126 REPORTS ON THE STATE OF SCIENCE. 



great mass of pre-Palaeozoic sedimentary rocks as well as the basal 

 schists; and we may take it that if one name is to be given to all the 

 pre -Palaeozoic, then one of Dana's two names, Archean or Archaeozoic, 

 has unquestionably strong claims for acceptance. 



In recent years there has been a widely felt tendency to divide the 

 pre-Cambrian rocks into two divisions — an upper division of non-foliated 

 sediments and a lower division of schists and gneisses to which the term 

 Archean is sometimes restricted. Sir A. Geikie, 1 for example, notes 

 the proposal to reserve Archean for the igneous rocks and Algonkian 

 for the pre-Cambrian sediments. 



As an example of another twofold arrangement may be quoted tbe 

 classification in Chamberlin and Salisbury's Geology: — 



Protcrozoic 



fKeweenawan. 

 irxuicruzuiu Aniuiikean= Upper Huronian of some authors. 



(Algonkian) | Huronian . 



. . . ["Great Granitoid series (Laurentian) (mainly intrusive). 



Arcnscozoic J Great g e hi s t series (Mona, Kitchi, Keewatin, Quinncssco, 

 ( Archean complex) j j^^ Huronian of somo author8) .a 



Chamberlin and Salisbury object to the names Algonkian and 

 Archean for the primary divisions, on the ground that the names suggest 

 that the divisions are systems, such as Cambrian, instead of being 

 groups, such as Palaeozoic. 



The Witwatersrand System may be the South African equivalent 

 of these non-schistose pre-Cambrian sediments ; and the Swaziland 

 System, or whatever name be adopted for the schists, would 

 represent the Archean. There seems a tendency to adopt the term 

 Algonkian for the non-schistose pre-Cambrian sedimentary rocks, 

 though it was founded to include the schists as well ; and a term of 

 world-wide application is wanted for such unaltered pre-Cambrian sedi- 

 ments as the British Torridonian and Longmyndian, the North American 

 Keweenawan, the Scandinavian Sparagmites, the Indian Purana, &c. 

 These rocks appear to represent a geological system between the under- 

 lying schists and the beginning of the Palaeozoic. 



Chamberlin and Salisbury's classification inverts the use of the word 

 'Archaeozoic, which was proposed by Dana in 1872 pre-eminently for 

 the pre-Cambrian rocks which might be proved to contain life. He in- 

 troduced the term Archean and Archaeozoic when describing one of 

 the quartzites, clearly showing that he included the sedimentary as well 

 ss the schistose series in the Archean. 



The term Proterozoic was first suggested by Emmons, and rejected 

 by Irving in 1888. He then proposed to limit Archean to the basal 

 schists, and called the overlying sediments Eparchean, as being upon 

 the Archean or Agnotozoic. 3 



1 Text-Book, vol. ii., p. 904. 



2 Chamberlin and Salisbury, Geology, vol. ii., p. 100. 



3 R. D. Irving, ' On the Classification of the Early Cambrian and Pre-Cambrian 

 Formations.' Seventh Ann. Rep. U.S. Geol. Surv., 1885-80, p. 454. 



