That definite period at which man was introduced upon the scene seems to have been specially determined by the conditions of correspondence which the phenomena of his habitation had at length come to assume with the predestined constitution of his mind. The large reasoning brain would have been wholly out of place in the earlier ages. It is indubitably the nature of man to base the conclusions which regulate all his actions on fixed phenomena,—he reasons from cause to effect, or from effect to cause; and when placed in circumstances in which, from some lack of the necessary basis, he cannot so reason, he becomes a wretched, timid, superstitious creature, greatly more helpless and abject than even the inferior animals. This unhappy state is strikingly exemplified by that deep and peculiar impression made on the mind by a severe earthquake, which Humboldt, from his own experience, so powerfully describes. “This impression,” he says, “is not, in my opinion, the result of a recollection of those fearful pictures of devastation presented to our imagination by the historical narratives of the past, but is rather due to the sudden revelation of the delusive nature of the inherent faith by which we had clung to a belief in the immobility of the solid parts of the earth. We are accustomed from early childhood to draw a contrast between the mobility of water and the immobility of the soil on which we tread; and this feeling is confirmed by the evidence of our senses. When, therefore, we suddenly feel the ground move beneath us, a mysterious force, with which we were previously unacquainted, is revealed to us as an active disturber of stability. A moment destroys the illusion of a whole life; our deceptive faith in the repose of nature vanishes; and we feel transported into a realm of unknown destructive forces. Every sound—the faintest motion of the air—arrests our attention, and we no longer trust the ground on which we stand. There is an idea conveyed to the mind, of some universal and unlimited danger. We may flee from the crater of a volcano in active eruption, or from the dwelling whose destruction is threatened by the approach of the lava stream; but in an earthquake, direct our flight whithersoever we will, we still feel as if we trod upon the very focus of destruction.” Not less striking is the testimony of Dr. Tschudi, in his “Travels in Peru,” regarding this singular effect of earthquakes on the human mind. “No familiarity with the phenomenon can,” he remarks, “blunt the feeling. The inhabitant of Lima, who from childhood has frequently witnessed these convulsions of nature, is roused from his sleep by the shock, and rushes from his apartment with the cry of ‘_Misericordia_!’ The foreigner from the north of Europe, who knows nothing of earthquakes but by description, waits with impatience to feel the movements of the earth, and longs to hear with his own ear the subterranean sounds, which he has hitherto considered fabulous.