Julius Plücker to Faraday   27 December 1857

My dear Sir!

My best thanks for your interesting paper on the Relations of gold to light¹, which I received some time ago. I tried myself to prepare one of your purple fluids, but - you will think me a bad experimentalist - I did not succeed. I was much interested to get such a fluid, being itself a bad conductor, but containing well conducting particles in suspension, in ordre to examine if no particular arrangement of these particles would appear, when electric currents of different kind were send through it. The discharge of Electricity through the tubes, exhibiting the stratified light, cannot be a transport of light, or luminous matter from one end of the tube to the other. There is, I think, within the tube a distribution of ponderable matter produced by the discharge, that matter becoming luminous by it, while the discharge is a dark one, as you call it, from one luminous place to another.

I had the opportunity to examine a great number of tubes containing traces only of matter of a different kind. Since I showed the beautifull effect they present, at the Meeting of Bonn², several hundred of them have been sent to all countries, except till now to England. If any of my English friends had assisted to the meeting, I would have found the opportunity to send to you and to Mr. Barlow some of them.- Since that time I observed a quite new series of phenomena, which exhibit a very fine appearance. I can, in a few words give no better account of them but by saying, that I am enabled by means of the electric light, to render luminous your lines of magnetic force.

There is round the positive electrode (where heat is produced) a luminous atmosphere, sometimes of some inches in diameter, separated by a dark space from the Stratified light. By means of the Magnet this light is concentrated, if the electrode be a single point, to a brightly coloured line of magnetic force, passing through that point. If the electrode be a platina wire every point of it produces such a luminous curve. The system of all these curves constitue luminous surfaces of different forms, depending only upon the position of the poles. By commutating the polarity these luminous curves and surfaces of magnetic forces do not change.

What will do the light surrounding under different circumstances the negative Electrode?

In a paper sent to Poggendorff³. I gave a first account of these curious phenomena. When printed I’ll send to you a copy of it.

With all my heart | Yours | Plücker

Bonn 27 / 12 57.