1862.] BIGSBY CAMBRIAN AND HTTRONTAN. 47 



the Huronian formation in America, whether in Canada, Wisconsin 

 (U. S.), or elsewhere, consist of: — 



1. Slate; chloritic, siliceous, and hornblendic. 



2. Slate ; conglomeratic, matrix impurely argillaceous ; the pebbles 

 and boulders being granitic, syenitic, and slaty. 



3. Conglomerates ; quartzose, with white quartzosc and red jasper 

 pebbles. 



4. Trap and pale greenstone, both conformable and intrusive. 



5. Granite ; red, moderately porphyritic, intrusive. 



6. Crystalline limestone ; with some serpentine. 



All these rocks are set down in the order of their abundance, the 

 most prevalent first ; Nos. 2 and 3 being very thick compared with 

 the other beds individually, i. e. 7900 feet out of 16,700 feet (be- 

 tween the Rivers St. Mary and Missassaga, Lake Huron*), if we add 

 up the separate beds. 



d. Connexion with the Laurentian. — The connexion of the Huro- 

 nian set of rocks with the Laurentian is not so fully made out in 

 America as in Norway; but we are not without some good materials, 

 and time will do the rest. Sir William Logan met with a conformable 

 junction of these two formations on the River Kaministiquia, on the 

 north side of Lake Superior, in the rear of Fort "William. At the 

 lower end of the Second Portage, above the Grand Falls, the Lauren- 

 tian appears as a massive syenite or, rather, as a hornblendic gneiss. 

 Hesting on it conformably, there occurs a series of dark, greenish- 

 blue or greenish-black slates (Huronian); the one rock almost running 

 into the other. The section extends for a quarter of a mile along the 

 river-bank. The Huronian has been observed to rest on granite in 

 two places, — on Spanish River in Lake Huron, and again on the same 

 granite 100 miles to the west, near Gros Cap, on Lake Superiorf. 



No particular succession of individual beds has been, as yet, made 

 out, either in Europe or America ; not but that there are, in parts, 

 long lines of distinct stratification, but because there are scarcely any 

 dips to be depended on. On Lake Huron, in the district just men- 

 tioned, this may well happen, through the occurrence of two enor- 

 mous downthrows in a wild and marshy country ; and then again 

 from the inextricable confusion created by the violent intrusion of 

 molten rocks at five distinct epochs t, the last of which produced large 

 deposits of copper-ores. 



e. Igneous intrusions. — Any description by words of the mutual 

 penetration, interweavings, and delicate inosculations of bright-green 

 greenstone and red granite, over considerable spaces of the mainland, 

 between the Rivers Missassaga and Thessalon, has been abandoned 

 in despair by Mr. Murray §. And Messrs. Foster and Whitney have 

 been equally foiled by similar Mendings of granite and greenstone 

 on the Menomonee, between Sandy Point and Sturgeon Point ||. 



* Murray, Canadian Geological Report, 1858, p. 76. 



f Canad. Geol. Report, 1849, p. 8. 



% Murray, Report on North Shore of Lake Huron, 1849, p. 14. 



§ Canad. Geol. Report, 1858, p. 76. 



|| Foster and Whitney, Geol. Surv. of Lake Superior Land District, 1851, p. 19. 



