— 39 — 
their silt and became quite clear. On page 100 of Vol. II of Werne’s 
work there is this significant sentence : “The report that the natives 
below (i.e. in latitude 5° to 7°) had blocked the river to cut off our 
retreat, turned out to be unfounded.” From the above it will be 
noticed that the aborigines in 1840-1841 spoke of their ability to block 
the course of the river, while the training works in the side channels 
and spills for fishing purposes were described as solid works regulated 
by rows of strong stakes driven into the ground. 
Between 1841 and 1863 the expeditions up the Nile considerably in- 
creased, while the aborigines were being brutally treated by the slave tra- 
ders. What could be more natural than that, as a measure of protection, 
the aborigines should have widened and deepened the side channels and 
spills which took off from the river between latitudes 5J° and 7J°,so that 
they might escape from the traders. Subsequently, when the main river 
was patrolled by Government boats, the slave-traders themselves used 
these side channels for prosecuting their traffic. All the channels and 
spills tailed into the Bahr Zeraf, which now began to form an appreci- 
able stream, and which was navigated over the lower part of its course 
by Petherick between 1853 and 1862. The Bahr Zeraf was however 
always described as sudded, while the Albert Nile was open to naviga- 
tion. This action of dissipating the waters of the river went on 
increasing till 1863, when there occurred a very high flood indeed ; 
the floating weeds * brought down from the south were excessive, the 
waters escaped everywhere from the main stream, while the floating 
masses of creepers were confined by the grasses and papyrus to the main 
channel, and sudded it downstream of Lake No. 
On ascending the White Nile and Albert Nile in January 1863, 
Sir Samuel Baker found the passage clear to the south. On returning 
in April 1865, he found the sudd of the flood of 1863 still in the 
Albert Nile downstream of Lake No. The sudd was 1000 metres long 
and had a passage 3 metres wide cut through the middle of it, down 
which the river ran like a mill race. 
In February 1869, Dr. Schweinfurth and his party, on their way 
to the Gazelle, took six days to get through this sudd, though the main 
obstruction was now only 200 metres long. In July 1872, Dr. Schwein- 
furth on his way back found the sudd to the downstream of Lake No 
as before, and described the opening through it as “a narrow stream of 
water which rushed along as a wild brook. The depth of the fairway 
varied from 2 to 3 metres, and the boat nowhere touched the bottom,” 
