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miiteriiil to assume the maximum angle of stability. In a 

 similar manner, isolated masses of ice gave rise to the kettles 

 and larger depressions or basins of the plains ; and the valleys 

 occupied by the modern drainage, although, doubtless, the 

 product, in part, of erosion, especially of erosion during the 

 formation of the lower plains, were probably outlined, at least 

 in their wider parts, by stationary masses of ice, and since such 

 remnants of the ice-sheet would naturally linger longest in tiie 

 valleys, we have here a cause determining an approximate 

 coincidence of the ancient and modern — the preglacial and 

 postglacial — drainage lines. 



Extending south from the railroad along the boundary 

 between Hingham and Cohasset, and forming the water- 

 parting between Weir River and Bound Brook, is a broad 

 and nearly continuous remnant of the ancient peneplain, bearing- 

 several accumulations of till, among which the Turkey Hills 

 and Prospect Hill are most prominent. South of Prospect Hill 

 and Accord Pond this high land separates the basins of Weir 

 lliver and Bound Brook from the much larger basin of North 

 River. This broad divide is diversified in its eastern half by 

 several large drumlins — Mt. Blue, Black Pond Hill, Otis Hill, 

 Simons Hill, etc. — and many smaller ones, and a remarkable 

 series of elevated swamps ; but west of the meridian of Prospect 

 Hill the surface deposits are almost wholly modified drift; 

 and southwest of Union Street in Hingham there is no pass out 

 of the Weir River basin below the 120 feet contour-line. 



When, during the retreat of the ice-sheet, its front rested 

 against the high land to the eastward, the water from the 

 ablation of a larixe area of ice must have flowed across the 

 divide west of Prospect Hill, forming the broadly extended 

 sand[)lains which enclose Accord Pond (Accord Plain), with a 

 height of from 160 to 180 feet, and slope gently southward for 

 several miles ; and when the ice-front had finally withdrawn 

 from the summit of this divide, the northward drainage was 

 obstructed bv tiie ice itself and the lake formed in which were 



