294 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



there was an unusually heavy snowfall in the Sierra Nevada 

 and the banks of snow that remained in the range during 

 the entire summer following were much larger than usual. 



y. Evidence of Trvo Periods of Glaciation. 



In Europe there are evidences of two periods of maxi- 

 mum glaciation, an interglacial period intervening, during 

 which the animals and plants that had been driven south by 

 the increasing cold of the advancing ice returned to more 

 northern latitudes. The remains of these animals and 

 plants are found in the deposits of this interglacial period. 

 There appears also to be evidence that at this time a subsi- 

 dence occurred and that much of Great Britain was 

 submerged. 



In the eastern United States likewise, Chamberlin and 

 others recognize what they regard as good evidence that 

 such an interglacial epoch^ existed in North America, prob- 

 ably contemporaneous with the European period. In the 

 eastern United States and in Europe the glaciation of the 

 second epoch was not so extensive as that of the first, and 

 thus Gilbert's conclusion that the maximum of glaciation in 

 the Cordilleran region occurred in the second glacial epoch 

 of that region does not bring the phenomena of glaciation 

 of the Cordilleras into complete harmony with the phenom- 

 ena observed elsewhere. The imperfect evidence here- 

 after presented, suggesting that there were two glacial 

 epochs in the Sierra Nevada, implies that during the first 

 epoch the ice was more extensive than during the second 

 epoch, and this plainly harmonizes with the results obtained 

 in the northern United States and in Europe. 



During early Pleistocene time the Great Basin contained 

 a large number of lakes. Remnants of these still exist, 

 but the surface now covered by the lake waters is trifling 

 compared with the surface so covered in early Pleistocene 

 time. There is here indisputable evidence that the climate 



1 The interglacial epoch here referred to is the first or main epoch. More than one 

 interglacial epoch is recognized by some geologists but there appears to be a marked 

 difference of opinion on this point. 



