Roman engineering

Origins

The Romans are generally famous for their advanced engineering accomplishments, although some of their own inventions were improvements on older ideas, concepts and inventions. Technology for bringing running water into cities was developed in the east, but transformed by the Romans into a technology inconceivable in Greece. The architecture used in Rome was strongly influenced by Greek and Etruscan sources. Roads were common at that time, but the Romans improved their design and perfected the construction to the extent that many of their roads are still in use today. Their accomplishments surpassed most other civilizations of the time, and many of their structures have withstood the test of time to inspire others, especially during the Renaissance. Moreover, their contributions were described in some detail by authors such as Vitruvius, Frontinus and Pliny the Elder, so there is a printed record of their many inventions and achievements.

Aqueducts

Three hundred million gallons of water were brought into Rome by 11 different aqueducts each day. Per capita water usage in Rome matched that of modern-day cities like New York City or modern Rome. Most water was for public uses, such as baths and sewers. The aqueducts could stretch from ten to sixty miles long, and decreased from an elevation of one thousand feet above sea level at the source, to two hundred feet when they reached the reservoirs around the city. Roman engineers used siphons to force water uphill when they judged it impractical to build a raised aqueduct across a particular depression. The Romans were among the first civilizations to harness the power of water. They built some of the first watermills outside of Greece for grinding flour and spread the technology for constructing watermills throughout the Mediterranean. A famous example occurs at Barbegal in southern France, where no less than 16 overshot mills built into the side of a hill were worked by a single aqueduct, the outlet from one feeding the mill below in a cascade. They were also skilled in conducting mining operations such as building the many aqueducts needed for prospecting for metal veins, in methods like hydraulic mining, and the building of reservoirs to hold the water at the minehead. It is certain that they were also capable of building and operating mine equipment such as crushing mills and dewatering machines. Large diameter vertical wheels of Roman vintage, for raising water, have been excavated from the Rio Tinto mines in Southwestern Spain. They were closely involved in exploiting gold resources such as those at Dolaucothi in south west Wales and in north-west Spain, a country where gold mining developed on a very large scale in the early part of the first century AD, such as at Las Medulas.

Bridges

Roman bridges were among the first large and lasting bridges built.They were built with stone and had the arch as its basic structure. Most utilized concrete as well.Built in 142 BC, the Pons Aemilius, later named "Ponte Rotto" (broken bridge) is the oldest Roman stone bridge in Rome, Italy. The biggest Roman bridge was Trajan's bridge over the lower Danube, constructed by Apollodorus of Damascus, which remained for over a millennium the longest bridge to have been built both in terms of overall and span length. They were most of the time at-least 18 m above the body of water.

An example of temporary military bridge construction are the two Caesar's Rhine bridges.

Dams

The Romans built many dams for water collection, such as the Subiaco dams, two of which fed Anio Novus, the largest aqueduct supplying Rome. One of the Subiaco dams was reputedly the highest ever found or inferred. They built 72 dams in Spain, such as those at Merida, and many more are known across the empire. At one site, Montefurado in Galicia, they appear to have built a dam across the river Sil to expose alluvial gold deposits in the bed of the river. The site is near the spectacular Roman gold mine of Las Medulas. Several earthen dams are known from Britain, including a well-preserved example from Roman Lanchester, Longovicium, where it may have been used in industrial-scale smithing or smelting, judging by the piles of slag found at this site in northern England. Tanks for holding water are also common along aqueduct systems, and numerous examples are known from just one site, the gold mines at Dolaucothi in west Wales. Masonry dams were common in North Africa for providing a reliable water supply from the wadis behind many settlements.

Architecture

The buildings and architecture of Ancient Rome were impressive even by modern standards. The Circus Maximus, for example, was large enough to be used as a stadium. The Coliseum also provides an example of Roman architecture at its finest. One of many stadiums built by the Romans, the Coliseum exhibits the arches and curves commonly associated with Roman buildings. The Pantheon, Rome still stands a monument and tomb, and the Baths of Diocletian and the Baths of Caracalla are remarkable for their state of preservation, the former still possessing intact domes. Such massive public buildings were copied in numerous provincial capitals and town across the empire, and the general principles behind their design and construction are described by Vitruvius writing at the turn of millennium in his monumental work De Architectura. The technology developed for the baths was especially impressive, especially the widespread use of the hypocaust for one of the first types of central heating developed anywhere. That invention was used not just in the large public buildings, but spread to domestic buildings such as the many villas which were built across the Empire.

Materials

The most common materials used were brick, stone or masonry, cement, concrete and marble. Brick came in many different shapes. Curved bricks were used to build columns, and triangular bricks were used to build walls.

Marble was mainly a decorative material. Caesar Augustus once boasted that he had turned Rome from a city of stone to a city of marble. The Romans had originally brought marble over from Greece, but later found their own quarries in northern Italy.

Cement, also known as mortar, was originally invented in Asia. It was made of hydrated lime (calcium oxide) mixed with sand and water. The Romans discovered that substituting or supplementing the sand with a pozzolanic additive, such as volcanic ash, would produce a very hard cement, known as hydraulic mortar or hydraulic cement. They used it widely in structures such as buildings, public baths and aqueducts, ensuring their survival into the modern era.

Roads

Roman roads were constructed to be immune to floods and other environmental hazards. Many roads built by the Romans are still in use today.

There was no standard design to a Roman road. However, most roads were composed of five layers. The bottom layer, called "pavimentum", was one inch thick and made of mortar. Above this were four strata of masonry. The layer directly above the pavimentum was called the "statumen". It was one foot thick, and was made of stones bound together by cement or clay. Above that, there were the "rudens", which were made of ten inches of rammed concrete. The next layer, the "nucleus", was made of twelve to eighteen inches of successively laid and rolled layers of concrete. "Summa crusta" of silex or lava polygonal slabs, one to three feet in diameter and eight to twelve inches thick, were laid on top of the rudens. The final upper surface was made of concerete or well smoothed and fitted flint.

Generally, when a road encountered an obstacle, the Romans preferred to engineer a solution to the obstacle rather than redirecting the road around it. Bridges were constructed over all sizes of waterway, marshy ground called for the construction of raised causeways with firm foundations, and hills and outcroppings were frequently cut or tunneled through rather than avoided.

Mining

The Romans were the first to exploit mineral deposits using advanced technology, especially the use of aqueducts to bring water from great distances to help operations at the pithead. Their technology is most visible at sites in Britain such as Dolaucothi where they exploited gold deposits with at least 5 long aqueducts tapping adjacent rivers and streams. They used the water to prospect for ore by unleashing a wave of water from a tank to scour away the soil and so reveal the bedrock with any veins exposed to sight. They used the same method (known as hushing) to remove waste rock, and then to quench hot rocks weakened by fire-setting. Such methods could be very effective in opencast mining, but fire-setting was very dangerous when used in underground workings. They were made redundant with the introduction of explosives, although hydraulic mining is still used on alluvial tin ores. They were also used to produce a controlled supply to wash the crushed ore. It is highly likely that they also developed water-powered stamp mills to crush hard ore, which could be washed to collect the heavy gold dust. At alluvial mines, they applied their hydraulic mining methods on a vast scale, such as Las Medulas in north-west Spain. Traces of tanks and aqueducts can be found at many other early Roman mines. The methods are described in great detail by Pliny the Elder in his Naturalis Historia. He also described deep mining underground, and mentions the need to dewater the workings using reverse overshot water-wheels, and actual examples have been found in many Roman mines exposed during later mining attempts. The copper mines at Rio Tinto were one source of such artefacts, where a set of 16 was found in the 1920s. They also used Archimedean screws to remove water in a similar way.

Military engineering

Engineering was also institutionally ingrained in the Roman military, who constructed forts, camps, bridges, roads, ramps, pallisades, and siege equipment amongst others. One of the most notable examples of military bridge-building in the Roman Empire was Julius Caesar's bridge over the Rhine River. This bridge was completed in only ten days by a dedicated team of engineers. Their exploits in the Dacian wars under Trajan in the early 2nd century AD are recorded on Trajan's column in Rome. The army was also closely involved in gold mining and probably built the extensive complex of leats and cisterns at the Roman gold mine of Dolaucothi in Wales shortly after conquest of the region in 75 AD.

References

*cite book|last=Davies|first=Oliver|title=Roman Mines in Europe|location=Oxford|year=1935
*cite book|last=Healy|first=A.F.|title=Pliny the Elder on Science and Technology|publisher=Clarendon |location=Oxford|year=1999
*cite book|last=Hodge |first=T.|title=Roman aqueducts and Water supply|publisher=Duckworth|edition=2nd|year=2001
*cite book|last=Smith|first=Norman|title=A History of Dams|publisher= Citadel Press |year=1972

External links

* [http://traianus.rediris.es/ Traianus] - Technical investigation of Roman public works
* [http://traianus.rediris.es/textos/presas_in.htm Roman dams in Spain]