The collyrium DIAMISYOS or DIAMYSOS derived its designation from containing as its principal ingredient the _Misy_, a metallic vitriolic preparation, used to a considerable extent as a stimulant and escharotic among the ancients; and it was retained even to a comparatively late period in the London Pharmacopœia.[573] It appears to be still used medicinally in the East.[574] The chemical nature, however, of _Misy_ has given rise to some considerable doubt and discussion. It was usually found, and generally described, along with two other cognate fossils, _Sori_ and _Chalcitis_. And Galen, who enters into an elaborate description of them, visited the copper mines of Cyprus, with a view of determining the precise nature of these three mineral substances.[575] Dr. Adams,[576] who has examined this question with all his well-known great learning and care, believes that these three minerals were merely varieties of _chalcanthum_ or copperas. In his opinion the _Chalcitis_ was probably a kind of pure sulphate of copper which had contracted an efflorescence from age; the _Sori_ was sulphate of copper combined with zinc or other impurities; and the _Misy_ was a combination of sulphate of copper with sulphate of iron, the predominance of the chalybeate salt giving to the fossil its peculiar colour. For the Misy, says Dioscorides, is “of a golden appearance, hard, shining like gold when broken, and glancing like stars.” In his remarks on the _Misy_, Dioscorides speaks of the analogy of its caustic power with those of Chalcitis; but the only diseases that he referred to as having the _Misy_ used in their treatment, are the diseases of the eye. And he does so in telling us that the Egyptian kind of _Misy_ is quite inferior to the Cyprian in forming eye-medicines (ocularia medicamenta).[577]