There may also be made a very good medicine out of the crystals of silver, which will be little inferior to the former, whereby the diseases and infirmities of the brain may be very well remedied, which is done thus. _How to make a green oyl out of Silver._ Pour upon Crystals of silver twice or thrice as much (in weight) of the strongest spirit of Salt Armoniack, put it in a glass with a long neck well closed, into a very gentle warmth for the space of 8. or 14. days in digestion, and the spirit of salt Armoniack will be tinged with a very fair blew colour from the silver, then pour it off, and filtre it through brown paper, and then put it in a little glass retort or glass body, and abstract in Balneo by a gentle fire, almost all the spirit of salt Armoniack (which is still good for use) and there will remain in the bottom a grass-green Liquor, which is to be kept for a Medicine. But in case that you should miss, and abstract too much of the spirit from the Tincture of silver, so that the Tincture be quite dry and turned to a green Salt, then you must pour upon it again as much of the spirit of Salt Armoniack, as will dissolve the green salt again to a green Liquor, but if you desire to have the Tincture purer yet, then abstract all moistness from it, to a stony dryness: upon which you must pour good spirit of Wine, which will quickly dissolve the stone, and then filtre it, and there will remain feces, and the Tincture will be fairer: from which you must abstract most of the spirit of wine, and the Tincture will be so much the higher in vertue. But if you please, you may distil that green salt or stone (before it be extracted again with that spirit of wine) in a little glass retort, and you will get a subtile spirit and a sharp oyl, and in the bottom of the retort there remaineth a very fusile silver which could not come over. It is to be admired, that when you pour spirit of salt Armoniack, or spirit of wine upon that stone, for to dissolve it, that the glass comes to be so cold by it, that you hardly are able to endure it in your hand, which coldness in my opinion cometh from the silver (being so well unlockt) which naturally is cold. _The Use of the green Liquor in Alchymy, and for Mechanical Operations._ This green Liquor serveth not only for a medicine, but also for other Chymical operations (for both Copper and glass may be easily and very fairly silvered over therewith) very useful for those that are curious and love to make a shew with fair houshold-stuff; for if you get dishes, trencher-plates, salters, cups and other vessels made of glass, after the same fashion as those of silver use to be made, you may very easily and without any considerable charge silver them over therewith within and without, so that by the eye they cannot be discerned from true silver plate.