A set of files relating to British expeditions to observe solar eclipses. The record is incomplete and mainly consists of notebooks and correspondence re equipment and supplies. Included are notebooks listing photographic plates for the solar eclipses of 1900, 1901, 1905, 1912 and 1914 [RGO 169/1], notebooks listing equipment for the 1905 and 1932 eclipses [RGO 169/2 and 5], and correspondence regarding preparations for the UK-based observation of the 1927 eclipse [RGO 169/4]. The 1940 eclipse file includes offprints and data sheets [RGO 169/6]. Sets of three Nautical Almanac Circulars on total solar eclipses of 1896, 1898 and 1901 are included at RGO 169/8.

The most complete set of records covers the 1926 total solar eclipse expedition to Sumatra [RGO 169/3]. The eclipse was of particular astronomical interest because of its relatively long duration, 3-4 minutes, and because the sun was almost at its maximum sunspot period. The files include notebooks recording instruments and plates, preparatory documents including a sketch of the camp, manuscript and typed reports, photographs of spectra, correspondence, and a contemporary news cutting showing the British Expedition team.