322 



SCIENCE. 



[Vol. II., No. 81. 



The papers of Professor Owen elicited, for tlie 

 greater part, unfavorable comment. It was urged 

 against them, that their generalizations were too broad, 

 and that tliey were based rather upon closet study 

 than actual observation. As to at least one of the 

 continents, we know as yet far too little of its geol- 

 ogy, especially in the interior, to frame a theory of its 

 history and constitution. 



The pre-Cambrian rocks of the Alps. 



BY T. STEKBY HUNT OP MONTBBAL, CAN. 



The writer began by reviewing the history of 

 Alpine geology, and noticed first that speculative 

 period when the crystalline rocks of the Alps, in- 

 cluding gneisses, hornblendic and micaceous schists, 

 euphotides, serpentines, etc., were looked upon as 

 altered sedimentary strata of carboniferous or more 

 recent times. He then traced the steps by which 

 these views have been discarded, and more and more 

 of these rocks shown to belong to eozoic or pre- 

 Cambrian ages. In this connection the labors of 

 von Hauer, Gerlach, Heim, Favre, Eenevier, Lory, 

 Gastaldi, and others, were analyzed; and reference 

 was made to the great progress since the writer in 

 1872 published a review of Favre on the geology of 

 the Alps. 



The sections by Neri, Gerlach, and Gastaldi in the 

 western, and those of von Hauer in the eastern Alps, 

 were described; and it was shown that all these 

 agree in establishing in the crystalline rocks four 

 great divisions in ascending order: 1°. The older 

 granitoid gneiss with crystalline limestones, graphite, 

 etc., referred by Gastaldi to the Laurentian. 2°. The 

 so-called pietre verdi, or greenstone group, consisting 

 chiefly of dioritic, chloritic, steatitio, and epidotic 

 rocks, with euphotides and serpentines, including 

 also talcose gneisses, limestones, and dolomites, and 

 regarded by Gastaldi as Huronian. 3°. The so-called 

 recent gneisses of von Hauer and Gastaldi, inter- 

 stratified with and passing into granulites and mica- 

 ceous and hornblendic schists, also with serpentines 

 and crystalline limestones. 4°. The series of argillites 

 and soft glossy schists with quartzites and detrital 

 sandstones, including also beds of serpentine with 

 talc, gypsum, karstenite, dolomite, and much crystal- 

 line limestone. This fourth series, well seen at the 

 Mont Cenis tunnel, is still claimed by Lory and 

 some others as altered trias; but the present writer's 

 view, put forth in 1872, that it is, like the preceding 

 groups, of eozoic age, was subsequently accepted by 

 Favre and by Gastaldi, and is now established by 

 many observations. To this horizon belong the crys- 

 talline limestones of the Apnan Alps, including the 

 marbles of Carrara. 



The writer next recalls the fact that he, in 1870, 

 insisted upon the existence of a younger series of 

 gneisses in North America, alike in the Atlantic 

 states, in Ontario, and to the north-west of Lake 

 Superior. These, in his address before the Ameri- 

 can association for the advancement of science, in 

 1871, he further described under the name of the 

 White-Mountain series, and subsequently, in the 



same year, called them Montalban. These rocks 

 were then declared to be younger than the Huronian, 

 and to overlie it; though, in the absence of this 

 latter, it was pointed out that in Ontario and in New- 

 foundland the Montalban reposes unconformably 

 upon the Laurentian. When these newer gneisses 

 and mica-schists were first described, in 1870, there 

 was included with them an overlying group of argil- 

 lites, quartzites, and crystalline limestones; and for 

 the whole the name of Terranovan was suggested, 

 provisionally. But in defining, in the following year, 

 the Wliite-Mountain series, this upper group was 

 omitted, and was subsequently referred to the Taco- 

 nian series, — the lower Taconic of Emmons, and the 

 so-called altered primal and auroral of H. D. Rogei'S, 

 in eastern Pennsylvania. 



The writer next describes his own observations in 

 the Alps and the Apennines in 1881. He aflBrms the 

 correctness of Gastaldi in referring the groups one 

 and two to Laurentian and Huronian, finds the 

 third, or the younger gneiss and mica-schist group of 

 the Alps, indistinguishable from the Montalban, and 

 regards the fourth as the representative of the 

 American Taconian. It was maintained by Gastaldi, 

 that these pre-Cambrian groups of the Alps underlie 

 directly the newer rocks of northern and central 

 Italy, forming the skeleton of the Apennines, re- 

 appearing in Calabria, and, moreover, protruding in 

 various localities in Liguria, Tuscany, and elsewhere. 

 The serpentines, euphotides, and other resisting 

 rocks thus exposed, have been regarded as eruptive 

 masses of triassic and eocene time. The writer, how- 

 ever, holds with Gastaldi, that they are indigenous 

 rocks of pre-Cambrian age, exposed by geological 

 accidents. 



The uncrystalline rocks of the mainland of Italy 

 are chiefly cenozoic or mesozoic, and the only paleo- 

 zoic strata known are carboniferous, the organic 

 forms in the limestone of Chaberton having been 

 shown to be triassic. Triassic, liassic, cretaceous, 

 eocene, and miocene strata are found in different 

 localities, resting on the various pre-Cambrian groups. 

 In the island of Sardinia, however, all these are over- 

 laid by a great body of uncrystalline lower paleozoic 

 rocks, in which the late studies of Bornemann and 

 Meneghlni have made known the existence of a 

 lower Cambrian fauna, including Paradoxides, Con- 

 ocepbalites, and Archeocyathus, succeeded by an 

 abundant fauna of upper Cambrian or Ordovian age. 



The existence of the younger or Montalban gneiss 

 in Sweden and in the Harz and the Erzgebirge was no- 

 ticed, and to it were referred the Hercynian gneisses 

 and mica-schists of Giimbel. The presence both in 

 Sweden and in Saxony of conglomerates, as described 

 by Hummel and by Sauer, wlierein pebbles of the 

 older gneiss are enclosed in beds of the younger 

 series, was discussed, and the diiect unconformable 

 superposition of the latter upon the older gneiss, in 

 the absence of the Huronian, was considered ; evi- 

 dences of the same relations being adduced from the 

 Alps. The gneisses of the St. Gothard, as seen on 

 the Italian slope, were also referred to the newer 

 series; and the important studies of Stapff in this 



