' THE TUSCUMBIA 91 



long on a low shore. They can hardly have come from the north, for 

 there the upper Logan, Reid's Olive shales, is very fine in grain, while 

 farther south it becomes coarse as it is in northwest Pennsylvania, east 

 from Reid's localities. It is equally improbable that the pebbles came 

 from the east, for the deposits become finer eastward toward the central 

 line of the basin, beyond which they become coarser. The sands must 

 have come from the western side. 



THE TUSCUMBIA 



The Tuscumbia is represented in the northern portion of the basin 

 by shale and the overlying silicious limestone. 



The limestone is present, though indefinite, within the anthracite 

 fields and is distinct in the Broad Top and Fulton County outliers. 

 According to Mr Meyer, quoted by Professor Lesley, it is present in the 

 Allegheny area as far north as Lycoming county ; only a trace remains 

 in Clinton, the next west, and there appears to be none in Center, south 

 from Lycoming. The boundary passes westwardly from Blair across 

 Indiana into Allegheny; thence across northern Washington into West 

 Virginia ; crosses the Ohio river below Wheeling into Ohio ; reenters 

 West Virginia near Saint Mary's and passes a little way east from Parkers- 

 burg; there bending, it crosses southeast Ohio to the Ohio river and 

 enters Kentucky just beyond the western border of Greenup county and 

 continues thence irregularly southwestwardly until it curves around the 

 Cincinnati peninsula. East and southeast from this irregular line, which 

 is very nearly the original shoreline, it is persistent in the main area as 

 well as in outlying areas, except those of Montgomery county, Virginia, 

 though very attenuated in those of Pulaski and Wythe in the same state. 



It is difficult to determine, by means of available observations, 

 whether or not the Fort Payne of the extreme southeasterly areas 

 embraces any Tuscumbia. For the most part the features are those of 

 the Lauderdale (Logan), there being an almost total absence of lime- 

 stone in the upper part; but in Calhoun county of Alabama, very near 

 the extreme southeast exposure, one finds the Tuscumbia clearly 

 present. One may conjecture that as the Lauderdale is practically 

 without limestone nearer the shoreline the Tuscumbia would undergo 

 the same change, so that the thin Fort Payne on the border would rep- 

 resent both. This is in accordance with the conditions in this region, 

 as each of the Mississippian formations apparently overlaps its prede- 

 cessor; but for the present the question must remain unanswered. 



The Tuscumbia limestone is absent from the whole of northwestern 

 Pennsylvania, about 15,000 square miles ; from almost the whole of 

 eastern Ohio, and is very irregular in distribution within eastern Ken- 



