1.«S.5.] ^4o [Lewis. 



here to the vicinity of West Chester, and in this part of its course may 

 possibly occupy a line of fault. A series of serpentine outcrops occupy 

 the same position, being sometimes north and sometimes south of the trap 

 dyke, but nearly always adjacent to it, and generally south of it. 



The dyke, containing here specks of pyrite, enters "Willistown town- 

 ship, south of Paoli, and skirts the north side of the Serpentine belt. 

 South of Malvern, at the northern edge of the Serpentine belt (about a 

 quarter of a mile south of the State road), the dyke is represented by 

 large and numerous boulders, and a much smaller dyke of trap appears 

 near the southern edge of the Serpentine about one half mile south ot the 

 last place. Massive hornblendic rocks lie immediately south of this. 



On the Township Line road between "Willistown and East Goshen, 

 close to the crossing of the State road, the trap occurs immediately north 

 of the Serpentine ridge. 



In East Goshen township it appears where the State road crosses Ridley 

 creek, and continuing thence in a south-westerly direction, still keeping 

 on the north side of the serpentine ridge, is broken by a small "jog" 

 north of Goshenville. The displacement is only a few hundred feet. 

 Small dykes of trap occur both on the north and south sides of the Serpen- 

 tine ridge, one-half mile north-west from Goshenville. Thence the dyke 

 passes into West Goshen township, crossing the road between East Goshen 

 and West Goshen townships, near the house of J. Patterson, where it 

 forms a prominent ridge, and the trap outcrops in large angular fragments 

 on the roadside. Ancient gneisses lie south of the dyke and hydromica 

 schists a short distance north of it. 



In this township (West Goshen), it is clearly shown where crossed by 

 the West Chester branch of the Pennsylvania Railroad, two miles north- 

 east of West Chester. Here again it is on the north side of the serpen- 

 tine ridge, or, as it is here called, the "Serpentine Barrens." Numerous 

 boulders lie along the railroad, and the decomposed dyke is exposed in 

 the carriage road alongside. It crosses the road leading from West Chester 

 to Lionville, a short distance north of Taylor's run, south of the cemetery. 

 Further west it appears in East Bradford township, one-eighth of a mile 

 north of an outcrop of limestone, and is well shown were crossed by a 

 branch of the Black Horse run. It was traced continuously by its boul- 

 ders to the west branch of the Brandywine creek, at Copesville, on the 

 Strasburg road. West of the Brandywine, where crossing the road, it 

 forms rounded boulders, often perfectly oval in shape as though rounded 

 by water action. These atmospheric boulders, produced by concentric 

 weathering, might readily be mistaken for water-worn cobble-stones. 



In West Bradford townsliip, the dyke keeps south of the Strasburg 

 road, and was noted when crossing each road. It passes a short distance 

 south of Marshalton, and thence reaches the west branch of the Brandy- 

 wine creek, one-half mile northwest of Trimbleville. Along its course 

 one frequently sees walls, and even barns and houses built of the trap. 

 The old Black Horse Tavern on the Strasburg road is built of it. 



