When the intensity of the Dervish rule was slackening, in the early nineties of the last century various Belgian officers, such as Lieutenant Van Kerckhoven, passed the Congo basin to the Bahr-al-Arab and the westernmost tributaries of the Bahr-al-Ghazal, and threw a little fresh light on the still mysterious hydrography of the Nile-Shari water-parting. They pointed the way, however, to Joseph Marchand and his associates. This gallant band of Frenchmen, in 1897, made their way from the Mbomu River (Congo basin) down the Jur (Sue) to the Bahr-al-Ghazal and the White Nile, to face England at Fashoda. Marchand was accompanied, amongst other European officers and non-commissioned officers, by Lieutenants A. H. Dyé and Tanguedec. Tanguedec remained till 1900 on the Mountain Nile near the Bahr-az-Ziraf. Dyé gave, in 1902, some account of the explorations of the Bahr-al-Ghazal region undertaken by the Marchand expedition. The swamps which characterise the northeastern part of the Bahr-al-Ghazal province render the definite mapping of the lower courses of its great rivers extremely difficult. Nevertheless, in the most systematic way, Marchand and his companions, in their little steam launch _Faidherbe_, surveyed the Sue or Jur (the longest stream flowing into the Bahr-al-Ghazal estuary), the Bahr-al-Arab, Bahr-al-Hamr, the Tonj, and Rōl. The Bahr-al-Ghazal itself, from Mashra-ar-Rak downwards, was carefully surveyed, and many indications were found of the changes which have taken place since the days of its early explorers, though M. Dyé considers the sketch given by Lejean in 1862 as wonderfully correct in its general outlines. After describing the ferruginous laterite plateau, which occupies the whole southern part of the Bahr-al-Ghazal province, as well as adjoining parts on the Congo basin, Lieutenant Dyé sketches the transition from this region, in which the streams flow in steep-sided valleys to the sea of swamps which lies along the ninth parallel. It is in about 7° 20′ north that the first change occurs, the river-banks opening out and leaving between them an alluvial-flood plain, grassy and intersected by swamps, through which the river winds in a tortuous course, much choked by sand-banks. At the height of the rains this is entirely flooded. Still lower, the rocky valley sides entirely disappear, and the clayey banks sink below the mean water-level, the rivers becoming more and more narrow, and diminishing in depth until they are finally lost, each in its own belt of swamp, which forms a sea of grass, “Um Suf” [fleecy reeds], and papyrus.