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    Re: Ancient mariners enjoyed Hawaiian holidays
    From: Clive Sutherland
    Date: 2007 Nov 6, 22:19 -0000

    Frank
    Thanks for your reply.
    
    You wrote
    
    > In the days of dead reckoning, navigators used currents for navigation
    > fairly often, but not in the way that a modern navigator might expect.
    > There
    > was no really reliable way to correct for a current, but you could use it
    > in
    > other ways. First, strong currents are visible. The water may be colored
    > differently, waves will refract into them giving a choppy surface. The
    > water
    > in a current may have a different temperature and salinity and a distinct
    > population of algae, jellyfish, salps, etc. If you find a current that you
    > know about, you can follow it for a speed advantage, or you can cross it
    > quickly if you need to avoid it.
    >
    > Also, many currents are reliable features in the ocean. If you find your
    > favorite current, then you know you must be in a particular part of the
    > ocean. Here's Joshua Slocum navigating by recognizing that he's in the
    > Brazil Current: "On May 10 there was a great change in the condition of
    > the
    > sea; there could be no doubt of my longitude now, if any had before
    > existed
    > in my mind. Strange and long-forgotten current ripples pattered against
    > the
    > sloop's sides in grateful music; the tune arrested the ear, and I sat
    > quietly listening to it while the Spray kept on her course. By these
    > current
    > ripples I was assured that she was now off St. Roque and had struck the
    > current which sweeps around that cape." and he adds: "I saw nothing of the
    > coast of Brazil, though I was not many leagues off and was always in the
    > Brazil current."
    >
    Frank writes that;
    
    
    
    Josua Slocum recognises that he is in the Brazil Current and therefore in no
    doubt of his longitude. He describes a great change in the  condition of the
    sea etc  and he was assured that she(the "Spray") was now off St Roque  and
    had struck the current that sweeps around that Cape.
    
    Now  St Roque is the cape of Brazil at about 5deg S Lat , 35deg W long that
    divides the S American coast into parts, To the north the coast sweeps NW to
    Venezuela and the Caribbean while to the south the coast sweeps SSW down to
    Cape Horn. My copy of "Ocean Passages of the World"  shows that St Roque
    divides the South Equatorial Current in two likewise. With some seasonal
    variations, the Northerly Flow is the stronger Guiana Current and the weaker
    flows SSW until it is picked up by the South Atlantic Gyre and becomes the
    Brazil Current from around about 20deg S until it meets the cold NE
    Falklands Current near the River Plate. The Brazil current starts a long way
    south from St Roque!
    
    Did Joshua Slocum's navigation falter here or perhaps these currents weren't
    so well known at the time of his famous voyage.
    
    
    
    David Lewis in his book " The Wandering Stars" also describes the appearance
    of the sea denoting the presence of a strong Current being recognised by his
    Polynesian Navigator during a voyage form the reef islands of Santa Cruz
    near the Solomons.The depth at that time was better than a mile deep.
    He(Lewis) suggests that the overfalls were occurring not over shallows but
    over a layer of stationary or contra-flowing water a few fathoms down.- a
    phenomenon hydrographic research shows to be exceedingly common! Has anyone
    in nav-l group heard of this?
    
    I concede that lore of this kind would be acquired by Pacific islanders from
    ancestral stories but it is one thing to be aware of  current flow in a
    local area when it briefly becomes strong but it is quite another to gain
    this awareness over a vast empty area of the ocean. I think the jury is
    still out.
    
    
    > Of course this sort of navigation by currents only works with the strong
    > ones, generally on the east coasts of large land masses, which happen to
    > be
    > the ones with famous names: the Gulf Stream, the Kuroshio, the EAC... Such
    > strong currents would have been mostly irrelevant for a Polynesian
    > navigator.
    >
    > There is another case where currents might be useful to Polynesian
    > seafaring. Near some islands, there are points with strong currents
    > running
    > away from shore, around headlands, etc. Knowledge of these would clearly
    > be
    > useful for local piloting.
    >
    > You also wrote:
    > "I also challenge the reliability of ancient voyagers knowledge.  In fact
    > some currents, for example the Gulf stream have swirls and eddies that
    > would
    > be hard to map even with the benefit of satellite imaging and it requires
    > an
    > explanation as to how they would have acquired this knowledge."
    >
    > Well, ok, but consider that the Gulf Stream was well-known and used for
    > navigation centuries before those "swirls and eddies" were clearly
    > observed.
    > This sort of navigation is not precision navigation, but it still counts.
    >
    > And you concluded:
    > "It is conceivable the pacific islanders navigated over long distances,
    > although I remain unconvinced that they did so with any prepared passage
    > plan, but principally I argue that it would be impossible to navigate
    > using
    > this method."
    >
    > It all depends on what you mean by a prepared plan. Suppose I want to sail
    > from Hawaii to Tahiti. I sail southeast (does not have to be exact). When
    > I
    > reach 15 South Latitude or so (again does not have to be exact), I turn
    > west
    > or southwest. Chances are excellent that I will run into some island in
    > the
    > Marquesas, the Tuamotus, or the Societies, and that's where local tricks
    > like looking for clouds over islands can come into play. Once you make
    > landfall, just look for a local and ask: "hey, which way to Tahiti?".
    
    
    But over thousands of miles of open ocean just a few knots of  currents
    incorectly allowed for could lead you to miss even a large chain of islands
    
    
    
    
    > There's much less controversy over voyages among the islands in that
    > region
    > so there would very likely have been local information available.
    > Navigators
    > encountered by Cook knew all the inhabited islands in that vast area of
    > the
    > ocean. Someone on the list, maybe George, worried that Polynesian
    > navigators
    > could not possibly have known the right way to enter the lagoons of the
    > atolls, the safest way around the reefs, etc., but of course this problem
    > faced every navigator, whether Polynesian or European or whatever
    > ethnicity,
    > when approaching these islands before the 20th century. And the answer is
    > obvious enough: you hire a local pilot (maybe the negotiation went
    > something
    > like this: "hey, I'll give you this amazingly hard Hawaiian rock if you
    > can
    > help me through the reefs...").
    >
    > This new evidence, which Peter brought up, demonstrating that some
    > volcanic
    > rock used in tools in the South Pacific is from Hawaii, does count as
    > rock-solid proof, pardon the pun, that these voyages took place now and
    > then. But clearly there was only a very limited contact between Hawaii and
    > the rest of Polynesia. There were only indistinct tales of voyages in the
    > past by the time the Europeans arrived in Hawaii. More interesting
    > perhaps,
    > there was apparently almost no contact between Rapa Nui (Easter Island)
    > and
    > the rest of Polynesia after the initial colonization.
    >
    > Someone on the list, I think Wolfgang, also mentioned that very little of
    > this discussion of Polynesian navigation is new. And except for a few
    > recent
    > archeological discoveries, the Hawaiian rock and the Lapita graves, which
    > Peter also mentioned I think, there hasn't been much new in decades. In
    > fact, you could go dig up an issue of National Geographic magazine from
    > the
    > 1970s and find pretty much the whole story including a nice pictorial on
    > the
    > voyage of Hokule'a and a very nice fold-out map (come on, how many on the
    > list still have that map today?). Of course, things are new to people who
    > have never heard them before, so I see problem with people telling these
    > stories of Polynesian navigation as if they are news.
    >
    > -FER
    > http://www.HistoricalAtlas.com/lunars
    >
    >
    > >
    >
    >
    >
    > --
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    > 05/11/2007 04:36
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    >
    
    
    
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