MINERALOGICAL DESCRIPTION OP THE ISLAND OF BANKA. 425 
usual on a slightly inclining ground. A vertical section exposed the 
^trata of the hill, and the extensive surface below contained the re¬ 
mains of many former works. 
On the side of of the hill 1 noticed. 
1. (Layer) soil 
2. Sand 
3. Coarse sand, consisting'of large particles of quartz. 
4. Clay of a reddish colour. 
5. Coarse sand. 
6 . Clay. 
7 Extremity of the layer from which the ore had been extract¬ 
ed : the fragments which composed it were chiefly siliceous, of the 
mixed kind above described, consisting* nearly of equal proportions 
of quartz and felspar combined into a variegated mass. 
The succession of strata was very distinctly exhibited in this mine ; 
the lowest was peculiarly characteristic and afforded me an ©pportu- 
ty of observing a vertical section of the stratum containing the ore 
in its. natural situation : the fragments which composed it could he 
separately removed ; they were of different sizes from less than an 
inch to several indies in diameter. 
Although it was evident that they consisted of portions of the de¬ 
composed, or disseminated primitive rocks of the surrounding dis¬ 
tricts their present arrangement shewed that they had undergone a 
revolution and had been removed out of the natural situation. A 
considerable proportion of the felspar was in a state of decomposi¬ 
tion and appeared as a clayey substance, to these the particles of 
tin-ore often adhered. Grains of sand were mixed, but in compara¬ 
tively small quantity, with the coarse fragments which formed the 
stratum. 
The surface which had been exposed by the successive works of 
this mine was very extensive ; they had been commenced in a low si¬ 
tuation, and the productiveness of the stratum had gradually dimi¬ 
nished as the acclivity of the hill increased : the miners, supposing it 
to be near its termination, had given up the work. The stones which 
remained here resembled those usually found at the aqueducts. The 
