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Chemislnj and Physics. , 2G7 



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Substituting for tlie cylinders of bismutli thin cylinders of iron, of 

 magnetic slate, of sulphate of iron, carbonate of iron, pi'otochlorid of 

 iron, red ferrocyanid of potassium, and other magnetic bodies, it was 

 found that when the position of the magnetic cylinders was the same as 

 that of the cylinders of bismuth, the deflection produced by the former 

 was always opposed in direction to that produced by the latter : and 

 hence the disposition of the force in the diamagnetic body must have 



been precisely antithetical to its disposition in the magnetic ones. 



But it will be urged, and indeed has been urged against this inference, 

 that the deflection produced by the bismuth cylinders is purely due to 

 the currents of induction excited in the mass by its motion within the 

 helices. In reply to this objection, it may be stated, in the first place, 

 that the deflection is permanent, and cannot therefore be due to induced 

 currents, Avhich are only of momentary duration. It has also been urged 

 that such experiments ought to be made with other metals, and with bet- 

 ter conductors than bismuth, for if due to currents of induction the better 

 the conductor the more exalted will be the effect. This requirement was 

 complied with. 



Cylinders of antimony were substituted for those of bismuth. This 

 metal is a better conductor of electricity, but less strongly diamagnetic 

 than bismuth. If therefore the action referred to be due to induced cur- 

 rents we ought to have it greater in the case of antimony than with bis- 

 muth ; but if it springs from a true diamagnetic polarity, the action of 

 the bismuth ought to exceed that of the antimony. Experiment proves 

 that the latter is the case, and that hence the deflection produ^ed by 

 these metals is due to their diamagnetic, and not to tlieir conductive ca- 

 pacity. Copper cylinders were next examined : here we have a^ metal 

 ■which conducts electricity fifty times better tlian bismuth, but its diamag- 

 iietic power is nearly null ; if the effects be due to induction we ought to 

 have them here in an enormously exaggerated degree, but no sensible de- 

 flection Wiis produced by the two cylinders of copper. 



It has also been proposed by the opponents of diamagnetic polarity to 

 coat fragments of bismuth with some insuli^ting substance, so as to ren- 

 der the formation of induced currents impossible, and to test the question 

 with cylinders of these fragments. This requirement was also fulfilled. 

 It is only necessary to reduce the bismuth to powder and expose it for a 

 short time to the air to cause the particles to become so far oxydized as 

 to render them perfectly insulating. The power of the powder in this 

 i-espect was exhibited experimentally in the lecture; nevertheless, this 

 powder, enclosed in irlass tubes, exhibited an action scarcely less ppwerful 

 than that of the massive cylinder. 



But the most rigid proof, a proof admitted to be conclusive by those 

 >vho have denied the antithesis of magnetism and diaraagnetism, remains 

 to be stated. Prisms of the same heaAT glass as that with which the 

 diamagnetic force was discovered, were substituted for the metallic cylin- 

 ders, and their action upon the magnet was proved to be precisely the 

 same in kind as that of the cylinders of bismuth. The inquiry was also 

 extended to other insulators: to phosphorus, sulphur, nitre, calcareous 

 spar, statuary marble, with the same invariable result: each of these sub- 

 stances was proved polar, the disposition of the force being the same as 



