THE LONG ISLAND COAST. 439 



island were carried under water. The evidences of this depression 

 are found in the numerous beds of stratified sand and gravel ele- 

 vated beaches and other shore-formations which lie along the cen- 

 tral ridge of hills, 1 and fronting the ocean from 100 to 260 or more feet 

 above the level of the sea. At whatever heights these deposits occur, 

 they suggest, if they do not prove, submergence of the coast to that 

 extent. 



From observations, made by the writer and others, it is ascer- 

 tained that the summit of Hempstead Harbor Hill, which is 384 feet 

 above tide, and the highest land upon Long Island, is a mass of 

 stratified sand and gravel. The same is true of Janes Hill, in the 

 West Hill group, said to be 383 feet high, and of Osborn's Hill, 

 southwest of Riverhead, the height of which, according the United 

 States Coast Survey, is 293 feet. In these instances, and in others 

 similar, the layers are distinct and well defined. The stratification 

 of this material was evidently the work of waves, but, whether of the 

 ocean, or of a glacial lake or sea, admits of doubt. At present we 

 cannot determine what the extent, contour, or elevation of the surface 

 around these dome-like hills may have been ; nor can we tell the 

 original extent of the beds of assorted material, remains of which 

 now cap the hills. That the denudation has been immense, is every- 

 where evident. 



From the summits of the hills mentioned one overlooks southward 

 a vast plain which extends to the ocean, ten miles distant ; and the 

 conclusion seems irresistible that every rood of that distance has been 

 the shore-line of first an invading, afterward of a receding ocean, and 

 the scene of those great coast-changes which waves produce. We 

 may restore, in imagination, the hills of glacial rubbish crumbling 

 before the stroke of waves, as during an immense period of time the 

 subsidence of the land went on. So complete was the work of dis- 

 integration, that scai-cely a bowlder remains in the low tracts fronting 

 the ocean, but are numerous along the margin of the hills, and abound 

 in the undisturbed drift 2 which constitutes much of the hill-region. 



The period of subsidence we are considering is referred to the 

 " Champlain " of the geologists, so called by Prof. C. H. Hitchcock 

 from the abundance of its peculiar deposits near that lake. It is a 

 marked one in geological history. During its progress the deposits 



1 A ridge of hills, varying in height from one hundred and fifty to three hundred and 

 eighty-four feet above tide, extends, with some interruptions, through Central Long Isl- 

 and. They are drift with bowlders ; but nowhere show rock in place, as some have 

 supposed. 



2 Many bowlders on Long Island are of immense size ; one, at Manhassett, contains 

 upward of 20,000 cubic feet. Two others now or recently in the same valley are, in cir- 

 cuit, 108 and 126 feet respectively. One, on Strong's Neck, in Suffolk county, has a 

 content of 14,000 cubic feet. Bowlders are found on the tops of the highest hills, 

 and form an enormous rip-raps in some places where they have fallen as the banks were 

 undermined by waves. 



