Joseph Le Conte
and then turning westward flowed through Car- son Canyon into the great Carson Valley. The evidence is complete and of every kind. From the same snowy summits another grt glacier flowed northward into Lake Valley and onward into L. Tahoe. On both sides of the valley and of the Lake the mountains are high and still snowy. Innumerable tributaries flowed down these into the - main icy stream. These tributaries - continued after the main icy stream had dried up - they have therefore by their debris somewhat obscured the evidences of the main glacier in the lower part of the valley. One of these tributaries I ex amined closely. It came down from John- son's summit. the scoring & polishing is per- fect. From the same summit amother Gl passed westward down the canyon of the Am. River at least 25 miles. Below this for 25 miles more the canyon is equally deep & bold. but ap parently [underlined: water] worn - at lest I could find no evidence of glaciers. This change however isnearly or quite coincident with the change of the rocks from Granite to Slate. In the glacial region the canyon is broader at bottom with succession of [underline meadows] and other evidences of [illegible] in the lower Gls region V shaped & not a single meadow. As to the question whether L Tahoe was - scooped out by Glaciers - Observe the main Gl did not run at steep incline into it, but through Lake Valley for 15 miles. That L. Tahoe was filled with ice - a true mer de glace, I have no doubt - but that it was scooped out by ice seems more doubtful I do not think it could have been scooped out by what I might call the Lake Glacier But I know not what an universal ice-sheet might have done at a still earlier period. I learn from my brother that the [underline: outlet gorge] is rocky and [underline: very narrow] in some places only 100 or more feet. Nevertheless there are abundant marks of [illegible] as I understand him about the upper margin of the gorge It has probably been deepened by water and the Lake partly drained off. I think
1872 Sep 7
Original letter dimensions: 20.5 x 25.5 cm.
Reel 02, Image 0889
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