One of the first, and most well-known, explorers to search the interior of Africa was Dr. David Livingstone, a British physician and missionary. He was sent to South Africa as a medical missionary during 1840, and thanks to his expeditions and discoveries many parts of the African map were revealed. Among his many important contributions were his discovery and exploration of the Zambezi river in its entirety, as well as several African lakes. During a visit to England in 1865, he wrote a story of an Expedition to the Zambezi and its tributaries, revealing the commercial possibilities of the Zambezi region. Dr. Livingstone marked the beginning of the invasion of explorers into Africa 's interior.
Sir Richard Burton and John Hanning Speke, both from England, together explored Somaliland during 1854, and located Lake Tanganyika in 1858. Speke who was traveling alone, discovered Lake Victoria, the main source of the Nile, a accomplishment which many explorers, even Dr. David Livingstone, had failed to accomplish. Their explorations contributed to the desire and idea that some parts of Africa could be used for economic purposes.
During 1850 to 1853, Heinrich Barth, from Germany, explored the middle section of the Niger River and Timbuktu. He published a magazine called Travels and Discoveries of North and Central Africa in 1858, which contained detailed maps and information on many of Africa
References: Study notes Handouts, Booklets and Worksheets received in class Britannica Encyclopedia Encarta My main source was some German program on TV (I live in Germany), name of program unknown.