92 THE CAMBRIAN. [bull. 81. 



tion rocks are extended north into the valley of Lake Champlaiu as far 

 as the Canadian border. On the south they terminate in Georgia a 

 short distance south of the Tennessee line. : 



In his first publication on the rocks between the Oatskill Mountains 

 west of the Hudson River and the Atlantic Ocean, Prof. Amos Eaton 2 

 separated the " Granular Limestone and Quartz" as No. 2 of the sec- 

 tion, and an argillaceous and siliceous slate as No. 9, giving the locali- 

 ties at which they occur. Two years later this classification was re- 

 viewed 3 and the " Granular Quartz" dropped out of the nomenclature, 

 only to reappear again with a very accurate description of the forma- 

 tion as it occurs in Vermont. 4 It is interesting to note in this publica- 

 tion, that the " Granular Limerock" is mentioned as accompanying the 

 u Transition Granular Quartz " from Whitehall on Lake Ohamplain, to 

 Barnegat on the Hudson. Up to this time Prof. Eaton appears to have 

 regarded the terms " Granular Quartz" and the " Granular Limerock n 

 as interchangeable. In the classification of 1S24. 5 however, the "Gran- 

 ular Quartz" is separated from the "Granular Limerock "and fully 

 described. The "Transition Argillite" and the " Primitive Argillite" 

 are also defined, and some of the localities given are now known as 

 localities of Lower Cambrian slates. The geologic profile accompany- 

 ing the memoir of 1824 exhibits the differentiation made by Prof. Eaton 

 in the classification of the rocks between the primitive granite and the 

 secondary. 



In the geologic nomenclature of to-day the "Granular Quartz" is 

 included in the Lower Cambrian, and the "Granular Limerock" equals 

 the Trenton Chazy -Calciferous limestone. The " Primitive Argillites" 

 of Williamstown Mountain equal the Upper Hudson or Lorraine 

 shales. The "Transition Argillite" is nearly all Cambrian, with the 

 exception of a small portion near the Hudson River. The Calciferous 

 sandrock is of the same age as the "Transition Argillite." The Gray- 

 wacke of Peterborough Mountain, and the Metalliferous limerock is 

 of Silurian (Ordovician) age. The "Transition Argillite" is mostly 

 of Lower Cambrian age, and much of the so-called Calciferous sand- 

 rock and Graywacke of the section, represented as resting on the up- 

 turned edges of the "Argillite," are portions of the same series to which 

 the "Argillite" belongs. Near the Hudson River a profound fault 



'In a review of Maclure's memoir by C. S. Rafinesque it is suggested by bim that " We must espe- 

 cially collect and describe all tbe organic remains of our soil, if we ever want to speculate with the 

 smallest degree of probability on the formation, respective age, and history [of our strata." (Obser- 

 vations on the geology of the United States of America, by William Maclure; a notice. Am. 

 Monthly Magazine, vol. 3, 1818, pp. 41-44.) 



2 An Index to the Geology of the Northern States, with a transverse section from Catskill Mountain 

 to the Atlantic. Leicester, 1818. 



s Eaton, Amos. An Index to the Geology of the Northern States, 2d ed., 1820, pp. 154-212. 



4 Eaton, Amos. A geological and agricultural survey of Rensselaer County, New York, with a geo- 

 logical profile from Onondaga to Massachusetts, p. 15, plate. Albany, 1822. Memoirs of the board of 

 agriculture of the State of New York, 1823, vol. 2, p. 9. 



6 A geological and agricultural survey of the district adjoining the Erie Canal, 1824, pp. 30, 56-58, 

 plate. Albany. 



