18o6.] i/i Paramagnetic and DiamaxjTietii: Bodies. 163 



made with other metals, and with better conductors than bismuth, for 

 if due to ctirrents 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 currents we ought to have it greater in the case of 

 antimony than with bismuth ; but if it springs from a true dia- 

 magnetic 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 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 electri- 

 city fifty times better than bismuth, but its diamagnetic 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 

 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 sub- 

 stance, so as to render 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 oxidised as to render them perfectly 

 insulating. The power of the powder in this respect was exhibited 

 experimentally in the lecture ; nevertheless, this powder, enclosed in 

 glass tubes, exhibited an action scarcely less powerful than that of 

 the massive cylinders. 



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

 those who have denied the antithesis of magnetism 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 otlier insulators : to phosphorus, 

 sulphur, nitre, calcareous spar, statuary marble, with the same 

 invariable result : each of these substances was proved 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 statue, on the con- 

 trary, has its feet a south pole, and its head a north pole, and there 

 is no doubt 'that the same remark applies to its living archetype; 

 each man walking over the earth's surface is a true diamagnet, with 

 its poles the reverse of those of a mass of magnetic matter of the 

 same shape and in a similar position. 



An experiment of practical value, as affording a ready estimate 

 of the different conductive powers of two metals for electricity, was 



