22 GEOLOGICAL SURVEY OF ALABAMA. 



it is rarely of the same quality from bottom to top at any- 

 place. Usually the members near the base of a lime forma- 

 tion are the best, yet to this rule there are many exceptions. 

 Much of this formation is profusely mixed with matter ot 

 Coralline origin. This contains too much silica ; and is there- 

 fore unfit for making lime, or for flux. Those coralline por- 

 tions are usually in the upper half of the formation. Some- 

 times they are wholly wanting, and the entire ledge .is good 

 limestone. In general, these coral formations are not scat- 

 tered promiscuously through the rocks, but lie mainly in 

 horizontal belts ; often beginning at a line, or terminating at 

 a line, with pure limestone below or above. Many of the 

 organic remains in this rock are of indistinguishable form, 

 probably sponge-like or gelatinous bodies, whose substance 

 has been replaced by silica. Many, however, are beautiful 

 and well defined corals ; among them were formed chain coral, 

 ^Lithostrotion Canadenes, Lithostrotion basaltiforme^ Cyatho- 

 phyllum, <&c. Great numbers of Encrinites and some char- 

 acteristic mollusks, Productus, Spirifers and Terebratula 

 .being prominent. 



b. Oxmoor Sandstone (Lagranye Sandstone). The next 

 formation below* the Carboniferous limestone is known, in 

 this State at least, by the name of the Lagrange or Oxmoor 

 Sandstone. It consists of a heavy ledge of sand rock, from 

 80 to 100 feet thick. It is prominent all along the Sand 

 Valley, forming generally a ridge of soft sandstone, some- 

 times rising into bold mural bluffs the whole thickness of 

 the rock. It is also very prominent at many places on the 

 south-east side, sometimes forming prominent ridges, though 

 nowhere presenting mural faces and bluffs, as it does on the 

 north-west side. The rock is properly a freestone, easily 

 crumbled into sand. The great quantity of it that has dis- 



*The Oxmoor Sandstone is one of the members of the Mountain Lime- 

 stone group, and in many places ha^ the limestone both above 'and below it. 

 The Mountain Limestone, as a group, appears to he the equivalent of the 

 Chester group of the Western geologists. E. A. S. 



