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    Re: "A history of marine navigation" by Per Collinder, and Neckam
    From: Ken Muldrew
    Date: 2009 Jul 17, 09:32 -0600

    On 17 Jul 2009 at 10:35, George Huxtable wrote:
    
     Some of what Collinder writes should be taken with a pinch of salt. For
    > example, in the extract Frank quoted in [9078], Collinder referred to the
    > requirement for a timekeeper for the longititude prize as "an average
    > error
    > of less than three seconds (of time) a day., adding - "There was no
    > pendulum
    > clock on land capable of that.". That last bit's nonsense. There had been
    > many regulators, in observatories, with much better performance than
    > that,
    > such as Tompions's great clocks at Greenwich, built 70 years earlier
    > (which
    > still survive).
    
    In WJH Andrewes "Quest for Longitude" there is a chapter on Harrison's
    regulators by Martin Burgess where it is claimed that he was able to keep
    time to one second in three months; the limit achievable with a pendulum
    in air clock. I don't think Tompion's regulators ever went better than 2
    seconds per week, but that figure is from memory and could very well be
    wrong.
    
    Ken Muldrew.
    
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