HANGING VALLEYS OF THE YO SEMITE 55 I 



of the Bridal Veil fall is a notch that may have been formed in 

 the fashion here indicated ; but if it was made in this manner, it 

 does not at present overlap the end of the valley trough where the 

 fall is. Seen from the Coulterville road across the valley to the 

 north, it looks as though a stream on the east side of the Bridal 

 Veil glacier may have fallen through the deep notch that opens 

 on the side of the valley toward Cathedral Rock. I cannot say 

 positively that this happened, however, for I did not go above 

 the fall to look for the evidence. 



It is worthy of note that in both instances where the falls 

 occur in pairs, namely at the Yosemite (upper and lower falls) 

 and at the Nevada and Vernal falls, narrow subglacial channels 

 are cut between. This was to have been expected. When the 

 ice broke at the upper fall, the water flowing from above entered 

 the crevasses below and flowed as subglacial streams at least as 

 far as the lower falls. 



Since the glacial epoch the rocks have exfoliated and dis- 

 integrated so rapidly that ice marks are still visible at less than 

 a dozen places on the exposed surfaces of the Yosemite valley 

 walls. At the top of Vernal falls a dark inclusion in the flat 

 granite surface preserves the ice marks perfectly, but the 

 surrounding rock has disintegrated to a depth of fully two inches 

 since the melting ice uncovered the spot. Similar instances may 

 be seen above the Nevada fall and about Inspiration Point on the 

 road from the valley to Wawona. Everywhere the exposed sur- 

 faces are rapidly going to pieces. The same agencies must have 

 hastened the formation of the valley before the glacial epoch. 



The evidence of the falls at the mouths of the hanging valleys 

 shows that the wearing done by the ice was trivial as compared 

 with the wearing done by the glacial streams. The subglacial 

 streams also cut channels beneath the ice a great deal faster than 

 the ice alone cuts the broader floors over which it moved. 



Considered alone, these canyons overlapping the streams that 

 enter them from above afford evidence that the period since the 

 glacial epoch has been very short as compared with the length 

 of the glacial epoch itself. 



I venture to add that I quite agree with Mr. Turner's views of 



