and this habit of mind was continued during the five years of the
voyage. I feel sure that it was this training which enabled me to do
whatever I have done in science."

It may be further assumed that Darwin was better equipped mentally--from
a scientific point of view--owing to his personal intercourse with
eminent scientific men previous to his assuming this responsible
position. Wallace, on the contrary, had practically little beyond
book-knowledge and such experience as he had been able to gain by
solitary wanderings in the localities in which he had, by circumstances,
been forced to reside. His plan of operations must, therefore, have been
largely modified and adapted as time went on, and as his finances
allowed. To both, therefore, credit is due for the adaptability evinced
under conditions not always congenial or conducive to the pursuits they
had undertaken.

Although the fact is not definitely stated by Wallace, it may readily be
inferred that the idea of making this the starting-point of a new life
was clearly in his mind; while Darwin simply accepted the opportunity
when it came, and was only brought to a consciousness of its full
meaning and bearing on his future career whilst studying the geological
aspect of Santiago when "the line of white rock revealed 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," he says, "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, and with
living corals in the tidal pools at my feet!"[11]