Opticks (1721, 3rd Edition) — part 16 of 18

To explain the nnufual Refradion of Ifland Cryflal by Predion or Motion propagated, has rot hitherto been attempted (to my knowledge) except by Huygens^ who for that end fuppofed two feveral vibrating Mediums wathin that Cry* Ikl. But when he tried the Refraftions in two fucceflive pieces of that Crydal, and found them fuch as is mention'd above: He confef- fed himfelf at a lofs for explaining them. For Preflions or Motions, propagated from a fhining Body through an uniform Medium , muft be on all fides alike ; whereas by thofe Experi- ments it appears, that the Rays of Light have different Properties in their different Sides. He fufpefted that the Pulfes of Mther in paf- fmg through the firft Cryltal might receive cer- tain new Modifications, which might determine them to be propagated in this or that Medium within the fecond Cryftal, according to the

Pofition of that Cryftal.

^Uh pour dire comment gyf what ModiflCationS ceUfefan,je na^ nen j^ ^ • , ^ ^ j^

trove pifqn ict qut me fa- '-»»-''>' "a^iv i^n,^ »iw x.vyMi«.

fhfaj^. c. H. de la lurai- not fay, nor thmk of any ere. c. 5. p. 91. thing fatisfadory in that

Point. And if he had known that the unufual Refraftion depends not on new Modifications, but on the original and unchangeable Difpofitions of the Rays, he would have found it as difficult to explain how thofe Difpofitions which he fuppofed to be imprefs'd

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m the Rays by the firft Cryflal, could be in them before their Incidence on that Cryfbl ; and in general, how all Rays emitted by fhi- ning Bodies, can have thofe Difpofitions in them from the beginning. To me, at leail, this feems inexplicable, if Light be nothing elfe than Preflion or Motion propagated through JEther.

And it is as difficult to explain by thefe Hy- pothefes, how Rays can be alternately in Fits of eafy Reflexion and eafy Tranfmiflion ; unlefs perhaps one might fuppofe that there are in all Space two iEthereal vibrating Mediums, and that the Vibrations of one of them conilitute Light, and the Vibrations of the other are fwift- er, and as often as they overtake the Vibrations of the firft, put them into thofe Fits. But how two Mthers can be diffufed through all Space, one of which adls upon the other, and by con- fequence is re-aded upon, without retarding, Ihattering, difperfmg and confounding one an^ others Motions, is inconceivable. And againlt filling the Heavens with fluid Mediums, unlefs they be exceeding rare, a great Objedion arifes from the regular and very lading Motions of the Planets and Comets in all manner of Courfes through the Heavens. For thence it is mani- feft, that the Heavens are void of all fenfible Refifta-nce , and by confequence of all fenfible Matter.

For the refifting Power of fluid Mediums a-

rifes partly from the Attrition of the Parts of

the Medium, and partly from the Vis inertia

fif tlje Matter, Tijat part of the Refiflance of

• Z i a fphe-

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a fpherical Body which arifes from the Attri- tion of the Parts of the Medium is very nearly as the Diameter, or at the molt, as the Fadturn of the Diameter, and the Velocity of the fphe- rical Body together. And that part of the Re- finance which arifes from the V'ts inertia of the Matter, is as the Square of that FaCium, And by this difference the two forts of Refi- nance may be diflinguifh'd from one another in any Medium ; and thefe being diltinguifh'd,- It will be found that almofl all the Refiftance of Bodies of a competent Magnitude moving in Air, Water, Quick filver, and fuch like Fluids " with a competent Velocity, arifes from the Vis inertia; of the Parts of the Fluid.

Now that part of the refilling Power of any Medium which arifes from the Tenacity, Fri- 6lion or Attrition of the Parts of the Medium, imay be diminifli'd by dividing the Matter into fmaller Parts, and making the Parts more fmooth and flippery : But that part of the Refillance which arifes from the Vis inertia^ is proportio- nal to the Denfity of the Matter, and cannot be diminilh'd by dividing the Matter into fmaller farts, nor by any other means than by decrea- fing the Denlity of the Medium. And for thefe ' Reafons the Denfity of fluid Mediums is very nearly proportional to their Relilhmce. Li- quors which differ not much in Denfity, as Wa- ter, Spirit of Wine, Spirit of Turpentine, hot Oilj differ not much in Rcfidance. . Water is thirteen or fourteen times lighter than Quick- illver, and by confequence thirteen or fourteen times rarer, and its Refillance is lefs than that

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cf Quick-filver in the fame Proportion, or there- abouts, as I have found 63^ Experiments made with Pendulums. The open Air in which we breathe is eight or nine hundred times lighter than Water, and by confequence eight or nine hundred times rarer, and accordingly its Refi- llance is lefs than that of Water in the fame Proportion, or thereabouts; as I have alfo found by Experiments made with Pendulums. And in thinner Air the rciiitance is Hill lefs, and at length, by rarifying the Air, becomes infenfi- ble. For fmall Feathers falling in the open Air meet with great Reiiltance, but in a tall Glafs well emptied of Air, they fall as fail as Lead or Gold, as I have feen tried ieveral times. Whence the Refiitance feems itill to decreafe in propor- tion to the denfity of the Fluid. For I do not find by any Experiments, that Bodies moving in Quick-filver, Water or Air, meet with any other fenfible Refiilance than what arifes from the Denfity and Tenacity of thofe fenfible Flu- ids, as they would do if the Pores of thole Flu- ias, and all other Spaces, were filled with a denfe and fubtile Fluid. Now if the Refiitance in a Vellel well emptied of Air, was but an hundred times lefs than in the open Air, it would be about a million of times lefs than in Quick-filver. But it feems to be muclT^lefs in fuch a VelTel, and flill much lefs in the Hea- vens, at the height of three or four hundred Miles from the Earth, or above. For Mr. Boyle has fliew'd that Air m.ay be rarified above ten thoufand times in Veflels of Glafs ; and the Heavens are much emptier of Air than any /^^«-

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cuum we can make below. For fince the Air is comprefs'd by the weight of the incumbent Atmofphere, and the denfity of Air is propor- tional to the Force comprefling it, it follows by Computation, that at the height of about fe- \tTiJ^ngl'tfl) Miles froni the Earth, the Atr is four times rarer than at the ^Surface pf the Earth ; and at the height of i% Miles, it is fix- teen times rarer than that at the Surface of the •7^ Earth ; and at the height oii%y -ar^^or is Miles, "^j^ it is refpedively 64, 25-6,. or 1024 times rarer, or thereabouts ; and at the' height of ^(^y i^ti^l i<iS Miles, it is about 1 000000, 1 000000000000 or 1060000000000000000 times rarer ; and fo on.

Heat promotes Fluidity very much> by dimi- nifhing the Tenacity of Bodies. It makes ma- ny Bodies fluid which are not fluid in cold, and increafes the Fluidity of tenacious Liquids, as of Oil, Balfam and Honey,, and thereby de- er eafes their Refillance. But it decreafes not the Refiftance of Water confiderably, as it would do if any confiderable part of the Refiftance^bf Water arofe from the Attrition or Tenacity of its Parts. And therefore the Refinance of Wa- ter arifes principally and almoll entirely from the Vii inertly of its Matter ; and by confe- quenc?, if the Heavens were as denfe as W^- ter, they would not have much lefs Hefi^ance than Water; if as denfe as Quick-filver, they would not have much lefs Reliitance than Quick- filver; if abfolutely denfe, or full of Matter without any Vacuum^ let the Matter be never fo fubtile and fluid, tjiey would h^ive a greater

Reliftance

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Refiftance than Quick-filver. A folid Globe in fuch a Medium would lofe above half its Mo- tion in moving three times th^ length of its Diameter, and a Globe not folid (fuch as are the Planets) would be retarded fooner. And therefore to make way for the regular and lad- ing Motions of the Planets and Comets, it's nc- celfary to empty the Heavens of all Matter, ex- cept perhaps fome very thin Vapours, Steams or Effluvia, arilmg from the Atmofpheresof the Earth, Planets and Comets, and from fuch an exceedingly rare ^Ethereal Medium as we de- fcribed above. A denfe Fluid can be of no ufe for explaining the Phaenomena of Nature, the Motions of the Planets and Comets being better explain'd without it. It ferves only to diliurb and retard the Motions of thofe great Bodies, and make the Frame of Nature languifli : And in the Pores of Bodies, it ferves only to flop the vibrating Motions of their Parts, wherein .their Heat and Adivity confifts. And as it is' o^.no ufe, and hinders the Operations of Na- ture, and makes her languiili, fo there is no e- vidence for its Exigence, and therefore it ought to be rejefled. And if it be rejeded, the Hy- pothefes that Light confiils in Predion or Mo- tion propagated through fuch a Medium, are reje(fted with it.

And for rejefting fuch a Medium, we have the Authority of thofe the olded and mod ce- lebrated Philofophers of Greece and Th(Bnic'tay who made a Vacuum and Atoms, and the Gra- . vity of Atoms, the fird Principles of their Phi- lofophy ; tacitly attributing Gravity to fome o-

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ther Caufe than denfe Matter. Later Philofo- phers banifli the Confideration of fuch a Caufe out of Natural Philofophy, feigning Hypothefes for explaining all things mechanically, and re- ferring other Gaufes to Metaphyficks: Whereas the main Bufinefs of Natural Philofophy is to argue from Phrenomena without feigning Hy- pothefes, and to deduce Caufes from Effeds, till we come to the very firlt Caufe, which cer- tainly is not mechanical ; and not only to un- fold the Mechaniim of the World, but chiefly to refolve thefe and fuch like Quellions. What is there in places almoit empty of Matter, and whence is it that the Sun and Planers gravitate towards one another, without denfe Matter be- tween them ? Whence is it that Nature doth nothing in vain ; and whence arifes all that Or- . der and Beauty which we fee in the World? To what end are Comets, and whence is it that Planets move all one and the fame way in Orbs •concentrick, while Comets move all manner of ways in Orbs very excentrick, and what hinders the fix'd Stars from flilling upon one another ? How came the Bodies of Animals to be contri- ved with fo much Art, and for what ends were their feveral Parts? Was the Eye contrived without Skill in Opticks, and the Ear without Knowledge of Sounds? How do the Motions, of the Body follow from the Will, and whence is the Inilincl in Animals ? Is not the Senfory of Animals that place to which the fenfitive Sub-, fiance is prefent , and into which the fenfible Species of Things are carried through the Nerves gnd Brain, that there they may be perceived . • '• ■ . by

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by tHeir immediate prefence to that Subftance ? And thefe things being rightly difpatch'd, does it not appear from Phacnomena that there is a Being incoporeal, living, intelligent, omnipre- fent, who in infinite Space, as it were in his Sen- Yory, fees the things themfelves intimately, and throughly perceives them, and comprehends them wholly by their immediate prefence to himfelf : Of which things the Images only car- ried through the Organs of Senfe into our little Senforiums, are there feen and beheld by that which in us perceives and thinks. And tho' every true Step made in this Philofophy brings us not immediately to the Knowledge of the Ml Caufe, yet it brings us nearer to it, and on that account is to be highly valued.

^i. 29. Are not the Rays of Light very fmali Bodies emitted from fliining Sublbnces? For fuch Bodies will pafs through uniform Me- diums in right Lines without bendmg into the Shadow, which is the Nature of the Rays of Light. They will alfo be capable of feveral Properties, and be able to conferve their Pro- perties unchanged in palling through feveral Mediums, which is another Condition of the Rays of Light. Pellucid Subllances aft upon the Rays of Light at a ditlance in refra61ing, re- lieving and infleding them, and the Ravs mu- tually agitate the Parts of thofe Subftances at a diltance.for heatings them; and this Adion and Re action at a diilance, very much refembles an attradive Force between Bodies. If Refraction be perform'd by Attradion of the Ravs, the ^ines of Incidence mult be to the Sines of Re--

fradion

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fradion in a given Proportion, as we fhcw'd ia our Principles of Philofopliy : And this Rule is true by Experience. The Rays of Light in going out of Glafs into a Vacuum^ are bent to- wards the Glafs ; and if they fall too obliquely on the Vacuum they are bent backwards into the Glafs, and totally reflefted ; and this Refle- xion cannot be afcribed to the Refiftance of an abfolute Vacuum^ but muft be caufed by the Power of the Glafs attrafting the Rays at their going out of it into the Vacuum^ and bringing them back. For if the farther Surface of the Glafs be moiften^d with Water or clear Oil, or liquid and clear Honey ; the Rays which would otherwife be reflected, will go into the Water, Oil, or Honey, and therefore are not reflected before they arrive at the farther Surface of the Glafs, and begin to go out of it. If they go out of it into the Water, Oil or Honey, they go on, becaufe the Attradion of the Glafs is almoil balanc'd and render'd inefFedual by the contrary Attraction of the Liquor. But if they go out of it into a Vacuum which has no Attraftion to balance that of the Glafs, the At- traftion of the Glafs either bends and refrads them, or brings them back and refleds them. And this is flill more evident by laying together two Prifms of Glafs, or two Objedt-glaffes of very long Telefcopes, the one plane the o- ther a little convex, and fo compreiTmg them that they do not fully touch, nor are too far a- funder. For the Light which falls upon the farther Surface of the.firft Glafs where the In- terval between the Glafles is not above the ten

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hundred thoufandth part of an Inch, will go through that Surface, and through the Air or P^acuum between the Glafles, and enter into the fecond Glafs, as was explain'd in the firft, fourth and eighth Obfervations of the firll Part of the fecond Book. But if the fecond Glafs be taken away, the Light which goes oxit of the fecond Surface of the firit Glafs into the Air or Va- cuum, will not go on forwards, but turns back into the firft Glafs, and is refleded ; and there- fore it is drawn back by the Power of the firfl Glafs, there being nothing elfe to turn it back. Nothing is more requifite for producing all the variety of Colours and degrees of Refrangibi- lity, than that the Rays of Light be Bodies of different Sizes, the leaft of which may make violet the weakefl and darkefl of the Colours, and be more eafily diverted by refrading Sur- faces from the right Courfe ; and the reil as they are bigger and bigger, may make the ftronger and more lucid Colours, blue, green, yellow and red, and be more and more diffi- cultly diverted. Nothing more is requifite for putting the Rays of Light into Fits of eafy Re- flexion and eafy Tranfmiflion, than that they be fmall Bodies which by their attraiSive Powers, or fome other Force, ilir up Vibrations in what they ad upon, which Vibrations being fwifter than the Rays, overtake them fucceilively, and agitate them fq as by turns to increafe and de- creafe their Velocities, and thereby put them into thofe Fits. And laftly, the unufual Refra- j^ion of Ifland Cryftal looks very much as if it ^ere perform'd by fome kind of attradlive vir- ■ ■ tue

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tue lodged in certain Sides both of the Rays, and of the Particles of the Cryrtal For were it not for fome kind of Difpofition or Virtue lodged in fome Sides of the Particles of the Cryttal, and not in their other Sides, and which inclines and bends the Rays towards the Coaft of unuiual Refraclion, the Rays which fall per- pendicularly on the Cryftal, would not be re- frad:ed towards that Coafl rather than to\x^rds any other Coalt, both at their Incidence and at their Emergence, fo as to emerge perpendi- cularly by a contrary Situation of the Coatl of unufual Refra(^lion at the fecond Surface; the Cryital ading upon the Rays after they have pafs'd through it, and are emerging into the Air, or, if you peafe, into a Vacuum. And fmce the Cryftal by this Difpofition or Virtue does not ad upon the Rays, unlefs when one of their Sides of unufual Refradion looks to- wards that Coail, this argues a Virtue or Dif- pofition in thofe Sides of the Rays, which an^ fwers to and fympathizes with that Virtue or Difpofition of the Cryilal, as the Poles of two Magners anfwer to one another. And as Mag- netifni may be intended and remitted, and is found only in the Magnet and in Iron : So this Virtue of refrading the perpendicular Rays is greater in liland Cryital, lefs in Cryftal of the Rock, and is not yet-found in other Bodies. I do not fay that this Virtue is magnetical ; it feems to be of another kind : I only fay, that what ever it be, it's difficult to conceive how rhe Rays of Light, unlefs they be Bodies, can have a permanent Virtue in two of their Sides

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which is not in their other Sides, and this with- out any regard to their Pofition to the Space or Medium though which they pafs.

What I mean in this Queftion by a Vacuum^ and by the Attradions of the Rays of Light to- wards Glafs or Cryltal, may be underftood by what was faid in the i8th, 19th and 20th Que- ftions.

^i. 30. Are not grofs Bodies and Light con- vertible into one another, and may not Bodies receive much of their adivity from the Parti- cles of Light which enter their Compofition ? For all fix'd Bodies being heated emit Light fo long as they continue fufficiently hot, and Light mutually Itops in Bodies as often as its Rays ftrike upon their Parts, as we fhew'd above. I know no Body lefs apt to fhine than Water ; and yet Water by frequent Diltillations changes into fix'd Earth, as Mr. Boyle has tried ; and then this Earth being enabled to endure a fufficient Heat, ihines by Heat like other Bodies.

The changing of Bodies into Light, and Light into Bodies, is very conformable to the Courfe of Nature, which feems delighted with Tranf- mutations. Water, which is a very fluid tafl- iefs Salt, fhe changes by Heat into Vapour, which is a fort of Air, and by Cold into Ice, which is a hard, pellucid, brittle, fufible Stone; and this' Stone returns into Water by Heat, and Vapour returns into Water by Cold. Earth by Heat be- comes Fire, and by Cold returns into Earth. Denfe Bodies by Fermentation rarify into feve- ral forts of Air, and this Air by Fermentation, and fometimes without it, returns into denfe

Bodies.

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Bodies. Mercury appears fometimes in the form of a fluid Metal, fometimes in the form of a hard brittle Metal, fometimes In the form of a corrofive pellucid Salt call'd Sublimate, fometimes in the form of a taltlefs, pellucid, volatile white Earth, call'd Mercurius dulcis% or in that of a r^d Opake volatile Earth, call'd Cinnaber ; or in that of a red or white Preci- pitate, or in that of a fluid Salt ; and in Diflil- lation it turns into Vapour, and being agitated in vactto, it Ihines like Fire. And after all thefe Changes it returns again into its firlt form of Mercury. Eggs grow from infenfible Magni^ tudes, and change into Animals ; Tadpoles into Frogs ; and Worms into Flies. All Birds, Beads and Fifties, Infeds, Trees, and other Vegeta- bles, with their feveral parts, grow out of Wa^ ter and watry Tindures and Salts, and by Pu- trefadion return again into watry Subftances. And Water (landing a few Days in the open Air, yields a Tindture, which (like that of Mault) by (landing longer yields a Sediment and a Spirit, but before Putrefadion is fit Nou- rilhment for Animals and Vegetables. And a- mong luch various and (trange Tranfmutations, why may not Nature change Bodies into Light, and Light into Bodies ?

• ^t. 31. Have not the fmall Particles of Bo- dies certain Powers, Virtues or Forces, by which they ad at a diftance, not only upon the Rays of Light for refleding, refrading and in* fleding them, but alfo upon one another for producing a great part of the Phaenomena of Nature? For it's well known that Bodies ad

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one upon another by the Attradions of Gravi* ty, Magnetifm and Eledricity; and thefe In- fiances fhew the Tenor and Courfe of Nature, and make it not improbable but that there may be more attractive Powers than thefe. For Na- ture is very confonant and conformable to her felf How thefe Attradions may be perform'd, I do not here confider. What I call Attradion may be perform'd by impulfe, or by fome other means unknown to me. I ufe that Word here to fignify only in general any Force by which Bodies tend towards one another, whatfoever be the Caufe. For we muft learn from the Phaenomena of Nature what Bodies attraft one another, and what are the Laws and Properties of the Attradion, before we enquire the Caufe by which the Attradion is perform'd. The At- tradions of Gravity, Magnetifm and Eledrici* ty, reach to very fenfible dillances, and fo have been obferved by vulgar Eyes, and there may be others which reach to lb fmall diftances as hitherto efcape Obfervation; and perhaps ele- drical Attradion may reach to fuch fmall di- fiances, even without being excited by Fridion.

For when Salt of Tartar runs fer deliqmumy is not this done by an Attradion between the Particles of the Salt of Tartar, and the Parti- cles of the Water which float in the Air in the form of Vapours ? And why does not common Salt, or Salt petre, or Vitriol, run per deliquiuniy but for want of fuch an Attradion? Or why does not Salt of Tartar draw more Water out of the Air than in a certain Proportion to its quantity, but for want of an attradive Force

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after it is fatiated with Water ? And whence is it but from this attractive Power that Water which alone diftils with a gentle lukewarm Heat, will not diftil from Salt of Tartar with- out a great Heat ? And is it not from the like attradive Power between the Particles of Oil of Vitriol and the Particles of Water, that Oil of Vitriol draws to it a good quantity of Water out of the Air, and after it is fatiated draws no more, and in Di/lillation lets go the Water ve- ry difficultly? And when Water and Oil of Vi- triol poured fucceiTively into the fame Veflel grow very hot in the mixing, does not this Heat argue a great Motion in the parts of the Liquors ? And does not this Motion argue that the Parts of the two Liquors in mixing coa- lefce with Violence, and by confequence rufll towards one another with an accelerated Mo- tion ? And when Aqua fortis or Spirit of Vi- triol poured upon Filings of Iron, dilTolves the Filings with a great Heat and Ebullition, is not this Heat and Ebullition effefted by a violent Motion of the Parts, and does not that Motion argue that the acid Parts of the Liquor ruili to- wards the Parts of the Metal with violence, and run forcibly into its Pores till they get be- tween its outmoft Particles and the main Mafs of the Metal, and furrounding thofe Particles loofen them from the main Mafs, and fet them at liberty to float off into the Water ? And when the acid Particles which alone would diflil with an eafy Heat, will not feparate from the Particles of the Metal without a very vio*

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lent Heat, doth not this confirm the Attrafiidn between them ?

When Spirit of Vitriol poured upon com'* mon Salt or Saltpetre makes an Ebulhtion with the Salt and unites with it, and in Dillillation the Spirit of the common Salt or Saltpetre comes over much eaiier than it would do be- fore, and the acid part of the Spirit of Vitriol ftays behind ; does not this argue that the fix'd Alcaly of the Salt attrads the :icid Spirit of the Vitriol more itrongly than its own Spirit, and not being able to hold them both, lets go its own ? And when Oil of Vitriol is drawn off from its weight of Nitre, and from both the Ingredients a compound Spirit of Nitre is diftil- led, and two parts of this Spirit are poured on one part of Oil of Cloves or Caraway Seeds, or of ^ny ponderous Oil of vegetable or animal Sub- ftances, or Oil of Turpentine thickert'd with a little Balfam of Sulphur, and the Liquors grow fo very hot in mixing, asprefently to fend up a burn- ing Flame: Does not this very great and fudden Heat arg;ue that the two Liquors mix with vio- lence, and that their Parts in mixing run to- wards one- another with an accelerated Motion, and clafli with the greatefl: Force i* And is ic not for the fame realbn that well re(!:tified Spi- rit of Wine poured on the fame compound Spi- rit flalhes; and that the Tnlvis fulminans^ com- pofed of Sulphur, Nitre, and Salt of Tartar, goes off with a more fudden and violent Ex- plofion than Gun-powder, the acid Spirits, of the Sulphur and Nitre ruOiing towards one an- other, and towards the Salt of Tartar, with io

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great a violence, as by the fhock to turn the whole at once into Vapour and Flame? Where the DilTolution is flow, it makes a How Ebulli- tion and a gentle Heat ; and where it is quick- er, it makes a greater EbulUtion with more Heat ; and where it is done at once, the Ebul- lition is contrafted into a fudden Blalt or vio- lent Explofion, with a Heat equal to that of Fire and Flame. So when a Drachm of the a- bove mentioned compound Spirit of Nitre was poured upon half a Drachm of Oil of Caraway- Seeds in vacuo ; the Mixture immediately made a tia;h like Gun- powder, and burft the exhau- fted Receiver, which was a Glafs fix Inches wide 5 and eight Inches deep. And even the grois Body of Sulphur powder'd, and with an equal weight of Iron Filings, and a little Water made into Palle, ads upon the Iron, and in five . or fix Hours grows too hot to be touch'd, and emits a Flame. And by thefe Experiments com- pared with the great quantity of Sulphur with which the Earth abounds, and the warmth bf the interior Parts of the Earth, and hot Springs, and burning Mountains, and with Damps, mi- neral Corufcations, Earthquakes, hot futfoca- ting Exhalations, Hurricanes and Spouts ; we may learn that fulphureous Steams abound in the Bowels of the Earth and ferment with Mi- nerals, and fometimes take Fire with a fudden Corufcation and Explofion ; and if pent up in fubterraneous Caverns, burfl: the Caverns with a great lliaking of the Earth, as in fpringing of a Mine. And then the Vapour generated by the Explofion, expiring through the Pores of the

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Earth, feels hot and fuffocates, and makes Tem^ peils and Hurricanes, and fometimes caufes the Land to Hide, or the Sea to boil, and carries up the Water thereof in Drops, which by their weight fall down again in Spouts. Alfo fome fulphureous Steams, at all times when the Earth is dry, afcending into the Air, ferment there with nitrous Acids, and fometimes taking fire caufe Lightening and Thunder, and fiery Me- teors. For the Air abounds with acid Vapours fit to promote Fermentations, as appears by the rufting of Iron and Copper in it, the kindling of Fire bf blowing, and the beating of the Heart by means ot Refpiration. Now the a- bove mention'd Motions are fo great and vio- lent as to (hew that in Fermentations, the Par- ticles of Bodies which almoft reft, are put into new Motions by a very potent Principle, which afts upon them only when they approach one another, and caufes them to meet and clafli with great violence, and grow hot with the Mo- tion, and dafh one another into pieces, and va- nifli into Air, and Vapour, and Flame.

When Salt of Tartar fer deUqiitunt^ being poured into the Solution of any Metal, preci-

Eitates the Metal, and makes it fall down to the ottom of the Liquor in the form of Mud : Does not this argue that the acid Particles are attraded more itrongly by the Salt of Tartar than by the Metal, and by the ftronger Attra- ftion go from the Metal to the Salt of Tartar ? And fo when a Solution of Iron in Aqua finis diirolves the Lapis Calammark and lets go the Iron? or a Solution of Copper dillblves Iron im*

A a 3* mgrlfdi

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merfed in it and lets go the Copper, or a So^ lution of Silver- diflblves Copper and lets go the Silver, or a Solution of Mercury in Aqua fortis being poured upon Iron, Copper, Tin or Lead, difTolves the Metal and lets go the Mercury, does not this argue that the acid Particles of the Aqua fonts are attracted more ftrongly by the Lafis Calammarls than by Iron, and more . ftrongly by Iron than by Copper, and more ftrongly by Copper than by Silver, and more ftrongly by Iron, Copper, Tin and Lead, than by Mercury ? And is it not for the fame reafon that- Iron requires more Aqua forth to diflblve it than Copper, and Copper more than the o- ther Metals ; and that of all Metals, Iron is dif- folved moft eafily, and is moft apt to ruft; and next after Iron, Copper?

When Oil of Vitriol is mix'd with a little Water, or is run per deliquium^ and in Diftil- lation the Water alcends difficultly, and brings over with it fome part of the Oil of Vitriol in the form of Spirit of Vitriol, and this Spirit be- ing poured upon Iron, Copper, or Salt of Tar- tar, unites with the Body and lets go the Wa- ter, doth not this Ihew that the acid Spirit is at- traded by the Water, and more attrafted by the fix*d Body than by the Water, and there- fore lets go the Water to clofe with the fix'd Body ? And is it not for the fame reafon that the Water and acid Spirits which are mix'd to- gether in Vinegar, Aqua fortis^ and. Spirit of Salt , cohere and rife together in Diflillation ; but if the Menjiruum be poured on Salt of Tar- tar, or on Lead or Iron or any fix'd Body

which

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which it can diiTolvc, the Acid by a ftronger At- tradlion adheres to the Body, and lets go the Water ? And is it not aUb from a mutual At- traftion that the Spirits of Soot and Sea Salt unite and compofe the Particles of Sal-armo- niac, which are lefs volatile than before, be- caufe grofler and freer from Water; and that the Particles of Sal armoniac in Sublimation car- ry up the Particles of Antimony, which will not fublime alone; and that the Particles of Mer- cury uniting with the acid Particles of Spirit of Salt cOmpofe Mercury fublimate, and with the Particles of Sulphur, compofe Cinnaber ; and that the Particles of Spirit of Wine and Spirit of Urine well redified unite, and letting go the Water which difToived them, compofe a confittent Body; and that in fubhming Cinna- ber from Salt of Tartar, or from quick Lime, the Sulphur by a ilronger Attraction of the Salt or Lime lets go the Mercury, and Itays with the fix'd Body; and that when Mercury fubli- mate is fublimed from Antimony, or from Re- gulus of Antimony, the Spirit of Salt lets go the Mercury, and unites with the antimonial Me- tal which attrads it more itrongly, and Itays with it till the Heat be great enough to make them both afcend together; and then carries up the Metal with it in -the form of a very fu- lible Salt, called Butter of Antimony, although . the Spirit of Salt alone be almoil as volatile as Water, and the Antimony alone as fix'd as Lead ?

When jf^qua fort is difTolves Silver and not Gold, and Aqua regia difTolves Gold and not

Aa 3 Silver,

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Silver, may it not be faid that Aqua fort is is fubtile enough to penetrate Gold as well as Sil- ver, but wants the attraftive Force to give it Entrance ; and that Aqua regia is fubtile enough to penetrate Silver as well as Gold, but wants the attradive Force to give it Entrance? For Jtqua regia is nothing elfe than Aqiia fortis mix'd with fome Spirit of Salt, or with Sal-ar- moniac ; and even common Salt diilolved in A- qua fortis y enables the Menfirnum to diilolve Gold, though the Salt be a grofs Body When therefore Spirit of Salt precipitates Silver out of Aqua fortis^ is it not done by attra^ling and mixing with the Aqua fortis^ and .not attraft- ing, or perhaps repelling Silver? And when Water precipitates Antimony out of the Subli- mate of Antimony and Sal-armoniac, or out of Butter of Antimony, is it not done by its dif- folving, mixing with, and weakening the Sal- armoniac or Spirit of Salt, and its not attraft- ing, or perhaps repelling the Antimony ? And is it not for want of an attradive Virtue be- tween the Parts of Water and Oil, of Quick- filver and Antimony, of Lead and Iron, that thefe Subftances do not mix ; and by a weak Attraction, that Quick-filver and Copper mix difficultly; and from a ftrong one, that Quick- filver and Tin, Antimony and Iron, Water and Salts, mix readily ? And in general, is it not from the fame Principle that Heat congregates homegeneal Bodies, and feparates heterogeneal C5nes }

When Arfnick with Soap gives a Regulus, and with Mercury fublimate a volatile fufible

• Salt,

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