Friction between a non-electric and an electric per se, will produce electrical fire;
not by creating, but collecting it: for it is equally diffused in our walls, floors,
earth, and the whole mass of common matter. Thus the whirling glass globe, during its friction
against the cushion, draws fire from the cushion, the cushion is supplied from the frame of the
machine, that from the floor on which it stands. Cut off the communication by thick glass or wax
placed under the cushion, and no fire can be produced, because it cannot be
collected.The Ocean is a compound of water, a non-electric, and salt an electric per se.
When there is a friction among the parts near its surface, the electrical fire is collected
from the parts below. It is then plainly visible in the night; it appears at the stern and in the
wake of every sailing vessel; every dash of an oar shows it, and every surff and spray: in storms
the whole sea seems on fire.—The detach'd particles of water then repelled from the
electrified surface, continually carry off the fire as it is collected; they rise, and form
clouds, and those clouds are highly electrified, and retain the fire 'till they have an
opportunity of communicating it.The particles of water rising in vapours, attach themselves to particles of air.
The particles of air are said to be hard, round, separate and distant from each other;
every particle strongly {39}repelling every other
particle, whereby they recede from each other, as far as common gravity will permit.The space between any three particles equally repelling each other, will be an equilateral
triangle.In air compressed, these triangles are smaller; in rarified Air they are larger.
Common fire joined with air, increases the repulsion, enlarges the triangles, and thereby
makes the air specifically lighter. Such Air among denser air, will rise.Common fire, as well as electrical fire gives repulsion to the particles of water, and
destroys their attraction of cohesion; hence common fire, as well as electrical fire, assists in
raising vapours.Particles of water, having no fire in them, mutually attract each other. Three particles of
water then being attached to the three particles of a triangle of air, would by their mutual
attraction operating against the air's repulsion, shorten the sides and lessen the triangle,
whereby that portion of air being made denser, would sink to the earth with its water, and not
rise to contribute to the formation of a cloud.But if every particle of water attaching itself to air, brings with it a particle of common
fire, the repulsion of the air being assisted and strengthened by the fire, more than obstructed
by the mutual attraction of the particles of water, the triangle dilates, and that portion of air
becoming rarer and specifically lighter rises.If the particles of water bring electrical fire when {40}they attach themselves to air, the repulsion between the particles of water
electrified, joins with the natural repulsion of the air, to force its particles to a greater
distance, whereby the triangles are dilated, and the air rises, carrying up with it the water.If the particles of water bring with them portions of both sorts of fire, the
repulsions of the particles of air is still more strengthened and increased, and the triangles
farther enlarged.One particle of air may be surrounded by twelve particles of water of equal size with
itself, all in contact with it; and by more added to those.Particles of air thus loaded would be drawn nearer together by the mutual attraction of the
particles of water, did not the fire, common or electrical, assist their repulsion.If air thus loaded be compressed by adverse winds, or by being driven against mountains,
&c. or condensed by taking away the fire that assisted it in expanding; the triangles
contract, the air with its water will descend as a dew; or, if the water surrounding one particle
of air comes in contact with the water surrounding another, they coalesce and form a drop, and we
have rain.The sun supplies (or seems to supply) common fire to all vapours, whether raised from earth
or sea.Those vapours which have both common and electrical fire in them, are better supported,
than those which have only common fire in them. For when vapours rise {41}into the coldest region above the earth, the cold will not diminish the
electrical fire, if it doth the common.Hence clouds formed by vapours raised from fresh waters within land, from growing
vegetables, moist earth, &c. more speedily and easily deposite their water, having but little
electrical fire to repel and keep the particles separate. So that the greatest part of the water
raised from the land is let fall on the land again; and winds blowing from the land to the sea are
dry; there being little use for rain on the sea, and to rob the land of its moisture, in order to
rain on the sea, would not appear reasonable.But clouds formed by vapours raised from the sea, having both fires, and particularly a
great quantity of the electrical, support their water strongly, raise it high, and being moved by
winds may bring it over the middle of the broadest continent from the middle of the widest
ocean.How these ocean clouds, so strongly supporting their water, are made to deposite it on the
land where 'tis wanted, is next to be considered.If they are driven by winds against mountains, those mountains being less electrified
attract them, and on contact take away their electrical fire (and being cold, the common fire
also;) hence the particles close towards the mountains and towards each other. If the air was not
much loaded, it only falls in dews on the mountain tops and sides, forms springs, and descends to
the vales in rivulets, which united make larger streams and rivers. If much loaded, the electrical
fire is at once taken from the {42}whole cloud; and, in
leaving it, flashes brightly and cracks loudly; the particles instantly coalescing for want of
that fire, and falling in a heavy shower.When a ridge of mountains thus dams the clouds, and draws the electrical fire from the
cloud first approaching it; that which next follows, when it comes near the first cloud, now
deprived of its fire, flashes into it, and begins to deposite its own water; the first cloud again
flashing into the mountains; the third approaching cloud, and all the succeeding ones, acting in
the same manner as far back as they extend, which may be over many hundred miles of country.Hence the continual storms of rain, thunder, and lightning on the east-side of the
Andes, which running north and south, and being vastly high, intercept all the clouds
brought against them from the Atlantic ocean by the trade winds, and oblige them to
deposite their waters, by which the vast rivers Amazons, La Plata, and
Oroonoko are formed, which return the water into the same sea, after having fertilized a
country of very great extent.If a country be plain, having no mountains to intercept the electrified clouds, yet is it
not without means to make them deposite their water. For if an electrified cloud coming from the
sea, meets in the air a cloud raised from the land, and therefore not electrified; the first will
flash its fire into the latter, and thereby both clouds shall be made suddenly to deposite
water.The electrified particles of the first cloud close when they lose their fire; the particles
of the other cloud {43}close in receiving it: in both,
they have thereby an opportunity of coalescing into drops.—The concussion or jerk given to
the air, contributes also to shake down the water, not only from those two clouds but from others
near them. Hence the sudden fall of rain immediately after flashes of lightning.To shew this by an easy experiment. Take two round pieces of pasteboard two inches
diameter; from the center and circumference of each of them suspend by fine silk threads eighteen
inches long, seven small balls of wood, or seven peas equal in bigness; so will the balls
appending to each pasteboard, form equal equilateral triangles, one ball being in the center, and
six at equal distances from that, and from each other; and thus they represent particles of air.
Dip both sets in water, and some cohering to each ball they will represent air loaded. Dexterously
electrify one set, and its balls will repel each other to a greater distance, enlarging the
triangles. Could the water supported by the seven balls come into contact, it would form a drop or
drops so heavy as to break the cohesion it had with the balls, and so fall.—Let the two sets
then represent two clouds, the one a sea cloud electrified, the other a land cloud. Bring them
within the sphere of attraction, and they will draw towards each other, and you will see the
separated balls close thus; the first electrified ball that comes near an unelectrified ball by
attraction joins it, and gives it fire; instantly they separate, and each flies to another ball of
its own party, one to {44}give, the other to receive
fire; and so it proceeds through both sets, but so quick as to be in a manner instantaneous. In
the collision they shake off and drop their water, which represents rain.Thus when sea and land clouds would pass at too great a distance for the flash, they are
attracted towards each other till within that distance; for the sphere of electrical attraction is
far beyond the distance of flashing.When a great number of clouds from the sea meet a number of clouds raised from the land,
the electrical flashes appear to strike in different parts; and as the clouds are jostled and
mixed by the winds, or brought near by the electrical attraction, they continue to give and
receive flash after flash, till the electrical fire is equally diffused.When the gun-barrel (in electrical experiments) has but little electrical fire in it, you
must approach it very near with your knuckle, before you can draw a spark. Give it more fire, and
it will give a spark at a greater distance. Two gun-barrels united, and as highly electrified,
will give a spark at a still greater distance. But if two gun-barrels electrified will strike at
two inches distance, and make a loud snap, to what a great distance may 10,000 acres of
electrified cloud strike and give its fire, and how loud must be that crack!It is a common thing to see clouds at different heights passing different ways, which shews
different currents of air, one under the other. As the air between the {45}tropics is rarified by the sun, it rises, the denser northern and southern
air pressing into its place. The air so rarified and forced up, passes northward and southward,
and must descend in the polar regions, if it has no opportunity before, that the circulation may
be carried on.As currents of air, with the clouds therein, pass different ways, 'tis easy to conceive how
the clouds, passing over each other, may attract each other, and so come near enough for the
electrical stroke. And also how electrical clouds may be carried within land very far from the
sea, before they have an opportunity to strike.When the air, with its vapours raised from the ocean between the tropics, comes to descend
in the polar regions, and to be in contact with the vapours arising there, the electrical fire
they brought begins to be communicated, and is seen in clear nights, being first visible where
'tis first in motion, that is, where the contact begins, or in the most northern part; from thence
the streams of light seem to shoot southerly, even up to the zenith of northern countries. But
tho' the light seems to shoot from the north southerly, the progress of the fire is really from
the south northerly, its motion beginning in the north being the reason that 'tis there first
seen.
For the electrical fire is never visible but when in motion, and leaping from body to body, or
from particle to particle thro' the air. When it passes thro' dense bodies 'tis unseen. When a
wire makes part of the circle, in the explosion of the electrical phial, the fire, though in great
{46}quantity, passes in the wire invisibly: but in
passing along a chain, it becomes visible as it leaps from link to link. In passing along
leaf-gilding 'tis visible: for the leaf-gold is full of pores; hold a leaf to the light and it
appears like a net; and the fire is seen in its leaping over the vacancies.—And as when a
long canal filled with still water is opened at one end, in order to be discharged, the motion of
the water begins first near the opened end, and proceeds towards the close end, tho' the water
itself moves from the close towards the opened end: so the electrical fire discharged into the
polar regions, perhaps from a thousand leagues length of vaporiz'd air, appears first where 'tis
first in motion, i. e. in the most northern part, and the appearance proceeds southward,
tho' the fire really moves northward. This is supposed to account for the Aurora
Borealis.
When there is great heat on the land, in a particular region (the sun having shone on it
perhaps several days, while the surrounding countries have been screen'd by clouds) the lower air
is rarified and rises, the cooler denser air above descends; the clouds in that air meet from all
sides, and join over the heated place; and if some are electrified, others not, lightning and
thunder succeed, and showers fall. Hence thunder-gusts after heats, and cool air after gusts; the
water and the clouds that bring it, coming from a higher and therefore a cooler region.An electrical spark, drawn from an irregular body at some distance is scarce ever strait,
but shows {47}crooked and waving in the air. So do the
flashes of lightning; the clouds being very irregular bodies.As electrified clouds pass over a country, high hills and high trees, lofty towers, spires,
masts of ships, chimneys, &c. as so many prominencies and points, draw the electrical
fire, and the whole cloud discharges there.Dangerous, therefore, is it to take shelter under a tree during a thunder-gust. It has been
fatal to many, both men and beasts.It is safer to be in the open field for another reason. When the clothes are wet, if a
flash in its way to the ground should strike your head, it will run in the water over the surface
of your body; whereas, if your clothes were dry, it would go thro' the body.
Hence a wet rat cannot be killed by the exploding electrical bottle, when a dry rat may.
Common fire is in all bodies, more or less, as well as electrical fire. Perhaps they may be
different modifications of the same element; or they may be different elements. The latter is by
some suspected.If they are different things, yet they may and do subsist together in the same body.
When electrical fire strikes thro' a body, it acts upon the common fire contained in it,
and puts that fire in motion; and if there be a sufficient quantity of each kind of fire, the body
will be inflamed.When the quantity of common fire in the body is small, the quantity of the electrical fire
(or the electrical {48}stroke) should be greater: if the
quantity of common fire be great, less electrical fire suffices to produce the effect.Thus spirits must be heated before we can fire them by the electrical spark. If they are
much heated a small spark will do; if not, the spark must be greater.Till lately we could only fire warm vapours; but now we can burn hard dry rosin. And when
we can procure greater electrical sparks, we may be able to fire not only unwarm'd spirits, as
lightning does, but even wood, by giving sufficient agitation to the common fire contained in it,
as friction we know will do.Sulphureous and inflammable vapours arising from the earth, are easily kindled by
lightning. Besides what arise from the earth, such vapours are sent out by stacks of moist hay,
corn, or other vegetables, which heat and reek. Wood rotting in old trees or buildings does the
same. Such are therefore easily and often fired.
Metals are often melted by lightning, tho' perhaps not from heat in the lightning, nor
altogether from agitated fire in the metals.—For as whatever body can insinuate itself
between the particles of metal, and overcome the attraction by which they cohere (as sundry
menstrua can) will make the solid become a fluid, as well as fire, yet without heating it: so the
electrical fire, or lightning, creating a violent repulsion between the particles of the metal it
passes thro', the metal is fused.If you would, by a violent fire, melt off the end of a nail, which is half driven into a
door, the heat given the {49}whole nail before a part
would melt, must burn the board it sticks in. And the melted part would burn the floor it dropp'd
on. But if a sword can be melted in the scabbard, and money in a man's pocket, by lightning,
without burning either, it must be a cold fusion.Lightning rends some bodies. The electrical spark will strike a hole thro' a quire of
strong paper.If the source of lightning, assigned in this paper, be the true one, there
should be little thunder heard at sea far from land. And accordingly some old sea-captains, of
whom enquiry has been made, do affirm, that the fact agrees perfectly with the hypothesis; for
that, in crossing the great ocean, they seldom meet with thunder till they come into soundings;
and that the islands far from the continent have very little of it. And a curious observer, who
lived 13 years at Bermudas, says, there was less thunder there in that whole time than he
has sometimes heard in a month at Carolina.
{50}
ADDITIONAL
PAPERS.
TO
Mr. Peter Collinson, F.R.S. London.
Philadelphia, July 29, 1750
SIR,
As you first put us on electrical experiments, by sending to our library company a tube, with
directions how to use it; and as our honourable proprietary enabled us to carry those experiments
to a greater height, by his generous present of a compleat electrical apparatus; 'tis fit that
both should know from time to time what progress we make. It was in this view I wrote and sent you
my former papers on this subject, desiring, that as I had not the honour of a direct
correspondence with that bountiful benefactor to our library, they might be communicated to him
through your hands. In the same view I write, and send you this additional paper. If it happens to
bring you nothing new (which may well be, considering the number of ingenious men in
Europe, continually engaged in the same researches) at least it will show, that the
instruments, put into our hands, are not neglected; and, that if no valuable discoveries are made
by us, whatever the cause may be, it is not want of industry and application.
I am, Sir,
Your much obliged
Humble Servant,
B. FRANKLIN.
{51}
OPINIONS and CONJECTURES,
Concerning the Properties and Effects of the electrical Matter, arising from Experiments and
Observations, made in Philadelphia, 1749.
§ 1. The electrical matter consists of particles extreamly subtile, since it can permeate
common matter, even the densest metals, with such ease and freedom, as not to receive any
perceptible resistance.
If any one should doubt, whether the electrical matter passes thro' the substance of bodies,
or only over and along their surfaces, a shock from an electrified large glass jar, taken thro'
his own body, will probably convince him.Electrical matter differs from common matter in this, that the parts of the latter mutually
attract, those of the former mutually repel, each other. Hence the appearing divergency in a
stream of electrified effluvia.But tho' the particles of electrical matter do repel each other, they are strongly attracted
by all other matter.[7]
{52}
From these three things, the extreme subtilty of the electrical matter, the mutual repulsion
of its parts, and the strong attraction between them and other matter, arise this effect, that
when a quantity of electrical matter, is applied to a mass of common matter, of any bigness or
length within our observation (which has not already got its quantity) it is immediately and
equally diffused through the whole.Thus common matter is a kind of spunge to the electrical fluid. And as a spunge would
receive no water, if the parts of water were not smaller than the pores of the spunge; and even
then but slowly, if there were not a mutual attraction between those parts and the parts of the
spunge; and would still imbibe it faster, if the mutual attraction among the parts of the water
did not impede, some force being required to separate them; and fastest, if, instead of
attraction, there were a mutual repulsion among those parts, which would act in conjunction with
the attraction of the spunge. So is the case between the electrical and common matter.But in common matter there is (generally) as much of the electrical, as it will contain
within its substance. If more is added, it lies without upon the surface, and forms what we call
an electrical atmosphere: and then the body is said to be electrified.'Tis supposed, that all kinds of common matter do not attract and retain the electrical,
with equal strength and force; for reasons to be given hereafter. And that those {53}called electrics per se, as glass, &c. attract
and retain it strongest, and contain the greatest quantity.We know that the electrical fluid is in common matter, because we can pump it
out by the globe or tube. We know that common matter has near as much as it can contain,
because, when we add a little more to any protion of it, the additional quantity does not enter,
but forms an electrical atmosphere. And we know that common matter has not (generally) more than
it can contain, otherwise all loose portions of it would repel each other, as they constantly do
when they have electric atmospheres.The beneficial uses of this electrical fluid in the creation, we are not yet well
acquainted with, though doubtless such there are, and those very considerable; but we may see some
pernicious consequences, that would attend a much greater proportion of it. For had this globe we
live on as much of it in proportion, as we can give to a globe of iron, wood, or the like, the
particles of dust and other light matters that get loose from it, would, by virtue of their
separate electrical atmospheres, not only repel each other, but be repelled from the earth, and
not easily be brought to unite with it again; whence our air would continually be more and more
clogged with foreign matter, and grow unfit for respiration. This affords another occasion of
adoring that wisdom which has made all things by weight and measure!If a piece of common matter be supposed intirely free from electrical matter, and a single
particle of the {54}latter be brought nigh, 'twill be
attracted and enter the body, and take place in the center, or where the attraction is every way
equal. If more particles enter, they take their places where the balance is equal between the
attraction of the common matter and their own mutual repulsion. 'Tis supposed they form triangles,
whose sides shorten as their number increases; 'till the common matter has drawn in so many, that
its whole power of compressing those triangles by attraction, is equal to their whole power of
expanding themselves by repulsion; and then will such piece of matter receive no more.When part of this natural proportion of electrical fluid, is taken out of a piece of common
matter, the triangles formed by the remainder, are supposed to widen by the mutual repulsion of
the parts, until they occupy the whole piece.When the quantity of electrical fluid taken from a piece of common matter is restored
again, it enters, the expanded triangles being again compressed till there is room for the
whole.To explain this: take two apples, or two balls of wood or other matter, each having its own
natural quantity of the electrical fluid. Suspend them by silk lines from the ceiling. Apply the
wire of a well-charged vial, held in your hand, to one of them (A) Fig. 7.
and it will receive from the wire a quantity of the electrical fluid; but will not imbibe it,
being already full. The fluid therefore will flow round its surface, and form an electrical
atmosphere. {55}Bring A into contact with B, and half the
electrical fluid is communicated, so that each has now an electrical atmosphere, and therefore
they repel each other. Take away these atmospheres by touching the balls, and leave them in their
natural state: then, having fixed a stick of sealing wax to the middle of the vial to hold it by,
apply the wire to A, at the same time the coating touches B. Thus will a quantity of the
electrical fluid be drawn out of B, and thrown on A. So that A will have a redundance of this
fluid, which forms an atmosphere round it, and B an exactly equal deficiency. Now bring these
balls again into contact, and the electrical atmosphere will not be divided between A and B, into
two smaller atmospheres as before; for B will drink up the whole atmosphere of A, and both will be
found again in their natural state.The form of the electrical atmosphere is that of the body it surrounds. This shape may be
rendered visible in a still air, by raising a smoke from dry rosin, dropt into a hot tea-spoon
under the electrised body, which will be attracted and spread itself equaly on all sides, covering
and concealing the body. And this form it takes, because it is attracted by all parts of the
surface of the body, tho' it cannot enter the substance already replete. Without this attraction
it would not remain round the body, but dissipate in the air.The atmosphere of electrical particles surrounding an electrified sphere, is not more
disposed to leave it or {56}more easily drawn off from
any one part of the sphere than from another, because it is equally attracted by every part. But
that is not the case with bodies of any other figure. From a cube it is more easily drawn at the
corners than at the plane sides, and so from the angles of a body of any other form, and still
most easily from the angle that is most acute. Thus if a body shaped as A, B, C, D, E, in Fig. 8, be electrified, or have an electrical atmosphere communicated to it,
and we consider every side as a base on which the particles rest and by which they are attracted,
one may see, by imagining a line from A to F, and another from E to G, that the portion of the
atmosphere included in F, A, E, G, has the line A, E, for its basis. So the portion of atmosphere
included in H, A, B, I, has the line A, B, for its basis. And likewise the portion included in K,
B, C, L, has B, C, to rest on; and so on the other side of the figure. Now if you would draw off
this atmosphere with any blunt smooth body, and approach the middle of the side A, B, you must
come very near before the force of your attracter exceeds the force or power with which that side
holds its atmosphere. But there is a small portion between I, B, K, that has less of the surface
to rest on, and to be attracted by, than the neighbouring portions, while at the same time there
is a mutual repulsion between its particles and the particles of those portions, therefore here
you can get it with more ease or at a greater distance. Between F, A, H, there is a larger portion
that has yet a less surface to rest on and to attract it; {57}here therefore you can get it away still more easily. But easiest of all
between L, C, M, where the quantity is largest, and the surface to attract and keep it back the
least. When you have drawn away one of these angular portions of the fluid, another succeeds in
its place, from the nature of fluidity and the mutual repulsion beforementioned; and so the
atmosphere continues flowing off at such angle, like a stream, till no more is remaining. The
extremities of the portions of atmosphere over these angular parts are likewise at a greater
distance from the electrified body, as may be seen by the inspection of the above figure; the
point of the atmosphere of the angle C, being much farther from C, than any other part of the
atmosphere over the lines C, B, or B, A: And besides the distance arising from the nature of the
figure, where the attraction is less, the particles will naturally expand to a greater distance by
their mutual repulsion. On these accounts we suppose electrified bodies discharge their
atmospheres upon unelectrified bodies more easily and at a greater distance from their angles and
points than from their smooth sides.—Those points will also discharge into the air, when the
body has too great an electrical atmosphere, without bringing any non-electric near, to receive
what is thrown off: For the air, though an electric per se, yet has always more or less
water and other non-electric matters mixed with it; and these attract and receive what is so
discharged.But points have a property, by which they draw on as well as throw off the
electrical fluid, at greater distances {58}than blunt
bodies can. That is, as the pointed part of an electrified body will discharge the atmosphere of
that body, or communicate it farthest to another body, so the point of an unelectrified body, will
draw off the electrical atmosphere from an electrified body, farther than a blunter part of the
same unelectrified body will do. Thus a pin held by the head, and the point presented to an
electrified body, will draw off its atmosphere at a foot distance; where if the head were
presented instead of the point, no such effect would follow. To understand this, we may consider,
that if a person standing on the floor would draw off the electrical atmosphere from an
electrified body, an iron crow and a blunt knitting kneedle held alternately in his hand and
presented for that purpose, do not draw with different forces in proportion to their different
masses. For the man, and what he holds in his hand, be it large or small, are connected with the
common mass of unelectrified matter; and the force with which he draws is the same in both cases,
it consisting in the different proportion of electricity in the electrified body and that common
mass. But the force with which the electrified body retains its atmosphere by attracting it, is
proportioned to the surface over which the particles are placed; i.e. four square inches of that
surface retain their atmosphere with four times the force that one square inch retains its
atmosphere. And as in plucking the hairs from the horse's tail, a degree of strength insufficient
to pull away a handful at once, could yet easily strip it hair by {59}hair; so a blunt body presented cannot draw off a number of particles at
once, but a pointed one, with no greater force, takes them away easily, particle by particle.These explanations of the power and operation of points, when they first occurr'd to me,
and while they first floated in my mind, appeared perfectly satisfactory; but now I have wrote
them, and consider'd them more closely in black and white, I must own I have some doubts about
them: yet as I have at present nothing better to offer in their stead, I do not cross them out:
for even a bad solution read, and its faults discover'd, has often given rise to a good one in the
mind of an ingenious reader.Nor is it of much importance to us, to know the manner in which nature executes her laws;
'tis enough if we know the laws themselves. 'Tis of real use to know, that china left in the air
unsupported will fall and break; but how it comes to fall, and why it breaks, are
matters of speculation. 'Tis a pleasure indeed to know them, but we can preserve our china without
it.Thus in the present case, to know this power of points, may possibly be of some use to
mankind, though we should never be able to explain it. The following experiments, as well as those
in my first paper, show this power. I have a large prime conductor made of several thin sheets of
Fuller's pasteboard form'd into a tube, near 10 feet long and a foot diameter. It is cover'd with
Dutch emboss'd paper, almost totally gilt. This large {60}metallic surface supports a much greater electrical atmosphere than a rod
of iron of 50 times the weight would do. It is suspended by silk lines, and when charg'd will
strike at near two inches distance, a pretty hard stroke so as to make one's knuckle ach. Let a
person standing on the floor present the point of a needle at 12 or more inches distance from it,
and while the needle is so presented, the conductor cannot be charged, the point drawing off the
fire as fast as it is thrown on by the electrical globe. Let it be charged, and then present the
point at the same distance, and it will suddenly be discharged. In the dark you may see a light on
the point, when the experiment is made. And if the person holding the point stands upon wax, he
will be electrified by receiving the fire at that distance. Attempt to draw off the electricity
with a blunt body, as a bolt of iron round at the end and smooth (a silversmith's iron punch,
inch-thick, is what I use) and you must bring it within the distance of three inches before you
can do it, and then it is done with a stroke and crack. As the pasteboard tube hangs loose on silk
lines, when you approach it with the punch iron, it likewise will move towards the punch, being
attracted while it is charged; but if at the same instant a point be presented as before, it
retires again, for the point discharges it. Take a pair of large brass scales, of two or more feet
beam, the cords of the scales being silk. Suspend the beam by a packthread from the cieling, so
that the bottom of the scales may be about a foot from the {61}floor: The scales will move round in a circle by the untwisting of the
packthread. Set the iron punch on the end upon the floor, in such a place as that the scales may
pass over it in making their circle: Then electrify one scale by applying the wire of a charged
phial to it. As they move round, you see that scale draw nigher to the floor, and dip more when it
comes over the punch; and if that be placed at a proper distance, the scale will snap and
discharge its fire into it. But if a needle be stuck on the end of the punch, its point upwards,
the scale, instead of drawing nigh to the punch and snapping, discharges its fire silently through
the point, and rises higher from the punch. Nay, even if the needle be placed upon the floor near
the punch, its point upwards, the end of the punch, tho' so much higher than the needle, will not
attract the scale and receive its fire, for the needle will get it and convey it away, before it
comes nigh enough for the punch to act. And this is constantly observable in these experiments,
that the greater quantity of electricity on the pasteboard tube, the farther it strikes or
discharges its fire, and the point likewise will draw it off at a still greater distance.
Now if the fire of electricity and that of lightening be the same, as I have endeavour'd to
show at large in a former paper, this pasteboard tube and these scales may represent electrified
clouds. If a tube of only 10 feet long will strike and discharge its fire on the punch at two or
three inches distance, an electrified cloud of {62}perhaps 10,000 acres, may strike and discharge on the earth at a
proportionably greater distance. The horizontal motion of the scales over the floor, may represent
the motion of the clouds over the earth; and the erect iron punch, a hill or high building; and
then we see how electrified clouds passing over hills or high buildings at too great a height to
strike, may be attracted lower till within their striking distance. And lastly, if a needle fix'd
on the punch with its point upright, or even on the floor below the punch, will draw the fire from
the scale silently at a much greater than the striking distance, and so prevent its descending
towards the punch; or if in its course it would have come nigh enough to strike, yet being first
deprived of its fire it cannot, and the punch is thereby secured from the stroke. I say, if these
things are so, may not the knowledge of this power of points be of use to mankind, in preserving
houses, churches, ships, &c. from the stroke of lightning, by directing us to fix on the
highest parts of those edifices, upright rods of iron made sharp as a needle, and gilt to prevent
rusting, and from the foot of those rods a wire down the outside of the building into the ground,
or down round one of the shrouds of a ship, and down her side till it reaches the water? Would not
these pointed rods probably draw the electrical fire silently out of a cloud before it came nigh
enough to strike, and thereby secure us from that most sudden and terrible mischief?
To determine the question, whether the clouds {63}that contain lightning are electrified or not, I would propose an
experiment to be try'd where it may be done conveniently. On the top of some high tower or
steeple, place a kind of sentry-box, (as in Fig.
9.) big enough to contain a man and an electrical stand. From the middle of the stand,
let an iron rod rise and pass bending out of the door, and then upright 20 or 30 feet, pointed
very sharp at the end. If the electrical stand be kept clean and dry, a man standing on it when
such clouds are passing low, might be electrified and afford sparks, the rod drawing fire to him
from a cloud. If any danger to the man should be apprehended (though I think there would be none)
let him stand on the floor of his box, and now and then bring near to the rod, the loop of a wire
that has one end fastened to the leads, he holding it by a wax handle; so the sparks, if the rod
is electrified, will strike from the rod to the wire, and not affect him.Before I leave this subject of lightning, I may mention some other similarities between the
effects of that, and these of electricity. Lightning has often been known to strike people blind.
A pigeon that we struck dead to appearance by the electrical shock, recovering life, droop'd about
the yard several days, eat nothing though crumbs were thrown to it, but declined and died. We did
not think of its being deprived of sight; but afterwards a pullet struck dead in like manner,
being recovered by repeatedly blowing into its lungs, when set down on the floor, ran headlong
against the wall, and on examination {64}appeared
perfectly blind. Hence we concluded that the pigeon also had been absolutely blinded by the shock.
The biggest animal we have yet killed or try'd to kill with the electrical stroke, was a
well-grown pullet.Reading in the ingenious Dr. Hales's account of the thunder storm at
Stretham, the effect of the lightning in stripping off all the paint that had covered a
gilt moulding of a pannel of wainscot, without hurting the rest of the paint, I had a mind to lay
a coat of paint over the filleting of gold on the cover of a book, and try the effect of a strong
electrical flash sent through that gold from a charged sheet of glass. But having no paint at
hand, I pasted a narrow strip of paper over it; and when dry, sent the flash through the gilding;
by which the paper was torn off from end to end, with such force, that it was broke in several
places, and in others brought away part of the grain of the Turky-leather in which it was bound;
and convinced me, that had it been painted, the paint would have been stript off in the same
manner with that on the wainscot at Stretham.Lightning melts metals, and I hinted in my paper on that subject, that I suspected it to be
a cold fusion; I do not mean a fusion by force of cold, but a fusion without heat. We have also
melted gold, silver, and copper, in small quantities, by the electrical flash. The manner is this:
Take leaf gold, leaf silver, or leaf gilt copper, commonly called leaf brass or Dutch gold:
cut off from the leaf long narrow strips the breadth of {65}a straw. Place one of these strips between two strips of smooth glass that
are about the width of your finger. If one strip of gold, the length of the leaf, be not long
enough for the glass, add another to the end of it, so that you may have a little part hanging out
loose at each end of the glass. Bind the pieces of glass together from end to end with strong silk
thread; then place it so as to be part of an electrical circle, (the ends of gold hanging out
being of use to join with the other parts of the circle) and send the flash through it, from a
large electrified jar or sheet of glass. Then if your strips of glass remain whole, you will see
that the gold is missing in several places, and instead of it a metallic stain on both the
glasses; the stains on the upper and under glass exactly similar in the minutest stroke, as may be
seen by holding them to the light; the metal appeared to have been not only melted, but even
vitrified, or otherwise so driven into the pores of the glass, as to be protected by it from the
action of the strongest Aqua Fortis and Ag: Regia. I send you enclosed two little
pieces of glass with these metallic stains upon them, which cannot be removed without taking part
of the glass with them. Sometimes the stain spreads a little wider than the breadth of the leaf,
and looks brighter at the edge, as by inspecting closely you may observe in these. Sometimes the
glass breaks to pieces: once the upper glass broke into a thousand pieces, looking like coarse
salt. These pieces I send you, were stain'd with Dutch gold. True gold makes a darker
stain, {66}somewhat reddish; silver, a greenish stain. We
once took two pieces of thick looking-glass, as broad as a Gunter's scale, and 6 inches long; and
placing leaf gold between them, put them betwixt two smoothly plain'd pieces of wood, and fix'd
them tight in a book-binder's small press; yet though they were so closely confined, the force of
the electrical shock shivered the glass into many pieces. The gold was melted and stain'd into the
glass as usual. The circumstances of the breaking of the glass differ much in making the
experiment, and sometimes it does not break at all: but this is constant, that the stains in the
upper and under pieces are exact counterparts of each other. And though I have taken up the pieces
of glass between my fingers immediately after this melting, I never could perceive the least
warmth in them.In one of my former papers, I mention'd, that gilding on a book, though at first it
communicated the shock perfectly well, yet fail'd after a few experiments, which we could not
account for. We have since found, that one strong shock breaks the continuity of the gold in the
filleting, and makes it look rather like dust of gold, abundance of its parts being broken and
driven off; and it will seldom conduct above one strong shock. Perhaps this may be the reason;
when there is not a perfect continuity in the circle, the fire must leap over the vacancies; there
is a certain distance which it is able to leap over according to its strength; if a number of
small vacancies, though each be very minute, taken {67}together exceed that distance, it cannot leap over them, and so the shock
is prevented.From the before mentioned law of electricity, that points, as they are more or less acute,
draw on and throw off the electrical fluid with more or less power, and at greater or less
distances, and in larger or smaller quantities in the same time, we may see how to account for the
situation of the leaf of gold suspended between two plates, the upper one continually electrified,
the under one in a person's hand standing on the floor. When the upper plate is electrified, the
leaf is attracted and raised towards it, and would fly to that plate were it not for its own
points. The corner that happens to be uppermost when the leaf is rising, being a sharp point, from
the extream thinness of the gold, draws and receives at a distance a sufficient quantity of the
electrical fluid to give itself an electrical atmosphere, by which its progress to the upper plate
is stopt, and it begins to be repelled from that plate, and would be driven back to the under
plate, but that its lowest corner is likewise a point, and throws off or discharges the overplus
of the leaf's atmosphere, as fast as the upper corner draws it on. Were these two points perfectly
equal in acuteness, the leaf would take place exactly in the middle space, for its Weight is a
trifle, compared to the power acting on it: But it is generally nearest the unelectrified plate,
because, when the leaf is offered to the electrified plate at a distance, the sharpest point is
commonly first affected and raised towards it; so that point, from its greater {68}acuteness, receiving the fluid faster than its opposite can
discharge it at equal distances, it retires from the electrified plate, and draws nearer to the
unelectrified plate, till it comes to a distance where the discharge can be exactly equal to the
receipt, the latter being lessened, and the former encreased; and there it remains as long as the
globe continues to supply fresh electrical matter. This will appear plain, when the difference of
acuteness in the corners is made very great. Cut a piece of Dutch gold (which is fittest
for these experiments on account of its greater strength) into the form of Fig. 10 the upper corner a right angle, the two next
obtuse angles, and the lowest a very acute one; and bring this on your plate under the electrified
plate, in such a manner as that the right-angled part may be first raised (which is done by
covering the acute part with the hollow of your hand) and you will see this leaf take place much
nearer to the upper than to the under plate; because, without being nearer, it cannot receive so
fast at its right-angled point, as it can discharge at its acute one. Turn this leaf with the
acute part uppermost, and then it takes place nearest the unelectrified plate, because otherwise
it receives faster at its acute point than it can discharge at its right-angled one. Thus the
difference of distance is always proportioned to the difference of acuteness. Take care in cutting
your leaf to leave no little ragged particles on the edges, which sometimes form points where you
would not have them. You may make this {69}figure so
acute below and blunt above, as to need no under plate, it discharging fast enough into the air.
When it is made narrower, as the figure between the pricked lines, we call it the Golden
Fish, from its manner of acting. For if you take it by the tail, and hold it at a foot or
greater horizontal distance from the prime conductor, it will, when let go, fly to it with a brisk
but wavering motion, like that of an eel through the water; it will then take place under the
prime conductor, at perhaps a quarter or half an inch distance, and keep a continual shaking of
its tail like a fish, so that it seems animated. Turn its tail towards the prime conductor, and
then it flies to your finger, and seems to nibble it. And if you hold a plate under it at six or
eight inches distance, and cease turning the Globe, when the electrical atmosphere of the
conductor grows small, it will descend to the plate and swim back again several times with the
same fish-like motion, greatly to the entertainment of spectators. By a little practice in
blunting or sharpening the heads or tails of these figures, you may make them take place as
desired, nearer, or farther from the electrified plate.It is said in section 8, of this paper, that all kinds of common matter are supposed not to
attract the electrical fluid with equal strength; and that those called electrics per se,
as glass, &c. attract and retain it strongest, and contain the greatest quantity. This latter
position may seem a paradox to some, being contrary to the hitherto received opinion; and
therefore I shall now endeavour to explain it.
{70}
In order to this, let it first be considered, that we cannot, by any means we are yet
acquainted with, force the electrical fluid thro' glass. I know it is commonly thought that it
easily pervades glass, and the experiment of a feather suspended by a thread in a bottle
hermetically sealed, yet moved by bringing a nibbed tube near the outside of the bottle, is
alledged to prove it. But, if the electrical fluid so easily pervades glass, how does the vial
become charged (as we term it) when we hold it in our hands? Would not the fire thrown in
by the wire pass through to our hands, and so escape into the floor? Would not the bottle in that
case be left just as we found it, uncharged, as we know a metal bottle so attempted to be charged
would be? Indeed, if there be the least crack, the minutest solution of continuity in the glass,
though it remains so tight that nothing else we know of will pass, yet the extremely subtile
electrical fluid flies through such a crack with the greatest freedom, and such a bottle we know
can never be charged: What then makes the difference between such a bottle and one that is sound,
but this, that the fluid can pass through the one, and not through the other?[8]It is true there is an experiment that at first sight would be apt to satisfy a slight
observer, that the fire thrown into the bottle by the wire, does really pass thro' {71}the glass. It is this: place the bottle on a glass stand,
under the prime conductor; suspend a bullet by a chain from the prime conductor, till it comes
within a quarter of an inch right over the wire of the bottle; place your knuckle on the glass
stand, at just the same distance from the coating of the bottle, as the bullet is from its wire.
Now let the globe be turned, and you see a spark strike from the bullet to the wire of the bottle,
and the same instant you see and feel an exactly equal spark striking from the coating on your
knuckle, and so on spark for spark. This looks as if the whole received by the bottle was again
discharged from it. And yet the bottle by this means is charged![9] And therefore the fire that thus leaves the bottle, though the
same in quantity, cannot be the very same fire that entered at the wire; for if it were, the
bottle would remain uncharged.If the fire that so leaves the bottle be not the same that is thrown in through the wire,
it must be fire that subsisted in the bottle, (that is, in the glass of the bottle) before the
operation began.If so, there must be a great quantity in glass, because a great quantity is thus discharged
even from very thin glass.That this electrical fluid or fire is strongly attracted by glass, we know from
the quickness and violence with which it is resumed by the part that had been deprived of {72}it, when there is an opportunity. And by this, that we
cannot from a mass of glass draw a quantity of electrical fire, or electrify the whole mass
minus, as we can a mass of metal. We cannot lessen or increase its whole quantity, for the
quantity it has it holds; and it has as much as it can hold. Its pores are filled with it as full
as the mutual repellency of the particles will admit; and what is already in, refuses, or strongly
repels, any additional quantity. Nor have we any way of moving the electrical fluid in glass, but
one; that is, by covering part of the two surfaces of thin glass with non-electrics, and then
throwing an additional quantity of this fluid on one surface, which spreading in the non-electric,
and being bound by it to that surface, acts by its repelling force on the particles of the
electrical fluid contained in the other surface, and drives them out of the glass into the
non-electric on that side, from whence they are discharged, and then those added on the charged
side can enter. But when this is done, there is no more in the glass, nor less than before, just
as much having left it on one side as it received on the other.
{73}
RE: Experiments and Observations on Electricity [Part 1/4]