10 GEOLOGICAL HISTORY OF LAKE LAHONTAN. 



deserts and their channels run dry. In general they are larger near their 

 sources than at their mouths. Commonly, too, instead of being pure, spark- 

 ling waters, refreshing to the lips as well as to the eye, they are heavy with 

 sediment and bitter and alkaline to the taste. 



The lakes into which much of the surface drainage finds its way are 

 commonly saline and alkaline — their shores desert wastes, shunned by 

 animals and by all but salt-loving plants. Of the saline lakes, the typical 

 example is furnished by Great Salt Lake in Utah, an inland sea whose fea- 

 tures call to mind the familiar descriptions of the Dead Sea in Palestine. 

 Mono Lake in California, and Abert and Summer lakes in Oregon, are 

 also highl}' charged with saline matter, and are remarkable for the amount 

 of sodium and potassium salts which they contain. Pyramid, Walker, 

 Winnemucca, and Carson lakes in Nevada, as well as many smaller lakes 

 throughout the Great Basin, are also without outlets, but yet, contrary to 

 what we would expect, they hold but comparatively small percentages of 

 saline matter in solution. 



Other lakes, which indicate still more pointedly the contrast between 

 an arid and a humid climate, we may call pJaya-lakes. These are sheets of 

 shallow water, covering many square miles in the winter season, but evap- 

 orating to dryness during the summer, their beds becoming hard, smooth 

 mud-plains or playas. Li man}^ instances a lake is formed on a playa dur- 

 ing a single stormy night, only to disappear beneath the next noonday sun. 

 When the weather is unsettled these lakes are scarcely more permanent 

 than the delusions of the mirage, but come and go with every shower that 

 passes over the land. Other playa-lakes retain their integrity for a longer 

 period, and only become dry during excessively arid seasons. Examples 

 of these are furnished by Honey Lake in California, North Carson Lake 

 ("Carson and Humboldt Sink") in Nevada, and Sevier Lake in Utah, all 

 of which have been known to become dry during the past few years. The 

 water of playa-lakes has a greenish yellow color, due to the extremely fine 

 silt which is held in suspension and not allowed to settle, because every 

 breeze stirs the sliallow alkaline water to the bottom. A remarkable lake (>f 

 this class is sometimes formed in the northern part of tlie Black Rock Desert, 

 in Nevada, during extrcuu^ly wet seasons. Its water is furnished mainly 



