two former soon perished, while their successor, Vogel, met with a violent end in Wadai, the same fate some years afterwards overtaking Beurmann in Kanem. In 1871 and 1872 better success attended Nachtigal, who, after visiting Borku and Kanem, successively traversed Bornu, Baghirmi, Wadai, and Dar-For. Matteucci and Massari followed in 1880, but no traveller has yet succeeded in crossing the water-parting which separates the waters flowing north to Lake Tsad and south to the Congo. Nor has any European yet reached the Mendif uplands, which may be regarded as the orographic centre of the continent, dominatin g at once the Nile, Niger, Tsad, and Congo basins.
Eastwards the natural limit of the Tsad geographical system is formed by the
Marrah range, which in Dar-For constitutes the divide in the direction of the Nile. Farther west the plains are broken by some secondary chains, such as the two parallel Tirdzé ridges running north and south in Dar-For and Wadai at an altitude of about 2,000 feet above the sea, falling imperceptibly northwards in the direction of the Sahara, and continued south-westwards by isolated eminences and by the Gheré hills occupying a large part of West Wadai. West of the Shari, some of whose affluents flow from the Gheré uplands, the divide between the Tsad and Benue is formed by the Wandala Mountains, which have a mean elevation of 2,600 feet, culminating in Mount Magar, about 8,000 feet high. Near this range tise two isolated peaks, Kamallé, terminating in a columnar mass, and much farther
