ore for two or three days.  They then add a certain quantity of quicksilver, squeezing it from a skin bag, to make it fall in drops equally on the mass or cuerpo, allowing to each mass ten, fifteen, or twenty pounds of quicksilver, according to the nature or quality of the ore, as the richer it is, it requires the more mercury to draw it to the silver contained in the mass, so that they know the quantity by long experience.  An Indian is employed to mould or trample one of these square cuerpos eight times a-day, that the mercury may thoroughly incorporate with the silver.  To expedite this incorporation, they often mix lime with the mass, when the ore happens to be what they call greasy, and in this great caution is required, as they say the mass sometimes grows so hot that they neither find mercury nor silver in it, which seems quite incredible.  Sometimes also they strew in some lead or tin ore, to facilitate the operation of the mercury, which is slower in very cold weather; wherefore, at Potosi and Lipes, they are often obliged to mould or work up their cuerpos during a month or six weeks; but, in more temperate climates, the amalgama is completed in eight or ten days.  To facilitate the action of the mercury, they, in some places, as at Puno and elsewhere, construct their buiterons or floors on arches, under which they keep fires for twenty-four hours, to heat the masses or cuerpos, which are in that case placed as a pavement of bricks.

When it is thought that the mercury has attracted all the silver, the assayer takes a small quantity of ore from each cuerpo, which he washes separately in a small earthen plate or wooden bowl; and, by the colour and appearance of the amalgama found at the bottom, when the earthy matters are washed away, he knows whether the mercury has produced its proper effect.  When blackish, the ore is said to have been too much heated, and they add more salt, or some other temper.  In this case they say that mercury is dispara, that is, shoots or flees away.  If the mercury remains white, they put a drop under the thumb, and pressing it hastily, the silver in the amalgam sticks to the thumb, and the mercury slips away in little drops.  When they conceive that all the silver has incorporated with the mercury, the mixed mass, or cuerpo, is carried to a basin or pond, into which a small stream of water is introduced to wash it, much in the same way as I shall afterwards describe the manner in which they wash gold, only that as the silver-ore is reduced to a fine mud without stones, it is stirred by an Indian with his feet, to dissolve it thoroughly, and loosen the silver.  From the first basin it falls into a second, and thence into a third, where the stirring and washing is repeated, that any amalgam which has not subsided in the first and second may not escape the third.