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. Also could someone state whether the Dunkirk-Barcelona meridian used in 1739-40 was the same as the meridian used in 1792-98? I think it was, but haven't confirmed this 100%. Many tanks in advance for any help ith this. David -- David Jones
