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Andres Ruiz wrote:
>
>  
>
> Antoine writes:
>
> In France both in the Military Navy and Civilian Merchant Navy (most 
> of the Merchant Navy Instructors come from the Military) , such 
> problem has long been known as Douwes's problem. To the best of my 
> memories, M. Douwe was a Dutch Navigator of the XIX (?) th century who 
> reportedly had already spent a lot of thoughts about tackling this 
> subject. I do not think he did find the exact solution.
>
> My response:
> Thanks Antoine, this is the first time I heard about Douwes. I found a 
> couple of relevant links:
>
> 
http://books.google.com/books?id=i4SJwNrYuAUC&pg=PA326&lpg=PA326&dq=Douwes's+problem&source=bl&ots=K0Ia6E1kKR&sig=Lc9cf62sEBlCRo4zb897EjYM_Y8&hl=en&ei=wa68SpqnAo3UsgOJ_9HcBQ&sa=X&oi=book_result&ct=result&resnum=5#v=onepage&q=&f=false 

> 
>
> 
http://books.google.com/books?id=UwtDAAAAIAAJ&pg=PA293&lpg=PA293&dq=Douwes+problem&source=bl&ots=4lT3lq3g52&sig=f4pUUZcyLP6e0sxz7LXYH40CA4U&hl=en&ei=2K68So_PH4aQsgO2-OzcBQ&sa=X&oi=book_result&ct=result&resnum=10#v=onepage&q=Douwes%20problem&f=false 

> 

>
In his 'Konst der Stuurlieden' (Zutphen, 2001) Willem M�rzer 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.

Nicol�s



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