Stream Diversion near St. Louisville, Ohio 345 



over a divide against which Rocky Fork then headed, the lake 

 was deeper than if the outlet was at the west end of part B; 

 under the former condition the lake would have been about 

 twice as large as under the latter; in either case we would expect 

 to find alluvial fans, deltas, lake clay and beaches along the valley 

 walls of the present stream course. Such evidences of a former 

 lake would seem inevitable, considering the great length of time 

 that would be required to change the supposed rock col into the 

 present channel. But no shoreline structures are to be found; 

 therefore it is questioned whether a lake ever stood here. 



Part C. A swampy condition exists in part C, extending from 

 the margin of the outwash plain northward for about one mile 

 and gradually disappearing. The soil is of a black mucky 

 nature and contains a great deal of vegetable matter. In several 

 places where attempts have been made to dispose of the tall 

 grass by firing it, this black peaty soil has burned to a depth of 

 over a foot. There is no surface evidence of unmodified drift 

 deposits found at any great distance from the margin of the 

 outwash plain. This part of the Rocky Fork Valley has a very 

 low gradient ; the farmers have to under-drain the fields to secure 

 sufficient drainage to carry on agriculture. 



Another hypothesis. Formerly a stream flowed westward from 

 a divide located in part A; and another stream flowed southward 

 through the present course of the Rocky Fork; this divide is 

 indicated approximately by cross-section 3 (fig. 1). The capture 

 of the headwater section of the west-flowing stream by the 

 Rocky Fork was indicated by differential tilting. A new divide 

 was established in part B; this divide progressed to the west, 

 probably to the position indicated by cross-section 2. This 

 secondary divide probably represents the position which the east- 

 flowing and west-flowing streams held with reference to each 

 other at the time of the Illinoian ice invasion; it is at this stage 

 in their life history that the reversal of part C of the present 

 stream must have taken place. This part of the valley was 

 glacially aggraded in the retreat of the ice to the barrier position 

 east of St. Louisville; outwash deposits tended further to estab- 

 lish a slope towards the secondarj^ divide. 



