Section IV., 1884. [ 12S ] Trans. Eoy. Soc. Canada. 



VI. — A Historical Account of the Taconic Question in Geology, with a Discussion of 

 the Relations of the Taconi'i Series to the Older Cri/staUine and to the Gainhrian 

 Rocks. By Thomas Sterry Hunt, LL.D. (Cantab.), F.R.S. 



SECOND PART. 



(Presented May 21, 1884.) 



VIIL— T7(t' Taconic History Scrinved. — Types of American Cambrian. Recent paleontological studies. Various 



opinions as to the age of the Lower Taconic rocks. The metamorphic Iiypothesis considered. 

 IX. — Conchmon. — Summary. AVide distribution of rocks like Taconian. Contents of sections and Note. 



VIII. — The Taconic History Reviewed. 



§ 136. lu the Traiisauctioiis of this Society for 1883, (Vol. I, Part IV, pages 21*7-270), 

 will be fouud the first part of this account of the Taconic Question. In this second and 

 concluding part, we shall continue the numbering of chapters and of sections begun in the 

 first. It is proposed to notice, in the first place, some of the characteristic differences of 

 the Cambrian or Upper Taconic rocks as seen in different parts of North America, to follow 

 the results of paleontological investigation from the disturbed region in eastern Canada 

 southward into Vermont and New li'^ork, and thus to prepare the way for a consideration 

 of the varying and contradictory hypotheses which have been from time to time put forth 

 as to the age of both the Upper and Lower Taconic series. 



§ 13*7. The Cambrian rocks of New York, as originally described by its Geological 

 Survey, were known only in the stable and little disturbed region around the Adiron- 

 dack Mountains, including the area west of Lake Champlain and the Ottawa basin, where 

 the series is represented by the quartzites and maguesian limestones of the Potsdam and 

 Calciferous subdivisions, which are shallow-water deposits, corresponding, apparently, 

 to small pojtions only of Cambrian time. The conditions of the Mississippi area are 

 similar to those of the Adirondack region. In Wisconsin, where the Potsdam beds rest 

 in a nearly horizontal position upon highly disturbed strata, often of Keweenian age, 

 these sandstones and magnesian limestones of the Cambrian, lying in undisturbed succes- 

 sion, have about 1,000 feet in thickness, and are overlaid by the St. Peter sandstone, which 

 divides them from the succeeding Trenton and may itself be regarded as the base of the 

 Ordovician. When, however, we reach the Cordilleras, we find a great augmentation in 

 the thickness of these lower rocks. In the Eureka district of Nevada, according to the 

 late stvidies of Arnold Hague and Wolcott, the fauna of the so-called Lower and Upper 

 Potsdam ranges through more than 6,000 feet of strata, and is succeeded by that of the 

 Chazy and Ti'enton subdivisions. 



^ 138. A similar great development of these lower rocks exists in north-western New- 

 foundland, where, from his studies of their organic remains, the late Mr. Billings was led 

 to admit a succession of over 9,000 feet of paleozoic strata below the Trenton horizon. 



