172 Professor TyndalFs further Researches 



V. 



Cylinders of Copper. 

 Position 1. 754 Position 2. 754 Position 3. 755 



Now if the effects obtained with bismuth were due to induced 

 currents, we should have the same effects forty times multiplied 

 in the case of copper, in place of which we have scarcely any 

 sensible effect at all. 



Bismuth is the only substance which has hitherto produced 

 an action in experiments of this nature; another illustration, 

 however, is furnished by the metal antimony, which possesses a 

 greater conductive power, but a less diamagnetic power than 

 bismuth. The following results were obtained with this sub- 

 stance : — 



VI. 



Cylinders of Antimony. 



Length 3 inches. Diameter 0*7. 



Current direct* . Current reversed f. 



Position 1. 693 244 



Position 2. 688 252 



Position 3. 683 261 



On comparing these numbers with those already obtained with 

 bismuth, we observe that for like positions the actions of both 

 metals are alike in direction. We further observe that the results 

 are determined, not by the relative conductive powers of the two 

 metals, but by their relative diamagnetic powers. If the former 

 were the determining cause, we should have greater deflections 

 than with the bismuth, which is not the case ; if the latter, we 

 should have less deflections, which is the case. 



The third and severest condition proposed by those who object 

 to the experiments of M. Weber is to substitute insulators for 

 conductors. T call this condition severe for the following rea- 

 sons : — according to the experiments of Faraday J, when bismuth 

 and sulphur are submitted to the same magnetic force, the re- 

 pulsion of the former being expressed by the number 1968, that 

 of the latter will be expressed by 118. Hence an action which, 

 with the means hitherto used, was difficult of detection in the 

 case of bismuth, must wholly escape observation in the case of 

 sulphur, the intensity of whose excitement is nearly twenty times 

 less. The same remarks apply, in a great measure, to all other 

 insulators. 



But the admirable apparatus made use of in this investigation 

 has enabled me to satisfy this condition also. To Mr. Faraday 



• As in III. and IV. t As in I. and II. 



% PhU. Mag. March 1853, p. 222. 



