In the same paragraph I have stated that M. Ampere says the disc turned “to take a position of equilibrium exactly as the spiral itself would have turned had it been free to move”; and further on I have said that my results tended to invert the sense of the proposition “stated by M. Ampere, that a current of electricity tends to put the electricity of conductors near which it passes in motion in the same direction.” M. Ampere tells me in a letter which I have just received from him, that he carefully avoided, when describing the experiment, any reference to the direction of the induced current; and on looking at the passages he quotes to me, I find that to be the case.  I have therefore done him injustice in the above statements, and am anxious to correct my error.

But that it may not be supposed I lightly wrote those passages, I will briefly refer to my reasons for understanding them in the sense I did.  At first the experiment failed.  When re-made successfully about a year afterwards, it was at Geneva in company with M.A.  De la Rive:  the latter philosopher described the results[A], and says that the plate of copper bent into a circle which was used as the mobile conductor “sometimes advanced between the two branches of the (horse-shoe) magnet, and sometimes was repelled, according to the direction of the current in the surrounding conductors.”

  [A] Bibliotheque Universelle, xxi. p. 48.

I have been in the habit of referring to Demonferrand’s Manuel d’Electricite Dynamique, as a book of authority in France; containing the general results and laws of this branch of science, up to the time of its publication, in a well arranged form.  At p. 173, the author, when describing this experiment, says, “The mobile circle turns to take a position of equilibrium as a conductor would do in which the current moved in the same direction as in the spiral;” and in the same paragraph he adds, “It is therefore proved that a current of electricity tends to put the electricity of conductors, near which it passes, in motion in the same direction.” These are the words I quoted in my paper (78.).

Le Lycee of 1st of January, 1832, No. 36, in an article written after the receipt of my first unfortunate letter to M. Hachette, and before my papers were printed, reasons upon the direction of the induced currents, and says, that there ought to be “an elementary current produced in the same direction as the corresponding portion of the producing current.”  A little further on it says, “therefore we ought to obtain currents, moving in the same direction, produced upon a metallic wire, either by a magnet or a current.  M. Ampere was so thouroughly persuaded that such ought to be the direction of the currents by influence, that he neglected to assure himself of it in his experiment at Geneva.”