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  A

  TREATISE

  ON

  ELECTRICITY:

  WHEREIN

  Its various _phænomena_ are accounted for, and the
  cause of the _attraction_ and _gravitation_ of solids,
  assigned.

  TO WHICH IS ADDED,

  A short account, how the electrical _effluvia_ act
  upon the animal frame, and in what disorders
  the same may probably be applied with success,
  and in what not.

  By FRANCIS PENROSE
  Surgeon at _Bicester_.

  They who are universally allowed the very greatest, and
  wisest of men, have been, and still are, intent upon
  the making of _observations_, and _experiments_: and surely
  that must be in order to some further end. These would
  be vain, and wholely useless, were not some reflections
  made, some conclusions drawn, some theory or hypothesis
  raised from them.

  _Woodward_’s state of _physick_ and of _diseases_, p. 55.

  _OXFORD_,

  Printed at the THEATRE for SACKVILLE PARKER, Bookseller
  at _Oxford_, and W. OWEN, at _Homer’s Head, Temple-Bar,
  London_. MD CC LII.




  ON
  ELECTRICITY.


The many surprising effects of _electricity_, and the great cures
performed by it, one would imagine, should awaken the attention of all
philosophers and physicians; but as these cures have been effected by
random experiments, every body has admired, but no body seems to have
considered how, or by what means, they were performed. Whence

Notwithstanding all these surprising _phænomena_, from which many
have entertained hopes of a great addition to the healing art; yet
not one tolerable account has been given, how, or from what cause,
these _phænomena_ proceeded; except what has been done by Mr. _Freke_,
surgeon to _Bartholomew hospital_; whose admirable piece shews the
great penetration of its worthy author, with whom I shall join in
thinking “it may possibly be the beginning of much good.”

One would think, this silence, on so interesting a subject, _in this
enlightened age_, can proceed from nothing but a prejudice in favour
of wrong principles of philosophy: That this is certainly the taste of
the present age, M. _Freke_ seems very well convinced; for, at the end
of his pamphlet, he takes notice of a show-man, who, “having published
some experiments in electricity, and hearing that Mr. _Freke_’s piece
was publishing, own’d, he was much affrightened, because of the hard
fate, as he said, of his booksellers; but, before he had read two
pages, he likewise owned he had recovered his spirits, when he found
Mr. _Freke_ pretended to think for himself, and did not let Sr. _Isaac
Newton_ think for him.”

Now, if all persons would take the same freedom of thinking for
themselves, as Mr. _Freke_ has done, I doubt not but we should soon
be as much ashamed of mentioning the _attraction_ of _gravitation_,
and the _attraction_ of _cohesion_ &c. as we now are of the _occult
qualities_ of the ancient philosophers; and should perhaps, then
agree with him, when, speaking of electricity, he says, that “it is a
subject which can, with more nobleness and dignity, employ the mind of
man, than any he can think of, relating to the sublunary part of the
world. For by it you may be acquainted with the immediate officer of
God Almighty, which he seems to send to all things living: Nay, this
power, (according to his conception,) seems to be the cause, under
HIM, both of life and death. And when it may be more fully understood,
it may afford us means, whereby we may be better enabled to reason
more intelligibly, than now we can, concerning various operations in
nature.” Therefore,

In the following essay, I shall endeavour to shew,

I. How, and from whence, this electrical fire and force are produced;
in doing of which I shall make some observations, in order to shew that
we may form a more exact idea of most of the great operations of that
complete machine, the universe, from electrical experiments, than can
be attained by any other means: I shall also produce some experiments
which demonstrate, that the terraqueous globe has no _attraction_;
nor a solid body, falling towards the earth, any _gravitation_; after
which, I shall bring other experiments to prove what is the cause of
_solidity_, and by what means bodies _gravitate_ towards the earth.

II. How this electrical fire and force act upon the animal frame, and
in what disorders they are likely to be of benefit, and in what not.

I. We are certain, that this electrical fire is produced, either from
the glass globe, or the air that surrounds it. As to the glass globe,
Mr. _Freke_ has fully proved it cannot proceed from that; “Because
nothing, we know of, can send out of it a quantity of matter, but there
must be less of that matter remaining, after it has been so discharged;
whereas it cannot be shewn, but that the glass globe, after ever so
many times using, remains as fit for the same use, as at first.” From
hence we assert, that this fire must proceed from the surrounding air
being acted upon by the glass globe; and our inquiry must be, how, and
by what means, fire is produced by the glass globe being made to act
upon the air by which inquiry we shall find, that _air_, _light_, and
_fire_ are of the _same substance_, or _essence_; only differently
modified, and appointed for performing different actions: that air (by
being divided or broke to pieces) produces light; and, if that action
is still encreased, it produces fire. Now as the greatest friction
or attrition are necessary to produce fire, so fire, when it is once
produced, having received the greatest force, of consequence _acts_
with the greatest force; and light, with a less; so, wherever there is
the greatest quantity of these small particles of air, (which we call
by the name of fire) in proportion to what we call gross air, there the
action must be the greatest; by which means the said fire or light will
expand itself, ’till, by mixing with what we call gross air, it becomes
of an uniformity with it. Now therefore, as experiments are the sure
way either of proving or disproving any _hypothesis_; so, to illustrate
this, I shall produce some experiments both from Mr. _Freke_, and other
authors of unblemished credit, which prove that air is convertible
into light and fire, and also that light and fire are convertible back
again into air; and likewise, as some parts of the air are present in
all places and things, that therefore, whenever a violent action either
of solids or fluids is brought on, there light, fire, or heat, are
produced.

To prove this, Mr. _Freke_ has brought, two very simple, common, but
good experiments--First, if you slide a wax thread, or small rope,
through your fingers, it will burn them; so likewise fire is produced,
by rubbing two hard bodies together, or two sticks; or, as is very
often the case, a cart or coach wheel will take fire, for want of
grease.

Another no small proof of this, is what Mr. _Freke_ has mentioned,
viz. that in the year 1703, in the night of the great hurricane and
high wind, in the strongest part of the tempest, great quantities of
fire were seen passing swiftly over the hills in the neighbourhood of
_Warham_ in _Dorsetshire_. The cause of which fire seems very easily
accounted for, according to the above theory, which might otherwise
perhaps, elude the searches of our greatest philosophers: for in this
phænomenon it is plain, that the attrition of the particles of the air
was so great by the motion of the wind, as to produce fire or light.
Mr. _Freke_ has some other observations, which much strengthen the
above theory, viz. that in tempestuous weather, at sea, great flakes
of fire are frequently seen passing, not only in the air, but on the
water. The like is also observed, in the night time, when the surface
of the water is disturbed with the feathering of oars, or by a vessel
or boat passing swiftly through it. This light or fire _in storms_ is
no new observation; for Mr. _Boyle_ says, it is common in storms for
the fire called _Helena_, _Castor_, and _Pollux_, to hover about the
masts of ships. And, indeed,

To shew that fire or heat are produced in any place, or thing, where
there is a sufficient motion, seems not to be very difficult; for water
is the opposite to fire; and yet, by mixing water and spirit of wine
_suddenly_ together, a heat ensues; and this will happen if they have
been separated ever so often; but this heat vanishes again after they
are mixed, or as soon as the _motion_ of their parts ceases. The like
will happen by mixing salt of tartar and water. This phænomenon seems
to proceed from the disposition and texture of the salt; whose pores
are made of such a proper size, that, on receiving the water by the
pressure of the atmosphere into them, the texture of the salt may be
thereby broken, and its parts put _into motion_; which _motion_ causes
an _attrition_ of the air, and so produces a sensible heat.

_Boerhaave_ has another observation, which seems to prove to a
demonstration, that fire or heat is caused by an _attrition_ of the
air; which observation I shall give in his own words. “A cannon ball,
shot in the winter time, will fly 600 feet in a minute through the cold
air, which makes a greater resistance than any wind, the most rapid
of which only moves 22-1/2 feet; hence it appears how much _friction_
the ball must have undergone in its passage, which by the way did
not proceed in a right line, but by its whirling motion continually
describes a cycloid with every point of its body. When it falls,
it is found quite hot; notwithstanding in its whole passage, it had
continually met with cold air. This heat could not have arisen from
the flaming gunpowder, whereby it was exploded, since it only remained
in that flame, an incredible small space of time, in which it is by no
means credible so solid a body should have acquired such a heat; which
is much more naturally accounted for from the great attrition of the
ball, driven with such a velocity through the air, and repelled by a
wind, which is above 27 times swifter than the strongest wind hitherto
observed.” _Boerhaave_’s Chym. by _Shaw_, Vol. 1. pag. 244.

I shall mention one more experiment from Mr. _Boyle_, which proves that
_air_ is not only convertible into _light_; but that it may afterwards
be forced through glass, and thereby the same _vacuum_ be made that
is by an air pump. “Liquid phosphorus being put into a vial, when
it was disposed to shine in the dark, the cavity of the vial above
the liquor seemed to be full of whitish fumes, though at other times
transparent. The vial, when close stopped, was not luminous in the
dark, but the light or flame appeared as soon as it was exposed to the
air, and the vial was unstopped; and that the occasion and propagation
of this flame depended on the contact of the air, appeared, since
agitation would not kindle it, but when the bottle was unstopped, the
kindled flame would gradually be propagated downwards; the flame always
appeared most vivid the nearer the air, and when it was extinguished,
it first disappeared in the bottom, and then expired at the top. When
the Vial was unstopped for some time, when it was stopped again, the
air that had leisurely insinuated itself would cherish the flame for
an hour or two. It was observable, that when the air had been long
pent up with this shining liquor, its resistance would be so weakened,
that when the vial was unstopped, the external air would presently
rush in with violence, from whence appears the interest of the air in
propagating the shining of this liquor. The agitation before the vial
was unstopped would not kindle the light; yet when it was opened, it
would be increased by it, and even when it was in its dull state, if
I poured a little of it upon my hand, and rubbed it with my finger,
it would presently become vivid, and emit store of luminous rays, as
well as fumes very offensive to the nostrils; and when I ceased to
rub, and the luminous quality was lost, it would be renewed again by
a repeated attrition; but in a little time its lucid virtue would
decay,” _Boulton_’s Epitome of _Boyle_’s works, vol. 2. pag. 246. From
these experiments it may be observed, that this liquid phosphorus could
not be made to emit light, without a communication with the air, not
even by the utmost agitation; though when it had a free communication
with the air, a small agitation greatly increased the quantity and
strength of the light; that, whenever the air was admitted to join it,
a violent intestine motion came on, by which motion or attrition, light
was not only produced, but also a great deal of the liquid was carried
off by it; which might be perceived either by the sight, or smell.
And when the vial had been long without a cork, by which means it was
filled to the utmost with air, the light would continue a considerable
time after the vial was stopped. We likewise find, that, after the vial
has been stopped some time, and the liquor has acted upon the air as
much as it possibly can, there is not only a less quantity of gross
air than there was when the vial was first stopped, but that there is
the same _vacuum_ as is made by the air pump; for as soon as ever it
is unstopped, the air presseth in with violence, the fluid above the
phosphorus (within the vial) being of a more subtle nature than the air
without.

This experiment seems sufficiently to prove, that air and light are
of the same essence or substance; for we are certain that gross air
entered the vial, and, when it was first stopped, the quantity of
gross air was of an uniformity with the air without the vial; but at
its being opened, we are assured, there was a less quantity than when
it was first stopped; for the air without presseth in with the same
violence it does into the exhausted receiver of an air-pump; by which
we may be assured, that some parts of the air have passed the vial in
form of _light_; and, as the pores of the glass are not big enough to
admit gross air to return, the consequence must be, that there is a
less quantity of gross air in the vial at the opening, than there was,
when it was first stopped.

Fire and light are easily proved to be dispersed through the whole air,
from the immediate action of _speculums_; and that air itself is of the
same substance with fire seems very plain; for as fire cannot subsist
without air, (and in proportion to the quantity of air forced into the
fire, in such proportion will be the force of the fire;) so, neither
can fire act but on the outside of bodies next the air; for even the
most inflammable bodies can only catch fire on their outermost surface
contiguous to the air; and fire in action, if immerged in a body of
the most inflammable matter, so as to leave no lighted part above such
surface in the air, will be so far from kindling the inflammable body,
that itself will be extinguished. Thus “if a flaming brimstone match
be plunged into the highest rectified spirit of wine, the spirit of
wine will extinguish it as intirely, as if dipped in cold water; it
will also extinguish a live burning sparkling coal; but in the former
experiment, if the least bit of the burning match remains above the
spirit of wine, it will then catch fire, and the flame will presently
spread over the whole surface.” This is an experiment of the great
_Boerhaave_, in the first vol. of his chymistry, by _Shaw_, pag. 316.

All these experiments, I think, prove to a certainty, that air is
convertible into light. I shall now bring one experiment, from
_Boerhaave_, Vol. 1. p. 998. which proves, that fire or light may be
changed into air.

“If a spherical glass vial be kept in a glass-house furnace, till ready
to melt, and then be hermetically sealed in that heat, and suffered to
cool; if now, it be held inverted, under cold water, and the end of the
neck be carefully broken off, the water will be violently forced into
it, and fill the glass, but so as to leave a bubble of true elastic
air at the bottom.”

The above experiments prove, that, whenever air is sufficiently divided
or broken to pieces, light is produced; so that the light or heat in
electricity, is no other than, we find, may be produced several other
ways. For the air being violently rubbed or ground to pieces between
your hand and the glass globe, whirled briskly about, the air between
your hand and the globe is ground so small as to be in the form of
_light_, which is expanded or sent off from the glass globe in the same
manner as _light_ from a candle, or other luminous body; which emission
is continually supplied by the common air pressing in between the rays
of _light_, emitted from the glass ball. That this is the method, by
which it acts, seems very clear: for you may not only hear the hissing
noise of the air pressing towards the globe, but also plainly feel the
air with your hand, near the globe or tube.

The chief reason (and what has been our great misfortune) that we
have not been able to discover the cause of electricity, seems to
be the leaving that philosophy, which has been _revealed_ to us,
and putting in its stead _theories_ of _our own invention_. For, if
we had considered (from the _revealed_ account that is given us of
the formation of light) the _method_ of its _first_ production, we
should not be at such a loss to account for that light in electricity,
as we hitherto seem to have been; for we are _there_ told, that
the _heavens_, or airs, were created in a state of _darkness_, or
inactivity; and that the first thing God did, was to cause a _motion_,
or _wind_ amongst the airs; which _motion_ was to _continue_, and
_encrease_, till it produced _light_; and, after this _light_ was
produced, God called it _Day_, or as it is expressed in the original,
_tumultuousness_; it being produced from the impetuous or violent
motion of the airs: and the _darkness_ he called _night_, or, as it
is likewise expressed, the time when this _languishes_ or _decays_;
for the _congealing_ or _thickning_ of the air, by which _darkness_ is
produced, is in proportion as the _force_ of the _light_ abates.

By all which, I think, we may be assured, that the _light_, and all the
_phænomena_ produced in electricity, are caused by a violent _friction_
or _grinding_ of the grains of air between the glass globe and the hand.

To illustrate and prove, that this is the method by which the
electrical _light_ is produced, I shall bring some experiments, from
Mr. _Hauksbee_, which, I imagine, will make it indisputable. In his
first and second experiments, he shews us, that by dropping mercury
on a glass in an exhausted receiver, the _action_ of the mercury
on that subtil fluid gives the mercury the appearance of fire; but
observes, that in all these experiments on mercury, no _light_ is to
be obtained without _motion_, and that the same motion which produced
this light in _vacuo_, did not produce it, when given to mercurial
globules in _open air_. This experiment shews us, that there was a
larger quantity of _light_ in the exhausted receiver than when it was
filled with common air; nay farther, that the _subtil fluid_ contained
in the exhausted receiver, was _light_; but, for want of _motion_, was
not perceptible by our senses; but by so small a motion as that of
the descending mercury, it was pushed forward in the same manner, as
_light_ from a candle, or other luminous bodies. We also find, that
the same experiments performed in an _unexhausted_ receiver, would not
produce the _phænomenon_ of _light_; which one might easily suppose to
be the case. For in the _exhausted_ receiver, any the least _motion_,
that is sufficient to _push_ this subtil fluid (_light_) from one
place to another must give us the perception of _light_; but in the
_unexhausted_ receiver the _motion_ or _friction_ must be great enough,
not only to _push_ the air from place to place, but also to _break
it_ so small, as to be in form of _light_: which he shews us by his
third, fourth, and fifth experiments to be the case; for by these
experiments he produced _light_ in an _unexhausted_ receiver; but then
the _motion_ or _agitation_ was required to be much _greater_ than that
which produced _light_ in _vacuo_. The difference of these two _lights
was very considerable_, and consisted particularly in this, that the
luminous particles are _distinct_ and _separate_ in the experiment
performed in the _open air_; and _united_ and _blended_ into one
continued body of _light_, in the other experiments in _vacuo_; which
difference proves to a demonstration, that the exhausted receiver was
full of nothing but _light_; for, on shaking the mercury therein, the
whole body of the receiver seemed to be _one continued body of light_;
but on shaking the mercury with ever so great a violence in the common
air, it seemed full only of _little_, _bright_, _twinkling sparks_;
and not one continued body, as in _vacuo_. For, as the appearance of
_light_ is produced in the common air, by the _friction_ of the mercury
against the glass receiver, _breaking_ or _grinding_ the air to pieces
(which small particles put on the form of _light_) so, when the common
air _presses_ in between these small particles, the appearance must be,
and cannot be otherwise than is shewn by these experiments.

These many and various experiments abundantly prove, that _light_ is
produced as above described; and not, as the generality of people have
imagined (from that mistaken notion of _action_ being performed by
_solids_ and not by _fluids_) that this electrical _light_ proceeded
from the glass globe, emitting, what they call, _electrical effluvia_,
which has been shewn before to be impossible; because if any quantity
of matter sends off part of its own body, there must be less of that
body remaining, than before the above matter was sent off, which we
find is not the case of the glass globe; and to prove that it does not,
I shall bring one experiment more from Mr. _Hauksbee_ which will put it
beyond doubt.

Pag. 27. he shews us, that by a violent _attrition_ of _woollen_
against _woollen_ in _vacuo_, he produced _light_, as well as from
any _hard_ or _electrical_ body; but not so vivid, nor in so large a
quantity. Now, as woollen is reckoned by all to be a _non-electrical_
body, it shews us that the _light_ must proceed from the _attrition_
of the air, and not from the _electrical body_, as has been falsely
imagined.

As _light_ may be produced by other methods than have been yet
described, as from _rotten wood_, _fish_, _meat_ &c. I shall endeavour
to give an account, how, and in what manner, that _light_ is produced.
Mr. _Boyle_ (in vol. 2. p. 233. of the epitome by _Boulton_) tells us,
that by putting _rotten wood_, _fish_, _flesh_ &c. in the receiver
of an air-pump, and then extracting the gross air, they all, in a
little time, lost their _shining_ or _luminous_ quality; but, upon
a re-admission of air, this _luminous_ quality returned. From which
we may learn, that the air is essentially necessary to continue
this _light_; and, of consequence, that this _light_ is produced by
the _action_ and _re-action_ of the air on the body, which cause an
_intestine motion_ of its parts; and thereby the emission of the said
light; for when any thing begins to ferment and _putrify_ (which cannot
be performed in any place, but where the gross air is present) the
_intestine motion_ of its parts is thereby _increased_; which _motion_
acting upon the air pressed into it, the air is thereby _ground_ very
small, and by the continual pressure of the atmosphere is sent out so
small, as to be in form of _light_.--In the common _fermentation_ of
liquids, when it rises to any height, those particles of _light_ being
_stopped_, and _entangled_ by the _watry parts_ of the fermenting mass,
thereby produce _heat_; and some mixtures will produce _light_, _heat_
and _flame_ on fermentation; as _steel_, _water_, and _sulphur_.

By these experiments we have a clear idea of the means and method by
which _fermentation_ is performed, which operation has been hitherto
unintelligible. From hence we may likewise see the reason why, in an
air either _too hot_ or _too cold_, _fermentation_ cannot be performed;
for in an air _too cold_, the pressure is _too great_, and also the
grains of air _too large_ to _enter_ and _divide_ the thing to be
_fermented_; by which means the _motion_ of its parts requisite to
_fermentation_ is prevented; but in air that is _too hot_, there must
be just the contrary effect, for there the parts of the thing to be
_fermented_ are so far _expanded_, and the air so _rarified_, as to
pass through the body with little or no obstruction, and of consequence
to produce little or no _intestine motion_ of its parts; and that
there is in _fermentations an intestine motion_ of the parts of a
_fermenting_ liquid, is easily discernible by the naked eye. This also
gives us the reason, why the _glow-worm_ shines only in the summer
months, when the air is greatly _rarified_, or _divided_, and then
requires but a small _motion_ to give it the form of _light_.

The _light_ proceeding from _diamonds_ &c. seems to be easily accounted
for from the _motion_ of the _airs_; that there is a _perpetual motion_
of the _airs_, may be proved by the following experiment. In a still
place, suppose a close darkened room, illuminated only by one small
hole in the window shutter; where, if a person at rest views the
enlightened current of air sideways, as it extends along the room,
he will perceive a _surprising motion_ of the dusty atoms therein,
_perpetually rolling and tossing_ about _with great rapidity_. This
_motion_ must be very _considerable_, as it is _perpetual_, and pushed
on with the power of _gravity_ in the air equal to a column of water
33 feet high. By this _action_ on _diamonds_, whose _pores_ are very
_small_, and the bodies themselves of such a _make_ and _hardness_, as
that, when the air is pressed on them with so great a _force_ as that
of the _incumbent atmosphere_, the air is _broke exceedingly small_,
and, by the continuance of the _pressure_, is sent off from the body
in form of _light_. We likewise find from experiments, that where
_diamonds_, or other bodies of that kind, have not their outward parts
of a proper _make_, or their _substance_ of a _sufficient hardness_ or
_closeness of parts_, to emit _light_ with no greater _force_, than the
pressure of the _atmosphere_ only, then this deficiency may be supplied
by _rubbing_; by which means the air is _ground_ to pieces, and emitted
in form of _light_, as is shewn in all electrical experiments.

One great property of _light_, or, as it is commonly called the
_electrical effluvia_, is (as Mr. _Hauksbee_ has proved from many
experiments,) that it passes _through glass_, as water does through a
sieve, or as if no body of matter interposed. This _light_ of itself,
when _pure_, or _simple_, hurts or destroys no material bodies;
but when _pushed_ on by the following air with _great violence_,
and _meeting_ with a _great resistance_ from an impeding body, the
_conflict_ is so great, that if the following air _presses_ on with
_sufficient violence_, it _dissolves_ or _destroys_ the _solidity_
of any material body. As all bodies become _solid_ according to the
_temperature_ of the surrounding air; some retaining their _solidity_
in such a degree of _heat_, as _metals_ of most kinds; whilst others
require a particular degree of _cold_ before they become _solid_,
as _water_ &c. which when froze is as much a _solid_ as any thing
else--this proves that the _solidity_ of bodies depends on the
_temperature_ of the air, as will be more fully proved hereafter.

The glass globe, with the electrical experiments, seems to give
a very clear idea in what manner the _sun_ is _supported_, how
this _terraqueous globe_ and the rest of the _planets_ are made to
_move_, and _continued in motion_; and also, what is the cause of
the _attraction_ of the _sun_, _earth_, _moon_ and the rest of the
_planets_.

That the _sun_ is the chief, material, ruling agent, is very clearly
revealed; as are some of its chiefest actions on the planets and the
rest of the universe. For, in the sun we find a power of melting,
dividing and (with the assistance of the air) expanding and sending out
the air, first in form of _fire_, and afterwards in that of _light_;
which power seems to be so regulated, as to be able to reach the
extremities of the universe, where it is _congealed_, _condensed_, and
_returned_ back again to the _sun_, to be again _melted_, _divided_,
and sent out as before. This action seems to be represented by water
in a _still_, for there the fire, forcing its way through the water
contained in the _still_, carries off some of the watry particles with
it; and when it has reached the head of the _still_, if it has no
passage into the outward air, and the _action_ of the fire is not great
enough to break the _still_, it is by the coldness of the surrounding
air (or as is commonly the case by the coldness of water placed thereon
for that purpose) _condensed_ and _returned_ into the water contained
in the body of the _still_, there to be _rarified_, _expanded_, and
sent off in _steam_, as before.

We must suppose the streams of _light_ to be always acting on one
side of this terraqueous globe, and there _dividing_, _expanding_
and _rarifying_ the air; the consequence of which must be a kind of
_vacuum_, which is immediately filled by the _pressing in_ of the
_congealed air_ from the extremities; and as the earth is placed in
this fluid of airs, we may as easily conceive that the air pressing
in as above, must, with it, turn round the earth, in the same manner,
and with as much ease, as water does a common mill-wheel, or the air a
wind-mill. By these powers also the terraqueous globe is kept _solid_
and _entire_; for, was this force once taken off, it would soon drop
to _atoms_, notwithstanding the pretended _attracting_ power of its
materials.

To confirm what is here advanced, I shall bring an experiment (which
Mr. _Boyle_ has laid down as a paradox) which proves that this
terraqueous globe has no _attraction_, nor any _solid_, falling towards
it, any _gravitation_; but that all bodies _are forced_ to it by the
_incumbent atmosphere_, as much as water is _forced_ up a pump by it
(the atmosphere) which, till the time of the great Mr. _Boyle_, was
imagined to be performed by, what they called, the _suction_ of the
pump. But this is no more than has often happened in philosophy, where
when we cannot well account for any thing, we put the _effect for the
cause_.

Mr. _Boyle_ found that a _solid body_, as _ponderous_ as any yet known,
though near the top of the water it would sink by _its own weight_,
yet if it be placed at a greater depth than twenty times its own
thickness, it will _not sink_, if its descent be not assisted by the
_weight_ of the _incumbent water_. To prove this, he gives us a curious
experiment, viz. by keeping off the _pressure_ of the water, from
the _top_ of the _sinking body_, and _sinking_ it to a proper depth,
he found, that the _most ponderous_ body would be _buoyed up_, and
_supported_ by the water only. See the 2d vol. of _Boulton_’s epitome,
pag. 305. This experiment shews us beyond all contradiction, that the
_earth_ has no power of _attraction_, nor a _descending body_ any power
of _gravitation_; for if it had, the farther it was sunk in the water,
the nearer it must be to the centre of the earth, and of consequence
the _attraction_ must be the greater; but this, we find, is contrary
to experience; so that the whole power of descending is impressed upon
it by the _air_, or by other bodies forced upon it by the _incumbent
air_. This experiment alone is more than sufficient to destroy the fine
theories of _attraction_ and _gravitation_; it also shews us how, and
by what means, two marble slabs, finely polished, are what they call
_attracted_ to each other, and require a great force to separate them;
a force in proportion to the breadth of the slabs; but this has been
shewn by other experiments to be nothing but the _pressure_ of the
_air_, or _atmosphere_; for put them into an air pump, and extract the
_gross air_, and they will immediately separate from each other.

One reason, which seems to have led us into the mistake that the
_solidity_, or _firmness_ of bodies is not caused by the _air_, has
been, that, for the generality, we consider the _air_, or _atmosphere_
as _pressing_ only _downwards_; for if we had considered that it
_presseth_ equally _every way_, as well as _downwards_, (as _Boerhaave_
in his chym. by _Shaw_, vol. 1. p. 389. has shew by the following
experiment) I believe we should not have overlooked that force, or have
thought it insufficient for this operation. “Fill three glass vessels,
the one of a cylindrical figure, the other conical, the third bellied
with a cylindrical neck; let these be filled to the brim with fair
water, and covered with a single piece of paper, so as to touch the
surface of the water, and by pressing it down with the hand, prevent
the external air insinuating between the paper and the water; if the
glasses be now inverted, whilst the paper remains close with the palm
of the hand, and the hand be afterwards gently withdrawn, the water
will still remain in the glasses. The same holds true, though the
glasses be held horizontal, or in any other position.” As the cause of
the _solidity_ or _firmness_ of bodies is the _pressure_ of the _air_
or _atmosphere_, so likewise it must depend on the _make_ and _size_ of
the _pores_ of such bodies; for bodies whose _pores_ are _smallest_,
must be acted upon with a greater power than those whose _pores_
are _largest_, or whose _pores_ are so _large_ as not only to admit
_light_, but also _common air_ into them. This Mr. _Hauksbee_ proves by
a curious experiment, for having placed two brass hemispheres, of 3-1/2
inches diameter, upon each other, and then extracting the gross air out
of them by the air pump, and by these means taking off the _resistance_
of the _common air_ that was _within_ the two brass hemispheres, he
says, it required 140 pound weight to separate them; this experiment
with that of the two marble slabs before mentioned, is a demonstration
of the _power_ that keeps _solid bodies_ from _falling_ to _pieces_.
And even, if these slabs are not so _perfectly smooth_, yet the weting
them with water, which prevents the gross air from _entering_, will
produce the like effect. That solids _expand_ themselves by _heat_ or
_fire_, is proved by heating an iron rod in the fire: in which case,
it is always found to be _bigger_ and _longer_ when _hot_ than _cold_;
and it was the opinion of _Boerhaave_, that cold _consolidates_ all
those that are called firm bodies; that is, brings that part, which
we call _body_ in them, into a _less compass_ than before, and thus
_unites_ the matter thereof more closely together: by which means the
_cohesion_ of the whole mass is usually increased; which makes what we
call, _strength_ and _firmness_ in bodies.

Having shewn that _solid bodies_ have no power either of _attraction_
or _gravitation_, and that their _firmness_ or _solidity_ depends on
the _pressure_ of the _atmosphere_; I shall now endeavour to shew, from
electrical experiments, how, and by what means they _descend_ towards
the earth.

What is called the _attraction_ of the _earth_ seems to be performed
in the same manner as that of the _glass globe_ in electricity; the
explaining of which will give us a clear idea, by what means _heavy
bodies_ are _forced_ towards the terraqueous globe. In accounting for
this electrical _attraction_, Mr. _Hauksbee_ seems to be very clear;
for, says he, “if by the heat and rarefaction, consequent upon the
attrition, the medium contiguous to the glass be made specifically
lighter; then of course, to keep up the ballance, the remoter air,
which is denser, must press in towards the tube, and so carry away (in
the torrent) the little bodies lying in its way, thither also. The
various irregularities in the excitation, or the emission and discharge
of the electrical matter or light from the tube (which will be followed
with proportional irregularities, in the motion and tendency of the
denser air, towards the glass globe, by the hydrostatical laws) may
be sufficient to account for the various uncertain motions of the
little bodies carried towards the glass globe.” This account of Mr.
_Hauksbee_’s being so very clear, it is a little surprising that he
should allow the power of _attraction_ to matter, as in some places he
does; for this is no more than in other words, telling us, that the
air round the ball is _divided_ and _rubbed_ or _ground_ to pieces by
the _friction_ between the glass globe and your hand, and thereby made
to _expand_ itself; so the air pressing in to make up that deficiency,
forces every thing towards the glass globe, that by its number of
particles is not able to withstand the _current_ of _air_, pressing
towards the globe. So in like manner near the surface of the earth, the
sun-beams being _reflected_ by the terraqueous globe, must by these
means be in a greater quantity near the surface of the earth, than at a
distance from it; and so _divide_, _expand_ and _rarify_ the air near
its surface, which _rarified_ or _divided_ air is forced off from the
earth on all sides, by the _pressing_ in of the air from above, which
must of consequence _drive_ every thing before it, towards the earth.
By which we find, that the cause of bodies _descending_ towards the
earth, is not from any _property_ either of the _earth_ or of the
_descending bodies_; but that these are _forced_ towards that, by the
surrounding _air_, in its said _motion_.

To prove that this is the method by which, in electricity, bodies are
forced towards the glass globe, I shall bring an experiment or two from
Mr. _Hauksbee_; and as these experiments prove to a certainty, that
this is the manner of the _attraction_ in _electricity_, it will give
us little room to doubt, but that the _attraction_ of the _earth_ is
performed in the same manner.

Mr. _Hauksbee_ observed, that the _electrical effluvia_ were not only
perceiveable by sight; but also, if the hand was held near the tube,
seemed to make such sort of strokes upon the skin, as a number of fine
limber hairs pushing against it might be supposed to do: and in order
to find whether the electrical _attraction_ was regular and uniform,
he made the following curious experiment, shewing that all bodies, not
too heavy, are _forced_ (or, as is commonly supposed, _attracted_) to
a cylindrical glass, equally all round, if these bodies are, as _they
term it_, within the sphere of its activity.

This experiment seemed to affect Mr. _Hauksbee_ so much, that (speaking
of electricity) he says, “it affords us a sort of _representation_ of
the _great phænomena_ of the _universe_.” Page 53.

[Illustration]

“For, says he, having observed (in electricity) that light bodies,
placed near any part of the rubbed cylinder, seemed to be equally
attracted, I contrived a semicircle of wire, which I could fasten at
a constant distance, making it encompass the upper semi-cylindrical
surface of the glass, at 4 or 5 inches distance. This wire had
several pieces of woollen threads fastened to it at pretty near equal
distances. The length of them was such, that being extended in a
direction towards the center of that imaginary circle, on the surface
of the glass, in the plane of which the wire was placed; they would
then reach within an inch of the circumference of that circle: but
if left to their own liberty, they hung in that parallel portion
represented, fig. 1. The cylinder was placed with its axis parallel to
the horizon; and in this posture, it was turned swiftly round; and
then by the rapid motion and agitation of the surrounding air, the
threads were placed into such portions, as are expressed fig. 2. viz.
they were all lifted up and bent upwards from the axis of the cylinder.

“All this while, there was only the swift motion of the cylinder
round its axis, without any attrition, but now when I came to apply
my hand to the lower part of the glass (so swiftly whirled about)
and consequently to add attrition to the former motion; the threads
presently began to change their direction, and all harmoniously pointed
to the center of the circle, in whose plane the wire was placed, as
in fig. 3. neither were they at all disordered or flung out of that
position, by the wind occasioned by that violent motion (but as if
there had been no such hurry of air about them) they still persisted
in their central direction; I found I could by shifting the place of
the attrition hither or thither, draw the threads towards this or that
end of the cylinder; but yet they all still went uniformly converging
towards some center in the axis of it; so that they formed themselves
into a sort of conical surface.

“Farther, if the wire with its loose threads was reverted, so as to
encompass the lower part of the cylinder (as before it did the upper
part) yet the effect still answered with the same exactness. For the
threads were all erected into so many strait lines, still directing
themselves towards a center in the axis of the glass.

“Hitherto the axis of the cylinder was placed horizontally; in the next
place I set it in a vertical position, so that it stood perpendicular
to the plane of the horizon; in which case I made use of a wire hoop,
which was necessary to be placed parallel to the horizon, that it might
encompass the cylinder, in the same manner as the semicircular wire did
before: only one small part of this wire was left open, to make way
for the touch of the hand, which was to give the attrition. And the
wire being thus placed, it was evident that the threads (without some
external force to support them) must all flag and hang perpendicularly
downwards. Yet, as soon as the motion and attrition were given, the
threads presently began to be extended; and as if they were become
stiff and hard, formed themselves into an horizontal plane; their loose
ends pointing to a center in the axis of the glass, as before.

“And thus (in all sorts of positions whatsoever, both of the wire and
of the glass too) were the threads acted upon by a sort of centripetal
force; to the laws of which they were always conformable.” See
_Hauksbee_’s experiments, page 53 &c.

It may be observed in this experiment, that the _attractive_ power of
bodies does not lie in _solids_, as has been falsly imagined, neither
have such bodies any _centripetal_ or _centrifugal_ force; but that
this _power_ and _force_ are given them from _without_. For, on placing
the wire with the threads round the cylinder, they were all _forced_
(or as it is often called, _attracted_) towards the _earth_; but, on
giving a _violent motion_ to the cylinder, they were drove from the
cylinder, as if forced by a strong wind; but, by applying the hand to
the glass cylinder, they were recalled, and all pointed to a center
in the axis of the cylinder: and this _central_ direction might be
altered at any time, by only moving the hand to different parts of
the cylinder; the threads always pointing to the place where the
_attrition_ was made: by which we find, that the _central_ force, both
of the cylinder and the threads, are caused by the _attrition_ of the
_air_ between your hand and the cylinder; whereas, at any other time,
they are quite inactive: so we are assured that these _central_ forces
which have been imagined to be _within_ the _solid_, are not there, but
in the _air without it_.

On putting something between any of the threads and the cylinder; then,
those threads would return to their first and _natural position_, viz.
point towards the center of the earth. So, as Mr. _Hauksbee_ observes,
“in these small orbs of matter we have some little resemblances of the
_grand phænomena_ of the _universe_.”

Another thing observable was, “that by putting these threads within a
glass, when they became extended, this position of the threads would be
altered at any time on the approach of one’s hand, finger, or any other
body, to the surface of the glass.” This is sufficient proof that the
_light_, or as it is generally called, the _electrical effluvia pass_
through the _glass_, with as much ease as water does through a sieve.

One thing which seemed a little surprising to Mr. _Hauksbee_ was, that
upon exhausting the _gross air_ out of the tube or globe made use of
in electricity, what he called the power of _attraction_, would cease;
but upon suffering the air again to enter, it returned as vigorous as
before. This must be the case; for (as was before observed) whenever
the gross air is extracted by an air pump, the fluid remaining is
nothing but _light_. So, whenever this attrition is performed on an
exhausted globe (for want of the resistance of the gross air within, to
force off the particles of air ground so small as _light_, and thereby
to make an _expansion_ or _rarefaction_ round the glass globe, which
has been shewn to be the cause of light bodies being _forced_ towards
the globe) these particles of _light_ do immediately enter the globe on
one side, and _force_ out the same quantity on the other; in the same
manner as water through a sieve, without ever making any _expansion_ or
_rarefaction_.

Having thus shewn how and by what means the _fire_ and _light_ in
electricity are produced; our next inquiry must be, why some bodies
communicate this _light_ to ever so great a distance, and that
instantaneously; whilst others will not; and also, why some bodies are
_electrical_ and others _non-electrical_.

_Electrical bodies_ are those, whose _pores_ are so _fine_, as to admit
nothing through them but _light_, or air ground to a proper fitness;
as _metalls_, _glass_, _amber_, _wax_ &c. Bodies _non-electrical_, are
all those, which, by the _largeness_ of their _pores_, admit, not only
_light_ but also _gross air_.

We see, when the air is _ground_ to pieces by an electrical machine,
and _put_ into _sufficient motion_, by the _friction_ between the glass
globe and the hand, a wire being hung from the iron barrel, so as very
near to touch the ball, part of the _light_ issuing from the ball,
as above described, _enters_ the wire, and is by it communicated to
the iron barrel, and from thence _carried_ by _another wire_ to any
distance, if not interrupted by some _non-electrical_ body: to the end
of which, by a third wire is hung an egg; as soon as the globe is put
in _motion_, and warm spirit of wine is placed so as to touch the egg,
the spirit of wine will immediately take fire from the contact of the
egg.

It has been already proved, that when the globe is put in _motion_, and
your hand is applied to it, it _grinds_ to pieces the air between the
globe and the hand, and so _rarefies_ and _expands_ it, and sends it
off with great force, in the same manner, as _light_ is sent from any
body of _fire in action_; as may be seen, if the electrical machine is
set at work in the dark; when the emission from the glass globe will
appear lucid.

The wires which are hung over the glass globe, by the _smallness_ of
their _pores_, admitting nothing through them but _light_, and light
being a body so _subtil_, as to penetrate the _pores_ of all other
bodies, even to the very center of the earth; the _interstices_ of the
_wires_ are filled with it from one end to the other.

As the _light_ is one continued body, throughout the whole extent of
the wire, the _force_ it receives at the end next the glass globe, is
_immediately_, and at the _same instant_ of time, communicated to the
other end, let the _length_ or _extent_ of the wire be ever so great.
As, for example, a pipe of any length, being filled with any sort
of fluid, as water; if you force in more water at one end, the same
moment, and in the same quantity, it will be forced out at the other.

By these experiments in electricity, we find that _fire_ and _light_
are produced as has been before observed, only by _breaking_ the air
to pieces, and putting it in _motion_; and that _fire_ and _light_ are
in _all_ bodies, water and ice not excepted; for, if a piece of ice is
hung at the end of the wire, it will set fire to spirit of wine, as
well as an egg.

The iron wire by the _closeness_ of its _pores_ prevents the
surrounding air from entering it, and by that means at the same time
forms a kind of _canal_ for the _light_ to pass through.

Having thus as I conceive, given a tolerable clear account, and, I
hope, a true one, how and by what means, the various _phænomena_ in
electricity are produced; I suppose, it will not be a very difficult
task, to form a judgment, what disorders electrical operations are
likely to be applied to, with hopes of service; as also in what others
they are likely to be detrimental.

As the _heat_ and _redness_ of the _blood_, may be easily proved, to
be in proportion to the _quantity_ and _motion_ of the _light_ it
contains; so, wherever the blood is _heated_ to a great degree, as in
_fevers_, _Inflammations_ of all kinds &c. there we are to expect the
worst and most pernicious consequences, from the use of electricity.

But, on the contrary, as the nerves have been proved to act by a
subtil fluid that passes through them, and that they, by the closeness
of their pores, will not admit a fluid to pass through them, whose
particles are much larger than those of _light_; the consequences we
must often expect from such a make, must be obstructions; and as the
_light_ in electricity is forced through our bodies and nerves, with
great violence, it seems very reasonable to think, that where these
obstructions are not too violent, there they may be broken through and
removed by its power, of which we have had many instances, especially
in palsies.

This is also confirmed by the success of the present practice of
physick; for, the greatest relief, in these cases, is always found to
proceed from _volatile_ and _penetrating_ medicines. But, care should
be taken, not to administer electricity, to a person of weak and
decayed nerves, instead of one whose nerves are obstructed.


_FINIS._





End of Project Gutenberg's A Treatise on Electricity, by Francis Penrose