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[AsSEiVIBLY 
III. LOCAL DETAILS OF THE ECONOMICAL GEOLOGY 
OF SUFFOLK COUNTY, L. I. 
Encroachment of the Sea, 
The coast of Long Island on the south side, from Montauk Point 
to Nepeague beach, a distance of about 10 miles, is constantly- 
washing away by the action of the heavy surf against the base of 
the cliffs, protected only by narrow shingle beaches of a few yards 
or rods in width. The pebbles and boulders of these beaches, serve 
as a partial protection to the cliffs during ordinary tides in calm wea- 
ther, but even then by the bouldering action of the surf as it tum- 
bles upon the shore, they are continually grinding into sand and 
finer materials, and swept far away by the tidal currents. During 
storms and high tides, the surf breaks directly against the base of 
the cliffs, and as they are formed only of loose materials, as sand 
and clay with a substratum of boulders, pebbles, gravel and loam,* 
we can easily appreciate the destructive agency of the heavy 
waves, rolling in unbroken from the broad Atlantic. The destruc- 
tion of land, from this cause, is less than one would be led to sup- 
pose, but still it is considerable. The road from Nepeague beach 
to Montauk Point, which was originally at some distance from the 
shore, has disappeared in several places by the falling of the cliffs. 
There are no data by which to estimate the inroads of the sea on 
this coast, as this part of the island is held in common by many as- 
sociated individuals, who use it for pasturage, and it is inhabited 
by three herdsmen only, who are frequently changed, and who 
live several miles distant from each other. 
From Nepeague beach to two miles west of Southampton, the 
south coast of Long Island is protected by a broad and slightly in- 
clined sand beach, which breaks the force of the surf as it rolls in 
from the ocean. From Southampton, westward, the coast of the 
island is protected by long narrow islands, from one mile to five 
or six distant from the main island. 
Some parts of the north shore of the south branch of the island, 
from Montauk Point towards Sagg Harbor, are washing away, but 
not so rapidly as on the south side of this branch of the island. 
The eastern parts of Gardner's and Plum islands, which are com- 
posed of loose materials, are washing away in consequence of the 
very strong tidal currents, and the heavy sea rolling in upon their 
* Vide Section at Montauk Point. 
