Drainage Features of the Upper Ohio Basin. 259 



portions of two streams each flowing northwestward but sepa- 

 rated by a divide below the mouth of the East Sandy creek. 

 This view is supported, not only by a notable constriction 

 there (to a width of scarcely 60 rods), but also by an abandoned 

 valley leading northward from the bend of West Sandy creek 

 at Waterloo to French creek valley just above the mouth of 

 Sugar creek, which would afford a northward outlet for the 

 western stream. The relationships of the present streams to 

 this abandoned valley and to the supposed col may be seen by 

 a comparison of maps 3 and 4. This comparison will also 

 serve to show how natural the restored system is as compared 

 with the disturbed and unnatural present system. 



Turning next to the line of evidence found in the rock 

 shelves and terraces, a general inspection of the French creek 

 valley shows that there has been broader and deeper excava- 

 tion than on the middle Allegheny. But inasmuch as the 

 French creek valley lies within the glacial boundary, and its 

 lower course nearly coincides with the direction of the ice 

 flow, the question is naturally raised whether its greater size 

 may not be due in the main to glacial excavation. An exam- 

 ination of the valley with this question in mind led to the dis- 

 covery of old channels and ox-bow curves of pre glacial streams 

 whose preservation is so complete as to furnish decisive evi- 

 dence that glacial excavation has been of little consequence in 

 determining the size of the valley. 



On the stream which, as indicated above, seems to have led 

 northward from the highland tract near the mouth of the 

 Clarion past Waterloo to the present French creek valley, 

 there are remnants of an old valley floor near the supposed 

 divide at an altitude of 375-400 feet above the river, or 1275- 

 1300 A. T., while at Waterloo in the abandoned valley which 

 leads from Sandy creek northward to French creek, the rock 

 floor is shown by several oil wells to have an altitude about 

 1060 feet A. T. This valley is filled with glacial gravel, ap- 

 parently of early glacial age, and its rock floor has not suffered 

 excavation since the gravel deposition. Its rock floor is the 

 probable continuation of the elevated rock floor of the head 

 waters and indicates a decliue of somewhat more than 200 feet 

 in 18-20 miles. This rate of fall would be natural in such a 

 small stream descending from the elevated tableland and dif- 

 fers but little from the rate of fall in southern tributaries of 

 the upper Allegheny of corresponding size, e. g., the fall on 

 the Tuna, a similar stream, from De Golier, Pennsylvania, to 

 the mouth of the stream, a distance of 14 miles, is 215 feet. 

 (See Carll, Penn. Rept. Ill, p. 334.) At the north end of 

 the abandoned valley, where it opens into French creek, rock 

 shelves appear at an altitude of about 1040 feet A. T., which 

 seem to mark the continuation of the old valley floor. 



