James Clerk Maxwell to Faraday   30 November 1859

Marischal College | Aberdeen | 1859 Nov 30

Dear Sir

I am a candidate for the Chair of Natural Philosophy in the University of Edinburgh, which will soon be vacant by the appointment of Professor J.D. Forbes to St Andrews¹[.] If you should be able from your knowledge of the attention which I have paid to science, to recommend me to the notice of the Curators, it would be greatly in my favour and I should be much indebted to you for such a certificate.

I was sorry that I had so little time in September that I could not write out an explanation of the figures of lines of force which I sent you², but Professor W Thomson to whom I lent them, seems to have indicated all that was necessary, and most of them can be recognised from their resemblance to the curves made with Iron filings.

The only thing to be observed is, that these curves are due to the action either of long wires perpendicular to the paper or of elongated magnetic poles such as the edge of a long ribbon of steel magnetized transversely. By considering infinitely long currents or magnetic poles perpendicular to the paper, we obtain systems of curves far more easily traced than in any other case, while their general appearance is similar to those produced in the ordinary experiments.

All the diagrams have two sets of lines at right angles to each other and the width between the two sets of lines is the same so that the reticulation is nearly square. If one system belongs to poles, the other belongs to currents, so that if the meaning of one be known, that of the other may be deduced from it.

I remain | Yours truly | James Clerk Maxwell

Professor Faraday