136 



PROCEEDINGS OP THE ACADEMY OP 



[1883. 



scended several thousand feet during tertiary times. Mr. C. King ^ 

 states that the fault along the eastern edge of the basin amounts 

 to 30,000 feet, and that along the western border, from 3000 to 

 10,000 feet. The elevation of P3'ramid Lake above the sea level 

 is now, according to King,^ 8890 feet. That of the Great Salt 

 Lake is, according to Emmons, 4200 feet.^ The depression, 

 according to King, took place on the eastern side during early 

 eocene times, and ma}^ have been nearly simultaneous on the 

 western border. As a consequence of it, the Manti and Amyzon 

 beds were deposited, representing the eocene period west of the 

 Wasatch Mouirtains. 



I. The Lahontan and Klamath Lakes. 

 The lakes of the Great Basin in Nevada and Oregon diminish in 

 alkalinity as we approach the Sierra Nevada Mountains. While 

 desiccation has concentrated the salts in all of them, those near 

 the mountains have been maintained in a more or less fresh con- 

 dition b}' the constant influx of the pure water of the mountain 

 streams. The lakes most remote from the mountains are not 

 habitable by fishes, their only animal population being Crustacea 

 and the larvae of insects. Such are Summer and Christmas 

 Lakes of Oregon ; and the Malheur and Harney Lakes are said 

 to have the same character. That of Pyramid Lake, although 

 receiving the fresh waters of the Truckee River, is too alkaline 

 to be potable. The following analysis is given in Mr. King's 

 II Yol. of the Survey of the 40th Parallel (p. 824), as made by 

 Prof. 0. D. Allen, of Yale College : 



3'23G5 



in 1000 parts of the water. 



1 Survey of the 40th Parallel, i, p. 744. 

 " Loc. cit., iii, p. 822. 

 * Loc. cit., ii, p. 466. 



