The Cyprian spodos[1] is the best. It is formed by fusing cadmia with copper ore. This substance, which is the lightest part of the metal disengaged by fusion, escapes from the furnace, and adheres to the roof, being distinguished from the soot by the whiteness of its colour. Such parts of it as are less white are indicative of incomplete combustion, and it is this which some persons call "pompholyx." Such portions of it as are of a more reddish colour are possessed of a more energetic power, and are found to be so corrosive, that if it touches the eyes, while being washed, it will cause blindness. There is also a spodos of a honey colour, an indication that it contains a large proportion of copper. All the different kinds, however, are improved by washing; it being first skimmed with a feather,[2] and afterwards submitted to a more substantial washing, the harder grains being removed with the finger. That, too, which has been washed with wine is more modified in its effects; there being also some difference according to the kind of wine that is used. When it has been washed with weak wine the spodos is considered not so beneficial as an ingredient in medicaments for the eyes; but the same kind of preparation is more efficacious for running sores, and for ulcers of the mouth attended with a discharge of matter, as well as in all those remedies which are used for gangrene.

There is also a kind of spodos, called "lauriotis,"[3] which is made in the furnaces where silver is smelted. The kind, however, that is best for the eyes, it is said, is that produced in the furnaces for smelting gold. Indeed there is no department of art in which the ingenuity of man is more to be admired; for it has discovered among the very commonest objects, a substance that is in every way possessed of similar properties.