Edward Thomas Mellor, geologist, studied at Victoria University, Manchester, where he won the Dalton prize for natural history. However, he did not graduate there. In 1893 he was in Australia, in the valley of the Macleay River, where he witnessed the effects of the greatest flood in living memory - an experience that affected his later views on the deposition of the gold-bearing conglomerates of the Witwatersrand. Back in England he graduated as Bachelor of Science (BSc), with honours, at the University of London in 1895. From 1897 to 1901 he was the first lecturer in biology and geology at Hartley College, Southampton. During this period he helped to save the passengers of the shipwrecked ship Stella, being a strong swimmer and able rock climber. He was elected a Fellow of the Geological Society of London in 1901. He came to South Africa towards the end of 1901, for in January 1902 he helped to rescue three climbers on Devil's Peak, Cape Town, for which he was made an honorary member of the Mountain Club of South Africa.
Mellor proceeded to the Transvaal Colony to take up an appointment as headmaster of the school at Balmoral, some 90 km east of Pretoria. However, in July 1902 he was appointed as the first geologist of the new Geological Survey of the Transvaal, directed from January 1903 by H. Kynaston*. Other members of staff were the geologists A.L. Hall*, and later W.A. Humphrey*. Mellor started his field work in 1903 and spent the next seven years surveying and mapping the geology of various areas of the Transvaal north of the Witwatersrand, mainly in the districts of Potchefstroom, Pretoria, Middelburg, Potgietersrus, Zoutpansberg and Letaba. His work was reported in the Annual Report of the Geological Survey and in many papers, memoirs and geological maps. His first paper in the Transactions of the Geological Society of South Africa, in 1904, dealt with the glaciated land surfaces and glacial (Dwyka) conglomerate between Pretoria and Balmoral. In "The sandstones of Buiskop and Springbok Flats" (Ibid, 1905) he proved that the Buiskop sandstone near Bella Bella, previously thought to form part of the Waterberg Group, was of Karoo age. During 1904-1906 he made a detailed study of the Transvaal coal measures and the underlying Dwyka tillite. His findings were reported in "The geology of the Transvaal coal measures, with special reference to the Witbank coalfield", in Memoir No. 3 of the Geological Survey (1906). This paper provided an excellent account of the structure and geological history of the coal seams and showed that the surface on which the glacial conglomerate was deposited can still be observed over wide areas. Other reports by him dealt with the Waterberg, Bushveld granite, and the stratigraphical setting of the Rooiberg felsites.
In 1909 Mellor was awarded the degree Doctor of Science (DSc) by the University of London. From 1910 to 1916 he made a detailed geological survey of the Witwatersrand, including a study of its gold-bearing conglomerates. It is this work, which first placed Witwatersrand stratigraphy on a firm foundation, for which he is best remembered. He made a meticulous study of the rocks exposed in the gold mines from the west Rand to the east Rand, reporting his findings on the stratigraphy of the sequence and on the nature and origins of the gold-bearing banket in the annual reports of the Geological Survey of the Union of South Africa (1910-1912), and in several papers in the Transactions of the Geological Society of South Africa and the Mining Magazine (London), during 1911-1915. An important conclusion was that the apparent variation in the Lower Witwatersrand beds over their main outcrop of some 80 km is caused by the local elimination at the surface, or repetition, of parts of the succession by strike-faults, and by variations in the thickness of some strata as a result of pressure on rocks of different strengths. This insight was of the greatest importance in the subsequent exploration of the goldfields. He compiled a coloured Geological map of the Witwatersrand on a scale of 1:60 000, which was published on three sheets by the Geological Survey of the Union of South Africa in 1917. It was accompanied by a brief explanation of the subdivisions of the Witwatersrand sequence. This work formed the sure foundation for later detailed investigations by others, which have proved its accuracy and thoroughness. His work led him to conclude that the conglomerates of the Main Reef and the Lower Witwatersrand were deposited under estuarine and deltaic conditions, rather than along a marine shore as was more generally believed. He also concluded that the gold was originally in the conglomerates, but was altered in form. His views encountered much opposition, but after various extensions and modifications found favour with many of his colleagues. More recently he has been described as "one of the most distinguished of all the geologists who have been involved in the problems of the Witwatersrand goldfields" (Pretorius, 1975, p. 25).
In 1916 Mellor was promoted to assistant director of the Geological Survey of the Union of South Africa, but he resigned later that year to become consulting geologist to the Central Mining and Investment Corporation, a post he held until he retired in 1930. During this period his work required him to visit Zimbabwe and Central Africa several times, but he did not publish anything on the geology of these regions. His outstanding qualities as a geologist were widely recognised, both locally and overseas. He was a member of the Society of Economic Geologists and in 1912 he became a member of the (British) Institution of Mining and Metallurgy, receiving its Goldfields Prize four years later. He joined the Geological Society of South Africa in 1903, served as president in 1911, and was awarded its Draper Memorial Medal in 1939. He was a member of the South African Association for the Advancement of Science by 1903, serving as president of Section B in 1922 and as president of the association in 1926. His presidential address dealt with "Science in relation to mining and other industries in South Africa". In 1906 he joined the South African Philosophical Society and in 1909 was elected a Fellow of its successor, the Royal Society of South Africa.
Mellor was a skilled draughtsman and illustrated many of his geological reports with his own drawings. His interest in biology led him to make provision for a student fellowship in biology at the University of the Witwatersrand. He was married twice, first in 1909 to Charlotte Payne of Manchester, with whom he had four sons. After his retirement he visited his sons in Britain several times and accompanied them on European tours. On 28 December 1938 he married Constance Evelyn Parker, born Oliver, who survived him.