In chapter fifth we have a minute and interesting account of such fossil human skulls and skeletons as have been found in caves and ancient tumuli, and a careful endeavor made to estimate their approximate age. In 1857, in a cave situated in that part of the valley of the Duessel, near Duesseldorf, which is called the Neanderthal, a skull and skeleton were found, buried beneath five feet of loam, which were pronounced by Professor Huxley and others to be clearly human, though indicating small cerebral development and uncommon strength of corporeal frame. In the Engis caves, near Liege, portions of six or seven human skeletons were found, imbedded in the same matrix with the remains of the elephant, rhinoceros, bear, hyena, and other extinct quadrupeds. In an ancient tumulus near Borrely, in Denmark, a human skull was discovered which was adjudged by its surroundings to belong to the 'stone period' of Denmark, or the era of the Scotch fir. The careful anatomical examination and comparison to which these skulls have been subjected, have led to important discussions, not only as to their age, but also as to their relation to existing races. Next comes an extended account of the flint implements and other works of art, found so abundantly in juxtaposition with the bones of extinct mammalia, in various localities--in a cave at Brixham, near Torquay, in Devonshire; in the alluvium of the Thames valley; in the gravel of the valley of the Ouse, near Bedford; in a fresh-water deposit at Hoxne in Suffolk; in the valley of the Lach at Icklingham; in a cavern in Somersetshire; in the caves of Gomer in Glamorganshire, in South Wales; and especially in the gravel beds of Abbeville and Amiens, in France, and various localities of the valley of the Somme. As to these flint implements, they are chiefly knives, hatchets, and instruments of that sort, and they have been found in such large numbers, and such diverse localities, and so uniformly in close proximity with the remains of the same species of extinct mammalia, that the evidence derived from them is, to say the least, of a very weighty character, and in the opinion of Sir Charles Lyell clearly establishes the fact that _Elephas primigenius_, _Elephas antiquus_, _Rhinoceros tichorrhinus_, _Ursus speloeus_, and other extinct species of the post-pliocene alluvium, _coexisted with man_.