BOOK VIII. 



341 



A — Strakes. B — Tank. C — Launder. D — Plug. E — Wooden shovel. 

 F — Wooden mallet. G — Wooden shovel with short handle. H — The plug 

 IN the strake. I — Tank placed under the plug. 



of the loaded strake with a vi'ooden mallet, in order that the tin-stone clinging 

 to the sides may fall off ; all that has settled in it, he throws out with a 

 wooden shovel which has a short handle. Silver slags which have been 

 crushed under the stamps, also fragments of silver-lead alloy and of cakes 

 melted from pyrites, are washed in a strake of this kind. 



Material of this kind is also washed while wet, in a sieve whose bottom 

 is made of woven iron wire, and this is the fourth method of washing. The 

 sieve is immersed in the water which is contained in a tub, and is violently 

 shaken. The bottom of this tub has an opening of such size that as much 

 water, together with tailings from the sieve, can flow continuously out of it as 

 water flows into it. The material which settles in the strake, a boy either 

 digs over with a three-toothed iron rake or sweeps with a wooden scrubber ; 

 in this way the water carries off a great part of both sand and mud. The 

 tin-stone or metalliferous concentrates settle in the strake and are afterward 

 washed in another strake. 



These are ancient methods of washing material which contains tin- 

 stone ; there follow two modern methods. If the tin-stone mixed with 



