concerning Heat. 155 



suiting from a change in their specific gravity, occa- 

 sioned by their being heated or cooled ; as the specific 

 gravity of water is very little altered by an inconsidera- 

 ble change of temperature when this fluid is near the 

 freezing point, it might have been foreseen that a solid 

 body a little heated, and plunged into cold water, would 

 be very slowly cooled. 



The result of the following experiment, which I 

 made with a view to elucidate this point, will put the 

 fact out of all doubt. 



The three thermometers being stationary, one, B, at 

 162, the second, C, at 132!, and the third, D, at 

 io6|, the water in contact with one of the extremities 

 of the cylinder being still boiling, while the water mixed 

 with pounded ice, which was in contact with the other 

 extremity, was constantly at the temperature of melting 

 ice, I began to stir this mixture of ice and water pretty 

 briskly with a little stick, and I continued to stir it 

 uninterruptedly and with the same velocity for 22 

 minutes. 



I had scarcely begun this operation when I had a 

 proof that my conjectures were well founded. The 

 mercury in the three thermometers immediately began 

 to descend, and did not stop till it had fallen very con- 

 siderably. 



The thermometer B fell from 162 to 152; C from 

 132! to inf; and D from io6J to 78^. 



On comparing these numbers, we find that, in con- 

 sequence of the agitation of the cold water for 22 

 minutes, the thermometer B fell 10 of Fahrenheit's 

 scale, the thermometer C 21, and the thermometer D 

 28V 



As soon as I had ceased to stir the cold water the 



