408T MINER A LOGICAL "DESCRIPTION OF THE ISLAND OF BANKA. 
2. Black-clay in extensive masses abruptly and irregularly in¬ 
terposed between the other strata. 
3. Fine whitish sand (with a small proportion of clay inter¬ 
mixed.) 
On another of the sides I remarked. 
L Soil. 
2. Black-day massive. 
3. Sand adhering partially by means of a elayey cement. 
4. Pure white sand. 
The difference between the two last mentioned layers was very 
evident, in the third the proportion of clay was very abundant, and 
united the particles of pure white sand to a mass which became so¬ 
lid by drying. The fourth was a pure sand consisting of minute 
crystals of quartz most of which were transparent, in distinction from 
the other it was perfectly loose without any adhesion of its particles. 
The manner in which the black clay is generally interposed or in¬ 
truded between the other strata deserves some attention, but will 
more properly be considered elsewhere. 
Most of the varieties of stone collected at the aqueducts of the 
mines of the Upper and Lower-furnace, were found here likewise ; 
and besides those above enumerated, I collected. 
1. A species of siliceous stone of the fracture and apparent 
qualities of hornstone. 
2. Felspar of a most pure and beautiful milk white colour. 
3. An amygdaloid consisting of white and coloured siliceous 
particles, considerably resembling porphyry in the frac¬ 
ture. Many of the masses of quartz, at this mine, had 
the colour of amethyst. 
On the road to this mine (of Sinhin) somewhat nearer the stock¬ 
ade of Klabbet, I visited the small mine of Tshentel. As the differ¬ 
ence between a small mine and a large mine will be pointed out in 
another place I shall only remark at present, that in small mines the 
stratum of ore is generally nearer the surface, and that they are 
worked, comparatively, with few hands. 
This mine was opened on an inclining ground. Immediately un- 
