686 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



Turning to the second cut on the east side, which was 50 feet farther 

 out in the lake and parallel to the two last described, we find the till homog-e- 

 neous in the lower 2 feet of its thickness. Then it runs up over the sands 

 and thins to a foot in thickness, and is then prolonged in a sti-atified bed of 

 the same dark greenish-black sandy clay, which ends abruptly (thickening 

 slightly before its ending) in a sharp point, the last portion lieing beauti- 

 fully cross-bedded and apparently the product of a single plunging wave 

 from beneath the ice. This is inclosed aliove and below in the light-yel- 

 low coarse sands, which beneath are undisturbed so far back as traces of 

 lamination occur in the stony clay aliove, and are conspicuou.sly con- 

 toi'ted farther liack beneath the amorphous and ice-carried portion of the 

 same bed. 



At the fourth cutting parallel to those last discussed (the most west- 

 erly), where the till runs up on the sand, it splits into three or four layers, 

 each successive one running up with sharper angle and being separated by 

 thickening sheets of flood sands; and the till reaches here its greatest height. 

 Some layers of the till bend irregularly and sink deeper into the sands 

 and extend farther south, but are cut off' by the brook erosion before the 

 connection southward is made. (PI. XVIII, fig. 2, p. 694.) 



The transition of the sands to clays beneath this till indicates a deep- 

 ening of the waters southwardly, by which the ice was more or less buoj^ed 

 up, allowing a portion of the sands described above to accumulate beneath 

 it, after which the ice dropped again upon the sands. This was re^jeated 

 several times, and at one of these times a mass of water from beneath the ice 

 swept into the sands the curious point of remanie drift descril^ed above, and 

 finally the ice was floated away to the south as icebergs, allowing the sands 

 to continue their accumulation over the till it had left. 



The days above the second sands. — These are, from one end of the 

 cutting to the other, the common Champlain clays of the valley, formed 

 from the wash of till, and where not disturbed are tliin-laminated in layers 

 8 to 12™™ thick, each layer buff" colored and sandy in the upper third, and 

 composed of fine fat clay in the lower two-thirds. 



jTJie fourth till and its effects npon the ctaijs and sands hcloir. — Starting 

 from the north end of the opening, the surface of the clays is an almost 

 perfectly level surface of erosion on to the drumlin. The ice has passed 

 over it, planing it down to this level, twisting and contorting it and the 



