In all the water of the sea there is gold--about 400 tons in a cubic
mile--in very much of the soil, some in all Philadelphia clay, in the
Pactolian sands of every river where Midas has bathed, and in many
rocks of the earth. But it is so fine and so mixed with other
substances that in many cases it cannot be seen. Look at the ore from
a mine that is giving its owners millions of dollars. Not a speck of
gold can be seen. How can it be secured? Set a trap for it. Put down
something that has an affinity--voracious appetite, unslakable thirst,
metallic affection--for gold, and they will come together.

We have heard of potable gold--"_potabile aurum_." There are metals to
which all gold is drinkable. Mercury is one of them. Cut transverse
channels, or nail little cleats across a wooden chute for carrying
water. Put mercury in the grooves or before the cleats, and shovel
auriferous gravel and sand into the rushing water. The mercury will
bibulously drink into itself all the fine invisible gold, while the
unaffectionate sand goes on, bereaved of its wealth.

Put gold-bearing quartz under an upright log shod with iron. Lift and
drop the log a few hundred times on the rock, until it is crushed so
fine that it flows over the edge of the trough with constantly going
water, and an amalgam of mercury spread over the inclined way down
which the endusted water flows will drink up all the gold by force of
natural affection therefor.

Neither can the gold be seen in the mercury. But it is there. Squeeze
the mercury through chamois skin. An amalgam, mostly gold, refuses to
go through. Or apply heat. The mercury flies away as vapor and the
gold remains.