557 



bear upon the suspended system four times that which would come 

 into play if only a single spiral and a single pole were made use of. 

 The mode of observation is the same as that applied by Gauss to 

 his magnetometer. The instrument is enclosed on all sides from 

 external air-currents ; the magnets have a mirror attached to them 

 which moves as they move, and which is observed by means of a 

 telescope and scale placed at a distance of about ten feet from the 

 instrument. 



When cylinders of bismuth are submitted to experiment, a very 

 marked deflection is produced, indicating, on the part of the bis- 

 muth, a polarity opposed to that of iron. This is the only sub- 

 stance which has hitherto been examined ; and against M. Weber's 

 results, obtained with this metal, it has been urged that the de- 

 flection observed by him was due to induced currents, aroused in 

 the bismuth by its mechanical motion up and down within the 

 spiral. With regard to this objection, as bearing upon the author's 

 experiments, he remarks, first, that the deflection produced is per- 

 manent, which could not be the case if the effect were due to 

 induced currents, which vanish instantaneously. Secondly, if 

 the effect were due to induction, it would be shown in the most 

 exalted degree by the best conductors. Now antimony is less 

 diamagnetic than bismuth, but it is a better conductor. The 

 deflection produced by it, however, shows that it is its diamagnetic 

 quality, and not its conductive quality, which is effective; the 

 deflection is less than that of bismuth. Copper is fifty times a 

 better conductor than bismuth, but its diamagnetic capacity is 

 nearly nil ; it produces no sensible action upon the magnets, which 

 could not possibly be the case were the result due to induction. 



Again, a quantity of bismuth was powdered, and the powder 

 suffered to become so tarnished that it was unable to conduct vol- 

 taic electricity. Tubes filled with this powder produced effects 

 almost as striking as those produced by the massive cylinders of 

 bismuth. 



But the experiments have been extended to a great number of 

 insulators, with the same result. Heavy-glass, sulphur, calcareous 

 spar, statuary marble, nitre, phosphorus, wax, and other insula- 

 tors, have been examined, and proved polar. Both paramagnetic 

 and diamagnetic liquids have also been embraced in the examina- 



