In the Bible narrative, for example, wherein, as has before been said, certain events of the world’s history are related with distinctness, but where as a rule nothing is said of the times which intervened between them, we are wont to make very insufficient allowance for these unmentioned periods, and form for ourselves a rather arbitrary picture of the real course of things, fitting two events on to one another which were really separated by long ages. To correct this view, to enlarge the series of known facts concerning the early history of the human race, comes in pre-historic inquiry; and again, to correct the picture we now form, doubtless fresh information will continue to pour in. All this is no reason why we should pronounce our present picture to be untrue; it is only incomplete. We must be always ready to enlarge it, and to fill in the outlines, but still we can only remember the facts which we have already acquired, if we look at them, not as fragments only, but as a complete whole. In representing, therefore, throughout the following chapters, the advance of the human race in the discovery of all those arts and faculties which go to make up civilization in the light of a continuous progress, it will not be necessary to pause and remind the reader in every case that these steps of progress which seem to spread themselves out so clearly before us have been made in an uncertain manner, sometimes rapidly, sometimes very slowly and painfully, sometimes by immense strides, sometimes by continual haltings and goings backwards and forwards. It will be enough to say here, once for all, that our history must be thought of as a history of events rather than a strictly chronological one; just as the geological periods are not measured by days and years, but by the mutations through which our solid-seeming earth has passed. * * * * * [Sidenote: The earliest traces of man.] First we turn to what must needs be our earliest inquiry--the search after the oldest traces of man which have been found upon the earth. It has been said that one of the first fruits of knowledge is to show us our own ignorance; and certainly in the early history of the world and of man there is nothing which science points out so clearly as the vast silent periods whereof until recently we had no idea. It is difficult for us of the present age to remember how short a time it is since all our certain knowledge, touching the earth on which we live, lay around that brief period of its existence during which it had come under the notice and the care of man.