COUNT RUMFORD I59 



If now the hemispheres be pressed strongly together, and at the 

 same time the rod C be turned, by some means or other, about its 

 axis, a very considerable quantity of heat is generated by means of the 

 friction which takes place between the flat surfaces of the two hemi- 

 spheres. 



The quantity of the heat excited in this manner is exactly propor- 

 tional to the force with which the two surfaces are pressed together, 

 and to the rapidity of the friction. When this force was equal to the 

 pressure of ten thousand pounds, and when the rod was turned with 

 such rapidity about its axis that it revolved thirty-two times a minute, 

 the quantity of heat generated by the continual rubbing of the two 

 surfaces together was extraordinarily great. It was equal to the 

 quantity given off by the flame of nine wax-candles of moderate size 

 all burning together. 



The quantity of heat generated in this manner during a given time 

 is manifestly the same, whether the globular vessel D is filled with 

 water, and the surfaces of the two hemispheres rub on each other in 

 this liquid, or whether there is no water in the vessel, and the appa- 

 ratus by which the friction is produced is simply surrounded by air. 



The source of the heat which is generated by this apparatus is in- 

 exhaustible. As long as the rod C is turned about its axis, so long 

 will heat be produced by the apparatus, and always to the same 

 amount. 



If the globe-shaped vessel D is filled with water, this water be- 

 comes hotter and hotter, and finally begins to boil. I have myself in 

 this way boiled a considerable quantity of water. 



If this experiment is performed in winter when the temperature of 

 the air is but little above the freezing-point, and if the vessel D is filled 

 with a mixture of water and pounded ice, the quantity of heat caused 

 in a given time by the rubbing together of the two surfaces can be 

 expressed very exactly by the amount of ice melted by this heat. 



Since the apparatus aflfords heat continuously, and aways to the 

 same amount, we can melt in this way as much ice as we please. 



But whence comes this heat ? This is the contested point, to deter- 

 mine which was the real aim of the experiment. 



It is certain that it comes neither from the decomposition of the 

 water nor from the decomposition of the air. Various experiments on 



