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    Re: Dava Sobel
    From: George Huxtable
    Date: 2006 Apr 30, 20:44 +0100

    Alex Eremenko  wrote:
    | " "the ship's  capitan learned his longitude in
    | the comfort of his cabin, by comparing his  pocket watch
    | to a constant clock that told him the correct time at home  port".
    | No other explanation is given in a book which is  called
    | "Longitude" and is written for "broad audience"!
    | I could not  believe my eyes... and this is was a bestseller...
    | are we really living in  "Dark age"?"
    And Frank replied-
    | First of all, that isn't true. I had to look it up to see.
    So did I, and Alex's quote is correct.
    Frank followed-
    | You are perhaps a
    | victim of a cursory reading... The sentence you've quoted is a  TEASER at the
    | very end of one chapter intended to draw the reader on into the  rest of the
    | book.
    So what, I ask? Is there anything special, about the last sentence in a 
    chapter, that gives it license to tell such nonsense?
    Journalism at its very worst.
    And Frank continues-
    | As for Shovell's shipwreck, there are only a  few sources. W.E. May in his
    | 'History of Marine Navigation' wrote that he had  examined in detail all of the
    | surviving logbooks from the fleet, and the  positions are not that far off in
    | general. He sees the real problem as a  charting failure. The Scillies had
    | been charted some ten to fifteen miles too  far north for a long time, leaving
    | Shovell with the mistaken impression that he  had more room to maneuver.
    I too have read May's account, and his implication that it was the result of 
    the position of the Scillies being charted too far
    North makes little sense. Shovell had no business to be at the position of the 
    Scillies, whether they were charted there or not. The
    Scillies are just about at the same latitude as the Lizard, 100 miles further 
    East, which Shovell's fleet had to pass well South of
    to reach his home port. A glance at any map will show that he was well out of 
    his way, far too far to the North. He should have
    turned NorthEast, up-Channel, from about 100 miles further South.
    Where Shovell failed was in neglecting to take soundings, and that failure 
    cost 2000 lives. Sounding was the standard tool for
    mariners when they were feeling their way into the English Channel, without 
    recent observations. That was not any new, or difficult,
    technology. But until Kelvin's piano-wire sounding machine, in the late 1800s, 
    such deep-sea soundings required the vessel to
    heave-to. That was a dangerous maneuvre when leading a fleet in the dark, but 
    not nearly as dangerous as failing to sound!
    Sobel' ignorance shows up again on page 98, where she writes-
    "The navigator also battled the problem of lunar parallax, since the tables 
    were formulated for an observer at the centre of the
    Earth, while a ship rides the waves at about sea level, and the sailor on the 
    quarterdeck might stand a good twenty feet higher than
    that." She may perhaps be forgiven for confusing parallax with dip, but not 
    for failing to have the text checked over by someone who
    understood those things.
    What about page 91-
    "As a bonus, Hadley's quadrant boasted its own built-in artificial horizon 
    when the real horizon disappeared in darkness or in fog."
    If only...
    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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