38 



SURFACE GEOLOGY. 



Horizontally 

 stratified sand. 



Fig. 8.— Section in Delta of Mink 

 Brook, Hanover. Scale, i inchz:=2o 

 feet. 



The lower sand shows the usual stratification of the 

 outer part of a delta, dipping towards the open 

 valley. A current of water has eroded a portion 

 of this, bringing a bed of gravel, upon which rests 

 a later deposit of sand. 



kame, and thence flows close on its west side to White River falls. 

 Along this distance of four miles we find the high plain well developed 

 in New Hampshire, averaging three fourths of a mile wide. Hanover 

 common, 545 feet above the sea and 172 above the river, represents its 

 greatest altitude. Westward, a gradual slope descends 30 feet in one 

 third mile to the kame ; one third mile east the farm of the agricultural 



college is 45 feet lower than the 

 common; and we have the same 

 height one mile south, at the high- 

 est portion of the road to West 

 Lebanon. Observatory hill, and 

 others in Norwich and Lebanon, 

 are examples of outcropping ledges 

 and till, surrounded by alluvium. 

 Half a mile south-east from Han- 

 over, a delta 20 to 40 feet higher 

 than the common has been brought 

 down by Mink brook, which, west 

 from this point, has also exxavated a large amount from the plain. On 

 the roads to Lyme and West Lebanon such erosion as this exposes a 

 clayey stratum, noticeable in the spring by remaining muddy after all the 

 rest of the road has become settled and dry. Two miles north of Hano- 

 ver this stratum appears from 488 to 503 feet above the sea, most nota- 

 bly at the height of 495; a mile and a half south, at the north side of the 

 Vale of Tempe, its height is 482; on the south side, 479 to 482; a mile 

 farther south, on the north side of Mink brook, it appears from 503 to 

 480, being most marked at 485; on its south side it occurs at two points, 

 with heights 470 and 478 to 483, the last being most prominent; and 

 about a mile farther south, at the descent just before the turn-off to the 

 falls, it is very noticeable, with about the same height. It also occurs in 

 Vermont at a corresponding height, just below the top of the ascent be- 

 tween the depot and Norwich village. This extensive and nearly level 

 stratum shows that deposition took place gradually and at the same time 

 over this whole area. 



In digging the first well at Hanover (near the residence of Prof. H. E. 

 Parker) a large log was found in this alluvium 40 feet below the surface, 



