See-saw searchlight emplacement at Fort Victoria

Summary

A concrete emplacement, originally built for searchlight apparatus of an experimental see-saw type. The searchlight was constructed at Fort Victoria in 1888 by the Royal Engineers to illuminate the minefield laid in the Solent protecting the approaches to the Royal Naval Dockyard at Portsmouth and the port of Southampton. Although the apparatus has been removed, the emplacement remains largely intact.

Reasons for Designation

The see-saw searchlight emplacement at Fort Victoria, constructed in 1888, is listed at Grade II for the following principal reasons:

Historic interest:

* as a rare surviving example of an emplacement for an early experimental type of military searchlight;
* as part of the defensive coastal landscape developed in the C19 along the approaches to the Royal Dockyard at Portsmouth and the port of Southampton.

Architectural interest:

* for the slight variations from the standard emplacement design, showing it belongs to the developmental phase of military searchlight technology in the 1880s.

Group value:

* as part of Fort Victoria, and more widely the network of designated fortifications either side of the west Solent channel.

History

Fort Victoria (Grade II, National Heritage List for Enfland (NHLE) entry 1209376) was constructed on the Isle of Wight between 1852 and 1855 to defend the Solent channel, which provided access to the Royal Dockyard at Portsmouth and the port at Southampton. In the late C19 the fort passed to No 22 Company, Royal Engineers who had responsibility for maintaining coastal minefields and manning the associated searchlights. Fort Victoria became the submarine mining depot covering the Solent channel. The main minefield under its control was laid between Hurst Castle and Cliff End.

Illumination of minefields at night was required from 1871 and searchlights for this purpose developed through experiments with prototype designs for their apparatus and emplacements.

The first known example of the see-saw type, to which the Fort Victoria example belongs, was constructed at Sheerness in 1885. The design comprised a projector lamp mounted at one end of a girder, with a plane mirror at the other. The girder was attached to a concrete emplacement by a traversing support upon which it could pivot and be raised in the manner of a see-saw and the apparatus housed in the sunken emplacement for protection. Power was provided by an engine - at Fort Victoria, this was in an engine room built into the hillside behind the western barrack block.

The searchlight could be operated in ‘direct’ mode, whereby the projector lamp is hoisted above a protective parapet to illuminate the target area and controlled remotely at distance by a series of wires, pulleys and motors. Alternatively, in ‘reflector’ mode only the mirror is hoisted above the parapet while the projector lamp remained within the emplacement, protected from enemy fire and operated manually. The mirror could be easily replaced if damaged. In both modes, the apparatus could be traversed on the emplacement to sweep the light across the target area.

Over time the see-saw type was found to be overly cumbersome and complex to operate. No examples of the apparatus survives but the best-preserved examples of their emplacements are understood to be at Chatham and Fort Balance, Wellington, New Zealand.

Details

Experimental see-saw searchlight emplacement of 1888, constructed by the Royal Engineers as part of the submarine mining depot at Fort Victoria. The searchlight apparatus has been removed, but the concrete emplacement remains largely intact.

MATERIALS: the emplacement comprises a concrete superstructure with a concrete base built into the foreshore embankment overlooking the sea. Steel beams are used to support the underside of the roof of the emplacement.

DESCRIPTION: the searchlight emplacement is largely semi-circular in plan with a centrally positioned truncated concrete cone upon which the traversing searchlight apparatus was positioned. Around this is a lower concrete platform within which the searchlight could be easily manoeuvred. This is partially covered by a reinforced concrete roof to provide protection. The emplacement is approximately 10m in width, 5m in depth, and partially sunken into the ground by around 2.5m.

Sources

Books and journals
Cantwell, A, Sprack, P, Solent Papers Number Two The Needles Defences 1525-1956 (1986),
Saunders, A D, Fortifications of Portsmouth and the Solent (1998),
Brown, WB, History of Submarine Mining in the British Army (1910),
Cantwell, A, Fort Victoria 1852-1969 (1985),
Kendall, P, Holman, J, The Lower Lines Brompton Kent Archaeological Investigations 2007-2009 (2023),

Other
Professional Papers of the Royal Engineers (Confidential Series)
Royal Artillery and Royal Engineers Works Committee reports and minutes
The Royal Engineers Journal

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