[ i8i ] 



little practice foon be convinced, 

 that by this method the degree of 

 falubrity of any air may be afcer- 

 tained with as much exactnefs as 

 the degree of heat and cold by the 

 thermometer of Reaumur; for the 

 difference of the remit will fcarce 

 exceed -~ of the two airs employed, 

 and it would be difficult to judge 

 upon the thermometer of Reaumur 

 of | of a degree of his fcale. 



Though I have for the moft part 

 made all my experiments according 

 to the prefent method of Mr. Fon- 

 tana, as I was not in poffeiiion of a 

 tube long enough to put the various 

 airs to the tell, according to the ori- 

 ginal method of the Rev. Dr. Priefl- 

 ley, with as much accuracy as I 

 could have wifhed, yet I made a 

 great many trials in a way not eflen- 

 %idllf different from his, by letting 

 N 3 up 



