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 BENDING AND PUNCHING ENGINES.

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 BORING-ENGINE.

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.

RIVETING THE BOILERS.

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 to the walls in various parts of the room, as seen in the engraving. Connected with these shafts are various drilling and boring machines, which can at any time be set in motion, or put to rest, by being thrown in or out of gear. One of these machines is seen on the right of the boiler above referred to, and another in the left-hand corner of the room quite in the back-ground. Near the fore-ground, on the left, is seen a forge, where any small mass of iron may be heated, as occasion may require.

The semi-cylindrical piece which lies in the centre of the room, toward the fore-ground, is part of a locomotive boiler, and is of course much smaller in size than the others, though it is constructed in the same manner with the large boilers used for sea-going ships. The process of riveting, as will be seen by the engraving, is the same. One man holds up against the under side of the plate a support for the rivet, while two men with hammers form a head above—striking alternately upon the iron which protrudes.

From the boiler we proceed to the cylinder, which is in fact the heart of the engine,—the seat and centre of its power. It is to the cylinder that the steam, quietly generated in the boiler, comes to exercise its energy, by driving, alternately up and down, the ponderous piston. The cylinder must be strong so as to resist the vast expansive force which is exercised within it. It must be stiff, so as to preserve in all circumstances its exact form. It must be substantial, so as to allow of being turned and polished on its interior surface with mathematical precision, in order that the piston in ascending and descending, may glide smoothly up and down, without looseness, and at the same time without friction. To answer these conditions it is necessary that it should be formed of cast iron.

The cylinders are cast, accordingly, in the iron foundry, which, as will be seen by the plan, is on the left, as the visitor enters the works. There is a range of monstrous cranes extending through the interior of the room, as represented in the plan, one of which is exhibited conspicuously in the engraving below. At different places in the ground, beneath this foundry, for it has no floor, there have been excavated deep pits, some of which are twelve feet in diameter and eighteen feet deep, the sides of which are secured by strong inclosures, formed of plates of boiler iron riveted together. These pits are filled with moulding sand—a composition of a damp and tenacious character, used in moulding. The mould is made and lowered into one of these pits, the pit is filled up, the sand being rammed as hard as possible all around it. When all is ready, the top of the mould, with the cross by which it is to be lifted and lowered surmounting it, presents the appearance represented on the right hand lower corner of the engraving below.

CASTING A CYLINDER.

A reservoir to contain the melted metal necessary for the casting is then placed in a convenient position near it, with a channel or conduit leading from it to the mould. This reservoir may be seen in the engraving near the centre of the view, at the foot of the crane. An inclined plane is then laid, as seen in the engraving, to the left of the reservoir, up which the workmen carry the molten metal in ladles, which, though they do not appear very large, it requires five men to carry. A party carrying such a ladle may be seen in the engraving in the back-ground on the left. These ladles are filled from the various furnaces, the iron throwing out an intense heat, and projecting the most brilliant scintillations in every direction, as it flows. In the case of the largest castings it requires sometimes four or five hours to get together, from the furnaces, a sufficient supply of metal. The largest reservoir thus filled will hold about thirty tons of iron.