2 July, 1812. GEOLOGY OF THE TRANSGARIEPINE. 
311 
stratum below it, I had no opportunity of discovering ; but am 
inclined to suppose it to be of great thickness. It lies every where 
in a horizontal position ; and in no place rises into hills, or above the 
general level of the country. I could not observe in its structure, the 
slightest appearance of stratification, nor have I ever seen, in any 
part of the Interior, the smallest trace of organic remains. It pro- 
bably forms the foundation of the whole land of the Transgariepine ; 
as far at least as the line of my travels extended ; and may be consi- 
dered as the great floor, upon which apparently all the mountains are 
placed ; and upon which a superstratum of sand forms those immense 
plains which occur almost every where throughout these regions. The 
depth of this sand appeared very unequal ; in some parts it is scarcely 
a foot : in many places the denuded rock itself forms the surface. 
It would seem that the abundance of springs depends on the 
proximity of this rock to the surface, or, in other words, on the less 
quantity of sand which covers it : for in those parts of the country 
where I have observed it near the surface, springs have more generally 
been met with ; and in those where it is not visible, and where 
immeasurable plains of deep sand extend for many leagues, there the 
land is totally deficient in water. The fact explains itself: the water 
which falls from the clouds quickly sinks through the sand ; and 
wherever springs flow out of the soil, or permanent ponds are found, 
it is evident that there must lie beneath them a stratum of compact 
rock, which prevents their being absorbed by the earth. This I 
believe, from many observations, to be the case in the Great Plains 
of Litakun ; and the numerous springs or ponds of clear water which 
are there met with seem to confirm this hypothesis. 
On this great floor of li?ne-stone rest, probably, the mountains of 
clay-slate, or of sand-stone. Green-stone, and sometimes serpentine 
or pot-stone, and granite, are found ; though rarely, and in small pro- 
portions. The bed on which these repose could not be ascertained ; 
but it seems not unlikely that it is the same primitive lime-rock, 
unless we adopt the supposition hereafter noticed on the i3th. The 
remarks in my journal are here anticipated, in order to give, pre- 
viously to entering these regions, some idea of their nature. 
