95 



terminates. Like the other corresponding tracts, it has the form 

 of a low narrow ridge, bounded on each side by limestone, 

 which dips beneath it, placing it in the middle of a synclinal 

 trough. 



The next tract of slate, though in the general synclinal arrange- 

 ment of its strata resembling the others, is one of far greater 

 extent. Both its southeast and northwest margins have been 

 already defined, when tracing the borders of the limestone, but 

 for the sake of connexion we may briefly recapitulate them here. 

 Beginning at the Wallkill, near the New York State line, the 

 southeast boundary of this tract of slate runs to the southwest, 

 passing near Deckertown, and northwest of Harmonyvale, New- 

 ton, and Johnsburg. Here it deviates more towards the west, 

 until it passes the Free Church between Centreville and Hope. 

 There it deflects to the south, passing Beaver Brook, and running 

 thence in a southwest course, reaching the Delaware a little above 

 Belvidere. The northwestern boundary, beginning on the Dela- 

 ware near the mouth of the Paulinskill, pursues the southern side 

 of that stream to Gravel Hill, near which it crosses it; recross- 

 ing a little east of White Pond, it thence extends in a northeast 

 direction for several miles to a point about three miles north of 

 Newton. Here it unites with the southeast margin of a narrow 

 belt of the formation which follows the course of the Paulinskill 

 for several miles. Beyond, where this smaller tract joins the 

 principal one, the boundary which we are tracing proceeds to 

 the northeast, again passing to the southeast of Augusta, and 

 terminating near Coursenville, where the whole zone of slate 

 southeast of the Paulinskill merges in the still more extensive one 

 which follows the base of the Blue Mountain. 



The southeast edge of this northwesternmost tract, beginning 

 at the Delaware, about three-fourths of a mile above Columbia, 

 pursues the northwest side of the valley of that stream to Coursen- 

 ville, passing north of the little village of Walnut Valley, and 

 northwest of Swartwout's Pond. Uniting with the former wide 

 belt at Coursenville, the two tracts beyond that point have for 

 their southeastern limit the boundary already traced, which 

 passes near Harmonyvale and Deckertown to the Wallkill. 



The base, or rather the southeastern flank of the Blue JMoun- 

 tain, constitutes the general northwestern boundary of the whole 



