1. From Historical Times To Electrification
As an island nation, we within the UK are used to seeing lighthouses around our coasts, however have you ever stopped to contemplate when they have been first constructed and the way they labored in those early days.
The aim of lighthouses is clearly to mark dangerous coastlines, rocks and reefs and to help navigation, particularly at night or in misty conditions.
The primary known warnings made to boats of hazardous rocks and shores, were fires, set at the edge of the water, but it was in Egypt that we first heard of actual structures being constructed, which used light to information ships.
The Lighthouse of Alexandria
Constructed on the island of Pharos, the lighthouse was commissioned by Ptolemy in 290 B.C. It took 20 years to build, and grew to become the tallest constructing in existence, aside from the nice Pyramid, standing at between 450 and 600 feet in height, and was recognised as one of many Seven Wonders of the World.
It is thought to have cost around the equal of three million dollars or £2.Eight million. Its design was nothing just like the slim constructions we are aware of as we speak. It consisted of three phases, the primary being within the shape of an enormous field constructed on a 20 foot high stone platform. On top of this was an eight sided tower, adopted by a cylinder that extended to an open cupola where the hearth burned to supply the light. On its roof was a large statue, thought to be of the sea god Poseidon. The fire’s gentle was believed to have been projected into a beam by way of a big curved mirror, in all probability made of polished bronze. It was mentioned that ships could detect its signals as much as 100 miles away, the light from the tower by night, and the smoke from the fire by day. This claim nonetheless appears a little bit excessive.
The lighthouse turned so famous that the name “pharos” became the root of the word “lighthouse” in many languages. It stood for over 1,500 years, surviving a tsunami in 365 Advert, but earth tremors resulted in cracks forming within the structure which wanted restoration. Then, a serious earthquake within the region, within the 14th century, brought about such severe injury that the structure eventually collapsed.
Other early lighthouses
In medieval times the Iranians apparently erected massive minaret towers within the mouth of the Persian Gulf to assist navigation. In China, the medieval mosque at Canton additionally had a minaret serving as a lighthouse, and in 1165 a pagoda known as the Liuhe Pagoda, was in-built Hangzhou and acted as a lighthouse for sailors within the Qiantang River.
One of many oldest working lighthouses in Europe is Hook Lighthouse, constructed at Hook Head in County Wexford, Eire in thirteenth century and in-built circular design. Two lighthouses, called stone island navy gloves the Pharos, were built at Dover (UK) quickly after the Roman conquest of Britain. They had been constructed on two heights (the Eastern and the Western). The one on the Japanese Height nonetheless stands in the grounds of Dover Castle.
One other well-known early Roman lighthouse is the Tower of Hercules, probably inbuilt the first century, on a peninsula at A Coruna in north-west Spain. It was originally identified as the “Farum Brigantium”, the Latin phrase farum being derived from the Greek pharos.
The sunshine was initially produced using a wooden fired system situated on the summit platform, however the lighthouse was abandoned after the Viking Invasions of 854-fifty six. It was restored within the 14th century when the town turned one of many kingdom’s largest ports, and by the 17th century it had been fitted with a dome shaped lantern. Extra restoration was accomplished in the early 18th century, and in 1847, a system utilizing Fresnel lenses (see later) was put in. It was electrified in 1926, with a beam visible for as much as 32 nautical miles and is the oldest Roman lighthouse in use as we speak.
Some early lighthouses used wick lamps as a light supply and often the beam could solely journey a few miles. The Argand hollow wick lamp and parabolic reflector had been developed in Europe around 1781, while within the USA, whale oil was used with wicks till the Argand system was launched around 1810,which was then later replaced with Colza oil (similar to rapeseed oil), lard oil and then Kerosene.
The Fresnel lens
In 1822 a Frenchman, named Augustin Fresnel, found out how to extend the sunshine depth using prisms, and the first Fresnel lens was installed in 1822 within the Cordouan lighthouse within the mouth of the Gironde estuary. This mild may very well be seen from 20 miles or 32 km away. By the 1860s, low-mild-loss Fresnel lenses, a lot larger than the unique ones, were in use in lighthouses round Britain and France, their use rapidly extending to Italy and additional afield to Australia and America.
To create the flashing impact, designers had to provide you with a means of constructing the lens revolve. This was accomplished using a rotating stand with a clockwork mechanism with descending weights on cables. The keeper periodically cranked up the weight to the highest of the lighthouse and because it descended, the lens revolved. The flashing effect was achieved each time a segment of the rotating lens handed between the lamp and the observer. The rate of rotation determined the frequency of the flash and made it attainable for each lighthouse to have its personal recognisable sample.
The appearance of electricity
Around the flip of the twentieth century, acetylene fuel (electricity and carbide) began changing kerosene, and round 1910 many lighthouses began using the clever system referred to as the Dalen Sun Valve, invented by the Swede, Gustav Dalen. The valve opened and closed the gasoline provide to the lamp according to how much sunlight it acquired, so the lights could be turned on robotically at dusk and off at daybreak. Dalen also discovered how one can store the gas in tanks and to interrupt its movement, causing the light to flash. Dalen’s innovations resulted in financial savings in fuel and maintenance, because the lamps solely needed servicing twice a year.
As electricity became obtainable, the clockwork mechanisms in the lighthouses have been replaced by electric motors, with 100W bulbs providing the light supply, and electronically operated fog alerts had been added. With all this electrification and automation, lighthouse keepers had been sadly obsolete and from the 1980 they became superfluous to necessities. The last lighthouse in the UK to be automated was North Foreland in Kent, in 1998.
At the moment
Many Fresnel lenses have been replaced by rotating aerodrome beacons which require less upkeep. The system of rotating lenses has in some circumstances been changed by a excessive depth gentle that emits brief flashes, similar to the obstruction lights used to warn aircraft of tall buildings.
Current innovations embody Vega Lights, (lighthouse beacons providing a spread of as much as 22 nautical miles with a one hundred Watt lamp). They can operate in distant, photo voltaic-powered areas, on unattended sites, and require upkeep only as soon as a 12 months. There are in the region of 600 of these in operation world wide.
Know-how strikes on, and as new innovations such as GPS make navigation easier and safer, it may be tempting to assume that lighthouses have had their day.
Personally I’d choose to have a dependable backup to my GPS, and there may be nothing so comforting on your first ever night time watch underneath sail, than to see the beam of a lighthouse shining via the darkness, to depend the flashes and know that you are where you have to be.
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