The geological construction of Spain is very peculiar, and unlike that of most other countries; it is almost one mountain or agglomeration of mountains, as those of our countrymen who are speculating in Spanish railroads are just beginning to discover. The interior rises on every side from the sea, and the central portions are higher than any other table-lands in Europe, ranging on an average from two to three thousand feet above the level of the sea, while from this elevated plain chains of mountains rise again to a still greater height. Madrid, which stands on this central plateau, is situated about 2000 feet above the level of Naples, which lies in the same latitude; the mean temperature of Madrid is 59°, while that of Naples is 63° 30´; it is to this difference of elevation that the extraordinary difference of climate and vegetable productions between the two capitals is to be ascribed. Fruits which flourish on the coasts of Provence and Genoa, which lie four degrees more to the north than any portion of Spain, are rarely to be met with in the elevated interior of the Peninsula: on the other hand, the low and sunny maritime belts abound with productions of a tropical vegetation. The mountainous character and general aspect of the coast are nearly analogous throughout the circuit which extends from the Basque Provinces to Cape Finisterre; and offer a remarkable contrast to those sunny alluvial plains which extend, more or less, from Cadiz to Barcelona, and which closely resemble each other in vegetable productions, such as the fig, orange, pomegranate, aloe, and carob tree, which grow everywhere in profusion, except in those parts where the mountains come down abruptly into the sea itself. Again, the central districts, composed of vast plains and steppes, Parameras, Tierras de campo, y Secanos, closely resemble each other in their monotonous denuded aspect, in their scarcity of fruit and timber, and their abundance of cereal productions.
Spanish geographers have divided the Peninsula into seven distinct chains of mountains. These commence with the Pyrenees and end with the Bætican or Andalucian ranges: these cordilleras, or lines of lofty ridges, arise on each side of intervening plains, which once formed the basins of internal lakes, until the accumulated waters, by bursting through the obstructions by which they were dammed up, found a passage to the ocean: the dip or inclination of the country lies from the east towards the west, and, accordingly, the chief rivers which form the drains and principal water-sheds of the greater parts of the surface, flow into the Atlantic: their courses, like the basins through which they pass, lie in a transversal and almost a parallel direction; thus the Duero, the Tagus, the Guadiana, and the Guadalquivir, all flow into their recipient between their distinct chains of mountains. The sources of the supply to these leading arteries arise in the longitudinal range of elevations which descends all through the Peninsula, approaching rather to the eastern than to the western coast, whereby a considerably greater length is obtained by each of these four rivers, when compared to the Ebro, which disembogues in the Mediterranean.
The Moorish geographer Alrasi was the first to take difference of climate as the rule of dividing the Peninsula into distinct portions; and modern authorities, carrying out this idea, have drawn an imaginary line, which runs north-east to south-west, thus separating the Peninsula into the northern, or the boreal and temperate, and the southern or the torrid, and subdividing these two into four zones: nor is this division altogether fanciful, for there is no caprice or mistake in tests derived from the vegetable world; manners may make man, but the sun alone modifies the plant: man may be fused down by social appliances into one uniform mass, but the rude elements are not to be civilized, nor can nature be made cosmopolitan, which heaven forfend.
The first or northern zone is the Cantabrian, the European; this portion skirts the base of the Pyrenees, and includes portions of Catalonia, Arragon, and Navarre, the Basque provinces, the Asturias, and Gallicia. This is the region of humidity, and as the winters are long, and the springs and autumns rainy, it should only be visited in the summer. It is a country of hill and dale, is intersected by numerous streams which abound in fish, and which irrigate rich meadows for pastures. The valleys form the now improving dairy country of Spain, while the mountains furnish the most valuable and available timber of the Peninsula. In some parts corn will scarcely ripen, while in others, in addition to the cerealia, cider and an ordinary wine are produced. It is inhabited by a hardy, independent, and rarely subdued population, since the mountainous country offers natural means of defence to brave highlanders. It is useless to attempt the conquest with a small army, while a large one would find no means of support in the hungry localities.
The second zone is the Iberian or eastern, which, in its maritime portions, is more Asiatic than European, and where the lower classes partake of the Greek and Carthaginian character, being false, cruel, and treacherous, yet lively, ingenious, and fond of pleasure: this portion commences at Burgos, and includes the southern portion of Catalonia and Arragon, with parts of Castile, Valencia, and Murcia. The sea-coasts should be visited in the spring and autumn, when they are delicious; but they are intensely hot in the summer, and infested with myriads of muskitoes. The districts about Burgos are among the coldest in Spain, and the thermometer sinks very much below the ordinary average of our more temperate climate; and as they have little at any time to attract the traveller, he will do well to avoid them except during the summer months. The population is grave, sober, and Castilian. The elevation is very considerable; thus the upper valley of the Miño and some of the north-western portions of Old Castile and Leon are placed more than 6000 feet above the level of the sea, and the frosts often last for three months at a time.
The third zone is the Lusitanian, or western, which is by far the largest, and includes the central parts of Spain and all Portugal. The interior of this portion, and especially the provinces of the two Castiles and La Mancha, both in the physical condition of the soil and the moral qualities of the inhabitants, presents a very unfavourable view of the Peninsula, as these inland steppes are burnt up by summer suns, and are tempest and wind-rent during winter. The general absence of trees, hedges, and enclosures exposes these wide unprotected plains to the rage and violence of the elements: poverty-stricken mud houses, scattered here and there in the desolate extent, afford a wretched home to a poor, proud, and ignorant population; but these localities, which offer in themselves neither pleasure nor profit to the stranger, contain many sites and cities of the highest interest, which none who wish to understand Spain can possibly pass by unnoticed. The best periods for visiting this portion of Spain are May and June, or September and October.
The more western districts of this Lusitanian zone are not so disagreeable. There in the uplands the ilex and chesnut abound, while the rich plains produce vast harvests of corn, and the vineyards powerful red wines. The central table-land, which closely resembles the plateau of Mexico, forms nearly one-half of the entire area of the Peninsula. The peculiarity of the climate is its dryness; it is not, however, unhealthy, being free from the agues and fevers which are prevalent in the lower plains, river-swamps, and rice-grounds of parts of Valencia and Andalucia. Rain, indeed, is so comparatively scarce on this table-land, that the annual quantity on an average does not amount to more than ten inches. The least quantity falls in the mountain regions near Guadalupe, and on the high plains of Cuenca and Murcia, where sometimes eight or nine months pass without a drop falling.