2& 
OF SOUTH CAROLINA. 193 
molluscous animals bury themselves, and which is often covered with the shells of littoral and 
pelagic species, thrown up by storms; back of this, a low marsh, intersected by channels in which 
oysters live; the marshes are covered with a coarse, tall grass, and, where more directly exposed to 
salt water, with Uniola spicata. Auricul« bidentata and Littorina irroratus are the only shells 
found on these marshes, but on their muddy edges vast beds of muscles exist. 
Thus far I have only aliuded to the accumulations going on upon the coast, or the encroachment 
of the land upon the ocean. It will be seen, however, that there are other changes in progress, 
equally important and reciprocal with these—the encroachment of the ocean upon the land. 
Before proceeding to the consideration of these, it will be proper to take a rapid view of the 
changes to which the rivers of the State are subject. 
In general the channel of a river will be subject to change, so long as the resistance presented 
by the banks and bed is less than the force of the stream. If the resistance of the bed be greater 
than that of the banks, the channel will widen at the expense of the latter; but if the bed present 
less resistance than the banks, it will deepen. It is for this reason that the rivers of the State are 
narrower below the falls than above, although the quantity of water is generally greater. 
When, by any cause, the current is made to impinge with greater force upon one bank than the 
other, it must be worn away, unless composed of materials offering a sufficient resistance; and a 
corresponding addition is generally made to the opposite bank. 'The addition, however, does not 
consist of the debris of the wasting bauk, but of sedimentary matter brought from above, and 
deposited in the eddy. ' 
I saw, below Silver Bluff, on the Savannah, a sunken steam-boat, that had so directed the cur- 
rent to the South Carolina side of the river, as to wash one hundred feet of the bank in a single 
season, and make a deposit, to the same extent, on the Georgia side. ‘The falling in of a tree, or 
the accumulation of a raft of wood, is often sufficient to produce serious changes in the channel of 
a river, where the banks are yielding. 
But the rate is often so slow as to render their progress almost imperceptible. It is in this way 
that the low grounds and swamps on the rivers are formed, which occur on the banks opposite to 
the bluffs.* The encroachment generally extends to a depth equal to that of the river, and hence 
the great depth of the swamps, which are only the changing beds of the rivers, filled up with 
drifted materials, often composed of purely vegetable matter. It was mentioned that these mate- 
rials are finer towards the mouths of the streams, and for the simple reason that the transporting 
power of the latter is diminished with their velocity, so that when they fairly meet the tide it is 
destroyed altogether; and hence that extensive and most interesting series of deposits lying along 
the coast, within the limits of tide-water, constituting the rice plantations, which are composed 
of the finest sedimentary matter, almost entirely of vegetable origin. 
I do not mean to say that they are composed altogether of drifted materials ; on the contrary, 
they were once swamps, covered with Cypress trees and a dense under-growth, which, jor ages, 
accumulated vegetable matter, extending, even now, to a depth of twenty or thirty feet. Prostrate 
logs of Cypress and Cedar are met with in every excavation, and stumps are found below the 
*Any one desirous of having vivid impressions of the extent and nature of these swamps, need only cross the Little Peedee, at 
Gallovant’s Ferry, and return by way of Potatoe-bed Ferry, lower down—the sooner after a freshet the better—or cross the Santce, 
at Murray’s Ferry, in February. 
49 
