RUDIMENTARY TREATISE ON THE MARINE ENGINE, ' AND ON Sbtearn Iftssds, anb hereto ; By ROBERT MURRAY, C. E. EEJitlj fillustratums. Double Part — Price Two Shillings. LONDON : JOHN WEALE. U fluv.of m. L ? bra ry Digitized by the Internet Archive in 2016 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/rudimentarytreatOOmurr FEONTISPIECE. SECTION OF STERN OF SCREW VESSEL IN THE ROYAL NAVY, SHOW- ING THE TRUNK OR A PORTION THROUGH WHICH THE SCREW IS RAISED OUT OF WATER WHEN DISCONNECTED. RUDIMENTARY TREATISE ON MARINE ENGINES STEAM VESSELS; TOGETHER WITH practical Ifamadis ON THE SCREW AND PROPELLING POWER AS USED IN THE EOTAL AND MERCHANT NAVY. By ROBERT MURRAY, C.E. SECOND EDITION. EonBon : JOHN WEALE, ARCHITECTURAL LIBRARY, 59, HIGH HOLBORN. MDCCCLII. LONDON: STEVENS AND CO., PRINTERS, BELL-YARD, TKMPLE-BAR. PREFACE. In adding a treatise on the Management of Marine Engines to Mr. Weale’s Series of Rudimentary Works, the Author trusts that it may prove a useful auxiliary to the various classes of practical men interested in the per- formance of our Steam Marine, whether in the Royal Navy or Merchant Service. Desirous of being under- stood alike by the non-professional man of business, who from his desk in the city controls the operations of a fleet of steam ships, as by the humblest assistant in the duties of the engine-room, he has endeavoured to express himself in as concise and matter-of-fact a manner as possible, avoid- ing as far as may be the use of technical language and mathematical demonstration, without attempting, at the same time, to render the text intelligible to the wholly uninitiated, by perplexing it with notes and explanations which ought to suggest themselves to every one acquainted with the rudiments of mechanical science. Some very es- sential Tables of the details of Engines and Vessels are added in the Appendix ; and such technical terms as do necessarily occur will be found explained in the Glossary at the end, and several corrections made in this second Edition. March 10 th, 1852. CONTENTS. CHAPTER I. GENERAL DESCRIPTION AND VARIETIES OF THE MARINE ENGINE. A previous acquaintance with the principles of the steam engine presupposed ..... General description of the marine engine Its varieties of form .... The fly-wheel inapplicable .... Consequent necessity for combining two engines on one shaft Single engines are sometimes employed High-pressure engines rarely used . The side-lever engine : its advantages . Ditto, ditto : its disadvantages Adoption of the direct-acting engine Varieties of the direct -acting engine Shortness of stroke a defect The steeple engine . . . . The double-cylinder engine .... The oscillating engine .... Machinery for screw propulsion . Internal gearing Protection of the machinery from shot . 1 1 2 2 3 3 4 4 6 6 6 13 13 13 15 16 16 17 Till CONTENTS. CHAPTER II. DETAILS OF THE MARINE ENGINE : THEIR PROPORTIONS AND USES. PAGE The steam pipes ....... The throttle valve The expansion valve Stephenson’s link-motion applied to give expansion How to set the slide valves The lap of the valve The lead of the valve ...... Reversing the engines Expanding by means of the lap of the valve The blow- through and snif ting valves . Clothing the cylinder, &c Clearance of the piston ..... Priming or escape valves Packing for the piston The condenser The injection valve Temperature of the condenser .... Elasticity of watery vapour at different temperatures Velocity of flow of the injection water The barometer gauge Ditto, sources of error An improved barometer for the condenser Evils arising from the use of sea water for condensation Surface condensation attempted and found ineffective Hall’s patent condensers The air pump The feed pumps The bilge pumps The hand pump connected with the large engines Ditto, driven by a supplementary engine or “ donkey” 18 19 19 21 21 22 23 23 24 25 25 25 25 26 26 26 27 27 27 28 28 29 30 30 31 31 31 32 32 32 CONTENTS. IX CHAPTER III. THE MARINE BOILER : ITS GENERAL PROPORTIONS, AND THE PRINCIPLES CONCERNED IN ITS OPERATION. PAGE Peculiarities of the marine boiler . 33 The flue boiler ....... 33 The form of the flues . 33 The arrangement of the heating surface . 33 Horizontal heating surface the best . 34 Bottom heating surface inefficient 34 Disadvantages of flue boilers .... . 35 Tubular boilers ...... 35 Furnaces ..... . 35 Fire bars ....... 36 The direct impact of the flame to be avoided . . 36 The bridge ....... 36 The water spaces . 36 Requisite amount of heating surface 37 Areas of flues and tubes 38 A roomy furnace desirable ..... . 38 Combustion is checked by the carbonic acid . 38 Loss of heat attending the combustion of the inflammable gases 38 Formation of carbonic oxide .... . 39 Smoke-burning apparatus . . 39 Recapitulation 40 Clothing marine boilers is sometimes found to be prejudicial 40 Bedding the boilers 41 Galvanic action to be guarded against . . 41 Copper boilers compared with iron ones . . 42 I CONTENTS. CHAPTER IV. THE MARINE BOILER: MANAGEMENT OF THE FIRES. PAGE The skilful management of the machinery necessary for its efficiency . . t 43 Economy of steam is the main question ... .43 The generation of heat in the furnaces 43 The management of the fires .44 The effects of mismanagement 44 Feeding the furnaces >44 Clearing the bars 45 Keeping the fire doors shut . . . . . . .45 Levelling the fuel 45 Each watch to leave their fires clean . . . . .46 Forcing the fires is expensive of fuel 46 The cinders to be reburnt when practicable ... .46 Superior economy of large boilers 47 The boiler-power is subdivided into sections . . .47 How to manage the boilers when full steam is not wanted . .47 Lord Dundonald’s experiments on slow combustion in marine boilers 48 Experiments with a tubular marine boiler in Woolwich Dockyard 48 Dimensions and description of the experimental boiler . . 49 Dimensions of the boilers of the Janus . > . . .50 Table of these experiments .51 Slow combustion in marine boilers is seldom practicable . . 52 Regulation of the draft .52 Banking-up the fires 52 To get up the steam rapidly .53 No water to be thrown in the ash pits 53 CONTENTS. XI CHAPTER V. THE MARINE BOILER: MANAGEMENT OF THE WATER AND STEAM. PAGE Regular supply of water to the boilers ... .54 The water level must not rise too high . . . . .54 Water gauges ........ .55 The glass water gauge 55 The brass gauge cocks . . . . . . .56 Only one feed pump to be worked . . . . . .56 Amount of the brine abstracted . . . . . .57 Proportions of salt in sea water from different localities . .57 Analysis of deep sea water . . . . . . .57 Blowing-off 58 The brine pumps .58 Lamb's blow-off apparatus 58 The refrigerator .59 Attempts made to supersede blowing-off 59 by mechanical means .60 by chemical means 60 The brine pumps found to be perfectly efficient at a trifling ex- penditure of fuel .61 Salinometers .......... 61 The thermometer used as a salinometer . . . .61 The hydrometer ditto, ditto ...... 63 Seaward's salinometer .64 Cases in which the amount of blow-off may be diminished . 65 How to manage in case the blow-off cock sets fast . . .65 The safety valve, its area . . . . . . .65 Ditto, its manner of loading ... .65 Ditto, occasional defects 66 How to manage in case the safety valve sticks fast . . 66 Steam gauge 67 The vacuum, or reverse valve .67 Supply of air to the fires 68 Staying boilers at long distances is very objectionable . . 68 Xll CONTENTS. CHAPTER VI. MANAGEMENT OF THE ENGINES. PAGE The bearings require attention . . . . . . .70 How to test the tightness of an engine before starting . .70 How to discover a leakage of air into the engines . . .71 How to cure leaky condensers . . . . . .72 The injection to be diminished when the ship labours much . 72 How to act when the injection cock leaks ... .73 Advantage derived from the bilge pipes . . . . .73 Injecting through the snifting valves .... .73 How to make steam-tight joints ...... 74 How to act in case of accident to the engines . . .74 The test cocks 75 The grease cocks . . . . . . . .75 Moving the engines round by hand . . . . .75 Galvanic action . . . . . . . . .76 Essential to have square regulating lines marked on marine en- gines ........... 76 To adjust the paddle shaft . . . . . . .77 To replace the levers on the valve shaft if carried away . . 77 To fix the gab lever on the valve shaft . .' . . .78 To find the length of the excentric rod if carried away . . . 78 To replace the stops on the intermediate shaft for driving the ex- centric 78 Essential to know the position of the steam valves from ex- ternal marks 79 CONTENTS. Xlll CHAPTER VII. USE OF THE EXPANSION VALVE, INDICATOR, AND DYNAMOMETER. PAGE The principle of expansion 80 The benefit derived from expansion . . . . .81 Rule for calculating the power of an engine working expansively 82 The indicator, its construction and principle . . . .83 The indicator scale .85 How to use the indicator 85 How to make the calculation .86 How to find the nominal horse power of an engine . .86 Distinction between the nominal and indicated horse power . 87 Use of the indicator for showing the internal state of the engine . 88 How to compare the efficiency of different engines by means of the indicator 89 Example of the calculation for ditto . . . . .91 Difference of effect between throttling the steam and cutting it off by the expansion valve 92 The dynamometer : its nature and application . .94 The counter 95 CHAPTER VIII. ON THE QUALITIES OF FUEL, WITH HINTS FOR ITS SELECTION. On the qualities and value of different coals . . . .97 Much depends on the construction of the boiler . . .97 Wicksteed’s experiments .97 M. Cave’s experiments 98 The parliamentary experiments ; description of the boiler used . 98 Management of the coals on the fire .... .98 Patent fuels, their advantages and defects . . . .98 Rapid corrosion of iron coal bunkers .... .99 The gases evolved from coal during exposure to the atmosphere . 100 Natural decay in coal . . . . . . . .100 Spontaneous combustion in coal .101 Advice in the selection of fuel 101 XIV CONTENTS. PAGE All the good qualities are never united in one coal . .102 Wood used for fuel in steamers . . . . .102 Turf used for fuel in steamers .103 CHAPTER IX. CONSIDERATIONS AFFECTING THE RATE OF CONSUMPTION OF THE FUEL IN A STEAM VESSEL. Importance of regulating the rate of consumption of the fuel . 104 Steaming against the stream .104 Natural law affecting the speed of a steamer . . . .104 Limit imposed to the possible speed . . . . .105 How to find the speed corresponding to a diminished consump- tion of fuel 105 How to find the consumption of fuel corresponding to an in- creased speed Relation existing between the consumption of fuel and the length and velocity of the voyage Economy attending a diminished speed in the vessel Assistance derived from the sails of a steamer . On disconnecting the engines 106 106 107 107 108 CHAPTER X. PROPORTIONS TO BE GIVEN TO THE PADDLE WHEEL AND SCREW PROPELLER, AND THE MANNER OF THEIR APPLICATION IN THE VESSEL. Varieties of the paddle wheel 109 Variable immersion the grand objection . . . .109 The most advantageous immersion or dip . . . .110 The slip of the paddle wheel 110 Explanation of the table of velocities of paddle wheels given at the end of the book .110 The area of the paddle boards Ill Braithwaite’s plan of disconnecting the paddle wheels . .111 Maudslay's plan for ditto . . . . . . .113 Seaward 5 s plan for ditto 113 The screw propeller 113 CONTENTS. XV PAGE The pitch of a screw .114 The slip of a screw . .114 Anomaly in its performance, called “ negative slip ” . .114 Dragging of the screw . . . . . . . .115 Disconnecting the screw . . . . . . .116 The propelling power of the screw 116 Explanation of the term i( screw-blade w 117 To find the pitch of a screw blade . . . . . .117 Introduction and progress of the screw propeller . . .118 Varieties of the screw propeller 120 Woodcroft’s screw . . . . . . . .120 Ericsson’s propeller 121 Maudslay’s feathering screw . . . . . . .122 Hodgson’s parabolic propeller . . . . . . . 124 Macintosh’s elastic propeller . . . . . .125 Comparison of the flexible propeller with the action of a fish . 125 In the application of the screw, fine after-lines are indispensable 126 Diameter of screw 127 Area of the screw 127 Relative value of coarsely or fine pitched screws . . .128 Extent of slip of the screw . . ... . . . 128 CHAPTER XI. COMPARATIVE MERITS OF THE SCREW AND THE PADDLE WHEEL. How to compare the general efficiency of different steam vessels 129 Ditto, for commercial purposes 129 Example No. 1 . 130 Example No. 2 131 Ditto, for scientific purposes .131 Example No. 1 132 Example No. 2 . 132 Comparison between the screw and the paddle wheel as a means of propulsion . . . . . . . .132 General view of their respective efficiency for full-powered pas- senger steamers 132 Efficiency of the screw for full-powered steamers of war . .133 Efficiency of the screw as an auxiliary in sailing vessels . .133 XVI CONTENTS. PAGE The success of the screw as an auxiliary in men-of-war . .134 The effect that auxiliary-screw vessels may have on the shipping interests of the country . . . . . . . . 134 Joyce’s iron steam ship, City of Paris 134 Pasha of Egypt, steam yacht Kassed Kheir 135 Of the spiral propeller or water-screw 136 CHAPTER XII. SCREW STEAMERS IN THE ROYAL NAVY AND MERCHANT SERVICE. The screw in H. M. service — full-powered vessels . . .138 Rattler — her best experiment .138 Fairy — dimensions and speed 138 Termagant — dimensions and particulars . . . .139 Encounter — dimensions and particulars 139 Arrogant — ditto, * ditto .140 ,, trials 141 La Hogue — steam guard ship .141 Ajax — ditto ditto 141 The use of screw vessels as tugs .142 The screw in the merchant service . . . . . .142 Performance of the screw in the vessels of the Gen. Screw Steam Shipping Company 144 Performance of the screw of canals 144 Bosphorus — dimensions and particulars . . . .145 ,, voyage under steam from Cape of Good Hope to Plymouth . 145 . Rattler — dimensions of vessel . . . . . .146 ,, epitome of 14 experiments .... . 146 „ thrust on the dynamometer 148 ,, loss of speed attending the use of the expansion gear . 150 ,, power consumed in driving her machinery . .150 Dwarfs experiments .151 Screw steamers on contract mail steamers . . . .151 Table of screw steamers and their machinery . .153 CONTENTS. XVII CHAPTER XIII. THR PADDLE WHEEL AND PADDLE-WHEEL STEAMERS IN THE ROYAL NAVY AND MERCHANT SERVICE. PAGE Paddle-wheel steamers in the royal navy ..... 154 Terrible — dimensions and particulars . . . . .154 ,, machinery 154 ,, speed, armament, and daily expenses . . . 155 Sidon — particulars .156 Odin — particulars, machinery, &c .156 Performance of government steamers with and without steam . 158 A high speed in the navy attainable only by an extravagant pro- portion of horse power to tonnage 159 Comparisons between the performance of government and mer- chant steamers are generally imperfect . . . .160 Economy of steam power is the best criterion of efficiency in the navy .......... 160 Performance of Inflexible in a steam voyage round the world . 161 Economy of a moderate proportion of horse power in combina- tion with the sails . • 163 A high proportion of horse power is requisite in the merchant service 164 Considerations to be attended to in proportioning the horse power to the tonnage in designing a new vessel . . .165 Banshee — dimensions and particulars . . * .166 Paddle-wheel steamers in the merchant service . . . .167 Asia — dimensions and particulars . . . . .167 Orinoco — ditto, ditto 168 Minerva — dimensions and particulars 173 Estimate of the number of merchant steamers . . .173 Ditto, of steamers in the Royal Navy . . . .173 Ditto, of steamers in the French Navy . * . .174 Ditto, of French merchant steamers 174 of registering paper used in trials of Government steamers 174 Speed of the vessel . • 175 XV111 CONTENTS. APPENDIX. PAGE Table No. I. — Admiralty formula of specification for marine engines, with paddle wheels .183 Tender to the Admiralty for a pair of steam engines of 260 horses power, with paddle wheels . . . . .187 List of tools and spare gear required with those engines . 189 Table No. II. — Admiralty formula of specification for marine engines, with screw propellers .... . 190 Tender to the Admiralty for a pair of steam engines of 450 horses power, with screw propellers . . . .194 List of tools and spare gear required with those engines . 195 Table No. III.— -The principal dimensions of 194 steamers of all classes, with paddle wheels . . . . .197 Table No. IV. — The principal dimensions of 28 merchant steamers, with screw propellers 202 Table No. V. — Paddle-wheel steamers in Her Majesty’s Navy and Post-Office Service 203 Table No. VI. — Experiments with H.M. screw tender — Dwarf . 205 Table No. VII. — Screw steamers in H.M. Navy, No. 1, vessel . 206 Ditto. Ditto, No. 2, propeller and proportional numbers 208 Ditto. Ditto, No. 3, engines .... 210 Table No. VIII. — Proportions of marine engines and boilers . 211 Table No. IX. — Form of log for a sea-going steamer, No. 1 . 213 Ditto. Ditto, No. 2 .214 CONTENTS. XIX PAGE Table No. X. — Velocities of paddle wheels of different diame- ters, in feet per minute, and miles per hour . . .215 Table No. XII. — Economic values of different coals . . 218 Ditto. Mean composition of average samples of the coals 220 Ditto . Amount of various substances produced by the destructive distillation of certain coals . . .221 Table No. XIII. — Temperatures and relative volumes of steam of different densities 222 Table No. XIV., used by Admiralty in calculating speed of vessels .223 Sir John Macneiirs report on screw steam boats for canals . 225 Glossary of terms connected with marine engines and boilers (with translations into French) . ..... 231 THE MARINE STEAM ENGINE. CHAPTER I. GENERAL DESCRIPTION AND VARIETIES OP THE MARINE ENGINE. A previous Acquaintance with the Principles of the Steam Engine presupposed . — As this little work professes to be a guide to the management of marine engines and steam vessels, and not a treatise on the steam engine, it will be necessary to presuppose a certain degree of knowledge of the facts and mechanical principles on which the structure and operation of steam engines depend. In short, to take it for granted that the reader has perused either Dr. Lardner’s Rudimentary Treatise, in this series,* or some other work on the same subject. This being understood, we shall proceed at once to the consideration of the marine engine of the present day, as it is found in vessels of the Royal navy and merchant service. General Description of the Marine Engine . — The princi- ples upon which the marine engine is constructed, as well as its general plan of operation, are identical with those of the stationary or land condensing engine ; the motive power * Rudimentary Treatise on the Steam Engine, by D. Lardner, LL.D. John Weale, is. B 9 GENERAL DESCRIPTION AND in both being derived from the pressure of the steam acting against a partial vacuum. Thus we have in each case a boiler to generate the steam ; a cylinder , piston , and valves to use it ; a condenser in which to condense it, and thereby gain the pressure of the atmosphere by causing the steam to work against a vacuum ; and lastly, an air pump to with- draw the condensing water, the condensed steam, and the uncondensed vapour, and gaseous matter. Such are the principal parts of every condensing or “ low-pressure 99 steam engine, whether it be used on land or at sea ; whether it be side-lever, direct-acting, oscillating, horizontal, or rotatory. Varieties of Form . — The terms last used are those em- ployed to designate different forms of the marine engine which have been imposed upon it by wants and necessities of various kinds. For as the services which steam vessels are called upon to perform are very different, so also must be their machinery, in order to suit the required form and displacement of the hull, the minimum draught of water, the comparative value of stowage, or of passenger accom- modation, the necessity of protection from shot, the effi- ciency of the armament, and a hundred other considerations which may enter into the plans of a steamer. In all marine engines the required object is to give a ro- tatory motion to a horizontal shaft — either the paddle shaft in the case of paddle-wheel steamers, or the screw shaft in the case of vessels propelled by the screw. The earliest form of engine used for this purpose was the side-lever, or beam engine, in which the reciprocating motion of the piston rod is transferred through upright side rods and horizontal side levers to the connecting rod, which then gives the shaft its continuous rotatory motion by means of the crank. The Fly Wheel not applicable. — If such an engine were VARIETIES OF THE MAEINE ENGINE. 3 used to drive machinery on sliore it would be furnished with a fly wheel, which, by becoming a reservoir of momentum, would supply power to continue the rotatory motion past the top and bottom of the stroke, where the crank is evidently (from its nature) powerless, and in this way a uniform speed would be maintained throughout each revo- lution of the shaft. But in the case of a vessel at sea, the fly wheel is inadmissible. Considerable irregularity in the revolutions results from this want, but not to such an extent as to be attended with any bad results. In some engines where the moving parts are not arranged so as to balance each other in their ascent and descent, one part of the stroke is made at a greater velocity, but this is generally obviated by admitting a greater quantity of steam on one side of the piston than on the other, until the propelling power for the up and down strokes accords with the resistance. The air-pump bucket is generally arranged in such a manner, that by its ascent it may balance the weight of the piston in the cylinder in its descent. Necessity for combining the Engines . — Hence arises the necessity for supplying the place of the fly wheel by com- bining two engines on one shaft, in such a manner that when the one engine is at its least effective point (at the top or bottom of the stroke) the other engine may be most effective — each alternately helping the other over its diffi- culties. Single Engines sometimes employed. — Biver steamers, how- ever, are occasionally fitted with only one engine, the moving parts of which are “ balanced” (by means of a cast- iron paddle board, or otherwise) in such a manner as may best assist the crank in passing the centres ; but such an arrangement is always objectionable from the difficulty experienced in starting, and from the impossibility of pre- B 2 4 GENERAL DESCRIPTION AND venting a disagreeable jumping motion in the vessel from the unequal speed at which the paddle wheels are driven. High-pressure Engines rarely used . — High-pressure en- gines are very rarely put into steamers in this country, the objections to their use being their increased consumption of fuel in comparison with condensing engines, and the presumed danger to passengers arising from explosion or escape of steam, which has made them extremely unpopular. As they possess, however, the countervailing advantages of cheapness and lightness, they have been adopted in some cases where economy of fuel is not so much considered as first cost and light draught of water. "While referring hereafter to the marine engine, it should be understood that the condensing engine alone is meant. Side-lever Engine — its Advantages. — It has been said that the side-lever engine was the first employed in steam boats. This construction, with the arrangement of which the reader is doubtless familiar, has several advantages which enabled it for a long while to resist innovation. Perhaps its chief merit consists in this, that the weights of the moving parts are so balanced, the one against the other, that the piston when not acted on by steam is nearly in equilibrio, and equally ready to start in either direction with the smallest application of force. The great length of the connecting rod, also, admits of the motion of the piston being trans- mitted to the crank in the most equable and effective manner, and the moving parts of the engine are supposed to do their work with less friction and wear than are to be met with in any other kind of engine. It can hardly be wondered at, therefore, that the side-lever engine was long a favourite, and indeed that it still continues to be so in certain cases, and under certain conditions. An example of a side-lever engine is given in Plate 1. PLATE I.* VARIETIES OE THE MARINE ENGINE. 5 * For examples, see Tredgold on the Steam Engine, new edition, Division B, Marine. John Weale. 6 GENEBAL DESCBIPTION AND Disadvantages of the Side-lever Engine . — There are two very important conditions, however, in the economy of a sea-going steamer which the side-lever engine does not fulfil — namely, lightness of weight, and compactness of form. As these properties were found to be most essential in the machinery of a war steamer, it soon became apparent that some other arrangement of parts must be adopted which would admit of the same power being stowed in less com- pass, and a portion of the weight of the machinery saved for additional coals, or stores, or armament. Adoption of the Direct-acting Engine. — Hence the adapta- tion and general use of direct-acting engines in the Eoyal Navy, by which means (in conjunction with the adoption of tubular boilers) the length of the engine room was di- minished by about one third, and the total weight of machinery by two fifths. It may be observed here, that the weight usually allowed for side-lever engines, flue boilers with water, and paddle wheels, is one ton per horse power ; whilst direct-acting engines with tubular boilers and water, paddle wheels, &c., scarcely exceed 12 cwt. per horse power. The distinguishing feature of all direct-acting engines con- sists in the connecting rod being led at once from the head of the piston rod to the crank without the intervention of side levers : and as it happens (unfortunately, we think) that this kind of engine is capable of almost endless variety, each manufacturing engineer has introduced his own child into the steam navy, where scarcely two pairs of direct- acting engines are to be found alike. Varieties of the Direct-acting Engine. — These may be all classed under three heads ; namely, those which obtain the parallelism of the piston rod by means of the system of jointed rods called a “parallel motion;” those which use guides or sliding surfaces for this purpose ; and those de- nominated “ oscillating engines,” in which the cylinder is VARIETIES OE THE MARINE ENGINE. 7 liung upon pivots and follows tlie oscillations of tlie crank. Belonging to the first class are those of Seaward, Bennie, Fairbairn, Forrester: and to the second class, Maudslay, Miller, Fawcett, Boulton and Watt, Bury, Bobert Napier, Joyce, &c. As these various arrangements cannot be ren- dered intelligible in words, sketches of some of the most characteristic are subjoined, in Plates 2, 3, 4, 5, 6, and 7. PLATE IL j Direct-acting Engine , as constructed by Messrs. Seaward, Capel & Co.* * See pages 8 and 9 ; and for full details of the engines of the Cyclops see the Appendices to Tredgold. John Weale. 8 GENERAL DESCRIPTION AND Direct -Acting Engine of 500 H. P. of H. M. S • Bull-Dog, constructed by Messrs. Rennie. VARIETIES OE THE MARINE ENGINE, PLATE V. Elevation of Main-lever of Parallel Motion of H. M. S. Cyclops. B 3 JO VARIETIES OF THE MARINE ENGINE. It. Murray , del. IT A 'tfTVTVT VARIETIES OE THE MARINE ENGINE. 11 R, Murray , del. 12 REKEEAL BESCBIPTIOX A2CD Marine 'Engine of the Rainbow Iron Steam Vessel , constructed by Messrs. Forrester & Co., Liverpool „ See Appendices to Tredyold. John Weale. VARIETIES OF THE MARINE ENGINE. 13 Shortness of Stroke a Defect , — The unavoidable shortness of the stroke and of the connecting rod in the majority of direct-acting engines is certainly a defect, and becomes sensible in practice by the increased wear and tear of brasses and packings, and a greater consumption of tallow and oil when compared with the old side-lever engines. Several of the direct-acting varieties, it is true, are not ne- cessarily confined in the length of stroke — as, for instance, the “ steeple engine,” which is such a favourite on the Clyde. Steeple Engine . — The latter derives its name from the high erection on deck required by the guide to the connect- ing rod, which works above the crank shaft, and can be recommended only in the case of river steamers where the increased height of the centre of gravity, and the increased surface exposed on deck to the action of the winds and the waves, are not so detrimental as would be the case in a sea- going steamer. See page 12, a successful example. She made, notwithstanding, very rapid passages between Lon- don and Antwerp. Double-cylinder Engine — Maudslay and Field’s double- cylinder variety also makes a good engine, and may have a tolerably long stroke and connecting rod, but for small powers it is heavy and expensive. It also occupies more space in the engine room than several other kinds of direct- acting engines ; but for very large powers, where the excessive diameter of a single cylinder may be considered objectionable, it appears to be most applicable, and has in- deed proved itself to be highly efficient. See Plate 9. GENERAL DESCRIPTION AND 14 PLATE IX. Direct -acting Double -cylinder Engine as constructed by Messrs. Maudslay, Sons & Field.* * See Tredgold on the Steam Engine, new edition, Division B, Marine Engines. John Weale. VARIETIES OF THE MARINE ENGINE. 15 Oscillating Engine . — Of all the direct kinds, however, the oscillating engine, which has derived from Mr. Penn so much of its elegant simplicity and present perfection of workmanship and arrangement, is generally preferred. It need hardly be explained that this engine derives its name from the fact of the cylinders “ oscillating ” upon hollow axes or “trunnions,” through which the steam is ad- mitted to, and withdrawn from, the valves — the piston rod by this means accommodating itself to the motion of the crank without any “ parallel motion” being required. This construction has now been proved as applicable to ocean steamers as to the small boats on the Thames, where it has long been a favourite ; and it appears to be also well adapted for driving the screw propeller. See Plate 10. PLATE X. Oscillating Engine as constructed by Messrs. John Penn & Son.* * See Tredgold on the Steam Engine, new edition, Division B, Marine Engines. John Weale. 16 GENERAL DESCRIPTION AND Machinery for Propulsion by the Screw . — The introduction of the new mode of propulsion by the screw has created the necessity for new modifications of the marine engine ; and as it is essential for the due performance of the screw pro- peller that it should revolve with a considerable velocity, it has been deemed necessary to employ gearing or straps, in many instances, to multiply the speed of the engines. The use of toothed gearing being objectionable, however, in sea- going vessels, from the liability of the teeth to be stripped or deranged by sudden shocks received by the screw in a rough sea, it is preferred to attach the engines directly to the screw shaft in all cases where the required speed of the screw renders this practicable. This can be readily accom- plished when a great speed is not expected from the vessel, as in the case of auxiliary steam power ; or where a long pitch in the screw, and a moderately short stroke in the en- gine, permit the requisite number of revolutions. For it is evident that the piston in an engine having a three-feet stroke will make twice the number of reciprocations per minute that it does in an engine with a six-feet stroke, sup- posing the actual speed of the piston to be the same in each case. Hence it is usual to subdivide the power of large screw engines amongst a number of small cylinders, all at- tached directly to tho same screw shaft, and making short and frequent strokes. "Where gearing cannot be dispensed with, toothed wheels are preferable to straps. Internal Gearing . — "With the view of affording additional security against accident, Mr. Eairbairn has introduced into a large pair of screw engines for the BoyalNavya system of internal gearing, where the small pinion on the screw shaft is driven by teeth on the internal periphery of the driving wheel attached to the engine. The advantage of this plan consists in the greater number of teeth which are thus brought into gear at one time, so that the strain is divi- VARIETIES OE THE MARINE ENGINE. 17 ded amongst several , in place of being wholly transmitted through one tooth. . Protection of the Machinery from an Enemy's Shot . — So long as the paddle wheel continued to be the propelling agent, it was plainly impossible to devise any means by which the machinery could be protected from an enemy’s shot ; but the recent adoption of the screw propeller has facilitated this very desirable object to the navy. For as the screw itself revolves entirely beneath the surface of the water, we are now enabled to place all the machinery which gives it motion under the water line also, (in some cases, so much as six or eight feet,) by which means it gains a comparative though not perfect safety. It is well known that a shot will not penetrate more than a foot or two under the water unless it meet the surface at a high angle, but then the bottom of a vessel at sea must be often exposed, during both the rolling and pitching motion, to a position considerably beneath the level water line, when an enemy’s shot would have a fair mark at the machinery, although in smooth water it might be perfectly protected. The addi- tional security, however, which such machinery does enjoy renders it a question of the utmost importance to dispose the engines and boilers of a screw-propelled vessel quite under the water line. Hence another plea for the practice of subdividing the power of large engines amongst a number of small cylinders, these being ranged (generally in a hori- zontal position) on either side of the screw shaft, so as to require as little height as possible for the reciprocation of their moving parts. The boilers are also made as low as practicable, and if a steam chest be added, provision should be made for shutting it off from the rest of the boiler in case of injury, the steam being in that case drawn directly from the top of the main boiler. 18 CHAPTEE II. DETAILS OE THE MARINE ENGINE: THEIR PROPORTIONS AND USES. Although it is not here contemplated to supply rules and formulae for proportioning the marine engine, a few remarks are made upon such proportions as the officer in charge of the engines may he able to alter or modify for himself if found necessary. Steam Pipes . — The steam pipe from the boiler must not be too contracted, otherwise the pressure of the steam upon the piston moving in the cylinder is not kept up during its stroke, the steam being then what is called “wire- drawn” in the pipes. The usual area allowed to the steam pipe is one square inch per horse power, but this may be increased with advantage in the case of small engines. It is of much importance that the pipes should have as short and direct a route as possible from the boiler to the engines, with few angular bends or changes of direction, as all such impediments act most injuriously by checking the supply of the steam. Where bends are unavoidable, they should be made of as large a radius as convenient. Much care must also be taken to prevent the loss of heat by radiation, and the consequent condensation of steam in the pipes, which should therefore be clothed with sheets of hair felt wrapped round with spun yarn, the whole being sewn up in canvas, and painted. Copper is the only material which should be used for steam pipes between the boiler and engine, as wrought-iron pipes gene- rate scales of rust which, becoming detached, are blown by the steam into the valves and cylinder, where they do DETAILS OE THE MA11INE ENGINE, ETC. 19 much mischief by scratching and cutting the surfaces. When a straight pipe forms the connection with the boiler, an expansion or “fawcett” joint must be provided, but this may be dispensed with when an elbow occurs in the length of pipe. Throttle Valve.— The throttle valve of a marine engine is always worked by hand, and should be used only in control- ling the speed of the engines for any temporary purpose, such as in passing through a crowded river, before stopping at a pier, &c., but should seldom or never be used for work- ing the engines expansively at a permanent reduction of speed. Expansion Valve . — This latter object is effected by the expansion valve, which should be fitted to all sea-going steamers. It usually derives its motion from the crank 20 DETAILS OF THE MARINE ENGINE: shaft of the engine, the valve spindle being connected by a series of rods and levers with a small brass pulley, which presses against the periphery of a graduated cam on the crank-shaft, by which means the steam is “ cut off” in the most advantageous manner at any required portion of the stroke. The valve employed is usually of the description called the “ Cornish double-beat,” or “equilibrium valve,” which has the advantage of being opened and shut with great facility, since, from its construction, the pressure of the steam has no tendency to jam it against its seat — the objection to which all flat or plate valves are subject. Also THEIR PROPORTIONS AND USES. 21 by a slight rise of this valve, a very large opening is obtained for the steam. This will be best understood by reference to the annexed engraving. The principle on which this valve is constructed is, that if steam be conducted by a branch pipe into a larger perpendicular pipe between two common conical valves placed in it, and connected together by a centre spindle or rod, and resting on their seats, it would exert a pressure on the under side of the upper valve, tend- ing to raise it ; and on the upper side of the lower one, tend- ing to keep it down ; these two pressures in opposite direc- tions thus neutralizing each other. It is therefore evident that these two valves form one double-seated valve, and may be opened in equilibrio , by means of their spindle. The steam then passes up one pipe and down the other, and, if desired, these pipes may be again immediately united. By the pecu- liar arrangement of the seats and partitions, this is done inside the outer casing of the valve, as shown in the engraving. Stephenson* s Link Motion applied to give Expansion . — A modification of Stephenson’s elegant and simple link motion for locomotives has been adapted to the marine engine, by which means the length of stroke of the cylinder slide valves may be varied at pleasure, so as themselves to act also as expansion valves ; but as their motion is derived from an eccentric of the usual form, it has a different character from that produced by the cam in the former instance ; the admission and exclusion of the steam now taking place more gradually, and, as is generally admitted, with less effect. To set the Slide Valves . — The manner of setting the cylin- der slide valves so that they shall admit and shut out the steam from the cylinder at the proper time, independently of the action of the expansion valves, is a matter of the greatest importance. The chief points to be attended to are these : 1st, that the steam shall be shut off a little before the end of the stroke, by closing the aperture of the steam port, which causes the piston to be brought gradually to rest without 22 DETAILS OE THE MABINE ENGINE: jarring the engine, independently of the advantage derived from expanding the steam ; 2nd, that the eduction port, or the passage to the condenser, should be closed before the end of the stroke, which is termed “ cushioning” the piston, because it then completes the stroke against an elastic air cushion , in consequence of a portion of uncondensed vapour being shut up between the piston and the top or bottom of the cylinder ; 3rd, that the steam port on the same side of the piston should be opened a very little before the end of the stroke, so that the steam may have acquired its full pressure as soon as the crank shall have turned the centre ; and, 4th, that the communication with the condenser should also be opened on the opposite side of the piston a little before the end of the stroke, so as to have a vacuum ready made in the cylinder before the return stroke begins. “Lap” of the Valve . — Now, if the slide valves had simply to admit and shut off the steam at each instant that the piston arrived at the top and bottom of its stroke, the face of the valve would have exactly the same depth as the aper- ture to be covered ; but that the steam may be cut off a little before these points, it is necessary that the valve faces should be made deeper towards that side from which the steam comes, so that after closing the steam ports they may move past the aperture for a certain space at each end of the stroke. This space, which they lap over the valve seat- ing, is called the “lap” or “cover” of the valve on the steam side. It is apparent that no lap is necessarily re- quired on the exhaust side, because we want the communi- cation with the condenser to open before the end of the stroke. The general practice on this point is to make the edges of the valve faces flush with the edges of the cylinder ports, when the valves are placed exactly in the middle of their stroke. The objection to lap on the eduction side is that the communication between the cylinder and the con- denser will be closed too early, and the effect termed cush- ioning will take place to an injurious extent. The uncon- THEIR PROPORTIONS AND USES. 23 densed vapour is compressed sometimes even to such an extent as to exceed in pressure the steam in the boiler, and an erroneous opinion has then been formed in examining the lead corner of an indicator diagram that the valve has been set to open too soon. In these cases after due exami- nation the cover on the eduction side should be cut off. By means of the lap , therefore, we are enabled to shut out the steam, and to open the passage to the condenser before the end of the stroke. But it is also necessary that the port should open to steam on the opposite side before the commencement of the return stroke. “Lead” of the Valve . — Steam is admitted to act upon the piston before it has quite completed its stroke, by giving the valve a motion in advance of the crank. The extent to which the port may be open for the admission of steam, when the engine is on its top or bottom centre, is varied much, but an allowance of one square inch of opening to every sixteen horses’ nominal power, will be found to give good results. In all engines where the velocity of the piston is greater, the lead may be increased beyond this extent with advantage. With common slide valves driven by an eccentric great breadth of port is evidently desirable, as a slight motion of the valve then gives at once a greater area of opening.. Reversing the Engines . — If marine engines were required to work only in one direction, the eccentric pulley might then be permanently fixed on the paddle shaft, (as it is on the fly shaft of a land engine,) in the most advantageous position for lead , &c . ; but as a steamer must be equally ca- pable of reversing the motion of the wheels, such an ar- rangement becomes unsuitable. Bor let us suppose that the engine has been stopped at half stroke in the usual way, by throwing the eccentric out of gear and shutting off the steam, and that steam has been admitted by hand to the opposite side of the piston, the shaft will then com- mence revolving in the opposite direction. But it is evi- 24 DETAILS OF THE MARINE ENGINE : dent that before the engine can be thus put into the proper position for enabling the eccentric to continue the reversing motion, the shaft must be free to rotate backwards within the eccentric pulley through half a revolution. Hence a necessity arises for placing the eccentric pulley loose upon the paddle shaft, the latter being fitted with a “ stop ” or “ snug,” with which another “ stop ” cast on the pulley comes into contact after half a revolution in either direction, and thus communicates motion to the valves with perfect indifference as to which end of the eccentric stop may be in contact. Expanding by Means of the Lap on the Slide Valves . — It is apparent that the lap of the slide valve presents a simple method of working the steam expansively to a small though definite extent, which is then fixed beyond the power of alteration until the valves are reset. The amount of ex- pansion which can be thus given, is limited by the effect produced upon the eduction port as before mentioned. It is, however, objectionable to carry expansion by this means to the full extent to which it is practicable, from the fact that when the vessel is placed in the most difficult cir- cumstances, struggling off a lee shore, with the speed of herengines reduced by a head wind, so that there is an abundant supply of steam, there are then no means of com- pletely filling the cylinders, and the full amount of power capable of being generated cannot be realized. The most beneficial practice therefore, when the common slide valves are used, is to have only a small amount of lap, so that it may be possible to obtain the utmost power that the engines are capable of exerting at such times as it may be essential, and to have an additional valve for regulating the amount of expansion to such extent as may be desired. The latter system is in accordance with the growing intelligence of those now generally entrusted with the working of marine steam engines. An excessive and wasteful expenditure of steam under circumstances when a corresponding result cannot be obtained from it need not be feared with a good superintending engineer on board, as so much interest has THEIR PROPORTIONS AND USES. 25 of late been excited not only amongst those parties, but also amongst commanding officers, on this most important point. Blow -through Valve. — Before the engines can be started it is necessary that the air should first be expelled from the cylinder, condenser, and air pump, and its place supplied by steam, in order that we may obtain a vacuum by its subsequent condensation. Hence a valve, called from its office the “ Blow-through valve,” is provided to open a temporary communication between the steam in the valve casing and the condenser, by which means a rush of steam is caused to pass through the internal parts of the engine. This operation is continued until the steam begins to issue, hot and transparent, from another valve on the condenser, called the “Snifting valve,” situated at the opposite point from wffiere the steam entered. These valves are of course closed as soon as the engine is set to work. Clothing the Cylinders , Sfc. — As it is of much importance that the internal heat of the cylinders and valve casings should be preserved from radiation (especially when high steam is used expansively) these must be carefully clothed with felt and dry timber, bound round with metal hoops. Clearance of the Piston. — The “clearance ” of the piston at the top and bottom of the stroke should be just as little as is consistent with safety, and is usually made from one half-inch to five eighths or three fourths of an inch. Priming Valves. — “Escape” or “ Priming valves” are now generally fitted to the top and bottom of the cylinder, to permit the escape of water without danger to the machinery from the shock of the piston against the incompressible fluid. This water collects partly from the condensation of steam within the cylinder, but is chiefly carried over from the boiler, either as “ priming,” or in a state of mechanical suspension with the steam. It may also overflow through the valves from the condenser. These valves should be C 26 DETAILS OF THE MARINE ENGINE: fitted with hoods to carry off the ejected water into the bilge, and prevent its being thrown about the engine room. Packing for the Piston . — Metallic packing is now univer- sally employed for the pistons of marine engines, this being made in the form of cast-iron rings, either possessed (from their construction) of elasticity in themselves, or deriving it from steel springs placed behind them. The cast-iron rings, unfortunately, lose their elasticity after being some time in use, in which case they must be taken out, and have this restored by hammering and thereby elongating their internal surface; or else steel springs must be added to press them out against the cylinder, when they are cut into segments to allow the springs greater freedom of action. The piston is lubricated with melted tallow through a grease cock on the cylinder cover, advantage being taken of the vacuum during the up- stroke to suck in the tallow. The grease-cock aperture also serves for applying the “Indicator” during the stroke above the piston. Condenser . — The condenser should have a capacity of half the cylinder as a minimum , but may be made larger with advantage. The size should depend, to a certain extent, upon the temperature or density of the steam used, as plenty of room should be allowed for high steam to expand into low-pressure steam before being condensed, if this has not been previously effected by expansion within the cylinder. Injection Valve . — The area of the injection valve should be about one square inch for every ten-horse power. This is an ample allowance in all cases, and is more than neces- sary when the injection water has a temperature of 52° Fahr. (which is the average for our seas), though in tropical climates it will not be found too much. The average tem- perature of the Mediterranean is about 65°; at 20° of latitude, about 75°: and at the equator, about 82°, Fahren- heit. The supply may be regulated at will by the opening THEIB PROPORTIONS AND USES. 27 given to tlie valve, as shown on an index plate. It is better in the case of large engines to have two injection cocks fitted between the sea and each condenser — one, the sea cock , close to the side of the vessel, as a security in case of injury to the internal pipe, and the other upon the con- denser. Besides these, it is usual to have an injection pipe led from the bilge of the vessel, so that in case of unusual leakage the sea cock may be closed, and the engine sup- plied with injection from this source. The mouth of this pipe should be carefully guarded and kept clean, as when the emergency arrives for its use it has too often been found choked up and unserviceable. Temperature of the Condenser. — The process of condensa- tion will be the more complete in proportion to the cold- ness and quantity of the injection water, the manner in which it is brought into contact with the steam, and the temperature of the steam itself on entering the condenser. The resulting temperature which is usually aimed at by engineers for the condenser is from 90° to 1 10°. The limit to a more perfect degree of condensation is imposed by the increased size of the air pump required to withdraw the additional injection water, which diminishes the work and increases the cost of the engine. Hence the engineer is well satisfied if the temperature of the condenser be not above 110°, with which a vacuum of 27i or 28 inches of mercury is obtained by a good engine. Elasticity of Watery Vapour at different Temperatures . — According to Dr. Ure’s experiments, uncondensed watery vapour at a temperature of 100° balances 1*86 inch of mercury ; at 110°, 2*45 inches; at 120°, 3*3 inches; at 130°, 436G inches ; at 140°, 5*77 inches; and at 150°, .7*53 inches Of mercury, or exerts a pressure of 3? pounds per square inch. Flow of the Injection Water . — The velocity at which injection water enters the condenser varies as the square C 2 28 DETAILS OP THE MARINE ENGINE : root of the pressure, and will be about 40 feet per second for the full pressure of the atmosphere against a pure vacuum. The sea injection should be taken from about mid-way be- tween the surface of the water and the bottom of the vessel, so as neither to draw impurities from the surface, nor be liable to become choked with sand or mud from the bottom, when working in shallow water, or when the vessel is aground. In many of the latter cases, the engines have been rendered useless at the time when most needed, by sand being sucked in and destroying the action of the air pump. Barometer Gauge . — A barometer gauge is attached to the condenser to show the vacuum. It is usually constructed like a common barometer, except that the top of the glass tube communicates through a small pipe and cock with the interior of the condenser, the partial vacuum of which then takes the place of the Torricellian vacuum of the ordinary barometer. The surface of the column of mercury in this case indicates the difference which exists between the pres- sure of the atmosphere and the pressure in the condenser, so that if we see a column of 27 inches of mercury sup- ported in the tube, and the pressure of the atmosphere at that time be 30 inches of mercury, we know that there is a pressure of three inches of mercury, or lb. on the square inch within the condenser. Sources of Error . — As we find by the common barometer that the pressure of the atmosphere is constantly varying, a correction should be made for this in estimating the va- cuum of the condenser. Another source of error arises from the varying level of the mercury in the open cup which supplies the gauge tube, according as the tube be- comes more or less filled ; since it is evident that only that portion of the column which rises above the surface of the mercury in the cup can be reckoned as the counterpoise to the atmosphere. The simplest manner of alleviating the last- mentioned source of error is to make the surface of mer- THEIR PROPORTIONS AND USES. 29 cury in the cup very large in comparison with the bore of the tube. As the barometer gauge is very often found to show incorrect results (either through ignorance or design on the part of the foreman who saw it fitted) it would be well if every commander of a steam vessel satisfied him- self of its accuracy, before giving credence to such wonders about vacuum as are sometimes published to the world. Improved Barometer for the Condenser . — Subjoined is a sketch of an improved barometer for the condenser, which has been tried and found useful. A glass syphon tube, a a , 34 or 35 inches long, is half filled with mercury ; one end at h being left open to the atmosphere, which is ad- mitted through a very small aperture to exclude the dust. A sliding brass scale, graduated from 0 at the bottom to 30 inches at the top, is fitted in the space between the two legs of the inverted syphon. When required to show the vacuum, the zero point of the scale must be shifted to where the mercury falls in the leg open to the atmosphere, and the height of the mercury in the other leg being then read off from the scale, the exact difference of height between the two columns is thus obtained. This baro- meter posesses also the advantage that the mercury cannot be blown out by a slight pressure of steam in the condenser (as is the case with the common barometer), which ad- mits of its being kept in constant use as a guide to the engineers in stopping and starting their engines in any time of difficulty. The sy- phon may be made, if preferred, by uniting two straight glass tubes in a short piece of bent iron pipe. 80 DETAILS 0E TILE MAItlNE ENGINE: Evils arising from the Use of Sea Water for Condensation. — The use of sea water for condensing the steam and sub- sequently feeding the boilers, entails upon marine engines the necessity for ejecting, or “ blowing off ” a portion of the saturated water, at intervals, into the sea, to prevent the deposition of scale and salt, and causes the loss of a con- siderable quantity of caloric. The specific gravity of the salt water in the boiler, taken at a medium degree of saturation, is about one-tenth part greater than that of fresh water ; and as the capacity of the water spaces requires to be in- creased to allow for cleaning, as well as for the more ready escape of the steam through the denser fluid, we may add about one fifth for the extra weight of salt water in the boiler as compared wflth fresh, taking into account the portion which is blown off. "When we consider also the very rapid wear of boilers using salt water, it is at once ap- parent that an efficient means of supplying them with fresh water at sea is one of the greatest desiderata in marine engineering. Surface Condensation attempted. — With this view, many attempts have been made to condense the steam by con- tact with cold metallic surfaces, instead of by the plan of injecting amongst it a large body of salt water from the sea. Could this be done effectively, the boiler might then be fed, during the whole voyage, with the fresh water which it had at starting ; the same water, after circulating through the cylinder as steam, being condensed without intermixture with other water in the condenser, and then returned to the boiler to be again formed into steam, being thus kept in a continuous round of action. Surface Condensation found to be Inefficient. — But, unfor- tunately, the principle of surface condensation has hitherto always proved inefficient. The difficulty has generally been to present a sufficiently large cooling surface to the steam, so as to produce a rapid condensation. TIIEIR PROPORTIONS AND USES. 31 1 Tail's Condensers . — This cannot be urged against Hall’s Condensers, however, in which the steam is passed through many miles of little copper pipes enclosed in a cistern of cold water, which is constantly renewed from the sea by means of a force pump worked by the engine, but in this case the small pipes through which the steam is passed are liable to become “furred” on the outside, or choked up al- together by deposits from the sea water. Besides this, the additional machinery required adds so much to the expense and intricacy of the engine, as well as to its weight and the space it occupies in the vessel, that this condensing appara- tus has not been found applicable in practice. In such an arrangement the loss of steam arising from leakage, or from blowing off at the valves, is compensated to the boiler by the use of a small apparatus for distilling sea water. The air pump is then, of course, much reduced in size, as it has no injection water to remove. Air Pump . — The capacity of the air pump is usually pro- portioned to the cylinder as 1 : 8, or thereabouts ; and the delivery valve has an area of one third of the air pump, though the orifice through the ship side for the escape of water from the hot well need not be more than one sixth of the area of the air pump, when the latter is single-acting. In large engines, a sluice valve is usually fitted inside the vessel across the mouth of the discharge pipe at the ship side, which being closed by hand when the engines are not working prevents the wash of the sea from enteiing the hot well. Feed Pumps . — The feed pumps supply to the boiler so much of the water which has been used in condensing the steam as will restore the waste from evaporation and blow- ing-off, and each of the two feed pumps which are usually fitted up is made sufficiently large to supply all the boilers in case of accident to the other pump, or to its feedpipes. The 32 DETAILS OF THE MARINE ENGINE, ETC. necessary quantity to be admitted to the boiler is judged of by observing the level in the glass water gauge, and is regu- lated by hand by means of the feed cock on each boiler — the surplus water, which is rejected by the boiler, being expelled into the sea by the feed pump through a loaded escape valve. Bilge Pumps . — Bilge pumps are fitted to marine engines as a security to the ship in case of extraordinary leakage, as well as to save the work of the crew in pumping the hold dry. The bilge pipes should be made of lead, which suffers less corrosion than copper from the acidulous bilge water of wooden ships, and care must be taken that they do not get choked with filth. Hand Pump connected with the Engines. — A hand pump must also be fitted for the purpose of feeding the boilers while the engines are at rest and the steam blowing off. This is made capable of being connected to and driven by the engines, so as either to assist in feeding the boilers, if necessary ; to act as a fire engine in case of need ; or for the every-day duty of washing decks. It should also be so ar- ranged that it may draw either from the sea or the bilge. II and Pump driven by a Supplementary Engine. — In the case of vessels with tubular boilers this pump usually receives its motion from a small high-pressure engine (technically known as “ the donkey”) which works by the pressure of steam in the large boilers. Such a provision becomes ne- cessary on account of the rapid evaporation of tubular boilers in comparison with their confined area at the water level ; but in the case of flue boilers, where the water sur- face is comparatively larger, and danger from the water level falling too low during a temporary stoppage is there- fore diminished, this pump is generally worked by hand S3 CHAPTER IIL THE MARINE BOILER : ITS GENERAL PROPORTIONS, AND THE PRINCIPLES CONCERNED IN ITS OPERATION. The Marine Boiler . — The Marine Boiler differs from one on shore in this essential particular, that, in the former, the fire and flues are wholly contained within the boiler itself, and are surrounded with water in every direction, — such an arrangement being rendered necessary as a precaution against fire. There are several varieties of this boiler in use, designated the Blue boiler, the Tubular boiler, the Sheet-water-space boiler, &c. Flue Boiler. — In the Blue boiler, the flame and hot gases generated in the furnace are confined in narrow flues, w r hich wind about amongst the water of the boiler until the heat of their contents has been nearly all absorbed ; after which, the flues are gathered together into the “up-take,” at the bottom of the chimney. Form of the Flues. — They should be so roomy as to allow of a boy getting readily through them to clean out any deposit of soot or ashes ; but their area must not be unduly increased in any one place, so as to check the velocity of the draft, as in that case a deposition of soot and ashes invariably takes place, by w r hich the heating surface is not only impaired, but the plates are corroded and destroyed. Arrangement of the Heating Surface. — It is a point of the utmost importance that no part of the heating surface of a boiler should be so situated that the steam may not readily C 3 34 TIIE MARINE BOILER: rise from it, and escape to the surface of the water ; since the plate, if left in contact with steam instead of water, becomes unduly heated and destroyed, and an explosion frequently ensues. Horizontal Heating Surface the best . — It is found in prac- tice that a perpendicular heating surface, such as the sides of rectangular flues, is by no means so efficient for raising steam as an equal area of horizontal surface, such as the tops of the same flues or of the furnaces. The reason of this is sufficiently apparent ; for the steam in the first case, rising perpendicularly from every portion of the surface, forms a film or stratum of vapour in contact with the sides of the flue, which prevents the free access of the water to the hot metal ; but, in the other case, the steam leaves the iron as soon as it is generated, and allows the water to be constantly in contact. Bottom Heating Surface inefficient . — Trom the same cause of imperfect contact, the flat bottom of a metal flue is very inefficient as heating surface ; and plates thus disposed are found to wear out much quicker than those forming the tops of flues or fire boxes. The plan of covering the bottom of the flues with a non-conducting material, as bricks or cement, has been found to cause hardly any diminution in the evaporative power of the boiler, and is by some thought to increase the durability of the bottom plates. The objection to this plan is, that from the unequal de- grees of expansion between the iron and the non-conducting lining, it is impossible to maintain an unbroken joint be- tween their surfaces, so that a space is formed in which brine may collect in contact with the plates, and thus do more mischief than the original disease. The flues generally increase a little in height as they recede from the furnaces, in order that the depth of water GENERAL PROPORTIONS AND OPERATION. 35 over them may be less in proportion as the contained air is cooler. Disadvantages of Flue Boilers. — Although flue boilers occupy at least one third more space in the vessel than tubular boilers of an equal evaporative power, and are nearly one third heavier, they are still preferred in some instances (as on board the West India mail packets), as being more economical both with regard to first cost, re- pairs, and durability. It is hardly believed, however, that these qualities, if really possessed, are not more than coun- terbalanced by the increased consumption of fuel neces- sarily attending any increase in the displacement of the vessel, as well as in the loss of so much valuable space for passengers, goods, or stores. Tubular Boilers . — In tubular marine boilers, the flame and hot gases from the furnaces are led through a great number of small tubes (of iron or brass), completely sur- rounded with water, to the flue or “ up-take” at the bottom of the chimney. By this arrangement we are enabled to condense a very large amount of “heating surface” within a comparatively small space; and in consequence of the extreme subdivision of the heated gases in passing through several hundreds of tubes not above three inches in dia- meter, every particle of them is brought into contact with the absorbent surface, and their caloric is thus extracted in the smallest possible time. Furnaces . — The furnaces, or “ fire boxes,” should be so deep as to allow of a roomy ash-pit under the doors, the front of the grate bars being fixed at a height of about 30 inches above the firing stage, and sloping down with an inclination of about two inches to the foot towards the u bridge.” 3G THE MARINE BOILER: Fire Bars . — The bars are best made of wrought iron in several lengths of about 30 inches each, to suit the length of the furnace, which should not exceed to 7 feet. The bars may be made from five eighths to three quarters of an inch thick on the top edge, about three inches deep, and may have from three eighths to seven sixteenths of an inch of air space between each for Welsh coal, though these dimensions should be modified according to the nature of the fuel it is intended to burn. No open space should be left between the outer bars and the sides of the furnace, as it is expedient to check the formation of flame at that part, in order to protect the plates from being “ burnt.” The direct Impact of Flame to he avoided . — It should be borne in mind that the direct impact of flame is very much hotter than radiant heat, and the plates of a boiler should be protected from it as much as possible. This forms a source of objection to many of the plans which have been proposed, or adopted, for burning the inflammable gases in the flues of a marine boiler by the admission of a jet of air, which too often acts like a blow-pipe by directing the flame thus generated against the plates. The Bridge . — The “ Bridge,” to which we have alluded, crosses the back of the furnace to support the ends of the fire-bars, and prevent the fuel being carried into the flues, and also tends to cause the flame to reverberate upon the roof of the furnace, although the construction of the boiler sometimes does not require it at all. It is either formed of fire-brick, or else constitutes a part of the boiler by being made hollow, and containing water, in which case the top of the bridge inclines at a considerable angle to allow tho escape of steam. Water Spaces . — The furnaces should be covered with 14 or 15 inches of water, and the tubes or flues with 10 or GENERAL PROPORTIONS AND OPERATION. 37 12 inches, in the case of sea-going steamers. The water spaces between the furnaces are usually five to six inches wide; and between the flues, four to five inches. The spaces between the crowns of the furnaces and the bottoms of the tubes should be not less than 10 inches, to allow of a “ man-hole” between the arched tops. The bottom water spaces should be not less than eight inches, to allow room for “ scaling” and cleaning. It is usual to allow a space of one inch between the tubes of a tubular boiler, these being arranged in perpendicular rows, one over the other, by which means the steam is supposed to escape more readily than when they are placed zig-zag. Although many of the proportions here set down are beyond the control of the officers in charge of a steam vessel, still we think it expedient to state, in as few words as possible, what proportions of engine and boiler are con- sidered by practical men to be most conducive to perfect efficiency. For unless a general knowledge of these pro- portions be acquired, it is plainly impossible to form a judgment as to whether any observed deficiency in the work of the engines is due to the fault of their original construction, or depends upon those details of management winch it is more particularly our present object to explain. And although it is but just to the talented constructing engineers of this country to assume, that in the majority of cases the machinery of a steam vessel leaves their hands in a perfect state, it is nevertheless most satisfactory to be enabled to prove this for one’s self. Requisite Amount of Heating Surface . — Before we can obtain a good average result from the combustion of the fuel, it is necessary that the boiler should present about twelve square feet of effective heating surface per horse power ; for if less surface than this be given, a wasteful quantity of heat escapes up the chimney, from not having been absorbed by the water. "What is termed “ effective” 38 THE MABINE BOILEB : heating surface, must he calculated independently of the bottoms of flues and fire-boxes, and of one fourth part of the whole tube surface. The grate-bar surface should be at least 80 square inches per horse power, and, where practi- cable, may be increased to 100 square inches with much advantage. Areas of Flues and Tubes. — The area of the first flue, or the clear area through the tubes, should equal one sixth of the grate-bar surface led into them ; and the area of the flues may be gradually diminished from the fires to the chimney by one fourth part. A Roomy Furnace desirable. — As a large furnace is found by experience greatly to facilitate the admixture of the gases, and to ensure their more perfect combustion, as well as to afford the most effective kind of heating surface, it is of great importance that there should be plenty of room over the fires. Combustion checked by the Carbonic Acid. — The carbonic- acid gas which results from the combustion of solid carbon, has a most injurious effect in checking combustion within the furnace, for we find by experiment that flame is barely supported in a mixture of one part of this gas with four of atmospheric air. Hence the necessity for admitting into the furnace at least twice the amount of air chemically required ; and even then, if we analyze the contents of the chimney, we shall find from one fourth to one-half of the oxygen which entered the fire still free and uncombined, mixed up with the products of combustion. Loss of Heat attending the Combustion of the Inflammable Gases. — How, as the whole of the air thus supplied in excess must be heated to a very high temperature before the combustion of the inflammable gases in the furnace GENERAL PROPORTIONS AND OPERATION. 2J can ensue, much heat is thus unavoidably wasted — so much, indeed, that it is now well ascertained that the evaporative value of a bituminous coal producing a large quantity of gaseous matter is very little, if at all, superior to the evaporative value of the same coal after being coked ; the heat generated by the combustion of its volatile pro- ducts proving, in practice, to be little more than that ex- pended in volatilizing them, and in heating the surplus air required for their subsequent combustion. t Formation of Carbonic Oxide . — When a stinted supply of oxygen is furnished to the incandescent fuel on the bars, an imperfectly oxygenated carbonic-acid gas, named u car- bonic oxide,’’ is partly produced, accompanied by a corre- sponding loss in the heat generated during combustion. As this gas is inflammable, and that at a comparatively low temperature, it may be burnt in the furnace, or flues, by the admission of a further supply of atmospheric air — otherwise, it escapes unconsumed up the chimney, where it may be often seen burning at the top, having caught fire upon coming into contact with the oxygen of the air. Although it may be beneficial to consume this carbonic- oxide, when once formed, by admitting fresh air into the flues behind the bridge, it is certainly preferable to pre- vent its formation altogether by using a large grate surface, a thin fire, and plenty of air space between the bars. Smoke-burning Apparatus . — Notwithstanding all that has been done and written with reference to the so-called “ smoke - burning” apparatus, it is the opinion of those most capable of forming a correct judgment on this subject, that by a proper construction of the furnace, and a skilful management of the fire, the smoke and gases may be as effectually, and certainly more safely, consumed, by admit- ting the requisite quantity of air for this purpose at once through the grate bars. THE MARINE BOILER: 40 Recapitulation . — It may be gathered from the preceding remarks, that some of the most important requisites to ensure efficiency in a steam boiler are the following: — 1st. That the boiler should be designed with a sufficient amount of heating surface, so contrived that as little of it as possible may be rendered ineffective, either from the retention of steam in contact with it, from the formation of scale within, or from the deposition of soot and ashes in the bottoms of the flues and tubes. 2nd. That the fire- bar surface should be sufficiently large to admit of the necessary quantity of coal being consumed with thin and open fires. 3rd. That the proper area be maintained through the flues or tubes, and that the passage to the chimney be such that the draft may not be interrupted. 4th. That the furnace should be roomy ; the bars thin, with plenty of air-space between them ; and, that the fires should not be longer than can be conveniently stoked. And, 5th (which is, perhaps, the most important requisite of all, and the one most neglected), That experienced and careful fire-men be provided. Clothing Marine Boilers , found to he sometimes preju- dicial. — Although it must be admitted that the practice of “ clothing” marine boilers with non-conducting materials, such as hair-felt, wood, &c., is in all cases highly beneficial for the production of steam; yet this is alleged to have induced, in some instances, a rapid wear in the plates of the boiler. This corrosion is most apparent in boilers which are frequently used and disused alternately, and takes place on the interior surface, attacking principally the top of the boiler and the steam chest. It is, probably, owdng to the alternate wetting and drying of the plates, which causes the rust to scale off, and thus present a fresh surface for corrosion each time that the water is blown out of the boiler. In the case of an unclothed boiler, on the other hand, the internal surface is scarcely ever “ quite dry,” GENERAL PROPORTIONS AND OPERATION. 41 from the evaporation being checked by the low tempera- ture, and the consequent saturation of the enclosed air. Marine boilers which are constantly in use, or which make long voyages only, do not experience this destructive cor- rosion of the steam chests to the same extent. Bedding of Marine Boilers . — The manner of bedding ma- rine boilers is a point of some importance, as it materially affects the durability of the bottom plates. The usual method adopted by the Admiralty, is to form a close plat- form of timber over the keelsons, upon which is spread a plaster of cement, or mastic, about one inch thick, on which the boiler is set. As this becomes quite hard, it prevents the bilge-water (which in wooden ships is highly acid) from washing up to and corroding the plates ; and it is also intended to stop any leaks which may break out in the bottom of the boiler, as well as to strengthen it in the event of an unusually rapid corrosion taking place from the inside. Unfortunately, however, it is impossible to preserve a close contact between the iron and the cement, on account of their different degrees of expansion by heat, so that when a leak does take place in the boiler, it extends itself for a large space between the two surfaces, and the corrosion is increased instead of diminished. Perhaps the best practice is to rest the boiler on saddles of cast-iron fixed on the boiler bearers, which leaves the bottom exposed for examination and painting, and even for small repairs if necessary. In this case the bottom of the vessel under the boilers must be kept quite clean and dry by the bilge- pumps. Galvanic Action . — It is necessary, both in marine engines and boilers, to guard against the destructive effects of gal- vanic action, which ensue in all cases where two metals of different degrees of solubility (or possessing different degrees of affinity for oxygen) are placed in juxtaposition ; 42 THE MAEINE B0ILEE, ETC. as, for instance, iron and brass, when the former metal suffers a rapid corrosion from being the more oxidable of the two, while the brass is quite protected. Copper Boilers . — In cases where the frequent renewal of boilers is attended with great expense and inconvenience, they are sometimes made of copper, which lasts about four times as long as iron. Their first cost, however, is about five times greater for boilers of the same weight, and cop- per is only three fifths of the strength of iron when cold, or less than half its strength at 500° Fahrenheit. Iron, on the contrary, increases in strength from 32° to 550°, when its strength is believed to be at a maximum . It is evident, however, that although a copper boiler is not so strong as a new iron one of the same weight, it retains its original strength unimpaired for a long time, whilst the iron boiler is every day becoming weaker by corrosion. An iron boiler, when new, has thus a great superabundance of strength, to allow for the wearing of the plates by use ; and it must on no account be forgotten, that a boiler which may show no symptoms of weakness on being first used under a pressure of 20 pounds on the square inch, may be very unfit to work at this pressure after a couple of years’ ser- vice. As copper conducts heat more readily than iron, in the ratio of 2*4 : 1, a copper boiler does not require so much heating surface as an iron one. Also, after tho copper boiler is worn out, the old material is still valuable, whereas the price obtained for the scrap iron is little more than what it costs to break up an old iron boiler. 43 CHAPTER IV. THE MARINE BOILER: MANAGEMENT OE THE EIRE9. The skilful Management of the Machinery necessary for its Efficiency. — Having endeavoured to show in a few words what the machinery of a steam vessel ought to be, we proceed to consider, in the next place, how it may best be used : for, notwithstanding all the talent and perfection of workman- ship which may be displayed by the constructor, it still rests mainly with those to whose care it has been entrusted whe- ther this costly machinery shall give satisfaction or not. Economy of Steam is the main Question. — The economical working of an engine evidently depends upon the quantity of steam which is required to do a given quantity of work, so that the whole question resolves itself into this, "how can we best save steam ? This question, again, naturally divides itself into two heads, which are really quite distinct, though too often associated together ; namely, the production of steam in the boiler, and its subsequent use in the engine — and we shall therefore consider those separately. The Generation of Heat in the Furnaces. — The economy of a steam boiler is again sub-divided into the generation of heat by the combustion of the fuel in the furnace, and the sub- sequent absorption of this heat by the water, as has been already commented upon. As the latter is beyond the con- trol of those in charge of the machinery, (except in keeping the surface of the flues and tubes as clean as possible,) we shall not further advert to it, but will pass on to the man- agement of the furnace. 44 TIIE MARINE BOILER: Management of the Fires. — The management of the fires on board a steam vessel affects the question of economy in the consumption of coal to so great an extent, that the im- portance of skilful firemen cannot be too much insisted upon. It is a great mistake to suppose, as too many cap- tains and owners of steam vessels do, that any able-bodied man who can throw coals on a fire is fit for a stoker : and under this false impression, sailors are frequently engaged, instead of regular firemen, “to stoke when required.” The only cases in which this should be allowed are, perhaps, in auxiliary-screw vessels, and in such vessels as may be ex- pected fco make a considerable portion of their voyage under canvas ; but even in such cases there should always be one well-trained fireman for each watch to have the charge of the other stokers. This man should be kept constantly at his post, and must not be liable to be called away while the vessel is under steam, except in cases of emergency ; and he should receive a higher rate of pay than the other stokers, if it were only for the purpose of giving him the necessary authority over them. Effects of Mismanagement. — Thus, many instances oi steamers are to be found at the present day in which the same quantity of coal is regularly burnt per hour, whether the engines are going fast or slow ; whether forty cylinders full of steam are used per minute, or only thirty. In such a case, one quarter of the fuel is thrown away through ig- norance of the despised art of stoking ; for the firemen may have either allowed the surplus steam generated to blow off at the waste-steam pipe ; or they may have thrown open the fire doors, by which means the steam is only prevented from being generated by the rush of cold air which takes place through the flues, while the same quantity of coal is burnt as before. Feeding the Furnaces . — Boilers of the proportions most MANAGEMENT OE THE FIRES. 45 usually adopted by constructing engineers are suited for the combustion of from 15 to 18 pounds of coal upon each foot of grate surface per hour. In applying this fuel, it is found most advantageous to throw on at one time a supply to last for about 12 minutes, the furnace door being opened in about eight minutes after the fire has been fed, to see how the coal is burning ; and if any part of the grate has burnt bare, a little coal must then be quickly and skilfully thrown over that place ; or should the coal appear to lie too thickly at any part, it must be levelled with the “rake.” Clearing the Bars .— In the case of a very bituminous coal it is often found necessary to open or break up the fire at this time, owing to the tendency of such a coal to cake on the bars, and thus prevent the passage of air through them; but this may be obviated to a certain extent by keeping the fires thinner with bituminous coal than would otherwise be desirable. Keeping the Fire Boors shat . — As it is of the utmost im- portance that the fire door should not be open longer than necessary, since the cold air which then rushes in acts most prejudicially and by absorbing heat from the flues, the experienced fireman will study to dress his fire, in the first instance, so as to demand as little interference as possible between the times for throwing on fresh fuel, or “ firing- up,’ ’ as it is termed. Levelling the Fuel . — The fires should be kept of a mode- rate and equal thickness throughout, and as the firemen are very apt to heap up coals at the far end of the bars, it is a good practice to make each set of men, before leaving their watch, lay the rake or pricker along the surface of each fire quite back to the end of the furnace, in order to find whe- ther the thickness of the fuel is uniform or not. Should any of the fires then want dressing, the firemen under 46 THE MARINE BOILER: whose charge they are should be forced to remain until those fires have been brought to a regular and proper thickness. Each Watch to leave their Fires clean. — It is the general practice for each set of men on first beginning their watch to clean their fires and clear the bars of all clinkers or vitreous matter, according as each fire burns down for the first time after taking charge. By this means the men are made responsible for the condition and efficiency of their own fires during their watch; and before leaving, they should clear out the ashes from the ash pits, collect the cin- ders to be re-burnt, and throw the refuse overboard. Forcing the Fires is expensive of Fuel . — If it is found that the boilers do not generate the requisite supply of steam, it will then be requisite to urge the fires to a greater extent by the frequent use of the “ slice,” which is inserted from under- neath between the bars, in such a manner that the coal is raised and broken up, and a larger supply of air is per- mitted to pass through. It is evident, however, that in this case a considerable waste must ensue from cinders falling through the bars into the ash pit before they are thoroughly consumed, and these cinders cannot now be again thrown on the fire, because it is necessary that the combustion should be as bright and active as possible, in order to “ keep the steam/’ The Cinders to he re-burnt when practicable . — Hence this valuable fuel is thrown overboard ; but in well-constructed boilers of sufficient capacity for the easy supply of the en- gines, a considerable economy will result from carefully separating the cinders from the ash and re-burning them. When using Welsh or other coals that are easily broken, it becomes of special importance that the fires should be allowed to burn regularly, without being frequently broke up or disturbed, for as these coals contain a large proper- MANAGEMENT OF THE FIEES. 47 tion of small and dust, this would be entirely lost by falling through the bars were the fires much worked. When, on the contrary, this small coal is thrown over the fire and allowed to cake, it then becomes available ; but as it deadens the fire when first thrown on, this cannot be done unless the boilers are large enough to generate a sufficient supply of steam with “dead” or slow-burning fires. Superior Economy of Large Boilers. — Hence arises a prin- cipal source of economy from the use of boilers of ample capacity to generate the steam without the fires being un- duly disturbed, and it is believed that on this ground alone can the alleged superiority of slow over rapid combustion be maintained, in cases where the flue surface is supposed sufficient to absorb all the heat generated. The Boiler Power is usually subdivided into Sections. — In large steam vessels the boiler power is usually subdivided into three or four sections, each independent of the other, and capable of being connected together, or disconnected, at pleasure. In such vessels it frequently happens that the full steam power is not required, so that a fourth part, or even a half of the steam which the boilers are capable of generating, may be dispensed with. When this is the case it is the usual practice for the engineer to disuse either one or two of the boilers altogether, urging the remaining sec- tions so as to make them generate the full quantity of steam of which they are capable. How to manage the Boilers when full Steam is not wanted. — It is now recommended, however, that instead of disusing one of the three or four boilers, they should all be kept in use, the fuel being burnt slowly and equally upon the fires. By this means not only will the fuel be used more economi- cally in the furnace, but an additional advantage will be derived from the flue or tube surface (in a marine boiler alwavs more or less insufficient), which will now be enabled 48 THE MAUINE BOILER: to absorb more of the beat generated. In like manner, where one half of the steam power is sufficient, one only of the four sections should be disused. This is considered preferable to using all the four in such a case, as it is dif- ficult in practice to carry out the system of slow combustion to its extreme limits;, because, when small quantities of coal are spread over the fires at long intervals between, they are apt to burn into holes and admit the entrance of jets of cold air, which rob the flues of their heat. If, how- ever, the engineer in charge can surmount this difficulty either by skill in managing the fires, or by bricking over a portion of the grate surface in each fire (which is perhaps the best mode of proceeding), he might then continue to use all the four boilers with decided advantage. Lord Dundonald's Experiments on Slow Combustion in Ma- rine Boilers. — The beneficial results which may be obtained from slow combustion, combined with large absorbing sur- face, in a marine boiler, have been clearly proved in a series of experiments conducted by Lord Dundonald, to whose in- ventive genius in mechanics, and steady perseverance in carrying out his projects, every engineer w T ho has been brought into contact with him must bear evidence. The weight of water evaporated by one pound of coal in marine boilers of the usual proportions varies from eight to ten pounds, whereas in those constructed by Lord Dundonald for the “Janus,” 12*9 lbs. were evaporated. This high re- sult was attributed by his lordship to the more effectual burning of the coal by “ slow combustion,” combined with a peculiar arrangement of the flues and tubes constituting the absorbing surface of the boiler, which, it must be kept in mind, was nearly double the size usually allowed for the supply of the same quantity of steam. Experiments ivith a Tubular Boiler in Woolwich Dockyard . — To form a comparison with these results, therefore, the furnaces of a common tubular boiler, such as are used in MANAGEMENT OE THE EIRES. 4 0 the Royal Navy, and which was at the time lying in Wool- wich dockyard, were partially bricked up — the absorbiog surface remaining the same as before. The result now ob- tained was quite equal to that from the boilers of the “Janus,” although the rate of combustion per square foot of grate-bar surface was more rapid in the case of the Wool- wich boiler. It is evident, therefore, that this boiler, when altered, was in precisely the condition into which marine boilers, not required to generate their full quantity of steam, may and should be brought by the engineer in charge, whenever the occasion presents itself. In the above in- stance, a saving of about one third of the fuel was thereby effected, although, as a necessary consequence, the quantity of steam which the boiler was capable of producing in a given time was diminished to nearly one half. The experiments above referred to are of considerable value, as indicating the economy of slow combustion on the bars of a marine boiler (when this is practicable), as well as the relative effect on the evaporative power of the boiler produced by a progressive diminution of the grate-bar sur- face, as will be seen from the subjoined table. Dimensions and Description of the Experimental Boiler . — The boiler experimented upon was an eighty-horse tubular marine boiler of the ordinary construction, with horizontal tubes over the furnaces. Its extreme measurements were 9 ft. long by 8ft. 6 in. wide, covering an area of 7 6J sq. ft. in the vessel, or *956 sq. ft. per horse power. It had 8 fires, each 8 ft. by 2 ft. 2 in., affording 98*6 sq. in* grate surface per horse. The total “ effective heating surface, after de- ducting one third for the bottoms of tubes, was estimated at 13 sq.-ft. per horse power. There were 176 iron tubes, each 3 in. outside diameter and 6 ft. long. The boiler was 12 ft. 2 in. high, and the furnaces 2 ft. 10 in. high. Capacity for steam was 167 cub. ft. Total space occupied by the boiler, 761 cub. ft. Total evaporating surface in the boiler estimated at 1057 sq. ft. D 50 THE MAEINE BOILEE : Dimensions of the Boilers of the “Janus ” — There were four boilers' originally in the “ .Tanus,” each measuring 12 ft. 2 in. by 8 ft. 4 in. and covering an area of 406J sq. ft. in the ves- sel, and three fires in each boiler, each 6 ft. by 2 ft. in. The boilers are 14 ft. high to top of steam chests; the total space occupied 4738 cubic feet. The total evaporating surface, measuring the outside of the tubes, as in the Wool- wich boiler, is 5137*4 sq. ffc. The North-country and Welsh coals having been mixed in the stores at Chatham dockyard, where the trials were ordered to be made, it was necessary to select by hand, lumps of Welsh coal for the trials; and, to render the comparison fair, this was done in the latter trials of the Woolwich boiler also. From this cause the results in both cases are beyond the average. MANAGEMENT OF THE FIKES. 51 Evaporating Surface per cub. ft. of Water evapo- rated per hour. P 'limn Temp, of the Water supplied to the Boiler. Coals burnt per sq. ft. of Bars per hour. lbs. 13 75 15*51 9 04 11-81 8-81 11 79 17-11 7*58 10-34 10-62 Coals burnt per sq. ft. of Bars, during the mtiiiisti Ratio of Effect in Pro- portion to Bar Surface. 8-83 : 1 8-38 : 1 14-14 : 1 9'36 : 1 11-28 : 1 8-55 : 1 6 02 : 1 13-25 : 1 8-49 : 1 8-49 : 1 Evaporation in hour in cub. ft. with the Feed at 100°, cub. ft. 105-06 110-76 65-69 65*21 54- 01 71*32 7735 70-49 55- 06 56- 86 Ratio of Effect with Feed at 100°. 9-18 8-58 8-73 10*11 11- 23 1 1 07 10*87 11-18 12- 80 12-86 Ratio of Effect at Temperature of Feed. ssKllllsI Quantity of Water evaporated. mm Quantity of Coal used. mrdmm Kinds of Coal used in the Experiments. Welsh Coal. Lewis’ Merthyr Wood’s do. )) » Lewis’ Merthyr. Handpicked. *9 Bar Surface, per cub. ft. evaporated per hour. pmmm Total Surface of Grate Bars. * S 1 * Dlm |u" the (M CM CM CM CM CM " S 5 S CM CM CM CM CM CM • X X X X X X a © co o o o o £00 Duration of Experiment. No. of Experiment. SS!=S SSSS 23S- 2222 asSga 2222 22 = 2 mi — cm cc D ,2 ,: - > , Lvcviqe has 1 LBIVEfiSITY OF ILLINOIS ai jflff .maaia aHi qw teg oi amvg asiii orfi audited aatoxilm jta&wi |feer. 52 THE MARINE BOILER: Slow Combustion generally impracticable in Marine Boilers . — In order to carry out this principle in the case of steam vessels constantly using their full power, the boilers would have to be made nearly double their present size, which of course in most vessels is wholly impracticable, and is cer- tainly not to be recommended in cases where the full supply of steam is rarely wanted. Prom a pamphlet of Captain Kamsay’s we find that the “ Terrible ” steam frigate used her full steam, and lighted all her fires, on one occasion only — and that for a trial of speed. Begulation of the Draft . — Where it is not convenient to lessen the grate-bar surface by bricking up the bars at the further end, the same object may be effected, though cer- tainly not so economically, by checking the draft. With this object in view, every boiler should be provided with damper doors upon the mouths of the ash pits, accurately fitted, and furnished with the means of regulating with nicety the amount of air entering beneath the bars, or, if necessary, of excluding it altogether. Dampers are besides fitted at the foot of the chimney* but these are not so com- pletely under control, nor do they admit of the draft of each fire being regulated separately. BanJcing up the Fires. — Cases frequently occur in which it becomes an object to check the rapid formation of steam for a longer or shorter period, but at the same time to re- tain the power of getting up full steam and starting the engines again on the shortest notice. This is done by pushing the burning fuel back against the bridge, and co- vering it with wetted small coal and ashes, by which means the fires will be kept in a smouldering state, ready to be broken up and spread over the bars when the order is given to get up the steam. But as this process requires at least twenty minutes before the fires can be brought to their proper state of efficiency, it is better, when such no- MANAGEMENT OE THE EIRES. 53 tice cannot be reckoned upon, merely to push back the fires and heap them up against the bridge, raking them forward again when required. To get the Steam up rapidly . — It is of great importance when wishing to get up the steam rapidly, to take care that the fire bars are so covered by coal, that a current of cold air is not allowed to pass through the flues, mixing with the small quantity of smoke or products of combustion at first formed. Every thing should be done to facilitate, or if possible cause a draught of air into the ash pits. No Water to he thrown in the Ash Pits . — It is a most reprehensible custom amongst firemen, and one which should not on any account be permitted, to throw water upon the ashes in the ash pit. They should be drawn out and the best of them, roughly separated by the shovel, be thrown again upon the fire, while the remainder should be drawn well away from the boiler and gradually quenched with a stream of water from a hose, so as not to fill the engine-room with steam and dust, nor keep the front of the boilers constantly wet, so as to corrode and destroy them at this spot. 54 CHAPTEE V. THE MARINE BOILER : MANAGEMENT OP THE WATER AND STEAM. Supply of Water to the Boilers . — The keeping up a due supply of water in the boilers demands the utmost care and watchfulness on the part of the engineer, for should the iron in any place be allowed to become red-hot from want of water, an explosion is almost inevitable. The immediate effect of the heat upon the unprotected plates is to warp and distort them, causing them either to separate at the joints by the giving way of the rivets, or to be torn asunder by the elasticity of the steam acting upon the distorted and softened surface. Explosions have also frequently taken place from water having been too suddenly admitted to the hot plates in the eagerness of the engineer to make up for his previous neglect, when steam is generated so rapidly that the safety valves are insufficient for its escape. It is said that in such cases a portion of the water, becoming de- composed into its elements by contact with the red-hot iron, may form an explosive compound of oxygen and hy- drogen gases, which, on ignition, causes the explosion. But whatever the theory, the fact itself is indisputable that explosions do frequently occur in this way, and should the engineer ever find himself in such a predicament he must instantly draw his fires, and then add w r ater very sparingly and cautiously until the plates be again cool. The Water Level must not rise too high . — Danger of ano- ther kind is to be apprehended if the water level is allowed to rise too high in the boilers, for the water may then boil over into the steam-pipe, or if the steam space be already somewhat contracted, it may increase the “ priming” of the MANAGEMENT OF THE WATEE AND STEAM. 55 boilers to a dangerous degree, for nothing is found to tend more to this most troublesome evil, than too limited steam room. Water Gauges . — To guard against such accidents as these, every boiler is fitted with two different sets of appa- ratus for indicating the water level, and thereby guiding the engineer in the admission of the feed. These are called the “ glass water gauge,” and the “ water-gauge cocks.” Glass Water Gauge . — The first apparatus consists of a glass tube about 18 inches long, fitting into brass sockets at top and bottom, by which it is connected vertically to the front of the boiler, in such a posi- tion that when the boiler is filled to the proper height, the water level may coincide with the centre of the tube. This tube is furnished with three stop- cocks, one at r, leading from the top into the boiler above the water level, another at r from the bottom into the boiler below the water level, and the third at s, leading from the tube itself into the stokehole through a small pipe. "When a communication is opened therefore, at a a , between each end of the tube and the boiler, the water being subjected to the same pressure of steam as within the boiler, will stand in the tube at the same height, thus accurately showing the water level. As the tube, if left to itself, is apt to become choked with salt or deposit (especially if the water be dirty), the third cock is provided, and by occasionally opening this the rush of steam and water through it clears away all ob- structions. Should there be much ebullition at the part of the boiler where the gauge is fixed, the level of the water in 50 THE MARINE BOILER: the glass 'will be very unsteady, and this must be remedied if possible by leading a small pipe from the top of the tube into the crown of the boiler, where the steam is dryer, and at the same time sinking another small pipe from the bottom of the tube into some place where the water is less agitated. It is also of importance that the gauge be fixed nearly in the centre of the front of the boiler, so as to be as little affected as possible by the rolling motion of the vessel. The last two remarks apply equally to the brass gauge cocks. Brass Gauge Cocks . — In case of accident to the glass water gauge three gauge cocks are fitted besides, one above the other, at six or eight inches distance between, the mid- dle one being placed at the average water level of the boiler. Upon opening these therefore, successively, steam ought to issue from the upper one, water and steam from the middle one, and water alone from the bottom cock, and any varia- tion from this will clearly indicate that the water is either too high or too low in the boiler. These cocks should be frequently opened, as they are also liable to become choked up with salt or deposit. As the surface of the water in the boiler is generally at a higher level than can be conveni- ently reached from the firing stage, the gauge cocks may be fixed at any convenient height to the front of the boiler, and pipes led up inside to the respective heights. Only One Feed Pump to be worked . — Although each of the feed pumps is made capable of supplying the full quan- tity of water required by the boilers, it is nevertheless the practice in many steam vessels to keep both the pumps constantly at work, the surplus water which is rejected by the boilers being returned to the hot well, or thrown over- board. This practice, arising from an over-anxiety for an abundant supply of feed water, is much to be deprecated, as when the pumps are both kept working, a partial failure in MANAGEMENT OF THE WATER AND STEAM. 57 either of them may escape detection until one meets with an accident, and is rendered useless, when it is probably found that the other pump is also out of order, and is insuf- ficient to do the full duty alone. In such a case recourse must be had to the supplementary pumps, which are always fitted for the purpose of feeding the boilers when the en- gines are not at work. Amount of the Brine abstracted.— We have already ad- verted to the necessity which exists for abstracting from the boiler a certain proportion of the super-salted water, in order to prevent the deposition of scale or salt upon the plates. The amount thus abstracted, or “ blown off,” as it is technically called, varies with the quantity of the salt and other impurities contained in the water, but this may be stated to be on an average about one-fourth part of the whole feed water admitted. Proportions of Salt in Sea Water from different Localities . — According to Dr. Tire’s experiment, the largest propor- tion of salt held in solution in the open sea is 38 parts in 1000 (by weight), and the smallest 32. In a specimen brought from the Bed Sea, 43 parts were found, the specific gravity of the water being 1*035. The Mediterranean con- tains about 38 parts, the British Channel, 35*5 ; the Arctic Ocean, 28*5 the Black Sea about 21 ; and the Baltic only 6*6. Analysis of Beep Sea Water. — The same authority states that deep sea water, from the ocean, from whatever locality, holds nearly the same constituents in solution, containing, on an average, in 1000 parts, 25 of Chloride of Sodium (common Salt). 5*3 Sulphate of Magnesia. 3*5 Chloride of Magnesium. 0*2 Carbonates of Lime and Magnesia. 0* 1 Sulphate of Lime. D 3 34*1; 58 THE MARINE BOILER: besides a little sulphate and muriate of potash, iodide of sodium, and bromide of magnesium. Blowing-off . — The operation of “Blowing-off” is per- formed sometimes by hand at regular intervals of half-an- hour or more ; but a preferable system has been for some time introduced by which the brine is constantly and uni- formly abstracted, in a fixed and determinate proportion to the feed water, by means of a set of “ brine-pumps,” worked by the engine. Brine Pumps . — This arrangement, introduced by Messrs. Maudslay and Field, has been fur- ther improved by Messrs. Seaward, who connect the valve for the exit of the brine with that for the ad- mission of the feed in such a man- ner that the two open and shut simultaneously; and, as their areas are proportioned to each other in the proper ratio, no more brine escapes than is demanded by the evaporation of the water. The brine- pipe is further fitted with a stop- cock for its better regulation, or in case it may be wished to shut it off altogether when using fresh water in the boilers. Lamb's Blow-off Apparatus . — Another mode of blowing- off has been successfully introduced into the boilers of the Peninsular and Oriental Steam Navigation Company, by Mr. Lamb, their resident Engineer. This consists in blow- ing off partly from the surface, in addition to the usual method from the bottom, by which means many of the par- ticles of insoluble matter, of which the scale is formed, which are ballooned up to the surface on bubbles of steam, Kingston’s Valve applied as Bloiv-off Cock. MANAGEMENT OE THE WATER AND STEAM. 59 are caught and removed from the boiler before they have an opportunity of aggregating and falling to the bottom. This apparatus, represented in the subjoined cut, may be made self-acting by means of a float, a, which, rising or fall- ing in proportion to the amount of feed water admitted, opens or closes the blow-off pipe, e. The Refrigerator . — The hot brine, ejected by the brine pumps at a temperature of perhaps 218° is generally made to pass through a cylindrical vessel, called the “refrigerator,” containing a number of copper tubes through which the feed water, at a temperature of about 100°, circulates on its way from the hot well to the boiler. A considerable por- tion of the heat of the brine being by this means transferred to the feed is again returned to the boiler, and a propor- tionate saving in fuel is effected. Attempts made to Supersede Blowing off \ — It has been attempted in various ways to modify the usual manner of 60 THE MARINE BOILER: blowing off, with the view of saving a portion of the fuel consumed in bringing the ejected brine to the boiling point. By Mechanical Means . — These have been either mechani- cal contrivances for collecting the insoluble particles at the surface of the water, and preventing their solidification at the bottom by agitation with foreign substances introduced for that purpose ; or else By Chemical Means . — A chemical solvent has been added to the water of the boiler, which it is intended shall act upon its mineral impurities without injuriously affecting the iron plates. The utmost that can be done, however, by even the most successful of these schemes, is to prevent the formation of a hard crystalline scale ; the impurities being now deposited in the shape of a loose powder from a state of mechanical suspension in the water. This powder, then, must still equally be removed by partial blowing off, if we would preserve the water from loss of heat by imperfect conduction, or the plates from danger of being burnt. For, since pure water alone can leave the boiler in the form of steam, it follows that all the foreign constituents must remain behind, however they may be disguised by solution in an acid ; and, unless this mineral solution be removed too, it must of necessity reach a limit at which the bases will be deposited, the point of saturation being deferred in propor- tion to the solvent power of the acid employed. It is also the case, as we shall presently see, that the greater the degree of saturation the more heat is required to bring the water to the boiling point, and the hotter, therefore, is that portion of brine which must, under any circumstances, be got rid of. There is also danger to be apprehended from the chance of an improper or too powerful solvent being employed, which may act injuriously upon the materials of the boiler. MANAGEMENT OF THE WATER AND STEAM. 61 The Brine Pumps are found to he perfectly efficient at a tri - fling Expenditure of Fuel* (seep. 69). — Hence it arises that the regular and constant blowing off b y the brine pumps is in every respect the best that can be adopted, and when this operation is properly performed, the boilers may be kept per- fectly free from scale at a comparatively trifling expenditure of fuel — not exceeding 4 or 5 per cent, of the whole fuel burnt. For it must be kept in mind that the brine blown off has had its temperature raised by about 120° only (from 100° to 220°), a considerable part of which is given back to the feed water during its exit through the refrigerators. Had this water been converted into steam (it is true), and absorbed heat in a latent form, the case would have been very different. Salinometers. — Since the freedom of the boiler from scale or deposit depends, as we have seen, upon the greater or less degree of saturation of the water, it is an object of much importance to be able to test the saltness of the water with ease and certainty. This may be done in two ways, each of which the engineer should have the means of trying from time to time ; namely, by ascertaining the true boiling point of the water at a given pressure, and by finding its specific gravity at a given temperature — the strength of the solution maintaining a fixed and known relation to its boiling point, and specific gravity. The instruments to be used are therefore the Thermometer and the Hydrometer . The Thermometer used as a Salinometer. — In using the ther- mometer for this purpose an instrument must be selected in which the scale is graduated in large degrees, capable of being subdivided into quarters, at least ; but the scale need not extend beyond twenty degrees above and below the boiling point of water. Such thermometers are in use for ascertaining the heights of mountains, by observing the temperature at which water boils at the top. This fact, of itself, plainly de- * Mr. Dinnen's Paper on Boilers, &c., in Vol. III., new edition, of Tredgold on the Steam Engine. 62 THE MARINE BOILER : monstrates the dependence of the boiling point of liquids upon the pressure, and it is therefore necessary always to take the pressure of the atmosphere into account. When we say that water boils at 212°, it is understood to mean when subjected to the usual pressure of the atmosphere, indicated by a column of 30 inches of mercury in the weather barometer at the level of the sea. The following Table shows the boiling point and specific gravity of sea- water (at 60° Fahr.) of different degrees of saturation expressed in parts of salt contained therein,, the barometer indicating 30 inches of mercury. Saltness. Boils. Sp. gr. Pure Water . 0 212° 1- Common Sea Water T2 213-2° 1-029 3? 214-4° 1-058 Up to this point no de- 3*2 215-5° 1-087 posit will be formed . 216-7° 1-116 A 217*9° 1-145 Wi 219-1° 1*174 ■h 220-3° 1-203 s\ 221-5° 1-232 1 9 2 222-7° 1-261 It 223-8° 1-290 » 225-0° 1-319 It 226-1° 1-348 saturated solution. As a general rule, the atmospheric boiling point of the water should never be allowed to exceed 216°. The tem- perature must be ascertained by drawing off a small quan- tity of the brine, and boiling it in a deep copper vessel in the engine room, a correction being made, if necessary, for the state of the barometer. The following Table shows the height of the boiling point in Fahrenheit’s scale at different heights of the barometer. Barometer. Inches. 27 274- Boiling Point. 206-96° 207*84° Barometer. Inches. Boiling Point. 28 208*69° 28i 209*55° MANAGEMENT OF THE WATER AND STEAM. 63 Barometer. Inches. Boiling Point. 29 21038° 29 ^ 211 - 20 ° 30 212° Barometer. Inches. 30£ 31 Boiling Point. 212-79° 21357° It will be seen that if we would preserve the water of the boiler at a degree of saturation indicated by A of salt; we must blow off one half of the feed water ; if at # 2 , then one third must be blown off ; at 3 %, one fourth, and so one. We have said that 3 % is the highest degree of saturation that should be permitted. The Hydrometer used as a Salinometer . — The hydrometer employed for measuring the density of water, or other liquids, consists of a hollow ball of glass or metal from which there rises a tall stem graduated with degrees, and ballasted so as to swim upright, the graduated stem being more or less immersed in proportion to the density or specific gra- vity of the liquid. The brine, therefore, increasing uniformly in density according to the salt it contains, may by this means be very conveniently tested ; but as the densities of fluids vary also in proportion to their temperature, care must be taken that the portions of brine experimented upon have the particular temperature for which the scale of the salino- meter has been calculated. Annexed is a table of specific gravities of sea water at 60° Fahrenheit, in various parts of the globe, as ascertained by Dr. Marcet. Spec, gravity. Spec, gravity. Arctic Ocean , . 1*02664 Sea of Marmora . 1*01915 Northern Hemisphere 1*02829 Black Sea . . . 1*01418 Equator . . . , . 1-02777 White Sea . . . 1*01901 Southern Hemisphere 1*02882 Baltic . . . . . 1*01523 Yellow Sea . , , . 1-02291 Ice Sea Waters . . 1*00057 Mediterranean . . 1-02930 Dead Sea . « • . 1*21100 64 THE MARINE BOILER: The specific gravities corresponding to various degrees of saturation of the sea water have been already given. Seaward's Salinometer . — To obviate the inconvenience of withdrawing the water from the boiler, in order to test its specific gravity, Messrs. Seaward have invented a salinometer of which the following is the description. It consists of a strong glass tube of about three-quarters inch bore, and four- teen inches long, firmly fixed at each end in a brass frame, to which are attached four cocks, one at each end and two at the side. By the two latter cocks the instrument is attached to the front of the boiler, being fixed at such a height that the water line in the boiler may show its level in the glass tube. Now, upon opening the two cocks which are attached to the boiler, the water will rise up from the bottom of the boiler, by a pipe attached to the lower cock, to the same level as in the boiler. These cocks are then closed and the upper one opened, and two metallic or glass balls are dropt into the tube. The ball first dropt in has been graduated to swim when the water of the boiler is one degree salter and denser than the proper degree of saturation ; and the second ball to sink when the water has become one degree more diluted and lighter. The upper cock is then closed, and the two cocks com- municating with the boiler remain open. It is evident, therefore, that when the water in the boiler is at the degree of saturation intended to be maintained, the lighter ball will float at the water level, and the heavier ball remain at the bottom ; and further, that any change of density will alter the position of the balls, the lower ball rising as the water becomes more saturated, and the upper one sinking upon the water becoming more diluted. The upper and lower cocks are for the purpose of changing and cleaning the balls when required, the bore of each cock being equal to the diameter of the balls. MANAGEMENT OF TILE WATER AND STEAM. G5 Cases in which the Amount of Blow-off may he diminished . — In the case of a vessel going at half speed, when the full quantity of steam is not evaporated, the quantity of water blown off may of course be proportionally diminished, un- less it be wished to take advantage of this circumstance and freshen the water in the boiler, while it may be done without checking the power of the engines. For it is apparent, that the less water is blown off so much less feed need be admitted to cool the boiler, and so much the more steam is generated. This renders it sometimes expedient, under critical circumstances, to stop the supply of feed altogether for a while, in order to ensure an abundant supply of steam to the engines, and it is the duty of an intelligent engineer to provide for such emergencies, if pos- sible, by having a good supply of water in the boilers before- hand. In making “ trials of speed” of steamers this is a usual jockeying trick. In case the Blow-off Cock sets fast. — In the case of the blow-off cocks or any of the apparatus on board for with- drawing the brine from the boilers becoming choked or getting out of order, water must either be let out of the boiler by some means into the bilges, or it may sometimes happen that one of the systems of feed-pipes may be made available to allow the escape of water into the sea. Safety Valve , its Area . — The area of the safety valve should obviously be proportioned to the evaporative power of the boiler ; but is usually made in the proportion of half a square inch to each horse power of the engines, which in the generality of cases is ample enough. Manner of loading. — It is loaded by the manufacturer to the extent best adapted for the machinery, and this per- manent load should not be augmented without his express 66 THE MARINE BOILER: sanction. The steam power of the vessel being subdivided amongst two or more boilers, each separate boiler must have its own safety valve ; and as the different sections com- municate with each other by means of stop valves, this constitutes an additional source of safety in case of one being out of order. Occasional Defects . — A properly constructed safety valve is not liable to get out of order, although, if suffered to lie long in contact with its seat without being raised, it will sometimes stick so fast as to defy all ordinary means of moving it. It should therefore be frequently tested by the engineer, to see that it moves freely. With this view, and also as a ready means of relieving the pressure of steam without mounting to the top of the boiler, a set of jointed rods lead from the firing stage to the bottom of the valve spindle ; being so contrived that the engineer may push the valve up off its seat, but at the same time offering no obstruction to the free rising of the valve by the steam pressure. It more frequently happens that the valve fits its seat so badly as to allow of the escape of steam. This should be guarded against by making the valve itself as solid and stiff as possible, and fixing the seating in a strong cast-iron valve box, which will not spring by the pressure of steam upon it. In case the Safety Valve sticks fast . — Should it happen that the safety valve of any one boiler becomes inoperative, the surplus steam will still have a free passage through the stop valve into the adjoining boiler, whose valve, it may be presumed, is in good order ; but should this means of escape either not exist, or prove inadequate to relieve the pressure, then the blow-through valves of the engines must instantly be opened, so that the steam may find an exit through the valve casing and condenser. The fire doors should at the MANAGEMENT OE THE WATER AND STEAM. 67 same time be thrown open and the ash pit dampers closed, to check the fires as much as possible, before they are quenched with water, and drawn. The first indication of an excessive pressure is usually given by the mercury being blown out of the mercurial steam gauge, where such is fitted, this acting to the best of its capacity as a safety valve also. Steam Gauge.— The steam gauge usually fitted to marine boilers is a bent iron tube, like a syphon tube reversed, attached vertically to the front of the boiler, one of the orifices opening into the steam chest, and the other open to the external air. The tube is partially filled with mer- cury, which of course stands at an equal level in both legs of the gauge, so long as there is no pressure of steam in the boiler. But as the pressure upon the surface of the mercury in the two legs becomes unequal, it is forced down the one leg and up the other, until the equilibrium is re- stored. Hence, a depression of one inch of mercury in the leg communicating with the boiler is followed by a corre- sponding rise of one inch in the other leg, but the difference of level between the surfaces of the mercury in the two legs is manifestly two inches. Thus, a rise of one inch in- dicates an additional pressure of one pound in the boiler, and not half a pound, as might at first sight be supposed. On the surface of the mercury in the open end of the tube there floats a light rod of wood, and this rising or falling with the level of the mercury indicates the pressure upon a fixed scale of inches or pounds. Vacuum , or Reverse Valve . — In addition to the safety valve each boiler should be provided with a vacuum valve, (of small dimensions,) to prevent the possibility of the boiler collapsing, when the pressure of steam inside falls below the pressure of the atmosphere. This is frequently ex- 68 THE MARINE BOILER: perienced in boilers whose supply of steam is insufficient for the engines, (as it is apparent that the latter may con- tinue to work with a negative pressure in the boilers, pro- vided there be a good vacuum in the condensers,) and it may happen to any boiler, by a sea breaking over the decks and suddenly condensing the steam. The action of this valve is sufficiently obvious, as it is only a reversed safety valve, slightly loaded ; and the only attention it requires is to try it occasionally, and see that the spindle moves freely. Supply of Air to the Fires . — The amount of air that is required to keep up combustion in steam-engine boilers is much greater than is generally supposed. For lib. of coal, of average quality, 150 cubic feet of air are required for exact chemical combination alone, and as this can never be perfect, from a variety of disturbing causes, a supply of about 300 cubic feet is found in practice to be beneficial. If 8 lbs. of coal be consumed for one-horse power per hour, an engine of 100-horse power will require a supply of 2400 cubic feet of air per hour, or 40 cubic feet per minute. Every facility therefore, by means "of hatchways, wind pipes and windsails, should be provided and carefully attended to for this large supply. Staying Boilers . — It is usual to stay the flat portions ot tubular boilers with rods of about one inch square, or one inch diameter, from sixteen to eighteen inches apart each way, and flue boilers (which are not so well adapted to bear a high pressure of steam as tubular boilers) not quite so heavily. It must be borne in mind, that it is highly inju- rious to stay weak plates at long distances, however strong the stay rod may be, as the alternate distension and con- traction of the plate between the stays causes it to buckle round each stay every time that the pressure of steam is added or removed. MANAGEMENT OF THE WATER AND STEAM. 69 This action, in time, wears a furrow round the fastening of the stay, by throwing off the scale from the surface of the plate, and opening the fibre of the iron, the circular piece of plate to which the stay rod is attached remaining at the s ime time quite sound. Brine-pumps , as fitted on board H. M. S. Medea, 220 Horse-power , Maudslay, Son & Field. 70 CHAPTER VI. MANAGEMENT OF THE ENGINES. The Bearings require Attention . — In the management of the engines, the points to be most attended to are the fol- lowing. The bearings of all the working parts must be constantly attended to, and regularly lubricated with oil or melted tallow. If the brasses are screwed or driven up too tight, the bearing will heat ; if, on the other hand, they be too slack, a jar is produced at every revolution, destructive, if not positively dangerous, to the engine. As the brasses wear by the friction, therefore, they must be driven up to a moderate tightness by the cutters. As these are apt to work loose unless properly secured, it is now the practice to make the main cutters with a screw and nut at the point to prevent this. When any of the main bearings heat, they must be slackened and bathed with melted tallow and sulphur ; or, if the heating has proceeded to a great extent, a stream of cold water from the hose of the hand pump should be directed upon them. The bearings most liable to heat are those of the crank pin and crank shaft; but care must be taken whilst cooling the latter, that the cold water does not crack the cast-iron plummer blocks. To avoid this, it must be thrown on very cautiously at first. The larger the surface of the bearing is in proportion to the friction to which it is subjected, the more easily it is kept cool and in good order, and the less oil is consumed in lubricating it. To test the Tightness of the Engine before starting . — The following method of ascertaining the tightness of the dif- MANAGEMENT OE THE ENGINES. 71 ferent parts of the engine subjected to steam pressure is recommended to be used in every case after the engine has been fresh packed, or has been out of use for some time. After getting up steam, and while the vessel is still at her moorings, blow through, and then, after obtaining a partial vacuum in the condenser by the admission of a little water, watch the barometer to see how long the engine holds her vacuum. If the condenser gradually becomes hot, while the cylinder ports remain closed, we know that steam is passing the packing of the valves ; or, if the valves are made without packing, the steam must be passing their faces. The tightness of the faces of D and other valves may be tested by shutting both ports to steam, and opening the cocks for taking indicator diagrams above and below the piston, the grease cocks, or any others communicating with the cylinder. If no steam passes through these cocks when the throttle valve is full open, the valve faces are then, of course, tight. The tightness of the piston may be proved in the same way, by admitting steam above or below it, and opening the indicator cock on the opposite side. The injection cock may be slightly opened for an instant, to withdraw any steam that may have collected on the opposite side of the piston, so that the passage of any steam may be the more readily perceived. The tightness of most parts of the engine may be tested in this way without moving it be- yond half a stroke. To discover a Leakage of Air into the Engines . — The en- gineer must watch strictly for leaks of air into the engines, by which the vacuum may be vitiated ; as well as for every leakage of steam into the engine room. If the engine draws air on the u steam side,” this may be discovered before it is set to work during the process of blowing through, when a jet of steam will be seen to escape ; but if the leakage be suspected after the engines are at work, the engineer must endeavour to discover it, either by the 72 MANAGEMENT OE TIIE ENGINES. whistling sound of the rush of air, or, taking a lighted candle in his hand, pass the flame along all the joints till he finds it sucked in by the vacuum. Leakage in a hori- zontal joint may be readily discovered by laying water along it. An air leak may also be discovered by closing the snifting valve and the discharge valve at the ship’s side, and filling the engines with steam. When the leak is found out, it must be stopped temporarily by driving in spun- yarn, or gasket steeped in red lead and oil, or other means. A Cure for Leaky Condensers.-— If the leakage be into the condenser, it is sometimes convenient to allow water to be injected through the orifice, by which means little harm is done. In several cases where, during a long voyage, the bot- tom of the condenser has become leaky by corrosion, (often induced by galvanic action with the copper bolts of the ship’s bottom, as well as the brass foot valve, &c.), a water- tight tank has been constructed at sea between the side keelsons. By this means the condenser and air pump are placed in a kind of well constantly replenished with cold water from the sea, which, forcing its way through the leaks by the pressure of the atmosphere, shares with the proper injection water the duty of condensing the steam — the injection-cock orifice being partially closed in propor- tion to the extent of leakage through the bottom. Injection to be diminished when the Ship labours much . — When the vessel is labouring in a heavy sea, it is recom- mended that the supply of injection water should be dimi- nished ; for in such a case, where the speed of the engines is subject to great and constant fluctuations, depending upon the greater or less submersion of the wdieels or screw- propeller, the condenser is liable to become choked with water, thereby causing the engines to stop. The effect of working the engines with a stinted supply of condensing water is, of course, that the condensers will become hot, MANAGEMENT OE THE ENGINES. 73 and the vacuum will be diminished; but this is a minor evil in comparison with endangering the machinery by subjecting it to too severe a strain. When the Injection Cock leaks. — Care must be taken, when the engines make a temporary stoppage, that the injection cock, or air pump, does not leak, and allow the condenser to fill with water, which causes much trouble and delay in starting the engines again ; so, should this be apprehended, the sea cock must also be closed at the same time with the injection cock. It is also advisable to blow through at short intervals, to keep the condenser free of water, and admit a little injection water to keep up a vacuum, so as to be able to start upon the shortest notice. Advantage to be derived from the Bilge Injection Pipes. — It is calculated that an engine requires about one ton of con- densing water per horse power per hour ; and it is apparent that the abstraction of this large body of water from the bilge , in case of the vessel springing a leak, constitutes a very valuable property in the machinery, and one which has ere now saved many steamers from foundering. It is essential, however, that the orifice of the bilge injection pipe be most carefully guarded against the entrance of chips of wood or oakum, which, by getting into the con- denser, may gag the valves of the air pump, &c., and stop the engines. The bilge injection pipe should have no rose, upon the orifice opening into the condenser, as such is liable to become choked ; but the water should be spread by striking against a flat surface, or otherwise. Injecting through the Snif ting Valves . — Where no bilge- injection has been fitted, a considerable body of water may be admitted into the condenser through the snifting valves, in case of a leak in the vessel. Should there be no means provided for lifting them, by stopping the injection and then E 74 MANAGEMENT OE THE ENGINES. blowing through, they will rise from the pressure of steam in the condenser, when they must be prevented from closing again ; or, should they be inaccessible, the cover of the foot valve, or the man-hole door of the condenser (if the water rise above it), should be slackened to allow the water to enter. To make Steam-tight Joints . — The usual mode of making air or steam-tight joints between two surfaces, is to inter- pose hemp packing, or gasket , soaked in red or white lead and linseed oil, the joint being made when the steam is down, and screwed well up when the engine gets hot. If the joints have been accurately chipped and filed, then sheet lead, thick paper, wire gauze, &c., are usually em- ployed, well smeared on both sides with red lead ; or, if the joint has been planed and made perfectly true, then a little thin red lead is all that is necessary between the surfaces to make them steam-tight. Cement joints are now almost wholly discarded from marine engines, and should never be made where there is a chance of the surfaces requiring to be again separated. How to act in case of Accident to the Engines. — The various accidents to which steam engines are liable are so nume- rous, that any directions to meet particular cases are likely to be fruitless. Any engineer who expects a list of re- medies for every evil that may occur, whether it be to smother a leak in a pipe with a stoker’s fearnought dress and lap it with spun yarn, or to fish an intermediate shaft, must be disappointed. He must rely on his own judgment when a flaw has shown itself, or a fracture taken place, and consider carefully the direction of the strain, and take steps to provide for this ; and also to guard against further injury if the weak part should give way. Wood and wrought iron are the materials with which all repairs at sea must be effected, and care should therefore be taken to have efficient means for adapting them to use when required. No hesita- MANAGEMENT OF TIIE ENGINES. 75 tion must be felt regarding the unseemliness of a massive piece of timber to strengthen the frame of an engine ; and the principle of the expansion of wrought-iron straps or bolts by heat, so as to effectually tighten them, must not be forgotten. A clear perception of the principles of truss- ing, of leverage, and of the resolution of forces, is most important ; and it is by such knowledge that a good and thorough mechanic will show his superiority in difficulties over the mere engine driver. Test Cocks . — Small cocks should always be fitted to the top and bottom of the cylinders for clearing them of any water. They are generally constructed with a ball or reverse valve at their mouth, so as to allow of their being kept open without the entrance of air, when there is a vacuum on the side of the piston with which they communicate, which would injure the action of the engines. Grease Cocks . — The grease cocks, for lubricating the pis- tons, must, of course, be opened only during the ascent of the piston, when the vacuum will suck in the melted tallow ; otherwise it would be forced out by the pressure of steam. Those grease cocks on the slides, where there is a constant pressure of steam opposed to them, may generally be made to act by one man suddenly closing the throttle valve of the engine which it is wished to lubricate, while another opens the grease cock at the same instant ; the throttle valve be- ing reopened, and the whole operation performed as quickly as possible, so as not to stop the speed of the engine more than is absolutely necessary. Turning the Engines by Hand . — One of the principal duties of the engineer, whilst in harbour, is regularly to move the engines round by hand through a portion of a revolution, in order to change the relative positions of all the touching surfaces. It is found, that when the iron E 2 76 MANAGEMENT OE THE ENGINES. piston rod, for example, remains for even a day or two in contact with the brass gland, a slight, though perceptible, furrow is eaten in the rod by the oxidation of the metal, induced by the galvanic action which results from the con- tact of the brass and the iron. Galvanic Action. — The same destructive effect is produced in all the other parts of the machinery where copper or brass remains in contact with iron ; but this proceeds more rapidly when sea water or moisture of any kind is present, and according as the temperature is greater. In the case of paddle engines, the wheels present a convenient leverage for moving the engines by hand ; but, with screw steamers, much difficulty is sometimes experienced in effecting this, and it has generally been found requisite to fit some me- chanical contrivance for the purpose. Essential to have square Regulating Lines marked on Ma- rine Engines. — As spirit levels and plumb rules cannot be used on board ship, every thing must be done by straight edges and squares. Every engineer, therefore, on taking charge of a pair of engines, on their coming out of the hands of the manufacturing engineers, should see that cen- tre lines are scored well into the framing, at a sufficient number of parts, to facilitate any future examinations as to whether the engines have altered their position in any way, as well as to facilitate his putting the engines very correctly, when so required, at half stroke, and many other operations. Athwartship lines should certainly be scored in on the cy- linder flanges, across the centres of the two cylinders, and on the base plates in beam engines, under the centre of the crank shafts. A fore and aft line in the centre line of each engine should also be scored in along as much of the base plate as possible. It is also usual in well-constructed en- gines to have four horizontal points in an athwartship line on the framing, dressed off so that four points in a true line MANAGEMENT OF THE ENGINES. 77 on the face of a straight edge may lie upon the whole of them, and thus prove at any time whether the engines have fallen in towards each other, or fallen away towards the sides of the vessel. To adjust the Paddle Shaft. — If the eye of the crank of the paddle shaft be perceived to bear hard upon the con- necting rod brasses at one part of its revolution, and to se- parate from them at another part, the engineer may know that the centre of the paddle shaft is out of line with the centre of the intermediate shaft. To rectify this defect, place the engines on the top stroke and measure the distance accurately between the faces of the two cranks at the side of the crank pin, then put the engines on the bottom stroke and measure the distance at the same place. If the dis- tance at the bottom be less, the outer end of the paddle shaft must be too low and require to be raised. Subtract the one distance from the other, and take one half of the remainder, and say, as the length of the crank is to the length of the paddle shaft, from the face of the crank to the centre of the outer bearing, so is this half-remainder to the amount that the outer bearing requires to be raised. Other examinations as to whether the crank and paddle shafts are true to each other, in other respects, can be made in a simi- lar manner. To replace the Levers on the Valve Shaft if carried away . — The length of the valve lever is the distance from the centre of the valve shaft to the centre line of the valve spindle, with the addition of half of the versed sine of the arc through which it vibrates. The length of the gab lever must bear such proportion to the length of the valve lever that the traverse given to it by the excentric shall produce the requisite amount of motion in the valves. The throw of the excentric, multiplied by the length of the valve lever. 78 MANAGEMENT OE THE ENGINES. must always be equal to tbe travel of the valves, multiplied by the length of the gab lever. To fix the Gab Lever on the Valve Shaft . — The valve lever or levers being fixed upon the shaft, it must then be put in place on the engine, and turned round till the centre line of the valve lever is at right angles with the centre line of the valve spindle. The shaft being fixed in this position, the gab lever is now to be put upon it in such a position that its centre line will be at right angles to a line stretched from the centre of the intermediate shaft to the centre of the gab pin on the end of the lever. To find the Length of the Excentric Mod if carried away.— Place the valve shafts with the valve lever at right angles to the centre line of the valve spindle, and then measure the distance from the centre of the intermediate shaft to the centre of the pin of the gab lever, and this is the length from the centre of the ring of the excentric rod to the centre of the gab at the other end of it. To replace the Stops on the Intermediate Shaft for driving the Excentric. — The excentric rod being out of gear, place the engines at top stroke, and place the valves in the posi- tion in wdiich they ought then to be, that is, with the requi- site amount of lead open to the steam. Now move the ex- centric, which is loose upon the shaft, in the direction in which it would revolve, if the engine was going a-head, until the excentric rod drops into gear ; the position of the stop for going a-head may now be marked upon the shaft, to meet the face of the stop upon the excentric block. The gab of the excentric rod being taken out of gear again without the engines or the valves having been moved, the excentric block is now to be turned back, in the direction in which it would be revolving if the engines were going MANAGEMENT OF THE ENGINES. 79 astern, and the excentric rod will again drop into gear as it comes round, and this, in the same manner, gives the posi- tion of the stop upon the shaft for going astern. Essential to know the Position of the Steam Valves from External Marks . — The valve rod being generally so fitted that its length can be varied with facility for the sake of ad- justment, it is essential that there should be a ready means of testing the correctness of its length at any time. This can only be done by a mark upon the rod, above the gland of the valve bonnet or cover, this mark being made when the valve is at its mid-stroke, at a certain known distance above a mark on the flange of the valve casing or some other fixed portion of the engine framing. These marks are generally made by a centre punch well struck in, and a record of the required distance is made by another mark on the valve casing or framing at the required distance. If the valve be placed at mid-stroke, the valve lever may now be connected with it, the only care requisite being that the centre line of the valve lever shall be at right angles to the centre line of the valve rod, when the valve is in this position. If any doubt is entertained of the correctness with which the parts in question have been originally constructed, due examina- tion of the steam ports and valve faces must be made, and the length of the valve rod and the marks tested. It is sometimes convenient to have a mark made on the framing, or some other ready means, by which it may be known when the valve lever is at right angles as stated. 80 CHAPTER VII. USE OE THE EXPANSION YALYE, INDICATOR, AND DYNAMOMETER. Principle of Expansion. — If steam be supplied to the cylinder of an engine at a uniform density during the whole length of the stroke, the resistance being at the same time uniform, the piston will move with a continually in- creasing velocity, until its momentum is suddenly and entirely destroyed upon commencing the next change of direction ; thus causing a destructive jar to the parts of the machine. To obviate this, therefore, the steam is “ cut off” before the end of the stroke, which is then completed under a diminished pressure. By this means the piston comes gently to rest at the top and bottom of the cylinder ; but this is neither the only nor the chief advantage which results from cutting off the steam, since it is found that the force actually exerted upon the piston by the isolated steam , during its expansion into the increased volume as the piston descends in the cylinder , is considerably greater than that due to the simple pressure of the same weight of steam acting at a uniform density . To render this intelligible, let us suppose a cylinder of one square foot area, and 20 inches long, to which steam at about the atmospheric pressure has been supplied during half the stroke. We may then suppose the pressure on the piston to equal one ton at the moment the steam valve is closed, the space under the piston being open to the con- denser. As the piston descends farther, the steam above it will become diffused through an increased volume, and will consequently acquire a diminished pressure. We may assume that this diminution of pressure follows the law of elastic fluids in general, and that it decreases in the same propor- USE OF THE EXPANSION YALYE, INDICATOR, ETC. 81 tion as the volume of steam is augmented. While the' piston, therefore, moves downwards from the centre of the cylinder (at 10 inches), it will be urged by a continually decreasing force, until it arrives, we will suppose, at 15 inches, when the space occupied by the steam will be in- creased in the proportion of tw'o to three. The pressure on the piston will also be diminished in the inverse ratio of three to two ; and will now equal two thirds of a ton at 15 inches from the top. In like manner, when the piston arrives at the bottom, the space occupied by the steam will be double that which it occupied at half-stroke, and the pressure will be diminished one half — being now, conse- quently, half a ton. By calculating in this way the pres- sure on the piston at the termination of each inch of the space through which the steam has been expanding, we find the pressure at the 11th inch expressed by tt of a ton ; at the 12th inch of a ton ; and so on to the 20th inch, where the pressure is or half a ton. Now, if the pressure of the steam through each of these ten divisions be supposed to continue uniform, and, instead of diminishing gradually, to suffer a sudden change in passing from one division to the other, the mechanical effect will be obtained simply by taking the average of the ten pressures. Thus, it has been supposed, in the present case, that the pressure on the piston at the beginning of the first division is 2240 lbs. ; and to obtain the pressures corresponding to each of the other divisions, it will only be necessary to multiply 2240 by 10, and divide successively by 11, 12, 13, &c. The pressures in pounds, at each inch below the half-stroke, will then be as follow, viz. : — At end of 1st inch 2036*3 lbs. 2nd „ 1866*6 ,, 3rd,, 1723*1 „ 4th „ 1600*0 „ 5th „ 1493*3 „ At end of 6th inch 1400*0 lbs. 7th „ 1317*6 „ 8th „ 1244*4 ,, 9th „ 1179*0 „ 10th „ 1120*0 „ Benefit of Expansion . — If the mean be now taken by adding these numbers together and dividing by 10, it will E 3 82 TJSE OE THE EXPANSION VALYE, be found to be 1498 lbs. as tbe mean pressure of steam during tbe expanding half of tbe stroke, which is nearly three fourths of the mechanical effect produced by the full steam during the first half of the stroke. In this calcula- tion we have assumed, for the sake of simplicity, that the pressure is uniform throughout each of the ten divisions : which of course it is not, owing to the expansive action which takes place within each division ; so, the more accu- rate calculation (which is a complicated one) makes the average pressure for the expanding half of the stroke equal to about 1545 lbs. It is evident that this principle is equally applicable at whatever part of the stroke the steam be cut off, a higher mechanical effect being obtained from a given weight of steam in proportion to the extent to which the expansive working is carried, and in proportion to the original density of the steam. Thus, in the Cornish en- gines, it is found to be most advantageous to use steam of from 30 to 40 lbs. pressure, and to cut it off in the cylinder at one sixth, or even one eighth part of the stroke, the remaining seven eighths being performed wholly by ex- pansion. The limit to this principle is imposed, in practice, by the increased size required for the cylinder, and the in- equality in the speed of the piston during the stroke. It is found, by calculation, that if the steam be cut off at half-stroke its mechanical effect is multiplied by 1*7 nearly ; if at one third, by 2T ; if at one fourth, by 2*4 nearly ; &c. The following rule will be found useful for calculating approximately the mean pressure of steam on the piston during the stroke, while working expansively. Rule . — Divide the length of stroke by the distance the piston moves before the steam is cut off, and the quo- tient will express the relative expansion it undergoes. Take from the annexed table the multiplier correspond- ing to this number, and multiply it by the full pressure of steam per square inch on entering the cylinder. The product will be the mean pressure per square inch, nearly. INDICATOR, AND DYNAMOMETER. 83 TABLE OF MULTIPLIERS. Relative Expansion. Multiplier. Relative Expansion. Multiplier. Relative Expansion. Multiplier. Relative Expansion. Multiplier. 1 1-0000 2 •8466 3 •6995 4 •5966 11 •9957 2*1 •8295 3*1 •6875 4-1 •5880 1-2 •9853 2-2 •8129 3*2 •6760 4*2 •5798 1-3 •9710 2-3 *7969 3*3 •6648 4*3 •5718 1*4 •9546 2-4 •7814 3-4 •6540 4*4 •5640 1*5 *9370 2-5 *7665 3-5 •6436 4*5 •5564 1*6 •9188 2-6 •7521 3-6 •6336 4*6 •5491 1*7 •9004 2-7 •7382 3-7 •6239 4*7 *5420 1*8 •8821 2-8 •7249 3-8 •6145 4*8 •5351 1-9 •8641 2-9 •7120 3-9 •6054 4-9 •5284 2- •8466 3 •6995 4 •5966 5 •5219 The Indicator . — In practice, a much simpler, and more accurate method is employed for finding the power exerted within the cylinder of a steam engine, namely, by the use of the indicator. The Indicator , its Construction and Principles.' — This little instrument, which ought to be familiar to every one in- trusted with the care of machinery, consists of a small cylinder placed in connection with the cylinder of the en- gine, either above or below the piston. This cylinder is open at top, and is fitted with a piston which presses against a spiral spring. The cock which connects the indicator with the cylinder of the 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 or pull alternately against the spiral spring. If the pressure were uniform throughout the stroke, the indicator piston would start at once from the top to the bottom, and vice versd , remaining stationary until acted upon by the opposite pressure. In such a case, the pressure exerted 81 USE or THE EXPANSION VALVE, would be simply proportional to the flexure of the spiral spring, and might be measured accordingly; but, as we have seen that the pressure on the piston is continually varying during each stroke, it follows that the pressure on the spring must also be a variable pressure corresponding to the movements of the indicator piston, either up or down. Now, if a pencil be fixed to the piston rod of the instrument, it will register the fluctuations of pressure upon a piece of paper held close to it ; but, unless some provision 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 mark- ings due to fluctuation of pressure will be undistinguish- able. To obviate this, the paper receives a circular motion in one direction during the down stroke of the piston, and a reversed motion during the return stroke, the result being that, as the pencil moves vertically up and down, a continuous curved line is traced upon the paper. By this line an oblong space is enclosed, called indifferently the Indicator Figure , Card , or Diagram , , the vertical ordinates of which will then represent the effective pressure at the corresponding portions of the stroke, and whose area will represent the whole pressure exerted during the stroke. Before the instrument is connected with the steam cylinder, the roller, with the paper attached, is set in mo- tion, and the pencil then describes a straight line (called the neutral or atmospheric line ), which represents the pres- sure of the atmosphere, the space enclosed above this line being the measure of the pressure above the atmospheric pressure, and below this line measuring the pressure below the atmosphere. If the junction between the indicator and the cylinder be now formed while steam is entering the cylinder, the indicator piston will evidently rise; and if steam be escaping from the cylinder it w T ill fall, — the ex- tent of the rise and fall depending upon the strength of the spiral spring. The alternating circular motion of the roller is given by connecting it with any reciprocating part INDICATOR, AND DYNAMOMETER. 85 of the engine, by means of a cord attached to a pully fixed bn the same axis with the paper-roller. This cord gives motion in one direction only, the return movement being communicated by a coiled spring attached to the instrument. Scale . — The scale of the indicator in general use is divided into tenths of an inch, each division representing one pound pressure on the square inch of the piston. When the instrument is not in use, the index stands at 0 ; but when communication is opened with the engine the pres- sure of steam is exhibited above zero, and the vacuum below. How to use the Indicator .* — To use the indicator, its cock must be made to fit the grease cock of the cylinder cover, or any other fitted for the purpose in a convenient place at the top or bottom of the cylinder, or both. The line may then be attached to the radius bar of the parallel motion at six or seven inches from the joint, and connected by a running loop to the hook on the small line at the bottom of the instrument. By means of the running loop the line must be lengthened or shortened, till it is of the proper length to allow the roller to traverse as far it can without coming into contact with the stop or the springs. This is easily effected by shifting the line upon the radius bar ; and when the proper length has been found, the running loop may be fixed permanently, to be ready for future trials. Having stretched the paper upon the roller, and fastened it by means of the clasp, a sharp-pointed pencil is put into the socket, and allowed to press lightly (by means of a little spring) upon the surface of the paper. When all is ready, the instrument is first made to work a few strokes with the cock shut, in order to form the “ atmospheric line,” after which, the cock is opened when the piston is at the top of the stroke, and the registration proceeds as described. * See p. 288, Marine Engines, new edition of Tredgold on the Steam Engine. 86 USE OE THE EXPANSION YALYE, ITow to make the Calculation . — When the figure is made, the pressure of the steam is calculated by drawing any number of lines across it at right angles to the atmospheric line, and taking their mean length as measured on the scale attached to the instrument. In practice, it is usual to divide the figure into ten spaces by equi- distant ordi- nates, measure each of those spaces in the middle, find their sum, and cut off a decimal figure for the division by 10, the result being the average force of the steam in pounds on the square inch. To find the power that the engine is actually exerting, therefore, we have only to take the area of the cylinder in square inches, multiply by the average pressure as found above, and again by the number of feet which the piston travels in a minute, when the product divided by 33,000 is the indicator or gross horse power of the engine. To find the Nominal Horse Power of an Engine. — The horse power of an engine, as found in this way (which is the most accurate method with which engineers are ac- quainted), must not be confounded with what is called the Nominal or Commercial Horse Power. The latter is ob- tained by the following formula, viz. : — Area of cylinder x effective pressure x speed of piston 33,000 = ‘ # The area of the cylinder must be taken in square inches, the “ effective pressure” assumed at 7 or 7^ lbs. per square inch of piston, and the speed is to be reckoned in the number of feet through which the piston travels, or is expected to travel, per minute. The divisor is 33,000 lbs. as before ; this weight when raised one foot high in a minute being the standard of a commercial horse’s power adopted by James Watt, and subsequently retained for convenience sake. In tendering for engines for the Government ser- vice, the “ effective pressure ” is assumed at seven pounds INDICATOR, AND DYNAMOMETER. 87 only, and the speed of the piston is presumed to vary with the length of stroke, according to the following table : — Stroke. Speed of piston. Stroke. Speed of piston. Ft. In. Ft. per min. Ft. In. Ft. per min. 4 0 196 6 6 226 4 6 204 7 0 231 5 0 210 7 6 236 5 6 216 8 0 240 6 0 228 We may observe, that on the Thames the effective pres- sure is usually taken at 7 lbs., and on the Clyde at 7\ lbs., which tends to mate the nominal horse power of the Glasgow and Greenock engines of somewhat less com- mercial value than those built in London. Distinction between Nominal and Real Horses 9 Power . — It will be seen that the horse power thus calculated is irre- spective either of the actual pressure of the steam used, of the perfection of the vacuum in the condenser, or the amount of friction arising from good or bad workmanship ; hence this rule, however useful in comparing the size of different engines, is a very imperfect guide to their actual power. We have thus two distinct values of horse power, which no one conversant with the steam engine ever con- founds ; the one, fixed and nominal, by which engines are bought and sold ; the other fluctuating, though real, as shown by the indicator. To discover, however, the effective power , or the power actually available for the purpose for which the engine is used, a deduction would require to be made for friction of the moving parts and for the power required to work the pumps and valves, but as this would be nearly alike for well-constructed engines of equal power, and no ready means exists of testing it, the total or indi- cator horse power is taken as the measure of the power in all ordinary cases. 88 USE OF THE EXPANSION YALYE, Use of the Indicator for showing the Internal State of the Engine . — The indicator, moreover, tells us not merely the power exerted by the engine, but the nature of the faults (where those occur) by which the power is impaired. Thus, one form of the indicator figure, or “ diagram,” may show that the cylinder ports are too small, or that there is condensation in the steam pipes ; another, that the engine is drawing air ; or a third may show that the valves are improperly set. Let us take, for example, the accompany- ing imaginary diagram : — INDICATOR, AND DYNAMOMETER. 89 When the pencil is at the point marked «, the piston is at the commencement of its stroke, and the paper being made to move, the line is traced from a to b and thence to c, at which point the stroke in one direction is finished. At the point b the valve is being shut to prevent the further ad- mission of steam ; and while the line from b to c is being traced the steam is expanding, and its pressure consequently decreasing as indicated by the falling of the line. The line from b to c, instead of being convex, should be concave, as in the double diagrams, page 93 ; and it is thus discovered that the slide is in bad order from steam being admitted after it is shut. If the engine had been working expan- sively, and the valve been shut before the pencil had reached the point b , the steam would have begun to expand at that point, and the line have begun to fall so as to indicate the degree of expansion in the most precise and definite manner. On the pencil approaching the point c, the valve is opened to the condenser, the steam escapes, is condensed, the pres- sure falls, and the pencil descends towards d. The action as here indicated is not very good, as the corner should be more nearly square. The piston now commences its return stroke, and the paper is made to move simultaneously also in the opposite direction, and the line towards e is traced. It is here seen to rise again towards the atmospheric line, thus indicating that there is some pressure increasing in the cylinder. Trom the form of the diagram at this point, it is gathered that the vapour remaining inclosed in the cylinder, after the communication with the condenser has been closed, is compressed, and exerts a pressure against the piston to an injurious extent. As the pencil approaches f, the valve is opened for the admission of steam, and the pencil rises towards a, ready again to trace another diagram of what takes place on one side of the piston during another stroke. To compare the Efficiency of different Engines by means of the Indicator . — The following method has been successfully 90 USE OE THE EXPANSION YALYE, adopted in comparing the relative economy of performance of different steam engines by means of their Indicator Diagrams. First, calculate the gross indicator horse power of the en- gine in the usual way, as already described. Then draw on the diagram a pure vacuum line at 15 lbs. below the atmospheric line ; and if, as is generally the case, the eduction begins before the end of the stroke, continue upon the diagram the sloping line of the expansion as if it had been uniform to the end of the stroke, as represented, for instance, at a , a , Fig. p. 93.* The pressure of steam thus found at the end of the stroke (being the pressure above a pure va- cuum) may be called the “Terminal” pressure. Now find the cubic contents of the cylinder in feet, by multiplying the area into the length of stroke, and adding the “clearance” of piston at top or bottom, and the steam space in one port between the valve-face and the inside of the cylinder. The contents of the cylinder at the terminal pressure must now be reduced into the corresponding num- ber of cubic feet of steam at the atmospheric pressure . This is easily done by reference to the table of relative volumes of steam pressure given at page 208. If our cylinder, for example, have 185 feet of cubic contents, and the terminal pressure be 8 lbs. above a vacuum, we must employ the fol- lowing proportion : — 2983 (vol. corresponding to 8 lbs. pressure) : 185 : : 1669 (vol. corresponding to steam at atmospheric pressure) : 103*5 cub. ft. of steam at atmospheric pressure. * There is in general no difficulty in continuing this line with certainty, but if there be a doubt as to where the eduction begins, take the diagram at any definite point, say at nine tenths of the stroke (after the valve has been certainly closed to all further admission of steam), and complete the figure by calculating, from the pressure of steam at this point, what would be its pressure if expanded into the increased space at the end of the stroke. This will be readily done by consulting the table of relative vo- lumes of steam to pressure, given in the end of the book. INDICATOR, AND DYNAMOMETER. 91 This amount being multiplied by the number of cy- linders filled with steam in one minute, and the product being divided by the gross indicator horse power as pre- viously calculated from the diagram, we thus obtain the number of cubic feet of atmospheric steam required by this engine to produce one horse power. It must not be for- gotten that the cylinder of each engine is filled twice with steam for each revolution of the crank shaft. The same simple process being gone through with the other engines under trial, or with the same engine under different circumstances of speed or expansion, affords a tolerably accurate method of comparing, in a general way, their relative efficiency. Example of Calculation . — The following is the calcula- tion made from the diagrams of Penelope , 650 nominal horse power (Figs. p. 93.). The Diameter of cylinder is 9 If in. Area of ditto 6593*5 sq. in. =45*8 sq. ft. Length of stroke 6 ft. 8 in., or with clearance 6* 75 ft. No. of strokes per minute, 14. Gross indicator horse power for both engines, as per diagrams, 1333 H. P. Then, 45*8 area of cyl. in feetx 6*75 ft. length of stroke =309-150 cub. ft. + 3*85 cub. ft. for steam space of port= 313 cub. ft. of steam required to fill the cylinder once : or 313 x 14 = 4382 cub. ft. of steam used above or below each piston in each cylinder during one minute. 92 USE OF THE EXPANSION YALVE, Taking now from the diagrams the four terminal pres- sures corresponding to the top and bottom of each cylinder, we have, — 4382 cub. ft. at 12 lbs. press. =3567 cub. ft. at atmospheric press. Do. ft 13 „ tt =3841 do. Do. tt 15 „ „ =4382 do. Do. tt 15 ft „ =4382 do. 16172 cubic feet of steam at atmo- spheric pressure used per minute by the two engines — or 16172 - 5 - 1333 gross indicator horse power = 12*13 cubic feet of atmospheric steam per horse power per minute. Difference of Effect between throttling the Steam and cut- ting it off by the Expansion Valve. — An experiment made in this manner to determine the difference of effect between expanding the steam in the cylinder by a proper system of expansion, and merely shutting it off by the throttle valve when it is wished to work the engines to a low power, gave the following result : — An engine of the nominal power of 400 horses was selected, and was first worked on the lowest grade of expansion, the steam in the boiler having its full pressure of 8 lbs. Under these circumstances, it was found that 10*87 cubic feet of steam at atmospheric pressure were consumed per horse power per minute. The expansion valves were then thrown out of gear, and the engines reduced by the throttle valve to exactly the same number of revolutions. It was now found that al- though the gross horse power, as shown by the indicator, was almost identical in both cases ; in the latter case the power exerted was obtained at an expenditure of 14*72 cubic feet of atmospheric steam per minute, in place of 10*87 cubic feet, as formerly; 3*85 cubic feet of steam per indicated horse power per minute being thus saved by the principle of expansion. It is apparent that this calculation will not give us the cause of any loss of effect by the steam escaping, or being INDICATOR, AND DYNAMOMETER. 93 INDICATOR DIAGRAM FROM PENELOPE'S ENGINES. FULL STEAM, 14 REVOLUTIONS, 650 NOMINAL H.P. Starboard Cyl. Top 16- 92 ,, Bott. 18*60 Port Cyl. . .Top. 17*35 „ Bott. 18*83 6593*5 x 186*2 x 17*92 ^Mean 17*76 >-Mean 18*09 j>Mean 17*92 33,000 = 666*6 x 2 = 1333 H.P. exerted by both engines. 94 USE OE THE EXPANSION VALVE, condensed in the pipes, &c., which must be sought for when suspected, either in the form of the indicator dia- gram, or by testing the engine for leakage of steam or air, as already explained. Dynamometer . — A Dynamometer is an instrument by which it is attempted to measure the force actually exerted in propelling a vessel. An excellent one, designed by Mr. Colladon of Geneva, has been erected in Woolwich Dock Yard, by which the pull of any vessel made fast to it can be accurately measured. An instrument of this kind, but subject to many disturbing influences, can be fitted on board screw steamers to show the thrust of the propeller shaft through a series of levers on a spring balance. The lever is sometimes made to take the pressure from the end of the shaft ; at other times, from a revolving frame with a number of fric- tion rollers in it, which works against a collar on the shaft at any part that may be most convenient. The lever or levers should have knife-edge centres, so as to work with as little friction as possible; and the rod connecting the lever with the spring balance has a small sliding rod at- tached to it carrying a pencil. By the side of this rod is a small cylinder, round which a piece of paper is coiled, as in the indicator. This cylinder receives a continuous rotatory motion by means of a small band from the screw shaft, the motion being so regulated that the speed of the cylinder (round which the paper is coiled) may be considerably less than that of the screw shaft. The pencil is now brought into contact with the paper on the cylinder, and a zero line traced before the pressure of the shaft is allowed to act upon the lever. The pencil should now be disengaged from the paper, and the connecting rod of the lever screwed up until it is ascertained that the whole forward pressure of the shaft acts upon the lever, and that the shaft is quite clear of every other part of the machinery which might re- ceive a portion of the pressure. Upon the pencil being INDICATOR, AND DYNAMOMETER. 95 again brought into contact with the paper, an undulating line is described upon it, showing the variable thrust of the engines upon the propeller during the period of each revo- lution. After the diagram is traced, the paper is taken off, and equidistant lines drawn at right angles to the zero line, the lengths of these ordinates from the curve to the zero line, measured upon the scale of pounds of the spring ba- lance, giving the action of the lever upon the balance at these places. The numbers being then marked upon the diagram, their sum taken, and divided by the number of ordinates for a mean, we shall have the force exerted on the lever, which, being multiplied by the leverage, will give the average forward pressure exerted by the propeller shaft upon the vessel. If it be only a single lever that is used for the dynamometer, the leverage is of course found by dividing the length from the fulcrum to the point where the rod of the spring balance is attached, by the length be- tween the fulcrum and the point which receives the pres- sure of the shaft ; but if it is a compound lever that is used, multiply together all the long arms of the levers, and divide the product by the product of all the short arms (measuring the length from the fulcrum of each lever), and the quo- tient is the leverage. When the forward pull or pressure in pounds has been found, the number of horses’ power may be calculated for paddle-wheel vessels attached to Mr. Col- ladon’s machine, by multiplying the velocity of the centre of effort of the paddle-board in feet per minute, by the total pull in pounds, and dividing the product by 33,000. The centre of effort of a paddle-board may be taken at J of its depth from the outer edge. In screw vessels, the speed of the screw must be taken for the velocity. Experiments with this instrument when worked out in this way, have generally shown the effective to be about one half the gross indicator horse-power. Counter . — The Counter is an instrument so contrived 96 USE OE THE EXPANSION YALYE, ETC. by the aid of wheelwork that an index hand is moved for- ward a certain distance for every stroke of the engine, thus registering or “ counting ” the number of strokes an engine makes during a day, a month, or any given period. The construction of the counter varies much; in most cases, however, the wheels are moved round by a pendulum at- tached to some vibrating part of the engine, the wheel being carried forward one tooth for every vibration, and an extreme slowness being obtained by a differential motion. Extract from p, 291, Tredgold on the Steam Engine , vol. ii. new edition , — “ The Counter. — To estimate the saving of fuel by the application of Watt’s engines, an apparatus was attached to the beam to ascertain the number of strokes the engines made in a given time : it is called the Counter, and consists of a train of wheel-work resembling that of a clock, so arranged that every stroke made by the engine moves one tooth, and the index shows how many strokes have been made between the times of examination. The counter is enclosed in a box, and locked, to prevent its being altered during the absence of the observer. If the box be attached to the axis of the beam, the inclination of the beam causes its pendulum to vibrate every time the engine makes a stroke, and this moves the counter round one tooth for every stroke. The box may also be fixed to the supports of the beam, and then at every stroke a small detent is moved one tooth.” 97 CHAPTEE VIII. ON THE QUALITIES OF FUEL, WITH HINTS FOE ITS SELECTION. On the Qualities and Value of Different Coals. — The fol- lowing observations upon the qualities and economic values of coal from different localities', are condensed chiefly from the Parliamentary “ Eeport on Coals suited to the Eoyal Navy,” drawn up in the years 1848-49, by Sir Henry de la Beche and Dr. Lyon Playfair. Much depends on the Construction of the Boiler. — In esti- mating the evaporative power of coals, much must of course depend upon the construction of the boiler, and the manner in which the fuel is burnt on the grate. Thus, in Cornwall, where every attainable advantage is given to the fuel by large heating surface, slow combustion, and prevention of loss of heat by radiation, the average evaporative value of 1 lb. of coals may be taken at 10 to 11 lbs. of water, while in marine tubular boilers it rarely exceeds 8 to 8| lbs. An evaporative power of 14 lbs. of water is the highest result theoretically possible for a good average sample of coal. Mr . Wichsteed's Experiments. — Mr. Wicksteed’s experi- ments on this subject give the following results in pounds of water evaporated by one pound of coal, in land boilers of good construction, viz. : — lbs. lbs. Best Welsh coal . 9*5 Average small Newcastle 8-07 Anthracite . . 9*01 Average Welsh 8*04 Best small Newcastle . 8-52 Average large Newcastle 7*66 E 98 ON THE QUALITIES OE EUEL, M. Caves Experiments . — Some recent experiments on tlie evaporating power of cylindrical boilers ashore, made by M. Cave, of Paris, give a mean result of 8*2 lbs. water for 1 lb. coal. Description of the Boiler used in the Parliamentary Experi- ments. — The boiler employed for the Parliamentary Experi- ments was made on the Cornish principle, being cylindrical with flat ends, and an internal flue, within which the grate was placed at one end. The hot air and gases, after leaving the furnace, passed through the central flue to the other end of the boiler, where they divided into two streams, and returned to the front of the boiler, along the outside, by a flue on each side ; these two were then united again under the front of the boiler, and returned along a flue under the bottom of the boiler, finally entering the chimney after a course of about 36 feet. The grate surface was five square feet, and the total heating surface of the boiler 197*6 square feet. The boiler was worked under a pressure of from 1 to 3 lbs. on the square inch. Management of the Fire.— In the management of the fire ? care was taken to supply the coals in pieces not exceeding 1 lb. weight, and in quantities of not more than one or two shovelsful at a time spread evenly over the fire, except in the case of anthracite, and of highly bituminous coal. With anthracite, it was found that the sudden application of heat caused the pieces to split and fall through the bars ; hence a gradual heating on the dead plate in front of the furnace (which in the experimental boiler was 10 inches wide) was found to be beneficial. With the highly bitu- minous coals, also, a partial coking on the dead plate pre- vented their caking together on the fire, which would have impeded the passage of air through the bars. On Patent Fuels , their Advantages and Defects . — The Be- WITH HINTS FOR ITS SELECTION. 99 port states that as the varieties of patent fuel are generally made up in the shape of bricks, they are well adapted for stowage, so that though the specific gravity of patent fuels is lower than that of ordinary coals, yet, from their shape and mechanical structure, there are very few coals that could be stowed in a smaller space per ton. While we look to the different varieties of patent fuel as of the highest importance, and from their facility of stowage as being peculiarly adapted for naval purposes, and perhaps even destined to supersede ordinary coal ; at the same time, the greater part do not appear to be manufactured with a proper regard to the conditions required for war steamers. It is usual to mix bituminous or tarry matter with bitumi- nous coal, and from this compound to make the fuel. An assimilation to the best steam coals would indicate, however, the very reverse process, and point to the mixture of a more anthracite coal with the bituminous cement. As the greater part is at present made, it is almost impossible to prevent the emission of dense opaque smoke, a circum- stance extremely inconvenient to ships of war, as betraying their position at a distance at times when it is desirable to conceal it. Besides this and other inconveniences, the very bituminous varieties are not well suited to hot climates, and are as liable to spontaneous combustion as certain kinds of coal. To avoid these inconveniences some kinds of patent fuel have been subjected to a sort of coking, and thus in a great measure obtain the desired conditions. There is little doubt, however, that notwithstanding the large number of patents in operation for the manufacture of fuel, its value for the purposes of war steamers might be much enhanced by its preparation being specially directed to this object. It will be seen by reference to the table, that the three patent fuels examined rank amongst the highest results obtained. Bapid Corrosion of Iron Coal Bunkers . — The retention of F 2 100 O H THE QUALITIES OE ETTEL, coal in iron bunkers, if these are likely to be influenced by moisture, and especially when by any accident wetted with sea- water, will cause a speedy corrosion of the iron, with a rapidity proportionate to its more or less efficient protec- tion from corroding influences. This corrosion seems due to the action of carbon, or coal, forming with the iron a vol- taic couple, and thus promoting oxidation. The action is similar to that of the tubercular concretions which appear on the inside of iron water pipes when a piece of carbon, not chemically combined with the metal, and in contact with saline waters, produces a speedy corrosion. Where the 66 make ” of iron shows it liable to be thus corroded, a mechanical protection is generally found sufficient. This is sometimes given by Homan cement, by a lining of wood, or by a drying oil driven into the pores of the iron under great pressure. Gases evolved from Coal during Exposure to the Atmo- sphere. — Keeent researches on the gases evolved from coal, prove that carbonic acid and nitrogen are constantly mixed with the inflammable portion, showing that the coal must still be uniting with the oxygen of the atmosphere, and entering into further decay. Instances have frequently occurred of men who had descended into the coal boxes having been rendered insensible by the carbonic acid col- lected there. Natural Decay in Coal. — Decay is merely a combustion proceeding without flame, and is always attended with the production of heat. The gas evolved during the progress of decay in free air consists principally of carbonic acid, a gas very injurious to animal life. It is well known that this change in coal proceeds more rapidly at an elevated tempe- rature, and therefore is liable to take place in hot climates. Dryness is unfavourable to the change, while moisture causes it to proceed with rapidity. When sulphur or iron WITH HINTS FOR ITS SELECTION. 101 pyrites (a compound of sulphur and iron) is present in con- siderable quantity in a coal still changing under the action of the atmosphere, a second powerful heating cause is in- troduced, and both acting together may produce what is called spontaneous combustion . The latter cause is in itself sufficient, if there be an unusual proportion of sulphur or iron pyrites present. Spontaneous Combustion . — The best method of prevention in all such cases is to ensure perfect dryness in the coals when they are stowed away, and to select a variety of fuel not liable to the progressive decomposition to which allusion has been made. Advice in the Selection of Fuel . — It may be desirable to sum up in a few words some of the principal points alluded to in this Eeport. It has been shown that the true practical value of coals for steam purposes, depends upon a com- bination of qualities which could only be elicited by care* fully and properly continued experiments. Their qualities, so far as regards steam ships of war, may be stated as follows : — 1 . The fuel should burn so that steam may be raised in a short period, if this be desired ; in other words, it should be able to produce a quick action. 2. It should possess high evaporative power, that is, be capable of converting much water into steam with a small consumption of coal. 3. It should not be bituminous, lest so much smoke be generated as to betray the position of ships of war, when it is desirable that this should be concealed. 4. It should possess considerable cohesion of its particles, so that it may not be broken into too small fragments by the constant attrition which it may experience in the vessel. 5. It should combine a considerable density with such mechanical structure, that it may easily be stowed away in 102 OK THE QUALITIES OE EUEL, small space ; a condition which, in coals of equal evaporative values, often involves a difference of more than 20 per cent. 6. It should be free from any considerable quantity of sulphur, and should not progressively decay, both of which circumstances render it liable to spontaneous combustion. All the Good Qualities are never united in one Coal . — It never happens that all these conditions are united in one coal. To take an instance, anthracite has very high evapo- rative power, but not being easily ignited, is not suited for quick action ; it has great cohesion in its particles, and is not easily broken up by attrition, but it is not a caking coal, and therefore would not cohere in the furnace when the ship rolled in a gale of wind ; it emits no smoke, but from the intensity of its combustion it causes the iron of the bars and boilers to oxidate, or waste rapidly away. Thus, then, with some pre-eminent advantages it has dis- advantages, which under ordinary circumstances preclude its use. Ey a due attention to these practical hints the com- mander of a steam vessel will be enabled to strike a balance between the good and bad qualities of the fuel offered him for sale, and to select that which appears likely to fulfil most of the conditions which his peculiar service may demand. Tables of the “ Economic values of different coals and patent fuels of the “ Mean composition of average samples of the coals and of the “ Substances produced by the destructive distillation of certain coals,” will be found at the end of the book. Wood used as Fuel in Steam Vessels. — When wood is used for fuel in steam vessels, it requires from to 3 lbs. (ac- cording to the degree of dryness) to equal one pound of coal. Wood tolerably well dried contains one fifth of its WITH HINTS FOE. ITS SELECTION. 103 own weight of water, in evaporating which about one quarter of the whole heat generated is absorbed ; peat, on the contrary, contains only from 1 to 3 per cent, of “ hygro- scopic” water. Turf used as Fuel in Steam Vessels . — Turf has been oc- casionally used for fuel in steam boats, though not hitherto with much success. Its calorific value depends wholly upon the degree of dryness to which it has been brought, and when kiln-dried it is found to have a strong tendency to re-absorb moisture ; so it should be used as soon after this process as possible. When burnt in a tubular marine boiler with 6| square feet of grate bar and 280 square feet of total heating surface, it required 51 lbs. of good peat to evaporate one cubit foot of water, being about one sixth of the duty of coal. 104 CHAPTER IX. , CONSIDERATIONS AFFECTING THE KATE OF CONSUMPTION OF THE FUEL IN A STEAM YESSEL. Rate of Consumption of the Fuel in a Steam Vessel .■ — The rate of consumption of the fuel in a sea-going steamer is a consideration of the first importance, not merely as it re- gards the question of expense, but also as it affects the capability of the vessel for increasing the length of her voyage under steam, as well as her safety in case of unusual detention from adverse weather. It is proved alike by theory and experience, that under ordinary circumstances of weather, a vessel will steam further with a given quantity of coals, by using only a fraction of her steam power, than she would if going at full speed. Theoretically speaking, the slower the vessel’s speed, the greater the economy of fuel, provided always that no steam escape from the safety valve, or is otherwise wasted; but if her progress be op- posed by contrary winds and currents, the engines should of course exert sufficient power, not merely to preserve her position, but to give forward motion if possible. Steaming against the Stream . — In this case it is found that the power is applied most economically when the vessel steams half as fast again as the velocity of the opposing stream or current. Thus, if the vessel be steaming up a river, or in a tide way where the current runs at four knots an hour, her speed should then not be less than six knots. Natural Law regulating the Speed of a Steamer. — These results chiefly depend upon the natural law that the power CONSUMPTION OF FUEL IN A STEAM VESSEL. 105 expended in propelling a steam ship through the water varies as the cube of the velocity . This law is modified by the retarding effect of the increased resisting surface, conse- quent upon the weight of the engines and fuel, so that the horse power increases in a somewhat higher ratio than that named. Limit imposed to the Possible Speed . — This consideration imposes a limit to the possible speed of a steamer, depend- ing upon the weight of the machinery and fuel which it can carry, relatively to its dimensions and tonnage. It is apparent also that this limit is extended according as the proportions of the engines and vessel are increased, for the larger the engines the less is their weight per horse power, and the greater is the effect of the steam in the cylinders ; while the larger the vessel, the less is the resisting surface increased by the displacement of each additional ton of machinery and fuel. To find the Speed corresponding to a Diminished Consump- tion of Fuel . — Hence, if a vessel of 500 horses power, we shall suppose, have a speed of 12 knots, with a consump- tion of 40 tons of coal per diem, if we wish to find the speed corresponding to a diminished consumption of 30 tons per diem, the following simple calculation is re- quired, viz. : — 40 : 30 ::12 3 : V 3 (cube of the required velocity), Or, reduced, 4 : 3:: 1728 : V 3 , As an equation, 3 x 1728=5184 = 4 V 3 , Or, 5184 = 4 \/ 1296 = 10*902 knots =V, required velocity. Thus, by diminishing the horses power, or the consump- tion of fuel, of this vessel by one fourth, we lose only a little more than one knot per hour in the resulting speed. F 3 106 CONSIDEEATIONS AFFECTING THE BATE OF The same calculation may be applied for comparing the effects of engines of different power in the same vessel, or of the same engines when worked at reduced pow r er. The results thus obtained are of course independent of the additional advantage gained by expanding the steam in the cylinders, which in the case of large engines working at low powers, is very considerable. To find the Consumption of Fuel corresponding to an In- creased Speed. — Again, if we find that the speed of our vessel has advanced from eight knots (we will suppose) to nine knots, in consequence perhaps of her having received new boilers, and using more steam in the cylinders, and we wish to find the corresponding increase in the consumption of fuel, the following calculation will be necessary, viz. : — 8 3 : 9 3 : : former consumption : present consumption, 512 : 729:: „ : Or, in the ratio of 1 to 1*424. Fetation between the Consumption of Fuel , and the Length and Velocity of the Voyage. — Again, the consumption of fuel during two or more voyages of known lengths will vary in the proportion of the square of the velocity multiplied by the distance traversed. Thus, if we find that during a voyage of 1200 miles, per- formed at the average speed of ten knots, the total con- sumption of fuel is 150 tons, and if we now wish to ascertain the consumption for a longer voyage of 1 800 miles (we will suppose), at a reduced speed of eight knots, the calculation will be as follows : — 150 tons : C required consumption :: 10 2 knots x 1200 miles : 8 2 knots x 1800 miles. Then, C x 100 x 1200 = 150 x 64 x 1800,* Or, C x 120,000 =*» 1 7,280,000 1 728 Reduced to C = =144 tons consumption. CONSUMPTION or FUEL IN A STEAM YESSEL. 107 If, on the other hand, we require to know at what rate the vessel must steam in order that her consumption during the longer voyage of 1800 miles may not exceed her pre- vious consumption of 150 tons during a voyage of 1200 miles at ten knots an hour, the calculation will be as follows : — If we substitute 150 tons (our supposed consumption) for C in the equation above, marked thus*, and V 2 (the square of the required velocity) for 64, we shall then have, 150 X 100 X 1200 = 150 x V 2 x 1800, Or, 120,000 = 1800 V 2 , „ , , 1200 _ 72 Reduced, — - - =V 2 , 1 o And V = n/ 66 66 =8*15 knots. Economy attending a diminished Speed in the Vessel.— These examples all show the great economy which attends a diminution of speed in the vessel ; and although in the case of merchant steamers, the loss of time is generally too serious a disadvantage to admit of any permanent reduction of speed, much benefit has resulted to ships in the Royal Navy from the judicious husbanding of the fuel in this manner, whether it be to meet the requirements of an unusually long run, or merely to save coal when the vessel is employed on a service not demanding extraordinary despatch. Use of Sails of a Steamer . — The steamer’s sails, also, form a most important addition to her capabilities, as for each knot that the vessel is propelled by their aid, as much fuel is saved as may afterwards propel her the same number of knots in a calm. The sails should therefore be set upon every occasion of a fair wind, and according as it is more or less favourable, so should the steam be more or less cut off and expanded in the cylinders. By this means we avoid the unnecessary consumption of dense steam, which would 108 CONSUMPTION or FUEL IN A STEAM YESSEL. otherwise be used at a disadvantage, for it is evident that however little the engines may assist in propelling the ship, they must nevertheless work very fast in order to overtake the vessel’s speed generated by the sails alone, and two cylinders full of steam must always be used for each revolution. Disconnecting the Engines. — Hence, when a moderate speed is attained by the sails alone, it is more economical (though otherwise not always to be recommended) to stop the engines entirely, and disconnect the wheels or screw when practicable, suffering them to revolve freely in their journals by the re-action of the water. When, on the other hand, the wind and sea are adverse, the full power of the engines must be applied, every knot gained being now of double value. 109 CHAPTER X. PROPORTIONS TO BE GIVEN TO THE PADDLE WHEEL AND SCREW PROPELLER, AND THE MANNER OE THEIR AP- PLICATION IN THE VESSEL. Varieties of the Paddle Wheel . — With regard to Paddle Wheels, it is believed that the common wheel, if properly proportioned and allowed the proper degree of immersion, is preferable, under ordinary circumstances, to any of the “improved” varieties which have from time to time appeared. Of these, the only one which can be recommended, and that only under peculiar circumstances, is Morgan’s feather- ing wheel, by the use of which the boards may be made deeper, and therefore narrower than in the common wheel, and the diameter may be somewhat diminished ; but it is objectionable from its weight (which is nearly twice that of the common wheel), from its complexity and consequent liability to derangement, and from its considerable addi- tional expense. Mr. Eield’s “ Cycloidal ” wheel, in which the paddle board is divided into steps with an open space between, can hardly claim any superiority over the undi- vided board, but the simple modification of this plan, formed by dividing the board into two breadths, and placing one on either side of the paddle arm, is probably the best form of wheel that can be adopted for large steamers. Variable Immersion the Grand Objection to the Paddle Wheel. — We have already hinted that the grand objection to the paddle wheel is the unequal “ dip ” or immersion of the boards, consequent on the varying draught of water, as the coals and stores continue to be consumed on the voyage. A vessel, for instance, with a displacement of 12 tons per 110 PADDLE WHEEL AJTD SCREW PROPELLER. inch at the load line, burning perhaps 460 tons of coals during a long run, will swim 3 feet 6 inches lighter, from the consumption of the fuel alone, at the end than at the beginning, so that it is only in the middle of her voyage that the wheels can have the dip best calculated for them. The most advantageous Dip . — The most advantageous dip varies with the diameter of the wheel, the speed of the vessel, and the service in which she is employed, as for sea or river navigation. Sea-going steamers of the first class are usually allowed 18 to 21 inches of water over the ver- tical float at the mean draught ; and smaller vessels may have 12 to 15 inches. It is usual in the case of fast river boats to allow only an inch or two over the boards, when the wheels are large. When the wheels are too deeply im- mersed, they may sometimes be “reefed” by disconnecting the boards, and securing them nearer the centre. The “ Slip ” of the P addle Wheel . — The “ slip 99 of the paddle wheel, by which is meant the excess of its velocity above that of the vessel, is usually reckoned at one fifth (or 20 per cent.) of the vessel’s speed, the wheel being sup- posed to be well-proportioned, and the water lines of the vessel tolerably good for speed. Explanation of Table of Velocities of Paddle Wheels . — As it is of considerable importance to observe and compare the slip of the wheel under different circumstances, or in different vessels, we have prepared a table of velocities of paddle wheels of varying diameters and speeds, in feet per minute, and miles per hour. The “ effective diameter ” of the wheel may be reckoned by subtracting one-third of the breadth of the boards from each end of the extreme dia- meter. This subtraction should therefore be made before referring to the Table given in the Appendix. The rule for finding the velocity of a paddle wheel, when its effective MANNER 0 E APPLICATION. Ill diameter and number of revolutions are given, is the fol- lowing : — Multiply the diameter by 3’ 1416, multiply the product by the number of revolutions per minute, multiply the last product by 60, and divide by 5280 for the velocity in statute miles, or by 6082*66 for knots per hour. The Table referred to will be found at the end of the book. Area of the P addle Boards . — In proportioning the area of the paddle boards we must take into consideration the estimated dip of the wheels. By taking an average of the practice with regard to large sea-going steamers, we find that the whole paddle-board surface for the two wheels is be- tween and 3 square feet per horse power; but for steamers with a lighter dip, from 4 to 5 square feet are al- lowed. The surface of each board, for large vessels, rarely exceeds one twenty-fifth of the total horse power, in square feet ; but increases as the dip and diameter of the wheel diminishes, to about one fifteenth : while for river steamers one tenth of the total horse power is a usual proportion. A long narrow board is more effective than a short and deep one, but is inconvenient, especially in sea-going ves- sels, from the increased breadth of the paddle box. Thus, in large steamers, the proportion of depth to length varies from one fourth to one fifth, but in river steamers the board is generally about seven times as long as it is broad. Disconnecting the Paddle Wheels . — As it is frequently desirable to disconnect the paddle wheels from the engines, and permit them to revolve in their bearings while the ship is under canvas, several kinds of disconnecting apparatus have been employed for this purpose. Description of Braithwaite s Disconnecting Apparatus . — Braith waite’s apparatus is represented in the subjoined 112 PADDLE WHEEL AND SCREW PROPELLER. wood-cut, and it may be thus described. A cast-iron disc, a , is keyed on the end of tbe paddle shaft, b 3 and a strong wrought-iron hoop, c c, lined with brass to diminish the friction, surrounds and slides over the periphery of the cast-iron disc. At one side of this hoop, at d, a projection H Braithwaite’s Disconnecting Apparatus. is forged, in which the eye is bored for the crank pin, and at the other side the hoop is swelled out to receive a brass cushion, e, inserted between the hoop and the cast-iron disc. Now, when this cushion is driven hard and tight against the periphery of the disc, by means of a strong key, f, the friction between the hoop (in which the crank pin is fixed) and the disc on the paddle shaft becomes so great that the former drags round the latter, and thus communi- cates motion to the wheels. These are again disconnected by driving back the key, and by this means loosening the friction cushion, when the hoop and the disc revolve each independently of the other. This apparatus is by no means perfect, and gives much trouble at sea by the slipping of the hoop, notwithstanding that the key may have been driven as tight as possible. The hoop has also itself frequently given way, as the forging is a difficult one to make perfectly sound. MANNER OE APPLICATION. 113 Maudslay's . — Messrs. Maudslay and Field adopt the plan of sliding the paddle shaft, with the outer crank upon it, out of the crank pin, using for this purpose a worm wheel and cogged collar on the shaft, worked from the deck. Seaward's Plan. — Messrs. Seaward form the pin end of their outer crank with a slot cut out of the thickness of the boss on the inside, the breadth of the slot being equal to the diameter of the pin, which is held fast by square keys in the boss while the engines are working. When it is wished to disconnect the wheels, the engines are stopped, and the keys withdrawn, when the boss of the outer crank clears and passes the pin by means of the slot, as the wheels re- volve in their bearings from the resistance of the water. The Screw Propeller . — An idea of a screw may be given by supposing a line or thread wound round a cylinder, and advancing along it in the di- rection of its length by a gra- dual and equal rate of pro- gression. This thread may be of any shape, either trian- gular, as in many cases, or it may be in the form of a thin plate of metal kept upon its edge, and wound round a cy- linder of so small a diameter that it would no longer be called a cylinder, but would become a mere rod or spindle in the centre. This will pro- bably be best understood by reference to the annexed dia- gram, which represents one thread of this kind wound 114 PADDLE WHEEL AND SCREW PROPELLER. round a spindle, and this is called a single-threaded screw. It will be at once evident that two, three, or more threads, if kept uniformly parallel to each other, may in the same man- ner be wound round the cylinder, and there is then produced a two-threaded or three-threaded screw accordingly. The properties of q, screw of this kind were first investigated and made known by Archimedes. The Pitch of a Screw. — Supposing that a line is drawn along the surface of a cylinder in the direction of its length, and that a line or thread as before is wound round it, the distances between the points where the thread crosses the longitudinal line, and which are always the same, is called the, pitch of the screw. The Slip of a Screw. — If a screw be made to revolve in a solid, as a carpenter’s screw in wood, it is evident that it will progress in the direction of its axis the distance of its pitch for each revolution, the latter portions following ex- actly in the course cut by the preceding or first entered portions of the thread. If, however, it be made to revolve in water, which is a yielding medium, the water will to some extent give way, and the screw will not progress the full amount of its pitch, this deficiency in its progress being denominated the slip of the screw. Anomaly in the Performance of the Screw , called c< Negative Slip.” — There is an anomaly in the performance of the screw, namely, the well-authenticated presence of “negative slip,” as it has been termed, or the fact of the vessel actually going faster than the rate at which the screw which propels it would advance if revolving in a solid. The explanation offered is, that the vessels in which this occurs have their after lines so badly formed for closing the water, that instead of the hull passing through the fluid with so little disturbance as scarcely to affect its condition of relative rest, a large body MANNER OF APPLICATION. 115 of “dead water” is created, which follows the vessel, being towed (as it were) in her wake. An opposing current, and therefore an increased resistance, is thus offered to the ac- tion of the screw. This seems to have the effect of anni- hilating the slip, the vessel appearing to outstrip the propeller by virtue of its advancing through still water (relatively to its own motion), while the screw revolves against an opposing stream. It cannot be supposed that in such a case the power of the engines is economically ap- plied, as a much larger portion of the power is expended in towing the dead water against which the screw re-acts, than is afterwards recovered by the increased effect of the screw. Thus, if the rate of progression of the screw be 10 knots through a solid, and if a current flows against it at the rate of three knots, this will be equal to a real progression of 13 knots for the screw, and we need not be much surprised if the speed of the vessel, under these circumstances, ex- ceeds the apparent speed of the screw by perhaps one knot per hour. Anomalies of this kind most frequently occur in auxiliary-screw steamers, where the vessel, after attaining a high velocity by sails alone, still continues to derive additional assistance from the screw, although its speed may not equal that of the vessel. Dragging of the Screw . — In such vessels, therefore, it does not always follow that the engines are no longer use- ful after the speed attained by the sails is equal to the progression of the screw, but the engineer should under these circumstances watch the thrust of his propeller shaft very narrowly, as there must be a limit to this in all vessels carrying a large spread of canvas. If he find the thrust to cease, he will then know that the screw is “ dragging,” and will recommend his commander to discontinue the use of the engines as being no longer serviceable. Direct evi- dence of the screw “ dragging ” has been obtained by the 116 PADDLE WHEEL AND SCBEW PBOPELLEB. fact of a propeller having been carried away by the strain brought upon it from the velocity of the ship due to the sails exceeding the velocity of the screw. The rupture in this case clearly showed that the blade, which was of iron plate riveted upon a wrought-iron arm, was torn off back- wards by the drag brought upon it. Disconnecting the Screw . — It is usual in the Government service to provide means for withdrawing the driving shaft out of a socket in the screw shaft, for the purpose of dis- connecting the screw and raising it entirely out of the water when the ship is under canvas. This is effected by having a hollow trunk constructed over it in the stern of the vessel, into which the screw is lifted by proper machinery, the outer screw shaft fitting into a vertical frame of gun metal which rises along with it. This ^ill be best understood by refer- ence to the frontispiece, which is a section of the stern of a vessel so fitted. In some vessels, the screw is only capable of being disconnected from the engines, and left free to revolve by the action of the water upon it, from the motion of the vessel. Contrivances have also been introduced to place the blades in a fore and aft direction, so that they may lie within the dead wood of the vessel, and present no projecting surface to impede her progress, or affect her steering. The Propelling Power of the Screw . — If the spindle of the screw (see fig. in page 113) be supposed to be passed through the side of a box filled with water, and made to revolve there without the power of moving in the direction of its axis, it will send the water away from it with a certain amount of force, and hence, as action and reaction are always equal, the screw is pushed forward with this amount of force ; and, if it were attached to a ship, the ship would thus be propelled. The reverse of this action would take place, and the ship would MANNER OE APPLICATION. 117 be pulled backwards, if the screw were made to revolve in the opposite direction. From the number of revolutions which a screw propeller of a known pitch makes in a minute, the progress which it would make in an hour is calculated ; and, if the speed of the ship be found by observation to be less than this, the difference is the slip. Explanation of the Tei'm “Screw Blade ” — If the screw (see fig. in page 113) be cut into any number of portions by planes passing across it at right angles to the axis, which would be represented in the figure by lines, any one of the portions would have the appearance of the vane of a windmill ; and, if the screw were two-threaded, the vanes or blades would be exactly opposite each other. If a sixth part of the length of the screw be marked off in the plate, it will be seen that the part will then resemble one of the blades of the screw propeller represented in its place in the vessel in the fron- tispiece, the latter screw however being two-bladed. To find the Bitch of a Screw Blade . — This operation pro- ceeds upon the fact that if a line representing the circum- ference of the screw’s disc at its extreme diameter, and another representing the pitch of the screw, be drawn at right angles to each other, to a scale of parts, the hypo- thenuse of this right-angled triangle will represent the length of the winding thread. After measuring the diameter in order to find the circumference from it, the length of the blade along its periphery is to be measured, this being a portion of the hypothenuse of the triangle whose sides we wish to determine ; then measure the distance that one corner of the blade is before the other in the line of the axis, and this being a portion of the pitch is a part of another side of the triangle. Now two sides of a right- angled triangle being known, the third can be found in this case by subtracting the square of the side from the square 118 PADDLE WHEEL AND SCREW PROPELLER. of the hypothenuse and finding tlie square root of the re- mainder, and the dimension so found will represent a por- tion of the circumference. And now, as this portion of the circumference is to the whole circumference, so is the por- tion of the pitch as measured to the whole pitch. Introduction and Progress of the Screw Propeller . — Having thus endeavoured in a popular manner to give an outline of what a screw propeller is, it may not be uninteresting or out of place to trace shortly the introduction and pro- gress of screw propulsion. Dr. Shorter, a practical me- chanic of this country, succeeded in propelling a vessel by a screw in 1802 ; but, as no power was at that time known capable of driving his propeller with proper effect, it fell into oblivion. The first introducers of Watt’s steam engine for marine purposes adopted the paddle wheel ; and its success, with such an agent to drive it, seems for a time to have drawn off the current of invention entirely from sub- merged propellers. Though other patents had been taken out, it was not till Captain Ericsson and Mr. E. P. Smith brought out their experimental vessels in 1837 that any real progress was made. Captain Ericsson’s small vessel of 45 feet in length and 8 feet beam, and drawing only 2 feet 3 inches of water, towed the American ship Toronto, of 630 tons burthen, on the Thames, on 25th of May, 1837, at the rate of 4|- knots per hour against tide, as authenticated by the pilot : and also towed the Admiralty barge, with their Lordships, from Somerset House to Blackwall and back at the rate of about 10 miles an hour. To Captain Ericsson’s anxious application, and after his pointing out the many advantages of a submerged propeller for vessels of war, he received the discouraging reply that their Lordships de- clined to entertain the project. Later in the same year Mr. Smith made some very successful trips with his small boat and screw propeller between Margate and Ramsgate. MANNEE OE APPLICATION. 119 The next screw vessel was the Bobert Stockton, in 1839, built for an American gentleman who had witnessed Cap- tain Ericsson’s experiments and taken a favourable and correct view of them. This vessel was eminently success- ful ; but the designer, finding himself still unable to move the Board of Admiralty, left this country for America, whither this vessel had proceeded, determined to prosecute his invention there. In the mean time some influential mercantile men had connected themselves with Mr. Smith with the view of purchasing his patent ; and the Archi- medes, a vessel of 232 tons and 80-horse power, was brought out in 1840. # The success of this vessel was complete, and the publicity given to her performances by her spirited owners, who took her round Great Britain and showed her powers in every port, rendered the capabilities of the screw no longer a matter of doubt. The Board of Admiralty having received most favourable reports of the perform- ances of this vessel from Captain Chappel, who had accom- panied her on this voyage, and from Mr. Lloyd who had witnessed her performances in making several trips between Dover and Calais in competition with the mail steamers then running, now ordered the Battler to be built on the same lines as the paddle-wheel steamer the Alecto, and with engines of the same nominal horse power. The next screw Vessel to be noticed whose performances influenced the pro- gress of the screw as a propeller is the Dove, constructed at Liverpool, of iron, under Mr. Smith’s direction. The speed realized, however, was not equal to what was expected if she had been fitted with paddle-wheels : the owners were in consequence dissatisfied, and ordered her to be altered as quickly as possible to paddle-wheels. She was built with very fine lines abaft ; and, most unfortunately, from this circumstance, and from some experiments in the Archi- medes which had proved the possibility of negative slip, * See Appendix D. to Tredgold on the Steam Engine, 4to. 120 PADDLE WHEEL AND SCEEW PEOPELLEE. Mr. Smith, and those with him on whose judgment as men of science he relied, took up the idea that full stern lines were the most advantageous for the screw. The Battler was now tried ; and, after her trials had fully satisfied the Board of Admiralty, they ordered the construction of several additional screw vessels, and Mr. Smith inculcated his views in favour of full sterns upon their different constructors. This was finally proved to he erroneous, and that a fine run with a ready access for the water to the screw, and as clear an escape for it ahaft as possible, was absolutely necessary, and the whole of these vessels had to be altered at great cost. In the mean time the screw had risen most rapidly in favour with the public, and fast vessels had been con- structed by Mr. Slaughter, of Bristol, with 'Woodcroft’s patent screw, and by other parties, as well as several aux- iliary screw vessels. Varieties of the Screw Propeller . — A great variety of patents for screw propellers were taken out, not only before, but also largely since the success of Captain Ericsson and Mr. Smith ; but it is proposed here to refer only to those which have been found successful on trial, and which seem to promise to be of any practical utility. The propellers formed of portions of a true screw, have been already de- scribed, and of these Smith and Lowe claim to be the pa- tentees ; the latter party having taken out a patent in Sep- tember, 1838, for the use of one or more screw blades, similar to what are now generally employed. Woodcroft's Screw . — Professor Woodcraft, in his patent of 1832, prior to Captain Ericsson and Mr. Smith, proposed a screw of such construction that the pitch or distance be- tween the revolutions of the thread should continually in- crease through its whole length, with the view that the after part might act with greater efficiency on the water that had been previously acted upon by the foremost part. MANNER OE APPLICATION. 121 He fell into the error, into which Mr. E. P. Smith also subsequently fell, of supposing that one full turn or more of the thread was requisite to make an efficient propeller ; and no practical progress was made with his invention, till the first experimental vessels already referred to had been tried and found to be successful. Woodcroft then reduced the length of his screw to that of Lowe’s blades, and a trial was made with it in the Rattler , when the fol- lowing results were obtained, in comparison with a pro- peller of similar proportions, but whose blades were portions of a true screw : — True Screw . 18th of March, 1844. Wooctcroft’s Screw. 13th of April, 1844. Number of Blades 4 4 Diameter of Propeller 9 ft. 0 in. 9ft. Oin. Length of ditto 1ft. 7 in. 1 ft. 7 in. Pitch of ditto lift. Oin. 11 ft. 0 in. to 11*55 ft. Strokes of the Engine per minute 26*28 24*152 Mean pressure of Steam, by indicator . . 14*38 14*57 Horse Power, by indicator 459 428*76 Speed of Ship 8*180 8*159 To compare these results, we know that if both propellers were equally efficient, the speed should be as the cube roots of the powers exerted; — now if 459-horse power gave a speed of 8T80, to find what speed 428*76 ought to give, we must use the following proportion, ^459 : ^428*76 : : 8*180 : 7*9962. But instead of 7*9962 knots, Woodcroft’s screw with this power gave a speed of 8*159, or nearly ^ knot more, thus proving its superiority to this extent in this case. Ericsson's Propeller . — Captain Ericsson’s propeller con- sists of a number of blades fixed at a distance from the axis upon the periphery of a short cylinder, or ring of metal, the ring being united to the axis by two or more a 122 PADDLE WHEEL AND SCBEW PBOPELLEE. arms. It is here represented. Both M. Carlsund and M. Sorenson of the Swedish navy are using a similar screw, hut with the ring on the periphery or exterior of the blades. The blades and arms are segments of a screw, and there is nothing to prevent this being a most efficient propeller. It seems to con- tinue in favour in America and in France ; but the great objection to it in this country is the difficulty of removing it, or preventing it from retarding the vessel when she is placed under canvas. Captain Ericsson at first used two of his propellers acting in combination, but he soon found that one was sufficient. Maudslay’s Feathering Screw . — This screw is represented in the opposite page. The object sought to be attained is, that the blades, whenever the vessel is put under canvas and the screw not required, 123 MAUDSLAY'S FEATHERING SCREW, 1$/. In position for use as a Propeller . 2nd. In position for sailing under canvas alone. 124 PADDLE WHEEL AND SCREW PROPELLER. should be placed in a direction parallel with the line of the keel, and so form as it were a portion of the dead-wood, as they cause considerable obstruction if permitted to re- main fixed in tbeir position, or even tbougb they be discon- nected from the engine and allowed to revolve. In auxiliary sailing vessels not fitted with a trunk or aperture for the pur- pose of raising the screw out of the water, this is particularly valuable ; but it will also be found useful in men of war, by lessening the width of the trunk through which it has to rise, if this be desired ; and also by the facility which it gives in emergencies, for placing a vessel quickly under canvas, or under steam, without requiring the aid of the crew ; and also for placing the vessel under canvas when it may not be pos- sible to keep the engines at work, from their having been injured by shot or any other cause, and when it may at the same time be imperative to keep the screw down in its place to permit the stern guns to be used over the aperture of the trunk. Hodgson's Parabolic Propeller . — This propeller is con- structed with two blades, placed at an angle to the centre line of the axis, but differing essentially from the blades of a true screw, or of Woodcroft’s screw, in their being hollow on the face, and being bent backwards in such a form as to be portions of a parabola. It is now much adopted in Holland. The peculiar principle of this propeller lies in this, that whereas the line of the action of other propellers upon the water is parallel to their axes, and the particles of water when driven off assume the form of a cone diverging as they recede ; the water acted upon by the parabolic pro- peller, when driven off from each blade, is projected by the nature of the parabolic curve to its focus in the line of its axis. The water is therefore forced towards the centre, and exerts a greater amount of resistance, from its not being &o readily thrown up to the surface in the line of least re- sistance, where it escapes in the form of broken water. MANNER OE APPLICATION. 125 Macintosh’ s Elastic Propeller . — This propeller is con- structed with flexible blades of steel, in such a manner that, when made to revolve, the action of the water in pressing against them to propel the vessel bends or springs their faces hack, so as to make them approach nearer to a disc at right angles to its axis ; and it is understood that Mr. Macintosh, if he could construct his blades to be so very flexible, would desire that they should be so bent as to assume this form when revolving at their highest velocity. In this case the propulsion of the vessel, instead of being obtained on the principle of the screw, may be looked upon as being obtained by the elastic spring or tendency of the blades to recover their form, thus keeping up a constant pressure upon the water behind them, and forcing the vessel forward. The higher the velocity of revolution is, the more the blades will be bent back, and the greater will be their propelling force, until they assume the form of a disc, when any further velocity would cease to produce additional effect. Comparison of the Flexible Propeller with the Action of a Fish. — The tails of three fishes — salmon, mackerel, and her- 126 PADDLE WHEEL AND SCREW PROPELLER. ring — that swim at high velocities are here represented; and, if the mode of their action he considered, it is con- ceived that it will be seen to resemble that of Macintosh’s propeller more than that of the Archimedean screw. When the tail of the fish is moved to the right, the web, or thin finny part, is bent to the left on account of its weakness in comparison with the stronger parts near the body ; and it is conceived that it is from the water pressing upon this oblique portion, while it keeps it bent back in opposition to the force exerted by the fish to send it to the right, that the motion is obtained. In the Application of the Screw , fine After -lines are in- dispensable . — With regard to the application of the Screw propeller, it is now well understood that the after-lines of the vessel must be kept as fine as practicable just before the screw, the body of the vessel terminating, if possible, at the inner stern post, so as to avoid the flat surface, or “ square tuck,” which occasioned so much disquietude to our dockyard engineers upon the first introduction of this principle. It was then shown by experiment with the Dwarf that the filling out of the lines immediately be- fore the screw produced a most injurious effect upon the speed of the vessel, and those of the Admiralty screw MANNER 0 E APPLICATION. 127 steamers which have had their lines fined away there, have since advanced in speed by several knots an hour. In wooden vessels, the edges of the screw aperture are strength- ened with gun-metal castings, by means of which a sharper finish can be given to them. And it is chiefly in this point of view that iron vessels have shown themselves better adapted for the screw propeller than wooden ones, in consequence of the extreme fineness to which they may be tapered at the stern-post, with a due regard to strength. Diameter of Screw . — The diameter of the screw should, in most cases, be made as great as the draught of water will admit, and for running in smooth water its upper edge need not be more than a few inches beneath the surface. In the case of sea-going vessels, it is preferable to keep it 18 inches or 2 feet below the mean surface of the water. Area of the Screw . — By the area of the disc of the screw is understood the area of the circle described by its extreme diameter. "When the area of the blades is spoken of, their actual oblique surface should always be specially distin- guished from the plane projection of the resisting surface. This latter measurement, as representing the actual amount of surface directly employed in the propulsion of the vessel, is probably the most important * of these areas. The Dwarfs experiments show that the speed of this vessel gradually increased a little as the length of her screw was diminished from 2 feet 6 inches to 1 foot, the area cor- responding to each length being 22*2 and 8*96 square feet respectively. It appears at first sight remarkable that so great a variation in the resisting surface should cause so little disturbance in the speed of the engines or of the vessel, thus showing very plainly how small a segment of the whole “pitch” is required to absorb all the power which the reaction of the water is capable of imparting. The fact seems to be that the water in which the screw revolves ac- 128 PADDLE WHEEL AKV SCEEW PROPELLED. quires very soon the same rotatory motion with the screw, and as its resisting power is thus destroyed by the action of the leading part of the thread only, any additional length ot screw, after the power has been absorbed, only retards by friction. The Rattler's experiments, conducted by the Engineering Department of H. M. Dockyard at Woolwich, were commenced with a screw 5 ft. 9 in. long, which was gradually shortened, followed always by an improve- ment in the speed of the vessel, until it reached its present length of only 15 inches. The result of numerous experi- ments has led to the now very generally received opinion that the length of the screw should be about one sixth of its pitch. Relative Value of Coarsely or Fine pitched Screws. — The question between the relative values of fine and coarsely pitched screws appears to be as yet quite undecided. The equally good results that have been obtained (more espe- cially in the merchant service) by the use of coarsely pitched screws running at a comparatively low speed, and very finely pitched screws running at a great velocity, tend to the con- clusion that a variation in pitch is not of much practical importance within certain limits. Extent of Slip of the Screw. — The diameter of the screw and the speed at which it is driven modify, in a great mea- sure, the amount of slip, which is usually found to diminish in proportion as the diameter and velocity increase. Thus, the diameter of the Rattler's screw during her experiments was 10 feet, and the average slip 15 per cent., while the Dwarf and Fairy , with screws of between five and six feet diameter, showed an average slip of about 85 per cent. The slip is also affected by the form of the vessel’s run, and the manner in which the water closes in upon the screw, so that it is necessarily very uncertain, and will pro- bably vary in every ship. 129 CHAPTEE XI. ’COMPARATIVE MERITS OE D EFFERENT STEAM VESSELS AND OF SCREW AND PADDLE-WHEEL VESSELS. To compare the General Efficiency of different Vessels . — It will be apparent from what has been already said that it is very difficult, if not wholly impracticable, to institute a just comparison between the degrees of efficiency of different steam vessels. In the first place, the performance of the machinery has to be separated from the question of the, form of the vessel, if we would enter minutely into the subject, and the performance of the machinery itself should again be subdivided into the relative efficiency of the en- gines and boilers . But as it cannot be expected that mercantile men should enter into these details, a simple method of drawing a general and approximate comparison between different ves- sels taken as a whole may be found useful. For Commercial Purposes . — It is at once apparent that the mere statement of the number of miles run for one ton of coals, can be a just criterion only between vessels of the same or nearly equal size, making the same voyage, at nearly equal speeds, and that it is by no means applicable as a general standard, since a ton of coals will, as a matter of course, carry a small vessel further than it will a larger one. As we have seen, too, that an increase of speed is obtained only at the expenditure of a very great increase of power, a proper allowance must also be made for this. Hence to draw even the most superficial comparison between the “ ef- ficiency ” of two steam vessels, their speeds must first be reduced to a common standard, and the relation must then be found between the consumption of the fuel at this speed and the size or tonnage of the vessel, the maximum speed of each being considered as a separate question. The signifi- cation of the term efficiency , varies so materially in different G 3 130 COMPARATIVE MERITS OE THE classes of vessels, that steamers of the same class only can be justly compared together ; the speed required by any particular service, or in other words, the estimation of time in each service, being a totally distinct consideration, as re- gards consumption of fuel and general efficiency. Thus, one vessel may make a voyage at a slow rate, and with a small consumption of fuel, while another vessel of the same power and tonnage, although it may be of very decidedly superior “ efficiency,” may consume a much greater quantity of fuel, by performing the same voyage in a much shorter time. In the Government service, the time occupied by a voyage is usually not so much considered as a low consump- tion of fuel, and the vessel is therefore limited to a slow and economical speed. In the case of merchant steamers, on the other hand, this system would be the reverse of economy. It is believed, that if the number of Register tons carried by one ton of coals, at the rate of 10 knots an hour, be taken as a common standard of comparison for estimating the duty of sea-going steamers, it will be found sufficiently accurate for mercantile purposes, the maximum speed of the vessel being treated as a separate consideration. Example No. 1. — Suppose, for example, that a vessel of 1300 tons, and 500 horse power is found, by experiment, when at her medium draught of water, to make 10*5 knots an hour, with a consumption of three tons of coal per hour. To reduce her performance to the proposed standard, therefore, the following calculation must be made : — 10*5 knots ! 10 knots:: \/ 3 tons, present consumption : \/ required consumption. Cubing these quantities, and working out the proportion, we have 1157 625 : 1000 :: 3 : 2*59 tons, required consumption. We have thus found that 1300 tons (tonnage) are carried 10 knots in an hour, by a consumption of 259 tons of coals : Therefore, 11^1= 501*9 tons (tonnage) carried by this steamer a distance of 10 knots in an hour, by one ton of coals. SCREW AND THE PADDLE WHEEL. 131 Example No. 2. — Again, a vessel of 1072 tons and 400 torse power, is propelled at the rate of 10*4 knots, with a consumption of 48-| cwt. of coals per hour : Then, as before, 10*4 : 10:.* v 48*5 : v required consumption. Or, 1124*8 : 1000 :: 48*5 : 43*1. And now, 43*1 : 1072 :: 20 : 4D7*4 tons (tonnage) carried by this steamer a distance of 10 knots in an hour, by one ton of coals. The comparison between those two steamers, therefore, shows that their performance is nearly equal, being in the proportion of 501*9 to 497*4. To compare Efficiency of Different Vessels for Scientific Purposes. — If it be wished to form a more scientific and accurate comparison, the separate question of the efficiency of the boiler being ascertained by an experiment as to weight of water evaporated by 1 lb. of coal, and the efficiency of the engine by finding the quantity of steam used in it to produce an indicator horse power, it will be necessary to substitute the indicator horse power for the consumption of fuel , and the actual displacement of the vessel for the nominal tonnage . With regard to the latter point, it is much to be regretted that a certain petty jealousy still existing amongst ship builders, though now happily ex- ploded amongst engineers, frequently steps in to obstruct the investigation of all questions relating to the form and displacement of a vessel’s body, by withholding the design from which it was built. As the lines of the vessel cannot be deduced from the scale of displacement, # however, we think that every owner of a steamer may insist upon this being supplied to the captain of his ship, without taxing too far the communicativeness of the designer, who, it would appear, is apt to forget that only quacks and charla- tans work in secret, while with the true scientific prac- titioner all is open and above-board, and publicity courted with a view to criticism and discussion, and consequently progressive improvement. * For an example of a scale of displacement, see Rudimentary Treatise on Shipbuilding, Vol. I., in this series, Plate C. 132 COMPAEATIYE MEEITS OF THE The number of tons of displacement, therefore, that 1 00 gross or indicator horse power will propel at the rate of 1 0 knots an hour, is proposed as a standard of comparison for enabling us to judge of the relative values of different forms of vessels. Example No. 1. — A vessel, upon trial, is found to have a speed of 10-5 knots an hour, the engines exerting an indicator power of 1410 horses, and the displacement being at the same time 2380 tons, as taken from the scale of displacement. Then, as 10*5 knots : 10 knots :: v/l440 H.P. V indicator power required ; Or, 1157*625 : 1000 :: 1440 : 1243'9. And 1243*9 : 2380 :: 100 : 191*3 =tons of displacement propelled, in this vessel, by 100 indicator horse power at the rate of 10 knots an hour. Example No. 2. — Another vessel, on trial, is found to have a speed of 10*4 knots; her engines exerting an indi- cator power of 919*6 horses, and her displacement at the same time being 1323 tons. Then, as 10*4 knots : 10 knots i: \/ 919 6 H.P. : \/ required H.P. Or, 1124*8 : 1000 :: 919*6 : 817*5, And 817*5 : 1323 :: 100 : 161*8 = tons of displacement propelled, in this vessel, by 100 indicator horse power, at the rate of 10 knots an hour. Comparison between the Screw and the Paddle as a Means of Propulsion . — This leads us to consider the broad question of the relative merits of the two great rival modes of pro- pulsion, by screw or by paddle wheel. General View of their respective Efficiency for full-powered Passenger Steamers. — Although the screw certainly possesses many advantages over its rival, which are at once apparent, these must, nevertheless, be considered of minor import- ance, in the case of passenger steamers, if it fail to ensure the same amount of regularity and speed which we are ac- customed to obtain from the paddle wheel, with engines of the same power. That this deficiency actually exists at present is incontrovertible, and this has hitherto prevented the adoption of the screw in steamers designed for quick SCREW AND THE PADDLE WHEEL. 133 passenger traffic, both for ocean and river navigation : the general impression amongst practical men of the present day being, that it is inapplicable in the first case from its observed deficiency of power when the vessel is pitching while steaming head to wind ; and, in the second case, that a con- siderable draught of water is requisite for its efficient action. Although experience certainly favours these views, the staunch advocates for the screw will not willingly admit their truth ; and if its very recent introduction be con- sidered, as well as the rapid advances which have really been made in improving it, it is, perhaps, natural that they should withhold their assent.. The slow progress that was made in bringing the paddle wheel to its present state of efficiency must not be forgotten, especially as the ship- builders of the present day have shown as much desire to box up the screw in its position, as their predecessors did to keep the paddle wheel buried in sponsons. Efficiency of the Screw for full-powered Steamers of War . — The value of the screw in vessels of war, not only as an auxiliary, but also in full-powered steamers, seems to admit of but little doubt. — A clear broadside for the guns ; the com- parative safety of the machinery from shot owing to its low position ; the increased stability of the ship from the same cause, enabling her to carry heavier armament on the upper decks ; and the freedom of these decks from the machinery ; and finally, the power of arranging the masts, sails, and rigging, so as to make her an efficient sailing vessel, are advantages of such moment, that even if a considerably higher power were required to realize the same speed as would be obtained from paddle-wheels, the adoption of the screw would appear to be justified. Efficiency of the Screw as an Auxiliary in Sailing Vessels . — The screw, as an auxiliary propeller, to be used either in a calm, or in conjunction with sails in light or contrary winds, stands unrivalled. Several attempts have been made to adapt the paddle wheel and other propellers to this purpose ; but 134 THE SCREW AS AH AUXILIARY. they have signally failed to meet the varying circumstances of the ship deeply laden, sailing light, or heeling over under a press of canvas. The efficiency of the screw, however, remains comparatively unimpaired under any of these circumstances. The Success of the Screw as an Auxiliary in Men of War . — In the Eoyal Navy, the best test of its success in this respect is, tjiat the screw vessels employed in cruizing for slavers have been pre-eminently serviceable. It has been also per- fectly successful in the various classes of vessels in which it has been fitted as an auxiliary, from the Plumper of 9 guns, up to the Erigate Arrogant of 46 guns, and the old 72-gun ships converted into guard ships, and it is anticipated that the largest ships of war will have this additional service. The Effect that Auxiliary Screw Vessels may have on the Shipping Interests of the Country . — The success of auxiliary- screw merchantmen has already been such, that it appears probable that the whole commerce of the country will be carried on by them at so reduced a cost as to beat out of the field all sailing vessels, not only of this but of other countries ; the value of speed and regularity being now so greatly and so truly appreciated by merchants. If there be any truth in this view of the case, the results to the country will be most important ; but they must be carried out with energy by the combined efforts of ship-owners, ship-builders, engine-makers, sailors, and engine-workers, and this will not be done without a struggle on the part of some of those in favour of their old-established habits. The City of Paris, built by Messrs. William Joyce & Co., is an iron steam ship built for the Commercial Steam Navi- gation Company, and plying with passengers and goods be- tween London and Boulogne. Her principal dimensions are — ft. in. Length between perpendiculars . . . 165 0 Breadth of beam . . . . 23 0 Depth of hold . . . . . 14 0 Draught of water . . . .6 6* Burthen ..... 425 tons. Speed per hour in still water, 15*75 statute miles. PEIVATE COMPANY’S IKON STEAM SHIP. 135 The vessel and engines were constructed by Messrs. Wil- liam Joyce & Co., of the Greenwich Iron Works ; and, as a matter of interest, it may be mentioned that this is the first iron steam ship ever built at Greenwich. Her engines are of the collective power of 140 horses, and are of the direct action kind. Each piston has two rods, between which there is a recess in the piston, which allows of a corres- ponding recess in the cylinder covers, and thereby permits the connecting rods to descend considerably lower than is prac- ticable in the single-rod direct action engine. The arrange- ment is most compact and simple; and it is manifest that the cylinders being fixed a most important advantage is secured. These engines occupy less space than any other descrip- tion of marine engine yet known ; and both the en- gines and boilers may be taken as a fair specimen of the great reduction of space and weight effect- ed by modern arrangements over the ear- lier examples of steam ma- chinery as ap- plied to naval purposes. Pacha of Egypt Steam Yacht Kassed Kheir , is a fine schooner-rigged steam screw yacht, constructed of iron. Her dimensions are — 136 PASHA OP EGYPT STEAM YACHT. Length between perpendiculars . ft. in. . 150 0 Breadth of beam . 18 0 Depth of hold . . 11 0 Mean draught of water . 6 6 Burthen, 0. M. . . 240 tons. Built by Messrs. "William Joyc e & Co., Greenwich Iron "Works, and fitted by them with a of collective pair of vibrating engines Horses’ power, nominal . 80 Horses’ power, by indicator 311 Diameter of cylinder . ft. 0 38 in. Length of stroke . Strokes per minute, 42. Multiple of gear, 5 to 1. . 0 30 Screw propeller diameter 6 6 ,, pitch 7 3 ,, length , . 1 3 ,, number of blades, 2. yy IlliUiUCl U Revolution of screw, 210. Speed of vessel, 14 miles. Of the Spiral Propeller or Water-Screw . — The acting por- tion is a spiral surface projecting from a cylindrical axis; # and, in order that it may he at all effective, each point in the surface must revolve so rapidly, that the motion of that point in the direction of the axis must be greater than that of the vessel. Also, if the angle of the spiral to the axis be constant, it is obvious, that by having more than one revo- lution, the rest add little to the effect, perhaps not equivalent to the additional friction. Let B A C * - a be the angle which the screw forms with * See Tredgold’s Work on the Steam Engine, Division B, Marine, new edition. OE THE SPIRAL PROPELLER OR WATER-SCREW. 137 the boat would move from C to B, a point in the surface must move from B to A, otherwise it would retard the boat ; and, in order that it may be effective, it must move at some greater velocity. But the velocity of the boat, v, is to that of a point in the surface, when no effect is produced, as BC: AB : : v : A B. v BC” tan. a Hence the actual effective velocity must be V tan. a V tan. a — v tan. a 2 ^ ^ Let x be the variable radius of the cylinder, then = J cos. a the length of the spiral, and 2 * x = the differential of cos. a. its area. Its resistance is therefore 7r (V tan. a — v ) 2 (2 sin. a 3 + sin. a 2 ) x d x cos. a tan . 2 a when the vessel is at rest : and when it is in motion, it in- . , . p V tan. a — v creases m the ratio ot — : v ; hence tan. a 1 7 rv(V tan. a — v) (2 sin. 12 a + sin. a) x dx = the differential of the resistance. The integral gives i 7 tv x 2 (V tan. a — v) (2 sin.* a + sin. a) = the resistance. This resistance is to the effect to impel the boat as the radius is to tan. a ; hence \ tv x 2 v (V tan. a — v) 2 (2 sin. a- + sin. a) tan. a = the force, and x 2 v 2 (V tan. a — v) (2 sin. 2 a + sin. a) tan. a = the effect, which should be equal to the resistance of the vessel. 138 CHAPTER XII. SCREW STEAMERS IN THE ROYAL NAVY AND MERCHANT SERVICE. Full-powered Vessels : The Rattler . — The Rattler is a vessel of 888 tons burthen, and has engines of 200 horse power collectively. The area of her submerged midship section (at 10 ft. 6 in. draught) is 380 square feet. Her most favourable experiments were made with the common or Smith’s two-threaded screw, 10 feet diameter, 15 inches long, and 1 1 feet pitch, the effective surface being about 23 square feet. With this screw the engines made 26’ 19 re- volutions per minute, and the screw 103*67 ; the speed of the vessel being 10*074 knots an hour, and the slip of the screw 10*72 per cent. Dimensions and Speed of the Fairy . — The following are the dimensions of H. M. steam yacht Fairy , also a favour- able specimen of screw propulsion. Length between the perpendiculars . 144 ft. 8 in. Breadth of beam for tonnage . . 21 ,, 1^ ,, Depth in hold . 9 „ 10 ,, Burthen in tons, builder’s old measurement . 312 „ Horses power ..... . 128 „ Draught of water .... . 6 „ Diameter of screw . 4 „ Length of screw ..... 16 „ Revolution of engines per minute 48 „ Ditto screw, per minute 240 „ Maximum speed of the vessel, 13 J knots. SCREW STEAMERS IN’ ROYAL NAVY, ETC. 139 Dimensions and Particulars of Termagant. — Termagant, steam frigate, 24, propelled by the screw. Designed by White of Cowes, engines by Seaward. Length between perpendiculars 210 ft. 1 in. Length of keel for tonnage . 181 „ 0 „ Breadth extreme ..... 40 „ 6 „ Breadth for tonnage ... o o Breadth moulded .... 39 ,, 4 ,, Depth in hold .... 25 ,, 9 ,, Burthen in tons 1547 „ 0 „ Horses power .... 620 ,, 0 ,, Length of space for machinery, placed under the water line o 00 The stores — 280 tons of coals in boxes, 6 weeks’ provisions for 320 men, and 53 tons of water. She mounts four 10-inch guns, and two 8-inch guns, on the upper deck; and eighteen 32-pounders on the main deck. During her trial of speed in Stoke’ s Bay, her draught of water was 16 feet forward and 18 feet aft, with 260 tons of coal in boxes. The pitch of her screw (14 ft. 6 inch, diameter), was 17 ft. 3 inch. The vacuum in the conden- sers 27J inches ; revolutions of screw 36 to 37 per minute. Steam in boilers 14 lbs. Under these circumstances she attained an average speed of 9^ knots an hour. # Dimensions and Particulars of Encounter . — Screw steam sloop, 14 guns, designed by Pincham ; engines by Penn. Length between perpendiculars . 190 ft. 0 in. Breadth extreme . . . . 32 ,, 2 ,, Depth in hold . . . . 20 „ 10 ,, * Although this trial is allowed to have been of the most favourable nature, the Termagant's speed falls short, by at least 2 knots an hour, of what similar vessels with the same high proportion of horse power to tonnage, and fitted with paddle-wheel engines by the same makers t have attained. 140 SCREW STEAMERS IN Tonnage, builder's old measurement . 953 Horses power, nominal . . . 360 Horses power, by indicator . . 646 Displacements at 12 ft. 6 in. mean draught 1290 tons This vessel has been one of the most successful of the full-powered screw steam vessels yet constructed. At her load draught of 12 ft. 10 in. aft and 12 ft. 2 in. forward, she realised a speed of knots under steam alone, and when light she has steamed at 10J and 1 0J knots. Her sailing powers are also good, as she has kept her place under can- vas when in company with a squadron. On a trial in going before the wind, when the frigates of the experimental squadron were making 10 knots, the Encounter was found to lose ground, but on her getting up her steam she over- hauled them, attaining a speed of 13 knots, with full canvas and full power of steam combined. The engines on this occasion made 7 4 strokes per minute, and as the pitch of the screw is 15 feet, and it is driven direct from the engine, the vessel over-ran her screw and gave a negative slip, and realized a higher velocity than could be obtained from her under any other circumstances. Dimensions and Particulars of the Arrogant.- — Screw fri- gate, 48 guns designed by Tincham ; engines by Penn. Length between perpendiculars . 200 ft. 0 in. Breadth extreme . . . . 45 ,, 9 „ Depth in hold . ... ... . 29 ,, 6 ,, Tonnage, builder's old measurement . 1872 Horses power, nominal . - 360 Horses power, by indicator . . 623 Displacements at 18 ft. 11 in. mean draught 2444 Trials of Arrogant (Auxiliary). — During the Arroganfs trial in the estuary of the Thames, she had on board her full complement of men, viz. 450; provisions for 140 days, stores for 12 months, and water for 80 days. Under these THE ROYAL NAVY AND MERCHANT SERVICE. 141 circumstances the engines made 63 revolutions per minute (working full power), and the speed of the vessel was 8*6 knots : consumption of fuel at the rate of 32 tons of coal in 24 hours : with a slight head swell, no sails being set. Trials of Arrogant. — Subsequently, upon the occasion of her steaming round to Portsmouth to be put into commis- sion, this fine frigate (which is one of the most successful of our auxiliary steam fleet) made an average speed of seven and a quarter knots an hour, at the measured mile in Long Beach, under the following circumstances : She had on board 246 tons of coal, 1 87 tons of water in tanks and 1 3 tons in casks ; also her full armament, viz. two 68 pounders of 95 cwt. each, mounted on traversing platforms and pivots, and sixteen 32-pounder guns of 32 cwt. each, on the upper deck ; twelve 8-inch guns for 56-pounder hollow shot, or 68- pounder solid shot, and sixteen 32-pounder guns of 56 cwts. each, for the main deck. Her draught of water on starting was 18 ft. 9 inch. aft. and 16 ft. 10 inch, forward. Average number of revolutions of screw, 62 per minute. The en- gines are 6 feet under the water line, and the top of the steam chest three feet. By trial on this occasion between the Nore and Mouse Lights (where there is deep water), she is said to have made 8*3 knots by the log, the engines mak- ing 57 to 59 revolutions against the wind, and 61 to 62 re- volutions with the wind. The engine room is ventilated by a fan driven by the supplementary engine. La Hogue . — La Hogue , steam guard ship, old 74-gun ship, 1750 tons of burthen, and fitted with engines by Seaward of 450 horses’ power, has a speed of 7*2 knots, the engines making 49 revolutions per minute, and consuming 28 tons of coal in 24 hours. Ajax. — Ajax , steam guard ship, old line-of-battle ship of 142 SCREW STEAMERS IN 60 guns, 1761 tons, with auxiliary steam power of 450 horses, propelled by the screw. Mean speed at the measured mile in Stoke’ s Bay, with all her weights aboard and lower masts in, 7T47 knots per hour. Draught of water forward 21 ft. 11^ in. ; aft, 23 ft. 1^ inch. Height of lower deck midship portsill, above the water, 5 ft. in. The engines are horizontal, by Messrs. Maudslay, with 4 cylinders, each 55 inches diameter and 2 ft. 6 in. stroke. Smith’s screw 16 ft. diameter, and 20 ft. pitch. The engines are applied direct to the screw shaft, and make 48 revolutions per minute. The use of Screw Vessels as Tugs . — Many experiments have been made with screw vessels in towing, and the results have generally been most favourable. With a paddle-wheel steam vessel not expressly designed for towing, the revo- lutions of the engines are much reduced on taking a heavy vessel in tow, and she is consequently unable to work up to her full power, while the screw vessel is comparatively little affected in this respect, and continues to work with compa- ratively little loss of power. In assisting a vessel that may have got on shore this difference becomes particularly appa- rent, because the engines of the paddle-wheel steamer when she is held fast are reduced to about one half their number of strokes, and consequently to nearly one half their power ; the engines of the screw vessel not being reduced under the same circumstances more than about 10 percent. Auxiliary . screw vessels also of moderate speed have been found to be : wonderfully efficient as tugs, arising no doubt mainly from the foregoing cause. The screw vessel can also be brought alongside or be communicated with more readily than the other. The Screw in the Merchant Service . — The machinery for screw vessels in the merchant service is not confined by the same requirements as in the Koyal Navy, and consequently THE KOYAL HAVY AND MEECHANT SEEVICE. 143 the screw has generally been made larger in diameter in proportion to the vessel, and in many instances engines of the same form as those nsed for paddle-wheel steamers have been continued and toothed wheels introduced to obtain the requisite number of revolutions for the screw shaft. The first results obtained from this course are good, on account of the less liability to derangement in engines of tried and good construction, but in all vessels of large power it is to be feared that the wear upon the teeth of the wheels will be such as to give much trouble and cause constant renewal necessary. If the amount of surface of the teeth in action and the intensity of the power passing through them be compared with the proportions in general use in wheel-work in the manufacturing districts, it will be evi- dent that it would be impossible on board ship to continue the same proportions without rendering the wheels much too heavy and cumbersome. In auxiliary vessels, there is no difficulty in obtaining a sufficient velocity for the screw with direct-acting engines and a somewhat coarse pitch, but in full-powered vessels the question becomes more difficult, though, it is believed, not insurmountably so, when it is considered that locomotive engines are running at 200 strokes per minute with ease and certainty. The difficulty of driving the air pump at the high velocity required has been the main difficulty in the way, but the introduction of canvas or vulcanized india rubber valves appears to be one way of getting over it, while the introduction of a pair of wheels to reduce the speed of the air pump, or of a totally different engine fitted on board for the express purpose of working the air pump, have also been proposed. By the latter proposal the engines for propelling the vessel are placed in all respects on a perfect equality with the common locomotive engine, or they may indeed be made even more simple than these by attaching the feed pumps to the sup- plementary engine, which would be driven at the ordinary speed. 144 SCBEW STEAMEES IN j Performance of the Screw in Vessels of General Screw Steam Shipping Company . — The following statement by the managing director of the “ General Screw Steam Shipping Company ” presents a highly favourable view of the per- formance of the screw as an auxiliary propelling power in the vessels of that company, from the 1st of January to the 31st of December, 1849. It is remarked, that the seven vessels specified have made altogether during the year 170 voyages, out and home, with cargoes, performing a distance of 110,849 knots, at an average speed of 8 to Si knots per hour. Only one casualty is stated to have happened during the year to any of the Company’s vessels, and that in the Thames. . Performance of the Screw on Canals. — An able report, made by Sir John Macneill, C. E,, is inserted in the Appendix, p. 225. # City of Rotterdam, 272 tons, 33 horse power, has made during the year 42 voyages to French and Dutch ports, performing 15,450 miles, at an average speed of 8 knots. City of London, 272 tons, 30 horse power, has made 44 voyages to Dutch ports ; total distance 1 3,327 miles ; ave- rage speed 8 knots. Lord John Russell, 320 tons, 40 horse power, has made /SO voyages to Dutch ports ; total distance 25,379 miles, at &n average speed of Si knots. Sir Robert Peel, 320 tons, 40 horse power, has made 3 voyages from Liverpool to Constantinople, and 21 voyages to ports of France and Holland ; total 24 voyages, 28,206 miles, at an average speed of 8-| knots. Pari of Auckland, 450 tons, 60 horse power, has made 4 voyages to. Constantinople, and 6 to ports of Holland, Por- tugal, and France ; total 10 voyages, 28,487 miles. * Kindly communicated by John M'Mullen, Esq., of Dublin. THE ROYAL N AYY AND MERCHANT SERVICE. 145 Bosphorus , 536 tons, 80 horse power. Laden with 360 tons of merchandise, and 120 tons of coal: took 16 days 15-g- hours on her first voyage from Liverpool to Constan- tinople. Sailed 15th September, 1849; average speed 8*02 knots. Left Constantinople October 1 0 ; time on passage 15 days 1 hours; average speed 8*50 knots. Hellespont , 536 tons, 80 horse power. Laden with 360 tons of merchandise, and 120 tons of coal. Sailed from Liverpool for Smyrna October 15th; time on the passage 16 days 20^ hours ; average speed 7*93 knots. Sailed from Smyrna November 14 ; time on the passage 18 days 6 hours 30 minutes ; average speed 7*20 knots. Average speed of four passages 7*91 knots. Speed at the trial of Bosphorus at the measured mile in Long Beach, 9 ’68 knots. Speed at the trial of Hellespont at the measured mile in Long Eeach, 9*65 knots. Dimensions and P articular s of Bosphorus. — Bosphorus is 175 feet long ; 25 feet beam ; 536 tons burthen ; and 80 horses’ power. Diameter of cylinders, 36 inches; stroke, 24 inches ; diameter of screw, 10 feet, 6 inches ; pitch, 18 feet, 6 inches; mean number of revolutions, 62 2 ; length of the engine-room, 30 feet, which includes space for the stowage of 150 tons of coal; draught of water on trial, forward, 6 feet, 8 inches ; aft, 9 feet, 6 inches, the screw being 14 inches out of the water. Mean speed as above, 9*679 knots ; speed of screw, 11*348 knots ; slip of screw, 1*669 knots, or 14*7 per cent. Builders of vessel (iron), Messrs. Mare and Co., of Blackwall. Engineers, Messrs. Maudslay, Sons, and Field. V oyage of Bosphorus under Steam from the Cape of Good Hope to Plymouth. — The Bosphorus made the following H 146 SCREW STEAMERS IN quick run from the Cape of Good Hope to Plymouth in the months of June and July, 1851. She left Table Bay at half-past two o’clock in the afternoon of May 31, passed St. Helena near midnight of the 8th of June. At daylight of the 17th anchored off Sierra Leone, where she stopped 17 hours to coal. Was off the Island of St. Yincent (of the Cape de Yerde group) on the morning of the 23rd. Left again at noon of the 24th, and arrived at Plymouth on the evening of July 7th. She consumed in her outward and homeward voyages, 787 tons of coal, and had an average speed of 74 to 8 knots. Epitome of Battler’s Experiments . — Before quitting the subject of screw-propelled vessels, I shall give a brief epi- tome of the results obtained from the extensive and valuable series of experiments made with the Rattler , in the year 1844. Dimensions of the Vessel . — This vessel has the following dimensions, viz : — Length between the perpendiculars Length on keel ...... Breadth of beam Depth in hold Burthen in tons, builder’s old meas. . . . 888 0-^f Mean draught of water during trials Horses’ power, 200; Maudslay, Sons, and Field, engineers. Speed of the engines is multiplied by gearing 4 times, nearly. The weight of ballast carried during the trials was . 132 tons. Ditto of coals 122 ,, FT. 176 157 32 18 888 11 IN. 6 9 i n Experiments . — Peb. 3, 1844. With a two-threaded com- mon screw, 9 feet diameter, 3 feet long, and 11 feet pitch, the vessel made 9*25 knots, the engines making 26*8 revo- lutions per minute, and the screw 106 ; slip, 19.5 per cent. THE ROYAL NAVY AND MERCHANT SERYICE. 147 Feb. 9. With a three-threaded common screw of the same dimensions as the last, the speed of the vessel was re- duced to 8*23 knots, the engines making 24*2 revolutions, and the screw 94*3 ; slip, 19 66 per cent. Feb. 23. When the last screw was shortened to 1 foot, * 1 \ inches, the vessel’s speed increased to 8*57 knots, the engines making 24*8 revolutions, and the screw 98 ’4 ; slip, 19-7. Feb. 28. With a two-threaded common screw, 10 feet diameter, 3 feet long, 11 feet pitch, the vessel made 8*958 knots, the engines making 24 revolutions, and the screw 95 ; slip, 13*8 per cent. March 11. When the same screw was shortened to 2 feet, the vessel’s speed increased to 9*448 knots, the engines making 25*5 revolutions, and the screw 107 ; slip, 13*5 per cent. March 18. With a four-threaded common screw, 9 feet diameter, 1 foot 7 inches long, and 11 feet pitch, the ves- sel’s speed was 9*18 knots, the engines making 26*3 revolu- tions, and the screw 104*4 ; slip, 27*7 per cent. April 13. With a four-threaded Woodcroft’s increasing pitch screw, of the same dimensions as the last, the pitch varying from 11 feet forward to 11 feet 6 inches aft, mean, 11*275, the speed of the vessel was 8*159 knots, the en- gines making 24*15 revolutions, and the screw 96; slip, 23*5 per cent. April 18. With the same screw as the last, 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, 25*97 per cent. April 23. With Smith’s or common screw (of cast brass), 9 feet diameter, 1 feet 2 inches long, and 1 1 feet pitch, three- H2 148 SCREW STEAMERS I1ST threaded, the vessel’s speed was 9*88 knots, the engines making 27*89 revolutions, and the screw 108*4 ; slip, 15*97 per cent. Air quite calm. June 13. "With a common two-threaded screw, 10 feet diameter, 1 foot 6 inches long, and 1 1 feet pitch, the speed of the vessel was 9*811 knots; the engines making 27*92 revolutions per minute, and the screw 110*7 ; slip, 18*3 per cent. June 27. The same screw as last, reduced in length to 1 foot 3 inches, gave a speed of 10*074 knots for the vessel ; the engines making 26*19 revolutions, and the screw 103*97 ; slip, 10.42 per cent. Note .— This is the most favourable result obtained during the experiments. October 10. "With Mr. Sunderland’s propeller, 8 feet in diameter, the vessel’s speed was 8*38 knots ; the engines making 17*49 revolutions, and the screw-shaft 69*97. October 12. "With Mr. Steinman’s propeller, 10 feet I inch diameter, the vessel’s speed was 9*538 knots ; the engines making 25*06 revolutions, and the propeller 104*24 ; the pitch 11 feet 6 inches ; slip, 29*32 per cent. October 17. "With the common screw, 10 feet diameter, II feet pitch, 1 foot 3 inches long, the speed of the vessel was 9*893 knots ; the engines making 27*03 revolutions, and the screw 108*12;— slip 15*65 per cent. The experiments show, therefore, that the common screw, of the dimensions last quoted, gave a higher result than either Mr. "Woodcroft’s, Mr. Sunderland’s, or Mr. Stem- man’s. Thrust on the Dynamometer . — Experiments were made during the last three trials to ascertain the actual thrust of THE ROYAL NAYY, ETC. 149 $ Sd the screw in propelling the ship, by observing the pressure on the spring of the dynamometer fitted to the end of the shaft. The re- sults were as follow : — October 15. With Sunder- land’s screw, the speed of the vessel being 8*346 knots, the pressure on the end of the shaft was 2*88 tons; the horse-power calculated by the dynamometer being 164*9, and by the indicator 320 horses : the ratio of the two powers being as : 1*94. When the speed of the vessel was re- duced to 6*698 knots, the pres- sure on the end of the shaft was 1*86 tons, equal to 85*85 horse- power by the dynamometer, the indicator showing 173*2 H.P. October 12. With Steinman’s screw, the speed of the vessel being 9*537 knots, the pressure on the end of the screw shaft was 3*35 tons; the horse power calculated by dynamometer being 219, and by indicator 452 — the ratio of the two powers being as 1 : 2*7. October 17. With the common screw, the speed of the vessel being 9*893 knots, the pressure on the end of the screw-shaft was 3*61 tons ; the horse-power cal- 150 SCREW STEAMERS Itf culated by dynamometer being 245, and by indicator 465-6 — the ratio of the two powers being as 1 : 1*9. Loss of Speed by Expansion Gear . — Experiments were likewise made with the expansion-gear of the Rattler's en- gines, to ascertain the loss of speed in the engines, caused by applying successively each of the expansion cams. The stroke of the engines is 4 feet, and the slide valve was set to cut off one-quarter of the stroke, or one foot. The ex- pansion cam has six steps, each cutting off four inches of the stroke ; so that when the last step is working, the steam is expanded for three feet, or three-quarters of the stroke. With the 1st step of the cam, the 2nd ,, 3rd 4th ,, 5th „ 6th ,, Each of these experiments lasted five minutes, the mean being then taken. Power consumed in driving her Machinery , per Indicator . — Another set of experiments were made with the indicator, to ascertain the amount of power consumed in driving the Rattler's machinery. The results were as follow: — I. Without any gearing attached, the mean working pressure on the piston (taking the mean of both en- gines) was 1*1 lb. per square inch, the engines making 26 revolutions per minute, and the vacuum in the con- denser being 28 inches. II. With the gearing and screw-shaft attached, but with the straps slack, the mean pressure was 1*67 lb., the engines making 25 revolutions, and vacuum in the con- denser 28£ in. ne made 25*2 double strokes per minute. 25*1 23*9 234 22*4 21*3 THE ROYAL NAVY AND MERCHANT SERVICE, 151 III. With gearing and screw-shaft attached and straps tightened (but the screw not in gear), the main pres- sure was 2*24 lbs., the engines making 25 revolutions, and the vacuum in the condenser 28j in. IY. With Woodcroft’s four-threaded screw in gear, the mean working pressure indicated was 14’ 57 lbs., the engines making 24*85 revolutions. V. With the three-threaded screw in gear, the mean working pressure indicated was 14*38 lbs., the engines making 26*2 revolutions. Dwarfs Experiments. — In connexion with this subject there will be found at the end of the book a Table of Expe- riments with Her Majesty’s Steam Tender Dwarf (of 164 tons and 98 horses’ power), undertaken at Woolwich in the year 1845, to determine the best relative proportions for the screw-propeller, with regard to pitch , length , and area . The whole of the screws used in these trials were true Archime- dean screws. From this Table it appears that the most fa- vourable results were obtained from a double-threaded screw of 5 feet 8 inches diameter, with a pitch of 8 feet, the length of segment being 18 inches, and the area 13*3 square feet ; and it is remarkable that in the experiment following this, when the length of the screw has been reduced to 12 inches and its area to 8*9 square feet, there is scarcely any appre- ciable variation in the resulting speed of the vessel or screw. The possible effect of Screw Steamers on future Mail Con - tracts . — The large sums paid by this country at the present time for the conveyance of the foreign mails by steam ves- sels, cause this question to be one of great importance. The increasing number of superior screw vessels between Liverpool and New York, which will undoubtedly make their passages within a short time of the regular mail 152 SCREW STEAMERS IN packets, necessarily attract public attention to tbe question of tbe amount to be paid for tbe receipt of tbe American or West Indian correspondence, perhaps not more than one day earlier, and also 'whether a different principle is to be adopted with these than with the mails carried on the rail- ways. The latter are not carried by the fastest possible express trains running at great cost ; and if this principle be once admitted, there is no doubt but that great economy would result, and, perhaps, ultimately without any loss of speed whatever. It is believed that the mails might be car- ried by steamers on all the great lines at an almost nominal cost, and the necessity of a large and wealthy company be obviated, if the Government were to make contracts to suit parties who are the ow r ners of, perhaps, only one or two such vessels as are required. If fortnightly voyages, for instance, are desired, there appears to be no difficulty, be- yond a little extra trouble to the Government authorities, in taking the contracts w r ith two or three, or any number of separate parties, to sail consecutively — one party under- taking to send their vessel on the 1st of every alternate month, or at such intervals as will suit the length of the trips to be made. Such an arrangement would ensure suffi- cient competition on taking the contracts to lessen the amount demanded, as parties owning competing vessels on the station would be ready to subject themselves to the necessary restrictions for almost no other consideration than the being able to advertise their “Royal Mail Steam- ers,” on account of the additional favour that they would thus obtain with the public. A competition would also be created between the different contractors, tending to in- crease the speed of the vessels beyond that required by the Government, with the view of getting the greater number of passengers — a competition of this kind having been already felt to be very much wanted. This principle would also enable the Government to make contracts for new THE ROYAL NAVY AND MERCHANT SERVICE. 153 lines where regular communication may be very much wanted by the country, but not of sufficient importance to induce the formation of a company with sufficient ca- pital to undertake the whole line, though one or two dif- ferent parties might each undertake to despatch a vessel at certain intervals. Tables of Screw Steamers and their Machinery . — Amongst the Tables at the end there will also be found a Table of the Dimensions of Screw Steamers and their Machinery, in the Eoyal Navy. Table of the Principal Dimensions of 28 Merchant Screw Steamers. Government Pormula of Specification for Marine Steam Engines with Screw Propellers. Tender to the Admiralty for Marine Engines, with Screw Propellers, of 450 horses power. Admiralty List of Tools and Spare Gear required with those Engines. 154 CHAPTER XIII. THE PADDLE WHEEL AND PADDLE-WHEEL STEAMEES IN THE EOYAL NAYY AND MEECHANT SEEYICE. Paddle-wheel Steamers in the Royal Navy . — We shall now note a few particulars of our most successful paddle- wheel steamees, both in the Royal Navy and Merchant Service, beginning with the Terrible . Dimensions and Particulars of Terrible. — This fine steam frigate, built from the designs of Mr. Oliver Lang, of W ool- wich, was commissioned in the year 1 846. She is built of Honduras mahogany, East Indian teak, and English oak. Her principal dimensions are as follow : — Terrible Steam Frigate of 1847 Tons and 800 Horse-power. Length between the perpendiculars .... Ditto keel for tonnage ...... Breadth extreme ,, for tonnage ,, moulded Depth in hold . ....... Burthen in tons, builders old measurement . 1847 Length from the figure-head to taffrail Depth from under side of keel to crown of figure-head Length of the engine room ..... Width of ditto, in the clear Depth of ditto Launching draught of water, forward Ditto ditto aft .... Load ditto mean ft. in, 226 0 196 10 42 6 42 0 41 2 27 0 253 9 37 7 78 7 38 0 27 4 8 10 11 6 17 6 Terrible’s Machinery . — The engines, of 800 horses power collectively, are by Messrs. Maudslay and Eield ; double- PADDLE WHEEL AND PADDLE-WHEEL STEAMERS, ETC. ] 55 cylinder direct action, with tubular boilers divided into sec- tions, placed two before and two abaft the engines. Dia- meter of cylinders each 72 inches ; stroke, 8 feet. Paddle wheels, 34 feet diameter x 13 feet. The contract weight of the engines was . 212 tons. n ii boilers . 150 „ u ii water in boilers CO CO ii ii paddle wheels . 44 „ if ii coal boxes • 16 „ Total estimated weight of machinery 560 The coal boxes were estimated to contain 800 tons of coal, although Sir Charles Napier affirms that 500 tons only are carried. The contract price of the machinery was £41*250. Speed . — The Terrible's speed at the measured mile, with sea-stores and guns on board, was found to be 11*78 miles, or 10 knots an hour, the engines making 13 strokes per minute. By Massey’s log the speed was found to be 10*9 knots, the engines making 14^ strokes per minute. Armament . — Her armament consists of 21 guns, viz. two 8-inch and two 56-pounder long guns of 98 cwt. each, on traversing platforms, on her upper deck, with two 12- pounder carronades, and one 6-pound brass gun, forward, and two 8-inch and two 56-pounder guns aft. The lower deck has the same armament, with the exception of the car- ronades and the brass gun. Terrible’s Daily Expenses . — The expense of this costly steamer has been recently brought to light by the Beport of the “ Select Committee on Navy Estimates,” where it is stated that the Terrible , with a complement of 320 men, costs per day in pay and provisions, £44 5s. 2 d . ; and in wear and tear of hull, masts, yards, &c., £25 — together, 156 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS £69 5s. 2d. per day. The wear and tear of machinery, and consumption of oil, tallow, &c., is estimated at £19 11s. 2d. per diem — making the total expenses, exclusive of fuel, £88 16«. 4 d. per diem. When the ship is under steam, an ad- ditional expense of £4 os. 6d. per hour is incurred, equal to £102 per diem for coals alone; or at 100 days steaming, to £10,200 per annum. The vessel and machinery thus cost £32,418 Is. 8 d. per annum, exclusive of coals ; or £42,618 Is. 8 d. when the steam power is used for 100 days of 24 hours each. She proved herself, however, to be a very effi- cient steamer, good speed having been obtained from a very reduced power. Sidon . — Sidon steam frigate, of 1328 tons, and 560 horse power. This vessel is constructed by Mr. Fincham, the machinery by Seaward under Sir Charles Napier’s superin- tendence. The following are her principal dimensions, viz. — ft. in. Length between the perpendiculars • 210 9 „ of keel for tonnage . . 185 9| Breadth, extreme . . . . 37 0 „ for tonnage . . . 36 6 ,, moulded . . . 35 10 Depth in hold . . 4 . 27 0 The Sidon carries about 700 tons of coal, with her main deck portsills 6 feet 6 inches above the water; the coal boxes being so fitted that when the coals are expended, water ballast may be taken in, to prevent too great a varia- tion in the dip of the wheels. Her armament is, we believe, twenty-four 68 pounders, on two decks. The speed of the Sidon with her coals, guns, and sea stores on board, equals 10 knots. Odin . — Odin steam frigate of 1326 tons, and 560 horses nower, has the same dimensions as Sidon 7 except being two IN ROYAL NAVY AND MERCHANT SERVICE. 157 feet shorter and three feet less depth in hold. The vessel is constructed by Mr. Fincham, the engines by Fairbairn. The principal dimensions of the machinery are as follow : — ft. in.. Diameter of cylinders ... 0 87J Length of stroke ..... 5 9 Stroke per minute ... 19 0 Diameter of paddle-wheels, extreme 27 0 Breadth of ditto ... 9 6 Diameter of necks of paddle-wheel shaft . 0 16 Coals stowed in boxes, 445 tons, or 12J days’ consumption at 6 lb. per horse power per hour. The engines are upon Messrs Fairbairn’ s direct-action principle. Weight of the engines and paddle shafts tons. 180 »» boilers and their apparatus 60 if water in boilers 48 a coal boxes ... 16 it paddle wheels .... 30 it spare gear, floor plates, &c. 25 Total weight of machinery . 359 Cost of engines, boilers (with iron tubes), and coal boxes . ^21,480 ,, paddle wheels 950 „ duplicates and spare articles, as per admiralty list . 1650 Total cost of machinery . . i?24,08U Length of the engine room, 52 feet ; of coal hold, 8 feet — together, 60 feet. Breadth of the engine room in the clear, 34 feet 4 inches ; depth, 20 feet ; centre of shaft, 8 feet 6 inches above the load water-line. Odin’s Machinery . — The boilers are tubular, with iron tubes 3* inches internal diameter, divided into four sections, placed two at each end of the engine room. Fire surface in boilers, 80 square inches per horse power. Effective heat- 158 PADDLE WHEEL AND PADDLE-WHEEL STEAMEES in g surface (after deducting one third of tube surface as non-effective), 13 square feet per horse. Diameter of steam pipes, for each engine . . 19 in., bore. „ injection pipes „ . . • 6 ,, ,, feed pipes, and bilge pipes . .5 £ „ Speed. — The speed of the Odin with coals, sea-stores, and armament on board, averaging 111 knots. Both Sidon and Odin are excellent sea boats, and sail well under canvas. Sir Charles Napier admits that the Odin beats Sidon a mile an hour, when each has her full complement of coals on board ; and still passes her when each is loaded with coals in proportion to the horse power, which may be chiefly attributed to the increased height and weight of the Sidon’ s hull. Odin carries main-deck guns. Performance of Steamers in the Royal Navy — with and without Steam. — In evidence before the Committee of the House of Commons, # on the subject of arming the Mercan- tile Steam Marine, Capt. Hendeeson, of the Sidon , declares his ship to be “ the best steam vessel he ever saw ; she could take 700 tons of coals, which would last 20 days at full speed. She is rigged as a barque, and spreads as much canvas as a 32-gun frigate — more than any other steamer he ever saw. In cruising without steam, she kept company with the Canopus line-of-battle ship. Has never tried the Sidon with merchant steamers, but has had 12^ knots with 300 tons of coals. The Odin is about equal to the Sidon . Merchant steamers with their present masts and yards would be unable to keep up with a fleet without steaming. The masts of vessels in the navy prevent them steaming so well ; but there is a great economy resulting from it, because they frequently sail for months without steaming at all. If a * This evidence in these and subsequent pages is given in a condensed form as published in the Artizan Journal for 1849. IN EOYAL NAVY AND MERCHANT SEEVICE. 159 mercliant steamer could perform 10 knots with sail alone, she would be able to accompany a fleet on ordinary occa- sions. Whilst commanding the Gorgon, found that in steaming head to wind, with all the masts and yards up, it might make two to three knots difference if they were struck.” Capt. Heney Chads “ has tested the capabilities of the Blenheim , auxiliary screw, of 1747 tons and 450 horse- power. She is a most useful vessel for every kind of ser- vice, her maximum speed, under steam alone, good 6 knots. Towed the Belter ophon (2000 tons) at 44 knots. Opinion that merchant steamers could not keep company under sail with a fleet. From their rig they could not keep way with- out steaming, and consequently they would soon run short of coals. The Blenheim can sail with a fleet without steam. We attach too much importance to speed, and forget the guns. The French steamers carry 14 to 16 guns, but give up speed. Few of our steamers of war are equal to go alongside a French steamer. They have broadside arma- ment, whereas many of ours are only armed at bow and stern. Our steam sloops carry two heavy guns ; a 95-cwt. 68-pounder, and an 86-cwt, 10-inch gun, and four broadside guns, 32 pounders of 40 or 42 cwt. We have only three real steam frigates (carrying guns on the main deck), namely, the Odin, Sidon, and Terrible — and the screw vessels.” A high Speed in the Navy attainable only by an Extrava- gant Proportion of Horse Power to Tonnage. — The three vessels last named (which we have already particularized) are probably the fastest war steamers, properly so called, in the Royal Navy ; but it is apparent that their comparatively high speed has been obtained only by the use of an extra- vagant proportion of power to tonnage, such as is very rarely found in ocean steamers in the merchant service. The average speed of government steamers, when using their full power, not exceeding 8 to 84 knots. 160 PADDLE WHEEL AND PADDLE-WHEEL STEAMEES Comparisons between the Performance of Government and Merchant Steamers are generally imperfect . — This compara- tively low result has given rise to many unjust comparisons between the performances of government and merchant steamers ; for when we consider the peculiar qualifications demanded by a vessel of war, it will be seen that the compa- rison cannot be made on equal terms. War steamers are built not only to steam but to sail well ; and moreover they must be able to carry a great weight of armament on the upper deck without prejudice to their stability, and since the only effectual way of doing this is by giving them a greater relative breadth than merchant steamers are limited to, the consequence is that the hull opposes an increased resistance to the water, and the speed is diminished. Then the weight of hull and equipment of a war steamer is usually much greater than in the merchant service, causing a corre- sponding increase of displacement : the masts, yards, and rig- ing, being of greater dimensions, oppose a greater resisting surface to the air : and owing to the weight of the large guns at the extremities of the vessel demanding support from the upward pressure of the water, the lines at the bow and stern cannot be made so fine as might otherwise be de- sirable. Hence it follows, that the speed of the contract mail steamers, for instance, averages from one to one and a half knots above that of vessels in the navy, with a similar proportion of power to tonnage ; but if the proportion of horse power to displacement be taken, the comparison will generally become more favourable to the war steamer. Economy of Steam Power the best Criterion of Efficiency in the Navy . — In estimating the performance of a govern- ment steam vessel, therefore, we should look rather to the di- rect distance run by the combined action of steam and sails, at a moderate but uninterrupted speed, and with a low rate of consumption of steam and fuel, than to the attain- ment of a high velocity, which is seldom wanted in war IN' ROYAL NAVY AND MERCHANT SERVICE. 161 steamers. The best exposition we can offer of the practical working of this combined system of steaming and sailing in the navy, has been supplied by Capt. Hoseason, in his account of the performance of the steam sloop Inflexible. Performance of the Inflexible in a Steam Voyage round the World . — This vessel, designed by Sir W. Symonds, is of 1122 tons burthen, and 378 horses power. The engines are di- rect-action, by Fawcett, and the boilers are loaded to 8 lbs. on the square inch. The whole distance run (without counting going in and out of harbour) during the time she was in commission, from the 9th of August 1846, to the 28th of September 1849, was as follows : — Steamed ..... Sailed ...... . 64,477 nautical miles, 4,392 68,869 Number of days under steam tt ^ under sail alone . . 3454 274 Average daily steaming . Average daily sailing , For the whole period . . 372f . 186*62 knots. . 161*18 „ . 57*44 „ Time under one boiler . . . , tt two boilers ,, three ,, . . . , ,, four „ . 764 hours. . 4047 „ . 33244 „ 844 Total Her fires have been lighted 483 days. 8,292 Total consumption of coals while under steam, 8121 tons 12 J cwt. ; coals expended in raising steam and banking the fires, 576 tons 16f cwt. ; average distance steamed per ton of coals, 7938 knots. Consumption of coals per hour, 19,588 cwt . ; ditto per day, 23 tons, 10 cwt., 124 lbs.; average consumption of coals per nominal horse power per hour, 5*85 lbs. It :s stated that the above-mentioned distances were ob- 162 PADDLE WHEEL A1SD PADDLE-WHEEL STEAMERS tained by the patent log, towed about 50 fathoms astern, out of the influence of the backwater from the wheels ; the error arising from this cause, while throwing the common or hand-log, having been found on board the Inflexible to vary from one to four knots. It is recommended, therefore, that the patent log only should be used by a steam vessel, its re- sults being verified by the bearings of the land, when the distances are known. The expenditure of coal was taken by measuring every tenth bag in the ship, and every tenth bag as used by the fires, a mean being taken every four hours for the hourly expenditure. Performance of the Inflexible. — The distance accomplished by the Inflexible is stated to have been reckoned only from the time the patent log was thrown overboard, and when the final departure from the land was taken. It is further stated that she was employed for 15 months on the coast of New Zealand, during which time about 4000 tons of the Newcastle Australian coal were consumed, the best quality of which, delivered at the mines, is about ten per cent, inferior to good English coal, but rendered fully 25 per cent, inferior by being exposed on the open beach at New Zealand. A deduction should, therefore, be made for this circumstance in considering the expenditure of fuel. On the outward voyage of the Inflexible to the Cape of Good Hope, in the months of August and September 1846, a run of 5502 nautical miles was accomplished on a single coaling, at a mean average speed of 7*81 knots per hour, and an average daily expenditure of 12 tons, 19 cwt. 3qrs. 14 lb. This run was accomplished in 32 days. On the voyage from the Cape of Good Hope to Port Jackson, Sydney, 5356 nautical miles were accomplished at one coaling, with an expenditure of 458 tons 10 cwt., being at the rate of 1 5 tons, 3 cwt. 2 qrs. per diem, and with a IN’ ROYAL NAVY AND MERCHANT SERYICE. 163 mean average speed of 7*87 knots per hour. Time taken, 30| days. In calculating the consumption of coal as above, an allow- ance of 5 per cent for “ wastage ” has been added to the actual weight burnt in the fires — such allowance being made in order that the captain may judge of the quantity of coals remaining in the boxes at any time. This per-centage was determined by experiment during the Inflexible 1 s first two voyages, when the difference of weight was accurately noted between the coals burnt, and those received on board in England. It is thence argued that 5 per cent should be subtracted from the gross quantity, if the true duty in miles per ton of coals is sought. We confess we are at a loss to account for so large a wastage. It is further stated that on one occasion, when the full power of the engines was exerted, the Inflexible towed the barque Claudine , and succeeded in transporting 1500 soldiers, tent equipage, and baggage, 1400 nautical miles in 12 days, four of which were occupied in the landing of one regiment and the embarkation of another. After service on the coasts of India and China, the In - flexible returned to England by Cape Horn, thus making the circuit of the globe, and fulfilling her comprehensive mission in a manner most creditable to her able commander, Captain Hoseason. Economy of a Moderate Proportion of Horse-power in com- bination with the Sails. — These results show, in a most favour- able light, the economy of a moderate proportion of horse- power in combination with the judicious use of the sails ; and it is a question of much interest to the navy whether a better average result might not be expected and obtained from such a system, than from the present expensive fashion of loading the vessel with very large engines whose full power is but seldom wanted, and which monopolize so much weight !o4 PADDLE WHEEL AND PADDLE-WHEEL STEAMEBS and space that sufficient coals cannot be carried for the proper development of the steam power. It is true, that by the use of a high proportion of power to tonnage the vessel has the advantage of having always a high speed at her command, so long as the coals last ; while, by expanding the steam in her large cylinders, she may burn the fuel, on ordinary occasions, most economically, still we must re- member the increased first cost of the machinery, and the increase of displacement consequent upon the great extra weight to be constantly carried (whether it be used or not), by which the speed of the vessel is permanently diminished. A high Proportion of Horse Power requisite in the Merchant Service . — Although we thus advocate the employment of a moderate proportion of power to tonnage for the Royal Navy, say, one-horse power to three tons, this question has a different aspect when considered with reference to the merchant service. For though, as is well understood, any increase of speed requires an increased power in the dupli- cate ratio of the increased speed ; and, therefore, a great economy would seem to result from the low proportion of power to tonnage ; still, if time be calculated as an element (and, in reality, a very important one) in the economy of mercantile conveyance, it will be generally found that a high speed at any expense of fuel will compensate for the addi- tional expense. As regularity of arrival, also, is of the ut- most importance in passenger traffic; this can be ensured only by the employment of a high ratio of power ; for it is apparent that, should the contrary forces of adverse winds and waves, of tides and currents, equal or exceed the power of the engines, the vessel may burn an indefinite quantity of fuel without making any progress. We believe that the proportion of one-horse power to tons (builders’ old mea- surement) will be generally found the most advantageous for merchant steamers, of from 500 to 1000 tons. IK ROYAE KAVY AKD MERCHAKT SERVICE. 165 Considerations to be attended to in proportioning the Horse Power to the Tonnage . — In proportioning the horse power of a vessel, the fact is seldom borne in mind that the effective power of the engines increases in a higher ratio than simply as the tonnage, the resistance of the water to the hull of the vessel varying as the square of the cube root of the tonnage. Thus, if a vessel of 1000 tons and 500 horses power have a speed of 12 knots, a vessel of 1600 tons and 800 horse power ought, ceteris paribus , to have a considerably greater speed, since the square of the cube root of 1600 (4/1600 2 , or 1T7 2 ) is 684' horses power only. This law is somewhat neutralized in practice, by the fact of the displacement usually increasing in a higher ratio than the nominal ton - ange . If it be desired to design a vessel of a proposed size and speed, the safest mode of proceeding is to take the vessel nearest in tonnage and general description to that which it is intended to construct as a groundwork. If greater speed is required, the natural law as given in page 104, will be the guide as to the amonnt of additional power that will be necessary ; thus if a. vessel of 1000 tons and 400 horses power now running, is found to have an average speed of 10 knots, and it be desired to have a vessel of the same tonnage, with' a speed' of 11 knots, the proportion becomes 10 3 : ll 3 : : 400 : horse power required. Ey means of this proportion 532 horses power is found to be necessary, supposing the new vessel to be of no better form, and the engines to work to the same amount of excess of indicator over nominal horse power. Much may un- doubtedly be done by an improvement in form, but too much ought not to be expected from it, and though some faults may be very apparent in the original and be capable of remedy, yet it ought not to be assumed that the new vessel will be entirely free from all retarding causes. 166 PADDLE WHEEL AND PADDLE-WHEEL STEAMEES Dimensions and Particulars of Banshee. — As a favourable example of wbat may be accomplished by Government builders when they are not trammelled by considerations of armament or displacement, we give the following particulars of the Holyhead Mail Packet, Banshee : — Banshee, designed by Mr. 0. Lang, jun., engines by Penn, is a wooden vessel. Her principal dimensions are as fol- lows : — Length between the perpendiculars . 189 ft. 0 in. from figure head to taffrail . , . 209 ft. 0 in. Breadth extreme . 27 ft. 2 in. “ over paddle boxes . 49 ft. 6 in. Depth in hold . . 14 ft. 9 in. Draught of water, forward 8 ft. 10 in. „ aft ... 9 ft. 2 in. Burthen in tons, builders’ old measurement Horse power ..... Diameter of paddle wheels Breadth of ,, ... Area of ,,.... Dip of ,, ... Area of midship section Diameter of cylinders Length of stroke .... Strokes per minute .... Speed at the measured mile, with the tide „ ,, against the tide Mean speed No. 670 No. 350 25 ft. 9 ft. 0 in. 0 in. 33*9 square feet 5 ft. 6 in. 190 square feet. 72 in. 5 ft. 6 in. No. 30 21*5 stat. miles. 15*75 stat. miles. 18*62 stat. miles. The Banshee has proved the fastest of the Holyhead packets, performing the trip from Holyhead to Kingston in a little under four hours on the average. Her shortest passage is about 3|- hours, her longest 4|-. The distance from Holyhead to Kingston is 55 nautical miles. She has, however been taken off this station and been sent to Malta, but it has been found necessary to remove one half of her boiler power to enable her to carry sufficient coals for the IN ROYAL NAVY AND MERCHANT SERYICE. 167 longer voyages there. Her speed has thus been reduced to 12 knots, or 13*82 statute miles. Paddle-wheel Steamers in the Merchant Service : Asia.—* As an example of a first-class merchant steamer, we subjoin the dimensions of the British and North American Boyal Steam-Navigation Company’s new vessel, the Asia. FT. IN. Length of keel and fore rake . 267 0 Breadth of beam . 40 6 Ditto over the paddle boxes . 63 6 Depth of hold, amid ships . 27 6 Length of the engine space . . 92 6 Tonnage, builders* old meas. . 2130 S7 94 Horses power . No. 800 Speed, per hour (between Glasgow and Liverpool) 15 miles, or 12§ knots. Load draught of water, forward 19 feet, aft 19 20 feet. Asia has a pair of side-lever engines, diameter of cylin- ders 96 in. : length of stroke, 9 ft. ; diameter of paddle wheels, extreme, 37 ft. 6 in. ; floats 9 ft. 2 in. long, x 3 ft. 2 in. broad, divided into two breadths ; number of floats in the water at one time, eight. The boilers are four in number, measuring together 20 feet in length, and 16 feet in breadth ; they have 20 furnaces, five in each section, each furnace 8 ft. long, 2 ft. 9 in. broad, and 5 ft. 9 in. deep. The coal bunkers hold about 900 tons. The engine-room staif comprehends 38 men, viz., eight engineers, 18 firemen, and 12 coal trimmers. The vessel is of timber, round sterned, carvel built, three masts schooner rigged, three decks all flush, and carries six boats. Builders, Messrs. Bobert Steele and Co. of Greenock ; engine maker, Mr. Eobert Napier, of Glasgow; completed in the year 1850. 168 PADDLE WHEEL AND PADDLE-WHEEL STEAMEES Dimensions and Particulars of ttie Orinoco. — Royal West Indian Mail Steam Packet ; designed by Pitcher ; engines by Maudslay. Length between perpendiculars . . 270 ft. 0 in. Breadth over paddle boxes . . .71 ,, 10 ,, Breadth of vessel, extreme . . . 41 ,, 10 ,, Depth of hold . . . . • 26 ,, 0 „ Tonnage, builder's old measurement . 2245AJ Horse power, double-cylinder engines . 800 This vessel on her first experimental trip at her medium draught of water attained a speed of 12 knots, as ascertained by careful trial at the measured knot in Stokes Bay off Portsmouth, with the engines making 13| revolutions per minute. She is fitted with feathering wheels, with all the latest improvements and a greatly increased length of bear- ing for the centres, on which the paddle boards vibrate. Some of the older vessels belonging to the same company have also lately had their paddle wheels altered and made to feather, with decidedly good results, arising chiefly from the circumstances that these wheels are not so much affected as common wheels by heavy seas, and by the variation in dip, to which these vessels, from their long voyage, are neces- sarily subject. The vessels on the North American station have hitherto been prevented from adopting these wheels by the fear of injury from ice, but it is a matter of doubt whether the advantage on those voyages on which no ice is encoun- tered would not be so great as to compensate for the risk, especially as any partial injury, though it might prevent the feathering of the boards for the remainder of the voyage^ would by no means render the wheel totally inoperative as a common paddle wheel with fixed boards. The engines of the Orinoco are fitted with double-beat equilibrium valves, opened by cams instead of the common slide valves or piston valves hitherto usually adopted, and in this case, as well as in the steam frigate Penelope , they seem to have been tho- roughly successful. In the Orinoco the cams, which are IN ROYAL NAVY AND MERCHANT SERVICE. 169 placed on a vertical sliaft driven by wheels from the inter- mediate shaft, drive levers which act upon a hell-crank shaft and lift the spindles of the valves. In the Penelope the cams are placed on a horizontal shaft driven by an in- clined shaft from the intermediate shaft, and running through an eye in an upright rod, attached by a projecting arm to the spindle of each valve. The steam cams are made movable on the shaft, so as to give any required degree of expansion, while the eduction cams are stationary. The horizontal shaft on which the cams are placed, is driven, in the same manner as in many machines with a reversing motion, by a clutch between two bevil wheels, running loose on it, so that it may revolve always in one direction, accord- ing to the motion of the wheel into which the clutch may be geared, while the intermediate shaft revolves either way for going ahead or going astern. Summary of the Peninsular and Oriental Company's Fleet of Steamers. — The Peninsular and Oriental Steam Navi- gation Company have 29 steamers, amounting in round numbers to 30,000 tons and 11,000 horses power. They navigate annually about 600,000 miles, with 29 vessels. Of their 29 vessels 10 are of wood and 19 of iron. The average speed of their Mediterranean packets is 10 to 11 knots : that of Cunard’s line of Transatlantic packets, nearly 12 knots. At the present moment the new iron steamer, the Himalaya, of the following extraordinary di- mensions, is estimated to run between Southampton and Alexandria, a distance of 3100 geographical miles, in 9 days : — Length between the Perpendiculars .... 325 ft. Breadth of Beam . . . . . . . 43 ,, Depth in Hold ....... 32 6 Burthen in Tons ....... No. 3000 Horses Power 1200 Estimated speed, 14 knots. I 170 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS Some Particulars of the Peninsular, and Oriental Com- pany's Fleet of Steamers. — Mr. Pitcher, of Kortlifleet, states before the Committee of the House of Commons, that he “ has lately built two vessels for this company, of 1200 tons each. The scantling in the midship part of those ships is rather larger than that of ships of the same size in the Government service, but fore and aft it is rather lighter. These vessels are constructed capable of carrying an 8- inch pivot gun forward, and a 10-inch pivot gun aft, and ten broadside guns — altogether 12 guns.” The weight of a 10-inch pivot gun, an 84 pounder, with carriage and fit- tings, is stated to be about 10 tons ; and an 8-inch gun, a 68 pounder, from 6 to 7 tons. These vessels by Mi Pitcher are “ framed of English oak ; outside planks of teak, many of them 70 feet long, wales 7 inches thick; and the general run of the interior parts, best Honduras mahogany.” He further remarks, u ¥e build the floors of vessels accord- ing to the station they are to go on. We cannot get so much speed out of a fiat floor without reducing the breadth a little. We rather like to have a rising floor, they roll easier. Steamers are always Weatherly by reason of their length, but a flat-floored vessel would not be so weatherly as a vessel with a rising floor. With vessels of this size we expect to get a displacement of 15| tons per inch, at a draught of 15 feet. Opinion that the vessels he has built for the Peninsular and Oriental Company are equal if not superior to any in the navy. They would steam 11 knots, and would sail better than most vessels in the navy because they are longer in proportion to their breadth ; their water tanks give them sufficient stability to carry sail. Has found the boilers in the West India Mail Packets last about six years. We have found that by having two boilers at each end of the engine room, and coal boxes right across the ship instead of at the sides of the boilers, the heat is kept from the cabins, the ship is kept in better trim, and fewer coal trimmers are required, as the coals run nearer the furnaces.” IN ROYAL NAVY AND MERCHANT SERYICE. 1 71 Mr. John Eon ald “is a ship builder, and has been captain of a steamer. Builds vessels now which beat the Govern- ment vessels in speed. A merchant steamer carries more weight than a ship of her class in the navy. The mainmast of the Peninsular and Oriental Company’s steamer Bombay is 81 feet, and the main yard 72 feet long. No vessel of that class in the navy has larger spars. Nor is there much dif- ference in their rigging and area of sails. It is a fancy of the Government to make their vessels sharp-floored and of a greater draught of water, but draught is not necessary to give stability. Colliers sail as well in ballast as when loaded, even in going to windward, but that is a part of ship build- ing they have not found out nor adopted yet in the navy.” Captain Samuel Lewis, “has been at sea thirty-four years, and with the Peninsular and Oriental Company since its commencement. Took the Malta out to Ceylon. She is 1225 tons, and was under sail almost the whole of the passage. Her greatest speed under sail alone, was 9*6 knots. When the floats were taken off she did 10 knots. She was uncommonly stiff and weatherly, and if she had had larger spars she would have done two knots more; the floats could be taken off in one hour forty minutes, and replaced in the same time. She was three months and eight days from Southampton to Ceylon. The Bentinck averaged 10 knots from Calcutta to Suez. Opinion that there would be no difficulty in adapting these superior vessels to war purposes ; that they would be very efficient in carrying troops and coals, and that the engineers and crews would enter the service when required.” J. B. Enoledue, Esq. “is superintendent of the Penin- sular and Oriental Company at Southampton. There would be no difficulty in giving merchant steamers the same masts, yards, and sails as similarly-sized vessels in the navy; they would be stiff enough with a little ballast or 12 172 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS cargo at the bottom. Their speed under canvas would not be less than vessels in the navy. I have run 13 knots an hour, for six or seven hours, down Channel with a steamer under canvas alone.” Government Mail Contracts withMer chant Steamers . — With reference to the Government mail contracts, we have the following evidence by Mr. Anderson, Managing Director of the Peninsular and Oriental Company. He says, “ The postal communication can be done much cheaper by private- contract steamers than by Government boats, because of the merchandise and passengers carried. The steam communi- cation between Southampton and Alexandria, with vessels of 300 to 400 horses power, was done for 4s. 6d. per mile. Prom Suez to Ceylon, Calcutta, and Hong Kong, with vessels of 400 to 500 horses power, for 17s. Id. per mile. The East India Company’s line between Suez and Bombay, with vessels of only 250 to 300 horses power, cost 30s. per mile. Her Majesty’s vessels in the Mediterannean cost about 21s. per mile. £189,000 a year is the gross sum paid for the three great contracts : Peninsular and East Indian, West Indian, and North American. Beceipts from post- age £380,000. The advantages of the communication should not be estimated merely by the postage. After steam communication to Constantinople and the Levant was opened, our exports to those quarters increased by £1,200,000 a year. The actual value of goods exported from Southampton alone, last year (1848-49) by those steamers is nearly £1,000,000 sterling. Greek merchants state that the certainty and rapidity of communication enable them to turn their capital over so much quicker. Eorty new Greek establishments have been formed in this country since steam communication was established. The imports in that trade, fine raw materials, silk, goats’ hair, &c., came here to be manufactured. Supposing the trade to increase one million, and wages amount to £600,000, cal- IN 110YAL NAVY AND MERCHANT SERVICE. 173 culating taxes at 20 per cent., an increase of revenue of £120,000 would result from steam Communication.” Minerva. — We shall close our examples of steamers by giving some details of the Cork Steam Navigation Com- pany’s iron vessel Minerva , running between Cork and Glasgow. She was built by Messrs. Thomas Yernon and Co., in 1846-47, and fitted with side-lever engines by Messrs. Bury, Curtis, and Kennedy, of Liverpool. FT. IN. Length on deck Length between the perpendiculars Breadth of beam, extreme Depth of engine room Length of engine room Burthen in tons, builders’ old meas. Horses power . . 197 0 . 190 0 . 26 0 . 16 6 . 57 0 No. 655 |f No. 384 Diameter of cylinders, each 70 inches x 6 ft. 2 in. stroke ; extrem diameter of paddle wheels 26 ft. 9 in. ; floats 9 ft. 10 in. long x 2 ft. 1 in. deep, No. 22 ; revolutions 19 to 21 per minute; two tubular boilers, toge- ther 19 ft. long, fixed from each end; total number of furnaces, 12; each boiler has 526 tubes, 3 in. diam. x 7 ft. 1 in. long ; has an elliptical stern ; is clinker-built to the waterline, and carvel-built above; and is schooner rigged, with two masts, without top masts. Maximum speed, 15 to 16 knots, or 17§ to 18§ statute miles. Estimate of the Number of Merchant Steamers. — The number of merchant steamers belonging to the United Kingdom at present is about 1200, the registered tonnage of which, exclusive of the engine-room tonnage, is 165,000, equal to a gross tonnage of about 295,000 tons ; propelled by engines of 100,000 horses power. Estimate of the Number of Steamers in the Royal Navy . — The number of steam vessels of all kinds in the Koyal Navy is at present about 190, representing a gross tonnage of perhaps 150,000 ; and propelled by engines of 51,000 horses power. The number of armed steamers in the Boyal Navy 174 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS is about 125, carrying 800 guns (exclusive of the armaments of the guard and block ships fitted with auxiliary engines), and propelled by engines of about 41,000 horses power. The French Steam Navy. — The Trench steam navy is believed to consist at present of 114 vessels propelled by engines of 26,000 horses power, irrespective of those not yet completed. The number of steam trading vessels in Trance during the year 1850 was returned at 279 ; having a tonnage of 40,098 tons, and a power of 22,893 horses. Amonst the Tables at the end of the book will be found one of paddle-wheel steamers in the Royal Navy. Also, a Table giving the principal dimensions of 195 paddle-wheel steamers of all classes. Registering Paper used in Trials of Government Steamers . — The following is the form of registering paper used by the Admiralty engineer officers in determining the maximum speed of a steam vessel at her trial : Remarks. Time, occu- pied by Experi- ment. Total Num- ber of Revolu- tions of Screw. Aver- age number of revo- lutions per mi- nute. Total number of Revo- lution of Engine. Aver- age number ofRevo- lutions per mi- nute. Observ- ed Rate of Ship. Reduc- ed Rate of Ship. True Rate of Ship. The “ Observed Rate” is deduced from the time taken to run the measured knot or mile in each separate experi- ment ; the “ Reduced Rate” is the mean of the two adjacent experiments, the one with and the other against the tide, IN E0YAL NAVY AND MEECHANT SEEYICE. 175 the mean of the first and second experiment giving the first reduced rate, and the mean of the second and third, the second reduced rate ; and so on, each experiment after the first being thus used twice in the calculations. The true rate is the mean of the first and second reduced rates, and of the second and third, and so on, thus using each reduced rate twice also as before, and the mean of the true rates is then taken as the speed of the vessel. Speed of the Vessel . — Two posts are erected on the shore to mark the distance either of a knot or mile, and at about 200 yards or farther inland from these, two other posts are erected at right angles to the first. It is evident that a vessel running at any distance out at sea from these posts, if kept by the compass or by any leading marks parallel to the line of measurement, will run the exact distance as mea- sured when she brings the inland posts into one with those on the shore as she passes them. It may be observed, that a mean of the times would not give a true result, as no com- pensation would in that case be given for the greater length of time that the tide would act against the vessel than it would in her favour. By the system adopted the influence of the tide is thrown out as far as possible ; and, if the tide should flow at the same rate, or should increase or diminish by regular gradations during the series of trials, the result would be mathematically correct. In making the experi- ments it is essential to avoid any change of the direction of the tide during the series, and also, if possible, to select a calm day. If the wind is in the direction of the course, the effect will be less detrimental to the mean speed of the vessel than if it be on her beam. In the latter case the vessel is driven to leeward while running both up and down the course, and thus subjected to a constant retarding force, while in the other case the wind is in favour of the vessel in one direction, though in the other it retards her in a somewhat greater degree. 176 PADDLE WHEEL AND PADDLE-WHEEL STEAMEES To facilitate these calculations, the Table (JSTo. XI Y.) which will be found on p. 223 of the Appendix is used by the officers of the Admiralty. With reference to the question of arming merchant steamers, the following also was given in evidence before the Committee of the House of Commons : Mr. Andeeson says, that, “ according to the present con- tracts for carrying the mails, the vessels are to be so con- structed in respect of scantling and arrangements as to carry and fire four guns of the largest calibre then used in her Majesty’s service. Also the Government have the power to take the vessels at two months’ notice, the indem- nification for the hire, purchase, or destruction of them, to be determined by arbitration. Thinks the same arrangement might be extended to all vessels capable of carrying heavy guns. Has ascertained from competent parties that all the merchant steamers of 400 tons and upwards are capable of carrying pivot guns, with some strengthening. Opinion, that in the greater number of cases exemption from the coast-light dues, and from the unjust law of being com- pelled to take a pilot whether he is wanted or not, would be sufficient compensation to owners for the additional expense incurred for strengthenings, &c. There are about 170 vessels from 400 to 1000 tons which would carry guns. Opinion, that the exemptions proposed would not induce steam-boat owners to put the machinery under the water line, the expense being too heavy. More than three times as much money is collected for the light dues than is ne- cessary to support them. It is expected that a bill will be brought in to reduce the light dues to a fixed rate per annum.” # * The entire amount of dues at present collected is about ,£430,000. The maintenance of the light houses costs about £140,000 per annum. IN ROYAL NAVY AND MERCHANT SERVICE. 177 John Ralph Engledtje, Esq. — “Has had experience in the Navy as gunnery officer. Considers nearly all our sea-going vessels might be made to carry guns. No extra risk from engines and boilers being above the water line. (?) Has had much experience with heavy guns, and thinks a 68 pounder worked as easily as a heavy 32 pounder, and with little more concussion. Opinion, that vessels of 600 tons are quite capable of carrying two pivot guns. Opinion, that the engineers would require better pay than those in the Navy. On board the Oriental boats a first-class engineer receives £16 to £26 per month. It is true that in the Queen’s service the chief first-class engineers get £17 a month and pensions, but we find our first engineer as good a table as you or I would sit down to — in fact, they live like princes. In the Navy they have to find their own table, except the common rations of the ship. As regards pensions, I have heard some of the engineers say, 1 What is the use of a pension ? Yery few of us will ever live to enjoy pensions ; if we go on a foreign station, perhaps there is not one of us that will return to receive it.’ In India we have scarcely kept a complete crew of engineers for more than a year together ; we have entire changes year after year, principally from death, and from liver complaints arising from the intense heat of the engine room. Opi- nion, that the average speed of the mail steamers is about one or one and a half knots more than those in the Navy. Increased speed is a great element of superiority. The conversion of the mail steamers into war steamers would not necessarily diminish their speed. The armament would be of far less weight than the cargo is now. War steamers are built to sail well, which accounts for their inferior speed. There may be a few fast vessels in the Navy, but they have extravagant power and carry but few coals. Our Mediterranean vessels average 10 to 11 knots. Cu- nard’s vessels make 280 to 300 miles a-day. One of these vessels carries more weight than a man-of-war of same 13 178 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS tonnage. The weight is all below ; but if part were put on deck in the shape of guns, it would be counteracted by putting weight below. In a vessel of this size it would have no material effect, and she would go just as fast. Private builders are not fettered, and competition produces a good article ; but in the Government yards there has been one surveyor and one system for a length of time. Second-class steamers of 500 to 800 tons would carry a 68 pounder in addition to the 82 pounder on the quarter- deck. Opinion, that the steam chest of the Hindostan would be well protected with 10 feet of coal on each side. Those vessels in the Navy which have their boilers below the water line would not be protected when the ship rolled. I have no doubt that the spar deck of the Hindostan could be strengthened to carry a 90-cwt. 10-inch gun. Would particularly draw the attention of the Committee to the Bombay steamer, which has been fitted to carry two 10-inch guns and 10 medium 32 pounders, and is in every way equal in fittings and efficiency to any vessel in H. M. service.” Mr. Andrew Lamb. — “ Is superintendent engineer to P. & O. Company. Opinion, that the engineers of the private companies would volunteer at a moment’s notice, if the vessels were required for H. M. service. There would be no difficulty whatever if a provision were gua- ranteed, the same as the engineers in the Navy have. “ It would be quite practicable to place the boilers and steam chests in merchant steamers below the water line, and it would not interfere materially with the stowage. In our first-class vessels like the Hindostan , there is 10 feet of coal between the steam chest and the ship’s side. In this vessel I should imagine the engineers to be safer than in any of H. M. steamers I have seen, because a body of coal is carried between the boilers and engines, against which the force of steam would spend itSelf in the event of an explo- IN ROYAL NAYY AND MERCHANT SERYICE. 179 sion ; tlie stokers would suffer most. The engineers and stokers would not be so safe from shot as if the engine room were below the water line. The coal that protects the boilers is left till the last, and by the time that is wanted it is time to look out for a coaling port. The Pe- ninsular and Oriental Company do not do their own repairs either to ships or machinery. It is more economical to employ private individuals. The machinery made at Wool- wich cannot be better than ours, and should not be worse. Has never found any obstacle in getting the repairs done efficiently and with readiness. The annual expenses on a vessel and machinery amount to seven per cent, on the total original cost.” Captain Edward Chappell, E. N". — “ Is Secretary and Joint Manager of West India Packets. Opinion, that all their vessels would carry even a 95-cwt. gun forward, but not in all cases abaft, as the sterns rake too much. Would put 32 pounders in the entrance ports for broadside guns. The average speed, including the intercolonial work, is 8 knots. On their trial trips, without cargo, they had a speed of 12 knots. Opinion, that they would surpass in speed all the men-of-war, with the exception of the five or six last new boats ; men-of-war have heavier scantling, which gives them greater weight. The Urgent mail steamer was bought by the Admiralty, but proved a complete pick-pocket from the lightness of her scantling. “ Opinion, that the engineers would remain on board if compensated. Thinks they are not a class of men who like martial law. We pay our engineers £16 to £20 per month. We commenced with all good men at £20 per month, and have had few accidents in consequence. We use the beam engine in all our boats, except the Conway ; she has direct- acting engines, and we very much regret it. We use all flue boilers on a peculiar plan of our own engineers.” Charles Wye Williams, Esq. — “I s manager of the 180 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS City of Dublin Steam-Packet Company, which owns 24 ships of 10,837 gross tonnage. Our vessels often carry very heavy deck loads. One of the smallest has often car- ried on deck, in bad weather, two locomotives, weighing 17 tons each. We have carried troops, a thousand men, with heavy baggage, besides women and children. In our mail boats, where the work is severe, we give our first engineer £2 15s. ; to the second, £1 17s. 6d\ to the third, £1 8s. In the other vessels, to the first engineer, £2 10s. ; to the second, £1 15s. ; no third engineer.” Lieutenant Julius Eoberts. — “Is a lieutenant of Eoyal Marine Artillery, and has been employed by the Admiralty to inspect contract steamers. Has surveyed a great many, and reported on thirteen for fittings. Ten have been equipped and completed for service. The others inefficient, and unable to carry armament on account of number and nature of fittings, windlasses, hatches, &c. Must have a clear deck, within sweep of bow and stern guns. Has found it necessary to strengthen knees and put in additional deck beams. Would put 82 pounders of 56 cwt. in merchant ships of 500 tons, as a pivot gun forward and aft. The four last vessels of Cunard’s line would carry a 95-cwt. gun very well, and some others also. The United States Trans- atlantic steamers are larger than ours, but less capable of carrying guns for want of proper arrangements. Some of the contract steamers are and will be capable of carrying the heaviest shell guns. Would not call a steamer armed, if only with broadside guns and paddle wheels. Wants heavy pivot guns. Would undertake, with enough hands, to alter and turn out 100 merchant steamers in two months, to carry heavy guns forward.” Captain Henderson, E.N. “has been in action in a steamer with batteries, but not with another steamer. Against batteries they answer admirably, because you can iight with steam down. ' Opinion, that in a general war IN ROYAL NAVY AND MERCHANT SERVICE. 181 large steamers would be available against line-of-battle ships, because the line-of-battle ship would be taken on her weak points by the larger guns of the steamer, which would keep at a distance, and could elevate her guns more than a sailing vessel could do. Opinion, that steamers might be brought into broadside action, and would not be so vulnerable as people generally fancy. That in half an hour a line-of-battle ship would be very much crippled by a steamer, if it were calm or a light wind. If the line-of- battle ship had an auxiliary screw she would be a more dangerous enemy, but the steamer of superior speed would still have the advantage. In case of a battle, each ship of the line would have a steamer to tow her into position. In the first of the war we ought to have a number of light fast steam vessels to protect our trade and act as privateers. Opinion, that there is an end of blockades, because men-of- war could always be towed out by steamers when the block- ading fleet was blown off shore. Blockading would become an observation by steamers. With reference to arming large merchant steamers, it is a great mistake attempting to put large guns of 80 cwt. and upwards in vessels that are built of light material, without immense strengthening. I am quite sure that merchant steamers are not near so strong in the scantling as Government steamers generally.” Captain Chads, B.N. — “ If I were in a 120-gun ship, I should not care for the Sidon. She dare not come under my guns. Supposing the line-of-battle ship in a calm, not having heavy pivot guns on deck, I should endeavour to cap- ture her if I were in the Sidon ; but I believe you might fire away the whole ammunition of the steamer without hardly striking the ship, if you kept out of range of her guns, say, 3000 yards. In a calm her boats would always keep her broadside on the steamer. Does not agree with Captain Henderson on this point. At 3000 yards, even under favourable circumstances, the steamer will not strike the 182 PADDLE WHEEL AND PADDLE-WHEEL STEAMERS, ETC. ship above eight or nine per cent. Pivot guns have little advantage over 32-pounders in the lower deck of a ship, as to precision. Opinion, that the merchant steamers would lose speed after they had taken in their armament and spars. Is not aware that vessels of a comparatively small class will carry 50 tons of cattle on their decks, and do very well with it.” Report of the Committee of the House of Commons . — The Eeport of the Committee of the House of Commons, with reference to the “ practicability of providing, by means of the commercial steam marine of the country, a reserve steam navy available for the national defence when required,” is as follows : — “ That mercantile steam ships of the size and strength necessary for the reception of such guns as are in use in the .Royal Navy, would be a most useful auxiliary force for na- tional defence ; and your Committee do not foresee any difficulty in carrying out such a measure, “ That the prompt development of the whole available ma- ritime resources of the country, in the event of threatened hostilities, is most desirable as a means for the preservation of peace. “ That the steps necessary for rendering such mercantile steamers available for the purpose, and the remuneration to be given by the public for fitting them and holding them liable to be called into the public service, must be matters of arrangement between the owners and the Government, upon which your Committee do not deem it necessary to offer an opinion.” APPENDIX. TABLE No. I ADMIRALTY FORMULA OF SPECIFICATION FOR MARINE ENGINES, WITH PADDLE WHEELS. Specification of certain Particulars to be strictly observed in the construction of a pair of Marine Steam-Engines with Paddle Wheels , referred to in the Admiralty Letter on Her Majesty's Service . 1845. The tenders are to be made (in triplicate) on the accompany- ing printed forms, every particular in which is to be strictly and carefully filled up; and all drawings, models, and boxes con- taining them are to be distinctly marked with the names of the parties transmitting them. The whole weight of each pair of engines, including the boilers (with the water in them), the coal boxes, the paddle wheels, the spare gear, the floor plates, ladders, guard rails, and all other articles to be supplied under the contract, is not to exceed 190 tons. The coal boxes (in the space of the engine room) are to con- tain eight-days’ coal, computed at 8 lbs. per horse power per hour, and at 48 cubic feet to the ton. Sufficient details of the coal boxes are to be shown in the drawing, to enable a computa- tion of their contents to be made. In this computation the space below the deck to the depth of six inches is to be excluded, to allow for the space occupied by the beams, and for the difficulty of completely filling the boxes with coals. To avoid the possibility of mistake in the dimensions given in the drawings furnished to the respective parties, it is to be understood that — The length of the engine room, in the clear, is not to exceed 48 ft. 0 in. JJ C JJ III U1 UIUIU . The centre of the shaft above tl Breadth of ditto Depth of ditto 184 APPENDIX. The situation of ditto, as per drawing, or as near as can be. The holding-down bolts are to be secured by nuts let into the sleepers, so as not to require the bolts to pass through the vessel’s bottom ; and the bolts are to have, at the lower end of their points, wrought-iron washers about eight inches square, and one inch thick, placed between the nuts and the wood. Should this mode of security be inapplicable to the particular kind of engine proposed, the engineer is fully to describe any other secure mode which he may think the most advisable to adopt. The pistons are to be fitted with metallic packings. The blow-off pipes are to be not less than inches in dia- meter, and their thickness not to be less than 1 inch. The thickness of the steam pipes is not to be less than 1 inch ; of the bilge pipes, not less than 1 inch ; of the feed pipes, not less than J- inch ; of the waste-steam pipe, not less than f inch ; and of the waste- water pipes (if of copper), not less than J inch. The cylinders are to be fitted with discharge or escape valves at the top and at the bottom of each, for allowing of the escape of water therefrom ; the valves to have suitable metallic cases to obviate the danger of persons being scalded by any escape of boiling water. Reverse valves are to be fitted to the boilers. Each cylinder is likewise to be fitted with a separate move- ment and valve, for the purpose of using the steam expansively in various degrees, as may from time to time be found eligible. The air-pumps are to be lined with gun metal of half an inch in thickness, when finished. The air-pump buckets are to be of gun metal, with packing Tings. The air-pump rods are to be of gun metal, of Muntz’s metal, chinery for driving it J Do. Spare gear, andl all fittings included > in contract J 30 18 Fifty-five. Forty-five. Fifteen. Thirty. Eighteen. Total weight 290 tons. Two hundred and ninety. Diameter of cylinders four, each 50 in. Length of stroke . . . . 3 ft. 0 in. Strokes per minute . . . Revolutions of propeller ] shaft per minute J Diameter of the necks of] No., 45 j. No., 45 13 in. L the engine shaft r Do. Propeller shaft 13 in. The quantity of coal which 1 can be stowed in the > coal boxes J Estimated consumption of! coals per horse power > per hour J Cost of engines, boilers and 1 coal boxes J Do. Propeller, shafts, and 1 all machinery connected l* with them 250 tons, being 9 days’ consumption. £17,620 3,650 6 lbs. [including the erection on | board. APPENDIX. — TOOLS, ETC. 195 Cost of Duplicate and spare articles as per inclosed list, and all fittings and other articles to be sup- plied under the contract Total cost . . Time required for complet- ing the work ready to be put on board Further time required for fixing the whole in the vessel, so as to be fit for service At what place the engines s The construction and dimension of the boilers to be here de- scribed, and the thickness of the plates of the various parts of them ; and if the boilers be tubular, the diameter and length of the tubes to be specified, as well as the material of which they are to be composed. Boilers to be tubular, over all 19 ft. 9 in. long, 24 ft. wide, and 12 ft. high, being kept (as well as the engine) entirely under the orlop deck. Heating surface to be 15 sq. ft. per horse power, and grate-bar surface, 80 sq. in. per horse. Engines to have four horizontal cylinders driving the screw shaft direct. The blow-off pipes to be 4 in. in diameter and i inch thick, of copper ; having their cocks, conical pipes, and stop valves of gun - metal. The whole to be of the best materials and best workmanship. H.B. The position of the engines, propeller, boilers and coal- boxes to be distinctly shown in the accompanying drawings of the engine room. List of Tools and Spare Articles for Engines (with Screw Propellers) of 450 Horses' Power. engineers’ tools. No. Brushes, for boiler tubes, to every 100 horse power . 20 Drifts, short and long do. do. . . 1 each. Eire irons 12 Mandrils do. do. . . 1 each. Scrapers, circular and forked, do. do. .5 each. Spanners and wrenchers of sorts . . . . 24 Stocks taps and dies from i inch to H . . .1 set. K2 1 £22,720 - £1,450 ""Including the entire fitting and trying of the same wherever and whenever re- quired ; and all the other items of expense mentioned at the end of the specifica- tion. 12 months. 3 months. ire to be fixed on board. 196 APPENDIX. GEAR. SPARE GEAR. Air pump, side rods, with straps and brasses complete (if so fitted) *....... Air-pump rod Air-pump cross head (if so fitted) Bars, furnace Bearers • . . . Boiler plates Bolts and nuts for engines properly assorted . . . Cylinder lid Cylinder cross head (if so fitted) Ferules for boiler tubes, to every 100 horse power Piston and rod Propeller and shaft complete Bod, connecting, with strap and brasses complete . . „ Feed pump (if so fitted) „ Bilge pump (if so fitted) . . . . . „ Slide Screws, packing, for slides, complete for one engine . Springs for each piston (if so fitted) .... Springs for other parts of engines, for 1 engine . . Tubes, boiler, to every 100 horse power Tubes, glass, for barometers Yalve, foot, without seat ...... Washers, iron No. 2 1 1 set. 3 6 cwt. 120 1 1 50 1 1 1 1 1 1 1 set. 1 set. 1 set. 10 2 1 100 Note. — Such articles contained in this list as are not to be found in the particular kind of engine tendered for, are to be struck out by the party tendering, and any articles may be added to it which, from the construction of the engines and propeller machinery, he may consider ought to be supplied. Note. — For Tables III. and IY. see also “Artizan Journal” for 1849 and 1850. This journal is the more specially devoted to steam navigation and machinery generally. APPENDIX. — DIMENSIONS OE STEAMERS, 197 TABLE No. III. TABLE OF THE PRINCIPAL DIMENSIONS OF 194 STEAMERS WITH PADDLE-WHEELS. Name of the Vessel. Length on Deck. Breadth, Extreme. Depth in Engine-room. Tonnage — Builder’s old Measurement. © f Scott . Scott and Sinclair Inverary 140 0 20 0 8 7 270 113 16 9 7 6 iron Tod and Tod and Castle M‘ Gregor M‘ Gregor Isaac New- ton . 345 0 40 6 2833 500 wood American . American Islay . 167 0 21 6 11 0 385 152 22 0 iron Tod and Tod and M c Gregor M* Gregor 85 Jenny Lind 145 0 15 0 7 9 165 70 14 0 Denny Penn Juverna 180 8 25 0 14 6 555 274 24 5 9 0 Lunell & Co. Lunell & Co. Kamtschat- ka . 215 0 36 0 24 6 600 16 0 wood American . American Lapwing (Tow-boat) 82 8 14 6 10 0 115 45 14 0 7 3 iron Reid and Co. Murdoch Laurel 190 0 23 0 12 9 500 180 23 6 f Caird . Caird 90 Leinster Lass 200 6 27 0 16 2 720 370 26 6 R. Napier . R. Napier Lightning . 90 0 11 0 6 0 24 10 4 2 0 Joyce . Lady Kel- 150 0 18 2 8 0 233 87 18 0 5 3 Barr and Barr and burne M'Nabb . M'Nabb Lion . 183 9 25 7 14 9 600 256 24 0 8 6 9t Smith and Smith and Rodger . Rodger Llewellyn . 190 0 26 7 15 0 643 350 9 0 Miller . Miller 95 Loch Lo- 126 0 16 9 6 11 175 56 15 5 3 0 Denny Smith and mond Rodger London- derry 160 8 25 3 15 11 488 240 21 5 10 9 wood R. Steele R. Napier Lyra . 218 6 25 6 12 10 600 275 25 4 10 3 iron R. Napier . Ditto Magicienne, R. N. 200 0 30 0 21 0 1000 400 28 0 13 8 wood Penn Maid of Lorn (Tow-boat) 85 0 14 3 9 0 80 60 15 0 7 6 iron 100 Manchester 165 0 22 6 10 6 400 150 18 0 Robinsons & Robinsons & Russell Russell Maria . 275 0 36 0 9 6 1747 h.pr. 30 0 wood American . American Marquis of Stafford . 103 0 23 0 12 1 365 154 22 0 iron Reid & Co. Thomson Medway 215 0 36 6 30 6 1350 450 30 0 17 0 wood Pitcher Maudslay Merlin 152 0 16 7 8 3 207 70 13 1 3 10 iron Wingate Wingate 105 Meteor 105 9 17 6 8 6 130 62 14 0 5 6 Caird . Caird Mindello 160 0 28 0 17 6 604 220 23 0 11 3 wood Green . Blyths Minerva 197 0 26 0 16 6 652 384 16 9 iron Vernon Bury Mississipi . 220 0 10 0 23 6 1600 600 28 9 wood American . American Mongibello. 160 0 26 0 18 0 500 200 10 6 Maudslay 110 Nemesis 170 0 29 0 11 0 600 120 17 6 5 0 iron Laird . Forrester Nevka . 150 0 18 0 9 6 230 70 15 6 4 0 M Fairbairn Fairbairn New Gren- 178 0 25 0 14 0 390 212 23 0 Smith and Smith and ada H Rodger . Rodger New York . 210 0 36 6 22 0 1700 420 16 0 wood Fawcett Niagara 251 0 38 1 25 6 1757 674 33 1 R. Steele R. Napier 115 Niagara 265 0 28 6 9 3 30 0 4 8 American . American Nile . 175 0 33 0 20 6 912 220 20 0 13 6 Boulton and Watt Nimrod 185 0 26 0 16 0 591 320 24 6 11 10 iron Vernon Bury. Nix, Pruss. 170 0 26 0 11 6 560 160 17 0 6 9 Robinsons & Robinsons & R. N. 1 Russell Kussell 200 APPENDIX. — DIMENSIONS OP STEAMERS. TABLE No. III. — Continued . Name of the Vessel. Length on Deck. j Breadth, 1 | extreme. Depth in Engine-room. Tonnage — Builder’s old Measurement Horses’ Power. Diameter of Wheels. Mean Load — Draught. Material. Builders of the Vessel. Makers of the Machinery. Nomi- ft. in. ft. in. ft. in. Tons. nal. ft. in ft. in. Nor ah 135 0 18 6 8 0 236 77 16 4 6 0 wood At Water- At Water- Criena ford ford 120 Ocean . 160 0 25 0 15 6 500 239 23 6 12 6 Wilson Scott and Sinclair Odin, K. N. 212 0 37 0 24 2 1326 560 27 6 70 0 Fincham Fairbairn Ohio . 265 0 46 0 33 0 2300 700 36 0 American . American Oregon 325 0 35 0 11 0 2000 h.pr. 35 0 Ditto . American Orion . 212 0 28 0 18 6 805 440 29 7 iron Caird . Caird 125 Peiki Tijaret 172 0 26 6 16 6 568 180 10 6 wood Fletcher MiUer Peloro 135 0 20 2 11 2 252 100 15 6 Pitcher Boulton and Watt Peterhoff . 190 0 21 6 9 0 412 15a 16 3 4 0 iron Mare . Rennie Petrel . 166 6 17 10 7 11 248 100 19 1 5 0 Barr and Barr and M‘Xabb . M‘Nab Pharos 146 0 21 0 12 9 303 150 19 0 7 6 ty Fairbairn . Penn 130 Philadelphia 200 0 33 0 18 3 1100 500 27 0 wood American . American Pioneer 161 0 18 2 9 0 252 95 19 0 5 0 iron Barr and Barr and M*Nab . M‘Nab Pizarro 187 0 30 0 20 0 800 350 wood Wigram MiUer Pottinger . 220 0 35 0 28 9 1250 450 16 0 iron Fairbairn . Miner Powhattan . 251 6 45 0 26 6 2400 800 31 0 19 0 wood American . American 135 Precursor . 230 0 37 0 25 0 1480 520 17 0 Hedderwick R. Napier President . 238 0 41 0 30 0 1921 540 34 0 17 0 Curling and Fawcett Young Premier 137 6 17 7 7 0 212 62 16 2 iron Denny Smith and Pride of Erin 195 0 27 2 16 0 715 368 25 6 R. Napier . Rodgers R. Napier Prince . 165 0 24 0 13 0 446 200 20 0 7 6 Fairbairn . Penn 140 Pr. Albert . 160 0 19 6 9 6 310 110 17 6 4 6 Coutts . Milner Pr. of Wales 165 0 26 6 14 6 575 260 25 0 7 9 Tod and Tod and M‘ Gregor M‘ Gregor Princess 166 0 24 6 16 0 637 298 23 10 12 2 wood Wilson Fawcett Princess 135 0 18 0 8 5 210 8 15 11 4 3 iron Tod and Tod and M‘ Gregor M‘ Gregor Prs. Alice . 164 0 24 1 14 0 479 212 22 9 9 0 „ Ditto . Ditto. 145 Prs. Alice R. N. 125 0 20 0 10 6 270 120 17 0 6 6 Ditehburn . Maudslay Prs. Royal . 200 0 28 0 17 0 800 380 29 0 10 0 „ Tod and Tod and M‘ Gregor M‘ Gregor Queen . 165 0 16 6 8 9 217 90 16 6 4 3 ,, Rennie R ennie Queen . 162 0 24 4 13 7 460 175 20 8 „ Vernon Fawcett Railway 150 0 19 1 9 10 258 90 15 6 „ Ditcliburn . Penn 150 Rainbow 195 0 25 0 12 0 581 180 5 6 Laird * Forrester Red Rover . 158 0 22 4 10 6 350 120 16 6 5 6 wood Seaward Retribution R. N. 220 0 40 6 26 4 1641 800 34 0 18 0 „ Symonds Maudslay Roberto 195 0 34 0 19 0 1056 300 „ Pitcher Ditto Rose . 153 0 20 6 11 6 305 100 17 0 6 6 iron Fairbairn . Fairbairn 155 Royal Alice 145 0 18 5 8 0 165 96 17 9 Tod and Tod and M‘ Gregor M c Gregor Royal Con- sort . 180 0 26 3 15 5 605 316 27 0 Ditto . Ditto Salamander. 170 0 26 0 11 6 560 160 17 0 6 9 Robinsons & Robinsons & Russell . RusseU Sampson, R. N. 208 0 37 6 23 0 1297 467 27 6 wood Symonds Rennie Sapphire 155 0 18 0 9 9 150 16 0 4 8 iron Seaward APPENDIX. — DIMENSIONS OE STEAMERS 201 TABLE No. III.— Continued. Name of a o AM A '■S c£ © a © SB O a o .5 t-i i%i 1 O ID 8u-g 03 d n © 9 Laird . Forrester R. Napier R. N. . 185 0 34 4 21 0 970 280 25 0 wood Symonds 170 Superb 164 0 17 2 9 6 200 74 15 2 iron J. Reid R. Napier Susque- hanna 256 6 45 0 26 6 2436 800 31 0 19 0 wood American . American Tagus . 188 0 28 1 17 4 700 260 ” J. Scott Scott and Sinclair Tay . Temparador 215 0 36 6 30 6 1350 450 30 0 17 0 Duncan Caird 175 155 0 24 0 14 0 418 140 9 9 »» Fletcher MOler Terrible, Lang . Maudslay R. N. 230 0 42 6 27 0 1800 800 34 0 17 0 „ Teviot . 215 0 36 6 30 6 1350 450 30 0 17 0 „ Duncan Caird Thames 215 0 36 6 30 6 1350 450 17 0 „ Pitcher Maudslay Thetis . 190 6 22 5 11 6 345 160 22 7 7 6 iron R. Napier . R. Napier Thistle 198' 0 26 4 16 0 655 336 25 9 11 0 „ Ditto . Ditto 180 Thistle 153 0 20 6 11 6 305 100 17 0 6 6 „ Fairbairn . Fairbairn Tiger, R. N. Trafalgar 210 0 36 0 24 6 1220 17 0 wood J. Edye Penn 192 0 28 1 16 11 750 346 26 7 10 6 iron Tod and Tod and M‘ Gregor M‘ Gregor Trent . 215 0 36 6 30 6 1350 450 17 0 wood Miller TridentR.N. 185 0 31 6 18 0 800 350 22 0 10 9 iron Ditchburn . Boulton and Watt 185 Urgent Vanguard . Vesper Victoria 175 0 26 0 17 5 562 280 24 6 R. Napier . Caird 183 0 27 3 16 7 663 324 27 0 11 6 iron R. Napier 155 0 18 0 9 6 250 70 wood Fletcher Mdler 150 0 20 4 10 5 290 100 15 0 7 0 iron Tod and Tod and M‘Gregor M - Gregor Victoria and Symonds Maudslay Albert R.N. 198 0 33 0: 22 0 1040 430 : 31 6 wood Waterman 9. 100 0 15 0 7 3 35 2 ' ‘9 iron D. Napier . D. Napier 190 Whitehaven 182 0 25 5 13 10 575 300 : 25 10 10 6 „ Vernon Butterly and Co. Windsor 205 0 28 0 16 3 764 340 : 28 2 12 3 »> Vernon Bury Wizard Scott and Scott and (Tug) . 75 0 14 2 9 0 82 40 : 12 9 Sinclair . Sinclair 194 Ysabel la Catolica . 235 0 38 o: 24 6 1567 500 17 0 wood Wigram Maudslay E 3 202 APPENDIX. TABLE No. IV. TABLE OF THE PRINCIPAL DIMENSIONS OF TWENTY-EIGHT MERCHANT STEAMERS WITH SCREW PROPELLERS. Name of the Vessel. Length on Deck. Breadth, extreme. Depth in Engine-room. Tonnage — Builder’s old Measurement. Horses’ Power. Diameter of Screw. Mean Load — 2 SJO 5 u Material. Builders of the Vessel. Makers of the Machinery. No- ft. in. 't. in. ft. in. Tons. tninal. ft. i in. ft. in. Albatross . 197 0 30 0 16 0 853 124 10 6 iron Smith and Smith and Rodger Rodger Antelope . 175 0 26 4 17 0 600 100 Hodgson Apollo 185 0 30 2 14 0 820 100 8 10 Smith and Smith and Rodger . Rodger Archimedes 180 0 44 0 24 0 1587 330 15 0 18 0 wood Rennie 5 Archimedes 115 0 22 6 13 0 237 90 8 0 9 4 Wynn Ditto Arno . 190 0 27 6 16 6 636 136 12 4 iron Reid & Co. . Thomson Astrologer . 186 0 25 0 15 0 553 124 19 8 Smith and Smith and Rodger Rodger Ayrshire Lass 88 3 19 0 7 4 94 16 § 0 Denny Wingate Bosphorus 180 0 25 0 16 0 530 80 10 6 8 6 Mare . Maudslay 10 Brit. Queen 190 0 29 0 18 0 800 130 Denny Caird City of Glas- 228 0 34 0 24 6 1200 380 13 0 99 Tod and Tod and gow M‘ Gregor M‘Gregor Erin’sQueen 135 0 21 0 12 9 283 20 7 0 10 6 Denny Caird European . 172 0 25 0 14 4 415 98 9 2 9 0 Smith and Smith and Rodger Rodger Fawn . 135 0 20 6 10 6 275 110 6 6 Penn . Penn 15 Gr. Britain 300 0 51 0 31 4 3500 1000 16 0 99 Gt. Western Co. . Acraman Gr. North- ern . 225 0 37 0 26 0 1750 370 12 0 wood At Derry At Derry Humming Bird 132 4 18 0 9 3 135 80 5 3 7 6 iron R. Napier . R. Napier Lady Seale 122 6 22 0 13 3 305 40 7 0 wood Follet & Co. Marshall Livorno 160 0 25 6 15 0 508 100 10 6 9 0 iron Denny Thomson 20 Loch Fine . 76 0 18 6 7 7 120 15 5 0 ,, Ditto . Wingate Marie . 145 0 20 € 14 6 375 80 10 0 Reid & Co. . Thomson Mars . 185 0 30 6 16 C 806 100 9 0 9 0 At Water- Smith and ford Rodgers Mermaid 135 0 16 6 9 c > 164 90 5 8 Rennie Rennie Monumental City . 185 0 30 0 >24 c > 120 12 0 13 0 wood American . American 25 i Pomone 170 7 ’42 7 17 3 260 „ Boucher Count Rosen Propontis . 175 0 25 € ! 17 e ! 532 80 iron Mare . Maudslay. Sarah Sands i 200 0 32 C >19 € ; iooo 200 14 6 14 6 Grantham 28 ! Vesta . ,114 0 ' 20 4 ^ 12 2 l| 180 38 8 0 8 0 APPENDIX, 203 TABLE No. V. PADDLE WHEEL STEAMEES IN HEE MAJESTY’S NAYY AND POST OEEICE SEEYICE. Name of Ship. Designer. Maker of Engine. Tonnage— Builders’ Old Measurement, Horse Power. Kind of Engine. Diameter of Cylinder. Length of Stroke. Kind of Boiler. Pressure in Boiler. Diameter of Wheels. Medium Speed under Steam only. in. f. i. lbs. f. i. knots Acheron . Sir W. Symonds Seaward 722 160 i Side-lever 49 4 9 » Flue 6 20 C ) 8 Adder Old P. 0. Packets Boulton & Watt 241 100 1 Side-lever 394 3 6 i Flue 4 14 C > n Advice Lang . Boulton & Watt 197 100 1 Side-lever 394 3 6 i Flue 4 14 C i 74 African La.ig . Maudslay . 295 90 Side-lever 38 3 6 i Flue 4 14 C » 7 Alban Lang . Boulton & Watt 295 100 Side- lever 394 3 6 Flue 4 14 C » 7 h Alecto Sir W. Symonds Seaward 800 200 Direct 53J 4 6 Flue 5 23 0 i s| Antelope ( Iron) Ditchburn . Penn . 620 260 Oscillat. 64 4 6 Tubular ■ 8 20 0 1 84 Ardent Sir W. Symonds Seaward 800 200 Direct 53* 4 6 Tubular 6 21 C 1 8£ Argus Fincham Penn . 975 303 Oscillat. 64 6 0 Tubular 14 23 5 ■ 9* Avon . Old P.O. Packets Boulton & Watt 361 170 Side-lever 484 4 6 Tubular 8 14 0 i 8 Banshee . Lang, iun. . Penn . 650 365 Oscillat. 72* 5 0 Tubular 14 25 0 » 12 Basilisk Lang . Miller . 1000 405 Oscillat. 74 6 0 Tubular 10 24 0 i 9* Bee . Sir W. Symonds Maudslay . 42 10 Side-lever 20 2 0 Tubular 10 9 0 ' 7 Birkenhead Laird . Forrester 1400 556 Side-lever 85 7 0 Tubular 6 30 0 • 10* Black Eagle Lang, jun. . Penn . . 540 261 Osciliat. 62 4 6 Tubular 10 22 0 Hi Blazer Sir W. Symonds Miller . . 527 136 Side-lever 43 3 6 Tubular 8 14 8 74 31oodhound (iron) Napier Napier . 378 150 Side-lever 48 4 0 Tubular 10 18 6 8 Bull-dog „ Sir W. Symonds Rennie 1124 500 Direct 82 5 8 Tubular 7* 26 0 »4 Buzzard . Edye . Miller . 997 303 Oscillat. 64 6 0 Tubular 14 23 4 94 (iron ) Sir W. Symonds Seaward 650 350 Direct 75 4 4 Tubular 12 25 6 12 3entaur Sir W. Symonds Boulton & Watt 1270 540 Direct 85* 6 0 Tubular 8 27 6 8* Cherokee . Sir W. Symonds Maudslay . 750 200 Side-lever 54 5 0 Flue 4 20 0 7 Colombia . Lang . Boulton & Watt 361 100 Side-lever 394 3 6 Flue . 4 14 0 8 Comet Lang . Boulton & Watt 338 80 Side-lever 35* 3 6 Flue . 4 14 0 8* Confidance Lang . Maudslay . 294 100 Side-lever 40 4 0 Flue . 4 16 0 8 Cormorant Sir W. Symonds Fairbairn 1057 300 Direct 65* 5 3 Flue . 7 24 0 10 Cuckoo Lang . Boulton & Watt 234 100 Side-lever 39* 3 6 Tubular 1 14 6 9* Cyclops Sir W. Symonds Seaward 1195 320 Direct 64 5 6 Flue . 5 26 0 84 Dasher Sir W. Symonds Seaward 260 101 Side-lever 40* 3 6 Tubular 8 16 0 9 Dee . Devasta- Lang . Maudslay . 704 200 Side-lever 54 5 0 Tubular 8 20 0 8 tion . Sir W. Symonds Maudslay . 1058 42') 4 cylinders 54 6 0 Tubular 6 25 4 10 Dover (iron) Laird . Forrester 224 90 Side-lever 38 3 0 Tubular 8 13 6 10 Dragon Sir W. Symonds Fairbairn . 1296 560 Direct 88 5 9 Tubular 8 27 0 10 Driver Sir W. Symonds Seaward 1056 280 Direct 62 5 3 Tubular 8 27 0 9* Echo . Lang . Butterley Co. 295 140 Side-lever 44* 4 6 Flue 5 17 0 84 Elfin . Lang, jun. . Rennie 111 40 Oscillat. 27 2 6 Tubular 16 11 4 12* Eearless Old P. 0. Packets Boulton & Watt 165 76 Side-lever 354 3 2 Flue 4 12 0 8 Eirebrand . Sir W. Symonds Seaward 1190 410 Direct 75 5 9 Tubular 8 26 8 8* Eire-fly Lang, jun. . Maudslay . 550 218 Side-lever 55* 5 0 Tubular 5 20 0 8 Eire-queen N apier Napier 312 115 Staple 60 3 9 Tubular 8 16 6 13* Eurious Fincham Miller . 1286 399 Oscillat. 72 1 7 0 Tubular 14 27 4 Eury . Sir W. Symonds Rigby . 1124 515 Direct 84 i 5 9 Tubular 10 25 6 94 Jar land Lang, jun. . Penn . 300 124 Oscillat. 434 4 0 Tubular 16 18 0 124 jeyser Sir W. Symonds Seaward 1060 273 Direct 62 1 5 3 Tubular 8 25 7 8* jladiator . Sir W. Symonds Miller . 1210 455 Direct . 79 ! 5 6 Tubular 7 25 2 94 Jorgon Sir W. Symonds Seaward 1108 320 Direct 64 J 5 9 Tubular 8 26 0 84 jrowler Sir W. Symonds Seaward 1059 280 Direct 62 I 5 3 Tubular 8 25 3 8* Harpy (iron) Ditchburn . Penn . 345 150 Oscillat. 49 - 4 0 Tubular 8 16 0 8 Hecate Sir W. Symonds Scott & Sinclair 817 240 Side-lever 60 ! 5 9 Tubular 8 24 6 8* H ecla SirW. Symonds Scott & Sinclair 817 240 Side-lever 60 ! 5 6' Tubular 8 24 6 8* Hermes Sir W. Symonds Maudslay . 830 218 4 cylinders 40* ‘ 4 6' Tubular 8 : 20 0 8* Hydra Sir W. Symonds Boulton & Watt 817 220 Side-lever 56 i 5 0 Tubular 8 ! 23 6 84 Inflexible . fackal Sir W. Symonds Fawcett 1122 379 Direct 72 1 5 9 Tubular 14 : 28 6 9 (iron) Napier Napier . 340 150 Side-lever 48 - 4 0 Tubular 10 18 0 8 fanus Lord Dundonald American . 763 220 Side-lever 56 1 5 0 Tubular 8 16 6 9* Caspar Old P. 0. Packets Fawcett 233 100 Side-lever 394 : 3 6 Flue . 4 14 0 74 £ite . Old P. O. Packets Fawcett 300 150 Side-lever 474 ■ 4 3 Flue . 4 18 0 8* lieopard . Fincham Seaward 1435 560 Direct 86*1 6 4 Tubular 14 30 0 Aghtning . Lang . Maudslay . 296 100 Side-lever 40J- 4 0 Flue . 6 16 6 8 (iron) Napier Napier 345 150 Side-lever 48 4 0 Tubular 10 18 0 8 204 APPENDIX. — HEE MAJESTY’S NAYY AND POST OEEICE SEEYICE TABLE No. Y. — Continued. Name of Ship. Designer. Maker of Engine. Tonnage— Builders’ Old Measurement. Horses’ Power. Kind of Engine. ■ Diameter of Cylinder. 1 Length of Stroke. Kind of Boiler. Pressure in Boiler. Diameter of Wheels. Medium Speed under Steam only. in. f. i. lbs. f. i. knots Locust Sir W. Symonds Maudslay . 284 101 Side-lever m 3 6 i Tubular • 8 15 7 f 7 Magicienne Edye . Penn . 1220 399 1 Oscillat. 72 7 0 'Tubular • 14 27 4 r 10 Medea Lang . Maudslay . 335 850 4 cylinders 50 5 3 ' Tubular ■ 10 23 2 ! 9 Medina Sir W. Symonds Fawcett 886 30, Side-lever 64 6 0 (Tubular • 8 24 6 i 8| Medusa Sir W. Symonds Fawcett 880 300 ' Side-lever 64 6 0 'Tubular • 8 24 f 1 8| Merlin Sir W. Symonds Fawcett 889 300 Side-lever 64 6 0 Tubular • 8 24 € 1 8| Minos Canada Ward & Co. 406 90 Side-lever 4 6: Flue 4 Mohawk (iron) Fairbairn Maudslay . 174 60 Side-lever 34 3 2! Flue . 4 11 6 i 8! Monkey Old P.O. Packets Boulton & Watt 212 130 Side-lever 45! 3 6! Tubular ■ 8 14 C I 8* Myrmidon ("iron) Ditchburn . Penn . 370 150 Oscillat. 48 4 O Tubular 10 17 C ! 8 Myrtle Old P.O. Packets Boulton & Watt 116 50 Side-lever 30 2 6 Flue . 4 10 9 > 7! (iron) Sir W. Symonds Rennie . 650 260 Oscillat. 61* 5 0 Tubular 10 21 0 > 9 Odin . Fincham Fairbairn . 1326 560 Direct 88 5 9 Tubular 10 27 6 1 9 Onyx (iron) Ditchburn . Penn . 300 124 Oscillat. m 4 0 Tubular 16 18 6 : 13 Otter . Old P. 0. Packets Boulton & Watt 237 120 Side-lever 44* 3 6 Flue . 5 14 0 7! Penelope . Edye .. Seaward 1616 625 Direct 91! 6 8 Tubular 10 31 0 9! Pigmy Old P. 0. Packets rFawcett 227 80 Side-lever 35 3 6 Flue . 4 12 6 8 Pike . Old P. 0. Packets Fawcett 111 50 Side-lever 30! 2 6 Flue . 4 10 9 8 Pluto . Lang . Boulton & Watt 365 100 Side-lever 39! 3 6 Flue . 4 14 0 8 Polyphe- mus . Sir W. Symonds Seaward , 800 200 Direct 53| 4 6 Tubular 8 23 5 8*' Porcupine . Lang . Maudslay . 380 132 Side-lever 44 4 0 Tubular 8 15 6 8* Alice (iron) Ditchburn . Maudslay . 270 117 Annular . 43 3 6 Tubular 16 18 0 12! Prome- theus Sir W. Symonds Seaward 796 192 Direct 53J 4 6 Tubular 10 23 5 8* Prospero . Old P. 0. Packets Coates & Yeung 249 144 Side-lever 46 4 0 Flue . 4 14 9 9 Retribution Sir W. Symonds Penn . 1640 399 Oscillat. 72 7 0 Tubular 14 24 4 10 Rhadaman- thus . Roberts Maudslay . 813 220 Side-lever 55! 5 0 Flue . 5 20 0 8 Rosamond . Sir W. Symonds Miller . 1059 298 Direct 65* 5 0 Tubular IQ 25 0 9! Salamander Sir W. Symonds Maudslay . 818 220 Side-lever 55 J 5 0 Flue . 4 21 0 8 Sampson . Sir W. Symonds Rennie 1299 476 Direct 81 5 8 (Tubular 6 26 4 9 Scourge Sir W. Symonds Maudslay . 1124 420 4 cylinders 54 6 O Tubular 8 26 6 11 Shearwater Graham Boulton & Watt 343 160 Side-lever 48! 4 6 Flue . 4 17 0 8 Sidon . Sir C. Napier Seaward 1328 560 Direct 6 4 Tubular 10 22 6 10 Sphinx Sir W. Symonds Penn . 1058 500 Oscillat. 82! 6 0 Tubular 8 28 0 9! Spiteful Sir W. Symonds Scott & Sinclair 1060 280 Side-lever 62 6 0 Tubular 8 26 0 9 Spitfire Lang . Butterley & Co. 430 140 Side-lever 44* 4 6 Tubular 8 17 6 - 8| Sprightly . OldP. O. Packets Boulton & Watt 234 100 Side-lever 39! 3 6 Flue 5 13 0 8 Stromboli . Sir W. Symonds Napier 970 280 Side-lever 63 6 0 Tubular 8 25 0 8! Styx . Sir W. Symonds Seaward 1057 273 Direct 62 5 3 Tubular 8 25 7 9! Tartarus . Sir W. Symonds Miller . 523 136 Side-lever 46 3 6 Tubular 8 15 6 8* Terrible Lang . Maudslay . 1850 829 4cylinders 72 8 0 Tubular- 7 34 4 11 Tiger . Edye . Penn . 1220 399 Oscillat. 72 7 0 Tubular 14 27 0 Torch (iron) Sir W. Symonds Seaward 345 150 Side-lever 49 3 9 Tubular 10 17 0 8 Trident (iron) Sir W. Symonds Boulton & Watt 850 350 Oscillat. 71 5 0 Tubular 10 23 0 8 Triton (iron) Sir W. Symonds Miller . 653 260 Oscillat. 64 4 6 Tubular- 10 21 0 9 Undine Pasco . Miller . 290 106 Oscillat. 42 3 0 Tubular 25 17 0 12* Vesuvius . Sir W. Symonds Napier • 970 295 Side-lever 63! 1 6 0 Flue 5 26 4 8 Victoria & Albert Sir W. Symonds Maudslay . 1034 420 4cylinders 54 i 6 0 Tubular 10 29 8 115 Violet Ditchburn . Penn . 300 124 Oscillat. 43! 4 0 Tubular 16 18 0 13 Virago Sir W. Symonds Boulton & Watt 1060 300 Direct 66! 5 0 Tubular 8 24 9 9! Vivid . Lang.juh. . Penn . 352 160 Oecillat. 49!- 4 O' Tubular 16 18 6 13 Vixen Sir W. Symonds Seaward 1059 280 Direct 62 ! 5 3 Tubular 8 : 25 8 9* Volcano . Sir W. Symonds Seaward 720 132 Side-lever 45 • 4 3 Flue . 5 ! 20 3 7! Vulture Sir W. Symonds Fairbairn 1190 470 Direct . 80§l 3 9! ' Pubular 10 ! 25 0 10 Widgeon . Sir W. Symonds Seaward 164 90 Side-lever 38 : 3 1 * Pubular 8 : 13 9 9 Wildfire . Old P. CL Packets Boulton & Watt 186 75 Side-lever 35* : 3 0' rubular 8 : 12 0 8 Zephyr Old P. 0. Packets Boulton & Watt 237 100 Side-lever 39! : 3 6 Flue 4 : 14 0 8 APPENDIX, 205 TABLE No. VI TABLE OF EXPERIMENTS WITH H. M. SCREW STEAM- TENDER, ‘‘DWARF.” Burthen in tons, 163 ff. Nominal horse power, 90. Draught of water, 7 feet aft ; 5 feet 10 inches forward. Fitted with a common two-threaded screw, 5 feet 1 inch in diameter, with common pitch. No of Experiments. | Pitch of the Screw. | Length of the Screw. Area of the Screw. Average revolutions of the engines per min. Average revolutions of the screw per min. Proportion of revolu- tions of screw to engine. Average pressure at the end of shafts, indicated by the Dynanometer. I Speed of the screw per hour. | Slip of the screw per hour. Speed of the Vessel per hour. 1 Gross average power 1 exerted in the cylinders. Speed of the Vessel com- puted as if the power ex- | erted had been 160 horses. Average power expended in propelling, by Dy- nanometer. Ratio of gross indi- cator to Dynano- meter power. feet. ft. . in. sq. f. 1 tons. knots knts. horses. knots. horses. 1 8 0 2 22 2 28-3 146-2 5 16 1 1-36 1 1 -53 25-0 8-65 130-7 9-25 si-o 1-62 2 »> 2 17*8 29-6 152-7 i9 1-49 12-05 257 8-95 151-5 9-12 92-1 1-65 g ,, 1 13-3 30-1 155-4 99 1-42 12-26 27 1 8-94 137-0 9 41 87*3 1-57 4 *» 1 o 7 8-9 32*2 166-0 1-51 13 09 30-4 9-11 168-8 8-95 95-1 1-78 5 10.32 1 8t6 13*3 31-8 127-1 4 1 1*07 12-93 33-4 8-60 148 7 8-82 63-5 233 6 99 2 8i 17-8 30-8 123 3 •96 12-55 30-8 8*74 136-3 9-22 57-6 234 7 99 1 l! 8-9 34-9139 7 1-00 14-22 36-4 9-05 154-0 9-16 62-6 2-44 8 2 ] j— 22*2 30-9 123-6 •91 12-57 29-3 8-89 143-8 9-21 55-9 2 57 9 13-23 1 ]0_9_ 13-3 36*6 1 14-2 3 13 1 1 117 14*90 40-4 8-88 161*7 8-85 71-8 2-25 10 3 0.1 6 22*2 34*0 106-6 99 1-35 13-90 38-7 8-52 149-5 8-72 79 4 1-9 11 1 lj_ 8-9 40'2 125-9 99 1-74 16-42 44-7 9-07 176-9 8-77 108-5 1-62 12 2 16 17-8 35-7 111-8 99 1*74 14-58 39-5 8 83 166-4 8-71 105-9 1-57 !3 2 17'8 26-2' 105 *7 4 1 1-78 13-79 33-9 8-29 151-9 8-43 101 6 1-49 44 3 6. 22-2 25-4,101-6 99 1-73 13-52 39-5 8 01 139-6 8-52 95-4 1-47 15 1 10t 9 tt 13 3 26 0|1 04-1 9 9 1-69 13-58 41-7 7-92 117-2 8-79 920 1-27 16 l 3 t V 9*9 29 8 119-3 9 > 1-93 15 57 46-1 8-38 147-4 8-61 110-6 1-32 17 1 3 JL 8*921*6 1 1 1*7 5 16 J 1-64 14-58 46*1 7-85 116-6 8-73 88-8 1-31 1H 1 10-9- 13-3 19-9 102-6 99 1-62 13-39 42-9 764 114 2 855 85-4 1-34 19 2 c 17*2 19-0 1 97*9 1-73 12-78 41-1 7-52 111-5 8-48 89-6 1-23 20 3 l! 22 2 18-5 95*4 99 171 12-45 39-5 7-52 108-8 8-56 88*5 1-22 21 10 32 2 lOrV 29-2 22*5 116-2 99 1-99 11-82 30*0 8-28 127*3 8 94 113-4 1-12 22 1 8r 7 ,T 13*3 24-9 i 128-4 99 1-91 13-06 36*4 8-39 134-0 8-81 109-3 1-23 23 1 l 5 8 9 26-6 137*5 1-99 14 0 38-5 8-61 138-5 9-03 113-1 1-17 24 „ 2 3} 17-8 23-9 1 123-1 1-94 12-53 32-9 8-40| 126-6 9-08 112*3 1 13 These experiments were made at Woolwich during the months of June, July:, August, 1845. The following are the dimension of “ Dwarf,” viz. Length between the Perpendiculars ft. . 130 in. 0 Breadth extreme . . 16 6 Depth in Engine-room . • . 15 9 Diameter of Cylinders 3 4 Length of Stroke . . 2 8 Note —For Tables VI. and VII. see the very valuable Table in the new edition ol “ Tredgold on the Steam Engine,” Yol. III. John Weale. TABLE TABLE OF SCREW-STEAMERS L— Name of the Vessel. Length be- tween the Per- pendiculars. Breadth, extreme. | Mean draught at the time of tiial. Area of im- mersed mid- ship section. Displacement at time of trial. 1 Tonnage — Builder’s old measurement. Horses’ power, Nominal. Horses’ power indicated at trial. ft. in. ft. in. ft. in. sq. ft. Tons. Tons. H. P. H. P. 1 Ajax 176 0 48 6* 22 64 807 3090 1761 450 846 2 Amphion . 177 0 43 2 19 0 546 2025 1474 300 592 3 Archer 180 0 33 0 14 1 372 1238 970 200 345 4 Arrogant . 200 0 45 18f 18 m 580 2444 1872 360 623 5 Bee , 63 0 12 2 3 H 28*2 33*2 43 10 6 Blenheim 181 48 6 21 738 2790 1832 450 938 7 Brisk 193 7 35 0 13 9 373 1474 1074 250 8 Conflict . 192 6 34 4 14 6 402 1443 1038 400 777 9 Dauntless 210 0 39 9 16 4 522 2240 1497 580 811 10 Ditto, lengthened 1 at the stern . 5 218 1 2251 1569 „ 1218 11 Desperate 192 6 34 4 15 9 443 1628 1037 400 12 Dwarf (iron) . 130 0 16 6 5 6 44 98 164 90 216 13 Encounter 190 0 33 2 {II 9 4 6 318 341 11921 1290 J 953 360 ) 672 1646 14 Erebus 105 0 28 10 14 1 328 715 372 30 15 Euphrates 215 7 40 6 16 7-1 570 2402 620 16 Fairy (iron) 144 8 21 1§ ( 4 1 5 10 10 71*5 82 1681 196 ) 312 128 f 364 1321 17 Greenock (iron) 213 0 37 4 1 15 0 450 1980 1418 338 18 Highflyer . 192 0 36 4 15 9 465 1737 1153 250 19 Hogue 184 0 48 4\ 22 10 820 3155 1846 450 20 Horatio . 154 3 40 2| 19 li 537 1707 1090 250 21 Megaera (iron) 207 0 37 10 16 0 487 2048 1395 350 780 22 Minx (iron) 131 0 22 1 5 24 82 203 303 100 234 23 Ditto, horse power") 10 32 diminished 9 9 99 99 ” 24 Miranda . 196 0 34 0 13 6 374 1522 1039 250 25 Niger 194 4 34 8 / 14 10 1 14 403 392 13621 13231 1072 400 (8 28 1919 26 Phoenix . 174 7 31 10 (13 1 13 9 J ,7 'j n 347 327 12251 1140) 809 260 r382 1489 27 Plumper . 140 0 27 6 no n 1 12 3 204 241 5391 652) 490 60 ( 148 1149 28 Rattler 179 6 32 8* ( ll 113 3 6 274 330 8701 1078) 888 200 r 428 1436 29 Reynard . 147 8 27 10 {. 9 « 6 11 184 222 4781 604) 516 60 f 165 1153 30 Rifleman . 150 0 26 7 {l 3 3 173 173 484 -» 484) 486 200 r 348 1366 31 Ditto, horse power diminished . J f 9 34 175 48 7 1 100 c 188 99 lio 2f 199 565} 99 i 190 32 Sanspareil 200 6 52 1 22 9 920 3484 2334 350 408 S3 Sharpshooter (iron) 150 0 20 71 • 2 ( 9 1 9 If 3 192 196 5051 518) 489 200 ) 365 1175 34 Simoom (iron) 246 0 41 0 17 0 567 2789 1980 350 35 Teazer (iron) . 130 0 21 9* 5 3 82-9 205 296 100 36 Ditto, horse power ( 40 128 diminished . / 99 99 ” ** 37 Termagant 210 1 40 6 17 1 587 2403 1547 620 1351 38 Vulcan (iron) . 220 0 41 5 15 6 465 2076 1764 350 793 39 Wasp 180 0 33 10 14 9 395 1337 970 100 N. B.— The Experiments made on each Vessel are continued, and No. VII IN HER MAJESTY^ NAVY. Vessel. , „ 6828 11 Desperate . 1037 400 13 0 14 0 2 4 87*28 12 Dwarf . . 164 90 5 8 8 0 1 0 180 182*8 13 Encounter . ■* 953 360 12 0 15 0 2 6 80 f 78 1 72 14 Erebus 372 30 70 15 Euphrates . 620 8 0 8 0 1 0 1 4 16 Fairy . 312 128 r 5 4 16 2 ( 258 1220 17 Greenock 1418 338 14 0 13 0 2 2 98 18 Highflyer 1153 250 85 19 Hogue . . 1846 450 16 0 20 0 3 4 45 50 20 Horatio 1090 250 55 21 Megsera 1395 350 55 22 Minx .... 303 100 4 6 5 0 1 0 220 254 23 Do. H. P. diminished. f9 10 5 0 3 8 77*72 140 24 Miranda 1039 250 25 Niger . . 1072 400 12 6 17 0 2 10 75 C 68*8 174 32 26 Phoenix . . 809 260 / 12 0 111 lOf 12 8 9 8 2 l \ 1 7/ 92 C68 196 27 Plumper • . 490 60 9 0 5 7 1 0 155 / 115 1112 28 Rattler . . 888 200 10 0 11 0 1 3 100 r 104 1 107*92 29 Reynard . ». 516 60 r 8 9 l 8 11 8 0 7 3 1 4 \ 1 4/ 120 r 108*86 U12 30 Rifleman 486 200 8 0 9 0 1 6 144 / 119*25 1129 31 Do.H. P. diminished . „ 100 r 8 0 19 0 9 0 9 0 1 6 1 1 6/ 144 f 110 198*75 32 Sanspareil . 2334 350 9 0 9 0 55 f 140*7 1124*5 33 Sharpshooter 489 200 r 8 0 19 0 1 6 1 1 6/ 144 34 8imoom . .. 1980 350 55 35 Teazer .... 296 100 4 6 5 10 1 0 220 200 36 Do. H. P. diminished . 40 5 0 7 0 1 2 192*09 37 Termagant . 1547 620 05 6 C 15 6 18 0 17 21 3 07 2 I0j 70 / 66 173 38 Vulcan . . 1764 350 14 0 16 6 2 9 65 66*5 [39 Wasp .... 970 100 121 N. B. — The Experiments made on each Vessel are continued and cor- VII. — Continued. IN HER MAJESTY’S NAVY, APPENDIX. 209 Proportional Numbers. Ratio of Vessel’s Screw’s Immersed Nominal Indicated Rate of Rate of lengthto Pitch to 0 Section H. Power H. Power Screw. Ship. Slip of the Screw. breadth. Diame- to Screw’s to 0 Sec- to 0 Sec- ter disc. tion. tion. Knots. Knots. Knots. p. Cent. 8-482 7-147 1-335 15-74 3-625 1-12 4-01 0-56 1-05 •321 6-75 2-571 27-58 4-1 1-4 309 0 55 1-08 8*293 7-818 0-475 5-73 5-32 086 5 84 0-54 0-93 f nega- nega-'l 4-37 8 211 8-295 ^ tive tive } 0-96 3*07 0-62 107 [ 0 084 1-02 J 8-877 6-822 2 055 23-15 517 1-21 3-76 0-35 8-483 5-816 2-667 31-4 3-73 1-25 3-67 0 61 1-27 5-53 1 1 067 9-289 1-778 16-06 5-6 1-22 2-81 0-99 1-93 9-818 7-366 2-452 24-97 5-28 1-22 3-09 111 1 55 12123 10-293 1-83 15-09 5-48 99 >» 99 2-33 5-6 1*08 14-427 10-537 3 89 26-96 7-87 1-41 1-74 2 04 4-91 11541 10-254 1-287 11 15 > 5-73 1-25 r 2*81 113 2-11 10-653 9-375 1-278 11-99 S l 3-01 1-06 1-89 3-64 5-32 20 359 13-324 7-035 34-55 6-84 / 1*5 3*2 1-79 5-08 17-36 11-891 5-469 31*5 1 1*29 2-74 1-56 3-91 5-69 {bylog. 5-28 9-864 2-364 23-96 38 1*25 408 0-55 3-83 5-47 12-533 9-137 3-396 27 09 5-93 1-11 515 1-22 2-86 5-062 4515 0-547 10-8 •76 0-73 4-17 012 0-38 11-537 9-494 2-043 17-7 \ 5-6 1-36 f 3-28 0-99 205 12-462 10-427 2-035 16-33 J l 3 19 1-02 234 8-496 7106 1-39 16-36 \ 5-48 rl-05 3-16 0-75 11 9153 8-74 0-413 4-51 J 10-81 2-97 0-79 1-49 f nega- nega- 5 0-72 6-333 7-418 1 tive tive 1 5-09 0-62 / 3-2 0-29 6-168 6-497 ) 1-085 17 13 f l 3-78 0-25 0-62 L 0 329 5 33 J 112 10 074 1 21 10-72 X 5-39 1-1 / 3-49 073 1-56 1 1 -709 9 639 2-07 17-67 / 1 4-2 0 6 1-32 8-59 8-258 G-352 4-09 5-3 r o*9i 3-06 0-32 089 8-009 7-3 0-709 8-85 / 10-81 355 0-27 0*69 10- 586 11- 452 8 096 9-499 1-49 1 953 23-52 ) 17 05 / 5-64 1*12 3*44 1-15 f 2-01 l 2-12 9-765 8-011 1-754 17 06 -) 5-64 / 1*12 3-48 0-57 1-07 8-766 7-977 0-789 9- ; i 1*0 312 0-5 0-95 3-84 12-49 9-782 2-708 21-68 \ 5-63 / 1*12 3*81 104 212 11-052 9-189 1-863 16-85 J i 1*0 3-08 1-02 1-86 6-0 11-507 6-315 5-192 45-12 5-96 1-29 5-21 1-2 2-11 13*263 7-685 5-578 42 05 596 1-4 4*22 0-48 1-54 11-718 9 16 2-552 21 77 1 5-19 / 1*16 2-74 1-2 2-4 12-391 9-51 2-881 23-25 J ll-ll 3-11 1 05 2*3 10-823 9-605 1-218 11-25 5-31 1-18 3*02 0-75 1-7 5-32 respond throughout the three Tables of Screw Steamers in H. M. Navy. TABLE No. VII. — Continued . TABLE OF SCREW STEAMERS IN HER MAJESTY’S NAVY. 3 . — Engines. a; -g m ftp. ' s 2 O o of rers of the of u .2 o S 1 Actual | at Trial. o c ■ d & ' 13 -d -*03 ; btPQ *•! G a o £ rt o *3 G H-l 3^ £- S Ajax | Cyls. Horizontal 4 inches i 55 ! f. i. : l 6' No. No. 18 lb 1224 lb 6 In. 24* H P 450 H P 846 Direct. 1 Field j 15 - 2 Amphion | Miller & 1 Ravenhill / Ditto . . 2 48 - 1 0< 18 < 15 15 10 25 300 592 »> 3 Archer Ditto Ditto . . 2 46 : 3 0 18 : 36*16 15-8 10 26 200 345 3 to 1 4 Arrogant . Bee | Penn & Son j Horizont.1 0 Trunk J 4 Beam . . 1 60-241 , = 55 J 20 3 0i GO ! 35*5 48 13 5 27 271 360 10 623 Direct. 5 Field ' j 2 0 5 to 1 6 Blenheim | Seaward & 1 Capel j Horizontal 4 52 3 0 45 43 14*13 10 27 450 938 Direct. 7 Brisk | Scott, Sin-1 clair & Co. j Ditto . . 2 52 3 6 40 250 2*25 to 1 8 Conflict | Seaward & 1 Capel j Rob. Napier . Ditto . . 4 46 2 0 75 68 14-19 16 25 400 777 Direct. 9 Dauntless . Ditto . . 2 84 4 0 36 243 12-42 8 25* 580 811 2-276 tol 10 Do. length- end &stern altered > Ditto . Ditto . . 2 ” tt 30 15-11 ” 26i >> 1218 ” 11 Desper- f ate 1 Field } Ditto . . 4 55 2 6 40 400 2* 182 tol 12 Dwarf C. J. Rennie . Vertical . 2 40 2 8 35 35-5 15 8 27 90 216 5-15 to 1 13 Encounter Penn & Son { Horizont.1 0 Trunk J 4 60-241 = 55 J 2 3 80 78 13-31 26 360 672 Direct. 14 Erebus | Maudslay & Field Locom. 1 0 H.Pres. J 4 30 15 Euphra- ( tes \ Seaward & 1 Capel / Penn & Son . Horizontal 4 62 3 6 35 620 2 tol 16 Fairy . Vert.Oscil. 2 42 3 0 36'5 51-6 14 128 364 5 tol 17 18 Greenock | Highflyer j Scott, Sin-1 clair & Co. j Horizontal 2 Ditto . . 2 71 55 4 0 4 0 42 31*5 338 250 •* 2*33 to 1 2-7 to 1 Field j • * 19 Hogue | Seaward &1 Capel J Ditto Ditto . . 4 51$ 3 0 45 50 26* 450 .. Direct. 20 Horatio Ditto . . 2 54 3 0 45 250 2 tol 21 Megsera . G & J. Rennie Ditto . . 4 49* 2 0 55 350 Direct. 22 Minx | Miller & 1 Ravenhill / Vert.Oscil. 2 34 2 9 55 63*5 12-19 10 26 100 234 4 tol 23 Ditto, H.P. Seaward & H. Press. 1 2 140 39 60 10 32 Direct. diminished Capel horizont . ) 4 24 Miranda . Rob. Napier . Horizontal 2 56 3 9 32 250 2*43 to 1 25 Niger j Field j Ditto . . 4 47 f 1 10 75 74*3 15*63 8 24* 400 919 Direct. 26 Phoenix Penn & Son . Vert.Oscil. 2 62 4 6 23 24 12-37 6 26* 260 489 4 tol 27 Plumper j Miller & 1 Ravenhill j Ditto . . 2 27 2 0 62 46 23-2 14 26* 60 148 2-5 to 1 28 Rattler | Maudslay &1 Field / G. 8c J. Rennie Vertical . 4 40} 4 0 25 26 13-42 5 200 428 4 to 1 29 Reynard . : Horizontal 2 28 2 0 60 54*4 20-27 14 60 165 2 to 1 30 Rifleman j Miller 8c 1 Ravenhill J Ditto . . 2 46 3 0 48 43 14-12 10 25* 200 360 3 tol 31 Ditto, H.P. diminished | Ditto . . Vert.Oscil. 2 34 2 9 48 44 14*12 10 26* 100 188 12*5 tol 32 Sans-pa- f reil 1 Boulton 8c Watt Horizont.1 . Oscil. J * 44 2 6 55 350 > . . Direct. 33 Sharp- f shooter 1 Miller 8c 1 Ravenhill / Horizontal 2 46 3 0 1 48 46-9 14-4 10 26 200 1 408 i 3 to 1 34 Simoom | Boulton 8c Watt Horizont. 1 A Oscil. 44 2 6 155 350 I . . Direct. 35 > Teazer | Miller 8c 1 Ravenhill J Vert.Oscil. 2 34 2 S 155 50 11-6 10 100 ) 17E > 4 to 1 36 ! Ditto, H.P. diminished [ j Penn 8c Soi i Ditto . . 2 27 2 6 51*5 14*31: » 9 26} r 4C ) 128 $3*73 tol 37 r Terma- f gant l $ Vulcan Seaward 8c 1 Capel j , G. 8c J.Rennii Horizontal 4 62 3 6 >35 36-5 14*4£ > 14 27 62C ) 1351 L 2 to 1 36 e Ditto . . 4 49* 2 ( ) 55 66-5 12-76 i 8 27 35( ) 791 J Direct. 86 1 Wasp { Miller 8c 1 Ravenhill j ■ Vert.Oscil. 2 34 2 1 ) 60 10< ) .. N .B . The experiments made on each vessel are continued and correspond throughout the three tables of Screw Steamers mH.M. navy. Weight of total Ma- chinery, per Admiralty Horse Power. cwt. 11-03 11-65 11-81 11-65 11- 07 12 12- 09 12- 39 S3 1304 13- 16 13-51 13-96 S3 1 It Cost per Horse, exclusive of spare Gear, Admiralty estimate. £ s. 43 17 41 4 46 8 43 18 45 18 36 0 32 0 44 10 43 13 38 18 44 11 45 3 40 0 43 1 35 16 14 35 3 39 3 39 Cost per Horse Power, Contractor’s £ s. 48 42 1 48 46 1 48 37 34 46 1 42 47 14 47 11 iUl 39 5 38*15 42 9 42 9 Extra cost for Brass * ii i i ii 1 1 iigiw Cost per Horse Power, Admiralty estimate. ” “"“S'- 1 “ “> a =«i S S SSSS S 338833 Total cost, with iron tubes. £ 26,100 18,720 17,000 22,800 S£g 21,940 21,390 19.250 19,440 16,480 13.250 13,250 13,250 Cost of Duplicates and spare Gear. , imi g i mi i mill Cost of the Paddle Wheels. ' mt. 8 . .188 . IISMi Cost of Engines, Boilers, and Coal- boxes. £ 1 22,400 19,820 23,000 20,350 23.0 16,2601 16.0 it] 18,!! Estimated consumption per horse per hour. Number of days’ consumption. £ * a sags? s sg&ss Weight of Coals in Boxes. 2 mil s i liii i mill Diameter of necks of Paddle shaft. | fsasS s & assS 2 ssssss Breadth of Paddles. a ®o^oo o » ©«5co<© O OOCOOOO 2 OOiCiOiCS C5 05 05050005 © 05 05 00 00 00 00 Diameter of Paddle Wheels. a 000050 O © OOOO 05 o«oooo 5 838S78 & 8 8888 8 888888 No. of Strokes per * ~ ,m - 1 8S8S * 288222 Length of Stroke. •2 ©C5©000 05 © ©^SO© O 050^000 £ tominvsm © m mining © m m m m <£> to Diameter of Cylinders. ' — / — ' Estimated total weight. = iiiii i i mi i mm Estimated weight of Du- plicates and spare Gear. C 2 8 2888 10 S88333 Estimated weight of Paddle Wheels. 2 S8S88 § § §388 8 SJ38SSS Estimated weight of Coal-boxes. 2 SSgSS 3 § SS38 “ ssssss Estimated weight of Water in Boilers. 2 3888S S S 38SS S gggsss Estimated weight of Boil- ers and their Apparatus. 2 eessss s s ssss k gssggg Estimated weight of Engines. s SSSSs * § ISSS 3 sssgsg Horses’ Power, Contractors’ estimate. 3 Sslii i 1 llll 3 333333 Horses’ Power, Admiralty estimate. 3 Isllg 1 I 1111 1 llllss 11 Oscillating Direct . . Oscillating Direct . . Oscillating Direct . . 99 99 Oscillating Double Cyl. Direct . . 99 g 99 Oscillating Numbers M f ° r -««»•** ® *> «®ga s ssasss VIII.— Table of Proportions of Marine Engines and Boilers— continued. Number of fires. h h h h 2 2 ^ ® « « « oo S2S Ratio per Admiralty 1 .o <» 9 © r 1 ® « os h horse power. I 2 S h ” 2 2 h HH2l2i2f252 22 22 Total area of effective I 4 !? 2 2 2 S w 2 , , heating surface. 1 !J{g § 8 & £ $ 2 1 ^§§11 §88 Total area through the K 1 « § | | g | 1 1 S 2 tubes. 1 ST 1 2 $ g g 2 2 1 1 2 2 8 8 8 8 888 Number of tubes. 1 I 1 1 I I § 1 1 S S 1 fi § § §§§ External diameter. ||^ « « m c? e? ^ « 1 e£e£3? Boilers, length of the ico ^ « <0 0 h ® ® t-oor-jo®. 000 tubes . Ici>eo«oeo«oeoeoso meomsoeomcososo Ratio, per Admiralty horse power. 3 S g 3 , 8 , 2 £ i 1 1 9 £ oc3” yi 0 m m w 1 h 1 0 m ® 1 1 h h meo«o Boiler’s area of the fire surface. sq.ft. 240 284*1 323*3 262*5 264*4 240 287 267*75 288 191*16 210 195 195 195 Boiler’s breadth of fires. s® « ® 0 ^ ® 50 | ©eoeocoeoincocoso 05 05 H 05 05 05 05 « « ft N IN W (NNN Ratio of the circumscrib- ing parellelopiped to the horse power. 3 U § [: § g 2 S S 3 8 f 2 282 Boiler’s height, with steam chest. ft. in. 16 7 18 1 16 8 14 6 15 4 16 7 17 6 14 6 C no < steam (. chest 15 7 16 1 16 2 16 1 18 2 15 6 17 5 17 5 17 5 Boiler’s height, without steam chest. ft. in. 12 3£ 14 2 11 n 10 4 10 11 11 7 11 Hi 9 7 n 0 12 8 11 6i 11 8 11 6i 12 1 12 3 12 10 12 10 12 10 Boiler’s extreme breadth. ft. in. 2 47 23 li 27 2 19 0 24 0 21 8i 23 2 19 1 23 5 25 1 23 9 24 0 19 5 22 1 18 6 19 0 19 0 19 0 Boiler’s Length. ft. in. 23 3 18 7 19 9 18 11 19 11 22 1 21 1 18 7 15 6 16 3i 21 1 18 11 22 1 20 2 20 0 17 10 17 10 17 8 Ditto, calculated by the Admiralty velocities. ft. perm. 1370 1469 1670 1571 1601 1452 1607 1609 1665 1670 1462 1766 1576 1562 1607 1655 1458 1486 Velocity of extremity of paddle floats, by the Manufacturers. ft. perm. 1379 1462 1665 1571 1602 1446 variable 1641 1748 1647 1487 1538 1557 1522 1602 1418 1418 1418 Ratio of diameter of wheel to crank. 7*72 9*04 9*94 9*01 9.35 8*12 9*56 9*48 9*86 9*98 7*89 10*76 9*20 9*27 9*59 10*03 j 8*36 1 8.6 Height of centre of wheel 1 above that line. | ,S© ® | j H* C5 05 © oT O 05 O O 05 05 r— j H H £c(0 CO CO CO CO COCO COCOCOCOCOOO COCOQO Dip of wheel, measured 1 from assumed waterline. | C _ mw HIM Hfc* r«| WttWHWht -05 « f co 05 | « 0 c m c<< 0 0 t'Ms £?eo co h H h h 0 ^ ■-ti ^ eococo Ratio of connecting rod to crank. | I 8 S S P j R S „ i « S S 8 g S3 Sftp I H 05 05 t* COCO CO in H in 05 IN5HH Length of the connect- ing rod. _c co i> 0 01 i>C 5 co © © In © © «? ^Tm t> eeo i>i>co 05 ao oo co co 05 eo h i> cococ 5 N ett Length of the Engine. ft. in. 17 6 17 1 17 7 13 5 11 10 17 1 11 11 13 3i 19 li 15 6 18 3 18 1 14 1| 16 7 12 3 9 5 21 0 15 11 Length of the Engine- Room. ft. in. 53 0 48 3 56 2 56 1 46 9 52 3 56 0 56 3 49 1 45 10 56 3 56 2 56 2 47 8 48 1 42 1 52 4 47 9 Place where fitted on board. E. I. Docks London or Liver- > pool. J Glasgow . E. I. Docks Liverpool . Greenock . Blackwall . Limehouse E. I. Docks Liverpool . E. I. Docks Liverpool . London . Greenock . Time for fixing. ■£ ^ HtN r*H -fcl m+MH-Mft geo COHC0050505C5C* 05 05 05 05 05 05 Hi- 1 r-l Time for making. £© cocoaooocDOooIrr >> © in © © ©s !>«>»> g H H Horses’ Power, Admiralty estimate. H.P 544 515 508 501 501 500 496 484 469 463 460 456 444 427 423 343 313 313 Numbers for Manu- facturers. HC5C0^»flC0*>C005 O ^ 05 co H in © r^co £ TABLE No. IX, FORM OF l,OG FOR A SEA-GOING STEAMER. Observations to be made at the End of each Watch of Four Hours by the Engineer in charge . H tTcfH ai O 2 © - • 3sS •ggHs S*« a W) . a> os fl M Ah H-d « g S O £ *-• m gS Rate in Knots per hour. Average during W atch. Slip of (Wheels or) Screw. Knots. 1-32 1-2 •9 05 (N © f— H “oo” *o Ship, by Patent Log. Knots. 8.8 10-6 7-9 (Wheels or) Screw. Knots. 1012 11-8 8-7 Revolu- tions per min. Aver- age during Watch. ( Wheels or) Screw. No. 52*5 57*6 ,45-3 Engines. No. 17-5 19*2 15*1 = Coals burnt during preceding 12 hours. Averages Expan- sion. Steam expanded after — part of Stroke. iaIoo w|ao *t|oo Temperature of O 1 ^ lO Sea. i ot«o o o 1 •a Coal Boxes, Maximum. cTI>» l>» Engine Room. 1 §?£ £ £ 1 ’O Hot well, Larboard. 1 .'CM CO 1 af O C5 05 | f-H Hot well, Starboard. CM 00 SfO O 05 •O H •— 1 Condensers. Height of Engine- Barometer, Larboard. inches 26-9 27*2 27*4 Height of Engine- Barometer, Starboard. inches 26*4 20*6 26*9 Height of external Barometer. inches 29*6 29*7 29*7 Boilers. Saltness, by Salino- meter Scale. g 00 CO *>. bto © © O.I-H r— 1 Average Pressure of Steam. W i— 1 05 O 5 ^ A. Coals burnt during the Watch. cwt. qrs. lbs. 95 3 6 98 2 5 64 2 18 f-H o 05 CM § o H No. of Fires in use. No. 9 9 6 No. of Sections in use. No. 3 3 2 Watch ending 10 a.m. 2 p.m. 6 p.m. CM 0) - S3 - fl *-5 a s pu eS ci O CM O Tons | I | Coals burnt during preceding 12 hours. Averages | ■Observations, and Reductions, from No. I, to be made evert/ 12 hours by the First Engineer, and submitted to the Captain^ of the Vessel^ Remarks. O Used in pre- ceding 12 Hours. pints. -w Remaining in Ship. a o 217 6 3 w. Coals. Burnt in the preceding 12 Hours. tns. cwt, qrs. lbs. 12 19 0 1 Pressure on Dynamometer. § 3 m ep Co u o Horse Power of one Engine. cJ K t£> co -u cS o •B Bottom. -Larboard. £ r-**o u>|ao ii cS . _ <» Z e S3 M i>> & Top — Larboard. .O 2 | <00 0> Bottom.- Starboard. £ £ Top.— Starboard. £ Co o Dip of the (Wheels or) Screw. ft. in. 2 10 Aft. _c d 15 7 Sm ^ A Forward. d 14 9 Distance run from beginning of Voyage. knots. 1086 Number of Hours under Steam. hours. June 12 CO TABLE No. X. TABLE OP THE VELOCITIES OP PADDLE WHEELS OP DIFFERENT DIAMETERS IN FEET PER MINUTE AND BRITISH STATUTE MILES PER HOUR. c to Mis. per hour |l^?S?^§|!fc?SSSD8S|{So?aS§583|IS?SS?8S|l8gfia?lS8 (o to l> 00 00 OS 05 © rH H 05 00 00 tJJ DO to tO g 00 00 05 05 gj F^H £5 0 J vj lij ^ rj. CQ pq 05 o - u C £ ft's «> £ O-J S&g$8§SSSg823££83££$838s3§§8a&38&&883§83£S2£ fill ^t'-pH-^t'r-l^Xi— l-^Xi— HnXr- SSSi^SS88g|gs|g||3§g8||§gg|||||§|||||g|| d to to m 3 s ft_g 8$gS8£38Sa83882£8gS288&3388o3§82§£2§3S8§gk8!3 • u £ £ 8.1 inn©t0l>l>XXO5©pp^^2ppp^pppp^|^XX©C5C5CJ>£H£HO5O5e^e^^^i^in to § &| £g8$8&2£88$8S3£8$$383£88$88Sg£8$883££3388 £ l! 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(M to os ot to os w m os o? m os oun os 05 m x oj in x (M m X oi in X -— i m ooi— i m x in x i— i ^ . . .^■+^minintototot'Nt>ooxxo505 05 000HrHr-ie)(?}eieoeo«^^T(iininintotfi o 7 S ftj . . . .8pg8^g232pSS8gp8pt:p^g22p^88888p8S?22^p • * • , T*inift©©©^r»^xxx©C505©©i^.^^e'»oio5MwecTH'7t«4t«iisihtb©©t'>£'»t'- • %. e £ ft's (M^int$xc5HeiT(iin®QC05HN«inxo5HM^intoxaiH(MT(iin®xo5H(Mcoin®xo5H ^NonofflMtooseunoOHinooH'f ^b.H^Kowoaiwtoos'MiQOQHinxH'fNOMD. 05050ocoHHHU»eie}MeoM>f^xxc5®05ooooHHH(M(S««nM'i<^^in®® i < Q 4!i II s Or-IC5X"^iint0l>X05©rH(?5e0'^intpt^X05O^0>M'4lint0t^X05pi-((N«vHintpt^X05O SHHHHHrtHHHNNNNNNeJNNNWcoeowSeoeoeocow^^^iit^^TtiTt-^^in TABLE OP THE VELOCITIES OF PADDLE issiissiii WM 3 BI —up mi gii iiiigg maa jwmm ^ I ^ m asiIIgliiBIlgii il mmt_ aawsai jti i iHSiiig iiinsigeiiii jjiiiiii 1 « 1 mmBaamB' £ I' IM ai wlslss llglllgf ISi ill Mjg iiiiiiii ii iisa a a smi t!|L||ISg 5 |: ~ in mmmm a rn ^, mi ill i«ls»a«llIlII!gISIllI 81 !iSIsIll Ml ill I lit M elf 1 TABLE OF THE VELOCITIES OF PADDLE WHEELS, ETC. — Continued, APPENDIX. 217 ! 40 ft. I Ml?. per hour as?83iaapiss85iffls?aas85JaS ■*-■ 'ZB I ^iocoqmJoSdo^Sm^co^cqSmcoSS CO iSs S^g lasssassaasgsasssasgs 1 o,>ooc 5 ss2^s^ss^^i5s;§^g5§ . f. 1 OOOOOOOOClfflOClOO'.C.OlOOOffi *- oj .5 intoi'-aororooHiNco^inco t.coaoHC'feo b o,p iocoj>aoc5©aoc>®Hco^jinco 4J •^1 CO i 2 S 5 «rH O | 1— 1 0 ? rH C? OJ 05 OJ OJ CO CO CO CO CO rfi TjH rh Tt< tJ< in in © rH T* CO QO © JCOCO »ft®J>CX©©--H(MCOTf>ftCOi>©©— iOJCOTtmeo©aoco'*i»©r-(eO'^© 00 ©(NCOiOl>©©(N CO IN ©© CO l> © -^1 00 rH in ds (N ©O CO 00 rH OJ C'» !» CO CO r* T#l rtun in in CO © GO 00 CO in © J>CO ©O rH (N CO rf in © t >00 ©O I— I CO Tjn HHrHHHHHHHH«NCIIM(S 0 } CO 5 5 *H - O ^ s: rHin©COt^O?©©HtrHin©rHCOO}®© injo do os © >h in » th in tr. oo <33 © Ah in (Jo in to hhhhhhhhiH(N«(NWIS(N« £|| §§^ 3 gg§§^^gg§gOrHrH S OJCO in®^«»o» gS g. SS jg S i ?aa g g g| S g ! 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Oil T^ih©^O)©©rHC2W^J3©f»0Qg©rHWW ft o.g | ocoTHHt^’HOtoccfficcwooiflHccino^eo cOrHO®i>-coinwcioo'.cocDinTtHc}rHooC)?r Til in © © i>GO © © rH IN a eo ■<* m © i-^oo ro © © r* r-t r-i rl r-l r -1 r* r* rl r-l rl G* I 27 ft. | - S | j ^in®f«a)©©r^(Nl>(NOrHCOrH©rHlO Tcun in co ©Sg oT eg ^ S© § p p CO co § °j 1 K^p£»s§?sp|;ss8S88ss3ag '^incoi-^aoa>©^o00©©rH^C?O3^HU3©^0063^j^N sgRsaMss^awasMfeas HjaooO©©rH{Ncoeortiincoi>erocos i < s 1 1 | «.2g »n©i>oo©©rHWco^incot^ g ©gjHc^go^ .geo •®£'! a iff! &aj >£ «a c P >.0 o b'.s*| a 3 p g o ^ 4H 'OJ £ “ SiS^a o - w ►>£ o ? « g a*gjs g O g'0« ^ c o « a *a s 2 ^ O ^ 11 y as S-ga is JS® 2 sisss 73 •11^1 g-s £ gs Nil | 'g a © o « g g g g.a jWh »® • 00 73 .£j 'g 4> go S **§ IH*? isfll - 0 SS« a - « « g Sls.sjs rt a"! °P .GP^l H.^'O 50 5iHf slls? .g g.S o ea'p. off L 218 TABLE No. XII. 1. — SHOWING THE ECONOMIC VALUES OF DIFFERENT COALS. Names of the Coals experimented upon. Economic evaporating power, or number of lbs. of water eva- porated from 212° by lib. coal. Weight of 1 cubic foot of the coal as used for fuel, Weight of 1 cubic foot as calculated from the density. Ratio of B to C, or of the economical to the theoretical weight. Difference per cent, between theoretical and economical weights. Space occupied by 1 ton, in cubic feet (economic weight). Results of experiments on co- hesive power of coals, per- centage of large co>ds. Evaporating power of the coal, after deducting lor the com- bustible matter in the residue. Weight of water evaporated from 212° by 1 cubic foot of coal. ! 3 Rate of evaporation, or g number of lbs. water s evaporated ner hour. WELSH COALS. A. B. C. D. E. F. G. H. I. K. | Craigola . 935 60-166 81-107 •742 34-8 37-23 49-3 9-66 581-20 44148 Anthracite (Jones & Co.) . 946 58-25 85-786 •679 47-26 38-45 68.5 97 565-02 409-37 Oldcastle Fiery Vein 8-94 50-916 80-42 •633 57-946 43-99 57-7 45578 464.30 Ward’s Fiery Vein 9-40 57-433 83-85 •685 460 390 46-5 10*6 508-78 529*90 Binea Coal 994 57-08 81-357 •702 42-53 39-24 51-2 10-3 587-92 486-95 Llangenneeh . 8-86 56-93 81-85 •695 4376 39-34 53-5 4-2 52375 376-22 Pentrepoth . 872 57-72 81-73 705 4077 38-80 46-5 8-93 518-32 381-50 Pentrefellin . 636 66-166 84-726 •781 28-051 33-85 52-7 7-4 489 62 247-24 Duffryn . 1074 53-22 82-72 •643 58-43 4209 56-2 11-80 540-12 409-32 Mynydd Newydd . 952 56-33 8173 •689 4509 3976 537 10-59 536-26 470-69 Three-quarter Hock Vein . 8-84 56-388 83-60 •674 48-26 3972 527 498-46 486-86 Cwm Frood Rock Vein . 870 55-277 78-299 706 41-648 40-52 72-5 9-35 480-90 379-80 Cwm Nanty-gros 8-42 560 79-859 701 42-60 400 557 8-82 471-52 40176 Resolven 9-53 58-66 82-354 713 40-39 38-19 350 10-44 55902 390-25 Ponty pool 7*47 557 82-35 •676 47-845 40-216 57-5 8-04 460-07 250-40 Bedwas . 979 50-5 82-6 •611 63-565 44-32 54-0 9-99 494-39 476-96 Ebbw Vale 10-21 53-3 78-81 •676 45-98 42-26 450 10-64 544-19 460-22 Porthmawr . 753 530 86-722 •614 62-7 42 02 600 7-75 401-34 347-44 Coleshill . 800 53 0 80-483 •658 51-85 42-26 62-0 8-34 424-0 406-41 Thomas’s Merthyr . 1076 530 8-2-29 •644 55-26 42-26 55-5 1072 538-48 520-8 Nixon’s Merthyr . 996 51-7 82-29 •628 5976 43-32 64-5 1070 514-93 511-4 Hill’s Plymouth Work . 975 51-2 84-78 •603 65-68 4374 640 1078 599-20 531-6 Aberdare Co.’s Merthyr 973 49-3 81-73 •603 6578 45-43 74-5 10-27 479-68 489-5 Gadley nine-feet Seam . 9.56 54-8 8376 •658 51-75 40-87 760 10-46 523-88 517-3 Neath Abbey . 938 59-3 83-57 •709 40-92 37-77 500 9-65 556-23 546.1 Gadley four-feet Seam . 929 51-6 8279 •623 60-44 43-41 68.5 1073 479-36 400 0 Llynvi 979 53-3 80-35 •663 50-56 42 02 9-58 429-82 399-5 Rock Vawz . 7-68 55-0 80-21 •685 45-83 4072 65*5 7-88 422-40 397-5 LANCASHIRE COALS. Balcarras Arley . 8-83 50-5 78-17 •646 54-79 44-35 760 9 09 445-91 4547 Blackley Hurst 8-81 48-0 78-90 •608 64-37 46-60 650 900 422-88 500-8 Blackbrook Little Delf . 8-29 510 78-16 •652 53-25 43-92 61-5 8-58 422-79 440-4 Rushy Park Mine . 8-08 47-0 80-04 •587 70-31 47-65 67-0 8-35 37976 4197 Blackbrook Rushy Park . 8-02 55-6 8075 •689 44-93 40-50 80-5 8-26 443-50 481-2 Johnson&Wirthing- ton’s Rushy Park 801 500 80-10 •624 60.20 14-80 69-0 876 400-50 454-5 Laffak Rushy Park 7-98 52-6 84-07 •625 59-82 42-85 75-5 876 419-74 435 0 Balcarres Haigh Yard . Cannel (Wigan) 7-90 50-8 80-10 •634 57-37 44-13 80-0 8-23 401-32 398-3 7-70 48-3 76-80 •628 5900 46.37 95-3 8-06 371-91 3817 Balcarras Lindsay. 7 -44 517 78-61 | -650 53-83 43-83 700 7-58 380-18 431-5 TABLE No. XII.— continued. Names of the Coals experimented upon. Economic evaporating power, or number of lbs. of water eva- porated from 212° by 1 lb. coal. Weight of 1 cubic foot of the coal as used for fuel. Weight of 1 cubic foot as calculated from the density. Ratio of B to C, or of the economical to the theoretical weights. Difference per cent, between theoretical and economical weights. Space occupied by 1 ton, in cubic feet (economic weight). Results of experiments on co- hesive power of coals, per- centage of large conls. Evaporating power of the coal, after deducting for the com- bustible matter in the residue. Weight of water evaporated from 212° by 1 cubic foot of coal. 3 Rate of evaporation, or 1 g number of lbs. water [ ? evaporated per hour. LANCASHIRE A. B. C. D. E. F. G. H. I. K. COALS. Balcarras five-feet . 7-21 49-0 79-11 •619 61-44 45-71 44-5 7-35 353-29 487-5 Johnson&Wirthing- ton’s, Sir John . 632 51-6 81-73 -631 58-39 43T3 82-0 6-62 326.11 362-7 NEWCASTLE COALS. Andrew’s House (Tanfield) . 9-39 52-1 78-86 •360 51-36 42-99 9-80 489-21 351-2 Newcastle Hartley 8-23 50-5 80-27 •629 58-95 44-35 78-5 8-65 415-61 308-0 Hedley’s Hartley . 8-16 520 81-79 •635 57-28 43 07 85-5 8-71 424-62 300-8 Bate’s West Hartley 8-04 50-8 78-17 •649 53-87 4413 69-5 8-26 408-43 406.8 Buddie’s West Hartley 7-82 50-6 77-11 •656 52-39 4009 800 801 395-69 413-3 Hasting’s Hartley . 777 48-5 78-04 •621 60-90 46 18 75-5 7-93 376-84 404-5 Carr’s Hartley 7-71 47-8 78-23 •611 63-66 46-86 77-5 813 368-53 344-3 Davison’s W est Hartley 7*61 47-7 78-36 •608 64-27 46-96 76-5 7-83 362-99 402-9 North PercyHartley Haswells Coal Co.’s Steamboat W all’s- end 7-57 491 78-29 •627 56.45 45-62 600 7-72 371-68 423-5 7*48 49-5 79-36 •623 60-32 45-25 79-5 7-85 373-66 291-8 Derwentwater’s Hartley 742 50-4 78-79 •639 56.32 44-44 63-5 7-66 37303 4511 Original Hartley . 6.82 491 77-98 •629 58-81 45-62 800 608 334-86 428-4 Cowpen & Sidney Hartley 6-79 47-9 78-67 •608 64-23 46-76 74-0 702 325-24 350-4 Lydney, Forest of Dean . 8-52 54-4 8004 •680 47-02 4114 550 8-98 463-86 487-19 Staveley, Derby shire 7-26 49-9 79-79 •625 52-90 44-88 88-5 7-46 362-27 466-2 Broom hill 7-30 52-5 79-79 •673 45-55 42-67 65-7 7-33 383-25 397-8 Slievardagh (Irish Anthracite). 9-85 62-8 99-57 •630 58-55 35-66 740 10-49 618-58 473-2 SCOTCH COALS. Dalkeith J ewelSeam 7-08 49-8 79-67 •625 5-98 49-98 85-7 7-10 352-58 355-2 Dalkeith Coro- nation Seam 7-71 51-6 78-61 •657 5217 43T6 88-2 7-86 398-29 370-1 Wallsend Elgin 8-46 54-6 78-61 •694 43-78 4102 640 8-67 460-82 435-7 Fordel Splint . 756 550 78-61 •699 42-92 40-92 630 7-69 415-80 464-9 Grangemouth . 7-40 54-25 80-48 •674 48-35 40-33 69-7 7-91 401-45 380-40 Wellewood 8-24 52-6 79-78 •659 53-57 42-58 80-0 8-39 433-42 438-5 Eglinton 737 520 79-84 •651 51-48 43-07 79-5 7-48 383-24 406.2 Conception Bay, Chili . 572 80-54 506 .. 4250 PATENT FUELS. W arlich’s Patent Fuel 10-36 6905 72-25 *955 449 32-44 10-60 71513 457-8 Lyon’s Patent Fuel W yl am’sPaten tFuel 9-58 61-1 74-73 •817 22-30 36-66 . . 9-77 585-33 409-1 8-92 65 08 68-63 •948 5-45 34-41 9-74 580-51 418-9 Bell’s Patent Fuel . 8-53 65-3 71-12 *918 8-91 34-30 8-65 567-0 549 1 L 2 220 APPENDIX. TABLE No. XII. — continued . 2 .— SHOWING THE COMPOSITION OF AVERAGE SAMPLES OF THE COALS. Locality or Name of Coal. Specific gravity of Coals, Carbon. Hydro- gen. Nitro- gen. Sulphr. Oxygen Ash. Per-cent- age of Coke left by each Coal. WELSH COALS. A. B. C. D. E. F . G. II. Craigola 1-30 84-87 3-84 0'41 0-45 7-19 3*24 85-5 Anthracite . 1-375 91-44 3-46 0-21 0-79 2*58 1-52 92-9 Oldcastle Fiery vein 1-289 87-68 4-89 1-31 0-09 3-39 2-64 79-8 f inclu- Ward’s Fiery vein 1-344 87-87 3-93 2*02 0-83 < dedin 7-04 lash. Binea coal 1-304 88-66 4-63 1-43 0-33 1-03 3-96 81-10 Llangennech 1-312 85-46 4-20 1-0 J 0-29 2-44 6-54 83-69 Pentrepoth . 1-31 88-72 4-50 0-18 3-24 3-36 82-5 Pentrefellin . 1-358 85-52 3-72 Trace 0-12 4-55 6*09 85 0 Duffryn .... 1-326 88-26 4-66 1*45 1*77 0-60 3-26 84-3 Mynydd Newydd 1-31 84-71 5-76 1-56 1-21 3-52 3-24 74-8 Three-quarterRockvein 1-34 75-15 4-93 1-07 2-85 5-04 10-96 62*5 Cvvm Frood Rock vein . 1-255 82-25 5-84 111 1-22 3-58 6-00 68-8 Cwm Nanty-Gros 1-28 78-36 5-59 1-86 3-01 5-58 5-60 65-6 rinclu. Resolven 1-32 79-33 4-75 1-38 5-07 J dedin 9-41 83-9 Pontypool 1-32 8070 5-66 1-35 2-39 4-38 5-52 64-8 Bedwas . . . . 1-32 80-61 6-01 1-44 3-50 1-50 6-94 71-7 Ebbw Vale . 1-275 89-78 5-15 2-16 1-02 0-39 1-50 77-5 Porthmawr Rock vein , 1-39 74-70 4-79 1-28 091 3-60 14-72 63-1 Coleshill 1-29 73-84 5*14 1-47 2-84 8-29 8-92 56-0 Thomas’s Merthyr 1-30 90-12 4-33 1-00 0-85 2 02 1-68 86-53 Nixon’s Merthyr . 1-31 90-27 4-12 0-63 1-20 2-53 1-25 79-11 Hill’s, PlymouthWorks 1-35 88-49 4-00 0-46 0-84 3-82 2-39 82-25 Aberdare Co.’s Merthyr 1-31 88-28 4-24 1-66 0‘91 1-65 3-26 85-83 Gadley nine-feet seam . 1-33 86-18 4-31 1-09 0-87 2-21 5-34 86-54 Neath Abbey 1-31 89-04 5-05 1-07 1-60 3-55 61-42 Gadley Four-feet seam . 1-32 88-56 4-79 0-88 1-21 4-88 88-23 Llynvi . . . . 1-28 87-18 5-06 0-86 1-33 2-53 3-04 72-94 RockVawz . 1*29 77-98 4-39 0-57 0-96 8*55 7*55 62-50 LANCASHIRE COALS. Balcarras Arley . 1-26 83-54 5-24 0-98 1*05 5-87 3-32 62-89 Blackley Hurst 1-26 82-01 5-55 1-68 1-43 5-28 4.05 57-84 Blackbrook Little Delf. 1-26 82-70 5-55 1-48 1-07 4-89 4-31 58-48 Rushy Park Mine 1-28 77-76 5-23 1-32 1-01 8 99 5 69 56-66 Blackbrook, Rushy Park 1-27 81-16 5-99 1-35 1-62 7-20 2-68 58-10 Johnson and Wirthing- ton’s, Rushy Park . 1-28 79-50 515 1-21 2-71 9-24 2-19 57-52 Laffak, Rushy Park 1-35 80-47 5-72 1-27 1-39 8-33 2-82 56-26 Balcarras Haigh Yard . 1-28 82-26 5-47 1-25 1-48 5-64 3-90 66-09 Cannel (Wigan) . 1-23 79-23 6-08 1-18 1-43 7-24 4-84 60-33 Balcarras Lindsay 1-26 83-90 5-66 1-40 1-51 5-53 2-00 57-84 Balcarras Five-feet 1-26 74-21 5-03 0-77 2-09 8-69 9-21 55-90 Johnson and Wirthing- ton’s (Sir John) 1-31 72-86 4-98 1-07 1-54 8-15 11-40 56-15 NEWCASTLE COALS- Andrew’s House (Tanfield) . 1-26 85-58 5-31 1-26 1-32 4-39 2-14 65-13 Newcastle Hartley 1-29 81-81 5-50 1-28 1-69 2-58 7-14 64-61 Hedlev’s Hartley . 1-31 80-26 5-28 1-16 1*78 2-40 9-12 72-31 Bates West Hartley . 1-25 80-61 5-26 1-52 1-85 6-51 4-25 Buddie’s West Hartley 1-23 80-75 5 04 1-46 1*04 7-86 3-85 Hastings Hartley . 1-25 82-24 5-42 1-61 1-35 6-44 2-94 35-60 Carr’s Hartley 1-25 79-83 5-11 1-17 0-82 786 5-21 60-63 Davison’sWest Hartley 1-25 83-26 5-31 1-72 1-38 2*50 5-84 59-49 North Percy Hartley . 1-25 80-03 5-08 0-98 0-78 9-91 3-22 57-18 Haswell Coal Co.’s Steamboat Wallsend. 1-27 83-71 5-30 1-06 1*21 2-79 5-93 61-38 Derwentwater’sHartley 1-26 78-01 4-74 1-84 1-37 10-31 3 73 54-83 Original Hartley . 1-25 81-18 5-56 0-72 1-44 8-03 307 58-22 Cowpen and Sydney Hartley 1-26 82-20 5-10 1-69 0-71 77*9 2-33 58-59 APPENDIX, 221 TABLE No. XII. — continued. Locality or Name of Coal. Specific gravity of Coal. Carbon. Hydro- gen. Nitro- gen. Sulphr. Oxygen Ash. Per-cent- age of coke left by each Coal. NEWCASTLE A. B. C. D. E. F. G. H. COALS. Park End, Sydney 1*28 73-52 5-69 204 2*27 6-48 10-00 57-80 Staveley (Derbyshire) . 1-27 79-85 4-84 1-23 0-72 10-96 2-40 57-86 Broom-hill . 1-25 81-70 6-17 1-84 2-85 4-37 3-07 59-20 f inclu- Slievardagh, Irish An- 1-59 80-03 2-30 0-23 6*76 < ded in > 10*80 90*10 thracite , l ash. J SCOTCH COALS. Dalkeith Jewel Seam . 1*27 74-55 5*14 o-io 0-33 15-51 4-37 49-80 Dalkeith Coronation Seam . 1-31 76-94 5-20 Trace 0-38 14-37 3-10 53-50 Wallsend Elgin . 1-20 76-09 5-22 1-41 1-53 5-05 10-70 58-45 Fordel Splint 1-25 79-58 5-50 1-13 1-46 8-33 4-00 52-03 Grangemouth 1-29 79-85 5-28 1-35 1-42 8*58 3-52 56-60 Welle wood . 1-27 81-36 6-28 1-53 1-57 6-37 2-89 59-15 Eglinton 1-25 80-08 6-50 1-55 1-38 8-05 2*44 54-94 FOREIGN COALS. • Formosa Island . T24 78-26 5-70 0-64 0-49 10*95 3-96 Borneo (Labuankind) . 1-28 64-52 5-74 0-80 1-45 20-75 7-74 Borneo, 3-feet seam 1-37 54-31 5-03 0-98 1-14 24-22 14-32 Borneo, 11-feet seam 1*21 70-33 5-41 0-67 1-17 19-19 3-23 Conception Bay, Chili > T29 70-55 5-76 0-95 1-98 13-24 7-52 43-63 Sydney, N. S. Wales > 82-39 5-32 1-23 0-70 8-32 2-04 Port Famine 64-18 5-33 0-50 1-03 22-75 6-21 Chirique 38-98 4-01 0-58 6-14 13-38 36-91 Laredo Bay . 58-67 5-52 t) 71 1-14 17-33 16-63 Sandy Bay, Patagonia, No. 1. 62-25 5-05 0-63 1-13 17-54 13-40 Ditto ditto, No. 2. 59-63 5-68 0-64 0-96 17-45 15-64 Talcahnano Bay . 70-71 6-44 1-08 0-94 13-95 6-92 Vancouver’s Island 66-93 5-32 1-02 2-20 8-70 15-83 Colcurra Bay, Chili 78-30 5-50 1-09 1-06 8-37 5-68 PATENT FUELS. C inclu- Warlich’s Patent Fuel . ri5 90-02 5-56 Trace 1-62 < dedin 2-91 85 10 Lash. Lyons ditto ditto . 1*13 86-36 4-56 1-06 1-29 2-07 4-66 Wylam’s ditto ditto 1*10 79-91 5-69 1-68 1-25 6-63 4-84 65-80 Well’s ditto ditto . 1-14 87-88 5-22 0-81 0-71 0-42 4-96 71-70 3. SHOWING THE AMOUNT OF VARIOUS SUBSTANCES PRO- DUCED BY THE DESTRUCTIVE DISTILLATION OF CERTAIN COALS. Name of the Coal. Coke. Tar. Water. Ammo- nia. Carbon. Acid. Sulph. Hydro- gen. Olefiant Gas and Hydro- Carbon. Other Gases in- flamma- ble. Graigola 85-50 1-20 3H0 0-17 2-79 Traces 0-23 7*01 Anthracite, from Jones, Aubrey and Co. 92-90 none 2-87 0-20 0-06 0-04 (?) 3-93 Oldcastle Fiery vein Ward’s Fiery Vein 79-80 5-86 1-80 3-39 3-01 0-35 0-24 0- 44 1- 80 0-12 0-21 oo to ►-<1 9-77 Binea Coal . 88-10 2-08 3-58 0-08 1-68 0-09 0-31 4-08 Llangennech 83 69 1-22 4-07 0-08 3-21 0-02 0 43 7-28 222 APPENDIX. TABLE No. XIII. TABLE OF THE TEMPERATURES AND RELATIVE VOLUMES OF STEAM OF DIFFERENT DENSITIES. Pressure in pounds per square inch. Correspond- ing tempera- ture, Fahren- heit. Relative Volume of the Steam. Pressure in pounds per square inch. Correspond- ing tempera- ture, Fahren- heit. Relative Volume of the Steam. lbs. degrees. volume. lbs. degrees. volume. 1 1029 20868 31 253-6 857 2 126-1 10874 32 255-5 833 3 141-0 7437 33 257-3 810 4 152*3 5685 34 2591 788 5 161-4 4617 35 260-9 767 6 169-2 3897 36 262*6 748 7 175-9 3376 37 264-3 729 8 182-0 2983 38 265-9 712 9 187*4 2674 39 267-5 695 10 192*4 2426 40 269-1 679 11 197-0 2221 41 270-6 664 12 201-3 2050 42 272 1 649 13 205-3 1904 43 273-6 635 14 209-1 1778 44 2750 622 15 212-8 1669 45 276-4 610 16 216-3 1573 46 277-8 598 17 219-6 1488 47 279-2 586 18 222-7 1411 48 280-5 575 19 225-6 1343 49 281-9 564 20 228-5 1281 50 283*2 554 21 231*2 1225 51 284-4 544 22 233-8 1174 52 285 7 534 23 236-3 1127 53 286-9 525 24 238-7 1084 54 288-1 516 25 241-0 • 1044 55 289-3 508 26 243-3 1007 56 290-5 500 27 245*5 973 57 291-7 492 28 247-6 941 58 292-9 484 29 249-6 911 59 294-2 477 30 251-6 883 60 295-6 470 Min. MILES PER HOUR. APPENDIX. 223 TABLE No. XIY. ©> 00 to CO iO lO .0 IN o CO H Tt< in ifO©(M'^t->.(Ml'>.COTf©©(M iON(£>(NOVOO(XKO^OCOh © C^00^»CHl>.(N(N(N©^rt i0H^?0(N(N^X^i05i0(N CM WCOOiOlOOcONNOO^r- i^cboa. cxi^'cbibkO^TtH'^ ^H H rH — r— 1 ^-1 (NC5IN05HOO U(MiOCOiOCOX(M(M(Mint>. iO.'^i— iCOCM 00 ocot^ooeoooeocoeo*— i o ^ !O0)iO(O«f0iOC0C0O5iON CM Cp^9.©ib»b4tcoNH(Nt>.ooiOio r-HCO©©CM iOQOWNCOH(NCOiOri^(N l>» ©ODOOlOO^^Tfr-H^iO O(Nl0«0c0C0i0XC001i0(N (M Cp^OMOHCOKlNOO^H co^HasooNOiOio^^^ t>.cOr-l©col>»6^kO»o^t | ^r ,, ^ r-H i-H r-H . H r— 1 i-H ®(NOMiNhcOhi0^hO OCOCOCOH^OONlflCON rr^KO*r. eoeociOCJiOfO © InCO^NNhcOO^CMOiCJ ®OiONMcOiOOOrtOiiO(N CM ^lOOOOrrCONWCO^H oo^»^6iooi>.sb»b»HTt<^'^ NcOHffici)NbibibT}NooTfpH QO^HCSOONOiOiO^^^ rH rH rH — i — 1 r-H NNOOHMiflHHMlNO NCOHlOOitMHOiCOOOlNCO ^lOiOiOOtOOHOOCOCi^ ^COHNO^XOOCONCO 0'^KDK^cO»OC5«05kOM CM COOHCpHnCONlNQO^H Ol^HOiQOKJOibiO^^^ AcoHcscJo^iibo'^’^^ 1 -H I-H rH — rH rH l-H O tO OO ifl fO l>» 05 H O iO CD >o HtGOkOOKtsCOOOOcOCOH lOHCOQOHNiOWOOtfO^ CO COXHfOi(Nif50l>» W Tjt GO b» hiQ50N^C0i005«OiO(N M N5DHCpHHWNN(»^H c^4t.cboo^t | ^4h rH rH r-H — P3 rH r— 1 rH rH©©©©.i— 1^© D COOO^^r-lONOOHOOCO lOtOWOCOCJXCOOiiONiO M o WHt00 »iO00K WiOKCO^COi-OCiCpCliOIN m rn CM w OONh^hhtjUnNX^h ^rtif^6^cbw«bkO»b^r^^ r-H r— 1 r— 1 s — P3 i — i rH r— H o o w ^H Ph lOTf^OONOOiOOOCiO c/2 OCOHCOCOirtNNOGO^H lOrttOCOOOQO^OOCOifl C/2 P2 HC5H^OGOH05GOknOOO wtOKOD'^Tfiocs'^aiioiN ►P ©^(M^^f^^^CMOOHjHr-H CM iN^HiooNibioifTfTt rH 1 r- < i-H I-H I-H i— 1 o^cortooiinortioioo ©COOcOhOOOCO^^OCi tOOiOtONINOOr (OQOO ©HtHkOi>.ao©0000'^t l '!t ( ^^fOO^OOfOCOOI>. NXClOiOrjtOOlrl'ClON C»©>kb*CTjHTt<4t< ©QOOCMi-hC'J^OOCOC'jO NCONCOOCO't^.OHCM^ C5(TOtOl>»OOOiOOi’^OiOOO ^OOSNifltONTfWOiNO X.CiCsO^iO'q'OOi'^CitpiN © ^OfOiOWCN^OOCOGOiOW 1— 1 l 1 I-H i— H rH rH rH OOOOrHOOO^OOiO h t>. QD © LO (M CO CO fO l> CO © OOOOUOOOiOOi-HQO iO •^HNONNXlflrtONH OOOOiOiOtOO'tOOIN HjHf^^©(MCM^C»Cp00>LOCOiOiO'1 ,, tf |1 ^ CM — 1 r— 1 r- H — rH rH CO^ifltONaOOHNCO^ c ^-^iOCOt>»GOC50iH(MfOTf rH IT PH. r-H r-t § HHHMH 224 APPENDIX. TABLE No. XIV. — continued . CO CO o 05 CO 00 CO i ^ . co > i 1 _ O CO 50 CO co CO CO CO co co ® CO MILES PER HOUR. MOiOOCDO^OOWOOW N^. 50 o 50 50 50 50 CO 50 CO 50 1— • 50 © 50 © GO to 50 _ MILES PER HOUR. MOi->.i-iio©®r-(toHOTr OrfCOOHNH^OWQO 000050©0^©©c0© *OCOOCOI>©©OlO'^tH-^ COiOiOCOirtiO’^COOCO'^ts ^COC5COUOONC5 COhNN HtOrCaNMHiCHNCOO OC0©G0*>»OO50 50Tri'^ | Tt< C0O5OC0rHHOrtCCNlf5C0 H00 50-ieo©cot>»^co©© r^©©0500©''t©OCO© 50 00000^005050'^'^^ OOOiOOOkOOOOl'C5« HOCOiOOOXOCOCONOO (NNOOU>OOH(OHNrtO OCOOCCt^005050'^Tt | 4fi *-H »— H r-H OH^cONTfOOOCOHerj CiCOXCO^OcONCQCOO^ r-ir-l0050l>.0'rtl00c00 lOINOXNOOsOiO^^'t C5HNINC5C505000 O 00 <— I 50 *>» ® © ©5 — 1 CO CO 00 CO NOOiCOOOOiHOHtscOO odo©c»i>.o© 50 5bTt<4t<4j< T|H(N WHC0OON0GO5ON 500— l500r-5T^OOCOCOOr-t (NHH(OipNO^OOrtO ON©(»N©©50 0 '^t! ( '^ COl>»X©^OcO«5iOCOOO®® ®>iO>GfO®COCOHCO^COC5C5 COOOiO®QO®CO®r-HI>.fOO OC0ONC0C1OO50 50HW HO^l.sNCOiOQCO^HIN CpNHOiflNO'I'OOrtO 5OC0©<»I^OO»O5brrrt''^ C0C005C0c0Tt^t>.C0®C0Oi0 ■^OHCg^cOHrtiOrl'OCi ^05©000©01©r-u>.c0© OCO©©5.l>»005050''f'^'^ 'f^05 50 50 HO'#NHOO Q0^0©0^00 'fiOH(N C0<^i^050i^05000c00 LON©XN©©5ClOTf('^'^ ^®COO®COOO(NNffiOC HOO'^OiCCO^iC'tOO OCi©OCOC5CO©fHt>.^r-i OCOOWUOOiOO^^^ OCOGCOOCOOcOOl^r-lr-l 50 0DC5r-HiONH^50CO« T)t(NHNON©50OOC0O 50»C0O5i— 1^500^ lO©O©Q0©0J©rHt>.Tj X N N N O H h o CO O in I—IC0C0C0C0OG0C050OC0C0 lOCONKONOiOOOMO lONOooNoiinin'f^ :::::::::::: :::::::::::: OCO'T©CO'^©OCOr- l r-H® O^H050NO©^.©5O©©C0© 50 w©t»N©©5bii:^^^ Tfc0®C0^®OO505 r 0G0Tt< lrHC500*>*0r-Hr- 1 t>ONH05C5CO©MNTj(H ©CO©©»>«©©kO»Ci'^'^'^ i— 1 r— 1 i— < coeoooacoHoooots't 50r-HQ00050050CO*>.l>.CO'^r' ©^rHC0O5 0 50HOlsOHT)*N® t^^C0.50COOOOOO— 15OOOC0O 0N©t»N0©0 5n^TH^ OiOcOcOrfp— icO®COt>»COOO ocorriooocooio^ooococo 0<^<»^®®CO.i>»yok©0' , ^'^4t' ©CON5O00HC0^HCOC0QC io^N^ococooo©505n X 50 CO CO NCD ^ I50OOC0O 50CO®00*^005050-^'^'^ ^^©iNOiO'tOXCOCOCO OOOt^.OOO'Tt'OOOOiCOCO ©WOOCO©©COt>.(NK^H t>»co®ciooi>«?©i©5iO'r)H'^4t< (NU'^l-NCO'tCOCO©®XCO ©X©OC0TH^tNC5©50O ©ip^XNOOrttOOfpOO 10(NO(»N©©500^^'^ COfO^OOWkO'^KOxt'tN 'tCOOCOCiOHHr- lOrjHCO H(pC5NOOCONCOOOTt*H l>.C0O©C0K©i0»0'^'^'Tf OH^MHNrtHOsOeON ®c0C0G0'tH505000©©OO OO^XNQOhOHNcOO oNoxtsooiniO'^^T)* 'c S rt^ioONoociOHWeo^ rH rH r-H r*H r-H Min. yj^iOONX©OHNCO-1< APPENDIX. 225 REPORT TO THE DIRECTORS OF THE GRAND CANAL COMPANY, ON SCREW STEAM BOATS. Gentlemen, I regret exceedingly that from various causes, over which I had no control, I have been prevented until now from reporting on the two steam boats in use on your canal, although the experiments made with them have been completed some time; but I hope my preliminary exa- mination and report on these two boats has prevented the inconvenience that would otherwise have arisen from this delay, as it has enabled you to order a boat which, I have no doubt, will be found more suited to the traffic on your canal than either of those now employed upon it. I do not, how- ever, claim any merit for the plans or arrangement of the machinery in- tended for this boat, all of which were prepared by your own officers, and whatever merit it may have is entirely due to them ; all that I could do was to satisfy myself from the experiments and examination of the two boats, which was tlie best constructed, and, under similar circumstances, produced the best effects, and to recommend to you that form of construction for the boat you were about to build, which from these experiments I was enabled to do with perfect confidence ; at the same time I do not by any means pretend to say that a better form of boat, and more efficient machinery, may not be hereafter constructed, when more experience and practical knowledge shall be obtained by the working of these boats ; for, when locomotive engines were first introduced upon railways, they were very much inferior to those now used. Almost every one which has been since made up to the present time has been an improvement on those previously constructed, either in strength, efficiency, or economy of working ; and I have no doubt but similar, or at all events very great and important improvements will be made in steam boats for canal purposes, when they become to be more generally used and more attention shall be paid to them by practical men. In ordeer, howevr, to enable me to report on the queries put to me by your Secretary, I thought it necessary to make a careful examination of the two boats at present at work on your canal, and also to ascertain by experi- ment the power and capabilities of each of these boats under different cir- cumstances, as well in reference to the load they could carry as to the load they could haul with different velocities. In making this examination and experiment I was assisted by your excellent Secretary and intelligent Super- intendent of Works, Mr. Talbot, who gave me every information, and aided me in every way in their power. L 3 226 APPENDIX. The first of these boats which I examined, called No. 2 Boat, was con- structed by Messrs. Robinsons and Russell, of London. It is built of iron, without ribs, is 60 feet long, and 12 feet beam, and is propelled by one screw, driven by an engine of the following dimensions : — boiler 2 feet 6 inches diameter, containing 74 tubes of 1} inches diameter each ; the length of the tubes is 4 feet 6 inches, with 2 oscillating cylinders of inches diameter, and 15f inches length of stroke. Pressure 50 lbs, and calculated to make 120 strokes per minute; the thickness of boiler f, with 5 stays of round £-inch iron to strengthen the steam chambers. The diameter of the screw is 4 feet, width of blade 1-11£; pitch of screw 6 feet, stern post 5f inches below keel level. No 1 Boat was built at the Ringsend Works, and the engines and ma- chinery were made and put into her by Mr. Inshaw, of Birmingham, who has constructed several steam boats used on English Canals. The length of this boat is 60 feet, and its width 12 feet. The boiler is 4 feet 6 inches in diameter, containing 48 tubes of 2^ inches diameter, and 6 feet long; the cylinders are 7 inches in diameter; length of stroke 18 inches, and calculated to make 120 strokes per minute, the pressure being 50 lbs. The boat is propelled by two screws, 4 feet pitch, 3 feet in diameter, and 2 feet long, placed at each side of the stern post, worked with bevelled gear and two-fold multiplying power. * This principle of construction appears to answer very much better than that of No. 2 Boat, with one screw, for it is capable of being stopped and the motion reversed with much greater ease than the other, and it steers stern foremost almost as well as when running forward, which is a most important and essential requisite in any steam boat employed in Canal traffic, where obstacles and interruptions are so frequent, and which might be attended with danger, if the power of reversing was not easy and effective : in this respect it is very superior to the boat with one screw, which does not steer at all when the motion is reversed, but runs direct across the Canal to one side or other, according to the position of the boat at the moment of reversing. This boat (No. 2) was engaged by the builders to * These screws are what is usually termed right and left handed ; they consequently work in opposite directions. This is an improvement first adopted by Mr. Inshaw, and is found to be most important as to the working effect. Any person who has attentively watched the effect of a single screw, will have observed that the current of water thrown back from it does not take a direction in a right line with the boat, but in one at a diagonal with that line. By Mr. Inshaw’s arrangement of the two screws, the two diagonal lines being in the direction of the streams from the two screws, are thrown inwards , meeting immediately behind the rudder. The resultant is neces- sarily a straight line of current in the centre of the canal, manifestly advan- tageous as regards the action of the screws, and strikingly so as regards th$ facility with which the boat is steered, and the power of the rudder. APPENDIX. 227 carry 40 tons gross, to be furnished with engines of 12-horse power, (nominal,) consisting of two oscillating cylinders, and a tubular boiler, with feed pipe3 and reversing gear, and capable of going with that load at about 5 to 6 miles per hour, and of propelling itself and another boat at the rate of about 3 Irish miles, or 3f English miles, per hour. This agreement does not however s'ate what load the boat to be propelled or towed was to carry, but it would appear to be the same as in the steam boat, that is 40 tons gross. By the experiments made w T ith this boat, it is evident that she falls very much short of this performance, for, with 41 tons, she went only at the rate of 3| miles per hour, instead of 5 to 6 miles ; and when towing a boat loaded with 52 tons, she went at a rate of only 2£ miles per hour, instead of 3J. In fact, when loaded with 20 tons only, she went at the rate of 4 miles only per hour ; this discrepancy would appear to arise from want of power in the engines, for it does not appear that they are more than 8-horse power, instead of 12 ; it may, however, be possible, that other circumstances connected with the form or arrangement of the screw may be the cause of the want of speed, but want of power in the engine is the most apparent defect ; before, how- ever, drawing any conclusion from the experiments referred to, it will be proper to describe them. The first set of the experiments was made on the 24th of April ; the weather was cold, but there was little or no wind to affect the free movement of the boats. First Experiment, 24th April, 1851, was made with Steam Boat No. 2, loaded with 41 tons. The distance of half-a-mile (measured) was run in 8' 25", being at the rate of 3*56 miles per hour. During this experiment the pressure on the boiler was 50lBs. and the average number of strokes was 102. Second Experiment . — In this experiment the boat was loaded with 41 tons as before, and a barge was attached to it by a tow-rope. This barge was loaded with 52 tons: the pressure was 42 IBs., and the average number of strokes per minute was 87. The same distance as before was run in 13' 6", or at the rate of 2 -29 miles per hour. Third Experiment . — In this experiment two barges were attached to the steam boat ; one was loaded with 53 tons, the other with 30 tons, besides the 41 tons in the steam boat, in all 124 tons. The pressure on the boiler was 50 IBs. as in the first experiment, and the average number of strokes of the piston was 98, whilst the time occupied in passing over the same space was 14" 40', or at the rate of 2*05 miles per hour. On the 26th April the following experiments were made with the same boat. 228 APPENDIX. First Experiment. — The boat was loaded with 20 tons, the pressure was 50fbs. on the safety valve, the average number of strokes was 100 per minute, and the same distance of half-a-mile was run in 7' 30", or at the rate of 4*0 miles per hour. Second Experiment. — In this experiment one barge, loaded with 50 tons, was attached to the steam boat loaded with 20 tons ; the pressure as before was 50 lbs., and the average number of strokes per minute was 90£, whilst the same space ran over required 12' 20", or at the rate of 2 ‘43 miles per hour. Third Experiment . — In this experiment two boats loaded with 50 tons each were attached to the steam boat loaded with 20 tons, in all 120 tons of goods ; the pressure was 50 lbs., the average number of strokes was 94, and the space was passed over in 12' 55", which was at the rate of 2*31 miles per hour. On the 5th of May the following experiments were made with No. 1 steam boat, having two screw propellers. First Experiment. — The boat was loaded with 20 tons of goods ; the same half-mile distance was run over as in the former experiments with No. 2 boat ; the pressure was 45 lbs., the number of strokes averaged 110 per minute; the distance was run in 6' 41", which was at the rate of 4*49 miles per hour. Second Experiment. — In this experiment a barge carrying 50 tons was attached to the steam boat, which was loaded with 20 tons ; the pressure was 49 lbs. as before; the average number of strokes per minute was 101, and the time was 9' 12", which was at the rate of 3*26 miles per hour. Third Experiment.— Tn this experiment three boats were attached to the steam boat — one was loaded with 50, the second with 27 tons, and the third with 34 tons, in all 131 tons, including the 20 tons in the steam boat; the pressure was 49 lbs., the average number of strokes per minute was 96, and the time occupied was 10' 58", which was at the rate of 2*73 miles per hour. One fact, but certainly a most important one, has been established by these experiments, and that is, that a very much greater and useful effect is produced by hauling than by carrying . This fact was exemplified in every experiment that was made, though it was more apparent in one of the boats than the other, as will be seen by reference to the experiments; it also appears that one form of boat and machinery is less affected in speed than the other by a proportional increase of weight hauled than carried ; from this, it is evident that the form of boat and machinery most suitable for carrying APPENDIX. 229 goods will differ from the form of boat and machinery suitable for haulage. The barges and boats on your Canal are much too large, heavy and unwieialy ; they are a heavy load in themselves, and require considerable power to move them, even at a slow rate, when empty ; they are also formed as if they were to be employed as sailing barges, similar to those on the Thames and other rivers : this is a very great mistake and quite unsuited to Canal navigation. If the boats were built 60 feet long, 6 feet 6 inches wide, with upright sides, and upright cornered bows, which would admit two of them to enter a lock at the same time, a great amount of saving would be effected on your Canal in the power required to haul such boats, as compared with those now in use, for I have no doubt that six of those boats carrying 35 tons each, would be as easily hauled as two of the present boats 50 tons each — or in the ratio of 210 to 100 — and that such a steam boat as No. 1, at present in use, would be enabled to haul these six boats carrying 210 tons of goods at the rate of three miles an hour, and carrying at the same time 20 tons of goods, besides the 210 tons hauled. I would, therefore, strongly recommend you to have two such boats built, and if you found that the saving in power required for hauling was what I have stated, it would be judicious to have all new boats built on the same plan. I am well aware that it is very difficult to get parties long accustomed to a particular form of boat or carriage to adopt a different one ; but I am convinced the advantages of the light and narrow boat would be so apparent that it would in a short time be universally used in Canals in this country, as such boats are at present used in most of the Canals in England and Scotland ; and in any future engines that may be ordered for your Canal, I would recommend that the fire-box should be made as large as the construction of the boat will admit of, and that the draught up the flue be as moderate as possible, as more suitable to a turf fire than one of coke, for there cannot be a doubt, but turf or peat fuel will answer every purpose of working steam boats on the Canal, and will be very much cheaper than either coal or coke. My replies to the queries put to me will form the subject of a further report, which shall be submitted with as little delay as in my power. JOHN MACNEILL. GLOSSARY OF TEEMS CONNECTED WITH MAEINE ENGINES AND BOILEES. (WITH FRENCH TRANSLATIONS.) Air-casing, of thin sheet iron, (la I chemise,) surrounds the bottom of the chimney to prevent the radia- tion of heat to the deck. Air-pipe , a small copper pipe lead- ing from the top of the hot-well through the ship's side, for the discharge of the air and uncon- densed vapour pumped by the air- pump. Air-pump , (la pompe a l’air,) is re- quired to maintain the vacuum in the condenser by withdrawing the condensing water, air, and uncon- densed vapour. Air tubes, are small wrought-iron tubes hung in the coal-boxes from the deck and filled with water, for the purpose of ascertaining the temperature of the coals by a thermometer, as a precaution against spontaneous combustion. Angle-iron, (corniere). Annular-piston , is one made in the form of a ring encircling an inner cylinder which is enclosed within the external one. This arrange- ment is sometimes adopted to gain length of connecting-rod, by caus- ing it to descend within the inner cylinder. Anvil , (masse). Ash-pits, (cendriers,) underneath the fire-bars of the furnaces, where the ashes collect. Atmospheric or single-acting engine, (machine avapeur atmospherique,) is a condensing engine in which the pressure of the steam acts during the up-stroke only, the return stroke being performed by the pressure of the atmosphere acting against a vacuum. Auxiliary or feeding engine, (machine alimentaire,) fitted to supply tubular boilers with feed-water when the large engines are not working, and the ordinary feed-pumps are there- fore inactive. Axle, (tourillon). Babbit* s patent bushes, are formed of an alloy of 1 lb. copper, 50 lbs. tin, 5 lbs. regulus of antimony. Ba^k-balance of eccentric, is fixed to the back of the eccentric pulley for the purpose of balancing its weight on the shaft. Back-balance of slide valves, is the weight fixed at the extremity of the valve-lever for balancing the weight of the slides. Back-lash, is the term given to the jar which ensues when one portion of the machinery which receives motion from another (but without being always in actual contact) has its velocity so increased from some extraneous cause, that it falls back, with a sudden blow, upon the part from which it ought to derive its motion. 232 GLOSSARY OF TERMS CONNECTED WITH Back-links , the links in a parallel motion which connect the air-pump rod to the beam. Ballast , (sable). Banking-up the fires, raking them to the bridge of the furnace, and then smothering them with cinders and small coal, the draft being at the same time checked. By this means the fires are kept in a state of languid combustion, but are ready to burn up briskly again when steam is wanted at short notice, the red-hot mass being then broken up, raked forward, and the draft re-admitted. Barometer or vacuum-gauge, (baro- metre,) is fitted to the condenser of an engine to show the vacuum. It resembles the common weather- barometer, except that the top of the tube is in communication with the condenser. Barrel of a pump, (corps d’une pompe). Base-plate, see Bole-plate. Beam or side-lever engines, (machines a balanciers,) are those in which the motion of the piston is communicat- ed to the crank through rocking beams or levers at the sides. Beams of a vessel, (travers). Bearers, are the cross bars in the furnaces supporting the ends of the fire-bars. Bear, is a small apparatus for punch- ing holes by hand. Bearing, neck, or journal, of a shaft, (coussinet d'une arbre,) is the part which revolves within the pedestal- brasses, and supports the weight or strain. Bedding of a boiler, is the seat on which it rests. Bilge-pumps, worked by the engine, to clear the water from the bilge of the ship. Blowing-off, the process of ejecting the super-salted water from the boiler in order to prevent the de- position of scale or salt. Blov)-off cocks and pipes, are those through which the brine is eject- ed. Blowing-through, (purger d’air,) is the process of clearing the engine of air by blowing steam through the cylinder, valves, and condenser, before starting. Blow -through valve, (soupape a purger d’air,) is fitted between the valve- casing and the condenser for the temporary passage of the steam used in blowing through. Boiler, low pressure, high pi'essure, (chaudiere a basse pression, a haute pression). Bolt, bolted, (boulon, boulonn6). Boss, ( renflement, ) is a centre or swelling of any kind in which a hole or eye is bored. Box-kegs, are the upright keys used for turning the nuts of large bolts, or where the common spanner cannot be applied. Bracket pedestal or plummer-block, is the fixed support for the bearing of a shaft in motion, formed so that it can be fixed vertically to the frame of an engine, or the side of a beam, &c. Brass, (bronze,) an alloy of copper, tin, and zinc, in different propor- tions. Tough brass, for engine- work, is formed of 10 lbs. copper, 1| lb. tin, and lg lb. zinc. Brass, for heavy bearings, of 1 lb. copper, 2g oz. tin, g oz. zinc. Break or brake, (frein). Bridge of a boiler, is the barrier of fire-bricks, or iron plates contain- ing water, thrown across the fur- nace at the extreme end of the fire-bars, to prevent the fuel being carried into the flues, and to quicken the draft by contracting the area. Brine-pumps, (pompes de saumure,) are worked by the engines to with- draw the super- salted water from the boilers methodically, instead of by periodical blowing-off. Bulkheads, (cloisons). Bush, is a lining of brass, steel, or other metal, fitted in an eye or bearing, either to diminish friction or prevent rapid wear. Callipers , are compasses with round legs, used for taking the diameter or thickness of circular or flat inside work about an engine. Inside callipers are used for measuring the internal diameter of a brass or hole of any kind. Cam, for expansion, is a disc of cast iron, having the periphery cut in an irregular figure, for giving the proper motion to the expansion MARINE ENGINES AND BOILERS. 233 valve. It is graduated in steps so as to suit the different degrees of expansion. Carriage by sea , (transportation) ; by land, (montage) . Cast , (coule). Cast-iron, (fonte). Cataract, is a contrivance introduced into marine engines for softening the fall of the expansion valves when these are made upon the Cor- nish principle. It consists of a little brass cylinder filled with water or oil, and fitted with a solid piston connected by a crosshead with the valve spindle. The fall of the valve is checked and regulated by the escape of the water or oil through a small hole bored for that purpose in the side of the cylinder, the pis- ton of the cataract descending ac- cording as the liquid is forced out from before it by the pressure due to the weight of the expansion- valve. Cement, (ciment, mastice). Centre-boss, of the paddle-wheels, (renflement central des roues a aubes). Chimney, (cheminee). Chisel, (ciseau, burin) . Cloxk-vaXve, a flat valve with a hinge- joint. Clearance of the piston, is the small space left between the piston and the top and bottom of cylinder at the end of each stroke. Clinkers, (scories,) are the incom- bustible matter left on the fire-bars during the combustion of the coal. Clinker-bar , is fixed across the top of the ash-pit to support the slice used for clearing the interstices of the bars. Clothing the steam-pipes, boilers, &c., means covering them with felt and other non-conducting materials, to prevent the radiation of heat. Coals; coal bunkers , (les houilles, charbon de terre ; soutes a char- bon). Coal-trimmer, a man whose duty it is to work within the coal-boxes, and bring the coals to the doors at the boiler front as they continue to be consumed. Cock, (robinet). Cogged wheels, (roues dentees,) are those fitted with wooden teeth or cogs , for the purpose of lessening friction and giving smoothness of action. Cold- chisel, a chisel properly tempered for cutting cold iron. Collar of a shaft, (collier,) is the pro- jecting rim on each side of the neck or bearing, to confine it sideways during its revolution. Common steam, (in contradistinction to super-heated steam,) is steam in contact with the water from which it was generated. Condenser , (condenseur,) is the cast- iron box in which the process of condensation takes place. Condensing engine, (machine a con- densation,) is one in which the steam is condensed after leaving the cylinder, for the purpose of gaining the effect of the atmosphe- ric pressure. Connecting-rod, (bielle de la mani- velle,) in a direct-acting engine, communicates the motion directly from the head of the piston-rod to the crank : in a side-lever engine, from the cross-tail to the crank. Consumption of fuel , (consumation de combustible). Counter, a little instrument employed for registering the strokes of an engine. Coupling of a shaft, is the mode of connecting together two or more lengths of a revolving shaft, by shaping the ends into flat surfaces or bearings, which are held together by a strong iron collar or coupling- box. Cover or lap of the slide-valve on the steam side, is the space which it advances beyond the opening of the steam-port after it has closed it, and is given for the purpose of causing the engine to work expan- sively, by cutting off the admission of steam before the end of the stroke. Cover or lap on the exhausting side of the piston, causes the passage to the condenser to be closed before the end of the stroke, the piston being then said to be cushioned by the elasticity of the confined vapour, upon which it descends. Crank; cranked, (manivelle, coude ; coude). Crew of a vessel, (Eequipage dhm vaisseau). 234 < glossary of terms connected with Cross-heady (traverse, tefce croissee,) in a side-lever engine, crosses the head of the piston-rod, and com- municates the motion to the side- rods. Cross-tail, in a side-lever engine, takes the motion from the side-rods and communicates it to the connecting- rod. Cup-valve, resembles a conical valve, but has no spindle, being turned in the form of a cup or portion of a sphere. Cushioning the piston, means that a small portion of steam is shut up between the piston and the cylinder top and bottom at the end of each stroke, which acts as a spring to soften the shock, and to give the piston a start forward after the centre is turned. This effect is produced by the lap of the side- valve on the exhausting side. Cutter, (clavette,) is the wedge-key used, in combination with the gib, (contre-clavette,) for tightening the strap and brasses of a bearing, as the latter wear by friction. Cutting-off the steam for expansion, (la detente). Cylinder- cover, (couvercle de cylin- dre). Dampers , (les registres,) are iron plates, fitted by a hinge or otherwise, across the fronts of the ash-pits and the bottom of the chimney, for the purpose of regulating the draft. They are capable of being adj usted by hand to any desired area. Dead- fires, when they burn sluggishly. Dead-plate, a flat iron plate frequently fitted before the bars of a furnace, for the purpose of coking bitumi- nous coal upon before it is thrown back upon the fire. Dead-water, (eaumort,) is the current following in the wake of a ship and partaking of her motion. Deck, (pont). Depth of a vessel, (hauteur d’un vaisseau) . Diagram of indicator , the figure traced by the pencil, from which the pressure is calculated. Dip of the wheels, the depth of water over the top of the vertical board. Direct-acting engines, are those in which the motion of a piston is communicated directly from the head of the piston-rod to the crank through the connecting-rod, with- out the intervention of side -levers. Discharge, delivery, or waste-water pipe and valve, (tuyeau et soupape de decharge, ou de sortie,) are those through which the heated condens- ing water and vapour are discharged into the sea by the air-pump. Disengaging or disconnecting the pad- dles or screw from the engines, (by suitable machinery,) permits them and their shaft to revolve freely in the brasses by the reaction of the water, by which means the speed of the' ship when under canvas is not so much affected as if they were dragged through the water. Displacement of a vessel, is the weight of water which she displaces, being of course equal to her own weight. Donkey or auxiliary engine, (ma- chine alimsntaire ) is used for feed- ing the boilers while the large en- gines are at rest. Double-acting engine, (machine a double action,) is one in which the steam acts against a vacuum on each side of the piston alternately, as in the ordinary marine engine. Double-acting pump is one which lifts and forces water alternately, by means of a solid piston or plunger and an entrance and exit valve communicating with each side, (as the feed and bilge pumps of a ma- rine engine). Double-cylinder engine, as patented by Messrs. Maudslay, has two cylin- ders, between which the lower end of the connecting rod descends, its motion being communicated from the piston-rod by a bent crosshead working in grooves between the cylinders. Draught of the chimney (tirage). Draught of water (immercion). Drift is a round piece of steel, made slightly tapering, and used for en- larging a hole in a metal plate by being driven through it. Drip-pipe, is a small copper pipe leading from the waste steam pipe inside, to carry off the condensed steam and other hot water which may be blown into the “ trap” at the top. Driving-wheel, (roue motrice,) in the MARINE ENGINES AND BOILERS. 235 gearing of a screw vessel, is that which communicates motion to the small wheel or pinion. Drum is a hollow cylinder fixed on a shaft for driving another shaft by a band. Dynamometer is an instrument for indicating the thrust of the screw- propeller by means of springs and levers. Eccentric, (Texcentrique,) is the ar- rangement usually adopted for giv- ing the proper stroke to the valves. It consists of the eccentric pulley of cast iron, which is loose on the intermediate shaft, and the hoop of wrought iron lined with brass, which encircles the pulley, and gives motion to the eccentric rod. The eccentric stops or snugs are two little projections fixed on the inter- mediate shaft for the purpose of carrying round the eccentric pulley, according as it is wanted to go ahead or astern, the pulley itself being free to revolve backwards or forwards between the two stops. The weight of the pulley is balanced on the shaft by the back-balance cast on it. Eduction or exhaust passages (tuyeaux de sortie, ou d'emission), through which the steam passes from the valves to the condenser. Effective diameter of a paddle wheel is generally reckoned at one third of the breadth of the boards from each extremity of the diameter. Effective heating surface in a boiler is that which is considered of value in evaporating the water. The bottom surface of the flues and furnaces, and one third of the whole surface of the tubes in tubular boilers, are usually rejected as ineffective. Engine beams cross through the en- gine room at the height of the en- tablatures, to steady them, and re- ceive part of the thrust of the paddle wheels. Engine bearers or sleepers, (poutres de fondement,) are the longitudinal keelsons through which the foun- dation plate is bolted. Engineer, engine tenter, (machiniste, mechanicien). Entablature is the strong iron frame supporting the paddle shaft. It usually receives additional stiffness from being confined between two beams of timber, called the entabla- ture or engine beams. Equilibrium, Cornish, or double-beat valves, are frequently used in marine engines as expansion valves. Their peculiarity consists in their being pressed by the steam equally in all directions, so that they rise with a very slight force, exposing at the same time a large area of steam with a very small rise of the valve. Escape or priming valves, (soupapes d'echappement,) are loaded valves fitted to the top and bottom of the cylinder, for the escape of the con- densed steam, or of water carried mechanically from the boilers with the steam. Escape-valves are also fitted to the feed pipes as a means of exit for the surplus water not used by the boilers. Expansion gear, (Tencliquetage pour Texpansion,) is fitted to marine engines, independently of the cy- linder valves, for the purpose of cutting off the steam at different portions of the stroke, according as it is wished to economize fuel more or less. It generally consists of a graduated cam on the paddle shaft, against which a roller presses and communicates the movement pecu- liar to the irregular surface of the cam, through a series of rods and levers to the expansion valve, situ- ated between the throttle valve and the slides. Expansion or Fawcett joint is a stuffing- box joint used when a straight metal pipe, (as the steam pipe,) which is exposed to considerable variations of temperature, has no elbow or curve in its length to enable it to expand without injury. In such a case the pipe is divided into two lengths, which are united by a steam-tight joint accurately bored and turned, so as to allow the one pipe to slip within the other, when they lengthen by expansion. Experiment, (experience). Eye of a crank, &c., (encoche, ceil,) is a hole bored to receive a shaft or pin. Fawcett joint, see Expansion joint. 236 GLOSSARY OR TERMS CONNECTED WITH Feathering paddle wheels (as Morgan’s patent), are those in which the requisite machinery for feathering the boards, or causing them to enter and leave the water in a perpendi- cular position. By this means, the board leaves the water without lifting it, and the effect of the wheel is somewhat increased. Feeding apparatus , (l’appareil alimen- taire,) for a marine boiler, consists of the feed pump, feed pipe, passing through the refrigerator, feed cock on the boiler, escape valve for the surplus water, and water gauges to show the level in the boiler. Feeding engine, see Auxiliary engine . Ferules (viroles) are rings of iron or brass frequently used for fastening the tubes of a tubular boiler in the tube plate. Files, (limes). Fire bars, (barres du foyer). Fire grate, (grille du foyer). Fire-hose, are made adjustible to the discharge pipes from the bilge- pumps, from the auxiliary engine where fitted, and from the hand- pump in engine room. File men or stokers, (chauffeurs,) the men who work the fires. Firing-up, urging the fires to make them form as much steam as possible. Flange, (rebord). Float boards or paddle boards , (Les aubes). Flues , (conduits). Foot-valve , ( clapet de fond,) is situated between the bottom of the con- denser and the air pump, opening towards the latter. Forcing pumps, (pompes foulantes). Fork, (fourche). Fork head, the double head of a rod which divides in order to form a connection by means of a pin. Foundation or base plate, (plaque du fond,) see sole-plate. Fox key, is a key with a thin wedge of steel driven into the end to prevent its working back. Frame of the engine, (chassis, cadre). Frames of a vessel, (membrures d’un vaisseau). Friction, (frottement). Fuel, (combustible). Fulcrum, (support, palier, crapau* dine). Furnace, (le foyer) . Fusible Plugs, (bondelles fusibles,) are sometimes fitted in boilers, being expected to melt by the high temperature of the confined steam, and thus allow it to escape in case of its attaining a dangerous pressnre from the safety valve not acting. Gasket, (garniture d’etoupe,) is the hemp packing, formed of soft cord plaited, which is used for making steam-tight joints. Gauge cocks, (robinets d’epreuve,) of brass, attached to the front of the boiler for indicating the level of the water. Gauge, steam or mercurial, (mano- metre de verre mercurial,) is a syphon tube half-filled with mer- cury, usually employed for showing the pressure of low steam. When a marine boiler uses steam of high tension, a spiral spring is employed. Gib (contre-clavette), is the fixed iron wedge used, in conjunction with the cutter or driving-wedge (clavette), for tightening the straps and brasses of the different bear- ings. Gland, is the cupped collar (lined with brass,) which encircles the piston and air pump rod, &c., where it passes through the cover, being for the purpose of holding oil or tallow for lubricating, and for compressing the packing of the stuffing-box upon which it is screwed down. Glass water gauges, attached to the fronts of the boilers for showing the level of the water. Governor, (regulateur,) in screw engines, is an apparatus by which the steam is shut off from the cylinders (when the speed of the engine becomes too great), by the divergence of two balls from the centrifugal force, according as their velocity is increased. Grease cock on the cylinder cover, for lubricating the piston with melted tallow, without permitting the escape of steam or the entrance of air. Groove, (trou, entaille). Guards for the bolts of an engine are light frames of brass or iron, into MAltINE ENGINES AND BOILEES. 237 which the nuts of the bolts fit, to prevent their working loose by un- screwing. Gudgeon, (goujon,) is any short pin or shaft used as a bearing for a moving portion of the machinery. Guides, (glissoirs,) are smooth sur- faces between which the head of a piston rod, &c., slides to preserve its parallelism ; the sliding block attached to the cross head being called the Guide block . Gun metal, an alloy of brass very generally employed in engine work. It is formed by melting together 1 lb. of tin, 1 lb. zine, and 8 lbs. copper. Hall’s condensers, a method of sur- face condensation in which the steam is condensed by passing through a large number of small tubes immersed in cold water. Hammers, (marteaux,) of three sizes, the largest being called sledge hammer; the next flogging hammer ; and the smallest hand hammer . Handle, (manette). Hand pump, (pompe a bras,) is fitted in the engine room for filling and feeding the boilers by hand, for washing the decks, extinguishing fire, &c. It is always made capable of being attached to the engines when they are working. Heat, heating power, (chaleur, puis- sance calorifique) . Helm, helmsman, (timon, timonier) . Hemp, (etoupe). High-pressure, or more correctly non- condensing engines, ( machines . a haute pression,) are those which work simply by the excess of the pressure of the steam above that of the atmosphere. Condensing en- gines, although sometimes using “ high-pressure” steam, are never called high-pressure engines. High-pressure steam, (vapeur a haute pression,) is a vague expression de- noting steaip. of a tension above 15 or 20 lbs. pressure above the atmo- sphere. Holding-down bolts, are the strong screw-bolts employed to fasten the foundation plate of the engines to the ship's bottom. Horse power, nominal, (puissance en chevaux, force de cheval,) is as- sumed equal to 33,000 lbs. raised one foot high in one minute. Hot-well, (reservoir a eau chaude, la citerne,) is the reservoir for the water pumped out of the condenser by the air pump. Hugging is the expression used when one vessel is running so close in the wake of another as to be influenced by the current of dead- water following her, in which case the two may continue to keep close together, although the vessel running behind may be, perhaps, a mile an hour slower than the other. Hull or shell of a boat, (coque d'un bateau). Incrustation or scale, (sediment,) is the hard coating of salt, lime, and other mineral substances which collect on the inner surface of the plates of a boiler which is not regularly and sufficiently t( blown off.” Index of a spring balance, (curseur). Indicator, (indicateur,) is the little instrument employed for ascer- taining the real power, as well as the state of efficiency of the in- ternal parts, of a steam engine, by indicating the actual pressure in the cylinder during each stroke, and the time and manner in which the steam is admitted and shut out by the valves. Injection, (injection,) is the process of admitting a jet of cold water from the sea into the condenser, to condense the steam as rapidly as possible. Inside bearings of paddle shaft, (upon a bracket bolted to the ship's side,) are employed when the wheels are overhung.” Intermediate shaft is the strong shaft crossing the centre line of the vessel and connecting the paddle shafts of the two engines. Iron-filings, (limaille). Joints, (charnieres, articulations). Journal , (coussinet,) is the neck or bearing part of a shaft, upon which it turns and by which it is supported. Junk ring, is a metallic ring confining the hemp packing of the piston (when such is employed,), and made 238 GLOSSARY OF TERMS CONNECTED WITH capable of being screwed down to compress it. Keelsons , (carlingues). Key , (clef,) a wedge piece of iron used for tightening the brasses of a bearing, &c. Kingston's valves , are conical valves with a screwed spindle, and are very generally used for closing the orifices of the injection and blow- off pipes where they pass through the ship’s side. Knees of iron, (equerres en fer). Laggings for the cylinder, &c., are the thin staves of wood employed in “ clothing,” to stop the radiation of heat and consequent condensation of steam. Lap of the slide valve , see Cover. Larboard engine , that on the left- hand side of the vessel when look- ing towards the bow. Latent heat , (chaleur latente,) is that portion of heat which is absorbed by gases and liquids, in a latent or insensible state, during their transi- tion from a denser to a rarer form ; as when water at 212° changes into steam at 212°, and when ice at 32° changes into water at 32°. Lead of the sliae valve , (avance du tiroir,)is the small space which the valve opens to steam at the end of each stroke, upon the opposite side of the piston. It tends to check the velocity of the piston at the end of the stroke, and allows of the valve being open and ready to admit a larger supply of steam the instant the motion of the piston is reversed. Leud of the crank, (avance de la manivelle). It is usual in direct- acting, and generally in all un- balanced engines, to give what is called lead to one of the cranks ; which implies that the crank of the one engine is set a little in advance of the right angle to the other; * namely, at 100° or 110° in place of 90. This assists in rendering the motion of the piston more uniform, by moderating its velocity at the end of the stroke. Leather , (cuir). Length of stroke, (longueur du coup, ou de la course). Level, (niveau). Lever, (levier). Lighter or barge, (gabarre). Links are short connecting pieces, with a bearing in each end, for transmitting motion from one rod or lever to another. Link motion, is an ingenious arrange- ment for working the slides, by which means the travel or stroke of the valve may be varied at plea- sure, and expansion given without a separate expansion valve being required. It also affords great facilities for stopping and reversing the engines. Log, engine-room, a tabulated sum- mary of the performance of the engines and boilers, and of the con- sumption of coals, tallow, oil, and other engineers’ stores. Lubricators, (godets, ou boites a huilej are the larger description of oil- cups for holding oil and dis- tributing it to the working parts of the engines. Main centre , (goujon central,) in side- lever engines, is the strong shaft upon which the side levers vibrate. Manhole, (trou d’homme,) is a hole in a boiler or tank, fitted with a steam-tight cover, through which a man may enter for the purpose of cleaning and examining the interior. Metallic packing, (for the piston,) is composed of a ring or several rings of iron or other mletal, sometimes cast so as to possess elasticity in. themselves, or sometimes cut into segments and’ pressed against the interior of the cylinder by springs, so as to form a steam-tight contact. Metre , equals 39*3702 English inches. Mile, Geographical or Nautical, or knot, contains 6082*66 feet. Mile, British Statute, contains 5280 feet, 1760 yards, ®r 1609 metres. Mile-post, (borne milliaire). Mitre-wheel, has its teeth set at an angle of 45° with the spindle, so as to transmit the motion to another mitre-wheel and shaft at right angles with it. Morgan's feathering paddle wheel, see Feathering paddle wheels. Morticed, (assemble a mortaise). Mud hole, (orifice de nettoiement,) fitted with steam and water-tight MARINE ENGINES AND BOILERS. 239 doors, through which the deposit may be removed from the boilers. Muntz* s metal, used for bearings, &c., is formed of 2 parts of zinc, 3 parts copper. Nave of a wheel, (moyen). Neck of a shaft, (cou:sinet d'un arbre,) is the journal or bearing on which it turns and is supported. Non-condensing or high-pressure en- gines, (machines a haute pression,) are those in which the principle of condensation is not applied, the motive power being due solely to the excess of the pressure of the steam above that of the atmosphere. Notch, (encoche). Nut, (ecrou). Oil-cups or lubricators, (boites a huile,) are fitted to the several bearings and rubbing surfaces of the engine for the purpose of lubricating them to diminish friction. Oscillating engines , (machines aux cylindres oscillantes,) are those in which the cylinders oscillate upon hollow axes or trunnions, through which the steam enters the valve casing. By this arrangement, the parallel motion and connecting-rod are dispensed with, the head of the piston-rod being attached directly to the crank-pin. Outside bearings to paddle shaft, when the shaft runs through to a bearing on the spring beams. Overhung paddle wheels, when the shaft does not run through to a bearing on the spring beams, but is supported by a bracket from the ship's side. Packing for the piston, slide-valves, &c., (garniture,) is employed to render them steam-tight, and is formed sometimes of rings of iron or other metal pressed outwards by springs, (when it is called metallic packing) ; sometimes by hemp con- fined by a “junk ring" and com- pressed by screws (called hemp packing) ; and sometimes by rings of vulcanized india rubber and other elastic material. Paddle wheels, paddle boxes, (roues a aubes, tambours). Paddle boards or float boards, (les aubes) ; paddle-arms, (les rais des roues). Parallel motion, (le parallelogram,) is the name given to the combination of jointed rods usually employed in side-lever engines (and others) for preserving the parallelism of the piston rod. Pedestal or plummer block is the sup- port for a shaft in motion, holding the brasses on which it turns. Pet cock or test cock is the name given to a little cock sometimes fitted at the top and bottom of the cylinder to allow the escape of water from above and below the piston, inde- pendently of the escape valves fitted for that purpose. They are kept open until the engines are fairly under weigh, and are then shut. Pin, (happe, boulon). Pitch of a screw is the distance between the threads, or the distance which the screw advances during each revolution when working in a solid. Pitch circles are the circles of contact of two or more toothed wheels working in combination. Pitching of a vessel, (plongement). Plates, (thin,) (lames, tolles). Plug, (bouchon). Plummer block , see Pedestal . Plunger, 1 (plongeur,) a solid piston without valves used in the feed and bilge pumps, &c. Ports of the cylinder are the short steam passages leading from the top and bottom of the cylinder to the slide-valve casing. Priming or foaming of the boilers implies that the water boils over into the steam pipes which lead to the engines, and is caused by the water being dirty, or there being a deficiency of steam-room in the top of the boilers. Priming valves, see Escape valves . Radius of curvature, (rayon de courbe) . Radius rods or bars, (la bride du paral- lelogram,) are the guiding rods in a parallel motion jointed to the con- necting links to counteract the vibratory motion communicated by the side levers. Reciprocating, (alternatif). Reefing the paddles, means disconnect- ing the float-boards from the paddle- arms, and bolting them again nearer 1 the centre of the wheel, in order to 210 GLOSSARY OF TERMS CONNECTED WITH diminish the dip when the vessel is deep. This is sometimes done by machinery in what are called reefing paddle wheels . Refrigerator, is a vessel containing a number of copper tubes through which the hot brine passes after being ejected from the boiler by the brine- pump. The feed water is at the same time passed through the vessel surrounding the tubes, and has its temperature thus raised by the waste heat of the brine before entering the boiler. Reverse or vacuum valves, (soupapes de surete interieures,) are small loaded valves opening inwards, and fitted to the boiler to admit air when a vacuum is formed by the condensation of the steam inside, or when the pressure of the steam falls to a few pounds below the pressure of the atmosphere. Reversing gear is the apparatus pro- vided for reversing the motion of the engine by changing the time of action of the slide-valve- This is done by bringing the eccentric behind in place of in advance of the crank. Ribs , (tirans). Rocking shaft, the shaft, with levers, frequently used for working the slide-valves, the notch of the eccen- tric rod dropping into a stud fixed in one of the levers, and the links of the slide-valve spindle being attached to the opposite lever on the same shaft. Rubbing part, (partie frottante). Rudder, (gouvernail). Rust joints, made by spreading over the surfaces to be united a mixture of one ounce of sal-ammoniac to one pound of cast-iron borings. Safety valves, (soupapes de surety,) are fitted to the boilers for the escape of the steam, before it attains a dan- gerous pressure. Salinometer, (salinometre,) is an in- strument for measuring the quan- tity of salt contained in solution in the water of the boiler, by indicat- ing either the specific gravity, or the temperature at which it boils. Scale, (sediment,) is the hard crust of salt, lime, &c., which collects upon the interior surface of the plates of a boiler when proper attention is not paid to “ blowing off.” The hammers used for loosening and re- ' moving the scale are called scaling hammers. Screw, screwed, (vis, visse). Screw bolts, (boulons en vis, boulons taraudes). Seat of the valve, (siege de la soupape). Sediment collectors or scale pans, are shallow vessels which are sometimes fixed in boilers about the level of the water, for collecting the parti- cles of sediment which are buoy- ed up to the surface by bubbles of steam, and which would otherwise settle at the bottom of the boiler. Sensible heat, (in opposition to latent heat,) is free caloric, which is sen- sible to, or whose presence is indi- cated by the thermometer. Shaft, (arbre). Sheet iron, (tole, fer en feuilles). Shovel, (pelle). Shrouds for the funnel are the sup- porting chains from the deck. Side-levers, in side-lever engines, (balanciers,) transmit the motion of the piston rod from the side-rods to the cross tail of the connecting rod. Sleepers or engine bearers, (traverses). Slice, (fourgon, tisonnier,) is the in- strument used for clearing the air spaces between the bars of a fur- nace, when they become choked with clunkers. Slide valves, (tiroirs, soupapes a tiroir,} are much used for the cy- linder steam valves of marine en- gines. The two kinds most com- monly found are called “long D ” and “short D” valves, from the form of their cross section ; the distinction being that in the first case the steam enters round the outside of the valve, and exhausts through it, while, in the second, the exhaust takes place alternately from the top and bottom of each of the t'vo short slides, which are strongly joined together by vertical rods. Slide-casing or jacket (boite des tiroirs) is the cast-iron box within which the slide valves work. Slip of the paddle wheel or screw is the amount which each slips back in its progress through the water, in con- MARINE ENGINES AND ROLLERS. 241 sequence of the imperfect resistance offered by the fluid, and is therefore equal to the difference between the rate of the wheel or screw and that of the vessel. Smith (forgeron). Smoke box (boite a fumee,) is the space in a tubular boiler between the ends of the tubes and the front or back of the boiler. It is fitted with doors which remove for the purpose of cleaning the tubes with tube-brushes , and removing ashes and soot. Smoke-burning apparatus is sometimes fitted to boilers with the view, of effecting a more perfect combustion of the inflammable gases by intro- ducing fresh atmospheric air behind the “ bridge.” Snap is a tool used by boiler-makers for giving the head of the rivet a round and symmetrical form before it cools, but after it has been closed. Snifting valve , (soupape reniflante,) is the small valve fitted to the con- denser, and opening outwards for the escape of the air and steam ejected during the process of “blow- ing through.” Socket (socle, crapandine). Solders are alloys of a medium degree of fusibility employed for joining metals together. “ Hard solder” for brass is formed of 3 parts copper, 1 part zinc : soft solder for brass, of 6 parts brass, 1 part tin, 1 part zinc. A common solder for iron, copper, or brass consists of nearly equal parts of copper and zinc. Sole plate , base plate, or foundation plate , (plaque du fond,) is the strong plate which is bolted on the engine bearers, and forms the foundation for the engine. Spanners are the keys used for screw- ing up nuts. Spare gear , (pieces de rechange,) are carried in Government and other steamers to replace any portions of the machinery which may be broken or injured at sea. Speed , (vitesse). Spindle , (axe, verge). Split pins are those which have a thin wedge of steel inserted in the end to prevent their falling out. Springs , (reports). / Spring balance, (balance a ressort,) is a spiral-spring weighing balance fitted with steam-tight piston, in- dex plate, and pointer, for showing the pressure of high steam. Spring beams are wooden beams stretched between the ends of pad- dle beams to support the bracket for the outside bearings of paddle-shaft . Square, square foot, (quarre, pied carre). Square tuck is the flat surface left at the stern of a vessel when the planks of the bottom are not worked round to the wing transom, but end in the fashion-piece. Starboard engine is that on the right- hand side of the vessel when look- ing towards the bow. Starting gear, (encliquetage r£gula- teur,) for starting the engines, comprises a wheel for working the slide valves by hand, and at the same time bringing the eccentric into gear, so as to continue the motion of the valves ; a handle to open the throttle valve, and ad- mit the steam, one to open the blow-through valve, and another to admit condensing water through the injection cock. Steam engine , steam boat, (machine a vapeur ; bateau a vapeur, pyros- caph). Steam chest, (reservoir pour la vapeur,) is the reservoir for steam above the water of the boiler. Steam room, (espace pour la vapeur,) is the capacity for steam over the surface of the water in the boiler. Steam gauge , mercurial, (manometre pour la vapeur,) is employed to show the pressure of steam in the boiler by marking the height to which it will raise a column of mercury in a syphon tube. Steam-tight, (etanche de vapeur). Steam tug, (pyroscaph remorquant). Steel, (acier). Steersman, (timonier). Stern, (poupe). Still or dead water , (eau morte). Stop valves, or communication valves, are fitted in the steam pipes where they leave the several boilers, and in the connecting pipes between the boilers, in such a manner that any boiler or boilers may be shut off from the others, and from the engines. 242 GLOSSARY OE TERMS CONNECTED WITH Stops or snugs of eccentric , are the catches on the eccentric pulley and intermediate shaft, for the purpose of communicating the motion of the shaft, through the eccentric, to the slide valves, either for goi ng ahead or astern. Stow goods , to, (charger des mar- chandises). Straight line , (ligne droite). St rain, (effort). Stroke of the piston, (course du piston.) Stuffing-box, ( boite a etouffe, le collet,) is the mechanical arrangement by which a rod passes steam-tight through the cover of a cylinder or air-pump, &c. This is effected by the rod being surrounded at that place by a packing of hemp or gasket, which is compressed by means of the collar (with its brass ) being screwed tight down upon it. The stuffing-box is lubricated with oil or melted tallow, which is poured into the cupped collar surrounding the rod. Sucking pump, (pompe aspirante,) is one which raises water by exhaust- ing the air from the barrel of the pump, into which the water is forced by the external pressure of the atmosphere. Suction pipes, (tuyaux a succion, su^oirs) . Super-heated steam, is steam whose temperature has been raised after it has left the water from which it was generated. Supplementary engine , see Auxiliary engine. Surcharged steam , is steam which has an excess of watery particles held in mechanical suspension. Syphon oil cups, are those fitted with a wick of cotton or worsted hanging over the edge of a little tube in the middle of the cup, the oil rising in the wick by capillary attraction, and dropping down the tube on to the bearing. Tallow, oil, (suif, huile). Taps and dies are employed for form- ing the threads of internal and ex- ternal screws. The former is a hard steel screw, grooved from end to end, so as to present a cutting section, and slightly tapered. This is turned round, by hand, inside the nut by means of the tap wrench. Dies are screwed nuts of hard steel, grooved in the same way, for cutting the threads of bolts. Template , (of a base plate, for in- stance,) is a model or gauge of it in thin sheet iron or wood, having the bolt holes cut out, and the various centres marked, for the purpose of transferring them to the hull of the vessel. Test cocks, see Pet cocks. Thread of a screw, (filet d'une vis). Throttle valve, (soupape regulateur,) is situated in the steam pipe, close to the slide valve casing, and is used for regulating the flow of steam, which in the marine engine is done by hand. Ton equals 2240 lbs. ; the French tonne equals 1000 kilogrammes, or 2204 , 86 lbs. avoirdupois. Travel of the valves, (course du tiroir,) is synonymous with their stroke. Trunk-engine, is one in which the end of the connecting rod is attached to the bottom of a hollow trunk fitted to the upper side of the piston, and alternating with it through the interior of the steam cylinder. The trunk itself passes steam tight through the cylinder cover, by means of a stuffing box. Trunnions of oscillating cylinders, are the hollow axes upon which they vibrate, and through which the steam passes into the belt which leads round the exterior of the cylinder to the valve casing. Tubular boilers, are those in which the flame and hot gases, after leaving the furnaces, pass through a great number of small iron or brass tubes surrounded with water. Tube plugs, formed of hard wood, are used for driving into the two ends of a tube that has been burst by the pressure of the steam, as a temporary remedy until a new tube can be put in. Tug, or towing boat, (remorqueur). Two-way cock, (robinet a deux eaux). Up-take, is the name given to the flue of a boiler into which the others are gathered at the end of their course, and thus taken up into the foot of the chimney. MARINE ENGINES AND BOILERS. 243 Vacuum gauge or barometer, is fitted to the condenser to show the vacuum. Vacuum pump, is sometimes fitted to the boilers for the purpose of filling them above the level of the sea, by withdrawing the air from the inside of the boiler, when the water will of course rise by the atmospheric pressure outside. Vacuum valves , see Reverse valves. Valves , (valvules, soupapes, clapets, tiroirs). Valve casing , (boite du tiroir, boite a vapeur,) is the cast-iron chest en- closing the slides. Valve- gearing, (armature du tiroir). Velocity, (vitesse). Wages, (gages, salaire ). Washers, are the round pieces of thin iron or brass interposed between the nut of a bolt, and the surface upon which it is screwed down. Waste-steam pipe leads from the valve chest on the top of the boilers, to carry off the steam escaping through the safety valves. W aste-water pipe, see Discharge pipe. Water gauges, namely, glass water gauge and the brass gauge cocks, are attached to the front of the boiler for showing the level of the water. Water-tight, (etanche d'eau) . Wear, (usure). Wedge, (coin). Weigh-chaft, is the rocking shaft used in working the slide valves by the eccentric. Worm wheel , is a wheel with teeth, formed to fit into the spiral spaces of a screw, so that the wheel may be turned by the screw, or vice versd .