90 



J. D. Dana oti the origin of some of the 



The Beaver Pond Meadows and the valley of Pine-Marsh Creek are natural 

 levels, the former over a mile long, the latter three-fourths of a mile, each con- 

 taining a range of nearly still water along the bottom through this distance; and 

 hence the height of the terraces on either side is ascertained with great facility. 

 It has already been stated that in the latter this water level is determined by the 

 Whitneyville dam, so that the height of the dam gives, after an allowance for the 

 back-water rise, the height of the water above mean-tide level, even for that of 

 the upper part of the valley west of Mill Rock. The edge of the dam over which 

 the water falls is 34 feet 8 inches above the base of the dam, according to Mr. 

 Eli Whitney ; and the surface of the water a few yards back is 4 inches hig-her, 

 making in all 35 feet for the whole height of the fall. The base of the dam is 

 very near mean-tide level. The back water above the dam extends about 2^ 

 miles, to within 300 feet of the dam at Augerville ; the inciease in the height of 

 the surface along this distance has been estimated to be about 6 inches a mile ; 

 or 15 inches for the whole distance, and 8^ inches to the mouth of Pine-Marsh 

 Creek. 



The elevation above mean-tide level of the water-surface in the Beaver Pond 

 Meadows near its outlet, is taken at 22 feet, in accordance with information re- 

 ceived from Mr. Eli W. Blake as to the heights of the dams between the Beaver 

 Pond meadows and West River. A few hundred feet above the outlet of the 

 Beaver Pond basin, the meadows commence a rising grade northward, as is obvi- 



