So with a glimpse of these human tadpoles, in their deep close gallery, with their boring machinery ringing away, and artificial lights glaring and casting black shadows, the Professor's horoscope concludes. Humanity in dismal retreat before the cold, changed beyond recognition. Yet the Professor is reasonable enough, his facts are current science, his methods orderly. The contemplative man shivers at the prospect, starts up to poke the fire, and the whole of this remarkable book that is not written vanishes straightway in the smoke of his pipe. This is the great advantage of this unwritten literature: there is no bother in changing the books. The contemplative man consoles himself for the destiny of the species with the lost portion of Kubla Khan. THE EXTINCTION OF MAN It is part of the excessive egotism of the human animal that the bare idea of its extinction seems incredible to it. "A world without _us_!" it says, as a heady young Cephalaspis might have said it in the old Silurian sea. But since the Cephalaspis and the Coccosteus many a fine animal has increased and multiplied upon the earth, lorded it over land or sea without a rival, and passed at last into the night. Surely it is not so unreasonable to ask why man should be an exception to the rule. From the scientific standpoint at least any reason for such exception is hard to find. No doubt man is undisputed master at the present time--at least of most of the land surface; but so it has been before with other animals. Let us consider what light geology has to throw upon this. The great land and sea reptiles of the Mesozoic period, for instance, seem to have been as secure as humanity is now in their pre-eminence. But they passed away and left no descendants when the new orders of the mammals emerged from their obscurity. So, too, the huge Titanotheria of the American continent, and all the powerful mammals of Pleistocene South America, the sabre-toothed lion, for instance, and the Machrauchenia suddenly came to a finish when they were still almost at the zenith of their rule. _And in no case does the record of the fossils show a really dominant species succeeded by its own descendants._ What has usually happened in the past appears to be the emergence of some type of animal hitherto rare and unimportant, and the extinction, not simply of the previously ruling species, but of most of the forms that are at all closely related to it. Sometimes, indeed, as in the case of the extinct giants of South America, they vanished without any considerable rivals, victims of pestilence, famine, or, it may be, of that cumulative inefficiency that comes of a too undisputed life. So that the analogy of geology, at anyrate, is against this too acceptable view of man's certain tenure of the earth for the next few million years or so.