198 GEOLOGICAL SURVEY 
the fresh water which it had previously received—being, as stated, salt at each end and fresh in 
the middle. Should the land at the mouth of the river continue to “make,” the creek will soon be 
fresh, excepting at its entrance into the sea. Had this marsh not been converted into a rice field 
it would be covered again with trees, at no distant period; and the simple removal of the accumu- 
lations at the mouth of the river would admit the salt water, and once more convert it into a salt 
marsh. This alternation would take place without the slightest necessity for an inch of subsidence 
of the coast. 
The sinking of swamp deposits, when exposed to the action of the atmosphere, is well known. 
There are accounts, in the “ Farmer’s Register,” of lands reclaimed, on James River, by the author 
of that work and others, that, after a few years, were abandoned, because of this sinking. The 
soil “rotted away,” so that drainage became impossible. Many of the rice plantations are three or 
four feet below their original level, from this cause: a fact that can be ascertained by comparing 
the level of the fields with that of the banks of the rivers—the latter being more compact, because 
composed of sedimentary deposits from the river, and, containing less vegetable matter, settle but 
little. The removal of wood and the annual crops being trifling, compared with the sinking from 
decomposition. 
It would be exceedingly interesting had we any means of knowing the changes that have taken 
place on the coast, in a series of years. On an old map, without date, which I saw in the Appren- 
tices’ Library, in Charleston, Fort Johnson is noted, as it then stood, on dry land. The remains 
of the foundation may now be seen on the strand, at low-water. To the north of the Fort the 
island is wasting for a distance of a mile. ‘The perpendicular bank was once a series of sand-hills, 
and even now sand is blown up at an angle of 45°. Stumps are seen in the water, 150 feet from 
the bank, and the remains of an old fort and a cannon are buried in the sands, on the shore, over 
which the tide rolls. At the date of the map the narrowest point of Kewaw Island was one and 
a half miles wide; it is now cut in two. 
In 1771 Catesby says of “Sullivan’s Island, which is on the’ north side of the entrance to 
Charleston Harbor, the bay, on the west side, has so encroached, (though most defended, it being on 
the contrary side to the ocean,) that it has gained, in three years’ time, a quarter of a mile, laying 
prostrate and swallowing up vast Pine and Palmetto trees. By such a progress, with the assis- 
tance of a few hurricanes, it probably, in some few years, may wash away the whole island, which 
is about six miles in circumference.” 
About nine or ten years ago a portion of Fort Moultrie was washed away. So completely sue- 
cessful have the plans for the protection of the island and fort been, that the dykes thrown out in 
frout have produced a deposit of sand which removes the fort 100 yards from ordinary high-water, 
and 300 from low-water mark. 
Such improvemeuts, though military in design, are nevertheless incidentally agricultural. What- 
ever tends to protect the mouths of the rivers, must. at the same time, shut out salt water, and so 
far protect the rice plantations. 
The islands south-west of Charleston offer many instructive examples of the changes taking 
place on the coast. 
Morris’s Island preseuts, on the beach side, a long line of sand-hills, rising to the height of thirty 
or forty feet, and, in some places, covered with Pines and Palmettoes. Inside of this is an immense 
