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THE PROGRESSIVE DESICCATION OF AFRICA 

 THE CAUSE AND THE REMEDY. 



By E. H. L. SCHWARZ, A.R.C.S., F.G.S. 



(With eight text figures.) 



That Africa is drying up is a fact that is as apparent in 

 the north as in the south of the continent. In the north within 

 the historic period there was a vast population living where 

 now the desert sand drives over the land. In the south the 

 forefathers of the present generation have left records of 

 forests, lakes and running rivers where to-day there are 

 practically desert — or at least Karroo — conditions. The two 

 great central reservoirs, Lake Chad for North Africa and 

 Lake Ngami for South Africa, are the insignificant remnants 

 of vast sheets of water, the old terraces of which are still to 

 be seen like those of Lakes Lahontan and Bonneville, in 

 North America. Even within the short period during which 

 these regions have been visited by white men they have shrunk 

 very considerably. This drying up is due to the fact that 

 Africa stands at a great height above sea-level as a plateau, 

 with an elevated edge bordering the sea; this edge I shall 

 call the Coastal Rampart.* Inland, great rivers once 

 traversed the continent, yielding fertility to all the lands 

 adjoining, but the short coast streams, rising in the mountains 

 along the edge, having precipitous courses to the sea and 

 consequently great tearing or erosive power, have cut back 

 into the inland basin and have drawn off the waters. Then 

 the rain falling in the area of the inland plateau, instead of 

 collecting in rivers which flowed placidly through the continent 

 amid plains covered with luxuriant vegetation, was drawn off 

 in the rocky channels of the coast streams and was hurried to 

 the sea. This process is still going on and every year more 

 territory is gained by the coast streams at the expense of the 

 inland system. The study of the cause of the progressive 

 desiccation of Africa resolves itself, therefore, into a study of 

 the river svstem, which, as I shall show, consisted origfinally 

 of four main streams, three flowing from the centre northwards 



* Livingstone, in his "' Missionary Travels." p. 474, describes how 

 on visiting Lake Dilolo on his return from St. Paul de Loando, he 

 came to regard Central Africa as an elevated trough, with a border 

 of mountain ranges. He was led awav from discovering the true 

 cause for the rivers being drawn away from this trough by a state- 

 ment bv Sir Roderick Murrhison. that the rents by which the rivers 

 escape have been suddenlv formed by volcanic upheavals. — President's 

 address, Royal Geographical Society, 1852, 



