[ xxi ] 



P be of confiderable practical ufe; 

 f and, particularly, that the air of 

 f diftant places and countries might 

 p be brought and examined together 

 *< with great eafe and fatisfac~tion i 

 & but I own, that hitherto I have 

 f* rather been difappointed in my 

 |S expectation from it." And he 

 concludes thus : & I have frequently 

 ** taken the open air in the moil 

 " expofed places in this country, at 

 different times of the year x and in 

 different ft ate s of the weather y 

 <kc. ; but never found the differ- 

 f ence fo great as the inaccuracy, 

 arifing from the method of 

 making the trial, might ealily 

 amount to or exceed," 

 Since Ifaw the manner of putting 

 different airs to the nitrous reft, 

 which Abbe Fontana now makes 

 ufe of, and which I have in my in- 

 b 3 quiries 



