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Page:Popular Science Monthly Volume 89.djvu/428

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414

��Popular Ficicncc Monihhi

���The Upper BoiJder Is of Massachusetts Granite. It Is Rest- ing on a Rock of Gneiss, and Both are Perched on a Granite Ledge of Different Texture From That of the UpperOranite Rock

��At Left Below, A Rock Transported and Deposited by Huge Glaciers from the Sierra Nevada. This Rock will Out- last Its Base Many Thousand Years

��Below, An Erratic Rock Fragment Resting on a Big Base, Brought to Its Present Posi- tion by an Agency Powerful Enough to Transport It Over Irregularities in Land Surface

�� �