146 Transactions of the Canadian Institute. [Vol. VII 



Darton has described a somewhat similar case in Virginia ('94, 582). 

 In the Grand Canon of the Colorado we have an actual transverse sec- 

 tion of two such intersecting plains, both older than the Cambrian, but 

 meeting at a much higher angle. 



Three Problems Stated.- — Among the many problems which 

 present themselves for consideration, three, which have reference to the 

 character of the sedimentary floor, seem worthy of special attention : — 



1. Have we here an ancient sub-maturely dissected plain of denuda- 

 tion, a kind of geographical fossil, or is this topography the result of 

 post-sedimentary causes ? 



2. In either event is there any possibility of approximately dating 

 its origin ? 



3. Is the plain wholly the product of sub-aerial processes, or have 

 we here a plain of submarine abrasion, and subsequent dissection ? 



First Problem, Pre-Sedimentary Topography. — Turning 

 now to a consideration of the first of these problems, it will be necessary 

 to describe, with some detail, a number of special localities which seem 

 to afford evidence for its solution. 



Inliers. — In the township of Verulam, about midway between 

 Sturgeon Point and Bobcaygeon at the foot of Sturgeon lake, conspicu- 

 ous among the hills just north of the lake, is a ridge of aplitic granite 

 known locally as Red Mountain. The exposed base is about sixty feet 

 and the crest one hundred and ninety feet above the level of Sturgeon 

 lake. The ridge itself is about 2,000 feet in length and 600 in breadth ; 

 the longer axis strikes N 23°E. The crest is rounded, but falls off at 

 the northwest corner very abruptly, at an angle of about 80°; on the east 

 the inclination, though less, is still too steep for a person to descend in 

 safety. At the south end the descent on both sides, though steep, is 

 less precipitous. The crest and sides, especially towards the north, are 

 free from boulders ; but the southern end, where the crest is lower, is 

 strewn with large and small sharply angular fragments derived from the 

 ridge itself, together with some large blocks of limestone. Forming a 

 belt one hundred yards in width is marshy ground, beyond which are 

 lower ridges of morainic material. Half a mile to the west of this ridge, 

 occurs a second much smaller granitic ridge trending in the same 

 direction. The deposits of drift seem to obscure any limestone deposits 

 which occur in the immediate vicinity. Four and a half miles to the 

 west, at Sturgeon Point, thin-bedded fossiliferous Trenton limestones 



