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    Re: The shipwreck of Admiral Shovell
    From: George Huxtable
    Date: 2007 Sep 17, 22:01 +0100

    Gary LaPook 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."
    
    That chart can be found in David W Waters' "The art of navigation in England 
    in Elizabethan and early Stuart times" (1958), which I recommend. The chart 
    is at plate LVIII. And a remarkable piece of work it is.
    
    "Bowditch (1962 ed.)
    gives the modern position of Bishop Rock as 49� 52' north and 6� 27'
    west and of the Lizard as 49� 58' north and 5� 12' west each of which
    are confirmed by Google Earth. Wright's chart gives the latitude of
    the Scillies as 49� 55' north only 3 nm north of the true position.
    The latitude of the Lizard on Wright's chart is 50� 00' north, two nm
    from its correct position."
    
    I agree with those latitude assessments, that Gary has made from the chart. 
    They are, as he says, very near to the true positions.
    
     What chart was Shovel using that had less
    accurate latitudes than Wright's chart?
    
    Probably that by Greenville Collins, who had been appointed by King Charles 
    II in 1682 to survey the coasts of Great Britain, there being at that time 
    "no sea-charts and maps of these Kingdoms but what were Dutch, and those 
    very erroneous". The charts were made over the next 7 years, and published 
    in 1693 as "Great Britain's Coasting Pilot". Those charts continued with 
    little change until the last publication in 1753. And they had serious 
    errors, particularly around Scilly and Lizard, which could, and should, have 
    been put right; but weren't
    
    Between Wright, in 1599, and Collins, in 1682, there had been little 
    improvent in seagoing instrumentation. The cross-staff was still in use, and 
    the backstaff had become adopted for observing Sun altitudes, but its main 
    advantage was in its eyesight-saving feature rather than in greatly 
    increased accuracy.
    
    Also interesting is that Wright has a scale of longitudes using Cape
    Verde as the prime meridian.
    
    Yes, that's a remarkable feature of the Wright chart, at such an early date. 
    It was an outstanding piece of work. It was also the first printed chart to 
    use the Mercator projection. There were earlier charts using that 
    projection, but they were manuscript.
    
    Using Wright's chart he gives the
    longitude of Bishop Rock as 8� 20' east while modern longitude gives
    it as 11� 04' east of Cape Verde. (Cape Verde is 17� 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 10� 05' east of Cape Verde so 1� 45' east of Bishop Rock. The
    modern difference is only 1� 15' making a 30' difference, an error of
    19 nm.  (I will scan this chart in tomorrow)
    
    Thanks to Gary for introducing that topic.
    
    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.
    
    
    
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