BOOK VIII. 



275 



to the ore whicli has bfcn roasted, while it is still hot, in order to make 

 it softer and more easily broken ; lur after lire has dried up the moisture 

 in the ore, it breaks up more easily while it is still hot, ol which fact burnt 

 limestone affords the best example. 



By iligL;ing out the earth they make the areas much larger, and square ; 

 walls should be built along the sides and back to hold the heat of the 

 fire more effectively, and the front should be left open. In these compart- 

 ments tin ore is roasted in the following manner. Fiist of all wood about 

 twelve feet long should be laid in the area in four layers, alternately straight 

 and transverse. Then the larger pieces of ore should be laid upon them, and 

 on these again the smaller ones, which should also be placed around the sides ; 

 the fine sand of the same ore should also be spread over the pile and pounded 

 with shovels, to prevent the pile from falling before it has been roasted ; the 

 w(.)od should then bo fired. 



A — Lighted pyre. 



-Pyre which is being constructed. C — Ore. D- 

 E — Pile of the same wood. 



Lead ore, if roasting is necessary, should be piled in an area just like the 

 last, but sloping, and the wood should be placed over it. A tree trunk should 

 be laid' right across the front of the ore to prevent it from falling out. The 

 ore, being roasted in this way, becomes partly melted and resembles slag. 



