278 BULLETIN OF THE 



brownish shale of somewhat coarser texture ; near the several trap 

 sheets, it is always black and brittle. Mud-cracks were noticed on 

 many loose slabs, and occasionally in place here and farther up the 

 river. Four beds of fine black trap occur in this little ravine : the first 

 two form a single shelf over which a fine thread of water falls (fig. 52), 

 the lower bed being four feet thick, the upper twelve, with four to 

 six inches of shaly slate between them. This parting of slate is seen 

 between the two beds of trap, extending with uniform dip for seventy 

 feet. The slate and trap are very much alike on fresh surfaces, but the 

 slate has a bluish tinge, and shows some signs of breaking on its bed- 

 ding; the trap is blacker, and its fracture is more conchoidal. Both 

 are jointed into sharp-edged columns, but these are most distinct in the 

 trap. Farther from the trap, the shaly structure is more apparent, 

 and bands of lighter and darker color are sometimes found. The other 

 two trap sheets make two small benches farther up the ravine, and 

 show about the same characters as those just given, but their junctions 

 with the slate could not be determined, so nearly alike were the tex- 

 tures of the two rocks near their contact, and so closely did joints in 

 the trap imitate beds in the slate. Weathered fragments of trap often 

 showed a pitted or scoriaceous surface, though no cause could be seen 

 for this in the structure. 



Eeturniug to the railroad, and going north again, the same trap 

 sheets are passed as they descend to cross the river. A quarter of a 

 mile above the station, dark red sandstone appears in the bank, and 

 continues without further interruption ; it is fine and hard, though not 

 at all quartzitic ; generally thick-bedded, but sometimes slialy and mud- 

 cracked ; fine green dots of epidote (1) are found in it. It is very 

 evident that the brittle black slate that adjoins the trap was never like 

 this sandstone. 



Rogers (c, 156) and Cook (b, 192) both refer briefly to this locality. 

 The trap here is shown on the Triassic Map of 1867, but not on the 

 Economic Map of 1881 (Cook, a and d). 



P. Lamhertville, N. J. — The section along the Delaware by Lam- 

 bertville is spoken of by H. D. Eogers (c, 153 ; g, 685) as affording 

 good examples of the metamorphic effect of the trap on the sandstone 

 on both sides of the igneous mass. Cook shows the same region in a 

 generalized section (a, sec. 1, here copied, fig. 26), with tlie traps lying 

 between the sandstones after the manner of sheets elsewhere. The 

 region is one of difficult study, for, in spite of the deep valley cut by 

 the Delaware, outcrops are not continuous enough to show junctions j 



