extract moisture, which they contract in places where they are purposely laid to render them heavier, as also for separating the mercury with which the bottom of the mass is always more or less impregnated.  The weight of these pinnas may be increased nearly a third, by dipping them while red hot into water.  It also sometimes happens that the same mass of pinna may be of different fineness in different parts.

The ore, or stones taken from the mines, or the mineray, as it is called in Peru, from which the silver is extracted, is not always of the same nature, consistence, and colour.  Some are white and grey, mixed with red or bluish spots, called plata blanca or white silver; of which sort the one in the Lipes mines mostly consists.  For the most part, some little grains of silver are to be discerned, and very often small branches are seen, ramifying along the layers of the stone.  Some ores are as black as the dross of iron, and in which no silver is to be seen, which is called negrillo or blackish ore.  Sometimes the ore is rendered black by admixture of lead, and is called plombo ronco, or coarse lead, in which the silver appears as if scratched by something harsh.  This ore is generally the richest in silver, and from it also the silver is got at the smallest charge; as instead of having to be moulded or kneaded with quicksilver, it has only to be melted in furnaces, where the lead evaporates by the force of fire, and the silver remains pure behind.  From this sort. of mines, the Indians drew their silver before the coming of the Spaniards, having no knowledge of the use of mercury, and they accordingly only wrought those mines of which the ore would melt; and, having but little wood, they heated their furnaces with ylo, the dung of the Llamas or Peruvian sheep, placing their furnaces on the sides of mountains, that the wind might render their fires fierce.

There is another sort of black ore, in which the silver does not at all appear; and which, when wetted and rubbed against iron, becomes red.  This ore is called rosicler, signifying that ruddiness which appears at the dawn of day.  This is very rich, and affords the finest silver.  Another kind, called zoroche, glitters like talc, and is generally very poor, yielding little silver:  Its outer coat is very soft and of a yellowish red, but seldom rich; and the mines of this sort are wrought on account of the easiness of extracting the ore, being very easily dug.  Another kind, not much harder than the last, is of a green colour, called cobrissa or copperish, and is very rare.  Although the silver usually appears in this kind, and it is almost mouldering, it is the most difficult of all to manage, as it parts very difficultly with the silver.  Sometimes, after being stamped or reduced to powder, it has to be burnt in the fire, and several other expedients must be used to separate the silver, doubtless because mixed with copper.  There is another very rare sort of ore, which has only been found in the mine of Cotamiso at Potosi, being threads of pure silver entangled, or wound up together, like burnt lace, and so fine that it is called arana, or spider ore, from its resemblance to a cobweb.