CASCO-WINDHAM SYSTEM. 235 



even to the edge of the deposit, as to prove that they were formed between 

 ice walls and not in the open sea. The student of the drift of Maine should 

 certainly explore this system, though in many places it is quite inaccessible 

 and considerable time is required to do it justice. 



LOCAL ESKEE IN WESTBROOK. 



A short kame is situated on the north side of the Presumpscot River a 

 short distance east of Cumberland Mills. 



CASCO-WINDHAM SYSTEM. 



Thompson Pond extends from Oxford south tlu'ough Otisfield and 

 Poland into Casco. It occupies a long north-and-south valley, which at the 

 north is 2 or 3 miles wide, but becomes narrower in Casco, so that at 

 the south end of the pond it is hardly one-eighth of a mile wide, while 

 south of the pond lies an almost V-shaped valley, bordered by high 

 granitic hills. At the foot of the pond the bases of the bordering hills are 

 strewn with a number of hummocks of till, also some morainal ridges, 

 which are somewhat transverse to the valley. They appear like moraines 

 of a local glacier occupying the basin of the jjond. This narrow valley 

 terminating the much broader valley toward the north would be favorable 

 for the formation of moraines during the final melting of the ice, on account 

 of the great convergence of the movement into so narrow a pass. In the 

 midst of the valley, at the south end of the pond, begins a series of low 

 bars of glacial gravel. The stones have been but little changed from their 

 till shaj)es, a fact which proves this to be near the north end of the system. 

 Only a small brook flows northward into the lake, and there is no way of 

 accounting for this gravel as fluviatile alluvium. Going south we find the 

 gravel becoming rounder. A very low divide separates the waters of 

 Thompson Pond, flowing north, from those flowing south. The glacial 

 river flowed over this divide and thence in a nearly straight line to Rattle- 

 snake Pond, Casco. Not far north of this pond it flowed over a vertical 

 cliff" of rock 20 feet high. The cliffy faces south, and a subglacial river 

 flowing in that direction would naturally have eroded the rock at the base 

 of the cliff if it flowed over it so as to form a watei'fall, but there is no pot- 

 hole or visible channel of erosion in the solid i-ock. The course of the 

 glacial river could easily be traced at this point by the piles of rounded 



