Julius Plücker to Faraday   9 February 1853

Dear Sir!

After a longer silence, allow me at first to thank you for your last paper¹, I received two months ago. From your admirable activity in science I may conclude, that your health be improved, and I am happy to do so.

I take the liberty to send you my last mémoir² on the way of library, two former ones³ will have reached you, six months ago, on the same way. The indications you gave of the contents of your lecture at the Royal Institution on magnetic lines of force⁴, engaged myself to send a paper of mine, unfinished as it was, to Poggendorff. When I was last time at London, I intended to explain to you what it contains, but I desisted to do so in that troublesome period, not thinking then I might meet you in these researches.

I part from the law of the action of an element of the current on a magnetic pole, as given by Biot, immediately after Oerstedt’s discovery⁵. From that law I deduce the law of the induction of a current by a revolving pole, admitting the Newtonian principle, of the equality of action and reaction, as existing between both classes of phenomena. A pole turning round a conducting wire is acting on this wire as an “electromotrice force”, I deduce the laws of its action, both experimentally and mathematically. In the case of a revolving magnet bar (if you take the case of the Earth) I conclude that there is a tension of negative Electricity in the equatorial zone and a tension of positive one in the arctic regions. &c &c &c.

Mr. Geissler⁶, our clever artist, constructed a year ago, for the use of wine-makers’, an apparatus, indicating the quantity of alcool, by the tension of the vapours of the mixture mixed with a certain quantity of air, all at the temperature of 100C. This apparatus improved on my advice by excluding all air, is that which Dr. Waller⁷ bought from Mr. Geissler and for which he took a “brevet” for England⁸. Dr Hofmann, as it is written to Mr. G., intends to present it at the R. Institution. This apparatus startled me by the regularity of its indications, non [sic] only on mixtures containing alcool but also in many other cases, namely in the case of solutions. I left to Mr Geiss[l]er the care to work out (exploiter) his technical apparatus, reserving to myself, after that was done, to take use of the principle, well known before, but not at all sufficiently appreciated, for scientific researches on the affinity of vapours, on Dalton’s⁹ law, modified for the case of mixed vapours &c &c. After Dr Waller’s departure I took up the question and I intend now to send to Poggendorff the first part of the results I obtained, assisted by Mr Geissler¹⁰. For this purpose new apparatus were constructed, the “Vaporimeter” not being able for scientific researches.

I beg you Sir to present my respects to Mad. Faraday.

Yours very truly | Plücker

Bonn, 9th February | 1853.

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