of his efforts, and likewise from all care and anxiety regarding domestic concerns; the latter being provided for him when on board the Beagle, or arranged by those who accompanied him on his travels overland and by river.  The elimination of these minor cares tended to leave his mind free and open to absorb and speculate at comparative leisure upon all the strange phenomena which presented themselves throughout the long voyage.

A further point of interest in determining the ultimate gain or loss lies in the fact that Darwin’s private excursions had to be somewhat subservient to the movements of the Beagle under the command of Captain Fitz-Roy.  This, in all probability, was beneficial to one of his temperament—­unaccustomed to be greatly restricted by outward circumstances or conditions, though never flagrantly (or, perhaps, consciously) going against them.  The same applies in a measure to Wallace, who, on more than one occasion, confessed his tendency to a feeling of semi-idleness and dislike to any form of enforced physical exertion; but as every detail, involving constant forethought and arrangement, as well as the execution, devolved upon himself, the latent powers of methodical perseverance, which never failed him, no matter what difficulties barred his way, were called forth.  Darwin’s estimate of the “habit of mind” forced upon himself during this period may not inaptly be applied to both men:  “Everything about which I thought or read was made to bear directly on what I had seen, or was likely to see; 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]