THE PHYSIOLOGY OF DEEP-SEA LIFE. 297 



The quantity of carbonic acid in the water is not yet definitely 

 settled. Water kept for several years is of no use for analyses. 

 Dittmar found that free carbonic acid in sea-water is the excep- 

 tion : as a rule, carbonic acid is less than the proportion cor- 

 responding to bicarbonate. In surface water the carbonic acid 

 increases when the temperature falls, and vice versa. Within 

 equal ranges of temperature, it seems to be lower in the Pacific 

 than in the Atlantic. The alkalinity of bottom waters was 

 found to be distinctly greater than that of surface water. There 

 is in sea-water salts a distinct preponderance of free over fixed 

 acid, the difference being probably due to carbonates. Dittmar 

 says that sea-water, even when alkaline, takes up additional car- 

 bonate of Hme, if sufficient time is given. 



The only source of oxygen and nitrogen present in sea-water 

 is in the atmosphere, their quantity being dependent on surface 

 conditions, and not on the depth. Thus, owing to the constant 

 oxidation which goes on, sea-water must continually be losing 

 its oxygen in proportion to the dejDth. Dittmar found that 

 there was nothing characteristic of bottom waters, as such, in 

 regard to their absorbed gases, — nothing to distinguish them 

 from waters of intermediate depths. With reference to the ab- 

 sorption of oxygen and of nitrogen by sea-water, the amount 

 of air which ought theoretically to be absorbed by sea-water 

 of the temperature and at the pressure at which samples were 

 collected was calculated ; from the quantity of nitrogen found, 

 the amount of oxygen which shoidd be associated with it was 

 reached. 



The quantity of air found is usually less than what is theo- 

 retically called for, — probably from the fact that the water in 

 the ocean is always in motion, the temperature and pressure 

 varying greatly with the locality. Air is not taken up in deep 

 water ; it is absorbed elsewhere at the surface, and its presence 

 at any point is due to the constant movement of the waters. 



There is no definite relation in the ratio of carbonic acid to 

 oxygen present over any area. It seems to depend not so much 

 on the depth as on the abundance and character of the fauna 

 found at certain depths. From the action of the waves, oxygen 

 finds its way down from the surface, and is resorbed subse- 



