velocity, touches the spring-timber under the tail, and the head is forced down by this recoil upon the hot steel on the anvil. The lift of these hammers is in most cases but a few inches; of the heaviest, but eight or ten inches. The force is chiefly produced by recoil. The speed of these hammers is unusually great, the heaviest kind making from two hundred to two hundred and fifty strokes per minute. Small hammers, for forging thin or small articles, make from four to five hundred strokes in the same time.

THE FACES

Of the hammers are from five to nine inches long, and from one and a half to two and a half inches wide The anvil is in most instances made of wroughtiron; and a hardened steel plate, a little wider than the face of the hammer, is dovetailed and wedged in, as represented in fig. 19. The anvil may also be made of cast-iron, and the cast-steel welded to it when casting the block; an operation now very well performed in a factory in Trenton, N. J. The anvil is fastened by wedges in a heavy

Fig. 19.

wooden log, which extends eight feet or more under

ground; so deep, that the earth is sufficiently solid to resist the further depression of the log. If the ground should be too loose, swampy or sandy, piles should be driven, and the anvil-log set upon them. The anvil-log is frequently three feet or more in diameter, taking the butt-end uppermost, and is provided on both ends with strong iron hoops, which prevent its splitting. The position of the anvil-log is a serious affairin erecting a hammer; if not well supported below, it will sink; and a rock foundation is equally bad, for on it the log is crushed. To protect the wood, and afford stability to the anvil, the vertical log is provided with a cast-iron crown, or chabote, which weighs from one to three tons. This chabote is fastened upon the log, and the anvil is set in a square hole on its upper face. This iron block receives the momentum of the strokes, and protects the anvil-log against sinking and crushing. Stone foundations for the anvil are expensive and insecure.

THE PILLARS,

Or housings in which the fulcrum of the hammer is fixed, are in most cases made of good hard wood. There are also cast-iron frames for this purpose; but, considering the first cost of such iron frames, and

their short durability, there is nothing gained in using that metal for these standards. We will not, therefore, further allude to iron standards, but proceed to describe the construction of those which are made of wood.

The two pillars of the housing are made of good white oak, eleven or twelve feet long, ten or twelve inches thick, and about twenty-four inches wide. In case such heavy timber cannot be had, two sticks are bolted together by iron screw-bolts. About three or four feet of the two pillars are above ground. The part below ground is provided with cross timbers, as shown in fig. 20, which is a view of the hammer

from above. The timbers, A, BB, are from five to six or more feet long, and are fastened to the pillars by screw-bolts, which are from eighteen inches to two feet apart. Below the surface of the earth, the cross-timbers are securely held down by heavy blocks of stone, and firmly walled into the ground,

so as to prevent all possible motion of the timbers. This stone-work can scarcely be too heavy. Above ground, the space between the pillars is open, to receive the fulcrum of the hammer. The fulcrum, F, which is fastened to the hammer-helve by wedges, is made of cast-iron with chilled points, or of wroughtiron with steel points. In the wooden pillars, two cast-iron plates of hard metal are inserted, with some half a dozen holes to receive the points of the fulcrum. These plates are from two to three inches thick, eight wide, and sixteen inches long. They are inserted in the wood so as to be moveable; for the adjustment of the hammer and anvil faces is regulated by the shifting of these plates. Wooden wedges are used for fastening these blocks, as iron screwbolts do not resist the raking force of the hammer. In making these plates large, so as almost to cover the interior of the pillars, and providing them with a sufficient number of screws, we no doubt gain an advantage; they are certainly preferable to the small plates. There is no need of large holes for the screwbolts, if the plates are provided with various centreholes. The pillars above ground are held together by three iron bolts, which serve in the mean time to hold the pillars close in the points of the fulcrum.

Hammers are generally worked by water-power,

partly because the speed necessarily varies, and such variation can be most conveniently regulated by a small water-wheel-partly also because the first outlay is generally less for a water-wheel than for a steam-engine—but chiefly, because the running cost is lower by the water-wheel.

The tap-ring is invariably a cast-iron hoop, of six or eight inches wide and three or four inches thick, in which there are from eight to twenty-four wipers. The cams, or wipers, are either of cast-iron, wroughtiron, or (if small) of steel, wedged by wood into the

The ring is to be of at

square holes of the ring. least four feet diameter; it may even be larger. Small tap-rings are very injurious to the hammer and its frame.

The shaft is sometimes of wood; but cast-iron is the best. It may be made hollow, to increase its strength with the same weight. The water-wheel, which is on the same shaft with the tap-ring, is either of wood or iron, but is to be strong in both cases, as the reaction upon the wheel from the hammer would soon shake it to pieces, if not well braced. The water-wheel is in most cases seven or eight feet in diameter, seldom more than nine or less than five feet. The size of the water-wheel depends partly on the head of water, but chiefly on its quantity. If