The Romans, a more cosmopolitan people than the Greeks, paid great attention to the mineral wealth of their conquests, and were careful to choose the best _acies_[366] for their weapons. Diodorus Siculus[367] describes the process by which the Celtiberians prepared their iron for Swords. Pliny, who was Procurator of Spain under Vespasian, may have studied iron-mining and ore-working in the country which still produces the Toledo blade. He characterises the metal generally as being universally used and occurring in every part of the world—especially in Ilva, now Elba, where there are mines of oligiste, specular iron or iron glance. His process of steel-making is that of the Greeks. ‘Fornacum maxima differentia est; in eis equidem nucleus ferri’ (the σίδηρος ἐργασμένος or worked iron of Aristotle) ‘excoquitur ad indurandum; aliter alioque modo ad densandas incudes, malleorumve rostra’ (xxxiv. 41). Hence it appears that the Romans had one way to make steel, and another to harden and temper tools, picks, and anvils. ‘Possibly,’ says Dr. Martin Lister, ‘the latter were boiled in “sow-metal,” as the term _densare_ seems to suggest.’ Roman mining-operations were often conducted on a large scale. The Forest of Dean and the Wealds of Kent and Sussex, not to mention other parts of England, show heaps of old slag containing classical pottery and coins of Nero, Vespasian, and Diocletian. They obtained the regulus[368] by the direct process, and used charcoal in rude Catalan furnaces; the work was imperfect, and the scoriæ contain a large percentage of metal. Ancient adits and shafts in Shropshire[369] and elsewhere have preserved the rude implements with which they made the natives labour in _corvée_. The hill-sides of Carthagena on the seaboard of Murcia (South-Eastern Spain) had been explored for lead and silver by the earliest Carthaginian colonists; and the industry was at its height when Nova Carthago, under Roman rule, became (B.C. 200) a flourishing municipium, the centre of a large population. At this time as many as forty thousand hands were regularly employed. In our seventh century the Arab invasion ruined the mines, not only of this district, but of every province occupied by the ‘Moors.’ About the mid-fifteenth century a revival was attempted; but this was checked at the beginning of the sixteenth, when the mines of Spanish America were opened: the Emperor Charles V. also would not see the soil of his European dominions disturbed by digging. The miners emigrated in mass, and New Carthage was forgotten till within the last half-century. According to M. Alfred Massart,[370] the ancient masses of plumbiferous scoriæ were large enough to pay for re-working. A superficial area of eight square leagues yielded some eight hundred thousand tons of iron-ore, of which two-thirds were ferro-manganese, and twenty thousand to twenty-five thousand tons of lead containing thirty thousand kilogrammes of silver.