108 GEOLOGY. 



Potassium sulphate (K2SO4) 20,358 



Sodium nitrate (NaNOg) 26,800 



Sodium chloride (NaCl) 16,657 



Lithium chloride (LiCl) 2,462 



Ammonium chloride (NH^Cl) 1,030 



Silica (Si02) 74,577 



Ferric oxide (Fe^g) 13,006 



Alumina (Aip,) 14,315 



Manganese oxide (Mn203) 5,703 



Organic matter 79,020 



Total dissolved matter 762,587 



Murray also estimates that the aggregate amount of water flowing into the 

 sea annually is about 6528 cubic miles, which, on the above basis, would carry 

 about 4,975,000,000 tons of mineral matter in solution. 



A large number of analyses of waters of rivers from the United States and 

 Canada give an average of about .15,044 part in a thousand of mineral matter 

 in solution, more than one-third being CaCOs. The average amount of mineral 

 matter in solution in 48 European streams cited by Bischoff ' is .2127 part in a 

 thousand, of which CaCOj is rather more than half. The average mineral matter 

 in solution in 36 rivers cited by Roth' (including some of those tabulated by 

 Bischoff) is .2033 part in a thousand, of which CaCOg is slightly less than one- 

 half. 



An average for American and European rivers, so far as determinable from 

 data at hand, is about .1888 part in a thousand in solution, of which CaCO^ 

 is slightly less than one-half. These last figures are probably not very far from 

 an average for river water in general. 



The following table shows the total amount of solids carried in solution by 

 the rivers indicated:' 



Rhine 5,816,805 tons per year. 



Rhone 8,290,464 



Danube 22,521,434 



Thames 613,930 



Nile 16,950,000 



Croton 66,795 



Hudson 438,000 



Mississippi 112,832,171 



ECONOMIC CONSIDERATIONS. 



Certain considerations of human interest in connection with river 

 eorsion are worthy of note. When a drainage system has reached its 



1 Chemical Geology, Vol. I, pp. 76, 77, English ed., 1854. 

 ^Allgemein und chemfeche Geologic, Vol. I, pp. 456, 457. 1879. 

 3 Russell. Rivers of North America, p. 79. 



