The task is quite easy, so long as we have books to help us, histories to tell us year by year all that went on in every part of the Great Round World, as our newspapers tell us day by day what is going on in it now.  But books do not take us very far back.  It is only four hundred years since printing was invented, and not more than six hundred since the art of making paper out of rags has been known.  But people could write hundreds and hundreds of years before that was invented, and used almost anything to record the memorable doings of their day—­bark of trees, skins of animals (parchment), “papyrus,” a material made of the fibres of a plant.  Short inscriptions over the entrances of temples and palaces, or cut with the chisel on monuments erected in memory of great events or above the graves of famous men, and long inscriptions covering whole walls or even the face of high rocks smoothed for the purpose, were like so many stone books, pages of which are continually discovered and read by our scholars.

But we come at last to times so remote that there is not a trace of the roughest writing, not a fragment of the crudest monument, to tell us the story of the men who, then as now, must have thought and labored and invented, only so much more slowly, under difficulties which we can hardly picture to ourselves.  “What, then,” is the natural question, “what can we know of such times, and of earlier ones still?  How do we know things happened in the manner described a few pages back?” We know it, in the first place, by analogy, i.e., because the same things have happened over and over again in the same manner in times which we know all about, and are happening now, under our eyes—­for what is the constant tide of immigration which keeps coming in from the East but, under modern conditions, the same swarming off from overcrowded native hives of seekers after more land and new fortunes?  In the second place, the oldest races of the world left abundant traces by which we can determine not only the places of their settlements, but their mode of life and the degree of culture they successively reached.

There has certainly been a time when men did not know enough to build dwellings for themselves—­or, not to be unfair, had not the necessary tools—­but lived in the forests which then very nearly covered the globe, using such natural shelter as they found ready for them, almost like the savage animals which it was their main business to fight and kill in self-defence and also for food and clothing.  Caverns in steep mountain-sides must have been their most luxurious, because safest and best-protected, retreats.  Many dozens of such caverns are known in all parts of the world, and the tale they tell is not difficult to read.  Several have become very famous, from the wealth of finds with which they rewarded the searchers.  Some appear to have been used as burying-places, for the ground in them is covered to a great depth with broken-up human skulls and skeletons, while outside, on the rocky ledges or platforms before the mouth of the cavern, are found the traces of large fires, built again and again on the same spot—­ashes, and cinders, and charred bones of animals; also broken marrow-bones, horns, hoofs, and other remains of plentiful meals, showing that then already it was the custom to feast at funerals.