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    Re: mechanical chronometers
    From: Alexandre Eremenko
    Date: 2006 May 15, 08:24 -0500

    Dear George and Coralline Algae,

    I am not an expert in marine chronometers,
    but I am following them on e-bay last month
    (just out of curiosity). I am afraid that
    $1500 is not enough, unless you want a Russian one.

    Here is the recent statistics:
    English 1865 chronometer by Brown $5211
    Thomas Mercer in fair condition (possibly not working) $986
    Thomas Mercer is good condition $4,626
    Thomas Mercer in good condition $3,728
    John Pool chronometer in good condition $3,250
    Russian "Polet" from Russian seller $810.

    As I understand, Thomas Mercer was the common British
    chronometer in WWII. They (and American Hamiltons) are
    most frequently seen on e-bay. I've seen an advertisement
    of Wempe, the only Westren company I know that makes mechanical
    chronometers now. It costs about $10,000.

    Of course, chronometers have nothing to do with
    the "time of Newton", not speaking of the "time of Kepler".
    Navigation at the time of Kepler used astrolabia for the Sun and
    cross-staff for the Polaris, while at the time of Newton, the most
    advanced technology was the Davis backstaff.

    By the way, a backstaff is made entirely of wood, and I can imagine
    that a decent one can be made by some very advanced amator even
    in modern time:-) Has anyone ever tried to make a good working replica?


    On Mon, 15 May 2006, George Huxtable wrote:

    > "As part of my plan to immerse myself in the time of kepler, newton
    > with respect to navigation and other things.  I have been researching
    > mechanical watches and chronometers. "
    > Well, Kepler's (and Tycho's before him) great misfortune was that they
    > lived before the era of accurate clocks. Otherwise, their observations
    > could have been much more precise. Instead, they had to resort to
    > complex stratagems to deduce time, such as by the altitudes of
    > celestial bodies: the same set of bodies for which they was trying to
    > determine the positions.
    > As for Newton, though he lived in the period in which pendulum clocks
    > and balance-spring watches were being developed, a practical seagoing
    > timepiece did not emerge until 50 years after his death.
    > Nevertheless, Coralline Algae's aim is a noble one.
    > I wonder if the purchase of a secondhand marine chronometer, in a
    > gimballed box, has been considered? Thousands of these instruments
    > were in use at sea, often in sets-of-three. They may seem expensive
    > now, usually sold as "antiques", but nothing compared with the outlay
    > of $1500 that is being contemplated. That would seem more in keeping
    > with the research intention, than an expensive Russian tick-tock. The
    > main problem might be to find a craftsman to put the instrument in
    > proper order, which might well call for no more than knowing where
    > (and where not) to apply a tiny drop of oil. And keeping it out of the
    > hands of those that don't know.
    > Not that I claim to have any special knowledge about marine
    > chronometers. Geoffrey Kolbe's advice is sound.
    > 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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