Experiments and Considerations Touching Colours – Robert Boyle


OBSERVATIONS Made this * 27th. of *October 1663. about Mr. Clayton’s Diamond.

Being look’d on in the Day time, * though in a Bed, whose Cur∣tains were carefulsy drawn, I could not discern it to Shine at all, though well Rubb’d, but about a little after Sun-set, whilst the Twilight yet lasted, Nay, this Morning a pretty while after Sun-rising, (but before I had been abroad in the more freely inlightned Air of the Chamber) I could upon a light Affriction easily perceive the Stone to Shine.

Secondly, The Candles being removed, I could not in a Dark place discern the Stone to have any Light, when I looked on it, without having Rubb’d or otherwise prepar’d it.

Thirdly, By two white Pibbles though hard Rubb’d one against another, nor by the long and vehement Affriction of Rock Crystal against a piece of Red cloath, nor yet by Rubbing two Diamonds set in Ring, as I had Rubb’d this Stone, I could produce any sen∣sible degree of Light.

Fourthly, I found this Diamond hard e∣nough, not only to enable me to write readily with it upon Glass, but to Grave on Rock Crystal it self.

Fifthly, I found this to have like other Diamonds, an Electrical fa∣culty. *

Sixthly, Being rubb’d upon my Cloaths, as is usual for the exciting of Amber, Wax, and other Electrical Bodies, it did in the Dark manifestly shine like Rotten Wood, or the Scales of Whitings, or other putrified Fish.

Seventhly, But this Conspicuousness was Fainter than that of the Scales, and Slabber (if I may so call it) of Whitings, and much Fainter than the Light of a Glow-worm, by  which I have been sometimes able to Read a short Word, whereas after an ordinary Affriction of this Diamond I was not able to discern distinctly by the Light of it any of the nearest Bodies: And this Glimmer∣ing also did very manifestly and considerably Decay presently upon the ceasing of the Affriction, though the Stone continued Visible some while after.

Eighthly, But if it were Rubb’d upon a convenient Body for a pretty while, and Briskly enough, I found the Light would be for some  moments much more conside∣rable, almost like the Light of a Glow-worm, insomuch after I ceased Rubbing, I could with the Chaf’d stone exhibit a little Luminous Circle, like that, but not so bright as that which Children make by moving a stick Fir’d at the end, and in this case  it would continue Visible about seven or eight times as long as I had been in Rub∣bing it.

Ninthly, I found that holding * it a while near the Flame of a Candle, (from which yet I was carefull to avert my Eyes) and

being immediately remov’d into the Dark, it disclosed some faint Glimmering, but in∣feriour to that, it was wont to acquire by Rubbing. And afterward holding it near a Fire that had but little Flame, I found the Stone to be rather less than more excited, than it had been by the Candle.

Tenthly, I likewise indeavour’d to make it Shine, by holding it a pretty while in a very Dark place, over a thick piece of Iron, that was well Heated, but not to that De∣gree as to be Visibly so. And though at length I found, that by this way also, the Stone acquired some Glimmering, yet it was less than by either of the other ways above mention’d.

Eleventhly, I also brought it to some kind of Glimmering Light, by taking it into Bed with me, and holding it a good while upon a warm part of my Naked Body.

Twelfthly, To satisfie my self, whether the Motion introduc’d into the Stone did generate the Light upon the account of its producing Heat there, I held it near the Flame of a Candle, till it was qualify’d to shine pretty well in the Dark, and then immediately I apply’d a slender Hair to try whether it would attract it, but found not that it did so; though if it were made to

shine by Rubbing, it was as I formerly noted Electrical. And for further Confir∣mation, though I once purposedly kept it so near the hot Iron I just now mention’d, as to make it sensibly Warm, yet it shin’d more Dimly than it had done by Affri∣ction or the Flame of a Candle, though by both those ways it had not acquir’d any warmth that was sensible.

Thirteenthly, Having purposely rubb’d it upon several Bodies differing as to Co∣lour, and as to Texture, there seem’d to be some little Disparity in the excitation (if I may so call it) of Light. Upon White and Red Cloths it seem’d to succeed best, especially in comparison of Black ones.

Fourteenthly, But to try what it would do rubb’d upon Bodies more hard, and less apt to yield Heat upon a light Affriction, than Cloath, I first rubb’d it upon a white wooden Box, by which it was excited, and afterwards upon a piece of purely Glazed Earth, which seem’d during the Attrition to make it Shine better than any of the other Bodies had done, without excepting the White ones, which I add, lest the Effect should be wholly ascrib’d to the dispo∣sition White Bodies are wont to have to Reflect much Light.

Fifteenthly, Having well ex∣cited the Stone, I nimbly plung’d * it under Water, that I had pro∣vided for that purpose, and per∣ceiv’d it to Shine whilst it was be∣neath the Surface of that Liquor, and this I did divers times. But when I indeavour’d to produce a Light by rubbing it upon the lately mentioned Cover of the Box, the Stone and it being both held beneath the Surface of the Water, I did not well satisfie my self in the Event of the Trial; But this I found, if I took the Stone out, and Rubb’d it upon a piece of Cloath, it would not as else it was wont to do, presently acquire a Luminousness, but need∣ed to be rubb’d manifestly much longer before the desired Effect was found.

Sixteenthly, I also try’d several * times, that by covering it with my warm Spittle (having no warm Water at hand) it did not lose his Light.

Seventeenthly, Finding that by Rubbing the Stone with the Flat side downwards, I did by reason of the Opacity of the Ring, and the sudden Decay of Light upon the ceasing of the Attrition, probably lose the sight of the Stones greatest Vividness; and supposing that the Commotion made in one part of the Stone will be easily pro∣pagated all over, I sometimes held the piece of Cloath upon which I rubb’d it, so, that one side of the Stone was exposed to my Eye, whilst I was rubbing the other, whereby it appear’d more Vivid than for∣merly, and to make Luminous Tracts by its Motions too and fro. And sometimes holding the Stone upwards, I rubb’d its Broad side with a fine smooth piece of Transparent Horn, by which means the Light through that Diaphauous Substance, did whilst I was actually rubbing the Stone, appear so Brisk, that sometimes and in some places it seem’d to have little Sparks of Fire.

Eighteenthly, I took also a piece of flat Blew Glass, and having rubb’d the Diamond well upon a Cloath, and nimbly clapt the Glass upon it, to try whether in case the Light could peirce it, it would by appearing Green, or of some other Colour than Blew, assist me to guess whether it self were sincere or no.

But finding the Glass impervious to so faint a Light, I then thought it fit to try whether that hard Bo∣dies would not by Attrition increase the Diamonds Light so as to become pene∣trable thereby, and accordingly when I rubb’d the Glass briskly upon the Stone, I found the Light to be Conspicuous enough, and somewhat Dy’d in its passage, but found it not easie to give a Name to the Colour it exhibited.

Lastly, To comply with the Suspition I had upon the whole Matter, that the chief manifest Change wrought in the Stone, was by Compression of its parts, rather than In∣calescence, I took a piece of white Tile well Glaz’d, and if I press’d the Stone hard against it, it seem’d though I did not rub it to and fro, to shine at the Sides: And however it did both very manifestly and vigorously Shine, if whilst I so press’d it, I mov’d it any way upon the Surface of the Tile, though I did not make it draw a Line of above a quarter of an Inch long, or there∣abouts. And though I made it not move to and ‘fro, but only from one end of the short Line to the other, without any return or Lateral motion.

Nay, after it had been often rubb’d, and suffer’d to lose its Light again, not only it seem’d more easie to be excited than at the beginning of the Night; but if I did press hard upon it with my Fin∣ger, at the very instant that I drew it briskly off, it would disclose a very Vivid but ex∣ceeding short Liv’d Splendour, not to call it a little Coruscation. * So that a Cartesian would scarce scruple to think he had found in this Stone no slight Confirmation of his Inge∣nious Masters Hypothesis, touching the Generation of Light in Sub∣lunary Bodies, not sensibly Hot.