ON THE HEAT PRODUCED BY FRICTION. 35 



Exp. 6 and 7. I sought to confirm the influence of pres- Fx P . 6 and 7. 

 »ure on the evolution of heat by two experiments, in one of 

 which I made it four times as great as in the other. For 

 this purpose I employed the cylinder of brass, and the rub- 

 ber of the same metal ; and the velocity being equal, the 

 pressure was at first 10 kil. [22 lbs.]. The temperature of 

 the water rose only 1° [l'8°] in 30 minutes. Having after- Quadruple 

 ward rendered the pressure equal to 40 kil. [88 lbs.], the g^^e&t 

 temperature acquired by the water in the same space of time heat, 

 was six times greater, or 7° [12'G ]. 



Exp. 7. The cause, to which we ascribe the most general Exp. 7. Brass 

 influence on the developement of the heat produced by ^^J* inst 

 friction, is the erosion of the surface rubbed, the particles 

 of which are separated with violence. In order to ascertain 

 this influence, I employed a rubber of steel, cut so as to 

 resemble a bastard file; and applied it to the surface of the 

 cylinder with a force equal to 20 kil. [44 lbs.]. Having ac* 

 curately weighed the cylinder in the air, I turned it with 

 the same velocity as in the preceding experiments; and in 

 the space of 60 minutes the temperature of the water was 

 raised only from 14° [57*2°] to 18° [64*4°]. The cylinder 

 had lost 3 decagr. [463 grs.] of its weight. This quantity produced but 

 of metal, a thousand times as much as that lost by the fric- , haIf as m " ch 



J neat as when 



tion of the same cylinder against a rubber of smooth po- rubhingagainst 

 lished brass, in Exp. 1, gave but half the quantity of heat smouth brass * 

 in the same time, though taken off by an equal pressure. 



Exp. 8. In the 8th experiment I proposed to ascertain Exp. 8 Rrass, 

 the influence, that the free communication of the parts of •unroantied by 



. -ii •• 1 t , „ , a bad conduc- 



the apparatus with the surrounding bodies by means of good t or of heat 

 conductors of heat, or their insulation by bad conductors, 

 might have on the production of heat. With this view I 

 placed the apparatus in a deal box, in which it was kept at 

 the distance of a decim. [3 '9 inches] from every side by 

 pieces of wood half charred. The interval between the two 

 boxes was filled with smallcoal, forming a stratum on all 

 sides near four inches thick. I employecl the brass cylinder 

 and rubber, subjected to the same pressure, and rubbed 

 with the same velocity. The time of the experiment was 

 divided into three equal portions of 30 min. each. In each 

 of these periods the temperature acquired by the water in 



D 2 the 



