MODIFIED DRIFT IN PISCATAQUA BASIN. 165 
river on the south and extending into Kensington, are alluvial sand and 
gray clay, 30 to 60 feet above the sea. 
A map on Plate VI (p. 146) shows the belt of plains which extends 
south from this river to the Merrimack at Haverhill, Mass. At the 
north line of Kingston their height is about the same as that of Spruce 
swamp in the east part of Fremont, which is shown by the survey for 
the Nashua & Rochester Railroad to be 160 feet above the sea, or about 
30 feet above Exeter river. Half of the township of Kingston is occu- 
pied by these sandy plains, which slope to a height of 125 feet above the 
sea at its south line. Numerous ponds, which are the sources of Powow 
river, mark where portions of the ice-sheet remained unmelted while 
the deposition of modified drift went on rapidly at each side. A large 
area of kames is indicated on the map in the northern part of Plaistow. 
Their southern portion consists of the ordinary water-worn gravel in 
short, steep ridges and mounds. At the north and north-west, these pass 
gradually into very coarse morainic débris, coritaining angular blocks of 
all sizes up to 10 feet in diameter, much of which is accumulated in low 
ridges like those of the kames. In Plaistow the plains continue their 
slope to about go feet above the sea. In Haverhill a large portion of the 
original deposit has been excavated by Little river; and its south end 
has been partly undermined by the Merrimack, on whose north side it 
forms a conspicuous terrace west of the railroad bridge. 
Fossils. Although it seems probable that the sea stood about 150 feet 
higher than now during the deposition of most of the modified drift in 
this basin, only very scanty relics of the life of this period have been 
found. A whale’s vertebra, now in the museum of Dartmouth college, 
was discovered in Somersworth in 1843 by the caving in of a gravel bank, 
but no other bones were found. Several wells in the village of South 
Berwick show marine remains at a depth of about 30 feet in a stratum 
of fetid mud, which resembles that of the tide-flats, and frequently ren- 
ders the water unfit for use, at least through a part of the year. The 
humerus, radius, and ulna of a seal, and shells of Mucula Portlandica 
(see foot-note on next page), are mentioned by Jackson from wells at this 
place, which are about 100 feet above the sea, the fossiliferous stratum 
having a height of about 70 feet. The surface here was three feet of 
_ sand, the whole depth below which was clay, the upper portion gray and 
