280 GLACIAL GEAVBLS OF MAINE. 



We now go back to the great marine delta-plains of New GloucestLi 

 and Gray. North Gray is situated in the valley of a tributary of Royul 

 River. To the south and west of this valley is a broad-topped hill, or 

 gently rolling plateau, which rises about 75 feet above North Gray and 

 extends for several miles southward. A gravel plain about 1 mile broad 

 and 3 miles long is found on the top of this plateau. It comes to the 

 eastern brow of the hill, where it ends in a rather steep slope, almost a 

 bluff. Toward the jiorth the plain consists of broad reticulated ridges, 

 inclosing numerous kettleholes, one of them being a large basin 70 or 80 

 feet deep. Bowlderets and bowlders are here very abundant, and most 

 of them are well rounded. Toward the south the plain becomes quite 

 level on the top, and changes to fine gravel, and finally to sand. Beyond 

 the sand is marine clay, but I am not certain whether the transition 

 between the sand and the clay is such as to prove that this is a delta 

 deposited in the sea or in a glacial lake. The external appearances favor 

 the hypothesis that this is a marine delta-plain. On the slopes of the hill 

 just north of this plain there are many moraine-shaped ridges running 

 nearly north and south. It is uncertain Avhether they were piled in their 

 present shapes by the glacier or are erosion ridges left after the glacial 

 streams had washed away portions of the till, leaving these as uneroded 

 ridges. 



South of this broad delta in Gray is a level country for 3 or 4 miles, 

 deeply covered by marine clay. Then the glacial gravel begins again as a 

 round plain near one-half mile in diameter, situated at the north end of 

 Walnut Hill, in North Yarmouth. From this point a low level plain one- 

 eighth of a mile or somewhat more in breadth borders the eastern base of 

 Walnut Hill, and continues with perhaps a few short gaps to Cumberland 

 Center, where it ends abruptly. This plain nowhere rises more than 10 to 

 25 feet above; the marine clay which overlies its flanks and which some- 

 times covers the gravel out of sight. A road is made on top of the gravel 

 plain for several miles in the midst of a thickly settled country. Hence 

 numerous wells have been dug in the gravel plain or near it. Often when 

 the siu-face shows only the marine clay, wells penetrate the clay into the 

 gravel and prove that the plain is nearly continuous from the north end of 

 Walnut Hill to Cumberland Center. In a few cases (e. g., in the western 

 part of Cumberland Center) wells have passed through the gravel into sedi- 



