DETAILED DESCRIPTION OF THE 



339 



ONE AND THREE-FIFTHS MILES ABOVE SAFE HARBOR, PENNSYLVANIA 



This lies near the east or left bank of the river opposite the Chanceford 

 bottoms. The water surface is about 177 feet above tide and the rock 

 bottom of the gorge between 180 and 170 feet above tide. The "deep" is 

 a narrow depression, 3,200 feet long and 150 feet wide at its deepest point, 

 which is 60 feet below the level of the rock bottom. The depression 

 widens upstream to 400 feet and extends as a shallow trench for an addi- 

 tional 1,700 feet. 



The rocks exposed on the banks are micaceous and chloritic schists and 

 gneisses in which the schistosity strikes north 70° east and dips about 

 20° upstream. They show jio diJTcrcnicos in resistance competei)t to 

 localize a strong waterfall. 



Grade 



of rockfhoroiyollf.^. 



"y'lGURE 3. — Profile of "Deep" above Dam at McCalls Ferry, Pennsylvania 

 Scale : Horizontal, 1 inch = 2,000 feet ; vertical, 1 inch = 500 feet 



The profile across stream, shows (figure 2) a steep gorgelike depression 

 incised in the U-shaped valley of the river. The longitudinal profile is 

 a gentle catenary curve, slightly steeper downstream. 



"DEEP" AT MC CALLS FERRY 



This '^deep" lies just above Fry Island, the site of the dam, and ex- 

 tends upstream for a distance of nearly 2 miles. ' The water surface was 

 originally 125 feet above tide and the rock floor along its edges about 

 115 feet. The bottom of the larger hole lies at 15 feet below sealevel, or 

 at a depth of 125 feet below the rock rim of the depression. The details 

 of the shape and profile of this hole are lacking (through loss of records) 



