16 NATURAL FEATURES OF AFRICA. 



Himmaleh, those stupendous heights of America and Asia, 

 as they traverse these continents in the direction of their 

 length, cover a much greater surface, and thus create ferti- 

 lity in the more limited plains which intervene between the 

 mountains and the ocean. But the largest of the African 

 rivers, directing their course through a vast extent of low 

 land, reach the sea only by a very circuitous course. Se- 

 veral of them, too, diffusing their waters into lakes or 

 marshes, expire in the very heart of the continent. The 

 result is, that the enormous breadth of the Sahara, or Great 

 Desert, is scarcely irrigated even by a streamlet. It depends 

 entirely on the periodical rains ; and these sink into the 

 sandy and porous surface, till being arrested at the depth of 

 eight or ten feet, they form that " sea under ground" which 

 has been traced over a large portion of the waste. 



Vegetable life, in consequence of this absence of mois- 

 ture, is scantily diffused over a great extent of the conti- 

 nent. In the heart of the mountains, however, and in the 

 kingdoms along their border, the soil is most profusely wa- 

 tered, and, under the influence of a tropical sun, produces, 

 perhaps, beyond any other part of the world, that luxuriant 

 growth and those gigantic vegetable forms, which distin- 

 guish the equatorial regions. The baobab, or great cala- 

 bash, appears to be the most enormous tree on the face of 

 the earth. Adanson assures us, that the circumference in 

 some cases is equal to thirteen fathoms, as measured by 

 his arms clasped round the trunk, that is, varymg from 

 seventy-four to seventy-seven feet. Branches extending 

 horizontally from the trunk, each equal to a large tree, make 

 the baobab a forest as it were in itself. The mangrove, 

 too, which rises on the borders of rivers, or inundated spots, 

 diffuses itself in a manner truly remarkable. The branches, 

 dropping down upon the watery bank, strike root and grow ; 

 hence the original plant, spreading farther and farther, 

 forms over the stream a species of natural arcade. Tj^se 

 mighty trees do not stand alone, but have their inten^rces 

 filled up by numberless shrubs, canes, creeping and pa- 

 rasitical plants, which intersect and entwine with each 

 other till they form a thick and impenetrable mass of un- 

 derwood. To cut even a narrow path through these dense 

 forests is a laborious process ; and as shoots are continually 

 protruding inwards on each side, the track, without constant 



