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    Re: Sextants in Little Rock
    From: Bill Morris
    Date: 2010 Jan 8, 23:15 -0800

    I very much enjoyed reading the old salt's story.

    I hope Henry won't mind my correcting his terminology for the micrometer sextants. They do use a rack, a term inherited from watch and clock makers and meaning a toothed segment of a circle, but the only real sextant that has a pinion,a gear wheel with a small number of teeth, usually fewer than 12) is the box sextant (see attachment for an interior view). Nearly all nautical micrometer sextants use a short length of a helical thread, a worm, to engage with the rack. The one exception that I know of is the Freiberger Skalensextant, that has an internal glass scale divided to degrees, viewed through a microscope having a micrometer eyepiece, which allows reading directly to one minute and estimation to 30 seconds.

    Bill Morris
    New Zealand
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