V \\ 



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Dr. Faraday on the Magneti^Affection x qf Eight. 257 



when the continuity exists, and so consecutive poles at short 

 distances and in different directions are produced; and hence 

 the reason why the solution of iron or nickel, or the platina, 

 does not behave as the peroxide of iron, though weaker in 

 magnetic force than it, but acts as metallic iron. 



If it had not been for the remarkable relation of a vacuum, 

 and with it of those attenuated forms of matter, air, gases and 

 vapours, which I have for this very reason amongst others in- 

 sisted on in the Experimental Researches (24-32, &c), it might 

 have become questionable whether those bodies which I have 

 called diamagnetics, were not acted upon strictly in the same 

 manner as magnetic bodies ; and the result, whether of attrac- 

 tion or repulsion, a consequence of a difference of degree only 

 between the body observed and the medium surrounding it 

 (2438, &c). But I cannot help looking upon a vacuum as 

 presenting a zero point in the phaenomena of attraction and 

 repulsion : and as magnetic bodies are attracted, and diamag- 

 netic bodies repelled (2406, 2436) by a magnet, when sur- 

 rounded by and in relation to it, so I believe that these two 

 conditions represent two antithetical forms of magnetic force. 

 This is the conclusion I have set forth in my original papers, 

 and notwithstanding my very great respect for the judgement 

 of MM. Becquerel, it is that which by the facts I am en- 

 couraged still to maintain*. 



When heavy glass is submitted to the action of a powerful 

 electro-magnet, the maximum degree of rotation of the ray is 

 not obtained at once, but requires a sensible interval of time 

 (Experimental Researches, 2170) ; this I have attributed to 

 the gradual rising in intensity of the force of the magnet, and 



* I take the liberty in this note to refer to a similar point in the philo- 

 sophy of static electricity. 1 have often been asked for the proof of an 

 absolute natural zero between positive and negative electricity ; and in re- 

 ference to M. Peltier's views, that the earth is negative to the space around 

 it, which in its turn is positive, have been told that if all parts of a portion 

 of its plane surface were equally negative, we on that surface could not tell 

 that it was not in a zero state. But such is not the case. A surface 

 which is truly negative may appear, in comparison, to be positive to one 

 still more highly negative ; or a negative surface may seem to be in a zero 

 state in relation to two other surfaces, one of which is more negative and 

 the other less so, or even positive ; but if referred to a true standard its 

 real state is shown at once, and this standard is given by the inside of any 

 metallic vessel, from which, by its shape or depth, external influence is ex- 

 cluded. Such a vessel always presents the same normal condition within, 

 whatever charge its external surface may have; and by comparing the sur- 

 face of the earth with the inside of such a vessel, which is easily done by 

 the use of carriers, such as Coulomb employed, any one may tell for him- 

 self whether that surface is in a negative or a zero state. 



