But first we must speak of the various mountain systems and river basins of Spain, without which it is impossible to understand either the physical conditions of the country, or the social and political state of the various populations which has resulted from them. First, on the north is the chain of the Pyrenees, a continuation of the great Alpine system of Central Europe, stretching from Cape Creuz, 3 deg. 19' E., to the Bay of Biscay, 2 deg. 12' W., a distance of 320 miles, and prolonging itself westward in lower chains of different denominations until it finally sinks into the Atlantic at Cape Finisterre. The culminating points of the Pyrenees are towards the centre of the chain, in Mounts Maladetta, 11,150 feet, and the Pic de Posets and the Mount Perdu, each about 11,000 feet, whence the heights gradually descend, on the east to the Mediterranean and on the west to the Bay of Biscay. With the exception of the little Bidassoa, which in the lower part of its course forms the boundary between France and Spain, at the bottom of the Bay of Biscay, all the other waters of the Spanish side of the Pyrenees belong to the Ebro and to the Mediterranean. Parallel to the coast of the Bay of Biscay the Pyrenees are prolonged, first, by the Cantabrian Mountains, which run through the Basque Provinces, and the Province of Santandar; thence by the Picos de Europa, 8300 feet--from the south-eastern spurs of which the Ebro and Pisuerga take their rise--and the Asturian Mountains, to the Sierra de Penamarella, at the junction of the three Provinces of Leon, Asturias, and Galicia. The chain here attains its greatest elevation, 9450 (?) feet, then descends to a plateau of about 4000 feet, whence it sinks rapidly to the Atlantic, forming the headlands of Ortegal, the extreme north-western, and of Finisterre, the extreme western, point of Northern Spain. The mountains of Leon form the western watershed, between the waters of the Ebro and those which fall into the Atlantic. The line is continued eastward by the Oca Mountains, the Sierra de Moncayo, and the Idubeda Mountains. These mountain chains divide the basin of the Ebro from that of the Douro. They also form the northern buttress of the great plateau of Central Spain, which attains an elevation of from 2000 to 4000 feet. The rise to the plateau from the Bay of Biscay is very abrupt. Within fifty miles of leaving the coast the railways from the north attain a height of 2000 feet, and reach the Central Plateau, at Quintanapalla, at an elevation of 3000 feet; while La Canada, the highest point on the line to Madrid, is nearly 4460 feet, or about sixty feet higher than the tunnel of the Mount Cenis. From the eastern side the rise is less abrupt, and the plateau is entered at the lower elevation of 2330 feet, on the line from Alicante to Madrid. The famous Pass of Somosierra, on the old northern coach-road from Madrid, is about 4700 feet above the level of the sea.