Roman commerce followed, in general, the routes which Phoenicians had discovered centuries before. After the annexation of Gaul the rivers of that country became channels of trade between western Europe and Italy. The conquest of the districts north and south of the Danube opened up an important route between central Europe and the Mediterranean. Imports from the far eastern countries came by caravan through Asia to ports on the Black Sea. The water routes led by way of the Persian Gulf to the great Syrian cities of Antioch and Palmyra and, by way of the Red Sea, to Alexandria on the Nile. From these thriving commercial centers products were shipped to every region of the empire. [24] [Illustration: A ROMAN FREIGHT SHIP The ship lies beside the wharf at Ostia. In the after-part of the vessel is a cabin with two windows. Notice the figure of Victory on the top of the single mast and the decoration of the mainsail with the wolf and twins. The ship is steered by a pair of huge paddles.] LOCAL TRADING AT ROME The importation and disposal of foreign goods at Rome furnished employment for many thousands of traders. There were great wholesale merchants whose warehouses stored grain and all kinds of merchandise. There were also many retail shopkeepers. They might be sometimes the slaves or freedmen of a wealthy noble who preferred to keep in the background. Sometimes they were men of free birth. The feeling that petty trade was unworthy of a citizen, though strong in republican days, tended to disappear under the empire. FREE LABORERS AT ROME The slaves at Rome, like those at Athens, [25] carried on many industrial tasks. We must not imagine, however, that all the manual labor of the city was performed by bondmen. The number of slaves even tended to decline, when there were no more border wars to yield captives for the slave markets. The growing custom of emancipation worked in the same direction. We find in this period a large body of free laborers, not only in the capital city, but in all parts of the empire. THE GUILDS