01 



Caution to in- 

 fure equality of 

 temperature. 



Method ofipb- 

 femtion. 



Table of the 

 courfe of cool- 

 ing. 



ON HEAT. 



to add new quantifies of pounded ice from time to time, in 

 order to keep the frigorific mixture conftantly at the precife 

 temperature of melting ice. 



As the fpecinc gravity of water at the temperature of three 

 or four decrees of the thermometer of Reaumur, is greater 

 than that of melting ice, the water which lies at the bottom 

 of a veflel Containing a mixture of water and pounded ice, 

 is ufually warmer than the fluid which occupies the upper 

 part of the veflel. To remedy this inconvenience my refri- 

 geratory for the frigorific mixture was a tin veflel fupported 

 on three feet of one inch in, length, and I placed this firft 

 veflel in a larger of wood, containing a certain quantity of 

 ice furrounding the bottom and part of the fides of the metallic 

 veflel. . .^ 



As in the firft moments of the experiment the thermometers 

 defcended too quickly to be obferved with precifion, I waited 

 till each of them had arrived at the 55th degree of Reaumur; 

 after which I carefully obferved the number of minutes and fe- 

 COnds employed in pafling through each interval of five de- 

 grees of the lower part of the fcaie of the thermometer to the 

 filth degree above zero. 



The following table exhibits the depreflion of the thermo- 

 meters during eight hours employed in the experiment. 



Degrees of the Ther- 

 mometer* 



From 55 to 50 



50 

 45 

 40 

 35 

 30 

 25 

 20 

 15 

 10 



45 

 40 

 35 

 30 

 25 

 20 

 15 

 10 



Time employed in cooling 7 

 from 55 Q to 5°, j 



478 



254 



It 



