86 GEOLOaiCAL RELATIONS OF ALABAMA CLAYS. 



clay proper) proves the singular fact that this clay, 

 though occurring in a formation characterized by 

 the large amount of iron it commonly bears, contains 

 a remarkably small amount of that substance, which, 

 together with minute porportions of lime and mag- 

 nesia, explains its infusibility. 



The two most important practical purposes which 

 the materials occurring in the deposits just describ- 

 ed will serve, are the manufacture of fine queenware 

 and that of fire proof brick. ( Not porcelain. Kaolin 

 or porcelain earth contains, besides the white clay, a 

 certain amount of undecomposed feldspar, which 

 imparts to it its property of being semi-fused at the 

 temperature of the porcelain kiln. The same prop- 

 erty might be imparted to the white clay in ques- 

 tion, by the artificial admixture of ground feldspar, 

 but it could not thus compete with the naturel kao- 

 lin of Alabama). 



As for the queenware, the plasticity of the mate- 

 rial leaves nothing to be desired ; and since the amount 

 of siliceous matter varies greatly in different lay- 

 ers, there could be no difficulty about givng to the 

 mass the precise degree of meagerness which may 

 be found most advantageous, by mixing the several 

 successive layers. The same may be said with reference 

 to the manufacture of fire brick (to which these ma- 

 terials are admirably adapted), which would proba- 

 bly, at the present time, be the most feasible and most 

 profitable manner in which the beds could be made 

 available. The manufacture of fire brick differs from 

 that of ordinary brick in this, that it requires more 

 care, both in working the clay and in moulding the 

 brick. Beyond their fireproof quality, it is demanded 

 of fire brick that their shape he perfect, their mass 

 uiiifona and without flaws in the interior; also that 



