250 GEOLOGICAL SURVEY OF NEW JERSEY. 
quality. his litter and mud are abundant and available to all 
those who have enterprise and energy enough to utilize them. 
The mainland and marine marshes are protected from the 
action of the ocean waves by a line of barrier beaches or sea 
islands. ‘These beaches, on which are located many famous 
resorts, are separated from one another by inlets through which 
the tide sweeps swiftly. Strictly speaking, a beach is that part 
of a shore between high and low water, but in New Jersey the 
term is applied to what are really sea-islands. ‘These islands 
consist of a fine white sand which in places is mobile. When 
-the tide falls, the sand of the beach proper, dried by the sun 
and wind, is blown either inland or into the ocean. ‘The pre- 
vailing winds blow toward the sea, and the sand as it dries flies 
back into the water to be whirled again on the beach by the 
waves. If the wind continues for some time from the sea, sand- 
hills are formed. Any small obstacle sufficient to diminish the 
energy of the wind may cause the commencement of a dune. 
‘As soon as a little hill is formed, it is easy to see how it may 
continue to form while the conditions remain the same. Soon 
a strong west wind, however, may hurl it back into the sea, or 
an eastern gale fling it inland on the marshes. And so it goes, .: 
forming and re-forming, changing in fact with every caprice of - 
the wind, gentle and almost unnoticeable during a light sea- 
breeze, but a stinging, blinding sand-blast in times of gale. In 
case of an obstruction, which interferes with the action of 
the wind, a dune forms equal in height to the obstacle. A 
great deal of the land on these islands is now occupied by 
resorts; it is all in fact owned by private parties, and is in 
places extremely valuable. But here and there are tracts of 
wild, shifting dunes. At Avalon there isa huge dune, caused 
by a dense forest which is being slowly but surely engulfed. 
The dune begins just above high-water mark, and then extends 
inland, gradually increasing in height until its summit is even 
with the foliage of the trees. It is a peculiar scene from the 
top of this dune; on the.land side there is a dense mass of dark 
green foliage, beyond which there is the broad expanse of green 
salt marshes with their bays and thoroughfares.* On the ocean 
side, sloping to the breakers, there is a huge mass of fine sea- 
* A waterway from one bay to another is called a “‘ thoroughfare’’ along the Jersey coast. 
