DIALOGUE VII.

The Experiments on ELECTRICITY continued.

Euphrofyne.

Long'd for the Return of this Evening, when you promised to fhew me the very Ellence, as it were, of Electricity itself. Pray, in what Manner do you propose to proceed in demonftrating this?

Cleon. For this Purpofe, my Euphrofyne, it will be neceffary, first of all, to make a Vacuum, by taking the Air from under a tall Glafs Receiver, placed on an AirPump, which, yon fee, I have here provided for this Intention. On the Top of the Receiver, you obferve a Cork fealed on with Wax, thro' which goes an Iron-wire, about 3 or 4 Inches below the Cork, and turned in the Form of a Ring, on the Outfide above it. To this, the Chain, which comes from the charged Phial, is hung, and conveys the Electricity to the Vacuum within the Glafs, which, when the Window-fhutters are clofe, will be evident enough to your Sight.

Euphrof. I am impatient to fee this Experiment.-Į have hut up the Windows, and made the Room dark.— The Chain is hung on the Glafs.-And now, Cleoni.us, let the Boy turn the Wheel, while I attend to view the Effect. But Heavens! What do I fee?--Not Fire of the common Sort, but fomewhat like Milk or Cream, defcending in a copious Stream from the Point of the Wire. It fills the whole Glafs, but with a furprizing Kind of material Light, which I can fcarcely call Fire.It is quite different in Quantity, Quality, and every other Circumftance, in which it appeared to me before.

Cleon. This plainly fhews, that the Matter of Electricity is not that very fine, or fubtle, etherial Medium, as many are fond of fuppofing it to be.It appears very plainly of a thick, grofs Sort of Matter, of a fluid Nature, and is rendered luminous by a Vacuum, and Want of common Light.-That it is the real Matter of Electricity is evident, by laying my Finger on the Conductor; for then it runs all off on myfelf, and you obferve it no longer in the Receiver. When I take off my Finger,

it rushes again from the Wire into the Receiver, and fills it with a luminous Fluid.-The Light, however, is but very weak, as it is not perceptible in common Day-light.

-It alfo depends upon a Vacuum, or Air extremely rarefied; for if I let the Air into the Receiver, it makes little or no Appearance, even in the dark, as you observe.

Euphrof. All thefe Particulars I cannot but fee with the highest Satisfaction, as they convey fresh Ideas to the Mind of fuch Things as I could never otherways have known. Indeed! in this View of it, it appears of a very grofs Confiftence, as if it were Particles of Fire, Air, Sulphur, and other Parts of Bodies, mixed together in one luminous Fluid. Pray, what have I further to obferve peculiar to this Matter?

Cleon. One thing is very extraordinary; viz. that, whereas all Objects appear coloured, when viewed through a Prism in common Light, the Light of Electricity affords no Colours at all.-For your own Satisfaction, take this Prifm, and view it.

Euphrof. I will.It appears to me no otherwise through the Prism than without.-I fee nothing of any different Colours of Light, and am fully fatisfied, as to this Particular.-Have I any further Ufe of the Prism ?

Cleon. No; but there is another Method of fhewing this Phæno enon ftill in greater Perfection, by making a more perfect Vacuum than can be made by the Airpump; the Apparatus of which I fhall now proceed to defcribe to you, having firft opened the Windows, that you may fee it.-On this tall Frame of Wood, you obferve two Cups of Glafs, partly filled with Mercury, in which are immerfed the two Ends of a long incurvated Glafs-tube, in each Part whereof, the Quickfilver rifes, above that in the Bafon, to the Height of about 30 Inches; and all the internal Part of the Tube, above the Quickfilver, is a Vacuum, or a Space, as void of Air, as can be made, perhaps, by Art. The Manner of making which, you will be hereafter more particularly taught; at prefent I move the electrical Machine to the Side of the Room, under the Frame, and you will find, when it is darkened, how furprizingly perfect both the Matter and Motion of Electricity will appear.

Euphrof. Then I will put the Window-fhutters clofe; for I long to fee the curious Phænomenon you speak of. -The Room is now dark; therefore hafte, Cleonicus, and fhew the wond'rous Spectacle.

Cleon. I am ready.-I lay a Wire from the Conductor to the Mercury, in one of the Glaffes, which conducts the Electricity to the Tube.-The Globe is whirl'd round, and behold! How quick the Lightning flies from the Mercury into the Vacuum of the Tube?-In that, how ftrong, how vivid, how fenfibly, and how quick it moves through that long Space of the Tube !-Afcending in one Part, running over the Top, and down the other Leg of the Tube, in an apparent Rivulet of Fire.-When I put my Finger on the Conductor, to intercept the Fluid, it flows no longer in the Tube.My Finger removed, the Torrent of Fire rushes on, as before, with an unequal, undulating Kind of Motion.

Euphrof. Such a wonderful Appearance of electrical Fire, or rather of a luminous Fluid, exceeds every Thing I could have thought, or expected; the Motion of it is unfpeakably quick, and yet fenfible at the fame Time. I prefume, it appears thus in the Tube, as being confined in Glafs, tranfmitted firft from the Mercury on one Side to the Vacuum, and from thence to the Mercury on the other, from which it is conducted into the furrounding Air.

Cleon. You judge very rightly, Sifter. Nothing but a Glafs, or other electric Tube, could confine the electric Fluid; but the Velocity of Motion in this Experiment you cannot really obferve. That is too great to be fenfible at the Distance of many Miles, as has been found by repeated Experiments made with an electrical Machine on the Top of Shooter's-hill, and a Chain-Conductor, fufpended by filken Strings, on the Road on either Side of the Hill, from one End to the other, more than 2 Miles. The Token was given by firing of a Gun, but the Electricity was found at the End of the Chain, as foon as the Light from the Fire; and, indeed, it is a Question with many judicious People, if there be much Difference between the Velocity of Electricity, and that of Light itfelf; and, therefore, were a Chain fufpended round the Globe of the Earth, the Time which the electrical

Fluid would take to run through it, would probably be altogether imperceptible.

Euphrof. Well! These are unaccountable Facts to me; but do not all thefe Appearances incline People to believe, that there is a great Similitude between Electricity and Lightning? It would appear to me to be almoft the fame Thing; but that the Force of Lightning is fo much fuperior in its Effects to that of Electricity; for Lightning will kill a Man, rend Trees, and melt Metals; but I have heard nothing more of Electricity, than of its killing a small Bird, and the like.

Cleon. Because you have not yet been told of the greatest Effects of Electricity, which has killed a MAN, as effectually as a Bird.

Euphrof. Indeed! Pray, how did this terrible Catastrophe happen?

-After

Cleon. I will give a fhort Account of it.obferving the Phænomena of Electricity, People were foon induced to enquire what Relation there was between that and Lightning, and to imagine, that what they had obferved of pofitive and negative Electricity, among feveral Bodies on the Surface of the Earth, might likewife obtain, in fome Measure, between the Clouds in the Heavens, i. e. the Clouds might be electrified fome of them pofitively, and others negatively; fo that thofe which are charged with a greater Quantity of this electrical Matter would, upon meeting with others that contained a lefs, difcharge their Overplus with fo much Violence and Explofion, as to caufe the Lightning and Thunder which we fee and hear. From hence they concluded, there was great Reafon to fuppofe, that the Air was filled with this electrical Fluid, and that of Course, they could contrive to find by Experiment the Reality of fuch a Thing. The flying of a Kite was looked upon as the best Expedient for this Purpose, which accordingly` was tried by feveral Gentlemen Abroad with great Succefs; for instead of holding the long Line by a Packthread, as ufual, they tied on two or three Yards of a filken String near the End, which they held in their Hands. This prevented the Electricity from coming to the Person who directed the Kite. At the Place where the Silk was tied on to the Hempen-cord, there defcended

a Pack

a Packthread-string, with the fame Phial at the End of it, ufually applied to the Conductor; now, by this Means, it was certain, as the Kite was a non-electric Body, and the String by which it was flown, they would certainly convey the Electricity in the Air to the Phial, which would be found by applying the Finger, or any other Object to it, as ufual. Which accordingly fucceeded, and at fometimes to almoft a dangerous Degree.

Euphrof. Well! this was carrying the Thing to a great Height indeed! The Story of Prometheus's ftealing Fire from Heaven was but a well-known Fable; but the modern Philofophers have, it seems, realized it. They make nothing to deprive Jove of his Artillery, and that which was thought to be a Miracle in Elifba's Time, is now but the common Amusement of the Virtuofi. -They not only call Fire from Heaven; but take it without afking, whenever they pleafe.-Such Exploits far exceed any Thing Antiquity has to boast of.-I fhould be extremely afraid to try any of these celeftial Experiments; but yet, methinks! I long to fee fomething of the Nature and Manner of it.

Cleon. I will take care to gratify you in this Respect very foon, by taking you to a Gentleman's Houfe, who has a proper Apparatus for that Purpose, and will be extremely pleafed with an Opportunity to fatisfy your Curiofity, in a moft entertaining and innocent Manner. Through an open Window, in the uppermoft Room of his House, a large Pole is fufpended on filken Strings within the Room, and duly balanced; fo that a tall iron Rod, fixed in the extreme Part without, and afcending above the Height of the House, fhall not be able by the Force of Wind, or otherwife, to turn the Pole about. From the inmoft End of this Pole, a Chain, on filken Strings, is carried down the Stairs to the lowermoft Part of the House, where is placed the ufual Apparatus of electrical Inftruments. As the Iron-rod on the outmost End of the Pole is the higheft Object in the Air, the electrical Fluid, when it abounds in the Clouds, and in the Air, will naturally flow to the Top of the Rod; from thence be conducted to the Apparatus below, where the Phial communicates the Electricity by a Snap.Where you will fee the Leaf-Gold, and other light Bodies, attracted