In this manner Schwalbe(11) confirms Boule's estimates of the variations in the cubic capacity of the brain in different members of the Neanderthal race as follows: Neanderthal race--La Chapelle 1620 c.cm. " " --Neanderthal 1408 " " " --La Quina 1367 " " " --Gibraltar 1296 " Thus the variations between the largest known brain in one member of the Neanderthal race, the male skull of La Chapelle, and the smallest brain of the same race, the supposed female skull of Gibraltar, is 324 c.cm., a range similar to that which we find in the existing species of man (_Homo sapiens_). [Illustration: FIG. 2. The skull and brain-case, showing the low, retreating forehead, prominent supraorbital ridges, and small brain capacity, of _Pithecanthropus_, the java ape-man, as restored by J. H. McGregor.] As another test for the classification of primitive skulls, we may select the well-known _frontal angle_ of Broca, as modified by Schwalbe, for measuring the retreating forehead. The angle is measured by drawing a line along the forehead upward from the bony ridge between the eyebrows, with a horizontal line carried from the _glabella_ to the _inion_ at the back of the skull. The various primitive races are arranged as follows: PER CENT _Homo sapiens_, with an average forehead frontal angle 90 _Homo sapiens_, with extreme retreating forehead " " 72.3 _Homo neanderthalensis_, with the least retreating forehead " " 70 _Homo neanderthalensis_, with the most retreating forehead " " 57.5 _Pithecanthropus erectus_ (Trinil race) " " 52.5 Highest anthropoid apes " " 56 For instance, this illustrates the fact that in the Trinil race the forehead is actually lower than in some of the highest anthropoid apes; that in the Neanderthal race the forehead is more retreating than in any of the existing human races of _Homo sapiens_. ARCHÆOLOGY OF THE OLD STONE AGE[I] The proofs of the prehistory of man arose afresh, and from an entirely new source, in the beginning of the eighteenth century through discoveries in Germany, by which the Greek anticipations of a stone age were verified. For a century and a half the great animal life of the diluvial world had aroused the wonder and speculation of the early naturalists. In 1750 Eccardus(17) of Braunschweig advanced the first steps toward prehistoric chronology, in expressing the opinion that the human race first lived in a period in which stone served as the only weapon and tool, and that this was followed by a bronze and then by an iron period of human culture. As early as 1700 a human skull was discovered at Cannstatt and was believed to be of a period as ancient as the mammoth and the cave-bear.[J]