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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



enjoying its full measure of prosperity ; there is 

 even a little steamboat for navigating the lake 

 and checking the slave-trade throughout this 

 whole region. Then there are Lakes Baringo and 

 Manyara, the one lying north, the other south of 

 Kilimandjero and Kenia, whose snowy peaks at- 

 tain an elevation of over 6,000 metres. In no 

 other portion of the globe do we find so many 

 inland seas, every one of which is admirably fitted 

 to beccme a centre of civilization. It is a second 

 Switzerland, but with gigantic proportions. Even 

 in antiquity it was known that the Nile had its 

 source in lakes situated in the heart of the con- 

 tinent. Marinus of Tyre and Claudius Ptolemy, 

 who lived in the second century after the Chris- 

 tian era, learned from Arab traders of the exist- 

 ence of two lakes, whose site they fixed in the 

 parallel of the island of Menuthias, now Zanzibar 

 — a very precise determination of its true locality. 

 The " Tabula Alinamuniana," of the year 833, 

 and the chart of Abul Hassan, of tbe year 1008, 

 indicate two lakes ; while the " Tabula Rotunda 

 Rogeriana," of 1154, and the chart of P. Assianus, 

 show three lakes answering closely enough to 

 Lakes Albert, Victoria, and Tanganyika ; ] but it 

 is only within the last twenty years, thanks to the 

 discoveries of Grant, Burton, Speke, and Living- 

 stone, that we have been enabled to demonstrate 

 the exactitude of these ancient indications. Ge- 

 ographers were beginning to call them in question, 

 and compilers of maps who were sticklers for 

 positive data left the whole central region of 

 Africa blank. 



From this central plateau, so admirably con- 

 stituted from the hydrographic point of view, de- 

 scend some of the mightiest rivers on the globe. 

 From its source to the Mediterranean the Nile 

 measures 3,900 kilometres in a straight line, and 

 hence its actual length is greater than that of the 

 Mississippi or the Amazon. It is a most singu- 

 lar river : in its upper portion it branches out in 

 all directions, and is fed by innumerable lakes 

 and affluents ; then, after receiving in Nubia the 

 Atbara, which comes down from the high land of 

 Abyssinia, it courses through an absolute desert, 

 without so much as a single rill bearing to it the 

 tribute of its water. According to Sehweinfurth's 

 calculation, the river-basin of the Nile comprises 

 8,260,000 square kilometres, while that of the 

 Amazon comprises only 7,000,000, and that of 



1 See the excellent summary of our knowledge concern- 

 ing Africa by Dr. Josef Chavaune, in the MittheiJungen 

 of the Vienna Geographical Society, " Central Africa nach 

 dem pepenwartigen Stande der geographischen Kent - 

 nisse, 11 1876. 



the Mississippi hardly 3,000,000 ; and soon Gor- 

 don's lieutenants will unfurl the Egyptian flag over 

 this immense territory. The Congo surpasses the 

 other rivers in the enormous volume of water 

 which it pours into the Atlantic Ocean. At its 

 mouth it is 2,950 metres wide, with the simply in- 

 credible depth of from 380 to 400 metres. Its 

 current flows at the rate of 7 kilometres per hour, 

 and its discharge (51,000 cubic metres per second) 

 is so enormous, that the river becomes entirely 

 lost in the sea only at the distance of 100 kilo- 

 metres beyond the shore-line, and at the distance 

 of 12 kilometres the water is still perfectly fresh. 

 This discharge, which is 200 times greater than 

 the flow of water in the bed of the Seine at Paris, 1 

 is nearly constant, a fact which appears to show 

 that the river receives affluents from both sides 

 of the line, drawing now upon those to the north, 

 again on those to the south, as both are alternate- 

 ly swollen by the rains in their respective zones. 

 The expedition of the brave and unfortunate 

 Tuckey in 1816 resulted in tracing the Congo only 

 as far as the Falls of Jelala, and since his time 

 no one had penetrated any farther. The dis- 

 coveries of Cameron now appear to have removed 

 all doubt as to the identity of the Congo with 

 the Lualaba, and hence its source must be the 

 river Tchambesi in the Bemba country of Living- 

 stone, situated between Lakes Nyassa and Tan- 

 ganyika, and not far from the sources of the 

 Nile. 



The Zambesi is the third of the great arteries 

 which descend from Cential Africa. Its course 

 was determined by Livingstone. It is not so long 

 as the Nile, and it has a less volume of water 

 than the Congo, but it presents more picturesque 

 views. Issuing from Lake Dilolo, as the Leeba, it 

 flows south, passing through the Makololo coun- 

 try, where it is known as the Leeamby, and 

 then, after receiving the Chobe, which comes 

 from the west, it reaches the granite plateau 

 of the Batokas. Here, precipitating from a 

 height of 450 metres, through a narrow rift 

 in the rock's, its waters, which before had been 

 spread abroad, it forms the famous cascade ap- 

 propriately named by the natives Mosiwatunya, 

 i. e., Thunder-Smoke, but for which Livingstone 

 substituted the more trivial title of Victoria Falls. 



» At low-water level the debit of the Seine is only 90 

 cubic metres per second : the mean debit is 250 cubic 

 metres. On March 17. 1876, when the river was at its 

 greatest height, it did not exceed 1,050 cubic metres at the 

 Pont-Royal. To equal the Congo, therefore, we should 

 have to combine 200 rivers like the Seine ; that is to say, 

 all the rivers of Europe taken together would hardly suf- 

 fice. 



