i9'2.J STEVENSON— THE FORMATION OF COAL BEDS. 461 



Some insignificant fragments, containing a score or two of square 

 miles, remain, at the northwest, between the northern field and the 

 bituminous region. In those, the rock is for the most part a massive 

 conglomerate, with occasional fragments as large as a walnut, but 

 there is little of fine material, showing marked selection by the 

 depositing agent. Along the Allegheny front, the Homewood is by 

 no means a coarse rock at the north in Clinton but in Center, the 

 next county south, it has one part exceedingly coarse, with mostly 

 quartz pebbles, at times as large as a hen's egg. In Blair, no pebbles 

 are reported but in Bedford there are some pebbly layers; thence 

 southward to the Potomac, it seems to be merely a massive sand- 

 stone. The only unexpected feature here is the presence of large 

 pebbles in Center county. 



This sandstone is exposed frequently in a strip, 75 miles wide, 

 west from the Allegheny crest. On the northern border in Bradford 

 county, it contains occasional layers of pea conglomerate, but those 

 disappear quickly toward the west so that pebbles are few in the 

 adjoining county. Southward to the Conemaugh River, half way 

 to the southern boundary of the state, there is at most localities only 

 sandstone, sometimes broken by shales ; but in Clearfield county, 

 midway in this strip, and just west from the Center county area, 

 very coarse rock is reported at this horizon, there being layers of 

 conglomerate with quartz pebbles often as large as a hen's egg. 

 The deposit is in an irregular narrow space, extending half way 

 across the county and the coarse material is wanting on the western 

 border. This marks the eroded crest of Alleghania and the Home- 

 wood rests on what seems to be the Logan or lowest deposit of the 

 J\Iississippian. South from the Conemaugh, the Homewood is vari- 

 able ; at one locality it has 70 feet of sandstone while at 4 miles away 

 the interval is filled almost wholly by shale. But for the most part, 

 from the Conemaugh to the Baltimore and Ohio railroad in West 

 Mrginia. the rock is a moderately coarse sandstone with occasional 

 pebbles, seldom larger than a pea. 



Farther west in Pennsylvania, the Homewood is sandstone at 

 all localities along the northern border, varying in thickness from 

 15 to 70 feet at expense of underlying beds. Pebbly layers occur 

 at times but the pebbles are small ; southward, in Clarion and 



