128 M. Lewy on the Constitution of the Atmosphere. 



The difference which exists between the atmospheric air of 

 the two seasons is therefore on an average 0*751 for the 

 carbonic acid, and 2*653 for the oxygen in 10,000 vols, of 

 air. 



Taking the maximum and minimum of the results obtained 

 in the analyses performed during the two seasons, we have, 



During the rainy season. During the fine season. 

 Carbonic acid, . 3-609 5-043 



Oxygen, . . 2099-032 2103-199 



Azote, . . 7897-359 7891-768 



Volumes, 10,000*000 Volumes, 10,000-000 



The greatest difference amounts consequently to 1*434 for 

 the carbonic acid, and to 4-167 for the oxygen. These dif- 

 ferences are nearly the same as those which I found between 

 the atmospheric air of Paris and that of Havre, analysed 

 under meteorological conditions corresponding to the two 

 seasons of South America. 



It follows that the composition of the air which we breathe 

 is the same in Europe and in the New World as far as re- 

 gards the oxygen and the azote, whether it be taken at the 

 level of the sea, or at an elevation of 3000 metres ; the only 

 difference is the amount of carbonic acid, which appears, 

 especially on the high mountains, to be somewhat greater 

 than in the valleys, and on the sea-shore. 



With respect to the analyses of the air collected on the 

 ocean, they have yielded a very interesting result. In the 

 day-time this air constantly contains a little more oxygen, 

 and a little more carbonic acid, than during the night. This 

 difference becomes more perceptible as we leave the coasts ; 

 and it is probably owing to the solar rays, which, heating 

 the surface of the sea during the day, disengage a portion 

 of the gases which the sea-water holds in solution, and which, 

 as is well known, contains more oxygen and carbonic acid 

 than atmospheric air. 



Taking for term of comparison the specimens of atmo- 

 spheric air collected on the Atlantic, on the same day, with 

 the same wind, and at more than 400 leagues distant from 

 land, we find : — 



