GENTLEMEN,

IN some Papers I lately did myself the Honour to lay before you, I

acquainted you of some Experiments in Electricity; particularly I took

notice of having been able to fire Spirit of Wine by what I call'd the

repulsive Power thereof; which I have not heard had been thought of by

any of those _German_ Gentlemen, to whom the World is obliged for many

surprizing Discoveries in this Part of natural Philosophy.

HOW far strictly speaking the Spirit in this Operation may be said to be

fired by the repulsive Power of Electricity, or how far that Power,

which repels light Substances when fully impregnated with Electricity,

fires the Spirit, may probably be the Subject of a future Inquiry; but

as I am unwilling to introduce more Terms into any Demonstration than

what are absolutely necessary for the more ready Conception thereof, and

as inflammable Substances may be fired by Electricity two different

Ways, let the following Definitions at present suffice of each of these

Methods.

BUT first give me Leave to premise, that no inflammable Substances will

take fire, when brought into or near the Contact of _Electrics per se_

excited to Electricity. This Effect must be produced by non-electrical

Substances impregnated with Electricity received from the exciting

_Electrics per se_. But to return,

_1st_, I SUPPOSE that inflammable Substances are fired by the attractive

Power of Electricity, when this Effect arises from their being brought

near excited non-Electrics.

_2dly_, THAT inflammable Substances are fired by the repulsive Power of

Electricity; when it happens, that the inflammable Substances, being

first electrified themselves, are fired by being brought near

non-Electrics not excited.

THIS Matter will be better illustrated by an Example. Suppose that

either a Man standing upon a Cake of Wax, or a Sword suspended in silk

Lines are electrified, and the Spirit, being brought near them, is

fired, this is said to be perform'd by the attractive Power of

Electricity. But if the Man electrified as before holds a Spoon in his

Hand containing the Spirit, or the same Spoon and Spirit are placed upon

the Sword, and a Person not electrified applies his Finger near the

Spoon, and the Spirit is fired from the Flame arising from the Spoon and

Spirit upon such Application; this I call being fired by the repulsive

Power. Of the two mention'd Kinds I generally find the repulsive Power

strongest.

SINCE my last Communication, the Spirit has been fired both by the

attractive and repulsive Power through four Persons standing upon

electrical Cakes; each communicating with the other either by the Means

of a walking Cane, a Sword, or any other non-electric Substance. It has

likewise been fired from the Handle of a Sword held in the Hand of a

third Person.

I HAVE not only fired _Frobenius_'s Phlogiston, rectified-spirit and

common proof-spirit, but also Sal volatile Oleosum, Spirit of Lavender,

dulcified Spirit of Nitre, Peony Water, _Daffy_'s Elixir, _Helvetius_'s

Stiptic, and some other Mixtures where the Spirit has been very

considerably diluted; likewise distilled vegetable Oils, such as that of

Turpentine, Lemon, Orange Peels and Juniper, and even those of them,

which are specifically heavier than Water, as Oil of Sassafras; also

resinous Substances, such as Balsam Capivi and Turpentine; all which

send forth, when warmed, an inflammable Vapour. But expressed vegetable

Oils, as those of Olives, Linseed, and Almonds, as well as Tallow, all

whose Vapours are uninflammable, I have not been able yet to fire; but

these indeed will not fire on the Application of lighted Paper. Besides,

if these last would fire with lighted Paper, unless their Vapours were

inflammable, I can scarce conceive they would fire by Electricity;

because in firing Spirits, _&c._ I always perceive that the Electricity

snaps before it comes in Contact with their Surfaces, and therefore only

fires their inflammable Vapours.

AS an excited non-Electric emits almost all its Fire, if once touch'd by

a non-Electric not excited, I was desirous of being satisfy'd, whether

or no the Fire emitted would not be greater or less in proportion to the

Volume of the electrified Body. In order to this I procur'd an Iron Bar

about five Feet long and near 170 Pounds in Weight; this I electrified

lying on Cakes of Wax and Rosin, but observed the Flashes arising

therefrom not more violent than those from a common Poker. In making

this Experiment, being willing to try the repulsive Force, it once

happen'd that whilst the Bar was at one End electrifying, a Spoon lay

upon the other, and upon an Assistant's pouring some warm Spirit into

the Spoon, the electrical Flash from the Spoon snapped and fired the

first Drop of the Spirit, which unexpectedly fired not only the whole

Jett as it was pouring, but kindled likewise the whole Quantity in the

Pot, in which I usually have it warm'd.

I FIND, in firing inflammable Substances from the Finger of a Man

standing upon Wax, that _cæteris paribus_ the Success is more constant,

if the Man instead of holding the Thread (the Use of which I

communicated in a former Paper) in his Hand, the Thread is suspended at

the End of an Iron Rod held in one Hand, and he touches the Spirit with

one of the Fingers of the other.

IF a Man, standing upon the electrical Cake with a Dish or deep Plate of

Water in one Hand, and the Iron Rod with the Thread in the other, is

made electrical; and a Person not electrified touches any Part either of

the Plate or Water, the Flashes of Fire come out plentifully, and

wherever you bring your Finger very near, the Water rises up in a little

Cone, from the Point of which the Fire is produced, and your Finger,

though not in actual Contact, is made wet. The same Experiment succeeds

through three or more People.

IN firing inflammable Substances, the Person who holds the Spoon in his

Hand to receive the electrical Flashes, when the Finger of the

electrified Person is brought near thereto, not only feels a tingling in

his Hand, but even a slight Pain up to his Elbow. This is most

perceptible in dry Weather, when the Electricity is very powerful.

THERE is a considerable Difficulty in firing _Electrics per se_, such as

Turpentine, and Balsam Capivi, by the repulsive Power of Electricity;

because in this Case these Substances will not permit the Electricity to

pass through them; therefore when you would have this Experiment

succeed, the Finger of the Person, who is to fire them, is to be applied

as near to the Edge as possible of these Substances when warm'd in a

Spoon, that the Flashes from the Spoon (for these Substances will emit

none) may snap, where they are spread the thinnest, and then fire their

Effluvia. This Experiment, as well as several others, serves to confute

that Opinion, which has prevail'd with many, that the Electricity floats

only upon the Surfaces of Bodies.

IF an electrical Cake is dipp'd in Water, it is thereby made a Conductor

of Electricity, the Water hanging about it transmitting the electrical

Effluvia in such a manner, that a Person standing thereon can by no

means be electrified enough to attract the leaf Gold at the smallest

Distance; though the Person standing upon the same Cake when dry,

attracted a Piece of fine Thread hanging at the Distance of two Feet

from his Finger. We must here observe that the Cake being of an unctuous

Substance, the Water will no where lie uniformly thereon, but adhere in

separate Moleculæ; so that in this Instance the Electricity jumps from

one Particle of Water to another, till the Whole is dissipated.

FROM the Appearance of the Threads amongst which I rub the Tube, I can

frequently judge, though the Spirit may be many Feet distant from them,

whether or no it will fire; because when the Persons standing upon the

Wax are made electrical enough to fire the Spirit, the Threads repel

each other at their lower Parts, where they are not confin'd, to a

considerable Distance, and this Distance is in Proportion as the Threads

are made electrical.

IF two Persons stand upon electrical Cakes at about a Yard's Distance

from each other, one of which Persons, for the Sake of Distinction, we

will call A, the other B: If A when electrified touches B, A loses

almost all his Electricity at that Touch only, which is receiv'd by B

and stopp'd by the electrical Cake; if A is immediately electrified

again to the same Degree as before and touches B, the Snapping is less

upon the Touch; and this Snapping, upon electrifying A, grows less and

less, till B being impregnated with Electricity, though receiv'd at

Intervals, the Snapping will no longer be sensible.

THAT Glass will repel and not conduct the Electricity of Glass, has been

mention'd by others, who have treated of this Subject; but the

Experiments to determine this Matter must be conducted with a great deal

of Caution; for unless the glass Tube, intended to conduct the

Electricity, be as warm as the external Air, it will seem to prove the

contrary, unless in very dry Places and Seasons. Thus, I sometimes have

brought a cold, though dry, Glass Tube near three Feet long into a Room,

where there has been a Number of People; when upon placing the Tube upon

Silk Lines, and laying some Leaf Silver upon a Card at one End and

rubbing another Glass Tube at the other, the Silver has, contrary to

Expectation, been thrown off as readily as from an Iron Rod. At first I

was surpriz'd at this Appearance, but then conjectur'd, that it must

arise from the Coldness of the Glass, condensing the floating Vapour of

the Room; in Order then to obviate this, I warm'd the Tube sufficiently,

and this Effect was no longer produced, but the Silver lay perfectly

still.

IF a Number of Pieces of finely spun Glass cut to about an Inch in

Length, little bits of fine Wire of the same Length of what Metal you

please, and small Cork Balls, are either put all together, or each by

themselves, into a dry pewter Plate, or upon a Piece of polish'd Metal,

they make in the following Manner a very odd and surprizing Appearance.

Let a Man, standing upon electrical Cakes, hold this Plate in his Hand

with the bits of Glass, Wire, _&c._ detached from each other, as much as

conveniently may be; when he is electrified, let him cause a Person

standing upon the Ground to bring another Plate, his Hand, or any other

Non-Electric, exactly over the Plate containing these Bodies. When his

Hand, _&c._ is about eight Inches over them, let him bring it down

gently: As it comes near, in proportion to the Strength of the

Electricity, he will observe the bits of Glass first raise themselves

upright; and then, if he brings his Hand nearer, dart directly up and

stick to it without snapping. The bits of Wire will fly up likewise, and

as they come near the Hand, snap aloud; you feel a smart Stroke, and see

the Fire arising from them to the Hand at every Stroke; each of these,

as soon as they have discharged their Fire, falls down again upon the

Plate. The Cork Balls also fly up, and strike your Hand, but fall again

directly. You have a constant Succession of these Appearances as long as

you continue to electrify the Man, in whose Hand the Plate is held; but

if you touch any part either of the Man or Plate, the Pieces of Glass,

which before were upon their Ends, immediately fall down.

SOME few Years ago, Sir _James Lowther_ brought some Bladders fill'd

with inflammable Air, collected from his Coal-mines, to the Royal

Society. This Air flam'd upon a lighted Candle being brought near it.

This Inflammability has occasion'd many terrible Accidents. Mr. _Maud_,

a worthy Member of this Society, made at that Time by Art, and shew'd

the Society, Air exactly of the same Quality. I was desirous of knowing

if this Air would be kindled by electrical Flashes. I accordingly made

such Air by putting an Ounce of Filings of Iron, an Ounce of Oil of

Vitriol and four Ounces of Water into a Florence Flask; upon which an

Ebullition ensued, and the Air, which arose from these Materials, not

only fill'd three Bladders, but also, upon the Application of the Finger

of an Electrified Person, took Flame and burnt near the Top and out of

the Neck of the Flask a considerable Time. When the Flame is almost out,

shake the Flask and the Flame revives. You must with your Finger dipped

in Water, moisten the Mouth of the Flask as fast as it is dried by the

Heat within, or the Electricity will not fire it: Because the Flask

being an Electric _per se_ will not snap at the Application of the

Finger, without the Glass being first made non-electric by wetting. It

has sometimes happen'd, if the Finger has been applied before the

inflammable Air has found a ready Exit from the Mouth of the Flask, that

the Flash has fill'd the Flask, and gone off with an Explosion equal to

the firing of a large Pistol, and sometimes indeed it has burst the

Flask. The same Effect is produced from the Spirit of Sea Salt, as from

Oil of Vitriol; but as the Acid of Sea Salt is much lighter than that of

Vitriol, there is no Necessity to add the Water in this Experiment.

THOSE who are not much acquainted with Chemical Philosophy, may think it

very extraordinary, that from a Mixture of cold Substances, which both

conjunctly and separately are uninflammable, this very inflammable

Vapour should be produced. In order to solve this, it may not be

improper to premise, that Iron is compounded of a Metallic as well as a

sulphurous Part. This Sulphur is so fix'd, that, after heating the Iron

red hot, and even melting it ever so often, the Sulphur will not be

disengaged therefrom: But upon the Mixture of the Vitriolic Acid, and by

the Heat and Ebullition which are almost instantly produced, the

Metallic Part is dissolved, and the Sulphur, which before was intimately

connected therewith, being disengaged, becomes volatile. This Heat and

Ebullition continues 'till the Vitriolic Acid is perfectly saturated

with the Metallic Part of the Iron, and the Vapour once fired continues

to flame, until this Saturation being effected, no more of the Sulphur

flies off.

I HAVE heretofore mentioned, how considerably perfectly dry Air conduces

to the Success of these Experiments; but we have been lately informed by

an Extract of a Letter, that _Abbé Nolet_ was of Opinion, that they

would succeed in wet Weather, provided the Tubes were made of Glass,

tinged blue with Zaffer. I have procured Tubes of this Sort, but, after

giving them many candid Trials, I cannot think them equal to their

Recommendation. I first tried one of them in a smart Shower of Rain

after a dry Day, when the Drops were large, and the Spirit fired three

Times in about four Minutes; the same Effect succeeded, under the same

Circumstances, from the white one; but after three or four Hours

raining, when the Air was perfectly wet, I never could make it succeed.

And to illustrate this Matter further, I have been able when the Weather

has been very dry, with once rubbing my Hand down this blue Tube, and

applying it to the End of an Iron Rod six Feet long, to throw off

several Pieces of Leaf-Silver lying upon a Card at the other End of this

Rod, whereas I never have been able to throw it off by any Means in very

wet Weather. Besides, I am of Opinion, that after the Electrical Fire is

gone from the Tube, the Tube has no Share in the conducting of it; my

Sentiments on that Head I laid before you in a former Paper: For if the

Silk Lines are wetted, they diffuse all the Electricity, and the same

Effects happen when the Air is wet, be your Glass of what Colour it

will. It may not be improper here to observe, that Zaffer, which is used

by the Glass-makers and Enamellers, is made of Cobalt or Mundick

calcin'd after the subliming the Flowers. This being reduced to a very

fine Powder, and mixt with twice or thrice its own Weight of finely

powdered Flints, is moisten'd with Water and put up in Barrels, in which

it soon runs into a hard Mass and is call'd Zaffer.

A DRY Sponge hanging by a Pack-thread at the End of an electrified

Sword, or from the Hand of an electrified Man, gives no Signs of being

made electrical; if it is well soak'd in Water, wherever it is touched,

you both see and feel the electrical Sparks. Not only so, but if it is

so full of Water, that it falls from the Sponge, those Drops in a dark

Room, receiv'd upon your Hand, not only flash and snap, but you perceive

a pricking Pain. If you hold your Hand, or any non-electrical

Substances, very near, the Water which had ceased dropping when the

Sponge was not electrified, drops again upon its being electrified, and

the Drops fall in Proportion to the receiv'd Electricity, as though the

Sponge were gently squeez'd between your Fingers. I was desirous to know

if I was able to electrify a Drop of cold Water, dropping from the

Sponge, enough to fire the Spirit; but after many unsuccessful Trials, I

was forced to desist; because the cold Water dropping from the Sponge

not only cool'd the Spirit too much, but also render'd it too weak;

likewise, every Drop carried with it great Part of the Electricity from

the Sponge. I then consider'd, in what Manner, I could give a Tenacity

to the Water, sufficient to make the Drops hang a considerable Time, and

this I brought about by making a Mucilage of the Seeds of Fleawort. A

wet Sponge then, squeez'd hard and fill'd with this cold Mucilage, was

held in the Hand of an electrified Man, when the Drops forced out by the

Electricity, assisted by the Tenacity of the Liquor, hung some Inches

from the Sponge, and by a Drop of this I fir'd not only the Spirit of

Wine, but likewise the inflammable Air before mentioned, both with and

without the Explosion. What an extraordinary Effect is this! That a Drop

of cold Water (for the Seeds contribute nothing but add Consistence to

the Water) should be the Medium of Fire and Flame.

CAMPHOR is a vegetable Resin, and of Consequence an Electric _per se_.

This Substance, notwithstanding its great Inflammability, will not take

fire from the Finger of a Man or any other Body electrified, though made

very warm and the Vapours arise therefrom in great Abundance. Because,

neither Electric's _per se_ excited, or electrified Bodies, exert their

Force by snapping upon Electric's _per se_, though not excited. If you

break Camphor small and warm it in a Spoon, it is not melted by Heat

like other Resins; but if that Heat were continued it would all prove

volatile. To Camphor thus warm'd, the Finger of an electrified Man, a

Sword or such-like, will in snapping exert its Force upon the Spoon, and

the circum-ambient Vapour of the Camphor will be fired thereby, and

light up the whole Quantity exposed. The same Experiment succeeds by the

repulsive Power of Electricity.

A POKER thoroughly ignited put into Spirit of Wine, or into the

distilled Oil of Vegetables, produces no Flame in either; it indeed

occasions the Vapours to arise from the Oil in great Abundance. But if

you electrify this heated Poker, the electrical Flashes presently kindle

Flame in either. The Experiment is the same with Camphor. These

Experiments, as well as the following, sufficiently evince, that the

electrical Fire is truly Flame, and that extreamly subtil.

I HAVE made several Trials in order to fire Gunpowder alone, which I

tried both warm and cold, whole and powder'd, but never could make it

succeed; and this arises in part from its Vapours not being inflammable,

and in part from its not being capable of being fir'd by Flame, unless

the Sulphur in the Composition is nearly in the State of Accension. This

we see by putting Gunpowder into a Spoon with rectified Spirit, which,

when lighted, will not fire the Powder, 'till by the Heat of the Spoon

from the burning Spirit, the Sulphur is almost melted. Likewise, if you

hold Gunpowder ground very fine in a Spoon over a lighted Candle, or any

other Flame, as soon as the Spoon is hot enough to melt the Sulphur, you

see a blue Flame, and instantly the Powder flashes off. The same Effects

are observ'd in the _Pulvis fulminans_, compos'd of Nitre, Sulphur, and

fixed Alkaline Salt. Besides, when the Gunpowder is very dry and ground

very fine, it (as you please to make the Experiment) is either

attracted, or repell'd; so that in the first Case, the End of your

Finger when electrified, shall be cover'd over with the Powder, though

held at some Distance; and in the other, if you electrify the Powder, it

will fly off at the Approach of any non-electrified Substance, and

sometimes even without it. But I can at Pleasure fire Gunpowder, and

even discharge a Musket, by the Power of Electricity, when the Gunpowder

has been ground with a little Camphor or with a few Drops of some

inflammable chemical Oil. This Oil somewhat moistens the Powder, and

prevents its flying away; the Gunpowder then being warm'd in a Spoon,

the electrical Flashes fire the inflammable Vapour, which fires the

Gunpowder: But the Time between the Vapour firing the Powder is so

short, that frequently they appear as the same and not successive

Operations, wherein the Gunpowder itself seems fired by the Electricity;

and indeed the first Time this Experiment succeeded, the Flash was so

sudden and unexpected, that the Hand of my Assistant, who touch'd the

Spoon with his Finger, was considerably scorch'd. So that there seems a

fourth Ingredient necessary to make Gunpowder readily take Fire by

Flame, and that such a one, as will heighten the Inflammability of the

Sulphur. In common Cases the lighted Match or the little Portion of red

hot Glass, which falls among the Powder, and is the Result of the

Collision from the Flint and Steel, fires the Charcoal and Sulphur, and

these the Nitre. But if to these three Ingredients you add a fourth,

_viz._ a Vegetable chemical Oil, and gently warm this Mixture, the Oil

by the Warmth mixes intimately with the Sulphur, lowers its Consistence,

and makes it readily take fire by Flame. In these Operations,

notwithstanding I always made use of the finest scented Oils of Orange

Peel, Lemons, and such like, yet upon the least warming the Mixture, the

rank Smell of Balsam (_i. e._ the ready Solution) of Sulphur was very

obvious.

Read before the R. S.

_Oct. 24. 1745_.

_A Continuation of the Above._

Read, _Feb. 6. 1745_.

AS Water is a non-electric, and of Consequence a Conductor of

Electricity, I had Reason to believe that Ice was endowed with the same

Properties. Upon making the Experiment I found my Conjectures not

without Foundation; for upon electrifying a Piece of Ice, wherever the

Ice was touched by a non-electric, it flashed and snapped. A Piece of

Ice also held in the Hand of an electrified Man, as in the

beforementioned Processes, fired warm Spirit, chemical vegetable Oils,

Camphor, and Gunpowder prepared as before. But here great Care must be

taken, that by the Warmth of the Hand, or of the Air in the Room, the

Ice does not melt; if so, every Drop of Water therefrom considerably

diminishes the received Electricity. In Order to obviate this, I caused

my Assistant, while he was electrifying, to be continually wiping the

Ice dry upon a Napkin hung to the Buttons of his Coat, and this being

electrified as well as the Ice, prevented any Loss of the Force of the

Electricity. The Experiment will succeed likewise, if, instead of the

Ice, you electrify the Spirit, _&c._ and bring the Ice not electrified

near them. I must observe, that Ice is not so ready a Conductor of

Electricity as Water; so that I very frequently have been disappointed

in endeavouring with it to fire inflammable Substances, when it has been

readily done by a Sword or the Finger of a Man.

In the first Paper[3] I had the Honour to lay before you upon this

Subject, I took Notice of my having observed two different Appearances

of the Fire from electrified Substances; _viz_. those large bright

Flashes, which may be procured from any Part of electrified Bodies, by

bringing a Non-Electric unexcited near them, and with which we have

fired all the inflammable Substances mentioned in the Course of these

Observations; and those, like the firing of wet Gunpowder, which are

only perceptible at the Points or Edges of excited Non-electrics. These

last also appear different in Colour and Form according to the

Substances from which they proceed: For from polished Bodies, as the

Point of a Sword, a Silver Probe, the Points of Scissors, and the Edges

of the Steel-bar made Magnetical by the ingenious Dr. _Knight_, the

electrical Fire appears like a Pencil of Rays, agreeing in Colour with

the Fire from _Boyle_'s Phosphorus; but from unpolished Bodies, as the

End of a Poker, a rusty Nail or such-like, the Rays are much more red.

The Difference of Colour here, I am of Opinion, is owing rather to the

different Reflection of the electrical Fire from the Surface of the Body

from which it is emitted, than to any Difference in the Fire itself.

These Pencils of Rays issue successively as long as the Bodies, from

which they proceed, are exciting; but they are longer and more

brilliant, if you bring any Non-Electric not excited near them, though

it must not be close enough to make them snap. If you hold your Hand at

about two or three Inches Distance from these Points, you not only feel

successive Blasts of Wind from them, but hear also a crackling Noise.

Where there are several Points, you observe at the same Time several

Pencils of Rays.

* * * * *

IT appears from Experiments, that besides the several Properties, that

Electricity is possess'd of peculiar to itself, it has some in common

with Magnetism and Light.