321 CD. Walcott — The Taconic System of Emmons. 



Professor Dana was in accord with the opinion of Professors 

 W. B. and H. D. Kogers, Edward and C. H. Hitchcock, W. 

 W. Mather and James Hall, as well as with the results of his 

 own field studies, when he called the " Granular Quartz" Pots- 

 dam, the " Stockbridge limestones, Lower Silurian (Calciferous- 

 Chazy-Trenton) and the overlying " Talcose" shales the Hudson 

 Kiver formation. He held the opinion that the " Lower Ta- 

 conic" was the typical " Taconic System," as first defined in 

 1842, but as that was proven to be Lower Silurian in age the 

 " Taconic System" could not longer be recognized. In opposi- 

 tion to this Professors Marcou and Winchell argue that if the 

 "Lower Taconic" was of Lower Silurian age the "Upper Ta- 

 conic" contains Primordial fossils and is, therefore, equivalent 

 to the Cambrian ; and, as the discovery of fossils in the 

 " Upper Taconic" was made before typical Primordial fossils 

 were published from Sedgwick's Cambrian System, the name 

 Taconic had priority over that of Cambrian and should be used 

 in place of it to designate the strata containing the First or 

 Primordial fauna of Barrande. 



I was influenced by the statement made by Dr. Emmons 

 that the slates of the " Upper Taconic" were unconformably 

 beneath Lower Silurian strata, and, also, by the views of Pro- 

 fessors Dana and Marcou when, in 1885, I wrote my observa- 

 tions, " On the Use of the JSTame Taconic," in the introduc- 

 tion to Bulletin 30, of the U. S. Geological Survey. I was 

 satisfied from the evidence presented by Professor Dana, that 

 the limestones of the "Lower Taconic" belonged to the Cal- 

 ciferous-Chazy- Trenton Terrane, and that the overlying schists 

 were properly referred to the Hudson Terrane. The reference 

 of the quartzite beneath the limestone to the Potsdam horizon, 

 also appeared to be consistent with the data known to him. I 

 was but partially convinced, however, from the evidence pre- 

 sented by Dr. Emmons and Professor Marcou that the " Upper 

 Taconic" slates were stratigraphically pre-Potsdam, or that 

 there was a valid claim for the substitution of the name Taconic 

 for that of Cambrian. 



Professor Jules Marcou, although a persistent advocate for the 

 use of the name Taconic, did not go to the typical Taconic area 

 to study the " Taconic System," but studied the extension of 

 the " Upper Taconic" slate and shales in northern Yermont, and 

 identified the " Upper Taconic " as the true " Taconic System." 

 I have carefully examined the localities where he describes the 

 occurrence of a non-conformity between the Georgia slates and 

 the superjacent so-called Potsdam sandstone and at none of them 



Dana and others within the past fifteen years on the ground that the writers were 

 putting forth the " old metamorphic hypothesis" of Mather, Rogers, etc. (See 

 Am. iSTat., vol. xxi, pp. 114-320, 1887). " 



