-^^ 



n< 



CANADA. 



359 



m 



*' IIT. Cambkian ; 



" 111 niiiiiy of the areas, especially tlie weaterii ones, the hase of this is well- 

 defined by im conformity, hut in the Eastern Townships and in soni'e parts of 

 Nova Scotia it has yet to be determined. The limit between it and Lower 



Silurian is debatable ground, upon which we need not enter One point 



I wish particularly to insist on is, that great local unconformities and lithologi- 

 cal differences may exist without indicating any important difference in age, 

 especially in regions of mixed volcanic and sedimentary strata, and that the 

 fact of crystalline rocks (greenstones, diorites, dolerites, felsites, norites, &c.,) 

 appearing as stralihed masses and passing into schistose rocks, is no proof of 

 their not being of eruptive or volcanic origin — their present metaniorphic or 

 altered character is, as the name implies, a secondary phase of their existence, 

 and is unconnected with their origin or original formation at the surface, but 

 is due partly to original differences of coniposition and partly to the varying 

 physical accidents to which they have, since their formation, respectively been 

 subjected." (I. c, pp. 1-15 A.) 



Mr. Sclwyn's views were discussed, and in part objected to, by Mr. 

 Thomas Macfarlane. (Canadian Naturalist, 1879, (2) IX. 91-103.) 



Dr. Hunt very ingeniously derives comfort from the preceding paper 

 by ignoring most of it and claiming : — 



*' The pre~Cambrian age of these crystalline schists in Eastern Canada has 

 now been clearly proved by the . . . '. recent stratigraphicid studies of Selwyn, 

 as announced by him in 1878." (Proc. Am. Assoc. Adv. Sci., 1879, XXYIIL 

 286.) 



In 1879 Dr. Dawson remarked that 



" the idea that the Middle Laurcntian, the horizon of Eozoon Canadense and of 

 the great Phosphate and Graphite deposits, is identical with the Hastings 

 group, or with the Tluronian, has, I am fully convinced, after some study of 

 the Lake Huron, Madoc and St. John exposures of these formations, no- foun- 

 dation in fact." (Canadian Nat., 1879, (2) IX. 180.) 



Dr. Dawson, however, gave no proof of this statement, while Mr. 

 Vcnnor had worked out the subject according to the stratigraphical 

 methods of the Canadian Survey, — a labor of ten years ; this is better 

 than an unsupported assertion. 



VOL. VII. — NO. 11. 



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