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to their pores. It is also observed, that urine pro* duceth no phosphorus, unless it be long exposed to the solar light. From all which it may be concluded, that bodies attract and fix the light; whence it should seem, as some have observed, that fire without burning is an ingredient in many things, as water without wetting.

194. Of this there cannot be a better proof, than the experiment of Monsieur Homberg, who made gold of mercury, by introducing light into its pores, but at such trouble and expence, that

prosit. By this junction of light and mercury, both bodies became fixed, and produced a third difserent from either, to wit, real gold. For the truth of which fact, I reser to the memoirs of the French academy of Sciences. From the foregoing experiment it appears, that gold is only a mass of mercury penetrated and cemented by the substance of light, the particles of those bodies attracting and fixing each other. This seems to have been not altogether unknown to former philosophers; Marsilius Ficinus the Platonist, in his commentary on the first book of the second Ennead of Plotinus, and others likewise before him, regarding mercury as the mother, and sulphur as the father of metals; and Plato himself in his Timæus describing gold, to be a dense fluid with a Ihining yellow light, which well suits a composition of light and mercury.

195. Fire or light mixeth with all bodies (a), even with water; witness the flashing lights in the sea, whose waves seem frequently ail on fire. Its operations are various according to its kind, quantity, and degree of vehemence. One

I suppose no body will


the experiment for


degree keeps water fluid, another turns it into elastic air (a). And air itself seems to be nothing else but vapours and exhalations, rendered elastic by fire. Nothing flames but oil: and sulphur with water, falt, and earth compose oil ; which sulphur is fire: therefore fire enclosed attracts fire, and causeth the bodies whose composition it enters to burn and blaze.

196. Fire collected in the focus of a glass operates in vacuo, and therefore is thought not to need air to support it. Calx of lead hath gone oft" with an explosion in vacuo, which Niewenty't and others take for a proof that fire can burn without air. But Mr. Hales attributes this effect to air enclosed in the red lead, and perhaps too in the receiver, which cannot be persectly exhausted. When common lead is put into the fire in order to make red-lead, a greater weight Of this comes out than was put in of common lead. Therefore the red-lead mould seem impregnated with fire. Mr. Hales thinks it is with air. The vast expansion of compound aqua fortis, Mr. Niewenty't will have to proceed from fire alone. Mr. Hales contends that air must necessarily cooperate. Though by Niewenty't's experiment it should seem, the phosphorus burns equally, with and without air.

197. Perhaps they who hold the opposite sides in this question, may be reconciled by observing that air is in reality nothing more than particles of wet and dry bodies volatilised, and rendered elastic by fire (b). Whatever therefore is done by air must be ascribed to fire, which fire is a subtile invisible thing, whose operation is not to be discerned but by means of some grosser body,

(a) 149. (b) 147, 150, 151.

M 2 which which serves not for a pabulum to nourish the fire, but for a vehicle to arrest and bring it into view. Which seems the sole use of oil, air, or any other thing, that vulgarly passeth for a pabulum or food of that element.

198. To explain this matter more clearly, it is to be observed, that fire, in order to become sensible, must have some subject to act upon. This being penetrated and agitated by fire affects us with light, heat, or some other sensible alteration. And this subject so wrought upon may be called culinary fire. In the focus of a burning glass exposed to the sun, there is real actual fire, though not discerned by the sense, till it hath somewhat to work on, and can shew it self in it's effects, heating, flaming, melting, and the like. Every ignited body is, in the foregoing sense, culinary fire. But it will not therefore follow, that it is convertible into pure elementary fire. This, for ought that appears, may be ingenerable and incorruptible by the course of nature. It may be fixed and imprisoned in a compound (a), and yet retain it's nature, though lost to sense, and though it return into the invisible elementary mass, upon the analysis of the compounded body: as is manisest in the solution of stone lime by water.

199. It should seem, therefore, that what is faid of air's being the pabulum of fire, or being converted into fire, ought to be understood only in this sense; to wit, that air being less gross than other bodies, is of a middle nature, and therefore more fit to receive the impressions of a fine ætherial fire (b), and impart them to other things. According to the antients, foul serveth for a vehicle to

(4 169, 192, 193. (b) 163.

. . in

intellect (aj, and light or fire for a vehicle to the soul; and, in like manner, air may be supposed a vehicle to fire, fixing it in some degree, and communicating it's effects to other bodies.

200. The pure invisible fire or æther doth permeate all bodies, even the hardest and most solid, as the diamond. This alone, therefore, cannot, as some learned men have supposed, be the cause of muscular motion, by a mere impulse of the nerves communicated from the brain to the membranes of the muscles, and thereby to the enclosed æther, whose expansive motion, being by that means increased, is thought to swell the muscles and cause a contraction of the fleshy fibres. This, it shou'd seem, the pure æther cannot do immediately, and of itself, because, supposing it's expansive motion to be increased, it must still pass through the membranes,- and consequently not swell them, inasmuch as æther is supposed freely to pervade the most solid bodies. It should seem therefore that this effect must be owing, not to pure æther, but to æther in some part fixed and arrested by the particles of air.

201. Although this æther be extremely elastic, yet, as it is sometimes found by experience to be attracted, imprisoned and detained in gross bodies (b)y so we may suppose it to be attracted, and its expansive force diminished, though it should not be quite fixed, by the loose particles of air, which combining and cohering therewith may bring it down, and qualify it for intercourse with grosser things. Pure fire may be faid to animate air, and air other things. Pure fire is invisible; therefore flame is not pure fire. Air is necessary both to lise and flame. And it is found by experi

ifi) 178. ft) la

ment, fenient, that air loseth in the lungs rhe power of feeding flame. Hence it is concluded, that the fame thing in air contributes both to lise and flame. Vital flame survives culinary flame in vacuo: therefore it requires less of that thing to sustain it.

202. What this may be, whether some certain proportion, or some peculiar parts of æther, is not easy to fay. But thus much seems plain, that whatever is ascribed to acid may be also ascribed to fire or æther. The particles of æther fly asun

to fir Ifaac Newton's doctrine, when united they must attract each other with the greatest force. Therefore they constitute the acid. For whatsoever strongly attracts and is attracted, may be called an acid, as fir Ifaac Newton informs us in his tract De acido. Hence it should seem, that the sulphur of Homberg and the acid of fir Ifaac are at bottom one and the fame thing, to wit, pure fire or æther.

'203. The vital flame or æthereal spirit, being attracted and imprisoned in grosser bodies, seemeth to be set free and carried off, by the superior attraction of a subtil and pure flame. Hence, perhaps it is, that lightening kills animals, and turns spirituous liquors vapid in an instant.

204. Hippocrates in his book concerning the Heart observeth, that the foul of man is not nourished by meats and drinks from the lower belly, but by a pure and luminous substance darting its rays, and distributing a non-natural nourishment, as he terms it, in like manner as that from the intestines is distributed to all parts of the body. This luminous non-natural nourishment, though it be secreted from the blood, is exprefly faid not to come from-the lower belly. It is plain, therefore,



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