438 STEVENSON— THE FORMATION OF COAL BEDS. [Nov. i, 



the rocks lose coarseness and within 40 miles, according to M. R. 

 Campbell, are no longer hard enough to affect the topography; but 

 in that interval a new sandstone, the Bonair, belonging lower in the 

 column, is reached : fine-grained at first, it soon becomes coarse and 

 within a few miles it is a pebbly rock, massive, 60 to 90 feet thick 

 and containing very little clay. The rate of fall in the original 

 stream cannot be determined as there was differential subsidence, 

 but some conception may be gained from the thickness of deposits. 

 The extreme along deepest part of the valley in northern Ohio is 

 175 feet; in southern Ohio, 310 feet remain and the original thick- 

 ness was not far from 400 feet ; in southern Kentucky, it was more 

 than 1,000 and in central Tennessee not less than 1,500. The de- 

 posits are all of river origin ; there is no trace of marine conditions, 

 except at the extreme south, nor is there any evidence of shore 

 action; the pebbles are round, not flat: proof of selective action by 

 running water abounds along the whole course. One has here 

 merely a subaerial valley, filled with river deposits. The main 

 western drainage line followed the same course until late in the 

 Athens.^^ 



Roy" has published some notes respecting the Sharon coal bed, 

 the first member of the Beaver formation, which show that the clos- 

 ing deposits of the New River had become dry land, exposed to 

 subaerial conditions. In the IMahoning valley that coal bed occupies 

 serpentine, usually narrow troughs, which sometimes unite, but ordi- 

 narily are separated by long intervals of barren ground. The 

 troughs were eroded in the old plain and the separating ridges are 

 merely planed down knolls. In some cases, the troughs were eroded 

 in Waverly rocks, which there are largely Devonian. The lowest 

 coal bed in Jackson county, in the southern part of the state, is 



^^ This summary is based on observations by J. S. Newberry, M. C. Read, 

 A. W. Wheat, E. B. Andrews, A. A. Wright for Ohio; A. R. Crandall, 

 J. Lesley, G. M. Sullivan, W. M. Linney, M. R. Campbell for Kentucky; 

 J. M. Safford, W. Hayes, M. R. Campbell for Tennessee. These are given 

 in "Carboniferous of the Appalachian Basin," Bull. Geol. Soc Amer., Vol. 

 15, 1904, pp. 37-210. 



"A. Roy, "Third Annual Report of the State Mine Inspector," Colum- 

 bus, 1876, pp. 12Q-131. 



