In most parts of the canyon the rocks are volcanic and crumbling, and therefore ill adapted to retain glacial marks; yet in some places where the rock is harder these marks are unmistakable.

On my way to and from Lake Tahoe, I observed that the Truckee Canyon glacier was joined at the town of Truckee by a short but powerful tributary, which, taking its rise in an immense rocky amphitheater surrounding the head of Donner Lake, flowed eastward.

Donner Lake, which occupies the lower portion of this amphitheater, was evidently formed by the down-flowing of the ice from the steep slopes of the upper portion near the _summit_.

The stage road from Truckee to the summit runs along the base of a _moraine_ close by the margin of the lake on one side, while on the other side, along the apparently almost perpendicular rocky face of the amphitheater, 1000 feet above the surface of the lake, the Central Pacific Railroad winds its fearful way to the same place.

In the upper portion of this amphitheater large patches of snow still remain unmelted during the summer.
My examination of these two glaciers, however, was very cursory.