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are kept open by the Dinkas living along the Atem river. They were 
noted by Werne in 1842. The Atem river at its tail apparently 
divides into two branches, of which one feeds the Zeraf river and the 
other returns to the Nile at Ghaba Shambe. 
Capt. Lyons has pointed out to me that all this course of the river 
is extraordinarily like the course of the Mississippi south of Vicksburg, 
with its severe curves and oxrings which correspond to the mayahs 
of the Albert Nile. Such mayahs or lagoons can be seen in the last 
20 kilometres of the Rosetta branch of the Nile. Placed as they are 
between Bor and Grhaba Shambe, they mean that while south of 
Bor, the Albert Nile has more or less formed its delta ; north of Bor, 
the delta is in a more embryonic stage, with probably the Atem 
river the more ancient of the two streams. North of Ghaba Shambe, 
the Zeraf river leaves the Albert Nile, and fed by the Atem Nile, takes 
off its water eastwards through marsh and swamp to again tail into 
the Albert Nile below Lake No. About 30 kilometres further north is 
the cut made by Sir Samuel Baker to enable him to enter the Albert 
Nile from the Zeraf river. 
The real Sudd region lies between Ghaba Shambe and Lake No, 
on a length of 380 kilometres. Between Fort Berkeley and Gondokoro, 
the flood as well as the summer supplies are within banks. Between 
Gondokoro and Bor, the summer supply is well within banks, but the 
floods overflow the valley. Between Bor and Ghaba Shambe the 
summer supply is just within banks, but the floods overflow freely. 
Between Ghaba Shambe and Lake No the summer supply overflows 
the banks, and hence there result the periodical barrings or sudds of 
the Nile by the floating vegetation so common in this region. While 
the summer supply is within banks it can insure a clear waterway ; but 
when not only the floods but the summer supplies ordinarily overflow 
the banks, the stream must be aided artificially if it is to keep its 
waterway clear. 
The ordinary width of the river south of Hillet-el-Nuer is between 
50 and 60 metres, but in the reach of the old sudd blocks numbers 16 
to 19 it diminishes in places to 25 metres, and in the reach blocked 
by sudd block number 15 increases to 200. North of Hillet-el-Nuer, 
the width varies from 60 to 150 metres, but the mean width may be 
taken as from 75 to 80 metres. The velocity is about 75 centimetres per 
second, which is a good velocity for clear water ; and Sir William Garstin 
remarks at one place that since the sudds were cleared the channel of 
3 
