Clay pole.] 
Perry Furnace, It cuts through the Oriskany ridge, almost at the point 
where the two outcrops are about to meet, and passing out of the Oris- 
kany near the high point behind Adam’s Glen school-hause, near Landis- 
burgh, cannot be followed through the monotonous red shale, of which the 
valley consists. There is, however, no ground for supposing that it con. 
tinues into the Blue mountains, no traces of displacement being visible in 
Kennedy’s valley or on Pilot Knob, 
Eastward beyond the display near Montebello narrows, described above, 
the fault continues, and its investigation becomes difficult. After leaving 
the exposure at No. 6, which is about a mile east of the narrows, and 
where the throw is greatest, it suddenly diminishes. The Hamilton sand- 
stone which has been faulted up and has formed the monoclinal ridge of 
Dick’s hill, suddenly sinksand vanishes underground, The land being low it. 
is not easy to find evidence of its presence, but sections along the river and 
in Watts township show that it continues to Half Falls mountain, 
From the facts that have been collected the only possible conclusion is 
that the fault here doubles itself and rapidly diminishes. The line already 
traced continues nearly along the course of Losh’s run and forms the most 
southern of the four separate ranges of Hamilton sandstone, which to- 
gether form Half Falls mountain. About the meridian line on which the 
sudden descent of the Hamilton sandstone takes place and Dick’s hill dis- 
appears, 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 third ridge of Hamilton sandstone immediately south of the 
second and nearly equaling it in height. 
These two minor faults—extensions of the Perry County fault—run 
westward along the range of Half Falls mountain to a distance which it is 
not possible to determine without a greater expenditure of time than the 
other work on the county would justify. The southern fault probably has 
but a short range, but the northern not improbably runs for two or three 
miles, 
The fault here describedis thus shown to be one of no trifling extent, hav- 
ing been traced in the above notes about eighteen miles along its outcrop 
from E.N. E. to W. 8. W. The changes which it renders necessary on the 
map are considerable. The whole outcrop of the Hamilton rocks ranging 
along the north side of Dick’s hill must be canceled and its place occupied by 
Chemung shales. The great patch of Chemung shales in the western end of 
the valley must be replaced by Hamilton and the Hamilton by Chemung. 
These changes may be seen in a moment by comparing two sketch maps 
accompanying this paper with one another. The narrow middle valley of 
Perry county is not a syncline but a monocline. Half of it has been re- 
moved and elevated above the level of the rest, from which height it has 
been washed by atmospheric action and swept into the Atlantic. 
The mass of material thus removed will be evident when the diagram 
shown below is compared with the maps and with the figures show- 
ing the amount of “‘throw’”’ of the fault. This section, though not 
9 
222 [April 20, 
