Page:Africa by Élisée Reclus, Volume 4.djvu/269

 I TRANSVAAL. 809 been driven, and the belief seems justified that this winged pest retreats with the advance of the plough. Hence it is probable that the increase of population and the development of agriculture will one day enable civilised man to introduce his domestic animals into the Limpopo valley. But on the eastern slopes the permanent difference of climate between the valleys draining to the Indian Ocean and the elevated Transvaal plateau is so great that horses and horned cattle cannot be transported without great danger from one region to the other. This circum- stance accounts for the large sums forwarders of convoys are always ready to give for " salted " animals, that is, those that have become accustomed to both climates. Pleuro-pneumouia, which is unfortunately very prevalent throughout the inland plateaux, is treated by the process of inoculation and amputation of the tail. Another terrible but, fortunately, intermittent plague, are the all-devouring locusts by which the Bosch-rcld, or central tableland, is more especially infested. The traveller Mohr gives a graphic account of the arrival of a swann of these winged insects, which on one occasion he witnessed when camping on the banks of the Vaal. They appeared like dense volumes of yellowish smoke, rolling up from the south-western horizon, and began to alight, first a few at a time, then by dozens, and presently by countless thousands. They came on in such vast clouds that the heavens were darkened, and the mid-day sun seemed muddy and beamless, as at sunset. No perceptible impression was made on this great surging sea of insect life by the flocks of locust-eaters which assailed it on all sides. It continued to flood all the land, changing the waters of the Vaal to a dirty yellowish grey colour. Nothing can check their onward march ; when their path is intercepted by a stream they rush headlong in, gradually choking its bed with their bodies, and thus forming a dry bridge for the myriads pressing on from behind. Where- ever they alight the country is speedily converted to an absolute desert, every green thing disappearing as by enchantment. But on the other hand the locusts are greedily devoured by domestic animals, such as horses, cattle, sheep, and goats, as well as by elephants and other large graminivorous wild beasts. The natives also regard them us a great delicacy, collecting them in large heaps and eating them dried and roasted. Mineral Wealth. As a mining region the South African Republic is no less highly favoured than as an agricultural country. Doubtless the rich diamond fields discovered in the adjacent lands on its northern frontier appear to be continued into the Transvaal territory only in the form of sporadic deposits without economic value. But on the other hand coal and other minerals occur in great abundance. The coal mines already opened in the northern part of Nutal extend far into the Boer State, where the farmers now make extensive use of this fuel, which bums with a clear flame, leaving little or no ash. In various parts of the country iron, cobalt, copper, and argentiferous lead mines are already being worked. But fur more widely diffused is the auriferous white quartz, which yields a large percentage of gold. In 18G7 the geologist Mauch discovered the precious metal on the banks of the Tati, a river 1 1 1— Af