in various Substances. 



By these experiments it appears that the conducting 

 power of air is to that of the Torricellian vacuum as 

 9|f to 1 6|| inversely, or as 1000 to 603. 



To determine whether the same law would hold good 



o 



when the heated thermometers, instead of being plunged 

 into freezing water, were suffered to cool in the open 

 air, I made the following experiments. The thermom- 

 eters No. i and No. 2 being again heated in boiling 

 water, as in the last experiments, I took them out of 

 the water, and suspended them in the middle of a large 

 room, where the air (which appeared to be perfectly at 

 rest, the windows and doors being all shut) was warm to 

 the 1 6th degree of Reaumur's thermometer, . and the 

 times of cooling were observed as follows : 



Here the difference in the conducting powers of air 

 and of the Torricellian vacuum appears to be nearly the 

 same as in the foregoing experiments, being as 6^ to 

 io||- inversely, or as 1000 to 605. I could not observe 

 the time of cooling from 80 to 70, being at that time 

 busied in suspending the instruments. 



