Now the north-west coast of Africa was known in Prince Henry’s days as far as Cape Bojador.  It would appear that Norman sailors had already advanced beyond Cape Non, or Nun, which was so called because it was supposed that nothing existed beyond it.  Consequently the problems that Prince Henry had to solve were whether the coast of Africa trended sharply to the east after Cape Bojador, and whether the ideas of the ancients about the uninhabitability of the torrid zone were justified by fact.  He attempted to solve these problems by sending out, year after year, expeditions down the north-west coast of Africa, each of which penetrated farther than its predecessor.  Almost at the beginning he was rewarded by the discovery, or re-discovery, of Madeira in 1420, by Joao Gonsalvez Zarco, one of the squires of his household.  For some time he was content with occupying this and the neighbouring island of Porto Santo, which, however, was ruined by the rabbits let loose upon it.  On Madeira vines from Burgundy were planted, and to this day form the chief industry of the island.  In 1435 Cape Bojador was passed, and in 1441 Cape Branco discovered.  Two years later Cape Verde was reached and passed by Nuno Tristao, and for the first time there were signs that the African coast trended eastward.  By this time Prince Henry’s men had become familiar with the natives along the shore and no less than one thousand of them had been brought back and distributed among the Portuguese nobles as pages and attendants.  In 1455 a Venetian, named Alvez Cadamosto, undertook a voyage still farther south for purposes of trade, the Prince supplying the capital, and covenanting for half profits on results.  They reached the mouth of the Gambia, but found the natives hostile.  Here for the first time European navigators lost sight of the pole-star and saw the brilliant constellation of the Southern Cross.  The last discovery made during Prince Henry’s life was that of the Cape Verde Islands, by one of his captains, Diogo Gomez, in 1460—­the very year of his death.  As the successive discoveries were made, they were jotted down by the Prince’s cartographers on portulanos, and just before his death the King of Portugal sent to a Venetian monk, Fra Mauro, details of all discoveries up to that time, to be recorded on a mappa mundi, a copy of which still exists (p. 77).

The impulse thus given by Prince Henry’s patient investigation of the African coast continued long after his death.  In 1471 Fernando de Poo discovered the island which now bears his name, while in the same year Pedro d’Escobar crossed the equator.  Wherever the Portuguese investigators landed they left marks of their presence, at first by erecting crosses, then by carving on trees Prince Henry’s motto, “Talent de bien faire,” and finally they adopted the method of erecting stone pillars, surmounted by a cross, and inscribed with the king’s arms and name.  These pillars were called padraos.  In 1484, Diego Cam, a knight of the king’s household, set up one of these pillars at the mouth of a large river, which he therefore called the Rio do Padrao; it was called by the natives the Zaire, and is now known as the River Congo.  Diego Cam was, on this expedition, accompanied by Martin Behaim of Nuernberg, whose globe is celebrated in geographical history as the last record of the older views (p. 115).