While exploratory enterprises have been centred largely in tropical Africa, no part of the continent has been neglected. We now know that large areas of the Sahara are underlaid by waters which need only be brought to the surface to cover the desert around them with verdure; that most of the rain falling on the south slopes of the Atlas Mountains sinks into the earth to impermeable strata of rock, along which it makes its way far out into the desert; that where the surface is depressed so that these waters come near to it, there are wells for the refreshment of the camel caravans, and oases, blooming islands of green, in the sterile wastes; and that artesian wells bring inexhaustible supplies of water within reach, so that millions of date palms have been planted along the northern edge of the desert in southern Algiers and Tunis, making these regions the largest sources of the world's supply of dates. It has also been discovered why there are very large areas of dry or desert lands in Africa. The Sahara and the southwest of Africa are deserts because the prevailing winds, the carriers of moisture, blow towards the sea instead of away from it, and consequently are always dry. The winds from the Indian Ocean crossing the highlands of Abyssinia are wrung nearly dry while passing the mountains, and so Somaliland and the lowlands to the south of Abyssinia are parched. It has been found that the most of South Africa stands so high above the sea that the influences of a temperate climate are projected far towards the Equator; so that many white men, women, and children are living and thriving on farms in Mashonaland, seven degrees of latitude nearer the equator than the south end of Florida. This fact will profoundly influence the development of South Africa. It is to be the home of millions of the white race, the seat of a highly civilized empire, whose business relations with the rest of the world will be to the advantage of every trading nation. The presence of these millions of toilers will vitally affect the work of developing tropical Africa which is now absorbing such enormous treasure and energy; for South Africa is to be brought by railroads to the very doors of the tropical zone.