380 P. REPOBT OF PROGRESS. K. W. CLAYPOLE. 



simple. Aii Inspection of the county geological map will 

 show that along this line are several distinct outcrops con- 

 verging to a junction near the Susquehanna liver. The 

 ranges of Buffalo hills. Limestone ridge, Mahanoy ridge, 

 and Dick's hill all tend directly to this point, and their near 

 approach and ultimate meeting render the structure of the 

 northern part of Watts township somewhat intricate. 



In the first place almost immediately south of the lime- 

 stone comes the continuation of Mahanoy ridge. It forms 

 the middle and highest point of the triple ridge of Half 

 Falls mountain, about 500 feet above the river. This promi- 

 nent feature in the geography of the township continues E. 

 N. E., gradually sinking to a lower level as it nears the 

 Susquehanna at Girty's Notch, where its south-southeast 

 dipping beds are well exposed. But immediately south of 

 this ridge is a second parallel and of almost equal height, 

 the presence of which can only be explained by the. exist- 

 ence of a fault running along the narrow valley between the 

 two ridges. This is probably a continuation on a rather 

 different line of the Perry county fault running through 

 Spring, Centre, and Miller townships, and of which an ac- 

 count may be found in the general report on the county. 

 At this point the effect of the fault is to bring the Hamilton 

 sandstone up a second time so that the base of its southern 

 lies against the summit of its northern outcrop. There is, 

 therefore, presented along the river side a double thickness 

 of the Hamilton Sandstone as may readily be proved by 

 horizontal measurement. The distance from the Oriskany 

 sandstone through the two ridges of Hamilton sandstone to 

 the iron ore bed is about 3500 feet, which, at a dip of 40°- 

 50°, is equivalent to a thickness of about 2400 feet. De- 

 ducting 600 feet for the thickness of the Oriskany. Mareel- 

 lus, an<l Hamilton lower shale, we have L800 feet remaining. 

 The Hamilton sandstone nowhere in the county exceeds 800 

 feet, and seldom reaches that figure, so that there is evi- 

 dently a rep etition of its whole mass and part of the upper 

 or lower shale or both. These are, however, concealed, and 

 therefore inaccessible. The amount of "throw" may be 

 Bel down at about 800 feet. 



