The region which we have under investigation, lying between the Green mountains on the east and the Archean heights on the west, and extending from Benson, Vermont, and Ticonderoga, New York, on the south, to Phillipsburgh, Canada, on the north, has a breadth of about twenty miles and a length of not far from eighty.
Near the western side of this geological cradle lies Lake Champlain, with its islands. On the Vermont side, east of the lake, all the rocks of the Lower Silurian series appear—Potsdam, Calciferous, Chazy, Black River, Trenton, and Utica slate. These rocks sometimes lie in their natural order, forming great monoclinals where the Archean mass to the west of them has been bodily raised, leaving these dipping principally to the east. Often, however, they appear as though an immense earth wave coming from the east had broken itself along the crest into great fragments, . . .