164 SURFACE GEOLOGY. 



wells to be principally composed of modified drift, a large part of which 

 is clay.* On its south side the surface is gravel, with few boulders, none 

 of which exceed 4 or 5 feet in diameter. 



The last of these kame-like deposits which remains to be described 

 within the limits of Piscataqua basin, is the extensive plain of Newington 

 and the north-west part of Portsmouth. This is three miles long from 

 north to south, and for most of this distance averages a mile in width, 

 forming a plateau 60 to 100 feet above Great bay and Piscataqua river 

 on each side. Outcropping ledges and scattered boulders are seen in 

 many places upon its surface ; but numerous wells show only modified 

 drift to depths of 30 or 40 feet, being first coarse gravel, 3 to 10 feet in 

 thickness, succeeded below by interstratified fine gravel and sand. The 

 entire western edge of this deposit is a gently sloping escarpment, which 

 descends 10 to 30 feet. On the north and east it rests mainly on ledges, 

 but at one place falls in an abrupt slope more than 50 feet. A section 

 at its base in the north part of Newington showed sand overlain by gray 

 clay, as at Dover. Southward, near the Concord & Portsmouth Railroad, 

 its surface is sand, obliquely stratified. Between this and the Eastern 

 Railroad it is changed to a broad ridge, 25 to 30 feet high, composed 

 mostly of pebbles six inches to a foot in diameter, packed as compactly 

 as possible with no layers of sand. This gravel is finely exposed in an 

 excavation, from which it is teamed two miles for repairing streets in 

 Portsmouth. The deposit terminates south-east from the Eastern Rail- 

 road in a small plain of horizontally stratified sand. 



Exeter River and the Plains at Kingston and sontJnvard. The prin- 

 cipal part of Exeter village, and several square miles bordering Exeter 



• The following are sections of wells upon this hill, noted in order from north-west to south-east : 



1. A well dug three years ago at C. C. Barton's, about 30 feet below the top of the hill, showed till on the sur- 

 face, 4 feet; gray clay, plainly stratified and sandy in some layers, but containing occasional pebbles seldom 

 more than 6 inches in diameter, 38 feet ; clear sand, with water, i foot ; blue clay, 9 feet, extending lower ; — total 

 depth, 52 feet. 



2. The former well here, about 150 feet distant to the south-west and nearly the same in height, was through 

 till, 4 feet ; gray clay, as in new well, 4 feet ; sand and fine gravel, 15 feet ; gray clay, 27 feet ; — total depth, 50 

 feet. The last eight feet were bored, and at the bottom the auger " fell," and a powerful flow of water came up. 



3. At A. Wiggin's, near the top of the hill, a well 52 feet deep through unknown material becomes dry in sum- 

 mer, and was recently bored 12 feet lower through sand without striking ledge; — total depth, 64 feet. 



4. At E. F. Wiggin's, perhaps 30 feet below the last place, the order was till containing boulders up to 500 pounds 

 in weight, with layers of gravel and sand, 20 feet; interstratified fine gravel, sand, and clay, 20 feet; very com- 

 pact gray clay, nearly free from rock fragments, 16 feet, underlain by quicksand with abundant water; — total 

 depth, 56 feet. 



5. A well dug two years ago at T. E. Marston's, about 20 feet lower than the last, passed through coarse water- 

 worn gravel, with the largest stones i^ feet in diameter, 8 feet; sand and fine gravel, 10 feet; gray clay, stratified 

 and containing layers of sand, 20 feet ; — total depth, 38 feet. 



