twenty-five to
thirty miles away. As the eye sweeps again up the canyon-beds,
little lakes, glacier scooped rock basins, filled with
ice-cold water, flash in the sunlight on every side. Twelve or
fifteen of these may be seen.

From appropriate positions on the surface of Lake Tahoe, also,
all the moraine ridges are beautifully seen at once, but the
glacial lakes and the canyon-beds, of course, cannot be seen.

There are several questions of a general nature suggested by
my examination of these three glacial pathways, which I have
thought best to consider separately.

_a. Evidences of the existence of the Great Lake Valley
Glacier_. On the south shore of Lake Tahoe, and especially
at the northern or lower end of Fallen Leaf Lake, I found
many pebbles and some large bowlders of a beautiful striped
agate-like slate. The stripes consisted of alternate bands
of black and translucent white, the latter weathering into
milk-white, or yellowish, or reddish. It was perfectly evident
that these fragments were brought down from the canyon above
Fallen Leaf Lake. On ascending this canyon I easily found the
parent rock of these pebbles and bowlders.
the It is a powerful outcropping ledge of beautifully striped
siliceous slate, full of fissures and joints, and easily
broken into blocks of all sizes, crossing the canyon about
a half mile above the lake. This rock is so peculiar and so
easily identified that its fragments become an admirable index
of the extent of the glacial transportation. I have, myself,
traced these pebbles only a little way along the western
shores of the great Lake, as my observations were principally
confined to this part; but I learn from my brother, Professor
John LeConte, and from Mr. John Muir, both of whom have
examined the pebbles I have brought home, that precisely
similar fragments are found in great abundance all along the
western shore from Sugar Pine Point northward, and especially
on the extreme northwestern shore nearly thirty miles from
their source. I have visited the eastern shore of the Lake
somewhat more extensively than the western, and nowhere did I
see similar pebbles. Mr. Muir, who has walked around the Lake,
tells me that they do not occur on the eastern shore. We have,
then, in the distribution of these pebbles, demonstrative