Photographic copy of plan and sections showing method of mounting glass. Northern Lights, sheet No. 1

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E 25798 CN

Description Photographic copy of plan and sections showing method of mounting glass. Northern Lights, sheet No. 1

Date 6/1857

Collection Records of the Northern Lighthouse Board, Edinburgh, Scotland

Catalogue Number E 25798 CN

Category Photographs and Off-line Digital Images

Copy of DC 9231A

Copies SC 781560

Scope and Content Photographic copy of plans and section showing method of mounting glass in the optic, Bound Skerry Lighthouse, Out Skerries, Shetland Islands This shows a section through the optic in the lightroom of the tower. The triangular blue shapes are glass prisms, which are arranged in rows around a central bull's eye lens. The angles of the prisms are carefully measured and indicated on the diagram, which would be used by engineers when constructing and installing the lens. A lighthouse optic consists of a series of linked lenses and prisms which gather light from the lamp and direct it forwards as a solid beam. Most optics have a series of panels which rotate around the light giving the familiar 'flashing' effect which helps mariners to identify individual lights. Bound Skerry Lighthouse was built 1856-8 to designs by engineers David (1815-86) and Thomas Stevenson (1818-87). It stands seven storeys high, and its light flashes white every 20 seconds, with a range of 32km. The lighthouse replaced a temporary light on Grunay island which was placed there in 1854. Bound Skerry Lighthouse was automated in 1972, and is now monitored from the Northern Lighthouse Board's headquarters in Edinburgh. Source: RCAHMS contribution to SCRAN.

Medium colour negative

External Reference C/82/56

Permalink http://canmore.org.uk/collection/744039