1885.] ■*■*' [Lewis. 



it was traced with difficulty. The rocks are decomposed to a depth of 

 fifty feet or more, and the trap appears only where streams have lowered 

 the surface. 



Two local branches of the great dyke appeared in London Grove town- 

 ship. One of these crosses the Street road at Woodville, and the other 

 crosses the same road about a quarter of a mile further west, just west of 

 a small creek and on the west side of an exposure of south dipping mica 

 schist. 



These dykes can be traced across a north and south road just west of 

 here. The one is marked by scattered boulders, only. The other and 

 more southern of the two is exposed as a narrow dyke about a yard wide, 

 cutting through a ridge made of decomposed gneiss, on the farm of S. H. 

 Hoopes, one-half mile north east of Chatham P. O. 



In Penn township the dyke is marked by scattered boulders only ; and 

 the decomposition of the soil is so profound that great care was necessary 

 in following, step by step, the true course of the dyke. It was found to 

 enter the north-eastern corner of the township and, passing a mile and a 

 half north of Jennersville, to go through the farms of .1. Vandegrift, S. B. 

 Reese, L. Mendenhall, D. Mackey, Sharlton, Underwood, Myers, Thos- 

 Jackson and Matlock in a continuous south-western line. It passes a quar- 

 ter of a mile north of Forrestville, where it is shown feebly by a few small 

 boulders on the road side. It crosses the east branch of Big Elk creek, 

 just below the bridge on the road from Jennersville to Russelville, where 

 large fragments occur, some of them ringing like a bell. From here to its 

 fine outcrop west of Lincoln University, it is traced with difficulty, being 

 shown by scattered boulders only. 



In Lower Oxford township the dyke is conspicuously shown one mile 

 south-west of Lincoln University, just west of the west branch of the Big 

 Elk creek. It here forms a marked ridge near the house of S. Massey, 

 and is as finely shown as anywhere along this part of its course. 



In the diabase at this place there is a soft chloritic mineral in nodules, 

 and a little chalcopyrite. * 



About one mile south west from here, it is well shown where crossing a 

 north and south road, near the entrance to Mrs. Flemings' farm, half-way 

 between the railroad and the Oxford and Jennersville road. 



Fragments five feet or more in length occur here. It runs past the 

 house and reaches the Philadelphia and Baltimore Central R. R., at the 

 meadow adjoining to the west the same house, being somewhat more than 

 a mile west of Oxford station. Crossing the railroad, it enters East Not- 

 tingham township and runs through the farms of Mrs. Mercer and W. 

 Pickering, thus just touching the borough of Oxford, though not getting 

 within a mile of the railroad station at Oxford. 



All through south-western Chester county the trap is known by the 

 farmers under the name of "Cammels," "Carmels," or "Cammell stone." 

 It is also sometimes called "Iron stone," from the rusty exterior. 



"Cammells" appear on the farm of Benjamin Pickering, near Oxford, 



