N. B. If the black stinking oyl be rectified from the calcined _Caput Mortuum_, it will be clear and subtle, and it will not only asswage very speedily all pains of the gout, but also dissolve and expel the conglobated gravel in the reines, applyed as a plaister or unguent. In like manner it will dissolve and extract the coagulated Tartar in the hands, knees and feet, so that the place affected will be freed and made whole thereby: because in such a despicable oyl there lyes hid a volatile salt which is of great vertue. But if you desire experimentally to know whether it be so, then pour upon this black stinking oyl an acid spirit, as the spirit of common salt, or of vitriol or salt nitre, or only distilled vinegar, and the oyl will grow warm and make a noyse and rise, as if _Aqua fortis_ had been powred upon salt of Tartar, and the acid spirit will be mortified thereby, and turn to salt. And this well purified oyl doth dissolve and extract the Tartar out of the joynts (unless it be grown to a hard stony substance) even as sope scowres the uncleanness out of cloths, or to compare it better, even as like receiveth its like, and is easily mixed with it, and doth love it; but on the contrary, nothing will mix it self with that wherewith it hath no affinity at all. As if you would take pitch out of cloth by washing it with water, which never will be done by reason of the contrary nature; for common water hath no affinity with pitch or other fat things, nor will it ever be taken out therewith without a mediator, partaking of both natures, _viz._ of the nature of pitch and that of the water, and such are sulphureous salts, and nitrous salts, whether they be fixed or volatile. As you may see at the soap boylers, who incorporate common water by the help of sulphureous salts with fat things, as tallow and oyl. But if you take warm oyl or any thin fat substance, and put it upon the pitch or rozin, then the oyl easily accepteth of and lays hold on its like, and so the pitch is dissolved and got out of the cloth, and the remaining fatness of the oyl may be fetcht out of the cloth with lye or sope and common water, and so the cloth recovereth its former beauty and pureness. And as it falleth out with sulphureous things, so it doth likewise with Mercurial. For example, if you would take the salt out of powdered flesh or pickled fish with a lixivium it would not succeed, because that the nitrous and acid salts are of contrary natures. But if upon the powdered flesh or pickled fish you pour on water wherein some of the same salt (wherewithall the flesh was powdered) is dissolved, that salt water will extract the salt out of the flesh, as being its like, much more than common sweet water, wherein there is no salt.