I9I2.] STEVENSON— THE FORMATION OF COAL BEDS. 463 



and southwestern Pennsylvania. For that area one can depend only 

 on the series of oil-well records, chiefly those collected and collated 

 by I. C. White. Where exposed along the eastern and southern 

 border in West Virginia, the horizon is marked usually by a sand- 

 stone, seldom very coarse and sometimes shaly. In the interior or 

 deep part of the basin, where the coal beds are indefinite, it is not 

 always easy to carry the section, though the drillers find no difficulty 

 in identifying the horizon. At the north, in the " Panhandle," the 

 Homewood seems to be represented in most cases by shale, sandstone 

 occurring, for the most part, as filling valleys. So also in Washing- 

 ton of Pennsylvania and Wetzel of West Virginia the interval is 

 frequently filled with shale. The horizon is indefinite throughout ; 

 in many records it is marked by sandstone, in many others by shale. 

 There is no room for doubt that, in considerable spaces, sandy shale 

 was consolidated into sandstone ; but careful tabulation has con- 

 vinced the writer that, in not a few of the long lines of records 

 reporting sandstone, one has merely the records of subaerial valleys 

 eroded not long before or after the close of the Beaver. 



The Homewood material came from all sides of the basin. On 

 the eastern side, the quartz pebbles from the old Appalachian land 

 decrease rapidly in size westward ; the strip of coarse rock in Center 

 and Clearfield counties of Pennsylvania with possibly related patches 

 in Jefiferson and Elk counties as well as a similar strip near the 

 northern outcrop may be records of valleys heading east from the 

 present Allegheny front. The materials at the west came clearly 

 from the low slopes of Cincinnatia and from the north. The very 

 marked variations in thickness, always at the expense of underlying 

 beds, leads one to suppose that the irregular crustal movements, so 

 characteristic of the Allegheny, had already begun. 



The Allegheny was a time of great irregularity of deposition, 

 there being abundant evidence of subaerial erosion at many places 

 and at dififerent horizons; and the old valleys have been filled, in 

 most instances, with more or less pebbly sandstone. At the south- 

 east the formation is marked by coarse massive sandstones extending 

 into the Conemaugh, which cross West \"irginia in southwest direc- 

 tion ; but they lose their coarseness quickly toward the northwest. 

 The sandstones of this formation as well as those of the Conemaugh 



