in various Substances. 



409 



From the result of these experiments it appears, 

 evidently, that the Torricellian vacuum, which affords 

 so ready a passage to the electric fluid, so far from being 

 a good conductor of Heat, is a much worse conductor 

 of it than common air,, which of itself -is reckoned 

 among the worst; for in the last experiment, when the 

 bulb of the thermometer was surrounded with air, and 

 the instrument was plunged into boiling water, the mer- 

 cury rose from 18 to 27 in 45 seconds; but in the 

 former experiment, when it was surrounded by a Torri- 

 cellian vacuum, it required to remain in the boiling water 

 i minute 30 seconds = 90 seconds, to acquire that de- 

 gree of heat. In the vacuum it required 5 minutes to 

 rise' to 4.8^ ; but in air it rose to that height in i min- 

 utes 40 seconds ; and the proportion of the times in 

 the other observations is nearly the same, as will appear 

 by the following table. 



The bulb of the thermometer placed in the center 

 of the glass ball, and 



Upon being plunged into 

 boiling water 



After remaining in it 



These experiments were made at Manheim, upon the 

 first day of July, 1785, in^the presence of Professor 

 Hemmer, of the Electoral Academy of Sciences of 

 Manheim, and Charles Artaria, meteorological instru- 



