348 BOOK VIII. 



they throw it into a copper sieve, and separate the very small pieces which 

 pass through the sieve from the larger ones ; of these the former are smelted 

 in a faggot pile and the latter in the furnace. Of such a number then are 

 the methods of washing. 



A — Trough. B — Launder. C — Hoe. D — Sieve. 



One method of burning is principally employed, and two of roasting. 

 The black tin is burned by a hot fire in a furnace similar to an oven^^ ; it 

 is burned if it is a dark -blue colour, or if pyrites and the stone from which 

 iron is made are mixed with it, for the dark blue colour if not burnt, consumes 

 the tin. If pyrites and the other stone are not volatihsed into fumes in a 

 furnace of this kind, the tin which is made from the tin-stone is impure. 

 The tin-stone is thrown either into the back part of the furnace, or into one 

 side of it ; but in the former case the wood is placed in front, in the latter 

 case alongside, in such a manner, however, that neither firebrands nor 

 coals may fall upon the tin-stone itself or touch it. The fuel is manipulated 

 by a poker made of wood. The tin-stone is now stirred with a rake with two 



'^From a metallurgical point of view all of these operations are roasting. Even 

 to-day, however, the expression " burning " tin is in use in some parts of Cornwall, and in 

 former times it was general. 



