350 MAN AXD THE GLACIAL PERIOD. 



the northeastern portion of the continent as usually esti- 

 mated. So, too, the andesites near Clear Lake, in Cali- 

 fornia, though beyond a doubt preglacial, have suffered 

 little erosion, and one of the masses, Mount Konocti (or 

 Uncle Sam), has nearly as characteristic a volcanic form 

 as Mount "Vesuvius." * 



This view of Mr. Becker is amply sustained by many 

 other obvious facts, some of which may be easily observed 

 by tourists who visit the Yosemite Park. The freedom of 

 the abutting walls of this canon from talus, as w T ell as the 

 freshness of the glacial scratches upon both the walls and 

 the floor of the tributary canons, all indicate a lapse of 

 centuries only, rather than of thousands of years, since 

 their occupation by glacial ice. 



The freshness of the high-level terraces surounding the 

 valleys of Great Salt Lake, in Utah, and of Pyramid and 

 North Carson Lakes, in Nevada, and the small amount of 

 erosion which has taken place since the formation of 

 these terraces, point in the same direction — namely, to a 

 very recent date for the glaciation of the Pacific coast. 



We have already detailed the facts concerning the for- 

 mation of these terraces and the evidence of their probable 

 connection with the Glacial period. It is sufficient, there- 

 fore, here to add that, according to Mr. Kussell and Mr. 

 Gilbert (two of the most eminent members of the United 

 States Geological Survey, who have each published mono- 

 graphs minutely embodying the results of their extensive 

 observations in this region),, the erosion of present streams 

 in the beds which were deposited during the enlargement of 

 the lakes is very slight, and the modification of the shores 

 since the formation of the high terraces has been insignifi- 

 cant. 



According to Mr. Gilbert : " The Bonneville shores 



* Bulletin of the Geological Society of America, vol. ii, pp. 196, 

 197. 



