62 THE OCEAN 



at the surface, and has been distributed by 

 currents and diffusion even into the deepest 

 parts. Nitrogen suffers no diminution, but the 

 oxygen is continually being used up by marine 

 organisms, in respiration during life, and in 

 putrefaction after death ; there is constant 

 renewal of the oxygen at the surface, but 

 were it not for the general circulation of its 

 waters, however sluggish the motion, the 

 proportion of oxygen in the depths of the 

 ocean might be reduced ultimately to zero. 

 Numerous analyses of deep-sea waters prove 

 the presence of absorbed oxygen everywhere, 

 so that in the open ocean not even at the 

 greatest depths is there absolute stagnation. 

 In some enclosed seas, like the Black Sea, 

 where vertical circulation is almost nil, there 

 is an absence of oxygen in deep water. 



Carbonic acid is found as a free gas in very 

 small quantities in sea-water, being more 

 abundant in combination as carbonates and 

 bicarbonates, so that though there may be 

 50 cc. per litre (or parts per thousand) of 

 carbonic acid in sea-water, only a few tenths 

 of a cc. is free gas in solution. The quantity 

 varies considerably, depending largely upon 

 the activity of plants and animals, and upon 

 atmospheric conditions. When there is much 

 carbonic acid in the air, as in regions near 

 land and near active volcanoes, much is 



