A. THE ATMOSPHERE. 



CHAPTER n. 



CONSTITUTION, PHYSICAL CHARACTERISTICS AND MOVEMENTS 

 OF THE ATMOSPHERE; GEOLOGIC WORK OF THE ATMOS- 

 PHERE. 



COMPOSITION OF THE ATMOSPHERE. 



As already noted, the atmosphere consists of a mechanical mix- 

 ture of oxygen and nitrogen with some argon, the proportion in 

 pure dry air being: 



By weight. By volume. 



Oxygen 23 . 024 20 . 941 



Nitrogen 75-539 78.122 



Argon 1.437 0-937 



100.000 



Air is always impure, water vapor and carbon dioxide, as well as 

 various organic and inorganic impurities being generally present in 

 variable quantities. The average volumetric composition of the 

 gases of the atmosphere in parts per 10,000 is as follows (2g:86o) : 



Oxygen 2,065.940 Ozone 0.015 



Nitrogen 7,7ii -600 Aqueous vapor 140.000 



Argon (about) 79 . 000 Nitric acid o . 080 



Carbon dioxide 3 . 360 Ammonia o . 005 



In addition to this there is often found free hydrogen, up to one 

 part in 5,000 by volume (Gautier), methane, benzine and its homo- 

 logues, etc. Other compounds are formaldehyde (2 to 6 gr. per 

 100 cu. meters), and sulphur compounds, especially HoS, which be- 

 comes oxidized to SOo. Sulphur dioxide is also derived from vol- 

 canoes and the combustion of coal, and has been found at Lille 

 (France) to the extent of 1.8 cu. cm. of SO2 in i cu. meter of air. 

 It is returned to the ground as HoSO^ in rain water. So universally 



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