682 GEOLOGY OF OLD HAMPSHIRE COLTNTY, MASS. 



the upper sands when the ice was plainly thrust out into the waters of the 

 lake — then risen higher — and plowed up its bottom. 



While I was studying- the sands the workmen were breaking off masses 

 of the frozen sand with wedges and heavy hammers to make way for the 

 steam shovel, and the rock thus formed was one of great hardness. The 

 depression which separates the two parts of the sand on the west side is 

 lined by a thick layer of unstratitied pebbles concentrated from the pink 

 sands, and seems to me a "pot-hole" in the sand, caused hj the waters of 

 a mouliu of the glacier, though it may be an old brook lied. The eroded 

 surface of these sands is the third erosion plane occupied by the ice. 



The second tiU.—(P\. XV, E to T.) Returning now to the south end 

 of the gi'eat drumlin, we find the second till, which rests upon the pink 

 sands, to have a thickness of 2 to 3 feet, and to be sharply demarcated 

 on the east from the pink sand and the bowlder bed below, the boundaiy 

 being a straight line, and separated above from a third layer of till by the 

 thin, disconnected remnants of a second sand, which thickens rapidly 

 southward, so that where the second till goes out of sight below, it is 

 separated from the third till aljove b}' 15 feet of sand. This second till 

 is the hardest stony clav, wholly indistinguishable from the oldest till of 

 the di'umlin, against which it seems to rest in a wedge-shaped end, although 

 no distinct line of demarcation can be seen between them. The ice seems 

 still to have rested upon the surface of the older till, or to have eroded 

 down to it, and a train of large bowlders api)ears in the second till a little 

 wav from the great till, quite plainly derived from it, as farther on they 

 are wanting in the second till. Farther south, where the ice rode i\\) over 

 the pink beach sands as already described, there is but slight trace of till — 

 a few large bowlders resting on the sands — that which we have followed 

 fi-om the oldest till seeming to have been derived from the erosion of the 

 drumlin; and here the material has failed or been removed at a later time 

 by water, as has much of the pink sand, which one can follow by its color 

 as it is swept southward and now lies between the layers of claj" of later 

 deposition, showing that ice and water worked together here. 



The second sands. — (PI. XV, H to L.) At the south slope of the 

 di'umlin the sands which cover the second till and separate it from the 

 third appear only as a thin, disconnected film, rising to a thickness of 8 to 

 10 inches on the east side, while on the west they are continuous and 



