_I put thirteen Grains of this last fix’d Powder (VIII.) into a Crucible, and set it over an open Fire before the Bellows: I increas’d the Heat of the Fire, by blowing till the whole Crucible was red hot: I kept it so for a Quarter of an Hour. The Powder remain’d fix’d in the Bottom, but swell’d up like a Spunge, and of a dark Colour. From hence I learn’d that this Powder had acquired a considerable Degree of Fixedness by Fire alone._ EXPERIMENT X. _Then I added to this fix’d Powder (IX.) some Borax in a Crucible, and increased the Fire by blowing. It became one Mass, brittle, growing like Glass, and fix’d in this great Fire._ EXPERIMENT XI. _I gave 2 Grains of that Powder, which had remained fix’d, to the Weight of 15 Grains (VIII.) to a sworn and very skilful Essayer of Metals at AMSTERDAM, to examine it with all possible Accuracy according to the Rules of Art, with Lead. Nothing fix’d remain’d: Therefore in that Powder there was not the least Gold or Silver._ EXPERIMENT XII. _The thirteen Grains melted down with the Borax into a Mass growing like Glass (almost vitrified) (X.) I gave to a sworn and very skilful Essayer of Metals at AMSTERDAM, to examine this whole little Mass with the greatest Accuracy, according to the Rules of Art, in Lead. Nothing fix’d remain’d of the whole Mass; so there was no Gold nor Silver in it._ COROLLARIES. 1. Quicksilver persists in the Fire, retaining its Nature unalterable. 2. Simple, and not separable, into different Parts by Distillation. 3. It is fixed by Fire, and seems changed in its outward Form. 4. Appearing so, in various Parts, it acquires different Degrees of Fixedness. 5. Yet none of these Parts acquired, by so strong and lasting a Fire, the Fixedness of Gold or Silver. 6. The fixating Cause is Fire passing thro’ the Glass; thus changing part of the Mercury, either by its simple Action, or by its uniting itself with the Quicksilver. 7. The Fire so acting, by 511 Distillations, by its Action or Conjunction, could not yet change the smallest Particle of the Mercury into Gold or Silver. 8. But from the Mercury so fixed by Fire, a greater Fire restores true Mercury; or the known Power of Lead makes it vanish out of the Cupell. 9. Therefore it does not appear, by these Experiments, that from Mercury and Fire so conspiring, any known Metal is produced. Those 13 Grains did not run by a Wind-Furnace; they did not persist in the Lead; they were not dissolved with the Mercury into an Amalgama. 10. Therefore Fire, by these Experiments, is not demonstrated to be the Sulphur of the Philosophers that fixes Mercury into Metals. 11. But it seems probable that the Sulphur of the Philosophers is something else very near it. 12. The fixed part is not the Feces of Mercury, nor its crude generating Sulphur; it returns into Mercury.