OVEELAXD ROUTE OGDEN TO SAN FRANCISCO. 199 



the shore and may be watched even at considerable depth tlirough 

 the clear water as they dart over the bowlder-strewn bottom. 



There is a dam and headgate at the outlet mto Truckee Kiver by 

 which the lake level is raised a few feet during the spring, the surplus 

 water being released during the dry season, when it is most needed 

 for maintaining a full flow at the power plant below and for irrigation 



in Nevada. 



The statement sometimes made that '^Tahoe is an ohl volcanic 



r 



crater" is not true. The region about the lake shows evidences of 

 volcanic activity of various kindsj and the lake waters themselves 

 have probably been dammed at times by outpourings of lava. A b^va 

 flow appears to have temporarily filled the outlet chamiel below 

 Tahoe City. The lake, however^ lies in a strurturul depression — a 

 dropped block of the earth's crust. 



Pleistocene 



epoch tlie waters of Lake Tahoe stood much higher than now, prob- 

 ably on account of lava dams wliich have since been cut through. 

 Distinct beaches that mark former higher levels are found up to about 

 100 feet above the present lake, but it is believed that the waters for- 

 merly rose to still greater heights. At Tahoe City the 

 of these old beaches is a terrace 35 to 40 feet above the level of the 



m 



terrace that makes the level eroun 



Tavern is built. 



from 



point to point almost aU the way around the lake. (See PL XLYI.) 



West 



mile to the mouth of Donner Creek and then runs 



stream 



Here morainal deposits and forms characteristic of glaciation are 

 conspicuous. Huge bowlders of granite, brought here on the moving 

 ice during the glacial epoch, strew the surface on all sides. 



At milopost 206, by looking across Donner Creek, the traveler may 

 see a large white cross at the forward edge of a low terrace on the 

 opposite side of the valley. This is a monument to the Donner party, 

 wdiose tragic story is told at length in most of the histories of early 

 California emigrations. About half a mile above this cross, in the 

 woods near the lower end of Donner Lake, is a cube of granite 

 inscribed as follows: 



This stone marks the site of the Donner party cabins, where a monument ^rill be 

 erected under the auspices of the N. S. G, W. [Xative Sons of the Golden West] to the 

 pioneers who crossed the plains. 



Donner Lake and the pass now used by the railroad are particularly 

 dentified with one of the emigrations that preceded the great gold 

 rush to CaUfornia in 1849. Of these earher emigrations to the Pacific 

 coast there were two. The first was that to O^gon in 1843, Gnring 



