LAKES OF THE GEE AT BASIN. 11 



Ijy Quinn River, and it has been known to have a length of 50 or 60 miles, 

 with a breadth of 20. During the summer it disappears entirely, leaving 

 an absolutely barren plain of mud, Quinn River at the same time shrinking 

 back a hundred miles towards its source. The peculiar history of playas 

 and playa-lakes will be more fuU^^ described in connection with the physi- 

 ography of the Lahontan basin, which is the subject of Chapter III. 



A few lakes situated on the borders of the Great Basin have outlets, 

 and discharge their surplus waters into reservoirs at lower levels within the 

 area of interior drainage. These are of the same type as the ordinary lakes 

 of humid climates, with waters as pure and fresh as springs a,nd melting 

 snow can furnish. Their finest example. Lake Tahoe, lies just within the 

 western rim of the Great Basin, at an elevation of 6,247 feet, amid the peaks 

 of the Sierra Nevada. Its outlet, the Truckee River, flows downward with 

 a descent of 2,400 feet to Pyramid and Winneniucca lakes, whei-e the water 

 is evaporated, leaving the lower lakes charged with srda salts. Just within 

 the eastern border of the Great Basin lie Bear Lake and Utah Lake, the 

 former discharging its waters tlu-ough the Bear River and the latter through 

 the Jordan River to Great Salt Lake. These streams carry down from the 

 mountains their small percentages of saline matter, as a contribution to the 

 already saturated solution of the inland sea where . their waters are evap- 

 orated. 



It may be taken as a rule that all lakes which overflow are fresh, and 

 all lakes which do not find outlet become in time charged with mineral 

 salts. River water is never absolutely pure, but contains a small percent- 

 age of mineral matter, which is left behind when the water is evaporated. 

 Should this process continue long enough it is evident that a lake without 

 an outlet would in time become a saturated solution, from which the less 

 soluble mineral salts would begin to crystallize. 



The examination of those inclosed lakes of the Great Basin that are 

 comparatively fresh, and especially of the lakes occupying the Lahontan 

 basin, shows that salt lakes may in some instances become essentially fresh 

 without ovei-flowing. It has been suggested by Mr. G. K. Gilbert, in expla- 

 nation of this apparent anomaly, that a lake may evaporate to dryness and 

 its salts become buried beneath the deposits of playa-lakes, so that on the 



