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TO THEROYAL SOCIETY
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.
