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this fummer, 17793 I mnft firft 

 acquaint the reader, that the me- 

 thod which I generally purfued, in 

 putting the different ipecies of air 

 to the nitrous teit, was the fame 

 which the celebrated Abbe Fontana 

 makes ufe of now, and pf which 

 he himfelf has not yet given an 

 account to the publick. As I had 

 no right either to claim the inven- 

 tion of his method, or to anticipate 

 the publication of it without his 

 leave, I have aiked his confent on 

 this head. He agreed to my re° 

 quell very readily, gave me his 

 notes to confult, and even permitted 

 me to get his inftruments engraved ; 

 for which purpofe he allowed me 

 to make ufe of his own drawings. 



As he had already ihewn me his 

 method of examining the different 

 kinds of air in regard to their degree 



of 



