CD. Walcott — The Taconic System of Emmons. 309 



with subordinate beds 'of chert, fine and coarse limestone, and 

 gray, brown and white sandstone.* 



The geological map, prepared to accompany the memoir of 

 1844-47, bears the date of 1844 and is a reprint of the Geo- 

 logical Map of New York, issued in 1842, with additional data 

 on the geology east of the Hudson and Champlain valleys. 

 The long, narrow range of the u Taconic System " is colored 

 drab in its extension from Canada to Westchester County, 

 N. Y. There is no reference to the " Taconic System " in the 

 legend on the map, and the formations composing it are not 

 distinguished by different colors, the reason for which is ex- 

 plained in the description of the map, published on page 361 

 of the Agriculture of New York, vol i, 184Y.f 



In 18564 Dr. Emmons divided the " Taconic System " into 

 an upper and a lower division : the upper division taking the 

 formations 4 to 8 of the section of 1844— '47, and the lower 

 division the formations 1 to 3 ; an arrangement that was re- 

 peated in 1859 (Manual of Geology), when the name " Mag- 

 nesian slate" was replaced by that of " Talcose slate." In the 

 diagram, fig. 10, the formations are represented in the order 

 of succession given in 1856 ; and, on the map, the geographic 

 area is given within which the typical localities of the various 

 formations occur and also the extension of the latter to the 

 north and south. This is the stratigraphic scheme of the " Ta- 

 conic System " as arranged by its author from the results of 

 his latest field observations.§ 



" Granular Quartz" (Terrane No. 1, of section on side of 

 map and fig. 10). — Dr. Emmons calls the " Granular Quartz " 

 the basal member of the " Taconic System," and, in his opin- 

 ion, the base of the Paleozoic sediments on the North Ameri- 

 can continent. He describes its occurrence in Vermont and 

 follows it, with interruptions, across Massachusetts into the 

 northeastern part of Dutchess County, N. Y., and also south 

 into Putnam and Westchester counties. | The stratigraphic 



* Loc. cit., p. 61. 



f The copy I have of this map was purchased by me from a second-hand book 

 dealer, in 1876. I have reason to state that 3000 copies were originally delivered 

 to the Secretary of State, of the State of New York, by the printers, and I think 

 that copies can still be obtained from the said Secretary's office, despite the pub- 

 lished statement that the edition was stolen or destroyed. (See letter of Dr. 

 Emmons to Prof. Jules Marcou: Am. Acad. Arts and Sci., vol. xii, p. 188, 1885, 

 also copied by Dr. Hunt, Am. Nat., vol. xxi, p. 122, foot note 3, 1887). 



X The first part of this volume is dated 1855. The second part, containing the 

 description of the '' Taconic System," was issued in 1856. 



§ I shall not comment on the so-called Taconic rocks, as identified by Dr. 

 Emmons in Canada, Maine, Rhode Island, Michigan, and the southern Appala- 

 chian region. All those determinations rested on lithologic characters ; and the 

 strata referred by him to the " Taconic System " range from pre-Cambrian to the 

 Niagara of the Silurian. 



| Agric. N. V., vol. i, p. 86, 1847. 



