JR. D. Irving — Is there a Huronian Group f 207 



the general term of "non-eruptive crystallines." These are 

 set off by themselves collectively because, while it is ad- 

 mitted that the larger part of them are of an age greater than 

 those of the recognized clastic groups, it is desired to avoid for 

 the present the still disputed points: (1) as to whether some of 

 them are not altered clastic rocks of later geological age ; and 

 (2) as to whether those which unquestionably belong below the 

 base of the ordinarily recognized Palaeozoic groups are, or are 

 not. divisible into members of a taxonomic rank equal with 

 that of those groups. 



It is with this latter question, or rather with a portion of it, 

 that the present essay concerns itself. I say a portion of it 

 because the general question as to what groups, if any, we 

 should recognize among the pre-Cambrian rocks would be 

 quite too broad a one for the space that can now be occupied. 

 Not to speak of other points that would have to be considered, 

 the answer to this general question would involve, in the first 

 place, a discussion as to the separate existence, and taxonomic 

 relations of the so-called Keweenaw Series of Lake Superior. 

 My design is then merely to inquire if there can be carved off 

 of the upper portion of the great complex which has been 

 called Archaean, a series of Huronian rocks; a series entitled — 

 by structural and genetic separateness, by clastic origin, by 

 largeness of volume, and by the being made up of subordinate 

 divisions of the formation rank — to the rank of a group, i. e., 

 to a rank equal in classificatory value to the Cambrian, Silu- 

 rian, etc. 



II. The term Huronian seems first to have been used in a 

 publication prepared for the Paris Exposition of 1855, by Sir 

 Win. Logan and Dr. T. S. Hunt, on part of the Geological Sur- 

 vey of Canada, and entitled "Esquisse G^ologique du Canada." 

 As used in this volume, however,* the term has but a very 

 vague and unsatisfactory signification. To begin with, it is 

 used only as a synonym of Cambrian, and is not made to ap- 

 ply especially to any one individual or typical area, but to em- 

 brace vaguely defined series of rocks occurring in various 

 wholly separated areas on Lakes Superior and Huron, which 

 series may or may not be geologically equivalents of one 

 another so far as any evidence presented goes to show. More- 

 over, the term is made to cover also the great and wholly dis- 

 tinct succession afterwards separated out as the Copper-Bear- 

 ing or Keweenaw Series. 



The term Huronian was afterwards used in various reports of a 

 the Canada Survey, with a somewhat changing signification, 

 until, in 1863, Sir William Logan gave, in the Geology of 

 Canada, a thoroughly definite account of the series, including 



