ANNOTATIONS AND ADDITIONS. 133 



tinent depends in its leading traits on several plastic relations, which 

 are usually among the latest to be discovered and unravelled. A 

 new and excellent work of our friend, Carl Zimmermann, on the 

 upper country of the Nile, and the eastern parts of Central Africa, 

 has again brought these considerations very vividly before me. His 

 new map shows in the clearest manner to the eye, by means of a 

 particular method of shading, what is still unknown, and what, by 

 the courage and perseverance of travellers of all nations among 

 whom our own countrymen happily hold an important place has 

 been already disclosed to us. It is a valuable service, and one which 

 opens the way for farther advances and more comprehensive infer- 

 ences, when persons, thoroughly acquainted with the existing, often 

 widely scattered, materials men who do not merely draw and com- 

 pile, but compare, select, and, wherever it is possible, check and 

 control the routes of travellers by astronomical determinations of 

 position undertake to represent graphically the results of the ele- 

 ments of knowledge possessed at the time. Those who have them- 

 selves given to the world so much as you have done, have an especial 

 right to expect much; since their combinations have largely aug- 

 mented the number of connecting points ; yet I believe that when 

 you executed your great work on Africa, in 1822, you could hardly 

 have expected so many accessions as we have now received. " The 

 knowledge acquired is, indeed, often only that of rivers, their direc- 

 tion, their branches, and the various synonyms by which they are 

 called in dialects belonging to different families of languages; but 

 rivers reveal to us by their course the form of the surface of the 

 earth, and are at once the nourishers of vegetation, the channels of 

 intercourse between men, and pregnant with unknown influences on 

 the future. 



The northerly course of the White Nile, and the south-easterly 

 course of the great Goschop, would indicate that a swelling of the 

 ground separates the domains or basins of these rivers. We know, 

 indeed, but imperfectly, how such a swelling or elevation may be con- 

 nected with the mountains of Habesch, and in what manner it may be 

 continued southward beyond the Equator. Probably, and this is also 

 the opinion of my friend Carl Hitter, the Lupata mountains, which, 

 according to the excellent Wilhelm Peters, extend to 26 S. latitude, 

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