The wooden sluices in the tunnels already described
are often made double for the convenience of "cleaning up" one of them,
while the other remains in action. The process of cleaning up is performed
according to the quantity and richness of the material worked upon, at
intervals of twenty to forty days, and consists in removing the pavement
and blocks from the bed of the sluice, and then gathering all the amalgam
of gold and rich dirt collected, and replacing the locks in the same way
as at first. Advantage is taken on this occasion to reverse the position
of the blocks and stones when they are worn irregularly, or substitute new
ones for those which are worn through. The mechanical action of the
washing process on the blocks is of course very rapid and severe,
requiring complete renewal of them once in eight to ten weeks. Some miners
prefer a pavement of egg-shaped stones set like a cobble-stone flooring,
the gold being deposited in the interstices. Most of the sluiceways are,
however, paved with rectangular wooden blocks, with or without stones as
described. Standing at the mouth of one of the long tunnels in full
action, any person unaccustomed to the process is struck with
astonishment, amounting almost to terror, as the muddy mass sweeps onward,
bearing in its course the great rolling bowlders, which add their din to
the roar of the water, the whole being precipitated down a series of
falls, at each of which it is caught up again by new sluices of timber,
lined like the first, and so onward and downward many hundreds of feet
until the level of the river is reached, at a distance of about a half
mile or more from the mouth of the first tunnel.
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