PARAMAGNETIC AND DTAMAONETIC FORGES. 249 



Cylinders of antimony were substituted for those of bis- 

 muth. This metal is a better conductor of electricity, but 

 less strongly diamagnetic than bismuth. If therefore the 

 action referred to be due to induced currents we ought to 

 have it greater in the case of antimony than with bismuth: 

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

 of the bismuth ought to exceed that of the antimony. Ex- 

 periment proves this to be the case. Hence the deflection 

 produced by these metals is due to their diamagnetic, and 

 not to their conductive capacity. Copper cylinders were 

 next examined: here we have a metal which conducts elec- 

 tricity fifty times better than bismuth, but its diamagnetic 

 power is nearly null; if the effects be due to induced cur- 

 rents we ought to have them here in an enormously exag- 

 gerated degree, but no sensible deflection was 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 insulating 

 substance, so as to render the formation of induced cur- 

 rents 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 oxidized as to render them perfectly 

 insulating. The insulating power of the powder was 

 exhibited experimentally; nevertheless, this powder, 

 enclosed in glass tubes, exhibited an action scarcely less 

 powerful than that of the massive bismuth cylinders. 



But the most rigid proof, a proof admitted to be con- 

 clusive by those who have denied the antithesis of magnet- 

 ism and diamagnetism, remains to be stated. Prisms of 

 the same heavy glass as that with which the diamagnetic 

 force was discovered, were substituted for the metallic 

 cylinders, 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, niter, calcareous spar, 

 statuary marble, with the same invariable result: each of 

 these substances was proved to be polar, the disposition of 

 the force being the same as that of bismuth and the 

 reverse of that of iron. When a bar of iron is set erect, its 

 lower end is known to be a north pole, and its upper end 

 a south pole, in virtue of the earth's induction. A marble 



