GEOLOGY. S3L 



the preceding groups, and consisting largely of gneisses with hornblendic 

 and micaceous schists, the latter often abounding in garnet and stau- 

 rolite, and iucludiug great veins of endogenous granite, the whole re- 

 sembling the upper gneisses of Brazil, which appear to belong to the 

 Montalban series. 



It would thus seem that the great series of crystalline rocks marked 

 by distinct mineralogical characters, which were first defined and named 

 in eastern Korth America, are repeated with the same strati graphical 

 relations in the British Isles, in central Europe, in Asia, and in South 

 America. 



THE TACONIC ROCKS. 



Under the name of the Taconic system, as is generally known, have 

 been described the quartzites and sandstones, with granular limestones 

 and intercalated crystalline schists and argillites, found in eastern North 

 America, which were by Eaton, and subsequently by E. Emmons, as- 

 signed to a horizon between the older crystalline series and the lower 

 Paleozoic strata, a portion of which, under the name of Ui)per Taconic, 

 was at first included in the Taconic system. The Lower or true Taconic 

 (Taconian), first recognized in the Taconic range of western New Eng- 

 land, includes the Primal and Auroral of Rogers in eastern Pennsylva- 

 nia, and the Itacolumite series of Lieber in the Carolinas. 



The granular limestones or marbles of the Taconian have been by dif- 

 ferent geologists referred to various horizons more recent than that 

 assigned to them by Emmons. They have been regarded as infra-Tren 

 ton (Calciferous, Chazy,or Quebec group), Trenton, and (Upper) Silurian 

 or Devonian. Each of these views has been sustained by specious argu- 

 ments from stratigraphy, and by others based on organic remains found 

 in rocks supposed to belong to the limestones in question, and found within 

 the limits of the Taconic belt. That fossils characteristic of each of these 

 horizons occur in such associations is certain, but whether the great mass 

 of the limestones belongs to any one of these three, or, as supposed by 

 others, to a still older Taconic horizon, is a question which many geolo- 

 gists, unacquainted with the whole of the facts in the case, regard as 

 unsettled. Hunt has maintained the view of Eaton and of E. Emmons, 

 that these rocks belong to a series older than the Potsdam sandstone of 

 New York, and has endeavored to show that they are represented in 

 their geognostical and lithological relations by the Hastings series of 

 the geological survey of Canada, which, a little to the north of Lake 

 Ontario, rests upon the Huronian, and is overlaid unconformably by the 

 Trenton limestone. 



Crosby has pointed out that the resemblances already traced between 

 the geognosy of eastern North and South America are further shown in 

 the development of a great series of rocks resembling the Taconian, 

 alike in Brazil, Guiana, and the island of Trinidad. In Brazil these 

 have been described as a newer series, resting, according to Derby, un- 



