478 Life of Count Rumford. 



blunt steel borer, by means of a strong screw with the force 

 often thousand pounds, against the bottom of the bore 

 of the cylinder while that cylinder was made to revolve 

 by horse-power thirty-two times in a minute. To di- 

 minish as much as possible the loss of any part of the 

 heat that might be generated, the cylinder was carefully 

 wrapped in thick and warm flannel, and defended from 

 the cold air of the atmosphere. The area of the surface 

 at which the rounded end of the steel borer was in contact 

 with the cavity at the bottom of the bore in the cylinder 

 was nearly two and one third inches. The temperature 

 of the air and of the cylinder at the beginning of the 

 experiment was 60 F. At the end of thirty minutes, 

 when the cylinder had made 960 revolutions, the mer- 

 cury, as indicated by the thermometer introduced into 

 the cavity above described, rose almost instantly to 

 130. 



In order to approximate to the amount of the heat 

 which had been given off during the time in which the 

 heat generated by the friction had been accumulating, 

 the experimenter took note of the rapidity with which 

 the heat escaped out of the cylinder. To this end, 

 while the machinery was stopped, he left the thermom- 

 eter in the cavity, observing at short intervals of time 

 the temperature which it indicated. This fell iioin 

 forty-one minutes. 



The weight of the metallic dust which had been de- 

 tached by the borer from the bottom of the cylinder was 

 found to be 837 grains Troy. The Count asks, "Is it 

 possible that the very considerable quantity of heat that 

 was produced in this experiment (a quantity which actu- 

 ally raised the temperature of above in pounds of gun- 

 metal at least 70 degrees of Fahrenheit's thermometer, 



