■ REVELATIONS OF THE YO SEMITE VALLEY 71 



sawing of corrasive forces. The pinnacled Cathedral Spires and Kocks, 

 the wrinkles of the Three Graces and the creases of Three Brothers 

 most distinctly illustrate the differentiation of zones of more friable, 

 granitic materials. Beneath one's feet is the remarkable floor of the 

 valley, whose gradient is but little more than a foot of fall to the 

 mile. Far above the rim of the main gorge of the Merced are dozens of 

 "hanging valleys" cut off abruptly by the transverse trend of the 

 precipitous walls of the Yosemite Basin. Above and beyond rise an 

 ascending series of polished domes and U-shaped troughs culminating 

 in the serrated crest of the High Sierra. Its eastern slope affords a 

 most striking contrast to the gentler gradient towards the Pacific. 

 The sunrise-fronting spurs of the Sierra plunge abruptly at a high 

 angle down to the Mono plain seven thousand feet below. Alternating 

 with steep escarpments, are deep-carved canons descending giant stair- 

 cases, whose hollowed treads are frequently filled with azure lakelets. 

 Beyond, over the drab desert, arise an array of dead " fire-mountains," 

 recording an important chapter in the history of the High Sierra. 



According to Professor Joseph Le Conte, this mighty range was 

 born out of the ocean during the Jurassic period, the strata bulging, 

 mashing and crumpling as it yielded to horizontal pressure. Its first 

 physical appearance in the poetic diction of John Muir was as " one vast 

 wave of stone in which a thousand mountains, domes, canons and ridges 

 lay concealed." Geologists agree that the original crest of the Snowy 

 Eange was in the vicinity of the Yosemite Valley, but, at the end of 

 the Tertiary and the beginning of the Quaternary periods, the Sierra 

 block was tilted upward by volcanic upheavals which burst forth all 

 along its eastern border. The Sierras were pitched en masse in a 

 steep slope toward the west, while a great fault system produced the 

 precipitous escarpment towering above the desert. Consequently, the 

 crest of the range was transferred to its eastern rim. Throughout the 

 Quaternary period, a newer system of rivers, accelerated by the in- 

 creased inclination of their watersheds, cut their beds deeper and 

 deeper along the lines of least resistance. Then followed an "over- 

 deepening" of these stream courses by corrasive forces of far greater 

 potentiality than the agency of running water. 



Early Hypotheses 



The fact that no concordance in the conjectures of geologists exists 

 is probably due to their different earlier environment and experience. 

 Some were more familiar with the phases of stream erosion, others 

 had studied the folding of sedimentary rocks, while certain savants 

 were so carried away with their theory of glaciation that, in their 

 imagination, they could only see the Sierras buried beneath a sea of 

 ice a thousand fathoms deep. More who came to guess at its genesis, 

 remained firm in their faith that " the bottom of the Yosemite dropped 



