Clarke.] 260 [January 15, 
Here in the Mt. Lyell group we learn the first rudimentary les- 
sons in the great work of glaciers, and after studying them we are 
better prepared to understand their agency in the formation of the 
Yosemite and other cafions of the Sierra Nevada. When we see 
the great number of streams of ice, and their great depth, carrying 
along great quantities of rock, grinding and wearing as they are 
crowded onward, and all concentrating into one great flow, like so 
many streams of water uniting to form a vast river, — we cannot but 
feel impressed with their wonderful agency in forming the Yosemite 
and other great cafions and lakes in the Sierra Nevada. Everywhere 
above the Yosemite and on each side we find the great moraines of 
boulders, and the polished and striated rocks, showing the direction 
of the flow as plainly as if it were flowing at the present day. 
I also went with Mr. Muir to explore the great Tuolumne Cajion, 
which from the Hetchy Valley below to the great meadows and soda 
springs above, a distance of over twenty miles, had never been ex- 
plored by any white man, and its general character was entirely un- 
known. 
After examining the region around the headwaters of the Yosemite 
Creek, which Seams the Yosemite Falls, we went directly to the 
Hetch-Hetchy Valley, which may be eatied the counterpart of the 
Yosemite on a smaller scale. The highest fall in this valley is eigh- 
teen hundred feet, but not perpendicular. It is a very beautiful val- 
ley, and probably will be more visited in future years. At its upper 
part we left our horses and packs, took our blankets and a few days’ 
provisions on our backs and started for the primeval forest. 
It was one of the most interesting trips I ever made, although a 
very hard and fatiguing one. “sas every moment was one of 
great interest throughout the whole distance of over twenty miles. 
The walls of the cafion are from three to four thousand feet above the 
river, — not perpendicular, but standing back at an angle of about 
sixty degrees, — and nearly the whole distance worn and polished 
by glaciers from top to bottom. There is but one place in the whole 
distance where it widens out into a valley of trees and grassland. 
Most of the distance the steep mountain sides come clear down to the 
water on both sides of the river. Sometimes we had to wade up the 
river, there being no foothold on the rocks on either side. In many 
places we climbed over immense boulders, which had fallen from 
above. One boulder formed a bridge across the river. In other 
places we crawled on our hands and knees under the chaparrel 
