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and conftant would ceafe to be rules. There is therefore a conftancy in things, which is ftyled the courfe of nature (a). All the phsenomena in nature are produced by motion. There appears an uniform working in things great and fmall, by attracting and repelling forces. But the particular laws of attraction and repulfion are various. Nor are we concerned at all about the forces, neither can we know or meafure them otherwife than by their effects, that is to fay, the motions, which motions only, and not the forces, are indeed in the bodies (b). Bodies are moved to or from each other, and this is performed according to different laws. The natural or mechanic phjlofopher endeavours to difcover thofe laws by experiment and reafoning. But what is faid of forces refiding in bodies whether attracting or repelling, is to be regarded only as a mathematical hypothefis, and not as any thing really exifting in nature.
235. We are not therefore ferioufly to fuppofe with certain mechanic philolbphers, that the minute particles of bodies have real forces or powers by which they act on each other, to produce the various phsenomena in nature. • The minute corpufcles are impelled and directed, that is to Jay, moved to and from each other according to various rules or laws of motion. The laws of gravity, magnetifm, and electricity are divers. And it is not known, what other different rules or laws of motion might be eftabiifhed, by the author of nature. Some bodies approach together, others fly afunder, and perhaps fome others do neither. "When fak of tartar flows per deliquium, it is vifib'e that the particles of water floating in the air
(a) 160. (£} 155.
are moved towards the particles of falt, and joined with them. And when we behold vulgar falt not to flow per deliquium, may we not conclude that the fame law of nature and motion doth not obtain between it's particles and thofe of the floating vapours? A drop of water afiumes a round figure, becaufe it's parts are moved towards each other. But the particles of oil and vinegar have no fuch difpofition to unite. And when flies walk in water without wetting their feet, it is attributed to a repelling force or faculty in the fly's feet. But this is obfcure, though the phasnomenon be plain.
236. It is not improbable, and feems not unfupported by experiments, that, as in algebra, where pofitive quantities ceafe there negative begin, even fo in mechanics, where attracting forces ceafe there repelling forces begin; or (to exprefs it more properly) where bodies ceafe to be moved towards, they begin to be moved from each other. This Sir Ifaac Newton infers from the production of air and vapours, whofe particles fly afunder with fuch vehement force. We behold iron move towards the loadftone, ftraws towards amber, heavy bodies towards the earth. The laws of thefe motions are various. And when it is faid, that all the motions and changes in the great world arife from attraction; the elafticity of the air, the motion of water, the defcent of heavy, and the afcent of light bodies, being all afcribed to the fame principle; when from infenfible attractions of moft minute particles at the fmalleft difhnce, are derived cohefion, diflblution, coagulation, animal fecretion, fermentation, and all chemical operations; and when it is faid, that without fuch principles there never would have been any motion in the world, and without
the the continuance thereof all motion would cea/e. Iji all this we know or underftand no more, than that bodies are moved according to a certain order, and that they do not move themfelves.
237. So likewife, how to explain all thofe various motions and effects, by the denfity and chillicity of sether, feems incomprehenIible (a). For inftance, why fhould the acid particles draw thofe of water and repel each other? why fhould fome fills attract vapours in the air, and others not? why mould the particles of common fait repell each other, fo as not to fubfide in water? why ihould the moft repellent particles be the moft attractive upon contract? Or why fhould the repellent begin where the attractive faculty leaves off. Thefe, and numberlefs other effects feem inexplicable on mechanical principles, or otherwife than by recourfe to a mind or fpiritual agent (b)t Nor will it fuffice from prefent phsenomena and effects, through a chain of natural caufes, and fubordinate blind agents, to trace a divine intellect as the remote original caufe, that firft created the world, and then fet it a going. We cannot make even one fingle ftep in accounting for the phsenomena, without admitting the immediate prefence and immediate action of an incorporeal agent, who connects, moves, and difpofes all things, according to fuch rules, and for fuch purpofes as feem good to him.
238. It is an old opinion adopted by the moderns* that the elements and other natural bodies are changed each into other (c). Now, as the particles of different bodies are agitated by different forces,attracting and repelling, or, to fpeak more accurately, are moved by different laws, how can thefe forces
(a) 153, 162. (t) i$4> 220. (t) 148.
or laws be changed, and this change" accounted for by an elaftfc sether? Such a medium, diftinct from light or fire, feemeth not to be made out by any proof, nor to be of any ufe in explaining the phasnomena. But if there be any medium employed, as a fubordinate caufe or inftrument ift attraction, it would rather feem to be light (*); fined by an experiment of Mr. Boyle's, amber, that fhewed no fign of attraction in the fhade, being placed where the fun- beams fhone upon lt, immediately attracted light bodies. Befides, it hath been difcovered by fir Ifaac Newton, and an admirable difcovery it was, that light is an heterogeneous mediuni (// confifting of particles endued with original diftinct properties. And upon thefe, if I ma/ venture to give my conjectures, it feemeth probable the fpecific properties of bodies, and the force of fpecific medicines may depend. Different fides of the fame ray mall, one approach and the other recede from, the Iflandlc cryftal; can this be account^ ed for by the elafticity of a fine medium, or by ifhe' general laws of motion, or by any mechanical principles whatever? And if not, what mould hinder but there may be fpecific medicines, whofe opera* tion depends not upon mechanical principles, how much foever that notion hath been exploded of hit years?
239. Why may we not fuppofe certain idlofyni crafies, fympathies, ,oppofitions, in the folids of fluids or animal fpirit of a human body, with regard to thri fine infenfible parts of minerals or re* getables, impregnated by rays of light of different properties, not depending on the different fize, figure", number, folidity or weight of thofe particles;
nor on the general laws of motion, nor on the denfity or elafticity of a medium, but merely and altogether on the good pleafure of the Creator, in the original formation of things? From whence divers unaccountable and unforefeen motions may arife in the animal osconomy; from whence allb various peculiar and fpecific virtues may be conceived to arife, refiding in certain medicines, and not to be explained by mechanical principles. For although the general known laws of motion are to be deemed mechanical, yet peculiar motions of the infenfible parts, and peculiar properties depending thereon, are occult and fpecific.
240. The words attraction and repulfion may, in compliance with cuftom, be ufed where, accurately fpeaking, motion alone is meant. And in that fenfe it may be faid, that peculiar attractions or repulfions in the parts, are attended with fpecific properties in the wholes. The particles of light are vehemently moved to or from, retained or rejected by objects. Which is the fame thing as to fay with Sir- Ifaac Newton, that the particles of acids are endued with great attractive force (m), wherein their activity cpnfifts; whence fermentation anddiffblution ; and that the moft repellent are, upon contact, the moft attracting particles.
241. Gravity and fermentation are received for. two moft extenfive principles. From fermentation are derived the motion and warmth of the heart and Wood in animals, fubterraneous heat, fires, and earthquakes, meteors and changes in the atmofphere. And, that attracting and repelling forces operate in the nutrition and diflblution of animal and vegetable bodies, is the doctrine both of Hip