EARLIEST ACCOUNTS OF THE HURONIAN AREA. 87 



the Mattawa and Ottawa ; respecting which he had made the following 

 remarks : 



"The succession of rocks in ascending order, * * * after crossing sixty-three 

 miles * * * occupied by the unbroken uniformity of the lower metamorphic or 

 syenitic gneiss formation, is as follows : 



" 3. Fossiliferous limestones. 



"2. Greenish sandstones (quartzites). 



" 1. Chloritic slates and conglomerates." 



The fossiliferous limestones were referred to the Niagara, and the " chlo- 

 ritic slates and conglomerates " were subsequently embraced in the Huro- 

 nian. This series of rocks Mr. Logan thought to " form a connecting link 

 between lakes Huron and Superior to the vicinity of Shebawenahning, a 

 distance of 120 miles." * 



Rocks supposed to be of the same age had already been studied at various 

 points along the Canadian shore of Lake Superior, as will be pointed out, 

 and the opinion at the time entertained was that they represented the Cam- 

 brian. In a communication made to the British Association in 1851,t speak- 

 ing of the geological position of these rocks, Logan said : 



"And in this sequence those [rocks] of Lake Huron, if not those of Lake Superior, 

 would appear to be contemporaneous with the Cambrian series of the British Isles. 



In the next paragraph he says " the Lower Silurian on the lower St. Law- 

 rence appears to rest upon gneissoid rocks without the intervention of the 

 Cambrian ; " J and in the next he uses the phrase " Cambrian formation of 

 Lakes Huron and Superior" (p. 227), and the same again on the next page. 

 It is evident, then, that in 1851 Sir William Logan considered the rocks on 

 the north shore of Lake Huron as equivalent to the Cambrian of Sedgwick. 



Murray on the Grouping and Details. — In his report for 1848-49 § Mr. 

 Murray gave further details of this region. He divided the rocks into a 

 lower " Granitic or Metamorphic group " and a higher " Quartz Rock 

 group." Of the latter group he says : 



"The rocks of this group, where they came under our observation, like those ex- 

 amined the previous season further to the west, were found to be partly of aqueous 

 and partly of igneous origin. The former consisted of sandstones, conglomerate slates 

 and limestones ; the latter, of beds of trap and trap dikes. The prevailing color of the 

 sandstones was white, sometimes with a tinge of pale green ; often the color was gray. 

 The rock was always very silicious, and most frequently fine grained, in some cases 

 of so close a texture as to assume the aspect of a compact, crystalline quartzite ; but 

 sometimes it was sufficiently coarse to constitute a fine conglomerate, of which the 

 component grains and pebbles were by far the greater part of the quartz ; but in the 



* Logan, Report on the North Shore of Lake Huron, p. 8, 



fRep. Brit. Assoc. Adv. Sci., 1851, Transactions of Sections, pp. 59-02; Amer. Jour. Sei., 2nd aer., 

 vol. XIV, 1852, pp. 224-229. See also Bull. Soc. geolog.de France, 1849-'50, 2nd ser., vol. VII, pp. 

 207-209. 



X Amer. Jour. Sci., 2nd sen, vol. XIV, p. 226. 



I Report Geolog. 8urv. of Canada for 1848-49, pp. 36-38. 



