The remaining medical works of that famous and renowned physician Dr. Thomas Willis ...: Viz I. Of fermentation, II. Of feavours, III. Of urines, IV. Of the ascension of the bloud, V. Of musculary motion, VI. Of the anatomy of the brain, VII. Of the description and uses of the nerves, VIII. Of convulsive diseases : the first part, though last published, with large alphabetical tables for the whole, and an index ... : with eighteen copper plates / Englished by S.P. esq.

CHAP. X. Of the Nature of Fire: and by the way of Heat, and Light.

WE may almost pronounce the same thing of Fire, what the Philosophers of old did of the first Matter, to wit, that it was potentially every where, and in all things; but in none, in act. For among these sublunaries, Fire hath got no existence of its own Nature, or certain means of duration: It is produced almost in every Subject, but is retained long in none, but it suddenly vani∣sheth, and expires: yea unless some external accidents, oftentimes should concur for its production, I think it had not at all been in the world. Some have dreamed, that its Sphear is scituate under the Moon: but this was introduced only, for the making the Hypothesis of the four Elements: for such a thing seems consonant neither to Sense, nor Reason. That we may rightly search out the Nature of Fire, we must seek in what Bodies it is chiefly to be found, and how they are disposed; and then we may proceed to the unfolding its essence.

The Subjects most convenient both for the producing, and the maintaining of Fire, are of that kind, in which there are very many Particles of Sulphur, and but only a moderate portion of Water, Salt, and Earth: for these do hinder its inkindlings, and being plentifully poured on it, extinguish it being inkindled: Wherefore Bituminous, Fat, and Oyly things, quickly take flame: so also Chips, Straw, light and dry Wood: in the mean time, Metals, Minerals, the glebe of the Earth, Dung, wet Straw, and green Wood, are hardly, or not at all to be inkindled.

Secondly, we observe, that all the time Fire continues in the Subject, Sulphureous Particles fly away in heaps, and from the departure of these, the substance of the burning body is by degrees destroyed; in the mean time, very much of Salt and Earth, remains in the form of Ashes, after the burning.

There is a third observation, that when the Sulphureous Particles are wholly, or for the most part flown out of any Subject, the burning wholly ceases, and the form of fire is quite destroyed; nor can it be renewed in the remaining matter, wanting of Sulphur.

Fourthly, we will note, that somtimes some Bodies conceive a burning with∣out the advention of another fire, only by their own effervency, and by the in∣testine motion of the implanted Particles, and of their own accord are reduced into Ashes; as when wet Hay is layd up close, it first grows hot, then afterwards breaks forth into smoke and flame; or the Wheels and Axeltrees of Carts or Wains, being heated by too great agitation, are inkindled.

According to these positions, we may affirm, that the form of fire, wholly depends upon Sulphureous Particles, heaped up in any Subject, and breaking forth from it in heaps: and that fire is no other thing, than the motion and eruption, of these kind of Particles, impetuously stirred up. For Sulphur is of an exceeding fierce and un∣tamed Nature, whose little bodies, when (the yoak of the mixture being shook off) they begin to be thickly heaped together, diffuse themselves on every side like a torrent, break whatsoever obstacles are in the Subject, destroy whatever comes in opposition, or fling it down headlong. Nor do they only unlock their proper Subjects, but also lay open the gates and doors of any other Subject near, that they can reach to, and there incite to the like fury, all the consimilary Particles of Sulphur, and provoke them to an eruption: wherefore fire every where inkindles fire.

The Sulphureous Particles, while they, heaped together within the confines of their Subject, or on its Superficies, are agitated with a rapid motion, but are detained by the Embrace of other little Bodies, from a more free eruption, and more aggregated, constitute the form of fire; as is to be seen in burning Coals, or in glowing Iron; but when these sort of Particles fly away by heaps, from the same Subject, and bound together, they produce flame, which is only an heap, or rather a torrent, of the Par∣ticles of Sulphur flowing together, and conjunctly flying away: if Watery, Earthy,

and Saline Particles, are commixt with the Sulphureous breaking away, and are able to disjoyn and separate them, only smoke is excited; which afterwards, the Sulphu∣reous little Bodies more plentifully breathing forth themselves, and getting together, breaks forth into flame.

The inkindling of Fire happens very many ways. The first and most simple is, when from hard bodies struck one against another, but oftenest from a Flint struck against Steel, sparks of fire break forth; which being received in Tinder, made of a Linnen Cloth burnt to blackness, dilate themselves, and then a Match or Sulphurated thing being applyed, they cause the inkindling of a flame. Secondly, a fire often happens in dry Wood, and dry things, when by the too great attrition of the parts, and agitation, being made hot, they conceive an inkindling of their own accord. And thirdly, when Bodies abounding with Sulphur, as Hay, or Flax laid up wet, (of which mention was before made) grow hot of their own accord, and afterwards are inkindled. The fourth way, is the most usual, of introducing fire into any Sub∣ject, that it may be inkindled by another fire. We will a little more consider the se∣veral processes of these.

1. Hard Bodies struck one against another, shake forth little sparks of fire: as a Flint with Iron, or with a Flint; Indian Canes, the Fire Stone, and many other things. The reason of this is, because the Particles of Sulphur, which reside in the Superficies of a hard Body, if they are smitten by another hard Body, are not able to go back inward, (because in hard things there is not afforded any cession of the parts, from place to place) nor can the smitten Particles of Sulphur evaporate by degrees; but that by reason of the vehemency of the stroke, they are necessitated to break forth in heaps: Wherefore, when by this means, many of them are moved together, and are aggregated, they exhibit the apparition of fire, The sparks being received into the half-burnt Linnen or Tinder, are dilated into a greater fire, for that the Sulphure∣ous Particles, in such a Subject are eminent, and are brought as it were to the very top it self of eruption or breaking forth, wherefore by the least spark being moved or stirred up, a way being made they fly away.

The very same reason is for Wood being made hot, and afterwards fired, by too great attrition; by which means, the Axeltrees and Wheels of Chariots, or of Mills, are frequently fired: for the Sulphureous Particles, being by this means very much moved, are more thickly heaped together; and when, having as it were made an Army, they are able to remove, or strike away the rest, they presently break forth in Troops, and by their going away cause a burning.

In Hay or Dung laid up wet, the Particles of Sulphur very much abound; which having gotten the watery Latex for a Vehicle, run themselves into motion: but when for want of Ventilation, they cannot by little and little exhale, being straitned with∣in, and so brought into their exaltation, they are able to joyn more one to another, and mutually to incite themselves: then afterwards, being very much heaped toge∣ther, they unfold themselves more largely, and begin to break the Dens of the Sub∣ject, and so produce a burning. For it is to be observed in any Subject, when the Particles of Sulphur, being more slowly moved, fly away by degrees, neither heat, nor fire, but only a dryness, and leanness, succeed. But if they are more rapidly moved, than that they may be able to exhale leisurely, a heat is stirred up in the Sub∣ject: then if yet they are agitated more vehemently, and impetuously, and being more thickly agglomerated or heaped together, they break forth in heaps, a deflagra∣tion or flame follows the heat.

Fire being inkindled in any Subject, enters and inkindles, whatever Sulphureous thing is next it. For as Saline Menstrua, viz. Stygian waters, assault Metals, stuffed with Mineral Salt, and loosen their Saline Particles, as being of kin, from the mix∣ture; so also the Sulphureous Particles, being inkindled, break whatever Sulphure∣ous Particles are next them, and stir them up into the like motion of burning, with themselves.

Thus much concerning the nature and production of Fire: it remains that we next inquire into the effects of Fire, and also concerning its virtue and efficacy; to wit, what kind of Bodies it dissolves, and by what means; and also for what uses it serves for. The chief effects of Fire are Heat and Light; either of them are excited by emanations, or Effluvia, sent from an inkindled Body; but after a far different man∣ner: for truly, heat is most often produced at a distance, without light; also light, without any sensible heat.

Heat, forasmuch as it belongs to the sense of the touch, is conceived, when a cer∣tain passion is induced in the skin, or any other Organ of the touch, whereby the lit∣tle Fibres and Nervous parts are drawn asunder, moved into light Spasms or Convul∣sions, and somtimes (if the stroke be vehement) suffer a solution of the union. This is wont to be done, either by the bringing near of Fire, or of another Body made hot by Fire, or by some other means. For from either, the Sulphureous or warming Par∣ticles being excited, into a more rapid motion, and breaking forth by heaps spread abroad, which, as so many little darts, being thrust into our skin, or other Sensory of the touch, either by tickling gently, they bring to it a pleasing sense of heat; or by striking it more grievously, the troublesom sense of burning or scorch∣ing.

For the effect of heat, Fire is applyed to Bodies, either immediatly, and so either for the sake of Burning, Rosting or Boyling; or mediatly, viz. by the interjection of another Body. Bituminous things, Coals, and other things dug out of the Earth, also Vegetables and chiefly their Leaves, and Woods, are burnt, for heat, necessary for human uses, and for the producing, and conserving it. Stones are burnt for Lime; Vegetables for the preparing of Salts. The flesh of Animals is wont to be Rosted, and the Fruits of Vegetables; whereby they may become better food for men. For by Roasting, the superfluous humidity is evaporated, and the Sulphureous parts be∣ing stirred by the neighbouring heat, are placed in their vigor and exaltation, by which means, they afford a more grateful food to the Palat, and of better digesti∣on to the Stomach. By fire Metals are fused or melted, and most Minerals, where∣by they are either very much purified, or they are better formed into various fi∣gures by Smiths. Metals, and very many Minerals, also Salts, although they are not inflamed, and take a firing (because they abound with less Sulphur, than Salt) yet by a violent fire, they glow, and suffer a fusion; for that the Sulphureous Particles of the Fire, enter the Saline little Bodies, tho most compact, and dissociate them for the time; which however pulled one from another, presently the fire being exhaled, come again together, and are strictly united.

Secondly, when fire is mediatly administred, the Particles of the soluted Sulphur, and heaped together into fire, are dissociated, as when a cloud is dispersed into most little drops of Rain: wherefore they lay aside the form of fire; but tho dispersed, they easily pass through any impediment, and induce a sufficient strong heat to every Subject. By this means, fire is accommodated to very many uses, the chief of which, and the more accustomed, are, elixation or boyling, digestion, and distil∣lation.

In Boyling, the Particles of heat do pass into a watery Menstruum, and being united with its Particles, insinuate themselves deeply into the thing to be boyled: whose su∣perfluous humidities they carry away, digest the crudities, and carry them into a state of maturity. Boyling is instituted, either that the Liquor might be impregnated with the strength of the thing to be Boyled, or that the thing to be Boyled might be made tender, by the Liquor entring into it, and its Particles exalted: for Meats and all Eatable things, are rendered more grateful to the Palate by Boyling, even as well as by Rosting.

Digestion is very much used in Medicines, that their more slow Particles, may be carried to a greater activity; and somtimes, that they being too fierce might be fixed, and rendred more mild.

The most noble use of heat, or of mediat fire, is had in distillations; for the Particles of heat, do pull away some Particles of the Subject from others, (as it were by a Spagyric Anatomy) they resolve all Bodies, into their parts and princi∣ples. But the consideration of this thing, is too laborious and hard, to be inserted into this Tract.

As heat respects the Sensory of the Touch, so Light that of the Sight, and affects it so after a proper and peculiar manner, that nothing at all is discerned, besides the rays of light, direct, or reflected: for the various appearances of Colours, and the divers proportions of Bodies, and whatsoever we see with our Eyes, is only light; to wit, either proceeding directly, or strait from a lucid Body, or retorted from another Body, to the Eye, and so formed into various figures and colours. The consideration of Light, contains in it self, very many stupendious things, and is of deep speculation; which are not however proper for this place: It will suffice to take notice here, of a few things, concerning its Original, Motion, and Perceptibility.

Light is wont to be distinguished, either that it is Etherial, which flows from the Sun and Stars; or Elementary, which only proceeds from a fired Body, enkindled into a flame. It seems, that either is only flame enkindled in a greater dimension, and di∣lated into a most thin composition: for it appears to the sense, that from Sulphureous things being inflamed, (as for example) from a burning Candle, most thin Effluvia's, or most small divided little Bodies perpetually do spring; which being diffused into an Orb, and stretched forth into right Lines, as it were from the Centre to the Cir∣cumference, are still expanded on every side, in a great heap, and fill all the space within the Sphear of its activity, with a luminous ray. The Particles of the flame, which first fall away or depart from a lucid Body, are still driven forward by those following behind; and so these also by others; and so by a continued Series of Particles of the flames still succeeding, the beams of light are formed, and are thickly or closly dire∣cted into all parts.

The motion of these is exceeding swift; like streams of water, breaking forth with a force, they pass through the medium in the twinckling of an Eye, and, as those wa∣ters, if the motion be cut off near the Spring, most swiftly vanish. When the Rays of light come directly from a Luminous Body, they constitute a medium, only clear or lucid, without the appearance of any colour or image: when the same Rays meet with a solid Body, they do not pass rightly through it, but being either broken off, they are drowned or lost, or else they are reflected and leap back or rebound, as when a Ball being cast against a Wall, with a continued motion is struck back, upon other parts, according to the Angles of what stopped it. The Rays of light, reflected from other Bodies, being fallen into the Eye, represent the Images of visible things, and the varieties of colours. For as the superficies of visible Bodies are rough, and indued with little pores, and innumerable eminences, or risings up, hence the Rays of light, being most thickly impacted in them, and reflected from every part, according to all the ways of inclinations, and directions, as far as they go, do meet together round about, into very many tops of Cones, in which the beams proceeding from the whole object, as from a base, represent the image or similitude of the whole; and in these kind of images, the medium is every where planted, that wherever the Eye is placed, it be∣holds the image of the same thing, though not wholly after the same manner. But forasmuch, as the beams of the same light, being impacted in every Body, and vari∣ously refracted and distorted, about its rough and unequal superficies, from thence re∣flected as it were with turnings and windings into the Eye, they cause the diverse Phae∣nomena or appearances of colours, to appear. For colous, and images of things, do not exist in their own nature, but as it were spectrums, only from another place, change their apparitions by the Rays of light. When dark night brings thick dark∣ness to this inferior world, things are not perceived but by the Touch, and lose all their appearances: when the Sun revisits the Hemisphere, he brings forth a new Creation of things; and the whole Atmosphere is filled at once, with a sudden and manifold progeny, to wit, with infinite images of Bodies, and appearances of colours.

Therefore Light does not only illustrate the medium, that sight may be made, as some would have it; but it also creates the very objects of sight, and introduces them into the Penetralia or inward parts of the Eye, yea to the most inward recesses of the Brain. This doth the same Office for the Eye, as the Intellect doth for the Soul, to wit, it forms the Ideas or Images of Bodies, and renders them perceptible by the vi∣sive faculty. Light only is able to penetrate the Coats and Humors of the Eye, to move the little Fibres of the Optic Nerve, and to stir them up into an act of sensati∣on. Because the Images of things, being forged by the Rays of light, variously re∣flected, and meeting together on the tops of the Cones, are stayed within the Pupil, or dark spot of the Eye; they seem as objects in a close Chamber, admitted by a small hole, to be represented to the life: and the Concave or Convex Glasses, whereby the parallel beams are broken, or the inverse reduced or brought back, do egregiously supply the humors placed in the Eye, beyond the industry of human Art; by the help of which, the image of every object is painted, near the thin skin of the Eye, in its just figure and proportion: and then, from the motion, which this Image impresses on the little Fibres of the Optick Nerve, the act of sight is performed in the Brain. Thus much for Heat and Light, the Speculation of which, tho it may seem to be alto∣gether besides the Doctrine of Fermentation, yet forasmuch as by the motion of these kind of Sulphureous Particles, many other Physical Operations are also performed, a

brief mention of them ought not to have been overpass'd in this place. But before we shall lay aside quite the consideration of Fire, it will be here worth our while to inquire concerning some Subjects, as it were irregular, to wit, in which fire shews ad∣mirable virtues, and beyond its common manner: of this sort, are among Simples common Sulphur, and Sal Nitre; among Compounds, Gun-Powder, and Aurum Fulminans.

Concerning common Sulphur we may observe, that it quickly catches fire, heat it immediatly breaks forth into flame such (as nothing besides) that by its deflagration it puts out the Kitchen fire, that it sends forth a blueish flame, and whitens all ob∣jects with its Smoke or Soot. If you behold the matter of this Subject, or the parts of which the mixture is composed, its Spagyrical Analysis will exhibit, great plenty of pure Sulphur, a moderate quantity of Vitriolic Salt, a little of Spirit, Water and Earth. For when common Sulphur is dissolved, by the Spirit of Turpentine, the Sulphureous part impregnates the Menstruum, with a very deep Tincture, and the Sa∣line grows into Crystals: or when it is fired under a Bell, the Sulphur wholly burns, in the mean time the Salt being resolved, and having taken a Flux, is fixed about the sides of the Vessel, and so exhibits a Liquor, most like the Spirit of Vitriol, or rather the very same. To which add, if you mingle the Oyl of Vitriol, and Antimony to∣gether, and distill it in a Retort, a Yellow Sulphur, just like the common, will be Sublimed in the neck of the Retort.

I say therefore, because there are very many Particles of Sulphur in this Concrete, and that they lie loose and unbound in the mixture, (to wit, neither divided and se∣parated by the coming between of Earth, or Water, nor much bound together by Salt) therefore they are of a most prompt motion: wherefore by the least spark of fire, they break forth from the loose frame; and because very many run forth adoors toge∣ther, therefore not a naked fire, as in every Combustible thing besides, but first of all and immediatly a flame is inkindled. Its flame becomes blueish, because 'tis almost pure Sulphur that burns, not mixed with the Particles of Water and Earth, as it is in Wood or Straw. The very same thing happens to Spirit of Wine being inflamed. It extinguishes the Kitchen fire by reason of the little Bodies of Vitriolic Salt left be∣hind; and the same being eventilated with the flame and fume of Sulphur, gives a white colour to things; the like to which, the Effluvia's, exhaled from the Spirit of Vitriol, or Stygian Waters, do effect.

Concerning Sal Nitre, we will take notice, that it is not to be inkindled at all by it self; but to be melted by an intense fire: but being mixed with any Sulphureous things, it breaks forth into a flame, with a certain force and explosion: For being ad∣ded to common Sulphur, Antimony, or Tartar, it burns with a thundering noise; also if you put into melted Nitre, a burning Cole, or Wood, the flame is exploded round about, with a wind, so that the matter put in is flung up and down here and there, and often times flung clear out of the Vessel: by this kind of deflagration, what is Nitrous is consumed, the fixed Salt (which is Tartar) remains. When Nitre is distilled, Sand or Brick dust, is mixt with it in a double quantity at least; other∣wise the Nitre melting is not at all loosened into a vapor. In the distilling the vapor sent forth is very red; so that the Receptacle shines with a splendor, as if a flame were shut up within it: a sharp corrosive Liquor is stilled forth, which dissolves most Metals; also Gold.

These things being truly weighed, it seems that this mixture consists chiefly of aboundance of Salt, and a little Sulphur, but these not fixed and idle, but either ex∣alted, and ready for motion, and not without a certain resistance bound together: to wit, the Sulphureous little Bodies, being rouled about by the Saline, and as it were strictly pressed, still endeavour to get forth; but being strictly bound within, they are not able to rise forth by their own strength, or endeavour: but as soon as, by the mixture and inkindling of another Sulphureous Body, the Particles of the Salt are disjoyned, and their Prisons unlocked, presently the included little Bodies of Sulphur, as it were breaking Prison, fling themselves forth with violence, remove every Obsta∣cle, and strike the Air violently with a sudden eruption.

The reason why fire doth not inkindle Nitre, being inclosed in a Vessel, but only melts it, when in the mean time, any Sulphureous matter being fired, makes it to flame forth with a noise, is, because the little Bodies, which fall away from the fire, enter the Nitre, make it a little loose, and dissociate the concretion of the Salt, but not so loosen it, that a way may be made for the included Sulphur: but by the addition

of Sulphureous things, the Saline compaction is more dissolved, and is so far unlocked, that the Particles of the inclosed Sulphur fly away all together, and being freed from their straightness, do hugely stretch themselves abroad, and seek greedily an im∣mense space.

That there is plenty of Sulphur in Nitre, besides its deflagration, the Genesis of it sufficiently testifies; for it is begot chiefly in places, where the Sulphureous Excre∣ments of Animals abound. The use of it in agriculture argues the same thing, be∣cause the fertility of the Earth depends very much upon it: And to this also, the flaming colour, shining in the distilling may persuade.

From these premises, it will not be difficult, to unfold the nature of Gun-Powder, used in Warlike Instruments. For the sudden firing, and vehement explosion of it arise, for that those very many, and almost infinite Particles of Sulphur, which con∣stitute that fire-dilating Body, being fired, fly away together in a moment; all which breaking forth at once, a force being made, and desiring a most free and ample space, for their expansion, violently move the Air, and all obstacles, and so are exploded or thrust forth with a noise. There is in this mixture, common Sulphur put, because its Particles are loose, and ready for motion, and therefore apt to move a quick in∣kindling: there is added Charcoal dust, because in that also, the little Sulphureous Bodies (as is seen in Tinder, that is made of half burnt Linnen) are brought to the very top of eruption; and therefore these presently conceive an inkindling, and both these being fired, and opposed to the Nitre, they quickly loosen its frame, and send forth the Sulphureous Particles inclosed in it; which indeed break forth from their im∣pediments with a force, and as the blast of a Bellows, encrease the strength of the whole in firing. The Charcoal dust is added in a moderate quantity; though it a∣bounds with Terrestrial matter, yet by reason of the Sulphur being carried forth in it, it accelerates the deflagration of this mixture: For the Coal and Nitre being beaten together, is sooner fired, and with a greater explosion, than Nitre and Sulphur: But if the Coals be added to this Composition, (as they are wont to make it for Cannon and great Guns) in a greater quantity than it ought, and improportionate to the Nitre, the immediat firing is somwhat retarded, by reason of the interjection of the Earthy matter; and it happens, that the Sulphureous little Bodies therein, apt to be too hastily inkindled, are a little disjoyned, and so the substance of the infused powder, takes fire successively, and by parts, and not all at once.

The reason of Aurum Fulminans does not so manifestly appear: but it seems won∣derful, that the Calx of a Metal, otherways inviolable by fire, should be brought into a powder, one grane of which, if it be but lightly heated by fire, is exploded with so great a force, and yields such a noise, that is an hundred fold beyond Gun-powder. I know many deduce the cause of this, as in Gun-powder, from a Nitrous-Sulphure∣ous mixture: For they suppose the Nitre drawn forth from the solvent Menstruum, to joyn together with the Sulphur of the Metal, and so the powder from thence prepared, to get that fulminating force. But in truth, if this matter be better thought on, it will appear far otherways; because this golden thundring powder, is not at all in∣kindled, as preparations of Nitre with Sulphur: for if fire be put to it, it goes off only successively, by grains, nor as in Gun-powder, doth the whole fulminate at once; but being put into an Iron, Silver, or other convenient Vessel, and for some time heated, by a sudden fire, at length all the Particles being stirred together into motion, it is ex∣ploded with a mighty noise; but yet being explosed, it yields neither flame nor sparks neither is the Gold lost. For if this powder fulminates in an open Vessel; whatso∣ever is of the Gold, remains after the thundering, in the form of a purple powder; and may be gathered up. That the genuine cause of this may be extricated, there are some things to be observed, concerning its preparations, which will give no small light.

For the making of this powder, it is altogether requisite, that a solution of Gold be made with a Menstruum, impregnated with Sal Armoniack, or at least Analogical to it: for I have tryed it in vain with the Spirit of Nitre, Salt, with the Bezoartic Spirit, and some others. Then next it is requisite, that the Calx be precipitated with Oyl of Tartar; for if the same be brought into a powder, with Silver or Mercury being cast in, it loses its thundring force. Also, if the Liquor of the Tartar, be too pre∣cipitately poured in, that with the great heat, a repercussion of the thing soluted be made, it often loses its fulminating virtue: but a precipitation being leisurely made, the powder setling in the bottom is washed away, by the often pouring on of warm water, which, though it be most often washed and dryed, far exceeds the weight of the dissolved Gold.

According to these positions, in seems most likely, that whilst the Gold is dissol∣ved by an appropriate Menstruum for this business, some little Bodies of Sal Armoniack, (or some other resembling it) being greatly akin to the Gold, do most strictly co∣here with its Particles; which then by the Salt of Tartar leisurely in the precipitating infused, are more fixed, and more strictly tyed fast together: and then the explosion of this powder, or Solary Calx, is nothing else than a violent eruption of those kind of Salts, from the Cohesion or Embrace of the Gold. For when the powder pre∣pared after this manner; is brought to the fire, or is otherways made hot: the heat causes the Sal-Armoniack Particles, or others of the same nature affixed to the Solar, to dissociate; which notwithstanding, (when they hardly depart one from another) are not pulled asunder but by a strong and continued heat: yet after∣wards being pulled asunder with a certain force, by reason of the sudden and violent breaking off, they strike the Air impetuously, and so cause a most strong noise, for their bulk. But in the mean time, if the explosion be made under a Silver Spoon, you will see a separation made of either Particles, here the Solar of a Purple colour, there the Saline of an Ash colour. But that this powder doth not make a noise, unless it be leisurely precipitated with the Oyl of Tartar, it is because some Particles of the Salt of Tartar, being before bound together with the Sal-Armoniac Par∣ticles, do couple together, by which means all are more strongly combined: For the Salt of Tartar being pounded with the mixture of Nitre and Sulphur fixes their Par∣ticles for a time; that this Composition is not presently inkindled by heat; but after∣wards is exploded with a strong noise. And powder prepared after this manner seems to imitate the Nature of Aurum Fulminans: and it is probable that from other Minerals dissolved and precipitated by reason of the strict Cohesions of the Salt with the Metal∣lic matter, and their violent abruptions, thundering Calxes may be prepared. That truly the preparation of this chiefly depends on the Combination of the Salts, it ap∣pears, because, if in the Precipitating (as I have known it somtimes to have hapned) the Oyl of Tartar, being too hastily infused, the Complexion of the Salts is dissolved with the Metallic matter, the powder falls in small quantity to the bottom, and of a very Purple colour, whose grains are fragments of almost most pure Gold, and there∣fore they do not fulminate at all: afterwards in that precipitated Liquor, very many slender Crystals grow together, which are indeed the Salts, having suffered a Divorce from the Metal. Besides, That the Salt of Tartar, brings somthing to the prepara∣tion of this powder, it is a sign, because those things which take away the fulminating force from this, are of the same Nature, which chiefly work upon the Salt of Tartar; as a beating it together with common Sulphur, Spirit of Salt, Oyl of Vitriol, or of Sulphur: for these grow hot, and greedily desire to be joyned with the Salt of Tartar, and so they call it away from the Embraces of the Gold; by which means the Combination of the Salts, with the Particles of the Gold, is loosned, and therefore loses its Gun-like force. What is commonly said, that this pow∣der will be presently inkindled, or exploded, by a most light heat, or by shak∣ing it in an Iron Ladle, is nothing true, as appears to me, for I have often tryed it. Nor is it more worthy of belief, what is said, that this only forces downwards, and breaks the thickest hollow Pipes with its force; in the mean time, that it doth not move or shake any thing laid over it, because long since I made tryal after this man∣ner; two grains of this being laid in a Silver Spoon, I covered with a Doller, then a Candle being held under the Spoon, upon the explosion of the powder, there follow∣ed a great noise, and there was a little hollow made in the bottom of the Spoon, almost through, and the piece of mony was carried up with a force to the Cieling, where∣fore, when this Aurum Fulminans is explosed, its force is diffused round.

Altho vehement heat, and incited, and also the emission of Smoke and Soot, de∣pends for the most part upon fire; yet somtimes we perceive it to be produced in some subjects, and that in a very high degree, without its being actually inkindled. A most known instance of which thing is, quick Lime sprinkled with water: which also Sty∣gian waters shew, being mingled with Iron, the Butter of Antimony, and with the Salts of the stagma of Vegetables. The learned men, Gunter, Conringius, Hogelan∣dus, and almost all that have touched on the Doctrine of Fermentation, have deli∣vered the effects of this Nature, as especial examples of Fermentations, wherefore it will be worth our labour, to inquire somthing concerning each of them: but on this condition (which I also have observed in other disquisitions) that I willingly let a∣lone the opinion of others; for a Traveller had rather drink at the Fountains

themselves: I will then as briefly and succinctly as I can dispatch the busi∣ness.

Quick-Lime is made of the Lime Stone, also of many others (excepting only such which consist of a reddish and as it were sandy grain) being Calcined in a close Fur∣nace, for many days, with a reverberating fire: by this means, the frame of the mix∣ture is loosned, that it goes into a friable matter, or that may be crumbled, which by reason of the high astriction or binding Nature, in which it excels, serves most ex∣cellently for the making of Cements for Walls: This Calx or Lime being taken from the Furnace, reteins still the form of Stone, and seems cold to the touch, but water being poured thereon, it swells up, and grows wonderfully hot, sending forth smoak, that it burns all Bodies that are put into it, besides it falls of it self into a white dust: To which Particles this motion and heat ought to be ascribed, viz. whether to those implanted in the Lime stone, or to the others acquired by the fire, doth not easily appear: but that we may loose this knot, if we can, I have instituted this Analysis of quick Lime. I put about half a pound of it into a large Cucurbit, then water being poured thereon, I fitted the little Head with a capacious Receiver, by and by, within five mi∣nutes of an hour, the matter began to swell, and to grow very hot; then a smoak, and a breath being raised, all the Vessels became so hot, that I could scarce touch them with my hands. A clear water Distilled forth into the Receiver, about six Ounces, which was not sharp, but of a Styptic or Astringent sweetish tast; the remaining powder in the Cucurbit, I boiled with common water, and the Lye thereof made, I endeavoured to boil away with a gentle Fire; while it did evaporate, there ga∣thered together on the Superfices of the Liquor, a white and crusty little skin, also of a sweetish tast, and the same being taken away, presently a new one succeeded; the humor being at last wholly exhaled, there remained in the bottom nothing that was sharp or salt.

We may Collect from this, that this heat doth not proceed from the implanted Principles of the Lime stone, viz. either Saline or Sulphureous however moved with∣in themselves: for only a sweetish Salt was to be found in it, which was also Volatile; and it is a sign that there is not much Sulphur in the Limestone, because by a long Cal∣cination, the form of the mixture is not quite destroyed, nor its substance wholly broken: wherefore, it is very likely, that whilst these stones are burnt in the Fur∣nace, some Particles of Fire do strictly cleave to the Saline, and so reside in that mix∣ture, as it were strangers; which whilst they lie a sleep, and continue idle, and being separated one from another, by the coming between of Earth, although they are ve∣ry many, do not raise up heat; For all heat depends upon motion: but when water is poured to it, those fiery Particles, being thrust out of their Cells, flow together, and fly aways by heaps from that Inn; so breaking forth by Troops, they cause a very intense heat, and because diluted with water, only a smoak, and not an actual Fire.

It is a sign that little Bodies of fire, or fiery Particles, do stick a long while in mat∣ters Calcined, because Iron Instruments, according as those Particles are driven forth of their pores, more or less, leisurely or by heaps, become soft or hard; tough or brittle: moreover it is observed, that bricks or fresh Earthen Vessels being dipped in water, cause a certain hissing; also Tobacco Pipes, if one end be put into water, and the other brought near to the Ear, yield a certain sharp noise and rumbling: add to these, that fixed Salts being Calcined, or having suffered a Flux by the Fire, become far sharper; also Stygian waters, by reason of those kind of little Bodies involved therein, which afterwards leisurely evaporate, perpetually send forth sharp fumes: and when these are poured upon Saline Calxes, not only an Ebullition is raised, by reason of the disagreeing Particles of the Salts, which strike one another mutually, whereby they might be more strictly combined; but besides, heat and smoak succeed, which for the most part arise from the fiery Particles being shuck out of their Dens. But it is not easie to give a reason why quick Lime, and no other Concretes, retain so copiously those kind of fiery Particles, and yield a strong heat, water being poured on them.

Tis plain enough that when the Sulphureous Effluviums of Fire, (forasmuch as they are most penetrating) enter all Bodies whatsoever, brought near, affect them af∣ter divers manners: those which are more lax, and stuffed with active Principles, are destroyed wholly by burning, and because their substance decays, the fiery Particles, as Soldiers in a City spoiled by themselves, do not continue long in the ruined place,

but go farther, and move their Tents: but where the Concretion of the Subject is very compact, and that its Elements cannot be so pulled in pieces by the fire, that they rather grow stiff, as is seen in Metals, Glass, Bricks, and other things made hard, either by boiling, or fusion; the fiery Particles entered in, being re∣ceived in an incommodious Inn, presently go forth again; and therefore few are wont to stay in mixt things of this kind, or in things fused, or Calcined: but if fire be so applyed to the more hard Concretes, of which sort are most stones, and shelly Concretes, that the bond of the mixture be unlocked, some parts, viz. the Watery and Sulphureous are driven away, and so some spaces are made hollow, very fit for the receiving any stranger; in the mean time, that the frame of the matter be not wholly destroyed, but that it may continue its compacted and stony form, which flows not away together with its Particles, and ever threatens its ruin; in such a Subject, chiefly the Particles of fire, possessing the spaces of the parts flown away, copiously remain; and there cleaving close to the Saline little Bodies, being detained one from another, by the coming be∣tween of the earthy, lie quiet; which notwithstanding afterwards, being violent∣ly driven from those Inns, are able to produce by their eruption, an intense, and almost fiery heat: in the mean time those Saline little Bodies, are so loosned, by the long familiarity of the fiery, and by the embrace of one another, and of the strangers, that they become Volatile, and being diluted with water, for the greatest part evaporate with it; and the remaining Salt, because also Volatile, and having suffered almost a divorce from all the rest of the Principles, is both sweetish, and becomes desirous of Conjunction, and astringent; and therefore al∣so is of excellent use for plastring of Walls.

But that Stygian waters, being poured upon the Stagmas of fixed Salts, pro∣duce heat, and the same mixed with Iron, or the Butter of Antimony, stir up a mighty ardor, with a blackning smoak, the reason seems plain. As to the Stygian waters and fixed Salts, it may be said that both these Concretes are on∣ly Salts, having got divers states by the fire, and so either being very much stuffed with fiery Particles (which are the most minute atoms of Sulphur:) But they being confused together, do forthwith rush into mutual embraces, and be∣cause the Particles of either, are made unlike, therefore, whereby they may be more strictly united, there is made a great attrition of parts, and together an excussion of the fiery Particles, from whence the great ebullition, with a heat is excited: when the same Menstrua, are poured on Iron, or the Ice of Antimo, the Salts of either come together, and shake forth the fiery Particles, and also the Sulphureous Particles, before implanted in either Subject; which flying away in heaps, cause a smoak with a heat, but not a flame.