252 GEOGNOSY OF THE APPALACHIANS. [XIII. 



uniting in one system the crystalline schists and the overlying 

 uncrystalline fossiliferous sediments, in direct opposition to the 

 plainly expressed teachings of Emmons, as laid down in his 

 report on the geology of the Northern District of New York, 

 and later, in 1846,* in his memoir on the Taconic System. 



In the geological survey of the State of New York, the 

 rocks of the Champlain division (including the strata from the 

 base of the Potsdam sandstone to the summit of the Loraine 

 or Hudson River shales) had, by his colleagues, been looked 

 upon as the lowest of the paleozoic system. Professor Ern- 

 mons, however, was led to regard the very dissimilar strata of 

 the Taconic hills as constituting a distinct and more ancient 

 series. A similar view had been held by Eaton, who placed, 

 as we have already seen, above the crystalline schists of the 

 Green Mountains, his primary quartzose and calcareous forma- 

 tions, followed to the westward by transition argillites and 

 sandstones, which latter appear to have corresponded to the 

 Potsdam sandstone of New York. Emmons, however, gave a 

 greater form and consistency to this view, and endeavored to 

 sustain it by the evidence of fossils, as well as by structure. 

 The Taconic system, as defined by him, may be briefly de- 

 scribed as a series of uncrystalline fossiliferous sediments 

 reposing unconformably on the crystalline schists of the Green 

 Mountains, and partly made up of their ruins ; while it is, at 

 the same time, overlaid uuconformably by the Potsdam and 

 Calciferous formations of the Champlain division, and consti- 

 tutes the true base of the palaeozoic column. 



Although he claimed to have traced this Taconic system 

 throughout the Appalachian chain from Maine to North Caro- 

 lina, it is along the confines of Massachusetts and New York 

 that its development was most minutely studied. He separated 

 it into a lower and an upper division, and estimated its total 

 thickness at not less than thirty thousand feet, consisting, in 

 the order of deposition, of the following members : 1. Granu- 



* Loc. cit. p. 130, and Agriculture of New York, I. 53. This formed a 

 part of the report by Emmons on the Agriculture of New York, but was 

 also published separately. 



