PENNSYLVANIA AND DEPOSITS THEREIN. 



73 



The torrential fall over Big Bend Col speedily tore a canyon 

 through the stagnant ice in the Conewango Valley as directly as pos- 

 sible to the Thompson outlet : removed the deposit of Conezvango 

 Clay, Upper and Lower Indian Hollozv Sands, and Clarendon Grav- 

 els from Glade to the mouth of Dutchman's Run (in the old Cone- 

 wango channel), and the scour operated so far up the valley of the 

 Run that it gave quickness to the sands in the formation at Stone- 

 ham, causing them to run out and the Clarendon Gravels there to 

 drop on top of the Conezvango Clay. Williams has shown^ that the 

 loss of the loo feet of Indian Hollozv Sands here, and so near the 

 apex of the gravels at Clarendon, at 1,513.32, permitted a shifting 

 of the latter towards Stoneham, and a dropping from their probable 

 elevation of such a height above the crest of Thompson Col that 

 they prevented a return to the Barnes discharge until the former col 

 was trenched below 1,500. 



In addition to opening a canyon through the stagnant ice in the 

 Conewango Valley, the Big Bend torrent cut off 1,000 feet of the 

 west end of the ridge between Morrison and Ott runs, and 1,500 

 feet to half a mile from the one between the latter and the old chan- 

 nel of Brokenstraw Creek, where it turned north to join the Cone- 



FiG. 12. Early Big Bend gravels, Oakland bar, South Warren. 



