Farmers turned for their profit to the production of wine or oil, or with a still keener eye to business devoted their energies to sheep or cattle breeding. This was the staple industry of rural districts, so extensive and flourishing that in the fourteenth century it had established a kind of trades-union, or _mesta_ to look after its interests and secure it privileges. During the winter months the cattle fed at will on the wide tablelands of Castile; but with the coming of summer their owners drove them to pasture in mountain districts such as Leon and Galicia. It was on these journeys to and fro that agriculture and grazing came into conflict; for where the herds had passed they left a wilderness. Legislation indeed forbade the trampling down of vineyards and of meadows of corn or hay, but compensation for these damages was difficult to obtain from a corporation so powerful that it had won for itself a large measure of royal protection. Tolls paid on the migratory cattle formed a considerable part of the public revenue; and kings of Castile had thus been persuaded to foster a trade so lucrative to their own pockets, granting graziers not only immunity from certain imposts but also special rights with regard to wood-cutting and the freedom of the regular cattle-tracks from any enclosure or limitation. Ferdinand and Isabel renewed these privileges and in 1500 placed a member of the Royal Council at the head of the _mesta_, bringing that important body under their immediate control. If the laws of the maximum and the protection of rival industries hit agriculture hard, so also did the _alcabala_, a tax of ten per cent. on the sale-price of all goods. Originally imposed as a temporary means of raising money, it had become one of the main sources of the sovereigns’ revenues, and, while it burdened every commercial transaction, laid a triple charge on corn in the form first of grain and then of meal and bread. The _alcabala_ has been described by a modern historian as “one of the most successful means ever devised by a government for shackling the industry and enterprise of its subjects”; and Queen Isabel herself seems to have realized its blighting nature, for, in 1494, she agreed, on Ximenes’s advice, to commute it in the case of certain towns for a fixed sum to be levied by the municipality. Even so, the question of its legality still troubled her conscience; but the request in her will that a special committee should collect evidence and decide the matter justly was, like her kindly thought for the Indians of the New World, afterwards disregarded.