Later on, the Jews can be seen exchanging luxury goods from east to west, just as much at home in Christian as in Muslim lands.
The development of long-distance trade in the Mediterranean regions demanded new approaches to mercantile financing, the organization of expeditions, and the settlements of debts. The sea crossings presented considerable dangers; the high value of many commodities demanded a system of payment which could not rely on barter or the transportation of large amounts of money and the sheer complexity of business relationships--middlemen and agents often intervened between the principals--led to the emergence of highly sophisticated trading mechanisms. The Genoese notarial records reveal two common methods of financing trading expeditions: the commenda, where the investor provided all the capital to finance the expedition and gained three-quarters of the profit (his travelling agent receiving one-quarter) and the societas maris where the investor who stayed at home provided twothirds of the capital, the travelling factor one-third, and each took half the profits. By the end of the twelfth century the increasing use of the commenda, backed up by loans to investors payable only when their ships returned ('sea loans'), reveals a growing number of small investors who wanted to gain as much from their investments as they could. Whilst there were, of course, powerful merchant élites in the Italian trading cities, such as the della Volta, Burone, and the aptly named Usodimare family, the evidence from Genoa, at least, suggests that a considerable proportion of the population was engaged in overseas trading ventures of one kind or another.
The importance of commerce in the Mediterranean world at this time influenced both the topographical and social structures of the urban societies in which it was based. Towns both Christian and Muslim organized their trading quarters on the bazaar system; the shops and booths of the traders in each commodity were grouped together, to encourage competition and benefit the consumer. The proximity in which merchants and traders found themselves contributed to the sense of group solidarity which had long been evident. But from the tenth
-215-