Experiments and Considerations Touching Colours (1664) Part 10

[26] Boetius de Boot. Gem. & Lapid. Histor. Lib. 3. Cap. 8.

[27] Musaei Wormiani. Cap. 17.

But, Sir, though I be very backward to admit strange things for truths, yet I am not very forward to reject them as impossibilities, and therefore I would not discourage any from making further Inquiry, whether or no there be Really in _Rerum natura_, any such thing as a true Carbuncle or Stone that without Rubbing will s.h.i.+ne in the Dark. For if such a thing can be found, it may afford no small a.s.sistance to the Curious in the Investigation of Light, besides the n.o.bleness and Rarity of the thing it selfe. And though _Vartomannus_ was not an Eye witness of what he relates, that the King of _Pegu_, one of the Chief Kings of the _East-Indies_, had a true Carbuncle of that Bigness and Splendour, that it s.h.i.+n'd very Gloriously in the Dark, and though _Garcias ab Horto_, the _Indian_ Vice-Roys Physician, speaks of another Carbuncle, only upon the Report of one, that he Discours'd with, who affirmed himself to have seen it; yet as we are not sure that these Men that gave themselves out to be Eye-witnesses speak true, yet they may have done so for ought we know to the contrary.

And I could present you with a much considerabler Testimony to the same purpose, if I had the permission of a Person concern'd, without whose leave I must not do it. I might tell you that _Marcus Paulus Venetus_[28] (whose suppos'd Fables, divers of our later Travellours and Navigatours have since found to be truths) speaking of the King of _Zeilan_ that then was, tells us, that he was said to have the best Rubie in the World, a Palm long and as big as a mans Arm, without spot, s.h.i.+ning like a Fire, and he subjoyns, that the Great _Cham_, under whom _Paulus_ was a considerable Officer, sent and offer'd the value of a City for it; But the King answer'd, he would not give it for the treasure of the World, nor part with it, having been his Ancestours. And I could add, that in the Relation made by two _Russian_ Cossacks of their Journey into _Catay_[29], written to their Emperour, they mention'd their having been told by the people of those parts, that their King had a Stone, which Lights as the Sun both Day and Night, call'd in their Language _Sarra_, which those Cossacks interpret a Ruby. But these Relations are too uncertain for me to build any thing upon, and therefore I shall proceed to tell you, that there came hither about two years since out of _America_, the Governour of one of the Princ.i.p.al Colonies there, an Ancient _Virtuoso_, and one that has the Honour to be a member of the Royal Society; this Gentleman finding some of the chief Affairs of his Country committed to another and me, made me divers Visits, and in one of them when I enquir'd what Rare Stones they had in those parts of the _Indies_ he belong'd to, he told me, that the _Indians_ had a Tradition that in a certain hardly accessible Hill, a pretty way up in the Country, there was a Stone which in the Night time s.h.i.+n'd very vividly, and to a great distance, and he a.s.sur'd me, that though he thought it not fit to venture himself so far among those Savages, yet he purposely sent thither a bold _Englishman_, with some Natives to be his guides, and that this Messenger brought him back word, that at a distance from the Hillock he had plainly perceiv'd such a s.h.i.+ning Substance as the _Indians_ Tradition mention'd, and being stimulated by Curiosity, had slighted those Superst.i.tious Fears of the Inhabitants, and with much ado by reason of the Difficulty of the way, had made a s.h.i.+ft to clamber up to that part of the Hill, where, by a very heedful Observation, he suppos'd himself to have seen the Light: but whether 'twere that he had mistaken the place, or for some other Reason, he could not find it there, though when he was return'd to his former Station, he did agen see the Light s.h.i.+ning in the same place where it shone before.

A further Account of this Light I expect from the Gentleman that gave me this, who lately sent me the news of his being landed in that Country. And though I reserve to my self a full Liberty of Believing no more than I see cause; yet I do the less scruple to relate this, because a good part of it agrees well enough with another Story that I shall in the next place have occasion to subjoyn, in order whereunto I shall tell you, that though the Learned Authors I formerly mention'd, tell us, that no Writer has affirm'd his having himself seen a real Carbuncle, yet, considering the Light of Mr.

_Claytons_ Diamond, it recall'd into my mind, that some years before, when I was Inquisitive about Stones, I had met with an old _Italian_ Book highly extoll'd to me by very competent Judges, and that though the Book were very scarce, I had purchas'd it at a dear Rate, for the sake of a few considerable pa.s.sages I met with in it, and particularly one, which being very remarkable in it self, and pertinent to our present Argument, I shall put it for you, though not word for word, which I fear I have forgot to do, yet as to the Sense, into _English_.

[28] _Purchas_'s Pilgrim. lib. 1. cap. 4. pag. 104.

[29] In the year 1619.

_Having promis'd_ (Says our Author)[30] _to say something of that most precious sort of Jewels,_ Carbuncles, _because they are very rarely to be met with, we shall briefly deliver what we know of them. In_ Clement _the seventh's time, I happen'd to see one of_ _them at a certain_ Ragusian _Merchants, nam'd_ Beigoio di Bona, _This was a Carbuncle white, of that kind of whiteness which we said was to be found in those Rubies of which we made mention a little above,_ (where he had said that those Rubies had a kind of Livid Whiteness or Paleness like that of a Calcidonian) _but it had in it a l.u.s.tre so pleasing and so marveilous, that it s.h.i.+n'd in the Dark, but not as much as colour'd Carbuncles, though it be true, that in an exceeding Dark place I saw it s.h.i.+ne in the manner of fire almost gone out.

But as for colour'd Carbuncles, it has not been my Fortune to have seen any, wherefore I will onely set down what I Learn'd about them Discoursing in my Youth with a_ Roman _Gentleman of antient Experience in matters of Jewels, who told me, That one_ Jacopo Cola _being by Night in a Vineyard of his, and espying something in the midst of it, that s.h.i.+n'd like a little_ glowing Coal, at the foot of a Vine, went near towards the place where he thought himself to have seen that fire, but not finding it, he said, that being return'd to the same place, whence he had first descry'd it, and perceiving there the same splendor as before, he mark'd it so heedfully, that he came at length to it, where he took up a very little Stone, which he carry'd away with Transports and Joy. And the next day carrying it about to show it divers of his Friends, whilst he was relating after what manner he found it, there casually interven'd a _Venetian_ Emba.s.sadour, exceedingly expert in Jewels, who presently knowing it to be a Carbuncle, did craftily before he and the said _Jacopo_ parted (so that there was no Body present that understood the Worth of so Precious a Gemm) purchase it for the Value of 10. Crowns, and the next day left _Rome_ to shun the being necessitated to restore it, and (as he affirm'd) it was known within some while after that the said _Venetian_ Gentleman did in _Constantinople_ sell that Carbuncle to the then Grand Seignior, newly come to the Empire, for a hundred thousand Crowns. _And this is what I can say_ concerning _Carbuncles_, and this is not a little at least as to the first part of this account, where our _Cellini_ affirms himself to have seen a Real Carbuncle with his own Eyes, especially since this Author appears wary in what he delivers, and is inclin'd rather to lessen, than increase the wonder of it. And his Testimony is the more considerable, because though he were born a Subject neither to the Pope nor the then King of _France_ (that Royal _Virtuoso_ _Francis_ the first) yet both the one and the other of those Princes imploy'd him much about making of their n.o.blest Jewels. What is now reported concerning a s.h.i.+ning Substance to be seen in one of the Islands about _Scotland_, were very improper for me to mention to Sr.

_Robert Morray_, to whom the first Information was Originally brought, and from whom I expect a farther (for I scarce dare expect a convincing) account of it. But I must not omit that some _Virtuoso_ questioning me the other day at _White-Hall_ about Mr. _Claytons_ Diamond, and meeting amongst them an Ingenious _Dutch_ Gentleman, whose Father was long Emba.s.sador for the Netherlands in _England_, I Learn'd of him, that, he is acquainted with a person, whose Name he told (but I do not well remember it) who was Admiral of the _Dutch_ in the _East-Indies_, and who a.s.sur'd this Gentleman _Monsieur Boreel_, that at his return from thence he brought back with him into _Holland_ a Stone, which though it look'd but like a Pale Dull Diamond, such as he saw Mr. _Claytons_ to be, yet was it a Real Carbuncle, and did without rubbing s.h.i.+ne so much, that when the Admiral had occasion to open a Chest which he kept under Deck in a Dark place, where 'twas forbidden to bring Candles for fear of Mischances, as soon as he open'd the Trunck, the Stone would by its Native Light, s.h.i.+ne so as to Ill.u.s.trate a great part of it, and this Gentleman having very civilly and readily granted me the request I made him, to Write to the Admiral, who is yet alive in _Holland_, (and probably may still have the Jewel by him,) for a particular account of this Stone, I hope ere long to receive it, which will be the more welcome to me, not onely because so unlikely a thing needs a cleer evidence, but because I have had some suspition of that (supposing the truth of the thing) what may be a s.h.i.+ning Stone in a very hot Countrey as the _East-Indies_, may perhaps cease to be so (at least in certain seasons,) in one as cold as _Holland_. For I observ'd in the Diamond I send you an account of, that not onely rubbing but a very moderate degree of warmth, though excited by other wayes, would make it s.h.i.+ne a little. And 'tis not impossible that there may be Stones as much more susceptible than that, of the Alterations requisite to make a Diamond s.h.i.+ne, as that appeares to be more susceptible of them, than ordinary Diamonds. And I confess to you, that this is not the only odd suspition (for they are not so much as conjectures) that what I try'd upon this Diamond suggested to me. For not here to entertain you with the changes I think may be effected ev'n in harder sorts of Stones, by wayes not vulgar, nor very promising, because I may elsewhere have occasion to speak of them, and this Letter is but too Prolix already, that which I shall now acknowledge to you is, That I began to doubt whether there may not in some Cases be some Truth in what is said of the right Turquois, that it often changes Colour as the wearer is Sick or Well, and manifestly loses its splendor at his Death. For when I found that ev'n the warmth of an Affriction that lasted not above a quarter of a minute, Nay, that of my Body, (whose Const.i.tution you know is none of the hottest) would make a manifest change in the solidest of Stones a Diamond, it seem'd not impossible, that certain warm and Saline steams issuing from the Body of a living man, may by their plenty or paucity, or by their peculiar Nature, or by the total absence of them, diversifie the Colour, and the splendor of so soft a Stone as the Turquois. And though I admir'd to see, that I know not how many Men otherwise Learn'd, should confidently ascribe to Jewels such Virtues as seem no way competible to Inanimate Agents, if to any Corporeal ones at all, yet as to what is affirm'd concerning the Turquois's changing Colour, I know not well how to reject the Affirmation of so Learned (and which in this case is much more considerable) so Judicious a Lapidary as _Boetius de Boot_[31], who upon his own particular and repeated Experience delivers so memorable a Narrative of the Turquois's changing Colour, that I cannot but think it worth your Perusal, especially since a much later and very Experienc'd Author, _Olaus Wormius_,[32] where he treats of that Stone, Confirms it with this Testimony. _Imprimis memorandum exemplum quod Anshelmus Boetius de seipso refert, tam mutati Coloris, quam a casu preservationis. Cui & ipse haud dissimile adferre possum, nisi ex Anshelmo pet.i.tum quis putaret._ I remember that I saw two or three years since a _Turcois_ (worn in a Ring) wherein there were some small spots, which the _Virtuoso_ whose it was asur'd me he had observ'd to grow sometimes greater sometimes less, and to be sometimes in one part of the Stone, sometimes in another. And I having encourag'd to make Pictures from time to time of the Stone, and of the Situation of the cloudy parts, thatso their Motion may be more indisputable, and better observ'd, he came to me about the midle of this very week, and a.s.sur'd me that he had, as I wish'd, made from time to time Schemes or Pictures of the differing parts of the Stone, whereby the several Removes and motions of the above mentioned Clouds are very manifest, though the cause seem'd to him very occult: these Pictures he has promis'd to show me, and is very ready to put the Stone it self into my hands. But the ring having been the other day casually broken upon his finger, unless it can be taken out, and set again without any considerable heat, he is loath to have it medled with, for fear its peculiarity should be thereby destroy'd. And possibly his apprehension would have been strengthen'd, if I had had opportunity to tell him what is related by the Learned _Wormius_[33] of an acquaintance of his, that had a _Nephritick_ stone, of whose eminent Virtues he had often Experience ev'n in himself, and for that cause wore it still about his Wrist; and yet going upon a time into a Bath of fair Water only, wherein certain Herbs had been boyl'd, the Stone by being wetted with this decoction, was depriv'd of all his Virtue, whence _Wormius_ takes Occasion to advertise the sick, to lay by such stones whensoever they make use of a Bath. And we might expect to find _Turcos_ likewise, easily to be wrought upon in point of Colour, if that were true, which the curious _Antonio Neri_, in his ingenious _Arte Vetraria_[34] teaches of it, namely, That _Turcois's discolour'd_ and grown white, will regain and acquire an excellent Colour, if you but keep them two or three days at most cover'd with Oyl of sweet Almonds kept in a temperate heat by warm ashes, I say if it were true, because I doubt whether it be so, and have not as yet had opportunity to satisfie my self by Tryals, because I find by the confession of the most Skilfull Persons among whom I have laid out for _Turcoises_, that the true ones are great rarities, though others be not at all so. And therefore I shall now only mind you of one thing that you know as well as I, namely, that the rare Stone which is called _Oculus Mundi_, if it be good in its Kind, will have so great a change made in its Texture by being barely left a while in the Languidest of Liquors, common Waters, that from Opacous it will become Transparent, and acquire a l.u.s.tre of which it will again be depriv'd, without using any other Art or Violence, by leaving it a while in the Air.

And before experience had satisfy'd us of the truth of this, it seem'd as unlikely that common Water or Air, should work such great changes in that Gemm, as it now seems that the Effluviums of a human Body should effect lesser changes in a _Turcois_, especially if more susceptible of them, than other Stones of the same kind. But both my Watch and my Eyes tell me that 'tis now high time to think of going to sleep, matters of this Nature, will be better, as well as more easily, clear'd by Conference, than Writing. And therefore since I think you know me too well to make it needfull for me to disclame Credulity, notwithstanding my having entertain'd you with all these Extravagancies; for you know well, how wide a difference I am wont to put betwixt things that barely _may be_, and things that _are_, and between those Relations that are but not unworthy to be inquir'd into, and those that are not worthy to be actually believ'd; without making Apologies for my Ravings, I shall readily comply with the drowsiness that calls upon me to release You, and the rather, because Monsieur _Zulichem_ being concern'd in your desire to know the few things I have observed about the s.h.i.+ning Stone. To entertain those with Suspicions that are accustomed not to acquiesce but in Demonstrations, were a thing that cannot be look'd upon as other than very improper by,

SIR,

_Your most Affectionate_

and

_most Faithfull Servant,_

RO. BOYLE.

[30] Benvonuto Cellini _nell Arte del_ Gioiellare, _Lib._ 1. _pag._ 10.

[31] The Narrative in the Authors own words, is this. _Ego_ (sayes he) _sancte affirmare possum me unam aureo Annulo inclusam perpetuo gestare, cujus facultatem (si gemmae est) nunquam satis admirari potui. Gestaverat enim ante Triginta annos Hispa.n.u.s quidam non procula puternis aedibus habitans. Is c.u.m vita functus esset, & ipsius suspellex (ut moris apud nos est) venum exposita esset, inter caetera etiam Turcois exponebatur.

Verum nemo (licet complures eo concurrissent, ut eam propter Coloris Elegantiam, quam vivo Domino habuerat emerent) sibi emptam voluit, pristinum enim nitorem & Colorem prorsus amiserat, ut potius Malachites, quam Turcois videretur. Aderat tum temporis gemmae habendae desiderio etiam parens & frater meus, qui antea saepius gratiam & elegantiam ipsius viderant, mirabundi eam nunc tam esse deformem, Emit eam nihilominus pater, satisque vili pretio, qua omnibus contemptui erat, ac presentes non eam esse quam Hispa.n.u.s gestarat, arbitrarentur. Domum reversus Pater, qui tam turpem Gemmam gestare sibi indecorum putabat, eam mihi dono dat, inquiens; Quandoquidem, fili mi, vulgi fama est, Turcoidem, ut facultates suas exercere possit, dono dari debere tibi eam devoveo, ego acceptam Gemmam sculptori trado, at gentilitia mea insignia illi, quamadmodum fieri solet, in Jaspide Chalcedono, aliisque Ign.o.bilioribus Gemmis, insculperat. Turpe enim existimabam, hujusmodi Gemma ornatus gratia, dum gratiam nullam haberet, uti. Paret Sculptor redditque Gemmam, quam gesto pro annulo Signatorio. Vix per mensem gestaram, redit illi pristinus color, sed non ita nitens propter Sculpturam, ac inaequalem superficiem.

Miramur omnes gemmam, atque id praecipue quod color indies pulchrior fieret. Id quia observabam, nunquam fere eam a manu deposui, ita ut nunc adhuc candem gestem._

[32] _Olaus Wormius, in Musae. 18 pag. 186._

[33] _Musae. Worm._ pag. 99.

[34] Arte Vetraria, lib. 7 cap. 102.

OBSERVATIONS

Made this 27th.[35]

of _October_ 1663. about Mr. _Clayton's_ Diamond.[36]

Being look'd on in the Day time, though in a Bed, whose Curtains were carefully drawn, I could not discern it to s.h.i.+ne at all, though well Rubb'd, but about a little after Sun-set, whilst the Twilight yet lasted, Nay, this Morning[37] 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 s.h.i.+ne.

[35] These were brought in and Read before the Royal Society, (the Day following) _Oct._ 28. 1663.

[36] _The Stone it self being to be shown to the Royal Society, when the Observations were deliver'd, I was willing (being in haste) to omit the Description of it, which is in short, That it was a Flat or Table Diamond, of about a third part of an Inch in length, and somewhat less in breadth, that it was a Dull Stone, and of a very bad Water, having in the Day time very little of the Vividness of ev'n ordinary Diamonds, and being Blemished with a whitish Cloud about the middle of it, which covered near a third part of the Stone._

[37] _Hast made me forget to take notice that I went abroad the same Morning, the Sun s.h.i.+ning forth clear enough, to look upon the Diamond though a_ Microscope, _that I might try whether by that Magnifying Gla.s.s any thing of peculiar could be discern'd in the Texture of the Stone, and especially of the whitish Cloud that possest a good part of it. But for all my attention I could not discover any peculiarity worth mentioning._

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 sensible degree of Light.

Fourthly, I found this Diamond hard enough, not only to enable me to write readily with it upon Gla.s.s, but to Grave on Rock Crystal it self.

Fifthly, I found this to have like other Diamonds, an Electrical faculty.[38]

[38] V. _For it drew light Bodies like Amber, Jet, and other Concretes that are noted to do so; But its attractive power seem'd inferiour to theirs._

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 s.h.i.+ne 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 Glimmering 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 considerable, 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 Rubbing it.

Ninthly, I found that holding it a while near[39] 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 inferiour 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.

[39] IX. _We durst not hold it in the Flame of a Candle, no more than put it into a naked Fire; For fear too Violent a Heat (which has been observ'd to spoil many other precious Stones) should vitiate and impair a Jewel, that was but borrow'd, and was suppos'd to be the only one of its Kind._

Tenthly, I likewise indeavour'd to make it s.h.i.+ne, 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 Degree 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 s.h.i.+ne 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 s.h.i.+ne by Rubbing, it was as I formerly noted Electrical. And for further Confirmation, though I once purposedly kept it so near the hot Iron I just now mention'd, as to make it sensibly Warm, yet it s.h.i.+n'd more Dimly than it had done by Affriction 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 Colour, 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 s.h.i.+ne 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 disposition White Bodies are wont to have to Reflect much Light.

Fifteenthly, Having well excited the Stone, I nimbly plung'd it under Water[40], that I had provided for that purpose, and perceiv'd it to s.h.i.+ne whilst it was beneath 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 needed to be rubb'd manifestly much longer before the desired Effect was found.

[40] XV. _We likewise Plung'd it as soon as we had excited it, under Liquors of several sorts, as Spirit of Wine, Oyl both Chymical and express'd, an Acid Spirit, and as I remember an Alcalizate Solution, and found not any of those various Liquors to destroy its s.h.i.+ning property._

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.[41]

[41] XVI. _Having found by this Observation, that a warm Liquor would not extinguish Light in the Diamond, I thought fit to try, whether by reason of its warmth it would not excite it, and divers times I found, that if it were kept therein, till the Water had leisure to communicate some of its Heat to it, it would often s.h.i.+ne as soon as it was taken out, and probably we should have seen it s.h.i.+ne more, whilst it was in the Water, if some degree of Opacity which heated Water is wont to acquire, upon the score of the Numerous little Bubbles generated in it, had not kept us from discerning the l.u.s.tre of the Stone._

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 propagated 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 formerly, 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 Diaphanous 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 Gla.s.s, and having rubb'd the Diamond well upon a Cloath, and nimbly clapt the Gla.s.s upon it, to try whether in case the Light could peirce it, it would by appearing Green, or of some other Colour than Blew, a.s.sist me to guess whether it self were sincere or no. But finding the Gla.s.s impervious to so faint a Light, I then thought it fit to try whether that hard Bodies would not by Attrition increase the Diamonds Light so as to become penetrable thereby, and accordingly when I rubb'd the Gla.s.s briskly upon the Stone, I found the Light to be Conspicuous enough, and somewhat Dy'd in its pa.s.sage, 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 Incalescence, 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 s.h.i.+ne at the Sides: And however it did both very manifestly and vigorously s.h.i.+ne, 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 thereabouts. 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 Finger, at the very instant that I drew it briskly off, it would disclose a very Vivid but exceeding short Liv'd Splendour, not to call it a little Coruscation.[42] So that a _Cartesian_ would scarce scruple to think he had found in this Stone no slight Confirmation of his Ingenious Masters _Hypothesis_, touching the Generation of Light in Sublunary Bodies, not sensibly Hot.