THE PREGLACIAL DRAINAGE OF OHIO. 37 



small stream flowed south uniting at Morrow with Todd's Fork, 

 a much larger stream. It is to the controling influence of the 

 latter that the present Miami makes its abrupt bend at Morrow. 

 From Morrow the preglacial Todd's Fork continued west to 

 South Lebanon in the valley now occupied by the Little Miami. 

 Just west of the last named village a small stream, having its 

 headwaters near Fosters, flowed north and then northwest 

 through the present valley of Muddy creek and soon united 

 with the ancient Todd's Fork, which from South Lebanon flowed 

 northwest through the valley of Turtle creek, and thence into 

 the valley of the present Great ^Nliami at Middletown. From 

 the col at Fosters a stream flowed south through the valley now 

 occupied by the Little Miami. 



The change from these early conditions to the present is not 

 difficult to explain. The margin of the ice sheet, known as the 

 early Wisconsin, crossed the old valley just west of South 

 Lebanon and also the valley of the present Miami between Ore- 

 gonia and Waynesville. This completely blocked the old courses 

 of these streams, and, ponding the waters in front of the ice, 

 formed small lakes. One of these lay between the ice front and 

 the col n^ar Ft. Ancient. Gradually the w^aters in this small 

 lake rose higher and higher until they crossed the col and started 

 on their southerly course. While this was happening a much 

 larger lake was forming in the Todd's Fork valley. This lake 

 extended from the margin of the ice west of South Lebanon up 

 the valley of Todd'sFork beyond Morrow. These waters rose 

 until they overflowed the col at Fosters which they soon low- 

 ered. The level of the waters fell proportionately and soon the 

 lake disappeared, but not until its bed had been much clogged 

 with drift. The thickness of the latter is not known. At King's 

 Mills the shot tower well passed through 62 feet of drift without 

 reacning rock. While this bed was being deposited the floor 

 of the lake near Ft. Ancient was likewise being silted, and the 

 same is true of the old valley west of Lebanon. The clogging of 

 the latter was rendered more complete by the moraine which 

 crosses the valley at that place. When finally the ice withdrew 

 the preglacial courses which were so filled with drift that the 

 streams were compelled to continue in their new channels. 



