the tufaceous layers of a pinkish colour and it is a most extraordinary
fact, that Professor Ehrenberg [5] finds it almost wholly composed of
matter which has been organized: he detects in it some
siliceous-shielded fresh-water infusoria, and no less than twenty-five
different kinds of the siliceous tissue of plants, chiefly of grasses.
From the absence of all carbonaceous matter, Professor Ehrenberg
believes that these organic bodies have passed through the volcanic
fire, and have been erupted in the state in which we now see them. The
appearance of the layers induced me to believe that they had been
deposited under water, though from the extreme dryness of the climate I
was forced to imagine, that torrents of rain had probably fallen during
some great eruption, and that thus a temporary lake had been formed
into which the ashes fell. But it may now be suspected that the lake
was not a temporary one. Anyhow, we may feel sure, that at some former
epoch the climate and productions of Ascension were very different from
what they now are. Where on the face of the earth can we find a spot,
on which close investigation will not discover signs of that endless
cycle of change, to which this earth has been, is, and will be
subjected?
On leaving Ascension, we sailed for Bahia, on the coast of Brazil, in
order to complete the chronometrical measurement of the world. We
arrived there on August 1st, and stayed four days, during which I took
several long walks. I was glad to find my enjoyment in tropical scenery
had not decreased from the want of novelty, even in the slightest
degree. 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 all parts 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 are
usually 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 are only a few spots where the bright red soil
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