Joseph Wolf became the preferred illustrator for this explorer who  had an obsession with discovering the sources of the Nile River 
Joseph Wolf:  He moved to the British Museum in 1848 and became the preferred illustrator for explorers and naturalists including David Livingstone, Alfred Russel Wallace and Henry Walter Bates. David Livingstone: His fame as an explorer and his obsession with discovering the sources of the Nile River was founded on the belief that if he could solve that age-old mystery, his fame would give him the influence to end the East African Arab-Swahili slave trade.
David Livingstone