178 GEOLOGICAL HISTORY OP LAKE LAHONTAN. 



nearly a universal solvent that all known mineral substances may be ex- 

 pected to occur in them. The recently discovered elements caesium and 

 rubidium were first obtained by Bunsen in the mineral waters of Durkheim 

 and Baden-Baden. It is to be hoped that a more minute examination of 

 the springs of this country may lead to a similar increase in our knowledge 

 of the constituents of the earth. 



OCEAN WATEES. 



Rivers with their loads of mineral matter in solution, derived both from 

 surface and subterranean drainage, commonly flow into the ocean and are 

 evaporated. The water rising in invisible vapor from the ocean's surface is 

 again condensed, and much of it falls on the land as snow, rain, and hail, 

 thus completing the cycle of changes. The mineral matter contributed to 

 the ocean in solution, together with the substances dissolved directly from 

 the bottom and sides of the oceanic basins, remains when the waters evap- 

 orate, and tends to increase the salinity of the sea. The precipitation of 

 mineral matter from the waters of the ocean or its assimilation during the 

 growth of plants and animals need not be considered at this time. 



The results of chemical investigations, particularly those of Forchham- 

 mer and the chemists of the Challenger Expedition, have shown that the 

 composition of the total solids dissolved in sea water from all portions of 

 the ocean — excepting in the immediate vicinity of the land or near the 

 mouths of large rivers — and for all depths, is remarkably constant. Disre- 

 garding the presence of the rarer substances, Dittniar gives llie average com- 

 position of the solids dissolved in sea water as follows : 



.81 



Chloride, of sodium 77. 7.')8 



Chloride of magnesium 10.878 



Sulphate of magnesia 4. 737 



Sulphate of lime 3.600 



Sulphate of potash 2. 405 



Bromide of inaguesiiim 0. 217 



Carbonate of lime 0. 345 



Total salts 100.000 



A table giving the com))osition of the waters of the ocean at many 

 localities, as determined by Professor Forchhammer,"^ is introduced here for 



*'The Voyage of H. M. S. Challenger, Phvsies and Chemistry, Vol.1, p. 204. 

 '■^Philosophical Transactions of Ilie linynl Siiciity of London, Vol. CLV, p. 257. 



