Souter Lighthouse

The lighthouse c. 1900.

The lighthouse and associated buildings were designed for Trinity House by their Chief Engineer, James Douglass; its construction was supervised by on-site engineer Henry Norris.[9] Alongside the lighthouse tower a number of other buildings were laid out around a quadrangle, including the engine room and boiler house, and five dwellings; all were built of rubble masonry, rendered with Portland cement.[3] The contract for building the lighthouse and keepers' cottages was reported in March 1869 as being £8,000[10] and was awarded to the local firm of James Todd,[11] after complaints that local builders had not had the opportunity to reply to tender as it had not been advertised locally.[12] The foundation stone was ceremonially laid by Admiral Collinson's sister on 9 June 1869.[13] Building works were completed in 1870, and the lighthouse entered service in January the following year.[3] After completing this project Douglass and Norris moved on to the building of Hartland Point Lighthouse in Devon.

The original arc lamp assembly, in use from 1871-1914, now on display in the lighthouse visitor centre.

Carbon arc lights for lighthouses were pioneered by Professor Frederick Hale Holmes, with experiments carried out in 1857–60 at Blackwall and at South Foreland Lighthouse (as described in a lecture [14] by Michael Faraday at the Royal Institution).[15] An initial installation at Dungeness Lighthouse in 1862 had proved problematic, however, with frequent failures of the lamps and machinery; so Trinity House carried out an extensive testing and selection process over five years (including comparisons with oil lights and examination of equipment in Britain and France)[16] before finalising its plans for a complete purpose-built electric installation at Souter.[3]

One of the original magneto-electric generators from Souter Lighthouse (now part of 'Making the Modern World' in the Science Museum, London).

The carbon arc lamp at Souter was placed within a lens array consisting of a third-order fixed catadioptric optic surrounded by a revolving assembly of eight vertical condensing-prisms which produced one bright flash every thirty seconds.[4] Its 800,000 candle power light could be seen for up to 26 miles.[6] The optics were designed and built by James Chance in 1870.[17]

In addition to the main light a red/white sector light shone from a window in the tower below the lantern, to highlight hazards to the south in Sunderland Bay (namely Hendon Rock and the White Stones); it was powered using light diverted (through a set of mirrors and lenses) from the landward side of the main arc lamp.[18]

Electricity for the light was provided by two of Holmes' own magneto electric generators for which he took out a series of patents[19] during those years. In normal operation only one generator was used, but in conditions of poor visibility both were connected to the lamp to provide a brighter light. The generators were driven by one of a pair of J. Whitworth & co. 5 nhp 'Allen' condensing steam engines.[3] (Prior to being installed at Souter, the engines and generators were exhibited by Trinity House at the Paris Exposition of 1867.) The engines were worked alternately: one week on, one week off. Located in the engine-house, they also drove an air-pump to feed the pressure tank of a foghorn.[20]

In December 1891 the lighthouse tower was painted with a broad red band, to make it more conspicuous during the day.[21]

Holmes also designed a reed fog signal for the new lighthouse, sounded from a separate foghorn house (east of the tower) through a pair of vertical trumpets (angled north-east and south-east, facing out to sea).[22][23] It sounded one blast every 45 seconds.[24] Compressed air for the foghorn was piped underground from the engine room, on the other side of the lighthouse, where the air compressor was driven by a common drive shaft from the engines powering the magnetos.[20]

A more powerful siren fog signal replaced the reeds in February 1879;[24] it sounded one blast every minute.[25] It required an additional and more powerful engine, which was installed in the engine room to drive the compressor for the new signal.[3]

• 
  East Elevation
• 
  Site plan
• 
  Ground plan
• 
  Machine room
• 
  Light room
• 
  Lens and Lanterns
• 
  Chart of vicinity (1875)

In 1914 the pioneering electric light at Souter was replaced with the latest type of incandescent oil lamps (i.e. paraffin vapour burners). At the same time Chance Brothers provided a new, much larger lens system: a bi-form first-order catadioptric revolving optic (a bi-form lens is double-height, containing two lamps, one above the other). At the same time a new lantern was provided, to accommodate the taller optic. Red shades were placed around the lamps, within the lenses, so that the light now flashed red, once every 5 seconds.[26] The 1914 optic remains in situ in the tower; it weighs 4.5 tonnes and floats on 1.5 tonnes of mercury.[27]

A separate lamp was used for the fixed red/white sector light, which continued to shine from its window lower down in the tower.

Having removed the two Holmes magneto-electric machines from the engine room, the Corporation of Trinity House presented one to the Institution of Electrical Engineers in 1915;[28] it is now on display at the Science Museum, London.[29]

The fog signal was improved in 1919 when a more powerful siren was installed, sounded through a pair of Rayleigh trumpets.[30] (These replaced the twin Holmes trumpets formerly employed; the foghorn house was remodelled at the seaward corners to accommodate them).[20] The siren gave a 4-second blast every minute.[31] Hornsby oil engines were installed to drive the compressors for the new siren.[20]

In 1952 the lighthouse was again converted to run on electric power (this time using incandescent lamps, powered by mains electricity).[6] The 4,500W bulbs used for the main light were the largest in the Trinity House service.[32] Should the electricity supply fail, a diesel generator would be engaged (and in the event that it too were to fail, an additional emergency battery lamp would be engaged). The mechanism which turned the lenses continued to be driven by clockwork at this time, until 1983 when it was replaced by a pair of electric motors.[33]

The foghorn building, looking out to sea.

The fog signal was upgraded in 1953: a Stone Chance diaphone signal was installed and a pair of exponential horns replaced the Rayleigh Trumpets on top of the foghorn building.[20] At the same time the engine room was provided with two new Reavell compressor sets, one driven by an electric motor, the other by a diesel engine. The diaphone produced a five-second blast every 30 seconds in poor weather, and remained in use up until 1988, when the lighthouse was decommissioned.[6]

Souter Lighthouse was decommissioned by Trinity House in 1988,[34] but continued to serve as a radio navigation beacon up until 1999 when it was finally closed.

• 
  The lighthouse viewed from the south-east.
• 
  Diesel compressor and standby generator in the Engine Room.
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  Electric compressor and air tanks for the foghorn in the Engine Room.
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  An incandescent oil burner: these replaced the arc lamps in 1914.
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  Some of the electric lamps used at Souter from 1952.
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  The emergency battery room.
• 
  Radiobeacon equipment at the base of the tower.