Repository: UIHistories Project: Board of Trustees Minutes - 1870 [PAGE 357]

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343

TUESDAY AFTERNOON—2 P . M.

PROF. STUART

repeated his lecture on the chemical constituents

of soils, after which J A S . SHAW, of Mt. Carroll, delivered an ad-

dress on the Soils of Northern Illinois. As it was in substance nearly the same as delivered by Mr. Shaw before the State Horticultural Society, the latter, which was revised by Mr. Shaw, is mainly inserted here.

THE SOILS OF NORTHERN ILLINOIS.

I propose to occupy your attention a short time in discussing the soils of Northern Illinois, and the dynamical forces which have originated, transported, and mingled these soils, clays, and superincumbent masses covering the bed rocks. I shall speak of that part of our State lying north of the old Silurian Beach, which crosses the State from a point near Hampton, on the Mississippi river, and passes eastward a few miles south of this place, bending up a little north of Morris, and thence passing on to the eastern line of the State, south of Chicago. The land north of this Silurian Beach was comparatively elevated table land at the time the coal deposits of the great coal basin lying south of this old beach were in process of formation. And there is evidence that over this comparatively elevated table land a great denudation has taken place. Some great force has worn off and swept away, from Southern Wisconsin and Northern Illinois, a large amount of material, which has been deposited over the face of the country south and west of that elevated region. It is estimated by Prof. Whitney, and other good geological authorities, that at least three hundred feet has been denuded and carried away in the region of the Illinois and Wisconsin mounds. These mounds—Scales Mound, the Blue Mounds, Terrapin Kidge, and the various elevated and island-like elevations left over the general level surface of that part of the State north of this old Silurian Beach—are monuments left standing when the rest of the formation was swept away. Any one with thoughtful mind, who stands upon their tops and looks over the surrounding country, or who examines the regular succession of outcrops up their sloping sides, cannot resist the conclusion that the general level of the whole country surrounding once corresponded with these highest points. As in reading a book we at once miss the pages which are torn out, so in examining these mounds, we at once miss whole leaves and parts of leaves in the Great Stone Book, which have been removed by the forces of which I shall presently speak. The Galena Limestone, the Cincinnati Group, and the Niagara Limestone, are the leaves, whose fragments yet remain to attest a time when each one of them in regular succession spread over the region now under discussion. Against this Silurian Beach of which I have spoken, the coal measures are shingled, as it were, or deposited. At the place where we are now assembled, the old St. Peters sandstone shines like sugary masses along the river banks, and is elevated in fantastic shapes at Deer Park and Starved Kock, a little to