of the Eastern States. 233 



If we examine the map which accompanies Prof. Rogers's 

 report, on which the areas of conglomerate are delineated, we 

 find that each patch of conglomerate occurs just where a 

 stream leaves the highlands to the westward, which are com- 

 posed of crystalline rocks, and becomes the broader and more 

 quiet river of the sandstone country. In other words, these 

 masses of conglomerate are situated opposite the extremities of 

 valleys in the crystalline rocks, which must have been the 

 mouths of rivers in the Triassic period. 



At Pompton, where the Eingwood and Pequannock rivers 

 leave the highlands, we find the most northerly of the patches 

 of conglomerate mentioned by Prof. Rogers. At Boonton, at 

 the mouth of the deep valley through which the ( Rockaway 

 river flows, is another heavy bed of this deposit. In each of 

 these cases, as we have mentioned, the coarse accumulation of 

 stones and gravel rests conformably on the rocks beneath, 

 which were deposited in more quiet waters. The next area 

 of conglomerate to the southward is at the mouth of the Lam- 

 ington river. Again, southward of this, where the Spruce 

 Run and the South Branch of the Raritan leave the highlands, 

 we find the conglomerate largely developed. The rocks in 

 these southern areas hold a large amount of calcareous pebbles, 

 and at times are cemented together by a calcareous cement. 

 Specimens of this rock will sometimes take a good polish, and 

 resemble closely the Potomac marble, which is, indeed, but 

 another exposure of this same series of conglomerates, farther 

 south on the Potomac. In the southwest corner of the State, 

 we find the largest development of this conglomerate which 

 occurs in New Jersey, just at the point where the Delaware 

 leaves the crystalline rocks and begins its course through the 

 beautiful pastoral valley which it has excavated through the 

 red sandstone country. This same series occurs all along the 

 western boundary of the Triassic formation in Pennsylvania,* 

 and extending through Maryland, appears again, as we have 

 mentioned, on the Potomac, and can thence be traced south- 

 ward to the James River. 



* H. D. Rogers's Rep. Geol. Penu., Vol. II, p. 681. 



