Lighthouse on the Isle of Portland, Dorset, England From Wikipedia, the free encyclopedia
Portland Bill Lighthouse is a functioning lighthouse at Portland Bill, on the Isle of Portland, Dorset, England. The lighthouse and its boundary walls are Grade II Listed.[2]
Portland Bill Lighthouse | |
 | |
| Location | Portland Bill Isle of Portland Dorset England |
|---|---|
| OS grid | SY6773768376 |
| Coordinates | 50.514155°N 2.456383°W |
| Tower | |
| Constructed | 1903-05 |
| Construction | sandstone tower |
| Automated | 1996 |
| Height | 41 metres (135 ft) |
| Shape | tapered cylindrical tower with balcony and lantern |
| Markings | white tower with a red horizontal band, white lantern |
| Operator | The Crown Estate[1] |
| Heritage | Grade II listed building |
| Light | |
| First lit | 1906 |
| Focal height | 43 metres (141 ft) |
| Lens | 1st order catadioptric rotating (original), LED lantern (current) |
| Intensity | 635,000 candela |
| Range | 18 nautical miles (33 km; 21 mi) |
| Characteristic | Fl (4) W 20s. |
As Portland Bill's largest and most recent lighthouse, the Trinity House operated Portland Bill Lighthouse is distinctively white and red striped, standing at a height of 41 metres (135 ft). It was completed by 1906 and first shone out on 11 January 1906.[3] The lighthouse guides passing vessels through the hazardous waters surrounding the Bill, while also acting as a waymark for ships navigating the English Channel.[4]
The two original lighthouses, now known as the Old Higher Lighthouse and Old Lower Lighthouse, operated as a pair of leading lights to guide ships between Portland Race and The Shambles sandbank.[1] They were constructed in 1716, both rebuilt in 1869, and decommissioned following the completion of the present lighthouse.[5] At the turn of the 20th-century, Trinity House put forward plans for building a new lighthouse at Bill Point. They acquired the required land in 1903.[6][7]
The builders, Wakeham Bros. of Plymouth, began work on the foundations in October 1903.[8] Chance & Co of Birmingham supplied and fitted the lantern.[9] A pressurised vapour paraffin lamp was used, placed at the centre of a large (first-order) revolving optic; weighing 3.5 tons, this was made up of four asymmetrical catadioptric lens panels and a concave prismatic reflector.[10] The lighthouse was completed in 1905 at a cost of £13,000, and the lamp first lit on 11 January 1906.[5] A red sector light was provided in addition to the main light, shining from a window in the lower part of the tower, to indicate the position of The Shambles.[1] The light was electrified in the mid-1950s.[11]
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In 1940 the lighthouse was provided with an F-type diaphone fog signal, sounding from a window part-way up the tower. Compressed air was provided to six cylindrical storage tanks by a pair of Reavell compressors, all located (together with a standby generator) within the base of the tower.[10] These were connected at a higher level to the sounding tanks, which fed the compressed air to the diaphone itself, mounted behind its trumpet-like emitter which protruded through the window. Admission of air into the diaphone was controlled by a clockwork (later electric) coder, which caused the diaphone to sound a 3.5-second blast every 30 seconds. The 180 Hz note had an audible range of 7 nmi (13 km; 8.1 mi) (which could be doubled under favourable conditions). The diaphone remained in regular use as an aid to navigation until 1995, when it was replaced by a high-frequency electric fog signal (sounding from another window, further down) in readiness for automation.[10]
On 18 March 1996, Portland Bill Lighthouse was demanned, and all monitoring and control transferred to the Trinity House Operations & Planning Centre in Harwich.[12] The original Type F diaphone was decommissioned in 1996, but in 2003 Trinity House restored it to occasional use for the benefit of visitors;[13] (it was sounded regularly for half an hour on Sunday mornings, except when foggy, until 2017).[14]
In the early 21st century the lighthouse used a 1 kW MBI lamp together with the same rotating lens system that had been in use since 1906. (It flashed four times every 20 seconds with an intensity of 635,000 candelas and a range of 25 nautical miles.) The fog signal was used in times of bad weather; it gave a four-second blast every 30 seconds with a range of 2 nautical miles.[4]
In November 2018 Trinity House applied for (and obtained) planning permission to remove the lamp and optic from the lantern room as part of a programme of modernisation.[15] It proposed relocating the lens array to the base of the tower,[16] which led to the removal of the historic diaphone fog-signalling equipment, installed there in 1940 and still in working order, on the basis that this was 'the only available [space] for retaining the historic optic on-site'.[17]
In 2019-2020 a new non-rotating LED light source was installed in the lantern room[17] and a new omnidirectional fog signal was installed on the exterior lantern gallery (replacing the electric emitter installed in the 1990s).[18] The two LED lanterns (one of which is used, the other kept on standby) have a reduced range of 18 nautical miles (33 km; 21 mi).[19]
As Portland's prime attraction, the Portland Bill Lighthouse is open to the public for tours. A visitor centre is housed in the former lighthouse keeper's quarters. The original centre closed in 2013 due to lack of funding,[20] however a new renovated centre opened in 2015.[21] The tours operated at the lighthouse last approximately 45 minutes and visitors are able to climb the 153 steps to the top of the lighthouse.[22]
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