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



Venango, it is coarse to somewhat pebbly sandstone at some locali- 

 ties but shaly at others ; there, as in northern Butler, it varies from 

 15 to 80 feet, always at expense of underlying beds. In Mercer it 

 is from 70 to 30 feet, being thickest at the north where it varies 

 from good building stone to pebbly rock, while farther south in 

 Lawrence the horizon is marked by shale to coarse pebbly rock, but 

 in most of the county it seems to be represented by fine material. 

 This is within the drift covered area and the exposures are not suffi- 

 cient for determining the relations of the pebbly areas.*^ 



The change beginning in western Pennsylvania becomes very 

 marked in Ohio. Along the northern and western outcrop the deposit 

 is wdiolly indefinite, being mostly shale, sandy to argillaceous, with 

 occasionally some shaly sandstone. So great is the contrast between 

 these and the eastern conditions, that for a generation the relations 

 between the Ohio and the Pennsylvania Pleasures were ground for 

 very serious dispute. The Homewood is nowhere in Ohio an impor- 

 tant member of the section. In Kentucky the interval is filled with 

 characterless shale and sandstone. In northern Tennessee, the sec- 

 tion extends to and above the Homewood horizon and without doubt 

 one of the important sandstones is equivalent to the Homewood. On 

 the eastern side in Virginia and West Virginia, the horizon is distinct, 

 though at some localities, north from New River in the latter state, 

 one cannot difi^erentiate the Homewood from underlying beds. But 

 the rock underlying the Allegheny flora is usually a well-marked 

 sandstone for at least 40 miles north from that river ; there, how- 

 ever, the outcrop turns toward the east and the rock becomes pebbly. 

 In Tucker county, the last eastward exposure shows 55 feet of rock, 

 the lower portion for 40 feet being massive conglomerate. West- 

 wardly from the outcrop, the rock rapidly becomes less coarse and. 

 within a score of miles, it is shaly sandstone or shale. 



The Homewood is buried deeply in the greater part of West 

 Virginia, north from the Kanawha River, as well as in eastern Ohio 



" The observations by F. Piatt. W. G. Piatt. I. C. White, H. M. Chance. 

 E. V. d'Invilliers and Stevenson are recorded in " Carboniferous of the 

 Appalachian Basin," as above, pp. 42-70. The reader will find an admirable 

 summary of earlier observations by H. D. Rogers, J. D. Whelpley, R. M. S. 

 Jacksdn, P. W. Shaeffer and J. P. Lesley in H. D. Rogers's "The Geology of 

 Pennsylvania," 1858, Vol. IL, pp. 21-26. 



