That is the line of thought according to which Boucher de Perthes was able, in 1839, to lay before the leading experts in Paris--at their head Cuvier himself--his discoveries proving the former existence of Drift man. But his demonstrations were not then sufficient to break the old ban of prejudices that were apparently founded on such good scientific bases; his proofs of the presence of man in the Somme valley at the time of the Drift, contemporaneously with the extinct Drift animals, were ridiculed. It was twenty years before these long-neglected discoveries in the Somme valley concerning the early history of man were recognised by the scientific world. This was only made possible by Lyell, whose authority as a geologist had risen above Cuvier’s, placing the whole weight of it on Boucher’s side, after having personally travelled over the Somme valley three times in the year 1859, and having himself examined all the chief places where relics of Drift Man had been discovered. According to Lyell’s description, the Somme valley lies in a district of white chalk, which forms elevations of several hundred feet in height. If we ascend to this height we find ourselves on an extensive tableland, showing only moderate elevations and depressions, and covered uninterruptedly for miles with loam and brick earth about five feet thick and quite devoid of fossils. Here and there on the chalk may be noticed outlying patches of Tertiary sand and clay, the remains of a once extensive formation, the denudation of which has chiefly furnished the Drift gravel material in which the relics of man and the bones of extinct animals lie buried. The Drift alluvial deposit of the Somme valley exhibits nothing extraordinary in its stratification or outward appearance, nor in its composition or organic contents. The stratum in which the bones of the Drift fauna are found intermingled with the relics of man is partly a marine and partly a fluviatile deposit. The human relics in particular are mostly buried deep in the gravel; almost everywhere one has to pass down through a mass of overlying loam with land shells, or a fine sand with fresh-water molluscs, before coming to beds of gravel, in which the relics of Drift Man are found. [Sidenote: Animals of the Ice Age]