List of sources:
Cape of Good Hope almanac and annual register... (title varies), 1839-1846.
Dictionary of South African biography, Vol. 3, 1977.
FamilySearch: John Skirrow. https://www.familysearch.org/ark:/61903/1:1:QP7L-92BY?lang=en
Regulations of the South African Literary and Scientific Institution (list of members). Cape Town, 1832. (National Library, Cape Town, Vol. SABP4).
Rules and regulations of the Cape of Good Hope Horticultural Society, 1827. (Library of Parliament, Cape Town).
Smit, J.J. Die paaie, passe en rivieroorgange in Suid-Kaapland, 1806-1858. D.Lit. et Phil. proefskrif in Geskiedenis, Universiteit van Suid-Afrika, 1975.
Warner, B. Astronomers at the Royal Observatory, Cape of Good Hope. Cape Town: Balkema, 1979.
Warner, B. Charles Piazzi Smyth, astronomer-artist: His Cape years, 1835-1845. Cape Town: Balkema, 1983.
Warner, B. Royal Observatory, Cape of Good Hope, 1820-1831. Dordrecht: Kluwer, 1995.
Warner, B. & Warner, N. Maclear & Herschel, letters and diaries at the Cape of Good Hope, 1834-1838. Cape Town: Balkema, 1984.