220. Force or power, ftrickly fpeak agent alone who imparts an equivocal invisible elementary fire, or animal the world, and this to the ignited bo flame, which produceth the fenfe heat. In this chain the first and last lowed to be incorporeal: the two int corporeal, being capable of motion, gravity, and other qualities of bod to diftinguish thefe things, in order biguity concerning the nature of fire. 221. Sir Ifaac Newton in his Opt not fire a body heated fo hot as copioufly? for what elfe, adds he, iron than fire? Now it fhould feem, fire by heat, would be to explain a felf. A body heated fo hot as to en ignited body, that is, hath fire in i ted and agitated by fire, but is And although it fhould in the third ceptation, or vulgar fenfe pafs for not the pure elementary (b) fire in philofophic fenfe, fuch as was under fages of antiquity, and fuch as is co focus of a burning glafs; much less force, or power of burning, destroyi melting, vitrifying, and raifing th of light and heat. This is truly and incorporeal agent, and not in the the univerfe. Motion, and even equivocal fenfe, may be found in th real fpirit, which ignites bodies, bu the ignited body, being an inftrumen (c) by which the real agent dot groffer bodies. 1 the ifible ate are faction, It is fit ɔid am fks; Is mit light ted in the (c) 160. 222. It hath been fhewed in Sir Ifaac Newton's Optics, that light is not reflected by impinging on bodies, but by fome other caufe. And to him it feems probable, that as many rays as impinge on the folid parts of bodies, are not reflected but ftifled and retained in the bodies. And it is certain, the great porofity of all known bodies affords room for much of this light or fire to be lodged therein. Gold itself, the most folid of all metals, feems to have far more pores than folid parts, from water being preffed through it in the Florentine experiment, from magnetic effluvia paffing, and from mercury entering its pores fo freely. And it is admitted that water, though impoffible to be compreffed, hath at least forty times more pores than folid parts. And as acid particles, joined with those of earth in certain proportions, are fo closely united with them, as to be quite hid and loft to all appearance, as in mercurius dulcis and common fulphur, fo alfo may we conceive the particles of light or fire to be abforbed and latent in groffer bodies. 223. It is the opinion of Sir Ifaac Newton, that fomewhat unknown remains in vacuo, when the air is exhausted. This unknown medium he calls æther. He fuppofeth it to be more fubtil in its nature, and more fwift in its motion, than light, freely to pervade all bodies, and by its immenfe elasticity to be expanded throughout all the heavens. Its denfity is fuppofed greater in free and open spaces, than within the pores of compact bodies. And, in paffing from the celeftial bodies to great distances, it is fuppofed to grow denfer and denfer continually; and thereby cause those great bodies to gravitate towards one another, and their refpective parts towards their centers, every - body body endeavouring to pafs from the d the medium towards the rarer. 224. The extreme minutenefs of th medium and the velocity of their mo with its gravity, denfity, and elaf thought to qualify it for being the c natural motions in the univerfe. To afcribed the gravity and cohefion of refraction of light is alfo thought to the different denfity and elaftic force rial medium in different places. The this medium alternately concurring ftructing the motions of the rays of pofed to produce the fits of eafy reflex miffion. Light by the vibrations of is thought to communicate heat to mal motion and fenfation are alfo ac the vibrating motions of this ætherial pagated thro' the folid capillaments In a word, all the phænomena and bodies, that were before attributed upon later thoughts feem afcribed together with the various attractions t 225. But in the philofophy of Sir the fits (as they are called) of eafy tr reflexion, feem as well accounted for excited in bodies by the rays of ligh fraction of light by the attraction of b plain the vibrations of light by those til medium, feems an uncouth expl gravity feems not an effect of the den city of æther, but rather to be prod other caufe; which Sir Ifaac himfel have been the opinion even of thof took vacuum, atoms, and the gravit the principles of their philofophy, 624 A f all the caufe are The es. eed from his æthe orations of h, or ob t, are fup n and tranf is 'medium' dies. Anianted for by edium, pro the nerves. roperties of attraction, this æther, emfelves. aac Newton, fmiffion and by vibrations and the redies. Toer f a more fub cation. And ity and claffi Iced by fome Finfinuates to e ancients who y of atoms for tacitly attri buting buting (as he well. obferves) gravity to fome other caufe diftinct from matter, from atoms, and confequently, from that homogeneous æther or elaftic fluid. The elafticity of which fluid is fuppofed to depend upon, to be defined and measured by it's denfity; and this by the quantity of matter in one particle, multiplied by the number of particles contained in a given space; and the quantity of matter in any one particle or body of a given fize to be determined by it's gravity. Should not therefore gravity feem the original property and first supposed? On the other hand, if force be confidered as prefcinded from gravity and matter, and as exifting only in points or centers, what can this amount to but an abftract fpiritual incorporeal force? 226. It doth not feem neceffary from the phanomena, to fuppofe any medium more active and fubtil than light or fire. Light being allowed to move at the rate of about ten millions of miles in a minute, what occafion is there to conceive another medium of ftill fmaller and more moveable parts. Light or fire feems the fame with æther.' So the ancients understood, and fo the Greek word implies. It pervades all things (a), is every where prefent. And this fame fubtil medium according to it's various quantities, motions, and determinations, fheweth itself in different effects or appearances, and is æther, light, or fire. 227. The particles of æther fly afunder with the greateft force, therefore when united they muft (according to the Newtonian doctrine) attract each other with the greateft force; therefore they are acids (b), or conftitute the acid; but this united with earthy parts maketh alkali, as Sir Ifaac teacheth in his tract De acido; alkali, as ap pears in cantharides and lixivial falts. cauftics are fire; therefore acid is f æther is fire; and if fire, light. therefore obliged to admit a new m from light, and of a finer and n fubftance, for the explication of which appear to be as well expl it. How can the denfity or elafti account for the rapid flight of a ray the fun, ftill fwifter as it goes far fan or how can it account for th tions and attractions of different b oyl and water, mercury and iron other bodies attract each other? o cle of light should repell on one fi on the other, as in the cafe of the ftal? To explain cohefion by hama counted ignotum per ignotius. Ar much fo to account for the gravity the elafticity of æther? ܐ܂ 228. It is one thing to arrive a of nature from a contemplation of na; and another to frame an h from thence deduce the phænomen fuppofed epicycles, and by them motions and appearances of the pl therefore be thought to have difcov true in fact and nature. And albei the premifes infer a conclufion, it w that we can argue reciprocally, conclufion infer the premises. fuppofing an elaftic fluid, whofe nute particles are equidiftant from of equal denfities and diameters, from another with a centrifugal for verfly as the diftance of the cent ting that from fuch fuppofitioni |