ae 
this farmer, 1779, | muft firt 
acquaint the reader, that the me- 
thod which I generally purfued, in 
putting the different fpecies of air 
to the nitrous teit, was the fame 
which the celebrated Abbé Fontana 
makes ufe of now, and of which — 
he himfelf -has not yet given an 
ng to the: “publick. as t had 
tion | of his method, or to ante ne ae 
the publication of it without his 
leave, I have afked his confent on 
this head, He agreed to my re- 
queit very ‘readily, gave me his 
“Notes to confult, and eyen permitted _ 
me to get his inftruments engraved; 
for which purpofe he allowed me . 
to make ufe of his own drawi ings. 
_As he had already fhewp mehis — 
method of examining the AiR a 
shins of gir in regard to their deg | 
