Cabot and his band of adventurers determined to neglect their surveying, trusting that the discovery of silver mines would excuse their disobedience. They spent three years in vain journeying and prospecting--exploring the Uruguay to the head of navigation and following up the Parana as far as the Apipe rapids. Signs of neither silver nor gold, nor of civilised inhabitants, were found on either river. Their upper courses came down from the east--the direction opposite to that in which Eldorado was reported. The gently flowing Paraguay, coming down the plains in the centre of the continent, seemed to offer a better hope of success. But Cabot's forces and provisions were inadequate to penetrating farther north than the present site of Asuncion. Returning to a fort he had left on the lower Parana, he found that it had been taken by Indians and its garrison massacred. Discouraged by such a succession of difficulties and misfortunes, he returned to Spain. The news of Cabot's expedition, and its failure, stimulated the Portuguese to undertake the colonisation of the east coast of South America. Affonso da Souza started from Lisbon with an expedition, intending to take possession of the Plate. Lack of provisions, fear of the Indians, the presence of a Portuguese castaway--one of those insignificant chances that sometimes change the course of empires as a twig diverts the current of a river--stopped Alfonso before he reached his destination. Instead of establishing a colony on the estuary he founded San Vicente, just south of the Tropic of Capricorn. This became the southern outpost of the Portuguese possessions, and the temperate zone of South America was left open for the Spaniards to occupy when they chose.