Chapter 15

And here I must not omit, _Pyrophilus_, to inform You, that we can shew You even in a Mineral Body something that may seem very near of Kin to the Changeable Quality of the Tincture of _Lignum Nephriticum_, for we have several flat pieces of Glass, of the thickness of ordinary Panes for Windows one of which being interposed betwixt the Eye and a clear Light, appears of a Golden Colour, not much unlike that of the moderate Tincture of our Wood, but being so look'd upon as that the Beams of light are not so much Trajected thorough it as Reflected from it to the Eye, that Yellow seems to degenerate into a pale Blew, somewhat like that of a Turquoise. And what which may also appear strange, is this, that if in a certain posture you hold one of these Plates Perpendicular to the Horizon, so that the Sun-beams shine upon half of it, the other half being Shaded, You may see that the part Shin'd upon will be of a much Diluter Yellow than the Shaded part which will appear much more Richly Colour'd; and if You alter the Posture of the Glass, so that it be not held Perpendicular, but Parallel in reference to the Horizon, You may see, (which perhaps you will admire) the Shaded part look of a Golden Colour, but the other that the Sun shines freely on, will appear considerably Blew, and as you remove any part of the Glass thus held Horizontally into the Sun-beams or Shade, it will in the twinkling of an Eye seem to pass from one of the above mention'd Colours to the other, the Sun-beams Trajected through it upon a sheet of White Paper held near it, do colour it with a Yellow, somewhat bordering upon a Red, but yet the Glass may be so oppos'd to the Sun, that it may upon Paper project a mix'd Colour here and there more inclin'd to Yellow, and here and there more to Blew. The other Phænomena of this odd Glass, I fear it would be scarce worth while to Record, and therefore I shall rather advertise You, _First_ that in the trying of these Experiments with it, you must take notice that one of the sides has either alone, or at least principally its Superficial parts dispos'd to the Reflection of the Blew Colour above nam'd, and that therefore you must have a care to keep that side nearest to the Eye. And next, that we have our selves made Glasses not unfit to exhibit an Experiment not unlike that I have been speaking of, by laying upon pieces of Glass some very finely foliated Silver, and giving it by degrees a much stronger Fire than is requisite or usual for the Tinging of Glasses of other Colours. And this Experiment, not to mention that it was made without a Furnace in which Artificers that Paint Glass are wont to be very Curious, is the more considerable, because, that though a Skilfull Painter could not deny to me that 'twas with Silver he Colour'd his Glasses Yellow; yet he told me, that when to Burn them (as they speak) he layes on the plates of Glass nothing but a _Calx_ of Silver Calcin'd without Corrosive Liquors, and Temper'd with Fair Water, the Plates are Ting'd of a fine Yellow that looks of a Golden Colour, which part soever of it you turn to or from the Light; whereas (whether it be what an Artificer would call Over-doing, or Burning, or else the imploying the Silver Crude that makes the Difference,) we have found more than once, that some Pieces of Glass prepar'd as we have related, though held against the Light they appear'd of a Transparent Yellow, yet look'd on with ones back turn'd to the Light they exhibited an Untransparent Blew.

_EXPERIMENT XII._

If you will allow me, _Pyrophilus_, for the avoiding of Ambiguity, to imploy the Word Pigments, to signifie such prepared materials (as Cochinele, Vermilion, Orpiment,) as Painters, Dyers and other Artificers make use of to impart or imitate particular Colours, I shall be the better understood in divers passages of the following papers, and particularly when I tell you, That the mixing of Pigments being no inconsiderable part of the Painters Art, it may seem an Incroachment in me to meddle with it. But I think I may easily be excus'd (though I do not altogether pass it by) if I restrain my self to the making of a Transient mention of some few of their Practices about this matter; and that only so far forth, as may warrant me to observe to you, that there are but few Simple and Primary Colours (if I may so call them) from whose Various Compositions all the rest do as it were Result. For though Painters can imitate the Hues (though not always the Splendor) of those almost Numberless differing Colours that are to be met with in the Works of Nature, and of Art, I have not yet found, that to exhibit this strange Variety they need imploy any more than _White_, and _Black_, and _Red_, and _Blew_, and _Yellow_; these _five_, Variously _Compounded_, and (if I may so speak) _Decompounded_, being sufficient to exhibit a Variety and Number of Colours, such, as those that are altogether Strangers to the Painters Pallets, can hardly imagine.

Thus (for Instance) Black and White differingly mix'd, make a Vast company of Lighter and Darker Grays.

Blew and Yellow make a huge Variety of Greens.

Red and Yellow make Orange Tawny.

Red with a little White makes a Carnation.

Red with an Eye of Blew, makes a Purple; and by these simple Compositions again Compounded among themselves, the Skilfull Painter can produce what kind of Colour he pleases, and a great many more than we have yet Names for. But, as I intimated above, 'tis not my Design to prosecute this Subject, though I thought it not unfit to take some Notice of it, because we may hereafter have occasion to make use of what has been now deliver'd, to illustrate the Generation of Intermediate Colours; concerning which we must yet subjoyn this Caution, that to make the Rules about the Emergency of Colours, fit to be Relied upon, the Corpuscles whereof the Pigments consist must be such as do not Destroy one anothers Texture, for in case they do, the produced Colour may be very Different from that which would Result from the Mixture of other harmless Pigments of the same Colours, as I shall have Occasion to shew ere long.

_EXPERIMENT XIII._

It may also give much light to an Enquirer into the Nature of Colours, to know that not only in Green, but in many (if not all) other Colours, the Light of the Sun passing through Diaphanous Bodies of differing Hues may be tinged of the same Compound Colour, as if it came from some Painters Colours of the same Denomination, though this later be exhibited by Reflection, and be (as the former Experiment declares) manifestly Compounded of material Pigments. Wherefore to try the Composition of Colours by Trajection, we provided several Plates of Tinged Glass, which being laid two at a time one on the top of another, the Object look'd upon through them both, appear'd of a Compounded Colour, which agrees well with what we have observ'd in the second Experiment, of Looking against the Light through differingly Colour'd Papers. But we thought the Experiment would be more Satisfactory, if we procur'd the Sun-beams to be so Ting'd in their passage through Plates of Glass, as to exhibit the Compounded Colour upon a Sheet of White Paper. And though by reason of the Thickness of the Glasses, the Effect was but Faint, even when the Sun was High and Shin'd forth clear, yet, we easily remedied that by Contracting the Beams we cast on them by means of a Convex Burning-glass, which where it made the Beams much converge Increas'd the Light enough to make the Compounded Colour very manifest upon the Paper. By this means we observ'd, that the Beams trajected through Blew and Yellow compos'd a Green, that an intense and moderate Red did with Yellow make differing degrees of Saffron, and Orange Tawny Colours, that Green and Blew made a Colour partaking of both, such as that which some Latin Writers call _Pavonaceus_, that Red and Blew made a Purple, to which we might add other Colours, that we produc'd by the Combinations of Glasses differingly Ting'd, but that I want proper Words to express them in our Language, and had not when we made the Tryals, the Opportunity of consulting with a Painter, who perchance might have Suppli'd me with some of the terms I wanted.

I know not whether it will be requisite to subjoyn on this Occasion, what I tried concerning Reflections from Colour'd Glasses, and other Transparent Bodies, namely, that having expos'd four or five sorts of them to the Sun, and cast the Reflected Beams upon White Paper held near at hand, the Light appear'd not manifestly Ting'd, but as if it had been Reflected from the Impervious parts of a Colourless Glass, only that Reflected from the Yellow was here and there stain'd with the same Colour, as if those Beams were not all Reflected from the Superficial, but some from the Internal parts of the Glass; upon which Occasion you may take notice, that a Skilfull Tradesman, who makes such Colour'd Glass told me, that where as the Red Pigment was but Superficial, the Yellow penetrated to the very midst of the Plate. But for further Satisfaction, not having the Opportunity to Foliate those Plates, and so turn them into Looking-glasses, we Foliated a Plate of _Muscovy_ Glass, and then laying on it a little Transparent Varnish of a Gold Colour, we expos'd it to the Sun-beams, so as to cast them upon a Body fit to receive them, on which the Reflected Light, appearing, as we expected, Yellow, manifested that Rebounding from the Specular part of the _Selenitis_, it was Ting'd in its return with the Colour of the Transparent Varnish through which it pass'd.

_EXPERIMENT XIV._

After what we have said of the Composition of Colours, it will now be seasonable to annex some Experiments that we made in favour of those Colours, that are taught in the Schools not to be Real, but only Apparent and Phantastical; For we found by Tryals, that these Colours might be Compounded, both with True and Stable Colours, and with one another, as well as unquestionably Genuine and Lasting Colours, and that the Colours resulting from such Compositions, would respectively deserve the same Denominations.

For first, having by the Trajection of the Sun-beams through a Glass-prism thrown an Iris on the Floor, I found that by placing a Blew Glass at a convenient distance betwixt the Prism and the Iris, that part of the Iris that was before Yellow, might be made to appear Green, though not of a Grass Green, but of one more Dilute and Yellowish. And it seems not improbable, that the narrow Greenish List (if I may so call it) that is wont to be seen between the Yellow and Blew parts of the Iris, is made by the Confusion of those two Bordering Colours.

Next, I found, that though the want of a sufficient Liveliness in either of the Compounding Colours, or a light Error in the manner of making the following Tryals, was enough to render some of them Unsuccessfull, yet when all necessary Circumstances were duely observ'd, the Event was answerable to our Expectation and Desire.

And (as I formerly Noted) that Red and Blew compound a Purple, so I could produce this last nam'd Colour, by casting at some Distance from the Glass the Blew part of the Prismatical Iris (as I think it may be call'd for Distinction sake) upon a Lively Red, (for else the Experiment succeeds not so well.) And I remember, that sometimes when I try'd this upon a piece of Red Cloath, _that_ part of the Iris which would have been Blew, (as I try'd by covering that part of the Cloath with a piece of White Paper) and Compounded with the Red, wherewith the Cloath was Imbued before, appear'd of a fair Purple, did, when I came to View it near at hand, look very Odly, as if there were some strange Reflection or Refraction or both made in the Hairs of which that Cloath was composed.

Calling likewise the Prismatical Iris upon a very Vivid Blew, I found that part of it, which would else have been the Yellow, appear Green. (Another somewhat differing Tryal, and yet fit to confirm this, you will find in the fifteenth Experiment.)

But it may seem somewhat more strange, that though the Prismatical Iris being made by the Refraction of Light through a Body that has no Colour at all, must according to the Doctrine of the Schools consist of as purely Emphatical Colours, as may be, yet even these may be Compounded with one another, as well as Real Colours in the Grossest Pigments. For I took at once two Triangular Glasses, and one of them being kept fixt in the same Posture, that the Iris it projected on the Floor might not Waver, I cast on the same Floor another Iris with the other Prism, and Moving it too and fro to bring what part of the second Iris I pleas'd, to fall upon what part of the first I thought fit, we did sometimes (for a small Errour suffices to hinder the Success) obtain by this means a Green Colour in that part of the more Stable Iris, that before was Yellow, or Blew, and frequently by casting those Beams that in one of the Iris's made the Blew upon the Red parts of the other Iris, we were able to produce a lovely Purple, which we can Destroy or Recompose at pleasure, by Severing and Reapproaching the Edges of the two Iris's.

_EXPERIMENT XV._

On this occasion, _Pyrophilus_, I shall add, that finding the Glass-prism to be the usefullest Instrument Men have yet imploy'd about the Contemplation of Colours, and considering that Prisms hitherto in use are made of Glass, Transparent and Colourless, I thought it would not be amiss to try, what change the Superinduction of a Colour, without the Destruction of the Diaphaneity, would produce in the Colours exhibited by the Prism. But being unable to procure one to be made of Colour'd Glass, and fearing also that if it were not carefully made, the Thickness of it would render it too Opacous, I endeavoured to substitute one made of Clarify'd Rosin, or of Turpentine brought (as I elsewhere teach) to the consistence of a Transparent Gum. But though these Endeavours were not wholly lost, yet we found it so difficult to give these Materials their true Shape, that we chose rather to Varnish over an ordinary Prism with some of these few Pigments that are to be had Transparent; as accordingly we did first with Yellow, and then with Red, or rather Crimson, made with Lake temper'd with a convenient Oyl, and the Event was, That for want of good Transparent Colours, (of which you know there are but very few) both the Yellow and the Red made the Glass so Opacous, (though the Pigment were laid on but upon two Sides of the Glass, no more being absolutely necessary) that unless I look'd upon an Inlightned Window, or the Flame of a Candle, or some other Luminous or very Vivid object, I could scarce discern any Colours at all, especially when the Glass was cover'd with Red. But when I did look on such Objects, it appear'd (as I expected) that the Colour of the Pigment had Vitiated or Drown'd some of those which the Prism would according to its wont have exhibited, and mingling with others, Alter'd them: as I remember, that both to my Eyes, and others to whom I show'd it, when the Prism was cover'd with Yellow, it made those Parts of bright Objects, where the Blew would else have been Conspicuous, appear of a light Green. But, _Pyrophilus_, both the Nature of the Colours, and the Degree of Transparency, or of Darkness in the Pigment, besides divers other Circumstances, did so vary the _Phænomena_ of these Tryals, that till I can procure small Colour'd Prisms, or Hollow ones that may be filled with Tincted Liquor, or obtain Some better Pigments than those I was reduc'd to imploy, I shall forbear to Build any thing upon what has been delivered, and shall make no other use of it, than to invite you to prosecute the Inquiry further.

_EXPERIMENT XVI._

And here, _Pyrophilus_, since we are treating of Emphatical Colours, we shall add what we think not unworthy your Observation, and not unfit to afford some Exercise to the Speculative. For there are some Liquors, which though Colourless themselves, when they come to be Elevated, and Dispers'd into Exhalations, exhibit a conspicuous Colour, which they lose again, when they come to be Reconjoyn'd into a Liquor, as good Spirit of _Nitre_; or upon its account strong _Aqua-fortis_, though devoid of all appearance of Redness whilst they continue in the form of a Liquor, if a little Heat chance to turn the Minute parts of them into Vapour, the Steam will appear of a Reddish or deep Yellow Colour, which will Vanish when those Exhalations come to resume the form of Liquor.

And not only if you look upon a Glass half full of _Aqua-fortis_, or Spirit of _Nitre_, and half full of _Nitrous_ steams proceeding from it, you will see the Upper part of the Glass of the Colour freshly mention'd, if through it you look upon the Light. But which is much more considerable, I have tried, that putting _Aqua-fortis_ in a long clear Glass, and adding a little Copper or some such open Metall to it, to excite Heat and Fumes, the Light trajected through those Fumes, and cast upon a sheet of White Paper, did upon that appear of the Colour that the Fumes did, when directly Look'd upon, as if the Light were as well Ting'd in its passage through these Fumes, as it would have been by passing through some Glass or Liquor in which the same Colour was Inherent.

To which I shall further add, that having sometimes had the Curiosity to observe whether the Beams of the Sun near the Horizon trajected through a very Red Sky, would not (though such rednesses are taken to be but Emphatical Colours) exhibit the like Colour, I found that the Beams falling within a Room upon a very White Object, plac'd directly opposite to the Sun, disclos'd a manifest Redness, as if they had pass'd through a Colour'd _Medium_.

_EXPERIMENT XVII._

The emergency, _Pyrophilus_, of Colours upon the Coalition of the Particles of such Bodies as were neither of them of the Colour of that Mixture whereof they are the Ingredients, is very well worth our attentive Observation, as being of good use both Speculative and Practical; For much of the Mechanical use of Colours among Painters and Dyers, doth depend upon the Knowledge of what Colours may be produc'd by the Mixtures of Pigments so and so Colour'd. And (as we lately intimated) 'tis of advantage to the contemplative Naturalist, to know how many and which Colours are Primitive (if I may so call them) and Simple, because it both eases his Labour by confining his most sollicitous Enquiry to a small Number of Colours upon which the rest depend, and assists him to judge of the nature of particular compounded Colours, by shewing him from the Mixture of what more Simple ones, and of what Proportions of them to one another, the particular Colour to be consider'd does result. But because to insist on the Proportions, the Manner and the Effects of such Mixtures would oblige me to consider a greater part of the Painters Art and Dyers Trade, than I am well acquainted with, I confin'd my self to make Trial of _several ways to produce Green_, by the composition of Blew and Yellow. And shall in this place both Recapitulate most of the things I have Dispersedly deliver'd already concerning that Subject, and Recruit them.

And first, whereas Painters (as I noted above) are wont to make Green by tempering Blew and Yellow, both of them made into a soft Consistence, with either Water or Oyl, or some Liquor of Kin to one of those two, according as the Picture is to be Drawn with those they call _water Colours_, or those they term _Oyl Colours_, I found that by choosing fit Ingredients, and mixing them in the form of Dry Powders, I could do, what I could not if the Ingredients were temper'd up with a Liquor; But the Blew and Yellow Powders must not only be finely Ground, but such as that the Corpuscles of the one may not be too unequal to those of the other, lest by their Disproportionate Minuteness the Smaller cover and hide the Greater. We us'd with good success a slight Mixture of the fine Powder of Bise, with that of Orpiment, or that of good Yellow Oker, I say a _slight_ Mixture, because we found that an _exquisite_ Mixture did not do so well, but by lightly mingling the two Pigments in several little Parcels, those of them in which the Proportion and Manner of Mixture was more Lucky, afforded us a good Green.

2. We also learn'd in the Dye-houses, that Cloth being Dy'd Blew with Woad, is afterwards by the Yellow Decoction of _Luteola_ or Woud-wax or Wood-wax Dy'd into a Green Colour.

3. You may also remember what we above Related, where we intimated, that having in a Darkn'd Room taken two Bodies, a Blew and a Yellow, and cast the Light Reflected from the one upon the other, we likewise obtain'd a Green.

4. And you may remember, that we observ'd a Green to be produc'd, when in the same Darkn'd Room we look'd at the Hole at which alone the Light enter'd, through the Green and Yellow parts of a sheet of Marbl'd Paper laid over one another.

5. We found too, that the Beams of the Sun being trajected through two pieces of Glass, the one Blew and the other Yellow, laid over one another, did upon a sheet of White paper on which they were made to fall, exhibit a lovely Green.

6. I hope also, that you have not already forgot, what was so lately deliver'd, concerning the composition of a Green, with a Blew and Yellow; of which most Authors would call the one a _Real_, and the other an _Emphatical_.

7. And I presume, you may have yet fresh in your memory, what the fourteenth Experiment informs you, concerning the exhibiting of a Green, by the help of a Blew and Yellow, that were both of them Emphatical.

8. Wherefore we will proceed to take notice, that we also devis'd a way of trying whether or no Metalline Solutions though one of them at least had its Colour Adventitious, by the mixture of the _Menstruum_ employ'd to dissolve it, might not be made to compound a Green after the manner of other Bodies. And though this seem'd not easie to be perform'd by reason of the Difficulty of finding Metalline Solutions of the Colour requisite, that would mix without Præcipitating each other; yet after a while having consider'd the matter, the first Tryal afforded me the following Experiment. I took a High Yellow Solution of good Gold in _Aqua-Regis_, (made of _Aqua-fortis_, and as I remember half its weight of Spirit of Salt) To this I put a due Proportion of a deep and lovely Blew Solution of Crude Copper, (which I have elsewhere taught to be readily Dissoluble in strong Spirit of Urine) and these two Liquors though at first they seem'd a little to Curdle one another, yet being throughly mingl'd by Shaking, they presently, as had been Conjectur'd, united into a Transparent Green Liquor, which continu'd so for divers days that I kept it in a small Glass wherein 'twas made, only letting fall a little Blackish Powder to the Bottom. The other _Phænomena_ of this Experiment belong not to this place, where it may suffice to take notice of the Production of a Green, and that the Experiment was more than once repeated with Success.

9. And lastly, to try whether this way of compounding Colours would hold ev'n in Ingredients actually melted by the Violence of the Fire, provided their Texture were capable of safely induring Fusion, we caus'd some Blew and Yellow Ammel to be long and well wrought together in the Flame of a Lamp, which being Strongly and Incessantly blown on them kept them in some degree of Fusion, and at length (for the Experiment requires some Patience as well as Skil) we obtain'd the expected Ammel of a Green Colour.