J. D. Dana — Brief history of Taconic ideas. 423 



tions from the Calcif erous to the Trenton ; and, consequently, he 

 had made it certain that whatever slates were really overlying 

 were of Utica or Hudson age. 



In 1869, an article by Prof. J. B. Perry appeared in this 

 Journal, sustaining, by the results of his observations in Ver- 

 mont, the Taconic system as presented by Emmons. As its 

 principal stratigraphic points have now been disproved by the 

 discovery of fossils, and evidence of the existence of faults and 

 flexures which he misunderstood, it need not be noticed here. 



1872 to 1886.— In 1871 the writer entered the field, believing 

 that the Chazy fossils of West Kutland — the only part of 

 Wing's discoveries then published — and the earlier discoveries 

 of the Vermont Survey, made the region a good and certain 

 base for a determination of the age of the Massachusetts and 

 more southern portions of the Taconic rocks, as well as of the 

 Vermont portion, and, thence, of the age of the schists through- 

 out the Taconic Bange. My purpose was (1) to prove the con- 

 tinuity from north to south of the three associated Taconic 

 formations, the quartzyte, the limestone and the slates, or 

 schists ; also (2) to work out the system of flexures ; (3) to ascer- 

 tain whether the Taconic Mountains were generally or not of 

 synclinal structure, as they were made by Pogers, Mather and 

 Hall, and in 1864 by Logan ;* (4) to settle the question as to con- 

 tinuity from east to west of the limestone of the different 

 north-and-south belts ; (5) to apply the evidence from fossils, 

 making them the sole basis for fixing the age of the beds ; and 

 finally (6), to use the evidence of the age, thus obtained, for 

 the determination of the age of the hydromica schists, chloritic 

 schists, garnetiferous and staurolitic schists, and other rocks of 

 the Taconic Mountains, and thus test the value of, or give 

 greater precision to, the assumed " lithological canon " first pro- 

 pounded by Prof. Emmons (p. 414). My work was continued 

 in Western New England and Eastern New York at intervals 

 from 1871 to the close of the season of 1886. In 1876 I ac- 

 companied Mr. Wing on a Vermont excursion, visiting besides 

 other places, the West Putland region of fossils in the lime- 

 stone ; a locality of small Orthocerata, apparently Calciferous, 

 in the limestone two miles north of Middlebury, which Mr. 

 Wing figured ;f and the region of the Snake Mountain over- 

 thrust fault which he well understood.^: 



By 1878, the problem began to receive new light from the 

 discoveries of fossils outside of Vermont. In 1878, Mr. T. N. 

 Dale announced Brachiopods of the Hudson Group in the Pough- 

 keepsie Taconic slate. § In 1878, Professor Wm. B. D wight 



*This J., II, xxxix, 96, 1865. 



f A. WiDg. this J., Ill, xiii, 406, 1877, where the Orthocerata are figured. 



tlbid., p. 413. 



§Dale, this J., Ill, xvii, 57. 1879. 



