plates, because it remains intact, while the rods, when worn by rubbing, can
easily be replaced by others.
Miners use the seventh method of washing when there is no stream of
water in the part of the mountain which contains the black tin, or particles of
gold, or of other metals. In this case they frequently dig more than fifty
ditches on the slope below, or make the same number of pits, six feet long,
three feet wide, and three-quarters of a foot deep, not any great distance
from each other. At the season when a torrent rises from storms of
great violence or long duration, and rushes down the mountain, some of
the miners dig the metalliferous material in the woods with broad hoes and
