INTRODUCTION. xix 



a proof that it is influenced by the tropical rains, and 

 that one branch of it, at least, must pass through some 

 portion of the northern hemisphere. 



Another objection has been made to the identity of the 

 Niger and the Zaire, grounded on the circumstance of no 

 traces being discovered of the IVIahomedan doctrines or 

 institutions on the coast where the latter terminates. It 

 would be a sufficient answer to observe, that as far as our 

 present knowledge extends, the Niger, in Northern Africa, 

 formed the boundary of Mahomedan invasion. What the 

 difficulties may have been, whether moral or physical, or 

 both, " to impede the spirit of enterprise and proselytisra 

 which belongs to the Mahomedan character," it vrould be 

 idle to conjecture; but that they have been impeded, and 

 in a great measure limited to the parallel of the Niger while 

 on its eastern course, is pretty certain ; yet there appears to 

 be neither difficulty nor want of means in crossing this 

 river, though there may be both in descending it. Inde- 

 pendently of the lakes and swamps, the sand-banks 

 and rapids, that may occur, the Africans have not at 

 any time, or in any part of the country, been famous for 

 river navigation. But it is far from improbable, that 

 Arab priests or traders may have penetrated into south- 

 ern Africa ; on the eastern coasts they held, at one 

 time, powerful settlements, and Arabic Avords. occur in 

 all the languages of the negroes even on the western 

 coast. 



Some vague objections have been stated to the identity 

 of the Niger and Zaire, from their difference of tempera- 

 ture, the precise meaning of which it is not easy to com- 



