2IO W. H. COLLINS 



conception of the time involved is obtainable by comparison with 

 the rate of formation and reduction of the Rocky, Coast, and 

 Appalachian Mountains. 



4. From the Bruce period until the Keweenawan the region was 

 apparently a land area or one of shallow and intermittent sub- 

 mergence. 



5. Following or during the Keweenawan another (third) process 

 of mountain-building (Killarnean) took place which affected only 

 the southern portion of the region. These Killamean Mountains 

 were reduced to a state of fairly low rehef before the Ordovician 

 marine sediments were deposited upon them. 



6. From Ordovician time until the present the region has been 

 subjected only to gentle epeirogenic oscillations and shallow sub- 

 mergence; its rehef was low throughout this interval and it now 

 forms a glaciated peneplain. 



7. From the earliest time of which a geological record remains, 

 the region of which northeastern Ontario is part, has behaved as a 

 positive element of the earth's crust. 



