148 SURFACE GEOLOGY. 
feet above the low modified drift on each side, or about 100 feet above 
the river. It is then cut through by the river, but only a short gap is 
made; and it continues thence unbroken for more than a mile to the 
south-east, forming a nearly straight ridge 75 to 125 feet high on the 
west side of the river. On its east side the modified drift is narrow; and 
the road passes over a hill which affords a fine view of this kame, and 
others of less height which extend parallel with it, and fill nearly the 
whole valley for two miles below Pine River pond. At the mouth of 
this pond the principal kame seen was just north-east of the bridge, with 
a height 40 feet above the river. Kames of the same or less height occur 
along the shores of this pond, and form its islands. The water-shed be- 
tween Pine River and Balch ponds is an area of kames, its lowest point 
being a hollow between high parallel ridges; and the same series con- 
tinues south-east along the sides of Balch pond. 
The material of these ridges is almost wholly water-worn, wherever it 
has been observed. It consists principally of gravel, which contains peb- 
bles or rounded boulders up to two or three feet in diameter. Layers of 
sand are sometimes interstratified with this gravel; and angular boulders 
up to five or six feet in diameter are occasionally found. The more level 
areas of modified drift in this valley are also mostly gravel, with the larg- 
est pebbles frequently six inches to one foot in diameter. 
The height of this series of kames where it is first met with, one to 
two miles above the mouth of Pine river, is about 40 feet above the lake, 
or 450 above the sea. At the water-shed between Pine River and Balch 
ponds it is about 600 feet above the sea. From this point the kames 
descend both to the south-east and north-west with the valleys, their 
slope along Pine river being 15 feet to a mile. 
The accompanying plains along the lower part of Pine river are only 
10 to 25 feet in height. At North Wakefield they are 60 feet above the 
river and pond; at East Wakefield depot they reach their greatest height, 
being 675 feet above the sea, or more than 100 feet above the lowest de- 
pression of the water-shed. The same belt of modified drift continues 
into Maine, forming extensive low plains in Acton and Shapleigh, with a 
height about 500 feet above the sea. 
