The great Swedish archæologist has, indeed, given us a most fascinating picture of the commercial relations of northern Europe in earlier periods and their effect on cultural development.[6] We learn with astonishment that in the ninth and tenth centuries of our era, trade was carried on with great intensity between the North of Europe and the Mohammedan culture sphere since tens of thousands of Arabic coins have been found on Swedish soil. But intercourse with remote countries dates back to a far greater antiquity. One of the most powerful stimuli of commercial relations between northern and southern Europe was the desire of the more southern populations to secure amber, a material confined to the Baltic region and occurring more particularly about Jutland and the mouth of the Vistula. Amber beads have been found not only in Swiss pile-dwellings[7] but also in Mycenæan graves of the second millennium B. C. Innumerable finds of amber work in Italy and other parts of southern Europe prove the importance attached to this article, which was exchanged for copper and bronze. The composition of Scandinavian bronzes indicates that their material was imported not from England but from the faraway regions of central Europe. That bronze was not of indigenous manufacture is certain because tin does not occur in Sweden at all while the copper deposits of northern Scandinavia remained untouched until about 1500 years after the end of the Bronze Age. Considering the high development of the bronze technique in Scandinavia and the fact that every pound of bronze had to be imported from without, it would be difficult to exaggerate the extent of contact with the southern populations. But intercourse was not limited to the South. For example, Swedish weapons and implements have been discovered in Finland. Again, crescent-shaped gold ornaments of Irish provenance have been found in Denmark, while a Swedish rock-painting represents with painstaking exactness a type of bronze shield common at a certain prehistoric period of England.