C. D. Walcott — The Taconic System of Emmons. 311 



Talcose Slates (Terr. No. 4 of Section and fig. 10). — 

 These slates, which are called " Magnesian slates " in the re- 

 ports of 1 842-'44-'47, were given the name " Talcose slates " 

 in 1856. A thickness of 2000 feet is assigned to them on the 

 Taconic range and they are represented as conformably super- 

 imposed upon the Stockbridge limestone. 



"Upper Taconic." — In the scheme published in 1844-'47 

 the Magnesian slate is succeeded by the Sparry limestone, 

 Roofing slate, a coarse brecciated bed, Taconic slate, and Black 

 slate, and on p. 13, Am. Geol., pt. 2, 1856, this succession is 

 recognized. On page 49 (loc. cit.), however, the entire scheme 

 is changed; the Black slate is placed at the bottom of the 

 series and then, in succession, siliceous slates: slates and sand- 

 stones, with thin-bedded blue limestones succeeded by thicker 

 beds of sandstone ; blue, green, purple and red roofing slates, 

 coarse sandstone and shale passing into conglomerates and brec- 

 ciated conglomerates. " The latter terminate the series east- 

 ward, and geographically near the Hoosick roofing slates. In 

 the foregoing brief enumeration in the ascending order, the 

 rocks follow each other in a conformable position, and begin- 

 ning with the thin black slates, end in thick bedded sandstones 

 and conglomerates," (loc. cit., p. 50). 



In this re-definition of the " Upper Taconic," the Sparry 

 limestone is no longer considered as belonging to it, and I have 

 failed to find it mentioned subsecmently as a distinct formation 

 of the " Upper Taconic." The sparry limestone spoken of in 

 describing the " Upper Taconic " section crossing Washington 

 County, refers to the thin interbedded sparry limestones, in 

 which I have found Olenellus and other Middle Cambrian fos- 

 sils. The sparry limestones west of Hoosick Falls are referred 

 to the Lower Silurian and removed entirely from the "Taconic 

 System." 



As is shown by Professor Dana, Dr. Emmons, in 1842, called 

 the Sparry limestone the oldest of the Taconic limestones, and, 

 in 1844, he placed it beneath the Taconic slate and above the 

 Stockbridge limestone.* In 1856,f however, a section was 

 published showing the Taconic Range by C and, at its western 

 base, the limestone (2) is identified with the Stockbridge lime- 

 stone (2), of B (Graylock Peak). What Dr. Emmons intended 

 by this, and why he did not mention the change in the text, is 

 not explained by him. Professor Dana called my attention to 

 it by letter, and says that he accepts the evident meaning given 

 by the section, which is, that Dr. Emmons identified the Sparry 

 and Stockbridge limestones as one formation. With our pres- 

 ent knowledge, this explanation is the only one open to us. 



* This Journal, III, vol. xxxiii, pp. 415, 416, 1887. 

 •f Am. Geol., vol. i, pt. 11, p. 19, fig. 2. 



