86 The Eozoic Bocks of North America. 



Norian) and the fossiliferous limestones of the second fauna 

 (Ordovician), of nothing more than those Cambrian subdivisions 

 known as the Potsdam sandstone and the Calciferous sandrock, 

 which in the vicinity of the Adirondack Mountains separate these 

 ancient crystalline rocks from the Ordovician strata. 



The other school of stratigraphists recognized the existence, in 

 this interval, in the region to the east of Lake Champlain, of 

 several series of crystalline rocks, including what we have already 

 described under the names of Arvonian, Huronian, Montalban 

 and Taconian, besides a younger series of uncrystalline sediments 

 of great thickness, designated by Eaton as the First or Transition 

 Graywacke. This was by him declared to be separated by the 

 limestones of the second fauna from the Secondary Graywacke, a 

 series closely resembling the Transition Graywacke. The first- 

 mentioned school denied the existence of the Transition Gray- 

 wacke, and maintained that the group thus designated was identical 

 with the Secondary Graywacke. The geologists of this school 

 further supposed that all the different series of crystalline rocks 

 just named were nothing more than the same Secondary Gray- 

 wacke, with the addition of the underlying fossiliferous limestones, 

 in a state of alteration more or less profound; the series in 

 different areas assuming successively the character of Taconian, 

 Montalban, Huronian, and even, as some imagined, of Laurentian. 



The recent progress of American stratigraphy has fully justified 

 the views of the second named and older school, that of Eaton. It 

 has been shown that the First or Transition Graywacke of this 

 author, which was the Upper Taconic of Emmons, and includes 

 the primordial or Cambrian fauna, rests in unconformable strati- 

 fication upon the various crystalline series named, and that all of 

 these great groups belong to Eozoic time. The Quebec group of 

 Logan, as well as what he called the Potsdam group, is this same 

 Cambrian or Transition Graywacke. The Hudson River group 

 also, as first described by Yanuxem and by Mather, and, later, 

 by Logan up to 1860 (when he proposed for it the name of the 

 Quebec group) is nothing else than this same Cambrian Gray- 

 wacke, with the addition, in certain localities, of a portion of 

 Laconian, and in others of schistose beds containing the second 

 fauna (Utica and Loraine shales). The above explanation 

 becomes necessary for the reason that the Canadian geologists 



