484 R. D. Verbeek — Geology of Sumatra. 



10,000 feet high; the others are lower, but all the volcanos of 

 Sumatra surpass 6000 feet. The volcanos of Java are described by 

 Mr. Junghuhn in his above-mentioned work. 



Borneo contains no volcanos. The mountain Kina-Baloe, in the 

 northern part of Borneo, which was formerly supposed to be a 

 volcano, is composed of a granitic rock. 



There are two lakes in the Highlands of Padang which owe their 

 origin to infallings of volcanic ground on a very large scale. 



The greatest length of the Lake Singkorah is 21,000 metres, the 

 greatest breadth 7700, the smallest breadth 3350, and the circumfer- 

 ence 53,000; the surface is 2*04 square geographical miles. The 

 only channel which carries off the water of this lake is the Oembilien 

 Biver, which is afterwards called Kwanten, and finally Indragiri, and 

 has its mouth on the east coast of Sumatra. The Lake Manindjoe 

 is 16,600 metres in length, the greatest breadth is 8000, the least 

 breadth 3650 metres ; the circumference is 48,900 metres, and the sur- 

 face 1-81 square geographical miles (1 geogr. mile^; 1 /^ of the Equa- 

 tor) . The water of this lake is carried off by the Antokkan Biver, 

 which has its mouth not far from Tikoe on the west coast. 



The surface of these two lakes is, in comparison with other lakes in 

 volcanic districts, as for example the "Maare " of the Eifel, very con- 

 siderable. The surface of the Lake Singkorah is 33 times, and 

 that of the Lake Manindjoe 29 times greater than that of the Lake 

 of Laach (Laacher See) in the Eifel. 



7. The Diluvium of the Highlands of Padang is a river-deposit ; 

 and is chiefly composed of tufaceous conglomerates and sandstones. 

 The beds are always horizontal, and contain many fragments of 

 trachytes. These are two characters by which the Diluvial conglom- 

 erates are easily separated from the conglomerates of Eocene age. 

 The Diluvial beds form river-terraces, which attain a height of twenty 

 to thirty metres above the alluvial deposits. 



8. The Alluvial river-deposits are for the greater part trans- 

 formed into rice- fields (sawahs). 



In the Section Fig. 2, the western part of Sumatra is represented 

 from Padang, on the west coast, to the village of Doerian-Gedang, 

 near the frontier of the independent districts. The eastern part of 

 Sumatra, from Doerian-Gedang to the east coast, is not given in the 

 Section, as that part is composed only of recent deposits of the Bivers 

 Djambi, Indragiri, and Kampar. With the exception of the quartz- 

 porphyry (3) and the diluvium (7), all the above-described rocks are 

 represented in the Section. The four groups of Eocene deposits are 

 generally conformable with each other, but unconformable to the old 

 Eusulina-limestone ; but, as was stated above, in some localities there 

 is a fault between 56 and 5c. 



II. — The Island of Nias (Government of the "West Coast of 

 Sumatra). See Fig. 3. 



This island is situated westward of Sumatra ; its surface is about 

 70 square geographical miles. It is chiefly composed of marls, clay- 



