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Hi Jacques,

Rainy day in St-Malo so, I'm back to the keyboard for few minutes.

I wrote my study about the double altitude problem last year to present and discuss the different methods and formulations used to solve this problem. But, I'm not a science historian ! In my paper, I have followed the historical framework given by Charles H. Cotter in his book "A History of Nautical Astronomy" published in 1968. Then I have added informations found in other french books (Guepratte, Ducom and Caillet for example).

If you want to know more about the history of astro-navigation and nautical astronomy, I advise you to contact Mr Guy Boistel who is doctor in history of sciences at Nantes University (Centre François Viète). He is a specialist in nautical astronomy and had writen articles and books on this subject; his doctoral thesis, writen in 2001, was about Lunars. It is easy to find his website and informations about him ... just type "guy boistel" on Google. I think, Boistel is, in France, the historical reference in nautical astronomy for the 18th and 19th centuries; he knows were are the first-hand informations and the value of those informations.

Paul.