128 SUPERFICIAL GEOLOGY OF DUNDAS VALLEY. 



hardly be inferred that it was the centre of a local glacier, radiating 

 in these directions. We have, therefore, little option in the matter, 

 but must ascribe these directions to two periods of glacial action, 

 which we may call first and second. This will be more readily under- 

 stood when we come to look at the drift filling the valley and cover- 

 ing the escarpment in many places. 



Ice, according to Mr. Carll, moves at different rates of speed at 

 different depths and on meeting any serious obstacle to its progress 

 would turn aside and pursue a course in the line of least resistance.* 

 This may account for the direction of the striae in the valley being 

 in different directions from those from those found on the top of the 

 escarpment! It is clear that the ice coming from the north-east 

 would impinge on the eastern escarpment, which would effectually 

 bar any further progress of the lower strata or stream in that direction. 

 It is also self-evident that on account of the pressure exerted from 

 behind by the whole weight of the moving glacier, the line of least 

 resistance would be along the face of the cliff to the westward, and 

 this course would be the direction pursued by the lower ice current, 

 while the upper division would pass over the top of the escarpment. 

 To this action I would ascribe the two lines of cliff, the upper and 

 lower, and the broken material found on the top of this lower east 

 ern escarpment, and which is wanting in most parts of the western or 

 West Flamboro' wall of the valley. 



In the stream near Ancaster, blocks of sandstone belonging to 

 the Medina formation have been found embedded in the sands and 

 clays filling the old ravine. This would seem to bear out the theory 

 of the movements of the lower ice. It would thus appear that this 

 stream is of pre-glacial date, or at least existed at a time before the 

 glacier tearing up these blocks covered the district. 



The position of Dundas Valley, however, in respect to the rock 

 bedding of the district, is peculiar. The valley lies on the top of the 

 anticlinal and must at one time have had an elevation of 520 feet 

 above lake level. At the time the bedding of the escarpment formed 

 the anticlinal, the escarpment would also be complete in the channel 

 of the present Niagara river, as far down as Queenstown Heights. 



* Report III. Second Geological Survey of Pennsylvania, page 330 et seq. 



