200 W. H. COLLINS 



The rock formations are all sediments, deposited by the subdued 

 agencies of water or of wind. They He in horizontal beds, free 

 from stress. 



The mild topographic aspect of most of northern Ontario might 

 lead one to expect somewhat the same undisturbed condition under- 

 ground. This is not found, however. It is not asserted here that 

 some of the rock formations are not fiat-lying or nearly so. Some 

 of them are ; but the prevailing condition is quite different. Char- 

 acteristically, the stratified formations of northern Ontario are 

 folded, twisted, sheared, and broken in the most extraordinary 

 manner. They spring from deep underground in arches that are 

 abruptly truncated by the surface of the peneplain. In places 

 they have been broken by faults so great that the two sundered 

 parts of a formation, that once lay face to face, are now found 

 from a few hundred feet to a mile apart. They are cut by dikes 

 and sills of rocks that were once molten, and a large share of the 

 present surface of the region is now underlain by bathoHthic 

 masses of granite, once molten, a hundred miles or so in diameter, 

 and of unknown depth. The condition is one of suspended geo- 

 logical turmoil of incredible magnitude and violence. 



There is something dramatic and stirring to the imagination in 

 this contrast between the mild landscape of the present northern 

 Ontario and the evidence of telluric convulsion that Hes just beneath 

 it; a contrast which impels one to speculate about the cause of 

 this violence, in what manner it expressed itself at the surface of 

 the earth, and what have been the processes of change between 

 then and now. 



The characteristic geological features of this region, as con- 

 trasted with those of a true plain, are the extreme deformation of 

 the stratified formations, and the presence of igneous formations, 

 particularly the bathoHths of granitic rocks. If one studies a 

 geological map of North America (Fig. i), it is soon apparent that, 

 outside of the great Precambrian Shield region, to which northern 

 Ontario belongs, the greatly folded and faulted rocks are confined 

 to the mountain regions — the Western Cordillera and the Appa- 

 lachian Mountains along the Atlantic Coast. It can be seen at 

 the same time that great granite masses, the bathoHths, are present 



