DORDOGNE, a river of central and south-western France, rising at a height of 5,640 ft. on the Puy-de-Saucy, a section of the volcanic core of the Plateau Central in the department of Puy-de-Dome, and flowing to the Garonne, with which it unites at Bec d'Ambes to form the Gironde estuary. It has a length of 295 m. and the area of its basin is 9,214 sq. miles. The Dordogne is a good example of a consequent stream of the western section of the Plateau Central. In its course it cuts across a large number of geological formations, as do its two great right-bank tributaries, the Vezere and the Isle. The Dor dogne descends rapidly from its source and enters deep gorges as it flows through the Archaean plateau-country, rich in granites, until it reaches Beaulieu (department of Correze) where it enters a wide fertile valley and is joined by the Cere. Entering the department of Lot, it abandons a south-westerly course for a westerly course. It now flows through limestone country, often in gorges with the Causses above on both sides. It traverses the department of Dordogne, where it receives the Vezere. The lower course of the latter is through a calcareous country, and its many caves have made it classic ground for the study of Palaeolithic man. Below the town of Bergerac the Dordogne enters the department of Gironde and is joined by the Isle at Libourne. The river is some 3,30o yd. wide at its union with the Garonne, 45 m. from the sea. In its lower course it flows over Tertiary material. There are important bridges at Cubzac les-Ponts. There is much river traffic after the confluence with the Vezere over the last 112 m. of its course. The estuary of the Gironde is one of the most conspicuous features of the western coast of France, and the highest tides ascend the Dor dogne as far as Pessac, a distance of approximately ioo m. from the ocean.