In Italy, however, trade does not seem to have altogether ceased. Venice, Genoa, Amalfi, and other towns appear to have developed a considerable Mediterranean commerce even before the Crusades. Their merchants, as we have seen, supplied the destitute crusaders with the material necessary for the conquest of Jerusalem. The passion for pilgrimages offered inducements to the Italian merchants for expeditions to the Orient, whither they transported the pilgrims and returned with the products of the East. The Italian cities established trading stations in the East and carried on a direct traffic with the caravans which brought to the shores of the Mediterranean the products of Arabia, Persia, India, and the Spice Islands. The southern French towns and Barcelona entered also into commercial relations with the Mohammedans in northern Africa. [Illustration: Street in Frankfort-on-the-Main] [Sidenote: Commerce stimulates industry.] This progress in the South could not but stir the lethargy of the rest of Europe. The new commerce encouraged a revolution in industry. So long as the manor system prevailed and each man was occupied in producing only what he and the other members of his group needed, there was nothing to send abroad and nothing to exchange for luxuries. But when merchants began to come with tempting articles, the members of a community were encouraged to produce a surplus of goods above what they themselves needed, and to sell or exchange this surplus for commodities coming from a distance. Merchants and artisans gradually directed their energies toward the production of what others wished as well as what was needed by the little group to which they belonged. [Sidenote: The luxuries of the East introduced into Europe.] The romances of the twelfth century indicate that the West was astonished and delighted by the luxuries of the East,--the rich fabrics, Oriental carpets, precious stones, perfumes, drugs (like camphor and laudanum), silks and porcelains from China, spices from India, and cotton from Egypt. Venice introduced the silk industry from the East and the manufacture of those glass articles which the traveler may still buy in the Venetian shops. The West learned how to make silk and velvet as well as light and gauzy cotton and linen fabrics. The eastern dyes were introduced, and Paris was soon imitating the tapestries of the Saracens. In exchange for those luxuries which they were unable to produce, the Flemish towns sent their woolen cloths to the East, and Italy its wines. But there was apparently always a considerable cash balance to be paid to the Oriental merchants, since the West could not produce enough to pay by exchange for all that it demanded from the Orient. [Sidenote: Some of the important commercial centers.]