Basil Hall, naval officer and author, was a son of Sir James Hall, who has been described as the father of experimental geology for his pioneering experiments on the effects of heat and pressure on rocks. Basil received his schooling in Edinburgh and joined the Royal Navy in 1802, at the age of thirteen. He was promoted to Lieutenant in 1808. Two years later he landed on Rockall, a small and lonely island in the North Atlantic west of Scotland, and became the first to collect a specimen of its unusual granite.
In 1812 Hall visited the Cape and ascended Table Mountain via the Platteklip Gorge. He observed the contact between the Cape granite and the highly inclined, metamorphosed Malmesbury shale which he called killas, a term used by Cornish miners for clay-slate. He described the intrusion of the granite into the shale and the isolated masses of shale surrounded by granite that can be seen at the contact zone. Higher up he observed the horizontal, undisturbed Table Mountain sandstone. As this had clearly been deposited in water he speculated that it had been uplifted by the intrusion of the granite. His remark that this sandstone is part of a geological formation which had also been found by Lichtenstein*, Barrow* and others in the interior of the country shows that Hall was familiar with the few earlier observations relating to the geology of the country. His description was sent in the form of one or more letters to Professor John Playfair, who based a paper on it which he read before a meeting of the Royal Society of Edinburgh in May 1813. It was published as "Account of the structure of the Table Mountain and other parts of the peninsula of the Cape: Drawn up by Professor Playfair from observations made by Captain Basil Hall", in the society's Transactions (Vol. 7, pp. 269-278).
Hall's observation and sketch of Cape granite veins intruding into slate were presented by Playfair as a crucial confirmation of the plutonist view that granite is an igneous rock, solidified from a hot, fluid magma [in contrast with the neptunist view of granite as a chemical precipitate]. Hall's sketch was later used by Charles Lyell in Volume 3 of his famous book Principles of geology (1834).
Hall received command of his first vessel in 1814. Two years later he was in command of the sloop Lyra which accompanied Lord Amherst's mission to China. The expedition touched at the Cape during both its outward and return voyages. One of its members was Clarke Abel*, who is credited with the first proper description of the better known contact between the Cape granite and the shale at Seapoint. It is not clear whether Hall also made geological observations during these visits. He did, however, publish an Account of a voyage of discovery to the west coast of Corea and the great Loo-Choo Island in the Japan Sea (London, 1818). Shortly after returning to Britain in October 1817 he was promoted to the rank of post-captain. His observations of the characteristics of the countries and peoples that he visited gave rise to articles in various journals and encyclopaedias. In 1820 he was sent to the Pacific coast of South America, where he carried out pendulum observations to measure the strength of the earth's gravitational attraction at various places. The pendulum observations were published in the Philosophical Transactions of the Royal Society of London in 1822. Other scientific and technical observations that he made in South America were reported in several additional papers, while he described his command during these years in a two volume work, Extracts from a journal written on the coasts of Chili, Peru, and Mexico in the years 1820-21-22 (Edinburgh, 1824, with many later editions and translations into Dutch and Spanish).
As early as 1816 Hall had been elected a Fellow of the Royal Society of London, and later was also elected a Fellow of the Royal Astronomical Society, the Royal Geographical Society, and the Geological Society of London. He left the navy in 1824 to become a traveller and author. During 1827 and 1828 he and his wife visited the United States and the next year he published his Travels in North America in the years 1827 and 1828 (Edinburgh, 1829, 3 vols) and Forty etchings, from sketches made with the camera lucida, in North America... (Edinburgh, 1829). Further journeys followed, which he described in Fragments of voyages and travels... (Edinburgh, 1831-1835). An article by him, "An account of the penitentiary, or state prison, at Sing-Sing, near New York..." was published in the South African Quarterly Journal in 1830. He was an enthusiastic enquirer and a welcome guest at social gatherings, with many stories and theories to relate. However, shortly after publishing his last book in 1841 he became insane and died a few years later.
