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also separate the concentrates from the broken rock in them and collect them
in tubs. The short strake is now rarely employed by miners, owing to the
carelessness of the boys, which has been frequently detected ; for this
reason, the jigging-sieve has taken its place. The mud which settles in the
launder, if the ore is rich, is taken up and washed in a jigging-sieve or on a
canvas strake.
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A canvas strake is made in the following way. Two beams, eighteen feet
long and half a foot broad and three palms thick, are placed on a slope ; one
half of each of these beams is partially cut away lengthwise, to allow the ends
of planks to be fastened in them, for the bottom is covered by planks three
feet long, set crosswise and laid close together. One half of each supporting
beam is left intact and rises a palm above the planks, in order that the water
that is running down may not escape at the sides, but shall flow straight
down. The head of the strake is higher than the rest of the body, and slopes
so as to enable the water to flow away. The whole strake is covered by six
stretched pieces of canvas, smoothed with a stick. The first of them occupies
the lowest division, and the second is so laid as to slightly overlap it ; on
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