History : Nov-Dec 2016
NATIONAL GEOGRAPHIC HISTORY 55 5 2 3 1 4 6 SOL 90/ALBUM WORKING WITH GEOGRAPHY ROMAN PIPING SYSTEMS carried water from sources to the city for dozens of miles. The route had to gen- tly slope to allow gravity to carry the water to its destination. Engineers followed the land’s natural grade wherever possible, building channels under- ground—even if that meant having to make long detours. The Aqua Traiana was a total of 37 miles long, but the distance, as the crow flies, between the spring and Rome was about 31 miles. Only when they had no other choice—when they had to cross a valley or avoid a sudden drop—did they build the spectacular archways, sometimes several stories tall, that dominate the Mediterranean landscape. 1 MATERIALS Basic Roman construction materials were stone blocks, concrete, mortar, tiles, and bricks. The structure was faced with a mix of lime and crushed ceramic. 4 ARCHES Bridges could have two or—less commonly—as many as three tiers of arches. Roman engineers opted for narrow arches, which provided maximum strength. 3 CENTERING This wooden structure bore the arch’s weight until the last stone was laid. When it was removed, the slotted stones could support their own weight. 6 SPECUS The specus, or water channel, was on the top level of the viaduct and covered with a roof or vault. Sometimes two or more channels were laid on top of one another. 2 SCAFFOLDING As the construction process advanced, wooden scaffolding was built to aid the workmen, many of whom would have been slaves. 5 PILLARS Massive pillars, measuring around 10 feet by 10 feet, were required to bear the weight of the arch tiers, and were usually longer at the base of the structure.