1 1 54 J la mman — Glacial Modification of Drainage 



the ravine at Van Pelt's, the rock floor must be far 

 beneath the surface of the drift filling. This, however, 

 is not the case. A well sunk at Van Pelt's in the lowest 

 portion of the valley, about ten feet from the stream 

 itself, reaches bed rock, as has been said, at a depth of 

 only 20 feet. The nearness to the surface of the bed 

 rock here, and the fact that a quarter of a mile down the 

 ravine the stream has eroded to a depth of at least 65 

 feet (45 feet below the level of the bed rock at Van Pelt's) 

 before encountering the bed rock, indicates that the slope 

 of the rock floor in this section is eastward. This, no 



Fig. 5. 



L 



M 



S^^K^>>v c ^ \> 



/Srz-sryy 





r£-_r^- ------ 



•■ - - -.. ■ - • -''•---;-•'--. 



". '-■*.***.*"*.' '•'■■?-*'■' v* 



-^§^5855^^5^^ 



'-^7^-tr~fP~I-Z- 



Fig. 5. Cross section between summits of Eowe and Davies Hills, along 

 line L-M (fig. 2), to indicate a possible explantion for the presence of 

 bed rock in the gorge of West Sixmile (b) and its absence in Moss Creek 

 Ravine (c). 



doubt represents the older preglacial floor of an early 

 mature valley. How then are we to account for the short 

 gorge at the lower end of West Sixmile? 



The probable relationship between the rock floor and 

 the drift filling is given in fig. 4. It is supposed that a 

 line extending between the summits of Rowe and Cole 

 Hills (W, fig. 2) and passing through Van Pelt's indi- 

 cates the position of the low preglacial divide (reduced 

 to a still lower level by ice erosion) existing between the 

 valleys of East and West Sixmile (fig. 7). Evidence to 

 be adduced later tends to substantiate Tarr's conclusion 

 that East Sixmile has been forced by morainic barriers 

 to flow over its eastern valley slope and has cut a rock 

 gorge down into the former valley side. If this deduc- 

 tion be correct then the gorge of West Sixmile may have 

 been cut into the end of the spur of Davies Hill project- 



