XXXI. Extract from the Minute Book of the Geological Society.
An extract of a letter from Dr. Macdonell, of Belfast, to Mr.
Horner, was read, in which an account is given of a stratum of submarine
peat and timber in Belfast Lough, situated under the level
of ordinary tides, but generally left bare at ebb tides. Nuts are
numerous in it, both on the east and west sides of the harbour.
On the east side, where calcareous rocks exist, the nuts are filled
with calcareous spar, but on the west side, where the rocks are
schistose, they are empty. Some of them are perfectly filled,
others only partially so, yet the shell appears quite entire, and unchanged
by any petrifactive process, although when put into acids
some effervescence takes place. Dr. Hutton alledges that no infiltration
can happen in circumstances similar to that in which these
nuts are placed, for they are immersed in a bed of peat four or five
feet thick, and this covered by a deposit of sand, shells, and blue
clay, and the whole kept moist and all evaporation prevented by
being covered three-fourths of the day by the tide.
1811, January 18.
An extract of a letter from Dr. MacDonnell, of Belfast, to Mr. Horner, was read, giving an account of some granite veins in slate, in the Mourne mountains.
In some part of these mountains, which are situated at the southern extremity of the county of Down, grey granite forms the summit