When the two great French cartographers Delisle and D'Anville determined not to insert anything on their maps for which they had not some evidence, these lakes and mountains disappeared, and thus it has come about that maps of the seventeenth century often appear to display more knowledge of the interior of Africa than those of the beginning of the nineteenth, at least with regard to the sources of the Nile.
[Illustration: DAPPER'S MAP OF AFRICA, 1676.] African exploration of the interior begins with the search for the sources of the Nile, and has been mainly concluded by the determination of the course of the three other great rivers, the Niger, the Zambesi, and the Congo.

It is remarkable that all four rivers have had their course determined by persons of British nationality.

The names of Bruce and Grant will always be associated with the Nile, that of Mungo Park with the Niger, Dr.Livingstone with the Zambesi, and Mr.Stanley with the Congo.

It is not inappropriate that, except in the case of the Congo, England should control the course of the rivers which her sons first made accessible to civilisation.
We have seen that there was an ancient tradition reported by Herodotus, that the Nile trended off to the west and became there the river Niger; while still earlier there was an impression that part of it at any rate wandered eastward, and some way joined on to the same source as the Tigris and Euphrates--at least that seems to be the suggestion in the biblical account of Paradise.

Whatever the reason, the greatest uncertainty existed as to the actual course of the river, and to discover the source of the Nile was for many centuries the standing expression for performing the impossible.