CHEMICAL SCIENCE. 233 



CONSTITUTION OF THE ATMOSPHERE. 



M. LEWY has presented to the French Academy the result of a 

 series of researches on the constitution of the atmosphere, made in 

 Europe and in South America. The comparison of the results obtained 

 in these investigations with previous ones, shows that the constitution 

 of the atmosphere is nearly the same in the New and Old World. 

 However, on examining carefully all the experiments hitherto made 

 on the constitution of the atmosphere, it is readily seen that the consti- 

 tution of the air is not absolutely constant. Perceptible differences 

 exist, which vary with the meteorological conditions ; thus, after a 

 long rain, the carbonic acid and oxygen are always in smaller propor- 

 tion than after a long drought ; however, these differences are only 

 appreciable when the analysis has been carried out with very great 

 accuracy. In the New World, where the seasons are more defined than 

 in Europe, these variations are more easily detected. During the fine 

 season the normal air always contains a little more oxygen and a little 

 more carbonic acid than in the season of the rains. The difference 

 which exists between the atmospheric air of the two seasons is, there- 

 fore, on an average, 0.751 for the carbonic acid, and 2.653 for the oxy- 

 gen, in 10,000 volumes of air. The difference between the maximum 

 and minimum observed is somewhat greater, being 1,434 for the car- 

 bonic acid, and 4.167 for the oxygen. M. Lewy has also observed 

 that the amount of carbonic acid is somewhat greater on the high 

 mountains 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 contains a little more 

 oxygen and a little more carbonic acid than during the night. The 

 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 sea-water holds 

 in solution, and which, as is well known, contains more oxygen and 

 carbonic acid than atmospheric air. The difference between samples 

 of atmospheric air collected on the Atlantic, 400 leagues from land, on 

 the same day, and with the same wind, at 3 A. M. and 3 P. M., were 

 2.074 for the carbonic acid, and 9.960 for the oxygen, in 10,000 vol- 

 umes of air. 



The analyses of the abnormal air of New Grenada, S. A., present us 

 with results of great interest. From time to time, once or twice in 

 the year, the atmosphere of New Grenada contains an extraordinary 

 proportion of carbonic acid, which coincides with an appreciable de- 

 crease of oxygen, and consequently alters the constitution of the atmos- 

 phere in a very marked manner. The great number of volcanoes which 

 exist in the New World, and the clearing of forests, which are effected 

 every year in this country, may cause alterations. It is-, in fact, dur- 

 ing these clearances that the constitution of the atmosphere experiences 

 the extraordinary changes which have been just mentioned. These 

 clearings, which are effected by vast conflagrations, produce consider- 

 able quantities of carbonic acid, which, mixing with the atmosphere, 

 alter its composition. The amount of carbonic acid found in this air 

 was from ten to eleven times greater than in air in its normal condi- 



20* 



