TRANSACXIOXS OF SECTION C. 629- 



eiiminated -while still retaiuiiig the important features. This must be largely a 

 matter of individual judgment, and I can only hope to present what appear to me 

 to be the essential points, with special reference to the geology of Canada. The 

 useful object of any such review is, of course, to bring out what may now actually 

 he regarded as established respecting these older rocks, and in what direction the 

 most hopeful outlook exists for improving our knowledge of them. For this pur- 

 pose, the best mode of approaching the subject, in the first place, and up to a 

 certain point, is the historical one, and it will thus be desirable to recapitulate 

 briefly the first steps made in the classification of the crystalline schists in Canada. 

 This is the more appropriate, because of the substantial accuracy of these first 

 observations, and the fact that they have since been largely buried out of sight by 

 a copious controversial literature of later growth. 



Soon after the Geological Survey of Canada was begun, now more than fifty 

 years ago, Logan (who in the earlier years of tlie work may almost be said to 

 have alone constituted the staff") found himself confronted with the great areas of 

 crystalline rocks forming the continental Protaxis. The existing geological edifice 

 has been so largely the result of the past half century of work, that it is not now 

 easy to realise the elementary condition in which its foundations lay at that time. 

 It was then but ten years since Sedgwick and Murchison had given form to their 

 discoveries in regard to the Cambrian and Silurian, and a still shorter time since 

 tlie definitive publication of the classification of the Cambrian and the appearance 

 of the ' Silurian System,' while Hall, Emmons and others, working upon these 

 lines, were actively engaged in building up a similar classification of the Palaeozoic 

 rocks of the Eastern States of the American Union. The Silurian and Cambrian 

 had, in fact, but just been reclaimed from what Murchison speaks of as the 'vast 

 unclassified heaps of grey wacke ' or ' transition limestones.' 



It would have been quite appropriate at this date to relegate all underlying and 

 more or less completely crystalline rocks to the * Primary,' or ' Primitive,' or 

 ' Azoic,' but such a solution fortunately did not recommend itself to Logan. 



It was along the Ottawa Valley, in 1845, that the rocks subsequently classed 

 under the Laurentian and Huronian systems were first examined in some detail. 

 In that year Logan met with and accurately described, severally, rocks which we 

 now refer to (1) The Fundamental Gneiss ; (2) The Grenville Series ; and (.3) 

 The Huronian. lie speaks of the rocks of the first class as being in the main 

 syenitic gneisses ' of a highly crystalline quality, belonging to the order which, in 

 the nomenclature of Lyeli, is called metamorpliic instead of primary, as possessing 

 an aspect inducing a theoretic belief that they may be ancient sedimentary forma- 

 tions in an altered condition.' In what we now call the Grenville Series, he de- 

 scribes the association of crystalline limestones and interbedded gneisses, adding 

 that it appeared to be expedient to consider this mass as a separate metamorphic 

 jrroup, supposed to be newer than the last. Of the Huronian, the relations were 

 at that time left undetermined, although it is observed that its beds hold pebbles 

 of the underlying rocks, here the Fundamental Gneiss. 



The following season was spent by Logan, and by his assistant Murray, on the 

 north shore of Lake Superior, Thunder Bay and its vicinity being one of the regions 

 especially examined. Without enumerating particular localities, it may be stated 

 that Logan there grouped the rocks met with as follows, beginning with the 

 lowest; the column added on the left giving the present nomenclature of the 

 several series defined : — 



Granite and syenite. 



Gneiss. 



Chloritic and partly talcose 

 and conglomerate slates 

 [schists.] 



Bluish slates or shales inter- 

 stratified with trap. 



Sandstones, limestones, in- 

 durated marls and conglo- 

 merates, inteistratified with 

 trap. 



