860 Twin Lakes and Teocalli Mountain, Central Colorado. | Dec., 
and one and a-half miles in width, the upper lake is one mile in 
length and a-half mile in width. As we have stated before, the 
greatest depth was found to be seventy to seventy-six feet. The 
Lake creek rises about twelve or fifteen miles away, at the crest 
of the Wasatch range, and flows through a deep gorge or cañon, 
with signs of glacial erosion its entire length, and as it issues 
from the mountains into the main valley, has become a consider- 
able stream. These lakes are really expansions or basins in this 
stream and a part of it. That these lakes have been slowly 
diminishing in area, we know by the land bordering on both of 
them. Above the Upper Twin lake, there is a half mile in width 
of boggy meadow, which at no distant period must have been 
covered by the lake. At the head of the valley, or where the 
gorge begins, there is a sort of natural bridge, where the stream 
has worn a narrow channel through the rocks. At the summit 
the gorge is about eight feet wide, and in it a huge boulder has 
lodged. The stream rushes down its steep, narrow, winding 
channel with great force. On the north side there is a huge — 
boulder just ready to topple off into the channel, which is fifty 
feet in diameter. On the sides of the channel are several most 
remarkable rounded cavities worn in, like pot holes, six to ten feet 
in diameter. One of these occurs twenty feet above the water level 
of the creek at the present time. The worn rocks, or roches mou- 
tonnes, are most admirably shown everywhere, and portions crop 
out in the bottom of the valley to indicate the force as well as the 
extent of the erosion. It is quite possible that if all the débris 
could be stripped off the gorge and valley, the grooved oF 
scratched surfaces would be apparent. One immense mountain 
mass on the north side seems to have resisted the eroding forces, 
so that from base to summit, a heighth of one thousand feet, it 1$ 
smooth, like enamel. The great glacier which must have filled up 
the channel, has probably been obstructed, in its slow downward e 
movement, by this projecting point of the mountain. The great n 
branch glaciers of Lake creek must have been at least 1500 feet 
thick. The valley or gorge is of nearly uniform width, about 
one-fourth of a mile, and the glacier must have ploughed its wayo 
along, removing a great thickness of the gneissic rocks on either 
side and on the bottom, rounded remnants of which can be seen 
cropping everywhere from the detritus. About six miles above . 
` Twin lakes, in a straight line, Lake creek forks, one branch eX 
tending up toward the north-west, and the other south-west. 
