Experiments and Observations Tending to Illustrate the Nature and Properties of Electricity In One Letter to Martin Folkes, Esq; President, and Two to the Royal Society — Reading Notes

pirit was at least ten Feet.

YOU all know, that there is the repulsive Power of Electricity, as well as the attractive; inasmuch as you are able, when a Feather or such-like light Substance is replete with Electricity, to drive it about a Room, which Way you please. This repulsive Power continues, until either the Tube loses its excited Force, or the Feather attracts the Moisture from the Air, or comes near to some non-electric Substance; if so, the Feather is attracted by, and its Electricity lost in, whatever Non-Electric it comes near. In electrified Bodies, you see a perpetual Endeavour to get rid of their Electricity. This induced me to make the following Experiment. I placed a Man upon a Cake of Wax, who held in one of his Hands a Spoon with the warm Spirits, and in the other a Poker with the Thread. I rubbed the Tube amongst the Thread, and electrified him as before. I then ordered a Person not electrified to bring his Finger near the Middle of the Spoon; upon which, the Flash from the Spoon and Spirit was violent enough to fire the Spirit. This Experiment I then repeated three Times. In this Method, the Person by whose Finger the Spirit of Wine is fired, feels the Stroke much more violent, than when the electrical Fire goes from him to the Spoon. This Method for the Sake of Distinction, we will call the repulsive Power of Electricity.

THE late Dr. _Desaguliers_ has observed in his excellent Dissertation concerning Electricity, "That there is a Sort of Capriciousness attending these Experiments, or something unaccountable in their Phænomena, not to be reduced to any Rule. For sometimes an Experiment, which has been made several Times successively, will all at once fail." Now I imagine that the greatest Part, if not the Whole of this Matter, depends upon the Moisture or Dryness of the Air, a sudden though slight Alteration in which, perhaps not sufficient to be obvious to our Faculties, may be perceived by the very subtle Fire of Electricity. For

_1st_, I CONCEIVE, that the Air itself (as has been observed by Dr. _Desaguliers_) is an _Electric per se_ and of the vitreous Kind; therefore it repels the Electricity arising from the glass Tube, and disposes it to electrify whatever non-electrical Bodies receive the Effluvia from the Tube.

_2dly_, THAT Water is a _non-Electric_, and of Consequence a Conductor of Electricity; this is exemplified by a Jett of Water being attracted by the Tube, _from either Electric_'s _per se_ conducting Electricity, and _non-Electric_'s more readily when wetted; but what is more to my present Purpose, is, that if you only blow through a dry glass Tube, the Moisture from your Breath will cause that Tube to be a Conductor of Electricity.

THESE being premised; in proportion as the Air is replete with watery Vapours, the Electricity arising from the Tube, instead of being conducted as proposed, is, by means of these Vapours, communicated to the circum-ambient Atmosphere and dissipated as fast as excited.

THIS Theory has been confirmed to me by divers Experiments, but by none more remarkably than on the Evening of the Day I made those before-mention'd; when the Vapours, which in the Afternoon by the Sun's Heat, and a brisk Gale were dissipated, and the Air perfectly dry, descended again in great Plenty upon the Absence of both, and the Evening was very damp. For between seven and eight o'Clock, I attempted again the same Experiments in the same Manner, without being able to make any of them succeed; though all those mention'd in this Paper with others of less Note, were made in Half an Hour's Time.

I AM the more particular in this, being willing to save the Labour of those, who are desirous of making these Kind of Trials; for although some of the lesser Experiments may succeed almost at any Time, yet I never could find that the more remarkable ones would succeed but in dry Weather.

_I am, Gentlemen,_ _Your most obedient,_ _humble Servant,_ W. WATSON.

_London, April 25. 1745._

TO THE ROYAL SOCIETY.

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.