284 
ALEDVITJM. 
I 
er, &c. In many places the alluvial deposites are 
from 20 to 50 feet deep, and logs, leaves, and other 
vegetable and animal relics are dug up from that 
depth. The banks, however, are so much elevated j 
by the gradual deposition of these deposites, that it 
is only during a time of flood or an unusual accu- 
mulation of water that they are overflowed. In 
some of them, as the Mississippi, the beds of the 
streams are also elevated by the same cause, so j 
that the river is considerably higher than the adja- 
cent country. This is not always the case ; for 
Professor Hitchcock states that, since the Connec- 
ticut and its tributaries began to flow, they have 
excavated their beds nearly 100 feet, though the 
Connecticut at Northampton is still more than 100 
feet above tide-water at New-Haven; so that its 
descent to the ocean is only at the rate of about a 
foot per mile. Where the descent, and, consequent- 
ly, the velocity of the water, is greater than this, the 
bed of the stream will be excavated ; where it is 
slower, it will fill up. 
We have, in a former chapter, briefly described 
the action of the sea upon its shores, and alluded 
to the rapid wearing away of some portions of the | 
coast, while on others there was as rapid increase I 
of land. This process is going on along our whole 
Atlantic border; but in no place, perhaps, is it ex- | 
hibited in a more striking manner than on the shores j 
of Long Island. The materials which form these ! 
extensive alluvial deposites are transported coast-, 
wise by tidal, marine currents, and by the action of 
the waves, in the direction of the prevailing winds 
and storms. 
The winds which produce the greatest transport 
of alluvial matter on the coast of Long Island come 
from the northeast, bringing in a heavy sea, which 
sweeps the sand along in a westerly direction. In 
this manner, outlets of small bays are more or less 
obstructed by bars and shoals, formed by the cur- 
