Rivers.— The northern slope extends be tween the Bay of Biscay and the Cantabrian Mountains. Here we find a long and narrow zone characterized by heavy rainfall upon ex tremely steep declivities — with the result that its rivers are torrents, without value for navi gation. The eastern slope is divided into three parts, namely, the slope of the eastern Pyrenees, the Ebro Valley and the southeast ern region. In the first part we find the Muga, Llobregat, Ter, Tordera, Galli and Francoli. In the second part, which embraces almost one sixth of the area of Spain, we find the Ebro and its affluents, the Zadorra, Ega, Aragon, Gallego, Sere, Cinca, JalOn, Calatayud, Huerva and Guadalupe. In the third part are the Jficar, Vinalop6 and Segura. The Ebro, if we may judge from data supplied by his tory, was formerly navigable from its mouth even to Logrofio; but it has suffered important changes, and canalization at two points became necessary. The Carlos Canal was cut through the delta formed by deposits of sand and pro jecting out into the Mediterranean; the Im perial Canal was constructed from a point 40 miles below Zaragoza (Saragossa) to Tudela. The western slope is, from the hydrographic point of view, most important of all, since in this wide zone are found the valleys of the great rivers Mifio. Duero, Tajo (Tagus), Guadiana and Guadalquivir. The last-men tioned has always been of highest value for transportation; and in early historical times it was navigable far beyond Seville— even to Cordoba or Montoro. The southern slope is even narrower than the northern, and is the least important of all in a hydrographic sense; the rivers of this slope being characterized by short course and small volume. Here we find emptying into the Mediterranean, the Almeria, Adra, Guadalfeo, Guadalhorce, Guadiaro; and, emptying into the Atlantic, the Guadalete. With a few important exceptions, then, all the rivers of Spain dash, rather than flow, along precipitous beds among deflecting mountains; their character is torrential, their courses sinuous. Consult Becker, J., 'El Medio Geografico en la Historia de Espana' (Boletin de la Real Sociedad Geognifico, Tomo LVIII, Madrid 1916).
The study of Spanish orog raphy concerns itself with the three exterior lines that mark the northern, eastern and south ern slopes, and the other three that extend through the interior. The northern system, in cluding the Cantabrian Cordillera and the Pyrenees, bounds on the north the central meseta and the Ebro Valley. According to the classification of the Geographical Institute of Madrid, this is followed by (2) the Iberian system, formed by mountain-masses which separate the central meseta from the Ebro Valley [on the northeast] and from the Mediterranean slopes; (3) the Central system, generally known as Cordillera Carpeto Vetonica or Carpetana, which extends through the centre of the peninsula and separates the mesetas of the two Castiles; (4) The system of the mountains of Toledo, extending east and west in the centre of the meseta of New Castile; (5) the Bede Gordillera, between the great central meseta and the depression of the Guadalquivir and formed mainly by the Sierra Morena; (6) the Penibetic system, which ex tends from Cape Tarifa to the Sierra Nevada, including both, and shuts in the valley of the Betis, or Guadalquivir, on the south.
Climate.— Extending approximately from lat. 36° N. to little less than 44° N., Spain forms a part of the southern region of the temperate zone, and would be endowed with a climate characterized by very distinctly marked seasons were such cosmic traits not greatly modified by various circumstances. We have already mentioned, among the geographical in fluences to which its climate is subject, the great heights and different orientation of its cordilleras and the varied configuration of its lands — such diversity of natural features of course affecting the atmospheric circulation and in part explaining sudden alternations of winds that are hot and damp with those that are cold and dry. But we must also remember that the
north coasts, influenced by the Bay of Biscay, the western by the Atlantic Ocean, the south ern and eastern by the Mediterranean Sea, ex perience particular effects which are far from being the same. Moreover, the.influence of the Gulf Stream is felt especially on the northwest coast, and that of the Sahara in the south. It is, therefore, proper to emphasize Spain's climatological diversity: it is not possible to say that a well-defined climate prevails in or throughout any extensive region whatever, since there exist in the country, and sometimes al most side by side, all the mixtures from sub tropical to Alpine. On the plains of New Castile and Estremadura, as in a large part of Andalusia, the climate in summer is rather fiercely torrid; in all the cordilleras one finds delicious valleys, of benign temperature; but the lands of Old Castile and Le6n are characterized by harsh and prolonged winters. The annual rainfall, greatest in the northwest, especially Santiago, is slightly less at Saint Sebastian and Bilbao; about half as great at Coruna, San Fernando, Caceres and Jaen; less than one-half as great at Malaga, Soria, Burgos, Huesca, Segovia and Barcelona; about one-third, or even less, at Sevilla, Murcia, Valencia, Granada, Alicante, Molina and Madrid; about one-fourth at Leon, Badajoz, Lerida, Cartagena and Valla dolid; and at Salamanca and Zaragoza the an nual rainfall amounts only to one-fifth or one sixth of that which makes the Spanish north west a beautiful green country.
Flora.— The diversities of temperature, etc., to which we have invited attention (see CLIMATE) occasion such a variety in the species of vegeta tion as no other country of Europe presents. For this reason Linnxus bestowed the title "India of Europe" upon Spain — which, indeed, in all historical ages has been considered the botanist's land of promise although the growths of forest and field are checked by the extreme aridity of the meseta. The number of indig enous species positively known to exist in Spain exceeds to-day 7,100, without counting those varieties and forms about which doubt is still entertained. This wealth becomes even more manifest on comparing it with that of other countries. Thus, if we reckon at 10,000 the number of species of vascular plants in Europe as a whole, about 5,400 of them exist in Spain, 4,225 in France, about 5,000 in Italy, including Sicily, and slightly more than 1,600 in England. Even in the small province of Madrid there are, despite the aridity of its plains, approxi mately 2,000 species. And if we compare the numbers of the exclusive species we shall find that 1,200 endemic species exist in Spain (about 22 per cent of the vasculars) ; in Italy about 300 or about 6 per cent of its flora). In France the strictly indigenous species number about 100 (or, say, somewhat more than 2 per cent). We may estimate very closely the affinity of the Spanish flora with that of other lands as fol lows: Of spontaneous vascular species in Spain 60 per cent are represented also in the other European floras; 25 per cent are very similar to those of northern Africa; slightly more than 13 per• cent Spain possesses in common with Asia; with South America not more than 7/2 per cent ; with North America less than 3 per cent; 2/ per cent with tropical and southern Africa; and with Oceania only about five species per mille.