302 R. R. HICE — NORTHWARD FLOW OF ANCIENT BEAVER RIVER 



Plates 34 and 35 are two views of a more advanced stage of pot-hole 

 erosion, in which the different holes have cut into one another, thus 

 forming an irregular channel. Plate 35 is a view taken looking up the 

 stream, while plate 34 is one looking down stream, both view^s being of 

 the same group of holes and thus showing the difference in their appear- 

 ance as viewed from opposite directions. The upper pot-hole of this 

 series, seen near the bottom of plate 34, is quite t3^pical. A small piece 

 of drift which has lodged on the downstream edge is clearly seen, and 

 its position shows the eroded condition of that edge of the hole, which 

 is so beveled as not to produce any reflection from the water's surface, 

 while the upstream edge is distincth^ undercut (left center of plate 35). 

 Looking up the stream (plate 35), the end of the piece of drift is seen on 

 the lower edge of the pot-hole. 



To the right of the line of the pot-holes is seen in plate 35 (on the left 

 side in plate 34) an " arm " or branch, which was originally a pot-hole 

 of irregular shape, now connected with the others. The difference be- 

 tween the two sides is clearly seen. In this case the downstream side 

 is not so much eroded as in the others shown, due to the fact that the 

 distance across, measured in the direction of the water's flow, is only 

 about one- half the diameter of the pot-holes shown in plate 33, and 

 hence the water does not 3^et strike with as great force in the one case as 

 the other. A number of other pot-holes are seen in these plates, all 

 telling the same story. 



Similar examples might be shown almost without number, but these 

 seem sufficient to indicate clearly the fact intended to be brought out 

 thus far, which is, that in the formation of pot-holes it is the downstream 

 edge that is eroded, while the upstream side is abrupt, and is often? 

 indeed, undercut, as shown in plates 33 and 35. This being the case, it is 

 the logical deduction that when we find such pot-holes their appearance 

 will clearly indicate the direction of flow of the stream that formed 

 them. 



PoT-HoLES IN ANCIENT RiVER BeD 



Plate 36, figures 1 and 2, are two views of a " fossil " pot-hole and sur- 

 roundings found on the ancient river bed, near Rock point, at the point 

 " X " in figure 1 (page 298). Figure 1 is a general view, and although the 

 pot-hole has been somewhat damaged by blasting, it clearly shows the 

 distinctive features of this phase of erosion. Figure 2 is a more detailed 

 view. The shadow of the tapeline (the picture was taken at noon) 

 defines the eroded side, and the steep upstream side is undercut. Both 

 views are taken looking southward, or down the present stream, and the 

 northioard flow of the water that formed them is distinctly indicated. 



