Mackle, Henry (1921–94), physical chemist and folklore writer, was born 12 May 1921 at Derrykeeran, Co. Armagh, the son of Patrick Mackle, farmer, and Sarah Mackle (née Byrne). He studied chemistry at QUB, graduating with first-class honours in 1942. Awarded a Ph.D. in May 1947, he was encouraged by the vice-chancellor of Queen's, Sir David Lindsay Keir (1895–1973), to continue his studies at Magdalen College, Oxford, where he obtained a second doctorate (D.Phil., 1950). While at Oxford he worked with Leslie Sutton and Peter Allen, studying the structure of molecules in gases using electron diffraction. An outstanding graduate student, Mackle constructed the machine that measured the distances between atoms in molecules. Much new information and many publications resulted from this work, and the members of the research team were world leaders in this subject in the early years after the second world war. The camera used in this research was donated to the Science Museum in London, as it represented the tradition of laboratory apparatus that was home-made yet at the cutting edge of technology.
Mackle had a long and distinguished career, but he is best remembered for his contributions to thermochemistry. Appointed a lecturer in physical chemistry (1951–62), he returned to QUB, where he remained for the rest of his life, and was subsequently senior lecturer in chemistry (1962–4) and reader in chemistry (1964–94). There, together with a small group of talented postgraduates and with little funding, he designed and built the first modern aneroid rotating bomb combustion calorimeter. This apparatus was used in thermochemical studies of organic sulphur-containing compounds, the results of which were of particular interest to the petroleum refining and pharmaceutical industries. In addition to this it was used in teaching, as a basis for understanding of the chemical bonding in sulphur. Mackle was very proud when three of the calorimeters were donated to the Science Museum in London in 1983.
Other positions held by Mackle in the university included academic secretary to the faculty of science (1952–3) and warden of Queen's Elms hall of residence for men (1953–63). In the latter position he created a sense of harmony among the international residents, attributed to the ‘remarkable, warm personality’ and the ‘innate courtesy’ (Ir. Times) he extended to all. He was elected fellow of the Royal Institute of Chemistry in 1958. In all, he published 114 scientific papers. He also held various positions in overseas institutions – as a visiting professor at the University of Calgary, an advisor to the Argonne National Laboratory, Chicago, and a lecturer at the USSR Academy of Science – and he had a contract with NASA for the design of rocket propellants. At home, he was appointed scientific adviser to the Northern Ireland Ministry of Home Affairs in 1952.
Though undoubtedly a talented researcher, Mackle had many other interests outside of science. A friend since his student days in Oxford, Raymond Bonham Carter, in a warm tribute to Mackle after his death, called him ‘a Renaissance man to his fingertips’ (Independent). Universally liked by his colleagues, he was by all accounts fun and interesting to work with. A superb teacher, he once said: ‘An educational system isn't worth a great deal if it teaches young people how to make a living but doesn't teach them how to live’ (ibid.). He was a man of considerable erudition, charm, and wit, and loved company, conversation, and debate. Able to see both sides of the political problems in Northern Ireland, he described himself as a ‘moderate nationalist’ and a ‘catholic humanist’ (ibid.).
In his youth Mackle was a talented football player. Good at tennis, he represented the Irish universities against the Scottish universities in 1951. His skills at debating and natural wit resulted in his presidency of numerous university societies at Oxford and Belfast. He was a passionate advocate of all things Irish and was a great admirer of W. B. Yeats (qv), whose poetry he enjoyed quoting. A founder member of the Ulster Folklife Society, dedicated to preserving Ulster Irish heritage, he contributed articles, some of them quite humorous, on the folklore of leprechauns and fairies to the society's journal, Ulster Folklife. He was president of the Ulster Arts Club and a member of the literature advisory panel of the Northern Ireland Arts Council.
Mackle married Rosemary (Rosie) Campbell in 1957, but the marriage was later dissolved. The couple had two sons and one daughter. He died 30 July 1994 in Armagh, aged seventy-three.