THE WORK OF RUNNING WATER 325 



stances which have been extracted from the land and 

 brought into the lake by the rivers remain there, since 

 only pure water is evaporated. In this way lakes with- 

 out outlet become salt. Great Salt Lake in Utah is an 

 example of this. Some salt lakes, like the Caspian Sea, 

 were probably once a part of the ocean, so that they have 

 always been salt. 



As time goes on, more salt is brought to these lakes 

 without outlets, and they become more and more salty. 



LAKE DRUMMOND. 

 A lake in Dismal Swamp, Virginia, which is being filled by vegetable growth. 



Great Salt Lake has something like 14 or 15 % of solid 

 material in its water and the Dead Sea about 25%. An 

 effort to swim in these waters gives one an exceedingly 

 queer sensation. The buoyancy is so great that a large 

 part of the body is out of water, and one finds oneself 

 bobbing around like a cork. 



Depressions that are very shallow and are largely filled 

 with vegetable growths are called swamps. 



155, The Work of Running Water. Running water has 

 the power of carrying solid materials. If it is moving 

 slowly, this power is not great ; if moving swiftly and in 

 great volume, it is tremendous. The carrying power of a 



