Down the African coast: 1434-1460 Many and varied motives lie behind Prince Henry's African expeditions. In part they are pure voyages of discovery, driven by a longing to know what new places, people, animals or plants may lie beyond the next forbidding headland. Partly they are a straightforward quest for Africa's gold. Then there is the hope of colonizing new lands for Portugal. There is the desire to spread Christianity and frustrate Islam. There is even the fanciful dream of coming across a fabulous Christian ruler, Prester John.

But the overriding purpose is to discover a sea route round Africa to the east, with its rich promise of trade in valuable spices.

Ocean-going ships are improving at this period (the era of the caravel), but the sheer difficulty faced by the sailors is well suggested by the long struggle to get round Cape Bojador - a promontory only about 150 miles south of the Canaries. Prince Henry sends out fourteen expeditions to attempt this feat before at last one is successful, in 1434.

In the 1440s progress is quicker. Caravels sail round Cape Verde in 1444 and Cape Roxo in 1446, bringing them to the northern part of what is later Portuguese Guinea. By the time of Prince Henry's death, in 1460, navigators have explored as far south as Sierra Leone. They have also discovered the uninhabited Cape Verde islands.

According to the "Down the African Coast" section, what was Prince Henry hoping to accomplish by exploring Africa?