Popular science monthly . e of the photographs the upperboulder is a rock about fi\e b> eight byeight feet, of coarse Massachusettsgranite. It is securely perched on adifferent kind of rock of nearly the samesize—a rock known as a gneiss. Bothare resting on a granite ledge, but of adifferent texture from that of the uppergranite rock. Even assuming that thetwo granite rocks were alike, withoutknowledge of glacial action, it would bedifticult to account for the presence oftlie middle boulder weighing at leastten tons. Nowhere in the Inited States are theevidences of the tremendous force ofth
Popular science monthly . e of the photographs the upperboulder is a rock about fi\e b> eight byeight feet, of coarse Massachusettsgranite. It is securely perched on adifferent kind of rock of nearly the samesize—a rock known as a gneiss. Bothare resting on a granite ledge, but of adifferent texture from that of the uppergranite rock. Even assuming that thetwo granite rocks were alike, withoutknowledge of glacial action, it would bedifticult to account for the presence oftlie middle boulder weighing at leastten tons. Nowhere in the Inited States are theevidences of the tremendous force ofthe great glaciers of the Ice Age morestriking than in the Sierra Nevadaof California. Rugged \-shaped moun-tain gorges have been scoured andsmoothed out into broad I-shaped\alle\s by the great descending icemasses. The dirt and rocks have beenspread about on the plains below or atthe mouths of the canyons, while theglacial scratches and furrows can beplainly seen on the remaining rocks in 413 414 Popular Ficicncc Monihhi. The Upper BoiJderIs of MassachusettsGranite. It Is Rest-ing on a Rock ofGneiss, and Bothare Perched on aGranite Ledge ofDifferent TextureFrom That of theUpperOranite Rock At Left Below, ARock Transportedand Deposited byHuge Glaciers fromthe Sierra Rock will Out-last Its Base ManyThousand Years Below, An ErraticRock FragmentResting on a BigBase, Brought toIts Present Posi-tion by an AgencyPowerful Enoughto Transport ItOver Irregularitiesin Land Surface Popular Srirnct Mnvlhl 41,
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
