Natural Waters 41 



tively few soluble solids and gases furnish the still 

 smaller number of chemical elements that go to make 

 up the living substance. The amount of dissolved 

 solids varies greatly, being least in rainwater, and 

 greatest in dead seas, which, lacking outlet, accumulate 

 salts through continual evaporation. Here is a rough 

 statement of the dissolved solids in some typical waters : 



In rain water 30 40 parts per million 



In drainage water off siliceous soils 50 So 



In springs flowing from siliceous soils 60 250 



In drainage water off calcareous soils 1 40 230 

 In springs flowing from calcareous 



soils 300 660 



In rivers at large 120 350 



In the ocean 33000 37370 



Thus the content is seen to vary with the nature of 

 the soils drained, calcareous holding a larger portion of 

 soluble solids than siliceous soils. It varies with 

 presence or absence of solvents. Drainage waters from 

 cultivated lands often contain more lime salts than do 

 springs flowing from calcareous soils that are deficient 

 in carbon dioxide. Spring waters are more highly 

 charged than other drainage waters, because of pro- 

 longed contact as ground water with the deeper soil 

 strata. And evaporation concentrates more or less 

 the content of all impounded waters. 



All natural waters contain suspended solids in great 

 variety. These are least in amount in the well filtered 

 water of springs, and greatest in the water of turbu- 

 lent streams, flowing through fine soils. At the con- 

 fluence of the muddy Missouri and the clearer 

 Mississippi rivers the waters of the two great currents 

 may be seen flowing together but uncommingled for 

 miles. 



The suspended solids are both organic and inorganic, 

 and the organic are both living and dead, the latter 



