Above this clay is a deposit resembling it, and yet differing from
it, called the "bowlder-clay." This is not so tough or hard. The
bowlders in it are larger and more angular-sometimes they are of
immense size; one at

###

SCRATCHED STONE (BLACK SHALE), FROM THE TILL.

Bradford, Massachusetts, is estimated to weigh 4,500,000 pounds. Many
on Cape Cod are twenty feet in diameter. One at Whitingham, Vermont,
is forty-three feet long by thirty feet high, or 40,000 cubic feet in
bulk. In some

{p. 7}

cases no rocks of the same material are found within two hundred
miles.[1]

These two formations--the "till" and the "bowlder-clay"--sometimes
pass into each other by insensible degrees. At other times the
distinction is marked. Some of the stones in the bowlder-clay are
furrowed or striated, but a large part of them are not; while in the
"till" _the stone not striated is the rare exception_.

Above this bowlder-clay we find sometimes beds of loose gravel, sand,
and stones, mixed with the remains of man and other animals. These
have all the appearance of being later in their deposition, and of
having been worked over by the action of water and ice.