Beneath the upper and central green circle, the wild valleys are quite
desolate and untenanted. Here, to the geologist, there were scenes of
high interest, showing successive changes and complicated disturbances.
According to my views, St. Helena has existed as an island from a very
remote epoch: some obscure proofs, however, of the elevation of the
land are still extant. I believe that the central and highest peaks
form parts of the rim of a great crater, the southern half of which has
been entirely removed by the waves of the sea: there is, moreover, an
external wall of black basaltic rocks, like the coast-mountains of
Mauritius, which are older than the central volcanic streams. On the
higher parts of the island, considerable numbers of a shell, long
thought to be a marine species occur imbedded in the soil.
It proved to be a Cochlogena, or land-shell of a very peculiar form;
[2] with it I found six other kinds; and in another spot an eighth
species. It is remarkable that none of them are now found living.
Their extinction has probably been caused by the entire destruction of
the woods, and the consequent loss of food and shelter, which occurred
during the early part of the last century.
The history of the changes, which the elevated plains of Longwood and
Deadwood have undergone, as given in General Beatson's account of the
island, is extremely curious. Both plains, it is said in former times
were covered with wood, and were therefore called the Great Wood. So
late as the year 1716 there were many trees, but in 1724 the old trees
had mostly fallen; and as goats and hogs had been suffered to range
about, all the young trees had been killed. It appears also from the
official records, that the trees were unexpectedly, some years
afterwards, succeeded by a wire grass which spread over the whole
surface. [3] General Beatson adds that now this plain "is covered with
fine sward, and is become the finest piece of pasture on the island."
The extent of surface, probably covered by wood at a former period, is
estimated at no less than two thousand acres; at the present day
scarcely a single tree can be found there. It is also said that in
1709 there were quantities of dead trees in Sandy Bay; this place is
now so utterly desert, that nothing but so well attested an account
could have made me believe that they could ever have grown there. The
fact, that the goats and hogs destroyed all the young trees as they
sprang up, and that in the course of time the old ones, which were safe
from their attacks, perished from age, seems clearly made out. Goats
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