SUPERFICIAL GEOLOGY OF DUNDAS VALLEY. 1 37 



mouth of the valley are underlaid in most places by beds of shingle 

 gravel and silt. 



Another feature of the upper blue beds is their want of uniform- 

 ity throughout the valley. In Mr. New's boring we find it within 

 eight feet of the surface, while in the boring at Mr. Burtram's, about 

 a mile and a half further south west, its place is supplied by beds of 

 brownish clay, inter-stratified with fine sand or silt. 



Again, at Mr. Arthur's the blue clay underlies a bed of gravel 

 27 feet thick, and at Dundas the blue clay under the gravel beds is 

 more than 90 feet. 



The positions of these underlying beds of clay, sands, gravels 

 and shingle correspond in many particulars to instances given by 

 Mr. Geikie, in his " Great Ice Age." 



The position and formation of the beds of gravel and shingle 

 underneath the blue clay can only be accounted for by assuming them 

 to have been in that position before the blue clay was laid down. 



Several reasons may be adduced in favor of the theory of 

 these beds being already in the positions they are now found in 

 prior to the deposition of the glacial bed : 



First — If Dundas valley was an arm of a pre-glacial sea, then, 

 from the shape of the valley, there would be a tendency of gravel, 

 sand and other material to gather within its bounds, but in that case 

 these beds of gravel and sand would stretch across the valley in a 

 semi-circular form. Many of the gravel beds appear to lie in this 

 position. 



Second — If Dundas Valley is the gorge or canyon of a pre- 

 glacial river, then these gravel beds would be ranged on one side or 

 both sides of the old river bed. In the case of modern rivers run- 

 ning through gravelly soil, all gravel or sand bars usually stretch 

 down and across the stream from one side or the other. If this rule 

 be applied to the gravels underlying the clay beds in Dundas valley, 

 we would be warranted in ascribing these beds to an existing pre-glac- 

 ial river. These gravels, if belonging to a pre-glacial age when the 

 valley was an arm of the sea, would not only be placed 111 a position 

 across the valley, but would be likely to contain fossil shells of the 

 species living in the waters of that time. None, however, have been 

 obtained from any of the beds. They would also have a stratified 

 appearance, the strata lying at a low angle and sloping down the bay 



