202 VARIOUS MECHANICAL APPLIANCES.
tages
over the Tangential wheel. It is more easily built, has a decided
advantage in the setting of the nozzle, and is not so dependent on the
precise size of nozzle used. The capacity of these wheels may be
doubled by adding another nozzle.
It
is quite likely that a wheel considerably larger than the one used at
the University could be made to give a still higher efficiency than the
82-1/2 per cent, found. The angles in the pattern for bucket castings
could be made more accurate.
THE PAN.
The
pan, an indispensable companion of the gold-miner, is pressed from a
single piece of Russia sheet iron. It is 12 inches in diameter at the
bottom and 15 to 16 inches on the top, the sides inclining outward at
an angle of about 36 degrees, and turned over a wire around the edge to
strengthen it. It is used in prospecting, cleaning gold-bearing sand,
collecting amalgam in the sluices, and, in fact, in every branch of the
business.
Its
proper manipulation for washing dirt requires a certain skill, which
can be acquired only by practice. The pan, filled with dirt, is
submerged in a tub or pool of water and the gravel worked with the
hands until all cernented material is disintegrated. The coarse stones
are cleaned and thrown out. In washing the residue the pan is held in a
tilted position. By a circular motion and by careful use of the water,
into which the pan is continually dipped, all the lighter dirt is
worked to the top and over the edge (pebbles being picked out by hand)
until only the fine gold and black iron sand remain.
THE BATEA.
The
batea is a shallow wooden bowl commonly used in Brazil and the
Spanish-American States for separating, on a limited scale, grains of
gold from sand, p}'ritic matÂter, and magnetic iron. "A disc of 17
inches diameter,
