OF THE NEW-YORK SYSTEM. 51 



As m}- object now is merely to state very briefly the order of succession of the lower 

 New- York rocks, I have only to say, that from the Calcifcrous sandrock upwards, there is 

 a series of limestones described in tlie New-York Reports as Ciiazy, Birdseye and Trenton 

 limestones; all of which, together wiili the black marble of Isle La Motte, are largely 

 formed in Northeastern New-York. It appears, also, according to Dr. Troost, that the 

 same limestones are found in East Tennessee, willi the same fossils ; a fact of great inte- 

 rest, as it sustains the position assumed in the Report of the Second District, namely, that 

 the Chazy rocks are not simply local interpolations, Init may be considered as well defined 

 general masses. 



Still proceeding upward in the New- York series, we now have reached those slates and 

 shales which have been denominated the Utica slates, and Hudson-river or Pulaski shales. 

 The first is really a black calcareous shale. The succeeding mass is more or less sandy, 

 and finally terminates in a thick-bedded sandstone interlaminated with a dark-colored 

 slate. The whole thickness in New-York, at the termination of the Helderberg range 

 towards the Mohawk valley, is not far from seven hundred feet. 



I have no occasion to extend this descriptive list of the lower rocks of the New-York 

 system farther. The succession is clear and unequivocal, determined directly by super- 

 position ; a superposition which may be at once seen by any one who will travel across 

 Jeflferson county from north to south. The Potsdam sandstone is here the inferior mass: 

 it gradually passes into the Calciferous sandstone ; and in both rocks there is a species of 

 Lingula, either identical or so closely allied as to lie distinguished with difficulty. The 

 bearing of this fact will be stated more fully hereafter. I may, however, say in this place, 

 that it entirely dissipates the notion advanced by Prof. Rogers, that the Potsdam sandstone 

 of the New- York system and the granular quartz of the Taconic system form one identical 

 rock. 



The lower rocks, those now luider consideration, are the onlj^ ones which, either in this 

 country or Europe, have ever been termed the Metamorphic rocks, or have ever been con- 

 founded with those that I have called tlie Taconic rocks or system. Some of them are 

 unquestionably equivalent to the Caradoc sandstones of the Silmian system. The Medina 

 sandstone, which succeeds the Hudson river rocks (black and grey shales and a thick-bedded 

 sandstone, with the Utica conglomerate at the superior part) , is no where found in the 

 vicinity of the Hudson river ; but here they are immediately succeeded l)y the tliin greenish 

 and reddish shales, which finall}' pass into the thin-bedded limestones called in the New- 

 York reports the Manlius water-limes. 



Having stated very succinctly the order of the lower palaeozoic rocks of the New- York 

 system, I deem it unnecessary to follow up the succession, inasmuch as there is scarcely 

 a possibility of confounding the Helderberg division with the Taconic system, and inas- 

 much too as it is admitted by all who dissent from my views in regard to this system, that 

 it is the lower division only which is metamorphosed into that long belt of slates, shales, 

 crystalline limestones and sandstones lying between the Hudson river on the west and 



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