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deposited the beds of sand and g-mvel forming Liherty Plain. 

 During the niaxinuun dcveh)pment of this lake the ice-front 

 must have joined the divide near the junction of Union and 

 Pleasant Streets and extended thence southwest and west along 

 the northern edge of Liberty Plain across Main, Gushing, and 

 Wiiiting Streets into Weymouth, as far at least as Old Swamp 

 Kiver, the valley of Avhich may have been occupied by a long 

 lobe of ice. This embaynient of the ice-sheet holding Lil)erty 

 Lake was thus from 3 to 4 miles in length and from 1 to 2 

 miles in breadth ; and the waters probably found an outlet in 

 the direct line of Beechwood Kiver, along the west side of 

 Prospect Plill, through Valley Swamp, and so over the divide 

 into the basin of North Kiver. 



The valleys occupied by Beechwood River, the small streams 

 draining into Fulling Mill and Cushing Ponds, and the branches 

 of Plymoutli Kiver, dividing Liberty Plain or indenting its 

 northern edge, prol)ably correspond in a large degree to irregu- 

 larities of the ice-front ; for where this lobate character of the 

 plain is best developed, the abruptness and steepness of the 

 marginal slopes clearly indicate that they are not the free and 

 natural forms or frontal slopes of deltas, and their relations 

 to the streams and to the internal structure of the [)lain forbid 

 us to regard them as the product of erosion. The hypothesis 

 that these lobes are deltas pure and simple, unmodified by 

 erosion or retaining walls of ice, requires us to postulate 

 streams flowing from the south of improbable magnitude. 

 Breakneck Hill, extending north from Whiting Street between 

 two branches of Plymouth Kiver, is a remarkably perfect lobe 

 of Liberty Plain. It rises abruptly from the bordering streams, 

 and its surface, save where dimpled with kettles, is ap])roxi- 

 mately level for a breadth of 1,000 feet, being much too broad 

 and plateau-like to be classed as a kame. Beyond Whiting- 

 Street, Liberty and Accord Plains, with occasional ledges of 

 granite protruding through them, embrace almost the entire 

 southwest corner of Hingham and the adjacent parts of 



