is, that the hammer always works parallel with the piece under operation, which is not the case with helves, the hammerman having to use thickness pieces to overcome

this difficulty. Both sides of the steam-hammer are also accessible for working.

It consists essentially of a vertical high-pressure engine with an inverted cylinder. The piston-rod is attached to a heavy block or "tup" moving between guides on the inner faces of the standards, which consist of a massive cast-iron framing. The ordinary hammer is double-acting,

the steam being exhausted above or below the piston. The slide-valve is balanced against the steam-pressure in the valve-chest so as to be easily moved. A lever moves the steam-admission-valve, and the exhaust is opened by the hammer moving a bent lever.

The hammer varies in weight from 30 to 60 cwts., but in forging very heavy masses the block may weigh 5 to 10 tons. The force of the blow is however, to a great extent, independent of the mass of the hammer head. The anvil is of great weight, having a massive foundation, which stands clear of the framing.

Squeezers. These machines have superseded hammers in some forges, the welding of the ball being effected by pressure without impact. There are two kinds in use -lever and rotatory squeezers.

The crocodile-squeezer Fig. 45 is used both with single and with double jaws. The lower jaws are fixed

Fig. 45.

while the upper ones are opened and closed by a crank and connecting rod attached to the end of one of them. The upper jaw is sometimes serrated so as to better grip the puddled ball, which is inserted at the wide end and gradually rolled by the workman towards the narrow end. By this means the slag is expelled and the particles of iron firmly welded.

Rotatory-Squeezers.-Fig. 46 represents a horizontal machine, which consists of a revolving cylinder (a) having its surface corrugated or studded with teeth. This cylinder is placed eccentrically with regard to that

of the outer casing (b), the inside of which is similarly roughened. The ball is placed by the workman in the space (c) and carried forward by the rotation of the cylinder (a). The pathway gradually narrowing, the ball is compressed into smaller dimensions, and finally leaves at the narrowest part (d) in a condition ready for rolling. The cylinder revolves at the rate of 12 revolutions per minute, and is driven by a bevel-wheel and pinion placed beneath. The distance between the pressing surfaces is fixed, so that balls of a somewhat uniform size and weight must always be used.

Fig. 46.

Fig. 47.

Mr. Danks uses a vertical squeezer on the rotatory plan Fig. 47. Two roughened parallel rolls (aa), 4 feet in length and 18 inches diameter, revolve in the same direction, and above these rolls, on a parallel shaft, is arranged a large cam (b), the periphery of which revolves at the same rate as the surface of the two rolls. At the end of the rolls is fixed a horizontal steam-hammer (c), the face of which hammers the bloom while it is being squeezed by the cam and rolls. The bloom is then re-heated and rolled.

Rolling-mill for puddled iron. The forge-train Fig. 48 contains two sets of rolls the roughing

rolls, represented at the right hand, and the finishing-rolls to the left hand. The roughing-rolls are

usually 5 feet long, and about 20 inches in diameter, forming a series of gothic and diamond-shaped grooves between them, diminishing in size from right to left. The larger grooves are gothic-shaped, and roughened, so as to more effectually lay hold of the iron; the smaller ones are diamond-shaped. The distance between the rolls is regulated by the screws (a) and the connection between them is established by means of the cogs attached to the ends (bb). The "journals" or necks of the rolls run in metal bearings, which are supported in cast-iron frames or "housings" (cc). The finishing-rolls are arranged in housings similar to the roughing pair, but have rectangular channels instead of the diamond grooves. These channels diminish in size from right to left. The two sets of rolls are connected together by heavy couplings (de) keyed tightly together. The two rolls of each pair revolve at the same speed, which in the roughing-rolls is about 70 revolutions per minute, and in the finishing-rolls about 90 revolutions per minute.

The bloom of iron is first passed through the largest groove of the roughing-rolls, then lifted back over the top roller, turned one quarter round, and passed through the next smaller hole. This operation is repeated until the

bloom is reduced to a square bar small enough to enter the flat grooves of the finishing-rolls. In this pair, the process of reduction is continued until a puddled-bar of the desired thickness is obtained.

Re-heating and welding.-The bars and slabs of iron, obtained by shingling and rolling puddled-bars, are of inferior quality, and require to be further improved, so as to form good malleable iron. This is done by cutting up the bars into short lengths, arranging them in fagots or bundles, then re-heating them and hammering or rolling to any desired shape.

The

Bars are generally cut up by means of powerful lever shears, containing knife edges of hardened steel, termed crocodile- or cropping - shears Fig. 49. lower blade is fixed to a cast-iron stancheon, and the upper one moves on a pin (a) passing through the same support. The lever (a b) is connected with the motor by the Fig. 49. crank (c). The top jaw opens and closes at every revolution of the shaft by which the power is supplied. Guillotine-shears are also used, see page 106.

The piles or bundles, for re-heating, vary greatly in size and arrangement, according to the desired size and shape of the finished bar. For ordinary bar-iron the piles are made about 2 feet long and 4 inches square. For large sizes they may be 5 or 6 feet long and 10 or 12 inches square. In all cases it is advisable to have the pieces forming the pile of uniform size. Each bundle is bound firmly together by stout wire. For common iron puddledbars are used, but for a better quality the iron from a second rolling is used to form the top and bottom plates of the pile; if the iron obtained from welding the latter pile is cut up and again fagoted, the iron is termed best-best.