But, leaving aside the question of their purpose, let us consider the evidence presented by the flints themselves. Do they exhibit the unmistakable traces of intentional chipping produced by a series of slight blows or thrusts, delivered in regular succession and in the same direction, with the result of forming a distinctly marked edge? And does the appearance of the action of fire upon their surface imply the intervention of intelligence? To both questions M. Adrien Arcelin, the well-known geologist of Mâcon, has given very sufficient replies in the negative. He has discovered numerous objects of precisely similar appearance in Eocene deposits in the neighborhood of Mâcon.[FC] But, instead of pushing man back on this account so much further into the past, he accounts for the marks of chipping to be seen on many of these objects as the result of the accidental shocks of one stone against another in the countless overturnings and movements to which the strata have been subjected during the long ages of geological time. He gives photographs of some of these objects, which are to me entirely convincing, and describes how he has surprised Nature in the very act of fabricating them in an abandoned quarry worked in an Eocene deposit. He thinks the "crackled" surfaces can be readily explained as the result of atmospheric action, or of hot springs charged with silex. Numerous examples of similar changes in the surface of flint, that have been noticed by himself and others in different localities, are instanced. Even if some have been caused by fire, this does not necessarily imply the intervention of man to have produced it. Similar discoveries have also been made by M. d'Ault de Mesnil, at Thenay, in Eocene deposits,[FD] and by M. Paul Cabanne, in the Gironde.[FE] My own opinion, based upon the experience of many years spent in the study of flints broken naturally as well as artificially, and upon a careful examination of Bourgeois's collections, is that the so-called Thenay flints are the result of natural causes. [Footnote FC: Matériaux pour l'Histoire Prim, et Nat. de l'Homme, tome xix, p. 193.] [Footnote FD: Matériaux, ibid., p. 246.] [Footnote FE: Id., tome xxii, p. 205.] The second locality where flints alleged to display marks of human action have been found is the vicinity of Aurillac, in the Auvergne, especially on the flanks of a hill called Puy-Courny. They occur in a conglomerate of the upper Miocene period, and are consequently much later than the Thenay flints. In this conglomerate, in 1869, M. Tardy discovered a worked flint flake which has every appearance of being artificial.[FF] Mortillet, however, says that it was found in the upper surface of the deposit, where there may easily have been a mingling with the Quaternary formation; and it certainly resembles worked flakes, which are not uncommon in the Quaternary. The geological determination of the find may consequently be regarded as uncertain.