Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/137

PYRENEES 125 by it about 13,000 square miles. For the most part the crest of the main chain constitutes the Franco-Spanish frontier; the principal exception to this rule is formed by the valley of Aran, which, belonging orographically to France but politically to Spain, is closed at the head by a transverse ridge running north and south and connecting the eastern and western halves of the chain. The whole range is remarkable for its regularity. The main chain is on the whole easy to trace ; its continuity is unbroken, and the variations in its height are mostly confined within narrow limits. The same regularity is seen in the arrangement of the valleys. Except that of Aran, all the principal valleys are given off at right angles, or nearly so, like the pinnae of a fern-frond, on both sides of the chain, and they are again subdivided by similar minor valleys at right angles to them. In all these re- spects the Pyrenees contrast in a very marked manner with the Alps. They have none of the great longitudinal valleys so characteristic of the latter range, none of the great lakes by which such valleys are occupied, and but few passes like those which are found in plenty leading across the great chains of the Alps at a level much below that of the adjoining peaks. In this last particular, in- deed, the Pyrenees are conspicuously deficient. Between the two extremities of the range, where the principal highroads and the only railways run between France and Spain, there are only two passes practicable for carriages, the Col de la Perche between the valley of the Tet and the valley of the Segre, and the Col de Somport or Port de Canfranc (where it is now proposed to pierce the range by a railway tunnel) on the old Roman road from Saragossa to Oloron. This latter pass marks the western extremity of what are known as the Central Pyrenees, which extend east- wards to the valley of Aran and include the highest sum- mits of the whole range Pic de Nethou or Maladetta (11,165 feet), Posets (11,047 feet), Mont Perdu (10,994 feet, Reclus; other authorities, 11,430 feet). In the Atlantic Pyrenees to the west of that pass the average height gradually but steadily diminishes till we come to the Mediterranean, while in the Eastern Pyrenees, with the exception of one break at the eastern extremity of the Pyrenees Ariegeoises, the mean elevation is maintained with remarkable uniformity, till at last a rather sudden decline occurs in the portion of the chain known as the Alberes. Narrow as the range is, the inclination of a straight line drawn from the base to the crest on the French side is not more than 3, or a rise of about 6 in 100. On the Spanish side it is said to be somewhat steeper, but this has not been definitely ascertained. This fact, however, gives no idea of the general character of the Pyrenean slopes. The descent from the crest to the plains is marked by a succession of terraces terminating in abrupt precipices. On the French side a long cliff marks the northern limit of the chain for the greater part of its length, and this feature is particularly well defined in the department of Aude, where a steep precipice marks the division between the true Pyrenees and the Corbieres, a minor chain re- markable for the complexity of its geological structure, stretching in that department from south-west to north-east. Besides these longitudinal precipices marking the steps in the descent from the summit -line to the plains, the transverse valleys almost everywhere form profound ravines, at the bottom of which brawl the innumerable mountain -torrents ("gaves," as they are locally called) that form the principal feature in the hydrography of the range. Frequently they form lofty cascades, surpassed in Europe only by those of Scandinavia. The highest is that of Gavarnie at the head of the Gave de Pau, 1515 feet high. The wildness which thus in general marks the scenery of the Pyrenees is even greater on the Spanish than on the French side. A peculiar and very striking feature in the Pyrenean valleys is the frequency with which their upper end assumes the form of a semicircle of precipitous cliffs. Such basins are called " cirques," and the most noted is that at the head of the valley just mentioned, the Cirque de Gavarnie. The origin of this form of valley is still a matter of discussion among geologists. Geologically the Pyrenees consist, like the Alps, of a core of granite overlaid by sedimentary strata of various age down to the Tertiary period. The granite is exposed chiefly in the east and centre, and appears in the west only in comparatively small isolated patches. Above the granitic core Cambro- Silurian rocks are very extensively developed, especially in the west, and it would appear that the first upheaval on the site of the present Pyrenees took place after the deposition of the rocks of this age, since those of the next epochs in geological history, the Old Red Sandstone, the Carboniferous, and probably also the Permian, are almost entirely unrepresented. The Secondary rocks down to the Lower Cretaceous were de- posited perfectly conformably upon one another, probably against the slopes of a gentle ridge rising out of the water. Among these, Triassic rocks occupy a considerable area in the west on both slopes of the mountains; those of Jurassic age are likewise found on both slopes, but at different points; while the Lower Cretaceous form an almost continu- ous band on the north and one quite continuous on the south. After the deposition of the last-mentioned strata a second upheaval took place, and then another period of quiet deposition, during which the Upper Cretaceous and Eocene beds were laid down, was brought to a conclusion by the grand upheaval which elevated the Pyrenees into one of the great mountain-chains of Europe and imparted to them the general outline of their present relief. The last deposits of the Eocene sea in this quarter, represented on the French side by the conglomerates of Palusson, have been raised by this upheaval up the slopes of the mountains, and are succeeded by the Miocene lacustrine molasse, which lies perfectly horizontally at their base. The next and last upheaval was one that did not affect the Pyrenees separately, but raised the whole area on which they stand, causing the emergence from beneath the sea of the region of the Landes and draining the lake that, washed the foot of the Pyrenees on the east, thus establishing the present land connexion between France and the Iberian Peninsula. The later rocks of the Pyrenees are to a large extent limestones, among which are conspicuous the characteristic hippuritic limestone of the southern Chalk and the nummu- litic limestone of the southern Eocene. For the most part the highest peaks belong to the granitic core of the moun- tains. But this is not always the case. In some instances limestone rocks have been carried up to the very crest of the mountains, as in Mont Perdu and in Marbore; the name of the latter, meaning "marble," indicates the nature of its constituent rock. Such limestone summits have a characteristic square massive form, very different from the sharp peaks of the granite and the schists. As in other limestone regions, caves are numerous in the Pyrenees, and several of these are of great interest to geologists and anthropologists on account of the traces of recent geological changes observable in them, and the remains of early man, both Palaeolithic and Neolithic, which they have yielded. The metallic ores of the Pyrenees are not in general of much importance, though there are considerable iron mines at Vic de Sos in Ariege and at the foot of Canigou in Pyrenees Orientales. Coal- deposits capable of being profitably worked are situated chiefly on the Spanish slopes, but the French side has numerous beds of lignite. Mineral springs are abundant and very remarkable, and specially