On the Geology fyc. near West Chester County, Pa. 1 7 



In general it is a rock of an homogeneous appearance, 

 fracture conchoidal, splintery on the edges, color dark grey, 

 passing to black, decomposes on the exterior, and is covered 

 with a light grey crust. The formation extends ten miles 

 in length, and half a mile to one mile in breadth. It is pro- 

 bably a continuation of the range which crosses the state of 

 New Jersey, and appears to be a superincumbent mass re- 

 posing on the second sandstone. The trap rocks occur in 

 immense masses on the surface of the ground. A highly 

 picturesque view of them is afforded at the falls of French 

 creek. The desolate wildness of the scene is seldom surpas- 

 sed. Large blocks of trap rock, some of them weighing two 

 or three hundred tons, have fallen from the summits of the 

 adjacent hills, and nearly filled the bed of the creek for a 

 space of two hundred yards. When the stream is small it 

 finds a passage between or underneath the masses of rock, 

 but, after much rain has fallen, the stream increased in size, 

 dashes over with violence, and presents a splendid scene. 



Localities of Minerals. 



In Gneiss; at Joseph and William Osborne's farm. 

 Oxide of Manganese. 

 Da. covering Gneiss. 

 Manganesian Garnet, massive. 



Schorl. This occurs abundantly in many other parts of 

 the gneiss formation. 

 At an eminence, one mile south of West Chester. 

 Garnets, crystallized and amorphous. 

 Zircon, crystallized in four sided prisms, in a bluish 

 quartz, in the vicinity. 



Near the spring house. 

 Zoisite, in rhomboidal prisms. 

 At Way's hill, near Brinton's ford, on the Brandywine. 

 Brucite or condrodite, in limestone. 

 Coccolite, grey, and various shades of green. 

 Diopside. 



Sahlite, in small crystals. 

 Augite. 

 Hornblende. 



In serpentine, at Mr. Taylor's quarry. 

 Amianthus. 

 Asbestos ligniform. 

 Talc. 



Scaly talc. 

 Vol. XIV.— No. 1. 3 



