



Mineralogical Description of the Island of Banka. 87 



1. The direction of the island is from northwest, to southeast : 

 in this direction it follows, not only the neighboring island of 

 Sumatra and the peninsula of Malaka, but the large chain of the 

 Asiatic mountains, one of the various branches of which termin- 

 ates in Ceylon, while another after having traversed Arracan, 

 Pegu, Malaka and probably Sumatra, sends off an inferior range 

 through Banka and Billiton, where it may be considered to dis- 

 appear and terminate. 



2. It is not only in the direction of its course that Banka fol- 

 lows the large Asiatic ranges of mountains ; the elevated parts of 

 the island, or those which are entitled to be called mountains or 

 hills, have the same constitution as the great chain above men- 

 tioned: they are composed principally of granite. 



3. Next to these, which must be considered as the more impor- 

 tant part of Banka, we meet with a species of rock, which for the 

 sake of distinction I have named red ironstone. It is very ex- 

 tensively distributed aud occurs in situations of secondary eleva- 

 tion, in single beds, or in veins of many united together, and 

 covering extensive tracts of country. The red color universally 

 predominates, and it contains a large proportion of iron in its com- 

 position ; but a more particular account of its distribution and 

 conjunction with other parts of the island, is one of the chief 

 subjects of the following description : the analysis will be added 

 separately. 



4. In many parts of the island, these tracts of country, which 

 | are composed of red ironstone, are bounded by the alluvial dis- 

 tricts. These are again subdivided into such as are formed of 

 ranges of waving hills, gradually rising on each other, apparently 

 °f prior formation, and such as are completely low and level, of 

 recent origin, and confining the discharge of the large rivers. 



5. In conjunction and often within the alluvial tracts are found 

 sandstones, breccias (or puddingstones), and various mixed stones, 

 bearing marks of a comparatively late origin. The former are 

 generally distributed in extensive veins or low ridges ; the brec- 

 cias occur in a great variety of form and disposition. Immense 

 conchoidal or tabular masses, in some instances, cover extensive 

 portions of the ground. 



6. Those districts which occur in juxtaposition to the primitive 

 portions, filling the space between these and the fixed veins of 

 red ironstone (iron-rock), or again between these and the alluvial 

 parts, are stratified: the strata are uniformly horizontally ar- 

 ranged, and characteristic of the tracts above mentioned, which 

 f °rm the basis of the island. 



~. The ore of tin is disseminated through these horizontal 

 strata, and, as far as has hitherto been remarked, either immedi- 

 ately under the surface or at no great distance below it ; they are 

 mostly found in low situations or near the primitive ridges. The 



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