There are indeed other ways or means also by which this oyl is attained, but this afore taught is the easiest of all, although it require the more time. But if any one stand in need of a greater quantity of the same, he may procure those greater Cans prepared of the best Earth, they being so joyned to each other, that the uppermost being placed on the fire, the rest might be placed without the fire, so that the lowermost may receive the oyl going out by descent.
V. A proof whether this Oyl of Vitriol be well prepared and strong, and fit enough for that operation of which we here treat.
Let down a quill or some small piece of wood into the Oyl, the which, when thou hast left in it for some small time, draw it out; if it shall be burnt unto a Coal the oyl is well prepared, but if not, it is a sign that somewhat of moisture is as yet therein, which is again to be expelled by fire.
VI. Another tryal or experiment.
Dip in the oyl a piece of woollen, linnen, or which is better a piece of cotton cloth extended to the breadth of a finger, and pour on the same being taken out and laid down some drops of the spirit or oyl of Turpentine, the which if being kindled they shall conceive a flame it is a sign that the oyl was well prepared.
VII. Another further Proof.
Pour into some little glass some small quantity of spirit of wine wanting all phlegm, and pour on the same some drops of this oyl by little and little; and if the spirit of wine kindle and burn all away the oyl is prepared after a due manner.
NB. I admonish that every one doth warily handle this operation: for in these two fires, to wit, saltish and sulphureous ones, there is great virtue hidden, the which seems probable but to a few, if it should be manifested unto them, neither that have I consulted or decreed that it should be made known to very many. These few particulars do sufficiently teach after what sort such fires are to be used in Medicine, Alchymy and other Arts; but these experiments are sufficient.
VIII. Concerning the use of this fire of Vitriol in Medicine.
The use of this fire, as also of the volatile spirit of the same, and of its flegm, thou shalt find described in the second part of my Furnaces, and among other Authours; so that the repetition thereof is here superfluous, this is onely to be known that this fire being onely besmeared or anointed with a feather on all uncurable and Cancerous or eating Ulcers, kills the Poyson, and causeth that such Ulcers do very easily admit of cure, if so be the Escharre be but first removed by the applying some ointment or emplaister which cures adustion or burning. For this oyl burns up all wild or forreign flesh, and that which (as proud) lifts up it self with an abounding poyson, like unto a certain bright burning Iron, and separates all evil and hurtfull flesh from the good and sound flesh.