Summary

A pair of acoustic mirrors, the eastern dating from circa 1916 and the western from 1920-23. The remains of the toilet blocks in front of the mirrors, and the tunnel entrances to the deep shelter behind (constructed during the Second World War), are not included in the scheduling.

Identification Images (2)

Most Recent Monitoring

None Recorded

Monument Types

Description

The eastern mirror was constructed first in circa 1916, part way down the cliff side, with the western mirror following circa 1920-23. Fan Hole is a deep depression at the top of the White Cliffs between Dover and St Margaret’s at Cliffe, overlooking Fan Bay. The monument has an uninterrupted view over the English Channel, essential for the function of the mirrors.

Both mirrors face out towards the sea and are carved directly into the side of the chalk cliff, faced in a layer of concrete approximately 10cm thick. The eastern mirror is set at a 16 degree angle, facing slightly toward the sky. It has an overall diameter of approximately 4.5m, whilst the spherical surface has an approximate radius of approximately 3m. There are no side walls, a feature which is present on a number of surviving comparative examples. The western mirror also has approximately an 4.5m diameter but there are some key differences. The spherical surface is larger, with a radius of approximately 5.1m, giving a larger focal length and consequently a longer range of sound detection. This mirror is also essentially vertical and has a triangular concrete apron above, which would have presumably been added to combat drainage issues. This addition is representative of this period of construction.

References

Designations

Other Statuses and References

Associated Events

None Recorded

Associated Finds

None Recorded

Related Records

None Recorded