The mode of working these mines, more fitly to be denominated washings, is simple, and may be easily explained:
Suppose a loose gravel-like stratum of rounded quartzose pebbles and adventitious matter, incumbent on granite, and covered by earthy matter of variable thickness. Where water of sufficiently high level can be commanded, the ground is cut in steps, each twenty or thirty feet wide, two or three broad, and about one deep. Near the bottom a trench is cut to the depth of two or three feet. On each step stand six or eight negroes, who, as the water flows gently from above, keep the earth continually in motion with shovels, until the whole is reduced to liquid mud and washed below. The particles of gold contained in this earth descend to the trench, where, by reason of their specific gravity, they quickly precipitate. Workmen are continually employed at the trench to remove the stones, and clear away the surface, which operation is much assisted by the current of water which falls into it. After five days’ washing, the precipitation in the trench is carried to some convenient stream, to undergo a second clearance. For this purpose wooden bowls are provided, of a funnel shape, about two feet wide at the mouth, and five or six inches deep, called _gamellas_. Each workman standing in the stream, takes into his bowl five or six pounds weight of the sediment, which generally consists of heavy matter, such as granular oxide of iron, pyrites, ferruginous quartz, &c. and often precious stones. They admit certain quantities of water into the bowls, which they move about so dexterously, that the precious metal, separating from the inferior and lighter substances, settles to the bottom and sides of the vessel. They then rinse their bowls in a larger vessel of clean water, leaving the gold in it, and begin again. The washing of each bowlful occupies from five to eight or nine minutes; the gold produced is extremely variable in quantity, and in the size of its particles, some of which are so minute, that they float, while others are found as large as peas, and not unfrequently much larger. This operation is superintended by overseers, as the result is of considerable importance. When the whole is finished, the gold is placed upon a brass pan, over a slow fire, to be dried, and at a convenient time is taken to the permutation office, where it is weighed, and a fifth is reserved for the Prince. The remainder is smelted with muriate of mercury, then cast into ingots, assayed, and stamped according to its intrinsic value, a certificate of which is given with it; after a copy of that instrument has been duly entered at the mint-office, the ingots circulate as specie.