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Pont du Gard (Roman Aqueduct)

UNESCO World Heritage Site
Criteria	Cultural: i, iii, iv
Reference	344
Inscription	1985 (9th Session)

The Pont du Gard is a notable ancient Roman aqueduct bridge that crosses the Gard River in southern France. It is part of a 50 kilometres (31 mi) long aqueduct that runs between Uzès and Nîmes in the South of France. It is located in Vers-Pont-du-Gard near Remoulins, in the Gard département. The aqueduct was constructed by the Romans in the first century AD and was added to UNESCO's list of World Heritage Sites in 1985. It is the highest of all Roman aqueduct bridges and is the best preserved after the Aqueduct of Segovia. Today it is one of France's most popular tourist attractions.

Description

The Nîmes aqueduct

The Nîmes aqueduct originally carried water from a source at the Fontaine d'Eure near Uzès to a delivery tank or castellum divisorum in Nemausus, Roman Nîmes. Although the straight-line distance between the two is only about 20 km, the aqueduct takes a winding route measuring around 50 km to avoid the Garrigue hills above Nîmes. The Garrigues are the southernmost foothills of the Massif Central. They are difficult to cross, as they are covered in dense vegetation and indented by deep valleys, and it was impractical for the Romans to attempt to tunnel through the hills. A roundabout course was therefore the only practical

The Fontaine d'Eure, at 76 metres (249 ft) above sea level, is only 17 metres (56 ft) higher than the delivery tank or castellium in Nîmes, but this provided a sufficient gradient to sustain a steady flow of water to the 50,000 inhabitants of the city. The aqueduct's average gradient is only 1 in 3,000. It varies widely along its course, but is as little as 1 in 20,000 in some locations. The Pont du Gard itself descends 2.5 centimetres (0.98 in) in 456 metres (1,496 ft), a gradient of 1 in 18,241. It is estimated that the aqueduct supplied the city with around 200,000,000 litres (44,000,000 imp gal) of water a day that took nearly 27 hours to flow from the source to the city.

The spring still exists and is the site of a small modern pumping station. It provides water that is pure but high in dissolved calcium carbonate leached out of the surrounding limestone. The carbonates caused significant problems for the maintenance of the aqueduct, as they precipitated out of the water during its journey through the conduit. This led to the flow of the aqueduct progressively becoming reduced by deposited carbonates. Another threat was posed by vegetation penetrating the stone lid of the channel. As well as obstructing the flow of the water, dangling roots would introduce algae and bacteria that would decompose in a process called biolithogenesis, producing concretions within the conduit. It had to be maintained continuously by circitores, maintenance workers responsible for its upkeep, who would crawl along the conduit scrubbing the walls clean and getting rid of any vegetation.

Like most Roman aqueducts, much of it was built underground. It was constructed by digging a trench in which a stone channel was built, enclosed by an arched stone roof and covered with earth. Some sections of the channel are tunnelled through solid rock. In all, 35 kilometres (22 mi) of the aqueduct was constructed below the ground. The remainder had to be carried on the surface, either on a wall or on arched bridges. Some substantial remains of the above-ground works can still be seen today, such as the so-called "Pont Rue" that stretches for hundreds of metres around Vers and still stands up to 7.5 metres (25 ft) high. However, the Pont du Gard is by far the best preserved section of the entire aqueduct.

The Pont du Gard

Built on three levels, the Pont is 49 metres (161 ft) high above the river at low water and 274 metres (899 ft) long. Its width varies from 9 metres (30 ft) at the bottom to 3 metres (9.8 ft) at the top. The three levels of arches are recessed, with the main piers in line one above another. The span of the arches varies slightly, each being constructed independently to provide flexibility to protect against subsidence. Each level has a differing number of arches:

The first level of the Pont du Gard adjoins a road bridge that was added in the 18th century. The water conduit or specus, which is about 1.8 metres (5.9 ft) high and 1.2 metres (3.9 ft) wide, is carried at the top of the third level. The upper levels of the bridge are slightly curved in the upstream directions, a fact long attributed to the engineers wanting to strengthen it against the flow of water, like a dam wall. However, a microtopographic survey carried out in 1989 showed that the bend is caused by the daily expansion and contraction of stones under the heat of the sun, by about 5 millimetres. Over the centuries, this process has produced the deformation witnessed now.

The Pont du Gard was constructed entirely without the use of mortar or clamps. It contains an estimated 16,000 tons of stone – some of the individual blocks weigh up to 6 tons – that were precisely cut to fit perfectly together by friction alone, eliminating the need for mortar. The masonry was lifted into place by block and tackle with a massive human-powered treadmill providing the power for the winch. A complex scaffold was erected to support the bridge as it was being built. Large blocks were left protruding from the bridge to support the frames and scaffolds used during construction. The builders also left inscriptions on the stonework conveying various messages and instructions. Many blocks were numbered and inscribed with the required locations, such as fronte dextra or fronte sinistra (front right or front left), to guide the builders.

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Although the exterior of the Pont du Gard is rough and relatively unfinished, the builders took care to ensure that the interior of the water conduit was as smooth as possible so that the flow of water would not be obstructed. The walls of the conduit were constructed from dressed masonry and the floor from concrete. Both were covered with a stucco incorporating minute shards of pottery and tile. It was painted with olive oil and covered with maltha, a mixture of slaked lime, pork grease and the viscous juice of unripe figs. This produced a surface that was both smooth and durable.

The Pont du Gard's design represents fairly early stage in the development of Roman aqueducts; it is quite inefficient in some regards. Its technique of stacking arches on top of each other is clumsy and expensive, as it requires the use of a great quantity of stone. Later aqueducts had a more sophisticated design, making greater use of concrete. The Aqueduct of Segovia and the Aqüeducte de les Ferreres are of roughly similar length but use far fewer arches. Roman architects were eventually able to do away with "stacking" altogether. The Acueducto de los Milagros in Mérida, Spain and a similar aqueduct near Cherchell, Algeria utilise tall, slender piers, constructed from top to bottom with concrete faced with masonry and brick.

History

It has long been thought that the Pont du Gard was built by Augustus' son-in-law and aide, Marcus Vipsanius Agrippa, around the year 19 BC. Newer excavations, however, suggest the construction may have taken place between 40 and 60 A.D.

It is believed to have taken about fifteen years to build, employing between 800 and 1,000 workers.

Post Roman

From the fourth century onwards, its maintenance was neglected, and deposits filled up to two thirds of the conduit space. By the ninth century, it became unusable, and the people of the area started using its stones for their own purposes. However, the majority of the Pont du Gard remains impressively intact.

From the Middle Ages to the 18th century, the aqueduct was used as a conventional bridge to facilitate foot traffic across the river, like its much smaller sister, the Pont de Bornègre. The pillars of the second level were reduced in width to make more room for the traffic, but this jeopardized the stability of the structure. In 1702 the pillars were restored to their original width in order to safeguard the aqueduct. In 1743, a new bridge was built by a French engineer Henri Pitot next to the arches of the lower level, so that the road traffic could cross on a purpose-built bridge. The aqueduct was restored in the 18th century, by which time it had become a major tourist site, and was restored again in the reign of Napoleon III in the mid-19th century.

The outstanding quality of the bridge's masonry led to it becoming an obligatory stop for French journeymen masons on their traditional tour around the country (see Compagnons du Tour de France), many of whom have left their names on the stonework. Markings left by the original builders can also be seen, indicating the positions in which the dressed stones were to be placed: for instance, FRS II (standing for frons sinistra II, or "front left 2"). This is a tradition that has been partly continued by modern visitors, often looking to make their own markings.

In May 1940 a French pilot, Séraphin Civera, flew his plane through one of the arches.

The Pont du Gard was added to UNESCO's list of World Heritage Sites in 1985. The description on the list states: "The hydraulic engineers and ... architects who conceived this bridge created a technical as well as artistic masterpiece."

In 1998 the Pont du Gard was hit by major flooding which caused widespread damage in the area. The road leading up to it and the neighboring facilities were badly damaged, although the aqueduct itself was not seriously harmed.

The French government sponsored a major redevelopment project in conjunction with local sources, UNESCO and the EU which concluded in 2000, pedestrianising the entire area around the aqueduct and greatly improving the visitor facilities, including establishing a museum on the north bank. The project has been criticized for its cost (€33 million) and for the perceived loss of natural beauty of the surrounding landscape and area. During the redevelopment it was not possible to walk through the conduit at the top of the aqueduct; however guided crossings are now provided by the museum. The redevelopment has ensured that the area around the Pont du Gard is now much quieter due to the removal of vehicle traffic, and the new museum provides a much improved historical context for visitors.

The Pont du Gard is today one of France's top five tourist attractions, with 1.4 million visitors reported in 2001. The 19th century Roquefavour Aqueduct of the Canal de Marseille replicates the Roman architecture of the Pont du Gard.

See also

• Eifel Aqueduct
• Roman aqueducts
• List of aqueducts in the city of Rome
• List of Roman aqueduct bridges

References

1. Bromwich, James (2006). Roman Remains of Southern France: A Guide Book. Routledge. p. 110. ISBN 9780415143585.
2. Lewis, Michael Jonathan Taunton (2001). Surveying instruments of Greece and Rome. Cambridge University Press. p. 187. ISBN 9780521792974.
3. ^ Langmead, Donald; Garnaut, Christine (eds.). Encyclopedia of architectural and engineering feats. p. 254.
4. Sobin, Gustaf (1999). Luminous debris: reflecting on vestige in Provence and Languedoc. University of California Press. p. 205. ISBN 9780520222458.
5. Bromwich, p. 112
6. Sobin, p. 217
7. Bromwich, p. 111
8. Bromwich, p. 112-113
9. Deming, David (2010). Science and Technology in World History, Volume 1: The Ancient World and Classical Civilization. McFarland. p. 176. ISBN 9780786439324.
10. ^ Michelin Green Guide Provence. Michelin Travel Publications. 2008. pp. 297–298. ISBN 9781906261290.
11. Fabre, G.; Finches, I.L. (1989). "L'aqueduc romaine de Nîmes et le Pont du Gard". Pour le Science (40): 412–420.
12. Gimpel, Jean (1993). The cathedral builders. Pimlico. p. 75. ISBN 9780060911584.
13. O'Rourke Boyle, Marjorie (1997). Divine domesticity: Augustine of Thagaste to Teresa of Avila. Leiden: BRILL. p. 105. ISBN 9789004106758.
14. Hill, Donald Routledge (1996). A history of engineering in classical and medieval times. Routledge. ISBN 9780415152914.
15. ^ Le Pont du Gard remarquable Aqueduc, retrieved 2010-06-15
16. http://auriol.free.fr/Perso/civera-seraphin.htm

External links

• Official Pont du Gard museum website
• Pont du Gard at Structurae
• Location of Pont du Gard (Michelin)
• Photos of the aqueduct le Pont du Gard
• Full Aqueduct (Uzès to Nîmes) website (in French)
• Pont du Gard: Picture Galerie
• 600 Roman aqueducts with 35 descriptions in detail among which is the Pont du Gard
• Ancient Places TV: HD Video of the Pont du Gard