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Page:Popular Science Monthly Volume 89.djvu/429

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���Above, A Perched Granite Boulder Left on a Sandstone Base by a Glacier Which Melted on a Slope of the Famous Yosemite Valley, California. The Sandstone Pedestal Is Greatly Weath- ered and in a Hundred Thousand Years, Perhaps, It Will Wear Away and Precipitate the Heavy Boulder Into the Canyon Below

��At Right, The Large Boulder Which Serves as the Base Is Rapidly Wasting Away While the Smaller. Boulder on Top of It — Weigh- ing a Ton or so — Shows No Signs of Deterioration, Al- though It Has Pro- bably Rested in This Position For the Better Part of a Thousand Cen- turies or More

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