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From: Nicolàs de Hilster <groups@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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