History of the Geology of JVew York Island. 113 



scales of silvery and golden talc, accompanied by a vein, about twelve 

 feet wide, of anthophyllite. This vein is in a vertical position. Actino- 

 lite is found imbedded in the serpentine. At the south end there is a 

 vein of carbonate of lime. This carbonate of lime has small specks of 

 serpentine diffused through it, and forms a kind of 'verd antique,' 

 which, when polished, makes handsome specimens. 



"4th. Gneiss. — This rock has a greater extent, and shows itself more 

 than any other on this island ; it begins at the Battery, which it under- 

 lies; it was to be seen also at the lower end of E. 14th st. ; in 8th st. 

 west of the 3d avenue, in digging a well, it was found eighteen feet 

 below the surface. 



" This rock begins on the south side of, and underlies Governor's 

 Island, which is its most southern extent, passing through New York 

 Island, and running through the greater part of Westchester Co. ; it 

 forms the rock at the straits called Hell-gate, and even at that place 

 (where it may be traced some eight or ten miles) underlying Long 

 Island. 



" The gneiss of New York Island is a peculiar variety. It has more 

 mica than common, and which is also in larger plates than usual for' 

 this rock. The dip of this rock varies from the extreme of horizontal 

 to vertical. 



"5th. Hornblende Slate. — This rock is associated with the gneiss in 



many parts of the island ; at Spuyten-Duyvel bluff, at the north end of 



the island, also at Manhattanville. 



» 

 "6th. Quartz Hock. — These are on the 10th avenue, near 60tk st. 



Veins of various thickness of grey, granular quartz. 



" 'Ith. Primitive Limestone of King's Bridge is well known; it is a 

 dolomite, and has all the varieties of white, grey, and light blue, granu- 

 lar, coarse marble ; it begins at the south end of Mr. Dyckman's farm, 

 and runs through the middle of the Island to Spuyten-Duyvel creek ; 

 this formation rests on granite. There were then (forty years ago) 

 three foot marks, two left feet, and one right one, on the smooth sur- 

 face of the limestone, on the north end of the formation near the 

 road. 



" 8th. Diluvium. — This formation covers almost all the island ; on the 

 lower end of the island it is of the greatest depth (100 feet), in it are 

 found types of all the rocks of the valley of the Hudson." 



