FOKMER GLACIATIOX OF THE SIERRA XEVADA. 35 



37^ 30', that is about the head of the San Joaquin and King's rivers, as in 

 the upper valleys of the Tuolumne. South of 36° the chain falls oft' at once, 

 and beyond that point to the south no trace of former glacial action has 

 ^been discovered by any member of the California Survey. 



Going north, on the other hand, froui the Tuolumne, the Sierra Nevada 

 diminishes rapidly in elevation, the passes sinking from 10,000 to 7,000 feet, 

 and the crest height being but little greater than the pass height. This 

 decreased elevation more than counterbalances the gain in latitude, so that 

 there are no more such jiroofs of long glaciers as that of the Tuolumne, 

 which was between forty and fifty miles in length, to be seen. The gla- 

 ciers about the head of the forks of the American River were large, it is 

 true, but not to be compared with those on the Tuolumne and the San 

 Joaquin. North of the head of the American, it would appear, from all our 

 observations, that the ancient glaciers were but small, and we saw but foint 

 traces of their former existence around Lassen's Peak, or in the region be- 

 3^ond that cone of nearly 11,000 feet in height, along the volcanic plateau 

 towards the foot of Mount Shasta. 



The region around Mount Shasta was only very hastily examined by the 

 Geological Survey, and no striking indications of former glaciation wei'e 

 observed around that great cone by any member of the corps at that time. 

 Later, Mr. King, as already mentioned, made a detailed exploration of the 

 mountain, and discovered abundant evidence of a previously greater ex- 

 tension of the glaciers now existing on its northern slope. 



The country north of Mount Shasta was examined al different times, both 

 by the writer and Mr. Ga-bb, as far north as Vancouver Island and New 

 Westminster on the Fraser River. What was observed in the course of those 

 explorations Avill be mentioned further on in this chapter. 



Returning now to the Sierra Nevada, for the purpose of giving the neces- 

 sary^ details in regard to the occurrence of the ancient glaciers of that range, 

 it will be desirable to fix as nearly as possible the most southerly point at 

 which unmistakable signs of former glaciation have been observed. 



Nothing has been seen, so far as known, of any glacial markings in the 

 high peaks and ranges of the southern part of the State of California. 

 Neither in the San Jacinto, San Bernardino, or San Gabriel ranges have 

 any such indications been observed. These ranges are from 8,000 to 11,000 

 feet in altitude, and cover an extensive area; but the latitude is too south- 

 erly. It is true that there are curiously deceptive appearances which are of 



