Box 15, Folder 3: Geology of Wisconsin 1869

Section of shore of Lake Michigan at Milwaukee

[illustration of shore strata]

The lake shore at Milwaukee towards the north exhibits the following section. a - Blue clay with embedded pebbles, very tough, among the pebbles often found bituminous shale. b - Gravel, at places fine, at others very course, almost large enough at some points to be called boulders. c - fine sand very free from pebbles or clay. d - reddish clay, its base maintains nearly a horizontal; it reaches the top of the bank, is free from boulder, sand, and pebbles, being a hard fine clay. When exposed to air it crumbles, and water then readily carries it off.

From the line between a nd b numerous springs gush out along the shore.

[illustration of strata]

Where the upper surface of the blue clay (a) happens to incline towards the lake and other circumstances being favorable extensive slides have taken place as represented above - so that a person examining the immediate shore of the lake might suppose that the red clay was occasionally deposited lower than the other strata. But this is not the case, its lower surface maintaining a pretty uniform elevation above the surface of the lake, except where disturbed. The larger boulders appear to lie in groups and when the lake in its encroachments upon the land happens to encounter one of these groups of rock it is arrested in its progress and a point of land or cape...

...is formed, and te space not so protected being more rapidly carried away by the waves forms a bay.

[illustration of shore]

Occasionally the bank of the lake slopes gradually down and is covered by forest trees, exhibiting no evidence of having been undermined. But such cares are occassioned by a valley running parallel (or nearly so) with the lake; one side has been carried off - the other remains as sown above (& below).

[illustration of shore]

L. Michigan

The prevailing winds in this lake, at least the storm winds are from the northward causing the waves to strke obliquely towards the south on the shores. The effect is not only a wearing of the shore but a transportation of the materials toward the southern extremity of the lake. This effect is son discovered when a solid pier is extended into the lake, by the great amount of sand and gravel deposited on the north side of the pier. The deposit soon reaches the extremity of the piers rendering further " appropriations" necessary to extend them further into the lake and to remove the usually formed at the mouth of the harbor around the end of the pier. The harbor at Milwaukee being situated at the bottom of a bay is comparatively exempt...

...from this evil. Harbor at Racine is now filled at about 175 feet (June 16, 1846). Three miles north of Racine on the U.S. road are some ridges resembling ancient lake beaches similar to those found about the lower lakes. They are probably 75 feet above the lake. They rest on Limestone rock, which probably accounts for their not having been destroyed: the diluvial soil at other places about Lake Michigan being easily affected and carried away by rains &c, would not now show much ridges. Had not time to examine them thorougly.