READFIELD-BEUNSWIOK SYSTEM. 191 



well-rounded cobbles, bowlderets, and bowlders up to 2 feet in diameter. 

 This gravel deposit is very irregular in outline, and it sends out several 

 sjDurs both north and south. The surface is very uneven, showing a great 

 variety of mounds, ridges, terraces, and shallow kettleholes. Most of the 

 ridges trend north and south. It rises 40 to 80 feet above the plain of 

 sedimentary (pi-obably marine) clay which partly covers its base. It is 

 about three-fourths of a mile long from east to west, and the longest spurs 

 are about a half mile from north to south. These dimensions show that it 

 contains a very large amount of glacial gravel. The formation is much 

 finer in composition in some parts than in others, but these parts are inter- 

 spersed irregularly among the areas containing coarser matter, so that it 

 must be considered a compound delta or plexus of broad reticulated ridges, 

 composed of a number of more or less distinct but adjacent deltas, rather 

 than a single delta. So far as I could discover, none of these incomplete 

 deltas pass into marine clays by degrees, and the glacial streams flowed into 

 pools within the ice rather than into the open sea. 



A broad low valley extends from the foot of Sabatis Lake, in Webster, 

 northeastward through Wales and Monmouth, broadening as it approaches 

 Cobbosseecontee Great Pond and Lake Anabescook. This plain is all the 

 way covered by clay, which in several places contains marine fossils. 

 It is thus proved that there was once a continuous body of salt water 

 extending from the Kennebec Bay westward to Winthrop, and thence 

 southwestward to Sabatis and Lisbon, where it broadened into the Andros- 

 coggin Bay of that period, which coyered a large part of Topsham, 

 Brunswick, Lisbon, and Durham. 



South of the plain at the cemetery in Monmouth there is a gap of 

 about 3 miles, where no glacial gravel was seen rising above the marine 

 clay. Then a series of low bars separated by short intervals begins not 

 far north of East Wales and extends south along the eastern base of the 

 high hills known as Monmouth Ridge and Sabatis Mountain. These gravel 

 deposits lie in the midst of the clay-covered plain before described, and are 

 partly covered by the clay. Near tlie south base of Sabatis Mountain the 

 series expands into a very high broad ridge, becoming broader toward 

 the southwest and of finer material, ending in sand, which is overlain at the 

 base by the marine clay. Here the glacial streams flowed into a glacial 

 lake or into the sea, but if the latter, the transition from the sand to the 



