The belt of islands, Sumatra, Java, and the chain to Timor and the Sarwatty group, represents a line of weakness in the crust of the earth, due to volcanic action, which still makes itself felt there. But the axis of elevation of Borneo is almost at right angles to this line, and in it are no active vents, and if there be extinct volcanoes, these are in the extreme north only. In Sarawak there are several hot springs, the water of which is impregnated with sulphuretted hydrogen. The island owes its origin, as far as we can judge, to a great upheaval of plutonic rock that has lifted aloft and shivered the overlying beds, but the granite does not come everywhere to the surface. Something analogous may be seen in Exmoor, where the superincumbent clay-slate has been heaved up and strained, but the granite nowhere shows save in Lundy Isle, where the superposed strata have been swept away, leaving the granite exposed. [Illustration: MOUNT ST. PEDRO, OR KINA BALU, 13,700 FEET.] Borneo is about 850 miles in length and 600 in breadth, and contains an area of 286,000 square miles. The centre of Borneo is occupied by broken hilly highland, with isolated mountains, of which the finest is the granite peak of Kina Balu (13,700 feet). Hills come down in places to the sea, as in the south of Sarawak, where they attain a height of from 2000 to over 5000 feet, and die into the sea at Cape Datu. The plains, chiefly swamps, are composed of the wash of the mountains, overlaid by vegetable mould, and these fringe the coast, extending inland from ten to thirty miles, with here and there isolated humps of hill standing up out of them. The island is probably the best watered in the world. On every side are numerous rivers, mainly rising in the central highlands, at first dancing down the mountain ledges in cascades, then, forming dangerous rapids, enter the plain, and there swelled by affluents and widening out advance with no strong current to the sea. Owing to the width of the river-mouths, and to the configuration of the coast, some of them, as the Batang Lupar, the Sadong, and Saribas, have tidal bores, as is the case with our River Severn, that run up as many as seventy miles into the interior, and most have deposited troublesome bars at their mouths, and have embouchures clogged by shoals. To the slight fall is largely due the remarkable way in which several of these rivers descend into the ocean through plural mouths, thus forming a network of lateral waterways, called Loba and Trusan, whereby they mix and mingle with other rivers, and, very much like the Rhine after entering Holland, lose their identity and are frittered away in many channels. The Rejang, for instance, finds issue through five mouths, and the land between the Rejang and Igan entrances, which meet at Sibu, the apex of the delta, is a vast unbroken swamp, 1200 square miles in area. The same phenomenon is noticed in the Sarawak river, and in the Limbang to a smaller degree.