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287 Remarkable ridges

to the broad sweep of the Lake shore. No visible difference of level is apparent in the beaches, while the marshy prairie between them is so low and sunked as to be almost impassable and apparently corresponds in level with the prairie in the rear of Chicago.

"At the termination of the above series, commences a new order of ridges, all of which are situated at a somewhat higher level. They have an average width of only one hundred and twenty feet, and are separated by depressions of the same dimensions. In these, both the ridge and the valley are dry and wooded. The road crosses them for a distance of one mile, after which assuming a mor easterly course, it descends upon a flat prairie, about three miles wide.

"The succession of beaches described would appear to have been occasioned by the action of northerly winds operating on the whole range of the lake, thereby producing an accumulation of water in this region, as well as a

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