842 E. IJ. AIATllEWH SUUMERGED ^'DEEPS" IN SUSQUEHANNA RIVER 



below water level, while others showed iiests of boulders part way down 

 the sides of the gorge. The general character is shown in plates 19 

 and 20. 



BELOW CULLEYS FALLS 



Tlie ^'deep" l)elow Cidleys Falls is cut in the level v(\-k bottom of tlio 

 river, which is here 100 feet above sealevel. It is situated close to the 

 left bank of the river, between it and the Bare Islands, which rise 70 feet 

 above the river. It is approximately 7,200 feet long, 250 feet wide, with 

 three depressions — the first 130 feet deep, the second and third 100 feet 

 deep, separated by a 25-foot ridge. The deepest of these holes lies be- 

 tween the shore and Wolf Island, Avhere the east channel is the entire 

 width of the depression. In longitudinal section (figure 5) these "deeps'' 

 show the usual downstream sag in the bottom profile. The rocks are 

 chloritic and mica schists striking north 70° east and dipping southeast. 

 There is no connection apparent between these deeps and Muddy Falls, 

 which empties into the river at this point. 



ABOVE FITES EDDY 



F>etween Sicily Island and the left bank of the river, 1,()0() feet above 

 Files Eddy Station, is a "deep" 3,400 feet long, which shows a well 

 defined terrace 30 feet below the valley floor and 70 feet ahoxc the bottom 

 of the "deeps." The breadth is here less uniform, the chasm varying 

 from 500 to 150 feet from rim to rim. The deepest portion is practically 

 level at an elevation of 10 feet above tide for a distance of 1,000 feet. 

 The rocks are chloritic and micaceous schists with the usual strike and 

 dip. The islands, with levels at an elevation of approximately 100 feet, 

 suggest remnants of the peneplain analogous to the Wicomico terraces in 

 Maryland. 



Origin 



Similarly appearing "deeps" in beds of rivers ha\e been frequently en- 

 countered and described. Their origin has usually been ascribed to some 

 form of "cliif" waterfall, as where the stream flows over the edge of a 

 hard horizontal stratum or down a crevasse in the ice, or over some re- 

 sistant stratum or dike. Apparently none of these explanations fits the 

 present case. The region is south of the former continental ice-sheets, 

 and the cuttings and pot-holes cannot, therefore, be ascribed to the action 

 of subglacial streams and waterfalls. The rocks show practically vertical 

 position and therefore can not have been produced by a fall due to the 



