42 TRAVELS IN 
plain, apparently liirown up by volcanic explosions ; but a 
nearer view of the alternate strata of earth and sand-stone, 
regularly disposed in every part, shewed them to be the quiet 
deposition of water rather than the violent ejection of subter- 
ranean fire, 'i'his part of the desert was more sterile and 
naked than any which had yet occurred. Scarcely a plant of 
any description threw its feeble leaves out of the slaty sur- 
face, except a lew species of the mesembryanthemum, among 
which was one more luxuriant than the rest, whose leather- 
like covering of its fleshy cylindrical leaves served our Hot- 
tentots, vvlicn dried, for tinder. 
About ten miles beyond the Buffalo river we encamped for 
the niglit upon the banks of a small running brook called Geel- 
beck, winding round a flat sandy marsh overgrown with rushes, 
and abounding with springs whose waters were strongly im- 
pregnated with salt. All the naked sandy patches were thinly 
sprinkled over with a fine white powdery substance not unlike 
snow : it was found in the greatest quantities where the cattle 
of travellers had been tied up at nights ; and it was observed 
almost invariably to surround the roots of a fruitescent plant 
that grew here in great exuberance. I collected a quantity of 
this white powder, together with the sand, and, by boiling the 
solution and evaporating the water, obtained from it chrystals 
of pure prismatic nitre. A small proportion of a different 
alkaline salt was also extracted from the liquor. The plant 
alluded to was a species of salsola, or salt-wort, with very mi- 
nute fleshy leaves closely surrounding the woody branches. 
It is known to the country-people by the Hottentot name of 
CoMua and is that plant from tlie ashes of which almost all, 
