THE OCEAN 



171 



appreciable. Accordingly, the regulation is 

 physiologically adequate. 



The concentration of sea water is another 

 nearly constant characteristic, though gener- 

 ally speaking the salinity is somewhat greater 

 on the high seas than near the coasts, where 

 fresh water is constantly diluting the salt 

 water, and there are some other causes which 

 produce slight variations. The average salt 

 content is about 3.45 per cent. The quan- 

 tities of the more important constituents, 

 calculated from Dittmar's data, 1 are as fol- 

 lows : — 



Sodium, Na . 

 Magnesium, Mg 

 Calcium, Ca . 

 Potassium, K 

 Chlorine, CI . 

 Sulphate, SO4 

 Carbonate, CO3 

 Bromine, Br . 



Most of the other numerous constituents are 

 present in very small quantities. For in- 

 stance, in each metric ton of sea water there 



1 Dittmar, Report of Voyage of the Challenger, 1884, p. 

 203. The original data were calculated upon the erroneous 

 assumption that the various salts exist in solution independ- 



