CANADA. 359 



" IIT. Cambrian : 



" In many of the areas, especially the western ones, the liase of this is well- 

 definetl by unconformity, but in the Eastern Townships and in some parts of 

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



Sihirian 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 ditierences 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, ielsites, norites, &c.,) 

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

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

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

 and is unconnected with their origin or oi-iginal formation at the surface, but 

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

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

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



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

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



Dr. Hunt very ingeuiously 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 stratigraphical studies of Selwyn, 

 as annoimced by him in 1878." (Proc. Am. Assoc. Adv. Sci., 1879, XXVIII. 

 286.) 



In 1879 Dr. Dawson remarked that 



" the idea that the ^Middle Laurentian, the horizon of Eozoon Canadense and of 

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

 group, or with the Huronian, 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 pi'oof of this statement, while Mr. 

 Yennor 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. vn. — NO. 11. 24 



