Cuvier, the great contemporary of Laplace, no doubt accepted the nebular hypothesis as a valid explanation of the origin of the world, but he held to the conception of about six thousand years for the age of man as rigidly as did any Middle Age monk. Cuvier was the first to demonstrate that certain fossil skeletons belonged to no existing species of animal. In other words, he believed that races of great beasts had once inhabited the earth, but no longer have living representatives. This, however, did not suggest to him that the earth had long been peopled, but only went to show, as he believed, that a great catastrophe, as the universal flood was supposed to have been, had actually taken place. It remained for Charles Lyell, the famous English geologist, working along the lines first suggested by another great Englishman, James Hutton, to prove that the successive populations of the earth, whose remains are found in fossil beds, had lived for enormous periods of time, and had supplanted one another on the earth, not through any sudden catastrophe, but by slow processes of the natural development and decay of different kinds of beings. Following the demonstrations of Lyell there came about a sudden change of belief among geologists as to the age of the earth, until, in our day, the period during which the earth has been inhabited by one kind of creature and another is computed, not by specific thousands, but by vague hundreds of thousands or even millions of years. The last refuge for champions of the old chronology was found in the claim that man himself had been but about six thousand years upon the earth, whatever might be true of his non-human forerunners. But even this claim had presently to be abandoned when the researches of the palæontologists had been directed to the subject of fossil man. The researches of Schmerling, of Boucher de Perth, of Lyell himself, and of a host of later workers demonstrated that fossil remains of man were found commingled in embedded strata and in cave bottoms under conditions that demonstrated their extreme antiquity; and in the course of the quarter century after 1865, in which year Lyell had published his epoch-marking work on the antiquity of man, the new idea had made a complete conquest, until now no one any more thinks of disputing the extreme antiquity of man than he thinks of questioning the great age of the earth itself. To be sure, no one pretends any longer to put a precise date upon man’s first appearance. The new figures take on something of the vagueness that characterise the estimates of the Babylonians; but it is accepted as clearly proven that the racial age of man is at least to be numbered in tens of thousands of years. The only clues at present accessible that tend to give anything like definiteness to the computations are the researches of Egyptologists and Assyriologists.