1. From Historic Instances To Electrification
As an island nation, we in the UK are used to seeing lighthouses round our coasts, but have you ever stopped to consider when they have been first constructed and the way they worked in those early days.
The purpose of lighthouses is obviously to mark dangerous coastlines, rocks and reefs and to aid navigation, particularly at night or in misty situations.
The primary recognized warnings made to boats of hazardous rocks and shores, have been fires, set at the edge of the water, but it was in Egypt that we first heard of precise buildings being built, which used light to information ships.
The Lighthouse of Alexandria
Built on the island of Pharos, the lighthouse was commissioned by Ptolemy in 290 B.C. It took 20 years to construct, and grew to become the tallest constructing in existence, apart from the great Pyramid, standing at between 450 and 600 ft in peak, and was recognised as one of many Seven Wonders of the World.
It’s thought to have value around the equivalent of three million dollars or £2.8 million. Its design was nothing like the slim buildings we’re accustomed to immediately. It consisted of three levels, the first being within the form of an enormous field constructed on a 20 foot high stone platform. On high of this was an eight sided tower, adopted by a cylinder that prolonged to an open cupola the place the hearth burned to provide 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 right into a beam by the use of a large curved mirror, in all probability product of polished bronze. It was mentioned that ships could detect its alerts as much as 100 miles away, the light from the tower by night time, and the smoke from the fire by day. This claim nevertheless appears somewhat excessive.
The lighthouse turned so well-known that the title “pharos” became the basis of the word “lighthouse” in lots of languages. It stood for over 1,500 years, surviving a tsunami in 365 Advert, but earth tremors resulted in cracks forming in the structure which wanted restoration. Then, a serious earthquake within the area, in the 14th century, induced such severe injury that the construction eventually collapsed.
Other early lighthouses
In medieval times the Iranians apparently erected massive minaret towers in 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 in the Qiantang River.
One of many oldest working lighthouses in Europe is Hook Lighthouse, constructed at Hook Head in County Wexford, Ireland in 13th century and in-built circular design. Two lighthouses, known as the Pharos, have been built at Dover (UK) soon after the Roman conquest of Britain. They have been constructed on two heights (the Japanese and the Western). The one on the Japanese Height still stands within the grounds of Dover Castle.
One other famous early Roman lighthouse is the Tower of Hercules, most likely inbuilt the first century, on a peninsula at A Coruna in north-west Spain. It was originally recognized because the “Farum Brigantium”, the Latin word farum being derived from the Greek pharos.
The light was initially produced utilizing a wood fired system located 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 city turned one of the kingdom’s largest ports, and by the seventeenth century it had been fitted with a dome formed lantern. More restoration was accomplished within the early 18th century, and in 1847, a system using Fresnel lenses (see later) was put in. It was electrified in 1926, with a beam visible for up to 32 nautical miles and is the oldest Roman lighthouse in use right now.
Some early lighthouses used wick lamps as a light source and sometimes the beam could only travel a number of miles. The Argand hollow wick lamp and parabolic reflector had been developed in Europe round 1781, while in the USA, whale oil was used with wicks till the Argand system was introduced around 1810,which was then later changed with Colza oil (just like rapeseed oil), lard oil after which Kerosene.
The Fresnel lens
In 1822 a Frenchman, named Augustin Fresnel, came upon how to increase the light depth using prisms, and the primary Fresnel lens was installed in 1822 within the Cordouan lighthouse within the mouth of the Gironde estuary. This light could possibly be seen from 20 miles or 32 km away. By the 1860s, low-gentle-loss Fresnel lenses, a lot bigger than the original ones, were in use in lighthouses around Britain and France, their use rapidly extending to Italy and further afield to Australia and America.
To create the flashing effect, designers needed to come up with a method of making the lens revolve. This was carried out using a rotating stand with a clockwork mechanism with descending weights on cables. The keeper periodically cranked up the burden to the top of the lighthouse and as it descended, the lens revolved. The flashing effect was achieved every time a section of the rotating lens passed between the lamp and the observer. The rate of rotation decided the frequency of the flash and made it potential for each lighthouse to have its own recognisable pattern.
The advent of electricity
Across the flip of the 20th century, acetylene gas (electricity and carbide) began replacing kerosene, and round 1910 many lighthouses started utilizing the intelligent gadget referred to as the Dalen Sun Valve, invented by the Swede, Stone Island Shop Gustav Dalen. The valve opened and closed the fuel provide to the lamp according to how a lot sunlight it received, so the lights might be turned on mechanically at dusk and off at dawn. Dalen additionally discovered how you can retailer the gas in tanks and to interrupt its flow, inflicting the sunshine to flash. Dalen’s inventions resulted in financial savings in gas and maintenance, as the lamps solely wanted servicing twice a yr.
As electricity grew to become available, the clockwork mechanisms in the lighthouses were replaced by electric motors, with 100W bulbs offering the sunshine source, and electronically operated fog indicators have been added. With all this electrification and automation, lighthouse keepers have been sadly out of date and from the 1980 they became superfluous to requirements. The last lighthouse in the UK to be automated was North Foreland in Kent, in 1998.
Many Fresnel lenses have been changed by rotating aerodrome beacons which require less upkeep. The system of rotating lenses has in some instances been changed by a excessive intensity light that emits brief flashes, similar to the obstruction lights used to warn aircraft of tall buildings.
Recent improvements embody Vega Lights, (lighthouse beacons providing a variety of as much as 22 nautical miles with a one hundred Watt lamp). They’ll function in distant, photo voltaic-powered areas, on unattended websites, and require upkeep only once a year. There are within the region of 600 of those in operation all over the world.
Know-how strikes on, and as new innovations resembling GPS make navigation easier and safer, it could also be tempting to think that lighthouses stone island dyed down jacket green have had their day.
Personally I’d prefer to have a dependable backup to my GPS, and there’s nothing so comforting in your first ever evening watch underneath sail, than to see the beam of a lighthouse shining through the darkness, to count the flashes and know that you’re where try to be.
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