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

By Benjamin Franklin

Page 128

possible que les particules de l'air,
étant électriques par elles-mêmes, tirassent leur feu électrique de la
terre dans les grands coups de vent par leur frottement contre les
arbres, les montagnes, les bâtimens, &tc. comme autant de petits globes
électriques frottans contre des coussins non-électriques, & que les
vapeurs qui s'élèvent reçussent de l'air ce feu, & que par ces moyens
les nuages devinssent électrisés.

J'imaginai que si la chose étoit ainsi, poussant violemment avec des
soufflets un courant d'air contre mon premier conducteur, je pourrois
l'électriser négativement, le frottement des particules de l'air le
dépoüillant d'une partie de sa quantité naturelle du fluide électrique;
mais l'expérience que je tentai dans cette vûe ne me réussit pas.

En Septembre 1752. j'élevai une verge de fer pour tirer l'éclair dans ma
maison, afin de faire quelques expériences dessus, ayant disposé deux
timbres pour m'avertir quand la verge seroit électrisée; cette pratique
est familière à tout Électricien.

Je trouvai que les timbres sonnèrent quelquefois quoiqu'il n'y eût ni
éclair ni tonnerre, mais seulement un nuage obscur au-dessus de la
verge, que quelquefois après un coup d'éclair ils s'arrêtoient tout d'un
coup, que d'autres fois, sans avoir sonné auparavant, ils commençoient à
le faire soudain après l'éclair, que l'électricité étoit quelquefois,
très-foible, ensorte qu'après en avoir tiré une petite étincelle, on
étoit quelque tems sans pouvoir en tirer d'autre; que d'autrefois les
étincelles se suivoient avec une extrême rapidité, en ayant eu un jour
un courant continuel d'un timbre à l'autre de la largeur d'une plume de
corbeau; il y eut même des variations considérables pendant le même
orage.

L'hyver suivant j'imaginai une expérience pour découvrir si les nuages
étoient électrisés positivement ou négativement; mais ma verge pointuë
avec tout son appareil s'étant dérangée, je ne la rétablis que vers le
printems, lorsque j'espérai que la chaleur occasionneroit plus de nuages
orageux.

Cette expérience consistoit à prendre deux bouteilles, à en charger une
du feu de la verge de fer & à donner à l'autre une charge égale avec le
globe de verre électrique par le moyen du premier conducteur, & après
les avoir chargées, à les placer sur une table à trois ou quatre pouces
l'une de l'autre, ayant suspendu au plat-fons avec un fil de soye fin,
une boulette de liége qui pût joüer entre les crochets. Si les deux
bouteilles étoient électrisées positivement, la boulette attirée &
repoussée par l'une, devroit aussi être repoussée par l'autre: si l'une
étoit positivement & l'autre négativement, la boulette seroit attirée &
repoussée tour à tour par chacune, & continueroit de joüer entr'elles
aussi long-tems qu'elles conserveroient quelque charge considérable.

Ayant fort à coeur de faire cette

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

Page 0
_ _And indeed the scene he opens, strikes us with a pleasing astonishment, whilst he conducts us by a train of facts and judicious.
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After the second, the upper part will have 22, the lower 18, and so on 'till after 20 strokes, the upper part will have a quantity of electrical fire equal to 40, the lower part none: and then the operation ends: for no more can be thrown into the upper part, when no more can be driven out of the lower part.
Page 3
Place an electrised phial on wax; a small cork-ball suspended by a dry silk-thread held in your hand, and brought near to the wire, will first be attracted, and then repelled: when in this state of repellency, sink your hand, that the ball may be brought towards the bottom of the bottle; it will there be instantly and strongly attracted, 'till it has parted with its fire.
Page 5
Lay two books on two glasses, back towards back, two or three Inches distant.
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--We suspend by fine silk thread a counterfeit spider, made of a small piece of burnt cork, with legs of linnen thread, and a grain or two of lead stuck in him to give him more weight.
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4.
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The _abounding_ of fire in one of the hooks (or rather in the internal surface of one bottle) being exactly equal to the _wanting_ of the other: and therefore, as each bottle has in itself the _abounding_ as well as the _wanting_, the wanting and abounding must be equal in each bottle.
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17.
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We then took two plates of lead of equal dimensions, but less than the glass by two inches every way, and electrified the glass between them, by electrifying the uppermost lead; then separated the glass from the lead, in doing which, what little fire might be in the lead was taken out and the glass being touched in the electrified parts with a finger, afforded only very small pricking sparks, but a great number of them might be taken from different places.
Page 17
--But if another bottle which had been charged through the coating be placed near the same wheel, its wire will attract the thimble repelled by the first, and thereby double the force that carries the wheel round; and not only taking out the fire that had been communicated to the thimbles by the first bottle, but even robbing them of their natural quantity, instead of being repelled when they come again towards the first bottle, they are more strongly attracted, so that the wheel mends its pace, till it goes with great rapidity twelve or fifteen rounds in a minute, and with such strength, as that the weight of one hundred _Spanish_ dollars with which we once loaded.
Page 20
We are surprized at the account given in Mr _Watson_'s book, of a shock communicated through a great space of dry ground, and suspect there must be some metaline quality in the gravel of that ground; having found that simple dry earth, rammed in a glass tube, open at both ends, and a wire hook inserted in the earth at each end, the earth and wires making part of a circle, would not conduct the least perceptible shock, and indeed when one wire was electrify'd, the other hardly showed any signs of its being in connection with it.
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14.
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The electrical spark will strike a hole thro' a quire of strong paper.
Page 32
Bring A into contact with B, and half the electrical fluid is communicated, so that each has now an electrical atmosphere, and therefore they repel each other.
Page 38
But having no paint at hand, I pasted a narrow strip of paper over it; and when dry, sent the flash through the gilding; by which the paper was torn off from end to end, with such force, that it was broke in several places, and in others brought away part of the grain of the Turky-leather in which it was bound; and convinced me, that had it been painted, the paint would have been stript off in the same manner with that on the wainscot at _Stretham_.
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fire must leap over the vacancies; there is a certain distance which it is able to leap over according to its strength; if a number of small vacancies, though each be very minute, taken together exceed that distance, it cannot leap over them, and so the shock is prevented.
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For experiments favouring (if I may not say confirming) this hypothesis, I must, to avoid repetition, beg leave to refer you back to what is said of the electrical phial in my former papers.
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Hence we see the.
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For if it was fine enough to come with the electrical fluid through the body of one person, why should it stop on the skin of another? But I shall never have done, if I tell you all my conjectures, thoughts, and imaginations, on the nature and operations of this electrical fluid, and relate the variety of little experiments we have try'd.
Page 50
But Take a wire bent in the form of a C, with a stick of wax fixed to the outside of the curve, to hold it by; and apply one end of this wire to the coating, and the other at the same time to the prime conductor, the phial will be discharged; and if the balls are not electrified before the discharge, neither will they appear to be so after the discharge, for they will not repel each other.