vapor, condensing it into the
liquid state again, and the quicksilver runs out of the end of the
pipe, ready for use once more. The pure gold is left.

"But, even with the use of quicksilver on the sluice there was still
40 per cent. of the gold that got away. For many years there was no
practical way of recovering this loss, and the chemists of the world
tore their hair in despair. What was needed was to find some other
chum of gold, even more affectionate than mercury. The chemists found
this new friend, at last, in cyanide, which is a salt of prussic acid.
Cyanide, Clem, is an arrant flirt, as I'll show you, in a minute.

"Nowadays, the tailings, after passing over the long sluice or flume,
and after having dropped the heavy gold in the riffles and given some
of the light gold to the quicksilver, are led to a huge churn. There
the earth and water are pounded together into a sort of slime. A wheel
lifts this slime into a movable chute from which it is poured into a
series of vats or tanks. These tanks contain cyanide, which has
already allied itself with a chum--potassium.

"But cyanide likes gold even better than it does potassium, and, as
soon as the slime strikes the vat, the cyanide lets go the potassium
and clings to the gold. Cyanide of gold is formed. So far, so good.
But what the miner wants is pure gold.

"The cyanide is pumped up out of those tanks into another chute, which
pours it into a second lot of tanks, fastened to the side of which are
large bundles of zinc shavings. The cyanide liked the gold better than
the potassium, but it has the bad taste to prefer zinc even to gold.
It releases the gold and flies to the embrace of the zinc. The gold,
suddenly deserted of the friendship of the cyanide, powders down to
the bottom of the tank, in absolutely pure form, ready to be melted
down into bars. By other processes, which I won't bother you by
describing now, the zinc is released from the cyanide, and the cyanide
is led to its old friend the potassium, ready to begin work anew. So,
you see, nothing is wasted.

"This process, and this only, has made the astounding wealth of South
Africa, for, as I told you, the reefs there are of very low-grade ore,
so low that Jim, here, would have turned up his nose at it. The
modern ability of chemists to get out the tiniest particle of gold
that lies in the most stubborn rock has made the Rand a richer region
than a prospector's wildest dream."

"If I'd known all