1883.] • NATURAL SCIENCES OV PHILADELPHIA. 247 



Outcrop 3 runs for nearly 1500 feet parallel, or nearly so. to a 

 lane. The bearing of this lane, by surveys recited in the deeds, 

 is N. 62° 40' E. 



Xow if the lines of strike given by Dr. Frazer be plotted on the 

 map, it will readily be seen that while a line about N. 83 E. will cross 

 all of them, the strike of all will cross this line at angles from 23° 

 to 43°, except the first. The strike of the outcrops, as given on 

 the map, is wrong, as shown by Dr. Frazer's own figures; but in 

 spite of this the echelon structure is deliiieated in the two out- 

 crops south and southwest of Old Eagle station, the error — making 

 them two parallel outcrops — being due to the fact that the westerly 

 one is not over 400 feet long, the easterly not over 200, while on 

 the map each is made over 1000 feet long. 



Mr. Hall remarks (Am. Nat., June, 1883, p. 647) that I do not 

 account for the absence of slates on the north side of the valley. 

 From the specimens exhibited it will be seen that there are in the 

 North Yalley Hill slaty rocks with segregated quarlz closely 

 resembling those of the South Valley Hill, though it is true that 

 as a whole the hills are not alike. 



I have here specimens to illustrate the succession of rocks north 

 and south of the Radnor gneiss belt. 



I would particularly call attention to the rocks immediately 

 south of the Radnor gneiss belt. Their resemblance to those on 

 the north is striking, and it seems worthy- of further investigation 

 whether the belt of fine grained gneiss breaking into rhomboidal 

 fragments and connected with a white feldspathic rock, may not 

 be identical with the eurite and adjacent rocks on the north. 



I have also two more specimens of the quartzite with supposed 

 fucoidal markings, one of which, from the Old Gulf road east of 

 Bryn Mawr, contains them unusually well defined. 



