21 



north, the valley of the Pequest is the boundary as far as Bridge- 

 ville. On the northwest, the margin is pretty nearly marked by 

 the road uniting this place and Oxford. It extends thence through 

 the spot called Concord to Harmony Church. 



The last belt of the primary strata to be traced is that of 

 Marble Mountain, at the Delaware: this is also surrounded by 

 the limestone, but its western base is almost washed by the Dela- 

 ware river. It terminates towards the southwest near Phillips- 

 burg, opposite Easton ; and towards the northeast almost unites 

 with Scott's Mountain, near Harmony Meeting-house. Its length 

 is about four miles, and its average breadth one mile. 



Of the Igneous Rocks and MelaJUferoiis Veins of the Highlands. 

 — The metalliferous veins of the primary region of the State, 

 though extremely numerous and widely distributed, embrace but 

 few varieties. As regards their general structure, they are all, 

 in fact, very nearly ahke ; while the only ores they comprehend 

 in large amount belong to the two metals, iron and zinc ; those 

 of iron being by far the most abundant. 



Structure of the Feins. — In their form they are unequivocally 

 genuine lodes or veins, and often of considerable longitudinal 

 extent coinciding with occasional slight deviations, with the 

 direction of the strata which include them. Their position is 

 usually between walls of the granitoid gneiss, to which they are 

 parallel, not only in strike, but in dip. They exhibit, however, 

 many minor irregularities, such as frequent changes in thickness, 

 suddenly bulging to great width, and rapidly thinning out to 

 almost imperceptible dimensions. This observation is to be re- 

 ceived as applying with fullest force to the whole body of injected 

 matter, regarding it as one vein, which it truly is ; while the dis- 

 tribution of the ore within the vein is liable to even greater irre- 

 gularities. Viewing these veins comprehensively, they consist 

 not exclusively of the metalliferous ore, whatever it may be, but 

 of tlie ore and other minerals, particularly hornblende and felspar, 

 in one general injected mass. In some instances, the ore consti- 

 tutes the body of the vein, resting in contact with the gneiss rock 

 of the walls; in others, it occupies only a part of the thickness 

 of the mass, being bounded on either one or both of its sides by 

 the non-metalliferous minerals, usually termed the gangue; while 

 in other cases again, the vein of ore is split by a wedge of the 



