208 GLACIAL GEAVELS OF MAINE. 



widely covered by sedimentary clay from Livermore Center eastward to 

 Livermore. The currents which deposited the delta south of Brettuns 

 Pond must have flowed for near a mile along- the west and southwest sides 

 of the pond, bordering it with high, steep banks of gravel, cobbles, and 

 bowlderets. If the area where the pond now is had been bare of ice at 

 the time these waters flowed south from Canton, the delta would have 

 been formed where the pond now is. The facts indicate that the valley of 

 Martins Stream Avas occupied by a glacial lake or other body of water at 

 the time this delta was formed, while the area where the pond now is must 

 have been occupied by ice. The finer sediment brought down by the 

 glacial stream passed beyond the delta of gravel and sand, and furnished 

 the clay which covers this valley. 



A rather level osar-plain, from one-eighth to one-half of a mile wide, 

 extends along the valley of Martins Stream southward nearly to the 

 Twentymile River. Between Livermore and North Turner the plain has 

 been irregularly eroded so as to leave a marginal terrace on each side of 

 the valley and a ridge, or, rather, series of ridges arranged as a single line 

 in its midst. These ridges appear as narrow islands in the midst of the 

 artiticial pond (produced by the dam at North Turner), which now occupies 

 the valleys of erosion on each side of the central ridge. The central ridge 

 here has the same height as the marginal terraces, except where it has been 

 reduced by erosion. South of North Turner the osar-plain is bordered by 

 a wide plain covered by sedimentary clay, overlain by some sand. This 

 alluvial plain is connected with the plain of sedimentary clay that covers 

 the valley of Twentymile River by two lines of clays, one southward 

 down the valley of Martins Stream, the other southeastward past the west 

 side of Pleasant Pond and then by a low pass to Bradford Village (Turner 

 Center). I could find no glacial gravel, along the last-named route, and 

 infer that this large area of fine sediment was not deposited in a broad 

 osar channel, but at a time when the lowlands were all bare of ice and 

 covered with water, probably either fluviatile or estuarine. 



The osar terrace becomes finer as it nears the Twentymile River, 

 and thus shows some of the characters of the delta-plain. It appears 

 to be interrupted for a half mile or more near Twentymile River, but 

 soon begins again as a series of low reticulated ridges or plains from 

 one-fourth to one-half of a mile broad. The reticulated jjlains extend 



