ALLUVIAL DIVISION. 
17 
Marine Alluvions. 
Salt Marshes, or Marsh Alluvions. 
Salt marshes are very extensive on some parts of the coast of Long Island, Staten Island, 
and Westchester county. These alluvions result from a combination of several causes. The 
first step in their formation, is the deposit of a sand or shingle beach, by marine currents 
sw^eeping along detrital matter, and depositing it in the eddy currents, in front of shalloiv bays 
and in the reenterings of the coast, so as to shelter these spaces from the action of the surf, if 
they were before exposed to it. They are also made shallower by the sand and silt carried in by 
the tide, the deposits from the surface waters of the adjacent country, and by sand drifted from 
the beach. Not only marine animals and plants, by their growth and decay, add new matter 
to the gradually shoaling pond or bay, but the accumulation of drifted sea-weed, trees, etc. 
serve to increase the alluvion at every successive storm. These various causes combined, 
gradually shoal the water with alluvial depositions, until marsh grass finally takes root upon 
the surface. In the formation of these marine alluvions, vegetable remains far exceed the 
other materials in volume, so that an imperfect marine peat results. The marine peat ob¬ 
served in most localities, was of inferior quality : it was light and spongy, containing unde¬ 
composed vegetable matter. 
The relative proportion of salt marsh on the coasts of Queens, Kings and Richmond 
counties, is much greater than on those of Suffolk county. These marshes are now forming, 
and have been for an unknown period of time. In some places they are washing away, in 
others they steadily increase in extent. I have been credibly informed that grass now grows 
on a marsh near Rockaway, where vessels have floated within the memory of my informant. 
On Coney island, also, Mr. John Wyckoff informed me, that many places which were ponds 
and pools within his recollection, now produce good crops of grass. A very aged man also 
recollects having seen the surf roll in at the foot of the upland north of the marsh towards the 
east end of Coney island. A broad marsh now intervenes between the upland and the beach. 
A combination of several of the causes producing salt marshes, is particularly favorable to 
their rapid increase ; such, for instance, as the alluvion washed down by streams; the fine 
materials swept from the headlands, and carried into the bays and reenterings of the coast by 
the flood tide, where they are deposited ; the fine earthy matters formed by the surf grinding 
the pebbles on the coast, being transported by the tidal currents into the bays and marshes, 
and deposited there ; the growth and decay of multitudes of marine animals ; the accumula¬ 
tions of marine plants, drifted sea weeds, and other refuse of the ocean, and clouds of drifting 
sand; all of which concur to shoal the water more or less rapidly in situations where it is 
protected seaward by beaches and islands. 
These marshes are valuable on account of the salt grass, of which they yield an abundant 
crop. Many of these marshes are so located that, with a trifling expense, the tide, surface 
Geol. 1st Dist. 3 
