460 STEVENSON— THE FORMATION OF COAL BEDS, t^^ov. i. 



the outcrop farther south. But where the horizon is exposed on the 

 eastern outcrop near the Alabama hne, and thence northward for 

 miles the rock is pebbly with layers of conglomerate : while farther 

 north, for an equally long distance, the rock is sandstone, rarely 

 containing conglomerate layers but not un frequently layers of shale. 

 It must be noted that spaces in which conglomerate features prevail 

 throughout the mass appear, from the descriptions, to be narrow and 

 that bands of conglomerate pass out from them into the sandstone 

 on both sides. At times the conglomerate is as a lentil in the sand- 

 stone. The features are the same in the southeastern basins of Ala- 

 bama, for there the conglomerate shows vertical as well as horizontal 

 passage into finer material. 



The other great sandstones of the New River show similar varia- 

 tions, but conditions in successive beds are rarely the same in any 

 locality. The Etna sandstone, below the Bonair, can be recognized 

 in an almost equally great area ; it varies in texture as does the upper 

 sandstone ; but it is often comparatively fine-grained and without 

 pebbles where the Bonair is very coarse, and very coarse where the 

 Bonair is not coarse. The sandstones were formed after the same 

 manner, though the local conditions varied. 



The Homewood sandstone of L C. White is the closing deposit 

 of the Pottsville, apparently the first bed to cover the whole extent 

 of AUeghania. It was recognized in the anthracite fields by its 

 lithological character and the identification was made complete by 

 D. White's study of the plants, which proves that it underlies the 

 first beds carrying an Allegheny flora. It can be followed in the 

 bituminous region from northwestern Pennsylvania into northern 

 Tennessee, beyond which to central Alabama it has been removed 

 by erosion. Its equivalent in Alabama has not been determined. 



The Homewood is, for the most part, a coarse conglomerate in 

 the southern and middle anthracite fields, becoming less coarse in the 

 latter, but even there containing pebbles up to the size of a hen's 

 egg. The coarseness decreases in the northern field and at the east- 

 erly end the deposit is a sandstone with layers of " pea conglomerate." 

 The small Broad Top area, which may be regarded as on the line 

 of strike with the northern field, shows only a moderately coarse 

 sandstone with occasional pebbles, rarely one half inch in diameter. 



