350 BOOK VIII. 



in order that, if there is in the cakes any alum or vitriol or saltpetre capable 

 of injuring the metals, although it rarely does injure them, the water may 

 remove it and make the cakes soft. The soUdified juices are nearly all 

 harmful to the metal, when cakes or ore of this kind are smelted. The cakes 

 which are to be roasted are placed on wood piled up in the form of a crate, 

 and this pile is fired^^. 



A — Pits. B — Wood. C — Cakes. D — L.\under. 



The cakes which are made of copper smelted from schist are first thrown 

 upon the ground and broken, and then placed in the furnace on bundles of 

 faggots, and these are lighted. These cakes are generally roasted seven 

 times and occasionally nine times. While this is being done, if they are 



^^There can be no doubt that these are mattes, as will develop in Chapter ix. The 

 German term in the Glossary for panes ex pyrite is stein, the same as the modern German 

 for matte. Orpiment and realgar are the yellow and red arsenical sulphides. The cadmia 

 was no doubt the cobalt-arsenic minerals (see note on p. 112). The "solidified juices" were 

 generally anything that could be expelled short of smelting, i.e., roasted off or leached out, 

 as shown in note 4, p. i ; they embrace the sulphates, salts, sulphur, bitumen, and 

 arsenical sulphides, etc. For further information on leaching out the sulphates, alum, etc., 

 see note 10, p. 564. 



