her machinery; though probably before these pages shall come under the eye of the reader, she will be steadily forcing her way over the foaming surges of the broad Atlantic. The machinery, as we saw it, was incomplete, and the parts in disorder – the various masses of which it was ultimately to be composed, resting on temporary supports, in different stages, apparently of their slow journey to the place and the connection in which they respectively belonged. The ingenious artist, however, who made the drawings, succeeded in doing, by means of his imagination, at once, what it will require the workmen several weeks to perform, with all their complicated machinery of derricks, tackles, and cranes. He put every thing in its place, and has given us a view of the whole structure as it will appear when the ship is ready for sea.
There are two engines and four boilers; thus the machinery is all double, so that if any fatal accident or damage should accrue to any part, only one half of the moving force on which the ship relies would be suspended. The heads of two of the boilers are to be seen on the left of the view. They are called the starboard and larboard boilers – those words meaning right and left. That is, the one on the right to a person standing before them in the engine room, and facing them, is the starboard, and the other the larboard boiler. It is the larboard boiler which is nearest the spectator in the engraving.
The boilers, the heads of which only are seen in the engraving, are enormous in magnitude and capacity, extending as they do far forward into the hold of the ship. In marine engines of the largest class they are sometimes thirty-six feet long and over twelve feet in diameter. There is many a farmer's dwelling house among the mountains, which is deemed by its inmates spacious and comfortable, that has less capacity. In fact, placed upon end, one of these boilers would form a tower with a very good sized room on each floor, and four stories high. The manner in which the boilers are made will be presently explained.
The steam generated in the boilers is conveyed to the engine, where it is to do its work, by what is called the steam pipe. The steam pipe of the larboard engine, that is, of the one nearest the spectator, is not represented in the engraving, as it would have intercepted too much the view of the other parts. That belonging to the starboard engine, however, may be seen passing across from the boiler to the engine, on the back side of the room. The destination of the steam is the cylinder.
The cylinder, marked C, is seen on the extreme right, in the view. It may be known, too, by its form, which corresponds with its name. The cylinder is the heart and soul of the engine, being the seat and centre of its power. The steam is generated in the boilers, but while it remains there it remains quiescent and inert. The action in which its mighty power is expended, and by means of which all subsequent effects are produced, is the lifting and bringing down of the enormous piston which plays within the cylinder. This piston is a massive metallic disc or plate, fitting the interior of the cylinder by its edges, and rising or falling by the expansive force of the steam, as it is admitted alternatively above and below it.
The round beam which is seen issuing from the centre of the head of the cylinder is called the piston rod. The piston itself is firmly secured to the lower end of this rod within the cylinder. Of course, when the piston is forced upward by the pressure of the steam admitted beneath it, the piston rod rises, too, with all the force of the expansion. This is, in the case of the largest marine engines, a force of about a hundred tons. That is to say, if in the place of the cross head – the beam marked H in the engraving which surmounts the piston – there were a mass of rock weighing a hundred tons, which would be, in the case of granite, a block four feet square and eighty feet high, the force of the steam beneath the piston in the cylinder would be competent to lift it.
The piston rod, rising with this immense force carries up the cross head, and with the cross head the two side rods, one of which is seen in full, in the engraving, and is marked S. There is a side rod on each side of the cylinders. The lower ends of these rods are firmly connected with the back ends of what are called the side levers. One of these side levers is seen in full view in the engraving. It is the massive flat beam, marked L, near the fore-ground of the view. It turns upon an enormous pivot which passes through the centre of it, as seen in the drawing, in such a manner that when the cylinder end is drawn up by the lifting of the cross head, the other end is borne down to the same extent, and with the same prodigious force. There is another side beam, on the other side of the cylinder, which moves isochronously with the one in view. The forward end of this other beam may be seen, though the main body of it is concealed from view. These two forward ends of the levers are connected by a heavy bar, called the cross tail, which passes across from one to the other. From the centre of this cross tail, a bar called the connecting rod rises to the crank, where the force exerted by the steam in the cylinders is finally expended in turning the great paddle wheels by means of the main shaft, S, which is seen resting in the pillow block, P, above. These are the essential parts of the engine, and we now proceed to consider the mode of manufacturing these several parts, somewhat in detail.
The boilers are formed of wrought iron. The material is previously rolled into plates of the requisite thickness, and then the first part of the process of forming these plates into a boiler is to cut them into proper forms. The monster that fulfills the function of shears for this purpose, bears a very slight resemblance to any ordinary cutting implement It resembles, on the other hand, as represented in the adjoining engraving, an enormous letter U, standing perpendicularly upon one of its edges. Through the centre of the upper branch of it there passes a shaft or axle, which is turned by the wheels and machinery behind it, and which itself works the cutter at the outer end of it by means of an eccentric wheel. This cutter may be seen just protruding from its place, upon the plate which the workmen are holding underneath. The iron plates thus presented are sometimes nearly half an inch thick, but the monstrous jaw of the engine, though it glides up and down when there is nothing beneath it in the most gentle and quiet manner possible, cuts them through, as if they were plates of wax, and apparently without feeling the obstruction.
The plates, when cut, are to be bent to the proper curvature. The machine by which this bending is effected is seen above, in the back-ground. It consists of three rollers, placed in such a position in relation to each other, that the plate, in being forced through between them, is bent to any required curvature. These rollers are made to revolve by great wheels at the sides, with handles at the circumference of them, which handles act as levers, and are worked by men, as seen in the engraving.
The separate plates of which a boiler is composed are fastened together by means of massive rivets, and it is necessary, accordingly, to punch rows of holes along the edges of the plates for the insertion of the rivets. This process may be seen on the left in the above engraving. Two men are holding the plate which is to be punched. The punch is driven through the plate by means of the great lever, which forms the upper part of the engine. The upright part in front is driven forward by means of the cam in the large wheel behind, a part of which only is seen in the engraving. This cam raises the long arm of the lever by means of the pulley in the end of it, and so drives the point of the punch through the plate. There is a support for the plate behind it, between the plate and the man, with a small opening in it, into which the punch enters, driving before it the round button of iron which it has cut from the plate.
On the right, in the above engraving, is a punching engine worked by men, the other being driven by steam power. These machines are sufficient to make all the ordinary perforations required in boiler-plates. Larger holes, when required, have to be bored by a drill, as represented in the following engraving.
The view below represents the interior of one of the great boiler rooms where the boilers are put together by riveting the plates to each other at their edges. Some men stand inside, holding heavy sledges against the heads of the rivets, while others on the outside, with other sledges, beat down the part of the iron which protrudes, so as to form another head to each rivet, on the outside. This process can be seen distinctly in the boiler nearest to the observer in the view below. The planks which are seen crossing each other in the open end, are temporary braces, put in to preserve the cylindrical form of the mass, to prevent the iron from bending itself by its own weight, before the iron heads are put in.
Sometimes operations must be performed upon the sides of the boiler requiring the force of machinery. To effect this purpose, shafts carried by the central engine to which we have already alluded, are attached