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the ice-sheet from Ohio. A deglaciation interval is believed to have preceded this stage, but as yet, decisive evidence in support of this view is not obtained.

We may now profitably review what is known concerning the altitude in each stage:

1. During the earliest advance little of value is known in this region. The scarcity, if not absence, of coarse overwash material seems to indicate feeble drainage and consequent low altitude. It is true that the Split rock and Middle creek conglomerate indicate powerful water action, but if formed as they appear to have been beneath the ice-sheet, they show little as to the altitude of the land.
2. During the period of deglaciation following the deposition of the earliest drift there appear, from the character of the changes effected, to have been fair drainage conditions. We may presume, therefore, that the altitude was not much lower than the present altitude of the region (800-1000 feet A. T.).
3. During the period of silt deposition there can be little doubt that the region stood several hundred feet lower than now.
4. During the formation of the outer moraine of the later drift there were apparently as good drainage conditions as are now afforded in the western Ohio region.
5. During the succeeding deglaciation interval the erosion effected indicates a fair altitude.
6. During the formation of the main morainic system the maximum of elevation was probably reached, there being an especially vigorous drainage at that time, not only in Ohio, but as far to the west as the moraine has been correlated.
7. During the formation of the later moraines there seems to have been a return to low altitude, and still later the Champlain submergence of the coast and St. Lawrence occurred. It is important to note that the Champlain submergence is separated from the submergence which produced the silts of southern Ohio by the periods of high altitude just mentioned, a succession of