The foils, in general, on this trad of country, are either of
ftiff clay, into which there is no poffibility of entering with a
plough till well foaked by heavy rains, or of a light and fandy
nature, commonly of a reddilh tinge, and abounding with fmall
round quartzofe pebbles. Seldom any free black vegetable
mould appears except in the fmall patches of garden ground,
vineyards, and/orchards that furround the habitations, where,
by long culture, manure, and the fertilizing influence of fprings
or a permanent rill of water, the foil is fo far mellowed as to
admit the ipade at all feafons of the year.
But thofe vaft plains, which are known in the colony by the
Hottentot name of Karroo, and which are interpofed between
the great chains of mountains, wear a ftill more difmal appearance
than the lower plains that are chequered with patches of
cultivated ground. Out of their impenetrable furfaces of clay,
glittering with fmall chryftals of quartz, and condemned to perpetual
drought and aridity, not a blade of grafs, and fcarcely a
verdant twig, occurs to break the barren uniformity. The hills,
by which the furface of thefe plains are fometimes broken, are
chiefly compofed of fragments of blue flate, or mafles of felt-
fpar, and argillaceous ironftone ; and the furfaces of thefe are
equally denuded of plants as thofe of the plains.
Yet as I have already had occafion to obferve, wherever the
Karroo plains are tinged with iron, and water can be brought
upon them, the foil is found to be éxtremely produttive. Thè
fame effe& is obfervable in the neighbourhood of the Cape,
where the foil is coloured with iron; or where mafles of a
! brown
brown ochraceous ftone (the oxyd of iron combined with clay)
lie juft below the furface, where they are fometimes found in
extenfive fl-rata. In fuch fituations they have the beft grape*
and the beft of every ibrt of fruit, which may be owing, probably,
to the manganefe that this kind of dark brown ironftone
generally contains, and which modern diicoveries in che-
miftry have afcertained to be particularly favourable to the
growth of plants.
There is neither a volcano nor a volcanic produit in the
fouthern extremity of Africa, at leaft in any of thofe parts
where I have been, nor any fubftances that feem to have undergone
the adion of fire, except mafles of iron-ftone found generally
among the boggy earth in the neighbourhood of fome
of the hot fprings, and which appear like the fcori* of furnaces
Pieces of pumiee-ftone have been picked up oh the fliore of
Robben Ifland, and on the coaft near Algoa Bay, which muff;
have been wafted thither by the waves-, as the whole bafts of
this ifland is a hard and eompad blue fehiftus, with veins of
quartz running through it, and of the eaffierh coaft iron-ftone
. and granite. - ,
The Climate of the Gape may be confidered as riot unfriendly
to vegetation ; but by reafon of its fituàtion, within the influence
of a kind of Monfoon or periodical winds, the rains are
very unequal, defcending in torrents during the cold feafon,
whilft fcarcely a ihower falls to refreih the earth in the hot
fummer months, when-the dry fouth-eaft winds prevail. Th'efé1
winds blaft the foliage,- bloflom, and .fruit of all thofe trees that
VOX. IX. Uu Uu are