514 CAUSES OF AELDITY AND MOISTURE. 



biy this lake is the watershed between the Zambesi and the Nile, 

 as Lake Dilolo is that between the Leeba and Kasai. But, how- 

 ever this may be, the phenomena of the rainy season show that 

 it is not necessary to assume the existence of high snowy mount- 

 ains until we get reliable information. This, it is to be hoped, 

 will be one of the results of the researches of Captain Burton in 

 his present journey. 



The original valley formation of the continent determined the 

 northern and southern course of the Zambesi in the centre, and 

 also of the ancient river which once flowed from the Linyanti 

 basin to the Orange River. It also gave direction to the southern 

 and northern flow of the Kasai and the Nile. We find that be- 

 tween the latitudes, say 6° and 12° S., from which, in all proba- 

 bility, the head waters of those rivers diverge, there is a sort of 

 elevated partition in the great longitudinal valley. Presuming 

 on the correctness of the native information, which places the 

 humid region to which the Nile and Zambesi probably owe their 

 origin within the latitudes indicated, why does so much, more 

 rain fall there than in the same latitudes north of the equator? 

 Why does Darfur not give rise to great rivers, like Londa and 

 the country east of it ? The prevailing winds in the ocean 

 opposite the territory pointed out are said to be from the N.E. 

 and S.E. during a great part of the year ; they extend their 

 currents on one side at least of the equator quite beyond the 

 middle of the continent, and even until in Angola they meet the 

 sea-breeze from the Atlantic. If the reader remembers the 

 explanation given at page 109,* that the comparative want of 



* Since the explanation in page 109 was printed, I have been pleased to see the 

 same explanation given by the popular astronomer and natural philosopher, M. 

 Baliinet, in reference to the climate of France. It is quoted from a letter of a 

 correspondent of the Times in Paris : 



" In the normal meteorological state of France and Europe, the west wind, 

 which is the counter-current of the trade-winds that constantly blow from the east 

 under the tropics — the west wind, I say, after having touched France and Europe 

 by the western shores, re-descends by Marseilles and the Mediterranean, Constanti- 

 nople and the Archipelago, Astrakan and the Caspian Sea, in order to merge again 

 into the great circuit of the general winds, and be thus carried again into the equa- 

 torial current. Whenever these masses of air, impregnated with humidity during 

 their passage over the ocean, meet with an obstacle, such as a chain of mountains, 

 for example, they slide up the acclivity, and, when they reach the crest, find them- 



