Geoscience Reference
In-Depth Information
across harbors to signal the time to ships at anchor. The cannon at Cape Town, South
Africa is still operated in this way, with a tug of a lanyard. Originally in 1786, the
cannon at the Palais Royal was similar but it was replaced in 1795 by M. de Chabrol,
the Prefect of the Seine, by a small cannon about 20 cm long and mounted on a gran-
ite column. It is an inelegant, squat column which had to be strong to withstand the
daily kickback of the cannon. Until 1914 the instrument was automatic, in an arrange-
ment invented by an engineer by name of Rousseau to replace a very accurate sundial
in the Rue des Bons-Enfants. The cannon was charged with gun-powder and the fir-
ing pan positioned under a magnifying glass. On a sunny day, when the Sun transited
the meridian and the lens concentrated solar heat, the cannon fired at 12 noon, local
time, plus or minus the so-called “equation of time” representing such effects as the
eccentricity of the Earth's orbit round the Sun. Since this correction ranges up to fif-
teen minutes and some of the circumstances of the firing pan are accidental (distribu-
tion of powder, intensity of sunlight, etc.), this was not a very accurate method of
signalling time but indeed has the advantage of being loud.
The lens mechanism is missing from the cannon in the Palais Royal, and in the
1990's the cannon was triggered at noon by a park attendant with a watch and lit
match in hand; alas, this exciting custom has been suspended.
2nd and 9th Arrondissements
Opéra
The meridian cuts across the 2
nd
Arrondissement, which is one of the smallest and passes
through rather anonymous streets. Medallion Number 99 is in Rue St. Augustin.
The Arago medallions continue northwards into the 9
th
Arrondissement, east of
the busy junction in front of the massive Opera House. The meridian passes through
a commercial area of elegant hotels, restaurants and busy department stores (Les
Galeries Lafayette are within sight). A
flâneur
(timewaster) seated at the café at 24
Bvd des Italiens may scuff his feet on Medallion Number 101 (
Fig. 39
), with
Number 102 around the corner in Rue Taibout. Numbers 103 and 104 are opposite
each other near the Hotel Ambassador on Bvd Haussmann.
18th Arrondissement
Montmartre
Today Montmartre has a varied reputation, with sophisticated nightclubs, shows
and sordid sex shops concentrated in the area around the Place Pigalle. Medallion
Number 111 lies nearby on the Bvd de Clichy but is often walked over by tourists
and by touts for the bars. If you accepted their invitations, you could sip a drink
