SOUTHERN AFRICA. 41 
pointing in every direction " like quills upon the fretful por- 
cupine," it becomes an impenetrable thicket to most animals 
except the rhinoceros, whose hide, though not proof against a 
musket-ball, as has been asserted by some naturalists, has little 
to fear from the spines of the mimosa. The bark, being power- 
fully astringent, is preferred to that of any other tree in the 
colony for preparing leather from raw skins ; and the wood, 
being hard and tough, is used for waggon-poles, and as lock- 
shoes for clogging the wheels in steep roads. The trunk 
of the tree yields large quantities of a clear transparent 
gum, which, however, does not seem to have been applied to 
any kind of use. It may be remarked that almost every 
tree, which furnishes tasteless gums or resins, is covered with 
a bark that is highly astringent and austere to the taste, 
-The following day we crossed the bed of the Buffalo river, 
which was at least fifty yards in width ; but tlie quantitj^ of 
water in it was barely sufficient to form a current. The deep 
shelving banks, however, and the wreck of roots and shrubs, 
indicated at least its periodical power, which had forced through 
the black mountains to the southward a grand chasm in its pass- 
age to the eastern ocean. The whole surface of the country 
was here strewed over with small fragments of a deep purple- 
colored slate, that had crumbled away from the strata which 
in long parallel ridges lay in the direction of east and west. 
Scattered among these fragments were black stones, whose 
surfaces w^ere blistered or tumefied, not unlike in appearance 
to volcanic slaggs, or the scoriae of an iron furnace. Several 
hills of the shape of cones, some truncated near the top pa- 
rallel to their bases, stood detached from each other on the 
