that the pressure on this, the subaqueous portion of the glacial bed, would be small, and become less and less until it becomes nothing at the point where the icebergs float away.  The pressure on the bed being small, not enough to overcome the cohesion of ice, there would be no spreading. A glacier running down a steep narrow canyon and out into the deep water, and forming icebergs at its point, would maintain its slender, tongue-like form, and drop its debris on each side, forming parallel ridges, and would not form a terminal moraine because the materials not dropped previously would be carried off by icebergs.  In the subsequent retreat of such a glacier, imperfect terminal moraines might be formed higher up, where the water is not deep enough to form icebergs.  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.  But higher up there are small, imperfect, transverse moraines, made during the subsequent retreat, behind which water has collected, forming lakes and marshes.  But observe:  these moraines are also in the vicinity of a great lake; and we have abundant evidence, in very distinct terraces described by Whitney[4] and observed by myself, that in glacial times the water stood at least six hundred feet above the present level.  In fact, there can be no doubt that at that time the waters of Mono Lake (or a much greater body of water of which Mono is the remnant) washed against the bold rocky points from which the debris ridges start. The glaciers in this vicinity, therefore, must have run out into the water six or seven miles, and doubtless formed icebergs at their point, and, therefore, formed there no terminal moraine.

[Footnote 4:  Geological Survey of California, Vol.  I, 451.]

That the glaciers described about Lake Tahoe and Lake Mono ran out far into the water and formed icebergs I think is quite certain, and that parallel moraines open below are characteristic signs of such conditions I also think nearly certain.

f.  Glacial Erosion.  My observations on glacial pathways in the High Sierra, and especially about Lake Tahoe, have greatly modified my views as to the nature of glacial erosion.