248 GEOLOGICAL SURVEY 
INo. Depth of Welt. Temperature. - 
Vier ce St ae L73iteet,- 2824-22 64° Fahr. 
Sih so le paca (99) ee ei 66° «“ } 
Oy alate el ee R58) eee 64°30’ zi 
ALPEN SN 2 2 F50h oi 368) i) 22 eee 65° ¢ ; 
Se eS et a 1 a a ee St 68° L 
Ors ane coe es ee 420 ee Se ose eee 66° us 
7 fe een ee 46800 es So SL Lee 66°30’ & 
Sian sess PA BSOR ORE eeiseseka sees 70° sf 
Coy a Ae Sa Bd cCmperad os. eae 720 « 
To return from what may appear a digression, though really connected with the subject. The 
springs formed by the percolation of water through fissures and porous strata, unite their waters as 
they flow down hill-sides, and form rivulets; these by their union produce rivers, which scoop out 
channels in their course to the coast line. The face of the country in this way is drained. Where 
the declivities are steep, the water passes off rapidly, and inundatiors are rare; but where the bed 
of a river towards its mouth has but little inclination, it is unable to vent the water that rushes down 
the steeper descents above, and which constantly accumulating, spreads out laterally, producing in- 
undated land, and swamps. 
The simplest mode of relieving the lands on the banks of sluggish streams, is the removal of ob- 
structions, and the clearing out of the channels of such streams. An interesting example of the ef- 
fects of this process occurred on the 8. Edisto; in order to improve the stream, for the purpose, of 
rafting lumber, it became necessary to remove submerged logs, accumulations of dead timber, &c. 
When this was completed the water had fallen 3 feet, which drained some very valuable rich swamps 
on the banks. Next to this is the effect preduced on drainage by straightening the channel of a 
stream. It is obvious that straightening the course of a meandering river increases its velocity ; if 
a stream 10 miles in length, having a fall of 20 feet, or 2 feet per mile, be reduced by straightening to 
5 miles, the fall becomes 4 feet per mile, the volume of water vented is proportionately increased, 
and its surface of consequence lowered. In navigable streams such improvements require great 
caution; but there are numerous small streams in the State, particularly those that flow along the 
strike of the rocks, that would be greatly improved by a little labor bestowed in this way. It seeins 
to me that the improvement of such streams, in relation to health and drainage, would be a proper 
subject for the premiums awarded by Agricultural Societies. 
Many of the upper districts present no other possible local cause of disease, than the obstruction 
of these streams, and the effect upon the rank growth of a warm climate. My. Ruffin was struck 
with this fact, and pointed out the remedy in his Report. 
The shutting out of the water of a river, by embanking, is a mode of reclaiming land that requires 
great judgment, and often considerable capital, and can consequently only be undertaken when the 
land is of great value. In the tide swamps, reclaimed for rice culture, it is necessary to enclose the 
land completely, in order to have the water under entire control, the drainage being conducted 
through flood gates. The rice plantations are perhaps the best models that the country affords of 
this mode of reclaiming Jands. But, in ordinary cases, that occur above the tide line, the land re- 
claimed is not enclosed altogether. 'The embankment is commenced at the upper end of the land 
to be drained, and is continued downwards until a sufficient fall is secured to allow of a free passage 
for the springs and surface water. The embankment is now discontinued, and when a freshet occurs, 
