J. D. Dana — Brief history of Taconic ideas. 411 



1818 to 1828. — The name Taconic first came into topograph- 

 ical geology through Professor Chester Dewey, who made the 

 earliest geological map of the region, observed the general 

 arrangement and eastward pitch of the beds, and called the 

 rocks in the style of the time, Transition rocks.* 



Prof. Amos Eaton gave credit in 1820 to Prof. Dewey for 

 the chief part of his knowledge of the Taconic rocks ;f but, by 

 1828, this pioneer in American geology had made fifteen sec- 

 tions of the rocks from the Hudson River to the Taconic 

 mountains, in order to ascertain, as he says, their conformability 

 and true order of succession. ;{; 



1836 to the close of 184,1. — Prof. Emmons, whose depart- 

 ment in the !New York Geological Survey covered the north- 

 ern and northeastern part of the State, and who was already 

 acquainted with the adjoining region of Williamstown in Mas- 

 sachusetts, continued his survey into Williamstown. But in 

 the New York Annual Reports no mention is made of the Ta- 

 conic system either by him or by any other of the ]S~ew York 

 geologists. This is true even of the latest — the fifth — annual 

 Report, that for 1810. Prof. Emmons, in his part of this Re- 

 port, under the date of transmittal of Feb. 1, 1811, says on 

 page 94 : 



"The Granular qnartz of Bennington, which occurs also in 

 Dutchess Co., N. Y., I believe to be Potsdam' sandstone in araet- 

 amorphic form, and the granular limestone associated, to belong 

 to the same geological epoch." I believe "that the rocks from 

 Lake Champlain, along the eastern part of the counties of Wash- 

 ington, Rensselaer, Columbia, Dutchess, all of Putnam, West- 

 chester, great part of Rockland and southeast part of Orange are 

 metamorphic and intruded rocks, and I would suggest that all the 

 rocks from the New York state line to the Connecticut valley are 

 similar. The talcose and micaceous and talco-micaceous divisions 

 of the Green Mountain range in Vermont, Massachusetts and 

 Connecticut have a strong analogy to the metamorphic slates of 

 the east part of Washington, Rensselaer and Columbia Coun- 

 ties, but are traversed by large granite veins and are interstrati- 

 fied with intrusive rocks which might be expected to produce a 

 greater change in mineral constitution." 



characteristics, and to which alone the discussions in 1842 to 1844 by Rogers, 

 Mather, Hall and Hitchcock had reference. Mr. Marcou's own special Taconic in- 

 vestigations were made in northern Yermont and its vicinity, a region barely 

 alluded to as Upper Taconic by Prof. Emmons. 



*C. Dewey, this J., i. 337, 1819; ii, 246, 1820; viii, 1, 240, with the map, 1824. 



f A. Eaton, Index to the Geology of the Uniied States, 1820. 



\ A. Eaton, this J., xiv, 147, 1828, where he says: "I have traversed the Tran- 

 sition range from Massachusetts line to Hudson River in fifieen places, since the 

 first part of my survey was published, for the purpose of ascertaining the true 

 superposition of rocks in this most complicated and difficult geological theatre." 

 Prof. G. H. Cook recently drew my attention to this statement of Prof. Eaton 

 which I had previously overlooked. 



