During the Tertiary period arms of the sea spread into France in the Paris basin from the north, in the basins of the Loire and the Garonne from the west, and in the Rhne area from the south.
The department is intersected by torrents belonging to the Garonne basin - the Salat, the Arize, which, near Mas d'Azil, flows through a subterranean gallery, the Ariege and the Hers.
The Entre-deux-Mers district forms a peninsula between the Garonne and Dordogne, comprising the arrondissements of La Reole, the south of Libourne and the east of Bordeaux.
Wellington wished to pass the Garonne above Toulouse in order to attack the city from the south - its weakest side - and interpose between Soult and Suchet.
The Canal du Midi, or Languedoc canal, uniting the Garonne with the Mediterranean, passes under the walls of the town, and the mouth of the Herault forms a harbour which is protected by a fort.
The Cotes district consists of the slopes rising from the lower marshy regions to the east of the Garonne and the Dordogne respectively.
Below the town of Bergerac it enters the department of Gironde, where at Libourne it is joined by the Isle and widens cut, attaining at its union with the Garonne 45 m.
But Soult did not attack; the bridge (April 8) was restored; Wellington crossed the Garonne and the Ers, and attacked Soult on the 10th of April.
The basin of the Garonne occupies south-western France with the exception of the tracts covered by the secondary basins of the Adour, the Aude, the Hrault, the Orb and other smaller rivers, and the lowlying plain of the Landes, which is watered by numerous coast rivers, notably by the Leyre.
The Medoc consists of a tongue of land to the north of Bordeaux, bounded by the Garonne and Gironde on the east, and by the sea on the west and north.