522 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



of the Eev. Professor Sedgwick." 



Barrande, in his earliest communication embodying the results of his 

 life-work among the Palaeozoic rocks of Bohemia (1846), did not use the 

 term " primordial/' which he later adopted,, and in which he included 

 the lowest zone of life ; but he speaks of his division " C " as " forming 

 the base of the Protozoic rocks, according to the latest classification 



His (Barrande's) groups "A" and 



"B" constitute the "Lower Division," comprising all the Azoic forma- 

 tions, subdivided into two groups, thciv upper one ("B") being identi- 

 fied by him as the equivalent of Sedgwick's Cambrian, — the confusion 

 in geological nomenclature caused by the introduction of this term hav- 

 ing begun as far back as these earliest days of discussion in regard to 



the Azoic and Palaeozoic rocks. 



It appears, however, that Sedgwick, as late as 1854, had not arrived 

 at any definite conclusions in regard to the existence of an Azoic scries, 

 for he says of his Cambrian, " that it seems to contain no organic re^ 

 mains." But ho hastens to add, that the answer to the question when 

 organic life began '*is involved in inextricable obscurity." * 



In 1851 1 Messrs. Foster and Whitney made known the existence of 

 a series of rocks on the south shore of Lake Superior, in regard to which 

 they wrote as follows : 



"Below all the fossiliferous groups of this [the Lake Superior] region, there 

 is a class of rocka, consisting of various crystalline schists, beds of quartz, and 

 saccharoidal marble, more or leas metamorphosed, which we denominate the 

 iizoic System. This term was first applied by Murchison and De Verneuil to 

 designate those crystalline masses which preceded the Palaeozoic strata. In it 

 they include not only gneiss, but the granitic and plutonic rocks by which it 

 has been invaded. We adopt the term, but hmit its signitication to those 

 rocks which were detrital in their origin, and which were supposed to have 

 been formed before the dawn of organized existence." | 



It is now known that a largo part of the vast region adjacent to Lake 

 Superior on the north and oast, and included within the limits of Can- 

 ada and British North America in general, is occupied by rocks which 

 by their infra-Silurian position and lithological character belong in the 



"Siluria" (1867), tho Azoic is called-" Laurcntian," and is regarded as being "the 

 base of all Palajozoic deposits." 



* British Palaeozoic Rocks and Fossils, 1854, Introduction, p. xxxii. 



t A synopsis of their results liad in the previous year (1850) been presented to 

 the Department of the Interior, and in thia the nature and geological position of the 

 "Azoic System" had been clearly set forth. Senate Documents, 2d Sc.^'^. 31st 

 Cong., 1850-51, IT., Doc. 2, pp. 147-152. 



Z Foster and Whitney's Kcport on the Geology of the Lake Superior Land Dis- 

 trict, Vol. 11. The Iron Kegion, together with the General Geology, 1851, p. 3. 



