APPENDIX IX
Philip Askell Benton translation
LAKE CHAD AND THE BAHR EL GHAZAL
The French Mission under Captain Tilho devoted a good deal of attention to the problem of the Bahr el Ghazal. Their conclusions are summed up on p. 61, vol. ii of the Documents scientifiques: ‘The Bahr el Ghazal, as far as we examined it (i.e. to Fantrassou), is neither an affluent nor an effluent but simply a prolongation of Chad. . . . This conclusion does not solve the problem of the mythical river, which, according to old maps, formerly connected Chad with the Nile.’[545] Twelve varieties of shells are common to Chad and the Nile, and indicate that there must at one time have been a connexion by water between the lake and the river (Doc. sc., ii. 170); cf. also note [343] of the present work.
Again, on p. 601 ff., vol. ii: ‘Topography and hypsometry on the one hand, chemistry, geology, and malacology on the other, agree in declaring that Lake Chad is not the remains of an ancient sea, that it is hardly a lake, in spite of its appearance of being an alluvial lake, and that it should be regarded as the expansion of a powerful sheet of fluvial water flowing north-eastwards, rather than a true lake. . . .
It appears legitimate, a priori, to suppose that this sheet of fluvial water, after having expanded to form Chad, may continue its course subterraneously, protected by a mantle of sand against the intense evaporation occasioned by the burning sun of the tropics and the parching winds of the desert. Besides, have we not in the Sahara many other examples of water-courses prolonged subterraneously very far from the place where they seem to lose themselves in the sands? . . .
Moreover, if topography and hypsometry can only show us the possibility of the waters of Chad being prolonged subterraneously, chemistry demonstrates the necessity. The amount of chloride in the waters of Chad is in fact so small, that one is bound to admit that there is an outlet somewhere. . . . Chemical analysis has shown that the water of Chad almost everywhere contains less chloride than the drinking water of Copenhagen for example. Consequently, it is absolutely impossible that it can be a self-contained lake. . . .
It is impossible to definitely trace the course of the connecting link between the Chad and the Nile, assuming that it existed, . . . until French Borku and English Darfur are really brought under control.’