Pygmy Forest (from the races inhabiting it), the Aruwimi or Ituri Forest (from the rivers traversing it), the Stanley Forest (from its discoverer), or the Great Congo Forest. It is the largest fragment within the colony of the immense forest which at one time seems to have covered the whole equatorial region. By the banks of the rivers occur the “gallery” formations; i.e. in what appears an impenetrable forest are found avenues of trees “like the colonnades of an Egyptian temple,” veiled in leafy shade, and opening “into aisles and corridors musical with many a murmuring fount” (Schweinfurth).
The Congo and its tributary streams are separately noticed. They form, both from the point of view of the physical geography and the commercial development of the colony, its most important feature; but next in importance are the forests. The wooded savannas are mostly situated on the higher lands of the central zone, where the land dips down from the Mitumba Mountains to the Congo.
The part of the colony within the Nile basin is geographically of great interest. It includes some of the volcanic peaks which, north of Lake Kivu, stretch across the rift-valley and attain heights of 13,000 and 14,000 ft.; Albert Edward Nyanza and part of the Semliki river; part of Ruwenzori (q.v.), the so-called “Mountains of the Moon,” with snow-clad heights exceeding 16,500 ft. The colony also includes the western shores of lakes Tanganyika and Kivu (q.v.).
Geology.—The portion of the great basin of the Congo included in the colony is mainly occupied, so far as it has been explored, by sandstones. These are separable into a lower group (Kundelungu) of red felspathic grits and into an upper group (Lubilasch) of white friable sandstones. Both are considered to represent the Karroo formation of South Africa. The basin in which these sandstones were laid down is limited on the east by ancient gneisses and schists overlain by the highly inclined red felspathic grits. The ancient rocks of Katanga form the southern boundary. The northern periphery lies in French Congo: the western boundary is formed by a zone of Archean and metamorphic rocks and a region composed of several rock groups considered to range between the Silurian and Carboniferous periods; but it is only in the limestones of one group that fossils, indicating a Devonian age, have been found. Rocks of Cretaceous and Tertiary ages are confined to the maritime zone.
Flora.—The most valuable of the forest flora are the lianas, notably Landolphia florida, which yield the india-rubber of commerce. There are also timber trees such as mahogany, ebony, teak, lignum vitae, African cedars and planes, while oil, borassus and bamboo palms are abundant. Other trees are the redwood and camwood. Gum- and resin-yielding trees and plants (such as the acacia) are numerous. Euphorbias attain great size and orchillas are characteristic of the forest weeds. There are innumerable kinds of moss and lichens and ferns with leaves 12 ft. in length. Of the creepers, a crimson-berried variety is known as the pepper climber. Orchids and aloes are common. In the savannas are gigantic baobab trees. In the densest forests the trees, struggling through the tangle of underwood to the light, are often 150 ft. and sometimes 200 ft. in height. The undergrowth itself rises fully 15 ft. above the ground. In many districts the coffee and cotton plants are indigenous and luxuriant. Of fruit trees the banana and plantain are plentiful and of unusual size. Peculiar to the maritime zone are mangoes and the coco-nut palm. Papyrus is found by the river banks.
Fauna.—The forests are the home of several kinds of monkeys, including the chimpanzee in the Aruwimi region; the lion, leopard, wild hog, wolf, hyena, jackal, the python and other snakes, and particularly of the elephant. Among animals peculiar to the forest regions are a tiger-cat about the size of a leopard, the honey badger or black Ituri ratel and the elephant shrew. The zebra, giraffe and the rare okapi are found in the north-eastern borderlands. In the more open districts are troops of antelopes, including a variety armed with tusks, and red buffaloes. Hippopotami and crocodiles abound in the rivers, which are well stocked with many kinds of fish, including varieties resembling perch and bream; and otters make their home in the river banks. The manati is confined to the lower Congo. Bird and insect life is abundant. Among the birds, parrots (especially the grey variety) are common, as are storks and ibises. Herons, hawks, terns, Egyptian geese, fishing eagles (Gypohierax), the weaver and the whydah bird are found in the lower and middle Congo. Whenever the crocodile is out of the water the spur-winged plover is its invariable companion. The innumerable butterflies and dragon-flies have gorgeous colourings. White and red ants are very prevalent, as are mosquitos, centipedes, spiders and beetles.
Climate.—Situated in the equatorial zone, Belgian Congo shows, over the greater part of its area, only a slight variation of temperature all the year round. The mean annual temperature is about 90° F. From July to August the heat increases slightly, with a more rapid rise to November. During December the thermometer remains stationary, and in January begins to rise again, reaching its maximum in February. March is also a month of great heat; in April and May the temperature falls, with a more rapid decline in June, the minimum being reached again in July. The mean temperature is lowered on the seaboard by the coast stream from the south, and the thermometer falls sometimes to little over 50° F. Again in the plateau regions in the south the night temperature is sometimes down to freezing point. There is a marked distinction between the wet and dry seasons in the western districts on the lower Congo, where rains fall regularly from October to May, the dry season being from June to September. But nearer the centre of the continent the seasons are less clearly marked by the amount of precipitation, rain falling more or less regularly at all times of the year. The seasons of greatest heat and of the heavy rains are thus coincident on the lower river, where fever is much more prevalent than on the higher plateau lands nearer the centre of the continent. The amount of the rainfall shows great variations in different years, the records at Banana showing a total fall of 16 in. in 1890–1891 and of 38 in. in 1893–1894. Even in the rainy season on the lower river the rain does not fall continuously for a long period, the storms rarely lasting more than a few hours, but frequently attaining great violence. The greatest fall registered as occurring during a single tornado was 6 in. at Bolobo. In July grass fires are of common occurrence, and frequently sweep over a great expanse of country. M. A. Lancaster, the Belgian meteorologist, formulated, as the result of a study of all the available data, the following rule:—That the rainfall increases in the Congo basin (1) in proportion as one nears the equator from the south, (2) as one passes from the coast to the interior. On the lower Congo the prevailing winds are from the west and the south-west, but this prevalence becomes less and less marked towards the interior, until on the upper river they come from the south-east. The wind, however, rarely attains any exceptional velocity. Storms of extreme violence, accompanied by torrential rain, and in rare instances by hailstones, are of not uncommon occurrence. On the coast and along the course of the lower river fogs are very rare, but in the interior early morning fogs are far from uncommon. Europeans are subject to the usual tropical diseases, and the country is not suited for European colonization. This is due more to the humidity than to the heat of the climate.
Inhabitants.—The population is variously estimated at from 14,000,000 to 30,000,000. The vast bulk of the inhabitants of the Congo basin belong to the Bantu-Negro stock, but there are found, in the great forests, sparsely distributed bands of the Pygmy people, who probably represent the aboriginal inhabitants of Central Africa. (see Akka; Bambute; Batwa; Wochua). In the north-east of the colony, in the upper basin of the Welle and the Mbomu, the Niam-Niam (q.v.) or Azandeh, a Negroid race of warriors and hunters with a social, political and military organization superior to that of the Bantu tribes of the Congo basin, have intruded from the north. They were forcing their way southwards when the Belgians appeared in the upper Congo about 1895 and arrested their further progress. Neighbours to the Azandeh are the Mangbettu and Ababwa, who are found chiefly in the country between the Welle and the Aruwimi. The Mangbettu, who formerly established a hegemony over the indigenous population, Mundu, Abisanga, Mambaré, &c., have practically disappeared as a tribe, though their language and customs still survive. The characteristics of the inhabitants of this region are well summed by Casati, who states that the Mege are considered the most skilful in elephant-hunting, the Azandeh in iron-work, the Mangbettu in wood-carving, the Abarambo in ivory-carving, and the Momfu in agriculture. Arab culture and traces of Arab blood are found in the districts where the slave traders from the east coast had established stations. This Arab influence extends, in varying degrees of intensity, over the whole eastern province, that is the region bounded east by Tanganyika, west by the Lualaba, and north by Stanley Falls and the Mangbettu country. It is mainly evident in the adoption of Arab clothing and the building of houses in Arab fashion. In the valley of the Sankuru the population has been slightly modified by Chinese influences. About 1894 a party of coolies from Macao who had been working on the railway in the cataracts region endeavoured to return home overland. They got as far as the Sankuru district, where the survivors settled and married native women.
Of the Bantu tribes several main groups may be distinguished. The lower Congo and coast regions are occupied by the Ba-Kongo (otherwise Ba-Fiot), a division including the Mushi-Kongo, found chiefly in the Congo division of Angola, and the Basundi,