Glaſsmen call the matter of the Purer ſort of Glaſs, wherewith it is Colliquated into a White Maſs, which if it be opacous enough is employ'd, as we elſewhere declare, for White Amel. But of the Colours which the other Metals may be made to produce in Colourleſs Glaſs, and other Vitrifiable Bodies, that have native Colours of their own, I muſt leave you to inform your ſelf upon Tryal, or at leaſt muſt forbear to do it till another time, conſidering how many Annotations are to follow, upon what has in this and the two former Experiments been ſaid already.
Annotation I.
When the Materials of Glaſs being melted with Calcin'd Tin, have compos'd a Maſs Undiaphanous and White, this White Amel is as it were the Baſis of all thoſe fine Concretes that Goldſmiths and ſeveral Artificers imploy in the curious Art of Enamelling. For this White and Fuſible ſubſtance will receive into it ſelf, without ſpoyling them, the Colours of divers other Mineral ſubſtances, which like it will indure the fire.
Annotation II.
So that as by the preſent (XLVIII.) Experiment it appears, that divers Minerals will impart to fuſible Maſſes, Colours differing from their own; ſo by the making and compounding of Amels, it may appear, that divers Bodies will both retain their Colour in the fire, and impart the ſame to ſome others wherewith they were vitrifi'd, and in ſuch Tryals as that mention'd in the 17. Experiment, where I told you, that ev'n in Amels a Blew and Yellow will compound a Green. 'Tis pretty to behold, not only that ſome Colours are of ſo fix'd a Nature, as to be capable of mixture without receiving any detriment by the fire, that do's ſo eaſily deſtroy or ſpoyl thoſe of other Bodies; but Mineral Pigments may be mingled by fire little leſs regularly and ſucceſsfully, than in ordinary Dyeing Fatts, the vulgar Colours are wont to be mingled by the help of Water.
Annotation III.
'Tis not only Metalline, but other Mineral Bodies, that may be imploy'd, to give Tinctures unto Glaſs (and 'tis worth noting
how ſmall a quantity of ſome Mineral ſubſtances, will Tinge a Comparatively vaſt proportion of Glaſs, and we have ſometimes attempted to Colour Glaſs, ev'n with Pretious Stones, and had cauſe to think the Experiment not caſt away. And 'tis known by them that have look'd into the Art of Glaſs, that the Artificers uſe to tinge their Glaſs Blew, with that Dark Mineral Zaffora, (ſome of my Tryals on which I elſewhere acquaint you) which ſome would have to be a Mineral Earth, others a Stone, and others neither the one, nor the other, but which is confeſſedly of a Dark, but not a Blew Colour, though it be not agreed of what particular Colour it is. 'Tis likewiſe though a familiar yet a remarkable practiſe among thoſe that Deal in the making of Glaſs, to imploy (as ſome of themſelves have inform'd me) what they call Manganeſs, and ſome Authors call Magneſia (of which I make particular mention in another Treatiſe) to exhibit in Glaſs not only other Colours than its own, (which is ſo like in Darkneſs or blackiſhneſs to the Load ſtone, that 'tis given by Mineraliſts, for one of the Reaſons of its Latine Name) but Colours differing from one another. For though they uſe it, (which is ſomewhat ſtrange) to Clarifye their Glaſs, and free
it from that Blewiſh Greeniſh Colour, which elſe it would too often be ſubject to, yet they alſo imploy it in certain proportions, to tinge their Glaſs both with a Red colour, and with a Purpliſh or Murry, and putting in a greater Quantity, they alſo make with it that deep obſcure Glaſs which is wont to paſs for Black, which agrees very well with, and may ſerve to confirm what we noted near the beginning of the 44th Experiment, of the ſeeming Blackneſs of thoſe Bodies that are overcharg'd with the Corpuſcles of ſuch Colours, as Red, or Blew, or Green, &c. And as by ſeveral Metals and other Minerals we can give various Colours to Glaſs, ſo on the other ſide, by the differing Colours that Mineral Oars, or other Mineral Powders being melted with Glaſs diſcloſe in it, a good Conjecture may be oftentimes made of the Metall or known Mineral, that the Oar propos'd, either holds, or is moſt of kin to. And this eaſie way of examining Oars, may be in ſome caſes of good uſe, and is not ill deliver'd by Glauber, to whom I ſhall at preſent refer you, for a more particular account of it: unleſs your Curioſity command alſo what I have obſerv'd about theſe matters; only I muſt here advertiſe you, that great circumſpection is