"Geologising in a volcanic country is most delightful; besides the interest
attached to itself, it leads you into most beautiful and retired spots.
Nobody but a person fond of Natural History can imagine the pleasure of
strolling under cocoa-nuts in a thicket of bananas and coffee-plants, and
an endless number of wild flowers. And this island, that has given me so
much instruction and delight, is reckoned the most uninteresting place that
we perhaps shall touch at during our voyage. It certainly is generally very
barren, but the valleys are more exquisitely beautiful, from the very
contrast. It is utterly useless to say anything about the scenery; it would
be as profitable to explain to a blind man colours, as to a person who has
not been out of Europe, the total dissimilarity of a tropical view.
Whenever I enjoy anything, I always look forward to writing it down, either
in my log-book (which increases in bulk), or in a letter; so you must
excuse raptures, and those raptures badly expressed. I find my collections
are increasing wonderfully, and from Rio I think I shall be obliged to send
a cargo home."

The indelible impression made on Darwin's mind by this first visit to a
volcanic island, is borne witness to by a remarkable passage in the
"Autobiography" written by him in 1876. "The geology of St. Jago is very
striking, yet simple; a stream of lava formerly flowed over the bed of the
sea, formed of triturated recent shells and corals, which it has baked into
a hard white rock. Since then the whole island has been upheaved. But the
line of white rock revealed to me a new and important fact, namely that
there had been afterwards subsidence round the craters which had since been
in action, and had poured forth lava. It then first dawned on me that I
might perhaps write a book on the geology of the various countries visited,
and this made me thrill with delight. That was a memorable hour to me, and
how distinctly I can call to mind the low cliff of lava beneath which I
rested, with the sun glaring hot, a few strange desert plants growing near