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disferent juices from the common mass. The fame holds also with regard to the capillary vessels (a) of vegetables, it being evident that through the fine strainers in the leaves and all over the body of the plant, there be juices or fluids of a particular kind drawn in, and separated from the common mass of air and light. And that the most elaborate spirit, whereon the character or distinguishing virtue and properties of the plant depend, is of a luminous (b) and volatile nature, being lost or escaping into air or aether, from essential oils and odoriserous waters, without any sensible diminution of the subject.

216. As different kinds of secreted light or sire produce different essences, virtues, or specific properties, so also different degrees of heat produce different effects. Thus one degree of heat keeps th$ blood from coagulating, and another degree coagulates the blood. Thus a more violent fire hath been observed to set 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 ætherial fiery spirit may be congenial and friendly to the spirits of a man, while another may be noxious. .

217. And experience fheweth this to be true. For the sermented spirit of wine or other liquors produceth irregular motions, and subsequent depressions in the animal spirits. Whereas the luminous spirit lodged and detained in the nativebak s.mi of pines and firs, is of a nature so mild and benign and proportioned to the human constitution, as to warm without heating, to cheer but not ine

(«) 30. 3«- 33. $J» - - (kj 371 43- .

briate, briate, and to produce a calm and stcddy joy like the efsect of good news, without that finking of spirits which is a subsequent efsect of all sermented cordials, I may add, without all other inconvenience, except that it may like any other medicine be taken in too great a quantity for a nice stomach.. In which case it may be right, to lessen the dose, or to take it only once in the four and twenty hours, empty, going to bed (when it is found to be least offensive) or even to suspend the taking of it for a time, till nature shall seem to crave it, and rejoice in it's benign and comfortable spirit.

218. Tar-water serving as a vehicle to this spirit is both diuretic and diaphoretic, but seems to work it's principal effect by assisting the visvitæ, as an alterative and cordial, enabling nature by an accession of congenial spirit, to assimilate that which could not be assimilated by her proper force, and so to subdue the somes morbi. And this should seem in most cases the best and fasest course. Great evacuations weaken nature as well as the disease; And it is to be seared that they who use falivations and copious bleedings may, though they should recover of the distemper, in their whole lise be never able to recover of the remedies.

219. It is true indeed, that . in chronical cases there is need of time to compleat a cure, and yet I have known this tar-water in disorders of the lungs and stomach to prove a very speedy remedy, and to allay the anxiety and heat of a sever in an instant, giving ease and spirits to the patient. This I have often experienced, not without surprise at seeing these falutary effects follow so imjnediately in a sever on taking a glass of tar-water. Such is the force of these active vivifying principles contained in this balfam.

:i .: 220. Force

*20. Force or power, strictly speaking, is Atf agent alone who imparts an equivocal force to the invisible elementary fire, or animal spirit (a) of the world, and the to the ignited body or visible flame, which produceth the sense of light and heat. In this chain the first and last links are allowed to be incorporeal: the two intermediate are corporeal, being capable of motion, rarefaction, gravity, and other qualities of bodies. It is fit to distinguish these things, in order to avoid ambiguity concerning the nature of fire.

221. Sir Ifaac Newton in his Optics, asks; Is not fire a body heated so hot as to emit light copiously? for what else, adds he, is a red hot iron than fire? Now it Ihould seem, that to define fire by heat, would be to explain a thing by it self.. A body heated so hot as to emit light is an ignited body, that is, hath fire in it, is penetrated did agitated by fire, but is not it self fire. And although it should in the third foregoing acceptation, or vulgar sense pass for fire, yet it is not the pure elementary (b) fire in the second or philosophic sense, such as was understood by the luges of antiquity, and such as is collected in the focus of a burning glass; much less is it the vis, -force,' or power of burning;, destroying, calcining, melting, vitrifying, and raising the perceptions -of light and heat. This is truly and really in the incorporeal agent, and not in the vital spirit of ,the iuniverse. Motion, and even power in an .equivocal sense, may be found in this pure æthe-re&\ spirit, which ignites bodies, but is not itself -the ignited body, being an instrument or medium fe) by Which the real agent doth operate on grosser bodies..

[a) 153,156, 157, (*) 190. {t) 160. t '- r" 222. It

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222. It hath- been fliewed in fir Ifaac New* ton's Optics, that Jight is not reflected by imping* ing on bodies, but by some other cause. And to him it seems probable, that as many rays as impinge on the solid parts of bodies, are not reflected but stifled and retained in the bodies. And it is certain, the great porosity of all known bodies affords room for much of this light or fire to be lodged therein. Gold it self the most solid of all metals, seems to have far more pores than solid parts, from water being pressed through it in the Florentine experiment, from magnetic effluvia pasting, and from mercury entering its pores fa freely. And it is admitted that water, though im* possible to be compressed, hath at least. forty times more pores than solid parts. And as acid particles, joined wich those of earth in certain proportions, are so closely united with them, as to be quite hid and lost to all appearance, as in mercuries dulcis and common sulphur, so also may we conceive the particles of light or fire to be absorbed and latent in grosser bodies. ti

223. It is the opinion of sir Ifaac Newton, that. somewhat unknown remains in vacuo, when the air is exhausted. This unknown medium he calls: æther. He sopposeth it to be more subtil in its; nature, and more swift in its motion, than light*' freely to pervade all bodies, and by its immense. elasticity to be expanded throughout all the heavens. Its density is supposed greater in free and. open spaces, than within the pores of compact bodies. And, in passing from the celestial bodies to great distances, it is supposed to grow denser' and denser continually and thereby cause those. great bodies to gravitate towards one another, and they- respective parts towards their centers, every. body endeavouring to pass from the denser parts ef the medium towards the rarer, i 224. The extreme minuteness of the parts of this medium and the velocity of their motion, together with its gravity, density, and elastic force, are thought to qualify it for being the cause of all the natural motions in the universe. To this cause are ascribed the gravity and cohesion of bodies. The refraction of light is also thought to proceed, from the ditserent density and elastic force of this ætherial medium in different places. The vibrations of this medium alternately concurring with, or obstructing the motions of the rays of light, are supposed to produce the fits of easy reflexion and transmission. Light by the vibrationsof this medium is thought to communicate heat to bodies. Animal motion and senfation are also accounted for by the vibrating motions of this ætherial medium, propagated through the solid capillamentsof the nerves. In a word, all the phænomena and properties of bodies, that were before attributed to attraction, upon later thoughts seem ascribed to this æther, together with the various attractions themselves.

225. But in the philosophy of fir Ifaac Newton, the fits (as they are called) of easy transmission and reflexion, seem 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 those of a more subtil medium, seem an uncouth explication. And gravity seems not an effect of the density and elasticity of æther, but rather to be produced by some other cause; which fir Ifaac himself insinuates to have been the opinion even of those ancients who took vacuum, atoms, and the gravity of atoms for the principles of their philosophy, tacitly attri

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