There is evidence of considerable volume of trade at this time. The Mediterranean was the theater of an extended commerce. Phœnician sailors not only ventured to brave the Mediterranean sea, but carried their vessels out on the Atlantic at as early a date as 500 B.C. The Greek traders were also active. Massilia, or as it is known in modern times, Marseilles, was the seat of a thriving trade. African ivory has been found in the tombs of Hallstadt, in Austria, in connection with ornaments of amber from the Baltic, and gold from Transylvania. The inhabitants of this town possessed in their salt mines the source of a lucrative trade. The trader of the Iron Age was able to take an immense stride by reason of the invention of money. Heretofore, in Europe, we have not met with coins, and trade must have been carried on by means of barter. Gallic Coin. Acquainted as we are at the present day with money and the mechanism of exchange, it is difficult to see how any extended trade could be carried on without some unit of value, yet no coins are known earlier than the Iron Age.12 The most ancient coins known are Greek, and date back to the eighth century before Christ. This coin is one found in one of the lake settlements. It is made of bronze, and the figures are not stamped, but obtained by melting and casting.13 This, however, is not a Greek coin, but a Gallic one. On the battlefield of Tiefenau, mentioned above, several Greek coins, struck at Massilia, were found.14 It is scarcely necessary to point out, that though iron gives its name to this age, it by no means follows that the only difference between this and the Bronze Age is the use of iron. “The pottery is different, the forms of the implements and weapons are different, the ornamentation is different, the knowledge of metallurgy was more advanced, silver and lead were in use, letters had been invented, coins had been struck.”15 That wonderful invention, the phonetic alphabet, was made during the early part of this age. The past was no longer simply kept alive in the memory of the living, handed down by tradition and song. Inscriptions, and monuments, and books abounded, and we are no longer confined to an inspection of their handiwork, or examination of their habitations, and explanation of ancient burial mounds for our knowledge of their life and surroundings. It is no longer the archæologists’ collections, but the writings of the historian that unfolds past times and customs.