tree trunk. Quicksilver12 is 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 little 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 ä 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 16th 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 thev
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 ; withoux
" it, neither silver nor brass can be properly gut. 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 (xxxm, 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. 1, 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 Probierbüchlein
(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 RelfcMetallica, 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 che tiene oro), well
" ground in a mortar and afterward washed and dried; and, with the above-mentioned
