. The preglacial drainage of Ohio; comprising the results of researches . at the gorge and valleyhave been cut from rock, and not from drift as above Clifton. South from Jacobis the valley widens comparatively rap-idly, owing to the stream having left the hard Niagara limestoneand entered the much more easily eroded Hudson series, con-sisting of shales and thin bedded limestones. Nowhere belowthe north margin of the latter foundation was the stream founddirectly on rock, but everywhere on a mantle of drift which isof variable but usually unknown depth. At Trebines stationa few miles west of Xe
. The preglacial drainage of Ohio; comprising the results of researches . at the gorge and valleyhave been cut from rock, and not from drift as above Clifton. South from Jacobis the valley widens comparatively rap-idly, owing to the stream having left the hard Niagara limestoneand entered the much more easily eroded Hudson series, con-sisting of shales and thin bedded limestones. Nowhere belowthe north margin of the latter foundation was the stream founddirectly on rock, but everywhere on a mantle of drift which isof variable but usually unknown depth. At Trebines stationa few miles west of Xenia a well located 50 vards from the riverwas sunk to a depth of 49 feet without penetrating rock. At Alpha the valley expands greatly, though the onlytributary there uniting with the Miami is Beaver Creek—avery small stream in a very large valley of which more will be said to. jt- O G A N / BellefonfnIrM ALLEN • L irp-Q HISTORY O F TH E LITTLE MIAMI RIVER BY in vicinity of Cincinnati aftenFowKe LEGEND Present Drainage — Preqiacial Drainoqe. THE PREGLACTAL DRAINAGE OF OTITO. 33 hereafter. About one mile south of Alpha the valley againcontracts, there havini^ a width of p(.M-ha])s one-tenth of a this point the valley lies about 75 feet below the top of thebluffs which are steep and composed of rock. Two miles fartherdown, the valley has again expanded and has a width ofone-half mile. From the latter point to Bellbrook there areseveral variations in the width of the valley. These resultlargely from the entrance of tributaries and in part from theirregularities in the deposits of drift, and perhaps also from varia-tions in the durability of the rock. Just east of P)ellbrook and north of the point at which theMiami turns abruptly to the east, there is a marked change in thewidth of the valley. Here the rock bluffs extend so close to theriver that the flood plain on one side is only 85 yards wide,while on the opposite side there is scarcely room
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