The oldest undisputed traces of the presence of man on the earth that have hitherto been discovered are met with in the strata of the Drift Epoch, and it is only during the last generation that the existence of “Drift Man” has been palæontologically proved beyond dispute. The late Sir J. Prestwick believed, however--and his results have been confirmed by later discoveries--in the existence of evidence of the presence of man in Western Europe before the present river system of our land was established, long before the age of the “Drift” relics. The evidence consists of rudely shaped pieces of flint, apparently artificially chipped along one or more edges. These supposed implements are termed “Eoliths.” They were first discovered by Mr. Benjamin Harrison in the high-level plateau, probably of the Upper Pliocene Age, in Kent, and their significance is now widely accepted. Up to the middle of last century research appeared to have established as a positive fact that man could not be traced back to the older geological strata; remains of man were said to be found only in the newest stratum of the earth’s formation--in the alluvial, or “recent” stratum. The bones of man were accordingly claimed to be sure guides to the geological formations of the present time, as the bones of the mammoth and cave-bear were to the strata of the Drift. Where traces of man were found it was considered as proved by natural science that the particular stratum in which they occurred was to be allotted to the most recent system, which we see forming and being transformed under our eyes at the present day. [Illustration: A PAGE FROM NATURE’S HISTORY BOOK It is in the successive layers of the earth’s strata with their human and animal remains that we read the story of the past. Embedded in the earth itself we have the existence of “Drift Man” established. Our illustration is that of a section of the famous Kent’s Cavern, near Torquay, which is rich in prehistoric remains. ] [Sidenote: The Theory of Natural Catastrophes]