Kneeland.] 46 [February 21, 
this fowed over them without being influenced by them; the form of 
the valleys and cafion was doubtless modified by the ice, which, had it 
produced them, would have greatly multiplied them, and have made 
these singular depressions the rule and not the exception ; and more- 
over the valleys would have borne in size a closer relation and pro- 
portion to the immense force that was at work over them. 
There seems no hypothesis left except the one given by Prof. 
Whitney, in the Geology of California, a hypothesis which his and 
_all subsequent investigations seem to me to strengthen, viz.: that dur- 
ing or after the upheaval of the Sierra, there was a subsidence, the 
bottom of these valleys sinking down to an unknown depth, the de- 
bris going to fill the abyss. During the glacial period they were filled 
with ice, which, gradually melting formed great lakes, imprisoned by 
moraines at the lower part; these have gradually been washed away 
by the floods, and scattered over the plains of the Merced, Tuolumne 
and San Joaquin meadows ; now only a small stream flowing along 
the bottom, which is slowly filling up, the small and comparatively 
undisturbed last terminal moraine extending across the valley about 
opposite El Capitan, the force of the diminished flood being enough 
to cut a passage for the Merced river without disturbing the glacial 
deposits above its highest level. 
Evidence of tremendous voleanic agency is not wanting in this re- 
gion. Some of the high peaks are found capped with lava; Mt. 
Dana, perhaps the highest, has its granite nucleus flanked with meta- 
morphic slates. This agency is even now active, as is shown by the 
hot springs and geysers which abound, and by the many severe 
shocks of earthquakes near the coast, of the extent and severity of 
the last of which, a few years ago, not the half of the truth has ever 
reached the public. : 
The general absence of debris on the sides —the splitting of the 
Half Dome, with its perpendicular face of nearly half a mile above 
the edge of the valley and facing it—such immense vertical masses 
as I] Capitan, can hardly be explaned by-any theory except that of 
subsidence. ‘This is an exceptional theory perhaps, but the phe- 
nomena are also exceptional. 
Whether this subsidence may have taken place during the Cham- 
plain epoch, which succeeded the Glacial period, future investigations 
must determine ; in either case, the valley must have been filled with 
ice, and the subsidence would seem especially liable to occur, whether 
from volcanic disturbance alone, or assisted by an immense weight 
