118 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1786. 



A Table of the conducting Powers of the under-mentioned Mediums, as deter- 

 mined by the foregoing Experiments. 



Thermom. N° 1. Thermotn. N° 4. 



Taken out of freezing water, and plunged into boiling water. 



In determining the relative conducting powers of these mediums, I have com- 

 pared the times of the heating of the thermometers from 0° to 70° instead of 

 taking the whole times from 0° to 80°, on account of the small variation in the 

 heat of the boiling water arising from the variation of the weight of the atmos- 

 phere, and also on account of the very slow mo- 

 tion of the mercury between the 70th and the 



80th degrees,andthe difficulty of determining the m^-^T^ 



precise moment when the mercury arrives at the Water 342 



80th degree. Common air, density = 1 . . 80|- 



Taking now the conducting power of mer- Rarefied air, density = | . . 8o| 



cury = 1000, the conducting powers of the other ^f"^^'^ air density = ^ 78 

 •;. , .111 . The Torricellian vacuvim . . 53 



mediums, as determined by these experiments, 



will be as annexed, viz. 



And in these proportions are the quantities of heat which these different mediums 

 are capable of transmitting in any given time ; and consequently these numbers 

 express the relative sensible temperatures of the mediums, as well as their con- 

 ducting powers. How far these decisions will hold good under a variation of cir 

 eumstances, experiment only can determine. 



