Yet before the middle of the sixteenth century America took on a value of its own, and ceased to be regarded as a mere obstacle, in the path of trade. After the conquest of Mexico and Peru, the New World, found to be rich in silver and gold, was thought to be a new Indies indeed. To the idealizing mind of the age America already spelled opportunity; and in the sixteenth and seventeenth centuries the maritime states of Europe established their spheres of influence there--still seeking, through its trackless forests, a waterway to the South Sea, still seeking gold, falling back at last upon the prosaic business of colonization and the exploitation of its less attractive resources. The Spaniards found no lack of treasure, but in North America gold ever turned to ashes, and the great South Sea receded like a mirage before every advance. Yet the failure of many voyages to the frozen North, and of many inland expeditions ending in disaster and death, could not quench the optimism which the gentlemen adventurers caught from the men of the Renaissance and bequeathed to the colonist, and which for two hundred years the frontiersman has preserved as a priceless heritage of the New World. When Columbus returned from his first voyage of discovery in 1493, he brought home some gold trinkets which the Indians had readily exchanged for glass beads. The transaction is symbolical of two centuries of South American history. The achievements of the Conquistadores have scarcely a parallel in the annals of conquest; but it was the desire for treasure that led them on; and the treasure they discovered became the foundation of the Spanish Empire. In exchange for their gold and silver, Spain imposed upon the native races of America an enlightened despotism and the benefits of Christian civilization.