1668.] RAINFALL IN AFRICA. 323 



shower, and it and another on the evening of the second 

 were quite partial. 



[As we shall see, he takes advantage of his late experi- 

 ence to work out an elaborate treatise on the climate of this 

 region, which is exceedingly important, bearing, as it does, 

 upon the question of the periodical floods on the rivers 

 which drain the enormous cistern-lakes of Central Africa.] 



The notion of a rainy zone, in which the clouds deposit 

 their treasures in perpetual showers, has received no con- 

 firmation from my observations. In 1866-7, the rainfall 

 was 42 inches. In 1867-8, it amounted to 53 inches : 

 this is nearly the same as falls in the same latitudes 

 on the West Coast. In both years the rains ceased 

 entirely in May, and Avith the exception of two partial 

 thunder showers on the middle of the watershed, no rain 

 fell till the middle and end of October, and then, even in 

 November, it was partial, and limited to small patches of 

 country; but scarcely a day passed between October and 

 May without a good deal of thunder. When the thunder 

 began to roll or rumble, that was taken by the natives as 

 an indication of the near cessation of the rains. The middle 

 of the watershed is the most humid part : one sees the 

 great humidity of its climate at once in the trees, old and 

 young, being thickly covered with lichens; some flat, on 

 the trunks and branches ; others long and thready, like the 

 beards of old men waving in the wind. Large orchids on the 

 trees in company with the profusion of lichens are seen no- 

 where else, except in the mangrove swamps of the sea-coast. 



I cannot account for the great humidity of the watershed 

 as compared with the rest of the country, but by the pre- 

 vailing winds and the rains being from the south-east, and 

 thus from the Indian Ocean : with this wind generally on 

 the surface one can observe an upper strong wind from the 



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