Faraday to William Whewell   19 September 1835

Royal Institution 19 Septr 1835

My dear Sir

Your letter¹ was quite refreshing for I had begun to imagine that I thought more about Electricity and Magnetism than it was worth: and so a notion was creeping over me that after all I was perhaps only a bore to my friends by the succession of papers I was bold to send forth, and not that successful labourer for science which I was striving to be. Perhaps you will think so too when I tell you I have the tenth series² in print and waiting to reach you; but whatever you may think I am resolved to take your last letter as encouragement to go on.

Your remarks on my phraseology I am quite willing to admit; but let me remind you that I and Ampere use words, i.e. names, in very different ways. My words Volta-induction - magneto- electric-induction - magneto-electricity - electro-magnetism &c are merely intended to indicate how the effects included under them are obtained whereas Ampere by the word "Electro- dynamic" essentially implies a theory which theory may be wrong. The origin of all these effects may be something in such a state that when we come to know what it is the word electrodynamic may not apply. Perhaps I may be equally wrong, nay more so by far, in the word induction but at all events the prefixes, Volta, magneto, magneto electric, electro magnetic, pledge me to no theory, and yet have a certain distinctness of sense which makes them useful. Besides Amperes term, however good it may be, is so general that we must have words as heads of the several divisions into which the great branch of Electrodynamic science practically divides itself, and it is in that way rather than any other I would wish to use mine though I am probably not always consistent with myself[.]

I ought to say that I accept Amperes theory as the best present representa‑tion of facts, but that still I hold it with a little reserve. This reserve is more a general feeling than any thing founded on distinct objections to it. Remember I am no Mathematician. If I were one and could go into a closer examination of the theory than is at present possible for me I might have no doubts left; but all my mathematics consist in that rough natural portion of geometry which every body has more or less. Hence the reason why I have never put my facts into terms of Amperes theory; and why I cling to the relations of Magnetic & Electric forces as the simplest I can perceive; these again are readily distin‑guished in practise and hence the most convenient if not the best for an experimentalist to refer to. I wish most sincerely some mathematician would think it worth his while to do that for the facts which I can not do for them[.]

With regard to your remarks on momentum I can see great force in them. In thinking of momentum I had considered the analogy of a fluid, elastic or not, moving in a tube and acting in proportion to its mass, velocity &c. on obstacles in the tube or at least in the current. Perhaps if I could see the true relation of the currents in the phenomena which I have called phenomena of ‑Volta-induction, and which relation I think you say is obscure I might admit that the idea of momentum is not opposed to the facts or even that it accurately ex‑plains them: of course the conclusion at (1077)³ would, being unfounded, fall to the ground. At present however I feel the difficulty as I did before. Why for instance in the experiment (1090)⁴ should the action be transferred from the wire carrying the original current to the neighbouring wire if it be an effect of momentum? The second wire is carrying no current during the time that the electricity is moving through the first, why then on stopping the current in that first wire does not its effect of momentum appear in it also? I am aware however we might talk this matter on a great distance in conversation though hardly by letter[.]

With respect to induction remember that when I first used the term I believed that the neighbouring wire assumed & retained a peculiar state (called the electrotonic state) as long as the original current was continued (60. 67)⁵; and considered the two currents produced only as the particular conditions belong‑ing to the commencement & conclusion of this state. Considered as parts of that induced state I think they might then fairly be called phenomena of induction. I have given up this electrotonic state for the time <(242)>⁶ as an experi‑mental result (remember my researches are experimental) because I could find no fact to prove it but I cling to it in fancy or hypothesis (242, 1114)⁷ from general impressions produced by the whole series of results[.] You on the contrary seem to me not merely to admit it but contend for it. You say "a substance when put in motion by another substance produces at the first instant an impulse opposite to that of the motion; if the velocity be uniform no further effect is perceived till the motion is stopped and at that instant an impulse is produced in the direction of the motion" and you say "this is a full & exact account of the laws alike of electrical currents & mechanical collision"; then afterwards you add "we see clearly what these facts of instantaneous action are. They are the reaction of the current in which motion is produced by induction &c"[.] Now if this second current had had an existence during the time that the first current was continued I could have better conceived the notion of momen‑tum[.] As the second instantaneous current does not exist I take it for granted you assume the electrotonic <(60)>⁸ or peculiar (1114)⁹ state; but still that will justify the application of the word induction to it either at its beginning its continuance or its termination. Now is it not possible that this state may be a condition accounting for the phenomena on some other principle than that of momentum merely? It is just my ignorance of these things and my inability to view the effects as a mathematician that makes me speak with doubt & hesi‑tation & it may be in great error, but it is the only reason, or rather excuse, I have to offer. I feel that my safety consists in facts; and even these I am but too anxious to pervert through the influence of preconceived notions. To you therefore & such as you I must look for help & assistance and nothing would delight me more than the idea of having, however accidentally or humbly, been the means of setting you of[f] in pursuit of the important object before us[.]

Ever My dear Sir Most Truly Yours | M. Faraday

Endorsed by Whewell: An. Sept. 25

Address: Revd W. Whewell | &c &c &c | Trinity College | Cambridge