76 THE POPULAR SCIENCE MONTHLY 



Survey to study the eastern slope of the High Sierra and particularly 

 the basin of Mono Lake, he devoted several summers during the early 

 eighties to extended observations of the adjacent region. Although he 

 mapped the ramifications of a vast system of Quaternary glaciers, 

 flowing down from the cirques of the Snowy Eange, he adopted in toto 

 the theory first advanced by Professor Whitney that dislocations of the 

 cross-fractured granite, comprising the former bulk of the Yosemite 

 Basin, had caused the orographic block to subside to an unknown depth, 

 forming an appalling abyss. 



" Those who seek to account for the formation of the Yosemite," 

 Professor Eussell wrote, "by glacial erosion should be required to point 

 out the moraines deposited by the ice streams that are supposed to have 

 done the work." It is evident that he did not seriously consider the 

 four reputed moraines on the floor of the valley which King first dis- 

 covered. " The glaciers of this region," he continued, " were so recent 

 that all the coarse debris resulting from their action yet remains in the 

 position where it was left when the ice melted." In reply to this rea- 

 soning, John Muir insisted that sufficient time had elapsed since the 

 recession of the glacier from the Yosemite to permit the disintegration 

 of most of the detritus and its transportation to the lower levels by the 

 Merced Eiver. And Mr. Muir has strengthened his argument by 

 demonstrating the rapidity with which aqueous and aerial agencies 

 transform loose granite into sand. The extreme depth of the alluvium 

 in the San Joaquin Valley far below is undeniable evidence of the 

 decomposition of thousands of cubic miles of igneous rock, crushed by 

 the mills of the glaciers and conveyed by the ground-sluices of the 

 streams. A general conclusion reached by Professor Eussell was, in 

 his words, that 



The main work of sculpturing the Sierra Nevada and the production of the 

 variety of scenery for which these mountains are remarkable is to be attributed 

 to water erosion; while only minor features, such as the rounding and broaden- 

 ing of the bottom contours of valleys, the smoothing of the higher mountain 

 slopes, the polishing and striation of rock surfaces are to be referred to glacial 

 action. 



Still, the relative importance to be attached to each of the several 

 agencies at work in this wonderland remains to be estimated accurately 

 by the geological engineer. 



Le Conte and Later Investigators 

 Joseph Le Conte, the eminent geologist, author of the " Elements of 

 Geology," a standard manual for two generations, was one of the first 

 to survey the valley with the vision of an engineer. In his " Eamblings 

 in the High Sierra," an account of his first visit to this region in 1870, 

 appear his preliminary observations. His practical eye discerned the 

 peculiar petrography of the walls of the Yosemite. "Already, I ob- 



