XVI 



INTRODUCTION. 



tioned on the subject, and who come frequently to Lagos, 

 and other places on the Coast of Guinea, with slaves, deny 

 that they meet on their journey with any mountains, and 

 that the onl}' difficulties and obstructions arise from the 

 frequent rivers, lakes, and swamps which they have to 

 cross. But admitting that such a chain did exist, and 

 that it was one solid, unbroken range of primitive gra- 

 nite, it would be, even in that singular case, the only in- 

 stance, perhaps, of such an extended barrier resisting the 

 passage of an accumulated mass of waters. Even the Him- 

 malaya, the largest and probably the loftiest range in either 

 the New or Old World, has not been able to oppose an 

 effectual barrier to the southern streams of Tartary. The 

 main branch of the Ganges, it is true, does not, as was once 

 supposed, pervade it, but the Buramputra, the Sutlej and 

 the Indus, have forced their Avay through this immense 

 granite chain. The rocky mountains of America have 

 opened a gate for the passage of the Missouri ; and the 

 Delaware, the Susquehanna and the Potomac have forced 

 their way through the Alleghenny range. This objection, 

 tlien, may fairly be said to fall to the ground. 



The objection to the length of its course is somewhat more 

 serious, but not so formidable as at first it ma}'^ appear. 

 The great difficulty, perhaps the only one that suggests 

 itself, arises from the vast height which the source of a 

 river must necessarily be above the level of the sea, in 

 order to admit of its waters being carried over a space 

 of 4000 miles ; and from the certainty that Park, (who, 

 it must be observed, however, measured nothing) passed 

 no mountains of extraoi'dinray height to get at the 

 Niger. A critic, in a popular journal, whose arguments 



