Maclear's Beacon - Table Mountain, Cape Town, South Africa - Cairns on Waymarking.com

In 1750, astronomer Abbé Nicolas Louis de Lacaille took measurements in the Cape Town area in order to determine the radius of the Earth. His surprising results indicated that the Earth was pear-shaped, with the Southern hemisphere having a larger radius than the Northern (it was later determined that large mountain masses in the area had skewed Lacaille's measurements). Irish-born South African astronomer Thomas Maclear repeated these measurements between 1838 and 1847, but this time using triangulation stations over a larger area than Lacaille used. Maclear's measurements corrected the errors in Lacaille's measurements and confirmed what astronomers and surveyors had suspected: that the Earth was actually an oblate sphere. This cairn was built in 1844 as one of the triangulation stations for Maclear's measurements. Its highly-visible position at the 1086-metre summit of Table Mountain made it an excellent spot for triangulation measurements.

After Maclear's work was complete, the beacon remained in place as both a triangulation station for surveyors and a summit marker. It collapsed in 1929, but was later restored in 1979 on the 100th anniversary of Maclear's death. A plaque on the side of the cairn reads:

Maclear's Beacon
This beacon was built as a triangulation station in December 1844 by Sir Thomas Maclear (1794-1879) in his survey for the verification and extension of the Abbé de la Caille's arc of meridian. It was restored to commemorate the centenary on 14 July 1979 of Maclear's death. As astronomer at the Royal Observatory he initiated the Geodetic Survey of South Africa.
National Monuments Council

Maclear - Baken
Hierdie klipstapel is in Desember 1844 as peilbaken deur Sir Thomas Maclear (1794-1879) opgerig in sy opmeting vir die kontrolering en uitbreiding van die Abbé de la Caille se meridiaanboog. Dit is gerestoureer met die oog op die honderdjarige herdenking op 14 Julie 1979 van Maclear se dood. As sterrekundige by die Koninklike Sterrewag het hy 'n begin gemaak met die Geodetiese Opmeting van Suid-Afrika. Raad vir Nasionale Gedenkwaardighede
1979

Cairn Location: Summit of Table Mountain Cairn Purpose: Other (please describe in description) Type if different from above list: Scientific experiment Types of rock: Peninsula Formation sandstone Cairn Condition:

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