in various Substances. 



417 



It appears, therefore, from these experiments, that the 

 conducting power of common atmospheric air is to that 

 of the Torricellian vacuum as y|- to II^Q inversely, or 

 as 1000 to 602 ; which differs but very little from the 

 result of all the foregoing experiments. 



Notwithstanding that it appeared, from the result of 

 these last experiments, that any difference there might 

 possibly have been in the forms or dimensions of the 

 instruments No. i and No. 2 could hardly have pro- 

 duced any sensible error in the result of the experiments 

 in question ; I was willing, however, to see how far any 

 considerable alterations of size in the instrument would 

 affect the experiment : I therefore provided myself with 

 another instrument, which I shall call Thermometer No. 

 3, different from those already described in size, and a 

 little different in its construction. 



