QUARTZITE TONGUE AT REPUBLIC, MICH. 



68l 



II. 



For the purposes of this article it is unnecessary to give a 

 detailed description of the Republic rocks, as their character is 

 sufficiently indicated by the names attached to the several 

 formations in the table below, which shows, with some slight 

 modifications, the divisions, the order of succession, and the 

 nomenclature as determined and used by Brooks, Wadsworth, 

 and the United States geologists, respectively. 



I have omitted from column I., the succession according to 

 Brooks, the diorites VII., IX., and XL, which are now known to 

 be later intrusive sheets and dikes. That Brooks should have 

 divided the ferruginous rocks between the quartzites V. and 

 XIV. into what we now think an unnecessary number of forma- 

 tions, is easily understood, when it is remembered that his 

 classification was a provisional one for field use, which the 

 exigencies of hurried publication forced him to retain in his 

 final report. 



