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taphysical rigor and truth, a passion or mere effect, yet, in physics, passeth for an action. And by this action all effects are supposed to be produced. Hence the various communications, determinations, accelerations of motion constitute the laws of nature.
162. The pure æther or invisible fire contains parts of different kinds, that are impressed with different forces, or subjected to different laws of motion, attraction, repulsion and expansion, and endued with divers distinct habitudes towards other bodies. These seem to constitute the many various qualities (e), virtues, Aavours, odours, and colours, which distinguish natural productions. The different modes of cohæsion, attraction, repulsion and motion, appear to be the source from whence the specific properties are derived, rather than different shapes or figures. This, as hath been already observed, seems confirmed by the experiment of fixed falts operating one way, notwithstanding the difference of their angles. The original particles productive of odours, Aavours, and other properties, as well as of colours, are, one may suspect, all contained and blended together in that universal and original seminary of pure elementary fire; from which they are diversly separated and attracted, by, the various subjects of the animal, vegetable, and mineral kingdoms; which thereby become classed into kinds, and endued with those distinct properties, which continue till their several forms, or specific proportions of fire return into the common mass.
163. As the soul acts immediately on pure fire, fo pure fire operates immediately on air. That is, the abrasions of all terrestrial things being rendered volatile and elastic by fire (f) and at the same time Jeflening the volatility and expansive force of the . Ved 37, 40, 44. (f) 149, 150, 152
fire, whose particles they attract and adhere to (k), there is produced a new fuid, more volatile than water or earth, and more fixed than fire. Therefore the virtues and operations imputed to air must be ultimately attributed to fire, as that which im. parts activity to air itself.
164. The element of æthereal fire or light seems to comprehend, in a mixed state, the feeds, the natural causes and forms (8) of all sublunary things. The grosser bodies separate, attract, and repel the several constituent particles of that heterogeneous element; which, being parted from the common mass, make distinct essences, producing and combining together such qualities and properties, asare peculiar to the several subjects, and thence often extracted in essential oils or odoriferous waters, from whence they exhale into the open air, and return into their original element.
165. Blue, red, yellow, and other colours, have been discovered by Sir Isaac Newton to depend on the parted rays or particles of light. And in like manner, a particular odour or flavour, seemeth to depend on peculiar particles of light or fire (b); as appears from heat's being necessary to all vegetation whatsoever, and from the extreme minuteness and volatility of those vegetable souls or forms, Aying off from the subjects without any sensible diminution of their weight. These particles, blended in one common ocean, should seem to conceal the distinct forms, but, parted and attracted by proper subjects, disclose or produce them. As the particles of light, which, when separated, form distinct colours, being blended are lost in one uniform appearance.
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, 166. Agreeably thereto, an æthereat substance or fire was supposed by Heraclitus to be the feed of the generation of all things, or that from which all things drew their original. The Stoics also taught, that all substance was originally fire, and should return to fire : that an active subcile fire was diffufed or expanded throughout the whole universe; the several parts whereof were produced, sustained, and held together by it's force. And it was the opinion of the Pythagoræans, as Laertius informs us, that heat or fire was the principle of Jife animating the whole system, and penetrating all the elements (a). The Platonists too, as well as the Pythagoræans, held fire to be the immediate natural agent, or animal spirit; to cherish, to warm, to heat, to enlighten, to vegetate, to produce the digestions, circulations, secretions, and organical motions in all living bodies, vegetable or animal, being effects of that element, which, as it actuates the macrocosm, so it animates the microcosm. In the Timæus of Plato, there is supposed something like a net of fire, and rays of fire. in a human body. Doth not this seem to mean the animal spirit, Aowing, or rather darting thro' che nerves ? :- 167. According to the Peripatetics, the form of heaven, or the fiery æthereal substance, contains the forms of all inferior beings (b). It may be faid co teem with forms, and impart them to subjects fitted to receive them. The vital force thereof in the Peripatetic sense is vital to all, but diverfly received according to the diversity of the subjects. So all colours are virtually contained in the light ; but their actual distinctions of blue, red, yellow, and the rest, depend on the difference of the objects which it illustrates. Aristotle in the book De (a) 152, 153. fb) 43.
'mundo, fupposeth a certain fifth efsence, an æthe real nature unchangeable and impassive ; and next in order a subtile, Aaming substance, lighted up, or set on fire by that æthereal and divine nature. He supposeth, indeed, that God is in heaven, but that his power, or a force derived from him, doth actuate and pervade the universe.
168. If we may credit Plutarch, Empedocles thought æther or heat to be Jupiter. Æther by the ancient philosophers was used to signify pro. miscuously sometimes fire and sometimes air. For they distinguished two sorts of air. Plato in the Timæus speaking of air, faith there are two kinds, the one more fine and subtile, called æther; the other more gross and replete with vapours. This æcher or purer medium, seems to have been the air or principle, from which all things according to Anaximenes derived their birth, and into which they were back again resolved at their death. Hippocrates, in his treatise De diæta, speakech of a fire pure and invisible; and this fire, according to him, is that which, stirring and giving movement to all things, causes them to appear, or, as he styles it, come into evidence, that is to exist, every one in it's time, and according to its
. 169. This pure fire, æther, or substance of light, was accounted in itself invisible and imperceptible to all our senses, being perceived only by its effects, such as heat, Aame, and rarefaction, To which we may add, that the moderns pretend farther to have perceived it by weight, inasmuch as the aromatic oils which most abound with fire, as being the most readily and vehemently enflamed, are above all others the heaviest. And by an experiment of Mr. Homberg's, four ounces of regu. Lus of antimony, being calcined by a burning glass
for an hour together, were found to have imbibed and fixed seven drams of the substance of light.
170. Such is the rarefying and expansive force of this element, as to produce in an instant of time the greatest and most itupendous effects: a suffici. ent'proof, not only of the power of fire, but also of the wisdom with which it is managed, and withheld from bursting forth every moment to the utter ravage and destruction of all things. And it is very remarkable, that this fame element, so fierce and destructive, should yet be so variously tempered and applied, as to be withal the falutary warmth, the genial, cherishing, and vital flame of all living creatures. It is not therefore to be wondered that Aristotle thought, the heat of a living body to be fomewhat divine and celestial, derived from that pure æther to which he supposed the incorporeal deity (zwersor sidos) to be immediately united, or on which he supposed it immediately to act.
171. The Platonists held their intellect resided in foul, and soul in an æthereal vehicle. And that as the soul was a middle nature reconciling intellect with æther; fo æther was another middle nature, which reconciled and connected the soul with groffer bodies (d). Galen likewise taught, that, admitting the foul to be incorporeal, it hath for it's immediate tegument or vehicle a body of æther or fire, by the intervention whereof it moveth other bodies and is mutually affected by them. This interior clothing was supposed to remain upon the soul, not only after death, but after the most perfect purgation, which in length of time according to the followers of Plato and Pythagoras cleansed the foul,
purumque reliquit Æthereum sensum atque auraï simplicis ignem.
(?) 152, 154.