100 B. KOTO : THE GEOLOGIC STRUCTUEE OF 



time, in Lis * Borneo ', and I cannot here do better tlian follow 

 his work, supplementing it with a few notes I have gathered 

 elsewhere. 



Borneo is the largest of the Sunda Islands and rather broad. 

 Our knowledge concerning its geography is very imperfect, espe- 

 cially of Bern and the 'central mountain '; the only exception being 

 the coast region and in some degree the interior of the south, 

 and the Chinese district of West Borneo. Mountains are crowded 

 together in the north-west, and trend generally north-eastwards. 

 At about the middle of the chain, one range bends north-west, 

 terminating at Cape Datu, while the south-western branch stretch- 

 es towards Cape Sambar. Near the junction of the two, the land 

 rises to a considerable height, the so-called 'central mountains', 

 and culminates at the granitic or dioritic G. Tedong. All the 

 principal rivers of Borneo rise in this unexplored region, radiating 

 towards the surrounding seas, each having an independent hydro- 

 graphic basin of its own, which nearly corresponds to the political 

 divisions, into which this large island is divided. From the cent- 

 ral water-shed, the axial ridge proceeds north-eastwards to the 

 peak of Kina-balu, 4175m. high, the loftiest of the whole island. 



Crystalline schists, alte Schieferformation (probably the De- 

 vonian), and the Carboniferous built up the above-mentioned 

 chains, with the strike corresponding to the longest extension of 

 the mountains, and pierced by igneous rocks of granitic and 

 dioritic composition. Among (1), crystalline schists, mica-schist, 

 hornblende- schist and the itacolumite-like quartz-schist are pre- 

 valent. By (2), the alte schiefer formation, we understand that 

 series of rocks, made up of the bluish phyllade and siliceous 

 slate which is conjectured by many to be the Devonian, prin- 

 cipally because of the occurrence of some imperfectly preserved 



