156 THE CANADIAN NATURALIST. [April 



" Having thus glanced briefly at his career, I now pass to the 

 discovery upon which Count Rurnford's fame in the future will 

 chiefly rest. It is described in a paper published in the transac- 

 tions of the Royal Society for 1798. 



11 He was led to it while superintending the operations of the 

 Munich arsenal, by observing the large amount of heat generated 

 in boring brass cannon. Reflecting upon this, he proposed to 

 himself the following questions : Whence comes the heat pro- 

 duced in the mechanical operations above mentioned ? Is 

 it furnished by the metallic chips which are separated from the 

 metal ? 



" 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 

 Rumford then cut away slices of the unheated metal, and found 

 that they had exactly the same capacity for heat 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, 

 Rumford proceeds to his principal experiments. 



" With the intuition of the true 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 introduced 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 contact 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 inser- 

 tion 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 

 60°f\ ; at the end of thirty minutes, and after the cylinder had 

 made 960 revolutions, the temperature was found to be 130°F. 



