ONT DU GARD, near Nimes, France.

This aqueduct spans the river valley of the Gard. It was built by Agrippa and served as a bridge capable of taking chariots as well as men.

DIMENSIONS:

• HEIGHT: 160 feet (49m)
• LENGTH: 895 feet (273m)

Historical Background

As early as 1200BC Nimes (the Roman Nemausus), in the south of Gaul, was under Roman control, but it was mainly in the time of Augustus that it flourished. In 27BC the town was raised to the status of a colonia by Augustus, and in 20-19BC Agrippa took a particular interest in the town and surrounding area. It is to this period, ca.19BC, that the Pont du Gard probably belongs. Nimes is also the home of the Maison Carree

Engineering

Although a natural spring existed within the city's walls, it proved necessary to supplement its supply of water by constructing an aqueduct, of which the Pont du Gard is a small part.

• It brought water to Nimes from another useable spring almost 31 miles (50km) away to the north.
• Much of the aqueduct was actually subterranean, and carefully built with a very gradual drop of about 1 in 3000 over its entire length.
• This use of a simple gravitational flow avoided the expense of installing pressure systems to channel water over obstacles.

At one stage the aqueduct had to bridge the river Gardon (or Gard), about 13 miles (21km) north-east of Nimes, and here it becomes the impressive monument to Roman engineering that survives today, with some restorations and additions (notably the 18th century bridge-road on the east side.

Composition

The arches which span the main current in the two lower stories were made wider (24.5m) than their neighbors on either side
they are surmounted by four, rather than three, of the small arches in the top story.

There are:

• six arches in the lowest story
• eleven in the second
• thirty-five in the top

Peg & Cliff at Pont du Gard

Those in the top level consist of one arch (10' [3.06m] deep), presenting a relatively narrow face to minimize wind stress at this height .

The second level has vaults each made of three parallel arches (15' [4.56m] deep), one set behind another.

At the bottom level, the vaults are made up of four parallel arches (21' [6.36m] deep), to withstand the river's currents

This method of juxtaposed parallel arches represents an economizing measure, since only one timber framework was necessary for the construction of each vault to support each arch as it was built. Repairs on the upper arches could be carried out by setting a timber framework on bosses which were left on the arches for this purpose.

Unlike most later arches and vaults those of Pont du Gard were made of un cemented masonry: The stone was quarried locally.

Pont Du Gard- over its 31 mile (50km) length (from Uzes to Nimes) there is a difference in height of only 56 feet (17m).

On to the house.

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