Complex sentence: When Oudney and Clapperton set out, December 1823, for the Hausa states, Denham remained behind to explore the western, south and south-eastern shores of Lake Chad, and the lower courses of the rivers Waube, Logone and Shari.
Split into simpler sentences: When Oudney and Clapperton set out, December 1823, for the Hausa states, Denham remained behind. He explored the western, south and south-eastern shores of Lake Chad, and the lower courses of the rivers Waube, Logone and Shari.