BEIDGTON-BALDWIISr SEEIES. , 247 



of Beech Hill, Sebago. The gravel soon becomes discontinuous, and at 

 the top of the col I could not discover any gravel. The gravels before 

 described as the Sebago series begin a short distance south of this point. 

 These facts make it probable that a glacial stream overflowed from Great 

 Hancock Pond over the divide and down the valley of Northwest River to 

 East Sebago. 



Another delta branch diverged from the main series at the point where 

 it crosses Breakneck Brook and followed the valley of that stream soath- 

 westward. Originally a plain of coarse gravel, cobbles, and bowlderets 

 extended across the narrow valley to a height of 20 to 40 feet above the 

 present level of the brook. This plain has been much eroded along the 

 central part of the valley, so that now small lateral terraces along the sides 

 of the valley are all that remain of the original plain. By aneroid this 

 brook falls 200 feet in flowing from where it leaves the main osar-plain to 

 West Baldwin, a distance of about 3 miles. With such a rapid fall it is 

 not surprising that only coarse sediment was dropped in the valley. At 

 West Baldwin this series becomes confluent with the great plains of the 

 Saco Valley. 



The history of the osar-plain in Breakneck Valley appears to be about 

 as follows: At first the Bridgton glacial river flowed across the valley, then 

 up and over the hill 210 feet high to East Baldwin. This becomes evident 

 when we consider that if the channel had first been opened southwest on a 

 down slope of 60 feet per mile it is extremely improbable that the water 

 could subsequently have been diverted over a hill 210 feet high. The 

 stream to East Baldwin has deposited miich more sediment at its terminal 

 plains than the other stream to West Baldwin, and if the former stream was 

 not the earlier, no reason can be assigned why the larger flow should take 

 place along its course. After the channel was opened southwest down the 

 Breakneck Valley the water would all flow that way, unless in time of 

 extraordinary flood. 



Few if any students of the drift can see the great contrast in compo- 

 sition between the broad osar of the Bridgton-Baldwin series and the 

 adjacent till, or see it rejecting valleys of natural drainage in order to go 

 up and over hills more than 200 feet higher than the ground to the north, 

 without admitting the utter impossibility of accounting for such plains of 

 sand and gravel in such situations by any freak of eolian, fluviatile, 



