Puddling-Box._--The puddling-box is a rough wooden box, about a foot
deep and six feet square, and is used for dissolving very tough clay.
The clay is thrown into the box, with water, and a miner stirs the
stuff with a hoe until the clay is all thoroughly dissolved, when he
takes a plug from an auger-hole about four inches from the bottom, and
lets the thin solution of the clay run off, while the heavier material,
including the gold, remains at the bottom. He then puts in the plug
again, fills up the box with water, throws in more clay, and repeats
the process again and again until night, when he cleans up with a
cradle or pan. The puddling-box is used only in small mining
operations, and never with the sluice, or in hydraulic claims.

_Quicksilver-Machine._--The quicksilver-machine, or Burke rocker, is a
cradle about seven feet long, two feet wide, and two feet high. In the
bottom are a number of compartments, all containing quicksilver. One
man rocks the machine without cessation. A constant stream of water
pours into the machine at its head. The riddle extends the whole length
of the machine; and the stones, after being washed clean, fall off the
riddle at the lower end. One man is employed constantly working with a
shovel to keep the dirt on the riddle under the stream of water, and in
throwing off the big stones. If the pay-dirt is very convenient, two
men can shovel enough to keep the machine in operation. The Burke
rocker was extensively used in California eight and ten years ago, but
now it is a great rarity.

_Tunnel-Mining._--A tunnel, in California mining, is an adit or drift
entering a hill-side, or running out from a shaft. Mining-tunnels are
usually nearly horizontal--those entering hill-sides having a slight
ascent, for the double purpose of draining the mine, and to facilitate
the removal of the pay-dirt. In a few hills the tunnels run downward at
an angle of twenty degrees or more, to avoid veins or ledges of rock,
which would have to be blasted through if the tunnel were cut
horizontally; but this can only be done with safety in hills which are
drained by older horizontal tunnels.

The mining-tunnel does not run through a hill, but only into it. The
length of tunnels varies greatly; the longest are about a mile. The
usual height is seven feet, the width five feet. Ordinarily the top
must be supported by timbers, to prevent it from falling in, and not
unfrequently the sides must also be protected by b