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 solidified 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 fired22.
	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 hghted. These cakes are generally roasted seven times and occasionally nine times. While this is being done, if they are 22There 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. 1 ; 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.