530	BOOK XI
	and then they dig out with pointed picks the holes in the cakes, which contain the same kind of copper. The head of the round hammer is three palms and a digit long ; one end of the head is round and two digits long and thick ; the other end is chisel-shaped, and is two digits and a half long. The sharp pointed hammer is the same length as the round hammer, but one end is pointed, the other end is square, and gradually tapers to a point.
	The nature of copper is such that when it is " dried " it becomes ash coloured, and since this copper contains silver, it is smelted again in the blast furnaces.23 I have described sufficiently the method by which exhausted liquation cakes are " dried " ; now I will speak of the method by which they are made into copper after they have been " dried." These cakes, in order that they may recover the appearance of copper which they have to some extent lost, are melted in four furnaces, which are placed against the second long wall in the part of the building between the second and third transverse walls. This space is sixty-three feet and two palms long, and since each of
	23See note 29, p. 540.