Geologically considered, the oldest formation is found in the northern part of the tableland and toward the northeastern end of the Quathlamba Mountains. The principal formations in this region are granite and gneiss, believed to be of great antiquity—probably of the same age as the Laurentian formations in America. The rocks of the Karoo district are not so ancient. There are no traces anywhere in South Africa of late volcanic action, nor has any active volcano been discovered there; but eruptive rocks of ancient date—porphyries and greenstones—are found overlying the sedimentary deposits in the Karoo district and in the mountain systems of Basutoland and the Orange Free State. The African coast is notably poor in harbors. There is no haven between Cape Town and Durban. From Durban to the Zambesi there are but two good ports—that of Delagoa Bay and Beira. With the exception of Saldanha Bay, twenty miles north of Cape Town, the western coast, for a thousand miles, has no harbor. The temperature in Southern Africa is much lower than the latitude would lead one to expect. This is accounted for by the fact that there is a vast preponderance of water in the southern hemisphere, which has the effect of giving a cooler temperature than prevails in a corresponding northern latitude. The difference in both heat and cold represents over two degrees of difference in latitude. Thus, Cape Town, 34° S., has a lower temperature in both summer and winter than Gibraltar and Aleppo, in 36° N. Nevertheless, the thermometer registers high in some parts of South Africa. Even at Durban, in latitude 30° S., the heat is often severe, and the northern part of the Transvaal and the British territories to the north of it lie within the Tropic of Capricorn. The mean temperature in South Africa proper is 70° Fahrenheit in January and 80° in July. Over most of the country the climate is exceptionally dry. In the region of Cape Colony there are well-defined summer and winter; but in the rest of South Africa for about two-thirds of the year there is only a dry season, when the weather is cooler, and a wet season of four or five months, when the sun is the highest and the heat is most intense. The rainy season is not so continuous, nor is there so great a precipitation, as in some other hot countries. In the parts where the rainfall is heaviest, averaging over thirty inches in the year, the moisture soon disappears by evaporation and absorption, and the surface remains parched till the next wet season. As a consequence of this the air is generally dry, clear and stimulating.