SUPERFICIAL GEOLOGY OF DUNDAS VALLEY. 1 35 



case, as Professor Spencer says, the Grand River at one time ran 

 into the Dundas Valley, it must have come up in a channel situated 

 to the west. This channel, most probably, was that now occupied 

 by Fairchild's Creek. In this district we find quicksand, or silt, at 

 the depths of 12, 16, 20, 30, 35, 50 and 60 feet. It is, however, 

 probable that the beds at 12 and 16 feet, and at 30 and 35 feet, 

 are the same beds pierced twice. This would reduce the number of 

 these sands to five distinct beds, or strata. 



It has already been noticed that the sand in the section shown 

 at Mud Run, on Fairchild's Creek, contain several species of recent 

 fresh-water shells. At Middleport and Onondaga, the inter-strati- 

 fied beds of sand also contain specimens of recent shells, most of 

 which, however, are of different genera from those at Fairchild : s 

 creek. Only one class seems to be common to the two places. 



The present lakes, notably Lake Superior and Huron, are laying 

 down deposits corresponding with what we see covering this district. 

 The maps of the U. S. Coast Survey also describe the bottom of 

 Lake Erie as mud and clay. Mr. Geikie, in his " Great Ice Age,'' 

 in describing several districts of Scotland as old lake bottoms, gives 

 sections nearly corresponding to the beds of clay and sand covering 

 the tract west of the Pleight of Land, at the head of the valley. 

 Some of his sections are so near a parallel that they might be sub- 

 stituated for what is found here. 



Looking at the deposits of clays and sands in this district, there 

 seems to be little doubt but that it is the bed of a lake of postglacial 

 date, the Height ot Land forming the barrier between it and Dun- 

 das valley. Mr. Geikie, in referring to these old lakes, says such 

 filled up lakes are probably far more numerous than we have any idea 

 of — for it is always difficult to prove that a wide flat of alluvial ground 

 marks the site of an ancient lake. The barriers that formerly held 

 the waters become obliterated, either by being swept away or buried 

 deeply under recent deposits. Such is the case with not a few rock 

 basins, where the lower lip of rock is often concealed below silt, sand 

 or gravel, and it is only by boring that this fact can be demonstrated. 



In this district, fortunately for the theory of its being an ancient 

 lake bed, the barriers are not wanting. The Height of Land, we can 

 easily see, formed the border of this lake on the north and eastern 

 sides. In all probability the western border will be found in the 



