In these wild tracts the highlanders in summer lead their flocks up to mountain huts and dwell with their cattle, struggling against poverty and wild beasts, and endeavouring really to keep the wolf from the door: their watch-dogs are magnificent; the sheep are under admirable control--being, as it were, in the presence of the enemy, they know the voice of their shepherds, or rather the peculiar whistle and cry: their wool is largely smuggled into France, and when manufactured in the shape of coarse cloth is then re-smuggled back again. [Sidenote: THE RIVERS OF SPAIN.] CHAPTER III. The Rivers of Spain--Bridges--Navigation--The Ebro and Tagus. [Sidenote: SPANISH RIVERS.] There are six great rivers in Spain,--the arteries which run between the seven mountain chains, the vertebræ of the geological skeleton. These water-sheds are each intersected in their extent by others on a minor scale, by valleys and indentations, in each of which runs its own stream. Thus the rains and melted snows are all collected in an infinity of ramifications, and are carried by these tributary conduits into one of the main trunks, which all, with the exception of the Ebro, empty themselves into the Atlantic. The Duero and Tagus, unfortunately for Spain, disembogue in Portugal, and thus become a portion of a foreign dominion exactly where their commercial importance is the greatest. Philip II. saw the true value of the possession of an angle which rounded Spain, and insured to her the possession of these valuable outlets of internal produce, and inlets for external commerce. Portugal annexed to Spain gave more real power to his throne than the dominion of entire continents across the Atlantic, and is the secret object of every Spanish government’s ambition. The _Miño_, which is the shortest of these rivers, runs through a bosom of fertility. The _Tajo_, Tagus, which the fancy of poets has sanded with gold and embanked with roses, tracks much of its dreary way through rocks and comparative barrenness. The _Guadiana_ creeps through lonely Estremadura, infecting the low plains with miasma. The _Guadalquivir_ eats out its deep banks amid the sunny olive-clad regions of Andalucia, as the Ebro divides the levels of Arragon. Spain abounds with brackish streams, _Salados_, and with salt-mines, or saline deposits after the evaporation of the sea-waters; indeed, the soil of the central portions is so strongly impregnated with “villainous saltpetre,” that the small province of La Mancha alone could furnish materials to blow up the world; the surface of these regions, always arid, is every day becoming more so, from the singular antipathy which the inhabitants of the interior have against trees. There is nothing to check the power of rapid evaporation, no shelter to protect or preserve moisture. The soil becomes more and more parched and dried up, insomuch that in some parts it has almost ceased to be available for