No. 2.] MACFARLANE — CANADIAN STRATIGRAPHY. 101 



nian rocks on the north shore run nearly east and west, dipping 

 34^ to 55° northward. To these, the ishind rocks are conse- 

 quently as unconformable as are the walls of a house to its roof. 



It is further to be remembered that the discordant relation of 

 the Nipigon group to the Huronian system is admitted by Mr. 

 Selwyn to be an "apparent great unconformity," and as the Ni- 

 pigon group is held by Mr. Selwyn to be part of the " Upper 

 Copper bearing rocks," this is almost conceding Dr. Hunt's posi- 

 tion. This admission is not at all weakened by Mr. Selwyn's 

 supposition that they are the products of an ancient volcanic cra- 

 teriform vent, and that Lake Nipigon is an extinct volcano, a 

 gigantic Maare, or water-filled ancient crater, like the Lake of 

 Laach, This invention almost justifies the opinion that Mr. 

 Selwyn is himself sometimes ready to invoke " almost impossi- 

 bilities in physical and dynamical geology." 



4. Writing of Dr. Hunt's Norian system, Mr. Selwyn pens 

 the following remarkable passage : ^' If it is admitted — which, 

 ^' in view of the usual associations of Labrador feldspar, is the 

 " most probable supposition — that these anorthosite rocks repre- 

 '■'■ sent the volcanic and intrusive rocks of the Laurentian period, 

 " then also their often massive and irregular and sometimes 

 ^' bedded character, and their occasionally interrupting and cut- 

 ^' ting off some of the limestone bands, as described by Sir W. E. 

 ^' Logan, is readily understood by any one who has studied the 

 ^' stratigraphical relations of contemporaneous and sedimentary 

 " strata of volcanic, palaeozoic, mesozoic, tertiary and recent 

 *' periods. Chemical and microscopical investigation both seem 

 " to point very closely to this as the true explanation of their 

 " origin. That they are eruptive rocks is held by nearly all geo- 

 " legists who have carefully examined their stratigraphical rela- 

 " tions. But I am not aware of any one having suggested that 

 " they are the products of volcanic action in the Laurentian or 

 "perhaps lower Huronian epoch." It is unnecessary here to 

 combat the doctrine that norites are not merely eruptive, but 

 volcanic rocks. I must content myself with remarking that on 

 Mr. Selwyn rests the burden of proving any new theories he may 

 choose to bring forward, and consequently of shewing that vol- 

 canoes were active in the Azoic age. 



5. Mr. Selwyn underrates the very praiseworthy efibrts which 

 Dr. Hunt has made towards bringing order out of the chaos of 

 our primary geology, and can see no utility in the names he 



