THE WORK OF THE OCEAN. 325 



Aside from the ingredients shown in the above tables, the presence 

 of the following has been proved: iodine, fluorine, phosphorus, silicon, 

 boron, silver, lead, copper, zinc, cobalt, nickel, iron, manganese, alumi- 

 num, barium, strontium, arsenic, lithium, caesium, rubidium, and gold. 

 Oxygen, nitrogen, and carbonic acid gas are also 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, ^ 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 

 mineral matter which it contains may be readily calculated. Assuming 

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

 the 3.5% by weight becomes 1.4% by volume, and 1.4% of 323,722,150 

 cubic miles is 4,532,110 cubic miles. This then represents the aggre- 

 gate volume of mineral matter in the sea if it were precipitated and 

 compacted so as to have an average specific gravity of 2.5. Assuming 

 the average depth of the sea to be 2076 fathoms (12,456 feet), as 

 given by Murray, the mineral matter in solution, if precipitated, 

 would cover the ocean bottom to a depth of about 175 feet. Assum- 

 ing the area of the land to be to that of the sea as 28 to 72, this amount 

 of mineral matter would make a layer about 450 feet deep over the land. 

 Its amount is equal to about 20% of that of all lands above sea- 

 level, and it falls but little short of that in all lands below 600 feet in 

 altitude. If it were precipitated and concentrated in the shallow waters 

 about the borders of the lands, it w^ould fill the sea out to the depth of 

 about 4000 feet, and would diminish its area by some 19,000,000 to 

 20,000,000 square miles, an area which is more than \ of the present 

 land surface. In other words, if the mineral matter in the sea- water 

 were precipitated and concentrated in the shallow waters about the 

 lands, it w^ould restore the continental shelves to the land areas, and 

 add an almost equal area beyond. 



These comparisons may perhaps help to give some idea of the amount 

 of mineral matter in solution in the sea, but they give no more than a 

 hint of the importance of the solvent power of water in the general 

 processes of rock decay, for most of the substances carried to the sea in 



^ For a discussion of the way in which this gas is held in solution, see Tolman, 

 Jour, of Geol., Vol. VII, pp. 598-618. 



2 Murray, Scot. Geogr. Mag., Vol. IV, p. 39. 



