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The lighting systems of the Cordouan Lighthouse


 

A research laboratory for new lighting systems

Ever mindful of its duty to light up the seaways, the remarkable monument that is Cordouan has always been at the forefront of new developments in lighting. Drawn to the prestige of the Lighthouse of Kings, France's finest engineers have come here to test their innovations, a far cry from the wood fire of the mediaeval beacon tower.

History of lighting systems


1611: The lighthouse designed by Louis de Foix was lit for the very first time, with a fire sheltered within a lantern. The fire, fuelled by a mixture of tar, pitch and wood, burned in a copper basin 37 metres above sea level, sheltered within a lantern protected by six closed windows. The smoke escaped via a stone chimney 6.5 metres in height. Before long, the chimney was spliced by a bolt of lightning. After that, the flame was produced by burning whale oil, found inside the heads of certain whale species, in an open-sided lantern.

1664: Burning whale oil. The lantern was demolished, having been burned to a crisp by whale oil aflame, and a basin took its place. But this lowered the height of the fire, which angered mariners.

1727: An open-topped iron lantern with a coal-fired stove sheltered within.
The coal-fired stove was positioned under a light-reflecting dome. The new lighting system proved very expensive and difficult to maintain: every day, the lighthouse keepers had to haul up the 225 pounds of coal needed to keep the light burning throughout the night.

1782-1791: Cordouan firstly adopted a system of oil lamps. 80 lamps were each fitted with a copper reflector. And so the enclosed metal lantern came to be. But the resulting light was too dim.  Teulère made a number of adjustments, and then Cordouan went on to experiment with a revolutionary machine developed by the clockmaker Mulotin: a rotational system that paved the way for the first rotating lamp.
Scientific research did its best to improve lighthouse lighting systems. As the centre of attention, Cordouan offered a superb testing ground for engineers.

1823: The Fresnel lens comes to Cordouan.  The engineer Fresnel chose Cordouan as the location for the installation of his innovative lens, running on rapeseed oil. His "technological marvel" was a lens device consisting of eight panels and mirrors, which concentrated light by refraction.

1854: A new device using catadioptric rings lights up the sea. Fresnel's lens was already rendered obsolete by a more modern system using catadioptric rings. The lens and lantern were replaced with those that we see today.

1948: Electrification of the lighthouse. Petroleum gas had been used since 1907; then came the advent of electricity. Two generators powered a 6,000 watt bulb, with a rotating screen.

2006: Automation and computerisation of the lighthouse. A 250 watt bulb and a new rotating screen completed the lighthouse's new lighting system.
The Cordouan lamp now has a range of 40 km out to sea, constantly blinking out to mariners its unchanging pattern of three flashes every 12 seconds. 

Watch: the video taken by the lighthouse keepers and posted on their Facebook page


lanterne cordouan