L 7 ] 
II. Experimental Researches in Electricity . — Twenty-fifth Series. By Michael 
Faraday, Esq., D.C.L., F.R.S., Fullerian Prof. Chem. Royal Institution, Foreign 
Associate of the Acad. Sciences, Paris, Ord. Boruss. Pour le Merite, Eq., Memh. 
Royal and Imp. Acadd. of Sciences, Petershurgh, Florence, Copenhagen, Berlin, 
Gottingen, Modena, Stockholm, Munich, Bruxelles, Vienna, Bologna, ^c. S^c. 
Received August 15, — Read November 28, 1850. 
§ 31 . On the magnetic and diamagnetic condition of bodies. 
^ i. Non-expafision. of gaseous bodies by magnetic force. ^ ii. Differential mag- 
netic action. ^ iii. Magnetic characters of Oxygen, Nitrogen and Space. 
^ i. Non-expansion of gaseous bodies by magnetic force. 
27I8. There can be no doubt that the magnetic force, the diamagnetic force, and 
the magneoptic or magnecrystallic force, will, when thoroughly understood, be found 
to unite or exist under one form of power, and be essentially the same. Hence the 
great interest which exists in the development of any one of these modes of action ; 
for differing so greatly as they do in very peculiar points, it is hardly possible that 
any one of them should be advanced in its illustration or comprehension, without a 
corresponding advance in the knowledge of the others. Stimulated by such a feeling, 
I have been engaged with Plucker, Weber, Reisch and others, in endeavouring to 
make out, with some degree of precision, the mode of action of diamagnetic as well 
as magnecrystallic bodies; and the recent investigation ( 2640 , &c.) and endeavour 
to confirm the idea of polarity in bismuth and diamagnetic bodies, the reverse of that 
in a magnet or in iron bodies, was one of the results of that conviction and desire. 
2719. Having failed however to establish the existence of such an antipolarity, and 
having shown, as I think, that the phenomena which were supposed to be due to it 
are in fact dependent upon other conditions and causes, I was induced, in the search 
after something precise as to the nature of diamagnetic bodies, to examine another 
idea which had arisen in consequence of the development of magnetic and diamag- 
netic phenomena amongst gaseous substances; this thought, with some of the results 
which have grown out of it during its experimental examination, I purpose making 
the subject of the present paper. 
2720. Bancalari first showed that flame was diamagnetic*. The effect, as I 
proved, was due chiefly to the heated state of gaseous portions of the flame-j'; but 
besides that, it appeared that at common temperatures diamagnetic phenomena could 
* Philosophical Magazine, 1847, vol. xxxi. pp. 401, 421. f Ibid. pp. 404, 406. 
