998 



3. " Experimental Researches in Electricity." Twenty-sixth Se- 

 ries. On Magnetic Conducting Power and Atmospheric Magnetism. 

 By Michael Faraday, Esq., D.C.L., F.R.S. &c. Received October 

 9, 1850. 



The remarkable results respecting oxygen and nitrogen described 

 in the last Series, and the absence of any change of volume under 

 strong magnetic action, led the author to apply for a time the idea 

 of conducting power to the magnetic phenomena there described, 

 meaning by that phrase the capability which bodies possess of affect- 

 ing the transmission of the magnetic force without any reference to 

 the process by which that transmission is effected ; and assuming 

 that two bodies are at the same time in the magnetic field, and that 

 one displaces the other, he considers the result as a differential effect 

 of their difference in conducting power. 



If a free portion of space be considered with lines of equal mag- 

 netic force passing across it, they will be straight and parallel lines. 

 If a sphere of paramagnetic matter be placed in such a space, they 

 will gather upon and in the sphere, being no longer parallel in their 

 course, nor of equal intensity in every part ; or if a sphere of dia- 

 magnetic matter replace the former sphere, the lines of force will 

 open out where the sphere is, being again no longer parallel in direc- 

 tion nor uniform in force. When the field of magnetic force is formed 

 between the opposite flat ends of two large magnetic poles, then 

 these are affected, and the globes also, and there are mutual actions; 

 a paramagnetic body, if a little elongated, points axially and tends 

 to go to the iron walls of the field, whilst a similar diamagnetic 

 body points equatorially, and tends to go to the middle of the field. 

 Paramagnetic bodies repel each other, and so also do diamagnetic 

 bodies ; but one of each class being taken, they attract one another. 



The convergence of the lines of force upon the opposite sides of 

 the paramagnetic sphere, and the corresponding divergence of them 

 on the opposite sides of the diamagnetic sphere, the author expresses 

 by the term conduction 'polarity. This polarity he carefully di- 

 stinguishes from that which depends upon the reversion of the di- 

 rection of the power ; the latter he considers as a property of the 

 particles of magnetic matter ; the former as dependent rather upon 

 the action of the mass : the latter is an absolute inversion of the di- 

 rection of the power, the former only a divergence or deflection of it. 



Applying the idea of conduction to magnecrystallic bodies, he 

 concluded that the magnecrystallic axis would coincide with the 

 direction of better conduction, and thence concluded, that, if a 

 symmetric crystal of bismuth were carefully examined in different 

 directions, it would be found to be less diamagnetic when its magne- 

 crystallic axis was perpendicular to the axis of magnetic force of the 

 field in wiiich it was to be submitted to experiment, than when it 

 was parallel to the magnetic axis. By means of the differential 

 torsion balance described in the former paper, he was able to make 

 the trial, and found the results were as anticipated. With calcareous 

 spar and his present balance he was not able to establish any dif- 

 ference, but concludes that it will prove most diamagnetic when the 



