A Dissertation on the course and probable termination of the Niger.

After Mungo Park had shown that a large river (identified as the Niger of the ancients) flowed from west to east, various theories emerged to explain its course beyond Sansanding, where Park's report ended. One of the strangest theories came from Donkin who suggested that the Niger flowed into Lake Chad, then out of Lake Chad toward the north, disappearing under the desert in an underground stream that finally emerged in the Gulf of Sidra. Lieut-General Sir Rufane Shaw Donkin (1772-1841), was a British army officer, Member of Parliament and one of the original fellows of the Royal Geographical Society.