Doubtless we all possess the feeling in some degree--the sense of loneliness and desolation and dismay at the thought of an uninhabited world, and of long periods when man was not. Is it not the absence of human life or remains rather than the illimitable wastes of thick-ribbed ice and snow which daunts us at the thought of Arctic and Antarctic regions? Again, in the story of the earth, as told by geology, do we not also experience the same sense of dismay, and the soul shrinking back on itself, when we come in imagination to those deserts desolate in time when the continuity of the race was broken and the world dispeopled? The doctrine of evolution has made us tolerant of the thought of human animals,--our progenitors as we must believe--who were of brutish aspect, and whose period on this planet was so long that, compared with it, the historic and prehistoric periods are but as the life of an individual. A quarter of a million years has perhaps elapsed since the beginning of that cold period which, at all events in this part of the earth, killed Palaeolithic man; yet how small a part of his racial life even that time would seem if, as some believe, his remains may be traced as far back as the Eocene! But after this rude man of the Quaternary and Tertiary epochs had passed away there is a void, a period which to the imagination seems measureless, when sun and moon and stars looked on a waste and mindless world. When man once more reappears he seems to have been re-created on somewhat different lines. It is this break in the history of the human race which amazes and daunts us, which "shadows forth the heartless voids and immensities of the universe, and thus stabs us from behind with the thought of annihilation." Here, in these words of Hermann Melville, we are let all at once into the true meaning of those disquieting and seemingly indefinable emotions so often experienced, even by the most ardent lovers of nature and of solitude, in uninhabited deserts, on great mountains, and on the sea. We find here the origin of that horror of mountains which was so common until recent times. A friend once confessed to me that he was always profoundly unhappy at sea during long voyages, and the reason was that his sustaining belief in a superintending Power and in immortality left him when he was on that waste of waters, which have no human associations. The feeling, so intense in his case, is known to most if not all of us; but we feel it faintly as a disquieting element in nature of which we may be but vaguely conscious.