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different juices from the common mafs. The fame holds allb with regard to the capillary veflels (a) of vegetables, it being evident that through the fine ftrainers in the leaves and all over the body of the plant, there be juices or fluids of a particular kind drawn in, and feparated from the common mafs of air and light. And that the moft elaborate fpirit, whereon the character or diftinguifhing virtue and properties of the plant depend, is of a luminous (b) and volatile nature, being loft or elcaping into air or sether, from eflential oils and odoriferous waters, without any fenfible diminution of the fubjecl:.

216. As different kinds of fecreted light or fire produce different eflences, virtues, o; fpecific properties, fo alfo different degrees of heat produce different effects. Thus one degree of heat keeps the blood from coagulating, and another degree coagulates the blood. Thus a more violent fire hath been obferved to fet free and carry off that very light, which a more moderate fire had introduced and fixed in the calcined regulus of antimony. In like manner, one kind or quantity of this aetherial fiery fpirit may be congenial and friendly to the fpirits of a man, while another may be noxious.

217. And experience fhcweth this to be true. For the fermented fpirit of wine or other liquors produceth irregular motions, and fubfequent depreffions in the animal fpirits. Whereas the luminous fpirit lodged and detained in the native balfam of pines and firs, is of a nature fo mild and benign and proportioned to the human conftitution, as to warm without heating, to cheer but not ine

.(a) 30. 3'. 33> 35- •'(*) 37. 43

briate,

briate, and to produce a calm and fteddy joy like the effect of good news, without that finking of fpirio . which is a fubfequent effect of all fermented cordiajs. I may arid, without all other inconvenience, exctpt that it may, like any other medicine, be taken in too great a quantity for a nice ftomach. In which cafe it may be right, to IcfTen the dole, or to take it only once in the four and twenty hours, empty, going to bed (when it is found to be leaft offenfive) or even to fufpcnd the taking of it for a, time, till nature fhall feem to crave it, and rejoice in it's benign and comfortable fpirit.

218. Tar-war ferving as a vehicle to this fpirit is both diuretic and diaphoretic, but feems to work it's principal effect by afTifting the vis vitas, as an alterative and cordial, enabling nature by an accefilon of congenial fpirit, to aflimilate that which could not be affimulated by her proper force, and fo to fubdue the forms morbi. And this fhoukl fcem in moft cafes the bef t and ftfeft courfe. Great evacuations weaken nature as well as the difeafe. And it is to be feared that they who ufe falivations and copious bleedings may, though they mould recover of the diftemper, in their whole life be never able to recover of the remedies.

219. It is true indeed, that in chronical cafes there is need of time to compleat a cure, and yet I have known this tar-water in diforders of the lungs and ftomach to prove a very fpeedy remedy, and to allay the anxiety and heat of a fever in an inftant, giving eafe and fpirits to the patient. This I have often experienced, not without furprife, at feeing thele falutary effects follow fo immediately in a fever on taking a glafs of tar-water. Such is the force of thefe active vivifying principles contained in this ball am.

4 220. Force

220. Force or power, ftrickly fpeaking, is the agent alone who imparts an equivocal force to the invifible elementary fire, or animal fpirit (a] of the world, and this to the ignited body or vifible flame, which produceth the fenfe of light and heat. In this chain the firft and iaft links are allowed to be incorporeal: the two intermediate are corporeal, being capable of motion, rarefadlion, gravity, and other qualities of bodies. Jt is fit to diftinguifh thefe things, in order to avoid ambiguity concerning the nature of fire.

221. Sir Ifaac Newton in his Optics, afks; Is not fire a body heated fo hot as to emit light copioufly? for what elfe, adds he, is a red hot iron than fire? Now it mould feem, that to define fire by heat, would be to explain a thing by it felf. A body heated fo hot as to emit light is an ignited body, that is, hath fire in it, is penetrated and agitated by fire, but is not itfelf fire. And although it mould in the third foregoing acceptation, or vulgar fenfe pate for fire, yet it is not the pure elementary (£) fire in the fecond or philofophic fenfe, fuch as was underftood by the fages of antiquity, and fuch as is collected in the focus of a burning glafs; much lefs is it the vis, force, or power of burning, deftroying, calcining, melting, vitrifying, and raifing the perceptions of light and heat. This is truly and really in the incorporeal agent, and not in the vital fpirit of the univerfe. Motion, and even power in an equivocal fenfe, may be found in this pure sethereal fpirit, which ignites bodies, but is not itfelf the ignited body, being an inftrument or medium (r) by which the real agent doth operate on grofler bodies.

(a) 153, 156, 157, (b) 190. (t) 160.

222. It

222. It hath been mewed 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 flirted 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 itfelf, the mof t folid of all metals, feems to have far more pores than folid parts, from water being prefled through it in the Florentine experiment, from magnetic effluvia pafling, and from mercury entering its pores fo freely. And it is admitted that water, though impoflible to be comprefled, hath at leaf t forty times more pores than folid parts. And as acid particles, joined with thofe of earth in certain proportions, are fo clofely 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 grofler bodies.

223. It is the opinion of Sir Ifaac Newton, that fomewhat unknown remains in vacuo, when the air is exhaufted. This unknown medium he calls a?ther. He fuppofcth 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 elafticity to be expanded throughout all the heavens. Its denfity is fuppofed greater in free and open fpaces, than within the pores of compact bodies. And, in pafling from the celeftial bodies to great diftances, it is fuppofed to grow denfer and denfcr continually; and thereby caufe thofe great bodies to gravitate towards one another, and their re/pective parts towards their centers, every

body

C

body endeavouring to pafs from the denfer parts of the medium towards the rarer.

724. The extreme minutenefs of the parts of phis medium and the velocity of their motion, together with its gravity, denfity, and elaftic fofce, are thought to qualify it for being the caufe of all the natural motions in the univerfe. To this caufe are afcribed the gravity and cohefion of bodies. The refraction of light is allb thought to proceed from the different denfity and elaftic force of this stherial medium in different places. The vibrations of this medium alternately concurring with, or obftructing the motions of the rays of light, are fupptafed to produce the fits of eafy reflexion and tranfmiflion. Light by the vibrations of this medium is thought to communicate heat to bodies. Animal motion and fenfation are alfo accounted for by the vibrating motions of this setherial medium, propagated thro' the folid capillaments of the nerves. In a word, all the phsenomena and properties of bodies, that were before attributed to attraction, upon later thoughts feem alcribed to this aether, together with the various attractions themfelves.

225. But in th'e philofophy of Sir Ifaac Newton, the fits (as they are called) of eafy tranfmiffion and reflexion, feem as well accounted for by vibrations excited in bodies by the rays of light, and the refraction of light by the attraction of bodies. To explain the vibrations of light by thole of a more fubtil medium, feems an uncouth explication. And gravity feems not an effect of the denfity and elafticity of sether, but rather to be produced by fbme other caufe; which Sir Ifaac himfelf infinuates to have been die opinion even of thole ancients who took vacuum, atoms, and the gravity of atoms for the principles of their philofophy, tacitly attri

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