The Toynbee convector is three years old today.
A capital city could neither become nor remain a capital if it could not import large supplies from distant sources by water. Rome was able to satisfy this condition without difficulty so long as she was the capital of a commonwealth whose area was limited to Peninsular Italy. Standing, as she did, on the bank of the Tiber, which is the biggest and longest river in the Peninsula – a river that was navigable for barges far up its course – Rome, in this first phase of her history as a capital, was able to supply herself with grain from higher up the Tiber valley, as well as with timber from the Appennine forests overhanging the Tiber’s source. When, however, in the course of half a century ending in the year 168 B.C., the Romans expanded the area under their political control from Peninsular Italy to the whole perimeter of the Mediterranean basin, the population of the City of Rome consequently grew to a size at which it could no longer live solely on the river-borne supplies that it could draw from Central Italy. The City now had to draw the major part of its food-supplies from overseas; the military and political ascendency (sic) that Rome had established by this date over Sicily enabled her to requisition food-supplies from there; the granaries of Sicily were subsequently supplemented by those of North-West Africa and Egypt, and the export of grain from Sicily and from Egypt presented no problems, since no cornfield in Sicily was far from the coast, while every cornfield in Egypt was close to the waterway of the River Nile or one of its arms. The City of Rome’s problem at this stage of its history was the conveyance of these sea-borne supplies on the last stage of their journey.
The costly work of excavating an artificial maritime harbour, Portus, connected by a water-link with the Tiber above the river’s mouth, could not eliminate the clumsy and still costly operation of trans-shipping the sea-borne cargoes into river-barges that could reach the City’s riverside quays. This handicap, under which imperial Rome laboured, did not afflict Constantinople, the New Rome by which the Old Rome was eventually superseded in the role of serving as the capital of the Roman Empire. Constantinople possesses a first-rate natural maritime harbour in the Golden Horn, a sheltered deep-water inlet of the Bosphorus that runs inland for the whole length of Constantinople’s northern waterfront, and an obliging current automatically diverts into the Golden Horn a ship drifting down the Bosphorus laden with a cargo of grain grown in the Ukraine and carried from there, down any one of half-a-dozen navigable rivers, to sea-ports on the shores of the Black Sea and the Sea of Azov. Rome’s inferiority to Constantinople in point of accessibility for the delivery of sea-borne supplies was one consideration, though not the only one, that led to the eventual transfer of the capital to Constantinople from Rome in spite of the enormous prestige that had enabled Rome to hold her position as the capital of the Mediterranean World for the five centuries that had elapsed between the Roman state’s crowning victory at Pydna in 168 B.C. and the laying-out out of Constantinople in A.D. 324.
Portus superseded Ostia. It was built by Claudius and extended by Trajan.
Cities on the Move, OUP, 1970