OBSERVATIONS MADE BY Mr. Boyle, ABOUT THE AERIAL NOCTILUCA CONTAINED In His Second Vial.
[Note, That this Vial was capable of holding, by our guess, about two Ounces of Water, but there was not in it above one small spoonful of our Liquor.
Observation I.
THE Liquor that afforded the Aerial Noctiluca, (for which Reason, and for Brevity, I often call it [Page 26] the shining Liquor) by Day-light was not near Diaphanous, and appear'd muddy, and of a greyish colour; somewhat like common water, rendered opacous, by having a quantity of wood-ashes well mingled with it.
Observ. II.
WHen no Light appear'd in the Glass, we observ'd all the Cavity of the Vial, that reach'd from the Liquor to the Neck, to be transparent, as if there were nothing in the Glass, save a spoonful of dirty water at the bottom.
Observ. III.
BUT when the Liquor was made to shine vividly, then all the Cavity of the Glass, untaken up by the Liquor, appear'd in an external Light to be full of Fumes. And this seeming smoke, being, in the Vial that contain'd it, remov'd into a dark place, appear'd lucid, and sometimes look'd like [Page 27] a flame that seem'd to be reverberated, and to be made, as it were to Circulate by the close stop'd Neck and the Sides of the Vial. And the appearance of whitish fumes, when the Glass was look'd upon in an external light, was so usual a Concomitant of its fitness to shine in the dark, that by looking upon the Vial by Day-light, I could readily tell, by the presence or absence of the whitish mist abovementioned, whether the Matter would, in a dark place, appear Luminous or not.
Observ. IV.
WHen this Liquor had been kept for a competent time (as an hour or two, and sometimes much less) in some dark and quiet place, or even in my Pocket; if in a darkned Room my eyes were cast toward the place where the Vial was held, I could not perceive it to afford any light at all. And though I shak'd the Liquor strongly enough, to give it at least a moderate agitation, yet I could not discern, [Page 28] that this Motion alone, was able to bring the included Liquor, or the Vapors it may be suppos'd to have sent up, to be manifestly lucid.
Observ. V.
BUT as soon as I unstopt the Vial in the dark, there began to appear, as I expected, a Light or Flame in the Cavity of it. I call it Light or Flame, because I dare not yet speak Dogmatically of it; though it agrees with Flame in divers particulars, and though (also) I am not sure that all Flames must agree in all points with common Flames, Experience having taught me the contrary; and particularly, that some Flames will burn, and be propagated in close-stopt Vessels. I shall therefore on this account, and for brevity's sake, allow the aggregate of our shining Fumes the name of Flame, (which Aristotle himself somewhere stiles Fumus accensus) but without positively asserting that it deserves it, unless further Phoenomena shall be found [Page 29] to intitle it thereunto. But whatever be the nature and subject of this light, the light itself appear'd to have, in great part, a dependance on the fresh Air, as I judg'd probable by the following Phoenomena.
Observ. VI.
FIrst, I never observ'd the light to disclose itself first, either in the liquor, or upon the surface of it; but still the shining began at the upper part, which was first touch'd by the outward Air, and made a progress, quick indeed, but not so instantaneous, as that the eye could not follow it, from the top to the bottom of the Vial.
Observ. VII.
SEcondly, The Contact of the Air seem'd necessary to the propagation as well as production of this flame or light: For if, having shaken the Vial, that the liquor might either wet the stopple, or communicate something [Page 30] to it, I warily bended the Cork this way and that way, so that only a few particles of the outward Air could insinuate themselves between the stopple and the neck of the Glass; there would appear on the sides, and (perhaps) beneath the Cork, little flames as it were; which yet, though very vivid, were not able to propagate themselves downwards: whereas when the Cork was quite remov'd, and access was thereby allow'd to a greater quantity of Air, the flame or light (as was lately noted) presently diffus'd itself through the whole Cavity of the Vial, and reach'd as low as the surface of the liquor.
Observ. VIII.
THirdly, Though oftentimes the light seem'd more vivid near the surface of the liquor, then elsewhere; (whether because the lucid matter was there more dense, I now examine not) yet when by stopping the Vial again, presently after I had opened it, I endeavoured [Page 31] to destroy the flame or light; I generally observ'd, that when it was ready to vanish, (which in that case it usually did in no long time) it began to disappear first in the bottom of the Vial, and seem'd to shrink as it were more and more upwards, till it expired at the neck of the Vial, (where it was nearest to the Air.)
Observ. IX.
FOurthly, But on the other side, when I kept it unstopt for some time, as for two or three minutes of an hour, though I afterwards stopt the Vial very close, the Air, that had more leisure than ordinary to insinuate itself, would so cherish the flame, that the light would continue sometimes an hour or two, and lasted once or twice no less than three hours.
Observ. X.
FIfthly and lastly, It seem'd that some Elastical Particles of the included Air, or some Substance that concur'd to the maintenance of the Flame, was wasted, or depraved and weakned, by being pen't up in the Vial with the Emanations of the Liquor; since, when the Vial had been kept stopt a competent time, and its Cavity appear'd transparent in the outward light; if I cautiously took out the stopple, the external Air seem'd manifestly to rush in, as if the springyness of the internal had been notably debilitated by the operation of the Flame, upon the Matter with which it was kept imprisoned.
Some of these Phoenomena easily brought into my mind some of those of an odd Experiment, that I formerly imparted to the Curious. In which Experiment I observ'd (among other things) that the Spirit of Ʋrine, impregnated with Copper, after the manner [Page 33] there prescrib'd, would continue limpid and colourless, as long as the Vial, that contained it, was kept close stopt. But when once the Air came to touch the surface of it, it would (sometimes in less than a minute of an hour) be so affected thereby, that in a very short time (for 'twas often within some minutes) the Liquor would become of a transparent Sky-colour; and afterwards, the Vial being well stopt, and kept in a quiet place, would by degrees grow diaphanous, and the Air included with it was wont to have its spring weakned. And as the change of colour was first produced at the surface, where the Liquor and Air touched one another, and was afterwards thence propagated downwards; so when this Coeruleous Colour began to disappear, the Liquor manifestly became limpid first at and near the bottom, that is, the part which is remotest from the superior Air.
But to return to our Noctiluca, the Five Phoenomena last recited, and some [Page 34] others, seem to favor the conjecture or suspicion I lately propos'd, about the interest of the Air in our unburning flame. And to examine that suspicion, I thought it less proper to make the foregoing Tryals with a more vigorous Noctiluca, then in a substance, wherein, as in that we have hitherto employ'd, the disposition to be kindled, or excited to shine, was but faint; so that being, as long as it remain'd, unexcited, opacous and dark, the absolute, or almost absolute, necessity of the concurrence of Air to the actual shining (that constantly ensu'd upon its Contact) of the dispos'd matter, seem'd manifest enough.
An Occasional DIGRESSION.
BUT to what, this concurrence or efficacy of the Air ought to be ascrib'd, is a Problem that seem'd to me so difficult, that my thoughts were put upon several conjectures for so much as a tolerable solution of it; for a taste of which, I shall venture to offer to you one or two of those that least displease me.
I thought it not improbable that the admitted Air, either by some subtle Salt that it contain'd, or upon some such account, excited in the fumes, it mingled with, a kind of Fermentation, or (if you please) a Commotion, by which means the matter acquired so brisk an agitation, as to propagate the [Page 36] motion to the eye, and there make an impression, the sense whereof we call Light: though it seem'd also not unlikely, that some of the particles of the superveneing Air may so associate themselves with those congruous ones, they met with in the cavity of the Vial, that, by that Coalition, Corpuscles were produc'd, fitted to be, by the subtle Aetherial matter, that abounds in the pores of the Air, so pervaded and briskly agitated, as to produce light. And it was not new to me, that the Air should associate itself with invisible Exhalations, and concur with them to make new Concretions: since I have several times prepar'd a volatile sulphureous liquor, red as a Ruby, which, when the Vial has been kept close for some time, suffers the empty cavity of the vessel to be transparent; but upon the unstopping it, and giving access to the outward Air, it appears presently full of white fumes, more opacous than a mist▪ And something like this, though in an inferior degree, may be observ'd when we unstop Glasses that are but [Page 37] partly full of Spirit of Salt, or Aqua Fortis, provided those liquors be rectified as much, and no more, then is fit. For the contact of the Air will presently make the former manifestly afford white fumes, and the latter sometimes red ones, and sometimes otherways coloured. But if I durst mention, what my love to Mankind has oblig'd me to conceal, even from my nearest Friends, I could give an instance of a strange power of the Air to excite a vehement Motion in fitly dispos'd Matter, though it be of a consistence far more unlikely to be thus agitated, than the fluid substances of our Phosphorus: since I experimentally know a Body, dry, and solid enough to be pulverable, that barely by the contact of the common Air, will, even when it is actually cold, in very few minutes have its parts brought to such a degree of agitation, that its heat is little less intense than that of some actually ignited Bodies, and may, if I please, by the further action of the Air, be brought to afford some light also.
[Page 38]But against this conjecture about the cause of the Air's concurrence to the shining of our Noctiluca, there came into my mind, among other things, a strong Objection, that may be drawn from the Constant Noctiluca formerly mention'd to have been shewn by Mr. Krafft, in which the lucidness was constant, though the Vial that contain'd it, was kept stopt. In answer to this, I thought it might be said, that the Particles of the lucid substance, being in great numbers crowded together into a little room, these concentrated Particles may be supposd to have been brought to such a state, that they needed not the renewed assistance of the outward Air, to continue shining; either because their intestine motions were brisk enough to discuss the minute parts of the matter, wherewith they were associated, and so from time to time to generate or extricate, & supply themselves with as many small Aerial Particles, as were necessary to keep the mass they belong'd to, luminous. Which conjecture may be illustrated by observing, [Page 39] that though our common culinary flames are presently extinguish'd, unless they be cherish'd with fresh Air, yet I elsewhere recite an Experiment, of a Composition, which is so fitted to generate as much Air, as it needs, that I have several times found, that it may be kindled, and made to flame away, even in vacuo Boyleano, (as they call that made by our Air-pump.)
Other things may be alledg'd both for and against the propos'd conjecture, about the account on which the Air concurs to the light of our liquid Noctiluca; but, I hope, it will not be impertinent to add, that perhaps the concurrence of the Air may be considerable to both the Phosphorus's, the fluid and the consistent, but the external Air be necessary only to the former: because in the latter, the luciferous Particles may have acquired such a texture, as that of rotten wood, or rather of whitings, or the liquor of glow-worms, taken out after they are dead. For in [Page 40] that state (whatever others have written) I have kept that Juice luminous for very many hours, (not to say some dayes;) and 'tis conceivable enough, that in the Consistent Noctiluca, by reason of the great numerousness and extreme minuteness of the parts, and the unctuousness or viscosity, or in a word, tenacity of them, the mass they make up, is much less dissipable than that, wherein the shining vertue of rotten wood, or the juice of dead glow-worms resides. This conjecture may be confirm'd, by observing as a thing very analogous to our Phoenomena, that I have found some lights in putrid Bodies to be so faint, that they would, like that of our fluid Noctiluca, (but far more quickly) disappear, when they were totally depriv'd of Air, as I several times found in parcels of rotten wood. And on the contrary, others had so vigorous or tenacious a light or flame, that, like the splendor of the constant Noctiluca, it would continue (though perhaps not in its full lustre) when the outward Air was in our [Page 41] Pneumatick Engine, diligently drawn off from it. And on this occasion I call to mind another Experiment, which seems yet more analogous, than any hitherto alledg'd, to our present production of flame or light. For having purposely kept certain Fish in a Glass, freed from Air, till I concluded it had lay'n longer than was necessary to bring it to that degree of Putrefaction, which was wont to make such Fish, at that time of the year, to shine, I could not perceive in the Cavity of the Glass the least glimpse of light: and presently after I had let in the outward Air, it did (according to my expectation) as it were, kindle a flame, in the proximately dispos'd matter, or at least produce in it a manifest light. And it may much conduce to shew, that the lately mentioned difference of shining Bodies may be but gradual, if I here observe, that I found by tryal, that in Bodies of the self same kind, as for instance Glow worms, or the same species of Rotten-fishes; if the light were but faint, the withdrawing of the Air [Page 42] would after a while make it quite disappear; and the readmission of the Air would presently make it reappear, as it happens in our Aerial Noctiluca. But in those individuals, wherein the luciferous matter was more copious and vigorous, and probably more tenacious, the absence of the external Air did somewhat lessen or impair, but not quite destroy the light, and so possibly it might happen in Mr. Krafft's Consistent Noctiluca: For though it shone without the renew'd accession of external Air, yet, that it would have been more brisk and active, if it had been assisted by such Air, I was induc'd to think, because (if I much misremember not) when once, to gratifie my curiosity, he took it out of the Vial, he usually kept it in, it did manifestly smoke and waste by the action of the Air, and produc'd considerable effects of actual heat; for this being done in the day-time, in a Room we could not darken, it could not indeed be expected, that we should discern any augmentation of light, but yet that there was [Page 43] one, may probably be argued from the newly mentioned things, that us'd to be its concomitants.
Such Observations and Reflections incline me to think, that, to speak in a general way, the light of our Noctiluca's depends upon a peculiar and very brisk agitation of some minute Particles of the shining matter, in point of Bulk, Shape, and Contexture, peculiarly fitted to impel the contiguous Aether to the bottom of our eyes, and made me think it not improbable, that the contact of fresh external Air, might contribute to this peculiar kind of agitation in the Gummous Noctiluca, as an helpful thing, and in the Aerial Noctiluca as an almost necessary concurrent. But whether the Air concur to this effect, as it does itself excite a brisk commotion in the fumid matter, it invades, or whether it makes a peculiar kind of dissipation of it, or whether the Air, or some fine substance contain'd in it, operates on this occasion as a kind of vital spirit, such as is [Page 44] found necessary, not only to common flame, but to that which is suppos'd to keep Animals alive; or whether the Corpuscles of the admitted Air so combine with those, that exhale from the grosser liquor, as to become fit to be vehemently agitated by some aetherial pervading substance? whether or no, I say, the agency of the Air in our Phoenomena, be to be refer'd to one or more of the newly mentioned things, or to some other cause of a peculiar and very brisk agitation, which, to speak in general, seems to have the main stroak in the production of light, is left to further inquiry.
But I forget, that my intention was to set down Observations, not Hypothesis's. And indeed the Historical Part, of what I had to say of Phosphorus's, is far more useful and certain, than the Conjectures I can yet make upon it. Because, though I am content to let them pass, in regard they may afford you some hints of further speculations; yet the true solution of the Problem, [Page 45] that has occasioned this Excursion, may depend so much upon further Experiments and Observations, that though, it is not impossible, that future Phoenomena may favor the propos'd conjectures, yet, it is not very unlikely, that I shall hereafter see cause to change them for some Hypothesis's, exceedingly different from them. To return therefore now to our Historical Observations.
Observ. XI.
ALthough, in the moderately shaken Vial, when the light was quite vanisht, I could not make the liquor begin to shine, yet when by unstopping it a little, the flame was kindled in the Cavity of the Glass, then, by shaking it again, though it were done more faintly than before, the light seem'd to be manifestly increas'd by this agitation.
Observ. XII.
IF I took a little of our Liquor, when 'twas in its dark state, and laid it upon my hand, or on the stopple of the Vial, it would oftentimes lie there without disclosing any glimpse of light; but if I rub'd it with my finger, or some other fit Body, it would then not only shine, but shine more vividly, than at best it us'd to do in the Vial, when the Neck of it was stopt; and this vivid light, whil'st I continued to rub the matter, it resided in, seem'd from time to time to flame and flash, and did not only invade the Nostrils with a strong and offensive smell, but visibly sent up store of smoke, as if it had been some common culinary flame; and when, upon my ceasing to rub the extravasated Liquor, it ceas'd to shine for a pretty while, yet when I return'd to rub it again, it would again appear luminous: But by little & little the lucid vertue decay'd, till 'twas to no purpose to rub any more.
Observ. XIII.
THE light of our Liquor, when excited, seem'd for degree much like that, that I observ'd in some species of rotten wood, that were not of the most vivid sort, and when surrounded with Bodies of black colour, the reflection of its light from them was little or none. But very white Bodies, that were held contiguous to it, were manifestly illustrated by it, especially, if the eye, having been long kept in the dark (whereby the Pupil uses to be much opened, and consequently capable of admitting more numerous beams) was made more susceptible of the fainter impressions of light.) Insomuch, that, when having plac'd the Vial by me, when I went to Bed, and was awake some time before Break of Day, I enclos'd both the Glass and my Head between the Sheets, the light seem'd to me to be very considerable, and to enlighten the compass of a foot or more in Diameter, and probably [Page 48] would have diffus'd itself further, if it had not been bounded by the sheets, whose whiteness made the reflection of the light from them appear very prettily. And by the help of this light, I could easily perceive my Fingers, and a Ring I wore upon one of them, though I could not distinguish the colours of a reddish Diamond, and a couple of Emeralds, that were set in it.
Observ. XIV.
IN reference to the light within, the included flame in our Vial was opacous; for both at some other times, and even when I made the last recited Observation, I could not at all perceive my finger, when the shining substance was interpos'd betwixt it and my eye. But in reference to the external light, the flame or shining matter was Diaphanous, for even in a very faint light, by which, I think, I could scarce have read an ordinary Print, if I held our luminous Vial between the window [Page 49] and my eye, I could very plainly see my finger on the further side of the Glass, though, if my eye were plac'd between that and the light, the transparency would appear somewhat lessened, because the Cavity seem'd, as was formerly noted, fill'd with a kind of whitish mist. And the like transparency and whitish fumes, observable in the same luminous steams or flame, when the Vial was look'd on, against, and from, the light, I found, if instead of the day-light, I employ'd the light of the Candle.
Observ. XV.
HAving the opportunity of a convenient place, and a fair Day, I set the Vial about Noon in a window, opened towards the South, and left it there expos'd to the Sun-beams for a considerable time, to try, whether they would, upon the account of their agitation, or some imaginable affinity of nature, kindle or excite the luciferous liquor, or its effluvia. But I [Page 50] could not perceive that the Sun-beams had such an operation, which I chiefly concluded from my not being able to perceive any whitish or mist-like fumes in the Cavity of the Glass, for I durst not rely upon my not perceiving any light, in the darkest corner of the Room, because I suspected, that might proceed from my eyes having been accustomed to the great light of the then fair day, which made it less susceptible of impressions from a faint light.
Observ. XVI.
ACid and Alcalisate Spirits being reckoned by Chymists amongst the most subtle and operative substances, obtainable from mixt Bodies by distillation, I thought it very well worth while to try, by taste, whether our shining Liquor did notably abound with Particles of either of those kinds? I did not find, that the Liquor I put upon my Tongue was in the least Acid; nor that it was sensibly [Page 51] Alcalisate, as divers Modern Chymists call such volatile Salts and Spirits, as are afforded by Harts-horn, Blood, and such like Subjects of the Animal Kingdom: But it seem'd to me to have an odd Empyreumatical taste, almost like that of the Spirit of Crude Tartar; its smell being also like that, of some Empyreumatical Oil, compounded with a stink, somewhat like that of stale Urine. I likewise, for further tryal, let fall upon a piece of white Paper some drops of blue Syrup of Violets, to which I put a little of our Liquor, stirring them together with the tip of my finger; but the mixture was not thereby turn'd green, which it would have been by a quarter so much of Spirit of Harts-horn, of Blood, or of some other Spirit, abounding with salt of an urinous nature, or (as some love to speak) with a volatile Alcaly. Some other Tryals I made, though but with very small quantities of our Liquor, (because I had but very little of it to spare) and these Tryals did, no more than the former, evince the Liquor to [Page 52] belong manifestly, to the Tribe of Acids, or that of Alcalies; though perhaps, this may not be the case of All the portions of Liquor, whether more dense, or more aqueous and dilute, that may be obtain'd by several degrees of fire, and some other varying circumstances, from the matter, that affords Noctiluca's.
Observ. XVII.
Sometimes, when for curiosity's sake, I shook the Vial, so that the whole Body, even to the bottom, of the Liquor, was spread all over the inside of the Glass, I could observe, with pleasure, that in many places divers little grains or corpuscles, belonging to the opacous matter, that concur'd to compose the Liquor, stuck here and there to the inside of the Vial, and that these, being of a consistent, not fluid nature, and therefore probably more dense than the thinner parts of the Phosphorus, did shine very prettily and distinctly, and look'd almost like extreamly [Page 53] little stars, or rather radiant sparks of fire, whose light was brisk enough to be distinctly notable, notwithstanding that of the flame, that was contiguoas to them, and fill'd the Cavity of the Vial. And these shining Corpuscles usually continued their peculiar vividness, as long as I thought fit to look on them. Which great vigor of theirs, together with their duration, gave me hopes, that the further prosecution of what had been brought thus far, may afford us some, not altogether despicable, quantity of the Consistent Noctituca, which, by reason of its density, tenacity, or other peculiar disposition of parts, may shine like the Constant Noctiluca of Mr. Krafft formerly mentioned.
Observ. XVIII.
BEing desirous to try, not so much what the Air and Agitation would do, towards the kindling or exciting (not the imprisoned Exhalation, but) the Liquor itself of our Noctiluca, [Page 54] (that having been partly done already Note: See above, Observ. 12.) as what Water would do to quench it; I thought fit to make the Experiment, when Time and many Trials had much impair'd its vigor. And accordingly having, in a dark place, unstopt the Vial, and wetted the tip of my finger with the included Liquor, I could not perceive that then (as when it was freshly made) it gave any sensible light. Wherefore, having rub'd the moistned finger against my other hand somewhat briskly, for a few moments, both the rub'd part of my hand and my finger appear'd adorn'd, each of them, with a flame, and though upon my dipping my finger in water (that stood by, ready for the purpose) the flame was, as it were, extinguisht, since the light presently vanish'd; yet, having taken out my wet finger again, and rub'd, without having previously dry'd it upon the other hand, as I had done before, the light, as I expected it would, did quickly re-appear.
[Page 55]Besides the foregoing Phoenomena of our luciferous Matter, that occur'd more regularly, there was one that hapned unexpected, and may perchance, (for till I have further observ'd, I dare not speak it confidently) prove referrable to the Paper, elsewhere publish'd, About some latent qualities of the Air.
Observ. XIX.
THE Phoenomenon was this: having one night opened the Vial so often mentioned, to shew the Production of light to a Virtuoso, I quickly stopt it again, and put it in my Pocket, till I went to sleep, and then laying it by me in the Bed (as I often did) when the Candles were carried out of the Room, I perceived the light, whose lasting, I did not expect, should exceed one hour, to continue still vivid enough; and then shaking it a little, before I compos'd my self to sleep, I laid it by, till I wak'd in the morning, and then looking upon it again, it appear'd [Page 56] to my eyes (that then for several hours had been unaccustomed to the light) to shine more vigorously, than it had done at first. And from the time I open'd it over night, till the last time I had occasion to look upon it the next morning, it had continued shining for twelve hours; to which, whether the extraordinary warmth, that was observ'd that particular night had contributed any thing, I dare not determine, but shall rather add, that though this Phoenomenon happen'd very rarely, yet this was not the onely time that I observ'd it: For once more it occur'd to me, and that time the light continued about 15 hours, that I took notice of, and how much longer it might have lasted, I was hindered from observing. But this Circumstance seem'd considerable, that the long duration of our unburning flame, hapned, after the rest of the Tryals and Observations had been made; when by them, the vigor of the luciferous matter might reasonably be expected to have been very much impair'd.
Observ. XX.
WHen I had set down the last mentioned Phoenomenon, I thought I had concluded the Observations, peculiarly belonging to the Aerial Noctiluca, contain'd in our second Vial, and hitherto treated of. But now I find my self, by Philosophical Sincerity, obliged to add another Phoenomenon, which did somewhat trouble, as well as surprize me, and it was this. After the foregoing Observations had been made with our second Vial, one night that I came to open it, to shew one of my best Friends the production of light, I found (little to my contept) that none at all appear'd, though I shook the contained liquor, and kept the Vial a pretty while unstopt; so that, if he had not known me well, he might have entertain'd sinister thoughts of me, till, having taken out some drops of the liquor, and rub'd it upon my hand, it afforded so vivid a light or flame, as satisfied him of the possibility [Page 58] of a true Noctiluca. And since that time, I have not found the Vial to afford any light, barely upon its being unstopt, so that either (in spight of my care) some Bodies unskilful curiosity has, unknown to me, spoil'd the liquor; or, (which is more likely) so little a quantity, as I had at first, by the many and various Tryals I made with it, is dispirited and become, as it were, effoet; which, 'twas lucky it did not do, till the forecited Observations had been made with it. But, as in one of those, it has been conjectured, that one of the chief accounts, on which the Air itself may concur to the shining of our Noctiluca, is, as it excited a certain kind of brisk motion in the parts of it, I thought fit to try, whether, though I had found the bare shaking of the Vial to be ineffectual, yet an actual heat, whereby the parts must be more vehemently and variously agitated, might not inable the Air to do, what otherways it could not perform; I therefore held our Vial near the fire, till it grew considerably warm, and then by [Page 59] shaking it a little, and unstopping it in a dark place, I perceived the exhalations, that possess'd the Cavity of the Vial, to shine, as formerly; but their light was so momentany, that it scarce sooner appear'd, than vanish'd; and though afterwards it sometimes appear'd, it was not vivid, nor lasted a minute of an hour, nor perhaps half so long; though it seem'd, that when fresh Air was then allow'd access to it, its duration was thereby somewhat lengthned. But how long our matter will retain a disposition to be excited, even by these means, to shine, experience alone can determine.