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Dear all,

a couple of days ago I came back from delivering a yacht from Sweden to
Rostock, which was delightful because we had a persistent west wind between
force 3 and 7 and lots of sun. When checking my e-mail on my return I was
surprised that the discussion about the causes of Sir Clowdisley's shipwreck
(ignorance of longitude or ignorance of latitude) was still raging.
So I checked some of the information available to me and this is what I
found out:

The story of the seaman warning against faulty dead reckoning, which Dava
Sobel recounts, cannot be found in two of the main sources relating the
incident:

Campbell, "Lives of the British Admirals, Vol. III" (London 1785), p. 381,
reports this:

" On the 22d of October, he came into soundings, and in the morning had
ninety fathom water. About noon he lay by; but at six in the evening, he
made sail again, and stood away under his courses, believing, as is
presumed, that he saw the light on St. Agnes, one of the islands of Scilly.
Soon after which, several ships of his ships of his fleet made signals of
distress, as he himself did; and it was with much difficulty that Sir George
Byng, in the Royal Anne, saved himself, having one of the rocks under her
main chains. Sir John Norris, and Lord Dudley, also ran very great risks;
and, as we have shewn elsewhere, several ships besides the admiral's
perished. (...) There is no saying how this unhappy accident fell out, or to
whose fault it was owing, though a report prevailed immediately after it
happened, that a great part of the crew had got drunk for joy that they were
within sight of land."

So much for this account.

Burchett's "A Complete History of the Most Remarkable Transactions at Sea"
(London 1720, p. 733; quite close to the incident in time) also does not
recount the incident Dava Sobel is so fond of. He simply remarks:

"I cannot but have a lively idea of the danger Fleets are exposed to upon
entering the British Chanel, when coming from foreign Parts, but more
especially when their Officers have not the Advantage of knowing their
Latitude by a good Observation..."

I guess that's what George tried to convey in his postings. (And he is the
one list member most intimately acquainted with these waters, I assume.)

Regards,
Wolfgang

-----Urspr�ngliche Nachricht-----
Von: NavList@fer3.com [mailto:NavList@fer3.com]Im
Auftrag von George Huxtable
Gesendet: Montag, 10. September 2007 11:10
An: NavList@fer3.com
Betreff: [NavList 3189] Re: The shipwreck of Admiral Shovell



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@huxtable.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@huxtable.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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