168 (U'oUnjy ttf Rirhninnil Coiinhj. y. Y. 



Third. — Tlie theory recently advanced by Prof. J. D. Dana 

 (Am. Jour. Sci., [Ill] Vol. "XX. pp. 21. 194, 359. 450), in 

 which he claims that tliey are of Lower Silurian age. My own 

 opinion is, that they will ultimately be found to be Lauren tian, 

 and only another fold of the strata forming the Xew Jersey 

 Highlands ; l3ut the object of this thesis is not to discuss this 

 much-disputed ])oint in American geology. 



Tia ASSIO Fo K M ATIO X. 



Strata of ^'riassie age extend over the parts of the county 

 bounded by the assumed western edge of the serpentine rocks, 

 the submerged gneissic belt, Arthur Kill and J^ewark Bay. 

 This area contains about 14.5 square miles. The rocks consist 

 of red ferruginous shales and sandstones, which dip to the north- 

 west, and are broken through by a dike of diabase or trap-rock. 

 They are in part the eastern extension of the Triassic strata 

 which cover such a large portion of New Jersey. 



S]iale>< and Sandstones. — These rocks are exposed at but two 

 places, to my knowledge, and there in but very small quantities. 

 These are on Shooter's Island, at the mouth of Newark Bay, 

 and on the adjacent shore, and were recorded by Mather. Here 

 the strata consist of shaly red micaceous sandstone, differing in 

 no essential particular from that so abundantly exjjosed in East- 

 ern Xew Jersey. 



No fossils have hitherto been found in these rocks on Staten 

 Island, and the surfaces exposed are not sufficient to warrant 

 any great expenditure of time or labor in search for tliem. 



Diabase, — Trap-rock. — The diabase ridge that disappears be- 

 neath the Kill von KuJl at Bergen Point, N. J., cuts through 

 the red sandstone of Staten Island from Port Eichmond to the 

 Freshkill marshes, and appears as a long, low, round-backed 

 hill, having a general strike of S. 40° W., thus being nearly 

 parallel with the serpentine. Towards its southern end, its ele- 

 vation is so little more than that of the sandstone that the posi-. 

 tion it occupies cannot well be distinguished. The length of 

 this diabase outcrop is about live and three-quarter miles, and 



