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270 



BULLETIN OF THE 



found with difficulty, and only after passing over it many times, up and 

 down stream. It was at last discovered in a block, slightly moved from 

 its original position by frosting and stream-work, but still preserving its 

 joint faces parallel to those in the ledges near by. The ledge from 

 which this block had been loosened was covered; but as trap in place 

 was found two feet below it, and baked sandstone in place three feet 

 above it, I have no doubt that it showed the true place of junction. Its 

 weathered face showed no change of color, and very little change in tex- 

 ture, and specimens showing the actual welded contact were found only 

 after much hammering. They closely resemble those found at the 

 "Weehawken tunnel at the under contact ; in both cases the igneous rock 

 is bluish black, dense, and fine, and for a quarter of an inch from tho 

 contact is chilled to a dark gray ; and the aqueous rock is gray or dark, 

 and the more distinctly crystalline of the two. The thickness of the 

 Palisade Eange trap between these contacts is, according to a true scale 

 section by Cook (&, 200), about seven hundred feet. Some twenty feet 

 of metamorphosed beds are seen farther down the brook ; then expos- 

 ures are rare. A hard reddish-white sandstone was found farther south 

 lying say one hundred and fifty feet over the trap. No posterior ranges 

 of trap are known in this district, unless the Snake Hills back of Hoboken 

 are so called. 



This excursion can easily be made in an afternoon from New York ; 

 going up the Hudson to Eort Lee by boat from Canal Street, and re- 

 turning from Walton Station, Northern Railroad of New Jersey, to the 

 Erie terminus. It is of value, as upper contacts are rare. 



J, Weehawlcen, N, J. (fig. 46). — The several exposures of the sand- 

 stones below the trap in this district have been fully described by 

 Bussell {d)\ some of his figiires are here copied (figs. 30, 31), and a 

 more detailed view of the junction at the point of rocks below the 

 Duel Ground* is added (fig. 46). H. Credner examined the Palisade 

 trap in 1865, and pronounced it intrusive; he regarded the Snake Hills 

 as a branch from the main '* emporbrechende Dioritmassc" (393). 



It is very probable that the advance of the Weehawken cliffs to the 

 river bank at this point is due in part to the resistance to erosion offered 

 by the chimney or dike of trap, which here descends close to the water's 

 edge, while elsewhere the trap generally rests on a sandstone base, thirty 

 to one hundred feet above the river ; but it is also quite possible that a 

 fault, similar to that seen at Garret Rock, Paterson (L), has aided tho 

 advance. The intersection of the sandy and shaly layers by the dense 



* The Hamilton -Burr duel ground of ISO-l. 



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