Merchant vessels and maritime commerce in Roman times

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During the Imperial period Rome was an enormous city inhabited by about one million people. It constituted an extraordinary market, such as would not be found again on western Mediterranean shores until the nineteenth century. The organisation of a constant traffic of heavy products across long distances led to the construction of extremely specialised vessels featuring exceptional nautical characteristics, in order to ensure the regular provisioning of food supplies for Rome.

Roman commercial ships

Merchant ships reached their apogee during the Imperial period. The numerous representations and shipwrecks brought to light thanks to underwater excavations have revealed an extraordinary typological variety: from vessels used for short and medium-length coastal voyages, to large merchant ships, including a range of vessels for fishing, auxiliary ships and other particular functions. One example of this range can be admired in the remarkable ensemble of vessels conserved at the Museum of the Roman Ships of Fiumicino where the Fiumicino 1 , 2, 3, 4 and 5 vessels are exhibited, and at Aquileia where the Monfalcone shipwreck is on display.

The diverse commercial vessels often bore different names, such as corbita, gaulus, ponto, cladivata, etc., which varied according to their geographical origin and hull shape. From a technical point of view, however, there must have been a certain typological homogeneity amongst these vessels as a consequence of the numerous exchanges across the Mediterranean Sea, which by this time was considered by the Romans to be mare nostrum -- that is, "our sea".

Thanks to ship iconography we can reconstruct a significant portion of the characteristics of this class of vessels. The hull shape, for instance, could be symmetrical or asymmetrical. In the first case the stern and bow were identical, while in the second case the bow was located at a lower height. Often the sternpost ended in a swan’s head which faced towards midships, and was fitted with an overhanging gallery. The bow was sometimes concave, due to the presence of a cutwater, which was not a ram but rather a structural feature which improved the nautical qualities of the vessel.

The hull sides were protected by wales and featured winglike projections, the housing, which protected the side rudder system. The cabin was usually situated at the stern and the steersman stood on its rooftop. The steering system was constituted by side rudders or steering oars, located at the stern quarters. They could be regulated by a system of cables and functioned simply by rotating them along their axis. The manoeuvre was controlled by a tiller, a bar set perpendicularly to the oar, known as the clavus. This ancient rudder worked on the basis of the principle of the lever, which minimised the steersman’s effort. Finally, although commercial galleys with mixed propulsion (the actuariae) must have been frequent, the majority of merchant ships were sailing vessels with one, two or three masts. The sails were square and were regulated by a complex rigging system. In addition, some ships featured a small triangular sail, the supparum, located above the yard.

The tonnage of Roman merchant ships

In order to satisfy the various requirements of commerce, ship tonnages were quite variable. According to written sources, ships with a capacity of 10,000 modii of grain (that is, about 70 metric tonnes) constituted the lower end of vessels whose tonnage was considered sufficient to be used for Rome’s food supply and thus to benefit from government concessions. These were the smallest among the medium-tonnage ships. They must have constituted the majority of vessels utilised in commerce, with a capacity which could easily exceed 100 tons, such as the 3,000-amphora (150-tonne) vessels mentioned in written sources, and as also confirmed by numerous underwater discoveries. However, there were also ships with higher tonnage capacity. The hull of the Madrague de Giens shipwreck in France (1st century B.C.) originally measured 40 metres in length and had a capacity of 400 tonnes. In this case we have confirmation of ancient written sources which considered the muriophorio -- the “10,000-amphora carriers” (500 tonnes) utilised at the end of the Republic or the beginning of the Roman empire -- to have been the largest ships of their time, and which set the threshold of these vessels at 50,000 modii (330 tonnes). We must wait until the sixteenth century before we see vessels of similar tonnages plying the waters of the Mediterranean again.

And yet there were even larger ships! During the Hellenistic period Hiero II of Syracuse had the "Syracusia" constructed for the transport of grain. Due to its enormous dimensions, it could not be admitted at any port except Alexandria (in Egypt), where it was sent as a gift to Ptolemy III. Not to mention Caligula’s obelisk-carrier (1,300 tonnes), which was utilised, after having been sunk, to construct the lighthouse at the port of Claudius, or even the "Isis", which Lucian writes about, which must have reached 1,200 tonnes. In this last case, the "Isis" was not a vessel intended for any particular purpose, like the two colossal ships found in Nemi Lake designed as floating palaces and measuring over 70 metres in length; it was merely one of the numerous granary ships of Alexandria’s regular fleet.

The importance of transport by sea

During the entire ancient period transport by sea facilitated the movement of bulky and heavy products across long distances, without a prohibitive rise in costs. Nonetheless, whatever the inconveniences of navigation, voyages by sea offered advantages with respect to land transport which was slow, uncomfortable and dangerous. Not to speak of the cargo capacity: several hundred kilogrammes for a cart, hundreds of tonnes for a seagoing vessel.

With regard to navigation, we can estimate that the distance travelled with a favourable wind in a day’s travel during daylight equalled 700 stadi , with an average speed of 4 or 5 knots. In the case of particularly swift trips, vessels could reach 6 knots. Pliny furnishes several examples: two days to travel from Ostia to Africa (Cape Bon), six days to reach Alexandria through the Straits of Messina, seven days to cross the entire western Mediterranean from Gades to Ostia. But voyages could be much longer: Strabo tells us of a crossing from Spain to Italy which took three months!

Rome at the centre of Mediterranean trade

Grain was the basic source of food for the population. According to an anonymous source of the fourth century A.D., under Augustus Egypt sent 20,000,000 modii of grain each year to Rome -- that is, about 140,000 tonnes. According to Flavius Josephus, during Nero’s reign Egyptian grain fed Rome for four months. Each year 60,000,000 modii of grain had to reach Rome by sea -- in other words, 420,000 tonnes or 525,000,000 litres.

In Nero’s time, the arrival of the grain fleet from Alexandria during the month of June was welcomed as an event of great importance. The merchant ships were escorted by warships and preceded by tabellariae ships, which announced the arrival of the fleet which would release the populace from hunger. Seneca has left us a dramatic description of the excitement that would overcome the crowds in the port of Pozzuoli, in the Campania region.

In addition to grain, wine constituted another widely consumed product, as did oil, which was not only used for food but also for lighting and for massage in the public baths. Furthermore, a type of fish sauce, garum, was much used in the Roman kitchen. In addition to these food products, metal products were transported by sea, including iron bars and ingots of copper or lead. The latter, for example, were transported by the Augustan ship of Comacchio. Finally, all sorts of luxury products flowed to the capital: rare animals for the circus games; polychrome marbles from Africa and Asia Minor, and granites from Egypt; spices and silk from the Far East.

Unfortunately all of these products of primary necessity, being perishable, have not reached us. Nonetheless, they were transported in containers which were indestructible because they were made of terracotta (baked clay): amphorae. Thanks to their recoveries, often in fragmentary condition, both in shipwrecks and land excavations, it has been possible to reconstruct several maritime routes.

Routes of maritime commerce

Provincial amphorae begin to appear at Ostia during the early Imperial period. Around the first century, wine came from Catalonia while garum arrived from southern Spain. The amphorae which contained oil from Baetica, after being transported to Rome, were emptied and discarded. The amplitude of this trade is represented by the Monte Testaccio, which is located near the right bank of the Tiber river. Thirty-five metres high, it is made up of fragments of oil amphorae, for a total of about 50,000,000 examples!

Gaul supplied Rome with wine starting at the end of the first century and especially during the second century. Then Africa became a great source of oil, fish products and wine, up to the end of the Roman period and later. During the whole period of the empire, furthermore, the eastern Mediterranean region maintained commercial exchanges with Rome, not only for the grain from Alexandria, but also for wine which arrived from Crete, Rhodes, Chios and the coasts of Asia Minor.

The ports of Rome: Ostia and Pozzuoli

Each year 60,000,000 modii of grain reached Rome -- that is, 1,200 large vessels containing 50,000 modii, or about 350 tonnes. If we consider that navigation was suspended during the four winter months (the famous mare clausum ,"closed sea", of the Romans), we reach an average of five large grain vessels per navigable day. The amphorae from Baetica, which constitute the majority of the 50,000,000 examples of Monte Testaccio, are very large vessels which, when full, weighed about 90 kg. Each ship must have transported over three thousand of these. Spread over two and a half centuries, the period during which the mountain was formed, we attain about seven ships per navigable month, to which must be added those which transported wine, fish products, the naves lapidariae (specialised in the transport of marble and stone blocks), and those which carried wild animals for the circus, in addition to those involved in local commerce.

All this merchandise was directed to Rome, where, however, the port destined to receive it was only constructed in the first century. Merchant ships which exceeded a 3000-amphora capacity (about 150 tonnes) could not travel upstream. They were obliged to anchor at sea and be unloaded onto smaller vessels, which shuttled between the ships and the river port of Ostia. These operations were very lengthy and dangerous: the coastline, in fact, was inhospitable, low and sandy.

At the end of the Republic, when Rome began its incredible demographic growth, the situation became untenable. The grain reserves became dangerously low and they were obliged to resort to winter navigations to replenish the storage reserves. Up until that point Pozzuoli, situated west of the bay of Naples, had functioned as the port of Rome for large merchant ships. Here arrived the large fleets bearing grain from Sardinia and Sicily, during the Republican period, and later from Alexandria. Smaller vessels journeyed back and forth to Ostia. They constituted a large fleet, numbering about 90 vessels only for grain transport. The bridge of boats which the emperor Caligula had built in A.D. 39 in order to connect Baia and Pozzuoli must have been made up of over 400 vessels which had probably been requisitioned from amongst the available merchant vessels. Thus immobilised, they could not restock the capital, which was struck by terrible famines that winter and during the following two winters as well.

The Pozzuoli-Ostia voyage took two days. The remaining time was taken up by the loading and unloading operations, to which were added three days to travel up the Tiber. Towing, from the right bank of the river, was undertaken by animals or slaves. In this regard there was a specific category of vessels, the naves caudicariae, employed for the river transport of merchandise transshipped from merchant ships. The Fiumicino 1 and 2 shipwrecks represent the archaeological evidence of these boats. The hulls of these vessels were abandoned in a marginal area of the port of Rome, constructed by the emperor Claudius in A.D. 42 and whose archaeological remains are still visible behind the Museum of the Roman Ships of Fiumicino.

Giulia Boetto
Translated into English by Claire Calcagno