It is probable, too, that since the melting of the great "mer de glace" and the formation of the Lake, the level of the water has gone down considerably, by the deepening of the Truckee Canyon outlet by means of erosion.

Thus not only did the glaciers retreat from the Lake, but also the Lake from the glaciers.
As already stated, similar parallel moraine ridges are formed by the glaciers which ran down the steep eastern slope of the Sierras, and out on the level plains of Mono.

By far the most remarkable are those formed by Bloody most Canyon Glacier, described by me in a former paper.

These moraines are six or seven miles long, 300 to 400 feet high, and the parallel crests not more than a mile asunder.

There, also, as at Lake Tahoe, we find them terminating abruptly in the plain without any sign of terminal moraine.