134 DETAILED REPORl ON ALABAMA CLAYS. 



jesist a high temperature. Some are used in situa- 

 tions requiring resistance to heat and these must be 

 coarse grained. Others when burned into bricks 

 must resist corrosion and consequently should burn 

 to a dense product, as in the case of glass pot clajiS. 

 Fire bricks. — These should show a resistance to 

 high temperatures, and also the fluxing action of 

 ashes from the fuel, which contain carbonates, sul 

 phates, and phosphates of the alkalies and alkaline 

 earths. In addition they should withstand the cor- 

 rosive action of fused metallic slags, alkalies, and 



The density of the fire brick is often of great im- 

 poitance especially where it is to resist the corrosive 

 action of molt^ material. The fat plastic clays are 

 those which usually burn to the most dense body, but 

 in doing so they frequently crack to such an extent 

 that grog has to be added to them. 



Porous, coarse grained bricks on the other hand 

 stand heat better. 



The fire-clays below reported! on come from four 

 geological horizons, viz., (1) The Cambrian and Sil- 

 urian limestone formations of the Coosa Valley regi- 

 on; No. 191 from Peaceburg, Calhoun county; No. 127 

 Stevens, from Oxanna, Calhoun Co.; the refractory 

 clays of Rock Run, Cherokee Co.; and the bauxites 

 from the same locality. (2) The cherty limestones 

 of the lower Subcarboniferous formation of Wills' 

 Valley; No. 117 and 116 from the Montague mines, 

 and No. 119 from near Valley Head in DeKalb 

 county. (3) The Tuscaloosa formation of the lower 

 Cretaceous, No. 112 from Bibbville, and No. Ill 

 from Woodstock in Bibb county; No. B from near 

 Hull's Station, and No. 118 from near Tuscaloosa in 

 Tuscaloosa county; Nos. 1 and 2 from Pearce's Mills 



