Part I. Report of progress in 1869, by J. S. Newberry, chief geologist. Part II. Report of progress in the second district, by E. B. Andrews, assist. geologist. Part III. Report on geology of Montgomery County, by Edward Orton, assist. geologist.

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Above all these drift deposits, and more recent than any of them, are
the "lake ridges"-embankments of sand, gravel, sticks, leaves, etc.,
which run imperfectly parallel with the present outlines of the lake margins. Of these the lowest on the south shere of Lake Erie is a little less
than 100 feet above the present level of the lake; the highest some 250
feet. In New York, Canada, Michigan, and on Lake Superior a similar
series of ridges has been discovered, and they have everywhere been
accepted as evidence that the waters of the lakes once reached the points
they mark; that they are nothing else than ancient lake beaches I shall
hope to prove further on.
In the southern half of the Mississippi Valley the evidences of glacial
action are entirely wanting, and there is nothing corresponding to the
wide spread drift deposits of the north. We there find, however, proots
of erosion on a stupendous scale-such as the valley of East Tennesseewhich has been formed by the washing out of all the broken strata
between the ridges of the Alleghanies and the massive tables of the
Cumberland Mountains-the canons of the Tennessee 1600 feet deep, etc.
Here, also, as in the lake basin, the channels of excavation pass below
the deep and quiet waters of the lower rivers, proving by their depth that
they must have been cut when the fall of these rivers was much greater
than now.
The history which I derive from the facts cited above is briefly this:
1st. At a period probably synchronous with the glacial epoch of Europe
-at least corresponding to it in the sequence of events-the northern
half of the continent of North America had a climate comparable with
that of Greenland; so cold, that wherever there was a copious precipitation of moisture from oceanic evaporation, that moisture was congealed,
and formed glaciers which flowed by various routes toward the sea.
2d. That the causes of these ancient glaciers corresponded in a general
way with the present channels of drainage. The direction of the glacial
furrows proves that one of these ice rivers flowed from Lake Huron
along a channel now filled with drift, and known to be at least 150 feet
doep, into Lake Erie, which was then not a lake, but an excavated valley,
into which the streams of Northern Ohio flowed, 100 feet or more below
the present lake level. Following the line of the major axis of Lake.
Erie to near its eastern extremity, here turning north-east this glacier
passed through some channel on the Canadian side-now filled up-into
Lake Ontario, and thence found its way to the sea, either by the St.
Lawrence or by the Mohawk and Hudson.
Another glacier occupied the bed of Lake Michigan, having an outlet
southward through a channel now concealed by the heavy beds of drift
which occupy the surface about the south end of the lake passing near
Bloomington, Illinois, and by some route yet unknown reaching the
trough of the Mississippi, which was then much deeper than at present.