THE SUCCESSION OF DEPOSITS. 47 



great quantities of boulders were brought down into it, 

 especially from the Laurentide hills, and were drifted 

 along the valley, principally to the south-west. Extensive 

 erosion also took place by the combined action of frost, 

 rain, melting snows, and the arctic current and the waves, 

 and thus was furnished the finer material of the boulder- 

 clay. On the south shore of the St. Lawrence, the Notre 

 Dame mountains, stretching out towards cape Gaspe, 

 afford indications of local glaciation, and Mr. R Chalmers 

 lias shown that the movement of ice from this elevated 

 re2:ion has been both south toward the baie des Chaleurs, 

 and north toward tlie St. Lawrence.* I have myself 

 seen ample evidence in large travelled boulders of Silurian 

 limestone on the south shore of the St. Lawrence, of drift 

 from the hills on the south intermixed with that from the 

 Laurentians on the north. Similar facts have been 

 observed by Ells and Low in tlie hills of the Eastern 

 Townships of the province of Quebec. 



It is further to be observed that oscillations of land 

 must be taken into account in explaining these phenomena. 

 Elevations increasing the height and area of land might 

 increase the space occupied by snow and land ice. 

 Depressions, on the other hand, would bring larger areas 

 under the influence of water-borne ice and marine 

 deposits, and these might take place either in a shallow 

 sea loaded with field and coast ice, or in deeper water in 

 which large icebergs might float or ground. The effects 

 would be the greater if, as Dr. G. M. Dawson has shown 

 in the case of the Cordilleran chain, there was unequal 

 •elevation causing contemporaneous depression of the 



* On the Glaciation and Pleistocene subsidence of northern New 

 Brunswick and south-eastern Quebec. Trans. R.S.C, 1886. 



