to their pores. It is alfo obferved, that urine produceth no phosphorus, unless it be long expofed to the folar light. From all which it may be concluded, that bodies attract and fix the light, whence it fhould feem, as fome have obferved, 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 Monfieur Homberg, who made gold of mercury, by introducing light into its pores, but at fuch trouble and expence, that I fuppofe no body will try the experiment for profit. By this junction of light and mercury, both bodies became fixed, and produced a third different from either, to wit, real gold. For the truth of which fact, I refer to the memoirs of the French academy of Sciences. From the foregoing experiment it appears, that gold is only a mafs of mercury penetrated and cemented by the fubftance of light, the particles of those bodies attracting and fixing each other. This feems to have been not altogether unknown to former philofophers; Marfilius Ficinus the Platonift, in his commentary on the first book of the fecond Ennead of Plotinus, and others likewife before him, regard. ing mercury as the mother, and fulphur as the father of metals; and Plato himself in his Timæus defcribing gold, to be a denfe fluid with a thining yellow light, which well fuits a compofition of light and mercury.

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

keeps water fluid, another turns it into elaftic air (a). And air itself feems to be nothing else but vapours and exhalations, rendered elaftic by fire. Nothing flames but oil: and fulphur with water, falt, and earth compofe oil; which fulphur is fire therefore fire enclosed attracts fire, and caufeth the bodies whofe compofition it enters to burn and blaze.

196. Fire collected in the focus of a glafs operates in vacuo, and therefore is thought not to need air to fupport it. Calx of lead hath gone off with an explofion 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 perfectly exhaufted. 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 fhould feem impregnated with fire, Mr. Hales thinks it is with air. The vaft expanfion of compound aqua fortis, Mr. Niewenty't will have to proceed from fire alone. Mr. Hales contends that air muft neceflarily co-operate. Though by Niewentyt's experiment it fhould feem, the phofphorus burns equally, with and without air.

197. Perhaps they who hold the oppofite fides in this question, may be reconciled by obferving that air is in reality nothing more than particles of wet and dry bodies volatilifed, and rendered elastic by fire (b). Whatever therefore is done by air must be ascribed to fire, which fire is a fubtile invifible thing, whofe operation is not to be dif cerned but by means of fome groffer body, which

(a) 149

(b) 147, 150, 151.

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ferves

ferves not for a pabulum to nourish the fire, but for a vehicle to arreft and bring it into view. Which feems the fole ufe 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 fenfible, must have some subject to act upon. This being penetrated and agitated by fire affects us with light, heat, or fome other fenfible alteration. And this fubject fo wrought upon may be called culinary fire. In the focus of a burning glass expofed to the fun, there is real actual fire, though not difcerned by the fenfe, till it hath fomewhat to work on, and can fhew itself in it's effects, heating, flaming, melting, and the like. Every ignited body is, in the foregoing fenfe, 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 imprifoned in a compound (a), and yet retain it's nature, though loft to fenfe, and though it return into the invifible elementary mafs, upon the analyfis of the compounded body: as is manifeft in the fo lution of ftone lime by water.

199. It should feem, 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 fenfe; to wit, that air being lefs grofs than other bodies, is of a middle nature, and therefore more fit to receive the impreffions of a fine ætherial fire (6), and impart them to other things. According to the antients, foul ferveth for a vehicle to

intellect (a), and light or fire for a vehicle to the foul; and, in like manner, air may be fuppofed a vehicle to fire, fixing it in fome degree, and communicating it's effects to other bodies.

200. The pure invifible fire or æther doth permeate all bodies, even the hardest and most folid, as the diamond. This alone, therefore, cannot, as fome learned men have fuppofed, be the cause of mufcular motion, by a mére impulfe of the nerves communicated from the brain to the membranes of the muscles, and thereby to the enclosed æther, whose expanfive motion, being by that means increased, is thought to fwell the muscles, and cause a contraction of the fleshy fibres. This, it fhould feem, the pure æther cannot do immediately, and of itself, because, fuppofing it's expanfive motion to be increased, it must ftill pass through the membranes, and confequently not fwell them, inásmuch as æther is fuppofed freely to pervade the moft folid bodies. It should feem therefore, that this effect must be owing, not to pure æther, but to æther in fome part fixed and arrested by the particles of air.

201. Although this æther be extremely elastic, yet, as it is fometimes found by experience to be attracted, imprisoned and detained in grofs bodies (b), fo we may fuppofe it to be attracted, and its expanfive 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 groffer things. Pure fire may be faid to animate air, and air other things. Pure fire is invifible; therefore flame is not pure fire. Air is neceffary both to life and flame. And it is found by experi

(a) 178.

(b) 169.

ment,

ment, that air lofeth in the lungs the power of feeding flame. Hence it is concluded, that the fame thing in air contributes both to life and flame. Vital flame furvives culinary flame in vacuo: therefore it requires lefs of that thing to sustain it.

202. What this may be, whether fome certain proportion, or some peculiar parts of æther, is not eafy to fay. But thus much feems plain, that whatever is afcribed to acid may be alfo afcribed to fire or æther. The particles of æther fly asunder with the greatest force: therefore, agreeably to Sir Ifaac Newton's doctrine, when united they muft attract each other with the greateft force. Therefore they conftitute the acid. For whatfoever

ftrongly attracts and is attracted, may be called an acid, as Sir Ifaac Newton informs us in his tract De acido. Hence it fhould feem, that the fulphur of Homberg, and the acid of Sir Ifaac are at bottom one and the fame thing, to wit, pure fire or æther.

203. The vital flame or ethereal spirit, being attracted and imprifoned in groffer bodies, feemeth to be fet free and carried off, by the fuperior attraction of a fubtil and pure flame. Hence, perhaps it is, that lightening kills animals, and turns fpirituous liquors vapid in an inftant.

204. Hippocrates in his book concerning the Heart obferveth, that the foul of man is not nouished by meats and drinks from the lower belly, but by a pure and luminous fubftance darting its tays, and diftributing a non-natural nourishment, as he terms it, in like manner as that from the inetines is diftributed to all parts of the body. This lantinous non-natural nourishment, though it be fecreted from the blood, is exprefly faid not to come from the lower belly. It is plain, therefore,

be

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