. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRINCIPLES OF THE MECHANICAL THEORY OF HEAT. 253 hammer was metre; tlie recoil of the same after impact metre; the recoil of the anvil after impact metre. Ilenco the living force which the iron hammer had attained in falling was, L=350- metre-kilograms; but the living force with which hammer and anvil after the blow recoiled from one another was, Z= () + 350 = 127-677 metre-kilograms; the
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. PRINCIPLES OF THE MECHANICAL THEORY OF HEAT. 253 hammer was metre; tlie recoil of the same after impact metre; the recoil of the anvil after impact metre. Ilenco the living force which the iron hammer had attained in falling was, L=350- metre-kilograms; but the living force with which hammer and anvil after the blow recoiled from one another was, Z= () + 350 = 127-677 metre-kilograms; the living force, therefore, expended in the compression of the lead is, L—?=— metre-kilograms. In order to determine the quantity of heat which was developed through the compression of the lead, the latter, after receiving Fis- 8. the blow, was quickly withdrawn from between the hammer and anvil, and by means of two threads, W'hich had been already attached to it, was sus- pended in the manner shown at Fig. 8. Into the cavity of the compressed piece of lead, grams of water at0° C. were poured, and the tem- perature thereof, which very quickly became the same with that of the lead, was ascertained by means of an immersed thermometer. This tempera- ture w'as: 4 minutes after the impact 12°.10 8 minutes after the impact .... 11°.75 Thus in four minutes, from the end of the fourth minute to the end of the eighth, the cooling amounted to 0°.35. If we assume, now, what may at least be accepted as an approximation, that the rate of cooling, during the first four minutes after the blow, was maintained during the following four minutes, we have : = : x; whence results a;= Since, therefore, the temperature of the lead had, at the moment of compression, been 12°.10-|-0°.36=12°.46,the calefaction from the blow would be 12°.46 —7°.87= 4°.59; consequently, the quantity of heat developed through the collision is, 4°.59 •
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