Marine development under the Romans was largely influenced by Greek precedent and practice, but there were points of difference.
The transportation of goods across the seas was conducted by shipowners, who formed themselves into corporations under the style of _navicularii marini_, but from the middle of November to the middle of March navigation was suspended until the finer weather returned. Under the Republic these shipmen worked for the companies of _publicani_, but Augustus abolished these financial companies, appointing in their stead superintendents who dealt direct with the owners of ships. The latter were regarded as anything but unimportant. On them the victualling of the capital largely depended, and the early emperors granted them, as owners of important merchant vessels, special privileges; but this was conditional on their ships possessing a capacity of 10,000 modii, and on their carrying corn to Rome for the period of six years. Though they were not in the permanent employ of the State, yet they were liberally rewarded for their services. In the corporations of the _navicularii marini_ there was no clear distinction between the shipowner who worked “on his own” and those engaged in working for the State.
From the time of Diocletian, however, the _navicularii_ were all servants of the State, and it was their duty to transport cargoes of corn, oil, wood, and bullion from the provinces to Rome or Constantinople. In their ships the Imperial post was carried. They received a fixed percentage and were responsible to the State for the goods placed in their holds. Membership of these corporations was handed down from father to son. They were allowed to engage in private trade and enjoyed the additional privilege of passing their cargoes duty free through the Customs. Similarly, additional to the overseas traffic, the internal navigation was organised by corporations of merchants and barge-owners. For example, the State employed them to handle the consignments of corn from Egypt on the Nile, Tiber, and the rivers and lakes of Northern Italy, Spain, Gaul, and Germany. So, too, the Rhone and Saône were navigated by them.
The reader is aware that we have had necessity to refer more than once to the corn-ships from Egypt, and in an age that was given up rather to the development of the fighting galley than to the exploiting of the cargo ship these trans-Mediterranean grain-carriers stand out prominently as a class by themselves. It is most unlikely that they altered much during a space of several hundred years, when even that much-petted craft, the galley, remained so little modified. Therefore the following account which has been left to us by Lucian may be regarded not merely as representative of the corn-ship in his immediate period, but as characteristic of the ship for probably five hundred years at least. Lucian lived in the second century, and was born probably about A.D. 120. In the dialogue from which the following extract is taken he taunts his friend Timolaus with being ever fond of a fine spectacle; to which the latter replies that he had had nothing to do, and being told of “this monster vessel of extraordinary proportions putting in at the Piræus,” he goes on to explain that “she is one of the Egyptian corn-ships and bound for Italy.”