In message <a05200f02ba12441abaf2@[193.250.27.4]>, Louis JOURDAN <[EMAIL PROTECTED]> writes >At 23:16 +0000 02/12/2, David Jones wrote: >>Hi, >> >>I'm trying to find out the longitude of the Dunkirk-Barcelona meridian >>along which measurements were made in 1739-40 (Lacaille and J Cassini) >>and 1792-98 (Mechain and Delambre) in order to define the metre. >> >>Some authors wrongly state or assume that this was the same as the Paris >>meridian which goes through the Paris Observatory. In fact, although the >>meridian along which the measurement was taken passes very close to >>central Paris, it does not pass through central Paris. >> >>I'd be very grateful if someone could let me know (or direct me to a >>source where I can find) the exact longitude of the Dunkirk to Barcelona >>meridian; or identify a building or site through which it was chosen to >>pass. I'm curious as to why they didn't choose the meridian going >>through the observatory. > >Paris (Observatoire) longitude : 2� 50' E >Dunkirk longitude : 2� 23 ' E >Barcelona longitude : 2� 20' E > >The "Dunkirk-Barcelona" meridian effectively did not pass through >Paris (Observatoire) but was very close. Necessary corrections were >easily made by triangulation calculation.
Thanks for this, Louis. May I ask your source for this info? I'm curious as to the reason why they didn't use the Paris Observatory meridian. The above figures would give a (quasi-)meridian some 25-30 miles to the west of it at Paris - a lot. David -- David Jones
