The apparatus subservient to the first objects are sieves, running
buddles, and gratings. The large sieves employed in Derbyshire for
sorting the ore at the mouth of the mine, into coarse and fine pieces,
is a wire gauze of iron; its meshes are square, and an inch long in each
side. There is a lighter sieve of wire gauze, similar to the preceding,
for washing the mud from the ore, by agitating the fragments in a tub
filled with water. But in Derbyshire, instead of using this sieve, the
pieces of ore are sometimes merely stirred about with a shovel, in a
trough filled with water. This is called a _standing buddle_; a most
defective plan.
The _running buddle_ serves at once to sort and cleanse the ore. It
consists of a plane surface made of slabs or planks, very slightly
inclined forwards, and provided behind and on the sides with upright
ledges, the back one having a notch to admit a stream of water. The ore
is merely stirred about with a shovel, and exposed on the slope to the
stream. For this apparatus, formerly the only one used at the mines of
Alston Moor, the following has been substituted, called the _grate_. It
is a _grid_, composed of square bars of iron, an inch thick, by from 24
to 32 inches long, placed horizontally, and parallelly to each other, an
inch apart. There is a wooden canal above the grate, which conducts a
stream of water over its middle; and an inclined plane is set beneath
it, which leads to a hemispherical basin, about 24 inches inches in
diameter, for collecting the metallic powder washed out of the ore.