BOOK VIII. 



321 



concentrates are washed separately in different bowls from those which have 

 settled on the canvas. This bowl is smooth and two digits wide and deep, 

 being in shape very similar to a small boat ; it is broad in the fore part, 

 narrow in the back, and in the middle of it there is a cross groove, in which 

 the particles of pure gold or silver settle, while the grains of sand, since they 

 are lighter, flow out of it. 



In some parts of Moravia, gold ore, which consists of quartz mixed with 

 gold, is placed under the stamps and crushed wet. When crushed fine it 

 flows out through a launder into a trough, is there stirred by a wooden 

 scrubber, and the minute particles of gold which settle in the upper end of 

 the trough are washed in a black bowl. 



A — Stamps, B — Mortar. C — Pl.-vtes full of holes. D— Transverse launder. 



E — Planks full of cup-like depressions. F — Spout. G — Bowl into which the 



concentrates fall. H — Canvas strake. I — Bowls shaped like a small boat. 



K — Settling-pit under the canvas strake. 



So far I have spoken of machines which crush wet ore with iron-shod 

 stamps. I will now explain the methods of washing which are in a measure 

 peculiar to the ore of certain metals, beginning with gold. The ore which 

 contains particles of this metal, and the sand of streams and rivers which 



