When at Egga, the highest point reached by the Albert on the Niger, he ventured upon an exploration further up, taking a few natives only, but sickness compelled the abandonment of the project.

As soon as his health improved Duncan proposed to penetrate the unknown land from the western coast to the Mountains of Kong, and between the Lagos and Niger rivers.

[2] His plans were approved by the Royal Geographical Society, and the lords of the admiralty granted him a free passage in HMS Prometheus, which left England on 17 June 1844, and reached Cape Castle on 22 July following.

After an attack of fever he commenced his journey from the coast to Whydah, and afterwards made the unexampled feat of a passage through the Dahomey country to Adofidiah, of which he sent particulars to the Royal Geographical Society, dated 19 April and 4 October 1845.

[3] In 1847, he published Travels in Western Africa in 1845 and 1846, comprising a Journey from Whydah through the Kingdom of Dahomey to Adofidiah in the Interior, 2 volumes, London, duodecimo.