210 The Sudd.

to an unusual height, and caused extensive floodings in the delta.

" It may be mentioned that in the lower reaches of the White Nile the current is too strong to allow of any accumulations. Here the smaller masses, breaking away from the southern barriers, are carried swiftly along to and beyond Khartum. But very little reaches Egypt itself, most of the floating growths being either arrested in the recesses along the banks, or else becoming waterlogged and sinking to the bottom, where they are slowly decomposed.

•' In the composition of the sudd, the prevailing element, at least in the Bahr el Ghazal region, is the so-called Om-Suf, or 'Mother of Wool* (Yossia procera), an aquatic grass, which, to the unscientific eye, looks more like a reed. It is a favourite food of animals, and in its midst grow patches of papyrus, but very little ambatch, which generally shoots up from deep water and enters only casually into the composition of the sudd.

" The varying texture of these obstructions depends largely on the different conditions under which they have been brought together, on their age and general constituents. Their tenacity is at times so great that huge amphibia, such as the hippopotamus and crocodile that occasionally get entangled iu their meshes, are unable to free themselves, and thus perish of hunger or want of air. As a rule they are more compact, and consequently present greater obstacles to navigation in the Bahr el Jebel and White Mle than in the Bahr el Ghazal. In this river we were generally able to force our way through such impediments, even though steaming against the current. But in the Bahr el Jebel the steamer alone is often helpless, and requires the aid of special apparatus to break through. " In most cases the object aimed at is simply to get through, leaving the obstruction to close up again or not behind the steamer. But when systematic and continuous operations are undertaken to clear the waterway, the course adopted is to break up the masses piecemeal, and send the fragments into the current to prevent them from again coalescing, at least in the same place. Solid masses can be attacked successfully from the north side only, that is, operating against the current. Iu this case most of