Prof. Faraday's Magnetic Remarks. 255 



vancing no principle, I say, that the hypothetical fundamental 

 ideas already advanced, when taken in relation to the body of 

 facts now known, are self-contradictory and inapplicable. The 

 following points, namely, — that the direction and polarity of 

 lines of magnetic force are always shown truly by the electric cur- 

 rent induced in metal moving within their influence; — that the 

 dualities of electricity and magnetism are always respectively and 

 essentially related; — that the dualities of an isolated magnet are 

 not related back in straight lines through the magnet ; — are to 

 my mind not hypothetical in character, but easily proveable by 

 experiment : — and they, with the considerations arising from the 

 principle of the conservation of force, seem to me to be left un- 

 explained by, and in opposition to, the usual hypotheses. No 

 difference arises about the laws of magnetic action and their 

 mathematical development ; and that, simply because they are 

 as yet applied only partially, and thus far are in accordance with 

 all the views taken, including mine. When the attempt is made 

 to apply them so as to include at once paramagnetic, diamagnetic, 

 and electro-magnetic phenomena, and at the same time to deduce 

 them from one hypothetical cause, then they may become so 

 large and yet precise as to enable us to distinguish between true 

 and false assumptions. On my part I endeavour not to assume 

 anything, but only to draw such conclusions from the assump- 

 tions already made, and the phamomena now discovered, as seem 

 subject to experiment and tangible by facts. 



Some persons may feel surprised that I dwell upon points 

 which are perfectly and mathematically explained by the hypo- 

 thesis of two magnetic fluids, as, for instance, places of little or 

 no action (3341. &c). My reason is, that being satisfied by the 

 phenomena of diamagnetism, &c. that that hypothesis cannot be 

 true, all these and such like phenomena acquire a new character 

 and a high importance which they had not before, and amongst 

 other philosophical uses, point most emphatically to the essen- 

 tial relation of the dualities and their equivalency in power. 

 They do not contradict the old hypothesis when that is partially 

 applied, but they are not the less strong and striking as evidence 

 in favour of the view of lines of force. 



I am, my dear Tyndall, 



Yours very faithfully, 



Itoval Institution, M. Faraday. 



March 14, 1855. 



