344 Geology of Long Island. 



with the yelloio drift or preglacial drift of New Jersey, a forma- 

 tion of very great extent in that State, and of which the origin 

 and source have not yet been fully explained, though it is always 

 overlain by the glacial drift proper where these formations occur 

 together. 



In the bills near Brooklyn the till attains its maximum depth. 

 This has never been definitely ascertained, but is probably be- 

 tween 150 and 200 feet. The only information we have on the 

 subject is from a boring in Calvary Cemetery, where the drift 

 was 139 feet deep, and this point is nearly five miles north of 

 Mt. Prospect, which is 194 feet high and probably consists for 

 the most part of till. The occurrence of this till is quite local 

 and very limited along the north shore between Eoslyn and Hor- 

 ton's Point. From the former locality eastward the hills are 

 mainly composed of stratified gravel and sand, probably under- 

 lain by clay. On the railroad between Syosset and Setauket, is 

 an abundance of coarse gravel with but slight stratification. 

 East of Setauket for some distance the drift is a fine yellowish 

 sand which washes white on the surface, and at Wading River 

 the drift with cobble-stones was only eighteen inches thick where 

 exposed, being underlaid with fine yellow sand. Along the re- 

 mainder of the north shore to Orient Point, 6 feet was the max- 

 imum depth of drift observed. Under this were stratified sands, 

 gravels and clays, usually dipping slightly from the shore. On 

 Brown's Hills, north of Orienty the drift is overlaid by 3 feet of 

 fine micaceous sand, which has probably been carried to its pres- 

 ent position by the wind. The drift at this locality is a clayey 

 till, and its surface is strewn with an abundance of boulders of 

 coarse red gneiss. On Shelter Island are high ridges of gravel 

 overlain by a few feet of till. The hills from Sag Harbor east- 

 ward are also composed partially of unmodified drift, but the 

 most extensive deposit on the east end of Long Island is between 

 Nepeague Bay and Montauk Point. Here the drift is disposed 

 in rounded hillocks from 80 to 200 feet above the sea, with bowl 

 and tro.ugh -shaped depressions between. The bluffs along the 

 south shore, which are rapidly yielding to the action of the waves ? 

 consist for the most part of boulder clay and hard-pan of consid- 

 able depth, covered by a shallow layer of till. At a few places, 

 however, on the south shore, west of the point, laminated blue 



