MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 419 
stratum was clearly demonstrated. At the extremity of this valley 
near the sea, numerous large granite rocks single or collected in clus¬ 
ters project from the surface : their external appearance is similar to 
those near the northern shore of the peninsula but less diversified by 
the felspar on the surface. In the composition of those which 1 ex¬ 
amined the component parts appeared to be in more equable pro¬ 
portion and more equally distributed. 
The hill of Klabbet which rises immediately to the north of the 
valley above described is also composed of granite ; and the numer¬ 
ous rocks which diversify the bay, and which have given a basis to 
several islands consist of the same kind of stone. 
I observed near the dwelling of one of the Chinese in the valley, 
a fragment of granite which had been brought hither from the sea, 
in a state of decomposition or separation of its component parts: it 
exhibited strikingly the appearance I had remarked in many of the 
stones taken from the strata of the mines, the felspar was changed 
into a white clayey mass in which the particles of quartz were im¬ 
bedded of various sizes. 
As it is inconsistent with the rule I have originally laid down, to 
mix reflexions of a theoretical nature with an essay which is intend¬ 
ed to be purely descriptive, I shall make no other remark than that 
the valley above mentioned may be considered as the boundary (in 
this part of the peninsula) of that district in which the strata of tin- 
ore are arranged, and which takes hence a western course until it 
meets the alluvial hills near the stockade of Sungie-bulu. Most parts 
of this district are unquestionably stratified; the chief layers are 
formed of sand, the particles of which are of different sizes, but al¬ 
ways transparent or semi-transparent, of the nature of quartz : these 
are united by clay of different shades of colour formed from the de¬ 
composed felspar. Next to these are often deposited fragments of 
Red-Iron-stone, which occurs in extensive veins and forms a con¬ 
siderable proportion of the fixed parts of this district. The separa¬ 
ted particles of the primitive rocks which abound in many parts of 
this peninsula enter also into these strata: from their magnitude and 
weight they generally occupy the lowest part and through them the 
