FOSSII, TREES. 565 



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 con- 

 centric 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 containing 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 imbedded exactly like those now seen on the 

 sea-beach, but I never could find a shell. There are many 

 nodules and mounds of hardened 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 has been stated, there once existed silver- 

 mines. The general rock is the grey, soft sandstone I 

 have mentioned, but at the rivulet Bangue, we come upon 

 a dyke of basalt six yards wide, running north and south. 

 When we cross this, we come upon several others, some of 

 which run more to the eastward. The sandstone is then 

 found to have been disturbed, and at the rivulet called 

 Nake we found it tilted up and exhibiting a section which 

 was coarse sandstone above, sandstone-flag, shale, and 

 lastly a thin seam of coal. The section was only shown 

 for a short distance, and then became lost by a fault made 

 by a dyke of basalt, which ran to the E.N.EJ. in the 

 direction of Chicova. 



This Chicova is not a kingdom, as has been stated, but 

 a level tract, a part of which is annually overflowed by 

 the Zambesi, and is well adapted for the cultivation of 

 corn. It is said to be below the northern end of the hill 

 Bungwe. I was very much pleased in discovering this 

 small specimen of such a precious mineral as coal. I saw 

 no indication of silver, and, if it ever was worked by the 

 natives, it is remarkable that they have entirely lost the 

 knowledge of it, and cannot distinguish between silver 



