1890.] NATURAL SCIENCES OF PHILADELPHIA. 99 



garnetiferous schists, and throughout the whole distance Laurentiau 

 rocks are found ch)se on the southeast. 



North and northwest of West Chester Laurentian also appears 

 close to the serpentine on the southeast side, while in many places on 

 the northwest side fragments of garnetiferous schists and loose garnets 

 are found in the soil with occasionally staurolite. 



About a mile and a quarter N. N. AV. of West Chester, the bold 

 serpentine ridge ends abruptly, the mica schist fragments appearing 

 in its line of strike, here S. 45° W. with an unusually uniform dip 

 in the serpentine about 45° S. E., or toward the Laurentiau. The 

 Laurentiau is not sufficiently exposed to give its dip, but the strike 

 seems to be about the same as that of the serpentine. 



Southwest of this is a small outcrop of serpentine, a little south 

 of the line of the strike of the former, and beyond are outcrops 

 nearly five hundred feet apart to the northwest and southeast of a 

 stream and low ground, evidencing a wide outcrop or two narrow 

 ones. Northwest of the serpentine is garnetiferous schist. 



Southwest of this outcrop is a ridge geographically the continua- 

 tion of the serpentine ridge, but apparently of Laurentian rocks, 

 not visible in place, but abundant as loose masses, but on the road 

 southeast of this hill garnetiferous schists with staurolite are exposed. 

 The great mass of the Laurentian lies still further southeast, so that 

 if the ridge is Laurentian, we have an included valley of the 

 schists. No serpentine is visible. The ridge ends at the road from 

 West Chester to Downingtown. At the time of my visit an 

 alteration of this road had caused a cut to be made making a cross- 

 section of the end of this ridge, showing to the southeastward 

 Laurentian, dipping northwestwardly about 22,° overlying which 

 was a bed of slaty steatite, or impure talc schist, and overlying this, 

 mica schist and quartz, much contorted, the lowest part dipping 

 conformably with the steatite and Laurentian, the upper so contorted 

 that no structure was apparent. To the northwestward the Laurentian 

 appeared dipping southeastwardly about 30° the middle being 

 occupied by the mica schists but no steatite or talc appearing to the 

 north. The exposure is probably two hundred feet wide. The rock 

 which I have termed Laurentian at this exposure I believe to be 

 such, but it is not so characteristic as to be beyond doubt. 



Further southwest on the line of this hill, after 400 to 500 feet of 

 low ground, is another hill which contains two outcrops of limestone 

 (Caleb Cope's). The southerly one has been excavated some two 



