Pyrenees, the mountain-chain that divides France from Spain, stretches across from the Mediterranean to the south-east corner of the Bay of Biscay, a distance of 270 miles; the breadth of the system varies between 15 and 70 miles, and the area it covers measures 13,000 sq. m. The Pyrenees form a regular and continuous chain, divisible into three portions, the Western, the Central, and the Eastern Pyrenees. The first-named division extends eastwards from the Bay of Biscay to the Port de Canfranc (or Col de Somport), a carriage-road that crosses the chain at an elevation of 5380 feet, and leads from Oloron to Saragossa. This division is the lowest in the entire chain, its average height being 3300 to 4300 feet. Here two passes give access to Spain, that of St Jean Pied de Port (or Roncesvalles) and that between Bayonne and Elizondo; the railway from Bayonne to San Sebastian passes the end of the chain close to the sea. The Central Pyrenees, extending from the Port de Canfranc to the Col de la Perche, this connecting the valley of the French Tet (dept. Pyrénées-Orientales) with the valley of the Spanish Segre (prov. Lerida), contain the highest peaks and the most imposing mountain-masses of the entire system, as Pic de Néthou (in Maladetta), 11,168 feet; Mont Perdu, 10,998; Vignemale, 10,794; Marboré, 10,673; and Pic du Midi, 9466. The summits of the Eastern Pyrenees, which extend eastwards from the Col de la Perche (5300 feet), the second pass over the lofty chain, range between 6500 and 7500 feet (Puignal, 9545; Canigon, 9138); and, although the altitude decreases as they approach the Mediterranean, they still reach 2100 feet in the Albères close to the sea. This portion is crossed by the old Roman road from Perpignan to Figueras and pierced by the railway tunnel for the line between the same two towns. The frontier between France and Spain coincides generally with the line of highest summits in the main chain; the principal exception is that at Maladetta the frontier strikes north so as to include within the boundaries of Spain the valley of Aran, which geographically belongs to France. On both north and south the mountains sink down to the plains in a series of terraces, with precipitous faces, the general slope on the Spanish side being somewhat steeper than that on the French side. The valleys cut into the mountain-mass on both sides almost directly at right angles, in the form of deep ravines, and with the regularity of the spines of a fish's backbone. Very many of them terminate in caldron-shaped basins, called cirques, or by the native mountaineers oules (= pots), the sides of which are precipitous and seamed with waterfalls; the most celebrated is the Cirque of Gavarnie, at the head of Gave de Pau, with a waterfall 1515 feet high. Of the numerous streams that have their origin in the mountains, those on the Spanish side are for the most part feeders of the Ebro, whilst the French streams—generally called gaves—feed the Adour, the Garonne, and certain little rivers that reach the Mediterranean. The lower Pyrenean valleys through which these streams flow are in many cases covered with grass or forest, or even vineyards and olive-groves. Snow lies on the highest pinnacles, the snow-line being put at 9200 feet on the south side and at 8300 on the north. A narrow belt of glaciers runs from east to west just below the peaks of the Central Pyrenees, but almost wholly on the French side. Vegetation is most developed in the Western division, where the rainfall is heaviest; but, whilst it is there central European in its characteristics, the vegetation of the Eastern division is subtropical, allied to that of the Mediterranean coasts. The geological nucleus of the range is granite, which comes to the surface in most of the highest peaks. But above the granite lie strata of nearly all subsequent ages, especially Silurian deposits, Cretaceous limestones (hippurite), and limestones (nummulite) of the Eocene period. Minerals are not generally abundant, though iron is worked in the French departments of Basses-Pyrénées and Pyrénées-Orientales; coal exists on the Spanish side and lignite on the French. There are numerous mineral springs (several being hot), those of Eaux-Bonnes, Cauterets, Eaux-Chaudes, Bagnères de Bigorre and de Luchon, and Barèges being the best known. Except the passes already mentioned, the Pyrenees are crossed only by mountain-paths, that none but foot-passengers can use, and they only in the summer; the most remarkable is Roland's Gap (9318 feet), on the west side of Mont Perdu. A great number of caves exist amongst the limestone formations, and in them valuable remains of prehistoric man have been found.
See works by Perret (1884), Prarond (1877), Taine (13th ed. 1893), Camena d'Almeida (1893), and Trutat (1894); guide-books by Gsell-Fels, Joanne, and Murray; and Count Henry Russell, Pau, Biarritz, and the Pyrenees (new ed. 1891).