When, in the year 1670, Afonso Furtado de Castro do Rio de Mendonça became governor-general of Brazil, and assumed the responsibilities of the highest office in the colony, the search for El Dorado was already something of a recognized pursuit on the part of many government officials and of many enterprising colonists. The existence of rich deposits of gold, silver, and precious stones within the confines of Portuguese America was pretty generally taken for granted; and numerous people were periodically diverted from agriculture, which early formed the basis of much of colonial wealth, to follow the will-o’-the-wisp of hidden treasure into the wilderness. The appeal of the unknown was, of course, enormous, and the vision of El Dorado had become fixed in many minds, especially after the news of Spain’s good fortune in Peru and Terra Firma was spread. With geographical knowledge as piecemeal and as imperfect as it then was, it was no difficult matter for a credulous age to suppose that by penetrating the jungle areas westward from the sea the Portuguese might in some way tap the sources of Spain’s Andean mines.