BOOK VIII.
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axle, one end of which is mortised into the large horizontal axle, and theother end is held in a hollow covered with thick iron plates in a beam. Thusthe paddles, of which there are three sets in each tub, turn round, andagitating the powder, thoroughly mix it with water and separate the minuteparticles of gold from it, and these are attracted by the quicksilver andpurified. The water carries away the waste. The quicksilver is pouredinto a bag made of leather or cloth woven from cotton, and when this bag issqueezed, as I have described elsewhere, the quicksilver drips through it intoa jar placed underneath. The pure gold 13 remains in the bag. Some peoplesubstitute three broad sluices for the tubs, each of which has an angular axleon which are set six narrow spokes, and to them are fixed the same number ofbroad paddles ; the water that is poured in strikes these paddles and turnsthem round, and they agitate the powder which is mixed with the water andseparate the metal from it. If the powder which is being treated containsgold particles, the first method of washing is far superior, because the quick-silver in the tubs immediately attracts the gold ; if it is powder in whichare the small black stones from which tin is smelted, this latter method isnot to be despised. It is very advantageous to place interlaced fir boughsin the sluices in which such tin-stuff is washed, after it has run through thelaunders from the mills, because the fine tin-stone is either held back by thetwigs, or if the current carries them along they fall away from the waterand settle down.
“ millstone, it is ground while being moistened with vinegar, or water, in which has been“ dissolved corrosive sublimate ( solimato ), verdigris ( verde rame), and common salt. Over" these materials is then put as much mercury as will cover them ; they are then stirred for“ an hour or two, by turning the millstone, either by hand, or horse-power, according“ to the plan adopted, bearing in mind that the more the mercury and the materials are“ bruised together by the millstone, the more the mercury may be trusted to have taken up“ the substance which the materials contain. The mercury, in this condition, can then be“ separated from the earthy matter by a sieve, or by washing, and thus you will recover“ the auriferous mercury (el vro mercurio). After this, by driving off the mercury by“ means of a flask (i.e., by heating in a retort or an alembic), or by passing it through a bag," there will remain, at the bottom, the gold, silver, or copper, or whatever metal was placed“ in the basin under the millstone to be ground. Having been desirous of knowing this“ secret, I gave to him who taught it to me a ring with a diamond worth 25 ducats ; he also“ required me to give him the eighth part of any profit I might make by using it. This I“ wished to tell you, not that you should return the ducats to me for teaching you the secret," but in order that you should esteem it all the more and hold it dear.”
In another part of the treatise Biringuccio states that washed (concentrated) ores maybe ultimately reduced either by lead or mercury. Concerning these silver concentrateshe writes: " Afterward drenching them with vinegar in which has been put green
“ copper (i.e., verdigris); or drenching them with water in which has been dissolved vitriol“ and green copper. . . He next describes how this material should be ground with
mercury. The question as to who was the inventor of silver amalgamation will probablynever be cleared up. According to Ulloa (Relation Historica Del Viage a la AmericaMeridional, Madrid, 1748) Dom Pedro Fernandes De Velasco discovered the process in Mexicoin 1566. The earliest technical account is that of Father Joseph De Acosta ( Historia Naturaly Moral de las Indias, Seville, 1590, English trans. Edward Grimston, London, 1604, re-published by the Hakluyt Society, 1880). Acosta was born in 1540, and spent the years1570 to 1585 in Peru, and 1586 in Mexico. It may be noted that Potosi was discoveredin 1545- He states that refining silver with mercury was introduced at Potosi by PedroFernandes de Velasco from Mexico in 1571, and states (Grimston’s Trans., Vol. 1, p. 219):“ . . . They put the powder of the metall into the vessels upon furnaces, whereas they
“ anoint it and mortifie it with brine, putting to every fiftie quintalles of powder five“ quintalles of salt. And this they do for that the salt separates the earth and filth, to the“ end the quicksilver may the more easily draw the silver unto it. After, they put quick-
13 Aurum in ea remanet purum. This same error of assuming squeezed amalgam tobe pure gold occurs in Pliny: see previous footnote.