Miss Agnes M. Clerke, historian of nineteenth century astronomy, was the daughter of John William Clerke, bank manager and amateur astronomer, and his wife Catherine Mary, born Deasy. She was educated at home and showed an early interest in the history of astronomy. She and her sister Ellen resided in Italy, mainly in Florence, from 1867 to 1877 and in the latter year began her career as a scientific writer with contributions to the Edinburgh Review. Among others she wrote a number of biographies for the ninth edition of the Encyclopaedia Britannica. Her first major work, A popular history of astronomy during the nineteenth century, was published in Edinburgh in 1885, with several later editions appearing to 1908.
After reading this book, David Gill*, astronomer at the Royal Observatory, Cape of Good Hope, invited her to visit the observatory, arguing that some experience in practical astronomy would improve the value of her writing on the subject. She visited the observatory and stayed with the Gills during September-October 1888. During her stay she gained considerable practical knowledge and also made some original observations of the spectra of southern stars, which were described in "Southern star spectra" (The Observatory, 1888). The same journal published her paper on "Some southern red stars" (1889). Her account of the visit, "A southern observatory", appeared in the Annual Report of the Smithsonian Institution for 1891. Two other papers by her appeared in the same volume: "Stellar numbers and distances by means of photographic star gauging", dealing with the spatial distribution of stars, and "The sun's motion in space".
In 1890 Clerke travelled to Copenhagen, Stockholm and St Petersburgh. Her subsequent works included The system of the stars (1890), Familiar studies in Homer (1892), The Herschels and modern astronomy (1895; including an account of J.F.W. Herschel's* work at the Cape), Astronomy (1898; with A. Fowler and J.E. Gore), Problems in astrophysics (1903), Modern cosmogenies (1905), and an essay, Low-temperature research at the Royal Institution of Great Britain, London, 1893-1900 (1901). In addition she published many astronomical papers in which she described globular star clusters, double stars, individual stars and star systems, stellar spectra, irregular clusters, and other astronomical phenomena. She also wrote numerous biographies for the Dictionary of National Biography.
Clerke resided in London and was an excellent paino player. Gill described her as "one of the ablest women and most original of thinkers that I ever met" (Forbes, 1916, p. 205) and following his recommendation she was elected an honorary member of the Royal Astronomical Society in 1903.