Letter from John Muir to Joseph Hooker 1879 Feb 1

lowlands as well as the highlands were covered with ice, but I cannot present it in a mere letter. I will however, give a few of the more important generalizations, based upon the observed facts. 1. At the beginning of the glacial period, the region now known as the Great Basin, was an elevated tableland, not furrowed as at present with parallel valleys and mountain ranges, but comparatively bald and featureless. 2. This ancient tableland, bounded on the east and west by lofty mountain ranges, but open to the north and south, was loaded with ice, which was discharged to the ocean both northward and southward, and in its flow brought most if not all of the interior ranges into relief by erosion. 3. As the Glacial winter drew near

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its close, the ice vanished from the lower portions of the basin, which then became lakes, into which separate glaciers descended from the mountains. Then these mountain glaciers vanished in turn after sculpturing the ranges into their present condition. 4. The few immense lakes, extending over most of the lowlands, and in the midst of which many of the interior ranges stood as islands, became shallow as the ice vanished from the highlands and separated into many distinct lakes whose waters no longer reached the ocean, and finally disappeared by the filling in of their basins and the general desiccation of the climate, all save a few fed by streams from the Sierra and [Wasatch]. These dry lake basins now form the Sage and Alkali plains.

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The transition from one to the other of these conditions was gradual and orderly: first a nearly simple tableland. Then a grand mer de glace shedding its slow-crawling currents to the ocean and becoming gradually more wrinkled as unequal erosion roughened its bed and brought its highest ridges above the surface. Then a land of lakes, an almost continuous sheet of water from the Sierra to the Wahsatch [Wasatch], adorned with innumerable mountain islands. Then a slow dessication [desiccation] and decay to present conditions. Such a mer de glace would form a fine barrier to the northward march of your Asiatic plants and hold them perhaps until they perished or came into competition with others better adapted to the changed conditions.

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[Seropis] fine book which you sent me long ago reached me since I began this letter. Gray kept it some time and finally sent it out here by Sargent, who gave it to one of the members of the Academy of Sciences. I have not yet read it, but am glad to get hold of so comprehensive a collection of facts relating to an agent that plays so important a part in the baking and breaking and building of our fine world, and will doubtless find it very interesting. When are you going to pay us another visit? What conclusions have you reached with regard to our pines and Silver firs. I found the true (?) P. Flexilis on all the higher ranges of the Great Basin. It also grows on the eastern slope of the southern Sierra. P. Balfouriana is compounded I think with P. Monticola and aristata. I fund P. edulis in western Utah mingling with P. Monophylla Cordially yours, John Muir.