240 NutalVs Geological and Mintralogical Remarks. 



and amygdaloid form the utmost summits of the hills, which 

 in height approach to mountains. Its junction with the red 

 sandstone is marked with some peculiar characters, highly 

 imposing to those who feel inclined to favour the Plutonic 

 theory. I mu.-t confess that at the point of union in these 

 formations the trap is peculiarly ambiguous: it presents a 

 regular porous structure; not, however, any thing like ptim- 

 mice; and many of the pores, if not ally seem dependent on 

 the decomposable nature of the carbonate of lime, which 

 still in the interior occupies those supposed pores. There 

 are, moreover, in some few places, larger cavities, appearing 

 somewhat glazed; and rugose masses, resembling slags; 

 these are, however, appearances which ought to be weigh- 

 ed with caution, and are insufficient to denionstrate any thing 

 like igneous origin. The porous quartz of Providence 

 townshio. in Pennsvlvania* and of West-Chester, in Dela- 



ware, connected with the greenstone formation, is far more 



imposing as a volcanic production ; yet distinctly traceable 

 into a reticular veined and compact jasper abundantly in 

 place near to the Black Horse Tavern, This porous texture, 

 perfectly original, is such as to render considerable masses 

 of the mineral buoyant on water. But what are we to 

 think of the serpentine, equally porous, in the same local- 

 ity, and several others, (as near Dixon's farm, Wilmington, 

 where it alternates with graphic granite,) which might be ad- 

 duced, also gradually and distinctly passing into perfect 

 compactness? If density alone is to be considered conclu- 

 sive of aqueous ongin, we must occasionally introduce a 

 double system of formation into every class of rocks the 

 globe exhibits, nor are even lavas less dense than other 

 rocks, when cooled under considerable pressure. 



In the ridge, about two miles west of Paterson, occur 

 very perfect basaltic columns of small magnitude, (about a 

 foot or eighteen inches in length, and from one to four inches 

 indiHmeter,)presentingfrom four to six sides; blackish green 

 and crystalline in the interior. This ridge throughout pre- 

 sents inclined beds perpendicularly divisible into columnar 

 concretions as far as the banks of the Little Falls of the 

 Passaic, 



This basaltic rock forms the summit of every ridge, for 

 ahout fifteen miles north-west, toPompton, where it ceases, 

 and is succeeded by grauwacke, grey, whitish, and liver 





