262 THE CANADIAN NATURALIST. [Vol. ix. 



to the east of this range, while regarded by Eaton and by Em-^ 

 mons, as also forming a part of the Primary, were, by Mather, as 

 we have already seen, supposed to be altered paleozoic strata. 

 These rocks in New England, with the exception of the quartzites 

 and limestones of the Taconic range, were by him assigned to a 

 horizon above the Trenton limestone of the New York system, 

 and portions of them were conjectured by other geologists, who 

 adopted and extended the views of Mather, to be of Devonian age. 



The characteristic crystalline schists of New England and 

 southeastern New York, passiug beneath the Mesozoic of New 

 Jersey, re-appear in southeastern Pennsylvania, where they were 

 studied and finally described by H. D. Rogers in 1858. Ac- 

 cording to him, these crystalline schists, while resting uncon- 

 formably upon an ancient (Hypozoic) gneissic system, were 

 themselves more ancient than the Scolithus-sandstone, which he- 

 regarded as the equivalent of the Potsdam. While he supposed 

 these newer crystalline schists, called by him Azoic, to be con- 

 nected stratigraphically with the base of the Paleozoic series, he 

 nevertheless assigned them to a position below the base of the 

 New York system ; thus recognizing in Pennsylvania, beneath 

 this horizon, two unconformable groups of crystalline rocks, cor- 

 responding stratigraphically as well as lithologically, with the 

 Lauren tian and the Huronian of the Lake Superior region. 



The existence among these newer crystalline schists of Penn- 

 sylvania, of a series distinct from the Huronian, and representing 

 the White Mountain or Montalban rocks (the Philadelphia and 

 Manhattan gneissic group), had not been then recognized. 

 Rogers at this time taught the igneous origin of the magnetic 

 iron ores, the quartz-veins, the serpentines and their associated 

 greenstones in this region. The belief entertained by Rogers of 

 an intimate connection between his upper or Azoic series and 

 the Paleozoic, had its origin, apparently, in the fact of the exist- 

 ence in this region of still another and a newer crystalline series, 

 the Lower Taconic of Emmons, or the Itacolumite group of 

 Lieber, which I have designated Taconian, and propose to con- 

 sider in detail in a future paper. In it are included the iron- 

 ores of Reading, Cornwall and Dillsburg, in Pennsylvania. 



The views of H. D. Rogers with regard to the crystalline 

 schists of the Atlantic belt were thus, in eflfect, if not in terms, a 

 return to those held by Eaton and by Emmons, but were in direct 

 opposition to .that maintained by Mather, which had been adopted 



