main glacier, of which they were once tributaries, had
dried up. On approaching the south end of the Lake by steamer,
I had observed these long ridges, divined their meaning, and
determined on a closer acquaintance. While staying at the
Tallac House I repeatedly visited them and explored the
canyons down which their materials were brought. I proceed to
describe them.

_Fallen Leaf Lake Glacier_. Fallen Leaf Lake lies on the plain
of Lake Valley, about one and a half miles from Lake Tahoe, its
surface but a few feet above the level of the latter Lake[2];
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