. Report of a geological survey of Wisconsin, Iowa, and Minnesota : and incidentally of a portion of Nebraska Territory : made under instructions from the United States Treasury Department . monite,m conjunction with calcareous spar, are also common. These beds also containmany thin veins of argillaceous iron ore, the sides of the veins being lined withstellular crystals of heulandite. I did not examine the bed of the stream beyond the second ridge; the latter isthree hundred and nineteen feet above the lake-level, and composed of a rock likethat which I have considered, at other localities, t
. Report of a geological survey of Wisconsin, Iowa, and Minnesota : and incidentally of a portion of Nebraska Territory : made under instructions from the United States Treasury Department . monite,m conjunction with calcareous spar, are also common. These beds also containmany thin veins of argillaceous iron ore, the sides of the veins being lined withstellular crystals of heulandite. I did not examine the bed of the stream beyond the second ridge; the latter isthree hundred and nineteen feet above the lake-level, and composed of a rock likethat which I have considered, at other localities, to be a volcanic grit. In 1848,however, Colonel Whittlesey, who struck this river several miles above its mouth,brought specimens of slaty hornblende, which he found in situ three miles from theLake. It may also be mentioned in connexion with this locality, that the amyg-daloid in contact with the basalt, often assumes an imperfectly columnar structure. Below the mouth of Waginokaning River, the lake-shore is bounded by columnarrock, which rises in rounded, dome-like exposures for more than half a mile. Oneof these domes is represented in the following sketch. They rise from twenty to. thirty feet above the water-level, and are surrounded by concentric layers of rockon every side, like the coats of an onion. Over this rock is a bed of basaltic trap,from three to fifteen feet in thickness, which seems to have been deposited sincethe underlying rock began to disintegrate. The bedded traps in this neighbourhood appear to have been deposited at diffe-rent periods of activity, with brief intervals of rest between them. At one pointon the lake-shore, about a mile above the mouth of Manidowish River, is an NORTHWEST SHORE OF LAKE SUPERIOR. 367 escarpment, showing six beds, with thin partings of ferruginous clay and shalebetween them, as represented by the annexed cut.
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Keywords: ., booksubjectbotany, booksubjectgeology, booksubjectpaleontology
