DETAILED DESCRIPTION OF THE '^DEEFS" 341 



MINGUA OR HOLT WOOD 



This "deep''' lies close to the left bank of the Susquehanna, between it 

 and Piney Island, and has been utilized by the engineers as a tail race 

 for their power plant. During the construction of the dam it was exposed 

 by a diversion of the w^ater to a depth of nearly 50 feet. The water sur- 

 face was about 110 feet above tide and the rock floor about 100 feet. 

 From the latter rise Fry and Piney islands to a height of 140 and 160 

 feet respectively. The hills above the power plant rise rapidly to an 

 elevation of over 500 feet. This depression is a gorge of 4,000 feet long, 

 with a width of from 200 feet to 300 feet within the rock floor of the 

 river, which at this point is about 100 feet above tide. The general level 



IXa'ATHOLTWOOD. PA. 



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■STAiSI/a. 



Figure 5. — Profiles of "Deeij" at Holtwood, Feiinsi/lraiiia 

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



of the bottom of the gorge is 60 feet above tide, or 40 feet below its rim, 

 and shows three local depressions (figaire 4). That opposite the upper 

 end of Piney Island reaches to 50 feet above tide, while the two at the 

 lower end, opposite Barkley Island, reach 40 feet above tide. The rock 

 barrier between it and the foot of Culleys Falls was removed, so that it is 

 now continuous with the "deep" described later. The withdrawal of the 

 water gave exceptional opportunity for studying the walls. Everywhere 

 were deep vertical pot-holes of varying diameter and perfection, so closely 

 placed that they suggested the fluting of a pipe organ or the fracture of 

 a block by the use of "plug and feathers." Some of the pot-holes extended 



