Mann W.

MANN, William

Professional Astronomer

Born: 25 October 1817, Kent, U.K.
Died: 30 April 1873


In brief :
Famous for:
Mann was chief assistant at the
Cape Observatory 1847 – 1872.
Mann came to the Cape Observatory as second assistant in 1839 with various pieces of equipment to re measure and extends La Caille‘s Arc of the Meridian. He spent six years on the task assisting Maclear and carried out the task with the greatest possible skill. It ruined his health.  He became assistant director to Maclear in 1847 and held the post until 1872. Mann also married the daughter of Maclear. In 1847 Mann fell of a horse and suffered severe injuries that would plague him the rest of his life.

Historical background :
  William Mann was born at Kent in 1817, the third son of Major General Cornelius Mann, commander of the Royal Engineers at Gibraltar.
During the early years at the
Cape Observatory there was a high turnover of assistants. However, due to the influence of Sir John Herschel, assistants of quality were found and appointed to the Cape Observatory. Charles Piazzi Smyth was appointed as assistant director in 1835. Due to the influence of Herschel the post was created for a second assistant, and in 1839 William Mann was appointed to this post.
Mann arrived at the Cape on 22 October 1839. He celebrated his twenty-second birthday 3 days after landing at the Cape. [Warner – Astronomers, p.55.]
The re-measurement of the
Arc of the Meridian was a priority at the Cape and most of the fieldwork was done between 1837 and 1847. The arrival of Mann in 1839 was very welcome to Maclear and Smyth in helping with the survey work.
The previous director to Maclear,
Thomas Henderson, now Astronomer Royal for Scotland, died on 23 November 1844. Charles Piazzi Smyth, assistant director to Maclear was offered, and accepted, the post as Astronomer Royal for Scotland. Piazzi Smyth however stayed on for another year at the Cape to help Maclear finish the surveying work for the Arc of the Meridian. William Mann was promoted to assistant director and George Childe now filled his post, second assistant. [Warner – Astronomers, pp. 60 – 62.]
A few months after Piazzi Smyth left for Scotland William Mann fell from his horse. (Approximately 1846) He suffered severe head injuries, which impaired his health for the rest of his life. [Warner – Astronomers, p.62.] In 1846 and again in 1867 Mann had to take leave due to bad health. He traveled to Europe for treatment and to recuperate.
The Cape Observatory was to receive an excellent new instrument, the
Airy Transit Circle, to replace both the Dollond Transit Instrument and the Greenwich Mural Circle. On 9 October 1852 Mann left for Greenwich to be instructed on the mechanical details, method of mounting the instrument etc. He returned on 22 December 1853. The instrument was crated to the Cape in 1854. [Warner – Astronomers, p.65.]
Maclear held Mann in high regard and wrote: “His powerful intellect, his unflinching integrity, and his industry enable me to trust him with confidence on all occasions and in every department, whether at the observatory or on the triangulation, being certain that whatever is practicable will be accomplished, and that what he does will be sure to be well done.” [Warner – Astronomers, p.62.]
This high opinion of Maclear helped Mann in his most formidable task. He asked Maclear’s second daughter, Caroline, to be his wife, with her father’s blessing of course. They married in 1854. [Warner – Astronomers, p.62.]
Mann received distinction in 1863 by the offer of the “Astronomer ship of Sydney.” He declined the offer. [Warner – Astronomers, pp.71 – 72.]
In 1868 it was suggested to Maclear that he should consider retirement due to old age. He refused, and said he would only resign if Mann was appointed in his place as director. The British Admiralty did not accept his proposal. (In 1870 Maclear was forced to retire at an age of 76.)  [Warner – Astronomers, pp.71 – 72.]
He was an artist of great ability, although he was colour blind. [Warner – Astronomers, p.55.]
In the 1870’s a scarlet fever epidemic broke out at the Cape Colony. Mann was severely stricken and two of his children succumbed. He retired on the grounds of ill health and died on 30 April 1873. [Warner – Astronomers, p.75.]
-1839: Joined the Cape Observatory. Worked on La Caille’s Arc of the Meridian. (1839 – 1847) Ruined his health.
-1846: Mann went on holiday to U.K. due to bad health.
-1847 to 1872: Chief assistant at the Cape Observatory. He was assistant to Maclear from 1847 – 1870, and to Stone 1870 – 1872.
-1852 (October 1852 until December 1853):  Went to U.K. and to be instructed in the use of the Airy transit. The instrument was crated and sent later.
-1859: Acting director whilst Maclear is on leave.
-1867: Bad health, takes holiday to England.
-1870: Resigned due to bad health.
Note: Resigned 1870 [Moore p. 70.] but assistant to Stone until 1872? [Moore p. 91.]
1817 (25 October): Born in Kent.
1853:  Married Caroline, 2nd daughter of Maclear.
1873 (April 30): Died.


Link to the Telescope Manufacturers.


Link to the Main Bibliography Section and more information about Sources.

Remaining Artifacts:
Sketch of transit circle he bought to South Africa. (Africana Museum) [Moore p. 69.]
Laing, J.D. (ed.), The Royal Observatory at the Cape of Good Hope 1820  – 1970 Sesquicentennial Offerings, p.
Moore, P. & Collins, P., Astronomy in Southern Africa, p. 59; pp. 68 – 70; p. 91.   (General Source)
Smits, P., A Brief History of Astronomy in Southern Africa. (Unpublished)
-Warner, B., Astronomers at the Royal Observatory Cape of Good Hope.
By Mann:
Journal: Typescript copy in South African Library. [Moore p. 59.]
-Maclear: Correspondence and financial accounts of Maclear and W.  M. Mann (Maclear’s assistant) 1843-45 concerning the measured arc of meridian (N.B.: the writer is recommending to the Trigonometrical Survey that these items be transferred to the extensive collection contained in the South African Archives).SOUTH AFRICAN ARCHIVES, ROELAND STREET, CAPE TOWN [JHA8, pp. 220 – 221.]
-Maclear-Mann Papers (Accession No. 515): this extensive accumulation  of manuscripts and correspondence is contained in 139 files. They  derive from presentations made by members of the Maclear family and from donations from the Trigonometric Survey and from the Royal Observatory, Cape. Although mostly concerning Sir Thomas Maclear and William Mann, a considerable amount of material relates to Sir  John Herschel and to the early history of the Cape Observatory. Excluding miscellaneous files of accounts, testimonials, newspaper  cuttings, etc., the most significant references are:
Files 92 – 95Correspondences of William Mann and Caroline Mann.

Related Internal Links:
Royal Observatory at the Cape of Good Hope.
Arc of the Meridian.




William Mann.
Courtesy Royal Society of Edinburgh. Source: Warner, Smyth