250 Mr. Colebrooke on the 
cirrhus, in all respects but elevation and extent. The inference 
is, that in their structure and nature they are alike. 
The periodical winds of South Africa are deducible from the 
trade-winds of the ocean. 
In the southern Atlantic, at the extremity of South Africa, 
the winds are periodical, consonant during summer to the south- 
east trade, which constantly blows on each side of the promon- 
tory; but conforming in winter with the western wind that 
prevails at all times in the southern ocean. In other words, 
the fluctuating boundary of the western current of air touches 
upon the extremity of the African continent in winter, and re- 
cedes from it in summer. 
It is this alternation of easterly and westerly winds, or of 
a south-eastern and a north-western monsoon, that determines 
the climate and seasons of the Cape of Good Hope. But the 
alternate monsoons of South Africa are confined to its extre- 
mity. The western wind touches upon a small portion of the 
continent, near its termination. Beyond that is the domain of 
perpetual south-eastern winds over the seas on either side, and 
the intermediate tract of land is unrefreshed by rain, or by north- 
ern winds which should bring it, and presents a parched desert. 
The interior of South Africa, according to the testimony of 
every person who has visited it, is aridin the extreme. 
Short of that barren tract, the Karroo plains, with a soil ca- 
pable of fertility, were it watered, are steril for want of season- 
able rain. They occupy the middle of the colony of the Cape. 
Encompassed by high mountains, they receive no benefit from 
the humidity which western winds bring from the Atlantic, or 
southern from the Indian ocean, or, without looking so far for 
its source, from the shallow sea over the Lagullas Bank. The 
moisture of those winds is intercepted by a double chain of 
lofty mountains. The barrier is continuous; and wind that 
passes over the summit of the western chain, has been stripped 
of its condensible moisture on the eastern side, and furnishes 
neither rain nor mist to supply a rivulet or a fountain on the 
inland side. Now and then a thunder-storm occurs, accompa- 
nied with hail, or with summer rain; and the only refreshing 
