**James MacCullagh** was an Irish mathematician who published on crystalline refraction and reflection.

- At the age of fifteen MacCullagh entered Trinity College, Dublin.
- Not long after failing the Fellowship examination MacCullagh submitted his first papers for publication.
- Two years later MacCullagh tried again for a Fellowship but this time, after being told that his first answer to the first mathematics question was wrong he refused to answer any further questions.
- The results were original but, unfortunately for MacCullagh, had been obtained independently by Poinsot who published them in 1834.
- MacCullagh did succeed in obtaining a fellowship in 1832 and he was appointed junior assistant to the mathematics professor in Dublin.
- This was a major discovery and, following Hamilton's announcement, MacCullagh published a note on conical refraction in which he claimed at least partial priority for the discovery of conical refraction.
- MacCullagh was particularly cross since he knew Hamilton had studied his 1830 papers containing these theorems since Hamilton had reviewed them.
- MacCullagh was forced to admit, what was clearly the truth, that although conical refraction could be deduced from his theorems he had only made that deduction after Hamilton had announced the discovery.
- MacCullagh had been close to a great discovery but had just failed to make the final step.
- In 1835 MacCullagh published on crystalline refraction and reflection.
- Although MacCullagh had priority, Franz Neumann had stolen the glory and again MacCullagh had missed out.
- Also in 1839 MacCullagh was made an honorary member of the St Andrews Literary and Philosophical Society which had been founded by David Brewster.
- In 1842 at a meeting of the British Association in Manchester, there was a discussion on the wave or particle nature of light in which Hamilton, MacCullagh, Bessel, Jacobi, Peacock, David Brewster and others took part.
- Later in 1842 MacCullagh was awarded the Copley medal of the Royal Society, a particularly great achievement since Bessel was among those considered for the award.
- In February 1843 MacCullagh was elected a fellow of the Royal Society.
- Also in 1843 MacCullagh published his most important work on geometry, namely On surfaces of the second order which described how surfaces such as the ellipsoid could be generated.
- MacCullagh corresponded with many scientists, in particular with John Herschel and with Babbage.
- On Sunday 24 October 1847 MacCullagh committed suicide in his rooms in Dublin.

Born 1809, Landahussy (near Strabane), Ireland. Died 24 October 1847, Dublin, Ireland.

View full biography at MacTutor

Origin Ireland

**Oâ€™Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive