M. Lewy on the Constitution of the Atmosphere. 129 



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



The difference is therefore 2074 for the carbonic acid, and 

 9*960 for the oxygen in 10,000 volumes of air. 



The analyses of the abnormal air of New Granada present 

 us with results not less interesting. From time to time, once 

 or twice in the year, the atmosphere of New Granada con- 

 tains an extraordinary proportion of carbonic acid, which 

 coincides with an appreciable decrease of oxygen ; and, con- 

 sequently, alters the constitution of the atmosphere in a very 

 marked manner. 



The great number of volcanoes which exist in the New 

 World, and the clearing of forests which are ejffected every 

 year in this country, may cause these alterations. It is, in 

 fact, during these clearances that the constitution of the at- 

 mosphere experiences the extraordinary changes which I have 

 just mentioned. 



These clearings which are effected by vast conflagrations 

 in the country las quemas^ produce considerable quantities 

 of carbonic acid, which, mixing with the atmosphere, alter its 

 composition. The amount of carbonic acid which I found in 

 this air, rose in some analyses to 49 in 10,000 volumes of air. 

 It is consequently from 10 to 11 times greater than in the 

 air in its normal condition. The diminution of oxygen 

 amounted sometimes to 68-350 in 10,000 volumes of air ; in- 

 stead of 2101-425 oxygen, I found only 2033-075. This de- 

 crease is therefore readily detected even by less sensitive 

 methods than the one which I employed. 



On the other hand, the air of the table-land of Bogota 

 sometimes presents an amount of carbonic acid far greater 

 than the atmosphere of the Tierra caliente. This difference 

 may be explained either by the existence of volcanoes, which 

 are situated not far from Bogota, or by the more or less active 

 influence of the solar light. It will be conceived, in fact, that 

 in the Tierra caliente, where the temperature is very ele- 

 VOL. LII. NO. cm. — JANUARY 1852. I 



