324 LIVINGSTONE'S LAST JOURNALS. [Chap. XII. 



north-west, that is, from the low humid West Coast and 

 Atlantic Ocean. The double strata of winds can easily be 

 observed when there are two sheets of clouds, or when 

 burning grass over scores of square miles sends up smoke 

 sufficiently high to be caught by the upper or north-west 

 wind. These winds probably meet during the heavy rains : 

 now in August they overlap each other. The probability 

 arises from all continued rains within the tropics coming in 

 the opposite direction from the prevailing wind of the year. 

 Partial rains are usually from the south-east. 



The direction of the prevailing wind of this region is well 

 marked on the islands in Lake Bangweolo : the trunks are 

 bent away from the south-east, and the branches on that side 

 are stunted or killed ; while those on the north-west run out 

 straight and make the trees appear lopsided. The same 

 bend away from the south-east is seen on all exposed situa- 

 tions, as in the trees covering the brow of a hill. At 

 Kizinga, which is higher than the Lake, the trees are 

 covered with lichens, chiefly on the south-east sides, and 

 on the upper surfaces of branches, running away horizon- 

 tally to or from the north-west. Plants and trees, which 

 elsewhere in Africa grow only on the banks of streams 

 and other damp localities, are seen flourishing all over 

 the country : the very rocks are covered with lichens, and 

 their crevices with ferns. 



But that which demonstrates the humidity of the climate 

 most strikingly is the number of earthen sponges or oozes 

 met with. In going to Bangweolo from Kizinga, I crossed 

 twenty-nine of these reservoirs in thirty miles of latitude, on 

 a south-east course: this may give about one sponge for 

 every two miles. The word " Bog " conveys much of the 

 idea of these earthen sponges ; but it is inseparably con- 

 nected in our minds with peat, and these contain not a par- 

 ticle of peat, they consist of black porous earth, covered 

 with a hard wiry grass, and a few other damp-loving plants. 



