174- Geology of J^icJiiiiund Counfij, y. F. 



The glucier moved across Staten Island in a south-southeast- 

 erly direction ; this is proved b}' the markings on the trai^-rock 

 near Port Eichmond, which have about that bearing ; the sur- 

 face of this rock is also smoothed like portions of the Palisades 

 and Newai'k Mountains. There are no snch markings on the 

 serpentine locks, because they are too soft to retain them ; the 

 ice extended over their whole extent, however, with the excep- 

 tion of a small area on Todt Hill, which is east of the moraine. 



North and west of the morainal hills, the drift is not so 

 abvmdant, rarely forming hills of any considerable size ; but 

 boulders are to be fonnd over all this area, except where it is 

 covered by newer formations, and the soil is often very clayey. 



Diabase of various degrees of coarseness is the mo^t abundant 

 rock in the drift; this has been carried from the Palisades and 

 the Newark Mountains, and probably in part from the tra]i- 

 dyke on Staten Island itself, and is found over the whole drift 

 area. 



Gneiss of various kinds, lai-gely sy^nitic, is perhaps the next 

 most abundant rock, and occurs often in very large masses. 

 One of these large bonlders rests directly on the top of Foi't Hill, 

 New Brighton ; another along a roadside near Pleasaiit Plains, 

 and a third worthy of notice, in a field near Huguenot. 



Moderately large boulders both of trap and gneiss abound on 

 the moraine between the Narrows and G-arretson's ; the gneiss 

 has come either from the New Jersey Highlands or from much 

 farther northward, and perhaps in part from New York Island. 

 Triassic red sandstone, carried from New Jersey or the north- 

 western parts of the county, is often met with ; a specimen im- 

 pregnated with copper salts was obtained from the bluff at 

 Prince's Bay. This locality has yielded many other interesting 

 specimens illustrating the material brought by the glacier. 

 Among these may be mentioned Potsdam sandstone, containing 

 the borings of the worm ScolithuH linearis ; a number of rocks 

 of Helderberg limestone, containing Strophomena rliomboidalis, 

 StrojjIioclBnta Beckii, Sjnrifer macrojjhura, and other braehio- 

 pods, with quantities of crinoid stems ; a specimen of granite 

 containing graphite; a cherty rock which may belong to the 

 Cornifcrous, and a conglomerate of uncertain age, but perhaps 

 of the Oneida epoch. 



