COMPOSITION OP THE ATMOSPHERE. ] 7 



The meaning of these numbers may be further illus^ 



trated. Let us put together all the deviations from 2 1 per 



cent, in air from the front of the laboratory and from less 



pure places (the front may not, after all, give the best air), 



we have — 



From backs of houses 

 Good air. ' and impure places. 



•lO '20 



•04 -15 



•02 . '21 



•10 '28 



•lo '13 



•02+ '24 



•04 -41 



•22 '15 



•17 'lO 



•09 79 



•08 "42 



•13 -26 



•024- '60 



•00 '27 



•17 'oi 



•02 "30 



■12 "12 



•01+ '54 



•13 -44 



•08 '21 



•02+ '36 



•12 '06 



•09 "33 



•08+ -47 



•04 '29 



•08 

 '01 



•OS 

 •02 

 •01 

 •01 

 •06 



Average 0*065 (sub- Average '293 



tracting those with ■^-). 



This is a remarkable illustration, to my eye, and a conclusive 

 proof. 



The results are very distinct; there is nothing exagge- 

 rated about them. There are no great deviations to astonish 

 us ; and there are so many irregularities, that if two or three 

 analyses only were made the effect would be bewildering 

 or uncertain : by making numerous analyses we are able to 



SER. III. VOL. III. c 



