Caravela Latina / Latin Caravel: Caravel Boa Esperana of Portugal.
Caravela Redonda / Square-rigged Caravel: Caravel Esprito Santo of Brazil

Portuguese caravel, adorned with the Cross of the Order of Christ. This was the standard model used by the Portuguese in their voyages of exploration. It could accommodate about 20 sailors.

In the summer of 1420 the people of Sagres, a seaport on Portugal’s southwestern coast, were puzzled by some strange goings-on: an entire horde of men lugging trunks of papers moved into a series of buildings under construction on the high cliffs overlooking the harbor. The men were not very enlightening about what they were doing; unusually tight-lipped in the traditionally open world of seafaring, they settled into the buildings, kept strictly to themselves, and seemed to spend most of their time poring over those papers and writing their own papers. In the harbor, it was noticed that a number of strange-looking craft were under construction, types of large ships no one had ever seen before. And there were workshops that seemed to be busy around the clock with the sounds of hammering and sawing.

What was happening at Sagres represented a large-scale scientific research and development effort that rivaled Alexandria. Thanks to the riches seized from the Moors, Henry had the deep pockets from which he paid top dollar to lure a glittering collection of scientific and technical talent—Greek shipwrights, Italian mathematicians, Jewish astronomers, Phoenician ship designers, Muslim cartographers—to a research institute he founded at Sagres with instructions to develop an entirely new design for oceangoing ships and the navigation tools that would allow them to sail anywhere with scientific exactitude. He decreed that the effort was top secret; they were not to breathe a word of what they were doing at Sagres, and they were never to use whatever knowledge they gained there on behalf of any other kingdom.

Over the next forty years, this intense research effort would revolutionize all human existence because the scientists and technicians of Sagres were able to lift the clouds of error and superstition that for many centuries had constricted exploration of the world. The clouds had been created by Aristotle and Ptolemy, who claimed that the sun was so close to the equator that that area of the planet was all boiling seas and desert—and ships would disappear in the cauldron. Sailors had long assumed that the earth was probably round, but were intimidated by what they believed was a huge bulge at its center. This bulge, they were certain, contained seas so thick with salt that no ship could cleave it. And they also believed that because of the great bulge, any human beings living on it were misshapen savages (young seamen were solemnly informed by their older shipmates that any Christian attempting to sail through the bulge would be turned into a Negro).

Such horror stories were regarded as fairy tales by the scientists working at Sagres. They had already concluded that earth was an imperfectly round globe, with the equator marking the exact halfway point in the globe’s north–south direction. True, it was probably warmer in equatorial latitudes, but as the astronomers pointed out, the sun did not approach the planet close enough to produce anything like the kind of heat needed to boil seas. They had conducted a number of experiments that revealed the large amount of heat required to bring even a small amount of seawater to a boil (mainly while trying to find out a way to distill salt), and the kind of heat needed to bring fathoms of seawater to a boiling point was beyond calculation. If the sun was hot enough to boil water at the equator, then it logically followed that such intense heat would have turned Europe into a desert. And it hadn’t.

Only a true oceangoing ship would prove whether the scientists were right, and that is where the main effort at Sagres was concentrated. The result was a revolutionary ship design that would open the world’s oceans to exploration. Called a caravelle, it was a 50-ton design that featured decks high above the waterline, multiple masts, a combination of triangle-shaped lateen and square sails, and a deep hull (to carry a lot of cargo). In technological terms, it represented that century’s equivalent of the switch from horse-drawn wagons to vehicles powered by the internal combustion engine. For centuries, the ideal ship design was considered the low-hulled galley powered by oars, supplemented by a lateen sail, a design the scientists and technicians at Sagres concluded would never work on the open sea. Galleys were too slow (an important factor when shipping goods); unseaworthy in rough seas (as the ancient wrecks still littering the bottom of the Mediterranean attest); too labor-intensive (it’s hard to recruit rowers, unless they’re slaves or convicted criminals serving out terms of penal servitude); and, most significantly, technologically unsuitable for the mounting of the new wonder weapons, cannons (a galley’s center of gravity could not handle the weight of heavy guns).

The caravelle changed all that. It was very sturdy, able to handle even the roughest seas, very fast, could haul a lot of cargo (or store a lot of provisions for long voyages), and had reinforced decks to allow for the addition of guns. But the real genius of the new design lay in its propulsion and navigation systems. Extensive testing had shown that the ideal propulsion for a sailing ship consisted of a combination of the triangle-shaped lateen sail that had powered ancient Mediterranean fleets since the time of Troy, working in tandem with a square sail. This design utilized the advantage of a lateen sail (maneuverability) while adding the advantage of a square sail (the best design to catch the maximum amount of wind). The new propulsion design also eliminated the lateen sail’s chief weakness, insufficient power; ships with only lateen sails were prisoners of prevailing winds—not a problem in the predictable wind flows of the Mediterranean, but useless in the more unpredictable winds of the Atlantic and other oceans.

The more striking scientific advance was reflected in the ship’s navigation system. First, the Sagres designers devised a sternpost rudder connected to a steering wheel, which made a sailing ship much faster, since a helmsman could now tack to take advantage of shifting winds with just a turn of a wheel. Moreover, he could keep the ship on course using the next Sagres innovation, a wondrous instrument called a compass, a revolutionary piece of technology whose needle always denoted north–south. The basic concept of the compass was borrowed from the Chinese, and meant ships could sail under cloudy skies, guided by an instrument unaffected by weather conditions and time of day or night. And finally, an entirely new innovation: sailing charts, the first attempt to map the seas. The early charts were not especially accurate due to lack of surveying data, but did include at least some of the important information any navigator needed to know: landmarks, compass directions, sea depths, and navigational hazards.

By 1435, Prince Henry’s new ships were cautiously poking their way to the equator, where the nervous crews made a happy discovery: lands around the equator weren’t deserts, they were lushly green. Six years later, in the process of developing shipping routes farther south along the western coast of Africa, two of these ships opened what would prove to be a dark chapter of history. They anchored off the coast one day and sent armed parties ashore to explore the lush vegetation. They immediately encountered several natives who fell to their knees in terror upon seeing these strange creatures. The Portuguese put them in chains, announced their baptism in the Christian faith, then bundled them aboard the ships as slaves. They were later put to work in Portuguese plantations, where their free labor so dramatically increased profits; Henry was soon bombarded with requests to bring back more—for which, of course, Henry noted, the plantation owners would be expected to pay. The result was the first great profit-making enterprise for Portugal’s merchant classes, trafficking in slaves. By 1448, some nine hundred African slaves had been brought to Portugal, just the beginning of what would eventually become a flood of enslaved human beings.

At the same time, another dark chapter was being opened: imperialism. For all his scientific enlightenment, Henry was a man of his time. Like his fellow European rulers, Henry believed fervently in the idea that the Europeans had a superior civilization that was to be imposed upon “heathens” and “savages” who needed to be converted to European religious and political orthodoxy. And if these barbarians happened to occupy land Europe coveted for its burgeoning economic and military interests, then it was perfectly justified for the Europeans to take the land in the name of “civilizing” inferior peoples.

The caravalle represented the best instrument to effect that policy, as demonstrated by Columbus, whose Santa Maria, a caravelle escorted by two smaller ships, conquered the land he christened El Salvador. Although he was not able to achieve his dream of finding vast gold deposits that would justify the royal investment that had propelled him westward, he set the pattern for European imperialism: a landing upon strange shores, a pronouncement that all the land was now within the domain of a particular European kingdom, enslavement or slaughter of the native population, and then exploitation of whatever natural resources could be found there.

But despite the great advantages of the caravelle—its ability to sail long distances, stand up to the rigors of lengthy ocean voyages, and carry plenty of cargo—from the moment the prototype sailed out of the harbor of Sagres, the new ship created two major headaches. One was protection. Caravelles loaded with valuable cargo would be prime targets in the event of war (they also would attract the attention of pirates). That meant the ships would have to be fitted with some sort of protection, enough firepower to deter predators. The design specifications of the caravelles included the necessary structural strength to arm them with cannons, but nobody had yet figured out how to put heavy cannons aboard ships. The problem was that mounting heavy cannons on a merchant ship’s deck created serious instability problems, threatening the ship’s center of gravity. Moreover, there was the problem of recoil; when fired, a heavy cannon recoiled backward several feet, and there was very little room for recoil on a crowded deck.

Consequently, caravelles could be outfitted with just a few small cannons, useful only for signaling. The truth was that to be invulnerable, merchant ships would have to serve double duty: merchant ship and man-of-war. One alternative was to build new warships armed with heavy cannons and capable of keeping up with merchant ships while they did escort duty. But warships faced the same technical problem: How to mount heavy cannons on the upper deck?

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