The ships and roads that carried goods, the bridges that bound the roads, the harbors and docks that received the ships, the aqueducts that brought clean water to Rome, the sewers that drained the rural marshes and the city’s waste, were the work of Roman, Greek, and Syrian engineers operating with armies of free labor, legionaries, and slaves. They raised or drew heavy loads or stones by pulleys on cranes or vertical beams, worked by windlasses on treadmills turned by animals or men.35 They banked the treacherous Tiber with walls set back in three stages, so that low water would not expose the muddy bed.II They dredged a multiple harbor at Ostia for Claudius, Nero, and Trajan, opened lesser havens at Marseilles, Puteoli, Misenum, Carthage, Brundisium, and Ravenna, and renewed the greatest of all at Alexandria. They emptied the Fucine Lake and reclaimed its bed for cultivation by boring a tunnel through a mountain of rock. They lined the subsoil of Rome with sewers of concrete, brick, and tile which lasted for hundreds of years. They drained the swamps of Campania sufficiently to make it habitable, for many sumptuous palaces are indicated by the ruins there.36III They executed the astonishing public works by which Caesar and the emperors mitigated unemployment and beautified Rome.
The consular roads were among their simpler achievements. How did these highways compare with those of today? They were from sixteen to twenty-four feet wide, but near Rome part of this width was taken up with sidewalks (margines) paved with rectangular stone slabs. They went straight to their goal in brave sacrifice of initial economy to permanent saving: they overleaped countless streams with costly bridges, crossed marshes with long, arched viaducts of brick and stone, climbed up and down steep hills with no use of cut and fill, and crept along mountainsides or high embankments secured by powerful retaining walls. Their pavement varied with locally available material. Usually the bottom layer (pavimentum) was a four- to six-inch bed of sand, or one inch of mortar. Upon this were imposed four strata of masonry: the statumen, a foot deep, consisting of stones bound with cement or clay; the rudens, ten inches of rammed concrete; the nucleus, twelve to eighteen inches of successively laid and rolled layers of concrete; and the summa crusta of silex or lava polygonal slabs, one to three feet in diameter, and eight to twelve inches thick. The upper surface of the slabs was smoothed, and the joints were so well fitted as to be hardly discernible. Occasionally the surface was of concrete; on less important roads it might be of gravel; in Britain it was composed of flint stones laid in cement upon a gravel bed. The substructure was so deep that little attention was given to drainage. All in all, these were the most durable roads in history. Many of them are still in use; but their steep gradients, designed for pack mules and small vehicles, have compelled their abandonment by modern traffic.37
The bridges that carried these roads were themselves high exemplars of wedded science and art. The Romans inherited from Ptolemaic Egypt the principles of hydraulic engineering; they employed them on an unprecedented scale, and the methods they transmitted remained unchanged till our time. They carried to its ancient limit the building of foundations and piers under water. They drove into the bed a double cylinder of piles, boarded each cylinder tightly, drained the water from between them, covered the exposed bottom with rock or lime, and on this basis raised the pier. Eight bridges crossed the Tiber at Rome: some sacredly ancient like the Pons Sublicius, on which no metal might be used; some so well built that like the Pons Fabricius they are functioning to this day. From these spans the Roman arch would go forth to bridge a hundred thousand streams in the white man’s world.
Pliny thought that the aqueducts were Rome’s greatest achievement. “If one will note the abundance of water skillfully brought into the city for many public and private uses; if he will observe the lofty aqueducts required to maintain a proper elevation and grade, the mountains that had to be pierced, the depressions that had to be filled—he will conclude that the whole globe offers nothing more marvelous.”38 From distant springs fourteen aqueducts, totaling 1300 miles, brought through tunnels and over majestic arches into Rome some 300,000,000 gallons of water daily—as large a quantity per capita as in any modern city.39 These structures had their faults; leaks developed in the lead pipes and required frequent repair; by the end of the Western Empire all the aqueducts had gone out of use.IV But when we consider that they fed ample water to homes, tenements, palaces, fountains, gardens, parks, and public baths where thousands bathed at once, and that enough remained to create artificial lakes for naval battles, we begin to see that despite terror and corruption Rome was the best managed capital of antiquity and one of the best equipped cities of all time.
At the head of the water department at the close of the first century was Sextus Julius Frontinus, whose books have made him the most famous of Roman engineers. He had already served as praetor, as governor of Britain, and several terms as consul. Like modern British statesmen he found time to write books as well as to govern states; he published a work on military science, of which the concluding portion, Stratagemata, remains,V and left us his personal account of the water system of Rome (De aquis urbis Romae). He describes the corruption and malfeasance that he found in his department on taking office, and how palaces and brothels secretly tapped the water mains, and so greedily that once Rome ran out of water.41 He describes his resolute reforms; tells in proud detail the sources, length, and function of each aqueduct; and concludes like Pliny: “Who will venture to compare with these mighty conduits the idle Pyramids, or the famous but useless works of the Greeks?”42 We sense here the frankly utilitarian Roman with little taste for beauty apart from use; we can understand him and admit that a city should have clean water before it has Parthenons. Through these artless books we perceive that even in the age of the despots there were Romans of the old type, men of ability and integrity, conscientious administrators who made the Empire prosper under the lords of misrule and opened a way for monarchy’s golden age.