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    Re: the Shovell Disaster
    From: George Huxtable
    Date: 2007 Nov 14, 18:04 -0000

    Responding to comments from Michael Daly, about Newton's reflecting
    instrument, Ken Muldrew wrote-
    |
    | In 1676 Newton said, "I will resolutely bid adieu to (science) externally,
    | excepting what I do for my private satisfaction or leave to come after me;
    | for I see a man must either resolve to put out nothing new or to become a
    | slave to defend it." This was over his dispute with Hooke over who
    | deserved the credit for various findings in optics, but it does show that
    | Newton was not universally held in awe by his contemporaries (at least he
    | didn't think so).
    
    Note from George-
    
    If Newton said that in 1676, he was a bit premature, having another 50
    productive years ahead of him.
    
    And his octant didn't appear until over 20 years later, at its one-and only
    public mention, noted in the Royal Society's Journal Book for 1699, when
    Newton referred to it as having been used at sea by Halley.
    
    There are many curious aspects to this business of the Newton instrument,
    discussed in the recent book "Astronomical Minds", by Ted Gerrard. For
    example, Halley never even mentioned what instrument he used to obtain such
    precise latitudes, in his three voyages, though it must have been something
    special, to achieve the results he did. Ted ascribes it to a demand for
    secrecy from the Admiralty, to keep such knowledge from England's enemies.
    But it's hard to see the point of also keeping such knowledge from England's
    instrument-makers and navigators.
    
    One aspect that I had hadn't appreciated until reading Ted's book is this:
    The engraving of the Newton instrument, which is to be found in any book
    about the history of navigation, was not based on any first-hand knowledge
    of what that instrument actually looked like. It was an imagined
    reconstruction, based on a note which Newton had left with Halley, referring
    to a diagram which no longer exists, of an instrument which had probably not
    yet been constructed when that note was written.. Indeed, the engraving was
    based on a drawing that had been made for the Royal Society, based on that
    note, long after Newton' death, and Halley's too. There are discrepancies
    between the Newton note, the drawing, and the engraving. So the engraving
    can't necessarily be taken at face-value; it has to be taken with a pinch of
    salt, because so many hands have intervened in its production.
    
    However, Newton's note itself is very clear, in describing an instrument
    that has all the necessary features of the double-mirror octant, and its
    application to lunar distances. It has only one statement I would question,
    quoted in Appendix 10 of "Astronomical Minds", where he writes- "...to make
    the observation true, let the star touch the Moon's limb, not on the outside
    of the limb, but on the inside".
    
    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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