WATER-POWERS OF SOUTH CAROLINA. 197 



the tertiary plain. In South Carolina the average elevation of the streams 

 at the upper edge of this belt above tide level is about seventy feet in an 

 average distance, following the windings of the streams of about two hun- 

 dred and fifteen miles ; this gives something like 0.3 foot fall per mile, 

 and of course renders the streams of this section, as a rule, unavailable 

 as motor powers, although the smaller streams sometimes have such fall 

 as to allow of their use for cotton gins, grist, and even for saw mills. For- 

 merly along the coast of Carolina tidal water-power was utilized for rice 

 mills, but this motor has been here superseded by steam. 



II. The middle belt comprises what has been described as the " Red 

 Hill," "Sand Hill " and " Piedmont" regions of South Carolina, with a 

 portion of the upper pine belt, in all about 18,000 square miles. It has a 

 general elevation above the sea level of about six hundred feet, and 

 the average fall of the streams passing through it varies from two feet to 

 seven feet per mile. This is the region of the great water-powers, and to 

 it Mr. Swain has devoted his chief attention. 



III. The western belt is among the mountains. In South Carolina it 

 is described as the Alpine region, and embraces about twelve hundred 

 square miles. The streams here are numerous, and tneir fall is very great, 

 but they are much inferior in volume to those of the middle belt, and 

 consequently rank below it, as affording water-power of tlie largest 

 capacity. 



The advantages offered by the water-power of South Carolina are much 

 enhanced by topographical and climatic conditions prevailing here. 



The undulating plateau of the Piedmont region has a pervious soil to 

 an average depth of fifty feet or more, formed by the unusuall}' deep dis- 

 integration of the metamorphic rocks, and presenting a mixture of sand 

 and clay, well adapted for the al)sortion of rain water. This pervious 

 soil rests at the depth indicated on the impervious strata of rock, granite, 

 and gneiss, or the various slates, which impede the deeper percolation of 

 water. The streams have cut their channels down to these underlying 

 beds of rock, and it is along their surface that constant supplies of water 

 held in reserve by the permeable soils of their water-sheds are received, 

 thus adding largely to the amount and the regularity of their flow. A 

 similar condition obtains among the sand hills, where the porous sands, 

 through the interstices of which the rain disappears almost as readily 

 and rapidly as it does through the air, rest at a depth of one hundred 

 feet to one hundred and fifty feet on impervious beds of kaolin clay. . As 

 a consequence the streams of the sand hill region lose little of the rain- 

 fall through surface evaporation and maintain a flow hardly affected per- 

 ceptibly by unusual seasons of rain or drought, and Mr. Swain more than 

 once expresses his astonishment at the horse-power furnished by streams 



