in various Substances. 



427 



To determine this question I made the following ex- 

 periments, the weather being clear and fine, the mercury 

 in the barometer standing at 27 inches 8 lines, the ther- 

 mometer at 19°, and the hygrometer at 44°. 



From these experiments it appears that the conduct- 

 ing power of air is very much increased by humidity. 

 To see if the same result would obtain when the experi- 

 ment was reversed, I now took the thermometer with 

 the moist air out of the boiling water, and plunged it in- 

 to freezing water ; and moving it about continually from 

 place to place in the freezing water, I observed the times 

 of cooling, as set down in the following table. N. B. 

 To compare the result of this experiment with those 

 made with dry air^ I have placed on one side in the fol- 

 lowing table the experiment in question, and on the 

 other side the experiment No. lo, made with the ther- 

 mometer No. 2. 



