12 SOUTU AND EAST AFRICA. siderable quantity of moisture present in the atmosphere.* From May to Septem- ber it often almost reaches the point of saturation, and then the horizon is everywhere veiled in the dense fogs of the cacimho. Yet the rainfall is compara- tively slight in the low-lying districts, the vapours being borne by the winds to the slopes of the hills, where frequent downpours occur regularly during the light rainy season from October to January, and the heavy from the beginning of April to the end of May. At Loanda the annual rainfall varies to a remarkable degree.t the average number of wet days being not more than fifteen in some years and four times as many in others. Over 20 inches have sometimes fallen in favourable years, while at other times the quantity has scarcely exceeded 5 or t) inches. In the northern districts the first rains are always unhealthy, the air being then charged with the foul exhalations with which the porous soil is saturated, and which are mingled with the decayed vegetation suddenly washed up from below the surface. In the direction from north to south the quantity of the rain- fall diminishes progressively along the low-lying coastlands. Copious at San- Salvador,* slight at Loanda, it ceases nearly altogether at Mossamedes and in the Lower Cunene basin. Hence this southern region lies on the verge of the desert, but is at the same time the most salubrious in Angola, thanks to the great dryness of the atmosphere and the ground, as well as to the relative coolness of the temperature. On the plateaux skirting the south side of the Lower Cunene the Quissaraa natives are obliged carefully to husband the rainwater in the hollow trunks of the baobabs. Flora. Since the explorations of Welwitsch in the province of Angola, the face of the land is well known in its broad features, and nothing now remains except to study its details. Hence the name of this learned botanist has justly been given to the Weluitachia mirabilis, the most remarkable plant in this part of the conti- nent. This tree, for it really is a tree, althougb in appearance more like an eccentric fungus than aught else, grows in the Mossamedes district, ranging north- wards only as far as the mouth of the intermittent river Sam-Nicolau, but reach- ing, south of the Cunene, far into the Damara country. The trunk, which is said to live for a hundred years, and which attains a compass of ten or twelve feet,
- Relative humidity during the three years 1879, 1880, and 1881 —
Mean .... 82-42 Highest mean . . . 87-69 Lowest mean . 76-69, Mean variation . . . 10^4 (Cotlho and Ribeiro). ainfall at Loanda : — Bainy Total Rainfill. Drtys. Inches. 1879. . . 62 24 1880. , . .'4 10 1881. • • 15 6 Mean 34 13 (Ribeiro) X Rainfall at San-Salvador in 1884, 63 days, with a total discharge of 36 inches.
