White.] 4 J4 [Oct 21, 



of a few feet for more than one-half mile in the vicinity of Albright's 

 bridge, its rapid dip into the hill preventing systematic mining. 



Just above the bridge, the Homeicood sundstune rises from the bed of the 

 river and makes a bold cliff along its north-eastern bank, revealing under 

 it a small coal bed beneath a few feet of shales. 



On above this to the south-east, the other members of No. XII. come up, 

 and make the steep north -vpest slope of Briery mountain. 



I shall close this paper with a single suggestion in regard to the parallel- 

 ism of the beds along the Cheat river that I have included under the name 

 Mauch Chunk shnle. 



A review of the sections will show that this interval, extending from the 

 base of XII down to the top of the Moimtain LimeHtone, has a thickness of 

 about 300', and can be subdivided into three well marked groups : 1st, at 

 top, a shale interval often containing iron ore and one or more thin red 

 beds, thickness 30' — 50' ; 2d, a series of flaggy, green sandstones, often 

 having a quite massive bed near the top, and sometimes containing calca- 

 reous bands l'-2' thick, thickness 165' ; 3d, a series of red and green 

 shales in which usually occur one or more thin beds of impure limestone, 

 thickness down to the main mass of Mountain Limestone, 80'-100'. 



Those who have read my summary of the Geology of Crawford and 

 Erie counties, Pa., in Report Q*, will recall that I there show the "Cuy- 

 ahoga shale, " of Dr, Newberry to be a very composite series, having a struc- 

 ture somewhat as follows, beginning with the base of XII, and descending 

 to the Berea Grit (Corry sandstone) : 



Shenango shales 35'-50' 



Shenango sandstone 25' 



Meadville Upper shales 20' 



" " Limestone V 



" Lower shales 45'-55' 



Sharpsville Upper sandstone 50' 



Meadville Lower limestone 2' 



Sharpsville Lower sandstone .■ 12' 



Orangeville shales 75' 



Berea Grit — 



Total average thickness about 280' 



The above succession, I have traced southward from Crawford county 

 to the mouth of the Beaver river at the Ohio, more than half way to Cheat 

 river, and in oil borings at Beaver fiills. Smith's ferry and other localities, 

 the series is still 270'-280' thick. 



As is well known, the geologists of the 2d Geological Survey of Penn- 

 sylvania, who have studied the Sub-conglomerate measures in the western 

 counties, have all heretofore placed the dividing line between XI and X, 

 in the Shenango shales, and regarded the massive sandstone below them 

 as the beginning of the Pocono. 



It will be seen at a glance that the "Mauch Chunk shale," interval on 



