William Thomson to Faraday   11 June 1847

St Peter's College, Cambridge, | June 11, 1847

My dear Sir,

I enclose the paper¹ which I mentioned to you² as giving an analogy for the electric and magnetic forces, by means of the strain, propagated through an elastic solid. What I have written is merely a sketch of the mathematical analogy. I did not venture even to hint at the possibility of making it the foundation of a physical theory of the propagation of electric and magnetic forces, which, if established at all, would express as a necessary result, the connection between electrical and magnetic forces, and would show how the purely statical phenomena of magnetism may originate either from electricity in motion, or from an inert mass such as a magnet. If such a theory could be discovered, it would also, when taken in connection with the undulatory theory of light, in all probability explain the effect of magnetism on polarized light³.

I have only just returned to Cambridge, and so I have not had time to look for the paper to which you kindly sent me a reference. I have lately received a number of a Pisa Journal, containing a paper by Matteucci on electro-statical induction⁴, in which the author seems to endeavour to resolve your results into effects of conduction; and I suppose this is the paper you alluded to, in speaking to me. I have not quite been able to learn its contents yet, as I do not understand the language, and it is not enlivened by any xs or ys.

I should consider it a great favour if you would allow your assistant to show me some of the lecture room apparatus belonging to the Royal Institution, when I am in London on my way to or from Oxford⁵, or at any other convenient time. As I am now Professor of Natural Philosophy at Glasgow, and have had a session's experience of the inadequacy of our apparatus, I am anxious to learn as much as I can about good apparatus, and how to procure it.

I remain Yours very truly | William Thomson

Prof. Faraday