The rivers which are really adapted to navigation are, however, only those which are perpetually fed by those tributary streams that flow down from mountains which are covered with snow all the year, and these are not many. The majority of Spanish rivers are very scanty of water during the summer time, and very rapid in their flow when filled by rains or melting snow: during these periods they are impracticable for boats. They are, moreover, much exhausted by being drained off, _sangrado_--that is, bled, for the purposes of artificial irrigation; thus, at Madrid and Valencia, the wide beds of the Manzanares and the Turia are frequently dry as the sands of the seashore when the tide is out. They seem only to be entitled to be called rivers by courtesy, because they have so many and such splendid bridges; as numerous are the jokes cut by the newly-arrived stranger, who advises the townsfolk to sell one of them to purchase water, or compares their thirsting arches to the rich man in torments, who prays for one drop; but a heavy rain in the mountains soon shows the necessity for their strength and length, for their wide and lofty arches, their buttress-like piers, which before had appeared to be rather the freaks of architectural magnificence than the works of public utility. Those who live in a comparatively level country can scarcely form an idea of the rapidity and fearful destruction of the river inundations in this land of mountains. The deluge rolls forth in an avalanche, the rising water coming down tier above tier like a flight of steps let loose. These tides carry everything before them--scarring and gullying up the earth, tearing down rocks, trees, and houses, and strewing far and wide the relics of ruin; but the fierce fury is short-lived, and is spent in its own violence; thus the traveller at Madrid, if he wishes to see its Thames, should run down or take the ’bus as he can, when it rains, or the river will be gone before he gets there. When the Spaniards, under those blockheads Blake and Cuesta, lost the battle of _Rio Seco_, which gave Madrid to Buonaparte, the French soldiers, in crossing the _dry river_ bed in pursuit of the fugitives, exclaimed,--“Why Spanish rivers run away too!” [Sidenote: THE EBRO.]