AMERICAN GEOLOGY THE TACONIC QUESTION. 661 



1. A coarse granular limestone of various colors which I have denominated the 

 Stockbridge limestone, taking its name from a well-known locality, one which has fur- 

 nished the different parts of the Union a large portion of the white and clouded 

 marbles which have been so extensively employed for building and other purposes 

 in construction. 



L'. Granular quartz rock, generally fine grained, in firm, tough, crystalline masses 

 of a brown color, but sometimes white, granular, and friable. 



.'!. Slate, which for distinction I have denominated Magnesian slate, from its con- 

 taining magnesia, a fact which is distinctly indicated by the soft feel peculiar to rocks 

 when this earth forms a constituent part. 



4. Sparry limestone, generally known as the Sparry limerock. 



5. A slate, which I have named Taconic slate, and which is found at the western 

 base of the Taconic range. It lies adjacent to the Lorrain or Hudson River shales, 

 some varieties of which it resembles. In composition it contains more alumina and 

 less magnesia than the magnesian slates. 



The series occupied an area extending- trom the Hoosac Mountains 

 westward, passing* over the Hoosac Valley, Saddle Mountain, and also 

 over the high ridge of granular quartz known as Oak Hill, just north 

 of the Williamstown Plain, the Taconic Mountains next west of the 

 Massachusetts boundary, and the eastern border of New York west of 

 this boundary to the Hudson. 



To this series, which Emmons conceived to be older than the Pots- 

 dam, he proposed in 1841 to give the name Taconic, after the Taconic 



Fiu. 131.— Section of Taconic Rocks. A, Primary schists; 1, granular quartz, or brown and white 

 sandstone: 2, 2, Stockbridge limestone; 3,3, magnesian slate: 4, Sparry limestone; 5, Taconic slate; 

 ti, roofing slate;. 7, rough coarse siliceous beds; 8, tiinty slate; 9, Hudson River shales. (After E. 

 Emmons, i 



range, elevating it to the dignity of a system. His persistent advocacy 

 of the actuality of this system gave rise to a controversy extending 

 over more than half a century and equaled by none in the annals of 

 American geology, not exceeded even by the Eozoon question noted 

 elsewhere. Unmoved by argument, to the day of his death Emmons 

 adhered faithfully to his ''system,' 1 although from the very first he 

 noted its most inherent weakness — that in no case had the Potsdam 

 sandstone been found resting upon any of its members. That this 

 system was actually an older, lower- lying series was indicated only by 

 the fact that neither were any of its members found intercalated with 

 the overlying series, which always occupied the position and relation- 

 ship given above. 



It must be remarked, by way of preliminary explanation, however, 

 that the region, as shown by subsequent studies, is one where fault- 

 ing, folding, erosion, and metamorphism have prevailed to an extent 

 then undreamed of, and where, as a consequence, all natural criteria 

 had become so obscured as to make a prompt solution of the problem 

 impossible. The science of geology grows through cumulative evi- 



