as a building stone ; but some of the layers are too hard for
freestone, and when struck by the hammer ring like flint.
The main line of beach is directed N.E. and S.W. ;
Lieutenant Evans informs me, that during the six months
included between the 1st of April and the 1st of October,
the sand accumulates towards the N.E. extremity, and
during the other six it travels back again towards the S.W.
end. This periodical movement is due to a change in the
direction of the swell, which is influenced by the general
direction of the trade-wind, during the two periods of the
year. Lieutenant Evans also informs me that during the
six years he has resided on this island, he has always
observed, that in the months of October and November,
when the sand commences travelling towards the S.W., the
rocks which are situated at that end of the long beach,
become coated by a white, thick, and very hard calcareous
layer. I saw portions of this remarkable deposit, which had
been protected by an accumulation of sand. In the year
1831 it was much thicker than during any other period.
It would appear that the water, charged with calcareous
matter by the disturbance of a vast mass of calcareous
particles, only partially cemented together, deposits this substance
on the first rocks against which it impinges. But
the most singular circumstance is, that in the course of a
couple of months this layer is either abraded or redissolved,
so that after that period, it entirely disappears. It is
curious thus to trace the origin of a periodical incrustation
on certain isolated rocks, to the motion of the earth with
relation to the sun; for this determines the atmospheric
currents, which give the direction to the swell of the ocean,
and this acts on the arrangement of the sea-beach, and this
again on the quantity of calcareous matter held in solution
by the waters of the neighbouring sea.
One of my excursions took me towards the S.W. extremity
of the island. The day was clear and hot, and I saw
the island, not smiling with beauty, but staring with naked
hideousness. The lava streams are covered with hummocks,
and are rugged to a degree, which, geologically speaking, is
not of easy explanation. The intervening spaces are concealed
with layers of pumice, ashes, and volcanic tuft. In
some parts rounded volcanic bombs, which must have
assumed this form, when projected red-hot from the crater,
lie strewed on the surface. Whilst passing at sea this end
of the island, I could not imagine what was the nature of
the white patches, with which the whole plain was mottled;
I now found they were seafowl, which were sleeping in such
full confidence, that even in midday a man could walk up
to, and seize hold of them. These birds were the only
living creatures I saw during the day. On the beach a
great surf, although the breeze was light, was tumbling over
the broken lava rocks.
Upon leaving Ascension the ship’s head was directed
towards the coast of South America, and on August 1st, we
anchored at Bahia or San Salvador. We staid here four
days, in which time I took several long walks. I was glad
to find my enjoyment of tropical scenery had not decreased
even in the slightest degree, from the want of novelty. The
elements of the scenery are so simple, that they are worth
mentioning, as a proof on what trifling circumstances exquisite
natural beauty depends. ■
The country may be described as a level plain of about
three hundred feet in elevation, which in every part has
been worn into flat-bottomed valleys. This structure is
remarkable in a granitic land, but is nearly universal in
all those softer formations, of which plains usually are composed.
The whole surface is covered by various kinds of
stately trees, interspersed with patches of cultivated ground,
out of which houses, convents, and chapels arise. It must
be remembered that within the tropics, the wild luxuriance
of nature is not lost even in the vicinity of large cities; for the
natural vegetation of the hedges and hill-sides, overpowers in
picturesque effect the artificial labour of man. Hence, there