CHAPTER 1

Geography of Borneo

Borneo is one of the largest islands of the world. Its area is roughly 290,000 square miles, or about five times that of England and Wales. Its greatest length from north-east to south-west is 830 miles, and its greatest breadth is about 600 miles. It is crossed by the equator a little below its centre, so that about two-thirds of its area lie in the northern and one-third lies in the southern hemisphere. Although surrounded on all sides by islands of volcanic origin, Borneo differs from them in presenting but small traces of volcanic activity, and in consisting of ancient masses of igneous rock and of sedimentary strata.

The highest mountain is Kinabalu, an isolated mass of granite in the extreme north, nearly 14,000 feet in height. With this exception the principal mountains are grouped in several massive chains, which rise here and there to peaks about 10,000 feet above the sea. The principal of these chains, the Tibang-Iran range, runs south-westward through the midst of the northern half of the island and is prolonged south of the equator by the Schwaner chain. This median south-westerly trending range forms the backbone of the island. A second much-broken chain runs across the island from east to west about 1[degree] north of the equator. Besides these two principal mountain chains which determine the main features of the river-system, there are several isolated peaks of considerable height, and a minor ridge of hills runs from the centre towards the south-cast corner. With the exception of the northern extremity, which geographically as well as politically stands apart from the rest of the island, the whole of Borneo may be described as divided by the two principal mountain chains into four large watersheds. Of these, the north-western basin, the territory of Sarawak, is drained by the Rejang and Baram, as well as by numerous smaller rivers. Of the other three, which constitute Dutch Borneo, the north-eastern is drained by the Batang Kayan or Balungan river; the south-eastern by the Kotei and Banjermasin rivers; and the south-western by the Kapuas, the largest of all the rivers, whose course from the centre of the island to its south-west corner is estimated at 700 miles. Although the point of intersection of the two principal mountain chains lies almost exactly midway between the northern and southern and the eastern and western extremities of the island, the greater width of the southern half of the island gives a longer course to the rivers of that part, in spite of the fact that all the six principal rivers mentioned above have their sources not far from this central point. The principal rivers thus radiate from a common centre, the Batang Kayan flowing east-north-east, the Kotei south-east by east, the Banjermasin south, the Kapuas a little south of west, the Rejang west, and the Baram north-west. This radiation of the rivers from a common centre is a fact of great importance for the understanding of the ethnography of the island, since the rivers are the great highways which movements of the population chiefly follow.

In almost all parts of the island, the land adjoining the coast is a low-lying swampy belt consisting of the alluvium brought down by the many rivers from the central highlands. This belt of alluvium extends inland in many parts for fifty miles or more, and is especially extensive in the south and south-east of the island.

Between the swampy coast belt and the mountains intervenes a zone of very irregular hill country, of which the average height above the sea-level is about one thousand feet, with occasional peaks rising to five or six thousand feet or more.

There seems good reason to believe that at a comparatively recent date Borneo was continuous with the mainland of Asia, forming its south-eastern extremity. Together with Sumatra and Java it stands upon a submarine bank, which is nowhere more than one hundred fathoms below the surface, but which plunges down to a much greater depth along a line a little east of Borneo (Wallace’s line). The abundance of volcanic activity in the archipelago marks it as a part of the earth’s crust liable to changes of elevation, and the accumulation of volcanic matter would tend to make it an area of subsidence; while the north-east monsoon, which blows with considerable violence down the China Sea for about four months of each year, may have hastened the separation of Borneo from the mainland. That this separation was effected in a very recent geological period is shown by the presence in Borneo of many species of Asiatic mammals both large and small, notably the rhinoceros (R. BORNIENSIS, closely allied to R. SUMATRANUS); the elephant (E. INDICUS, which, however, may have been imported by man); the wild cattle (BOS SONDIACUS, which occurs also in Sumatra); several species of deer and pig (some of which are found in Sumatra and the mainland); several species of the cat tribe, of which the tiger-cat (FELIS NEBULOSA) is the largest; the civet-cat (VIVERRA) and its congeners HEMIGALE, PARADOXURUS, and ARCTOGALE; the small black bear (URSUS MALAYANUS); the clawless otter (LUTRA CINEREA); the bear-cat (ARCTICTIS BINTURONG); the scaly ant-eater (MANIS JAVANICUS); the lemurs (TARSIUS SPECTRUM and NYCTICEBUS TARDIGRADUS); the flying lemur (GALEOPITHECUS VOLANS); the porcupine (HYSTRIX CRASSISPINIS); numerous bats, squirrels, rats and mice; the big shrew (GYMNURA); several species of monkeys, and two of the anthropoid apes. The last are of peculiar significance, since they are incapable of crossing even narrow channels of water, and must be regarded as products of a very late stage of biological evolution. Of these two anthropoid species, the gibbon (HYLOBATES MULLERI) is closely allied to species found in the mainland and in Sumatra, while the MAIAS or orang-utan (SIMIA SALYRUS) is found also in Sumatra and, though not now surviving on the continent, must be regarded as related to anthropoids whose fossil remains have been discovered there.[2]

The zoological evidence thus indicates a recent separation of Borneo and Sumatra from the continent, and a still more recent separation between the two islands.

The climate of the whole island is warm and moist and very equable. The rainfall is copious at all times of the year, but is rather heavier during the prevalence of the north-east monsoon in the months from October to February, and least during the months of April and May. At Kuching, during the last thirty years, the average yearly rainfall has been 160 inches, the maximum 225, and the minimum 102 inches; the maximum monthly fall recorded was 69 inches, and the minimum .66, and the greatest rainfall recorded in one day was 15 inches. The temperature hardly, if ever, reaches 100[degree] F.; it ranges normally between 70[degree] and 90[degree] F.; the highest reading of one year (1906) at Kuching was 94[degree], the lowest 69[degree]. Snow and frost are unknown, except occasionally on the summits of the highest mountains. Thunder-storms are frequent and severe, but wind-storms are not commonly of any great violence.

The abundant rainfall maintains a copious flow of water down the many rivers at all times of the year; but the rivers are liable to rise rapidly many feet above their normal level during days of exceptionally heavy rain. In their lower reaches, where they traverse the alluvial plains and swamps, the rivers wind slowly to the sea with many great bends, and all the larger ones are navigable by small steamers for many miles above their mouths: thus a large steam launch can ascend the Rejang for 160 miles, the Baram for 120, and some of the rivers on the Dutch side for still greater distances. The limit of such navigation is set by beds of rock over which the rivers run shallow, and which mark the beginnings of the middle reaches. In these middle reaches, where the rivers wind between the feet of the hills, long stretches of deep smooth water alternate with others in which the water runs with greater violence between confining walls of rock, or spreads out in wide rapids over stony bottoms. The upper reaches of the rivers, where they descend rapidly from the slopes of the mountains, are composed of long series of shallow rapids and low waterfalls, alternating at short intervals with still pools and calm shallows, bounded by rock walls and great beds of waterworn stones, which during the frequent freshets are submerged by a boiling flood. The whole river in these upper reaches is for the most part roofed in by the overarching forest.

Practically the whole of Borneo, from the seacoast to the summits of the highest mountains, is covered with a dense forest. On the summits this consists of comparatively stunted trees, of which every part is thickly coated with moss. In all other parts the forest consists of great trees rising to a height of 150 feet, and even 200 feet, and of a dense undergrowth of younger and smaller trees, and of a great variety of creepers, palms, and ferns. Trees of many species (nearly 500) yield excellent timber, ranging from the hardest ironwood or BILIAN, and other hard woods (many of them so close-grained that they will not float in water), to soft, easily worked kinds. A considerable number bear edible fruits, notably the mango (from which the island derives its Malay name, PULU KLEMANTAN), the durian, mangosteen, rambutan, jack fruit, trap, lansat, banana of many varieties, both wild and cultivated, and numerous sour less nutritious kinds. Wild sago is abundant in some localities. Various palms supply in their unfolding leaves a cabbage-like edible. Among edible roots the caladium is the chief. Rubber is obtained as the sap of a wild creeper; gutta-percha from trees of several varieties; camphor from pockets in the stem of the camphor...