[Illustration: FIG. 18. A KNIFE OF THE IRON EPOCH.] Some of the Swiss lake-dwellings of Neuchatel and Bienne belong to this epoch. Dr. Keller, in summing up some of his observations, has made use of the following language: "The phenomenon of the lake-dwellings, so important in the history of civilization, the time of their first establishment, their original design, their development, and their final extinction, in spite of many accumulated facts, is in many respects clouded in doubt.... It is certain from the very beginning of this peculiar mode of living to the latest period of its existence, while outward circumstances remained the same, a quiet advance to a better development of the conditions of life may be observed, in which there was neither retrogression nor any sudden advance by the intervention of foreign elements. The general diffusion of metals in a country which had none, is explained simply by the barter which existed throughout Europe in the very earliest ages. The question why the inhabitants of a lake-dwelling of the stone age abandoned their settlements, while those of another, not many hours' or many minutes' walk distant, remained quietly living on their platforms, is of no greater importance than the inquiry why, during the middle ages, so many localities have disappeared, the names and situations of which are known to us. The presence of objects of industry on the area of the lake-dwellings has nothing in it very surprising, if we consider what misfortunes villages of straw-covered huts were exposed to, in which not only the houses themselves, but even the platforms on which they stood, were formed of very combustible materials. It is possible, if we are to take Cæsar's account literally, that when the Helvetii, whose arrival in the country is neither mentioned in history nor shown by archæology, withdrew, the lake-dwellings then existing were, as a whole, burned down; but there can also be no doubt that some remained standing, or were rebuilt after the return of the population. Their continuing down to the Roman time is only astonishing to any one who imagines that at this time the whole population had gone over to the Roman manner of life, while the proof lies before him that the lower class adhered to their own manners and customs till the entrance of the German races."[79] CHAPTER XIV. TRACES OF MAN IN AMERICA.