BOOK VIII. 



287 



the cam-shaft ; in this case the cams on both sides raise the stamps, which 

 either both crush dry or wet ore, or else the one set crushes dry ore and the 

 other set wet ore, just as circumstances require the one or the other ; 

 further, when the one set is raised and the iron clavises in them are fixed 

 into openings in the first cross-beam, the other set alone crushes the ore. 



Broken rock or stones, or the coarse or fine sand, are removed from 

 the mortar of this machine and heaped up, as is also done with the same 

 materials when raked out of the dump near the mine. They are thrown 

 by a workman into a box, which is open on the top and the front, and is three 

 feet long and nearly a foot and a half wide. Its sides are sloping and made 

 of planks, but its bottom is made of iron wire netting, and fastened with 

 wire to two iron rods, which are fixed to the two side planks. This bottom 

 has openings, through which broken rock of the size of a hazel nut cannot 

 pass ; the pieces which are too large to pass through are removed by the 

 workman, who again places them under stamps, while those which have 

 passed through, together with the coarse and fine sand, he collects in a large 

 vessel and keeps for the washing. When he is performing his laborious 



A BOX LAID FLAT ON THE GROUND. B ITS BOTTOM WHICH IS MADE OF IRON WIRE. 



C BOX INVERTED. D IRON RODS. E BOX SUSPENDED FROM A BEAM, THE INSIDE 



BEING VISIBLE. F BOX SUSPENDED FROM A BEAM, THE OUTSIDE BEING VISIBLE. 



