Chemically speaking, they make compounds easily.

"It's the same way with mercury, or, as it is generally called,
quicksilver. Gold and quicksilver are chums, and the minute they get
together they join to form a mixture which is called an amalgam.
That's one of the great discoveries of the age. Gold-mining has taken
a big jump forward since that was found out.

"You can see yourself how that would work. Whether with a pan, a
cradle, or a sluice, the only thing that enables a miner to separate
the gold from the worthless dirt is that the gold is smaller and
heavier. But suppose the gold dust is so fine as to be invisible, it
will be so light as to wash away easily; if it is in fine flakes, the
flakes will almost float. All that light gold would be lost in the
dirt that flows out of the bottom of the sluice, the tailings, as they
are called.

"In the days that Jim is describing, two-thirds of the gold was lost
that way. Every one, absolutely every single one of the forty-niners
would have made a fortune, if the chemistry of gold had been as far
advanced then as it is to-day. Even now, men are working over with
profit the tailings that the forty-niners threw away.

"Suppose, now, you make your sluice, cover the bottom of it and the
riffles with copper plates to hold the quicksilver better, and then
cover your copper with quicksilver. What happens when the dirt and
water come flowing down the sluice? The riffles will catch your heavy
gold, just as well as before, and the quicksilver will catch a lot of
the light gold that used to escape. You've got your gold in the
riffles, then, and you've got a mixture of gold and quicksilver which
has formed an amalgam.

"Now, the mixture has to be made to give back that gold. First of all
it is pressed through canvas or buckskin in order to get rid of the
liquid quicksilver, which will pass through the weave of the first and
the pores of the second, leaving inside only such of it as has firmly
allied itself with the gold to form the amalgam.

"The next thing to do is to put this amalgam into a retort, out of
which leads a long pipe, and to subject this retort to intense heat.
Quicksilver is vaporized at a comparatively low temperature--for a
metal. It is driven from the amalgam in the form of vapor, much as
water may be driven off in steam. The quicksilver vapor passes along
this long pipe, which leads to several coils placed in a tank of
running cold water. The cold chills the