On a certain occasion in Air when news was received of a raid being about to fall on the country, I was honoured by receiving a communication from the French officer commanding the Fort at Agades, indicating the locality in his general scheme of defence whither I might lead on a reconnaissance an armed band of local Tuareg from the village in which I was then living by myself. On another occasion, after travelling for some hundreds of miles with a French Camel Corps patrol, the men were paraded and in their presence I was nominated an honorary serjeant of the “Peloton Méhariste de Guré,” a type of compliment which those associated with the French Army will best realise. It is to the officer commanding this unit, Henri Gramain of the French Colonial Army, that I owe the most perfect companionship I have ever had the fortune to experience. I know that when we meet again we shall resume conversation where we left off at Teshkar in the bushland of Elakkos, one evening in the summer of 1922. He and my other friends, Tuareg, British, French, Arab and Fulani contributed to make that year the happiest I have ever spent. No reader of the works of that great traveller, Dr. Heinrich Barth, will need to be told how much of the data collected in the succeeding pages has been culled from the monumental account of his _Travels in Central Africa_. This German, who most loyally served the British Crown in those far countries, is perhaps the greatest traveller there has ever been in Africa. His exploits were never advertised, so his fame has not been suffered to compete with the more sensational and journalistic enterprises accomplished since his day down to modern times. But no student will require to have his praises sung by any disciple. I have to thank the Royal Geographical Society for permission to use the map which was prepared for a paper I had the honour to read in 1923 before a meeting of the Fellows. More especially do I wish to thank E. A. Reeves, their Keeper of Maps, both for the instruction in surveying which he gave me before my journey and for the assistance afforded after my return in checking and working up my results. My cartographic material in the form of road traverses, sketch maps based on astronomical positions, and theodolite computations are all in the Society’s library and available to students. A small collection of ethnographic material which I brought back is at Oxford in the Pitt Rivers Museum, to whose Curator, Henry Balfour, I am indebted both for advice and for plates Nos. 24-26, 37 and 42.