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536 This table is as eloquent as figures alone can be. We are forced to the conclusion that the general rule of one-sided marginal chipping, beginning at the edge and extending over the back, is the expression of a distinct definite purpose. We know the reason for it, namely, utility. Natural agencies are not moved by any such definite purpose. Thus, when we find flint flakes, no matter where, that possess a bulb of percussion; when, further, these flakes show series of chippings all on one side, and when 95 per cent of the specimens are chipped according to the rule laid down, we can not then escape the conclusion that the pieces in question are artifacts. Among the eolithic industries at present known, there are only two where the bulb of percussion is at all common. The first is the Cantalian of upper Miocene age, the second is at the top of the eolithic series, the so-called Mesvinian at the summit of the lower Quaternary.

Before definitely lopping off the first and third divisions of the stone age, it would be well to note their position and relative weight in the chronological scale. A table of classification in harmony with the teachings of both Rutot and Penck is reproduced in plate 1. It will be seen that the eolithic probably begins with the middle Oligocene, reappears in the Miocene and Pliocene, and is carried up through the lower Quaternary. The paleolithic, once considered as commensurate with the whole of the Quaternary, is now limited to its middle and upper horizons. The neolithic is confined to post-Quaternary times.

The contributions to our knowledge of the paleolithic during the decade in question may for convenience be grouped under three heads: (1) Those relating to finds in valley deposits; (2) cavern explorations, and (3) the discoveries of human skeletal remains. As examples of the first group, I have chosen the researches of Commont at Saint-Acheul (France) and of Szombathy, Hoernes, and Obermaier at Willendorf (Austria-Hungary).

The housing and transporting required by modern civilization have led to the discovery of the culture levels attained by our paleolithic forebears. At Saint-Acheul the deposits of the Somme Valley have been exploited since 1771 at least. They yield not only material for building purposes, but also sand for foundries and flint for road metal. The first discovery of a paleolithic industry at Saint-Acheul was made by Doctor Rigollot in 1854, following on and inspired by Boucher de Perthes's discoveries at Abbeville. Then came Gaudry, Prestwich, and Evans, all now dead. Explorations at Saint-Acheul have been carried on for the past twenty-five years by d'Acy. The most active investigator on the ground at present is V. Commont, whose systematic work there covers a period of nearly ten years.