150 F J . REPORT OF PROGRESS. E. W. CLAYPOLE. 



strata are here so disturbed, that a slight dislocation may- 

 exist. Evidently there are here beds indicating a gradual 

 transition from the Lower Helderberg limestone to the Oris- 

 kany sandstone. Similar beds may be found in the west of 

 Tuscarora township. 



The Orislcany sandstone. 



No good exposure of this sandstone occurs in the town- 

 ship, but its presence is plainly indicated in places all round 

 the outcrop of the limestone. It is coarse in texture, being 

 a conglomerate of fine white quartz pebbles as at many 

 other places in the county. A reef of this rock here crosses 

 the river and helps to form the rapid. 



The Marcellus and Hamilton lower shale. 



An outcrop of the Marcellus black shale is said, in the 

 report of the first survey, to exist at Half Falls mountain. 

 I have seen no natural exposures of it, but it has been dug 

 into in the woods near the lime quarry. 



The Hamilton sandstone and upper shale. 



Along the southern line of the township the Hamilton 

 sandstone makes a long line of outcrop in Half Falls mount- 

 ain, a high bold wooded ridge extending from the Juniata 

 to the Susquehanna and forming a continuation, geologi- 

 cally speaking, of Buffalo hills, Limestone ridge, Mahanoy 

 ridge, and Dick's hill, the latter thrown up by the Perry 

 county fault. All these four ranges converge and meet at 

 different points along the line of this township between the 

 rivers, and finally die out at the Susquehanna. The influ- 

 ence of their hard sandstones may, however, be seen in the 

 bend of the river to the eastward, about Girty's notch, where 

 they project into its channel. This eastward or southeast- 

 ward course is continued until the river strikes the Catskill 

 and Pocono sandstone of Peters mountain, when it turns 

 again to the southwest, and at length finds, or rather has 

 made lor itself a passage at Duncannon. 



Near the east end of Half Falls mountain is the place so 

 well known, locally, as Girty's notch, the home, or rather 



