188,5. ] 451 [Lewis. 



mountain," bounding "Buckingham valley " (of limestone) on the south. 

 The fault runs immediately south of this Potsdam sandstone mountain, 

 dividing it sharply from the upper Triassic red shales to the south, from a 

 point nearBushington to the Delaware river below Limeport. All along 

 its route, the characteristic signs of fault-rock may be detected by care- 

 ful examination. 



At "five points," on the "Street road," in the line between Buckingham 

 and Solebury townships, a large mass of coarse-grained trap, known as 

 Solebury mountain, abuts against the south side of the fault, while lime- 

 stone is quarried north of the fault. Buckingham mountain dies down at 

 this point, and the Potsdam sandstone from here to the river is either 

 absent or represented only by fragments in the soil. The unusual feature 

 of a trap mountain and a sandstone mountain abutting against one another 

 and separated by a fault is exhibited at this point. 



The fault passes "Ingham spring" and thence across the hills and 

 through the woods to a point just below Limeport on the river, having 

 been followed by the fragments of characteristic fault-rock lying on the 

 surface. Mr. J. S. Ash, from a study of the position of springs in the vicin- 

 ity, suggests that the line of fault is a water course, with vent at Ingham 

 spring. This suggestion appears to be corroborated by an unsuccessful 

 attempt recently made (May, 1885) to sink an artesian well a few hundred 

 yards west of Chalfont Station, just south of the line of fault. The drill 

 was sunk 160 feet, the workmen encountering two "boggy " places where 

 black mud and broken stone hindered further operations. 



On the New Jersey side of the Delaware, a great outburst of coarse 

 grained diabase has apparently split the fault, since well-marked exposures 

 of fault-rock occur both north and south of the eruptive trap. This trap 

 extends into New Jersey only a mile or so, but beyond it, still extending 

 in a north-east direction, is a horizon either of true fault rock or of black- 

 ened shales, indicating a continuance of the fault. Professor Cook has 

 noted the occurrence of northeast dips in the Triassic slates for many 

 miles in the same direction. 



These abnormal north-east dips of the Upper Triassic strata immediately 

 south of the fault, seem to be due to the disturbance which produced the 

 fault. As is well known, the usual dip of these strata is a gentle one to the 

 north west. A large number of localities of abnormal dips were noted in 

 Bucks county throughout the district south of the fault. Some examples 

 may here be given. In Buckingham township, west of Foreslville, some 

 ringing, baked shales dip 30° E. 250 N. ; near Worthington's store the dip 

 is 30° d= E. 30° N. ; at Carver's mill on Mill creek, three dips were taken 

 successively going east, some ten feet apart, viz : 55° N. 30^ E., N. 35° E., 

 N. 40*^ E., indicating an anticlinal. Farther north-west there are flatter 

 dips, but to the north-east there is again a steep dip to N. 30° E., and just 

 east of Pineville the dip is vertical. Farther west, at Bridge valley on the 

 old York road, some hardened, dark, ringing, fine-grained slaty strata, show- 

 ing fine ripplemarks, dip 11° S. 70^ E. ; fifty feet farther south, the over- 



