Page:Cyclopaedia, Chambers - Volume 1.djvu/212

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ATT

Particles of all Bodies, mutually tend towards each other.— Or, more juftly, Attraction is the efted of fuch Power, whereby every Particle of Matter tends towards every other Particle. See Matter and Particle-

Attraction* its Laws, Phenomena, &e make the great Hinge of Sir ljaac Newton's Pbilolophy. See Newtonian Pbito- fophy.

It muft be obferved, that though the great Author makes ufe of the Word Attraction-, in common with the School Philofo- phers ; yet he very ftudioufly diftinguiflies between the Ideas.— i he antient Attraction was a kind or Quality, inherent in certain Bodies themfelves ,- and arifing from tneir particular or fpecific Forms. See Quality and Form.

The Newtonian Attraction is a more indefinite Principle ; deno- ting not any particular Kind or Manner of Adtion, nor the phy- fieal Caufe of fuch Action ; but only a Tendency in the Gene- ral, a Conatus accedendi\ to whatever Caufe, phyficalor metaphy- seal, fuch effect be owing ; whether to a Power inherent in the Bodies themfelves, or to the Impulfe of an external Agent.

Accordingly, the great Author, in his Philof. Nat. Prin. Math. Notes, " that he ufes the Words Attraction, Impulfe, and Pro- « penfion, to the Centre, indifferently; and cautions the Reader " not to imagine that by Attraction he expreffes the Modus of « the Action, or the efficient Caufe thereof; as if there were tr any proper Powers in the Centres, which in reality are only I. p. 5.— So, he " confiders centripetal Po wees "as Attraffions; te though, phylically fpeakirig, it were perhaps more juft to call " them Impulfes." lb. p. 147. He adds, Cc that what he calls « Attraction may pofiibly te effected by Impulfe, though not a " common or corporeal Impulfe ; or in fome other Manner un- « known to us." Optic, p. 322.
 * mathematical Points,- or, as if Centres could attract. Lib.

Attraction, if coniider'd as a Quality arifing from the fpecific Forms of Bodies, ought, together widi Sympathy, Antipathy, and the whole Tribe of occult Qualities to be exploded. (See Occult Quality.) But when we have fet thefe afide, there will remain innumerable Phenomena of Nature, and particularly the Gravity or Weight of Bodies, or their Tendency to a Centre, which argue a Principle of Action feemingly diftinct from Im- pulfe; where, at leaft, there is nofenfible ImpuHion concein'd. Nay, what is more, this Action, in feme refpedts, differs from all Impullion we know of; Impulfe being always found to aft in Proportion to the Surfaces of Bodies; whereas Gravity acts ac- cording to their folic! Content, and confequently muft arife from fome Caufe that penetrates or pervades the whole Subftance thereof— This unknown Principle, (unknown we mean in re- fpect of its Caufe, for its Phenomena and Effects are moft no- torious) with all the Species and Modification/ thereof, we call Attraction ; which is a general Name, under which all mutual Tendencies, where no phyfieal Impulfe appears, and which can- not, therefore, be accounted for from any known Laws of Na- ture, may be ranged.

And hence arife divers Kinds of Attractions ; as, Gravity, Magnetif>;>, Electricity, &c. which are fo many different Princi- ples, acting by different Laws; and only agreeing in this, that we do not lee any phyfieal Caufes thereof; but that, as to our Senfes, they may really arife from fome Power or Efficacy in fuch Bodies, whereby they arc enabled to act, even upon diiiant Bodies; though our Reafon abfolutely difallows of any fuch Action.

Attraction may be divided, withrefpect to the Law it ob- ferves, into two Kinds. — 1° That "which extends to a fenfble Di- jtance— Such are the Attraction of Gravity, found in all Bodies; and the Attractions of Magnetijm and Electricity, found in parti- cular Bodies. — The feveral Laivs and Phenomena of each, fee un- der their refpective Articles, Gravity, Magnetism, and Elec- tricity.

The Attraction of Gravity, calfd alio among Mathematicians, the Centripetal Force, is one of the grcateft and moft univerfal Principles in ali Nature. — We Ice and feel it operate on Bodies near the Earth, (See Weight.) and find, by Obfervation, that the fame Power, (i. e. a Power which acts in the fame Manner, and by the fame Rules; viz. always proportionally to the Quan- tises of Matter, and as the Squares of the Diftanccs) does alfo obtain in the Moon, and the other Planers, primary and fecon- dary as well as the Comets : And even that this is the very Power whereby they are all retained in their Orbits, &c. And hence, as Gravity is found in ail the Bodies which come under our Obferva- tion, it is eafily infer'd, by one of the fettled Rules of philofo- fhizing, that it obtains in all others; and as it is found to be as the Quantity of Matter in each Body, it muft be in every Particle thereof; and hence every Particle in Nature is proved to attract every other Particle, <&c. See the T>emonf ration hereof laid doiun at large, -with the Application of the Principle to the Celefiial Motions, wider the Articles, Newtonian Phitofophy, Sun, Moon, Pla- net, Comet, Satellite, Centripetal, Centrifugal, &c. From this Attraction arifes all the Motion, and confequently all the Mutation, in the great World.— By this, heavy Bodies de- fcend, and light ones afcend ; by this Projectiles are directed, Vapours and Exhalations rife, and Rains, &c. fall. By this Ri- vers glide, the Air preffes, the Ocean fwells, &c. See Moti-

on, Descent, Ascent, Projectile, Vapour, Rain, Ri- ver, Tide, Air, Atmosphere, &c.

In effect, the Motions arifing from this Principle make the Subject of that extenfive Branch of Matbemaricks, call'd Me- chamcks, or Staticks, with the Parts or Appendages thereof, Hy- drofatir.ks, Pneumatich, &c. See Mechantcks, Staticks, Hydrostaticks, Pneumaticks. See alfo Mathematicks, Philosophy, <&c.

a. That which does not extend to finable Diftanccs.— Such is found to obtain in the minute Particles whereof Bodies are compofed, which attract each other at, or extremely near, the Point of Contact; with a Force much fuperiorto that of Gravity; but which at any Diftance therefrom decreafes much fatter than the Power of Gravity.— This Power, a late ingenious Author chufes to call the attraction of Cohef on ; as being that whereby the Atoms or infenlible Particles of Bodies are united into fenfi- ble Mattes. See Cohesion, Atom, Particle, &c.

This latter Kind 0$ Attraction owns Sir tfaat Newton for its Dif- coverer; as the former does, its Improver. — The Laws of Mo- tion, PercufiiOn, &c. in fenlible Bodies under various Circum- ftances, as falling, projected, <&c. as afcertain'd by the later Pbi- lofophers, do not reach to thofe more remote, inteltine Motions of the component Particles of the fameBudies, whereon the Changes of the Texture, Colour, Properties, &c of Bodies depend : So than our Philofophy, if only founded on the Principle of Gravi- tation, and carried fo far as that would lead us, wouti neceftarily be very deficient. See Light, Colour, &c.

But, beiide the common Laws of fenlible Mafles, the minute Parts they are compoied of, are found fubject to lome others, which have been but lately taken notice of, and are yet very im- perfectly known. Sir Ifaac Newton, to whofe happy Penetrati- on we owe the hint, contents himfejf to eftablilh, that there arc fuch Motions in the minima nature, and that they How from cer- tain Powers or Forces, not reducible to any of thofe in the great World.— In virtue of thefe Powers, he fhews, " that the lmall ' f Particles act on one another even at a Diftance ; and that ma- " ny of the Phenomena of Nature are the Refult thereof! " Senlible Bodies, we have already obferved, act on one ano- cC Courfe of Nature, it appears highly probable that there may " form and confiftcntv/ithberfelf. — Thofe juft mentioned, reach « to feniible Diftances, and fo have been obferved by vulgar tc Eyes : But there may be others, which reach to fuch lmall Di- cC ftances, as have hitherto efcaped Obfervation ; and 'tis proba- " ble Electricity may reach to fuch Diftances, even without be- tC rag excited by Friction."
 * £ ther divers ways ; and as we thus perceive the Tenor and
 * be other Powers of the like Kind; Nature being very uni-

The great Author juft mentioned, proceeds to confirm the Reality of thefe Sufpicions from a great Number of Phenome- na and Experiments, which plainly argue fuch Powers and Acti- ons between the Particles, e. gr. of Saks, and Water, Oil of Vitriol and Water, Aqua Fortis and Iron, Spirit of Vitriol and Sak-petre. — He' alio fhews, that thefe Powers, &c, are unequally ftrong between different Bodies ; ftronger, e.gr. between the Par- ticles of Salt of Tartar, and thofe or Aqua Fortis, than thofe of Silver; between Aqua Fortis and Lapis Calminaris, than Iron; between Iron than Copper, Copper than Silver, or M.i- cury. So Spirit of Vitriol acts on W ater, but more on Iron or Copper, &c.

The other Experiments which countenance the Exiftcnce of fuch Principle of Attraction in the Particles of Matter are innu- merable; many of them the Reader will find enumerated under the Articles Matter, Acid, Salt, Menstruum, &c.

Thefe Actions, in virtue whereof the Particles of the Bodies above mentioned tend toward each other, the Author calls by a general, indefinite Name, Attraction* which is equally applica- ble to all Actions, whereby diftant Bodies tend towards one a- norher, whether by ImpuUe, or by any other more latent Power : And from hence accounts for an Infinity of Phenomena, other- wife inexplicable, to which the Principle of Gravity is ineffici- ent.— Such are Cohcfion, Diffolution, Coagulation, Cryftalliza- tion, the Afcerit of Fluids in Capillary Tubes, Animal Secreti- on, Fluidity, Fixity, Fermentation, &c. See the refpective Ar- ticles, Cohesion, Dissolution, Crystallization, As- cent, Secretion, Sphericity, Fixity, Fermentation,

" Thus," adds our immortal Author, « will Nature be found " very conformable to herfelf, and very fimplc; performing all « the great Motions of the heavenly Bodies, by the Attraction <f of Gravity, which intercedes thofe Bodies, and almoft all the cC fmall ones of their Parts, by fome other attractive Power dif- (C fufed through the Particles thereof— Without fuch Principles, eC there never would have been any Motion in the World i and " without the continuance thereof, Motion wou'd foon perifh, " there being otherwife a great Decreafe or Diminution there- « of, which is only fupplied by thefe active Principles." Opthh, p. 373.

We need not fay how unjuft it is in the generality of foreign Philofophers, to declare againft a Principle which furnifhes fo beautiful a View; for no other Reafon but becaufe we cannot conceive how a Body ihould act on another at a Diftance. — 'Tis

certain