

FAULTS OF PERKY COUNTY. F 2 . 87 



From the facts that have been collected the only possible 

 inference is that the fault here doubles itself and rapidly di- 

 minishes. The line already traced continues nearly along 

 the course of Losh's run and forms the most southern of 

 the four ranges of Hamilton sandstone which together form 

 Half Falls mountain. 



Near the meridian line on which the sudden descent of 

 the Hamilton sandstone takes place and Dick's hill disap- 

 pears, a subsidiary fault develops itself about half a mile 

 northward near the end of Mahanoy ridge and continues to 

 and across the river where it throws up a second ridge of 

 Hamilton sandstone immediately south of the first and 

 nearly equaling it in height. (See below, and report on 

 Watts township.) 



The Perry county fault is thus shown to be one of no 

 trifling extent, having been traced about 18 miles from E. N. 

 E. to W. S. W. The changes which it renders necessary 

 in the State map are considerable. The whole north dip- 

 ping outcrop of Hamilton sandstone supposed to range along 

 the north side of Dick's hill must be cancelled, and its place 

 occupied by south dipping Chemung shales. The supposed 

 Chemung shales in the western end of the valley must be 

 replaced by Hamilton, and the supposed Hamilton by Che- 

 mung. These changes may be seen in a moment by* com- 

 paring the two sketch maps on page plate VI, Figs. 3 and 4, 

 with one another. The narrow middle valley of Perry 

 county is not a syncline but a monocline. Half of it has 

 been elevated above the level of the rest, removed by at- 

 mospheric action and swept into the Atlantic, leaving the 

 monoclinal south dipping half of the Dick's hill anticline 

 as a monument of its former existence. 



The section through Montebello Narrows five miles east 

 of New Bloomfield (see page plate VI, fig. 1) and that south 

 of New Bloomfield, although not drawn accurately to scale, 

 will suffice to show the amount of throw and the horizons 

 brought into juxtaposition, which vary to some extent, but 

 these variations do not in any way affect the general truth. 



The fault is indicated on the surface only by a slight and 

 interrupted depression not in any way noticeable ; but 



