d later the sub-Saharan African southwestern coast. In the Iberian Peninsula, Jewish and Muslim astronomers and mathematicians kept alive and improved upon ancient classical Eastern wisdom concerning navigation. From the 12th century onwards, major breakthroughs occurred there in maritime technology. These included the arts of celestial navigation, the development of the magnetic compass, the astrolabe and the quadrant, the use of Arab lateen sails and newly designed vessels, such as the caravel, which together enabled Portuguese sea captains to overcome the resistance created by the currents and winds off the African coast to further southern and western exploration. The conquest of the tradewinds opened up not only coastal Africa and the Indian Ocean to exploration and trade, but also the Americas. By the 1480s this experience was disseminated at schools of navigation in Spain and Portugal and codified in the Portuguese regimento, a set of navigation rules and known techniques.
Motivations. Fifteenth century Portuguese rulers sponsored and largely financed trans-Atlantic voyages of discovery for a variety of reasons. The lure of profits from the West African gold fields, the slave trade and the spice and other treasures of Asia were causative factors, as was the desire by Catholic Iberia to bypass the Ottoman blockage of the land routes to the riches of the East. The desire to spread Catholicism was a major impulse behind the Spanish voyages of discovery, but less so initially among the Portuguese elite which practiced religious toleration and thereby made welcome Muslim and Jewish scholars expelled by Spain in the late 15th century (Seed, p. 135). The conquest of the Americas provided a convenient outlet for the energies of Spain's young and largely disinherited sons following the completion of the reconquista. For the Spanish, settlement of the New World was incidental to the conquest, looting and conversion of Amerindians. It ...