It is recognized, however, by means of the proofs furnished by archæological and philological researches, that the different races of mankind which have succeeded one another in Europe have exhibited a constant progression, not only in physical development, but also in intelligence and in the aptitude to practise various industries and arts. The remains found in many regions exhibit this gradual advancement, until, from a state which appears that of savagedom, we arrive at a period when domestic animals are kept, and a knowledge of metallurgy is obvious. It is only, however, when we come to the epoch of the early migrations of the Aryan or Indo-Germanic races, that we find substantial traces of the employment of metals. The most important of these migrations, that of the Cimbri, who, with the Gauls, founded the Celtic race some eighteen hundred years before our era, and introduced Druidism into Gaul, when it reached Europe knew no other metals than gold, copper, tin, and the combination of the last two—brass. A study of Sanscrit, the mother-tongue of all these Aryan peoples, shows this to have been the case. The working in iron, or the 'IronAge,' even with some civilized peoples, did not occur until a comparatively recent time. Lucretius admits that gold and brass were known before iron:
Sed prius æris erat quam ferri cognitus usus.
As no other migration of any importance occurred until that of the hordes who destroyed the Roman empire, and as we have seen that iron was worked by the Gauls long before the Christian era, it is between the period when the Gallo-Cimbri arrived, and the conquest of Gaul by
