336 F". REPORT OF PROGRESS. B. W. OLAYPOLE. 



Bridgeport and extending thence to the east and northeast. 

 In various parts of this exposure maybe found all the 

 upper portion of the group including the gray calcareous 

 beds and the variegated shale as well as the red shale pro- 

 per. Bui owing to the irregularity of dip and the flatness 

 of the ground the measurement of its thickness would re- 

 quire much time and care. 



Another shale tract occurs in the south occupying the 

 valley between Blue mountain and Mount Pisgah. It is 

 pair of the Polecat valley, extending from west to east and 

 gradually narrowing towards the Susquehanna where, near 

 Marysville, it is too narrow for profitable cultivation and is 

 consequently still covered with wood. 



The softness of the shales is the geological cause of these 

 valleys. Exposed for ages to the wash of rain and the car- 

 rying agency of streams, their surface has been gradually 

 worn down leaving the somewhat harder portions protrud- 

 ing until the whole now forms a gently undulating surface 

 which is as suitable for farming purposes as any land in 

 the county. The soil, too, is warm and fertile, standing 

 well in comparison with the limestone land adjoining it, 

 which is the strongest and most durable soil. 



The Bridgeport sandstone, (V.) 



s This very singular bed of hard flinty sandstone is found 

 in Spring township. One of its best outcrops is on Sher- 

 man's creek, south of Bridgeport, where it is brought up 

 by the extension of the Welsh mountain anticlinal. Both 

 sides are visible, dipping from the middle line with a gentle 

 slope, and disappearing in a lew yards. It is here about 8 

 Eeel i hick and very hard and solid in the middle, but more 

 soft and shaly toward the top and bottom. It is somewhat 

 thicker in Tyrone township, but nowhere coarser than here. 

 It i^ used as a rough building stone, but like tin 1 Oriskany 

 cannot be dressed with success as it breaks very irregu- 

 larly. 



How far il extends eastward cannot be known. Its eleva- 

 tion con i j'il >i it es to the formation of Quaker hill under which 





