forests on coast of Hants._--We have already seen that the
submarine position of several forests, or the remains of trees standing
in a vertical position on the British shores, has been due, in some
instances, to the subsidence of land.[1065] There are some cases which
require a different explanation. My friend, Mr. Charles Harris,
discovered, in 1831, evident traces of a fir-wood beneath the mean level
of the sea, at Bournmouth, in Hampshire, the formation having been laid
open during a low spring tide. It is composed of peat and wood, and is
situated between the beach and a bar of sand about 200 yards off, and
extends fifty yards along the shore. It also lies in the direct line of
the Bournmouth Valley, from the termination of which it is separated by
200 yards of shingle and drift-sand. Down the valley flows a large
brook, traversing near its mouth a considerable tract of rough, boggy,
and heathy ground, which produces a few birch-trees, and a great
abundance of the _Myrica gale_. Seventy-six rings of annual growth were
counted in a transverse section of one of the buried fir-trees, which
was fourteen inches in diameter. Besides the stumps and roots of fir,
pieces of alder and birch are found in the peat; and it is a curious
fact, that a part of many of the trees have been converted into iron
pyrites. The peat rests on pebbly strata, precisely similar to the sand
and pebbles occurring on the adjoining heaths.

As the sea is encroaching on this shore, we may suppose that at some
former period the Bourne Valley extended farther, and that its extremity
consisted, as at present, of boggy ground, partly clothed with
fir-trees. The bog rested on that bed of pebbles which we now see below
the peat; and the sea, in its progressive encroachments, eventually laid
bare, at low water, the sandy foundations; upon which a stream of fresh
water, rushing through the sand at the fall of the tides, carried out
loose sand with it. The superstratum of vegetable matter, being matted
and bound together by the roots of trees, remained; but being
undermined, sank down below the level of the sea, and then the waves
washed sand and shingle over it. In support of this hypothesis, it may
be observed, that small streams of fresh water often pass under the
sands of the sea-beach, so that they may be crossed dry-shod; and the
water is seen, at the point where it issues, to carry out sand and even
pebbles.

_Mineralization of plants_--Although th