The cradle begat Long Tom and Broad Tom, the 'tom' proper being the upper
box with a grating to keep out the pebbles. 'Long Tom's' body is a wooden
trough, from twelve to fourteen feet long by a foot or a foot and a half
broad, with ripples, riffles, or cross-bars. There is usually another
grating at the lower end to intercept the smaller stones. The machine is
fixed in a gently sloping position, at an angle determined by
circumstances; the wash-dirt is lifted into the upper end by manual
labour; when stiff it must be stirred or shovelled, and a stream of water
does the rest. The greater gravity of the gold causes it to be arrested by
the riffles. Instead of the bars grooves may be cut and filled with
quicksilver. When the sludge is very rich, rough cloths rubbed with
mercury, or even sheepskins, the lineal descendants of the Golden Fleece,
may be used, 'Broad Tom,' _alias_ the 'Victoria Jenny Lind,' is made about
half the length of its long brother: the upper end is only a foot wide,
broadening out to three below.
'Tom' begat the sluice, which is of two kinds, natural and artificial. The
former is a ditch cut in the floor, with a _talus_ of one to forty or
fifty.
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