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Show 161. to Alaska or Greenland to see these agents working in their full sublime power. They needed a living glacial reality to satisfy the second tenet of Lyell's concept of Uniformity. Lyell thought that "Processes now operating should explain the events of the past." Muir argued in the Studies that the glacier was simply another, less understood agent: "The erosive energy of ice is almost universally underrated, because we know so little about it. Water is our constant companion, but we cannot dwell with ice. Water is far more human than ice, and also far more outspoken." When an agent, however strong it is, may be studied and understood, then it can be placed in the theory of uniformity- Catastrophic theory depended not so much on the power or violence of geological forces as on their inscrutability. Thanks to Agassiz's Etudes, Muir could explain the mechanism of glaciation in the Sierra. And Agassiz put his seal of approval on Muir's work, exclaiming, "Here is the first man who has any adequate conception of glacial action." The third tenet of Lyell's geological uniformity is that "Geologic change is slow, gradual, and steady, not cataclysmic or paroxysmal." This is the basis for Muir's resistance to Whitney's theory that Yosemite was created by "subsidence," when its bottom suddenly dropped out. Had the "violent hypothesis," catastrophe, or subsidence, been true, Muir's method of study could achieve virtually nothing in Yosemite. He could neither read Nature's book nor follow geological history with his feet. Muir echoed Lyell's argument when he |