Portuguese Nautical Cryptography

Abstract

In 1474, King Alphonse V published an order that ‘increased the privileges of shipowners’. The experience acquired by Portuguese seamen had taught them that the bulky merchant galleys were unsuitable for navigating the high seas. A vessel with a narrower beam and rigged with lateen sails was needed, so that it could tack and sail on any point of the compass.¹ This type of lighter and faster ship had been constructed in Portugal since at least 1225, as is mentioned in the charter of Vila Nova de Gaia. When King Alphonse II conquered Faro in 1249, he had used heavy ships (galleys with oars and sails) and ships which had no oarsmen and were stepped with two large masts and a small one. The usual ship for faster sailing, however, was the Arab-type caravel.² The caravels were bigger in the reign of King John II and could sail in any sea. It was with one of these that Bartolomeu Dias rounded the Cape of Good Hope.