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    Re: Manual calculation of compass variation
    From: Frank Reed CT
    Date: 2004 Oct 16, 16:35 EDT
    From the preface to the online version of the official journal:
    "Cook was assiduous in obtaining observations to ascertain the Variation
    of the compass--i.e., the difference between the direction shown by the
    magnetic needle and the true north. He is constantly puzzled by the
    discrepancies in these observations made at short intervals. These arose
    from the different positions of the ship's head, whereby the iron within
    a certain distance of the compass is placed in different positions as
    regards the needle working the compass card, the result being that the
    needle is attracted from its correct direction in varying degree. This is
    known as the Deviation of the compass. The cause of this, and of the laws
    which govern it, were only discovered by Captain Flinders in 1805.
    Happily for the navigators of those days, little iron entered into the
    construction of ships, and the amount of the Deviation was not large,
    though enough to cause continual disquiet and wonderment."

    Frank R
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
       
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