BOOK VIII. 307 



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. 



A — Short strake. B — Small launder. C — Transverse launder. D — Wooden 



SCRUBBER. 



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 nmning 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 sUghtly overlap it ; on 



