Oeuvres complètes. Tome IV. Correspondance 1662-1663

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N^o 1194.
R. Boyle à R. Moray.
[1663].
Appendice au N^o. 1193.

La pièce se trouve à Leiden, coll. Huygens.

Observations made the 27^th of October 1663 on Mr. Clayton's Diamond.

1.	Being looked on in the day-time, though in a bedd, whose curtains were carefully drawne, J could not discerne it to shine at all, though well rubb'd; but about a little after Sun-set whilest the Twilight yet lasted, nay this morning a pretty while after Sun-rising, (but before J had been abroad in the more sreely inlightened air, of the Chamber) J could upon a light affriction, easily perceiue the Stone to shine within the Curtains of my Bed.
2.	The Candles being removed, J could not in a dark place discerne the Stone to haue any light when J looked upon it, without having before rubbed or otherwise prepared it.
3.	By two white Pebbles, though hard rubb'd against one another, nor by the long and vehement affriction of rock-Chrystall against a peice of red Cloath, nor yet by rubbing two diamonds set in a ring, as J had rubb'd this Stone, J could not produce any sensible degree os Light.
4.	J found this Diamond hard enough, not onely to enable me, to write readily with it upon Glasse, but to graue upon rock-Chrystall it selfe.
5.	J found this to haue like other Diamonds an Electrical faculty.
6.	Being rubb'd upon any Cloaths, as is usuall 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 and other putrified fish.
7.	But this Conspicuousnesse was fainter, then that of the Scales and Slabber (if J may so call it) of Whitings, and much fainter than the light of a Glow-

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	worme, by which J haue been sometimes able to read a short word, whereas, after an ordinary affriction of this Diamond, J was not able to discerne distinctly by the light of it, any of the neerest Bodies. And this Glimmering also, did very manifestly and considerably decay presently upon the Ceasing of the affriction though the Stone continued visible some while after.
8.	But if it were rubbed upon a convenient Body for a pretty while, and briskly enough, J found the light would be for some moments much more considerable, almost like the light of a Glow-worme, insomuch, that immediatly after J ceased rubbing, J could with the chafed stone exhibit a little luminous circle like that, but not so bright, as that which Children make by moving a stick fired at the end, and in this case, it would continue visible about seven or Eight times as long as J had been in rubbing it.
9.	J found that holding it a while neer the flame of a Candle, from which yet J was carefull to avert my Eyes, and being immediatly removed into the dark, it disclosed some faint Glimmering, but far inferiour to that, which it was wont to acquire by rubbing; and afterwards holding it neer a fire that had but little flame, J found the stone to be rather lesse than more excited, than it had been by the Candle.
10.	J likewise endeavoured to make it shine by holding it a pretty while in a very dark place ouer a thick plate of Jron, that was well heated, but not to that degree as to be visibly so; and though at length J found, that by this way also, the stone acquired some glimmering, yet it was lesse than by either of the other wayes aboue mentioned.
11.	J also brought it to some kind of Glimmering light by taking it into bed with me, and holding it a good while upon some warme part of my naked body.
12.	To satisfy my selfe, whether the motion introduced into the stone, did generate the light upon the account of its producing heat there, J held it neer the flame of a Candle till it was qualified to shine pretty well in the dark, and then immediatly J applyed, to it, a slender hair, to try, whether it would attract it, but found not that it did so, though if it were made to shine with rubbing, it was, as J formerly noted, Electricall. And for further confirmation, though J once purposely kept it so neer the hot Jron, J just now mentioned, as to make it sensibly warme, yet it shined more dimly, than it had done by affriction, or the flame of a candle, though by both these wayes it had not acquired any warmth that was sensible.
13.	Having purposely rubbed it upon severall Bodyes, differing either as to Colour or as to Texture, there seemed to be some little disparity in the Excitation (if J may so call it) of Light. Vpon white and red Cloaths it seemed to succeed best, especially in comparison of black ones.
14.	But to try, what it would do rubbed upon Bodies neer hand, and lesse apt to yeild heat upon a light affriction, than Cloath, J first rubb'd it upon a white

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	wooden box, by which it was Excited, and afterwards upon a peice of purely white and well glased Earth, which seemed during the attrition, to make it shine better than any of the other Bodyes had done, without excepting the white ones, which J adde, least the Effect should be wholly adscribed to the disposition, white Bodies are wont to haue, to reflect much light.
15.	Having well excited the Stone, J nimbly plung'd it under water, that J had provided for that purpose, and perceived it to shine, whilst it was beneath the surface of that Liquor, and this J did divers times. But when J endeavoured 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, J did not well satisfy my selse in the Event of the Tryall. But this J found, if J took the stone out, and rubbed it upon a peice of Cloath, it would not, as else it was wont to doe, presently acquire a Luminousnesse, but needed to be rubbed manifestly much longer, before the desired Effect was found.
16.	J also tryed severall times that by covering it with my warme Spittle (having no warme water at hand) it did not loose its light.
17.	Finding that by rubbing the Stone with the flat side downward J did by reason of the Opacity of the Ring, and the sudden decay of light upon the ceasing of the Attrition, probably loose the sight of the stones greatest vividnesse, and supposing that the commotion made in one part of the Stone, will be easily propagated all over, J sometimes held the peice of Cloath, upon which J rubb'd it, so that one side of the stone was exposed to my Eys, whilst J was rubbing the other, wherby it appeared more vivid than formerly, and to make Luminous Tracts by its motion to and fro. And sometimes holding the Stone upwards, J rubbed its broad side with a fine smooth peece of transparent horne, by such meanes, the light through that Diaphanous Substance, did, whilst J was actually rubbing the Stone, appear so brisk, that sometimes, and in some places it seemed to haue little sparks of fire.
18.	J took also a peice of flatt blue glasse, and having rubbed the Diamond well upon a Cloath, and nimbly clapt the glasse upon it, to try, whether, in case the light would peirce it, it would by appearing green, or of some other colour than blew, assist me to guesse, whether it selfe were sincere or no. But finding the glasse impervious to so faint a light, J then thought fit to try, whether the hard Bodies would not by attrition increase the Diamonds Light so, as to become penetrable thereby. And accordingly, when J rubbed the Glasse briskly upon the stone, J found the light conspicuous enough, and somewhat dyed in its passage, but found it not easy to giue a Name to the Colour it exhibited. Lastly to comply with the suspition, J had upon the whole matter, that the cheif manifest chang wrought upon the stone, was by compressing of its parts, rather than incallescense J took a peice of white Tyle well glaz'd,

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and if J pressed the Stone hard upon it, it seem'd, though J did not rubb it to and fro, to shine at the sides. And however, it did both very manifestly and vigorously shine, if, whilst J so prest it, J moved it any way upon the surface of the Tyle, though J did not make it draw a line of aboue a quarter of an Jnch long, or thereabouts. And though J made it not moue to and fro, but onely from one end of that short line to the other, without any returne, or any laterall motion. Nay after it had been often rubbed, and suffer'd to loose its light againe, not onely it seemed more easy to be excited, than at the beginning of the night, but if J did presse hard upon it with my finger, at the very instant thàt J drew it briskly off, it would disclose a very vivid, but exceeding shortliu'd splendor, not to call it a litle coruscation; so that a Cartesian would scarse scruple to think, he had found in this Stone, no slight confirmation of his ingenuous Masters Hypothesis touching the Generation of light in sublunary Bodies not sensibly hot.

Post-script.

So many particulars taken notice of in one night, may make this stone appear a kind of Prodigy, and the rather because having tryed, as J formerly noted, not onely a fine Artificial Chrystall, and some also that is natural, but a Ruby and two Diamonds, J did not find that any of those disclosed the least glimmering of light, yet after all perceiving by the hardnesse, and the testimony of a skillfull Goldsmith, that this was rather a Naturall than an Artificial stone, for fear least there might be some difference in the way of setting or in the shape of the Diamonds, J made use of, neither of which was like this, a flat Table-stone, J thought fit to make a further Tryal of my own Diamonds, by such a brisk and assiduous affriction, as might make amends for the disadvantages abouementioned, in case they were the cause of the unsuccessfullnesse of the former attempts: And accordingly J found, that by this way J could easily bring a Diamond J wore upon my finger to disclose a light, that was sensible enough, and continued so, though J covered it with Spittle, and used some other tryalls about it. And though this will much lessen the wonder of all the formerly mentioned Observations, by shewing that the Properties, that seem so strange, are not peculiar to one Diamond, but may be found in others also, and perhaps in divers other hard and diaphanous Stones.

Yet J hope, that what this discovery taketh away from the wonder of these Observations, it will adde to the instructiuenesse of them, by affording pregnant hints, toward the investigation of the nature of Light.