28 Geology of Hudson County, New Jersey. 



Avestwurd at an angle of about fifteen degrees, thus giving the 

 western side of the hill a drainage in that direction. On the 

 west, the trap passes beneath the sand-dunes and swamp- 

 deposits of the ISTewark meadows. To the eastward, this out- 

 cropi:)ing sheet of rock presents a bold mural escarpment, fre- 

 quently forming cliffs from one to two hundred feet in height, 

 having usually a bank or talus at the base, composed of huge 

 angnlar fragments of trap that have been broken from the face 

 of the precipice, mingled in some places with boulders and 

 boulder-clay that can only be referred to the glacial drift. The 

 appearance presented by the outcropping edge of this trap- 

 sheet to the eastward is typically shown in the Palisades. 



The relation that the trap bears to the softer sedimentary 

 strata of Triassic age associated with it, is represented in the 

 section across Hudson County accompanying this paper. On 

 either side of the conspicuous hill of trap are beds of sandstone, 

 slate and shale, all inclined to the north-westward at about the 

 same angles as the sheet of trap itself ; these sedimentary strata 

 form the bed-rock along each side of the hill, and also of the 

 greater portion of the country for twenty miles west of Hudson 

 County. 



Besides the trap-rock, sandstones, slates, and shales already 

 mentioned,' there is an area of small extent, underlying the 

 easteni portion of Jersey City, composed of very ancient crystal- 

 line gneiss; northward of this, and resting upon it or inter- 

 stratified with it, occurs a limited exposure of jasperoid-rock 

 and serpentine, composing the hill at Hoboken known as Castle 

 Point. 



In the section referred to above, it will be noticed that the 

 older strata forming the rocky floor of the county, are overlaid 

 by a sheet of material of a totally different nature, occurring 

 both on the hill-tops and in the valleys. This covering of earth 

 and stones, now^ forming the surface of the larger portion of our 

 county, is glacial drift, and will be more fully described under 

 the head of surface geology. 



Along the western side of Bergen Hill, this covering of su- 

 perficial material is overlaid in turn by the sand-dunes and 

 swamp-dejiosits of the Newark meadows ; to the eastward, along 



