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evening. When you happen to have nothing else to do (if that ever happens), it may afford you some amusement.*
Proposal of an Experiment to measure the Time taken
up by an Electric Spark in moving through any given Space. By James Alexander, of New York.t
READ AT THE ROYAL SOCIETY, DECEMBER 26Th, 1756.
IF I remember right, the Royal Society made one experiment to discover the velocity of the electric fire, by a wire of about four miles in length, supported by silk, and by turning it forwards and backwards in a field, so that the beginning and end of the wire were at only the distance of two people, the one holding the Leyden bottle and the beginning of the wire, and the other holding the end of the wire and touching the ring of the bottle ; but by this experiment no discovery was made, except that the velocity was extremely quick.
* These letters and papers are a philosophical correspondence between Mr. Franklin and some of his American friends. Mr. Collinson communicated them to the Royal Society, where they were read at different meetings during the year 1756. But, Mr. Franklin having particularly requested that they might not be printed, none of them were inserted in the Transactions. Mr. Franklin had at that time an intention of revising them, and pursuing some of the inquiries farther; but, finding that he is not like to have sufficient leisure, he has at length been induced, imperfect as they are, to permit their publication, as some of the hints they contain may possibly be useful to others in their philosophical researches.
Note in Mr. Collinson's edition.
As some of the papers transmitted in the above letter to Mr. Collinson do not relate to electricity, they are transferred to the parts of the work in which they belong, according to their subjects. They are all inserted, as far as it can be ascertained, in the order of their dates. — EDITOR.
† This paper and the following one were among those communicated to Mr. Collinson, November 23d, 1753. Their dates are uncertain. - EDITOR.
As water is a conductor as well as metals, it is to be considered, whether the velocity of the electric fire might not be discovered by means of water; whether a river, or lake, or sea, may not be made part of the circuit through which the electric fire passes, instead of the circuit all of wire, as in the above experiment.
Whether in a river, lake, or sea, the electric fire will not dissipate, and not return to the bottle ? or, will it proceed in straight lines through the water the shortest course possible back to the bottle?
If the last, then suppose one brook that falls into Delaware doth head very near to a brook that falls into Schuylkill; and let a wire be stretched and supported as before, from the head of one brook to the head of the other; and let the one end communicate with the water; and let one person stand in the other brook, holding the Leyden bottle; and let another person hold that end of the wire not in the water, and touch the ring of the bottle. If the electric fire will go as in the last question, then will it go down the one brook to Delaware or Schuylkill, and down one of them to their meeting, and up the other and the other brook; the time of its doing this may possibly be observable, and the farther upwards the brooks are chosen, the more observable it would be.
Should this be not observable, then suppose the two brooks falling into Susquehanna and Delaware, and proceeding as before, the electric fire may, by that means, make a circuit round the North Cape of Virginia, and go many hundreds of miles, and in doing that, it would seem, it must take some observable time.
If still no observable time is found in that experiment, then suppose the brooks falling the one into the
Ohio, and the other into Susquehanna or Potomac; 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.
Answer to the Foregoing.
READ AT THE ROYAL SOCIETY, DECEMBER 26Th, 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 shortest way.
Remarks on the Abbé Nolleťs 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
The Abbé Nollet published in Paris a volume entitled, “ Lettres sur l'Electricité, dans lesquelles on examine les Découvertes qui ont été faites sur cetle Matière depuis l’Année 1752, et les conséquences que l'on en peut lirer.” 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 the 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 pourroit passer pour un abandon que je ferois 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 que 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 savoit peut-être pas que j'existois; mais, quand il auroit connu mes ouvrages, et qu'il les auroit eu en vue en écrivant le contraire de ce qu'ils contiennent, je ne lui en saurois pas plus mauvais gré, s'il a cru, comme je n'en doute pas, opposer des vérités à des erreurs. reste, je ne me suis point borné à disputer contre ce physicien; j'ai