1879.] -"JJ [Stevenson. 



Some of the low gaps, which extend to but a short distance below the 

 summit are beautifully terraced. The benches in Wymp's gap, exposed 

 by removal of the timber, are distinct to one standing even on the opposite 

 side of George's Creek Valley. The gorges made by the larger streams are 

 usually so narrow and have so abrupt walls that no benches remain, and it is 

 doubtful if benches could have existed in any but very few of them. For 

 this reason no benches below the eighth have been fully recognized along 

 the greater part of this face, south from the Youghiogheny river. 



Benches along the Youghiogheny River. 



The river " bottom" at M'Keesport is at 765 feet above tide. Thence it 

 is continuous to Connellsville, at the mouth of the Chestnut Ridge gap, 

 where it is 894 feet above tide. 



At Perryopolis, just south from the river, a fine bench is shown covered 

 by sand, which contains many enormous bowlders, all of which have been 

 brought down from the mountain gaps. 



Possum run enters the river almost opposite Connellsville. On the road 

 leading along this run from that borough to Brownsville, a bench, reached 

 at the first summit, barely 200 feet above the river, is the highest limit of 

 transported fragments. All of the bowlders are of huge size and many of 

 them weigh not less than a ton. They have polished surfaces and are so 

 numerous that the farmers use them in building fences. This bench is the 

 same with that seen at Perryopolis. 



This bench is persistent along the river above Connellsville, but it can be 

 followed only with difficulty as slides in the gaps have masked it at several 

 localities. It is very nearly 200 feet above the river at Connellsville, but 

 thence it rises less rapidly than the river bed, so that at Ohiopyle Falls it 

 is not quite 140 feet above the stream. While flowing on this bench as its 

 bed, the river ran directly across the neck of the peninsula at Ohiopyle 

 Falls, and the gorge through which the stream now flows has been eroded 

 since the bed fell below that bench. 



At Confluence, immediately above the east end of the gap through Laurel 

 Ridge, the river "bottom," which is only 765 feet at M'Keesport, is 1346 

 feet above tide or 581 feet higher than the same bench at the mouth of the 

 river. A very fine bench was seen southwest from Confluence at 1820 feet 

 above tide. The persistent bench to which reference has been made, is 

 still seen along the river, but is much nearer the stream than it is at Ohio- 

 pyle. Riding up Castleman's river, which unites here with the Youghio- 

 gheny, one soon rises above this bench or rather finds the river bottom 

 merged into it. 



Benches in Westmoreland County West from Chestnut Ridge. 

 Few available measurements were obtained in this part of Westmoreland 

 count} 7 . The survey was made during the autumn of 1876, a season 

 strangely marked by violent fluctuations of the barometer ; but no measure- 

 ments have been accepted as trustworthy except such as were verified by 

 direct comparison with a spirit-leveled line as a base. 



