100 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



In the western part of the county, beyond the Allegheny river, one 

 reaches the western limit of the Johnstown cement, which is absent at the 

 north though present at the southwest in unimportant development. Of 

 the other limestones, the Upper Freeport and Vanport are persistent, but 

 the Lower Freeport is very irregular. The Freeport sandstone is con- 

 spicuous and at times, as in a portion of Jefferson county, sandstone fills 

 practically the. whole interval from the Vanport to the Homewood sand- 

 stone. The coal beds are unimportant, though the Upper Freeport is 

 good at the north, and in many places the Upper Kittanning shows its 

 tendency to accumulate cannel slate on top. Two measurements, one at 

 the north, the other at the south, show the relations of beds on this west- 

 ern side: 



Feet. Feet. Inches Feet. Feet. Inches 



Upper Freeport 7 2 6 



Interval 60 54 



Lower Freeport 4tol 6 1 



Interval Go 35 



Upper Kittanning 12 to 10 1 



Interval 45 -\ 



Middle Kittanning 4 1 117 



Interval 35 to 40 OJ 



Lower Kittanning 3 6 3 to 4 



Interval '. 33 6 25 



Vanport limestone 15 Thin 



Interval 30 25 



Clarion 2 to 3 2 6 



Interval 22 to 32 



Brookville Thin 



But the interval from the Upper Freeport to the Lower Kittanning is 

 practically the same in both sections.* 



Butler county, south from Venango, west from Armstrong, is east from 

 Mercer, Lawrence, and Beaver. 



The Vanport limestone is present throughout except in small patches 

 at the northwest. The Lower Kittanning, hitherto the most persistent 

 of the coal beds, is somewhat uncertain on the northern border and seems 

 to be wanting in considerable areas within the central part of the county. 

 The interval to the Vanport varies from 10 to 45 feet, the least thickness 

 being on the Lawrence border at, say, 10 miles south from the Venango 

 line; thence it increases eastwardly to 15, 20, 30, and 45 feet within 10 

 miles, and similar increase appears southwardly. The Middle Kittan- 

 ning is persistent, and in the absence of the Lower Kittanning might be 



* W. G. Piatt: Armstrong (H 5), pp. 6, 9, 16, 67, 02. 100, 105, 100. 115, 122, 143, 

 147, 153, 165, 177, 101, 215, 222, 224, 267, 271, 288. 



