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Geology-Sandstone District

in thickness at the Falls of St. Anthony, & about the same at Prairie du Chien; but along the Wisconsin Hills it [exceeds] attains a thickness of over two hundred feet. The cliffs along the Mississippi for a distance of thirty five miles below the Falls of St. Anthony appear to be composed chiefly of this crumbling sandstone.

Large blocks are occasionally undermined and fall down, lying in confused heaps at the base of the bluffs. The rivers running through the districts where this sandstone prevails are characterized by shallow water, filled with moving sand, forming bars that are constantly carried away from some points, and accumulating at othrs, rendering the navigation difficult. By far the larger proportion of the river Bluffs along the Mississippi are calcareous, and present high perpendicular rocky fronts towards the river supported by immense quantities of broken fragments at the base extending usually half way to the summit. They are said to attain their greatest deviation [height] in the vicinity of Lake Pepin.

The limestone which lies above the sandstone in Wisconsin was found by Dr. Locke to be the same that he had described in Ohio as the "Blue