The review has been a pleasant one, for it is a record of progress. The difference between the culture of the Neolithic and the Iron Age is great, but it is simply a development, the result of a gradual growth. Civilization and history have only hastened this growth. If we look around us to-day we can trace the elements of our civilization back through the eras of history, and though the faint beginning of some can be noticed, yet many of them come down to us from prehistoric times. We have treated of these early people in the three stages of culture known as the Neolithic, Bronze, and Iron Ages. We have seen there is no hard and fast line dividing the different stages of culture. To borrow the words of another, these stages of progress, like the three principal colors of the rainbow, overlap, intermingle, and shade off the one into the other, and yet in the main they are well defined.16 We instinctively long to set bounds to the past, to measure it by the unit of years. It affords us satisfaction to give dates for events long since gone by. For any event in the domain of history, it is natural and appropriate to gratify this desire. It gives precision to our thoughts, and more firmly fixes the march of events. But the historical portion of human life on the globe is but a small part of the grand whole. When we pass beyond history, or into prehistoric times, we find ourselves utterly at a loss as to dates. We have referred in the preceding pages to the commonly accepted belief of a few years ago, that, at most, a few thousand years express the whole period of human life on the globe. This was supposed to be the teaching of the Scriptures, but Infinite Wisdom left not only his word, but he left an imperishable record of the past in rocky strata and excavated valley, in dripping caves and mountain masses. When it was seen that the claims of geology for a greatly extended past, one transcending the powers of the human mind to conceive its length, could no longer be successfully denied, then it was that earnest investigators in the field of human antiquity could no longer shut their eyes to the fact that if geological evidence were worth any thing, man must have existed in the world for a far longer time than one covered by the brief period hitherto relied on.