HISTORY OF DYNAMICAL THEORY OF HEAT. 213 



periments, or excited, as I would rather choose to express it, was not furnished 

 at the expense of the latent heat, or combined caloric of the metal, I pushed my 

 inquiries a step farther, and endeavored to find out whether the air did, or did 

 not, contribute anything in the generation of it." 



In this, his Experiment No. 2, the only modification consisted in 

 fitting the steel borer with an air-tight piston, packed with oiled 

 leather, by which any circulation of air from without to the interior 

 was prevented. But in the use of this device the oiled leather itself, 

 by its friction with the sides of the borer, produced considerable heat, 

 so that, to obviate any possible objection as to this point, Rumford 

 had recourse to his third and most celebrated experiment. 



In this, the friction cylinder was made to rotate in a water-tight 

 box, which, being filled with water, completely submerged all the heat- 

 producing parts. Here, therefore, the only supply of caloric, if any, 

 lay in the Avater, which itself was to be heated by the friction ; for 

 had any caloric been abstracted by the heated water from the ambient 

 air, there would have necessarily been a flow of heat from a cool body 

 to a warmer, which every one admitted to be contrary to experience. 

 The apparatus, therefore, having been arranged, the box was filled 

 with water at the temperature of 60 Fahr., and the machinery put in 

 motion. 



With reference to what followed, Rumford remarked: 



" The result of this beautiful experiment was very striking, and the pleasure 

 it afforded me amply repaid me for all the trouble I had had in contriving and 

 arranging the complicated machinery used in making it. 



" The cylinder, revolving at the rate of about thirty-two times in a minute, 

 had been in motion but a short time, when I perceived, by putting my hand into 

 the water and touching the outside of the cylinder, that heat was generated ; 

 and it was not long before the water which surrounded the cylinder began to be 

 sensibly warm. 



" At the end of one hour I found, by plunging a thermometer into the water 

 in the box (the quantity of which fluid amounted to 18.77 pounds, avoirdupois, 

 or two and a quarter wine-gallons), that its temperature had been raised no less 

 than 47 ; being now 107 of Fahrenheit's scale. 



" When thirty minutes more had elapsed, or one hour and thirty minutes 

 after the machinery had been put in motion, the heat of the water in the box 

 was 142. 



" At the end of two hours, reckoning from the beginning of the experiment, 

 the temperature of the water was found to be raised to 178. 



" At two hours twenty minutes it was at 200 ; and at two hours thirty 

 minutes it actually boiled ! 



" The quantity of heat excited and accumulated in this experiment was very 

 considerable ; for, not only the water in the box, but also the box itself (which 

 weighed 15} pounds), and the hollow metallic cylinder, and that part of the 

 iron bar which, being situated within the cavity of the box, was immersed in 

 the water, were heated 150 Fahr., namely, from 60 (which was the tempera- 

 ture of the water and of the machinery at the beginning of the experiment) to 

 210, the heat of boiling water at Munich." 



