SOUTHERN AFRICA. 
lOI 
fiderable diftance from the fummit, covered with fnow. Thefe 
mountains were apparently compofed of the fame materials as 
thofe already palTed ; but the detached hills, near their bafe, 
confifted entirely of that fpecies of rock called by Mr. Kirwan 
the amygdaloid^ which is nearly allied to the ftone that the 
miners of Derbyfhire have diftinguifhed by the name of toad- 
Jione. The rounded pebbles, embedded in this argillaceous 
matrix, were almoft invariably tinged with a bright grafs-green 
color. The fubftratum of the mountains ftill continued to be 
a blue and purple-colored fchiftus* 
Having completed our flock of provifions, and procured 
from the inhabitants of Zwarteberg the loan of fixty flout bul- 
locks, we once more launched upon the wide defert, and pro- 
ceeded, on the twenty-third, near thirty miles to a fpring of 
water called the Sleutel fonteyn^ and the following day encamped 
on the banks of the Traka or Maiden river. The little water 
it contained was both muddy and fait, and the fand on its banks 
was covered with a thin pellicle of nitre out of which was 
growing abundance of the falfola before mentioned.. 
At fun- rife this morning the thermometer was down to five 
degrees below the freezing point. This great diminution of 
temperature appeared the more extraordinary, as no change, 
either in the diredion or the ftrength of the wind, had taken 
place. The air was clear and ferene, without a cloud in the 
fky, and the weather apparently the fame it had been for feve- 
ral days in every refpe£t, except in the degree of temperature. 
The fnow on the mountains could have had little influence. 
The 
