The inhabitants of Ennedi, nomads or semi-nomads, are very poor; the chief tribes are the Bideyats (or Annas), the Gaedas, and the Mourdias, which all together represent hardly more than 2000 souls. But they are by tradition so addicted to brigandage and so untamable that as large a troop of police is needed to keep them in hand as for a population of 40,000 in the settled regions. Ennedi has no vegetable food resources; there are neither palm plantations, nor native gardens, nor millet fields. And yet the soil is more fertile than in Borkou and the periods of drought shorter. The chief agricultural interest of the region lies in its excellent pasture, where the camels find abundant provender of very good quality. _In Mortcha._—From Archei I went to the post of Fada, 40 miles or so to the north-west, for a few days’ rest, after which I undertook a new series of reconnaissances westwards, for the purpose of exploring the still imperfectly known desert regions of northern Mortcha, too often visited by the raids of the refractory tribes. I was thus enabled during the early days of January 1915 to trace the course of the temporary rivers that receive the waters from the western slopes of Ennedi. For a few days every year these rivers roll down a volume of water sufficient to stop the march of caravans and convoys for a longer or shorter time, and continue their course for 200 or 300 kilometres before each of them reaches the pool in which it ends. As they have not force enough to go further, all one finds beyond the terminal pool is a valley-way more or less clearly marked, and blocked with sand from place to place, but still visible for fairly long distances. It has been concluded that they formerly ran into the ancient lake of Djourab, the level of which is from 200 to 300 yards lower. The most interesting of these rivers from the geographical point of view is the wadi Soala, which in the central and lower parts of its course separates the granitic zone of Mortcha from the sandstone of Ennedi. The whole region is one succession of good grazing-grounds for camels, but which can be made use of only a few months a year while there is water in the temporary pools. The one that lasts longest, that of Elléla, in which the wadi Oum-Hadjar comes to an end, is not entirely dry till April or May when the annual rains have been normal, in which case it makes direct communication possible between Borkou and Wadaï.