igoi] Ells — Ancient Channels. 21 



It is scarcely to be supposed that the decay of the granitic 

 rocks alone could give rise to the extensive deposits of clay which 

 spread over so wide an area of the Ottawa valley underlying- the 

 sand. These clays are seen at elevations up to the summit of the 

 dividing ridge, at several points reaching a height not far from 

 1,000 teet above the sea. The source of this clay must also be 

 largely conjectural. It may be safely assumed, however, that the 

 amount of denudation throughout the entire area has been some- 

 thing enormous. In the Eastern Townships of Quebec this has 

 been undoubtedly more than 1,000 feet. In the area around 

 Ottawa city it has been lully as much, since at the faulted contact 

 of the Calciferous and the Utica the upraised beds have been 

 entirely removed and the rocks reduced to a uniform level. It is 

 quite possible that there was at one time a regular succession of 

 the Palaeozoic formations throughout the Ottawa valley, extending 

 over the whole country both north and south to the present height 

 of land, since even now we find at many widely detached points, 

 patches of these rocks which have in some way escaped the 

 denuding agents. It is therefore quite possible that much of the 

 clay throughout the district has been the result of the decomposi- 

 tion of the more recent formations. 



While therefore this grand scheme of denudation has been 

 going forward from the earliest times, this has been supplemented 

 by the agency of ice in the glacial period. How many of these 

 periods of glaciation have been in operation in this area we can 

 not say, but we have distinct evidence of at least three which are 

 presumably the most recent, and the traces of other and earlier 

 ones are probably long since removed. That ice moved over the 

 area in different directions and at diff"erent times is shown from 

 the direction of the striae and groovings now seen on the rock 

 surface. The presence of a third and apparently last set of mark- 

 ings with a western trend seems to indicate that a series of large 

 floating ice-pans moved westward up the Ottawa in a direction 

 almost opposite to that recorded for the earliest known glacier 

 which would seem to have followed down the present channel of 

 the river. 



In discussing the history of this valley therefore several 

 periods of upheaval and depression must be considered, and some 



