The numerous islands and promontories of Lake Champlain afford excellent opportunities for the study of the Lower Silurian. Along its western border are the steep, high hills of the Archean, apparently the former shore of the old Silurian sea; along its eastern border stretch the hills of red sand-rock and dolomite of the Cambrian age, brought up by the great overthrust that continues on northward to Quebec. East of this overthrust, toward the Green mountains, the Lower Silurian rocks are extensively crumpled and metamorphosed, and hard to decipher; but westward through the lake region they are less disturbed, retain their fossils, and present many remarkably fine exposures along the shores where the waves have washed away the soil.

The geological importance of this region was recognized by Professor Emmons, who, in his New York report in 1842, named these formations the Champlain group. Subsequently Professors Thompson, Adams and Hitchcock . . .

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