ALLUVIAL DIVISION. 
25 
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 understood 
by visiting the localities, or having accurate detailed topographical maps, like those now in 
progress under the supervision of the Superintendent of the National Coast Survey. The map 
of Long Island accompanying this report, and for which that of J. Calvin Smith is the basis, 
and which is far more accurate than any heretofore published, will enable the reader and 
student to understand most of the alluvial changes of Long, Staten and Gardiner’s islands. 
The transporting action, above alluded to, has been the most effective agent in the forma¬ 
tion of the marine alluvions of Long Island. This island has been composed of one principal 
and several small detached islands, which are now connected 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 
Atlantic 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, 
which is situated on the main island, was originally three islands, now connected with each 
other and with the main island, by beaches and marshes of alluvial formation.* 
Those long points of alluvion called sand-spits, projecting from the land, in the line of the 
eddy currents, and formed by them, are very common ; and they are, in fact, the unfinished 
beaches which will eventually obstruct the outlet of harbors and bays, and connect islands 
with each other. An interesting alluvial formation is now in progress on the north and north¬ 
west sides of Loyd’s neck, in Huntington, and formed entirely by the deposit of the coarse 
detrital matter, swept along by the current from the destruction of the high cliffs in the vici¬ 
nity. This deposit is about one quarter of a noile broad, partly marsh and salt pond, protected 
* The effects of alluvial action can be distinctly seen on the map of Oyster-pond point. This map shows where two of the 
islands which were once separated from the east end of the north branch of Long Island, have been connected by the beach E, 
and the sand-spit C, enclosing a large pond F, with an outlet only wide enough for a mill-sluice. A tide mill is constructed at 
this outlet. Mr. W. H. Sidell, a highly promising and accomplished civil engineer, has made a minute topographical map of the 
country from Riverhead to Oyster-pond point, in the discharge of his duties as engineer of the Long Island railroad; and I am 
indebted to his kindness for being able to illustrate graphically the transporting power of the waves and of tidal currents, and the 
effects produced by the deposit of sand and shingle forming on these spits and beaches. (Vide Plate 32.) 
Geol. 1st Dist. 4 
