CAI^TON-AUBURN SYSTEM. 209 



southward along- a low pass. They inclose several lakelets, some without 

 visible outlets. Toward the south the ridges coalesce into a level plain, the 

 materials of which become finer, the gravel passing by degrees into fine 

 sand, and this into sedimentary clay about a mile north of the northeast 

 angle of Lake Auburn. This clay extends along the east side of the lake 

 and thence to Auburn and Lewiston, where it is plainly marine. A little 

 silt or clay is found in the valleys of the small brooks which flow into Lake 

 Auburn, which is probably valley or lake drift. With these insignificant 

 exceptions, the only clay found along the shores of the lake is that found 

 along tlie northeastern side, where a plain of fine blue clay rises 30 feet 

 above the lake and apparently forms part of the barrier that holds it back. 

 If Lake Auburn was bare of ice or was occupied by an open arm of the 

 sea at the time this clay was being laid down, the clay ought to have 

 extended farther west, probably all around the lake. The water which 

 poured south from Turner was certainly muddy, as is shown by the great 

 depth of clay at the northeast angle of the lake. This makes it highly 

 probable that the clay was deposited in a broad channel within the ice at a 

 time Avhen the area which Lake Auburn now occupies was covered by ice. 



No gravel rises above the clay for about 2 miles, and then we find a 

 rather level gravel plain near the southeast angle of Lake Auburn. It is 

 about a mile long and more than half as broad. The gravel, cobbles, and 

 bowlderets of which it is composed at its north end are not much water- 

 worn, and often have almost a till shape. Toward the south and east the 

 material is somewhat finer and the plain appears to be a delta deposited 

 either in a bay of the sea that was inclosed between ice walls or in a glacial 

 lake. About half a mile south of this is another similar one. It ends in 

 steep banks on all sides except one, where it lies like a terrace ag-ainst a 

 hill. This plain is only about one-fourth of a mile in diameter, and becomes 

 sandy on tlie south and east aides, and is thus shown to be an incomplete 

 delta. 



South of this point I have been able to find no glacial gravel for about 

 8 miles. The system ends on a hill overlooking the valley of the Little 

 Androscoggin. The system dates from a time when the sea had advanced 

 up the valleys of the Androscoggin and Little Androscoggin to a point 

 some distance west of Auburn. The ice still lingered to the north. Three 

 delta-plains were formed in Auburn during the flow of this large glacial 

 MON xxxiv 14 



