662 NEW YORK STATE MUSEUM 



ami a low bluff faces the sea. Ears of sand have been partially or 

 wliolly thrown across the old glacial stream channels by the waves. 

 Tlie most notable of these marine deposits are in the form of off- 

 shore bars, subject to frecpient changes in hight and position.^ 



On tlie north shore, wiiere the wave action is less vigorous, there 

 has been less cutting back, but, the cliffs being higher, other factors, 

 such as landslips and the ordinary work of gravity on loose materials, 

 nearly compensate for this difference in the quantity of materials 

 handled by tlie waves. The wave action on this side of the island 

 has been in part resisted by the numerous boulders which come to 

 rest upon the beaches from the undercutting of the till, a feature 

 which is wanting on the soutli shore. Numerous small barrier 

 beaches occur, usually with outlets at their western end for the 

 lagoons or back bays which they inclose. A few small masses of 

 land, which otherwise would stand out as islands along the north 

 shore, are tied together and so to the main island by these beaches, 

 as in the case of Center island in Oyster Bay harbor, which is thus 

 joined with Oak neck, and that in turn to the land. The upper and 

 iinier portions of these beaches are composed of dune sand. 



In the narrower bays and creeks behind the barrier beaches marine 

 marshes have developed on both sides of the island. The extent of 

 these dej)0sits on the south side is very much less than on the south 

 coast. The land in such situations usually slopes beneath the inner 

 margin of the marsh flats without evidence of former wave action 

 at this level. Both the beaches and the marshes have developed in 

 post-glacial time. If during all this time the sea stood at its present 

 level, before the barrier beaches were formed the waves must have 

 had a relatively free run against the sides of certain inclosed uncut 

 l)ay shores c^ the present time, and would have nipped the incoher- 

 ent materials so as to form a small but perceptible cut bench and 

 bluff. The absence of this feature in what but for the barrier 

 beaches would be exposed bay shores seems explicable only on the 

 hypothesis that the land has sunk, so that the wave-cut terraces, 



' For a recent discussion of the origin and terminology of seashore deposits, 

 coDsiilt F. I*. Gulliver, Shore line topogniphy. Am. acad. arts and sci. Proc. 

 1899. 34: 151-2r)8: also F. .1. II Merrill. Barrier beaches of the Atlautic coast, 

 Pop. sci. mo. 1890. 37:736-45. 



