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    Re: The shipwreck of Admiral Shovell
    From: George Huxtable
    Date: 2007 Sep 10, 10:09 +0100

    Frank Reed had written, in Navlist 3173,
    
    | Did you look at the full diagram in the article? George clipped it just to
    | the left of a couple of small X's in the original diagram. Do you see what
    | those little X's represent?? They change EVERYTHING. That's where the
    | Scillies would be relative the fleet's DR positions assuming something as
    | trivial as a different catalogued source for the longitude difference
    | between the Isles of Scilly and Cape Spartel. Longitude was the primary
    | error in the fleet's position.
    |
    | -FER
    | PS: I want to be very clear on this: I do not mean to imply that George
    | clipped the diagram to remove the X's. He clipped it there, quite
    | appropriately, to save on image size. However, I would contend that W.E.
    May
    | made the X's small, and almost un-noticeable, in order to minimize their
    | significance, which would have been a distraction from the point he
    | (W.E.May) was trying to make.
    
    and I protested-
    
    | What on Earth is all this about "clipping the diagram"? The attachment I
    | sent, with a slightly magnified view of the diagram in the original paper,
    | was complete, border and all. So was the copy I (and presumably everyone
    | else), received back, as Navlist 3148. Nothing was clipped, nothing even
    | appeared to be clipped.
    
    But I was quite wrong there, as Gary LaPook has kindly pointed out, and a
    second look has now convinced me. Indeed, the Eastern end of the image,
    magnified from the diagram in the original paper, was missing from that
    posting, Navlist 3148, just as Frank said. Sorry about that. All I can say
    is that the intention, at the time, was to send the whole picture, even if
    it didn't work out that way.
    
    If you can refer back to Navlist 3148, to save the trouble of downloading
    the whole paper, there are two missing "+" marks, just off the Eastern edge
    of the picture, South of Start Point (also just off the picture) and at the
    same latitude as Scilly. They are indeed relevant, as Frank says. This is
    why-
    
    Ships of the fleet had no means, other than dead reckoning, to estimate
    their longitude, and that had to be from their departure point, which
    happened to be Cape Spartel, just on the African side of the exit from the
    Med. Generally speaking, charts of those days had no scale of longitude.
    Instead, longitudes of important headlands had to be taken from lists given
    in various navigation manuals. May has investigated several such manuals of
    the time, looking for the difference between the quoted longs between Cape
    Spartel and Scilly, and found that Spartel ranged from 1deg 48'E of Scilly
    (in Newhouse) to 1deg 50' W of Scilly (in Colson). The true value is 0 deg
    26' E. Those are immense discrepancies, which show the awful state of
    geography of the time, that mariners had to do their best with.
    
    We have no way of knowing which ships used which texts; there was no such
    thing as a standard issue, and navigators had to acquire their own
    information as best they could. What those (missing off the edge) + marks
    would show is where a navigator, taking his longitudes from Colson, and
    correctly dead-reckoning from Spartel, would expect Scilly to be found,
    though after three rough weeks at sea, with no sight of land, no mariner
    would put much reliance on that dead reckoning anyway. On that basis, their
    navigation would put them, still, quite a long way out in the Atlantic. In
    that case, we would expect those vessels to be shaping-up, with a latitude
    that would take them somewhere through that Ushant-Scilly gap. And looking
    at that scatter of presumed latitudes in May's diagram, for the two noons
    preceding the wrecking, that appears to be exactly the intention.
    
    But we know that they (or at least most of them) were wrong. We know that
    from the hard evidence that, a few hours later, the whole fleet ended up at
    the Scilly rocks, and those that got away did so by good fortune. Remember,
    the fleet was sailing as a fleet, in sufficiently close convoy that signals
    from the flagship could be seen from all twenty vessels, so they would cover
    a patch no more that a few miles across. Look at the May's diagram, with its
    immense spreads in both latitude and longitude, in that light.
    
    Whatever the longitude these vessels thought they had, they had no business
    to be up at the latitude of Scilly, or anywhere near it, until soundings had
    shown them to be well East of the Lizard.
    
    George.
    
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.contact George
    Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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