It is a history book. Since my return from a first tour of exploration in the Great Sahara I had carefully revolved in my mind the possibility of a much greater undertaking, namely, a political and commercial expedition to some of the most important kingdoms of Central Africa. The plan appeared to me feasible; and when I laid it in all its details before her Majesty’s Government, they determined, after mature consideration, to empower me to carry it out. Two objects, one principal, necessarily kept somewhat in the background—the abolition of the slave-trade; one subsidiary, and yet important in itself—the promotion of commerce by way of the Great Desert; appeared to me, and to the distinguished persons who promoted the undertaking, of sufficient magnitude to justify considerable sacrifices. Much preliminary discussion took place; but the impediments and difficulties that naturally start up at the commencement of any enterprise possessing the character of novelty were gradually overcome, and in the summer of 1849 it was generally known that I was about to proceed, by way of Tripoli and the Sahara, and the hitherto unexplored kingdom of Aheer, to endeavour to open commercial relations and conclude treaties with any native power so disposed, but especially with the Sultan of Bornou.