Aqueduct of Gier

The Aqueduc of Gier is one of the Aqueducs of Lugdunum, longest of the four aqueducts having fed the city out of water, and that of which the structures are best preserved. It owes its name with the fact that it draws with the sources of the Gier, affluent of the the Rhone.

The aqueduct

With its 85 km, it is one of longest known Roman aqueducts the. Its layout was well reconstituted, according to the visible vestiges on the surface and the localization of many inspection chambers. On the basis of the heights of Saint-Chamond in the solid mass of the Pilat, department of the the Loire. He marries the relief of the plate and crosses the Département of the Rhone, while passing towards Mornant, Orliénas, Chaponost and Holy-Foy-the-Lyon to finish with Lyon.

Its course implements almost all the Roman techniques of construction of aqueduct:

average slope of 0,1% for the drain
73 km of distinct glaze, with a concrete conduit of 3m top for on 1,5m of width (external dimensions) buried until 4m of depth.
11 Tunnel S taking of the short cuts through the relief, including 825 m length one towards Mornant
about thirty air passages in tubular bridge
10 air passages on walls and arches, of which that of the Dish of the Air, where 72 arches remain.
4 siphon S of crossing of the valleys of Durèze, Garon, Yzeron and Trion.
nearly 90 inspection chambers located at the date of 2001, with an average interval between consecutive glances of 77m, in conformity with the council of Vitruve of a glance all 2 actus (either 240 Roman feet converts with 32 cm/pied). It is estimated that the real number of glances on the aqueduct reached the thousand!

This remarkable work of art presents nevertheless a bizarrery: the crossing of the small valley of Durèze is carried out by a siphon, and also by a trench circumventing this small valley. This skirting adds 10 km to the overall length of the aqueduct. The justification of this redundancy can be an operating fault of the siphon.

The crossing of Yzeron with Holy-Foy-the-Lyon

Construction visible with the arches of the Dish of the Air is out of stone, out of brick and in Blocage, the external parts are aesthetically neat, with beautiful hardcore facings in rhombus ( Opus reticulatum ), alternate two thicknesses in broad red bricks (Arase S), and interior brick edges for the arcades. The interior coating of control is visible on the arches of the Dish of the Air, and makes it possible to observe the pink color of a mortar tight with the Tuileau ( Opus signinum ). The crossing of Yzeron to the Dish of the Air is most spectacular and the best visible one: the aqueduct was to cross a broad depression of almost 3 km, for a unevenness of some 140m. The produced siphon, only possible solution, is a technical feat of ingenuity:

2600 m length, tank to another
123 m of arrow (height between the reserve of hunting and the low part of the siphon)
trained low part of a bridge channel of 270m of length and 17m top
13 bars of pressure to be supported in the low part
drain on all the siphon by a beam of 12 lead pipes 27 cm in diameter drowned in the mortar to ensure their pressure resistance.

The vestiges of important size which remain are the frame of the reserve of hunting, and the beginning of the descent (it “crawling”, plan inclined out of 5,8 m broad concrete), they made it possible to establish the above mentioned characteristics of the lead drains.

Pierre de Chagnon

The only element writes related to the aqueducts of Lugdunum which one lays out is the stone of Chagnon . This plate of sandstone was found in 1887 in the sector of the aqueduct of Gier to the skirting of the valley of Durèze. It measures 1,58m on 0,62 and carries the Latin inscription E following ('' LASH '' XIII, 1623):

EX AVCTORITATE/ IMP (eratoris) CAES (aris) TRAIA/ NOR HADRIANI/ AVG (usti) NEMINI/ ARANDI SER/ ENDI PANG/ ENDIVE VENTURA SYSTRAN INTERFACE/ IS INTRA ID/ SPATIUM AG/ IH QVOD TVTE/ LAE DVCTVS/ DESTINATVM EAST

What is translated as follows:

“ By order of the emperor César Trajan Hadrian Auguste, nobody has the right to plow, sow or plant in this space of ground which is intended for the protection of the aqueduct ”

This text takes again the terms of a general legislation definite under Auguste into 11 and 9 av J.C and consigned by Frontin in its treaty on the aqueducts. The stone of Chagnon is a rather general warning. A similar inscription for the aqueduct of Venafro in Italy quantifies the distance imposed on 8 feet. Here nothing tel. Two interpretations is possible:

the aqueduct of Gier probably dates from the period augustéenne (A. Desbat); Hadrian taking again only one law from less 9 before our era;

But the warning misses precision useful to its application.

Under Hadrian, a simple recall of the law was necessary, perhaps after an inspection and a resequencing of the protected area. In this case the aqueduct would be older than the time of Hadrian.

See Too

Aqueducts of Lugdunum

External bonds

the Roman aqueduct of Gier
Displacement of a glance of the aqueduct of Gier 30 09 2006
" Aqua Lugdunensis"

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