Lake Uniamési or the Uniamesi Sea was the name given by missionaries in the 1840s and 1850s to a huge lake or inland sea they supposed to lie within a region of Central East Africa with the same name.
Three missionaries, confined to the coastal belt, heard of the region of Unyamwezi in the northwest of what is now Tanzania and exaggerated its size to include a large part of the continental interior. They heard of a great lake, and imagined an enormous lake that would be the source of the Benue, Nile, Zambezi and Congo rivers. They drew a map showing a huge "Lake Uniamesi" that was published in 1855. The map spurred the expedition of Burton and Speke to investigate the African Great Lakes region, where they found that lakes Victoria, Tanganyika and Nyasa were separate bodies of water. It was not until 1877 that it was confirmed that these lakes did feed the Nile, Congo and Zambezi, albeit separately.
Background
The Great Lakes of East Africa include lakes Albert, Edward, Kivu and Tanganyika, all of which lie in the western or Albertine branch of the East African rift system, Lake Victoria to the east of this chain and Lake Nyasa (Malawi) to the south. Lake Victoria is the third largest lake in the world, and lies on the plateau between the west and east rifts. Unlike the long, narrow and deep lakes of the rift, Lake Victoria is wide and relatively shallow.
Bantu peoples moved into the region between the Great Lakes and the Indian Ocean some time after 1000 BC and mingled with the local population. By the first century AD ships from the Arabian peninsula were trading along the East African coast. Muslim Arabs from Oman began to colonize the coast in the 8th century AD. The coastal Bantu peoples intermarried with the Arabs to form the Swahili people, with a language that combines Bantu, Arabic and Persian elements. The Swahili culture incorporated many Arabic and Islamic aspects, while remaining essentially Bantu in nature.
The Unyamwezi region lies around the modern town of Tabora, between the coast and Lake Tanganyika, and includes the Tabora, Nzega and Kahama districts of the western plateau of modern Tanzania. In the 19th century the inhabitants were called Nyamwezi people by outsiders, although this term covered various different groups. Unyamwezi lay at a juncture where a trade route from the coast split, with one branch continuing west to the port of Ujiji on Lake Tanganyika while another branch led north to the kingdoms of Buganda and Bunyoro. Coastal traders settled in Unyamwezi, some with hundreds of well-armed retainers. The Nyamwezi provided most of the porters for the caravans organized by the coastal Arabs and Swahilis, and also conducted their own caravans. The Nyamwezi were long-distance traders throughout East Africa.
Ivory was not widely used by the Nyamwezi, but at some point they became aware that there was an overseas market for the product, and began to carry ivory along the route from Tabora down to the Indian Ocean coast opposite Zanzibar. There are records of Sultan Sayyid Said of Zanzibar negotiating with envoys from Unyamwezi in 1839 for safe passage for caravans to the interior. The Nyamwezi did not sell their own people as slaves, since they needed manpower for the ivory trade, but after the 1850s the slave trade began to become important. Slaves brought from the Congo Basin or the Great Lakes region would be held at Tabora, then sent down to the coast in small groups for onward shipment.
Early European contacts
Early in 1844 Sultan Sayyid Said gave the German missionary Johann Ludwig Krapf (1810–1881) permission to establish a mission on the coast. Krapf arrived in Mombasa on 13 March 1844. He was joined in 1846 by Johannes Rebmann (1820–1876). On 12 November 1848 Rebmann started a journey into the interior. The Church Missionary Intelligencer reported that, "The ultimate object, which our Missionaries had in view, has been to reach Uniamési, that interior country where the roads to East Africa and West Africa diverge." Uniamési was said to lie about 150 to 200 hours to the west of the Chagga kingdom, which lay on the slopes of Mount Kilimanjaro.