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    Re: How Many Chronometers?
    From: John Huth
    Date: 2009 Sep 24, 10:51 -0400
    I don't really see a contradiction  - the challenge of making a chronometer that works in the face of temperature variations and motion was extremely difficult and Harrison's work definitely qualifies for the term "genius".    

    As a benchmark for how far ahead of his time he was, here's a clip from a journal where the author talks about how to use the equation of time to set watches from sundials  - it gives some flavor for the state of time-keeping in the late 18th century.

    It is well known that common dials give what the English call apparent, and the foreign astronomers true time; which, on account of the unequal motion of the sun, is unequal:  the natural day being sometimes longer, and sometimes shorter, than the mean day, shewn by clocks and watches which go equably.   In order, therefore to find whether a clock or watch goes right, by a common sun-dial, or to set a clock or watch to mean time, when wrong, it is necessary to add to, or subtract from, the time shewn by the dial, a certain number of minutes and seconds, usually called “the Equation of time;” in order to find the time which the clock or watch ought to shew or to which it should be set[i].

    [i] Francis Wollaston, “Directions for making a universal Meridian Dial,” The Monthly Review or Literary Journal V7, London, R. Girffiths September – December 1793    P.336


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