ON THE HEAT PRODUCED BY FRICTtON. 33 



axis, moving with the same quickness, produces a friction, 

 the velocity of which is more than 84 cent. [32*8 inches in 

 the same space of time. This velocity, sufficient to produce 

 sensible effects, is that which [ have generally employed in 

 my experiments. The other parts of the apparatus are hol- 

 low cylinders, equal in surface but of different materials, 

 and rubbers of copper and of steel 3 cent. [1*2 inch high.] 



The heat developed by the friction of the pieces of this The hea* pro- 

 apparatus is employed to raise the temperature of a mass Q^ the tenmefL 

 water of 3 dec. 664 cent, cubic measure [2l6 cub. inches], ture of water 

 which the box is capable of containing, and this tempera- ' nlhea PP ara - 

 ture is measured by the thermometer immersed in it. The 

 water employed was in general nearly of the temperature 

 of the air of the room, in order to avoid the influence 

 this might have had on that of the water during the course 

 of the experiment. This influence was farther diminished 

 by preventing the air from being renewed, and shortening 

 the period of the operations. 



Exp. 1. The first trial was made with a cylinder and Exp 1 with a 



rubber of brass. These pieces, before they were subjected brdSS c y ,inder 



r • i.- i i • i i i. i • , • aud rul >ber. 



to friction, were accurately weighed both in air and in wa- 

 ter. Their temperature was 4° [39*2 F.] : the spring acted 

 with a force equivalent to a pressure of 20 kil. [44ibs.] : and 

 the mean velocity was 60 turns of the greater wheel in a mi- 

 nute. After 15 minutes continued friction, the tempera- 

 ture of the water was 6° [42*8] ; and it was pretty regularly 

 raised 2° [3'6°] in every interval of 15 minutes, so that at 

 the expiration of 70 min. the temperature was 13° [,55*4°]. 

 The cylinder and rubber, weighed anew in air and water, 

 showed no diminution in bulk or weight, that the balance 

 could detect, though it was sensible to half a grain. The 

 two pieces rubbed together however, exhibited a polish at 

 the points in contact, which indicated a slight loss of sub- 

 stance. This was chiefly visible" on the rubber. Thus a 

 surface of 3 cent. [1*2 inch] broad, and 21 cent. [8'3 inches] 

 long, rubbed with a velocity of 84 cent. [32*8 inches] per 

 second, produced a quantity of heat capable of raising the 

 temperature of 3 dec. 666 cent. cub. [216 cub. inches] of 

 water 9* [l6*2°] ; or in other words of melting more than an 

 eighth part of ice, though the quantity of metal detached 

 Vol. XXVI.— May, 1 810. D from 



