The arguments from geology in favor of a great antiquity for man may be summarized thus: (1) Human remains are found in caverns under very thick stalagmitic crusts, and in deposits of earth which must have accumulated before these stalagmites began to form, and when the caverns were differently situated with reference to the local drainages. (2) Remains of man are found under peat-bogs which have grown so little in modern times that their antiquity on the whole must be very great. (3) Implements, presumably made by men, are found in river-gravels so high above existing riverbeds that great physical changes must have occurred since they were accumulated. (4) One case is on record where a human bone is believed to have been found under a deposit of glacial age. (5) Human remains have been found under circumstances which indicate that very important changes of level have taken place since their accumulation. (6) Human remains have been found under circumstances which indicate great changes of climate as intervening between their date and that of the modern period. (7) Man is known to have existed, in Europe at least, at the same time with some quadrupeds formerly supposed to have been extinct before his introduction. (8) The implements, weapons, etc., found in the oldest of these repositories are different from those known to have been used in historic times. These several heads include, I think, all the really material evidence of a geological character. It is evidence of a kind not easily reducible into definite dates, but there can be no doubt that its nature, and the rapid accumulation of facts within a small number of years, have created a deep and widespread conviction among geologists and archaeologists that we must relegate the origin of man to a much more remote antiquity than that sanctioned by history or by the Biblical chronology. I shall first review the character of this evidence, and then state a number of geological facts which bear in the other direction, and have been somewhat lost sight of in recent discussions. Of the facts above referred to, the most important are those which relate to caverns, peat-bogs, and river-gravels. We may, therefore, first consider the nature and amount of this evidence. That the reader may more distinctly understand the geological history of these more recent periods of the earth's history which are supposed to have witnessed the advent of man, in Western Europe at least, I quote the following summary from Sir Charles Lyell of the more modern changes in that portion of the world. These are: