Thomas Arbousset, a French Protestant pioneer missionary in Lesotho, entered the seminary of the Maisons des Missions (Missionary Society) in Paris in 1829. The subjects he studied included history, geography and science, and as part of his practical training he served as apprentice to both a carpenter and a locksmith. He was ordained in October 1832. Two months later, accompanied by two other missionaries, he came to South Africa and at the invitation of Chief Moshoeshoe settled at Morija, some 40 km south of Thaba Bosigo, Lesotho, in June 1833. Arbousset was based there for most of the next three decades and was visited by, among others, Dr Andrew Smith* in 1834 and James Backhouse* in 1839. On 18 July 1837 he married Catherine Rogers in Cape Town and eventually they had nine children.
From 13 March to 11 May 1836 Arbousset undertook a journey of exploration accompanied by his colleague Francois Daumas. They travelled by ox-wagon to near present day Ficksburg in the Free State, and from there eastward and northward on horseback. Daumas and others turned back towards Ficksburg near Joel's Drift, while Arbousset continued upstream along the Caledon River on the Free State side with a single guide. Travelling through the area presently known as Golden Gate, they eventually reached the headwaters of the Namahadi River. He satisfied himself that the Caledon, Orange, Tugela, and Namahadi rivers all arise in the highest mountain in the area, called Pofung by the local inhabitants, and named it Mont-aux-Sources.
Arbousset and Daumas wrote a report on their journey which was published, with their map of the region, in the Journal des Missions Evangeliques for November 1836. Even though Arbousset did not reach the summit of Mont-aux-Sources and did not locate it accurately, his discovery and name were officially recognised by French geographers.
Arbousset accompanied Moshoeshoe and his retinue to the same area from 15 February to 2 March 1840. They followed roughly the present road to the Oxbow scheme, finally reaching the Malibamatso River. Although he again wrote a report, this has not been published in full. However, in 1842 he and Daumas published a book on their earlier expedition which contains also some information about this second journey. An English translation by Rev. J.C. Brown* (later Colonial Botanist at the Cape) was published in Cape Town in 1846, entitled Narrative of an exploratory tour to the north-east of the Colony of the Cape of Good Hope. An appendix contains meteorological observations made by Arbousset during his second journey. During one of his journeys he found some fossil shells, which he described as oysters, near the source of the Caledon River. They were probably freshwater molluscs from the Clarens Sandstone Formation. His description constitutes the first written record of fossils in Lesotho.
Arbousset produced many religeous publications from 1836 onwards, including several of the earliest works in the Southern Sotho language. He furthermore acted as advisor to Moshoeshoe for many years. In 1858 the buildings at Morija were destroyed by a commando from the Orange Free State and two years later Arbousset left Lesotho for Europe. The ship in which the family was travelling ran aground off the coast of Cornwall and during the rescue operation his wife drowned. After returning to Paris he undertook several preaching tours and in 1862 settled on the island Tahiti, which had just come under French protection. He returned to Europe in 1867 to become the minister of Saint-Sauvant in western France, where he died ten years later, aged 67. A book by him, Tahiti et les iles adjecentes (Tahiti and adjacent islands; Paris, 1887) was published after his death.