C 160 1 



dephlogifticated air if it be very 

 pure. 



What has been already faid of 

 this method of putting different airs 

 to the nitrous teft will be fufEeient* 

 I hope, to guide the reader in imi- 

 tating it. But he will find in the 

 refult of every trial, made with the 

 fame fpecies of air, lb much differ- 

 ence, that he would miflruft the 

 whole method if he did not obierve 

 every minute circumftance in the 

 courfe of the whole experiment* 

 It has coft the Abbe fome years afli- 

 duous labour before he reduced this 

 r . method to that degree of accuracy 

 which it has now acquired in his 

 hands. 



Thofe who with to perform this 

 amufing experiment themfelves 

 will think it worth their while to 

 look over the following neceffary 



cautions 



