246 Geology of Martha’s Vineyard. 
Clay Formation.* It cannot, however, be referred to any 
other European formation, of which I have seen a descrip- 
tion. It is coloured, on the accompaning map, only asa 
belt along the coast, in those parts where | have noticed it 
to be more or less distinctly laid bare; although, as before 
observed, it probably constitutes the basis of all the dilu- 
vial part of the island. But the diluyial is so remarkable, 
that it seemed to deserve a place. Probably, also, the 
Plastic Clay underlies the diluvium of the Elizabeth Islands: 
although the clay beds are not so distinct in the cliffs, and 
are in general, hid by the sand. And from all I can leara 
of Natucket, this island is, with little doubt, referable to the 
same formation: if so, where, but to the same place in 
the geological scale, shall we refer the sands of Cape 
Cod? unless, indeed, they may belong to a formation still 
more recent. ong Island, in those places where I have 
seen it, is unquestionably very similar in its geologival 
structure to Martha’s Vineyard ; and probably belongs to the 
same era. I take it for granted, that the vast region along 
the sea coast in the middle and southern states, marked on 
Maclure’s map as alluvial, can no longer be considered 
: ‘in the modern sense of that term. He describes 4 
part of it, at least, as consisting of sandstone and limestone, 
and regular beds of sand, gravel and clay; and some of this 
gravel is cemented by oxide of iron: and, therefore, it can- 
not be alluvial; but agrees with the European strata above 
the chalk. If we take his map, and prolong the line, oF 
rather curve, that separates the alluvial tract above name 
from the primitive towards the north-east, we shall find 
that it passes between Martha’s Vineyard and the conti- 
nent, and crosses Cape Cod, leaving us to conclude that the 
Vineyard and Nantucket are a continuation of that exten- 
sive formation, hitherto called alluvial, of which Long-Is!- 
anh has been regarded the north-eastern limit. If we pro 
long this curve still farther, it will include within it Nova 
Scotia, and, at least, a part of Newfoundland. Here ¥@ 
are reminded of the vast sand banks along that coast, and 
- * The remarks of Mr. Fi who appears to be ocenlarly acquainted 
Ppa ces ae pation ap Englan, on the veg nana Be of Nort 
more haan a oe me bie ihe so 
eel indebted to tha’ 
Plastic Clay 1 ormation in the Vineyard. I feel t gentle- 
ts he has thrown out, 
