impenetrable thicket to moft animals except the rhinoceros,
whofe hide, though not proof againft a muiket-ball, as has
been afferted by a great naturalift, has little to fear from the
fpines o f the mimofa. The bark, being powerfully aftringent,
is preferred to that of any other tree in the colony for preparing
leather from raw ikins; and the wood, being hard and
tough, is ufed for waggon-poles, and as lock-ihoes for the
wheels. The trunk of the tree gives out great quantities of a
elear tranfparent gum, which, however, does not feem to have
been applied to any kind of ufe. It is remarkable that almoft
every tree which furnifhes taftelefs gums or refins is covered
with a bark that is highly aftringent and auftere to the tafte.
The following day we crofted the bed of the Buffalo river,
which was at leaft fifty yards in width; but the quantity of
water in it was barely fufficient to form a current. The deep
fhelving banks, however, and the wreck of roots and ihrubs,
indicated at leaft its periodical power, which had forced through
the black mountains to the fouthward a grand chafm in its paff-
age to the eaftern ocean. The whole furface o f the country
was here ftrewed over with fmall fragments of a deep purple-
colored flate, that had crumbled away from the ftrata which in
long parallel ridges lay in the direition o f eaft and weft.
Scattered among thefe fragments were black tumified ftones that
had much the appearance o f volcanic fluggs, or the fcorise of an
iron furnace. Several hills of the ihape of cones, fome truncated
near the top parallel to their bafes, flood detached from
each other on the plain, apparently thrown up by volcanic ex-
plofions; but a nearer view of the alternate ftrata o f earth and
fandfand
ftone, regularly difpofed in every part, ihewed them to be
the effed of water and not of fire. This part of the defert
was more fterile and naked than had yet occurred. Scarcely a
plant of any defcription threw its feeble leaves out of the
ilaty furface, except a few fpecies of the mefembryanthemum,
among which was one more luxuriant than, the reft, whofe
leather-like covering of its fleihy cylindrical leaves ferved our
Hottentots, when dried, for tinder.
About ten miles beyond the Buffalo river we encamped for
the night upon the banks of a fmall running brook called Geel-
beck, winding round a flat fandy marih overgrown with rufties,
and abounding with fprings whofe waters were ftrongly impregnated
with fait. All the naked fandy patches were thinly
fprinkled over with a fine white powdery fubftance not unlike
fnow: it was found in the greateft quantities where the cattle
of travellers had been tied up at nights; and it was obferved
almoft invariably to furround the roots of a fruitefcent plant
that grew here in great exuberance. I colleded a quantity of
this white powder, together with the fand, and by boiling the
folution and evaporating the water, obtained from it chryftals
of pure prifmatic nitre. A fmall proportion of a different alkaline
fait was alfo extraded from the liquor. The plant alluded
to was a fpecies of falfola, or falt-wort, with very minute
fleihy leaves dofely furrounding the woody branches. It is
known to the country-people by the Hottentot name of Canna,
and is that plant from the alhes of which almoft all the foap,
that is ufed in the colony, is made. Thefe allies, when carefully
burnt and colleded, are a pure white cauftic alkali, a
■ N 2 folution