Frederic Philip Mennell, geologist, was educated at University College, London, and in Bruxelles, Belgium. In November 1901 he arrived in Southern Rhodesia (now Zimbabwe) to become the first curator of the newly established Rhodesia Museum (later the National Museum) in Bulawayo, which housed the collections of the Rhodesia Scientific Association. The museum, which was partly funded by the Rhodesia Chamber of Mines, played a vital role in the collection and dissemination of geological knowledge and its first two curators were required to be geologists. Mennell was recommended for the position by Professor J.W. Judd of the Royal College of Science, London, who regarded him as a good mineralogist even though he was only 21 years old and had less than a year's formal training in geology. He became an active member of the Rhodesia Scientific Association, serving as its secretary for 1903/4 and thereafter as a member of council to 1907, and was elected its president for 1910/11. Immediately after his arrival he began a study of he country's geology and mineral deposits and was so successful that he came to be regarded as the "father of Zimbabwean geology" (Fey, 1997, p. 384). He resigned from his post in August 1908 to become a consulting geologist and was succeeded as curator by A.E.V. Zeally*. By this time he had made over 1300 identifications of minerals.
In March 1902 Mennell delivered his first scientific paper, "Telluride ores and their occurrence in Rhodesia", before the Rhodesia Scientific Association. The paper was published in the Proceedings (Vol. 3, pp. 21-28) and was followed by "Stratigraphical and petrographical notes on the oldest South African rocks" (1905). Other reports, dealing with his geological work in the field as well as in the laboratory, were included in the Annual Report of the Rhodesia Museum. One of his more extensive early publications was a first account of "The geology of Southern Rhodesia", published as Special Report No. 2 of the Rhodesia Museum (1904, 42 pp), and accompanied by a geological map of the Bulawayo area. It was partly based on information provided by miners and prospectors who visited the museum, and included descriptions of the Bulawayo Schists (now the Bulawayo Group), the Zimbabwean coal measures, superficial deposits, correlation and age of the older rocks, petrography, and physical features of the country. A few years later he produced The Rhodesian miner's handbook (Bulawayo, 1908, 143 pp), intended as a guide to prospectors and miners in southern Africa. It included considerable information on the mines and minerals of Zimbabwe. Later similar publications by him were A miner's guide (London, 1909, 196 pp) and A guide to mining in Rhodesia (Bulawayo, 1930, 162 pp).
Mennell was an early member of the South African Association for the Advancement of Science, serving as president for Section B (which included geology) in 1920. At the association's first annual congress, held in Cape Town in 1903, he presented a paper on "The minerals of some South African granites", dealing with the granites of Zimbabwe and Botswana. The paper was published in the association's Report for that year. When the association met with its British counterpart in South Africa in 1905 he contributed a paper on "The plutonic rocks and their relations with the crystalline schists", which was included in the Addresses and papers... published after the meeting. By this time he had already been elected a Fellow of the Geological Society of London. During subsequent years he addressed members of the association on "The Somabula diamond-field in Rhodesia" (1906), "Notes on some diamond-bearing and associated rocks" (1908), and "The sedimentary rocks of the Rhodesia plateau" (1911). He became a member of the Geological Society of South Africa and from 1905 contributed a number of papers to its Transactions, including "The Banket Formation in Rhodesia" (1905), "Note on the Rhodesian diamond fields" (1908), and "Geology of the Sabi Valley, Mashonaland" (1919).
In 1902 Mennell joined the South African Philosophical Society and remained a member for some years after it became the Royal Society of South Africa in 1908. In later years he was a member also of the (British) Institution of Mining and Metallurgy.
Mennell was a prolific writer, producing over 100 publications between 1902 and 1955, though most of them were short papers. A number of his geological papers appeared in the Geological Magazine (London), including "Contributions to South African petrography" (1902), dealing with his microscopic observations of some igneous rocks; "The Rhodesian banket beds" (1905); "Some notes on Archaean stratigraphy (Bulawayo)" (1906); "Note on the occurrence of corundum in Rhodesia" (1909); "The constitution of the igneous rocks" (1909); "The northward and eastward extension of the Karroo lavas" (1922); "Some Mesozoic and Tertiary igneous rocks from Portuguese East Africa" (1929); and "Sedimentation and the problem of the gneisses" (1945).
Except for a short period in London Mennell continued his career in the geology of Africa for the rest of his life, travelling an estimated 48 000 km on foot while prospecting, during which he discovered many economically important mineral deposits. He became interested in the syndicate that mined asbestos in the territory, which later became the Rhodesian and General Asbestos Corporation. By 1924 he was consulting geologist to the Manica Trust, reporting favourably on the prospects of finding oil at Inyaminga, some 160 km north of Beira, Mozambique. However, drilling by Inyaminga Petroleum during the next few years proved unsuccessful. During these years many of his papers dealt with mining and appeared in the Mining Magazine (London), the Rhodesian Mining Review, the South African Mining Journal, and other mining and industrial publications. Among others he contributed a two-part article on "The mineral resources of Rhodesia" to the South African Journal of Industries in 1917.
Outside geology Mennell's main scientific interest was in the prehistoric remains of Zimbabwe. As early as 1903 he published a pamphlet on The Zimbabwe ruins (Bulawayo, 16 pp), attributing them to builders from the Middle East, like most of his contemporaries. He briefly described the main ruins of the country in "The prehistoric monuments of Rhodesia", read before the South African Association for the Advancement of Science at its annual meeting in 1904 (Report, pp. 509-518). That same year he described the stone tools in the Rhodesia Museum in his annual report. In 1906 he and E.C. Chubb*, while exploring the Matopo Hills on bicycles, found the magnificent Silozwane Cave, on the southern edge of the Matopos National Park. It contained many unusual rock paintings of animal and human figures and was later declared a national monument. They also turned their attention to the Broken Hill (now Kabwe) lead and zinc mine in Zambia, where large deposits of mineralised bone had been found in association with crudely flaked quartz artefacts. Their description of the site, "On an African occurrence of fossil mammalia associated with stone implements", was published in the Geological Magazine in 1907. Many years later Mennell commented on "The evidence for the age of Homo Rhodesiensis" (a skull found at Broken Hill) in the South African Journal of Science (1929) and much later still, in the same journal, on "Evidence of human workmanship below Kalahari sands" (1951).
When responsible government was instituted in Rhodesia in 1923 Mennell became a member of the first Parliament, representing Bulawayo District. The black-eared canary, Serinus mennelli, was named in his honour by Chubb in 1908.