invented for explaining the Phaenomena of Light, by new Modifications of
the Rays? For those Phaenomena depend not upon new Modifications, as has
been supposed, but upon the original and unchangeable Properties of the
Rays.
_Qu._ 28. Are not all Hypotheses erroneous, in which Light is supposed
to consist in Pression or Motion, propagated through a fluid Medium? For
in all these Hypotheses the Phaenomena of Light have been hitherto
explain'd by supposing that they arise from new Modifications of the
Rays; which is an erroneous Supposition.
If Light consisted only in Pression propagated without actual Motion, it
would not be able to agitate and heat the Bodies which refract and
reflect it. If it consisted in Motion propagated to all distances in an
instant, it would require an infinite force every moment, in every
shining Particle, to generate that Motion. And if it consisted in
Pression or Motion, propagated either in an instant or in time, it would
bend into the Shadow. For Pression or Motion cannot be propagated in a
Fluid in right Lines, beyond an Obstacle which stops part of the Motion,
but will bend and spread every way into the quiescent Medium which lies
beyond the Obstacle. Gravity tends downwards, but the Pressure of Water
arising from Gravity tends every way with equal Force, and is propagated
as readily, and with as much force sideways as downwards, and through
crooked passages as through strait ones. The Waves on the Surface of
stagnating Water, passing by the sides of a broad Obstacle which stops
part of them, bend afterwards and dilate themselves gradually into the
quiet Water behind the Obstacle. The Waves, Pulses or Vibrations of the
Air, wherein Sounds consist, bend manifestly, though not so much as the
Waves of Water. For a Bell or a Cannon may be heard beyond a Hill which
intercepts the sight of the sounding Body, and Sounds are propagated as
readily through crooked Pipes as through streight ones. But Light is
never known to follow crooked Passages nor to bend into the Shadow. For
the fix'd Stars by the Interposition of any of the Planets cease to be
seen. And so do the Parts of the Sun by the Interposition of the Moon,
_Mercury_ or _Venus_. The Rays which pass very near to the edges of any
Body, are bent a little by the action of the Body, as we shew'd above;
but this bending is not towards but from the Shadow, and is perform'd
only in the passage of the Ray by the Body, and at a very small distance
from it. So soon as the Ray is past the Body, it goes right on.
[Sidenote: _Mais pour dire comment cela se fait, je n'ay rien trove
jusqu' ici qui me satisfasse._ C. H. de la lumiere, c. 5, p. 91.]
To explain the unusual Refraction of Island Crystal by Pression or
Motion propagated, has not hitherto been attempted (to my knowledge)
except by _Huygens_, who for that end supposed two several vibrating
Mediums within that Crystal. But when he tried the Refractions in two
successive pieces of that Crystal, and found them such as is mention'd
above; he confessed himself at a loss for explaining them. For Pressions
or Motions, propagated from a shining Body through an uniform Medium,
must be on all sides alike; whereas by those Experiments it appears,
that the Rays of Light have different Properties in their different
Sides. He suspected that the Pulses of _AEther_ in passing through the
first Crystal might receive certain new Modifications, which might
determine them to be propagated in this or that Medium within the
second Crystal, according to the Position of that Crystal. But what
Modifications those might be he could not say, nor think of any thing
satisfactory in that Point. And if he had known that the unusual
Refraction depends not on new Modifications, but on the original and
unchangeable Dispositions of the Rays, he would have found it as
difficult to explain how those Dispositions which he supposed to be
impress'd on the Rays by the first Crystal, could be in them before
their Incidence on that Crystal, and in general, how all Rays emitted by
shining Bodies, can have those Dispositions in them from the beginning.
To me, at least, this seems inexplicable, if Light be nothing else than
Pression or Motion propagated through _AEther_.
And it is as difficult to explain by these Hypotheses, how Rays can be
alternately in Fits of easy Reflexion and easy Transmission; unless
perhaps one might suppose that there are in all Space two AEthereal
vibrating Mediums, and that the Vibrations of one of them constitute
Light, and the Vibrations of the other are swifter, and as often as they
overtake the Vibrations of the first, put them into those Fits. But how
two _AEthers_ can be diffused through all Space, one of which acts upon
the other, and by consequence is re-acted upon, without retarding,
shattering, dispersing and confounding one anothers Motions, is
inconceivable. And against filling the Heavens with fluid Mediums,
unless they be exceeding rare, a great Objection arises from the regular
and very lasting Motions of the Planets and Comets in all manner of
Courses through the Heavens. For thence it is manifest, that the Heavens
are void of all sensible Resistance, and by consequence of all sensible
Matter.
For the resisting Power of fluid Mediums arises partly from the
Attrition of the Parts of the Medium, and partly from the _Vis inertiae_
of the Matter. That part of the Resistance of a spherical Body which
arises from the Attrition of the Parts of the Medium is very nearly as
the Diameter, or, at the most, as the _Factum_ of the Diameter, and the
Velocity of the spherical Body together. And that part of the Resistance
which arises from the _Vis inertiae_ of the Matter, is as the Square of
that _Factum_. And by this difference the two sorts of Resistance may be
distinguish'd from one another in any Medium; and these being
distinguish'd, it will be found that almost all the Resistance of Bodies
of a competent Magnitude moving in Air, Water, Quick-silver, and such
like Fluids with a competent Velocity, arises from the _Vis inertiae_ of
the Parts of the Fluid.
Now that part of the resisting Power of any Medium which arises from the
Tenacity, Friction or Attrition of the Parts of the Medium, may be
diminish'd by dividing the Matter into smaller Parts, and making the
Parts more smooth and slippery: But that part of the Resistance which
arises from the _Vis inertiae_, is proportional to the Density of the
Matter, and cannot be diminish'd by dividing the Matter into smaller
Parts, nor by any other means than by decreasing the Density of the
Medium. And for these Reasons the Density of fluid Mediums is very
nearly proportional to their Resistance. Liquors which differ not much
in Density, as Water, Spirit of Wine, Spirit of Turpentine, hot Oil,
differ not much in Resistance. Water is thirteen or fourteen times
lighter than Quick-silver and by consequence thirteen or fourteen times
rarer, and its Resistance is less than that of Quick-silver in the same
Proportion, or thereabouts, as I have found by Experiments made with
Pendulums. The open Air in which we breathe is eight or nine hundred
times lighter than Water, and by consequence eight or nine hundred times
rarer, and accordingly its Resistance is less than that of Water in the
same Proportion, or thereabouts; as I have also found by Experiments
made with Pendulums. And in thinner Air the Resistance is still less,
and at length, by ratifying the Air, becomes insensible. For small
Feathers falling in the open Air meet with great Resistance, but in a
tall Glass well emptied of Air, they fall as fast as Lead or Gold, as I
have seen tried several times. Whence the Resistance seems still to
decrease in proportion to the Density of the Fluid. For I do not find by
any Experiments, that Bodies moving in Quick-silver, Water or Air, meet
with any other sensible Resistance than what arises from the Density and
Tenacity of those sensible Fluids, as they would do if the Pores of
those Fluids, and all other Spaces, were filled with a dense and
subtile Fluid. Now if the Resistance in a Vessel well emptied of Air,
was but an hundred times less than in the open Air, it would be about a
million of times less than in Quick-silver. But it seems to be much less
in such a Vessel, and still much less in the Heavens, at the height of
three or four hundred Miles from the Earth, or above. For Mr. _Boyle_
has shew'd that Air may be rarified above ten thousand times in Vessels
of Glass; and the Heavens are much emptier of Air than any _Vacuum_ we
can make below. For since the Air is compress'd by the Weight of the
incumbent Atmosphere, and the Density of Air is proportional to the
Force compressing it, it follows by Computation, that at the height of
about seven and a half _English_ Miles from the Earth, the Air is four
times rarer than at the Surface of the Earth; and at the height of 15
Miles it is sixteen times rarer than that at the Surface of the Earth;
and at the height of 22-1/2, 30, or 38 Miles, it is respectively 64,
256, or 1024 times rarer, or thereabouts; and at the height of 76, 152,
228 Miles, it is about 1000000, 1000000000000, or 1000000000000000000
times rarer; and so on.
Heat promotes Fluidity very much by diminishing the Tenacity of Bodies.
It makes many Bodies fluid which are not fluid in cold, and increases
the Fluidity of tenacious Liquids, as of Oil, Balsam, and Honey, and
thereby decreases their Resistance. But it decreases not the Resistance
of Water considerably, as it would do if any considerable part of the
Resistance of Water arose from the Attrition or Tenacity of its Parts.
And therefore the Resistance of Water arises principally and almost
entirely from the _Vis inertiae_ of its Matter; and by consequence, if
the Heavens were as dense as Water, they would not have much less
Resistance than Water; if as dense as Quick-silver, they would not have
much less Resistance than Quick-silver; if absolutely dense, or full of
Matter without any _Vacuum_, let the Matter be never so subtil and
fluid, they would have a greater Resistance than Quick-silver. A solid
Globe in such a Medium would lose above half its Motion in moving three
times the length of its Diameter, and a Globe not solid (such as are the
Planets,) would be retarded sooner. And therefore to make way for the
regular and lasting Motions of the Planets and Comets, it's necessary to
empty the Heavens of all Matter, except perhaps some very thin Vapours,
Steams, or Effluvia, arising from the Atmospheres of the Earth, Planets,
and Comets, and from such an exceedingly rare AEthereal Medium as we
described above. A dense Fluid can be of no use for explaining the
Phaenomena of Nature, the Motions of the Planets and Comets being better
explain'd without it. It serves only to disturb and retard the Motions
of those great Bodies, and make the Frame of Nature languish: And in the
Pores of Bodies, it serves only to stop the vibrating Motions of their
Parts, wherein their Heat and Activity consists. And as it is of no use,
and hinders the Operations of Nature, and makes her languish, so there
is no evidence for its Existence, and therefore it ought to be rejected.
And if it be rejected, the Hypotheses that Light consists in Pression
or Motion, propagated through such a Medium, are rejected with it.
And for rejecting such a Medium, we have the Authority of those the
oldest and most celebrated Philosophers of _Greece_ and _Phoenicia_,
who made a _Vacuum_, and Atoms, and the Gravity of Atoms, the first
Principles of their Philosophy; tacitly attributing Gravity to some
other Cause than dense Matter. Later Philosophers banish the
Consideration of such a Cause out of natural Philosophy, feigning
Hypotheses for explaining all things mechanically, and referring other
Causes to Metaphysicks: Whereas the main Business of natural Philosophy
is to argue from Phaenomena without feigning Hypotheses, and to deduce
Causes from Effects, till we come to the very first Cause, which
certainly is not mechanical; and not only to unfold the Mechanism of the
World, but chiefly to resolve these and such like Questions. What is
there in places almost empty of Matter, and whence is it that the Sun
and Planets gravitate towards one another, without dense Matter between
them? Whence is it that Nature doth nothing in vain; and whence arises
all that Order and Beauty which we see in the World? To what end are
Comets, and whence is it that Planets move all one and the same way in
Orbs concentrick, while Comets move all manner of ways in Orbs very
excentrick; and what hinders the fix'd Stars from falling upon one
another? How came the Bodies of Animals to be contrived with so much
Art, and for what ends were their several 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
Instinct in Animals? Is not the Sensory of Animals that place to which
the sensitive Substance is present, and into which the sensible Species
of Things are carried through the Nerves and Brain, that there they may
be perceived by their immediate presence to that Substance? And these
things being rightly dispatch'd, does it not appear from Phaenomena that
there is a Being incorporeal, living, intelligent, omnipresent, who in
infinite Space, as it were in his Sensory, sees the things themselves
intimately, and throughly perceives them, and comprehends them wholly by
their immediate presence to himself: Of which things the Images only
carried through the Organs of Sense into our little Sensoriums, are
there seen and beheld by that which in us perceives and thinks. And
though every true Step made in this Philosophy brings us not immediately
to the Knowledge of the first Cause, yet it brings us nearer to it, and
on that account is to be highly valued.
_Qu._ 29. Are not the Rays of Light very small Bodies emitted from
shining Substances? For such Bodies will pass through uniform Mediums in
right Lines without bending into the Shadow, which is the Nature of the
Rays of Light. They will also be capable of several Properties, and be
able to conserve their Properties unchanged in passing through several
Mediums, which is another Condition of the Rays of Light. Pellucid
Substances act upon the Rays of Light at a distance in refracting,
reflecting, and inflecting them, and the Rays mutually agitate the Parts
of those Substances at a distance for heating them; and this Action and
Re-action at a distance very much resembles an attractive Force between
Bodies. If Refraction be perform'd by Attraction of the Rays, the Sines
of Incidence must be to the Sines of Refraction in a given Proportion,
as we shew'd in our Principles of Philosophy: And this Rule is true by
Experience. The Rays of Light in going out of Glass into a _Vacuum_, are
bent towards the Glass; and if they fall too obliquely on the _Vacuum_,
they are bent backwards into the Glass, and totally reflected; and this
Reflexion cannot be ascribed to the Resistance of an absolute _Vacuum_,
but must be caused by the Power of the Glass attracting the Rays at
their going out of it into the _Vacuum_, and bringing them back. For if
the farther Surface of the Glass be moisten'd with Water or clear Oil,
or liquid and clear Honey, the Rays which would otherwise be reflected
will go into the Water, Oil, or Honey; and therefore are not reflected
before they arrive at the farther Surface of the Glass, and begin to go
out of it. If they go out of it into the Water, Oil, or Honey, they go
on, because the Attraction of the Glass is almost balanced and rendered
ineffectual by the contrary Attraction of the Liquor. But if they go out
of it into a _Vacuum_ which has no Attraction to balance that of the
Glass, the Attraction of the Glass either bends and refracts them, or
brings them back and reflects them. And this is still more evident by
laying together two Prisms of Glass, or two Object-glasses of very long
Telescopes, the one plane, the other a little convex, and so compressing
them that they do not fully touch, nor are too far asunder. For the
Light which falls upon the farther Surface of the first Glass where the
Interval between the Glasses is not above the ten hundred thousandth
Part of an Inch, will go through that Surface, and through the Air or
_Vacuum_ between the Glasses, and enter into the second Glass, as was
explain'd in the first, fourth, and eighth Observations of the first
Part of the second Book. But, if the second Glass be taken away, the
Light which goes out of the second Surface of the first Glass into the
Air or _Vacuum_, will not go on forwards, but turns back into the first
Glass, and is reflected; and therefore it is drawn back by the Power of
the first Glass, there being nothing else to turn it back. Nothing more
is requisite for producing all the variety of Colours, and degrees of
Refrangibility, than that the Rays of Light be Bodies of different
Sizes, the least of which may take violet the weakest and darkest of the
Colours, and be more easily diverted by refracting Surfaces from the
right Course; and the rest as they are bigger and bigger, may make the
stronger and more lucid Colours, blue, green, yellow, and red, and be
more and more difficultly diverted. Nothing more is requisite for
putting the Rays of Light into Fits of easy Reflexion and easy
Transmission, than that they be small Bodies which by their attractive
Powers, or some other Force, stir up Vibrations in what they act upon,
which Vibrations being swifter than the Rays, overtake them
successively, and agitate them so as by turns to increase and decrease
their Velocities, and thereby put them into those Fits. And lastly, the
unusual Refraction of Island-Crystal looks very much as if it were
perform'd by some kind of attractive virtue lodged in certain Sides both
of the Rays, and of the Particles of the Crystal. For were it not for
some kind of Disposition or Virtue lodged in some Sides of the Particles
of the Crystal, and not in their other Sides, and which inclines and
bends the Rays towards the Coast of unusual Refraction, the Rays which
fall perpendicularly on the Crystal, would not be refracted towards that
Coast rather than towards any other Coast, both at their Incidence and
at their Emergence, so as to emerge perpendicularly by a contrary
Situation of the Coast of unusual Refraction at the second Surface; the
Crystal acting upon the Rays after they have pass'd through it, and are
emerging into the Air; or, if you please, into a _Vacuum_. And since the
Crystal by this Disposition or Virtue does not act upon the Rays, unless
when one of their Sides of unusual Refraction looks towards that Coast,
this argues a Virtue or Disposition in those Sides of the Rays, which
answers to, and sympathizes with that Virtue or Disposition of the
Crystal, as the Poles of two Magnets answer to one another. And as
Magnetism may be intended and remitted, and is found only in the Magnet
and in Iron: So this Virtue of refracting the perpendicular Rays is
greater in Island-Crystal, less in Crystal of the Rock, and is not yet
found in other Bodies. I do not say that this Virtue is magnetical: It
seems to be of another kind. I only say, that whatever it be, it's
difficult to conceive how the Rays of Light, unless they be Bodies, can
have a permanent Virtue in two of their Sides which is not in their
other Sides, and this without any regard to their Position to the Space
or Medium through which they pass.
What I mean in this Question by a _Vacuum_, and by the Attractions of
the Rays of Light towards Glass or Crystal, may be understood by what
was said in the 18th, 19th, and 20th Questions.
_Quest._ 30. Are not gross Bodies and Light convertible into one
another, and may not Bodies receive much of their Activity from the
Particles of Light which enter their Composition? For all fix'd Bodies
being heated emit Light so long as they continue sufficiently hot, and
Light mutually stops in Bodies as often as its Rays strike upon their
Parts, as we shew'd above. I know no Body less apt to shine than Water;
and yet Water by frequent Distillations changes into fix'd Earth, as Mr.
_Boyle_ has try'd; and then this Earth being enabled to endure a
sufficient Heat, shines by Heat like other Bodies.
The changing of Bodies into Light, and Light into Bodies, is very
conformable to the Course of Nature, which seems delighted with
Transmutations. Water, which is a very fluid tasteless Salt, she changes
by Heat into Vapour, which is a sort of Air, and by Cold into Ice, which
is a hard, pellucid, brittle, fusible Stone; and this Stone returns into
Water by Heat, and Vapour returns into Water by Cold. Earth by Heat
becomes Fire, and by Cold returns into Earth. Dense Bodies by
Fermentation rarify into several sorts of Air, and this Air by
Fermentation, and sometimes without it, returns into dense Bodies.
Mercury appears sometimes in the form of a fluid Metal, sometimes in the
form of a hard brittle Metal, sometimes in the form of a corrosive
pellucid Salt call'd Sublimate, sometimes in the form of a tasteless,
pellucid, volatile white Earth, call'd _Mercurius Dulcis_; or in that of
a red opake volatile Earth, call'd Cinnaber; or in that of a red or
white Precipitate, or in that of a fluid Salt; and in Distillation it
turns into Vapour, and being agitated _in Vacuo_, it shines like Fire.
And after all these Changes it returns again into its first form of
Mercury. Eggs grow from insensible Magnitudes, and change into Animals;
Tadpoles into Frogs; and Worms into Flies. All Birds, Beasts and Fishes,
Insects, Trees, and other Vegetables, with their several Parts, grow out
of Water and watry Tinctures and Salts, and by Putrefaction return again
into watry Substances. And Water standing a few Days in the open Air,
yields a Tincture, which (like that of Malt) by standing longer yields a
Sediment and a Spirit, but before Putrefaction is fit Nourishment for
Animals and Vegetables. And among such various and strange
Transmutations, why may not Nature change Bodies into Light, and Light
into Bodies?
_Quest._ 31. Have not the small Particles of Bodies certain Powers,
Virtues, or Forces, by which they act at a distance, not only upon the
Rays of Light for reflecting, refracting, and inflecting them, but also
upon one another for producing a great Part of the Phaenomena of Nature?
For it's well known, that Bodies act one upon another by the Attractions
of Gravity, Magnetism, and Electricity; and these Instances shew the
Tenor and Course of Nature, and make it not improbable but that there
may be more attractive Powers than these. For Nature is very consonant
and conformable to her self. How these Attractions may be perform'd, I
do not here consider. What I call Attraction may be perform'd by
impulse, or by some other means unknown to me. I use that Word here to
signify only in general any Force by which Bodies tend towards one
another, whatsoever be the Cause. For we must learn from the Phaenomena
of Nature what Bodies attract one another, and what are the Laws and
Properties of the Attraction, before we enquire the Cause by which the
Attraction is perform'd. The Attractions of Gravity, Magnetism, and
Electricity, reach to very sensible distances, and so have been observed
by vulgar Eyes, and there may be others which reach to so small
distances as hitherto escape Observation; and perhaps electrical
Attraction may reach to such small distances, even without being excited
by Friction.
For when Salt of Tartar runs _per Deliquium_, is not this done by an
Attraction between the Particles of the Salt of Tartar, and the
Particles 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
Deliquium_, but for want of such an Attraction? 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 attractive Force after it is satiated
with Water? And whence is it but from this attractive Power that Water
which alone distils with a gentle luke-warm Heat, will not distil from
Salt of Tartar without a great Heat? And is it not from the like
attractive 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 satiated draws no more, and in
Distillation lets go the Water very difficultly? And when Water and Oil
of Vitriol poured successively into the same Vessel 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 coalesce with Violence, and by consequence rush
towards one another with an accelerated Motion? And when _Aqua fortis_,
or Spirit of Vitriol poured upon Filings of Iron dissolves the Filings
with a great Heat and Ebullition, is not this Heat and Ebullition
effected by a violent Motion of the Parts, and does not that Motion
argue that the acid Parts of the Liquor rush towards the Parts of the
Metal with violence, and run forcibly into its Pores till they get
between its outmost Particles, and the main Mass of the Metal, and
surrounding those Particles loosen them from the main Mass, and set them
at liberty to float off into the Water? And when the acid Particles,
which alone would distil with an easy Heat, will not separate from the
Particles of the Metal without a very violent Heat, does not this
confirm the Attraction between them?
When Spirit of Vitriol poured upon common Salt or Salt-petre makes an
Ebullition with the Salt, and unites with it, and in Distillation the
Spirit of the common Salt or Salt-petre comes over much easier than it
would do before, and the acid part of the Spirit of Vitriol stays
behind; does not this argue that the fix'd Alcaly of the Salt attracts
the acid Spirit of the Vitriol more strongly 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 distilled, and two parts of
this Spirit are poured on one part of Oil of Cloves or Carraway Seeds,
or of any ponderous Oil of vegetable or animal Substances, or Oil of
Turpentine thicken'd with a little Balsam of Sulphur, and the Liquors
grow so very hot in mixing, as presently to send up a burning Flame;
does not this very great and sudden Heat argue that the two Liquors mix
with violence, and that their Parts in mixing run towards one another
with an accelerated Motion, and clash with the greatest Force? And is it
not for the same reason that well rectified Spirit of Wine poured on the
same compound Spirit flashes; and that the _Pulvis fulminans_, composed
of Sulphur, Nitre, and Salt of Tartar, goes off with a more sudden and
violent Explosion than Gun-powder, the acid Spirits of the Sulphur and
Nitre rushing towards one another, and towards the Salt of Tartar, with
so great a violence, as by the shock to turn the whole at once into
Vapour and Flame? Where the Dissolution is slow, it makes a slow
Ebullition and a gentle Heat; and where it is quicker, it makes a
greater Ebullition with more heat; and where it is done at once, the
Ebullition is contracted into a sudden Blast or violent Explosion, with
a heat equal to that of Fire and Flame. So when a Drachm of the
above-mention'd compound Spirit of Nitre was poured upon half a Drachm
of Oil of Carraway Seeds _in vacuo_, the Mixture immediately made a
flash like Gun-powder, and burst the exhausted Receiver, which was a
Glass six Inches wide, and eight Inches deep. And even the gross Body of
Sulphur powder'd, and with an equal weight of Iron Filings and a little
Water made into Paste, acts upon the Iron, and in five or six hours
grows too hot to be touch'd, and emits a Flame. And by these Experiments
compared with the great quantity of Sulphur with which the Earth
abounds, and the warmth of the interior Parts of the Earth, and hot
Springs, and burning Mountains, and with Damps, mineral Coruscations,
Earthquakes, hot suffocating Exhalations, Hurricanes, and Spouts; we may
learn that sulphureous Steams abound in the Bowels of the Earth and
ferment with Minerals, and sometimes take fire with a sudden Coruscation
and Explosion; and if pent up in subterraneous Caverns, burst the
Caverns with a great shaking of the Earth, as in springing of a Mine.
And then the Vapour generated by the Explosion, expiring through the
Pores of the Earth, feels hot and suffocates, and makes Tempests and
Hurricanes, and sometimes causes the Land to slide, or the Sea to boil,
and carries up the Water thereof in Drops, which by their weight fall
down again in Spouts. Also some sulphureous Steams, at all times when
the Earth is dry, ascending into the Air, ferment there with nitrous
Acids, and sometimes taking fire cause Lightning and Thunder, and fiery
Meteors. For the Air abounds with acid Vapours fit to promote
Fermentations, as appears by the rusting of Iron and Copper in it, the
kindling of Fire by blowing, and the beating of the Heart by means of
Respiration. Now the above-mention'd Motions are so great and violent as
to shew that in Fermentations the Particles of Bodies which almost rest,
are put into new Motions by a very potent Principle, which acts upon
them only when they approach one another, and causes them to meet and
clash with great violence, and grow hot with the motion, and dash one
another into pieces, and vanish into Air, and Vapour, and Flame.
When Salt of Tartar _per deliquium_, being poured into the Solution of
any Metal, precipitates the Metal and makes it fall down to the bottom
of the Liquor in the form of Mud: Does not this argue that the acid
Particles are attracted more strongly by the Salt of Tartar than by the
Metal, and by the stronger Attraction go from the Metal to the Salt of
Tartar? And so when a Solution of Iron in _Aqua fortis_ dissolves the
_Lapis Calaminaris_, and lets go the Iron, or a Solution of Copper
dissolves Iron immersed in it and lets go the Copper, or a Solution of
Silver dissolves Copper and lets go the Silver, or a Solution of Mercury
in _Aqua fortis_ being poured upon Iron, Copper, Tin, or Lead, dissolves
the Metal and lets go the Mercury; does not this argue that the acid
Particles of the _Aqua fortis_ are attracted more strongly by the _Lapis
Calaminaris_ than by Iron, and more strongly by Iron than by Copper, and
more strongly by Copper than by Silver, and more strongly by Iron,
Copper, Tin, and Lead, than by Mercury? And is it not for the same
reason that Iron requires more _Aqua fortis_ to dissolve it than Copper,
and Copper more than the other Metals; and that of all Metals, Iron is
dissolved most easily, and is most apt to rust; and next after Iron,
Copper?
When Oil of Vitriol is mix'd with a little Water, or is run _per
deliquium_, and in Distillation the Water ascends difficultly, and
brings over with it some part of the Oil of Vitriol in the form of
Spirit of Vitriol, and this Spirit being poured upon Iron, Copper, or
Salt of Tartar, unites with the Body and lets go the Water; doth not
this shew that the acid Spirit is attracted by the Water, and more
attracted by the fix'd Body than by the Water, and therefore lets go the
Water to close with the fix'd Body? And is it not for the same reason
that the Water and acid Spirits which are mix'd together in Vinegar,
_Aqua fortis_, and Spirit of Salt, cohere and rise together in
Distillation; but if the _Menstruum_ be poured on Salt of Tartar, or on
Lead, or Iron, or any fix'd Body which it can dissolve, the Acid by a
stronger Attraction adheres to the Body, and lets go the Water? And is
it not also from a mutual Attraction that the Spirits of Soot and
Sea-Salt unite and compose the Particles of Sal-armoniac, which are less
volatile than before, because grosser and freer from Water; and that the
Particles of Sal-armoniac in Sublimation carry up the Particles of
Antimony, which will not sublime alone; and that the Particles of
Mercury uniting with the acid Particles of Spirit of Salt compose
Mercury sublimate, and with the Particles of Sulphur, compose Cinnaber;
and that the Particles of Spirit of Wine and Spirit of Urine well
rectified unite, and letting go the Water which dissolved them, compose
a consistent Body; and that in subliming Cinnaber from Salt of Tartar,
or from quick Lime, the Sulphur by a stronger Attraction of the Salt or
Lime lets go the Mercury, and stays with the fix'd Body; and that when
Mercury sublimate is sublimed from Antimony, or from Regulus of
Antimony, the Spirit of Salt lets go the Mercury, and unites with the
antimonial metal which attracts it more strongly, and stays with it till
the Heat be great enough to make them both ascend together, and then
carries up the Metal with it in the form of a very fusible Salt, called
Butter of Antimony, although the Spirit of Salt alone be almost as
volatile as Water, and the Antimony alone as fix'd as Lead?
When _Aqua fortis_ dissolves Silver and not Gold, and _Aqua regia_
dissolves Gold and not Silver, may it not be said that _Aqua fortis_ is
subtil enough to penetrate Gold as well as Silver, but wants the
attractive Force to give it Entrance; and that _Aqua regia_ is subtil
enough to penetrate Silver as well as Gold, but wants the attractive
Force to give it Entrance? For _Aqua regia_ is nothing else than _Aqua
fortis_ mix'd with some Spirit of Salt, or with Sal-armoniac; and even
common Salt dissolved in _Aqua fortis_, enables the _Menstruum_ to
dissolve Gold, though the Salt be a gross Body. When therefore Spirit of
Salt precipitates Silver out of _Aqua fortis_, is it not done by
attracting and mixing with the _Aqua fortis_, and not attracting, or
perhaps repelling Silver? And when Water precipitates Antimony out of
the Sublimate of Antimony and Sal-armoniac, or out of Butter of
Antimony, is it not done by its dissolving, mixing with, and weakening
the Sal-armoniac or Spirit of Salt, and its not attracting, or perhaps
repelling the Antimony? And is it not for want of an attractive virtue
between the Parts of Water and Oil, of Quick-silver and Antimony, of
Lead and Iron, that these Substances do not mix; and by a weak
Attraction, that Quick-silver and Copper mix difficultly; and from a
strong one, that Quick-silver and Tin, Antimony and Iron, Water and
Salts, mix readily? And in general, is it not from the same Principle
that Heat congregates homogeneal Bodies, and separates heterogeneal
ones?
When Arsenick with Soap gives a Regulus, and with Mercury sublimate a
volatile fusible Salt, like Butter of Antimony, doth not this shew that
Arsenick, which is a Substance totally volatile, is compounded of fix'd
and volatile Parts, strongly cohering by a mutual Attraction, so that
the volatile will not ascend without carrying up the fixed? And so, when
an equal weight of Spirit of Wine and Oil of Vitriol are digested
together, and in Distillation yield two fragrant and volatile Spirits
which will not mix with one another, and a fix'd black Earth remains
behind; doth not this shew that Oil of Vitriol is composed of volatile
and fix'd Parts strongly united by Attraction, so as to ascend together
in form of a volatile, acid, fluid Salt, until the Spirit of Wine
attracts and separates the volatile Parts from the fixed? And therefore,
since Oil of Sulphur _per Campanam_ is of the same Nature with Oil of
Vitriol, may it not be inferred, that Sulphur is also a mixture of
volatile and fix'd Parts so strongly cohering by Attraction, as to
ascend together in Sublimation. By dissolving Flowers of Sulphur in Oil
of Turpentine, and distilling the Solution, it is found that Sulphur is
composed of an inflamable thick Oil or fat Bitumen, an acid Salt, a very
fix'd Earth, and a little Metal. The three first were found not much
unequal to one another, the fourth in so small a quantity as scarce to
be worth considering. The acid Salt dissolved in Water, is the same with
Oil of Sulphur _per Campanam_, and abounding much in the Bowels of the
Earth, and particularly in Markasites, unites it self to the other
Ingredients of the Markasite, which are, Bitumen, Iron, Copper, and
Earth, and with them compounds Allum, Vitriol, and Sulphur. With the
Earth alone it compounds Allum; with the Metal alone, or Metal and
Earth together, it compounds Vitriol; and with the Bitumen and Earth it
compounds Sulphur. Whence it comes to pass that Markasites abound with
those three Minerals. And is it not from the mutual Attraction of the
Ingredients that they stick together for compounding these Minerals, and
that the Bitumen carries up the other Ingredients of the Sulphur, which
without it would not sublime? And the same Question may be put
concerning all, or almost all the gross Bodies in Nature. For all the
Parts of Animals and Vegetables are composed of Substances volatile and
fix'd, fluid and solid, as appears by their Analysis; and so are Salts
and Minerals, so far as Chymists have been hitherto able to examine
their Composition.
When Mercury sublimate is re-sublimed with fresh Mercury, and becomes
_Mercurius Dulcis_, which is a white tasteless Earth scarce dissolvable
in Water, and _Mercurius Dulcis_ re-sublimed with Spirit of Salt returns
into Mercury sublimate; and when Metals corroded with a little acid turn
into rust, which is an Earth tasteless and indissolvable in Water, and
this Earth imbibed with more acid becomes a metallick Salt; and when
some Stones, as Spar of Lead, dissolved in proper _Menstruums_ become
Salts; do not these things shew that Salts are dry Earth and watry Acid
united by Attraction, and that the Earth will not become a Salt without
so much acid as makes it dissolvable in Water? Do not the sharp and
pungent Tastes of Acids arise from the strong Attraction whereby the
acid Particles rush upon and agitate the Particles of the Tongue? And
when Metals are dissolved in acid _Menstruums_, and the Acids in
conjunction with the Metal act after a different manner, so that the
Compound has a different Taste much milder than before, and sometimes a
sweet one; is it not because the Acids adhere to the metallick
Particles, and thereby lose much of their Activity? And if the Acid be
in too small a Proportion to make the Compound dissolvable in Water,
will it not by adhering strongly to the Metal become unactive and lose
its Taste, and the Compound be a tasteless Earth? For such things as are
not dissolvable by the Moisture of the Tongue, act not upon the Taste.
As Gravity makes the Sea flow round the denser and weightier Parts of
the Globe of the Earth, so the Attraction may make the watry Acid flow
round the denser and compacter Particles of Earth for composing the
Particles of Salt. For otherwise the Acid would not do the Office of a
Medium between the Earth and common Water, for making Salts dissolvable
in the Water; nor would Salt of Tartar readily draw off the Acid from
dissolved Metals, nor Metals the Acid from Mercury. Now, as in the great
Globe of the Earth and Sea, the densest Bodies by their Gravity sink
down in Water, and always endeavour to go towards the Center of the
Globe; so in Particles of Salt, the densest Matter may always endeavour
to approach the Center of the Particle: So that a Particle of Salt may
be compared to a Chaos; being dense, hard, dry, and earthy in the
Center; and rare, soft, moist, and watry in the Circumference. And
hence it seems to be that Salts are of a lasting Nature, being scarce
destroy'd, unless by drawing away their watry Parts by violence, or by
letting them soak into the Pores of the central Earth by a gentle Heat
in Putrefaction, until the Earth be dissolved by the Water, and
separated into smaller Particles, which by reason of their Smallness
make the rotten Compound appear of a black Colour. Hence also it may be,
that the Parts of Animals and Vegetables preserve their several Forms,
and assimilate their Nourishment; the soft and moist Nourishment easily
changing its Texture by a gentle Heat and Motion, till it becomes like
the dense, hard, dry, and durable Earth in the Center of each Particle.
But when the Nourishment grows unfit to be assimilated, or the central
Earth grows too feeble to assimilate it, the Motion ends in Confusion,
Putrefaction, and Death.
If a very small quantity of any Salt or Vitriol be dissolved in a great
quantity of Water, the Particles of the Salt or Vitriol will not sink to
the bottom, though they be heavier in Specie than the Water, but will
evenly diffuse themselves into all the Water, so as to make it as saline
at the top as at the bottom. And does not this imply that the Parts of
the Salt or Vitriol recede from one another, and endeavour to expand
themselves, and get as far asunder as the quantity of Water in which
they float, will allow? And does not this Endeavour imply that they have
a repulsive Force by which they fly from one another, or at least, that
they attract the Water more strongly than they do one another? For as
all things ascend in Water which are less attracted than Water, by the
gravitating Power of the Earth; so all the Particles of Salt which float
in Water, and are less attracted than Water by any one Particle of Salt,
must recede from that Particle, and give way to the more attracted
Water.
When any saline Liquor is evaporated to a Cuticle and let cool, the Salt
concretes in regular Figures; which argues, that the Particles of the
Salt before they concreted, floated in the Liquor at equal distances in
rank and file, and by consequence that they acted upon one another by
some Power which at equal distances is equal, at unequal distances
unequal. For by such a Power they will range themselves uniformly, and
without it they will float irregularly, and come together as
irregularly. And since the Particles of Island-Crystal act all the same
way upon the Rays of Light for causing the unusual Refraction, may it
not be supposed that in the Formation of this Crystal, the Particles not
only ranged themselves in rank and file for concreting in regular
Figures, but also by some kind of polar Virtue turned their homogeneal
Sides the same way.
The Parts of all homogeneal hard Bodies which fully touch one another,
stick together very strongly. And for explaining how this may be, some
have invented hooked Atoms, which is begging the Question; and others
tell us that Bodies are glued together by rest, that is, by an occult
Quality, or rather by nothing; and others, that they stick together by
conspiring Motions, that is, by relative rest amongst themselves. I had
rather infer from their Cohesion, that their Particles attract one
another by some Force, which in immediate Contact is exceeding strong,
at small distances performs the chymical Operations above-mention'd, and
reaches not far from the Particles with any sensible Effect.
All Bodies seem to be composed of hard Particles: For otherwise Fluids
would not congeal; as Water, Oils, Vinegar, and Spirit or Oil of Vitriol
do by freezing; Mercury by Fumes of Lead; Spirit of Nitre and Mercury,
by dissolving the Mercury and evaporating the Flegm; Spirit of Wine and
Spirit of Urine, by deflegming and mixing them; and Spirit of Urine and
Spirit of Salt, by subliming them together to make Sal-armoniac. Even
the Rays of Light seem to be hard Bodies; for otherwise they would not
retain different Properties in their different Sides. And therefore
Hardness may be reckon'd the Property of all uncompounded Matter. At
least, this seems to be as evident as the universal Impenetrability of
Matter. For all Bodies, so far as Experience reaches, are either hard,
or may be harden'd; and we have no other Evidence of universal
Impenetrability, besides a large Experience without an experimental
Exception. Now if compound Bodies are so very hard as we find some of
them to be, and yet are very porous, and consist of Parts which are only
laid together; the simple Particles which are void of Pores, and were
never yet divided, must be much harder. For such hard Particles being
heaped up together, can scarce touch one another in more than a few
Points, and therefore must be separable by much less Force than is
requisite to break a solid Particle, whose Parts touch in all the Space
between them, without any Pores or Interstices to weaken their Cohesion.
And how such very hard Particles which are only laid together and touch
only in a few Points, can stick together, and that so firmly as they do,
without the assistance of something which causes them to be attracted or
press'd towards one another, is very difficult to conceive.
The same thing I infer also from the cohering of two polish'd Marbles
_in vacuo_, and from the standing of Quick-silver in the Barometer at
the height of 50, 60 or 70 Inches, or above, when ever it is well-purged
of Air and carefully poured in, so that its Parts be every where
contiguous both to one another and to the Glass. The Atmosphere by its
weight presses the Quick-silver into the Glass, to the height of 29 or
30 Inches. And some other Agent raises it higher, not by pressing it
into the Glass, but by making its Parts stick to the Glass, and to one
another. For upon any discontinuation of Parts, made either by Bubbles
or by shaking the Glass, the whole Mercury falls down to the height of
29 or 30 Inches.
And of the same kind with these Experiments are those that follow. If
two plane polish'd Plates of Glass (suppose two pieces of a polish'd
Looking-glass) be laid together, so that their sides be parallel and at
a very small distance from one another, and then their lower edges be
dipped into Water, the Water will rise up between them. And the less
the distance of the Glasses is, the greater will be the height to which
the Water will rise. If the distance be about the hundredth part of an
Inch, the Water will rise to the height of about an Inch; and if the
distance be greater or less in any Proportion, the height will be
reciprocally proportional to the distance very nearly. For the
attractive Force of the Glasses is the same, whether the distance
between them be greater or less; and the weight of the Water drawn up is
the same, if the height of it be reciprocally proportional to the
distance of the Glasses. And in like manner, Water ascends between two
Marbles polish'd plane, when their polish'd sides are parallel, and at a
very little distance from one another, And if slender Pipes of Glass be
dipped at one end into stagnating Water, the Water will rise up within
the Pipe, and the height to which it rises will be reciprocally
proportional to the Diameter of the Cavity of the Pipe, and will equal
the height to which it rises between two Planes of Glass, if the
Semi-diameter of the Cavity of the Pipe be equal to the distance between
the Planes, or thereabouts. And these Experiments succeed after the same
manner _in vacuo_ as in the open Air, (as hath been tried before the
Royal Society,) and therefore are not influenced by the Weight or
Pressure of the Atmosphere.
And if a large Pipe of Glass be filled with sifted Ashes well pressed
together in the Glass, and one end of the Pipe be dipped into stagnating
Water, the Water will rise up slowly in the Ashes, so as in the space
of a Week or Fortnight to reach up within the Glass, to the height of 30
or 40 Inches above the stagnating Water. And the Water rises up to this
height by the Action only of those Particles of the Ashes which are upon
the Surface of the elevated Water; the Particles which are within the
Water, attracting or repelling it as much downwards as upwards. And
therefore the Action of the Particles is very strong. But the Particles
of the Ashes being not so dense and close together as those of Glass,
their Action is not so strong as that of Glass, which keeps Quick-silver
suspended to the height of 60 or 70 Inches, and therefore acts with a
Force which would keep Water suspended to the height of above 60 Feet.
By the same Principle, a Sponge sucks in Water, and the Glands in the
Bodies of Animals, according to their several Natures and Dispositions,
suck in various Juices from the Blood.
If two plane polish'd Plates of Glass three or four Inches broad, and
twenty or twenty five long, be laid one of them parallel to the Horizon,
the other upon the first, so as at one of their ends to touch one
another, and contain an Angle of about 10 or 15 Minutes, and the same be
first moisten'd on their inward sides with a clean Cloth dipp'd into Oil
of Oranges or Spirit of Turpentine, and a Drop or two of the Oil or
Spirit be let fall upon the lower Glass at the other; so soon as the
upper Glass is laid down upon the lower, so as to touch it at one end as
above, and to touch the Drop at the other end, making with the lower
Glass an Angle of about 10 or 15 Minutes; the Drop will begin to move
towards the Concourse of the Glasses, and will continue to move with an
accelerated Motion, till it arrives at that Concourse of the Glasses.
For the two Glasses attract the Drop, and make it run that way towards
which the Attractions incline. And if when the Drop is in motion you
lift up that end of the Glasses where they meet, and towards which the
Drop moves, the Drop will ascend between the Glasses, and therefore is
attracted. And as you lift up the Glasses more and more, the Drop will
ascend slower and slower, and at length rest, being then carried
downward by its Weight, as much as upwards by the Attraction. And by
this means you may know the Force by which the Drop is attracted at all
distances from the Concourse of the Glasses.
Now by some Experiments of this kind, (made by Mr. _Hauksbee_) it has
been found that the Attraction is almost reciprocally in a duplicate
Proportion of the distance of the middle of the Drop from the Concourse
of the Glasses, _viz._ reciprocally in a simple Proportion, by reason of
the spreading of the Drop, and its touching each Glass in a larger
Surface; and again reciprocally in a simple Proportion, by reason of the
Attractions growing stronger within the same quantity of attracting
Surface. The Attraction therefore within the same quantity of attracting
Surface, is reciprocally as the distance between the Glasses. And
therefore where the distance is exceeding small, the Attraction must be
exceeding great. By the Table in the second Part of the second Book,
wherein the thicknesses of colour'd Plates of Water between two Glasses
are set down, the thickness of the Plate where it appears very black, is
three eighths of the ten hundred thousandth part of an Inch. And where
the Oil of Oranges between the Glasses is of this thickness, the
Attraction collected by the foregoing Rule, seems to be so strong, as
within a Circle of an Inch in diameter, to suffice to hold up a Weight
equal to that of a Cylinder of Water of an Inch in diameter, and two or
three Furlongs in length. And where it is of a less thickness the
Attraction may be proportionally greater, and continue to increase,
until the thickness do not exceed that of a single Particle of the Oil.
There are therefore Agents in Nature able to make the Particles of
Bodies stick together by very strong Attractions. And it is the Business
of experimental Philosophy to find them out.
Now the smallest Particles of Matter may cohere by the strongest
Attractions, and compose bigger Particles of weaker Virtue; and many of
these may cohere and compose bigger Particles whose Virtue is still
weaker, and so on for divers Successions, until the Progression end in
the biggest Particles on which the Operations in Chymistry, and the
Colours of natural Bodies depend, and which by cohering compose Bodies
of a sensible Magnitude. If the Body is compact, and bends or yields
inward to Pression without any sliding of its Parts, it is hard and
elastick, returning to its Figure with a Force rising from the mutual
Attraction of its Parts. If the Parts slide upon one another, the Body
is malleable or soft. If they slip easily, and are of a fit Size to be
agitated by Heat, and the Heat is big enough to keep them in Agitation,
the Body is fluid; and if it be apt to stick to things, it is humid; and
the Drops of every fluid affect a round Figure by the mutual Attraction
of their Parts, as the Globe of the Earth and Sea affects a round Figure
by the mutual Attraction of its Parts by Gravity.
Since Metals dissolved in Acids attract but a small quantity of the
Acid, their attractive Force can reach but to a small distance from
them. And as in Algebra, where affirmative Quantities vanish and cease,
there negative ones begin; so in Mechanicks, where Attraction ceases,
there a repulsive Virtue ought to succeed. And that there is such a
Virtue, seems to follow from the Reflexions and Inflexions of the Rays
of Light. For the Rays are repelled by Bodies in both these Cases,
without the immediate Contact of the reflecting or inflecting Body. It
seems also to follow from the Emission of Light; the Ray so soon as it
is shaken off from a shining Body by the vibrating Motion of the Parts
of the Body, and gets beyond the reach of Attraction, being driven away
with exceeding great Velocity. For that Force which is sufficient to
turn it back in Reflexion, may be sufficient to emit it. It seems also
to follow from the Production of Air and Vapour. The Particles when they
are shaken off from Bodies by Heat or Fermentation, so soon as they are
beyond the reach of the Attraction of the Body, receding from it, and
also from one another with great Strength, and keeping at a distance,
so as sometimes to take up above a Million of Times more space than they
did before in the form of a dense Body. Which vast Contraction and
Expansion seems unintelligible, by feigning the Particles of Air to be
springy and ramous, or rolled up like Hoops, or by any other means than
a repulsive Power. The Particles of Fluids which do not cohere too
strongly, and are of such a Smallness as renders them most susceptible
of those Agitations which keep Liquors in a Fluor, are most easily
separated and rarified into Vapour, and in the Language of the Chymists,
they are volatile, rarifying with an easy Heat, and condensing with
Cold. But those which are grosser, and so less susceptible of Agitation,
or cohere by a stronger Attraction, are not separated without a stronger
Heat, or perhaps not without Fermentation. And these last are the Bodies
which Chymists call fix'd, and being rarified by Fermentation, become
true permanent Air; those Particles receding from one another with the
greatest Force, and being most difficultly brought together, which upon
Contact cohere most strongly. And because the Particles of permanent Air
are grosser, and arise from denser Substances than those of Vapours,
thence it is that true Air is more ponderous than Vapour, and that a
moist Atmosphere is lighter than a dry one, quantity for quantity. From
the same repelling Power it seems to be that Flies walk upon the Water
without wetting their Feet; and that the Object-glasses of long
Telescopes lie upon one another without touching; and that dry Powders
are difficultly made to touch one another so as to stick together,
unless by melting them, or wetting them with Water, which by exhaling
may bring them together; and that two polish'd Marbles, which by
immediate Contact stick together, are difficultly brought so close
together as to stick.
And thus Nature will be very conformable to her self and very simple,
performing all the great Motions of the heavenly Bodies by the
Attraction of Gravity which intercedes those Bodies, and almost all the
small ones of their Particles by some other attractive and repelling
Powers which intercede the Particles. The _Vis inertiae_ is a passive
Principle by which Bodies persist in their Motion or Rest, receive
Motion in proportion to the Force impressing it, and resist as much as
they are resisted. By this Principle alone there never could have been
any Motion in the World. Some other Principle was necessary for putting
Bodies into Motion; and now they are in Motion, some other Principle is
necessary for conserving the Motion. For from the various Composition of
two Motions, 'tis very certain that there is not always the same
quantity of Motion in the World. For if two Globes joined by a slender
Rod, revolve about their common Center of Gravity with an uniform
Motion, while that Center moves on uniformly in a right Line drawn in
the Plane of their circular Motion; the Sum of the Motions of the two
Globes, as often as the Globes are in the right Line described by their
common Center of Gravity, will be bigger than the Sum of their Motions,
when they are in a Line perpendicular to that right Line. By this
Instance it appears that Motion may be got or lost. But by reason of the
Tenacity of Fluids, and Attrition of their Parts, and the Weakness of
Elasticity in Solids, Motion is much more apt to be lost than got, and
is always upon the Decay. For Bodies which are either absolutely hard,
or so soft as to be void of Elasticity, will not rebound from one
another. Impenetrability makes them only stop. If two equal Bodies meet
directly _in vacuo_, they will by the Laws of Motion stop where they
meet, and lose all their Motion, and remain in rest, unless they be
elastick, and receive new Motion from their Spring. If they have so much
Elasticity as suffices to make them re-bound with a quarter, or half, or
three quarters of the Force with which they come together, they will
lose three quarters, or half, or a quarter of their Motion. And this may
be try'd, by letting two equal Pendulums fall against one another from
equal heights. If the Pendulums be of Lead or soft Clay, they will lose
all or almost all their Motions: If of elastick Bodies they will lose
all but what they recover from their Elasticity. If it be said, that
they can lose no Motion but what they communicate to other Bodies, the
consequence is, that _in vacuo_ they can lose no Motion, but when they
meet they must go on and penetrate one another's Dimensions. If three
equal round Vessels be filled, the one with Water, the other with Oil,
the third with molten Pitch, and the Liquors be stirred about alike to
give them a vortical Motion; the Pitch by its Tenacity will lose its
Motion quickly, the Oil being less tenacious will keep it longer, and
the Water being less tenacious will keep it longest, but yet will lose
it in a short time. Whence it is easy to understand, that if many
contiguous Vortices of molten Pitch were each of them as large as those
which some suppose to revolve about the Sun and fix'd Stars, yet these
and all their Parts would, by their Tenacity and Stiffness, communicate
their Motion to one another till they all rested among themselves.
Vortices of Oil or Water, or some fluider Matter, might continue longer
in Motion; but unless the Matter were void of all Tenacity and Attrition
of Parts, and Communication of Motion, (which is not to be supposed,)
the Motion would constantly decay. Seeing therefore the variety of
Motion which we find in the World is always decreasing, there is a
necessity of conserving and recruiting it by active Principles, such as
are the cause of Gravity, by which Planets and Comets keep their Motions
in their Orbs, and Bodies acquire great Motion in falling; and the cause
of Fermentation, by which the Heart and Blood of Animals are kept in
perpetual Motion and Heat; the inward Parts of the Earth are constantly
warm'd, and in some places grow very hot; Bodies burn and shine,
Mountains take fire, the Caverns of the Earth are blown up, and the Sun
continues violently hot and lucid, and warms all things by his Light.
For we meet with very little Motion in the World, besides what is owing
to these active Principles. And if it were not for these Principles, the
Bodies of the Earth, Planets, Comets, Sun, and all things in them,
would grow cold and freeze, and become inactive Masses; and all
Putrefaction, Generation, Vegetation and Life would cease, and the
Planets and Comets would not remain in their Orbs.
All these things being consider'd, it seems probable to me, that God in
the Beginning form'd Matter in solid, massy, hard, impenetrable,
moveable Particles, of such Sizes and Figures, and with such other
Properties, and in such Proportion to Space, as most conduced to the End
for which he form'd them; and that these primitive Particles being
Solids, are incomparably harder than any porous Bodies compounded of
them; even so very hard, as never to wear or break in pieces; no
ordinary Power being able to divide what God himself made one in the
first Creation. While the Particles continue entire, they may compose
Bodies of one and the same Nature and Texture in all Ages: But should
they wear away, or break in pieces, the Nature of Things depending on
them, would be changed. Water and Earth, composed of old worn Particles
and Fragments of Particles, would not be of the same Nature and Texture
now, with Water and Earth composed of entire Particles in the Beginning.
And therefore, that Nature may be lasting, the Changes of corporeal
Things are to be placed only in the various Separations and new
Associations and Motions of these permanent Particles; compound Bodies
being apt to break, not in the midst of solid Particles, but where those
Particles are laid together, and only touch in a few Points.
It seems to me farther, that these Particles have not only a _Vis
inertiae_, accompanied with such passive Laws of Motion as naturally
result from that Force, but also that they are moved by certain active
Principles, such as is that of Gravity, and that which causes
Fermentation, and the Cohesion of Bodies. These Principles I consider,
not as occult Qualities, supposed to result from the specifick Forms of
Things, but as general Laws of Nature, by which the Things themselves
are form'd; their Truth appearing to us by Phaenomena, though their
Causes be not yet discover'd. For these are manifest Qualities, and
their Causes only are occult. And the _Aristotelians_ gave the Name of
occult Qualities, not to manifest Qualities, but to such Qualities only
as they supposed to lie hid in Bodies, and to be the unknown Causes of
manifest Effects: Such as would be the Causes of Gravity, and of
magnetick and electrick Attractions, and of Fermentations, if we should
suppose that these Forces or Actions arose from Qualities unknown to us,
and uncapable of being discovered and made manifest. Such occult
Qualities put a stop to the Improvement of natural Philosophy, and
therefore of late Years have been rejected. To tell us that every
Species of Things is endow'd with an occult specifick Quality by which
it acts and produces manifest Effects, is to tell us nothing: But to
derive two or three general Principles of Motion from Phaenomena, and
afterwards to tell us how the Properties and Actions of all corporeal
Things follow from those manifest Principles, would be a very great step
in Philosophy, though the Causes of those Principles were not yet
discover'd: And therefore I scruple not to propose the Principles of
Motion above-mention'd, they being of very general Extent, and leave
their Causes to be found out.
Now by the help of these Principles, all material Things seem to have
been composed of the hard and solid Particles above-mention'd, variously
associated in the first Creation by the Counsel of an intelligent Agent.
For it became him who created them to set them in order. And if he did
so, it's unphilosophical to seek for any other Origin of the World, or
to pretend that it might arise out of a Chaos by the mere Laws of
Nature; though being once form'd, it may continue by those Laws for many
Ages. For while Comets move in very excentrick Orbs in all manner of
Positions, blind Fate could never make all the Planets move one and the
same way in Orbs concentrick, some inconsiderable Irregularities
excepted, which may have risen from the mutual Actions of Comets and
Planets upon one another, and which will be apt to increase, till this
System wants a Reformation. Such a wonderful Uniformity in the Planetary
System must be allowed the Effect of Choice. And so must the Uniformity
in the Bodies of Animals, they having generally a right and a left side
shaped alike, and on either side of their Bodies two Legs behind, and
either two Arms, or two Legs, or two Wings before upon their Shoulders,
and between their Shoulders a Neck running down into a Back-bone, and a
Head upon it; and in the Head two Ears, two Eyes, a Nose, a Mouth, and
a Tongue, alike situated. Also the first Contrivance of those very
artificial Parts of Animals, the Eyes, Ears, Brain, Muscles, Heart,
Lungs, Midriff, Glands, Larynx, Hands, Wings, swimming Bladders, natural
Spectacles, and other Organs of Sense and Motion; and the Instinct of
Brutes and Insects, can be the effect of nothing else than the Wisdom
and Skill of a powerful ever-living Agent, who being in all Places, is
more able by his Will to move the Bodies within his boundless uniform
Sensorium, and thereby to form and reform the Parts of the Universe,
than we are by our Will to move the Parts of our own Bodies. And yet we
are not to consider the World as the Body of God, or the several Parts
thereof, as the Parts of God. He is an uniform Being, void of Organs,
Members or Parts, and they are his Creatures subordinate to him, and
subservient to his Will; and he is no more the Soul of them, than the
Soul of Man is the Soul of the Species of Things carried through the
Organs of Sense into the place of its Sensation, where it perceives them
by means of its immediate Presence, without the Intervention of any
third thing. The Organs of Sense are not for enabling the Soul to
perceive the Species of Things in its Sensorium, but only for conveying
them thither; and God has no need of such Organs, he being every where
present to the Things themselves. And since Space is divisible _in
infinitum_, and Matter is not necessarily in all places, it may be also
allow'd that God is able to create Particles of Matter of several Sizes
and Figures, and in several Proportions to Space, and perhaps of
different Densities and Forces, and thereby to vary the Laws of Nature,
and make Worlds of several sorts in several Parts of the Universe. At
least, I see nothing of Contradiction in all this.
As in Mathematicks, so in Natural Philosophy, the Investigation of
difficult Things by the Method of Analysis, ought ever to precede the
Method of Composition. This Analysis consists in making Experiments and
Observations, and in drawing general Conclusions from them by Induction,
and admitting of no Objections against the Conclusions, but such as are
taken from Experiments, or other certain Truths. For Hypotheses are not
to be regarded in experimental Philosophy. And although the arguing from
Experiments and Observations by Induction be no Demonstration of general
Conclusions; yet it is the best way of arguing which the Nature of
Things admits of, and may be looked upon as so much the stronger, by how
much the Induction is more general. And if no Exception occur from
Phaenomena, the Conclusion may be pronounced generally. But if at any
time afterwards any Exception shall occur from Experiments, it may then
begin to be pronounced with such Exceptions as occur. By this way of
Analysis we may proceed from Compounds to Ingredients, and from Motions
to the Forces producing them; and in general, from Effects to their
Causes, and from particular Causes to more general ones, till the
Argument end in the most general. This is the Method of Analysis: And
the Synthesis consists in assuming the Causes discover'd, and
establish'd as Principles, and by them explaining the Phaenomena
proceeding from them, and proving the Explanations.
In the two first Books of these Opticks, I proceeded by this Analysis to
discover and prove the original Differences of the Rays of Light in
respect of Refrangibility, Reflexibility, and Colour, and their
alternate Fits of easy Reflexion and easy Transmission, and the
Properties of Bodies, both opake and pellucid, on which their Reflexions
and Colours depend. And these Discoveries being proved, may be assumed
in the Method of Composition for explaining the Phaenomena arising from
them: An Instance of which Method I gave in the End of the first Book.
In this third Book I have only begun the Analysis of what remains to be
discover'd about Light and its Effects upon the Frame of Nature, hinting
several things about it, and leaving the Hints to be examin'd and
improv'd by the farther Experiments and Observations of such as are
inquisitive. And if natural Philosophy in all its Parts, by pursuing
this Method, shall at length be perfected, the Bounds of Moral
Philosophy will be also enlarged. For so far as we can know by natural
Philosophy what is the first Cause, what Power he has over us, and what
Benefits we receive from him, so far our Duty towards him, as well as
that towards one another, will appear to us by the Light of Nature. And
no doubt, if the Worship of false Gods had not blinded the Heathen,
their moral Philosophy would have gone farther than to the four
Cardinal Virtues; and instead of teaching the Transmigration of Souls,
and to worship the Sun and Moon, and dead Heroes, they would have taught
us to worship our true Author and Benefactor, as their Ancestors did
under the Government of _Noah_ and his Sons before they corrupted
themselves.