The particles of gold being separated, by washing, from the stratum in which they are fottnd, are brought to the nearest mint, where a fifth part is taken for the crown. The remainder undergoes a process of amalgamation with mercury, and is af terwards poured into an ingot, which being sent to the assay master, he ascertains its weight and fine ness, and puts upon it the public stamp, when it is delivered to the owner for circulation. The operation of melting seldom occupies more than ten minutes ; and those who deliver into the mint any quantity of gold dust, may reckon on having it returned to them for circulation in less than an hour. The gold is of different qualities. Some of the bars which are in circulation are so low as 16 carats, while others are as fine as 2St carats, which is within carat of what is de nominated pure gold. The standard is 22 carets fine, and gold exceeding this standard_ receives a premium in proportion to its fineness. Gold of a low standard is generally of a pale colour, which is ascribed to the mixture which it contains of silver, platina, or some other metals.
The washing for diamonds is another favourite employment in Brasil, and, being esteemed too lucrative a branch of business for individuals to enjoy, is now prosecuted by the state as a royal monopoly. The district of Cerro do Frio, or of the cold mountains, in which the diamond works are es tablished, is situated on the highest ridge of those mountains ; which, running nearly parallel with coast of Brasil, rise to their height at the distance of about SOO miles in the interior, and divide the streams which fall into the Atlantic by the Rio Doce and the Rio Grande from those which, running west ward into the Rio Francisco, are carried to the north by that' river, and fall into the Atlantic about the 11th degree of south latitude. It is at the sources of these streams that the diamond works are situate ed. This district consign; of a range of rugged mountains that run north and south, and are gene rally considered to be the highest in Brasil. The tract of country termed the diamond ground, ex tends about 16 leagues from north to south, and about 8 leagues from east and west. Nearly in the middle of it stands the town of Tejuco, 400 miles north of Rio Janeiro, in a straight line, but nearly double that •distance by the winding roads of the mountains. It contains about 6000 inhabitants, and is chiefly supported by the diamond works in its neighbourhood. The most considerable of these is situated on the head waters of the ri ver Jijitonhonha, a branch of the Rio Grande, while others are established on the Rio Veiho, a branch of the Francisco, and on the other numerous small streams have their rise in this mountainous region. The river Jijitonhonha, where the diamond works are established, is about as wide as the Thames at Windsor, and is in general from three to nine feet deep. The cascalhao consists of nearly the same materials as that which contains the gold, and it bas to be dug from the bottom of the river, which, for this purpose, is diverted into a new channel. When Mr Mawe visited these works, they were working at a bend of the river, from which the water was diverted by means of a canal cut across the tongue of land round Which it held its course ; an embankment formed•of several bags of sand, being carried quite across the old channel, just below the head of the canal. After this operation, the deeper
parts of the river are laid dry by means of pumps, and, the earth being removed, the cascara° is dug up and removed to a convenient place for washing. This fatiguing work was until lately performed by the unassisted• labour of the Ingram, who carried the cascalhao in bowls on their heads, and in many es tablishments this mode of working still prevails. Two inclined planes have been since contrived, along which, by means of a water-wheel, two carts are set in motion, one of which descends empty by one inclined plane, while the other, loaded with cascalheo, is drawn to the top of the other. At some of the diamond works, on the same river, the cascalh,ao is conveyed to the place for washing by different and more im proved Machinery, and railways are even constructed on some parts of the uneven ground. The cascalhao, when it is carried from the bed of the river whence it is dug, is laid down in heaps, containing apparent lyYrom five to fifteen tons each ; and they calculate in digging as much during the rainy season, as will give full employment to all their hands during the . months which are not subject to rain. Into all the various parts of the works erected for washing the cascalhao, water is distributed by means of aque ducts, constructed with great ingenuity and skill. The following is an account of the mode of washing for diamonds, as it was observed by Mr Mawe, which appears to be highly curious and interesting.
" A shed is erected in the form of a parallelo gram, 25 or 80 yards long, and about 15 wide, consisting of upright posts, which support a roof thatched with long grass. Down the middle of the area of this shed, a current of water is conveyed through a canal, covered with strong planks, on which the cascalhao is laid two or three feet thick. On the other side of the area is a flooring of planks, from four to five yards long, imbedded in day, ex tending the whole length of the shed, and having a slope from the canal, of three or four inches to a yard. This flooring is divided into about twenty compartments or troughs, each about three feet wide, by means of planks placed upon their edge. The upper ends of all these troughs (here called ca noes) communicate with the canal, and are so form ed that water is admitted into them between two planks that are about an inch separate. Through this opening, the current falls about six inches into the trough, and may be directed to any part of it, or stopped at pleasure by means of a small quantity of day. For mstance, sometimes water is required only from one corner of the aperture, then the re maining part is stopped ; sometimes it is wanted from the centre, then the extremes are stopped ; and sometimes only a gentle rill is wanteci, then the clay is applied accordingly. Along the lower ends of the troughs, a small channel is dug to carry off the water.