NEW YORK. 463 



what has been published bearing on the question of the division of the 

 Adirondack rocks into two or more systems, first calUng the reader's 

 attention, however, to the fact that no one of the theoretical views 

 advanced has been supported by sufficient evidence to make its adop- 

 tion a necessity. 



In 1864, Messrs. Hall and Logan announced, in a paper read before 

 the Natural Histor}' Society of Montreal, (Canadian Xatui-alist, 18G4, 

 (2) I., pp. 3G8, 3G9 ; Am. Jour. Sci., 1865, (2) XXXIX., pp. 96, 97,) 

 that the gneiss of the New York Highlands " presented all the aspects 

 and characteristics of that ^f the Laurentian system, as seen in North- 

 ern New York and in Canada." Here it is assumed, as a matter of 

 course, that the Adirondack region is Laurentian. 



Nothing further appears to have been done iintil Mr. A. M. Edwards 

 announced, in 1870, the discovery of Eozo'un Canadense in serpeutinous 

 marble from Warren County, N. Y., this indicating, according to him, 

 the Laui-entian age of that rock. (Proc. Lyceum Nat. Hist. New York, 

 1870, pp. 96-98.) 



Later, in 1876, Professor James Hall, in a paper entitled "Note 

 upon the Geological Position of the Serpentine Limestone of Northern 

 New York, and an Inquiry regarding the Relations of this Limestone to 

 the Eozoon Limestones of Canada," (Am. Jour. Sci., 1876, (3) XII., 

 pp. 298-300,) i-emarked of the Azoic area in question that the forma- 

 tions occupying that space, " originally called Primary, and afterwards 

 Laurentian," were now known to " represent several geological periods." 

 No pi'oof of this is furnished ; but it is further stated that there is a 

 lower division of the Laurentian, " succeeded by massive beds of labra- 

 dorite rock and other granite rocks." The lower division is said to 

 consist of black hovnblendic, gray garnetiferous, and coarse feldspathic 

 and quartzose gneisses, with extensive beds of magnetic iron ore. The 

 succession between this lower series and the upper one is said to be un- 

 conformable. In regard to this unconformability it is furtlier stated 

 that " the interval between the two series of rocks is not determined, 

 nor does it appear to be determinable from examinations thus far made 

 within the State of New York." 



Professor Hall makes a third unconformable series out of the lime- 

 stone masses of that region, of which rock he says that it " unconform- 

 ably overlies the upturned edges of the gneissic beds." He also further 

 states that this limestone " does not conform to the upper or labradorite 

 portion of the system." Hence, he considers that the limestone in 

 question " does not belong to the Laurentian system, either lower or 



