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



light. It would not have been so, we are sure from his care- 

 ful Bohemian work, had lie been within reach of the strati- 

 graphical problem, for he would have withheld his general 

 conclusion until he had investigated the region of the Taconic 

 rocks. 



Trouble came in 1860 again through the recognition by 

 Logan of the Quebec Group in Canada — based on fossils from 

 the vicinity of Quebec that corresponded in age apparently to 

 the combined Calciferous and Chazy Groups.* For this step 

 was followed by Logan's announcing, without previously mak- 

 ing a careful stratigraphical study of the region, that the 

 Taconic slates and limestone were, for the most part at least, 

 of the Quebec Group. 



Light came in again through the Vermont Geological Sur- 

 vey ;f (1) by the discovery of fossils of undoubted Silurian age 

 at several localities in the Stockbridge (Eolian) limestone of 

 Vermont, the Report sa} r s (p. 421) Silurian, Devonian, and 

 possibly Carboniferous) ; (2) by the exhibition of the topo- 

 graphical relations of the rocks on the colored geological map 

 of Vermont ; and (3) through the stratigraphical sections across 

 the limestone and slates, making in Mt. Anthony, Mt. Equinox, 

 Spruce Peak, Mt. Eolus or Dorset and Danby Mountain the 

 slates to lie in synclines with the limestone underneath, precisely 

 as had been proved for Greylock by Emmons. Here at one 

 stroke, Emmons was sustained in his stratigraphy as regards 

 his " Lower " Taconic, and shown to be probably wrong in his 

 conclusion as to the pre-Potsdam age of the limestone, and 

 part at least of the slates. No definite conclusion was reached 

 by the survey as to the age of the quartzyte, opinion varying 

 between Potsdam and Medina.^: 



* Sir Wm. Logan, Remarks on the Fauna of the Quebec Group of Rocks and 

 the Primordial Zone of Canada, Jan., 1861, Letter to Barrande, this Journal, II, 

 xxxi, 216, 1861 ; Considerations relating to the Quebec Group, Can. Nat. and 

 Geol., p. 199, May, 1861. 



Mr. Billings first observed the peculiar features of the fossils of the so-called 

 Quebec Group in May, 1860 (Geol. Rep. Can., 1863. p. viii), and the Canadian 

 Nat. and Geol. for 1860 contains his earliest descriptions of the fossils, afterward 

 given in full, with an account of the rocks by Logan in the Can. Geol. Rep. for 

 1868, and more completely in Billings's Palaeozoic fossils, vol. 1. 



f Rep. Geol. Vermont by E. Hitchcock, E. Hitchcock, Jr., A. D. Hager and C 

 H. Hitcncock, 1861. In a note published in the Proceedings of the Boston N. H. ■ 

 Soc, vol. xxiv, 1888, Prof. C. H. Hitchcock states that the printing of the Report 

 commenced in 1861, and was all completed that year, excepting the Appendix on 

 " Lower Silurian fossils " by E. Billings. 



\ Ibid . pp. 356, 500. On the latter page, the opinion is cited from Professor 

 Hall, based on the discovery of a species of Liugula, that the quartzyte is "of 

 the age of the Clinton Group -or of the Medina Group," Upper Silurian formations. 

 Bearing on the history we find in the Proc. Boston Soc. N. H.. vii, 237, 1860, a 

 note by Professor W. B. Rogers, in which, in view of the reference to the Medina 

 group, he cites approvingly, from a manuscript paper of his written in 1851, para- 

 graphs sustaining the Medina age of the Yermont Quartzyte and Red Sandrock. 

 The latter rock Emmons never included in the Taconic. 



