298 BOOK VIII. 



axle, one end of which is mortised into the large horizontal axle, and the 

 other end is held in a hollow covered with thick iron plates in a beam. Thus 

 the paddles, of which there are three sets in each tub, turn round, and 

 agitating the powder, thoroughly mix it with water and separate the minute 

 particles of gold from it, and these are attracted by the quicksilver and 

 purified. The water carries away the waste. The quicksilver is poured 

 into a bag made of leather or cloth woven from cotton, and when this bag is 

 squeezed, as I have described elsewhere, the quicksilver drips through it into 

 a jar placed underneath. The pure gold 13 remains in the bag. Some people 

 substitute three broad sluices for the tubs, each of which has an angular axle 

 on which are set six narrow spokes, and to them are fixed the same number of 

 broad paddles ; the water that is poured in strikes these paddles and turns 

 them round, and they agitate the powder which is mixed with the water and 

 separate the metal from it. If the powder which is being treated contains 

 gold 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 which 

 are the small black stones from which tin is smelted, this latter method is 

 not to be despised. It is very advantageous to place interlaced fir boughs 

 in the sluices in which such tin-stuff is washed, after it has run through the 

 launders from the mills, because the fine tin-stone is either held back by the 

 twigs, or if the current carries them along they fall away from the water 

 and 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 mer curio). 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 may 

 be ultimately reduced either by lead or mercury. Concerning these silver concentrates 

 he 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 probably 

 never be cleared up. According to Ulloa (Relation Historica Del Viage a la America 

 Meridional, Madrid, 1748) Dom Pedro Fernandes De Velasco discovered the process in Mexico 

 in 1566. The earliest technical account is that of Father Joseph De Acosta (Historia Natural 

 y 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 years 

 1570 to 1585 in Peru, and 1586 in Mexico. It may be noted that Potosi was discovered 

 in 1545. He states that refining silver with mercury was introduced at Potosi by Pedro 

 Fernandes de Velasco from Mexico in 1571, and states (Grimston's Trans., Vol. i, 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 to 

 be pure gold occurs in Pliny : see previous footnote. 



