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Page:Popular Science Monthly Volume 38.djvu/351

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into action. This consisted of a heavy lever, X, which had its fulcrum on the hammer-block, F F. The shorter arm of this lever rested in contact with a vertical bar connected with the valve-gear, P, in such a way that at whatever point of its length the bar chanced to receive a side pressure from the short arm of the lever, X, it caused the admission of steam to the lower end of the cylinder, D, thus causing the "hammer-block" to make its upward stroke. This occurred automatically the instant after the delivery of the blow; the inertia of the weighted end of the lever not being overcome, it moved downward after the "hammer-block" came to rest, and forced its short arm against the vertical bar in the manner described. Such, in brief, were the construction and operation of the first steam hammer built in America, and placed by its builders in the smith's shop of their Southwark Foundry, at Philadelphia, where (Mr. J. Vaughn Merrick writes me) it was "continuously employed till after the sale of the works in 1871."

The original invention of Nasmyth has undergone many changes, and since the expiration of his patents a multitude of modifications having for their object the improvement of its action or its adaptation to some particular variety of work have been brought forward; but they all involve the fundamental ideas of lifting a vertically guided heavy mass, or hammer-block, by the direct action of steam upon a piston with which it is connected, and letting it fall at pleasure upon the work in hand by cutting off the supply of steam and releasing that already beneath the piston; and this combination of ideas and methods originated with James Nasmyth, who, by his invention, augmented the strength of the arm of Vulcan and conferred new powers and possibilities upon the skill of man.

The appearance of a modern forge and all its Vulcanian activities is well represented by Fig. 30, which to an experienced eye presents what may be called a scene of well-regulated confusion, in which, amid smoke and flame, coal and iron, the hissing of steam, beating of sledges, ringing of anvils, and the scorching glare of white-hot metal, the stalwart, half-naked sons of Vulcan strain and sweat at their appointed tasks, while the solid earth for miles around quakes under the ponderous blows of the Cyclopean hammer[1] that

... upheaves its mighty arm
While on the anvil turns the glowing mass—

  1. This is no exaggeration, as it has been authoritatively stated that the blows of the steam hammers in Woolwich Arsenal have been felt at Greenwich Observatory, about two miles distant.