he re Ee 
A J 
PROCESS OF AMALGAMATION. 109 
The moliendas, or crushing-mills (arrastres, as 
called at some mines), employed for the pur- 
pose of grinding the ores, are somewhat sin- 
gular machines. A circular (or rather annu- 
lar) cistern of some twenty or thirty feet in di- 
ameter is dug in the earth, and the sides as well 
as the bottom are lined with hewn stone of 
the hardest quality. Transversely through an 
upright post which turns upon its axis in the 
centre of the plan, passes a shaft of wood, at 
each end of which are attached by cords one 
or two grinding stones with smooth fiat sur- 
faces, which are dragged (by mules fastened 
to the extremities of the shaft) slowly around 
upon the bottom of the cistern, into which the 
ore is thrown after being pounded into small 
pieces. It is here ground, with the addition 
of water, into an impalpable mortar, by the 
constant friction of the dragging stones against 
the sides and bottom of the cistern. A suita- 
ble quantity of quicksilver is perfectly mixed 
with the mortar; to which are added some 
muriates, sulphates, and other chemical sub- 
stances, to facilitate the amalgamation. The 
compound is then piled up in small heaps, 
and not disturbed again until this process is 
supposed to be complete, when it is transfer- 
red to the washing-machine. Those I have 
observed are very simple, consisting of a kind 
of stone tub, into which a stream of water is 
made to flow constantly, so as to carry off all the 
lighter matter, which is kept stirred up by an 
upright studded with pegs, that revolves in the 
centre, while the amalgamated metals sink 
VOL. It. 10 
