gf)2 NKW YORK STATK ^f^sF^M 



both of which are an effect of the early invasion of this part of the 

 island by the ice. 



On the other hand, it is possible that this bar may be the inner 

 margin of a stratum of these yellow gravels, the low ground north 

 of it being the unfilled portion of a longitudinal valley but it does 

 not seem possible at present to demonstrate this view. 



Glaciated ledges 



Frontal moraines mark the position of the ice front. The motion 

 of the ice, at least near its margin, will tend to be toward that front ; 

 hence, since the moraine in this part of the island trends to the south 

 of west, forming a lobate line across this region and that adjacent 

 in Xew Jersey, glacial striae in this .part of the island should run 

 to the east of south. A number of ledges of gneiss in Long Island 

 City meet this reqnii-ement. One of the largest exposures of bed 

 rock occupies a vacant lot adjoining the Queens county courthouse 

 on the west. The ledge is heavily glaciated, forming a long, low 

 rorhe moutoiinee. The striae range in direction from 29° to 30° 

 west (magnetic). A. few striae run from n 15 w, and one set of 

 scratches lies in a northwest direction. The strike of the foliation 

 of the gneiss is n 25 e magnetic. Other outcrops occur to the north- 

 east with striae running from the north northwest. A series of 

 shallow oval depressions extends in a northwest and southeast direc- 

 tion across one outcrop, the whole bearing evidence of water action, 

 presumably that of a subglacial stream. 



The southeastward movement of the ice on this side of the Hud- 

 son valley is further attested by the drift. The moraine from 

 Brooklyn as far east as Oyster Bay contains trap boulders, the 

 nearest known site of which rock is in the Palisade trap ridge on 

 the west bank of the Hudson river. 



Stratified red sands, also undoubtedly derived from the area of 

 Triassic red sandstones now found only on the west bank of the Hud- 

 S4JI1, occur in a section by the roadside from Corona to Astoria, being 

 there overlain by 8 or 9 feet of gray till with trap boulders.^ 



' B<niUlers of trap and red sandstone were seen by Sir Charles Lyell in an exca- 

 vation made in a Ixjiildcr bed at the Brooklyn navy yard. See Lyell, Charles. 

 Tniv.k it. Vortl, \M„rioi. N. Y. 1845. 1 : l«y-90. 



