Читать книгу Atlantic: A Vast Ocean of a Million Stories - Simon Winchester - Страница 22

It has to be remembered that until Amerigo Vespucci, there was no knowledge — nor even a suspicion or a hint — that the Atlantic was a separate sea. Culturally, this was an ocean that until the end of the fifteenth century was not known to exist. Then, and at a stroke, with Vespucci’s voyage, the Atlantic Ocean was born; suddenly it was there.

With this realisation of a brand new sea, anchors were weighed and sails unfurled, brass clocks were wound and heaving lines leaded. Scientists were appointed and chart makers assigned, and bold and fearless skippers in their legions took their little ships out of port and headed off to measure and to mark this new body of water.

At the edges of a sea, it is the daily tides that prove the most obvious features to measure and record. Out in the deeps, beyond the influence of tides, the seaman must look for other things: for the size of waves and the direction of swells, the tenor of storms, the press of fish and birds, the depths beneath the bow. And, most importantly, the unexpected and initially mysterious ways that the waters appear to move.

Since these motions are among the most clearly influential on the passage of any ship - as Gil Eannes experienced off Cape Bojador, and then made use of - they were noticed very early on in the exploration of the Atlantic. They seemed like great underwater rivers, or torrents. Currents-from the French, things that run — were the first of the ocean’s many unseen features to become properly known. And perhaps no stream was more famously so than that immense rushing extension of the North Equatorial Current known, from Florida, where it begins, to the west of Scotland, where it ends (with palm trees growing beside the waters that it so conveniently warms), as the Gulf Stream.

Like many mariners around the world, Columbus noticed the currents — and here the exceptionally strong currents that seemed to him so unusually prevalent in Caribbean Atlantic waters. “I found the sea ran so strangely to the westward,” he wrote in the log of his third voyage, describing his passing through the notorious Dragon’s Mouth, between Trinidad and the Venezuelan mainland, “that between the hour of Mass, when I weighed anchor, and the hour of Complines, I made sixty-five leagues of four miles each with gentle winds …” There are also accounts by Peter Martyr, the Spanish court historian who, coincidentally, was among the first to recognise the huge potential importance of the Gulf Stream, of a vain attempt by Columbus to take a sounding off the coast of Honduras, only to have the “contrary violence of the waters” force his lead upward and never once allow it to touch bottom.

But Columbus was too far south to experience the power of the Gulf Stream. That happy discovery was left to his successor, Ponce de León,²² who found it in 1513, while on his quest for the fountain of youth - a search that eventually won him the ironic substitute of being the first European to find Florida. He was charting the topography of this new coast - thinking it to be a large island, the flowered one.

Ponce made rendezvous with two other ships coming north from Puerto Rico, and the three vessels set themselves to sailing farther south, keeping Florida just in sight on their starboard side. One afternoon, when they were perhaps thirty miles from shore, Ponce de León and his fellow sailors suddenly found themselves swept into and caught up in “a current such that, although they had a great wind, they could not proceed forward, but backward, and it seems that they were proceeding well; at the end it was known that the current was more powerful than the wind.” Whatever was the cause, this wide river of water, which he soon found swept northwards and in time turned towards the east, had huge and unstoppable power. The Spaniard became swiftly aware of its commercial implications :that however difficult it might be for ships to beat their way westwards across the middle reaches of the Atlantic, the power of this submarine river offered the guarantee that anyone who floated onto it would be taken home, in style and with considerable speed. Empty galleons might find the outbound passage a trial, but treasure-laden and stately, they could dip home from the Isthmus of Panama, pushed along by this new-found current, with a very welcome dispatch.

Riding the Gulf Stream home quickly became a kind of navigational sport. The traditional means of return to Spain -though it was barely a tradition, since the passage had only been opened two decades before - was to use the winds alone, to take advantage of the westerlies that blew for most seasons in the middle latitudes of the ocean. But there was a risk inherent: on a voyage from the Main it was tempting to turn east, to turn for home, too early, and in doing so chance becoming becalmed in the fickle breezes of what is now known as the Bermuda High.Now that the Gulf Stream was known, the solution was simple — though, as with the sharp turn to sea made by Gil Eannes in rounding Cape Bojador, it was also counterintuitive. He headed west to go south; homebound Atlantic skippers needed to head north to go east.

Coming from the Isthmus they would tease out the Gulf Stream’s beginnings in the Caribbean and then more properly in the shallow waters off what is now known as Cape Hatteras. Once it was found, a homebound sailor would attempt to slot his ship neatly into the sixty-mile-wide band of its warm, fast flowing waters, let the current carry him north at nearly six miles per hour, and then as it turned, head eastwards with it too, following its warm blue stream for most of its two-thousand-mile curving, Europe-bound length.

Once this marvel had been discovered, and once its spread and its speed had been mapped and measured, the Gulf Stream swiftly became an object of widespread fascination. Its most resolute early champion was perhaps its most improbable: the polymathic American statesman and founding father, Benjamin Franklin. In a most remarkable letter written on board a Falmouth, England-bound packet boat in the summer of 1785, he ruminated with precision and wisdom on Sundry Circumstances Relating to the Gulph Stream — a document of such intellectual richness that it is easy to see why this most unforgettable of men went on to invent such wonders as the lightning rod, bifocal lenses, lending libraries, a superior kind of fireplace,²³ and the underlying principle behind the glass harmonica.

The letter, to a French academician and friend named Alphonsus le Roy, is quite stunning, fascinating at every line. The Gulf Stream does not appear until halfway through - and by the time of getting down to writing his thoughts about it, Franklin had already offered to his friend a meandering dissertation on the design of ships’ hulls, on the possible use of propellers to steer balloons, on the most common causes of accidents at sea and on the kinds of foodstuffs best stowed for long ocean voyages (almonds, rusks, lemons and “Jamaica spirits” foremost among them).

But then came the Gulf Stream moment, when Franklin reminded le Roy that a decade before, he had been America’s first postmaster general, and colonial postmaster before that, and that this was when he first fully apprehended the North Atlantic’s most unusual phenomenon of the time:

About the year 1769 or 70, there was an application made by the board of customs at Boston, to the lords of the treasury in London, complaining that the packets between Falmouth and New York, were generally a fortnight longer in their passages, than merchant ships from London to Rhode-Island…. There happened then to be in London, a Nantucket sea-captain of my acquaintance, to whom I communicated the affair. He told me the difference was that the Rhode-Island captains were acquainted with the gulf stream, which those of the English packets were not. We are well acquainted with that stream, says he, because in our pursuit of whales, which keep near the sides of it, but are not to be met with in it…. I then observed that it was a pity no notice was taken of this current upon the charts, and requested him to mark it out for me which he readily complied with, adding directions for avoiding it in sailing from Europe to North-America, I procured it to be engraved by order.

This stream is probably generated by the great accumulation of water on the eastern coast of America between the tropics, by the trade winds which constantly blow there. It is known that a large piece of water ten miles broad and generally only three feet deep, has by a strong wind had its waters driven to one side and sustained so as to become six feet deep, while the windward side was laid dry. Having since crossed this stream several times in passing between America and Europe, I have been attentive to sundry circumstances relating to it, by which to know when one is in it; and besides the gulf weed with which it is interspersed, I find that it is always warmer than the sea on each side of it, and that it does not sparkle in the night.

Franklin then helpfully drew a map - a map somewhat short on both accuracy and elegance, but one that heralded a new field of oceanic cartography and by extension helped inaugurate the entirely new science of oceanography.