It is interesting to note the effect upon climate of the physical structure described above. The prevailing and rain-bringing winds are from the east and the southeast. They bring sufficient moisture to the low plain along the sea coast, and passing inland the rain-bearing clouds water the foothills of the Quathlamba Mountains and precipitate snow on the loftier peaks beyond them. A portion of the moisture is carried still farther to the west and falls in showers on the eastern part of the plateau—the Transvaal, the Orange Free State, the eastern border of Bechuanaland and the region northward toward the Zambesi. Sections farther to the north and west receive but little of the annual rainfall, ranging from five to ten inches in the year. That little is soon dissipated, the surface becomes dry and hard, and such vegetation as springs up under the brief showers soon dies. Much of this region is a desert, and so must remain until more and more continuous moisture is supplied, either by artificial irrigation or by some favorable change in natural conditions. From these permanent physical features—the lowlands along the coast, the elevated plateau in the interior, the mountain range running between them, a burning sun and a dry atmosphere—have developed many of the other natural phenomena of South Africa. The rivers of that country—laid down in great numbers on the maps—are not rivers during much of the year. In the dry season they are either without water altogether or consist of a succession of little pools scarcely sufficient to supply the cattle on their banks with drink. And when they are rivers they are, most of the time, such as can neither be forded nor navigated; the violent rains—continuing for hours and sometimes for many days—have converted them into roaring torrents. Now, if that country could have been entered by waterways, as were North and South America, it would not have remained an unknown land so long. But there was no other means of penetrating it than the lumbering ox-wagon, making at best a dozen miles a day, with frequent long halts in the neighborhood of good grass in order to rest and recuperate the cattle. It is this lack of navigable rivers that now compels the people to depend exclusively on railways for internal transportation and travel. With the exception of tidal streams there is no internal water communication of any value. Another peculiarity of the east coast rivers arises out of the nearness of the Quathlamba Mountains to the sea. Such rivers as take their rise in the mountains have very short courses, and the few that come from beyond, finding channels through the mountain passes, are so obstructed by rapids and cataracts at the point of descent from the higher levels that no boat can ascend them.