It is a remarkable fact, that if we pour water into a vessel of lead, it will not melt; but that if we throw into the water a pebble or a copper quadrans,[1730] the vessel will be penetrated by the fire. CHAP. 50. (18.)—FIFTEEN REMEDIES DERIVED FROM LEAD. Lead is used in medicine, without any addition, for the removal of scars; if it is applied, too, in plates, to the region of the loins and kidneys, in consequence of its cold nature it will restrain the venereal passions, and put an end to libidinous dreams at night, attended with spontaneous emissions, and assuming all the form of a disease. The orator Calvus, it is said, effected a cure for himself by means of these plates, and so preserved his bodily energies for labour and study. The Emperor Nero—for so the gods willed it—could never sing to the full pitch of his voice, unless he had a plate of lead upon his chest; thus showing us one method of preserving the voice.[1731] For medicinal purposes the lead is melted in earthen vessels; a layer of finely powdered sulphur being placed beneath, very thin plates of lead are laid upon it, and are then covered with a mixture of sulphur and iron. While it is being melted, all the apertures in the vessel should be closed, otherwise a noxious vapour is discharged from the furnace, of a deadly nature, to dogs in particular. Indeed, the vapours from all metals destroy flies and gnats; and hence it is that in mines there are none of those annoyances.[1732] Some persons, during the process, mix lead-filings with the sulphur, while others substitute ceruse for sulphur. By washing, a preparation is made from lead, that is much employed in medicine: for this purpose, a leaden mortar, containing rain water, is beaten with a pestle of lead, until the water has assumed a thick consistency; which done, the water that floats on the surface is removed with a sponge, and the thicker part of the sediment is left to dry, and is then divided into tablets. Some persons triturate lead-filings in this way, and some mix with it lead ore, or else vinegar, wine, grease, or rose-leaves. Others, again, prefer triturating the lead in a stone mortar, one of Thebaic stone more particularly, with a pestle of lead; by which process a whiter preparation is obtained. As to calcined lead, it is washed, like stibi[1733] and cadmia. Its action is astringent and repressive, and it is promotive of cicatrization. The same substance is also employed in preparations for the eyes, cases of procidence[1734] of those organs more particularly; also for filling up the cavities left by ulcers, and for removing excrescences and fissures of the anus, as well as hæmorrhoidal and condylomatous tumours. For all these purposes the lotion of lead is particularly useful; but for serpiginous or sordid ulcers it is the ashes of calcined lead that are used, these producing the same advantageous effects as ashes of burnt papyrus.[1735]