Dr. H. Hichs — Cambrian Rocks of N. America. 



157 



Dr. Sterry Hunt has strongly advocated ' the adoption of the term 

 Ordovician (first proposed by Prof. Lapworth and now used by 

 many authors in this country) for the American second division 

 (Lower Silurian), and it is highly advisable that it should be adopted 

 by American authors, as it would then be possible to know exactly 

 to which portion of the Lower Palseozoic rocks the author referred. 

 The tripartite division of the Lower PalEeozoic rocks of Great Britain 

 under the names Cambrian, Ordovician, and Silurian, seems at 

 present the only means of avoiding confusion, and it is highly satis- 

 factory, therefore, to find that some American authors are prepared 

 to accept these terms to designate the primary divisions of the 

 American Lower Palaeozoic rocks.^ 



On the other hand, it is advisable that groups and series should 

 still have local names, and the names should be those of places where 

 the beds were first examined, or are well exposed. The following 

 table expresses Mr. AValcott's views on the classification of the various 

 groups that go to make up the Cambrian system of North America. 



Classification of North American Cambrian Rocks. 



1 Trans. Roy. Soc. Canada, 1883, and " Mineral Physiology," etc. 1886, p. 528. 



2 In a former paper (Geol. Mag. Aug. 1885) I ventured to suggest that the term 

 " Cambrian," instead of being coniined to the lowest rocks, might fairly be extended 

 as a main terra to indicate the whole of the Lower Palasozoic rocks, and that the 

 name "Georgian" (from St. George's Channel, on the borders of which the lower 

 rocks are best exposed) would b^ a suitable term for the lowest rocks. I have since 

 found that the Middle Cambrian rocks of Franklin County, Vermont, America, had 

 previously been designated the " Georgia Group " ; therefore it is evident that the 

 adoption for a much larger division of the term "Georgian" would only lead to 

 confusion. It is better, therefore, to confine the term" Cambrian" as in the present 

 paper to the rocks underlying the "Ordovician." 



