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SO-CALLED PORPHVRITIC GNEISS OF NEW HAMPSHIRE 697 
tions of the lower series into two groups—the Laurentian, which 
he qualifies by an interrogation point, and the Labradorian. The 
former included the ‘‘porphyritic gneiss,’ Bethlehem gneiss, 
White Mountain, or andalusite-gneiss, and the breccia of Fran- 
conia, in the order of decreasing age. The eight members of 
the Labradorian ‘“ constitute one horizontal series of formations, 
the lowest resting upon the upturned edges of all the parts of 
group I.” The greater antiquity of the “porphyritic gneiss” 
than thaworm une souner series “is inferred from the occurrence 
of several bands of andalusite and granitic gneisses upon both 
flanks.”” Itis interesting to note that in discussion on this paper 
Dr. C. T. Jackson declared his belief that ‘‘the classification pro- 
posed was hypothetical to a great extent, and that sufficient 
reason for the adoption of the New York nomenclature was not 
shown.” 
The first volume of the Final Report of the Hitchcock Sur- 
vey was issued in 1874. The ‘ porphyritic gneiss’’ was there 
explained as the product of altered sediment, the primitive 
stratified rocks having been metamorphosed in Archean, or, as 
then expressed, Eozoic time.t The second volume, published 
three years later, reiterated this opinion, making the terrane the 
representative of the ‘first territory in the state that was 
redeemed from the primeval ocean.’ 
‘“A porphyritic, or augen-gneiss, is eminently characteristic 
of the fundamental rocks in every part of the world, and hence 
ours may readily be called Laurentian.’’3 A still closer correla- 
tion was suggested whereby the “ porphyritic gneiss” of the 
White Mountain district, and inferentially that of the whole state, 
was put in the ‘‘upper division of the Laurentian system, as it is 
developed in Canada and New York.’* In the general résumé 
of the stratigraphical relations, a thickness of five thousand feet 
was estimated for the formation. With it was included the 
‘younger Bethlehem and Lake Winnipiseogee gneisses to form 
the whole Laurentian, aggregating 34,900 feet in thickness. 
=(Caolk OF INic ley WOlls Ie, me joe Ie 3 [oid., p. 668. 5 [bid., p. 668. 
(Ell OF ING Isl, Wola Wh USF jos Huo) 4 Tbtd., p. 252. 
