Climate of South Africa. 247 
observations should be taken as near as may be practicable to 
the mountain. At the distance of a mile or two, a different de-. 
gree of dryness may be found. 
A mountain, being colder than the plain below, condenses, and 
renders visible the passing vapour, whenever the dryness of the 
wind is less than the difference of temperature between its sum- 
mit and base. Owing to. radiation, the influence of the moun- 
tain’s summit extends to the column of air over it, and a cloud 
at rest is accordingly often seen suspended high above. 
The heat of the plain has a like influence on the atmosphere 
over it, and affects the temperature immediately above. The 
vapour then, as it quits the mountain, passes into a warmer 
region, where itis dissolved, and which thus it traverses, trans- 
parent and invisible, to be again condensed, and made apparent 
on approaching another mountain. 
This, as I conceive, is the simple explanation of the appear- 
ances which are so conspicuous during the continuance of a 
strong south-east wind at the Cape. Volumes of vapour are 
seen rolling over the summits and down the sides of Hanglip, 
Hottentots’ Holland, and the rest of the chain of high mountains. 
Above the valleys, and over the isthmus, scarcely a passing 
cloud is seen. But the vapour is thickly condensed on the 
peninsular group of mountains, rolls over their summits, 
descends to a certain distance down the cliffs, and is dissipated 
and becomes ffansparent as it passes onwards. 
The wind, fed by cold and damp, descending from the moun- 
tains, blows with great violence, approaching to tempestuous 
force. But it is partial, and extends to no distance from the 
shore. It is the boisterous rush of colder air, to replace 
warmer, in a fervent atmosphere, over an intensely heated land. 
On the windward brow of the mountain, the breeze is moderate ; 
on the lee side, the blast is strong; at sea, a mile from the 
shore, there is calm. 
In fact, both the south-east and the west winds are, to the pro- 
montory terminating South Africa, sea-breezes; and the south- 
east wind has not parted with that character in a short and 
rapid passage across the promontory. The parched earth 
