In message <a05200f00ba12b9a232c4@[193.250.66.211]>, Louis JOURDAN <[EMAIL PROTECTED]> writes >At 17:22 +0000 02/12/3, David Jones wrote: >>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 > >My sources are simply Google : just type "Dunkirk longitude" and you >get a number of sites giving the coordinates of Dunkirk (Dunkerque in >French). Same for Barcelona or any other city in the world.
Such figures are in atlases too but would just be for central points in each city (e.g. Charing Cross in London), probably the points from which distances to other cities are measured, rather than having to do with the meridian along which measurements were made. >Now I forgot something : Delambre and M�chain actually used the Paris >Observatory meridian, which at that time was the 0� meridian (which >would give for Dunkirk 0� 30' W and for Barcelona 0� 33' W). >Effectively the "mean" meridian Dunkirk-Barcelona is a few kilometers >west of Paris (Observatory). Those figures would give a line about 30km west of the observatory, which I'd say would be a surprisingly great distance. Such a line lies well outside Paris even today - it is on the other side of Versailles, which has never been considered to be in Paris. But the longitude for the Paris meridian, measured from Greenwich, is not 2� 50' E. The correct figure is 2� 20' E. This gives the longitudes of the centres of Dunkirk and Barcelona, measured from the Paris meridian, as 0� 00' W and for Barcelona 0� 03' W, which I think sounds more right. This then gives a 'mean' meridian only 1.5km west of the observatory meridian, which would certainly go through Paris by anyone's definition - indeed I have checked and it might go through the Elysee Palace :-) Not that the assumptions allow us to work with great accuracy... >But already at that time Paris was a >large city... I strongly suspect they had an exact idea of the course of their meridian through Paris, and what I'm really curious about is where that course ran if it didn't go through the Observatory. There were some celebrations in 1999, picnics and tree planting etc. along a line that stretched from Dunkirk to Barcelona. See <http://www.metropoleparis.com/1999/448/448scen2.html>. The first tree planted was in the Jardin du Luxembourg, which suggests that the meridian along which measurements were made was, as you say, the Paris observatory meridian. It's just that I've heard it was a short way away from that meridian. David -- David Jones
