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338 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



series, a name founded on that given by Mr. Garncan to the chain of hills 

 which they compose. The geological formations which underlie the district in 

 ascending order would thus be as follows : — 



"1. Lauren tian series. 



** 2. Potsdam sandstone/' etc. (/. c, p. 8.) 



It will thus be seen that when the name Laurcntian was thus pro- 

 posed, it was the exact equivalent of the Azoic of Foster and Whitney 

 proposed four years before. 



In *' A Sketch of the Geology of Canada," by Dr. Hunt, occurs the 

 first mention of the Huronian system as such. 



"The shores of Lakes Huron and Superior offer a series of schists, sand- 

 stones, limestones and conglomerates interstratificd with heavy l)edy of green- 

 stone, and resting unconformably upon the Laurentian formation. As these 

 rocks underlie those of the silurian system, and have not as yet alforded any 

 fossils, they may i)robably be referred to the Cand)rian system (lower Cam- 

 brian of Sedgwick.) This Huronian formation is known for a distance of 



about 150 leagues upon Lakes Huron and Superior, and everywhere offers 

 metalliferous veins, which have as yet been very little explored." (Canada at 

 the Universal Exhibition of 1855, pp. 427, 428.) 



In the same paper Dr. Hunt says of the Laurentian system : — 



" The rocks of this system are, almost without exception, ancient sedimentary 

 strata, which have become highly crystalline." (p. 421.) 



So far as we are able to find in the Reports of the Canada Geological 

 Survey no evidence was advanced to prove this position ; it was a purely 

 theoretic assumption, as Logan states (ante, pp. 331, 332). Dr. Hunt 

 also declares that the Huronian on tlie shores of Lakes Huron and Su- 

 perior rests unconformably upon the Laurentian formation. This too 

 was a theoretical belief instead of an observed fact, so far as the Reports 

 bore evidence (p. 427), except in the case of the Lake Sui)erior copper- 

 bearing rocks (Keweenawan, Potsdam), at that time regarded as being 

 the equivalent of the schists (Huronian) north of Lake Huron. (See 

 Azoic Rocks, pp. 71, 72 ; also ante, pp. 334, 335.) 



Of the chlorite schists in the valley of Lake Teraiscaming it is writ- 

 ten : — 



*' The chloritic schists probal)ly correspond to the Huronian rocks, but it is 

 difficult to fix the age of the sandstones which are destitute of ioasils." (/. c, 

 p. 447.) 



The first mention of the Huronian formation by name, found in the 

 Reports of Progress of the Canada Geological Survey, is in Mr. Murray's 

 Report for 1854, under date of June 11, 1855, (p. 125,) as follows : 



