This Defence Electric Light is situated on the Northern coastline of St George’s Island, adjacent to the Station Hospital. Authority to built this unique emplacement was given on 18th December 1890, although the Engine Room had been approved two years earlier. The underground searchlight position was built between 21st January 1891 and 23rd December 1892. The Engine Room was completed in 1889.
The whole complex was underground with an engine room to the rear which was connected to the searchlight emplacement by a tunnel. The searchlight itself was of a unique configuration. The design was similar to the vertical lift mount, and example of which can be seen on the Chatham Lower Lines. The searchlight is in a central position where it can be raised and lowered on hydraulics. The light is reflected through a mirror that can rotate. In this case the whole structure has been placed underground, and the searchlight mounted on a platform protected by five feet (2 metres) of medium rock. The beam shies down to a mirror that can be rotated through 45 degrees before shinning though a two foot metal hatch.
This emplacement is different to the See-Saw Searchlight but the basic concept is the same, to protect the projector from incoming hostile fire.