Mendoza was reached on March 27th, and on the 29th the return journey by the northern or Uspallata pass was commenced. On the 10th of April Santiago was again arrived at, and Mr. Caldcleugh most hospitably welcomed the traveller, delighted with his expedition. "Never," he says, "did I more deeply enjoy an equal space of time." Various excursions in Northern Chili and Peru followed. Little was seen of Peru, owing to the troubled state of public affairs, and there was very little regret when the _Beagle_ started early in September on her journey across the Pacific. The Galapagos Islands, with their two thousand volcanic craters, their apparently leafless bushes and wretched weeds, their peculiar animals, so unsuspicious of man that they did not move when stones were thrown, were extremely interesting to the naturalist, and gave rise to numerous observations and suggestions in later works. The huge tortoises slowly carrying their great bodies about, appeared like strange antediluvian animals. The hideous large water-lizard (_Amblyrhynchus_), swimming with perfect ease, and capable of an hour's immersion in sea-water; and the land lizard of the same genus, so numerous that at James Island it was hardly possible to find a spot free from their burrows, the roofs of which constantly give way under the pedestrian, were equally strange denizens of this group of islands, where reptiles replace herbivorous mammals. With regard to the last-mentioned species we find a remark indicating the persistence of a belief in special creation up to this date. "It would appear as if this species had been created in the centre of the Archipelago, and thence had been dispersed only to a certain distance." During the years intervening between the first and second editions of the Journal, reflection intensified Darwin's perception of the singularity of the Galapagos fauna. "Considering the small size of these islands," he says, "we feel the more astonished at the number of their aboriginal beings, and at their confined range. Seeing every height crowned with its crater, and the boundaries of most of the lava streams still distinct, we are led to believe that within a period geologically recent the unbroken sea was here spread out. Hence, both in space and time, we seem to be brought somewhat nearer to that great fact--that mystery of mysteries--the first appearance of new beings on this earth." And he afterwards says, "One is astonished at the amount of creative force, if such an expression may be used, displayed on these small, barren, and rocky islands; and still more so at its diverse yet analogous action in points so near each other."