CAUSES OF ARIDITY AND MOISTURE. 443 



The southern end of this lake is ten days north-east of 

 the town of Cazembe ; and as that is probably more 

 than five days from Shmte, we cannot have been nearer 

 to it than 150 miles. Probably this lake is the watershed 

 between the Zambesi and the Nile, as Lake Dilolo is that 

 between the I,eeba and Kasai. But however this may 

 be, the phenomena of the rainy season show that it is 

 not necessary to assume the existence of high snowy 

 anountains, 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 deter- 

 mined the northern and southern course of the Zambesi 

 in the centre, and also of that 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 between the 

 latitudes, say 6° and 12 S., from which, in all probability, 

 the head waters of these rivers diverge, there is a sort of 

 •elevated partition in the great longitudinal valley. Pre- 

 suming 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, 

 <mite 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 

 94,* that the comparative want of rain on the Kalahari 



* Since the explanation in page 94 was printed I have been 

 pleased to see the same explanation given by the popular astronomer 

 and natural philosopher M. Babinet, 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 con- 

 stantly 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, Constantinople and the 



