but its bottom far, probably several hundred feet, below that level.  It is about three to three and one-half miles long and one and one-fourth miles wide.  From its upper end runs a canyon bordered on either side by the highest peaks in this region.  The rocky walls of this canyon terminate on the east side at the head of the lake, but on the west side, a little farther down.  The lake is bordered on each side by an admirably marked debris ridge (moraine) 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 canyon.  On one side the moraine lies wholly on the plain; on the other side its upper part lies against the slope of Mount Tallac.  Near the lower end of the lake a somewhat obscure branch ridge comes off from each main ridge, and curving around it forms an imperfect terminal moraine through which the outlet of the lake breaks its way.

[Footnote 2:  Professor Price informs me there is a difference of eighty feet between the level of Lake Tahoe and Fallen Leaf Lake.]

On ascending the canyon the glaciation is very conspicuous, and becomes more and more beautiful at every step.  From Glen Alpine Springs upward it is the most perfect I have ever seen.  In some places the white rocky bottom of the canyon, for many miles in extent, is smooth and polished and gently undulating, like the surface of a glassy but billowy sea.  The glaciation is distinct also up the sides of the canyon 1000 feet above its floor.

There can be no doubt, therefore, that a glacier once came down this canyon filling it 1000 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 debris 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.

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, probably 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 along each side of the lake up to the rocky points which terminate the true mountain canyon 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.  From the surface of the little lake the curving branches of the main moraine, meeting below the lake to form a terminal