BOOK VIII. 297 



tree trunk. Quicksilver^^ jg placed in each tub, across which is fixed a small 

 plank, and through a hole in the middle of each plank there passes a small 

 upright axle, which is enlarged above the plank to prevent it from dropping 

 into the tub lower than it should. At the lower end of the axle three sets 

 of paddles intersect, each made from two httle boards fixed to the axle 

 opposite each other. The upper end of this axle has a pinion held by a 

 bearing set in a beam, and around each of these axles is a small drum made 

 of rundles, each of which is turned by a small toothed drum on a horizontal 



**HiSTORiCAL Note on Amalgamation. The recovery of gold by the use of mercury 

 possibly dates from Roman times, but the application of the process to silver does not 

 seem to go back prior to the i6th Century. Quicksilver was well-known to the Greeks, 

 and is described by Theophrastus (105) and others (see note 58, p. 432, on quicksilver). 

 However, the Greeks made no mention of its use for amalgamation, and, in fact, 

 Dioscorides (v, 70) says " it is kept in vessels of glass, lead, tin or silver ; if kept in 

 " vessels of any other kind it consumes them and flows away." It was used by them 

 for medicinal purposes. The Romans amalgamated gold with mercury, but whether they 

 took advantage of the principle to recover gold from ores we do not know. Vitruvius 

 (vii, 8) makes the following statement : — " If quicksilver be placed in a vessel and a 

 " stone of a hundred pounds' weight be placed on it, it will swim at the top, and will, 

 " notwithstanding its weight, be incapable of pressing the liquid so as to break or separate 

 " it. If this be taken out, and only a single scruple of gold be put in, that will not swim, but 

 " immediately descend to the bottom. This is a proof that the gravity of a body does not 

 " depend on its weight, but on its nature. Quicksilver is used for many purposes ; without 

 " it, neither silver nor brass can be properly gilt. When gold is embroidered on a garment 

 " which is worn out and no longer fit for use, the cloth is burnt over the fire in earthen pots ; 

 " the ashes are thrown into water and quicksilver added to them ; this collects all the 

 " particles of gold and unites with them. The water is then poured off and the residuum 

 " placed in a cloth, which, when squeezed with the hands, suffers the liquid quicksilver to 

 " pass through the pores of the cloth, but retains the gold in a mass within it." (Gwilt's 

 Trans., p. 217). Pliny is rather more explicit (xxxni, 32) : " All floats on it (quicksilver) 

 " except gold. This it draws into itself, and on that account is the best means of purifying ; 

 " for, on being repeatedly agitated in earthen pots it casts out the other things and the 

 " impurities. These things being rejected, in order that it may give up the gold, it is squeezed 

 " in prepared skins, through which, exuding like perspiration, it leaves the gold pure." It 

 may be noted particularly that both these authors state that gold is the only substance that 

 does not float, and, moreover, nowhere do we find any reference to silver combining with 

 mercury, although Beckmann (Hist, of Inventions, Vol. i, p. 14) not only states that the 

 above passage from Pliny refers to silver, but in further error, attributes the origin of silver 

 amalgamation of ores to the Spaniards in the Indies. 



The Alchemists of the Middle Ages were well aware that silver would amalgamate with 

 mercury. There is, however, difficulty in any conclusion that it was applied by them to 

 separating silver or gold from ore. The involved gibberish in which most of their utterances 

 was couched, obscures most of their reactions in any event. The School of Geber (Appendix B) 

 held that all metals were a compound of " spiritual " mercury and sulphur, and they clearly 

 amalgamated silver with mercury, and separated them by distillation. The ProbierhUchlein 

 (1520 ?) describes a method of recovering silver from the cement used in parting gold and 

 silver, by mixing the cement (silver chlorides) with quicksilver. Agricola nowhere in 

 this work mentions the treatment of silver ores by amalgamation, although he was familiar 

 with Biringuccio (De La Pirotechnia), as he himself mentions in the Preface. This work, 

 published at least ten years before De Re Metallica, contains the first comprehensive 

 account of silver amalgamation. There is more than usual interest in the description, 

 because, not only did it precede De Re Metallica, but it is also a specific explanation 

 of the fundamental essentials of the Patio Process long before the date when the Spaniards 

 could possibly have invented that process in Mexico. We quote Mr. A. Dick's translation 

 from Percy (Metallurgy of Silver and Gold, p. 560) : 



" He was certainly endowed with much useful and ingenious thought who invented 

 " the short method of extracting metal from the sweepings produced by those arts which have 

 " to do with gold and silver, every substance left in the refuse by smelters, and also the 

 " substance from certain ores themselves, without the labour of fusing, but by the sole 

 " means and virtue of mercury. To effect this, a large basin is first constructed of stone or 

 " timber and walled, into which is fitted a millstone made to turn like that of a mill. Into the 

 " hollow of this basin is placed matter containing gold (della materia vra cite tiene oro), well 

 " ground in a mortar and afterward washed and dried ; and, with the above-mentioned 



