é 
Alembic for distilling Amalgam of Gold. 67 
these sometimes give twenty five or fifty and in some instances even 
seventy five per cent. more of gold by assays made in the closet, than 
they will yield in the practical way of extracting the metal ona 
large scale. 
Either Chilian mills or stamps, commonly the latter, are used for 
reducing the gangue (slate or quartz) to the state of fine sand; by 
this operation the larger particles of gold are detached from its ma- 
trix, and remain mixed with the sand. ‘The stamps are large cast 
iron pounders, weighing four or five cwt. They tend, by repeated 
blows, and by keeping up a constant trituration among the grains of 
pounded quartz, to render the particles of gold, how minute soever 
these in the first instance may be, still more impalpable. 
The gold and sand thus pounded and mixed together, are washed 
out through a copper sieve, by a constant stream of water from un- 
der the stamps, and by it carried thence over several feet of bul- 
Jocks’ hides, resting on an inclined plane, having their hair upwards 
and the grain of the hair turned down stream. ‘The heavier parti- 
cles of gold, and other weighty minerals, such as the sulphate of ba- 
ryta, the sulphurets of lead, zinc, iron, copper, and the like, lodge 
im the hair of the roughly tanned skins, while the sand, and much 
of the gold in attenuated particles, are carried off together into the 
waste by the force of the water. At some of the mines the gold is 
disseminated through the quartz, in particles so minute, that they are 
seldom visible to the naked eye. When this is the case, much of 
the precious metal is floated off by reason of its buoyancy. ‘The 
phenomenon of solid particles of gold being floated on water may 
be readily understood ; for if we imagine a solid cube to be cut from 
a flake of gold leaf, and this cube to be further diminished by trun- 
cation and bevelment, it is very evident, that the specific gravity of 
this crystal, will not be less than that of the ingot from which the 
gold beater obtained it; but if it be placed in a vessel of water, in 
order to sink, it must, in consequence of it and the water not actu- 
ally touching each other, displace a quantity of that fluid many times 
greater in volume than the crystal; therefore the latter, whatever 
its size might be, would not sink, so long as the volume of water to 
be displaced by sinking, should exceed the crystal in weight. Upon 
the same principle, a cambric needle will float on water, while the 
bar of steel from which it was manufactured, will displace several 
jimes its own volume of the same fluid, and carry with it to the 
bottom large pieces of cork and the like. 
