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Frank wrote-

| Here's a link to the file George provided:
| http://fer3.com/arc/img/Clowdisley_Shovel_1707_JIN_1960.pdf
|
| For convenience, I also inserted a direct link at the end of the archive
| copy of the previous message.
|
| Is this article under copyright? If so, please let me know in a couple of
| weeks.

=========================

from George-

Thank you Frank.

I hope readers will take a serious look at it. It's a salutary tale of the
dreadful state of Royal Navy navigation, in 1707. How things had changed by
Cook's day, half a century later!

Not entirely their own fault, of course. The concept of longitude, as a
quantity that could be specified for locations around the world, with some
common reference-point (perhaps at Greenwich), hadn't really sunk in then.
Instead, mariners thought about changes in longitude, with reference to
their starting point, derived from their dead-reckoning.

But what I find so surprising are the discrepancies in latitude, in a fleet
that was sailing together as a convoy. As long as the Sun shone at noon (and
it had been doing so, reasonably often) latitude should have been clear-cut.
Well, limited by the precision of their backstaffs, to perhaps 15 minutes or
so.

And not helped by the scandalous errors in charts, in the days when these
were commercial ventures, before the Admiralty Chart existed. How many ships
were lost because the Scillies, and Lizard, were plotted on the chart nearly
10 miles North of their true position, I wonder?

There's a decent gap, enshrined in the words of the old song, "Twixt Ushant
and Scilly is thirty-five leagues ...", or 105 nautical miles. That was what
mariners had to find their way between, and without even lighthouses, in
early days. In the days before longitude could be measured, they had to do
it by latitude sailing, taking deep soundings to establish how close in to
the Western channel they had got. In thick weather, even latitudes were
unavailable. That situation remained true, until radio aids became available
(in the 1930s ?). I wonder if Henry Halboth can recall approaches made
without even radio DF help, and how ships then managed, in prolonged thick
weather?

================================

Frank asked about copyright-

Yes, that paper is only 47 years old, so I suppose that copyright
restrictions apply, strictly speaking, and I should really have pointed that
out. Readers should respect that. It has here been made available for the
purpose of academic discussion, but should not be disseminated further, and
it might be wise for Frank to make it unavailable again after it's had time
to serve its purpose.

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.





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