William Whewell to Faraday   2 September 1850

Lancaster | Sept. 2, 1850

Dear Dr Faraday

Since I wrote to you I have read your “Twenty Third Series”¹ as well as the letter which you sent me²; and the result is that I have some doubts whether the suggestions which I sent you respecting names are sound³. I had entertained a view which your paper is employed in refuting, that the magnetism of bismuth &c on the one hand and of iron &c on the other is of a coördinate kind, and that therefore it was desirable to designate the two by two coördinate words, such as paramagnetic and diamagnetic. But as I now understand your view is that bismuth &c have no real polarity but only a seeming polarity arising from each particle having a tendency to go from strong to weak magnetic spaces; while iron &c have a polarity, or at least hard iron is capable of a polarity which may be defined directly and finally as a tendency to arrange its polar axes parallel to the magnetic lines of the earth. This want of exact symmetry in the two kinds of magnetism, and the seeming connection of one with the earth’s magnetism make me hesitate about the term paramagnetic, and reconsider whether your term terromagnetic ⁴, or the corresponding Greek compound, geomagnetic, might not be better. But all things considered, I am still disposed to recommend the use of the term paramagnetic, advising only that the term should be explained at the outset (if I am right in my view) as implying that iron &c have a (seeming) polarity which places them parallel to the magnetic lines of the earth. Perhaps it is still conceivable that there may be planets so constituted that diamagnetic bodies shall arrange themselves parallel to their lines of force; but whether or not, the reference to the earth may I think be understood in your sense, as safely as expressed.

I am much interested in the hints you give me about the magnetic constitution of the atmosphere and its results. I am exceedingly struck by the ingenuity of the modes of experimenting explained in your 23d Series, but I think you might have given a Diagram to make the construction of the apparatus more evident. For instance, in 2643 what is the position of the brass rod and the core with reference to the wooden lever? I suppose at right angles, and in the plane of the motion; but I think you have not said so.

I am travelling in the lake country but am always accessible at Cambridge. I was there the other day and found your card⁵, as if I had missed seeing you there also⁶, which I am sorry for[.]

Believe me always | Yours most truly | W. Whewell