RUWENZORI, more correctly Runsoro, said to be known also as Kokora, a mountain range in Central Africa, lying just north of the equator, and intersected near its eastern edge by 30° E. It has a length of about 65 m., with a maximum breadth of about 30 m., and its highest peaks rise above the limits of perpetual snow.' The range as a whole, the major axis of which runs a little east of north, falls steeply on the west to the Central African rift-valley traversed by the Semliki, the western head stream of the Nile, while on the east the fall is somewhat more gradual towards the highlands of western Uganda. The upper parts are separated by fairly low passes into six groups of snowy summits, lying a little to the west of the central line, rising in each case more than 15,000 ft. above the sea and reaching, in the culminating point of the western group (Mount Stanley), about 16,800 ft.
The origin of the range seems connected with that of the rift-valley on the west, both being due to vertical displacements of the earth's crust. Ruwenzori has been formed by an upheaval en masse of a portion of the archaean floor of the continent, bounded east and west by lines of fracture, but resulting in a general dip from west to east. A further upheaval seems to have produced an ellipsoidal anticline, causing the strata to dip outwards at a generally high angle. Traces of volcanic action are almost non-existent. Composed in its outer parts of gneisses and mica-schists offering no great resistance to denudation, in its centre the range consists of much more refractory rocks (amphibolites, diorites, diabases, &c.), to which fact, coupled with the existence of vertical fractures, the persistence and separation of the higher summits is probably due. The snow-clad area does not now extend more than ten miles in any direction, though there is abundant evidence that the glaciers were formerly far more extensive.
The upper region is almost entirely enveloped by day in thick cloud, which descends on the east to about 9000 ft., and lower still on the west. It sometimes lifts towards evening, giving a sight of the snowy peaks, but by 9 a.m. these have once more been hidden. As a result, the climate is very humid, the rainfall being probably at least 100 in. annually, and the slopes are furrowed by numberless streams, the most important fed by the glaciers of the upper region, and afterwards flowing in deeply cut valleys between the outer spurs. From the innermost recesses between Mounts Stanley, Speke and Baker, the main branches of the Mobuku descend to the east, while the four principal streams on the west unite to form the Butagu, the drainage on both sides ultimately finding its way to the Semliki, either directly or through Lake Dweru and the Albert Edward Nyanza.
As in other ranges of Central Africa the vegetation displays well-marked zones, varying with the altitude; but owing to the lower level to which the cloud descends on the west (probably an outcome of the general climatic régime of Central Africa, as the range lies between the east African plateau and the relatively low-lying basin of the Congo), the limits of the several zones reach a lower level on the west than on the east. They have been defined as follows by Mr R. B. Woosnam of the British Museum scientific expedition of 1906–7:—
|Zones.||Upper Limits (East Side).|
|Tree heaths||12,500 ,,|
|Lobelias and Senecios||14,500 ,,|
above which is the summit region of snow and bare rock. The boundaries between the zones are not of course hard and fast lines, but merely indicate the levels between which the respective forms are specially characteristic, though they occur also in higher or lower zones. The forest zone is perhaps the best marked, being visible from a distance as a dark ring. On the west it merges in part with the low-lying forest of the Semliki valley. Owing to the abundance of moisture, mosses, hepaticae and lichens are prevalent in several of the zones, and bogs, with Vaccinium and other low-growing plants, are common above the forest zone. Helichrysums are abundant in the zone immediately below the snow, where they form large bushes. The larger mammals are found chiefly on the lower slopes, but bushbuck, pigs, leopards, monkeys, a hyrax and a serval cat occur at higher altitudes. The birds include kites, buzzards, ravens, sun-birds, touracos, a large swift, and various warblers and other small kinds. The upper limit of human settlement, with cultivation of colocasia and beans, has been placed at 6700 ft.
Attempts have been made to identify the range with the “Mountains of the Moon” of Ptolemy and other ancient writers, the snows of which were thought to feed the Nile lakes. But in view of the extreme vagueness of the statements and the absence of all detailed knowledge of the geography, it is far more likely that the rumours of snowy mountains really referred to Mounts Kenya and Kilimanjaro, especially as they seem to have been obtained rather from the east coast than from the direction of the Nile. In modern times the existence of a snowy range in this part of Africa was first made known by Sir Henry Stanley during the Emin Pasha relief expedition of 1887–89, though hints of high mountains had been obtained by Stanley himself and by Romolo Gessi in 1876 and by others from the neighbourhood of the Albert Nyanza. Stanley named the main mass Ruwenzori, and outlying eastern peaks he called Mt. Gordon Bennett, Mt. Lawson, Mt. Edwin Arnold, &c.—the last named lying N.E. of Lake Dweru. Subsequently Stanley’s own name was given to the chief summit. One of Stanley’s officers, Lieut. Stairs, ascended the western slopes to over 10,000 ft. in 1889, and partial ascents were afterwards made by Dr Stuhlmann, Mr Scott Elliot, Mr J. E. Moore, Sir Harry Johnston, Mr Douglas Freshfield, and others. Early in 1906 some of the secondary ridges above the snowline were scaled by Messrs Grauer, Tegart and Maddox, and by Dr Wollaston and other members of the British Museum expedition, while later in the year the duke of the Abruzzi led a well-equipped expedition, including various scientists, to the upper parts of the range, and with the help of trained Alpine guides ascended not only the culminating twin summits (which he named Margharita and Alexandra after the queens of Italy and England), but all the principal snow-clad peaks. The expedition produced for the first time a detailed map of the upper region, and threw much light on the geology and natural history of the range.
Authorities.—Sir H. M. Stanley, In Darkest Africa (London, 1890; F. Stuhlmann, Mit Emin Pasha ins Herz von Afrika (Berlin, 1894); G. F. Scott-Elliot, A Naturalist in Mid-Africa (London, 1896); J. E. S. Moore, “Tanganyika,” &c., Geog. Jnl. (January 1901); To the Mountains of the Moon (London, 1901); Sir H. H. Johnston, The Uganda Protectorate (London, 1902); The Duke of the Abruzzi, in Geog. Jnl. (February 1907); R. B. Woosnam, ibid. (December 1907); F. de Filippi, Ruwenzori (London, 1908), the general account of the Abruzzi expedition, and Il Ruwenzori, Parte Scientifica (2 vols., Milan, 1909); A. R. F. Wollaston, From Ruwenzori to the Congo (London, 1908); R. G. T. Bright, “The Uganda-Congo Boundary," Geog. Jnl. (1909). (E.He)