THE
Experimental
Hiſtory
OF
COLOURS.
Begun.
The Third PART.
Containing
Promiſcuous Experiments
About
COLOURS.
EXPERIMENT I.
Ecauſe that, according to the Conjectures I have above propos'd, one of the moſt General Cauſes of the Diverſity of Colours in Opacous Bodyes, is, that ſome reflect the Light mingl'd with more, others with leſs of Shade (either as to Quantity, or as to Interruption) I hold it not unfit to mention in the firſt place, the Experiments that I thought upon to examine this Conjecture. And though coming to tranſcribe them out of ſome Phyſiological Adverſaria I had written in looſe Papers, I cannot find one of the chief Records I had of my Tryals of this Nature, yet the Papers that ſcap'd miſcarrying, will, I preſume, ſuffice to manifeſt the main thing for which I now allege them; I find then Among my Adverſaria, the following Narrative.
October the 11. About ten in the Morning in Sun-ſhiny Weather, (but not without fleeting Clouds) we took ſeveral ſorts of Paper Stain'd, ſome of one Colour, and ſome of another; and in a Darken'd Room whoſe Window look'd Southward, we caſt the Beams that came in at a hole about three Inches and a half in Diameter, upon a White wall that was plac'd on one ſide, about five foot diſtance from them.
The White gave much the Brighteſt Reflection.
The Green, Red, and Blew being Compar'd together, the Red gave much the ſtrongeſt Reflection, and manifeſtly enough alſo threw its Colour upon the Wall; The Green and Blew were ſcarce Diſcernable by their Colours, and ſeem'd to reflect an almoſt Equal Light.
The Yellow Compar'd with the two laſt nam'd, Reflected ſomewhat more Light.
The Red and Purple being Compar'd together, the former manifeſtly Reflected a good deal more Light.
The Blew and Purple Compar'd together, the former ſeem'd to Reflect a little more Light, though the Purple Colour were more manifeſtly ſeen.
A Sheet of very well fleck'd Marbl'd Paper being Apply'd as the others, did not caſt any or its Diſtinct Colours upon the Wall; nor throw its Light upon it with an Equal Diffuſion, but threw the Beams Unſtain'd and Bright to this and that part of the Wall, as if it's Poliſh had given it the Nature of a ſpecular Body. But comparing it with a ſheet of White Paper, we found the Reflection of the latter to be much Stronger, it diffuſing almoſt as much Light to a good Extent as the Marble Paper did to one part of the Wall.
The Green and Purple left us ſomewhat in ſuſpence which Reflected the moſt Light; only the Purple ſeem'd to have ſome little Advantage over the Green, which was Dark in its kind.
Thus much I find in our above mention'd Collections, among which there are alſo ſome Notes concerning the Production of Compounded Colours, by Reflection from Bodyes differingly Colour'd. And theſe Notes we intended ſhould ſupply us with what we ſhould mention as our ſecond Experiment: but having loſt the Paper that contain'd the Particulars, and remembring onely in General, that if the Objects which Reflected the Light were not Strongly Colour'd and ſomewhat Gloſſy, the Reflected Beams would not manifeſtly make a Compounded Colour upon the Wall, and even then but very Faintly, we ſhall now ſay no more of that Matter, only reſerving our ſelves to mention hereafter the Compoſition of a Green, which we ſtill retain in Memory.
EXPERIMENT II.
We may add, Pyrophilus, on this Occaſion, that though a Darken'd Room be Generally thought requiſite to make the Colour of a Body appear by Reflection from another Body, that is not one of thoſe that are commonly agreed upon to be Specular (as Poliſh'd Metall, Quick ſilver, Glaſs, Water, &c.) Yet I have often obſerv'd that when I wore Doublets Lin'd with ſome ſilken Stuff that was very Gloſſy and Vividly Colour'd, eſpecially Red, I could in an Inlightned Room plainly enough Diſcern the Colour, upon the Pure White Linnen that came out at my Sleeve and reach'd to my Cufs; as if that Fine White Body were more Specular, than Colour'd and Unpoliſh'd Bodyes are thought Capable of being.
EXPERIMENT III.
Whilſt we were making the newly mention'd Experiments, we thought fit to try alſo what Compoſition of Colours might be made by Altering the Light in its Paſſage to the Eye by the Interpoſition not of Perfectly Diaphanous Bodies, (that having been already try'd by others as well as by us (as we ſhall ſoon have occaſion to take notice) but of Semi-opacous Bodyes, and thoſe ſuch as look'd upon in an ordinary Light, and not held betwixt it and the Eye, are not wont to be Diſcriminated from the reſt of Opacous Bodyes; of this Tryal, our mention'd Adverſaria preſent us the following Account.
Holding theſe Sheets, ſometimes one ſometimes the other of them, before the Hole betwixt the Sun and the Eye, with the Colour'd ſides obverted to the Sun; we found them ſingle to be ſomewhat Tranſparent, and appear of the ſame Colour as before, onely a little alter'd by the great Light they were plac'd in; but laying two of them one over another and applying them ſo to the Hole, the Colours were compounded as follows.
The Blew and Yellow ſcarce exhibited any thing but a Darker Yellow, which we aſcrib'd to the Coarſeneſs of the Blew Papers, and its Darkneſs in its Kind. For applying the Blew parts of the Marbl'd Paper with the Yellow Paper after the ſame manner, they exhibited a good Green.
The Yellow and Red look'd upon together gave us but a Dark Red, ſomewhat (and but a little,) inclining to an Orange Colour.
The Purple and Red look'd on together appear'd more Scarlet.
The Purple and Yellow made an Orange.
The Green and Red made a Dark Orange Tawny.
The Green and Purple made the Purple appear more Dirty.
The Blew and Purple made the Purple more Lovely, and far more Deep.
The Red parts of the Marbl'd Paper look'd upon with the Yellow appear'd of a Red far more like Scarlet than without it.
But the Fineneſs or Coarſeneſs of the Papers, their being carefully or ſlightly Colour'd, and divers other Circumſtances, may ſo vary the Events of ſuch Experiments as theſe, that if, Pyrophilus, you would Build much on them, you muſt carefully Repeat them.
EXPERIMENT IV.
The Triangular Priſmatical Glaſs being the Inſtrument upon whoſe Effects we may the moſt Commodiouſly ſpeculate the Nature of Emphatical Colours, (and perhaps that of Others too;) we thought it might be uſefull to obſerve the ſeveral Reflections and Refractions which the Incident Beams of Light ſuffer in Rebounding from it, and Paſſing through it. And this we thought might be Beſt done, not (as is uſual,) in an ordinary Inlightn'd Room, where (by reaſon of the Difficulty of doing otherwiſe) ev'n the Curious have left Particulars Unheeded, which may in a convenient place be eaſily taken notice of; but in a Darken'd Room, where by placing the Glaſs in a convenient Poſture, the Various Reflections and Refractions may be Diſtinctly obſerv'd; and where it may appear what Beams are Unting'd; and which they are, that upon the Bodyes that terminate them, do Paint either the Primary or Secondary Iris. In purſuance of this we did in the above mention'd Darken'd Room, make obſervation of no leſs than four Reflections, and three Refractions that were afforded us by the ſame Priſm, and thought that notwithſtanding what was taught us by the Rules of Catoptricks and Dioptricks, it would not be amiſs to find alſo, by hiding ſometimes one part of the Priſm, and ſometimes another, and obſerving where the Light or Colour Vaniſh'd thereupon, by which Reflection and by which Refraction each of the ſeveral places whereon the Light rebounding from, or paſſing through, the Priſm appear'd either Sincere or Tincted, was produc'd. But becauſe it would be Tedious and not ſo Intelligible to deliver this in Words, I have thought fit to Referr You to the Annexed Scheme where the Newly mention'd particulars may be at one View taken Notice of.
EXPERIMENT V.
I know not whether you will think it Inconſiderable to annex to this Experiment, That we obſerv'd in a Room not Darken'd, that the Priſmatical Iris (if I may ſo call it) might be Reflected without loſing any of its ſeveral Colours (for we now conſider not their Order) not onely from a plain Looking-glaſs and from the calm Surface of Fair Water, but alſo from a Concave Looking-glaſs; and that Refraction did as little Deſtroy thoſe Colours as Reflection. For by the help of a large (double Convex) Burning-glaſs through which we Refracted the Suns Beams, we found that one part of the Iris might be made to appear either beyond, or on this ſide of the other Parts of the ſame Iris; but yet the ſame Vivid Colours would appear in the Diſplac'd part (if I may ſo term it) as in the other. To which I ſhall add, that having, by hiding the ſide of the Priſm, obverted to the Sun with an Opacous Body, wherein only one ſmall hole was left for the Light to paſs through, reduc'd the Priſmatical Iris (caſt upon White Paper) into a very narrow compaſs, and look'd upon it througn a Microſcope; the Colours appear'd the ſame as to kind that they did to the naked Eye.
EXPERIMENT VI.
It may afford matter of Speculation to the Inquiſitive, ſuch as you, Prophilus, that as the Colours of outward Objects brought into a Darken'd Room, do ſo much depend for their Viſibility upon the Dimneſs of the Light they are there beheld by; that the ordinary Light of the day being freely let in upon them, they immediately diſappear: ſo our Tryals have inform'd us, that as to the Priſmatical Iris painted on the Floor by the beams of the Sun Trajected through a Triangular-glaſs; though the Colours of it appear very Vivid ev'n at Noon-day, and in Sun ſhiny Weather, yet by a more Powerfull Light they may be made to diſappear. For having ſometimes, (in proſecution of ſome Conjectures of mine not now to be Inſiſted on,) taken a large Metalline Concave Speculum, and with it caſt the converging Beams of the Sun upon a Priſmatical Iris which I had caus'd to be projected upon the Floor, I found that the over-powerfull Light made the Colours of the Iris diſappear. And if I ſo Reflected the Light as that it croſs'd but the middle of the Iris, in that part only the Colours vaniſh'd or were made Inviſible; thoſe parts of the Iris that were on the right and left hand of the Reflected Light (which ſeem'd to divide them, and cut the Iris aſunder) continuing to exhibit the ſame Colours as before. But upon this we muſt not now ſtay to Speculate.
EXPERIMENT VII.
I have ſometimes thought it worth while to take notice, whether or no the Colours of Opacous Bodies might not appear to the Eye ſomewhat Diverſify'd, not only by the Diſpoſition of the Superficial parts of the Bodyes themſelves and by the Poſition of the Eye in Reference to the Object and the Light, (for theſe things are Notorious enough;) but according alſo to the Nature of the Lucid Body that ſhines upon them. And I remember that in Proſecution of this Curioſity, I obſerv'd a manifeſt Difference in ſome Kinds of Colour'd Bodyes look'd on by Day-light, and afterwards by the light of the Moon; either directly falling on them or Reflected upon them from a Concave Looking-glaſs. But not finding at preſent in my Collections about Colours any thing ſet down of this Kind, I ſhall, till I have opportunity to repeat them, content my ſelf to add what I find Regiſter'd concerning Colours look'd on by Candle-light, in regard that not only the Experiment is more eaſie to be repeated, but the Objects being the Same Sorts of Colour'd Paper laſtly mention'd, the Collation of the two Experiments may help to make the Conjectures they will ſuggeſt ſomewhat the leſs uncertain.
Within a few dayes of the time above mention'd, divers Sheets of Colour'd Paper that had been look'd upon before in the Sunſhine were look'd upon at night by the light of a pretty big Candle, (ſnuff'd) and the Changes that were obſerv'd were theſe.
The Yellow ſeem'd much fainter than in the Day, and inclinable to a pale Straw Colour.
The Red ſeem'd little Chang'd; but ſeem'd to Reflect Light more ſtrongly than any other Colour (for White was none of them.)
A fair Deep Green look'd upon by it ſelf ſeem'd to be a Dark Blew: But being look'd upon together with a Dark Blew, appear'd Greeniſh; and beheld together with a Yellow appear'd more Blew than at firſt.
The Blew look'd more like a Deep Purple or Murray than it had done in the Daylight.
The Purple ſeem'd very little alter'd.
The Red look'd upon with the Yellow made the Yellow look almoſt like Brown Cap-paper.
N. The Caution Subjoyned to the third Experiments is alſo Applicable to this.
EXPERIMENT VIII.
But here I muſt not omit to ſubjoyn, that to ſatisfie our Selves, whether or no the Light of a Candle were not made unſincere, and as it were Ting'd with a Yellow Colour by the Admixtion of the Corpuſcles it aſſumes from its Fuel; we did not content our ſelves with what appears to the Naked Eye, but taking a pretty thick Rod or Cylinder (for thin Peeces would not ſerve the turn) of deep Blew Glaſs, and looking upon the Candles flame at a Convenient diſtance througn it, we perceiv'd as we expected, the Flame to look Green; which as we often note, is the Colour wont to emerge from the Compoſition of Opacous Bodies, which were apart one of them Blew, and the other Yellow. And this perchance may be the main Reaſon of that which ſome obſerve, that a ſheet of very White Paper being look'd upon by Candle light, 'tis not eaſie at firſt to diſcern it from a light Yellow or Lemon Colour; White Bodyes (as we have elſewhere obſerv'd) having more than thoſe that are otherwiſe Colour'd, of a Specular Nature; in regard that though they exhibit not, (unleſs they be Poliſh'd,) the ſhape of the Luminary that ſhines on them, yet they Reflect its Light more Sincere and Untroubl'd, by either Shades or Refractions, than Bodyes of other Colours (as Blew, or Green, or Yellow or the like.)
EXPERIMENT IX.
We took a Leaf of Such Foliated Gold as Apothecaries are wont to Gild their Pills with; and with the Edge of a Knife, (lightly moyſten'd by drawing it over the Surface of the Tongue, and afterwards) laid upon the edge of the Gold Leaf; we ſo faſten'd it to the Knife, that being held againſt the light, it conctinu'd extended like a little Flagg. This Leaf being held very near the Eye, and obverted to the Light, appear'd ſo full of Pores, that it ſeem'd to have ſuch a kind of Tranſparency as that of a Sive, or a piece of Cyprus, or a Love-Hood; but the Light that paſs'd by theſe Pores was in its Paſſages So Temper'd with Shadow, and Modify'd, that the Eye diſcern'd no more a Golden Colour, but a Greeniſh Blew. And for other's ſatisfaction, we did in the Night look upon a Candle through ſuch a Leaf of Gold; and by trying the Effect of Several Proportions of Diſtance betwixt the Leaf, the Eye and the Light, we quickly hit upon ſuch a Poſition for the Leaf of Gold, as that the flame, look'd on through it, appear'd of a Greeniſh Blew, as we have ſeen in the Day time. The like Experiment try'd with a Leaf of Silver ſucceeded not well.
EXPERIMENT X.
We have ſometimes found in the Shops of our Druggiſts, a certain Wood, which is there called Lignum Nephriticum, becauſe the Inhabitants of the Country where it grows, are wont to uſe the Infuſion of it made in fair Water againſt the Stone of the Kidneys, and indeed an Eminent Phyſician of our Acquaintance, who has very Particularly enquir'd into that Diſeaſe, aſſures me, that he has found ſuch an Infuſion one of the moſt effectual Remedyes, which he has ever tried againſt that formidable Diſeaſe. The ancienteſt Account I have met with of this Simple, is given us by the Experienc'd Monardes in theſe Words. Nobis, ſays he,16 Nova Hiſpania mittit quoddam ligni genus craſſum & enode, cujus uſus jam diu receptus fuit in his Regionibus ad Renum vitia & urinæ difficultates ac arenulas pellendas. Fit autem hac ratione, Lignum aſſulatim & minutim conciſum in limpidiſſima aqua fontana maceratur, inque ea relinquitur, donec aqua à bibentibus abſumpta ſit, dimidia hora post injectum lignum aqua cæruleum colorem contrabit, qui ſenſim intenditur pro temporis diuturnitate, tametſi lignum candidum fit. This Wood, Pyrophilus, may afford us an Experiment, which beſides the ſingularity of it, may give no ſmall aſſiſtance to an attentive Conſiderer towards the detection of the Nature of Colours. The Experiment as we made it is this. Take Lignum Nephriticum, and with a Knife cut it into thin Slices, put about a handfull of theſe Slices into two three or four pound of the pureſt Spring-water, let them infuſe there a night, but if you be in haſt, a much ſhorter time may ſuffice; decant this Impregnated Water into a clear Glaſs Vial, and if you hold it directly between the Light and your Eye, you ſhall ſee it wholly Tincted (excepting the very top of the Liquor, wherein you will ſome times diſcern a Sky-colour'd Circle) with an almoſt Golden Colour, unleſs your Infuſion have been made too Strong of the Wood, for in that caſe it will againſt the Light appear ſomewhat Dark and Reddiſh, and requires to be diluted by the addition of a convenient quantity of fair Water. But if you hold this Vial from the Light, ſo that your Eye be plac'd betwixt the Window and the Vial, the Liquor will appear of a deep and lovely Cæruleous Colour, of which alſo the drops, if any be lying on the outſide of the Glaſs, will ſeem to be very perfectly; And thus far we have try'd the Experiment, and found it to Succeed even by the Light of Candles of the larger ſize. If you ſo hold the Vial over againſt your Eyes, that it may have a Window on one ſide of it, and a Dark part of the Room both before it and on the other ſide, you ſhall ſee the Liquor partly of a Blewiſh and partly of a Golden Colour. If turning your back to the Window, you powr out ſome of the Liquor towards the Light and towards your Eyes, it will ſeem at the comming out of the Glaſs to be perfectly Cæruleous, but when it is fallen down a little way, the drops may ſeem Particolour'd, according as the Beams of Light do more or leſs fully Penetrate and Illuſtrate them. If you take a Baſon about half full of Water, and having plac'd it ſo in the Sun-beams Shining into a Room, that one part of the Water may be freely illuſtrated by the Beams of Light, and the other part of it Darkned by the ſhadow of the Brim of the Baſon, if then I ſay you drop of our Tincture, made ſomewhat ſtrong, both into the Shaded and Illuminated parts of the Water, you may by looking upon it from ſeveral places, and by a little Agitation of the water, obſerve divers pleaſing Phænomena which were tedious to particularize. If you powr a little of this Tincture upon a ſheet of White Paper, ſo as the Liquor may remain of ſome depth upon it, you may perceive the Neighbouring drops to be partly of one Colour, and partly of the other, according to the poſition of your Eye in reference to the Light when it looks upon them, but if you powr off all the Liquor, the Paper will ſeem Dy'd of an almoſt Yellow Colour. And if a ſheet of Paper with ſome of this Liquor in it be plac'd in a window where the Sunbeams may ſhine freely on it, then if you turn your back to the Sun and take a Pen or ſome ſuch ſlender Body, and hold it over-thwart betwixt the Sun and the Liquor, you may perceive that the Shadow projected by the Pen upon the Liquor, will not all of it be a vulgar and Dark, but in part a curiouſly Colour'd ſhadow, that edge of it, which is next the Body that makes it, being almoſt of a lively Golden Colour, and the remoter verge of a Cæruleous one.
Theſe and other Phænomena, which I have obſerv'd in this delightfull Experiment, divers of my friends have look'd upon not without ſome wonder, and I remember an excellent Oculiſt finding by accident in a friends Chamber a fine Vial full of this Liquor, which I had given that friend, and having never heard any thing of the Experiment, nor having any Body near him that could tell him what this ſtrange Liquor might be, was a great while apprehenſive, as he preſently after told me, that ſome ſtrange new diſtemper was invading his Eyes. And I confeſs that the unuſualneſs of the Phænomena made me very ſollicitous to find out the Cauſe of this Experiment, and though I am far from pretending to have found it, yet my enquiries have, I ſuppoſe, enabled me to give ſuch hints, as may lead your greater ſagacity to the diſcovery of the Cauſe of this wonder. And firſt finding that this Tincture, if it were too copious in the water, Kept the Colours from being ſo lively, and their Change from being ſo diſcernable, and finding alſo that the Impregnating Virtue of this Wood did by its being frequently Infus'd in New Water by degrees Decay, I Conjectur'd that the Tincture afforded by the Wood muſt proceed from ſome Subtiler parts of it drawn forth by the Water, which ſwimming too and fro in it did ſo Modifie the Light, as to exhibit ſuch and ſuch Colours; and becauſe theſe Subtile parts were ſo eaſily Soluble even in Cold water, I concluded that they muſt abound with Salts, and perhaps contain much of the Eſſential Salt, as the Chymiſts call it, of the Wood. And to try whether theſe Subtile parts were Volatile enough to be Diſtill'd, without the Diſſolution of their Texture, I carefully Diſtill'd ſome of the Tincted Liquor in very low Veſſels, and the gentle heat of a Lamp Furnace; but found all that came over to be as Limpid and Colourleſs as Rock-water, and the Liquor remaining in the Veſſel to be ſo deeply Cæruleous, that it requir'd to be oppos'd to a very ſtrong Light to appear of any other Colour. I took likewiſe a Vial with Spirit of Wine, and a little Salt of Harts-horn, and found that there was a certain proportion to be met with betwixt the Liquor and the Salt, which made the Mixture fit to exhibit ſome little Variety of Colours not Obſervable in ordinary Liquors, as it was variouſly directed in reference to the Light and the Eye, but this Change of Colour was very far ſhort from that which we had admir'd in our Tincture. But however, I ſuſpected that the Tinging Particles did abound with ſuch Salts, whoſe Texture, and the Colour ſpringing from it, would probably be alter'd by peircing Acid Salts, which would in likelihood either make ſome Diſſipation of their Parts, or Aſſociate themſelves to the like Bodies, and either way alter the Colour exhibited by them; whereupon Pouring into a ſmall Vial full of Impregnated Water, a very little Spirit of Vinegar, I found that according to my Expectation, the Cæruleous Colour immediately vaniſh'd, but was deceiv'd in the Expectation I had, that the Golden Colour would do ſo too; for, which way ſoever I turned the Vial, either to or from the Light, I found the Liquor to appear always of a Yellowiſh Colour and no other: Upon this I imagin'd that the Acid Salts of the Vinegar having been able to deprive the Liquor of its Cæruleous Colour, a Sulphureous Salt being of a contrary Nature, would be able to Mortifie the Saline Particles of Vinegar, and Deſtroy their Effects; And accordingly having plac'd my Self betwixt the Window, and the Vial, and into the Same Liquor dropt a few drops of Oyl of Tartar per Deliquium, (as Chymiſts call it) I obſerv'd with pleaſure, that immediately upon the Diffuſion of this Liquor, the Impregnated Water was reſtor'd to its former Cæruleous Colour; And this Liquor of Tartar being very Ponderous, and falling at firſt to the Bottom of the Vial, it was eaſie to obſerve that for a little while the Lower part of the Liquor appear'd deeply Cæruleous; whilſt all the Upper part retain'd its former Yellowneſs, which it immediately loſt as ſoon as either Agitation or Time had made a competent Diffuſion of the Liquor of Tartar through the Body of the former Tincture; and this reſtored Liquor did, as it was Look'd upon againſt or from the Light, exhibit the Same Phænomena as the Tincted Water did, before either of the Adventitious Liquors was pour'd into it.
Having made, Pyrophilus, divers Tryals upon this Nephritick Wood, we found mention made of it by the Induſtrious Jeſuit Kircherus, who having received a Cup Turned of it from the Mexican Procurator of his Society, has probably receiv'd alſo from him the Information he gives us concerning that Exotick Plant, and therefore partly for that Reaſon, and partly becauſe what he Writes concerning it, does not perfectly agree with what we have deliver'd, we ſhall not Scruple to acquaint you in his own Words, with as much of what he writes concerning our Wood, as is requiſite to our preſent purpoſe. Hoc loco (ſays he)17 neutiquam omittendum duximus quoddam ligni candidi Mexicani genus, quod Indigenæ Coalle & Tlapazatli vocant, quod etſi experientia hucuſque non niſi Cæruleo aquam colore tingere docuerit, nos tamen continua experientia invenimus id aquam in omne Colorum genus transformare, quod merito cuipiam Paradoxum videri poſſet; Ligni frutex grandis, ut aiunt, non rarò in molem arboris excreſcit, truncus illius eft craſſus, enodis, inſtar piri arboris, folia ciceris foliis, aut rutæ haud abſimilia, flores exigui, oblongi, lutei & ſpicatim digeſti; eſt frigida & humida planta, licet parum recedat à medio temperamento. Hujus itaque deſcriptæ arboris lignum in poculum efformatum, aquam eidem infuſam primo in aquam intenſe Cæruleam, colore floris Bugloſſæ; tingit, & quo diutius in eo ſteterit, tanto intenſiorem colorem acquirit. Hanc igitur aquam si Vitreæ Sphæræ infuderis, lucique expoſueris, ne ullum quidem Cærulei coloris veſtigium apparebit, ſed inſtar aquæ puræ putæ fontanæ limpidam claramque aspicientibus ſe præbebit. Porro ſi hanc phialam vitream verſus locum magis umbroſum direxeris, totus humor gratiſſimum virorem referet; ſi adhuc umbroſioribus locis, ſubrubrum, & ſic pro rerum objectarum conditione, mirum dictu, colorem mutabit; in tenebris verò vel in vaſe opaco poſita, Cæruleum colorem ſuum reſumet.
In this paſſage we may take notice of the following Particulars. And firſt, he calls it a White Mexican Wood, whereas (not to mention that Mornardes informs us that it is brought out of Nova Hiſpania) the Wood that we have met with in ſeveral places, and employ'd as Lignum Nephriticum, was not White, but for the moſt part of a much Darker Colour, not unlike that of the Sadder Colour'd Wood of Juniper. 'Tis true, that Monardes himſelf alſo ſays, that the Wood is White; and it is affirm'd, that the Wood which is of a Sadder Colour is Adulterated by being Imbu'd with the Tincture of a Vegetable, in whoſe Decoction it is ſteep'd. But having purpoſely enquir'd of the Eminenteſt of our Engliſh Druggiſts, he peremptorily deny'd it. And indeed, having conſider'd ſome of the faireſt Round pieces of this Wood that I could meet with in theſe Parts, I had Opportunity to take notice that in one or two of them it was the External part of the Wood that was White, and the more Inward part that was of the other Colour, the contrary of which would probably have appear'd, if the Wood had been Adulterated after the afore-mention'd manner. And I have at preſent by me a piece of ſuch Wood, which for about an Inch next the Bark is White, and then as it were abruptly paſſes to the above-mention'd Colour, and yet this Wood by the Tincture, it afforded us in Water, appears to have its Colour'd part Genuine enough; for as for the White part, it appears upon tryal of both at once, much leſs enrich'd with the tingent Property.
Next, whereas our Author tells us, that the Infuſion of this Wood expos'd in a Vial to the Light, looks like Spring-water, in which he afterwards adds, that there is no Tincture to be ſeen in it, our Obſervation and his agree not, for the Liquor, which oppoſed to the Darker part of a Room exhibits a Sky-colour, did conſtantly, when held againſt the Light, appear Yellowiſh or Reddiſh, according as its Tincture was more Dilute or Deep; and then, whereas it has been already ſaid, that the Cæruleous Colour was by Acid Salts aboliſhed, this Yellowiſh one ſurviv'd without any conſiderable Alteration, ſo that unleſs our Author's Words be taken in a very Limited Senſe, we muſt conclude, that either his Memory mis-inform'd him, or that his White Nephritick Wood, and the Sadder Colour'd one which we employ'd, were not altogether of the ſame Nature: What he mentions of the Cup made of Lignum Nephriticum, we have not had Opportunity to try, not having been able to procure pieces of that Wood great enough, and otherwiſe fit to be turned into Cups; but as for what he ſays in the Title of his Experiment, that this Wood tinges the Water with all Sorts of Colours, that is much more than any of thoſe pieces of Nephritick Wood that we have hitherto employ'd, was able to make good; The change of Colours diſcernable in a Vial full of Water, Impregnated by any of them, as it is directed towards a place more Lightſome or Obſcure, being far from affording a Variety anſwerable to ſo promiſing a Title. And as for what he tells us, that in the Dark the Infuſion of our Wood will reſume a Cæruleous Colour, I wiſh he had Inform'd us how he Try'd it.
But this brings into my mind, that having ſometimes for Curioſity ſake, brought a round Vial with a long Neck fill'd with the Tincture of Lignum Nephriticum into the Darken'd Room already often mention'd, and holding it ſometimes in, ſometimes near the Sun-beams that enter'd at the hole, and ſometimes partly in them, and partly out of them, the Glaſs being held in ſeveral poſtures, and look'd upon from ſeveral Neighbouring parts of the Room, diſclos'd a much greater Variety of Colours than in ordinary inlightn'd Rooms it is wont to do; exhibiting, beſides the uſual Colours, a Red in ſome parts, and a Green in others, beſides Intermediate Colours produc'd by the differing Degrees, and odd mixtures of Light and Shade.
By all this You may ſee, Pyrophilus, the reaſonableneſs of what we elſewhere had occaſion to mention, when we have divers times told you, that it is uſefull to have New Experiments try'd over again, though they were, at firſt, made by Knowing and Candid Men, ſuch Reiterations of Experiments commonly exhibiting ſome New Phænomena, detecting ſome Miſtake or hinting ſome Truth, in reference to them, that was not formerly taken notice of. And ſome of our friends have been pleas'd to think, that we have made no unuſefull addition to this Experiment, by ſhewing a way, how in a moment our Liquor may be depriv'd of its Blewneſs, and reſtor'd to it again by the affuſion of a very few drops of Liquors, which have neither of them any Colour at all of their own. And that which deſerves ſome particular wonder, is, that the Cæruleous Tincture of our Wood is ſubject by the former Method to be Deſtroy'd or Reſtor'd, the Yellowiſh or Reddiſh Tincture continuing what it was. And that you may ſee, that Salts are of a conſiderable uſe in the ſtriking of Colours, let me add to the many Experiments which may be afforded us to this purpoſe by the Dyers Trade, this Obſervation; That as far as we have hitherto try'd, thoſe Liquors in general that are ſtrong of Acid Salts have the Power of Deſtroying the Blewneſs of the Infuſion of our Wood, and thoſe Liquors indiſcriminatly that abound with Sulphureous Salts, (under which I comprehend the Urinous and Volatile Salts of Animal Subſtances, and the Alcaliſate or fixed Salts that are made by Incineration) have the vertue of Reſtoring it.
A Corollary of the Tenth Experiment.
That this Experiment, Pyrophilus, may be as well Uſefull as Delightfull to You, I muſt mind You, Pyrophilus, that in the newly mention'd Obſervation, I have hinted to You a New and Eaſie way of Diſcovering in many Liquors (for I dare not ſay in all) whether it be an Acid or Sulphureous Salt, that is Predominant; and that ſuch a Diſcovery is oftentimes of great Difficulty, and may frequently be of great Uſe, he that is not a Stranger to the various Properties and Effects of Salts, and of how great moment it is to be able to diſtinguiſh their Tribes, may readily conceive. But to proceed to the way of trying other Liquors by an Infuſion of our Wood, take it briefly thus. Suppoſe I have a mind to try whether I conjecture aright, when I imagine that Allom, though it be plainly a Mixt Body, does abound rather with Acid than Sulphureous Salt. To ſatisfie my ſelf herein, I turn my back to the Light, and holding a ſmall Vial full of the Tincture of Lignum Nephriticum, which look'd upon in that Poſition, appears Cæruleous, I drop into it a little of a ſtrong Solution of Allom made in Fair Water, and finding upon the Affuſion and ſhaking of this New liquor, that the Blewneſs formerly conſpicuous in our Tincture does preſently vaniſh, I am thereby incited to ſuppoſe, that the Salt Prædominant in Allom belongs to the Family of Sour Salts; but if on the other ſide I have a mind to examine whether or no I rightly conceive that Salt of Urine, or of Harts-horn is rather of a Saline Sulphureous (if I may ſo ſpeak) than of an Acid Nature, I drop a little of the Saline Spirit of either into the Nephritick Tincture, and finding that the Cæruleous Colour is rather thereby Deepned than Deſtroy'd, I collect that the Salts, which conſtitute theſe Spirits, are rather Sulphureous than Acid. And to ſatisfie my ſelf yet farther in this particular, I take a ſmall Vial of freſh Tincture, and placing both it and my ſelf in reference to the Light as formerly, I drop into the Infuſion juſt as much Diſtill'd Vinegar, or other Acid liquor as will ſerve to Deprive it of its Blewneſs (which a few drops, if the Sour Liquor be ſtrong, and the Vial ſmall will ſuffice to do) then without changing my Poſture, I drop and ſhake into the ſame Vial a ſmall proportion of Spirit of Hartſhorn or Urine, and finding that upon this affuſion, the Tincture immediately recovers its Cæruleous Colour, I am thereby confirm'd firm'd in my former Opinion, of the Sulphureous Nature of theſe Salts. And ſo, whereas it is much doubted by Some Modern Chymiſts to what ſort of Salt, that which is Prædominant in Quick-lime belongs, we have been perſwaded to referr it rather to Lixiviate than Acid Salts, by having obſerv'd, that though an Evaporated Infuſion of it will ſcarce yield ſuch a Salt, as Aſhes and other Alcalizate Bodyes are wont to do, yet if we deprive our Nephritick Tincture of its Blewneſs by juſt ſo much Diſtill'd Vinegar as is requiſite to make that Colour Vaniſh, the Lixivium of Quick-lime will immediately upon its Affuſion recall the Baniſhed Colour; but not ſo Powerfully as either of the Sulphureous Liquors formerly mention'd. And therefore I allow my ſelf to gueſs at the Strength of the Liquors examin'd by this Experiment, by the Quantity of them which is ſufficient to Deſtroy or Reſtore the Cæruleous Colour of our Tincture. But whether concerning Liquors, wherein neither Acid nor Alcaliſate Salts are Eminently Prædominant, our Tincture will enable us to conjecture any thing more than that ſuch Salts are not Prædominant in them, I take not upon me to determine here, but leave to further Tryal; For I find not that Spirit of Wine, Spirit of Tartar freed from Acidity, or Chymical Oyl of Turpentine, (although Liquors which muſt be conceiv'd very Saline, if Chymiſts have, which is here no place to Diſpute, rightly aſcrib'd taſts to the Saline Principle of Bodyes,) have any Remarkable Power either to deprive our Tincture of its Cæruleous Colour, or reſtore it, when upon the Affuſion of Spirit of Vinegar it has diſappear'd.
EXPERIMENT XI.
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.
I know not, Pyrophilus, whether it be worth while to acquaint you with the ways that came into my Thoughts, whereby in ſome meaſure to explicate the firſt of the mention'd ways of making a Green; for I have ſometimes Conjectur'd, that the mixture of the Biſe and the Orpiment produc'd a Green by ſo altering the Superficial Aſperity, which each of thoſe Ingredients had apart, that the Light Incident on the mixture was Reflected with differing Shades, as to Quantity, or Order, or both, from thoſe of either of the Ingredients, and ſuch as the Light is wont to be Modify'd with, when it Reflects from Graſs, or Leaves, or ſome of thoſe other Bodies that we are wont to call Green. And ſometimes too I have doubted, whether the produced Green might not be partly at leaſt deriv'd from this, That the Beams that Rebound from the Corpuſcles of the Orpiment, giving one kind of ſtroak upon the Retina, whoſe Perception we call Yellow, and the Beams Reflected from the Corpuſcles of the Biſe, giving another ſtroak upon the ſame Retina, like to Objects that are Blew, the Contiguity and Minuteneſs of theſe Corpuſcles may make the Appulſe of the Reflected Light fall upon the Retina within ſo narrow a Compaſs, that the part they Beat upon being but as it were a Phyſical point, they may give a Compounded ſtroak, which may conſequently exhibit a Compounded and new Kind of Senſation, as we ſee that two Strings of a Muſical Inſtrument being ſtruck together, making two Noiſes that arrive at the Ear at the ſame time as to Senſe, yield a Sound differing from either of them, and as it were Compounded of both; Inſomuch that if they be Diſcordantly ton'd, though each of them ſtruck apart would yield a Pleaſing Sound, yet being ſtruck together they make but a Harſh and troubleſome Noiſe. But this not being ſo fit a place to proſecute Speculations, I ſhall not inſiſt, neither upon theſe Conjectures nor any others, which the Experiment we have been mentioning may have ſuggeſted to me. And I ſhall leave it to you, Pyrophilus, to derive what Inſtruction you can from comparing together the Various ways whereby a Yellow and a Blew can be made to Compound a Green. That which I now pretend to, being only to ſhew that the firſt of thoſe mention'd ways, (not to take at preſent notice of the reſt) does far better agree with our Conjectures about Colours, than either with the Doctrine of the Schools, or with that of the Chymiſts, both which ſeem to be very much Disfavour'd by it.