Page:Popular Science Monthly Volume 12.djvu/223

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HISTORY OF DYNAMICAL THEORY OF HEAT.

have gained the unqualified recognition which they most certainly deserve.

Taking the casting of a brass cannon, solid and rough as it came from the foundery, and with the cylindrical mass of metal a (Fig. 1), called the verlorner Kopf, still adhering to the muzzle, Rumford caused to he turned upon the superfluous end a smaller cylinder, b (Fig. 2),

PSM V12 D223 Cannon boring lathe setup.jpg
Fig. 2.

7¾ inches in diameter and 9.8 inches long, and which remained connected to the cannon proper by the neck, e, 2.5 in diameter and 3.8 inches long.

The whole mass being then secured in the apparatus used for boring (Fig. 2), a cavity 7.2 inches long and 3.7 in diameter was bored in b, in the direction of its axis, so that a metal bottom, 2.6 inches thick, remained between the borer and the neck. In this also a small round hole, c d (Fig. 3), was radially bored for the insertion of a thermometer. The cylinder, neck, etc., are represented upon a somewhat larger scale in Fig. 3.

PSM V12 D223 Cannon boring head.jpg
Fig. 3.

The borer used to create friction upon this metallic bottom was a flat piece of hardened steel, 0.63 inch in thickness, four inches long, and nearly as wide as the cylindrical bore in which it turned, 3½ inches; so that the area of contact with the bottom was about 2.33 square inches. This borer was securely held in place against the bot-