Arthur John Charles Molyneux, geologist and son of the geologist William Molyneux*, was a pioneer investigator of the geology, palaeontology and archaeology of Zimbabwe. He appears to have been trained (perhaps informally by his father) as a mining geologist. With his mother and family he migrated to Natal in 1881. From there he entered Rhodesia (now Zimbabwe) as a staff officer in the Victoria Column, under Major Alan Wilson, that occupied Matabeleland during the Matabele War of 1893. He remained in the country for the rest of his life, making Bulawayo his headquarters and devoting himself to prospecting and mining. He travelled widely, especially in the form of traverses across the mid-Zambezi valley, mapping the country, making geological notes and collecting specimens. He was particularly interested in the pure science aspects of his work.
In February 1899 Molyneux convened a meeting in Bulawayo at which the Rhodesia Scientific Association was formed. During the next eight years he was a member of the association's council, serving as its first secretary (1899/1900), joint vice-president (1901/2, 1905/6, 1906/7), and president (1902/3). At early meetings of the association he exhibited local minerals and land shells (January 1900) and fossil ferns from Bechuanaland (now Botswana, March 1900). In April 1900 he delivered the first paper before the association, "On some rock paintings in the Tuli district", which was published in the Proceedings (Vol. 1, pp. 7-8). He was furthermore a member of the committee and a trustee of the Rhodesia Museum, established in Bulawayo in 1901.
In his "Notes on some fossils from the Sengwe Coalfields", read in November 1901 (Proceedings, Vol. 2, pp. 88-92, 126-127), Molyneux described fossil fishes that he had collected in the Sengwe district in the south-east of the country. From 1898 onward he had also collected bivalve shells and plants from the Karoo sediments and these are recognised as the first recorded fossils to be found in Zimbabwe. Specimens were sent to Britain for identification. In a more comprehensive paper in the Quaterly Journal of the Geological Society of London (1903) he described "The sedimentary deposits of Southern Rhodesia". The paper included appendices by A.S. Woodward*, W. Hind and E.A.N. Arber*, in which various plant and animal fossils were described.
Much of Molyneux's time was spent on prospecting for coal and studying the rocks of the Karoo Supergroup. In 1908 he addressed the South African Association for the Advancement of Science on "The correlation of the Karroo System in Rhodesia" (Report, 1908, pp. 107-110), in which he attempted to correlate the Zimbabwean strata of Karoo age with those in the Cape Colony and the Transvaal. He returned to the problem in 1911, in his presidential address before Section B of the association (Report, 1911, pp. 31-45). Meanwhile he had also published a paper on "The Karroo System in Northern Rhodesia [now Zambia] and its relation to the general geology" in the Quaterly Journal of the Geological Society (1909).
In two other important papers, "The physical history of the Victoria Falls" (Geographical Journal, January 1905) and "The Zambezi River and the Victoria Falls" (Proceedings of the Rhodesia Scientific Association, 1905, Vol. 5, pp. 25-29), Molyneux provided convincing evidence that the falls and the gorge below it were developed slowly through the erosive power of the Zambesi River, and not by the sudden opening of a zigzag crack in the earth's crust by tectonic forces as all previous visitors, following the opinion of David Livingstone*, had supposed. Other papers by him included "A contribution to the geology of Bechuanaland Protectorate" (Botswana; 1906) and "Diatoms in hot springs of Northern Rhodesia" (1910).
In 1903 Molyneux found the country's first handaxe - a fine late-Acheulian implement - at the Victoria Falls. Some years later he published "Notes on some stone implements from North-West Rhodesia" (now Zambia; Proceedings of the Rhodesia Scientific Association, 1909), in which he described crude Early Stone Age artefacts from four different sites. A much later note by him dealt with rock engravings at Metsang, Botswana (South African Journal of Science (1920, Vol. 17, pp. 206-207).
In April 1918 Molyneux was appointed to the Geological Survey of Southern Rhodesia. He joined H.B. Maufe* north of Bulawayo, publishing an account of "The geology of the country round Pasipas, near Bulawayo" in the Transactions of the Geological Society of South Africa (1919, Vol. 22, pp. 26-45). After a short while he was sent to do geological mapping west of Sinoia (north-west of Harare), where deposits of copper and gold had been discovered. His preliminary report on this region, as well as an account of the Sinoia Caves, were published by the Geological Survey of Southern Rhodesia. Failing health induced him to visit Britain in 1920, but he died of heart failure shortly after his return to Bulawayo. His final paper on the Karoo Supergroup, describing the strata in the Gokwe district, was published in the South African Journal of Science in 1920 (Vol. 17, pp. 249-258).
Molyneux was a Fellow of the Geological Society of London and of the Royal Geographical Society. In recognition of his geological work the Geological Society of London awarded him its Wollaston Fund in 1909. He was a member of the South African Association for the Advancement of Science by 1906, serving as joint vice-president from 1910 to 1913 and as president of its Section B when the association met in Bulawayo in 1911. In 1910 he became a member of the Geological Society of South Africa. The geologist A.L. du Toit* (1945, p. x) described him as "a quiet person who seemingly enjoyed plodding through the bush-clad expanses of Bechuanaland and the Rhodesias, to the detriment of his health", and evaluated his field work as follows: "It is a remarkable commentary that, despite the vast amount of systematic geological mapping since done on both sides of the Zambezi Valley, Molyneux's accounts even after thirty-five years remain our prime source of published information in regard to wide stretches, and particularly for the Karroo basins."
Molyneux married his cousin Katherine ("Kitty") Harriette Pullen in January 1899 and they had one daughter.