140 SURFACE GEOLOGY. 



three fourths of a mile wide on Newell's brook, and on the stream which 

 is the outlet of Dummer ponds. These tracts consist mainly of sand or 

 fine silt, and are very level and in many portions swampy. On the south- 

 east side the river is bordered by a narrow margin of modified drift, 

 beyond which the hills rise from 100 to 200 feet above the stream. 



Pontoocook falls extend about a mile from the most western point 

 reached by the river, which here flows between hills of till or ledge. 

 Near the foot of these falls is Pontoocook bay, which is an expansion of 

 the river containing several islands. This is bordered by sandy terraces ; 

 and thence southward for ten miles, extending through Milan and nearly 

 to Berlin falls, the modified drift is continuous, being usually one eighth 

 to one third of a mile wide upon both sides of the river. This consists 

 of sand or gravel, which is not often very coarse. About half of its 

 whole width is interval, being from 5 to 15 feet above the ordinary 

 height of the river ; and all above this is irregular in contour, with no 

 well defined terraces, the modified drift reaching in irregular slopes about 

 40 feet above the river. The Androscoggin along this distance is nearly 

 level, having a height of about 1,050 feet above the sea ; and the hills on 

 each side are of moderate height and gentle slopes. 



At Berlin Falls the precipitous front of Mt. Forest rises close at hand 

 on the west, and the river here enters the White Mountain area. Along 

 the rest of its course in New Hampshire, and for some distance in Maine, 

 the valley is closely bordered by high and abrupt mountains. From the 

 head of Berlin falls the river descends nearly 200 feet in the first mile, 

 and its current is rapid to the east boundary of the state, which it crosses 

 at a height of 690 feet above the sea. For the first five miles of this dis- 

 tance the course continues to the south towards the highest of the White 

 Mountains ; but at Gorham the river turns at a right angle, and after flow- 

 ing nine miles to the east it enters Maine. The very rapid portion of the 

 river at Berlin Falls is destitute of any modified drift, and the channel is 

 principally ledge. Below these falls the modified drift through Gorham 

 and Shelburne is continuous on one or both sides, though often narrow, 

 and it is nowhere more than a mile between the steep mountain walls 

 which enclose the valley. 



Through Gorham, the terraces which border the Androscoggin are 10 

 to 50 feet in height, and they are best shown on the west and south sides 



