In 1822, Hugh Clapperton, a young naval lieutenant, agreed to go with Walter Oudney and Dixon Denham to try and discover the source of the River Niger in North Africa. They journeyed south cross the Sahara from Tripoli to Lake Chad, the first white men to visit the region. Oudney died at Murner, and the other two separated, Clapperton going on alone to Kano, a great trading city west of Lake Chad. He then traveled to Sokoto, where he became friendly with the sultan who ruled the vast area, returning to meet up with Denham again in Kuka. Having established that none of the rivers flowing into Lake Chad was associated with the Niger, Clapperton returned to England and wrote a book of his adventures. In order to solve the problem of the Niger he returned to Africa in 1825, and set out on another journey starting from the Bight of Benin. Nine months later Clapperton arrived in Sokoto, where his detention by the sultan, added to the hardships of the journey, so affected his health that he died soon afterwards, at the age of thirty-nine, and was buried outside the walls of Sokoto.