94 THE CAMBRIAN. [bull.8L 



Troy, on the Hudson. 1 In this section the relations of the quartz forma- 

 tion to the mica slates of the Archean are shown, and in a general way 

 the Lower Cambrian slate is described. This is referred to the Transi- 

 tion argillite. In 1824 2 he described the formation more in detail. On 

 the map accompanying this paper the distribution of the various rock 

 masses is more accurately given than in any maps published prior to 

 those of Prof. James D. Dana, when studying the strata referred to the 

 Taconic system. It exhibits an acquaintance with the surface distribu- 

 tion of the rock masses and a clear comprehension of the classification 

 and correlation of rocks on the principle of lithologic characters. The 

 distribution of the Granular Quartz and its relation to the subjacent 

 primitive rocks, or the mica slate of the map, is particularly well worked 

 out. 



Dr. E. Emmons, a pupil of Prof. Eaton, adopted the order of succes- 

 sion of the strata as proposed by Eaton, and separated the u Granular 

 Quartz" (2), "Granular Limerock" (3), and "Argillite" (1) to form a 

 distinct series of rocks between the "Granite" (1) and the " Gray- . 

 wacke" (2) of the Transition. To this series of rocks he gave the name 

 " Taconic," as Nos. 3 and 1 are largely developed in the Taconic range of 

 mountains. His central idea was that the rocks were nonfossiliferous 

 and beneath the zone of animal life, and were separated by their miuer- 

 alogical characters from the subjacent and superjacent rocks. 3 



Iu accordance with the belief that the "Granular Quartz" belonged 

 to a system of rocks which were beneath the zone of animal life, Dr. 

 Emmons considered it the oldest of the sedimentary rocks, and far 

 beneath the Potsdam sandstone surrounding the Adirondack moun- 

 tains. He thus differentiated the Potsdam sandstone and the "Granu- 

 lar Quartz n as two distinct formations. The work of Messrs. Dewey 

 and Emmons added little to the knowledge of the true position of the 

 " Granular Quartz" in the geologic series, as they did not discover 

 fossils in it or the associated formations. 



Prof. H. D. Rogers, in summing up the results of his study of the 

 marbles and sandstones of the western portion of Berkshire County, 

 Massachusetts, states that he considered the Berkshire limestone and 

 marble to be the equivalent of the (Trenton) limestone series of the New 

 York section ; and that the semi-vitrified quartz was equivalent to the 

 sandstone at the base of the same series (the Potsdam sandstone). 4 In 

 the same year, 184.1, a discussion of these formations was published in 



1 Geological section from Taconick iange, in Williamstown, to the city of Troy, on the Hudson. Am. 

 Jour. Sci., vol. 2, 1820, pp. 246-248. 



2 A sketch of the geology and mineralogy of the western part of Massachusetts, and a small part of * 

 the adjoining States. Am. Jour. Sci., vol. 8, 1824, pp. 1-60. 



3 Geology of New Tork, Part 2, comprising the survey of the second geological (Northern) district, 

 1842, pages 135-164. 



4 Someobservaiions on the geological structure of Berkshire, Massachusetts, and neighboring parts 

 of New York. Am. Phil. Soc. Proc, vol. 2, 1841, pp. 3,4. On the physical structure of the Appa- 

 lachian Chain, as exemplifying the laws which have regulated the elevation of great mountain ohaius 

 generally, Trans. Am. Assoc. Geol, Nat., 1842, p. 482. 



