CHAPTER VI. 



THE WORK OF THE OCEAN. 



The general facts concerning the depth of the ocean and the distri- 

 bution of its water have been given on a preceding page (p. 8), and 

 the origin of the ocean and the ocean basins is discussed in the second 

 volume. This chapter has to do primarily with the processes now going 

 on in the sea and its borders, in so far as they are of importance in the 

 interpretation of geologic history. The study of these processes is 

 prefaced by a few words concerning the amount and composition of 

 the sea-water, the Hfe of the ocean, and the topography of its bed.^ 



Volume and composition. — Every 1000 parts of sea-water contain 

 about 34.40 parts by weight of mineral matter in solution. The prin- 

 cipal soUds, acids, and bases, combined according to the principles laid 

 down by Dittmar, are shown in the following table: ^ 



Chloride of sodium 77 . 758 



Chloride of magnesium 10 . eS78 



Sulphate of magnesium 4 . 737 



Sulphate of calcium 3 . 600 



Sulphate of potassium. 2 . 465 



Bromide of magnesium. . . 217 



■ Carbonate of calcium . 345 



Total salts 100 .000 



Expressed in terms of tons per cubic mile of sea-water, the com- 

 position is as follows : ^ 



Tons per Cubic Mile. 



Chloride of sodium (NaCl) 117,434,000 



Chloride of magnesium (MgCy 16,428,000 



Sulphate of magnesium (MgSO^) 7,154,000 



Sulphate of calcium (CaSO^) 5,437,000 



Sulphate of potassium (K2SO4) 3,723,000 



Bromide of magnesium (MgBr,) 328,000 



Carbonate of calcium (CaCOg) 521,000 



For sea-water, total dissolved matter 151,025,000 



^ Much information on these and other points is to be found in the following books: 

 Wild's Thalassa; Thompson's Depths of the Sea; Barker's Deep Sea Soundings, 

 and Maury's Physical Geography; Agassiz' The Three Cruises of the Blake, and the 

 Challenger Reports give much more detailed information concerning these and other 

 matters. 



2 Dittmar, Challenger Reports, Physics and Chemistry, Vol. I, p. 204. 



324 



