GLACIATION OF THE SIERRA NEVADA. 25 



The most striking feature in this glaciated region is, that the extent of the 

 former glaciers Avas strictly in harmony with that of tlie elevated reo-ion 

 which was the field of supply for the ice-stream. A large area, at a suffi- 

 ciently high elevation, where the snow could collect and hecome consolidated 

 into ice, gave birth to a proportionately large glacier, just as now in the 

 Alps the Aletsch and the Corner glaciers, and the Mer de Glace, have at their 

 heads the largest amphitheatres, or cirques, and are consequently the longest 

 and best developed glaciers of the Swiss momitains. 



Before proceeding to a description of the phenomena of extinct glaciation 

 in the Sierra Nevada, it is desirable to say something in regard to the present 

 distribution of snow and ice in that range, and in the Cordilleras generally. 

 And in the first place it may be stated that there are no glaciers at all in 

 the Sierra Nevada proper, and none in the Great Basin or Rocky Mountain 

 ranges, at least south of the parallel of 42°. With the exception of some 

 recent discoveries said to have been made in 1878, in the Wind River Range 

 (about lat. 43°), by tlie U. S. geological surveying parties, of which no 

 definite account seems as yet to have been published,* it may be stated that 

 there are no proper glaciers anywhere within the limits of the United States 

 (Alaska not included), except around the great isolated volcanic cones of the 

 Pacific Coast. There .are certainly none in the highest portions of the Sierra 

 Nevada or the Rocky Mountains, these most elevated regions having been 

 sufficiently explored to ascertain that fact. The Wind River Range and 

 the region adjacent to it is considerably inferior in height to the peaks and 

 valleys around the South Park and the upper part of the Arkansas River; 

 but the difference of four degrees in latitude more than counterbalances the 

 difference of elevation, as respects the conditions necessary for the formation 

 of glaciers. 



The precipitation on the fianks of the Sierra Nevada is mucli larger on the 

 western slope than on the eastern, and it undoubtedly is considerably greater 

 near the summit tlian lower down on the slope. Unfortunately, statistics are 

 almost entirely wanting. It is well known, however, that the precipitation 

 is nearly all in the form of snow along the crest of the Sierra, and that it 

 falls in the winter months almost exclusively. Near the summit of the range 

 there is, in tlie sunnner, an occasional heavy thunder-storm, attended with a 



* Nothing seems yet to liave been published in regard to these glaciers, beyond the statement, in the Preliminary 

 Report of the Field Work of the U. S. Geological and Geographical Survey for the Season of 1878, that " three 

 genuine glaciers were discovered ou the east base of Wind River and Fiemont Peaks." Dr. Hayden informed the 

 writer that the largest of these glaciei-s might be jierhaps a mile in length. 



