SOTES ON RECENT RESEARCH. 



1123 



The Nile Sadd, or Sudd. 



Sadd, The, of the Upper Nile: its Botany compared with 

 that of similiar obstructions in Bengal and American waters. 



By C. W. Hope (Ann. Bot. vol. xvi. p. 496). — This interesting article 

 opens with the following paragraph of the introduction : — " The Cataracts 

 of the Nile are well-known obstacles to navigation between its mouth and 

 the Soudan, but they are beginning to yield to the attacks of modern 

 engineers, who are throwing dams across the river, and providing side- 

 channels through which navigation will be carried on by means of locks. 

 The cataracts are caused by barriers of granite rock which cross the bed 

 of the river. But it is not so well known that an almost more serious 

 obstruction to navigation is caused by the accumulation of a few species 

 of plants floating in the Bahr-al-Jebel, or Mountain Nile, beginning 

 about 435 miles south of Khartum, and extending thence southwards for 

 about 250 miles ; and that this accumulation also seriously reduces the 

 flow of water northwards to the Lower Soudan and Egypt. The great 

 Equatorial Lakes store the rainfall of vast catchment basins, and so 

 regulate its off-flow northwards by means of the Mountain Nile ; but this 

 function is greatly neutralised by the vegetable accumulation which 

 begins 715 miles northward, in a comparatively flat country, and which 

 reduces the velocity of the current, and also causes the water to spill 

 right and left over the country and go to waste in shallow lakes and 

 lagoons, where it is subject to evaporation to a serious extent." 

 Seriously contributing to this " Sadd " is the common Papyrus. " Mac- 

 gregor, in the Illustrated London News, April 24, 1869, describing the 

 Papyrus on the waters of Merom, Syria, said: — 'On this (morass) is a 

 vast floating forest of Papyrus and cane, perfectly dark inside. I could 

 never penetrate more than 3 feet. Many of the stalks of the Papyrus 

 are as thick as my arm. The water percolates below and through the 

 spongy mass, and there loses at least half its volume by absorption and 

 evaporation. This impassable barrier is about a mile wide.' The other 

 main factor in the composition of Sadd is, according to Sir William 

 Garstin, the ' um-soof ' reed. That is the Arab name of the plant : the 

 botanical name is, according to Dr. Georg Schweinfurth (the author of 

 Beitrag zur Flora Aethiopiens, Berlin, 1867, and other works on the 

 botany of the Nile region), Vossia procera, a grass belonging to the 

 Piotiboelliea" Another of the " Sadd " plants is " Ambatch " (Herminiera 

 elaphroxylon), belonging to the Legaminosce, of which Dr. Schweinfurth 

 writes in his book of travel The Heart o f A frica : " It plays so prominent 

 a part in the waters of the Upper Nile that it might fairly be designated 

 the most remarkable of the aquatic plants. . . . The ' Ambatch ' is 

 distinguished by the almost unexampled lightness of its wood, if the 

 fungus-like substance of the stem deserves such a name at all. It shoots 

 up to fifteen or twenty feet in height, and at its base generally attains 

 a thickness of about six inches. The weight of this fungus-wood is so 

 insignificant that it really suggests comparison to a feather ; only by 

 taking it into his hands could anyone believe that it were possible for one 

 man to lift on his shoulders a raft made large enough to carry eight 

 people on the water." Mentioned among the smaller plants of the Sadd 



