248 GLACIAL GRAVELS OP MAINE. 



lacustrine, or marine action. No way remains for accounting for these 

 plains except dy the action of glacial streams confined between ice walls. 



ALBANY-SACO RIVER SERIES. 



Measured by the amount of assorted matter which it contains, this 

 is one of the greatest gravel series or systems in the State. 



The northern connections are obscure, and involve one of the most 

 difficult questions relating to the diift of Maine, i. e., the determination 

 of the true history of the sedimentary drift of the Androscoggin Valley 

 from Bethel westward to the White Mountains. The pebbles, cobbles, and 

 bowlderets of the central parts of this sedimentary drift of the Andros- 

 coggin are as well rounded as those in the kame plains, and usually more 

 so than those in the beds of the White Mountain streams having a fall 

 of 100 feet or more per mile. In places the alluvium of the main valley 

 rises considerably above that of the lateral valleys. In a word, most of 

 this drift presents all the external characters of the broad osar or plain. 

 Also in some places reticulated ridges are common, and there are many 

 kettleholes and some lakelets in the plain, thereby presenting the features 

 of the plains of reticulated kames. At Bethel the character of the alluvium 

 of the valley rapidly changes. Instead of the terraced plains of coarse 

 matter, which are found from Grorham, New Hampshire, to Bethel, the 

 drift of the valley from the last-named place eastward becomes finer, and 

 consists almost wholly of clay and sand, except where the osar-plains 

 crossed the valley, as at Rumford Point and in part of the valley from 

 the Swift River to Canton. My explorations of this portion of the Andros- 

 coggin Valley were made before I had fully distinguished the osar-plain, 

 and I was then chiefly occupied in studying the Avork done by the local 

 glacier which, for a time after the general ice movement ceased, filled the 

 valley as far east as West Bethel. I do not therefore assert positively 

 that the plain of coarse alluvium that extends from the White Mountains 

 east to a point about a half mile west of Bethel Village is cliiefly glacial 

 gravel, but all my later studies point to that conclusion. The relation of 

 the earlier osar or osar-plain, if it existed, to the local glacier, will form 

 an interesting subject for study, as will also the distinguishing of an osar- 

 plain proper from frontal gravels deposited while the ice was retreating 

 up the valley. The probable course of this glacial stream w^as down the 



