Dear Sir!
I got the last number of the philosophical Magazine with de la Rive’s letter1, who characterizes my experiments as his own under a different form. Allow me a few words. Davy’s2 and de la Rive’s beautifull experiments are inscribed into the annals of science. In both cases the free luminous arch is substituted to the moveable copper wire, to which in your original experiments the current is bound. In that sense de la Rive’s experiment of 18493 is that of “Faraday’s pendulum”4. I published a series of experiments of the same kind which in like manner emanate i<line>mediately from yours and may be easily predicted.
But there is a second series of experiments, which I described in my first paper5, of quite a different description. Such is the rupture of the current too. A copper-wire cant change its form under the influence of the Magnet, an electric beam, starting from a fixed point, can. The new class of phenomena show this change of form of the luminous current in a most splendid way. I am enabled now to explain the connection of these phenomena with the experiments you made about thirty [sic] years ago and particularly with the mathematical law deduced from them by M. Biot and Laplace6.
The form which a flexible current assumes when in equilibrium under the influence of the Magnet is given by the following laws.
1º. When the current is free only to move on a given surface (that arrives, for instance, in the case of the double helix in Gassiot’s induction tube) each moveable element of the current, acted upon by the magnet, is to be, by this action, compelled perpendicularly against the given surface: therefore the line perpendicular to the element and the line of force passing through it, must be a normal to the surface.
2º. When the flexible current, starting from a fixed point, is free to move in any direction whatever, each of its elements must be directed thus, that there is on it no action not at all emanating from the Magnet; id est it must be directed along a line of magnetic force. Whence you may imediately conclude that the whole current, when in equilibrium, is bent along the line of magnetic force passing through the fixed point.
I hope, my dear Sir, you will be satisfied by the simplicity of these new laws.
Most truly yours | Plücker
Bonn 28 / 6 58.
PS. Since my last letter7 I observed a great variety of new facts. I am preparing a fourth paper8. My third one is printed since a month9 but I could not yet obtain the copies. With regard to the two spirals, I mentioned in my last letter, by a “lapsus pennae” I said one “dextrorsum the other one sinistrorsum”. But both are either dextrorsum or sinistrorsum (independently of the direction of the primitive current of Ruhmkorff’s coil and of the polarity of the Magnet) the tube in its oblique position being inclined either +45° or -45° to the equatorial plane.
DAVY, Humphry (1821): “Farther researches on the magnetic phaenomena produced by electricity; with some new experiments on the properties of electrified bodies in their relations to conducting powers and temperature”, Phil. Trans., 111: 425-39.
DE LA RIVE, Arthur-August (1849): “Extrait d’une Lettre … à M. Regnault”, Comptes Rendus, 29: 412-5.
DE LA RIVE, Arthur-August (1858): “On the Rotation of Electrical Light round the Pole of an Electro-magnet”, Phil. Mag., 15: 463-66.
FARADAY, Michael (1838b): “Experimental Researches in Electricity. - Twelfth Series. On Induction (continued)”, Phil. Trans., 128: 83-123.
JAMES, Frank A.J.L. (1983b): “The Study of Spark Spectra 1835-1859”, Ambix, 30: 137-62.
Please cite as “Faraday3466,” in Ɛpsilon: The Michael Faraday Collection accessed on 5 May 2024, https://epsilon.ac.uk/view/faraday/letters/Faraday3466