MODIFIED DRIFT IN PISCATAQUA BASIN. 163 



brook. Its north-west portion is quite thickly strewn with boulders, the 

 largest of which are 5 or 6 feet in diameter ; and over nearly its whole 

 extent these have been sufficiently abundant for walling the fields. Four 

 wells, however, between the school-house and the Eastern depot, varying 

 from 20 to 30 feet in depth, passed all the way through stratified gravel, 

 sand, and blue clay. In three of these wells the upper portion was fine 

 gravel or sand. One of them, a half mile south-east, and a cistern a 

 quarter of a mile south from the school-house, showed at the top 10 feet 

 of very coarse but water-worn gravel, which was underlain by clear sand. 



Two thirds of a mile farther east, beyond the railroad and Berry's 

 brook, a well at the house of L. & F. A, Berry (county map) encountered 

 10 feet of coarse gravel, below which were interstratified fine gravel, 

 sand, and blue clay, extending 16 feet to ledge. Mussel shells which 

 still retained their purple color, but were easily broken in pieces, were 

 found in this well eighteen feet below the surface. Three fourths of a 

 mile south from the school-house, a well at N. Norton's (county map) 

 passed through 40 feet of coarse gravel containing pebbles up to 5 or 10 

 inches in diameter, with layers of sand. At a depth of about 25 feet in 

 this well several white pine cones were found, and about 5 feet lower 

 numerous mussel shells, both being well preserved and distinct. The 

 two last wells are one and a quarter miles apart, each being at the surface 

 about 100 feet above the sea. 



The very thin covering of till and frequent scattered boulders which 

 lie on the north-west portion of this plain, were probably in large part 

 distributed by floating ice ; but this appears to have taken place at a time 

 when the ice-sheet paused in its retreat, and once more overspread areas 

 from which it had withdrawn. Evidence of a readvance of the ice-sheet 

 was also afforded by a well in Stratham, a third of a mile east of Barker's 

 hill. Here the surface was 5 feet of upper till, which also extended fully 

 twenty rods on every side, containing boulders up to 6 or 8 feet in diam- 

 eter, underlain by 2 1 feet of sand and fine gravel, the bottom of which 

 was not reached. A hill in the north-west corner of North Hampton, 

 which rises 75 to 100 feet above the lowland by which it is entirely sur- 

 rounded, or about 150 feet above the sea, is covered to the top on its 

 north side with very coarse glacial drift, containing abundant angular 

 boulders of all sizes up to 10 feet in diameter; yet this hill is shown by 



