This almost complete absence of examples renders it difficult to estimate precisely the style of ornaments then in use. But as far as can be judged, Byzantine influence seems to have affected all forms of jewellery. It is known, at all events, that until about the twelfth century active commercial transactions between France and Germany on the one hand, and Byzantium on the other, were carried on by way of Venice. Not only did Byzantine workmen settle in the great seaport of the Adriatic, but imitations of work from the Eastern Roman provinces were probably made there at an early date by native artists. Such traffic appears to have been particularly active during the Carlovingian period; while the close friendship of Charlemagne with Haroun al-Raschid, the celebrated caliph of the Saracens, renders it further probable that models of Oriental art abounded in the West in the ninth century. These were not merely confined to articles of jewellery and other goldsmith's productions, but included also sumptuous dress materials interwoven with threads of gold, embroideries studded with gems and pearls, and other objects which the splendour of the rulers of the West and the princes of the Church borrowed from the magnificence prevalent in the East and at the Byzantine Court.[28] [28] Luthmer, _op. cit._, p. 72. The Eastern influence which during the fourth and fifth centuries had come westwards by way of Byzantium, and had acquired new power owing to the sovereignty of the Arabs in Spain and Sicily during the eighth and ninth centuries, increased considerably at the time of the Crusades. The knights and princes of the West brought back not only impressions of culture from Syria and Palestine, but also actual specimens of gold ornaments and precious stones. There then began an invasion of skilled workmen from the towns of Asia Minor, and a regular importation of such treasures by the merchants of the Italian republics, to wit, Venice, Genoa, and Pisa, who, under the banner of the Cross, re-established their trade with the East.[29] [29] _Ibid._, p. 50. Until about the twelfth century ornaments followed for the most part the style of those in use in the Eastern Roman provinces. Some were adorned with cloisonné enamel introduced from Byzantium, and first executed by Continental workmen about the eighth century. Cloisonné, however, was, in turn, abandoned for champlevé enamel, the manufacture of which upon the Lower Rhine had been encouraged by the Church, through the instrumentality of the Greek monks.