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    Re: Douwes
    From: Peter Hakel
    Date: 2009 Sep 26, 08:46 -0700
    Thanks Nicolàs, for providing more information on Douwes.  Would you, or anyone familiar with Douwes, consider creating a Wikipedia entry for him?

    Googling his complete name yielded the following interesting link:

    http://etext.lib.virginia.edu/jefferson/bibliog/Authors/T.html

    which includes:

    Reference: 453
    Author: Tattersall, James J.
    Title: "Thomas Jefferson and the Douwes' Method of Determining Latitude."
    Publication: Historia Mathematica
    Volume: 14
    Date: (1987)
    Extent: 275-81.
    Notes: Discusses an unpublished manuscript of trigonometry problems which relate to TJ's computations of the latitude at Poplar Forest done in the winter of 1811. TJ used the method of Cornelius Douwes as simplified by the tables of Nevil Maskelyne. Reproduces the manuscript and explains the computations.


    Peter Hakel



    From: Nicolàs de Hilster <groups{at}dehilster.info>
    To: navlist@fer3.com
    Sent: Saturday, September 26, 2009 3:13:29 AM
    Subject: [NavList 9943] Re: Douwes


    In his 'Konst der Stuurlieden' (Zutphen, 2001) Willem Mörzer Bruyns
    spend several pages (pp. 26, 58, 59-63) on Douwes.

    In very short Cornelis Douwes was born on 24 August 1712 and was
    particularly known for solving the problem as described in that first
    link, calculating the meridian altitude of a body by taking two
    observations; one before and one after the meridian passage at a timed
    interval. The method was first described by him in a report he wrote as
    a response on critics by Martinus Martens (a teacher in the art of
    navigation in Amsterdam) and several Dutch naval officers concerning
    deficiencies in the knowledge of the art of navigation among Dutch
    navigators. One of the chapters was called 'Van het Breete Neemen Buyten
    den Middag' (of taking the altitude outside noon) and described above
    method. Timing was done using a watch, which by that time reportedly
    were accurate enough for the task. Douwes had his pupils test the method
    at sea and improved on it were necessary. Finally in 1754 the method was
    published in the 'Verhandelingen' (discourses) of the 'Hollandsche
    Maatschappij der Wetenschappen' (Royal Holland Society of Sciences and
    Humanities). The accompanying tables were at first only available as
    manuscript, but finally printed in 1761 by Van Keulen in Amsterdam (the
    last edition was printed in 1858).

    Douwes' method was revolutionary as the navigator did not had to rely on
    the meridian passage alone, which was especially useful under partially
    clouded conditions. The method was used in and outside Holland. The
    English used it already before 1761 and in other countries (France,
    Germany, Spain and America) the method was soon known and used as well.

    In addition to above feat Douwes may also be noted for his contribution
    in introducing the octant in Holland. He taught on the subject and wrote
    a manual for the navigator concerning the instrument.

    Douwes died 7 July 1773 in Amsterdam.

    In the Netherlands the periodical for former students of the Maritime
    Institute Willem Barentsz on Terschelling is named after him.

    Nicolàs




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