At the end of the rue Cassini, we can see the Observatory through the gates. The
building was built in 1667 under King Louis XIV by the architect Claude Perrault, best known for the colonnade of the Louvre. He is also the brother of Charles Perrault, famous author of fairy tales. The meridian bisects the Observatory oriented to the
four points of the compass. The meridian is marked by a brass line inlaid across the white marble stone floor of the large room on the second floor.
The Paris meridian was serving French navigators as zero degree longitude,
until Greenwich meridian was adopted in 1911 as prime meridian. Paris longitude is now 2°20 east. Not a small detail, if you ever have to find an old treasure located on ancient maps ... like in the story of Red Rackham's Treasure with confused Tintin
and Captain Haddock. Comics books can be instructive indeed !
Although Paris meridian is no longer used to calculate longitudes, at least it can provide the true solar time. This reminds me the speaking clock. As a child, I loved dialing the number of the talking clock. Maybe a long line of clock-makers let in my genes some obsession with exact times ... maybe it was the voice of the time keeper announcing
the exact hour and minute: « At the 3rd stroke, it will be exactly ... ». Introduced in 1933 by the Observatory, the speaking clock still provides the precise time to those calling 36 99. Now completely electronic, the mute version of
the speaking clock is also available on the Internet.