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Ohio, and the other into Susquehanna or Potomac j in that the electric fire would have a circuit of some thousands of miles to go down Ohio to Mississippi, to the Bay of Mexico, round Florida, and round the South Cape of Virginia; which, I think, would give some observable time, and discover exactly the velocity.
But, if the electric fire dissipates or weakens in the water, as I fear it does, these experiments will not answer.
JInswer to the Foregoing.
READ AT THE ROYAL SOCIETY, DECEMBER 2CTH, 1756.
Suppose a tube of any length, open at both ends, and containing a movable wire of just the same length, that fills its bore. If I attempt to introduce the end of another wire into the same tube, it must be done by pushing forward the wire it already contains; and the instant I press and move one end of that wire, the other end is also moved; and, in introducing one inch of the same wire, I extrude, at the same time, an inch of the first, from the other end of the tube.
If the tube be filled with water, and I inject an additional inch of water at one end, I force out an equal quantity at the other, in the very same instant.
And the water forced out at one end of the tube is not the very same water that was forced in at the other end at the same time; it was only in motion at the same time. (,
The long wire, made use of in the experiment to discover the velocity of the electric fluid, is itself filled with what we call its natural quantity of that fluid,
before the hook of the Leyden bottle is applied to one end of it.
The outside of the bottle being, at the time of such application, in contact with the other end of the wire, the whole quantity of electric fluid contained in the wire is, probably, put in motion at once.
For, at the instant the hook connected with the inside of the bottle gives out, the coating, or outside of the bottle, draws in, a portion of that fluid.
If such long wire contains precisely the quantity that the outside of the bottle demands, the whole will move out of the wire to the outside of the bottle, and the over quantity which the inside of the bottle contained, being exactly equal, will flow into the wire, and remain there, in the place of the quantity the wire had just parted with to the outside of the bottle.
But, if the wire be so long as that one tenth (suppose) of its natural quantity is sufficient to supply what the outside of the bottle demands, in such case the outside will only receive what is contained in one tenth of the wire's length, from the end next to it; though the whole will move so as to make room at the other end for an equal quantity issuing, at the same time, from the inside of the bottle.
So that this experiment only shows the extreme facility with which the electric fluid moves in metal; it can never determine the velocity.
And; therefore, the proposed experiment (though well imagined and very ingenious) of sending the spark round through a vast length of space, by the waters of Susquehanna, or Potomac, and Ohio, would not afford the satisfaction desired, though we could be sure that the motion of the electric fluid would be in that tract, and not under ground in the wet earth by the
Remarks on the Abbé Nollefs Letters to Benjamin Franklin on Electricity. By David Colden, of New York*
Coldenham, in New York, 4 December, 1753.
Sir, In considering the Abbé Nollet's letters to Mr. Franklin, I am obliged to pass by all the experiments which are made with, or in, bottles hermetically sealed, or exhausted of air; because, not being able to repeat the experiments, I could not second any thing which occurs evident, that whatever is placed on the side opposite to that which receives the electricity from the conductor, receives also an evident electrical virtue." Which, Mr. Franklin says, is that equal quantity of electric matter, driven out of this side, by what is received from the conductor on the other side; and which will continue to give an electrical virtue to any thing in contact with it, till it is entirely discharged of its electrical fire. To which the Abbe thus objects; "Tell me," says he, (p. 68,) "I pray you, how much time is necessary for this pretended discharge? I can assure you, that, after having maintained the electrization for hours, this surface, which ought, as it seems to me, to be entirely discharged of its electrical matter, considering either the vast number of sparks that were drawn from it, or the time that this matter had been exposed to the action of the expulsive cause; this surface, I say, appeared rather better electrized thereby, and more proper to produce all the effects of an actual electric body."
* The Abbé Nollet published in Paria a volume entitled, a Lettres sur FEltctricili, dans lesquelles on examine les Découvertes qui ont été faites sur cette Matière depuis PAnnie 1752, et les Conséquences que Von en peut tirer.'" These letters were directed to various persons. One volume only was published originally, but the work was afterwards extended to three. In the first volume were six letters directed to Franklin. The author, having formed a theory of his own on electricity, attempted to confute the doctrines and hypotheses of thé American philosopher. The following is an extract from the preface to the edition of the Abbé Nollet's work published in 1764.
"Le Livre de M. Franklin est devenu célèbre par le goût qu'on a pris aux expériences curieuses qu'il contient, et par les nouvelles merveilles qu'il nous a fait découvrir; cet ouvrage est entre les mains de tout le monde, et, la doctrine qu'il renferme étant par bien des endroits opposée à celle que j'ai enseignée jusqu'à présent sur les mêmes matières, si je n'en disois rien, mon silence pourrait passer pour un abandon que je ferais de mes opinions. Ne fût-ce qu'en reconnoissance de l'honneur que l'Académie des Sciences m'a fait de les insérer dans ses Mémoires, et de l'accueil favorable que le public a bien voulu leur faire, je me suis cru obligé de les examiner de nouveau, et d'en prendre la défense, quand j'ai vu quo je le pouvois faire par'de bonnes raisons et malgré les prétentions de l'Ecole de Philadelphie. Voilà encore ce qui a donné lieu aux Lettres que je publie aujourd'hui; elles doivent moins passer pour une critique de la doctrine de M. Franklin, que pour une défense de la mienne; cet auteur n'a commencé à écrire qu'après moi.
"Ce n'est pas que je croie que M. Franklin ait eu dessein de me critiquer; il ne savoir peut-être pas que j'existois; mais, quand il aurait connu mes ouvrages, et qu'il les aurait eu en vue en écrivant le contraire de ce qu'ils contiennent, je ne lui en saurais pas plus mauvais gré, s'il a cru, comme je n'en doute pas, opposer des vérités à des erreurs. An reste, je ne me suis point borné à disputer contre ce physicien; j'ai applaudi tres-sincerement aux endroits de son ouvrage qui m'ont paru solidement etablis, ou ingenieusement penses, et c'est ce que j'ai fait avec le plus de plaisir."
Franklin never answered the Abbe's book, though he says, in a letter to Mr. Bowdoin, that he had collected and methodized short hints for that purpose. And in his autobiography he thus speaks of the subject, after alluding to the publication of his papers on electricity.
"A copy of them happening to fall into the hands of the Count de BufFon, (a philosopher deservedly of great reputation in France, and indeed all over Europe,) he prevailed with Monsieur Dubourg to translate them into French; and they were printed at Paris. The publication offended the Abbe Nollet, preceptor in Natural Philosophy to the royal family, and an able experimenter, who had formed and published a theory of electricity, which then had the general vogue. He could not at first believe that such a work came from America, and said it must have been fabricated by his enemies at Paris to oppose his system. Afterwards, having been assured that there really existed such a person as Franklin at Philadelphia, (which he had doubted,) he wrote and published a volume of Letters chiefly addressed to me, defending his theory, and denying the verity of my experiments, and of the positions deduced from them. I once purposed answering the Abbe, and actually began the answer; but, on consideration that my writings contained a description of experiments, which any one might repeat and verify; and, if not to be verified, could not be defended; or of observations offered as conjectures, and not delivered dogmatically, therefore not laying me under any obligation to defend them; and reflecting, that a dispute between two persons, written in different languages, might be lengthened greatly by mistranslations, and thence misconceptions of one another's meaning, (much of one of the Abbe's letters being founded on an error in the translation;) I concluded to let my papers shift for themselves; believing it was better to spend what time I could spare from public business in making new experiments, than in disputing about those already made. I therefore never answered Monsieur Nollet; ;md the event gave me no cause to repent my silence ; for my friend, Monsieur Lc Roy, of the Royal Academy of Sciences, took up my cause and refuted him."
David Colden was a son of Cadwallader Colden, and devoted to the study of electricity. — Editor.
The Abbe does not tell us what those effects were; all the effect I could never observe, and those that are to be observed can easily be accounted for, by supposing that side to be entirely destitute of electric matter. The most sensible effect of a body charged with electricity is, that, when you present your finger to it, a spark will issue from it to your finger; now, when a phial prepared for the Leyden experiment is hung to the gun-barrel or prime conductor, and you turn the globe in order to charge it, as soon as the electric matter is excited, you can observe a spark to issue from the external surface of the phial to your finger, which, Mr. Franklin says, is the natural electric matter of the glass, driven out by that received by the inner surface from the conductor. If it be only drawn out by sparks, Vol. v. 41