The consequences of this general structure are apparent on every hand. The population of Galicia is in many respects similar to that of the Portuguese mountaineers, who occupy the same band of naked granitic and primary rocks. The inhabitants of the varied and fertile Secondary band of Andalusia and Valencia have many traits in common. The Biscayans are a race apart, like the labyrinth of Cretaceous precipices and green rainy valleys which they inhabit. All are distinct from the Castilians, whose monotonous and isolated existence on the vast treeless steppes of crumbling Tertiary sands and marls that carpet the primary plateau 2000 feet above the sea has deeply influenced their character. Finally, the inhabitants of the Ebro basin, a region where the dry Tertiary soil of Castile is combined with many characteristics of the Secondary tracts, afford a curious mixture of Castilian with Basque or Valencian traits. The inhabitants of the greater Spanish cities are of course products of civilization, not of the soil. Of the visible surface of Spain 37 per cent. is occupied by Crystalline and Palaeozoic rocks, 34 per cent. by Tertiary, 19 per cent. by Secondary, and 10 per cent. by Quaternary deposits. The Palaeozoic rocks are greatly contorted and fractured, the Secondary scarcely less so, the older Tertiary are crumpled up against the flanks of the mountain chains, and even upturned Pliocene deposits testify in some places to the late continuance of the movements that have contributed to the production of the peculiar elevated character of the Peninsula. The remains of undoubted volcanoes are confined to the insignificant groups of Olot, Cabo de Gata, and Ciudad Real, but innumerable dykes and bosses of igneous rock are scattered over the primitive plateau where unconcealed by Tertiary sheets, and are also frequent in the Secondary tracts. This abundance of igneous injections is intimately connected with the exceptionally metalliferous character of Spain, while the fractured and contorted condition of even the latest rocky formations has contributed to a general diffusion of mineral wealth.