Hope . — The * Sadd ’ of the Upper Nile. 497 
be pronounced like the first syllable of 4 sudden/ and there- 
fore, to all but Britons, 4 Sadd * would be the better guide.) 
Sir William Garstin says that his Report is the result of his 
observations made during three consecutive years. In 1900 
he had 4 the advantage of studying the actual process of its 
formation on the spot/ as he was imprisoned for three days in 
the Gebel River, owing to the 4 Sudd having burst in 1 (from 
the side lakes and lagoons) 4 and blocked the channel down- 
stream of the steamer/ 
In 1890-91 a reconnaissance survey of the Rahr-al-Gebel 
(or Jebel) from Lake No southwards to Gondokoro was 
finished ; and a map to the scale of 1 inch to 10 kilometres is 
given with Sir William Garstin ’s report : it shows very clearly 
the features of the river’s course ; the lakes and lagoons met 
with ; the positions of the 4 Sadd ’ blocks then found, and the 
nature of the swamps, whether papyrus or grass. The last 
block met with, the nineteenth, was just above the 400 kilo- 
metres point from Lake No, near Ghaba Shambe, one of the 
Nile Posts of the Bahr-al-Ghazal Province. Papyrus swamps 
ceased at about 460 kilometres, and the plant does not seem 
to have been found south of about 520 kilometres. 
4 In the Bahr-al- Jebel/ says Sir William Garstin , e the main 
factors of the 44 Sadd ” are — the papyrus, and the 64 um-soof ” 
(or omm-soof) reeds. These two, with the earth adhering to 
their roots, form the real obstacle. Many of the smaller 
swimming plants, such as the Azolla, the Utricularia^ and 
Ottelia, are mingled with the others ; but they certainly do 
not play any important part in the formation of the obstacle. 
The ambatch, too, has been unjustly accused of assisting in 
forming the barrier. This is not the case. This plant does 
not grow in any great quantity in the vicinity of the Bahr-al- 
Gebel, and its stem is so light and brittle that it would break 
when subjected to great pressure. 
4 On the Bahr-al-Ghazal, on the contrary, the sudd is chiefly 
composed of the swimming plants above mentioned. Their 
breeding places are Lake Ambadi and the other lakes to the 
south. The Ghazal sudd is much lighter in texture than that 
