POSTSCRIPT. ]xxxix 



potamus of South Africa bo of the same species with the hip- 

 popotamus of the Nile, how did that animal migrate from 

 North Africa to South, or from South Africa to North? The 

 old maps made such a migration almost impossible. There is 

 now, perhaps, no difficulty in our reply. The animal might 

 have found its way through the lakes and swamps of the great 

 table-land north of the Zambesi; and its tracks were seen by 

 Livingstone not far from the water-shed. 



5. Physical Geography. Strictly speaking, this cannot be 

 separated from the hydrography of the continent. The two 

 are connected as cause and consequence. But discovery sel- 

 dom follows the chronological order of nature : for we are 

 compelled to ascend from consequence to cause. It has long 

 been known to geographers that South Africa was bounded by 

 chains of mountains. One chain runs parallel to its western 

 coast and stretches northward far beyond the limits of our 

 Author's travels. In like manner the southern end of the 

 continent is bounded by mountains of considerable elevation. 

 And chains of mountains extend, almost continuously, parallel 

 to its eastern coast, and run to latitudes many degrees North 

 of the Zambesi. In the centre of South Africa is a great 

 plain — the Kalahari desert. Again, it was inferred, though 

 upon imperfect evidence, that high land extended across the 

 continent, somewhere to the North of the great river ; and 

 this high land appeared to connect the eastern and western 

 chains of South Africa. But the physical nature of this high 

 table-land was often hypothetically misrepresented in the old 

 maps of Africa. 



There were also reasons to believe that the low central por- 

 tions of South Africa — bounded by the high regions above 

 noticed — were once occupied by a great lake, which had its 

 probable issue somewhere about the latitude of the Orange 

 river. All the known geographical facts were admirably put 

 together, and the probable consequences drawn from them in 

 1852 by Sir R. I. Murchison, in his address to the Geographical 

 Society. Probable consequences and facts are not necessarily 

 in accordance ; but physical geographers have been delighted 

 to find that, in this instance, the logic had been good. For 



