George Johnstone was the elder son and third child of George Stoney and Anne (née Blood). The Stoney family's country property in Co. Offaly greatly depreciated in value after the Napoleonic wars and had to be sold at the time of the Irish Famine (1846-48). The family moved to Dublin and George Johnstone and his brother Bindon entered Trinity College, earning their fees by coaching other students. Both graduated with distinction, George Johnstone in 1848 and Bindon in 1850. On completing his studies in physics and mathematics, Stoney became the first astronomical assistant to the third Earl of Rosse, spending a total of two and a half years at Parsonstown (Birr) from July 1848 to August 1850 and from August to December 1852. As well as observing galaxies with the great 6-foot reflector, Stoney was tutor to Lord Rosse's children.

While at Parsonstown, Stoney read for Fellowship in Trinity College Dublin. He took second place in 1852 and thereby was awarded the Madden Prize which was worth about £300; this was the last occasion when the examinations were held in Latin. As Stoney could not afford to try again for Fellowship, Lord Rosse used his influence to have him appointed to the Chair of Natural Philosophy in Queen's College, Galway. Stoney remained five years in Galway and then became Secretary to the Queen's University which brought him back to Dublin in 1857.

As a university administrator, Stoney devoted himself enthusiastically to improving the effectiveness of the provincial colleges in Belfast, Cork and Galway. It was therefore a great blow to him when the Queen's University was dissolved in 1882 and its place was taken by the Royal University which had the power of conferring degrees purely by examination. The Irish government frequently consulted him on educational matters and he was for many years superintendent of civil service examinations in Ireland.

Stoney played a very active part in the affairs of the Royal Dublin Society, serving as Honorary Secretary from 1871 to 1881 and as Vice-President from 1881 to 1911. During his tenure, the Society underwent profound changes: it handed over its great collections to the government and received capital to pursue its scientific functions and to improve Irish agriculture. His own research work was usually communicated first to the Society and was then reported in its publications and the Royal Society publications. Stoney and his gifted nephew, George Francis FitzGerald, played central roles in the Society's scientific meetings and discussions.

In 1863 Stoney married his cousin, Margaret Sophia (née Stoney) and they had two sons and three daughters. The death of his wife in 1872 followed by two severe illnesses (smallpox in 1875 and typhoid in 1877) undermined his health. Yet, despite these misfortunes and his heavy load of administrative duties, he still managed to carry out scientific research, often rising at five in the morning to write or to experiment before going to his office. In 1874 Stoney moved house from 89 Waterloo Road to Weston House, Dundrum where he lived for four years with his young family. From 1878 to 1893 he lived at 3 Palmerston Park, Rathmines.

In 1893 Stoney left Dublin for London, in order to give his daughters the opportunity of a university education which was not possible for them at that time in Dublin. In retirement he developed lines of research he had not fully explored while he had been occupied with his administrative duties.

One of the main themes of Stoney's research was his interest in the kinetic theory of gases. In a paper published in the Proceedings of the Royal Irish Academy in 1858 he showed that Boyle's Law is contrary to the view that the particles of a gas are at rest or that it can be a continuous homogeneous substance. Ten years later in the Philosophical Magazine, he estimated the number of molecules in a given volume of gas at normal temperature and pressure; this number is equivalent to the Avagadro number. Also in 1868, in his paper 'On the Physical Constitution of the Sun and Stars', he first considered the limits of atmospheres. This theme was developed in 'On Atmospheres of Planets and Satellites' where he explained the absence of hydrogen and helium in the Earth's atmosphere and the absence of an atmosphere on the Moon or the minor bodies of the solar system in terms of the concept of escape velocity. This paper was reprinted in The Astrophysical Journal and caused some controversy but Stoney's position was unshaken. He deduced that the planet Mars was too small to retain water and its temperature too low for the presence of water in liquid or vapor form. He correctly reasoned that Martian polar caps were composed of carbon dioxide.

Stoney was the first (Philosophical Magazine, 1876) to see that the rotation of the vanes of a Crooke's radiometer was not due directly to radiation but arose from unsymmetrical impacts from the molecules within the glass envelope.

Stoney introduced the word 'electron' (from Greek for amber) into the scientific vocabulary. In a paper 'On the Physical Units of Nature' which he read before the British Association at Belfast in 1874, he pointed out that "an absolute unit of quantity of electricity exists in that amount of it which attends each chemical bond or valency". Seven years later, in February 1881, he read a paper with the same title before the RDS and it was published soon after in the Philosophical Magazine (1881). In it he discussed three systems of units, one being a system of natural units which he devised himself. In 1899 Max Planck proposed a similar set of units based on the gravitational constant, the velocity of light and Plank's constant; these units are significant in cosmology (see Barrow, 2002).

In the 1881 paper Stoney also deduced from the principles of electrolysis that electricity existed in discrete units which he called 'electrines' and he estimated their numerical value. In 1891, He read a paper at the RDS on the cause of double lines in the spectra of gases. In referring to the unit of electric charge associated with each chemical bond, he used the term 'electron' for the first time in a scientific paper.

From 1896 onwards Stoney wrote a series of papers in Monthly Notices of the Royal Astronomical Society on observing and predicting the Leonid meteor showers. With A.M.W. Downing he showed in principle how meteor storms could be predicted. Recently these ideas have been successfully developed to predict the behavior of individual dust trails within the broader streams (see Asher, 2000).

Stoney wrote extensively on the optical theory of microscopes and telescopes using his concept of spherical wavelets. In 1868 he considered how periodic motions of electrons within atoms could give rise to spectral lines. In later work on the origin of atomic spectra, he proposed that electrons described elliptical orbits in molecules and used this idea to explain double and triple lines in gas spectra. These ideas were later taken up by Joseph Larmor and Thomas Preston in relation to the Zeeman splitting of spectra lines by magnetic fields.

Although primarily a theorist, Stoney was also a practical man. He invented a novel form of heliostat which could be made more cheaply than contemporary instruments of French design. The titles of some of his papers include: 'On Collimators for Adjusting Newtonian Telescopes', On the Equipment for the Astrophysical Observatory of the Future' and 'On the Mounting of the Specula of Reflecting Telescopes'.

Stoney was keenly interested in music both scientifically and artistically. The titles of some of his papers include: 'On musical shorthand', 'On modes of dealing with echoes in rooms' as well as papers on equal temperament and the possibility of prolonging the tones of a piano. By persuading the Royal Dublin Society to hold chamber music concerts by leading artists, musical culture in Dublin was much enhanced. These concerts continued until quite recent times.

He received many distinctions during his long and laborious life. Probably the one he valued most highly was the award of the first Boyle Medal from the Royal Dublin Society in 1899. The Medal was instituted to commemorate the great Irishman Robert Boyle who played a large part in setting up the Royal Society of London.

Stoney was elected to the Royal Society in 1861, was Vice-President 1898-99 and served on Council 1898-1900. He was a member of the Royal Irish Academy and a fellow of the Royal Astronomical Society. He regularly attended the meetings of the British Association and was President of Section A at the 1879 meeting in Sheffield; he served on several of its committees. He was a Visitor to the Royal Observatory at Greenwich and to the Royal Institution, a Foreign Member of the U.S. Academy of Science and of the Philosophical Society of America and a corresponding member of Sci. di Lettere ed Arti di Benevento. He also became hon. D.Sc. of the Queen's University in Ireland in 1879 and hon. Sc.D. of the University of Dublin in 1902. The 45-kilometre diameter lunar crater at 55°.3S and 156°.1W is named in his honor.

Stoney died on 5 July 1911, after a prolonged illness and his ashes were interred in the graveyard of the little suburban town of Dundrum, south of Dublin. He was universally respected for "his intellectual power, his nobility of purpose and his kindly and sympathetic disposition."

His elder son George Gerald, F.R.S. became Manager of Sir Charles Parsons' Steam Turbine Works at Newcastle upon Tyne, his second son was a doctor in Australia, his daughter Edith lectured in physics at the London School of Medicine and his daughter Florence had a medical practice in London. The mathematician Alan M. Turing (1912-1954) was a grandson of a cousin, Edward Waller Stoney.

Asher, David J. 'Leonid dust trail theories' in Proceedings of the International Meteor Conference, Frasco Sabino 1999. Editor R. Arlt, International Meteor Organization (2000): 5-21.

Barrow, John D. The Contants of Nature from Alpha to Omega. London: Jonathan Cape, 2002.

Joly, John. 'George Johnstone Stoney, 1826-1911.' Obituary Notices of Fellows deceased. Proceedings of the Royal Society, Series A 86 (1912): xx-xxxv.

Stoney, George Johnstone. 'On the internal Motions of Gases Compared with the Motions of Waves of Light.' Philosophical Magazine 36 (1868): 141-.

  - 'On the Physical Constitution of the Sun and Stars.' Proceedings of the Royal Society, Series A,16 (1868): 25-34.

  - 'On the Physical Units of Nature.' Proceedings of the British Association for the Advancement of Science, Belfast, August 1874. See also Scientific Proceedings of the Royal Dublin Society 3 (1881): 51-60 and Philosophical Magazine (Series 5) 11(1881): 381-.

  - 'On the cause of double lines and of equidistant satellites in the spectra of gases.' Scientific Transactions of the Royal Dublin Society 4 (1891): 563-608.

  - 'Of atmospheres upon planets and satellites.' Scientific Transactions of the Royal Dublin Society 6 (1897): 305-328.

  - 'On the perturbations of the Leonids.' Proceedings of the Royal Society, Series A 64 (1899): 403-.

O'Hara, James G. 'George Johnstone Stoney, F.R.S. and the concept of the electron.' Notes and Records of the Royal Society of London 29(2), (1975): 265-276.

  - 'George Johnstone Stoney and the conceptual discovery of the electron.' Occasional Papers in Irish Science and Technology, No. 8, Stoney and the Electron, Royal Dublin Society (1993).

© Ian Elliott 2004