it communicates a slight depressing action to the hand-lever, н, when the attendant, taking the hint, depresses it still further, to give the proper blow.

The steam comes from the boiler through the horizontal pipe, P. The curved end of this pipe delivers the steam to the central portion of the valve casing, A, whence it finds its way by longitudinally divergent thoroughfares to the two ends of the internal oscillating valve-piece, and thence to the steam cylinder port. The exhaust steam passes off by the branch, on the other side. The steam-pipe has a throttle-valve at B, from which a vertical rod, s, descends to the standing place of the attendånt, who can adjust the steam flow by the handle T.

Ths balanced valve used at the Low Moor Iron Works, where the experiment was first tried, is 8 inches in diameter, with ports 14 inches long, by 2 inches wide. The steam pressure is 60 pounds, and yet a child could move the valve with ease, by working a 16-inch lever; so that with these improvements coupled with certain others in the furnaces, the Low Moor forge-men can now do as much work with this hammer in nine or ten hours, as they formerly could in eleven or twelve hours.

The valve attached to this hammer, has found other important uses. The makers have now above a hundred of them at work for winding and common steam engines. With the winding engine-men they are especial favourites. In one case, where two 30-horse engines are fitted with them, the owner states that he saves 120l. a year by each in oil and labour, whilst he gets more work out of his steam.

Condie's Steam Hammer.-Mr. Condie's steam hammer has attained nearly as much celebrity as Mr. Nasmyth's, and is in some respects superior to it. In this hammer the cylinder moves instead of the piston, and the piston rod is hollow and serves as a pipe through which the steam is admitted and discharged. The cylinder is in point of fact the hammer, and a hammer face is attached to the bottom of it, by a proper dove tail. Mr. Condie's great hammer, erected for Mr. Fulton, of Glasgow, in 1857, is represented in fig. 368.

Fig. 368.

COVAN IRON WORKS

CLASEDW: 1857

CONDIE'S STEAM HAMMER. Elevation.

This hammer is 6 tons in weight, and has a stroke of 7 feet 6 inches. The foundation on which the hammer stands is a massive bed of iron and timber combined. The visible framing standing upon this base consists of a pair of vertical cast-iron columns, of rectangular transverse section, placed 20 feet apart, and bound together laterally

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by a strong horizontal cast-iron beam of equal solidity. An opening is cast in the centre of this beam for the passage through of the steam cylinder, which is really the hammer block. These two lower columns are surmounted by a pair of segmental frame pillars, which, conjoined, form a complete open semicircular arch, springing up to a height of 26 feet. These segmental frame pillars are joined together at the crown centre by internal flanges, leaving sufficient space to receive the entablature containing the valves, and to which part of the valve gearing is attached. The upper and lower columns are jointed to each other internally in "spigot and faucet" fashion, and their junction flanges are also firmly secured by bolts. The vertical guide pieces for the hammer traverse are fixed to the central or intermediate horizontal beam, and also to the arc above, provision being made for adjusting them by means of liners.

The hammer cylinder is cast of great strength, particularly at the lower end, which is formed with a dovetail socket to receive the acting hammer face,—this arrangement permitting of the replacement of the striking portion when worn. At each side of the cylinder is a channel, communicating with the interior of the cylinder by means of ports near the bottom, for the purpose of allowing the air to escape from beneath the piston during the ascent of the cylinder, preparatory to a stroke, and to re-enter during the cylinder's descent. But when the cylinder is elevated to its full height, the ports pass the piston, and the air beneath, having no means of egress, is consequently compressed, and acts as a recoil spring, in adding force to the descending blow of the hammer.

A small horizontal steam cylinder is fixed upon the entablature, and the piston rod is connected to the main cylinder valves by a lever and link arrangement. The steam slide valve of this small cylinder is acted upon by the self-acting gear, but whilst the tool is perfectly self-acting, it is so arranged that the attendant can arrest the motion of the hammer whilst falling, or cause it to fall at any moment whilst ascending.

Morrison's Steam Hammer.-In Morrison's steam hammer, the piston rod is taken through the top of the cylinder, and guided above; and the hammer is attached to the lower end of the piston-rod, as in Nasmyth's arrangement.

Bowling Steam Hammer.—In the Bowling Company's steam hammer, the steam cylinder is bolted on the back of the hammer block, whereby the height of the machine is reduced.

Brown's Steam Hammer.-In Brown's steam hammer the cylinder moves as in Condie's.

Farcot's Steam Hammer.-M. Farcot, of Paris, has taken out a patent for improvements in steam hammers, which improvements are as follows:-First, in so arranging steam hammers that the steam acts from above; for this purpose it is proposed to add a lateral reservoir and steam jacket to the hammer cylinder, so that the piston will be elevated by the action of the steam in the reservoir in communication with the bottom of the cylinder, or by a spring of any convenient construction. Second, in the application and use of a circular equilibrium distributing valve, which is easily worked, and may be applied to existing hammers. Third, of an arrangement of mechanism or gear for working the valve either by hand, with the aid of a spring, or by means of the hammer itself-such mechanism being also applicable to existing hammers. For this purpose the valve is connected by means of an overhead lever and connecting rod to the handle of the valve gear, the movement of which is greatly facilitated by the use of springs acting on each side, so as to hold it when at rest in the centre of the guiding quadrant, and so keep the valve closed. The head of the piston may be made to open the valve by striking the valve stem, a buffing spring being interposed to avoid shocks. By another modification, a single helical spring may be placed on the valve connecting rod, for arresting the movement of the valve. Fourth, of a buffing arrangement for deadening the shocks, and preventing the breakage of the piston rods. This arrangement consists in interposing between the hammer head and piston rod layers of leather, indiarubber, felt, gutta-percha, card-board, or other good buffing material. A similar buffer may be placed on the top of the hammer head, to prevent its striking the cylinder when raised too high. A mode of connecting or joining the rod to the hammer, applicable to existing hammers, is also specified, which consists in the use of a spherical or

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conical joint, and in the interposition of a block of wood beneath such joint, between the end of the rod and the hammer. Fifth, in raising or lowering the portion of the hammer which is made hollow on the piston rod. This is effected either by a screw thread on the piston rod, and working through the centre of the hammer, or by keys and mortices or slots, so as to reduce the space left for steam when the piston does not travel to the end of its course. Sixth, in lubricating the hammer guides by collecting the grease or oil which falls from the stuffing box, and directing it thereto. Seventh, in the use of bars of iron or pieces of timber, against which a buffer on the hammer strikes when the latter is unduly elevated, thereby preventing the bottom of the cylinder from being damaged. Eighth, in a mode of working the valve by the continuous rotatory motion of a cam or eccentric, or by any motion independent of the hammer itself.

Steam Pile-driver.-A form of the steam-hammer adapted for driving piles of timber into earth to serve for the foundation of heavy structures, has been extensively introduced by Mr. Nasmyth. In this form of the instrument the cylinder is attached to the top of the pile, and the hammer, by successive blows upon the head of the pile, forces it into the earth. The boiler is set in any convenient situation on the ground below, and the steam is conducted through jointed pipes, which fold up as the cylinder falls with the penetration of the pile into the ground. A form of pile driver was several years ago introduced by Mr. Cochrane in America, and was also imported into this country, in which the ram and guides were the same as those of a common pile-driving machine; but the chain which draws up the ram was wound up by means of a small high-pressure engine, which engine also gave motion to a circular saw revolving at the end of a swivelling arm, which could be moved so as to bring the saw against the side of the pile, and thus cut it off fair with the others when driven sufficiently far. Neither of these expedients, however, has yet superseded the old hand-pile driver, which is still very extensively used.

The pressure which a ram will exert upon the head of a ram in driving it into the ground will, other things being the same, be pro

portionate to the distance which the pile penetrates during the blow. Thus if the ram weigh 5 cwt. and falls through a distance of 20 ft. while the pile penetrates with such a blow 1 ft., the pressure exerted on the head of the ram will be 20 times 5 cwt., 100 cwt.,

or 5 tons.

Steam Rivetting Machine.*-One form of steam-hammer is the application of the principle to the rivetting of boilers, as practised by Messrs. Garforth, Messrs. Cook, and others. In Mr. Garforth's rivetting machine an upright post of iron has a die inserted on one side to receive the head of the rivet and resist the blow of the hammer, and the rivetting is effected by a die attached to the pistonrod of a short horizontal cylinder of about 2 feet diameter, behind which steam is admitted. In the case of Cook's rivetting machine, the same end is attained by the intervention of a lever which enables the cylinder to have a longer stroke.

Steam Quartz crusher. The steam hammer has been employed in several instances to crush auriferous quartz, to enable the gold to be extracted. By calcining the quartz in which much of the iron ore in India is embedded, the mass becomes easily pulverulent, and the natives then winnow away the powdered quartz by a blast of air, leaving the heavy ore behind.

Steam Quarrying.— A form of steam hammer has been employed in some instances to strike the head of the borer, by which holes are made in stone to deposit the blasts of gunpowder in the operation of quarrying. By the aid of such an instrument the holes may be bored with great rapidity.

Steam Ram.†-A species of vessel called a steam-ram has lately been introduced, of which the purpose is to run down ships of war by its enormous momentum when urged at a high speed, while its strength is such that it will be able with impunity to sustain the shock.

The first steam rivetting machine that I know of was one made by myself out of an old punching press in 1834. A few years afterwards Mr. Fairbairn brought out a similar apparatus, which was, and still is, extensively used.-J. B.

The first suggestion of a steam-ram that I have heard of was made by my father, the late Captain Bourne, about 1832. He proposed to have a steamer of great strength and power to run down ships, without being damaged herself.-J. B.

MARINE steam engines are now divisible into two great classes, Paddle engines and Screw engines, and each of these classes is again divisible into Direct acting engines and Indirect acting engines. In the case of paddle engines all those are called direct acting which are formed without the introduction of side levers, and therefore, oscillating engines and all other in which there are no side levers come into this class. In the case of screw engines, all those are called direct acting, whatever be their other features, which dispense with the use of gearing. As the screw propeller has to be driven with a much greater velocity of rotation than paddle wheels, it follows that the engines employed to drive it must either move with a much greater velocity than has heretofore been usual in the engines of steam vessels, or else gearing must be interposed between the engine and the screw, so that while the screw maintains the required velocity of rotation the engine shall not be required to move at any high degree of speed. At the first introduction of the screw propeller, the use of gearing was considered to be a less evil than that of driving the engine at a high velocity; but in the early editions of this work, it was maintained that this preference for gearing could not be continued, inasmuch as it confessedly arose from the manifest defects of the direct acting engines as then constructed, and which defects were susceptible of an obvious remedy, These defects consisted chiefly in the deficient strength of the parts, the deficient area of the bearings, the deficient size of the ports and passages, and the want of adequate provision for preventing the bolts from screwing up or screwing down, and the cutters from getting too tight or too loose in consequence of the trembling motion produced by the high speed. Further than this, the valves of the air pump required to be of such a character, that they would open and close without shock, and the momentum of the moving parts required to be balanced by counterweights to enable the engine to work smoothly. In the accomplishment of these adjustments there did not appear to be any insuperable difficulty, and it was quite obvious that if they were accomplished and the direct acting engine was enabled to work with equal efficiency, durability, and exemption from accident to the geared engine, the important advantage would be gained not merely of the dismissal of the gearing, but of the realisation of the required power with a much smaller engine, since an engine generates power just in the proportion of the increased velocity with which it is worked. We maintained, therefore, that the thing to be done was to construct not geared engines, as was then the common expedient, but direct acting engines of a really efficient character which it was quite possible to do, and which has since been done by all the most eminent manufacturers. The geared engine in point of fact is now virtually extinct, and it is needless therefore to give it further consideration.

In steam vessels of every class the propulsion is effected by the reaction of the propelling instrument upon the water, and a pressure must exist at the point of contact of the propeller and the vessel, by which pressure or thrust the vessel is forced forward in the water. In paddle vessels the paddle shaft has a forward thrust, which is received by the bearings, and by them communicated to the ship; and the brasses of paddle vessels in consequence of this thrust always wear most on the forward side as is well known to engineers.

In screw vessels the thrust produced by the revolution of the screw in the water is communicated to the screw shaft, and if the screw shaft had no collars upon it and no plate at the end to receive the thrust, it would move forward in the vessel when it was turned round upon its axis until it came in contact with some object which prevented it from proceeding further, and then, and not till then, the vessel would be propelled. In all screw vessels proper provision of some kind or other has to be made to receive this thrust, and to communicate it to the vessel without causing injury to any part; and the amount of this thrust is measurable by the dynamometer as already explained at page 126. The amount of this thrust multiplied by the space that the vessel passes through in a given time represents the amount of power utilised in the propulsion of the vessel, and by comparing it with the indicator power the loss resulting from the slip and friction of the screw can be readily determined. The losses incident to the use of paddle wheels may be ascertained by a similar process.

SIDE LEVER PADDLE ENGINE, BY MESSRS. CAIRD.

Plate XIX. is a representation of the species of side lever marine engine constructed by Messrs. Caird and Co., for the paddle steam vessels Clyde, Tweed, Tay, and Teviot, which were vessels of the original fleet of the Royal Mail Steam Packet Company. These engines have proved themselves to be most efficient and satisfactory engines in every respect and they have done great credit to Messrs. Caird. The details of these same engines are given in Plates XXXIII. XXXIV. XXXV. and XXXVI., and we could not now select a more useful example of an engine than this as a guide for the construction of other engines of a similar character. There is no redundancy of materials, neither is there upon the whole any deficiency, and all the parts are planned to wear well, to be easily accessible, and to present a symmetrical ensemble. The diagonal

stay where it joins the cylinder is perhaps rather weak, and upon the whole it appears to be a preferable arrangement instead of casting the condenser on the sole plate, and causing the main centre to pass through it to form the condenser of a tall cylindrical pipe set at the back of the valve casing, and to support the main centre by proper pedestal blocks provided for that purpose. The main centre when it passes through and is supported by the sides of the condenser is liable to be worked slack, and to cause a leakage of air in that situation unless an encircling pipe is cast in, and when this is done the irregular shrinkage is apt to cause the condenser sides to crack when heated by the steam in the operation of blowing through, and then suddenly cooled by the admission of the injection water. By separating the condenser from the sole plate, moreover, the difficulties in the execution of the sole plate casting are very much abridged, for the hydrostatic pressure of the molten iron is so great, when so high a head as the height of the condenser operates over so large a surface as the area of the sole plate, that it is difficult to introduce sufficient fastenings to bind the boxes containing the sand together. For this reason, when such a casting has to be made, it will be better to cast it upside down, whereby the hydrostatic head will act on a comparatively small surface.

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The details of these engines are amply explained and illustrated in the plates to which we have referred, and they will be adequately discussed in the course of the remarks which we have to make on the general details of marine engines. In the plates, every part has its name attached, and the particular view which is represented is also specified. Finally, all the dimensions are marked on in figures, so that no engineer could have the least difficulty in constructing the engines from these drawings

SIDE LEVER ENGINE BY MESSRS. NAPIER.

This engine, which is represented in Plate XX. is a section and end view of the engines of the City of London steamer, constructed by Messrs. Napier of Glasgow. This vessel has approved herself one of the most successful and efficient vessels that has ever been constructed, and her engines have given the most eminent satisfaction, as they have done their work efficiently for a number of years without requiring any repairs of the least importance. The names of the different parts are marked upon this engine to assist the comprehension of tyros.

The framing in this engine, it will be observed, is of malleable iron, and malleable iron framing is now very generally employed for marine engines of every class.

The piston rod is secured into the cross head with a nut on the top, as well as a cutter through, which is a good practice. There appears to be rather little taper in the part of the rod which fits into the cross head, so that it will be apt to jam, and will not be got out without difficulty in the event of such disconnexion being wanted. In the piston-rod where it passes through the piston, there is a counter-sink to take the strain, which will prevent the piston rod from splitting the piston. If the cone on the piston rod end be made slight and nothing be added to take the strain, the rod will be drawn up through the hole, and the piston will be split: this accident has happened to many pistons, from the amount of cone on the piston rod being too small. The piston packing consists of a double tier of rings. A single ring turned, of an eccentric form, and fitted with a tongue-piece, is now more commonly employed.

The valve is of the long D variety. There are no packing ports formed in the back of the valve casing, but the packing is put in from the inside, and the valve has to be drawn every time that it is packed. It is a defect we conceive for the eduction passage to enter the condenser at so low a level, as if too much injection is admitted it will soon overflow into the cylinder. The faucet joint in the valve casing is a good arrangement, and ought to be applied to all engines above a moderate size. The air pump bucket is unprovided with a junk-ring for screwing down the packing, the want of which is, in large engines, a disadvantage. The bucket valve is of the common pot-lid description. There are two delivery valves, one in the mouth of the pump, and the other in the hot-well. We do not see the use of this multiplication, especially when there are engines working well without any delivery valve at all. The objection that we brought against the want of sufficient cone in the ends of piston rods applies to the air pump rod in this engine. The connecting rod is needlessly heavy: the connecting rod at the smallest part need not be so thick as the piston rod, and here it is much thicker. The starting gear in the City of London, consists merely of a long lever, by which it is difficult to obtain sufficient power for moving so large a valve: a great number of men are required to start the engine, and the travel of the starting lever is so great, when the engine is thrown into gear, as to be a source of danger to persons in the vicinity. This is not a common fault of Mr. R. Napier's; in the engines of the Precursor, the starting gear was one of the most elegant and convenient that has come under observation, and in the engines of the Persia the same distinction is preserved. In the Precursor and British Queen steamers, the engines of both of which vessels are by Mr. R. Napier, the starting gear consisted of a wheel, like the steering wheel of a ship, which, by means of a pinion working into a sector on the valve shaft, gave motion to the valve, and the power was thus so multiplied that one man could start the engines. To prevent inconvenience from being experienced by the engineer from the rapid

whirling round of the starting-wheel when the engines were thrown into gear, the disconnecting apparatus was so contrived that the act of throwing the eccentric rod into gear threw the starting-wheel out of gear, and vice versa. In the Precursor the eccentric rod was thrown out of gear by means of a lever, with a pulley on the end of it, and which, being forced up against the under side of the eccentric rod, lifted the rod out of a notch. The centre of this lever was attached to an eccentric stud in the framing, which was so contrived, that when the lever was in the position which allows the eccentric rod to fall into gear, the eccentric stud drew back the valve shaft, so that the teeth of the pinion were no longer in gear with the teeth of the sector; but when the lever was forced up into the position which throws the eccentric rod out of gear, the valve shaft was pushed forward until the connexion of the pinion and sector was again established. The link motion is now so widely applied to engines of every class, and it is so easily moved in comparison with the valve, that arrangements of this character are not much required. But where the link motion is absent it is very desirable that the above or some equivalent contrivance should be adopted in all cases where the starting handle requires to have a large travel, as the rapid movements of the starting handle, when the engine is thrown into gear, will otherwise be a source of much danger to the engine attendants.

DOUBLE CYLINDER ENGINE BY MESSRS. MAUDSLAY.

Of this engine a representation is given in Plate XXI., which shows the engines on this plan introduced by Messrs. Maudslay into the steam frigate Retribution. There are two cylinders and pistons entering into the composition of each engine. The two pistons of each engine rise and fall simultaneously, so as to act in the same manner as a single piston; but by the division of the piston area into parts in the manner here effected, it becomes practicable to introduce a connecting rod between them, whereby the necessary length of connecting rod becomes obtainable without giving an undue elevation to the paddle shaft. To give effect to this idea the top of each piston rod is connected to the opposite end of a T crosshead, the perpendicular part of which descends between the cylinders and is guided thereupon; and from the bottom of the T, the connecting rod proceeds to engage the crank,-the cylinders being set sufficiently wide apart to enable the connecting rod to angle itself without coming into contact with them. The air pump is wrought by an unequally ended lever, of which the long end is connected to the bottom of the connecting rod by suitable links, while the short end is connected by similar links to the rod of the air pump. The paddle shafts are formed in such a manner, that they may each be moved outwards a few inches, the effect of which is to withdraw the eye of the paddle crank from the crank pin, and either paddle-wheel may by this expedient be disconnected from the engine.

These engines were constructed with all the fidelity and elegance for which Messrs. Maudslay's engines are celebrated. Nevertheless, at the time of their introduction, we ventured to predict that such engines never would become popular or general, and this prediction has been completely verified by the result. The main purpose proposed to be attained in marine engines, by dismissing the side levers, is to save room. But these double cylinder engines of Messrs. Maudslay's very imperfectly fulfil this indication, as they save very little room,-a truth of which any one may easily satisfy himself by comparing the length of these engines with those of the Persia, by Messrs. R. Napier and Sons, represented in Plate XXVII. The engines are of about the same power, and those of the Persia are a foot or two longer. In the double cylinder engine there is increased radiation, increased leakage, and some other disadvantages, without any compensating benefit that is of much account. It is not surprising, therefore, to find that double cylinder engines of this class have now been discarded, or rather to speak more correctly, that engines of this kind are not now made. The oscillating engine is a very much better species of direct acting engine, and it has consequently obtained a very wide introduction.