We can readily see that a knowledge of iron would spread in much the same way as did bronze. When first introduced, it would be rare and costly, and so would be used sparingly. Bronze axes have been found with the edge of iron. Afterwards, as it became more abundant, it would be used altogether for cutting instruments and weapons, while bronze, being more easily worked, would still be used for ornaments, brooches, etc. At Hallstadt, in Austria, was discovered a cemetery which evidently belongs to a time when iron was taking the place of bronze. In this case, the implements of bronze are those forms which we have learned were produced near the close of the Bronze Age. The iron implements are not those forms best suited for that metal, but imitations of those of bronze.5 We remember when bronze was first introduced, the weapons were simply copies of those forms already made in stone.6 We may suppose that a knowledge of iron would spread rapidly. The knowledge of metallurgy necessary for the production of bronze was at this time widely disseminated. It would require, therefore, but a hint to start them in experiments. In the dissemination of this knowledge, commerce, of course, played a most important part. Whenever the early Greek and Roman writers have occasion to mention the arms of the less civilized tribes of Europe, we learn they were of iron. This shows that at a very early time this knowledge had spread all over Europe.7 It is scarcely necessary to remark that the use of iron would not drive out the use of bronze. That would still be used for many purposes; and even stone would continue in use, at least for some purposes. At the battle of Marathon, arrow-heads and lances of stone were largely used. We can easily understand how, by one of a number of causes, some rude tribes, yet unacquainted with the use of metal, would come to occupy the site of some settlement, the inhabitants of which had been in the Bronze or Iron Age. This actually happened at ancient Troy, where the remains of a stone-using folk have been found above those of a people using metal. This, though an exception to the general rule, need give us no surprise.