1872.] ST [Kneeland. 
these marks are plain on the Sentinel Dome, 4,150 feet above the 
valley, and the Society have seen, and will soon be in possession of, 
a slab from Tenaya cafion polished by the ice, brought home by Mr. 
Waterston, which I have here. This glacier filled the upper or little 
Yosemite valley, a counterpart of the larger one, but 2,000 feet 
higher, communicating with it above the Nevada fail, the main stream 
of the Merced river flowing through both. Also, a glacier passed 
down the Ililouette cafion from the Obelisk group to the edge of the 
oreat valley. It has been generally assumed that the land at the 
head of the Merced river was not high enough for the formation 
of a glacier into the valley. | 
Now comes the question, which Mr. Muir proposes to discuss: Was 
the valley once occupied by a glacier ? 
The following are Mr. Muir’s observations, almost‘in his own words, 
in a recent letter to Prof. Runkle : 
“J have been over my glacial territory, and am surprised to find 
that it isso small and fragmentary. The work of ancient ice, which 
we proposed to christen ‘glacial system of the Merced,’ is only a few 
tiny topmost branches of one tree in a vast glacial forest. The 
Merced ice basin was bounded by the summits of the main range, 
and by the spurs which once reached to the summits, viz., the Hoff- 
man and Obelisk ranges. In this basin not one island existed, for all 
of its hizhest peaks were overflowed by the ice, Mt. Starr King, South 
Dome, and all. Vast ice currents broke over into the Merced basin 
from the Tuolumne, and most of this Tuolumne ice had to cross the 
Tuolumne cajion. 
“Tt is only the vastness of the glacial pathways of this region, that 
prevents their being seen and comprehended at once. A scholar 
might be puzzled with the English alphabet, if it were written large 
enouch, and if each letter were made up of smaller ones. 
“The beds of these vast ice-rivers are veiled with forests, and a 
network of small water channels. The sketch shows that Yosemite 
was completely overwhelmed with glaciers, and they did not come 
down gropingly to the main valley of the Merced by the narrow, 
angular, tortuous cafions of Tenaya, Nevada and Illilouette, but they 
flowed grandly and directly above all of its highest domes, like a 
steady stream, while their lower currents went mazing down in the 
crooked and dome-blocked channels of cafions. 
“Glaciers have made every mountain form of this whole region; 
_ even the summit mountains are only fragments of their pre-glacial 
