. Wind No. 1. 19 26 9 3 G 13 4 13 55 14-513 3707 25-54 4-34 1-41 3-96 2-51 8-85 503-3 142-G Strong breeze, with swell. Trial not considered satisfactory. 11 16 2 C 7 1 4 4 86-75 13-691 2-789 20-37 G-35 1-45 -2-50 2-98 8-43 434-7 153-7 Wind No. 5 to No. 6. 14 1 20 1 3 OJ 9 6 8 64 12-678 1-885 14-87 4-46 1-42 2-98 2-41 7-78 .522-4 161-5 Nearly a calm. U f|lG 4 2 10 9 7 7 3 70-556 11-368 1-332 11-S9 5-52 1-11 3-18 2-48 7-62 404-3 131-9 14 t (17 3 3 9 7 8 8 69-418 11-812 1-G79 14-21 5-52 1-17 3-35 2-23 7-25 446-7 143-6 13 14 2 4 8 6 6 4 82-414 11-381 0-615 5-40 5-60 1-08 2-92 •2-30 7-16 542-5 174-4 13 14 2 4 8 6 7 3 82-91G 11-450 1-590 13-69 5-60 1-08 3-19 1-91 G-07 501-2 158-0 Wind No. 5, with some swell. 18 16 3 2 93 12 4 U 11 66-G 10-675 0525 4-92 4-01 0-90 388 2-00 6-70 522-0 166-1 Wind No. 4. 12 15 94 2 8 7 31 6 61 81-75 12-735 2-03G 15-99 5-72 1-32 3-38 2-21 6-56 554-3 186-7 Calm. Ship fully rigged. 13 2* 18 93 3 2 9 2 8 G8-5 12712 3-273 25-75 5-30 l-.>4 4-02 1-40 4-51 601-6 186-4 Griftiths's patent screw propeller. Wind No. 3. 12 0' 20 3 2 9 2 8 63 12-4-29 3-210 25-83 5-30 1-67 4-16 1-36 4-07 6221 192-7 Common propeller. Wind No. 2. G 6 8 1 9 3 4 1 177-5 14-007 2-698 19-26 6-85 1-23 6-33 4-13 10-17 346-0 142-1 Scott's propeller. Calm- 6 S 9 93 1 6 3 4 1 174 16-843 4-5S3 27-21 6-85 1-51 6-33 4-06 9-87 5441 186-7 Common propeller, cut with blades like GrifRtbs's propeller. Wind No. 4. 6 6 9 93 1 6 3 4 1 17G-25 17-060 4-923 23-86 6-85 1-51 G-33 4-11 10-00 435-1 178-7 Common propeller, same as 2-4th Dec. 1853, with sphere attached to the [boss. Wind No. 4. 5 10 7 8 2 4i 3 4 1 226 25 17-110 5-411 31-62 6-85 1-31 3-22 390 9-49 110-9 168-8 Bomerang propeller. Wind No. 4. 6 6i 14 U 1 8 3 4 31 187-5 26-1-24 14-466 •5.5-37 6-85 2-34 3-51 4-49 10-95 353-8 144-8 Lowe's propeller. Calm. 6 7 11j 9J 3 4 1 207-5 16-:!3-i 3-299 20-20 G-85 1-33 2-97 4-88 11-37 453-G 186-5 Fisher's Venetian propeller with flange. 6 5a 8 3 1 7 3 4 1 212-5 17-293 4-023 23-26 685 1-27 2-55 4-88 U-87 473-7 196-9 GrifRths's propeller. Wind No. 1. 6 5i 7 103 1 10 3 4 01 203 15-967 2-738 17-15 6-85 1-22 2-60 4-78 11-69 434-3 198-1 Common propeller cast at Portsmouth in 1850. Wind No. 1 to No. 2. Lew sey's blades fitted in boss of Griffiths's propeller. 6 33 10 1 81 3 4 1 202-5 19975 6-759 33-84 6-85 1-58 2-75 4-84 11-77 477-2 196-0 11 21 4 3 6 10 5 5 82 17-255 5-G70 32-86 6-59 1-94 2-8G 4-63 12-30 3.35-5 126-5 Wind No. 3. 13 2 19 lU 19 115 3 ni 5 61 75 14-765 3-0-29 20-.51 G-59 1-52 2-00 4-29 11-29 376-8 14-3-1 Wind No. 4 to No. 5. Additional false keel aft. 13 2 3 3 Gi 74-5 14-667 3-064 20-89 G-59 1-52 2-03 4-19 11-08 372-8 141-0 Wind No. 3. Sea moderately calm. 12 10 1 8 7 8 1) 1 114 11-245 1-."61 16-55 3-77 0-83 4-5G 1-62 5-65 511-5 146-3 Wind No. 3 to No. 4. S 2i U 2 3i 3 6 5 2 1-27 17-539 13-039 74-35 3-82 •2-25 12-48 1-83 4-99 498 18-3 Speed by common log. 17 12 6 2 1 11 9 8 10 04-87 7-999 0-601 7-51 3-74 074 3-42 1-38 4-83 461-4 131-6 Speed by common log. Launcbing cleets not removed. Negative slip. 12 03 9 8» 21 l| 1 8 9 8 4 106-74 10-222 0-823 8-05 5-28 0-80 4-17 1-47 4-79 .363-0 173-0 16 1 3 2 11 5 12 5 47 9-799 1-990 20-31 3-80 1-31 3-93 0-99 3-77 480-0 136-5 Fully rigged and complete with sea stores. IG Oi 18 9 3 4 11 5 12 5 56 10-357 2-029 19-59 3-SO 1-17 3-97 0-99 377 583-3 153-4 Fully rigged and complete with sea storos. 14 13 2 2 10 8 8 80-37 10-300 1-451 14-08 3-83 0-93 -2-54 1-41 4-97 490-3 139-8 Preliminary trial ; veasel not in trim. 16 16 2 8 10 7 7 8 67-7 0-GS5 0-012 0-11 4-24 1-00 1-2-61 2-OG 6-34 589-5 191-7 Fresh breeze. 17 24 4 3 1 12 2 11 8 51 12-241 2-880 23-53 4-15 1-43 4-58 1-43 5-31 552-7 154-3 Wind No. 4, 11 15 7i 2 G 7 1 4 5 185 13101 2-080 15-88 G-35 1-42 2-53 2-87 8-13 466-2 164-7 Wind No. 2. 19 1 26 9 3 Gi 12 8 10 2 53-3 14-117 2-.'51 13-95 4-01 1-40 3-24 2-39 9-83 577-8 170-0 Wind variable, No. 1 to No. 2. 14 a! IG 2 83 8 7 6 8 74-21 11-711 1-470 1-2-55 5-47 1-11 2-34 2-42 6-90 444-4 155-7 6 12 6 3 6 4 6 39 17-139 11-369 6G-3S 3-93 2-08 0-96 1-71 4-34 112-4 44-2 [Negative slip. 12 U 6 1 "ii 7 8 5 3 87-87 9-9G8 0-782 7-S5 5-77 0-96 2-97 1-82 5-02 630-8 247-5 Speed by patent log. Wind No. 5 abeam. Propeller 11 in. out ot the irat«r. U 1 14 3 2 63 7 1 4 e 88 12-370 1-649 13-13 G-35 1-29 2-51 2-65 7-54 4G4-9 163-6 Wind No. 2 to No. 3. 18 23 3 2 12 3 14 7 62-75 14-236 2-790 19-60 4-27 1-28 3-86 2-37 7-89 632-4 190-1 Wind varying from No. 1 to No. 3. 16 23 6 3 10 7 9 2 59 13-677 2-364 17-29 4-9G 1-47 2-69 2-45 8-04 590-5 180-2 Common screw. 16 25 6 10 7 9 2 49 12-3-25 1-G5G 13-44 ♦-9G 1-59 2-71 3-92 663 601-9 193-2 Griffiths's propeller. 11 20 G 3'"o 6 10 5 2 82 16-583 5-216 31-46 6-59 1-86 2-87 437 11-50 336-1 137-7 Wind No. 1. 8 8J 6 05 \\i G 1 9 91 111 6-627 0-591 8-92 509 0-69 3-26 0-70 -2-11 540-4 177-8 Wind No. 3 to No. 4 abeam. No gnns on board. Negative slip. 17 1 21 CJ 3 11 10 58 12-324 1-293 10-49 3-73 1-26 3-51 1-85 6-59 734-7 203-6 Wind No. 3 to No. 5. 15 9 20 3 10 2 8 10 6-2-5 12-330 2-211 17-93 5-02 1-27 2-68 2-12 7-04 489-0 147-2 Wind No. 4. 10 11 1 3 7 5 11 103-04 11-18 1-4 10 12-61 .5-39 110 3-39 1-88 5-61 4-96-4 166-2 Partly riirgcd ; no yards. 9 8 5 1 53 5 4 6 6 89-64 7-441 O-Wl 3-91 5-64 0-94 3-66 0-71 2-16 511-5 169-4 Fully rigged and ready for sea. U 15 8« 2 6 7 1 4 2 84 13-016 2-192 16-84 6-35 1-43 •2-35 3-04 8-47 417-8 149-7 Wind No. 1. 17 19 2 3 2 12 5 14 11 69 13 045 3-045 23-34 3-82 1-13 5-11 1-55 5-73 644-2 174-5 Calm, smooth water. Ship fully rigged and equipped. [broken. Speed could not be accurately ascertained. Mean ot two runs. Indicaior 17 17 3 11 4 12 6 62 10-397 1-022 9-83 3-77 1-00 4-16 18 21 3 3 6 11 9 13 3 GI 13-037 1-838 1410 4-30 1-20 4-19 200 6-99 701-6 200-9 Wind No. 1. 476 tons of coal on board. 16 23 3 11 5 14 2| 58 13-159 3-859 29-33 3-83 1-44 4-94 1-4,8 G-04 543-5 133-2 Speed by patent log. Weather calm ; water smooth. [swell 16 23 6 3 10 7 5 9 63 14-G04 3-204 21-94 4-96 1-47 2-01 3-37 10 39 439-5 143-3 Lpper edge of propeller2 feet 4 in. out of the water. Wind No.4; a little 12 10 1 8 7 8 11 1 11-2-25 11-072 1-774 16-02 380 83 4-58 1-61 6-63 500-2 143-8 Wind No. 3. 18 L |2.3 3 3 G 11 8 7 4 56 13-948 2-141 15-35 4-70 1-40 244 3-20 9-76 513-7 168-7 Upper edge of propeller 1 foot 8i inches out of the water. Wind No. 4. ,«10 9 lOJ 1 53 5 31 6 5J 114-75 11-166 1-8-39 16-47 5-6S 1-12 3-68 1-47 4-62 553-7 175-5 15 in IG 6 2 n 9 3 8 7 52-5 8-545 0-202 2-36 6-00 1-03 2-78 0-97 2-78 688-5 240-5 Vacnnra imperfect. Negative slip. [the stem. 15 a' 24 7 2 84 9 3 9 11 55 13-337 2-690 20-17 6-00 1-54 2-90 ■2-15 6-21 561-7 194-4 Wind No.4. Speed not considered an average, vessel being bo much by 11 14 3 2 r 7 1 4 4 92 12932 1-867 14-41 6-35 1-30 2-53 3-02 8-56 448-1 158^3 Wind No. 2 to No. S. 11 IG 2 6 7 1 4 5 88 13-889 2-740 19-73 6-35 1-45 2-57 3-19 9-04 434-5 153-3 Wind No. 2. IS 6i 18 3 9 6 7 11 69 12-251 3-470 •2S-32 6-19 1-16 -2-97 1-99 6-48 340-0 104-5 Wind No. 2 to No. 5. Variable. 15 7J 24 2 lOJ a 7 8 53 12-547 2-954 23-54 6-19 1-54 2-88 1-96 6-34 450-4 139-3 Wind No. 3. 14 1 17 7 2 10} 9 6 9 10 72-5 13-575 2-157 17-15 4-47 1-25 371 1-85 623 611-9 180-3 Wind No. 2. a 20 6 3 6 9 5 3 82 16-5SI 4-998 30-14 6-G3 1-86 2-78 442 11-51 331-9 lK-0 Wind No, I. 11 03 14 lOj 2 6.1 7 1 4 11 6G-5 12-692 0-833 656 G-32 1-35 •2-24 3-13 9-46 533-0 176-4 a IG ■J 6 7 1 4 4 83-25 13-1-39 2-406 18-31 6-35 1-45 2-43 3-OG 8-60 404-1 143-8 Wind No. 4 to No. 5. 151 TIMBER The term Timber is applied to wood of sufficient size to be adapted for building or engineering purposes, whether it be standing in the tbrest or after it is felled. While the timber forms part of the growing tree, it is called standing timber; when felled, it is called rough timber. After the rough log is converted — that is, sawn into the various forms for which it appears best adapted — the products are then known as sided timber, balk, thick-stuff, plank, or board, according to tlie shape and dimensions of the pieces. It is proposed in the following article to consider this subject in three or four principal lights ; as, the growth and cultivation of timber ; its use tor constructive purposes ; the supply of timber from foreign sources ; and the most eflSca- cious means for arresting its decay. Under Sihpbuildixg, and in the article Strength of Materials (Eiicy. Brit.), nnich additional information regarding timber will be found. Growth of If we examine the cross-sectior of the trunk of a tree, the tree. «e shall find it to consist of three principal parts — namely, the pith, the wood, and tiie bark — the perfect or heart- wood occupying the larger portion. As all timber trees belong to the exogenotts tribe of plants, which gain their increase by addition to the external surfaces, it therefore follows that the wood of oldest growth is found in the centre of the tree, and that the several concentric layers are younger in proportion as they recede from the centre. Around the perfect wood there is seen a concentric belt of younger growth, which has not yet attained to the maturity of the heart-wood. This belt is called the alburnum or sap-wood ; around it is another concentric belt, called the liber or inner bark, surrounded again by the outer bark. The centre of the heart-wood is occupied by the pith ; and there is a communication between the pith and the bark that is maintained by what are called the medullary rays, which, as their name expresses, radiate from the pith, in the centre of the perfect wood, to the external coating of the tree, the bark. From their hardness and compactness the medullary rays may serve, in some measure, to resist the pressure of the accumulating annual rings, and to keep open the tubes for the passage of the sap in the in- terior of the tree. When cut in a sloping direction, they produce the beautifullv-varied appearance called Jigwe in ornamental woods. The pith, which seems to perform an important part in the growing economy of the tree while it is still young, appears afterwards to lose its utility ; for as the central portions of the tree become indurated and formed into heart-wood, the pith is then nearly or alto- gether obliterated. Early The first English writer on timber was the celebrated authorities Evelyn, who published his Sijlva, or Discourse of Forest on timber. Xree's, in 1664. This book still continues one of the standard works on the subject in our language. In 1774 a new edition of it, with most extensive notes, and also engravings of the trees mentioned in the text, was pub- lished by the celebrated Dr Alexander Hunter of York. The last edition with these notes was published in 1825. In France the two celebrated philosophers, Buffon and Du Hamcl, have each devoted a great portion of their useful lives to the investigation of the physiology of timber, and their writings on the subject have long been the text-books of arborists. In modern times, the phenomena of the growth of plants have occupied the attention of many men, some of whom have eminently distinguished themselves in tills particular branch of natural history. The experiments on the physiology of trees so success- fully prosecuted by Mr Knight, president of the Horticul- tural Society, deserve especial notice. He removed a ring of bark, about ha f an inch in breadth, from a number of Timber, trees, and then compared the growth of these trees with ^^^^/-^^ that of others not so treated. This was done early in the Mr spring, and in every case he found the result to be the Knight's same ; namely, that those parts of the stem and branches experi- which were above the incision, and had a communication the physirt* with the leaves through the bark, increased rapidly in size, louy „f while those beloiv the incision scarcely grew at all, until a trees. new communication was obtained with the leaves through the bark ; the increase of the timber thus evidently depend- ing upon the growth of the leaves. These experiments were so far conclusive as to establish Mode of that the current of sap which ran upwards from the roots, increase of was not impeded in its passage by the annular incisions and ^ """ the removal of the belt of bark ; but that it was probably the downward current which was interrupted, and also that it was this downward current by which the annual increase of the tree was effected. By a series of experiments with coloured infusions, Mr Knight traced the upward current through the pores of the wood beyond the annular incisions in the bark, and found that it had neither coloured the bark nor the sap between it and the wood. He traced the coloured infusion along the leaf-stalk into the leaf, througt one series of vessels ; and he observed another series of vessels which were conveying a colourless fluid in an oppo- site direction, that is, out of the leaf. He traced this second series of tubes downwards, and found that they entered the inner bark, and, without having any communication with the tubes of the wood, descended through the inner bark from the very extremities of the leaves, apparently to the points of the roots. Mr Knight considers that there are two series of these descending tubes, one of which forms the new an- nual layer of alburnum, and the other the new annual layer of internal bark. It thus appears that the sap is conveyed upwards, through the pores of some part of the wood, into the leaves, and that when there, probably by its exposure to light and air, and by the evaporation which takes place, it undergoes some peculiar process of elaboration which fits it for contributing to the sustenance and growth of the tree. It also appears that the cause of the growth is the deposi- tion which takes place in the downward passage of this per- fected sap. The sap, after this curious preparation in the leaves, is called cambium. The same persevering physiologist then pursued his in- vestigations a step farther. He took trees, and not only removed a ring of bark, but also a ring of the younger wood, to such a depth as to cut through and remove the whole of the alburnum. These trees did not exhibit the slightest symptom of vegetation in the ensuing spring ; which fact evidently proved that the ascent of the sap had been pre- vented by the removal of the alburnum ; tor the previously- mentioned experiment had shown that the removal of the bark was not attended with such an effect. It is the generally-received opinion, that the ascent of Hardening the sap through the albmnum is the reason why this gra- o^ '^e sap- dually becomes perfect wood, in consequence of the depo-""** " sition of matter which then takes place and fills up its pores ; so that the rationale of the process seems to be, that the sap of each year deposits a certain amount of nourishment in its upward passage, which goes to strengthen and solidify the sap-wood (or alburnum) of previous years ; that then, after being elaborated in the leaves, this same sap becomes cambium, and in its decent adds bulk both to the alburnum and the bark. It must, however, be ob- served, that there is not in timber any appearance of a gradual change from alburnum to perfect wood. On the 152 T I M B E R. Timber, contrary, in all case? the division is most decided ; one con- trees, that they will flourish upon, and indeed prefer situa- Timber, ^^■^y""^ centric layer bcin" perfect wood, and the next in succession tions which are altogether unfit for the production of corn **^V^^ Nature of being sap-wood. Mr Knii;ht gives it as his opinion, that and other crops. This is chiefly owin^; to the small pro- the circula- towards the conclusion of simuiiur, the true saj) — that is, the portion of mineral nutriment which trees require in com- tion of cambium simply accumulates in the alburnum, and thus parison with grain. For several remarks of much practical the asp. _^^|j^ ^^ jl^g specific gravity of winter-felled timber. lie value occurring in this portion of our article, (he author is thinks that the true sap descends through the alburnum as indebted to the professional knowledge and sagacity of Mr well as through the bark — that is, that " the superabundance John Hlenkarn, who has recently published an excellent of true sap is there deposited, and enriches the upward treatise on British timber trees. A certain portion of the current of aqueous sap, or the sap of the ensuing spring." article Timbkr, wTitten for the preceding edition of the In confirmation of this, he tested the ascending current of Enci/clo/xedia Britannica, has also been incorporated in spring sap, extracted from the trunks of trees at various the present article. heights, and found that the specific gravity increased with The mineral constituents of timber vary with the nature Mineral the° height, and that the taste also very sensibly altered, of the soil on which it is grown, but these consist chiefly ofconstitu- He argues from the foregoing facts, that by girdling trees the carbonates of potash, soda, lime, and magnesia, with *[J^°jj°J in the spring, and suffering them to grow until the en- generally a small portion of the sulphates, chlorides, and ' * " suing winter'^ the wood above the girdling would be in- phosphates of the same substances. The following table creased in specific gravity. In one experiment, in which exhibits the weight of mineral ash remaining after the com- the belt of bark had been abstracted for several years, he bustion of 1000 lb. weight of different woods, all equally found that the specific gravity of the wood above was dry when weighed : — 0-590, while below it was only 0-491 ; and also that the ^^^^ ,^_ ^y^,^ ^^,^^^ ,9 j^ ^^ ^^ alburnum had acquired a greater degree of hardness, and ^^ pojilar „ 20 1b. „ consequently of durability. This is important, as Du j, willow „ 4J lb. „ Hamel has very conclusively established by experiment „ beech 2to61b. „ that the strength of timber of the same species varies very .. birch „ 3J lb. „ ■ .. ° . 1 . „ oak „ 2 lb. „ nearly as Its weight. " -^^ " litoSlb. Function The leaves of a tree perform the important office of in- " ^,j " ■'.''"'""."[[".I'j.'.'l]; g to 61b.',', assigned haling and fixing in a solid form the gaseous food con- *" '*** tained in the atmosphere. In the day-time they absorb Although in most parts of England there is soil favour- Influence leaves of a ^.^^^(5^^;^ ^^-^^ j-^„^ jj,g ^ir, which then becomes deconi- able to the growth of timber, it may well be supposed thatof »oil on posed, and the oxygen is given off; this process being re- all soils are not equally favourable to all kinds of ''™''«'''' p'j'tfjjb^ versed at night, although in a slower degree. About one- nor will they produce timber of equally good quality, third of the entire carbon of which the tree is composed is Thus, while England is, par excellence, the country of oak believed to be thus extracted from the atmosphere. timber, the Sussex oak has always been celebrated as supe- Formation As the sap descends, it forms a layer or ring of sap- rior to all others. In France, the oak of Provence enjoys of the an- ^ood and inner bark, by which the circumference of the a siniilar reputation. Still, an oak-tree grown in a soil but nual rings. ^^^^ j^ <;radually increased year by year. By counting the ill adapted lor it, as, for instance, a marshy soil, will retain number of these so-called " annual" rings, which are very its superiority of species over the inferior timbers, such as distinct in some species, it is generally supposed that the willow and pojjlar, to which svich a soil is less unfiivourable, a^e of a tree can be ascertained. It is now believed, how- although in quality it will fall far short of the standard of ever, that this is not always a true indication of the age of perfection for oak timber. In fact, oak grown on such soils a tree, a " ring," more or less distinct, being formed in the will, in some measure, partake of the qualities of the timber wood by any sudden augmentation of growth, consequent to which they are better adapted, and be of more open tex- upon a track of warm weather succeeding a colder season, tore, of softer fibre, and of less durability, than average oak or a moist period succeeding to extreme drought in sum- timber. Oaks of slow growth, those for instance from the mer. It may thus happen that several rings are formed in mountains of Scotland, and from Cumberland and York- the wood during one year's growth only. Although the shire, are proverbially liard and durable. The oak from Diseases sap of a tree is most active in the spring, and during the marshy soils is often of a dull-red colour, or has " foxey"a"J »"'" season of vegetation, it has been ascertained that it is never stains in it, as this incipient decay is called. These stains ^^}^^ altogether stationary, except during severe frosts. are generally around the heart of the tree. Timber grown growing Wbcn the When the induration of the sap-wood has reached its in loose soils is often what is termed " quaggy ;" that is, the timber is treeshould extreme limits, the proper time has arrived for the tree to centre of the tree is full of shakes and clefts. Sometimes liable. J® *"' be cut down. This may arise, however, from other causes a shake will extend around a great portion of the trunk, down. ^^^^ ^^^^^ ^Ij ^^^^ Ungenial climates and situations check between two of the annual concentric layers, so as to divide the free circulation of the sap, and the new layers of wood them from each other. This is called a cup-shake, and and inner bark are thus imperfectly formed or greatly at- the timber is said to be " cuppy." It is not attributable to tenuated in substance, and the tree shows all the symptoms the soil, but is supposed to originate in the effect of frosts of premature old age at a period of its growth, when, had on the aqueous sap in its ascent. When the alburnum of it been reared under more favourable circumstances, it a tree has been wounded, or a branch improperly lopped Situations would have been still young and vigorous. External in- or damaged, the subsequent growth of the tree will coyer for plant- jury, by which water is admitted into the substance of the it, and it is then called a rind-gall, which, shoidd the in- ing timber, j^gg^ ^^.jjj equally induce premature decay in a tree other- jured part have had time to become decayed, or partially wise sound and flourishing. Hedge-row timber is particu- so, or even sodden with the rains, will frequently cause an larly exposed to accidents of this kind, and the practice of extensive rottenness in the plant. This is remarkably the planting valuable trees in such situations should either be case with elm timber. " Doatiness," probably dottiness, sparingly adopted, or avoided altogether, more especially which is a spotted or speckled appearance, like small stains as the growing crops are much injured by them. At the in the wood, is most commonly a disease of beech timber ; same time, waste corners and outlying pieces of ground, it is, however, occasionally seen in all, and frequently in perfectly suitable for trees, and indeed only profitable when the American oak. These diseases are in general inciden- planted, are too often left vacant in their native barrenness; tal to the soil, for a wise Providence has so constituted the majority of In treating of soils in connection with the qualities of the T I M B E K. 153 Timber. ffects of ftrshy •il. le most vourable il for Dber. rowth of e oak. timber which urows upon them, it may be necessary to re- ' member that the object is not to compare various sorts of timber, but to compare the differences in the same species in connection witli the soils wiiich produced them. It may also be observed, that as oak is l)y far the most vahiable timber of Eiighsh growth, the general inquiries we may enter into in the course of this article princi|)ally apply to it, unless other species of timber are particularized. 1 We have already casually adverted to marshy soils, and to the state of tlie timber grown on them. The grain of such timber is open, its colour of a dee|) yellow, sometimes with a tinge of red, especially towards the heart ; the texture is soft, and the fibre coarse. The quantity of alburnum, and also of bark, is large in comparison vv'th the quantity of perfect wood, and the outer surface of the bark is very coarse and rough. The wood splits easily, and when split it has not tlie same bright and varnished appearance pos- sessed by the best timber. The chips from the axe do not cling well together, but fall into separate fragments ; and a shaving or a small splinter may be easily crumbled between the finger and thumb. When such timber is weighed, although it is far more saturated with moisture, it is of less specific gravity ; and when weighed after seasoning, the weight lost will be comparatively greater. Such timber, it is evident, will be more subject to decay, and to become worm-eaten, the softness of its texture inviting the attacks of insects. These peculiar characteristics attach more or less to timber grown in all soils which are of a moist nature, whether they are marshy, or wet from long continued pe- riodical inundations. They also apply to timber grown in deep sandy soil, in which almost the only nutriment for the mots is tlie water which percolates downward, and the bottom damps which rise upward through it. In all these soils the timber is of rapid growth, and the trees attain early to a large size. A similar result attends the timber grown in sandy soils on a clay bottom, for the water which falls, not being able to penetrate the clay, cannot escape, and the roots of the trees are therefore virtually in the same circumstances as if they were growing in marshy land. As a general axiom, timber trees have an antipathy to stagnant waters ; and, therefore, these observations on marshy soils, and on sandy soils with clayey bottoms, refer themselves to this fact. The soil generally the best adapted for the growth of timber appears to be a rich loam. This may have a considerable admixture of s.ind, without any apparent detriment to the timber. In such soils roots can penetrate and spread without difficulty, while the loam is capable of retaining sufficient moisture to dis- solve and hold in solution the various substances that are found combined with it, so as to iit them to be absorbed as food by the roots of the plants. If the soil be too sandy, it neither retains the moisture sufficiently long in it, nor does it contain adequate nutriment. If, instead of a loam, some of the very stiff clays be mixed with the sand, they do not counteract this quality ; for although such clay is callable of combining with a great quantity of water, it will not easily absorb and mix with it ; and the tender roots have great difficulty in penetrating the masses of clay. For these reasons, soils composed wholly of stiff clay are not favourable to the growth of good timber, but the lighter clayey earth produces very fine oaks. As has been before stated, sand or gravel, with a large mixture of rich loamy earth, is precisely that sort of dry generous soil which affords ample nourishment to the roots of trees, and allows of their spreading themselves freely in search of it. Of all timber oak accommodates itself most easily to soil ; growing in almost every thing but sterile sand, if there be sufficient depth of stratum. Wherever oak will grow, even in those soils the least genial to its growth, it is a valuable timber. This fact cannot be too often pressed upon the attention of landholders. It is well adapted for Timber, planting in hedge-rows between arable fields, because it is ^-^^^-m^ tbund to be less destructive to the undergrowth than almost any other timber ; and as its roots seek their nourishment deep in the soil, they not only do not impoverish the ground for the growing crop, but are themselves protected from any injury which they might otherwise sustain from the tillage. Oaks so planted require, however, to be pro- tected during several years, as their early growth is slow. The timber grown in such exposed situations is seldom large ; the trees are stunted and crooked ; but this rather increases their value for ship-building purposes, as they convert as compass or knee timber. The timber of hedge- row oak is very close grained ; that of park-grown oak is more open, and the trees being better protected, spread more freely, and grow to a very large size, with strong lateral branches ; while forest-oak will frequently grow to a great height without pushing out any lateral shoots. Forest-oak is invariably inferior in quality to that which grows singly; and in forests the trees that grow on the skirts are always the best timber. The oak flourishes in variable climates, which is probably the cause of the supe- riority of the English oak. The roots of the oak strike very deep into the soil, at the same time those of no other tree, perhaps, take so wide a range. The top root of an oak has been known to descend to a depth equal to the height of the tree. A curious fact has been established in connection with Connectino the supply of food ibr trees, which proves that there is not I'etwee" only a proportion between the spread of the roots and that ""* '°"*'^ of the branches of a tree, but that the branches on any f"*^ '^® one side of the trunk of the tree are dependent for their support on the roots which protrude from the trunk on that same side. Both Buffon and Du Hamel found ex- perimentally, that when the limbs and branches of any part of a tree showed symptoms of decay, the correspond- ing roots were invariably in a diseased state. They also found, that on that side of a tree from which the roots had pushed most vigorously, the annual concentric layers of wood were thicker, and that, consequently, the form of a section of the tree would be excentric towards that side. The determination with which the roots of trees seek The roots out for themselves the best localities is surprising. If will seek trees of different species be growing on the edge of a""' for marshy place, that tree which requires most moisture will 'hemselves push its roots towards the marsh, while that which requires ^ '*' a dry soil will push its roots into the dry firm ground. Du Hamel relates an instance in which he dug two trenches, crossing each other at right angles ; he then re- turned the soil into these trenches, and planted a tree at the point of their intersection. Some years after, upon examining the roots, it was found that they had invariably pushed into the four lines of trenches, leaving the inter- mediate undisturbed earth wholly untouched. An equally imjiortant consideration with the quality of Depth of the soil is its quantity — that is, its depth below the surface, soil re- in speaking of soils in connection with the growth of tim- quired, ber trees, it must of course be understood that it is not merely the surface-soil which is meant, but that soil in which the roots of the trees would push and spread, the soil Ibr several feel iu depth. It often hap[)ens, indeed, that the surface-soil may be well adapted for tillage and for vegetation in general, and yet the sub-soil, that which is essential to the growth of timber trees, may be totally incapable of supplying them with nourishment. Trees which grow singly, as in hedge-rows or in parks, do not require an equal depth of soil with those that grow in forests, because they have facilities for spreading their roots in search of food. But for forest-trees, whether oak, chestnut, or birch, a depth of at least 4 feet of appro- priate soil is absolutely necessary tor tlie production of fine V Timber. The depth of ^oil de- termines the a^e of the tree. How to jud^e of the good- ness of tlie soil. 154 T I M timber trees. Elm and asli do not require so great a deptli. HiiHbn has given a scale for tlie ages at which it is de- sirable to fell timber, dependent upon the depth of soil in which it grows. He says that a depth of from 2 to 3 feet of soil will not support a tree in a thriving condition for a longer (leriod than fifty years. From 3 to 4 feet of soil will enable the tree to go on improving till about seventy vears of age ; and in soil (roni 4 to 5 feet deep it will fldurish for a century. These periods are for strong and favourable soils. In lighter soils, at least ten years must be taken from each period, and the timber will then also be inferior in quality. As a general rule, the more gene- rous and favourable to the growth of tlie timber the soil may be, the longer it is advantageous to wait before felling it. Trees should never be allowed to become stag-headed — that is, to have their upper branches bare of leaves. It is in the top branches that the first synijitoms of the decline of the tree are to be perceived. The leaves there acquire a tiided, weakly appearance, gradually diminish in number, and finally the branches become barren of foliage, and decay. The least appearance of want of vigour in the top of a tree should be the signal for its being cut down ; and even then it is a sure token that the timber is past its prime. The nature of the soil in a track of co\mtry may be ascertained either by opening it, or by observing the plants which grow upon its surfiice. Thus, if plants which flourish only on marshy land are found at all times of the year on any particular track, we may assume that track to be marshy land, whatever its temporary appearance may be. The nature of the subsoil may often be ascertained by ex- amining the ditches. The goodness of earth may be tested, approximately, in the following way. If a hole be dugout, and the whole of the excavated earth can be afterwards returned into the hole, the soil is poor ; but if, on the con- trary, there is an excess, its q\tantity is a criterion by which to judge of the richness of the soil. Although, as we have seen, too much moisture is unfa- vourable to the growth of good timber, a deficiency of it mvist equally be guarded against, the timber then suf- fering, not in quality indeed, but in size. Wood grown under such circumstance — as, for instance, the Scotch mountain-oak — is extremely heavy, liard, and dense, and when not "overgrown," or allowed to attain too great an age before being felled, is very durable, and little liable to shrink or warp. Mountain-oak is therefore well adapted for furniture and panelling, &c. As a general rule, the quicker the growth of the tree, the more it w ill shrink when converted into timber. These general remarks afford an idea of the difference in the appearance and qualities of timber grown on good Properties soil from that produced on bad soil. It may, however, be de- of the best sirable to enter a little more into detail. An oak-tree, grown oak timber, on the soil adapted •.o the development of its best proper- ties, not only has its concentric rings thin and close together, but they are also of very uniform thickness, and the texture , of the grain is fine. When the wood is split, it has a glossy, varnished appearance, and is of a very pale yellow or straw colour. There is sometimes as much as one-fourth differ- ence in weight between samples of oak timber ; and the heaviest loses a much less proportion of its weight in dry- ing, and will also, if immersed in water, absorb less than the lightest. The amount of sap-wood in the best timber is comparatively small, and the bark is thin and of a smooth, even texture. In breaking such wood, it produces a sharp, decided noise. Having but little moisture in its composi- tion, and being less hygrometric in its nature than wood of more open texture, it is little s\ibject to decay ; and its grain being hard, it is not easily [lierced by insects. The great size to which oak-trees will attain, when fa- Deficiency of moisture niu^t be guarded ugaLost, B E R. vourably situated as to soil and locality, is tnily astonishing. Timber The celebrated Chapel Oak of Allonville, in the Pays de v^.^,,— Caux in France (which is still standing, we believe), mea- Thelurgi sures at its base 35 feet in circumference, and at 6 feet oakB on above the level of the ground it is 26 feet in girth. It is record, hollow, the interior having been fitted up as a chapel in 1696, and being still employed in that capacity. The com- puted age of this tree is between eight and nine centuries. A very large oak was felled in Monmouthshire in 1791 ; when converted, it produced the following enormous quan- tity of timber : — The main stem, 91 feet long, when tided 330 cub. ft. A branch, 29 feet long, sided 17 inches S8 „ 24 „ „ 19 60 „ 19 „ „ 17 „ 38 „ The two main slabs produced SSJ feet of 3-ioch plank, malting, with other conversions 216 „ 13 sided knees, taken together 217 „ Other minor but useful conversions 276 „ Total 1195 The weight of useful timber in this tree was nearly 30 tons. The bark weighed 3 tons, 17 cwt., 3 qrs. But the largest oak on record, known as Damory's Oak, grew in Dorset- shire, and was used as an ale-house. It was 68 feet in cir- cumference, and the room formed in it was 16 feet in length. This tree was blown down in 1703. The Cow- thor[)e Oak, near Wetterby, in Yorkshire, measured (in 1708) 40J feet in circumference at 4 feet from the ground, the height of the tree being 85 feet. The Bentley Oak measured (in 1759) 34 feet in circumference at 7 feet from the ground. The Boddington Oak, in the Vale of Glou- cester, measures, at 3 feet from the ground, 42 feet, and at 6 feet from the ground, 36 feet in circumference. There are not less than 140 species of oak known, and DiflVren although there are many sorts cultivated and growing in "I'^'^'es c England, botanists and arborists agree that there are prin- °* '* cipally two varieties ; these are, the Durmast oak, and another, which is commonly called the old English oak, although both are supposed to be indigenous. In the Dur- mast oak, the QueTcus sessilijiora, the acorns grow in clus- ters close to the twig, and the leaves are set on short leaf- stalks, while in the old English oak the Quercus liohur, or Quercus pedunculala, the acorns grow generally singly, at most two together, on stalks of from 1 to 2 inches in length, and the leaves are close to the twig, without the interven- tion of any length of leaf-stalk. These are the principal distinguishing marks between the two varieties. Many writers attempt to draw distinctions from the colour and shape of the leaves, and the colour and appearance of the bark ; but it is doubtful whether these may be depended upon, as, from a careful examination of the evidence, it is more than probable that the colour and appearance vary much with the soil and locality. There is no doubt, however, as to the comparative inferiority of the timber of the Dur- mast oak. Almost all the English writers on timber have asserted it, and both Btifl'on and Du Hamel corroborate their assertions, and give a most decided preference to the oak bearing large acorns on separate stalks over the oak bearing acorns in clusters ; which characteristics are just those which distinguish the English from the Durmast oak. In favourable soils, the old English oak has seldom more Proporti than 12 to 15 concentric rings of sap-wood; but in theof^*!'-* Durmast oak there are frequently from 20 to 25, or even ^ ^«^'^ nrt r,., . ^ , ■ r • ■ <• 1 T-k X wood in 30. 1 his seems to prove the inferiority of the Durmast ^iffefgn, oak ; for it is an established fact, that the best hardwood trees. timber is that in which the proportion of heart-wood to sap is the largest. The Spanish chestnut has usually but 5 or 6 rings of sap-wood , English elm, about 10; white larch, 15; Scotch fir, 30 ; yellow Canada pine, 42 ; Memel fir, 44 and red Canada jiine as many as 80 to 100. TIMBER. 155 iber. As a general average of the size of oak timber, 56 cubic .,-"*^ feet for eachi end or log of rough timber, and 30 cubit feet of oak for each end of sided timber, may be assumed as tolerably '-'• correct. In order to convert rough timber into sided timber, about two-thirds the diameter of the rough log, in the middle of its length, is assumed as the most advantageous siding ; and, on an average, it is estimated that not above one-third of each log or end of rough timber is used in tiie principal conversion from it, and this principal conversion is estimated to be about three-fourths of the total conversions. With reference to the size that an oak will attain in a given number of years, much must depend upon the soil and the situation. The plan adopted by the late Duke of Portland of planting tablets of iron or stone with the trees, with the date inscribed upon them, will probably throw much light on this subject. Mr Blenkarn adduces the following case : — Three thriving oaks, growing on a hard, gravelly, and poor soil, were felled in Nottinghamshire, which, on an average, girded 15 feet at 3 feet from the ground, and each tree contained about 430 cubic feet of timber. These trees were known to have been planted in 1692 or 1693, and they were above 149 years old (say 150 years) when they were felled. As they were perfectly sound, and were yearly increasing in size, it is probable that had they been allowed to remain another century, their bulk and cubic contents would have increased at least one-half, s of The value of these trees when cut down was more than i"- L.120, a sum equal to 303. per acre (without taking in- terest into account) for the land they occupied during the 150 years of the growth, — a reply to those who assert that timber will not pay the rent of the ground it occupies, or injures by its shade. For the first 50 years the land would not be much injured by those trees ; and as they grew older the acorns, as food for swine, would compensate for the loss of herbage under the trees. But the land on which these trees grew was not worth 15s. an acre when they were felled, and of course was much less valuable when the trees were planted. " It frequently happens," says Mr Blenkarn, " that pro- prietors of large estates have not the slightest idea of the value of the timber growing upon them, regarding the trees on the property as merely an ornamental accessory, little supposing that they may be worth more than half of the value of the estate estimated on the basis of the rental. It may be further affirmed that, on most large estates, a great portion of the timber could be cut down to the benefit of the trees which are left standing. An acre of oak woodland, containing 100 loads of timber (vvhich is a low estimate), is worth L.650 at a moderate computation ; and 50 acres of such property would therefore yield L.32,500 worth of timber." This calculation, offered by a professional sur- veyor, certainly holds out a strong incentive to planting, without taking into account the beauty imparted to the landscape, the shelter obtained for cattle, the cover for game, and other advantages. It is a well-known fact that estates abounding with timber will command a high price in the market, and are eagerly sought after, in preference to others possessing a better soil, but destitute of trees, tations In making large plantations of hard wood, it is usual in "■d this country to intermix an equal number of birches with '• the young oaks, lor tlie sake of the shelter they afford, a few beeches, larches, sweet chestnuts, &c., being sprinkled amongst them. It is believed that oaks raised from acorns, which have been sown where the tree is to grow, will ulti- mately become the largest and finest trees; since, from the great length of its top-root (or tap-root), it is almost im- possible to transplant an oak without injury to it. They shouUI at any rate be moved while small. Fir-trees make but indifferent nurses for young oaks, as they neither grow so fast on forest land as the birch, nor will the oak thrive under them. A screen offir-trees is often ofgreat benefit, how- ever, when the young plantation is much exposed. Furze Timber, and tall grass also, while useful as a protection for game, ^^"^/^-^ will not injure the young trees planted amongst them, as these, though at first overgrown, and apparently choked by the furze, will soon rear their heads above the cover, thank- ful for the shelter thus afforded them while young. It has been found that the best season for planting on Time of light ground is as soon as possible after the beginning of planting. October, and for heavy, moist land, in February and March. When the quality of the ground varies very much, which is almost sure to be the case in extensive plantations, the species of the trees should be varied accordingly, and the ap|)earance of the wood will be much more beautiful than if unilbrmly planted with trees of one kind. As the oak, however, fortunately thrives on almost any soil, no portion of the wood should be destitute of them. Where artificial drainage becomes necessary, open drains Artificial are preferable to close ones, as being less liable to get 'drainage, choked up with the fibres of the roots. Strong clay soil (of which a great portion of wood-land consists), when so overshadowed by trees that the natural evaporation from the surface is much impeded, becomes almost impervious to water, and the stunted growth of trees, particularly the oak and the ash, and the dead branches in the tops of the oaks, called slag-heads, are mostly attributable to this cause. Good drainage has also the effect of increasing the tem- perature of the soil. In large woods which are planted on nearly level ground. Open it is recommended to leave occasional open spaces or glades, glades in the thickest parts most remote from the boundaries, should be unencumbered with brush-wood. These tend greatly to encourage the free circulation of air through the wood, a point of considerable importance in the economy of vege- tation. These glades may be rendered very beautiful by planting in them a few choice specimens of ornamental trees, which will generally thrive well in such a situation in consequence of the protection afforded by the surrounding wood. In thinning woods, care should be taken to remove Thinning such trees as show any signs of decay, or when one tree woods, interferes with the growth of another, the cleanest, straight- est, and those with well-formed compact heads, being alone reserved for timber. The oak and chestnut, as the most enduring trees, should be chiefly left to posterity ; the beech, ash, and others, being cut down as they arrive at maturity. In consequence of the great value of the bark of oak, it Best season is the practice to fell the timber in the spring of the year, for felling because then the bark is easily detached from the tree, ''™^«r. while the bark of winter-felled timber is lost. There can be little doubt, however, that the durability of the wood is much deteriorated by this practice. It was a received opinion among the ancients that timber should be felled in the fall of the year ; and not only do modern experiments confirm this ojiinion, but modern discoveries as to the flow and return of the sap, and its nature at various seasons, tend to show the reason for its correctness. The practice w hich almost all the eminent arborists have recommended, and supported by their experiments, is to bark trees standing in the spring, and then allow them to remain in this state at least one twelvemonth. This was not an uncommon practice in some of the midland counties of England, and was first strongly recommended in the reign of James the Second by Dr Plott, an arborist of great celebrity at that time. Buffon presented a memoir in 173S to the Royal Academy of Sciences in Paris, " On increasing the Solidity, Strength, and Durability of Timber ;" for which purpose it was recommended to strip the tree of its bark during the season of the rising of the sap, and then to leave it to dry completely before being felled. Du Hamel gives most minute accounts of experiments made by himself, all tend- ing to the same conclusion ; and Dr Hunter, in his notes on TIMBER. Kim tim- ber. ClieftTiat timber. Evelyn's Syha, says, " that by stripping off the bark, and allowifi"; the tree to stand and die btdbre it is cut, tlie sappy part becomes as hard and (irni as the heart." Here is a collection of opinions, of such weiglit, that the general fact which they assert must be considered to be established be- yond contradiction. Huffon also says that he caused pines, firs, and other species of evergreens, to be barked standing ; and :is he found them live longer after the operation than oaks which had been also stripped, he considered their wood acquired proportionately greater hardness, strength, and durability. He recommended the practice for fir-trees destined to be converted into ships' masts. We shall now notice a (cw of the peculiarities of other trees most esteemed in this country for their timber. The Elm, of which, like oak, there are tivo principal varieties, will not bear a damp soil with stagnant wateis, but it thrives well in moist declivities, provided the land be not too rich. The trees grown on too damp a soil either die prematurely, or their timber is of a soft spongy nature, and prone to decay. There are two British varieties of this timber, the Ulnuts Montana, or Wych elm, and the Ulmtis Campestris, or, as they are sometimes called, the Scottish and the English elms. Of these the Wych elm is decidedly the most valuable as timber, and, when used in situations where it is kept constantly moist, is extremely durable ; but no elm timber will bear the trials of change of temperature and moisture to which oak in all its varieties is comparatively insensible. The close and interivoven grain of elm, the absence of decided longitudinal fibre, and its power to resist rending from exposure to the heat of the sun, and the alternations of weather, cause its timber to be very useful for small articles, such as the blocks used in the rigging of a ship. It is valual)le in many parts of the millwright's machinery, where the wood is subjected to cross strains or great friction. It is also valuable and much used both for the timbers and for the planking of ships below the surface of the water; and the planks of clinker-built boats are very generally of elm. There is one peculiarity about elm timber, namely, that the alburnum or sap-wood is possessed of nearly equal power to resist decay with that which is matured ; that is, when both are used in situations where they are not exposed to alternations in moisture. A variety of timber has of late years been introduced into the market under the name of Canada elm, or American rock elm. It is a smooth, even textured, pale-coloured, and strongly fibrous wood, almost devoid of knots, and admir- ably adapted for boat-building, and all works which require a flexible and close-textured wood. The Canada elm appears to have many of the peculiarities of toughness and flexibility which distinguish the ash. The elm-tree, which is much to be admired for the stateliness of its growth, sometimes arrives at an enormous bulk. King Charles' elm at Hampton Court measures 38 feet in circumference, at the height of 8 feet from the ground. The Wych elm at Field, StafTordshire, is 25 feet in girth. The Cdestnut, Fagus caslanea (called Spanish, or sweet chestnut), is a very valuable timber tree, its wood being equally durable with that of oak. It was much used for building purposes in former times, both in this country and on the Continent, but its cultivation has been too much neglected of late in England. Chestnut timber may be seen in a state of perfect preservation in many parts of an- cient ecclesiastical buildings, Pugin having specially dis- tinguished it by name in the engravings of some of his works. This tree, as well as tlie beech, appears to suffer less than any other of the timber trees from being planted in a moist sandy soil ; but as the roots of the chestnut extend far downwards, they require a proportionate depth of soil. It grows with frequent twists and contortions of the stem, which, while it adds to its picturesqueness for ornamental purposes, certainly detracts from its value as a timber tree. Timber Some of the largest chestnuts in Europe are lourid on the ^-^.^^r™. flanks of Mount Etna. The largest knovvn in this country is at Tortworth in Gloucestershire. As their shade is de- trimental to other trees, they should either be planted in clumps by themselves, or be given full room to spread. When the timber of the chestnut has been some time in use for roofs or joinery, it is difficult to distinguish it from oak. The I?EF,cn, Fagus, is a timber that easily adapts its(lfH<"<'ch t'" to, and flourishes in, almost any soil. Even among rocks ''*''• its roots will, like those of firs and larches, insinuate them- selves into the smallest fissures, and find means to extract sufficient nourishment to produce a useful timber. Ueech timber, when used shortly after being felled, and for works where it will always remain in a damp state, is a long-en- during wood. It is largely ajiplied in the mercantile navy for the lower planks of the bottoms of ships. The best variety has its wood of a yellow tinge. It is much used for making cheap furniture ; also by railway contractors and others for temporary purposes, and by coopers. The sym- metrical shape of the beech, and its bright glossy leaves, render this tree highly ornamental in the park or shrub- • bcry, and the varying hues which its leaves assume as the I autumn approaches are a great additional recommendation. ' As no tree suffers more li-om injudicious pruning of the roots or branches than the beech, it is better raised from seed in the situation it is intended permanently to occupy. The Ash, Fraxinus Excelsior, will also accommodate •*"'' ''■"" itself to all soils. It will grow in marshy groiuids, and in"*''" arid land, in deep or in shallow soil. The value ol its wood lor general ])urposes is second only to the oak in the list of liritisli timber trees. The ash timber from very poor soils is brittle, wanting the elasticity which is the valuable pecu- liarity of this wood. It is a very useful timber for carts and implements of husbandry, fi)r machinery, for tools of almost all trades, and it sup|)lies oars to our shipping. When planted in a genial situation, it attains to a very great size, specimens being sometimes found which measure 30 feet in circumference, and 100 feet in height. We have hitherto confined our remarks to the hard- wood J^"" '""' timber trees, without noticing the nimierous Fius whicli are so valuable to us. Their timber is admirably adapted by its manner of growth, its lightness, and strength, to supply our navies with masts and spars; while from its comparatively small cost, and the ease with which it is worked, it is used very largely for all purposes of building. Indeed, it is ques- tionable whether fir is not more generally useful to us than any other species of timber. Du Haniel, in his treatise JJu Transport et de la conservation des Hois, has drawn a distinction between firs and pines, although it is usual to designate the timber of both as fir timber. Pines, he says, have the leaves thready and slender, growing in clusters from the same leaf-stalk, while firs have straight leaves, each growing separate, but many growing on the same leaf- stalk like the teeth of a comb, 'i'rees of the pine tribe have one princifial root growing straight down like a carrot, with few fibres, while the roots of the fir are more lateral and super- ficial. The pines grow with their trunks much less taper- ing towards their tops than the firs ; they are, therelbre, from shape, more ada|)ted for masts than firs. Their wood is also more resinous, and the resin is of a more glutinous nature, and therefore less easily eva[iorated. This quality enables the timber to resist better the absorption of water or moisture. The pine is more durable than the fir, and its fracture is, even when partially decayed, much more fibrous, and takes place with more previous warning. The timber of the (line, when healthy, is close-grained, even- textured, and of a bright yellow colour. The fir, although frequently little inferior in appearance in other respects, is always of a much paler shade of colour. ber. TIMBER. 157 Timber. The most valuable of all the varieties of fir timber is v.— ^^^^ that H'liicli is called Riga Fir. It is the red-wood pine of Ki"aorred t'le north of Europe, the Pinus Silvcstris, which, altliOMfjh pine. spread over a very large portion of the globe, appears to flourish in its greatest perfection in the forests of Lithu- ania and Poland, where the cold is severe and the soil generous. Riga fir is not only extremely flexible and elas- tic, but is by far the most durable of all the pine timbers; and as long as it could be procured of sufficient size, it was generally used in the royal navy, not only for topmasts, but also to build the lower or standard masts. At present, from the difficulty of procuring large sticks, the use of it is con- fined to topsail-yards and the smaller description of spars. The American continent also produces this red pine tim- ber of good quality, although much inferior to that of the north of Europe. It is imported from Canada and from Virginia. The Canadian red pine is of small size, seldom exceeding 14 hands. The Virginian pine is large, sticks of 24 and 25 inches in diameter not being uncommon. It is a resinous and flexible wood; but the sticks are more subject than the Canadian red pine to the defect of large knots, which, from not being firmly united to the surrounding timber (technically, "well-collared"), injure its value. The Scotch fir. red pine thrives extremely well in Scotland, wiiere it is called Scotch fir, but is not equal in quality to that imported from the north of Europe. The French dockyards are supplied with mast-timber from the red pine of the Pyrenees and of the island of Corsica, but neither of these is of first-rate quality. Indeed, a climate of low temperature appears to be essential to the growth of superior fir timber. The firs on the northern sides of hills and mountains, in all tem- perate climates, thrive better than those growing on the southern slope; and even the timber of the northern side of an exposed fir-tree is much superior to that of its south- ern side. Yellow Yellow Pine, the Pinus Slrobits, which is imported pine. from Canada, is the principal timber now available for large masts and yards, and is very generally used both in the royal and mercantile navies, as well as for building purposes. It has neither the flexibility nor the elasticity of the red pine, nor is it so durable, but it is much lighter. Its great recommendations are its large size and its com- paratively small cost. Sticks of this timber run from 16 to 27 or 28 inches in diameter ; and for bow-sprits they are sometimes received in the royal yards as large as 29 and 30 inches in diameter ; but sticks of these large dimensions are becoming very scarce. This timber grows also in Great Britain, where it was first introduced by an Earl of Weymouth, whence it is called the Weymouth pine ; but it does not appear to thrive well in this climate. Spruce The Sprvck ¥ JR. PiJius Abies, grows m Scotland, Nor- fir. way, and other northern countries. It is very generally used in the mercantile navy for yards and top-masts, and also in the royal navy for the smaller description of spars and boats' masts. They are tough, close-grained, and elastic, but are very full of large knots ; and care is therefore required in selecting them. The timber also is soft and for from durable, it having very little appearance of resin. The Norwegian spruce grows frequently to a large size. Cedar. Cedar, Pinus Cedrus, would be among the luost valuable of all timber trees, were it sufficiently common to be avail- able lor building purposes. It is almost indestructible from time, and no insects will ever attack it. It thrives well in this climate, but hitherto has only been planted either as an object of curiosity or of ornament. It requires a more generous soil than any other of the tribe of pines, and is considered to be a timber of very slow growth. Pitch- pine is also a very valuable timber for building purposes, but it is too heavy for spars. Fir sticks, the Riga hand-masts especially, are very liable to have serious defects in them, w liich it is often impossible Timbe to discover until the stick is worked. They are techni- cally called " upsets." The grain a])pears to be partly sepa- *"— v^"— ^ rated, so that a shaving from the stick at that place would Defects in bend to a sharp angle at the upset, as if partly broken, fir timber. There always appears to be a greater or less accumulation of the turpentine about the injury, as if it had originally exuded at the wound, and become congealed around it. These defects are most frequently found in the smaller sticks, those especially that are more resinous and knotty than others ; and they sometimes are so numerous as to extend, at very short distances apart, for a great portion of the length of the stick. Mr Cradock, who long super- intended the mast-making at Portsmouth dock-yard, con- siders them to be the effect of violent winds on the more exposed trees of a forest. He founds this opinion on the facts that they are most common in the most flexible timber ; that they are not perceived in sticks of large dia- meter; and that in the firs of little flexibility, as the yellow pine, they are seldom or never found ; although the sticks of this fir, from being cut in every variety of direction, to form the components of made-masts, are more searched than any other. The cowdee, a New Zealand timber, lately introduced both in the royal and mercantile navies, is, he says, much subject to this defect ; and he has observed it once in a poon topmast. The defect seldom or never appears in the outer layers of the timber, but only after some of these have been removed by the axe, and the older timber laid bare of the sap-wood. The sap-wood in all fir timber is tiseless, and very gene- Sap-wood rally there is a large proportion of it in comparison to the '" ^^ ''™' quantity of heart-wood. It is rather a curious fact, that " there appears to be a difference between the pines and the generality of the hard- wood timber in this, that a small proportion of sap-wood in fir is indicative of the in- feriority of the timber. Thus the red pine of Scotland has fewer layers of sap-wood than either the red pine of Ca- nada or of the Baltic. As a general remark, it may be stated, that the greater the quantity of sap-wood there is about a tree of any description of fir timber, the better wil". be the quality of the "spine," which is the technical name given to the mature wood. The Cowdee, which is now largely imported into this Cowdee. country, is a close and even-grained timber, almost entirely free from knots. It grows to so large a size as to be available for the topmasts and other principal spars of the largest classes of vessels ; but from its want of elasticity, and its liability to warp and rend, it is not so suitable for small conversions. It varies greatly in its quality, even so much as often to be of different colours, grain, and texture, in the same stick. It is about the same average weight as Virginia red pine. Larch timber, Pinus Larix, formerly unknown in Great Larch tim- Britain, has, within the last century, been very extensively t'^"'- planted. The first plantations of it were made on the vast estates of the Duke of Atholl, in the Highlands of Scotland. The following account, which is extracted from Knowles On Presercing the Navy, was, as the author of that work states, furnished to him by the late duke, and it contains, consequently, the results of the longest experience as to the growth of larch timber in Britain which can be ob- tained. The account is interesting, because plantations of larch are becoming very numerous, as tlicy are found to be very profitable. The returns from a larch plantation dur- ing the time the trees are arriving at their full growth, are estimated to be at least double what they would have been from an equal plantation of any other timber. '" Seedlings of larch were probably first brought into Scotland in the year 1738 by Mr Menzies ; but it has been asserted by some, that they were introduced into that p;u-t of this coun- try in 1734 by Lord Karnes. Some were left at Dunkeld, and some at Blair-Athole, by the former genderaan ; and 158 TIM Timber, bfinji exotic plants, were placed by the gardeners in green- ^^»»/— ^ hoii-ies. Not ihriviiisr in those situations, they were plant- ed ill the pleasure-grounds, where they grew luxuriantly. When the present duke succeeded to the titles and estates (in 1774), tliere was a considerable number of trees in a thriving state; and on a general survey of his estates in 1783, there were ftnind to be 900 Scottish acres of planta- tion, 6(X) of which were of larch ; since which time his grace has planted extensively every year, and in the spring of 1820, 10,820 Scottish, or about'l2,9S4 English acres, were covered with trees. The different species were, of — Scotch Acres. Oak 800 Scottish firs 1500 Spruce firs 500 Mixed plantations in the pleasure-grounds 200 Birch 200 Larch 7G20 10,820 " The larch thrives in very exposed situations. The lower range of the Grampian Hills, whicli extends to Dun- keld, are at an altitude there of from 1000 to 1700 feet above the level of the sea. The larch-trees are planted as high as 1200 feet up these hills, and grow exceedingly well ; a situation where the hardy Scottish firs cannot rear their heads. The spruce fir, however, thrives equally well as the larch on high and exposed hills. The growth of the larch-trees is very rapid, and Scottish fir of the same age will measure only half the quantity ; and so much is the wood esteemed in Scotland, that while the former is worth 2s. 6cl. per cubic foot, the latter brings only Is. 3d. The following account of a larch-tree, planted in the year 1738, and measured February 1819, will give some notion of its growth: — 1 foot above the ground, girth 17 feet 8 inches; 2 feel, 14 feet 6 inches; 3 feet, 12 feet 7 inches; 5 feet, 1 1 feet 5 inches ; 10 feet, 10 feet 4 inches ; 20 feet, 9 feet 7 inches ; 50 feet, 6 feet 3 inches ; 70 feet, 3 feet 2 inches; 75 feet, 1 foot 10 inches. " The top was fifteen feet in height, making the whole height 9() lieet ; and the tree measured 300 feet, or 6 loads, in cubical contents. The white and red larch-trees are those chiefly planted. The duke has made trial of the black or .\nierican, and also of the Russian larch, but has found that they do not thrive well. The timber in ques- tion has been used lor many years in Scotland for almost all local purposes, such as posts, rails, mill-wheels, fishing ■and ferry boats ; and in all these situations has been found to be very durable. The author has seen part of a ferry- boat twenty-three years old, which remained very sound, and the iron nails driven into it as perfect as when they first came from the forge. This, perhaps, was occasioned by their being constantly covered with an insoluble var- nish, with which the larch abounds. One of the qualities of larch for building merchant-ships is its great lightness, a cubic foot, weighing, when seasoned (which it does rapidly), only 34 lb. Although it is not so strong as many sorts of wood, it has great resilience. Cabinet-work of great beauty has been made from larch ; it polishes well, and when seasoned is not found to warp or shrink. A most important fact in agriculture has arisen from planting larch-trees on rocky ground ; the vegetable compost formed thereon by the falling of the leaves has been the cause of producing herbage for feeding cattle, and made that land, which, on the average, did not formerly bring more than 8d. or 9d. per acre, now to be worth from 12s. to 14s. per acre annually." Cultivation Larch timber, although so generally planted, and so of the generally thriving, requires considerable attention in the larch. selection of proper soil for it. It is very subject to a heart- rot, which seizes on the roots, and rapidly proceeds up the centre of the stem of the plant, the latter swelling con- B E R. siderably for several feet above the surface of the ground. Timber. Larch cannot bear a cold damp soil, or any stagnation of \^m.^^-m^ water, or even the moisture of the rich vegetable moulds. Nor will it thrive in the light sandy soils ; for although it dislikes marshy stagnant waters, its roots require to be pre- served from the droughts of sinnmer. Sandy and gravelly soils, if situated so as to receive from declivities the mois- ture percolating through them, will produce excellent larch timber ; as will also the sides of rocky hills and moinitaing, in which no moisture can stagnate, and into the fissures and clefts of which the roots easily penetrate and find ample nourishment. Larch-trees attain to a very great height. In some of the public buildings of Venice there are said to be single-pieced beams of larch which are 120 feet in length. It must be very durable, for it is almost the only wood which was used in the palaces and public buildings of that city. The timber imported from Canada under the name of American hackmatack is believed to be identical with the Scottish timber, larch. The timber of America in general is very inferior to that grown in the north of Europe, being much softei in its nature, not nearly so durable, and more liable to the dry-rot. American timber is therefore seldom used in ship-building, except for deck-deals, and but sparingly also in the construction of first-class houses. In consequence of the immense consumption of timber Foreign for the maintenance of our fleets, we are obliged to import '""""r. much from abroad. We obtain oak of excellent quality Oak. for planking from Poland and the shores of the Baltic ; while from Italy, and from both sides of the Adriatic, sided timber and plank are imported in large quantities. Ame- rican oak and rock-elm are both valuable timbers, and are now coming into very general use in this country, being introduced in considerable quantity. The f()riner is used by cabinet-makers and carriage-builders, principally on ac- count of its great size, unilisrm texture, straightness of grain, and little tendency to warp. Its specific gravity is some- what less than that of English oak. Rock-elm is becoming Rock-elm. much used for engineering purposes. It is remarkably uniform in texture and growth, and perfectly straight and free from knots. Its great length and uniform siding ren- der it extremely useful for longitudinal ties, piles, and other purposes, which require great length, combined with uniformity in dimension. For example, a baulk of rock- elm, 54 feet long, was found to taper only 1^ inch, and when slabbed, was 12^ inches square in section, and 51^ feet long. A specimen cut from this baulk weighed 50 lb. per cube foot, its specific gravity being equal to that of English oak. One of the most largely imported woods of tropical Teak, countries, and one of the most valuable, is teak. It grows to an enormous size, is particularly straight and free from knots, and has the peculiar property of resisting the attacks of insects. It possesses greater toughness than almost any other wood of equal weight, and is little liable to dry-rot or other disease. The great durability of teak is to be attributed to the large amount of oleaginous matter con- tained in this timber. Like all other woods, it varies much in quality, according to the locality where it is grown, The finest teak comes from Malabar ; then follow the im- portations from Travancore, Ceylon, Java, the Malayan Peninsula, from Pegu and Moulmein. The two last de- scriptions of teak are very inferior to the Malabar variety, being comparatively coarse, porous, and open-grained; but this inferiority is believed to be due rather to the low swampy locality from which it is cut for the foreign mar- ket, than to any inherent bad quality of the timber. Its weight, when moderately seasoned, may be stated to be 42 lb. per cubic fiiot, while the weight of Malabar teak, on an average, is from 45 to 52 lbs. per cubic foot. The forests of Tonga and Irrawaddy supply the whole of the TIMBER. 159 Pegu teak. Tliat of the Tonga forests is of the best qua- ' lity, the country heing high, and not flooded during the rainy season ; whereas the forests of the Irrawaddy are always in a swampy state, and are part of the year covered with water sufficient to allow of the trees being floated from where they are felled. The Birmans are in the habit of tapping the teak-trees, particularly those which are straight grown, to extract a varnish or oil, which is highly prized by them, and used chiefly for protecting their pa- godas or temples from the weather, for which purpose it is very effectual. These edifices are built entirely of untapt teak, as the Birmans consider the timber to be much in- jured, both in its strength and its durability, by being deprived of this oil. The principal parts of these temples are sunk in the ground, and although so fixed, the timber remains perfectly sound, notwithstanding many of them have stood nearly a century. Inferior as the Pegu and Moulmein teak is to the Mala- bar or Bombay teak, it is still preferable to the saul, which is now imported to this country in considerable quantity. This is a hard heavy wood, growing in Behar, Oude, and the inexhaustible forests skirting the hills that form the northern boundaries of Bengal. It varies much in quality, the best timber being found occupying the rocky ground at the foot of the hills, while that grown in the alluvial plains is very inferior. As a rule, it deteriorates in quality the further it is produced to the westward. Sauls of large dimensions are now becoming very scarce, as the whole of the forests within a reasonable distance of the navigable streams are quite exhausted ; but it is hoped, that as the Indian railways extend into the interior of the country, a further supply of valuable timber will thus become avail- able for exportation. The best description of saul, if well seasoned, may be classed, in point of durability, with the best sort of African timber, no%v so extensively used by ship-builders in this country. The greatest care is neces- sary in the selection of saul for immediate use, on account of its requiring a long time to season, and it must not be employed in ship-building for any part exposed to the sun, as it shrinks very much. Saul is used for the frame, beams, shelf-pieces, breast-hooks, and inside planking of ships built in Calcutta. The principal woods used in India for ship-building are, besides teak and saul, sissoo, jarrol, poon, and toon, teak being the most durable of them all. Indeed, from the sreat length of time which several vessels built of Malabar teak have lasted (from thirty to fifty years, and in some particular instances nearly a century), this may be said to be the most valuable timber for ship-building purposes yet known. It is, however, like every other kind of wood, liable to premature decay, if not properly and gradually seasoned by exposure to a moderate current of air, after being felled. Java teak is of very superior quality, little if at all inferior to that from the Malabar coast, and is extensively used for ship-building at Calcutta. '^ The teak which is grown on high, dry, and open land," says Mr Leonard Wray, in a paper read to the Society of Arts, " is generally of a fine quality, close and compact, and abounding in a mild oil, which exerts no injurious effect upon the iron bolts which may be driven into it. That grown in the dense forests of the wet, low-lying alluvials, on the contrary, is lighter, coarser grained, and contains an acrid oil, which not only affects iron very materially, but even, to a certain extent, poisons and inflames the hand which has been pierced by its splinters." As a test of the durability of a Calcutta-built ship, we may cite the Hastings, 74 gun frigate, built at Calcutta in 1818. The hull is composed of saul, sissoo, Pegu and Java teak, all of the best kind. So great was the expense incurred m the building of this ship, that when completed, tlic account, alter giving credit lor her freight, exhibited the cost of the hull for sea. 1,163,754 Sicca rupees, or. Timber, ten rupees to the pound, L. 116,375 sterling. It is usual •«— ^^-^ in Calcutta-built ships to convert the frame, with the knees. Durability breast-hooks, &c., from sissoo timber ; the beams and inside of Indian planking being of saul, and the bottoms, wales, topsides, woo<l*- decks, keels, stem, and stern-post, of the Pegu teak. Mahogany is the produce of America and the West Indies, Mahogany, being principally imported from Honduras and Campeachy. That imported from the islands is called Spanish mahogany. It differs very much in quality according to soil and locality, the weight of a cubic foot var\ ing from about 53 lb. to 35 lb. Although mahogany may be stated to be a durable and valuable timber both for ship-building and general pur- poses, it varies so very much in texture and quality, that the utmost care and judgment are necessary in its selec- tion. There are many well authenticated instances of the extraordinary strength and durability of ships built almost exclusively of mahogany, the most famous being that of the Spanish 80 gun ship Gibraltar, captured by the Eng- lish in 1757, and broken up at the age of 100 years, when all her timbers were found to be perfectly sound. This, however, only proves the excellent quality of carefully selected Spanish mahogany (the Gibraltar having been built at Havannah), it being equally well known that light, porous, "swamp mahogany ,"orindeed any of inferior quality, is highly treacherous and unsafe when employed for the timbering of a ship. It is an error to suppose that all Hon- duras mahogany is light and spongy, the best quality of this timber being as heavy as Malabar teak or English oak, and only the inferior qualities of mahogany being so very light and buoyant. Mahogany is highly prized for the paddle- beams and deck-beams of steam-vessels, in positions where these are exposed to the moist heat of the engine-room, which is very destructive to most other species of timber. According to " Lloyd's" classification of timbers, those ciassifica- in the first class are the following only : — English oak, tion of African oak, the live oak of America, the morra and green- timbers at heart of British Guiana, the teak and saul of India, and i^^oyda. the iron bark of Australia. These are all close-grained, compact woods, hard, heavy, strong, and durable, being more or less impregnated with certain oily, resinous, or astringent matters. Mahogany of hard texture, though treated as a second-rate timber, is so far admitted in the construction of A 1 ships, as to include beams and hooks, knees, rudder, and windlass, main-pieces, outside planking to light mark, and the whole of the inside planking. Greenheart, the produce of British Guiana, is a very Green- valuable timber. It is a hard, close-grained wood, contain- heart, ing a considerable quantity of oil, like teak. Its specific gravity is about equal to that of African oak, but it is decidedly superior to it in strength, toughness, and dura- bility. These, however, are not its chief advantages, its great value consisting in its complete exemption from the attacks of marine worms. It is therefore an excellent timber for sluice-gates, piles, and all marine engineering works, which would be exposed to their ravages. It is imported in logs of from 12 to 16 inches square, and from 20 to 40 feet in length. It has been used in some instances for the planking of ships. Mr Wray, from whose interesting paper " On Timber for Ship-Building" we have already quoted, says, that greenheart is very abundant within 1C)0 miles of the coast of British Guiana, and can be had almost to any extent. Another excellent timber of British Guiana, still more jiorni. abundant than the last, is morra. This tree grows to a very great size, often attaining the height of 100 to 150 feet, the lowest branches being 60 feet from the ground. The wood is extremely tough, close, and cross-grained, which properties make it difficult to split, and render it peculiarly ap|)licable to ship-building purposes. It is stated to be little subject to dry-rot. '1 he other British possessions 160 Timber. Sapply of jtolonial timber. Tuart. TIMBER. Blue gum. Jarrah. from which we midit readily draw a supply of excellent timber are .Asi-aiii and Tenasscrim in the nortli of India, our settlements in the Straits of JIalacca, and Western Australia. From the latter country we have the iron- bark, a first-class timber ; tiie tuart, the jarrah, the blue- gum, and the morell. The tuart is a noble timber tree, growing in tolerable abundance on the coast. Planks are somrtimes obtained of it 10 feet wide; and it is said to be pec\iliarly adapted to the building of ships of war, as it is difficult to split, and not liable to splinter. In colour it is pale-vellow, or white. Its timber is remarkably cross- grained, hard, and tough, and very strong and durable. The blue-gum is also an enormous tree, " sometimes," savs Mr Wray, " yielding planks 14 feet wide, and more than 120 feet long." The jarrah of Western Australia is frequently confounded with mahogany, to which some species of it bear a certain resemblance. Mr Reveley, a government engineer in Australia, thus describes the jarrah : — " First, in colour, there is every variety of shade, from almost crimson to redtlish brown, and pale bro"n, inclining to white. In the second place, as to grain, there b almost every variety, from the perfectly straight fibre to every species of curl, including the zebra and satin speci- mens. The length of the stem of this tree, taking the average, may be 65 feet (many being much longer), with- out a branch or a knot in all that length, and very nearly equal in size all the way up. It is not attacked by insects of any kind, nor has it any tendency to dry-rot, and is scarcely affected in any way by damp or inoisture." There are tbrests of this wood in Western .Australia of more tlian 4 miles in depth, and which are known to extend for a length of 150 miles. Here, then, is timber enough to maintain our navy for a hundred years to come, if we would only avail ourselves of the resources of this valuable colony, and encourage the exportation of its timber, by providing a ready means of access to a shipping port. We sliall now mention a itw other species of timber trees, of minor importance to the preceding, but still useful for many purposes of construction. Acacia, is of small dimensions, seldom exceeding two feet in diameter ; but when used in house-carpentry is very durable. It is harder, tougher, and more elastic than the best oak. It is a valuable timber for tree-nails for ship- building ; also, for posts and rails for fences, in which capa- city it is very enduring. Alder. — The wood of this tree lasts a long time under water, which renders it valuable for piles, water-pipes, &c. It has a close texture, a fine colour, and works well under the plane, which makes it a favourite with the cabinet- maker. The best charcoal for gunpowder is made from this wood. When burned in the open air, 1000 lbs. of the ashes yield 65 lbs. of potash. Birch. — This wood is hard, hut not very durable. It is chiefly used for making cheap furniture, and for firewood. Bo.v is a valuable wood, being very close-grained, hard, and heavy, and cuts very clean under the chisel or graving- tool, being therefore used almost exclusively by the wood- engraver. Being susceptible of a fine polish, it is much used by the turner, mathematical instrument-maker, &c. It is also very durable. Cedar (Cedrus pinus) grows to a great size ; the timber is resinous, of a reddish-white colour, light and spongy in its texture, easily worked, but apt to shrink and warp if great attention be not paid to the seasoning. It was much valued by the ancients for its durability and preservative properties. The wood is odoriferous, and admirably adapted for joiner-work, being light and easily worked. Although a resinous wood, it contains but a small quantity of that substance. It resists the attacks of insects. Cedar, Indian (Cedrus dcodara), is also a very large tree. The wood is very compact, highly impregnated with resin, and possessed of a hard and fine grain. Its durabl- Tiiiib»r. lity when exposed to the weather is very great, some briilncs ^•^"v^"' constructeil of it in India bavins; lasted for five hundred years. It is much used by the Hindoos in their buildings. Chestnut (Castanea) has been already mentioned as a very excellent timber for building purposes. The Horse Chestnut, on the other hand, is a soft, inferior wood of but little strength or durability. It resists moisture, however, anti may be advantageously used for water-pipes under ground. Ci/press is a fine-grained wood, remarkable for its great durability, and its freedom from injury by worins or insectij. Owing to this property, it was employed in Egypt for mummy-casts. Hornbeam is a hard, heavy, tenacious wood, very close grained. It is much used (or cogs of wheels and other engineering purposes, where the material is exposed to friction. Lignum vita is a very hard, dense wood, much used by millwrights and turners ; its chief use, liowever, is for the sheaves of blocks. It is also employed by the engineer for lining the sockets of shafts, which are found to revolve in it with little friction and wear. Lime, though a highly ornamental tree, and growing to a great size, is not of much value for its timber, which is soft and light, and deficient in strength and durability. Being close grained and smooth in its texture, however, it is well adapted for carving and cabinet-work. Maple is a clean, white wood, prized for its lightness, and is used by the turner for making dishes, bowls, and trenchers; and by the joiner for common furniture. As it is not liable to warp or split, it is readily stained to imitate mahogany and other woods. Plane. — The wood of this tree much resembles the beech. It is used by the joiner and cabinet-maker, but is not remarkable for strength or endurance. It keeps best under water, and is used in America for quays and other marine works. Poplar. — The wood of this tree (of which several kinds are grown in this country) is much used by builders for floors, especially, as it does not easily split by driving nails into it, and it has the pro|)erty of not readily catching fire. When used for tnis purpose, however, it rcijuires from two to three years' seasoning, as it shrinks much in drying. Sycamore, when kept dry, is durable ; but is readily attacked by the worm. It is a species of maple, and is pos- sessed of similar qualities. Walnut is one of the most valuable of English timbers. The wood is solid and compact, easy to work, not liable to crack or warp, and handsome in apjiearance ; it is there- fore much used for the better class of furniture. The screws of presses and gun-stocks are generally made of it. The black Virginia walnut is the most prized. It prefers hilly, calcareous soils. Willow is a soft, smooth, light wood, of little value ; but, if kept dry, it will last a long time in situations where much strength is not required. Yew was principally used of old for the making of bows, and is now a favourite wood with turners from the smooth- ness and toughness of its grain, and from its taking a high polish. It sometimes attains an extraordinary bulk. At Gresford, near Wrexham, there is a yew 29 feet in circum- ference at a little distance below the branches ; and in Dibdin churchyard. New Forest, there is a yew-tree mea- suring 30 feet in girtli at the ground ; while others, of large size, occur at Iffley, Hampton Court, Dorly-in-the- Dale, Tisbury, and other places. When found growing in churchyards, they may be generally reckoned as coeval with the church itself. As the strength of timber has been already treated of in tiie articles, St&£NOXH of Mat£KIAls, and Shif-Buildikq, TIMBER. 161 )3ition of e gtron^- t wood. we have little to add here upon this important subject. It may be observed, liowever, tiiat the weight or density of a timber is in general a sure index to its strength, tiie dens- est Hocjd being at the same time the strongest and the most durable. The oak, as well as all other timbers, varies in its specific gravity according to the soil which produces it, the density mainly depending upon the length of time occu- pied in the formation of the wood. Those trees wliich grow fast from being located on moist, sandy soils, never produce such strong timber as others of slower growth. It has been found by experiment, that the bottom part of the trunk, with the corresponding branches, is denser and stronger than the upper part of the same tree. Those trees which are suffered to complete their full term of growth before being cut down, have their heart-wood throughout of the same weight and strength, taking a cross section of the trunk at any one place, whilst those that are felled prematurely are found to possess these qualifications in the central portion of the wood only, which is then consider- ably harder than that immediately surrounding the sap- wood. In trees which have been over-grown, on the other hand, the central portion of the wood is the weakest, the process of natural decay always commencing in the heart of the tree. It is a common thing to see the heart of some fine tree (blown over by the wind, perhaps), which, to an untrained eye, looks perfectly sound and flourishing, to be already disintegrated by the spreading filaments of dry-rot, which have attacked it so soon as its vigour began to flag. The age at which oak timber is at its prime, is generally supposed to be from eighty to a hundred years, although this depends, as we have before explained, upon the nature of the soil on which it is grown. The weight of good oak timber is about 60 lbs. in the green state ; and, when sea- soned, about 50 lbs. If the seasoning is carried beyond this by artificial desiccation, the strength of the timber is impaired. The decay of wood by the growth of fungus, denomi- nated dry-rot, may be traced to the putrifying of the sap, when this has been left within the pores of the timber in the same condition as it exists in the living tree. The various means which are employed to arrest this destructive fermentation are, either to wash out the sap by long soak- ing in water, aided by the action of the sun ; to dry up the sap, either naturally by exposure to the sun and wind, or artificially by baking, or by heated currents of air ; or else by injecting into the pores of the wood some metallic salt to combine with the albumen and render it insoluble, or some antiseptic substance to preserve the vegetable tissue. The processes of natural seasoning and artificial desicca- tion, being those most in use for the preservation of ship- timber, will be found amply described in the article Ship- Bdxldixg ; also, the best mode of creosoting, although the latter process, from the increased inflammability and the strong smell it imparts to timber, is scarcely appli- cable to the building eitlier of ships or houses. For the preservation of railway-sleepers, and other wood-work out of doors, which is not particularly liable to danger from fire, the creosoting process has been proved to be most valuable. Its efficiency depends, in a great measure, upon the mode of operation, and the quantity of creosote injected into the timber, which should be done under pressure in a closed cylinder. The process is most applicable to fir and other soft woods, which should imbibe, at least, 7 lbs. of the creo- sote oil per cubic foot, oak imbibing not more than 2 or 3 lbs., even under a pressure of 120 lbs. per square inch. This substance seems to act, Jirslli/, by coagulating the albumen ; second/^, by furnishing a water-proof covering to the fibre of the wood ; and, thirdly, by preventing the putrefaction of the sap by its antise|)tic properties. The various processes for the preservation of timber by the absorption of metallic salts, have all more or less failed in practice, and are now very generally abandoned. These Timber, are known by the names of the inventors, as Kyan's, ^^-^^-^ Margary's, Burnett's, and Payne's processes. The object by absorp- sought by each of the three first of these methods was tion of to coagulate the albumen in the capillary tubes of the "netellic timber, and thus prevent, or retard, the putrefaction of the '*'"• sap. Kyan >ised chloride of mercury for this purpose, dis- Kyan's solving, at first, 1 lb. of the salt in 4 gallons of water ; but procesa. as it was found that the wood absorbed about 6 or 7 lb. of this costly salt per load, more water was added to lessen the expense, until the solution became so weak as, in a great measure, to lose its effect. This process has, there- fore, been entirely abandoned. The salt employed by Margary was sulphate of copper, which, being much cheaper srargary'n. than chloride of mercury, could be used as a stronger solu- tion. Its efficacy, however, has proved doubtful in many cases, while in not a few instances it has failed altogether. Better than either of the preceding is Sir William Burnett's Burnett's, plan of injecting a solution of chloride of zinc, in the pro- portion of about 1 lb. of the salt to 4 or o gallons of water. This process is still in use, and has certainly proved bene- ficial in a great many cases, but it cannot always be relied upon. Payne's process consisted in the successive injec- tion of two substances in solution — the first, a metallic or earthy solution, and the second a decomposing fluid — the consequence being that the capillary tubes of the timber became filled with an insoluble substance. The process of Superior- creosoting timber, already referred to, was first patented ''X °^ by Mr Bethell in the year 1848. One great advantage of "^'J^'^'* creosoted timber is, that it perfectly resists the attacks of '"° ^'' marine worms and insects, as well as the white ant of India, which is more than can be said for timber prepared with solutions of metallic salts. Even that prepared with corrosive sublimate (as in Kyan's patent) has no immunity in this respect, the albumen appearing to neutralize the poisonous property of the salt. For ship-building purposes such chemically prepared, or Artificially " salted," timber is scarcely to be recommended, as it at- prepared tracts much moi?ture, and is very destructive to the metal timb" not fastenings. Empyreumatic oils and resinous solutions, al- ^['•''"u'*-,'f though these certainly render the wood impervious tOj^ moisture, and preserve the iron or metal bolts from oxida- tion, are still very objectionable from the increased inflam- mability which they impart to the structure. The time necessarily required in preparing the wood with the preser- vative substance is also a great drawback to its employ- ment in ship-building, where a delay of even two or three days, more especially in repairing, is often of serious con- sequence ; and it should be remembered, the timber must be operated upon after it has been shaped or " converted." Timber may be very perfectly preserved from subsequent Soakini; decay by long submergence in shallow salt water, or, which timber, is still better, in salt mud. When thus treated for a period of from ten to twenty years, the sap gets thoroughly washed out of the pores of the wood by the alternate ab- sorption and expulsion of air or other gases, caused by suc- cessive variations of temperature. It need scarcely be hinted, however, that such a mode of procedure, though sometimes adopted in government dockyards, would be ruinously expensive to the private ship-builder. Having pointed out the fatal objections generally attend- Import- ing the use of chemically-prepared timber for ships oranceof houses, it remains to show « hat means can be employed S/'O'l ven- (and that with tolerable certainty) for preserving the tim- !.' *''°" ber of these structures from premature decay. The means servini?" at our command for this purpose are summed up in the timber, two words, '"seasoning" and "ventilation:" namely, thorough seasoning or drying of the timber on shore, when this is practicable ; but, by all means, good ventilation on board. If these well-known and universally approved prin- ciples were but carried out in an honest and common-sense 102 Timber. Cheaply- built ships often last the longest, Ifece«aity for system- atic venti- lation. TIM fashion, we sliouU! licar but little of rotten gun-bonts, or hfavyiepairs to fVif^atcs after a first commission. Thouijli it is undoubteiily true that the closely-packed timbers ami double planking of a vessel of «ar present sjreat obstacles to a thorough ventilation of the bottom, much may still be tlone by conducting currents of air down into the hold, and between the timbers, by means of wind-sails, or, if necessary, by fanners worked either by steam or hand, and by so arranging the internal accommodation that there may be as little stagnation of air as possible. However well seasoned and dry the timber may be when the ship is launched, it will rapidly absorb moisture tioin the damp atmosphere of the hold, unless evaporation from its surface be kept up by a forced circulation of air. It is certainly unbecoming the scientific character of the age that shi|)s built hurriedly and cheaply, and of very in- ferior timber, by what are contemptuously called " slop" builders, are knotvn to resist the rav.ages of dry-rot much better than the expensively and elaborately-constructed ships of Her Majesty's dockyards ; nay, more, that these same "slop-built" ships, even when constructed entirely of green timber (as they frequently are), "ill last longer than a government ship built with the best seasoned oak 1 The whole secret is, of course, the internal ventilation of the holds and frame of the ship. In a cliea])ly-built merchant- ship the timbers are spaced at some distance apart, and the ceiling planks are not placed so close together as hermeti- cally to seal the spaces between the limbers, the conse- quence being that good ventilation is maintained amongst the planks and timbers of the bottom and sides. Even when such a ship is built of green wood, the circulation of air is generally sufficient to season the timber in its place and prevent its decay, for the dry-rot fungus will not thrive in an atmosphere less moist and stagnant than that of an underground cellar. The shrinkage of green timber in such a case would also conduce to its preservation by ad- mitting the air between the ceiling planks. These remarks are not intended to excuse the use of unseasoned timber in ship-buiUiing, a practice which should be resorted to only from dire necessity, but rather to show that if ships built of green timber can be preserved by what may be termed accidental ventilation, those built of sea- soned timber should, d fortiori, be still more easily pre- served by systematic ventilation. The action of heat in causing an upward current of air naturally suggests itself as a ready means of effecting this object on board ship. The dry-rot has been frequently arrested in a ship by thoroughly drying the timbers, holes having been previously cut in the ceiling planks to promote circulation. Yachts and other small vessels, when not in use, may be preserved from dry- rot by hauling them up out of the water in an exposed situation where the wind will get to them, keeping sky- lights and hatches open, .and if a plank be removed from the bottom they will be all the safer. Should they be entirely closed up, on the other hand, the dry-rot will flourish within like mushrooms on a hot-bed. T I U Sap-wood should always be removed from the timbers Timber. ' and planks of a ship, as from its spongy texture and im- '^s^^s^.™-' perfect development, it is more liable to dry-rot than the Sap-wood heart-wood (besides being much weaker) ; and when the should bo dry-rot has once commenced either in a ship or a house, it removed is rapidly propagated by contagion. The process of season- ing timber q\iickly by a current of heated air will be found amply detailed in the article Siiir-15uii.uiSG. Timber is bought and sold by solid measure, according Measure- to the number of cubic feet in the tree or log. The mea- ment of surement of timber is therefore the operation by which ''"'"•■• these cubic contents are determined ; that is, multiplying together the three dimensions, or the mean length, the breadth, and the depth, of each log. If the log should vary much in sibc iii different parts, then the length, breadth, and depth of each of these parts must be multiplied together, and the contents of the log will be the sum of the products. When the log tapers, a mean breadth or de|)th is taken ; the object in every case being to attain the most correct approximation to the contents of the log. In measuring rough logs, it is however usual to gird the log at the mea- suring place with a string, and then, folding the string into four equal parts, to assume this fourth pan of the girth to be one side of the square area at the measuring place ; which area, when multiplied by the length, will give the solid contents of the log. The arithmetical operation, simple as it is, is universally su|)crseded by the more simple and liir more correct plan of referring to published tables of contents, calculated for every foot in length of a log, and every quarter of an inch in tlie side of the square. Those most generally used tor this purpose are in Hopjius's Prac- tical Measurer. In measuring standing timber, the length is taken as high as the tree will measure 24 inches in circumference, less than which measurement is not considered as timber. At half this height, the measurement for the mean girth of the timber in the stem of the tree is taken ; one-fourth of this girth is assumed to be the side of the equivalent square area. The buyer has in general the option of choosing any spot between the but-end and the half height of the stem as the girding place. All branches, as far as they measure 24 inches in girth, are measured in with the tree as tim- ber. An allowance, which varies according to circumstan- ces, is generally deducted for the bark. In oak it is from about one-tenth to one-twelfth of the circumference at the girding place ; in other sorts of timber it is less. In all, how- ever, this allowance depends much upon special agreement. It is usual to speak of timber by the load, which means oO cubic feet of squared timber, or 40 cubic feet of rough timber. A load of plank is dependent upon its thickness. Thus it will require 200 square feet of 3-inch plank to make the load of 50 cubic feet ; therefore the load of plank is the number of square feet of its respective thickness, which is necessary to make the load of 50 cubic feet. Deals are measured, accordmg to their thickness and lengths, by the hundred, reckoning 120 to the hundred. (u. m — t.) 163 TONNAGE. les ior mage. innage id for mmcr- il iini- ses. 'onnage. TilE term tonnage, as applied to sliipping, was originally »N/— »^ intended to express the actual burthen tiiat any ship could rnifica- carry, in order that the various dues and customs which n of the are, and always have been, levied upon ships might be ™' proportioned to their carrying powers. To avoid cavilling and uncertainty as to the real tonnage of a vessel (which, it is evident, depends upon the draught of water at which she can safely swim), it must have been soon found neces- sary to establish one universal mode of calculating the tonnage of merchant-shipping, depending on certain fixed and definite measurements of the hull. A fixed rule, strictly enforced by law, has consequently been adopted iportance by all maritime nations for this purpose. Upon the prin- good ciples recognised in framing these rules depends, in a great measure, the preponderance of good or bad qualities in the ships themselves, the body of shipowners in general being found unequal to the temptation of sacrificing the prospec- tive safety, and the wealherly qualities, of their ships to the present sure gain arising from a low rate of register tonnage, when this can be compassed by any peculiarity of build, however extravagant. Legislation on this sub- ject requires, therefore, to be conducted with the utmost caution and circumspection, an irreparable injury having been already done to the merchant-shipping of this country from the erroneous principles on which the measurement for tonnage used to be made. Not only are all dues and customs levied according to tonnage, but ships are also built, bought, and sold for a cal anJ certain price per ton of their admeasurement ; and by the conditions of Lloyd's classification-list of shipping, they must be timbered and fastened, and must have their anchors, cables, and boats, all in proportion to the same datum. The tonnage of a ship, therefore, in so far as these considerations are involved, is virtually assumed to be a correct representation of her size, e true The true principles upon which the register tonnage of inciples shipping should be computed appear to be the following : — which ist^ Jt should afford a practically correct measurement of all space eligible for stowage or passenger accommodation ; 2d, The measurements and dimensions involved should be such, both as regards their number and position, as to effectually prevent even our most ingenious builders from escaping the due influence of the rules, whatever form or dimensions of vessel may be resorted to ; and, 3d, It should be such as to ensure the dues levied being justly propor- tional for all classes of vessels. The question has been raised whether the legal tonnage of a ship should not re- present numerically the commercial tons actually carried either of measurement or dead-weight cargoes, or both of them, rather than merely express, as at present, the relative capacity of ships. On this subject it was remarked by Mr G. Moorsom, surveyor-general for tonnage to the Board of Trade, at a meeting of the Institution of Naval Architects (as reported in the Mechanic's Magazine of 6th April 1860), " that the preservation of the expression of the pre- sent aggregate tonnage of the kingdom has been the sine qua non with all the public commissions on the question, and is upheld also by the shipping community, as consti- tuting a fairer standard of capacity, vinder general circum- stances, than the estimated cargoes carried, whether of measurement or weight, which must necessarily vary with the ever-varying circumstances of longer or shorter voy- ages — to say nothing of the acknowledged almost impossi- bility of satisfactorily arriving, by any general rule, at the proper positions of the load and light draughts of water, on which the calculation of the weights carried solely de- pends." In regard to the question of weight-cargoes, Mr inage ould be mputed. r Moor- in, sur- !yor- !neral for nnase. Moorsom observed that " parties were agitating as to the Tonnage, desirableness of placing a scale of tonnage (or displace- ^^^^z^-' ment) on a ship certificate of registry, to show the weight On scales of cargo carried at different lines of flotation, for the con- of displace- venience of ship owners, brokers, and masters. He ques- ment. tioned, however, if the utility of that object was at all commensurate with the labour and difficulty of its produc- tion, and he had yet to learn that the parties themselves, for whose interest it was proposed, desired such a docu- ment. But, if needed, it could be furnished to the ship owner or broker by any respectable builder or surveyor of shipping, and ought not to be prepared at the public ex- pense. It would require ten or twelve practised drauglits- men for a period of nine or ten years to prepare such scales for the existing commercial navy, and two or three others in addition for the ships annually building. Tables had been prepared at the Board of Trade by which it ap- peared that the weights due to one inch of immersion at the two different draughts of the load and the light lines varied, on an average, to the extent of about 10 per cent, only, so that, for all commercial purposes, it would be suffi- cient to know what weight of cargo corresponded to an inch of depression." Until January 1836, the rule for computing the tonnage Old rule of ships was as follows : — The length was taken on a ^°^ ''^°" straight line along the rabbet of the keel of the ship, from "*,;®;f .''^*^ 1 ? I p 1 • 111- Builders the back of the main sternpost to a perpendicular line qj^ jj^^, from the fore part of the main stem under the bowsprit, surement' The breadth was taken from the outside of the outside plank in the broadest part of the ship, either above or below the main wales, exclusively of all manner of doub- ling planks that might be wrought upon the sides of the ship. If the ship to be measured was afloat, a plumb-line was dropped over the stern, and the distance between such line and the after part of the stern-post, at the load water- mark, was measured ; then was taken the length fi-om the top of this plumb-line, in a direction parallel with the water, to a perpendicular immediately over the load water- mark, at the fore part of the main stem. Subtracting from this length the before -mentioned distance between the plumb-line and the after part of the stern-post, the re- mainder was reckoned to be the ship's extreme length, from which three inches were deducted for every foot of the load draught of water. With die dimensions thus ob- tained, the rule then was : — " From the length taken in either of the ways above mentioned, subtract three-fifths of the breadth taken as above ; the remainder is esteemed the just length of the keel to find the tonnage ; then mul- tiply this length by the breadth, and that product by half the breadth, and dividing by 94, the quotient is deemed the true contents of the tonnage." This rule (called " builders' old measurement," or when contracted, b.o.m.) is still much in vogue as a guide for the purchase and sale of ships. It is evident that the tonnage as determined by it was intended to express the size or bulk of the ship, the half-breadth being an assumed equiva- lent for a mean depth. The evils which arose out of this assumption were very great. As the de[)th was not at all involved, it might be increased to any extent without in- creasing the tonnage ; while, on the contrary, as the square of the breadth was involved, an undue preponderance was given to this dimension, and it became necessary, on the part of shipowners, to restrict it within the least possible limits. The efiect of such a law was obvious. The British merchant ships, in order to profit by its inconsistencies, were built exceedingly narrow and deep in proportion to the length, so that, according to parliamentary returns, we 1G4 TONNAGE. Tnnnage law of I83(>. Tonnopc. find, on an averafre, the mercantile navy ivoiild carry a 'i^^y-^-' tliiiil more wtijilit tlian its it'sially registered tonnage. In fict, llie slii|)s became little more tlian oblong boxes, most dangerous as sea-boats, and, from their want of stability, not capable of earrying sufficient sail to insure their safety on lee shores. Hence, alter every gale of wind, the leeward coasts were covered with their wrecks; and hence Lloyd's books registered aninially the average loss of six ships in four days. This tonnage law, as we have said, was happily altered in January 18;i6, when the following rule for cal- culating the tonnage of vessels was substituted for it: — " The tonnage of every ship or vessel required by law to be registered shall, previously to her being registered, be measured and ascertained while her hold is clear, and ac- cording to the fiillovving rule: (that is to say), divide the length of the upper deck between the after part of the stem and the fore part of the sternpost into six equal parts. Depths — at the foremost, the middle, and the aftermost of those |)oints of division, measure in feet and decimal parts of a t()ot the depths from the under side of the upper deck to the ceiling at the limber-strake. In the case of a break in the upper deck, the depths are to be measured from a line stretched in a contintuuion of the deck. Breadths — divide each of those three depths into five equal parts, and measure the inside breadths at the fi)llowing points : ride- licit, at one-fifth and foiir-fiftlis from the u|)per deck to the foremost and aftermost depths, and at two-fifths and four-fifihs from the upper deck of the midshij) depth. Length — at half the midship depth measure the length of the vessel from the after part o( the stem to the fore part of the sternpost ; then to twice the midship depth add the foremost and the aftermost depths for the sum of the de])tlis; add together the upper and lower breadths at the f()remost division, three times the upper breadth, and the lower breadth at the midslii|) division, and the upper and twiee the lower breadth at the after division, for the s\im of the breadths; then multiply the simi of the depths by the simi of the breadths, and this product by the length, and divide the final product by 3500, which will give the number of tons for register. If the vessel have a poop or half-deck, or a break in the upjier deck, measure the inside mean length, breadth, and height, of such part thereof as may be included within the bulkhead; nndtiply these three measurements together, and divitiing the pro- duct by 92'4, the quotient n ill be the number of tons to be added to the result as above found. In order to ascertain the tonnage of open vessels, the depths are to be measured from the upper edge of the upper strake." Mode of ascertaining the Tonnage of Steam- Vessels. " In each of the several rules hereinbefore prescribed, wlien applied for the purpose of ascertaining the tonnage of any shi[) or vessel propelled by steam, the tonnage due to the cubical contents of the engine-room shall be deducted from the total tonnage of the vessel, as determined by either of the rules aforesaid, and the remainder shall be deemed the true register tonnage of the said ship or vessel. The tonnage due to the cubical contents of the engine-room shall be determined in the follow ing manner : that is to say, measure the inside length of the engine-room in feet and decimal parts of a foot, from the foremost to the aftermost bulkhead ; then multiply the said length by the de|)th of ship or vessel at the midship division, as aforesaid, and the product by the inside breadth at the same division, at two- iiiths of the depth from the deck, taken as aforesaid, and divide the last product by 92'-l, and the quotient shall be deemed the tonnage due to the cubical contents of the engine-room." For ascertaining the Tonnage of Vessels tchen laden. " And be it further enacted, that for the purpose of ascer- taining the tnnnage of all such siiips, whether belonging to Toniinge. the United Kingdom or otherwise, as there shall be occasion ^<^>yaa./' to measure while their cargoes are on beard, the following rule shall be observed and is hereby established : that is to say, measure, first, the length on the upper deck, between the after part of the stem and the fore part of the sternpost ; secondly, the inside breadth on the under side of the u|)per deck, at the middle point of the length ; and, thirdly, the depth from the underside of the u[)per deck, down the |)ump- weli, to the skin ; nndtiply these tlirec dimensions together, and divide the product by 130, and the ipiotient will be the amomit of register tonnage of those shi|)s." It was soon found that this rule was somewhat partial in Olijodions its operation in diHerent classes of vessels, and that it could 'o it. be, within certain limits, evaded by an ingenious builder; but still the evasions were not so destructive to the good qualities of shifis as those which were commonly practised during the continuance of the old law. It is exceeding:y difficult, probably even impossible, to T) iff! cult y frame a rule for computing the tonnage which shall be at of framing once of practical application, and yet not have in some de- " P<"'f<-'ct gree the t ll'cct of restricting improvement in the qualities of!"""'^® merchant-ships. It is difficult to induce a man to forego a constant and positive gain for one that is only prospective and uncertain. We have seen that the obstacles which oppose themselves to correctly and satisfjjctorily determin- ing either the light or tlie load draughts of water, are suffi- cient to preverit the diffi.-rence between the light and load displacements from being taken to represent the tonnage. This is, however, the only correct measure of a ship's power to carry cargo ; the diftlrence being, of course, exactly equal in weight to the cargo which either has caiised or may cause it. All other ()uaiuities which can be taken as measures of that power are little more than assumptions, and whether they represent the external dimensions of a ship, or her internal capacity, they scarcely give an approximation even to the power wiiich she may possess of carrying burthen ; w hilc, in either of the above cases, the fact that these quan- tities must be determined by measurements at fixed measur- ing places, affords opportunity lor evasion, and indeed invites it. For if, by any arrangement of the dimensions, or by any peculiarity of the shape, a ship can be enabled to carry a greater burthen than her registered tonnage, the freight of that greater burthen is a premium which is offered to that one proportion between her dimensions, or that one peculiar form for her body, and a restriction is, to a certain extent, placed upon ini[)rovement ; because the shipowner will con- tent himself with the best ships that he can obtain possess- ing the advantages of those dimensions or of that form. The rule last quoted for computing the tonnage assumes it to be the space for stowage, and tlie internal capacity of the vessel is calc\ilated in order to determine it. As there are necessarily fixed measuring places, the rule may, as w"e have said, be evaded by a certain build. Its phraseology might also be easily evaded by building accommodations on deck, which would not come within the meaning of the terms that are used in it — " poop," "half deck," or " break in the deck." Under its operation, vessels might also be advantageously built of very small register tonnage to carry cargoes of heavy goods; for which purpose they should be of the lightest materials, but with very large scantlings, that the internal capacity may bear but a small proportion to the load displacement of the vessel. This rule, however, was far less injurious to the mercantile navy of Great Hritain than that which had preceded it. The present rule for tonnage was introduced in the year New ton- 1854, constituting one of the most important sections of nape law the Merchant Shipping Act of that year. It is universally pf '854 ; admitted to be a vast improvement upon all that had gone J'* advaa- before, and indeed to be one of the greatest benefits ever ° ' confi;rrcd by the Legislature upon naval architecture, tend- TONNAGE. ^onnafre. innage ck. lie I., for ips where e hold is ble of ISfiCS. 'ansverso eos. ing, as it does, to advance the character of the merchant marine of this country. The builder is at leni;th free to construct his ship in the way he thinks best for the require- ments of her particular trade ; the very impossibility of evading the law by any alterations in the dimensions or form making shipowners content to have good trustworthy ships, in place of the dangerous abortions of twenty years since. It is found that the vessels built since the new law came into operation have an average length of 5 times their breadth, in place of 3| times as formerly, and that their average depth has decreased from above f ths of the breadth to f ds ditto, their speed and weatherly qualities being im- proved in like proportion. The following is the present law for measurement of tonnage (introduced 1854): — " Throughout the following rules, tlie tonnage-deck shall be taken to be the upper-deck in ships which have less than three decks, and to be the second deck from below in all other ships ; and, in carrying sucli rules into effect, all mea- surements shall be taken in feet, and fractions of feet, and all fractions of feet shall be expressed in decimals. " The tonnage of every ship to be registered, with the exceptions mentioned in the next section, shall, previously to her being registered, be ascertained by the following rule, hereinafter called Rule I. ; and the tonnage of every ship to which such rule can be applied, whether she is about to be registered or not, shall be ascertained by the same rule. " (1.) Measure the length of the ship in a straight line above the upper side of the tonnage-deck from the inside of the inner plank (average thickness) at the side of the stern, to the inside of the midship stern timber or plank there, as the case may be (average thickness), deducting from this length what is due to the rake of the bow in the thickness of the deck, and what is due to the rake of the stern timber in the thickness of the deck, and also what is due to the rake of the stern timber in one-third of the round of the beam ; divide the length so taken into the number of equal parts required by the following table, according to the class in such table to which the ship belongs. " Table. — Class 1. Ships of which the tonnage-deck is (according to the above measiuement) 50 feet long or under, into 4 equal parts. 2. Ships of which the tonnage-deck is (according to the above measurement) above 50 feet long, and not exceeding 120, into 6 equal parts. 3. Ships of which the tonnage-deck is (according to the above mea- surement) above 120 feet long, and not exceeding ISO, into 8 equal parts. 4. Ships of which tlie tonnage-deck is (according to the above measin-ement) above 180 feet long, and not exceeding 225, into 10 equal parts. 5. Ships of which the tonnage-deck is (according to the above mea- surement) above 225 feet, into 12 equal parts. " (2.) Then, the hold being first sufficiently cleared to ad- mit of the required depths and breadths being properly taken, find the transverse area of such ship, at each point of division of the length, as follows : — Measure the depth at each point of division from a point at a distance of one-tliird of the round of the beam below such deck ; or, in case of a break, below a line stretched in continuation thereof, to the upper side of the floor-timber at the inside of the limher- strake, after deducting the average thickness of the ceiling which is between the bilge-planks and limber-strake ; then, if the depth at the midshij) division of the length do not exceed 16 feet, divide each depth into four equal parts; then measure the inside horizontal breadths at each of the three points of division, and also at the upper and lower points of the deptl), extending each measurement to the average thickness of that part of the ceiling which is be- tween the points of measurement ; number these breadths from above {i.e., number the upper breadth one, and so on down to the lowest breadth); multiply the second and fourth by 4, and the third by 2 ; add these products to- getlier, and to the sum add the first breadth and the fifth ; multiply the quantity thus obtained by one-third of the common interval between the breadths, and the product shall be deemed the transverse area ; but if the midship depth exceed 16 feet, divide each depth into 6 equal parts instead of 4, and measure, as l)el()re directed, the horizontal breadths at the five points of division, and also at the upper and lower points of the depth ; number them from above as before ; multiply the second, fourth, and sixth by 4, and the tl'ird and fifth by 2 ; add these products together, and to the sum add the first breadth and the seventh ; multiply the quantity thus obtained by one-third of the common in- terval between the breadths, and the product shall be deemed the transverse area. " (3.) Having thus ascertained the transverse area at Compurn- each point of division of the length of the ship, as required '■<"> '^'"om by the above table, proceed to ascertain the register '"'"^^' Tonnage of the ship in the following manner : — Number the areas successively 1, 2, 3, &c., No. 1 being at the extreme limit of the length at the bow, and the last number at the extreme limit of the length at the stern ; then, whether the length be divided according to the table into 4 or 12 parts, as in classes 1 and 5, or any intermediate number, as in classes 2, 3, and 4, multiply the second and every even-numbered area by 4, and the third and every odd-numbered area (except the first and last) by 2 ; add these products together, and to the sum add the first and last if they yield anything; multiply the quantity thus ob- tained by one-third of the common interval between the areas, and the productwill bethe cubical contents of thespace under the tonnage-deck ; divide this product by 100, and the quotient being the tonnage under the tonnage-deck shall be deemed to be the register tonnage of the ship, subject to the additions and deductions hereinafter mentioned. " (4.) If there be a break, a poop, or any other perma- Poop and nent closed-in space on the upper-deck, available for cargo any other or stores, or for the berthing or accommotlation of passen- ciosed-in gers or crew, the tonnage of such space shall be ascertained 'P**^*- as follows : — Measure the internal mean length of such space in feet, and divide it into two equal parts ; measure at the middle of its height three inside breadths — namely, one at each end, and the other at the middle of the length; then to the sum of the end-breadths add four times the middle breadth, and multiply the whole sum by one-third of the common interval between the breadths, the product will give the mean horizontal area of such space ; then measure the mean height, and multiply by it the mean hori- zontal area ; divide the product by 100, and the quotient shall be deemed to be the tonnage of such space, and shall be added to the tonnage under the tonnage-deck, ascertained as aforesaid, subject to the following provisos: — First, That nothing shall be adiled for a closed-in space solely appropriated to the berthing of the crew, unless stich space exceeds one- twentieth of the remaining tonnage of tlie ship, — and in case of such excess, the excess only shall be added ; and, seco/iilli/, that nothing shall be added in respect of any building erected for the siielter of deck-pas- sengers and approved by the Board of Trade. " (5.) If the ship has a third deck, commonly called a spar- In case of deck, the tonnage of the space between it and the tonnage- t"^o or deck shall be ascertained as follows: — Measure in feet the ™°" ''^<^'"' inside length of the space at the miildle of its height from the plank at the side of the stem to the lining on the tim- bers at the stern, and diviile the length into the same number of equal parts into which the length of the ton- nage-deck is divided as above directed ; measure (also at the middle of its height) the inside breadth of the space at each of the points of division, also the breadth of the stem and the brcailth at the stern ; number them successively, 1, 2, 3, &c., connnencing at the stem; multiply the second, and all the other even-numbered breadths by four, and 166 TONNAGE. Allowance for engine' room in steamers. To be rate, able in ordinary steamers. May be measured where ihe space is unusually large or small. Tonnago, Ac, to be carved on main beam. Practical W'orking of the rules. Allowance to steamers not satis- factory. the tliird and all tlic otlicr oild-numbcreil hreadiiis (except ■ the first and last) by Iho ; to the sum of tliese [)r<)diii-ts add the first and last breadths; multiply the whole simi by one-third of the common interval belHCcn the breadths, and the result will give, in superficial feet, the mean hori- zontal area of such space ; measure the mean height of such space, and multiply by it the mean horizontal area, and the product will be the cubical contents of the space ; divide this product by 100, and the quotient shall be deemed to be the tonnage of such space, and shall be added to the other tonnage of the ship, ascertained as al'ore- said ; and if the ship has more than three decks, the ton- nage of each space between decks above the tonnage- deck shall be severally ascertained in manner above de- scribed, and shall he added to the tonnage of the ship ascertained as aforesaid. " In every ship propelled by steam, or other power re- quiring engine-room, an allowance shall be made for the S|)ace occu|)ied by the propelling power, and the amount so allowed shall be deducted from the gross tonnage of the ship, ascertained as aforesaitl, and t!ie remainder shall be deemed to be the register tonnage of such ship ; and such deduction shall be estimated as follows (that is to say): (n) As regards ships propelled by |)addle-wheels, in which the tonnage of the space solely occupied by and necessary for the proper working of the boilers and machinery is above 20 per cent, of the gross tonnage of the ship, such deduc- tion shall be 37 hundredths of such gross tonnage ; and in ships propelled by screws, in which the tonnage of such space is above 13 per cent, and tmdcr 20 per cent, of such gross tonnage, such deduction shall he 32 hundredths of such gross tonnage, (b) As regards all other ships, the deduc- tion shall, if the Commissioners of Customs and the owner both agree thereto, he estimated in the same manner, but either they or he may, in their or his discretion, riquire the space to be measured, and the deduction estimated accordingly ; and w henever such measurement is so re- quired, the tieduction shall consist of the tonnage of the space actually occupied by, or required to be enclosed fur the proper working of the boilers and machinery, with the addition in the case of ships j)ropellid by paddle-wheels of one-half, and in the case of ships |iropelled by screws of three-fourths, of the tonnage of such space. In the case of screw-steamers, the contents of the shaft-trunk shall be added to and deemed to form part of such space. " In every registered British ship the number denoting the register tonnage, ascertained as hereinbefore directed, and the number of her certificate of registry, shall be deeply carved, or otherwise permanently marked, on her main beam, and shall be so continued ; and if it at any time cease to be so continued, such ship shall no longer be recognised as a British ship." These rules have now been in operation for a period of five years, during which about 16,000 British, and a much greater number of foreign ships, have been measured by them. The experience of their operation thus afforded has proved highly satisfactory, with the single exception of the method of estimating the allowance made to steamers for their propelling power, by the plan of percentages on their gross tonnage. After exi)laining certain abuses under the old law, which led to the adoption of this mode of allowance, Mr Moorsom, in the paper before alluded to, stated, that " it had been found practically to admit of the intended allowance being anomalously increased by other means, and had given dissatisl'action even to the owners themselves, by its unjust action between steamer and steamer." In illustration of this, Mr Moorsom gave a paper of examples, by which it was seen that, in two paddle- ships of about the same gross tonnage and [)ower, there could be, and frequently was, a diStrence in their allow- ances to the extent of 20 per cent. ; and that in a similar ment of steamers. case of screw-vessels, the difference was to the still greater TonnaTe extent of about 40 per cent. He likewise founil that ^^ .-^ " the system of percentages frequently gave to large- powered coasting steamers undue allowances ; to extreme- power tugs to within I per cent, of a negative tonnage ; and to long-voyage auxiliary-power vessels, on the con- trary, a less allowance than the old system." Steam-ves- sels seem to have gained by the new law, as regards their register tonnage, an average advantage over sailing vessels of a decrease of about 6^- per cent., which is very unequally and unjustly distributed between steamer and steamer. To give an example, the steam-tug United States, of Cardiff. GO horse-power, is but 4 tons register. This ano- maly will probably be soon remedied, such an alteration in the law being already provided lor, without further legisla- tive interference, under the provisions of the 29th section of the Merchant Shi|>ping Act of 1854. The following alteration in the mode of measuring steam- Alteratior crs for tonnage has been recently introduced, with the view '" the of making a more equitable allowance than herelolbre for "ea«"re. the space occupied by their propelling power : — Copi/ of Minute of the Board of Customs, dated 23d October 1860. " In pursuance of the powers granted by the 29th sec- tion of ' The Merchant Shipping Act, 1854,' the Board, with the ap|)roval of the Board of Trade, direct, with a view to the more accurate and uniform application of the princi()le of granting a certain allowance to steamers for their propelling power, that, in lieu of the rules set forth in sec. 23 of the Merchant Ship|)ing Act, the following rule be adopted in future, viz. : — " Klle. — In every ship propelled by steam, or other power, requiring engine-room, an allowance of space or tonnage shall be made for the space occupied by the pro- pelling power, and the amount so allowed shall be deducted from the gross tonnage of the ship ; and such deduction shall he estimated as follows ; that is to say : — " 1. Measure the mean length of the engine-room be- tween the foremost and aftermost bulkheads, or limits of its length, excluding such parts, if any, as are not actually occupied by, or required for, the proper working of the machinery ; — then measure the depth of the ship at the middle [)oint of this length, from the ceiling at the limber strake to the upper deck in ships of three decks and under, and to the third deck, or deck above the tonnage-deck, in all other ships; — also the inside- breadth of the ship clear of spousing, if any, at the middle of the depth ; multiply to- gether these dimensions of length, depth, and breadth for the cubical contents; — divide tliis product by 100, and the quotient shall be deemed to be the tonnage of the engine- room, or allowance to be deducted from the gross tonnage on account of the propelling power. " 2. In the case of ships having more than three decks, the tonnage of the space or spaces betwixt decks, if any, above the third deck, which are framed in for the machi- nery, or for the admission of light and air, found by multi- plying together the length, breadth, and depth thereof, and dividing the product by 100, shall be added to the tonnage of such space. 3. " In the case of screw-steamers, the tonnage of the shaft tiunk shall be deemed to form part of, and added to, such space, and shall be ascertained by multijilying together the length, breadth, and depth of the trunk, and dividing the product by 100. " 4. In any ship in which the machinery may be fit- ted in separate compartments, the tonnage of each such compartment shall be measured severally in like man- ner, according to the above rules, and the sum of their results shall be deemed to be the tonnage of the said space." (r. ji — y.) 3 s II 1 1' ji 11 J.I) I m;. PLAT/: // ■'j.s.-1'u.'i/ . o-'- . --/' '■■■ — ftiblishcd W A.i *" Biads Edinliiir^ SHIP Hril.DINf^'- Dmiuilit «r ihr M'lHKln, CLIPPEIi SHIP SrHOWt'i<(' /'""'' ''Jl ■''''■■ ■ iH''ii\-c"„r,-i,,,„i,.„ I'UTK m. )'l'Ill(]|),ll BhUl'USlOUS I 2HL' <• ■J I '. 8,V 2.V I.%- liODY I'LAX l.'-iu/lh hclw.,rit thr /',.,/,,, „fc«iA"» l.rnifth of h'rrl hf»:aiith E.vt/ynu 7.7 JSrva/ith of I'tvnu- 42 Depth of Bold 2n ■ U Burtheji it, Ttm.i /hii/./.'t-s /tiifauu/vmf/>/ i'fiOfi Tons MiKSini' SKrTKKX ^ BODY I'LA.N' MliT n ^on SHIP BCILDINC. BBAUGHT OF the IBON CLIPPER .SAfUNG-miP "WBJJ of the /SM'S." Itisplacemcur lull IWII DWi uw^i PLATE fV LiG 122 IIB 114 110 106 10_' 98 9'1- 90 8li «_' 78 1- 10 6 Eeet If & 10 SO 30 40 30 "^ HALF BREiVPTH PLAX ,l„k,dV'->'-''"'"*>fcWo I 1^ SHIP iniLDIN^'- THK EXGLISn SAILIXG-YJCJIT "TFTAXW Bij J.Sr.mHiiastU. t'MS. I'LATi: V S.-.nliv « ii"l' '■'■■' '■■""I O ( SHIP BUILDING. THEMIS, (formerly TITANU) Euglisli Sailing Yacht Btj J. Scott Russell FRS. pj.iTi-: r; ^i-v Bo'ly '■'"'■«■ BodF I*rincipal Dimensions Length, in. Load wtUer Wit 82 6' BrtaiUh, Exlrmie 19 ' Sfftlh at thf Sidr J4' e' Tonnaiif OM 99 Torts -T:H' ■• V.:.- _.L \ --N-- . ^ — .-^— . j i j . J J n .* IWih jWi V>- ^ "^ ""^ EtnlM * } SHI? BriLDTN^T- yilF .IMERICIX SAlLISa YACH'l' AMERICA PLATE VI. I'l.AX OF UORTZOST.U. WATEK I.IXKS pg===q rn ==: £ ^, ^ :.:^;.p: .r,\ '.h_ ■-^^■"^--: -._ 1 2,--'' '' 1---' 1«^._..^. -___:: i__ '■'-----■4---'-"'-' 1 __^ ;- scid.-, 8 iiifii i^ilgi — sii ?s lvl.u.t.ilo.lU.Wd, t.tah„d » KODY l»l.A3J "^^y^^. SHIP B ITILU 1 N G nHM'Girr of tuk paddle woekl stkam ship "okj/ta' HelontfifUf t/> th*' JWi . Sc fMenfuf Sf/'r/m jVar. C\9 PrmctiiaJ DiineiisioiiK jo. 0. Do fif kefl for fonnupe iSKP'ir Br>'iidth t'of Ttmna<fi: J:' "A • llepth in Miilskipif ffrsmi top nf k(A} '^h . C>. BiirUiat ill form N" /'JO'J h //orxey pnwet^ inontaiii.1) JOO . iinilders of Ou: Ship 'Uiamcs Iron Skip /fuJ^intf i Maimers of the- Machj/UT\- J.Pemi k S^n . ScaJe oi' UuFpl&cempTit r/.iTi; VII k 1 sht!i:r PL as. ^^m^ -J 1 L i.-.j:::: 5* IS 4Z II \I.I' ItltKADTll IM,A\ GJtKin-ui Sr. /yWr i.AP =4l Pnhl»b«lTT i *^ ''"*W>ui J DiiiieusiDUS nl' iJn' Uiill ivmith Hum reu/rr ,>f niiUff pn.tl /*. M.-m i.e/iifth tin ihf f'ppfr decJ^- hreatid, or Bull Hi-ni/ltJi over tlte PtiMlr hitxr.i flfifiht lt> undo- sidr of Upper iteek- Tormiiqe of Ship. fiia/der.T- olit mra.iurrmmr Displar^iifiit at .VI feet Dnwijht ft If - CM) f,!)2 s:' C> Ui> 5fi :• JJ.lHH) ton.i S H I 1' Br I 1.1) I N'<' "(;j{fi:AT i-:Asrj;/{K" stk.im s/n p. run: \iii . IHlill'llsilllls ,lf Iho M.lclllUIMV. Totiil S,v.fe [Hnrfr nntiiuuiJ II ,11 21- II Mi /I) 16m hiirm imo 261)0 _ so feet .45 SHIP JHTli.DIiVCr. (ilfEAT EASTERX'' STAAM SIIII\ ,, -J. .■/■ .s VERTICAL SECTIONS. PLATE !X. ijasc <£ CpperDeck .!•/ t'ffi Jrtuufht :iO feft Jiiniifht IS ftrt Jroiiifltt JX) I'er-I tIniiiJ/Tr/ ZS- IS. O I X s t sooo SCALE OF DISPLACEMENT. Asstaniiuf 35 Cuh. feet of Sail water to a ton . IS.ooo io.ooo Pai..iMi.a b-i AJtC.BUck:Eaiiibiir0i. -.sonoTons c Djim-nsuius. f, ;„ Ltn^th of Kf^ arul Kirv rwAr 3tS Breadth of fiemw {'F^clfwru-' Dtpt/i iifOild Ut-Vpar dfcJr Tannage . BiixUjr* ' old nini.n//vnuvt< . Hitrim' ftmrr, tupmuuii , Btal/ltra of Ship tmd Naehmtry. Mfa^fhaA tC^ t^ Grrttuu^ SHIP B r 1 L I) I N t- DILirCIlT Ol' TIIK SntKW STEAM SllfPS lilUlMKS" ASD W'EW YORK: PL.ITE X . Scale of Displnccnent- 1500 2000 IIALK BHK.VDTH p ,_ I'uWi^lieil tn A ■ K BODY PLAN SHIP BUILDING. DRAUGHT OF THE SCREW STEAM SHIP "PER A'. liflnnfjintf to the I'm ,\- Onpriinl Sttui/n Sii^' I " Prinripal Dimensions Lfnijih lirtwrrn Perpend i/rular.i D? of Kaei for Tonnage Breadth, for Tannagr Df^th in, Midships (iram. top of Keel ) Burthen- iji Ton.t N?* ^622 -if- O.M. BiiUdnv of tjie Ship. Mtire it C? MllktTS of Ote MftcJrinn-u . (i H-J.Reiune . Ferf In'. :w:i a -A2 I 29 2'/, Scale of Displacfnicnl _Z'7^/or*wiOT/ per /nrh fit^ lhts_l>npitfhr 21 Tons SHEEK PLAN ITH 17» ITO I«e I0< UB IB* ISO 14« 1*2 ISB IS«- 1!>0 13fi 122 HB U+ UU 106 102 a« B> 80 7« 7 2 es G4- BO 66 6! *S *♦ 40 80 S2 28 S* 20 hiLlwilu'd V-A-ftC Shu^ Fii" J SHIP Brii'i>i^^ nn.iiGjfr oi- tiik scrrk steam shjp "yvBj.r BELOKCmO TO THE PENINSULAS AND OBlENTAl. STEAM NAVIGATION C? v. l'/..ITK SJI . for loruiin^ I)imt'nsious. 1\ Ml 320- 292.2 firt^aiitA. tiir ti/imiMn jO ■ O i of ffoM th'm r^jlina t4> spar deck 27 9 T»nn'H^ ■ f^tuJ^rtf ntd mea.vummgnt ftcna) 22'M.fi J.f^if/ ftmuffht or natrr IS .JO Dmplni^ment 'U Uxui -firuufffu (twm ) 7808 Aryj uf ntttMiip ^^fW*^* «/ /Sft JOm (sg. Ft } 550-0 //••rvff.jf-povef ^nomtn'tJ t ffwrse^) -tSO . /iuiliifr ff tJif Sht/> John. /.turd. fOrhfnhfoid ■ O \ SHIl- H LI LI' INC.. DUArc.iir til' THE iitox sciiKW sri-.iM t^iiii' cjn/.oy' I'l.ATK XIII. Sial<- ,il' Dis|j|:ir,-nn-nt TJODY PLAN, «;!T;f Bttrfh.-n in tons .1"' 237:1 s^f-. fiJl Htirsi's pinwr f/inntf/i't/ J •h50. Builders i>t' tJir Ship. Samutli\ .t CI ALiATff 'ifth€ Marfunrry. llunipfuy.-.- H-Tennfint , HEER l>I,AX [nx{'l"->r'ii.tif 'It Iff. .V ih^iutpht. -Jin" t-iit. __ _ ufiJer Side ^ heel a: Jikiiiii'i .*f-/'«l*"T c SIIII' BUILDING.. (' K Y 1,0 X. Dnniiihl 1)1' InliiHiriJ H'd/'/.-.v. I- LATE XIV V^^ hiUislied by A&C Black. Edinliiirgh STEAM XAVK; AT I X. SIDE LEVKJf MAIi/.\J: ILXfllXK. J^LATJ-: XV I § ^ ^ s s I a "5 I o o ^ ^ b -^" t! ^ ^ J =^ ~? ■^ ■o •< c — ^ cc i :§ STEAM NAVIGATION. ENGINES OE STEAMERS CALLAO.LIMA Sc BOGOTA. 320 Horse Power. PLATE XXI FKOXT ELEVATION. Publinhed hy A.&C.Bhidc. Edinburgh. :s s £ ^ 1 ^ d § ii' ^ ^ ^ o a^ >-H '^ H 5! •< 5: s 1— 1 r- Vo <^ ^ ^ ^ g <j tq '^ S rO ft W S5. •5 STEAM .NAVIGATION STEAM SHIP JJELTJ Pl'lTE XT/V 1 i)r,.ii, :■:' I ScaU J.li. !.inli I I'uol Pu!)!uVd bv tjrf Black Eaiiihut . '. s 5 ^ I ■3 I f : UNIVERSITY OF CALIFORNIA LIBRARY Los Angeles This book is DUE on the last date stamped below. JUL 2 1958 JUN 1 8 DPHO JUN 2 3 RECD t tB 2 1 13041 FEB 2 5 RCC^^ OCT 3 RECEIVED DEC 1 5 Z001 ARTS LIBRARY 1 S ^it'^ JUL 1 1364 JUN 1 6 REClfe Form L9-100m-9.'52(A310S)444 \963 S 2 6 RECD FEB 1 7 1370 FEB 13 RECD NOV 4 19?o ■'■^\^ 4 RECm Xli^ Library Via )4^ ■ ! mr 'ilil <M II III III 1 D 000 374 857 i University of California ^SOUTHERN REGIONAL LIBRARY FACILITY 405 Hllgard Avenue, Los Angeles, CA 90024-1388 Return this material to the library from which It was borrowed. r'^ M ( I ( ■. M (