THE SEA 13 



freezing of the surface, which removes nearly pure 

 water and leaves a large part of the salts behind. 



The uniformity of composition of ocean water is 

 of much greater importance than most people 

 suspect. Dr. Edwin B. Powers, of the Puget Sound 

 Biological Station, finds that fish are very sensitive 

 to changes in the carbon dioxide content of the water, 

 and suggests that the desertion of the shores by 

 herring after storms may be due to the mixing of the 

 carbon dioxide of the air with the sea-water by the 

 breakers, thus causing the herring to seek deeper 

 water of lower carbon dioxide content. Doubtless 

 slight changes in the composition of the ocean water 

 in one part of the sea accounts for some of the sudden 

 unexplained migrations of fish. 



The average salt content of a gallon of sea-water 

 is about a quarter of a pound. And, since the average 

 density of rock-salt is 2.24 times that of water, the 

 entire ocean, which has a volume of about 300,- 

 000,000 cubic miles, if dried up would yield 

 approximately four and a half million cubic miles of 

 salt. In the face of these figures, the extensive beds 

 of rock-salt at Stassfurt, Germany, and in Ohio, 

 Michigan, New York, and Kansas, seem trivial. 



In addition to the large number of salts, sea-water 

 contains considerable amounts of dissolved gases, 

 principally oxygen, nitrogen, and carbon dioxide, 

 and some small amounts of the inert rare gases, 

 argon, neon, krypton, and xenon. These gases are 

 derived chiefly from the atmosphere, but are not in 

 solution in the water in the same proportion in which 

 they occur in the atmosphere, as a larger proportion 



