i po ee eR : 
\ OF SOUTH CAROLINA. : 2 2a 
of course the water is shut out; and when it rises to an extraordinary. height, even the back water 
can ouly overflow it when its level at the lower end of the embankment is equal to that of the land 
‘ reclaimed ; besides, such an overflow does but little injury, excepting when the crop is on the ground. 
The cause of failure in attempts at improvements of this sort, generally arise either from contvacting 
the bed of the river too much, by the embankment, or the defective construction of the latter. ‘There 
is great temptation to encroach upon the river, for, immediately on the river bank the land is usually 
higher than it is farther from it. But it is better to forego this advantage, considerable as it is, and 
give the river a ‘ wide berth, than to endanger the entire improvement. 
Very serious mistakes are committed in the construction of dams and embankments, for want of 
knowledge of the enormous force exerted by a mass of water in motion ;* in such cases it is best to 
be on the safe side. 
There are two capital improvements of this character in the State; one on the Peedee at Society, 
and the other on Santee at the head of the canal, that will long remain monuments of the judgement 
and perseverance of the proprietors. 
At the junction of the high land and the swamp, there is very generally a space lower than that 
part of the swamp intervening between it and the river; advantage is often taken of this depression, 
a ditch is cut, and a part of the water of the river turned into it, which soon excavates a considerable 
channel; the river, by being thus divided is lowered, and the land to be drained is converted into 
an island. 
The extensive swamps of some of the rivers of South Carolina offer, it appears to me, a fine field 
for the profitable investment of capital in their improvement. The cost, and prospects of success and 
profit, are susceptible of pretty accurate calculation, from data that it is the business of the engineer 
tofurnish. There is a vast amount of land of this sort in the State, the improvement of which, to be 
profitable, should be conducted on a scale that would place it beyond the reach of private enterprize. 
The swamps of the State in relation to drainage, admit of a two fold division, those on the banks 
of rivers, and that result from their overflow, and those that are produced in depressions having im- 
pervious bottoms that retain the surface water and that flowing in from the sides. When the latter, 
as is often the case, are sufficiently elevated, and far removed from the channels of drainage, they 
may be reclaimed by a canal, and the question becomes one of expense and profit. Before any im- 
provement of this sort is undertaken, we should-be satisfied that our swamp is not composed of light 
spongy vegetable matter, such as is produced by certain mosses, for if so, it will be sure to sink, as 
decomposition proceeds, which will be very rapidly, when once drained, till the surface is below the 
drains; when our draining operations must be renewed or the whole abandoned. These sphagnous 
swamps generally occur where there is nothing washed in from the surrounding land ‘to give them 
solidity. 
There is a vast amount of labor wasted,.in the defective location and construction of ditches, and 
it is much to be regretted that we have no men who study the subject of draining, and pursue it as a 
business. It appears to me that it would be a proper and useful addition to the duties of our surveyors, 
to examine the ground to be drained, estimate the amount of water to be vented, locate and proportion 
the ditches accordingly for the ditcher; but instead of this the matter is often committed to persons 
utterly ignorant of its principles. 
. Experiments made on the force of waves in the British seas, give that force, in storms, at3 tons per square foot. 
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