Edward J. Stone, British astronomer, suffered from poor health in his youth and spent most of his childhood with relatives in Devon. His aptitude for mathematics became apparent only at the age of twenty. He became a student at King's College, London, where he made rapid progress. From 1856 he continued his studies at Queen's College, Cambridge, where he graduated in 1859, placed fifth among students with first class honours in mathematics, despite continued health problems. He was subsequently awarded the degree Master of Arts (MA) in 1862.
In 1860 he was appointed as chief assistant at the Royal Greenwich Observatory. His interest was mainly in the theoretical side of astronomy, rather than in making observations. During his ten years at the observatory he became an authority on positional astronomy. He spent much time deriving a more accurate value of the solar parallax, for example, he derived its value from observations of the declination of Mars during its opposition in 1862 (including observations made by Thomas Maclear* at the Cape), and from a re-analysis of earlier observations of the transit of Venus in 1769. He also made a new determination of the moon's horizontal parallax by comparing observations made at Greenwich and at the Cape (Memoirs of the Royal Astronomical Society, 1865). His thoroughness was shown by his detection of minute variations of latitude, resulting trom slight wobbles of the earth's axis (now known as the Chandler wobble). He also carried out pioneering work in stellar spectroscopy. In 1868 he was elected a Fellow of the Royal Society of London. The next year he was awarded the gold medal of the Royal Astronomical Society for his discussions of the value of the solar parallax. He served as secretary of the society from 1866 to 1870. On 12 September 1866 he married Grace Tuckett, with whom he had four children.
In June 1870 Stone was appointed to succeed Thomas Maclear as Her Majesty's Astronomer at the Royal Observatory, Cape of Good Hope. He arrived for duty on 13 October that year. His position was at first somewhat uncomfortable as his scientific achievements were not known at the Cape and public opinion had favoured the appointment of William Mann*. However, he soon established his authority over the observatory and its staff, which included both Mann and George W.H. Maclear*. After Mann's retirement William H. Finlay* was appointed as first assistant in 1873.
Fort nine years Stone focussed most of his energy on producing a definitive catalogue of star positions for the southern hemisphere. At first he spent much time reducing and preparing for publication star observations made by his predecessor. This work led to the publication of The Cape catalogue of 1159 stars, deduced from observations at the Royal Observatory, Cape of Good Hope, 1856 to 1861... (Cape Town, 1873) and The Cape catalogue of stars, deduced from observations made at the Royal Observatory, Cape of Good Hope, 1834 to 1840... (Cape Town, 1878). However, new observations were also initiated and reduced, leading to his main achievement, the Catalogue of 12 441 stars, for the epoch 1880; from observations made at the Royal Observatory, Cape of Good Hope, during the years 1871 to 1879 (London, 1881). The catalogue listed the positions of all stars brighter than the seventh magnitude between the south celestial pole and 25º South declination. This work earned him the Lalande Medal of the French Academy of Sciences in 1881.
In April 1874 Stone and his wife travelled to Port Nolloth by sea and proceeded to Klipfontein, just west of Steinkopf in Namaqualand, where they observed a total eclipse of the sun on the 16th of that month. (The next total solar eclipse to be observed from South Africa occurred on 1 October 1940). Using a borrowed portable telescope and a small spectroscope he observed the spectra of the sun's corona and chromosphere - the first significant application of spectroscopy in South Africa. His findings, published in the Monthly Notices of the Royal Astronomical Society, confirmed an earlier discovery of a comparatively lower temperature layer (a so-called reversing layer) overlying the sun's surface, in which absorption lines in the solar spectrum were believed to be produced. However, the observations have since been interpreted differently. During this expedition he made the first series of measurements of the earth's magnetic field in Namaqualand. These were published in the Proceedings of the Royal Society in 1875. On 8 December 1874 he observed the transit of Venus from the Cape Observatory, describing his observations in Memoirs of the Royal Astronomical Society (1883). Under his direction a Cape photographer, J.E. Bruton, photographed the transit - a significant achievement at the time. He discussed the limitations of transit observations and their use in deriving a more accurate value of the solar parallax in several other papers.
Stone's other scientific activities included a description of a remarkable display of the aurora australis (southern lights) on 4 February 1872, which was visible from Cape Town (and in the northern hemisphere from places as far south as Mumbai, India). His account, with those of others, was published in Nature. During 1871 he accurately determined the velocity of sound by measuring the time taken for the sound of the time gun on the Imhoff Battery (near the Castle) to reach the observatory, correcting the results for changes in air temperature and wind speed. The results were published in the Philosophical Transactions of the Royal Society and reprinted in the Cape Monthly Magazine (February 1873, Vol. 6, pp. 127-128). His analysis of the temperature observations made at the Royal Observatory between 1841 and 1870, published in the Proceedings of the Royal Society (1881), showed a weak oscillation in the mean annual tempterature with a period of about 20 years, which he ascribed to the cyclical variation of sunspot numbers. He also published Tables for facilitating the computation of star-constants (Cape Town, 1874?). Some of his papers during the eighteen-seventies dealt with the application of the theory of probability to the interpretation of repeated observations.
Stone's role in public life at the Cape appears to have been somewhat restricted by the fact that Sir Thomas Maclear remained active for some years after his retirement. For example, after Maclear gave up his position as a member of the Meteorological Commission of the Cape of Good Hope in 1873 the Commission was reconstituted in 1874 with Stone as one of its members. However, already in December 1870 he presided over the prizegiving at the South African College. During 1873 he served as a member of the commission appointed by the government to investigate the establishment of a university at the Cape. The commission, chaired by Sir Langham Dale*, recommended the formation of an examining university that was named the University of the Cape of Good Hope. Stone was a member of its council from 1873 to 1879. From 1875 to 1879 he served as one of the university's examiners in science, setting papers for the Certificate in the Theory of Land Surveying in spherical trigonometry, astronomy and geodesy, and for the BA and MA degrees in geometry, trigonometry, calculus, mechanics, light and heat, and hydrostatics. By 1879 he was a member of the committee of the South African Public Library.
He resigned on 27 May 1879 and was succeeded by Dr David Gill*. He left, partly because of health problems and disenchantment with the Cape, to take up the position of Radcliffe Observer at the Radcliffe Observatory in Oxford. There he organised a government expedition to observe the transit of Venus in 1882. His report on the results was published in 1887 and included a careful examination of the problems involved in accurately timing the visual contact between Venus and the edge of the sun's disc, as well as a new determination of the solar parallax. Most of his time was spent continuing his work in positional astronomy, which included the determination of the proper motions of some 400 southern stars. In 1894 he published the Radcliffe catalogue for 1890, which contained the positions of 6424 stars between the celestial equator and 25º South declination, thus complementing his earlier work at the Cape. On 8 August 1896 he made further successful spectroscopic observations of the eclipsed sun on Novaya Zemlya.
Stone's work resulted in more that 150 publications on a wide variety of astronomical topics and constituted a considerable contribution to astronomy. None the less he harboured a strange misconception about mean solar time, which he applied in 1883 to "explain" errors in the tabulated position of the moon, and which repeated arguments by Professor Simon Newcomb* and others failed to change. He served as president of the Royal Astronomical Society from 1882 to 1884. The University of Padua, Italy, conferred a Doctor of Science degree on him in 1892. He died at the Radcliffe Observatory.