The French physicist Augustin Fresnel is one of the most significant figures in the field of lighthouse technology due to the fact that he was responsible for the introduction of his optical systems to lighthouses and beacons all over the world.
The first lighthouse to be equipped with this type of optic was at Corduan in France in 1823. Given its success, it was gradually progressively introduced in many other lighthouses as the most effective way to improve light range.
Fresnel’s design meant that lens size could be significantly reduced at the same time as range was increased.
STATIONARY OPTICS FOR 6th ORDER LIGHTHOUSES
The optics acquired by the Spanish Government during the second half of the 19th Century were mainly built by three French companies, Lepaute, Sautter and Barbier & Benard (later BBT). After this, at the beginning of the 20th Century, German optical equipment, manufactured by Julius Pintsch was also employed. However from the 1920s, the Swedish company AGA, founded by the inventor Gustav Dalen became the market leader.
In the Balearic Islands, the lighthouses with the greatest ranges built as part of the 1847 plan were of the 2nd Order. Some of their optics are now on display at the Portopí exhibition. However the great majority were of the 6th Order, such as the lighthouses at Cala figuera, Maó, Botafoc, Cap Blanc, Cap Salines, Sa Creu, Alcanada and Portocolom.
The optical equipment employed at these lighthouses used a lens with a diameter of 30cm with a dioptric central section and two upper and lower sections consisting of a varying number of catadioptric rings.
As a consequence of the new 1902 Plan, new rotating mechanisms consisting of clockwork machinery and a mercury flotation tank were introduced. The first lighthouse in the Islands to be equipped with this technology was that at Punta de l’Avançada in 1905. In the remaining lighthouses, this process took place in two different stages. In the second decade of the 20th Century and especially in 1917, 6th Order lighthouses were equipped with systems consisting of rotating screens that eliminated the old stationary light pattern for, in most cases, a system of light with occultations.
Later on, in the 1930s, and especially in 1928, many of the old 2nd Order lenses were adapted to the new rotating systems with mercury flotation tanks.
OPTIC FROM THE ILLA DE L’AIRE LIGHTHOUSE
This 2nd Order optic was built by the French company Sautter and started working at the L’Illa de l’Aire Lighthouse in Menorca on the 15th August 1860. It is similar to other rotating optics provided or in the first Plan and therefore includes a system of galets (small metallic wheels that supported the lens) for the rotation of the apparatus. The optic produced a light pattern of isolated flashes every minute using a Legrand lamp equipped with pistons. It saw continuous service until 1965, being the last lighthouse in the Balearic Islands to use this system.
OPTICS FROM THE TRAMUNTANA (DRAGONERA) AND PORTOCOLOM LIGHTHOUSES
This optic was originally installed 1910 at the Tramuntana lighthouse, working through a system of weights and employing a single wick Maris lamp. However, after automation in 1960 using new Dalen solar valve systems, the optic was dismantled and then installed at Porto Colom lighthouse in 1965 when the system there was converted to run on electricity. At both lighthouses it emitted a light pattern consisting of two white flashes every ten seconds.
OPTIC FROM THE CAP LLEBEIG LIGHTHOUSE
This is one of the most singular optics on display at the exhibition, not only for its spectacular design, but also for the way it was transported from Dragonera Island to Portopí lighthouse.
It started working at Llebeig Lighthouse in 1910, emitting a light signal consisting of isolated flashes every seven seconds. In 1969 it was dismantled and taken out of service, being replaced by a “universal apparatus” (provisional lighting equipment) until the new automatic Dalen system was installed in the summer of 1971.
In 1980 the difficulties caused by the considerable weight of the base meant the help of the US Navy’s 6th Fleet was requested and the optic was finally transported by helicopter to the site of the future exhibition at Portopí.