EIVEES OF THE LAHONTAN BASIN. 43 



The sample, the analysis of which is reported, was collected in October, 

 1882, on the eastern border of the lake near Glen Brook, one mile from 

 shore and one foot below the surface. 



The most interesting feature to the geologist in the present condition 

 of the Truckee River is its bifurcation shortly before reaching Pyramid 

 Lake. As represented on Plate IX, the stream divides so as to deliver a 

 part of its waters to Pyramid Lake and a part to Winnemucca Lake. The 

 branch entering Pyramid Lake has the ordinary features of a river winding 

 through an alluvial bottom, and has formed a low-grade delta of broad 

 extent, as shown on the map. The waters that are tributary to Winne- 

 nuxcca Lake leave the main stream at nearly a right angle and flow through 

 a deep narrow channel carved in Lahontan sediments. This stream, or 

 "slough," when measured in September, 1882, had a volume of 2,400 cubic 

 feet per second From the manner in which the bifurcation takes place it 

 cannot be considered as the breaking up of a stream on a delta or an 

 alluvial slope, as in the case of the Carson River after entering the Carson 

 Desert, but must have been originated by the waters overflowing from 

 Pyramid to Winnemucca lakes, or vice versa. This matter, however, will 

 receive further consideration in connection with the fluctuation of Pyramid 

 and Winnemucca lakes (page 63). 



CARSON RIVER. 



The Carson River rises on the eastern slope of the Sierra Nevada, south 

 of Carson City, and, after flowing 60 or 70 miles, enters the Lahontan basin 

 through a deep canon at Dayton. From this point to the Carson lakes its 

 course is through a channel carved in Lahontan lake-beds. Near its mount- 

 ain source its waters are fresh and pure, as mountain streams usually are, 

 but in passing through Carson and Eagle valleys, once occupied by Qua- 

 ternary or late Tertiaiy lakes, its waters become somewhat impregnated 

 with soda salts, and in its course through Lahontan lake-beds this percent- 

 age is increased. The waste from a large number of stamp-mills now pol- 

 lutes the river to such an extent that it was not thought desirable to have 

 its waters analyzed. The valley of the Carson from Eagle Valley to Carson 

 Desert was largely excavated by stream erosion in pre-Quaternary times, 



