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Show ss FI Whether it be mechanically producible from other Bodies, by inducing fome Alteration in the Particles of it? Among the Modern Writers, Homberg, Boer haave, the Younger Lemery, and Dr. Graveande maintain the former, and the Englifh Authorschiefly maintain the latter. Mout. Homberg holds, That the Chymical Principle or Element Sulphur, which is fup- pos'd one of the Simple, Primary, Pre-exiftent Ingredients of all Natural Bodies, is Real Fire ; and of Confequence, Fire is coéval with all Bodies. Effai du Souffre Principe, Mem. de YAcad. Anno 1705. Dr. Gravefande proceeds much on the fame Principle: According to him, Fire enters the Compofition of all Bodies, is contain’d inall Bodies, and may be feparated or procured fromall Bodies, by rubbing them againft each other, and thus putting their Fire in Motion. And he adds, That Fire is by no means gene- rated by fuch Motion. cap. lei. Phyf: tom. 2. I. Mr. Lemery the Youngerafferts the abfolute and ingenerable Nature of Fire; and alfo extends it farther. Not contented to confine it as an Element to Bodies, he endeavours to WERT ay 2h OQ er ibeing hits .19 produc’d in it by a Motion great enough ftrongly to agitate the Parts of fo finalla Body as the Piece of Iron, without being able to have the like Effe@ upon fo much greater Maffes of Metal as the Hammer and Anvil: Tho’ if the Percuffions were often * and briskly renew’d, and the Hammer were fmall, this alfo might be heated: Whence * it is not neceflary that a Body it {elf fhould be hot to give Heat. “ If a large Nail be driven by a Hammer into a Plank of Wood, it will receive feveral Strokes on its Head ere it grows Hot: but whenit is once driven to the Head, few Strokes fuffice to give it a confiderable Heat. For while at every Blowwiththe Hammer the Nail enters farther into the Wood, the Motion produc’d is chiefly pro* greflive, and is of the whole Nail tending one Way : but when the Motion ceafes, the Impulfe given by the Stroke being unable to drive the Nail farther on, or break it, muft be fpent in making a various, vehement, andinteftine Commotionof the Parts “ among themfelves, wherein the Nature of Heatconfifts.” See Heat. That Fire is the real Caufe of all the Changes in Nature, will appear from the following thew, that it is “ Equablydiffus'd throughall ** Space ; is prefent in all Places ; in the void Confideration. * Space between Bodies, as well as the infenAll Bodies are either /olid or fluid; the * fible Interftices between their Parts? Mem, folid of themfelves are either commonly fupde PL . Anno 1413. pos'd to be unactive or motionleis ; the fluid laft Sentiment falls in with that of both move, and are mov’d. Boer hi f And all Solids are found to be fo much the Of the contrary Opinion is the Lord Bacon, more firm and contracted, as they have the who, in his Treatife de Forma Cal, di, deduces lefs Fire in them: This is evident in Tron, from a great Number of Particulars, That which whenheated, expands it felf into a much Heat in Bodies is no other than Motion; only greater Space than when it was cold; fo that a Motion foandfo circumftantiated to produce Heat in a Body, ; fo that, nothing is requird but to excite fuch Motion in the Parts of it. His Opinion is feconded by Mr. Boyle, in any folid and hard Body, by being freed from all Fire, would fink into a much lef Bulk, and its Parts would cohere more nearly, and with greater Force thanbefore, 4 _As to Fluids, theyall harden, fo as to be his Treatife of the Mechanical Origin of Heat vifible to the Eye upon the Abfence of Fire: atrine, with new Obfervations and Experi- will form it {elf into a folid Globe, and yet and Cold, where he maintains the fame Doments ; of which, two are as follow: Hefays, “ In the Produ@ion of Heat, there appears nothing on the Part either of the Agent or Patient but Motion, and its Natural Effects. When a Smith briskly hammers a fimall Piece of Tron, the Metal thereby becomes exceedingly hot ; yet there is nothing to make it fo, except the forcible Motion of the Hammer, imprefling a vehe- ment andvarioufly-determin‘d Agitation on as Water, by the Cold of a fevere Winter, even then contains a great deal of Fire; asappears evidently upon applying a Thermon to it, whichis capable of falling twenty Divifions lower before it arrive at the Point of the moft intenfe Cold: And henceit is that the Spirit of Wine is kept from freezing in the Thermometer, which would undergo the common Fate of other T hings, were there not abundantly more Fire in it, So the Air it felf expands by a greater Quantity of Fire, and condenfes byalefs ; but it ftill contains a large Quantity 0 where it is moft of all contraéted: “his is evident _ Word, with regard to fome other Bodies from the ftriking of a Flint againft aSteel, whichis follow’d by Sparks of Fire. compar'd with which, it was Cold befor, : Likewife, if this Hire could be taken from 2 Rant ently Hots becaufe this Agitation the dir, it would become folid and perfectly ¢ Ring, oe that of the Parts of our at reft, and by Confequence uncapable of Jeers. And in this Inftance, o ften-times Change the Hammer and Anvil continue * Cold after cour the Operatior a oe ‘ “ Fire Cfays Dr. Gravefande, in Elen the {mall Parts of the Iron 3 which being a : ri Body before, becomes, bythat faperae ee of its {mall Parts, Hot: it, In a more loofe Acceptation of the By aie ae 2 that the Heat : T as not communicated z Phy/’) naturally unites it felf with Bod zp And hence it is that a ither of thefe Implements, n as Heat, but "to the Fire grows Hot;Bodybro in whi : alfo : which Expanfion is not only obferv’d in very folid Bodies, but © in thofe whofe Parts do not cohere; in which Cafe they likewife acquire a great ing with thofe of the pure Hire, confticute pure Flame. This latter is improperlycall’d Fire, in that only a {mall Part ofit is real or pure Fire ; and Degree of E afticity, as is obferv’d in Air in ignated Bodies, that which flames, {mokes, &e. is not fimply Fire; whereas pure Fire, fach and Vapours. ive being thus acknowledg’d the Inftru- as is colleéted in a Burning-Glafs, yields no mental Caufe of all Motion; it remains, that Flame, Smoke, Afhes, or the like. Fire may be prefent in the greateft Abunit felf be moved. Nay, to move, muft be more natural and immediate to Fire than to dance, yet without any Heat: This is evident any other Body ; and hence fome have ven- in the Tops of the higheft Mountains, illumitured to make Motioneffential to Fire. But as nated by the Sun, where the Cold is always this is inconfiftent with the Notion of Matter, extremely pinching, and this even under the whichis defin’d to be inert and paffive, andas Equator, there being Mountains there which Fire is capable of being prov’d material ; we are perpetually cover’d with Snow, tho’ there ought rather to agree, that the Motion of Fire can be no Want of Fire. it {elf is derived from fome higher and MetaSoa large Burning-Glafs has no Effeét, the phyfical Caufe. A Property of Perpetual f{malleft Warmthcannot be felt in its Focus, in Mobility may indeed be fuperadded to the a Place where the Sun doesnot fhine, or when other Properties of Fire: but it has no natural the Sun is cover’d with a Cloud; but a Piece I fary Connection with them; nor can it be ofMetal maybe feen to melt the very Moment maintain’d with them otherwife than by fome the Sun emerges. strinfick Efficacy of a Superior Caufe, Fire may be in exceeding {mall Quantity, However, that it is by Motion that Fire and yet burn with great Violence: ‘Thus Spirit produces its Effects, is evident: And hence of Wine, when fet on fire, does not burn the the Action of Fire cannot make any Alteration Hands, and tho’ pour’d on a Piece of red-hot in the Elementary Subftance of Bodies: For it Iron, does not take Fire; fo that the Fire that is neceflary that what acts upon an Object, be isin fhould not appear very great, yet if it without that Object; z.¢. the Fire muft not meet with fome harder Bodywhile it is burnpenetrate the ElementaryParts, but only enter ing, the Particles of which Bodyit is capable the Pores and Interftices of Bodies: fo that it to agitate by the Attrition ofits own, it will does not feem capable of making thofe Tranf- yield a fierce Flame capable of burning a mutations whichSir J/aac N m#afcribesto it. harder Body than the Hand. In effect, as to all our Purpofes, it may From this it appears, that the Relation of perhaps be faid, That Fire is always in Mo- Heterogeneous Particles agitated by the Fire, tion, For inftance: ‘Take fix feveral Sorts has more effect in refpeét to Heat than the of Thermometers, and two Veflels of Water Actionof the Fire it felf: Nor need we be far with Sal Armo mix’d therein, and apply to feek for the Mechanical Reafon of this; for the Thermometers to it ; and the Confequence the Particles of Fire being all equal and {phewill be, that the Air being condenfed in them, rica], muft of themfelves be harmlefs ; but if t b e Spirit will defcendin all of ’em: Remove theycarrycertain SpicuJa, or any other Bodies t h1¢ Veffels of Water, and the Air growing along with them, they then become capable warmer, and fo rarefying, the Spirit will afcend of doing much Harm. in. So that the active Force in Air which produces {0 manyEffects, does really all arife from the Fire contain’din it, Again: As all Bodies plac’d in a very folid Air, do by degrees grow Cold, Motion8, Rigid, ec. e. though there be ftill fome Remains of Fire; and in Proportion, as thatis diminifhed, the Effet is accelerated : it fols, that Cold, a lef§ Degree of Heat, is Effect of a leffer A@tion of Fire. And fo, on arifes apparently from the fame Then as Fire can render the moft folid i€s, as Stones, Metals, €%c. fluid, (as ap"s very evident in large Burning-Glaffes, in vhich Gold jt {elf immediatelycalcines, and emits Pumes, 7, e. becomes fluid) fo the Want of F uld convert the moft fluid Bodies, rits of Wine, &c. into Solids. € is diftinguifh’d into two Kinds, call’d ¢ Fire, which is fuch as exifts nd alone is properly call’d Fire ; ary Fire, whichis rais’d and e former, and is that which ignited, combuftible and e Particles of which join- Hence, though the Flame of a Piece of Wood maygive a Senfe of Heat, and burn fuch things as are apply’d to it, it does not therefore neceffarily follow that there is any pure Fire init, fo that the Diftinétion of pure and common re is abfolutely neceffary : Tho’ this Diftin€tion has been overlook’d by moft or all the Authors before Dr. Boerbaave, who have written on Fire, which has led them into egregious Miftakes, infomuch, that moft of them have held, that the Flame ofa Piece of Woodis all Fire; which appears to be falfe from what has beenalreadyfaid, and alfo what follows. Elementary or pure Fire is of it felf imperceptible, and only difcovers it felf bycertain Effects that it produces in Bodies ; and thefe Effects are only to be learnt by the Changes which arife in Bodies: Thefe Effects are threenerit, Bodies, and Rave Motion. Y, Dilatation in all folid o# in all Fluids ; 3dly, The firft Effe& of Elem dies is Heat ; Heat avifes whe in fuch a manner, that the Meafure of Heat is always the Meafure of |