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 Mecanique Celeste.  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 refraction,” 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 refraction 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.