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CANADA. 



331 



PART I. 



Syno2')sis of the Evidence on which the Racks of the Azoic System 

 have hecn variously grouped into Distinct Divisions hj American 

 Geologists, 



In" tlio following discussion the various regions where rocks of the 

 Azoic System occur will be taken up and examined in a geographical 

 order, beginning with that part of the North American coutinent where 

 these rocks have their greatest development, and where, in course of 

 a geological survey carried on continuously for more than forty years, a 

 large portion of the material has been published which will here come 

 under review. In order to prevent misunderstandings, and as an im- 

 portant assistance to those who may hereafter wish to make an inde- 

 pendent examination of the questions here discussed, the exact language 

 of the author quoted will be given in as much fulness as seems desirable, 

 although this course must necessarily considerably increase the length 

 of this paper. 



CANADA. 



Sir Wm. Logan, in the Report of Progress of the Canada Geological 

 Survey for 1845-46 (pp. 40-51), described a series of rocks which he, 

 following Lyell, called the *' Mctamorphio Series." This ho divides into 

 two divisions, one composed in general of "sycnitic gneiss," the other of 

 the same rock with intercalated bands of crystalline limestone. The 

 relations of these to each other can be best expressed In Logan's own 

 words : — 



" To the south of the Mattawa and of the Ottawa in \U continuation after 

 the junction of tlie two streams, important beds of crystalline limestone become 

 interstratificd with the syenitic gneiss, and their presence constitutes so marked 

 a chasacter tliat it appears to me expedient to consider the mass to which they 

 belong as a separate group of metamorphic strata, supposed from their geo- 

 graphical position and general attitude to overlie the previous rocks conform- 

 ably. The limestone beds appear to be fewer at the bottom than at the top 



BULL. MUS. COMP. Z0(3l. VOL. VII. — NO. 11. 



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