724 MIN ERA LOGICAL DESCRIPTION OP THE ISLAND OF BANKA. 
tion : where it was exposed by a new fracture it exhibited a very 
compact substance of a pure white or reddish colour, and some of 
the separate particles were elegantly marked or inscribed with va¬ 
rious figures by a combination of these two colours. 
Although the appearance of this stone was on the first view ano¬ 
malous, it is by no means difficult to account for its source on Ban¬ 
ka : the same substance which in the more primitive parts enters in¬ 
to the composition of granite appears here as pure felspar, or in 
combination with substances of the secondary and alluvial districts. 
It is in some degree modified by tbe causes which influenced its pre¬ 
sent disposition, and by the foreign substances united to it: but its 
configuration and qualities leave no doubt in my mind that it belongs 
to the class just mentioned. The strong mineral acids do not effect 
it. 
It occurs not only on the ascent of the hill Pungong*ake, but also 
in large loose fragments at some distance from the road, in different 
directions. Besides the manner just described, existing in a pure 
state, I have found it, on the same hill, combined with the Red- 
Iron-stone of the neighbourhood into a species of Breccia. The 
fracture here, exhibits the felspar, with its peculiar characters, but 
the manner in which the Red-Iron-stone is combined with it forms 
several distinct varieties. In one of these the Red-Iron-stone is 
compact, ponderous, approaching to lustrous and of a dark brown 
or blackish colour; in another the Red-Iron-stone is oehreous, friable 
and of a light red or yellowish colour. I have in some instances 
found both varieties in one specimen ; when the fracture of the fels¬ 
par, between the colours of the other substances contributed to form 
a very beautiful mass. Some of tbe fragments of felspar are per¬ 
vaded with narrow lines of a black substance of a different kind, 
while others present enclosed in the usual white or reddish mass a 
mineral approaching to the nature of horn-stone or flint. In some 
cases fragments of sand-stone are amited to the portions of felspar. 
On the further route across the Island I found above half a mile 
westward from Dshuruk in the rivulet Ayer-Bulin, numerous frag¬ 
ments of stone which bad been a long time exposed to a current of 
water : tbe appearance of this confirmed my opinion concerning the 
substance found on Pungong-ake and these had probably been de¬ 
rived from the same or a neighbouring eminence. Their colour 
was generally white, their sides and angles regular, though they 
shewed by the rounded extremities the force of a current: many 
