John Alexander McClelland (1870–1920) was educated at Queen’s College Galway and the Cavendish Laboratory in Cambridge. He was Professor of Experimental Physics at University College Dublin from 1900 to 1920. He was best known for his pioneering work on the scattering of β rays and on the conductivity of gases and the mobility of ions. He established a research school on atmospheric aerosols that was continued by his successor, John James Nolan (1887–1952), which strongly influenced physics research in Ireland up to the present. A recently discovered manuscript of a commemorative address by Nolan in 1920, which is reproduced in Appendix I, is a unique contemporary summary of McClelland’s research and character, and is an important contribution to the history of experimental physics in Ireland.
