MINING. 279 
the size of a pigeon’s egg, are called a “ charge” for an arastra 
ten feet in diameter, aud are put in at a time. The mule is 
started and in four or five hours the quartz is pulverized. 
Water is now poured in until the powder is thoroughly mixed 
with it, and the mass has the consistence of thick cream Care 
is taken that the mixture be not too thin, for the thickness 
of it is important to the amalgamation. The paste being all 
right, some quicksilver (an ounce and a quarter of it for every 
ounce of gold in the quartz, and the amount of gold is guessed 
at from the appearance of the rock) is scattered over the aras- 
tra. The grinding continues for about two hours more, dur- 
ing which time it is supposed the quicksilver is divided up into 
very fine globules and mixed all through the paste (which is so 
stiff that the metal does not sink in it to the bottom), and that 
all the particles of gold are caught and amalgamated. The 
amalgamation having been completed, some water is let in 
three or four inches deep over the paste, and the mule is made 
to move slowly. The paste is thus dissolved in the water, and 
the gold, quicksilver, and amalgam have an opportunity to fall 
to the bottom. At the end of half an hour, or sooner, the 
thin mud of the arastra is allowed to run off, leaving the pre- 
cious material at the bottom. Another charge of broken 
quartz is now put in and the process is repeated, and so on. 
The length of a “run,” or the period from one cleaning up to 
another, varies much in different places. In the rude arastra 
a run is seldom less than a week, and sometimes three or four. 
The amalgam having settled down between the paving stones, 
the bed must be dug up and all the dirt between them carefully 
washed. In the improved arastra the paving fits so closely 
ingether, that the quicksilver and amalgam do not get down’ 
between them, but remain on the surface, and can readily be 
brushed up into a little pan, and therefore cleaning up is much 
less troublesome and is more frequently repeated than in the 
rude arastras; besides there is a greater need of frequent 
cleaning up in the improved arastras, because the amount of 
work done within a given time is usually greater. 
