The American journal of science and arts . ology of Upper Illinois. 135 try, or one whose rapid descent might measurably compensatefor want of area in giving rise to alluvial deposits. Neither dorivers of any magnitude find their outlet here, which, like theSt. Clair where it enters Lake St. Clair, might produce flat plainsof considerable extent. Its origin seems to have been connectedwith a higher level of the lake, when its waters advanced inlandquite to the rolling prairie. Nor would this supposition be at allsatisfactory perhaps, except for the knowledge we possess of thealmost universal,
Image details
Contributor:
The Reading Room / Alamy Stock PhotoImage ID:
2AN5N97File size:
7.2 MB (318.4 KB Compressed download)Releases:
Model - no | Property - noDo I need a release?Dimensions:
1994 x 1254 px | 33.8 x 21.2 cm | 13.3 x 8.4 inches | 150dpiMore information:
This image is a public domain image, which means either that copyright has expired in the image or the copyright holder has waived their copyright. Alamy charges you a fee for access to the high resolution copy of the image.
This image could have imperfections as it’s either historical or reportage.
The American journal of science and arts . ology of Upper Illinois. 135 try, or one whose rapid descent might measurably compensatefor want of area in giving rise to alluvial deposits. Neither dorivers of any magnitude find their outlet here, which, like theSt. Clair where it enters Lake St. Clair, might produce flat plainsof considerable extent. Its origin seems to have been connectedwith a higher level of the lake, when its waters advanced inlandquite to the rolling prairie. Nor would this supposition be at allsatisfactory perhaps, except for the knowledge we possess of thealmost universal, rocky substratum which prevails over the wetprairie, coming for the most part to within a few feet of the topof the ground, —thus giving us the conditions of a hard bottomas forming the shore of the lake, upon which the sediment andwash of the coast was in the progress of ages spread out. Thedeposit covering this rocky floor, is a horizontally stratified blueclay, on top of which at Chicago, rests a yellowish clayey loam. Xa/u Mi/^Id^aTi. On the subsidence of the lake to its present level, the beach-line in the region of Chicago must have begun to form. For along distance up and down the lake, it is confined to one or twoembankments; but on drawing near the head of the lake, by theway of the road to Michigan city, we find the surface of theprairie invaded far inland by a succession of ancient beaches, formed with the utmost regularity as to width and height, aswell as conformity to the existing shore of the lake. I shall de-scribe them as they came into view on the stage road, endeavor-ing to render their character the more intelligible by means of theabove sketch, constructed from recollection. Leaving Chicago, the 136 Geology of Upper Illinois. road for about fifteen miles is on the beach, or just behind it, onthe border of the level prairie. It then begins to diverge fromthe shore, and passes obliquely across a succession of ridges, eachresembling a turnpike in its rounded f