THE SAND HILL REGION. 119 



up with some force, and throwing out considerable quantities of fine, 

 white sand. The action of these underground streams in removing and 

 transporting these fine sands, accounts for a number of circular depres- 

 sions not very different in appearance from lime-sinks, found scattered 

 here over the elevated flats and plateaus, and when, by an accumulation 

 of vegetable growth or a caving in of the earth, the channels of these 

 streams are obstructed, rains sometimes fill these depressions, giving rise 

 to clear sheets of water or lakelets. Another phenomenon occurring here, 

 and not well understood, are blowing wells, of which there are several. 

 For example, on a high sand hill in Hammond township, Aiken county, a 

 number of unsuccessful attempts were made during many years to dig a 

 well. At length an auger, eight inch diameter, penetrating the loose, 

 coarse, white sand, and nothing else, to a depth of one hundred and 

 twenty feet, encountered a bold stream of excellent water. When the 

 well was curbed and completed, it was found that a current of air issued 

 from it all the time, which, in threatening and stormy weather, acquired 

 such force as to make itself heard at some distance, and to blow several 

 feet into the air a hat or cloth laid over the orifice. 



GEOLOGICAL FEATURES. 



These hills form a dividing ridge between the more recent formations 

 of the low country and the very ancient formations of the upper country. 

 Their southern aspect overlooks the tertiary plane descending to the sea 

 shore of the Atlantic. On the north they reach the clay slates (dipping 

 north) of Edgefield, Lexington, Richland and Chesterfield counties, and 

 the granite and gneiss rocks of Kershaw county. Outcrops of these most 

 ancient rocks occur among the sand hills themselves, as follows : 



In Aiken county, granite occurs on Horse creek, and granite overlaid 

 by gneiss rock and hornblende slate on the South Edisto, where the 

 Columbia road crosses in. 



In Lexington county, granite is found at Quattlebaum's mill, on 

 Lightwood creek. 



In Kershaw county, masses of steatite occur on Spears, Twenty-five 

 Mile, and Pine Tree creeks, and at Liberty Hill and at other places 

 rounded blocks of coarse granite are seen, " as though they were pushed 

 up through the sand." 



Next to the granite is found a stratum of sandstone, consisting of the 

 ruins of the granite consolidated into a pretty hard rock. It occurs on 

 Horse creek, on the ridges at the head of Lightwood creek, on Congaree 

 creek, where Mr. Tuomey observed in it comminuted fossils of the eocene 

 type ; at the Rock House, in Lexington count}', ^^•here it has been quarried 

 for architectural purposes, and on Second creek, in the same neighbor- 



