340
PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Feb. 21,
2. On the Tertiary and more recent Deposits in the Island of
Nantucket. By M. E. Desor and Edward C. Cabot.
(In a letter to Sir Charles Lyell, Pres. Geol. Soc.)
Knowing how mnch you are interested in all inquiries about the
drift of this country, we take the liberty to forward to you some
specimens of shells which we have lately collected from the cliffs of
Sancati Head, in the island of Nantucket. Allow us to accompany
them with some observations upon this locality.
The cliff of Sancati, as you know, constitutes the eastern border
of the island of Nantucket, rising to a height of ninety-two feet above
the beach. Although covered in a great measure with the loose sand
that is carried by the wind from the beach, yet there are several
points where the successive layers are to be seen, as for example near
the tripod : fig. 1 will give an idea of their superposition.
•■r\.'.-/:'^.-:.y.\;':\yy/.'^'i^^^
Fig.
1.
6 feet
«. Dune sand.
1
d. Peat.
37
c. Sand with an occasional stra
5
10
).
turn of coarse gravel.
d. Ferruginous gravel.
e. Sand.
2
/. Worn shells.
3
1
.)
g. Serpula.
//. Ovsters.
1
i. Tough clav. •
4
2
..
y. Homogeneous white sand,
k. Gravel.
20
.)
/. Brown clay.
At the base of the cUff is found a stratum of brown, very brittle
and partly sandy clay (/), nearly twenty feet thick. Over this rests
a bed of gravel several feet thick (A), which is overlaid by a stratum
of homogeneous white sand (J). On this is found a layer of very
tough clay (z), very similar in its aspect to the plastic clay near Paris,
except that it contains a great many nodules of ferruginous sand.
This clay -bed is overlaid by an oyster-bank (/«) one foot thick, inter-
mixed and covered by large masses of Serpula ((/), which are, like the
oysters, in their natural position. There are besides a great many
other shells scattered through this bank, all of them in a most perfect
condition, although it is difficult to preserve them entire when taken
out from the layer. This oyster-bank is followed by another fossi-
liferous stratum (/), in which the shells are in a different state : they