In addition to his studies at the University of Wisconsin, John Muir mostly taught himself geology and glaciology. After arriving in Yosemite, he read the landscape and changed our understanding of when and how the Sierra and Yosemite Valley was formed. Later he visited Alaska to help confirm his theories.

On the drawing of Davidson Glacier in Alaska (likely 1890) he added, "The mills of God grind slowly, but they grind exceedingly fine."