through wild countries, or in the boats, some of which lasted
several weeks, were deeply interesting: their discomfort and
some degree of danger were at that time hardly a drawback, and
none at all afterwards. I also reflect with high satisfaction on
some of my scientific work, such as solving the problem of coral
islands, and making out the geological structure of certain
islands, for instance, St. Helena. Nor must I pass over the
discovery of the singular relations of the animals and plants
inhabiting the several islands of the Galapagos archipelago, and
of all of them to the inhabitants of South America.

As far as I can judge of myself, I worked to the utmost during
the voyage from the mere pleasure of investigation, and from my
strong desire to add a few facts to the great mass of facts in
Natural Science. But I was also ambitious to take a fair place
among scientific men,--whether more ambitious or less so than
most of my fellow-workers, I can form no opinion.

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