CHAPTER VII 

 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. 6), and 

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

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

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

 water 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 parts of sea-water 

 contain about 34.40 parts by weight of mineral matter in solution. 

 The principal solids are shown in the following table : 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 



Bromide of magnesium .217 



Carbonate of calcium . 345 



The presence of many other mineral substances in sea-water 

 has been proved, and oxygen, nitrogen, and carbon dioxide are 

 present in quantity. The amount of carbonic acid is estimated 

 to be 18 times as great as in the atmosphere. 



The amount of sea-water is estimated by Murray at 323,722,150 

 cubic miles, 3 or about 15 times the volume of the land above sea- 

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



1 Much information on these and other points is to be found in the follow- 

 ing books: Wild's Thalassa; Thompson's Depths of the Sea; Barker's Deep 

 Sea Soundings, and Maury's Physical Geography. Agassiz's The Three 

 Cruises of the Blake, and the Challenger Reports give much more detailed 

 information for certain regions. 



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



3 Murray, Scot. Geog. Mag., Vol. IV, p. 39. 



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