262 Description of the Great Bridge 



middle are of equal dimensions, and are eighty-seven feet in di- 

 ameter. The opening of the first and the last arches is sixty- 

 eight feet, and the rest are of intermediate dimensions. The 

 vaults have the form of arcs of a circle, whose rise or height 

 is equal to a third part of their cord. The thickness of the 

 pier is thirteen feet nine inches. The tympanum or interval 

 between two arches is adorned with the royal cipher, encir- 

 cled with a crown of oak, and engraven on a ground of bricks. 

 Above the arches is a fine bold cornice, and two pavilions, 

 adorned with porticoes and columns of the Doric order, are 

 built at each extremity of the bridge. 



The parapet is five feet ; the width of each footpath eight 

 feet two inches ; the width of the road thirty-two feet four 

 inches, and the whole width of the bridge forty-eight feet 

 eight inches, A slight declivity, commencing at the fifth arch 

 on each side, and descending towards the banks, facilitates the 

 union of the road-way with quays, and allows the rain-water 

 to flow off. The injury, however, produced by rains, will be 

 more certainly prevented by an ingenious arrangement, of 

 which no other building presents an example. The impos- 

 ing mass of contiguous vaults, already mentioned, and in ap- 

 pearance so heavy, is bound together interiorly by a multitude 

 of galleries, similar to the apartments of cloisters, which com- 

 municate with each other, from one end of the bridge to the 

 other. By means of these vaults, the engineer can, at any 

 time, examine the condition of the arches below the road- way, 

 and it will be easy to keep them up and repair them without 

 interrupting the passage of carriages. There exists even un- 

 der each foot-path of the road-way a continuous gallery, in the 

 form of an aqueduct, by which the springs from the hills, oij 

 the right bank of the Garonne, may be conveyed and distri- 

 buted through the city. 



In order to give an idea of the extent of this bridge, the 

 following table has been drawn up, showing its magnitude in 

 comparison with some of the principal bridges in Europe. * 



* Full drawings and descriptions of the bridges of Tours, La Guillotiere, 

 and Dresden, will be found in Mr Telford's article on Bridge in the 

 Edinburgh Encyelopcediu. 



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