EVIDENCE OF PREGLACIAL EROSION. 29] 



of preglacial origin. There appears to be. no evidence that these rivers 

 themselves removed so large an amount of rock ; and drift materials, similar 

 to those of the higher levels, are deposited equally below the more ancient 

 walls." * The channels of the Clearwater and of the lower part of the Atha- 

 basca evidently form a continuous valley of large size, through which a 

 greater river flowed for ages before the glacial period. The direction of the 

 current of this stream would depend upon the slope of the country at the 

 time. There is said to be a continuous water-course between the head of 

 Clearwater river and Clearwater lake, connecting again with Isle ;i la Crosse 

 lake, out of which the Churchill river flows. A slight elevation to tin- cast- 

 ward would send the waters of the upper Churchill and all the drainage of 

 the Isle a la Crosse basin down the Clearwater river, while on the other 

 hand a greater elevation to the westward would turn the waters of Lake 

 Athabasca and Peace river into the Churchill. 



In the lower part of the Churchill river I found, in 187!), ancient gravel- 

 filled valleys, excavated in solid limestone, and all covered over with bowlder- 

 clay. Similar evidence of preglacial erosion was noticed in limestone in 

 the lower part of Nelson river. On the Missinaibi river (southwest of 

 James's Bay) I discovered several beds of lignite with till both above and 

 below them. Another bed of lignite, three feet thick, which I have de- 

 scribed on Coal brook, a channel of this river, rests upon blue and light 

 colored clays and is overlain by about seventy feet of till. Traces of lignite, 

 of the age of the drift, were also met with on Albany and Abittibi rivers. 

 In one place the Kenogami river, which discharges Long lake into the 

 Albany, cuts across an ancieut valley, excavated in Silurian strata with a 

 bed of lignite in the bottom and filled with drift materials, which also over- 

 spread the surface of the older rocks on either side of the preglacial chan- 

 nel. Lignite occurs beneath the drift on Rainy river and on the western 

 side of the main body of Lake of the Woods. The lignite, or buried peat, 

 of the south shore of Lake Superior and that of theGoulais river, on itseasf 

 side, are overlain by modified sand and clay of more recent date than the 

 till. But evidence of this kind is comparatively rare. It is seldom that 

 anything is found between the till and the glaciated surface of the funda- 

 mental rocks. 



The Evidence of Glacial Action. — With the exceptions already noted, the 

 whole surface of the Dominion from the boundary of the United States 

 northward to Baffiuland has been thoroughly ice-swept. In spite oft lie 

 mammillated aspect of the vast Archean region, the evidence of this greal 

 planing and denuding force is everywhere manifest. Its appearance on the 

 grand scale may be compared to that of a hummocky surface of plastic clay 

 which had been stroked by the han 1. The valleys and the sides and tops 



*Geol. Survey Report for 1882, page 30cc. 



