A vessel arriving from Khartoum in her
passage to Gondokoro would find, after passing through a broad river of
clear water, that her bow would suddenly strike against a bank of solid
compressed vegetation - this was the natural dam that had been formed to
an unknown extent: the river ceased to exist.
It may readily be imagined that a dense spongy mass which completely
closed the river would act as a filter: thus, as the water charged with
muddy particles arrived at the dam where the stream was suddenly
checked, it would deposit all impurities as it oozed and percolated
slowly through the tangled but compressed mass of vegetation. This
deposit quickly created mud-banks and shoals, which effectually blocked
the original bed of the river. The reedy vegetation of the country
immediately took root upon these favourable conditions, and the rapid
growth in a tropical climate may be imagined. That which had been the
river bed was converted into a solid marsh.
This terrible accumulation had been increasing for five or six years,
therefore it is impossible to ascertain or even to speculate upon the
distance to which it might extend. The slave-traders had been obliged to
seek another rout, which they had found via the Bahr Giraffe, which
river had proved to be merely a branch of the White Nile, as I had
suggested in my former work, and not an independent river.
