Scanned image of photographic copy of method of mounting glass. Sheet No. 1.

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SC 781560

Description Scanned image of photographic copy of method of mounting glass. Sheet No. 1.

Date 6/1857

Collection Records of the Northern Lighthouse Board, Edinburgh, Scotland

Catalogue Number SC 781560

Category Photographs and Off-line Digital Images

Copy of E 25798 CN

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.

External Reference C/82/56

Permalink http://canmore.org.uk/collection/781560

File Format (TIF) Tagged Image File Format bitmap