MODIFIED DRIFT IN PISCATAQUA BASJN. l6$ 



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 debris, containing 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 90 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 Nitatla 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 



