QUOTE : In the Palæozoic period, as we have said, life had not spread beyond the swampy river valleys and the borders of sea lagoons and the like; but in the Mesozoic, life was growing ever more accustomed to the thinner medium of the air, was sweeping boldly up over the plains and towards the hillsides. It is well for the student of human history and the human future to note that. If a disembodied intelligence with no knowledge of the future had come to earth and studied life during the early Palæozoic age, he might very reasonably have concluded that life was absolutely confined to the water, and that it could never spread over the land. It found a way. In the Later Palæozoic Period that visitant might have been equally sure that life could not go beyond the edge of a swamp. The Mesozoic Period would still have found him setting bounds to life far more limited than the bounds that are set to-day. And so to-day, though we mark how life and man are still limited to five miles of air and a depth of perhaps a mile or so of sea, we must not conclude from that present limitation that life, through man, may not presently spread out and up and down to a range of living as yet inconceivable.