Beaver County, Pennsylvania. 15 



eastwaruly at the rate of little more than twenty-five feet 

 per mile. 



•The section as obtained along this line is as follows : 



21. Sandstone, "Mahoning" 30-75 feet. 



20. Shale 0-8 " 



19. Coal, " Upper Freeport " 2-4 " 



18. Fireclay.. 3-4 " "j Interval 



17. Limestone "Freeport" 2J-4 " j. 25-68 



16. Shale and Sandstone 20-60 " j feet. 



15. Coal U-lj " 



14. Shale 15-20 " 



13. Coal, " Lower Freeport " li-4 " 



12. Shale and Sandstone 25-30 •< 



11. Coal, " Kittanning " 2-3 " 



10. Shale 25-30 " 1 



9. Shale 15-25 " | Interval 



8. Limestone, " Ferriferous " 1-8 " K 53-79 



7. Shale 8-10 " feet. 



6. Sandstone 4-6 " 



5. Coal, "Clarion" IJ-lj ' 



4. Sandstone and shale 20-25 ' 



3. Coal, 1 ' Brookville" 6in-2 < 



2. Shale 15-20 < 



1. Sandstone, "Tionesta" 60-70 ' 



The Mahoning Sandstone is usually a massive rock, and is 

 seen capping the hills in the vicinity of New Brighton, 

 where it rests directly upon the Upper Freeport coal. The 

 decomposing pyrites of the coal, acting upon the base of 

 this stratum, forms alum, so that in some portions of the 

 county the mass is known as the "Alum Rocks." This 

 sandstone shows the fantastic forms of weathering so charac- 

 teristic of it. It presents marked irregularities in thickness, 

 and its composition is not persistent. At some localities it 

 occurs in sandstone bluffs seventy-five feet high, while in 

 others it is simply a mass of shale. 



The Upper Freeport Goal, owing to its impurity, as well 

 as to its abrupt variations in thickness, is of little impor- 

 tance. It contains a very large proportion of pyrites, and 

 within a few hundred feet will vary from one to three feet in 

 thickness. It is occasionally mined for domestic use by 

 those living on the hills near its outcrop, and it is the source 



