Expériences et observations sur l'électricité faites à Philadelphie en Amérique

By Benjamin Franklin

Page 109

& sur cette table j'ai fait dresser & affermir
un tabouret électrique. Ce tabouret n'est autre chose qu'une petite
planche quarrée portée sur trois bouteilles à vin; il n'est fait de
cette manière que pour suppléer au défaut d'un gâteau de résine qui me
manquoit.

5º. Tout étant ainsi préparé, j'ai fait élever perpendiculairement la
verge de fer au milieu des trois perches, & je l'ai affermie en
l'attachant à chacune de ces perches avec de forts cordons de soye par
deux endroits seulement. Les premiers liens sont au haut des perches
environ trois pouces au-dessous de leurs extrémités supérieures: les
seconds sont vers la moitié de leur hauteur. Le bout inférieur de la
verge de fer est solidement appuyé sur le milieu du tabouret électrique,
où j'ai fait creuser un trou propre à le recevoir.

6º. Comme il étoit important de garantir de la pluye le tabouret & les
cordons de soye, parce qu'ils laisseroient passer la matière électrique
s'ils étoient mouillés, j'ai pris les précautions nécessaires pour en
empêcher: c'est dans cette vûe que j'ai mis mon tabouret sous la
guérite, & que j'avois fait courber ma verge de fer à angles aigus, afin
que l'eau qui pourroit couler le long de cette verge ne pût arriver
jusques sur le tabouret. C'est aussi dans le même dessein que j'ai fait
clouer sur le haut & au milieu de mes perches à trois pouces au-dessus
des cordons de soye, des espèces de boëtes formées de trois petites
planches d'environ 15. pouces de long, qui couvrent pardessus & par les
côtés une pareille longueur des cordons de soye sans leur toucher.

Il s'agissoit de faire dans le tems de l'orage deux observations sur
cette verge de fer ainsi disposée; l'une étoit de remarquer à sa pointe
une aigrette lumineuse semblable à celle qu'on apperçoit à la pointe
d'une aiguille, quand on l'oppose assez près d'un corps actuellement
électrisé: l'autre étoit de tirer de la verge de fer des étincelles,
comme on en tire du canon de fusil dans les expériences électriques.
J'étois bien assuré du succès de la première de ces observations,
m'étant rappellé que cette aigrette est connuë il y a deux ou trois
mille ans. Les plus anciens auteurs, Homère, Aristote, Plutarque,
Horace, &c. en ont parlé sous le nom d'astre d'Hélène, quand il n'en
paroissoit qu'une, & sous les noms de Castor & Pollux, quand on en
voyoit deux.

Il n'est point rare aux navigateurs d'appercevoir ces aigrettes
lumineuses au haut des mâts, au bout des vergues, en un mot dans les
endroits élevés, où il y a des pointes dressées en l'air, surtout
pendant la

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Text Comparison with Experiments and Observations on Electricity Made at Philadelphia in America

Page 0
_ _The Editor was therefore prevailed upon to commit such extracts of letters, and other detach'd pieces as were in his hands to the press, without waiting for the ingenious author's permission so to do; and this was done with the less hesitation, as it was apprehended the author's engagements in other affairs, would scarce afford him leisure to give the publick his reflections and experiments on the subject, finish'd with that care and precision, of which the treatise before us shews he is alike studious and capable.
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EXPERIMENT II.
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_ _SIR_, In my last I informed you that, in pursuing our electrical enquiries, we had observed some particular Phaenomena, which we looked upon to be new, and of which I promised to give you some account, tho' I apprehended they might possibly not be new to you, as so many hands are daily employ'd in electrical experiments on your side the water, some or other of which would probably hit on the same observations.
Page 8
The light of the sun thrown strongly on both cork and shot by a looking-glass for a long time together, does not impair the repellency in the least.
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Hence have arisen some new terms among us: we say, _B_, (and bodies like circumstanced) is electrised _positively_; _A_, _negatively_.
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--We encrease the force of the electrical kiss vastly, thus: Let _A_ and _B_ stand on wax; give one of them the electrised phial in hand; let the other take hold of the wire; there will be a small spark; but when their lips approach, they will be struck and shock'd.
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The operator, who holds the picture by the upper-end, where the inside of the frame is not gilt, to prevent its falling, feels nothing of the shock, and may touch the face of the picture without danger, which he pretends is a test of his loyalty.
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--If one of these thin bottles be electrified by the coating, and the spark taken out thro' the gilding, it will break the glass inwards at the same time that it breaks the gilding outwards.
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quantity, so will the cork be repelled again: And so may the experiment be repeated as long as there is any charge in the bottles.
Page 26
And also how electrical clouds may be carried within land very far from the sea, before they have an opportunity to strike.
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56.
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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.
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But that is not the case with bodies of any other figure.
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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.
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17.
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Take a pair of large brass scales, of two or more feet beam, the cords of the scales being silk.
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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.
Page 37
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.
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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] 29.
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So the air never draws off an electric atmosphere from any body, but in proportion to the non-electrics mix'd with it: it rather keeps such an atmosphere confin'd, which.