208 RECORD OF SCIENCE FOR 1886. 



systematic field-work — sometliiDf? the Taconic district had never re- 

 ceived up to within a few years past. 



60. In regard to the use of the terra Taconic, opinions will always 

 differ, whatever the issue. No one now questions the fact that Em- 

 mons was the first to definitelj'^ call attention to the occurrence of a i^ri- 

 mordial series in America, and notwithstanding the great opposition, 

 much of which was prejudiced, persisted in his views. It seems unfor- 

 tunate that his typical Taconic proves to be in greater part Lower Silu- 

 rian ; but he also applied the term to other areas by lithologic anal, 

 ogy, and as these are now found to be Cambrian, some will always be 

 in favor of giving the name Taconic to this series as an honor to the 

 geologist who first recognized the primordial in America. In the lit- 

 erature ot the past year Winchell* is in favor of this. Walcott uses 

 the term for his Middle Cambrian, but Danat is opposed to this on the 

 grounds that Emmons's typical Taconic is not primordial, and that his 

 application of the term to others arose from the very faulty supposition 

 of identity of age in rocks of lithologic similarity. 



61. Walcott announced before the American Association his discov- 

 ery of a Middle Cambrian or Georgian fauna in limestone in the slate, 

 near Middle Granville, Washington County, New York. These slates 

 aggregate 10,000 feet in thickness. The red slates of the same district 

 are found to be of Hudson Kiver age. | 



62. Dwight calls attention to the occurrence of Trenton fossils in 

 metamorphic limestone of Emmons's original Taconic, at Canaan, New 

 York,§ and Bishop finds similar exposures at approximately the same 

 horizon farther north, near Chatham and Kent, in Cohimbia County. || 

 Dana discusses Dwight's discovery in its bearings on the Taconic ques- 

 tion, and shows that the limestone is unipiestionably part of Emmons's 

 original Taconic, and that the same strata comes upon the other side of 

 the synclinal as the Stockbridge limestone, and is traceable for many 

 miles northward into Vermont. It is conformably overlain by slates un- 

 qnestionably Hudson River in age, which at some i)()iuts have yielded 

 characteristic graptolites to Hall. The question of overthrust in the 

 Taconic district is discussed, and it is shown that this could be easily 

 detected if it existed to a suflicient extent to invert the order of 

 succession, as in the Scottish Highlands. Some slightly overturned 

 flexures occur, and most of the faults are overthrust to the eastward ; 

 but these are purely local results and do not afiect the general problem. 

 The absence of fossils and increasingly crystalline condition of the 

 rocks eastward is thought to be due to an increased amount of meta- 

 morphism in that direction.^ 



* Science, vol. 7, p. 34. 



t Am. Jour. Sci., in, vol. 31, pp. 242-243. 



t Amer. Assoc, Proc, vol. 35, p. 220-221. 



§ Am. Jour. Sci., in, vol. 31, pp. 248-2.'}6. 



li Ibid., vol. 32, pp. 438-441. 



'^Ibid., vol. 31, 241-248; vol. 32, pp. 236-239. 



