Whilst the general characteristics of the climate are as here outlined, in a country of so large an area as Cape Colony there are many variations in different districts. In the coast-lands the daily range of the thermometer is less marked than in the interior and the humidity of the atmosphere is much greater. Nevertheless, the west coast north of the Olifants river is practically rainless and there is great difference between day and night temperatures, this part of the coast sharing the characteristics of the interior plateau. The division of the year into four seasons is not clearly marked save in the Cape peninsula, where exceptional conditions prevail. In general the seasons are but two—summer and winter, summer lasting from September to April and winter filling up the rest of the year. The greatest heat is experienced in December, January and February, whilst June and July are the coldest months. In the western part of the colony the winter is the rainy season, in the eastern part the chief rains come in summer. A line drawn from Port Elizabeth north-west across the Karroo in the direction of Walfish Bay roughly divides the regions of the winter and summer rains. All the country north of the central mountain chain and west of 23° E., including the western part of the Great Karroo, has a mean annual rainfall of under 12 in. East of the 23° E. the plateaus have a mean annual rainfall ranging from 12 to 25 in. The western coast-lands and the Little Karroo have a rainfall of from 10 to 20 in.; the Cape peninsula by exception having an average yearly rainfall of 40 in. (see [Cape Town]). Along the south coast and in the south-east the mean annual rainfall exceeds 25 in., and is over 50 in. at some stations. The rain falls, generally, in heavy and sudden storms, and frequently washes away the surface soil. The mean annual temperature of the coast region, which, as stated, is 63° F. at Cape Town, increases to the east, the coast not only trending north towards the equator but feeling the effect of the warm Mozambique or Agulhas current.
On the Karroo the mean maximum temperature is 77° F., the mean minimum 49°, the mean daily range about 27°. In summer the drought is severe, the heat during the day great, the nights cool and clear. In winter frost at night is not uncommon. The climate of the northern plains is similar to that of the Karroo, but the extremes of cold and heat are greater. In the summer the shade temperature reaches 110° F., whilst in winter nights 12° of frost have been registered. The hot westerly winds of summer make the air oppressive, though violent thunderstorms, in which form the northern districts receive most of their scanty rainfall, occasionally clear the atmosphere. Mirages are occasionally seen. The keen air, accompanied by the brilliant sunshine, renders the winter climate very enjoyable. Snow seldom falls in the coast region, but it lies on the higher mountains for three or four months in the year, and for as many days on the Karroo. Violent hailstorms, which do great damage, sometimes follow periods of drought. The most disagreeable feature of the climate of the colony is the abundance of dust, which seems to be blown by every wind, and is especially prevalent in the rainy season.
That white men can thrive and work in Cape Colony the history of South Africa amply demonstrates. Ten generations of settlers, from northern Europe have been born, lived and died there, and the race is as strong and vigorous as that from which it sprang. Malarial fever is practically non-existent in Cape Colony, and diseases of the chest are rare.
(F. R. C.)
Geology.—The colony affords the typical development of the geological succession south of the Zambezi. The following general arrangement has been determined:—
Table Of Formations.
Post-Cretaceous and Recent.
| Cretaceous System | Pondoland Cretaceous Series Uitenhage Series | Cretaceous |
| Karroo System | Stormberg Series Beaufort Series Ecca Series Dwyka Series | Carboniferous |
| Cape System | Witteberg Series Bokkeveld Series Table Mountain Sandstone Series | Devonian |
| Pre-Cape Rocks | Includes several independent unfossiliferous formations of pre-Devonian age | Archaean to Silurian(?) |
The general structure of the colony is simple. It may be regarded as a shallow basin occupied by the almost horizontal rocks of the Karroo. These form the plains and plateaus of the interior. Rocks of pre-Cape age rise from beneath them on the north and west; on the south and east the Lower Karroo and Cape systems are bent up into sharp folds, beneath which, but in quite limited areas, the pre-Cape rocks emerge. In the folded regions the strike conforms to the coastal outline on the south and east.
Pre-Cape rocks occur in three regions, presenting a different development in each:—
| North. | West. | South. |
| Matsap Series | Nieuwerust Beds | Cango Beds |
| Ongeluk Volcanic Series | ||
| Griquatown Series | Ibiquas Beds | |
| Campbell Rand Series | ||
| Black Reef Series | ||
| Pniel Volcanic Series | ||
| Keis Series | ||
| Namaqualand Schists | Namaqualand Schists and Malmesbury Beds | Malmesbury Beds |