NavList:

I have attached a copy of Wright's chart. It is in four parts. I have also included a section where I have marked in more clearly the latitude near England.

gl



glapook@PACBELL.NET wrote:

You state that the Scillies were plotted ten nm north of their true
positions. I am looking at Edward Wright's chart published in 1599,
more than one hundred years before the disaster. Bowditch (1962 ed.)
gives the modern position of Bishop Rock as 49º 52' north and 6º 27'
west and of the Lizard as 49º 58' north and 5º 12' west each of which
are confirmed by Google Earth. Wright's chart gives the latitude of
the Scillies as 49º 55' north only 3 nm north of the true position.
The latitude of the Lizard on Wright's chart is 50º 00' north, two nm
from its correct position. What chart was Shovel using that had less
accurate latitudes than Wright's chart?

Also interesting is that Wright has a scale of longitudes using Cape
Verde as the prime meridian. Using Wright's chart he gives the
longitude of Bishop Rock as 8º 20' east while modern longitude gives
it as 11º 04' east of Cape Verde. (Cape Verde is 17º 31' west of
Greenwich.) Wright puts Bishop Rock 121 nm west of its correct
position which isn't too bad using Cape Verde. Wright put the Lizard
at 10º 05' east of Cape Verde so 1º 45' east of Bishop Rock. The
modern difference is only 1º 15' making a 30' difference, an error of
19 nm.  (I will scan this chart in tomorrow)

gl

On Aug 27, 2:19 am, "George Huxtable" <geo...@huxtable.u-net.com>
wrote:
  

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 geo...@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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