New experiments and observations touching cold, or, An experimental history of cold begun to which are added an examen of antiperistasis and an examen of Mr. Hobs's doctrine about cold / by the Honorable Robert Boyle ... ; whereunto is annexed An account of freezing, brought in to the Royal Society by the learned Dr. C. Merret ...

New THERMOMETRICAL EXPERIMENTS And THOUGHTS.

The I. Discourse, Proposing the I. Paradox, Viz. That not only our Senses, but common Weather-glasses, may mis-inform us about Cold.

IT may to most men ap∣pear a work of needless Curiosity, or superflu∣ous diligence, to examine sollicitously, by what Criterion or way of estimate the Coldness of Bodies, and the degrees of it are to be judg'd, Since Coldness

being a Tactile Quality, it seems im∣pertinent to 〈◊◊〉〈◊◊〉 any other judges of It then the Organs of that sense, whose proper object it is. And ac∣cordingly, those great Philosophers, Democritus, Epicurus, Aristotle, (and till of late) all others both Ancient and Modern seem to have contented themselves in the matter with the Re∣ports of their Sensories.

But this notwithstanding, since we can scarce imploy too much care and diligence in the Examining of those 〈◊〉〈◊〉, which we are to Exa∣mine many other things by, perhaps it will be neither unseasonable nor useless to 〈◊〉〈◊〉 something touching this Subject.

For though it be true, that Cold in its primary and most Obvious Noti∣on be a thing relative to our Organs of Feeling, yet since it has also no∣table Operations on divers other Bo∣dies besides ours; And since some of them seem more sensible of its chan∣ges, and others are less uncertainly affected by them, it would be Expe∣dient to take in the Effects of Cold upon other Bodies, in the Estimates

we make of the degrees of it.

And to make this appear the more reasonable, I shall not scruple to pro∣pose the following Paradox, namely, That our Sensories either alone, or as∣sisted by Common Weather-glasses are not too confidently to be relied on in the judging of the degrees of Cold.

To make this Paradox Plausible (which is almost as much as I here pretend to) I shall represent in the first place, that the account, upon which we are wont to Judge a Body to be Cold, seems to be, that we feel its particles less vehemently agi∣tated then those of our Fingers or other parts of the Organ of Touching. And consequently, if the temper of that Organ be chang'd, the Object will appear more or less Cold to us, though it self continue of one and the same Temper.

This may be exemplified by what has been observ'd by those that fre∣quent Baths, where the milder de∣grees of heat, that are us'd to prepare those that come in for the higher, seem very great to them that coming

out of the cold Air dispose them∣selves to go into the Hot Baths, but are thought cold and chilling to the same persons when they return thi∣ther out of much warmer places; which need not be wondred at, since those, that come out of the cold Air, find that of the moderately warm Room more agitated, then the cold Ambient would suffer the Exter∣nal Parts of their Bodies to be, where∣as the same warm Air, having yet a less agitation then that in which the hotter parts of the Bath had put the sensitive parts of the Bathers Bodies, must seem cold and chilling to Them.

But 'tis not only in such cases as this, wherein Men can scarce avoid taking notice of a manifest change in them∣selves, that these mistaken Reports of our senses may have place. For oft-times we are impos'd upon by more secret changes in the disposition of our Sensories, when there needs something of attention and of Rea∣soning, if not of Philosophy to make us aware of them. For being apt to take it for granted that our Temper is the same, when there is no very ma∣nifest

cause why it should be chang'd, we often impute that to 〈◊〉〈◊〉, whereof the Cause is in our selves; and if this change in our selves be wrought by unsuspected Agents, or by insensible degrees, we do not easily take notice of it. Thus though in Summer divers Cellars, that are not deep, are perhaps no colder then the External Air was, (when it was judg'd but Temperate,) in Winter or the Spring; yet it will seem very Cold to us that bring into it Bodies heated by the Summer Sun, and ac∣customed to a warmer Air; nay cold does so much depend upon the degree of Agitation in the parts of the Object in reference to the Sentient, that even when we may think the Sen∣sory unalter'd, it may judge an Object to have a degree of Coldness which indeed it hath not; as I remember, that to satisfie some Friends, that 'tis not every Wind which feels cold to us, that is really more Cold, then the still Air, I have sometimes shewen, that even in nice Weather∣glasses Air blown out of a pair of Bellows does not appear to have ac∣quired

any Coldness by being turn'd into Wind, though if it were blown against the hands or face, it would produce a new and manifest sense of Cold; of which the reason seems to be, That though the Organ in general seems not to be alter'd, yet the Wind by reason of its Motion, is able not only to drive away the parts of the Air contiguous to the hand, or face, and the warm steams of the Body which temper'd its Coldness; but to pierce deeper then the calm Air is wont to do into the pores of the skin, where by comparison to the more in∣ward and hotter parts of the Sensory it must needs appear less agitated and consequently colder.

Besides, that sometimes we may meet with certain Steams in the Air that have in reference to the Blood and Spirits of humane Bodies (though not perhaps to divers other Liquors) a certain hidden power of chilling, as Opium, ev'n in outward applicati∣ons (for in such ways I have known a great Chirurgion much use it and highly extol it) strikes a Coldness in∣to the Body by the subtile Effluvium's

that insinuate themselves at the pores of the Skin; and perhaps too, that Coldness is ascrib'd to External Bo∣dies, which is produc'd in us by some Frigorifick Vapour, or other di∣stemper; which being too slight to be taken notice of as a disease, may yet be of Kin to those Agents, that produce what Physicians call horrors and Rigors at the beginning of Fea∣vers, and some other distempers; or produce that strange and universal Coldness of the external parts, which is frequently enough observ'd among other Symptomes in Hysterical Wo∣men. Moreover, Bodies may often appear colder to us then to a Wea∣ther-glass, because our Sensories are more affected by the density and Pe∣netrancy of the parts. This may seem somewhat strange, but being sutable enough to some of my Con∣jectures about Cold, I have often made Tryals with very nice Wea∣ther-glasses, that have assur'd me, that (at least oft-times) when wa∣ter seems to be cold enough to our touch, it appears not to be colder to the Weather-glass then the Ambient Air.

These Trials I have sometimes made with seal'd Weather-glasses, but the most with another sort of Weather-glasses (whose structure and use are by and by to be mention∣ed) which though they seldom prove durable, nor of any great use in any other then such nice and short Expe∣riments, yet they discover slighter changes of the Temper of the Air then would be notable (not to say sen∣sible) in ordinary Thermometers. But of multitudes of Trials that I sometimes made with these Glasses, I can at present find among my loose Papers but a very few; and though I remember, that in one or two (made about the same time with some of those that follow) I observ'd Things that make me now wish I had had Opportunity to make those further Trials of Them, which some of their Phaenomena seem to direct the making of: yet I shall annex these that follow as I find them entred, because they are not perhaps desti∣tute of hints improvable by further prosecution. June 26. between two and four in the afternoon (the Wea∣ther

moderate for the season) I took a thin white glass-Egge blown at a Lamp about the bigness of a Walnut, with a stem coming out of it about the bigness of a large Pigeons Quill four or five Inches long, and open at the Top; this slender pipe being dipp'd in water, admitted into its Cavity a little Cylinder of Water, of half an Inch long or somewhat more, which (the Glass being erected) subsided by its own weight, or the Temper of the Air in the Egge (in reference to the outward Air) till it fell to the lower part of the Pipe, where it comes out of the Egge, and therea∣bout it would rest. Now if taking this Glass by the Top betwixt my Thumb and forefinger, I deprest the Egge under the surface of a Bason of fair water (cold enough to the touch) the little Aqueous Cylinder, that parted betwixt the Air in the Egge, and the external, would, in∣stead of being made to subside by the Eggs immersion into the Cold wa∣ter, presently rise up from the lower part of the Pipe, till it reach'd about the middle of it, though the Glass

were, in this and the following Tri∣als, held erected; and as soon as it was taken out of the Water into the Air, the water would again subside, whether I held the Glass, or let it rest upon the Boards, or a Linen Carpet, that cover'd the Table, on which the Trials were made. And this I did several times as well with as without witness. I tried also that if, instead of water, I made use of Quicksilver, though not big enough to cover the Egge much above half way, and in the rest proceeded as above; the cold Quicksilver would presently make the Aqueous Cylin∣der hastily ascend near three Inches, sometimes almost, and sometimes quite to the Top of the slender pipe, whence the water would again quickly subside, when the Glass was taken out into the free Air, or set to rest upright as before.

Besides, having set the vessel of Quicksilver and the Bason of water very near one another, I did at least upon three or four several Trials find, as I expected, that when by immersing the Egge in water, the

pendulous Cylinder was rais'd so high, that it did no longer sensibly ascend, by nimbly taking the Egge out of the water and depressing it in the Quicksilver, it would rise far higher: and I also tri'd, that nimbly removing the Egge out of the Quick∣silver into the water, the pendulous Cylinder would subside, after plung∣ing the Egge under water, though not so fast, nor near so low as it would do, in case the Glass were re∣mov'd from the Quicksilver into the Air. Upon another Trial made much about this time, though not the self same day; the pendulous water in the same Glass, (the day being for the most part windy and rainy) did subside upon the immersi∣on of the Glass into water, not only a while before noon, but an hour or two after dinner, and at distant hours afterwards, though the De∣scent of the Pendulous water was nei∣ther so quick, nor so considerable as it had been formerly in the Morn∣ings.

June 27. In the morning a small Cylinder of Water pendulous in the

above mentioned Glass, upon the im∣mersion of the Egge in a Bason of wa∣ter, would immediately and very considerably subside, whereas the same glass, being immersed in the Vessel of Quicksilver formerly men∣tioned, 〈◊〉〈◊〉 presently ascend. Both parts of this Experiment we several times tried, and the Reason was sus∣pected to be, that the Quicksilver had stay'd all night in my Chamber, which was somewhat warm, where∣as the water was brought up that morning, and to the touch seem'd colder then the Quicksilver, and a while after dinner, the same water having been still kept in the room, we divers times found, that as well That, as the Quicksilver, did immediately upon immersion impel up the pendu∣lous water in the slender pipe. Ano∣ther time in frosty weather (and about the beginning of January) we did with such a glass (as has been al∣ready several times mention'd) take somedrops of water out of a vessel, wherein that Liquor had for a good while been kept; that it might be re∣duc'd as near as we could to the Tem∣perature

of the Ambient Air; then 〈◊〉〈◊〉 the suspended water to con∣tinue a convenient while in the long and slender stem of the Weather∣glass, that the internal Air might be reduc'd to the temper of the exter∣nal, we took up the Glass by the open end; and immersing the obtuse part of It into a shallow Vessel con∣taining some of the above mentioned Water, we found the suspended drop suddenly impell'd upwards about half an Inch or more, and the Ball of the Thermometer being taken out of the Water into the Air, the pendulous drop did again (though far more slowly then it ascended) subside. This was repeated three or four times with some intervals be∣tween (and that in a Room where there was no Chimney) and still with the like success, save that in the two last Trials we took the Weather∣glass out of the shallow water, and plunging it into a deep vessel of the same water (that stood very near the other) we found (for further con∣firmation of the Experiment) that the pendulous water was upon these

new immersions, impell'd up, near (if not full) as high again, as when we had immers'd it only in the shal∣low vessel: and taking it out of this deep Glass, we found the Cold of the external Air to reduce It to its former humble station. Thus far the notes, I have yet been able to reco∣ver: and though, as I said, I dare not build very much upon them, yet by small seal'd Weather-glasses I find enough to invite me to suspect, that of the degrees of heat and cold in the Air we may receive differing infor∣mations, when we imploy only our Organs of Touching, and when we make use of fit Instruments.

I shall add on this occasion, that not only water it self, but moist va∣pours abounding in the Air, may make Us think it colder then the Weather-glass discovers it to be. For though it be generally taken for granted, that the Thermometer does only more exactly measure or deter∣mine the Effects, which cold hath both upon it and upon our Sensories, yet I have long suspected that there is somewhat else in the case. And I

have observ'd, that sometimes the weather seem'd more or less cold to me, then that which preceded, when the contrary appear'd in the Wea∣ther-glass; and that, when upon consideration of the whole matter, that difference did not appear to de∣pend upon those circumstances of Exercise or Rest, or the Tempera∣ture of the Air I came out of, or any of those other things, to which a considerate man, that goes upon no better then the common opinions about Weather-glasses, would be apt to impute to that Phaenomenon. And I was the less dispos'd to think my self mistaken, because having purposely enquir'd of others in the same house, who were not told, what Information the Weather-glass gave, they agreed with me in the sense I had of the Temperature of the Weather. And having since, as occasion serv'd, communicated my Observations and suspitions to divers Ingenious Men, I have been by their recenter Observations confirm'd, that what I have taken notice of, was not the Effect of any 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉.

From which, and other particulars, that we may have elsewhere oppor∣tunity to mention, we may plausibly enough infer, that it were not amiss, not only to take notice, when we have opportunity, of the sense, that is Express'd of the degrees of Cold by Birds and other animals, whose diet is more simple and regular then ours, and whose perceptions are commonly more delicate and less di∣verted; but, especially, to examine the coldness of the Air and other Bo∣dies as well by Experiments and in∣struments, as by the touch. And on this Occasion I must not pretermit that memorable Account, that is gi∣ven us by Martinius in that Noble piece of Geography which he calls Atlas Chinensis, where speaking of the Air of that populous Countrey he has this singular passage: Ad Caeli (says he) solique temperiem quod atti∣net,* 1.1 majus in hac provinciâ frigus est, quàm illius poscat poli altitudo: vix enim illa excedit gradum secundum supra qua∣dragesimum; & tamen per integros quatuor saepe menses flumina omnia adeò durè concrescunt gelu, ut currus equosque

〈◊〉〈◊〉 gravissima etiam onera glacies ferat, innoxiè acsecurissimè transeant: ex iis ingentia etiam glaciei frusta exscindūtur, quae in futuram aestatem ad delicias ser∣vant. His 〈◊〉〈◊〉 omnes naves ita in ipsâ glacie defixae sunt, ut progredi ne∣queant ubicunque illas frigus occupat (quod certo certius circa medium No∣vembris ingruere solet) per quatuor illos menses immotae ibi perstare coguntur, neque enim resolvitur glacies ante Martii initium; haec plerumque glaciei concretio uno fit die, cum non nisi pluribus fiat li∣quefactio; to which he adds what makes most to our present purpose, 〈◊〉〈◊〉 illud mirum, tantum non videri aut sentiri illud frigus ut Europeos ad hy∣pocausta subeunda videatur posse cogere, aut in Europâ ad glaciem producendam 〈◊〉〈◊〉 unde ad subterraneas illic exha∣lationes pro harum rerum causis indagan∣dis 〈◊〉〈◊〉 recurrendum est, &c.

But all that I have been implying of the Necessity and Usefulness of the Weather-glass, is no way inconsistent with the truth of the latter part of our formerly propos'd paradox, name∣ly that we are not rashly to rely up∣on the Informations even of common

Weather-glasses themselves. For though they be an excellent Invention, and their Informations in many Cases preferable to those of our senses, be∣cause those Dead Engins are not in such cases obnoxious to the same Causes of uncertainty with our Li∣ving Bodies, yet I fear they have too much ascribed to them, when they are look'd upon as such exact Instru∣ments to measure heat and cold by, that we neither can have nor need de∣sire any better. For, not yet to men∣tion some inconveniences in the con∣trivance of them, which makes them unapplicable to some purposes, and less proper in others, then Thermo∣scopes might be made, even in divers cases, wherein they are presum'd to be unexceptionable, their Reports are not to me, I confess, quite exempt from suspicion. For in ordinary Weather-glasses some part of the Li∣quor being contiguous to the Exter∣nal Air, it is subject to be impell'd more or less upwards, not only ac∣cording as heat or cold affects the in∣cluded Air, but according as the in∣cumbent Air happens to be heavier or

lighter. And though this be a thing not taken Notice of by those that have treated of Weather-glasses, yet 〈◊〉〈◊〉 what we have elsewhere mani∣fested concerning the weight and spring of the Air, aud what we have probably 〈◊〉〈◊〉 concerning the varying height of the Mercurial Cy∣linder in the Torrecellian Experi∣ment; I see not why It should* 1.2 not much call in Question the Infor∣mations we receive from common Weather-glasses in those cases, where the height or weight of the Atmosphaerical pillar, that presses upon the Water in the Weather∣glass, is considerably longer or shor∣ter, lighter or heavier then is usual.

For besides the reason of the thing, we have Experience on our side. I might mention on this Occasion an Experiment I thought on, and also attempted last winter to show ev'n upon a Ballance the varying gravity of the Atmosphaere in one and the same place, by hanging a small Me∣talline weight at one End of a pair of Scales so strangely exact, that they would turn with far less then the 500.

part of a grain; and counterpoising it at the other end with a Hermeti∣cally seal'd Glass Bubble, which be∣ing blown as large and as thin as could possibly be procur'd of so small a weight, might by its great dispro∣portion in Bulk to the Metalline Bo∣dy lose more of its weight then That would upon the Ambient Airs grow∣ing more heavy. But the particular Account of this Attempt belonging to another place, the trial ought not to be more then hinted here, especi∣ally since it may suffice for our present purpose to alledge that having found* 1.3 (as we have already in other papers noted) that in a Weather-glass, where the Water is not fenc'd from the External Air, the weight of the Atmosphaere may make it alter con∣siderably between the Top and Bot∣tom even of a Church or Steeple, though it appear'd by more certain Thermoscopes, that 'twas not the differing Temperature of the Air as to Cold and Heat, but the differing gravity of the Atmosphaere, which being shorter and lighter at the Top press'd less forcibly upon the subja∣cent

Water and the included Air, as is more fully made out in the Trea∣tise above related to. And having by the intervention of a Learned Ac∣quaintance desir'd to have some Ex∣periments made of the Effect of the Air upon Weather-glasses in deep Pits or Mines, where the Atmosphae∣rical Cylinder is longer and heavier, I receiv'd Information that an Ingeni∣ous* 1.4 Physician, who had the Oppor∣tunity of trying what I desir'd, had found, that in the Bottom of one of those very deep Pits, the water in a common Weather glass rose near three Inches higher then at the top, in a shank or pipe of about thirty Inches long. And this notwithstand∣ing the warmth, that is usual in such deep places, which seems not any thing near so plausibly referable to any other cause, as to the increas'd gravity of the Atmosphaerical Pillar incumbent on the Water, that Pillar being heavier at the Bottom then at the Mouth of the Pit, by the weight of an aerial Pillar equal in length to the pits perpendicular height or depth.

But these are not the only Cases wherein the differing gravities of the Atmosphaere may, as well as Heat and Cold, have an interest in the rising and falling of the Liquor in Common Weather-glasses. For though you should not remove them out of one place, and though consequently it may seem that the Atmosphaerical Pillar, that presses upon the water, must be still of the same length, yet (not to urge, that That may alter, unknown to us) if retaining its length it retain not its gravity, we may be easily impos'd upon, and take that Ascension or Subsidence of the Li∣quor for the Effect of a higher or remiss degree of Cold, which may either totally or at least in part (and in what part, we are left to guess) be the Effect of the increas'd or lessen∣ed weight of the Atmosphaerical Pillar, happening either by the co∣pious dispersion of Vapours and other heavy Steams through the Air, or upon other Occasions not necessary to be here discours'd of, or by the Praecipitation of such vapours by rain or into dew, or else by the Removal

of the Occasions of the Augmented Gravity or Pressure of the Air. For we have often observ'd great Varia∣tions to happen in the height of the Mercurial Cylinder in the Torricel∣lian Experiment upon great rains and fogs, and other sudden and conside∣rable mutations of the Incumbent Air. But since I my self thought fit, notwithstanding the plausible ratiocination, that led me to this Conjecture, to examine it by Expe∣rience; I can scarce doubt but that others may have the like Curiosity that I had. And therefore, because it may seem a paradox, it will not be amiss, of many to annex three or four Trials I made to examine the propos'd doctrine, especially ours having been the first observations of this kind, that, for ought we know, have been made by any. And in∣deed others could scarce have well made such, though they had lighted on the same thoughts, for want of such seal'd Weather-glasses to make them with. To omit then those that I made with a seal'd Weather-glass, and an ordinary one (in which the

water remains suspended beneath the included Air) I shall briefly relate, that in a Room unfurnished with a Chimney, I kept two Weather∣glasses, which for more exactness sake, I caus'd to be made of a length far greater then ordinary; so that the divisions of the one were half inches, and those of the other not much less, and yet were Numerous. The one of these which was furnished with good spirits of Wine, was seal'd, the other not, but this last I caus'd to be so made of the shape represented by the Scheme, that the Air being shut up in the lower part of the In∣strument (not as in common Wea∣ther-glasses at the Top) the Liquor might as well in this as in the seal'd Weather-glass rise with heat and fall with Cold. In these Thermoscopes (where the Ascension and relapse of the Liquors were, by reason of the length of the Pipes, far more con∣spicuous then in Vulgar Weather∣glasses) I observ'd with pleasure, that the Hermetical Thermoscope (if I may for distinction sake so call It, by reason of its being Hermetically

seal'd) did regularly enough descend in cold weather, and ascend in 〈◊〉〈◊〉: But the other, which was not seal'd, but had a little hole left open at the Top of the Pipe, though, when the Atmosphaere continued of the same weight, it would like the other rise with Heat and fall with Cold, yet when the Atmosphaeres gravity was alter'd, they would not uniformly move together, but when (as we gather'd from other observations) the Atmosphaere grew heavier, the Liquor in the Pipe did not ascend, as high as it would have done, if the Atmosphaere had continued in its former degree of gravitation. And on the contrary, when the incumbent Air came to be lighter, the Liquor would rise in the open Weather-glass in a proportion greater then the single increase of heat would have exacted; so that by comparing the two Weather-glasses together, I did usually foretel, whether the Mercu∣ry in the Torricellian Tube (which I keep purposely by me in a frame) were risen or fallen, and consequent∣ly whether the external Air were

heavier or lighter then before. As on the other side, by looking on the height of the Mercurial Cylinder, I could easily tell before hand, whe∣ther the Liquor in the open Wea∣ther-glass were higher or lower then that in the Hermetical; the rising or falling of the Mercurial Cylinder one quarter of an Inch (the Tempe∣rature of the Air continuing as to heat and cold) usually signifying a great disparity betwixt the Ascension or the falling of the Liquors in the two Instruments.

Among the several notes, I find among my loose papers, and in a Diary I kept for a while of these ob∣servations, I shall content my self to transcribe the following two, be∣cause, though divers others were made by my Amanuensis, whose care is not to be distrusted, yet by reason of my absence I could not take notice of them my self. The first of these Memorandums runs thus:

Last night I took notice, that there was but one or two Divisions difference betwixt the two Thermo∣meters, but upon such a change of

Weather, that happened this day, as made me imagine, that the At∣mosphaere would be lighter then 〈◊〉〈◊〉, consulting the Barometer (if to avoid Circumlocutions I may so call the whole Instrument wherein a Mercurial Cylinder of 29. or 30. Inches is kept suspended after the manner of the Torricellian Experi∣ment.) I found the Quicksilver lower then it had been a great while, and thereupon concluding, there would be a notable disparity, be∣tween the seal'd and open Weather∣glass, I hastned to them, and found that the latter being much alleviated from the weight of the Incumbent Air, was no less then 17. Divisions higher then the others, and compa∣ring the height the two Instruments were this day at, with an observati∣on I my self made about a week ago, when the Quicksilver was much high∣er then now it is; I found, that al∣though this afternoon the seal'd Glass being at 41, the other was at 58; yet Then, when the seal'd Weather∣glass, was five divisions higher, namely, at 46, the unseal'd Wea∣ther-glass

was but at 27. So that betwixt that time and this, the Li∣quor in the seal'd Weather-glass, has descended five Divisions, but that in the open Weather-glass has ascend∣ed 31.

Thus far the first of the above mentioned Notes; the second is as follows.

The Mercurial Cylinder being higher, then it has been a good while, and yet the Weather warm and Sun∣shiny, when the Liquor in the seal'd Glass stood very near the 50^th divi∣sion, that in the unseal'd was fallen down as low as the 32.

So that it is very possible, that the unheeded change in the weight of the external Air may have a greater po∣wer to compress the included Air in an unseal'd Weather-glass, then a not inconsiderable degree of warmth may have to dilate it, and conse∣quently in an ordinary Weather∣glass, where the Air is included at the Top, it may often fall out, that contrary to what men suppose must needs happen, the pendulous Water may rise in warmer weather, and fall in colder.

And ev'n since the writing of the immediately foregoing part of this page, within a few days that interven'd, I have my self made observations, that do yet more clearly manifest this truth, as may appear by the follow∣ing notes. The first of which speaks 〈◊〉〈◊〉.

Memorandum, that Yesterday night the Quicksilver being at 29 Inches, the Liquors in the seal'd and unseal'd Weather-glasses, were near about the same Division, the former being at 40, and the other being but half a Division short of that Number. But this night the Quicksilver being risen about ¼ of an Inch; the Liquor in the seal'd is ascended to 45, and the other descended beneath 35 about half a Division, so that there is now 10 Divisions between them.

This is the first Note, to which the following night enabled me to add this other.

The Quicksilver being risen almost ¾ of an Inch above the station it rest∣ed at the night before last night, the Hermetical Weather-glass being as it was then above the 40 Division; the

Liquor in the other, which was open, in two days and nights is fal∣len to the 17, and consequently is subsided about 23 Divisions, whilest the other is about the same height at which it was at the beginning of that time.

Two or three days after, being re∣turned to the place wherein I had made this last observation, and from which some urgent Occasions had for that time exacted my absence; I found the Disparity, betwixt the two Thermometers that is express'd in the following Memorial.

This day the Quicksilver being ri∣sen to 30 Inches, when the Liquor in the seal'd Weather-glass was at about 41 Divisions, that in the other was depress'd a pretty deal below the Ninth Division, so that the differ∣ence between the two Thermometers was increas'd since the last Observa∣tion from 23 to near 33 Divisions, all which the Liquor in the open Weather-glass had sunk down, whilest that in the seal'd continued almost at a stand. And the day af∣ter this Memorial, I had occasion to

register another, which being the last, I shall here think requisite to take notice of in this 〈◊〉〈◊〉, I shall subjoyn it with that, which im∣mediately preceded in order of Time.

This day the Quicksilver continu∣ing at the same height, at which I observ'd it yesterday, but the Wea∣ther being grown much colder, the Liquor appears in both the Glasses to have uniformly enough subsided; that in the seal'd Weather-glass, be∣ing about the 33, and the other be∣ing sunk quite below the lowest mark of all, which was more then I apprehended it would have done, when there was no frost, especially since by my Diary it appears, that one of the last times I observ'd the Hermetical Weather-glass to stand at near about the same height, name∣ly, the 34; the Liquor in the other Glass was no lower then the 41: nor probably would there be now so great a difference, if the Atmo∣sphaere had not been this day very heavy; whereas, when this freshly recited observation was made, I find

by the Diary, the Quicksilver to have ascended but to 29 Inches, and a pretty deal less then a half.

Since that time, being forced by several Avocations to be often absent from the place where my Thermo∣scopes were kept, I was not careful to prosecute such Observations, those already set down (not to mention those that are not here transcrib'd) being judg'd abundantly sufficient to evince the Paradox propos'd to be prov'd by them: Only, to manifest that after I desisted from registring my Observations, the Phaenomena may probably have been as remarkable as before; I shall add, That one of the last times I chanc'd to take notice of the Difference to be gather'd by com∣paring the two Weather-glasses, I found (the weather happening to be warmer then ordinary) the differ∣ence between them to exceed any that I remembred my self to have then observ'd, amounting to forty four, if not to forty five Divisions.

And ev'n since the writing of the Last Line, we have had opportunity to observe a Phaenomenon, which if it had occurr'd to us in the place where we might have compar'd the Bara∣scope with the Exact Weather-glas∣ses hitherto mention'd, (and whereby we had been invited to rely upon it) would perhaps appear more Consi∣derable then any of the Observations yet recorded. For not very many hours ago, finding in the Morning the Quicksilver to be risen in a good Ba∣rascope of mine (though another from that, all this while referred to, and elsewhere kept) above ¾ of an Inch higher then the place it rested at the Night foregoing, and a some∣what Nice Weather-glass (where the included Air is kept in the lower part of the Instrument, which is sha∣ped like that already describ'd in this Discourse) being consulted to show what Effect so great and sudden a change of the Atmosphaeres gravity would have upon it; I saw the tinct∣ed Liquor in the shank depress'd a full Inch or more beneath the Surface of the Ambient Liquor in the Viol,

which strange depression of the Li∣quor in a pipe above 20 Inches long, and where the alterations of the Air as to Heat and Cold are not wont to produce any thing near so great an Effect, I could not but take much no∣tice of. Since the season of the year makes it no way likely that the night, though Cold, could have had so po∣werful an Operation on it, especially since an Amanuensis that watch'd it much longer then I, affirms that he saw the Liquor driven down quite to the very Bottom of the pipe, and a Bubble of the outward Air to make its passage through the water, and to joyn with the Air contain'd in the ca∣vity of the Viol.

The II. Discourse, Containing some New Observations about the De∣ficiencies of Weather-glasses, together with some Considera∣tions touching the New or Hermetical Thermometers.

ANd since I had occasion to speak of the Deficiencies of Wea∣ther-glasses, and the mistakes where∣to men are liable in the Judgement they make of Cold and Heat upon Their Informations, it will not per∣haps appear impertinent to add three or four Considerations more to ex∣cite men to the greater Wariness and Industry, both in the making and using Weather-glasses, and in their Judging by them.

1. And first, I consider, that we are very much to seek for a Standard

or certain Measure of Cold, as we have setled Standards for weight, and magnitude, and time, so that when a man mentions an Aker, or an Ounce, or an Hour, they that hear him, know what he means, and can easily exhibit the same measure: but as for the degrees of Cold (as we have elsewhere noted concerning those of Heat) we have as yet no cer∣tain and practicable way of determi∣ning them; for, though, if I use a Weather glass long, 'tis easie for me to find, when the Weather is colder, or when warmer, then it was at the time when the Weather-glass was first finished, yet that is a way of estimating, whereby I may in some degrees satisfie my self, but cannot so well instruct others, since I have no certain way to know determinate∣ly, so as to be able to communicate my knowledge to a remote Corres∣pondent, what degree of Coldness or Heat there was in the Air, when I first finished my Thermoscope; For besides that, we want distinct Names for the several gradual diffe∣rences of Coldness, we have already

declar'd, that our sense of feeling cannot safely be relied upon to mea∣sure them; and as for the Weather∣glass, that is a thing, which in this case is suppos'd to be no fit Standard to tell us what was precisely the tem∣per of the Air, when it self was first finished, since that does but inform us of the recessions from it, or else that the Air continues in the Temper it was in at the making of the Instru∣ment, but does not determine for us that Temper, and enable us, to ex∣press it; as indeed it is so mutable a thing, ev'n in the same place, and oft-times in the same day, if not the same hour, that it seems little else then a Moral impossibility, to settle such an universal & procurable Stan∣dard of Cold, as we have of several o∣ther things. And indeed there is scarce any Quality, for whose differences we have fewer distinct Names, ha∣ving scarce any for the many degrees of Coldness that may be conceiv'd to be intermediate, betwixt Lukewarm∣ness and the Freezing degree of Cold, and even these are undefin'd enough; for that, which to some mens senses

will feel Lukewarm, by others will be judg'd Hot, and by others perhaps cold; nor is even the glaciating de∣gree of Coldness well determin'd, since not only differing Liquors, as oyl, wine, and water, will mani∣festly freez much more easily one then another, but even Liquors of the same denomination; and of waters themselves some are more easily turn'd into Ice then others, and I see no great cause to doubt but that there may be sufficiently differing degrees of Cold, whereof the mildest may suffice for the congelation of some waters. I must not forget to add, that the same person, that has made many observations with a Weather∣glass, is so confin'd by that numeri∣cal Instrument, that if by the spilling of the Liquor, or the cracking of the Glass, or the casual intrusion of some Bubbles of Air, or by any of divers other Accidents that may happen, the Instrument should be spoil'd, he would, though he should imploy again the same Instrument, be re∣duc'd to seek out 〈◊〉〈◊〉 new Standard, wherewith to measure the varying

temperature of the Air. And though it be not difficult to include in the Cavity of a Weather-glass some other fluid Body instead of Air, yet it will be very difficult, if not im∣possible, to include a Body, fit to resent and show the Alterations of the Ambient Air, without being also li∣able to receive impressions from it at the time of its being first shut up.

Yet I will not here omit that I have sometimes consider'd whether the es∣sential oyl of Aniseeds (which is that that is distill'd by the intervention of water in a Limbeck) might not, du∣ring a good part of the year, be of some use to us, in making and judg∣ing of Weather-glasses. For this Liquor, as we 〈◊〉〈◊〉 also note, having the peculiarity of loosing its fluidity during almost all the Win∣ter, and a good part of the Spring, and Autumn too, when the Wea∣ther* 1.5 or the time of the day is colder; this Liquor, I say, being such, in

case you very gently thaw it, and then putting into it, the Ball of a Wea∣ther-glass furnish'd with spirit of Wine that will burn all away, you suffer the oyl to re-congeal leisurely of it self, you may by observing the station of the spirit of Wine in the Thermoscope, when the Oyl begins manifestly to curdle about it, be in some measure assisted, to make ano∣ther Weather-glass like it. For if you put such rectified spirit of Wine into a Glass, the Cavity of whose Sphaerical, and that of its Cylindri∣cal part, are as near, as may be, e∣qual to the correspondent Cavities in the former Glass, you may by some heedful Trials, made with thaw'd and recongeal'd oyl of Aniseeds, bring the second Weather-glass to be somewhat like the first; and if you know the Quantity of your spirit of Wine, you may easily enough make an estimate, by the place it reaches to in the Neck of the Instrument, whose capacity you also know, whe∣ther it expands or contracts it self to the 40, the 30, or the 20 part, &c. of the 〈◊〉〈◊〉 it was of, when the

Weather-glass was made. By the help of the same Oyl you may make some kind of estimate, though a more uncertain one, of the difference of two Weather-glasses of unequal bigness: And though I know how much may be alledg'd to show the uncertainty of this way of making a Standard for Weather-glasses; yet as what I have formerly represented, may manifest me to be far enough from looking on it as an exact Stan∣dard of Cold; so perhaps the way propos'd may not be altogether use∣less in the making and comparing Weather-glasses, since in such cases, where we are not to expect to hit the mark it self, it is of some advantage to be able to shoot less wide of it then otherwise we should.

II. But not to insist any further on a difficulty, which is so hardly 〈◊〉〈◊〉 as that, which occurs about setling a perfect Standard of Cold, there are unaccuratenesses in the mea∣suring of Cold by Weather-glasses, which may be avoided, but are not; For, Men are not wont to take care, that the Stems be even and Cylindri∣cal

enough, but are wont to make use of such, as are much wider at the upper part near the bubble, then otherwhere; nor do they observe, as they might, a proportion betwixt the Diameter of the Bore of the Cylin∣der, and that of the Cavity of the Sphaerical Bubble, and divers other circumstances are commonly negle∣cted, which if well order'd would make much towards the Certainty and instructiveness of the Informati∣ons, afforded us by Weather-glasses. To which may be added, that even in those, where some part of the Li∣quor is expos'd to the external Air, there may be made Contrivances much more convenient, in order, at least, to some particular purposes, then that of the Vulgar Weather∣glass, some of which we have im∣ploy'd, and others have been either skilfully devis'd, or also happily at∣tempted by some eminently ingeni∣ous* 1.6 Members of the Royal Society. And though that, which we have al∣ready* 1.7 discrib'd in another Treatise, be very simple, yet it is much more commodious for several of the fol∣lowing

Experiments of Cold, then that, which is commonly in use. For in this, where the included Air is as it were pendulous at the Top of the Glass, 'tis very troublesome and difficult so to apply Cold Bodies, and especially Liquid ones to it, as there∣with to measure their Temper, whereas the Thermometers, I speak of, being made by the insertion of a Cylindrical pipe of Glass (open at both ends) into a Viol or Bottle, and by exactly stopping with sealing wax, or very close Cement the Mouth of the Viol, that the included Air may have no communication with the Ex∣ternal, but by the newly mentioned Pipe: In this kind of Instrument, I say, by chusing a Viol as large, as you please, and fitting it with a Cy∣lynder, slender enough, the propor∣tion between the part of the Viol pos∣sest by included Air, and the Cavity of the Cylinder, in which the Liquor is to play up and down, may be easi∣ly made so great, as to make the Li∣quor in this Instrument, with the same degree of Heat or Cold, rise or fall four or five, or more times as

much as the pendulous Liquor is wont to do in an Ordinary Weather∣glass, where the cavity that lodges the Air, is wont to be much too small, considering the Bigness of the pipe, whereinto the Air must, when 'tis rarifi'd, expand it self. But 'tis not the greater sensibility (if I may so speak) of this very kind of Wea∣ther-glasses, nor their not needing frames, that makes me take notice of them in this place (where I pur∣posely pass by contrivances that I know to be more curious) but this other Quality, which makes them fit for divers of the following Experi∣ments, wherein we shall have occasi∣on to mention them, namely, that with little or no trouble and inconve∣nience we may imploy Liquors or other Bodies to refrigerate the inclu∣ded Air, by immersing the Viol, if need be (by a weight) into the Liquor to be examin'd, and letting it stand there as long as we please. And so we may also measure the Coldness of Earth, Snow, powder'd Ice, and other consistent Bodies, which may be heap'd about the Viol, or in which it may be buri'd.

III. I consider too, that though men are wont confidently enough to conclude, that in case (for instance) the Coldness of the weather make the Liquor in a Thermoscope yester∣day an Inch higher then 'twas the day before, and this day an Inch higher then 'twas yesterday, the Air must be this day as cold again as it was ye∣sterday, or at least that the increase of Cold must be double to what it was yesterday, and so in other pro∣portions, yet the Validity of this Collection may very justly be Questi∣on'd; For, though we should grant, that Cold is that which of it self, or by its own power contracts the Air, yet how does it appear, that a double degree of Cold must produce a dou∣ble degree of condensation in the Air, and not either more or less. Since besides that 'tis taken for granted, but not prov'd, that the differing Quantities of included Air in several Instruments, and the differing big∣nesses of the Pipes, and the differing degrees of Expansion, wherein the in∣cluded Air may happen to be, when the Ascension of the Water begins to

be reckon'd, may render this Hypo∣thesis very suspicious; besides all this, (I say) I am not inclin'd to grant (what Philosophers have hitherto suppos'd) that the Condensation of the Air, and the ascension of the Wa∣ter is only, or so much as principally, affected by the proper Virtue of the Cold, but by the pressure of the Ambient Air, as we shall ere long more fully declare: And if this be made out, then the computation, we are considering, will be found to be very fallacious, for we have else∣where* 1.8 shown, That the strengths re∣quir'd to compress Air, are in reciprocal proportion, or there abouts, to the spaces comprehending the same portion of Air; so that if a Cylinder (for instance) of four Inches of Air, be just able to resist a strength or pressure equivalent to 10. pound weight, when it comes to be compress'd into two Inches; in this case, I say, an equal force super∣added to the former, (which makes that a double force, or equivalent to 20 pound weight,) will drive up that already comprest Air into half the space; that is, into one Inch or

thereabouts; whence it follows, that in estimating the condensation of the Air in a Weather-glass, we must not only consider, how much space it is made to desert, but also, what pro∣portion that deserted space bears to the whole space it formerly possest, and to what degree of density it was reduc'd, before the application of the then force; and we must remem∣ber, that the resistence of the inclu∣ded Air is not to be look'd upon, as that of a weight, which may remain always the same, but that of a spring forcibly bent, and which is increas'd more and more, as it is crowded into less and less Room. But these Nicer speculations it would here be some∣what improper to pursue.

IV. Wherefore I shall proceed to what may seem a Paradox, that even the particular Nature of the Liquors, imploy'd in Weather-glasses, is not altogether to be neglected, till we have a better and more determinate Theory of the causes of Cold, then I fear we have: For, though usually it matters not much, what Liquor you imploy, yet 'tis not impossible,

that in some cases men may slip into mistakes about them, for it will not follow, that if of two Liquors, the one be much the more obnoxious to the higher degree of Cold, that of Glaciation, the other must be less easily susceptible of the lower degrees of Cold; since those, that make seal'd Weather-glasses, some with water, and some with spirit of wine, have confessed to me, that they find these (last nam'd) much more apt to receive notable impressions from faint degrees of Cold, then those that are furnished but with water, and (which yet is easily turn'd into Ice) by the cold of our Climate, which will by no means produce the like effect upon pure spirit of Wine.

Besides we cannot always safely conclude (as Philosophers and Chy∣mists generally do) that the more subtile and spirituous Liquors must be the least capable of being congeal∣ed (that is, made to lose its fluidity, as oyl and some other substances are wont to be reduc'd to do by the Acti∣on of Cold) for the Chymical Oyl of Aniseeds distill'd by a Limbeck is

so hot and strong a Liquor, that a few drops of it conveniently dissolv'd will make a whole Cup of Beer taste as strong, and perhaps heat the Bo∣dy as much as so much Wine, and yet this hot and subtile Liquor I have found upon Trial, purposely made, to be more easily congealable (in the sense freshly explain'd) by cold, then even common water; and to continue so several days, after a Thaw had resolv'd the common Ice into fluid water again. And I know some distill'd Liquors, whose component particles are so piercing and so vehe∣mently agitated, that the tongue cannot suffer them, and they are not perhaps inferior to most Chymical Oyls, nor to Aquafortis it self, and yet these may be congeal'd by far less degrees of Cold, then such, as would yet prove ineffectual to freez either the generality of Chymical Oyls, or the generality of saline spi∣rits.

And indeed till we attain to some more determinate Theory of Cold, and come to know more touching its causes, then we yet do, I see not,

why it should be absurd to suspect, that though there be some kind of Bodies, which seem fitted to pro∣duce Cold indiscriminately in the Bodies they invade or touch, yet if the refrigeration of a Body be but the lessening of the wonted or former agitation of its parts (from what cause soever that remisness proceeds) it seems not impossible, but that be∣sides those Bodies or Corpuscles, that may be look'd upon as the Ca∣tholick Efficients of Cold, there may be particular Agents, which in reference to this or that particular Body may be call'd frigorifick, though they would not so much re∣frigerate another Body, which per∣haps would be more easily affected, then the former, by 〈◊〉〈◊〉 efficients of Cold. For we may observe, that Quicksilver may be congeal'd by the Steams of Lead, which have not been taken notice of to have any such Effect upon any other fluid Body, and yet Quicksilver is not to be depriv'd of its fluidity by such a degree of Cold, as would freez not only water but wine. And by what we have for∣merly

related upon the credit of that great Traveller, the Jesuit Martini∣us, it seems, that water it self may in some Regions be so dispos'd by the constitution of the Soyl, that 'tis sus∣ceptible of strange impressions of Cold in proportion to the Effect, which that degree of Cold produces there in humane Bodies. Besides, Opium also, of which three or four grains have too oft destroyed the heat of the whole mass of Blood in a mans Body, though that be a very hot, subtile, and spirituous Liquor, does not sensibly refrigerate water, as far as I could observe with a good seal'd Weather-glass, which I put some∣times in a glass of ordinary water, and sometimes into a glass of water of the same Temper, and (as we guess'd) of the same Quantity, wherein Opium, enough to kill very many men, was put in thin slices, and suffered to dissolve; which seems to argue, that as differing Liquors have each their peculiar Texture, so there may be certain Bodies, whose mi∣nute particles by their peculiar seize, shape and motion, may be qualified

to hinder, or at least lessen the agita∣tion of the particles of the appropria∣ted Liquor, into whose pores they insinuate themselves; And thereby, according to the lately mention'd supposition, they may refrigerate that particular Liquor without ha∣ving the like Effect on other Liquors, whose Textures are differing. And I might countenance this by adding, that as fiery and agitated a spirit as that of wine, when well 〈◊〉〈◊〉, is justly thought to be; yet I know more liquors then one, that being mingled with it, will in a trice de∣prive it of its 〈◊〉〈◊〉; and the like change I have sometimes made in some other liquors also. But I must not insist on such matters, having mention'd them but only to awaken mens curiosity and circumspection, and not to build much upon them, which will be easily credited, if it be remembred, that a little above I my self sufficiently intimated, that this Conjecture supposes something about the Theory of Cold, which is not yet sufficiently clear'd. Only, because the former Experiments show, That

the various Agitation of the minute parts of a Liquor, whereon its Flui∣dity depends, may be hindred or sup∣pressed by the intervention of adven∣titious 〈◊〉〈◊〉: But do not clearly show, That the Liquor by being de∣priv'd of that Kind of Agitation does actually acquire a Coldness: I might subjoyn thus much, that by the Ad∣dition of a certain substance (which for just reasons I must forbear to de∣scribe) that would scarce sensibly re∣frigerate common Water; I can make a certain (and for ought I know, one only) Liquor, that is wont to the touch to be much of the Temper of Water, to conceive a considerable degree of Coldness: This, I say, (as strange as it may seem) I might here subjoyn to coun∣tenance the Conjectures, I have been delivering, and afford some new Corrolaries; but for the Reason newly intimated I forbear, and the rather because I think it high time to return thither, whence the Consi∣derations, I have offer'd about Weather-glasses, have made me di∣gress.

I was going then to take notice, upon the Occasion offer'd by what I related of the Influence of the At∣mosphaeres gravity upon common Weather-glasses, of the difference between them and those that are Her∣metically seal'd. And indeed, these are in some things so much more con∣venient then the others, that (if I be not mistaken) it has already prov'd somewhat serviceable to the Inquisi∣tive, that I have directed the making of the first of them, that have been blown in England; At the Beginning indeed I had difficulty to bring men to believe, there would be a rarefa∣ction and condensation of a liquor Hermetically seal'd up, because of the School Doctrine touching the impossibility of a vacuum, and espe∣cially, because I had never seen any Experiment of this kind, nor met with any that had, but after some Trials, which my Conjectures led me to make succesfully enough, that in Hermetically seal'd Glasses, both Air and Water might be alternately rarifi'd and condens'd; I found my work much facilitated by the sight of

a small seal'd Weather-glass, newly brought by an Ingenious Traveller from Florence, where it seems some of the Eminent Virtuosi, that eno∣bled that fair City, had got the start of us in reducing seal'd Glasses into a convenient shape for Thermoscopes. But since that, the Invention has in England by a dexterous hand, that uses to make them for me, been im∣prov'd, and the Glasses we now use are more conveniently shap'd, and more Exact then the Pattern, I cau∣sed the first to be made by. But the filling of these long ones that we now use, is a work of more niceness and difficulty, then they that have not tri∣ed will be apt to imagine, and there∣fore may elsewhere deserve either from our Pen, or his, that is most vers'd in making them, a more par∣ticular account of the way of Per∣forming it: The advantages of these Weather-glasses being at no hand in∣considerable. For, the weight or pressure of the Atmosphaere (which, as we have noted, may work very much upon others,) their being seal'd defends them from: And by

this Advantage they may be us'd in the highest and in the deepest places, with as much certainty as any where else. Next, whereas in other Ther∣mometers the Liquor is very subject to be spilt, in case they be removed from place to place, and which is worse, though they be not remov'd, is subject to be prey'd upon and wast∣ed by the Air, whereby informati∣ons of such Weather-glasses are ren∣dred in Tract of time somewhat un∣certain: In seal'd Weather-glasses, there is no danger, that Liquor should either spill or evaporate, And upon the same Account, 〈◊〉〈◊〉 have this Advantage, that you may safely let them down into the Sea, and immerse them in any Liquor, you please, without excepting the most corrosive to examine their Coldness: Not to mention, that in∣stead of the courser Liquors used in common Weather-glasses, which are some of them not unapt to freez, and others unapt enough to comply with the slighter alterations of the Air, and instead of the colourless Liquor, whether water or no (I know

not) us'd in the Florentine Weather∣glass I saw, We imploy highly recti∣fi'd spirit of Wine, whose being brought to a lovely red with Co∣chinele, open'd by the most subtile volatile spirit of Urine, by which means the included Liquor is not on∣ly very conspicuous and secur'd from freezing, but so susceptible of even the slighter impressions of external Bodies (which would work but faint∣ly on water) that 'tis pleasant to see, how many Inches a mild degree of heat will make the Tincture ascend in the very slender Cylindrical stem of one of these useful Instruments; of which we have spoken the more par∣ticularly in this place, because we shall have frequent occasions to men∣tion them in the following Papers; and no body as yet, that we know, has written any Account of them.

But though these Weather-glasses be much more to be relied on, then those that are commonly in use, yet we would have a Philosopher look upon both these and our Sensories, but as Instruments to be imployed by his Reason, when he makes his Esti∣mates

of the Coldness of Bodies: And though perhaps it will signifie nothing in the Event, yet I see not, why it should misbecome a Natura∣lists Diligence and circumspection to try, whether ev'n such weather-glas∣ses ought to be so far allow'd of, as to hinder men from looking after any other kind of ways of estimating Cold.

For, though the sealing of these Weather-glasses protect the included Liquor from the pressure of the Air, and keep it from evaporating, yet it will not follow from hence, that they must be exempt from all the other imperfections, which we formerly mention'd to be imputable to Wea∣ther-glasses.

I know not whether you will allow me to add on this occasion, that the tincted spirit of Wine (and the like may (for ought we know) be said of any such Liquor) being a particular mixture, in case it be allow'd possible, that the subtile steams of such Bodies (as we formerly noted to be frigori∣fick in respect to some Liquors) may insinuate themselves through the

pores of Glass; as 'tis granted, that the Effluviums of the Loadstone do readily per-meat It: in this Case, I say, though I willingly allow it not to be likely, yet it is not absolutely impossible, that some Steams, that wander through the Air, may be more or less Cold, or may more pro∣mote or hinder an agitation among the minute parts in reference to It, then in reference to other Liquors: as we formerly noted, that a grain or two of Opium will exceedingly allay the warmth and motion of the whole mass of Blood in a mans Body, though ten times that Quantity will not sensibly refrigerate the tenth part of so much water. And that this may appear the less extravagant, I shall here add some mention of an odd Phaenomenon, that, as it were, by some Fate has occur'd to me, since I began the Discourse I am now up∣on; for whilest I was yesterday wri∣ting It, I had occasion to Examine by such a Seal'd Weather-glass (as I have been speaking of) the Temper of a certain strange kind of mixture, that towards the close of this Trea∣tise,

I shall have Occasion to take special Notice of: and though to the touch it appear'd but Lukewarm, yet having put into it the Ball, and part of the stem of the seal'd Wea∣ther-glass, I found the Included Li∣quor slowly enough impell'd up so high, that at length, to my wonder, it rose eight or nine Inches in a Stem, which was not much above a foot long; but that which I relate, as the surprizing Circumstance, is, that when I had taken out the Thermo∣scope, and remov'd it again into a deep Glass full of Cold water, whence I had just before taken it out, to put it into the Anomalous mix∣ture, I had a mind to examine; the Tincture in the Weather-glass did not (as it was wont, and as any one would have expected) begin to sub∣side again towards its former station, but continued within about half an Inch or less of the very Top of the In∣strument, though neither my own busie Eyes, nor those of a person ve∣ry well Vers'd in making and using Thermoscopes, could perceive, that the expanded Tincture was any

where discontinued by any Air or Bubbles, which at first we suspected might possibly (though it were very unlikely) have been generated by the Tepor of the mixture. But that which continued our wonder, if not increa∣sed it, was, that during four or five hours, that the Instrument continued in the Cold water, and during some hours also, that it was expos'd to the Air, the Tincture did not subside above half an Inch; and which is yet more strange, having left the Glass all night, in the window of a Room, where there was no Chimney, I found in the morning, that its de∣scent was scarce sensibly greater, for it continued about eight Inches high∣er, then the mark it stood at, when I first put it into the Lukewarm mix∣ture, and how long it will yet retain this strange expansion, is more then I can tell. But by this and what I may have occasion hereafter to relate concerning this mixture, it may ap∣pear somewhat the more reasonable to suspect, that even seal'd Weather∣glasses furnished with high rectifi'd spirit of Wine, may in some (though

very rare) conjunctures of Circum∣stances, and from some peculiar Agents, either by their insinuating themselves through the Pores of the Glass, or on some other Account, receive impressions, that, as far as can easily be discern'd, are not pure∣ly the genuine and wonted Operati∣ons of Heat and Cold.

The Chymist Orthelius tells us, that* 1.9 the Liquor distill'd from the Oar of Magnesia or Bismute (which seems to be the same Mineral, that we in English call Tin-glass) will swell in the Glass 'tis kept in, not only manifestly, but very considerably at the full Moon; and shrink at the new Moon; and if all my endeavours to procure that Oar had not prov'd fruitless, I should be able by my own Experi∣ence to disprove or confirm so admi∣rable a Phaenomenon; but being as yet unfurnish'd to make the Trial my self, lest it might appear a Vanity, so much as to mention (without re∣jecting it) a thing so very unlikely: I shall add, that since I find the Thing for the main, which was de∣livered by the Chymist, imploy'd

as an Argument by a* 1.10 famous Mathematici∣an (the Jesuite Casa∣tus) whose expressions are such, as if he him∣self had observ'd, that even in stopt Glasses, the foremention'd Mi∣neral spirit increased very sensibly in Bulk about the time of the full Moon, which wonder being admit∣ted, may not only countenance what we were saying, but hint some other very strange things in Na∣ture. This brings in∣to my mind (what I have elsewhere men∣tion'd) that a Tincture of Amber, I had made with high rectifi'd spirit of Wine, did for many Moneths in a well stopt Glass discover it self to be affected with certain changes, which were thought to proceed from some secret mutations of the Air, that did

sensibly so work, as I had not obser∣ved it to do upon other Liquors, wherein the spirit of Wine abounded. And perhaps upon long and diligent observation, one might find a Dispa∣rity betwixt Weather-glasses kept in the same place, but furnished with differing Liquors, a Disparity, I say, that could not be so well ascrib'd to any thing as to the peculiar Nature of the Respective Liquors, which, though of divers kinds, may (to add that towards the facilitation of Tri∣als) be made of a very conspicuous colour, by the self-same Metal, Cop∣per, which not only gives the Known colour in Aqua fortis, but affords a fair solution in Aqua Regis, and it makes a Liquor of a most deep and lovely blew in spirit of Urine, or of Sal Armoniack, and the like; nay, I have found, that in good Chymical Oyl of Turpentine (for express'd oyls are too easily congeal'd) the bare fi∣lings of it will yield a sufficient Tin∣cture. But because it is yet but a bare suspicion, that Seal'd Weather∣glasses made of differing Liquors, but in other points alike may be

otherwise then uniformly affected by the Temperature of the External Air; I shall now add an observation already made, to show, that even the Seal'd Weather-glasses furnish'd with spirit of Wine are not so per∣fectly secluded from all commerce with external Bodies, and liableness to their operations, but that they may be wrought upon otherwise then we think. For I have more then once observ'd, that even in seal'd Thermoscopes (made purposely at home for me, and with great care by the expertest maker of Them) after a good while, and when no such matter was expected, there have emerg'd Bubbles, which, whether they proceeded from some undiscern∣able Particles of Air, harbour'd in the Pores of the Water, which in process of time, by their Union came to make conspicuous Bubbles, or from some dispos'd particles of the spirit of Wine it self by successive al∣terations brought to a state of Elasti∣city, I now examine not; but only affirm, that sometimes I have had of these Bubbles great enough to possess

the space of many Inches in the shank of a long seal'd Weather-glass, and I have been troubled with them in more Weather-glasses then one or two: which I therefore take Notice of, not only, because it serves to prove what I was saying, but because it is very fit, an Advertisement should be given of it to prevent mistakes. For when these Bubbles are small, and are generated or happen to stay at or about the Place, where the Sphaeri∣cal and Cylindrical parts of the Glass meet, they may easily (as I have ob∣serv'd) lurk unheeded, and reaching from side to side, so divide the spirit of Wine in the Ball from That in the Stem, that the latter shall not be able 〈◊〉〈◊〉 rise and fall according to the chan∣ges of the weather; the Bubble not∣withstanding its aerial nature, being more indispos'd to be mov'd up and down in the slender Stem of a small Weather-glass, then the spirit of Wine it self, as we have elsewhere shown, that when Air is not forc'd, a Bubble of it will not in several cases so readily pass through a very narrow passage, as would that grosser fluid, Water.

But all these difficulties (not to call them extravagances) which I have been mentioning about seal'd Weather-glasses, I represent not to show, that it is (at least as yet) worth while to suspect ours so far, as to imploy all the Diligence and In∣ventions, that were 〈◊〉〈◊〉 to pre∣vent or silence the suspicions of a Sceptick, or that might be thought upon, in case the matter did require or deserve such extraordinary Nicety, but only to give men a rise to consi∣der, whether it would be amiss to take in (when Occasion presents it self) as many collateral Experiments and Observations as conveniently we can, to be made use of as well as our Sensories and Weather-glasses in the Dijudications of Cold. And per∣haps an Attentive Enquiry purposely made, would discover to us several other Bodies, Natural or Factitious, which we might make some use of in estimating the degrees of Cold. For though (to give an instance) 〈◊〉〈◊〉 be thought the Liquor, that is most susceptible of such an Intensity of Cold, as will destroy or suspend its

Fluidity, yet not here to repeat, what we formerly deliver'd of the easie congealableness of Oyl of Ani∣seeds, we have (as we elsewhere note to another purpose) distill'd a sub∣stance from Benzoin, which becomes of a fluid, a consistent Body, and may be reduc'd to the state of fluidity again by very much lesser alterations of the Ambient Air, as to Heat and Cold, then would have produc'd Ice or Thaw'd it. I could also here take notice of, what I have sometimes ob∣serv'd in Amber-greese, dissolv'd in high rectifi'd spirit of Wine, or in other Sulphurous or Resinous con∣cretions dissolv'd in the same Liquor; for now and then, though it seem'd a mere Liquor in warm Weather, it would in Cold weather let go part of what it swallow'd up, and after∣wards redissolve it upon the return of warm weather; some of these con∣cretions, as I have seen in Excellent Amber-greese, shooting into fine fi∣gur'd masses, others being more rudely congeal'd. And I might also add, what I have observ'd in Chymi∣cal Liquors, (not unskilfully pre∣par'd

out of Urine, Harts-horn, &c.) which would sometimes seem to be totally clear Spirits, and at other times would suffer a greater or lesser proportion of Salt to Chrystallize at the Bottom, according to the Mutati∣ons of the Weather, in point of Cold and Heat. Such kind of instan∣ces (I say) I could mention, but I shall rather chuse to prosecute my Examples in that obviousest of Li∣quors, Water, and add, that even That may afford us other Testimo∣nies of the increased or lessen'd cold of the Air, then that which it gives us in Common Weather-glasses. For in some parts of France the Wa∣termen observe, that the Rivers will* 1.11 bear Boats heavier loaden in Winter, then in Summer; and I have upon inquiry been credibly inform'd, that Seamen have observ'd their ships to draw less water upon the Coasts of frozen Regions (where yet the Sea is wont to be less brackish) then they do on our British Seas: which ar∣gues, that water is thicker and hea∣vier in Winter then in Summer. Nay, I shall add, that not only in

differing Seasons of the Year, but even at several times of the same day I have often observed the Coldness of the Air to be (regularly enough) so much greater at one time of the day then at another, that a Glass bubble Hermetically seal'd and pois'd so as to be exactly of the same weight with its equal Bulk of Water, as that Liquor was constituted at one time of the Day, would about Noon, when the warmth, that the Summers Sun produc'd in the Air, had some∣what rarifi'd the water, and thereby made it bulk for bulk somewhat lighter then before, the Bubble would sink to the Bottom of the wa∣ter, which (for the better marking the Experiment) I kept in a Glass∣Tube; but when at night the cool∣ness of the Air had recondens'd the water, and thereby made it heavier, it began by little and little to buoy up the Bubble, which usually by morn∣ing regain'd the Top of the Water; and at other times of the day it not unfrequently happen'd, that the Bubble continued swimming up and down betwixt the Top and the Bot∣tom,

without reaching either of them, sometimes staying so long in the same part of the Tube, that it much sur∣priz'd divers of the Virtuosi them∣selves, who thought the poising of a weight so nicely, not only a very great difficulty (as indeed it is) but an insuperable one. But of this Ex∣periment I elsewhere say more; and because about other Weather-glasses I have said so much already, I think it may not be improper to Sum up my thoughts concerning the Criteria of Cold, by representing the follow∣ing particulars.

1. That by reason of the various and unheeded predispositions of our Bodies, the single and immediate in∣formations of our senses are not al∣ways to be trusted.

2. That though Common Wea∣ther-glasses are useful Instruments, and the informations they give us are in most cases preferrable to those of our sense of touching, in regard of their not being so subject to unheeded mutations: yet ev'n these Instruments being subject to be wrought upon by the differing weights of the Atmo∣sphaere,

as well as by Heat and Cold, may (upon that, and perhaps some other accounts) easily mis-inform us in several cases, unless in such Cases we observe by other Instruments the present weight of the Atmosphaere.

3. That the seal'd Weather-glas∣ses, we have been mentioning, are so far preferrable to the Common ones, as (especially they not being obnoxious to the various pressure of the external Air) that there seems no need in most cases to decline their re∣ports, or postpose Them to those of any other Instruments: But yet in some nice Cases it may be prudent (where it may conveniently be done) to make use also of other ways of ex∣amining the Coldness of Bodies, that the concurrence or variance to be met with in such ways of Examinati∣on, may either confirm the Testimo∣ny of the Weather-glass, or excite or assist us to a further and severer in∣quiry.

4. That I would not have Men too easily deterr'd from devising and try∣ing various Experiments (if other∣wise not unlikely or irrational) about

the estimating of Cold, by their ap∣pearing disagreeable to the vulgar Notions about that Quality. For I doubt, our Theory of Cold is not only very imperfect, but, in great part ill grounded. And I should ne∣ver have ventur'd at trying to make seal'd Weather-glasses, if I could have been withheld either by the grand Peripatetick Opinion, that (to shun a void) water must re∣main suspended in Glasses, where if it fall, the Air cannot succeed it; or the general opinion ev'n of Philoso∣phers as well new as old, That Air must be far easier then any visible Li∣quor condens'd by Cold.

The III. Discourse, Containing The II. Paradox, Viz. Touching the Cause of the Con∣densation of Air, and Ascent of Water by Cold in Common Weather-glasses.

THough I thought here to end the Praeliminary Discourse, as doubting it may be thought prolix enough already, yet for confirmation of what I was lately noting, about the incompleteness of the Theory of Cold (and because the evincement thereof may give rise to many Trials that may inrich the History of Cold) I will here subjoyn a Discourse for∣merly written on another Occasion. For though upon that Account I am

fain to leave out the beginning of It, as not suted to the present Occasion, yet the main Body of the Discourse may be (I think not improperly) an∣nex'd to what has been already said about Weather-glasses, since it exa∣mines the causes of the principal Phae∣nomenon of them, and will perhaps help to discover the incompleteness of mens Notions about Cold, by show∣ing that the true cause, ev'n of the most obvious Phaenomenon of Com∣mon Weather-glasses (though al∣most every man thinks he under∣stands It) has not yet been sufficient∣ly inquir'd into.

The discourse then (that first part of It as forreign to our present pur∣pose) being omitted, is as follows.

— To prosecute our Disquisition sa∣tisfactorily, it will concern us to consider, upon what Account the wa∣ter rises in Cold Weather and falls in Hot, in common Weather-glasses, whose Construction being so well known, that we need not spend time to set it down, we may forthwith proceed to take notice, That con∣cerning the reason, why in these

Weather-glasses the water, or other Liquor in the shank or pipe, ascends with Cold, and descends with Heat: there are three opinions, that will deserve our Consideration.

The first is the common opinion of the Schools and Peripateticks, and indeed of the generality of learned Men of differing Sects, who teach, that the Cold of the External Air, contracting the Air included in the Weather-glass, and thereby reducing it into a narrower Room then for∣merly it possest, the water must ne∣cessarily ascend to fill the place de∣serted by the retired Air, lest that space should become a vacuum, which Nature abhors.

But against this Explication we have several things to object.

For first, I am not satisfi'd, that any of the Schoolmen or Peripate∣ticks (at least of those I have met with) have solidly evinc'd that Na∣ture cannot be brought to admit a vacuum. Nor do I much exspect to see that assertion well prov'd, by these, or by any other, that forbear to make use of the Argument of the

Cartesians drawn from the Nature of a Body, whose very essence they place in its having extension: which I say, because about this Argument I neither have yet published, nor do now intend to deliver my thoughts.

Next, it seems a way of Explica∣ting, that little becomes a Naturalist, to attribute to the senseless and inani∣mate Body of water an Aim at the good of the Universe, strong enough to make it act, as if it were a free Agent contrary to the tendency of its own private Nature to prevent a Va∣cuum, that, as is presum'd, would be hurtful to the Universe.

But these Arguments we have else∣where urg'd, and therefore need not insist longer on them here.

Thirdly, if you take a Bolthead, with a large Ball and long stem; and do, with that and Quicksilver make the Torricellian Experiment, there will be an Instrument prepar'd like a Common Weather-glass, save that the stem is longer, and that the Li∣quor is Mercury instead of Water, and yet in this case we see not, that the Mercury, which remains pendu∣lous

in the pipe at the height of about 30. Inches, offers to ascend into the cavity of the Bolthead, to fill up the space, whence the Air was expell'd by the Mercury, and which the Quicksilver also by its subsiding de∣serted. And the outward applicati∣on of Cold Bodies to the 〈◊〉〈◊〉 part of the head will not perhaps Oc∣casion the rising of the Quicksilver a ¼ of an Inch, is half so much, though the like degree of Cold would make the water ascend in a Vulgar Ther∣mometer, though shorter, to the height of several Inches. But this Argument I also on another Occasion further display and vindicare.

Wherefore I shall add one more, taken from the Consideration of these seal'd Weather-glasses, that are describ'd in this 〈◊〉〈◊〉 History of Cold. For, in these the Air does not shrink, but rather seems to be expanded, when the weather grows Colder. If it be said, that water be∣ing contracted by the Cold, the Air follows it to prevent a Vacuum: I an∣swer, that those, that say this, should explain, why, whereas in Common

Weather-glasses the water ascends to follow the Air, in these the Air must descend to follow the water: And why, since to avoid a Vacuum the one in common Weather-glasses, and the other in seal'd ones resists con∣traction, Nature does not rather make the Air in Common Thermo∣meters, retain the extension, they conceive due to its nature, then put her self to the double Labour of suf∣fering the Air to be preternaturally condens'd, and compelling the wa∣ter to ascend contrary to its nature. But these Arguments I will not urge so much, as this other, that in our present case, the above propos'd An∣swer will by no means salve the diffi∣culty. For if the water be really condens'd into less, and the Air ex∣panded into more space then they re∣spectively possest before; I see not, how a Vacuum or a worse Inconveni∣ence will be avoided; for I demand, since Glass is granted to be impervi∣ous to Air and water (as indeed else Nature would not need to make wa∣ter ascend contrary to its own tenden∣cy in a Common Weather-glass)

what becomes of the Body, that was harbour'd in the space deserted by the water upon its Condensation? Which Question, those that do not say, any thing escaped away through the Glass, or that any thing was an∣nihilated, will not easily answer. But this is not all, for I further de∣mand, when the Air expands it self to follow the water, how by that ex∣pansion of the Air, a Vacuum both coacervatum (as the old Epicureans spoke) and interspersum, is avoided. For the aerial Corpuscles cannot ad∣vance into this space deserted by the water, without leaving either in whole or in part the spaces they fill'd before, so that by this remove an ae∣rial Corpuscle only changes place, but does not adequately fill any more place then it did before. But if it be said, that the same Air without any sub∣stantial Accession, may adequately fill more space at one time then at another: If this, I say, be pretend∣ed, I shall not urge that it appears not, why it were not more easie for Nature in common Weather-glasses, as well as in seal'd ones, to rarifie the

Air, which they reach to be so very easily rarifi'd and condens'd, then to make the heavy Body of water to as∣cend. For I may very well reply, that I scarce know any Opinion in Natural Philosophy, that to me seems more unintelligible, and more worthy to be confidently rejected, then This harsh Hypothesis of Rarefa∣ction. Of which I should think it in∣jurious to so judicious a Philosopher, as my Lord Brouncher, to indeavour here to manifest the absurdity,* 1.12 though I had not in another place shewn it already.

The next Opinion, we are to con∣sider touching the cause of the ascen∣sion of Water by cold in Weather∣glasses, is that of Mr. 〈◊〉〈◊〉, who, in the last Chapter of his Book de Cor∣pore, Sect. the 12. having premis'd a delineation of a common Weather∣glass, subjoyns this Explication:

In the sixth and seventh Articles of the 27. Chap. (where I consider the cause of Cold) I have shewn, that fluid Bodies are made colder by the pressure of the Air, that is to say, by a constant wind that presseth them.

For the same cause it is, that the su∣perficies of the water is press'd at F, and having no place, to which it may retire from this pressure, besides the Cavity of the Cylinder between H and E, it is therefore necessarily for∣ced thither by the Cold, and conse∣quently it ascendeth more or less ac∣cording as the Cold is more or less increas'd. And again, as the Heat is more intense, or the Cold more re∣miss, the same water will be depress'd more or less by its own gravity, that is to say, by the cause of gravity above explicated.

But however the Author of this Explication, to prepare us to receive it, tell us, that however the above mention'd Phaenomenon be certainly known to be true by experience, the cause nevertheless has not yet been discover'd: yet I confess, I think, this newly reci∣ted assertion might as well have been plac'd after his explication, as just be∣fore it.

For first, whereas he remits us to the sixth and seventh Articles of the 27. Chapter (for the reference is misprinted) as containing the

grounds of this Explication, I must profess my self far from being satis∣fi'd with the general Theory of Cold deliver'd in that Chapter, as being partly precarious, partly insufficient, and partly scarce intelligible, as I shall elsewhere have Occasion to shew: and as for what he particular∣ly alledges in the sixth and seventh Articles of a constant wind, that presses fluid Bodies, and makes them Cold, besides that that is prooflesly affirm'd, we shall anon have Occasi∣on to mention an Experiment, where water was not only much refrigera∣ted, but turn'd into Ice, though it were seal'd up in Glass Vessels, and those suspended too in other Glasses, wherein some of them had Air about them, and some others were totally immers'd in unfreezing Liquors, so that the water that was seal'd up was sufficiently protected from being ra∣ked by the wind, as Mr. Hob's con∣ceipt of the Cause of freezing re∣quires.

Secondly, I see no necessity, that the Cold should press up the superfi∣cies of the Water into the shank of

the Weather-glass, especially since 'tis manifest, that the Water will rise with Cold in a Weather-glass kept in a still place, and free from any sensible wind. Besides that, it should be prov'd, and not barely affirm'd, that an insensible Motion deserves the name of wind, and that such a one is the cause of the refrigeration of water, and it should be also shewn, how this wind comes to be able to raise the water, and that to the height of many Inches more in one part of the superficies then in another. Be∣sides all this, I say, we find by Ex∣perience, that Water powred into a Bolthead, till it have fill'd the Ball, and reach'd a good way into the Stem, will upon a powerful refrige∣ration, short of freezing (which is the case of water in Weather-glasses, when the Air grows colder) mani∣festly shrink into a narrower room, instead of being impell'd up higher in the Pipe. And if in an ordinary Weather-glass, with a long shank, you apply a mixture of Ice or Snow, and Salt to the Bolthead, the water will readily ascend in the shank to the

height of divers Inches, which how it will be explain'd by Mr. Hob's Hypo∣thesis, I do not well see.

Thirdly, I wonder he should tell us, that the reason why the press'd water ascends into the shank of the Weather-glass, is, because it hath no other place into which it may re∣tire from the pressure of the wind, since he, rejecting a Vacuum, and af∣firming the world to be every where perfectly full, should not, methinks, have so soon forgotten, that in the very Paragraph or Section immedi∣ately preceding this, himself had told us, that he cannot imagine, how the same place can be always full, and never∣theless* 1.13 contain sometimes a greater, some∣times a less Quantity of matter; that is to say, that it can be fuller then full. So that I see not, why the water should find more room to entertain it, in the Cylindrical cavity of the Weather∣glass already adequately fill'd with Air, then otherwhere. And in the seal'd Weather-glasses, we have above been mentioning, and where∣in the water descends with Cold, 'twill be very hard for Mr. Hobs to

make out the Phaenomenon according to his doctrine. Besides that his Ex∣plication gives us no account of the Condensation of the Air by cold in such Weather-glasses, as those, wherein the water descends with Cold and rises with Heat.

Fourthly and lastly, whereas Mr. Hobs takes notice of no other cause of the 〈◊〉〈◊〉 of water in Weather-glasses by Heat, but its own gravity, he seems to have but slightly consider'd the matter. For though in some cases the gravity of the water may suffice to depress it, yet in other cases that gravity alone, will by no means serve the turn, but we must have recourse to the expan∣sive Motion or spring of the Air in∣cluded in the Cavity of the Glass. For if you place a Thermometer with a large Ball, wherein the water ascends but a little way into the shank, in a window expos'd to the warm Sun, you will often perceive the sur∣face of the water in the Pipe to be a good deal lower, then that of the water on the outside of the Pipe, which shews, that this depression

proceeds not from the bare sinking of the water, but from its being thrust down by the pressure of the in∣cumbent Air; since the waters own weight, would make the internal wa∣ter fall but to a level with the surface of the external water, and not so much beneath it. And for further proof, you may, by keeping such a Weather-glass long enough in the hot Sun, bring the Air so far to expand it self, as to drive the water out of the shank, and break through the exter∣nal water in divers conspicuous Bubbles, after whose eruption the remaining Air being again refrigera∣ted by the removal of the Weather∣glass into a cooler place, the loss of that part of the Air, that escap'd away in Bubbles, will make the wa∣ter ascend higher in the shank, then in the like degree of Cold, it would formerly have been impell'd. And thus much may suffice to shew the unsatisfactoriness of Mr. Hob's con∣ceipt.

The third and last opinion we shall mention, is, that of some ingenious modern Naturalists, who acknow∣ledging

that the Air has a weight (which Mr. Hobs also does in effect admit, though he make not so good use of it as they) do by that explicate the ascension of water in Weather∣glasses, teaching that the Cold of the Ambient Air making the included Air shrink into far less room then it possest before, the water in the sub∣jacent Vessel is, by the weight of the incumbent Air, which presses on it more forcibly in all the other parts of its surface, then it is press'd upon in that included in the shank, impell'd up into that part of the shank, which was newly deserted by the self-con∣tracting Air.

But though this Account be prefer∣able by far to those which we menti∣on'd before it, and though it be not only ingenious, but, as far as it reach∣es, true, yet to me I confess it seems not sufficient, and therefore I would supply what is defective, by taking in the pressure, (and in some cases the spring) of the external Air, not only against the surface of water (for That the newly mention'd explication like∣wise does) but also against the internal

or included Air. For the recited Hypothesis gives indeed a rational ac∣count, why the water is impell'd in∣to the place deserted by the Air; but then supposes, that the Air is made to contract it self by cold alone, when it makes room for the water that suc∣ceeds in its place, whereas I am apt to think, that both the effects may pro∣ceed, at least in great part, from the same cause, and that the pressure of the contiguous and neighbouring Air, does according to my Conjecture eminently concur to reduce the cool'd Air, shut up in the Weather-glass, into a narrower space. This it does in common Weather-glasses, be∣cause the Ambient Air retains the whole pressure, it has upon the Ac∣count of its weight, whereas the in∣ternal Air by its refrigeration, even when but equal to that of the Exter∣nal Air, looses part of the pressure, it had upon the account of its now weakned spring.

But this, as I newly intimated, is not the sole account, upon which the Air may in some sorts of Weather∣glasses impel up the water, and con∣tribute

to the condensation of the Air incumbent on the water. For in some circumstances (one or two of which we shall produce by and by) it may so happen, that the rest of the Air, that bears upon the wa∣ter to be rais'd, will not be so much refrigerated, as the included Air, that is to be condens'd, and conse∣quently the other Air will have a stronger spring, then this last men∣tion'd Air will retain, and therefore the former will have a greater pres∣sure, then the latter will be able to resist.

We shall not now examine, whe∣ther the spring of the Air depend up∣on the springy structure of each aeri∣al Corpuscle, as the spring of wool does upon the Texture of the particu∣lar hairs it consists of, or upon the agitation of some interfluent subtile matter, that in its passage through the aerial particles whirles each of them about, or upon both these causes together, or upon some other differ∣ing from either of them; but this seems probable enough, that as, when Air, being seal'd up in a Glass,

is afterwards well heated, though it acquire not any greater dimensions, as to sense, then it had before, yet it has its spring much increased by the Heat, as may appear, if the seal'd Tip be broken under water, by the eruption of Bubbles by the indeavour of the imprison'd Air to expand it self; so upon the refrigeration of the Air, so seal'd up, though the additi∣onal spring (if I may so speak) which the Heat gave it, will be lost upon the recess of that Heat, or as soon as the effect of that heat is distroy'd, yet there will remain in the included Air a considerable spring, and suffi∣cient to make it as well fill (at least as to sense) the cavity of the seal'd Glass, as it did, when its spring was stronger. And proportionably we may conceive, that though Cold, at least such as we meet with in this cli∣mate of ours, do make the spring of an included parcel of Air weaker, then it was before the refrigeration of that Air, yet it may not make it so much weaker, but that the aerial Corpuscles may be kept so far exten∣ded as not at all (or, scarce sensibly)

to quit the room they possest before, in case there be not contiguous to them any other Body, which by its pressure indeavours to thrust them inwards, and so make them desert part of that space: which clause I therefore add, because, that if the case propos'd do happen, 'tis obvious to conceive, that the weakned spring of the Air cannot retain so much force to resist an external pressure, as it would have, if the Cold had not de∣bilitated it, and consequently this cooled Air must yield and suffer it self to be condens'd, if it come to be expos'd to a pressure, to which it was but equal before its being weakned. And such in common Weather-glas∣ses is the pressure, that is constantly upon the surface of the water with∣out the Pipe, upon the account of the gravity of as much of the Air or At∣mosphaere, as comes to bear upon it.

Having thus explain'd our conje∣cture, we will now proceed to the Experiments we made to counte∣nance it, as we find them entred in our loose notes.

In one of which I find what fol∣lows.

We took a Viol capable of con∣taining five or six ounces of water, and having fill'd it almost half full with that Liquor, we inverted into it a Glass-pipe of about 10. Inches long, and much bigger then a large Swans Quill, seal'd at one end, and at the other fill'd top full with water, so that the open Orifice being immers'd under the Vessell'd water (of the Viol) there remain'd no Air at the Top of the Pipe: Then, as much of the Orifice of the Viols neck, as was not fill'd by the pipe, being carefully clos'd with Cement, that no Air could get in or out, the Viol was plac'd in snow and salt, till the ves∣sell'd water began to freez at the Top and Bottom: And according to our expectation we found, that notwith∣standing this great degree of infrige∣ration of the Air in the Viol, the wa∣ter in the Pipe did not at all descend. So that either the Air did not shrink by so great a Cold, or the water, whether to avoid a vacuum, or other∣wise, did not remove out of the Pipe to possess the place deserted by the refrigerated Air.

Afterwards we endeavoured to repeat the Experiment with the same Glasses, but having had occasion to be absent a little too long (though not very long) we found at our re∣turn the upper and seal'd part of the pipe beaten out, which we suppos'd to have been done by the intumes∣cence of the water in the Viol upon its glaciation.

Wherefore we fastned into the same Viol another Pipe some Inches longer then the former, and drawn very slender at the seal'd end, that it might easily be broken there, and having set the viol to freez as before, without finding the water to descend in the Pipe, we did with a forceps break off the slender seal'd end, that the outward Air might come to press upon the suspended water, and, by it, upon the cool'd Air in the viol, whereupon, as we expected, the water was swiftly depress'd, by our estimate, eight or ten Inches, but not so low by a pretty deal, as the surface of the water in the viol.

After this, by rarifying the Air in the Viol, and by blowing into it

through the pipe, the water was rais'd within about half an Inch of the Top of the Pipe, whose slender end being seal'd, the viol was again plac'd in snow and salt, but the spring of the Air at the Top, which was ra∣rifi'd before, was by refrigeration so weakned, that it was unable sensibly to depress the water; wherefore breaking off the Apex, as before, the upper Air immediately drove it down divers Inches.

Our last Tryal therefore, was to leave in the same Pipe about 3 ½ In∣ches of Air rarifi'd, as little as we could, and placing the viol in salt and snow, as before, we observ'd, that the Air in the Pipe did, upon the refrigeration of the Air in the vi∣ol, expand it self very little, though the water in the Viol were in part turned into Ice; but upon breaking off the slender seal'd end, the out∣ward Air presently depress'd the wa∣ter above two Inches beneath the last level, and by removing the Glass in∣to a warmer room, we found, that the water ascended a pretty deal above an Inch higher, then the same

uppermost level, whereby we pro∣bably concluded our Weather-glass to be stanch.

Thus much I find together in one place among my promiscuos collecti∣ons: but after this coming to have the conveniency of Glasses so shap'd as to be easily seal'd, I judg'd it fit to make use of some of them to keep ev'n the most suspicious from object∣ing, that I should also have made some Trials with Glasses, which be∣ing Hermetically seal'd, would be sure most accurately to hinder all im∣mediate Intercourse betwixt the in∣ternal and external Air. And I re∣member, that once we took a Glass, like the Bolthead of a common Wea∣ther-glass, save that the small End was drawn very slender, for the more easie breaking of the Apex: And into this Glass a convenient Quantity of water was powr'd, and then the Glass being seal'd up at the sharp end and inverted, the water fell down to that end, and possest its due space in the Pipe: Then the round end of the Glass, having a mixture of snow and salt appli'd,

about it, though the internal air must needs have been thereby much refri∣gerated (as will be readily granted, and may be gather'd from divers of the Experiments mention'd in these papers) yet we observ'd not the wa∣ter manifestly to rise. And though an attentive Eye should in such a Tri∣al discern some sensible intumescence in the water; yet that may well enough proceed from some little ex∣pansion of the Aerial particles, which we have elsewhere shewn to be usually latitant in Common wa∣ter, upon the diminution of the pres∣sure of the Air above the water, cau∣sed by weakning that air's spring by the Cold. But when we had, to complete the Experiment, broken the slender end of the Glass under water, the included air, becoming then contiguous to water, that had ob∣tain'd immediate Intercourse with that water, whose surface was every where prest by a pillar of the Exter∣nal air that leaned upon it, the water was by the gravity of that outward air hastily impell'd into the Cavity of the Pipe (the spring of whose air

was, as we said, weakned by the Cold) to the height, if I misremem∣ber not, of several Inches.

Another sort of Trials I remember we made after the following manner. We took Glass Bubbles (blown with a Lamp) some of about the bigness of a Nutmeg, and some much great∣er; each of these Bubbles we fur∣nished with a very slender stem (of∣ten no bigger then a Ravens Quill) which was usually divers, and some∣times many Inches long. Into this stem a drop or two of water being convey'd, might easily enough, by reason of the Lightness of so little Li∣quor, together with the slenderness* 1.14 of the Cavity (which permitted not the included air to penetrate the wa∣ter at the sides, but rather impel up the intire Body of it) be kept suspen∣ded, and so betray very small chan∣ges, (and much smaller then to be taken notice of by common Wea∣ther glasses) as to rarefaction and condensation in the air it lean'd upon. Now when in one of these Instru∣ments, if watching when the pendu∣lous water was somewhat near the

Top of the stem, we nimbly applied to the Orifice of that stem the flame of a Candle, we could by that Heat almost in a moment seal it up, by rea∣son of the thinness of the Glass, and the slenderness of the stem. And if then we plac'd the thus seal'd Glass in a mixture of snow and salt, how much soever the air within the cavity of the Ball must be, in all probabili∣ty, refrigerated by this operation, yet it would scarce sensibly, and not at all considerably shrink, as we ga∣ther'd from the pendulous waters re∣maining in the same place, or its fal∣ling at most but inconsiderably low∣er. But if then, with a pair of Scis∣sars or otherwise, we dexterously broke off the seal'd end of the stem, and thereby expos'd the internal re∣frigerated, to the pressure of the ex∣ternal air, the water immediately would be hastily thrust down, some∣times divers Inches below its former station, and sometimes quite into the cavity of the round end of the Glass. To which we shall add, that not only, when these Thermometers were seald, neither the usual degrees

of Cold, nor those of the Heat in the Ambient Air would at all considera∣bly depress or raise the pendulous water, which if the Glass were not seal'd, would, as we formerly no∣ted, shew it self wonderfully sensible of the mutations of the Air as to those two Qualities: But we sometimes purposely tri'd, that though upon the refrigeration of the sormerly rarified air in the Glass, the pendulous water were descending fast enough, yet if ev'n then we nimbly seal'd up the open Orifice of the stem (which may easily be done in a trice) the descent of the water would be presently stopt, and it would stay either just in, or very near the same part of the shank, wherein it chanc'd to be, when by sealing of the Glass it came to be fen∣ced from the pressure of the Atmo∣sphaere, and in that place it would continue till the seal'd end were bro∣ken off. For then in case the ambi∣ent air were as cool as it was, when the Glass was seal'd, the water would for the reason already given be fur∣ther deprest, according as the weak∣ned spring of the inward rarifi'd air

was more or less remote from an equality to the pressure of the ambi∣ent air.

Besides, for further Trial, we took a large Glass-egg with a long stem, which stem was purposely so bent, that it represented a glass-Sy∣phon, in whose shorter leg the glass was drawn very small, that it might be the more easily first seal'd, and then broken.

This done, we got in a convenient Quantity of water, which ascended to a pretty height in both the legs of the bent glass, after which the shor∣ter leg being nimbly seal'd, after the manner hereafter to be mention'd, there remained a pretty Quantity of air above the water in that shorter leg, which was purposely left there, that it might by its spring impel up the water in the longer leg upon the refrigeration of the Air included in* 1.15 that longer leg. All this being done, the whole glass was so plac'd in a con∣venient frame, that the oval part of it was supported by the frame, be∣neath which the bended shank of the Weather-glass did hang so, that a 〈1 page duplicate〉〈1 page duplicate〉

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mixture of Ice and Salt might be con∣veniently laid upon this frame to sur∣round and refrigerate the air inclu∣ded in the Egg, without much cool∣ing the air in the Cylindrical part of the Glass. The account that I find of this Trial in one of my notes, is this.

In the greater bent Egg, that was seal'd up with water, in both legs, upon the application of Ice and Salt to the Ellipsis at a convenient time, the water in the longer leg ascended a little, but not by our guess above a barley Corns length, if near so much, and about four Inches of air (as I re∣member) that were left in the shor∣ter leg, expanded it self (to sense) as much; but, as soon as I broke off the slender wire, wherein the shorter leg ended, the external air rushing in, made the water rise about two inches and a quarter in the longer leg, and then, there not being water enough, broke through it in many bubbles.

Thus far the note, to which I shall only add, that in this case the ascensi∣on of the water in the longer leg can∣not

be attributed to the weight of the air in the shorter leg, that being, I know not how much, too small to lift up so much water, but to the spring of that air. And also that we need not marvel, the Expansion of that 〈◊〉〈◊〉 should be so small, since some of the Experiments, 〈◊〉〈◊〉 to be related, will shew us, that the refrigeration of the air in such Trials (as that new∣ly 〈◊〉〈◊〉) does not weaken the spring of it any thing near so conside∣rably as one would expect. So that the air in the longer leg could yield but a very little to that in the shorter leg, especially since the smallness of this last nam'd portion of air made its spring to be more easily and consi∣derably weakned by a small Expansi∣on.

Thus far our Paradoxical Dis∣course, which contains divers particu∣lars, that, being added to the consi∣derations, whereunto we have (by way of Appendix) subjoyned It, might afford us several Reflections: But having dwelt too long on one subject already, we shall now con∣clude with This, upon the whole matter;

That there is somewhat or other in the Business of Weather-glasses, which (I fear) we do not yet suffici∣ently understand, and which yet, I hope, that by other Trials and more heedful Observations we shall discover.

Notes

• * 1.1

  Pag. 27, 28.
• * 1.2

  See the 18. of our New Phy∣sico-Me∣chanical Experi∣ments.
• * 1.3

  In the de∣fence a∣gainst Li∣nus Cap. 4
• * 1.4

  Dr. H. P.
• * 1.5

  An Inge∣nious man has propo∣sed another way of setling a Standard for Weather-glasses; namely, by ob∣serving the coldness, which is requisite to make distill'd water be∣gin to freez: But though the accurateness of this way may be as well as the other justly Question'd, and cannot often be put in pra∣ctise, even in Winter it self, nor without trouble; yet it may also be advantagiously made use of, when the cold happens to be great enough to freez water.
• * 1.6

  Dr. Wren. Dr. God∣dard.
• * 1.7

  Mr. Hook.
• * 1.8

  Defence against Linus Cap. the 5th.
• * 1.9

  Theatr. Chynic. volum. 6.
• * 1.10

  Vitrum optimè clausum ne quid exspir are posset, in loco ubi qui∣esceret statui, 〈◊〉〈◊〉 sine animi voluptate lice bat in Pleniluniis manifesta inclusi liquoris in∣crementa observare, in Novilu∣niis vero Decrementa, &c. They are the words of Paulus Casatus in his Terra Machinis mota, Pag. 143. But since the writing of these Praelimi∣nary Discourses, the Author of them having consulted by the means of some Ingenious friends, the learned Casatus, finds, that He never made nor saw the Experiment himself, but relates it upon the autho∣rity of a certain Dutchman, whose name he adds not, and who therefore may probably be the same Orthelius that is mention'd by the Author of these Praeliminary Discourses, who thinks it requisite to give the Reader this Adver∣tisement, because Casatus himself did not, as he should have done, intimate that he de iver'd this but upon ano∣thers credit.
• * 1.11

  L' Hydro∣graphie du P. Four∣nier, liv. 18. Cap. 12.
• * 1.12

  Defence against Linus Cap. 3.
• * 1.13

  Sect. 11. of the same 30. Chap.
• * 1.14

  See more concerning these Wea∣ther-glas∣ses in the first of these three Discourses.
• * 1.15

  See th〈…〉〈…〉gure〈…〉〈…〉 rest 〈…〉〈…〉