482 B. D. VerbeeJc — Geology of Sumatra. 



fort-on-tlie-Maine ; and the memoirs will appear in the " Palasonto- 

 graphica." (See two memoirs of mine, on the geology of the South- 

 eastern part of Borneo, in the " Jaarboek voor het Mynwezen in 

 Nederlandsch Oost-Indie," Amsterdam, 1874 and 1875. I have 

 formerly described the Nummulites of the Borneo limestone in the 

 "Neues Jahrbuchfiir Mineralogie, etc., 1871, pages 1-14, pi. i. ii. iii.) 



The coal-bearing sandstones of the south coast of Bantam, in Java 

 (not those in the interior of Bantam, which are younger), according 

 to Mr. F. Junghuhn's description (Junghuhn's " JaA r a," etc., Ger- 

 man translation, Leipzig, 1852, part iii. pages 163-179), are covered 

 first by marl-stones and clays, and next by limestone, which contains 

 Nummulites more to the east, on the Biver Kaso (Junghuhn, "Java," 

 part iii. pages 64, 87, and 203) ; and Prof, von Hochstetter confirms 

 the occurrence of these fossils in the limestone to which the cavern 

 of Linggo-Manik belongs ("Novara-Beise ; Geologie," ii. page 146). 



It seems to me highly probable that these three series of rocks of 

 Java are the equivalent of the rocks of Borneo described above ; and 

 that thus the coals of Java and Borneo, and perhaps those of Sumatra 

 too, belong to the same part of the Eocene period. In order to avoid 

 errors, I must state here that in several parts of the Archipelago 

 coal-beds are also found in rocks which are younger than Eocene ; but 

 these coals belong to the brown coal, and are always much inferior 

 in quality to the black Eocene coals. These brown coals are found, 

 1. in the interior of Bantam (Java), in the neighbourhood of the 

 village of Bodjong-Manik ; 2. in the neighbourhood of Doesson- 

 Caroe, in Lai's and Kataoen (Benkoelen, Sumatra), and Palembang 

 (Sumatra) ; and 3. in the marls of the Island of Nias. 



6. The Trachtjtia rocks of Sumafra are all younger than the Eocene 

 period ; they are of middle and late Tertiary age (Miocene and Plio- 

 cene); and it seems that this is the case in Borneo and Java also. 



There are two different groups of trachytic rocks ; the one, probably 

 the older of the two, composes mountains and mountain-ranges, with- 

 out craters, and having no connexion with volcanos ; the other com- 

 prises the trachytic rocks belonging to the volcanos, those giants of 

 Sumatra and Java, which are often more than 10,000 feet high. 



The trachytes of the first class, found in Sumatra in the immediate 

 neighbourhood of Padang and Sibogha, and at several other local- 

 ities, are oligoclase-trachytes, the so-called andesites (Zirkel) ; they 

 contain no sanidine, but exclusively a triclinic felspar, either with 

 amphibole (and now and then some quartz and mica), or with 

 pyroxene. 



These andesites are widely distributed in the south-east part of 

 Borneo, where they have dislocated the coal-bearing rocks; they are 

 known too in Java. 



The rocks composing the volcanos of Sumatra are of various kinds ; 

 there are andesites, trachytes with sanidine and oligoclase, trachyte- 

 pitchstones (Trachytpechsteine, with sanidine and without oligoclase), 

 obsidians, and pumice-stones. The volcanos of the Highlands of 

 Padang are named : — the Talang, the Singalang, the Merapi, the 

 Sago, and the Ophir. The Singalang and the Merapi are about 



