460 THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



shire, has lower Helderberg beds overlying, un conformably, folded or upturned 

 roofing slates (similar to those on the western side), the Lower Silurian age of 

 which is not improbable ; and at Littleton in New Hampshire, and on Lake 

 Memphreniagog, in northern Vermont, occur unconformable Upper Helder- 

 berg (Lower Devonian) beds with fossils In view of these various con- 

 siderations, the evidence, although not yet beyond question, is manifestly 

 strong for embracing the whole region between the Connecticut and the Hud- 

 son (and to an unascertained distance beyond) within the limits of the Green 

 Mountain synclinorium." 



Professor Dana makes this statement in reference to a letter sent him 

 by Prof. C. H. Hitchcock (Am. Jour. Sci., 1880, (3) XIX., p. 237) : — 



" Prof. Hitchcock also says, in the recent letter to me, after remarking on 

 his disbelief in ' Taconism ' : ' Within the past two years I have gone over 

 most of the Vermojit sections, and have felt that they demonstrated the essen- 

 tial equivalence of the Taconic system with the Potsdam and the overlying 

 limestones and slates [of the Lower Silurian]. I have been throughout in 

 essential accord with you and Mr. Wing.' He adds that Mr. Wing's views had 

 been his for years." 



Professor Hitchcock is further quoted as saying regarding the Report 

 on the Geology of Vermont (1861), "There is nothing in the Report 

 anywhere favorable to * Taconism.' " 



In 1877 Professor Hitchcock gave his ideas of the Green Mountain 

 or Quebec rocks as follows : — 



" Sir W. E. Logan has described them under the general name of Quebec 



group He has grouped together a large series of fossiliferous Cambrian 



and metamorphic rocks, assuming that the one was the equivalent of the 

 other. I have endeavored to separate the fossiliferous from the metamorphic 



portions, with the assistance of Dr. T. Sterry Hunt From this series, 



as proposed by Logan, we must eliminate all the fossiliferous portions and in- 

 vert the order This is in agreement with the recently quoted view of 



Mr. Macfarlane, and has been also insisted upon by Dr. Hunt. Separating 

 the eastern part of the area called Quebec group by Logan, we may clearly 

 understand it to be older than the fossiliferous Cambrian of any part of the 



world, and therefore to be named Huronian The Vermont Huronian, 



save that along Connecticut river, is the southward continuation of the Quebec 

 group of Canada. It is divided into two parts by the central ridge of the 

 Green Mountains, which continues a few miles into Canada. Macfarlane fol- 

 lows the report on the geology of Vermont in regarding the Green Mountain 

 ranges as older than the adjacent Upper Huronian. We have in that early 

 publication (1861) insisted that these Green Mountain rocks underlaid the 

 green schists upon both sides, .... and they are consequently older. The 

 nau)e Green Mountain gneiss, as applicable to this formation, was in use in 



