64 SOUTH AND EAST AFRICA. shore stretching north of Walvisch Bay are seen masses of sulphur mingled with sand and gypsum, and here the ground emits an odour of sulphureted hydrogen. To these noxious exhalations may probably be due the sudden destruction of the fish in the bay, which has been recorded on several occasions, and especially in the year 1883. At ebb tide observers have even noticed a kind of craters resembling protuberances on the surface of the exposed beach. Climate. On the physical structure of the land partly depend its climatic conditions. The south and south-west winds, which are the most prevalent on this seaboard, bring very few moisture- bearing clouds, while the opposing north-easterly gales predoijrinating in May, June, and July are even still less humid. Hence not more than an average of five or six rainy days in the year can be relied upon about the shores of Walvisch Bay, and scarcely one or two on the more southerly coast of Angra Pequena. To this and the night dews, at times very copious, is reduced the so-called " rainy season," whose normal period coincides with the beginning of the year, when the sun again moves northwards. But if the low-lying seaboard thus lies in an almost rainless zone, the marine currents discharge a more liberal supply on the uplands of the interior. As many as seventeen wet days were recorded at Hope-mine in 1886, yielding a total rainfall of nearly two inches. The rains are almost invariably heralded by whirl- winds, by which the sand is raised and borne along in moving columns. To these dust storms the Damaras give a name, which in their language means " Rain- bearers." Thanks to this supply of moisture, the inland plateaux are covered with a vast carpet of verdure, while lower down, at least south of the relatively well- watered district of Kaoko, the whole land remains arid, or dotted over with a few patches of thorny scrub, except in the rare oases fed by some intermittent springs. Here domestic animals perish of hunger and thirst, exotics pine and wither away, and the hardiest shrubs are reared with difficulty, the soil being everywhere saturated with salt to a depth of nearly two feet. Thanks to the moisture precipitated on the higher summits, the upland valleys are traversed by rivulets, which, however, nowhere unite in a common watercourse, and which fail to reach tlie sea except during exceptionally wet seasons. The torrents are in fact mere wadys, which serve as paths, and in which the wayfarer sinks a few wells in the hope that a little water may collect in the depressions. Their steep banks are fringed with shrubs, which draw the necessary moisture from the saturated sands. But the gradual decay of vegetation along the course of these torrents leads to the conclusion that the whole country is slowly becoming drier. AVhen any sudden freshet revives the sickly plants along the upland brooks, the fresh sprouts soon wither again, the roots being unable to strike dee]) j'uough in search of the vivifying stream. But in several parts of the neigh- bouring plateaux, the Hereros have bored through the limestone rock down to the underground reservoirs. In the Otavi hills north of this district one of these
