52 ROCKS OLDER THAN THE TACONIC SYSTEM. 



[ioosii •■! Green mountain on the east. The succession of this Lower division is represented 

 by an actual section extending from Glen's falls live miles northeast, or to the primary 

 upon which the Potsdam sandstone rests. 



Hit. i. 



; c Calciferous sandstone ; </. Trenton limestone ; e. Black marble, extending 

 towards the river 



The gorge at tins place is aol sufficiently deep to expose the Potsdam sandstone, but the 



ii is well exhibited in passing over the countrj in the direction stated above. The 



- ite iii the falls has been atlj destroy ed bj denudation ; but it appears both above 



and below, upon the river banks, with its characteristic fossils, succeeding the Trenton 

 limestone. 



1 1 1 point i" be shown, is thai ihe Lower dii ision of the New- York ^imi reposes upon 

 e of the members of the Taconic system ; that is, i" show bj actual superposition that 

 the former rests upon the Latter. I trust I shall be aide thus to do: not onlj to point out 

 where the two Bystems appn ach each othei so t loselj that there is but Little space Inter- 

 vening between them, but where the finger maj be placed directlj upon the Line of 

 demarkation; the one being the inferior and unconformable, and the other the superior. 

 Tins great fad being shown, us bearing on American geology is not confined to one or 

 two subjects, as metamorphism and aire; but ii is also important as furnishing a base from 

 which may be formed a general nomenclature of sedimentary roi ks. At any rate, ii is a 

 point to be established before a nomenclature can be de\ ised, thai shall express the order 

 in which the series follow each oilier, and the designations proper to applj to them. 



;. Rocks below and older than those constituting the taconk system. 



In Massac hu setts and Vermont, a- well as m New-York, what lias been usually deno- 

 minated the Primary skirts the Taconic Bystem upon the east, and forms with it 



parallel belts of Low mountain ridges, which unitedly form the Green mountains. Different 

 portions have received different names: as Hoosic mountain, immediately east of Adams 

 in Berkshire (Massachusetts) ; and Mansfield mountain, to the east of Burlington (Vermont) . 



The Taconic range is parallel with the mam ranges constituting the Green mounts 



and is a few miles only to the west. The ridge dividing New-York from Massachusetts is 



one to which this nam.- was originally given. The ranges are, however, connected 



by spurs, though not so intimately as to destro] the integrity of either, and make it 



. to merge them both in on-- mam range. The name Green mountains is a more 



