392 POPULAR SCIENCE MONTHLY 



conclusion that the phenomena are the result of a double period of 

 ice erosion." 



Of these facts the most important was the discovery of a series of 

 buried gorges on the steepened slope in close association with the post- 

 glacial gorges or glens. In some cases the present stream has re- 

 occupied these older gorges; in others it crosses them or follows them 

 for only short distances. They are both broader and deeper than the 

 postglacial gorges, and therefore required a longer period for their 

 formation than has elapsed since the last ice recession. Being occupied 

 by drift deposits of the last, or Wisconsin, ice advance, these gorges 

 were evidently formed before the oncoming of this ice invasion. At 

 first it was uncertain whether these gorges were of interglacial or pre- 

 glacial age, though the former was strongly suspected. 



A definite step toward the solution of the problem was made when it 

 was discovered that in the Seneca Lake valley these older gorges do 

 not extend below lake level. This is proved with especial definiteness 

 on the western side of the Seneca valley, where for many miles there 

 is a continuous rock outcrop along the shore just above lake level, and 

 extending continuously across areas down which the older gorges must 

 have passed. Watkins Glen illustrates this. The older, buried gorge 

 leaves the Glen Creek valley just above the head of the postglacial glen 

 a hundred yards or more above the point where the bridge of the 

 Pennsylvania Division of the New York Central Railroad crosses the 

 glen. It passes under the railway station and down the steepened 

 main-valley slope under the sanitarium, its position there being in- 

 dicated by a moderate sag in the hillslope, and, still better, by well 

 borings at the sanitarium. Two wells, one at the sanitarium, the other 

 a short distance west of it, fail to reach rock at 10.5 and 175 feet, re- 

 spectively; but to both the north and the south of these wells rock is 

 reached at depths of ten to twenty feet, proving the presence of a 

 buried gorge. Below the sanitarium, along the line of this buried 

 gorge, continuous rock outcrojDS occur, proving that the gorge is not 

 continued there. 



These facts prove that the buried gorges are also hanging, at 

 Watkins fully 1.100 feet above the rock floor of the main valley. 7 The 

 interpretation placed upon these facts is as follows : Before the glacial 

 period there was a system of mature drainage, with main valleys along 

 tin 1 axes of Seneca and Cayuga Lakes, and with tributaries entering 

 them at grade at the level of the mouths of the hanging valleys, that is, 

 at elevations of about 000 feet above present sea-level. The advent of 



6 Tarr, Jour. Geol., Vol. XIV., 1906, pp. 18-21. 



'A deep well at Watkins. 1.0S0 feet in depth, did not reach the rock bottom 

 of the valley, striking the side of a cliff and bending the tool so that further 

 boring was impossible. 



