1TALCOTT.1 



GRANULAR QUARTZ. 



93 



with a great horizontal thrust has forced the Lower Cambrian over and 

 on to the Silurian (Ordovician) rocks. The misunderstanding of the 

 true relations of these rocks and a dependence upon their lithological 

 characters led Prof. Eaton into an error that has come down to the 

 present day in memoirs relating to the "Taconic System." 



Prof. Eaton reviewed his work from time to time until LS32, when his 

 final scheme of classification appeared. It is reprinted in the following 

 tabulation, with the equivalents of his formations as known in the no- 

 menclature of to-day. 1 





Eaton's Nomenclature (1832). 



1891. 



I.— Primitive. II. — Transition. III.— Lower. 



Secondary. 





Upper Holderberg. 



Niagara. 



Oneida, Clinton, Medina* 



Utica, Hudson. 



Trenton. 

 Calciferous. 

 Trenton, Gfaazy. 



Lower and M iddle Cambrian and Silu- 

 rian. 

 Hudson. 



Considerable Hudson, but includes a 

 great mass of Lower Cambrian in 

 Rensselaer County, N. Y. 



Trenton-Cbazy limestone, Calciferous. 



Cambrian limestone. 

 Lower Cambrian. 

 Algoukian, pro Cambrian, and Ar- 



chean. 



2. Millstone grit and rubble 1 C 

 1. Second Graywackeslate. $ Sec0nd Gray wacke . J 



3. -\ Calciferous sand rock 



f Millstone gri) and gray rubbl< ) V i r s t G r a y- J 

 2 r i I 



( Roof slate ) ( 



1. ArgilliteJ Wacke slate > J 



I Clay slato J [ 



2. Granular quartz 



1. Granite, Mica slate, Hornblende and Talcose rock 



The stratigrapbic position of the" GranularQuartz" (2 of the Primitive) 

 is correctly represented, and it is now known to contain Olenellus sp.? 

 A large portion of the strata referred to the " Argillite" (1, of the Tran- 

 sition) is also known to carry Olenellus asaphoides and to belong to the 

 Lower Cambrian terraue. In the text the u Gray wacke slate " (2, of the 

 Transition) is described as resting uuconformably upon the upturned 

 edges of the " Argillite r (1), and it is so represented in the section. This 

 is essentially the same as the section of 1820 and as in the more detailed 

 section of 1824. 



Rev. Chester Dewey studied the geology of the vicinity of Williams- 

 town, Massachusetts, and in 1819 l published a short sketch of the 

 mineralogy and geology of this region. He followed this in 1820 by a 

 geologic section from the Taconic range in Williarnstow n to the city of 



1 Geological Text-book for aiding the study of North American Geology ; being a .systematic arrange- 

 ment of facts collected by tbe author and bis pupils under the patronage of the Hon. Stephen Van 

 Rensselaer. Second edition, 5 plates. Albany, 1832. 



'Sketch of the Mineralogy and Geology of tbe, vicinity of Williams' College, Williamstown, Massa- 

 chusetts. (With a map.) Am. Jour. Sci., vol. 1, 1819, pp. 337-345. 



