GEOLOGICAL HISTORY OF THE PLATEAF. 477 



copper-mines they contain. Sibumbun is a peak of 

 greenstone rising out of syenite. Westward, one 

 passes from tlie granite into marble, and tlien on to 

 a sandstone of a late formation, wliicli contains layers 

 of coal that is jirobably of the same age as that I saw 

 at Siboga. 



The whole geological history of this part of Su- 

 matra may be summed up as follows : On the syenite 

 and granite, layers of mud and coral were deposited ; 

 then the whole was raised and plicated; and after 

 this period was deposited the sandstone, the strata of 

 which we have abeady noted as being unconformable 

 to the rocks on which they rest, and more nearly hori- 

 zontal. If, as ]\Ii\ Van Dijk thinks, and is very prob- 

 able, the marble in the cleft of Padang Pangjang is 

 formed from corals, at least not older than the eocene 

 age, it follows that the mountain-ranges of Sumatra 

 have been formed within a comparatively recent pe- 

 riod. The process of covering these strata by lava, 

 pumice-stone, and volcanic sand and ashes, has been 

 going on since historic time. 



The most remarkable thing in this kampong of 

 Sinkara, is the hali^ or town-hall. Either end, on 

 the inside, is Iniilt up into a series of successive })lat- 

 forms, one rising: over the other. On the outside these 

 elevated ends resemble the stern of the old three and 

 four decked fi-igates Avhich the Dutch generally used 

 when they first became masters of these seas, and such 

 as can yet be seen used as hulks in the ports of the Brit- 

 ish colonies. The exterior of the hall^ as well as the 

 l)etter private houses, are painted red, and ornamented 

 ^vith flowers and scroll-work in white and l>lack. 



