the Heat excited by Friction. 477 



side of the cylinder, when the mercury rose almost in- 

 stantly to 130. 



Though the Heat could not be supposed to be quite 

 equally distributed in every part of the cylinder, yet, as 

 the length of the bulb of the thermometer was, such that 

 it extended from the axis of the cylinder to near its sur- 

 face, the Heat indicated by it could not be very different 

 from that of the mean temperature of the cylinder ; and 

 it was on this account that a thermometer of that par- 

 ticular form was chosen for this experiment. 



To see how fast the Heat escaped out of the cylinder 

 (in order to be able to make a probable conjecture re- 

 specting the quantity given off by it during the time the 

 Heat generated by the friction was accumulating), the 

 machinery standing still, I suffered the thermometer to 

 remain in its place near three quarters of an hour, observ- 

 ing and noting down, at small intervals of time, the 

 height of the temperature indicated by it. 



The Heat, as shown by 

 the thermometer, was 



Thus at the end of 4 minutes . . . . . . 126 



after 5 minutes, always reckoning from the first 



observation ..... 125 



at the end of 7 minutes . ... . . . 123 



12 " 120 



H " ' "9 



16 " 118 



20 " Il6 



24 " . . . . . .115 



28 " . .... 114 



% 31 " . ... 113 



34 " "2 



37^" - .... in 



and when 41 minutes had elapsed . . . no 



Having taken away the borer, I now removed the 



