342 On the Secondanj and Tertiary Formations. 



county, N. C The silica is the least injurious ingredient, its 

 principal effect being, unless the rock is burned at too intense a 

 heat, merely to render less sand necessary in tempering it for 

 mortar, while the magnesia is not only of small quantity but 

 doubtful tendency, and the oxide of iron is generally in too 

 minute proportion to seriously injure the lime by giving it a very 

 dark color. 



Besides the lime that will hereafter add to the mineral wealth 

 of this region, there is near Pocataligo, on navigable tide water, 

 a deposit of the purest quality of quartz sand, suitable for the 

 manufacture of glass. The pebbles of which it consists are 

 small, sharp, angular fragments of perfectly pure quartz, without 

 any foreign mixture. It may be obtained in any quantity, and 

 would probably pay for transportation as ballast under the cotton 

 loads, either to the northern glass-houses or across the ocean. 

 The locality is just half way between Charleston and Savan- 

 nah, by the turnpike, on Mr. Spike's plantation. 



There is one more locality of the secondary limestone I vis- 

 ited, which is near the Savannah river, in Georgia, at a place 

 called Jacksonboro'. The perfect similarity of the rock with 

 that in Jones county, North Carolina, and on the Santee and 

 Edisto in South Carolina, admits of no doubt that it is the same 

 with them, and continuous through this wide extent of country. 

 Even to the straw color of the rock, the brooks flowing out at 

 its base, the lukewarm water, and the little shells that inhabit 

 it, they are all nearly alike. This has been partially quarried, 

 and the limestone burned. On opening the bed it is found to be 

 about twelve feet thick, and within from the surface, the stone is 

 of a much whiter color, closely resembling chalk, and appearing 

 as if it had already been burned. The heap of rock in a hot 

 southern sun presents so dazzling an appearance that one's eyes 

 and head seriously suffer from closely examining the pieces. 

 They contain a great variety of fossil shells, affording most beau- 

 tiful specimens ; but I have not succeeded in obtaining those I 

 collected. A rude kiln has been constructed of the coarse sand- 

 stone belonging to the same formation, and a considerable quan- 

 tity of lime made. It is very white and good lime, such proba- 

 bly as the other localities described would afford, if worked as 

 extensively. It is packed in boxes, which hold about three 

 bushels, and these are sold along the river at the same price as a 



