Professor Cormac O Ceallaigh, one of the most distinguished Irish scientists of this century, died on October 10th in Dublin, at the age of 84. He was the son of an eminent Dublin obstetrician. In 1930, he entered UCD to study physics. Obtaining a post graduate scholarship in 1934, he went to Paris, working in the laboratory of Pierre Auger. Three years in Cambridge followed, and he returned to Ireland in 1938. He had been appointed to a lectureship in Cork in 1937.
During the war years he managed to continue research in Cork, and published work, but in 1949 he applied for leave of absence to work abroad. He visited former colleagues from Cambridge in Oxford and Harwell, but was unable to obtain a suitable position. Finally he arrived in Bristol and was offered a modest post by Professor C. F. Powell. It was a fortunate outcome, for Powell had gathered a colourful and talented group from all over the world; and it seems fair to say that Bristol at that time was the best physics university in the world. Cormac and his wife Millie made a considerable financial sacrifice to go there.
Powell had introduced a technique which had languished in obscurity. It was called the nuclear emulsion method, and basically consisted of thick photographic films stacked together and exposed to cosmic ray particles. The tracks made in the emulsions could be followed and measured by scanners and physicists, using microscopes. It was enormously effective.
It was a golden age in physics. Most European physicists had been working on radar during the war and returned eagerly to their laboratories to take up work unfinished since 1939. There was, therefore, a great upsurge in basic physics between 1945 and 1950. New, strange, unstable particles were discovered. To gain access to the cosmic rays which produced unstable particles, physicists took their equipment up mountains or flew enormous balloons to great heights, a dangerous undertaking.
Cormac rapidly became a leading figure in Bristol. Given his ebullient temperament, one might have thought that his physics would perhaps be brilliant but erratic. It was brilliant, but not erratic; it was careful and painstaking. In his work on one particular reason, the Kappa, he examined over 700 particle decays in emulsion to find just two of the Kappa mesons.
In 1953 he was appointed a senior professor in the School of Cosmic Physics in the Dublin Institute for Advanced Studies. He held this post for 29 years, until his retirement in 1982. He built up an emulsion group, which joined a large international collaboration. Later he took his group into a project which used accelerators instead of cosmic rays. After some years, though, he returned to cosmic rays. This time he used a new material, a plastic sheet which responds to very highly charged primary particles. Large areas of this were carried on a satellite, to expose them to the primaries. This work continues successfully in the institute.
At conferences, he was a brilliantly witty speaker. Apart from his physics and his family, he had two great activities. One was cabinet making, at which he was highly skilled; the other was sailing. In his yacht club he was known as "The Voice", because in full flight he could be heard all over the coal harbour in Dun Laoghaire.
His wife Millie died in 1987. We offer our sympathy to his daughters, his grandchildren and great granddaughter, and remember him with gratitude.