I brought
away specimens of one of the tufaceous layers of a pinkish colour
and it is a most extraordinary fact that Professor Ehrenberg finds
it almost wholly composed of matter which has been organised; 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. (21/5. "Monats. der Konig. Akad. d.
Wiss. zu Berlin" Vom April 1845.) 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.
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