Five Weeks in a Balloon the need to release gas or throw ballast overboard to control his altitude, allows very long trips to be taken. This voyage is meant to link together the voyages of Sir Richard Burton and John Hanning Speke in East Africa with those of Heinrich Barth in the regions of the Sahara and Chad. The trip begins in Zanzibar on the east coast, and passes across Lake Victoria, Lake Chad, Agadez, Timbuktu, Djenné and Ségou to St Louis in modern-day Senegal on the west coast. The book describes the unknown interior of Africa near modern-day Central African Republic as a desert,
Jakob Erhardt then in the "Church Missionary intelligencer" in 1856. The map was reproduced with commentary in other publications. The reports of snow on mounts Kilimanjaro and Kenya, near to the equator, caused considerable controversy. The map caused the British government and the Royal Geographical Society to hire Richard Francis Burton and John Hanning Speke to investigate the great lake, or lakes, and determine if they were the source of the Nile. The map came to be known as the "slug map" from the shape of the Uniamesi or Niassa inland sea. Burton called it the Mombas Mission Map. Erhardt worked in