ACADEMY OF SCIENCES. 4] 
admirably marked débris ridge (moraines) three hundred feet high, four miles 
long, and one and one-half to two miles apart. These moraines may be traced 
back to the termination of the rocky ridges which bound the cafion, On the 
one side the moraine lies wholly on the plain; on the other side its upper 
part lies against the slope of Mt. Tallac. Near the lower end of the lake a 
somewhat obscure branch ridge comes off from each main ridge, and curving 
around they form an imperfect terminal moraine, through which the outlet of 
the lake breaks its way. é 
On ascending thé cation the glaciation is very conspicuous, and becomes 
more and more splendid at every step. From Soda Springs (map s.s.) up- 
wards, it is the most beautiful I have ever seen. In some places, for many 
acres in extent, the whole rocky bottom of the caion is smooth and polished, 
aod gently undulating, like the surface of a glassy but billowy sea. The 
glaciation is distinct, also, up the sides of the cafion 1,000 feet above its floor. 
There can be no doubt, therefore, that a glacier once came down this canon, 
filling it 1,000 feet deep, scooped out Fallen Leaf Lake just where it struck 
the plain and changed its angle of slope, and pushed its snout four miles out 
_on the level plain, nearly to the present shores of Lake Tahoe, dropping its 
débris on either side, and thus forming a bed for itself. In its subsequent 
retreat it seems to have rested its snout some time at the lower end of Fallen 
Leaf Lake, and accumulated there an imperfect terminal moraine. The out- 
lines of this little lake, with its bordering moraines, are shown in the diakram 
map. 
2. Cascade Lake Glacier.—Cascade Lake, like Fallen Leaf Lake, is about 
one and one-half miles from Lake Tahoe, but, unlike Fallen Leaf Lake, its 
discharge creek has considerable fall, and the lake surface is, therefore, prob- 
ably 100 feet above the level of the greater lake. On either side of this creek, 
from the very border of Lake Tahoe, runs a moraine ridge up to the lake, 
and thence close along each side of the lake up to the rocky points which 
terminate the true mountain canon above the head of the lake. I have never 
anywhere seen more perfectly defined moraines. I climbed over the larger 
western moraine and found that it is partly merged into the eastern moraine 
of Emerald Bay to form a medial at least 300 feet high, and of great breadth, 
(see map.) From the surface of the little lake, the curving branches of the 
main moraine, meeting below the lake to form a terminal moraine, are 
very distinct. At the head of the lake there is a perpendicular cliff over 
which the river precipitates itself, forming a very pretty cascade of 100 feet 
or more. On ascending the canon above the head of the lake, for several 
miles, I found, everywhere, over the lip of the precipice, over the whole floor 
of the canon, and up the sides 1,000 feet or more, the most perfect glaciation. 
There cannot be, therefore, the slightest doubt that this also is the pathway 
of aglacier which once ran into Lake Tahoe. After coming down its steep 
rocky bed, this glacier precipitated itself over the cliff, scooped out the lake 
at its foot, and then ran on until it bathed its snout in the waters of Lake 
Tahoe, and probably formed icebergs there. In its subsequent retreat it seems 
to have dropped more débris in its path, and formed a more perfect terminal 
moraine than did Fallen Leaf Lake Glacier. 
