COMPOSITION OF THE ATMOSPHERE. 81 



ence in this kind of work to aflfirm that the general differ- 

 ence which is found in this table could not result from 

 errors of observation. 



" It remains for me to discover if this difference is main- 

 tained in the middle of winter, or when vegetation is 

 inactive. 



" The air taken at the middle of Lake Leman, opposite 

 to Chambeisy, contains on an average a little less car- 

 bonic acid than the air taken a hundred toises from the 

 bank. After eight observations, made at different periods, 

 on the same days at noon the quantities of carbonic acid 

 at the two stations are as loo to 98*5; but the air of 

 both places follows the same variations relatively to the 

 seasons. 



" The air of Geneva contains more carbonic acid than the 

 air of a meadow at Chambeisy— almost in the ratio of 100 

 to 92, from six observations made at the same time at both 

 stations. A greater purity in the air of the country could 

 be foreseen. I cite this result only because the other 

 eudiometrical experiments indicate no difference in the air 

 of those two places, and as it shows the utility of the ex- 

 periment by which this result was obtained." 



At first Saussure was led to believe that rain increased 

 the carbonic acid, but changed his mind on finding, on 

 the contrary, that this acid increased in dry weather even 

 with a freezing temperature. 



