CHAPTER VI 

 THE WORK OF THE OCEAN 



A few facts concerning the depth of the ocean and the distribu- 

 tion of its water have been given on a preceding page (p. 5), and 

 reference to the origin of the ocean basins and the ocean will be 

 made later. We are concerned here chiefly with the geologic proc- 

 esses now going on in the sea; but a few facts concerning the sea- 

 \vaU-r and its life, and the topography of the ocean's bed, 1 may 

 well precede the study of the processes now in operation. 



Mineral matter in solution. Every 1,000 pounds of sea- water 

 contain about 34.40 pounds of mineral matter in solution. The 

 principal substances in the water are the following: 2 



Chloride of sodium 77 . 758 



Chloride of magnesium 10. 878 



Sulphate of magnesium 4 . 737 



Sulphate of calcium 3 . 600 



Sulphate of potassium 2. 465 



Carbonate of calcium o . 345 



Bromide of magnesium 0.217 



There are many other mineral substances in sea-water, and 

 the gases oxygen, nitrogen, and carbon dioxide are present in quan- 

 tity. The amount of the last is estimated to be 1 8 times that in 

 the atmosphere. 



The amount of sea- water is estimated at about 324,000,00x5 

 cubic miles, or about 15 times the volume of the land above sea- 

 level. The volume and composition of the sea-water being known, 

 the amount of its mineral matter may be calculated. Assuming 

 the average specific gravity of the mineral matter to be 2.5, the 

 3.5% (nearly) by weight becomes about 1.4% by volume, and 1.4% 

 of 324,000,000 cubic miles is 4,536,000 cubic miles. This represents 

 approximately the volume which the mineral matter of the sea 



1 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 

 Sun iid ings, and Agassiz's Tlie Three Cruises of the Blake. The Challenger Reports 

 give more detailed information for certain regions. 



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



I6 7 



