404' GEOGRAPHICAL SYSTEMS. 
leave void those spaces which science afforded no 
materials for filling. In Abyssinia also, although 
his predecessor had done much, D'Anville found 
some important additions to make. On a dili- 
gent comparison of ancient and modern materials, 
he ascertained, that the river, which all modern 
geographers had considered as the Nile, was not 
the Nile of the ancients ; that it was merely the 
tributary to a larger stream, which alone had been, 
and ought to be, regarded as the river of Egypt. 
Subsequent observation has fully confirmed this 
discovery. 
In Western Africa, the reform effected by these 
two great geographers was equally important ; but 
for reasons already assigned, it will be more con- 
venient to reserve the consideration of them till 
the following chapter. 
From this time, the investigation of African 
geography was conducted upon sound principles, 
and proceeded in a regular train. There remain- 
ed only the inevitable evil of imperfect knowledge; 
but this was no longer combined with systematic 
error ; it was not that hopeless ignorance which 
is unconscious of itself. It has prompted to vast 
exertions for the extension of discovery in this 
part of the world. In Major Rennell, too, the 
materials thus collected have happily found an 
illustrator, who, in the precision of his data, and 
the accuracy with which he applies them, is scarce- 
