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Show 162 satirized the catastrophic theory, "seeming to account for the remarkable sheerness and angularity of the walls, and by its marvelousness and obscurity. . . . " But the mechanism which Muir proposed as an alternative to the violent origin of Yosemite was not considered by Lyell to be a gradual geological change. Agassiz's notion of a past Ice Age suggested, as did Muir's view of the Sierra, that the glaciers working in the past were not only more powerful than those one found in the Sierra's present, but represented a sudden change during the earth's past. And this in turn contradicted Lyell's fourth and last tenet of uniformity. Lyell believed that "the earth has been fundamentally the same since its formation." This was not a belief about method of study at all, but about the nature of Nature. This was where Agassiz parted from Lyell, and opened the door on a new vista. Agassiz argued not only that natural history had direction, but that there was a complete discontinuity between the pre-glacial and post-glacial earth. "Since I saw the glaciers," Agassiz said in 1838, "I am quite of a snowy humor, and will have the whole surface of the earth covered with ice, and the whole prior creation dead by cold." If Muir were following the letter of the Agassizean law, his description of the Sierra following the glacial age would be a genesis indeed, but not the first one for the earth. Agassiz described the glacial age as a vast and sudden metamorphosis from a tropical earth to a "huge ocean of ice." "The silence of death succeeded to the movement of a powerful |