And now let me remind you that this second zone of knowledge outside the bright area of what we have felt and witnessed and handled for ourselves--this zone of hearsay and history and tradition--completed the whole knowledge of the past that was accessible to Shakespeare, for example. To these limits man's knowledge of the past was absolutely confined, save for some inklings and guesses, save for some small, almost negligible beginnings, until the nineteenth century began. Besides the correct knowledge in this scheme of hearsay and history a man had a certain amount of legend and error that rounded off the picture in a very satisfactory and misleading way, according to Bishop Ussher, just exactly 4004 years B.C. And that was man's universal history--that was his all--until the scientific epoch began. And beyond those limits--? Well, I suppose the educated man of the sixteenth century was as certain of the non-existence of anything before the creation of the world as he was, and as most of us are still, of the practical non-existence of the future, or at any rate he was as satisfied of the impossibility of knowledge in the one direction as in the other. But modern science, that is to say the relentless systematic criticism of phenomena, has in the past hundred years absolutely destroyed the conception of a finitely distant beginning of things; has abolished such limits to the past as a dated creation set, and added an enormous vista to that limited sixteenth century outlook. And what I would insist upon is that this further knowledge is a new kind of knowledge, obtained in a new kind of way. We know to-day, quite as confidently and in many respects more intimately than we know Sargon or Zenobia or Caractacus, the form and the habits of creatures that no living being has ever met, that no human eye has ever regarded, and the character of scenery that no man has ever seen or can ever possibly see; we picture to ourselves the labyrinthodon raising its clumsy head above the water of the carboniferous swamps in which he lived, and we figure the pterodactyls, those great bird lizards, flapping their way athwart the forests of the Mesozoic age with exactly the same certainty as that with which we picture the rhinoceros or the vulture. I doubt no more about the facts in this farther picture than I do about those in the nearest. I believe in the megatherium which I have never seen as confidently as I believe in the hippopotamus that has engulfed buns from my hand. A vast amount of detail in that farther picture is now fixed and finite for all time. And a countless number of investigators are persistently and confidently enlarging, amplifying, correcting, and pushing farther and farther back the boundaries of this greater past--this prehuman past--that the scientific criticism of existing phenomena has discovered and restored and brought for the first time into the world of human thought. We have