The unlearned multitude of artisans distinguish three kinds of chrysocolla; the rough chrysocolla, which is valued at seven denarii per pound; the middling, worth five denarii; and the bruised, also known as the “herbaceous” chrysocolla, worth three denarii per pound. Before laying on the sanded[934] chrysocolla, they underlay coats of atramentum[935] and parætonium,[936] substances which make it hold, and impart a softness to the colours. The parætonium, as it is naturally very unctuous, and, from its smoothness, extremely tenacious, is laid on first, and is then covered with a coat of atramentum, lest the parætonium, from its extreme whiteness, should impart a paleness to the chrysocolla. The kind known as “lutea,” derives its name, it is thought, from the plant called “lutum;” which itself is often pounded with cæruleum[937] instead of real chrysocolla, and used for painting, making a very inferior kind of green and extremely deceptive.[938] CHAP. 28.—SEVEN REMEDIES DERIVED FROM CHRYSOCOLLA. Chroysocolla, too, is made use of in medicine. In combination with wax and oil, it is used as a detergent for wounds; and used by itself in the form of a powder, it acts as a desiccative, and heals them. In cases, too, of quinsy and hardness of breathing, chrysocolla is prescribed, in the form of an electuary, with honey. It acts as an emetic also, and is used as an ingredient in eye-salves, for the purpose of effacing cicatrizations upon the eyes. In green plasters too, it is used, for soothing pain and making scars disappear. This kind of chrysocolla[939] is known by medical men as “acesis,” and is altogether different from orobitis. CHAP. 29.—THE CHRYSOCOLLA OF THE GOLDSMITHS, KNOWN ALSO AS SANTERNA. The goldsmiths also employ a chrysocolla[940] of their own, for the purpose of soldering gold; and it is from this chrysocolla, they say, that all the other substances, which present a similar green, have received their name. This preparation is made from verdigris of Cyprian copper, the urine of a youth who has not arrived at puberty, and a portion of nitre.[941] It is then pounded with a pestle of Cyprian copper, in a copper mortar, and the name given to the mixture is “santerna.” It is in this way that the gold known as “silvery”[942] gold is soldered; one sign of its being so alloyed being its additional brilliancy on the application of santerna. If, on the other hand, the gold is impregnated with copper, it will contract, on coming in contact with the santerna, become dull, and only be soldered with the greatest difficulty: indeed, for this last kind of gold, there is a peculiar solder employed, made of gold and one-seventh part of silver, in addition to the materials above-mentioned, the whole beaten up together. CHAP. 30.—THE MARVELLOUS OPERATIONS OF NATURE IN SOLDERING METALLIC SUBSTANCES, AND BRINGING THEM TO A STATE OF PERFECTION.