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,
Hamites races were too broad to have stemmed from a single common ancestor, but were instead consistent with separate racial origins. In his "Crania Aegyptiaca" (1844), Morton analyzed over a hundred intact crania gathered from the Nile Valley, and concluded that the ancient Egyptians were racially akin to Europeans. His conclusions would establish the foundation for the American School of anthropology, and would also influence proponents of polygenism. In the second half of the 19th century, the British explorer John Hanning Speke would further popularize the ancient Hamitic peregrinations in his publications on his search for the source of the Nile