1895.] NATURAL SCIENCES OF PHILADELPHIA. 205 



moraine at Belvidere, I think offers further proof that the first 

 mentioned portion was cut before the coming of the ice sheet, and the 

 last since the melting of the ice ; for from Port Jervis to the 

 slates the Delaware flows in a deep, ancient river valley or valleys. 

 Its bed, except at a few points where there is a rock bottom for a 

 short distance, is in the glacial drift which still fills the old water 

 course to an unknown depth, even the deepest portion of the Gap 

 itself being so filled, while from the beginning of the slates to 

 Belvidere, the river has a rock bed, its channel is broad, the valley 

 wide, with hills rising only one or two hundred feet above the river. 



Looking southward from the top of Mt. Minsi, on the Pennsylvania 

 side of the southern entrance to the Gap, from a height of 1,100 

 feet, the country has the appearance of a gently sloping plain nearly 

 to Belvidere, 13 miles away. The fall in the river in this distance 

 is 4] feet per mile, while in the unglaciated area between Belvidere 

 and Easton the descent is 61 feet per mile. This fell, with the vast 

 volume of water which must have continually poured through the 

 Gap during the melting of the ice, would certainly, I think, give a 

 torrent of sufficient force to accomplish the work which I have assumed 

 has been done since the melting of the ice sheet. 



If I have proven that the gorge from the Point of Rocks to the 

 northern entrance of the Gap was the work of a north-flowing river, 

 and the gorge from the Point of Rocks to the southern entrance of the 

 Gap is the work of the south-flowing Delaware, it follows that the 

 Delaware Water Gap doe* consist of two river gorges united, eroded 

 from different directions and in different geological epochs. 



