336 



BOOK VIII. 



A LARGE BOWL* B ROPES. C BEAM. D OTHER LARGE BOWL WHICH COINERS 



USE. E SMALL BOWL. 



it. This bowl, when shaken, is held in one hand and thumped with the other 

 hand. In other respects this method of washing does not differ from the 

 last. 



I have spoken of the various methods of washing sand which contains 

 grains of gold ; I will now speak of the methods of washing the material in 

 which are mixed the small black stones from which tin is made 20 . Eight 

 such methods are in use, and of these two have been invented lately. Such 

 metalliferous material is usually found torn away from veins and stringers 

 and scattered far and wide by the impetus of water, although sometimes 

 venae dilatatae are composed of it. The miners dig out the latter material 

 with a broad mattock, while they dig the former with a pick. But they dig 

 out the little stones, which are not rare in this kind of ore, with an instrument 

 like the bill of a duck. In districts which contain this material, if there is 

 an abundant supply of water, and if there are valleys or gentle slopes and 

 hollows, so that rivers can be diverted into them, the washers in summer- 



20 As the concentration of crushed tin ore has been exhaustively treated of already, 

 the descriptions from here on probably refer entirely to alluvial tin. 



