TACONIC QUESTIOîT IN GEOLOGY. l4l 



what he called " metamorphic ageucies," aud the intrusiou of igueous rocks, in which cate- 

 gory he included not only the interbedded serpentines, but apparently, under the name of 

 granites, much of the granitic gneiss, which characterizes large areas of the region, as well 

 as the abundant endogenous granitic veins, — true intrusive or exotic granites being rare in 

 the region. In Mather's cosmogony there was nothing in the geological sequence, at least 

 in north-eastern America, between the New York paleozoic series, as seen in the Adiron- 

 dack area, and the fundamental Laureutian gneiss which there underlies it. Consequently 

 all crystalline rocks which could not be referred to the latter, were, unless plutonic, the 

 result of some unexplained transformation of the lower part of this paleozoic column, 

 designated by him as the Champlain division. 



§ 176. This hypothesis, extravagant as it now seems, was, during the next few years, 

 accepted by many geological students on the authority of Mather and the brothers, H. D. 

 and W. B. Rogers. These latter, in 1846, extended this view of Mather to the White 

 Mountains of New Hampshire, and suggested that the gneissic, hornblendic and micaceous 

 rocks of this series, since named Moutalban, instead of belonging, as hitherto believed, to 

 the "so-called Primary periods of geological time," were probably altered paleozoic strata 

 of Silurian age, including the Oneida, Medina and Clinton subdivisions of the New York 

 system. These observers then proceeded to name many species of characteristic organic 

 forms of the Silurian period, which they thought to recognize in certain crystalline aggre- 

 gates in the mica-schists of the region. In 18-il, however, the same observers announced 

 that they no longer considered these forms of organic origin, '' and, although they did not 

 then formally retract their opinion as to the paleozoic age of the gneisses and mica-schists 

 of the White Mountains, are known, from their subsequent writings, to have abandoned it 

 as unfounded, though it was for some years afterward maintained, with some variations, 

 by Logan, Lesley and the present writer.^" 



§ 1*7Y. As regards the ancient crystalline series of the Highlands of the Hudson and 

 of New Jersey, which differs in lithological characters from the last, we find that H. D. 

 Rogers, while he did not accept the notion of Nuttall and of Mather that its gneisses are 

 altered j)aleozoic sediments, imagined the crystalline limestones, which are really inter- 

 stratified with them, to be portions of a younger limestone, altered by supposed igneous 

 agencies. In the words of Lesley, Rogers, while maintaining the Primary age of the 

 Highland gneisses, " mistook the crystalline limestone engaged among the Highlands for 

 metamorphosed syncliual outlyers of No. II, as at Franklin," in New Jersey, whereas Cook 

 has since shown that the horizontal strata of this later period overlie the upturned crys- 

 talline limestones of Franklin."' As a consequence of this, H. D. Rogers was quoted by 

 Mather as supporting the extreme notions of metamorphism maintained by Nuttall in 

 1824, which Mather himself accepted, and which, as I have elsewhere said, " were adopted 

 by PI. D. Rogers, as far as regards the crystalline limestones of the Highlands in New 

 Jersey," " while he soon after applied the same doctrine, in its fvillest extent, to the great 

 gneissic series of the White Mountains. 



" Amer. Jour. Science, [2] i, 411, and v, 116. 



™See, for hiatorical notes, Hunt, Amer. Jour. Science, vol. 1, 84 ; also Azoic Rocks, pjj. Ii2, ISl, 1S2, and Trans- 

 Roy. Soc. Canada, vol. i, sec. iv, p. 195. 



^^ Lesley, Amer. Jour. Science, 1865, xxxix, 222. 

 " Hunt, Azoic Rocks, p. 41. 



