170 A. '. LAWSON — Till PRE-PALEOZOK SURFACE. 



To the north the explorations of McOual ami Low have established the 

 existence of another large and important outlier of undisturbed Paleozoic 



rocks over inn miles in extent, about 150 miles bey 1 Lake St. John, at 



Lake Mistassini. These rocks arc chiefly limestone in which as vet no 



lis have been found, and which an' referred provisionally to the ( lambrian 



from certain resemblances to the Hat Btrata of the east coast of Hudson's 



hay which are BUpposed to he of that age. These latter rocks occur along 

 the Bast-main coast, resting in undisturbed attitudes upon tin- Archean. 

 Inlaml from this coast, al-o. Mr. Low found in the drift which come- from 

 the east, "l- the interior of Labrador, a limestone boulder containing Silurian 



-ils. which indicates the presence of an outlying area of such rocks in that 

 region. 



On the upper Ottawa, in the vicinity of Pembroke, we find extensive 

 Canihro-Silurian outlier- as much a- 50 miles from the edge of the present 

 main Paleozoic basin. Other outliers are also found on the islands of Lake 

 Nipissing, ami on Lake Temiscaming nearly ion miles north of Lake 

 Nipissing. There is thus L r <>"d reason for supposing that the Paleozoic sea- 

 extended tar over the whole of the upper Ottawa country. 



The great Siluro-Devonian basin of the west side of James's hay extends 

 southward to within Inn miles of the north shore of Lake Superior, and 

 farther wot the rucks of the Nipigon basin extend northward for 100 miles. 

 The former extends south and the latter north of the 50th parallel of latitude, 

 and the east and west distance between the two basins along the parallel is 

 only about inn miles. It is entirely probable that both of these basins only 

 represent what is left by erosion of a much more extensive distribution of 

 the respective formations constituting them ; and that they do not in reality 

 correspond in area to the original basins of deposition, hut are rather basins 

 of shelter from erosion, such as all the Paleozoic outlier.- appear to he. 



( )n tie- southwest -ide of Hudson's hay there is another extensive area of 

 Silurian rocks, traversed by the lower stretches of the Churchill, the Nelson, 

 the Have-, and the Severn rivers. These rocks resemble those of the same 

 in the basin of the Red river and Lake Winnipeg, both as regards their 

 t "• • — 1 1 remains and their lithological characters. The Hudson's bay area of 

 these ruck- i- separated from that on Lake Winnipeg by about -"" mile of 

 Archean country, with no prominent elevations betwei a, and it i- therefore 

 quite probable that they were once connected, and that the formations of 

 which they are constituted extended continuously across this northwestern 

 arm of the V-shaped Archean "nucleus." An outlying ana of sand- 

 stones of unknown age also rests upon the Archean at the east end of 

 Athabasca lal 



Thus, considering the very limited extent to which this Archean "nucleus" 



. Vol. Mi 



