XXI 



The common hypothesis affirmed that the heat produced had 

 been latent in the metal, and had been forced out by condensation 

 of the chips. But if this were the case the capacity for heat of the 

 parts of metal so reduced to chips ought not only to be changed, 

 but the change undergone by them should be sufficiently great to 

 account for all the heat produced. With a fine saw Kumford then 

 cut away slices of the unheated metal, and found that they had ex- 

 actly the same capacity for Jieat as the metallic chips. No change 

 in this respect had occurred, and it was thus conclusively proved 

 that the heat generated could not have been held latent in the 

 chips. Having settled this preliminary point, Eumford proceeds to 

 his principal experiments. 



"With the intuition of the tru investigator, he remarks that 

 " very interesting philosophical experiments may often be made, 

 almost without trouble or expense, by means of machinery con- 

 trived for mere mechanical purposes of the arts and manufactures." 

 Accordingly, he mounted a metallic cylinder weighing 113.13 

 pounds avoirdupois, in a horizontal position. At one end there was 

 a cavity three and a half inches in diameter, and into this was in- 

 troduced a borer, a flat piece of hardened steel, four inches long, 

 0.63 inches thick, and nearly as wide as the cavity, the area of con- 

 tact of the borer with the cylinder being two and a half inches. 

 To measure the heat developed, a small round hole was bored in 

 the cylinder near the bottom of the cavity, for the insertion of a 

 small mercurial thermometer. The borer was pressed against the 

 base of the cavity with a force of 10,000 pounds, and the cylinder 

 made to revolve by horse-power at the rate of thirty-two times per 

 minute. At the beginning of the experiment the temperature of 

 the air in the shade and also in the cylinder was 60F. at the end 

 of thirty minutes, and after the cylinder had made 960 revolutions 

 the temperature was found to be 130F. 



Having taken away the borer, he found that 839 grains of me- 

 tallic dust had been cut away. " Is it possible," he % exclaims, " that 

 the very considerable quantity of heat produced in this experiment 



