No. 161.] 
77 
from the sea by the long sandy islands, which have been mention- 
ed in the preceding article, have their outlets blocked up entirely 
by the materials deposited,, or so nearly, as to leave only narrow 
entrances. Strong currents set along the shore, and these, aided 
by the oblique action of the surf, roll the pebbles and sand up 
the beach, which, on the retiring of the waves, are swept again 
into the surf, having described a semicircular line, and perhaps 
progressed several feet by the action of a single wave. This mode 
of transport is seen almost every where on these coasts. The 
cliffs are undermined, and the coarser parts of their wrecks are 
thus tumbled along from place to place, by each succeeding storm. 
The particular local effects of such causes can only be fully under- 
stood by visiting the localities, or having accurate detailed topo- 
graphical maps, like those now in progress under the supervision 
of the superintendent of the National Coast Survey. It is hoped, 
that those maps of Long Island will be published before the geolo- 
gical survey of the State of New-York shall have been completed, 
in order, that an accurate, detailed, geological map of this part of 
the State may be formed, so as to illustrate the numerous impor- 
tant geological details. The transporting action, above alluded to, 
has been the most effective agent in the formation of the marine 
alluvions of Long Island. This Island has been composed of one 
principal, and several small detached islands, which are now con- 
nected with each other and with the main island. The east end of 
the Island, from Montauk Point to Nepeague beach, seems to have 
been at some former time two separate islands, which have since 
been connected with each other, and with the main island, by the 
westward currents sweeping along detrital matter, derived from 
the continual destruction of cliffs of loose materials. Nepeague 
beach is five miles long, a great part of which is loose, drifting 
sand, enclosing marshes and salt ponds. This beach is so low in 
some places, that the tides frequently overflow it. The skeleton 
of a whale is said to be now imbedded in these sands. At Fort 
Pond bay, a few miles east of Nepeague beach, a narrow strip of 
shingle, frequently overflowed by the tides, separates the Atlan- 
tic from this bay, which is separated from Long Island Sound by a 
beach, sometimes open, but often blocked up with sand. Great 
Hog Neck, and Little Hog Neck, near Sagg Harbor, were once 
islands which have been united by a sand and shingle beach, and 
the latter with the main island. Farrington Neck, a few miles 
west of these, was an island which is now united with the main 
Island by a low beach. That part of the township of Southold, 
