Julius Plücker to Faraday   2 June 1849

Sir, I thank you very much for the unexpected kindness, with which you received my last co<bar>munication¹. A letter not being a memoir, I am very satisfied you sent mine to be printed by Mr. Taylor². My bad English, I know very well, is to be changed before going to press; therefore I am much obliged to you, for having altered some expressions. There is only one word, introduced by you, which I do not understand. You say “It is a true compass-needle and more than that, you may obtain its declination” ³[.] My meaning was “you may dispose on the direction, it shall take” or “you may give to it any declination you like, from about 25˚ to the East to 65˚ to the West”.

I’ll go again to work as soon as I get crystals, I am expecting from Berlin. Since my last letter I tried only a few crystals, ascertaining all the general law. I found that angite is acted upon by the magnetic power of the Earth, quite in the same way as cyanite.

I examined also rock crystal. If you suspend a prism of it horizontally it will, according to the smal[l]er or greater distance from the poles, point either equatorially by the diamagnetism of its substance or axially, its optic axis being attracted. Why did I not try that before? To excuse my stupidity I might write a long psychological memoir.

I did not yet receive your paper⁴.

Most sincerely | Yours | Plücker

Bonn 2th of June 1849

Address: Professor M. Faraday | &c &c | London | Royal Institution