Faraday to Julius Plücker   27 July 1858¹

Royal Institution | 27. July 1857 [sic]

My dear Sir

I seemed to have two or three of your letters unanswered & wondered at it but then I remembered that you had been here since some of them & we had talked them over. Your last I shewed as you desired to Mr. Gassiot & also to Dr. Tyndall[.] The latter is now in Switzerland amongst the Glaciers[.] I do not know whether you will see him at some of your German meetings. I have been obliged to give up thinking about the luminous current but whilst such as you Gassiot and others work at the subject I know it is progressing. The Arch which you shewed me corresponding to the Magnetic line of force and that other one of which you speak in one of your letters of like nature interest me very much inasmuch as their course seems to be directly at right angles to the course of the Electric current - The alternate light & dark parts of the stratified column are also exceedingly exciting: What is the essential difference of these parts? It is very easy to imagine a difference or even two or three kinds of it but what is the real difference?

Then again the question of transmission of the discharge across a perfect vacuum or whether a vacuum exists or not? is to me a continual thought and seems to be connected with the hypothesis of the ether. What a pity one cannot get hold of these points by some experiments - more close & searching than any we have yet devised[.]

You seem surprized to have had the double current when one end of the Ruhmkorf was connected with the coating of the tube & the other with the wire. With Gassiot & myself this was an instant conclusion from the experiment with two coatings & is described in his paper² as such. A very pretty variation of it is made by connecting the two wires a.b. with one end of the Ruhmkorf & the coating c with the other: double currents are obtained in both halves of the tube but in opposite directions as is shewn by their examination with a magnet[.]

Ever | My dear Sir | Very Truly Yours | M. Faraday

Profr. Plucker | &c &c &c