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different juices from the common mass. The same 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 Auids 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 loft or escaping into air or æther, from effential oils and odoriferous waters, without any sensible diminution of the subject.

216. As different kinds of secreted light or fire produce different essences, virtues, or specific properties, so also 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 observed to set free and carry off chat 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 sheweth this to be true. For the fermented spirit of wine or other liquors produceth irregular motions, and subsequent de. pressions in the animal spirits. Whereas the luminous spirit lodged and detained in the native balfam 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

{a) 30, 31, 33, 35.

(6) 37, 43.

briate,

briate, and to produce a calm and steddy joy like the effect of good news, without that sinking of spirits which is a subsequent effect of all fermented 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-war serving as a vehicle to this spirit is both diuretic and diaphoretic, but seems to work it's principal effect by allisting the vis vitæ, as an alterative and cordial, enabling nature by an acCession of congenial spirit, to assimilate that which could not be asimulated by her proper force, and so to subdue the fomes morbi. "And this should feem in most cases the best and safest course. Great evacuations weaken nature as well as the disease. And it is to be feared that they who use salivations and copicus bleedings may, though they should recover of the distemper, in their whole life 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 fever in an inftant, giving ease and spirits to the patient. This I have often experienced, not without surprise, at seeing there falutary effects follow so im. mediately in a fever on taking a glass of tar-water. Such is the force of these active vivifying principles contained in this balsam.

220. Force

cs.

220. Force or power, strickly speaking, is the agent alone who imparts an equivocal force to the invisible elementary fire, or animal spirit (c) of the world, and this 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 Isaac 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 should feem, 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 and agitated by fire, but is not itself fire. And although it should in the third foregoing ac.ceptation, or vulgar sense pass for fire, yet it is not the pure elementary (6) fire in the second or philosophic sense, such as was understood by the sages 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 universe. Motion, and even power in an equivocal sense, may be found in this pure æthereal spirit, which ignites bodies, but is not itself the ignited body, being an instrument or medium (c) by which the real agent doth operate on grosser bodies. . (a) 153, 156, 157. (6) 190. (c) 160.

222. It

S, Dhable, that as an are not renter is cerseems probvarts of bodies: bodies. Ang

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222. It hath been shewed in Sir Isaac Newton's Optics, that light is not reflected by impinging 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 Itified 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 itself, the most folid 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 passing, and from mercury entering its pores so freely. And it is admitted that water, though impossible to be compressed, hath at least forty times more pores than solid parts. And as acid particles, joined with those of earth in certain proportions, are so closely united with them, as to be quite hid and loft to all appearance, as in mercurius dulcis and common sulphur, so also may we conceive the particles of light or fire to be absorbed and latent in grosser bodies.

223. It is the opinion of Sir Isaac Newton, that somewhat unknown remains in vacuo, when the air is exhausted. This unknown medium he calls æther. He suppofith it to be more subtil in its nature, and more swift in its motion, than light, freely 10 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 their respective parts towards their centers, every

body body endeavouring to pass from the denser parts of the medium towards the rarer.

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 different 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 lupposed to produce the fits of easy reflexion and transmission. Light by the vibrations of this medium is thought to communicate heat to bodies. Animal motion and sensation are also accounted for by the vibrating motions of this ætherial medium, propagated thro' the solid capillaments of 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 Sir Isaac 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, seems 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 Sir Isaac 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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