ARTICLES O^ EXPORTATION. 455 into it, constitutes the ladder by which the descent and ascent into the mine is effected. The smaller mines, besides being generally more superficial, are commonly situated upon acclivities, and thus an accumulation of water seldom incommodes the mining, but the larger ones are more frequent- ly in vallies, and soon filled with water, which it is necessary to remove. This is effected by a common and cheap hydraulic Chinese machine. Sometimes a canal is made to pass close to the mine for the purpose of facilitating the labour of removing the upper strata of sand and clay, which are thrown into it as extracted, and thus carried off by the stream. This is, of course, practicable on- ly in situations where the fluid has a considerable impetus. The stratum of tin is pursued by a suc- cession of pits, following the first opening or shaft. The washing of the mineral is performed in a manner remarkably cheap and easy. The abun- dance of mountain streams, which characterize the physical aspect of Banca, in common with all the other considerable islands of this tropical region, are the sources of this facility. When there is much room for selection it becomes a material ob- ject to choose a mine in the neighbourhood of such mountain stream which is either itself, or a canal from it, directed to the neighbourhood of the mine, where an aqueduct is regularly formed, the sides
