200 THE CANADIAN NATURALIST. [June 



When, however, further investigation showed that the great 

 and progressive thickening which takes place in the paleozoic 

 formations from the west, eastward, is not confined to the aug- 

 mentation of existing subdivisions, but inckides the intercala- 

 tion of new ones ; when the few hundred feet of typical Pots- 

 dam sandstone in New York are represented in Vermont, Quebec 

 and Newfoundland, by thousands of feet of strata lithologically 

 very unlike the type ; while the Quebec group, not less in volume, 

 appears representing the beds of passage between the Calciferous 

 and Chazy divisions of New York, we begin to conceive that con- 

 ditions of sedimentation, very unlike anything hitherto suspected 

 in the west, prevailed to the eastward. When, moreover, we find 

 widely separated areas of Labradorian and Huronian rocks, — 

 remaining fragments of great series, — resting upon the Laurent- 

 ian, from Lake Huron to Newfoundland, we get evidences of a 

 process of denudation in past ages, not less remarkable than the 

 sedimentation. 



My observations of last year have led me to a conclusion, 

 which had previously been taking shape in my mind, that there 

 exists above the Laurentian, a great series of crystalline schists, 

 including mica-slates, staurolite and chiastolite-schists, with 

 quartzose and hornblendic rocks, and some limestones, the whole 

 associated with great masses of fine-grained gneisses, the so-called 

 granites of many parts of New England. The first suggestions 

 of this were given me by the observation of Dr. Bigsby, confirm- 

 ed by specimens since received from that region, that there exists 

 to the northwest of Lake Superior, an extended series of crystal- 

 line schists, unlike the Laurentian, and resembling those of the 

 White Mountains. I have already called attention to this re- 

 semblance in a review of the progress of American Geology, in 

 1861 {Can. Naturalist, VI., 84). It was contrary to my notions 

 of the geological history of the continent to suppose that rocks of 

 Devonian age could, in that region, have assumed such litholog- 

 ical characters, and I was therefore led to compare these rocks 

 with a great series of crystalline schists, abounding in mica-slates 

 and micaceous limestones, which occupy considerable areas in 

 the Laurentian region in Hastings county^ to the north of Lake 

 Ontario. The distribution of this series has been traced out by 

 Mr. Vennor, who in 1869, was able to show that, although much 

 contorted, it rests unconformably upon the old Laurentian 

 gneisses, while it is, at the same time overlaid by the horizontal 



