20 



to near the road last mentioned, its noriliwestern margin passing 

 by Alamuche. 



From tiie vicinity of Hacketstovvn to near Mount Bethel Meet- 

 ing-house, there ranges another low ridge of the gneiss, having a 

 length of about four miles and an average breadth of one. Rest- 

 ing upon the priinary strata of this tract, is a small patch of 

 nearly white sandstone, well adapted for purposes of architec- 

 ture, for which it has been occasionally used. This is one of a 

 few isolated patches of the lowermost rock of the older secondary 

 or Appalachian series, in New Jersey; a formation displayed so 

 extensively in contact with the primary rocks of the same general 

 chain, both in New York and Pennsylvania. Another locality 

 of the sandstone is to be found between Flanders and Succasunny, 

 northeast of the former village ; and two other exposures, are visi- 

 ble near Macapin Pond, where the rock is in contact with the 

 overlying blue limestone. 



Another considerable surface of the gneiss extends from near 

 the village of Mansfield southwestward to the Easton turnpike, 

 a little west of Bloomsburg; bounded on the northwest by the 

 Pohatcong stream, and on the southwest by the valley of the 

 Musconetcong. 



The next important belt of primary rocks is that of the moun- 

 tain called Jenn}?- Jump. This ridge, extending from near the 

 outlet of Bear Brook at the Great Meadows, almost to the village 

 of Sarepta, is about seven and a half miles long, by about one in 

 mean breadth. 



Its rocks are every where overlapped around its base by the 

 ancient secondary limestone ; an interesting zone of which, in a 

 highly crystalline and altered condition, ranges along its south- 

 eastern foot for nearly its whole length. 



Two small patches of the primary rocks, which seem to have 

 been exposed by denudation of the limestone, occur in the valley 

 of the Pequest, between that stream and the foot of Jenny Jump. 



South of the Pequest rises the conspicuous ridge of primary 

 rocks, called Scott's Mountain. Its length is about twelve miles, 

 while its general breadth somewhat exceeds three. Encom- 

 passed at its base by the limestone, the southeastern limit of the 

 gneiss ranges parallel for several miles with the Pohatcong 

 stream, and afterwards with the Morris canal ; while, on the 



