92 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



differs from that employed by Mr Piatt. At the time his work was done 

 the succession of the Allegheny coal beds had not been determined and 

 the nomenclature had not been fixed. The terms employed by him should 

 be corrected as follows to agree with Professor Lesley's classification pub- 

 lished in the Armstrong report in 1880 : 



Upper Kittanning limestone. Johnstown cement. 



Lower Kittanning. Middle Kittanning. 



Clarion coal bed. Lower Kittanning. 



Stevenson gives a section on the east side of the basin showing 160 feet 

 of conglomerate, beginning at 120 feet below the Upper Freeport, and 

 identifies the coal resting upon it with the Brookville. But this was an 

 error, for there one has merely an enormous expansion of the sandstones at 

 the bottom of the Allegheny, making them continuous with the Pottsville, 

 as in many extensive areas within western Pennsylvania and West Vir- 

 ginia. The interval between the Freeport coals is as variable as in In- 

 diana; at 10 miles south from the Conemaugh, on the east side of the 

 basin, those coals are 92 feet apart, with all members of the section 

 present down to the Johnstown cement; but within a few miles this in- 

 terval decreases to 39 feet in a section showing all three of the limestones. 

 The general succession in Westmoreland and Fayette is shown by a sec- 

 tion in each county, thus: 



Feet. Inches. Feet. Inches 



1. Upper Freeport coal bed 4 3 



2. Interval 62 44 



3. Lower Freeport coal bed 6 6 



4. Interval 18 30 



5. Upper Kittanning coal bed and 



shale 6 7 4 to 7 



6. Interval 47 7 \ 



7. Middle Kittanning coal bed 3 to 4 C 118 



8. Interval 51 6 ) 



9. Lower Kittanning coal bed 5 Blossom 



10. Interval 75 60 



11. Brookville coal bed 2 2 to 3 



12. Shale and clay 25 10 



to the Pottsville. The Clarion coal bed evidently disappears in southern 

 Indiana, as no trace of it was seen in any Westmoreland section, though in 

 some cases the exposure below the Lower Kittanning (Clarion of Steven- 

 son) is complete. The Brookville is persistent to the Maryland-West 

 Virginia border, often attaining a considerable thickness and yielding 

 good coal, though ordinarily so badly broken by clay beds as to be un- 

 available. The Lower Kittanning is persistent, but is seldom workable, 



