Atlantic: A Vast Ocean of a Million Stories. Simon Winchester

is indeed coastal danger that is most memorable along this stretch of the African shore. At latitude 27 South, some 150 miles south of the wrecks of Cape Juby, there rises a long, low headland, extremely undistinguished in appearance. This is a headland that remains hugely important in the history of Atlantic navigation, though in reality it is disappointingly not at all like those other famous Atlantic capes — Finisterre, Horn, Good Hope, Farewell, St Vincent, Race -that are the stuff of great poetry and legend. This, more modest in its majesty and its menace, is Cape Bojador.

      Though the Portuguese word bojador hints at “protrusion”, the land that makes up this low hurdle of cliffs is not a protrusion at all; nor does it pose anything but the smallest inconvenience to a vessel passing south along the African coast. But for many centuries no sailing vessel ever dared to pass it, nor was one physically able to do so. Quern quer passar além do Bojador, Tern que passar além da dor, wrote the modern Portuguese poet, Fernando Pessoa. He who wants to pass beyond Bojador, must also pass beyond pain.

      Beyond it lay a totally unknown sea — a terror-inspiring, monster-filled wilderness known in all ports as the Green Sea of Darkness.

      Until the fifteenth century, no sailor — whether Spaniard, Portuguese, or Venetian, whether Dane or Phoenician, and by all existing accounts no African sailors, either — had ever successfully rounded Cape Bojador from the Atlantic Ocean side. All the early navigational academies of Europe regarded the sea beyond Bojador as quite impassable. Its very existence stands as one of the reasons why the central Atlantic Ocean, despite having almost certainly the world’s most populous shores, was the last of the great seas to be properly navigated. Polynesian navigators had long before crisscrossed the Pacific; Persians and Gulf Arab sailors had taken their reed-and-creosote sailing craft across upper parts of the Indian Ocean; Chinese sailors knew the intricacies of the eastern Indian Ocean and their various littoral seas; and the Vikings knew the navigational complexities of the far north. But traditional navigation seemed not to work so well or so speedily in the Atlantic as it did elsewhere, and Cape Bojador, so far as the literature records, was one of the reasons why.

      The problem with Bojador was created by a unique combination of circumstances - topographic, climatic, and marine. No hint of impending difficulty would be apparent to a southbound sailor, who would perhaps leave from an Iberian port, head past the Strait of Gibraltar with light winds still favourably on his starboard quarter, and dip steadily along the African coast at a comfortable five or six knots. He would mark his passage each day by the sight of the three obvious Moroccan capes: Rhir, Draa, and Juby. He would see the twinkling fires of the settlements of Casablanca, Essaouira, and El Ayoun, taking comfort from their proximity - for like most in those early days he was probably a nervous sailor, and would always be most reluctant to leave the sight of shore, finding a degree of security in his crabwise progress along the edge of land.

      And then he would come to Bojador — and in an instant his illusion of comfort would evaporate. An unseen sandbar, stretching twenty miles out from the low cape and reducing the depth under his keel to a mere couple of fathoms, would first compel him to turn to starboard and, against his better judgment, head out into the deep ocean. At the same time the telltales on his mainmast would show that the slow winds off Morocco had suddenly changed to full easterly, and may well have picked up to a steady half gale. (For most of the year the winds veer east just at this point, and modern satellite pictures will show trails of desert sand being wafted each summer out across the Atlantic.²⁰) And thirdly, once clear of the submerged point, a current -the North Equatorial Current — would catch his vessel in its powerful maw and begin to drag it westwards, too, for possibly as much as six hundred miles.

      The perils of the cape are actually even more conspiratorial than this. For most of the voyage down along the coast a persistent southbound current, called by the Portuguese mariners the Guinea Current (modern mariners call it the Canary Current), helped sailors of old to scurry along the shore, providing only that they kept close to land. This was important, because one characteristic of the Guinea Current was that it became steadily weaker the farther offshore. This then gave a ship’s master two equally unpalatable options: remain close inshore and risk being swept into the irresistible arms of the westbound equatorial stream, or sail well away from land and encounter only a fading current and weak winds, and remain motionless at sea, with food and water running out, the vessel trapped in doldrums of your own making.

      Small wonder not a single seaman managed to get past the cape - until a seminal moment, seventy years before Vespucci, in 1434. It was the growing intelligent acquaintance with the complexities of the sea that eventually allowed the Bojador problem to be solved - as the early phase of exploration of the Atlantic steadily gave way to a period of rigorous ocean education. To know the sea became the working phrase, for only by knowing it could its dangers be avoided and its treasures exploited. The Cape Bojador story is a classic example of this shift in attitude.

      It was a young Portuguese navigator named Gil Eannes who is commonly credited with having the maritime intelligence and feel for the sea so necessary for blazing a southbound trail. Though most of the papers relating to his voyage were lost in the Lisbon earthquake three centuries later, sufficient anecdotal evidence remains to hint at just how he did it. It was entirely a matter of intelligence: of using such intellectual techniques as observation, forethought, timing, planning and calculation.

      Prior to Eannes, sailors merely set themselves a goal (or had it set it for them by their financial sponsors), victualled their ship and set off — and in the case of their West African ventures, all were forced to turn back after little more than a thousand miles. These sailors employed the rituals of old - they followed the currents, they sailed before the winds, they followed the paths of seabirds. But what Gil Eannes did next involved an immense amount of planning, and it invoked the growing science of celestial navigation, already known to the Arab merchants after diffusing slowly from the East, where it had evolved to a fine degree under the Chinese.

      Eannes believed it would be possible now to move through the Atlantic and reach places unfavoured by winds and currents and migrating birds if a mariner used the new tools fast becoming available: astronomy, timekeeping, a sophisticated knowledge of weather and climatic history and the geography of the sea. To get around Cape Bojador specifically, or to double it, in seamen’s jargon, involved the scrupulous measuring of the water speeds and directions, and the measuring in detail of the average directions and strengths of the winds. It involved the development of a technique now known as current sailing. Eannes also drew current triangles onto his crude but ever-improving charts sets, and used vectors, intelligent tacking and careful, hour-by-hour timing. Once he knew the currents and the winds, their directions and their speeds, it remained a matter of simple trigonometry to plot a course that would take advantage of them both. However, his planning also involved choosing a season when the winds of one kind would be blowing while those of another would not.

      Only after all that information had been digested and calculated and factored in could Eannes set his rudder and trim his sails and point his bowsprit in a direction that might have seemed to his unsuccessful predecessors eccentric - but eccentric in the way that modern Great Circle routes seems oddly counterintuitive when compared with the apparent directional simplicity of a voyage made along a straight line of constant bearing, in other words a rhumb line or loxodrome.

      The precise details of his famous voyage remain unclear -there is no surviving diary, no ship’s log, not even the name of the ship is recorded. All we know is that Eannes went south on the explicit orders of Henry the Navigator, the princely architect of Portugal’s imperial ambitions. Henry had drily remarked that fourteen previous attempts to double the cape had failed. Eannes, who was no more than one of the personal servants in Henry’s court, might just as well make an attempt, too.

      He did precisely as he was ordered - he sailed south-west to Madeira and the Canaries, then performed all his complicated arithmetical elaborations. He initiated a deep-sea twisting-and-turning voyage that has been known for many years since as the Portuguese volta, and by doing so succeeded finally in rounding the dreaded cape. He was then blown by the gusts of a harmattan wind onto the African desert coast some thirty miles south of Bojador