PENNSYLVANIA AND DEPOSITS THEREIN. 59 



(connecting the preglacial Allegheny and Tionesta) ; at Foster (con- 

 necting East Sandy and West Sandy creeks — ^branches of the Tio- 

 nesta) ; at Emlenton (connecting the Tionesta and Clarion basins). 

 The cutting of these to present stream level formed the modern 

 Allegheny River. 



An ephemeral connection between the preglacial Allegheny and 

 Tionesta, and which has resulted in the piracy, by the latter, of the 

 headwaters of the preglacial Conewango, occurred during the ap- 

 proach of the glacial margin towards Clarendon, when there was a 

 discharge of the Conewango ponding over the Barnes col and trench 

 into the Tionesta. There was also a trenched col at Titusville ; but 

 it had little or no influence in the formation of the gravels to be con- 

 sidered. Its elevation was i,6io.^ 



The following passes and cols enter more or less into the history 

 of the ponding :^ 



A. On the Potter-McKean County Plateau. Discharges from Big 

 Bend Ponding : 



Keating Summit. Trench used by the Iroquois as a portage between the 

 Allegheny and Sinnemahoning basins. Plateau top 2,400 feet ; trench 

 bottom 1,878 feet. Immediately east of the McKean County line. 



Clermont. Broad shallow pass. Floor 2,068 feet. Allegheny discharge 

 from Potato Creek through Mill Brook into East Branch of Clarion 

 River. 



Glad Run. Shallow pass. Floor below 2,100 feet. Into West Branch of 

 Clarion River. 



Kane. Forked pass, broad and shallow. The eastern fork into West 

 Branch of Clarion River : the western, into the headwaters of the pre- 

 glacial Conewango Creek; now, of the Tionesta. Floor 2,025 feet. 



B. On the Allegheny-Tionesta Watershed. Discharges from Cone- 

 wango Ponding : 



Barnes. Trench. Top 1,500; bottom 1,300; filled with 2 terraces of 

 gravel for 60 feet. Preglacial outlet into Tionesta River. Present out- 

 let of preglacial branches of Conewango Creek, dammed by moraine at 

 Clarendon, and now headwaters of Tionesta River. 



Thompson. Trench. Elevation considered below. Outlet into Tionesta 

 River after the arrival of the glacial margin at Clarendon. 



C. On the Allegheny-preglacial Upper Oil Creek Watershed. Dis- 

 charge from Conewango Ponding into Titusville Ponding. No 

 cutting or trenching : 



