One final conclusion is no less interesting. These absolutely countless flints, these monuments of imposing size, these stones of immense weight often brought from afar, these marvellous mounds and tumuli, bear witness to the presence of a population which was already considerable at the time of which we are endeavoring to make out the traces. A long series of centuries must have been needed for a people to increase to such an extent as to have spread over entire continents. And time was not wanting. Whatever antiquity may be attributed to the human race, whatever the initial date to which its first appearance may be relegated, this antiquity is but slight, this date is but modern, if we compare it with the truly incalculable ages of which geology reveals the existence. At every turn we are arrested by the immensity of time, the immensity of space, and yet our knowledge is still confined to the mere outer rind of the earth, and science cannot as yet even guess at the secrets hidden beneath that rind. In concluding these introductory remarks, we must add that very great difficulties await those who devote themselves to prehistoric studies—difficulties such as noise but those who have attempted to conquer them can realize. The rare traces of prehistoric man must be sought amongst the effects of the cataclysms that have devastated the earth, and the ruins piled up in the course of ages. We must show mall wrestling with the ever-recurrent difficulties of his hard life, and gradually developing in accordance with a law which appears to be immutable. Such is the aim of this work, and it is with gratitude that we assert at the beginning that the _pianta uomo_, the human plant, as Alfieri calls our race, was endowed by the Creator from the first with a very vigorous vitality, to enable it to contend with the dangers besetting its steps in the early days of its existence, and with a truly marvellous spirit, to be able to make so humble a beginning the starting-point for a destiny so glorious. 1 M. Gaston. 2 Pliny calls them _ceraunia gemma_ (“Natural History,” book ii., ch. 59 book xxxvii., ch. 51). 3 S. Reinach proves clearly enough that the collections of the Emperor Augustus were from Capri. 4 This skeleton was discovered in 1726 by Scheuchzer, a doctor of Œningen, and by him placed in the Leyden Museum, with the pompous inscription _Homo diluvii testis (Philosophical Transactions_, vol. xxxiv.). Cuvier, by scraping away the stone, revealed the true nature of the fossil. 5 “Ossium Fossilium Docimasia.” 6 “Mém. Acad. des Inscriptions,” 1734, vol. x., p. 163. 7 _Archæologia_, vol. ii., p. 118. 8 “The Antiquities of Warwickshire,” vol. iv., 1656. 9 _Archæologia_, vol. xiii., p. 105. 10 Castelfranco: _Revue d’Anthropologie_, 1887. 11 _Annales des Sciences Naturelles_, vol. xvii., p. 607. Cartailhac: _Matériaux_, 1884. 12 “Recherches sur les Ossements Fossiles de la Province de Liège.” 13 _Athenæum_, 16 July, 1859.