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    Re: recommendation for slide rule ?
    From: George Huxtable
    Date: 2009 May 18, 00:21 +0100

    Paul put up a nice posting on slide rules.
    
    Anyone with a serious interest in these devices should take a look at the
    website of the Oughtred Society. Also, in Britain, there's the UK Slide Rule
    Circle (not just circular slide rules!).
    
    I still have a couple of ten-inch rules, that once got a lot of use. The
    wood-based Thornton version is still in working order, the plastic Aristo is
    falling apart.
    
    William Oughtred produced the first slide rules, in hand-engraved solid
    brass. I've been allowed to handle his navigator's version, all of 18 inches
    diameter, of 1630, at the History of Science Museum in Oxford. With gloved
    hands, I should add. Unfortunately, it's lost its two radial arms, which
    were intended to move together, around the centre,  like a pair of dividers.
    I'll be taking a closer look next week. It has two log sin circles, four log
    tan circles, each circuit covering a decade of change in sin or tan. So four
    decades of the tan scale are spread over about 20 feet of scale length,
    which must rival the Bygrave.
    
    It doesn't aim to solve great-circle triangles, as the Bygrave does, though
    I suspect it could be used in a similar three-step sequence to do that job.
    It's intended for a navigator to solve rhumb-line sailing problems, such as
    you would do by traverse tables, and including Mercator sailing, for which
    it provides a 2-turn scale of meridional parts. I have a scanned copy of
    part of Oughtred's book, translated from Latin to English in 1660, available
    to anyone that asks. It's just the "navigational addition", nor the complete
    text, occupying  70 of his pages. For its date, it is very advanced, for
    example advocating decimal rather than sexagesimal subdivision of degrees,
    though rather impenetrable.
    
    George
    
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
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