VALLEY OF THE MISSISSIPPI. 39 



of hotFyoidal agate. These marigenous beds are 

 nearly horizontal, though here elevated into hills, 

 and appear, as far as I could previously observe from 

 analogy, to be underlaid by a formation of trap and 

 argillite. From hence, to the little town of Man- 

 chester, there intervenes a succession of coarse- 

 grained and ferruginous sand-stone hills, washed 

 into deep gullies, presenting a prevalence of red and 

 very sandy clay, indicative of the decomposed trap. 

 Eighty miles from Charleston, along what is called 

 the river-road, on the high and sandy banks of the 

 stream produced by the Drowning Spring, I noticed 

 scattered masses of a stone, consisting in great 

 part of flinty confluent silex, bordering on chalcedony, 

 including seams of broken shells, as well as others 

 which were imbedded and retained their calcareous 

 substance. Some of them were spiral univalves, 

 others cardiums, and pectinites resembling those of 

 the present sea-coast. In some places this stone ap- 

 pears to pass into a granulated ' quartz, resembling 

 sand-stone, but of a very fine and drusy grain. 

 This bed appeared to be about twelve inches in thick- 

 ness, and sensibly compressed ; beneath, it passes 

 into a sand-stone, which is again underlaid by a 

 thick bed of light grey schistose and indurated mar- 

 lite, containing also rounded nodules of the same 

 substance. The Utaw spring is one of those large 

 bodies of clear water which issue at once in consi- 

 siderable streams from the bosom of this stratum. 

 This formation is considerably allied to the siliceous 



