Our Sea

Part 9 - Roman Engineering

Mining

As it expanded, the Roman empire needed metals for its armies, shipping and agriculture and these were produced in quantities not seen again until the industrial revolution.

Annual Roman metal production (t = metric ton = 1000 kg = 2204 pound))Iron and steel 82,500 t Copper 15,000 tLead 80,000 t (A bi-product of silver mining)Silver 200 t Gold 9 t and smaller amounts of Tin, Zinc, Mercury, Arsenic, and Antimony.

Tin was a rare metal needed to make bronze. It was found in only a few places and evidence of tin trade in the Mediterranean comes from shipwrecks such as the Uluburun which sank off the coast of Turkey about 1300 BCE. It carried over 300 copper bars weighing 10 tons, and approximately 40 tin bars weighing 1 ton.

Wood, especially charcoal, was the most commonly used fuel for smelting and forging metals although coal was also used in Britain and northern Europe.

Mechanization

The Romans pioneered mass production techniques for military armour, weapons, brooches, coins, and metal ingots and used power from overshot water wheels to grind grain and saw timber or stone and reverse overshot water-wheels to drain mines. They may have also used water wheels to crush ore using trip hammers.

Trade and commodities

The main Roman trade commodities were grain, olive oil and wine, fish sauce, slaves, metal ores and manufactured metal objects, textiles, timber, pottery, glassware, marble, papyrus, spices and herbs, ivory, pearls, and gemstones. Oil and grain were typically transported in amphora until the Gauls invented wooden barrels during the 2nd century CE.

Shipping

The Romans built ships of a size unequalled in Europe until the 16th century CE and used these to trade over a large number of busy shipping routes. Apart from trade they also transported supplies to the Roman army and returned to Rome with metal extracted from all corners of the empire. Roman seamen navigated across the Mediterranean, Red Sea, and Indian Ocean and out into the Atlantic along the coasts of Portugal, France, Britain and Africa. They used written sailing directions detailing landmarks and calculated their position from the position of the sun, moon, stars and planets.

The cargo capacity of Roman merchant ship's ranged from 70 tons to 600 tons, the largest being 46 m (150 feet) long. They were driven by large square sails on one, two or three masts with a small triangular sail at the bow and driven by oarsmen in calm weather. Speed and manoeuvrability were not a priority so the ships were build for strength and durability in bad weather. Their Vee-shaped hulls were double planked, with a length to breadth ratio of about 3 to 1, and ballasted for stability. They were usually equipped with two large side rudders.

The fast, light and manoeuvrable warships of the Roman navy protected the shipping lanes from pirates. The dominant warships were the shallow draft triremes, with three rows of oars and about 150 rowers, up to the quinquereme which had a total of 300 rowers and 90 oars on each side. Quinqueremes were about 45 m (148 ft) long and 5 m (16 ft) wide and displaced about 100 tons. They were faster than the triremes and performed better in bad weather. The rowers were not slaves but mostly Roman citizens enlisted in the military.