ATMOSPHERIC GASES IN SEA-WATER 91 



the atmospheric pressure or by an increase in the température 

 of the water; in the other this is not the case, and the solution 

 in this latter case is not purely physical, but must be of a 

 chemical nature. Both kinds of solution are met with in sea- 

 water. For the most part, the oxygen, nitrogen, and argon 



South Pôle Cfiarfc 



FiG. 15.— South Polar Ice Limits. 



Outer limit of icebergs. 



Outer limit of pack-ice. 



of the atmosphère are absorbed according to physical laws, 

 but the atmospheric "carbon dioxide, partly at any rate, is 

 absorbed not strictly in accordance with thèse laws, and so its 

 solution falls into the second class above mentioned. 



The conditions under which gases are absorbed by water 

 are set out in détail in textbooks of physical chemistry. 



