124 GEOLOGICAL SURVEY OF ALABAMA. 



fractary to the action of fire, but as yet has mainly been 

 used for inside lining for fireplaces, for which purpose it is 

 well adapted. Whether its refractory character is sufficient 

 to withstand a very high degree of heat, is not yet known. 

 But as it is mainly pure Silica, and therefore alone infusible, 

 the inferences are in its favor. 



This rock would furnish large amounts of good material 

 for the manufacture of glass. And the amount of it that 

 has decomposed into sand along its base, will give inex- 

 haustible quantities of that very useful material. 



The limestones of the Trenton, and the Sub- Carboniferous 

 formations, are both well exposed and very abundant. They 

 both contain a superabundance of good building material, 

 and of a character of already well known excellence for 

 heavy work. And some of these, especially the latter, are 

 well adapted for the manufacture of lime on a large scale. 

 And as a flux for the reduction of the iron ores, their close 

 proximity makes them of very great economic importance. 

 This ledge of Carboniferous Limestone has only been tested 

 at Compton Mines, but it extends in equal volume and purity 

 the whole length of this valley. 



FIRE PROOF ROCK. 



Among the industrial materials in this valley, one of 

 much probable importance, is a fire proof conglomerate. Its 

 place is among the upper members of the Knox Dolomite in 

 that debatable ground beneath the Trenton, where the 

 Chazy belongs, wherever it exists. This rock has been seen s 

 at many places in the Silurian Valleys of Alabama, but no- 

 where in such abundance as in T. ]3 of R. 1 E., in this 

 valley. It is in some places nearly, or quite 100 feet thick. 

 The lower members, where seen, were quartzite and breccia. 

 The upper portion a more uniform and finer conglomerate. 

 The small pebbly particles, nearly of uniform size, are gen- 

 erally flattened, of various colors, but mostly light yellow 

 and white, giving the rock a light grey color. The rock is 

 firm, massive, strong, but porous or open jointed. It has 



