Geologist. Born in Govan, Phemister was educated at the University of Glasgow. Having served in the army during the First World War, he was briefly a teacher before joining the Geological Survey of Great Britain in 1921. Phemister was responsible for the mapping and detailed documentation of significant areas of Scotland, including Assynt, W Sutherland and Shetland. He was also responsible for pioneering geophysical work in Iran (Persia) in the 1920s. In 1934 he was involved in creating exhibits for the new Geological Museum in South Kensington (London) and the following year Phemister transferred to London to become Chief Petrographer of the Survey.
His younger brother, Professor T.C. Phemister, occupied the Kilgour Chair of Geology at the University of Aberdeen from 1937.
Phemister was honoured relatively early in his long career by his election as a Fellow of the Royal Society of Edinburgh (1931).