72 



GEOLOGICAL HISTOEV OF LAKE LAHONTAN. 



Soundings macJe by Professor Le Conte, beginning at the northern 

 enci, near the "Lake House," and advancing along the longer axis of the 

 lake directly north towards the "Hot Springs," at the northern end, give 

 depths of from 900 to 1,645 feet 



Between the 11th and the 18th of August, 1873, Professor Le Conte 

 made a large number of temperature measurements at different deptlis in 

 the lake, an abstract of which is here copied: 



Professor Le Conte's paper also contains many valuable observations 

 on the transparency and color of the lake water, and on rhythmic variations 

 of level. An analysis of the water of Lake Tahoe has already been 

 given on page 42. 



Besides Lake Tahoe, there was another lake among the mountains of ' 

 Northern California during Quaternary times which was tributary to Lake 

 Lahontan. This was a comparatively shallow water body that occupied 

 the basin now known as the Madeline Plains. A small stream from Horse 

 Lake Valley joined that draining the Madeline Plains; as did also the 

 waters escaping from Eagle Lake, which, without evidence to the con- 

 trary, we may consider to have discharged, tlien as now, through beds 

 of gravel beneath a lava couliie. 



