Even before Columbus discovered the Antilles in 1492, the Portuguese had been aware of lands across the Atlantic and had made several expeditions to the West, but they had kept this knowledge secret from their ambitious neighbors. The official discovery of Brazil was made on April 22, 1500 by the Portuguese explorer, Pedro Álvares Cabral. To expand on Cabral's discovery the Portuguese employed Italian navigator Amerigo Vespucci who in 1499, under Spanish patronage, had explored the mouth of the Amazon and the northern shore of South America. In 1501, in Portuguese service, Vespucci returned to the South Atlantic, this time exploring the southern coast of what is now Brazil. It was Vespucci, using a system he devised for computing nearly exact longitude (previously determined by dead reckoning), who proved that a new continent had been discovered. And it is Amerigo Vespucci in whose honor America was named.