Robert James Mann, medical practitioner and writer on science, was the son of James Mann, watchmaker and jeweler, and his wife Elizabeth Hilling. After being apprenticed to a surgeon at the age of 17 he studied at University College, London, and qualified as a member of the Royal College of Surgeons (MRCS) and a licentiate of the Society of Apothecaries (LSA) in 1840. That same year he published his first scientific paper, a list of the flowering plants of Norfolk. His first book, The planetary and stellar universe (1845) was an excellent popular exposition of astronomy. He practiced medicine in Norfolk from 1840 to 1853 and in 1850 married Charlotte E. White. In 1854 he was awarded the degree Doctor of Medicine (MD) by the University of St Andrews. Subsequently he wrote books and articles for an income.
At the invitation of bishop John Colenso, Mann emigrated to Natal in 1857 to become the lay head of Colenso's mission station at Ekukanyeni (or Bishopstowe), about 8 km outside Pietermaritzburg, where he taught science and medicine. Although he was licensed to practice in the colony as a physician, surgeon and apothecary in November 1858 he did not enter any of these professions, but his interest in medical matters is shown by publications such as The book of health (London, 1850); A guide to the knowledge of life... (London, 1855), which dealt with physiology relating to the maintenance of health and was written for schools; and Medicine for emergencies (London, 1861), aimed at settlers, sailors and students. He served on the Medical Board of Natal from about 1863 and on the Visiting Committee of Grey's Hospital, Pietermaritzburg, until his departure from the colony in March 1866.
In July 1859 Mann was appointed Natal's first inspector (later superintendent) of education, stationed in Pietermaritzburg. He served in this position until he left Natal. His views led to the rapid growth of the number of primary schools in Natal, to the establishment of the first high schools in Pietermaritzburg and Durban, and to the introduction of science courses.
Mann's wide scientific interests included astronomy, on which he published an introductory Guide to the knowledge of the heavens (2nd ed., London, 1853); also papers on a meteorite (1856) and an occultation of Jupiter (1857) in the Monthly Notices of the Astronomical Society. Before coming to Natal Sir John Herschel* asked him to make astronomical and meteorological observations in the colony. He set up his observatory at Ekukanyeni. His astronomical observations were among the first in Natal and provided a daily time signal for Pietermaritzburg by regulating the Fort Napier noon gun.
In the field of meteorology Mann was a pioneer in Natal and did outstanding work. The only earlier systematic meteorological obsevations were those made by John Ecroyd* near Durban during 1850-1852. Mann started his observations at Ekukanyeni in January 1858 and continued them at Pietermaritzburg from 1859 to 1866. A summary of his results (rainfall, atmospheric pressure, humidity, and cloudiness) was published annually in the Reports of the Cape of Good Hope Meteorological Commission. In 1878 he published "Contributions to the meteorology of Natal - observations taken at Maritzburg" in the Quarterly Journal of the Royal Meteorological Society - the first substantial description of the Natal climate in terms of rainfall, thunderstorm frequency, atmospheric pressure and temperature, supported by tables of data for the years 1860-1865. He believed that the climate of Natal was largely determined by the prevalence of the sea breeze, which brought more rain in summer than in winter. Two notes by him in the same journal dealt with the heavy rains in Natal in 1868, and 1873. Other contributions by him relating to Natal in the Quarterly Journal and Proceedings of the society dealt with atmospheric pressure (1867) rainfall (1868, 1870, 1878), temperatures from 1858 to 1867 (1870), and hot winds (1884). In 1867 he published a paper on "The physical geography and climate of Natal" in the Journal of the Royal Geographical Society, and in 1871 an "Account of Mr [Thomas] Baines's exploration of the gold-bearing region between the Limpopo and Zambese Rivers" in the same journal. The latter paper was based on Baines's journals and contained tables of the temperatures and atmospheric pressures observed during his travels.
In the field of the earth sciences Mann read papers on "The gold-field of South Africa" and "On the coal-fields of Natal" before the British Association for the Advancement of Science in 1868, and another "On the physical geography, geology and mineralogy of the Colony of Natal, South Africa" before the Royal Dublin Society during the same year. Two articles by him on insect life in Natal were published in the Intellectual Observer in 1869 and 1870.
Mann actively strove to promote the development of Natal throughout his professional life, not only through his scientific work, but also by lecturing and writing popular articles. As an active member of the Natal Society (Pietermaritzburg) he arranged its exhibition of 1858, which was of both artistic and scientific interest. He served as president of the society from 1864 to 1866, contributed mineralogical specimens to its museum, and was the leading figure in its museum activities. He was also vice-president of the Natal Horticultural Society from 1864 to 1866, and served on the committee of the Natal Acclimatisation Society from 1865. At the time of the International Exhibition of 1862 he was secretary of the local organising committee and compiled a Catalogue of contributions to the International Exhibition from Natal (Pietermaritzburg, 1862). He wrote various publications in which the colony was described and emigration to it encouraged, for example, The colony of Natal (1860, 229 p.), A description of Natal (1860, 24 p.), Emigration to Natal... (1866, 64 p.), The emigrant's guide to the colony of Natal (1868, 206 p.), and "Statistical notes regarding the Colony of Natal" (Journal of the Statistical Society of London, 1869). In 1866 he became Natal's emigration agent in London, but his activities had little effect on emigration figures and in 1870 the London office of the emigration agency was closed. Thereafter he busied himself with literary and scientific pursuits in London. He was president of the Meteorological Society from 1873 to 1875 and was elected a Fellow of the Royal Astronomical Society (1855), the Geological Society of London (1866) and the Royal College of Surgeons (1878).
Mann was a kindly, frail-looking, talkative and modest gentleman with a slight lisp, a soft manner, and an extensive general knowledge. Betweem 1878 and 1882 he contributed many short, popular meteorological articles to R. Brown (ed.), Science for all. The topics included "Dew and hoar-frost", "Fogs", "How a snow-flake is formed", "How electricity is generated in the air", "why the wind blows", and many more. Six of his lectures delivered under the auspices of the Royal Meteorological Society were published under the title Modern meteorology in 1879. After his death his wife published A sketch of the life and work of Robert James Mann... (London, 1888).