Chap. XXIX. FOSSIL TREES. 603 



identical with that of the Nile. It would not be influenced by 

 any streams in the Kalahari, for there, as in a corresponding part 

 of the Nile, there would be no feeders. It is to be remembered 

 that the great ancient river which flowed to the lake at Boochap 

 took this course exactly, and probably flowed thither until the 

 fissure of the falls was made. 



This flood having filled the river, we found the numerous rivu- 

 lets which flow into it, filled also, and when going along the Zam- 

 besi, we lost so much time in passing up each little stream till 

 we could find a ford about waist-deep, and then returning to the 

 bank, that I resolved to leave the river altogether, and strike 

 away to the S.E. We accordingly struck off when opposite the 

 hill Pinkwe, and came into a hard Mopane country. In a hole 

 of one of the mopane-trees, I noticed that a squirrel (Seiurus 

 cepapi) had placed a great number of fresh leaves over a store 

 of seed. It is not against the cold of winter that they thus lay 

 up food, but it is a provision against the hot season, when the 

 trees have generally no seed. A great many silicified trees are 

 met with lying on the ground all over this part of the country ; 

 some are broken off horizontally, and stand upright ; others are 

 lying prone and broken across into a number of pieces. One was 

 4 feet 8 inches in diameter, and the wood must have been soft 

 like that of the baobab, for there were only six concentric rings 

 to the inch. As the semi-diameter was only 28 inches, this large 

 tree could have been but 168 years old. I found also a piece of 

 palm-tree transformed into oxide of iron, and the pores filled with 

 pure silica. These fossil trees He upon soft grey sandstone con- 

 taining banks of shingle, which forms the underlying rock of the 

 country all the way from Zumbo to near Lupata. It is met with 

 at Litubaruba and in Angola, with similar banks of shingle im- 

 bedded exactly like those now seen on the sea-beach, but I never 

 could find a shell. There are many nodules and mounds of hard- 

 ened clay upon it, which seem to have been deposited in eddies 

 made round the roots of these ancient trees, for they appear of 

 different colours in wavy and twisted lines. Above this, we have 

 small quantities of calcareous marl. 



As we were now in the district of Chicova, I examined the 

 geological structure of the country with interest, because here, it 

 lias been stated, there once existed silver-mines. The general 



