the time overthrew, the idea of the alchemists that there was a materia prima, asserting as he did that theory of chemical "elements" which held good until the discoveries in connection with radium led to a modification in chemical teaching: This may be said of Boyle, that his writings profoundly modified scientific opinion, and his name will always stand in the forefront amongst those of chemists. He made important improvements in the air-pump, was one of the earliest Fellows of the Royal Society, and founded the "Boyle Lectures." He died in 1691.

Sir Thomas Molyneux was born in Dublin, in 1661, of a family which had settled in Ireland about 1560-70. He practised as a physician in his native city, was the first person to describe the Irish Elk and to demonstrate the fact that the Giant's Causeway was a natural and not, as had been previously supposed, an artificial production. He was the author of many other scientific observations. He died in 1733.

We may now turn to more recent times, and it will be convenient to divide our subjects according to the branch of science in which they were distinguished, and to commence with

MATHEMATICIANS,

of whom Ireland may boast of a most distinguished galaxy. Sir William Rowan Hamilton (b. in Dublin 1805, d. 1865), belonged to a family, long settled in Ireland, but of Scottish extraction. He was a most precocious child. He read Hebrew at the age of seven, and at twelve, had studied Latin, Greek, and four leading continental languages, as well as Persian, Syriac, Arabic, Sanscrit, and other tongues. In 1819 he wrote a letter to the Persian ambassador in that magnate's own language. After these linguistic contests, he early turned to mathematics, in which he was apparently self-taught; yet, in his seventeenth year he discovered an error in Laplace's Mécanique Céleste. He entered Trinity College where he won all kinds of distinctions, being famous not merely as a mathematician, but as a poet, a scholar, and a metaphysician. He was appointed Professor of Astronomy and Astronomer Royal whilst still an undergraduate. He predicted "conical refrac

tion," afterwards experimentally proved by another Irishman, Humphrey Lloyd. He twice received the Gold Medal of the Royal Society: (i) for optical discoveries; (ii) for his theory of a general method of dynamics, which resolves an extremely, abstruse problem relative to a system of bodies in motion. He was the discoverer of a new calculus, that of Quaternions, which attracted the attention of Professor Tait of Edinburgh, and was by him made comprehensible to lesser mathematicians. It is far too abstruse for description here.

Sir George Gabriel Stokes (born in Sligo 1819, d. 1903) was, if not the greatest mathematician, at least among the greatest, of the last hundred years. He was educated in Cambridge, where he spent the rest of his life, being appointed Lucasian Professor of Mathematics in 1849, and celebrating the jubilee of that appointment in 1899. He was member of parliament for his University, and for a time occupied the presidential chair of the Royal Society. He devoted himself, inter alia, to optical work, and is perhaps best known by those researches which deal with the undulatory theory of light. It was on this subject that he delivered the Burnett lectures in Aberdeen (1883-1885).

James McCullagh, the son of a poor farmer, was born in Tyrone in 1809, d. 1847. His early death, due to his own hand in a fit of insanity, cut short his work, but enough remains to permit him to rank amongst the great mathematicians of all time, his most important work being his memoir on surfaces of the second order.

Humphrey Lloyd (b. in Dublin 1800, d. 1881), F. R. S. His father was Provost of Trinity College, Dublin, a position subsequently occupied also by the son. Lloyd's work was chiefly concerned with optics and magnetism, and it was in connection with the former that he carried out what was probably the most important single piece of work of his life, namely, the experimental proof of the phenomenon of conical refrac tion which had been predicted by Sir William Hamilton. He was responsible for the erection of the Magnetic Observatory in Dublin, and the instruments used in it were constructed under his observation and sometimes from his designs or modifications. He was also a meteorologist of distinction.

George Salmon (b. in Dublin 1819, d. 1904), like the last mentioned subject, was, at the time of his death, Provost of Trinity College, Dublin. Besides theological writings, he contributed much to mathematical science, especially in the directions of conic sections, analytic geometry, higher plane curves, and the geometry of three dimensions. He was a Fellow of the Royal Society, and received the Copley and Royal medals, as well as distinctions from many universities and learned societies.

John Casey (b. Kilkenny 1820, d. 1891), F. R. S., was educated at a National School and became a teacher in one in later years. Entirely self-taught as a mathematician, he raised himself from the humble position which he occupied to be a university professor (in the Catholic University of Ireland, and afterwards in the Royal University), and earned the highest reputation as one of the greatest authorities on plane geometry. He was a correspondent of eminent mathematicians all over the world.

Henry Hennessey (b. in Cork 1826, d. 1901), F. R. S., was also a professor in the Catholic University of Ireland and afterwards in the Royal College of Science in Dublin. He was a writer on mathematics, terrestrial physics, and climatology.

Benjamin Williamson (b. in Cork 1827), F. R. S., is a Senior Fellow of Trinity College, Dublin, and a distinguished writer on mathematical subjects, especially on the differential, integral, and infinitesimal calculuses.

Sir Joseph Larmor (b. in Antrim 1857), F. R. S., was educated at Queen's College, Belfast, and in Cambridge, in which last place he has spent his life as a professor. He now represents the University in parliament and is secretary to the Royal Society. He is well-known for his writings on the ether and on other physical as well as mathematical subjects.

ASTRONOMERS.

William Parsons, Earl of Rosse (b. in York 1800, d. 1867), F. R. S., was a very distinguished astronomer who experimented in fluid lenses and made great improvements in casting specula for reflecting telescopes. From 1842-45 he was engaged upon the construction, in his park at Parsonstown, of

his great reflecting telescope 58 feet long. This instrument, which cost £30,000, long remained the largest in the world. He was president of the Royal Society from 1848 to 1854.

Sir Howard Grubb (b. 1844), F. R. S., is known all over the world for his telescopes and for the remarkable advances which he has made in the construction of lenses for instruments of the largest size.

Sir Robert Ball (b. in Dublin 1840, d. 1913), F. R. S. Originally Lord Rosse's astronomer at Parsonstown, he migrated as professor to Trinity College, Dublin, and subsequently became Lowndean Professor of Astronomy at Cambridge. He was a great authority on the mathematical theory of screws, and his popular works on astronomy have made him known to a far wider circle of readers than those who can grapple with his purely scientific treatises.

William Edward Wilson (b. Co. Westmeath 1851, d. 1908), F. R. S. A man of independent means, he erected, with the help of his father, an astronomical observatory at his residence. In this well-equipped building he made many photographic researches, especially into the nature of nebulae. He also devoted himself to solar physics, and wrote some remarkable papers on the sudden appearance in 1902 of the star Nova Persei. He was the first to call attention to the probability that radium plays a part in the maintenance of solar heat. In fact, the science of radio-activity was engaging his keenest interest at the time of his early death.

A. A. Rambaut (b. Waterford 1859), F. R. S., formerly Astronomer Royal for Ireland and now Radcliffe Observer at Oxford, is one of the leading astronomers of the day.

PHYSICISTS.

Lord Kelvin, better known as Sir William Thompson (b. Belfast 1824, d. 1907), F. R. S. Amongst the greatest physicists who have ever lived, his name comes second only to that of Newton. He was educated at Cambridge, became professor of natural philosophy in Glasgow University in 1846, and celebrated the jubilee of his appointment in 1896. To the public his greatest achievement was the electric cabling of the Atlantic Ocean, for which he was knighted in 1866. His electrometers

and electric meters, his sounding apparatus, and his mariners' compass are all well-known and highly valued instruments. To his scientific fellows, however, his greatest achievements were in the field of pure science, especially in connection with his thermodynamic researches, including the doctrine of the dissipation or degradation of energy. To this brief statement may be added mention of his work in connection with hydrodynamics and his magnetic and electric discoveries. His papers in connection with wave and vortex movements are also most remarkable. He was awarded the Royal and Copley medals and was an original member of the Order of Merit. He received distinctions from many universities and learned societies.

George Francis Fitzgerald (b. Dublin 1851, d. 1901), F. R. S., was fellow and professor of natural philosophy in Trinity College, Dublin, where he was educated. He was the first person to call the attention of the world to the importance of Hertz's experiment. Perhaps his most important work, interrupted by his labors in connection with education and terminated by his early death, was that in connection with the nature of the ether.

George Johnston Stoney (b. King's Co. 1826, d. 1911), F. R. S., after being astronomer at Parsonstown and professor of natural philosophy at Galway, became secretary to the Queen's University and occupied that position until the dissolution of the university in 1882. He wrote many papers on geometrical optics and on molecular physics, but his great claim to remembrance is that he first suggested, "on the basis of Faraday's law of Electrolysis, that an absolute unit of quantity of electricity exists in that amount of it which attends each chemical bond or valency and gave the name, now generally adopted, of electron to this small quantity." He proposed the electronic theory of the origin of the complex ether vibrations which proceed from a molecule emitting light.

John Tyndall (b. Leighlin Bridge, Co. Carlow, 1820, d. 1893), F. R. S., professor at the Royal Institution and a fellowworker in many ways with Huxley, especially on the subject of glaciers. He wrote also on heat as a mode of motion and was the author of many scientific papers, but will, perhaps, be best remembered as the author of a Presidential Address to the British Association in Belfast (1874), which was the high