404 MIN ERALOGI CAL DESCRIPTION OF THE ISLAND O.F BANKA, 
The first mine, near the southern boundary of the district which 
I examined was that of Sungie-Bulak, named after a river of the 
same name ; the ground in the neighbourhood has been worked, 
nearly for thirty successive years. 
As the manner in which the business of mining is conducted on 
B&nka, will be minutely described in the sequel, I shall, at present 
only premise, introductory to the description of the appearances 
which I noticed under the surface, that, in large mines, the ground 
is perforated by a square or oblong excavation or pit from which 
the successive layers are carried out by the workmen until they ar¬ 
rive at the stratum which contains the ore of tin. These strata, as 
has already been remarked, are all disposed horizontally and, com¬ 
paratively, at no great distance below the surface ; extensive tracts 
of ground are thus, in many places, worked and exposed in succes¬ 
sion. In this place particularly, where the stratum had been found 
very productive, I observed the remains of a great number of pits 
from which the ore had been extracted. 
In the pit on whiclvthe workmen were at the time employed. I 
noticed the following successive strata : 
On the west side 
No. 1. Stratum, black vegetable mould. 1 ft. 
2. Sand and yellow clay loosely mixed.... 1 ,, 
3. Black clay, an extensive irregular mass 
unqual in depth from. 0 to S ft, 
4. Coarse white sand... 3 „ 
On the north side 
1. Stratum, black vegetable mould. 1 ,, 
2. Sand disposed in dark coloured clay (ir- 
gular).... * 3 
3. Black clay, variegated with narrow stra¬ 
ta of yellow clay ; irregular massive.. . 5 to 6 ,, 
4. Coarse sand. 3 ,, 
On the south side 
I. Stratum, vegetable mould. . , T ... 1 ,, 
