1892.] NATURAL SCIENCES OF PHILADELPHIA. 447 



the Schuylkill, but, from the rising of its floor, almost obliterated 

 beyond Wayne. The limestone is narrow and rarely visible west of 

 "West Conshohocken, but at points distant respectively as follows : 

 Gulf 1-2 ; Stacker's 2^ ; and Pechin's 3 miles from the Schuylkill 

 it appears in place, beyond which occasional sink-holes indicate its 

 underlying. Northwest of West Chester it once more appears 

 accompanied by the same schists as form much of the floor of Cream 

 Valley, and which can be followed the whole distance. 



Beyond this, and in almost the same line outcrops are numerous, 

 accompanied by the same rocks until we reach the great outcrops 

 near Doe Run in middle Chester Co., where, again, the existence of 

 the Cambrian south of the limestone is universally admitted. 



He could not, therefore, admit the futility of all endeavors to 

 discover a southerly synclinal rise of the quartzite along the South 

 Valley Hill, but would submit that if in a lineal distance of about 

 thirty miles, section lines be drawn a mile apart, and more than one- 

 half of these show an orderly succession from the outside to the 

 center, while the others show in part the same with the remainder 

 concealed by surface soil, the evidence of a simple synclinal is incon- 

 trovertible. It is only by the assumption that rocks, which anyone 

 who seeks may find, do not exist, that the necessity of a fault 

 becomes apparent. It is true that the sandy mica schists, at times 

 garnetiferous, present a difficulty, but if these be divorced from the 

 South Valley Hill hydromica schists with wdiich they have no con- 

 nection, and be regarded as a part of the Cambrian, and the Lime- 

 stone, also Cambrian, as Walcott's recent discoveries seem to indicate, 

 the objection vanishes. It is certainly true that in Chester County 

 the limestones are both underlaid and overlaid with schists and 

 gneisses, among which, close to, but not in contact with the limestone, 

 so far as he had seen, occurs at numerous localities the characteris- 

 tic Cambrian Sandstone with its micaceous parting, its rhomboidal 

 jointing and its minute and usually disjointed tourmalines. One of 

 the most remarkable facts is the wonderful uniformity of this rock 

 from numerous and widely scattered outcrops over an area of more 

 than fifty miles in length, and ten miles in greatest breadth. 

 Indeed so exactly alike is the rock that it is impossible to determine 

 the locality by inspection of the specimens. The specimens shown 

 to-night verify this. 



December 13. 

 The President, General Isaac J. Wistar, in the chair. 



Thirty-one persons present. 



A paper entitled " The Principle of the Conservation of Energy 

 in Biological Evolution, a Reclamation and Critique," by John A. 

 Ryder, was presented for publication. 



