Prof. Faraday on some Points of Magnetic Philosophy. 113 



copper, mercury, &c, they produce magneto-electric currents 

 when moved. When bodies (media) occupy the space around 

 the magnet, they modify its capability of transmitting and re- 

 lating the dual forces of the magnet, and as they increase or 

 diminish that capability, are paramagnetic or diamagnetic in 

 their nature ; giving rise to the phsenomena which come under 

 the term of magnetic conduction (2797.). The same magnet 

 can hold different charges, as the medium connecting its poles 

 varies; and so one, fully charged with a good medium, as iron 

 between its poles, falls in power when the iron is replaced by 

 air, or space, or bismuth. Corresponding effects occur with 

 longer or shorter magnets (3290.), or with magnets made thick 

 by adding many sideways together (3287.). The medium about 

 a magnet may be mixed in its nature, and then more dual 

 power is disposed of through the better conductor than the worse, 

 but the whole amount of power remains unchanged. The powers 

 and utility of the media, and of space itself, fail, if the dual force 

 or polar action be interrupted. The magnet could not exist with- 

 out a surrounding medium or space, and would be extinguished 

 if deprived of it, and is extinguished, if the space be occupied 

 adversely by the dual power of a dominant magnet of sufficient 

 force. The polarity of each line of force is in the same direction 

 throughout the whole of its closed course. Pointing in one 

 direction or another, is a differential action due to the con- 

 vergence or divergence of the lines of force upon the substance 

 acted on, according as it is a better or a worse conductor of the 

 magnetic force. 



3362. But though such is my view, I put it forth with all 

 the reservation made on former occasions (3244. 3299.). I 

 do not pretend to explain all points of difficulty. I have no 

 clear idea of the physical condition constituting the charged 

 magnetic state ; i. e. the state of the source of magnetic 

 power : — or of the coercitivity by which that state is either 

 resisted in its attainment, or sustained in its permanent condi- 

 tion ; for the hypotheses as yet put forth give no satisfaction 

 to my mind. I profess rather to point out the difficulties in 

 the way of the views, which are at present somewhat too easily 

 accepted, and to shake mens' minds from their habitual trust in 

 them ; for, next to developing and expounding, that appears to 

 me the most useful and effectual way of really advancing the 

 subject : — it is better to be aware, or even to suspect, we arc 

 wrong, than to be unconsciously or easily led to accept an error 

 as right. 



Royal Institution, 20 Dec. 1854. 



Pint. Mag, S. 4. Vol. 9. No. 57. Feb. 1855. I 



